December 2009 

Emission Estimation Protocol 

for Petroleum Refineries 

Version 1.0 

Submitted to: 

Office of Air Quality Planning and Standards 

U.S. Environmental Protection Agency 

Research Triangle Park, NC 27711 

Submitted by: 

RTI International 

 3040 Cornwallis Road 

Research Triangle Park, NC 27709-2194 
Appendix A—Average Stream Compositions 

Appendix A 

Average Stream Compositions 

A-1 
Appendix A—Average Stream Compositions 

A-2 

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Appendix A—Avera

Table A-1. Refinery Average Stream Hazardous Air Pollutant Compositions—Default Values 

CAS 

Number HAP Component 

Gasoline Alkylate Crude Oil Reformate Naphtha Avg. Co

Liquid Vapor Liquid Vapor Liquid Vapor Liquid Vapor Liquid Vapor Liquid 

106-99-0 1,3-Butadiene 0.0037 540-84-1 2,2,4-Trimethylpentane 4.72 0.953 35.4 9.4 0.263 0.247 0.799 0.355 8.51 

71-43-2 Benzene 1.61 0.626 0.118 0.061 0.446 0.807 4.61 3.32 1.244 1.06 1.61 92-52-4 Biphenyl 0.01 0 0 0 0.061 0.00002 0.025 0 0 0 0.02 

1319-77-3 Cresols 0.789 0.00065 0 0 0.218 0.0008 0.141 0.0002 0.0191 0.00003 0.23 

98-82-8 Cumene 0.849 0.01565 0.004 0.0001 0.126 0.0108 0.968 0.033 0.91 0.0368 0.57 

100-41-4 Ethylbenzene 1.605 0.0631 0.011 0.0006 0.346 0.0633 3.73 0.272 1.366 0.118 1.41 110-54-3 Hexane 7.138 4.428 3.22 2.63 2.46 7.11 3.9 4.48 7.53 10.27 4.85 

1634-04-4 Methyl tertiary-butyl ether 3.54 3.62 0 0 0 0 0 0 0 0 0.71 

91-20-3 Naphthalene 0.444 0.0006 0.012 0.00002 0.219 0.00125 0.798 0.0018 0.399 0.0011 0.37 

108-95-2 Phenol 0.0551 0.0001 0 0 0.323 0.0031 0.0276 0.0001 0.066 0.0003 0.09 100-42-5 Styrene 3.528 0.0882 0 0 0 0 0.0907 0.0042 0 0 0.72 108-88-3 Toluene 7.21 0.842 0.503 0.077 0.878 0.477 14.54 3.14 5.05 1.295 5.64 

1330-20-7 Xylene 7.17 0.235 0.0212 0.0009 1.42 0.216 13.79 0.8367 5.49 0.395 5.58 

Sum of listed HAP 38.7 10.9 39.3 12.2 6.76 8.94 44.0 12.6 22.9 13.5 30.3 

A-3 
Appendix A—Average Stream Compositions 

Property Calculations 

If the weight composition of a commodity is available but other property data are not, estimates can be 

made. For example, if the liquid component mixture and the weight fraction for gasoline are known, then 

the vapor pressure of the liquid, the MW of vapor, and the weight fraction of the vapor can be estimated. 

The following steps and equations may be used for calculating these estimates: 

1. From the weight fraction values in the gasoline (liquid), Equation A-1 should be used to estimate 

the number of moles of component “i.” 

i

i

i MW

Wtfrac

n = (Eq. A-1) 

2. From moles of component “i” (liquid), Equation A-2 should be used to estimate the mole fraction 

of component “i” (liquid). 

T

i

i

n

n

x = (Eq. A-2) 

3. Equation A-3 should be used to calculate the partial pressure of each component “i” in liquid. 

i = × xP)i(P (Eq. A-3) 

where: 

 P(i) = Partial pressure of component “i” (psia) 

 P = Vapor pressure of pure component “i” at the liquid temperature (psia) 

 xi = Liquid mole fraction 

4. To estimate the total pressure of the liquid, Equation A-4 should be used to estimate the average 

vapor pressure for the gasoline mixture by summing the partial pressure of each component “i” 

(liquid). 

= ∑ (Eq. A-4) 

n

PtotalVP Pi

1

5. From mole fraction of component “i” (liquid), Equation A-5 should be used to estimate the mole 

fraction of component “i” in the vapor using Raoult’s law. 

totalVP

i

i P

P

y = (Eq. A-5) 

6. Equation A-6 should be used to estimate the MW of the gasoline vapor, MWVAP, using the mole 

fraction of vapor (yi) and the MW of the pure component “i”(MWi). 

∑ ×= (Eq. A-6) 

n

MWVap i MWy i

1

where: 

 MWVAP = Molecular weight of the vapor (lb/mol) 

 MWi = Molecular weight of component “i” (lb/mol) 

A-4 
Appendix A—Average Stream Compositions 

7. Equation A-7 should be used to estimate the gasoline vapor weight fractions using the gasoline 

vapor mole fractions and the MWVAP. 

