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Electrostatistic Precipitation 189

of sulfuric acid, gases from the smelter contain approx 3–10% sulfur dioxide and con-
taminated particulates. They must be removed before being introduced into the converter
to prevent fouling of the catalyst. Precipitators designed for the chemical industry are gen-
erally of the tubular type with vertical gas flow. The particulate collection efficiencies
of ESP range from 97% to 99.5% (9).
4.6. Municipal Solid-Waste Incinerators

The use of precipitators on municipal solid-waste incinerators is a relatively new
application. Emission of particulates ranges from 50 to 300 g/kg of refuse or from 1.2
3
to 5.7 g/m of gas (5). The properties and composition of the particulate matter vary
greatly because the composition of refuse is highly variable. Particle size varies from a
median diameter of 15–30 µm (9). The resistivity of fly ash varies with temperature,
moisture content, and particle size. Gases from municipal solid-waste incinerators are
at temperatures of 655–900°C and must be cooled before entering the precipitator (9).
The particulate collection efficiencies of ESP range from 90% to 99%.

4.7. Petroleum Industry
Principal uses in the petroleum industry are for the collection of particulate emitted
from fluidized-bed catalytic cracking units (FCC), for the removal of tar from gas
streams, such as fuel gases, acetylene, and shale oil distillation gases, and for the collec-
tion of particulates emitted from fluidized-bed waste sludge incinerators. The median
particle size is approx 10–12 µm (9).

4.8. Others
Two-stage precipitators are applied for aerosol sampling, food processing, asphalt
saturating, high-speed grinding machines, galvanizing kettles, rubber-curing ovens, and
radioactive particle collection (5,9,12). They are also used at hospitals as well as in
office buildings, where particle-free air is essential.

5. PROBLEMS AND CORRECTIONS
Despite many successful installations in various industrial operations, electrostatic pre-
cipitators in many cases have failed to meet performance requirements by somewhat large
margins. Even the best available precipitator cannot handle all situations. The problems
for the precipitator are classified in the four major categories: fundamental, mechanical,
operational, and chemical.

5.1. Fundamental Problems
Fundamental problems are associated with (1) the assumptions in the derivation of
the Deutsch–Anderson equation, (2) the high resistivity of particles, (3) nonuniform
gas flow, (4) improperly designed electrode systems, (5) insufficient high-voltage
electrical equipment, (6) inadequate rapping equipment, and (7) re-entrainment of
collected particles.
Much effort has been spent via theoretical, empirical, and statistical methods at refin-
ing the Deutsch–Anderson equation and to make the resulting collection efficiency
expression more useful for design purposes. In a study dealing with precipitation of fly