The Oil Drum

63 comments on Refining 101: Summer Gasoline

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OilcoEx on March 17, 2007 - 3:45am

the word that usually comes after light straight run is ....
naphtha (sometimes gasoline). At least in my oil boiling education. Top cut is LSR, next HSR, then jet, diesel and so on. Whoever wrote the wikipedia page must have been to the same jargon school.

http://en.wikipedia.org/wiki/Image:RefineryFlow.png

I tossed most of my spec file when it molded after I retired so I can't drag out typical naphtha actuals. But I did find a sample crude unit distillation for AL. Unrectified gas was shown as 22 PSI RVP(eyeball 85->230 cut). Rectified 10.
(eyeball 100-->230 F). For a Texas crude another assay shows RVP of 7 on the LSR "gasoline". The world wide Dow Open Spec Naphtha calls for 13 RVP max though this is a notoriously loose contract. For trading purposes, we generally assumed naphtha had about the same RVP as gasoline to estimate the loses from vaporization en route.

I kinda doubt anyone would just take summer gas and jam 8% more butane in to make winter though my blending experience is limited to tank farm stocks for a trading house. I'm too lazy to start WAGing VLIs or Driveability indexes but I have to believe those might go a little wonky. Not to mention the octane #'s for nC4 are 89.6/93.8 so you'd be giving away octane something rotten. I always felt sorry for the real refinery mogas blenders. Lots of components, crappy price forecasts, pressure to hit octane with nil giveaway etc, etc. And by the way, never run out or have tanks too full.

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Robert Rapier on March 17, 2007 - 4:24am

I always felt sorry for the real refinery mogas blenders. Lots of components, crappy price forecasts, pressure to hit octane with nil giveaway etc, etc. And by the way, never run out or have tanks too full.

Prior to my current job (Process Engineering Team Leader over North Sea projects), I was doing blending and scheduling in a refinery in Montana. I have done a few hundred gasoline blends over the past few years.

You are correct that octane giveaway is a constant concern, and units are tweaked to balance everything. But the vast majority of the difference in summer and winter blends boils down to butane.

You should post here more often. We need more people who understand the energy industry and are willing to share that knowledge. Of course you may get the occasional "Big Oils sucks, and so do you", but most people here will engage and are seriously interested in learning new things.

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OilcoEx on March 17, 2007 - 5:40pm

thanks

I worked in a Process Design shop for 6-8 years on FCCs, visbreakers, H2 plants, hydrocrackers/treaters, some upstream processing (nat gas treating) etc. Had lunch every day with the Shale oil folks, the reformer experts, the crude unit designers and had a little rub off as can be expected. When the fun stopped in the mid 80's I found a way to get into the S&D end of things and ended up trading for a large bank's oil group. That didn't take long to get old.

I wander here from time to time. Comment when I think I have something useful to add. I don't worry much about negative feedback of the "big oil sucks" variety. What I do sometimes find offputting is the "we'e all going to die" pessimism. The problem is large but I can't accept the Kunstler collapse model.