DEPARTMENT OF ENVIRONMENTAL QUALITY

AIR QUALITY DIVISION

BART Application Analysis

AP-6045

August 4, 2008

NAME OF FIRM: FMC Wyoming Corporation

NAME OF FACILITY: Westvaco Facility 

FACILITY LOCATION: Sections 14, 15, 22, and 23, T19N, R110W

Sweetwater County, Wyoming

TYPE OF OPERATION: Trona Mine and Sodium Products Plant

RESPONSIBLE OFFICIAL: Otto Schnauber, Environmental Team Leader

MAILING ADDRESS: PO Box 872

Green River, WY 82935

TELEPHONE NUMBER: (307) 872-2257

REVIEWERS : Cole Anderson, Air Quality Engineer

Josh Nall, Air Quality Modeler

PURPOSE OF APPLICATION:

Sections 169A and 169B of the 1990 Clean Air Act Amendments require states to improve visibility at 

Class I areas. On July 1, 1999, EPA first published the Regional Haze Rule, which provided specific 

details regarding the overall program requirements to improve visibility. The goal of the regional haze 

program is to achieve natural conditions by 2064.

Section 308 of the Regional Haze Rule (40 CFR 51) includes discussion on control strategies for 

improving visibility impairment. One of these strategies is the requirement under 40 CFR 51.308(e) for 

certain stationary sources to install Best Available Retrofit Technology (BART) to reduce emissions of 

three (3) visibility impairing pollutants, nitrogen oxides (NOx), particulate matter (PM), and sulfur 

dioxide (SO2). EPA published Appendix Y to part 51 - Guidelines for BART Determinations Under the 

Regional Haze Rule in the July 6, 2005 Federal Register to provide guidance to regulatory authorities for 

making BART determinations. Chapter 6, Section 9, Best Available Retrofit Technology was adopted 

into the Wyoming Air Quality Standards and Regulations (WAQSR) and became effective on December 

5, 2006. The Wyoming Department of Environmental Quality, Air Quality Division (Division) will 

determine BART for NOx and PM10 for each source subject to BART and include each determination in 

the §308 Wyoming Regional Haze State Implementation Plan (SIP).

Section 309 of the Regional Haze Rule (40 CFR 51), Requirements related to the Grand Canyon 

Visibility Transport Commission, provides states that are included within the Transport Region addressed 

by the Grand Canyon Visibility Transport Commission (i.e., Arizona, California, Colorado, Idaho, 

Nevada, New Mexico, Oregon, Utah, and Wyoming) an alternative to the requirements established in 40 
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 2

CFR 51.308. This alternative control strategy for improving visibility contains special provisions for 

addressing SO2 emissions, which include a Market Trading program and a provision for a 2018 SO2

Milestone. Wyoming submitted a 309 Regional Haze SIP to EPA on December 29, 2003. As of the date 

of this analysis, EPA has not taken action on the SIP. Sources that are subject to BART are required to 

address SO2 emissions as part of the BART analysis.

On March 8, 2007 FMC Wyoming Corporation (FMC) submitted a BART application for two existing 

coal-fired boilers and one existing natural gas-fired boiler at the Westvaco Facility in accordance with the 

requirements of WAQSR Chapter 6 Section 9(e)(i). A map of FMC Westvaco Facility‟s location is 

attached as Appendix A.

On April 14, 2008 FMC submitted an addendum to the BART application to address visibility impacts on 

an individual unit basis. Updated visibility modeling was performed as part of the application addendum. 

BART ELIGIBILITY DETERMINATION:

In August of 2005 the Wyoming Air Quality Division began an internal review of sources that could be 

subject to BART. This initial effort followed the methods prescribed in 40 CFR part 51, Appendix Y:

Guidelines for BART Determinations Under the Regional Haze Rule to identify sources and facilities. 

The rule requires that States identify and list BART-eligible sources, which are sources that fall within the 

26 source categories, have emission units which were in existence on August 7, 1977 but not in operation 

before August 7, 1962 and have the potential to emit more than 250 tons per year (tpy) of any visibility 

impairing pollutant when emissions are aggregated from all eligible emission units at a stationary source. 

One hundred two (102) sources at fourteen (14) facilities were identified that could be subject to BART in 

Wyoming.

The next step for the Air Quality Division was to identify BART-eligible sources that may emit any air 

pollutant which may reasonably be anticipated to cause or contribute to any impairment of visibility. 

Three pollutants are identified by 40 CFR part 51, Appendix Y as visibility impairing pollutants. They 

are sulfur dioxide (SO2), nitrogen oxides (NOx), and particulate matter (PM). Particulate matter with an 

aerodynamic diameter of 10 microns or less (PM10) was used as an indicator of PM. In order to determine 

visibility impairment of each source, a screening analysis was performed using CALPUFF. Sources that 

emitted over 40 tons of SO2 or NOx or 15 tons of PM10 were included in the screening analysis. Using 

three years of meteorological data, the screening analysis calculated visibility impacts from sources at 

nearby Class I areas. Sources whose modeled 98th percentile 24-hour impact or 8th highest modeled 

impact, by year, was equal to or greater than 0.5 deciviews (dv) above natural background conditions 

were determined to be subject to BART. For additional information on the Division‟s screening analysis 

see the Visibility Improvement Determination: Screening Modeling section of this analysis. FMC 

Westvaco Facility‟s two existing coal-fired boilers and one existing natural gas-fired boiler were 

determined to be subject to BART. FMC was notified in a letter dated June 14, 2006 of the Division‟s 

finding.
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 3

DESCRIPTION OF BART ELIGIBLE SOURCES:

FMC Westvaco Facility‟s two existing coal-fired boilers (NS-1A and NS-1B) are located at the mono 

powerhouse. The existing natural gas-fired boiler (PH-3) is located at the sequi powerhouse. All three 

units supply 600 lb steam to a common steam header for the facility. High pressure steam is initially fed

into six turbines to generate plant electricity. The steam exits the turbines at a pressure of approximately 

200 lbs and is distributed as process steam to the sequi, mono, ELDM (Evaporation, Lime neutralization, 

Decahydrate crystallization, and Monohydrate crystallization), and caustic plants that comprise the 

Westvaco Facility.

NS-1A and NS-1B have a design heat input rate of 887 MMBtu/hr and were constructed in 1975. They 

are both wall-fired, wet-bottom boilers burning subbituminous coal. At the time this BART application 

was filed combustion air control was used to reduce NOx emissions from the boilers. Particulate matter 

emissions from each of the boilers were controlled using an electrostatic precipitator (ESP). SO2

emissions were controlled by alkaline wet scrubbers.

Table 1: NS-1A and NS-1B Coal-fired Boilers’ Baseline Operations

Operating Permit 3-1-132 Emission Limits

Source

Firing Rate 

(MMBtu/hour)

Existing 

Controls

NOx

(lb/MMBtu)

SO2

(lb/MMBtu)

PM/PM10

(lb/MMBtu)

NS-1A 887

Combustion air, 

dry ESP, alkali 

wet scrubber

0.7

(3-hour rolling)

1.2

(2-hour fixed) 0.05 (a)

NS-1B 887

Combustion air, 

dry ESP, alkali 

wet scrubber

0.7 

(3-hour rolling)

1.2 

(2-hour fixed) 0.05 (a)

(a) Operating Permit 3-1-132 PM/PM10 limit for the two boilers is 0.10 lb/MMBtu, however each unit is limited to 45 lb/hr which 

equates to a 0.0507 lb/MMBtu rate when divided by the maximum heat input rate.

On December 26, 2006 FMC filed a Chapter 6, Section 4 permit application to modify NS-1A and NS-1B 

boilers with the installation of low NOx burners (LNB), enhanced overfire air (OFA), and upgrades to the 

two existing alkali wet scrubbers. Air Quality Permit MD-5723 was issued July 17, 2007 authorizing the 

modifications to the boilers. New emission limits for NOx, CO, PM, and SO2 were established in this 

permitting action that take effect upon installation of the LNB on each boiler and completion of the wet 

scrubber upgrades. FMC notified the Division by letter dated August 24, 2007 that the LNB with OFA

and wet scrubber upgrades were installed on NS-1A and the unit had successfully started up on August 

22, 2007. The new emission limits permitted in MD-5723, as shown in Table 2, are in effect for NS-1A.

