ERG No. 0195.00.002 TECQ Contract No. 582-04-65589 Work Order No. 05-06



### ASSESSMENT OF NO x 

### EMISSIONS REDUCTION STRATEGIES FOR CEMENT KILNS - ELLIS COUNTY

FINAL REPORT

TCEQ Contract No. 582-04-65589 Work Order No.05-06

Prepared by:

ERG, Inc. 10200 Alliance Road, Suite 190

Cincinnati, Ohio 45242-4716

Prepared for:
Air Quality Planning Section Chief Engineer’s Office Texas Commission on Environmental Quality Austin, Texas 78711-3087

July 14, 2006i This study is the work project of a panel of experts assemble d at the request of the Texas Commission on Environmental Quality. This st udy was performed under contract to Eastern Research Group that provided overall contract management and subcontracted the outside experts and laboratory services. While each of th e experts brought specific skills to this study and was the principal author of individual sections of the report , the overall study represents a team effort. The general conclusions of the st udy have been reviewed and are endorsed by the entire expert panel.

Walter Koucky, Senior Project Engineer - C ontract Manager, Eastern Research Group

Dr. Ray Merrill, Senior Chem ist, Eastern Research Group

David Gossman, FAIC, Presiden t, Gossman Consulting Inc.

Dr. Gabe Miller, Professor of Chemistry, New York University

Dr. Greg Miller, Principal, Cement Etc., Inc.TABLE OF CONTENTS

1.0 INTRODUCTION ...........................................................................................................1-1 1.1 Executive Summary.............................................................................................1-2 1.1.1 Control Alternatives for Holcim Inc........................................................1-4 1.1.2 Control Alternatives for TXI Cement......................................................1-5 1.1.3 Control Alternatives for Ash Grove Cement ...........................................1-5

2.0 DEFINING PARAMETERS FOR CONTROL EVALUATION ....................................2-1 2.1 Overview of Portland Cement Manufacturing Process and NO x Generation......2-1 2.1.1 Description of the Cement Industry.........................................................2-4 2.1.2 Kiln Types and Operation........................................................................2-8 2.1.3 Thermal Characteristics .........................................................................2-12 2.1.4 Process Variables...................................................................................2-14

3.0 NO X FORMATION IN CEMENT KILNS.......................................................................3-1 3.1 Overview of NO x Formation Mechanisms ..........................................................3-1 3.1.1 Thermal NO x Formation ..........................................................................3-2 3.1.2 Fuel NO x Formation.................................................................................3-3 3.1.3 Feed NO x Formation................................................................................3-5 3.1.4 Factors Affecting NO x Emissions in Cement Manufacturing..................3-6 3.1.5 Suspension Preheater (SP) Kiln s with Riser Duct Firing. .......................3-9 3.1.6 Precalcining Kiln Systems. ....................................................................3-10 3.1.7 Energy Efficiency of the Cement-Making Process................................3-11

4.0 OVERVIEW OF POTENTIALLY APPLICABLE CONTROL TECHNIQUES AND TECHNOLOGIES ...........................................................................................................4-1 4.1 High Temperature Emissions Controls................................................................4-3 4.1.1 Selective Catalytic Reduction (SCR).......................................................4-3 4.1.2 Selective Noncatalytic Reduction (SNCR)............................................4-20 4.2 Combustion Optimization..................................................................................4-33 4.2.1 Staged Combustion of Air .....................................................................4-34 4.2.2 Flue Gas Recirculation...........................................................................4-34 4.2.3 Low-NO x Burners ..................................................................................4-35 4.2.4 Staged Combustion of Fuel....................................................................4-38 4.2.5 Preheater/Precalciner and Tire Derived Fuel.........................................4-38 4.2.6 Low- NO x Precalciners ..........................................................................4-40 4.2.7 Mid-Kiln Firing......................................................................................4-41 4.3 Lower Temperature Oxidation Based Technologies .........................................4-43 4.3.1 Introduction............................................................................................4-44 4.3.2 LoTOx TM ................................................................................................4-44 4.3.3 Hydrogen Peroxide ................................................................................4-51 4.3.4 OXONE (Dupont – potassium monopersulfate)....................................4-56 4.3.5 Sodium Acetate Process.........................................................................4-57 4.3.6 Potential Applicability of Oxidati on Technology to Ash Grove Plant..4-59 4.3.7 Potential Applicability of Oxida tion Technology to Holcim Plant .......4-60 4.3.8 Potential Applicability of Oxid ation Technology to TXI Plant.............4-60TABLES OF CONTENTS (Continued)

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Cement Kiln Report (FINAL – 7/14/2006) iii 4.4 Process Modification .........................................................................................4-63 4.4.1 Combustion Zone Control of Temperature and Excess Air...................4-64 4.4.2 Feed Mix Composition ..........................................................................4-64 4.4.3 CemStar Process ....................................................................................4-65 4.4.4 Kiln Fuel ................................................................................................4-67 4.4.5 Increasing Thermal Efficiency...............................................................4-68 4.5 Performance of Current NO x Control Techniques and Technologies in the Cement Industry.................................................................................................4-74 4.5.1 Summary of Current Performance of NO x Control Technologies.........4-74 4.5.2 Summary of Current Regulations ..........................................................4-74 4.5.3 Summary Of European Experiences......................................................4-79

5.0 CHEMISTRY OF ELLIS COUNTY MATERIALS AND IMPACTS ON CONTROL DETERMINATIONS ......................................................................................................5-1 5.1 Results..................................................................................................................5- 1 5.1.1 Organic Carbon........................................................................................5-2 5.1.2 Total Kjeldahl Nitrogen ...........................................................................5-3 5.1.3 Total Sulfur ..............................................................................................5-4 5.2 Conclusions..........................................................................................................5-5

6.0 REFERENCES ................................................................................................................6 -1
Attachment A ERG Summary of EPA 2000 NO x Controls for Cement Kilns
Attachment B Sampling Plan
Attachment C ERG Report on LoTOx TM Application to Refineries
Attachment D Summary of Current US Cement Regulations for NO xLIST OF TABLES

Page
1-1 Summary of Technologies for Holcim #1 ....................................................................... 1-4
1-2 Summary of Technologies for Holcim #2 ....................................................................... 1-5
1-3 Summary of Technologies for TXI #1 & #4.................................................................... 1-6
1-4 Summary of Technologies for TXI #2 & #3.................................................................... 1-7
1-5 Summary of Technologies for TXI #5............................................................................. 1-8
1-6 Summary of Technologies for Ash Grove #1.................................................................. 1-9
1-7 Summary of Technologies for Ash Grove #2.................................................................. 1-9
1-8 Summary of Technologies for Ash Grove #3.................................................................. 1-9
1-9 Summary of Technologies – Seasonal for Holcim #1 ................................................... 1-10
1-10 Summary of Technologies – Seasonal for Holcim #2 ................................................... 1-10
1-11 Summary of Technologies – Seasonal for TXI #1 & #4 ............................................... 1-10
1-12 Summary of Technologies - Seasonal for TXI #2 & #3 ................................................ 1-11
1-13 Summary of Technologies - Seasonal for TXI #5 ......................................................... 1-11
1-14 Summary of Technologies – Seasonal for Ash Grove #1.............................................. 1-11
1-15 Summary of Technologies – Seasonal for Ash Grove #2.............................................. 1-12
1-16 Summary of Technologies – Seasonal for Ash Grove #3.............................................. 1-12
1-17 Environmental and Other Imp acts of Control Technologies ......................................... 1-19
2-1 Basic Clinker Compounds (3).......................................................................................... 2-3
3-1 Calculated Equilibrium Concentrations (In PPM) Of NO x and NO x In Air and Flue Gas (15)....................................................................................................................... ..... 3-3 4-1.1 Summary of Modeling Results for S CR on Ellis County Kilns – Performance Results....................................................................................................................... ..... 4-18 4-1.2 Summary of Modeling Results for SCR on Ellis County Kilns – Economic Results ... 4-19
4-1.3 Summary of Test Re sults for SNCR Test...................................................................... 4-23
4-1.4 Emissions Reductions From Two Kilns Using NOxOUT ® ........................................... 4-29LIST OF TABLES (Continued)

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Cement Kiln Report (FINAL – 7/14/2006) v 4-1.5 Summary of Modeling Results for SN CR on Ellis County Kilns – Performance Results....................................................................................................................... ..... 4-32 4-1.6 Summary of Modeling Results for SNCR on Ellis County Kilns – Economic Results....................................................................................................................... ..... 4-33

4-2.1 NO x Emissions from a Precalciner Equipped with a Low-NOx Burner........................ 4-36

4-2.2 NO x Emissions Before and After Installation of Pyro-Jet Low-NO x Burners............... 4-37

4-2.3 NO x Emissions with 3 Channel and Rotaflam ® Low-NO x Burners............................... 4-37

4-2.4 Emissions Before and Afte r Installation of a Rotaflam ® Burner on a Wet Kiln ........... 4-37

4-2.5 Emissions From Kilns W ith Mid-Kiln Firing................................................................ 4-43
4-3.1 Comparison Of Comm on Post Combustion NO x Abatement Technologies For NO x Emissions C ontrol.......................................................................................................... 4-47

4-3.2 Oxone Constituents....................................................................................................... . 4-56 4-3.3 Reaction Steps and Pathway Equations fo r the Sodium Acetate Direct Absorption Process For Simultaneous NO x And SO x Removal (OECD, 1983)............................... 4-58
4-3.4 Summary of Modeling Results for LoTOx TM on Ellis County Kilns – Performance Results....................................................................................................................... ..... 4-62 4-3.5 Summary of Modeling Results for LoTOx TM on Ellis County Kilns – Economic Results....................................................................................................................... ..... 4-63

4-4.1 Results of Short-Term Cemstar Test s on a Preheater/Precalciner Kiln......................... 4-66

4-4.2 Results of Cemstar Tests on a Wet Kiln ........................................................................ 4-67
4-4.3 Summary of Modeling Results for Wet to Dry Conversion of Ellis County Kilns – Performance Results ...................................................................................................... 4-73
4-4.4 Summary of Modeling Results for Wet to Dry Conversion of Ellis County Kilns – Economic Results........................................................................................................... 4-73
4-4.5 Summary of Modeling Results for Calc iner Upgrade for Ellis County Kilns – Economic Results........................................................................................................... 4-74

4-5.2 National SO 2 and NO x Emission Limits for the Produc tion of Cement Within the European Union (EU 15), in mg/Nm 3 , Around 2000 .................................................... 4-77

4-5.1 National SO 2 and NO x Emission Limits for the Produc tion of Cement Within the European Union (EU 15), in mg/Nm 3 ............................................................................ 4-77LIST OF TABLES (Continued)

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Cement Kiln Report (FINAL – 7/14/2006) vi 4-5.2 National PM Emission Limits for the Producti on of Cement Within the European Union (EU 15), in mg/Nm 3 ....................................................................................................... 4-77 4-5.3 Midwest RPO – LADCO Study..................................................................................... 4-79
4-5.4 Fall Line Air Quality Study (Georgia)........................................................................... 4-79

4-5.5 NO x Control Techniques Summary From Eu ropean Best Available Techniques Report 1 ........................................................................................................................... 4-80

Tables in Attachments

Table A-1 ERG Summary of EPA 2000 NO x Controls for Cement Kilns
Table B-1. Feed Chemical Composition
Table D-1. Summary of US NO x Control Regulations for Cement Kilns – EPA 2004

NOTE: Table 4-5.1 is a separate spreadsheet that is too large for inclusion in the body of the report. It is available as an Excel spreadsheet.Cement Kiln Report (FINAL – 7/14/2006) vii LIST OF FIGURES

Page
2-1 Temperature of the Gas and Material in the Rotary Cement Kiln 1.............................. 2-13
2-2 The Relationship Between Process Temp eratures and the Chemistry of Cement Clinker Formation.......................................................................................................... 2-13
3-1 Theoretical Equilibrium Concentrations of NOx............................................................. 3-4

4-1.1 SCR at Solnhofen Zement ............................................................................................. 4-22
4-1.2 Dependence of NOx Reduction on Temp erature for Ammonia and Urea..................... 4-22
4-1.3 Application of SNCR at Holcim.................................................................................... 4-24
4-2.1 Schematic of Preheater (58)........................................................................................... 4-3 9
4-2.2 Schematic of Precalciner(58)......................................................................................... 4-39
4-3.1 Overall Process Diagram of the LoTOx TM System........................................................ 4-45 4-3.2 EDV Wet Scrubbing System with LoTOx TM Injection ................................................ 4-46
4-3.3 Ideal Operating Conditions for NO x Removal from 80% to 95% ................................ 4-49
4-3.4 Conceptual Design of Hydrogen Peroxide NO x Control System .................................. 4-52
4-3.5 Effect of Temperature on Peroxide Oxidation of NO.................................................... 4-53

4-3.6 Effect of Molar Ratio on Peroxide Oxidation of NO..................................................... 4-54Cement Kiln Report (FINAL – 7/14/2006) 1-1 1.0 INTRODUCTION

This study was conducted to explore potential NO x emissions reduction strategies for cement kilns in Ellis County. This project included a ssessing existing NO x control technologies as well as new technologies that ha ve not been previously considered by TCEQ. This project evaluated th e general performance and cost of applicable NO x control technologies for the cement kilns present in Ellis County and fu rther evaluated the applic ation of these control technologies to the site-specific requirements of the kilns and raw materials present in Ellis County.

This study was initiated in order to fulfill ob ligations in the Dallas/Fort Worth Litigation Settlement Agreement. TCEQ, in consultation with the Plaintiffs, EPA, and Intervenor the Portland Cement Association, developed the scope of work and selected Eastern Research Group (ERG) and a panel of experts (the ERG Team) to perform this cement kiln NO x control technologies study. This study evaluated the appli cability of existing control technologies and the potential availability of new air pollution cont rol technologies for cement kilns located in the
Dallas/Ft. Worth ozone nonattainment area. This report evaluates and es tablishes the types of controls that may be t echnically applied to the three nonatt ainment area cement plants with specific evaluations of applicability to the 10 cement kilns located at the three plants. This report focuses largely on three ac tive types of control te chnology: SCR, SNCR and NO x Oxidation.
This focus in based on the need to evaluate t echnologies that go beyond cu rrent requirements of 30 Texas Administrative Code (T AC) Chapter 117. Economics of these control technologies are also investigated and reported.

The intent of this study was to establish im partial parameters for the determination of applicable controls. Controls we re included to the extent that they were technically feasible.
Control costs and cost effectiveness va lues, in terms of cost per ton of NO x controlled, were then assigned to all technically feasib le controls. The ERG Team has not applied value judgments nor assessed the economic viability of technically feasible cont rols. The ERG Team has not excluded any control technology on the basis of cost . This study puts forward technically viable
NO x control technologies and evaluate s their cost effectiveness for specific application to EllisCement Kiln Report (FINAL – 7/14/2006) 1-2 County cement kilns with the inte nt of allowing TCEQ to have sufficient information to make control technology selections.

This report uses the USEPA report “NO x Control Technologies for the Cement Industry” of September 2000 (EPA 2000) as a baseline for th e technical analysis and as boilerplate for describing the cement industry and applicable control technologies. The ERG Team has
reviewed and edited this text to reflect the Team’s understandi ng of the processes and control techniques. As mentioned prev iously, this report looks at ac tive control technologies beyond the combustion and process optimization techniques of 30 TAC Chapter 117. The EPA 2000 report evaluates Selective Catalytic Reduction (SCR) and Selective Non-cata lytic Reduction (SNCR) for the cement industry. This study takes th is EPA 2000 information and updates it to the present. In addition, this study conducts si te-specific evaluations including control cost evaluations for the 10 Ellis County cement kilns. This study focuses on application of SCR, SNCR and oxidation technologies including LoTOx TM to control oxides of nitrogen. Energy improvements are also examined, including replacem ent of the seven Ellis County wet kilns with two large, modern dry process units.

1.1 Executive Summary

The tables presented below contain summ aries of control technology evaluations conducted as part of this study. The summaries below generally contain conservative costs and scenarios for the selected technologies. For exam ple, performance levels for selective catalytic reduction (SCR) and LoTOx TM oxidation are conservatively estimated at 80-85%. These technologies typically perform bette r than these levels in other i ndustrial applications. However, using a slightly lower performance value presents a more conservative evaluation of control costs, allowing potential difficultie s in initial application of th ese technologies to Ellis County
cement kilns.

The tables include a column discussing the status of the control technology for the application. This column uses the Top-Down BACT terms, available, transferable and

innovative , to describe the statuses of the control technologies. However, for the purposes of this report, available essentially means that the technology is commercially available and in useCement Kiln Report (FINAL – 7/14/2006) 1-3 on similar types of cement kilns. Transferable means that the technology is commercially available and in use on similar process equipmen t and could reasonably be expected to work on that type of cement kiln. Innovative describes technologies that have not been successfully applied to a type of cement kil n, but in the judgment of the ER G Team could be expected to work on the type of cement kiln if correctly opti mized through experimental application.

Wet kilns use more energy and have higher em issions rates than dr y kilns. The only
available wet kiln control technique fully evaluated in this study is conversi on of the wet kilns to modern dry preheater/calciner units. This is a hi gh cost alternative with a cost of approximately $11 per metric tonne (the metric tonne is the standa rd unit of measure for cement production and is used in this report) of cli nker produced, including consideration of substantial fuel savings due to increased efficiency. As the cost of altern ative controls approaches this value, there is reasonably expected to be a point where the cost of control technologies may create a substantial incentive to replace the wet kilns. This deci sion is complex and may require consideration of expanded production and use of alte rnative energy sources to be co mmercially justified. At the time this report was completed, Holcim of Fran ce was giving preliminary reports of trials of selective non-catalytic reduction (SNCR) on a wet kiln. While these preliminary reports do not provide sufficient information for technical evalua tion of the results, this may mean that SNCR
has become an available contro l technology for wet kilns.

Burden costs in dollars per tonne clinker produced ($/tonne) are provided to provide insight into the impacts of control costs on the ce ment plant’s cost of product. The emissions
reductions calculated in Tables 1-1 through 1-8 are based on opera tion of the control equipment for the entire year and not just during the Dall as/Ft. Worth ozone season. Tables 1-9 through 1- 16 are based on operation of the control equipmen t for just the Dallas/Ft. Worth ozone season.
The metric tonne is the standard unit both in the US and worldwide for measuring cement production. This causes confusion because the metric tonne is often spelled “ton”. This report uses the spelling “tonne” to refer to the metr ic tonne (i.e., 1,000 kil ograms or 2,205 pounds). Current regulations in Texas are based on pounds of NO x per short ton (i.e., 2,000 pounds). For consistency in the technical discus sions of controls and regulations in the US and worldwide, this report discusses production related information based on the metric tonne of production. ToCement Kiln Report (FINAL – 7/14/2006) 1-4 assist in comparison with existing Texas regula tions, values in pounds per short ton have been added in parentheses to the tables in this Executive Summary.

1.1.1 Control Alternatives for Holcim Inc.

Holcim operates two modern dry preheat precalcination kilns, each with an annual production capability of slightly over one million t ons per year of clinker. Holcim has recently completed testing of SNCR on these kilns. SNCR performed reasonably well on Holcim #1, but additional optimization ma y improve performance.

Holcim #1

Holcim’s Line #1 began operation in 1987. This unit is a modern design, typical of units built in the 1980’s; this kiln may be a candida te for a reconstructed preheater precalcination tower to a larger, more energy efficient desi gn (see Section 4.4.5 of the report). This reconstruction could also allow for imp roved staging of combustion, lower NO x generation and improved integration with controls such as SN CR or an oxidation cont rol technology. Without modification, Holcim #1 will likely achieve some what lower control performance than Holcim #2 or TXI #5 based on application of similar t echnologies. However, in spite of its older generation of design, Holcim #1 is currently perf orming nearly as well as Holcim #2. Neither Holcim #1 nor Holcim #2 is currently performing as well as TXI #5 in terms of energy efficiency
or NO x emissions rates even though Holcim #2 is approximately the same age.

Note on the conventions used in the Tables 1-1 through 1-16.

The metric tonne (1,000 kg. or 2,205 lbs.) is used by the cement industry for measuring and reporting production. Emissions are reported in shor t tons containing 2,000 lbs./ton. This results in a 10% difference between the metric tonne and the short ton. A controlled emissions rate of 1.1 lbs./tonne is equivale nt to a controlled emissions rate of 1.0 lbs./ton. Emissions reported in tpy are in short tons per year. As Texas has used lbs./ton (based on the US ton – or short ton) in the past, these values are provided in parentheses in appropriate locations in the tables in this chapter.Cement Kiln Report (FINAL – 7/14/2006) 1-5 

### Table 1-1 Summary of Technologies fo r Holcim #1 – Full Year Control

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Available 2,222 3.76 (3.41) 85% 1,888.7 0.56 (0.51) $1,600 $2.60 LoTOx TM Transferable 2,222 3.76 (3.41) 85% 1,888.7 0.56 (0.51) $2,200 $3.50 SNCR Available 2,222 3.76 (3.41) 50% 1,111 1.9 (1.7) $1,400 $1.30 Calciner Upgrade Available 2,222 3.76 (3.41) 40% 888.8 2.2 (2.0) $2,795 $2.70 40% for new low-NOx calciner based on literature. Cost effectiveness for calciner upgrade calculated by ratio of burden costs using SCR data.

Holcim #2 Holcim’s Line #2 began operation in 1999. Holcim #2 is a modern design, but emits substantially more NO x than TXI #5 that was built only two y ears later. There may be process or combustion optimization options for Holcim #2 that can lower NO x prior to control. Holcim has recently completed testing of SNCR on these kiln s. SNCR did not perform as well as would be expected on Holcim #2 and additional optim ization should improve performance.



### Table 1-2 Summary of Technologies fo r Holcim #2 – Full Year Control

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Available 1,778 3.01(2.73) 85% 1,511.3 0.45(0.41) $1,900 $2.20 LoTOx TM Transferable 1,778 3.01(2.73) 85% 1,511.3 0.45(0.41) $2,100 $2.80 SNCR Available 1,778 3.01(2.73) 50% 889 1.5(1.36) $1,600 $1.20

1.1.2 Control Alternatives for TXI Cement

TXI operates five kilns, one modern dr y preheat precalcination kiln and four
1960’s era wet kilns. Two of the wet kilns are operated full time and two are operated as backup
units about 15% of the time.

TXI #1 and #4 TXI #1 began operation in 1960 and TXI #4 began operation in 1972. These are wet kilns that use the old process of making cement fr om wet slurry. This makes high quality cement but uses substantially more energy to make cement. Both energy use and NO x emissions rates are substantially higher for wet kilns than for dry pr ocess kilns. Because the kilns are of similarCement Kiln Report (FINAL – 7/14/2006) 1-6 size and used in a similar manner, one estimate has been created to represent both TXI #1 and
TXI #4. Cost and control estimates are based on averaging the operation of these kilns; a similar approach has been used for TXI #2 and #3. A cont rol option for replacemen t of the wet kilns at TXI with a new large dry kiln of equal capacity to the old wet kilns is also presented. The model for wet to dry conversion contains a calculation for fuel savings that is not entirely accurate for
TXI because of the use of waste fuels in the wet kiln s. However, to the extent that a new, larger dry kiln would continue to utilize a similar amoun t of waste fuels, the savings in fuel expressed as coal, would still provide an accurate view of a potential fuel savings. The models for TXI #1 and #4 presume that mid-kiln firing will be appl ied as required under the current SIP and that
this will achieve a 30% reduction in NO x emissions. This 30% assumption is based on
evaluation of literature and other installations and is not intended to predict the actual ability of
TXI to reduce emissions through mid-kiln firing.

Assuming mid-kiln firing reduces the emi ssions rate from current actual rates and
decreases control cost effectiveness. As less NO x is available for control, the cost per ton controlled is increased. However, as mid-kiln firing is already required under Texas regulations, this was deemed the proper starting place for cont rol analysis. The analyses for TXI #1 and #4 presented below are based on an average for the tw o kilns and values presented below, such as emissions reductions, should be doubl ed to account for both kilns.



### Table 1-3 Summary of Technologies for TXI #1 & #4 – Full Year Control

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Transferable 838 5.67(5.14) 85% 712.3 0.85(0.77) $4,900 $12.30 LoTOx TM Transferable 838 5.67(5.14) 85% 712.3 0.85(0.77) $2,800 $6.80 SNCR Innovative 838 5.67(5.14) 35% 293.3 3.7(3.36) $2,100 $2.10 Wet to Dry Available 1,802 5.67(5.14) 65% 1,171.3 2.0(1.81) $6,700 $11.00 Large 3 Kiln SCR Transferable 1,802 5.67(5.14) 85% 1,531.7 0.85(0.77) $5,400 $8.00 SCR includes the cost of installing and op erating RTO’s to reheat gas after ESPs. Wet to dry conversion analysis based on one large kiln to replace existing capacity.

TXI #2 and #3 TXI #2 began operation in 1963 and TXI #3 began operation in 1967. Similar to TXI #1 and #4, these are wet kilns that use the old pro cess of making cement from wet slurry. BecauseCement Kiln Report (FINAL – 7/14/2006) 1-7 the kilns are of similar size and used in a si milar manner, one estimate has been created to represent both TXI #2 and TXI #3. Cost and control estimates are based on averaging the operation of these kilns. A lthough the kilns are physically si milar to TXI #1 and #4, they are used as backup units. As backup units, these kiln s have a low utilization rate (averaging 15% for the two kilns in 2004); the low uti lization rate will show poor econom ics of control, as the fixed costs will be averaged over very small NO x reductions. The control option for replacement of the wet kilns at TXI with a new large dry kiln of equal capacity to the old wet kilns is an option
for all four kilns and has identi cal economics and environmental be nefits as described above for TXI #1 and #4. Also, as with TXI #1 and #4, mid- kiln firing is assumed as the starting place for this analysis as this is alr eady required by Texas regulations. The analyses for TXI #2 and #3 presented below are based on an average for the tw o kiln and values presented below, such as emissions reductions, should be doubl ed to account for both kilns.



### Table 1-4 Summary of Technologies for TXI #2 & #3 – Full Year Control

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Transferable 85 3.4(3.08) 85% 72.3 0.51(0.46) $66,400 $14.00 LoTOx TM Transferable 85 3.4(3.08) 85% 72.3 0.51(0.46) $8,000 $11.50 SNCR Innovative 85 3.4(3.08) 35% 30 2.2(2.00) $11,000 $6.50 Wet to Dry Available 1,802 5.67(5.14) 65% 1,171.3 2.0(1.81) $6,700 $11.00 Large 3 Kiln SCR Transferable 1,802 5.67(5.14) 85% 1,531.7 0.85(0.77) $5,400 $8.00 SCR includes the cost of installing and op erating RTO’s to reheat gas after ESPs. Wet to dry conversion analysis based on one large kiln to replace existing capacity. The higher emissions rate of TXI 1 & 4 is used as representative of operation for combined solutions wet to dry and large single SCR.

TXI #5 TXI #5 began operation in 2001 and is the largest and most efficient kiln line in the study area. It is relatively fuel e fficient and intrinsically low in NO x emissions. The low NO x emissions rate is a function of the design and may al so be partly the result of the chemistry of the feed materials (see discussion of chemistry in the main report) that may be causing reduction of
NO x . Because of the relatively low NO x concentrations in the offgas, the expected NO x removal
efficiencies are lower for TXI #5 than for othe r kilns. For example, both European and US experience with SNCR indicates that re moval is less efficient at lower NO x concentration and that practical removal is curren tly understood to be limited to about 200 mg/m3 or 100 ppm. ForCement Kiln Report (FINAL – 7/14/2006) 1-8 this reason, TXI #5 is modeled for 35% contro l for SNCR compared to 50% for the Holcim
kilns.



### Table 1-5 Summary of Technologies for TXI #5 – Full Year Control

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Available 1,710 1.50 (1.36) 80% 1,368 0.30 (0.27) $2,000 $1.10 LoTOx TM Transferable 1,710 1.50 (1.36) 80% 1,368 0.30 (0.27) $2,400 $1.40 SNCR Available 1,710 1.50 (1.36) 35% 598.5 1.0 (0.91) $2,300 $0.60

1.1.3 Control Alternatives for Ash Grove Cement

ASH GROVE #1, #2 and #3 Ash Grove operates three wet kilns that began operation in 1966, 1969 and 1972. Similar to the wet kilns at TXI, these are wet kilns that use the older process of making cement from wet slurry. This makes high quality cement but uses substa ntially more energy to make cement. Both energy use and NO x emissions rates are substantially higher for wet kilns than for dry process kilns. The Ash Grove kilns are currently complying with the SIP requirement for midkiln firing. The NO x emissions rate at Ash Grove from mi d-kiln firing of tires appears to be substantially lower than at TXI where the mid- kiln firing project has been delayed by permit
issues.

Because the Ash Grove kilns are of similar si ze and used in a similar manner, separate discussions are not provided for each kiln. Slight differences in flow rates and emissions rates are modeled and presented in the tables below. Similar to the TXI presentation, a control option for replacement of the wet kilns at Ash Grove with a new large dry kiln of equal capacity to the old wet kilns is presented. A single, large SCR is modeled that combines the emissions and flow of the three kilns into one large control unit is modeled to demonstrat e the impact on control
costs. SCR is more cost effective at Ash Grove than at TXI due to higher gas temperatures and less required reheat of stack gas.Cement Kiln Report (FINAL – 7/14/2006) 1-9 

### Table 1-6 Summary of Technologies fo r Ash Grove #1 – Full Year Control

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Transferable 702 5.57(5.05) 85% 596.7 0.84(0.76) $5,200 $12.00 LoTOx TM Transferable 702 5.57(5.05) 85% 596.7 0.84(0.76) $2,900 $7.00 SNCR Innovative 702 5.57(5.05) 35% 245.7 3.6(3.27) $2,200 $2.20 Wet to Dry Available 2,205 5.68(5.15) 65% 1,433.3 2.0(1.81) $6,500 $11.00 Large 3 Kiln SCR Transferable 2,205 5.83(5.29) 85% 1,874.25 0.88(0.80) $4,200 $10.00 SCR includes the cost of installing and op erating RTO’s to reheat gas after ESPs. Wet to dry conversion analysis based on one large kiln to replace 3 small emissi ons are averaged for these scenarios.



### Table 1-7 Summary of Technologies fo r Ash Grove #2 – Full Year Control

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Transferable 750 5.95(5.40) 85% 637.5 0.89(0.81) $5,200 $13.00 LoTOx TM Transferable 750 5.95(5.40) 85% 637.5 0.89(0.81) $2,900 $7.50 SNCR Innovative 750 5.95(5.40) 35% 262.5 3.9(3.54) $2,200 $2.30 Wet to Dry Available 2,205 5.68(5.15) 65% 1,433.3 2.0(1.81) $6,500 $11.00 Large 3 Kiln SCR Transferable 2,205 5.83(5.29) 85% 1,874.25 0.88(0.80) $4,200 $10.00 SCR includes the cost of installing and op erating RTO’s to reheat gas after ESPs. Wet to dry conversion analysis based on one large kiln to replace 3 small.



### Table 1-8 Summary of Technologies fo r Ash Grove #3 – Full Year Control

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Transferable 764 6.06(5.50) 85% 649.4 0.91(0.83) $5,500 $14.00 LoTOx TM Transferable 764 6.06(5.50) 85% 649.4 0.91(0.83) $3,000 $7.90 SNCR Innovative 764 6.06(5.50) 35% 267.4 3.9(3.54) $2,200 $2.30 Wet to Dry Available 2,205 5.68(5.15) 65% 1,433.3 2.0(1.81) $6,500 $11.00 Large 3 Kiln SCR Transferable 2,205 5.83(5.29) 85% 1,874.3 0.88(0.80) $4,200 $10.00 SCR includes the cost of installing and op erating RTO’s to reheat gas after ESPs. Wet to dry conversion analysis based on one large kiln to replace 3 small.Cement Kiln Report (FINAL – 7/14/2006) 1-10 1.1.4. Ozone Season Only Control Costs

The emissions reductions calculated in the tables below are based on operation of the control equipment during the Dallas/Ft. Wort h ozone season unless otherwise noted. For example, SCR is presumed to operate only during the ozone season in the modeling. This results in a higher annualized co st effectiveness in dollars per ton of NO x controlled as less NO x is
controlled on an annual basis. Wet kiln to dry preheat/precalciner unit conversions provide benefit for the full year and are not seasonal meas ures. Tables 1-9 through 1-16 are similar to Tables 1-1 through 1-8 except that adjustments ha ve been made to represent seasonal operation.

Holcim Ozone Season Results 

### Table 1-9 Summary of Technologies fo r Holcim #1 – Ozone Season Control

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Available 2,222 3.76 (3.41) 85% 1,267.3 0.56 (0.51) $1,900 $2.00 LoTOx TM Transferable 2,222 3.76 (3.41) 85% 1,267.3 0.56 (0.51) $2,400 $2.35 SNCR Available 2,222 3.76 (3.41) 50% 745.4 1.9 (1.7) $1,500 $1.00 Calciner Upgrade Available 2,222 3.76 (3.41) 40% 888.8 2.2 (2.0) $2,795 $2.70 Emissions reductions are for ozone season unless otherwise noted. 40% for new low-NOx calciner based on literature. Cost effectiveness for calciner upgrade calculated by ratio of burden costs using SCR data. Calciner upgrade is not a seasonal ozone measure.



### Table 1-10 Summary of Technologies fo r Holcim #2 – Ozone Season Control

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Available 1,778 3.01(2.73) 85% 1,014.0 0.45(0.41) $2,000 $1.70 LoTOx TM Transferable 1,778 3.01(2.73) 85% 1,014.0 0.45(0.41) $2,300 $1.90 SNCR Available 1,778 3.01(2.73) 50% 596.5 1.5(1.36) $1,700 $0.90 Emissions reductions are for ozone season unless otherwise noted.Cement Kiln Report (FINAL – 7/14/2006) 1-11 TXI Ozone Season Results


### Table 1-11 Summary of Technologies for TXI #1 & #4 – Ozone Season Only

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Transferable 838 5.67(5.14) 85% 477.9 0.85 (0.77) $5,500 $8.90 LoTOx TM Transferable 838 5.67(5.14) 85% 477.9 0.85 (0.77) $3,300 $4.70 SNCR Innovative 838 5.67(5.14) 35% 196.8 3.7 (3.36) $2,400 $1.60 Wet to Dry Available 1,802 5.67(5.14) 65% 1,171.3 2.0 (1.81) $6,700 $11.00 Large 3 Kiln SCR Transferable 1,802 5.67(5.14) 85% 1,027.7 0.85 (0.77) $5,400 $6.00 Emissions reductions are for ozone season unless otherwise noted. SCR includes the cost of installing and op erating RTO’s to reheat gas after ESPs. Wet to dry conversion analysis based on one large kiln to replace existing cap acity, emissions reduction is full year.



### Table 1-12 Summary of Technologies for TXI #2 & #3 – Ozone Season Only

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Transferable 85 3.4 (3.08) 85% 48 0.51(0.46) $96,000 $13.50 LoTOx TM Transferable 85 3.4 (3.08) 85% 48 0.51(0.46) $11,000 $10.50 SNCR Innovative 85 3.4 (3.08) 35% 20 2.2 (2.00) $13,000 $5.00 Wet to Dry Available 1,802 5.67(5.14) 65% 1,171.3 2.0 (1.81) $6,700 $11.00 Large 3 Kiln SCR Transferable 1,802 5.67(5.14) 85% 1,027.7 0.85 (0.77) $5,400 $6.00 Emissions reductions are for ozone season unless otherwise noted. SCR includes the cost of installing and op erating RTO’s to reheat gas after ESPs. Wet to dry conversion analysis based on one large kiln to replace existing cap acity, emissions reduction is full year.



### Table 1-13 Summary of Technologies for TXI #5 – Ozone Season Only

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Available 1,710 1.50 (1.36) 80% 918.0 0.30 (0.27) $2,200 $0.87 LoTOx TM Transferable 1,710 1.50 (1.36) 80% 918.0 0.30 (0.27) $2,600 $0.90 SNCR Available 1,710 1.50 (1.36) 35% 401.6 1.0 (0.91) $2,500 $0.45 Emissions reductions are for ozone season unless otherwise noted.Cement Kiln Report (FINAL – 7/14/2006) 1-12 Ash Grove Ozone Season Results



### Table 1-14 Summary of Technologies fo r Ash Grove #1 – Ozone Season Only

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Transferable 702 5.57(5.05) 85% 400.4 0.84 (0.76) $5,800 $9.20 LoTOx TM Transferable 702 5.57(5.05) 85% 400.4 0.84 (0.76) $3,400 $5.00 SNCR Innovative 702 5.57(5.05) 35% 164.9 3.6 (3.27) $2,500 $1.70 Wet to Dry Available 2,205 5.68 (5.15) 65% 1,433.3 2.0 (1.81) $6,500 $11.00 Large 3 Kiln SCR Transferable 2,205 5.83 (5.29) 85% 1,257.6 0.88 (0.80) $4,600 $7.80 SCR includes the cost of installing and op erating RTO’s to reheat gas after ESPs. Wet to dry conversion analysis base d on one large kiln to replace 3 small, emissions reduction is full year.



