On a highly reactive Fe2O3/Al2O3 oxygen carrier for in situ gasification chemical looping combustion

Abstract

Interest in the direct use of solid fuel in chemical looping combustion (CLC) technology makes the in-situ Gasification Chemical Looping Combustion (iG-CLC) an attractive approach for the low-cost capture of CO2. Highly reactive material is required in iG-CLC in order to achievea fast reaction between the fuel and oxygen carrier. In this work, a material,Fe2O3/Al2O3 synthesized by sol-gel,was evaluated in a fluidized-bed reactor by reaction with lignite. This is the first time sol-gel-derived Fe2O3/Al2O3 material has been used in an iG-CLC process. Operation conditions, including steam content in the fluidization gas, temperature and potential oxygen ratio were investigated to explore their influence on combustion and char conversion. The results show that a higher steam concentration can greatly enhance the rate of char gasification and hence the reaction between the lignite and the oxygen carrier, where as a negligible effect of the steam content was noticed on volatile combustion. In addition, the use of the highly reactive Fe-based material prepared by the sol-gel method significantly increased the char gasification rate as compared to other previously evaluated materials. Moreover, the combustion efficiencies of volatiles and char from the lignite,respectively,were studied. Using the Fe2O3/Al2O3 material enabled a low oxygen carrier inventory of 600 kg/MWth to be reached in order to achieve 99% char combustion, which is much lower than that reported in other works. These findings suggest that Fe2O3/Al2O3 prepared by sol-gel is a highly reactive oxygen carrier for iG-CLC.