Introduction to the Operating Procedures for Liquid Nitrogen Fire Extinguishing
Laser gas mixtures: Common laser gas mixtures include helium–neon laser mixtures, carbon dioxide laser mixtures, krypton–fluorine laser mixtures, sealed-beam laser mixtures, and excimer laser mixtures.
Liquid nitrogen is an inert gas with a typical temperature of about −195.8°C. It is characterized by excellent stability, high nitrogen content, and non-corrosiveness. Moreover, the heat absorbed during its vaporization has a certain fire-extinguishing effect, which is the principle behind using liquid nitrogen for mine fire suppression. So, do you know what the specific fire-extinguishing procedure entails?
I. System Composition
The system primarily consists of surface boreholes, DN50 stainless steel liquid nitrogen pipelines, coal-pillar boreholes, parameter-monitoring instruments, and safety devices.
II. Process Flow
The liquid nitrogen fire-extinguishing process flow is as follows: liquid nitrogen tanker → tank pressurization unit → cryogenic stainless steel piping → surface well casing → goaf.
III. Operating Procedures
1. If a fire breaks out in a mined-out area, we can directly drill boreholes on the surface and inject high-temperature fluid into the hot zone through these boreholes.
2. Connect surface boreholes to dedicated pipelines within the mine roadway, then carry out high-temperature oxidation.
3. In the event of a mine fire, we can transport a liquid nitrogen tanker to the site and inject the liquid nitrogen into the high-temperature oxidation zone via pipelines.
4. On open sections of the coal mining face, we must first implement appropriate safety measures and then inject liquid nitrogen directly into the mined-out area via pipelines to prevent and extinguish fires.
The foregoing has outlined the operational procedure for liquid-nitrogen fire suppression. As is well known, liquid nitrogen’s extremely low temperature enables it to absorb ambient heat as it vaporizes at room temperature, thereby cooling the fire zone and reducing its thermal energy. At the same time, the nitrogen content in the air increases while the oxygen content decreases. When the oxygen level drops below 5%, coal oxidation and spontaneous combustion can be effectively suppressed; and when the oxygen level falls below 3%, the spontaneous ignition and re-ignition of coal and other combustible materials can be comprehensively inhibited.
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