Dust separation

Other Centrifugal Collectors. Cyclones and modified centrifugal collectors are often used to remove entrained Hquids from a gas stream. Cyclones for this purpose have been described (167—169). The rotary stream dust separator (170,171), a newer dry centrifugal collector with improved collection efficiency on particles down to 1—2 pm, is considered more expensive and hence has been found less attractive than cyclones unless improved collection in the 2—10-pm particle range is a necessity. A number of inertial centrifugal force devices as well as some others termed dynamic collectors have been described in the Hterature (170). 

Dust Separation It is usuaUy necessaiy to recover the solids carried by the gas leaving the disengaging space or freeboard of the fluidized becl GeneraUy, cyclones are used to remove the major portion of these sohds (see Gas-Sohds Separation ). However, in a few cases, usuaUy on small-scale units, filters are employed without the use of cyclones to reduce the loading of solids in the gas. For high-temperature usage, either porous ceramic or sintered metal has been employed. Multiple units must be provided so that one unit can be blown back with clean gas while one or more are filtering. 

Staub, m. dust powder pollen, -abscheider, m. dust separator. 

The Sylvan Chart [2] of Figure 4-3 is useful in preliminary equipment selection, although arranged primarily for dust separations, it is applicable in the appropriate parts to liquid separations. Perry [23] presents a somewhat similar chart that is of different form but contains much of the same information as Figure 4-1 and 4-lA. 

Figure 4-46. General efficiency curves, applies specifically to helical entry cyclone dust separators. Courtesy of The Ducon Co.

Figure 4-47. General efficiency curve applies specifically to involute entry cyclone dust separators. Courtesy of American Blow/er Div., American Radiator and Standard Sanitary Corp.

Figure 4-56. Inertial centrifugal dust separator. Courtesy of American Air Filter Co.

Figure 4-55. Specification Sheet, gas phase centrifugal entrainment Figure 4-57. Inertial centrifugal dust separator. Courtesy of Univer-separator (liquid or solid particles). sal Road Machinery Co.

Dowtherm(R) pressure drop, charts, 94,113 Draft tubes, mixing, 309, 313 Dust clouds, 517 Dust explosions, 513 Calculations, 513 Dust separator, applications, 278 Characteristics, 234 Table, 232... 

Figure 7.2-11. Spray drier with heat recovery system 1. Spray tower and drying system 2. Air heater 3. Air fan 4. Cyclone dust separator 5. Wet dust separator and entrainment separator 6. Exhaust air fan 7. Pneumatic product conveyer 8. Intermediate product storage 9. Product sieving and packing 10. Wet product pumping system (by courtesy of BMA, TAG-Division). 

F. Loffler 2002, (Dust separation), in Ullmann s Encyclopedia of Industrial Chemistry, (vol. 11), 6th edn, Wiley VCH, Weinheim. 

The principles of fluidisation, discussed in Chapter 6, are applied in this type of dryer, shown typically in Figure 16.25. Heated air, or hot gas from a burner, is passed by way of a plenum chamber and a diffuser plate, fitted with suitable nozzles to prevent any back-flow of solids, into the fluidised bed of material, from which it passes to a dust separator. Wet material is fed continuously into the bed through a rotary valve, and this mixes immediately with the dry charge. Dry material overflows through a downcomer to an integral after-cooler. An alternative design of this type of dryer is one in which a thin bed is used. 

Textile mill dusts investigated include samples collected using a vertical elutriator cotton dust sampler, seunples of fine dust separated mechanically from carding filter cake material, Scimples collected on electrostatic precipitators in a card room, coarse condenser trash from a card room, and weave room dusts. 

The sieve frames should be made of wood to avoid the danger of friction and impact. Brass mesh (formerly perforated parchment) or silk muslin is used, stretched on frames so that the sieves can be easily arranged according to the grain sizes required. Dust separated out by sieving is sent back to the edge runners. 

Mechanism and Type of Rotary Flow Dust Separators... 

Catalytic filters should possess the following properties 1) high thermal, chemical, and mechanical stability 2) high dust separation efficiency attained by cake filtration (no penetration of particulates into the filter structure) 3) low cost 4) high catalytic activity (operation at high superficial velocities) and 5) low pressure drop. 

This dust separated by pneumatic filters or cyclones can be recycled and used as internal seeds (disperse phase) for the production of new particles or for the layered growth (continuous phase) of existing particles. One effect of the production of internal seeds is the formation of a wide particle size distribution, while the deposition of the re-fed dust yields to growth of particles. 

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