Canadian Air Systems Co. is a designer and manufacturer of industrial dust collection systems including dry type dust collectors. Dust collection equipment utilizing the principle of wet dust collecting is available in numerous designs utilizing a number of principles and featuring wide variation in effectiveness, initial cost, operating and maintenance expense, space, arrangements and material of construction.

The use of centrifugal force to throw a dust particle to the periphery of an air stream has been used in the cyclone collector for many years. Dry centrifugal dust collectors can be divided into two basic groups cataloged by their effectiveness in removal of smaller dust particles.

Cyclone Dust Collectors are frequently applied for the removal of coarse dusts from an air stream, as a pre-cleaner to more efficient dry or wet dust collectors and / or as a separator in product conveying systems using an air stream to transport material. Principle advantages are low cost, low maintenance and low pressure drop (in order 0.75" to 1.5" WG), but this type dust collector can not be used for collection of fine particles.

High Efficiency Centrifugal Dust Collectors have been developed whereby higher centrifugal forces are exerted on dust particles in a gas stream. Improvement in dust separation efficiency has been obtained by 1) increasing velocities through a cyclone shape dust collector, 2) utilizing a skimmer or other design feature, 3) using a number of small diameter cyclones in parallel and 4) placing units in series in some unusual applications.

While such collectors do not generally reach as high an efficiency on small particles as do the electrostatic, fabric type, or some wet type dust collectors,  their effective collection range is appreciable extended beyond that of the conventional low-pressure cyclone. Pressure losses of dust collectors in this group range from 3" to 8" WG.

In Dry Type Dynamic Precipitators dust is precipitated by centrifugal force on to specially shaped blades on an exhauster wheel and then conveyed through a dust circuit in the fan casing to the dust storage hopper.

In Louver Type Dust Collector centrifugal forces can be applied to a particle by a rapid change in direction of air flow by series of plates set at an angle to the air stream. Coarse particles traverse the air stream and will project back to the dirty air side by the forces that can be produced from such an impact. Efficiency is essentially a function of louver spacing. The closer the spacing, the higher the efficiency but also the greater the probability of plugging of the air passages - plugging due to both buidup on the front and back of the louver and mechanical obstruction by larger particles.

In Settling Chambers dust is settled out in a large chamber when conveying velocities are reduced to the point where the particles are no longer conveyed. Extreme space requirements and the presence of edde currents to nullify the effective velocity mean that settling chamber type of dust collectors can be used only for removal of extremely coarse particles.

Potable Unit Collectors fill the need for dust collection from isolated, portable or frequently relocated dust producing operations, a number of unit collector designs are availbale having capacities in the range of 200 to 1,000 CFM. Featuring small space and designed to recirculate the air, collectors of this type have been used extensively, especially in the metal working industry. Unit Dust Collectors fall into two groups. Fabric collectors use cloth envelopes quite closely spaced with some manual means of vibration and with air velocities through the fabric of 8 to 12 fpm. The fan filter group uses an air filter, usually of the visousos type, preceeded by some primary collector which may be a simple settling chamber or a more effective centrifugal dust collector.

For additional information please refer to http://www.nis-co.com/fumeextractor/Index.html.

Oleg Tchetchel
Air process engineer
Canadian Air Systems
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