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Dust Collectors and Fume Extractors |
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| Date Added: February 21, 2012 10:20:55 PM | |
| Author: Oleg Tchetchel | |
| Category: Blogs: Business | |
Some Factors influencing dust collection equipment selection aree: * Concentration and particle size of contaminant. In most dust conveying systems, usual dust range from 0.1 to 100 micron - a rather wide range of particle sizes. * Degree of collection required. Evaluation will consider the need for high efficiency high cost equipment such as electrostatic precipirators; high efficiency moderate cost equipment such as fabric or wet collector units; and the lower cost primary units such as the dry centrifugal group. Degree of dust collection required can depend on plant location; compariosn of quantities of material released to atmoshere with different type of dust collectors; nature of contaminant - its salvage value or its potential as a health hazard, public nuissance or ability to damage property - and the requirements of the local or state air pollution regulations. * Characteristics of air or gas stream. High temperature gas streams exceeding 180 F will prevent the use of standard cotton media in fabric collectors; presence of steam or condensation of water vapor will cause packling and plugging of air or dust packages in fabric and dry centrifugal collectors. Chemical composition can attack fabric or metal in dry collectors and cause extremely corrosive conditions when mixed with water in wet type collectors. * Characteristics of contaminant. Chemical composition can cause attack on dust collector elements or corrosion in wet type dust collectors. Sticky materials like metallic buffing dust impregnated with buffing compounds can adhere to collector elements plugging dust collector passages. Linty materials such as dust from textile opener, picker and napper will adhere to certain types of collector surfaces or elements. Abrasiveness of many materials in moderate to heavy concentrations such as dust from sand blasting will cause rapid wear particularly on dry type centrifugal collectors. Particles size and shape will rule out certain collector designs. The parashute shape of particles such as "bees wings" from grain will "float" through centrifugal collectors due to their velocity of fall being slower than much smaller spherical particles of the same specific gravity. Combustible nature of many finely divided materials will influence selection of explosion proof dust collectors for such products. * Methods of disposal. Methods of removal and disposal of collected materials will vary with the material, plant process, quantity involved and the collector design. Dry collectors can be unloaded continuously or in batches through dump gates, trickle valves and rotary locks to conveyors or containers. Wet collectors can be arranged for batch removal or continual ejection of dewatered material by flight conveyors or draining as a slurry. Material characteristics can influence other problems, such as packing and bridging of dry materials in dust hoppers, floating of slurry forming characteristics in wet collectors, etc. CAS Co. offers the following types of wet dust collectors: CHAMBER OR SPRAY TOWER Consists of a round or rectangular chamber into which water is introduced via spray nozzles. There are many variations in design but the principal mechanism is impaction of dust particles on the liquid droplets created by nozzles. These droplets are separated from the air stream by centrifugal force or impingement on water eliminators. PACKED TOWERS Collectors in this group are essentially contact beds through which gases and liquid pass either concurrently, counter=concurrently or in cross-flow and are used primarily for applications involving gas, vapor and mist removal. WET CENTRIFUGAL COLLECTORS Wet centrifugal dust collectros utilize centrifugal force to acceslerate the dust particle and impigne it upon a wetted collector surface. These collectors are more efficient than the chamber type. Some are availbale with different number of impingement sections. WET DYNAMIC PRECIPITATORS This type uses water sprays within a fan housing and obtains precipitation of the dust particles on the wetted surface of an impeller with special fan blade shape. No internal pressure drop is involved although mechanical efficiency is somewhat lower than the mechanical efficiency of standard exhaust fans. ORIFICE TYPE COLLECTORS In this group of wet collectors designs, the air flow through the collector is brought in contact with a sheet of water in a restricted passage. Water flow may be induced by the velocity of the air stream or maintained by pumps and weirs. For additional information please refer to http://nis-co.com/scrubber/Index.html. Oleg Tchetchel Designer of Industrial HVAC Systems CAS Air Systems http://nis-co.com/contact/Index.html http://www.nis-co.com/scrubber/Index.html |
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