Eulerian-Lagrangian simulation study of the gas-solid reacting flow in a bubbling fluidized coal gasifier

A reactive multiphase particle-in-cell approach is developed to explore the air-blown coal gasification in a bubbling fluidized bed reactor. The model is validated by comparing the predicted bed hydrodynamics and product yields with experimental data. Subsequently, the gas thermal properties and particle-scale behaviours are comprehensively explored. The results show that: (i) the density difference between two solid species gives rise to spatial segregation, which further affects the gasification process. The presence of coal feeding port causes the non-uniform distribution of bed hydrodynamics. (ii) the combustible gases species distribute above the coal feeding port. The concentration of gas species continuously increases while the gas temperature changes little in the dense region. (iii) the slip velocity of sand particles ranges from 0 to 4 m/s; the temperature ranges from 1000 K to 1150 K, and the heat transfer coefficient ranges from 80 W/(m2.K) to 200 W/(m2.K). Compared with sand, coal particles have a larger heat transfer coefficient and particle Reynolds number (Rep). Coal particles reach the maximum temperature of about 1100 K in the period of 3 s after being injected into the bed. (iv) bubble and emulsion phases give a larger Rep and smaller Rep due to the dominant role of the interphase drag force and inter-particle collision force, respectively.