Study On The Kinetics And Micro-structures Characteristics Of Huainan Coal In The Oxidation Process

Study on the microscopic mechanism of coat oxidation is the essence of controlling and preventing coal spontaneous cmbustion.This thesis combined three method of theory analysis.experimental analysis and statistical calculation to study the macro characteristics and micro characteristics and the relationship between them of 6 medium rank of coal in Huainan.China,show the regulation changes in functional groups of coal molecule and the kinetic characteristics of gas productions during oxidation.It provides an important theoretical basis for scientific prevention and control measures.To adopted experiments of elemental analysis,proximate analysis,BET specific surface area and pore size distribution analysis,thermal conductivity analysis,X ray diffraction(XRD)microcrystalline structure parameter analysis,and Fourier transform infrared spectrometer(FTIR)analysis to study the physical and chemical characteristics,and mastered the composition of coal samples and the characteristics of the functional groups in Huainan coal samples.The experimental results show that the characteristics of Huainan coal quality is low ash.high volatile and low sulfur.The specific surface of coal is small,the pore size is mainly of the medium pore and macro pore,which is difficult to oxidize under the normal temperature.Thermal conductivity is decreased by the temperature raised,and thermal diffusivity and specific heat capacity arc increased while the temperature raised.The degree of condensation of aromatic rings in the microcrystalline structure of coal is moderate,and the structure of the lamellae is orderly.The mineral composition of coal mainly contains kaolinite,calcite.quartz and siderite.The functional groups of different coal samples were detected hydroxyl,a aliphatic hydrocarbon,aromatic hydrocarbons and oxygen-containing groups with similar kinds but different amounts.The characteristics of microstructure and its variation during coal oxidation were analyzed by in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS).The characteristics of the 21 groups in the four kinds of functional groups were analyzed.The results showed in the process of heating,the hydroxyl group decreased,the aliphatic hydrocarbon increased at first and then decreased,Ar-CH group increased at first and then decreased,and finally increased,the C=C group had been slowly reduce,oxygen-containing groups increased before the ignition temperature,and on the contrary after it.Based on the high temperature-programmed experimental system,which was independently research and developed by Xi’an University of Science and Technology,to test the gas productions during the heating temperature to 500℃.Moreover,to calculate the characteristic temperatures by growth rate method of indicate gas.Additionally,to divided the whole oxidation process into four stages:a critical temperature stage,a crack-active-speedup temperature stage,a speedup-ignition temperature stage,and an ignition temperature stage.The results proved that CO and CO2 increased slowly in critical temperature stage,beyond this stage till speedup-ignition temperature stage the content of carbon-oxygen gas increased rapidly,and the gas concentration in the ignition temperature decreased,and then continued to rise due to the rupture of stable functional groups.CH4,C2H6 and C2H4 gases increased gradual before crack-active-speedup temperature stage,and then sharply increased till the peak point in ignition temperature stage.According to the data of high temperature-programmed experimental system,two different dynamic methods were used to calculate the dynamic characteristics of the four stages.The reaction activation energy decreased at first and then increased with the temperature raised,the ignition temperature stage of the required activation energy is higher than the speedup-ignition temperature stage.In addition,the heat release coefficient was calculated by differential scanning analysis.To analyze the relationship of micro and macro characteristics,grey correlation analysis was chosen to statistically analyze the correlation between the amount of gas,heat release and 14 different active groups in the four stages.The main functional groups that affect the release of gas and heat in each stage were deduced.In the first three stages,carbonyl was the main functional groups which effect gas release and heat generation.Aliphatic hydrocarbon and aromatic ring structure were the main functional groups effect gas and heat release in the ignition temperature stage,and aromatic ring structure began to participate in reaction until the ignition temperature stage.