How to model vapor recompression distillation in Aspen Plus? I want to simulate it "With no condenser", but it`s giving following Error:
A LIQUID FEED/PUMPAROUND TO THE TOP STAGE IS REQUIRED WHEN 'Q1=0' IS SPECIFIED IN 'COL-SPECS'; REQUIRED FEED/PUMPAROUND HAS ZERO FLOW
I don't use ASPEN Plus but I think adding a liquid stream with a miniscule rate(3 or 4 orders of magnitude lower than overhead product rate) might work
trays should not work in dry, therefore, you may add a artificial stream (i.e., with 0.0001 kmol/h) entering to 1st tray to work as reflux. Your scheme maybe in-corrected if you delete condenser and dont have any liquid stream in 1st tray
Hi Muhammad,
the problem seems to be, that ASPEN needs a vapor AND liquid phase. Are you trying to run the model without reflux?
The easiest way to avoid this problem is probably to run a simple column with reboiler and condenser, because it's easy to converge.
Add a pseudo-stream (vapor phase) on stage 1 and route it to the compressor. In the compressor model, specify the required output pressure needed to reboil the bottoms (include a reasonable DT of ~ 10 to 12 K).
Note, that the vapor leaving the compressor model will be superheated. To make sure your energy balance adds up, add a heat exchanger representing the condensation side of the integrating reboiler / condenser to the compressor output stream. Here specify the reboiler duty required in the column. Probably, this block does not completly condense the vapor. You should add a flash block representing the condensate drum, where you reduce the pressure to the value in the columns top stage. Additional flashing will probably happen: At some point you have to remove the compressor duty from the system.
Once you have acquainted yourself with the inner workings of your physical system, you can try run a more realistic simulation. A column with external condenser, flash vessel (i.e. reflux drum), flow splitter for distillate and reflux, additional cooler to remove excess heat and reflux stream routed back as liquid feed to stage 1 of your column. Now you will have a liquid for stage one, as ASPEN correctly desires. A fully integrated simulation will be difficult to converge.
Have lots of fun
Armin
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