Ⅱ Mine ventilation
In the underground, due to the mining operation and mineral oxidation and other reasons, the air composition will change, mainly manifested as oxygen reduction, the increase of toxic and harmful gases, mineral dust mixing, temperature, humidity, pressure change, etc. These changes cause harm and impact on the health and safety of workers. In order to ensure the health of workers and appropriate working conditions, and ensure safe and continuous production, it is necessary to send fresh air from the ground to the underground, and discharge the dirty air from the underground to the ground, which is the purpose of mine ventilation.
1 Mine ventilation system
In order to send enough fresh air to the underground mining face along a certain direction and route, and at the same time to discharge the dirty air from the mine in a certain direction and route, it is necessary to require the mine to have a reasonable ventilation system.
1)According to the unified or regional classification of the whole mine
A mine constitutes a integral ventilation system called uniform ventilation. A mine is divided into several relatively independent ventilation systems, and each system has its own air inlet, exhaust shaft and ventilation power. Although there is a connection between the shaft and roadway, the wind flow does not interfere with each other and is independent of each other, which is called partition ventilation.
Unified ventilation has the advantages of concentrated exhaust, less ventilation equipment and convenient centralized management. For the mines with small mining scope and few surface exits, especially the deep mines, it is reasonable to adopt the unified ventilation of the whole mine.
Zone ventilation has the advantages of short air road, small Yin force, less air leakage, low energy consumption, simple network, easy to control the air flow, beneficial to reduce the pollution air series and air volume distribution, and can receive better ventilation effect. Therefore, partition ventilation is widely used in some mines with shallow and scattered ore bodies or mines with shallow ore bodies and more Wells on the surface.
Zone ventilation can be divided according to ore body, mining area and stage level.
2) Classification according to the arrangement of the inlet air shaft and the exhaust air shaft
Each ventilation system should have at least a reliable air inlet well and a reliable exhaust well. Usually the cage lifting well is used as air shaft, some mines also use special air shaft. Because the exhaust air flow contains a large number of toxic gas and dust, the exhaust Wells are generally special.
According to the relative position of the inlet air shaft and the exhaust air well, it can be divided into three different arrangements: central, diagonal and central diagonal mixed forms.
① Central style
The air inlet well and the exhaust well are located in the center of the ore body, and the flow route of the wind flow in the underground is reversed, as shown in Figure 3-7.
central ventilation system
The central layout has the advantages of less infrastructure cost, fast production, centralized ground building, easy management, convenient shaft depth work, easy to achieve anti-wind. The central layout is mostly used for mining laminated ore bodies.
② The diagonal
Into the air shaft in the ore body wing, exhaust shaft in the other wing of the ore body, called single wing diagonal, as shown in figure 3-8 into the air shaft in the middle of the ore body, the return air shaft in the two wings, called two wings diagonal, as shown in figure 3-9 when the ore body is very long, into the air shaft and exhaust shaft along the interval layout or ore body thickness, into the air shaft, exhaust shaft around the ore body layout, called interval diagonal type. In the diagonal ventilation, the flow route of the air flow in the mine is direct.
Single-wing diagonal ventilation shaft
Diagonal arrangement has the advantages of short air line, less air pressure loss, less air leakage, stable air pressure during mine production, uniform air volume distribution, and far distance from the surface from the industrial site. Diagonal layout mode is generally used in metal mines.
③ Central diagonal mixing type
When the ore body is long and the mining range is wide, the central development, can be arranged in the middle of the ore body, to solve the ventilation of the central ore body mining in the exhaust shaft in the two wings of the mine, solve the ventilation of the remote ore body mining, the whole ore body has both central and diagonal, forming the central diagonal mixed.
Although the arrangement forms of air inlet well and exhaust well can be summarized as the above types, due to the complex occurrence conditions of ore body and different exploitation and mining methods, in the design and production practice, the arrangement should be made according to the specific conditions of each mine, without the limitations of the above types.
3) Classification according to the working mode of the fan
The working modes of the fan include pressure type, extraction type and mixed type.
