Introduction to the safe use of cryogenic liquids and storage tanks

- Jul 29, 2019-

At 10:25 am on December 18, a chemical company in Rugao City, Jiangsu Province, suffered a liquid nitrogen leak accident causing 2 deaths and 1 injury. At present, the cause of the accident is under investigation. The gas circle has compiled the contents of cryogenic liquids and the safe use of cryogenic storage tanks, and hopes to provide help or reference for everyone's work.

Low temperature liquid characteristics and safe use points

1. Low temperature liquid has low boiling point, large expansion, strong asphyxiating and strong oxidizing properties.

1.1 The boiling point of the cryogenic liquid at a pressure of 101.3 KPa: liquid nitrogen is -196 ° C, liquid oxygen is -183 ° C, and liquid argon is -186 ° C. When in contact with the human body, it can cause severe frostbite to the skin and eyes. When a small amount of cryogenic liquid leaks or the inner leakage of the pipe valve, it will absorb the heat of the surrounding environment, and the leaking point will quickly dew condensation, and if it is serious, it will freeze.

1.2 The cryogenic liquid accepts high heat or a large amount of leakage from the surrounding environment to absorb the surrounding energy, and its volume will expand due to rapid gasification. At 0 ° C and 101.3 KPa, the volume of gas after gasification of 1 L of cryogenic liquid: 674 L for nitrogen, 800 L for oxygen, and 780 L for argon. In a closed container or pipe, the internal pressure rises due to the vaporization of the cryogenic liquid, which may cause the explosion of the container or the pipeline.

1.3 In the environment around the low temperature tank of the low temperature storage tank, the low temperature liquid leaks easily forms a gas rich area after gasification. If the concentration of nitrogen, argon and carbon dioxide is large, it is easy to cause suffocation injury. In addition, when the oxygen concentration is large, oxygen-rich damage also occurs.

1.4 Oxygen is a strong combustion improver with extremely strong oxidizing properties. Liquid oxygen is close to combustibles. It is easy to cause burning when exposed to open flames. It is easy to produce knocking due to vibration and impact when it comes into contact with combustible materials. It is potentially explosive when mixed with combustible materials. Liquid oxygen can adhere to the fabric of the clothes, and it is easy to cause flashing and injure the human body in case of ignition.