Kinetic analysis of gasification reaction of coke with CO2 or H2O

•The reaction kinetics of coke with CO2 or H2O was studied by single particle device.•The controlling steps of gasification reaction were determined in CO2 and H2O.•The pore microstructure evolution of coke after reaction in CO2 and H2O were revealed.

Using granular coke gasification reaction equipment and an unreacted core shrink model, this study examined the gasification reaction and conducted kinetic analysis of coke under CO2 and H2O atmospheres. Results show that in CO2 or H2O, solution loss rate increases with increasing temperature. The reaction rate of coke with H2O is approximately two to four times faster than that with CO2 at the same temperature. From 1173 K to 1373 K, the apparent activation energies of the gasification reaction of coke with CO2 and H2O are 143.33 kJ mol−1 and 104.53 kJ mol−1, respectively. The internal diffusion resistance in H2O was far below that in CO2, demonstrating that the gasification reaction rate between H2O and coke was quicker. In CO2 at low temperatures (≤1273 K), coke gasification was controlled by interfacial reaction during the early stage, interfacial reaction and gas diffusion in the middle stage, and gas diffusion in the final stage. At high temperatures (>1273 K), gasification was controlled by interfacial reaction. However, coke gasification in H2O at low temperatures (1173 K) was controlled by interfacial reaction during the early stage, and was under mixed control by interfacial reaction and gas diffusion during the final stage. At high temperatures (≥1223 K), gasification was controlled by interfacial reaction.