Dust collection electrical precipitators

When corona occurs, current starts to flow in the secondary circuit and some dust particles are precipitated. As potential is increased, current flow and electric field strength increase until, with increasing potential, a spark jumps the gap between the discharge wire and the collecting surface. If this "sparkover" is permitted to occur excessively, destmction of the precipitator s internal parts can result. Precipitator efficiency increases with increase in potential and current flow the maximum efficiency is achieved at a potential just short of heavy sparking. 

Electrical precipitators are probably the most versatile of all types of dust collectors. Veiy high collection efficiencies can be obtained regardless of the fineness of the dust, provided that the precipitators are given proper maintenance. The chief disadvantages are the high initial cost and, in some cases, high maintenance costs. Furthermore, caution must be exercised with dusts that are combustible in the carrier gas. 

The electrical precipitator is a dry dust or liquid mist removal unit which utilizes the ionization of the process gas (usually air) to impart electrical charges on the suspended entrained particles and effect particle collection by attraction to an oppositely charged plate or pipe. This type of unit is in use in services which are difficult for other types of entrainment removal equipment. Figures 4-79, 4-80, and 4-81 illustrate the usual fundamental action of these units. 

Most of the results presented in the previous chapters are based on idealized conditions. In practice, the performance of an electrostatic precipitator can be significantly influenced by the dust layers on discharge and collection electrodes i.e., dust layers may alter the electrical properties of the system. It is also possible that dust layers are not stable i.e., collected particles become loose, increasing the particle concentration in the outlet of the precipitator. These problems play a much smaller role if the surface collection electrode is continuously flushed with water. These wet elearostatic precipitators, however, cannot be used in all applications. 

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