Study On The Microcosmic Characteristics And Macro Parameters In The Process Of Coal Oxidation And Spontaneous Combustion

A majority of coal seams in our country are prone to spontaneous combustion, whichpollutes environment, deplete precious coal resource with no benefit and seriously threatensmining production. In this paper, experimental analysis and quantum chemistry simulation areconducted to study the process of oxidization of different rank of coal at lower temperature;the microcosmic properties and characteristic parameters of coal oxidized at low temperatureare also studied to reveal mechanism of coal spontaneous combustion. The study is importantin directing coal spontaneous combustion prediction and prevention technology researchtheoreticallyUsing specific surface area analyzer, X-ray diffraction instrument and coal spontaneouscombustion propensity testing instrument, the relation of coal composition, specific surfacearea and porosity to coal rank are studied. The law of coal physical adsorption of oxygen andaromatic microcrystalline structure varies with the rank, the progress of oxidation and thegrain size of coal sample, which proved that the microcrystalline structure of coal largelydetermines physical, chemical properties of coal, as well as activation time and oxygenconsumption which are used to characterize physical adsorption of coal.The law of variation of functional groups’ structure of different rank and particle size ofcoal sample during oxidation at different temperature is studied with FTIR. By means ofquantum chemistry simulation of the main active groups’ stepwise oxidation progress, theactivation energy, thermodynamics and kinetic parameters and enthalpy change of the processare obtained.The study reaffirmed that the high activation of side chains and bridge bond in coalmicrostructure are the major inducements of coal spontaneous combustion. The carboxyl group is a symbol of coal oxidation, and CO is a symbolic gas of coal spontaneouscombustion. It proved from the microcosmic viewpoint that the differences of coalspontaneous combustion propensity are due to molecular micro-structure of different coalsamples.According to the oil-bath programmed temperature oxidation experiments, someparameters characterizing coal spontaneous combustion including oxygen consumption rate,gas generation rate and exothermal intensity of different rank of coal is studied, and theimpact of coal sample’s grain size on macroscopic characterization parameter is analyzed. Bymeans of microstructure analysis and characteristic parameters study, the correspondingrelation between the macro structure and the characteristic parameters of different coal sampleis studied, and the characteristic parameters is explained in microscopic view.