posted by Anonymous on .
Why doesn't water distill simultaneously with alcohol when heat is applied to the mixture? Could it ever be the first component to distill in a mixture?
I don't understand this. I have no idea how to answer this. Can you help?
Concentrated alcohol and distillery slop are produced from fermented beer with a reduced amount of energy by employing a vapor recompression distillery slop evaporator in which evaporator vapors are used to strip alcohol from the fermented liquor before they are returned as the heat source for evaporation. Vents in the evaporator permit passage of uncondensed vapors used to drive the evaporator to a rectifier, in which they constitute the principal heat and alcohol source. Condensed vapors from the evaporator and the bottom stream from the rectifier are stripped of their remaining alcohol content in a condensate stripper, which is also driven by the recompressed vapors from the evaporator. This prevents dilution of the slops and the additional energy cost that would be necessary if the water content of these streams had to be removed in the slop evaporator.
So would it be correct to say "Water doesn’t distill simultaneously with the alcohol when heat is applied to the mixture because of their differing amounts of energy"?
Anonymous, that is nonsense. It sounds like someones dream of a new gadget for distilling that has never been built.
Alcohol molecues are not held with intermolecular forces strong as water to water, so when energy is added (heat), the alcohol is the first to break free of the liquid and become vapor. Another way of measuring this is called vapor pressure...alcohol is much higher vapor pressure than water, ie, it turns to vapor easier at any temperature.
So, to answer your question, alcohol will be the first to vaporize.
I must admit I don't understand the answer by Jess; however, it sounds as if Jess has been around a distillery and I haven't. To add to Bob Pursley's answers, and from a chemistry standpoint but said a little differently as follows:
1. Why doesn't water and alcohol distill simultaneously. Forgetting that they do sometimes, usually the alcohol comes off first simply because the alcohol has a lower boiling point than water. So the alcohol comes off first, then the water comes off.
2. Could it ever happen in a million years that the situation might be reversed OR that both might distill simultaneously. The answer is yes to both. Have you studied about azeotropes?
When the alcohol/water mixture gets to approximately 95%alcohol/5% water, both distill simultaneously. Ethyl alcohol and water form an azeotrope. Here is a site that is a pretty good azeotrope page. http://en.wikipedia.org/wiki/Azeotrope