Feature Summary

Types of Designs

Reverse flow, or straight through, with tangential, scroll, and swirl vane entries

Gas Flow Rates

50 to 50,000 m3/hr

Pressure Drop

Between 0.5 and 8.0 in of water

Operating Temperatures Up to 1000°C

Applications

Cement and lime kilns, grain elevators, milling operations, thermal coal dryers, and detergent manufacturing

Dust Particle Sizes Greater than 5 /m

Partial List of Suppliers

Advanced Combustion Systems Inc.; Alfa-Laval Separation Inc.; Bayliss-Trema Inc.; Beckert and Heister Inc.; Clean Gas Systems

Inc.; Dresser Industries Inc.; Ducon Environmental Systems; Emtrol Corp.; Fisher-Klosterman Inc.; Hough International Inc.; HVAC Filters Inc.; Interel Environmental Technologies Inc.; Joy Technologies Inc.; Quality Solids Separation Co.; Thiel Air Technologies Corp.; United Air Specialists Inc.; Wheelabrator Inc.

Cyclones operate by accelerating particle-laden gas in a vortex from which particles are removed by centrifugal force. One of the most widely used dust collecting devices, cyclones are inexpensive to construct and easy to maintain because they do not have any moving parts. Although cyclones are inefficient for collecting particles smaller than 5 / m in diameter, they operate with low to moderate pressure drops (0.5 to 8.0 in w.g.).

Cyclones can be constructed to withstand dust concentrations as high as 2000 g/m3, gas temperatures as high as 1000°C, pressures up to 1000 atm, and corrosivity. Such conditions are encountered in the pressurized, fluidized-bed combustion of coal, where cyclones are an economic control option. In addition, cyclones are used to control emissions from cement and lime kilns, grain elevators, grain drying and milling operations, thermal coal dryers, and detergent manufacturing.

Various cyclone designs have been proposed; however the reverse-flow cyclone is the type most commonly used for industrial gas cleaning. Figure 5.16.2 shows the dimensions of a reverse-flow cyclone. Dust-laden gas enters the cyclone at the top; the tangential inlet causes the gas to spin. After entry, the gas forms a vortex with a high tangential velocity that gives particles in the gas a high centrifugal force, moving them to the walls for collection. Below the bottom of the gas exit duct, the spinning gas gradually migrates to the cyclone axis and moves up and out the gas exit. Thus, the cyclone has an outer vortex moving downward and an inner vortex flowing upward (Dirgo and Leith 1986). Collected dust descends to the duct outlet at the bottom of the cone.

Cyclone dimensions are usually expressed as multiples of the diameter D. The dimension ratios a/D, b/D, De/D,

Gas Outlet

Gas Outlet

Inlet

Dust Outlet
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