5 replies to this topic

[Fire on dire]

Its my first post on this blog. I have acquired alot of knowledge through this.

I m in the middle of a project of a large petrochemical plant which consists of quite a number of columns.

The types of reboilers that are common are thermosyphon (once through & circulation) and kettle type.
All of them have different behaviours and pro and corns. i have also gone through the literature but i couldnt find which one to prefer in my case.

Process fluid is HC and heating fluid is steam. Infact i need to distinguish b/w circulation & kettle type in terms of controlling as my bottom product needs to back mixed.

Two options for controlling (1) controlling inlet steam (2) controlling HT area. which one is better as the condensate would be run in to return header directly.

I would appreciate if such experienced engineers would help me clarifying this confusion. Which one is better for operation

Thanks

[Fr3dd]

If you need to control Heat Transfer area you will need a condensate collection pot in order to control the condensate level. Doing this, you will be able to "hide" portions of the tubes by flooding them in condensate, thus reducing the Heat Transfer area. Obviously, you can't do this if you just return the condensate directly to the header (with no condensate pot involved).

This kind of arrangement is common in thermosiphon type reboilers and its important to take care of the piping arrangement of your equipment, especially on heights (column bottom baffle must be in line with the reboiler tubesheet). If condensate must be returned directly to header, you may need another control scheme or maybe a kettle type reboiler.

[Fire on dire]

Thanks for the reply Fr3dd.
As you mentioned this is common in thermosyphon types. Instead of controlling condensate, why not control steam at inlet. this would be more fast in response and no need for condensate pot at outlet. cascading it with flow of heating media & temperature of column, or analyzers etc.
Whereas condensate valve scheme would slow in response as we have to wait for the condenate level to meet A requirements of reboiler.

your comments plz.

[ankur2061]

Fire on Dire,

GPSA Engineering databook has a fantastic reboiler selection chart. I had converted that chart into an excel file a long time back and it is time to share it with the members of "Cheresources".

Regards,
Ankur.

Attached Files

•  Reboiler_Selection_Chart.xls   114.5KB   192 downloads

[Fire on dire]

thank u sir, its very informative

[Zauberberg]

In addition to advices given earlier, have a look at:

http://www.distillat...question011.htm
http://www.aidic.it/cet/09/18/134.pdf