Study On The Mechanism Of Gas-oxygen-separation In Non-ventilation Excavation Based On The Simultaneous Mining Of Coal And Gas

Gas disaster is more serious in the production of coal mine,the current theory and technology of gas prevention and control cannot eliminate gas accidents completely,gas exceeding limits and explosive problems occur time to time.Based on the theory that exploiting coal resource and gas of highly gassy coal seam in a sealed space simultaneously which is proposed by academician Zhou Shi-ning,a new type of non-ventilation excavation system model which ventilating in central tunnel but not ventilating in excavating roadway is established.The tunnel deploying,coal and material transporting,personnel safety and comfort maintaining,gas extracting,gas and oxygen blocking subsystems are analyzed,the merits and demerits of non-ventilation excavation system and its feasibility are studied.The key matter of non-ventilation excavation is blocking gas and oxygen effectively,on this purpose,the mechanism of blocking gas and oxygen is studied.To control the gas,the main work is to clarify the gas spatial density distribution which affected by gas effusion amount,extraction amount,leakage amount,and nitrogen barrier speed.As the working face moving ahead,considering the gas emission total time of coal wall and coal blocks are different,the expression of total gas emission amount in one working cycle is derived with the methods of integral and summation.Through the establishment of leakage gas transport mechanical model,momentum equations,energy equations and the gas transport laws which affected by emission amount,extraction amount,buoyant force,viscous resistance and other aspects are obtained.Temporal and spatial distribution of gas concentration law is derived by applying the Fourier transformation onto the Fick’s law and Gaussian puff model.According to the jet entrainment effect,the relation between nitrogen curtain speed and gas concentration are obtained.According to the gas transport law,a gas linkage controlling method is proposed which consisted by air door hard-blocking,extraction pressure dynamic adjusting and nitrogen curtain soft-blocking.The affection of four kinds of variables to the gas transport law is studied by analogy simulation,numerical simulation and field simulation experiment,the results show the validity of gas linkage control method on the condition of door open and close.The blocking of oxygen is studied on condition of door open and door close,respectively.Method of oxygen control while the door is open is similar to the gas control.Turning on the nitrogen curtain before opening the door,replacing the air by nitrogen in the door rotating space,at the same time,turning on the nitrogen curtain in barotropic zone to stop the oxygen flowing to excavation roadway.When the door is closed,according to Bernoulli’s equation,the way to block oxygen is to make sure the pressure of barotropic zone higher than that in middle buffer zone and the rear central tunnel-bypass tunnel zone.By building analogy simulation and numerical simulation analytical model,the mechanism validity of blocking oxygen in bypass tunnel is proved.The study shows that,in non-ventilation excavation,gas and oxygen can be blocked effectively by using air door,gas drainage and nitrogen curtain linkage control.It provides a theoretical and experimental foundation for the application of non-ventilation excavation processing.