What is mine dust? How is the dust produced? Sources of mineral dust at coal mines mainly in the following several ways: (1) The mining face is broken and the coal (rock) process is loaded, such as electric drill, wind hammer, blasting, mining machinery cutting coal (rock), manual loading and mechanical loading. (2) The processing of the goaf, such as the manual return column topping, the hydraulic support shifting and the top coal operation process of the top coal mining. (3) Transportation and transfer processes of coal (rock), such as self-slip transportation of coal (rock), conveyor transportation, transfer, unloading, coal caving and coal turning over the cage. (4) Spraying process, a large amount of cement and ore dust will be generated during the shotcreting operation. What are the effects of mine natural conditions on the production of mine dust? The main impacts of natural conditions on mine dust are as follows: (1) Geological structure. The geological structure is complex, the fault folds are developed, and the area damaged by geological movement is strong. The amount of dust generated during mining is large, and vice versa. (2) Conditions for the occurrence of coal seams. Under the same technical conditions, the mining of thin coal seams is greater than that of mining thick coal seams, because in the same dust-producing environment, thin coal seams have less space than thick coal seams, which increases the concentration of ore dust; mining slow-sloping coal seams than mining The amount of sharply inclined mine dust is small. (3) Physical properties of coal (rock). Under normal circumstances, the coal (rock) body joint development, loose structure, low water, coal (rock) hard and brittle, the mining dust production in the mining process is larger, and vice versa. What are the effects of mine production conditions on the production of mine dust? The main factors affecting the production of mining dust are the following: (1) The degree of mechanization of mining. As the degree of mechanization of mining increases, so does the amount of dust generated. If no dust-proof measures are taken, the dust collection capacity of the cannon is 300-500mg/m3, the dust production by the machine is 1000-3000 mg/m3, the dust production of the fully mechanized mining is 4000-8000 mg/m3, and the dust production by the cannon is 1300- 1600 mg/m3, the amount of dust generated by machine drilling is 2000-3000 mg/m3. (2) The degree of concentration of production. The increase in the degree of centralized production will accelerate the speed of the mining face, and at the same time, the air volume will increase, and the dust will be raised to generate more dust in the smaller space. (3) Coal mining method. If different coal mining methods are used, the amount of dust generated is different. For example, the steeply inclined coal seam adopts the inverted step coal mining method than the horizontal layer coal mining method, and the slow inclined coal seam adopts the top coal mining ratio. The production of coal dust by inclined layered mining is much larger; the roof of all slumping management is also larger than that of the roofing method. (4) Mining machinery. The cutting machine shape shape, traction speed, cutting speed, cutting depth, etc. also affect the dust production and particle size of coal (rock). What effect does the ventilation condition of the mining face have on the generation of coal dust? The effects of ventilation on the coal dust generated in the mining face are mainly as follows: (1) Ventilation method. For example, the downward ventilation method is smaller than the upstream ventilation method; the series ventilation method is larger than the partition ventilation method. (2) Wind speed. The relationship between wind speed and dust is relatively close. With proper wind speed, the concentration of dust in the wind is the smallest, and the dust is discharged into the mine. The wind speed is too small, affecting the dilution and elimination of the dust; if the wind speed is too large, the dust that has settled will be blown up to increase the dust in the air. According to the research data, the best dust-removing wind speed of coal mining face is 1.2-1.6m/s, and the optimal dust-discharge wind speed of boring working face is 0.25-0.5m/s. What are the hazards of mine dust? Dust has serious harm to human health and mine safety, mainly in the following aspects: (1) Harm to human health. Long-term inhalation of a large amount of mineral dust, light cause respiratory inflammation, and heavy lead to pneumoconiosis. At the same time, the skin is contaminated with mineral dust, clogged pores, can cause skin disease or inflammation, and mineral dust can also irritate the eye mask. (2) Coal dust explosion. Coal dust can explode under certain conditions, and coal dust explosion is one of the five major disasters in coal mines. For gas mines, coal dust may also participate in the explosion at the same time as the gas explosion, which will intensify the damage. (3) Contaminated working environment. The increase of mining dust will reduce the visibility of the working place and the roadway, which not only affects the labor efficiency, but also easily leads to error operation and misjudgment, which often causes casualties of the workers. (4) Harm to mechanical equipment. Mine dust can accelerate mechanical wear, shorten the service life, and increase the maintenance workload of personnel on equipment. How is the dust classified? There are many classification methods for mine dust. At present, China's coal mines mainly have the following classification methods for mine dust: (1) Classification by mineral composition 1 Coal dust: coal particles less than 1 mm in diameter. 2 Rock dust: rock particles less than 5μm in diameter. (2) According to the content of free sio2 in the dust. 1 Dust: The content of free sio2 in the dust is above 10%. 2 non-dusting: the content of free sio2 in mine dust is below 10% and below (3) Classification according to the state of presence of mineral dust 1 Floating dust: Mineral dust suspended in the mine air. 2 Dust: Dust deposited on the circumference of the well, on the support, equipment and materials. (4) Classified by hygiene perspective 1 Total dust: The sum of dust particles of various particle sizes suspended in the mine air, also known as full dust. It refers to the dust that can be inhaled through the nose and mouth during normal breathing. 