Effect of Ash Melting on the High Temprature Gasification of a Single Large Particle of Coal Char.

A single particle of coal char was gasified with CO2/Ar atmosphere at the temperature of 1273 to 1773K. The pore structure and the ash properties in a gasified char particle were investigated.Two kinds of reacting zone (B, C zone) were observed in the char. Primary gasification occurred in inner shell (B zone) and the thickness of the shell decreased with temperature. The thickness of C zone which consists of ash and unreactive residue (carbon content is below 30 wt%) maximized at the temprature range of 1473 to 1573K. This suggests that the residue is surrounded by cohered ash or high viscous melting ash and that gasification reaction is prevented. Above 1673K, ash was completely melted and the thicknese of C zone, therefore, decreased. Small sphere ash particles were observed within unreactive char.