## BART F IVE 

## F ACTOR 

## A NALYSIS 

##  A SH 

## G ROVE 

## C EMENT 

## M ONTANA 

## C ITY 

## , M ONTANA



### V ERSION 

### 0

Prepared by:

T RINITY C ONSULTANTS 9777 Ridge Drive Suite 380 Lenexa, Kansas 66219 (913) 894-4500

June 2007

Project 071601.0069Ash Grove Cement Company i Trinity Consultants BART Analysis 

## T ABLE OF 

## C ONTENTS



### 1. E XECUTIVE 

### S UMMARY 

### ........................................................................................ 1-1

2. I NTRODUCTION AND 

### B ACKGROUND 

### .................................................................... 2-3

3. BART A PPLICABILITY 

### D ETERMINATION 

### ........................................................... 3-5

4. SO 2 

### BART E VALUATION 

### .................................................................................... 4-1 4.1 I DENTIFICATION OF 

### A VAILABLE 

### R ETROFIT 

### SO 2 

### C ONTROL 

### T ECHNOLOGIES 

### .......... 4-1 4.2 E LIMINATE 

### T ECHNICALLY 

### I NFEASIBLE 

### SO 2 

### C ONTROL 

### T ECHNOLOGIES 

### ................ 4-2
4.2.1 F UEL S UBSTITUTION ...........................................................................................4-2 4.2.2 R AW M ATERIAL S UBSTITUTION .........................................................................4-2 4.2.3 L IME S PRAY D RYING ..........................................................................................4-3 4.2.4 W ET L IME S CRUBBING .......................................................................................4-3 

### 4.3 R ANK OF 

### T ECHNICALLY 

### F EASIBLE 

### SO 2 

### C ONTROL 

### O PTIONS BY 

### E FFECTIVENESS 

### .. 4-4 4.4 E VALUATION OF 

### I MPACTS FOR 

### F EASIBLE 

### SO 2 

### C ONTROLS 

### ..................................... 4-4
4.4.1 W ET L IME S CRUBBING .......................................................................................4-5 4.4.2 F UEL S UBSTITUTION ...........................................................................................4-9 

### 4.5 E VALUATION OF 

### V ISIBILITY 

### I MPACT OF 

### F EASIBLE 

### SO 2 

### C ONTROLS 

### .................... 4-12 4.6 P ROPOSED 

### B ART FOR 

### SO 2 

### ..................................................................................... 4-1

5. NO X 

### BART E VALUATION 

### ................................................................................... 5-3 5.1 I DENTIFICATION OF 

### A VAILABLE 

### R ETROFIT 

### NO X 

### C ONTROL 

### T ECHNOLOGIES 

### ......... 5-3 5.2 E LIMINATE 

### T ECHNICALLY 

### I NFEASIBLE 

### NO X 

### C ONTROL 

### T ECHNOLOGIES 

### ............... 5-4 5.2.1 L OW -NO X B URNER IN THE R OTARY K ILN .........................................................5-4
5.2.2 F LUE G AS R ECIRCULATION ................................................................................5-6 5.2.3 C EMENT K ILN D UST I NSUFFLATION ...................................................................5-6 5.2.4 M ID -K ILN F IRING OF S OLID F UEL (T IRES ) WITH M IXING A IR F AN ....................5-7 5.2.5 S ELECTIVE N ONCATALYTIC R EDUCTION ............................................................5-8 5.2.6 S ELECTIVE C ATALYTIC R EDUCTION ...................................................................5-9 

### 5.3 R ANK OF 

### T ECHNICALLY FEASIBLE 

### NO X 

### C ONTROL 

### O PTIONS BY 

### E FFECTIVENESS 

### 5-12 5.4 E VALUATION OF 

### I MPACTS FOR 

### F EASIBLE 

### NO X 

### C ONTROLS 

### ................................. 5-13
5.4.1 SNCR AND LNB ...............................................................................................5-13 

### 5.5 E VALUATION OF 

### V ISIBILITY 

### I MPACT OF 

### F EASIBLE 

### NO X 

### C ONTROLS 

### ................... 5-14 5.6 P ROPOSED 

### B ART FOR 

### NO X 

### .................................................................................. 5-15

6. PM BART E VALUATION 

### ..................................................................................... 6-1Ash Grove Cement Company ii Trinity Consultants BART Analysis 

## L IST OF 

## T ABLES

T ABLE 1-1. V ISIBILITY I MPAIRMENT I MPROVEMENT AT G ATES OF THE M OUNTAINS W ILDERNESS A REA

............................................................................................................................... .......1-2

T ABLE 3-1. S UMMARY OF U.S. EPA R EGION 8 BART A PPLICABILITY M ODELING R ESULTS ...........3-6

T ABLE 3-2. S UMMARY OF M ODELING M ETHOD D IFFERENCES B ETWEEN EPA AND AGC ...............3-7

T ABLE 3-3. K ILN E MISSION R ATES IN BART D ATA S UBMITTAL VS

. 2006 A NALYZER D ATA ...........3-8

T ABLE 3-4. E XISTING MAXIMUM 24-H OUR SO 2 , NO X , AND PM 10 E MISSIONS (A S H OURLY E QUIVALENTS ) .......................................................................................................................3-8

T ABLE 3-5. S UMMARY OF E XISTING S TACK P ARAMETERS ................................................................3-9

T ABLE 3-6. E XISTING V ISIBILITY I MPAIRMENT A TTRIBUTABLE TO M ONTANA C ITY PLANT K ILN AND C LINKER C OOLER ...................................................................................................................3-9

T ABLE 4-1. E XISTING A CTUAL M AXIMUM 24-H OUR SO 2 E MISSION R ATES ......................................4-1

TABLE 4-2. A VAILABLE SO 2 C ONTROL T ECHNOLOGIES .....................................................................4-2

T ABLE 4-3. R ANKING OF T ECHNICALLY F EASIBLE K ILN SO 2 C ONTROL T ECHNOLOGIES BY E FFECTIVENESS ......................................................................................................................4-4

T ABLE 4-4. C OST A NALYSIS FOR W ET L IME S CRUBBING ..................................................................4-6

T ABLE 4-4. C OST A NALYSIS FOR W ET L IME S CRUBBING ( CONTINUED )............................................4-7

T ABLE 4-4. C OST A NALYSIS FOR W ET L IME S CRUBBING ( CONTINUED )............................................4-8

T ABLE 4-5. S UMMARY OF C OST E FFECTIVENESS FOR F UEL S UBSTITUTION ....................................4-11

T ABLE 4-6. S UMMARY OF E MISSION R ATES M ODELED I N SO 2 C ONTROL V ISIBILITY I MPACT A NALYSIS .............................................................................................................................4- 12

T ABLE 4-7. S UMMARY OF M ODELED I MPACTS FROM SO 2 C ONTROL V ISIBILITY I MPACT A NALYSIS 4-1

T ABLE 4-8. S UMMARY OF C OST E FFECTIVENESS OF SO 2 C ONTROL T ECHNOLOGIES ........................4-1

T ABLE 5-1. E XISTING A CTUAL M AXIMUM 24-H OUR NO X E MISSION R ATES .....................................5-3

T ABLE 5-2. P OSSIBLE NO X C ONTROL T ECHNOLOGIES ......................................................................5-4

T ABLE 5-3. R ANKING OF T ECHNICALLY F EASIBLE K ILN NO X C ONTROL T ECHNOLOGIES BY E FFECTIVENESS ....................................................................................................................5-13Ash Grove Cement Company iii Trinity Consultants BART Analysis T ABLE 5-4. S UMMARY OF E MISSION R ATES M ODELED I N NO X C ONTROL V ISIBILITY I MPACT A NALYSIS .............................................................................................................................5- 15

T ABLE 5-5. NO X C ONTROL V ISIBILITY I MPACT A NALYSIS ...............................................................5-15

T ABLE 6-1. E XISTING M AXIMUM 24-H OUR PM 10 E MISSION R ATE ....................................................6-1

T ABLE 6-2. VAP V ISIBILITY I MPAIRMENT C ONTRIBUTIONS A T G ATES OF THE M OUNTAINS ............6-1Ash Grove Cement Company 1-1 Trinity Consultants BART Analysis 

## 1. E XECUTIVE 

## S UMMARY

This report documents the determination of th e Best Available Retrofit Technology (BART) as proposed by Ash Grove Cement Company (AGC) for the Portland cement manufacturing plant located in Montana City, Montana (Montana City plant). There are two emission units at the Montana City plant for which AGC has made a BART determination: the kiln and the clinker cooler. Currently, particulate matter emissions from the kiln are controlled by an electrostatic precipitator. Particulate matter emissions from the clinker cooler are controlled by a baghouse. The Montana City plant has other lesser emitting BART-eligible emission s units, but the negligible visibility impairment attributable to these sources concludes that no a dditional controls are necessary to satisfy the requirements of the BART rule. 1

AGC used the U.S. Environmental Pr otection Agency’s (EPA’s) guidelines 2 in 40 CFR Part 51 to determine BART for the kiln and clinker cooler. Specifically, AGC conducted a five-step analysis to determine BART for SO 2 , NO X , and PM 10 that included the following:

1. Identifying all available retrofit control technologies;

2. Eliminating technically infeasible control technologies;

3. Evaluating the control effectiveness of remaining control technologies;

4. Evaluating impacts and document the results;

5. Evaluating visibility impacts

Based on the five-step analysis, AGC proposes the following as BART:

Kiln:

• PM 10 – AGC proposes that the existing electrosta tic precipitator constitutes BART. This control device is the most effective for controlling PM 10 from a wet kiln.

• NO X – AGC proposes to comply with a BART emission limit of 227.25 lb/hr on a 30-day rolling basis by installing and operating a dir ect-fired low-NOx burner (LNB) and a selective noncatalytic reduction (SNCR) system. Compliance with the emission limit will be demonstrated by continuous emissions monitoring.

• SO 2 – AGC proposes that no additional SO 2 controls are required for BART compliance. Additional SO 2 controls would provide little visibilit y improvement and require significant expenditures.

