6 replies to this topic

[ande1866]

I’m researching ethanol water mixtures and trying to quantify the energy requirement in the distillation and dehydration processes of creating 200 proof ethanol. I recognize the ideas of a multi column distillation process, but what’s the best way to quantify the energy required to remove the water from the ethanol water mixtures? Has anybody read any papers on this topic, or know of a good way to model this energy requirements in Btu’s/gal?

[Padmakar Katre]

Dear ,
Please could you tell us the water-ethanol mixture composition %. So that I could tell you something about the ethanol purification and the dehydration based on my prior experience.

[ande1866]

I'm researching water ethanol blends from 50/50 to 100/0 ethanol/water. I have found a few papers referring to the McCabe-Thiele method, but non discuss how to pull quantifiable values for energy requirements out of that.

[Andrei]

As, I am sure you know, Ethanol and Water form an azeotrope mixture, boiling at 78 ºC with a composition of 96% Ethanol and 4 % Water (by weight). As a consequence Ethanol-Water separation cannot be performed beyond this point using a thermal process. A kind of solvent extraction is required to obtain Ethanol with purity better than 96%.
It is relatively simple to determine the heat required for purification up to 96%; above that, the requirements are not so easy to determine, and depend on the type of the process used.
McCabe-Thiele method is used to determine the number of theoretical stages needed for a distillation. Heat required is determined by good, old and simple heat balance.
You guys ever studied a heat-mass transfer book? Because your question sounds like kind of fundamental to me. Don't look for papers, what you are looking for was published centuries ago, look for fundamentals books.
Good luck

[ande1866]

Andrei,
Thank you for the tip, all i need to know is energy required through distillation, so up to 96%. I will look into mass and heat transfer, but as i am not a chemical engineer, a little guidance would be greatly appreciated.

[Andrei]

I can recommend a very good book on the subject:
KA Jacques, TP Lyons and DR Kelsall, THE ALCOHOL TEXTBOOK, 3rd Edition, Published by Nottingham University Press, 1999. Chapter 18, Page 277, Figure 8. Steam requirements ethanol stripper/rectifier. It gives you a very rough indication for the steam requirements as a function of Beer concentration. I cannot send you the graph, for obvious copyright reasons, but find the book, there is other interesting stuff there.
As of Heat&Material Balance, maybe you should contact a chemical engineer and work with him.
Not everybody should know everything. For example, I am not asking about disease cures on medical forums when I am sick, I am simply going to see a doctor, it is much more efficient and safer for me in the first place.

Be good

Dear
As above discussion ethanol water is azeotropic. There is different process to break the azeotrope of ethanol water system. energy required is depend on the process you selection. If you fallow the molesieve method and conc of feed is 96% V/V ethanol then steam required is near about 0.45 kg/lit of ethanol.

I hope it help you
steam required for distillation is depend on concetration of ethanol in feed and you can calculate with help of any simulation software


MK