Electrical Precipitators in Air
Pollution Control
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P. R. GAUDETTE
Sales Engineer
Research-Cottrell, Inc.
Chicago, Illinois
As industrial processes have increased in number and complexity
during the past several decades, air pollution problems and controls have
increased in almost direct ratio. Greater and greater need has developed
for effective removal of wanted (and unwanted) materials suspended
in industrial gases. To meet this need, industry has spent millions of
dollars for dust removal equipment in order to prevent a nuisance
problem, build good community relations, and, in many instances, recover valuable materials or clean gases for subsequent use in other
processes.
This paper is a description of the Cottrell Electrostatic Precipitator
and its application in the field of air pollution problems. As a combatant
against "aerial sewage" from industrial plants, the electrostatic precipitator is a major weapon. It is a device that can be operated economically and it will handle tremendous gas volumes at recovery efficiencies in the 95% or more range even when the concentration of
material to be removed is merely a fraction of a grain per cubic foot.
Electrical precipitators have been extensively applied in the power
generating industry since about 1923 for the collection of fly ash from
pulverized coal fired boilers. In addition to the standard pulverized
coal-fired boiler, there has been developed in recent years, a so-called
cyclone type of boiler. The resultant fly ash from burning coal in these
two types of boilers is extremely fine in particle size, due to improvements in pulverizing equipment and better firing practices. Modern
steam generating units are increasing in size, so that stack gas volumes
in excess of 1,000,000 cubic feet per minute must be cleansed before
release to the atmosphere.
It is interesting to note that the requirements on efficiency of removal
of fly ash have been increased steadily in the power industry. Table I
shows the percentage of installations for fly ash removal wherein the
efficiency of removal was specified as over 95% for the various periods
noted.
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