### Table 1-15 Summary of Technologies fo r Ash Grove #2 – Ozone Season Only

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Transferable 750 5.95 (5.40) 85% 427.8 0.89 (0.81) $5,800 $9.90 LoTOx TM Transferable 750 5.95 (5.40) 85% 427.8 0.89 (0.81) $3,500 $5.40 SNCR Innovative 750 5.95 (5.40) 35% 176.1 3.9 (3.54) $2,400 $1.70 Wet to Dry Available 2,205 5.68 (5.15) 65% 1,433.3 2.0 (1.81) $6,500 $11.00 Large 3 Kiln SCR Transferable 2,205 5.83 (5.29) 85% 1,257.6 0.88 (0.80) $4,600 $7.80 Emissions reductions are for ozone season unless otherwise noted. SCR includes the cost of installing and op erating RTO’s to reheat gas after ESPs. Wet to dry conversion analysis base d on one large kiln to replace 3 small, emissions reduction is full year.



### Table 1-16 Summary of Technologies fo r Ash Grove #3 – Ozone Season Only

Control Technology Control Technology Status Emissions Rate before control tpy Emissions Rate before control lbsNO x /tonne (lbsNO x /ton) Percent Control Emissions Reduction from Control tpy Controlled Emissions lbsNO x /tonne (lbsNO x /ton) Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker SCR Transferable 764 6.06 (5.50) 85% 435.7 0.91(0.83) $6,100 $10.60 LoTOx TM Transferable 764 6.06 (5.50) 85% 435.7 0.91(0.83) $3,700 $5.70 SNCR Innovative 764 6.06 (5.50) 35% 179.4 3.9 (3.54) $2,400 $1.70 Wet to Dry Available 2,205 5.68 (5.15) 65% 1,433.3 2.0 (1.81) $6,500 $11.00 Large 3 Kiln SCR Transferable 2,205 5.83 (5.29) 85% 1,257.6 0.88 (0.80) $4,600 $7.80 Emissions reductions are for ozone season unless otherwise noted. SCR includes the cost of installing and op erating RTO’s to reheat gas after ESPs. Wet to dry conversion analysis base d on one large kiln to replace 3 small, emissions reduction is full year.Cement Kiln Report (FINAL – 7/14/2006) 1-13 1.1.5. Summary of Performance and Cost Modeling Assumptions

The ERG Team used best engineering j udgment in determining modeling parameters
from the various data available. The ERG Team relied primarily on permit materials and
emissions statements submitted to the State of Texas as well as material supplied by the companies in establishing the modeling parameters used to estimate control performance, cost
and cost effectiveness. The ERG Team considered long term trends to derive estimated values for factors such as annual production capacity of clinker, which was adjusted by an assumed capacity factor that may be lower than current high operating levels. Values for airflows and temperatures were not always available for th e proposed control device locations and values were estimated based on temperatur e and moisture adjustments.

Cost effectiveness is calculated for NO x reductions only. A wet to dry kiln conversion, calciner upgrade or the addition of a scrubber will result in reduction of other pollutants. As this study is performed to assess ozone control measures, these benefits have not been included in the cost benefit analyses. A simple spray to wer that would not effectively control SO 2 is priced as part of the LoTOx TM analysis for wet kilns. If a flue gas desulfurization (FGD) scrubber were added, the price would increase. However, add itional benefits for other pollutants controlled would also occur. For example, adding FGD scr ubbers to Ash Grove wet kilns could result in approximately 1,800 tons per year of SO 2 emissions reduction per kiln and a wet kiln conversion would result in approximatel y 1,300 tons per year of SO 2 reduction per kiln. Both the oxides of nitrogen and sulfur are also pr ecursors of fine particle format ion. Control technologies that remove these precursors would provi de additional, unquantified benef its to regional air quality.

1.1.5.1. Kiln replacement or upgrading

Both kiln replacement and upgrading were considered for modeling of the wet kilns. Replacement is the only option actually modeled b ecause none of the wet kilns is large enough to be practically upgraded to a semi-wet system. Conversion of wet to semi-wet systems has been shown to result in significant production increases and NO x decreases, but fuel savings have proven to be limited. Upgrading th e preheater/calciner tower on Holcim #1 was also considered as an option. This process line is somewhat older than Ho lcim #2 or TXI #5 and the designCement Kiln Report (FINAL – 7/14/2006) 1-14 somewhat less energy efficient. The assume d performance of Holcim #1 with a modern, redesigned low-NO x preheater/calciner tower was based on the survey of the performance of recently constructed new facilitie s and the performance of TXI #5 which is using similar Ellis County limestone to make cement. Although Holcim #2 is approximately the same age as TXI #5, TXI #5 produces much less NO x per tonne of clinker produce d. The expert panel believed that a new, intrinsic low- NO x designed tower for Holcim #1 should perform substantially better
than Holcim #2 and more like TXI #5. The co st values for wet to dry conversions and for upgrading the design of Holcim #1, as well as the energy improvements, are taken primarily from Department of Energy reports. The emissions rates in tons per year of NO x used in these model runs are based on the assumption that a large new modern dry pr eheater/calciner unit would replace several older units. At Ash Grove , where all the kilns ar e highly utilized, this represents a composite of all the kilns. At TXI, where primarily kilns #1 and #4 are used, the replacement model looks at the emissions from these units pl us a small amount from kilns #2 and
#3.

1.1.5.2. SCR

The SCR cost model is a boiler cost model deve loped for use on coal-fired utility boilers. The SCR model is developed from the OAQPS Co st Manual and has been applied to other processes such as refinery FCCU s with reasonable success.

For the dry kilns, the model assumes that a location for SCR can be found where reheat of the process gas is not required. This is a hi gh dust assumption. For the wet kilns, installation
is assumed to be located after the dust collector s (low dust) and that re heat of the exhaust gas will be required. The impact of reheat of the gas on NO x emissions was examined and found to be negligible. An increase of 5 to 10 tons per year of NO x was estimated to occur based on modeled natural gas fuel use. As the gas reheater emissions could also be controlled by the SCR,
the increase would reduce to one to two tons per year and was not included in the modeling.
Based on the installation at Solnhof en (see Figure 4-1.1) of the SCR on the side of the tower, it was assumed that this configura tion could work at the preheat/cal ciner kilns in Ellis County. The wet kilns, with the SCR located after the particulat e controls were also as sumed to have adequateCement Kiln Report (FINAL – 7/14/2006) 1-15 space available. The reheat cost model is based on the OAQPS cost model for regenerative thermal oxidizers with 70% heat recovery.

Although current assumptions fo r coal-fired power plants w ould predict 90% or better control for SCR, this assumption has been lowere d to 85% for these model runs. This was done to represent a conservative approach to the cost modeling that included c onsideration of potential problems in applying SCR, such as higher variabil ity of the gas stream co mparing a utility boiler to a cement plant, and lack of experience in ac hieving high levels of control using SCR in the cement industry. Due to the lower emissions rates at TXI #5, the control efficiency was modeled
at 80%. This was based on the evaluation of th e current relatively low concentrations of NO x in the TXI stack and uncertainty about SCR perfor mance in a cement kiln at very low endpoint
concentrations. These control efficiencies are not intended to define the final performance of this technology, but to evaluate costs under cons ervative assumptions. The actual decrease in performance, if any occurs, cannot be determined in advance. In the application of SCR to coalfired boilers, higher levels of performance are typically achieved by incr easing the amount of catalyst, and, thereby increasing the contact betw een reagent and catalytic material. Achieving higher control efficiencies increases the initial capital cost and maintenance costs for the unit. The lower performance rates were selected for the purposes of the cost modeling based on the engineering judgment of the expert panel and may not reflect the final capabi lity SCR if installed
at these locations.

1.1.5.3. SNCR

The SNCR cost model is also a boiler cost m odel developed for use on coal-fired utility
boilers. The SNCR model is derived from th e OAQPS cost manual and EPA’s OTAG cost modeling. It has been simplified to obtain capita l costs primarily on flow rates. The ERG team attempted to verify the reasonabl eness of these models’ results fo r the Ellis County dry kilns. The estimates for wet kilns are conjecture. No accurate costing can be developed without an understanding of the ultimate desi gn of the control system. Limited information on installation
of SNCR on a wet kiln in France su ggests that this is a technica lly feasible option. Lacking any
detailed information on the unit in France, controls costs were estimated based on the dry kilnCement Kiln Report (FINAL – 7/14/2006) 1-16 model. Reagent costs are a substantial part of the annualized cost of SNCR, so this rough cost
estimate for wet kilns was still consid ered to be a valuable approximation. As with the SCR control efficiencies, the cost mo dels were run at conser vative control efficiency
values. A value of 50% was used for the Holcim kilns and 35% was used for TXI #5 and the wet kilns. The control efficiency of 35% at TXI wa s consistent with the reported performance of a European application at approximately 100 ppm. The value for wet kilns represented a reduced expectation for this experimental approach. The performance rates were selected for the purposes of the cost modeling based on the engineering judgment of the e xpert panel and may not reflect the final capability of SNCR if inst alled at these locations.

1.1.5.4. Oxidation Technologies

LoTOx TM

The LoTOx TM model is based on the OAQPS mode l for thermal oxidation. Specific inputs to this model were developed with assistance from the BOC Group, PLC (BOC) and should produce results reasonably close to the current costs of their oxidation technology. For the dry process kilns, no scrubbers were assumed to be required as the existing scrubbers were expected to be sufficient for removal of oxidatio n products from the process gas. For the wet kilns, BOC provided approximate costs for installing LoTOx TM with spray towers. BOC provided generalized costs; de tailed estimates on scrubber op erating costs have not been developed. No cost model runs were performed for single LoTOx TM units to control multiple
kilns as was done for SCR. The LoTOx TM cost model does not have th e same benefit of scale for larger units as does SCR. Because little or no cost benefit would be predicted from a single, large LoTOx TM unit, no cost estimates were done for combined control of multiple kilns.

The same control efficiencies were used for LoTOx TM as for SCR. Again, this was done
to make the cost estimates conservative due to la ck of application of th ese technologies to the cement industry. BOC asserted that control e fficiencies of 95% and 98% could be obtained using this technology. However, for this modeli ng effort, the same performance levels were
modeled for LoTOx TM as for SCR. As with the SCR modeling, this was not done as a reflectionCement Kiln Report (FINAL – 7/14/2006) 1-17 on the final performance capability of the technol ogy, but rather to provide an equivalent and conservative basis for evaluating the cost of control.

The accuracy of OAQPS cost modeling approaches is typically within 30% or so for instances where parameters are accurately define d and the process well known. This is a useful tool for comparing different technologies. Howe ver, closely scrutinize d vendor quotes should be the basis of any final comparison of technologie s. Minor differences in modeling results are likely to be the product of assumpti ons regarding cost of electricity or reagents. For example, for Holcim #2, the cost of SCR was predicted to be $1,700 per ton of NO x and LoTOx TM was modeled at $2,100 per ton.

A relatively small difference in the cost effectiveness for SCR and LoTOx TM should not be viewed as significant wit hout understanding the contributing factors. Reagent cost and control efficiency assumptions can account for th ese differences. Cost for ammonia reagent is currently very volatile due to re latively high natural gas costs. A value of $500 per ton was used to reflect higher costs experien ced in 2005, but not the currently hi gher short-term prices. If current high prices persist, the cost difference between these two technologies would be negligible. If LoTOx TM proves better at respondi ng to fluctuations in NO x concentrations and achieves a higher level of control than SCR, this would also tend to push co st effectiveness of the two technologies closer together . Differences of 20% in the cost effectiveness of two technologies should not be a basis for selecting one tec hnology over another. If initial modeling results produce similar economic and performa nce values, both technologies should be considered for vendor pricing unless other factor s dictate a clear preference for one over the other. Other factors, such as a determination th at reheat was needed for application of SCR to dry kilns, would have a substantial impact a nd the two technologies would no longer appear equivalent in cost effectiveness.

Other Oxidation Technologies

There are other oxidation tec hnologies using hydrogen peroxide or other chemical reagents. Most of these technol ogies are new; relatively low te mperature end-of-pipe control techniques. As mentioned under the discussion for SCR above, the cost for ammonia reagents isCement Kiln Report (FINAL – 7/14/2006) 1-18 currently higher than it has been historically. Other oxidation technologies may allow use of lower cost reagents that may im prove cost effectiveness for plan ts with existing wet scrubbers. There is one higher temperature hydrogen peroxi de technology that may be able to be implemented inside an existing precalciner syst em, although it still requir es a wet scrubber. At current hydrogen peroxide commodity prices, one of these alternative technologies may be more cost effective than ozone or ammonia based reag ent alternatives. None of these technologies was
found to have been used on a cement kiln or co mparable system. Therefore, costing of these options was not attempted. All of these system s should be considered innovative but should not be ruled out of consideration, as a lower cost reagent would have a substantial impact on annual
control costs.

1.1.6. Evaluation of Chemistry and Process Variables on NO x Formation

As part of the overall evaluation of the pot ential to control, correlate and predict NO x formation in the Ellis County K ilns, short-term process and emissions data were evaluated. These analyses were performed on data that wa s considered confidential business information and are, therefore, not summarized or reported. The statistical correla tions evaluated included comparison of NO x emissions rate to:
Kiln Feed of SiO 2 , Al2O 3 , Fe 2 O 3 , CaO, MgO,
SO 3 , Na 2 O,

K 2 O passing 200 mesh,
Clinker K 2 O, Production rate, Coal/Coke passing 200 mesh, Chain zone temp, and Kiln drive amps.
In addition, graphs were produced looking at the relationships between gaseous pollutants and
NO x emissions rate. The conclusion of this investig ation was essentially ne gative. None of theCement Kiln Report (FINAL – 7/14/2006) 1-19 process parameters and relations to formation of gaseous pollutants that were evaluated produced any relationships that indicated the potential for further control of NO x beyond the control measures already in place (with the exception of the wet kilns at TXI that are not yet permitted for mid-kiln injection while burning hazardous wa ste). Furthermore, these parameters did not indicate that changes in feed constituents had an adverse or positive correlation to NO x emissions

rate.

This investigation did not show any correla tions between feed and process materials and
NO x formation rates that would prohibit the us e of the control technologies and techniques reviewed in this report. This investigation did not show any di rect relationships between feed
materials and NO x formation rates that could potentia lly be exploited to further reduce NO x emissions rates through process modifications. However, one intere sting aspect of the investigation of the chemistry of the feed materials was a strong suspicion that nitrogen bearing feed materials present in Ellis County ma y be producing some limited non-selective noncatalytic reduction of NO x . The exact nature of the material was not identified in this study.
Similar effects have been noted in other kilns bei ng fed materials such as nitrogen bearing sands. This may help to explain the current low NO x emissions rates of TXI #5. This is discussed in Section 5.2 of this report. The chemical anal yses of the feed materi als was requested by the three plants to be treated as confidential busine ss information and the site specific information is not included in this report for that reason. Generally summaries of the overall characteristics based on averages for all three plants are presented in Sectio ns 5.1 and 5.2 of this report.

1.1.7. Summary of Environmental and Other Impacts

Sampling of the materials fed to the kilns was conducted and is summarized in Section 5 of this report along with characte rizations of the kiln feed ma terials supplied by the cement plants. This testing showed th at the materials fed to the Ellis County kilns was substantially uniform for the purposes of eval uating the impacts of feed mate rials on control equipment. Although there was variation, the va riation between different samples, wet and dry kiln feed and the different Ellis County plants was not cons idered by the experts evaluating the individual control technologies to be signi ficant enough to impact any of th e control determinations. The main concerns were levels of sulfur and orga nics in the feed materials and the resultingCement Kiln Report (FINAL – 7/14/2006) 1-20 concentration of sulfur oxides, hydrocarbons a nd, additionally, carbon mo noxide in the process gas streams emitted by the kilns and precalciners. These concerns and potential impacts are
discussed under Section 4 of this report to the extent that these issues needed to be specifically evaluated in considering applicati on of any of the control technologi es to Ellis County kilns. For example, the concentrations of sulfur dioxide in the gas streams of the Ellis County kilns are discussed in Section 4.1.1 in comparison to leve ls where selective cata lytic reduction has been applied to electric utility boilers.

The potential impacts are summarized and co mpared in Table 1-17 below for all of the major control options considered in this report. To the extent that issues such as reagent release to the atmosphere (slip) or clogg ing and/or corrosion re sulting from reagents or reactions in process and control equipment were concerns in applying control techno logies in Ellis County,
these issues are also discussed in Section 4 of this report. Table 1-17 summarizes and compares potential impacts to allow comp arisons between technologies.Cement Kiln Report (FINAL – 7/14/2006) 1-21 

### Table 1-17 Environmental and Other Impacts of Control Technology

Impact Selective Catalytic Reduction Selective NonCatalytic Reduction Oxidation Technologies Kiln Modernizations Process Chemistry Limits Application of Control Technology in Ellis County Ellis County chemistry within limits a Ellis County chemistry within limits a Ellis County chemistry within limits a Chemistry not a factor

Release of Additional Criteria Pollutants Accelerated formation of PM 2.5 b Accelerated formation of PM 2.5 b Possible decrease in VOCs, scrubbers can produce co-control of SO x and other

pollutants c Potential large decreases unless capacity increased d

Reagent Release to

the Atmosphere Possible ammonia slip < 5 ppm e Possible ammonia slip < 10 ppm e Reactive reagents unlikely to "slip" No
Clogging and/or Corrosion Potential Possible depending on location f Possible depending on location f Possible - scrubber & ducts design g No

Formation of Solid or Hazardous

Pollutants Periodic removal of ammonia salt

deposits h Periodic removal of ammonia salt

deposits h No, potentially can decrease emissions of organics. No

Formation of Wastewater Contaminants No No Probably used onsite as fertilizer i No

Explanation of notes in Table 1-17. a The constituents in feed materials and gaseous pollutant concentrations have been evaluated by the experts for each control technology and determined to be within acceptable limits for depl oying the control technology on Ellis County kilns.
b Presence of "slip" ammonia reagent is expected to form sulfate and nitrate fi ne particles closer to the stack and may cause increased opacity at the stack . However, this is not a “new” pollutant in that the precursor pollutants released by cement kilns will tend to form fine particle s in the atmosphere using atmospheric ammonia. The excess ammonia from SCR and SNCR will cause formation to occur closer to the stack. Excess opacity with the raw mill off-line may be exacerbated using SNCR. This occurs in units that do not use SNCR and wet lime injection has been suggested as a control measure.
c Oxidation technologies can also ox idize hydrocarbons, particularly the high er temperature peroxide-based control technologies. These technologies have the potential to reduce VOC emissions. Oxidation technologies also require the use of a scrubber to remove oxidized pollutants and th e scrubber can also be designed to control pollutants such as SO 2 and acid mists.
d The major “modernization” projects considered in this report were wet to dry kiln conversion and efficiency improvements for the older dry kiln at Holcim. Efficien cy improvements result in substantial energy savings and emissions reductions. However, these options require large capital investments that may only be economically justified by production increases that could negate the efficiency improvements and emissions reductions.

e In preheater/calciner units, recent German experience suggests that most of th e ammonia ends up in the raw meal during drying and grinding and is not released to the atmosphere. As discussed above under footnote “b”, this recycling of ammonia and ammonia salts may result in increased opacity when the raw mill is off-line.
f SCR is not likely to produce corrosive byproducts. The potential for clogging is discussed below as sulfate deposits.Cement Kiln Report (FINAL – 7/14/2006) 1-22 g As the cement kiln exhaust gas steam is typically moist, oxidation products can become hydrated and acidic prior to removal in the scrubber. Dependin g on the reagent and injection location selected, this may require replacement of ductwork and components with more corrosion resistant materials.

h Periodic removal of deposits of ammonia salts (ammoni um sulfate/chloride) may be required from equipment downstream of SCR and SNCR ammonia injection points. In preheater/calciner units, recent German experience suggests that most of the ammonia ends up in the raw meal during drying and grinding and is not released to the atmosphere. To the extent that ammonia salts form pr imarily in the raw mill, this limits potential downstream problems except when the raw mill is off-line.

i Scrubber waters rich in nitrates could be used on-s ite as fertilizer to promote plantings used to control wind erosion in and around quarry areas.Cement Kiln Report (FINAL – 7/14/2006) 2-1 2.0 DEFINING PARAMETERS FOR CONTROL EVALUATION

This section of the report is taken from th e EPA 2000 Report and is included, with minor editing by the ERG Team. This information is included to provide the Texas environmental communities with the comprehensive background information necessary to understand the parameters that dictate NO x control options at cement kilns.

2.1 Overview of Portland Cement Manufacturing Process and NO x Generation

Portland cement, a fine gray or white powder, is the generic term for the type of cement used in virtually all concrete, which is a mixtur e of aggregates (e.g., crushed stone, gravel, sand), water, and cement. The American Society for Testing and Materials (A STM) defines Portland cement as "hydraulic cement (cement that not only hardens by reacting with water but also forms a water-resistant product) produced by pulverizing clinkers cons isting essentially of hydraulic calcium silicates, usually containing one or more of the forms of calcium sulfate as an inter ground addition."

In 2004, the Portland cement industry in the U. S. consisted of 114 facilities in 37 States (and two facilities in Puerto Rico). Approxi mately 90 million tons of Portland cement were produced in 2004, with California, Texas, Penns ylvania, Michigan, Missouri, and Alabama accounting for approximately 50 percent of the production (1).

Hydraulic Portland cement, the primary pr oduct of the cement industry, is made from clinker blended with gypsum. Clinker is produced by heating a mixture of limestone, clay, and other ingredients to incipient fu sion at a high temperature. Li mestone is the single largest ingredient required in the cement- making process, and most cement plants are located near large limestone deposits. Portland cement is used in almost all construction applications including homes, public buildings, roads, industrial plants, dams, bridges, and many other structures.

In the cement-making process, the solid raw materials are heated to their fusion temperature, typically 1400 to 1500 EC (2550 to 2750 EF), by burning various fuels such as
coal. Portland cement has been defined as A a hydraulic cement produced by pulverizing PortlandCement Kiln Report (FINAL – 7/14/2006) 2-2 cement clinker and usually containing calcium sulfate.”(2) Portland-cement clinker has been
defined as A a clinker, partially fused by pyroprocessing, consisting predominan tly of crystalline hydraulic calcium silicates.”(2) Burning an appr opriately proportioned mixture of raw materials at a suitable temperature produces hard fused nodul es called clinker, whic h are further ground to
a desired fineness.

Five types of Portland cement are recognized in the United States which contain varying amounts of the basic clinker compounds given in Table 3-1. (3) Different types of cements are produced by starting with appropriate kiln f eed composition, blending the clinker with the
desired amount of calcium sulf ate, and grinding the product mixt ure to appropriate fineness.
Manufacture of cements of all of the various types involves the same basic high temperature fusion and clinkering proce ss responsible for the NO x emissions from cement kilns.

The five basic types of Portland cement rec ognized and produced in the United States are described below. (3,4) In a ddition, different varieties are pr epared by using various blending formulations. (5)

Type I Portland cement is a normal, general-purpose cement suitable for all uses. It is used in general construction projects such as bu ildings, bridges, floors, pavements, and other precast concrete products. Type I is also know n as regular cement and most commonly known as gray cement because of its color. White cemen t typically contains less ferric oxide and is used for special applications. There ar e other types of cements in gene ral use such as oil-well cement, quick-setting cement, and others for special appli cations. Type IA Portland cement is similar to Type I with the addition of air-entraining properties.Cement Kiln Report (FINAL – 7/14/2006) 2-3 Table 2-1. Basic Clinker Compounds (3)

Formula Name 2CaO SiO 2 Dicalcium silicate 3 CaO Si O 2 Tricalcium silicate 3CaO AL 2 0 3 Tricalcium aluminate 4CaO A1 2 0 3 Fe 2 0 3 Tetracalcium aluminoferriteMgO Magnesium oxide in free state or combined in di- or tricalcium silicate lattice.

Type II Portland cement generates less heat at a slower rate and has a moderate resistance to sulfate attack. Type II Po rtland cements are for use where moderate heat of hydration is required or for general concrete construction ex posed to moderate sulfate action. Type IIA Portland cement is identical to Type II, with the exception of inclusion of an air-entraining admixture, and produces ai r-entrained concrete.

Type III Portland cement is a high-early-strength cement and causes concrete to set and gain strength rapidly. Type III is chemically an d physically similar to Type I, except that its particles have been ground finer. It is made fr om raw materials with a lime to silica ratio higher than that of Type I cement. It contains a higher proportion of tricalcium silicate (3CaO

. SiO 2 ) than regular Portland cements. Type IIIA is an air-entraining, high-early-strength cement.

Type IV Portland cement has a low heat of hydration and develops strength at a slower rate than other cement types, making it ideal for use in dams and other massive concrete
structures where there is little ch ance for heat to escape. Type IV Portland cement contains a lower percentage of tricalcium silicate (3CaO

. SiO 2 ) and tricalcium aluminate (3CaO

. A1 2 O 3 ) than type I, thus lowering the heat evolution. Conse quently, the percentage of dicalcium silicate is increased substantially and the percentage of tetracalcium aluminoferrite (4CaO

. A1 2 O 3 . Fe 2 O 3 ) may be increased or may stay the same.

Type V Portland cement is used only in concre te structure that will be exposed to severe sulfate action, principally where concrete is expo sed to soil and groundwater with a high sulfate content. Type V Portland cements are those which, by their composition or processing, resist sulfates better than the other four types.Cement Kiln Report (FINAL – 7/14/2006) 2-4 The use of air-entraining agents increases the resistance of the hardened concrete to scaling from alternate freezing a nd thawing. By adding these materi als to the first three types of cements, IA, IIA, and IIIA varieties of cements are produced. Additional varieties of cements are produced for special applications by blendi ng different ingredients: masonry cement, expansive cement, oil-well cement, etc. Masonr y cements are commonly finely ground mixtures of Portland cement, limestone, a nd air-entraining agents. Granulated blast furnace slags and natural or artificial pozzolans are mixed and in terground with Portland cement to prepare still other varieties such as blended type s IP, IS, S, I(PM), and I(SM). (5)

2.1.1 Description of the Cement Industry

About 77.6 million metric tons of gray Port land and 274,000 metric tons of white cement were produced in a total of 198 ceme nt kilns at 118 plants in the United States in 1998. (6) This was a 6.0 percent increase from the 1990 reporte d total production of 73.5 million metric tons. As shown in Figure 3-1, cement industry annual c linker capacity steadily declined from the 1975 peak through 1990 and has steadily increased since the 1990 low. While the number of kilns has dropped sharply, average kiln size has increased . Since 1973 when average kiln size was 173,000 metric tons, average kiln size has now reached 393,000 metric tons. Although 42 cement companies produced clinker in 1998, the t op 5 companies provided about 44.2 percent of the total finish grinding capacity. This is evidence of a high con centration of the U.S. production among a limited number of top producers. Table 2-2 provides a list of a ll companies along with
their share of the total clinke r production. Table 2-3 lists the clinker producing capacity in the United States by States. The locations of the operating kilns are shown in Figure 2-2. California and Texas are the two largest states in terms of clinker capacity with Pennsylvania, Missouri, and Alabama rounding out the top five. Fourteen states and the Dist rict of Columbia had no cement clinker-producing plants in 1998. (6)

The large majority of the cemen t plants (about 82.4 pe rcent) in the United States are coal fired with about 2.8 percent using natural gas, an d 0.9 percent using oil as the primary fuel. (6) The remaining 13.9 percent of the plants used ot her combinations, e.g. coal/waste as primaryCement Kiln Report (FINAL – 7/14/2006) 2-5 fuel. In 1998, 11 plants used waste as a primar y fuel with 49 plants reporting waste as an
alternate fuel.

Overview of Cement Manufacturing Process

The process of Portland cement manufacture consists of: (7)

y Quarrying and crushing the rock;

y Grinding the carefully proportione d materials to high fineness;

y Subjecting the raw mix to pyroproc essing in a rotary kiln; and

y Grinding the resulting clinker to a fine powder.

A layout of a typical plant is shown in Fi gure 3-3, which also illustrates differences between the two primary types of cement proce sses: wet process and dry process. (7) Newer designs of dry process plants are equipped w ith innovations such as precalciners and/or suspension preheaters to increase the overall energy efficiency of the cement plant. (7) Figure 34 is an illustration of a preheater/precalc iner type of dry process system. (8)

The choice between the wet or dry process for cement manufactur ing often depends upon
the moisture content in the raw feed materials mi ned from quarries. If the moisture content of the feed materials is already very high (15 to 20 percent), a wet process may be attractive. The recent trend, however, has been toward the dry pr ocess with preheater/precalciner systems. In 1998, about 20.6 million metric tons of clinker were produced by the wet process with 57.4 million metric tons produced by a dry process. Within the dry process category, 14.2 million metric tons were produced by facilities equippe d with a preheater system and 26.1 million metric tons were produced by facilities equi pped with a precalciner system. (6)

The different steps involved in the cement manufacturing process are described in the following subsections.

Raw Materials and Kiln Feed Preparation

Calcium carbonate and the oxides of silic on, aluminum, and iron comprise the basic ingredients of cement raw mix. Because of th e large requirement for calcium, the plants areCement Kiln Report (FINAL – 7/14/2006) 2-6 generally located near the source of the calcare ous material. The requi site silica and alumina may be derived from a clay, shale, or overbur den from a limestone quarry. Such materials usually contain some of the re quired iron oxide, but many plants need to supplement the iron with mill scale, pyrite cinders, or iron ore. Silica may be supplemented by adding sand to the raw mix, whereas alumina can be furnished by ba uxites and alumina-rich flint clays. (7) Industrial byproducts are becoming more widely used as raw materials for cement, e.g., slags contain carbonate-free lime, as well as substantia l levels of silica and alumina. Fly ash from utility boilers can often be a suitable feed com ponent, since it is alre ady finely divided and provides silica and alumina.

The bulk of raw materials originates in the pl ant quarry. A primary jaw or roll crusher is frequently located within the quarry and reduces the quarried limestone or shale to about 100 mm top size. A secondary crusher, usually roll or hammer mills, typically gives a product of about 10 to 25 mm top size. Combination crusher-d ryers can utilize exit ga ses from the kiln or clinker cooler to dry wet material during crushing. Each of the ra w materials is stored separately and proportioned into the grinding mills sepa rately using weigh feeders or volumetric
measurements. Ball mills are used for both wet and dry processes to grind the material to a fineness such that only 15 to 30 wt% is retained on a 74-μm (200 mesh) sieve.

In the wet process the raw materials are ground with about 30 to 40 percent water, producing a well-homogenized mixture called slurry. Raw material for dry process plants is ground in closed-circuit ball mills with air separators, which may be adjusted for the desired fineness. Drying may be carried out in separate units, but most often is accomplished in the raw mill simultaneously with grinding. Waste heat can be utilized directly in the mill by coupling the raw mill to the kiln- and/or clinker cooler exhaust. For suspension preheater-type kilns, a roller mill utilizes the exit gas from the preheater to dry the material in suspension in the mill. A blending system provides the kiln with a homogeneous raw feed. In the wet process the mill slurry is blended in a series of continuously agitated tanks in which the composition, usually the calcium oxide content, is adjusted as required. Th ese tanks may also serve as kiln feed tanks or the slurry may be pumped to large kiln feed basins. Dry process blending is usually accomplished in a silo with compressed air. (7)Cement Kiln Report (FINAL – 7/14/2006) 2-7 Pyroprocessing

All cement clinker is produced in large rotary kiln systems. The rotary kiln is a refractory brick-lined cylindrical steel shell [3 to 8 m (10 to 25 ft) diameter, 50 to 230 m (150 to 750 ft) long] equipped with an electr ical drive to rotate the kiln on its longitudinal ax is at one to three rpm. It is a countercurrent heating device slightly inclined to the horizontal, so that material fed into the upper end tr avels slowly by gravity to be disc harged into the clinker cooler at the lower, discharge end. The burners at the firing end, i.e., the lower or discharge end, produce a current of hot gases th at heats the clinker, and the calcined and raw materials in succession, as it passes upward toward the feed e nd. Refractory bricks of magnesia or alumina combinations line the firing end. In the less heat-intensive midsecti on of the kiln, bricks of lower thermal conductivity are often used. Abrasion-resi stant bricks or monolithic castable linings are used at the feed end. (7)

Pyroprocessing may be conveniently divided in to four stages, as a function of location and temperature of the materials in the rotary kiln. (9)

1. Evaporation of uncombined water from ra w materials, as material temperature increases to 100°C (212°F);
2. Dehydration, as the material temperat ure increases from 100oC to approximately 430°C (800°F) to form dehydrated clay mi nerals composed of oxides of silicon, aluminum, and iron;
3. Calcination, during which carbon dioxide (CO 2 ) and CaO are formed from calcium carbonates, primarily between 900°C (1,650°F) and 982°C (1,800°F); and
4. Reaction, of the oxides in the burning zone of the rotary kiln, to form cement clinker at temperatures of approximately 1,510°C (2,750°F).

The duration and location of these stages in an actual kiln depend upon the type of process used, e.g., wet or dry, and the use of pr eheaters and precalciners as discussed in the following section.

It is desirable to cool the clinker rapidly as it leaves the burning zone. Heat recovery, preheating of combustion air, and fast clinker cooling are achieved by clinker coolers of theCement Kiln Report (FINAL – 7/14/2006) 2-8 reciprocating-grate, planetary, rotary, or shaft type. Most commonly used are grate coolers where the clinker is conveyed along the grate an d subjected to cooling by ambient air, which passes through the clinker bed in cross-current h eat exchange. The air is moved by a series of undergrate fans and becomes preheated to 370 to 1,000°C (700 to 1,830°F) at the hot end of cooler. A portion of the heated air serves as secondary combustion air in the kiln. Primary air is that portion of the combustion air ne eded to carry the fuel into the kiln and disperse the fuel. (7)

2.1.2 Kiln Types and Operation

There are four main types of kilns used in Portland cement manufacture:

y Long wet kilns;

y Long dry kilns;

y Dry kilns with preheaters; and

y Dry kilns with precalciners.

Wet kilns tend to be older units and are often located where the moisture content of feed materials from local sources (qua rries) tends to be high. (10)

Long Wet Kilns

In a long wet-process kiln, the slurry introduced into the feed end first undergoes simultaneous heating and drying. The refractory lining is alternately he ated by the gases when exposed and cooled by the slurry when immersed; thus, the lining serves to transfer heat as do the gases themselves. Large quantities of water must be evaporated; thus most wet kilns are equipped with chains suspended across the cross s ection of the kiln to maximize heat transfer from the gases to the slurry, or chain garlands that serve to rec uperate heat and simultaneously convey the slurry. After most of the moisture has been evaporated, the nodules, which still contain combined water, move down the kiln and are gradually heated to about 550°C (1,022°F)
where the calcination reactions commence. The calcined material furt her undergoes clinkering reactions. As the charge leaves the burning zone and begins to cool, clin ker minerals crystallize from the melt, and the liquid phase solidifies. The granular clinker ma terial drops into the
clinker cooler for furthe r cooling by air. (7)Cement Kiln Report (FINAL – 7/14/2006) 2-9 Wet kilns typically represent an older cemen t technology with smalle r capacity kilns. In the United States wet cement kiln capacities range from 77,000 to 1,179,000 metric tons/year with an average of 307,000 metric tons/year. (6)

Dry Process Kilns

The dry process utilizes a dry kiln feed rather than a slurr y. Early dry process kilns were short, and the substantial quant ities of waste heat in the exit gases from such kilns were frequently used in boilers to generate electric po wer, which often satisfied all electrical needs of the plant. In one modification, the kiln has been lengthened to nearly th e length of wet-process
kilns and chains were added. The chains serve almost exclusively a heat exchange function. Refractory heat-recuperative devices, such as cros ses, lifters, and trefoils, have also been installed. So equipped, the long dr y kiln is capable of better ener gy efficiency than wet kilns. Other than the need for evaporation of water, its operation is similar to that of a wet kiln. To improve the energy efficiency of the dry process, variations such as su spension preheaters and precalciners have been introduced as discussed in the next sections. (7)

Long dry process kilns are generally of a sma ller capacity compared to long wet kilns. In the United States dry cement kiln capacities range from 50,000 to 590,000 metric tons/year with an average capacity of 265,000 metric tons/year. (6)

Dry Kilns With Preheaters

In dry kilns with suspension preheaters, th e pulverized feed passe s by gravity through a series of cyclones and riser ducts in a vertical arrangement, wher e it is separated and preheated several times, typically in a four-stage cyclone system. The partially (40 to 50 percent) calcined feed exits the preheater tower into the kiln at about 800 to 900°C (1,500 to 1,650°F). The kiln length required for completion of the cement forma tion is considerably s horter than that of conventional kilns, and heat exch ange is very good. Suspension preheater kilns are very energy efficient compared to wet or long dry kilns. Th e intimate mixing of the hot gases and feed in the preheater riser ducts promotes condensation of alkalies and sulf ur on the feed, which sometimes results in objectionable high alkali and sulfur contents in the clinker, or occasions buildups in theCement Kiln Report (FINAL – 7/14/2006) 2-10 preheater tower. To alleviate this problem, some of the kiln exit gases can bypass the preheater through a slipstream, or fewer cyclon e stages can be used in the pr eheater with some sacrifice of efficiency.

Suspension preheater kilns represent a newe r cement technology comp ared to the long dry kilns. They are also somewhat larger in production capacity th an the conventional long rotary kilns. In the United States the preheater type kiln capacities range from 223,000 to 1,237,000 metric tons/year with an average capacity of 406,000 me tric tons/year.

Dry Kilns With Precalciners

The success of preheater kiln systems, led to precalciner kiln systems. These units utilize a second burner to carry out calcina tion in a separate vessel att ached to the preheater. The calciner utilizes preheated combustion air drawn from the clinker cooler or kiln exit gases and is equipped with a burner that typically burns about 60 percent of the total k iln fuel. Most often coal is used as a fuel in a calciner furnace; however, almost any fuel may be used including chipped tires. The raw material is calcined almost 95 percent, and the gases continue their upward movement through successive cyclone/riser duct preheater stages in the same manner as in an ordinary preheater. Th e precalciner system permits the use of smaller dimension kilns, since only actual clinkering is carried out in th e rotary kiln. Energy efficiency is often even better than that of a preheater k iln, and the energy penalty for bypass of kiln exit gases is reduced since only about 40 percent of the fuel is being burned in the kiln. Th e burning process and the clinker cooling operations for the modern dry-pro cess kilns are the same as for long wet kilns.

