Knowledge Sharing: Introduction to the Working Principle and Performance Parameters of Membrane-Based Nitrogen Generators

In the field of industrial gas production, membrane nitrogen generators are widely used due to their high efficiency and convenience, and the hollow fiber membrane is the core component for efficient nitrogen production. Next, let's take a detailed look at its working principle and key performance parameters.

I. Working Principle

Air is mainly composed of 78% nitrogen, 21% oxygen, and a small amount of other gases. The hollow fiber membrane in the membrane nitrogen generator achieves gas separation based on the difference in solubility and diffusion coefficient of different gases in the membrane material.

When raw air with a pressure of usually 0.6 - 0.8 MPa enters the membrane module, the components of the air contact the membrane surface. Oxygen, water vapor, and other gas molecules, due to their small kinetic diameter and high diffusion coefficient, preferentially pass through the membrane wall under pressure drive and accumulate on the other side of the membrane to form permeate; nitrogen molecules have a relatively large diameter and low diffusion coefficient, resulting in a slow permeation rate, and continuously accumulate on the raw gas side to form high-purity nitrogen. By adjusting parameters such as inlet pressure, flow rate, and the number of membrane modules, the flow rate and purity of the produced nitrogen can be controlled to meet the needs of different users.

II. Performance Parameters

Gas Permeability:

Refers to the amount of gas passing through the membrane per unit time and unit membrane area under a certain pressure difference. It is an important indicator for measuring the performance of hollow fiber membranes. The higher the gas permeability, the faster the membrane separation of gases, and the higher the nitrogen production efficiency. For example, the polyimide hollow fiber membrane has a high oxygen permeability, which allows oxygen to quickly pass through the membrane wall and be discharged, thereby efficiently enriching nitrogen.

Selectivity:

Characterizes the difference in the membrane's permeability to different gases, usually expressed as the ratio of the permeability of a certain gas to that of nitrogen. The higher the selectivity, the better the membrane's separation effect between nitrogen and other gases, and the higher the purity of the produced nitrogen. An ideal hollow fiber membrane should have high selectivity, minimizing the mixing of impurities and achieving efficient nitrogen enrichment.

Mechanical Strength:

Since the hollow fiber membrane needs to withstand a certain pressure during operation, its mechanical strength determines whether the membrane can maintain its structural integrity during long-term operation, avoiding breakage and deformation, to ensure the stable operation of the nitrogen generator. Hollow fiber membranes made of polysulfone material have high mechanical strength and can adapt to complex industrial environments.

Chemical Stability:

During nitrogen production, the membrane will contact trace impurities and other chemical substances in the compressed air. Membranes with good chemical stability can withstand the corrosion of these chemical substances and maintain their separation performance in different chemical environments, extending their service life.

Thermal Stability:

Some nitrogen production processes involve temperature changes. Hollow fiber membranes with good thermal stability will not experience performance degradation or deformation due to temperature fluctuations within a certain temperature range, ensuring that the nitrogen generator operates normally under different temperature conditions. For example, polyimide hollow fiber membranes have excellent high-temperature resistance and are suitable for high-temperature nitrogen production processes.

The working principle and performance parameters of the hollow fiber membrane directly affect the nitrogen production effect and operational stability of the membrane nitrogen generator. With continuous technological development, the performance of hollow fiber membranes will continue to be optimized, providing higher-quality nitrogen production solutions for industrial production and other fields.