Control of submicron lead and cadmium emissions by kaolin during solid waste incineration: Mechanisms and sorbent evaluation

摘要

This paper is concerned with the metal capture mechanisms of kaolin and its performance during the waste incineration in a fluidized bed furnace. The analysis on products of kaolin/metal system at different temperatures indicates that it is easier for Pb to react with kaolin than for Cd. Besides the reaction with metals, the conglutination of the nanoscale crystal metals on the melting surface of kaolin is considered as another submicron metal capture form. Pb has stronger capability to cause conglutination than Cd which can reduce the conglutination by increasing the melting point of reaction products. When kaolin addition was more than 3%, Pb and Cd capture fractions did not increase any more. High temperature was in favor of Pb capture and especially of Cd capture whose fractions were less than 12% at the temperature lower than 950 °C, but up to 40% at 1000 °C. The maximum of submicron Pb capture fraction was 83% at 1000 °C. The toxicity of Cd is considered 5 times that of Pb. According to the toxicity factors and the leaching fraction, the total toxicity emission control efficiency was proposed to evaluate the comprehensive performance of sorbent. The increase of addition amount can improve the comprehensive performance of kaolin but the increase of temperature has only a little effect on the comprehensive performance of kaolin.