Introduction to the safe use of cryogenic liquids and storage tanks

- Jan 09, 2019 -

At 10:25 am on December 18, a chemical company in Rugao City, Jiangsu Province, caused a sudden death of liquid nitrogen. 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, and it is easy to cause burning when exposed to open flames; it is easy to cause 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.

Liquid nitrogen leakage emergency treatment

When the concentration of inhaled nitrogen is not too high, the patient initially feels chest tightness, shortness of breath, weakness and weakness; then there is irritability, extreme excitement, running, screaming, screaming, gait instability, called nitrogen strontium, which can enter drowsiness. Or coma. High concentrations may cause suffocation. Choking may result in loss of consciousness without warning, which is very fast and the victim cannot protect himself. The hypoxic person should be carried to the air circulation. If you can't breathe, you need to take artificial respiration, provide oxygen, and seek medical attention immediately.

skin contact:

1. Take off some parts of the frostbite and do not rub the frostbite to avoid tissue damage.

2. Rinse the frostbite with hot water not exceeding 40 °C. Do not heat with hot air. Seek medical attention immediately.

3. Frostbite muscle tissue is painless and exhibits a yellowish color. When it begins to thaw, the skin feels swollen, painful, and prone to infection. If the frozen part of the body has been thawed, it should be covered with a dry sterile cloth and wrapped in a large protective cover for medical treatment. For large-scale frostbite, first take off your clothes, then wash it with warm water and ask your doctor for treatment.

Eye contact: Immediately flush frostbited eyes with warm water not exceeding 40 °C.

Leakage treatment:

1. Immediate evacuation of personnel from contaminated areas, and isolation, strict restrictions on access.

2. Personnel handling leaks must take protective measures.

3. Increase the amount of ventilation in the area and monitor the oxygen content.

4. Spray a large amount of water from the headwind to the leak area.

5. If the liquid nitrogen tank or its valve leaks, please contact the manufacturer's emergency number and do not spray water at the leak.

6. If the leak is in use, shut off the container valve and relieve pressure before repairing.

7. Persons are prohibited from staying in low-lying or leeward