FMC anticipates installing LNB, OFA, and upgrades to the existing alkali wet scrubber on unit NS-1B 

during the scheduled 2008 turnaround. Installation of these control measures will subject NS-1B to the 

emission levels established in MD-5723, as shown in Table 2 below.
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 4

Table 2: NS-1A and NS-1B Coal-fired Boilers’ Modified Operations

Permit MD-5723 Emission Limits

Source

Permitted 

Controls

NOx

(lb/MMBtu)

SO2

(lb/MMBtu)

PM/PM10

(lb/MMBtu) / (lb/hr)

NS-1A

LNB, dry ESP, 

modified alkali 

wet scrubber

0.39 

(30-day rolling)

1.2 

(2-hour fixed)

0.54 

(30 day rolling)

0.05 / 45

NS-1B

LNB, dry ESP, 

modified alkali 

wet scrubber

0.39 

(30-day rolling)

1.2 

(2-hour fixed)

0.54 

(30-day rolling)

0.05 / 45

The natural gas-fired boiler, PH-3, has a design heat input rate of 336 MMBtu/hr and was constructed in 

1967. Clean combustion of natural gas does not typically produce appreciable amounts of SO2 or PM10. 

Therefore the boiler is not currently required to control SO2 or PM10 emissions through any additional 

add-on control devices. NOx emissions from PH-3 are controlled through combustion air control. 

Emissions from PH-3 are listed in Table 3 below. While the unit is not subject to limited operation, it is 

required to perform an emission test if it operates over 3,000 hours in a calendar year and at least once in 

the term of Title V Operating Permit 3-1-132 permit ending on September 15, 2009.

Table 3: PH-3 Natural Gas-Fired Boiler Operations

Operating Permit 3-1-132 Emission Limits

Source Control

NOx

(lb/MMBtu)

PM/PM10

(lb/hr)

PH-3

Combustion Air 

Control 0.23 8.40

CHAPTER 6, SECTION 9 – BEST AVAILABLE RETROFIT TECHNOLOGY (BART)

A BART determination is an emission limit based on the application of a continuous emission reduction 

technology for each visibility impairing pollutant emitted by a source. It is established on a case-by-case 

basis taking into consideration six factors for each proposed BART control. The six factors are: (1) The 

available retrofit control options, (2) Any pollution control equipment in use at the source, (3) The costs 

of compliance with control options, (4) The remaining useful life of the facility, (5) The energy and nonair quality environmental impacts of control options, and (6) The visibility impacts analysis. A BART 

determination must address air pollution control measures for each emissions unit or pollutant emitting 

activity subject to review. 
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 5

Visibility control options presented in the application for each of the emissions unit were reviewed using 

the methodology prescribed in 40 CFR 51 subpart Y, as required in WAQSR Chapter 6 Section 9(c)(i). 

This methodology is comprised of five basic steps:

Step 1: Identify all1available 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

Step 5: Evaluate visibility impacts

The five steps were applied to each pollutant emitted from the coal-fired boilers to determine a BART 

control measure for NOx, PM, and SO2. Refined modeling of PH-3 for this BART analysis shows 

visibility impacts are below screening levels and therefore not subject to additional BART controls. This 

conclusion is covered in more detail within the visibility section of this analysis.

NOx: INDENTIFY AVAILABLE RETROFIT CONTROL TECHNOLOGIES

FMC identified two primary types of NOx controls: combustion control techniques and add-on control 

technologies. Fourteen combustion control techniques are indentified in the application. These controls

focus on reducing combustion temperatures below the NOx formation temperature of approximately 

2900 F. Overfire air and low NOx burners are two commonly used technologies. Both technologies 

increase the amount of combustion air to reduce peak combustion temperatures thereby lowering NOx

emissions. 

In addition to the fourteen combustion controls, FMC identified three add-on controls:

1. Selective Catalytic Reduction (SCR) – SCR is a post combustion control technique in which 

vaporized ammonia or urea is injected into the flue gas upstream of a catalyst. NOx entrained in 

the flue gas is reduced to molecular nitrogen (N2) and water. The use of a catalyst facilitates the 

reaction at an exhaust temperature range of 300 to 1100 F, depending on the type of catalyst 

used. When catalyst temperatures are not in the optimal range for the reaction or when too much 

ammonia is injected into the process, unreacted ammonia can be released to the atmosphere 

through the stack. This release is commonly referred to as ammonia slip.

2. Selective Non-Catalytic Reduction (SNCR) – SNCR is similar to SCR in that it involves the 

injection of a reducing agent such as ammonia or urea into the flue gas stream. The reduction 

chemistry, however, takes place without the aid of a catalyst. SNCR systems rely on appropriate 

injection temperatures, proper mixing of the reagent and flue gas, and prolonged retention time in 

place of the catalyst. SNCR operates at higher temperatures than SCR. The effective 

temperature range for SNCR is 1500 to 2100 F. SNCR systems are very sensitive to temperature 

changes and typically have lower NOx emissions reduction (up to fifty or sixty percent) and 

higher ammonia slip than SCR systems.

 

1

Footnote 12 of 40 CFR 51 Appendix Y defines the intended use of „all‟ by stating “...you must identify the most stringent 

option and a reasonable set of options for analysis that reflects a comprehensive list of available technologies.”
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 6

3. Sorption (adsorption) – A post combustion control in which NOx in the flue gas contacts a 

carbon, ceramic, or zeolite substrate that contains an adsorbent and chemically binds on the 

surface of the material as a nitrate. NOx adsorption occurs in a temperature range of 350 to 

700 F. Once the adsorbent has reached saturation, the nitrate-containing material can be replaced 

or regenerated. This technology is typically applied to internal combustion engines and not 

boilers, therefore only a limited amount of information is available for NOx adsorption 

applications on utility or process boilers.

In addition to applying these controls separately, they can be combined to increase the overall NOx

reduction. FMC evaluated LNB and OFA in combination with both SNCR and SCR add-on controls. 

NOx: ELIMINATE TECHNICALLY INFEASIBLE OPTIONS

FMC did not eliminate any of the seventeen individual control technologies as technically infeasible. A

review of EPA‟s RACT/BACT/LAER Clearinghouse (RBLC) was done to identify recent control 

determinations for modified coal-fired boilers subject to Prevention of Significant Deterioration (PSD)

review at existing facilities. FMC listed four such modified units in the application, which are presented 

in the table below.

Table 4: RBLC Modifications for Nitrogen Oxides

Facility

Firing Rate 

(MMBtu/hour) Control

NOx

(lb/MMBtu)

Mansfield Mill 645 LNB (staged) 0.7

TECO-Big Bend Station 645 Equipment design

and operation 0.6

W.A. Parish Electric Generating 

Station Unit 8 6700

Combustion Tuning 

(CT), LNB, OFA, &

SCR

0.43

Limestone Electric Generating 

Station Units 1 & 2 7863 Water Injection 0.5

After reviewing the RBLC database, FMC concluded that LNB with enhanced OFA, LNB with SNCR, 

and LNB with SCR are the three dominant technologies used to retrofit existing coal-fired boilers for 

controlling NOx emissions. Based on this conclusion, FMC proposed control option 1 as LNB with 

enhanced OFA. LNB could be installed with no modification to the existing boilers or boiler windboxes. 

The existing OFA ports would be enlarged to accommodate new hardware to control the air flow.

FMC proposed control option 2 as the installation of SNCR in addition to LNB with enhanced OFA. 

SNCR would consist of urea injection directly into the combustion zone of the furnace. SNCR injection 

ports would be installed through the enhanced OFA ports. The existing ESP on each boiler would be 

used to control any additional increase in PM10 emissions.

FMC‟s final control option, option 3, is the installation of SCR in combination with LNB and enhanced 

OFA. This option would require the most structural modification because of limited amount of available 

space to install the associated control equipment. FMC would decommission an existing precipitator to 

house SCR hardware and install a new pulse jet fabric filter to control particulate emissions.
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 7

NOx: EVALUATE EFFECTIVENESS OF REMAINING CONTROL TECHNOLOGIES

In the original BART application, FMC proposed a NOx reduction of approximately 63%, which equates 

to an emission level of 0.26 lb/MMBtu, based on a performance guarantee from Advanced Combustion 

Technology, Incorporated. The guarantee was issued based on computational fluid modeling of the coal 

combustion process inside each boiler. As mentioned earlier, FMC has already installed LNB and OFA 

on unit NS-1A. Operational information gathered over the past eight months indicates that unit NS-1A 

can only achieve the 0.26 lb/MMBtu NOx emission level when the unit is fully loaded. NS-1A is a 

process boiler and therefore often subject to changing steam demands from plant operations, which is 

different from a utility boiler that typically operates near full load. NS-1A demonstrated that on an 8-

month average of 30-day rolling averages, the unit can achieve a 0.33 lb/MMBtu NOx emission rate. In 

the BART application addendum, FMC proposed that the application of LNB with enhanced OFA could 

control NOx emissions to a maximum rate of 0.35 lb/MMBtu, or a 50% reduction in NOx emissions, 

based on the current 0.70 lb/MMBtu New Source Performance Standard (NSPS) subpart D limit. 

