Desulfurization behavior of zinc oxide based sorbent modified by the combination of Al2O3 and K2CO3

In order to reduce the unfavorable effect of carbon oxide on desulfurization efficiency for zinc oxide based sorbent and decrease the concentration of carbonyl sulfide in effluent gas during desulfurization process, the modification of zinc oxide based sorbent is necessary in the preparation of zinc oxide based desulfurization sorbent. In this paper, the modified ZnO based desulfurization sorbents were obtained by mixing of active zinc oxide with different additives, which include graphite, Al2O3 and K2CO3, then shaping at ambient temperature, drying at 120 degrees C and calcinating at 550 degrees C. The desulfurization performances for the prepared ZnO based desulfurization sorbents were tested in a quartz upflow fixed-bed reactor under the condition of 300 degrees C, 2000 h(-1) and simulated coal-derived gas. The phases of sorbents before and after desulfurization were characterized by X-ray diffractometer, and their pore structures were measured by N-2 adsorption-desorption method. The experimental results show that COS was present in effluent gas for ZnO based sorbent while removing H2S from simulated coal-derived gas at experimental condition. ZnO based desulfurization sorbent modified by the combination of K2CO3 and Al2O3 achieves obvious improvements in the desulfurization performance, and H2S and COS concentrations in exit gas are below 0.1 mgS/m(3) before breakthrough point as well as the accumulated breakthrough sulfur capacity reaches 14 wt.%. Adding Al2O3 can improve the pore structure of ZnO based desulfurization sorbent, which benefits H2S to diffuse in the pore of sorbent and improves desulfurization performance. Loading K2CO3 can increase the basicity of ZnO based desulfurization sorbent, which raises the COS catalytic hydrolysis rate on sorbent and decreases concentration of COS present in exit gas. (C) 2011 Elsevier Ltd. All rights reserved.