Clinker Cooler:

1 AGC submitted an inventory of all of the BART-eligib le emission sources to the Montana Department of Environmental Quality. EPA Region 8 subsequently evaluated th e kiln and clinker cooler to determine the applicability of BART to the Montana City plant. Trinity Consultants condu cted two BART applicability vi sibility modeling analyses for the Montana City plant. One modeling anal ysis included all of the BART-eligible s ources at the plant. The other modeling analysis included the kiln and clinker cooler only. The diffe rence in the modeled visibility impact predicted for the two scenarios was negligible; thus, it was conc luded that the contribution of the non-kiln and clinker cooler sources to visibility impairment is negligible, and controlling these sources would not improve any existing visibility impairment. 2 40 CFR 51, Regional Haze Regulations and Guidelines for Best Available Retrofit Technology (BART) DeterminationsAsh Grove Cement Company 1-2 Trinity Consultants BART Analysis • PM 10 – AGC proposes that the existing baghouse constitutes BART. This control device is the most effective for controlling PM 10 from a clinker cooler.

The proposed BART control strategies will result in re ductions of the visibility impacts attributable to the Montana City plant. A summary of the visi bility improvement at the Gates of the Mountains Class I area based on the existing emission rates and proposed BART emission rates is provided in Table 1-1.

T ABLE 1-1. V ISIBILITY I MPAIRMENT I MPROVEMENT AT G ATES OF THE M OUNTAINS W ILDERNESS A REA

98% Impact ( Δ dv) Existing 2.874
BART 1.377 Improvement 52.09%Ash Grove Cement Company 2-3 Trinity Consultants BART Analysis 

## 2. I NTRODUCTION AND 

## B ACKGROUND

On July 1, 1999, the U.S. EPA published the fina l Regional Haze Rule (RHR). The objective of the RHR is to improve visibility in 156 specific area s across with United States, known as Class I areas. The Clean Air Act defines Class I areas as certain na tional parks (over 6000 acres), wilderness areas (over 5000 acres), national memorial parks (over 5000 acres), and international parks that were in existence on August 7, 1977.

On July 6, 2005, the EPA published amendments to its 1999 RHR, often called the Best Available Retrofit Technology (BART) rule, which included guidance for making source-specific BART determinations. The BART rule defines BART-e ligible sources as sources that meet the following criteria:

(1) Have potential emissions of at least 250 tons per year of a visibility-impairing pollutant, (2) Began operation between August 7, 1962 and August 7, 1977, and (3) Are included as one of the 26 listed source categories in the guidance.

A BART-eligible source is subject to BART if th e source is “reasonably anticipated to cause or contribute to visibility impairment in any federal mandatory Class I area.” EPA has determined that a source is reasonably anticipated to contribute to visibility impairment if the 98 th percentile visibility impacts from the source are greater than 0.5 delta deciviews ( ∆ dv) when compared against a natural background. Air quality modeling is the tool that is used to determine a source’s visibility impacts.

Once it is determined that a source is subject to BART, a BART determination must address air pollution control measures for the source. The vi sibility regulations define BART as follows:

“...an emission limitation based on the deg ree of reduction achievable through the application of the best system of continu ous emission reduction for each pollutant which is emitted by...[a BART-eligible sou rce]. The emission limitation must be established on a case-by-case basis, taking in to consideration the technology available, the cost of compliance, the energy and n on air 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 reasonable be anticipated to result from the use of such technology.

Specifically, the BART rule states that a BART determination should address the following five statutory factors:

1. Existing controls
2. Cost of controls
3. Energy and non-air quality environmental impacts
4. Remaining useful life of the source
5. Degree of visibility improvement as a result of controls

Further, the BART rule indicates that the five b asic steps in a BART analysis can be summarized as follows:

1. Identify all available retrofit control technologies;Ash Grove Cement Company 2-4 Trinity Consultants BART Analysis 2. Eliminate technically infeasible control technologies;

3. Evaluate the control effectiveness of remaining control technologies;

4. Evaluate impacts and document the results;

5. Evaluate visibility impacts

A BART determination should be made for each visi bility affecting pollutant (VAP) by following the five steps listed above for each VAP.

BART applicability was determined for the Mont ana City plant based on a combination of an applicability analysis performed by U.S. EPA Regi on 8 and a refined applicability analysis performed by AGC. Both analyses determined that the kiln and clinker cooler are subject to BART. The details of the applicability determination can be found in Section 3.

Subsequently, AGC performed an analysis to dete rmine BART for each VAP for the kiln and clinker cooler. The VAPs emitted by the kiln and clinker cooler include NO
x , SO 2 , and particulate matter with a mass mean diameter smaller than ten microns (PM 10 ) of various forms (filterable coarse particulate matter [PM c ], filterable fine particle matter [PM f ], elemental carbon [EC], inorganic condensable particulate matter [IOR CPM] as sulfates [SO 4 ], and organic condensable particulate matter [OR CPM] also referred to as secondary orga nic aerosols [SOA]). The BART determinations for SO 2 , NO X , and PM 10 can be found in Sections 4, 5, and 6, respectively.Ash Grove Cement Company 3-5 Trinity Consultants BART Analysis 

## 3. BART A PPLICABILITY 

## D ETERMINATION

As stated in Section 2, a BART-eligible source is subject-to-BART if the source is “reasonably anticipated to cause or contribute to visibility im pairment in any federal mandatory Class I area.” EPA has determined that a source is reasonably antic ipated to contribute to visibility impairment if the 98 th percentile of the visibility impacts from the source is greater than 0.5 ∆ dv when compared against a natural background. U.S. EPA Region 8 (EPA) conducted air quality modeling to predict the existing visibility impairment attributable to th e Montana City plant in the following Class I areas:

• Gates of the Mountains Wilderness Area

• Scapegoat Wilderness Area

• Anaconda – Pintler Wilderness Area

• Bob Marshall Wilderness Area

• Mission Mountains Wilderness Area

• Selway – Bitterroot Wilderness

• Yellowstone National Park

• Red Rock Lakes Wilderness Area

• Glacier National Park

• North Absaroka Wilderness Area

• Washakie Wilderness Area

• Teton Wilderness Area

Based on this modeling, EPA concluded that the Mo ntana City plant was subject to BART since the 98 th percentile of the visibility impacts attributable to the kiln and clinker cooler are greater than 0.5 Δ dv when compared against a natural background for one Class I area: Gates of the Mountains Wilderness Area. The results of the applicability modeling are summarized in Table 3-1.Ash Grove Cement Company 3-6 Trinity Consultants BART Analysis T ABLE 3-1. S UMMARY OF U.S. EPA R EGION 8 BART A PPLICABILITY M ODELING R ESULTS

Minimum Distance 98th Percentile Visibility Impact for Each Year ( ∆ dv) Overall 98 th
Percentile Visibility

Impact
Class I Area (km) 2001 2002 2003 ( ∆ dv)

Gates of the Mountains 30 2.17 1.82 2.52 2.17 Scapegoat 80 0.36 0.42 0.26 0.34
Anaconda - Pintler 113 0.09 0.09 0.07 0.08
Bob Marshall 116 0.39 0.30 0.18 0.30
Mission Mountains WA 162 0.05 0.06 0.04 0.05 Selway-Bitterroot Wilderness 173 0.01 0.01 0.01 0.01
Yellowstone NP 175 0.00 0.01 0.01 0.01
Red Rock Lakes 207 0.00 0.00 0.00 0.00
Glacier NP 223 0.10 0.04 0.04 0.05
North Absaroka Wilderness 228 0.00 0.00 0.00 0.00
Washakie Wilderness 276 0.00 0.00 0.00 0.00
Teton Wilderness 289 0.00 0.00 0.00 0.00

AGC verified EPA’s results by performing a refined modeling analysis for the Class I area located closest to the Montana City plant: Gates of the Mountains Wilderness Area. The modeling methods used by AGC and EPA Region 8 differed slightly and are summarized in Table 3-2.Ash Grove Cement Company 3-7 Trinity Consultants BART Analysis T ABLE 3-2. S UMMARY OF M ODELING M ETHOD D IFFERENCES B ETWEEN EPA AND AGC

Processor/Model Parameter Ash Grove (AGC) Mode ling Analysis EPA Region 8 (EPA) Modeling Analysis
CALMET Surface Stations AGC included all the 36 surface stations listed in the MDEQ Draft Protocol ("protocol”) in the CALMET processing. EPA included all the 36 surface stations listed in the MDEQ Draft Protocol as well as 3 additional surface stations in the CALMET processing.
CALMET Precipitation Stations AGC included 146 precipitation stations in the CALMET processing. EPA did not include precipitation stations in the CALMET processing.
CALMET Surface Station for Surface Temperature AGC used the Helena Regional Airport surface station for the surface temperature, as this is the surface station nearest the Montana City plant (7.6 km). EPA used the Billings Logan Airport surface station for surface temperature. This station is 272.4 km from the Montana City plant.
CALPUFF Puff Splitting AGC included puff splitting, per the protocol. EPA did not include puff splitting.

CALPUFF Coordinate System AGC used Lambert Conformal Coordinates. The following are the reference coordinates: Reference Latitude: 43.1861N Reference Longitude: -116.2657 W Latitude 1: 43 N Latitude 2: 49 N EPA used Lambert Conformal Coordinates. The following are the reference coordinates: Reference Latitude: 44.29 N Reference Longitude: -109.5 W Latitude 1: 45 N Latitude 2: 49 N False Easting: 600 meters

CALPUFF Grid Size AGC used a grid size of 2 km. This smaller grid size was selected due to the distance of the closest Class I area to the Montana City plant (Gates of the Mountains, 30 km). EPA used a grid size of 6 km.

CALPUFF Background Ozone AGC used default background ozone concentrations of 30 parts per billion (ppb) for October through May and 50 ppb for June through September. EPA used a default background ozone concentration of 80 ppb for the entire
year.

CALPOST Monthly Relative Humidity Adjustment Factor AGC used the monthly relative humidity adjustment factors based on the representative IMPROVE site location for the Class I area, as shown in the MDEQ protocol. EPA used the monthly relative humidity adjustment factors based on the centroid of the Class 1 Area.

