Technical article

How to use carbon molecular sieve?

2022-03-29

Carbon molecular sieve is a new type of adsorbent developed in the 1970s. It is an excellent non-polar carbon material. Carbon Molecular Sieves (CMS) is used to separate air and enrich nitrogen. Compared with the traditional cryogenic high-pressure nitrogen production process, the low-pressure nitrogen process has the advantages of less investment cost, faster nitrogen production, and lower nitrogen cost. Therefore, it is currently the preferred pressure swing adsorption (PSA) air separation nitrogen-rich adsorbent in the engineering industry. This nitrogen is used in the chemical industry, oil and gas industry, electronics industry, food industry, coal industry, pharmaceutical industry, cable industry, metal industry It is widely used in heat treatment, transportation and storage.
The working principle of carbon molecular sieve:
Carbon molecular sieve uses the characteristics of sieving to achieve the purpose of separating oxygen and nitrogen. When the molecular sieve adsorbs impurity gas, the macropores and mesopores only play the role of channels, and the adsorbed molecules are transported to the micropores and submicropores. The micropores and submicropores are the real adsorption volumes. As shown in the previous figure, the carbon molecular sieve contains a large number of micropores, which allow the rapid diffusion of molecules with small kinetic sizes into the pores, while restricting the entry of large-diameter molecules. Due to the differences in the relative diffusion rates of gas molecules of different sizes, the components of gas mixtures can be effectively separated. Therefore, in the manufacture of carbon molecular sieve, according to the size of the molecular size, the distribution of micropores in the carbon molecular sieve should be 0.28-0.38 nm. Within this micropore size range, oxygen can quickly diffuse into the pores through the orifice of the micropore, while nitrogen is difficult to pass through the orifice of the micropore, thereby achieving the separation of oxygen and nitrogen. The pore size of the micropores is the basis for the separation of oxygen and nitrogen by carbon molecular sieves. If the pore size is too large, oxygen and nitrogen molecular sieves can easily enter the micropores and cannot achieve separation; and if the pore size is too small, neither oxygen nor nitrogen can enter. In the micropores, there is no separation effect.


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Tracy Chen
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