Reduction Kinetics of Fe-based Oxygen Carriers Using Syngas in a Honeycomb Fixed-Bed Reactor for Chemical-Looping Combustion

Abstract

Chemical-looping combustion (CLC) is considered to be a vital method for utilizing hydrocarbon fuel with low carbon emissions. A honeycomb fixed-bed reactor is a new kind of reactor for CLC. However, the further application of the reactor is limited by the inadequacy of the kinetic equations for CLC. In this paper, the experimental studies on the kinetic of Fe-based oxygen carriers were carried out by the CLC experiments using syngas which was obtained from one typical type of coal gasification products. The experimental results show that there were two individual stages for the kinetic characteristics during the fuel reaction process. Therefore, the CLC fuel reaction process could be described by a two-stage unreacted-core shrinking model and the reaction rate equations for each of the two phases were provided. In both stages, the dominant resistances were analyzed. The activation energy and the reaction order in both stages were calculated respectively as well. Comparing the experimental results of reaction rate with the calculated results of the obtained rate equations, it could be clearly seen that the reaction kinetics model was appropriate for the CLC in the honeycomb reactor. This work is expected to provide a guideline for the future development and industrial design of the honeycomb CLC reactors from the perspective of kinetics.