The precalciner technology is the most modern cement manufacturing technology and almost all of the newer cement plants are based on these designs. Precalciner kilns are also much larger in capacity than the conve ntional rotary kilns. The pre calciner type kilns in the United States range from 449,000 to 1,580,000 metric tons/year with an average of 869,000 metric tons/year. Because of the new large precalciner plants replacing older and smaller plants, the overall average kiln capacity has been steadily in creasing in the United States. It has increased from an average of 239,000 metric tons/year in 1980 to an average ca pacity of 393,000 metric tons/year in 1989.Cement Kiln Report (FINAL – 7/14/2006) 2-11 Finish Grinding

The cooled clinker is conveyed to clinker storage. It is subsequently mixed with 4 to 6 percent gypsum and introduced directly into the fi nish mills. These are large, steel cylinders [2 to 5 m (7 to 16 ft) in diameter] containing a char ge of steel balls, which rotate at about 15 to 20 rpm. Rarely, the desired size reduction may be acco mplished in a roller mill, rather than in ball mills. Recently, the industry has also adopted the use of roller presses to precrush the clinker to smaller size prior to introduction to the finish mills . The roller press is more efficient than the crushing stage of the ball mill, and production cap acities of finish grinding systems have been substantially increased a nd electrical energy requirements re duced by the incorporation of roller presses into finish circuits. The clinke r and gypsum are ultimately ground to a fine, homogeneous powder. About 85 to 96 percent of the product is in particles less than 44 μm in diameter. This grinding may be accomplished by two different mill systems. In open-circuit milling, the material passes directly through the mill without any separation. A wide particle size distribution range is usually ob tained with substantia l amounts of very fine and rather coarse particles. Open circuit grinding is, however, rare ly practiced in U.S. cem ent plants. In closedcircuit grinding, the mill product is carried to a cyclonic air separator in which the coarse particles are rejected from th e product and returned to the mill for further grinding. (7)

Quality Control

Beginning at the quarry operation, quality of the end product is maintained by adjustments of composition, burni ng conditions, and finish grindi ng. Control checks are made for fineness of materials, chemical compositi on, and uniformity. Clinker burning is often monitored by the liter weight te st (which involves weighing a por tion of sized clinker), a free lime test, or may be checked by microscopic evalua tion of the crystalline structure of the clinker compounds. Samples may be analyzed by wet ch emistry, X-ray fluorescence, atomic absorption, or flame photometry. Standard cement samples are available from the National Institute of Standards and Technology. Fineness of the cement is most commonly measured by the air permeability method. Finally, standardized perf ormance tests are conducted on the finished cement. (7)Cement Kiln Report (FINAL – 7/14/2006) 2-12 2.1.3 Thermal Characteristics

Figure 2-1 provides a detailed look at the mate rial and gas temperatures inside cement kilns. The concepts of high-grade heat and lo w-grade heat are well disc ussed by Weber. (11) Weber states, “The boundary between the main a nd the subsidiary thermal system is assumed always to correspond to a material temperature of 550°C, since deca rbonation in the rotary kiln in general already begins at this temperature. A certain amount of h eat whose temperature is below the gas temperature at the commencement of decarbonation will always be left over from the calcining zone. This heat is ‘lower-grade’ in the sense that, because of the low temperature,
it cannot be further used for decarbonation or sintering, but only for preheating and drying.”

In turn, Figure 2-2 provides a graphical l ook at the relationship between temperatures in the cement manufacturing process and the chemistr y of cement clinker formation. Except for the process of drying the raw material slurry in wet kilns these prof iles are essentially the same for both wet and dry process cement kilns. The only substantive difference is that the difference between the gas and material temperature in a preh eater tower is less than in the back end of a
wet kiln because of the more effici ent heat transfer in the cyclones.Cement Kiln Report (FINAL – 7/14/2006) 2-13 Figure 2-1. Temperature of the Gas and Ma terial in the Rotary Cement Kiln 1

Figure 2-2. The Relationship Between Proce ss Temperatures and the Chemistry of Cement Clinker FormationCement Kiln Report (FINAL – 7/14/2006) 2-14 2.1.4 Process Variables

The formation of clinker of suitable quality for manufacture of Portland cement depends
on the characteristics of feed materials and the temperature profile of the pyroprocessing step. The most critical process variables are:

y Feed composition;

y Feed particle size;

y Feed moisture concentration;

y Feed mass flow rate;

y System heat losses; and

y Ambient air infiltration.

More than 30 raw materials (primarily calcium carbonate, aluminosilicates, silica and iron oxide)
are known to be used in Portland cement manu facturing. (12) These materials are ground and
mixed to create a feed that ha s the appropriate chemical and physical properties to produce clinker with the desired properties. Uniform f eed composition and size ensure consistent quality and characteristics of the clinker produced.

Higher moisture contents require more heat input to maintain proper temperature profile
in the kiln. Cement raw materials are received w ith an initial moisture content varying from one to more than 50 percent. In dr y kilns, the moisture content is usually reduced to less than one percent before or during the gr inding process (e.g., using drum dryers, air separators, or supplying supplemental heat to the raw mill). In the wet process, water is added to the raw mill during the grinding of the raw mate rials, thereby producing a slurry of approximately 65 percent solids. (12)Cement Kiln Report (FINAL – 7/14/2006) 3-1 3.0 NO X FORMATION IN CEMENT KILNS

This section of the report is taken from the EPA 2000 Report and is included, with minor editing by the ERG Team. This information is included to provide the Texas environmental communities with the comprehensive background information necessary to understand the parameters that dictate NO x control options at cement kilns.

3.1 Overview of NO x Formation Mechanisms

In cement manufacturing, conditions favorab le for formation of nitrogen oxides (NO x ) are reached routinely because of the high process temperatures involved. Essentially, all of the
NO x emissions associated with cement manufactur ing are generated in the cement kilns. Although, there are other heating operations in a cement plant, such as drying of raw feed or coal, often the heat from the kiln exhaust ga ses is used for these operations making their
contribution to NO x emissions negligible. In cement kilns, NO x emissions are formed during fuel combustion by two primary mechanisms:

y Oxidation of the molecular nitrogen presen t in the combustion air which is termed thermal NO x formation; and

y Oxidation of the nitrogen compounds presen t in the fuel, whic h is termed fuel NO x formation.

Sometimes the raw material feed to the kiln may also contain nitrogen compounds, which may
lead to feed NO x formation similar to fuel NO x formation. Because of the high temperatures involved in the burning or clinke r formation step, the thermal NO x formation provides the
dominant mechanism for NO x formation in cement manufacturing. The term NO x includes both
NO and NO 2 species, although NO 2 normally accounts for less than 10 percent of the NO x emissions from a cement kiln exhaust stack. (13) The concentration and emission of NO x are, however, typically expressed in equivalent NO 2 form.Cement Kiln Report (FINAL – 7/14/2006) 3-2 3.1.1 Thermal NO x Formation

Thermal NO x is formed by the homogeneous reaction of oxygen and nitrogen in the gas phase at high temperatures. In the overall re action mechanism proposed by Zeldovich, (14) the two important steps in NO x formation are given as:

N2 + O x NO x + N kf = 2 x 10 14 exp(-76500/RT)

N + O 2 x NO x + O kf = 6.3 x 10 9 exp(-6300/RT)

where kf are the rate constants for the reacti ons shown. The high activat ion energy of reaction (4-1), 76.5 kcal/mol, means that this reaction is the most temperature sensitive. An equilibrium
reaction of NO x with O 2 further results in NO 2 formation.

The equilibrium concentrations of NO x and NO 2 formed thus depend strongly upon the gas-phase temperature as well as the concentration of O 2 and N 2 in the gas phase. Table 3-1 shows the equilibrium concentrations of NO and NO 2 for two conditions. (15) First, the equilibrium concentrations of NO x and NO 2 for N 2 and O 2 concentrations found in ambient air are shown. Secondly, Tabl e 3-1 also shows the NO x and NO 2 concentrations at flue gas
conditions where the O 2 and N 2 concentrations are defined fo r this table as 3.3 percent O 2 and 76 percent N 2 . The equilibrium NO x concentrations for the flue ga s conditions are lower than those
for ambient conditions due to the lower O 2 concentration. The excess air used during fuel combustion can substantially affect NO x formation by determining the amount of oxygen
available for NO x reaction. The cement kiln burning zone s usually have about 5 to 10 percent excess air while higher excess air levels are not uncommon. Figure 3-1 shows the theoretical equilibrium concentrations of NO in the fl ue gas for different excess air levels. (13) As can be seen from this figure, over 1000 ppm of NO may possibly be form ed at the typical kiln solids temperatures of 1430 to 1480°C (2600 to 2700°F) as the corresponding gas- phase temperatures are on the order of 1650°C (3000°F).Cement Kiln Report (FINAL – 7/14/2006) 3-3 Table 3-1. Calculated Equilibrium Concentrations (In PPM) Of NO x and NO x In Air and Flue Gas (15)

Temperature Air Flue Gas K °F NO NO 2 NO NO 2 300 80 3.4 (10) -10 2.1 (10) -4 1.1 (10) -10 3.3(10) -3
800 980 2.3 0.7 0.8 0.1 1440 2060 800 5.6 250 0.9

Fuel combustion in the kiln burning z one is the primary source of thermal NO x , formation in cement kilns due to temperatures well above 1,40 0°C (2,550°F). In contrast , the fuel combustion temperature in a precalciner or in a kiln riser duct is well below 1,200°C (2,200°F), suppressing
thermal NO x formation. (16) Mainly fuel and feed NO x may be formed in the secondary firing zone of preheater and precalciner kiln systems. Along with the combustion temperature, the gasphase residence time and the available oxygen con centration in the high temperature kiln burning zone are important parameters. Longer residence times at the high temperatures will allow the NO to be formed in the equilibrium quantities. Greater amounts of oxygen in the combustion zone will of course lead to greater amounts of NO formation. Once formed, the decomposition of NO at lower temperatures, although thermodyna mically favorable, is kinetically limited. Thus, strategies to reduce NO x emissions need to be based upon reducing formation of NO x, which may be achieved by reducing combustion temperature, oxygen concentration in the high temperature combustion zone, and the gas residence time at high temperatures.

3.1.2 Fuel NO x Formation

Fuel NO x is formed by the conversion of nitroge n present in the fuel used. A recent survey of the cement industry by Portland Cement Association (PCA) indicates that almost 82 percent of the energy requiremen t of the cement industry is provided by coal. (17) Natural gas contributed about 3 percent of the energy demand, o il about one percent, a nd other fuels such as waste solvents provided about 14 percent of the energy. Both oil and natural gas have relatively low fuel bound nitrogen content, whereas coal ma y contain one to three percent of nitrogen by weight depending upon the source of coal. Waste-de rived fuels (WDF) such as scrap tires, used motor oils, surplus printing inks, dry-cleaning solv ents, paint thinners, slu dge from the petroleum industry, agricultural wastes su ch as almond shells, and even municipal biosolids (dewateredCement Kiln Report (FINAL – 7/14/2006) 3-4 sewage sludge) are finding an in creasing application in the ceme nt kilns. (18) The nitrogen content in these fuels may be significant depe nding on the chemicals in cluded in the waste mix being burned.

Figure 3-1. Theoretical Equilibrium Concentrations of NO x

The maximum possible fuel NO x formation may be estimate d from the fuel nitrogen content by assuming 100 percent nitrogen conversi on. The typical heat requirement for a wet process is estimated to be about 6 million Bt u for a ton of clinker and the corresponding requirement for a dry process is estimated to be about 4.5 million Btu for a ton of clinker. Assuming an average heat requirement of 5.3 million Btu for a ton of clinker, and a coal heating value of 12,000 Btu/lb, about 442 lb. of coal will be required per t on of clinker produced. With a nitrogen content of one percent by weight, appr oximately 9.5 lb. of NO (14.5 lb. expressed as
NO 2 ) would be produced per ton of clinker with 100 percent nitrogen c onversion. Thus, even with only 10 percent conver sion of coal nitrogen to NO x , 1.5 lb. of fuel NO x (expressed as NO 2 ) may be formed per ton of clinker when coal is used as a primary fuel.

The amount of fuel NO x formed is difficult to identify separately from thermal NO x as measurements indicate the overall NO x formed. In general, however, thermal NO x is assumed to be the dominant mechanism in cement kilns. (1 9) Typically, gas burners produce more intense and hot flames compared to the less intense "l azy" flames produced by coal burners. Thus, gasfired kilns may be expected to produce greater thermal NO x as compared to coal-fired kilns.Cement Kiln Report (FINAL – 7/14/2006) 3-5 Coal, on the other hand, contains much greater amounts of fuel-bound nitrogen than natural gas, which has almost no fuel-bound nitrogen. The coal -fired kilns may thus be expected to produce
more fuel NO x than gas-fired kilns. A study of gas- and coal-fired kilns, however, clearly indicated that gas-fired, dry- process kilns typically produce almost three times more NO x than the coal-fired, dry-process kilns. (19) This fact indicates the dominance of thermal NO in overall
NO formation.

3.1.3 Feed NO x Formation

Similar to coal, the raw materials used in cement production may contain a significant amount of nitrogen. In most cases, limestone is the major raw material, with the remainder of the raw mix being composed of clays, shales, sa ndstones, sands, and iron ores. Fly ash from coal-fired power plants is us ed as a raw material and may contain substantial amounts of nitrogen compounds, since it is usually derived from coal. Most of these raw material components are sedimentary minerals and they may contain small amounts of chemically bound nitrogen, presumably of organic origin. Vari ous kiln feeds contain appreciable amounts of nitrogen, ranging from about 20 ppm up to as mu ch as 1,000 ppm (as N). (20) The higher values (>100 ppm) are generally associated with minera ls displaying noticeable kerogen contents. Since 100 ppm N in a kiln feed is equivalent to about one lb. NO x per ton of clinker (if it all converted), NO x emissions from the kiln feed may represent a major source of NO x from cement kilns. Nevertheless, it is probabl y less important than thermal NO x and fuel NO x in most cases.

The same study indicated that c onversion of feed nitrogen to NO x occurs mainly in the 300 to 800°C (570 to 1,470°F) temperature range a nd depends upon the feed heating rate. (20) Rapid heating rates (~1,000°C flash heating) of the kiln feed mixt ures were found to give much lower conversion efficiencies, whereas slow heat ing rates of kiln feed mixtures (~60°C/min) gave fairly high conversion of a bout 50 percent of bound nitrogen to NO x . These results were explained by assuming that the organic nitroge n must vaporize from the sample prior to oxidation if high conversi on efficiencies to NO x are to be achieved. If heating rates are rapid, "cracking" of these volatile compounds may occur in situ, and this may result in conversion of the bound nitrogen directly to N 2 before it comes into contact with gaseous oxygen, thus reducing the fraction converted to NO x . Such a hypothesis is also c onsistent with the observationCement Kiln Report (FINAL – 7/14/2006) 3-6 that, during coal combustion, the involatile or "char" nitrogen is converted to NO x much less efficiently than the volatile nitrogen. (21)

3.1.4 Factors Affecting NO x Emissions in Ceme nt Manufacturing

There are four primary types of cement kilns used in the industry: wet kilns, long dry kilns, kilns with a preheater, a nd kilns with a preheater/precalciner. The wet and long dry kilns and some preheater kilns will have only one fu el combustion zone, whereas the newer preheater and precalciner kiln designs have two or three fuel combustion zones: kiln burning zone, riser duct and precalciner. Because the typical temperatures present in the combustion zones are different, the factors affecting NO x formation are also somewhat di fferent in different kiln types and are discussed in the following sec tions. In addition to the specific NO x formation mechanisms, the energy efficiency of the cem ent-making process is also important as it determines the amount of heat input needed to produce a unit quantity of cement. A high thermal efficiency would lead to less consump tion of heat and fuel, and would generally produce
lower NO x emissions.

NO x Formation in the Kiln Burning Zone

In the kiln burning zone, thermal NO x provides the primary mechanism for NO x formation. Thermal NO x formation depends upon the combustion zone temperature, the gasphase residence time and the oxygen concentrat ion in the high temperature combustion zone. The flame temperature strongly depends upon the type of fuel burned. The temperature and intensity are generally greater fo r gas burners than coal burners. The oxygen concentration in the combustion zone depends upon the overall excess air used and on the source and proportion of primary and secondary combustion air. Le ss primary air may produce an initial hightemperature, fuel-rich combustion zone follo wed by a low-temperature fuel-lean combustion zone. Such a combination is likely to reduce NO x formation.

The firing system used in the kiln aff ects the proportion of primary and secondary combustion air. Direct firing systems introduce a large proportion of combustion air with the fuel being burned. This produces two conflicting effects for NO x emissions: higher oxygenCement Kiln Report (FINAL – 7/14/2006) 3-7 concentration or fuel lean combustion and lower gas temperature. Indirect firing systems on the other hand use only a small portion of combustion ai r to convey fuel and thus use less primary air. In general, direct fired system s may be expected to produce greater NO x emissions compared to indirect fired systems. The flam e shape and the theoretical flame temperature are important factors in thermal NO x formation as these factors determine the hottest points in the flame. A long "lazy" flame will produ ce less NO than a short intense flame.

The flame shape depends on the fuel being bur ned as well as the proportion of air. For the same amount of primary air, gas burning ma y be expected to produ ce a shorter and more intense flame than coal burning. The lower th e secondary air temperat ure and the greater the
dust content in the second ary air, the lower the NO x formation in the kiln burning zone. A large amount of water in the primary air (from a direct firing coal mill) and injection of cement kiln dust (CKD) in the burning zone (i nsufflation) may also reduce NO x formation. With increasing excess air percentage, the NO x formation in the kiln will increase, but only up to a certain point as an increasing excess air rate will reduce the secondary air temperatur e and, consequently, the flame temperature.

Process conditions that can affect NO x emissions substantially are: temperature stability, stability of raw mix feed rate, bu rnability of raw mix, and alkali a nd sulfur control. Temperature stability is important to maintain the quality of clinker and is achieved by stable-flame conditions and energy efficiency. Clinker formation r eactions require temperatures of 2,650 to 2,800°F (1,450 to 1,540°C) and an oxidizing environment. Sometimes natural gas or liquid waste derived
fuel is used to control flame conditions and im prove clinker quality. The excess air used during
combustion has a substantial influence on NO x emissions. Oxygen levels of 4 to 5 percent in kiln exhaust gases would correspond to high NO x emissions, whereas oxygen levels of only 0.5 to 1.5 percent would mean lower NO x emissions. Thus, NO x emissions in a kiln may depend upon the care exercised by the operator in mini mizing excess oxygen needed to maintain the quality of the clinker produced. All but one of the clinker formation reactions are exothermic and represent a dynamic process that requires cons tant operator adjustments which can vary NO x formation.Cement Kiln Report (FINAL – 7/14/2006) 3-8 The heating value of the fu el burned may also affect NO x emissions. High heating value fuels, such as petroleum coke may re quire less combustion air and produce less NO x per ton of
clinker.

Different raw material compos itions require different burnin g conditions to maintain the quality of clinker produced. Thus, similar type s of kilns with differe nt feed materials may produce different levels of NO x emissions. The alkali content of finished cement needs to be below a certain acceptable level. Low alkali requ irements may require higher kiln temperatures and longer residence times at hi gh temperatures to volatilize th e alkali present in the molten
clinker. Raw materials with greater alkali content may need to be burned longer at higher temperatures to meet alkali require ments and thus may produce greater NO x emissions.
Increased volatilization of alkali results in increa sed alkali emissions in kiln exhaust gases. To control alkali emissions, a part of the kiln exhaust gases may be bypassed around a downstream unit, e.g., a precalciner. The bypassed gases ar e quenched to remove alkali and sent through a particulate matter collector. This alkali-rich particulate matter is removed from the process and disposed. The bypass of kiln exhaust gases ty pically involves a fuel penalty, e.g., about 20,000 Btu/tonne clinker for every one percent gas bypass. The additional heat requirement will
contribute to increased NO x emissions.

Wet kilns require about 33 pe rcent more thermal energy than a dry kiln. This means a greater volume of exhaust gas from a wet kiln for the same production. On the other hand, the greater amount of combustion air will also mean a somewhat lower secondary air temperature. Based on these contradicting fact ors, one might expect the NO x emissions from a wet process kiln to be similar to the dry and pr eheater kilns without riser duct firing.

NO x Formation in Secondary Firing

In the secondary firing region of precalcini ng kilns, where temperatures range from 820 to 1100°C (1500 to 2000°F), the following reactions may take place:

"N" + O → NO (4-3) "N" + NO → N2 + O (4-4)Cement Kiln Report (FINAL – 7/14/2006) 3-9 where "N" means nitrogen origina ting from nitrogen compounds in the fuel. (13) Reaction (4-3) shows that NO formation in the secondary firi ng zone will depend upon the nitrogen content in the fuel and the oxygen level in the firing zone. R eaction (4-4) indicates that , if there is already NO present in the gas introduced into the sec ondary firing zone, a re duction of this NO may occur with the fuel nitrogen compounds acti ng as reducing agents. Accordingly, the net formation of NO in the secondary firing zone wi ll also depend upon the initial NO concentration in the combustion gas. Finally, measurements have shown that the volatile content in the solid fuel and the temperature in the secondary firing zone also influence the NO formation in the secondary firing zone. (22) With increased volatile content in the fuel, the ratio of fuel nitrogen conversion into NO seems to decrease and, as the reaction rate of reactio n (4-4) increases more rapidly with the temperature than that of reaction (4-3), an in crease in the temperature of the secondary firing region may reduce-the net NO formation. (13)

3.1.5 Suspension Preheater (SP) Kilns with Riser Duct Firing.

In many SP kiln systems 10 to 20 percent of th e fuel is fired into the riser duct. The preheater systems are more energy efficient compar ed to long dry kilns. The increased energy efficiency and the reduction in the amount of fuel burned at the higher clinker burning temperature may be expected to reduce the NO x emissions from preheater kilns when compared with the long dry and wet kilns. Measurements at several riser-duct fire d kiln systems indicate that firing coarse fuel (e.g., tires) in to the kiln riser duct will reduce NO x emissions from the kiln systems. (23) This may be explained by the fact that a large part of the fuel falls directly down into the kiln charge, crea ting a reducing atmosphere in the kiln back-end where NO x from the burning zone is reduced.

Conversely, when firing finely ground fu el into the kiln riser duct, the NO x content in the exhaust gas may increase on passing through the riser duct. As the NO x emissions from the kiln may also increase slightly due to an increased excess air rate, the total NO x emissions from the kiln system may increase when starting up rise r duct firing with finely ground fuel. (13)Cement Kiln Report (FINAL – 7/14/2006) 3-10 3.1.6 Precalcining Kiln Systems.

In precalcining kiln systems with a tertiary air duct, firing into the rotary kiln typically accounts for only 40 to 50 percent of the total heat consumption and the specific amount of combustion gases from the kiln burning zone is reduced proportionally. Precalciner kilns also typically require the least amount of energy pe r unit amount of clinker produced. The lower energy requirement and the substantial reduction in the proportion of the fuel burned at clinker burning temperatures may be expected to reduce the NO x emissions from the precalciner kilns as compared to the preheater kilns. On the other hand, the NO x concentration (in ppm) in the kiln gas may be considerably higher th an in preheater kilns. This is probably due to the shorter material and longer gas retention times in the precalciner kiln burning zone combined with a very high secondary air temperature. (13)

When examining the contribution from the calciner firing to the emission of NO x , two basically different types of precalcining kiln systems need to be considered:

y The in-line (ILC) type in which the kiln gas passes through the firing region of the precalciner; and

y The separate line (SLC) type in which the kiln exha ust gas bypasses the firing region of the precalciner.

ILC systems: In these systems, the fuel combustion in the calciner takes place in a mixture of the kiln exhaust gas and hot air from the cooler (tertiary air). So me of the nitrogen in
the fuel reacts with NO from the kiln exhaust gas while another part reacts with oxygen to form NO. The result may be a net increase or a net reduction of NO in the calciner.

SLC systems: In these systems, the fuel combustion in the calciner take s place in pure hot
air. In the case of oil firi ng, NO production in the calciner is ne gligible; but when using fuels containing fuel-bound nitrogen, up to 50 percent of the nitrogen co mpounds in the fuel may be
converted into NO x . The specific NO x , production in an SLC calcine r may be as high as 4 lb.
NO x per ton of clinker as measured in a calcine r fired with petroleum coke which has a high nitrogen content and low volat ile content. (13) The NO x in the calciner exha ust gas is added to
the NO x in the gas from the rotary kiln which leav es this type of kiln system without beingCement Kiln Report (FINAL – 7/14/2006) 3-11 reduced. When fired with solid fuels, SLC syst ems may therefore be expected to generate somewhat higher NO x emissions than the ILC systems. (13) We should note, however, that some of the oxygen for combustion of the fuel in ILC systems passes through the burning zone, so the NO generated there may be higher (or lo wer due to lower temperatures) than for SLC systems.

3.1.7 Energy Efficiency of th e Cement-Making Process

Since NO x formation is directly related to fuel combustion, any reduction in the amount of fuel burned per unit amount of clinker produced should reduce NO x emissions per unit clinker. Attempts to improve energy efficiency of the process by avoiding excessive clinker burning and utilizing waste heat effectively for preheating co mbustion air, coal, and raw mix is likely to
reduce NO x emissions. Improving heat transfer betw een hot gases and solid materials, e.g., by chain systems, will improve energy efficiency. Th e newer preheater and precalciner kiln designs provide very efficient preheati ng and precalcining of the raw mix with intimate gas-solids contact in cyclone towers. New cement kiln installations or renovations of older kilns thus predominantly involve precalciner designs for th eir energy efficiency. The inherent energy efficiency of these kiln designs is likely to produce lower NO x emissions per unit amount of clinker as compared to the wet or long dry kilns.Cement Kiln Report (FINAL – 7/14/2006) 4-1 4.0 OVERVIEW OF POTENTIALLY APPLICABLE CONTROL TECHNIQUES AND TECHNOLOGIES

Nitrogen oxides are formed by the oxidat ion of nitrogen during the fuel combustion process. The formation of thermal NO x is a function of the flame temperature, flame turbulence, the amount of nitrogen and oxygen available fo r the thermal reaction, and the gas phase residence time at high temperature. To reduce the amount of thermal NO x formed, one or more
of these variables needs to be minimize d. The formation of fuel and feed NO x is not as well
understood as the thermal NO x formation. In general, however, the greater the concentration of nitrogen in the fuel and feed, the greater the fuel NO x emissions. Therefore, reducing the amount of fuel and feed-bound nitrogen should reduc e the contribution of the fuel and feed NO x .

The typical NO x emissions from a cement plant depend upon the type of the cement kiln as shown in Table 4-1. For any give n type of kiln, the amount of NO x formed is directly related to the amount of energy consumed in the cement- making process. Thus, measures that improve the energy efficiency of th is process should reduce NO x emissions in terms of lb. of NO x /tonne clinker. With the rising costs of energy a nd the very competitive cement market, greater attention is being paid to in creasing overall energy efficienc y, such as through reduction of overburning of clinker and improvement in ga s-solids heat transfer. Continuous emissions monitoring of CO, NO x , and O 2 provide an indication of kiln c onditions and also provide inputs for process control. Newer cement kiln designs are generally based on preheater/precalciner systems which provide very efficient gas-solids contact and greater energy efficiency. NO x control approaches are evaluate d below under four categories:

y High Temperature Emissions Controls;

y Combustion Optimization;

y Low Temperature Oxidation Emissions Controls; and

y Process Modifications.

This section of the report uses the EPA 2000 Report as the baseline for evaluating current control options for Ellis County kilns. The co mbustion and process optimization sections are included, with editing, from this report and desc ribe the essential controls that have been considered and largely instal led under the requirements of 30 TAC Chapter 117. Additions to sections for process modifications to improve energy efficiency through calciner modificationsCement Kiln Report (FINAL – 7/14/2006) 4-2 and wet to dry conversions is discussed as site-s pecific options where applicable for Ellis County
kilns. The section on oxidation controls is en tirely new and was not considered in EPA 2000.
The sections on SCR and SNCR consider EPA 2000 background information, but are written to
reflect current status of these te chnologies and site-specific applica tion to the Ellis County kilns. For the purposes of this report, available essentially means that the technology is commercially available and in use on similar types of cement kilns. Transferable means that the technology is commercially available and in use on similar process equipment and could reasonably be expected to work on the speci fied type of cement kiln. Innovative describes technologies that have not been successfully applied to a type of cement kiln, but in the judgment of the ERG Team could be expected to work on the type of cement kiln if co rrectly optimized through experimental application.

When discussing the transfer of technol ogies, comparisons are made between cement kilns, coal-fired utility boilers and refinery fluidized catalytic cracking units (FCCUs). While the emissions from these units vary widely, they are all capable of emitting thousands of tons of NO x and SO 2 and typically use electrostatic precipitators (ESPs) to contro l particulate emissions that
would also be thousands of tons per year prior to control. For the purposes of this discussion, a modern cement kiln producing one million tons pe r year of clinker woul d be roughly comparable to a coal-fired utility boiler of approximately 200 megawatts ge nerating capacity and an FCCU of approximately 80,000 barrels pe r day. All of these units woul d have a typical air flow of approximately 300,000 cubic feet per minute. For comparison with the Ellis County kilns, a typical refinery of comparable air fl ow rate would tend to produce less NO x and a utility boiler would typically produce more NO x . The amount of SO 2 from these units w ould vary widely due to site specific operating condi tions including fuels and feeds ma terials. The impact of SO 2 and particulate matter concentrations on the opera tion of SCR is discussed in depth below under Section 4.1.2. Other constituent pollutants in the ga s stream are not consider ed to interfere with

LoTox TM operation. Both SCR and LoTox TM have been demonstrated in units of comparable air flow to the Ellis County kilns.Cement Kiln Report (FINAL – 7/14/2006) 4-3 4.1 High Temperature Emissions Controls

4.1.1 Selective Catalytic Reduction (SCR)

SCR is a process that uses ammonia in the presence of a catalyst to selectively reduce
NO x emissions from exhaust gases. Th is technology is widely used for NO x abatement in other industries, such as coal-fired power stations a nd waste incinerators. The SCR process has been used extensively throughout the world to achieve a 90 percent reduction in NO x emissions from
fossil fuel fired boilers. In the United States SCR technology has successfully been used for gas turbines, internal combustion en gines, and utility boilers.

In SCR, anhydrous ammonia, usually diluted with air or steam, or urea, is injected through a grid system into hot flue gases that ar e then passed through a catalyst bed to carry out
NO x reduction reactions. The tw o principal reactions are:

4 NH 3 + 4 NO + O 2 --- 4 N 2 + 6 H 2 O and
4 NH 3 + 2 NO 2 + O 2 --- 3 N 2 + 6 H 2 O

The first reaction represents the predomin ant reaction since 90 to 95 percent of NO x emissions in the flue gas are in the form of NO . A number of material s have been used for catalysts. Titanium dioxide (TiO 2 ) and vanadium pentoxide (V 2 O 5 ) mixtures are most commonly used as catalysts due to their resistance to SO x poisoning. Zeolite-based catalyst materials have also been developed capable of operating at higher temperatures than conventional metal-based catalysts. The catalys t is typically supported on ceramic materials, e.g., alumina in a honeycomb monolithic form. The active ingredients of the base metal (titaniavanadia) and zeolite catalysts of ten make up the bulk of the subs trate material. The catalyst shape and reactor design vary depending upon the manufacturer.

The optimum temperature for the catalytic reactions depends upon th e specific catalyst used and is usually in the range between 300 to 450oC (570 to 840oF) . Without pre-heater and/or pre-calciner systems this temperature range may be higher than typical cement kiln flue gas temperatures, especially in pl ants using heat recovery syst ems or baghouses for particulateCement Kiln Report (FINAL – 7/14/2006) 4-4 collection. But it may be possible to reheat th e exhaust using heat recovery systems. Of particular relevance, then, is the ability to use SCR at wet kilns.

Ammonia is typically in jected to produce a NH 3 : NO x molar ratio of 1.05-1.1:1 to
achieve NO x conversion of 80 to 90 percent with an ammonia "slip" of about 10 ppm of unreacted ammonia in the gases leaving the reactor. The NO x destruction efficiency depends upon the temperature, NH 3 : NO x molar ratio, and the flue gas residence time (or the space velocity) used in the catalyst bed. The SCR reactor system can be designed for a desired NO x reduction using appropriate reagent ratio, catalyst bed vo lume, and operating conditi ons. In general, the catalysts may be fouled or deactivated by the partic ulates present in the flue gas. In the case of cement plants, the presence of alkalis and lime, as well as sulfur dioxide, in the exhaust gases is also of concern. Recent developm ents, however, have led to sulf ur tolerant SCR catalysts. In addition, soot blowers may be used to pr event dust accumulation on SCR catalysts.

In the cement industry, basically two S CR systems are being considered: low dust exhaust gas and high dust exhaus t gas treatment. Low dust exhaust gas systems require reheating of the exhaust gases after de-dusting, resulting in additional cost. High dust systems are considered preferable for technical and economical reasons.

SCR may only be available as an applicable technology for dry kilns with preheat, as is described later herein. There are currently no in stallations of SCR units in any United States cement plants, however, a full-scale unit has be en operating in Germany for over three years with SCR. As set forth in greater detail belo w, selective catalytic reduction has been installed and successfully operated at this one cement pl ant in Germany and SCR is now commonly used
to control NO x emissions from coal-fired power plants. This technology achieves NO x emission reductions in the range of 80 to 90 percent or higher.

The experience of the German cement plant may be sufficient to demonstrate that the concerns regarding catalyst poiso ning and fouling have been addr essed with the development of a special catalyst specifically desi gned for the cement industry. In a typical design of a dry kiln with preheat, the SCR system could be located do wnstream of the pre-heat er cyclones, prior toCement Kiln Report (FINAL – 7/14/2006) 4-5 the roller mill. The process exhaust temperature at the outlet of the pre-he ater cyclones would be approximately 320°C (608°F), which is ideal for a SCR system.

Potential Advantages of SCR

The potential advantages of SCR are as follows:

y SCR can potentially provide a high degree of NO x removal. Presently, guarantee levels on SCR systems being provi ded in the power industry are in the 90% to 94% range. Even on difficult applicat ions such as coal-fired power plants, which have very dusty flue gases, NO x control efficiencies of 90%+ are being guaranteed by vendors and being achieved.

y SCR is an add-on or end-of-pipe control technology. For dry kilns with preheat, the SCR system would be locat ed downstream of the cement kiln and pre-heater furnace and cyclones and hence it would not interfere with or affect the cement manufacturing process. This woul d be a big advantage over the Selective Non-Catalytic Reduction (SNCR) process, which must be carried out in process conditions.

y SCR can use urea (CO(NH 2 ) 2 ) rather than ammonia as the reducing agent. To use urea, a conversion system is require d. In a typical conversion system, urea is mixed with water and then heated. The process converts the urea to gaseous ammonia, which is then injected into the flue gas. This system is commonly used where there are safety concerns arisin g from the transport and storage of ammonia.

SCR at Coal-Fired Power Plants

Prior to 2001, there were approximately 12 co al-fired power plants in the United States utilizing SCR for NO x control. According to the Electric Power Research Institute, there are now about 200 coal-fired power plants (tota ling 100,000 megawatts of ge nerating capacity) online utilizing SCR control. Most of the plants on which SCR has been installed are designed for, and have been achieving, 80% to 90% control of NO x .

One possible problem mentioned with respect to utilizing SCR in cement plants is the technical feasibility of installing SCR in an e nvironment where dust from the kiln could poison the catalyst, making SCR technically infeasible. On coal-fired power plants, the SCR catalyst is usually installed downstream of the boiler (between the economizer and the air pre-heater) priorCement Kiln Report (FINAL – 7/14/2006) 4-6 to the particulate control device. As a result, the catalyst is subject to the full dust loading from coal combustion, just as it would be at a cement plant. Typically, coal contains 6% to 20% ash on a dry basis. The high dust, high temperature characteristics of coal plant emissions thus are
similar to those of cement kiln exhaust gases. The experience of the power industry with SCR on coal-fired power plants sugge sts that the catalyst poisoning and fouling concerns may be manageable.

SCR Experience in Cement Kilns

Differences in the nature of the cement kiln and coal fired power plant processes, the chemical composition of the ash and other factor s mean that the success of SCR in controlling
NO x emissions from coal-fired power plants is not definitive evidence that the technology can be successfully applied at a cement pl ant. Among other things, dust from cement kilns is high in calcium, relative to coal dust, and calcium deactiv ates most conventional SCR catalysts. Also, the grain loading of cement kilns is likely to be different from that of coal-fired power plants, placing different stresses on the c ontrol device. As discussed in greater detail below, however,
the recent successful use of SCR at a German ce ment plant demonstrates that these and other issues may have been resolved and that SCR is , under certain conditions, a technically feasible alternative for significantly reducing NO x emissions from cement kilns.

The Solnhofen Portland-Zementwerke AG ceme nt plant in southern Germany located between Munich and Nuremburg has been in su ccessful operation with SCR since 2001. Lurgi, the engineering company who supplied the SCR system, addressed the problem of catalyst deactivation discussed above (caused by the hi gh calcium content of cement plant ash) by developing a catalyst specifically for the cement industry. The cat alyst can use ammonia or urea as a reagent. If urea is used, a conversion unit is used to convert the ur ea to ammonia prior to injection in the SCR system. These units, wh ich are quite common, avoid the need to store ammonia on-site for use as a reagent.