In addition to different modeling methods, AGC also modeled slightly different NO X and SO 2 emission rates for the kiln. EPA modeled the Mont ana City plant based on emissions data that AGC had submitted to MDEQ (and, subsequently, EPA) fo r the BART applicability analysis. The kiln NO X and SO 2 emissions data provided in that submittal w as from stack testing performed in April of 2006. In May of 2006, a SO 2 /NO X analyzer was installed on the kiln exhaust and AGC has collected additional data on SO 2 and NO X emissions from the kiln. The data from May 2006 through the end of 2006 show that the maximum actual SO 2 and NO
x emission rates from the kiln are higher than the SO 2 and NO
x emission rate originally submitted to MDEQ . The emissions data are summarized in Table 3-3.Ash Grove Cement Company 3-8 Trinity Consultants BART Analysis T ABLE 3-3. K ILN E MISSION R ATES IN BART D ATA S UBMITTAL VS

. 2006 A NALYZER D ATA

Pollutant BART Data
Submittal to

MDEQ (lb/hr) Comment 2006 Analyzer
Data (lb/hr) Comment

SO 2 285.83 Stack Test Data, April 2006 473.87 2006 Maximum Actual 24-
Hour SO 2 Emission Rate From Analyzer Data (Hourly Equivalent)
NO X 439.17 Stack Test Data, April 2006 848.74 2006 Maximum Actual 24-
Hour NO X Emission Rate From Analyzer Data (Hourly Equivalent)

PM 10 37.17 Stack Test Data, April 2006 37.17 Stack Test Data, April 2006

AGC updated the emission rates used in the refi ned BART applicability modeling to the emission rates based on the analyzer data. Table 3-4 summarizes the emission rates that EPA and AGC modeled for SO 2 , NO X , and PM 10 , including the speciated PM 10 emissions. The total PM 10 emission rates include both the filterable and condensable fractions and are speciated into the following:

▲ Coarse particulate matter (PM C )
▲ Fine particulate matter (PM f )
▲ Sulfates (SO 4 )
▲ Secondary organic aerosols (SOA)
▲ Elemental carbon (EC)

T ABLE 3-4. E XISTING MAXIMUM 24-H OUR SO 2 , NO X , AND PM 10 E MISSIONS (A S H OURLY E QUIVALENTS )

Model Source SO 2 NO X Total PM 10 SO 4 PM c PM f SOA EC

(lb/hr) (lb/hr) (lb/hr) (lb/hr) (lb/hr) (lb/hr) (lb/hr) (lb/hr) EPA Region 8 Kiln 285.83 439.17 37.17 6.80 7.28 21.35 0.93 0.82 Applicability Clinker Cooler 0.00 0.00 6.00 0.00 0.00 5.94 0.00 0.06 AGC Refined Kiln 473.87 848.74 37.17 6.80 7.28 21.35 0.93 0.82 Applicability Clinker Cooler 0.00 0.00 6.00 0.00 0.00 5.94 0.00 0.06

Table 3-5 summarizes the stack parameters that were used to model the kiln and clinker cooler.Ash Grove Cement Company 3-9 Trinity Consultants BART Analysis T ABLE 3-5. S UMMARY OF E XISTING S TACK P ARAMETERS

Kiln Clinker Cooler Latitude (degrees) 46.544 46.539 Longitude (degrees) -111.921 -111.922 Stack height (ft) 100 50 Stack Diameter (ft) 9 4 Exhaust Velocity (ft/s) 47 54 Exhaust Temperature (K) 384 132

The results of AGC’s refined modeling verified EPA’s BART determination; the results are summarized in Table 3-6. The 98 th percentile of the visibility impacts attributable to the kiln and clinker cooler are greater than 0.5 Δ dv when compared against a natural background for the Gates of the Mountains Wilderness Area.

T ABLE 3-6. E XISTING V ISIBILITY I MPAIRMENT A TTRIBUTABLE TO M ONTANA C ITY PLANT K ILN
AND C LINKER C OOLER

Class I Area

Minimum Distance 98th Percentile Visibility Impact for Each Year ( ∆ dv) Overall 98 th
Percentile Visibility

Impact (km) 2001 2002 2003 (dv)
Gates of the Mountains 30 2.736 2.874 3.038 2.874Ash Grove Cement Company 4-1 Trinity Consultants BART Analysis 

## 4. SO 2 

## BART E VALUATION

Sulfur, in the form of metallic sulfides (pyrite), sulfate, or organosulfur compounds, is often found in the raw materials used to manufacture cement and in the solid and liquid fuels burned in cement
kilns. 3 The raw materials and fuels for the Montana C ity plant are no exception. Sulfur dioxide can be generated by the oxidation of sulfur compounds in the raw materials and fuels during operation of the pyroprocess. Constituents found in fuels, ra w materials, and in-process materials, such as the alkali metals (sodium and potassium), calcium car bonate, and calcium oxide often react with SO 2 within the pyroprocess to limit emissions of SO 2 as much of the sulfur leaves the process in the principle product of the kiln system called clinker.

The kiln is the only BART source which emits SO 2 , thus an SO 2 BART evaluation was performed only for the kiln. The maximum actual 24-hour kiln SO 2 emission rate that was modeled for the BART applicability determination is summarized in Table 4-1. The SO 2 24-hour maximum actual emission rate was determined from analyzer data for 2006.

T ABLE 4-1. E XISTING A CTUAL M AXIMUM 24-H OUR SO 2 E MISSION R ATES

SO 2 24-Hour Emission Rate SO 2 Hourly Equivalent Emission Rate (ton/24-hr) (lb/hr)
Kiln 5.69 473.87



## 4.1 I DENTIFICATION OF 

## A VAILABLE 

## R ETROFIT 

## SO 2 

## C ONTROL 

## T ECHNOLOGIES

Step 1 of the BART determination is the identification of all available retrofit SO 2 control technologies. A list of control technologies was obtained by reviewing the U.S. EPA’s Clean Air Technology Center, publicly-availabl e air permits, applications, and technical literature published by the U.S. EPA, state agencies, and Regional Planning Organizations (RPOs).

The available retrofit SO 2 control technologies are summarized in Table 4-2.

3 Miller, F. MacGregor and Hawkins, Garth J., ”Formation and Emission of Sulfur Dioxi de from the Portland Cement Industry”, Proceedings of the Air and Wa ste Management Association , June 18-22, 2000.Ash Grove Cement Company 4-2 Trinity Consultants BART Analysis TABLE 4-2. A VAILABLE SO 2 C ONTROL T ECHNOLOGIES

SO 2 Control Technologies

Fuel Substitution Raw Material Substitution Lime Spray Dryer Wet Lime Scrubbing



## 4.2 E LIMINATE 

## T ECHNICALLY 

## I NFEASIBLE 

## SO 2 

## C ONTROL 

## T ECHNOLOGIES

Step 2 of the BART determination is to eliminate technically infeasible SO 2 control technologies that were identified in Step 1.



### 4.2.1 F UEL 

### S UBSTITUTION
AGC uses a mixture of coal and petroleum coke as the primary fuels for the kiln; natural gas is combusted during startup. The 2006 fuel usage breakdown, on an energy input basis, was 58 percent petroleum coke, 41 per cent coal, and 1 percent natural gas. The sulfur content of the petroleum coke is approxi mately 4.5 percent and the sulfur content of the coal is approximately 0.8 percent.

The design of the long wet kiln syst em is such that much of the SO 2 resulting from fuel combustion is emitted. Therefore, if AGC reduces sulfur in fuel input to the kiln, a corresponding reduction in SO 2 emissions from the kiln would be expected. Fuel sulfur content could be reduced by burning a different blend of coal and coke which results in a lower overall sulfur content. Therefore, AGC anticipates that lowering the input of sulfur through fuel substitution would be an effective and technically feasible SO 2 control technology for the kiln.



### 4.2.2 R AW 

### M ATERIAL 

### S UBSTITUTION
Sulfide sulfur in the raw materials, usually in the form of iron pyrite, is thermally decomposed and oxidized or “roasted” to form SO 2 . The pyritic sulfur reacts with oxygen according to the following reaction:

4FeS 2 + 11O 2 Æ 2Fe 2 O 3 + 8SO 2

Using raw materials with lower pyritic su lfur content can reduce the potential for SO 2 emissions from a wet kiln system. While pyrites are present in the limestone and other raw materials used at the Montana City plant, th e concentrations of sulfide sulfur in these materials are already very low. With rare ex ceptions, cement plants are built at or near a source of limestone, the primary raw material fo r cement manufacture. To do otherwise is an economic penalty that would cause most plants, including Montana City plant, to be economically infeasible. During the production of cement clinker, the limestone loses about one-third of its weight as CO 2 . The shipping costs for the “lost” weight in the limestone often can be economically prohibitive.Ash Grove Cement Company 4-3 Trinity Consultants BART Analysis Since material substitution would resu lt in a negligible reduction in SO 2 for the kiln, raw material substitution is not considered an SO 2 control technology for the kiln and is
removed from further consideration as BART.



### 4.2.3 L IME 

### S PRAY 

### D RYING
Lime spray drying (LSD) consists of injecting an aqueous Ca(OH) 2 suspension in fine droplets into the flue gas. The Ca(OH) 2 reacts with SO 2 in the flue gas stream to create fine particles of CaSO 3 or CaSO 4 . The moisture evaporates from the particles, and the particles are collected in the particulate matter control device (PMCD) serving the kiln. For optimum effectiveness, the reaction of Ca(OH) 2 with SO 2 must have adequate gas retention time and must be followed by a PM CD for capturing the sulfates created by the reaction.

Unlike a preheater/precalciner kiln system that provides by its design a natural location for a spray dryer type control system to be utili zed between the top of the preheater tower and the PMCD, a wet kiln does not have that attri bute. In other words, the back-end of a wet kiln has a relatively short retention time between that and it’s associated PMCD. Additionally, the PMCD in place was not desi gned for the additional loading or for the increased water vapor that would need to be moved through the system to accommodate adequate lime spray drying control. It is also expected that with the added moisture generated from the wet process slurry that rat es of evaporation for spray drying to occur could be retarded as compared to other combus tion systems that might employ this type of system.

Lastly, the added gas cooling that would resu lt from the injection of slurry prior to the PMCD would have the potentia l for undesirable acid dewpoint conditions to occur in the PMCD that could reduce its effectiveness. For these reasons and as there are no known applications of lime spray dryers on wet ce ment kilns, this technology considered is technically infeasible and is removed from further consideration as BART.



