[eugenedakin]

Hi technologist,

Here is a way in which you can determine the success of separation:

Almost every laboratory has a centrifuge (usually 50 mL size batches).

Take a sample of your material, have the laboratory spin the sample: depending on the gravity-force of the centrifuge, the larger gravity-force will take less time for separation.

You will see two layer, MEG (density approximately 1.13 Kg/L on the bottom, and water ~1.00 Kg/L on top).  Each of these two layers can then be tested in the lab for purity.  This is the best way to ensure that this method will work with your particular blend.

I hope this helps.

Sincerely,

Eugene

[technologist]

Right Eugene,

I'll plan for the final step only after lab test.

But if I start from 42% to 99%, can I request for some more validating data from U.

Actually, Somebody raised a doubt that this way it is not possible for completely miscible liquids.
Can I have some Literature Info on separation of two miscible liquids by this method?

[eugenedakin]

Hi technologist,

I 'googled' your request and got some hits.  You should be able to find some supporting data there.

You can definately centrifuge 2 miscible liquids.  It becomes difficult to centrifuge when the densities of the two liquids are close (example, 1.00 and 1.01).  When the densities are far from one another (such as EG and H20), then there is less energy required.

Like I mentioned before, run a centrifuge test in the lab to prove it to yourself.

Happy to help,

Eugene

[technologist]

Can u refer those hits here?
I'll try tomorrow.

[eugenedakin]

Hi technologist,

I'll reference some of the hits later on today (I am heading to work).

Your friend is partially correct with miscible liquids.  If you centrifuge the liquid, for lets say 3 minutes, you will not see any separation.  It took quite a while to have separation occur in a laboratory centrifuge, but it will happen.  Be careful when you slow down the lab centrifuge, as the two liquids like to mix 

Sincerely,

Eugene

[technologist]

Did U carried out it again?
Also, can it be extended to any miscible liquids e.g. Alcohol & water?

Your statement now gives me a feeling that it is possible but with practical limitations?
Let me lis out possibilities.

1. In a continuous process the problem of re-mixing wont occur.
2. However, it is essential to apply certain minimum amount of force.
3. If it is possible for this MEG water system, it can be applied to other systems also.

When I think of separating cream/fat from Milk using centrifuge, I feel confident. However, there is no such industrially followed process as on date, I feel bit doubtful.

Fully confused by Now.

[eugenedakin]

Hi technologist,

I havent had a chance to re-try it ... I have been quite busy ... sorry...

You are absolutely correct when mentioning limitations to this application.

1.  Correct.  Re-mixing will not occur in a continuous process.
2.  Correct.  A minimum-threshold amount of force is needed to allow separation (as a function of time) which is directly related to the difference in density of the liquids
3. Yes.  This has been successfully applied to other systems.

You are absolutely correct with the cream/fat separation technique.  I have used this when de-watering sludge in industrial water systems.  The purpose of removing water was to minimize transportation costs (dont ship water, transport mud concentrate).

I think that you have got it ... you dont seem to be confused at all ..

Well done !!!

Eugene

[technologist]

Last Bothering.

Can u arrange some docs for your experiment.
Any Info.

[eugenedakin]

Hi technologist,

You are not bothering at all, really, don't worry about it.

Unfortunately, I cannot share the actual specifics about any of the applications.  This is due to company contractual agreements.  If you have access to a laboratory with a centrifuge, you should be able to develop a simple testing procedure based on the 'time' required for separation of samples based on your specific situaiton (more time = closer product density and lower separation volume rates).

I wish you the best.

Sincerely,

Eugene

[eugenedakin]

Hi technologist,

Here is some starting information.

http://en.wikipedia.org/wiki/Centrifuge

Sincerely,

Eugene

[technologist]

I want calculation demo for the crystallization separation.
Feed 10% MEG + 90% Water Say 1000 Kg/hr.
Now I chill this mixture to say -20°C where equilibrium concentration of MEG is say 40%.
So how to calculate amount of crystals & liquid separated.
I am attaching the diagram here.

[technologist]

Is it clear from the curve that WATER will separate out given the feed condition.?

[Donaldson Tan]

No, actually I am looking it as a cost effective method for the removal of water from MEG compared to distillation/Evaporation systems.

Although I am not directly answering this thread, I know your intention. You want an alternative method to extract MEG from aqueous MEG instead of the usual multistage distillation at reduced pressure.

According to Baker (BAKER, R.W. (2000). Membrane Technology and Applications. New York: McGraw-Hill), pervaportion with water-selective membranes should do the trick.

I also realised that i cannot extract anything from a mixture that is already frozen. How can you use fractional crystallisation to seperate 2 miscible liquids, especially when ethylene glycerol  has a very high affinity for water?

F.R. Chen from Tianjin University developed a pervaporation model in 1997.

Look for this journal:
A diffusion model of the pervaporation separation of ethylene glycol-water mixtures through crosslinked poly(vinyl alcohol) membrane, by FR. Chen & H.E Chen, Journal of Membrane Science 139 (1998) 201-209

[Donaldson Tan]

I wonder if there any substance that can disrupt the intermolecular bonding between water and ethylene glycerol. Maybe salt like NaCl can do the trick. This method is used in DNA extraction.

[technologist]

Will it react with MEG or is to separate out MEG from NaCL solution? I mean what is the mechanism for using this.