There are many various hazard factors in coal mines, such as gas, carbon dioxide and other harmful gases and coal dust, rock dust and other dust hazards, which cause great difficulties in the prevention and treatment of occupational hazards. In recent years, the prevention and control of harmful gases, especially gas, has been mentioned to a high degree, which has attracted great attention and wide attention. The high monitoring means, the accuracy of monitoring, and the advanced instrument have all reached the level that can completely prevent accidents. It also has the 12-character guideline of “fixing production by wind, monitoring and monitoring, and picking up after miningâ€. However, the prevention and control of dust such as coal dust and rock dust is not enough. In fact, dust (mainly coal dust) is no less harmful than gas. Coal dust can not only cause explosion accidents, but also cause people to produce pneumoconiosis. Diseases can also cause equipment to be damaged, affecting people's sights and increasing accidents. Under the situation that the degree of deuteration of the coal mining machine is gradually improved, it is extremely urgent to do a good job in dust control and management.
At present, for the production mines of our new mining group, the large-scale promotion of coal mining is carried out. Taking 2004 as an example, the proportion of fully mechanized mining production reached 46.6%, and the comprehensive mining output reached 5.788 million tons. The entire group's fully mechanized mining face reached 15, with the ability to equip 18 fully mechanized mining faces, and still rising. Potential, the monthly average yield of fully mechanized mining face has also reached 63,500 tons, which is 105.5% higher than the high-end general mining 30,900 tons. The dust production in each process of fully mechanized mining face is the highest when the coal mining machine falls coal, and its dust concentration can reach more than 100 milligrams per cubic meter, which is more than ten times higher than the standard. The higher-grade general mining is several times higher. Taking eleven-layer coal as an example, the dust production of high-grade general mining coal is generally around 30mg/m3, while the comprehensive mining is more than 70mg/m3. It is higher in other coal seams with harder coal quality, and some are about 15 times higher than the standard. Therefore, effective measures must be taken when controlling coal seams to control the generation of dust.
The control of dust in various production sites in coal mines should take measures mainly from two aspects:
First, grab the source. Coal seam water injection, gun spray, coal loading (rock) watering, wet drilling, etc. Among them, coal seam water injection before mining and excavation face is the main and most effective method.
According to different water injection working places, there are two types: coal mining face and water injecting face.
According to the different water injection methods, there are two types: long hole water injection and short hole water injection. The so-called long hole water injection means that a drilling hole is arranged along the working face at a certain distance [generally 15-20 meters], and the drilling is inclined along the coal seam. The direction of the drilling is consistent with the coal seam tendency, and the depth should be the working surface. The length of the hole is 1/2---2/3, and the height of the hole is generally 2/3 of the coal thickness from the bottom of the coal seam. Generally suitable for mining work surface. The so-called short hole water injection is on the working surface, along the working surface tends to be arranged at a certain distance [generally 3--5 meters], the depth of the drilling is 3--5 meters, and the position of the drilling hole is 2 /3 mining height. Generally suitable for tunneling work surface.
The place where the largest amount of dust is produced in coal mines is the coal mining face. In the process of coal falling, blasting, support, transportation, etc., falling coal is the largest process of dust production. The purpose of water injection is to increase the water content in the cracks and voids in the coal body as much as possible, and absorb the original coal dust, so that when the coal mining machine falls coal, since the coal body has been wetted, the coal machine is broken when the coal is crushed. No or little dust is produced.
In today's high degree of mechanization, the coal mining speed has increased greatly, and the cycle progress per shift has increased. Short-drilling water injection is no longer suitable for the current coal mining operations. It is necessary to use advanced mining face and long borehole water injection. In order to facilitate drilling, without affecting the construction and reducing the phenomenon of collapse, the hole can be punched before the working face is put into production, or the hole can be punched outside the pre-stress zone during the advancement of the working face, and the water injection is advanced to ensure the water injection effect.
