Sorry Coker Squirrel – I have throw a flag on this comment. Clarified oil (aka Decant/Slurry) is FCC bottoms, but Resids to Cokers making shot coke are high in asphaltenes. Clarified oil has been thermal & catalytic cracked & hence has little asphaltenes remaining. It is however high in aromatics that do solublize the asphaltenes which slows down the rate of coking & the rapid change in viscosity that promotes foaming. The draw back for Clarified addition is recycle loop between coker and FCC.
Garyville’s problem doesn’t sound like the asphaltenes are too high however, it sou nds like MAP is running a lighter (potentially less asphaltenes) crude than they normally do & they need crank back on operation parameters. Since they normally run lot Maya that the coker was designed around, and with recent Hurricane’s impact on Pemex crude deliveries – I would guess they are running Arab Light mixtures from US Strategic reserves (they could get mix makeup from DOE site if Grarryville knows which SPR its coming from).
When too much of asphaltene is precipitated, it leads to rapid change in viscosity, this is major factor controlling the surface tension that antifoams are trying to control in order to minimize the foaming tendencies.
Regards Charlie Randall