Effects of 1-butyl-3-methylimidazolium tetrafluoroborate on the exothermic and heat transfer characteristics of coal during low-temperature oxidation

The effects of the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate [Bmim] [BF4] on the exothermic and heat transfer characteristics of three metamorphic grades of coal during low-temperature oxidation were investigated. The C80 microcalorimeter results showed that the IL inhibited the exothermic process and characteristics of long-flame and non-caking coals, whereas the IL had a growth-promoting influence on gas-fat coal. The kinetics calculation results showed that the apparent activation energy of long-flame and non-caking coals increased after treatment but gas-fat coal was subjected to the opposite effects. According to the consequences of the LFA457 laser flash system, the IL decreased the thermal diffusivity and increased the specific heat of long-flame and non-caking coals. It had a notable inhibiting effect on the heat transfer properties of the two coals. However, the influence of IL on the heat transfer characteristics of gas-fat coal shows a salient promoting effect. Therefore, we conclude that the IL inhibited the generation and transfer of heat during the low-temperature oxidation of long-flame and non-caking coals. This prevented the occurrence and development of coal spontaneous combustion, but it had the opposite effect on gas-fat coal. The effect of the IL on the thermal behaviour of coal oxidation at low temperature varied with the degree of metamorphism of coal, and such an influence played a dual role in this because of its inhibition and promotion in relation to this reaction. This demonstrated that the IL did not inhibit the spontaneous combustion of all types of coal.