Application of full negative pressure guiding air

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The use of full negative pressure to guide air flow ventilation and gas drainage

the mine full negative pressure area is the area where the air pressure caused by the main fan is lower than the ground atmospheric pressure, and the negative pressure area does not cover the blind lane and local fan ventilation area. The main reason for air flow is that there is a pressure difference along the roadway in the full negative pressure area. According to the above theoretical basis, when the blind roadway at the return air side after the recovery of the mining face is used underground for other purposes, the full negative pressure can be considered to guide the air flow ventilation when the local fan ventilation is installed, although the cost is not low enough, economic and reasonable, and the maintenance and management is troublesome. In case of large amount of gas emission from goaf during operation, full negative pressure can be used to discharge part of gas

this method has achieved remarkable results in the practical application of Xingyun coal mine

Xingyun coal mine is a low gas mine, but the natural gas accumulation and emission of coal seam C9 are large. In june2003, the mining of 9096 working face in C9 coal seam was completed. After the goaf was closed, in order to solve the difficulty of drainage, the 9096 return air connecting roadway, which has become a closed single head roadway, was temporarily used as a water sump after transformation, and an electric pump was operated here. The closed goaf control box mainly consists of oil tank, oil pump, oil filter, motor, speed valve, oil return valve, etc. the pressure difference between the upper and lower roadways and the goaf actually exists. There is air leakage due to roadway deformation, sealing quality and other reasons, and the air leakage will bring out the high concentration gas in the goaf. How to ventilate and deal with the frequent gas overrun has become a thorny problem

for this reason, three schemes have been adopted successively:

initial scheme:

firmly grasp the air door at the central part of the market leading order in the return air connection lane, install a section of iron air duct on the door wall, and set it in the iron air duct Φ The 400 rubber air duct extends to the water pump and uses full negative pressure to press in the fresh air flow. After a week or so of field observation, it is found that this scheme has the following disadvantages

1. It is difficult to manage the damper, and the local system is unstable

the air door is often opened. If two air doors are opened at the same time for roadway cleaning and maintenance, the gas concentration at the pumping point can reach 2% within 10min

2. There are many air leaks, and the gas below the upper return air outlet of the connecting inclined roadway is partially out of limit

due to the influence of mining, the roof and side walls of the roadway are broken, and the air door is deformed after long-term use. In addition, the air path is too short, and the air door has a lot of air leakage, resulting in the loss of air volume. Moreover, due to the flexibility of the rubber air duct itself, the introduced fresh air volume is insufficient, so that the gas at the top of the roadway above the water pump and below the inlet of the connecting inclined roadway accumulates (up to about 1.5%)

3. The service life of the connecting inclined roadway is long, and the roadway section is less than one third (2.2m2) of the design section. It is difficult for people to pass after hanging an air duct in the roadway

in the secondary scheme, 2.2kW fan is selected for air supply:

a 2.2kW small fan is installed at the fresh air flow side of the damper to increase the air supply. After this scheme is selected, there are also many problems of air leakage and difficult management of air doors. The gas in the upper part of the inclined roadway still cannot be reduced below the safety value. Keep burning the extracted lubricating oil to ashes for chemical analysis or spectral analysis at about 1.5%, and increase the power consumption after the fan, which is uneconomical for long-term use

three schemes:

set airtight at the lower entrance of 9096 return air uphill, and lay one time along the floor in the lane Φ 400 iron air duct, the upper port of the iron air duct is connected with the return air uphill, and the lower port extends to the water pump to expand the full negative pressure area from the return air uphill and downhill to the water pump in the blind lane, and use the full negative pressure to supply fresh air flow in the blind lane

advantages of the scheme: there is fresh air flow in the lane, which can save one fan and fan power consumption

disadvantages of the scheme: after the scheme was implemented for 8 hours, it was observed that the gas in the upper part of the inclined roadway began to accumulate and gradually increased. After 24 hours, the accumulated gas concentration reached 5%, which attracted great attention of the mine. After careful analysis, the main reason for the overrun is that the passing air volume of the iron air duct is small, and the speed of the air flow in the roadway is too low, resulting in the situation that the 9096 return air roadway is closed and the high concentration gas brought out by the air leakage in the surrounding cracks can not be completely pumped into the iron air duct to escape into the inclined roadway and flow in layers with the fresh air flow. The gas gradually flows to the upper part of the inclined roadway and accumulates, forming a "gas cloud"

after identifying the causes, the three schemes were improved

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