Installation of SNCR when used in combination with LNB and enhanced OFA provides an additional

20% NOx reduction, which equates to an emission rate of 0.21 lb/MMBtu from each boiler. Using option 

3, the installation of SCR, FMC projects a total NOx reduction efficiency of 85% when operated in 

combination with LNB and OFA. The resulting NOx emission rate with the application of SCR would be 

0.1 lb/MMBtu from each boiler.

Table 5: NOx Emission Rates Per Boiler

Control

Option Control Technology

Resulting NOx

Emission Rate 

(lb/MMBtu)

Baseline Good Combustion Practices 0.70 (a)

1 LNB, OFA 0.35 (b)

2 LNB, OFA, SNCR 0.21 (c)

3 LNB, OFA, SCR 0.1 (c)

(a) 40 CFR part 60, subpart D, limit

(b) Emission level based on actual operations of the installed control on NS-1A

(c) Advanced Combustion Technology, Inc. performance guarantee

NOx: EVALUATE IMPACTS AND DOCUMENT RESULTS

FMC evaluated the economic, environmental, and energy impacts associated with the three proposed 

control options for both NS-1A and NS-1B. Vendors‟ quotes were obtained by FMC for control 

equipment capital costs for each of the proposed control options. The capital recovery factor used to 

estimate the annual cost of control was based on a 7% interest rate and a control life of 15 years. Current 

FMC labor and service costs were used to calculate the annual operating and maintenance costs. Annual 

power costs and annualized capital costs associated with downtime for installation of pollution controls 

were not included. Economic and environmental costs are summarized in the following two tables.
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 8

Table 6: NS-1A & NS-1B Economic Costs Per Boiler

Cost Baseline

Option 1: LNB, 

enhanced OFA

Option 2: LNB, 

enhanced OFA, 

SNCR

Option 3: LNB, 

enhanced OFA, 

SCR

Control Equipment Capital Cost $0 $1,721,091 $3,160,918 $44,719,163

Capital Recover Factor N/A 0.1098 0.1098 0.1098

Annual Capital Recovery Costs $0 $188,976 $347,069 $4,910,164

Annual O&M Costs $0 $224,169 $934,782 $3,231,013

Annual Cost of Control $0 $413,145 $1,281,851 $8,141,177

Table 7: NS-1A & NS-1B Environmental Costs Per Boiler

Baseline

Option 1: LNB, 

enhanced OFA

Option 2: LNB, 

enhanced OFA, 

SNCR

Option 3: LNB, 

enhanced OFA, 

SCR

NOx Emission Rate (lb/MMBtu) 0.7 0.35 0.21 0.1

Annual NOx Emission (tpy) (a)

2719.5 1359.8 815.9 388.5

Annual NOx Reduction (tpy) (a)

N/A 1359.7 1903.6 2331.0

Annual Cost of Control $0 $413,145 $1,281,851 $8,141,177

Cost per ton of Reduction N/A $304 $673 $3,493

Incremental Cost per ton of Reduction N/A $304 $1,597 $16,051

(a) Annual emissions based on individual heat input rate of 887 MMBtu/hr for 8,760 hours of operation per year.

The final step in the BART determination process, Step 5: Evaluate visibility impacts, for NOx is 

addressed in a comprehensive visibility analysis covering all three visibility impairing pollutants and 

associate control options. The visibility analysis follows Steps 1-4 for SO2 emissions in this application 

analysis.

PM10: INDENTIFY AVAILABLE RETROFIT CONTROL TECHNOLOGIES

FMC reviewed EPA‟s RBLC to identify recent particulate control determinations for modified coal-fired 

boilers subject to PSD review at existing facilities. FMC listed six such modified units in the application, 

which are presented in the table below. After reviewing the RBLC, FMC proposed four applicable 

technologies for controlling PM10 emissions from the two boilers. They are fabric filters or baghouses, 

wet and dry ESPs, mechanical collectors (MC), and wet scrubbers (WS).

1. Fabric filters (FF) – FF are woven pieces of material that collect particles with sizes ranging from 

submicron to several hundred microns in diameter at efficiencies generally in excess of 99%. The 

layer of dust trapped on the surface of the fabric, commonly referred to as dust cake, is primarily 

responsible for such high efficiency. Joined pores within the cake act as barriers to trap 
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 9

particulate matter too large to flow through the pores as it travels through the cake. Limitations 

are imposed by the temperature and corrosivity of the gas and the by adhesive properties of the 

particles. Most of the energy used to operate the system appears as pressure drop across the bags 

and associated hardware and ducting.

2. Electrostatic precipitators – ESPs use electrical forces (charge) to move particulate matter out the 

gas stream onto collection plates. The particles are given an electrical charge by directing the gas 

stream through a corona, or region in which gaseous ions flow. The charged particles acted upon 

by an induced electrical field from high voltage electrodes in the gas flow that forces them to the 

walls or collection plates. Once the particles couple with the collection plates, they must be 

removed without re-entraining them into the gas stream. In dry ESP applications, this is usually 

accomplished by physically knocking them loose from the plates and into a hopper for disposal. 

Wet ESPs use water to wash the particles from the collector plates into a sump. The efficiency of 

an ESP is primarily determined by the resistivity of the particle, which is dependent on chemical 

composition, and also by the ability to clean the collector plates without reintroducing the

particles back into the gas stream.

3. Mechanical collectors (cyclones) – Cyclones funnel the exhaust gas into a vortex where 

centrifugal force pushes the particulate matter to the sides of a conical shaped vessel. The 

particles fall down the walls to a collection point at the bottom. Cyclones are very effective at 

controlling large particles where the inertial force overwhelms the drag force of the particle and 

drives the particle to the vessel wall. Smaller particles have stronger drag forces and are more 

likely to be carried out of the vessel with the exhaust gas. Cyclones do not typically attain 

removal efficiencies of either the fabric filter or the ESP on similar applications.

4. Wet scrubber – Each boiler is currently equipped with an alkali wet scrubber to remove acid gas 

and SO2 emissions from the gas stream. Particulate matter is also controlled by the scrubber. 

Wet scrubbers can remove particulate matter through impaction, diffusion, interception and/or 

absorption. Impaction occurs when the velocity of the particle is high and it collides with the 

water droplets in the scrubber. Interception is similar to impaction, but when the particle is 

traveling at lower velocities the surface tension of the water droplet can capture the particle. 

Diffusion and absorption occur at lower particle velocities and are affected by chemical 

composition of both the particle and the water droplet. Wet scrubbers can achieve high

particulate matter removal efficiencies, but they are limited to lower exhaust gas flow rates and 

temperatures than ESPs or fabric filters. They can also increase stack corrosion by saturating the 

wet scrubber exit gas stream with water, reducing the gas velocity, and lowering the flue gas 

temperature to promote condensation in the exhaust stack.
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 10

Table 8: RBLC Modifications for Particulate Matter

Facility

Firing Rate 

(MMBtu/hour) Control

PM

(lb/MMBtu)

Inland Paperboard and Packaging, Inc. 

Rome Linerboard Mill 565 Electrostatic Precipitator (ESP) 0.05

Mansfield Mill 645 Single Stage Dust 

Collector/ESP 0.10

W.A. Parish Electric Generating Station 

Unit 7 6700 Fabric Filter 0.085

W.A. Parish Electric Generating Station 

Unit 8 6700 Fabric Filter 0.03

W.A. Parish Electric Generating Station 

Units 5 & 6 7400 Fabric Filter 0.088

Limestone Electric Generating Station 

Units 1 & 2 7863 Cold Side ESP 0.03

PM10: ELIMINATE TECHNICALLY INFEASIBLE OPTIONS

FMC did not eliminate any of the four control technologies as technically infeasible. Two of the 

proposed controls, a hot side dry ESP and an alkali wet scrubber, are currently installed on each boiler to 

control PM10 emissions. Based on the current allowable PM emission rate of 45 lb/hr, the boilers are 

controlled to 0.0507 lb/MMBtu when dividing the emission rate by the maximum heat input of 887 

MMBtu/hr. This emission rate is comparable with the PSD determinations identified as possible retrofit 

technologies in the previous section. FMC states that since the boilers are already equipped with highly 

efficient particulate controls, they focused on augmenting the current controls with additional control 

measures.

FMC proposed the installation of a fabric filter on the wet scrubber bypass stream to reduce PM10

emissions as option 1. The polishing filter would reduce PM10 emissions without significantly lowering 

the exhaust gas temperature, which is needed to reheat the gas stream leaving the wet scrubber to above 

the dew point temperature to prevent stack corrosion.

FMC proposed a second option, option 2, the installation of an additional wet ESP down stream of the 

wet scrubber. The existing scrubber bypass would be removed and 100% of the gas stream from the hot 

side ESP would be routed to the wet scrubber and the new wet ESP. Treating the inside of the stack with 

a corrosion inhibitor helps protect it from the flue gas exiting the wet ESP.

