Application of Mn–Fe Composite Oxides Loaded on Alumina as Oxygen Carrier for Chemical Looping Gasification

Abstract

The reactivity of oxygen carriers is curial for biomass chemical looping gasification (CLG) process. In this work, Mn–Fe composite oxides were loaded on Al2O3 through sol–gel combustion synthesis to improve their reactivity. The feasibility of these composite oxygen carriers for straw CLG process was proved in a thermogravimetric analyzer and better recyclability was found from oxygen carriers with Al2O3. Fixed-bed tests showed that the addition of Al2O3 could enhance the stability at relatively high temperature but decrease the oxygen transfer ability when temperature was low. Mn–Fe composite oxide with 60 wt% Al2O3 was chosen as the ideal oxygen carrier and the optimum condition was temperature at 850 °C, steam flow of 0.0432 g/min and OC/C mole ratio of 0.2. Under these parameters, gasification efficiency and carbon conversion efficiency reached 92.93% and 94.52% respectively. Moreover, cyclic experiments indicated that Al2O3 enhanced the stability of Mn–Fe composite oxides and gasification efficiency was decreased by 1.96% after 10 cycles. It was contributed to the porous structure supported by Al2O3, which could improve the sintering resistance and lattice oxygen transmission ability.