distillation column simulation
distillation column simulation
(OP)
Hello,
I have a distillation column and the overhead stream is to be condensed, pumped and some %age of the pumped liquid is to be sent back to the column as Top feed stream. As to converge the column all the feed streams to the column must be already converged, I can not converge the column if I dont specify the pump discharge stream. and by specifying the pump discharge stream, it shows inconsistency message in the stream and can not converge...
so anyone can please guide how to simulate the column overhead that is sent back to the column as reflux stream after condensation???
I have a distillation column and the overhead stream is to be condensed, pumped and some %age of the pumped liquid is to be sent back to the column as Top feed stream. As to converge the column all the feed streams to the column must be already converged, I can not converge the column if I dont specify the pump discharge stream. and by specifying the pump discharge stream, it shows inconsistency message in the stream and can not converge...
so anyone can please guide how to simulate the column overhead that is sent back to the column as reflux stream after condensation???





RE: distillation column simulation
Usually the program will determine how much reflux is needed and you don't have to specify a pump for that...If there is a message about inconsistencies, it's probably due to the fact that the amount flow you are sending back to the tower is less than what the tower needs to meet the specifications.
RE: distillation column simulation
can you please have a look at the attachment to get better idea. Thanks
RE: distillation column simulation
I think your column may be under-specified. Check the DOF in the HYSYS window (everything should be green). If not that sometimes adding another specification and rebooting your computer helps. HYSYS can be kludgy when you have played around with a simulation for a time. You may need to specify something on the bottoms. Steam flow rate etc.
Yours,
Mike F.
RE: distillation column simulation
I am having trouble simulating overhead condensor and pump outside the column.
RE: distillation column simulation
If you already have the recycle installed then another less likely cause of your problem may be the flash calcs between the column subflowsheet and the main flowsheet...I think I only had this happen to my once when I was trying to get overly creative with my simulation.
A screen cap from HYSYS might be able to help us figure out the problem...otherwise we are just speculating here.
RE: distillation column simulation
I guess the 'Recycle' option is installed but I never used it before. Is it the proper way to do the reflux by using Recycle button?
RE: distillation column simulation
RE: distillation column simulation
Hysys allows you to use reflux condensor duties to be passed on to your "condensor" in the model.
RE: distillation column simulation
RE: distillation column simulation
You reminded me of a process engineer setting up a simulation once. The plant had platefin flooded chillers with external vessels that you controled the level of the refrigerant in. He litterally put a flash drum in front of the exchanger and then spent days trying to fiquire out how he could change the level in the exchanger with the simulation package. He was not doing a full exchanger analysis with dimensional data.
But, he had to make the process sheet look just like the P&ID.