Level Measurement in ESP Hoppers at Coal-Fired Power Plants

Fly ash is captured and removed from flue gas by electrostatic precipitators (ESP) or fabric bag filters located at the outlet of the furnace before the induced draft fan. The hot fly ash is continuously collected in hoppers below the precipitators/bag filters and periodically removed. Along with humidity and high temperature, fly ash tends to stick to the sides of the hopper, causing build-up, clogging, and possible damage to the plates.

Users continuously monitor the content and distribution of fly ash in the hopper so they can be emptied, maintained, and cleaned when necessary. This prevents damage to the ESP plates, which can also create environmental and health concerns. At coal-fired power plants where level measurement is not used in ESP processes, the hopper emptying is disconnected from the filling. With no reliable way to measure the fly ash in the hopper, a timer is set to turn on the emptying process regardless of the amount of fly ash in the hopper, which is inefficient.