Partial Condenser

[functionlake]

Hi everybody,
I use shortcut methods to calculate Nmin, Rmin for the distillation column which has a partial condenser (means top product phase is vapour).

If the condenser were total (top product phase were liquid), it could be easy to do because the compositions of the overhead vapor, the distillate, and the reflux are all the same. And apply Fenske equation or Winn's modificaton for this case to find Nmin.

However, for partial condenser, how to define temparature of condenser because the condenser like such as a phase flash? due to determine the compositon of the reflux flow? how to find Nmin and Rmin? What methods are used?

And a problem when I use shortcut column of Hysys is K-values. Why do K-values increase when temparature raises?
Example: A reboiler has higher temp than a condenser, but K-values of some component (Nitrogen, methane) in condenser is higher.
If I use K-values from De Priester chart, another temp of either reboiler or condenser result is showed different from Hysys result.

Pls help me. Thank you very much!

[functionlake]

Can someone help me? Why is shortcut column of HYSYS easy to dertermine Nmin and Rmin in this case? But I need a basic theory for this problem?

[mobek]

Re-phrase your question in a concise and clear way. Get a unit operation textbook (I recommend the one written by Coulson & Richardson) and read the distillation chapter thoroughly.

[functionlake]

Re-phrase your question in a concise and clear way. Get a unit operation textbook (I recommend the one written by Coulson & Richardson) and read the distillation chapter thoroughly.

Okie. I want to determine minimum stage Nmin and minimum reflux ratio Rmin for distillation column when the type of condenser is partial condenser (top product phase is vapour). What method or equation is applied in this case? Can use Fenske equation and Underwood equation?
Thanks for your attention! Thank you.
[IMG]http://www.image**************/ims/pic.php?u=20740TjWtN&i=128855[/IMG]

[vnpetroleum]

Hi functionlake,

Your problem may be happened in LPG Plant for C3+ Splitter. When the Gas product is taken from the top and is cooled by the out let line of the discharge of Turbo expander then flashed in Cold Separator. The liquid from Separator will be fed to the top of C3+ Spliter. The operating temperature in Cold Sep is very low (-70 to 80 degree C)

I tried to calculate in HYSYS to know Nmin for your scenario but cannot find any method to apply for this case.

Is there anyone to help? Many thanks.

[ubaid_nedian]

Assalamoalikum
everybody,
I use shortcut methods to calculate Nmin, Rmin for the distillation column which has a partial condenser (means top product phase is vapour).

If the condenser were total (top product phase were liquid), it could be easy to do because the compositions of the overhead vapor, the distillate, and the reflux are all the same. And apply Fenske equation or Winn's modificaton for this case to find Nmin.

However, for partial condenser, how to define temparature of condenser because the condenser like such as a phase flash? due to determine the compositon of the reflux flow? how to find Nmin and Rmin? What methods are used?