① Pressure
Pressure-in ventilation is to make the whole ventilation system to form the state of positive pressure above the local atmospheric pressure under the action of the main pressure fan. Due to the concentration of air flow, the high pressure gradient in the air inlet section can make the fresh air flow quickly sent into the underground along the designated ventilation route, to avoid pollution by other operations, and the air quality is good.
The disadvantage of pressure inlet ventilation is that the air flow control facilities such as air doors need to be located in the air inlet section. Due to frequent transportation and pedestrians, it is not easy to manage and control, and the bottom of the well has large air leakage. The low pressure gradient is formed in the main ventilator in the exhaust section, and the dirty air cannot be quickly discharged from the air well according to the designated route, making the underground air flow disordered. Add the interference of natural wind, even wind reverse, pollution of new wind phenomenon.
②Out type
Extractive ventilation is to make the whole ventilation system under the action of the main fan to form a negative pressure lower than the local atmospheric pressure. Due to the concentration of exhaust air and large exhaust volume, the exhaust ventilation causes high pressure gradient on the exhaust air side, which makes the dirty air of each working surface quickly concentrated to the exhaust 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 big advantage of suction-out ventilation. In addition, the air conditioning and control facilities are installed in the exhaust duct, do not hinder pedestrian transportation, convenient management, reliable control.
The disadvantage of suction ventilation is that when the exhaust system is not tight, it is easy to cause short circuit air absorption phenomenon. Especially when the collapse method is used to mine, the surface subsidence area and the goaf are connected, this phenomenon is more serious. In addition, the wind pressure of the working surface and the whole air inlet system is low, and the air inlet air road is affected by the natural wind pressure, which is easy to reverse, resulting in underground air flow disorder. The extraction ventilation system makes the main lifting well in the air inlet position, and the northern mines should consider the lifting well in winter.
Most of the metal and other non-coal mines in China adopt drawn-out ventilation.
3) Pressure and pumping mixture
Pressure-pumping mixed ventilation is controlled by the main fan in the inlet side and the exhaust side, so that the inlet section and exhaust section under the action of higher wind pressure and pressure gradient, wind flow according to the designated route, smoke exhaust is fast, air leakage is reduced, not easy to be disturbed by natural wind and cause wind reverse. The advantage of both pressure ventilation mode and suction ventilation mode is an important way to improve the effect of mine ventilation.
The disadvantage of pressure and pumping mixed ventilation is that there are more ventilation equipment required, and the air flow in the wind section cannot be controlled. Air leakage in the bottom of the inlet of the well and the collapse area of the exhaust side still exists, but it is much smaller.
When choosing the ventilation mode, whether the surface has a collapse area or other difficult to isolate channels is a very important factor. For the mines containing radioactive elements or mineral rocks with spontaneous combustion risk, pressure pumping type or pressure pumping mixed type should be adopted, and multi-stage machine station controllable type should be adopted. For the mine that has no surface subsidence area or no subsidence area but can keep the exhaust duct tight by filling and sealing, the extraction type or the extraction type mainly by the extraction type should be adopted. For the mines with a large number of surface subsidence areas, and the mines that are not easily isolated between the exhaust duct and the goaf, or the mines opened from the open air to the underground mining, the main pressure and pumping mixed type or multi-stage machine station controllable type should be adopted.
The installation site of the main ventilator is generally on the ground and can also be installed underground. The advantage of the installation on the ground is that the installation, overhaul, maintenance and management are more convenient and not easy to be damaged by underground disasters. The disadvantage are that the wellhead closure, reverse device and wind tunnel have high construction cost and short-circuit air leakage; when the mine is deep and the working face is far from the main ventilator, the installation and construction costs are high. The advantage of the main ventilator installed in the underground is that the main ventilator device leaks less, the fan is close to the wind section, less air leakage along the way can use more air or exhaust at the same time, which can reduce the ventilation resistance and seal less. Its disadvantage is that the installation, inspection, management is inconvenient, easy to be damaged by underground disasters.
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