Study On The Anti-oxidative Composite Inhibitor For Retarding Key Active Groups During Coal Spontaneous Combustion Process

Coal spontaneous combustion has been continuously threatening coal mining,storage and application,and influencing coal mines safe production and sustainable development.Spraying inhibitor is one of the important techniques to prevent this disaster,while effectiveness of existing inhibitors are incomprehensive and too low for ideal applications.Therefore,based on the chain reaction mechanism of coal spontaneous combustion,efficient antioxidant melatonin was employed as the chemical inhibiting composition and poly acrylic acid sodium alginate was employed as the physical inhibiting composition to produce novel antioxidant physical-chemical compound inhibitor.Then the in-situ Fourier Transformed Infrared Spectrum(FTIR)testing method and coal spontaneous combustion tendency kinetic testing method were utilized to verify the inhibiting effect of the compound inhibitor to coal spontaneous combustion.This study is of vital importance to the research of inhibitors and the development of prevention and control of coal spontaneous combustion.First,melatonin was selected as the chemical composition of coal spontaneous combustion inhibitor from various highly effective antioxidant based on coal oxidation mechanism and inhibiting mechanism of anti-oxidants.Besides,some other antioxidants were selected for comparison.Their influences on coal’s active functional groups were analyzed using in-situ FTIR testing method.Subsequently,melatonin was proved to be the best anti-oxidant.Second,quantum chemistry calculation was employed to analyze and deduce the microcosmic mechanism of melatonin suppressing coal oxidation.During the process of coal oxidation,melatonin is well performed in inhibition of methyl,methylene and hydroxyl oxidation and promotion of ether bond generation.To be specific,acting as the active orbital,the double bond between carbon atoms embodied in the side chain of benzene ring in the melatonin molecular can react with lipid and peroxide radicals generated from coal oxidation,producing stable ether bond R-O-R’.Thus active chain reactions of coal oxidation can be suppressed,coal temperatures cannot reach high values,and then spontaneous combustion of coal can be inhibited.In practical application,the optimum coefficient proportion of melatonin is 6wt%.Based on above research,an antioxidant physical-chemical composite inhibitor was produced through chemical crosslinking,which consists of melatonin and poly acrylic acid sodium alginate.Compared with using melatonin as the inhibitor,its inhibiting effect was significantly enhanced.On the high temperature stage,the stability of melatonin is well protected due to the crosslinking network and caged cladding structure of poly acrylic acid alginate,realizing multistage release and continuous inhibiting effect.Besides,the best quality ratio of melatonin and poly acrylic acid sodium alginate is 1:4.