Degradation Behaviors of Coke in CO₂ and H₂O Gasification Reactions at Low Temperatures

抄録

This study aims to investigate the degradation behavior of coke during CO₂ and H₂O gasification reactions. Gasification experiments were conducted in CO₂ and H₂O atmospheres at 1000°C using cokes with different coke reaction indices (CRIs) at 20% reaction ratio. After gasification, the shrinkage ratio in CO₂ gasification was higher than that in H₂O gasification. Moreover, the shrinkage ratio increased with increasing CRI, indicating that the ratio of the surface reaction became larger than that of the internal reaction with increasing CRI at same reaction ratio. The increase value in porosity by gasification reaction decreased with increasing CRI. Owing to the faster diffusion rate of water vapor at 1000°C, water vapor diffuses into the inner part of coke faster, whereas CO₂ gasification reacted from the outer to the inner slowly. Therefore, the increase in porosity of the inner part of coke by H₂O gasification is larger than that by CO₂ gasification. In addition, the degradation behavior in same coke by CO₂ or H₂O gasification did not have obviously difference at same reaction ratio in 1000°C.