Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

reboiler return below the reboiler draw-out

reboiler return below the reboiler draw-out

reboiler return below the reboiler draw-out

Hi all
regarding the title, it is a naphtha stabilizer column which separate LPG from hydrotreated naphtha with a bottom temp. of 176 deg C at the reboiler draw-out and 190 deg C at the reboiler return.
the feed flow into this column is ranging from 24~35 ton/h
* my question is why the reboiler return is designed below the reboiler draw-out?
thanks in advance

RE: reboiler return below the reboiler draw-out

To mahmmoud30, for low-boiling applications, once-through thermosiphon reboilers vaporizing about 20-30% of the liquid descending down the column can be fed from a trapout pan attached to the bottom tray, therefore located above the reboiler return line.

In these cases, a valved start-up line is generally provided from the bottom of the column.

RE: reboiler return below the reboiler draw-out

dear 25362,
thanks very much for ur valuable contribution, i just want more elaboration on the below,if you have a time,:
1- once-through thermosiphon reboilers
2- In these cases, a valved start-up line is generally provided from the bottom of the column.

thanks again

RE: reboiler return below the reboiler draw-out

Natural circulation or "thermo-siphon" reboilers may be horizontal (process fluid on the shell side) or vertical (process fluid inside the tubes).

In the horizontal units the process fluid velocity is lower although the vaporization % is higher than in vertical units, therefore they need more liquid head as by trapping the liquid off the bottom tray.

The start-up connection is needed to generate vapors (boil up) and bring the column to steady state conditions.
See also:

thread124-95533: Best Elevation for Thermosiphon Reboiler?,

thread124-265704: Column reboiler low boilup rate,

thread124-163883: Column high level protection .. above reboiler return worthwhiles,

thread483-199678: what is "thermosyphon" in connection with a reboiler?,

thread798-206595: Vertical thermosiphon hydraulic calculation

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close