Numerical Simulation of a Counter-Current Moving-Bed Reducer Reactor for Gaseous Chemical-Looping Combustion Using Methane As Feedstock

Chemical-looping combustion (CLC) is a promising CO₂ capture technology that integrates power generation and CO₂ capture in a single step with low energy penalties. The CLC process developed at The Ohio State University employs iron based oxygen carrier particles and a unique counter-current moving bed reducer reactor design to achieve nearly complete fuel conversion and in-situ CO₂ capture. In this work, a two-dimensional numerical simulation is conducted to investigate the performance of a counter-current moving-bed reducer reactor in a gaseous CLC using methane as its feedstock. The simulation scheme coupled the hydrodynamic characteristics of gas-solids counter-current flow, the kinetics of the particles, as well as energy and mass transfers between the gas and solids phases in the CLC reducer simultaneously. The gas-solids drag is described by the Ergun-type equation, and the reaction kinetics of the particles is modeled by the Unreacted Shrinking Core Model (USCM), where the oxygen carriers are reduced successively from hematite to magnetite, wustite, and metallic iron. The simulation results are validated by bench-scale experiments. Key parameters, including the geometry of the reactor, the gas-solids feed ratio, and the operation temperature are examined for their influences on the gas and solid conversions. The obtained gas flow pattern, temperature distribution, and composition profiles provide necessary information to achieve the optimum reactor design and operating conditions.