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28 comments on Cracking oil is not a funny business

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zero CO2 on March 26, 2006 - 2:34pm Permalink | Subthread | Comments top
Thank you for another great post.

Can you give some estimate on how much energy is lost during the refinery process and what happens to that number when crude is of a more heavy grade.

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Heading Out on March 26, 2006 - 5:19pm Permalink | Subthread | Parent | Comments top
Grin, this is, unfortunately a bit of the problem in trying to simplify what is generally a fairly complicated process, since there a fair number of other steps that also eat up energy within the separation and conversion.  But as a starting point you might note that if you can pull 15% of the oil as gasoline without having to crack it, then you are saving the energy that would be required to heat that subsequently to cracking temperature. Such considerations, and the changing efficiencies that happen when a new and better catalyst is used, make it difficult to come up with an accurate measure of the energy costs of refining.
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zero CO2 on March 26, 2006 - 5:53pm Permalink | Subthread | Parent | