Full-loop CFD simulation of lignite Chemical Looping Gasification with phosphogypsum as oxygen carrier using a circulating fluidized bed

Abstract

The excellent gas-solid mixing efficiency of the Circulating Fluidized Bed (CFB) makes it the recommended choice for coal Chemical Looping Gasification (CLG). In this paper, a 3D Computational Fluid Dynamics (CFD) full-loop model with multiphase distribution was developed to investigate the fluidization behavior and the CLG performance in CFB. Cold flow simulations show that particle size, static particle stock and inlet gas velocity were critical to the CFB stable operation. The optimal conditions for this system were: a static particle stock of 0.300 m, a particle size of 150 μm, and an inlet gas velocity lower than 0.2 m s−1 was recommended. Thermal flow simulations show that increasing the temperature increased the syngas yield. However, extremely high temperatures inhibit the H2 production. The contribution of CO production to syngas production was particularly obvious. To ensure sufficient H2 production, the molar content of water vapor and the PG/lignite molar ratio should be controlled at approximately 0.3 and 0.2, respectively. Cold flow model was extended to thermal simulation. This would lead to an undesirable phenomena, which should be corrected according to the kinetic model. The simulation results were in a well agreement with the experimental results, which verified the validity of the simulation model.