Gasification reactivity and kinetics of typical chinese anthracite chars with steam and CO2

The gasification reactivities of six typical Chinese anthracite chars with steam and CO2 at 0.02-0.1 MPa and 920-1050 degrees C were investigated by using thermogravimetric analysis (TGA). The reactivities of anthracite chars during steam gasification were found to have a good correlation to the coal volatile matter contents. The higher the coal volatile matter content, the higher the reactivity. The difference in reactivities of anthracite chars during CO2 gasification seems to be more dependent on the catalytic effect of inherent minerals in anthracite. The results show that the greater the alkali index, the higher the reactivity. The reactivities of demineralized anthracite chars vary very little compared with those the undemineralized chars at higher temperatures, whereas the reactivities of demineralized chars from Jincheng and Rujigou are lower than those of undemineralized ones and the reactivities of demineralized chars from Yangquan, Hunan, Guangdong, and Longyan are higher than those of undemineralized chars at lower temperatures. The homogeneous model and shrinking core model were examined as ways to interpret the experimental data. The experimental results could be well-described by the shrinking core model for anthracite chars during steam and CO2 gasification. Comparison of the reactivities for anthracite chars during steam and CO2 gasification shows that the reactivities of anthracite chars during steam gasification are far higher than those during CO2 gasification. The reactivities of the former are about 10 times higher than those of the latter, and this ratio is far greater than that of the lignite and bituminous coal. The mechanism leading to this difference is discussed.