Q & A > Question Details
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?
 
Answers
26/07/2018 A: NS Murthy, GE, murthy.ns@ge.com
Not sure whether you have foaming issues in all drums or only in some drums. Typically, the steam stripping starts on the live drum with feed on before switch over. If steam has any condensate accumulation in the line, this practice helps to avoid 'foam out' at drum top. Further, it helps to keep the flow channel (in coke bed) clear and prevent 'hot spot' during coke cutting.
As regards feed related foaming, higher the solids (inorganic) content and higher the paraffins, higher the tendency for foaming. There are good articles from FW and KBC. You may like to refer as well.