### 4.2.4 W ET 

### L IME 

### S CRUBBING

Wet lime scrubbing (WLS) is a name for a traditional tailpipe wet scrubber. This process involves passing the flue gas from the main PMCD through a sprayed aqueous suspension of Ca(OH) 2 or CaCO 3 (limestone) that is contained in an appropriate scrubbing device. In the case of the Montana City plant, the basic underlying economics would dictate the use of ground limestone as the scrubbing reagent. In WLS, the aqueous suspension of scrubbing reagent is not taken to dryness as it is in LSD. The SO 2 reacts with the scrubbing reagent to form CaSO 3 that is collected and retained as aqueous sludge. Typically, the sludge is dewatered and disposed in an on-site landfill. In some cases involving cement plants, the CaSO 3 sludge could be oxidized to CaSO 4 and used in the finish mills as a substitute for purchased gyps um for regulation of the setting time of the cement product.Ash Grove Cement Company 4-4 Trinity Consultants BART Analysis Typically, WLS is considered to have a scrubbing efficiency of up to 90 percent of the SO 2 in the flue gas treated by the scrubber. 4 WLS is a high maintenance process with high rates of downtime expected as the scrubber ma tures and corrosion of components becomes a serious problem. Conceivably, a pair of we t scrubbers ultimately would be required so that one is in operation while the other is repaired.

Despite these identified drawbacks, WLS is considered a technically feasible BART option.



## 4.3 R ANK OF 

## T ECHNICALLY 

## F EASIBLE 

## SO 2 

## C ONTROL 

## O PTIONS BY 

## E FFECTIVENESS

The third step in the BART analysis is to rank the technically feasible options according to effectiveness. Table 4-3 presents potential SO 2 technically feasible control technologies for the kiln
and the associated SO 2 emission levels.

T ABLE 4-3. R ANKING OF T ECHNICALLY F EASIBLE K ILN SO 2 C ONTROL T ECHNOLOGIES BY E FFECTIVENESS

Pollutant Control Technology Effectiveness SO 2 Emissions Level (lb/hr)

SO 2 Wet Lime Scrubbing 25.35 lb/hr as a 30-day rolling average † Fuel Switching 126.76 lb/hr as a 30-day rolling average * † Based on a 90% removal efficiency from the 2006 average 24- hour emission rate hourly equivalent (253.52 lb/hr). The 90 percent reduction was applied to the 2006 average 24-hour SO 2 emission rate rather than the maximum 24-hour SO 2 emission rate to best reflect the performan ce of the control on a 30 day rolling basis.

* Based on a fuel switching scenario that reduces sulfur em issions by 50% from the 2006 average 24-hour emission rate hourly equivalent (253.52 lb/hr). The 90 percent reduction was applied to the 2006 average 24-hour SO 2 emission rate
rather than the maximum 24-hour SO 2 emission rate to best reflect the perfo rmance of the control on a 30 day rolling
basis.



## 4.4 E VALUATION OF 

## I MPACTS FOR 

## F EASIBLE 

## SO 2 

## C ONTROLS

Step four for the BART analysis procedure is the impact analysis. The BART determination guidelines list the four factors to be considered in the impact analysis:

• Cost of compliance

• Energy impacts

• Non-air quality impacts; and

• The remaining useful life of the source

4 EPA Air Pollution Control Technology Fact Sheet – Flue Gas Desulfurization (FGD) Wet, Spray Dry, and Dry Scrubbers. A control efficiency of up to 95% is listed. Ho wever, at an uptime of 95%, the actual annual control efficiency would be 90.2%Ash Grove Cement Company 4-5 Trinity Consultants BART Analysis AGC has conducted an impact analysis for the two control options with the highest SO 2 control efficiencies: WLS and fuel switching.



### 4.4.1 W ET 

### L IME 

### S CRUBBING

Cost of Compliance AGC obtained a site-specific WLS proposal from a vendor and performed an economic analysis to determine the annualized cost for WLS. AGC divided the annualized cost of WLS by the annual tons of SO 2 reduced to determine the cost effectiveness for WLS. The “annual tons reduced” were determined by subtracting the estimated controlled annual emissions from the existing annual emissions. The existing annual emissions are based on the average 24-hour SO 2 emission rate (hourly equivalent) in 2006, as recorded by the gas analyzer, multiplied by the 2006 operating hours. The estimated controlled annual emissions were calculated by applying the 90 percent control efficiency to the existing annual emissions. Table 4-4 provides the cost e ffectiveness analysis related to WLS. Note that the cost effectiveness analysis does not include the cost to construct a new exhaust stack, which would be needed to employ the WLS technology.Ash Grove Cement Company 4-6 Trinity Consultants BART Analysis T ABLE 4-4. C OST A NALYSIS FOR W ET L IME S CRUBBING



### Direct Costs Purchased Equipment Costs Wet Scrubber Unit $5,687,500 Instrumentation (10% of EC) $568,750 Sales Tax (3% of EC) $170,625 Freight (5% of EC) $284,375 Subtotal, Purchased Equipment Cost (PEC) $6,711,250

Direct Installation Costs Foundation (6% of PEC) $402,675 Supports (6% of PEC) $402,675 Handling and Erection (40% of PEC) $2,684,500 Electrical (1% of PEC) $67,113 Piping (30% of PEC) $2,013,375 Insulation for Ductwork (1% of PEC) $67,113 Painting (1% of PEC) $67,113 Subtotal, Direct Installation Cost $5,704,563

Site Preparation N/A Buildings N/A

Total Direct Cost $12,415,813



### Indirect Costs Engineering (10% of PEC) $671,125 Construction and Field Expense (10% of PEC) $671,125 Contractor Fees (10% of PEC) $671,125 Start-up (1% of PEC) $67,113 Performance Test (1% of PEC) $67,113 Contingencies (3% of PEC) $201,338 Total Indirect Cost $2,348,938

Total Capital Investment (TCI) $14,764,750Ash Grove Cement Company 4-7 Trinity Consultants BART Analysis T ABLE 4-4. C OST A NALYSIS FOR W ET L IME S CRUBBING ( CONTINUED )



### Direct Annual Costs Hours per Year (365 days per year, 24 hours per day) 8,760

Operating Labor Operator (0.5 hr/shift, 3 shifts/day, 365 d/yr, $16/hr) $8,760 Supervisor (15% of operator) $1,314 Subtotal, Operating Labor $10,074

Maintenance Labor (0.5 hr/shift, 3 shifts/day, 365 d/yr, $16/hr) $8,760 Material (100% of maintenance labor) $8,760 Subtotal, Maintenance $17,520

Utilities Electricity Pump (kW) 380.48 Cost ($/kW-hr) $0.0537 Subtotal, Electricity $179,082

Limestone Slurry Amount Required (ton/yr) 2,847 Cost ($/ton) $15.00 Subtotal, Lime $42,705

Water Amount Required (gpm) 31.0 Cost ($/1000 gallons) $3.075 Subtotal, Water $50,101

Sludge Disposal Amount Generated (tpy) 5,913 Disposal Fee ($/ton) $23.00 Subtotal, Sludge $135,999

Subtotal, Utilities $407,887

Total Direct Annual Costs $435,481Ash Grove Cement Company 4-8 Trinity Consultants BART Analysis T ABLE 4-4. C OST A NALYSIS FOR W ET L IME S CRUBBING ( CONTINUED )



### Indirect Annual Costs Overhead (60% of sum of operating, supervisor, maintenance labor & materials) $153,839 Administrative (2% TCI) $295,295 Property Tax (1% TCI) $147,648 Insurance (1% TCI) $147,648 Capital Recovery (10 year life, 7 percent interest) $2,102,168 Total Indirect Annual Cost $2,846,597



### Conclusion

Total Annualized Cost $3,282,078

Pollutant Emission Rate Prior to Scrubber (tons SO 2 /yr) 981 Pollutant Removed (tons SO 2 /yr) 883 Cost Per Ton of Pollutant Removed $3,716

Energy Impacts A wet scrubber requires an additional fan of c onsiderable horsepower to move the flue gas through the scrubber.

Non Air-Quality Impacts WLS may lead to an increase in PM emissi ons because some particles of limestone or CaSO 3 will be entrained in the flue gas and s ubsequently be emitted from the scrubber.
WLS is also known to increase emissions of sulfuric acid mist. 5 A frequent steam plume can be expected at the discharge of the wet scrubber that would result in visual impairment in the area.

Utilization of a wet scrubber would require the use of a significant amount of water. An appropriately sized wet scrubber would cons ume approximately 16 million gallons of water per year. Most of this water would be emitted as vapor with a small portion in the sludge that would be generated by the control device.

In addition to the consumption of a large am ount of water, the WLS technology would also generate a large amount of sludge. Dispo sal or treatment of WLS sludge presents additional environmental impacts.

Remaining Useful Life

5 Innovations in Portland Cement Manufacturing, Portland Cement Association, 2004, pg. 660 & 669Ash Grove Cement Company 4-9 Trinity Consultants BART Analysis The remaining useful life of the kiln does not impact the annualized cost of WLS because the useful life is anticipated to be at least as long as the capital cost recovery period, which is 10 years.



### 4.4.2 F UEL 

### S UBSTITUTION

Cost of Compliance The cost of fuel substitution was determined by calculating the cost of the current coal/coke fuel blend and determining the increased cost of switching to combusting a fuel blend that would reduce fuel sulfur content by 50 percent from the 2006 levels. The proposed solution discussed in this evaluation would equate to reduc ing coke usage from the proportions used in 2006. At this time, AGC has not fully evaluated the potential fuel blends that could be used to reduce fuel sulfur content.

The current coal/coke fuel blend costs are b ased on 2006 fuel usage and cost data for the Montana City plant. The fuel switching costs are based on a switch to an 18.5% coke and 81.5% coal blend, where the specific coal a nd coke assumed for the blend are the coal and coke that are currently burned at the plant. This fuel blend results in an approximate 50% reduction in fuel sulfur content from the fuel blend used in 2006. Again, AGC has not fully evaluated all potential fuel blends that would result in a 50% reduction in fuel sulfur content; this fuel blend was used only for costing purposes. In practice, AGC may utilize higher quality coal or lower sulfur coke to meet the energy requirements of the kiln. It was assumed in this analysis that fuel switchi ng will not require any capital expenses.

