Chemical Forums
Specialty Chemistry Forums => Chemical Engineering Forum => Topic started by: technologist on June 20, 2006, 07:56:52 AM
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30% MEG + water antifreeze system has freezing point of -16°C.
What will happen if I chill 30% MEG-Water solution to say -10°C. Will it separate out any water as Ice OR Not?
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Shouldn't do - should all freeze at -16deg.
If this is a really important application - put yourself at ease by testing a litre at -10 to -12 deg just to make sure.
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How are you cooling the mixture?
Is the MEG/water mix running through a chiller as the coolant medium?
If it is be aware that the evaporator temperature will be lower than -10°C to achieve a coolant temperature of -10°C. Try more glycol or switch to MPG.
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No, actually I am looking it as a cost effective method for the removal of water from MEG compared to distillation/Evaporation systems.
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30% MEG + water antifreeze system has freezing point of -16°C.
Is this an azeotrope?
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Hi technologist,
The mixture is an azeotrope (as geodome has inquired).
When the freezing point has been reached, this homogenous mixture will freeze together, and it will not separate out into its individual components.
I hope this helps answer your question. If you have any suggestions or comments, feel free to submit them.
Sincerely,
Eugene
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Thanks Eugene
I Believe so, but was not sure.
Can U suggest any ref for phase diagram of this system.
Now, is there any other alternate possible to separate out MEG & Water into its component to any extent possible.
The reason for posting this question is only Commercial aspect. We are manufacturing MEG @500 TPD. After reaction it contains ~11% MEG solution which is concentrated to ~80% MEG in 3 stage evaporators (MEE). This consumes lot of heat energy.
SO I am searching for options like, Icing of water (May be an stupid Idea, but I read it somewhere) OR liquid liquid extraction (LLE). However dont know suitable solvent for this.
Any other Idea is welcome for the separation to any extent? Even if its able to separate any fraction say by 30 - 60% that will reduce my cost significantly.
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Hi technologist,
Its intreguing that you mention your situation. In my former position, I developed and many industrial separation techniques (due to necessity out of time constraints) by taking off-specification product and making it near original purity specifications. This was usually performed in a minimum of one - 20,000 litre batch per day.
The most common one-pass method that I used for separating MEG from water (and having almost 99% pure MEG) was to centrifuge it. MEG is denser than water. I am unsure as to the difference in energy requirements and maintainence energy differences between evaporation and centrifuege separation techniques.
The good news is that centrifugation works, the bad news is that I am unsure if it is more efficient/reliable (due to mechanical maintenance) than evaporation.
I hope this helps, and feel free to ask more questions.
Sincerely,
Eugene
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Exciting Info Eugene. Thanks for this.
Let me work out Economics. (I feel more confident when U say that U have already worked on MEG Water System at Industrial scale of 20 KL batch).
So for this, if u can recollect some info, probably this can give us some direction.
For this 20 KL size
1. What was the actual batch size? (20 KL is for one day which may be diff / batch if no of batches were more than 1)?
2. What was the initial MEG concentration? I presume final MEG was >99% as U said, correct me if I'm wrong.
3. What was the batch running time?
4. What was the motor size for centrifuge?
5. Was it a normal centrifuge OR any special design?
Hope U understand the need of this.
It will let all of us know that Improvements come only if we start silly thinking like this. I may or may not succeed but I'll learn from it.
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Hello technologist,
Here are the answer to your questions:
1) At one time, there were 3 x 20 m3 batches (there were many more than this, and this was the largest batch in one day).
2) The initial MEG concentration was approximately 42 %, and the final concentration was over 99 %.
3) The batch running time was approximately 8 hours.
4) The centrifuge was small (electric motor, 120 volts), approximately 24" diameter.
5) It was a generic centrifuge.
I wish you the best.
Sincerely,
Eugene
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4. What was the motor size for centrifuge?
4) The centrifuge was small (electric motor, 120 volts), approximately 24" diameter.
Actually I meant kW rating of motor OR power consumed.
I can't figure out from this motor size as its different in India.
OR
If anybody can tell me the most probable kW rating for this size of motor talked by Eugene.
Eugene,
Its really going to help me a lot.
U R again a great help to me. U deserve 2 Scooby. Here it goes.
______________________________________________
Do U have any idea on centrifuge size (Diameter Or Volume Or Weight Capacity)
Thanks
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Hi technologist,
I am taking a guess at this, but the motor is probably between 1000 - 1500 watts (120 volts x 10 amps?..maybe?), the centrifuge diameter was approximately 24 inches, and had two 1 inch ports (one for less dense fluid, and one for higher dense material.
Chuckle .. you are welcome for the help.
Thanks for the scooby snacks !! ;)
Sincerely,
Eugene
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Wonderful It will be cheaper than distillation.
So all should get benfited from this FINDING of Eugene & myself.
Now I am goin to convert it for Commercial level in my plant.
Well Eugene,
I have one more info to share. I found that Phenol can dissolve MEG completely so can water. But Solubility of Phenol is only ~8-9% in water @20°C. But I am not sure if I can separate it that way using LLE. (I know in this case Phenol loss in water will be an issue, So searching more).
OR
if I use MCB which has 6% solubility of MEG & almost insoluble in water then probably that would be better than Phenol.
Just sharing all this info.
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I guess than U have fed 20 M3 in ~8 Hours in your centrifuge as continuous feed.
Am I right?
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Eugene
I am bit skeptical on success of Centrifuging for Separation.
(I am not doubting on your batches - 20 M3 size in 8 hours itself is sufficient to prove it)
But the characteristic of MEG+Water (Completely Miscible) made me to prompt this.
Is it really possible??
If I see Density Nos - Hope is still alive.
If I see Miscibility - I'm drowned.
Results of your batch are already there - No reason to doubt about.
Actually I'm depending on this project a lot. Therefore, want to make it sure.
I hope U wont mind.
Can U tell me centrifuge suppliers who can give it to us.
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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
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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?
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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
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Can u refer those hits here?
I'll try tomorrow.
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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
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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.
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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
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Last Bothering.
Can u arrange some docs for your experiment.
Any Info.
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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
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Hi technologist,
Here is some starting information.
http://en.wikipedia.org/wiki/Centrifuge
Sincerely,
Eugene
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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.
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Is it clear from the curve that WATER will separate out given the feed condition.?
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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
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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.
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Will it react with MEG or is to separate out MEG from NaCL solution? I mean what is the mechanism for using this.
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It isn't a chemical reaction. It is a physical process.
NaCl, being ionic, bonds with the water molecules, thus competing with ethylene glycerol (EG) for H-bonding sites for water. Moreover, NaCl may form H bonds with EG, thus making EG less readily to form H bonds with water.
If no H bonding sites are available, then EG should seperate from the mixture.
I suggest NaCl because it is chemically inert, unless heavy metal ions are present.
You ought to experiment this in the lab before actually carrying it out even on a pilot plant scale.
Moreover, the centrifugation technique suggested by Eugenedakin must be carried out in an open flow process. It will not work in a batch configuration because EG will remix with water as soon as the centrifugal force is no longer applied.
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Thanks Geodome
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Hi Geodome,
Great suggestions !! Well done.
Sorry for the delayed response, I just arrived back in my home province from business.
Technologist, Geodome is quite right. Ensure that you spend some time trying different methods of separation in the laboratory before designing the process. This will help you feel comfortable with the results.
Sincerely,
Eugene