What are the uses of nitrogen? How much do you know about these fields?

With the rapid development of the air separation equipment manufacturing industry for the cryogenic production of O2 and N2, the application range of N2 has been rapidly expanded. N2 is not only used in industry, but also widely used in food and medical fields. In the past, many substances were extracted using CO2, but with the significant increase in liquid N2 production capacity, replacing CO2 with liquid N2 in extraction has become highly possible and practical.

Under normal pressure, the solubility of N2 in liquids and solids is extremely low, but it increases with increasing pressure, especially for organic compounds. Although gases such as SO2, NH2, and C2H4 also have good solubility in liquid or supercritical states, they are not chemically inert substances, and their residue in the extracted substance is harmful. When CO2 dissolves in water or contains a certain amount of water, it becomes acidic, affecting the activity, pH value, and quality of the extracted substance.

Liquid N2, as an inert substance, is non-acidic and does not affect the extracted substance, offering greater safety. Liquid N2 has many advantages as a solvent to replace CO2. As an extraction solvent, liquid N2 can dissolve low- and medium-molecular-weight esters, ketones, alcohols, ethers, aldehydes, and non-polar organic compounds, and can dissolve some alkaloids, chlorophyll, carotene, fruit acids, and sugars in critical N2.

The N2 solvent extraction process is roughly divided into solvent extraction (separation of extract and raffinate) and solution regeneration (separation of extract and extractant). The extraction rate of the extract should be considered in the extraction process. Using N2 as a solvent to extract and purify substances is a new topic requiring in-depth research, with high scientific value. Industrial applications of using N2 to extract food, beverages, oils, spices, and pharmaceuticals have been reported both domestically and internationally.

As an extraction solvent, N2 does not damage the structure of natural substances at low temperatures, which is beneficial for preserving the substance structure. Therefore, the physicochemical properties of N2 can be used to our advantage.

The application space of cryogenic liquids is very broad. We use relevant data as examples of cryogenic liquid applications. A naval hospital in Shanghai used a cryogenic scalpel with cryogenic liquids, achieving good medical results for malignant tumor patients where radiotherapy and chemotherapy were ineffective.

Under CT guidance, the cryosurgical probe (argon-helium cryosurgical probe) is accurately inserted into the lung cancer mass. The action of low-temperature argon gas (liquid argon vaporization) freezes the tumor tissue to -130℃ within 10 minutes, forming an ice ball. Then, helium gas melts the ice ball, killing tumor cells at extremely low temperatures. This surgery is performed under computer monitoring. Data shows that the cancerous tissue can be frozen into an ice ball within minutes, causing the cancerous tissue to rupture and necrosis. This is an advanced international cryotherapy technology that not only solves the problem of cryogenic injury to normal tissues but also allows for rapid heating to a certain temperature followed by secondary rapid freezing for more thorough elimination of cancerous tissue.

Argon-helium cryosurgery technology was developed by simulating space rocket guidance technology in the United States. It is reported that cryosurgery technology has been successfully used to treat patients in Shanghai, Xi'an, and Beijing. The application of cryosurgery has promoted deeper research in some scientific research units, using high-purity to ultra-high-purity N2 (6-7N) in cryosurgery technology. It must also be mentioned that cryosurgery technology has completely solved the problem of thermal insulation of the cryoprobe.

N2 is widely used in food and medicine. Some health products on the market now utilize the low-temperature physicochemical properties of N2. Under low-temperature and vacuum conditions, health products are ground into powder, vacuum-dried, and then filled into capsules. This method can be applied to tortoise shell, snake gall, bear gall, and biological system products.

In the 3D printing industry, N2 is mainly used for gas protection and nozzle cooling during various 3D printing processes. This results in smooth product surfaces without further polishing, prevents material oxidation to achieve optimal density, and offers advantages such as ease of use, stable performance, and convenient operation. The future applications of N2 and other cryogenic liquids are very broad, requiring continuous research and development.