Nitrogen production equipment by membrane separation

Working principle and product characteristics

Membrane separation technology is a kind of high-tech developed in the middle of the 20th century. In the past 20 or 30 years, it has been developed rapidly in the world. Membrane separation technology is bringing great benefits to human beings. The membrane has the characteristics of selective permeation and diffusion to some gas groups, so the purpose of gas separation can be achieved. Hollow fiber membrane is actually a number of microporous tube fiber membranes with the same internal and external diameters, and its structure is similar to that of tubular heat exchanger. The fiber bundles are independent of each other and sealed with epoxy resin at both ends of the membrane group. Hundreds of thousands of fibers are bundled together to provide the required surface area. Under the action of pressure, the adsorption, diffusion and permeation rates of various gases in the hollow fiber membrane are different. They are arranged in order. We call the gas with high penetration rate as "fast gas", such as oxygen and water gas; the gas with low penetration rate is called "slow gas", such as nitrogen. After the gas mixture passes through the membrane, the "fast gas" is enriched at the outer side of the low pressure, and the "slow gas" is enriched in the inner side of the high pressure.

Generally, all gases can permeate through the polymer membrane. The process is that the gas molecules are firstly absorbed and dissolved on the surface of the high pressure side of the membrane, then diffused in the membrane with the help of concentration gradient, and finally resolved from the low pressure side of the membrane. The result is that small molecules and highly polar components (such as water vapor, oxygen, carbon dioxide, etc.) pass through faster and are enriched at the permeation side of the membrane However, macromolecules and molecules with weak polarity (such as nitrogen, argon, etc.) pass slowly and are trapped in the retention side of the membrane and enriched to achieve the purpose of gas mixture separation. Membrane separation is to use the different permeation rate of various gases on the polymer membrane to separate gas. The driving force of separation is the differential pressure of gas on both sides of the membrane. Therefore, membrane gas separation has no phase change and no regeneration. It has the advantages of simple equipment, low operation and maintenance costs. A membrane separator (module) is composed of thousands of hollow fiber separation membranes assembled in a shell. Its structure is similar to the tubular heat exchanger. It can provide the maximum separation membrane surface area in the smallest space. Therefore, the membrane separation system has the advantages of small footprint, light weight and high separation efficiency.