Study Of Coupling Of Gas And Spontaneous Combustion In Highly Gassy And Spontaneous Combustion Goafs

Highly gassy and spontaneous combustion goafs are the greatest disaster sources of working faces, which includes gas effusion caused by caving and carbon monoxide released by the spontaneous combustion of coal remains, at the same time, there is a coupling problem of gas effusion and the spontaneous combustion of coal remains in goafs, and a systematic study to this problem is carried on. In a flow field, the spontaneous combustion of coal remains and gas effusion are taken into account synthetically, a mathematical model for the coupling of gas and spontaneous combustion in goafs are established based on the continuity equation for anisotropic seepage, the diffusion equation for the compounding of multiphase gases and the integrative heat transfer equation for porous medium. The general laws of the mechanism of coupling action and the reciprocal influences are analyzed by the finite element method of windward format, and the locale conditions are considered too.According to the characteristics of goafs, a modified function is introduced to streamline equation. A applied computing scheme which can achieve self-adapting split according to boundary style and the automatic identification of boundary conditions is put forward, and the flow law of air leakage and velocity field can be displayed on computer display. A diffusion equation for the compounding of gas and atmosphere is put forward. A negative exponent attenuation function adopted by the model for gas effusion intensity of goaf is used to compute the motion and distributing state of goafs. A simulating test method is used to analyze the general law of gas effusion from goafs to working faces, and the result is closed to practice.The general equation for the compounding and diffusion of multiphase gases of the exchange and variation of gas components during the spontaneous combustion is developed from the diffusion equation of two phase compounding, at the same time, gas, oxygen and carbon monoxide are considered unitedly, which provides a precondition for the study of the coupling of gas and spontaneous combustion in the same flow field.The velocity constant of coal oxidation is considered as the characteristic index of weighing the spontaneous combustion environment in goafs. According to the computation, a problem of oxygen consumption along the courses of air leakage exists in goafs, and there is no consequent relationship between the disequilibrium of oxygen concentration distribution and the intensity of air leakage. The oxidation zone of spontaneous combustion is determined by the superposition of velocity field and oxygen concentration field. The whole process of the forepart of spontaneous combustion in goafs is simulated by computing the temperature field of goafs with spontaneous combustion, and a lot of distributing solves in the form of figures with dynamic variations are given.In the study of the thesis, some more comprehensive mining and gas geology factors, such as the air leakage of flow field, the air quantity of working face, the oxidation of spontaneous combustion and the advance of working face are taken into account, moreover, the influence of some technical measures for hazard prevention, such as gas drainage and nitrogen injection to gas and spontaneous combustion in goafs are considered too.The contradiction between gas overrun and of highly gassy and spontaneous combustion of coal in goafs is implacable. The safe regulating range index of air quantity and the judge condition of the unbalance between the two hazards are put forward. The interaction relationship under the conditions of implementing technical measures of hazard prevention is discussed in detail. The following problems are solved: (1) the relationship between gas effusion intensity and spontaneous combustion conditions and spontaneous combustion scale. (2) The influence of gas effusion on the process of spontaneous combustion. (3) The action intensity of oxygen dilution caused by gas effusion. (4) The law of spontaneous combustion in goafs caused by gas drainage. (5) The influence of the spontaneous combustion control measures of nitrogen injection on the absolute gas effusion quantity in goafs. The problem of spontaneous combustion in goafs caused by mass flow gas drainage can not be neglected.