The total annual cost of fuel switching was divided by the annual tons of SO 2 reduced to determine the cost effectiveness for fuel switching. The “annual tons reduced” were determined by subtracting the estimated c ontrolled annual emissions from the existing annual emissions. The existing annual emissions are based on the average 24-hour SO 2 emission rate (hourly equivalent) in 2006, as recorded by the gas analyzer, multiplied by the 2006 operating hours. The estimated cont rolled annual emission rates were calculated by reducing the existing annual emission rate by 50%. The sulfur content of the existing coal/coke fuel blend is 2.09 percent; this is calculated based on the sulfur contents of the fuels (3 percent for coke and 0.8 percent fo r coal) and the 2006 fuel usage (by MMBtu). The calculation for the sulfur content of the coal/coke fuel blend is as follows:

905,045 Coke MMBtu 4.5% Sulfur + 643,376 Coal MMBtu 0.8 % Sulfur = 2 96 % Sulfur 1,548,421 Total MMBtu 1,548,421 Total MMBtu

The sulfur content of the fuel switching scenar io is calculated based on a 11% coke and 89% coal blend. The calculation of the sulfur content of the fuel blend and the reduced emissions are shown below:

286,458 Coke MMBtu 4.5% Sulfur + 1,261,963 Coal MMBtu 0.8 % Sulfur = 1.48 % Sulfur 1,548,421 Total MMBtu 1,548,421 Total MMBtuAsh Grove Cement Company 4-10 Trinity Consultants BART Analysis 2.96 % Sulfur - 1.48% Sulfur = 50 % 2.96 % Sulfur

253.52 lb 7,741 hr ton 50 % = 491 ton SO2 Reduced hr yr 2,000 lb yr

The cost of fuel switching is summarized in Table 4-5.Ash Grove Cement Company 4-11 Trinity ConsultantsBART AnalysisTABLE4-5.SUMMARY OFCOSTEFFECTIVENESS FORFUELSUBSTITUTIONExistingAnnualEmissionsControlledAnnualEmissionsReducedAnnualEmissionsExistingAnnualEnergy(Coal/Coke)UsageExistingCoal/CokeCost*AverageHeating ValueAnnual FuelUsageCostAnnualFuel CostCost ofSwitchingFuelsCostEffectiveness(tons/yr) (tons/yr) (tons/yr) (MMBtu/yr) ($/yr) Btu/lb Tons/yr $/ton ($/yr) ($/yr) ($/ton)981 492 490 1,548,421$1,860,96714,582 (Coke) 9,822 (Coke) 16.38 (Coke) 2,814,066 953,099 1,946.818,426 (Coal) 74,885 (Coal) 35.43 (Coal)*The existing coal/coke cost is based on 2006 actual usage data(31,033 tons coke * $16.38/ton + 38,178 tons Coal * 35.43/ton =$1,860,967).Ash Grove Cement Company 4-12 Trinity Consultants BART Analysis Energy Impacts and Non Air-Quality Impacts There are no energy or non-air quality im pacts associated with fuel switching.

Remaining Useful Life The remaining useful life of the kiln does not impact the annualized costs for fuel switching, since, for this analysis, it is assu med that fuel switching will not require any capital costs.



## 4.5 E VALUATION OF 

## V ISIBILITY 

## I MPACT OF 

## F EASIBLE 

## SO 2 

## C ONTROLS

A final impact analysis was conducted to assess the visibility improvement for existing emission rates when compared to the emission rates of WLS and fuel switching. The existing emission rates and emission rates associated with WLS and fuel switc hing were modeled using CALPUFF. The existing emission rates are the same rates that were mode led for the BART applicability analysis. The SO 2 emissions rates associated with WLS and fuel sw itching are the proposed BART emission limits in lb/hr based on reductions from the 2006 average 24-hour emission rate (as an hourly equivalent).

The SO 2 emission reductions from the WLS and fuel sw itching control options were applied to the 2006 average 24-hour SO 2 emission rate rather than the maximum 24-hour SO 2 emission rate because the BART limit is proposed as a 30-day rolling averag e. Had the reductions been applied to the maximum 24-hour SO 2 emission rates, the controlled emission rates would be much higher than what AGC anticipates could be achieved by the WLS and fuel switching control options on a 30-day rolling basis. The emission rates are summarized in Table 4-6.

T ABLE 4-6. S UMMARY OF E MISSION R ATES M ODELED I N SO 2 C ONTROL V ISIBILITY I MPACT A NALYSIS

Emission Rate Scenario Emission Rate
SO 2 NO X PM 10 (lb/hr) (l b/hr) (lb/hr)
WLS 25.35 848.74 37.17
Fuel Substitution 126.76 848.74 37.17

Comparisons of the existing visibility impacts a nd the visibility impacts based on WLS and fuel switching for the Gates of the Mountains Wilderness Area are provided in Table 4-7. The visibility improvement associated with WLS and fuel switching are also shown in Table 4-7; this value was calculated as the difference between the existing vi sibility impairment and the visibility impairment for the controlled emission rates as measured by the 98 th percentile modeled visibility impact.Ash Grove Cement Company 4-1 Trinity Consultants BART Analysis T ABLE 4-7. S UMMARY OF M ODELED I MPACTS FROM SO 2 C ONTROL V ISIBILITY I MPACT A NALYSIS

98% Impact ( Δ dv) Improvement Existing 2.87 -- Fuel Switching 2.70 6.05%
WLS 2.63 8.39%

As shown in Table 4-7, the installation of a WLS on the kiln results in an 8.39 percent improvement to the existing visibility impairment. Fuel switc hing results in a 6.05 percent improvement to the existing visibility impairment. Therefore, utilizati on of WLS as compared to fuel switching results in only a 2% incremental improvement (0.07 Δ dv). The minimal visibility improvement was expected due to the low contribution of sulfates to the existin g visibility impairment when compared to nitrates.



## 4.6 P ROPOSED 

## B ART FOR 

## SO 2

In order to determine BART for SO 2 , AGC evaluated each control option’s cost of compliance, energy impacts, and non-air quality impacts, as well as the remaining useful life of the kiln. Table 4- 8 summarizes the cost effectiveness for each control option based on the tons of SO 2 reduced and the visibility improvement in deciviews. The cost effectiveness for the fuel switching is $1,947 per ton of SO 2 reduced and $5.5 million per deciview of vi sibility improvement. This corresponds to a nominal visibility improvement from 2.87 Δ dv to 2.70 Δ dv . The cost effectiveness for the WLS is $3,716 per ton of SO 2 reduced and $13.6 million per deciview of visibility improvement. This corresponds to a nominal visibility improvement from 2.87 Δ dv to 2.63 Δ dv . The incremental cost of utilizing WLS as opposed to fuel switching is $33,271,129 per deciview.

T ABLE 4-8. S UMMARY OF C OST E FFECTIVENESS OF SO 2 C ONTROL T ECHNOLOGIES

Existing Emissions Controlled Emissions Reduced Annual Emissions Annual Cost Cost Effectiveness

(tons/yr) (tons/yr) (tons/yr) ($/yr) ($/ton) Fuel Switching 981 492 490 953,099 1,947 WLS 981 98 883 3,282,078 3,716

Base 98th
Percentile

Impact 98 th Percentile Impact 98th
Percentile Improvement 98th
Percentile Improvement Cost
Effectiveness

(DV) (DV) (DV) (%) ($/DV) Fuel Switching 2.87 2.70 0.17 6.05 5,477,581 WLS 2.87 2.63 0.24 8.39 13,618,583Ash Grove Cement Company 4-2 Trinity Consultants BART Analysis Based on the five step analysis outlined by EPA, fuel switching and WLS were identified as the two technically feasible technologies. Cost, energy and environmental impacts were assessed for both technologies and the visibility improvements associat ed with both options were evaluated against existing conditions. This analysis demonstrates th at the cost of compliance associated with both control options is high while the visibility im pact analysis demonstrates that the visibility improvements associated with both control options are nominal due to the fact that the percentage of visibility impairment attributable to SO 4 is relatively low. As a result, AGC has determined that additional SO 2 control technologies (fuel switching a nd WLS) would provide little visibility improvement and require significant expenditures. Therefore, AGC proposes that limiting the kiln to the existing levels of SO 2 emissions constitutes BART for the kiln.Ash Grove Cement Company 5-3 Trinity Consultants BART Analysis 

## 5. NO X 

## BART E VALUATION

In Portland cement kilns, the NO x that is generated is primarily classified into one of two categories, i.e., thermal NO x or fuel NO x 6 . Thermal NO x occurs as a result of the high-temperature oxidation of molecular nitrogen present in the combustion air. Fuel NO x is created by the oxidation of nitrogenous compounds present in the fuel. It is also possible for nitrogenous compounds to be present in the raw material feed and become oxidized to form additional NO x referred to as feed NO x .

Due to the high flame temperature in the burning zone of the rotary kiln (3400 o F), NO x emissions from the kiln tend to be mainly comprised of thermal NO x . Although NO x emissions from cement kilns include both nitrogen oxide (NO) and nitrogen dioxide (NO 2 ), typically, less than 10% of the
total NO x in the flue gas is NO 2. 7

The kiln is the only BART source which emits NO
x , thus a NO
x BART evaluation was performed only for the kiln. The maximum actual 24-hour kiln NO
x emission rate that was modeled for the BART applicability determination is summarized in Table 4-1. The NO
x 24-hour maximum actual emission rate was determined from analyzer data for 2006.

T ABLE 5-1. E XISTING A CTUAL M AXIMUM 24-H OUR NO X E MISSION R ATES

NO x 24-Hour Emission Rate NO x Hourly Equivalent Emission Rate (ton/24-hr) (lb/hr)
Kiln 10.18 848.74



## 5.1 I DENTIFICATION OF 

## A VAILABLE 

## R ETROFIT 

## NO X 

## C ONTROL 

## T ECHNOLOGIES

Step 1 of the BART determination is the identification of all available retrofit NO X control technologies. A list of control technologies was obtained by reviewing the U.S. EPA’s Clean Air Technology Center, control equipment vendor information, publicly-available air permits, applications, and technical literature publis hed by the U.S. EPA and the RPOs.

The available retrofit NO X control technologies are summarized in Table 5-2.

