Interaction of Cadmium and Flyash Sorbents in an Experimental Waste Incineration Furnace—Flue Gas System

Abstract

The interaction of cadmium and different flyash sorbents has been examined in an experimental reactor under a variety of conditions simulating those found in waste incinerator furnace—flue gas systems. The experimental system consisted of two stainless steel reactors independently heated by electrical furnaces, enabling a temperature regime of between 100 and 1000°C to be investigated. Cadmium was vaporized in the furnace section of the reactor and the cadmium species formed were passed to the flue gas section where interaction with various flyash sorbents was investigated. The sorbents examined were three different aluminium oxides, silicon oxide and two aluminium silicates and the adsorption of cadmium species under various temperatures and flue gas compositions was determined. Flyash analysis consisted of a microwave extraction—ICP procedure to determine the adsorbed cadmium. In addition, SEM-EDX analysis of the surface of the flyash sorbents was used to characterize the surface adsorption. The results showed that at lower temperatures the cadmium species were adsorbed onto the flyash through physical adsorption whereas at temperatures above 765°C chemical adsorption occurred. SEM-EDX analysis of the surface showed that discrete particles of cadmium metal were produced in the flue gas system and were deposited on the flyash. The particle size of the flyash samples was found to influence the sorption of the cadmium. The presence of HCl and O2 in the flue gas altered the sorption capacity of the cadmium.