Development of High Performance Desulfurization Sorbent in the Coal Combustion and Gasification

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In order to mitigate carbon dioxide emission in the utilization of coal, increase in the thermal efficiency is indispensable. For this purpose, Integrated Coal Gasification Combined Cycle (IGCC) has been proposed. Further increase in the thermal efficiency of IGCC, high temperature gas cleaning is indispensable. This project is aimed at development of efficient absorbent of H_2S in the coal gasification gas from an entrained bed coal gasifier. Ferrites were reported to be a good absorbent of H_2S at an elevated temperature. However, a ferrite produced by dry method exhibited very low surface area and only the surface of the ferrite was utilized as an absorbent. To overcome this, we have developed a new process preparing ferrite at a low temperature in a wet method using an activated carbon as ferrite carrier. The zinc ferrite produced in the presence of an activated carbon exhibited a high surface area. H_2S absorption behavior of this sorbent exhibited excellent performance, where alm … More ost all of Fe and Zn in the ferrite was sulfided at 400 to 600℃. Moreover, effluent gas after absorption by using a fixed bed flow reactor, contained very low H_2S concentration of less than 1 ppm. Such high performance has never been observed with zinc ferrite prepared other methods. Ferrites prepared in the presence of low sulfur coal exhibited similar behavior as that prepared in the presence of activated carbon. Cost of the absorbent with coal would be reduced considerably as compared to the ferrite prepared with activated carbon. Calcium ferrite prepared in the presence of coal also exhibited excellent performance for the absorption of H_2S. Detailed studies on the performance of ferrites were done in order to understand performance of the ferrites. Characteristic feature of the ferrite was elucidated.In addition to H_2S absorbent, SO_2 absorbent in coal combustion was developed with CaO and oyster shell. Oyster shell treated with Yallourn coal at 850℃. Improved SO_2 absorption capacity compared to raw oyster shell was achieved. Less