Liquid nitrogen is a convenient cold source. Because of its unique properties, it has been paid more and more attention and recognized by people, and has been widely used in animal husbandry, medical care, food industry, low temperature research and so on. Its application in electronics, metallurgy, aerospace, machinery manufacturing and other aspects has been continuously broadened and developed.
First, the application of liquid nitrogen in animal husbandry
1, which is widely used in the improvement technology of livestock frozen preparation.
2. Embryo transplantation of livestock and various animals to prepare viable embryos.
Nowadays, more embryo freezers are accepted, belonging to intelligent freezers. The instrument adopts microcomputer control technology and special software, which can correctly control the amount of liquid nitrogen, thus ensuring the frozen biological products to be cooled and frozen at an appropriate freezing speed.
3, liquid nitrogen ultra-low temperature microbial collection skills
The method of liquid nitrogen permanent preservation of bacteria at-196℃ is based on the principle that the metabolism of microorganisms tends to stop below-130℃ and microorganisms are collected usefully.
4. Genetic survival of agricultural organisms
5. Survival liquid nitrogen vaccine
6. Liquid nitrogen is used to treat the external closure of nipple and breast hole in dairy cows, and skin tumors in livestock are also very common.
Application of liquid nitrogen in medical miracle
1, cryomedicine
2. Clinical medicine
Liquid nitrogen is the most widely used refrigerant in cryosurgery. It is one of the best refrigerants invented so far. It can be injected into cryogenic medical equipment, just like a scalpel, and can be used in any operation.
Three. Application of liquid nitrogen in food industry
Application of 1 and liquid nitrogen in food quick freezing
Liquid nitrogen quick freezing has the following obvious advantages:
① Fast freezing speed (the freezing speed is about 30-40 times faster than the usual freezing method): accepting liquid nitrogen for quick freezing can make food quickly pass through the maximum ice crystal growth zone of 0℃ ~ 5℃, and food researchers have done beneficial experiments in this regard.
② Linking food quality: Because the quick freezing time of liquid nitrogen is short, the food frozen by liquid nitrogen can link the cost of color, fragrance, taste and nutrition before processing to the maximum extent. Duan Zhenhua and others carried out liquid nitrogen quick freezing treatment on betel nut, and the results showed that the betel nut treated with liquid nitrogen had high chlorophyll content and good charm.
③ Low dry consumption of materials: the loss rate of dry consumption during freezing is usually 3-6%, which can be eliminated to 0.25-0.5% during quick freezing with liquid nitrogen.
(4) low equipment configuration and power consumption, easy to realize mechanization and active assembly line, and improve productivity.
At present, there are three important methods of liquid nitrogen quick freezing: spray freezing, immersion freezing and cold atmosphere freezing, among which spray freezing is the most widely used.
2. Application of liquid nitrogen in beverage processing
At present, many beverage manufacturers have accepted nitrogen or a mixture of nitrogen and CO2 to replace the traditional CO2, and kept the aerated packaging of beverages. High carbonated drinks filled with nitrogen have fewer problems than drinks filled with carbon dioxide only; Nitrogen is also very suitable for filling still drinks, such as wine and juice. The advantage of filling liquid nitrogen into non-aerated beverage cans is that a small amount of injected liquid nitrogen can remove oxygen from the headspace of each can, making the gas in the upper space of the tank inert, thus prolonging the storage period of perishable products.
3. Application of liquid nitrogen in fruit and vegetable storage.
Liquid nitrogen has the advantage of modified atmosphere in fruit and vegetable storage, which can adjust the supply and demand of agricultural and sideline products in peak season and off season and eliminate storage loss. The function of modified atmosphere is to increase the concentration of nitrogen, and at the same time control the gas ratio of nitrogen, oxygen and CO2, so that they can be connected in a stable state, reduce the respiratory intensity of fruits and vegetables, delay the after-ripening process, thus connecting the unfamiliar state of fruits and vegetables with the original nutritional cost and prolonging the fresh-keeping period of fruits and vegetables.