6 NO x Formation and Variability in Portland Cement Kiln Systems, Penta En gineering, December 1998.
7 IBID.Ash Grove Cement Company 5-4 Trinity Consultants BART Analysis T ABLE 5-2. P OSSIBLE NO X C ONTROL T ECHNOLOGIES

Kiln Control Technologies

Low NO x Burner Flue Gas Recirculation CKD Insufflation Mid-Kiln Firing of Tires Selective Noncatalytic Reduction Selective Catalytic Reduction



## 5.2 E LIMINATE 

## T ECHNICALLY 

## I NFEASIBLE 

## NO X 

## C ONTROL 

## T ECHNOLOGIES

Step 2 of the BART determination is to eliminate technically infeasible NO X control technologies that were identified in Step 1.



### 5.2.1 L OW 

### -NO X 

### B URNER IN THE 

### R OTARY 

### K ILN

Low NO x burners (LNBs) reduce the amount of NO
x formed at the flame. The principle of all LNBs is the same: stepwise or staged combustion and localized exhaust gas recirculation (i.e. at the flame). As a pplied to the rotary cement kiln, the low-NO x burner creates primary and secondary combustion zones at the end of the main burner pipe to reduce the amount of NO
x initially formed at the flame. In the high-temperature primary zone, combustion is initiated in a fuel-rich environment in the presence of a less than stoichiometric oxygen concentration. Th e oxygen-deficient condition at the primary combustion site minimizes thermal and fuel NO x formation and produces free radicals that chemically reduce some of the NO x that is being generated in the flame.

In the secondary zone, combustion is complete d in an oxygen-rich environment. The temperature in the secondary combustion zone is much lower than in the first; therefore, lower NO x formation is achieved as combustion is co mpleted. CO that has been generated in the primary combustion zone as an artifact of the sub-stoichiometric combustion is fully oxidized in the secondary combustion zone.

The EPA has indicated that a 14% reduction in NO
x emissions may be anticipated in switching from a direct-fired standard burner to an indirect-fired LNB 8 . This is based on a study conducted on an indirect-fired LNB at the Dragon Product Company cement kiln at the plant located in Thomaston, Maine. Howe ver, the EPA has also determined that the [emission reduction] contribution of the LNB itself and of the firing system conversion [direct to indirect] can not be isolated from the limited data available 9 . The terms direct and indirect firing have unique meaning in the context of kiln firing (unlike the more general meanings where direct firing implies that the products of combustion contact the

8 NO X Control Technologies for the Cement Industry, EC/R Incorporated, Chapel Hill, NC, USA, U.S. EPA Contract NO. 68-D98-025, U.S. EPA RTP, September 19, 2000. 9 USEPA, Office of Air Qua lity Planning and Standards. Alternative Controls Technology Document - NOx Emissions from Cement manufacturing. EPA-453/R-94-004, Page 5-5 to 5-8.Ash Grove Cement Company 5-5 Trinity Consultants BART Analysis process materials whereas indirect firing involves a heat transfer medium). In kiln firing, direct and indirect firing describes the manner in which pulverized fuel is conveyed from the fuel grinding mill to the burner.

In the direct firing configuration, fuel is pneumatically conveyed directly from the coal mill to the burner. The quantity of air introduced to the primary combustion zone is dictated by the minimum air requirements of the coal mill and the conveyance system, rather than the optimum flame requirements. The Montana C ity plant kiln uses a direct firing system.

In the indirect firing configuration, the coal mill air is separated from the pulverized fuel which is stored in a tank before being fed to the kiln. The pulverized fuel is then conveyed to the burner with the quantity of air that is optimum for flame considerations. There have been no controlled studies conducted on cement kilns that verify that this method of burning solid fuel reduces the formation of NO
x .
The AGC Midlothian, Texas plant, which also operates direct-fired wet kilns, utilizes a direct fired LNB system that consists of a plugged annual burner pipe. In this design, the burner pipe has a central plug, which reduces the pr essure at the core of the jet. As a result, the pressure of the primary air jet is relieved inward, reducing the rate of the expansion of the flame. This produces a non-divergent flame that minimizes surface area of the flame and maintains the fuel concentrated in the co re of the flame. The annual burner pipe is shown in Figures 5-1 and 5-2.



### F IGURE 

### 5-1 A NNUAL 

### B URNER 

### P IPE WITH 

### C ONTRACTED 

### F LAME



### F IGURE 

### 5-2 S CHEMATIC OF 

### A NNUAL 

### B URNER 

### P IPE

When compared to simple free jet burners without the annual nozzle, these burners enhance NO X control by reducing flame turbulence, delaying fuel/air mixing, andAsh Grove Cement Company 5-6 Trinity Consultants BART Analysis establishing a fuel rich core in the flame for initial combustion. Low-NO x burners are considered to be a technically feasible option for NO X control.



### 5.2.2 F LUE 

### G AS 

### R ECIRCULATION

Flue gas recirculation involves the use of oxygen-deficient flue gas from some point in the process as a substitute for primary air in the main burner pipe in the rotary kiln. Flue gas recirculation (FGR) lowers the peak flame temperature and develops localized reducing conditions in the burning zone through a signifi cant reduction of the oxygen content of the primary combustion “air.” The intended effect of the lower flame temperature and reducing conditions in the flame is to decrease both thermal and fuel NO x formation in the rotary kiln.

While FGR is a practiced control technology in the electric utility industry, AGC is not aware of any attempt to apply FGR to a cement kiln because of the unique process requirements of the industry, i.e., a hot flame is required to complete the chemical reactions that form clinker minerals from the raw mate rials. The process of producing clinker in a cement kiln requires the heating of raw materials to about 2700°F for a brief but appropriate time to allow the desired chemical reactions that form the clinker minerals to occur. A short, high-temperature flame of about 3400°F is necessary to meet this process requirement. The long/lazy flame that would be produced by FGR would result in the production of lower or unacceptable quality c linker because of the resulting undesirable mineralogy. Clinkering reactions must take place in an oxidizing atmosphere in the burning zone to generate clinker that can be used to produce acceptable cement. FGR would tend to produce localized or genera l reducing conditions that also could detrimentally affect clinker quality. Due to these important limitations on the application of FGR and the lack of a successful demonstra tion on a cement kiln in the United States, FGR is not a technically feasible control option for NO x control at this time.



### 5.2.3 C EMENT 

### K ILN 

### D UST 

### I NSUFFLATION

Cement kiln dust (CKD) is a residual byproduct that can be produced by any of the four basic types of cement kiln systems. CKD is most often treated as a waste even though there are some beneficial uses. However, as a means of recycling usable CKD to the cement pyroprocess, CKD sometimes is injected or insufflated into the burning zone of the rotary kiln in or near the main flame. Th e presence of these cold solid s within or in close proximity to the flame has the effect of cooling the flame and/or the burning zone thereby reducing the formation of thermal NO x . The insufflation process is somewhat counterintuitive because a basic requirement of a ce ment kiln is a very hot flame to heat the clinkering raw materials to about 2700 o F in as short a time as possible. Because there is an increased requirement for thermal energy in the burning zone when insufflation is employed, it is not an attractive technology for recirculation of CKD in wet kiln systems. Other, more efficient procedures are available. Therefore, this option is removed from consideration for BART.Ash Grove Cement Company 5-7 Trinity Consultants BART Analysis 

### 5.2.4 M ID 

### -K ILN 

### F IRING OF 

### S OLID 

### F UEL 

### (T IRES 

### ) WITH 

### M IXING 

### A IR 

### F AN

Secondary combustion is defined as follows: a portion of the fuel is fired in a location other than the burning zone. This reduces thermal NO
x generation because the temperature in the secondary combustion zone is less than 2100 ° F. Mid-kiln firing (MKF) of solid fuels, such as used tires, is an example of secondary combustion. MKF allows part of the kiln fuel to be burned at a material calci nation temperature (secondary combustion zone) which is much lower than the clinker burning temperature.

The Cadence feed form MKF technology was first introduced in 1989. It is comprised of three primary components: (1) a staging arm or “feed fork,” that picks up the fuel modules and positions them for entry into the kiln, (2) two pivoting doors that open to allow the fuel to drop into the kiln, and (3) a drop tube that extends through the side wall of the kiln. In addition to these basic components, feed fork technology also requires a delivery system which positions the fuel models so they can be picked up by the feed fork and a mechanism for opening the doors so the fuel can enter the kiln. Due to rotation of the kiln, fuel can only be injected once per revolution from the top, as shown in Figure 5-3.



### F IGURE 

### 5-3. M ID 

### -K ILN 

### F IRING 

### S CHEMATIC 10

High-pressure air, in the range of a 2-10 percent replacement of the primary combustion air, could be injected through the shell of th e rotary kiln and into the calcining zone to where a mixing air fan mixes the air with the g as and fuel within the rotary kiln for more complete combustion of the solid fuel.

By adding fuel mid-kiln, MKF changes both the flame temperature and flame length. These changes should reduce thermal NO X formation by burning part of the fuel at a lower temperature and by creating reducing conditions at the mid-kiln fuel injection point which may destroy some of the NO X formed upstream in the kiln burning zone.

10 NO X Control Technologies for the Cement Industry, EC/R Incorporated, Chapel Hill, NC, USA, U.S. EPA Contract NO. 68-D98-025, U.S. EPA RTP, September 19, 2000.Ash Grove Cement Company 5-8 Trinity Consultants BART Analysis The discontinuous fuel feed from MKF may al so result in increased carbon monoxide (CO) emissions. To control CO emissions, the kiln may have to have increased combustion air which can decrease production capacity.

AGC currently utilizes MKF of tires on three we t kilns at the Midlothian, Texas plant; approximately 4 million tires are burned each year for the three wet kilns. This accounts for about 20% of the fuel usage (BTU basis) at the Midlothian plant. It is estimated that approximately 1.3 million tires would be required at Montana City to achieve the same fuel replacement and equivalent NO X reductions. A study by the Montana Environmental Quality Council 11 estimated that between 527,400 and 879,000 waste tires are generated each year in Montana. Therefore, in orde r for the Montana City plant to obtain the required amount of tires, tires would likely need to be imported from surrounding states. Furthermore, the Holcim Trident cement pl ant located in Three Forks, Montana, is currently seeking approval from MDEQ to burn up to 1,137,5 39 tires per year as supplemental fuel. In the Draft Environmenta l Impact Statement submitted by Holcim to MDEQ in July 2006, Holcim states that it will transport tires from out of state to supplement the number of tires available in M ontana. This would create an additional strain on the supply of tires available in the region for the Montana City plant.

