Effect of residual carbon on coal ash melting characteristics in reducing atmosphere

Abstract

The melting behavior of coal ash at high temperatures directly affects slag discharge in gasifiers. Residual carbon is a key factor that influences the melting and transformation process of coal ash, affecting its melting characteristics, mineral composition, phase transformation, and melt structure. This study examines how residual carbon affects the melting process through mineral transformation, melt structure, phase transformation, atmosphere reaction, dissolution, and collapse of the physical structure of slag. The type and amount of residual carbon have different effects on the melting process. Changes in minerals result in complex changes in the phase transformation process. Residual carbon deprives some Fe and Si elements of the liquid phase, forming new aggregated minerals that compete with others. Residual carbon disrupts the equilibrium and eutectic structure of the system, dissociates the Si-O structure, and reduces the Fe-O structure, forming Fe0 or Fe2+. Free iron atoms form melt structures, such as Fe3C and FeSi.