Microwave technique for online monitoring and control of dust layer thickness inside electrostatic precipitators

A procedure is proposed for real time non-intrusive measuring of the thickness of the ash layer on the plates of electrostatic precipitators (ESP) commonly used in energy plants. The method is based on the measurement of the phase shift of a surface electromagnetic wave, which propagates on the plate under test, equipped with input-output electromagnetic couplers. It is shown that the phase shift depends on the mean thickness of the ash layer. Results are reported that were obtained from a laboratory-scale experimental ESP model, using a microwave test signal at 2500 MHz. The experiments confirm the possibility of using the proposed technique for on line determination of the collection efficiency of ESP and also to prevent electrostatic discharge.