Guidelines and specific application sites of molecular sieves
Time:2025-07-16
There are many types of molecular sieves in the market, so which one should be chosen to better suit customers' applications?
Step 1: Clarify the characteristics of the separated substances
|
Molecule Substance |
Recommendation |
Reason |
Project |
|
H2O |
3A molecular sieve |
Pore diameter 0.3nm which just adsorb water |
Ethanol dehydration, lithium battery electrolyte drying |
|
CO2 |
13X molecular sieve |
Strong polarity adsorption, CO2 capture rate>90% |
Biogas purification, CO2 recovery from breweries |
|
Butane |
5A molecular sieve |
Pore size 0.5nm, sieving isomeric alkanes |
Separation of Normal/Isomeric Alkanes in Petroleum Refining |
|
O2 |
LiLSX molecular sieve |
Selective adsorption of nitrogen and oxygen |
Medical oxygen generator (93% purity oxygen) |
Step 2: Check the operating environment and select the "pressure resistant" molecular sieve
|
working conditions |
Preferred molecular sieve |
Advantage |
|
High temperature>150 ℃ |
High silicon Y-shaped |
Thermal decomposition temperature>800 ℃ |
|
Acidic environment pH<5 |
ZSM-5 |
Acid resistant and corrosion-resistant, with a threefold increase in lifespan |
|
Oil and fog scenes |
Pre filter+4A molecular sieve |
Prevent oil poisoning, regeneration times>3000 times |
Step 3: The followings are several common used application scenarios
1. New energy battery moisture-proof guard
* Common problem: Decomposition of electrolyte upon contact with water
* Solution: The filtration tank with 3A molecular sieve
* Effect: Moisture content below 10ppm
2. Core materials for hospital oxygen concentrators
* Common problem: Traditional oxygen production purity <90%
* Solution: The adsorption tower with LiLSX molecular sieve
* Effect: 93% medical oxygen, in line with ventilator standards
3. Dehydration of natural gas pipelines
* Common problem: Moisture condensation corrodes pipelines
* Solution: The drying tower with 4A molecular sieve
* Effect: Dew point -70 ℃, pipeline life extended by 5 years
4. Purification of alcohol fuel
* Common problem: Ethanol contains water and is difficult to burn
* Solution: The fixed bed with molecular sieve 3A
* Effect: Fuel grade ethanol (moisture<0.3%)
5. Refrigerator refrigerant protection
* Common problem: R134a refrigerant hydrolysis and acid corrosion
* Solution: Built in 5A molecular sieve desiccant
* Effect: Cooling efficiency increased by 15%, compressor lifespan extended by 3 years
Air adsorption dryers are familiar in the chemical industry, and their core components are adsorbents , such as activated alumina, molecular sieves, silica gel. They adsorb water and gas through a porous structure, and their performance affects the drying effect directly. As the adsorption regeneration cycle progresses, the adsorption capacity gradually decreases and needs to be replaced regularly to ensure stable system operation.
The replacement cycle is usually 3-5 years, but it needs to be adjusted based on the following factors:
1. Frequency of use: High frequency use will accelerate the saturation of the adsorbent, and the cycle needs to be shortened; Long term high load operation will accelerate the decline of adsorbent performance;
2. Environmental humidity: The higher the humidity of the inlet air, the greater the adsorption load and the corresponding decrease in lifespan; High temperature, high dust and other harsh environments may require early replacement.
3. Operating parameters: Abnormal pressure or increased dew point temperature may indicate adsorbent failure.
Meanwhile, during work, it is important to pay attention to the following matters:
1. Monitoring indicators: Regularly monitor the dew point temperature at the outlet, and if it continues to exceed the standard, check the status of the adsorbent.
2. Replacement operation: Thoroughly clean the adsorption tower during replacement to avoid mixing of new and old adsorbents; The filling should be evenly compacted to prevent air flow short circuits.
3. Selection matching: The new adsorbent should be consistent with the prototype number to ensure that the porosity and mechanical strength meet the requirements.
4. Regeneration inspection: After replacement, verify the regeneration effect and confirm that the heating temperature and cooling time are normal.
So how to choose the right adsorbent for an adsorption dryer?
1) Molecular sieve: It is a crystal structure with uniform pore size and strong adsorption ability for water molecules, especially suitable for precision industrial scenarios with dew point below -60 ℃. However, due to its low strength, it is easy to be pulverization under high-intensity compressed air impact, so it can only be used in small quantities in traditional twin tower adsorption dryers.
2) Activated alumina: It is a high-strength adsorbent and the most widely used adsorbent in adsorption dryers currently. It can withstand the high-pressure impact of compressed air without powdering. Excellent performance in moderate humidity environments, suitable for places with dew point below -40 ℃, with a regeneration temperature 30-50 ℃ lower than molecular sieves.
3) Silica gel adsorbent: It’s getting less and less in compressed air drying. It is only suitable for drying at room temperature and is used in pressure dew point environments of -20 ℃.
In terms of drying performance, molecular sieves are much stronger than activated alumina, but the replacement cost is higher. Therefore, before choosing which adsorbent, it is necessary to understand the user's requirements or expectations for dew point, so as to choose the best solution that can meet the user's requirements and reduce the cost of use.
