Emission characteristics of fine particles from wet flue gas desulfurization system using a cascade of double towers

Abstract

The removal of fine particles from coal-fired flue gas using chemical and physical reactions was investigated experimentally in a wet flue gas desulfurization (WFGD) system with a cascade of double-towers system. The flue gas particles were collected by an Andersen 8-stage impactor, and their mass concentration and particle size distribution were investigated. Based on analysis via scanning electron microscopy/energy dispersive X-ray spectrometry (SEM-EDX), X-ray diffraction (XRD) and inductively coupled plasma atomic emission spectrometry (ICP-AES), the morphological characteristics and the major and minor-element concentrations of particles were studied. The results indicate that the size distribution of fly ash particles at the inlet of the WFGD system was typically distributed bimodally. Although a bimodal distribution was still observed after the desulfurization, all the peaks had decreased. Furthermore, the content of S and Ca increased. Fine particles in the flue gas consisted of about 26.48% limestone and 41.19% gypsum particulate matter, eventually forming the Ca11.3Al14O32.3 crystal. The net removal efficiency of the double tower WFGD system reached 84.16% for the original particles, which was similar to that of the conventional single tower system. The entrainment of recirculated slurry contributed to the submicron particle emissions, and the total removal efficiency of the double tower WFGD system decreased to 51.1%.