Feature Summary

Pressure Drop

Less than 0.5 in of water

Operating Temperatures Up to 1000°C

Applications

Precleaners for removing dry dust produced by grinding in cement and lime kilns, grain elevators, rock crushers, milling operations, and thermal coal dryers

Dust Particle Sizes Greater than 50 ¡xm

Settling chambers serve as preliminary screening devices for more efficient control devices. These chambers remove large particles from gas streams by gravity. The chambers slow the gas sufficiently to provide enough time for particles to collect (Leith, Dirgo, and Davis 1986). Figure 5.16.1 shows a chamber of length L, width W, and height H. A mass balance for an infinitesimal slice dL yields:

where:

Vg = the uniform gas velocity

Vts = the particle terminal settling velocity

C = particle concentration in the slice dL

This equation assumes that the particles are well-mixed in every plane perpendicular to the direction of air flow due to lateral turbulence. This assumption is reasonable because even at low velocities, gas flow in industrial-scale settling chambers is turbulent. Rearranging Equation 5.16(1) and integrating between the two ends of the chamber yields the collection efficiency of the chamber as:

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