Transportation of tires from surrounding stat es would increase the cost associated with MKF and generate additional air pollutant em issions for motor vehicle transportation and fugitive dust from traffic at the Montana City plant. Therefore, while MKF of tires is technically feasible, AGC proposes to eliminate this control option from further consideration as BART due to th e supply shortage of tires.



### 5.2.5 S ELECTIVE 

### N ONCATALYTIC 

### R EDUCTION
In the relatively narrow temperature window of 1600 to 1995°F, ammonia (NH 3 ) reacts with NO x without the need for a catalyst to form water and molecular nitrogen in accordance with the following simplified reactions.

4NO + 4NH 3 + O 2 Æ 4N 2 + 6H 2 O
2NO 2 + 4NH 3 + O 2 Æ 3N 2 + 6H 2 O

As applied to NO x control from cement kilns and other combustion sources, this technology is called selective noncatalytic reduction (SNCR). Above this temperature range, the NH 3 is oxidized to NO x thereby increasing NO x emissions. Below this temperature range, the reaction rate is too slow for completion and unreacted NH 3 may be emitted from the pyroprocess. This temperature window generally is available at some location within the rotary kiln. The NH 3 could be delivered to the kiln shell through the use of anhydrous NH 3 , or an aqueous solution of NH 3 (ammonium hydroxide) or urea.

11 Status of and Alternatives for Ma nagement of Waste Tires in Montana : Report to the 56th Legislature

, Montana Environmental Qua lity Council, October 1998.Ash Grove Cement Company 5-9 Trinity Consultants BART Analysis A concern about application of SNCR tec hnology is the breakthrough of unreacted NH 3 as “ammonia slip” and its subsequent reaction in the atmosphere with SO 2 , sulfur trioxide (SO 3 ), hydrogen chloride (HCl) and/or chlorine (Cl 2 ) to form a detached plume of PM 10 – PM 2.5

.

SNCR is currently being used successfully as an independent technology on wet cement kiln systems in Europe and recently, authoriza tion was granted to AGC to test SNCR at its wet kiln in Midlothian, Texas. AGC installed a full scale SNCR system on one of its wet kilns and the system has been running for several months; it is achieving a 35 to 40% NOx reduction on a consistent basis.

As SNCR is currently being opera ted on one of AGC’s wet cement kiln at the Midlothian Texas plant, it is considered a technically feasible NO x control option for the Montana City plant



### 5.2.6 S ELECTIVE 

### C ATALYTIC 

### R EDUCTION

Selective Catalytic Reduction (SCR) is an a dd-on control technology for the control of emissions of the oxides of nitrogen (NO
x ) from a combustion process. SCR has been successfully employed in the electric power indus try. The basic SCR system consists of a system of catalyst grids placed in series with each other within a vessel that is located in a part of the process where the normal flue gas temperature is in the required range. An ammonia-containing reagent is injected at a controlled rate upstream of the catalyst grids that are designed to ensure relatively even flue gas distribution within the grids, to provide good mixing of the reagent and flue gas, and to result in minimum ammonia (NH 3 ) slip. 12
The NH 3 reacts with NO x compounds (i.e., NO and NO 2 ) on the surface of the catalyst in equal molar amounts (i.e., one molecule of NH 3 reacts with one molecule of NO x ). Common reagents include aqueous NH 3 , anhydrous NH 3 and urea [(NH 2 ) 2 CO]. In the presence of the catalyst, the injected ammonia is converted by OH - radicals to ammonia radicals (i.e., NH 2 - ), which, in turn, react with NO x to form N 2 and H 2 O. The SCR catalyst enables the necessary reactions to occur at lower temperatures than those required for Selective Non-Catalytic Reduction (SNCR). While catalysts can be effective over a larger range of temperatures, the optimal temperature range for SCR is 570 - 750o F.

The catalyst system used in SCR applications usually consists of (1) a porous honeycomb of a ceramic substrate onto which catalyst has been attached to the surface of the ceramic material, or (2) a flat or corrugated plate onto which catalytic material has been deposited on the surface. A porous metal oxide with a high surface area-to-volume ratio acts as a catalyst base. On this base, typically titanium dioxide (TiO 2 ), one or more metal oxide catalysts are deposited in various concentrati ons. In SCR applications, the active catalyst material typically consists of vanadium pentoxide (V 2 O 5 ), tungsten trioxide (WO 3 ), and molybdenum trioxide (MoO 3 ) in various combinations. The composition, also known as the catalyst formulation, is tailored by the catalyst vendor to best suit a particular SCR

12 Slip refers to the quantity of unreacte d reagent that exits the SCR reactor.Ash Grove Cement Company 5-10 Trinity Consultants BART Analysis application. Catalyst deactivation through poisoning, fouling, masking, sintering and erosion are common problems for SCR catalysts that, without careful process design and operation, could be exacerbated. If not fouled by sulfur dioxide (SO 2 ), the catalysts used in SCR have a propensity to oxidize sulfur dioxide (SO 2 ) in the flue gas to sulfur trioxide (SO 3 ), a more undesirable pollutant.

Because the reaction rate of NH 3 and NO x is temperature dependent, the temperature of the flue gas stream to be controlled is the mo st important consideration in applying SCR technology to any combustion source. The optimum temperature range for SCR application is about 300o C (570o F) to 45 0o C (840o F). This range of normal process temperature may be found in the exhaust g as from the wet kiln at the PMCD inlet.

SCR has not been applied to a cement plant of any type in the United States. SCR has been applied successfully at a cement plant in Solnhofen, Germany. The Solnhofen plant has a kiln with a preheater tower as opposed to the wet kiln system at AGC’s Montana City plant. SCR has also been successfully applie d at a cement plant in Moncelice, Italy; however, this plant is also a preheater plant as opposed to the wet cement kiln system at Montana City.

Earlier this year, as part of permitting a ne w cement plant to be located on the Moapa Pauite Indian Reservation in Nevada (Moapa Paiute plant), AGC carefully assessed all of the publicly available information regarding S CR application at Solnhofen to determine (1) whether the Solnhofen testing indicates that the SCR technology exceeds the performance of SNCR and (2) whether the technology is commercially available for preheater/precalciner system such as that intended for AGC’s proposed Moapa Paiute plant. In order to ensure a comprehensive review, AGC engaged an independent expert in SCR technology to conduct an extensive analysis of SCR and its availability in relation to the Moapa Paiute plant. This analysis dete rmined that the SCR system at Solnhofen does not result in a lower NOx emission rate th an that which can be gained from SNCR. 13 The study also concluded that the cost and ti me required for pilot testing to select the appropriate catalyst and SCR size/configura tion needed to achieve the same emission levels achievable by SNCR is unknown. In th e draft Moapa Paiute PSD permit put out for public comment this spring, EPA Region 9 c oncluded that SCR did not constitute BACT for cement kilns as it could not be demonstr ated to outperform SNCR (that permit is expected to be issued upon completion of the Endangered Species Act consultation).

The major SCR vendors have also indicated th at SCR is not commercially available for cement kilns at this time. The St. Lawren ce Cement Company recently issued a Request for Proposals (RFP) for SCR for the company’s proposed new cement kiln in Greenport, New York. Of the four major vendors contacted, two, Lurgi PSI Inc. (Lurgi) and Babcock & Wilcox, did not provide any proposal, with Lurgi stating that their technology was not yet ready for commercial release. A third with relevant experience from the Solnhofen

13 Schreiber, Robert J., Evaluation of Suitability of Selective Catalytic Reduction for Use in Portland Cement Manufacturing, 2006Ash Grove Cement Company 5-11 Trinity Consultants BART Analysis demonstration plant, KWH, 14 indicated that technical uncertainties prevented them from designing an SCR system without pilot plant testing. Only Alstom provided a proposal that suggested SCR could be supplied to a cement kiln system. However, careful review of the Alstom proposal, indicated that the Alstom proposal did not identify a commercial SCR system that would be viable for a cement kiln system application

AGC has reviewed the publicly available S CR assessments and vendor documents related to the Greenport plant. Ash Grove believes th at the Greenport vendor evaluation continues to be relevant and supports the conclusion that an SCR system is not commercially available as defined in the NSR Workshop Manual, pages B.17 and B.18, which states that:

...Two key concepts are important in determining whether an undemonstrated technology is feasible: “availability” and “applicability.“

As explained in more detail below, a tec hnology is considered "available" if it can be obtained by the applicant through commercial cha nnels or is otherwise available within the common sense meaning of the term. An available technology is “applicable” if it can reasonably be installed and operated on the source type under consideration. A technology that is available and applicable is technically feasible. Availability in this context is further explained using the following process commonly used for bringing a control technology concept to reality as a commercial product: con cept stage; research and patenting; bench scale or laboratory testing; pilot scale testing; licensing and commercial demonstration; and commercial sales.

A control technique is considered available, within the context presented above, if it has reached the licensing and commercial sales stage of development. A source would not be required to experience extended time delays or resource penalties to allow research to be conducted on a new technique. Neither is it e xpected that an applicant would be required to experience extended trials to learn how to apply a technology on a totally new and dissimilar source type. Consequently, technologies in the pilot scale testing stages of development would not be considered availabl e. An exception would be if the technology were proposed and permitted under the qualifi cations of an innovative control device consistent with the provisions of 40 CFR 52. 21(v) or, where appropriate, the applicable SIP [in which case it would be considered available].

Commercial availability by itself, however , is not necessarily sufficient basis for concluding a technology to be applicable and therefore technically feasible. Technical feasibility, as determined in Step 2, also means a control option may reasonably be deployed on or "applicable" to the source type under consideration. (NSR Page B.18)

As SCR would require pilot scale testing, Ash Grove concluded that SCR was not “available” with respect to the Moapa Pa iute plant because it was not commercially

14 KWH teamed with Elex, a German en gineering firm who was responsible for some aspects of the Solnhofen installation. Elex holds a patent c overing certain applications of SCR to cement kilns in the United States.Ash Grove Cement Company 5-12 Trinity Consultants BART Analysis available. This determination has also been the finding of the Florida DEP as recently as March 2005, which in a BACT determination for Florida Rock Industries, Newberry Plant, concluded that “ there has been no pilot study conducted in the United States, and there have been no indications that a pilot plant w ill be constructed to test SCR by any Portland cement facilities in the United States.” Furthe r, “...Some additional time would be needed to conduct tests to determine the correct catal yst formulation” and, “The Department does not consider SCR necessary to achieve a BACT level of control in Florida.” 15

.

