Trace elements retention in bottom ashes during coal combustion with hydrated lime additions

摘要

Trace elements (TEs) content in coal, industrial hydrated lime, and bottom ashes from coal combustion and coal with hydrated lime additions were studied in this article. The favorable effect of hydrated lime (HL) addition to coal on TEs retention in ashes was reported for As, B, Co, Li, Mo, and V. However, at the same time, less Cu, Ni, Pb, and Sr were retained in the ash. An experimental studies results was supplemented with thermodynamic equilibrium calculations performed in Factsage software. Based on calculations, it has been shown that addition of HL to coal: (i) reduces formation of liquid slag phase containing, among others, TEs in the following form: As2O3(l), CoO(l), Cu2O(l), NiO(l), PbO(l) and ZnO(l); (ii) favors retaining As, B, Mo, and V in ash, as a result of stable components formation: Ca-3(AsO4)(2)(s), Ca-3(BO3)(2)(s), CaMoO4(s) and Ca-3(VO4)(2)(s). Interestingly, most of the arsenic in the ash was trapped in Ba-3(AsO4)(2)(s).