(97g) Reducer Performance of Chemical Looping Reactors: Mixing and Reaction Effects

With the pressing need for clean, efficient, and cost-effective energy sources, the chemical looping strategy has evolved as a promising alternative to the traditional carbonaceous fuel conversion process. The syngas chemical looping (SCL) process co-generates electricity and hydrogen with in-situ CO₂ capture from coal derived syngas through the cyclic reduction and oxidation of an iron oxide based oxygen carrier. The SCL process features countercurrent gas-solid moving-bed reactor that converts syngas to CO₂ while reducing the oxygen carriers. The countercurrent reducer in the SCL process at the Ohio State University has been operated for a combined time of more than 300 hours in a 2.5 kW_th bench scale moving-bed reactor and a 25 kW_th subpilot scale integrated system. A syngas conversion in excess of 99.5% and an oxygen carrier conversion of nearly 50% have been obtained. The thermodynamic analysis indicates that the countercurrent moving-bed reducer offers better gas and solids conversion behavior, compared to the fluidized-bed reducer. In this study, effects of the mixing and the reaction in the reducer of a chemical looping reactor system operated in the two distinct flow patterns represented by these two types of reactors, i.e., countercurrent moving-bed and the fluidized-bed, are described in terms of experimental results and reactor modeling. Further, the importance of the thermodynamic properties of the oxygen carrier in the reducer performance is highlighted in this study.