166C
CHEMICAL EFFECTS : see EFFECTS OF CHEMICALS; AIR POLLUTANT
EFFECTS; POLLUTION EFFECTS ON FISH
CHEMICAL TREATMENT : see PHYSICAL AND CHEMICAL TREATMENT OF
WASTEWATERSCOAL GASIFICATION PROCESSES
In spite of temporary oil “gluts,” elements of a new coal-
based synthetic fuels industry are slowly emerging in oil
importing nations. This coal conversion activity involves
the commercial integration of process and power systems.
Overcoming both process engineering and environmental
problems will be crucial factors in the development of coal
liquefaction and gasification plants. Depending upon proj-
ect size and complexity, the associated expenditures for the
total compliance effort could require multimillion dollar
budgeting.
The concept of gasification of coal is not a new one.
John Clayton proved conclusively that gas could be obtained
from coal in the early 1680s. His initial experiments were
observations of the products formed upon heating coal. In
the presence of air, heat will invariably be generated by
burning a portion of the coal. In order to increase the yield of
secondary fuels with higher hydrogen to carbon (H/C) ratio
than that of coal, it is required to gasify the coal in the pres-
ence of steam and an oxygen containing gas. The products
formed during high yield gasification are typically hydrogen,
carbon monoxide, and variable amounts of light hydrocar-
bons, especially methane. Carbon dioxide may be scrubbed
from the product. The coal, steam, air mixtures are contacted
at temperatures above 700°C in fluidized, entrained flow or
moving bed configurations.
Liquefaction of coal may be accomplished by reacting
with heavy oil derivative hydrocarbons at temperatures of
400 to 500°C. Contaminants are typically hydrogenated
to gases which may be absorbed (sulfur to H 2 S, nitrogen to
ammonia and oxygen to water).According to Quig and Granger (1983), a coal conver-
sion facility impacts the environment through the handling
of large amounts of coal, and discharges from the conver-
sion process and associated facilities. Also, there will be
impacts related to the construction and operation of any
large industrial complex. The major health concerns for
both occupational and offsite populations include potential
exposure to particulates, sulfur compounds, trace elements,
aromatic amines, and other nitrogenous compounds and
radioactive nuclides.
Considerations of these issues and concerns for this
facility will begin with the coal handling facilities. Fugitive
dust, consisting mainly of coal fines, is generated by the
disturbance of the coal in the unloading, transfer and stor-
age facilities. Particulates can remain airborne and be trans-
ported from the site under certain meteorological conditions
and therefore must be evaluated in terms of their potential
impacts and control mechanisms. Coal pile runoff and coal
wetting wastewater contain varying amounts of coal fines
and dissolved constituents depending on variables such as
rainfall intensity and duration, contact time, coal storage
configuration and coal pile sealing techniques. Values of
over 2000 mg/l total suspended solids and 10,000 mg/l total
dissolved solids have been reported by EPA and TVA for
runoff from coal piles. The magnetic separation of metal-
lic materials from the coal during preliminary coal cleaning
operations will generate a variable quantity of pyretic solid
waste which must be addressed. The coal processing facili-
ties, that is coal grinding and slurry preparation, include con-
trols which minimize the discharges from these operations.C003_001_r03.indd 166C003_001_r03.indd 166 11/18/2005 10:16:46 AM11/18/2005 10:16:46 AM