FMC‟s final proposed control option, option 3, is to remove the existing hot-side ESPs and install new 

pulse jet fabric filters to control particulate emissions emitted from the boilers. The FFs would be 

installed upstream of the existing wet scrubbers. The higher removal efficiencies of the fabric filters 

would increase the overall effectiveness of the entire system, including the wet scrubbers.
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 11

PM10: EVALUATE EFFECTIVENESS OF REMAINING CONTROL TECHNOLOGIES

Option 1 will treat only the alkali wet scrubber bypass portion of the total exhaust gas stream. Based on 

operational information provided by FMC, the reduction in PM emissions equates to approximately a 

0.01 lb/MMBtu reduction resulting a net emission rate of 0.04 lb/MMBtu. Redirecting all exhaust gas 

through the wet scrubber and adding an additional wet ESP after the wet scrubber, option 2, will reduce 

particulate emissions by 0.0317 lb/MMBtu to 0.019 lb/MMBtu per boiler. Finally, removing the existing 

dry ESP and installing a fabric filter, option 3, will reduce emissions by 0.0357 lb/MMBtu from current 

operations. This reduction results in a final emission rate of 0.015 lb PM /MMBtu from each boiler.

Table 9: PM10 Emission Rates Per Boiler

Control

Option Control Technology

Resulting PM10

Emission Rate 

(lb/MMBtu)

Baseline Existing hot side ESP and WS 0.0507 (a)

1 FF on WS bypass 0.04 (b)

2 Wet ESP after WS (c) 0.019 (b)

3 FF control before WS 0.015 (b)

(a) Current permit limit of 45 lb/hr divided by maximum heat input rate

(b) “Emissions Control Analysis Evaluation of Alternatives” prepared by CH2M Hill

(c) Based upon 100% of the flue gas routed through wet scrubber

PM10: EVALUATE IMPACTS AND DOCUMENT RESULTS

FMC evaluated the economic, environmental, and energy impacts associated with the three proposed 

control options for both NS-1A and NS-1B. FMC based control equipment capital costs for each of the 

proposed control options on a technical evaluation study performed by CH2M Hill and equipment vendor 

quotes. The same capital recovery factor used to estimate the annual cost of NOx control was also used to 

estimate annual cost to control PM10. Current FMC labor and service costs were used to calculate the 

annual operating and maintenance costs. Annual power costs and annualized capital costs associated with 

downtime for installation of pollution controls were not included. The following two tables summarize 

the economic and environmental costs.
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 12

Table 10: NS-1A & NS-1B Economic Costs Per Boiler

Cost Baseline

Option 1: FF on 

WS bypass

Option 2: Wet 

ESP after WS

Option 3: 

Replace ESP 

with FF

Control Equipment Capital Cost $0 $9,486,434 $20,766,772 $23,273,405

Capital Recover Factor N/A 0.1098 0.1098 0.1098

Annual Capital Recovery Costs $0 $1,041,610 $2,280,192 $2,555,420

Annual O&M Costs $0 $749,754 $1,227,425 $1,560,616

Annual Cost of Control $0 $1,791,364 $3,507,617 $4,116,036

Table 11: NS-1A & NS-1B Environmental Costs Per Boiler

Baseline

Option 1: FF on 

WS bypass

Option 2: Wet 

ESP after WS

Option 3: 

Replace ESP 

with FF

PM10 Emission Rate (lb/MMBtu) 0.0507 0.04 0.019 0.015

Annual PM10 Emission (tpy) (a)

197.1 155.4 73.8 58.3

Annual PM10 Reduction (tpy) (a)

N/A 41.7 123.3 138.8

Annual Cost of Control $0 $1,791,364 $3,507,617 $4,116,036

Cost per ton of Reduction N/A $42,958 $28,448 $29,654

Incremental Cost per ton of Reduction N/A $42,958 $21,033 $39,253

(a) Annual emissions based on maximum heat input rate of 887 MMBtu/hr for 8,760 hours of operation per year.

Given the high cost of control, FMC did not proceed further to Step 5: Evaluate visibility impacts for 

PM10. Previous visibility modeling analyses indicate that the contribution in visibility degradation from 

PM/PM10 is minor when compared to the contributing effects of NOx and SO2. Results from the 

screening analysis confirmed this conclusion and are discussed in further detail within the comprehensive 

visibility analysis. The Division did not require FMC to perform additional visibility analyses for the 

three PM control options.

SO2: INDENTIFY AVAILABLE RETROFIT CONTROL TECHNOLOGIES

FMC identified three processes for controlling SO2 emissions: (1) reducing the sulfur content in the fuel, 

(2) adsorption of sulfur compounds in the flue gas, and (3) absorption of sulfur compounds. Wyoming 

coal typically has lower sulfur content than coal produced in most other states, which makes it difficult to 

further reduce the sulfur content. Coal blending can be used to reduce the overall amount of sulfur 

combusted in a boiler, but again it is most effective when low sulfur coal is mixed with high sulfur coal.
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 13

Adsorption control systems are designed to capture SO2 as either a sulfate or sulfite at the surface of a 

sorbent. Dry alkaline powder, often lime, is injected into the exhaust gas upstream of a particulate control 

device such as a fabric filter. SO2 in the gas binds to the surface of the alkaline powder and is captured by 

the particulate control device for disposal. This control method works best in low moisture gas streams 

and when the sorbent has a high affinity for SO2.

The absorption process can be categorized as physical or chemical. Physical absorption occurs when the 

absorbed compound dissolves in the solvent. Chemical absorption occurs when the absorbed compound 

and the solvent react. SO2 absorption control technologies identified by FMC are discussed below.

1. Alkali wet scrubbers – WS remove SO2 through absorption by mass transfer as soluble SO2 in the 

exhaust gas mixture is dissolved in an alkaline water solvent that has low volatility under the 

process conditions. SO2 diffuses from the gas into the scrubber water when the liquid contains 

less than the equilibrium concentration of the gaseous SO2. The rate of SO2 mass transfer 

between the two phases is largely dependent on the surface area exposed and the time of contact. 

A properly designed alkali wet scrubber or gas absorber will provide sufficient contact between 

the gas and the liquid solvent to allow diffusion of SO2. Once the SO2 enters the alkaline water 

phase, it will form a weak acid and react with the alkaline component dissolved in the scrubber 

water to form a sulfite or sulfite. The acid/alkali chemical reaction prevents the SO2 from 

diffusing back into the flue gas stream. When the alkaline scrubber water is saturated with sulfur 

compounds, it can be converted to a wet gypsum by-product that may be sold. SO2 removal 

efficiencies for wet scrubbers can be as high as 99%.

2. Spray dryer dry scrubbers – Dry scrubbers are similar to adsorption injection systems, however 

the dry scrubber provides greater contact area and enhances chemical reactivity. A spray dryer 

dry scrubber sprays an atomized alkaline slurry into the flue gas upstream of particulate control 

system, often a fabric filter. Water in the slurry evaporates, hydrolizing the SO2 into a weak acid, 

which reacts with the alkali to form a sulfate or sulfite. The resulting dry product is captured in 

the particulate control and physically moved from the exhaust gas into a storage bin. The dry byproduct maybe dissolved back into the lime slurry or dried and sold as a gypsum product. Spray 

dryer dry scrubbers typically require lower capital cost than a wet scrubber. They also require 

less flue gas after-treatment. When exhaust gas leaves the wet scrubber, it is at or near saturation. 

A wet scrubber can lower exhaust gas temperatures down a temperature range of 110 to 140 F, 

which may lead to condensation in the exhaust stack, causing corrosion. A spray dryer dry 

scrubber does not enhance stack corrosion like a wet scrubber because it will not saturate the 

exhaust gas or lower the gas temperature. Removal efficiencies for spray dryer dry scrubbers are 

in the range of 70% to 95%.
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 14

SO2: ELIMINATE TECHNICALLY INFEASIBLE OPTIONS

FMC did not eliminate any of the controls listed above as technically infeasible. However, each boiler 

currently has an existing alkali wet scrubber installed. Since wet scrubbers are a proven and efficient SO2

control technology, they focused on ways to enhance operations of the existing wet scrubbers.

