[Industry safety knowledge] Gas explosion accident prevention and rescue!

Recalling the damage caused by gas explosions:

September 27, 7 pm, Linley Ningxia Coal Limited mine No. 3 Well after a gas explosion. The more we search and rescue, rescue teams on September 27 found the bodies of 18 dead miners, and on September 29 all Masui. Accident aftermath disposal group also simultaneously working as of October 4, 18 victims have been properly handle the funeral.

March 29, 2013, is located in Baishan City, Jilin Province Tonghua Mining (Group) Co., Ltd. Eight of Eight Coal mine gas explosion occurred, killing 41 people trapped, 13 people were rescued, 28 people were killed.

Gas explosions are not well understood by many people. Gas explosion, in the end is how the same thing?

1 What is a gas explosion?

Gas is the initial stage of the accumulation of coal in ancient plants. Cellulose and organic matter are decomposed by the action of anaerobic bacteria. The main components of gas are alkanes, of which methane constitutes the majority, and small amounts of ethane, propane and butane. In addition, they generally contain hydrogen sulphide, carbon dioxide, nitrogen and water vapor, and traces of inert gases such as helium and argon. .

Mine gas explosion is a kind of heat --- chain reaction (also called chain reaction). When the explosive mixture absorbs some energy (usually the heat energy given by the ignition source), the chain of the reaction molecules breaks and dissociates into two or more radicals (also called free radicals). These radicals have a large chemical activity and serve as the activation center for the continuous reaction. Under suitable conditions, each of the radicals can be further decomposed to generate two or more radicals. This cycle is endless, more and more free radicals, chemical reactions faster and faster, and finally can be developed into a combustion or explosive oxidation reaction. Therefore, gas explosion is, by its very nature, an intense oxidation reaction caused by moderate concentrations of methane and air.

Two basic conditions that two gas explosions must possess at the same time

First, the gas concentration is in the explosive range, generally 5% -16% ; Second, the oxygen concentration in the mixed gas is not less than 12% ; Third, the high-temperature fire source is enough energy, generally 650 °C -750 °C .

( 1 ) The concentration of gas

The concentration limit of a gas explosion refers to the volume concentration of gas in the gas mixture of gas and air. When the gas concentration reaches 9.5% , theoretically, gas can safely react with the oxygen in the air, so that the maximum amount of heat is released, and therefore the maximum intensity of the explosion. When the gas concentration is less than 5% , gas cannot be used to participate in the chemical reaction. Accumulation of heat builds up, so it can't explode and it can only burn. When the concentration of gas is higher than 16% , due to the lack of oxygen in the air, it can't meet all the needs of oxygen reaction, only part of the gas reacts with oxygen, and the generated Heat is absorbed and cooled by excess gas and surrounding medium, so no explosion can occur.

( 2 ) Sufficient oxygen content

The concentration of oxygen in the mixture of gas and air must be greater than 12% , otherwise the explosion reaction cannot continue. Coal mines in closed areas, goaf areas and other crevices, etc., due to oxygen consumption or no oxygen supply conditions, the oxygen concentration may be less than 12% ; other roadways, workplaces, etc. according to the provisions of oxygen content of not less than 20 %, generally less than 12% oxygen concentration does not exist, because in some cases, people will in a short time died of suffocation.

( 3 ) Energetic ignition sources

The three conditions that the ignition source can cause a gas explosion are: (1) The temperature is not less than 650 degrees. ( 2 ) The energy is greater than 0.28mJ. (3) The duration is greater than the explosion induction period. These three conditions are usually easily met, such as open flames, coal spontaneous combustion, impact sparks, electric sparks and so on. In the coal mining process, special techniques are sometimes required for some unavoidable sources of fire, making it impossible to meet the ignition conditions of gas . For example, the flame produced by a millimeter detonator used in a downhole blast, other temperatures up to 2000 degrees, but the duration is very short, less than the explosion induction period, so it will not cause gas explosion.

3 Causes of common gas explosions in coal mines

( 1 ) Inadequate equipment, lack of management to implement mine safety equipment configuration, and the principle of “first pumping, post-harvest, monitoring and monitoring, and production by wind” have not been fully implemented. Many gas accidents in coal mines are not equipped with a gas drainage system or a drainage system cannot be operated effectively, and the monitoring system cannot function effectively. In addition, the occurrence of gas explosion accidents was mainly due to defects in management that resulted in the misconduct of some operators.

