CFD investigation in the temperature effect on coal catalytic hydrogasification in the pressurized bubbling fluidized bed

Abstract

Temperature is a critical factor influencing the performance of coal catalytic hydrogasification in bubbling fluidized bed gasifiers. Numerical simulations at various temperatures (1023 K, 1073 K, 1123 K, and 1173 K) are conducted to elucidate the mechanisms by which temperature affects bubble size, global reaction performance, and particle-scale reactivity. The simulation results indicate that bubble size increases at elevated temperatures, while H₂-char hydrogasification reactivity is enhanced. Particle trajectory analyses reveal that particles sized between 100 and 250 μm undergo intense char hydrogasification in the dense phase, contributing to the formation of hot spots. To assess the impact of temperature on the particle-scale flow-transfer-reaction process, the dimensionless quantities of Reynolds, Nusselt, and Sherwood numbers, along with the solids dispersion coefficient, are calculated. It is found that higher temperatures inhibit bubble-induced mass and heat transfer. In general, 3 MPa, 1123 K, and 3–4 fluidization numbers are identified as the optimal conditions for particles ranging from 0 to 350 μm. These findings provide valuable insights into the inherent interactions between temperature and gas-particle reaction.