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

ABSTRACT

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.

KEYWORDS:

• Zhundong coal
• ammonium dihydrogen phosphate
• combustion performance
• ash-forming characteristics
• sodium retention ratio

Acknowledgments

The authors are grateful to the anonymous reviewers for their insightful and constructive comments, which greatly improved the quality of the paper.

Disclosure statement

There is no potential conflict of interest.

Additional information

Funding

This research was supported by National Key Technology Research and Development Program of the Ministry of Science and Technology of China: [Grant Number 2015BAA04B02] and the Fundamental Research Funds for the Central Universities: [Grant Number 2016XS19].