How to safely discharge gas in underground working

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How to safely discharge gas is a local enterprise from Linhai Yanjiang town. The underground working face gas

discharge gas has two categories: local ventilator discharge gas and full air pressure discharge gas. Among them, the local fan discharge gas is divided into when the excavation work is faced with air stoppage and gas discharge of closed roadway or long-term non ventilated roadway. The full air pressure gas drainage includes the tail drainage to deal with the corner gas of the mining face. Except for the gas drainage at the heading face, there is a problem of unsealing and sealing gas drainage

gas discharge when the air is stopped in the face of tunneling work

1. wind tunnel method: before starting the local fan, tie up the air duct in front of the local fan, leave only small holes, start the local fan, and supply air to the working face. The gas moves outward in the roadway as a whole, causing it to produce initial friction on the clamping surface. It is diluted at the full air pressure, and the size of the air duct is determined by the gas volume. After discharging the gas, open all the air ducts

2. local fan blocking method: block a part of the local fan with a board or belt before starting the local fan, and then start the local fan, determine the size of the block according to the gas situation, and remove the baffle or belt after the gas is discharged

3. set a trident air duct for gas drainage: set a trident air duct in front of the local fan, one fork supplies air to the working face, and the other fork is tightly tied during normal ventilation. When it is necessary to exhaust gas, open the fork whose power of the three power supplies should be greater than the total power of the instrument, and then start the local fan. Part of the fresh air is supplied to the working face, and part of the fresh air comes out of the Trident and directly enters the return air roadway. The air flow of the working face also pushes the gas of the roadway outward to the full air pressure and then dilutes it. According to the gas situation, control the air volume at the Trident until the gas is discharged, and tighten the air leakage of the Trident air duct

4. disconnect the air duct method: before starting the local fan, the gas drainage personnel use the methane detection alarm to check the gas in the direction of the working face. When the gas concentration reaches 1%, disconnect the air duct, directly start the local fan, and half connect the air duct according to the gas concentration. One person checks the gas at the place 5 ~ 10 meters behind the disconnected air duct, and the concentration is not allowed to exceed 1.5%. If it exceeds the concentration, remove the air duct and have more fresh air, When the concentration drops, connect the air duct more, and repeat until the gas does not exceed the limit

compare these four gas drainage methods: the advantages of the first three methods are simple and easy to operate. Its principle is to reduce the air supply to the working face, the gas moves outward as a whole, and the gas is diluted at the full air. Disadvantages: first, there is less air supply, and the gas moves outward slowly. If a tunnel is hundreds of meters or thousands of meters, the gas drainage time is too long. Second, it is not easy to know when high concentration gas arrives at the full wind pressure. It is easy for people to contact high concentration gas by checking gas frequently. Third, when starting to discharge gas, the air supply is too large and the wind blows. Fourth, the air volume is adjusted near the local fan, which is noisy and inconvenient to contact

the advantage of the fourth method is that the gas is diluted with the air volume of all local fans, the discharge time is short, the gas concentration is easy to control, people do not contact high concentration gas, and high concentration gas only exists in high gas areas. The disadvantage is that it needs to disconnect the air duct, and then start the local fan outside. In case of sudden power failure, personnel should immediately withdraw from the tunneling roadway. It is safer to evacuate people, because the gas outside is all below 1.5%

the first three methods have many disadvantages. If the wind pressure return duct is steep and steep, it is very difficult to check the gas. The fourth method has strong adaptability. Generally, if there is no special gas emission point in the tunneling roadway, the gas emission time of the outer roadway is long, and the gas emission decreases. The gas will gradually extend the out of limit area from the working face. The method of air cut-off can quickly discharge gas, reduce the time of gas accumulation, and quickly restore normal ventilation

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