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TECHNICAL MEMORANDUM 

TO: Tina Ndoh, U.S. EPA/OAQPS/SPPD - Minerals and Manufacturing Group 

FROM: Eastern Research Group, Inc.

DATE: July 21, 2015

SUBJECT: Beyond-the-Floor Analysis for Phosphate Rock Calciners at Phosphoric Acid 

Manufacturing Plants – Final Rule

1.0 INTRODUCTION 

The U.S. Environmental Protection Agency (EPA), under section 112 of the Clean Air 

Act (CAA), is required to establish national emissions standards for Hazardous Air Pollutants 

(NESHAP) emitted from phosphoric acid and phosphate fertilizer production facilities. The 

complete set of HAP is listed under CAA section 112(b). EPA must also examine more stringent 

“beyond-the-floor” (BTF) regulatory options to determine MACT. Unlike the minimum 

stringency requirements of the floor, EPA must consider various impacts of the more stringent 

regulatory options such as costs and emissions reductions in determining whether MACT 

standards are to reflect BTF requirements. 

Upon review of the phosphoric acid and phosphate fertilizer source categories in 

conjunction with the risk and technology review, the EPA identified emission sources that do not 

have MACT standards for all pollutants emitted. As a result, the EPA determined that MACT 

standards should be established for mercury (Hg) and total fluoride from the phosphate rock 

calciners. We then evaluated BTF options for Hg and total fluoride. For total fluorides we were 

unable to identify any cost effective BTF technologies. Emissions of Hg from the phosphate rock 

calciners are the largest source of Hg emissions from this industry and comprise approximately 

80 percent of the Hg emissions from the combined source categories Phosphoric Acid 

Manufacturing and Phosphate Fertilizer Production. BTF options for Hg emissions were 

identified for phosphate rock calciners that would be more stringent than the MACT floor level 

of control. 

This memorandum documents the phosphate rock calciner BTF evaluation for total 

fluorides and describes the cost and emissions reductions for phosphate rock calciners achieved 

by applying BTF regulatory options for Hg. Section 2.0 presents the total fluorides BTF 

evaluation. Sections 3.0 and 4.0 discuss the identification of more stringent Hg controls that were 

reviewed for this analysis for existing and new sources, respectively. Section 5.0 discusses the 

methodology used to estimate costs and emissions reductions of the more stringent Hg controls, 

and Section 6.0 summarizes the results of the Hg BTF analysis. 
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2.0 BTF EVALUATION FOR TOTAL FLUORIDES 

Each of the six phosphate rock calciners currently controls emissions with a venturi 

scrubber and wet electrostatic precipitator (WESP). Therefore, the phosphate rock calciners 

currently employ technology that will control total fluoride emissions. However, we evaluated 

the addition of a packed bed scrubber for additional total fluoride control for the BTF analysis. 

Test data were available from one phosphate rock calciner, which set the MACT floor limit. 

Using this data, we determined that installation of an additional scrubber to control total fluoride 

emissions was not cost effective, and thus we did not set a BTF limit for total fluorides from 

phosphate rock calciners. Of note, phosphate rock calciner total fluoride emissions are 

comparable to total fluoride emissions from other controlled emission points at phosphoric acid 

manufacturing and phosphate fertilizer production facilities and are not a significant source of 

total fluoride emissions. 

3.0 IDENTIFICATION OF MORE STRINGENT MERCURY CONTROLS FOR 

EXISTING SOURCES 

The emissions reductions and costs of the MACT floor level of control for Hg were 

estimated based on the following information: 

1. Hg test data were only available from two phosphate rock calciners, as only one 

facility operates phosphate rock calciners in the production of phosphoric acid; 

therefore, the two phosphate rock calciners set the Hg MACT floor limit. 

2. The cost of the one facility to meet the Hg MACT floor for phosphate rock 

calciners was estimated based on periodic testing and associated recordkeeping 

and reporting requirements. No additional controls were anticipated. 

