Research On The Fire Prevetion And Extinguishing Performance Of Inert Medium

Mine fire threaten the safety of coal mine production seriously. Pouring into inert medium is one of the fire prevention technologies, which has been widely used to prevent and control mine fire. However, in the practice of pouring into inert medium for preventing and controlling mine fire, people found that the fire-fighting index gases, such as CO, can hardly reach safety level, and fire sealing can easily recrudescence after unsealing. Thus, the performance of inert medium for preventing and controlling mine fire is questioned. A reasonable index is expected to make scientific evaluation of fire extinguishing performance of inert medium. And after the systematical research by using comprehensive techniques which include theoretical analysis, laboratory experiments and case analysis, the main results and conclusions are as follows:The cooling performance of liquid inert medium was theoretically analyzed. When pouring into liquid inert medium straightly for controlling fire, since the temperature of liquid inert medium is extremely low, its cold stress easily damage pipelines, even burst; At the same time, a large amount of liquid inert medium has vaporized in the process of long distance transmission. In fact, what diffuse in the goaf is actually low temperature gaseous inert medium. When the temperature of 1kg cold carbon dioxide(-20℃) and nitrogen(-196℃) rise to room temperature(25℃), they will absorb heat 24 k J and 229 k J respectively, the performance endothermic cooling is extremely limited. When gas diffuse from infusion mouth to around, gaseous medium temperatures soared and will lose its ability to cool down before arriving at fire area, the cooling effect of high temperature area is limited, its function mainly reflects in explosion suppression of fire area.Fire prevention performance of gaseous inert medium was studied. In this paper, high precision trace heat meter C80 was used to test heat release of the coal low temperature oxidation in 140℃, 145℃ and 150℃, and reaction mechanism functions and kinetics parameters change rule in the process of the coal temperature oxidation was accurately solved. Research has shown that with the reduction of oxygen concentration, heat release of coal oxidation gradually reduce, and activation energy increased. In the atmosphere of nitrogen and carbon dioxide, when oxygen concentration down to 1.5% and 3% respectively, the reaction activation energy of coal oxidation changed from negative to positive, the spontaneous reaction changed into non-spontaneous reaction. When using inert gas to prevent fire, oxygen content of inert gas should be controlled under 1.5%. But pouring into inert gas for fire prevention on the scene is open region nitrogen injection and the purity of inert gas is not high, so the effective fire prevention area oxygen whose oxygen concentration below 1.5% is small, the performance of fire prevention is extremely limited.Fire extinguishing performance of gaseous inert medium was studied. Gas fire performance of inert medium was studied. The characteristic of coal temperature is one of the important parameters of characterization of coal combustion process. In this paper, the TG and DSC curve of coal samples burning process under the conditions of different lean oxygen oxidation and different inert gas were gotten by using Thermogravimetric Analyzer, the corresponding temperature and heat release were analyzed. The results show that characteristic temperature point of coal sample on the TG curve decreases with the rise of oxygen concentration, and the lower oxygen concentrations can inhibit the development of the coal combustion reaction. When oxygen concentration was 1.5%, the coal sample could still burn completely. Therefore, when using inert gas to extinguish fire, the oxygen content of inert gas should be controlled under 1.5%. Due to the complexity of air leakage conditions and the purity of inert gas is often low, the oxygen concentration of fire area is hard to fall below 3% after a large number of inert gas perfusion, and fire cannot be extinguished. Therefore when using the inert gas fire extinguishing technology, in order to give full play to their role in suffocation, the purity of inert gas should be improved and the effect of the fire enclosure should be ensured.