When coal mines are naturally ventilated, why does air enter the return shaft?
In the case of natural ventilation in coal mines, the phenomenon of air inlet from the return air shaft is usually caused by the air pressure difference. This phenomenon is due to the air flow caused by the difference in air pressure inside and outside the mine. The following are some reasons that may cause air to enter the return air shaft:
1. Temperature difference: The temperature underground in the mine may be lower than the ground, which will cause the air in the return air shaft to become cooler than the air outside. heavier, thus creating a downward airflow. This sinking of cold air may cause air to enter the return air shaft.
2. Air pressure difference: When the air pressure in the mine is lower than the air pressure on the ground, outside air will be "sucked" into the mine. This can be due to weather effects, such as low pressure weather systems, or due to differences in mine depth and altitude.
3. Influence of topography and architecture: Factors such as the surrounding terrain and the layout of buildings may change the direction of the air flow and produce a certain air pressure difference, causing air to enter the return air shaft.
4. The mine is not tightly sealed: If the mine is not sealed tightly enough, it will cause the air pressure and temperature around the return air shaft to be closer to the outside world, reducing the possibility of air intrusion. However, if there is air leakage in the mine, the air flow in the return air shaft will be affected, causing air to enter.
The interaction of these factors may lead to air intake in the return air shaft. In order to operate the mine safely, it is necessary to scientifically and reasonably monitor and manage the air flow in the mine to ensure the normal operation of the mine ventilation system to maintain the safety and stability of the mine working environment.