BEST AVAILABLE 

RETROFIT TECHNOLOGY 

(BART) ANALYSIS 

Holcim (US) Inc. 

Prepared for: 

Holcim (US) Inc. 

4070 Trident Road 

Three Forks, Montana 59752 

Prepared by: 

Bison Engineering, Inc. 

1400 11th Avenue 

Helena, MT 59601 

(406) 442-5768 

www.bison-eng.com 

July 6, 2007
HCM Air Quality Issues\BART 7/6/07 pg. ii 

Project #: HCM207541

TABLE OF CONTENTS 

1.0 INTRODUCTION............................................................................................... 1-1 

1.1 Summary ................................................................................................ 1-1 

1.2 Background and Purpose ....................................................................... 1-3 

1.3 Site Location and Description ................................................................. 1-4 

2.0 PROCESS DESCRIPTION ............................................................................... 2-1 

3.0 EMISSIONS INVENTORY AND BART ANALYSIS SOURCE SELECTION...... 3-1 

3.1 Initial BART Emission Summary ............................................................. 3-1 

3.2 SO2 Applicable Units Emissions ............................................................ 3-3 

3.3 NOX Applicable Units Emissions............................................................. 3-3 

3.4 PM Applicable Units Emissions ............................................................. 3-3 

4.0 BEST AVAILABLE RETROFIT TECHNOLOGY REVIEW................................. 4-1 

 4.1 Summary ................................................................................................ 4-2 

 4.1.1 Affected Units............................................................................... 4-2 

 4.1.2 Applicable Pollutants.................................................................... 4-2 

 4.2 BART Analysis Methodology .................................................................. 4-3 

 4.3 SO2 BART Analysis for the Kiln .............................................................. 4-4 

 4.3.1 Step 1 – Identify All Available SO2 Retrofit 

 Control Technologies ................................................................... 4-5 

 4.3.2 Step 2 – Eliminate Technically Infeasible SO2 Control Options.... 4-7 

 4.3.3 Step 3 – Evaluate Control Effectiveness of Remaining 

 Control Technologies ................................................................... 4-9 

 4.3.4 Step 4 – Evaluate Impacts and Document Results .................... 4-10 

 4.3.5 Step 5 – Evaluate Visibility Impacts ........................................... 4-11 

 4.3.6 Select SO2 BART ....................................................................... 4-12 

 4.4 NOx BART Analysis for the Kiln ........................................................... 4-12 

 4.4.1 Step 1 – Identify All Available NOx Retrofit 

 Control Technologies ................................................................. 4-13 

 4.4.2 Step 2 – Eliminate Technically Infeasible NOx 

 Control Options .......................................................................... 4-18 

 4.4.3 Step 3 – Evaluate Control Effectiveness of Remaining 

 NOx Control Technologies ......................................................... 4-22 

 4.4.4 Step 4 – Evaluate Impacts and Document the Results .............. 4-22 

 4.4.5 Step 5 – Evaluate NOx Visibility Impacts ................................... 4-24 

 4.4.6 Select NOx BART ...................................................................... 4-25 

 4.5 BART Analysis for PM10 from the Kiln .................................................. 4-25 

 4.5.1 Step 1 – Identify Available Particulate Control Technologies ..... 4-25 

 4.5.2 Step 2 – Eliminate Technically Infeasible Options...................... 4-27 

 4.5.3 Step 3 – Evaluate Control Effectiveness of Remaining 

 PM10 Control Technologies ........................................................ 4-27 

 
HCM Air Quality Issues\BART 7/6/07 pg. iii 

Project #: HCM207541

 4.6 BART Analysis for PM10 from the Clinker Cooler.................................. 4-28 

 4.6.1 Step 1 - Identify Available Particulate Control Technologies...... 4-28 

 4.6.2 Step 2 – Eliminate Technically Infeasible Options...................... 4-29 

 4.6.3 Step 3 - Evaluate Control Effectiveness of Remaining 

 PM10 Control Technologies ........................................................ 4-29 

4.7 BART Analysis for PM10 Emissions from Material 

Handling Systems................................................................................. 4-29 

4.7.1 Step 1 - Identify Available Particulate Control Technologies...... 4-30 

4.7.2 Step 2 – Eliminate Technically Infeasible Options...................... 4-31 

 4.7.3 Step 3 - Evaluate Control Effectiveness of Remaining 

 PM10 Control Technologies ........................................................ 4-31 

LIST OF TABLES 

Table 1-1: Sources Addressed by Holcim BART Analysis ....................................... 1-1 

Table 1-2: Summary of BART Selections and Visibility Impacts .............................. 1-3 

Table 3-1: Potential BART-Eligible Emitting Units.................................................... 3-2 

Table 3-2: Initial EPA BART Modeled Sources and Emissions................................ 3-3 

Table 3-3: PM10 Sources Analyzed for BART .......................................................... 3-4 

Table 4-1: Summary of SO2 Control Technology Efficiency................................... 4-10 

Table 4-2: Summary of SO2 Cost Analysis ............................................................ 4-11 

Table 4-3: Summary of SO2 Visibility Impacts........................................................ 4-12 

Table 4-4: Summary of Remaining NOx Control Technology Efficiency................ 4-22 

Table 4-5 Summary of NOx Cost Impacts ............................................................ 4-24 

Table 4-6: Summary of NOx Visibility Impacts....................................................... 4-25 

Table 4-7: Kiln PM/PM10 Control Technology Effectiveness .................................. 4-27 

Table 4-8: Clinker Cooler PM/PM10 Control Technology Effectiveness ................. 4-29 

Table 4-9: Listing of Material Transfer Emission Points ......................................... 4-30 

Table 4-10: Material Transfer PM/PM10 Control Technology Effectiveness ............. 4-31 

APPENDICES 

Appendix A: EPA letter to Holcim of February 27, 2007 

Appendix B: Visibility Impacts Modeling 

Appendix C : BART Cost Analyses 

 
HCM Air Quality Issues/BART 7/6/07 pg. 1-1 

Project #: HCM207541

1.0 INTRODUCTION 

1.1. Summary 

Holcim (US) Inc. (Holcim) is submitting a Best Available Retrofit Technology (BART) 

analysis to the U.S. Environmental Protection Agency Region VIII office (EPA). EPA 

submitted a letter to Holcim on February 28, 2007, regarding the preparation of a BART 

analysis for their cement manufacturing facility (Trident) located near Three Forks, 

Montana. The February letter notified Holcim that EPA had [through Western Regional 

Air Partnership (WRAP)] completed visibility modeling and determined that Holcim was 

a BART-eligible source due to the possibility that Holcim could cause visibility 

degradation in nearby Class I areas (Yellowstone National Park and Gates of the 

Mountains Wilderness Area). The notification requires Holcim to submit a BART 

analysis within 90 days of the February letter.1

 The letter also noted that if Holcim 

chooses not to perform an engineering analysis, then EPA will develop the analysis 

instead. Holcim chose to analyze the EPA modeling results and prepare a BART 

engineering analysis to submit to EPA. 

Holcim analyzed the existing emission units for specific BART eligibility, and determined 

that there is one sulfur dioxide (SO2) emission source, one nitrogen oxides (NOx) 

emission source and twelve particulate matter with an aerodynamic diameter equal to or 

less than 10 microns (PM10) sources which must be addressed by a BART analysis. 

Table 1-1 lists those sources. 

Table 1-1: Sources Addressed by Holcim BART Analysis

PTE (Ton/year) 

Emission Unit 

NOx SO2 PM10 

BART Analysis 

Performed 

(Yes or No)

005 – Xfer-convey-screen Nil1 Nil1 15.89 Yes 

010 – 013 Raw material silos 1-7 Nil1 Nil1 19.52 Yes

015 and 018 Coal and coke xfer, 

crush, store, (un)load & grinding Nil1 Nil1 33.1 Yes

021 Kiln 6,8682 543.12 163.63 Yes

022 Clinker cooler Nil1 Nil1 75.09 Yes

026 Cement kiln dust silo unload Nil1 Nil1 16.92 Yes 

032a Clinker xfer to #2 finish mill Nil1 Nil1 17.72 Yes

047 Cement load/unload at silos 14-

25 Nil1 Nil1 20.12 Yes

1

 Nil means that emissions of this pollutant from this emitting unit are un-quantifiably small and deserve no further consideration. 2

 Value is from Section II.C.1.c of Permit #0982-10 (see also Page 11 of the Permit Analysis). 3

 Value is from Section II.C.1.a of Permit #0982-10 (0.77 lb/ton * 425,000 tons/year * 1 lb/2,000 tons = 163.63 tons/year). 

 

1

 An extension of this deadline to June 29, 2007, was granted by an EPA letter from Cynthia Cody on 

May 3, 2007. A verbal extension to July 6, 2007, was granted on June 29, 2007, by Ms. Cody. 
HCM Air Quality Issues/BART 7/6/07 pg. 1-2 

Project #: HCM207541

Holcim determined that the kiln is the only BART-eligible source of SO2. Holcim 

performed a BART analysis on the kiln for SO2, and determined that there is no add-on 

control or process alteration which achieves a significant visibility improvement that 

meets the definition of best available retrofit technology. See Section 4.3 of this report 

for the SO2 BART analysis. 

Holcim determined that the kiln is the only BART-eligible source of NOx. Holcim 

performed a BART analysis on the kiln for NOx, and determined that there are control 

and process alterations that meet the definition of best available retrofit technology 

which can, in total, achieve a 20% reduction in NOx and have an associated modeled 

15% visibility improvement. The selected NOx technologies which will be applied to the 

kiln are: process alterations including a fixed inlet on the clinker cooler and a low-NOx 

burner. Along with the equipment changes, Holcim selected a more stringent NOx 

emission limitation for the kiln of 1,254 lbs/hour in a rolling 30-day period. This new 

emission limit represents a 20% reduction in NOx emissions from the existing permit 

limitation of 1,568 lbs/hour in a rolling 30-day period. See Section 4.4 of this report for 

the detailed NOx BART analysis. A summary of the expected visibility improvement 

estimated by the modeling analysis is shown in Table 1-2 below. 

Holcim determined that there are twelve BART-eligible sources of PM10 at the facility. 

The sources are the kiln, the clinker cooler and ten materials handling and processing 

sources. Holcim performed a BART analysis on the kiln, clinker cooler and materials 

handling and processing sources for PM10, and determined that there are no add-on 

controls or process alterations that meet the definition of best available retrofit 

technology. Holcim determined that add-on controls with the highest level of PM10 

control were already installed on these ten sources. See Section 4.5 for the kiln PM10

BART analysis, Section 4.6 for the clinker cooler PM10 BART analysis and Section 4.7 

of this report for the ten materials handling and processing sources PM10 BART 

analysis. 

Table 1-2 below briefly summarizes the BART controls selected by Holcim, and the 

resulting visibility improvements modeled on the Gates of the Mountains Wilderness 

Area, the closest and most impacted Class I area to Holcim. See Appendix B for 

complete modeling results. 
HCM Air Quality Issues/BART 7/6/07 pg. 1-3 

Project #: HCM207541

Table 1-2: Summary of BART Selections and Visibility Impacts 

Gates of the Mountains 

Pollutant Control Technology 

Approximate 

Control 

Efficiency 

Modeled 

Emission 

Rate 

(lb/hour) Modeled 

Deciviews 

Modeled 

Deciview 

Improvement 

(above baseline) 

% 

Improvement 

in Visibility 

(from 

baseline) 

SO2 No Additional Controls 0% 340 1.56 0.00 0% 

Process Alterations 

(including installation of 

fixed inlet on clinker 

cooler) 

3% 1,521 1.49 0.04 3% 

Low-NOx Burner 17% 1,301 1.32 0.21 13% 

NOx 

Total NOx Improvement: 20% 1,254 1.28 0.24 15% 

PM10 No Additional Controls 0% 23 1.56 0.00 0% 

The remainder of this report details all of the BART steps and analyses performed for 

the Holcim Trident facility. 

1.2. Background and Purpose 

Congress amended the Federal Clean Air Act in 1977 to include a new Section 169A 

and 169B for the purpose of protecting visibility in certain scenic areas. The areas 

afforded this visibility protection are identified as “Mandatory Class I Federal Areas.”2

The rules EPA promulgated to implement these actions of the Act are generally found in 

40 CFR 51, Subpart P. 

Specific to this document, EPA promulgated 40 CFR 51.308(e) which requires certain 

types of existing stationary sources to install best available retrofit technology (BART). 

The term BART is defined in §301 as follows: 

Best Available Retrofit Technology (BART) means an emission 

limitation based on the degree of reduction achievable through the 

application of the best system of continuous emission reduction for 

each pollutant which is emitted by an existing stationary facility. The 

emission limitation must be established, on a case-by-case basis, 

taking into consideration the technology available, the costs of 

compliance, the energy and nonair quality environmental impacts of 

compliance, any pollution control equipment in use or in existence at 

the source, the remaining useful life of the source, and the degree of 

 

2

 These areas are identified in 40 CFR 81.401 et seq. Those areas within Montana and Wyoming are 

found in §417 and §436, respectively. 
HCM Air Quality Issues/BART 7/6/07 pg. 1-4 

Project #: HCM207541

improvement in visibility which may reasonably be anticipated to result 

from the use of such technology. 

As noted in Section 1.1 above, EPA has identified the Holcim Trident plant as a ‘existing 

stationary source’3

 which is subject to the BART requirements. EPA has further 

identified guidelines for identifying BART-eligible sources and suggested methodologies 

to be employed for conducting a BART analysis. These guidelines are codified in 40 

CFR 51, Appendix Y. 

It is the purpose of this document to fulfill the requirements for conducting a BART 

analysis for the Holcim Trident facility. The remainder of this document conducts a 

BART analysis for each unit and pollutant subject to the regulation [40 CFR 51.308(3)]. 

The methodologies and guidelines found in 40 CFR 51, Appendix Y were used to 

develop this BART document. 

1.3. Site Location and Description 

The Holcim Trident facility (Trident) is approximately five miles northeast of Three 

Forks, near the headwaters of the Missouri River. The plant site is located in Section 9, 

Township 2 North, Range 2 East in Gallatin County, Montana, with approximate UTM 

coordinates of the facility of Zone 12, Easting 464 km, and Northing 5,088 km. The 

elevation is approximately 4,200 feet above sea level. Maps of the Holcim facility are 

on file with the Montana Department of Environmental Quality (MDEQ). Site description 

information is also on file with MDEQ. Copies of the maps and descriptions are 

available upon request. 

