The working principle of liquid nitrogen quick freezing is "indirect contact freezing of frozen objects and cryogenic liquid (liquid nitrogen)"; Put packaged fresh food (fish, meat, etc. ) into the quick freezer, and quickly reduce the temperature in the liquid nitrogen quick freezer to below-120℃ (the temperature can be set according to different foods).
Extended data
Liquid nitrogen (N2) is liquid nitrogen. Liquid nitrogen is an inert, colorless, odorless, non-corrosive and nonflammable liquid with extremely low temperature.
Nitrogen constitutes most of the atmosphere (78.03% by volume and 75.5% by weight), and nitrogen accounts for 78% of the air. Nitrogen is an inert gas and does not support combustion. A large number of endothermic contacts during vaporization lead to frostbite.
The boiling point of nitrogen is _196 C. Under normal atmospheric pressure, if the temperature is lower than this, liquid nitrogen will be formed. If pressurized, liquid nitrogen can be obtained at a higher temperature. If the human body is exposed without protective measures, the skin will be in danger of severe frostbite. If there is too much nitrogen produced by vaporization under normal pressure, the partial pressure of oxygen in the air will drop, causing hypoxia and suffocation.
In industry, liquid nitrogen is fractionated from air. After air is purified, it is liquefied in a pressurized cooling environment, and separated by using the difference of boiling points of each component in the air. There is no problem for human skin to contact liquid nitrogen directly, and it will be frostbitten for more than 2 seconds, which is irreversible.
Precautions for operation: closed operation. Closed operation to provide good natural ventilation. Operators must be specially trained and strictly abide by the operating procedures. Operators are advised to wear winter clothes and gloves. Prevent the gas in the workplace from leaking into the air. Lightly load and unload when handling, so as to prevent the cylinders and accessories from being damaged. Equipped with leakage emergency treatment equipment.
Precautions for storage: Store in a cool and ventilated warehouse. The reservoir temperature should not exceed 30℃. The storage area should be equipped with emergency treatment equipment for leakage.
Engineering control: closed operation and good natural ventilation.
Respiratory system protection: generally no special protection is needed. However, when the oxygen concentration in the air in the workplace is lower than 18%, air respirator, oxygen respirator or long tube mask must be worn.