Mass transfer coefficient and effective internal diffusion coefficient for coke solution loss reaction with non-equimolar diffusion

The mass transfer process of coke solution loss reaction (Ccoke + CO2 = 2CO) was rather complex due to coke porous structure and non-equimolar diffusion. However, non-equimolar diffusion in the external and internal diffusion process was often neglected in the study of coke solution loss reaction. This study has treated the mass transfer coefficient and effective internal diffusion coefficient as the object with the effect of non-equimolar diffusion. The experiments of metallurgical coke gasification with CO2 in the temperature range of 1100-1300 degrees C and at atmospheric pressure were carried out. When the weight-loss rate of coke reached 25%, the experiments were stopped. The calculated results showed that, after modification, mass transfer coefficients were decreased markedly, and they were changing over time during the coke gasification, from 1100 degrees C to 1300 degrees C, the deviation of correction was 38.89%, 37.94%, 36.96%, 35.99% and 35.61% individually. Effective internal diffusion coefficients were modified from 2D curves to 3D surface, they were increased not only with weight-loss rate, but also decreased with radius at each temperature. Kinetic parameters were also significantly affected, especially the activation energy, which increased from 213.41 to 232.02 kJ/mol. Finally the controlling steps at different temperatures were analyzed by comparing the effectiveness factor, which was approximately 0.7, 0.5, 0.4, 0.35 and 0.28 in the temperature range of 1100-1300 degrees C, the conclusion could be drawn that the controlling steps maintained stable at each temperature with non-equimolar diffusion.