 

3

 As defined in 40 CFR 51.301. 
HCM Air Quality Issues/BART 7/6/07 pg. 2-1 

Project #: HCM207541

2.0 PROCESS DESCRIPTION 

The production of Portland cement begins at the quarry. Most of the raw material used 

in the cement process is combined high and low-grade limestone quarried from 

Holcim’s quarry. Limestone rock and other raw materials are blasted and loaded onto 

trucks and transported to the crusher or to stockpiles. 

The raw materials are conveyed from the primary crusher to the storage bins. From the 

storage bins, the raw materials are conveyed to the ball mill where they are ground with 

water to form slurry, which is then sent to storage tanks. In the tanks, the slurry is 

blended thoroughly before entering the kiln. 

The slurry is pumped to the uphill end of the kiln where it is heated. The water (H2O) 

evaporates from the slurry and natural minerals from the raw materials recombine to 

form clinker in the kiln. The plant uses a combination of natural gas, coal and/or 

petroleum coke as fuel sources for the clinker production. 

When the clinker leaves the kiln, it is cooled, then transported to the finish mill feed bins 

or other storage. From the finish mill feed bins, clinker, gypsum, and other additives are 

transported to the “finish” ball mills, where it is ground to produce Portland cement. The 

final cement product is conveyed to storage silos where it is loaded into railroad cars or 

bulk trucks. 
HCM Air Quality Issues/BART 7/6/07 pg. 3-1 

Project #: HCM207541

3.0 EMISSIONS INVENTORY AND BART ANALYSIS SOURCE 

SELECTION 

3.1 Initial BART Emission Summary 

In a series of letters MDEQ requested that Holcim submit a list of the BART-eligible 

sources at the Trident facility and supply sulfur dioxide (SO2), nitrogen oxides (NOx), 

and particulate matter less than 10 microns (PM10) emission data for the BART-eligible 

sources. Holcim concluded 29 emitting units (as provided in the Title V permit) from the 

Trident facility qualify as BART-eligible. The emission data requested was for annual 

potential to emit (PTE) and the highest 24-hour emission rates occurring during the 

three year period of 2001, 2002, and 2003. Annual emissions were based on the 

permitted limits in Holcim’s Operating Permit #0982-10. The highest 24-hour NOx and 

SO2 emissions for the cement kiln were determined from continuous emissions monitor 

(CEM) data collected during the specified 3 years. It should be noted that the highest 

24-hour SO2 emission rate of 340 pounds per hour (lb/hr) is significantly greater than 

the permitted 30-day rolling average SO2 emission rate of 124 lb/hr. However, the 

facility did not exceed its permitted emission rate. 

Table 3-1 below lists the original 29 BART-eligible emitting units and their 

corresponding emission rates. Table 3-1 also shows the 12 emission units selected for 

BART analysis due to their significant emission rates. 
HCM Air Quality Issues/BART 7/6/07 pg. 3-2 

Project #: HCM207541

Table 3-1: Potential Bart-Eligible Emitting Units 

PTE (Ton/year) 

Emission Unit 

NOx SO2 PM10 

Eligible for 

Detailed BART 

Analysis 

(Yes or No)

005 – Xfer-convey-screen Nil1 Nil1 15.89 Yes 

008/009 – Primary 

crusher/screen Nil1 Nil1 10.96 No4

010 – 013 Raw material silos 1-7 Nil1 Nil1 19.52 Yes

014 Coal/coke unload Nil1 Nil1 7.88 No4

015 and 018 Coal and coke xfer, 

crush, store, (un)load & grinding Nil1 Nil1 33.1 Yes

016 Coal outside storage pile Nil1 Nil1 0.28 No4

017 Coke outside storage piles Nil1 Nil1 0.28 No4

019 Coal silo loading and 

unloading Nil1 Nil1 3.00 No4

020 Coke silo loading and 

unloading Nil1 Nil1 1.13 No4

021 Kiln 6,8682 543.12 163.63 Yes

022 Clinker cooler Nil1 Nil1 75.09 Yes

023 Inside clinker xfer from 

cooler Nil1 Nil1 5.26 No4

025 Cement kiln dust silo load Nil1 Nil1 2.25 No4

026 Cement kiln dust silo unload Nil1 Nil1 16.92 Yes 

027 Emergency clinker bins 

loading Nil1 Nil1 4.13 No4

028-031 Emergency clinker 

storage silos 1-4 Nil1 Nil1 0.09 No4

032a Clinker xfer to #2 finish mill Nil1 Nil1 17.72 Yes

047 Cement load/unload at silos 

14-25 Nil1 Nil1 20.12 Yes

049-050 Bulk cement railcar xfer 

loadouts 1 & 2 Nil1 Nil1 1.80 No4

051 Bulk cement rail xfer loadout Nil1 Nil1 0.00 No4

1

 Nil means that emissions of this pollutant from this emitting unit are un-quantifiably small and deserve no further consideration. 2

 Value is from Section II.C.1.c of Permit #0982-10 (see also Page 11 of the Permit Analysis). 3

 Value is from Section II.C.1.a of Permit #0982-10 (0.77 lb/ton * 425,000 tons/year * 1 lb/2,000 tons = 163.63 tons/year). 4 Under 40 CFR 51 Appendix Y, EPA establishes de minimis levels of emissions under which a source is not BART-eligible. 
HCM Air Quality Issues/BART 7/6/07 pg. 3-3 

Project #: HCM207541

For purposes of BART applicability determination only, EPA modeled emitting units #21 

and #22, the kiln and the clinker cooler, respectively. Table 3-2 summarizes the SO2

and NOX emissions and PM10 speciated emissions for the two sources EPA modeled 

(via the University of California Riverside) in the initial BART applicability determination. 

Table 3-2: Initial EPA BART Modeled Sources and Emissions 

Total Emission Ratea 

(lbs/hr) 

Emitting Unit SO2 SO4 NOx HNO3 NO3 SOAb ECb PMCb PMFb 

Kiln 340 7.215 784 - - 0.01 0.01 0.093 9.31 

Clinker Cooler 0.01 0.01 0.01 - - 0.01 0.01 0.137 13.7 a

 Emissions obtained from documents on WRAP Regional Modeling Center website http://pah.cert.ucr.edu/aqm/308/bart.shtml. b

 The abbreviations are as follows: 

SOA = Sulfur-Oxidizing Activity, 

EC = Elemental Carbon, 

PMC = Condensable Particulate Matter, and 

PMF = Filterable Particulate Matter. 

Although EPA only modeled the two sources above, Holcim’s analysis was conducted 

for all potential BART-eligible sources identified in Table 3-1 above

3.2 SO2 Applicable Units Emissions 

The kiln is the only SO2 emitting unit subject to BART analysis. The PTE (federally 

enforceable permit limit) for SO2 from the kiln is 124 lbs/hr on a rolling 30-day average 

(543 tons/yr). To remain consistent with the BART modeling analysis performed by 

EPA, Holcim has performed the BART analysis with the highest 24-hour SO2 emission 

rate of 340 lbs/hr as recorded by Holcim’s CEM during the 3-year period of 2001-2003. 

 

3.3 NOx Applicable Units Emissions 

The kiln is also the only NOx emitting unit subject to BART analysis. The PTE (federally 

enforceable permit limit) for NOX from the kiln is 1,568 lbs/hr on a rolling 30-day average 

(6,868 tons/yr). The BART modeling analysis performed for Holcim used the permitted 

NOx PTE to establish the baseline visibility impacts used in this analysis. 

3.4 PM Applicable Units Emissions 

As listed in Table 3-1, there are a total of 12 emission sources of PM10 to be analyzed 

for BART comprising a total of 362 tons/yr of PM10. The largest (potential) emitters of 

PM10 are the kiln (164 tons/yr) and the clinker cooler (75 tons/yr) which compose 

approximately 66% of the total PM10 emissions. 

Table 3-3 provides a summary of the 12 emitting units subject to further BART analysis. 

The table also shows the current emissions control associated with those units. 
HCM Air Quality Issues/BART 7/6/07 pg. 3-4 

Project #: HCM207541

Table 3-3: PM10 Sources Analyzed for BART 

Source Current Source Control 

005 – Xfer-convey-screen Baghouse 

010 – 013 Raw material silos 1-7 Baghouse 

015 and 018 Coal and coke xfer, crush, store, 

(un)load & grinding 

Baghouse 

021 Kiln Electrostatic Precipitator 

022 Clinker cooler Baghouse 

026 Cement kiln dust silo unload Dustless Unloader and Baghouse 

032a Clinker xfer to #2 finish mill Baghouse 

047 Cement load/unload at silos 14-25 Baghouse 
HCM Air Quality Issues/BART 7/6/07 pg. 4-1 

Project #: HCM207541

4.0 BEST AVAILABLE RETROFIT TECHNOLOGY REVIEW 

The Clean Air Act (CAA), in section 169(a)(2), requires that State Implementation Plans 

(SIPs) for visibility protection must apply BART to certain large-emitting sources. BART 

is required for sources that meet all of the following criteria: 

1. The source is in one of 26 specific listed source categories;4

2. The source was in existence as of August 1977, but was not in operation in 

August of 1962;5

3. The facility has the potential to emit 250 tons per year of any visibility-impairing 

pollutant; and 

4. The BART-eligible source emits an air pollutant that “may reasonably be 

anticipated to cause or contribute to any impairment of visibility in any mandatory 

Class I federal area, . . .” 6 

The term Best Available Retrofit Technology (BART) is defined in 40 CFR 51.301 and

means: 

“an emission limitation based on the degree of reduction achievable 

through the application of the best system of continuous emission 

reduction for each pollutant which is emitted by an existing stationary 

facility. The emission limitation must be established, on a case-by-case 

basis, taking into consideration the technology available, the costs of 

compliance, the energy and nonair quality environmental impacts of 

compliance, any pollution control equipment in use or in existence at the 

source, the remaining useful life of the source, and the degree of 

improvement in visibility which may reasonably be anticipated to result 

from the use of such technology.”

Appendix Y further explains how to identify sources subject to BART: 

“Once you have determined that your source or sources are subject to 

BART, you must conduct a visibility improvement determination for the 

source(s) as part of the BART determination. When making this 

determination, we believe you have flexibility in setting absolute 

thresholds, target levels of improvement, or de minimis levels since the 

deciview improvement must be weighed among the five factors, and you 

are free to determine the weight and significance to be assigned to each 

factor.” 

 

4

 The 26 source categories are found in the definition of “Existing stationary facility” found in 40 CFR 

51.301. 

5

 The terms “in existence” and “in operation” are defined in 40 CFR 51.301. 

6

 40 CFR 51.308(e). 
HCM Air Quality Issues/BART 7/6/07 pg. 4-2 

Project #: HCM207541

4.1 Summary 

The CAA, in section 169(a)(2) requires that SIPs for visibility protection must apply 

BART to certain large-emitting sources. EPA identified Holcim as a possible BARTeligible source because it is a Portland cement plant, which is one of the 26 BART 

source categories under 40 CFR Part 51.301 under the definition of “Existing stationary 

source.” The Holcim facility has emitting units that meet the time frames specified in 

item 2 above. In addition, the entire complex has a potential to emit greater than 250 

tons per year. 

EPA has completed initial visibility modeling through the WRAP program. As a result of 

those investigations EPA has determined that Holcim is subject to a BART analysis in 

accordance with the BART provisions of 40 CFR 51.308. The EPA documentation of 

this requirement and conclusion is found in a letter from EPA Region VIII dated 

February 27, 2007, addressed to Mr. Ned Pettit of Holcim. A copy of that letter and 

conclusion is found in Appendix A of this document. 

In accordance with the February 27, 2007 letter, Holcim has conducted a BART 

analysis using EPA-recommended methodologies and dispersion modeling 

recommendations found in 40 CFR 51, Appendix Y, more specifically the CALPUFF 

dispersion model, to assist with the proposed BART determination. The purpose of the 

modeling analysis is to determine the visibility improvement expected at Class I areas 

from the potential BART control technology applied to the source. The modeling 

analysis is found in Appendix B of this document. 

4.1.1 Affected Units 

There are a total of 29 emitting units at the Holcim facility that have been identified as 

potentially “BART–eligible.” These units have received that designation since they meet 

the definition of BART-eligible since they were “in existence”7

 as of August 1977, but not 

“in operation”8

 in August of 1962 and having (collectively) the potential to emit 250 tons 

per year of an air pollutant that could cause visibility degradation in a Class I area 

(applicable pollutants are listed in Section 4.1.2 below). See Table 3-1 for a list of 

potential BART-eligible emitting units. 

Of the units subject to a BART engineering analysis, the kiln and clinker cooler 

comprise the majority of interest for BART purposes. The other ten units which are also 

subject to a BART engineering analysis are those units shown in Table 3-3 above. 

4.1.2 Applicable Pollutants 

The visibility impairing pollutants analyzed in this BART analysis are: 

 

7

 As defined by 40 CFR 51.301 

8

 Ibid. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-3 

Project #: HCM207541

y Sulfur dioxide (SO2), 

y Nitrogen oxides (NOx), and 

y Particulate matter less than 10 microns (PM10). 

PM10 is used as an indicator for particulate matter. As emissions of PM10 include the 

components of PM2.5 as a subset, there is no need to have separate 250 ton thresholds 

for PM10 and PM2.5; 250 tons of PM10 represents at most 250 tons of PM2.5, and at most 

250 tons of any individual particulate species such as elemental carbon, crustal 

material, etc.

4.2 BART Analysis Methodology 

In general terms, EPA has identified a methodology for conducting a BART analysis that 

is similar to the Best Available Control Technology analyses conducted under the PSD 

permitting program (40 CFR 51.166 and elsewhere). For BART, the methodology is 

more refined to include pollutants related to visibility impairment and to include an 

analysis of the impacts the proposed technology has on the visibility directly. 

The BART methodology is a case-by-case procedure. The BART methodology chosen 

for this analysis follows the guidelines established by EPA in 40 CFR 51, Appendix Y. 

Hereafter, these guidelines will be referred to as either the “Appendix Y Guideline” or 

simply “Appendix Y.” Appendix Y suggests that the case-by-case BART analysis should 

follow the five steps below (Section IV.D of Appendix Y). 

Case-by-Case Five Step BART Analysis: 

 Step 1 - Identify all9

 available retrofit control technologies; 

 Step 2 - Eliminate technically infeasible options; 

 Step 3 - Evaluate control effectiveness of remaining control technologies; 

 Step 4 - Evaluate impacts and document the results; and 

 Step 5 - Evaluate visibility impacts. 

