4 replies to this topic

Dear friends
I work in the ammonia plant. There are CO2 raschig packings in the inside of the stripper beds that has been rumpled and they spill to the reboiler inside. What cause of this will be able to be to your mind?
Thanks for your help

Attached Files

•  stripper.xls   101KB   96 downloads

[Zauberberg]

It could be anything: pressure surge, flooding, corrosion, or some other issue (e.g. inadequate bed support, or misinstallation) that could have caused damage to the beds and allowing Raschig rings to escape and find their way to the reboiler and - probably - tower bottoms as well. Partial blockage of reboiler circuit will definitely limit your ability to inject heat to the tower, which further causes reduction of feed rate and/or off-spec products.

Have you inspected the tower, any interesting indications that could point out at the main cause of bed upset?

[sm5r3]

The main cause may be, because of high differential pressure (pressure surge) across the column. The high differential pressure may cause of reboiler pump circuit may fall in the column connection, else the gas line may come in contact with the shell side. Also the stripper bottom raschig rings holding plate to be checked for withstanding bedheight. Because of pressure surge, the rashig rings (metallic/plastic), tend to crumble and may fall down through the liquid weir holes in the mounting plate...

[Satyajit]

Hi,
I suspect damage in bed hold down grid of Bed-1 and strainer on take off tray.
As mentioned by others that it could be becuase of high pressure drop causing flooding and channeling.

This is also possible if a fast de-pressurisation or draining of stripper reboiler is done during plant shut down.
It is also possible if you have a tube leak in the reboiler and putting too much steam ( possible during quick start up or foaming incident)
which will exert high vapour pressure at the bottom of bed-1.
So, these are probable causes for the upset.
Is it a benfield system?
Who is the designer of this unit.
The attached PFD has some mistakes; could you attach total PFD with solution analysis and gas composition for further discussion.

Kind regards,
Satyajit

[Qalander (Chem)]

Dear AZDNA Hello/Good Night,

In Case there was a recent loading of raschig rings from new source then we must not forget about the quality(strength-wise)& loading placement problems.other than these most of the issues are idetified very accurately by Zauberberg& Satyajit above.

Hope you may have found the way forward in problem resolution.