For existing phosphate rock calciners it was determined that emissions reductions of Hg 

could be achieved by routing the phosphate rock calciner exhaust through a Hg control device, 

such as a fixed-bed (FB) carbon adsorption system or activated carbon injection (ACI). Based on 

a review of vendor supplied information and previous control technology studies1

, a FB carbon 

adsorption system would achieve at least a 90 percent reduction of the Hg in the calciner exhaust 

stream. Similar emissions reductions are anticipated with ACI (EPA, 1997; Jones, 2007). 

During the comment period for the proposed rule PCS Aurora (the one facility with 

phosphate rock calciners) contracted with URS to review our Hg control technology evaluation. 

The complete evaluation is available in their commenter letter, docket item EPA-HQ-OAR2012-0522-0037. As a result of this additional information, the EPA agreed that a traditional 

fixed-bed carbon adsorption system and ACI installed prior to or after the existing WESP are not 

technically feasible for phosphate rock calciners. However, information in the PCS Aurora 

comment letter noted that certain other control technologies would be feasible: use of ACI 

installed upstream of the existing venturi scrubber and the Gore Mercury Control System 

(GMCS). We have, therefore, revised the BTF analysis for Hg based on installing ACI upstream 

 

1

 Refer to vendor information from Calgon Carbon Corporation (Calgon, 2006, Calgon, 2012a, Calgon 2012b), APC 

Technologies, Inc. (APC, 2011), and EPA’s Mercury Study Report to Congress (EPA, 1997). 
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of the existing venturi scrubber and installing GMCS. See section V.C.3.a.i of the final preamble 

for the EPA’s complete response regarding Hg control devices and the BTF Hg limit. 

4.0 IDENTIFICATION OF MORE STRINGENT MERCURY CONTROLS FOR 

NEW SOURCES 

Data from two phosphate rock calciners were available to EPA to establish the existing 

and new source MACT floor emission limits for Hg. By rounding up to two significant figures, 

the new source floor was equivalent to the existing source floor. As a result, the same BTF 

options available for existing phosphate rock calciners are available for new phosphate rock 

calciners. 

5.0 METHODOLOGY USED TO ESTIMATE COSTS AND EMISSION 

REDUCTIONS FOR MERCURY CONTROLS 

Emissions reductions of Hg from application of the BTF controls relative to the current 

performance were calculated for the six phosphate rock calciners at the PCS Aurora facility 

using the following procedure. First, baseline Hg emissions were estimated using the facility 

reported test data and operating hours for one of the tested calciners. Then emissions were 

estimated for the other five calciners by calculating a ratio of annual operating hours for each 

phosphate rock calciner to the annual operating hours for the tested phosphate rock calciners; this 

ratio was then multiplied by the annual emissions for the tested calciners. See the memorandum 

“Emissions Data Used in Residual Risk Modeling: Phosphoric Acid and Phosphate Fertilizer 

Production Source Categories” for the annual Hg emissions estimated for each phosphate rock 

calciner based on data from the Ontario-Hydro test method (ERG 2014). Ontario-hydro data was 

used for the Risk Assessment because this method provides speciated Hg results. However, 

Method 30B Hg data were used to calculate the BTF limit and facilities will use also use Method 

30B to determine compliance. Therefore, baseline emissions and emissions reductions for this 

memorandum are based on Method 30B data. The total Hg baseline emissions using Method 30B 

for the six phosphate rock calciners equals 169 pounds per year. 

As previously described, it is assumed that Hg emission reductions of approximately 

90 percent are possible with appropriate control technology. However, the BTF Hg numerical 

limit of 1.4E-02 milligrams per dry standard cubic meter corrected to a three percent oxygen 

basis represents an 86 percent reduction because variability in the test data was taken into 

account when determining the emission limit. Therefore, annual Hg emissions reductions as a 

result of the phosphate rock calciners meeting the BTF numerical limit were calculated by 

multiplying the annual Hg baseline emissions by the percent reduction necessary to comply with 

the BTF Hg limit (86 percent). This results in Hg emissions reductions of approximately 

145 pounds per year. 

