Charging of Particles

The corona surrounding a discharge electrode of an ESP is a gas plasma of electrons and cations. The cations are drawn into the electrode, which is biased negative. The electrons are repelled into the interelec-trode space where, within one centimetre travel, they ionize gas particles. These gas particles are drawn toward the grounded collector electrodes. On the way, many of them collide with and attach to the particles to be collected, charging them. The charged particles are then drawn towards the collector electrodes. This particle charging is efficient. Typical charging time is 5 ms; typical residence time in an ESP is 2-5 s.

Charging processes are of two types: field charging, where ions moving with the electric field charge the particles, and diffusion charging, where charging is due to collision with ions moving with random thermal motion. The types are distinguished to facilitate mathematical description. Field charging is dominant in charging particles with radius (a) greater than 0.5 |im; diffusion charging is dominant with < 0.2 |im particles. Both mechanisms are important in the intermediate size range.

The charge on an ion at time t (q(t)) resulting from field charging, derived by Pauthenier and Moreau-Hanot is:

Solar Panel Basics

Solar Panel Basics

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