Technical article

Why does the nitrogen purity of carbon molecular sieve fluctuate greatly


Pressure swing adsorption nitrogen generator is the most important equipment for industrial nitrogen production. And carbon molecular sieve is the most important gas separation material in nitrogen generators. However, carbon molecular sieve can not be used all the time, and it also has a certain service life. It needs to be replaced when it reaches or exceeds this time to ensure the gas purity of nitrogen production.
Usually there are four points that determine the service life of carbon molecular sieves:
* Grade of carbon molecular sieve: Generally, the higher the grade of carbon molecular sieve, the longer the service life. We have type carbon molecular sieve CMS260, CMS240, CMS220 and high efficiency carbon molecular sieve CMS280, CMS300, CMS330.
* The use environment of carbon molecular sieve need keep away from moisture and oil pollution,
to ensure that the air of the air intake button is free of oil and water. The coal-based activated carbon can be preheated in advance to remove the oil and gas in the air. Make sure that no water enters the adsorption tower at the inlet end of the nitrogen generator. A dry and oil-free environment can also maximize the lifespan of carbon molecular sieves.
* Compactness of carbon molecular sieve packing: The premise is the packing density of carbon molecular sieve in the pressure swing adsorption nitrogen generator. It must be compacted to ensure that when the nitrogen generator is working, the carbon molecular sieve in the adsorption tower does not vibrate during the vibration process. It will be too loose, causing the carbon molecular sieve to pulverize.
* Regular maintenance of carbon molecular sieve nitrogen generator: the intake air temperature should not be too high, preferably 20-25 degrees. If this temperature cannot be reached, a refrigeration dryer can be configured. Generally, the higher the carbon molecular sieve grade is, the longer the service life is. A dry and oil-free environment can also maximize the lifespan of carbon molecular sieves. Of course, the premise is the packing density of the carbon molecular sieve in the pressure swing adsorption nitrogen generator.
According to actual assembly experience, under standard working conditions and regular maintenance of all components, the service life of sodium type oxygen molecular sieve and lithium molecular sieve (oxygen molecular sieve zeolite) is 5 to 8 years, and carbon molecular sieve (carbon molecular sieve for nitrogen production) ) has a service life of 6 to 10 years. Among them, the quality of the feed air has the greatest impact on the performance of molecular sieves, so the moisture in the feed air must be minimized. All in all, as long as it is scientifically used and well maintained, it is possible to prolong the life of carbon molecular sieves. 
Nitrogen purity is a very important equipment indicator. Under normal circumstances, the nitrogen purity of carbon molecular sieve remains basically unchanged. However, in actual production, the purity will also fluctuate greatly, and the main faults are as follows:
1. The adsorption pressure of the nitrogen generator is unstable, and the situation is too high or too low, which affects the production efficiency of the nitrogen equipment and causes a large change in the nitrogen purity.
2. There is a problem with the filtration system, so that the gas source contains too much water and oil, which leads to "poisoning" of the carbon molecular sieve and reduces the working efficiency of molecular sieve zeolite.
3. Air leakage at the outlet part of the interface can also lead to large fluctuations in nitrogen purity.
4. The gas consumption of the nitrogen generator is too large to cause the pressure to fluctuate too much.
When we encounter large fluctuations in the purity of product nitrogen, the improvement measures that can be taken are:
*. Reduce the outlet pressure and increase the inlet pressure.
*. Replace the carbon molecular sieve.
*. Add an air storage tank and increase the nitrogen storage tank to the air inlet of the nitrogen making system.

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Tracy Chen
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