Molecular sieve air separation for nitrogen production mainly relies on the microporous structure of molecular sieve materials to achieve the separation of oxygen and nitrogen. This technology separates oxygen and nitrogen by filtering the mixed gas through a molecular sieve bed. The size of micropores in molecular sieve materials can be precisely controlled, allowing for selective adsorption of oxygen rather than nitrogen. Therefore, this technology can achieve efficient and precise preparation of nitrogen.

The molecular sieve air separation nitrogen production technology has the following advantages:

1. Efficient and energy-saving. This technology does not require the use of energy intensive substances such as liquid air or compressed air, and can directly use air for nitrogen preparation, thereby achieving energy conservation and cost reduction.
2. Environmental protection. The molecular sieve air separation nitrogen production technology does not produce any pollutants, so it can achieve green nitrogen production.
3. Strong flexibility. The microporous structure of molecular sieve materials can be adjusted as needed to achieve the separation of oxygen and nitrogen under different pressures.

This technology also has some drawbacks, such as:

1. High quality molecular sieve materials are required. The preparation of molecular sieve materials requires precise processes and high-purity raw materials, so the price is relatively expensive.
2. There are certain limitations on the service life of molecular sieve materials. The service life of molecular sieve materials is limited by usage conditions, such as airflow velocity, operating temperature, etc.

General methods for nitrogen production

At present, there are various methods for nitrogen production, including ambient temperature adsorption gas separation, low-temperature separation, membrane separation, compression adsorption, etc. These methods each have their own advantages and disadvantages, but in practical applications, low-temperature separation and compression adsorption are commonly used.

The principle and process of nitrogen production from molecular sieves

Molecular sieve nitrogen production is a low-temperature separation technology for nitrogen production. Its principle is to use the adsorption and desorption of gas molecules by molecular sieves to separate gases from the air through pressure and temperature changes, thereby obtaining pure nitrogen.

The specific process is as follows:

After pre-treatment, the air enters the nitrogen production unit.

2. The air first passes through an alternating adsorption device to remove impurities such as moisture and carbon dioxide.
3. Air enters the molecular sieve adsorption column, where nitrogen molecules are selectively captured at low temperatures, while other gas molecules such as oxygen are rapidly released.
4. After the nitrogen molecules in the molecular sieve adsorption column are saturated, pure nitrogen is released from the molecular sieve adsorption column through steps such as desorption column and pressure swing.

Air is an inexpensive industrial raw material that contains nitrogen, oxygen, argon, as well as moisture, carbon dioxide, and hydrogen sulfide. The oxygen produced by air separation can be used for steelmaking, and pure oxygen and oxygen enriched air can also be used for non-ferrous metal smelting and biological fermentation; The nitrogen obtained from air separation can be used in fertilizer production, metallurgical industry, refrigerants, etc. However, in both direct and indirect applications of air, it is necessary to first remove moisture and substances such as carbon dioxide from the air. Because these ingredients often cause serious harm.

Drying air with molecular sieves is very convenient and effective. It can completely remove moisture at room temperature and pressure. At medium and high pressure, in addition to dehydration, it can also simultaneously remove carbon dioxide and acetylene. Moreover, under the same conditions, drying air with molecular sieves can achieve a lower dew point than using silica gel, and the adsorption capacity is 3-4 times higher.

Before using molecular sieve air separation for oxygen production, it is necessary to first remove moisture, carbon dioxide, and acetylene from the air. Otherwise, water and carbon dioxide can cause freezing of the low-temperature fractionation system, while acetylene can cause explosions.

Water, carbon dioxide, and acetylene are highly polar or unsaturated molecules, and molecular sieves have a strong affinity for them. The order of affinity is H2O ≥ C2H2 ≥ CO2, therefore, the degree of air purification is mainly determined by the effectiveness of CO2 removal.

The kinetic activity of molecular sieves for CO2 adsorption is related to temperature, air pressure, and flow rate. Practice has shown that using 13X and 5A molecular sieves under medium and high pressure can simultaneously remove moisture, carbon dioxide, and acetylene from the air. When using an oxygen concentrator to produce oxygen, compressed air can be sent to a distillation tower for cryogenic separation into nitrogen and oxygen after being adsorbed by a molecular sieve once.