Characterizing fly ash particles followed by prediction of removal efficiencies of fly ash and CO2 in an Indian Wet ESP

Abstract

In this article, characterization of fly ash particles followed by prediction of removal efficiencies of fly ash and CO2 by a wet electrostatic precipitator (WESP) attached to a coal fired thermal power plant of M/s CESC Ltd., located in Kolkata, India is reported. The characterization of the fly ash samples collected from the inlet and exit of the WESP as well as from the settling tank includes particle size distribution, Brauner–Emmette–Teller (BET) surface area and pore volume analyses, Fourier transform infra red (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and measuring the pH of fly ash samples. The area mean diameters of the respective samples were 39.73, 4.32 and 12.04μm. The BET surface areas of the respective samples were 3.292, 3.641 and 9.809m2/g. The peaks observed from FTIR analyses of the samples indicated presence of mullite, quartz and silica. The XRD of the samples showed the major mineralogical components as quartz and mullite with traces of lime, hematite and magnetite. The observations made from FTIR, BET and SEM analyses followed the trend of the particle size determined. XRD analyses further followed the results obtained in FTIR analyses. The values of pH of the particles collected from the settling tank before and after alkaline treatment were observed to be 1.45 and 7.12 respectively. Scrubbing of acidic gases was responsible for the reduction of pH in the acidic range. Finally, separate correlations were developed to predict the fly ash and CO2 removal efficiencies by the WESP as functions of different system variables by multiple non-linear regression analysis. The predicted values agreed well with the measured values (−4.36% and +10% deviations for fly ash and CO2 removals respectively).