Leading explosion suppression technology for South African coal mines

I. Overview of coal mine safety production in South Africa

South Africa's coal resources are stable, coal quality is good, and mining conditions are good. At present, the annual output of coal is about 250 million tons, of which one-third is exported and the rest is for personal use. The capacity of the top five coal mining enterprises in production capacity accounts for 70% of the total production capacity. There are nearly 100 production mines in the country, 60% of which are mined and the others are open-pit mining. Most of the wells in the mines use continuous coal mining and roadway mining.

South Africa's coal mine safety production work is subject to adjustment and restriction by the National Mining Safety Law and its supporting regulations, similar to China's mine safety law and coal mine safety regulations. The gas concentration control standard of coal mine underground working environment is similar to that of China's standard. When the gas concentration reaches 1%, the alarm will be automatically turned off when it reaches 1.2%. When it reaches 1.4%, the operation must be stopped.

In the history of South Africa, it was also a country with frequent coal mine gas accidents. A coal mine gas explosion occurred in May 1993, killing 53 people. After the accident, a series of measures were taken. Since then, no gas explosion has occurred in 13 years. In 2004, there were 20 deaths in coal mines nationwide, and the death rate per million working hours was 0.19% (the death rate was converted to millions of tons was 0.08). In 2005, there were 16 deaths in coal mines nationwide, including 4 roof accidents and 10 mechanical accidents. Other accidents 2 People, a million working hours mortality rate of 0.15 (converted to a million tons mortality rate of 0.06). The overall level of coal mine safety production is relatively high.

Second, the production of active explosion suppression technology in South African coal mines

The prevention of gas and coal dust explosions in South Africa is also controlled by the gas concentration of the control workspace. In ventilation systems, ventilation facilities, air volume configuration and wind speed control, it is essential to ensure that the gas concentration in the working space is not exceeded. If the gas concentration in the monitoring area exceeds the limit, it will alarm, power off, stop work, and withdraw. Once a gas dust explosion has occurred, passive suppression measures such as explosion-proof water sheds and explosion-proof rock sheds are adopted to weaken the power of the explosion shock wave and to suppress shock wave reflection and secondary explosion.

In the South African well coal mine, the continuous coal mining machine is used to carry out the roadway-type coal mining. The actual production process of the mining face is equivalent to the comprehensive mining face in China. Since the cutting section of the continuous miner is always at the forefront of the working face, the gas monitoring probe cannot be set at the end of the working face in the production dynamics. In the actual work, the cutting head of the working face is basically in the blind area of ​​ventilation, but the gas emission is often the most prominent, and the spark of the high-power continuous miner is inevitable. If the amount of gas emission reaches a local explosion or combustion concentration, it is highly likely to cause small-scale gas explosion or combustion when a pick-up spark is encountered. Therefore, the three factors such as the instability of the working face gas, the pulsation of the air volume, and the inevitability of the picking spark constitute the basic contradiction in the gas management of the working face of the continuous miner. How to timely and effectively suppress the small-scale gas explosion or combustion caused by the pick spark, and eliminate it in the initial stage of small space and small energy, and not develop into an accident, has become a major technical problem that must be solved. This is the background for the development and production of active suppression technology.

Third, the application of active explosion suppression technology in South African coal mines

The South African coal mine active explosion suppression technology was developed by a research center supported by the government's energy and safety department and has been put into use. The basic principle is as follows: When a gas explosion occurs in the operation monitoring area, the monitoring device captures the signal by optical principle and transmits it to the signal recognition device for spectral analysis. If the signal is analyzed and identified as the set accident object, the explosion suppression command is issued, and the trigger is triggered. The device and its associated energy storage device respond immediately, discharge the explosion-proof medium in a compressed state, rapidly generate a high-energy explosion-proof barrier, and the explosion-proof barrier depressurizes and reduces the shock wave pressure and high temperature generated by the explosion to achieve active explosion suppression. The active explosion suppression can generate a explosion-proof barrier in a specific medium in a short time of milliseconds, blocking, canceling, and suppressing the high-temperature shock wave generated by the local explosion, and destroying the explosion in a small space and a small energy stage. The shock wave pressure and temperature that are transmitted to the work area after suppression by the explosion suppression barrier cannot cause injury to personnel.

Depending on the application, the suppression device can be airborne and fixed to the shearer or roadheader. It can also be lane-type and placed in the roadway where it is necessary to install a blasting device. The explosion suppression device is charged under the power supply condition, and the external power supply can also work normally after charging, and functions.

At present, South Africa has applied this technology to continuous miners and put them into practical use. This is a typical airborne explosion suppression device. Spain, Egypt, and Romania have been introduced, and Australia and the United States are studying and testing. The active explosion suppression technology has obtained the national patent of South Africa and applied for an international patent and was approved. The National Energy and Security Department of South Africa has listed this technology as a key promotion project and requires extensive use of coal mines. In order to promote the mandatory use of active suppression devices, consideration is being given to modifying relevant laws and standards.

Fourth, the application prospects of China's active explosion suppression technology

Most of the coal mining face in China is long-wall mining. Some of the excavation faces are artificial blasting, and some are boring machines. In view of the two arrangements of active anti-explosion technology - airborne and lane-mounted, the following considerations can be made: First, the installation of the tunnel-type explosion suppression device outside the two ends of the wall-type mining face, in the shearer The airborne explosion suppression device is installed at the front and rear of the cylinder; the second is to install the roadway type explosion suppression device near the blasting working face; the third is to install the airborne explosion suppression device on the boring machine used for the driving face; the fourth is temporary An alley-type explosion suppression device is installed near the engineering operation point.

It is necessary to point out the following two points: First, the active blasting device realizes the real-time monitoring of the job site by optical principle, so it is only applicable in the straight roadway; second, the active blasting device has the effect of reducing pressure and cooling, but for the local gas explosion. Toxic gases do not eliminate. This is a gap in the active explosion suppression technology.

In summary, first, South Africa's active explosion suppression technology is an advanced technology with strong vitality; second, the active explosion suppression device is effective for preventing gas and coal dust explosion accidents, with promotion value and application prospects. Broad; third, the current active anti-explosion technology and its device can only be reduced pressure and can not be disinfected. It should be organized on the basis of the original research and research, so that it has three functions of blood pressure reduction, cooling and disinfection.

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