p.1 

OAR Box 1784 

Prepped by Ollie Stewart 

Document Number: 

35) II-C-6 

Docket Number: 

A-84-44 

Printed 10/31/2008 8:05:39 AM Sheet 35 of 143 
P.2 

Date: August 8, 1986 

MEMORANDUM 

TO: Docket A-84-44 

FROM: Wm. Larry Elmore, P.E. 

Industrial Studies Branch 

SUBJECT: SO2 Emissions Calculations 

The attached information was developed by Larry Elmore, EPA:ISB, 

to compute SO2 emissions from refinery fuel gas and potential reductions 

by lowering the NSPS. This procedure was mailed out to various trade 

organizations and industry representatives for review. The mailing list 

is attached. This method was not used to derive the SO2 emissions 

presented in the refinery fuel gas document. 
P.3 

PROCEDURE DESCRIPTION 

Table 1 on page 1 lists the sulfur emissions from model sulfur 

recovery unit (SRU) of various sizes which treat various concentrations 

of hydrogen sulfide (H2S) in the refinery fuel gas (RFG) to various 

emission limits. The model SRU range from 5 long tons/day (LT/D) to 

100 LT/D and the H2S concentration ranges from 1 to 10 percent by volume. 

The emission limits that were analyzed are the current new source performance 

standard (NSPS) emission limit of 230 mg/dscm (0.10 gr/dscf or 162 ppmv (? 

STP); one half the NSPS emission limit which is equal to 115 mg/dscm 

(0.05 gr/dscf or 81 ppmv @ STP); and one fourth the NSPS emission limit 

which is equal to 57.5 mg/dscm (0.025 gr/dscf or 40.5 ppmv @ STP). The 

Environmental Protection Agency defines STP as 20°C and 1 atmosphere 

pressure (760 mm Hg). 

Figure 1 on page 2 illustrates the flow diagram of an amine treatment 

unit and SRU used to compute the sulfur emissions. Please note that the 

tail gas treatment unit was omitted from Figure 1 and the computations. 

This omission creates a worse case situation which produces maximum sulfur 

emissions. Total sulfur emissions per day based on this flow scheme are 

the sulfur emissions from treated RFG that is burned in combustion devices 

plus sulfur emissions from the SRU. It was assumed that the amine treatment 

unit and the SRU operate 350 days per year. The reduction in sulfur 

emissions at the two lower emission limits is computed by subtracting the 

sulfur emissions at the lower emission standard from the current NSPS 

emission limit. 
P.4 

2 

Table 2 on page 3 lists the percent efficiency of the amine treatment 

unit needed to comply with the various emission limits at the various H2S 

concentrations. These efficiency numbers were used to compute sulfur 

emissions from the amine treatment unit. The efficiency of the SRU, a 

three pass Claus SRU, was assumed to be 96.6 percent (efficiency ranges from 

96-97 percent). 

Sample calculations using all of these assumptions are located on 

page 4. The sample calculations are for an amine treating unit that is 

treating RFG containing 1 percent H2S by volume with a 100 LT/D SRU converting 

the concentrated H2S into elemental sulfur. 
P.5 

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P.10 

502 Ecission Reduction Fros Various Levels of H2S in Refinery Fuel Gas 

(July 198b) 

SRU Model 

Plants 

LT/D 

5 

10 

50 

100 

H2S -

Percent 

by vol.i 

1 : 

5 : 

10 

1 

5 

10 

1 

5 

10 

1 

5 

10 

S02 Efiissions 

at 162 ppav. 

ftTU 

LT/D 

0.162 

0.032 

0.016 

0.324 

0.064 

0.032 

1.62 

0.32 

0.16 

3.24 

0.64 

0.32 

SRU 

LT/D 

0.334 

0.338 

0.339 

0.668 

0.677 

0.678 

0.039 

0.039 

0.039 

0.078 

0.079 

0.079 

Tot/yr 

LT/Y 

173.7 

129.8 

124.4 

347.5 

259.6 

248.8 

580.7 

125.9 

69.97 

1161. 

251.9 

139.9 

S02 Eaissions at 81 

ATU 

LT/D 

0.081 

0.016 

0.008 

0.162 

0.032 

0.016 

0.81 

0.16 

0.08 

1.62 

0.32 

0.16 

SRU 

LT/D 

0.337 

0.339 

0.339 

0.674 

0.678 

0.679 

0.039 

0.039 

0.039 

0.079 

0.079 

0.079 

Tot/yr 

LT/Y 

146.3 

124.4 

121.7 

292.7 

248.8 

243.4 

297.3 

69.97 

41.98 

594.7 

139.9 

83.97 

ppmv. 

Reduction 

LT/Y 

27.3861 

5.4096 

2.7048 

54.7722 

10.8192 

5.4096 

283.3866 

55.9776 

27.9888 

566.7732 

111.9552 

55.9776 

SD2 Emissions at 40.5 ppuv. 

ATU 

LT/D 

0.041 

0.008 

0.004 

0.082 

0.016 

0.008 

0.41 

0.0B 

0.04 

0.82 

0.16 

0.08 

SRU 

LT/D 

0.338 

0.339 

0.339 

0.677 

0.679 

0.679 

0.039 

0.039 

0.039 

0.079 

0.079 

0.079 

Tot/yr 

LT/Y 

132.8 

121.7 

120.3 

265.7 

243.4 

240.7 

157.4 

41.98 

27.99 

314.8 

83.97 

55.98 

Reduction 

LT/Y 

40.9101 

8.1144 

4.0572 

81.8202 

16.2288 

8.1144 

423.3306 

83.9664 

41.9832 

846.6612 

167.9328 

S3.9664 

ATU=Aaine Treataent Unit Operating Days=350 davs/vear 

SRU=SuHur Recovery Unit 1 Ton of Sulfur=2 Tons of SQ2 

TBTU=Tail Gas Treatment Unit 

SRU <20 LT/D are not required to have T6TU. 

SRU efficiency w/o T6TU=96.6X 

SRU efficiency */ T6TU=99.9X 

ATU S02 Et3issions=((SRU Pit. size)-((SRU Pit. size) (ATU Eff.)))t 2 

SRU S02 Esissions=((SRU Pit. size)(ATU Eff.)-(SRU Pit. size)(ATU Eff.)(SRU Eff.))l 2 

Total S02 Eaissions=(IATU S02 Eaissions)+(SRU S02 Efiissions) 1*350 

Aeine Treater Efficiency at 

Various K2S Levels 

RFG H2S !AT X EfflAT I EfflAT X Eff 

Cone. lat NSPS lat NSPS Eat NSPS 

ppav. 1162 ppavl 81 ppav140.5 ppav 

10000 1 0.9838 . 0.9919 ! 0.9959 

50000 ! 0.9968 ! 0.9984 ! 0.9992 

100000 ! 0.9984 1 0.9992 1 0.9996