Cyclone dust separators pressure drop

Current designs for venturi scrubbers generally use the vertical downflow of gas through the venturi contactor and incorporate three features (I) a wet-approach or flooded-waU entry sec tion, to avoid dust buildup at a wet-dry pmction (2) an adjustable throat for the venturi (or orifice), to provide for adjustment of the pressure drop and (3) a flooded elbow located below the venturi and ahead of the entrainment separator, to reduce wear by abrasive particles. The venturi throat is sometimes fitted with a refractoiy fining to resist abrasion by dust particles. The entrainment separator is commonly, but not invariably, of the cyclone type. An example of the standard form of venturi scrubber is shown in Fig. 17-48. The wet-approach entiy section has made practical the recirculation of slurries. Various forms of adjustable throats, which may be under manual or automatic control. 

Many types of particulate collection devices are available commercially (see Table 53.2). Each operates on a different principle for accomplishing removal of particulates from the gas stream. Four basic types are common in drying systems (1) the drying vessel itself (in the case of vessel dryers), (2) cyclones, (3) bag filters, and (4) wet scrubbers. Electrostatic precipitators (ESPs) are not used widely in drying installations in spite of their low-pressure drop and high collection performance. The initial cost of purchase and construction is high. For this reason, the emphasis in Section 53.3 will be on the three most widely used devices, e.g., cyclones, fabric filters, and wet scrubbers. For a concise discussion of various types of solid-gas separation equipment and guidelines for selection of dust collectors,... 

In general today, most catalyst is removed from the converter by vacuum. The catalyst is collected in a cyclone-like vessel and fed by feeder on to a two-layer mechanical screen which separates the quartz from the catalyst and the catalyst from the dust in one operation. In some instances, it is desirable to separate pellet catalyst from ring catalyst, so that the ring catalyst can later be reinstalled on top to maximize dust penetration which minimizes pressure drop build up. 

Obermair and Staudinger (2001) studied the gas flow, pressure drop and separation efficiency in cyclones with the dust outlet configurations shown in Fig. 15.1.9. The corresponding performance data is presented in Table 15.1.2. Upon comparison, we see that configuration a is not as efficient a design as the others. This is probably due to re-entrainment from the solids hopper. It does exhibit a comparatively low pressure drop, however. Its two vortex-stabilized... 

Figure 4-4 shows a typical system under positive pressure. It differs from the vacuum system in that the material enters from one source and is distributed directly to several tanks. In this case no cyclone separator is used the air laden with solids enters the process bins directly. The decrease in velocity of the stream and its change in direction will cause most of the solids to drop out. For this system each receiver must have a filter to remove the remaining solids. Note that the blower is placed at the air entrance, instead of after the filter as in the vacuum system. Should a bag in the fiber filter break, no dust will get into the blower or its motor. Another advantage is that no contaminants from the atmosphere can enter the system when it is under positive pressure, except through the air inlet system. 

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