Particle size classification and CO₂ gasification of the char fines from fluidized bed gasification of Shenhua coal

The char fines from fluidized bed gasification (fines for short) are classified into 7 components based on particle size. The basic physicochemical properties, the constant and programmed increasing temperature CO₂ gasification behaviors were investigated by coal quality analyzer, elemental analyzer, X-ray powder diffractometer, gas sorption analyzer and thermogravimetric analyzer. The difference of gasification reactivity and its reasons were discussed. The results show that after partial gasification, fixed carbon of the fines is higher than that of its parent coal but lower than the corresponding coal char because of the escape of volatiles. The particle size distribution of fines is very wide and multimodal distribution with the shape of "M". In addition, the ash content of fines approximately increases with decreasing particle size. However, the carbon content decreases with decreasing particle size. Both the constant and programmed increasing temperature CO₂ gasification show the same result. The gasification reactivity firstly decreases and then gradually increases with decreasing particle size. Furthermore, the carbon crystalline structure and ash content are contributed to the difference in gasification reactivity of fines, and the different reactivity is not related to the pore structure in this experimental condition.