Ethanol recovery by Distillation

Question

Ethanol recovery by Distillation

zamu2010 (Bioengineer)

(OP)

12 Oct 10 05:33

Hi folks,
I am doing a sensitivity analysis for ethanol recovery by distillation unit (coupled with dehydration unit) from a ethanol water mixture at various ethanol concentrations. By changing the conc. of ethanol in the feed the height of distillation unit will be change. and also the price. Could something suggest how can I proceed further.
Thanks in advance for your help on the issue.....

dcasto (Chemical) · Answer 1 · 2010-10-13 13:30:53

why does the height have to change?  It only changes for a fixed reflux ratio.  You need to look at the whole picture of energy costs versus height for different feed concentrations

for example;

a 20 vol% ethanol feed has this
+++COLUMN PARAMETERS BY SHORT CUT METHOD+++

% MIN REFLUX STAGES FEED TRAY CONDENSER DUTY  REBOILER DUTY
REFLUX RATIO      LOCATION     BTU/HR         BTU/HR
------   ------  ------------    -----------   ------------
105.0     2.493   15.80  6.06     0.7794E+06    0.6202E+06
110.0     2.612   13.65  5.32     0.8059E+06     0.6467E+06
120.0     2.849   12.09  4.79     0.8588E+06     0.6996E+06
140.0     3.324   10.57  4.27     0.9648E+06     0.8056E+06
175.0     4.155    9.16  3.79     0.1150E+07     0.9910E+06
200.0     4.748    8.56  3.58     0.1283E+07     0.1123E+07
130.0     3.086   11.21  4.49     0.9118E+06     0.7526E+06

and a 10 vol% ethanol feed has this

+++COLUMN PARAMETERS BY SHORT CUT METHOD+++

% MIN  REFLUX STAGES FEED TRAY CONDENSER DUTY REBOILER DUTY
REFLUX RATIO        LOCATION      BTU/HR         BTU/HR
------   ------  ---- ------    ------------   ------------
105.0     4.953   15.19 4.88     0.7124E+06     0.6520E+06
110.0     5.189   13.27 4.35     0.7406E+06     0.6803E+06
120.0     5.660   11.75 3.94     0.7971E+06     0.7367E+06
140.0     6.604   10.21 3.52     0.9100E+06     0.8496E+06
175.0     8.255    8.82 3.14     0.1108E+07     0.1047E+07
200.0     9.434    8.24 2.98     0.1249E+07     0.1188E+07
130.0     6.132   10.85 3.69     0.8535E+06     0.7932E+06

price out the cost of all the combinations

dtlb26 (Chemical) · Answer 2 · 2010-12-10 19:50:26

Nice post dcasto.

Should also point out that, depending on the technology used, some use an additional colum to capture ethanol from bottom streams.

Vodka stills utilize a 4 column design.

Fuel ethanol is 2-3 stills (depending on technology).

seasar (Mechanical) · Answer 3 · 2011-02-01 15:14:37

Can someone point me in the direction of how to learn more about the science of engineering of distillation?

I am a process engineer with responsibility for, among things, an alcohol distillation unit with a molecular sieve dehydrator that I've inherited. I'd like to learn more about how and why it was designed.

Thanks

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Ethanol recovery by Distillation