The following paragraphs will evaluate BART for each source or source group emitting 

any of the pollutants noted above as being released in significant quantities. BART for 

NOx and SO2 emissions from the kiln, essentially the only source of these compounds, 

will be addressed first. BART for the various sources of particulate emissions will be 

addressed at the end of this section. 

As suggested by Appendix Y, Holcim reviewed the New Source Performance Standards 

(NSPS) Subpart K for cement kilns to determine if any control technologies or emission 

restrictions were applicable to new facilities. This review showed that NSPS for cement 

kilns applies only to particulate emissions and opacity. 

 

9

 Appendix Y notes that the term “all” refers to identifying the most stringent option and a reasonable set 

of options for analysis that reflect a comprehensive list of options. It is not necessary (according to 

Appendix Y) to list all permutations of available control levels for a given technology. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-4 

Project #: HCM207541

To facilitate the following BART determinations, Holcim queried the EPA RACT-BACTLAER Clearinghouse (RBLC) database for listings of pollutant emission limits and 

required control technologies at other cement manufacturing facilities across the 

country. The information generated by these queries serves as a helpful guideline to 

indicate expected emission rate ranges and control technologies that may have been 

successfully applied at facilities similar to the Holcim cement plant. When reviewing 

specific emission limits applied at other kilns, it is important to recognize that cement 

manufacturing operations and their associated emissions characteristics can vary 

significantly from one facility to another, and even within a single facility. Some of the 

inherent differences will be addressed in succeeding paragraphs. Further, the database 

is not always well maintained and includes some outdated information. In some cases, 

for instance, an owner may have accepted a stringent emission limit or an unproven 

control technology only to find the limit or the technology was inappropriate for the 

particular operation, leading to a permit change that may not be reflected in the 

database. 

Another factor that must be kept in mind when comparing emission limits across 

facilities is that the averaging period associated with the limit significantly affects the 

source’s ability to comply. A source may be able to comply with a particular emission 

limit over a rolling 30-day averaging period for example, but find it impossible to 

consistently comply with the same limit applied to a one-hour averaging period. 

In following the five-step BART analysis, Holcim initially reviewed all available retrofit 

technologies, and then condensed this list to only include those technologies that are 

applicable to a long wet kiln. For example, technologies may be only available for dry or 

preheater/precalciner kilns, but are not appropriate to consider for a long wet kiln, such 

as the Trident plant. 

4.3 SO2 BART Analysis for the Kiln 

SO2 forms during coal combustion as sulfur in the coal is liberated and subsequently 

oxidized by the oxygen present in the combustion air. Sulfur in the feed limestone can 

also contribute significantly to the kiln’s SO2 emissions. SO2 emissions can be reduced 

by capturing and converting it once it has formed. It is possible to limit SO2 formation 

both by limiting the amount of sulfur fed to the kiln system and by controlling the 

conditions necessary to oxidize sulfur. Capture and conversion of SO2 in the exhaust 

stream through add-on controls is generally accomplished by mixing the exhaust gas 

stream with an alkaline reagent, facilitating the chemical conversion of SO2 to a neutral 

salt. The salt is solid at system conditions and can be removed by physical means. The 

control equipment that accomplishes this is commonly referred to as a gas scrubber. 

Cement kiln systems inherently act as large gas scrubbers with varying degrees of 

effectiveness depending, in part, on the excess alkali (e.g., Na and/or K) or alkali earth 

(e.g., Ca) compounds available to combine with sulfur to remove SO2 as described. 

Holcim’s Trident plant has an excess of alkali compounds to sulfur input indicating a 

capacity to absorb much more sulfur in its kiln system. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-5 

Project #: HCM207541

4.3.1 Identify All Available SO2 Retrofit Control Technologies – Step 1 

In accordance with Step 1 described in Section 4.2 above, Holcim has sought to identify 

all “available” retrofit technologies. To that end, EPA’s RBLC describes several 

permitted cement kiln installations and lists their pollutant emission limits and the control 

technologies approved to achieve those limits. Another source of information regarding 

potentially applicable SO2 control technology for cement kilns is EPA’s AP-42 for 

Portland cement manufacturing (Chapter 11, Section 6). The following were identified 

as potentially applicable for controlling SO2 from cement manufacturing: 

(i) Proper kiln design and operation (baseline); 

(ii) Process alterations; 

(iii) Hot meal injection; 

(iv) Spray dryer absorber; 

(v) Wet SO2 scrubber. 

Control Technology Description: 

(i) Proper Kiln Design and Operation

Sulfur is present in coal and limestone as organic sulfur compounds and as minerals 

pyrite or iron sulfide. In these forms it is readily volatilized and then oxidized to SO2

under calcining conditions. Sulfur may also be homogeneously present in limestone as 

calcium sulfate. This form of sulfur does not normally volatilize at calcining temperatures 

and tends to remain in the lime. In fact, lime reacts under dry conditions with SO2 to 

form calcium sulfate (CaSO4) as follows:10

(calcium sulfate) 2 (lime) 1 CaO + SO2 + O2 ↔ CaSO4

Similar reactions with sodium and potassium also reduce SO2 in the kiln. All three of 

these elements are in excess supply in Trident raw materials, available for reaction. To 

the degree thermodynamic and kinetic factors allow the reverse reaction (i.e., 

conversion of sulfate to lime), a lack of oxygen, or a reducing atmosphere, will favor a 

desulfurization of the limestone. Conversely, increasing oxygen will cause the 

equilibrium to shift toward increased formation of sulfate. This is where a balance must 

be struck between product quality and emissions of SO2. If specifications call for low 

levels of sulfur, and especially if the limestone feed contains relatively high proportions 

of sulfur, kiln conditions must be established that inhibit SO2 absorption within the kiln. 

Neither is the case for Holcim’s Trident Plant. If such is not the case, it may be possible 

to operate the kiln under conditions that favor sulfur oxidation. 

(ii) Process Alterations

The process alteration that Holcim evaluated was changing their fuel to a low sulfur fuel 

in order to reduce their sulfur emissions. In many cases, the fuel used to fire the kiln is 

the primary source of sulfur, and ultimately, of SO2. One method to “control” SO2

 

10 “Chemistry and Technology of Lime and Limestone,” Second Edition, 1980, R.S. Boynton, pg. 181. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-6 

Project #: HCM207541

emissions is to “control” the sulfur in the native fuel. For example, natural gas contains 

very little sulfur. Coal may vary from 0.7% to over 5% sulfur. Petroleum coke typically 

contains 3% to 6% sulfur. 

(iii) Hot Meal Injection 

Another possibility is the hot-meal bypass in a preheater/precalciner kiln system, where 

calcined hot meal is, in part, discharged in front of the kiln entrance after the 

precalcining process. The type of hot meal produced varies by facility. Different hot 

meal materials have different thermal content and pollutant emissions. 

(iv) Spray Dryer Absorber

The term Spray Dryer Absorber (SDA) here refers to those technologies that use a dry, 

semi-dry or semi-wet alkaline material to control SO2 emissions from the postcombustion gases. While there are a number of injection methods and designs, it is 

generally understood that an SDA provides a high degree of controls (within this group) 

and represents a fair characterization of this class of control device. 

A spray dryer absorber is an SO2 scrubbing process that involves both acid gas and 

particulate matter control. In a typical SDA system, hot combustion gases enter a 

reactor where atomized hydrated lime slurry (or near slurry) is introduced at a controlled 

velocity. Upon injection, the water in the lime slurry quickly evaporates which cools the 

flue gas. The acid gas constituents (primarily SO2) quickly react with the reagent 

(CaOH, etc.). The result is a dried product that is removed from the exhaust stream by a 

particulate control device. In general, SDAs are used in combination with either 

electrostatic precipitators or fabric filter baghouses. 

(v) Wet SO2 Scrubber 

A wet SO2 scrubber is one that uses an aqueous chemical system. These systems have 

been successfully employed in various industries to remove SO2 from concentrated 

waste streams. These systems use aqueous solutions or slurries as the contact and 

reaction media. A typical installation uses spray tower scrubbers to introduce a reagent 

slurry as atomized droplets through the spray nozzles at the top of, or in stages within, 

the scrubber. The SO2-laden gas enters at the bottom of the column and travels 

upward through the tower in a countercurrent flow, though horizontal spray towers 

which use a crosscurrent design also exist. In most cases the sorbent is an alkaline 

slurry, commonly limestone, slaked lime, or a mixture of slaked lime and alkaline fly ash, 

though many other sorbent processes exist. Absorption of SO2 is accomplished by the 

contact between the gas and the reagent slurry. The sulfur oxides react with the 

sorbent, forming a wet mixture of calcium sulfite and sulfate. 

The slurry combines with the SO2-laden waste gas to form a waste slurry in the bottom 

of the scrubber. The sludge is removed from the scrubber and, depending upon the 

reagent or sorbent used to react with the SO2, the waste reacted sludge is disposed of, 

recycled or regenerated, or, in some cases, sold as a salable product. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-7 

Project #: HCM207541

4.3.2 Eliminate Technically Infeasible SO2 Control Options – Step 2 

The following discusses the feasibility or infeasibility of each technology identified in 

Section 4.3.1 above. The decision regarding whether a particular technology was 

deemed “technically feasible” was based on discussions found in 40 CFR 51, Appendix 

Y. Appendix Y describes guidelines for BART determinations under the regional haze 

rule. Hereafter, the document will be referred to as the “Appendix Y Guideline.” 

The issue of feasibility is found in Section IV.2.STEP 2 of the Appendix Y Guideline. 

The guideline states that control technologies are technically feasible if either: 

“(1) they have been installed and operated successfully for the type of source 

under review under similar conditions, or 

 (2) the technology could be applied to the source under review.” 

The Appendix Y Guideline goes on to describe these circumstances further and discuss 

the meaning of “available” and “applicability” within the meaning of BART. As a general 

rule, “available” means that the owner of the facility may obtain the technology through 

commercial channels. In the alternative, the technology is “available” within the 

common-sense meaning of that term. 

Commercially available is further discussed in the Appendix Y Guideline as having 

attained either stage (5) or (6) of the following stages of bringing a control technology to 

reality as a commercial product: 

(1) Concept stage; 

(2) Research and patenting; 

(3) Bench scale or laboratory testing; 

(4) Pilot scale testing; 

(5) Licensing and commercial demonstration; and 

(6) Commercial sales. 

Also of note in the Appendix Y Guideline is the following statement: 

Similarly, we do not expect a source owner to conduct extended trials to 

learn how to apply a technology on a totally new and dissimilar source 

type. Consequently, you would not consider technologies in the pilot 

scale testing stages of development as “available” for purposes of BART 

review. 

The reader is referred to further discussion in the Appendix Y Guideline on this matter. 

Using the Appendix Y Guidelines above, infeasible technologies are rejected where 

appropriate. Those technologies deemed infeasible are no longer discussed in further 

sections of this BART analysis. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-8 

Project #: HCM207541

(i) Proper Kiln Design and Operation

Proper design and operation of kilns is clearly feasible and serves as the baseline case. 

Conclusion: Proper kiln design and operation is considered feasible for purposes 

of Step 2 in this BART analysis. 

(ii) Process Alterations

Holcim has identified fuel selection as a process alteration which can possibly reduce 

SO2 emissions. Fuel selection as a means to “control” SO2 emissions is technically 

feasible. However, Holcim believes that the kiln currently has excess capacity for SO2

absorption due to the alkali nature of the kiln interior. Therefore, Holcim believes that 

switching fuels will not significantly reduce SO2 emissions because the kiln will remain 

an effective SO2 scrubber regardless of fuel type used. 

Appendix Y Guideline explicitly addresses this issue. Specifically, STEP 1: How do I 

identify all available retrofit emission control techniques? of the guideline contains the 

following statement: 

“...........note that it is not our intent to direct States to switch 

fuel forms, e.g. from coal to gas.”

Given this statement, it is clear that it is not the intent of EPA to use fuel switching as a 

form of BART control. 

Conclusion: This process alteration is considered infeasible for purposes of Step 2 

in this BART analysis. No further discussion of this technology will be 

presented. 

(iii) Hot Meal Injection

As previously stated, hot meal is produced in a preheater/precalciner kiln. Holcim does 

not have a preheater/precalciner kiln design from which hot meal can be obtained; 

therefore, this is not a feasible option for Holcim. 

Conclusion: This technology is considered infeasible for purposes of Step 2 in this 

BART analysis. No further discussion of this technology will be 

presented. 

(iv) Spray Dryer Absorber

This type of technology is not considered to be effective for large sources with relatively 

dilute SO2 concentrations. The kiln and baghouse system acts as a large dry scrubber 

mixing gaseous SO2 with active lime and alkali surfaces to create and capture sulfate 

salts. Adding a separate spray dry scrubber would only provide additional lime with 

which SO2 can react. Supplemental scrubbing by an SDA is expected to provide no 

more than inefficient redundancy. The performance of a lime spray dry scrubber is 

sensitive to operating conditions. A “close approach” to adiabatic saturation temperature 

is required to maximize the removal of SO2. However, excess moisture causes the wet 
HCM Air Quality Issues/BART 7/6/07 pg. 4-9 

Project #: HCM207541

solids to deposit on the absorber and downstream equipment. In spray dry systems, 

the flue gas must be cooled to a temperature range of 10°C to 15°C (20°F to 35°F) 

below saturation temperature. This temperature range avoids wet solids deposition and 

plugging on the downstream particulate control device. An evaporative cooler, or a heat 

exchanger is typically used to cool the gas, as flue gas with high temperature reduces 

the performance of the scrubber. 

The SDA must be designed in conjunction with the particulate control device as a 

system. Therefore, to retrofit the existing process with an ESP will likely involve 

substantial modifications to the ESP. 

Conclusion: Although there are serious concerns with this technology, it will be 

presumed that it remains technically feasible for purposes of Step 2 in 

this BART analysis. 

(v) Wet SO2 Scrubber 

This type of technology is not considered to be effective for large sources with relatively 

dilute SO2 concentrations. The kiln and baghouse system acts as a large dry scrubber 

mixing gaseous SO2 with active lime and alkali surfaces to create and capture sulfate 

salts. Adding a separate wet scrubber would only provide additional alkali solution with 

which SO2 can react. Adding a wet scrubber is expected to provide no more than 

inefficient redundancy. Scrubbing effectiveness is not linearly related to additional 

removal media concentration. At some optimal lime concentration, a point of diminishing 

returns is reached after which incremental effectiveness rapidly decreases. This effect is 

hastened by decreasing SO2 concentrations. The kiln system is expected to inherently 

provide excess desulfurization media. Adding further excess with a supplemental 

scrubber cannot be expected to appreciably increase control efficiency. Aqueous 

chemical absorption cannot be considered applicable to the proposed project but is 

technically feasible. 