SO2: EVALUATE EFFECTIVENESS OF REMAINING CONTROL TECHNOLOGIES

Condensation of the exhaust gas is a critical design factor for the wet scrubbers. About 50% of the 

exhaust gas from each boiler bypasses the wet scrubber and is used to reheat the gas exiting the wet 

scrubber to above condensation temperature. FMC investigated ways to increase the amount of exhaust 

gas routed through the wet scrubber, while maintaining sufficient exhaust temperature to avoid 

condensation in the exhaust stack. Option 1 is upgrading the wet scrubber by replacing the top section 

and installing new mist eliminator and wash water system. This upgrade would allow up to 85% of the 

exhaust gas to enter the wet scrubber. Option 2 includes the same wet scrubber upgrades as option 1 and 

adds a flue gas reheat system prior to the exhaust stack. Reheating the flue gas allows an addition 5% to 

10% of the gas to enter the wet scrubber while maintaining the flue gas temperature above condensation 

as it exits the exhaust stack.

The existing wet scrubbers were designed to meet the 40 CFR part 60, subpart D, emission limit for SO2

of 1.2 lb/MMBtu. Based on operational experience and design evaluations, FMC proposes that by 

upgrading the wet scrubber according to option 1, the new emission level will be 0.45 lb/MMBtu. 

Adding an exhaust gas reheat system and modifying the wet scrubber according to option 2 will reduce 

SO2 emission to 0.30 lb/MMBtu.

Table 12: Emission Rates Per Boiler

Control

Option Control Technology

Resulting SO2

Emission Rate 

(lb/MMBtu)

Existing WS 1.2 (a)

1 WS upgrade 0.45 (b)

2 WS upgrade and stack reheat 0.30 (b)

(a) 40 CFR part 60, subpart D, limit

(b) Advanced Combustion Technology, Inc. performance guarantee

SO2: EVALUATE IMPACTS AND DOCUMENT RESULTS

FMC evaluated the economic, environmental, and energy impacts associated with the three proposed 

control options for both NS-1A and NS-1B. FMC based control equipment capital costs for each of the 

proposed control options on technical evaluation and equipment vendor quotes. The same capital 

recovery factor based on 7% interest rate and control life of 15 years used to estimate the annual cost of 

NOx and PM10 control was also used to estimate annual cost to control SO2. Current FMC labor and 

service costs were used to calculate the annual operating and maintenance costs. Annual power costs and 

annualized capital costs associated with downtime for installation of pollution controls were not included. 

The following two tables summarize the economic and environmental costs.
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 15

Table 13: NS-1A & NS-1B Combined Economic Costs

Cost Baseline

Option 1: WS 

upgrade

Option 2: WS 

upgrade and 

stack reheat

Control Equipment Capital Cost $0 $4,660,211 $8,086,762

Capital Recover Factor N/A 0.1098 0.1098

Annual Capital Recovery Costs $0 $511,691 $887,926

Annual O&M Costs $0 $555,291 $2,625,112

Annual Cost of Control $0 $1,066,982 $3,513,039

Table 14: NS-1A & NS-1B Combined Environmental Costs

Baseline

Option 1: WS 

upgrade

Option 2: WS 

upgrade and 

stack reheat

SO2 Emission Rate (lb/MMBtu) 1.2 0.45 0.30

Annual SO2 Emission (tpy) (a)

9324.2 3496.6 2331.0

Annual SO2 Reduction (tpy) (a)

N/A 5827.6 6993.2

Annual Cost of Control $0 $1,066,982 $3,513,039

Cost per ton of Reduction N/A $183 $502

Incremental Cost per ton of Reduction N/A $183 $2,099

(a) Annual emissions based on individual heat input rate of 887 MMBtu/hr for 8,760 hours of operation per year.

Step 5: Evaluate visibility impacts for SO2 is addressed in the comprehensive visibility analysis covering 

all three visibility impairing pollutants and associated control options is shown below.

VISIBILITY IMPROVEMENT DETERMINATION:

The fifth of five steps in a BART determination analysis, as required by 40 CFR part 51 Appendix Y, is 

the degree of Class I area visibility improvement that results from the possible options for control 

technology. This factor was evaluated for the FMC Westvaco facility by using an EPA-approved 

dispersion modeling system (CALPUFF) to predict the change in Class I area visibility. The Division had 

previously determined that the FMC Westvaco facility was subject to BART based on the results of initial 

screening modeling that was conducted using current (baseline) emissions from the facility. The 

screening modeling, as well as more refined modeling conducted by the applicant, is described in detail 

below. 

Bridger Wilderness Area (WA) and Fitzpatrick WA are the two closest Class I areas to the FMC 

Westvaco facility, as shown in Figure 1 below. Bridger WA is located approximately 118 kilometers 

(km) northeast of FMC Westvaco and Fitzpatrick WA is located approximately 151 km northeast of the 

facility. 
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 16

Only those Class I areas most likely to be impacted by the Westvaco sources were modeled, as 

determined by source/Class I area locations, distances to each Class I area, and professional judgment 

considering meteorological and terrain factors. Areas greater than 300 km from Westvaco were excluded

from consideration. All source-Class I area distances from Westvaco to Bridger WA and Fitzpatrick WA 

exceed 50 km and are less than 300 km, thus falling within the range of recommended CALPUFF 

application. If impacts are less than the BART threshold for the Class I areas modeled, it can be 

reasonably assumed that areas at a greater distance and in directions of less frequent plume transport will 

not experience significant impacts.
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 17

Figure 1

-400 -300 -200 -100 0 100 200

LCC East (km)

FMC Westvaco and Class I Areas

-300

-200

-100

0

100

200

300

400

LCC North (km)

Billings

Casper

Lander

Pocatello

RockSpr

Sheridan

SLC

WestVaco

Bridger WA

Fitzpatrick WA

SCREENING MODELING

To determine if the FMC Westvaco facility would be subject to BART, the Division conducted 

CALPUFF modeling using three years of meteorological data. These data, from 1995-1996 and 2001, 

consisted of surface and upper-air observations and gridded output from the Mesoscale Model (MM5). 

Resolution of the MM5 data was 36-km for all three of the modeled years. Sources input to the modeling 

included the potential emissions (current operation) from three emission units at the Westvaco facility, the 

coal-fired boilers NS-1A and NS-1B and the gas-fired boiler PH-3. 
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 18

Results of the modeling showed that the 98th percentile value for the change in visibility (delta deciview 

[Δdv]) was above 0.5 Δdv for Bridger WA for all three years of meteorology, and above 0.5 Δdv for 

Fitzpatrick WA for 1996 and 2001 meteorology. As defined in EPA‟s final BART rule, a 98th percentile 

0.5 Δdv impact or more from a given source indicates that the source contributes to visibility impairment, 

and therefore is subject to BART. The results of the screening modeling are shown in the table below.

Results of the Class I Area Screening Modeling

Class I Area

Maximum 

Modeled 

Value (Δdv)

98th

Percentile 

Value (Δdv)

1995

Bridger WA 2.06 0.75

Fitzpatrick WA 1.00 0.36

1996

Bridger WA 2.79 1.30

Fitzpatrick WA 1.81 0.54

2001

Bridger WA 2.21 1.43

Fitzpatrick WA 1.24 0.63

Δdv = delta deciview

WA = wilderness area

REFINED MODELING

Because of the results of the Division‟s screening modeling, FMC was required to conduct a refined 

BART analysis that included CALPUFF visibility modeling for the facility. The modeling approach 

followed the requirements described in the Division‟s BART modeling protocol, BART Air Modeling 

Protocol - Individual Source Visibility Assessments for BART Control Analyses (WDEQ-AQD, September 

2006).

CALPUFF System

Predicted visibility impacts from the FMC Westvaco sources were determined with the EPA CALPUFF 

modeling system, which is the EPA-preferred modeling system for long-range transport. As described in 

the EPA Guideline on Air Quality Models (Appendix W of 40 CFR part 51), long-range transport is 

defined as modeling with source-receptor distances greater than 50 km. Because all modeled areas are 

located more than 50 km from the sources in question, the CALPUFF system was appropriate for use.

The CALPUFF modeling system consists of a meteorological data pre-processor (CALMET), an air 

dispersion model (CALPUFF), and post-processor programs (POSTUTIL, CALSUM, CALPOST). The 

CALPUFF model was developed as a non-steady-state air quality modeling system for assessing the 

effects of time- and space-varying meteorological conditions on pollutant transport, transformation, and 

removal. 

CALMET is a diagnostic wind model that develops hourly wind and temperature fields in a threedimensional, gridded modeling domain. Meteorological inputs to CALMET can include surface and 

upper-air observations from multiple meteorological monitoring stations. Additionally, the CALMET 
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 19

model can utilize gridded analysis fields from various mesoscale models such as MM5 to better represent 

regional wind flows and complex terrain circulations. Associated two-dimensional fields such as mixing 

height, land use, and surface roughness are included in the input to the CALMET model. The CALMET 

model allows the user to “weight” various terrain influence parameters in the vertical and horizontal 

directions by defining the radius of influence for surface and upper-air stations. 

