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Acetone/water Separation

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#1 Guest_jnadeau_*

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Posted 08 November 2005 - 02:02 PM

I'm working on an idea that involves the use of an acetone/water binary mixture as a working substance.

Here is some background:
The working substance (acetone/water - low H2O concentration <5%) picks up water in a subsequent step, and is redirected to a distillation step where the water is stripped back out. The overhead stream then becomes the working substance, etc. Thus the purpose of the separation is not to purify acetone, but to cycle as much water as possible for the least amount of energy input.

My question is this: is this arrangement energy intensive, and how much energy must I expend per pound of cycled water, for instance. I know I can calculate this and am in the process of doing so, I just want some ChemE's with direct experience with this mixture (or MEOH/water for instance) to give me a feel for the applicability of this choice (plus, I haven't pulled out my textbooks in a while). Ideally, I want to put in no more heat than the heat of vaporization/condensation of H2O.

#2 gvdlans


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Posted 11 November 2005 - 05:09 AM

What am I missing? What is the use of "cycling as much water as possible"?

#3 Guest_jnadeau_*

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Posted 11 November 2005 - 03:35 PM

I want to use the organic to dry a solid and avoid having to operate at 250+. I'm interested in using the low temperature of distillation instead.

The water is cycled from the solid to the organic phase, then removed in the column.

#4 djack77494


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Posted 15 November 2005 - 08:41 AM

As I understand it, you have a starting mixture of 95% acetone and 5% water. You expose wet solids to this mixture in order to dry them, thereby producing a spent sorbent solution of <95% acetone, >5% water. Now you want to return to the original solution and you choose distillation as the way to do so.

I'm not sure what high temperature operation you're talking about since you did not specify units of degrees F or C. Certainly if you are "boiling off" all of the acetone and the 5% water in the circulating solution, your process is going to be extremely energy intensive. With acetone's higher volatility, I suspect distillation is a poor choice of regeneration methods. I don't believe you can limit the energy input to what you'd like to see.

If you'd like a further commentary, Please offer us more specifics. What concentration of water appears in the spent sorbent solution? What pressure is used when regenerating the solution? Why are you using acetone for this purpose? If you conclude your system is best for your application, then consider alternate regeneration technologies such as membrane separation to dry the spent sorbent.

Good luck,

#5 Guest_Guest_*

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Posted 21 November 2005 - 11:16 AM

The solid is a desiccant which I want to regenerate without having to operate at high temperature (250F +). The amount of energy required to regenerate the desiccant is directly related to the amount of water adsorbed. Also, if I use a heated air stream, it has to be heated to a temperature high enough to reduce its relative humidity, thus the temperature requirement is related to the humidity of the heated air stream itself.

What I'm trying to accomplish is to use a "dry" stream of an organic that I can separate from water at a lower temperature (to take advantage of waste heat). The dry stream would be passed over the desiccant as a gas with a low humidity, into which the bound water would desorb.

I believe that the energy requirement would be approximately the same as in the heated air example above, since there is no 'boiling off' of the organic from the desiccant (it's already a gas). The amount of energy required in the distillation, if that is what is chosen, should be comparable to the heat of adsorption/desorption of water in the desiccant.

Any comments from anyone on this idea?

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