Numerical study on a single char particle gasification considering Stefan flow effects in a hot CO2/O2/H2O atmosphere

CO2 gasification of biomass provides a new approach to the resourceful solidification and utilization of CO2. The level of char conversion is critical to the overall efficiency of the gasification process. The aim of this numerical study was to investigate the external multifactorial effect of char conversion in a hot CO2/O-2/H2O atmosphere at the particle scale with considering the effects of particle size and ash layer. The results demonstrated that increasing inlet temperature promotes gasification mainly by convective heat transfer between the gas stream and the particle surface. This effect diminishes as the inlet temperature increases. The promotion by enhanced convection is mainly due to the thinner boundary layer at the head of the particle, which allows for enhanced heat and mass transfer processes. The gasification process is susceptible to changes in O(2 )concentration. Despite the fivefold increase in H2O mole fraction (0.1 % ~ 0.5 %), the gasification process was not significantly accelerated. The influence of Stefan flow on the gasification process is mainly reflected in the rate distribution of the homogeneous reactions. When considering the ash layer cover, the temperature of the particle surface is affected by multiple effects of the increased specific surface area of the char core and convective heat transfer.