Influence of Ammonium Dihydrogen Phosphate on Combustion Performance and Ash Characteristics during Combustion of Zhundong Coal.

In this study, the co-combustion of Zhundong coal and NH₄H₂PO₄ was investigated in a laboratory-scale tube furnace. The ash fusibility, combustion performance, and ash characteristics were quantified by experimental approaches. This study also used Gibbs free energy theory to analyze the chemical reactions. The results showed that NH₄H₂PO₄ can extend the burning time of coal and reduce combustion intensity. Moreover, NH₄H₂PO₄ significantly changed the composition of ash, which was caused by reactions between alkali/alkaline earth metals and NH₄H₂PO₄, increasing the sodium retention ratio of the formed ash. In addition, the newly formed phosphate crystals (i.e., Mg₂P₂O₇, AlPO₄, and Ca₃(PO₄)₂) with higher melting temperatures contributed to the increase in fusion temperature of the formed ash, and the sodium-containing crystals (i.e., Na₂CaP₂O₇ and NaMg₄(PO₄)₃) contributed to the increase in the sodium retention ratio. Furthermore, NH₄H₂PO₄ had a significant effect on the microcosmic structure, with ash showing more rough and sintering being inhibited. [ABSTRACT FROM AUTHOR]