Mine dust damage and preventive measures

In the process of mine production, a large amount of fine dust containing free silica is generated, and the miners inhale these dusts to cause lung disease and get lung cancer.

The factors that cause silicosis in the mine are:

1 Dust weight concentration (mg/m3); 2 dust dispersion, less than 5μm for respirable dust; 3 free silica content; 4 dust mineral composition, that is, dust contains toxic mineral components or radioactive minerals; Dust accumulation time.

1. Dust production

In the mining process, due to the process of rock drilling, blasting, loading and unloading, etc., a large amount of fine dust is generated, and the dust of less than 5 μm is called respirable dust. In China, dust particles are generally divided into four ranges, namely, 2 μm or less, 2 to 5 μm, 5 to 105 μm, and 10 μm or more. The more small particles, the higher the dispersion, and the higher the dispersion of dust in the well. Under the conditions of wet operation, the dust below 5 μm accounts for 80-90% or more.

According to the mine measurement, in the case of wet rock drilling, the proportion of dust generated in the underground is: rock drilling accounts for 41.3%, blasting accounts for 45.6%, and mine (rock) accounts for 13.1%. Silica is the most common oxide of silicon and an important part of many ores or rocks. Silica in various ore rocks has a combined state and a free state, and the serious damage to the human body is free silica, that is, free silica. Content of free silicon metal underground mine dust is generally 39 to 70%, a few up to 90%.

2. Measures to prevent dust hazards

The measures to prevent the dust hazard are mainly to take comprehensive measures of dust prevention. China's comprehensive eight-character measures are: wind (ventilation), water (wet operation), dense (closed, isolated dust source), protection (personal protective equipment), management (organizational management measures), teaching (education and training), leather ( Technological innovation), inspection (inspection). Among them, "wind" and "water" are the most important.

The main technical measures for ventilation and dust prevention are:

1 district ventilation system - improved the qualified rate of mine effective air volume rate and dust concentration; 2 using the pulsed ventilation lane ventilation ventilation network, the piercing ventilation bridge comb ventilation network, the raft ventilation network, the middle section Ventilation network, vertical ventilation network, etc., avoiding the combination of sewage and wind in the middle section and mining sections of the underground, and improving the effective air volume rate of the mining face; 3 Wet rock drilling and upward rock drilling machine that insist on using the side water supply Measures such as magma protection cover, rock drilling machine feng shui linkage switch, humectant dust removal, blow blasting dust removal, rock drill degreaser, etc., effectively reduce the dust concentration during rock drilling and suppress the dust source; 4 comprehensive measures for ventilation and dust prevention include: Pressure, suction mixing ventilation, air duct anti-blasting, flying stone, baffle, blasting water curtain, local fan shunt protector, etc., to improve the effect of ventilation and dust removal in the driving face; 5 insist on cleaning the roadway and the sprinkler of the mine Wet and automatic water curtains of various roadways, 6 promote the patio roller drill, reform the patio tunneling process, use wet gravitation sampling; 7 insist on wearing personal protective equipment.

According to domestic and international experience, it is necessary to fundamentally prevent the dust hazard of mines, and should take measures from the following aspects:

(1) The most basic measure to suppress the suppression of respiratory dust by the dust source of respiratory dust is to prevent dust from escaping. Wet operation is a simple and economical dust removal measure, but the water capture rate of fine dust is very low. The addition of hygroscopic salts (such as calcium chloride) to water has a good wetting effect. Or use foam to remove dust, the high-foam dust removal effect studied in the United States is more significant. Water cannon mud (or paste mud) blasting is commonly used abroad to suppress dust and toxic gases generated during blasting. Before and after blasting and loading and unloading of ore (rock), spray watering measures are still widely used to suppress dust at the dust source with the highest dust density. The moisture content of the wet operation is 6%. Wide application of spray watering is an indispensable measure for downhole wet work. According to a statistically good spray device, it can reduce respiratory dust by about 30%. In a free wind, the use of a moving water particle to kill the suspended dust in the air is very rare. Since the fine dust of 1 to 10 μm is more like a gas, it is very difficult to capture. Increasing the water particle velocity and reducing the water particle size can increase the water capture efficiency of fine dust, but the smaller the water droplet, the faster the deceleration rate of the falling velocity in the air, and the jetting distance is limited.

(2) Using dust physicochemical properties to suppress dust sources

1 dust wettability and cohesion

The nucleation or coagulation mechanism of "cloud physics" can be used to set up an aerosol cloud chamber to suppress respiratory dust.

2 dust charged properties

Industrial dust will get electric charge when it is dispersed into the atmosphere. Respirable dust (below 3μm) is generally negatively charged, and large particles of dust are positive or neutral. These respirable dusts settle extremely slowly and are repelled because the ground is generally negatively charged, making the dust removal problem of respirable dust more complicated. The solution is to use a water droplet of opposite polarity to the dust for spray dust removal. For the sedimentation of dust particles in the wind current, the capture efficiency of water droplets is basically a function of the relative velocity between the water droplets and the dust particles and the relationship between the dust particles and the diameter of the water particles, and also as a function of the distance that the water droplets can reach in the wind current. Relationship, for dust particles between 1 and 5 μm, the corresponding particle size of the water droplets should be 50 to 300 μm. Using high-pressure water to speed up the spray can result in deterioration of the dust-proof effect. The form and arrangement of the nozzle should be carefully designed and selected. The design principle is to produce water droplets of 150-200 μm. In the blasting, the shock wave is used to start the water curtain spray, and the ore is wetted while the ore shovel is being shoveled. The use of spray sprinkling to suppress the dust flying in the ore unloading and transferring process is an important means to suppress the dust source.

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