Conclusion: Although there are serious concerns with this technology, it will be 

presumed that it remains technically feasible for purposes of Step 2 in 

this BART analysis. 

4.3.3 Evaluate Control Effectiveness of Remaining Control Technologies – Step 3 

Of the alternative SO2 control technologies identified above, proper kiln design and 

operation, SDA, and wet SO2 scrubbers remain as technically feasible options. Proper 

kiln design and operation is the baseline case for this analysis. Other control methods 

will be evaluated for their potential to improve upon this basis. Table 4-1 summarizes 

the control effectiveness of the remaining control technologies. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-10 

Project #: HCM207541

Table 4-1: Summary of SO2 Control Technology Efficiency 

Control Option 

Efficiency

 (%) 

SO2

Emissions

(lbs/hr) 

SO2 

Emissions

(tpy) 

Tons 

Removed 

Wet SO2 Scrubber 95% 6.20 27 516 

Spray Dry 

Absorber 90% 12.40 54 489 

Baseline 0% 124 543 0 

4.3.4 Evaluate Impacts and Document Results – Step 4 

(a) Spray Dry Absorbers Impacts 

Spray Dry Absorbers Economic Impacts

Holcim has calculated the cost-effectiveness for employing an SDA for SO2 control, with 

the results presented in Table 4-2 below. Holcim has utilized the EPA’s Air Pollution 

Cost Control Manual to estimate costs of SDA control. The manual provides the EPA’s 

recommended methodology for estimating the costs for add-on control technology. To 

calculate the cost-effectiveness of a control technology in dollars per ton ($/ton), the 

following factors are used: 

Cost-effectiveness ($/ton) = [(total capital investment x capital recovery factor 

{CRF}) + Direct Annual Cost + Indirect Annual Cost]/(tons SO2 controlled) 

Capital Recovery Cost (= total capital investment x CRF) 

• Total capital investment = direct and indirect costs for purchasing and 

installing control equipment. 

• Capital recovery factor (CRF) = multiplier to determine the uniform end-ofyear payment necessary to repay an investment in n years with an interest 

rate of i.

o Control system life, n = 10 to 20 years, typically 

o Interest rate, I = 7% recommended interest rate 

For this BART analysis, CRF = 10 years @ 7% = 0.142 

Direct Annual Cost (utilities, labor, taxes) 

Indirect Annual Cost (overhead, insurance, taxes) 

Table 4-2 summarizes the cost-effectiveness for each of the technically feasible control 

options, compared against a baseline of proper kiln design and operation. Details of the 

SDA cost analysis can be found in Appendix C. 

Spray Dry Absorbers Energy Impacts

EPA Publication EPA-542/F-03-034 states that modern spray dry absorber designs 

result in an energy penalty of less than 1% of the total plant energy consumption. This is 

a minor energy impact which is considered in the economic analysis. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-11 

Project #: HCM207541

(c) Wet SO2 Scrubber Impacts 

Wet SO2 Scrubber Economic Impacts

Holcim has calculated the cost-effectiveness for employing a wet scrubber for SO2

control, with the results presented in Table 4-2 below. The table summarizes the costeffectiveness for each of the technically feasible control options, compared against a 

baseline of proper kiln design and operation. Details of the wet scrubber cost analysis 

can be found in Appendix C. 

Wet SO2 Scrubber Energy Impacts

EPA Publication EPA-542/F-03-034 states that modern wet scrubber designs result in 

an energy penalty of less than 1% of the total plant energy consumption. This is a minor 

energy impact which is only further considered in the economic analysis. 

Alternatives Analysis Summary 

For the purposes of this cost analysis, it has been assumed that the remaining life of all 

of the equipment is at least the 10 years used to calculate the annualized costs. 

Table 4-2: Summary of SO2 Cost Analysis 

As shown in Table 4.2, the cost per ton for the wet SO2 scrubber and the SDA are 

substantial, both higher than what is generally considered BACT in Montana. The 

annualized costs of both options are cost-prohibitive. In addition, the incremental cost of 

$498,491 per ton SO2 removed by the wet scrubber versus the SDA is enormous. 

4.3.5 Evaluate Visibility Impacts – Step 5 

Holcim has performed modeling using the CALPUFF model to predict visibility impacts 

of the identified potentially applicable SO2 control technologies, using the 98th percentile 

visibility result as recommended by EPA. The results of the modeling are shown in 

Table 4-3 below. The results are only presented for the Gates of the Mountains 

Wilderness Area, as it is the closer, and more impacted Class I Area. Details of the 

modeling are found in Appendix B to this document. 

Control 

Option 

Annualized 

Cost 

Efficiency 

 (%) 

SO2 

Emissions 

(lbs/hr) 

SO2 

Emissions 

(tpy) 

Tons 

 SO2

Removed 

Cost 

Effectiveness

 ($/ton) 

Incremental 

Cost 

Effectiveness 

($/ton) 

Wet SO2

Scrubber $19,607,665 95% 6.20 27 516 $38,011 $498,491 

Spray Dry 

Absorber 

(includes 

baghouse) $6,070,650 90% 12.40 54 489 $12,422 -- 

Baseline $0 0% 124.00 543 0 -- -- 
HCM Air Quality Issues/BART 7/6/07 pg. 4-12 

Project #: HCM207541

Table 4-3: Summary of SO2 Visibility Impactsa 

Gates of the Mountains Wilderness Area 

Control Option 

Annualized 

 Cost 

Efficiency

 (%) 

SO2

(lbs/hr) 

Visibility 

Impact 

(deciview) 

Visibility 

Improvement 

(deciviews 

24 hr) 

Cost 

($/deciview) 

Incremental 

Cost 

($/deciview) 

Wet SO2 Scrubber $19,607,665 95% 6.20 1.291 0.269 $15,185,614 $2,990,183,225

Spray Dry Absorber 

(includes baghouse) $6,070,650 90% 12.40 1.296 0.264 $4,683,421 -- 

Baseline $0 0% 124 1.56 0.000 -- -- 

a

Deciviews at each % reduction for the Gates of the Mountains are calculated using the equation: 

y = 0.001x + 1.2862 derived from using the best fit trendline of the average 98th percentile modeling values.

4.3.6 Select SO2 BART 

Based upon the modeling results, the addition of add-on controls, in practice, will result 

in minimal visibility improvement. The 340 lbs/hr of SO2 utilized in the models as a 

worst-case 24-hour value is approximately ten times higher than normal levels of SO2 

emissions. Even when using this larger figure in the models, the deciview change 

accomplished by employing the best control technology (wet scrubber) at 95% control 

has only a 0.269 deciview impact on visibility. Holcim believes this change is well below 

the human eye’s ability to detect. 

The costs of the add-on controls are deemed to be unjustifiable in terms of dollars spent 

per ton of SO2 removed and per deciview of improvement. Even worse are the 

incremental dollar per ton and dollar per deciview values in moving up to the best 

control. At the lesser 90% control level, the cost per deciview of improvement is over 4.7 

million dollars. Holcim believes this amount is excessive, especially considering the 

minimal visibility improvements achieved. A cost of over 6 million dollars per year to 

achieve an undetectable visibility improvement seems unjustified and outside the 

intention of the BART program. 

Of the alternative SO2 control technologies identified above, none is feasible at the 

Trident facility. Holcim proposes to continue to employ the baseline of proper kiln design 

and operation and comply with the existing SO2 emission limitation (124 lbs/hour on a 

rolling 30-day basis). Therefore, no new requirements for SO2 are proposed under the 

BART program. 

4.4 NOx BART Analysis for the Kiln 

Most of the NOx formed within a rotary cement kiln is classified as thermal NOx. Thermal 

NOx results when the heat from fuel combustion causes atmospheric nitrogen to 

combine with atmospheric oxygen. Virtually all thermal NOx is formed in the region of 

the flame at the highest temperatures, approximately 3000°F to 3600°F. A small 

proportion of NOx emissions results from nitrogen that is liberated from the fuel and 

reacts with oxygen in the air. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-13 

Project #: HCM207541

Theoretically, the following principles can be employed to reduce NOx formation: 

• Reduce peak flame zone temperatures, 

• Reduce fuel residence time in the flame zone, 

• Reduce mixing of fuel and combustion air, 

• Reduce oxygen concentrations in the flame zone, and 

• Reduce excess air in the combustion process. 

There are also post-combustion NOx control technologies which remove NOx from the 

flue gas after formation, using technologies that chemically convert it to nitrogen and 

water. 

4.4.1 Identify All Available NOx Retrofit Control Technologies – Step 1 

EPA’s RBLC describes several permitted cement kiln installations and lists their 

pollutant emission limits and the control technologies approved to achieve those limits. 

Other sources of information regarding potentially applicable NOx control technology for 

cement kilns include EPA’s 2000 NOx Control Technologies for Cement Kilns, and the 

Assessment of NOx Emissions Reduction Strategies for Cement Kilns – Ellis County, 

TX. First, Holcim evaluated all NOx control technologies for cement manufacturing using 

the documents stated above, and then identified the control technologies that were 

potentially applicable to long, wet kilns. The technologies that were identified as 

potentially applicable for controlling NOx from Holcim’s cement kiln are divided into three 

categories: process modifications, fuel and raw material substitutions and postcombustion control technologies. These are detailed below. 

(i) Proper kiln design and operation (baseline), 

(ii) Process modifications 

• Increased thermal efficiency, and 

• Combustion system modifications including low-NOx burner (LNB) 

(iii) Fuel and raw material substitutions 

• Mid-kiln fuel injection, and 

• CemStar process, 

(iv) Post-combustion control technologies 

• Selective non-catalytic reduction (SNCR). 

• Selective catalytic reduction (SCR), and 

• LoTOxTM

The following is a brief discussion of each of the control technologies. 

(i) Proper Kiln Design and Operation

Many interdependent and sometimes competing factors must be considered in the 

design and operation of a cement kiln. Primary among them are product quality 

requirements, operating costs, and pollution mitigation. Burner operation is central to all 

three. Product quality is critically dependent upon flame temperature and kiln 
HCM Air Quality Issues/BART 7/6/07 pg. 4-14 

Project #: HCM207541

atmosphere composition. Both of these conditions are also primary factors in the 

production of NOx. Low temperatures reduce the production of NOx. Temperatures that 

are too high, besides aggravating NOx production, can result in over-burned clinker. A 

specific concentration of oxygen in the kiln is required to properly control combustion 

and oxidize the limestone and other minerals. Some of that oxygen is supplied with the 

combustion air and strongly affects fuel combustion characteristics such as 

temperature. 

Fuel costs are a major portion of the cost of cement production. Consequently, every 

effort is made to conserve heat and thereby reduce costs. Efforts to maximize fuel 

efficiency also serve to reduce pollutant emissions; increasing the amount of cement 

produced per unit of fuel decreases the amount of combustion-related pollutants emitted 

per unit of product. 

Fuel selection can influence NOx production in two ways: the amount of chemically 

bound nitrogen in the fuel helps determine the fuel’s direct contribution to NOx

emissions, and the fuel’s combustion characteristics help determine the amount of 

thermal NOx created. Natural gas kilns produce approximately three times more NOx on 

an equivalent production basis than coal-fired kilns. Although coal contains more fuelbound nitrogen than natural gas, it burns at lower temperatures and so produces less 

thermal NOx. Petroleum coke may produce less NOx than coal because it contains less 

nitrogen per unit of heat value and burns with a lower flame temperature.11 Holcim 

currently uses coal and coke as the main fuel source, using natural gas only for start-up 

and shut-down. 

In some cases, reducing emissions of a particular pollutant can cause an increase in 

emissions of another. This is especially true of the relationship between NOx and CO. 

CO is generally produced as a result of incomplete combustion of organic materials. 

Attempts to achieve more complete combustion typically involve increasing oxygen 

concentration and flame temperatures, two factors that lead to increased NOx

production. 

Cement kiln operation is designed to balance and optimize the above parameters for a 

specific set of external constraints such as feed quality, product quality requirements, 

pollutant emissions restrictions, and fuel availability. The design includes operational 

monitoring and control systems that allow the maintenance of optimum operating 

conditions. 

(ii) Process Modifications 

There are many process modifications which could be made to a cement production 

facility in order to reduce NOx emissions. These modifications are very site-specific and 

must factor in existing equipment, processes, fuels and raw materials, etc. Holcim has 

 

11 USEPA “Alternative Control Techniques Document – NOx Emissions from Cement Manufacturing,” 

EPA-453/R-94-004, Office of Air and Radiation, Office of Air Quality Planning Standards, March 1994, 

page 5-4. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-15 

Project #: HCM207541

identified the following process modifications as feasible at the Trident facility, with 

potential to significantly reduce NOx emissions. 

Increased Thermal Efficiency

One process modification Holcim has reviewed to improve the thermal efficiency of the 

Trident kiln is the installation of a fixed inlet at the clinker cooler. A fixed inlet 

modification to the clinker cooler improves the heat recovery to the kiln inlet and the 

overall efficiency of clinker cooler operation. With increased cooler efficiency, a greater 

amount of heat in the clinker is recovered, which increases the secondary air 

temperature of the kiln/cooler system. Consequently, the amount of fuel required in the 

kiln can be reduced because more heat has been captured from the cooler and does 

not need to be supplied by the combustion system. With the reduction in fuel usage, a 

proportional reduction of thermal NOx from the combustion process is achieved. A 0 to 

5% reduction in NOx emissions can be expected from the installation of the fixed inlet on 

the clinker cooler. 

Combustion System Modifications Including Low-NOx Burner (LNB) 

Another process modification Holcim believes is applicable in reducing NOx emissions 

at the Trident facility is addition of a low NOx burner in conjunction with other 

combustion system modifications. The addition of an LNB will reduce NOx formation by 

controlling the mixing of fuel and air to provide low-excess-air firing or off-stoichiometric 

combustion. These burners are designed to reduce peak flame temperature and/or 

reduce the residence time at high temperature. The most common LNBs include staged 

air burners or staged fuel burners. 

Staged air burners consist of a two-stage combustion process. Combustion initiates 

under fuel-rich, oxygen-deficient conditions in the primary combustion zone. These 

conditions allow attainment of the required flame temperature while reducing the 

formation of fuel and thermal NOx. They also lead to incomplete fuel combustion. In the 

secondary zone, relatively cool additional air (staged air) is introduced to complete the 

combustion process. The cooler temperatures resulting from introduction of the staged 

air suppress NOx formation in this stage. 

