distillation column pressure

[thubelihle]

i have the following utilities to use:
Available steam for reboiler: 25 psig and 100 psig
Cooling water: 30 C
Delta temperature approach between process and utility: >20C, <90C
My questions are
1. Should the bubble point temperature of the condenser be at least 50C to accommodate the cooling water temperature and the delta approach? if so, since l know the distillate composition can l calculate the bubble point pressure that will result in bubble point temperature of 50C, in this case -6.5 psig as shown in the attachment?
2. for the re-boiler, is the pressure not fixed by the condenser pressure less stage pressure drops, if so why are we given steam pressure, not temperature for the re-boiler utilities. How then do l determine the required re-boiler pressure?

[jasper]

Are these questions part of a course?

[thubelihle]

No, l am self teaching simulation so l google papers around and try to reproduce staff

[jasper]

Not sure how to answer these questions. But yes, if you impose 30 C cooling water temperature and 20 C approach temperature you cannot cool below 50C. That does not imply vaccuum distillation is warrented. In practice you may want to pick a larger cooling area and lower your approach temperature perhaps. Not sure. Hard to tell. Depends on the problem.

Same for your pressure drop question - you can only impose so many constraints. If you set some constrains other values will have to match.