1. Air Compression and Purification Process
It is essential that the raw feed air entering the carbon molecular sieve (CMS) adsorption tower is clean; the entry of particulates or organic vapors into the tower can clog the micropores of the CMS and gradually degrade its separation performance.
Methods for purifying raw feed air include: (1) positioning the air compressor intake away from areas containing dust, oil mist, or organic vapors; and (2) passing the air through systems such as refrigerated dryers and adsorbent purification units before it enters the CMS adsorption tower.
2. Product Nitrogen Concentration and Output
When generating nitrogen using CMS, both the N2 concentration and the gas output can be adjusted according to user requirements. For a fixed production cycle time and operating pressure, reducing the gas output rate increases the N2 concentration, while increasing the output rate decreases it. Users can make adjustments based on actual needs.
3. Pressure Equalization Time
In the CMS nitrogen generation process, when the adsorption phase in one tower concludes, the pressurized gas within that tower is transferred-from both the top and bottom-into the other tower (which has already been regenerated) until the gas pressures in both towers equalize. This step is known as pressure equalization. Selecting an appropriate equalization time allows for energy recovery and mitigates the impact forces exerted on the molecular sieve, thereby extending the service life of the CMS. Based on typical valve switching speeds, the pressure equalization time is generally set between 1 and 3 seconds.
4. Gas Production Time
Due to the differing adsorption and diffusion rates of oxygen and nitrogen on CMS, oxygen adsorption reaches equilibrium quickly, while nitrogen adsorption remains minimal. A shorter gas production time can effectively increase the gas generation rate of the CMS; however, it also increases the frequency of valve operations, making valve performance a critical factor. The adsorption time is typically set between 30 and 120 seconds. Shorter production times are recommended for small-scale, high-purity nitrogen generators, while longer production times are recommended for large-scale systems producing lower-purity nitrogen. 5. Operating Pressure
Carbon molecular sieves exhibit both kinetic and equilibrium adsorption effects; higher adsorbate partial pressures result in greater adsorption capacities, making pressurized adsorption advantageous. However, excessively high adsorption pressures impose stricter requirements on air compressor selection. Additionally, atmospheric regeneration and vacuum regeneration processes have different pressure requirements. Considering these factors, it is recommended to set the adsorption pressure at 5–8 kg/cm² for atmospheric regeneration processes and 3–5 kg/cm² for vacuum regeneration processes.
6. Operating Temperature
Lower adsorption temperatures enhance the performance of carbon molecular sieves; therefore, whenever feasible, it is beneficial to lower the adsorption temperature within the nitrogen generation process.