×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

Running distillation column with missing trays

Running distillation column with missing trays

Running distillation column with missing trays

(OP)
Dear all,
I am having a shutdown maintenance. Just open a distillation column and found three trays are damaged. Due to the exotic material, we only have one tray for replacement. To order new will take months.
The total number of trays in the column is 50. If we run the column with two missing trays, what will the concern? Is there any calculation that I can refers to. Do you have any experience in running a distillation column with missing trays

Thanks

RE: Running distillation column with missing trays

Assuming you can box up the column with proper downcomer and downcomer seals in the damaged area and assuming only two products (top & bottom) from the column, you will lose about one theoretical tray (50% effcy)i.e., around 5%  in total tray count. It should not really matter, as you can easily compensate this with additional reflux and additional reboil. This can be confirmed by a simulation if you have access to one simulator. Otherwise dont bother and go ahead and box it up and start the unit with one theoretical tray less. In case one of the products ( top OR bottom is having a mission critical spec) keep all the trays in that section(rectification/Stripping) and reduce it on the other side by relocating the trays in case they are interchangeable. Best of luck

RE: Running distillation column with missing trays

Have you found the reason for the three trays' damage ?
Are they adjacent or located in different sections of the tower ?
What kind of damage ? What kind of trays ? Why can't you use non-exotic materials of construction ?

I'm asking these questions because continued operation under the conditions that caused the damage may return and more damage would likely be found in future column openings.

RE: Running distillation column with missing trays

C4Reactor,
it could be useful to know the column service and where the damaged trays are located.

RE: Running distillation column with missing trays

(OP)
Thanks for the response so far.
The damaged trays are located at the bottom. All three bottom-most tray of the Stripping section. The reason it is made of exotic material is due to the high corrosivity of the process fluid at that high temperature. The most likely reason for the damage is like what Alloy said, a sudden increase in heat input to the column causing a boil-up.
I'll keep you updated on the latest.

RE: Running distillation column with missing trays

It is very important to note in which section the trays are missing. Missing trays as the bottom and the top are not as much a concern as ones in the middle. Missing middle trays should be a concern as it would lead to trays on the top not having the liquid level. Is it possible to give random/ structured packing so that the loss due to missing trays can be minimized?

RE: Running distillation column with missing trays

Generally speaking you will have problems to meet the purity spec on the btm product. Anyway you could avoid big troubles by using other possible operating margins. For example:
- reduce the capacity
- increase the stripping duty
- take benefit of margins in the downstream plants, if any, where the bottom product is sent.

In order to better address these points it should be helpful to know the column service.

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!


Resources