convergence issue

[aken]

hi Jasper,
This problem solves in aspen but not in COCO. where can l see the output report, so l can try to troubleshoot the non convergence issue. It says l should see the full output report, but not sure where. the example is taken from this paper under distillation: https://www.academia.edu/keypass/YnBraV ... n_Students

[jasper]

[jasper]

Quoting Ross Taylor: you could switch the solution method to 2-pass Ideal K and constant H first. Also, he notices that the column is too tall.

[aken]

Hi. As l read down the paper l noticed their feed tray position was positioned differently as the optimized it. I then took for 30 stages, and put feed on tray number 9 and boom it converged. For 30 stages, and tray 15 (middle) used as a feed tray and with the same specifications, it doesn't converge. My question is, is there a way to tell that non convergence of a distillation column is due insufficient number of trays, or lower reflux ratio than the minimum or its just infeasible separation. if one knows then it will be easy to troubleshoot nonconvergence.

[jasper]

Again borrowing on Ross Taylor's wisdom: the shortcut method (FUG, Fenske - Underwood - Gilliland), in the shortcut panel in the Chemsep GUI should give you quick insight in what may work well. This is not the final answer, as the shortcut method is inexact.

[aken]

Hi. I noticed the FUG only appears after the simulation has converged.

[jasper]

That is correct. The fug panel uses results from a simulation.

Attached is a document that contains tips to solve ChemSep columns if it does not work automatically.