fug question

[aken]

hi. does the ChemSep distillation column use a rigorous method approach. l say so because l designed a column, went to FUG and obtained the number of stages and feed stage number, reflux ratio, bottoms flowrate. I then input these parameters back but the specified recover in FUG was not met. see attachment. regards

[hkooijman]

yes, ChemSep is performing a rigorous calculation using the PR equation of state. in your example the feed is put at the wrong place, you can tell this by the McCabe-Thiele plot (look up some text books on this if you need). By setting it to the middle (stage 75) will get you a much better separation with >99% purity with 150 stages. I then entered the Eduljee proposals from the FUG page, 118 stages (accepting the feed stage as 59) and a reflux ratio of 14.7. The products were 98.7% pure, close to the specified 99%. The difference may lie in the fact that in a rigorous calculation the relative volatility is not constant. However, I noticed that the Fenske feed stage indicated on the FUG page was 114, which is close to your original feed location. I suspect there may be a bug there, I will investigate.

Do realize that for close boiling components like these, you need accurate binary interaction parameters to get good answers. Also, this separation would normally be done at higher pressures to be able to run the condenser at temperatures > 45 deg C.

HK

[hkooijman]

This bug has been fixed in v8.11 which will be released in January 2019

HK

[aken]

hi, ok thank you.



regards
Akan