Pneumatic conveying filters

Grinding and packing, air separator, grinding, pneumatic conveying, materials handling, packaging Particulates (dust) Local exhaust system and fabric filters... 

The separation step requires (1) application of a force that produces a differential motion of the particles relative to the gas, and (2) sufficient gas-retention time for the particles to migrate to the collecting surface. Most dust-collections systems are comprised of a pneumatic-conveying system and some device that separates suspended particulate matter from the conveyed air stream. The more common systems use either filter media (e.g., fabric bags) or cyclonic separators to separate the particulate matter from air. 

The fluffy carbon black coming out of the filter is pneumatically conveyed into a first storage tank. Small amounts of impurities ( grit, e.g., iron, rust, or coke particles) are either removed by magnets and classifiers or milled to an appropriate consistency. 

A gas black apparatus consists of a burner pipe approximately 5 m long, which carries 30-50 diffusion burners. The flames burn in contact with a water-cooled drum, where about half of the carbon black formed is deposited. This black is scraped off and transported by a screw to a pneumatic conveying system. The gas black apparatus is surrounded by a steel box open at the bottom. At the top of it, fans suck the off-gas into filters, which collect the carbon black suspended in the gas. 

Figure 5.6. Components of pneumatic conveying systems, (a) Rotary positive displacement blower for pressure or vacuum, (b) A rotary airlock feeder for fine materials (Detroit Stoker Co.), (c) A four-compartment receiver-filter (Fuller Co., Bethlehem, PA), (d) A two-stage cyclone receiver, (e) The Fuller-Kinyon pump for cement and other fine powders. Powder is fed into the aeration chamber with a screw and is fluidized with compressed air (Fuller Co., Bethlehem, PA).

The flow sheet of this process is shown in Figure 26.2. Prepared plastic fluff is sent to a bag filter set on the top deck (Figure 26.1) by a pneumatic conveyer after treatment by a second magnetic separator and an aluminum separator. Then, the plastic fluff is sent to two series of dehydrochlorinators, specially designed, reciprocally rotating twin-screw-type extruders, through a vertical screw conveyer. This equipment is composed of a melter of plastic fluff aud circulator of waste plastic melt. Each is a horizontal type... 

Figure 9.12. Examples of pneumatic conveying dryers corresponding performance data are in Table 9.13. (a) Raymond flash dryer, with a hammer mill for disintegrating the feed and with partial recycle of product (Raymond Division, Combustion Engineering), (b) Buttner-Rosin pneumatic dryer with separate recycle and disinte ation of large particles (Rosin Engineering Ltd.), (c) Berks ring dryer the material circulates through the ring-shaped path, product is withdrawn through the cyclone and bag filter [Pennsalt Chemical Co.).

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