Abstract
The application of liquid nitrogen injection is an important technique in the field of coal mine fire prevention. However, the mechanism of heat and mass transfer of cryogenic nitrogen in the goaf porous medium has not been well accessed. Hence, the implementation of fire prevention engineering of liquid nitrogen roughly relied on an empirical view. According to the research gap in this respect, an experimental study on the heat and mass transfer of liquid nitrogen in coal porous media was proposed. Overall, the main mechanism of liquid nitrogen fire prevention technology in the coal mine is the creation of an inert and cryogenic atmosphere. Cryogenic nitrogen gas vapor cloud, heavier than the air, would cause the phenomenon of “gravity settling” in porous media firstly. The cryogen could be applicable to diverse types of fires, both in the openings and in the enclosures. Implementation of liquid nitrogen open-injection technique in Yangchangwan colliery achieved the goals of fire prevention and air-cooling. Meanwhile, this study can also provide an essential reference for the research on heat and mass transfer in porous media in the field of thermal physics and engineering.
Highlights
Liquid nitrogen, a safe, highly efficient, clean, obtained, and low-temperature refrigerant, has been widely used in biology, medical treatment, animal husbandry, food, metallurgy, electronics, aerospace and cryogenic industry, and other fields
Previous studies showed that liquid nitrogen can rapidly and effectively put out the sodium fire [1], for which water and carbon dioxide extinguishing agents fail to achieve the effect
Liquid nitrogen can be employed to extinguish isopropanol [2], ethanol, propanol and diesel [3], and other oil pool fires, as well as building fires [4], avoiding damage to property caused by water extinguishing agent
Summary
A safe, highly efficient, clean, obtained, and low-temperature refrigerant, has been widely used in biology, medical treatment, animal husbandry, food, metallurgy, electronics, aerospace and cryogenic industry, and other fields. Liquid nitrogen is a highly efficient fire extinguishing agent. Previous studies showed that liquid nitrogen can rapidly and effectively put out the sodium fire [1], for which water and carbon dioxide extinguishing agents fail to achieve the effect. Liquid nitrogen can be employed to extinguish isopropanol [2], ethanol, propanol and diesel [3], and other oil pool fires, as well as building fires [4], avoiding damage to property caused by water extinguishing agent. It is very difficult to extinguish the fire; causing underground fires may continue for months or even years. Use of water or chemical fire extinguishers may cause unwanted side effects, such as extensive “water damage,” air pollution, or underground water contamination.
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