How does carbon molecular sieve enhance the nitrogen recovery rate?
"Nitrogen recovery rate" refers to the proportion of the actual nitrogen quantity obtained from the raw air to the theoretically obtainable nitrogen quantity, which is an important indicator for measuring the efficiency of the nitrogen production system. Increasing the nitrogen recovery rate means obtaining more nitrogen with the same amount of air or reducing waste gas emissions. Carbon molecular sieves do not directly "create" nitrogen, but they indirectly increase the nitrogen recovery rate through the following mechanisms:
1. Excellent oxygen-nitrogen selective adsorption capacity
Carbon molecular sieves have a much higher adsorption rate for oxygen than for nitrogen, allowing most of the oxygen to be adsorbed within a short period (several seconds to several tens of seconds), while nitrogen passes through preferentially, achieving efficient separation.
2. Fine pore size control and adsorption kinetics differences utilization
The micro-porous structure of CMS has been specially regulated, making it exhibit significant adsorption rate differences (kinetic separation) for different gases, rather than just differences in equilibrium adsorption amounts. This kinetic separation effect is a major advantage of carbon molecular sieves compared to traditional zeolite molecular sieves (such as 5A, 13X) in PSA nitrogen production.
3. Optimized adsorption cycle and process control
By reasonably designing PSA process parameters (such as adsorption pressure, time, bed layers, gas flow distribution, etc.) and selecting high-performance carbon molecular sieves, it can:
• Extend the nitrogen production time (i.e., prolong the adsorption step, preventing oxygen from penetrating too quickly);
• Shorten the ineffective time during the adsorption cycle;
• Increase the nitrogen output per cycle;
• Reduce nitrogen loss during the purge (exhaust) stage;
4. Reduce oxygen penetration and product nitrogen pollution
If the performance of CMS is poor (such as aging, fragmentation, contamination, etc.), it may lead to increased oxygen penetration, and to ensure nitrogen purity, more gas needs to be switched or discharged in advance, thereby reducing the nitrogen recovery rate. Using high-quality, stable carbon molecular sieves can maintain high oxygen-nitrogen separation efficiency, allow for longer nitrogen production time, and thereby increase the overall recovery rate.
5. High utilization rate of adsorbent and excellent regeneration effect
During the low-pressure or vacuum desorption stage (usually at atmospheric pressure purge or reduced pressure), the carbon molecular sieve can thoroughly desorb the adsorbed oxygen, achieving efficient regeneration. This enables the adsorbent to maintain good performance after multiple cycles and produce stable nitrogen.
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