Staged fuel burners mix all of the air and a portion of the fuel to create a fuel-lean 

environment in the primary combustion chamber. This leads to lower flame 

temperatures and, consequently, reduced NOx production. The remaining fuel is then 

injected at high pressures into the secondary combustion zone where the relative lack 

of oxygen inhibits NOx formation. Staged fuel burners are compatible only with gas-fired 

combustion units. 

LNBs can also create oxygen-deficient conditions in a primary combustion zone by 

recycling a portion of the kiln exhaust gas to the burner, either in the primary air that 

accompanies the injected coal or directly into the flame. This is referred to as flue gas 

recirculation (FGR). This effect can also be achieved by creating a low-pressure zone at 

the center of the burner. The low-pressure zone tends to draw in oxygen-poor 

combustion gases that mix with the fuel and primary combustion air. Using an FGR 
HCM Air Quality Issues/BART 7/6/07 pg. 4-16 

Project #: HCM207541

would result in unacceptable cement product quality and has not been applied at a 

cement kiln. 

LNB control technology typically has reductions between 15 and 30% in NOx emissions. 

(iii) Fuel and Raw Material Substitutions 

Mid-Kiln Fuel Injection

During mid-kiln injection, typically, a combustible material such as tire-derived fuel 

(TDF) or other lump fuel, is introduced near the center of the kiln. This addition of a heat 

source midway through the calcining process reduces the temperature required in the 

primary combustion chamber, thereby reducing the formation of thermal NOx. 

Reductions in NOX occur as a result of the radiative transfer of heat from the primary 

combustion zone prior to reaching the secondary combustion zone. In addition, the 

entrained secondary fuel acts to reduce the temperature of the primary combustion 

products. NOx is reduced in the kiln combustor by following simplified reactions: 

NO + C → N + CO 

and 

NO + CO →N + CO2 

TDF combustion also lowers the amount of fuel-bound nitrogen introduced to the kiln 

and thereby lowers NOX emissions through another mechanism. Some fuels, such as 

TDF also introduce material to the cement clinker (such as steel) that may add 

beneficial qualities to the final product. 

EPA, Environment Canada, and many US Regional Air Agencies documents have 

identified combustion of TDF, especially mid-kiln introduction of tires, as an NOx control 

technology. 12,13 This technology typically has reductions between 30 and 50% in NOx

emissions. 

CemStar Process

CemStar is a patented process developed by TXI industries that can reduce NOx

emissions by the addition of steel slag to the feed end of the kiln. Steel slag has a low 

melting temperature and desirable chemical components of clinker in its material. The 

slag is directly added to the cement clinker manufacturing process. Due to the chemical 

composition of the steel slag, the material requires less fuel to convert it into cement 

slag, potentially resulting in lower total fuel consumption. The decreased need for 

limestone calcination per unit product and improved thermal efficiency of the process 

can lead to lower thermal NOx emissions. 

 

12 Assessment of NOX Emission Control Technologies for Cement and Lime Kilns. April 1995. 13 EPA-453/r-94-004, March 1994. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-17 

Project #: HCM207541

(iv) Post Combustion Control Technologies 

 

Selective Non-Catalytic Reduction (SNCR) 

SNCR is a proven technology in the cement industry for preheater/precalciner kilns to 

efficiently reduce NOx emissions. Like SCR technology, SNCR reduces NOX to nitrogen 

and water, but it does so without the use of a catalyst. It injects a nitrogenous reducing 

agent, typically ammonia or urea, into the upper reaches of the furnace. Because a 

catalyst is not used to drive the reaction, a temperature of 1600 to 2100o

F is required for 

the reduction reaction to proceed. 

NOX removal efficiency is dependent on inlet NOX concentrations, fluctuating flue gas 

temperatures, residence time, amount and type of nitrogenous reducing agent, mixing 

effectiveness, and the presence of interfering chemical substances in the gas stream. 

In the past, SNCR technology was only considered feasible for preheater/precalciner 

type kilns and not for long wet or dry kilns. The reason is the difference in design 

between preheater/precalciner kilns and long wet or dry kilns. Preheater/precalciner 

kilns, which are shorter than long kilns, have the optimal temperature range (1600o

F to 

2100oF) for the necessary reaction to take place at the end of the kiln, without having to 

inject ammonia- or urea-based reagents into the rotating kiln itself. In long kiln designs 

(both wet and dry), the optimal temperature range to make an SNCR effective occurs in 

the middle of the kiln; therefore, mid-kiln injection of the ammonia- or urea-based 

reagents would have to be incorporated into the kiln design. Until recently, this has 

made the installation of an SNCR technically infeasible because the injection of the 

reagents was not continuous and not effective. 

Selective Catalytic Reduction (SCR)

SCR is a post-combustion gas treatment technique that uses a catalyst to reduce NO 

and NO2 to molecular nitrogen, water, and oxygen. Ammonia (NH3) is commonly used 

as the reducing agent. Ammonia is vaporized and injected into the flue gas upstream of 

the catalyst bed, and combines with NOX at the catalyst surface to form an ammonium 

salt intermediate. The ammonium salt intermediate then decomposes to produce 

elemental nitrogen and water. The catalyst lowers the temperature required for the 

chemical reaction between NOX and ammonia. 

In general, the installations of SCRs are operated in clean gas circuits; i.e., dust and 

heavy metals are separated from the exhaust stream before the catalyst in order to 

prevent rapid wear and deactivation of the catalysts through catalyst poisons. 

Technical factors that impact the effectiveness of this technology include the catalyst 

reactor design, operating temperature, type of fuel fired, sulfur content of the raw 

material, design of the ammonia injection system, and potential for catalyst poisoning. 

An SCR characteristic common to all catalyst types is the narrow window of acceptable 

system inlet temperatures. Below the minimum acceptable temperature of about 575°F, 

the NOx reduction reaction will not proceed, while operation above the maximum 
HCM Air Quality Issues/BART 7/6/07 pg. 4-18 

Project #: HCM207541

acceptable temperature of about 750°F results in shortened catalyst life and can lead to 

the oxidation of NH3 to nitrogen oxides, thereby actually increasing the NOx emissions, 

or possibly generating explosive levels of ammonium nitrate in the exhaust gas. 

Another critical factor affecting SCR performance, especially in an application such as 

coal-fired lime and cement kilns, is related to SO2 in the exhaust gas. The SCR catalyst 

will oxidize SO2 to SO3, which can form ammonium bisulfate and sulfuric acid. 

Ammonium bisulfate is a sticky solid that causes clogging within the catalyst, while 

sulfuric acid can cause corrosion within the system and result in increased visible 

emissions. 

LoTOxTM

LoTOxTM is a patented technology that uses ozone to selectively oxidize NOX to higher 

forms of oxides of nitrogen, which become soluble and can be easily removed by a wet 

scrubber. This technology may require reheating of the gas stream and has a high 

electrical energy consumption which would raise the power consumption of Holcim’s 

facility. Furthermore, there is potential to create new waste streams like waste water or 

sludge that require further treatment. There are no known LoTOx installations in the 

cement industry. 

According to TCEQ’s ASSESSMENT OF NOx EMISSIONS REDUCTION 

STRATEGIES FOR CEMENT KILNS – ELLIS COUNTY, FINAL REPORT (dated 

7/14/06)14 Section 4.3.2, states: 

“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 LoTOxTM system.” 

4.4.2 Eliminate Technically Infeasible NOx Control Options – Step 2 

The methodology used to eliminate technically infeasible control technologies for NOx 

was described in Section 4.3.2 above. The reader is referred to that section for details 

of this process. 

(i) Proper Kiln Design and Operation

Proper design and operation of cement kilns is clearly feasible and serves as the 

baseline case. Holcim’s kiln design includes control systems for balancing primary and 

secondary combustion air flow rates and velocities. This will enable operators to 

optimize fuel and air mixing and ratios for minimal NOx formation. 

 

14 The final report itself (dated on 7/14/06) may be found at: 

http://www.tceq.state.tx.us/implementation/air/sip/BSA_settle.html.

 
HCM Air Quality Issues/BART 7/6/07 pg. 4-19 

Project #: HCM207541

Conclusion: This technology is considered feasible for purposes of Step 2 in this 

BART analysis. 

(ii) Process Modifications 

Increased Thermal Efficiency

Holcim has identified a process modification that has the potential to increase thermal 

efficiency of the kiln and reduce NOx emissions. The process alteration involves adding 

a fixed inlet to the clinker cooler, which will increase thermal efficiency of the kiln, and 

thereby reduce fuel consumption and reduce thermal NOx formation in the kiln. 

Conclusion: This technology is considered feasible for purposes of Step 2 in this 

BART analysis. 

Combustion System Modifications Including Low-NOx Burner (LNB)

Control of NOx emissions using methods employed by LNBs such as staged air 

combustion, though extremely limited in practice, is technically feasible for a coal-fired 

rotary kiln. As noted above, cement production requires balancing many combustion 

parameters to optimize cement quality and energy efficiency while limiting emissions of 

multiple air pollutants. The cement production system must be capable of adjusting and 

responding quickly to changes in external conditions. Because of these requirements, 

some LNB technologies, such as staged fuel combustion units, may not be practical or 

effective when applied to Holcim’s kiln. 

FGR in conjunction with an LNB has not been demonstrated in kiln applications to 

provide better NOx reduction than can be achieved by controlling primary and 

secondary combustion air in a properly designed and operated kiln. Adding FGR to a 

burner that is already designed for optimum flame shaping and control would distort the 

thermal profile of the kiln such that product quality would be unacceptably 

compromised. Such a flame profile would also reduce kiln efficiency and potentially 

result in increased NOx emissions. 

Holcim believes a carefully selected LNB in conjunction with proper combustion system 

modifications can achieve approximately a 17% NOx emission reduction. 

Conclusion: This technology is considered technically feasible for purposes of 

Step 2 in this BART analysis. 

(iii) Fuel and Raw Material Substitutions

Mid-kiln Fuel Injection

Holcim has previously identified mid-kiln injection of tires as a desirable process to add 

to the facility. In 2001, Holcim applied for an air quality permit from the Montana 

Department of Environmental Quality to authorize the addition of a mid-kiln tire injection 

system. To date, there has not been any final action taken on that application. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-20 

Project #: HCM207541

Conclusion: This technology is considered technically feasible for purposes of 

Step 2 in this BART analysis. 

CemStar Process

Holcim is not aware of any source of steel slag for use in the CemStar Process within a 

reasonable distance of the Holcim facility. Therefore, there is no commercially available 

source of steel slag for the kiln that would be considered “available” to Holcim for 

purposes of BART. 

Conclusion: This technology is considered technically infeasible for purposes of 

Step 2 in this BART analysis. No further discussion of this technology 

will be presented. 

(iv) Post-Combustion Control Technologies

Selective Non-Catalytic Reduction (SNCR)

In the past, SNCR technology was only considered feasible for preheater/precalciner 

type kilns and not for long wet or dry kilns. More recently, there has been a trial 

installation of an SNCR system on a wet kiln in France. This installation was a trial run 

conducted over a four-month period. 

The Holcim Trident facility believes there is very limited experience with the application 

of SNCR to a long, wet kiln. Therefore, the Holcim Trident facility believes it is currently 

an emerging technology and the application of SNCR is not an available BART 

technology. 

Holcim has investigated the feasibility of adding urea into the existing mid-kiln injection 

system, the dust scoops mechanism. The dust scoops are a mechanism which recycles 

cement kiln dust by injecting it into the kiln as it rotates. By adding urea to the dust 

scoops during normal operations, the reagent would be injected into the postcombustion zone of the kiln. The downfall of this application is that the temperature 

profile of the kiln shows a temperature of 1400o

F at the location of the dust scoop 

mechanism. This is below the range of temperatures (1600o

F to 2100oF) necessary for 

the NOx reduction reaction to take place and be effective. The other drawback to this 

application is that the short physical distance from the dust scoops downstream to the 

radiative cooling section of the kiln would give the flue gas a very short residence time. 

Thus, the mixing of reagent and flue gas would likely be incomplete. Holcim believes 

these two factors combined would either substantially reduce or completely eliminate 

the SNCR reaction and NOx reductions would not be achieved. 

Conclusion: Holcim believes SNCR is not available to the Trident facility for 

purposes of Step 2 in this BART analysis. No further discussion of this 

technology will be presented. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-21 

Project #: HCM207541

Selective Catalytic Reduction (SCR)

SCR is not feasible for application to the Holcim cement kiln for the following reasons. 

● First, SCRs are not sufficiently developed to make them commercially available 

in the U.S.; therefore, it should not be considered a feasible control technology. 

Although this technology has been used in coal-fired power plants, its 

commercial application to the cement industry is limited to two cement plants in 

the world, one in Solnhofen, Germany, and one in Di Monselice, Italy. The 

Solnhofen Portland cement plant located in southern Germany started operating 

an SCR system in 2001 and, after seven years of trials, the facility has not been 

able to finalize its design and resolve all its operational issues. During this 

period, the facility has worked on problems associated with catalyst design, 

sizing, and plugging. Application of SCR at Solnhofen has been a long, drawn 

out pilot-test, not a full-scale commercial success. Due to the operational 

problems, the SRC technology is no longer being used as an NOx control 

technology at Solnhofen. The plant in Di Monselice, Italy, installed SCR 

approximately a year ago, and at this time there is not enough experience and 

information from this installation to evaluate its performance or draw any 

conclusions. Consequently, its reliability and effectiveness in this application are 

unknown. 

The Texas Commission on Environmental Quality (TCEQ) adopted new rules on 

May 23, 2007, to control NOx emissions from cement kilns in the Dallas-Fort 

Worth ozone non-attainment area. Based on TCEQ’s study, in Chapter 117 –

Control of Air Pollution from Nitrogen Compounds, pg 256: 

“...........however, neither SCR nor LoTOx has been applied to 

wet process cement kilns, and only SCR has even been 

attempted on dry process cement kilns with results that are in 

question and that cannot necessarily be transferred to the kilns 

in Ellis County.” 

• Second, the sulfur concentrations in the raw materials at Trident are much higher 

than that of the European plants. Thus, the higher concentrations of SO2 in the kiln 

exhaust gas could cause sticky dust formation, leading to catalyst plugging, 

poisoning, and shortened lifespan. 

• Third, the high particulate loading of the exhaust stream would require that the unit 

be located downstream of the ESP. Otherwise, catalyst effectiveness and longevity 

would be severely limited due to poisoning and plugging. Because the highest 

exhaust gas temperature is typically near 400°F – well below the optimum SCR inlet 

temperature range of approximately 575 to 800°F – the gas stream would require 

reheating. This would increase the cost of controls, generate additional combustion 

pollutant emissions, and impose substantial energy penalties. 

