Experimental research on the inhibitory effect of the controlled-release inerting inhibitor on coal spontaneous combustion

Abstract

ABSTRACT A controlled-release inerting inhibitor (CRII) was prepared by embedding the little inhibiting balls (LIB) into the sodium alginate (SA) hydrogel. The water retention and flowability of the SA hydrogel were studied, and the controlled-release effect of the CRII was analyzed by CO2 production rate and scanning electron microscopy. At last, the inhibiting performance and the long-lasting effect of the CRII were investigated. The experimental results show that the 1.5 wt% SA hydrogel has the best water retention and good flowability. Meanwhile, the SA hydrogel also has a great effect on CO2 retention. During the heating process, 88.86% of CO2 produced by the LIB escaped into the air, while only 42.57% of the CRII did. As the temperature gradually increases, a large number of micropores are formed on the surface of LIB, which achieves the controlled-release of inhibitory components. In comparison to the raw coal, the temperature at which CO enters the exponential growth is delayed by 18.8°C for the CRII-treated coal sample, and the release of CO is reduced by 86.3% at 127.8°C. Comparing the CRII-treated coal samples placed for 1 and 8 days, the average inhibition rate of the latter decreased by 0%, −1.81%, 0.56% and 2.59% in four stages (45 ~ 75°C, 75 ~ 100°C, 100 ~ 160°C and 160 ~ 180°C), respectively. The average inhibition rate of the coal samples treated by CRII did not decrease basically before 160°C, while the coal samples treated by NaCl aqueous solution under the same conditions showed a significant decrease in the early stage. In future studies, it is a worthwhile focus that how to optimize the ratio of each component in the LIB and further study the controlled-release performance.