Industrial nitrogen refers to nitrogen gas used in industrial production processes. Nitrogen is a colorless, odorless, and tasteless gas with the chemical symbol N ₂. It is chemically inactive at room temperature and pressure. The purity of industrial nitrogen varies according to different application requirements, generally ranging from 99% to 99.999%.
1. Preparation method
Cryogenic air separation method:
This is one of the main methods for producing nitrogen in industry. This method is based on the different boiling points of various components in the air, by deeply freezing and liquefying the air, and then using the principle of fractionation to separate gases such as oxygen and nitrogen. At standard atmospheric pressure, the boiling point of oxygen is -183 ℃, and the boiling point of nitrogen is -195.8 ℃. After compressing, cooling, and liquefying the air, the liquid air is first heated in the distillation tower, and the nitrogen gas with a lower boiling point is first vaporized and separated to obtain high-purity nitrogen gas. This method produces nitrogen with high purity, reaching over 99.999%, which can meet the extremely high requirements for nitrogen purity in industrial applications such as the electronics industry.
Pressure swing adsorption (PSA) method:
The pressure swing adsorption method utilizes the difference in adsorption capacity of adsorbents for oxygen, nitrogen, and other components in the air to produce nitrogen gas. Adsorbents (such as carbon molecular sieves) have a strong adsorption effect on impurities such as oxygen under pressure, but a weaker adsorption effect on nitrogen. When air passes through an adsorption tower equipped with an adsorbent, impurities such as oxygen are adsorbed on the surface of the adsorbent, while nitrogen flows out through the adsorption tower. By periodically changing the pressure of the adsorption tower for adsorption and regeneration, nitrogen is continuously produced. This method has the advantages of simple equipment, easy operation, and low energy consumption. The purity of nitrogen is generally between 99% and 99.99%, and it is commonly used in industries such as chemical and metallurgical.
2. Application Fields
Chemical industry:
Synthetic ammonia production: Nitrogen is one of the important raw materials for synthetic ammonia. In the Haber Bosch process for synthesizing ammonia, nitrogen and hydrogen react under high temperature, high pressure, and the action of a catalyst to produce ammonia. The reaction equation is:$ N_{2}+3H_{2}\rightleftharpoons2NH_{3}$。 Industrial nitrogen provides a stable nitrogen source for the synthesis of ammonia, and during the production process, nitrogen can also be used for system purging and displacement to prevent oxygen and other impurities from mixing with flammable and explosive hydrogen gas and causing explosions.
Protective gases for chemical products: In chemical production, many organic compounds and fine chemicals are sensitive to oxygen, moisture, and other substances. For example, when producing products such as plastics, rubber, coatings, etc., using industrial nitrogen as a protective gas can prevent the products from being oxidized and dampened during processing and storage, thereby ensuring the quality and performance of the products.
electronics industry:
In the semiconductor manufacturing process, there are extremely high requirements for environmental cleanliness and gas purity. Industrial nitrogen is used for cleaning, etching, and drying processes in the manufacturing process. For example, during the silicon wafer cleaning process, nitrogen can blow away impurities and moisture on the surface of the silicon wafer, and due to its stable chemical properties, it will not undergo chemical reactions with the silicon wafer. In photolithography and etching processes, nitrogen can be used as a carrier gas to transport the reaction gas to the reaction chamber and prevent external air from entering, ensuring the accuracy and reliability of the process.
Metallurgical industry:
Steel production: In the steelmaking process, nitrogen can be used as a stirring gas for converter steelmaking and electric furnace steelmaking. By blowing nitrogen into the molten steel, the stirring of the steel can be strengthened, making the composition of the steel more uniform, and also helping to remove impurities such as hydrogen and oxygen from the steel, improving the quality of the steel. In addition, in the production of some special steels, such as stainless steel and high-strength alloy steel, nitrogen can also be added as an alloying element to improve the performance of the steel.
Nonferrous metal smelting: In the smelting process of non-ferrous metals such as aluminum, copper, etc., nitrogen can be used to cover the surface of the melt to prevent the metal from being oxidized. For example, in the smelting process of aluminum, nitrogen can effectively prevent the reaction between aluminum liquid and oxygen in the air to produce alumina, reduce metal loss, and improve product recovery rate.
Food industry:
Food packaging: Industrial nitrogen is used for food packaging mainly to extend the shelf life of food. For example, in the packaging of snack foods such as potato chips and cookies, filling nitrogen can eliminate the oxygen inside the packaging, preventing the food from oxidizing, deteriorating, and getting damp. Because oxygen can cause problems such as fat oxidation and microbial growth in food, while nitrogen as an inert gas can effectively avoid these situations. At the same time, nitrogen can also cause packaging to expand, providing cushioning and protecting food from compression damage during transportation and storage.
Beverage industry: Nitrogen is also used in the production process of beverages such as beer and carbonated drinks. For example, in the process of beer canning, filling an appropriate amount of nitrogen can improve the taste of beer and make the beer foam more delicate and lasting.