Conclusion: SCRs are not sufficiently developed for cement kilns to overcome the 

potential problems listed above, and are not considered commercially 
HCM Air Quality Issues/BART 7/6/07 pg. 4-22 

Project #: HCM207541

available for this purpose. Therefore, SCR is not considered 

“available” to Holcim for purposes of BART. This technology is 

considered technically infeasible for purposes of Step 2 in this BART 

analysis. No further discussion of this technology will be presented. 

LoTOxTM

To be thorough in the analysis, Holcim identified LoTOxTM technology as a potential NOx

control technology; however, there are no known LoTOxTM installations in the cement 

industry. Therefore, LoTOxTM is not considered “available” to Holcim for purposes of 

BART. 

Conclusion: This technology is considered technically infeasible for purposes of 

Step 2 in this BART analysis. No further discussion of this technology 

will be presented. 

4.4.3 Evaluate Control Effectiveness of Remaining NOx Control Technologies – Step 3 

Of the alternative NOx control technologies identified above, proper kiln design and 

operation, process alterations, combustion system modifications including a low-NOx

burner and mid-kiln tire injection remain as technically feasible options. Proper kiln 

design and operation is the baseline case for this analysis. Table 4-4 summarizes the 

control effectiveness of the remaining control technologies. 

Table 4-4: Summary of Remaining NOx Control Technology Efficiency 

Control Option 

Efficiency

 (%) 

NOx 

Emissions 

(lbs/hr) 

NOx 

Emissions

(tpy) 

Tons NOx 

Removed 

Mid-Kiln Injection of Tires 30% 1,098 4,807 2,060 

Combustion System 

Modifications including 

Low-NOx Burner 17% 1,301 5,700 1,168 

Process Alterations 

(Install fixed inlet on clinker 

cooler) 3% 1,521 6,662 206 

Baseline 0% 1,568 6,868 0 

4.4.4 Evaluate Impacts and Document the Results – Step 4 

Process Alterations Impacts 

Process Alterations Economic Impacts

Holcim has calculated the cost-effectiveness for the process alterations, including a 

fixed inlet to the clinker cooler for NOx control, with the results presented in Table 4-5 

below. The table summarizes the cost-effectiveness for each of the technically feasible 

NOx control options, compared against a baseline of proper kiln design and operation. 

Details of the process alteration cost analysis can be found in Appendix C. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-23 

Project #: HCM207541

Process Alterations Energy Impacts

There are no negative energy impacts associated with installing a fixed inlet on the 

clinker. A fuel savings through improved kiln efficiency is expected. 

LNB Impacts 

LNB Economic Impacts

Holcim has estimated the cost of combustion system modifications, including the 

addition of an LNB based on EPA’s NOx Control Technologies for Cement Industry 

(Table 6-8), which estimates an annualized cost of $398,000 (1997 $) for retrofit LNB 

installations for a 50 ton/hr long wet kiln. It is assumed this is a representative cost. The 

cost in 1997 dollars was adjusted to 2006 dollars using the 1.25607 CPI multiplier15. 

The adjusted annualized cost was calculated to be $498,065. The results are presented 

in Table 4-5 below. Details of the cost analysis can be found in Appendix C. 

LNB Environmental Impacts

There are no negative environmental impacts associated with LNB technology. There 

are, however, heightened safety concerns associated with the LNB fuel delivery system. 

Because the flow rate of air used to inject pulverized coal is reduced, there is increased 

risk of combustion occurring within the coal mill system. 

LNB Energy Impacts

There are no significant negative energy impacts associated with the combustion 

system modifications and an LNB. 

Mid-Kiln Fuel Injection Impacts 

Mid-Kiln Fuel Injection Economic Impacts

Kiln modifications and a tire handling and injection system are required for mid-kiln 

introduction of TDF. The guidance document (EPA NOx Controls for Cement Industry 

Final Report, Sept. 19, 2000 Table 6-10) estimates an annualized cost of $370,000 

(1997 $) for mid-kiln firing conversion for a 50 ton/hr long wet kiln. It is assumed this is a 

representative cost. The cost in 1997 dollars was adjusted to 2006 dollars using the 

1.25607 CPI multiplier. The adjusted annualized cost was calculated to be $473,738. 

The results are presented in Table 4-5 below. Details of the cost analysis can be found 

in Appendix C. 

Mid-Kiln Fuel Injection Environmental Impacts

Holcim has studied the environmental impacts extensively, as reported in multiple 

submissions to Montana DEQ. CO emissions are expected to increase slightly. PM 

 

15 The CPI multiplier calculator may be found at: http://www.minneapolisfed.org/research/data/us/calc/. 

 
HCM Air Quality Issues/BART 7/6/07 pg. 4-24 

Project #: HCM207541

emissions are not expected to show any appreciable change. SO2 emissions are 

expected to be unchanged. VOC emissions are expected to decrease slightly. Metal 

emissions are expected to decrease. Dioxin/furan (D/F) emissions are not expected to 

change significantly. Holcim believes combusting TDF in the kiln will have a net 

environmental benefit by reducing the number of tires placed in solid waste landfills, 

reducing the amount of coal and coke currently combusted, reducing the impacts 

associated with mining the coal, and reducing fossil fuel dependence. 

Mid-Kiln Fuel Injection Energy Impacts

There are no significant negative energy impacts associated with the combustion of 

tires through mid-kiln injection. 

Alternatives Analysis Summary 

Holcim has identified several NOx reducing techniques which all have acceptable cost, 

energy and environmental impacts. Table 4-5 below summarizes the cost impacts of the 

remaining alternatives. For this analysis, it has been assumed that the remaining life of 

all of the equipment is at least the 10 years used to calculate the annualized costs.

Table 4-5: Summary of NOx Cost Impacts 

Control Option 

Estimated 

Annualized 

Cost 

Efficiency

 (%) 

NOx 

Emissions

(lbs/hr) 

NOx 

Emissions

(tpy) 

Tons 

Removed 

Cost 

Effectiveness

($/ton) 

Mid-Kiln Injection of Tires $473,738 30% 1,098 4,807 2,060 $230 

Combustion System 

Modifications with Low-NOx 

Burner 

$498,065 17% 1,301 5700 1168 $427 

Process Alterations 

(Install fixed inlet to cooler) $448,250 3% 1,521 6662 206 $2,176 

Baseline $0 0% 1,568 6868 0 -- 

 

The costs per ton for NOx removal are all in the range of generally what would be 

acceptable for NOx control in a Montana BACT analysis. The annualized costs of all 

three options are also considered acceptable by Holcim. 

4.4.5 Evaluate NOx Visibility Impacts – Step 5 

Holcim has performed modeling using the CALPUFF model to predict visibility impacts 

of the identified potentially applicable NOx control technologies, using the 98th percentile 

visibility result as recommended by EPA. The results of the modeling are shown in 

Table 4-6 below. The results are only presented for the Gates of the Mountains 

Wilderness Area, as it is the closer and more impacted Class I area. Details of the 

modeling are found in Appendix B to this document. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-25 

Project #: HCM207541

Table 4-6: Summary of NOx Visibility Impactsa 

Gates of the Mountains Wilderness Area 

Control Option 

Estimated 

Annualized 

 Cost 

Efficiency 

 (%) 

NOx 

Emissions

(lbs/hr) Visibility 

Impact 

(deciview) 

Visibility 

Improvement 

(deciviews 

24 hr) 

Cost 

Effectiveness

($/deciview) 

Mid Kiln Injection of Tires $473,738 30% 1,098 0.976 0.584 $811,195 

Combustion System 

Modifications with Low-NOx 

Burner 

$498,065 17% 1,301 1.122 0.438 $1,136,097 

Process Alterations 

(Install fixed inlet to clinker 

cooler) 

$448,250 3% 1,521 1.278 0.282 $1,591,797 

Baseline $0 0% 1,568 1.560 0 -- 

a

Deciviews at each % reduction for the Gates of the Mountains are calculated using the equation: 

y = 0.0112x + 0.248 derived from using the best fit trendline of the average 98th percentile modeling values.

4.4.6 Select NOx BART 

SCR, SNCR, LoTOxTM and CemStar technologies have been eliminated as 

inappropriate for controlling NOx emissions from the facility’s cement kiln. The remaining 

options are the baseline condition of proper design and operation of the kiln, process 

alterations including a fixed inlet on the clinker cooler, combustion system modifications 

including a Low NOx Burner, and mid-kiln injection of tires. 

Holcim believes that all of the remaining NOx control technologies are effective and 

economically feasible. However, Holcim cannot ensure the use of mid-kiln injection of 

tires within the five year timeline spelled out in the BART program. Holcim cannot use 

tires as a fuel source until the Montana DEQ issues a final air quality permit and any 

legal appeals are concluded. The current permitting and EIS process has been ongoing 

for at least six years, and Holcim has no control over the timeline or the outcome of the 

process. More negotiation and litigation is expected. For these reasons, Holcim cannot 

propose mid-kiln injection of tires as BART. 

Therefore, for the purpose of NOx control, Holcim selects a combination of process 

alterations, including a fixed clinker cooler inlet, and combustion system modifications, 

including a low NOx burner as BART. Holcim proposes to make the 20% NOx reduction 

federally enforceable by reducing the current permit limitation of 1,568 lbs/hour on a 

rolling 30-day basis to 1,254 lbs/hour on a rolling 30-day basis. 

4.5 BART Analysis for PM10 from the Kiln 

4.5.1 Identify Available Particulate Control Technologies – Step 1 

EPA’s RBLC describes several permitted cement kiln installations and lists their 

pollutant emission limits and the control technologies approved to achieve those limits. 

Another source of information regarding potentially applicable PM control technology for 
HCM Air Quality Issues/BART 7/6/07 pg. 4-26 

Project #: HCM207541

cement kilns is the EPA’s AP-42 for Portland cement manufacturing (Chapter 11, 

Section 6). The following technologies were identified as potentially applicable for 

controlling particulate matter from cement manufacturing using a wet process kiln: 

(i) Proper kiln design and operation with an electrostatic precipitator (ESP) 

(baseline), 

(ii) Fabric filter baghouse, and 

(iii) Cooling tower, multiclone, and ESP combination. 

Control Technology Description: 

(i) Proper Kiln Design and Operation

Many interdependent and sometimes competing factors must be considered in the 

design and operation of a cement kiln. Primary among them are product quality 

requirements, operating costs, and pollution mitigation. Burner operation is central to all 

three. Product quality is critically dependent upon flame temperature and kiln 

atmosphere composition. 

Holcim currently operates an ESP to control particulate emissions from the kiln. An ESP 

uses electrical forces to move entrained particles onto a collection surface. To remove 

dust cake from the collection surface, the collection surface is periodically “rapped” by a 

variety of means to dislocate the particulate, which drops down into a hopper. 

Particulate-laden air must be able to be collected and ducted to the ESP. 

(ii) Fabric Filter Baghouse

Directed air flow passes through tightly woven or felted fabric, causing PM in the flow to 

be collected on the fabric by sieving and other mechanisms. As PM collects on the filter, 

collection efficiency increases while pressure drop through the system increases. Bags 

are intermittently cleaned by shaking the bag, pulsing air through the bag, or temporarily 

reversing the airflow direction. Particulate-laden air must be able to be collected and 

ducted to the baghouse. 

(iii) Cooling Tower, Multiclone, and ESP Combination

A multiclone system is an application where many small cyclones are operating in 

parallel. The small cyclones remove particulate by centrifugal and inertial forces, 

induced by forcing particulate-laden gas to change direction. This type of technology is 

a part of the group of air pollution controls collectively referred to as “precleaners,” 

because they are often used to reduce the inlet loading of particulate matter to 

downstream collection devices by removing larger, abrasive particles. 

The cyclones are used to control PM, and primarily particulate matter greater than 10 

micrometers (μm). However, there are high efficiency cyclones designed to be effective 

for PM less than or equal to 10 μm and less than or equal to 2.5 μm (PM10 and PM2.5). 

Although cyclones my be used to collect particles larger than 200 μm, gravity settling 

chambers or simple momentum separators are usually satisfactory and less subject to 
HCM Air Quality Issues/BART 7/6/07 pg. 4-27 

Project #: HCM207541

abrasion. The combination of a multiclone and an ESP can achieve a very high 

collection efficiency. 

4.5.2 Eliminate Technically Infeasible Options – Step 2 

All of the control devices listed for the kiln have been successfully applied to many 

cement kilns with favorable results in controlling particulate matter. 

Conclusion: These technologies are considered technically feasible for 

purposes of Step 2 in this BART analysis. 

4.5.3 Evaluate Control Effectiveness of Remaining PM10 Control Technologies – Step 3 

Table 4-7 lists available technologies with their respective efficiencies for controlling 

PM/PM10 emissions from a long wet kiln. 

Table 4-7: Kiln PM/PM10 Control Technology Effectiveness 

Control Option Efficiency (%)

Proper Kiln Design and 

Operation with ESP (baseline) 99.9% 

Fabric Filter Baghouse 99.9% 

Cooling Tower, Multiclone, 

and ESP Combination 99.9% 

Emissions from the kiln are currently controlled by an electrostatic precipitator (ESP). In 

December of 2004, MDEQ completed an analysis titled “Air Quality Technical Analysis 

Report for the Review of Submittals Supporting the Holcim (US) Inc. Tires Combustion 

Proposal.” 

In Section 4.4, paragraph 6 of the analysis, MDEQ concluded: 

 

“Based on the above equation, the efficiency of a single field of the Holcim ESP 

would be greater than 99.9%. This calculation does not account for the variable 

including re-entrainment and rapping. The use of two fields in series provides 

additional particulate removal.” 

Because the ESP has an efficiency equal to the highest control available from the other 

listed control technologies, Holcim proposes that the current ESP control of PM/PM10

emissions from the kiln is BART, with associated emission rate limits of 0.10 gr/dscf, 

and 0.77 lbs/ton of clinker produced. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-28 

Project #: HCM207541

4.6 BART Analysis for PM10 from the Clinker Cooler 

4.6.1 Identify Available Particulate Control Technologies – Step 1 

EPA’s RBLC describes many clinker cooler installations and lists their pollutant 

emission limits and the control technologies approved to achieve those limits. Another 

source of information regarding potentially applicable PM control technology for cement 

kilns is the EPA’s AP-42 for Portland cement manufacturing (Chapter 11, Section 6). 

