1 Overview

In the production of coal mines, mining, excavation, each transport step will generate a lot of dust. There are two main aspects of dust hazard: First, the harm to the human body. If a person's lungs inhale a large amount of mineral dust for a long time, they may suffer from pneumoconiosis. Pneumoconiosis is a serious occupational disease of miners. The second is the danger of coal dust explosion. Coal seam explosion is one of the serious disasters in coal mines, which seriously threatens the safety of mines. In recent years, gas and coal dust explosion accidents have occurred from time to time, seriously affecting mine safety production and employee life. Therefore, it is extremely urgent to do a good job in comprehensive control of mine dust. The dust in the coal mine production process mainly comes from the mining face, especially the rapid development of mining machinery, which greatly improves the mechanization of coal mines and increases the mining capacity, which promotes the multiplication of coal production. However, under such production conditions, the dust production intensity of coal mines also increases, and the dust concentration of the mining face increases greatly. According to statistics, under the same conditions of geological conditions and ventilation, the dust concentration of different mining methods A big difference. For example, in the absence of dust-proof measures, the dust concentration during blasting is 300-500 mg/m3, while the dust concentration during machine mining is 1000-3000 mg/m3, and the comprehensive mining is 4000-8000 mg/m3. Therefore, it is necessary to study and apply dust prevention technology in modern mines.

2 Dust-proof technology for fully mechanized mining face

Xuchang Coal Mine is a modern large-scale mine that was put into operation in 1998. The designed production capacity is 1.5 million t/a. In 2002, the actual output reached 3.2 million tons, and in 2003 it will exceed 3.4 million tons. The main feature of the mine is that there are few people (now less than 1,000 people) and the degree of mechanization is high. The coal mining face adopts the German imported SL-300 continuous miner and the domestic support shield bracket. The dust reduction measures normally used in the working face include: internal and external spraying of the shearer, spraying between the front frame, spraying the coal mouth after the surface, and spraying the spray at each transfer point. After actual measurement on site, after the above dust-proof measures were taken, the dust concentration still reached 116-337 mg/m3, which exceeded the national health standards. Therefore, we have studied and applied the following new dust prevention technologies.

2.1 Coal mining face unit walking automatic light control spray device

Each group of sprays in the random automatic spray device of the fully mechanized mining face consists of a main machine, an infrared sensor, a solenoid valve, a set of nozzles, and cables. The nozzle is controlled by a solenoid valve, and the main engine controls the solenoid valve; the power source is 127V AC (using the working surface lighting power source). Each group of sprayed mainframes is cabled for spray interlocking. Installation method and use process: starting from the air inlet of the working face, every 5 sets of nozzles are arranged (the nozzle is fixed on the front probe beam), and when the shearer passes the position of the automatic spray point, the light source on the shearer The light signal emitted by the device is accepted by the sensor (the sensor is mounted on the front beam of the bracket), then all the sprays in the return air flow are automatically opened (including this point) (if the light source is weak or the light source is far away from the sensor) Then open the spray group is relatively small, perform automatic spray, and delay for a period of time, the delay time can be adjusted according to the walking speed of the unit and the number of open spray groups (see Figure 1 for detailed arrangement). The development and use of the automatic spray device reduces the manual opening of the one-way valve during the shifting to realize the spray dust removal between the racks. The original manual operation is frequently started and stopped frequently, and the workers are afraid of trouble. Sometimes the spray between the racks does not open, causing the coal dust to fly. Affect the dustproof effect.

1--photo-controlled automatic spray between brackets; 2-handle spray between brackets; 3-light sensor; 4-light source;

5-Shearer internal source spray; 6-Shearer external spray.

Fig.1 Schematic diagram of light control automatic spray for coal mining machine

2.2 Shearer negative pressure secondary dust-proof device

The secondary dust reduction of the shearer negative pressure is a negative pressure secondary dust reduction technology developed recently under the guidance of colleges and universities. It uses a squirting device to spray a mist flow to the dust source area to reduce dust, and at the same time, a negative pressure zone is formed behind the jet inside the squirting device, and the dust-containing air in the pressure-reduction field at the tail of the squirting device is sucked and sucked. The device is then ejected and the coal dust is captured during this process. The dust reduction effect of the dust reduction method is related to factors such as the mist flow parameter, the negative pressure intensity, the intake air amount, the suction port negative pressure field range, the working area wind speed and the direction; for the squirting device, the structure of the device, Size, mounting position, orientation, nozzle form, spout size, spray pressure and flow rate are all related factors. The negative pressure secondary dust reduction technology should be combined with the site conditions to design the technology to achieve the best dust reduction effect.

2.3 Transfer machine synchronous automatic spray

The return air duct of the original coal mining face is installed with a set of return air flow purification water curtains 5 to 10m away from the transfer machine. The manual manual control is adopted by the valve. However, due to human factors, the water curtain often forgets to start when the reloading operation is run, resulting in dust. To effective control; sometimes the belt conveyor and the transfer machine are out of service, but the water curtain is sprayed normally, which not only fails to reduce the dust, but also causes waste of water resources and affects the quality of coal.

