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To investigate the desorption behavior of O2 through CO2/N2 injection in the gob of a gassing mine, we focused on the adsorption configuration of coal containing O2–CH4. The mechanism underlying the enhancement of O2 desorption in coal due to CO2/N2 injection was elucidated using the Grand Canonical Ensemble Monte Carlo (GCMC) and Molecular Dynamics (MD) methods. Furthermore, the impact of CH4 on O2 desorption was unveiled by detailed calculations and studies of energy variation, concentration distribution, and diffusion coefficients of oxygen.Our findings indicate the following: (1) CO2 and N2 facilitate the displacement of oxygen primarily by occupying adsorption sites. The CO2–O2 model exhibits a significantly higher concentration of free O2 molecules compared to the N2–O2 model, and the CO2–O2–CH4 model surpasses the N2–O2–CH4 model in free O2 molecules. (2) The total energy of the CO2–O2 model is lower than that of the N2–O2 model, indicating greater stability in the former. Similarly, the total energy of the CO2–O2–CH4 model is lower than that of the N2–O2–CH4 model, highlighting its superior stability. It is concluded that CO2 injection is more effective in promoting oxygen desorption than N2, regardless of the presence of methane. (3) Under equivalent injection pressure, the root mean square displacement of O2 in the CO2–O2 system surpasses that in the N2–O2 system. Furthermore, compared to the N2–O2–CH4 system, the CO2–O2–CH4 system exhibits a larger root mean square displacement of O2, signifying higher O2 molecule activity. The diffusion coefficient of O2 in the CO2–O2 system is higher, underscoring the superior effectiveness of CO2 in promoting O2 desorption.In summary, our research outcomes offer valuable theoretical insights for fire prevention technology in goaf. [ABSTRACT FROM AUTHOR]

In order to solve the problems associated with the local resistance calculation of roadway fire flames around fire source and resistance coefficient determination, a model based on flame cross-section area calculation was developed, where the flames local resistance coefficient is a function of flame truncated area. The study points out that the fire area is the result of roadway fire combustion intensity under certain conditions and merry speed interaction, and determines that the resistance coefficient values must take into account the deterrent effects of roadway romantic flame. The analysis on the relationship of local resistance with airflow velocity flame and fire burning intensity shows that with the increases of flame intensity, the flame area and local resistance increase, the wind velocity decreases and the phenomenon of so-called throttling occurs. When the wind speed is equal to the critical velocity of oxygen-enriched combustion, the fire source fully combusted, the flame area and flame local resistance reach maximum values. When the wind speed is less than the critical velocity, the source of fire burning is weakened, the flame area and local resistance become smaller. When the wind speed is too large, the wind flow velocity compresses flame, fire truncated area and flames local resistance decrease. The above variations are obtained with two classic experimental results of ignition sources and line sources match. The parameters of the model can be determined based on the experimental data. According to the different strength of the fire source, the coefficient values of the largest flame area are generally between 0.285 to 0.410. [ABSTRACT FROM AUTHOR]

The mathematical model of disaster process in mine ventilation system during mine fire period was built based on source-containing ventilation network and previous fire studies, and the software TF1M(3D) was developed based on MATLAB. Combined with the typical mine ascensional airflow fire example, the airflow movement during fire period, the distribution ol fume concentration and temperature, the ventilation system variations were simulated in a whole mine scale. Simulation results show that the air quantity in main airway increases with lire when ascensional airflow fire occurred in mine, while the airflow in the side branch of lire source decreases, stagnate and reverse;driven by fire burning power (fire ventilation pressure), overflowing quantity and reverse air quantity have consistent symmetry; and in complex ventilation network, reverse airflow in side branch orderly occurs. A series of changes of ventilation system during lire period are all produced by the interaction of ventilation power and fire ventilation pressure, which also lead to the dynamic drift of mine system total wind drag. This paper provides the relationship between fire severity and wind drag drift value. The software TflM(3D) offers a good platform lor analyzing mine fire because of its large amount of information, good animation and intuitive phenomenon. [ABSTRACT FROM AUTHOR]

For the study of gas floating characteristics and distribution in 3D goaf, according to mass conservation, conservation of momentum, and Fick's law, suitable for fully mechanized goaf, describing the variable density of the air-gas mixture, nonlinear flow-diffusion equations were built. Combined N2-706 coal face in Daxing Mine, using CFD software, the author simulated the transport and distribution of gas in 3 D goaf. Heterogeneity of caving in flow field was described as the "0" type. RNG k-ε turbulence model was used, and taking into account the gravity field conditions. The results of theoretical calculations were consistent with the actual conditions and gas monitoring data. Authors point out that gas floating characteristics and distribution in 3D goaf, is due to the air flow moves, gas diffusion-dispersion, and the floating migration of gas-flow which caused by its density difference, and it is also a dynamic balance, which depends on constant desoiption of gas in flow field and continuous inflow of air leakage. The results show that the flux of extracting gas from high drill holes is approximately inversely proportional to the volume percent concentration of extracting gas, and has a negative exponential relationship with volume percent concentration of gas in return air tunnel. [ABSTRACT FROM AUTHOR]

Aiming at the problem of the computation of ventilation heat resistance in a roadway during mine fire, to the ventilation roadways with airflow temperature and density variation, a normative computing formula was deduced. It was pointed out that according to generalized ventilation principle, the ventilation resistance during mine fire includes frictional resistance and local resistance, as well as an additional resistance caused by the external ventilation source, namely fire smoke. In the new formula, the computation of ventilation resistance is expressed from two media, namely fluid and roadway, and the conception of roadway geometry air resistance were introduced. Geometry air resistance is the resistance characteristic of roadway itself, and it has nothing to do with fluid. Geometry air resistance includes frictional resistance and local resistance too. Conceptually, the new formula has a clear discrimination to the essence of heat resistance, so the mistakes easily appear during computation and analysis will be avoided. The conclusion that the ventilation resistance of high temperature smoke flow is in direct proportion to fire temperature was drawn. To verify the heat flow resistance effect, an experimental pipeline facility was designed to determine the variation of heat resistance with temperature. The experimental results are identical to the conclusion drawn from theoretical derivation. The additional resistance of exogenous smoke flow was extracted successfully by using the experimental facility. Experimental results show that exogenous resistance is the physical image of combustion process. A practical method for computing the heat resistance with the participation of exogenous gas is provided. [ABSTRACT FROM AUTHOR]

From the point of calculating spontaneous combustion temperature field for goaf, distribution characteristics of spontaneous combustion for goal based on the "O" type risked falling and non-uniform oxygen consumption was studied. A numerical model of nonlinear seepage-multicomponent gas-temperature field and the non-uniform oxygen consumption for goaf was established, which took into account the dynamic changes of mine ventilation and working face forward. One kind of model expression was given that describes the falling roof strata according to "O" type circle compaction distribution. Allow for grouting, injecting water, spraying inhibitor, and the changes of local air current leading to non-uniformity of oxygen consumption for goaf, the 0-1 random change model of non-uniform oxygen consumption after resistance was built. The results show that the ability of overall oxygen consumption is declining for goaf after resistance, the temperature increases, and the distribution area of CO has greatly reduced after resistance though regional oxygen consumption exists fluctuations, the results is close to the actual situation. The research points out that the non-uniformity model of oxygen consumption for goaf can account for the influence process of mutability and factors denaturations of the temperature rising process caused by spontaneous combustion for actual goaf. It plays an assist instruction role on fire prevention and extinguishing of survived coal in goaf behind working faces. [ABSTRACT FROM AUTHOR]