Ethanol recovery by Distillation

[zamu2010]

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]

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]

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]

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