Effects of sludge on the ash fusion behaviors of corn stalk and its modification mechanisms

Abstract

The ash fusion behaviors of corn stalk (CS) and its variation mechanisms by two sludges [municipal-water sewage sludge (MW) and textile dyeing sludge (TD)] additions in an oxidizing atmosphere were investigated. Increasing the MW mass ratio led to an initial slow rise in the ash fusion temperatures (AFTs), but then they slowly decreased. The four characteristic temperatures for CS-TD all gradually increased as the TD proportion rose. An increase in the MW percentage led to changes in the generation and proportions of Ca2MgSi2O7, CaAl2Si2O8, CaMgSi2O6, KAlSi2O6, and Ca3(PO4)2, and these changes increased the AFTs. The formation of AlPO4 and its subsequent transformation into amorphous matter at high temperatures slowly decreased the AFT when the MW percentage exceeded 70%. The generations of Fe3O4 and Fe2O3 and the increases in their proportions as the TD percentage rose led to a gradual increase in the AFTs. The results from this study improve current understanding about the AFT variation mechanisms operating when sludge is added to CS and provide information that can be used to mitigate ash-related issues during the co-combustion of CS and sludge.