Kinetics studies and structure characteristics of coal char under pressurized CO2 gasification conditions

•Porous structures of char had major impacts on char CO2 gasification.•Porous structures quickly developed and rapidly collapsed during the reaction.•The graphite crystallites experienced limited change in CO2-gasification process.

The combined effects of surface area, pore structure, degrees of graphitization and graphite crystallites on the char gasification kinetics were studied under elevated pressure and temperature conditions using a High-Pressure Thermo-Gravimetric Analyzer (HP-TGA) and characterization methods, such as BET, XRD, Raman spectroscopy, FTIR and SEM. The BET and SEM results indicated that the porous structures of the chars developed quickly until the carbon conversion reached 0.9, and then rapidly collapsed to the end of the whole carbon conversion. The changes in char structures were in good agreement with the gasification rate. XRD, Raman and FTIR analysis provided evidence demonstrating an increased ratio of graphite to amorphous carbon in bone-structure of chars, which was attributed to the consumption of the amorphous carbon and the retention of the graphite carbon during the gasification process. The collected data implied that the contributions of surface area and pore volume of the char on its kinetics were much greater than its graphite crystallites during the char CO2 gasification.