Fiber bed mist eliminators

Packed fiber bed mist eliminators can be designed to operate at almost any desired particle collection efficiencies, depending on the allowable pressure drop and cost. A good discussion of sulfuric acid mist generation, control, and mist eliminator design is available (109,110). 

Packed columns, 10 769-772, 773 band broadening, 6 412 for distillzation, 5 768-776 gas chromatography, 6 377, 379 instrumentation, 6 423-424 Packed column supercritical fluid chromatography (pSFC), 19 567 Packed fiber-bed mist eliminators, 23 781 Packed towers, 25 810, 811 Packing(s)... 

FIGURE 3.2-14 Fiber bed mist eliminator oonfignration, Courtesy Monsanto Envirochem Co. 

Tightly packed fiber bed mist eliminators are another option for impmgement separations. These devices were developed by the Monsanto Compaiiy for sulfuric acid plant mist qrplications, but they are now also available firm various companies. Their main advantt is to allow efficient mnoval of paries down to the 0.1-1 fim range. These very small particles are not separated by havit greater momentum than the vapor or gas, but by the random Brownian movement or raiidom diffimion. The particles diffuse to the fiber surface in the very densely packed beds. Browitian movement actually increases as particle size decreases, improving the separation of very small particles. 

Monsanto Enviro-Chem. Systems Fiber Bed Mist Eliminator, 1979. 

More recentiy, sulfuric acid mists have been satisfactorily controlled by passing gas streams through equipment containing beds or mats of small-diameter glass or Teflon fibers. Such units are called mist eliminators (see Airpollution control methods). Use of this type of equipment has been a significant factor in making the double absorption process economical and in reducing stack emissions of acid mist to tolerably low levels. 

This type of technology is a part of the group of air pollution controls collectively referred to as wet scrubbers. Fiber-bed scrubbers are also known as wetted-filter scrubbers and mist eliminators. The technology is based on the removal of air pollutants by inertial and diffusional interception. 

Fiber-bed scrubbers are used to collect fine or soluble particulate matter or as mist eliminators to collect liquid aerosols, including inorganic (e.g., sulfuric acid mist) and volatile organic compounds. Insoluble or coarse PM will clog the fiber bed with time, and VOCs that are difficult to condense will not be collected efficiently. 

Fiber-bed scrubbers are used to control aerosol emissions from chemical, plastics, asphalt, sulfuric acid, and surface coating industries. They are also used to control lubricant mist emission from rotating machinery and mists from storage tanks. Fiber-bed scrubbers are also applied downstream of other control devices to eliminate a visible plume. Despite their potential for high collection efficiency, fiber-bed scrubbers have had only limited commercial acceptance for dust collection because of their tendency to become plugged. 

Mist Eliminators. Most modem mist eliminators use fiber beds enclosed or supported by stainless steel or alloy-20 wire mesh or the tike. Fibers are generally glass, or in some cases Teflon. Mist eliminator design, ie, fiber diameter, packing density, bed depth, etc, is determined by particle size and loading, which is in turn determined largely by the application. 

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