Some Aspects of "Long Term" Modelling of Electrostatic Precipitators

Nowadays modelling of collection efficiency in electrostatic precipitators is commonly examined by using numerical models. Different models exist for simulation of the multi-variable complex system of ESPs, the several determining physical processes [1]. One group of them determines the particle trajectories inside a half channel of a precipitator assuming that they were more or less the same during the operation of the precipitator. Advanced models take it into consideration, that some phenomena in the ESP build up in a longer time period, so the calculated trajectories must be modified as the function of time, too. One of these basic, typical phenomena is the formation of back corona [2]. Some other phenomena (e.g. changes of environmental parameters and the pollutants stepping into the chamber of electrostatic precipitators) have even longer time constant, so their examination needs much longer period of time. The advanced model described in the paper is able to monitor these "long term" changes explaining some unexpected behaviour of the precipitator. The complexity of the phenomena has been analysed by the newly improved ESP model of the authors, and "long term" simulations have been presented in several case studies of the paper.