As of the beginning of 2005, there was no evid ence of catalyst poisoni ng or deactivation. The problem of fouling from th e heavy dust loading has proven to be quite manageable with regular maintenance (i.e., cleaning of the catalyst with a vacuum cleaning system).Cement Kiln Report (FINAL – 7/14/2006) 4-7 The SCR system is achieving NO x emission reductions far in excess of those achievable using SNCR. Prior to installation of SCR, th e Solnhofen plant, with SNCR, was achieving NO x emissions of 700 to 800 mg/ Nm 3 (equivalent to 2.8 to 3.2 lb./tonne clinker). With SCR, the plant has been achieving approximately 200 mg of NO x /Nm 3 (0.8 lb./tonne clinker). Based on an
uncontrolled NO x emission rate of 1050 mg/Nm 3 (4.2 lb./tonne clinker), the emission rate corresponds to a NO x control efficiency of 80% for SCR compared with approximately 25-35% control efficiency for SNCR. It has been indi cated, however, that the SCR system was capable of achieving a lower NO x emission rate (they are not using all of their beds), but that they were operating at 200 mg/Nm 3 since German law only required a NO x emission limit of 500 mg/Nm 3 .(23a, 23b, 23c, 23d)



### Figure 4-1.1 SCR on Preheater Tow er at Solnhofen Zement, GermanyCement Kiln Report (FINAL – 7/14/2006) 4-8 At approximately 500,000 tonnes per year of clinker, Solnhofen is smaller in capacity than the preheater/calciner units in Ellis County and larger than the wet kilns. With an
uncontrolled NO x emission rate of approximately 4.2 l b./ton, Solnhofen has a slightly higher emissions rate than the Holcim units and slightly lower than the Ash Grove kilns. The emissions rate is much higher than TXI #5 and mu ch lower than the TXI wet kilns.

Site Specific Application of SCR to Ellis County Cement Kilns

SCR offers the possibi lity of significant NO x reduction at the plants in Ellis County. As an “add on” technology, which can achieve 90% or greater NO x reduction, with demonstrated performance at hundreds of coal fired power plants , SCR is a viable technology that is available for both dry and wet kilns. The economics of SC R are greatly influenced by the temperature of the flue gas at the point of in stallation. For the three dry pr ecalciner kilns in Ellis County, a location in process with suitable temperatures is assumed and this leads to lower overall costs and cost effectiveness. For the wet kilns, a location downstream from the electrostatic precipitators (ESPs) is se lected for installation, and reheat of the process gas is required. This substantially increases the overall cost and decreases the cost effectiveness of SCR in comparison to the dry kiln applications.

The technology has been available at only one cement plant, the Solnhofen Portland – Zementwerke AG dry kiln plant in Southern Germ any, now in its fourth year of operation with SCR. While there are, at this time, no operating units in the U.S., the German experience leads one to assess the possibility that SCR can make a significant impact on NO x reduction in Ellis County. In fact, the Midwest Regional Planning Organization has recently concluded that SCR is a reasonably available t echnology for controlling NO x at cement plants (23e), and the possibility exists, with reheat, to utili ze SCR at wet, as well as dry, kilns.

Applicability of SCR to Cement Kilns and Areas of Concern

Before examining site-specific data, it is important to first examine the areas of concern with respect to SCR, many of which have been raised in the literatur e (23f, 23g, 23h, 23i). This is necessary to see whether the data from the coal fired plants and from the one cement plant, isCement Kiln Report (FINAL – 7/14/2006) 4-9 sufficient to attempt to make even qualified stat ements with respect to existing facilities, even though some analyses now suggest that the German data indicates that these problems will not exist for the cement industry in the U.S. (23g). These concerns are delineated and discussed here. They include: catalyst deactivation due to catalyst poisoning; cata lyst plugging and fouling due to high dust loading and deposits; reduction in NO x control efficiency due to high sulfur levels; temperature related factors leading to lower NO x removal efficiencies; NO x concentration variability and ammonia slip; and undesirable by-product form ation in the SCR causing adverse affects on downstream equipment.

Catalytic Deactivation Due to Catalyst Poisoning

Poisoning occurs when the contaminants in th e gas being treated react with the catalyst, resulting in catalyst deactivation. It has been argued that the S CR catalyst in a cement plant will be subject to poisoning, principally from sodium (Na), potassium (K), and arsenic trioxide (As 2 O 3 ). Phosphorus, chromium and lead compounds can also poison an SCR catalyst, but since these are expected to be present in lower concen trations at cement kilns, they are of lesser concern. However, the typical c oncentration of sodium oxide (Na 2 O) in the particulate matter (PM) of certain coal-fired plants is gr eater than double the concentrations of Na 2 O in the PM of the average cement plant, and the maximum concentration of Na 2 O can be significantly greater than the maximum expected concentration of Na 2 O in the PM of the average cement plant. Similarly, the concentration of As 2 O 3 in the flue gas of the typical coal fired plant is well above
the concentration of As 2 O 3 in the expected flue gas from th e average cement plant. Regarding the availability of catalyst poisons, an additional argument deals with the solubility of Na and K in the fly ash and the form of the fly-ash particles.

It is argued that in cement pre-heater pre-calciner kilns, materials such as sodium and potassium compounds may be present in relativel y elevated concentrations on the surfaces of particles in “water soluble” form that can cont act the surface of the SCR catalyst bed and thereby provide an opportunity to poison the V 2 O 5 “active ingredient” in the SCR bed. Conversely, it is argued, in coal-fired boilers, the sodium and potassium are, to a major extent, trapped within a glass-like fly-ash particle. It is widely known however that fly- ash particles from coal-fired boilers are in the form of tiny spheres (cenosphe res) and that during the combustion of the coal,Cement Kiln Report (FINAL – 7/14/2006) 4-10 the particles are actual ly liquid and the spheres are form ed as tiny bubbles by evolved gases trying to escape. Boilers are desi gned to cool the molten particles to a solid state such that they can be easily removed from boiler tubes. Howeve r, depending on the temperature of the fly ash and its chemical composition, some of the fly ash will deposit in various sections of the boiler. The deposits that form at the back-end of the boiler (on the economizer an d air heater) are called “low-temperature deposits”. Low temperature deposits are usually ch aracterized by low pH (highly acidic); many contain hydra ted salts, and for most bitumi nous coals are water-soluble. Therefore, coal-fired boilers have fly-ash deposit s in the economizer secti on of the boiler that are water-soluble. However, deactivation has not be en found to occur. In addition, SCR systems
have been installed on oil-fire d boilers despite the relatively higher levels of water-soluble alkaline metals found in the fly ash from such boilers.

Catalyst Plugging and Fouling Due To Hi gh Dust Loading and Depositing of “Sticky” Materials

Catalyst plugging and fouling involves the accumulation of dust that blocks access to the pores of the catalyst. It is ar gued that high dust loadings coul d plug or foul the SCR catalyst beds. However, the Solnhofen SCR system has operated at a dust loading of 80 g/Nm 3 , a relatively high dust loading. The level of NO x removal shows that high dust loading can be managed to avoid catalyst plugging and fouling while maintaining high levels of control. Related to the plugging and fouling issues, it is argued that “stic ky deposits” in the pre-heater exhaust gas could foul and plug the SCR catalyst. Specifically, certain cement kiln operations could be prone to producing sticky deposits at exactly the temperature ranges in which SCR systems operate. Sticky deposits are a widesp read problem occurring throughout the world on cement kiln induced draft (I.D.) fans. In many plan ts it is an extremely hard, layered, brick-like build-up that is associated with impingement of particulate at high veloci ty against the rotating parts of the fan impeller.

While the presence of alkali in the cement k iln system is a factor in the build-up, the mechanical aspect (namely, impact velocity) is mo re critical to the formation of build-up. The recommendation for avoiding build-up is to select a fan that minimizes the gas/dust velocity at
the inlet of the fan rotor. Alte rnatives include using double inlet fans or using larger diameter, lower RPM (revolutions per minute) fans. Sticky deposits or build-up de veloping on other partsCement Kiln Report (FINAL – 7/14/2006) 4-11 of the cement kiln system are not common. Th us, the sticky deposit problem appears to be related solely to the I.D. fan and is due to the high impact velocity of the dust particles mostly on the fan. This problem should not affect an SCR cat alyst that is subject to comparatively low gas velocities in comparison to an I.D. fan.

For instance, gas velocities through an SCR sy stem are typically less than 6.2 meters per second (1220 ft./min.), whereas peripheral gas sp eed at the kiln I.D. fan rotor inlet is approximately 15,000 ft./min. Possible problems relating to thermal sintering and catalyst erosion have been addressed by advances in cata lyst technology and proper system design. The problem of thermal sintering has been avoided by the incorporation of tungsten in the catalyst formulation and also by providi ng a bypass around the SCR system so that the catalyst is not exposed to high temperature excursions. Hardeni ng the leading edge of the catalyst and also arranging the catalyst bed so that the airflow is parallel to the catalyst channels have addressed catalyst erosion.

Reduction in NO x Control Efficiency Due to High Sulfur Levels

In general, operational histories of SCR in stallations at coal fi red plants and the one cement plant indicate that NO x reductions are being achieved in a reliable manner. The reason that many of the older units are not achieving NO x removals greater than 80% is that the plants were not designed to achieve such high removal e fficiencies. Great advances in the application of SCR technology have taken place. Present day SCR systems are typically achieving NO x reduction efficiencies of 90% or greater. It is argued that when only a low NO x reduction is required, the catalyst manufacturer can use a cataly st with a lower vanadium oxide content which
will reduce the oxidation of SO 2 to SO 3 and thereby avoid the potential for CaSO 4 masking. However, the Solnhofen SCR system is achieving a high degree of NO x control.

It is argued that high SO 3 concentrations could lead to catalyst deactivation and other serious problems relating to SO 2 oxidation. A high SO 3 concentration (10 -20 ppmv) when coupled with the high calcium level in the ce ment kiln flue gas c ould purportedly cause deactivation of the SCR catalyst due to the masking effect of calcium sulfate (CaSO 4 ). In addition, any SO 3 that does not react with the calcium could react with any unused NH 3 to formCement Kiln Report (FINAL – 7/14/2006) 4-12 ammonium sulfate (AS) or amm onium bisulfate (ABS) that coul d cause fouling of downstream equipment. Sulfur in the raw mix can be in several forms, namely: calcium sulfate, magnesium sulfate, and sulfides such as pyrites or or ganically bound sulfur. Only the volatile sulfur compounds (namely: the sulfides and organically bound sulfur) are oxidized and released in the pre-heater as SO 2 . With respect to these concerns, the success of SCR systems at a number of coal-fired boilers show that SCR systems can be designed for high calcium and high sulfur flue gases and the SCR catalyst supplie rs have indicated that CaSO 4 formation does not pose a major concern, as they assert that the SO 3 generated in the process is captured by the large amount of free lime in the gas stream. SO 2 oxidation by the catalyst will th en have no negative impact on
the amount of SO 3 formed and subsequently captured. There is also concern regarding the possible formation of ammonium salts, which can form in SCR systems at temperatures below 580 to 590°F. However, this problem can be a voided by ensuring that the SCR inlet temperature is always 600F or greater.

Temperature Related Factors Leading to Lower NO x Removal Efficiencies

Several temperature-related factors have been identified as important to successful operation of an SCR system. These are: (1) an acceptable normal operatin g temperature; (2) an even temperature distribution; and (3) avoidi ng temperature extremes (which may lead to catalyst deactivation or sintering). Low temperatures can lead to lower NO x reduction efficiencies and/or higher catalys t activity (leading to possible SO 2 oxidation) and to possible ABS/AS formation in the catalyst po res. Concerns regarding a slightly lower than desirable inlet temperature, however, can be resolved by installi ng equipment to ensure a desired temperature of 600°F or greater going into the SCR system. Su ch control systems are commonly used on boiler air supply systems and economizer bypass ducts. No te that the SCR reactor should also have an automatically activated bypass duct around the S CR reactor, so that in the event of high temperature fluctuations (great er than approximately 800°F), au tomatically controlled dampers would send the hot flue gas to a reactor bypass duct, thus preventing any damage to the SCR catalyst. Therefore, temperature issues, whet her involving normal operating temperatures or temperature fluctuations, shoul d be correctable with simple process reconfigurations.Cement Kiln Report (FINAL – 7/14/2006) 4-13 NO x Concentration Variability and NH 3 Slip

It has been argued that unlike a coal-boiler SCR application, an SCR system applied to a cement kiln will be faced with highly variable inlet NO x loadings and that elevated NH 3 slip levels are possible, which, coupled with possibly higher sulfur oxide leve ls, represent a serious risk. However, in an SCR system, the injected NH 3 is adsorbed onto the surface of the catalyst. Thus, there is a reservoir of unused NH 3 on the surface of the catalyst that is available to handle sudden peaks in inlet NO x concentrations and thereby enable SCR systems to control fluctuating
levels of NO x . SCR systems do not have to overfeed ammonia to handle surges in inlet NO x concentration and so tend to have very low NH 3 slip levels.

Coal-fired boilers have been operating SCR systems successfully for years despite
considerable NO x fluctuations in their flue gases. SCR suppliers typically guarantee a NH 3 slip of no more than 2 ppmv for any coal-fired boile r SCR application. In addition, the Solnhofen plant is a cement kiln with all of the inherent variability and has nevertheless been achieving a high degree of NO x control with a low ammonia slip level. Data at Solnhofen indicates that the
SCR inlet NO x concentration varies consider ably, from less than 1000 mg/Nm 3 to 2030 mg/Nm 3

while the outlet NO x concentration varies from approximately 300 to 726 mg/Nm 3 , but maintains an average outlet NO x concentration of less than 500 mg/Nm 3 . At these variable conditions, however, NH 3 slip has been maintained in the 1-2 ppmv range.

Undesirable Byproduct Formation in the S CR Causing Adverse Effects on Downstream Equipment

Concerns have been raised regard ing the generation and release of SO 3 that could cause corrosion of downstream equipment, or that the SO 3 may react with unused NH 3 to form ammonium salts (ABS and AS), which could pl ug or corrode downstream equipment. In addition it is argued that ammoni um salts could increase condensa ble particulate matter levels, making it difficult for a facility to meet its part iculate matter emission limit. In SCR systems
with SO 3 , NH 3 and moisture present, ammonium salts will form at temperatures below 580- 590°F. The best way to prevent their formati on is to continuously control the SCR inlet temperature such that it is always 600°F or greater. Regarding th e possible release of SO 3 , catalyst manufacturers report that the SO 3 gas is totally captured by conversion to particulateCement Kiln Report (FINAL – 7/14/2006) 4-14 calcium sulfates and sulfites as it is contact ed by free lime upstream, within, and downstream of the SCR catalyst. Thus, the formation of undesi rable byproducts should be inherently controlled by the free lime in the system and can be further controlled by controlling the SCR inlet temperature.

General Conclusions

The experience of coal-fired power plants and the one cement plant with SCR offers the following lessons. First, the succ ess of coal-fired power plants shows that catalyst deactivation from alkali poisoning is not expect ed to be a significant problem fo r cement kiln applications. Second, the success of SCR systems on a number of coal-fired boilers reveals that even when flue gases have significant levels of both calcium oxide (CaO) and sulfur dioxide (SO 2 ), the condition can be handled in SCR systems without the occurrence of pore masking from calcium sulfate (CaSO 4 ) formation. Third, the power plant experience shows that SCR systems can be designed to achieve at least 85% NO x reduction despite extremely large gas flow rates with significant NO x variability and relatively high partic ulate loadings. Last, the power plant experience shows that equipment can be designed and operated such that the flue gas entering the SCR catalyst will always be in the proper temp erature range. For wet kiln applications, this can lead to a requirement fo r significant gas re-heat.

Site-Specific Analyses

The follow sub-sections are specific to TXI, Holcim, and Ash Grove. In what follows, the
additional NO x associated with gas re-heat, if requir ed, has not been added, as the level of
additional NO x would be below 10 tons per year and 85% of that would be removed.

SCR at the TXI Kilns

To consider SCR at the TXI facilities, one mu st perform separate analyses for Kiln 5 (the dry kiln with pre-heater/pre-calciner, as found at the Solnhofen plant) and Kilns 1-4 (the long wet kilns, which usually operate as kilns 1 and 4 in tandem, or 2 and 3 in tandem). Neither the alkali percentages, the sulfur fuel percentages nor the stack c oncentrations (extrapolated toCement Kiln Report (FINAL – 7/14/2006) 4-15 uncontrolled for TXI #5) would be considered high fo r SCR utilization in coal-fired power plants (see Confidential Attachment – TXI).

With respect to the dry kiln (TXI 5), it w ould be expected that an SCR system would be installed downstream of the pre-heater, where th e temperature would be in the range required. With respect to process economics, this temper ature is assumed to be 700°F (the temperature
utilized in all the cases at all th e plants studied). With respect to this particular kiln, the present
data indicates a low NO x level in the 150-ppm range. For co nservatism, it is therefore assumed that an SCR system for this kiln would operate at an 80% reduction efficiency, as opposed to a significantly higher level (85%) to be expected at the other kilns at TXI and at the other facilities in Ellis County.

The economic analysis for this case is found in the confidential attachments. It is found that the cost effectiveness, based on NO x removed ($/ton NO x removed) is approximately $2,200/ton. With respect to cost effectivene ss based on metric tonne s of clinker produced ($/tonne clinker), the cost is approximately $0.87/tonne.

The wet kilns have been economically modele d based on a number of possible scenarios. The reported stack gas temperatur e 160°C (320°F) was utilized in the reheat calculations (to 700 oF at the SCR inlet) in all cas es, and natural gas, at $12.00/ther m is utilized. Three different scenarios were studied. In the first scenario, one SCR system serves kilns 1 and 4 consistent with TXI’s operation (85% of the time). In the second scenario, one SCR system serves kilns 2 and 3 again consistent with TXI’s operation (15% of the time). In the third scenario, one SCR system serves all four wet kilns with pipi ng and controls to match the normal operating
scenarios. These three scenar ios were again modeled based on the possibility that TXI might introduce mid-kiln firing as a method of NO x control in its four wet kilns. Therefore, a total of six economic analyses for the TXI wet kiln s are found in the confidential attachment.

For the scenario without mid-kiln firing in kilns 1 and 4, the cost effectiveness based on
NO x removal ($/ton NO x removed) is approximately $5,500/ton. The cost effectiveness based on metric tonnes of clinker produced ($/tonne clinker) is approximate ly $8.90/tonne. These estimates are based on the assumption that mid-k iln firing is in place as required under theCement Kiln Report (FINAL – 7/14/2006) 4-16 existing Texas regulations. Mid-ki ln firing is currently required at Ash Grove, but has not been installed due to permit issues. Assuming mid-kiln firing avoids possible double counting of the
emissions reductions achie ved by mid-kiln firing.

The scenarios involved with kilns 2 and 3 w ith SCR lead to what must be considered unacceptable economics, since capital cost is esse ntially equal to that for kilns 1 and 4, but operation (both from the standpoints of NO x removed and clinker produced) is only 15% of the total. Therefore, without mid-kiln firing, the economics yields a cost effectiveness based on NO x removal of approximately $96,000/ton, while the cost effectiveness based on clinker produced is in the $13.50/tonne range. Mid-kiln firing is also a ssumed for kilns 2 and 3.

Based on economies of scale, utilizing one large SCR unit to service all four kilns (the model assumes a capacity equivalent to approxima tely 3 kilns in operation at any time) should
lead to the most cost effective manner of control. With mid-kiln firing, the cost effectiveness
based on NO x removal is approximately $5,300/ton, while the cost effectiveness based on clinker produced is about $5.90/tonne.

It is clear that while the reheat required in the wet kilns significantly increases the costs
associated with NO x control with the utilizati on of SCR, the cost effectiveness is best when one
SCR unit is installed for all f our wet kilns. For the dry ki ln, the economics is, of course, significantly better and assuming space for the catalyst beds and ancillary equipment is available, SCR must be seriously considered.

SCR at the Holcim Kilns

To consider SCR at the Holcim facilities, se parate analyses are performed for each of the two dry units. Each is equipped with precalciners and preheaters, but Holcim 2 is a newer, more efficient unit, emitting 26% less NO x (in mg/m 3 ). The temperature after the preheater for both Holcim 1 and 2 is expected to be adequate (i.e . 700°F), so no reheat would be required, and 85%
NO x removal is assumed. Neither the alkali percen tages, the sulfur fuel percentages, nor the stack concentrations extrapolat ed to uncontrolled would be cons idered high for SCR utilizationCement Kiln Report (FINAL – 7/14/2006) 4-17 in coal-fired power plants (see Confidential Attachment – Holcim). The utilization of SCR is, therefore, not precluded.

The annual cost spreadsheets are found in th e confidential attachments for each cement plant. The cost effectiveness based on NO x removal ($/ton NO x removed) for Holcim 1 is approximately $1,950/ton. The cost effectivenes s based on metric tonnes of clinker produced ($/tonne clinker) is about $2.00/tonne.

For Holcim 2, which is more efficient, the NO x removed is less (since less NO x is produced) and the clinker production is greater. Therefore, the cost efficiency based on NO x removal is slightly greater for Holcim 2, at approximately $2,000/ton, and the cost effectiveness based on tonnes of clinker produ ced is approximately $1.70/tonne.

SCR at the Ash Grove Kilns

Ash Grove has three wet kilns with mid-ki ln firing: Ash Grove 1, Ash Grove 2 and Ash Grove 3. Data indicate nearly id entical operating conditions and NO x emission levels (in the 350 ppm to 400 ppm range). Neither th e alkali percentages, the sulfur fuel percentages nor the stack concentrations would be considered high for SCR utilization in coal-fired power plants (see Confidential Attachment – Ash Grove). In addi tion, Ash Grove reports te mperatures at the air pollution control device (APCD) inlets of 330°F to 370°F. Assuming the installations of SCR between the APCDs and the stacks, these temperat ures indicate that As h Grove can install SCR at each of their kilns with reheat required, and 85% NO x removal can be expected.

Four scenarios are presented, that of the in stallation of an SCR at each of the three wet kilns, the fourth being the inst allation of one SCR for all three units. For Ash Grove 1, the cost
effectiveness based on NO x removal ($/ton NO x removed) is about $5,800/ton (all reheat at $12.00/therm). The cost effectiveness based on clinker produced ($/tonne clinker) is approximately $9.20/tonne.

For Ash Grove 2, the cost effectiveness based on NO x removal is approximately $5,800/ton. The cost effectiveness based on clinker produced is about $9.90/tonne.Cement Kiln Report (FINAL – 7/14/2006) 4-18 For Ash Grove 3, the cost effectiveness based on NO x removal is approximately $6,100/ton. The cost effectiveness based on cl inker produced is approximately $10.60/tonne
clinker.

If space is available and operation is not impeded, one SCR unit can be installed to
service all three kilns. In this ca se, the cost effectiveness based on NO x removal improves to about $4,600/ton. The cost effectiveness based on clinker production improves to approximately $7.70/tonne.

It is clear that if space is available for one SCR unit and its ancillary equipment, in order to serve all three kilns, the economics is far mo re favorable than if three SCRs are installed. SCR, therefore, for these wet kilns is an available technology at 85% NO x control, albeit at a high cost/tonne of clinker removed.

Table 4-1.1. Summary of Modeling Results for SCR on Ellis County Kilns – Performance Results

Existing Unit Control Technology Emissions Rate tpy before Emissions Rate tpy after (a) Controlled Emissions Rate ppm Controlled Emission Rate lb./tonne clinker Control Efficiency % Reduction tpy
Ash Grove #1- wet SCR 702 301.6 60 0.84 85% 400.4

Ash Grove #2- wet SCR 750 322.2 58 0.89 85% 427.8

Ash Grove #3- wet SCR 764 328.3 53 0.91 85% 435.7 Ash Grove #1,2,&3 (c) SCR 2205 947.4 57 0.88 85% 1,257.6 TXI #1 and #4–wet (b) SCR 838 155.3 109 0.85 85% 478.0 TXI #2 and #3–wet (b) SCR 121 52 109 0.51 85% 69.0 TXI #1,2,3,4 –wet (c) SCR 1802 774.2 109 0.85 85% 1,027.8 TXI#5 – dry SCR 1710 734.7 29 0.30 80% 975.3 Holcim #1 – dry SCR 2222 954.7 108 0.56 85% 1,267.3 Holcim #2 – dry SCR 1778 763.9 80 0.45 85% 1,014.1 (a) NO x emission rate after SCR does not reflect SCR efficiency reduction due to adjustme nt by the ozone season factor of 0.671 (NO x reduction is modeled to occu r only during the ozone season). (b) The results for TXI 1 & 4 and #2 & #3 are average per kiln – for example, total emissions re ductions for controlling both T XI #1 & #4 are double the value listed in the table. (c) A large single SCR was modeled fo r the Ash Grove and TXI wet kilns with the capacity of 3 wet kilns. (d) Models assume mid-kiln firing installe d at TXI as required under current SIP.Cement Kiln Report (FINAL – 7/14/2006) 4-19 Table 4-1.2. Summary of Modeling Results for SCR on Ellis County Kilns – Economic Results

Existing Unit Control Technology Capital Cost Annual Cost Cost Effectiveness

$/ton NO x Energy Penalty or

Benefit Emissions Penalty or

Benefit Burden Cost $/tonne clinker Ash Grove #1- wet (e) SCR $5.0MM $2.3 MM $5,800 (a) (b) $9.20 Ash Grove #2- wet (e) SCR $5.2MM $2.5MM $5,800 (a) (b) $9.90 Ash Grove #3- wet (e) SCR $5.3MM $2.7MM $6,100 (a) (b) $10.60 Ash Grove #1,2,&3(d) SCR $11.8MM $5.7 MM $4,600 (a) (b) $7.70 TXI #1 & #4–wet (c,e) SCR $5.7MM $2.6MM $5,500 (a) (b) $8.90 TXI #2 & #3–wet (c,e) SCR $5.7MM $0.6MM $96,000 (a) (b) $13.50 TXI #1,2,3,4 –wet (d,e) SCR $11.2MM $5.4MM $5,300 (a) (b) $5.90 TXI#5 – dry SCR $8.4MM $2.2MM $2,200 (a) $0.87 Holcim #1 – dry SCR $7.5MM $2.4MM $1,900 (a) $2.00 Holcim #2 – dry SCR $6.7MM $2.0MM $2,000 (a) $1.70 (a) Increased fan power due to pressure dr op across catalyst bed included in the models (b) Increase in NO x from gas reheat occurs, but is controlled by the SCR (c) The results for TXI #1 & #4 and #2 & #3 are average per kiln – for example, total capital costs for controlling both TXI #1 & #4 are double the value listed in the table. (d) A large single SCR was modeled for the Ash Grove an d TXI wet kilns with the capacity of 3 wet kilns. (e) Costs for wet kilns include cost of RTO to reheat flue gas.Cement Kiln Report (FINAL – 7/14/2006) 4-20 4.1.2 Selective Noncatalytic Reduction (SNCR)

This control technique relies on the reduction of NO x in exhaust gases by ammonia or urea, without using any catalyst, with the same reactions as in the case of the SCR process. Because of low capital and mainte nance costs associated with this technology vis-à-vis other end-of-pipe technologies like SCR and oxidative methods, it is lik ely to command attention in the near future within the industry. This approach combines a low initial capital cost and avoids the problem related to catalyst fouling and replacement associ ated with SCR technology. SNCR requires injection of the reagen ts in the kiln at a temperature between 870 to 1,090°C (1,600 to 2,000°F). In principle, any of a number of nitr ogen compounds may be used as SNCR reagents (e.g., cyanuric acid, pyridine, and ammonium acet ate). However, for reasons of cost, safety, simplicity, and by-product formation, ammonia and urea have been used in most of the SNCR applications. The selection of reagents is process and temperature specific. At higher temperatures, urea decomposes to produce ammonia, which is responsible for NO x reduction. In cement kiln applications, ammonia typically ha s performed best as the reducing reagent.

Because no catalyst is used to increase the reaction rate , the temperature window is critical for conducting this reacti on. At higher temperatures, the ra te of a competing reaction for the direct oxidation of ammonia, which actually forms additional NO x , becomes significant. At lower temperatures, the rates of NO x reduction reactions become too slow resulting in too much unreacted ammonia being released to the atmos phere (i.e., ammonia slip). The effective temperature window range can be lowered to about 700°C (1,300°F) by the addition of hydrogen along with the reducing agent. (24) Add ition of hydrogen can promote SNCR reactions (enhanced SNCR), but high levels of sulfur oxi des may interfere with this reaction (Recent evidence tends to call into question this tentativ e conclusion). Nalco Fuel Tech, the producer of the SNCR technology NOxOUT ® , has also introduced NOxOUT ® PLUS which is said to broaden the operating temperature window a nd to reduce ammonia slip and CO and NO 2 formation.

In a conventional long kiln, the appropriat e temperature window is in the middle of a kiln. Until quite recently, because of the rotati ng nature of a long kiln, continuous injection of ammonia- or urea-based reagen ts had not been considered po ssible. The technology developedCement Kiln Report (FINAL – 7/14/2006) 4-21 for mid-kiln firing of containeri zed solid fuels allows injection of a certain amount of material once during the kiln revolution. Injection of solid ammonium or urea salts in this manner had not been used because of the assumption of rapi d decomposition of such salts. Therefore, SNCR technology had not been thought app licable to date for long dry or wet kilns. There is some limited evidence from Europe, sugge sting that injection of urea into long wet kilns may have promise(25). Urea injection was reportedly con tinued over a four month period with satisfactory results at a wet kiln in France. The publicized information does not, however, give detailed data
needed to evaluate this test. The test does not stipulate:

• Location of reagent injection,

• Titration rate for reagent,

• Reagents tried and their performa nce (only urea is mentioned),

• NOx reduction rate vs. titration rate,

• NOx reduction rate vs. temperature,

• Average NOx emissions rates for cont rolled and uncontrolled operation,

• Operating costs,

• Other NOx control measures employed at the kiln, and

• A physical description of the kiln and inform ation on feed and production materials. (25)

Without this type of detailed information, it is difficult to draw any definitive conclusions about the potential for application to wet kilns in Ellis County.

In addition, Fuel Tech Inc. is currently evaluating dry dust or pellet injection methods for direct injection into kilns. (26) The possibili ty of injection of amm onia or solid urea inside automobile tires that are injected into the kiln has stil l to be evaluated. With the known ability of mixing air fans to induce turbulence in th e system, mixing combus tion gases containing NO x with ammonia, either generated from urea or fro m ammonium salts, may also offer possibilities. Chain gas temperatures generally are in the range of 1500-1600oF (815-8 71oC). The mid-kiln injection systems are usually down kiln somewhat from this point, which means that they will be higher than this in gas temperatur e. There is a good possibility th at the correct temperature range can be achieved if mixing is induced and volat ilization or decomposition of the urea can be delayed by inserting it in a solid form in a carri er such as a tire. This option needs to be explored. It will clearly be necessary to mix the NO x with the reagent before the latter has an opportunity for decomposition. Inducing turbulence is presently conceived as a key element in this strategy.Cement Kiln Report (FINAL – 7/14/2006) 4-22 In preheater/precalciner type cement kilns, the temperatures at th e cooler end of the rotating kiln, in the riser duct, a nd in the lower section of the cy clone preheater tower are likely to be in the temperature window appropriate for SNCR. Such k ilns are therefore good candidates for application of SNCR technology.

The NO x reduction efficiency of SNCR depends upon the temperature, oxygen, carbon monoxide, and residence time, as well as the ammonia and NO x concentrations in the flue gas. Injection of ammonia at a NH 3 :3 NO x proportion of 1 to 1.5 will reduce NO x emissions between 60 to 80 percent. Using a molar ratio of 0.5 will give NO x reductions of approximately 40 percent. (27) Work done by the German equipm ent supplier Polysius (28) has shown that the optimum temperature for reduction of NO x by ammonia is about 950oC (1,740oF), while for urea, the temperature increases to about 1,000oC ( 1,830oF). Ammonia is also somewhat more efficient, as shown in Figure 4-1.2. below.

Figure 4-1.2. Dependence of NO x Reduction on Temperature for Ammonia and Urea

Actual SNCR results with ammonia (19% a queous solution) at one US plant employing a calciner are given in Table 4- 1.3. It can be seen that th e reduction was remarkably good, considering that ammonia was never added at gr eater than a stoichiometric equivalent to NO xCement Kiln Report (FINAL – 7/14/2006) 4-23 Due in part to the fact that no excess ammonia was introduced in to the system, no ammonia slip
was demonstrated. The ammoni a emissions were undetectable.

Table 4-1.3. Summary of Test Results for SNCR Test

Run # Molar Ratio NH 3 :NO NO x Reduction % Average NO x Before lb./hr Average NO x During SNCR lb./hr 1 0.918 65.49% 325.47 112.31 2 0.533 36.71% 322.90 204.35 3 0.425 44.93% 345.52 190.27 4 0.331 16.90% 282.70 234.91 5 0.465 15.49% 290.18 245.25 6 0.286 12.95% 269.35 234.47 7 0.534 45.06% 269.35 147.97 8 0.552 31.91% 281.71 191.81 Long term 0.368 47.78% 329.83 172.24

These results were very good. The temperat ure and oxygen concentrations were nearly optimum for the SNCR system. The carbon monoxi de levels were somewhat higher than has been considered optimum, but according to Brouwe r et al. (29), CO may promote the reaction at the lower end of the temperature range, because of the temperature increase due to the heat given off by the reaction of CO with OH radicals. Among other SNCR tests recently performed, tests have been carried out at a preheater plant and fo ur calciner plants. Some of these tests were carried out using ammonia, and others using ur ea. At the preheater plant, both ammonia and urea were tested, injecting the reagents into the kiln riser duct. Ammonia proved to be considerably more effective th an urea, in keeping with the Polysius plot given above.

Despite these successes, reagent consumpti on can be significantly higher with greater ammonia slip in SNCR systems as compared to SCR systems. Operating experience has
identified several concerns with both ammoni a and urea-based SNCR pr ocesses. The most frequently reported is the buildup of ammonium bisulfite or bisulf ate scale, which is significant for sulfur-containing fuels. SNCR proce sses also appear to convert some NO x to N 2 O. (30) The
rate of N 2 O formation is a weak function of both th e reactant and the NO concentration. However, N 2 O formation seems to be inherently more pr evalent in systems using urea than those using ammonia. (31)Cement Kiln Report (FINAL – 7/14/2006) 4-24 The NO x destruction efficiency also depends upo n the flue gas residence time in the appropriate temperature window. Unlike an SC R system where the reaction temperature is
controlled in a dedicated reactor, an SNCR system relies on the existing gas te mperature profile to provide an adequate residence time for a desired NO x destruction. Maximum achievable NO x reduction in a cement kiln may thus depend upon the gas temperature profile.

The SNCR process was demonstrated in Europe in a preheater type kiln. Both ammoniaand urea-based reagents were investigated. The r eagents were injected in the gas duct as shown in Figure 4-1.3. (32) With a molar ratio of reagent to NO 2 of 1:1, about 70 percent reduction in
NO x emissions was observed with ammonia- based reagent and about 35 percent NO x reduction was obtained with urea. (32) With this reagen t ratio, there was no major increase in ammonia emissions in exhaust gases over the background le vel of ammonia emissions generated by kiln
feed material. Greater NO x reductions were observed with more than stoichiometric amount of reagent, although there was increasing ammonia 'slip' in the exhaust gases. Figure 4-1.3. Application of SNCR at Holcim

Albert Scheuer, of the Research Institute of the Cement Industry in Düsseldorf, Germany, reported on 148 SNCR trials carried out on five different kilns. Three kiln systems had cyclone preheaters and two had grate preheate rs. A 25% molar concentration of NH 3 in water was the main reagent tested, with some additional test ing done with ammonium sulfate solutions andCement Kiln Report (FINAL – 7/14/2006) 4-25 with urea solutions. Scheuer reported that NO reductions with the NH 3 /water solution ranged from 15% to 75% and that temperature appeared to be one of the main determinants of the effectiveness of the reagent. Maximum NO reduction occurred at 980°C (1796°F). NH 3 escape occurred when temperatures were less than 900°C (1652°F) and when the NO concentration
fluctuated. NH 3 utilization decreased significantly with increasing NH 3 :NO molar ratio and with decreasing NO concentration in the exhaust gase s, indicating that SNCR appears to be a less promising methodology at low NO emissions rates. (33,34)

SNCR is presently being used in 18 cement kilns in Europe. Fifteen kilns are in Germany, two are in Sweden, and one is in Switzerland. These kilns are either suspension preheater kilns or precalciner kilns. The names a nd locations of these installations have not been found in any of the European references that discuss these installations. The most common reagent used is 25% ammonia water. (35) NO x reduction rates vary from 10 to 50 percent with

NH 3 /NO 2 molar ratio of 0.5 to 0.9, NO x emissions at these reducti ons are 2.4 to 3.8 lb./tonne clinker. Two dry process cyclone preheater/preca lciner kilns in Sweden achieve 80 to 85 percent reduction (1.0 lb./tonne clinker) at a NH 3 /NO 2 molar ratio of 1.0 to 1.1. (35) One reason for the
remarkable results in these kilns is the use of multiple injection poi nts (12 in all) that ensure long enough retention time for the reaction to take place. The optimum temperature is said to be 900- 1,100oC (1,650-2,010oF) in good agreement with other au thors. These results suggest that some SNCR tests may have been carried out under lower-than-optimum temperatures.

