Coke fines in the main tower

[Hedewandro Lucredi]

We had a sudden leaking in the main tower bottom reboiler. This reboiler is by heavy gasoil circulation. Almost in the same time the bottom pump suffered a cavitation. We observed coke fines in the light gasoil and the sour water in top vessell . Is it possible that besides the coke fines carry over to the top sidestreams some coke fines affected the bottom pump ? The steam inside the tower from the leaking “washed” the internal tower and produced a lot of coke fines and part went to the bottom tower and affected the bottom pump? We observed coke fines in the pump suction filter or this coke fines found was from the bottom tower ?

[dblewis]

Are there generally a lot of coke fine carryover from the drums? Do you have a foaming problem in the coke drums? Do you use a anti foaming additive?

[Hedewandro Lucredi]

We checked and there is no fine carryover (huge space in drum top). No foaming problem. We use anti foaming 100000 cST. We think the problem was from any coke fines from packing beds, trays that the steam removed part of it.

[cjaviervarela]

Coke fines will reduce the pump lifetime, but not probably cavitation. You can check fine at the bottom once per week to make history and try to predicted this kind of event.

Yo could be ok with the foam control, but still suffer upset, check level indication (gamma or neutronics) and also top drum pressure (it usually suffer fluctuation during a foam over)

Leaking of ligther material to the bottom could generate cavitation, how is yours experience with that pump during start up?

[Hedewandro Lucredi]

During the start up we have some cavitation but after above a determined temperature the cavitation stopped.

[cjaviervarela]

Lucredi, at the cavitation moment, you were operating at typical pressure and products?
If not that could be the cause

[Author]

Posts