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Distillation Column - Uncoverged

Distillation Column - Uncoverged

(OP)
Good Day Engineers,

I have got a question in regards to the HYSYS model for Distillation Column.

Im modelling Reboiled Absober Column Sub-flowsheet to get the bottoms product of mainly pentanes+.

Input data:

Column Ptop = 2105 kPa and Pbottom = 2107 kPa
T in = 20 oC
Number of stages = 20 stages

1. Top Inlet
Inlet flow = 4,100 kg/hr
Feed Composition:
Methane 5.96%
Ethane 18.91%
Propane 42.13%
i-Butane 10.77%
n-Butane 13.39%
i-Pentane 4.17%
n-Pentane 4.64%
Hexane 0.00%
Nitogen 0.04%

2. Optional Inlet Stream
Inlet flow = 25,000 kg/hr
Feed Composition:
Methane 41.22%
Ethane 30.34%
Propane 22.35%
i-Butane 2.54%
n-Butane 2.32%
i-Pentane 0.26%
n-Pentane 0.27%
Hexane 0.00%
Nitogen 0.70%

The column running and reached the maximum iteration without converging. Im not really sure with the column problem, my preliminary assumption is because the feed composition with Hexane 0%mol. If that the case is there any other way to converged the column? What are the others aspects leading to this problem?

Could you please give me some explanation for this problem?

Thanks in advance

RE: Distillation Column - Uncoverged

You will have to look at your specs. If it dosnt converge its most likely because you specified something that does not make sense (sorry to be blunt).

Best regards, Morten

RE: Distillation Column - Uncoverged

If there is no hexane in the problem, take it completely out of the model.

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

RE: Distillation Column - Uncoverged

nicely spotted! Anything with zero or near zero adds problems! You might also want to consider removing the N2 and just adding it again to the gas phase assuming that all N2 goes that way. Use a component splitter.

RE: Distillation Column - Uncoverged

(OP)
By following the steps from them I can run my model and the column is converged. I deleted the Zero Component and played around with my column specs, the simulation now can converge.

Thanks all

RE: Distillation Column - Uncoverged

Akry,

My recollection is, the difficulty and resources a separation simulation uses is proportional to the number of components (N) factorial or N!. So a 9 component simulation is 9X the resource user than a 8 component simulation. Almost an order of magnitude easier when you removed hexane.

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

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