carbon molecular sieve, China Carbon Molecular Sieve Co, Ltd.


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The Principle and process of producing nitrogen by carbon molecular sieve

       1,The carbon molecular sieve (CMS)is a kind of nonpolarity sorbent and they have the pore size of 3-5a micropores . The capability of air separating is based on its skeletal framework.and Pressure-swing adsorption (PSA) nitrogen-making is realized through the features that carbon molecular sieve has selective of adsorption and the difference adsorption capacity under different pressure.

In dynamics, CMS has different adsorptive rate for oxygen and nitrogen. Under balanced condition , the adsorption by CMS towards O2 and N2 is very close, however, the speed O2 molecule passing through the framework is faster than N2 molecule, this principle is the bases of CMS N2 generation. Before the adsorption, oxygen and other impurities are adsorbed by the CMS, allowing unabsorbed nitrogen to pass through the bed.
 2This apparatus is often called Air Separation Nitrogen Plants. The process uses the principle of Pressure Swing Adsorption(PSA).

Pressure-swing adsorption nitrogen-making is realized through the features that carbon molecular sieve has, of selective adsorption and the difference adsorption capacity under different pressure. Oxygen molecular are withheld by carbon molecular sieve because its spreading speed is much quicker than nitrogen molecular in the carbon molecular sieve' minute hole structure when the pressure is raising, while the adsorption to nitrogen molecular are relieved by the oxygen gas. It makes carbon molecular sieve regenerate, forms circulatory operation, and realizes nitrogen-making continuously.
 The PSA process includes; Pressure adding, Nitrogen producing, Pressure balancing; Pressure reducing, Nitrogen releasing; then repeat these procedures again,...and the circulation process was formed by these procedures .According to the style of regeneration, the process can be concluded into regelaeration in vacuum process (VPSA)and regeneration in normal pressure process.
 According to the demands of clients, the nitrogen generation plant based on the PSA-process can consist into; the air pressing and purifying system, pressure swing and adsorption system, programmable valve controller system(the VPSA process even in need of the vacuum pump),and Nitrogen supply system.
 ,3The principle in controlling nitrogen generation by CMS
 (1),.Air compressing and purifying process.
 It is very necessary to let purified air into the adsorption tower, because if mote and organic gas entered the adsorptiorn tower, they will jam the skeletal framework, later it will lower the effects of generating.
 The means to purify air; a. To keep the inlet of air compressing machine far away from dust, oil frog as well as organic gas; b. The raw material air, which pumped into the CMS adsorption tower, should first get through filter and cooler, also the purifying system filled with sorbent, later it will undergo a further transaction.
 (2),.The N2 purity and production capacity.
 When generation nitrogen by CMS, the N2 concentration and production capacity can be adjusted according to the needs of users. In a certain time and under a certain pressure, when reducing the production, the purity would rise; Otherwise, it would fall. User can adjust according to their practical needs.
 (3).The time period for pressure balancing.
 In the process of generation, when one tower ends its adsorption, the compressed air can be immitted both from top and bottom into the other adsorption towers which had been regenerated, and then the two towers reach the same pressure, this process is called the pressure balancing between the two adsorption towers. If choosing a proper time for pressure balancing, it cannot only reclaim the energy, but also reducing the impingement CMS received, as a result, the purpose of prolonging the longevity of CMS is reached. With the reference to the speed of valve switching, the time for pressure balancing should be 1 to 3s.
 (4).N2 producing time period.
 According to the fact that CMS have different rate in adsorption of N2 and it can saturate in a short time when adsorbing O2,while at the same time the amount of N2 adsorbed is small. The relatively short time period of nitrogen generation can also adds the frequency of valve switching, SO the performance of the valve is also very important. The normal time period of adsorption is 30 to 120s.Small-sized high purity N2 generator is recommended to have short period of generation time, while large-sized low purity generation long.
 (5).Operational Pressure
 CMS has both the effect of dynamics and the effects of adsorption by depressurization. The capacity of adsorption raises when the pressure put on to the CMS is high, so adsorption by adding pressure is favorable, but the pressure adding demands higher model of air compressor.
 Concerning adsorption pressure, the requirements in the process of normal pressure regeneration and vacuum generation is different. After considering an these conditions, the adsorption pressure under normal pressure is suggested to choose 5 to 8kg/cm2, vacuum 3 to 5kg/cm2.
 As a sorbent, the relatively lower tempemture is good for the exertion of CMS. If possible, it is favorable for the nitrogen generator to lower the temperature of adsorption.
 4. The package and usage of the product.
 1.The products undergo strict check and measure in line with the standards of our company, so as to insure the quality of the product.
 2),The products are airproofed in plastic barrels; the performance of hermetic package is reliable, open when padding into the generation towers, proof from moisture.
3).The padding should be tight, please make them tight and firm with proper method, don't pug it with a stick directly.