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Procedures to follow after molecular sieve water ingress

Release Date:

2023-04-10

Source:

Network

After a molecular sieve becomes heavily saturated with water, several regeneration cycles are required to remove the moisture and restore its adsorption capacity.

The usual practice is to close the main inlet valve and switch between the two molecular sieves for adsorption, using the dry air from the non‑inlet sieve to regenerate the one that is currently in service. However, once the previously wetted sieve resumes operation, moisture from its downstream side can migrate into the now‑dry sieve. As a result, both molecular sieves become saturated with water and begin to regenerate each other. With repeated cycles of adsorption and regeneration, the water content in both decreases, and both eventually regain their full adsorption capacity.

However, I came across an article in a magazine that described their experience: after the molecular sieves were flooded with water, they attempted to regenerate them using the method mentioned above. Yet this resulted in both molecular sieves becoming saturated with water; despite being regenerated, neither regained its adsorption capacity. The reason is that when a molecular sieve absorbs a large amount of water, the water interacts with the sieve, transforming from free‑water into structural water bound within the molecular‑sieve framework. Even at a regeneration temperature of 200°C, this structural water cannot be removed; only by sending the material back to the manufacturer and subjecting it to a 400°C calcination can the molecular sieve’s adsorption performance be restored.

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Procedures to follow after molecular sieve water ingress

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