Using the site-specific costs that were provided in the PCS Aurora commenter letter (see 

docket item EPA-HQ-OAR-2012-0522-0037), costs were determined for the BTF Hg analysis. 

Gore Mercury Control System 

The cost of adding GMCS for control of Hg from the phosphate rock calciner exhausts 

was estimated in the PCS Aurora comment letter and we are maintaining their cost estimate for 
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our BTF Hg analysis. Capital costs for GMCS were based on vendor data provided by W.L. 

Gore & Associates to URS, on behalf of PCS Aurora. Capital costs for the GMCS are 

enumerated in Figure 10 of Attachment A in the PCS comment letter. Annual costs for GMCS 

are presented in Appendix B-4 of Attachment A in the PCS comment letter. 

Activated Carbon Injection Cost 

The cost estimate for installing ACI prior to the existing venturi scrubber was estimated 

based on data provided in the PCS Aurora commenter letter. ACI capital costs were based on 

vendor data provided by ADA to URS, on behalf of PCS Aurora; see Figure 6 of Attachment A 

in the PCS comment letter. Annual costs for ACI are presented in Appendix A-4 of Attachment 

A in the PCS comment letter. However, we are revising their annual cost estimate by applying 

carbon injection rates of 5 lb/MMacf and 10 lb/MMacf, instead of 30 lb/MMacf. The rationale 

for using lower carbon injection rates is provided in section V.C.3.a.i of the final preamble. See 

Attachment A for the revised ACI annual cost calculations. 

6.0 MERCURY BTF ANALYSIS RESULTS 

Applying BTF control to reduce Hg emissions from the six existing phosphate rock 

calciners is estimated to result in a total capital investment (TCI) (2014 dollars) of approximately 

$21.15 million for ACI installed upstream of the existing venturi scrubber or $32 million for 

GMCS. Applying BTF control to reduce Hg emissions from the six existing phosphate rock 

calciners is expected to result in a total annualized cost (TAC) (2014$) ranging from $4.32 

million (using a carbon injection rate of 5 lb/MMacf) to $5.28 million (using a carbon injection 

rate of 10 lb/MMacf) for ACI installed upstream of the existing venturi scrubber or $5.78 million 

for GMCS. Reducing phosphate rock calciner emissions to the BTF limit (an 86 percent 

reduction) would achieve Hg reductions of 145 pounds per year (based on the results of the U.S. 

EPA Method 30B test results). The cost effectiveness for ACI installed upstream of the existing 

venturi scrubber was estimated to range from $29,800 to $36,400 per pound of Hg and the costeffectiveness for GMCS was estimated to be $39,800 per pound of Hg. Table 5-1 presents a 

summary of the BTF analysis for existing phosphate rock calciners. The BTF Hg controls 

evaluated were technically feasible. Because ACI installed upstream of the existing venturi 

scrubber was the lower cost option, only this control technology was considered regarding the 

economic impact and cost-effectiveness of the BTF limit. GMCS data are presented in Table 5-1 

for completeness.

Table 5-1. Summary of Hg Beyond-the-Floor Analysis Results for 

Existing Phosphate Rock Calciners 

BTF Control Technology 

Scenario

TCI 

(2013 $)

TAC[1]

(2013 $)

Hg Emissions 

Reduction 

(pounds/year) 

Cost 

Effectiveness 

($/pound of 

Hg) 

ACI (Installed Upstream of the 

Existing Venturi Scrubber) – Carbon 

Injection Rate of 5 lb/MMacf 

$21,150,000 $4,320,000 145 $29,800 
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ACI (Installed Upstream of the 

Existing Venturi Scrubber) – Carbon 

Injection Rate of 10 lb/MMacf 

$21,150,000 $5,280,000 145 $36,400 

GMCS $32,000,000 $5,780,000 145 $39,800 

[1] – Calculated using a 7 percent discount factor.

