Mine fire causes, classification, characteristics, hazards and fire-fighting measures

Causes, Classifications, and Characteristics of Mine Fires Fires that occur downhole, as well as fires that occur near the wellhead but endanger the safety of the mine, are called mine fires.

There are two reasons for mine fires:

First, the fire caused by an external fire source;

The second is the fire caused by the inherent factors of the physical and chemical properties of the coal itself.

Therefore, mine fires fall into two categories:

Exogenous fires:

Exogenous fire, also known as foreign fire. Violation of smoking in underground mines, dismantling miner's lamps, clear cannons, electric welding, gas welding, etc. downhole can cause underground fires.

Electric arc sparks caused by improper use of underground electric equipment or short-time maintenance may cause downhole fires.

Mine gas or coal dust combustion or explosion can ignite downhole combustibles and form a mine fire.

There are also violations of operating procedures and illegal firing. For example, open flames or power line shots, deterioration of gunpowder, cannon discharge, etc. may all result in underground fires. Exogenous fires generally occur near wellheads, underground chambers, mining work surfaces, and wooden support tunnels with cables.

Internal Cause Fire:

Internal causes of fire, also known as spontaneous combustion of coal. Some coals have self-ignitability due to their own physical and chemical properties, and they can oxidize and generate heat when in contact with air. If the heat dissipation conditions are not good, they will spontaneously ignite. The internal cause fires mainly occurred in the goaf area, the roof collapse area and the compressed coal pillars. Among the goafs, coal mining methods with low recovery rate are particularly used, and coal remaining in the goaf is more than that, which is most likely to cause coal spontaneous combustion. The natural fire in the goaf accounts for about 80% of the total number of natural fires in the mine . Therefore, for mines with natural fire hazards, the gob area should be closed in time to prevent air leakage, and yellow mud grouting or sprinklers should be used. Prevent the spontaneous combustion of coal in the goaf.

Mine fire is different from ground fire. It has its own characteristics:

The underground space is small, the workplace is narrow, there are many electrical equipments, and there are many flammable materials such as pit wood. The coal itself can ignite. In addition, the fire prevention facilities are not perfect, the fire-extinguishing equipment is not complete, and the underground has fresh air flow. Once a fire occurs, It is not as easy to save as the ground fire. In addition, various types of fires (such as electrical fires, oil fires, fires from gas explosions, and spontaneous combustion of coal) can occur, and methods of fighting fires vary. If the fire is not timely or handled improperly, it will spread and develop, often resulting in a large fire, which makes the fire fighting work more difficult. At the same time, the underground staff are concentrated and in the event of a fire, they do not know where they are, and it is difficult to avoid and evacuate. This will increase the damage caused by the fire.

Spontaneous fires often occur in coal pillars or goafs. There is no obvious flame and the combustion process is slow. It is not easy to be discovered by people and it is not easy to find the exact location of the fire source. Once it is detected, it becomes a fire and it has to be closed. Therefore, this type of fire lasts for a long period of time, up to several months, years or even decades. Spontaneous fires also generate a large amount of carbon monoxide, causing poisoning and death.

Subsurface spontaneous combustion fires generally occur in poorly ventilated, dilapidated, or roof-drained areas; closed or un-closed goafs; piles of coal that are compressed to produce pressure; coal seams produced by stratified coal seams have a low extraction recovery rate. There are many goafs where coal is lost. In these locations, more attention should be paid to preventing spontaneous combustion of coal.

Due to the limited conditions, downhole fires are different from ground fires. Each staff member must not only be vigilant, but must be prepared for precautions, and must strictly implement operational procedures and operating procedures. In addition, special fire fighting measures must be taken for the specific situation of underground prosperity. The use of fire extinguishers can effectively save them in the event of a fire.

How to extinguish the fire:

1. Use water to extinguish fire (fire should be extinguished from the outside of the fire to the inside, and do not put the water directly toward the center of the fire to prevent the water vapor from exploding);

2. Use inert gas to extinguish (non-combusting gas, commonly used nitrogen, carbon dioxide, and wet chamber inert gas, pay attention to the prevention of skin frostbite on contact with hands 3 use high school multiple foam extinguishing (BGP-400);

3. Fire extinguishers with fire extinguishers

4. Use sand rock powder and other incombustible rocks to directly extinguish the flame;

5, break open and remove the combustion and then use water to extinguish;

6. Fill the fire area with water;

Extinguishing conditions:

1, clear fire source

2, water, human resources, material resources, adequate;

3, there is a smooth return air;

4. The gas concentration should not exceed 2.

Mine fire hazards:

1, produce a large number of harmful gases;

2, produce high temperature;

3, triggering gas dust explosion;

4, causing major economic losses.

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