Numerical Simulation Of Microthermal Nitrogen Injection For Fire Prevention And Extinguishing In Gob

As a technology for fire prevention and extinguishing, nitrogen receivesextensive attention in domestic and abroad because it can put out fire quickly,effectively, and operates simply, safely and reliably.Through theoretical analysis,numerical simulation and field application, on account of the measurement data of themine, this paper has simulated migration rules of microthermal nitrogen in gob torealize the optimization of nitrogen injection process, putting theoretical analysis andnumerical simulation as forerunner.Firstly，according to the characteristics of nitrogen for fire prevention andextinguishing, this paper has analyzed the problems of liquid nitrogen direct-injectionprocess and vaporization process comprehensively and the controlled evaporation ofnitrogen injection process is put forward, in order to overcome the difficulties to keepheat, easily vaporization of liquid nitrogen and freezing damage of pipe created in thelong-distance transmission.By analyzing the collapse characteristics of mined overlying strata and the heightof “three zones” in gob, this paper has researched the relationship of the coefficient ofbulk increase, porosity, permeability and viscous drag coefficient and theirdistribution character in the gob, which provides significant basis for theestablishment of porosity and viscous drag coefficient by UDF function.Through the derivation of gas flow basic equations, airflow migration model ingob has been established to simulate the temperature field, gas concentration field andairflow field, working out the migration rules of microthermal nitrogen in gob. Thispaper has proposed inerting index and cooling index, and quantitatively analyzed theinfluence of temperature and quantity of flow on cooling and inerting effect in gob,which can obtain the best place of nitrogen injection and the best quantity of flow aswell. A comprehensive analysis of effects on oxygen concentration of nitrogeninjection in the working face is conducted.Finally, by combinating the theory analysis and numerical simulation results, thispaper has designed the site nitrogen injection process and ascertained the nitrogeninjection location and quantity of flow, according to spontaneous combustion situationof120204working face in Yangchangwan mine of Shenhua Ningxia coal Industrygroup. By monitoring the concentration of CO and the temperature of gas, cooling andinerting effects of nitrogen injection in goaf is analyzed.