Vol. 11, No.1, pp.104-111 (2017)
Relation Between Gas Velocity Profile and Apparent Migration Velocity in Electrostatic Precipitators
A. Bäck
GE Power Sweden AB, Sweden
Abstract
The impact of the gas velocity profile on the collection efficiency for electrostatic precipitators is considered from a theoretical point of view. If non-ideal effects such as rapping, re-entrainment and gas sneakage are neglected, the maximum collection efficiency is obtained with a perfectly uniform cross sectional velocity profile throughout the precipitator. Employing a linearization of the exponential function in the equation for collection efficiency, a closed form analytical expression for the impact of non-uniform gas flow is derived. In the expression, the square of the coefficient of variation of the gas flow profile enters as a correction factor to the migration velocity. The analytical expression corresponds rather well to exact calculations on actual gas velocity distributions, up to coefficient of variations around 30%. Moreover, it is demonstrated that the same type of approach can be used to derive similar correction factors also when other variables deviate from uniformity.
Keywords - ESP, electrostatic precipitation, gas distribution, coefficient of variation, migration velocity