TO: Petroleum Refinery NSPS Docket No. EPA-HQ-OAR-2007-0011

FROM: Bob Lucas, EPA/SPPD

DATE: July 6, 2010

SUBJECT: Revised NO X Impact Estimates for Process Heaters

I. Purpose
This memorandum documents the revised nitrogen oxides (NO X ) impact estimates for petroleum refinery process heaters that become s ubject to 40 CFR part 60, subpart Ja.

II. Background
The impacts for various control techniques for NO X from process heaters were considered previously (Coburn, 2008), but the impacts did not acc ount for differences in the draft design of the process heater (forced ve rsus natural draft). This memorandum provides additional information to support the development of NO X emission standards for process heaters when considering the differences between baseline em issions for natural and forced draft process heaters. Additionally, the EPA is considering providing NO X emission limits in terms of pounds per million British thermal units (lb/MMBtu) as an alternative to the concentration-based NO X emission limits. This memorandum provides addi tional information regarding the appropriate NO X emission limits in terms of lb/MMBtu that ar e equivalent to a given concentration-based NO X emission limit.

III. Cost Estimates of Process Heater NO X Control Systems
The cost analysis for process heaters was simila r to the cost analysis performed previously (Coburn, 2008), except that costs were estimated for two different scenarios. Scenario 1 assumes all of the process heaters are na tural draft process heaters and Scenario 2 assumes all of the process heaters are forced draft process heater s. We do not have much data on the precise proportion of process heaters that are forced versus natural draft, so the nationwide impacts are expressed as a range bounde d by these two scenarios.

The cost factors, model plant sizes, and the num ber and size distribution of process heaters per model plant are identical to thos e used previously. However, the control option effectiveness and the baseline emissions are slightly different based on whether the proc ess heater is natural draft versus forced draft. Table 1 provides a summary of the distribution of baseline NO X concentrations for different types of process heaters.Memo: Revised NO X Control Cost Estimates for Process Heaters July 6, 2010

2 Table 1. Summary of Representative Baseline NO X Concentrations for Affected Process Heaters

Representative Average NO X Concentration (ppmv) Fraction of Affected Natural Draft Process Heaters Represented by Average NO X Concentration Fraction of Affected Forced Draft Process Heaters Represented by Average NO X Concentration
80 0.40 0.00
100 0.40 0.50
150 0.15 0.35
200 0.05 0.10
240 0.00 0.05

Various NO X concentration limits were evaluated for pr ocess heaters with a capacity greater than 40 MMBtu. The costs include costs for O 2 monitoring equipment for process heaters with a capacity less than 100 MMBtu /hr and the costs for a continuous emission monitoring system (CEMS) for NO X . Table 2 provides the projected impact s for new or modified natural draft process heaters. Table 3 provide s the projected impacts for new or modified forced draft process heaters. The incremental cost effectiveness for na tural draft process heater s is reasonable at an emission limit of 40 ppmv, but ju mps to over $30,000 per ton of NO X removed at an emission limit of 20 ppmv. For forced draft process heater s, incremental cost effectiveness is reasonable at an emission limit of 60 ppmv, but ju mps to approximately $14,000 per ton of NO X removed at an emission limit of 20 ppmv. Based on these impact s, the performance level for the best system of emission reduction (BSER), which is a combination of enhanced combustion monitoring controls and ultra-low NO X burners, is 40 ppmv for natural draf t process heaters and 60 ppmv for forced draft process heaters.Memo: Revised NO X Control Cost Estimates for Process Heaters July 6, 2010

3 Table 2. Summary of Nation wide Impacts of Various NO X Regulatory Alternatives for Scenario 1: All Natural Draft Process Heaters
Regulatory Alternative NO X Emission Limit (ppmv) Total Capital Investment

($1,000) Total Annualized Costs ($1,000/yr) NO X Emission Reduction from Baseline (tons/yr) Overall Option Cost Effectiveness ($/ton) Incremental Cost Effectiveness ($/ton) Nationwide Costs for Newly Constructed Units (70% of affected units) 80 6,460 3,050 2,390 1,280 1,280 60 7,570 5,410 4,140 1,310 1,350 40 8,050 7,440 5,000 1,490 2,360 20 34,100 13,300 5,200 2,560 30,200 Nationwide Costs for Modified or Reconstructed Units (30% of affected units) 80 5,070 1,570 1,030 1,540 1,540 60 10,300 3,120 1,770 1,760 2,070 40 15,200 4,520 2,140 2,110 3,800 20 28,000 7,230 2,230 3,250 32,500

Table 3. Summary of Nation wide Impacts of Various NO X Regulatory Alternatives for Scenario 2: All Forced Draft Process Heaters
Regulatory Alternative NO X Emission Limit (ppmv) Total Capital Investment

($1,000) Total Annualized Costs ($1,000/yr) NO X Emission Reduction from Baseline (tons/yr) Overall Option Cost Effectiveness ($/ton) Incremental Cost Effectiveness ($/ton) Nationwide Costs for Newly Constructed Units (70% of affected units) 80 7,450 4,900 4,840 1,010 1,010 60 8,050 7,440 6,030 1,230 2,120 40 14,600 8,910 6,140 1,450 13,600 20 75,300 22,400 6,830 3,290 19,700 Nationwide Costs for Modified or Reconstructed Units (30% of affected units) 80 9,060 2,770 2,070 1,340 1,340 60 15,200 4,520 2,600 1,750 3,420 40 18,400 5,200 2,630 1,980 14,700 20 48,500 11,500 2,930 3,910 21,300

