Microprocessor control of electrostatic precipitators

The aim of this research was the development of new techniques for the control of the high voltage supply to an electrostatic precipitator. Using published information on the electrostatic precipitation process and test results from the Swanbank installation, it was found that the poor precipitator performance at Swanbank was mainly due to back corona. High resistivity ash causes back corona to form at low precipitator currents. Further testing indicated that the formation of back corona within the precipitator caused the minimun precipitator voltage to fall. This fall in voltage was fo~nd to be coincident with a fall in precipitator performance. The control techniques investigated maintained the precipitator current equal to that present at the minimun voltage, which was periodically measured. These techniques were irrplemented on one precipitator using a microprocessor. Many tests were performed to ascertain the relationship between minimun precipitator voltage, other process variables, precipitator performance and back corona. Using collector plate current measurement, minimum precipitator voltage was shown to be a good indication of back corona severity. Throughout the tests the control techniques developed maintained the precipitator energization at a level consistent with maximun dust collection. The results of this research provide useful information on the relationship between process variables, such as boiler load, electrode cleaning and gas temperature, and precipitator variables such as performance, voltage and current. The control techniques developed have been shown to provide reduced emissions, approximately 20% on the installation tested, when collecting high resistivity ash