7 replies to this topic

[leon_aurel]

i have butanol-water mixture with butanol concentration is 4 mol% and the rest is water. At first i plan to use simple distilation column, but now i think that it is not economically feasible , because of the amount of water that i should vaporized.

can anyone give me more option to do this separation? or maybe do you think that any separation method will not be economically feasible?

thanks..

[milenkom]

i have butanol-water mixture with butanol concentration is 4 mol% and the rest is water. At first i plan to use simple distilation column, but now i think that it is not economically feasible , because of the amount of water that i should vaporized.

can anyone give me more option to do this separation? or maybe do you think that any separation method will not be economically feasible?

thanks..

Single distillation column will do you no good. Based on VLE data for Buthanol Water system

http://ddbonline.ddb...nol;Water.shtml

it clearly shows you've got an azeotropic point at 75 vol. % water. Since you are operating at Buthanol conc. of 4 mol % single distillation column will give you pure water on the bottom and an azeotropic mixture overhead. Also it seems to me that buthanol water system will form two liquid phases once condensed. I used to do steady steate simulation of azeotropic mixture of system furfural water in which case two columns were used with decanter located in between. Decanter separated two liquid phases and returned on liqud phase (buthanol rich phase or other one I can't really remember) to column as reflux stream. It think this is the best way to separate buthanol water mixture.

Edited by milenkom, 10 March 2010 - 02:50 PM.

[breizh]

HI
what about Extraction liquid liquid then distillation to recover the solvent ?
Hope it helps
Breizh

Note : I'm thinking IPE as solvent (Iso propyl ether), not sure

[riven]

The paper you want is
http://pubs.acs.org/....1021/ef8004064

This details the butanol (BuOH) water separation from a control point of view. There is some data on the energy requirement. I would suggest contacting the author as well to see if you can get more data.

To separate a heterogeneous azeotrope you will traditionally use a combination of 2 distillation columns and a decanter. For BuOH the decanter is used to get beyond the azeotrope allowing you to potentially save a lot of energy.

There are other methods but none come close to the simplicity and cost of this method yet. The only other possible 'viable' alternative I see is a pervaporation process. In theory you would have 1st membrane removing the 4% BuOH enriching it. This would be fed to the decanter and the organic rich phase can be dehydrated using a 2nd membrane. Currently the 1st membrane is not cost competitive with the distillation process.

[leon_aurel]

using 2 distillation column and a decanter will not be a good option for me since this butanol is the unreacted reactant. sorry, i forget to mention it earlier, i plan to design a butyl acrylate reactive distillation column. i have found the journal concerned to it. in this journal, it is told that butanol will reacts with acrylic acid to form butyl acrylate, with some butanol left (4% in this journal). i plan to add a design of recovery system of the butanol.. so i don't think adding 2 more distillation column will be viable, but thanks for the vapor liquid data..

breizh, thanks for the idea..

riven, is the pervaporation process you mention is the distillation with pervaporation membrane?

[riven]

Please redefine your process

Do you have as originally stated a stream containing
4mol% butanol balance water
4mol% butanol in butyl acrylate water solution
4mol% butanol in water with butyl acrylate as an impurity

Now I am not sure but from your previous description it seems that your stream with contain BAc Butanol and water from a reaction. The separation scheme will be based on the distillation residue curve map for this system which I do not have. I know that the RCM involves 3 distillation areas with two phase regions in these areas. So a distillation train employing decanters at the appropriate point seems likely. However since I do not know exactly your system I cannot say with any certainty.

The pervaporation process would be stand along with a decanter but is theoretical. A pervaporation process with decanter and primary distillation is possible. But only for butanol water separation.

[leon_aurel]

my stream contain Butyl Acrylate 0.05%, Butanol 4.05%, Acetic Acid 1.89E-3 %, water 95.90%

Sorry for my lack of knowledge, but what is RCM??

[riven]

my stream contain Butyl Acrylate 0.05%, Butanol 4.05%, Acetic Acid 1.89E-3 %, water 95.90%

Sorry for my lack of knowledge, but what is RCM??

RCM residue curve map


The amount of impurities is very low. I do not expect that these levels will significantly change the butanol water system in terms of where the phase split occurs though you will have to check this probably by experiment. The question is where these impurities go in the first column. If both happen to primarily go out the bottom with water then the phase split indeed unaffected and a two column and decanter is the best solution.

If the components go out wit the low boiling butanol water azeotrope there could be issues.
1. The two phase behaviour of the system may disappear or diminish. The extent of this is required.
2. Assume 1. to be untrue both products could end up in the final butanol product from column two. The significance of these amounts is needed.

Without going into detail I have yet to see data that says that a distillation decanter scheme cannot be used or is even plausible. You must get this data to decide if the scheme can be used.