Mine ventilation

The disadvantage of pressurized ventilation is that air flow control facilities such as air doors need to be located in the air intake section. Due to frequent transportation and pedestrians, it is not easy to manage and control, and the wind leakage at the bottom of the well is large. In the exhaust section, the main fan forms a low pressure gradient, which can not quickly discharge the dirty air from the air shaft according to the specified route, so that the underground air flow is disordered. Coupled with the interference of natural air flow, the phenomenon of air flow reversal and pollution of fresh wind will even occur.

2) Withdrawable type

Extraction ventilation is to make the whole ventilation system under the action of the main extraction fan, forming a negative pressure state below the local atmospheric pressure. Because the exhaust air is concentrated and the exhaust air volume is large, the extraction ventilation causes a high pressure gradient on the exhaust air side, so that the dirty air of each operation surface is rapidly concentrated in the exhaust air duct, and the smoke of the exhaust system is not easy to spread to other roadways, and the smoke exhaust speed is fast. This is a major advantage of extraction ventilation. In addition, the adjustment and control facilities of air flow are installed in the exhaust duct, which does not hinder pedestrian transportation, convenient management and reliable control.

The disadvantage of extraction ventilation is that when the exhaust system is not tight, it is easy to cause short circuit suction phenomenon. This phenomenon is more serious when the caving method is used and the surface subsidence area is connected with the goaf. In addition, the operating surface and the whole air inlet system have low wind pressure, and the air inlet path is affected by natural wind pressure, which is easy to reverse air flow, resulting in the disturbance of underground air flow. The extraction ventilation system makes the main lifting shaft in the position of air intake, and the northern mines should consider the anti-freezing of the lifting shaft in winter.

Most metal and other non-coal mines in our country use extraction ventilation. 3) Pressure pumping mixed type

Pressure pumping mixed ventilation is controlled by the main fan on both the intake side and exhaust side, so that the air flow in the intake section and exhaust section can flow according to the specified route under the action of higher wind pressure and pressure gradient, smoke exhaust is fast, air leakage is reduced, and it is not easy to be disturbed by natural air flow and wind flow reverse. This kind of ventilation is an important way to improve the effect of mine ventilation because of the advantages of both manual ventilation and extraction ventilation.

The disadvantage of pressure pumping mixed ventilation is that more ventilation equipment is required, and the air flow in the required air section cannot be controlled. The air leakage in the shaft bottom yard on the inlet side and the subsidence area on the exhaust side still exist, but to a much smaller extent.

When choosing a ventilation method, the presence of subsidence areas or other difficult to isolate passages on the surface is a very important factor. For mining mines containing radioactive elements or where there is a risk of spontaneous combustion of ore and rock, the press-in type or press-in type based pressure pumping mixed type should be used, and the multi-stage machine station controllable type should also be used. For the mine without surface subsidence area or the mine with subsidence area but can keep the exhaust duct with good tightness through filling and sealing, the extraction type or the pressure pumping mixed type based on extraction type should be used. For mines that have a large number of surface subsidence areas and are not easily isolated between the exhaust duct and the goaf, or the mines that are transferred from the open pit to underground mining, the pressure pumping mixed type or the multi-stage machine station controllable type should be used.

The installation site of the main fan is generally on the ground, but also can be installed in the underground. The advantage of installation on the ground is that installation, overhaul, maintenance and management are more convenient and not easily damaged by underground disasters. The disadvantages are the sealing of the wellhead, the high capital construction cost of the anti-wind device and the wind tunnel, and the short circuit leakage; When the mine is deep and the working face is far away from the main fan, the air leakage along the way is large. In the case of complex terrain conditions, the installation and construction costs are high. The main ventilator installed in the underground has the advantage of less air leakage from the main ventilator device. The fan is closer to the required air section, and less air leakage along the way can simultaneously utilize more inlet air or exhaust air from the shaft and lane, which can reduce the ventilation resistance. Its disadvantages are inconvenient installation, inspection and management, and easy to be damaged by underground disasters.