Running distillation column with missing trays

[C4Reactor]

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

 

[krsmani77]

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

 

[25362]

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.

 

[gegio1960]

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

 

[C4Reactor]

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.

 

[Explode]

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?

 

[gegio1960]

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.