FROM: Karen Schaffner and Jeff Coburn, RTI International 

TO: Brenda Shine, EPA/OAQPS/SPPD 

FOR: Docket ID No. EPA-HQ-OAR-2010-0682 

DATE: November 22, 2013 

SUBJECT: Review of HAP Emission Factors for Fluid Catalytic Cracking Units based on 

Component 4 Source Test Data 

1. Purpose 

This memorandum compares the emissions factors derived from recent source test data of fluid 

catalytic cracking units (FCCU) to those provided in the Emission Estimation Protocol for 

Petroleum Refineries (RTI, 2011). 

2. Background 

On April 1, 2011, the U.S. Environmental Protection Agency (EPA) sent an information 

collection request (ICR) to facilities in the petroleum refining industry (EPA, 2011). The ICR 

was comprehensive and designed to collect information on processing characteristics, crude slate 

characteristics, emissions inventories and source testing to bolster our current data and fill known 

data gaps. The ICR had four components: (1) a questionnaire on processes and controls to be 

completed by all petroleum refineries (Component 1); (2) an emissions inventory to be 

developed by all petroleum refineries using the emissions estimation protocol developed for this 

effort (Component 2); (3) distillation feed sampling and analysis to be conducted by all 

petroleum refineries (Component 3); and (4) emissions source testing to be completed in 

accordance with an EPA-approved protocol for specific sources at specific petroleum refineries 

(Component 4). 

Component 4 of the ICR requested source testing for twelve different types of emission sources 

or units, one of which was the FCCU. For FCCU sources, source testing was requested for 

10 different units, selected to cover a variety of operating conditions (e.g., units using complete 

burn FCCU versus partial burn FCCU followed by a carbon monoxide (CO) boiler; units using 

electrostatic precipitators versus wet scrubbers for particulate matter (PM) control). Owners or 

operators of the FCCU at the selected facilities were required to test for: 

 Speciated volatile organic hazardous air pollutants (HAP) 

 Speciated semi-volatile organic HAP 

 Total hydrocarbons, methane, and ethane 

 Aldehydes 

 Carbon monoxide 

 Dioxins, furans, and polychlorinated biphenyls 
Technical Memorandum – Review of HAP Emission Factors for Fluid Catalytic Cracking Units 

November 22, 2013 

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 Hydrogen chloride, chlorine, hydrogen fluoride, and hydrogen cyanide 

 Mercury (speciated) 

 Hexavalent chromium and multiple metals 

 Particulate matter (PM, filterable PM with a diameter less than 2.5 micrometers (PM2.5

filterable), and PM condensable) and ammonia 

 Nitrogen oxides (NOX), sulfur dioxide (SO2), oxygen (O2), carbon dioxide (CO2), 

moisture, and gas flow rate 

3. Developing Emission Factors from the FCCU Source Tests 

For most source tests, the hourly mass emission rate of a pollutant was directly reported. For 

some tests, the pollutant concentration may have been reported and the hourly mass emission 

rate was calculated based on the process vent flow rate. The hourly mass emission rates were 

divided by the hourly average process feed rate to calculate an emission factor in units of pounds 

per million barrels of feed (lb/MMbbl). Thus, in order to develop emission factors from the 

source test results, one must have both the emissions data (emission rates) and process data. The 

pollutant concentrations and emission rates determined during the source tests are considered 

emissions data and cannot be claimed as confidential business information (CBI). However, 

process operating data, such as process feed rates, may be claimed as CBI. For the purpose of 

this analysis, only non-CBI data were used. If process rates were reported and not claimed as 

CBI, then the process data reported was used. For facilities that claimed all their process data to 

be CBI, process feed rates were estimated based on the process unit capacity as reported by the 

Energy Information Agency (EIA, 2011). The Emission Estimation Protocol for Petroleum 

Refineries (RTI, 2011), hereon simply referred to as the Protocol, also includes emission factors 

normalized by coke burn-off rates. However, coke burn-off rates were generally claimed CBI 

and there was no easy way to estimate the coke burn-off rates (other than assigning a fixed coke 

burn-off rate per feed rate), so independent emission factors based on coke burn-off rates could 

not be derived from the non-CBI data. 

4. Comparison of FCCU Emission Factors 

As part of the ICR, refineries were required to submit a complete emissions inventory file 

following the guidelines provided in the Emission Estimation Protocol for Petroleum Refineries

(RTI, 2011). This Protocol included default emission factors for a variety of HAP from FCCU. 

