Assessment of the Applicability of Ca-Based Sorbents for Arsenic Removal from Flue Gases

Abstract

Arsenic is one of the most hazardous compounds released into the atmosphere from coal conversion processes. One possibility to limit its amount in the flue gas is to inject dusty sorbents directly into the flue gas duct. The aim of this study was to analyze the removal efficiency of gaseous forms of As on selected Ca-based materials, with a focus on sorbents based on waste materials versus traditionally used sorbents. Coal combustion byproducts, waste (such as filter cake, fly ash, and gypsum), sedimentary rocks (dolomite and limestone), and chemical reagents like Ca(OH)2, Fe2O3, and Mg(OH)2 were examined in the quartz retort in a heated furnace where the temperature of the sorbent bed was 120 °C. The source of Asgas was the direct combustion of coal at 1200 °C. Among the tested materials, calcined limestone, calcined dolomite, Fe2O3, Mg(OH)2, and Ca(OH)2 were the most effective (removal efficiency: 85–98%). In the case of waste materials, the highest efficiency was obtained for filter cakes. However, because of their high content of toxic elements, they could be used as sorbent only after thermal preparation at 250 °C. Furthermore, the analyses showed that an increased Ca concentration in the sorbent may promote Asgas adsorption more than the development of the sorption surface area.