BTF – Beyond-the-floor 

TCI – Total capital investment for the BTF option 

TAC – Total annual cost for the BTF option 

$/pound – Dollars per pound 

After consider the economic impact to PCS Aurora, we determined the BTF limit for 

existing phosphate rock calciners would impose a significant economic impact to PCS Aurora, 

and as such, we are not finalizing the BTF Hg limit for existing phosphate rock calciners. We are 

finalizing a MACT floor Hg limit of 0.14 mg Hg/dscm @ 3% O2 for existing phosphate rock 

calciners and do not anticipate that any facilities will need to install a new control device to meet 

the existing phosphate rock calciner Hg limit. 

We also evaluated the BTF Hg limit for new phosphate rock calciners. We estimated the 

costs and emission reductions for installing a new phosphate rock calciner; see Table 5-2. These 

estimates were based on the same costs provided by PCS Aurora, and assumes the new 

phosphate rock calciner has similar emissions as the existing phosphate rock calciners at PCS 

Aurora. Installing ACI upstream of the existing venturi scrubber was considered to be cost 

effective for new sources and facilities should be better able to plan for the costs of controls. As 

a result, it was determined that 90 percent Hg reduction is achievable and the new source BTF 

limit for Hg is 10 percent of the calculated MACT limit. We are finalizing the proposed BTF Hg 

limit (i.e., 0.014 mg Hg/dscm @ 3% O2) for new phosphate rock calciners. We are not aware of 

any new phosphate rock calciners that are under development, and therefore, there will not be 

near-term costs for this limit. See section V.C.3.a.i of the final preamble for the complete BTF 

Hg limit response and discussion. 

Table 5-2. Summary of Hg Beyond-the-Floor Analysis Results for 

New Phosphate Rock Calciners 

BTF Control Technology 

Scenario

TCI 

(2013 $)

TAC[1]

(2013 $)

Hg Emissions 

Reduction 

(pounds/year) 

Cost 

Effectiveness 

($/pound of 

Hg) 

ACI (Installed Upstream of the 

Existing Venturi Scrubber) – Carbon 

Injection Rate of 5 lb/MMacf 

$3,500,000 $720,000 24 $29,800 

ACI (Installed Upstream of the 

Existing Venturi Scrubber) – Carbon 

Injection Rate of 10 lb/MMacf 

$3,500,000 $880,000 24 $36,400 

[1] – Calculated using a 7 percent discount factor.

BTF – Beyond-the-floor 

TCI – Total capital investment for the BTF option 

TAC – Total annual cost for the BTF option 

$/pound – Dollars per pound 

 
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7.0 REFERENCES 

APC, 2011. “Air Emission Control Systems and Service MercPure Series Mercury Emission 

Control Systems.” APC Technologies, Inc. 24 October, 2011. 

http://www.apctechnologies.net/pdf/APC-MercPure.pdf 

Calgon, 2006. “HGR® for Mercury Removal Granular Activated Carbon.” Calgon Carbon 

Corporation. CPM-PB1047-0406. 

http://www.calgoncarbon.com/carbon_products/documents/HGRforMercuryRemoval.pdf 

Calgon, 2012a. “Fixed bed for wet exhaust streams, 10,000 SCFM, CCC Ref# Hg050412-1.” 

Calculation sheet prepared by Calgon Carbon Corporation for ERG. 5 May, 2012. Docket ID: 

EPA-HQ-OAR-2012-0522. 

Calgon, 2012b. “Fixed bed for wet exhaust streams, 200,000 SCFM, CCC Ref# Hg050412-1.” 

Calculation sheet prepared by Calgon Carbon Corporation for ERG. 5 May, 2012. Docket ID: 

EPA-HQ-OAR-2012-0522. 