Owners or operators of FCCU that did not have any test data or other “higher ranked” 

methodologies for estimating HAP emissions from the FCCU were expected to use these default 

emission factors. In general, most FCCU owners or operators have not conducted HAP emission 

tests, so it is anticipated that most refineries used the default emission factors from the Protocol 

document to develop their FCCU emission estimates. Table 1 summarizes the default HAP 

emission factors for FCCU from the Protocol and those derived from the Component 4 source 

tests. Note: Table 1 does not include metals. Metals were generally expected to be estimated 

based on the PM emission rate and HAP concentration of the FCCU dust. Default concentration 

ratios of certain HAP to nickel were provided in the Protocol; it was assumed all facilities would 

know nickel FCCU dust concentrations. 
Technical Memorandum – Review of HAP Emission Factors for Fluid Catalytic Cracking Units 

November 22, 2013 

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Table 1. Comparison of HAP Emissions Factors for FCCU Catalyst Regenerator Vent 

CAS No.a Compound 

Emissions Factor 

from Protocol

Document 

(lb/MMbbl)b

Preliminary 

Emissions Factor 

from Source Test 

Data 

(lb/MMbbl)b,c

Volatile Organics 

75-07-0 Acetaldehyde 20 54 

67-64-1 Acetone 2.4 5,100 

107-02-8 Acrolein 1.0 

71-43-2 Benzene 18 38 

74-83-9 Bromomethane 2.1 

106-99-0 1,3-Butadiene 0.033 

100-41-4 Ethylbenzene 0.24 

50-00-0 Formaldehyde 260 52 

75-09-2 Methylene chloride 6.7 490 

108-95-2 Phenol 8.7 

108-88-3 Toluene 3.5 370 

75-69-4 Trichlorofluoromethane 2.4 

1330-20-7 Xylene 3.2 

Semi-volatile Organics 

83-32-9 Acenaphthene 0.0033 0.0012 

208-96-8 Acenaphthylene 0.13 0.0025 

120-12-7 Anthracene 0.10 0.020 

56-55-3 Benzo(a)anthracene 0.00052 0.029 

50-32-8 Benzo(a)pyrene 0.011 0.0048 

205-99-2 Benzo(b)fluoranthene 0.0035 0.0048 

192-97-2 Benzo(e)pyrene 0.00045 0.0054 

191-24-2 Benzo(g,h,i)perylene 0.0046 0.00026 

207-08-9 Benzo(k)fluoranthene 0.0026 0.0026 

218-01-9 Chrysene 0.0033 0.024 

53-70-3 Dibenz(a,h)anthracene 0.0042 

206-44-0 Fluoranthene 0.093 0.041 

86-73-7 Fluorene 0.037 0.0069 

193-39-5 Indeno(1,2,3-cd)pyrene 0.0044 0.0048 

91-57-6 2-Methylnaphthalene 0.026 0.028 

91-20-3 Naphthalene 1.0 0.52 

85-01-8 Phenanthrene 0.24 0.078 

129-00-0 Pyrene 0.0031 0.11 

Dioxins/Furans 

57117-31-4 Pentachlorodibenzofurans 5.5E-07 1.8E-06 

57117-44-9 Hexachlorodibenzofuran 1.1E-06 8.8E-07 

35822-46-9 Heptachlorodibenzo-p-dioxin 9.4E-07 4.3E-07 
Technical Memorandum – Review of HAP Emission Factors for Fluid Catalytic Cracking Units 

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Table 1. Comparison of HAP Emissions Factors for FCCU Catalyst Regenerator Vent 

CAS No.a Compound 

Emissions Factor 

from Protocol

Document 

(lb/MMbbl)b

Preliminary 

Emissions Factor 

from Source Test 

Data 

(lb/MMbbl)b,c

Inorganics 

7664-41-7 Ammonia 13,000 690 

75-15-0 Carbon disulfide 0.56 71 

7647-01-0 Hydrogen chloride 1,800 120 

74-90-8 Hydrogen cyanide 770 7,700 

7439-97-6 Mercury 1.1 0.094 

a

 CAS No. = Chemical Abstracts Service registry number. 

b

 Emissions factors for FCCU controlled for organics in lb/MMbbl of CCU feed. 

c

 Emissions factors from the Component 4 source test based on reported data. These data have not been fully 

reviewed in terms of quality assurance of results and method detection limits. As such, these emission factors 

are considered preliminary. 

Generally, emission factor agreement within a factor of 2 is reasonable considering the HAP 

emission data set used when developing the emission factors for the Protocol document 

(generally tests conducted in the 1990’s). There are some differences that appear significant, and 

these are discussed briefly in the following paragraphs. 

