Thermal behavior effects of 1-butyl-3-methylimidazole tetrafluoroborate on coals spontaneous combustion with different metamorphic levels

Ionic liquid (IL) is a new type inhibitor,which can inhibit the active functional groups in the molecular structure in coal,and inhibit coal oxidation process. However,different metamorphic coal samples have different micro- structures. Moreover,IL has high cost,which is difficult to implement in the field of coal spontaneous combus-tion (CSC). To investigate the effects of IL on the thermal properties of CSC with different metamorphic levels,consid-ering economics and practicality, low concentration ( 5 mass% ) 1-butyl-3-methylazole tetrafluoroborate ( BMIMBF4 ) is used to treat coal samples. Using simultaneous thermal analysis (STA) and laser flash apparatus (LFA), the oxidation and exothermic behaviors of four types of coal were analyzed. The characteristic temperature,thermal effects and thermophysical parameters of coal with different metamorphic levels of IL treatment were obtained. The re- sults show that the BMIMBF4 delayed the characteristic temperature of coal mass loss,increased the initial / maxi- mum heat release temperature,and reduced the maximum heat release rate / thermal release during CSC. Moreover,the inhibition effect decreases as the levels of coal metamorphism increases. Compared with the raw coal sample,the ther- mal diffusion coefficient and thermal conductivity of the treated coal sample are lower,and the specific heat capacity is higher. Namely,the BMIMBF4 reduces the rate of heat transfer between coal bodies and weakens the ability to transfer heat due to temperature difference,increases the heat required to raise the temperature of the coal bodies. In addition,the lower the levels of coal metamorphism,the more significant the inhibiting impact on CSC. The study re- sults provide a theoretical basis for the promotion and application of IL inhibit at CSC field.