Page 182 - Wastewater Solids Incineration Systems

Emission Control and Monitoring 149

rotational speed causes centrifugal action to force the particulates to the outside of
the chamber where friction with the wall of the cyclone causes them to slow down
and drop vertically to the discharge at the bottom of the chamber. The sizing of a
cyclone depends on the gas stream volume, the size and amount of particulate that
must be removed, and the pressure drop through the cyclone. For installations
where the gas volume is high, clusters of more than one cyclone can be fabricated
into a single unit, as shown in Figure 7.4.
2.3.1 Performance
The performance of a cyclone depends on the dimensional relationship between the
diameter and the height of the unit, gas viscosity, the number of turns that the gas
takes in the cyclone, inlet and outlet gas velocities, particle and gas densities, and a
dust concentration factor. The first graph in Figure 7.5 shows a typical cyclone curve
relating the percent removal efficiency by weight as a function of the inlet dust par-
ticle diameter and the fractional efficiency characteristic of the cyclone, denoted by
the letter “N.” The fractional efficiency characteristic is a function of the parameters
listed above and is specific to a particular cyclone size and configuration (i.e., single,
parallel, or series arrangement). This parameter is determined by the cyclone manu-
facturer. The second graph in Figure 7.5 shows the percent removal efficiency of var-

FIGURE 7.4 A multiple cyclone unit.