F. L. Smidth and Company tested SNCR on a preheater/precalciner kiln. (36) Ammonia was injected into the lower cyclone of the preheater tower where temperatures are favorable for
the reduction reactions to occur. NO x emissions reductions during th is experiment averaged 40 percent, but NO x reductions of over 90 percent were obtai ned when the ammonia injection rate was 10 to 20 percent in excess of stoichiometric.

In North America, SNCR has been tested on at least nine kilns. In some of the earlier work, NOxOUT ® technology was tested under ten diffe rent operating conditions at a preheater/precalciner kiln in Seat tle, Washington during October 1993. NO x emissions were effectively reduced from 3.5 to 6.0 lb. NO x /tonne clinker to less than one lb. NO x /tonne clinker. (37,38) Another test of NOxOUT ® technology was conducted during October 1998 inCement Kiln Report (FINAL – 7/14/2006) 4-26 Davenport, Iowa. This test found NO x reductions of 10 to 20 percent from a baseline of approximately 350 pounds NO x /hour, although higher levels of reduction are thought to be achievable when the baseline is high er. (39) An evaluation of NOxOUT ® technology was conducted in 1994 for a long dry kiln in Southern California, but the study concluded that application of the NOxOUT ® technology at the subject kiln was technically infeasible. (40) The details of this testing are not known.

Biosolids Injection (BSI)

. The Mitsubishi Cement Corpor ation’s Cushenbury plant in Lucerne Valley, CA, uses biosolids inject ion technology (BSI) to achieve SNCR of NO x . The BSI process was developed by the Cement Indus try Environmental Consortium (CIEC). The founding participants in the CI EC are Southdown, Inc., Riverside Cement Company, Mitsubishi Cement Corporation, California Department of Commerce (now Trade & Commerce Agency), and the San Bernardino County Air Pollution Contro l District (now Mojave Desert Air Quality Management District). This technology is covered under U.S. Patent No. 5,586,510 issued December 24, 1996. (33)

The basic principle is to utilize the natu rally occurring ammonia content of dewatered biosolids as the reagent. The de watered biosolids are obt ained from wastewater treatment plants. Since the biosolids are mechanically dewatered without heat input, the solids content varies between 16 and 30 percent (moisture content of 84 to 70%). Depending on the moisture content, the net Btu content (after evaporating the mois ture) of the biosolids varies between -750 and +2200 Btu/lb. Since the biosolids heating value is relatively small, the net effect on kiln fuel combustion is expected to be small. (41)

The same conditions that affect NO x reduction performance in SNCR affect BSI performance: temperature (927°C / 1,700°F is optimal), residence time (> 0.5 seconds is desirable), inlet NO x concentration, inlet CO concentration, and NH 3 / NO x molar ratio. Another key issue is mixing effectiveness, which affect s the extent of contact and, hence, reaction
between NH 3 and NO x . The BSI technology is applicable to preheater/precalciner kilns because the temperature window for BSI (927°C / 1700°F) occu rs in a location where it is feasible to inject biosolids. (41)Cement Kiln Report (FINAL – 7/14/2006) 4-27 The biosolids are injected into the mixing chamber where the flue gas stream leaves the kiln and precalciner mix. The mixing chamber offers the benefits of good residence time in the appropriate temperature window (927°C / 1700°F) and high mixing effectiveness. (41)

At the Cushenbury plant, BSI underwent long- term testing and eventual adoption in 1994 and 1995. The kiln is fueled with coal (85 percen t) and tires (15 percent) . The plant began using tire-derived fuel (TDF) in mid-1993, so it is diffi cult to isolate the eff ects of TDF or BSI on NO x emissions. The company estimates that the use of TDF reduces NO x emissions from the kiln by 30 to 40 percent. (42) Before the SNCR t echnology was adopted, the company estimated NO x emissions averaged 2.4 lb./tonne c linker; afterwards, the average fe ll to 1.2 lb./t onne clinker, a 50 percent reduction. The effects of BSI on CO emissions varies between a large increase and no change at all, but in all cases it has re mained below 500 ppm. BSI has not caused any significant changes in either metal HAP or or ganic HAP emissions. Using the SNCR biosolids technology, the kiln also reduced its fu el consumption by 5 percent. (41)

NOxOUT ®

. An SNCR process using aqueous urea was developed by Electric Power Research Institute (EPRI) and is now marketed by Nalco Fuel Tech, Inc., under the trade name
NOxOUT ® . In the urea reaction with NO, one mole of urea reacts with two moles of NO to complete the reaction to nitrogen, carbon dioxide and water. Normalized Stoichiometric Ratio (NSR) is used to express the re agent feed rate relative to the reaction stoichiometry. The NSR
takes into account the 2:1 mole ratio of the NO: urea reaction as the “nor malized” ratio. If 50% of the urea reacts to reduce NO to nitrogen, reduction of 100% NO x occurs at NSR=2; 80% reduction at NSR=1.6; 50% reductio n at NSR=1.0, etc. Performance improves with increased turbulence or mixing, residence time, and more favorable temperature conditions. A higher NO x baseline generally leads to a higher percentage of NO x reduction. (26)

Urea is safer to handle than anhydrous ammoni a. Both ammonia and urea need to be injected in a similar temperature window, which is 870 to 1090°C (1600 to 2000°F). The Polysius results earlier noted, however, appear to suggest that the am monia optimum may be lower than the urea optimum. Proprietary additi ves have been developed by Nalco to widen the temperature window. (43) One m odification of the urea-based SNCR system is the addition of methanol injection downstream of the ur ea injection point to improve overall NO x removal.Cement Kiln Report (FINAL – 7/14/2006) 4-28 Nalco also introduced an improved NOxOUT ® PLUS, which is said to further broaden the operating temperature window and to reduce ammonia slip and CO and NO 2 formation.

The Ash Grove plant in Seattle is a preheate r/precalciner kiln with average processing rates of 160 tons dry feed/hour producing approximately 100 tonnes clinker/hour. NOxOUT ® was tested on this kiln under varying conditions, in cluding the use of differ ent fuel types (natural gas and coal), heat input to the calcin er (5 to 9 percent), and preheater O 2 (1.8 to 2.9 percent). (It is probably necessary to point out that this calciner is an example of the so-called “air through” unit which employs no tertiary air duct; all air for combustion in the calciner must be furnished through the kiln. As of the present time, this h eat input is in the range of 20-30% of the total.
The baseline NO x levels varied from 350 to 550 lbs. NO x /hour. When NOxOUT ® was used,
NO x emission reductions varied significantly depending on the conditions, with a maximum reduction of 90 percent (less than 100 lbs. NO x /hour). Typical reductions were greater than 50%. (38)

NOxOUT ® was tested for one week in October of 1998 on the preheater/precalciner kiln at the Lafarge-Davenport Plant. Operating conditi ons were unstable most of that week and only five hours of testing produced re sults that could provide a reasona ble indication of what may be
achievable with NOxOUT ® . The baseline NO x rate was approximately 350 lbs. NO x /hour. Using NOxOUT ® , emission reductions of 10 to 20 per cent were achieved. (39) Operating conditions such as residence time, te mperature, and the use of coal at this kiln were contrasted to
conditions at the Ash Grove kiln that achie ved greater reductions to explain why NOxOUT ® may achieve better results on some kilns than others.

Nalco also has conducted a number of dem onstrations and commer cial projects in preheater/precalciner cement kilns. The fuels have included coal, and coal in combination with No. 6 heavy fuel oil, waste oil, and/or tire chips. The clinker capacity on these kilns ranged from approximately 1,000 metric tons to 3,200 metric tons per day. The result s of two tests with average NO x reductions of approximately 50%, were featured in a recent report (see Table 4-1.4). (26)Cement Kiln Report (FINAL – 7/14/2006) 4-29 Table 4-1.4. Emissions Reduction s From Two Kilns Using NOxOUT ®

Baseline NO x Emissions (ppm) NO x Emissions with NOxOUT ® (ppm) Percent Reduction (%) Kiln A, Test 1 412 203 51 Kiln A, Test 2 389 185 53 Kiln B 525 284 46

Site-Specific Analyses

SNCR at Holcim

Holcim Kiln #1

Holcim carried out trial SNCR tests on both of their precalciner kilns in Midlothian, TX. For the injection in line 1, (the older unit) the optimum location was identified to be on the riser duct, after the precalciner and before the bottom stage cyclone. This location would address NO x formed both in the kiln (principally presumably thermal NO x ) and in the calciner (principally presumably fuel NO x ). The reports do not indicate the temperature, oxygen, or carbon monoxide concentrations of the flue gas, considered ve ry important for optimum efficiency. There is therefore no basis for concluding that conditions had been optimi zed. With this condition, it proved possible to obtain about 50% removal of NO x at a molar ratio of ammonia to NO x of 0.75. This is not considered to be as good as obtai ned in the Florida kiln indicated earlier, nor for some of the Northern European kilns. However, the removal efficiency appears to be in good agreement with the data cited earlier, where a molar ratio of 0.5 is cited as achieving 40% removal, while a molar ratio of 1.0 is said to achieve 60% removal. While the conditions may not have been optimized, the results are consider ed acceptable compared to performance at other similar kilns. Experience at other kilns indi cates further optimization may result in better performance at Holcim #1 than was achi eved during the initi al trial period.

Holcim Kiln #2

For the Kiln #2 system, the inje ction point was on the riser duct after tertiary air input and before the Pyroclon (calciner). This differs fr om the location for the K iln #1 system, where theCement Kiln Report (FINAL – 7/14/2006) 4-30 injection point is post-calciner. This difference implies that the gases from the calciner were treated in the Kiln #1 system, but no SNCR was applied to calciner exhaust gases in the Kiln #2 system. Experience to date suggests that with normal bituminous coal fuel, roughly 70% of the system NO x may be generated in the kiln, and 30% in th e calciner as a general rule of thumb. To the extent that this supposition is justified, it appears as though an SNCR injection location that does not treat gases from the calciner may be omitting treatment of about 30% of the NO x . In addition, the injection location for this kiln system may be expe riencing a temperature decrease from the cooler tertiary air. Any residual ca rbon monoxide from the kiln exit gases was probably oxidized by the high O 2 content at this location, further compro mising the results. If this is the case, further erosion of the efficiency of the SNCR system may be occurring.

As a result, with a molar ratio of 0.75, the efficiency of removal of NO x was only 35%. This cannot be considered satisfactory. It proved possible to increase the NO x removal to as high as 80%, but this was with a molar ratio of about 2.0. At this molar ratio, ammonia slip and detached plumes were severe. In additi on, the plant reported a buildup of ammonium
sulfate/ammonium bisulfate in the top preheater stage forming under conditions of high ammonia injection. They claim that this buildup had the potential to assume catastrophic dimensions, but
was removed before this occurred.

It does not appear likely that the location for NO x removal on Kiln #2 was optimized. The lack of any data on temperature, oxygen, a nd/or carbon monoxide sugge sts that these data were not collected. It was discovered during the Florida test that optimization of these parameters was important to the success of the e xperiment. We believe that if the conditions are properly optimized using the necessary temperature, oxygen, and CO data, that better results are
achievable at Holcim#2.

SNCR at TXI

TXI Kiln #5

This kiln is already achieving very good NO x control without employing any end of pipe technologies. It appears that th e kiln is running at about 1.9 lb. NO 2 /tonne clinker at present –Cement Kiln Report (FINAL – 7/14/2006) 4-31 this may be the lowest value for any Portland ce ment kiln in the country. The application of SNCR may be worth considerati on for further reduction of NO x . It should be recognized, however, that 35% removal may be the best ac hievable, and even this level may not be achievable without optimization of the location in the preheater tower for temperature, oxygen,
and CO. SNCR becomes less effective at lower NO x concentration and European experience indicates that 200 mg/m 3 or approximately 100 ppm may be a lower limit for efficient application of SNCR at cement kilns. As earlier indicated, TXI has a high level of relatively nonvolatile organic carbon, a high leve l of total Kjeldahl nitrogen ( unfortunately, the temperature profile of nitrogen release from the feed at TX I is not known), and an apparently relatively easy burning mix. All these factors mitigate in the direction of lower uncontrolled NO x numbers.

TXI Wet Kilns

The ERG Team has estimated that the TXI wet kilns are currently operating at over 8 lb.
NO 2 /tonne clinker. The Texas Code (Chapter 117) requires mid-k iln injection or meeting an
emissions limitation of 4.0 lbs./tonne clinker. For the purposes of modeling SNCR and other control techniques on the TXI we t kilns, a 30% reduction in NO x emissions is assumed to result in emissions similar to the Ash Grove wet kilns when the mid-kiln firing is installed. The ERG Team understands that TXI is waiting for permit approval to convert the wet kilns to mid-kiln firing with tire injection. As discussed above, the lack of available alternative NO x controls for
wet kilns leads the ERG Team to a recommenda tion of trying innovative or experimental techniques involving some SNCR injection involving urea or another reagent in tires. This experimentation would determine if mixing and th e proper form of ammonia might travel into the proper temperature range of the kiln to be effective. These ideas will have to be verified or disproved with experimentation. For the purposes of cost modeling, a 35% efficiency is assumed to be achievable through a mid-kiln injection of a SNCR reagent.

SNCR at Ash Grove

Ash Grove Wet Kilns

The Ash Grove wet kilns are already using mid-kiln firing and are emitting approximately 5.0 lbs./tonne clinker. Mid-kiln firing is traditionally regarded as the mostCement Kiln Report (FINAL – 7/14/2006) 4-32 effective wet kiln method for controlling NO x . As discussed above, it may be worthwhile considering a modification of traditional SNCR here, in which the urea is introduced inside whole tires, and mixing air is us ed to promote reaction with NO x before the urea is decomposed. This is innovative and specula tive, and requires testing to verify, but it should be quite inexpensive and cost effective for a plant alr eady employing mid-kiln firing. Attempting an
innovative control method for wet kilns based on SNCR seems to be a worthwhile option since other control options have not been a pplied to wet kilns. SCR and LoTOx TM appear to be transferable from other applicati ons but have high costs associated with reheating the flue gas in the case of SCR and installing a sp ray tower in the case of LoTOx TM . As mentioned in evaluating TXI #5, there appears to be the potential for some NO x reduction to be occurring from the materials already being fed to this kiln. With other mid-kiln injection in long kilns, NO x reduction has occurred through feeding nitrogen containing sands at mid-kiln. It might be possible to introduce another mate rial high in non-vol atile carbon and/or TKN nitrogen at midkiln to see whether the foregoing explanation for the low NO x from the TXI kilns is valid. Again, this would not be expensiv e as an experimental investig ation. Similar to the TXI wet kilns, for the cost models, it was assumed that one of these experimental techniques could result
in 35% NO x reduction and that the costs would be si milar to the costs of installing SNCR on a utility boiler.

Table 4-1.5. Summary of Modeling Re sults for SNCR on Ellis County Kilns – Performance Results

Existing Unit Control Technology Emissions Rate tpy before Emissions Rate tpy after (a) Controlled Emissions Rate ppm Controlled Emission Rate lb./tonne clinker Control Efficiency % Reduction tpy
Ash Grove #1- wet SNCR 702 537.1 200 3.6 35% 164.9

Ash Grove #2- wet SNCR 750 573.9 200 3.9 35% 176.1

Ash Grove #3- wet SNCR 764 584.6 200 3.9 35% 179.4 TXI #1 and #4–wet (b) SNCR 838 641.2 250 3.7 35% 196.8 TXI #2 and #3–wet (b) SNCR 121 92.6 250 3.7 35% 28.4 TXI#5 – dry SNCR 1710 1,308.4 100 1.0 35% 401.6 Holcim #1 – dry SNCR 2222 1,476.5 190 1.9 50% 745.5 Holcim #2 – dry SNCR 1778 1,181.5 150 1.5 50% 596.5 (a) NO x emission rate after SNCR does not reflect SNCR efficiency reduction due to adju stment by the ozone season factor of 0.671 (NO x reduction is modeled to occu r only during the ozone season). (b) The results for TXI 1 & 4 and #2 & #3 are average per kiln – for example, total emissions re ductions for controlling both T XI #1 & #4 are double the value listed in the table. Models assume mid-kiln firing installe d at TXI as required under current SIP.Cement Kiln Report (FINAL – 7/14/2006) 4-33 Table 4-1.6. Summary of Modeling Results for SNCR on Ellis County Kilns – Economic Results

Existing Unit Control Technology Capital Cost Annual Cost Cost Effectiveness

$/ton NO x Energy Penalty or

Benefit Emissions Penalty or

Benefit Burden Cost $/tonne clinker Ash Grove #1- wet SNCR $1.2 MM $0.4MM $2,500 (a) (b) $1.70 Ash Grove #2- wet SNCR $1.3MM $0.4MM $2,400 (a) (b) $1.70 Ash Grove #3- wet SNCR $1.4MM $0.4MM $2,400 (a) (b) $1.70 TXI #1 and #4–wet (c) SNCR $1.4MM $0.5MM $2,400 (a) (b) $1.60 TXI #2 and #3–wet (c) SNCR $1.4MM $0.3MM $13,000 (a) (b) $5.00 TXI#5 – dry SNCR $2.3MM $1.0MM $2,900 (a) $0.45 Holcim #1 – dry SNCR $2.3MM $1.1MM $1,500 (a) $1.00 Holcim #2 – dry SNCR $2.3MM $1.0MM $1,700 (a) $0.90 (a) SNCR should not have energy impacts. (b) Ammonia slip can be significant for SNCR when not properly optimized. (c) The results for TXI 1 & 4 and #2 & #3 are average per kiln – for example, total capital costs for controlling both TXI #1 & #4 are double the value listed in the table.

4.2 Combustion Optimization

This section of the report is taken from the EPA 2000 Report and is included, with minor editing by the ERG Team. This information is included to provide the Texas environmental communities with the comprehensive background information necessary to understand the parameters that dictate NO x control options at cement kilns. Combustion optimization is largely in place in the Ellis County kilns, with the exception of the TXI wet kilns that are awaiting permits for mid-kiln firing to comply with the requirements of 30 TAC Chapter 117.

Combustion optimization is generally applicable to all types of kilns and is an efficient way to reduce the formation of thermal NO x . The combustion modifications discussed in this section focus on staging the combustion to mini mize combustion at the maximum temperatures. This can be accomplished by modifying the way oxyge n or fuel is provided for combustion. For the purposes of this report, th e level of emissions reduction c ontained in 30 TAC Chapter 117 is the level associated with combustion and proces s optimization. As such, the techniques below have largely been already required and implemented at the Ellis County cement plants. However, the differing performance of the kilns may indicate that more combustion and process optimization could be implemented as part of the effort to reach higher NO x emissions reductions
levels.Cement Kiln Report (FINAL – 7/14/2006) 4-34 4.2.1 Staged Combustion of Air

Staging of combustion air allows combustion of fuel to proceed in two distinct zones. In the first zone, the initial com bustion is conducted in a fuel-ric h, oxygen-poor flame zone. This zone provides the high temperatures necessary fo r completion of the clin kering reactions, but the lack of available oxygen minimizes the formation of thermal and fuel NO x . The lack of sufficient oxygen leads to only pa rtial combustion of the fuel.

In the second, fuel-lean zone, additional (sec ondary) combustion air is added to complete the combustion process. However, the temperatur e in this second zone is much lower than the first zone because of mixing with the cooler secondary air, so the formation of NO x is minimized in spite of the excess av ailable oxygen. This staged approach can be used for combustion of all fossil fuels. Staged combustion is typically ach ieved by using only a part of the combustion air (primary air) for fuel injection in the flame zone , with remaining secondary air being injected in the subsequent cooler zone.

For effective staging of combustion air to reduce NO x emissions, cement plants must
have indirect-fired kilns. In a direct-fired cement kiln, air used for conveying pulverized coal from a coal mill, i.e., primary air, is typically 17 to 20 percent of the total combustion air. The amount of primary air may be reduced by separating the coal mill air from coal. A cement kiln using less than 10 percent of prim ary air is an indirect-fired kil n. Conversion of a direct-fired
kiln to an indirect-fired kiln involves adding particle separation equipment such as a cyclone or a baghouse and a fan to provide the primary air used to transport the powdered coal from storage to the kiln. An indirect-firing system increases overall energy e fficiency by allowing a greater proportion of hot clinker cool er air to be used as secondary combustion air.

4.2.2 Flue Gas Recirculation

In addition to changing the combustion air di stribution, the oxygen c ontent of the primary air may be reduced to produce a fuel-rich combusti on zone by recycling a portion of the flue gas into the primary combustion zone. (44) The recycl ed flue gas may be premixed with the primaryCement Kiln Report (FINAL – 7/14/2006) 4-35 combustion air or may be injected directly into the flame zone. Direct injection allows more precise control of the amount and location of the fl ue gas recirculation (FGR). In order for FGR
to reduce NO x formation, recycled flue gas must enter the flame zone. The FGR also reduces the peak flame temperature by heating the inert combus tion products contained in the recycled flue

gas.

The use of FGR may not be a viable method of reducing NO x in a full-size cement kiln burning zone. FGR’s effectiveness relies on cooling the flame and generating an oxygendeficient (reducing) atmosphere for combustion to reduce NO x formation, conditions that may not be compatible with cement kiln opera tion. High flame temperature and an oxidizing atmosphere are process requirements to produce a qua lity clinker product. A cement kiln differs from a utility boiler and other combustion de vices because minimum temperatures and an oxidizing atmosphere are required to initiate chem ical reactions in a cement kiln in addition to providing the required h eat (Btu/tonne clinker). Reduced flame temperatures and reducing conditions in the burning zone of a cement kiln may not be compatible with the production of cement clinker. (33)

Coupling a low-NO x step burner with flue gas recirculation has been shown to reduce
NO x emissions further in a cement kiln. (45) The additional NO x reduction attributable to FGR was estimated to be about 15 to 38 percent de pending upon the proportion of FGR used. (45) Incorporation of FGR in a cement kiln also re sults in somewhat incr eased power consumption and reduced kiln output.

4.2.3 Low-NO x Burners

Some cement kiln burners, specifically marketed as low- NO x , burners, typically use 5 to 7 percent primary air (46,47) and thus can be us ed only on indirect-fired kiln systems. Low-NO x burners can be installed on any type of kiln. Low-NO x burners are designed to reduce flame turbulence, delay fuel/air mixing, and establis h fuel-rich zones for initial combustion. The longer, less intense flames resulting from the st aged combustion lower flame temperatures and
reduce thermal NO x formation. Some of the burner designs produce a low pressu re zone at the burner center by injecting fuel at high velocitie s along the burner edges. Such a low pressureCement Kiln Report (FINAL – 7/14/2006) 4-36 zone, as shown in Figure 4-2, (46) tends to re circulate hot combustion gas which is retrieved through an internal reverse flow zone around th e extension of the bur ner centerline. The recirculated combustion gas is deficient in oxyge n, thus producing a similar effect as FGR. Combustion of the fuel in the first stage thus ta kes place in an oxygen-deficient zone before the
fuel is diluted in the secondary air. Installi ng such a burner reduces NO x emissions from the kiln-burning zone by up to 30 percent. (46,48,49)

Low- NO x burners have been used by the cement industry for twenty years. (50) Many suppliers offer low-NO x burners and most of these systems focus on lowering the NO x formation in the calciner by air or fuel staging, by reburning, or by high te mperature combustion. (51) Test
data from several different low-NO x burners are now available. Thomsen, Jensen, and Schomburg reported on tests of a F.L. Smidth in-line calciner low-NO x system in a preheater/precalciner kiln where different percenta ges of coal were added to the reduction zone of the precalciner (the remaining coal was added to the oxidizing zone). (51) When 100 percent
of the coal was added to the reduct ion zone of the precalciner, the NO x content at the preheater exit was reduced by 44 percent relative to wh en zero coal was added (see Table 4-2.1).

Table 4-2.1. NO x Emissions from a Precalciner E quipped with a Low-NOx Burner

Percent Coal Added to Reduction Zone a (lb. NO x /tonne clinker) Nox Emissions b (lb. NO x /tonne clinker) Percent Reduction c (%) 0 2.8 - 50 1.9 31 100 1.6 44

a The remaining percentage of the coal was added to the oxidizing zone. b Emission measurements were taken at the preheater exit.

c Percent reductions are relative to emissions wh en zero percent of the coal was added; the original measurements were in kg NO x /tonne clinker to the hundredth place - the percent reductions were calculated using the original measurements, which results in slightly different values than when lb. NO x /tonne clinker are used.

Steinbiß, Bauer, and Breidenstein reported em issions changes for five kilns before and after the installation of Pyro-Jet low-NO x burners (see Table 4-2.2) . (50) The emission reductions ranged from 15 to 33 percent. Information on kiln-type was not provided.Cement Kiln Report (FINAL – 7/14/2006) 4-37 Table 4-2.2. NO x Emissions Before and After In stallation of Pyro-Jet Low-NO x Burners

Kiln Before Installation (ppm) After Installation (ppm) Percent Reduction (%) A 970 650 33 B not given not given 30 C 650 460 29 D 900 730 19 E not given not given 15

There are two new data sources on emissi ons reductions from the use of Rotaflam ® lowNO x burners. The Pillard Combustion Equipment and Control Systems published data on four kilns, comparing NO x emissions with a 3 channel burne r to emissions when a Rotaflam ® burner was used (see Table 4-2.3). (52) The emissi on reductions ranged from 23 to 47 percent. Information on kiln-type was not provided.

Table 4-2.3. NO x Emissions with 3 Channel and Rotaflam ® Low-NO x Burners

Kiln With 3 Channel Burner (ppm) With Rotaflam ® Burner (ppm) Percent Reduction (%) A 774 409 47 B 865 664 23 C 484 350 28 D 487 336 31

Emissions data are also availa ble before and after a Rotaflam ® low-NO x burner was installed on a long-wet kiln (see Table 4-2.4). (53) The average emissions decreased 14 percent.

Table 4-2.4. Emissions Before and A fter Installation of a Rotaflam ® Burner on a Wet Kiln

Year Average Emissions (lb. NO x /tonne clinker) Percent Reduction a (%) 1990 277 - 1992 b 288 - 1993 269 - 1994 275 - 1995 (Rotaflam ® installed) 239 14

a Percent reduction is relative to the 1990, 1992-1994 average NO x emissions, 277.25 lb. NOx/hr. b 1991 data were not provided

.Cement Kiln Report (FINAL – 7/14/2006) 4-38 The Fuller Company low NO x In-Line Calciner was installed in an RMC Lonestar kiln, which reported 30-40 percent reductions in the amount of thermally formed NO x after installation. (54)

In January 2000, the PCA provided results of a survey of cement facilities where the respondents indicated 14% of the operating U.S. kilns (22 kilns) have already installed a lowNO x burner (81% of the facilities representing 81% of the operating U.S. kilns responded to the survey). The remaining 139 kilns that are represented by the surv ey have not installed low- NO x burners. (55,56)

4.2.4 Staged Combustion of Fuel

In conventional long (wet or dry) rotary k ilns, all heat required for the cement-making process is supplied in the primary kiln burning zo ne, where the combustion occurs at the hottest temperature in the kiln. In the cement-making pr ocess, the preheating a nd calcination of the raw materials requires a large amount of heat but are typically at a temperature of 600 to 900°C (1,100 to 1,650 °F) which is much lower than th e kiln’s clinker-burning temperature of 1,200 to 1480 °C (2,200 to 2,700 °F). (57) In the second ary combustion method, part of the fuel is burned at a much lower temperature in a second ary firing zone to complete the preheating and
calcination of the raw materials.

4.2.5 Preheater/Precalciner and Tire Derived Fuel

This concept of a secondary firing zone is the basis of the preheater/precalciner cement kiln design. Almost all new cement kilns have a preheater/precalciner-type design. In the preheater kilns, the primary emphasis is on efficien t heat recovery from kiln exhaust gases (see Figure 4-4.1). (58) However, up to 15 to 20 percen t of the fuel may be fired in the riser duct in preheater designs. (58)

Precalciner systems typically employ a tower of four-stage cyclones for efficient gassolids contact, which improves the energy efficien cy of the overall process (see Figure 4-4.2).Cement Kiln Report (FINAL – 7/14/2006) 4-39 (58) In a typical precalciner kiln almost 40 to 50 percent of the fuel is burned at a lower (calcination) temperature wh ich reduces the thermal NO x formation considerably.

Figure 4-2.1. Schematic of Preheater (58) Figure 4-2.2. Schematic of Precalciner(58)

Tire-derived fuel can also be added to the f eed end of a preheater or precalciner kiln. The Mitsubishi Cement Company’s Cushenbury Plan t in Lucerne Valley, CA began using whole waste tires as a fuel supplement in 1993. The wa ste tires are delivered in enclosed container trucks and dumped into the plant’s automa ted handling system. A live bottom hopper and singulator place the waste tires on a conveyor system . This conveyor system transports the tires to the feed end of the kiln and drops the tire into an airlock system that allows the waste tire to fall onto the feed plate inside the kiln at a rate of five to six tires per minute.

Currently, 8,000 to 9,000 tires are burned per da y, totaling about 13 percent of the fuel. Tires have a fuel content of approximately 14,000 Bt u/lb. and a sulfur cont ent that is roughly the
same as the coal that would be used. The st eel belting in the waste ti res supplements the iron requirements and approximately two percent of the iron in the final product comes from the tires.
The addition of waste tires reduces NO x emissions from the kiln by 30 to 40 percent, and there is no significant change in toxic, hyd rocarbon, or metal emissions. (59,60,61)Cement Kiln Report (FINAL – 7/14/2006) 4-40 4.2.6 Low- NO x Precalciners

Most of the major cement kiln suppliers are now offering “low NO x ” precalciner designs for new kilns. These designs typically inject a por tion of the fuel into the feed end of the kiln, countercurrent to the exhaust gas flow.(62) Th is fuel is burned in a substoichiometric O 2 environment to create a strongl y reducing atmosphere (relativel y high concentrations of CO) by following the simplified reactions:

NO + C → N + CO
and
NO + CO → N + CO 2

This reducing atmosphere inhi bits the formation of fuel NO x and destroys a portion of the
NO x formed in the kiln burning zone. In some de signs, additional fuel is then added, again with
insufficient O 2 for complete combustion, to create anot her reducing zone. Several precalciner kilns in the US have recently be en retrofitted with these “low NO x ” precalciners and preliminary
information indicates a noticeable reduction in NO x per ton of clinker. (33) Up to 46 percent
reduction of NO x emissions has been reported without cau sing excessive coating difficulties in the kiln. (62)

Nitrogen present in the fuel may also participate in the reduction of NO x . The primary
NO x formation mechanism in the secondary firing is the fuel NO x formation that depends upon the nitrogen content of the fuel used. In order for the above re actions to proceed at reasonable rates the temperature in the reduction zone should be maintained between 1000 and 1200°C (1830 to 2190°F). These temperatures may lead to coating difficulties, particularly if the fuel used is coal with high ash content. (63)

It is not possible to use “staged combustion” on preheater kilns that are firing fuel in the riser since in staged combustion it is necessary to add the fuel in an oxygen deficient atmosphere and then supply additional combustion air to full y combust the fuel. Preheater kilns do not have tertiary air ducts to supply the additional co mbustion air. The air for combustion of theCement Kiln Report (FINAL – 7/14/2006) 4-41 secondary fuel must come through the kiln, whic h precludes introducing th e secondary fuel into an atmosphere with insufficient oxygen for complete combustion. (33)

Emissions reductions have also been f ound when tire derived fuel was burned in a precalciner. In one case, when 47 percent of the coal fired in th e calciner was substituted with tire-derived-fuel, a reduction in NO x emissions of about 29 percent was observed. (64)

4.2.7 Mid-Kiln Firing

The concept of staged combustion of fuels may also be used in conventional wet and long-dry kilns by injecting solid fuel into the calcining zone of a rotating long kiln using a specially designed feed injection mechanism. ( 65) This system is known as mid-kiln firing (MKF) and allows part of the fuel to be burne d at a material calcinati on temperature of 600 to 900°C (1100 to 1650°F) which is much lower than the clinker burning te mperature of 1200 to 1480°C (2200 to 2700°F). (57)

To maintain continuity in the heat input, so lid and slow burning fuel s (such as tires) are most amenable for MKF. The Cadence feed fork MKF technology was first introduced in 1989. It can be installed during an annual maintenan ce shutdown. It is comprised of three primary components: (1) a staging arm or ‘feed fork’ that picks up the fuel modules and positions them for entry into the kiln, (2) two pivoting doors that open to allow the fuel modules to drop into the kiln, and (3) a drop tube that exte nds through the side wall of the kiln. In addition to these basic components, feed fork technology also require s a delivery system, which positions the fuel modules so they can be picked up by the feed fo rk and a mechanism for opening the doors so the fuel modules can enter the kiln. (66) Due to th e rotation of the kiln, fu el can be conveniently injected only once per revolution from the top.

Although most feed forks today are dedicated to whole tires, one facility uses baled industrial waste as a fuel, and many others are in vestigating a variety of energy containing waste materials from carpet scrap to pharmaceutical wast e. These energy-bearing waste materials can
be containerized or dimensionalized into discrete fuel modules to be fed to the kiln using the feed fork. (66)Cement Kiln Report (FINAL – 7/14/2006) 4-42 Inserting whole tires into mid-kiln locations can give precalciner stabil ity to the kiln. The operators have two points of cont rol to assist in stabilizing ki ln operation. Tires burn for 15 to 20 minutes within the kiln after entry. This is de duced from observations of the rate of change in kiln exit oxygen levels af ter entry of tires begins. With proper instrumentation, control of the kiln can be improved by adding solid fuels midkiln. (67)

Mid-kiln firing of tires or other waste- derived fuels does not reduce the final product quality; in fact, many of Cadence’s cement kiln partners have reported an improvement in the clinker burnability and mineralogy. The enhanced control has shown to impart better formation
of clinker. Reductions in cement fineness have been shown while maintaining similar seven-day strengths. Several facilities also have reported an extended life of the re fractory in the burn zone. (66,67)

By adding fuel in the main flame at mid- kiln, MKF changes both the flame temperature and flame length. These changes may reduce thermal NO x formation by burning part of the fuel at a lower temperature and by cr eating reducing conditions at th e solid waste in jection point, which may destroy some of the NO x , formed upstream in the kiln burning zone. MKF may also produce additional fuel NO x depending upon the nitrogen content of the fuel. (68) However, as discussed in section 5.1.3, fuel NO x is unimportant relative to thermal NO x formation. Additionally the discontinuous fuel feed from MFK can result in increased CO emissions especially if hazardous wastes ar e used. To control CO emissions, the kiln may have to have increased combustion air, which can d ecrease production capacity. (69)

According to literature from Cadence, in tests of its feed fork technology, one kiln
reduced NO x emissions by 38%, overall particulate emissions by 14%, metal emissions by 30%,
SO 2 emissions by 36%, and net emissions of all hydrocarbons by 29%. (66,67) In the research conducted for this report, test data were compile d for seven dry kilns an d three wet kilns with MKF technology. In nine tests on the dr y kilns, the average reduction in NO x emissions was 33%, with a range from 11% to 55%. In three te sts on the wet kilns, the average reduction in
NO x emissions was 40%, with a range from 28% to 59% (see Table 4-8). (69,70,71,72,73) ItCement Kiln Report (FINAL – 7/14/2006) 4-43 should be noted that the three kilns that ar e known to have CEMS all reported emissions reductions of 45 percent or more.

Table 4-2.5. Emissions From Kilns With Mid-Kiln Firing

Emissions (lb. NO x /tonne clinker) Percent Reduction (%) Emissions Based on CEMS Data Dry Kilns a A 40 not given 13.6 unknown B 40 not given 11.1 unknown C 24,44 not given 45.1 yes C 40 not given 55.3 yes D 21,41 2.7 not given unknown E 22,42 10.2 13.9 unknown F 40 not given 46.6 unknown F 40 not given 50.4 unknown F 40 not given 28.3 unknown Average (Dry Kilns) 6.4 33.3 Wet Kilns G 23,43 not given 59.0 yes H 40 not given 35.0 unknown I 40 not given 27.6 unknown Average (Wet Kilns) n/a 40.5 Average (Dry & Wet Kilns) 6.4 35.1

a There was more than one test at some kilns.

Waste-derived fuels with high heating values represent an economical source of energy for the cement industry and its consumption ha s been increasing duri ng the past decade. 12 Midkiln firing is a proven techno logy and so far at least 21 long k ilns in the U.S. and nearly 40
kilns worldwide have been modified to allow mi d-kiln firing of solid and hazardous waste. (66,74)

4.3 Lower Temperature Oxidation Based Technologies

Oxidation technologies were not evaluate d in the EPA 2000 Report. One of these technologies, LoTOx TM , is currently being installed in refi neries at fluidize d catalytic cracking units (FCCUs). The temperatures, gas flow rates and other characteristics of FCCUs are similarCement Kiln Report (FINAL – 7/14/2006) 4-44 enough to cement plants that these technologi es should be considered as candidates for evaluation as transferable technologies to application at cement kilns.

4.3.1 Introduction

Oxidation technologies for flue gas NO x control developed in recent years have become commercially successful and economi cally viable as an alternative to ammonia and urea based technologies using reduction chemistry to remove NO x . Commercially available technologies such as Selective Catalytic Reduction (SCR) and Selective Non-Catalytic Reduction (SNCR),
which reduce NO x to nitrogen using ammonia or urea as an active chemical are optimized to specific temperature windows and have similar reagent costs for the varying ammonia based reagents. Oxidation technologies can work in other temperature regimes and use different reagents that are not linked to ammonia costs an d, thereby, provide import ant control options to
ammonia-based NO x reduction technologies.

