Essay On Electrostatic Precipitator

WORKING OF ESPs

Electrostatic Precipitators, as the name suggests, works on the principle of Electrostatic Attraction. Every particle has or can be given a charge – positive or negative. Thus all the particles in the gas stream entering the electrostatic precipitator are imparted a negative charge and these particles, due to electrostatic attraction, migrate to the grounded collection plate and thus are collected. This dust layer is then removed from the plates from time-to-time by rapping or washing it with a water stream. So the complete process involves – Charging, collection and removal. Figure 1 Electrostatic Precipitator
As shown in Fig. 1, a typical Electrostatic Precipitator has major components namely – Discharge Electrodes, Collection Electrodes, Rappers and Hoppers. The discharge electrodes have a negative, high voltage, pulsating, direct current applied to then which creates a negative electric field around them. The collection electrodes are evenly spaced plates which are placed alternately with the discharge electrodes. These electrodes are grounded and as the name suggests are used for collection of the dust particles. The electric

This depends on the type of electrode that is being used. In some ESPs the discharge electrodes are tubes rather than plates in which case they are washed by a water stream. In case of the electrodes being plates, rapping is used to remove the dust layer on the electrode. It is a process in which dust particles are dislodged from the electrodes by sending mechanical impulses or vibrations through the electrodes which causes the dust layer to fall off as sheets and thus avoiding any re-entrainment. The removal of the layer is carried out when the thickness of the layer is between 0.3-0.5 in. The intensity and frequency of rapping depends upon the particle concentration in the flue