Vap

i i

vap MW

MWy Wtfrac× = (Eq. A-7) 

A-5 

Example A-1: Calculation of Vapor Pressure and Molecular Weight for Gasoline 

Loading Example 

Calculate the vapor pressure of gasoline and MWVAP for submerged loading of gasoline into 

dedicated-service gasoline transport tank trucks (each with a volume of 8,000 gallons) based 

on the following information: 

The refinery loads 100 tank trucks per year at a bulk temperature of 90°F. Property data are 

available for liquid composition of the gasoline only and are provided in Table A-2. 

First, the vapor pressure for each constituent is determined at the loading temperature using 

Antoine’s equation and Antoine’s coefficients, such as those provided in Table 7.1-5 of AP-42 

(U.S. EPA, 1995a). 

Using Steps 1 through 7 from this Appendix A, the gasoline liquid mole fraction can be 

calculated from the weight fraction or weight percent component composition, the partial 

pressure of each component in liquid, and the gasoline vapor mole fraction using Raoult’s law 

(see each calculation “step” in the columns in Table A-2). 

 Step 1. 

i

Wtfraci ni MW =

 Step 2. 

T

i xi = n

n

 Step 3. = * xP i iP )(

 Step 4. = ∑Pi

n

PtotalVP

1

 Step 5. 

totalVP

i

i = P

P

y

 Step 6. MW = ∑ MWii

n

Vap y

1

*

 Step 7. 

Vap

ii wtfracvap MW

* MWy =

See Table A-2 for the calculations of thee variables. At 90°F, the total system vapor pressure is 5.641 

psia and the MW of the vapor, MWGasolineVAP, is 65.984 lb/lb-mol. 
Appendix A—Avera

Table A-2. Sample Calculation of Average Molecular Weight and Vapor Weight Fraction 

Step 1 Step 2 Step 3 Step 4 Step 5 

A B C D=C/A E=D/(ΣD) F=E*B G=F/(ΣF) 

CAS Number Compound MolWt Pvap at 90°F (psia) Gasoline Liquid (wt%) 

Gasoline 

Liquid (moles/ 

100 g) 

Gasoline 

Liquid (mole 

fraction)

Gasoline 

Partial 

Pressure 

(psia) 

Gasoline Vapo

(mole fraction)

106-99-0 1,3-butadiene 54.09 50.53 0.0037 6.840E-07 6.206E-05 3.136E-03 5.559E-04 

1634-04-4 Methyl tertiary butyl ether 88.15 3.666 3.54 4.016E-04 3.643E-02 1.336E-01 2.368E-02 

110-54-3 Hexane 86.18 3.970 7.138 8.283E-04 7.514E-02 2.983E-01 5.288E-02 540-84-1 2,2,4-Trimethylpentane 114.2 1.336 4.72 4.132E-04 3.749E-02 5.008E-02 8.878E-03 

71-43-2 Benzene 78.11 2.544 1.61 2.061E-04 1.870E-02 4.758E-02 8.434E-03 

108-88-3 Toluene 92.14 0.7911 7.21 7.825E-04 7.099E-02 5.615E-02 9.955E-03 

1330-20-7 Xylene 106.1 0.2542 7.17 6.755E-04 6.128E-02 1.558E-02 2.762E-03 

100-41-4 Ethylbenzene 106.2 0.2758 1.605 1.512E-04 1.371E-02 3.782E-03 6.704E-04 100-42-5 Styrene 104.2 0.1921 3.528 3.387E-04 3.073E-02 5.904E-03 1.047E-03 

98-82-8 Cumene 120.2 0.1369 0.849 7.064E-05 6.408E-03 8.774E-04 1.555E-04 91-20-3 Naphthalene 128.2 0.008555 0.444 3.4642E-05 3.143E-03 2.689E-05 4.766E-06 92-52-4 Biphenyl 154.2 0.001059 0.01 6.485E-07 5.883E-05 6.231E-08 1.105E-08 

108-95-2 Phenol 94.11 0.01253 0.0551 5.855E-06 5.311E-04 6.656E-06 1.180E-06 

1319-77-3 Cresols 108.1 0.008422 0.789 7.296E-05 6.619E-03 5.574E-05 9.881E-06 

74-98-6 Propane 44.1 162.5 0.001 2.268E-07 2.057E-05 3.342E-03 5.924E-04 

106-97-8 n-Butane 58.12 43.79 4.7 8.087E-04 7.336E-02 3.213E+00 5.695E-01 

75-28-5 Isobutane 58.12 17.04 1.7 2.925E-04 2.654E-02 4.521E-01 8.015E-02 

109-66-0 n-Pentane 72.15 13.32 3.9 5.405E-04 4.904E-02 6.533E-01 1.158E-01 

78-78-4 Isopentane 72.15 4.920 7.9 1.095E-03 9.933E-02 4.888E-01 8.664E-02 

Other VOC 100.2 0.5531 43.13 4.304E-03 3.904E-01 2.159E-01 3.828E-02 

nT PtotalVP 

Totals 100.0 1.102 1.000 5.641 1.000 

A-6