Drift velocity of fine particles estimated from fractional efficiency measurements in a laboratory-scaled electrostatic precipitator

Abstract

The process of electrostatic precipitation that depends on the migration of particles toward the grounded collecting plates and, therefore, on their associated drift velocity, is investigated using a laboratory-scaled electrostatic precipitator (ESP). The migration of the charged particles due to the electric force exerted by the field is affected by the turbulent gas flow. Estimating the particles drift velocity requires controlling the electric conditions inside the ESP (electric field of collection, particles charge) as well as knowing the flow field. A two-stage-like electrostatic precipitator was designed. In the first zone of the filter, barbed ionizing electrodes were used, leading to charging of the particles and also to some dust precipitation. The collection of precharged fine particles is studied in the second section where the electric field is uniform. Using some models of electrostatic precipitation, the drift velocity of particles is derived from measurements of collection efficiency in the second section of the precipitator for different values of the turbulent diffusivity. Finally, the influence of gas flow turbulence is discussed.