( 2 ) The employees' safety awareness is low and their cultural quality is low. According to the analysis of relevant data, most gas explosions in coal mines are caused by illegal operation of workers, and most of the gas accidents are caused by “three violations”. . Many employees of coal mines have low levels of education. They go down without formal safety training. They often use divisions to participate in mining and other operations. They lack knowledge of safe production, do not understand ventilation safety management and operating procedures, and are paralyzed and operate illegally. Risky and reckless.

( 3 ) The existence of gas accumulation. Gas accumulation refers to the phenomenon that the concentration of accumulated gas in the space larger than 0.5m3 reaches or exceeds 2% in the excavation working face and other places . Gas accumulation is the root cause of the gas explosion. There are many reasons for the accumulation of methane, mainly due to the lack of ventilation capacity of the main ventilator of the mine or the unreasonable ventilation system, and the lack of wind in the mine. The driving face of the mine or other roadways that need to be supplied by the wind alone causes the gas due to the local fan or fan cylinder. Accumulation; accumulation of gas in gob angles and goafs on coal mining face; poor ventilation due to roadway deformation, damper adjustment, etc.

( 4 ) The phenomenon of detonation of the fire source exists. In individual coal mines, the problem of detonating the fire remains. If there are mines still have open electricity, open flames go down, downhole electrical equipment there is the phenomenon of explosion, and even some electricians do not understand technology or irresponsible, in the demolition or damage of the explosion-proof closed loop, causing the explosion. The fire sources for underground detonation gas in coal mines include : blasting sparks, electrical sparks, frictional impact sparks, static sparks, and coal spontaneous combustion.

4 Measures to prevent gas explosion

( 1 ) Optimize the ventilation network and ventilation system to prevent the accumulation of gas Reasonable and reliable ventilation system is an important measure to prevent gas accidents and control the expansion of disasters. Gas control engineering and mining engineering must be simultaneously designed, advanced, and put into use. The coal mining face must keep the air flow unimpeded, and each driving face must have reasonable air inlet and return air routes to avoid the formation of series ventilation. In addition, in the coal mining process, the gas return angle at the return face of the coal mining face tends to accumulate gas, and the accumulated gas in the area should be handled in a timely and effective manner. The methods of treatment include : hanging wind barrier drainage method, wind tube air conduction method, mobile pumping station drainage method, tailgate drainage gas method, hydraulic local fan blowing method.

( 2 ) Mine gas concentration and fire source monitoring technology The real-time automatic monitoring of mine gas concentration and fire source is very important to prevent gas explosion. When gas anomaly or fire source is found, immediate measures shall be taken to prevent the explosion accident. China developed the KJ series mine safety monitoring system, as well as various types of detection sensors, alarms, and power cutoff devices. According to the requirements of the National Bureau of Coal Mine Safety Supervision, all mines are required to install a comprehensive mine safety monitoring system. The application of the safety monitoring system has made a great contribution to the safety production of coal mines, but it must not replace the downhole on-site inspections of full-time safety inspection personnel.

3 , to strengthen safety inspections should focus on checking people in the underground operations, violations of the fire to bring people underground, illegal use of electricity, illegal firing, violations of the miner's lamp and other causes of gas explosion caused by abnormal behavior, in addition to focusing on inspection of gas drainage, Ventilation management, gas monitoring, explosion protection of electrical equipment, and so on, and to change its anomaly to achieve the objective requirements of safe production, thereby controlling the occurrence of gas explosion accidents.

( 3 ) Strengthen safety training for all employees First, the company’s leading cadres must carry out safety production training so that they understand the technology, understand the operation and management, and understand safety production regulations. They learn to act according to the law of coal mine production and strictly implement “safety first, prevention as The main "safety production policy", "clear responsibility, perfect system, strong enforcement, strict supervision." In addition, the workers are the first producers. Through the production technology and safety training, the technical quality, resilience, safety awareness, and self-protection ability of coal miners can be improved to prevent illegal operations, risk-taking, and avoiding gas accidents.

( 4 ) Strengthening safety inspections should focus on inspecting people in underground operations, illegally carrying fires downhole, using electricity illegally, illegally firing cannons, illegally striking miner's lamps and other abnormal behaviors that cause gas explosion accidents, and focusing on checking gas drainage. , Ventilation management, gas monitoring, explosion protection of electrical equipment, etc., and must do to change its anomaly to achieve the objective requirements of safe production, thereby controlling the occurrence of gas explosion accidents.

