Multiphase particle-in-cell simulation study of sorption enhanced steam methane reforming process in a bubbling fluidized bed reactor

Abstract

The hydrodynamics and thermochemical characteristics of the sorption enhanced steam methane reforming process in a fluidized bed reactor are studied with a multiphase particle-in-cell model, featuring steam methane reforming and CaO carbonation reaction kinetics. After model validation, the high-fidelity information of solid phase at the particle-scale level is presented with the discussion of the effects of several critical operating parameters on the gas thermal properties. The results show that bubble evolution leads to bed expansion and the density-segregation mechanism causes the elutriation of dolomite particles. The highest velocity and Reynolds number of particles are observed around the bubble, and the magnitudes of these variables are higher than that in the dense region. The heat transfer coefficients (HTC) of Ni-catalyst and dolomite particles range from 100 W/(m2·K) to 600 W/(m2·K), which increase with the slip velocity and Reynolds number but decrease with solid volume fraction. The time-averaged particle dispersion coefficient in × , y, and z directions for the Ni-catalyst particles are 1.63 × 10-4, 1.82 × 10-4, and 9.92 × 10-4 m2/s, respectively while for the dolomite particles are 2.17 × 10-4, 2.52 × 10-4, and 1.3 × 10-3 m2/s, respectively. The temperature of bubbles near the wall is lower than that in the core region. Superficial gas velocity shows a positive effect on CH4 and H2O, gas temperature, and gas density while a negative effect on CO and H2, gas specific heat capacity. Bed temperature significantly influences the gas properties and gas product yields due to its intrinsic relation with chemical reactions. Ni-catalyst particle diameter performs an insignificant impact on the thermochemical characteristics in the bed.