Deethaniser simulation
Deethaniser simulation
(OP)
Hello,
I am trying to simulate a Deethaniser to give 95 mol % ethane in the OVHD and minimum Propane. It is not converging with recovery spec or vapor fraction spec in the OVHD. Can anyone give any idea how to converge the column and which specs to be used. The Feed stream contains 9.5% Ethane, 0.5% Methane, 13.5% Propane, 18% Butane, and the rest higher HCs i.e. Pentane etc.
Thanks
I am trying to simulate a Deethaniser to give 95 mol % ethane in the OVHD and minimum Propane. It is not converging with recovery spec or vapor fraction spec in the OVHD. Can anyone give any idea how to converge the column and which specs to be used. The Feed stream contains 9.5% Ethane, 0.5% Methane, 13.5% Propane, 18% Butane, and the rest higher HCs i.e. Pentane etc.
Thanks





RE: Deethaniser simulation
Besides the feed stream and OH stream, what else is specified within the system? I would suggest doing a DOF analysis on the system after you determine all the parameters you have specified (depending on the software, this may be done for you).
NGB
RE: Deethaniser simulation
RE: Deethaniser simulation
RE: Deethaniser simulation
RE: Deethaniser simulation
Not sure if this will help, but I'll give it a shot. For me it was insightful to understand that HYSYS models REAL things (not only that it is retardedly/brilliantly dedicated to that idea). That means if you want a model to actually work in reality you need to know some reasonable variables to "define" it. Say, feed rate of stuff going in, condenser duty, re-boiler duty, tray efficiency. Given those physical variables a real column is defined. In other-words it could be constructed in the real world. I believe mathematically you could define several linearly independent equations but they don't specify a physically real case.
Perhaps thinking in terms of a real physical situation will give you insights into why the column is not converging. Hope this helps a bit.
Yours,
Mike F
RE: Deethaniser simulation
RE: Deethaniser simulation
9.5% ethane feed + 0.5% methane + 13.5% propane + remaining C4+s feed
Since the cut between ethane and propane cannot be made perfectly, even in a simulation, the overhead mol% ethane can never get to 95%. (Think if it were ONLY ethane and methane, ethane would be 95% and methane 5% based on the feed).
Wow, I feel dumb.
RE: Deethaniser simulation
Since you cannot condense methane, you must have an overhead vapor leaving the accumulator. The overhead liquid distillate would need to be a draw from the accumulator.
I ran a simple simulation and have attached the report. This simulation contains many assumptions, such as feed rate (1000 lbmole/h), and feed thermal condition (saturated liquid). The tower overhead pressure was 300 psia, with a profile supplied as usual for condenser and tower DP.
Then, I specified the overhead distillate liquid impurities at 5%, and a reasonable bottoms C2 leakage (2%), all on a mole basis.
The calculated reflux ratio was 14.3 and the condenser duty was 5.49 MMBTU/h.
Hope that suffices.
Umesh Mathur
RE: Deethaniser simulation
RE: Deethaniser simulation
Hope it shows up for you.
Umesh Mathur
RE: Deethaniser simulation
Meanwhile your 300 psia column has an overhead temp of 16 F, if you raise the pressure to 450, its a 45 F chiller.
Since we still can not see your runs I'm guessing on the trays and like.
RE: Deethaniser simulation
Best regardcs
Morten