The following technologies were identified as potentially applicable for controlling 

particulate matter from the clinker cooler at a cement production facility: 

(i) Fabric Filter Baghouse (baseline) 

(ii) Electrostatic Precipitator (ESP), 

(iii) Gravel Bed Filter. 

Control Technology Description: 

(i) Fabric Filter Baghouse (Baseline)

Emissions from the clinker cooler are currently controlled by a fabric filter baghouse. 

Directed air flow passes through tightly woven or felted fabric, causing PM in the flow to 

be collected on the fabric by sieving and other mechanisms. As PM collects on the filter, 

collection efficiency increases while pressure drop through the system increases. Bags 

are intermittently cleaned by shaking the bag, pulsing air through the bag, or temporarily 

reversing the airflow direction. Particulate-laden air must be able to be collected and 

ducted to the baghouse. 

 

(ii) Electrostatic Precipitator

An ESP uses electrical forces to move entrained particles onto a collection surface. To 

remove dust cake from the collection surface, the collection surface is periodically 

“rapped” by a variety of means to dislocate the particulate, which drops down into a 

hopper. Particulate-laden air must be able to be collected and ducted to the ESP. 

(iii) Gravel Bed Filter

Gravel bed filters are commonly used to control particulate emissions from a clinker 

cooler. Generally, a cyclone is used to pre-clean the exhaust stream of larger 

particulate. The exhaust stream is then directed through a bed of gravel, commonly 

crushed quartz, which captures smaller particulate through agglomeration. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-29 

Project #: HCM207541

4.6.2 Eliminate Technically Infeasible Options – Step 2 

All of the control devices listed for the clinker cooler have been successfully applied in 

other installations. 

Conclusion: These technologies are considered technically feasible for 

purposes of Step 2 in this BART analysis. 

4.6.3 Evaluate Control Effectiveness of Remaining PM10 Control Technologies – Step 3 

Table 4-8 lists available technologies with their respective efficiencies for controlling 

PM/PM10 emissions from a clinker cooler. 

Table 4-8: Clinker Cooler PM/PM10 Control Technology Effectiveness 

Control Option Efficiency (%)

Fabric Filter Baghouse 

(baseline) 99.9% 

Electrostatic Precipitator 99.9% 

Gravel Bed Filter 95% (est.) 

Emissions from the clinker cooler are currently controlled by a fabric filter baghouse. 

Because the fabric filter baghouse has an efficiency equal to the highest control 

available from the other listed control technologies, Holcim proposes that the current 

emission limit and baghouse control of PM/PM10 emissions from the clinker cooler are 

BART. No further analysis is needed. 

4.7 BART Analysis for PM10 Emissions from Material Handling Systems 

The facility includes systems for transporting, transferring, and storing limestone, coal, 

and finished cement product. Emissions associated with these activities occur as a 

result of transferring the material from one system to another. These transfers, referred 

to as “drop transfers,” occur, for example, when material is transferred from one 

conveyor to another or from a chute to a load-out truck. 

Table 4-9 lists the 10 material transfer emission sources that will be considered in this 

BART analysis. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-30 

Project #: HCM207541

Table 4-9: Listing of Material Transfer Emission Points 

Source Current Source Control 

005 – Xfer-convey-screen Baghouse 

010 – 013 Raw material silos 1-7 Baghouse 

015 and 018 Coal and coke xfer, crush, store, 

(un)load & grinding 

Baghouse 

026 Cement kiln dust silo unload Dustless Unloader and Baghouse 

032a Clinker xfer to #2 finish mill Baghouse 

047 Cement load/unload at silos 14-25 Baghouse 

4.7.1 Identify Available Particulate Control Technologies – Step 1 

The following technologies were identified as potentially applicable for controlling 

particulate matter from raw materials and product handling in the cement manufacturing 

process: 

(i) Fabric Filter Baghouse (baseline), 

(ii) Electrostatic Precipitator (ESP), 

(iii) Enclosures, and 

(iv) Wet Suppression. 

Control Technology Description: 

(i) Fabric Filter Baghouse

The Holcim Trident plant currently utilizes baghouses to control PM emissions from the 

sources in Table 4-9. Directed air flow passes through tightly woven or felted fabric, 

causing PM in the flow to be collected on the fabric by sieving and other mechanisms. 

As PM collects on the filter, collection efficiency increases while pressure drop through 

the system increases. Bags are intermittently cleaned by shaking the bag, pulsing air 

through the bag, or temporarily reversing the airflow direction. Particulate-laden air must 

be able to be collected and ducted to the baghouse. 

(ii) Electrostatic Precipitator

An ESP uses electrical forces to move entrained particles onto a collection surface. To 

remove duct cake from the collection surface, the collection surface is periodically 

“rapped” by a variety of means to dislocate the particulate, which drops down into a 

hopper. Particulate-laden air must be able to be collected and ducted to the ESP. 
HCM Air Quality Issues/BART 7/6/07 pg. 4-31 

Project #: HCM207541

(iii) Enclosures

Enclosure technology employs structures or underground placement to shelter material 

from wind entrainment. Enclosures can either fully or partially surround the source. 

(iv) Wet Suppression

A fogging water spray adds water with or without surfactant to material. Emissions are 

prevented through agglomerate formation by combining small dust particles with larger 

aggregate or with liquid droplets. Water retained by sprayed material prevents 

emissions from storage piles and downstream transfers in a similar manner.

4.7.2 Eliminate Technically Infeasible Options – Step 2 

All of the control methods listed for materials transfers have been successfully applied 

to many industries with favorable results in controlling particulate matter. 

Conclusion: These technologies are considered technically feasible for 

purposes of Step 2 in this BART analysis. 

4.7.3 Evaluate Control Effectiveness of Remaining PM10 Control Technologies – Step 3 

Table 4-10 lists available technologies with their respective efficiencies for controlling 

PM/PM10 emissions from the BART-eligible materials transfers. 

Table 4-10: Material Transfer PM/PM10 Control Technology Effectiveness 

All of the listed PM/PM10 emission sources from the materials handling analyzed for 

BART are currently controlled by fabric filter baghouses. The fabric filter baghouses are 

equivalent to the highest control efficiency of any of the control devices analyzed; 

therefore, Holcim proposes that the current baghouse control of PM/PM10 emissions 

from the materials transfers is BART. No further analysis is needed. 

Control Option Efficiency (%) 

Fabric Filter Baghouse 

(baseline) 99.9% 

Electrostatic Precipitator 99.9% 

Enclosures 90% 

Water Suppression 50-90% 
APPENDIX A: EPA LETTER TO HOLCIM 





APPENDIX B: VISIBILITY IMPACTS MODELING 
Holcim BART Analysis pg. B-1 

Appendix B 

VISIBILITY IMPACTS 

1.1 Introduction and Summary 

Holcim has concurred with the initial EPA BART analysis that the Trident facility is a 

BART-eligible source. The following sections detail the modeling analysis that Bison 

performed on behalf of Holcim to comply with the intent of 40 CFR 51, Appendix Y. This 

document describes the methodologies and results of those analyses. 

In conducting the BART modeling analyses, Bison closely followed the Montana 

Department of Environmental Quality’s (MDEQ) modeling protocol for regional modeling 

in support of the BART program, entitled State of Montana Draft CALPUFF BART 

Modeling Protocol For Federal Mandatory Class I Areas, September 2006 Draft 

(“Montana BART protocol”). The analysis also relied on guidance in the Interagency 

Workgroup on Air Quality Modeling (IWAQM) Phase 2 Summary Report for Modeling 

Long Range Transport Impacts (EPA, 1998), and the Federal Land Managers’ Air 

Quality Related Values Workgroup (FLAG) Phase I Report, December 2000 (“FLAG 

document”). 

The BART modeling analysis specifically requires demonstrations of impacts to visibility 

at surrounding mandatory federal Class I areas. The mandatory federal Class I areas 

evaluated are: 

• Yellowstone National Park, and 

• Gates of the Mountains Wilderness Area. 

Visibility Impacts: The visibility impacts analysis began with the permitted emissions 

from the cement kiln and clinker cooler located at the Trident facility. These impacts 

were developed to establish a visibility baseline to analyze what effects, if any, different 

control technologies or operating practices had on visibility at the surrounding Class I 

areas. 

The visibility impacts analyses included the appropriate potential NOx, SO2, and PM10

emissions from the sources modeled since all three pollutants contribute to visibility 

impairment. 

1.2 Model Selection 

Selection of the appropriate dispersion model for assessing visibility impacts in Class I 

areas is typically based on the distance from the emitting source to the Class I area. 

Appendix W in 40 CFR Part 51 recommends different models for different applications 

and identifies appropriate models for short- and long-range impacts. 

Since EPA has already established CALPUFF for the visibility analysis, the CALPUFF 

model was used in the present analyses of Class I visibility impacts. 
Holcim BART Analysis pg. B-2 

Appendix B 

CALPUFF is a non-steady-state Lagrangian dispersion model that simulates pollutant 

releases as a continuous series of “puffs.” It includes algorithms for building downwash, 

pollutant removal due to wet scavenging and dry deposition, chemical transformation, 

and plume fumigation. It is supported by two primary sub-programs, CALMET and 

CALPOST. CALMET is used in refined analyses to create three-dimensional wind fields 

based on multiple sources of geophysical and meteorological data. The output of the 

CALPUFF model consists of binary data files with information on pollutant 

concentrations, wet and dry flux rates, and visibility parameters. CALPOST processes 

these data based on specified input parameters, and reports calculated impact values. 

The present CALPUFF analysis utilized the most current version of the following 

primary programs and pre- and post-processors obtained from the CALPUFF 

developer, Atmospheric Studies Group (ASG) at: 

http://www.src.com/calpuff/calpuff1.htm. 

Geophysical Data Processors

• TERREL (Version 3.311, Level 030709) 

• CTGCOMP 

• CTGPROC (Version 2.42, Level 030709) 

• MAKEGEO (Version 2.22, Level 030709) 

Meteorological Preprocessors 

• SMERGE (Version 5.31a, Level 040706) 

• PXTRACT 

• PMERGE (Version 5.31, Level 030528) 

• READ62 (Version 5.52, Level 040716) 

Main Models 

• CALMET (Version 6.211, Level 060414) 

• CALPUFF (Version 6.112, Level 060412) 

Postprocessors 

• CALPOST (Version 6.131, Level 060410) 

• PRTMET 

• CALSUM 

• POSTUTIL 

The version and level identifiers for the major modules used for this project are 

identified above. Electronic executable files for the primary modules and the primary 

electronic input and output files associated with this analysis are available upon request. 

1.3 Regional Modeling Domain 

The regional modeling domain was defined to follow the Montana Protocol. The 

modeling domain is defined in a Lambert Conformal Conic (LCC) system. The LCC 

coordinate system for this project has a projection origin at 44.25° N and 109.5° W and 
Holcim BART Analysis pg. B-3 

Appendix B 

matching parallels of latitude of 44.0° and 49.0° N. The coordinates of the southwest 

corner of the domain are 0.000 km easting and 0.000 km northing. This varies from the 

WRAP modeling domain which defined matching parallels of latitude of 45.0° and 49.0° 

N. 

1.4 CALMET 

CALMET, the meteorological preprocessor for CALPUFF, was used to compile and 

process land use data, terrain data, and meteorological data for use in the CALPUFF 

model program. The CALMET output files defined gridded fields of wind speed, wind 

direction, mixing heights, stabilities, micrometeorological parameters, and precipitation – 

all parameters required for input to the CALPUFF dispersion model. The following 

sections provide a brief description of each of these data sets. 

1.4.1 Land Use Data 

CALMET uses specific land use data developed by the U.S. Geological Survey 

(USGS)1. The data files used for this project were 1:250,000-scale files. Each land use 

cell, typically 200 meters square, is assigned a land use code. Using several data 

processing programs provided by ASG, the land use data were processed and 

combined with other geophysical data into a single data set for input to the CALMET 

model. 

1.4.2 Terrain Data 

CALMET uses USGS 1:250k Digital Elevation Models (DEMs) to determine the terrain 

elevation in the model domain. The terrain data is preprocessed into a data set 

recognized by CALMET and used to help create the CALMET output file. Terrain data 

obtained from www.webmet.com were used to create the appropriate files for CALMET. 

1.4.3 Meteorological Data 

CALMET output files representing meteorological data for the 2001, 2002, and 2003 

calendar years were prepared for the analysis in accordance with the Montana BART 

protocol. Input meteorological data consisted of Mesoscale Model (MM) meteorological 

data, observed hourly surface data, upper air rawinsonde data, and hourly precipitation 

data. 

Mesoscale Model Data 

The MM meteorological data for the 2001, 2002, and 2003 calendar years obtained 

from the Western Regional Air Partnership (WRAP) are available at the following 

website: http://pah.cert.ucr.edu/aqm/308/bart.shtml. These data are generated by 

Pennsylvania State University/National Center for Atmospheric Research mesoscale 

models. The mesoscale models are limited-area, nonhydrostatic or hydrostatic, terrainfollowing sigma-coordinate models designed to simulate or predict mesoscale and 

 

1

 Available for download from the USGS Earth Resources Observation and Science (EROS) web site. 
Holcim BART Analysis pg. B-4 

Appendix B 

regional-scale atmospheric circulation. The data are used as a basis for generating an 

“initial guess field” of multilayer wind vectors in CALMET. The meteorological data for all 

three years are in the MM5 format. They reflect a spatial resolution of 36 km. 

Surface Data 

Hourly observed surface data for 2001, 2002, and 2003 were also obtained from the 

WRAP internet site. In accordance with the Montana BART protocol, National Weather 

Service (NWS) hourly surface data for 39 stations for 2001 and 36 stations for 2002 and 

2003 were processed in CALMET. The data files were provided in the SMERGE format 

and were ready for input into CALMET. 

Surface data from the following locations were used for the CALMET analysis: 

• Badger Peak, MT (2001 only) 

• Billings, MT 

• Bismarck, ND 

• Boise, ID 

• Bozeman, MT 

• Butte, MT 

• Casper, WY 

• Coeur d’Alene, ID 

• Cut Bank, MT 

• Dickinson, ND 

• Dillon, MT 

• Estevan, SK 

• Havre, MT 

• Kalispell, MT 

• Garfield Peak, MT (2001 only) 

• Glacier National Park, MT 

• Glasgow, MT 

• Great Falls, MT 

• Helena, MT 

• Havre, MT 

• Lander, WY 

• Lewistown, MT 

• Livingston, MT 

• Medicine Hat, AB 

• Miles City, MT 

• Minot, ND 

• Missoula, MT 

• Morningstar, MT (2001 only) 

• Peabody Coal, MT 

• Pocatello, ID 

• Rapid City, SD 
Holcim BART Analysis pg. B-5 

Appendix B 

• Rexburg, ID 

• Riverton, WY 

• Salmon, ID 

• Sheridan, WY 

• Spokane, WA 

• Spring Creek Coal, MT 

• Theodore Roosevelt National Park, ND 

• Williston, ND 

• Yellowstone National Park, WY 

Upper Air Data 

The Montana Protocol included the use of upper air data; however, the EPA Protocol 

specified that upper air data would not be used, and consequently the WRAP modeling 

omitted this data. Bison followed the Montana modeling protocol and included the 

upper air station data in the BART modeling analysis. 