4. Application of liquid nitrogen in meat processing.
5. Application of liquid nitrogen in food low-temperature crushing.
Low-temperature crushing is the process of crushing materials cooled to the embrittlement point temperature into powder under the action of external force. Low-temperature pulverization of food is a new food processing technology developed in recent years. This skill is suitable for processing foods with high aromatic content, high fat content, high sugar content and high gum content. The punishment of low-temperature crushing with liquid nitrogen can crush all the bones, skins, meat and shells of the material at one time, making the finished product tiny and connecting with its useful nutrition.
6. Application of liquid nitrogen in food packaging
A company in London, England, has developed a simple and practical food preservation packaging method, which is to add a few drops of liquid nitrogen to the packaging bag when packaging food. When liquid nitrogen is evaporated and converted into gas, its volume expands rapidly, which quickly replaces most of the original gas in the packaging bag, eliminating the deterioration of food due to oxidation, thus greatly prolonging the shelf life of food.
7. Application of liquid nitrogen in food refrigerated transportation.
Refrigerated transportation is an important part of food industry. Opening the skills of liquid nitrogen refrigeration and developing liquid nitrogen refrigerated trains, refrigerated trucks and refrigerated containers are the same growth trend in the world today.
8. Other applications of liquid nitrogen in food industry
Due to the refrigeration effect of liquid nitrogen, egg juice, liquid seasoning and soy sauce can be roughly processed into granular frozen food that can be freely moved and poured out. These foods can be used at any time and are easy to prepare. When grinding spices and water-absorbent food additives, such as sugar substitutes and lecithin, liquid nitrogen is injected into the grinder to cover valuable identities and increase grinding output.
Application of liquid nitrogen in electronic industry
1, superconducting skills
The unique characteristics of superconductors make them widely used in various fields. Using liquid nitrogen instead of liquid helium as superconducting refrigerant to obtain superconductors enables superconducting technology to be developed and widely used, which is considered as one of the greatest inventions in science in the 20th century.
2, electronic components manufacturing and testing
Liquid nitrogen is a faster and more useful method for shielding and testing electronic components and circuit boards.
3, low temperature ball milling skills
The low-temperature planetary ball mill is a planetary ball mill equipped with a thermal insulation cover, in which liquid nitrogen gas is continuously input, and the cold air absorbs the heat generated by the high-speed rotating ball mill tank in real time, so that the ball mill tank filled with materials and grinding balls is always in a certain low-temperature environment. It is an essential equipment for high-tech material mixing, fine grinding, new product development and small batch production in low temperature environment. This product has the advantages of small size, full efficacy, high compliance and low noise, and is widely used in medicine, chemical industry, environmental protection, light industry, building materials, metallurgy, ceramics, minerals and other parts. .
4, green cutting skills
Verb (abbreviation of verb) Other application categories of liquid nitrogen
Jiuquan satellite ordered the central special combustion station to produce liquid nitrogen, which is the propellant of rocket fuel. A large amount of liquid nitrogen pushes rocket fuel into the combustion chamber at high pressure.
Used in the development of high temperature superconducting power cables; Used for emergency maintenance to freeze the liquid pipeline; Used for low-temperature stabilization and low-temperature quenching of substances; The technique of liquid nitrogen cooling device (the application of signs of thermal expansion and cold contraction in industry) is also widely used; Artificial precipitation enhancement by liquid nitrogen; Liquid nitrogen drainage technology is being deeply studied in real time. Accepting nitrogen to put out the fire underground, the fire was quickly extinguished, and the gas explosion damage was eliminated at the same time.
Choose liquid nitrogen: because it cools faster than other methods and does not react with other substances, it greatly reduces the space and provides a dry atmosphere. Environmental protection (liquid nitrogen directly volatilizes into gas and returns to the atmosphere without leaving any pollution), and it is simple and convenient to use.