2 non-respiratory dust: Although entering the body, due to the interception and retention of the nose, pharynx, tracheobronchial, and bronchioles, the dust in the alveolar region cannot be entered. 3 Respirable dust: A dust that can breathe into the alveolar region of the human body. It is the dust of pneumoconiosis. The aerodynamic diameter of the respirable dust is below 7.07 μm, and the aerodynamic diameter of 5 μm is 50%. (5) According to the explosive classification of mineral dust 1 Explosive dust: It is explosive, and it can explode under certain conditions. 2 Non-explosive dust: It is not explosive in itself, and there is no explosive dust under any conditions. What is the particle size of mineral dust? What is the relationship between particle size and human health? The particle size of the dust refers to the size of the dust particles, also known as the particle size. Since the shape of the dust is irregular, the particle size is generally expressed by the average diameter of the dust particles or the projected length thereof, and the unit is μm (micrometer). In general, the smaller the particle size of the dust, the greater the harm to human health, and the respiratory dust with a particle size of less than 5 μm can be inhaled into the bronchioles and alveolar regions to cause pneumoconiosis. What is the dispersion of mineral dust? What is the relationship between dispersion and mine safety and human health? The dispersion of mineral dust refers to the degree to which the substance is broken and is used to indicate the composition of the particle size of the dust. The so-called mineral dust dispersion refers to the amount of dust in a certain grade and the total order of magnitude of the dust. According to the percentage of the dust of different grades in the total amount of dust, the dispersion of the dust can be divided into high-dispersion mine dust and low-dispersion mine dust. The high-dispersion dust contains many fine dust particles, which accounts for a large proportion, while the low-dispersion dust contains a large amount of coarse dust particles and a large proportion. The higher the dispersion of mineral dust, the greater the harm to mine safety and human health, and the more difficult it is to capture. Therefore, in the development of dust prevention measures, the dispersion of mineral dust must be considered to achieve the best results. What is the concentration of mine dust? How is the concentration of mine dust expressed? The concentration of mineral dust refers to the number of particles of dust in the mine air per unit volume or the quality of floating dust. There are two ways to represent it: (1) Weighting method The weighting method refers to the mass of floating dust contained in the mine air per unit volume, and the unit is g/m3 or mg/m3. The weighting method indicates the mass concentration of the dust. (2) counting method The counting method refers to the number of particles of floating dust contained in the mine air per unit volume, and the unit is granule/cm3. The counting method indicates the amount of mineral dust. What is the suspension of mineral dust? What harm does suspension have on human health? The suspension of mineral dust refers to the nature that the dust is not easy to fall and can be suspended in the air for a long time. The time the dust particles are suspended in the air is related to its volume, density, shape, and operating environment temperature, humidity, and wind speed. According to the experimental data, the dust particles with a diameter of 5μm can be suspended in the air for about 3h. The smaller the diameter of the dust particles, the slower the sedimentation rate in the air. These dust particles play a major role in the occurrence of pneumoconiosis. What is the adsorption of mineral dust? What is the harm of adsorption to human health? The adsorption of mineral dust refers to the property that the mineral dust has an adsorption capacity to the surrounding medium (air), so that a surface of the fine particles forms a gas film. The adsorption of mineral dust is not conducive to the sedimentation of the dust. At the same time, the surface of the dust on the job site will also absorb harmful toxic gases and radioactive substances (such as strontium) contained in the air, which will increase the harm of the mine dust to human health. What is the wetness of mineral dust? What is the relationship between wettability and dust? Wettability refers to the affinity of mineral dust particles to water molecules. When the dust particles are combined with the water molecules, the volume of the dust particles is increased, the mass is increased, and the falling speed of the particles is increased or it is difficult to fly. The spray watering used in coal mines is to use the principle of wettability of mineral dust to set off the floating dust from the air and make the dust not float, so as to reduce the harm of the dust. What is the dust chargeability? What harm does the chargeability have on human health? Chargeability refers to the property that the dust particles rub against each other during the process of being crushed, and the surface gets or loses electrons to charge the dust. The dust suspended in the air can also directly absorb ions in the air to generate electric charges. The chargeability of the dust has a certain influence on the stability of the dust in the air. The same-sex charge repels, increasing the movement of dust particles in the air; the opposite-phase charge attracts the dust particles to agglomerate and collide during collision. Some foreign countries use spray droplets to carry out spray dust reduction, and have achieved remarkable results. However, the charged dust particles are easily trapped in the human body, and the charge of the dust particles affects the phagocytosis rate of the cells. The greater the charge of the dust, the greater the harm to human health.
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