Figure 1
Cyclones by themselves are generally not adequate to meet stringent air pollution
regulations, but they serve an important purpose. Their low capital cost and their
maintenance-free operation make them ideal for use as precleaners for more expensive
final control devices such as baghouses or electrostatic precipitators. In addition to use
for pollution control work, cyclones are used extensively in process industries; for example, they are used for recovering and recycling certain catalysts in petroleum
refineries and for recovering freeze-dried coffee in food processing plants.
In the past, cyclones have often been regarded as low-effrciency collectors. However,
efficiency varies greatly with particle size and cyclone design. During the past two
decades, advanced design work has greatly improved cyclone performance. Current
literature from some of the cyclone manufacturers advertises cyclone that have
efficiencies greater than 98Yo for particles larger than 5 microns, and others that routinely
achieve efficiencies of 90Yo for particles larger than 15 - 20 microns.
In general, operating costs increase with efficiency (higher efficiency requires higher
inflow pressure), and three categories of cyclones are available: high efficiency,
conventional, and high throughput. Generalized efficiency curves for these three types of
cyclones are presented in Figure 2