In conclusion, AGC has determined that SN CR is as good as SCR based on Solnhofen and, due to commercial unavailability that AGC de termined for the Moapa Paiute plant and since there is no known application of SCR on a wet kiln system, SCR is eliminated from further consideration as BART for NO
x control at the Montana City plant.



## 5.3 R ANK OF 

## T ECHNICALLY FEASIBLE 

## NO X 

## C ONTROL 

## O PTIONS BY 

## E FFECTIVENESS

The third step in the BART analysis is to rank the technically feasible options according to effectiveness. Table 5-3 presents potential NO x technically feasible control technologies for the kiln and the associated NO
x emission levels. The emission rates are largely based AGC’s experience with wet kiln NO X control technologies at AGC’s Midlothian, Texas plant.

15 Air Permit No: 0010087-013-AC; PSD-FL-350 - BACT De termination, Comment wr itten by Al Linero, Florida DEP, 3/30/2005, Pages BD-10 and BD-11.Ash Grove Cement Company 5-13 Trinity Consultants BART Analysis T ABLE 5-3. R ANKING OF T ECHNICALLY F EASIBLE K ILN NO X C ONTROL T ECHNOLOGIES BY E FFECTIVENESS

Pollutant Control Tech nology Effectiveness NO X Emissions Level (lb/hr)

NO X LNB and SNCR 227.25 lb/hr (~35 % control) † SNCR 295.36 lb/ hr (~35 % control) § LNB 422.59 lb/ hr (~7% control) ††
† The effectiveness level for SNCR and LNB corresponds to a 50% NO X reduction from the 2006 average 24-hour emission rate as an hourly equivalent (454.50 lb/hr). The 90 percent reduction was applied to the 2006 average 24-hour

NO
x emission rate rather than the maximum 24-hour NO
x emission rate to best reflect th e performance of the control on a 30 day rolling basis. § The effectiveness level for SNCR corresponds to a 35% NO X reduction from the 2006 average 24-hour emission rate as an hourly equivalent (454.50 lb/hr). The 90 percen t reduction was applied to the 2006 average 24-hour NO
x emission rate
rather than the maximum 24-hour NO
x emission rate to best reflect the perfo rmance of the control on a 30 day rolling
basis. †† The effectiveness level for the direct-fir ed LNB system is based on AGC’s experi ence with a system at the Midlothian, Texas plant. The effectiveness corresponds to a 7% NO X reduction from the 2006 average 24-hour emission rate as an hourly equivalent (454.50 lb/hr). The 90 percent reduction was applied to the 2006 average 24-hour NO
x emission rate
rather than the maximum 24-hour NO
x emission rate to best reflect the perfo rmance of the control on a 30 day rolling
basis.



## 5.4 E VALUATION OF 

## I MPACTS FOR 

## F EASIBLE 

## NO X 

## C ONTROLS

Step four for the BART analysis procedure is the impact analysis. The BART determination guidelines list four factors to be considered in the impact analysis:

• Cost of compliance

• Energy impacts

• Non-air quality impacts; and

• The remaining useful life of the source



### 5.4.1 SNCR AND 

### LNB

Cost of Compliance Since AGC is proposing the most stringent control option as BART, the cost of compliance is not evaluated.

Energy Impacts and Non Air-Quality Impacts SNCR systems require electricity to operate th e blowers and pumps. The generation of the electricity will most likely involve fuel combustion, which will cause emissions. While the required electricity will result in the emissions , the emissions should be small compared to the reduction in NO
x that would be gained by operating an SNCR systemAsh Grove Cement Company 5-14 Trinity Consultants BART Analysis Ammonia slip from SNCR systems occurs either from ammonia injection at temperatures too low for effective reaction with NO x , leading to an excess of unreacted ammonia, or from over-injection of reagent leading to uneven distribution; which al so leads to an excess of unreacted ammonia. Based on AGC’s experience at the Midlothian, Texas plant, we believe that ammonia slip will be less than 10 ppm above baseline emissions. While the presence of ammonia slip is recognized here as an impact attributable to SNCR systems, it is an air-quality impact and so is legally not part of the BART analysis process.

Remaining Useful Life The remaining useful life of the kiln doe s not impact the annualized costs of SNCR because the useful life is anticipated to be at least as long as the capital cost recovery period, which is 10 years.



## 5.5 E VALUATION OF 

## V ISIBILITY 

## I MPACT OF 

## F EASIBLE 

## NO X 

## C ONTROLS

The final impact analysis was conducted to assess the visibility improvement for existing emission rates when compared to the emission rates of the SNCR and LNB combined control option. The existing emission rates and emission rates associated with SNCR and LNB were modeled using CALPUFF. The existing emission rates are the same rates that were modeled for the BART applicability analysis.

The NO
x emission rate associated with the SNCR a nd LNB control option is the 2006 average 24- hour NO
x emission rate (hourly equivalent) reduced by 50 percent. This 50 percent reduction was applied to the 2006 average 24-hour NO
x emission rate rather than the maximum 24-hour NO
x emission rate because the BART limit is proposed as a 30-day rolling average. Had the 50 percent reduction been applied to the maximum 24-hour NO
x emission rate, the controlled emission rate would be much higher than what AGC anticipates could be achieved by the SNCR and LNB on a 30- day rolling basis. The emission rates are summarized in Table 5-4.Ash Grove Cement Company 5-15 Trinity Consultants BART Analysis T ABLE 5-4. S UMMARY OF E MISSION R ATES M ODELED I N NO X C ONTROL V ISIBILITY I MPACT A NALYSIS

Unit Emission Rate S cenario Emission Rate

SO 2 NO X PM 10 (lb/hr) (lb/hr) (lb/hr)
Kiln SNCR and LNB 473.87 227.25 37.17 Existing 473.87 848.74 37.17

Comparisons of the 98 th percentile existing visibility impacts and the visibility impacts based on LNB and SNCR for the Gates of the Mountains Wilderness Area are provided in Table 5-5. The visibility improvement associated with LNB and SNCR are also shown in Table 5-5; this was calculated as the difference between the existing visibility impairment and the visibility impair ment for the remaining control options as measured by the 98 th percentile modeled visibility impact.

T ABLE 5-5. NO X C ONTROL V ISIBILITY I MPACT A NALYSIS

98% Impact ( Δ dv) Improvement Existing 2.874 - SNCR and LNB 1.377 52.09%

As seen in Tables 5-5, the SNCR and LNB result in a visibility improvement of 52.09 percent.



## 5.6 P ROPOSED 

## B ART FOR 

## NO X
Based on the five step analysis outlined by EPA, SNCR with LNB was identified as the sole technically feasible add-on control technology. Cost, energy and environmental impacts were assessed for this technology and the visibility im provements were eval uated against existing conditions. Consistent with EPA guidance, ec onomic impacts were not assessed as AGC was willing to utilize the highest ranked control technology. The visibility impact analysis demonstrates that the utilization of SNCR and LNB to achieve a 227.25 lb/hr NO
x emission rate results in significant visibility improvements. Neither non-air quality nor energy impacts associated with this control technology are material and so do not present a basi s for eliminating SNCR/LNB in favor of retaining the existing rates as BART. Therefore, AGC proposes that a direct-fired LNB system with SNCR is BART for NO
x . AGC proposes to comply with a BART emissions limit of 227.25 lb/hr on a 30-day rolling basis. Compliance with the emission limit will be demonstrated by continuous emissions monitoring.Ash Grove Cement Company 6-1 Trinity Consultants BART Analysis 

## 6. PM BART E VALUATION

PM is generated by the kiln and clinker cooler. The PM emissions are from the kiln are currently controlled by an ESP, and the PM emissions from the clinker cooler are controlled by a baghouse.

The maximum daily PM 10 emission rates that were modeled fo r the BART applicability determination are summarized in Table 6-1.

T ABLE 6-1. E XISTING M AXIMUM 24-H OUR PM 10 E MISSION R ATE

PM 10 24-Hour Emission Rate PM 10 Hourly Emission Rate (ton/24-hr) (lb/hr)
Kiln 0.45 37.17 Clinker Cooler 0.07 6.00

A comparison of Table 6-1 with Table 4-1 and Table 5-1 shows that the current PM 10 emission rates for the kiln and clinker cooler are much less than the current emission rates of SO 2 and NO X for the kiln. The low PM 10 emission rates correspond to low visibility impacts attributable to PM 10 when compared to the impacts attributable to SO 2 and NO X , as shown in Table 6-2.

T ABLE 6-2. VAP V ISIBILITY I MPAIRMENT C ONTRIBUTIONS A T G ATES OF THE M OUNTAINS

98 th Percentile Impact Visibility Impairment Attributable to SO 4 1 Visibility Impairment Attributable to NO 3 2 Visibility Impairment Attributable to PM 10 3

( ∆ dv) (%) (%) (%)

2.16 23.1 66.5 10.4 1 The visibility impairment attributable to SO 4 is primarily from SO 2 emissions. A very small portion is from SO 4 emitted as condensable particulate. 2 The visibility impairment attributable to NO 3 is entirely from NO X emissions. 3 The visibility impairment attributable to PM 10 is the sum of the visibility impairment attributable to all modeled primary PM species (PMc, PMf, EC, and SOA).

As mentioned, the kiln has an existing ESP for pa rticulate matter control. The ESP is the most effective particulate matter control device for a we t kiln, due to the temperature of the exhaust exiting the kiln. The exhaust from the kiln is well over 500 0 F at times under normal operations and would require an extensive gas conditioning system to operate a fabric filter PMCD properly.

Also, as mentioned, the clinker cooler has an ex isting baghouse for particulate matter control. A baghouse is currently the best device for cont rolling particulate matter from a source.

As no particulate control devices were identified th at are more effective than the existing PMCDs, AGC proposes that no additional PM control technologi es are required for either the kiln or clinker cooler for BART. AGC believes that the existing c ontrols are the best, most technically feasible controls for these types of sources. Because AGC is proposing to retain the most effective particulateAsh Grove Cement Company 6-2 Trinity Consultants BART Analysis control devices on the two BART units, there is no need to evaluate other impacts in establishing these control technologies as BART.