Oxidation technologies convert lower nitrogen oxides such as nitric oxide (NO) and nitrogen dioxide (NO 2 ) to higher nitrogen oxides such as nitrogen sesquioxide (N 2 O 3 ) and nitrogen pentoxide (N 2 O 5 ). These higher nitrogen oxides are highly water soluble and are efficiently scrubbed out with water as nitric and nitrous acids or w ith caustic solution as nitrite or
nitrate salts. NO x removal in excess of 90% has been achieved using oxidation technology on
NO x sources with high sulfur content, acid gases, high particulates and processes with highly
variable load conditions. Genera lly these technologies work at relatively low temperatures (100- 950oF) and some of these technol ogies are likely most cost ef fective for use on plants with existing scrubbers. But may also prove to be cost effective options due to their potential application in lower temperature windows whic h can avoid expensive options like gas reheat. These technologies are used for NO x control for a variety of NO x emission sources but are not
known to have been used to date on a cement kiln.

4.3.2 LoTOx TM

General description. The LoTOx TM System uses ozone as the oxidizing agent, which selectively oxidizes relatively insoluble NO x to higher oxides of n itrogen. These higher oxidesCement Kiln Report (FINAL – 7/14/2006) 4-45 are readily soluble and easily removed in a wet scrubber. The patented system, which can be
installed as a stand-alone or retrofit design, provides suffici ent residence time under maximum load conditions to allow complete reaction of the ozone. The system's small and adaptable footprint, as well as its ability to produce ozone on demand, provides control of the installation to
maximize NO x control and minimize capital a nd operating costs. The LoTOx TM System is very
selective for NO x removal, oxidizing only the NO x and therefore efficiently using the treatment chemical, ozone, without causing any significant SO x oxidation and without affecting the performance of the downstream SO x scrubber.

Figure 4-3.1. is an overall process diagram of the LoTOx TM System.

Figure 4-3.1. Overall Process Diagram of the LoTOx TM System

Figure 4-3.2. provides anot her example of a LoTOx TM system where the ozone injection
is included in the scrubber.Cement Kiln Report (FINAL – 7/14/2006) 4-46 Figure 4-3.2. EDV Wet Scrubbing System with LoTOx TM Injection

Potential applicability . The large gas volumes, high moisture levels and large quantities of dilution air needed to reach the operating temperature range in some systems may limit the applicability of the LoTOx TM system.

Advantages . Table 4-3.1 provides an overview comparing the LoTOx TM process with SNCR and SCR technologies.Cement Kiln Report (FINAL – 7/14/2006) 4-47 Table 4-3.1. Comparison Of Common Post Combustion NO x Abatement Technologies For NO x Emissions Control

SNCR SCR LoTOx TM

Mode of Treatment Reduction Reduction Oxidation Active Chemical NH 3 / Urea NH 3 / Urea Ozone Gas Temperature Required °F 1650 - 2000 500 - 900 150 – 250

Pressure Required, psig 0+ 0++ 0+ Placement in Exhaust System Near Combustion Chamber Between Air Pre-Heater and Economizer (boiler) Tail End

Catalyst Bed No Yes No Gas Phase Reaction Duct Yes No Yes Scrubber Optional Optional Yes
NO x Reduction Achieved 40 - 70 Percent 60 - 95 Percent 90 - 95 Percent Slip of Active Agent NH 3 – Yes NH 3 - Yes Ozone - No CO Emissions After Treatment May Increase May Increase No Effect

SO x Emissions After Treatment Little Effect – Maybe H 2 S Little Effect - Maybe H 2 S No Effect or Significantly Reduced Gas Temperature Outside Operating Range - Overshoot More NO x Emissions Through NH 3 Oxidation More NO x Emissions Through NH 3 Oxidation, Ammonia Slip Increased O 3 Consumption for the Time Period of Overshoot Gas Temperature Outside Operating Range - Undershoot More NO x Emissions Through Reduced Reduction by NH 3 More NO x Emissions Through Reduced Reduction by NH 3 , Ammonia Slip No Effect

An additional advantage is the control of SO x emissions that would likely be achieved if
the LoTOx TM system were added to any system that currently does not have a wet scrubber if joint control of SO x and NO x is required. Lower cost spray towers that do not appreciably control
SO x can be installed at lower cost than flue gas desulfurization scrubbers. The cost models for application of LoTOx TM at wet kilns are based on installi ng simple spray towers that do not
control SO x .

Disadvantages

. It is likely that for most applications, the LoTOx TM option would be an add-on to existing APCD systems. Because of high electrical power usage, costs are reported to be high. Electricity and oxygen costs alone are estimated to be grea ter than $1,600/ton of NO x controlled.Cement Kiln Report (FINAL – 7/14/2006) 4-48 Additional nitrate captured in the existing sulfate scrubber co uld impact the quality of the plant’s artificial gypsum although, with a typical dewatering sy stem, this should not be a problem because of the much higher solubility of the nitrates relative to sulfates. High nitrate wastewater could be used by local farmers as fertilizer or could be used at the plant to fertilize grass areas as well as water/fertilize in quarry reclamation areas. Lowering the exit gas temperature and adding moisture may result in problems with condensation in the stack.

Emissions performance . There are three primary process variables which impact the
NO x control capabilities of the LoTOx TM process: temperature of the flue gas (T), residence time of the flue gas in the reactor duct (RT) and amount of ozone (O 3 Factor) injected into the reactor
duct. Based on the results of LoTOx TM demonstration testing, th e most efficient control parameters for a full scale system on the Quemet co, Inc., furnace are a temperature of 175 °F or less, a residence time of four seconds, and an ozone injection factor of 80 to 90. The O 3 Factor represents the O 3 to NO x ratio at the inlet to the reacti on duct. The presen ted data uses O 3 Factor for the sake of clarity and to provide meaningful data while maintaining confidentiality of proprietary intellectual information. Figure 4-3.3. depicts the performa nce conditions of the
LoTOx TM process for the design conditions of RT = 4 seconds, T = 175 °F and O 3 Factor = 70 to 90. Under these design conditions the NO x removal achieved ranges from 80 percent at an O 3 Factor of 70 to 95 percent at an O 3 Factor of 90.

This technology should be considered transfer able in nature. It has not been used on a cement kiln but it has been used on similar larg e sources. Discussions with this technology’s vendors reveals that existing SO x and CO levels at the cement plan ts in Midlothian should not be
a factor in the use of this tec hnology. Applications or tests have already been performed at CO
and SO x levels well above those seen in any of these cement plants.Cement Kiln Report (FINAL – 7/14/2006) 4-49 Figure 4-3.3. Ideal Opera ting Conditions for NO x Removal from 80% to 95%

Cost

. Ohio Coal Development Office (OCDO) provided 65 percent of the capital to install a $6.3 million LoTOx TM unit at the Medical College of Ohio. The project includes two processes: LoTOx TM for NO x and particulate material cont rol and Rapid Absorption Process (RAP, another BOC licensed process) for sulfur dioxide control. The controls are for 25 megawatt capacity boilers burning Ohio coal cont aining 3 percent sulfur. According to the BOC Company literature, the unit is designed to remove about 90 percent of the NO x in emission gases. The RAP process uses a slurry of lim e injected into the flue gas to capture SO 2 and a fabric filter (baghouse) to remove the calcium su lfate particles. Cost effectiveness has been estimated to be in the range of $1,700 to $1,950 per ton NO x removed. (54)

In June 2001, BOC announced that they had installed, started up and commissioned a
LoTOx TM unit at J & L Specialty Steel’s Midland, PA plant. Details of the installation are notCement Kiln Report (FINAL – 7/14/2006) 4-50 published in any detail. However, Robert Ferrell, BOC Vice President of Business Development, said, “We were able to modify the system to achieve a higher level of control than was originally anticipated. We have been able to reduce NO x emissions by more than 95 percent.” No costs or capac ity numbers were available.

A subsequent search of EPA’s RBLC27 Database indicates that at le ast two other plants in the U.S. are using (or are planning to use) BOC’s LoTOx TM process in their facilities. These plants are Lion Oil Company in El Dorado, AR and Marathon-Ashland Oil in Texas City, TX. Both plants use (or will use) the LoTOx TM on their Fluidized-Bed Catalytic Cracking Units (FCCU) for NO x control. Operating conditions and pe rformance results ar e not available.

Another article, written by a BOC employ ee, stated, “The capital (recovery) and operating costs for the (LoTOx TM ) system have been evaluated for various system sizes and (they) fall well within the costs per ton of NO x removed typical for post-combustion treatment technologies in non-utility applica tions.” Unfortunately, this info rmation is not very helpful for determining cost for the cement industry sin ce a paper published by NESCAUM gives the cost effectiveness range for NO x removal from $390 to $5,450 per ton NO x . Cost effectiveness is heavily dependent on each individu al facility’s situation. This includes their existing control equipment, extent of modifications necessary to install new control equipment, and the degree of DRE required to achieve the desired results.

Based on the data available, capital costs for adding LoTOx TM to a system that does not
have a wet scrubber such as the wet kilns in Midlot hian are likely to be much more costly than the kilns that already have wet scrubbers. Vendor information was used to calculate costs associated with the application of LoTOx TM to the cement plants in Midlothian. Estimated costs associated with the precalciner kilns which already have scrubber systems in place are $2,300- $2,600/ton of NO x controlled. Estimated costs associated with the wet kilns which do not have scrubber systems in plac e are $3,000-$3,700/ton of NO x controlled. The costs for the wet kilns include installation of a spray tower to remove the soluble NO x oxidation products produced by
the LoTOx TM system. (74a, 74b, 74c, 74d, 74e, 74f, 74g, 74h, 74i, 74j, 74k, 74l, 74m, 74n)Cement Kiln Report (FINAL – 7/14/2006) 4-51 4.3.3 Hydrogen Peroxide

General description

. There are several methods for controlling NO x emissions. Gas scrubbing is one of the mo st common forms of NO x treatment, with sodium hydroxide being the conventional scrubbing medium. However, the absorbed NO x is converted to nitrite and nitrate, which may present wastewater disposal prob lems. Scrubbing solutions containing hydrogen peroxide are also e ffective at removing NO x , and can afford benefits not available with NaOH. For example, H 2 O 2 adds no contaminants to the scrubbing solution and so allows commercial products to be recovered from the pr ocess, e.g., nitric acid or nitrat e salts (for use as fertilizer). In its simplest application, H 2 O 2 (0.5-1 wt.%) and nitric acid ( 35-45 wt.%) are used to scrub both nitric oxide (NO) a nd nitrogen dioxide (NO 2 ) -- the chief components of NO x from many
industrial sources. The reactions are rapid at moderate temperatur es (30-80 °C), with about 1.7
and 0.37 lb. H 2 O 2 required per lb. NO and NO 2 , respectively. The ch emistry controlling the process is outlined below:

3NO 2 + H 2 O < == > 2HNO 3 + NO
NO + HNO 3 + H 2 O ----> 3HNO 2 HNO 2 + H 2 O 2 ----> HNO 3 + H 2 O

There are several other processes that also use hydrogen peroxide to remove NO x . The Kanto Denka process employs a scrubbing solu tion containing 0.2% hydrogen peroxide and 10% nitric acid while the Nikon process uses a 10% sodium hydroxide solution containing 3.5% hydrogen peroxide. A fourth proce ss, the Ozawa process, scrubs NO x by spraying a hydrogen peroxide solution into the exhaus t gas stream. The liquid is then separated from the gas stream,
and the nitric acid formed is neutralized with potassium hydroxide. The excess potassium nitrate is crystallized out, and the solution reused afte r recharging with hydrogen. In addition to the
methods cited above in which NO x is oxidized to nitric acid or ni trate salts, a series of Japanese patents describe processes and equipment for reducing NO x to nitrogen using hydrogen peroxide and ammonia. The processes are efficient but must be carried out at higher temperatures than the processes cited earlier.Cement Kiln Report (FINAL – 7/14/2006) 4-52 The injection of hydrogen peroxide (H 2 O 2 ) into hot flue gases to prevent emissions of nitrogen oxides (NO x ) has been demonstrated at the pi lot scale at a bo iler at Kennedy Space Center (KSC). That project was an outgrowth of research funded by the Gulf Coast Hazardous Substance Research Center from the years 1993-1996. The H 2 O 2 is injected into hot boiler flue gases to oxidize the NO into NO 2 , HNO 2 and HNO 3, which can then be removed in a wet or dry scrubber (see Figure 4-3.4). (74o)

Figure 4-3.4. Conceptual Design of Hydrogen Peroxide NO x Control System

In one of several sets of experiments to demonstrate the feasibili ty of the method, the optimum temperature for conversion of NO to HNO 2 , HNO 3 , and NO 2 by use of injected H 2 O 2 was found to be about 5 00 °C (see Figure 4-3.5).Cement Kiln Report (FINAL – 7/14/2006) 4-53 The conversion of NO by oxidation to other sp ecies was measured as a function of reactor temperature. The reactor inlet co nditions for the points shown he re were 400 ppm NO and 400 ppm H 2 O 2 for a molar ratio of 1:1.
Figure 4-3.5. Effect of Temperature on Peroxide Oxidation of NO

In a study performed under guidelines of the EPA, EPRI compared the economics of SCR and the experimental H 2 O 2 -injection/scrubbing method for a design base case and a variety
of alternative cases. This st udy illustrated the tradeoff between capital and operating costs for the two methods. The single largest factor in determining the total cost of one method relative to
the other method was found to be the H 2 O 2 :NO molar ratio. At the H 2 O 2 :NO molar ratio of 1.92, which was previously demonstrat ed in the laboratory, the H 2 O 2 -injection/scrubbing method was shown to be uneconomical. However, it was also concluded that the molar ratio in a full-size coal-fired power plant could be lower than that found in the laboratory, a nd that on the basis of all the assumptions of the study, at an H 2 O 2 :NO molar ratio of 1.37, the H 2 O 2 injection/scrubbing method could be an economically feasible alternative to SCR.

Pilot-scale tests run at Kennedy Space Ce nter demonstrated the feasibility and competitiveness of this new technology. The H 2 O 2 to NO molar ratio, at 500 °C shown to achieve a NO conversion efficiency of greater than 90 percent was 1:1, which is significantly lower than the required 1.37: 1 (See Figure 4-3.6). (74l)Cement Kiln Report (FINAL – 7/14/2006) 4-54 The outlet concentration of the O was significantly reduced when the H 2 O 2 was injected. At 500 °C, 400 ppm NO, and various inlet concentrations of H 2 O 2 (represented as the molar ratios), 90 percent conversion of NO was achieved at the r eactor outlet for a mo lar ration of 1:1.
Figure 4-3.6. Effect of Molar Rati o on Peroxide Oxidation of NO

Potential applicability

. This option is a solution that may have particular applicability to kilns with existing scrubber systems. Data suggests it may work over a wide range of temperatures depending on the specific version of this technology that is implemented. For the high temperature version of this process, in jection of the hydrogen peroxide into the upper portion of the preheater tower of a precalciner kiln at the appropriate temperature may be possible.

Advantages

. The biggest advantage of this tech nology may be a relatively low capital investment for plants with existing scrubbers . An additional advantag e is that there are indications that hydrogen peroxide based scrubbers may also enhance SO x scrubbing and may lower hydrocarbon emission depending on the oper ating temperature, reagent system and retention time of the system.

An additional advantage of this technology is that it operates in a unique temperature window that is slightly below the temperat ures commonly used for SCR. The optimal technology for any specific cement kiln process ma y be the technology that installs best in theCement Kiln Report (FINAL – 7/14/2006) 4-55 existing temperature windows of the process with the least potential adverse impact on downstream processes and equipment. Prices of ammonia-based re agents fluctuate with natural gas prices and are currently rela tively high. Cement plants may elect to use more than one NO x control technology to take advantag e of changes in the market fo r reagents. Hydrogen peroxide currently appears to be a more cost eff ective reagent than ammonia-based reagents.

Disadvantages

. For plants without scrubbers, add on systems are required. An additional factor is that the cost of hydrogen peroxide has risen significantly in r ecent years with increased natural gas prices and fluctuating supplies. H ydrogen peroxide has become a major commodity chemical as a bleaching agent for paper producti on free of chlorine. Recent production capacity increases appear to be stabilizing prices.

Additional nitrate captured in the existing sulfate scrubber co uld impact the quality of the plant’s artificial gypsum although, with a typical dewatering sy stem, this should not be a problem because of the much higher solubility of the nitrates relative to sulfates. High nitrate wastewater could be used by local farmers as fertilizer or could be used at the plant to fertilize grass areas as well as water/fertilize in quarry reclamation areas.

Emissions performance

. At 500 °C and with a molar ratio of 1:1 H 2 O 2 /NO x removal efficiencies of greater than 80% appear to be achievable. Scr ubber efficiency data for the wet low temperature process was not available. Eith er of these technologies should be considered investigative in nature. Appli cation of this technology would cl early be an innovative approach that does not have a history of commercial application comp ared to SCR, SNCR or LoTOx TM

. Testing in a cement plant appli cation would clearly be required to determine performance and process impacts.

Cost

. Assuming a cost of $0.50/lb. of hydrogen pe roxide the reagent cost would be approximately $739/ton of NO 2 removed (depending on the existi ng oxidation state of the NO in the system). This might be offset to some exte nt by the sale of solutions of nitrate salts as fertilizer. This cost appears to be favorable relative to the el ectrical and oxygen costs of the
LoTOx TM that exceed $1,600/ton of NO x controlled. It is also favor able to the current ammonia cost of about $1,200/ton of NO x controlled using SNCR.Cement Kiln Report (FINAL – 7/14/2006) 4-56 4.3.4 OXONE (Dupont – potassium monopersulfate)

General description

. Scrubbing with strong aqueous oxidants promises to be less expensive than competing post-combustion methods for NO x removal such as selective catalytic reduction (SCR) and thermal NO x removal. The goal of a project by Yusuf G. Adewuyi at North Carolina A&T State University is to develop an innovative and cost-effective aqueous scrubber
for the simultaneous removal and destruction of oxides using strong oxidi zing agents such as oxone. Oxone (2KHSO 5 .KHSO 4 .K 2 SO 4 ) is a triple salt of potassium and may be regarded as a mono-substituted derivative of hydrogen peroxide. However, it has an oxida tion potential greater than that of hydrogen peroxide (E HSO 5 - /HSO 4 - = 1.82 eV compared to E H 2 O 2 /H 2 O = 1.77 eV). The aqueous absorption and kinetics of oxidation of nitrogen oxides (NO x ) and SO 2 by OXONE in a bubble column operated as batch or continu ous OXONE was presented at an AIChE meeting in October of 2005. Table 4-3.2 provides a breakdow n of the chemical constituents of the Oxone reagent. (74p)

Table 4-3.2. Oxone Constituents

Material CAS Number % "Oxone" Monopersulfate Compound 70693-62-8 Potassium Peroxymonosulphate 10058-23-8 34-43 Potassium Bisulfate 7646-93-7 18-23 Potassium Sulfate 7778-80-5 23-29 Potassium Peroxydisulfate 7727-21-1 2-3 Sodium Carbonate 497-19-8 0-20 Magnesium Carbonate 546-93-0 1-2Cement Kiln Report (FINAL – 7/14/2006) 4-57 Potential applicability . Applicability is similar to the wet low temperature hydrogen peroxide option.

Advantages . Advantages are similar to the hyd rogen peroxide option. Costs may be
lower.

Disadvantages . This is an experimental technol ogy. Additional nitrate captured in the existing sulfate scrubber could impact the quality of the plant’s artificial gypsum although with a typical dewatering system this should not be a pr oblem because of the much higher solubility of the nitrates relative to sulfates. High nitrat e wastewater could be used by local farmers as
fertilizer or could be used at th e plant to fertilize grass areas as well as water/fertilize in quarry
reclamation areas.

Emissions performance . As an experimental technology performance is not clear but is likely to be similar to the hydr ogen peroxide technology. This te chnology should be considered investigative in nature.

Cost . Oxone is a commercial product manuf actured by Dupont. Inquiries to Dupont about cost have not been responded to at this time.

4.3.5 Sodium Acetate Process

General description . This process involves absorpti on and subsequent reaction of NO x in the aqueous phase. Direct absorption i nvolves a reaction chain that achieves both SO x and
NO x removal. One form involves an SO 2 reaction step, a subsequent NO reaction, and a termination step that produces gypsum. Table 4-3.3 shows the different steps involved in the

process.Cement Kiln Report (FINAL – 7/14/2006) 4-58 Table 4-3.3. Reaction Steps and Pathway Eq uations for the Sodium Acetate Direct Absorption Process For Simultaneous NO x And SO x Removal (OECD, 1983).

Absorption and Gypsum Formation Absorption SO 2 + 2CH 3 COONa + H 2 O →

 Na 2 SO 3 + 2CH 3 COOH 2NO + 5Na 2 SO 3 + 4CH 3 COOH →

 2NH(NaSO 3 ) 2 + Na 2 SO 4 + 4CH 3 COONa + H 2 O Gypsum formation Na 2 SO 4 + Ca(OH) 2 +2CH 3 COOH →

 CaSO 4 .2H 2 O + 2CH 3 COONa Imide Treatment Step Hydrolysis NH(NaSO 3 ) 2 + 2H 2 O → NH 4 HSO 4 + Na 2 SO 4 Release of NH 3 NH 4 HSO 4 + Ca(OH) 2 →

 NH 3 + CaSO 4 _2H 2 O Nitrogen gas formation 4NH 3 + 3O 2 →

 2N 2 + 6H 2 O

Potential applicability. Applicability is likely to be si milar to the wet low temperature hydrogen peroxide process.

Advantages

. The advantage of this process is its ability to eliminate gaseous NO x and
SO x simultaneously. For plants with existing SO x scrubbers the application may be as simple as adding selected reagents to the recirculating scrubber solution and subsequent scrubber treatment tanks. For plants with cooling towers the opti on of adding the reagents to the cooling tower water feed may be functional.

Disadvantages

. SO x is required in adequate quantities to maintain the chain-reaction mechanism. Also, this process turns an air- pollution problem into a wastewater problem. Additional nitrate captured in the existing sulfate scrubber could impact the quality of the plant’s artificial gypsum although with a typical dewateri ng system this should not be a problem because of the much higher solubility of the nitrates rela tive to sulfates. High nitrate wastewater could be used by local farmers as fertilizer or could be used at the plant to fertilize grass areas as well as water/fertilize in quarry reclamation areas.Cement Kiln Report (FINAL – 7/14/2006) 4-59 Emissions performance

. Unknown. Data for applicati on of this technology to cement
kilns and similar emission sources was not found in the literature. Th is technology should be considered investigative in nature.

Cost . Costs are not clear at this time but may be lower than the hydrogen peroxide option.

4.3.6 Potential Applicability of Oxidation Technology to Ash Grove Plant

General Discussion

. The Ash Grove plant has three wet process kilns without any existing wet scrubber system. That would requir e them to place a complete oxidation system in place as an add-on technology including the scrubber or alternatively just a spray tower after the existing ESPs. Assuming that all of the available options would have a similar capital cost for a spray tower/scrubber system careful evaluation of the alternative reagent systems is warranted.

A trial system for evaluating the reagent sy stems may be warranted. As an example, three one-month trials using alternative reagents in a skid-mounted scrubber could be performed prior to scaling up to a full system. It may be possible to combine the gas flows from the three kiln systems into a single flow to minimize the cost of the scrubber system.

Because of the high moisture levels in the gasses from wet kilns it may be necessary to bypass a portion of the stack gasses around the spray tower/scrubber for use as reheat gas after the spray tower/scrubber to prev ent condensation problems in the st ack. To the extent that such a strategy is required the efficiency of the NO x removal would be proportionately impacted.

Conclusions . SCR at the Ellis County wet kilns would require reheat of the exhaust gas. This suggests that further investigation of the oxidation technologies is likely to be a cost effective option. As these technologies would requ ire a scrubber, consideration of the benefits of
control of sulfur oxides should also be consid ered in evaluating scrubber options. The cost modeling for oxidation technologies is based on a simple spray towe r that does not control sulfur oxides. However, additional air quality benefits, including reduction in fine PM precursors
would occur should a source choose to install flue gas desulfuriza tion. A combination of midkilnCement Kiln Report (FINAL – 7/14/2006) 4-60 combustion, midkiln SNCR and a low temp erature oxidation technology may provide exceptional NO x control at the most effectiv e aggregate cost per ton of NO x controlled for wet
kilns.

4.3.7 Potential Applicabilit y of Oxidation Technology to Holcim Plant

General Discussion

. The Holcim Plant has two large precalciner kiln systems with existing scrubbers. An oxidative control technolo gy for these kiln lines ha s significant potential to provide NO x control using the existing scrubber system.

A variety of low temperature oxidation reagen t systems could be tested for efficiency in the existing wet scrubber system. It should also be relatively simple to set up a temporary system to test the high temperature hydrogen per oxide control option in a manner similar to the set up that was used to test SNCR. The critic al factor in the succe ssful use of the high temperature hydrogen peroxide control technology will be determining the best location for injection. Careful gas phase temperature measur ements and modeling should help determine the optimum location.

Conclusions

. It may be possible to add a hydrogen peroxide injection system to the preheater tower at the correct location with a re latively low capital expenditure. By combining SNCR and the high temperature hydrogen peroxide sy stem, an effective control system could be put in place at a minimal capital expenditure that would then allow the plant to use more or less of the hydrogen peroxide and ammonia reagents based on their current costs – thus optimizing the long term cost per ton of NO x control.

4.3.8 Potential Applicability of Oxid ation Technology to TXI Plant

General Discussion

. The TXI plant has 4 wet process kilns without any existing wet scrubber system. That would require them to place a complete oxidation system in place as an add-on technology including the scrubber for these systems. Assuming that all of the control options would have a similar capital cost for a spray tower/scrubber system careful evaluation of the alternative reagent systems is warranted.Cement Kiln Report (FINAL – 7/14/2006) 4-61 A trial system for evaluating the reagent sy stems may be warranted. As an example, three one-month trials using alternative reagents in a skid-mounted scrubber could be performed prior to scaling up to a full system. It may be possible to combine the gas flows from the kiln systems into a single flow to minimize the cost of the scrubber system.

Because of the high moisture levels in the gasses from wet kilns it may be necessary to bypass a portion of the stack gasses around the spray tower/scrubber for use as reheat gas after the spray tower/scrubber to prev ent condensation problems in the st ack. To the extent that such a strategy is required the efficiency of the NO x removal would be proportionately impacted.

TXI also has a large modern precalciner kiln with a scrubber system on-site. An oxidative control technology for the preca lciner kiln has significant potential to provide NO x control using the existing scrubber system. A variety of low temperature oxidation reagent systems could be tested for efficiency in the existing wet scrubber system. It s hould also be relatively simple to set up a temporary system to test the high temp erature hydrogen peroxide control option. The
critical factor in the successful use of the hi gh temperature hydrogen per oxide control technology will be determining the best location for injection. Careful gas phase temperature measurements and modeling should help determine the optimum location.

For TXI the added benefit of the high te mperature hydrogen peroxi de control technology might be the added control of hydrocarbons. There is the real potential that at the temperatures, which the hydrogen peroxide system operates at , those hydrocarbons will also be oxidized. Because these hydrocarbons may be evolved from the raw feed at a lower temperature this is not a certainty but, if it were to occur, the potenti al does exist for such a system to replace the existing catalytic control system. In that event, the savings on natural gas costs would be
substantial.

Conclusions . For the precalciner the addition of th e high temperature hydrogen peroxide oxidation control technology to th e preheater tower has significan t potential. In addition to controlling NO x emissions this oxidation technology ha s the potential to control hydrocarbon emissions and eliminate the need for the existing catalytic control system and the associatedCement Kiln Report (FINAL – 7/14/2006) 4-62 operating costs. These potential cost savings co uld more than offset th e cost of the hydrogen peroxide and capital investment for this kiln line to achieve even greater NO x control than its already relatively low levels. Tests of this technology should be able to be conducted with minimal investment. Alternatively tests of vari ous wet scrubber reagent systems could also be conducted in the existing SO x scrubber system.

In the wet kilns, because of the reheat cost s, further investigation of the low temperature oxidation technologies is likely to be the most co st effective and is therefore recommended for further investigation. Combination of midkiln combustion, midkiln SNCR and a low temperature oxidation technol ogy may provide exceptional NO x control at the most effective aggregate cost per ton of NO x controlled for these kilns.

Table 4-3.4. Summary of Modeling Results for LoTOx TM on Ellis County Kilns – Performance Results

Existing Unit Control Technology Emissions Rate tpy before Emissions Rate tpy after (a) Controlled Emissions Rate ppm Controlled Emission Rate lb./tonne clinker Control Efficiency % Reduction tpy

Ash Grove #1- wet LoTOx TM 702 301.6 60 0.84 85% 400.4

Ash Grove #2- wet LoTOx TM 750 322.2 58 0.89 85% 427.8

Ash Grove #3- wet LoTOx TM 764 328.3 53 0.91 85% 435.7
TXI #1 and #4–wet (b) LoTOx TM 1197 514.3 109 1.21 85% 682.7 TXI #2 and #3–wet (b) LoTOx TM 121 52 109 0.49 85% 69.0 TXI#5 – dry LoTOx TM 1710 734.7 29 0.30 80% 975.3
Holcim #1 – dry LoTOx TM 2222 954.7 73 0.38 85% 1,267.3 Holcim #2 – dry LoTOx TM 1778 763.9 53 0.30 85% 1,014.1 (a) NO x emission rate after SCR does not reflect SCR efficiency reduction due to adjustme nt by the ozone season factor of 0.671 (NOx reduction is modeled to oc cur only during the ozone season). (b) The results for TXI #1 & #4 and #2 & #3 are average per kiln – for example, total emissions reductions for controlling both TXI #1 & #4 are double the value listed in the table. (c) Models assume mid-kiln firing installe d at TXI as required under current SIP.Cement Kiln Report (FINAL – 7/14/2006) 4-63 Table 4-3.5. Summary of Modeling Results for LoTOx TM on Ellis County Kilns – Economic Results

Existing Unit Control Technology Capital Cost Annual Cost Cost Effectiveness

$/ton NO x Energy Penalty or

Benefit Burden Cost $/tonne clinker Ash Grove #1- wet (c} LoTOx TM $4.8 MM $1.4 MM $3,400 (a) $5.00 Ash Grove #2- wet (c} LoTOx TM $5.2MM $1.5MM $3,500 (a) $5.40 Ash Grove #3- wet (c} LoTOx TM $5.8MM $1.6MM $3,700 (a) $5.70
TXI #1 & #4–wet (b,c) LoTOx TM $5.4MM $1.6MM $3,300 (a) $4.70 TXI #2 & #3–wet (b,c) LoTOx TM $2.8MM $0.5MM $11,000 (a) $10.50 TXI#5 – dry LoTOx TM $5.2MM $2.4MM $2,600 (a) $0.90
Holcim #1 – dry LoTOx TM $6.7MM $3.1MM $2,400 (a) $2.35 Holcim #2 – dry LoTOx TM $5.4MM $2.5MM $2,300 (a) $1.90 (a) Increased fan power due to pressure dr op across scrubber included in the models (b) The results for TXI 1 & 4 and #2 & #3 are average per kiln – for example, total capital costs for controlling both TXI #1 & #4 are double the value listed in the table. (c) Costs for wet kilns include addition of spray tower to scrub oxidation products.

4.4 Process Modification

Process modifications are applicable to any t ype of kiln and are usually done to reduce heat consumption, to improve cli nker quality, and to increase the lifetime of the equipment (such as the refractory lining) by stab ilizing process parameters. Re duction of emissions, such as NO x , SO x , and dust, are secondary effects of these modi fications. Smooth and stable kiln operation close to design values for process parameters is beneficial for all kiln emissions. Process modifications can include many elements, such as instruction and training of the kiln operators, homogenizing raw material, ensuring uniform co al dosing, improving the c ooler’s operation, and installing new equipment. Pro cess modifications are primarily done to reduce operating costs, increase capacity, and improve product quality. Adopting process modifica tions usually results in a reduction of operating costs for a kiln. The savings result fr om reduced fuel and refractory consumption, lower maintenance costs, and hi gher productivity, among ot her factors. (35)

This section describes process modifications that improve fuel efficiency and kiln operational stability with an emphasis on reducing NO x formation. Since NO x formation is directly related to the amount of energy consumed in cement-making, improving fuel efficiency and productivity will reduce NO x emissions.Cement Kiln Report (FINAL – 7/14/2006) 4-64 4.4.1 Combustion Zone Control of Temperature and Excess Air

Continuous monitoring of O 2 and CO emissions in the cement kiln exhaust gases
indicates the amount of excess air. At a given excess air level, NO x emissions increase as the temperature of the combustion zone increases . A typical kiln combustion zone solids temperature range is about 1,430 to 1,540 °C (2,600 to 2,800 °F) for completion of clinkering
reactions and to maintain the quality of the cement produced. ( 75) The corresponding gas-phase temperature is usually greater than 1,700 °C ( 3,100 °F). (76) Maintaining the combustion zone temperature at a necessary minimum value woul d minimize both the process energy requirement
and the NO x emissions.

Along with the appropriate temperature, it is also necessary to maintain an oxidizing atmosphere in the clinker burning zone to ensure the quality of the c linker produced. Although a kiln could be operated with as little as 0.5 per cent kiln exhaust oxygen level, typically the kiln operators strive for an oxygen level of one to two percent to guarant ee the desired oxidizing conditions in the kiln burning zone. An experi mental test on a cement kiln showed that by reducing excess air from 10 to 5 percent (i.e., reducing exhaust oxygen levels from two to one percent) NO x emissions per unit time can be reduced by approximately 15 percent. (77,78)

With state-of-the-art continuous emissions monitoring systems (CEMS) and feedback control, excess air can be accurately controlled to maintain a level that promotes optimum combustion and burning conditions in addition to lowering NO x emissions. Reducing excess air
level also results in increased productivity per unit amount of en ergy consumed and thus results
in an indirect reduction of NO x emissions per unit am ount of clinker product.

4.4.2 Feed Mix Composition

Heat requirements for producing clinker are dependent on the composition of the raw feed which varies among cement plants. Experi ments have demonstrated that by improving the burnability of the raw feed, the heat requirement of clinker can be reduced by 15 percent
. (79) If the raw feed composition can be formulated to require less heat input per ton of clinker, less fuelCement Kiln Report (FINAL – 7/14/2006) 4-65 is burned and less NO x per unit product is produced. This approach of changing the feed composition may, however, be highly site specific and may not be applicable at all locations.

Reduction of Alkali Content of Raw Feed

. The alkali content of finished cement generally needs to be below a cer tain acceptable level. Low alkali requirements need higher kiln temperatures and longer residence times at high te mperatures to volatilize the alkali present in
the semi-molten clinker. Raw ma terials with greater alkali cont ent need to be burned longer at higher temperatures to meet alkali requi rements and thus may produce greater NO x emissions.
Increased volatilization of alkali al so results in increased alkali em issions in kiln exhaust gases. To control alkali emissions, a part of th e kiln exhaust gases may be bypassed around a downstream unit, e.g., a precalciner . The bypassed gases are quenche d to remove alkali and sent through a particulate collector. The bypass of kiln exhaust ga ses typically involves a fuel penalty, e.g., about 20,000 Btu/tonne clinker for every one percent gas bypass. The additional heat requirement may also contribute to increased NO x emissions; thus, reducing the alkali content of the raw feed mix may co ntribute to a reduction in the NO x emissions.

4.4.3 CemStar Process

Another feed modification that can reduce NO x emissions is the addition of a small amount of steel slag to the raw kiln feed. Th is patented technique is known as the CemStar Process and was developed by TXI Industries. St eel slag has a low melting temperature and is chemically very similar to clinker. Since ma ny of the chemical reactions required to convert steel slag to clinker ha ve already taken place in a steel furnace, the fuel needed to convert steel slag into clinker is low. The decreased n eed for limestone calcina tion per unit product and improved thermal efficiency of the proce ss both contribute to reduced thermal NO x and CO 2 emissions. (80)

Eleven facilities are using or in the pro cess of incorporating CemStar. (81) CemStar requires little extra equipment and the addition of steel slag to the f eed mix can result in a
reduction or elimination of the need for some minera l sources, such as shale or clay. This process can also increase product ion by 15 percent. (80)Cement Kiln Report (FINAL – 7/14/2006) 4-66 According to the Entellect Environmental Se rvices “Evaluation of the Effects of the
CemStar Process on a Wet Process Cement Kiln” report, the CemStar pro cess reduces the kiln material temperature in the region of the flame by an av erage of 200°F (from 2,610°F to 2,405°F); the lower gas temperature of the flame results in lower NO x emissions. (82) Another test of CemStar technology found an average reduction in burn zone temperature of 160°F, a six percent reduction. (82) The amount of NO x emissions reductions achievable with CemStar varies by kiln type but ranges from over 20 to 60 percent. (80) Short- and long-term tests of
CemStar were conducted at two di fferent types of TXI cement k ilns in 1999. Short-term tests (two days) on a preheate r/precalciner kiln found NO x emissions reductions in lbs. NO x /tonne clinker of 44 percent when operated at maximu m capacity, and between 9 and 30 percent when operated at normal capacity, depending on the qu ality of the raw feed mix (see Table 4-4.1).

Table 4-4.1. Results of Short-Term Cemstar Tests on a Preheater/Precalciner Kiln

Poor Quality Feed Mix (lb. NO x /tonne clinker) Percent Reduction a (%) Ideal Quality Feed Mix (lb. NO x /tonne clinker) Percent Reduction a (%) Without CemStar 4.98 - 5.59 With CemStar at normal feed rate b 4.51 9 3.89 30

With CemStar at maximum feed rate c (no test) - 3.15 44

a Percent reductions are relative to the emission rate without CemStar. b The normal feed rate is 170 - 180 tons per hour of dry feed.

c The maximum feed rate is 195 tons per hour of dry feed.

