thermosyphon side reboiler

[manuelp]

Hi

We are thinking about revamping one of our distillation columns by installing a side reboiler. We would use a thermosyphon reboiler to put some heat at an intermediate location between the feed tray and the tower bottoms.

The return tray for the vapor/liquid coming out from the thermosyphon is around 80 feet height. As I have an 80 feet liquid column in the reboiler entrance, I can expect a large lift, but I saw some threads about liquid slip in thermosyphon when the return line is very long (and this is the case)

Do you have any experience in thermosyphon side-reboilers placed at the bottom of the column? Would it be better to place it near the level of the return tray? (but a new structure should be installed)

Thanks in advance

 

[sshep]

Horizontal thermosyphon reboilers are often located a considerable distance below the draw and return points. These units are designed for significantly higher vapor fraction discharge conditions than vertical thermosyphons (40% or more vs 10% to 20%). I think this may be a possibility for you if you want to go at grade and do not have significant turndown requirements. This will make access easier as a bonus.

We have several side vertical thermosyphon reboilers in structures next to columns- this is typical. The problem with lifting a low vapor fraction in a vertical thermosyphon begins at the outlet channel. Even if you do swage down to a high velocity return line for the lift, your starting diameter must at least be as large as the tubesheet and more area than the tubes. My experience with some outlet designs requiring lift have not been good. You would really like a vertical thermosyphon to have an outlet channel which returns to the column via horzontal connection.

best wishes,
sshep