Upper air rawinsonde data collected by seven NWS stations were obtained from the 

rawinsonde data repository maintained by NOAA at http://raob.fsl.noaa.gov/. The data 

were obtained in the standard FSL data format for use in the CALMET system. The 

seven NWS upper air rawinsonde locations used for this project are: 

 

• Bismarck, ND 

• Boise, ID 

• Glasgow, MT 

• Great Falls, MT 

• Rapid City, SD 

• Riverton, WY 

• Spokane, WA 

Upper air data substitution and extrapolation were accomplished as needed according 

to ASG’s FAQ 2.3.4, which recommends temporal substitution (for example, substituting 

an afternoon sounding with the previous or succeeding afternoon sounding) or spatial 

substitution from a nearby location if soundings are missing. For in-sounding values 

flagged by READ62, the data values were corrected using an in-house computer 

program (Fix6201.exe) developed for this purpose. Nearly all of these flagged values 

were due to either (1) the pressure remaining constant or rising with height, or (2) the 

elevation remaining constant or decreasing with height. These were corrected by the inhouse program by changing the flagged values by a small amount so that the pressure 

decreased with height or the elevation increased with height as appropriate. For spatial 

substitutions, another in-house program (AdjUa.exe) was used to adjust for the 

difference in elevation between the two locations. Temporal substitutions were 

accomplished manually using a text editor. All raw and processed data and data 

processing algorithms are available upon request. 
Holcim BART Analysis pg. B-6 

Appendix B 

Precipitation Data 

The use of precipitation data was referenced in the Montana and EPA Modeling 

Protocols. The WRAP modeling omitted this precipitation data. Bison followed the 

modeling protocols and included the precipitation station data in the BART modeling 

analysis. 

Hourly precipitation data in NCDC’s TD-3240 format were obtained from the data set 

developed by MDEQ for their BART modeling analysis effort. All precipitation stations 

located within the CALMET modeling domain were extracted from the data set and were 

used in the CALMET analysis. A total of 286 stations were selected for each of the three 

modeled years. A complete list of precipitation stations is included as an attachment to 

this report.

No precipitation data interpolation or substitution was required for this project.

1.5 Ozone 

The ozone data provided on the WRAP website contained all the ozone sites in the 

United States and for the year 2002 the number of ozone sites exceeded the number of 

stations allowed in the CALPUFF model. Bison obtained ozone data for the following 

three ozone stations in the modeling domain: 

• Yellowstone National Park 

• Glacier National Park 

• Theodore Roosevelt National Park 

1.6 CALPUFF 

CALPUFF applies mathematical algorithms to calculate pollutant concentrations at 

Class I receptors. CALPUFF requires CALMET output files, source emissions, and 

receptor grids to model Class I impacts. 

1.6.1 CALPUFF Parameters 

CALPUFF was run in the refined mode using the MESOPUFF III chemical 

transformation scheme and dry and wet deposition calculations. Model settings were 

based on recommendations found in the Montana BART protocol. The table below 

summarizes the model control file settings used for this analysis. Complete CALPUFF 

input files will be provided upon request. 
Holcim BART Analysis pg. B-7 

Appendix B 

CALPUFF Model Control File Settings 

Model Parameter/Option Value 

Number of chemical species 9 

Number of chemical species emitted 7 

Vertical distribution near field Gaussian 

Terrain adjustment method Partial plume path adjustment 

Subgrid-scale complex terrain Not modeled 

Slug model Not used 

Transitional plume rise Yes 

Stack tip downwash Yes 

Vertical wind shear Yes 

Puff splitting Yes 

Chemical mechanism MESOPUFF II scheme 

Wet removal Yes 

Dry deposition Yes 

Dispersion coefficient method PG dispersion coefficients for rural areas 

Partial plume penetration – elevated inversion Yes 

PDF used under convective conditions No 

CSPEC SO2, SO4, NOX, HNO3, NO3, SOA, EC, PMC, 

PMF 

Chemical parameters – dry gas deposition Default 

Size parameters – dry particle deposition Default 

Reference cuticle resistance (RCUTR) 30 s/cm 

Reference ground resistance (RGR) 10 s/cm 

Reference pollutant reactivity (REACTR) 8 

Number of particle-size intervals (NINT) 9 

Vegetation state in un-irrigated areas (IVEG) 1 

Wet deposition parameters Default 

Ozone data input option 0 

Background ozone concentration Ozone data: Yellowstone NP, Glacier NP, 

Theodore Roosevelt NP 

Background ammonia concentration 

(values specific to each Class I area analyzed) 

1.22, 1.23, 1.6, 1.94, 2.29, 1.63, 1.65, 1.69, 

0.98, 1.04, 1.37, 1.06 ppb 

SYTDEP 550 m 

MHFTSZ 0 

JSUP 5 

XSAMLEN 1.0 grid units 

MXNEW 99 

MXSAM 99 

Maximum mixing height 3,000 m 

Minimum mixing height 50 m 

NSPLIT 2 

IRESPLIT Hour 17-22 = 1 

ZISPLIT 100 m 

ROLDMAX 0.25 

Notes: 

ppb = parts per billion 

s/cm = seconds per centimeter 
Holcim BART Analysis pg. B-8 

Appendix B 

1.6.2 Receptors 

The Air Resources Division (ARD) of the National Park Service (NPS) has developed a 

database of modeling receptors for all federal Class I areas in the United States. ARD 

has also developed a file conversion program to convert the data from latitude/longitude 

to either Lambert Conformal or UTM coordinates. Receptor grids for each federally 

mandated Class I area of concern were developed using the ARD data files converted 

to the appropriate LCC coordinate system. 

1.6.3 Modeled Sources - General 

The visibility analyses included potential emissions for the Holcim BART-eligible 

sources and the projected emission reductions for the applicable pollutant controls. The 

BART-eligible sources that were included in the analysis are: 

• Cement Kiln 

• Clinker Cooler 

1.6.4 Modeled Sources - Physical Parameters 

The physical parameters for each of the sources included in the models remained 

consistent with WRAP model inputs. 

1.6.5 Modeled Sources – Baseline Emission Rates 

Class I visibility impacts demonstrations were performed using the maximum actual 

emission rates for each modeled eligible source. These emission rates were obtained 

from Holcim’s current air permits. The following table provides the emission rates used 

to demonstrate the BART impacts for regional haze: 

Baseline Modeled Emission Rates 

Source ID 

NOx 

 (lb/hr) 

SO2 

(lb/hr) 

PM10

(lb/hr) 

Kiln 1568 340 37.36 

Clinker 

Cooler - - 45.82 

To accurately demonstrate the changes in visibility impacts at surrounding mandatory 

Class I areas, potential kiln and clinker cooler emissions of NOx, SO2, and PM10

emission rates were entered into the CALPUFF models to establish a baseline case for 

comparison. The current permit limits NOx emissions from the kiln to 1568 lb/hr on an 

hourly average basis. SO2 permit limits are 124 lb/hr on a 30-day rolling average; 

however, the 340 lb/hr highest rate was used in the modeling to be consistent with the 

WRAP model inputs. The potential hourly kiln filterable PM10 emissions of 37.36 lb/hr 

are based on the permit limit of 0.77 lb/ton of clinker and the annual clinker production 
Holcim BART Analysis pg. B-9 

Appendix B 

limit of 425,000 tons of clinker per year. The clinker cooler filterable PM10 emissions of 

45.82 lb/hr are limited by the process weight rule (E=55.0*P^0.11-40) and 500,000 tons 

of clinker per year. 

Including particulate matter emissions in the model is not as straightforward as including 

SO2 or NOx emissions. Particulate matter can be present in different forms, or species, 

and each species can affect visibility to a different degree. The NPS has provided 

several spreadsheet templates that speciate PM10 emissions resulting from various 

combustion sources.2 These spreadsheets allow generalized speciation of the PM10 for 

a specific source and as such do not necessarily accurately reflect potential speciated 

emissions. WRAP did not document the speciation of PM10 used in the initial BART 

determination model. Therefore, Bison relied on the NPS speciation templates. 

The following analysis was conducted to develop a source-specific PM10 speciation for 

visibility impacts modeling. First, the following general distribution of PM10 species was 

generated using an NPS spreadsheet for dry-bottom PC-fired boilers with flue gas 

desulfurization and fabric filter baghouse emissions controls. 

Guideline PM10 Speciation 

Species 

NPS 

Kiln 

Distribution 

NPS 

Clinker Cooler 

Distribution 

Coarse (PMC)(a) 19.6% 39.6%

Fine Soil (PMF)(b) 57.4% 42.4%

Fine Elemental Carbon (EC) 2.2% 1.6%

CPM IOR (SO4)

(c) 18.3% 14.4%

CPM OR (SOA)(d) 2.5% 2.0%

Total: 100.0% 100.0%

(a) PMC = Particulate Matter, Coarse (filterable PM > 2.5 microns and ≤ 10 microns) 

(b) PMF = Particulate Matter, Fine (filterable PM ≤ 2.5 microns) 

(c) IOR = Inorganic 

(d) CPM = Condensable Particulate Matter; OR = Organic; SOA = Secondary Organic 

Aerosols 

Applying these percentages to the maximum PM10 emission rate of 31.3 lb/hr, less 

estimated H2SO4 emissions, and adding back the estimated SO4 emission rate yields 

the following particulate species distribution. 

 

2

 See web address: http://www2.nature.nps.gov/air/Permits/ect/index.cfm 
Holcim BART Analysis pg. B-10 

Appendix B 

Final PM10 Speciation 

Species 

Kiln 

Modeled PM10

Speciation (lb/hr) 

Clinker Cooler 

Modeled PM10

Speciation (lb/hr) 

Coarse (PMC) 9.2 21.7 

Fine Soil (PMF) 27.1 23.2 

Fine EC 1.0 0.9 

CPM IOR (SO4) 8.6 7.9 

CPM OR (SOA) 1.2 1.1 

Total: 47.2 54.8 

1.6.6 Modeled Sources – BART Contolled Emission Rates 

The BART modeling analysis required that the baseline emissions be adjusted to reflect 

the predicted emission reductions for each pollutant. The following table shows the 

proposed emissions used in this second step in the BART modeling analysis. 

BART Controlled Modeled Emission Rates 

Source ID 

NOx 

(lb/hr) 

Percent 

NOx 

Reduction

SO2 

(lb/hr)

Percent 

SO2

Reduction

PM10

(lb/hr)

Percent 

PM10 

Reduction 

Kiln 784 50% 340 0% 37.36 0%

Clinker 

Cooler - - - 45.82 0%

1.7 CALPOST 

Data generated by CALPUFF was entered into the CALPOST program to summarize 

peak Class I visibility impacts as required. For the visibility analysis, CALPOST used 

modeled sulfate, nitrate, and PM10 concentration data to determine the light-absorbing 

and light-scattering effects resulting from the project’s emissions. The method 

recommended and used for calculating light extinction was “Method 6: Compute 

extinction from speciated particulate matter measurements.” The background extinction 

coefficients were calculated based on the annual relative humidity factors and data 

presented in Section 6.1 and Appendices C and D of the Montana BART Protocol. 

Inputs to CALPOST for visibility processing are summarized in the following table. The 

attached CD-ROM contains the CALPOST input files. 
Holcim BART Analysis pg. B-11 

Appendix B 

CALPOST Visibility Control File Settings 

CALPOST Parameter/Option Value 

Maximum relative humidity (RHMAX) 95% 

Included species Sulfate, nitrate, coarse particulate (as PM10), and 

fine particulate (as PM2.5) 

Coarse particulate extinction efficiency 0.6 (l/Mm per μg/m3) 

Fine particulate extinction efficiency 1.0 (l/Mm per μg/m3) 

Ammonium sulfate extinction efficiency 3.0 (l/Mm per μg/m3) 

Ammonium nitrate extinction efficiency 3.0 (l/Mm per μg/m3) 

Organic carbon extinction efficiency 4.0 (l/Mm per μg/m3) 

Soil extinction efficiency 1.0 (l/Mm per μg/m3) 

Elemental carbon extinction efficiency 10.0 (l/Mm per μg/m3) 

Method used for background light 

extinction MVISBK = 6 

Relative humidity From *.VIS Files 

Background extinction coefficients, SO4 0.120 

Background extinction coefficients, NO3 0.100 

Background extinction coefficients, PMC 3.006 

Background extinction coefficients, OC 0.471 

Background extinction coefficients, soil 0.501 

Background extinction coefficients, EC 0.2 

Extinction due to Rayleigh scattering 10.0 

Notes: 

NO3 = Nitrate 

1.8 Modeling Results 

1.8.1 Regional Haze (Visibility) 

Impacts to natural background visibility, expressed in terms of percentage change in 

24-hour average background extinction (ΔBex) were calculated by CALPOST. The 

guidelines also reference 40 CFR §51.301(a) in asserting that determinations must be 

made on a “...case-by-case basis taking into account the geographic extent, intensity, 

duration, frequency and time of visibility impairments....” The 98th percentile impact 

results are summarized in the following table. 
Holcim BART Analysis pg. B-12 

Appendix B 

Summary of BART Selections and Visibility Impacts 

Gates of the Mountains 

Pollutant Control Technology 

Approximate 

Control 

Efficiency 

Emission 

Rate 

(lb/hour) 

Modeled 

Deciviews 

Modeled 

Deciview 

Improvement 

(above baseline) 

% 

Improvement 

in Visibility 

(from 

baseline) 

SO2 No Additional Controls 0% 340 1.56 0.00 0% 

Process Alterations 

(install fixed inlet on 

clinker cooler) 

3% 1,521 1.49 0.04 3% 

Low-NOx Burner 17% 1,301 1.32 0.21 14% 

NOx 

Total NOx Improvement: 20% 1,254 1.28 0.24 17% 

PM10 No Additional Controls 0% 23 1.56 0.00 0%