pa1778data.pdf

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U.S. STEEL DUQUESNE WORKS
HAER No. PA-115
(Page 102)
of the original gas scrubbers installed in 1908. A more
significance industry-wide innovation was the installation of a
new ferromanganese gas cleaning system in 1953. Begun in 1949 at
blast furnace number two, the production of ferromanganese
generated waste gases with qualities much different than those
produced in furnaces on basic iron. The temperature of the gas
(750° F.), for example, was nearly double the temperature at
which gas from basic iron production left the furnace. Second,
after leaving the dust catcher, the quantity of fine entrained
particulate (about eight grains per cubic foot) was also double
that contained in the flue gas emanating from furnaces on basic
iron production. Consequently, it was impossible to clean all of
the gas flowing from a furnace on ferromanganese by conventional
methods. This meant that much of the fume had to be emitted into
the atmosphere through bleeder stacks located at the top of the
furnace. Third, the floury composition of the flue dust from
ferromanganese furnaces made it difficult to store as it would
become air-borne in the slightest breeze. Compounding the
problems associated with ferromanganese production was the
pyrophoric nature of the flue dust which made it susceptible to
spontaneous combustion upon exposure to the atmosphere.
Efforts to find solutions to these practical problems were
further influenced by smoke control legislation passed by
Allegheny County in 1949. Among the most stringent in the nation
for its time, the ordinance limited flue dust emissions to .5 or
less pounds per 1,000 pounds of gas produced, mandating that 85
percent of all industrial gas produced be removed.
Over the years several cleaning methods and types of
equipment were tried at Duquesne without appreciable success.
For example, ferromanganese gas was run through an electrical
precipitator after it had passed through the plant's conventional
gas cleaning equipment. This experiment lasted less than a year
as the great quantity of dust generated in ferromanganese
production completely clogged up the precipitator at frequent
intervals. Finally, after years of research conducted by the
United States Steel Corporation in conjunction with engineers
from the Research Corporation at the Isabella furnace plant in
Etna, Pa., a workable solution to the cleaning problem was found.
It resulted in the installation of the industry's first cleaning
plant devoted solely to ferromanganese gas at the Duquesne Works.
The plant consisted of five parallel units, each composed of a
gas conditioning tower, an electrical precipitator, a screw
conveyor-fed rotary kiln, and a continuous mixer. Two additional
bucket conveyor-fed intensive mixers served all five units before
discharging the flue dust into a briquetting press.
The process began with the transfer of the flue gas from the