abstract
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In recovering flue gas desulfurization (FGD) processes, sulfur dioxide is removed from the flue gas and converted into useful products, typically, sulfuric acid, liquid sulfur dioxide or elemental sulfur. For sulfur dioxide producers located far from their customers of sulfur-containing products, elemental sulfur is desirable since it is easy to ship and to store, and is the raw material of many sulfur consuming processes. The existing technologies for elemental sulfur production from sulfur dioxide in flue gas are mainly limited by high capital and operating costs due to the complexity of process. To overcome this limitation, a new process based on aqueous Na$\sb2$S solution has been proposed by Lu and co-workers at McMaster University, in which SO$\sb2$ absorbed by Na$\sb2$S solution lowers the pH of solution and hydrogen sulfide is generated from the acidified solution. For the purpose of converting SO$\sb2$ in the flue gas to H$\sb2$S, and then to elemental sulfur, thermodynamics and kinetics of Na$\sb2$S$\sb{\rm (aq)}$-SO-H$\sb2$S$\sb2$-H$\sb2$S reacting system have been studied, both experimentally and theoretically. Based on experimental and computed results obtained in the present work, it is concluded that aqueous solution of sodium sulfide may be used to absorb sulfur dioxide and to generate hydrogen sulfide simultaneously by acid-base reactions. Recommendation has been made towards further development of this new technology for its commercialization.