the mixture of last issue (Acetonitril/water) i fed into a destillation. There are some issues with that where i ask you for help/improvement:
minor bug: When conecting feed streem all streams are listed instead only available streams (as it is done in other objects like heater)
Column only converges with WangHenke but not with Russell_InsideOut below aceotropic point (example 10% Acetonitrile, 90% water). Above aceotropic point (example 90% Acetonitrile, 10% water) there is no solution found whatever specification i try.
If you try specification of duty for reboiler or cooler you will get astronomical values for to other duty.
other ways of specifying column with these components like component recovery, heat duty, ... don't work.
even switching between nested loop / IO method dosn't give any improvement
Is all this because the known issue with instability in flash algorithmus, a problem with that special mixture with an aceotrop, a problem with column calculation or a wrong specification of column?
1 - Fixed.
2 - I changed the inlet mole fractions to 0.9/0.1 and the column did converge with Wang-Henke and Napthali-Sandholm algorithms... I think Russell's won't work at all with your case but not because of the mixture, it is the algorithm that is broken for full condensers...
3 - The energy balance when you specify duties is wrong. I'm working on it.
4 - Component recovery might work only with Napthali-Sandholm method, and you will need good initial estimates in order for it to converge.
5 - Same as 2
The column model is very, very, very difficult to work with due to the number of specification possibilities that the user might want to use. I've already worked a lot on them and was able to get some stability and reliability improvements, but I eventually gave up on them because it is really too much time consuming, and I had other things to do. Anyway, you can always use ChemSep column model through the CAPE-OPEN interface.
That doesn't mean that I won't work on them anymore, but for that I need some free time to dig deep on the mass and energy balances to track (my) mistakes... ;-)
Regards,
Daniel
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Hi Daniel,
the mixture of last issue (Acetonitril/water) i fed into a destillation. There are some issues with that where i ask you for help/improvement:
Is all this because the known issue with instability in flash algorithmus, a problem with that special mixture with an aceotrop, a problem with column calculation or a wrong specification of column?
yours
Gregor
Last edit: Gregor Reichert 2013-01-08
Hi Gregor,
1 - Fixed.
2 - I changed the inlet mole fractions to 0.9/0.1 and the column did converge with Wang-Henke and Napthali-Sandholm algorithms... I think Russell's won't work at all with your case but not because of the mixture, it is the algorithm that is broken for full condensers...
3 - The energy balance when you specify duties is wrong. I'm working on it.
4 - Component recovery might work only with Napthali-Sandholm method, and you will need good initial estimates in order for it to converge.
5 - Same as 2
The column model is very, very, very difficult to work with due to the number of specification possibilities that the user might want to use. I've already worked a lot on them and was able to get some stability and reliability improvements, but I eventually gave up on them because it is really too much time consuming, and I had other things to do. Anyway, you can always use ChemSep column model through the CAPE-OPEN interface.
That doesn't mean that I won't work on them anymore, but for that I need some free time to dig deep on the mass and energy balances to track (my) mistakes... ;-)
Regards,
Daniel