Problems to be paid attention to injecting water into coal seams:
1. The difficulty of coal seam water injection, measured by coal seam permeability coefficient, coal void ratio, pressure state, firmness coefficient, etc., can be divided into easy to inject coal seam; easier to inject coal seam; difficult to inject coal seam.
2. The actual depth of the borehole is limited due to changes in the storage structure of the coal seam, the tendency to stability, the mechanical properties of the borehole, and the level of construction technology.
3. Pressure change of water injection, water injection time, actual water injection amount, etc.
4. The quality of the sealing hole.
According to the experience of coal seam water injection at home and abroad, if the coal seam water injection effect is good, the dust reduction effect is the most significant, and the dustfall rate is 75-85%. Therefore, Article 154 [2] of the “Safety Regulations for Coal Mines†clearly states: “The coal mining face should be Take coal seam water injection and dust prevention measures -".
In daily production, in order to achieve the purpose of dust reduction, we must do a good job in coal seam water injection work, so that the coal mining face must be injected, first note and then harvest. Mainly for dust prevention, and later management is paid.
Currently, explore coal seam water injection should remain with the research stage, although the experiment began in the early fifties, but for various reasons, such as: limit geological conditions, technical level, capital investment and production urgency and other factors. There is no strict implementation and assessment, sometimes flow and form, even the assessment is up to the point, because the length of the borehole is difficult to measure, the amount of water injection is difficult to count, and sometimes the rush to produce and cope often occurs. So far, there is no mature experience and typical promotion.
Other reasons for the difficulty in seeing water injection in coal seams remain to be solved, such as: borehole collapse, water injection pressure, water injection time and water injection volume, and deep hole drill cuttings. At present, it should be relatively mature in theory. Further experience is needed to achieve results.
Second, the dust that has been generated is captured and dust reduction measures are taken. If the source preventive measures are not done well, or because the coal seam geology itself does not achieve the expected results, effective measures must be taken to carry out the dust. The measures of “enclosure, blockage and interception†should be taken mainly.
1. The main measures taken are to collect the dust generated in the coal or other production process and carry out centralized elimination. This method is suitable for processes or locations where the amount of dust is large. The negative pressure dust collector of the coal mining machine (a dust collector on the return air side of the coal machine drum, centralized dust removal), and a water jet fan for driving the working face.
2, blocking, is the method of dusting when the dust is about to be produced or just produced. For example, the main dust-producing process of the mining face is the coal falling of the coal mining machine. When the coal machine cuts the coal, the internal spraying is effectively used, and the internal spraying is used reasonably. Spray to prevent the spread of dust.
3. Cut off, in each ventilation tunnel, set up a purification water curtain that can cover the section of the roadway, and capture the dust flying in the wind flow. The requirements of the water curtain are more strict than the first two types of dust reduction devices, because the flying dust particle size Small, difficult to capture, its requirements: (1). The pressure of water must be high, (2). The sprayed mist is moderate, the fog is too large, and it stays in the air for a short time, landing quickly. It is difficult to dust, and when it is too small, it will evaporate quickly. (3). The fog particles should have a higher speed. According to the shape of the water curtain according to the section of the ventilation tunnel, only the high-speed collision between the dust and the fog particles has a high effect, because the dust is oily. (4). The direction of the spray is as close as possible to the direction of the dust.
In short, the spray to achieve a good dust-reducing effect generally requires a water pressure of 7.5---12.5 MPa, and the diameter of the fog particles is 100 microns.
In summary, through the use of equipment, the use of new technology, the mine dust concentration is minimized, eliminating the hidden dangers caused by dust. At the same time, with the in-depth development of coal mine safety and quality standardization, the degree of civilized production has increased year by year. The concept of people-oriented and creating a harmonious society has been formed. Cherish life, care for health, safety first, and production second thought have been deeply rooted in the hearts of the people. Abandoning the dirty, chaotic, and poor environment, improving the environment with their own hands, and establishing a brilliant image of the miners in the new era.
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