Study on high temperature gasification kinetics of coal char by TGA and in situ heating stage microscope

The study aims to explore the kinetics of coal char during high temperature gasification by thermogravimetric analyzer and in situ heating stage microscope. Yangchangwan coal (YCW) and Shenfu coal (SF) were selected as the feedstock. The kinetics was fitted by using shrinking core, random pore, and homogeneous models, respectively. The in situ heating stage microscope was used to observe the ash morphology change of coal char. The results show that the random pore model was optimal for fitting the kinetics of coals. At 1273-1673 K, the range of apparent activation energy of YCW and SF chars were 82.27-90.74 kJ mol(-1) and 89.78-91.42 kJ mol(-1), respectively. Most of the YCW and SF chars were observed to participate in gasification by random pore mode and amorphous ash was formed. A few of YCW char particles were observed to undergo gasification by both homogeneous and shrinking core modes. The area shrinkage ratio of YCW char involved in the gasification by shrinking core mode was reduced by 58% after 20 min of reaction. At 1573-1673 K, the char gasification was controlled by ash layer diffusion. Compared with the reactivity at 1273-1473 K, SF char gasification reactivity at higher temperatures was reduced for that SF coal ash could agglomerate into sphere to wrap the residual carbon, while YCW char reactivity was increased since YCW ash was agglomerated into sphere, the sphere were melting and flowing with each other, so the residual carbon was exposed on YCW char surface.