EPA, 1997. “Mercury Study Report to Congress Volume VIII: An Evaluation of Mercury 

Control Technologies and Costs.” U.S. Environmental Protection Agency. December 1997. 

Publication Number EPA-452-R-97-010. 

ERG, 2014. “Emissions Data Used in Residual Risk Modeling: Phosphoric Acid and Phosphate 

Fertilizer Production Source Categories.” Eastern Research Group, Inc. August 2014. EPA–HQ–

OAR–2012-0522. 

Jones, 2007. DOE/NETL’s Phase II Mercury Control Technology Field Testing Program, 

Updated Economic Analysis of Activated Carbon Injection. Jones, A., Hoffmann, J., Smith, D., 

Feeley III, T., Murphy, J.; prepared for U.S. DOE, Office of Fossil Energy, National Energy 

Technology Laboratory. May 2007. 
Attachment A 

Annual ACI Cost and Cost Effectiveness For 

Each Carbon Injection Rate 
Attachment A: Annual ACI Cost and Cost Effectiveness For Each Carbon Injection Rate 

Parameter 

Cost for Carbon 

Injection Rate 

of 5 lb/MMacf 

Cost for Carbon 

Injection Rate 

of 10 lb/MMacf 

Cost for Carbon 

Injection Rate of 

30 lb/MMacf1

No

Total Capital Investment $21,149,568 $21,149,568 $21,149,568 Same as PCS2Direct Annual Costs (DAC) 

Operating Labor

Operator $142,403 $142,403 $142,403 Same as PCS3Supervisor $21,360 $21,360 $21,360 Same as PCS3

Maintenance

Labor $160,714 $160,714 $160,714 Same as PCS3

Activated Carbon (PAC)

Carbon Feed Rate (lb/MMacf) 5 10 30Exhaust gas flow rate per calciner (acfm) 64,253 64,253 64,253Carbon Sorbent Cost ($/lb) $1 $1 $1 Same as PCS3Operating Hours 8300 8300 8300 Same as PCS3Carbon Feed Rate (lb/hr/calciner) 19.3 38.6 115.7 = (Carbon Feed Rate (lb/MMa

calciner (acfm)) * (60 min/hr) 

Carbon Sorbent Cost ($/yr/calciner) $159,990 $319,980 $959,940 = (Carbon Feed Rate (lb/hr/ca

($/lb)) * (Operating Hours) 

Total Carbon Sorbent Cost ($/yr) $959,940 $1,919,880 $5,727,000 = (Carbon Sorbent Cost ($/yr/

Total DAC $1,284,417 $2,244,357 $6,051,477Indirect Annual Costs (IAC)

Overhead $194,686 $194,686 $194,686 Same as PCS3

Administrative Charges $422,991 $422,991 $422,991 Same as PCS3

Property tax $211,496 $211,496 $211,496 Same as PCS3Insurance $211,496 $211,496 $211,496 Same as PCS3Total Capital Recovery Cost $1,996,370 $1,996,370 $1,996,370 Same as PCS3

Total IAC $3,037,039 $3,037,039 $3,037,039Total Annual Cost $4,321,455 $5,281,395 $9,088,516 = Total DAC + Total IAC Annual Hg Emissions (lb/yr) 169 169 169 Hg Emissions Reduced (lb/yr) (Meeting Limit, 86% Reduction) 145 145 145 Cost Effectiveness (Meeting Limit) ($/lb) $29,803 $36,423 $62,679 = (Total Annual Cost) / (145 lbNotes: 1. The costs for a carbon injection rate of 30 lb/MMacf are identical to those provided in Appendix A-4 of Attachment A in the PCS commendocket item EPA-HQ-OAR-2012-0522-0037). 2. The total capital cost was not revised, same as Figure 6 of Attachment A in the PCS comment letter (see docket item EPA-HQ-OAR-2012-3. This cost item was not revised, same as Appendix A-4 of Attachment A in the PCS comment letter (see docket item EPA-HQ-OAR-2012-05