Principle of Industrial Gas Separation Technology

Principle of Industrial Gas Separation Technology

Industrial gas separation technology refers to the technology of separating different components in a mixed gas by physical or chemical methods. These technologies are widely used in the fields of chemical industry, petroleum, medicine, food, etc. The following are several common industrial gas separation technologies and their principles:

1. Cryogenic method (low temperature method)

Principle
The cryogenic method utilizes the liquefaction characteristics of gas at low temperature. It liquefies the mixed gas by cooling it to an extremely low temperature, and then separates it according to the difference in boiling points of different components. For example, the boiling points of oxygen and nitrogen in the air are -183℃ and -196℃ respectively. By gradually increasing the temperature, nitrogen can be evaporated first, and the remaining is mainly liquid oxygen.

Application
The cryogenic method is mainly used for large-scale production of high-purity oxygen, nitrogen and argon. It has been widely used in air separation units (ASU).

2. Adsorption method

Principle
The adsorption method utilizes the selective adsorption ability of porous materials (such as molecular sieves) for different gas molecules to adsorb the target components in the mixed gas. Molecular sieves have different selective adsorption capacities for oxygen and nitrogen, so these two gases can be separated by adsorption.

Application
Adsorption is often used in small gas separation equipment, especially when rapid separation is required. It is easy to operate and has low operating costs, but it is difficult to obtain high-purity products.

3. Membrane separation method

Principle
Membrane separation method uses the difference in permeability of certain polymer membranes to different gas molecules. When the mixed gas passes through the membrane, the permeation speed of different gas molecules is different, thereby achieving separation. For example, oxygen passes through the membrane much faster than nitrogen, so oxygen and nitrogen can be separated by membrane separation.

Application
Membrane separation method is suitable for the production of oxygen-rich products, but due to the low purity of the product and the small scale, its application in industry is limited.

4. Pressure swing adsorption (PSA)

Principle
The pressure swing adsorption method uses the adsorption and desorption characteristics of gas at different pressures. By periodically changing the pressure, the target gas is adsorbed at high pressure and desorbed at low pressure, thereby achieving separation. For example, under high pressure, molecular sieves adsorb nitrogen, while under low pressure, nitrogen is released, thereby separating oxygen.

Application
Pressure swing adsorption is widely used in small and medium-sized oxygen and nitrogen production plants, especially when flexible adjustment of production is required.

5. Vacuum pressure swing adsorption (VPSA)

Principle
Vacuum pressure swing adsorption is based on pressure swing adsorption and introduces vacuum operation to improve separation efficiency and product purity. By introducing vacuum at low pressure, the adsorbed gas can be desorbed more thoroughly, thereby improving the separation effect.

Application
VPSA technology is often used in the production of high-purity gases, especially when extremely high purity oxygen and nitrogen are required.

Conclusion
Industrial gas separation technology plays an important role in modern industry. Different separation technologies have their own advantages and scope of application. Choosing the right technology can greatly improve production efficiency and product quality. Cryogenic method, adsorption method, membrane separation method, pressure swing adsorption method and vacuum pressure swing adsorption method are several common industrial gas separation technologies, which play an important role in their respective fields.