Debutanizer Reboiler Fouling
Debutanizer Reboiler Fouling
(OP)
Hello Everybody:
We are suffering from Reboiler fouling of our Debutanizer tower, sever coke on the shell side have been observed during our recent shutdown. I'm not sure if you guys have experienced similar problem in the past and how you mitigate the fouling mechanism in your system.
Do you guys know the exact mechanism(s),?
We are suffering from Reboiler fouling of our Debutanizer tower, sever coke on the shell side have been observed during our recent shutdown. I'm not sure if you guys have experienced similar problem in the past and how you mitigate the fouling mechanism in your system.
Do you guys know the exact mechanism(s),?





RE: Debutanizer Reboiler Fouling
One mitigation that we use is a system of spared reboilers. Although this requires some extra safety considerations because the reboilers need isolation valving and an independent relief system from that of the tower, the solution is a pretty sure mitigation against the need to shutdown the whole train due to a fouled reboiler.
best wishes,
sshep
RE: Debutanizer Reboiler Fouling
We have a debutanizer tower in a steam cracker plant and during a 5 years run, we also suffer from severe fouling in the reboilers and loss of heat duty. A steam pressure increase is usual along time.
To overcome that problem we will install a new reboiler, a spare one in parallel with the existing one (already taught by the licensor - tie-in from plant startup).
As sshep said you need isolation valves and for this you also need to change the supporting system in the column for the two reboilers.
AndreChE
RE: Debutanizer Reboiler Fouling
The reason is that the base temperature causes the conversion of dienes to form polymerization material.
You can do the following:
- Add a spare reboiler if you are concerned about down time and do not want to cut the products to users for some days
- Add inhibitor (antipolymerization chemical in the DeC4 feed or DeC4 bottom)to prevent polymers formation and prolong the life of the reboiler.
- Desuperheat the steam to the rebolier to reduce shell skin temperature that will help reducing polymerization problems.
Hope this would help you
Cheers
SmartEngineer
RE: Debutanizer Reboiler Fouling
If you are making any new design, I would focus on getting the tubewall temperatures down by not only desuperheating, but designing for higher process side circulation (lower % vaporization). Not sure what you have downstream but if you have another tower (deC5 tower) recieving the bottoms, a possible mitigation is to recycle some C5 distillate back to your deC4 bottoms to reduce your tower bottoms temperature. Incidently, what sort of temperatures are you getting across your reboiler (tower bottoms vs reboiler outlet)?
best wishes,
sshep
RE: Debutanizer Reboiler Fouling
yes we are thinking to re-design the current exchanger. one of the proposed modification is to go for counter current to co-current operation, some people tried this and it did work.
We do have isolation valves across the DeC4 reboilers, when ever we notice a problem with one of them such as tube leak, we will isolate the bad one and run with one reboiler. Feed to the tower must be reduced to maintain product specs if we run with a single reboiler.
RE: Debutanizer Reboiler Fouling
We had film boiling problems in the deC2 and deC3 (I work in a deC2 front end SC plant). We have installed desuperheaters to LP steam (2.8 barg) and it worked.
RE: Debutanizer Reboiler Fouling
RE: Debutanizer Reboiler Fouling
You have a deltaT between the cold and the hot side in the reboiler very high. In those conditions fouling is very severe.
Is it possible to reduce that oil temperature? The best option should be to install a spare reboiler with isolation valves.
AndreChE
RE: Debutanizer Reboiler Fouling
Regards,
RE: Debutanizer Reboiler Fouling