In one of our Delayed Coker units we suffer frequent re-foam events: sudden foaming during the steam stripping stage. These events sometimes happen when we turn to stripping to blowdown, so probably the main reason for these events is depressurizing of the coker drum. However, other foaming events happen in the first stage of stripping, when we have stopped feeding VR and we are stripping to main fractionator.
We always carry out the stripping following the same procedure (steam feedrate, time, etc). However, with some vacuum residues we suffer these re-foaming events, while other don’t foam over.
My questions are:
– What are the best practices to avoid re-foam during steam stripping?
– What are the main variables that cause re-foam?
– Is the re-foaming dependent of the VCM of the coke? (this unit has a very short cycle and have a higher VCM in coke)
– Is the re-foaming dependent of the coke morphology?