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Principle of Nitrogen Purification by Pressure Swing Adsorption on Carbon Molecular Sieve

Цаг: 2021-04-29 Үзсэн: 15

A complete adsorption and separation process is usually composed of adsorption and desorption cycle operation. Due to different engineering means to achieve adsorption and desorption operation, the process is divided into pressure swing adsorption and temperature swing adsorption. Pressure swing adsorption completes the operation cycle of adsorption and desorption by adjusting the operating pressure (pressure adsorption, decompression desorption), while temperature swing adsorption completes the operation cycle by adjusting the temperature (cooling adsorption, heating desorption) to complete the cycle operation. Pressure swing adsorption is mainly used in physical adsorption process, and temperature swing adsorption is mainly used in chemical adsorption process.

Pressure swing adsorption of нүүрстөрөгчийн молекулын шигшүүр is to use air as raw material and carbon molecular sieve as adsorbent to separate nitrogen and oxygen in air by pressure swing adsorption, so as to achieve the purpose of purifying nitrogen.


The adsorption of substance on adsorbent (solid) surface must go through two processes: one is to reach the solid surface by molecular diffusion, the other is to adsorb on the solid surface by Van der Waals" force or chemical bonding force. Therefore, in order to achieve the separation of mixtures by adsorption, the separated components must have obvious differences in molecular diffusion rate or surface adsorption capacity.

The adsorption and separation of N2болон О2in air by нүүрстөрөгчийн молекулын шигшүүр is based on the difference of diffusion rate between them. N2болон О2are both nonpolar molecules, and their molecular diameters are very close (O2is 0.28nm, N2is 0.3nm). Due to their similar physical properties, there is little difference between them and the surface of carbon molecular sieve. Therefore, from the perspective of thermodynamics (absorption equilibrium), carbon molecular sieve has no selectivity for N2болон О2adsorption, so it is difficult to separate them.


However, from the kinetic point of view, because нүүрстөрөгчийн молекулын шигшүүр is a rate separation adsorbent, the diffusion speed of N2болон О2in the micropores of carbon molecular sieve is obviously different. For example, at 35 , the diffusion speed of O2нь 2.0 юм × 106, and the speed of O2is 30 times faster than that of N2. Therefore, when air contacts carbon molecular sieve, O2will be preferentially adsorbed on carbon molecular sieve and separated from the air,so that N2in the air can be purified. Since the adsorption separation process is a rate controlled process, the control of adsorption time (that is, the control of adsorption--desorption cycle rate) is very important. When the adsorbent dosage, adsorption pressure and gas flow rate are fixed, the appropriate adsorption time can be determined by measuring the breakthrough curve of the adsorption column.