Molecular sieve powdering is the main fault of PSA system, which is mostly caused by equipment commissioning, filling and molecular sieve quality problems.
Raw Material Gas Carries Water
Molecular sieves have strong water absorption and a strong affinity for water. It is difficult to desorb it by ordinary physical methods after absorbing water. The PSA system can hardly be removed under normal temperature conditions, resulting in a significant drop in the adsorption capacity of the molecular sieve and an increase in system pressure. After the molecular sieve absorbs water, the lateral pressure resistance is greatly reduced, and the molecular sieve is easily damaged during the frequent pressure equalization process of the PSA system.
High System Pressure
Molecular sieves are particles with a porous structure. In the original design of PSA, full consideration should be given to the pressure resistance of molecular sieve. High pressure is good for adsorption, but it will cause bed fluctuations. The fluctuation of the bed layer will cause the friction between the molecular sieve particles to produce powder, causing the molecular sieve micropores to block and fail, the adsorption capacity will be greatly reduced, and the system pressure will increase. And this phenomenon gradually deteriorated, and finally a large amount of powder was discharged from the bed.
Poor Filling Quality Of Molecular Sieve Causes Powdering
When the molecular sieve is too loosely packed and the filling amount is not enough, the friction between the molecular sieves is the largest, which can easily cause the molecular sieve to pulverize.
The Splitter Plate And Filter Cotton In The Adsorption Tower Have a Large Layering Error
When the molecular sieve is filled, the internal splitter plate and filter cotton have a large layering error, which will cause hidden gaps. When the system pressure is high, these gaps are released to the molecular sieve, causing the molecular sieve to become too loose and the bulk density to decrease, causing the molecular sieve to pulverize.
Frequent System Switching And Pressure Equalization
PSA system design should consider the optimal dosage and switching period of molecular sieve, so that the gas production efficiency of molecular sieve is within a certain reasonable range. Short switching period will increase the gas production rate, but will increase the wear between the molecular sieves and cause the molecular sieve to pulverize.
How to Avoid Molecular Sieve Pulverization？
Equipment Pressure Design
Reasonably design the air inlet and gas distributor of the adsorption tower to make the gas distribution uniform, let the compressed air diffuse quickly after entering the adsorption tower, reduce the gas flow rate, and reduce the impact on the pulverization of molecular sieves. If the gas distribution is not good, the compressed air will affect the local molecular sieve too much, and the long-term influence can easily cause the pulverization of the molecular sieve.
Inlet And Outlet Buffer
The molecular sieves at the top and bottom of the adsorption tower are impacted. Therefore, it is necessary to redesign the design of the gas distribution end distributor of the adsorption tower to reduce the impact on the top molecular sieve.
Vibration Compaction
When filling molecular sieve, it should be tamped every 30-40 cm to eliminate the excessive gap formed by the natural introduction of the molecular sieve and prevent the density difference between the beds from being too large. It is strictly forbidden to fill the adsorption tower at one time and then vibrate the adsorption tower. It is difficult to ensure that the bed is dense.
