5 replies to this topic

[Clayton]

Does anyone have any advice on how to converge a CDU. Any general advice would be helpful.

My main problem is when i add the kerosene stripper it doesn't converge.

Are there any specific variables i should use to specify the column. I dont have overflash liquid flows and i saw that is what was used in the Hysys example as one of them.

Also, should i fixed the reflux ratio??

[Zauberberg]

Clayton,

You don't give us any feedback or any inofrmation about your particular system, so it's impossible to come up with any suggestion.
Please upload the model or provide a sketch of CDU tower system - otherwise there is no chance to get any answer from the forum members, simply because we don't have any idea about your particular application.

Best regards,

[Clayton]

This is the Column and the Specs are
the AGO Kero and Basestock(BS) Boiling points

BS - 95% 140-150 oC
Kero - 95% 230 - 240 oC
AGO - 90% 345 - 355 oC
any other information that you may need from me just post
its converged as it is but once i hit reset i cant re-converge it and i think that makes it unstable as i have to add other things to it

well i tried to upload th HYSYS file but it keeps telling me i cant so i wasa wondering if i can email you

[Zauberberg]

You can use this website for uploading files: http://www.engineeri...32/Default.aspx

Upload it, and paste the link inside this thread. Is that OK?

[Padmakar Katre]

Does anyone have any advice on how to converge a CDU. Any general advice would be helpful.

My main problem is when i add the kerosene stripper it doesn't converge.

Are there any specific variables i should use to specify the column. I dont have overflash liquid flows and i saw that is what was used in the Hysys example as one of them.

Also, should i fixed the reflux ratio??

Dear,
Once you add any side stripper to the main fractionator of the CDU you get 2 degrees of freedom which you need to specify. Once these active specifications you have given it should be an issue to get it converge. Whenever you are simulating CDU in Hsysy start the flowrate values with the small numbers then try to achive the actual flows of the pump arounds and side strippers products. Always have a rough material balance or the column split before running the column as this will you to identify that any of the active specification is not overriding the convergence of the simulation model. Hope this could help you a little.

[Clayton]

Thank you i think i have solved it except that i cannot get the AGO to meet product spec (cut point temp)