Reduction and oxidation kinetics of nickel-based oxygen-carriers for chemical-looping combustion and chemical-looping reforming

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• 作者：Cristina Dueso¹ ; Marí ; a Ortiz¹ ; Alberto Abad¹ ; Francisco Garcí ; a-Labiano¹ ; Luis F. de Diego¹ ; Pilar Gayá ; n¹ ; Juan Adá ; nez ; ^{jadanez@icb.csic.es}
• 关键词：Chemical-looping combustion ; Chemical-looping reforming ; Oxygen-carrier ; Nickel oxide ; Reaction kinetics
• 刊名：Chemical Engineering Journal
• 出版年：2012
• 期刊代码：16_13858947
• 类别：ce
• 出版时间：15 April, 2012
• 卷：188
• 期：Complete
• 页码：142-154
• 文件大小：749 K

摘要

The kinetics of reduction with CH₄, H₂ and CO and oxidation with O₂ of two NiO-based oxygen-carriers for chemical-looping combustion (CLC) and chemical-looping reforming (CLR) prepared by impregnation, NiO18-伪Al and NiO21-纬Al, have been determined in this work. In both solids, nickel was present as NiO and NiAl₂O₄ in the oxidized state and the NiO/NiAl₂O₄ ratio in the particles was a function of the solid conversion reached in the previous reduction process. Both nickel compounds were active for oxygen transfer although with very different reactivities. Therefore, kinetic parameters for NiO and NiAl₂O₄ reduction were determined for each oxygen carrier and each reacting gas. The reaction rate of NiO reduction was the same in NiO18-伪Al and NiO21-纬Al particles. A model which assumed a linear relationship between time and conversion was used to describe NiO reduction. Nevertheless, differences in reactivity were observed during NiAl₂O₄ reduction depending on the type of support, 伪-Al₂O₃ or 纬-Al₂O₃, probably due to a different crystalline structure of the alumina. The changing grain size model for spherical grain geometry was used to obtain the kinetic parameters of the NiAl₂O₄ reduction working with both NiO-based oxygen-carriers. Chemical reaction control was assumed for NiO18-伪Al whereas diffusion through the product layer was also considered when NiO21-纬Al was used as oxygen-carrier. The oxidation reaction was very fast with both materials although small differences were observed again between NiO18-伪Al and NiO21-纬Al oxygen carriers, probably owing to the presence of a higher amount of NiAl₂O₄ in the solid supported on 纬-Al₂O₃. The combined model for consecutive reduction of NiO and NiAl₂O₄ in the oxygen-carrier particles with the kinetic parameters obtained in this work predicted adequately the experimental results with both materials. These kinetic data could be used for the design of CLC and CLR systems.