Page 117 - Fundamentals of Air Pollution

III. Stationary Sources 87

Loading facilities must be designed to recover all vapors generated during
filling of tank trucks or tanker ships. Otherwise these vapors will be lost
to the atmosphere. Since they may be both odorous and photochemically
reactive, serious air pollution problems could result. The collected vapors
must be returned to the process or disposed of by some means.
2. Coal
The air pollution problems associated with combustion of coal are of
major concern. These problems generally occur away from the coal mine.
The problems of atmospheric emissions due to mining, cleaning, handling,
and transportation of coal from the mine to the user are of lesser significance
as far as the overall air pollution problems are concerned. Whenever coal
is handled, particulate emission becomes a problem. The emissions can be
either coal dust or inorganic inclusions. Control of these emissions can be
relatively expensive if the coal storage and transfer facilities are located
near residential areas.

1. Primary Metals Industry
Metallurgical equipment has long been an obvious source of air pollution.
The effluents from metallurgical furnaces are submicron-size dusts and
fumes and hence are highly visible. The emissions from associated coke
ovens are not only visible but odorous as well.
2. Ferrous Metals
Iron and steel industries have been concerned with emissions from their
furnaces and cupolas since the industry started. Pressures for control have
forced the companies to such a low level of permissible emissions that
some of the older operations have been closed rather than spend the money
to comply. The companies controlling these operations have not gone out
of business but rather have opened a new, controlled plant to replace each
old plant. Table 6-3 illustrates the changes in the steelmaking processes
that have occurred in the United States.
Air-polluting emissions from steelmaking furnaces include metal oxides,
smoke, fumes, and dusts to make up the visible aerosol plume. They also
may include gases, both organic and inorganic. If steel scrap is melted, the
charge may contain appreciable amounts of oil, grease, and other combusti-
bles that further add to the organic gas and smoke loadings. If the ore used
has appreciable fluoride concentrations, the emission of both gaseous and
particulate fluorides can be a serious problem.
Emissions from foundry cupolas are relatively small but still significant,
in some areas. An uncontrolled 2-m cupola can be expected to emit up to
50 kg of dust, fumes, smoke, and oil vapor per hour. Carbon monoxide,
oxides of nitrogen, and organic gases may also be expected. Control is