OLD MOLSIEVE! IT IS OK TO USE? 1

[devaxrayz]

Hello all...

I have a dead stock of molecular sieve. It's been in my logistic warehouse since maybe 15 or 20 years ago, and i'm looking for any possibilities that i can still use it.

It is a 13X type molecular sieve with 1/16" pelleted grain size. I will using it for an absorption of H2O and CO2 and any hidrocarbon in air pretreatment before entering coldbox of N2 plant

What is the parameter for determining that the molecular sieve is still in good condition?

What kind of analysis that my laboratorium should run to that molsieve?

What is the ideal run time for a molecular sieve in operation since my N2 plant have never change its molsieve since 15 years? And what is the parameter for changing molsieve decision?

thanks before for your response

Devax Rayz,
Junior Process Engineer

 

[epoisses]

Pff... I wouldn't run the risk if it is not a HUGE quantity. It may have been adsorbing H2O and CO2 for 15-20 years. What's the potential gain compared to other items on your job list? Anyway, what you could do to at least make the best of it without turning it into a research project, put it in the lead position if you have a lead-lag bed configuration, and put a fresh sieve behind hit.

 

[quark]

Generally you should not have problems if they are packed in a good condition and not exposed.

You can check the dew point of an air sample before and after exposing the sample to molecular sieves. Check Mr. Montemayor's post for a detailed description of the method at thread1036-104873(there are dew point meters already available but they are expensive)

There is no rule, as far as I am concerned, for replacing molecular sieves. You can use them as long as they are not contaminated with oil nor mechanically detiorated(your final dew point will tell you whether they are good or not). My experience is that we have to top up atleast 5-10% every year.

Regards,

 

[toothless]

The manufacturer can probably test it for you.

 

[epoisses]

He will probably tell you the shelf life is 12 months or so... The thing is, even if properly packaged, an LDPE liner or whatever internal packaging is used is not an eternal barrier against humidity or CO2. A can of beans eventually goes bad too. The question is whether you want to spend the time required to figure out what the actual condition of the sieve is, or spend the money to buy a new one.

 

[Samiran]

This can be an economics issue. Determine the consequence of an offspec product - what it will lead to against buying the new mol sieves. However, usually they are nitrogen sealed (if in drums) and stay good. You can send samples to the manufacturer to check the H2O and CO2 adsrption capacities remaining. You may also mix this with fresh material to minimize any impact.

Samiran

 

[toothless]

I had some old sieve (13X-APG) sitting in a warehouse for several years. I had it tested and it was fine. Eventually, we figured we'd never use it and threw it away, but it was still good at the time. It was stored in drums. I think there was a plastic lining (bag) in the drum.

 

[devaxrayz]

thanx all,

from quark response i'm thinking of doing some lab test for my molsieve

By recording the dew point inlet and outlet and also the air flow, i can calculate the total moisture pickup/liter of adsorbent

Compare with the condition in real process i can determine whether the molsieve is still in good condition

how about that?

DevaxRayz

 

[Yordif]

There are couple of companies that buy overstock catalyst and supports. They may also buy adsorbents as well. At least you can get some of your capital back if you don't think you will use it.