Interaction Effect Between Metal Oxides As Hot Coal Gas Desulfurization Sorbent

Coal is the most abundant fossil energy in the world.Integrated gasification combined cycle(IGCC)power generation process is an attractive option for using coal for electricity generation with a high efficiency and a low environmental pollution,and is regarded to be the most promising technology in this century.In IGCC system,the removal of sulfur species(mainly H₂S)is crucial for the efficient and economic coal utilization.Up to now,the attention is paid to desulfurizing evaluation and characterization base on increasing durability of sorbents for hot coal gas desulfurization.But,studying on interaction effect between metal oxides in sorbents is scarce.It is very necessary to master the interaction effect between metal oxides in order to increase durability and desulfurization of sorbents.In terms of the requirment for coal gas clean-up National Key Foundational Program of China(No.2005CB221203),Fe₂O₃,ZnO,CuO,MnO₂ and CaO were prepared by decomposition & precipitation method from nitrate salt or chloridate salt,and a series of the mixed metal oxides hot gas desulfurization sorbents were also prepared by dry-mixing method.The desulfurization activities for single metal oxides and the mixed metal oxide sorbents for hot gas desulfurization were carried out in lab-scale fixed bed with quartz tub under the conditions of atmospheric pressure,500℃,space velocity of 3600 h^-1,gas composition of 40%H₂,0.4-0.6%H₂S and balance N₂.And the structures phase and surface composition of fresh and sulfided sorbnets were characterized by X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS) respectively.The reduction properties of sorbents were test by temperature-programmed reduction(TPR).Based on the lab-scale evaluation,the results showed that the desulfurization efficiency of the mixed metal oxide sorbents was higher than that of the single metal oxide sorbents,and the mixed metal oxide sorbents avoided fluctuating phenomenon in outlet H₂S concentration in sulfidation process, enhanced sulfur capacity in a certain extent.The desulfurization efficiency was not necessarily relation to whether to form new phase in sorbents,and the metal oxide ratio was not significant to sorbents structure phase by XRD characterization.TPR test results showed that the reduction temperature of the mixed metal oxide was lower than that of the corresponding metal oxide,it was deduced that there is not or little new phase in it,which was agree with the result by XRD.Surface atomic ratio of the mixed metal oxide sorbents gived by the preparation process was not accorded with ratio gived by XPS analysis.And it was deduced that metal atom on the surface of sorbents was migrating in sulfidation process,a part of metal atom migration inner and another opposited.