Page 179 - Synthetic Fuels Handbook

FUELS FROM COAL 165

In addition, coal combustion produces particulate matter (fly ash) that can be trans-
ported by winds for many hundreds of kilometers and solids (bottom ash and slag) that
must be disposed. Trace elements originally present in the coal may escape as volatile
material (e.g., chlorine and mercury) or be concentrated in the ash (e.g., arsenic and
barium). Using such devices as electrostatic precipitators, baghouses, and scrubbers
can trap some of these pollutants. Alternate means for combustion (e.g., fluidized bed
combustion, magnetohydrodynamics, and low nitrogen dioxide burners) are also avail-
able to provide more efficient and environmentally attractive methods for converting
coal to energy.
When carbon dioxide is released into the atmosphere it does not prevent the shorter-
wavelength rays from the sun from entering the atmosphere but does prevent much of the
long-wave radiation reradiated from the earth’s surface from escaping into the space. The
carbon dioxide absorbs this upward-propagating infrared radiation and reemits a portion of
it downward, causing the lower atmosphere to remain warmer than it would otherwise be
(the greenhouse effect). Other gases, such as methane and ozone also cause this effect and,
consequently, are known as greenhouse gases.

5.9 CLEAN COAL TECHNOLOGIES

Clean coal technologies (CCTs) are a new generation of advanced coal utilization processes
that are designed to enhance both the efficiency and the environment acceptability of coal
extraction, preparation, and use. These technologies reduce emissions waste and increase
the amount of energy gained from coal. The goal of the program was to foster develop-
ment of the most promising CCTs such as improved methods of cleaning coal, fluidized
bed combustion, integrated gasification combined cycle, furnace sorbent injection, and
advanced flue-gas desulfurization.
Acid rain is the result of a series of complex reactions involving chemicals and com-
pounds from many industrial, transportation, and natural sources. Sulfur dioxide emissions
from new coal-fired facilities have been controlled since the 1970s by the various govern-
ment regulations. The goal of the various regulations is to ensure the continued decrease
in emissions of nitrogen and sulfur oxides from coal combustion into the atmosphere. As a
result, emissions of sulfur dioxide have dropped even though coal use has increased.

5.10 REFERENCES

Aczel, T., R. B.Williams, R. A. Brown, and R. J. Pancirov: In Analytical methods for Coal and Coal
Products, vol. 1, C. Karr Jr. (ed.), Academic Press Inc., New York, 1978, chap. 17.
Anderson, L. L. and D. A. Tillman: Synthetic Fuels from Coal: Overview and Assessment, John Wiley
and Sons Inc., New York, 1979.
Anderson, R. B.: In Catalysis on the Energy Scene, S. Kaliaguine and A. Mahay (ed.). Elsevier,
Amsterdam, Netherlands, Netherlands, 1984, p. 457.
Anthony, D. B. and J. B. Howard: AIChE Journal, 22, 1976, p. 625.
Argonne: Environmental Consequences of, and Control Processes for, Energy Technologies, Argonne
National Laboratory. Pollution Technology Review No. 181, Noyes Data Corp., Park Ridge, N.J.,
1990, chap. 6.
Armstrong, J: Carbonization Technology and Engineering, Lippincott Publishers, London, 1929.
Baker, R. T. K. and N. M. Rodriguez: In Fuel Science and Technology Handbook, J.G. Speight (ed.),
Marcel Dekker Inc, New York, 1990, chap. 22.