Prevention and treatment of fires in mines

Fire hazard analysis of coal spontaneous combustion

The internal fire of the mine is caused by the long-term slow oxidation of coal in the underground. According to the special situation of coal mine production, the main places are: 1 goaf; 2 high-rise area of ​​the two-slot during the excavation and mining, broken Belt; 3 pieces of gang, roof, coal road broken by surrounding rock; 4 long-term coal accumulation point; 5 poorly ventilated coal roadway; 6 selected workshop coal bunker, coal pile and so on. The main reasons are the slow recovery of the working face, the spontaneous combustion of the floating coal in the goaf, the fire area where the coal is spontaneously burned but not completely extinguished; the air supply condition of the air leakage; the inspection is not in place, not found in time; the coal roadway heading face The roof area did not take timely fire prevention measures for reasons such as insufficient air volume. According to the natural fire of coal in the mine over the years, the most prone to fire accidents in our mine are: the fully mechanized mining face goaf and the two-slot trough, the long-term bare coal road heading zone, the fracture zone, and the shotcrete are not tight. Coal road heading area and so on. In recent years, active and effective measures have been taken (mainly in the goaf, pressure equalizing ventilation, reasonable working surface distribution, so as to minimize the leakage of the roof area and the goaf, periodically inject water into the roof area, and strengthen the use of coal roadway spray. Etc.), as well as the comprehensive use of anchor net support in the coal roadway, greatly reducing the roof hot spot area, thus ensuring that no natural fires have occurred in the mine in recent years.

1. General warning of mine fires

(1) The temperature in the roadway increases, and fog or doorway “hanging sweat” appears, and water drops are hung on the bracket. This phenomenon is different from the foggy gas phase that occurs at the intersection of two different temperature streams at the bottom of the well.

(2) During the process from heat collection to spontaneous combustion, coal will produce low-temperature dry distillation products (aromatic hydrocarbons), releasing kerosene, gasoline, turpentine or tar-flavored gases (hydrocarbon gases). When smelling tar, It shows that spontaneous combustion has developed to a certain extent.

(3) The water or air flowing out from the coal gathering or self-ignition is higher than normal.

(4) Because coal emits harmful gases such as carbon dioxide and carbon monoxide from the heat accumulation to the spontaneous combustion stage, and reduces the oxygen content in the air, when people approach the fire source, they may feel headache, sultry heat, dizziness, nausea, weakness of the limbs, lack of energy, etc. Uncomfortable.

2. The warning sign of the goaf

(1) The air temperature of the working surface or its upper corner is higher than 30 °C, or rises by 1 °C every day for 5 consecutive days.

(2) The temperature of the falling coal is higher than 34 °C.

(3) The corners on the working surface, CO appearing behind the tail beam of the hydraulic support and the top of the frame, the concentration has reached 40PPm, and it is still rising, or the CO concentration has reached 60PPm.

(4) The outlet temperature of the goaf exceeds 25 °C.

(5) There is sweat or fog on the work surface.

(6) The working surface or the upper corner has aroma, kerosene, turpentine, tar or smoke.

(7) The working face is stopped for more than 3 to 5 days, or the speed of advancement is slow, and the average is less than 2 meters per day.

3. Two working faces and the signs of fire in the coal roadway and bare coal roadway

(1) Fog and smoke appear on the lower part or the leeward side of the falling or broken belt;

(2) The CO concentration on the windward side is normal, while the CO concentration on the downwind side is rising;

(3) The top plate breaks down the coal, and the temperature of the dropped coal exceeds 30 ° C;

(4) The temperature of the peripheral wall of the roadway is significantly higher than the normal temperature of the roadway, or the person has a burning sensation here;

(5) CO appears in the roof area, its concentration reaches 40PPm, and it still shows an upward trend or the CO concentration reaches 60PPm;

(6) The internal coal body temperature in the roof area is higher than 34 °C;

(7) The temperature of the water injected into the fracture zone or the roof zone exceeds 30 °C.

In combination with the general law of fire and the uniqueness of the coal seam in this mine, the coal mine is combined with the GC-4085 chromatographic tube detection system, and the early prevention and prediction of mine fires are carefully carried out, and targeted selection is made. The iconic gas for spontaneous combustion of mines.

Section 2 Main Measures to Prevent Coal from Spontaneous Combustion

The main signs of spontaneous combustion of coal are: the temperature of coal, rock, air and water in the nearby roadway increases, the fog appears in the roadway, accompanied by the smell of coal tar, the concentration of CO and CO2 increases, the concentration of O2 decreases, and fog, fossil, flame, etc. appear. phenomenon. The measures to prevent spontaneous combustion of coal are mainly: various spontaneous combustion conditions considered under current technical conditions, and control of coal spontaneous combustion in the mechanism of spontaneous combustion of coal. At present, it is mainly during the excavation, scientific construction, to minimize the loose circle of surrounding rock of roadway. In the daily management, in the excavation stage, the comprehensive mechanized excavation technology should be adopted as much as possible, strictly in accordance with the construction process, reduce the over-excavation of the roadway construction project, and at the same time grasp the location and scope of the high-rising area of ​​the coal lane, and Large-flow nitrogen injection in the area of ​​the caving area and the working area, and assisting the use of yellow mud grouting, pressure equalizing ventilation, injection gel, Roxie, etc. to achieve the purpose of comprehensive fire prevention. The mined-out area of ​​the working face at the end of mining is mainly treated by yellow mud grouting. Under normal circumstances, the working surface advancement is increased, the air volume of the working face is properly allocated, and the suspended roof of the lower corner of the working surface is timely degraded to control the oxidation zone of the goaf. Width and oxidation rate of the floating coal.

Section III Treatment Plan after Coal Spontaneous Combustion

1. After the above-mentioned symptoms are discovered by the underground workers, they must report to the dispatching room immediately. If the degree of spontaneous combustion is serious or the safety of the personnel is threatened, personnel should be immediately evacuated from the disaster area.

2. The dispatching room shall promptly notify the ventilation department and relevant leaders to organize the rescue team to rescue and rescue the disaster in a timely manner when the degree of spontaneous combustion is serious.

Third, the ventilation department must take timely measures to prevent further expansion of the fire, and use gas analysis, infrared detection, drilling detection and other means to determine the location of the fire source according to the actual situation on the site, and then take targeted measures for treatment.

4. After discovering the signs of spontaneous combustion of coal, the beam monitoring points, gas and temperature measuring points should be arranged in time to analyze the changes in gas composition and temperature at the ignition site, so as to take corresponding fire-fighting measures.

5. When the coal spontaneous combustion reaches the level of smoke generation, it is necessary to have a special person to check the gas condition and to have measures to prevent gas explosion.

6. Treatment of fire in confined area: When there is a fire in the confined area and the goaf of the working face, high-flow nitrogen injection and grouting should be carried out immediately. The fire in the goaf is mainly used to accelerate the advancement of the working face and The method of small coal release will eliminate the fire area, and at the same time strengthen monitoring and inspection. When a fire occurs in the landing area, all the involved personnel should be evacuated immediately, and measures should be taken to drill water, gel or intubate. Yellow mud grouting, etc., should pay attention to the degree of fire when the fire is extinguished in the inclined road. Firstly, the wind flow and pressure difference in the system must be adjusted to ensure that the wind flow is reversed without the occurrence of fire pressure. In addition, special safety technical measures must be prepared before fire fighting.

7. All personnel involved in fire prevention must wear well-separated self-rescuers. Otherwise, it is strictly forbidden to enter the well.

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