( 5 ) Accelerate the research of new technologies, realize the leap-style development of comprehensive gas management, increase the intensity of “first extraction and later acquisition”, and realize the fundamental transformation of coal mine gas control. Actively implement the comprehensive gas control strategy of “guaranteeing the need for maximum conservation, exhausted extraction, extraction after extraction, and co-production of gas” and relying on scientific and technological progress to achieve integration of coal mining and gas extraction, integration of surface and downhole drainage, and gas extraction. Put and use integration. Actively carry out research on key technologies such as soft drilling, long-term borehole drilling technology in coal seams, fast, high-efficiency and enhanced permeability drainage technology in low-permeability coal seams, and solid-hole drilling technology in surface drilling. Accelerate the research progress of non-contact continuous forecasting and warning technology on working face such as roadway gas emission characteristics, acoustic emission monitoring technology, electromagnetic radiation monitoring technology, etc., and incorporate signals into mine safety monitoring system to realize innovative research on continuous monitoring technology. Through technological research and research, we have achieved technological breakthroughs in gas comprehensive management.

5 gas explosion accident rescue

After the gas explosion occurred, it must be quickly established disaster relief organizations headquarters, unified command, responsible for gradual, orderly manner. It is imperative to ascertain the situation in the disaster area as soon as possible, understand and master the accident situation and development situation in many aspects as soon as possible, scientifically analyze, make decisive decisions, adhere to the people-centered approach, and rescue safely, and formulate scientific and effective disaster relief plans and measures to improve the efficiency of accident rescue.

( 1 ) Whether to cut off the power immediately

The industry has different views on whether or not to cut off the power immediately after a gas explosion occurs, because cutting off the power supply in the disaster area may generate electric sparks, which may cause secondary explosions and expand the scope of disaster destruction, but do not cut off the power supply in the disaster area, due to the original power supply system in the disaster area. If it is damaged, the route may be diverted, damaged, etc., which may cause electric shock hazards to trapped and rescue personnel in the disaster area. According to past rescue experience, whether or not to cut off the power supply in the disaster area must be judged according to the type of gas explosion. If it is a gas outburst explosion, there is still a large amount of gas in the roadway. In this case, it is not appropriate to cut off the power supply. The rescue team should strengthen their awareness of protection against electric shock. For a cumulative gas explosion, the gas emission rate is not fast and the volume is small. Usually, after the explosion, the residual gas gas concentration is low, and generally it will not cause secondary explosion. At this time, the power supply can be cut off to improve the safety of rescue work. .

( 2 ) Establishing ventilation conditions to exclude harmful gases from explosion

After the explosion, ventilation conditions should be established as far as possible to restore ventilation in the disaster area. On the one hand, harmful gases from gas explosions can be eliminated and the living environment of trapped people can be improved. On the other hand, oxygen can be added to the disaster area to maintain the survival needs of trapped people. . However, before establishing ventilating conditions to restore ventilation in the disaster-affected area, we must first determine whether the explosion caused a fire and whether the ventilation is safe. The basis for this is to judge according to the change of toxic and harmful gases such as the CO in the return air system in the disaster area; and through the investigation of the disaster area by the ambulance personnel. If it is determined that there is a fire in the disaster area, safety measures must be taken to extinguish the fire before ventilation. As for how to properly manage the ventilation system ( reverse wind, short circuit, enhanced ventilation, etc. ) , remove toxic and harmful gases in the disaster area as soon as possible, and control the scope of accidents to be expanded. This needs to be dealt with according to the specific conditions of the rescue site. In short, ventilation channels must be established quickly.

( 3 ) Recover the ventilation of the excavation roadway and establish a rescue channel

If the explosion occurs in the excavation roadway, a large amount of gas and harmful gases accumulate in it, and there may be a fire source or an electric explosion device. In order to safely and quickly restore the ventilation of the excavation roadway and find the victims, follow the conventional method. To restore the ventilation of the excavation roadway, there is still the risk of secondary explosion. To ensure safe rescue, the “one-time recovery, long-distance start-up” method can be adopted, that is, rescue workers wear a positive pressure oxygen respirator to pick up the wind tube in the disaster area and then evacuate. Go to a safe area, and then start long-distance ventilation, so that even if an explosion occurs, it will not harm the rescue workers. This method has been applied in the rescue of multiple gas explosion accidents and has achieved good results.

The information in this article comes from the Internet and was reorganized and edited by China Rescue Equipment Network.