Batch preparation of Fe2O3/Al2O3 oxygen carriers for chemical looping combustion of lignite

Batch preparation of Fe2O3/Al2O3 oxygen carriers for chemical looping combustion of lignite

L. Guo, Haibo Zhao, Jinchen Ma, Daofeng Mei

Abstract

Freeze granulation, spray drying, impregnation and mechanical mixing methods were adopted to prepare Fe2O3/Al2O3 oxygen carriers. To identify the appropriate technologies for batch preparation of the oxygen carriers, the four preparation methods were compared in terms of yield rate, preparation period, physical and chemical characteristics and performance in chemical looping combustion (CLC) of lignite. The experimental results show that freeze granulation has the highest yield rate of carrier with the best mechanical strength. CLC tests of lignite demonstrate that the oxygen carriers prepared by freeze granulation and spray drying bring the highest carbon conversion rate, followed by impregnation and mechanical mixing; and the oxygen carriers prepared by the first two methods have higher chemical reactivity and more stable performance. In the four reduction processes with oxygen carriers prepared by all the four preparation methods, CO2 capture efficiencies exceed 88%; the yield rate of CO2 increases with the rate of carbon conversion, finally approaching 100%; and the combustion efficiencies are above 90%. These indicate that the oxygen carriers prepared by the four methods all have good performances for CO2 capture and high utilization degree of the combustible components. Freeze granulation and spray drying methods can be considered preferentially for batch preparation of oxygen carriers for the CLC of lignite.

Keywords:

Freeze granulation, spray drying