Study On The Secondary Oxidation Spontaneous Combustion Miro-characteristics Of Coal

China has a large quantity of coal, as well as a great production of it. The phenomenon of coal spontaneous combustion is serious and may be disastrous so that coal reignition comes to appear frequently, as so called secondary oxidation. The secondary oxidation means the raw coal comes to spontaneous combustion and the temperature rises to the point after critical temperature, then cooling to original temperature and recurrence of redox reaction process.In this study, different ranks of coal were taken as study object. Experimental analysis was adopted to being a using method to investigate the macroscopic and microscopic characteristic of different ranks of coal and the comparison between initial and the second oxidation. The experimental results showed that the secondary oxidation has much available to oxidate and presented the basis of building the mechanism, prediction and prevention technology of secondary oxidation.The industrial analyzer, elemental analyzer, density analyzer, autosorb-iq-c fully-automatic physical and chemical adsorption analyzer and X- ray diffractometer were adopted to test the elemental constituent, moisture, ash content and volatile of original and the second oxidation. Investigate the change of specific surface area and crystal structure during oxidation. The experiments take above master the basic physical properties of different ranks of coal sample, it is found that moisture decreases, specific surface area increases, crystal structure becomes loose, and much easier to oxidation in second oxidation of coal.Aim to the characteristic temperature during twice oxidation, Fourier infrared spectrometer was used to investigate the change rule of functional group in coal molecular structure. Therefore,-OH,-CH2, –CH3, carbonyl group and ether bond were confirmed being major influence active groups to the oxidation reaction in secondary oxidation.With the analysis of experiment on the secondary oxidation between different ranks of coal, gas concentration, oxygen consumption rate, the gas production rate, heat intensity, and characteristic temperature were obtained. The findings suggest that the volume of CO and CO2, which were produced by the reaction of the secondary oxidation, which are more than the volume of initial oxidation in the earlier stage and lower in the later stage. The volume of CH4, C2H6, and C2H4 which were produced by the reaction of the secondary oxidation, were lower than the volume of initial oxidation. The sequence and all kind of produced gas above did not be changed. Oxygen consumption rate, the gas production rate, and heat intensity values of secondary oxidation were higher in the earlier stage in comparison with later stage. Gas index growth analysis was adopted to obtain the characteristic temperature points of secondary oxidation which were shifted to lower than initial oxidation.