Andover Technologies also reported on short-te rm and long-term tests of a wet kiln using CemStar Technology. The short-term tests (one day) found emission reductions of 36 to 55 percent in lbs. NO x /tonne clinker, and the long-term tests (approximately two and a half months) found reductions of 24 percent (see Table 4-4.2). (80)

Kilns with lower initial baseline NO x emissions would have less NO x reduction with CemStar than those with higher baseline emission s. Wet and long-dry ki lns would have greater
NO x reductions with CemStar because more energy is used per ton of clinker produced than preheater/precalciner kilns. Wet kilns may achieve the greatest NO x reductions with CemStar because the addition of steel slag would reduce the amount of water needed to create the slurry and consequently decrease the amount of heat needed to dry it. (80)Cement Kiln Report (FINAL – 7/14/2006) 4-67 Table 4-4.2. Results of Cems tar Tests on a Wet Kiln

Test 1 (lb. NO x /tonne clinker) Test 2 (lb. NO x /tonne clinker) Percent Reduction a (%) Short-Term Test Without CemStar 17.53 24.7 - With CemStar 11.24 no 2 nd test Test 1 = 36 Test 2 = 55 Long-Term Test Without CemStar 5.23 no 2 nd test - With CemStar no 2 nd test 24

a Percent reductions are relative to the emission rate without CemStar.

4.4.4 Kiln Fuel

Changing the primary kiln fuel from na tural gas to coal can reduce the flame temperatures significantly, re sulting in lower thermal NO x emissions. (83,84) Although nitrogen present in coal may pr ovide greater fuel NO x contribution, switching the fuel burned in kilns from natural gas to coal has been shown to provide substantial reduction in the total NO x emissions in one experimental study. (83) In th e dry process kilns test ed in this study the average NO x emissions decreased from 20.4 lb./tonne c linker to 6.2 lb./tonne clinker when the fuel was changed from natural gas to coal. A number of cement kilns have already made the switch from natural gas to coal and currently 87 percent of cement kilns in the United States use coal as the primary fuel. (85)

When natural gas (with no nitrogen in the fu el) is used in the bur ning zone of a cement kiln, the NO x emissions are significantly higher than wh en coal is used. There may be additional environmental impacts when coal is burned as opposed to natural gas (e .g., sulfur dioxide and sulfate emissions may increase). Although switching to a lower nitrogen fu el in a precalciner may reduce NO x , the fuel nitrogen content in the burni ng zone has little or no effect on NO x generation. Some researchers have found no rela tionship between fuel nitrogen content and the
NO x emissions from a cement kiln. (86)Cement Kiln Report (FINAL – 7/14/2006) 4-68 Switching to a fuel with a higher heating value and lower nitrogen content may reduce
NO x emissions in a cement kiln, e.g., petroleum c oke has a lower nitrogen content per million
Btu than coal. Petroleum coke is also more uniform in terms of heat value, lower in volatile matter content and burns with a lower flame temperature. However, some claim that petroleum
coke cannot be burned alone because it does not provide enough volatile matter. (87)

4.4.5 Increasing Thermal Efficiency

The thermal efficiency of the cement-ma king process has improved substantially as energy costs have increased and new technol ogy has been developed. Although there are a variety of cement process technol ogies used in the US, the kilns in this study are all either 1960’s wet kiln technologies that are not energy efficient or modern dry process kilns w ith preheat and precalcination that represent the most energy effi cient process for making Portland cement. Both Holcim #2 and TXI #5 are new and energy efficient units. Holcim #1 began operation in 1987 and is slightly less efficient and could potenti ally be upgraded by options such as calciner modification discussed below. In addition, there ar e interim steps that impr ove the efficiency of wet process to semi-wet or semi-dry process. However, the main opportunity for substantial
reductions in NO x emissions in Ellis County from ener gy improvements comes from closing the wet process units and replacing them with modern, dry-process production.

Calciner Modifications

A study for the Department of Energy (88) evaluates use of low pressure drop cyclones for suspension preheaters. Worre ll reports, “Cyclones are a basic component of plants with preheating systems. The installation of newer cyclon es in a plant with lower pressure losses will reduce the power consumption of the kiln exhaus t gas fan system. Depending on the efficiency of the fan, 0.6-0.7 kWh/ton clinker can be sa ved for each 50 mm W.C. (water column) the pressure loss is reduced. For most older kilns this amounts to savings of 0.6-1.0 kWh/ton (89). Fujimoto (1994) discussed a Lehigh Cement plant retrofit in which low-pressure drop cyclones were installed in their Mason City, Iowa plant an d saved 4 kWh/ton clinker (90). Installation of the cyclones can be expensive, however, since it may often entail the rebuilding or modification of the preheater tower, and th e costs are very site specific. Also, new cyclone systems mayCement Kiln Report (FINAL – 7/14/2006) 4-69 increase overall dust loading and increase dust ca rryover from the preheater tower. However, if an inline raw mill follows it, the dust carryover problem becomes less of an issue. A cost of $2.7/annual ton clinker is assumed for a low pressure drop cyclone system.”

The only candidate for a calciner upgrade am ong the Ellis County kilns is Holcim #1. This process line represents a slightly older ve rsion of the technology than Holcim #2 or TXI #5.
Low-NO x and low energy consumption performance is largely inherent in the design and Holcim #1 would appear to be the unit that could best be nefit from this upgrade. Cost modeling has been provided based on the assumption that this unit could move to a le vel of performance similar to TXI #5 after the upgrade. The expert panel revi ewed the current performance of the Holcim kilns in comparison to TXI #5. Although Holcim #2 and TXI #5 were both built near the year 2000, TXI #5 has typical NO x emissions that are substantially lower than Holcim #2. It was the judgment of the expert panel that an intrinsic low- NO x redesign of Holcim #1 should produce performance more similar to that of TXI #5 than Holcim #2. Thes e results are provided in Table
4-4.5.

Semi-Wet Upgrades to Wet Kilns

Hendriks and Worrell (91) repor t that conversion from a wet to a semi-wet process can
save between 0.8 and 1.6 GJ/tonne clinker. There is a penalty of increased electrical energy use of approximately 3 to 5 kWh asso ciated with this conversion.

Worrell (88) also reviews this option and desc ribes it as a filter press system. “In the wet process the slurry typically contains 36% wate r (range of 24-48%). A filter press can be installed in a wet process kiln in order to reduce the moisture content to about 20% of the slurry and obtain a paste ready for extrus ion into pellets (92). In the U.S. several plants have tried slurry filters, but have not been very successful. Current ly, there seem to be no plants in the U.S. using this technology (93). Additional electricity consumption is 3-5 kWh/ton clinker (94). In this analysis it is assumed that energy use incr eases by 4 kWh/ton clinker to reduce the moisture content to 20%. The corresponding fuel savi ngs are 1.0 MBtu/ton (94). Jaccard and Willis (1996) estimate the conversion co st to run $1.6/annual ton clinke r capacity with increased operation costs of $0.1/ ton clinker (95).”Cement Kiln Report (FINAL – 7/14/2006) 4-70 Semi-Dry/Semi-Wet Upgrades to Wet Kilns

Hendriks and Worrell (91) repor t that conversion from a wet to a semi-dry process can save approximately 2.0 GJ/tonne cli nker. They report a “small” in crease in electrical energy use
associated with this conversion of approximately 3 to 5 kWh.

Buzzi-Unicem operates a semi-dry/semi-wet sy stem in Greencastle, IN, which had been converted from a large wet kiln system. While anticipated increases in production capacity were achieved, predicted improvements in thermal effici ency were not fully realized. Actual thermal efficiency improvement was only about 15%. Capita l cost for this type of conversion are likely to be in the range of $75-85/tonne. Significant NO x improvements have been observed in this conversion although not to the leve ls predicted by the vendor. Ev en with a 50% increase in production total NO x emissions have been significantly reduced.

Because kiln conversion economics are signific antly impacted by the size of the existing kiln the conversion of any of th e wet kilns at TXI or Ash Grove is not considered a feasible alternative for further analysis.

Replacement of Wet Kilns with Dry

Worrell evaluates conversion of a wet kiln to a dry preheat/precalciner process (88). This conversion is essentially a recons truction of the main kiln and processing areas with a new, modern dry plant. Worrell reports “If economically feasible a wet process kiln can be converted to a state-of-the art dry process production facility that includes e ither a multi-stage preheater, or a pre-heater/pre-calciner. Averag e specific fuel consumption in U.S. wet kilns is estimated at 6.0
MBtu/ton clinker. Studies of several kiln convers ions in the U.S. in the 1980s found fuel savings of 2.9 MBtu/ton or less (96). In Hranice (C zech Republic) a 1,050 tonne per day wet process plant was converted to a dry k iln plant with a new kiln specific fuel consumption of 2.7 MBtu/ton clinker (97). Fuel savings of 2.7 MBtu /ton clinker and an increase in power use of about 9 kWh/ton clinker (98) are assumed. The co st of converting a wet plant to a dry processCement Kiln Report (FINAL – 7/14/2006) 4-71 plant may be high, as it involves the full reconstr uction of an existing facility. Costs may vary between $50/annual ton clinker capacity and $100/annual ton clinker capacity (99,100).”

This option is also discussed by Hendriks (9 1). Hendriks gives a cost of approximately $133/tonne of annual capacity as the cost of building the new dry process plant. Hendriks estimates that about 2.2 GJ/tonne of energy can be saved. Increased energy use of about 10kWh/tonne is required for operation of the preh eat/precalcination tower. These models do not consider any lost revenues that may be associated with wet to dry convers ion. Certain types of cement, such as oilfield cement, are typically produced by wet kilns. This means that a plant that converts from a wet to dry process may lose some revenues. Companies that operate wet kilns and companies that operate preheat /calciner kilns are likely to ha ve differences of opinion about the magnitude of difference in cement quality. This cost impact depends on the amount of materials sold by a particular pl ant and may include subjective crit eria regarding cement qualities that cannot be quantified as part of this project.

Wet to Dry Conversion of Ellis County Kilns

On average, dry preheat/precalciner kilns emit substantially less NO x per tonne of cement produced and require less energy per tonne of ceme nt produced. Both in terms of energy use and
NO x emissions rates, the wet process units are ofte n nearly double the modern dry process units. The cost modeling presumed that the wet kilns could obtain a value appr oximately that of high performing modern kilns and that would resu lt in an approximate 65% decrease in NO x emissions. A substantial energy savings was pred icted to result in fuel savings in the cost models (see Confidential Attachment Wet to Dry Conversions).

The economics of wet kilns compared to dry kilns are very comple x and involve issues such as lower production capacity of wet kiln s, use of waste fuels and quality of cement products. However, as the energy costs of wet production are higher than for modern dry process units, there is a point at which the higher costs of pollution controls that may result from
the final determinations of this study would trigger a decision to close the wet kilns and replace them with dry. Stating this anothe r way, it is likely that at a cert ain cost of pollution controls in terms of dollars per tonne of clinker produced, the economics of the wet process including higherCement Kiln Report (FINAL – 7/14/2006) 4-72 fuel costs and higher pollution control costs w ould reach a point where replacement of the wet units with larger dry process uni ts would be the reasonable alte rnative for a cement plant to continue operations at that site.

It is likely that any new kilns built to repl ace the wet kilns in E llis County would include increased production capacity in the economic jus tification. However, for purposes of control cost modeling, the units need to replace the existing capac ity for the evaluations to make sense in the context of our control option evaluations. Fo r this reason, two dry process kiln replacement scenarios were modeled. One involved replacing the three wet kilns at Ash Grove with one new dry process unit and the second i nvolved replacing the four wet kilns at TXI with one new dry process unit. The capacity of th e new units was modeled as essent ially equal to the capacity of the existing wet units combined. It is likely that Ash Grove and perhaps TXI would replace the existing kilns with a new dry preheat/precalcinat ion process typical of current generation dry process plants with approximately twice (over two million tons per year of clinker) the capacity of the existing wet kilns (under one million tons per year of clinker) and the added production capacity would be an important part in cost just ification of the expense of the new dry process
unit.

The modeling, summarized in Table 4-15, show s an annualized cost of approximately $11 per tonne clinker for the replacement dry proce ss units. This cost includes an annual benefit of approximately $4.0 to $4.5 million in reduced fu el costs. An increased annual cost of electricity of approximately $0.5 million results from the additional fan power required to move air through the preheat and precalcin ation tower. This information indicates that energy savings are very significant, but are not sufficient for a company to justify replacement of the wet kilns. Annual operating costs (cap italization of the new equipment) are reduced by nearly one third to approximately $9 million dollars by energy savings; however, even with the current high costs of energy this would not by itself justif y replacement of the wet kilns.

The current use of alternative fuels complicates this analysis. The fuel savings are based on an assumption that the energy for the current wet kilns is all based on coal. Lower cost
alternative fuels lessen the economic benefit of th e increased energy efficiency. Preserving these alternative fuel programs may be important economi c considerations in company analyses of wetCement Kiln Report (FINAL – 7/14/2006) 4-73 to dry conversions and the overa ll economics of cement production on a dollars per tonne clinker basis. The realistic assumption that larger modern units of a size similar to TXI #5 are needed to achieve the energy efficiency desired and using in creased production to offs et the high cost of these projects both impact fuel economics. If it is assumed that the current amounts of alternative fuels are permitted to be used in a new larger kiln, the amount of coal predicted to be
reduced would still be reflected in the overall reduction in fuel use.

Conversion of the Ellis County wet kilns to dry process would result in year-round
emissions reductions for NO x , SO 2 , particulate matter and hazardous air pollutants. The modern dry process unit would have update d controls that would result in potentially large emissions
reductions for SO 2 and other air quality benefits for the region including reduction in fine PM

precursors.

Table 4-4.3. Summary of Modeling Results for Wet to Dry Conversion of Ellis County Kilns – Performance Results

Existing Unit Replacement Unit Emissions Rate tpy before Emissions Rate tpy after (a) Controlled Emissions Rate ppm Controlled Emission Rate lb./tonne clinker Control Efficiency % Reduction tpy Ash Grove #1- wet Ash Grove #4 - dry 2,200 772 180 1.99 65% 1,428

Ash Grove #2- wet

Ash Grove #3- wet TXI #1 –wet TXI #6 – dry 1,800 630 180 1.94 65% 1170

TXI #2 –wet

TXI #3 –wet

TXI #4 –wet

Table 4-4.4. Summary of Modeling Results for Wet to Dry Conversion of Ellis County Kilns – Economic Results

Existing Unit Replacement Unit Capital Cost Annual Cost Cost Effectiveness

$/ton NO x Energy Penalty or Benefit* Emissions Penalty or Benefit** Burden Cost $/tonne clinker

Ash Grove #1- wet Ash Grove #4 - dry $169 M $9.3 M $6,500 -$4.4 M -1,428 tpy $10.94

Ash Grove #2- wet

Ash Grove #3- wet TXI #1 -wet TXI #6 - dry $143 M $7.9 M $6,700 -$3.7 M -1,170 tpy $10.94

TXI #2 -wet

TXI #3 -wet

TXI #4 -wetCement Kiln Report (FINAL – 7/14/2006) 4-74 * Large benefit in fuel efficiency partly o ffset by increased electrical use in tower ** Large benefit in reduced fuel – does not account for increas ed emissions at power plant for power used in tower.

Table 4-4.5. Summary of Modeling Results fo r Calciner Upgrade for Ellis County Kilns – Economic Results

Control Technology Control Technology

Status Emissions Rate Before Control tpy Emissions Rate Before

Control lbsNO x //tonne Percent Control Emissions Reduction from Control tpy Controlled Emission

Rate lbNO x /tonne Cost Effectiveness

$/ton NO x Burden Cost $/tonne clinker
Holcim #1 Available 2,222 3.76 40% 888.8 2.2 $2,795 $2.70 40% for new low-NO x calciner based on TXI #5 performance. Cost effectiveness for calciner upgrade calculate d by ratio of burden costs using SCR data. Calciner upgrade is not a seasonal ozone meas ure – emissions benefit is for full year.

4.5 Performance of Current NO x Control Techniques and Technologies in the Cement Industry

4.5.1 Comparison of Current Performance of NO x Control Technologies

Table 4-5.1 is a spreadsheet th at is too large for inclusion as a table in the body of this report. This table compares the performance of different technologies against a standard performance criterion of pounds of NO x per tonne (lbs./tonne) of clinker produced. Only information on complete references is included in this table. When sufficient information could be located to identify the plan t and calculate performance of th e control technology in lbs./tonne clinker, the information was included in this table. There are additional, less complete references to performance in this report that could not be included in this table because insufficient information was available to compare performance.

4.5.2 Summary of Current Regulations

This report focuses on evaluating the NO x control measures for Portland cement manufacturing that go beyond current 30 TAC Chapte r 117 requirements. In the US, it appears that several areas of the country are in a simila r position to Texas in that they are currently evaluating more stringent active controls of NO x for ozone attainment under the 8-hour standard.
While active NO x controls may be required under New Source Review requirements, current State SIP requirements are less stringent. ERG reviewed and summarized current US NO x control requirements for cement kilns and this su mmary is presented in Attachment D as Table
D-1. This review showed that four states ha d performance standards that were similar in stringency to Texas (Maryland, Illi nois, Indiana and Michigan). Fi ve states (Pennsylvania, SouthCement Kiln Report (FINAL – 7/14/2006) 4-75 Carolina, Tennessee, Ohio and Alabama) had t echnology based standards that were similar in stringency to the option under Texas regulations to comply by installing a technology such as mid-kiln injection instead of meeting a specific performance standard. Kentucky and California’s South Coast Air Qualit y Management District has sta ndards that appear to be less stringent than Texas. New York uses a case-by- case approach so that the stringency of the regulation is not clear. States are currently considering more stringent measures to comply with
the NO x SIP Call and with projected noncompliance w ith the 8-hour ozone standard. Both the State of Georgia and the Great La kes States are considering more stringent control requirements of cement kilns; these meas ures are discussed below.

Control requirements in Europe are genera lly moderately stringent emissions limitations based on a performance requirement such as 500 mg/m 3 . These requirements have prompted use of SNCR (recent documents report as many as 50 in stallations), but generally are not stringent enough to require higher performing technologies. One exception is Sweden, that has a very stringent performance re quirement of 200 mg/m 3 (approximately 98 ppm). There are currently two cement plants in Europe cap able of meeting this 200 mg/m 3 limit. The Solnhofen Portlandzementwerke in Germany (using SCR) a nd Scancem Slite in Sw eden (using SNCR with multi-point injection). European control requi rements are presented in Tables 4-5.2 and 4-5.3

Japan has a national standard for NO x from cement plants an d divides the emissions limits into those that apply to plants built be fore 1975 and those built after 1975. For pre-1975 plants the NO x standard is 480 ppmv and for those built after, the standard is 250 ppmv. The 250 ppmv standard is very similar to the German standard of 500 mg/m 3 . For the purposes of evaluating the particulate matter standards table, a US standard of 0.02 grains per dry standard cubic foot would be equivalent to a European standard of 50 mg/Nm 3

.

As noted above, the US is somewhat behi nd Europe in requiri ng active controls on
Portland cement manufacturi ng plants. Communications be tween TCEQ and EPA Region 6 indicate that recent BACT determinations ty pically require 1.95 lbs./tonne clinker (2.15 lbs./tonne) and SNCR. Other re cent US studies include planning studies for compliance with the
8-hour ozone standard.Cement Kiln Report (FINAL – 7/14/2006) 4-76 Two recent documents that recommend measures beyond current 30 TAC Chapter 117 requirements are the Midwest Regional Planning Organization’s “Identif ication and Evaluation of Candidate Control Measures, April, 2005” an d the “Fall Line Air Quality Study. November,
2004”. Both of these studies are evaluations of potential measures to reduce ozone and
recommend consideration of SCR for contro l of cement kilns. The Fall Line Study was conducted for the State of Georgia and recomme nds SCR for wet kilns as well as dry process kilns and provides estimates of co st effectiveness per ton of NO x controlled. The Midwest RPO Study also discusses the potential for control of wet kilns with SCR, particularly for low-dust applications (after pollution contro ls) and mentions the high cost of gas reheat as a limitation in application of this technology. SCR cost s are only estimated for long dry and dry preheat/precalcination process kilns. The cost information from these two studies is
summarized in Tables 4-5.4 and 4-5.5.Cement Kiln Report (FINAL – 7/14/2006) 4-77 Table 4-5.2. National SO 2 and NO x Emission Limits for the Production of Cement Within the European Union (EU 15), in mg/Nm 3 , Around 2000

Country Data Based

on New/Modified or Existing Plant SO 2 Normal Situation SO 2 S-rich Raw Materials NO x PCDD/Fs* ng TEQ/Nm 3 Austria Na (a) New/modified Existing 200 200 400 400 500 1000 Belgium P New/modified Existing 1000 1000 1800 1800 Denmark P (a) Existing 5/250/450 (b) No limit 1200/2500/850 (c) no limit Finland P (d) Existing 150–400 1200–1800 France Na New/modified Existing 500 500 (e) 1200/1800 (f) 1200/1800 (e)(f) 1200/1500/1800 (g) 1200/1500/1800 (g) Germany Na New/modified Existing 400 400 400 400 500 800 Greece Ireland Na New/modified Existing 400 400 700 700 1300 1300 n.a.
n.a. Italy Na/P New/modified Existing 600 1800 10000 (h) 10000 (h) Luxembourg P Existing 100 (i) 80(j) 0.1 (k) Netherlands P Existing (l) 1300(j) 0.1 Portugal Na New/modified Existing 400 1300 0.1 0.1 Spain Na New/modified
Existing 2400/6000 (m) 600 (n) 2400/6000 (m) 600 (n) 2400/6000 (m) 1800 (n) 2400/6000 (m) 1800 (n) 1300-1800 (n)

Sweden P Existing - <200 <200 0.1 UK Na (o) New/modified Existing 200 (p)(q) 600-2500 (r) 900 (p) 500-1200 (q)(s) Source: EIPPC Cement BREF (2000). Based on Cembureau report (1997) and information provided by expe rts of the Technical Working Group set up in order to support the production of the BREF * Polychlorinated dibenzo diox ins and furans (total emitte d quantity in nano g/ Norm m 3 ). Na = National law; R=Regional law; P=Typical permit; in mg/ Norm m 3

. a) Daily averages and reference condition of 273 K, 101.3 kPa, dry gas and 10% O 2 . b) 5 for semi-dry process, 250 for wet process and 450 for wet pr ocess with wet scrubber and heat recovery. Limits under discus sion. c) 1200 for semi-dry process, 2500 for wet process and 850 for wet process with wet scrubber and heat recovery. Limits under di scussion. d) Monthly averages, reference condition of 10% O 2 and dry gas. e) Existing plant must meet limit for new plant by 2001. f) 1200 mg/Nm 3 if ≥ 200 kg/h; 1800 mg/Nm3 if < 200 kg/h. g) 1200 mg/Nm 3 for dry process with heat recuperation, 1500 mg/Nm 3 for semi dry and semi wet processes, and 1800 mg/Nm 3 for wet and dry processes without heat recuperation. h) General rule for any ki nd of industrial emission. i) Half hour average. j) Daily average value. k) 6 hour average. l) 90 kg/h as daily average, maximum 375 tonne/year. m) Current limits. n) Limits under discussion. o) IPC Guidance Note S2 3.01. p) ‘Benchmark releases’. q) Benchmark releases are, in particular, not applicable to ex isting plant but are a factor in considering appropriate limits. r) Limit values reflect the actual levels of releases. Daily averages and reference cond ition of dry gas and actual O 2 content. s) Actual releases, daily averages, not all plants currently have limits.Cement Kiln Report (FINAL – 7/14/2006) 4-78 Table 4-5.3. National Emissions Standards for PM of the European Union Countries for Cement Manufacturing in mg/Nm3

Country Data Based

on New/Modified or Existing Plant Kiln Stack Clinker Cooling Cement Grinding Other Point Sources Austria Na (a) New/modified Existing 50 50 50 50 50 50 50 50 Belgium P New/modified Existing 50 50 - 150 50 50 - 400 50 50 - 150 50 – 300 Denmark P Existing 50 (b) 50 (b) 50 (b) 50 (b) Finland P New/modified Existing 50 50 (c) 50 50 30 – 50 30 - 50 30 – 50 30 – 50 France Na New/modified Existing 50 50 (d) 100 100 (d) 50 50 (e) 30 30 Germany Na New/modified Existing 50 50 50 50 50 50 50 50 Greece Na/R New/modified Existing 100 150 100 150 100 150 Ireland Na New/modified Existing 50 50 100 100 75 75 50 50 Italy Na/P Existing 50 50 50 50
Luxembourg P Existing 30 (f) Netherlands P Existing 15 (f) 10 (f) 10 (f) 10(f) Portugal Na New/modified Existing 50 100 100 100 75 75 50 50 Spain Na New/modified
Existing 400/250 (g) 100 (h) 170/100 (g) 100 (h) 170/100 (g) 100 (h) 300/250 (g) 75 (h) 300/250 (g) 75 (h) 300/250 (g) 50 (h) 300/250 (g) 50 (h) Sweden P Existing 50 (i) 50 50 20 UK Na (j) New/modified Existing 40 (k) (l) 50 (k) (l) 40 (k) (l) 50 (k) (l)

Na= National law; R= Regiona l law; P= Typical permit a) Daily averages and reference condition of 273 K, 101.3 kPa, dry gas and 10% O 2. b) Limits under discussion. Reference cond ition of 273 K, 101.3 kPa, dry gas and 10% O 2. c) Existing plant must meet 50 mg/Nm 3 by January 1, 2001. Monthly averages a nd reference condition of 10% and dry gas. d) Existing plant with emission < 150 mg/Nm 3 must meet limit for new plant by 2001. e) Existing plant must meet limit for new plant by 2001. f) Daily average values. g) Current limits. h) Limits under discussion. i) Daily average value. A limit value of 90 mg/Nm 3 , including start/stop and CO-trips, applies for monthly averages. j) IPC Guidance Note S2 3.01. k) “Benchmark releases.” l) Benchmark releases are, in particular, not applicable to exis ting plant but are a factor in considering appropriate limits. [Based on [Cembureau report, 1997] and information provided by the Technical Working Group of the European Commission BREF Report (2000) ].Cement Kiln Report (FINAL – 7/14/2006) 4-79 Table 4-5.4. Midwest RPO – LADCO Study (Large Preheater Kiln SCR 1,200,000 tpy c linker 2,880 tpy uncontrolled emissions)

70% Removal Efficiency 90% Removal Efficiency Low Capital Cost High Capital Cost Low Capital Cost High Capital Cost Total Capital Investment – TCI $1,760,296 $14,668,188 $1,760,296 $14,668,188 Total Annual Cost $1,305,377 $3,040,107 $1,305,377 $3,040,107 Pollutant Removal - tpy 2,016 2,016 2,592 2,592 Cost Per Ton of NO x Removed $648 $1,508 $504 $1,173

Table 4-5.5. Fall Line Air Quality Study (Georgia)

In-process fuel use – coal SNCR $1,726 Cement manufacturing dry Mid-kiln firing $62 Mid-kiln firing $62 Medusa Cement (Houston) Cement manufacturing wet SCR $3,947 Mid-kiln

In summary, current US emissions limitati ons indicate that 1.95 lb s./tonne clinker using SNCR is currently considered BACT for dry kilns. In order to meet 8-hour ozone standards, several areas of the country are l ooking at requiring more stringent NO x controls on Portland cement plants and at least two areas are looki ng at requiring SCR. Experience in Europe
indicates that emissions leve ls of approximately 200 mg/m 3 (98 ppm) and less than 1.0 lb./tonne clinker are being achieved at tw o dry precalciner kilns, one us ing SNCR and one using SCR.

4.5.3 Summary of European Experiences

In Europe, many cement plants have adopted general primary measures, such as process control optimization, use of modern, gravimetric solid fuel feed systems, optimized cooler connections and use of power management syst ems. These measures are usually taken to improve clinker quality and lower production co sts but they also reduce energy use and air
emissions. 1

In March 2000, the European Integrated Po llution Prevention and Control (IPPC) Bureau issued a report on Best Available Techniques for European cement kilns. (35) The report
collected emissions data from several sources. Em ission rates for European kilns included in thisCement Kiln Report (FINAL – 7/14/2006) 4-80 study range from less than 0.8 to 12 lb. NO x /tonne clinker. A set of German kiln emission measurements presented in the European report found NO x emissions for a cyclone preheater with heat recovery of 1.2 to 6.2 lb./tonne clinker, for a cyclone preheater without heat recovery of 1.6 to 7.0 lb./tonne clinker, and for a grate preh eater of 1.6 to 8.2 lb./tonne clinker. These rates are similar to the averages for preheater and precalciner kilns found by EC/R in the new data presented in Chapter 4 (1.7 and 2.7 lb./tonne c linker respectively), but are less than those reported in the ACT document (5.9 and 3.8 lb./tonne clinker respectively). (35)

Table 4-5.5 presents a summary of NO x control device applicability, reduction efficiency, and reported average emissions from the IPPC Bur eau report on BAT for European cement kilns. (35) There are no emissions data in the IPPC report for kilns with CemStar technology or midkiln firing. For low-NO x burners, the IPPC report found a lower average NO x emissions rate (1.6 lb./tonne clinker) than EC/R found in the new State data (8.98 lb./tonne clinker). Both the IPPC report and the 1994 ACT document had es timated reduction efficiencies for low- NO x burners of up to 30 percent. The reduction effi ciencies in the IPPC report for SNCR (10 to 85 percent) and SCR (85 to 95 percent) are close to but slightly great er than those reported in the 1994 ACT document (30 to 70 percent and 80 to 90 percent respectively). (35)

Table 4-5.5. NO x Control Techniques Summary From European Best Available Techniques Report (35)

Reported Emissions

Technique Kiln Systems Applicability Reduction Efficiency mg/Nm 3 a kg/tonne b (lb./ton) Flame cooling All 0 to 50% Low-NO x burner All 0 to 30% 400 0.8 (1.6)

Staged combustion Preheater and Precalciner 10 to 50% <500 to 1000 < 1.0 to 2.0 (2.0 to 4.0) Mid-kiln firing Wet and long dry 20 to 40% no info no info SNCR Preheater and Precalciner 10 to 85% 200 to 800 0.4 to 1.6 (0.8 to 3.2) SCR - data from pilot plants only Possibly all 85 to 95% 100 to 200 0.2 to 0.4 (0.4 to 0.8)

a Normally referring to daily averages, dry gas, 273 K, 101.3 kPa and 10% O 2 . b kg/tonne clinker is based on 2000 m 3 /tonne clinker.Cement Kiln Report (FINAL – 7/14/2006) 4-81 The IPPC report concludes that BAT for reducing NO x emissions are a combination of general primary measures, primary measures to control NO x emissions, staged combustion and
SNCR. The BAT emission level associ ated with the use of these te chniques is 0.4 to 1.0 lb./tonne clinker (200-500 mg NO x /m 3 (as NO 2 )). This emission level could be seen in context of the current reported emission range of 0.4 to 6.0 lb./tonne clinker (<200-3000 mg NO x /m 3 ), and that the majority of kilns in the European Union is sa id to be able to achieve less than 2.4 lb./tonne clinker (1200 mg/m 3 ) with primary measures. (35)

While there was support for the a bove concluded BAT to control NO x emissions, there was an opposing view that the BAT emission level a ssociated with the use of these techniques is 1.0 to 1.6 lb./tonne clinker (500-800 mg NO x /m 3 (as NO 2 )). There was also a view that selective catalytic reduction is BAT with an associated emission level of 0.2 to 0.4 lb./tonne clinker (100- 200 mg NO x /m 3 (as NO 2 )). (35)Cement Kiln Report (FINAL – 7/14/2006) 5-1 5.0 CHEMISTRY OF ELLIS COUNTY MATERIALS AND IMPACTS ON CONTROL DETERMINATIONS

In order to evaluate the characteristics of feed material and th eir potential impacts on controls, the expert panel worked together to sele ct the parameters they determined necessary for their evaluations. During the team’s site visi ts, it was determined which of these parameters could be supplied by the companies, and which would need to be obtained through chemical analyses. The expert panel assisted TCEQ in preparing an information request for the parameters that could be obtained from the pl ants and a sampling protocol for the additional chemical analyses that would be required. The additional testing that was required is discussed below under analytical results.

5.1 Analytical Results

Analysis was conducted to determine the ch emical, mineral and elemental composition of
limestone and other raw materials used in cli nker production in Ellis County. Total organic carbon, total sulfur, various forms of sulfur incl uding sulfite and sulfat e, chloride, and total Kjeldahl nitrogen content were determined. Three samples of each type (dry powder, wet slurry, slag) were collected from representative operati ng kiln sites using Ellis County limestone feed material. Analyses were chosen based on the need to identify composition that was expected to
affect NO x emissions or control option performance.

Total organic carbon results are determined using a technique known as differential scanning calorimetry (DSC). Analyses are carri ed out in gas with a composition of 20% carbon dioxide, 3% oxygen, and 77% nitrogen similar to the basic constituents of kiln flue gas. This causes an oxidative pyrolysis, which closely para llels actual kiln conditions. The formation of char residues is very unlikely for this testing method. Several sa mples were also analyzed by an alternative technique that gradually heats the mate rial electrically from an external source using nitrogen as the carrier gas. The results re flect a pyrolysis regimen and provide additional supplemental data on the temperature pr ofile at which carbon is released.

Total Kjeldahl Nitrogen (TKN) is a meas ure of organic nitrogen and ammonia in any form found in the samples. Total nitrogen result s are determined by a h eated digestion of theCement Kiln Report (FINAL – 7/14/2006) 5-2 samples. The ammoniacal nitrogen is the most vol atile form of nitrogen. The TKN test does not
measure nitrite or nitrate. Since nitrate and nitrite nitrogen w ould not react with NO x they are of
little interest for the feed evaluation.

There are some distinct differences among th e feed types that ar e independent of the
incinerator site or treatment. Sl ag is a manufactured feed materi al that aids burnability and so would be expected to reduce thermal NOx generati on. It also has lower c ontent of some of the key chemicals of concern for emissions control or new control technology application. For instance, nitrogen and total sulfur in slag is less than the am ount found in wet slurry or dry powder, sulfate in slag and slurry less than sulfate in dry powder, and pyritic sulfur in slag is present at lower concentrations than pyritic sulfur in all other feed types. As a percent of total mass, organic sulfur tends to be higher in slag than other feed materials. There is a caveat: The methodology used by the laboratory lumps organic su lfur with simple sulfide (non pyrite). The sulfate in feed tends to be relatively constant compared to other compou nds tested in the feed material. Site specific results of kiln feed sample chemical analysis are summarized in
confidential attachments for each kiln site (Appendix A, B, and C, and Tables 1 through 5).
Results are summarized in the remainder of this section.

5.1.1 Organic Carbon

One set of kiln feed materials had higher or ganic content than all others. Organic carbon in these dry feed materials is mu ch greater than in all other feed material. Organic carbon in wet slurry from the same site is also higher than the organic carbon in other slurry feed materials. One kiln dry feed material had hi gher total organic carbon than the others in this sample set. The highest carbon containing feed ma terial also contained higher or ganic nitrogen. This site also
demonstrated lower NO x emissions than other sites. Results for feed sample carbon analysis from this site are provided in confidential data Appendix A.

The lowest organic carbon content was f ound in dry powder limestone feed from a different site and supplier. The organic content in these feed materials is quite variable, Total nitrogen was also lower in samples from the same site. This site demonstrates higher NO xCement Kiln Report (FINAL – 7/14/2006) 5-3 emission than other comparable sites. Results of percent carbon analysis in feed are shown in confidential data Appendix B.

Most of the organic material in the dr y feed is released between 350 and 500 oC indicating high molecular weight or ganic or pure carbon material. It was noted in the DSC data that some of the samples began generating heat at temperatures below 150 oC, while others only began above 200 oC. The higher temperatures re quired to liberate the ca rbon are a function of the volatility (molecular weight) of the carbonaceous material. It is not known whether this has any effect on NO x emissions, but could influence VOC emissions. However, NO x emissions were lower from the site supplying samples containing higher molecu lar weight carbon compounds. Efforts to control VOC emission s hould take into account the resulting oxidative
conditions that do not favor reduction of NO x .

The pattern of organic combustion determined by DSC appears to be fairly similar for all samples, except of course the slags. Much of the exothermic activity at 400-450 oC for all kiln feeds is probably attributable to pyrite oxidation. In preheater or calciner kilns, this may be occurring in Stage 2 of the preheater. Whether this has any impact on NO x emissions is questionable. It is possible, of c ourse, that nascent, freshly formed SO 2 may reduce NO 2 .

The results for total heat generated during carbon analysis by th e alternative nitrogen purged technique appear to be higher for samp les containing higher molecular weight carbon. The heat release results for these higher ca rbon containing samples show characteristics indicating considerable amounts of char, as evidenced by the lower heating results vis-à-vis the DSC results on samples analyzed using both approach es. If this char is produced in the kiln, it may serve as a reducing agent for NO x assuming it was available in the hot zone of the process, or it may be oxidized to CO which itself may be acting as a reducing agent. The additional carbon could be a partial explanation for the very low NO x emissions at this site.

