Electrostatic precipitator for medium combustion plants : Data collection framework for dimensioning

Combustion of solid fuels is the main source of particulate matter (PM) emissions. PM emissions are harmful to both human health and the environment. As environmental awareness increases, emission limits are being tightened to reduce environmental and health impacts. Electrostatic precipitator (ESP) is one solution to reduce PM emissions. ESP works by charging particles and removing them from the flue gas flow using an electric field. This thesis focuses on electrostatic precipitators for medium (1-50 MW) biomass combustion plants. The main objective of the work is to find out how different parameters affect the operation of the ESP and what data needs to be collected from the existing units for more accurate dimensioning. PM emission regulations and the market potential of ESP are also examined in this thesis. The effect of the parameters on the operation of the ESP is evaluated using literature and a mathematical model. In addition, the requirements for theoretical and empirical data based dimensioning processes are reviewed. Accurate mathematical modelling of the ESP is difficult, therefore the dimensioning is usually based on empirical data. Based on the effects of the parameters and the requirements of the empirical dimensioning process, a framework for collecting reference data from existing units is created. The data to be collected is classified into mandatory, extensive and supporting parameters. The classification is based on the significance of the parameter for the dimensioning and the difficulty of its determination. The mathematical model used in this thesis does not take into account all the phenomena involved in the operation of the ESP. This makes it difficult to estimate the real effect of the parameters. The collection area given by the model differs from the real one by 4 % for 0.1 um particles, but for 5 um particles the difference is 230 %. According to the model, the electric field strength is the most important of the parameters studied. This emphasizes the importance of considering the factors affecting the electric field when collecting reference data and dimensioning. The parameters identified as mandatory for dimensioning are those that define the design parameters and the type of process. The parameters required to define the design parameters are the inlet and outlet dust load, the flue gas flow rate, the dimensions of the mechanical parts and the operating current and voltage. Other data to be collected must be considered on a case-by-case basis, as the effect of the parameters depends on the prevailing conditions. In the future, reference data should be systematically collected when new equipment is delivered. The impact of parameters on specific processes could be assessed using the mandatory parameters defined in this thesis