How an electrostatic smoke precipitator works ?

Electrostatic smoke precipitators work by forcing dirty flue gas (the gas escaping from a smokestack) past two electrodes (electrical terminals), which take the form of metal wires, bars, or plates inside a pipe or smokestack. The first
electrode is charged to a very high negative voltage. As the dirt particles move past it, they pick up a negative charge. Higher up the pipe (or further along, if it's a horizontal pipe), there's a second electrode consisting of metal plates charged to a high positive voltage. Since unlike charges attract, the negatively charged soot particles are attracted to the positively charged plates and stick there. From time to time, the collecting plates have to be shaken to empty away the soot; that can be done either manually (by someone brushing them clean) or automatically (by some kind of automated shaking or brushing mechanism in a process called rapping).

Illustration: Electrostatic smoke precipitators use static electricity to remove the soot from smoke. Dirty air moves past negatively charged wires (shown as −ve) so the soot particles pick up a negative charge. The negatively charged particles of soot then stick to positively charged plates (shown as +ve) further along the pipe. Much cleaner air emerges from the pipe as a result. Most precipitators also have simple fabric filters at each end of the pipe (shown by the orange bars) to remove larger soot particles.