Use of fly ash, bottom ash and zeolite as additives for enhancing lime reactivity towards flue gas desulfurization

Abstract

Lime reactivity toward desulfurization was examined by blending lime with pozzolanic additives namely fly ash, bottom ash, and zeolite. The reactivity was tested in a pH-stat apparatus. Apart from lime to additive ratio, other important operating conditions, namely, temperature, solid to liquid ratio, and stirring speed, were varied accordingly using the design expert's design of experiments. Central cubic design was used to investigate linear, quadratic, cubic, and cross-product effect of these operatives. Sorbents made from lime-zeolite blends were found to have the highest reactivity followed by fly ash then bottom ash. These results were confirmed through sorption capacities of the best sorbents using a fixed bed reactor. BET surface area analysis of the best sorbents indicated that surface area improvement is the root cause of improvements in reactivity and sorption capacities. Temperature had the largest effect on reactivity. The other operative's effect varied from one additive to the other.