Experimental Study on the Inhibitory Effect of Organic Phosphonic Acid Compound on Coal Spontaneous Combustion

ABSTRACT

The minerals in coal contain a certain amount of metal ions, among which transition metal ions have a catalytic effect on coal spontaneous combustion (CSC). Therefore, the addition of metal ion chelating agent to coal will weaken this catalytic effect, thereby inhibiting CSC. As a class of highly effective metal ion chelating agent, two kinds of organic phosphonic acid compounds (OPAC), 1-Hydroxy Ethylidene-1,1-Diphosphonic Acid (HEDP) and 2-Hydroxyphosphonoacetic Acid (HPAA), were investigated for their inhibitory effect on CSC. First, the low-temperature oxidation experiment was performed on coal samples before and after OPAC treatment. The experimental results show that HEDP and HPAA could reduce CO generation during spontaneous combustion of coal with different metamorphic degrees. Besides, the inhibiting efficiency of HEDP on CSC is higher than that of HPAA. Then, the effects of HEDP and HPAA on the thermal properties of CSC were investigated using synchronous thermal analysis experiment. The experimental results show that HEDP and HPAA could significantly weaken the oxygen adsorption, mass loss, and heat release during the high-temperature oxidation stage of CSC and exhibit the same result that HEDP is better than HPAA. Finally, the reasons for the difference in the inhibitory effects of HEDP and HPAA were analyzed and the inhibition mechanism of them on CSC was revealed via quantum chemical calculation. The results can provide new ideas for preventing CSC and developing new inhibitors.

KEYWORDS:

• Coal spontaneous combustion
• organic phosphonic acid compound
• transition metal ions
• metal ion chelating agent
• inhibition mechanism

Acknowledgements

The authors gratefully acknowledge the financial support of the National Natural Science Foundation of China [grant number 51974128] and the National Natural Science Foundation of Hebei [grant number E2020209111].

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the National Natural Science Foundation of China [51974128]; National Natural Science Foundation of Hebei [E2020209111].