In view of the above problems, we organized engineering and technical personnel to carry out the research. Through repeated experiments, the device was used to open and stop the sensor card on the reloading motor power supply cable. As long as the transfer machine rotates, current flows, and the start-stop sensor will have signal output, using light control. Or voice-activated automatic spray host, the signal obtained by the start-stop sensor is processed to control the solenoid valve to realize automatic opening and closing of the water curtain. When the transfer machine starts to generate dust, the water curtain will automatically open to spray and reduce dust. When the transfer machine stops running, no dust will be generated and the water curtain will automatically close. The research and application of this technology not only saves a lot of water resources, but also has obvious effect of dust reduction.

3 Dust-proof technology for driving face

In several major production systems such as mining, excavation and transportation in coal mines, except for mining, roadway excavation is the main dust source of the mine. According to the way of excavation, it can be divided into two types: excavation and gun excavation. With the improvement of the level of coal mine organization, most of the current mine excavation uses roadway with high speed and low labor intensity. Xuchang Coal Mine is a modernized mine. Now all the tunnels are excavated by comprehensive excavation machine. There are 5 comprehensive excavation machines, including 2 imported MRH-S200 excavators in Japan. 3 excavators. Due to the powerful cutting of coal by the high-power comprehensive excavator, the amount of dust generated is particularly large. According to the actual measurement, the dust concentration of the excavation face is 2000-3000 mg/m3, and the individual is up to 6000 mg/m3. It is easy to see that the dust is the mine's comprehensive dust-proof. A very important and important part.

3.1 Comprehensive excavation machine spray and roadway airflow purification water curtain linkage automatic spray dust reduction technology

Spray watering and dust reduction is one of the main dust prevention measures taken by the mining face. There are two ways to spray water when the roadheader is working, namely internal spray and external spray. At present, the internal sprays of various types of roadheaders used in coal mines in China are not well utilized. The main reason is that the floating cylinders of the cutting section are not closed, so it is easy to make the dust water flow into the motor, causing the motor to be short-circuited. The spray sprinkling water mainly relies on the external spray of the comprehensive excavator. The opening and closing of the external spray is controlled by the operator of the comprehensive excavator, and the purifying wind water curtain in the heading is also equipped with a valve type manual opening and closing. Therefore, the water curtain often fails to be used normally, resulting in excessive dust. In view of the above problems, we have developed a self-propelled automatic spray dust-reducing device for rotary drum cutting and roadway airflow purification of the comprehensive excavator drum. The principle of the device is to use the cutting unit of the roadheader to control the operating power supply (110V), and draw a control line from it to enter the three links. The junction box separates two paths from the junction box, and controls the electromagnetic valve of the external spray device of the boring machine drum, and controls the air flow water curtain within 30m of the working surface; when the tunneling, as long as the drum rotates, the outer spray device and the air flow purification water curtain It will automatically turn on for automatic spray. When the drum stops running, the two sets of dust-reducing devices will automatically stop the spray. That is: when there is dust generated in the heading face, the two groups of dust-reducing devices will automatically open to achieve spray dust reduction. When there is no dust generated in the heading face, the two groups of sprays will automatically close. After the on-site trial, a good dust reduction effect was obtained.

3.2 Fengshui high pressure remote shooting automatic spray technology

In the blasting face, although the duration of the firing process is short, the concentration of dust generated is higher than other processes. The semi-coal rock and the whole rock roadway of Xuchang Coal Mine are all used for gun excavation. In view of the high concentration of working dust during shooting, we designed a muzzle spray device. The working principle is a combination of voice-controlled Feng Shui linkage, which is formed by the combination of the supply and supply water supply pipes of the tunneling face. The wind and water are sprayed together in the spray gun tube, the water outlet is at the front end of the barrel, and the high pressure air outlet is at the rear end. The direction can be flexibly adjusted at will. The explosion shock wave emitted by the shot is received by the sensor and converted into a weak electrical signal and transmitted to the host. The host will simultaneously control the solenoid valves of the supply and supply lines to achieve high-pressure remote automatic spray. And the repeated experiment of the spray gun angle, the spray distance can reach up to 30m (see Figure 2), and the atomization effect is good. Through the field measurement, the high-pressure remote shotgun automatic spray dust reduction rate reaches more than 90%.

Figure 2 Schematic diagram of high pressure remote shooting automatic spray device

4 implementation effect

In summary, in the case of relatively high degree of mechanization, in addition to the normal dust-proof measures taken by the mining face, combined with the implementation of several above-mentioned automatic dust-proof technologies, the dust in the underground of Xuchang Coal Mine has been effectively controlled. According to the actual measurement of dust on site, the total number of dust spots (times) was 122 points (times), reaching the national health standard 112 points (times), the pass rate reached 100%; coal dust 83 points (times), qualified 73 points (times) The pass rate is 88%. The concentration of rock dust is controlled at 0.8-10 mg/m3, and the concentration of coal dust is controlled at 4~66 mg/m3, which creates a good working environment for underground production and makes the overall appearance of the mine a new level. In 2000, Xu Factory successfully passed the ISO9002 quality certification system and ISO14001 environmental protection system certification. In the second half of 2003, the external audit work of OHSMS18000 employee health and safety management system certification was being organized, so that the comprehensive management level of mines was continuously improved. Xuchang Coal Mine has been rated as a national high-yield and high-efficiency double top ten mine for 2 consecutive years.

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