Use of full negative pressure to guide airflow ventilation and the use of gas

The full negative pressure zone of the mine is the area where the air pressure of the main fan is lower than the ground pressure caused by the underground, and the negative pressure area does not cover the blind alley and the local fan ventilation area. The pressure difference along the roadway in the entire negative pressure zone is the main cause of air flow. According to the above theoretical basis, when using the return air side blind alley after the recovery of the face is used for other purposes, it is considered that the fan ventilation is not economical and reasonable, and the maintenance and management troubles may consider using full negative pressure to guide the airflow ventilation. When using the gas in the goaf, a large amount of gas can be used in conjunction with the use of full negative pressure to extract part of the gas.

This method has achieved remarkable results in the practical application of clouds and coal mine in.

Xingyun Coal Mine is a low-gas mine, but the natural gas in the C9 coal seam is large and the amount of gushing is large. In June 2003, the C9 coal seam 9096 working face was finished, and after the goaf was closed, in order to solve the drainage difficulties, the 9096 return air connection lane which has become the closed road of the single head roadway was temporarily used as a water tank after being modified, and there is an electric pump. Run here. The pressure difference between the upper and lower lanes and the goaf of the closed goaf actually exists. Due to the deformation of the roadway and the quality of the airtightness, there is air leakage, and the air leakage brings out the high concentration gas in the goaf. How to ventilate and deal with frequent gas overruns here becomes a tricky problem.

To this end, three sets of programs have been adopted:

Initial plan:

Use the return air to connect the upper damper in the middle of the lane, install a section of iron air cylinder on the door wall, and set the Φ400 rubber air cylinder in the iron air cylinder to extend to the water pump, and use the full negative pressure to press the fresh air flow. After a week of field observation, it was found that this program has the following disadvantages.

1. The damper management is difficult, and this local system is unstable.

The damper is often opened. If the roadway is cleaned and the two dampers are opened at the same time, the gas concentration of the pumping point can reach 2% within 10min.

2. There is a lot of air leakage, and the gas below the upper return air inlet of the inclined lane is partially exceeded.

Due to the influence of mining, the top of the roadway is broken, the damper is deformed after long-term use, and the wind path is too short, and the damper leaks more air, resulting in loss of air volume. And because of the flexibility of the rubber air duct itself, the amount of fresh air introduced is not enough, and even above the water pump, the gas at the top of the roadway below the lower back of the mountain is connected to the back of the inclined lane (up to about 15%).

3. The contact inclined lane has a long service life, and the section of the roadway does not reach one-third of the design section (22M2). After the wind tunnel is hung in the lane, the personnel access is difficult.

The second option is to use 22KW fan for air supply:

Install a 22KW small fan on the fresh airflow side of the damper to increase the air supply. After adopting this set of schemes, there are also problems of more air leakage and difficulty in managing the damper. The gas in the upper part of the inclined lane still falls below the safe value, and remains at around 15%, and the power consumption after the fan is increased, and the long-term use is uneconomical.

Three options:

In the back of the 9906 returning wind, the lower mouth of the mountain is closed, and a Φ400 iron air duct is laid along the bottom of the road. 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 reach the return of the full negative pressure zone. The Shangshan lower mouth extends to the water pump in the blind alley, and uses the full negative pressure to supply the fresh air flow to the blind alley.

Advantages of the scheme: The fresh air flow in the lane can save the power consumption of one fan and fan.

Disadvantages of the scheme: After 8 hours of implementation, it was observed that the gas in the upper part of the inclined lane began to accumulate and gradually increased. After 24 hours, the accumulated gas concentration reached 5%, which caused the mine to attach great importance. After careful analysis, the main reason for the overrun is that the air volume of the iron air duct is small, the speed of the air flow is too low when flowing in the roadway, and the high concentration gas that is formed by the air leakage in the 9096 return air duct and the surrounding cracks cannot be completely completed. It is drawn into the iron air duct and dissipated into the inclined lane to stratify with the fresh air flow. The gas gradually flows to the upper part of the inclined lane to form a "gas cloud."

After identifying the reasons, the three programs were improved in a targeted manner.

Improvement plan for three programs:

On the basis of the three schemes, a closed (2m spacing) space is added outside the permanent sealing of the 9906 return airway. The two closed spaces are used to store the high-concentration gas leaking from the goaf, and the gas emission point is led from the water pump. Separated and isolated. After that, the Φ80mm hard rubber air duct is used to connect the storage space in the closed space with the open iron air duct mouth, and the high concentration gas (10%-15%) is taken out from the storage room by the pressure difference between the airtight and the iron air nozzle. After being diluted by the wind flow in the iron cylinder, it was discharged into the 9096 and returned to the wind.

After the improvement, long-term observation shows that the gas in the whole roadway is stable at 03-05%, and the total air volume is stable at 45m3/min-60m3/min.

Summarize the advantages of three improvements:

1. Save the power consumption of one fan and fan.

Calculated according to the fan power of 22KW, the electricity consumption can be saved 22KW×24h=52.8kwh every day.

Monthly savings in electricity bills:

52.8kwh × 30d × 0.46 yuan / kwh = 729 yuan.

2. Saving air volume: The wind measurement results show that the wind is supplied by a 22kw fan, and the total air volume is 110m3/min-130m3/min. Compared with the improvement scheme, the airflow is 70m3/min-80m3/min. .

3. The local ventilation system is stable and reliable.

The damper, fan and rubber air duct are removed, and the system is not affected by personnel traffic, fan power failure, and air door opening and closing. Gas has no overrun record.

4. Reduced management difficulty and maintenance investment.

5. Prevent the gas from escaping into the upper part of the inclined lane to form a “gas cloud”.

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