Effect of particle size on gasification of char with different coal ranks

Eight coal chars of different coal ranks were prepared to investigate the effects of coal rank, reaction temperature and particle size on char-CO₂ gasification using a thermogravimetric analyzer (TGA). The variation of char-CO₂ gasification rate with carbon conversion was studied, especially at high conversion stage. As a result, the crystalline structures of higher rank chars are more orderly, resulting in a lower gasification rate. For high rank coals like anthracite, the CO₂ gasification rate of char with 40 μm size is about 7 times higher than that with 300 μm size to reach 95% conversion at 1 300℃. For low rank coals, particle size has little effect on the gasification rate. The results indicate that the effect of particle size on char-CO₂ gasification is dependent on coal rank. The specific surface area of high rank coals is much smaller than that of low rank coals, which contributes to the significant effect of particle size on high rank coal gasification. The effect of gasification temperature and particle size on gasification rate for high rank coals is more significant than that for low rank coals.