Synergistic Inhibitory Effect of Free Radical Scavenger/Inorganic Salt Compound Inhibitor on Spontaneous Combustion of Coal

ABSTRACT

From the aspects of isolating oxygen, lowering temperature and terminating free radical chain reaction, an inorganic salt inhibitor and a radical scavenger were combined to form a compound inhibitor for preventing of coal spontaneous combustion. A long-flame coal with easy self-ignition was chosen to study the inhibitory performance of different inhibitors using inhibition performance tests and by characterizing reactive functional groups and performing thermal analysis. The experimental results show that the compound inhibitor has a coordinated inhibitory effect throughout the whole process of coal spontaneous combustion, with physical and chemical double inhibition effect. Compared with the raw coal, the amount of CO released from the coal sample treated by the compound inhibitor was reduced by 88.7% at 128°C, and the inhibition rate reached 82.5% at 100°C. The inhibition ratio is higher than 80% during the initial weight loss stage and the oxygen absorption and weight increase stage. The compound inhibitor plays an inhibitory role by reducing the contents of hydroxyl, methyl, methylene groups and active components containing carbonyl groups in the coal, wherein, the relative content of a carbonyl compounds decreased obviously. During the initial weight loss stage, the water retention due to inorganic salts physically isolated oxygen and cooled the coal. During the oxygen adsorption and mass gain stage, free radicals were released from the compound inhibitor and captured both oxygen free radicals and carbon free radicals via chemical inhibition. N,N-Dibenzylhydroxylamine (DBHA) contains multiple absorption sites that can simultaneously capture multiple free radicals in coal. Butylated hydroxyl toluene (BHT) reacts with free oxygen-containing functional groups to form stable compounds, which interrupts the formation paths for ketones and aldehydes. Moreover, the inhibition mechanism of the compound inhibitor on coal spontaneous combustion was also explored.

KEYWORDS:

• Coal
• spontaneous combustion
• free radical
• inorganic salt
• synergistic inhibitory

Acknowledgments

The authors gratefully acknowledge the financial supports of National Natural Science Foundation of China (51274146), Research Project Supported by Shanxi Scholarship Council of China (2020-043), Science and Technology Innovation Project in Higher Education Institutions of Shanxi Province (2020-70), and Shanxi Overseas Talents Pioneer Park Entry Project (20180020).