Mathematical model of the reduction process of iron-based oxygen carriers in chemical looping combustion

To study the reaction characteristics of iron-based oxygen carriers, a one-dimensional mathematical model was developed for the reduction process of iron-based oxygen carriers in moving beds based on the unreacted shrinking core model. In this model, the multi-stage reduction between iron-based oxygen carriers and H₂/CO was considered. The average error of gas species concentration between the simulative and experimental values is 6.92%, and the average error of reduction is 11.16%. The results show that the final reduction rate of iron-based oxygen carriers is about 23%, with the main reactions including the first-stage reduction and the second-stage one, whose reduction rate is 95% and 40%, respectively. A higher reaction temperature, suitable diameter of oxygen carrier particles and suitable gas-solid ratio are helpful to improve the depth of reaction and enhance the utilization efficiency of syngas and iron-based oxygen carriers. The recommended particle diameter is 1 to 2 mm.