S02 SCRUBBER SLUDGE DEWATERING
Michael J. Humenick, Associate Professor
Department of Environmental Health Engineering
The University of Texas
Austin, Texas 78712
Adrian J. Huckabee, Project Engineer
Goodwyn and Mills
Montgomery, Alabama 36106
INTRODUCTION
In the quest for meeting future energy requirements in the United States, many existing and developing technologies and fuel sources are being investigated.   One increasingly
stressed energy source derives from combustion of the most abundant fossil fuel in this
country—coal.   While coal is on the top of the list of fossil fuels for being abundant, it
is unfortunately on the bottom of the list of fossil fuels for being a clean energy source.
As more and more coal is used to fire electric power plant boilers, air pollution from
combustion gases will similarly increase without proper abatement.
Coal combustion in power plant boilers results in the emissions of stack gases containing sulfur oxides, particulate matter and, to a lesser extent, nitrogen oxides.   Particulate
matter results from the incombustible ash in varying amounts in coal.   Sulfur oxides result from the reaction of elemental sulfur and oxygen during combustion.
The value of removing sulfur dioxide from stack gases is somewhat controversial because of the lack of sufficient data in regard to environmental effects [ 1 ]. However, it
is clear that sulfur oxide emissions can lead to adverse health effects.
The quantity of sulfur dioxide emitted depends upon the sulfur content of the coal
being fired.   In the United States sulfur content in coal can range from 0.3 to 5.0% by
weight resulting in the emissions from 70 to 1950 lb of sulfur dioxide per megawatt (M**
each day [2].   The new source performance standards for sulfur dioxide emissions from
coal-fired power plant boilers require that installation of emission controls be implemented
when burning coal which contains more than about 0.6 to 1.0% by weight sulfur. Table I
compares untreated pollutant discharges and the U.S. EPA emission standards [3].
Table I. Untreated Emission Rates and New Source Allowable
Emissions Rates from Coal-Fired Power Boilers
Untreated Discharges Allowable Emissions
Parameter Sulfur Oxides* Sulfur Oxides
lb/106 Btu 0.4-9.8 12
lb/ton coalb                                    7-195 24
lb/MW/dayc 70-1,950 240
ton/MW/yrd 12-350 43
"Range reflects sulfur concentrations between 0.3 to 5.0 wt% in coal.
bBased on a net heating value of 10,000 Btu/lb or 20 million Btu/ton coal (as-fired basis).
cBased on 10 ton coal/MW/day.
dBased on 360 days per year of operation.
The control of sulfur dioxide emissions from power plant stack gases is restricted b>
present technology to one of three methods:   (a) dilution by tall stacks; (b) use of low-
sulfur coal; and (c) flue gas desulfurization.   Research is also presently continuing on coai
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