Improving lime’s reactivity towards flue gas desulfurization by using fly ash, bottom ash and waste activated sludge

Abstract

Lime reactivity was improved by blending it with either fly ash, bottom ash or waste activated sludge (W.A.S). The reactivity was tested using a pH-stat apparatus which simulates wet flue gas desulfurization (FGD). Temperature, solid to liquid ratio and stirring speed were varied in addition to lime to additive ratio in optimization tests. Design expert’s central cubic design was used in the design of experiments to aid with regression analysis. Temperature had the highest effect whereas W.A.S was the best additive then fly ash and finally bottom ash. The results were confirmed by the use of fixed bed apparatus where the best sorbents from each additive was tested in dry FGD. In a bid to explain the results, BET surface area analysis was used where the sorbent from the blend of lime and W.A.S had the highest improvement in surface area.