5.1.2 Total Kjeldahl Nitrogen

The high carbon content feed also has th e highest Total Kjel dahl Nitrogen (TKN) content. Dry powder feed from this site contai ns slightly more Total Kjeldahl Nitrogen (TKN)Cement Kiln Report (FINAL – 7/14/2006) 5-4 than similar dry feed materials from other site s. While the ratio of %carbon to TKN feed materials is approximately the same for all samp les, the total carbon and TKN in wet slurry from sites generating higher NO x is less than that found in sites using dry powder limestone feed that generate lower NO x emissions. Results sorted by TKN values are shown in separate tables in confidential Appendices A-4, B-4, and C-4. Assuming the TKN nitrogen is the nonvolatile nitrogen component of the feed, it is likely to be organic based and that nitrogen and carbon are released in the process from the feed at approx imately the same time. Such nitrogen release
could act as a source of ammoni acal nitrogen at high temperatures, which could establish a quasi-”SNCR/SCR” reductive path for NO, particul arly in the presence of iron based catalysts, which at that point in the pro cess have not yet been converted to the ferrite phase of cement clinker, and so may exert a catalytic action. This is admittedly unproven.

5.1.3 Total Sulfur

Total Sulfur and speciated sulfur results are shown in Appendices A, B, and C, and confidential Tables A-4 through C- 4. Total sulfur in samples w ith higher carbon and nitrogen is generally higher than total sulfur fr om other kiln sites. Total sulfite in dry feed material follows the same trend with the highest carbon containing material also showing the highest sulfur as sulfite. Pyritic sulfur content in high organic samples trends higher than other kiln sites.

5.1.4 Summary of Analytical Results

As discussed above, the results of the testing conducted at th e three Ellis County plants to
characterize feed materials are considered confid ential business information and are, therefore, reported in confidential attachments to this report. The table below summarizes testing results. All feed material is averaged together for the results below and the slag samples are omitted. Averaging the results from the three plants provide s protection of confidentiality. As the slag
material was understood to be obtained from onl y one source, this information could not be presented in a manner that protected confidentiali ty. Table 5-1.1 presents the results for both wet and dry feed materials averaged together, as there are only two plan ts running wet and two running dry, reporting the results of the averag es of two plants’ da ta does not protect confidentiality.Cement Kiln Report (FINAL – 7/14/2006) 5-5 Table 5-1.1. Summary of Analytic al Results on Feed Materials

Carbon Evolution

Temp. range, o C Total DH, J/g Organic % Organic Sulfur

% Pyritic Sulfur

% Sulfate % Sulfite % Sulfur % Chloride (Water Soluble) % Kjeldahl Nitrogen

mg/kg mean NA 161.01 0.320 0.110 0.295 0.099 0.035 0.539 0.003 236.27 std. deviation NA 51.73 0.1028 0.0346 0.0696 0.0296 0.0207 0.0782 0.0012 93.73 range 115-630 NA NA NA NA NA NA NA NA NA

5.2 Data from Plant Surveys

The other source of data on the composition of feed materials was an information request that the expert panel assisted TC EQ in preparing and forwarding to the plants. This information was also requested to be treated as confidential by the plants. As discussed above, data from all three plants was averaged to protect confidentia lity. Although other da ta were requested and obtained, when less than all three plants reported a parameter, th at parameter was not included in Table 5.2.1 to protect confidentiality.

Table 5-2.1. Summary of Plant Reports on Feed Materials

Feed Composition (% wt typical) Kiln Feed Size Sulfur

Limestone Shale Silica Other Lime Saturation

Factor Silica Ratio Alkali % + 200 mesh weight % mean 88.1% 3.8% 5.8% 2.4% 100.9% 2.985 0.4927 29.5% 1.3% std. deviation 0.0078 0.0359 0.0238 0.0076 0.0494 0.3066 0.1153 0.2948 0.0023

5.3 Conclusions

Total carbon nitrogen and su lfur content seem to be ma jor factors in the difference between kiln feed materials. TKN can impact NO x emissions by oxidation to NO, but also as a component that may reduce NO formed in the burning zone, by a reaction similar to SNCR or SCR. We do not know the temperature profile of organic nitrogen generation from these feeds, only that nitrate or nitrite nitr ogen is not reflected in the valu es. However, process emissions tests from the site providing hi ghest carbon organic nitrogen and sulfur also show the lowestCement Kiln Report (FINAL – 7/14/2006) 5-6 uncontrolled NO x release. Other sites use dry powder feed material contains slightly lower levels of TKN but do not show the organic carbon or nitrogen content found in the lower NO x emitting
site.

Feed nitrogen under high carbon loading may be released into a reducing environment and need not generate NO. The temperatures re quired for organic carbon and nitrogen release are too cold for authentic SNCR, and the proce ss doesn't have the right catalysts for SCR. However, the low NO emissions at the site with the higher carbon in feed limestone suggest that these latter reactions may be occurring. On e possible conclusion from the feed analysis
information is a reaction under reducing conditions, similar to SNCR or SCR, as follows:

CO + NO ==> CO 2 + N

12NH 3 (from TKN in feed) + 8NO + 5 O 2 ==> 10N 2 + 18H 2 O

While this site may not have the right te mperature/oxygen/CO conditions in the tower for SNCR to be maximally effective, there seems to be some combination of chemistry and process conditions occurring that reduces the NO x emissions. Further evidence of this possibility can be found in a paper from Zement-Kalk-Gips (Germa n cement journal) written by M. Ono and coworkers, Japan, the authors show the effects of certain iron compounds in catalyzing the reaction of carbon monoxide with NO at temperatures below those usual in SNCR (the reference for this report has not been located).

It is possible that the calcin er design and process conditions at the site with the lowest
NO x emissions may be better in general or that its design may produce th e right conditions for
reduced NO x emissions with the higher carbon/higher organic nitrogen containing feed. Several additional feed analyses (e.g. temp erature related nitrogen releas e, speciated metals analysis) coupled with measurement of gases in kiln emissi ons are necessary to vali date this conclusion.

SO 2 is a high-temperature scavenger for high oxygen radicals like OH and O, and may thereby help reduce NO x . Feed material containing higher carbon and a higher level of sulfur than other kiln feed materials may contribu te to the reducing environment and lower NO xCement Kiln Report (FINAL – 7/14/2006) 5-7 emissions. The “organic sulfur” found in samp les also includes sulf ide (nonpyritic) sulfur. Sulfite is not usually present in materials taken di rectly from ore deposits. There is more sulfite
in the feed at the lower NO x emission site than in the other feed from the other sites. This may
reflect the return kiln dust and its sulfite conten t, which in turn may reflect the effect of oxygen upstream of the dust collect or. If the available O 2 is lower in the kiln process gas this may also reduce low temperature formation of NO.Cement Kiln Report (FINAL – 7/14/2006) 6-1 6.0 REFERENCES

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(74j) “Applications and Economics of Low Temp erature Oxidation NOx Control.” BOC Gases 575 Mountain Avenue Murray Hill, NJ 07974. M.H. Anderson, R.J. Ferrell, Dr. S.C. Hwang, Dr. N. Suchak, Dr. James Tseng, R. Kelton
(74k) “Application of Low Temperature Oxidat ion for NOx Emissions Control on a Lead Recovery Furnace.” R. Ferrell RJF Consu ltants 196 Hollister Avenue, Rutherford, NJ 07070. Dr. N. Suchak, R. Kelton The BOC Group, Inc., Process Gas Solutions 575 Mountain Ave., Murray Hill, NJ 07974. H. Hine, RSR Corporation, Dallas, TX M. Vondersaar, Quemetco, Inc., City of I ndustry CA. Shyam Nadkarni, 144 Woodmere Blvd., Woodmere, NY 11598.
(74l) “New Process and Equipment for Waste Minimization: Conversion of Nitrogen Oxide (NOx) Scrubber Liquor to Fertilizer.” C onversion of Nitrogen Oxide (NOx) Scrubber Liquor to Fertilizer. http://rtreport.ksc.nasa.gov/techre ports /95 report/ environf/environ0

. (74m) “Using Non-Thermal Plasma to Control Air Pollutants.” EPA-456/R-05-001. The Clean Air Technology Center (CATC). U.S. Envi ronmental Protection Agency (E143-03). Research Triangle Park, North Carolina 27711.Cement Kiln Report (FINAL – 7/14/2006) 6-8 (74n) “ETV for Add-On NOx APT Update.” Douglas VanOsdell.
(74o) “Nitrogen Oxides (NOx) Abatement With Hydrogen Peroxide.” Reference Library/Applications: Industrial Wastewater http://www.h2o2.com/applications /industrialwastewater/nox.html
(74p) “Kinetics of NOx Absorption into Aqueous Solutions of Oxone.” Kinetics of NOx Absorption into Aqueous Solutions of Oxone. http://aiche.confex.com/a iche/2005/techprogram/P15564.HTM (75) Helmuth, R.A., F.M. Miller, T. R. O'Connor, and N.R. Greening. Kirk-Othmer Encyclopedia of Chemical Technology. Vol. 5. Third Edition . New York, NY. John Wiley & Sons, Inc. 1979. pp. 163-193. (76) Yee, G.M. Suggested Control Measure for the Cont rol of Emissions of Oxides of Nitrogen from Cement Kilns . Presented to the State of California, Air Resources Board for Discussion on October 21, 1981. (77) Miller, F.M. Oxides of Nitrogen . GTC Presentation, Kansas City, MO, September 20, 1977. (78) Hansen, E.R., “The Use of Carbon Monoxide and Other Gases for Process Control,” 27 th IEEE Cement Industry Technical Conference Proceedings, May 1985. (79) Mehta, P.K. Energy, Resources and the Environment - A Review of the U.S. Cement Industry. World Cement Technology. July/August 1978. (80) Andover Technology Partners. NOx Reduction from Cement Kilns Using the CemStar Process, Evaluation of CemStar Technology - Final Report to Texas Industries. Dallas, Texas. April 18, 2000. (81) Battye, R., and S. Edgerton, EC/R Incorpor ated. “December 2, 1999 Trip Report to Texas Industries (TXI) Riverside Cement, Oro Grande facility.” Oro Grande, CA. Submitted to Dave Sanders, US EPA, under contract No. 68-D-98-026, work assignment No. 2-28. August 31, 2000. (82) En-tellect Environmental Services, Inc., “E valuation of the Effects of the CemStar Process on a Wet Process Cement Kiln,” (no date, but includes data for July-Sept 1999). (83) Hilovsky, R.J. NO X Reductions in the Portland Ceme nt Industry With Conversion To Coal-Firing : Presented at the 1977 U.S. EPA Em ission Inventory/Fa ctor Workshop. Raleigh, NC. September 13-15, 1977.
(84) Radian Canada, Inc. Assessment of NO X Emission Control Technol ogies for Cement and Lime Kilns . Radian Report No. 714-061-01. Prepared for Environment Canada, Contract No. K2035-3-7044. October 1994. Pg.iv.Cement Kiln Report (FINAL – 7/14/2006) 6-9 (85) Portland Cement Association. U.S. and Canadian Portland Cement Industry Plant Information Summary . Skokie, IL. December 31, 1998. (86) Penta Engineering Corporation Report on NO X Formation and Variability in Portland Cement Kiln Systems Potential Control Techniques and Their Feasibility and Cost Effectiveness. Penta Project No. 971212. Prepared for the Portland Cement Association. PCA R&D Serial No. 2227. Skokie, IL. 1999. (87) Comments on Alternative Control Te chniques Document - NO X Emissions from Cement Manufacturing submitted by Greer, W.L. to William Neuffer, U.S. EPA through T.B. Carter, APCA. October 27, 1999. (88) Worrell, Ernst and Galitsky, Christina, “Ene rgy Efficiency Impr ovement Opportunities for Cement Making An ENERGY STAR Guide for Energy and Plant Managers”, Energy Analysis Department, Environmental Ener gy Technologies Divisi on., Ernest Orlando Lawrence Berkeley National Laboratory, Un iversity of California, January 2004. (89) Birch, E., “Energy Savings in Cement Kiln Systems” Energy Efficiency in the Cement Industry, London, England, 1990. (90) Fujimoto, S., “Modern Technology Impact on Power Usage in Cement Plants, 1994. (91) Hendriks, C.A., E. Worrell, D. de Jage r, K. Blok, and P. Riemer. 1998. Emission Reduction of Greenhouse Gases from the Ceme nt Industry Lawrence Berkeley National Laboratory, Berkeley, California. IEA. (92) COWIconsult, Internahsauon and the Exte rnal Cost of Tran sport Lyngby, Denmark Danish Ministry of Energy, EFP-91, 1993.
(93) Young, Gerald L. “Review of NOx Control Te chnologies for Cement Kilns, Associated Costs and NOx Reduction Efficiencies, 2002.
(94) COWIconsult, Internahsauon and the Exte rnal Cost of Tran sport Lyngby, Denmark Danish Ministry of Energy, EFP-91, 1993.
(95) Jaccard and Willis Energy Services, “I ndustrial Energy End-Use Analysis and. Conservation Potential in Six Major Industries in Canada, 1996.
(96) Venkateswaran, SR and HE Lowitt, “The US Cement Industry: an Energy Perspective, DOE, Washington, DC, USA, 1988.
(97) Anonymous, “Cement Plant Modernization in Central Europe,” World Cement, November 1994.
(98) Vleuten, Cement in Development: Energy and Environment. Petten, Netherlands: Netherlands Energy, 1994.
(99) van Oss, US Geological Survey, Communicatio n with authors (see reference 88) , 1999.Cement Kiln Report (FINAL – 7/14/2006) 6-10 (100) Nisbet, M., 1996. “The Effects of New Climate change Commitments on Energy Intensive Industries, Th e Cement Industry”, 1996.Cement Kiln Report (FINAL – 7/14/2006) Attachment A ERG SUMMARY OF EPA 2000 NO x CONTROLS FOR CEMENT KILNSAttachment A – Table A-2Table A-1. Summary of EPA Reported NOxControl Technologies for Cement Kilns – EPA 2000NOxControl StrategiesApplicabilityNOxReductionEfficiency (%)Estimated CostsNumber ofInstallationsExcess air and temperatureoptimization (using CO andO2CEMS and feedbackcontrol)All kiln types 15aCapital cost = ~$750,000sUnknownReduce alkali content offeed where feasibleAll kiln types Not available Not available UnknownCemStar (addition of steelslag)All kiln types although higher NOxreductions expected from wet and long-drykilns due to greater heat input offsets9 - 60bCapital cost = $200,000 -$500,000tAnnual costs are highlysite-specific (e.g., slaginjection rate, potential costsavings due to increasedproduction)11Fuel switching (natural gasto coal)All kiln types 70cNot available ~ 87% of existing kilnsuse coalProcessmodificationsImproving thermalefficiencyAll kiln types Not available Not available UnknownStaged air combustion -staged fuel combustionAll kiln types (most effective with indirectfired kilns)Not available Not available UnknownStaged air combustion -flue gas recirculationMay not be suitablefor cement kilns.Incorporation of FGR in a cement kiln alsoresults in somewhat increased powerconsumption and reduced kiln output.Not available Not available UnknownStaged air combustion -flue gas recirculationw/low-NOxburner15 - 38dNot available UnknownCombustionmodificationStaged air combustion -Low-NOxburnerAll kiln types (burners that use 5-7%excess air are only for indirect-fired kilns)44e15 - 33f23 - 47g14hCapital cost = $511,000 -$966,000uAnnual cost = $136,000 -$204,000u~ 22 existing kilns uselow-NOxburnersAttachment A – Tables A-1 (continued)Cement Kiln Report (FINAL – 7/14/2006)NOxControl StrategiesApplicabilityNOxReductionEfficiency (%)Estimated CostsNumber ofInstallationsStaged fuel combustion -Tire-derived fuel (TDF)All kiln types 30 - 40iUnknown.Approximately53,300,000 tires areburned in cement kilnsannuallyhttp://www.epa.gov/epaoswer/nonhw/muncpl/tires/tdf.htm#cementStaged fuel combustion -Low-NOxprecalcinerNot applicable to preheater kilns that fire fuel in the riser<46jNot available UnknownCombustionmodification(cont.)Staged fuel combustion -Mid-kiln firingWet and long-dry kilns 38k11 - 55l28 - 59mCapital cost = ~$3,000,000vAnnual cost = ($370,000) -$189,000v21 long kilns (US),40 kilns (worldwide)Selective catalyticreduction (SCR)No cement kilns had SCR at the time of theEPA Study prior to 2000.Not available in 2000. No installations werereported on cementkilns in EPA 2000.Selective non-catalyticreduction (SNCR)Best application is for preheater/precalciner kilns. Generally not applicableto long-dry or wet kilns71 -98n10-20oNot available 2 kilns (US), 18 inEuropeBiosolids (SNCR) Preheater/precalciner kilns Not available Capital cost = $240,000wAnnual cost = ($322,000)wUnknownNOxOUT (SNCR) Preheater/precalciner kilns > 50 - 90p10 - 20q46 - 53rCapital cost =~$1,200,000xAnnual cost = $560,000 -$2,000,000xNonePostformationremovalLow TemperatureOxidation (LoTOxTM,Hydrogen Peroxide,OXONE (Dupont) &Sodium Acetate)Oxidation technologies were not discussedor considered in the EPA 2000 report.Not considered Not considered Oxidation technologieswere not discussed orconsidered in the EPA2000 report.aResults based on experimental test on one kiln.bResults derived from short- and long-termtests on two different kiln types.cResults based on emission tests of dry kilns.dResults based on a single 1988 study. The percent reduction depends on degree of flue gas recirculation.eResults based on emission tests of a preheater/precalciner kiln.fResults based on emission tests of five kilns.gResults based on emission tests of four kilns.Attachment A – Tables A-1 (continued)Cement Kiln Report (FINAL – 7/14/2006)hEmission test of one kiln.iResults based on tests conductedat one California facility.jResults based on a test conducted bythe Portland Cement Association.kResults based on one study.lResults based on testing of seven dry kilns.mResults based on testing of three wet kilns.nBased on emission tests of a preheater/precalciner kiln at one facility.oResults based on emission test at one facilitypResults based on emission tests of a single kiln.qResults based on a emission tests ofa single kiln (operating conditions during most of the test were unstable).rResults based on emission test of two kilns.sEstimate for a commercially available process control system.tCost estimates obtained fromTexas Industries (TXI).uCosts derived for retrofitting low-NOxburners to eight model kilns with clinker production capacities ranging from 25 to 150 tons of clinker per hour.vCosts derived for retrofitting low-NOxburners to four model kilns with clinker production capacities ranging from 25 to 50 tons of clinker per hour. Annual costs reflect the fuelcredit associated with using tire-derived fuel.wCosts based on a clinker production rate of 215 tons per hour.xCosts based on two preheater/precalciner kilns with a clinker production rates of 92 tons per hour and 133 tons per hour.Cement Kiln Report (FINAL – 7/14/2006) ATTACHMENT B SAMPLING PLANCement Kiln Report (FINAL – 7/14/2006) B-1 Sample Acquisition and Handling
Clean, clear, pre-labeled, one (1) liter sample bottles were shipped to each Kiln site on August 23, 2005 via Federal Express. The nine (9) samples returned on August 25 in good condition from Texas Industries Inc. includ ed three wet slurry, three dry pow der and three slag samples. The six (6) samples returned from Ash Grove Ce ment on August 26 included three (3) wet slurry and (3) slag samples. The 6 samples return ed from Holcium on August 31 included three (3) samples from line 1 and 3 samples from line 2.
All were samples returned to ERG’s analytical laboratory with chain of custody and security seals. ERG consulted with three cement kiln ex perts, F. MacGregor Miller, Gabriel Miller, and David Gossman on the analyses required to determ ine key features of the kiln feed chemistry important to NO x emissions and control. Recommenda tions were sought from the experts on laboratories experienced in each analysis. Thr ee laboratories were ulti mately selected on the basis of expertise and price. Table 1 summari zes the analyses requested for each sample.
ERG repackaged samples for distribution to the specialty analysis labo ratories scheduled to perform feed material composition analysis . Repackaged samples were give unique identification numbers to keep Kiln ident ity anonymous to the analysis laboratories.Cement Kiln Report (FINAL – 7/14/2006)B-2Table B-1. Feed Chemical CompositionPlant NameSamplesReceivedSample TypeTotalSulfurSulfateSulfitePyriticSulfurOrganicSulfurChlorideNitrogen(TKN)VOCsTexas Industries Inc(TXI)3 Wet Slurry X X X X X X X XTexas Industries Inc(TXI)3 Dry Powder X X X X X X X XTexas Industries Inc(TXI)3 Slag X X X X X X X XHolcim US Inc0 Dry Power Line 1 X X X X X X X XHolcim US Inc0 Dry Power Line 2 X X X X X X X XAsh Grove CementInc3 Wet Slurry X X X X X X X XAsh Grove CementInc3 Slag X X X X X X X XCement Kiln Report (FINAL – 7/14/2006) ATTACHMENT C ERG Report on LoTOx TM Application to RefineriesCement Kiln Report (FINAL – 7/14/2006) 1 

### ERG Report - Refinery Application of Low Temperature Ox idation Emissions Controls

LoTOxTM
LoTOxTM is a trademark of the BOC Group Inc. for an end-of-pipe process that uses ozone to oxidize insoluble species of NO x , such as NO and NO 2 , to highly soluble species, primarily N 2 O 5 . N 2 O 5 then reacts with moisture in the flue gas to form nitric acid (HNO 3 ) and is removed from the gas in a wet gas scrubber. LoTOx TM is a developing technology for NO x control, and there are currently only about three commercial applications of LoTOx TM . Another three installations are planned in the next two years. LoTOx TM has been demonstrated using slipstream testing at ten types of facilities, including a smelting plant, a glass furnace, a lead furnace, a petroleum coke and high sulfur coal fire d boiler, a chemical plant, a steel pickling bath process, a gas-fired boiler, a composite fuel fi red boiler, a petroleum refinery fluid catalytic cracking unit (FCCU), and a lign ite-fired boiler. No cement plants have tested LoTOx TM

.
In the LoTOx TM process, ozone is formed from o xygen using a corona-discharge ozone generator. The resulting concen tration of ozone is between 7 a nd 15 weight percent (1). The ozone/oxygen mixture is injected into the flue gas stream as it ente rs either a wet gas scrubber or a reaction vessel adjacent to a wet gas scrubber. The ratio of ozone to NO x is 0.2-2.8:1, and varies with factors such as flue gas temperature and residence tim e. The principal reactions for NO x oxidation are:

NO + O 3 → NO 2 + O 2 2 NO 2 + O 3 → N 2 O 5 + O 2 N 2 O 5 + H 2 O → 2 HNO 3 The maximum temperature for the oxidation reactions is 325 °F (163 °C), while the optimal temperature is generally less th an 300 °F (149 °C). The NO x oxidation reactions become unstable over 325 °F. Trials at a coal-fired pow er plant and a steel pickling process found the optimal temperature was in the range of 160 to 250 °F (1). A trial at a battery lead recovery furnace found the optimal temperature was 175 °F or less, although the temperature could be increased up to 225 °F without sacrificing NO x removal, but at the cost of increased ozone demand (2). A trial at Marathon Ashland Petr oleum’s (MAP) Texas City refinery FCCU found the optimal temperature was 140 to 150 °F (3). These temperatures are lower than typical cement kiln flue gas temperatures. In additi on to cooling using heat recovery systems, quenching with water is typically used to lower the gas temperature to the adiabatic saturation temperature.

After NO x is oxidized to N 2 O 5 , it is absorbed from the flue gas by water spray in a wet gas scrubber. The relative solubility of N 2 O 5 compared to other flue gas species is presented below.Cement Kiln Report (FINAL – 7/14/2006) 2 Relative Solubility of Flue Gas Components

Species Relative Solubility at 25 °C NO 1 NO 2 20 SO 2 2000 N 2 O 5 >>2000 HNO 3 Mixes with water in all proportions Ferrell 2003, p. 4

N 2 O 5 reacts immediately and irreversibly with water to form nitric ac id. The nitric acid then is neutralized with caustic or lime in the scrubber liquor to form sodium or calcium nitrates.
Potential Advantages of LoTOx TM

The potential advantages of LoTOx TM are as follows.

LoTOx TM can provide a high degree of NO x removal. Based on slipstream testing, 70 to 90 percent NO x removal is typical, with greater than 95 percent NO x removal achievable.

LoTOx TM can respond quickly to variable NO x emissions. Since ozone is produced on demand, changes in NO x load can be met without loss of NO x removal efficiency. Swings in NO x concentration by 100 percent or more over the course of minutes have been accommodated using combined feed-for ward/feed-back control schemes (Ferrell 2000, pp. 8-9; Ferrell 2003, pp. 13-14) . Although most LoTOx TM trials have been for combustion processes (90:10 NO to NO 2 ratio), the steel pickli ng process had variable NO to NO 2 ratios, with NO 2 sometimes higher than NO. Ozone production was decreased since less ozone was required to oxidize NO x to N 2 O 5 , while NO x removal was maintained above 95 percent (1).

LoTOx TM does not emit excess reactant . Unlike SCR and SNCR, which can emit excess ammonia, the ozone that does not react with NO x in the LoTOx TM process is scavenged by sulfite in the scrubber soluti on. A trial at a lead furnace examined the potential for unreacted ozone to be emitted from the process. It wa s found that the ozone addition had to be increased by a factor of eight over what was required for NO x removal to cause 0.6 ppm of ozone to be measured in the stack gas (2).

LoTOx TM is highly selective for NO x . Although ozone can oxidize SO 2 and CO, the presence of SO 2 and CO does not impact NO x removal. This is due to the faster reaction rates for NO x oxidation compared to oxidati on of other gas species.Cement Kiln Report (FINAL – 7/14/2006) 3 Relative Reaction Rates of Flue Gas Components with Ozone

Species Relative Reaction Rates NO + O 3 → NO 2 + O 2 62,500 2 NO 2 + O 3 → N 2 O 5 + O 2 125 SO 2 + O 3 → SO 3 + O 2 5 CO + O 3 → CO 2 + O 2 1 Ferrell 2003, p. 3

LoTOx TM does not interfere with other pollution control technologies. The trial at MAP’s Texas City refinery FCCU indicated LoTOx TM does not have a negative impact on SO 2 scrubbing efficiency. The scrubber maintained SO 2 removal in excess of 99 percent during the LoTOx TM trial (3).
Areas of Concern
Wet Gas Scrubber Required
A wet gas scrubber is necessary to take a dvantage of the increased solubility of N 2 O 5 over NO and NO 2 . For cement plants with an existing wet gas scrubber for SO 2 and particulate matter removal, LoTOx TM can be installed as an upstream retrofit. For plants that do not require a scrubber for SO 2 or particulate matter rem oval, installing a scrubber for NO x removal only may not be cost effective.

Gas Temperature
Cement kiln flue gases typically have temperatures greater than the LoTOx TM maximum temperature of 325 °F. If the flue gas temperat ure is greater than 325 °F after useful heat has been recovered, quenching with water is required prior to ozone injection. BOC indicates that water quenching can be used on gas streams with temperatures up to 650 °F and moisture contents of 30 to 35 percent.

Nitrates in Wastewater
Sodium nitrate is typically th e primary byproduct of the LoTOx TM process. This may be a concern for treatment and/or discharge of the wastewater. MAP examined the possible problems of increased nitrates in the study at the Texas City refinery (3). Regarding sodium toxicity, MAP found that the cont ribution of sodium nitrate from LoTOx TM was small compared to sodium sulfate from SO 2 scrubbing. Regarding wastewater treatment impacts, monovalent cations, such as sodi um, can have a destabilizing effect on bioflocculation by displacing diva lent cations, such as calciu m or magnesium. This can lead to decreased biofloc settling and increa sed suspended solids. This problem does not occur if the monovalent to divale nt cation ratio is maintained at 2:1 or less (by addition of divalent cations if necessary). In addition, nitrogen gas produced by denitrification in the secondary clarifier sludge bed can cause the bed to rise, incr easing suspended solids. In this case, a holding tank can be installed to shift the denitrificati on reactions out of the secondary clarifier.Cement Kiln Report (FINAL – 7/14/2006) 4 Cost

BOC indicates NO x removal of 70 percent or greater must be required for LoTOx TM to be cost effective. In ERG’s experience, the estimated cost effectiveness for LoTOx TM installations at refineries has ranged from approxima tely 2,500 to 10,000 dollars per ton of NO x (as NO 2 ) removed. In general, the cost per ton of NO x removed was lower for units with high NO x removal (greater than 85 percent), due to economy of scale. Similarly, the annual operating cost was at least 50 percent of the total annualized cost for those units with the lowest cost per ton of NO x removed. The costs of oxygen and electricity for the ozone generator accounted for 80 to 90 percent of the annual operating costs.
For a 200 MW coal-fired power plant, BOC estimated the cost to be only 1,696 dollars per ton of NO x removed (1). This application was designed for 95 percent NO x removal, and the annual mass of NO x removed was 4 to 46 times larger than the refinery applications.
References Cited
(1) (Ferrell 2000). Ferrell, R ., M.H. Anderson, S.C. Hwang, N.J. Suchak, R. Kelton, J.T. Tseng. “Applications and Economics of Low Temperature Oxidation NO x Control.” Paper presented at Power-Gen 2000, November 14, 2000, Orlando, FL.
(2) (Ferrell 2003). Ferrell, R., N. Sucha k, R. Kelton, H. Hine, Shyam Nadkarni. “Application of Low Temperature Oxidation for NO x Emissions Control on a Lead Recovery Furnace.” Paper presented at ACE 2003, June 22-26, 2003, San Diego, CA.
(3) (Sexton 2004). Sexton, J., N. Confuo rto, M. Barrasso, N. Suchak. “LoTOxTM Technology Demonstration at Marathon Ashla nd Petroleum LLC’s Refinery in Texas City, Texas.” Paper presented at NPRA Annual Meeting, March 21-23, 2004, San Antonio, TX.Cement Kiln Report (FINAL – 7/14/2006) 5 ATTACHMENT D SUMMARY OF CURRENT US REGULATIONS FOR NOxCement Kiln Report (FINAL – 7/14/2006)1Table D-1. Summary of US NOxControl Regulations forCement Kilns – EPA 2004StateEffectiveDateSourceType Description Emission Limit Applicability Avg. Time Test/CEM RuleNY 5/1/03NOxBudgetTradingProgramEGUs≥15 MW; nonEGUs≥250mmBtu/hr;Portland CementPlants≥250mmBTU/hrAllowances & TradingProgramAllstatewideOzoneseason CEM Part 20405/31/95PortlandcementkilnsSources with PTE 25TPY in NYC andlower Orange countymetro areas; PTE 100TPY elsewhere inStateAnalysis of RACTcontrols; select control;NY approves RACTemission limit &submits to EPA as a SIPrevisionPart 220RACTMD11/24/03CementkilnsCapacity no morethan 600,000 TPY 0.5 tons per hour30 dayrolling avg CEMCOMAR26.11.09.0811/24/03Capacity greater than600,000 TPY 0.9 tons per hour30 dayrolling avg CEMCOMAR26.11.09.0805/1/03Nontradingsource Cement KilnsLong wet-6.0 lb./T ofclinker;long dry5.1;preheater/precalcineror pre-calciner-2.8 CEM 26.11.29.15PA Proposed Cement KilnsLNB or mid-kiln firingor alt. that achieves 30%reduction Statewide Season CEMChapter 145-SubchapterC-proposedAL04/06/01CementkilnsLong dry -12 TPH;Long wet -10TPH;Preheater16TPH ; Precalciner& PH/PC-22 TPHLNB or mid-kiln firingor equivalent controlsVariouscountiesOzoneseason 335-3-8-.01KY08/15/01CementkilnsProcess rates atleast(TPH)-long dry12;long wet10;preheater16;PH/PC-22 6.6 lbs./T of clinker Statewide30 dayrolling avg-ozoneseason CEM401 KAR51:170Cement Kiln Report (FINAL – 7/14/2006)2Table D-1. Summary of US NOxControl Regulations forCement Kilns – EPA 2004SC05/31/04CementkilnsProcess rates atleast(TPH)-long dry12;long wet10;preheater16;PH/PC-22 orNOx>1 TPDLNB or mid-kiln firingor similar controlsAllStatewideozoneseasonCEM orannualsourcetest61-62.99Subpart BEarlyActionCompact(EAC) Cement kilnsLNB or equivalentcapable of achieving30% reductionReg 61-62.5;StandardNo.5.2TN05/31/04CementkilnsProcess rates(TPH) atleast-long dry12;long wet10;preheater16;PH/PC-22LNB or mid-kiln firingor similar controls orRACTStatewideozoneseason1200-3-27-.04IL05/30/04CementkilnsLong dry kilns atleast 12 TPH5.1 lb./T or 30%reduction or LNB ormid kiln firing StatewideOzoneseasonAnnualstack testPart 217;Subpart T05/30/04CementkilnsLong wet kilns atleast 10 TPH6.0 lb./T or same asaboveStatewideOzoneseasonAnnualstack testPart 217;Subpart T05/30/04CementkilnsPreheater kilns atleast 16 TPH3.8 lb./T or same asaboveStatewideOzoneseasonAnnualstack testPart 217;Subpart T05/30/04CementkilnsPreheater/precalcinerkilns at least 22 TPH2.8 lb./T or same asaboveStatewideOzoneseasonAnnualstack testPart 217;Subpart TIN08/04/97EmissionlimitsCement kilns - longdry-at least 20 TPHDaily – 10.8 lb./T;Rolling 30 day - 6.0lb./TClark, FloydCos;may avgamongplantsstatewideunder sameownerozoneseason CEM326 IAC 10-1-408/04/97Preheater kilns atleast 20 TPHDaily - 5.9 lb./T;Rolling 30 day – 4.4lb./TSame asaboveozoneseasonCEM326 IAC 10-1-4Cement Kiln Report (FINAL – 7/14/2006)3Table D-1. Summary of US NOxControl Regulations forCement Kilns – EPA 200403/01/04Reduction -certaincategoriesCement kilns - longdry at least 12TPH;long wet- 10TPH5.1, 6.0 lb./T or LNB ormid kiln firing or30%control StatewideozoneseasonCEMunlessLNB ormid-kiln 326 IAC 10-303/01/04Preheater kilns atleast 16TPH;precalciner andPH/PC - 22 TPH3.8, 2.8 lb./T; same asaboveStatewideozoneseasonsame asabove326 IAC 10-3MI12/04/02Non SIPCallCement kilnsLNB or mid-kiln or 25%red from 1995Statewideozoneseason336.180112/04/02CementkilnsLong dry -12 TPH;Long wet -10TPH;Preheater16TPHLNB or mid-kiln or longwet - 6.0 lbs./T; longdry - 5.1 lbs./TFine gridozoneseasonAnnualstack testor CEM336.181612/04/02CementkilnsPrecalciner &PH/PC-22 TPHPreheater - 3.8 Lb/T;PH/PC-2.8 lb./T or30%red Fine gridozoneseason336.1816OH04/30/04CementkilnsLong dry -12 TPH;Long wet -10TPH;Preheater16TPHLNB or mid-kiln firingor similar controls StatewideozoneseasonAnnualstack testor CEM3745-14-1104/30/04CementkilnsPrecalciner &PH/PC-22 TPHLNB or mid-kiln firingor similar controls StatewideozoneseasonAnnualstack testor CEM 3745-14-11TX *03/27/03CementkilnsWet kilns 6.0 lb./T of clinkerBexar, Hays,Comal andMcLennanCos30 dayrolling avgCEM orPEMSChap.117;Sec.26503/27/03CementkilnsWet kilns 4.0 lb./T Ellis Co.30 dayrolling avgCEM orPEMSChap.117;Sec.26503/27/03CementkilnsLong dry kilns 5.1 lb./TBexar, Hays,Comal andMcLennanCounties30 dayrolling avgCEM orPEMSChap.117;Sec.265Cement Kiln Report (FINAL – 7/14/2006)4Table D-1. Summary of US NOxControl Regulations forCement Kilns – EPA 200403/27/03CementkilnsPreheater kilns 3.8 lb./TAbovecounties30 dayrolling avgCEM orPEMSChap.117;Sec.26503/27/03CementkilnsPreheater/precalcineror precalciner kilns2.8 lb./TAbovecounties30 dayrolling avgCEM orPEMSChap.117;Sec.265SCAQMD07/01/86CementkilnsAny gray cement kiln 11.6 lbs./T; 6.4 lbs./T Districtwide24 cons.Hrs/30consecutivedays Rule 1112TPH refers to tons of clinker per hour of cement production.* Texas has the option of complying with the following technical standard:Each long wet or long dry kiln for which the following controls are installed and operatedduring kiln operation is not required to meet the NOx emission limits of subsection (a) of this section,provided that each owner or operator choosing thisoption submits written notification of this choice tothe executive director, the appropriate regional office, and any local air pollution control program withjurisdiction before the appropriate compliance date in §117.524 of this title:(1) a low-NOx burner and either:(A) mid-kiln firing; or(B) some other form of secondary combustion achieving equivalent levels of NOxreductions; or alternatively;(2) other additions or changes to the kiln system achieving at least a 30% reduction inNOx emissions, provided the additions or changes are approved by the executive director withconcurrence from EPA.(d) Each preheater or precalciner kiln for which either a low-NOxburner or a low-NOxprecalciner is installed and operated during kiln operation is not required to meet the NOx emissionlimits of subsection (a) of this section. Eachowner or operator choosing this option shall submitwritten notification of this choice to the executivedirector, the appropriate regional office, and anylocal air pollution control program with jurisdiction before the appropriate compliance date in §117.524of this title.ERG reviewed US EPA’s Summary of State / Local NOx Regulations for Stationary Sourcesand selected and reviewed those control measures that apply to cementkilns to create this table. This file is locate at :www.epa.gov/ttn/naaqs/ozone/ozonetech/statenoxregs518.pdf