Electrostatic Separation
Principle of Electrostatic Separation:
If one or more of the materials in a granular mixture acquires a surface charge on or just before entering an electrostatic field, the grains/particles of that material will be attracted or repelled from the active electrode depending on the sign of the charge on the grains/particles.
What is Electrostatic Separation ?
• Electrostatic separation is a method of solid particle separation based on the differential attraction or repulsion of charged particles in the presence of an electric field. The variation in electrical characteristics of different materials is responsible for such separation.
• Charging of the particles is an essential step in these separation. Solid particles can receive a surface charge by any one of the following methods :
(i) Contact electrification.(ii) Electrification by conductive induction.
• Electrification by conductive induction : When an uncharged solid particle is placed on a grounded conductor in the presence of an electric field (i.e., when the particle comes in contact with a charged surface), the particle will quickly acquire a surface charge by induction. A conductive particle is acquires the same charge as grounded conductor (it becomes charged to the same potential as the grounded conductor within a very short period of time) through its contact with the conductor while a dielectric particle is polarised and thus no net charge is generated on it. As a result of this induction, the conducting particle will be repelled by the surface/grounded conductor, while the dielectric particle will be unaffected. This method is used for making a finite separation between relative conductors and non-conductors.
Also Read: Rotameter Working Principle
Also Read: Ball Mill Working Principle
Electrostatic Separator Working Principle:
• Electrostatic separation depends on differences in the electrical properties (conductivity) of the materials to be treated.
• The electrostatic separator shown in Fig. consists of a grounded rotor/rotating drum, collecting bins, and an active electrode located at a small distance from the drum, and a hopper for feeding the solids.
• The solids to be separated are fed onto a revolving drum that is either charged or grounded, from a hopper. In very short time the conductive particles will assume the potential of the rotating drum, which is opposite to that of an active electrode and hence, they get attracted towards the active electrode. The non-conductive material is repelled or rejected by the electrode and attracted by the drum. The non-conductive substance or material falls down straight under the influence of gravity and it is collected in a separate bin.