Techniques to Reduce Particulate Pollutants

Particulates can be removed from air using several devices, each suited to a different particle size and gas volume. An electrostatic precipitator passes the dust-laden gas past a high-voltage discharge electrode, which charges the particles; they then migrate to and are collected on an oppositely-charged plate, giving very high removal efficiency (often over 99%) and making it the standard device at large thermal power plants. A gravity settling chamber simply slows the gas stream in a large chamber long enough for heavier particles to fall out under gravity -- cheap but effective only for coarse particles. A wet scrubber sprays water (or another liquid) through the gas stream so particulates are trapped in the droplets and washed out, and can additionally absorb some soluble gaseous pollutants like SO2 at the same time. A cyclone collector spins the gas stream in a conical c …