Dilute-phase conveying combined system

Positive displacement blowers Positive displacement blowers are probably the most commonly used type of compressor for dilute phase conveying systems. They provide an ideal match, in terms of pressure capability, with the conventional low pressure rotary valve, and are a typical working combination on many plants. They can be used as vacuum pumps, or exhausters, as well as blowers. The principle of operation is illustrated in Figure 4.26. Twin rotors are mounted on parallel shafts within a casing, and they rotate in opposite directions. As the rotors turn, air is drawn into the spaces between the rotors and the casing wall, and is transported from the inlet to the outlet without compression. As the outlet port is reached, compression takes place when the air in the delivery pressure pipe flows back and meets the trapped air. 

Dense-phase conveying, also termed "nonsuspension" conveying, is normally used to discharge particulate solids or to move materials over short distances. There are several types of equipment such as plug-phase conveyors, fluidized systems, blow tanks, and, more innovative, long-distance systems. Dilute-phase, or dispersed-phase conveyors, are more versatile in use and can be considered the typical pneumatic conveying systems as described in the literature. The most accepted classification of dilute-phase conveyors comprises pressure, vacuum, combined, and closed-loop systems. 

Dilute-phase pneumatic conveying systems (a) pressure system, (b) vacuum system, (c) combined system, and (d) closed-loop system. 

Quite often the root cause of a conveying problem is a lack of appreciation and understanding of the relevant fundamentals. This is particularly true even for dilute-phase systems, which are quite simple in appearance . Due to this apparent simplicity, many Signers, operators and even researchers can often overlook some of the unique and unusud phenomena resulting from a combination of product, mode of transport and component design or selection. 

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