The influence of unburned carbon particles on electrostatic precipitator collection efficiency

Laboratory tests have shown that the chemical composition of fly ash (in that unburned coal) as well as its size distribution has significant influence on the dust cleaning process. Likewise the design of discharge electrodes has shown a strong influence on the dust cleaning. Tests of precipitation efficiency were carried out on a laboratory electrostatic precipitator (ESP) model using fly ash samples of diverse size distribution and unburned coal content collected from several grate boilers. Test results show explicit dependency of the ESP precipitation efficiency on physical and chemical characteristics of the fly ash, design of discharge electrodes and amount of electrical energy delivered to the ESP. Mercury concentration measurements show higher levels in the fly ash than in the fired coal indicating high sorption capacity of the fly ash. Prior observation suggests good mercury adsorption on fine fly ash particles in the presence of elemental coal. Hence the improvement of ESP collection efficiency of fine particles containing unburned coal may help decrease the emission of mercury.