Reaction characteristics of sintering ore used as an oxygen carrier in chemical looping combustion

The reduction kinetics of sintering ore used as an oxygen carrier in the chemical looping combustion was experimentally investigated by thermogravimetry. The redox reactivity of sintering ore was compared with that of self-made Fe₂O₃/Al₂O₃ oxygen carriers prepared by the dissolution method. Experiments were conducted on the reduction of sintering ore by diluted hydrogen during the temperature range of 500 to 1250℃, and 30 cycles of redox reaction experiments were performed at 950℃. Experimental data was analyzed by four kinetic models. It is found that sintering ore can be used as an oxygen carrier with a reduction conversion larger than 80%, complete oxidization, and a good performance of recyclability. The reduction reaction rate and final fractional conversion of sintering ore both increase with rising temperature from 500℃ to 950℃, while both have a trend of decline when the temperature is above 1100℃. The second order reaction model (M2) can properly fit the experimental data of the reduction of sintering ore in the first reaction stage (Fe₂O₃-Fe₃O₄/FeO, reduction conversion X < 25%) during the temperature range of 500 to 950℃, achieving the apparent activation energy E=36.018 kJ·mol^-1 and the pre-exponential factor A₀=1.053×10^-2 s^-1, whereas the shrinking core model (M4) fits well in the second reaction stage (Fe₃O₄/FeO-Fe, reduction conversion X > 25%), achieving the apparent activation energy E=51.176 kJ·mol^-1 and the pre-exponential factor A₀=1.066×10^-2 s^-1.