CFD MODELING FOR MOVING BED REDUCER IN SYNGAS CHEMICAL LOOPING PROCESS

摘要

The syngas chemical looping (SCL) process efficiently coproduces hydrogen and electricity from coal derived syngas while capturing CO_2. The reducer reactor in the SCL process converts syngas with the oxygen carrier particles. Therefore, the reducer performance is of vital importance to the overall process efficiency. Thermodynamic analysis indicates that a countercurrent moving bed design enhances the gas and solids conversions in the reducer. Although thermodynamic calculation can predict the reducer conversions at equilibrium conditions, a comprehensive CFD model that takes into account the complex gas and solid flow behavior and reaction kinetics and thermodynamics is needed in order to accurately simulate the reducer performance. In the present work, a CFD model for the moving bed reducer is developed using FLUENT. A two-dimensional cylindrical moving bed reactor is constructed with comprehensive geometrical and operational parameters. A shrinking core submodel is adopted for reaction kinetics with the physical and chemical property data retrieved from an external database. The continuity equation for each species and the governing equations for continuity, momentum, and energy for the solid and gas phases are established. Therefore, the comprehensive CFD model takes into account the hydrodynamics, heat transfer, reaction kinetics and mass transfer behavior in the reducer. Important reducer performance data such as the gases and solids conversions, the temperature and gas and solid compositions, and the flow pattern inside the reactors are obtained using the CFD model.