Flow and turbulence studies in electrostatic precipitator

Abstract

There is an urgent need to address the ambient air quality standards. Economic and infrastructure growth has lead to increased demand for power. As more and more coal based power plants are being set up, so is the deterioration of ambient air quality. An electrostatic precipitator (ESP) is being used to capture particles suspended in the flue gas stream of a coal based power plant. The gas stream consists of polydisperse particles. The particles get ionised due to the applied electric field in the gas flow path, and gets deposited on the collector plates from where it is rapped off periodically. Experiments were carried out with a 1:10 scale model of an ESP, to study the flow distribution in the collection chamber of the ESP for a typical 210 MW coal based power plant. CFD simulations were performed using CFX for the same and the result showed good agreement with the experimental values. Also CFD simulations were done for flow distribution studies with perforated plates of different porosity, and location along the diffuser of an ESP. Simulations were performed using FLUENT to predict the flow distribution at the diffuser exit with two and three perforated plates located at different regions along the diffuser length. Intensity of electric field, gas velocity, particle size, plates spacing and electro geometry also affects the collection efficiency of an ESP. To capture smaller particles (particles less than 2.5 and#956;), high electric field intensity as high as 80 kV is required. The gas velocity should be low enough to have sufficient time for particles to get ionised and deposited at the collector plates. An attempt was made to model the discrete phase of the flue gas, namely the particles using FLUENT. The effects of change in flow parameters on collection were then analysed.