Development of an online monitoring method for electrostatic precipitators on commercial biomass combustion plants

Abstract

Combustion plants based on wooden biomass as fuel can contribute to a decarbonization of the energy sector by reducing the need for fossil energy usage, which decreases the net carbon dioxide output in the atmosphere. However, the flue gas of biomassbased combustion plants contains increased amounts of particulate matter, which need to be separated before release into the environment because of legal emission limits. In medium-sized plants, electrostatic precipitators (ESP) are commonly used separators to minimize the particulate matter concentration. Due to new regulations based on the medium combustion plants directive introduced by the EU, continuous surveillance of secondary precipitation technologies like ESP has to be implemented. The method proposed in this paper focuses on the readily available current (I) and voltage (U) data of the high-voltage unit supply of an ESP to calculate the efficiency of the particle separation. Consequently, a continuous proof of function can be delivered without high cost for additional measurement equipment. This article proves the effectiveness of the method in calculating the precipitation effectiveness of the ESP. It is shown that the deviation from the separation efficiency calculated by the method and the measured efficiency is smaller than 7%. Additionally, it is necessary to define a suitable reference signal that indicates whether the combustion plant is running or not. Hence, the availability of the system can be evaluated. This method will help operators to meet legal requirements.

Using threshold values to continuously evaluate how effectively electrostatic precipitators operate

“…In a previous paper [10], the efficiency calculation for the particle precipitation was presented. This uses the available current and voltage values of the high-voltage unit supply of an ESP.…”

“…The aim of this method was to avoid the high costs of continuous measurements and yet still be able to validate the mentioned function. One significant result was that the deviation between measurement and calculation is less than 7% for plants that operate under stationary conditions, when the operation is comparable with the one during adjustment of the method [10].…”

“…The measurement setup consists of continuously operating particulate matter sensors using light scattering and gravimetric particulate matter measurement equipment working according to VDI 2066 part 1 for calibration [28]. Additionally, gas analysers to determine the flue gas temperature as well as flow velocity via differential pressure sensors were used [10,29,30]. The particle matter concentration was continuously measured before and after the ESP to determine the precipitation efficiency.…”

“…The method proposed is based on the readily available current and voltage supplied to the electrostatic precipitator. A previous paper developed a monitoring method and showed its successful application on two biomass heating plants [10]. However, the method has to be further refined and tested to guarantee the reliability.…”

“…In the course of the investigations, the method proposed in [10] was also tested on a plant with a modulating load. The results using the original proposal were not satisfactory because the plant did not have a stationary operation mode.…”