- Operating a column under vacuum is typically for following scenarios
1. Low temperature constraint due to Heat sensitive material
2. Lowering of high boiling component boiling point
So, while operating a column under vacuum with vertical thermosiphon reboiler one should carefully decide steam temperature and pressure required at reboiler inlet flange-based process side conditions and not at column bottom flange.
The Process side temperature at reboiler flange inlet will always be higher than column bottom temperature due to additional static head based on thermosiphon requirement which will have a direct impact on steam temperature and pressure requirement.
Take into consideration the above point when finalizing the utility conditions for plant.
Written by: Rajesh Pingale