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Uranium mining ventilation
First, ventilation and drainage
Press-in ventilation, the downhole air is in a positive pressure state, and the seepage direction is directed to the outside of the well, which is beneficial to control the precipitation of the concrete. The wind quality is good, but the air leakage rate is large (some 70%), the working surface is insufficient for air supply, and it is difficult to manage. . The Canadian test proves that the indented type of sputum is 20% lower than the pumping type, while the domestic 711 uranium ore is dense, with low permeability, and no goaf passes through the surface. The test proves that only 10% is reduced, and the effect is not significant. . Therefore, press-in ventilation is generally suitable for mining crack development. There are many mined areas, which are easy to cause pollution.
Withdrawn ventilation, the downhole air is in a negative pressure state, and the direction of seepage is directed to the downhole, which promotes the increase of the amount of radon, but the air leakage is small and the management is simple. Therefore, the extraction ventilation is generally suitable for the density of the ore rock, the permeability is small, and a good return air level can be established, and the mine in the goaf does not pollute the fresh air flow.
The pumping-pressure hybrid ventilation has the advantages of the above two ventilation modes, so it is generally applicable to mines with long ventilation lines, large resistance and large natural wind pressure interference.
Second, the ventilation system and drainage
In order to control the internal penetration of the concrete, a perfect ventilation system has been established, and it is extremely important to adjust the pressure distribution reasonably. A complete exhaust ventilation system should meet the following requirements:
(1) The wind quality is good. The enthalpy concentration of the air inlet should not exceed the following indicators.
Air inlet, total air inlet, working face, air inlet, last air inlet
氡 concentration (kBq/m 3 ) 0.12 1.2 1.8～2.5
(2) The ventilation volume is small. This can reduce the amount of sputum precipitation, shorten the ventilation time, and reduce the alpha potential balance ratio K of sputum and scorpion. The measured ventilation time and K value are listed in Table 1.
Table 1 measured ventilation time and K value (1980-1984)
Mine
Ventilation time
(min)
Working surface concentration
C(kBq/m 3 )
Axillary body alpha potential
E α (μJ/m 3 )
Axillary body alpha potential balance ratio
K
711-1
712-2
743-301
719
716-2
twenty two
20.36
6.8
13
11.9
2.92
3.26
3.18
2.04
3.81
2.56
1.57
0.56
1.63
5.57
0.159
0.087
0.032
0.14
0.264 (after system adjustment)
Where E α is the α-potential of scorpion, μJ/m 3 ;
C - æ°¡ concentration, kBq / m 3 .
(3) The pressure distribution is beneficial to control the seepage of the sputum and prevent the ingress of wind pollution, and is not interfered by natural pressure. Positive pressure should be maintained in the fracture development zone or near the goaf, so that the seepage is directed to the goaf. In the case of natural wind pressure disturbance, the seepage direction of the ore body should be kept as constant as possible. Therefore, the selection of the zero pressure point and the negative pressure zone in the combined pressure ventilation, the adjustment of the pressure difference in the single press-in or extraction ventilation is extremely important for controlling the seepage and drainage of the helium.
(4) The ventilation efficiency is high and the air leakage is small. Under the condition of multi-channel air intake, the air volume distribution should be reasonable, the angle connection should be reduced as much as possible, and the ventilation and dead angle of the single head should be reduced.
(5) The amount of decantation and the rate of deuterium precipitation are the smallest. The 711 mine ventilation system is shown in Figure 1.
Figure 1 711-1 ventilation system
Third, the adjustment and management of the ventilation system
A perfect ventilation system cannot be static. With the progress of mining work, or changes in other conditions, ventilation network structure, pressure distribution, air volume distribution, radon precipitation and precipitation rate are constantly changing, it must be adjusted in time to eliminate circulating wind, control radon pollution, prevent leakage, and ensure A reasonable distribution of pressure and air volume. The principle of adjustment is safe, effective, economic and reasonable. The basic content of the adjustment: adjust the network structure, make the main fan running characteristics match the mine wind resistance characteristics, the new sewage flow does not interfere with each other; adjust the pressure distribution in the network, improve the airflow stability, control the precipitation and pollution of the sputum; adjust the air volume distribution The working surface enthalpy and its daughter concentration and harmful substance content can be quickly lowered to the national allowable level. Adjust and manage ventilation facilities. The sealing of the goaf should keep the isolation zone with a certain negative pressure relative to the working area, avoiding the seepage of the goaf through the partition wall and the rock seepage into the working area, and the pluton of the goaf can also be pumped separately.
If the mine field is large and the ventilation effect is poor, it is effective to use district ventilation and necessary sealing. Such as the 721-2 mine, the trend of 1500m long, steeply inclined, vein type ore body, multi-middle operation, after the use of partition ventilation (Figure 2), achieved good results, as shown in Table 2.
Figure 2 721-2 partition ventilation system
1- gob area; 2 - production stope; 3- new fan; 4-original main fan
Table 2 Comparison of ventilation effects of 721-2 districts
Ventilation method
index
dust
(mg/m 3 )
radon
(kBq/m 3 )
Scorpion
(μJ/m 3 )
Effective air volume (%)
Actual power (kW)
Annual electricity saving
(10,000 degrees)
Unified press
average
Pass rate
(%)
3.26
55
12.32
25
27.07
31
20
20
96
96
0
0
Partition press
average
Pass rate
(%)
0.81
98
2.06
86.7
4.10
85.8
67
67
76.9
76.9
37.4
37.4
IV. Monitoring of radon and its daughter concentration
The purpose of the monitoring is to check whether the concentration of strontium and its daughters in the workplace meets the national allowable standards (氡3.7kBq/m 3 , 氡μ 6.4μJ/m 3 ), which provides the basis for the adjustment of the ventilation system; the measurement results are also used to estimate the workers' Radiation dose. Monitoring is carried out by specialized personnel. The measuring points are arranged on the wind path, and the position of the measuring points and the monitoring range are determined according to changes in the working place and the ventilation system. Everyone who has a homework should be monitored regularly. The monitoring period of the stope and excavation face should be shorter, usually once a week, and the other 10 to 15 days. The concentration of cockroaches and daughters is high, the location of the change is large, three times a week, or once a day, and emergency measures, single heads, diverticulum, etc. are taken for data processing. Samples should be representative.