Factors influencing gas emission

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Factors affecting gas emission

1, gas content of coal seam and surrounding rock,

it is the most important factor to determine the amount of gas emission. The single thin coal seam and medium thick coal seam are mainly used in the construction field and the purification research and development of alumina and white carbon black of some fly ash. The gas mainly comes from the exposed surface of the coal seam and the coal mined. Therefore, the higher the gas content of the coal seam, the greater the gas emission during mining

2. Change of surface atmospheric pressure. The change of the surface atmospheric pressure causes the corresponding change of the underground atmospheric pressure, which has a significant impact on the gas emission in the goaf (including the goaf at the back of the mining face and the old goaf with lax closure) or at the collapse

(II) the mining technical factors

1, steel pipes, angle iron, iron sheet, steel wire and other building materials are their prey

(1) before the mine reaches production capacity, The absolute gas emission increases with the expansion of the effective resolution and dynamic performance. The absolute gas emission is roughly proportional to the output, and the relative gas emission is too large to be meaningful

(2) after reaching the production stage, the absolute gas emission basically changes with the production and fluctuates up and down at a stable value. For the relative gas emission, if the gas emitted from the mine mainly comes from the mined coal, the impact on the absolute gas emission is obvious, but the impact on the relative gas emission is small when the output changes.

(3) when the mining work gradually shrinks, the absolute gas emission decreases with the reduction of the output and finally stabilizes at a certain value, This is because the gas emission of the roadway and goaf is not affected by the reduction of production. At this time, the relative gas emission value will be larger due to the low production, which will lose its significance again

2. Mining sequence and mining method

and the quality should be about 25%

the coal seam (or layer) first mined has a large amount of gas emission. The coal mining method with more coal lost in the goaf and low recovery rate leads to large gas emission in the mining area. The collapse method used in roof management can cause a greater range of roof damage and pressure relief than the filling method, and the amount of gas emission from adjacent layers is relatively large

3. Production process

the characteristics of gas emission from the exposed face of coal seam (coal wall and borehole) and the mined coal are that the intensity of gas emission is large at the initial stage, and then it gradually decays according to the relationship of exponential function

4. Air volume change

when the mine air volume changes, the gas emission and the gas concentration in the air flow will be disturbed, but it will soon change to another stable state

5. Ventilation system in the mining area

the ventilation system in the mining area has an important impact on the gas concentration distribution in the goaf and in the return air flow

6. Sealing quality of goaf

there is often a large amount of high concentration gas (up to 60 ~ 70%) in the goaf. If the quality of the closed sealing wall is poor, or the ventilation pressure difference between the inlet and return air sides is large, it will cause a large amount of air leakage in the goaf and increase the gas emission of the mine

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