411FOSSIL FUEL CLEANING PROCESSES
The amount of pollutants, especially sulfur oxides and par-
ticulates emitted to the atmosphere may be reduced by treat-
ing fuels prior to combustion. This approach may be more
energy effi cient than treatment of fl ue gases as per Vapor and
Gaseous Pollutant Fundamentals. More than thirty million
tons of sulfur dioxide are discharged annually in the United
States, 75% of which is the result of fuel burning.FOSSIL FUEL PRODUCTION, RESERVES AND
CONSUMPTIONThe world’s production of oil in 1980 was 66 million barrels
per day with a projected value of 77 MBPD for the year 2000.
The relatively small anticipated increase refl ects increased con-
servation and alternate fuel source application. The overall oil
output of the USSR was about 14 MBPD^1 as compared to about
12 MBPD for combined US and Canadian production (1980).
About 2500 trillion cubic feet of natural gas reserves are
estimated to exist worldwide. The US reserves are 200 TCF
with an annual consumption of about 20 TCF. Soviet bloc
production was about 15 TCF in 1980. Most oil and natural
gas reserves fall in a crescent shaped area extending from
Northern Algeria Northward to West Siberia. Lynch^2 felt
that the level of surplus capacity would remain stable for
the early ’90s with the then world stock level of about 100
gigaliters (1.3 giga barrels).
Coal is consumed at a rate of 600 million tons annually
in the US utility industry. Only a small portion of Eastern
US coals fall in the low (less than 1% sulfur) category—see
Table 1. The US, USSR and China own about two thirds of the
world’s 780 billion tons of presently recoverable coal reserves.
The US has about one quarter of the total. Coal accounts for
90% of the US’s proven reserves.^3
Consumption of fuel might be measured in “quads” or
quadrillion Btu’s. It has been estimated that US electric con-
sumption was 13 quads and nonelectric industrial about 16
quads for the year 1980.^3 Total US fossil fuel consumption is
about 76 quads, most in the non-industrial sector. Worldwide
energy consumption is predicted to double over the next 25
years according to the World Energy Council. 3a The pre-
dicted fossil fuel usage in terms of billions kwh electric gen-
eration in the year 2015 is for coal-2000, natural gas-1000,
nuclear-400, and petroleum-less than 100. Renewables are
estimated at 400 billion kwhs. Divide these numbers by 100
to estimate the number of quads; assuming a plant effi ciencyof current Rankine cycle plants (about 34%) or by 170 if a
combined cycle (Brayton Rankine) is assumed.SULFUR REMOVALTypical legislative actions have been the setting of limits on the
allowable sulfur content of the fossil fuel being burned or on
the SO 2 emission rates of new sources. In California, regula-
tions have limited the use of fuel oil to those of 0.5% or less
sulfur. Since 1968, a limit of a 0.3% sulfur oil has been in effect
in New York City. In 1980, Massachusetts set a 1% sulfur limit
on the coal to be burned. This limit is being considered for
other Atlantic seaboard states as coal conversion is increasingly
encouraged. Chemical and physical desulfurization of fossil
fuels can be used to produce levels of sulfur which comply
with government standards. To reduce a 3% sulfur coal to a 1%
sulfur coal may add about 10% to the cost of coal F.O.B., but
may save on transportation and fl ue gas desulfurization costs.
The amount of sulfur dioxide emitted worldwide might
double in the next decade due to increased energy demands
(approximately 3.5% annually) and the use of more remote
crudes having higher sulfur concentration.
The chemical and power industries must strike a delicate
balance between the public’s dual requirement of increased
quantities and preparation of fossil fuel. More fuel must now
be desulfurized more completely and/or more sulfur diox-
ide must be removed from stack gases. The techniques for
cleaning fossil fuels used throughout the petroleum, natural
gas and coal production industries are covered in this arti-
cle. Treatment of stack gases to effect particulate and sulfur
removal are discussed separately in other articles.PROCESSES INVOLVING THE BASIC FUELSThe two most commonly combusted energy sources are coal
and fuel oil having typical sulfur ranges of 1–4% and 3–4%,
respectively; a 3% sulfur oil produces about the same SO 2
emission as a 2% sulfur coal when based on a comparable
energy release. Fuel oil desulfurization is used by most major
oil producers. Hydrogenation, solvent extraction, absorption
and chemical reaction are used to varying extents at petro-
leum refi ners. Finfer^4 claims a possible sulfur reduction from
2.5 to 0.5% by a hydrodesulfurization process. Coal contains
sulfur which may be combined with either the organic orC006_002_r03.indd 411C006_002_r03.indd 411 11/18/2005 10:27:08 AM11/18/2005 10:27:08 AM