Investigating Effects of Zeolites As an Agent to Improve Limestone Reactivity toward Flue Gas Desulfurization

Abstract

Natural zeolite was utilized as an agent to increase the reactivity of lime for desulfurization. Due to the presence of hydrous silica−aluminates in zeolite, a pozzolanic reaction ensued which ended up with an increase in the surface area of lime thus making it more reactive. Tests were done in a pH-stat apparatus and a fixed bed reactor, representing wet and dry flue gas desulfurization (FGD), respectively, to check if lime reactivity was augmented by the addition of zeolite. It was found that zeolite amplifies reactivity of lime with the highest reactivity being achieved with a lime to zeolite ratio of 1:1 (by mass). This was confirmed by Brunauer−Emmett−Teller (BET) surface area analysis (surface area increment with the reactivity) and scanning electron microscopy (SEM) imaging (rough morphology being formed). Further optimization tests were conducted in the pH-stat apparatus with the aid of design expert software to quantify linear, quadratic, and interactive effects of four variables (temperature, lime to zeolite ratio, liquid to solid ratio, and stirring speed). Temperature as a variable had the highest effect, followed by lime to zeolite ratio. Stirring speed had the least effect on the reactivity.