SO2 Emission Factors

Kristin Burford

23/April/01

ME 449A: Sustainable Air Quality

Source: Environmental News Service

Table of Contents

Purpose and Methods EPA Emission Preparation Major Sources of SO2

– Coal Combustion– Oil Combustion– Gas Combustion– Petroleum Refining– Non-Road Diesel

Trends of SO2 Emissions

Summary and Recommendations

Purpose and Methods

Determine how the SO2 emissions were calculated by the EPA– Find out general emission calculation

information– Determine major sources of SO2 according to

1996 Trends Data– Explore the specific factors which influence the

the SO2 emissions for the major sources

EPA Emission Preparation How are emissions determined?

– Two factors: source information and emission factors

General Equation: Emission = Emission Factor*Quality of Consumed Fuel

emission factors found in AP-42 qualities of consumed fuel include amount of fuel, energy

produced, % of precursor element in the fuel

In this study, the focus is on emission factors and how they are calculated

– EPA rates the emission factors from A (best) to E according to how well the calculated emission correlates with the actual emission

Major Sources of SO2 (1996)

SO2 Emissions

Fuel Combustion

83%

Industrial Processes

10%

Transportation7%

The major sources of SO2

emissions include:•Fuel Combustion

•Coal•Oil•Gas

•Industrial Processes

•Petroleum Refining

•Transportation•Non-Road Diesel

For more detailed information on the SO2 sources, consult EPA SO2 trends data for 1996

Coal Combustion Emission Factors

60-70% of SO2 Emissions Coal Rank:

– anthracite - more C, less volatile, rare– bituminous - less C & more volatile than anthracite, most common– sub-bituminous - lower S, more volatile & moisture than bituminous

Uncontrolled emission factors (lbs SO2/ton coal):– 38*%S - bituminous Rating: A– 35*%S - sub-bituminous Rating: A– 39*%S - anthracite Rating: B

Have shown good correlation between calculated and actual emissions

Oil Combustion 10-20% of total SO2 emissions Uncontrolled emission factor (lbs SO2/103 gal):

0.98(MWSO2/MWS)(%S/100)x oil density x 1000 (oil gallons)

Rating: A Variables and Assumptions:

– 98% conversion assumed– %S – MW– oil density

assumed 7 for distillate and 8 for residual actual range 6.97- 7.03 (distillate)

7.95-8.17 (residual)

Gas Combustion 5-10% of total SO2 emissions Uncontrolled emission factor:

(S grains/100 ft3)(lb/7000 grains)(ft3/1000 gal)(2 lb SO2/lb S)

= 0.6 lbs SO2/106 std. ft3 (scft) gas

Rating: A Assumes 100% conversion of fuel S to SO2 and 2000 grains

of S/106 scft. Can convert emission factor to energy units using the

average heating value of the gas (good approximation?) Actual emissions not measured, therefore accuracy of

emission factor is difficult to determine Conservative, assume all S --> SO2

Petroleum Refining 1-5% of total SO2 emissions

No background on emission factor calculation in AP-42 Refining includes converting crude oil to over 2500

different products Multiple Processes

– Separation– Conversion– Treating– Feedstock and product handling– Auxiliary processes

The emission factors in the AP-42 have large ranges,

probably depending on the product purity desired

Non-Road Diesel

1-5% of total SO2 emissions

Data indicates that non-road diesel has a much larger contribution than any other transportation source

Not included in AP-42 online– EPA has limited information on emissions of non-road sources– Emissions based on : travel & rate of emission– SO2 based on 0.25% S in fuel (can be adjusted)

EPA recently decided to reduce the amount of sulfur in diesel fuels, however this will only effect road sources (see Federal Register for more information)

Trends of SO2 Emissions

SO2 Trends (1970-1998)

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

1965 1970 1975 1980 1985 1990 1995 2000

Year

Thou

sand

Sho

rt T

ons

Total SO2Emission

Coal

•Total SO2 emission & Coal SO2 emission have virtually the same trend

•Other sources did not have a great impact on the total SO2 emissions (see other trend plots)

Summary and Recommendations Summary:

– Generally, the emission factors for combustion are accurate. – Petroleum refining and non-road diesel sources emission

factors are not clearly defined Recommendations:

– Further work should be done on controls for the combustion sources

– Improve accuracy of emission factors for other sources which significantly contribute to total SO2 emissions

– Consider regulating sulfur in non-road diesel fuels