CALPUFF is a multi-layer, Lagrangian puff dispersion model. CALPUFF can be driven by the threedimensional wind fields developed by the CALMET model (refined mode), or by data from a single 

surface and upper-air station in a format consistent with the meteorological files used to drive steady-state 

dispersion models. All far-field modeling assessments described here were completed using the 

CALPUFF model in a refined mode.

CALSUM is a post-processing program that can operate on multiple CALPUFF output files to combine 

the results for further post-processing. POSTUTIL is a post-processing program that processes 

CALPUFF concentrations and wet/dry flux files. The POSTUTIL model operates on one or more output 

data files from CALPUFF to sum, scale, and/or compute species derived from those that are modeled, and 

outputs selected species to a file for further post-processing. CALPOST is a post-processing program that

can read the CALPUFF (or POSTUTIL or CALSUM) output files, and calculate the impacts to visibility. 

All of the refined CALPUFF modeling was conducted with the version of the CALPUFF system that was 

recognized as the EPA-approved release at the time of the development of the Division‟s modeling 

protocol. Version designations of the key programs are listed in the table below.

Key Programs in CALPUFF System

Program Version Level

CALMET 5.53a 040716

CALPUFF 5.711a 040716

CALPOST 5.51 030709

Meteorological Data Processing (CALMET)

As required by the Division‟s modeling protocol, the CALMET model was used to construct the initial 

three-dimensional windfield using data from the MM5 model. Surface and upper-air data were also input 

to CALMET to adjust the initial windfield, but because of the relative scarcity of observations in the 

modeling domain, the influence of the observations was minimized. Because the MM5 data were afforded 

a high degree of influence on the CALMET windfields, the Division obtained MM5 data at 12-km 

resolution that spanned the years 2001-2003. Surface, upper-air, and precipitation data for the domain was 

incorporated into the CALMET windfield. Locations of the various observations are shown in the figure 

below. The Division provided the BART applicants all raw meteorological inputs for the CALMET 

model.

Default settings were used in the CALMET input files for most of the technical options. The following 

table lists the key user-defined CALMET settings that were selected. 
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 20

Key User-Defined CALMET Settings

Variable Description Value 

PMAP Map projection LCC 

DGRIDKM Grid spacing (km) 4 

NZ Number of layers 10 

ZFACE Cell face heights (m) 0, 20, 40, 100, 140, 320, 

580, 1020, 1480, 2220, 3400 

RMIN2 Minimum distance for extrapolation -1 

IPROG Use gridded prognostic model output 14 

RMAX 1 Maximum radius of influence (surface 

layer, km) 

30 

RMAX 2 Maximum radius of influence (layers 

aloft, km) 

50 

TERRAD Radius of influence for terrain (km) 15 

R1 Relative weighting of first guess wind 

field and observations (km) 

5 

R2 Relative weighting aloft (km) 25 
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 21

-400 -300 -200 -100 0 100 200 300

LCC East (km)

CALMET Surface, Upper-Air, and Precipitation Stations

-300

-200

-100

0

100

200

300

400

LCC North (km)

BIL

CPR

CYS

LND

PIH

RKS

SHR

SLC

WestVaco

Precipitation Station

Surface Station

Upper-Air Station

RIW

DEN
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 22

CALPUFF Modeling Setup

To allow chemical transformations with the recommended CALPUFF chemistry mechanism 

(MESOPUFF II), the model required input of background ozone and ammonia. For ozone, hourly data 

collected from the following stations were used:

Rocky Mountain National Park (NP), Colorado

Craters of the Moon National Monument, Idaho

Highland, Utah

Thunder Basin, Wyoming

Yellowstone NP, Wyoming

Centennial, Wyoming

Pinedale, Wyoming

For any hour that was missing ozone data from all stations, a default value of 44 parts per billion (ppb) 

was used by the model as a substitute. For ammonia, a domain-wide background value of 2 ppb was 

used. 

Discrete receptors for the Class I areas that were modeled (Bridger WA and Fitzpatrick WA) were 

provided by the Division. 

CALPUFF Inputs – Baseline and Control Options

The first step in the refined modeling analysis was to perform visibility modeling for current operations at 

the facility (baseline), followed by modeling for the various control options. Baseline source release 

parameters and emissions are shown in the table below, followed by tables with data for the control 

options. 
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 23

Source Parameters and Emissions for the Baseline Scenario

Parameter

Baseline

#6 Coal-Fired 

Boiler NS-1A

#7 Coal-Fired 

Boiler NS-1B

#4 Gas-Fired 

Boiler PH-3

SO2 Control - Wet Scrubber 

NOx Control - Combustion 

Controls 

 PM Control - ESP 

SO2 Control -

none 

NOx Control -

Combustion 

Controls

PM Control -

none

Heat Input (MMBtu/hr) 887 887 333.6

Base Elevation (m) 1922 1922 1899

Stack Height (m) 91.4 91.4 21.3

Stack Diameter (m) 3.51 3.51 2.29

Stack Temperature (K) 414.8 414.8 394.3

Exit Velocity (m/s) 17.56 17.56 8.34

SO2 Emissions (lb/MMBtu) 1.2 0.45 0.0006

SO2 Emissions (lb/hr) 1064.4 1064.4 0.2

H2SO4 Emissions (lb/MMBtu) 0.015 0.015 0

H2SO4 Emissions (lb/hr) 13.4 13.4 0

NOx Emissions (lb/MMBtu) 0.7 0.7 0.23

NOx Emissions (lb/hr) 620.9 620.9 76.7

PMF Emissions (lb/MMBtu) 0.0507 0.0507 0.0075

PMF Emissions (lb/hr) 45.0 45.0 2.5

Note: H2SO4 emissions modeled in CALPUFF as SO4 [H2SO4 * (96/98)] 

ESP = electrostatic precipitator

K = Kelvin

lb/hr = pounds per hour

lb/MMBtu = pounds per million British thermal units

m = meters

m/s = meters per second

MMBtu/hr = million British thermal units per hour

NOx = nitrogen oxides

PMF = fine particulate matter

SO2 = sulfur dioxide
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 24

Source Parameters and Emissions for BART Control Options

Parameter

BART Control 

Scenario 1

BART Control 

Scenario 2

BART Control 

Scenario 3

BART Control 

Scenario 4

BART Control 

Scenario 5

NOx Option 1 -

LNB/OFA

(Baseline SO2)

NOx Option 2 -

LNB/OFA & 

SNCR

(Baseline SO2)

NOx Option 3 -

LNB/OFA & SCR

(Baseline SO2)

SO2 Option 1 –

Scrubber Upgrade, 

New Bypass

(Baseline NOx)

SO2 Option 2 –

Scrubber Upgrade, 

New Bypass & 

Reheat

(Baseline NOx)

Boiler 

NS-1A

Boiler 

NS-1B

Boiler 

NS-1A

Boiler 

NS-1B

Boiler 

NS-1A

Boiler 

NS-1B

Boiler 

NS-1A

Boiler 

NS-1B

Boiler 

NS-1A

Boiler 

NS-1B

SO2 Emissions (lb/MMBtu) 1.2 1.2 1.2 1.2 1.2 1.2 0.45 0.45 0.30 0.30

SO2 Emissions (lb/hr) 1064.4 1064.4 1064.4 1064.4 1064.4 1064.4 399.2 399.2 266.1 266.1

HS2O4 Emissions (lb/hr) 13.4 13.4 13.4 13.4 13.4 13.4 10.3 10.3 9.6 9.6

NOx Emissions (lb/MMBtu) 0.35 0.35 0.21 0.21 0.1 0.1 0.7 0.7 0.7 0.7

NOx Emissions (lb/hr) 310.4 310.4 186.3 186.3 88.7 88.7 620.9 620.9 620.9 620.9

PMF Emissions (lb/hr) 45.0 45.0 45.0 45.0 45.0 45.0 45.0 45.0 45.0 45.0

Note: H2SO4 emissions (sulfuric acid mist) modeled in CALPUFF as SO4 [H2SO4 * (96/98)]

lb/hr = pounds per hour

lb/MMBtu = pounds per million British thermal units

LNB/OFA = low NOx burners/overfire air

NOx = nitrogen oxides

PMF = particulate matter

SCR = selective catalytic reduction

SNCR = selective non-catalytic reduction

SO2 = sulfur dioxide
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 25

Source Parameters and Emissions for the Proposed BART Option

Parameter

Proposed BART

SO2 Option 1 -

Scrubber Upgrade 

 NOx Option 1 -

LNB/OFA

Boiler 

NS-1A

Boiler

NS-1B

Stack Temperature (K) 349.8 349.8

Exit Velocity (m/s) 17.56 17.56

SO2 Emissions (lb/MMBtu) 0.45 0.45

SO2 Emissions (lb/hr) 399.2 399.2

HS2O4 Emissions (lb/hr) 10.3 10.3

NOx Emissions (lb/MMBtu) 0.35 0.35

NOx Emissions (lb/hr) 310.4 310.4

PMF Emissions (lb/hr) 45.0 45.0

Note: H2SO4 emissions (sulfuric acid mist) 

modeled in CALPUFF as SO4 [H2SO4 * (96/98)]

K = Kelvin

lb/hr = pounds per hour

LNB/OFA = low NOx burners/overfire air

m/s = meters per second

lb/MMBtu = pounds per million British thermal units

NOx = nitrogen oxides

PMF = particulate matter

SO2 = sulfur dioxide

Note that the gas-fired boiler is not included in the tables for the control option modeling. This is 

because baseline modeling demonstrated that the contribution to visibility impairment from that 

source was negligible, as described later. 

