feed stock changes

[Christy BohannonParticipant]

We are currently running a feed stock that is much lighter than what we normally run and are designed for. We have had some problems with excessive foaming and channeling during the quench cycle. Is there any precautions (increased / decreased heater temp, drum pressure) that have help others to prevent carryovers while running abnormal feed slates?

[coker squirrelParticipant]

Some crudes tend to foam more than others. If the foaming is happening after switch, be careful not to inject too much quench steam. If the coke is shot, you may try decreasing heater outlet temperatures. Quench water tends to channel through shot coke. You may also want to track your crude slates to develop a history of how certain crudes react. You can also try adding a little clarified oil to settle things down.

[Christy BohannonParticipant]

How does clarified oil help? What are your specs on this?

[coker squirrelParticipant]

Clarified Oil is Cat Cracker bottoms. Shot coke is low in asphaltenes. Clarified Oil will help with additional asphaltenes as a bonding agent.

[Anonymous]

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

[coker squirrelParticipant]

Thanks for the explaination. I didn’t know exactly how the clarified oil worked but your explaination makes sense.

[Anonymous]

Dear Mr. Garyville,

I understand that you had problems while processing Low Asphaltenic VR feed in your Coker. Could you please explain the problems you had faced in ur drums during Low Asphaltenic VR feed processing?. Were there any problems on Hot spots in drums, Coke Splillage, Blocking / plugging of bottom nozzles, etc.

Could you please also share what was the typical Asphaltene (C7 Insoluble) content in VR below which you had faced these problems in your drums.

I would be glad if you could also share what was the typical Crude slate which was being processed in ur refinery during this period of problem.

Thanks & Regards

D.P. Prasanna
INDIA

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