Understanding molecular sieves is critical for optimal PSA plant performance. Here, we clarify widespread misconceptions, thanks to our vast hands-on experience in the field of Adsorption. Read more about Molecular Sieves in our previous blog here.
Table of Contents
- 0.1 1. Topping up of Molecular Sieves requires top up every year.
- 0.2 2. Contaminated molecular sieves can be checked with physical inspection.
- 0.3 3. Contaminated molecular sieves can be regenerated.
- 0.4 4. Smaller size sieves are better.
- 0.5 5. Desorption can happen at higher pressures.
- 0.6 6. The performance of PSA plants only depends on molecular sieve quality.
- 0.7 7. The life of molecular sieves is more than 10 years.
- 0.8 8. Higher sieve quantity means better performance.
- 1 Contact Us for Expert Advice
1. Topping up of Molecular Sieves requires top up every year.
Myth.
Explanation : If the PSA bed (known as the molecular sieve bed) is properly packed and the PSA plant is designed to keep gas velocity within limits, molecular sieves will not powder, eliminating the need for annual topping up.This myth arises from experiences where poorly packed PSA beds or inadequately designed PSA plants caused sieves to powder over time. In such cases, topping up becomes necessary. However, such issues are avoided when purchasing a PSA plant from a reputable manufacturer. Proper design and packing save significant costs since molecular sieves are one of the most expensive PSA plant components.
2. Contaminated molecular sieves can be checked with physical inspection.
Myth.
Explanation: Oil and moisture contamination in input gas can degrade molecular sieves, but it is impossible to detect this contamination through physical inspection, especially in trace amounts. Even minimal oil or moisture levels can significantly affect PSA plant performance, necessitating air dryers and oil filters to maintain clean input gas before the PSA system.The most reliable method to test for contamination is using a PSA test bed to evaluate sieve performance compared to industry standards. Relying on this method ensures operational efficiency and avoids performance depletion.
3. Contaminated molecular sieves can be regenerated.
Myth.
Explanation: Regenerating molecular sieves contaminated by oil is technically challenging and economically unfeasible. Oil-contaminated sieves require extensive purging with hot gas, consuming excessive time and energy.Moisture-contaminated sieves can be regenerated by heating with dry, hot gas, but moisture weakens their structure, increasing susceptibility to powder formation. Since PSA systems operate on pressure-difference principles, weakened sieves compromise performance. Prevention through proper filtration and moisture removal systems is more cost-effective and sustainable.
4. Smaller size sieves are better.
Reality.
Explanation: Adsorption is a surface phenomenon, so smaller molecular sieve sizes provide more surface area, enhancing adsorption and improving gas separation.Additionally, smaller sieves enable better packing density, minimizing void spaces in the PSA bed. This tighter packing leads to improved performance during the separation process, further validating the use of smaller sieve sizes.
5. Desorption can happen at higher pressures.
Reality.
Explanation: Desorption occurs whenever gas transitions from a higher to a lower pressure. While maximum desorption efficiency is achieved when gas is released from high pressure to atmospheric or negative pressure (as in VPSA systems), desorption can still occur at intermediate pressures but the rate of desorption is higher when released to atmospheric or negative pressureThe adsorption rate in a PSA system increases with pressure, and desorption is most effective at lower pressures. This dynamic ensures flexibility in PSA processes, allowing desorption even when complete pressure release to atmospheric levels isn’t possible.
6. The performance of PSA plants only depends on molecular sieve quality.
Myth.
Explanation: While molecular sieve quality is critical, several other factors influence PSA plant performance, including:- a. PSA Bed Design: Ensures optimal packing and performance.
- b. Input Gas Quality: Oil- and moisture-free gas prolongs sieve life.
- c. Correct PSA Operational Cycles: Proper timing and pressure transitions enhance efficiency.
Without addressing these factors, even high-quality molecular sieves can fail. Proper system design, manufacturing, and operational practices are essential to maximize performance and avoid sieve degradation.
7. The life of molecular sieves is more than 10 years.
Reality.
Explanation: When PSA plants are properly designed and include measures to remove oil and moisture from input gas, molecular sieves can easily last over a decade. Routine maintenance and adherence to operational best practices further extend their lifespan, ensuring long-term cost-effectiveness and reliability.The adsorption rate in a PSA system increases with pressure, and desorption is most effective at lower pressures. This dynamic ensures flexibility in PSA processes, allowing desorption even when complete pressure release to atmospheric levels isn’t possible.
8. Higher sieve quantity means better performance.
Myth.
Explanation: A prevalent notion in the industry is that the quantity of the molecular sieves filled inside the PSA towers directly correlates with the PSA plant performance and output gas quality. On the other hand, the required quantity of molecular sieves depends on the desired flow and purity of the output gas.Leading PSA manufacturers perform precise engineering calculations to ascertain the sieve quantity and other additives. It is to be noted that a higher quantity of sieves may harm plant performance as it will lead to higher air consumption and longer time cycles.
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the best molecular sieves or optimizing your PSA plant performance?
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