Monitoring the availability of electrostatic precipitators (ESP) in automated biomass combustion plants

Abstract

To achieve emission limit values on particulate matter emissions of less than 20 mg·m−3 at 11% O2 volume fraction for 1 MW–5 MW, automated biomass combustion plants are often equipped with electrostatic precipitators (ESPs). To ensure low emissions, a high availability of the precipitators, i.e. a high ratio between the uptime of the ESP and the uptime of the boiler, has to be guaranteed including operation at part load and during start-up. In the present work, an investigation on seven heating plants with tube-type and plate-type ESP in the size range of 450 kW–3.5 MW was conducted. The signals on load, temperatures, fans, lambda sensors, voltage and currency were measured during two years. From these data, the availability is determined based on specific definitions for the operation modes of the ESP and the boiler. To evaluate threshold values for the ESP operation and to validate the method, gravimetric measurements on the particulate matter emissions in different operation modes were performed.The investigation reveals that ESPs in today's biomass plants can achieve availabilities of greater than 90%. Further, malfunctions and maintenance issues that are not immediately repaired are identified as main source for low availabilities, while availabilities of greater than 95% are considered achievable for new plants. To ensure optimum ESP operation with low particle emissions under real-life conditions, a reliable monitoring of the availability based on the presented method is recommended for automated biomass combustion plants.