Dear Gunter Reinig
Thank yoy for your email about distillation models.
>Would you agree to use the ColumnA models and files
>in the above course for the students of Mechanical Engineering
>with the specialization "Verfahrenstechnik" ("Process Engineer") ?
Yes, certainly (please give appropriate credit)
>Additionally I would like to ask / to discuss the following
>questions:
>1. Aren't you afraid that ignoring the heat balance /
>accumulation completely introduces a big model error ?
We are not really ignoring the heat balance, but we have used the
assumption of constant molar flows. In this case, mixing
two saturated streams will gives another saturated stream, so
we can neglect the heat balance, provided the mixture is relatively
ideal so that the assumption of constant molar flows holds.
Here are some cases where we cannot "neglect" the heat balance:
1. Mixtures with large differences in molar heat of vaporization
2. Cases with large pressure variations
3. Cases where heating/cooling of the walls/internals
may be important (usually only important during startup).
Please tell me if you make a more detailed model
(we have made some initial attempts; see the file colap.m)
>
>2. Realistic distillation columns most often are controlled via
>temperature controllers instead of concentration controllers or
>at least using temperature controllers as slave of cascade
>concentration controllers. On page 9 of matlab_m/cola/cola.html
>you propose a simple correlation to calculate temperatures on the
>trays. Is the dynamic behaviour of these temperatures close to the
>real plant ones although heat accumulation is not considered ?
Same answer as above (that is, OK for many relatively ideal mixtures
like separation of similar components).
>
>3. If not can you eventually advice me to other user friendly
>distillation models which include the heat balances ?
There are many models, but O do not knos of any
easily available Matlab models.
Best regards,
Sigurd Skogestad
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