Visibility Post-Processing (CALPOST) Setup

The changes in visibility were calculated using Method 6 within the CALPOST post-processor. 

Method 6 requires input of monthly relative humidity factors [f(RH)] for each Class I area. 

Monthly f(RH) factors that were used for Bridger WA and Fitzpatrick WA are shown in the table 

below. 
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 26

Relative Humidity Factors for CALPOST

Month

Bridger WA

Fitzpatrick WA

January 2.50

February 2.30

March 2.30

April 2.10

May 2.10

June 1.80

July 1.50

August 1.50

September 1.80

October 2.00

November 2.50

December 2.40

According to the final BART rule, natural background conditions as a reference for determination 

of the Δdv change within CALPOST should be representative of the 20% best natural visibility 

days. EPA BART guidance provides the 20% best days deciview values for each Class I area on 

an annual basis, but does not provide species concentration data for the 20% best background 

conditions. 

Species concentrations corresponding to the 20% best days were calculated for each Class I area

by scaling back the annual average concentrations given in Table 2-1 of the EPA document

Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule. A separate 

scaling factor was derived for each Class I area such that, when multiplied by the guidance table 

annual concentrations, the 20% best days dv value for that particular Class I area would be 

calculated. The scaled aerosol concentrations were averaged for the Bridger WA and Fitzpatrick 

WA because of their geographical proximity and similar annual background visibility. The 20% 

best days aerosol concentrations that were used for each month are listed in the table below.
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 27

Natural Background Aerosol Concentrations (μg/m3)

Aerosol

Component

Fitzpatrick WA

Bridger WA

Ammonium Sulfate 0.045

Ammonium Nitrate 0.038

Organic Carbon 0.178

Elemental Carbon 0.008

Soil 0.189

Coarse Mass 1.136

Visibility Post-Processing Results

The results of the baseline and control option visibility modeling for each of the two coal-fired 

boilers are shown in the tables below. Baseline 98th percentile results for each of those units 

exceeded 0.05 Δdv at Bridger WA for 2001 and 2003 meteorology. The contribution from the 

gas-fired boiler (PH-3) is negligible. The highest predicted 98th percentile impact from PH-3 for 

any of the three years is only 0.05 Δdv at Bridger WA and only 0.02 Δdv at Fitzpatrick WA, and 

therefore PH-3 does not contribute to Class I area visibility impairment. The conclusion drawn 

from the baseline modeling was that further modeling for the BART control options would focus 

on reducing emissions from the coal-fired boilers NS-1A and NS-1B.

The refined modeling also focused on reductions in NOx and SOx emissions rather than reductions 

in particulate (PM) emissions. This is because the effect of reduced PM from the proposed 

control options was not significant. Even with the most stringent control option (fabric filter 

before scrubber), the difference in the predicted 98th percentile visibility impact from the baseline 

condition from both coal-fired units combined using 2001 meteorology was only 0.03 Δdv at 

Bridger WA and 0.02 Δdv at Fitzpatrick WA.

The control option proposed by FMC as BART results in an average reduction of 0.3 Δdv in the 

98th percentile result at Bridger WA as compared to the baseline conditions for each unit, and a 

reduction of 0.2 Δdv in the 98th percentile result at Fitzpatrick WA as compared to the baseline 

conditions for each unit. As for the predicted number of days above 0.5 Δdv at Bridger WA and 

Fitzpatrick WA, the average reduction is 7 days and 2 days, respectively, between the baseline 

and the proposed option for each unit. These results show that under each control option, the 

facility would not contribute to Class I area visibility impairment (i.e., the 98th percentile results 

are less than 0.5 Δdv).
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 28

CALPUFF Visibility Modeling Results: NS-1A

Scenario/

Class I Area

2001 2002 2003

98th

Percentile 

Value 

(Δdv)

Total

No. of 

Days > 

0.5 Δdv

98th 

Percentile 

Value 

(Δdv)

Total

No. of 

Days > 

0.5 Δdv

98th 

Percentile 

Value 

(Δdv)

Total

No. of 

Days > 

0.5 Δdv

Baseline

Bridger WA 0.566 10 0.429 5 0.538 11

Fitzpatrick WA 0.327 4 0.311 2 0.263 1

NOx Control Option 1 – LNB/OFA

Bridger WA 0.432 5 0.302 3 0.393 2

Fitzpatrick WA 0.252 2 0.247 1 0.206 0

NOx Control Option 2 – LNB/OFA & SNCR

Bridger WA 0.368 5 0.256 2 0.340 1

Fitzpatrick WA 0.221 1 0.203 1 0.181 0

NOx Control Option 3 – SCR

Bridger WA 0.321 2 0.225 1 0.295 1

Fitzpatrick WA 0.194 1 0.191 1 0.161 0

SO2 Control Option 1 – Scrubber Upgrade, New Bypass

Bridger WA 0.404 6 0.358 4 0.386 2

Fitzpatrick WA 0.241 1 0.234 1 0.187 0

SO2 Control Option 2 - Scrubber Upgrade, New Bypass & Reheat

Bridger WA 0.384 5 0.339 4 0.348 2

Fitzpatrick WA 0.215 1 0.219 1 0.169 0

Proposed BART – LNB/OFA (NOx), Scrubber Upgrade/New Bypass (SO2)

Bridger WA 0.275 3 0.179 1 0.260 1

Fitzpatrick WA 0.143 1 0.123 1 0.128 0

Δdv = delta deciview

LNB/OFA = low NOx burners/overfire air

WA = wilderness area
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 29

CALPUFF Visibility Modeling Results: NS-1B

Scenario/

Class I Area

2001 2002 2003

98th 

Percentile 

Value 

(Δdv)

Total

No. of 

Days > 

0.5 Δdv

98th 

Percentile 

Value 

(Δdv)

Total

No. of 

Days > 

0.5 Δdv

98th 

Percentile 

Value 

(Δdv)

Total

No. of 

Days > 

0.5 Δdv

Baseline

Bridger WA 0.566 10 0.429 5 0.536 11

Fitzpatrick WA 0.327 4 0.312 2 0.263 1

NOx Control Option 1 – LNB/OFA

Bridger WA 0.432 5 0.303 3 0.394 2

Fitzpatrick WA 0.252 2 0.248 1 0.206 0

NOx Control Option 2 – LNB/OFA & SNCR

Bridger WA 0.368 5 0.256 2 0.340 1

Fitzpatrick WA 0.221 1 0.204 1 0.181 0

NOx Control Option 3 – SCR

Bridger WA 0.321 2 0.225 1 0.295 1

Fitzpatrick WA 0.193 1 0.192 1 0.162 0

SO2 Control Option 1 – Scrubber Upgrade, New Bypass

Bridger WA 0.404 6 0.357 4 0.386 2

Fitzpatrick WA 0.241 1 0.235 1 0.187 0

SO2 Control Option 2 - Scrubber Upgrade, New Bypass & Reheat

Bridger WA 0.384 5 0.339 4 0.349 2

Fitzpatrick WA 0.216 1 0.219 1 0.169 0

Proposed BART – LNB/OFA (NOx), Scrubber Upgrade/New Bypass (SO2)

Bridger WA 0.275 3 0.179 1 0.260 1

Fitzpatrick WA 0.143 1 0.123 1 0.129 0

Δdv = delta deciview

LNB/OFA = low NOx burners/overfire air

WA = wilderness area

BART DETERMINATION:

NATURAL GAS-FIRED BOILER (PH-3)

The highest predicted 98th percentile impact from PH-3 for any of the three years is only 0.05 Δdv

at Bridger WA and only 0.02 Δdv at Fitzpatrick WA, significantly below the 0.5 Δdv threshold.

