Reaction mechanism of carbon gasification in CO2 under non-isothermal conditions

Experiments of carbon (graphite) gasification in CO2 have been carried out by thermal analysis techniques (TG-DTG-DSC) under non-isothermal conditions. The results indicate that the entire carbon gasification process can be divided into an exothermic slow gasification stage during the initial period and an endothermic fast gasification later. The analyses of energy conservation and non-isothermal kinetics arrive at the following conclusions; (1) The exotherm of the initial stage is caused by the combined effect of the exothermic chemisorption and the endothermic chemical reaction. The gasification reaction may be expressed by the series of chemisorption and chemical reaction and the overall process is controlled by interface reaction via chemisorption. (2) The endothermic effect of fast gasification stage is almost equal to the reaction heat of carbon gasification, which implies that the chemisorption step disappears. The gasification process can be expressed by a simple interface reaction.