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POLLUTANTS
Mists/Aerosols
Acid Mist
A number of inorganic acids may, under certain conditions, hydrolyze with water vapor present
in the gas stream to form extremely fine aerosols. These include SO3 (H2SO4), phosphoric acid
relatively concentrated HCl, HF, HBr, etc. These aerosols are not easily removed with
conventional wet scrubbing techniques because of their small size (0.1-o.5 microns). The most
effective treatment method is the use of wet electrostatic precipitation, particualrly with
respect to H2SO4 and phosphoric acid mist. The sulfuric acid industry has used wet ESPs for
decades to capture acid mist.
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Sulfur Trioxide
In those cases where SO3 exists in a gaseous form only (not converting to H2SO4
aerosol) it can be effectively treated by Jet Venturi Fume Scrubbers and/or Counter Current Packed Towers using
aqueous NaOH or water. Because of the extremely low vapor pressures of aqueous H2SO4
solutions, H2SO4 in water may be used to scrub SO3 forming a more concentrated
and usable H2SO4 (97 - 98% strength) solution. If SO3 is hydrolized to form
sulfuric acid mist , 0.1-0.5 microns in size, the most effective control device is a wet ESP.
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Oil Mists
Fine oil mists can result from a number of sources. Food processing, textile manufacturing, plastic
manufacturing, are typical sources of fine (much of it sub-micron) oil mists. The use of wet electrostatic
precipitation has proven to be the most effective technology for the treatment and elimination of visible oil
mist plumes. Croll Reynolds’ CONDENSING WESP® can be used even in those instances in which the oil mist is
viscous at ambient temperatures and APC equipment maintenance is a problem. The ability to keep the collecting
tubes at elevated temperature by using hot water to surround the tubes keeps the collected oils in a relatively
free flowing state.
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