The nationwide impacts for Scenarios 1 and 2 pr ovide a range of potential impacts. Table 4 presents the nationwide impacts combined for new, modified, and reconstr ucted process heaters for the two scenarios. The costs of the cont rol systems are identical for the two scenarios because the scenarios are based on identical controls (enhanced combustion monitoring controlsMemo: Revised NO X Control Cost Estimates for Process Heaters July 6, 2010

4 and ultra-low NO X burners). The projected emission reductions differ due to the different baseline emission distribution. In the June 2008 final rule, tota l nationwide emission reductions were estimated to be 7,500 tons/yr. In the curr ent analysis, the emission reductions are projected to range between 7,100 and 8,600 tons/yr. If natu ral draft process heaters are approximately 75 percent of the newly affected process heaters, then the originally projected emission reductions are in agreement with the revised estimates.

Table 4. Range of Nationwide Impacts of Se lected Regulatory Alternatives for Process Heaters

Regulatory Alternative NO X Emission Limit (ppmv) Total Capital Investment

($1,000) Total Annualized Costs ($1,000/yr) NO X Emission Reduction from Baseline (tons/yr) Overall Option Cost Effectiveness ($/ton)
Nationwide Costs for Scenario 1: All Natural Draft Process Heaters
40 23,000 12,000 7,100 1,700
Nationwide Costs for Scenario 1: All Forced Draft Process Heaters
60 23,000 12,000 8,600 1,400

IV. Comparability of NO X Emission Standards
The proposed concentration emission limits of 40 or 60 ppmv are to be determined on a dry basis at 0 percent oxygen. The stoichiometric combus tion of most fuel gases will produce a fairly constant volume of exhaust gas on a dry basis unle ss the hydrogen content is very high. Table 5 of this memorandum is a copy of the proposed Table 1 to 40 CFR part 60, subpart Ja and contains the molar exhaust volume and molar h eat content of typical compounds that make-up part of the fuel gas.
Looking at each constituent as th e only fuel available, a 40 ppmv concentration can be converted to a lb/MMBtu basis us ing the following equation.Memo: Revised NO X Control Cost Estimates for Process Heaters July 6, 2010

5 MGV MWMHC MEV ppmv Conc MMBtulb EmissLimit /2045.2 /)()/(     (Eq. 1)

Where: EmissLimit = the emission limit in lb/MMBtu eq uivalent to a concentration limit, lb/MMBtu Conc = the NO X concentration limit, ppmv dry ba sis, corrected to 0% excess air MEV = molar exhaust volume, dry standard c ubic feet per mole (dscf/mol) at standard conditions of 68°F and 1 atmosphere, 0% excess air. MHC = molar heat content (higher heati ng value basis), Btu per mole (Btu/mol) MW = Molecular weight of NO X = 46 kg/kg-mol 2.2045 = unit conversion, lb/kg MGV = molar gas volume, scf/kg-mol

Table 5. Molar Exhaust Volumes and Molar Heat Content of Fuel Gas Constituents

Constituent MEV a dscf/mol MHC b Btu/mol Methane (CH 4 ) 7.29 842 Ethane (C 2 H 6 ) 12.96 1,475 Hydrogen (H 2 ) 1.61 269 Ethene (C 2 H 4 ) 11.34 1,335 Propane (C 3 H 8 ) 18.62 2,100 Propene (C 3 H 6 ) 17.02 1,947 Butane (C 4 H 10 ) 24.30 2,717 Butene (C 4 H 8 ) 22.69 2,558
Inerts 0.85 0

a MEV = molar exhaust volume, dry standard cubic feet per mole (dscf/mol) at standard conditions of 68°F and 1 atmosphere, 0% excess air. b MHC = molar heat content (higher heating value basis), Btu per mole (Btu/mol)

Applying Equation 1 to the various constituents of fuel gas (other than inerts, which do not contribute to the heating value of the fuel gas stream) yields the values presented in Table 6.Memo: Revised NO X Control Cost Estimates for Process Heaters July 6, 2010

6 Table 6. Emission Limit Conversion Factors for Fuel Gas Constituents

Constituent NO X Concentration Limit (ppmv) Equivalent NO X Emissions Limit (lb/MMBtu) Methane (CH 4 ) 40 0.041 Ethane (C 2 H 6 ) 40 0.042 Hydrogen (H 2 ) 40 0.029 Ethene (C 2 H 4 ) 40 0.041 Propane (C 3 H 8 ) 40 0.042 Propene (C 3 H 6 ) 40 0.042 Butane (C 4 H 10 ) 40 0.043 Butene (C 4 H 8 ) 40 0.042

Based on typical gas composition (mixture of C1 to C4 hydrocarbons with some hydrogen), a NO X concentration of 40 ppmv is essentially equal to 0.040 lb/MMBtu. Only when the hydrogen content exceeds 20 or 30 percent does a 0.040 lb/MMBtu emission limit becomes less stringent than the 40 ppmv emission limit. At high hydrogen concentration, the water content in the exhaust gas becomes significan t, so that the dry basis corr ection of the concentration limit makes the concentrations limit more stringent ev en though the mass emission rate is the same. As the other factors in Equation 1 are constant s for each constituent of fuel gas, a 60 ppmv NO X concentration limit is similarly equivale nt to a 0.060 lb/MMBtu emissions limit.

V. References

Coburn, J. 2008. “Documentation of Final NO X Control Cost Estimates.” Memorandum to Bob Lucas, EPA/SPPD. Docket Item No . EPA-HQ-OAR-2007-0011-0222. April 28.