Considering the volatile organic HAP, the emission factors derived from Component 4 test data 

for acetone and methylene chloride are much greater than those provided in the Protocol. These 

pollutants are common laboratory contaminants and they are not expected to be released in 

significant concentrations. Initial review of supporting documentation revealed that many of the 

tests had high acetone and methylene chloride concentrations in the blank. Consequently, we 

concluded that the preliminary Component 4 test data emission factors were likely overstated. 

The toluene Component 4 emission factor was also much higher than the Protocol default factor. 

There was only one Component 4 test that measured toluene above the method detection limit. 

This test is being further reviewed to understand the source of the high toluene emissions, but it 

is not appropriate to develop an emission factor based on one test. 

The emissions factors developed for different semi-volatile organics varied widely, with some 

test data emission factors much higher than the Protocol default factors and others much lower. 

These compounds are also referred to as polycyclic aromatic hydrocarbons (PAH) and they can 

be grouped by their cancer risk factor relative to benzo(a)pyrene. Thus, one can calculate a 

toxicity equivalent emission factor for PAH considering all of the individual PAH emission 

factors. The total PAH emission factor, weighted as benzo(a)pyrene, from the Protocol is 

0.098 lb/MMbbl, and it is 0.050 lb/MMbbl from the test data. Thus, although there is significant 

differences in the emission factors for individual PAH, the cumulative toxicity-weighted PAH 

emission factors agree reasonably well. 
Technical Memorandum – Review of HAP Emission Factors for Fluid Catalytic Cracking Units 

November 22, 2013 

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The dioxin/furan emission factors agree quite well between the Protocol and Component 4 

source tests; however, the inorganic emission factors are widely different. The emission factor 

for carbon disulfide is based on a single emission test, as all other tests were below detection 

limit. As stated previously, it is not appropriate to develop an emission factor based on one test. 

Ammonia is not a HAP, so ammonia emissions were not included in the emission inventory 

modeling file used to assess risks from petroleum refinery emission sources. There is essentially 

and order of magnitude (i.e., factor of 10) difference in the emission factors for hydrogen 

chloride, hydrogen cyanide and mercury between the Protocol defaults and the Component 4 

source test results. For these HAP, the Protocol default emission factors were based on very 

limited data and, in the case of hydrogen chloride, source test detection limits. For these HAP, it 

was deemed appropriate to revise the emissions inventory modeling file to incorporate the 

Component 4 source test emission factors. 

5. Corrections Made to the Emission Inventory Modeling File 

As seen in Table 1, the average emission factor derived from the Component 4 source test data 

for hydrogen cyanide is approximately a factor of 10 higher than the Protocol emission factor. 

Given this large difference, the reported emission inventories were revised assuming the 

facilities used the Protocol emission factor. Facilities that conducted source tests were assigned 

hydrogen cyanide emissions based on their tested emissions rate. For other facilities, the 

reported FCCU hydrogen cyanide emissions were multiplied by 10 to better match the emissions 

that would have been projected had the Component 4 source test data been available at the time 

the Protocol document was developed. 

The average emission factors derived from the Component 4 source test data for mercury and 

hydrogen chloride are approximately a factor of 10 lower than the Protocol emission factors. 

Therefore, the emission inventory modeling file was also adjusted to correct FCCU mercury 

emission estimates to better match the emissions that would have been projected had the 

Component 4 source test data been available at the time the Protocol document was developed. 

Facilities that conducted source tests were assigned emissions based on their tested emissions 

rate. For other facilities, the reported FCCU mercury emissions were divided by 10. For FCCU 

hydrogen chloride emissions, no adjustments were made to the emission inventory modeling file. 

Hydrogen chloride was below all environmental risk benchmarks and, therefore, limited EPA 

resources were not used to make these revisions. 

6. References 

EIA (Energy Information Administration). 2011. Refinery Capacity Report 2011. Prepared by 

the Energy Information Administration, Washington DC. June 24, 2011. 

EPA (U.S. Environmental Protection Agency). 2011. Petroleum Refinery Database, based on 

Refinery Information Collection Request (ICR) for Calendar Year 2010. September 2011. 

Docket Item Nos. EPA-HQ-OAR-2010-0682-0061 through 0069. 

RTI (RTI International). 2011. Emission Estimation Protocol for Petroleum Refineries. 

Version 2.1.1, Final ICR Version Corrected. Prepared for U.S. Environmental Protection 
Technical Memorandum – Review of HAP Emission Factors for Fluid Catalytic Cracking Units 

November 22, 2013 

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Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC. May 

2011. Docket Item No. EPA-HQ-OAR-2010-0682-0060. Most current version also 

available at http://www.epa.gov/ttn/chief/efpac/protocol/.