The Effects of Solid Sorbents on Heavy Metal Emission under Various Combustion Conditions

摘要

Experimental studies on heavy metals captured by solid sorbents were carried out in a down/low reactor. The effects of various sorbents on heavy metal emissions under different combustion conditions were investigated. The operating parameters evaluated included: (1) different ratios of sorbent/coal (2%, 4% and 6%); (2) elevated temperatures (950℃, 1100℃ and 1250℃); (3) un-staged and staged combustion. The experimental results indicated that the best metal capture efficiency occurs when the ratio of bauxite/coal is 2%, and 4% for both limestone/coal and calcium sulfate/coal systems. It was found that increasing temperature has a negative effect on heavy metal capture by sorbents. The experimental results also showed that the staged combustion has no effect on heavy metal removal, although it is effective in the control of NOx emissions. The leaching tests indicated that the mechanisms of heavy metal capture by solid sorbents include both physical adsorption and chemical reaction.