Based on the results of the baseline visibility modeling, the Division determined that the gas-fired 

boiler (PH-3) at the Westvaco facility does not contribute to Class I area visibility impairment at 

the Bridger WA and Fitzpatrick WA and no additional controls are required by BART for PH-3.
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 30

COAL-FIRED BOILERS (NS-1A and NS-1B)

FMC‟s proposed BART control option results in an average reduction of 0.3 Δdv in the 98th

percentile result at Bridger WA as compared to the baseline conditions for each unit, and a 

reduction of 0.2 Δdv in the 98th percentile result at Fitzpatrick WA as compared to the baseline 

conditions for each unit. The 98th percentile values for both units, NS-1A and NS-1B, were 

below a 0.3 Δdv increase from background conditions for all three years of meteorology. 

Therefore, the proposed BART controls for each unit reduce visibility impacts below the 0.5 Δdv

threshold used in the screening analysis to determine if sources contribute to visibility 

impairment. Based on the results of this analysis, the Division has determined that the 

installation of low NOx burners with enhanced OFA meeting NOx emission limits of 0.35

lb/MMBtu (30-day rolling average) and 310.5 lb/hr (30-day rolling) represents BART for each of 

the coal-fired boilers, NS-1A and NS-1B. No additional controls are required by BART for 

PM/PM10 emissions from the two boilers and they will continue to meet a PM/PM10 emission 

limit of 0.05 lb/MMBtu as set in Air Quality Permit MD-5723.

WESTERN BACKSTOP SULFUR DIOXIDE TRADING PROGRAM:

Wyoming is a §309 state and will participate in the Western Backstop Sulfur Dioxide Trading 

Program should it be triggered. FMC Westvaco evaluated an SO2 emission rate of 0.45 

lb/MMBtu from the coal-fired boilers with upgrades to the existing alkali wet scrubbers in the 

BART application and determined that the emission rate is achievable. In accordance with

Wyoming‟s §309 Regional Haze SIP and WAQSR Chapter 6, Section 9, FMC will not be 

required to meet the proposed emission limit under BART. Instead, FMC will be required to 

participate in the emission trading program authorized under Chapter 14 of the WAQSR should 

the program be triggered.

CHAPTER 6, SECTION 4 – PREVENTION OF SIGNIFICANT DETERIORATION 

(PSD):

FMC‟s Westvaco Facility is a “major emitting facility” under Chapter 6, Section 4, of the 

Wyoming Air Quality Standards and Regulations because emissions of a criteria pollutant are 

greater than 250 tpy. Installation of the LNB and OFA as required by BART will result in a CO 

emission increase above 40 tpy. Under Chapter 6, Section 4, FMC would be required to submit a 

permit application addressing the increase in CO emissions and Prevention of Significant 

Deterioration (PSD) applicability prior to commencing construction to install the LNB and OFA 

controls. However, FMC has already permitted the installation of the controls determined to be 

BART, for both units NS-1A and NS-1B in Air Quality Permit MD-5723. Upon installation of 

the permitted controls, NS-1A and NS-1B will be subject to a NOx limit of 0.39 lb/MMBtu on a 

30-day rolling average, a CO limit of 0.29 lb/MMBtu, SO2 limits of 1.2 lb/MMBtu on a 2-hour 

fixed average and 0.54 lb/MMBtu on a 30-day rolling average, and a PM limit of 0.05 lb/MMBtu 

or 45 lb/hr. As of August 22, 2007 these limits are in effect for NS-1A because FMC installed 

LNB and wet alkali scrubber upgrades on the unit.
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 31

CHAPTER 5, SECTION 2 – NEW SOURCE PERFORMANCE STANDARDS (NSPS):

The installation of the LNB and OFA and wet alkali scrubber upgrades will not change New 

Source Performance Standard applicability for the two coal-fired boilers NS-1A and NS-1B at the 

Westvaco Facility.

CHAPTER 5, SECTION 3 – NATIONAL EMISSION STANDARDS FOR HAZARDOUS 

AIR POLLUTANTS (NESHAPs) AND CHAPTER 6, SECTION 6 – HAZARDOUS AIR 

POLLUTANT (HAP) EMISSIONS AND MAXIMUM AVAILABLE CONTROL 

TECHNOLOGY (MACT):

The installation of the LNB and OFA and wet alkali scrubber upgrades will not change 40 CFR 

part 63 applicability for the two coal-fired boilers NS-1A and NS-1B at the Westvaco Facility.

CHAPTER 6, SECTION 3 – OPERATING PERMIT:

The Westvaco Facility is a major source under Chapter 6, Section 3 of the Wyoming Air Quality 

Standards and Regulations. Operating Permit 3-1-132 was issued for the facility on October 24, 

2007. In accordance with Chapter 6, Section 3 of the Wyoming Air Quality Standards and 

Regulations (WAQSR), FMC Wyoming Corporation will need to modify their operating permit

to include the changes authorized in this permitting action.

CONCLUSION:

The Division is satisfied that the FMC Wyoming Corporation‟s Westvaco Facility will comply 

with all applicable Wyoming Air Quality Standards and Regulations. The Division proposes to 

issue a BART Air Quality Permit for the Westvaco Facility modification.

PROPOSED PERMIT CONDITIONS:

The Division proposes to issue an Air Quality Permit to FMC Wyoming Corporation for the 

modification of the Westvaco Facility with the following conditions:

1. Authorized representatives of the Division of Air Quality be given permission to enter 

and inspect any property, premise or place on or at which an air pollution source is 

located or is being constructed or installed for the purpose of investigating actual or 

potential sources of air pollution, and for determining compliance or non-compliance 

with any rules, standards, permits or orders.

2. All substantive commitments and descriptions set forth in the application for this permit, 

unless superseded by a specific condition of this permit, are incorporated herein by this 

reference and are enforceable as conditions of this permit.

3. That FMC Wyoming Corporation shall modify their Operating Permit in accordance with 

Chapter 6, Section 9(e)(iv) and Chapter 6, Section 3 of the WAQSR.
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 32

4. All notifications, reports and correspondence associated with this permit shall be 

submitted to the Stationary Source Compliance Program Manager, Air Quality Division, 

122 West 25th Street, Cheyenne, WY 82002 and a copy shall be submitted to the District 

Engineer, Air Quality Division, 510 Meadowview Drive, Lander, WY 82520.

5. Effective January 1, 2009, emissions from boiler NS-1A shall not exceed the levels

below. The limits shall apply during all operating periods.

Pollutant lb/MMBtu lb/hr tpy

NOx 0.35 (30-day rolling) 310.5 (30-day rolling) 1360.0

6. Effective July 1, 2009, emissions from boiler NS-1B shall not exceed the levels below. 

The limits shall apply during all operating periods.

Pollutant lb/MMBtu lb/hr tpy

NOx 0.35 (30-day rolling) 310.5 (30-day rolling) 1360.0

7. Performance tests shall be conducted prior to the effective dates set forth in conditions 5 

and 6 and shall consist of the following:

i. Coal-fired Boilers (NS-1A, NS-1B):

NOx Emissions – Compliance with the NOx 30-day rolling average shall be 

determined using a continuous emissions monitoring system (CEMS) certified in 

accordance with 40 CFR part 60.

8. Prior to any performance testing required by this permit, a test protocol shall be 

submitted to the Division for approval, at least 30 days prior to testing. Results of the 

tests shall be submitted to this office within 45 days of completing the tests.

9. If the Western Backstop Sulfur Dioxide Trading Program is triggered in accordance with 

Chapter 14 then FMC Wyoming Corporation shall participate in the trading program as 

required by Chapter 14, Section 2(c)(i).
FMC Wyoming Corporation

AP-6045 BART Application Analysis

Page 33

10. After the effective dates set forth in conditions 5 and 6, compliance with the limits set 

forth in this permit for the NS-1A and NS-1B coal-fired boilers shall be determined with 

data from the existing continuous monitoring systems as follows:

a. Exceedances of the NOx limits shall be defined as follows:

i. Any 30-day rolling average of NOx emissions which exceeds the 

lb/MMBtu limits calculated in accordance with 40 CFR part 60, subpart 

D.

ii. Any 30-day rolling average calculated using valid data (output 

concentration and average hourly volumetric flowrate) from the existing 

CEM equipment which exceeds the lb/hr NOx limit established in this 

permit. Valid data shall meet the requirements of WAQSR, Chapter 5, 

Section 2(j) and follow the compliance provisions and monitoring 

requirements of §60.48Da and §60.49Da. The 30-day average emission 

rate shall be calculated as the arithmetic average of hourly emissions 

with valid data during the previous 30-day period.

b. FMC Wyoming Corporation shall comply with all reporting and record keeping 

requirements as specified in WAQSR, Chapter 5, Section 2(g) and 40 CFR part 

60, subpart D. All excess emissions shall be reported using the procedures and 

reporting format specified in WAQSR, Chapter 5, Section 2(g).

11. Records required by this permit shall be maintained for a period of at least five (5) years 

and shall be made available to the Division upon request.
Appendix A

Facility Location