Study On The Emission Characteristics Of CO And The Dangerous Area Judgement Of Coal Spontaneous Combustion In The Fully-mechanized Working Face

In order to make clear the emission characteristics of carbon monoxide and the dangerous area of coal spontaneous combustion in the fully-mechanized working face, the methods of the laboratory experiment, the field synthetical testing, the theoretical analysis and the numerical simulation in this paper. This has important theoretical significance and practical value for the spontaneous fire prevention of coalmine. In terms of the basic characteristics of coal spontaneous combustion and the mine pressure behavior, the oxidation-pyrolysis process of coal sample is separated into three stages which are respectively the weightless stage of moisture, the weightmore stage of oxidation and the weightless stage of combustion. And the reaction essence and the change law of the characteristic temperatures of every stage are given. Then the objective phenomenon which the different weightmore and weightless stages of coal oxidation-pyrolysis process have different critical oxygen volume fraction is discovered. The gaseous products released by the process of coal spontaneous combustion can be divided into three categories, which respectively are desorption gas, oxidative gas and pyrolysis gas. Then it reveals that the generation of CH4, C2H6, C3H8, C2H4 and C3H6 is the combined action of multi-component reactions according to the activation energy of the oxidative gas and pyrolysis gas. After the main roof of the fault zone, the step of the first and periodic weighting is analyzed and gained through the field observation of mine pressure and numerical simulation of UDEC software. It is pointed that the destabilizing form of the main roof is the sliding instability and the caving form of the main roof is the whole falling of the rock-step beam structure. The three-zone of mine pressure in the horizontal direction is divided by the regularities of distribution of the bottom bearing pressure. This provides the theoretical support for the three-zone of coal spontaneous combustion in goaf.In terms of the emission and source identification of carbon monoxide, the genetic type and generating mechanism of carbon monoxide were described in detail, the source of carbon monoxide which was divided into the primary and secondary carbon monoxide was put forward. After the correlation analysis of the gas and thermal parameters, the specific source of carbon monoxide in the fully-mechanized working face was made clear. The out-flow rule of carbon monoxide which was periodic increase with the progradation of the fully-mechanized working face was pointed out. The periodic increase cause of carbon monoxide emission caused by the synergistic effect of the impact extrusion by the approximate wall in the deep goaf and the impact force forming by the periodic sliding of structure was revealed. In terms of the synthetic judgment of dangerous zone of coal spontaneous combustion in goaf, firstly the three-dimensional map and the isoline map of oxygen and carbon monoxide in the goaf are drawn according to the field observation data by self-programming. The regularities of distribution of oxygen and carbon monoxide in the dip direction and strike direction are gained. Then the critical value of the volume fraction about oxygen and carbon monoxide which is used to determine the three-zone of coal spontaneous combustion in goaf is obtained through comprehensive analysis. And the three-zone of coal spontaneous combustion in goaf is divided according to carbon monoxide volume fraction. Then the method of carbon monoxide volume fraction which is used to divide the three-zone of coal spontaneous combustion is proved to be feasible and practical using the method of oxygen volume fraction and the leakage wind speed.The corresponding relation between the three-zone of coal spontaneous combustion and mine pressure in the horizontal direction is analyzed. Then the dangerous zone of coal spontaneous combustion in goaf is judged by the intersection of self-oxygen combustion zones according to the division method of the volume fraction of oxygen, carbon monoxide and the leakage wind speed. Finally the safety mining speed for the prevention of coal spontaneous combustion is calculated.