Effect of Binder on Iron Oxide Sorbents in Hot Gas Desulfurization

摘要

Integrated gasification combined cycle (IGCC) power generation process is an attractiveoption for using coal for electricity generation with a high efficiency and a low environmentalpollution. The efficient removal of sulfur species (mainly H_2S) from coal-derived fuel gases atelevated temperature is to be crucial for the efficient and economic coal utilization in IGCC. Theemphases of the prior work on hot gas desulfurization are mostly on the selection of activecomponent, little is known of the effect of binders on the performance of desulfurizer, although itis considered that adding inorganic binder such as bentonite can improve the mechanical strengthof the sorbent. The objective of this study is to investigate the effect of binder materials on theperformance of the sorbent made from red mud, which is a side product of steel plant. In thispaper, six kinds of clay were chosen as the binder of the sorbent. The sorbents made fromdifferent clays were each subjected to five sulfidation /regeneration cycles in a fixed-bed reactor.Simulated coal gas was utilized for sufidation of sorbent. Fresh, sulfided and regeneratedsorbents were characterized with mechanical strength, crystalline phase by XRD, BET surfacearea by nitrogen adsorption, pore volumes and distribution by mercury porosimer. Six clays wereanalyzed by XRD and DTA. The elemental compositions of the sorbents and clays were allverified by atomic absorption spectroscopy. The experimental results revealed that the sorbentprepared from mixed clay appeared the best overall performance in the respect of sulfurcapacities during cycles and mechanical strengths durability. Although the sorbents preparedfrom kaolinite had the higher initial and final mechanical strengths, sulfur capacity decreasedsharply with the increasing of cycle. The content of active component were not the main reasonof the differences in sulfur capacity, while structural property changes were considered to play asignificant role for the performance of the sorbent. Mechanical strength may possibly relate toAl_2O_3 content.