Separation principle of nitrogen and carbon molecular sieve
The gas is compressed and filtered by the compressor and then enters the polymer membrane filtration device. Because the solubility and diffusion coefficient of various gases in the membrane are different, the different vapors in the membrane depend on the infiltration rate. According to this feature, various types of gas can be divided into "fast gas" and "slow gas".
There are two adsorption towers, A and B, equipped with special carbon molecular sieve for nitrogen production. When the pure compressed air enters the inlet end of the A tower and flows through the carbon molecular sieve to the outlet end, O2, CO2 and H2O are adsorbed by it, and the product nitrogen flows out from the outlet end of the adsorption tower. After a period of time, the carbon molecular sieve in Tower A was saturated with adsorption. At this time, tower A automatically stops adsorption, compressed air flows into tower B for oxygen absorption and nitrogen production, and the carbon molecular sieve in tower A is regenerated. The regeneration of the carbon molecular sieve is achieved by quickly lowering the adsorption tower to atmospheric pressure to remove the adsorbed O2, CO2 and H2O. The two columns alternately perform adsorption and regeneration, complete the separation of oxygen and nitrogen, and continuously output nitrogen. The above processes are controlled by a programmable logic controller (PLC).
When the purity value of the nitrogen at the gas outlet is set, the PLC program acts and the automatic vent valve opens to automatically vent the unqualified nitrogen to ensure that the unqualified nitrogen does not flow to the gas point. When the gas is vented, the muffler is used to reduce the noise to less than 75dBA.
When the mixed gas has the effect of the pressure difference between the two sides of the membrane, the penetration rate depends on the fast gas, such as water, hydrogen, helium, hydrogen sulfide, and co2, etc. After it penetrates the membrane, it is enriched on the infiltration side of the membrane, and the infiltration rate depends on Gases that are too slow, such as methane, hydrogen, carbon monoxide, and argon, are retained on the side of the membrane to be enriched, thereby achieving the purpose of separating the mixed gas.
When to replace the carbon molecular sieve adsorbent in the nitrogen generator adsorption tower
During the production process of the nitrogen generator, if a large amount of oil and water impurities enter the adsorption tower directly with the air and are adsorbed by the carbon molecular sieve, which causes poisoning, the adsorption capacity is seriously damaged, and the nitrogen production and nitrogen production purity of the nitrogen generator will be very large Decline. In addition, after the molecular sieve reaches a certain service life (3-5 years), its nitrogen purity will significantly decrease (it will decrease every year after replacing with a new adsorbent), and the use requirements cannot be guaranteed. In such cases, it is necessary to consider replacing the carbon molecular sieve in the adsorption tower.
Carbon molecular sieve English name: carbon molecular sieve, is an excellent non-polar carbon material, a new type of adsorbent.
The pressure swing adsorption principle (PSA) is used to separate nitrogen from air. The separation effect of carbon molecular sieve on oxygen and nitrogen in the air is mainly based on the different diffusion rates of these two gases on the surface of carbon molecular sieve. Gas molecules (O2) with smaller diameters diffuse faster and more enter the pores of the carbon molecular sieve. Larger diameter gas molecules (N2) have a slower diffusion rate and fewer pores entering the carbon molecular sieve, so that nitrogen-rich fractions can be obtained in the gas phase. Therefore, using the characteristic of the difference between the amount of oxygen and nitrogen adsorbed by a carbon molecular sieve in a certain time, the fully automatic control system applies a cycle of pressure adsorption and atmospheric pressure analysis according to a specific programmable sequence to complete the separation of nitrogen and oxygen. The desired high purity nitrogen is obtained.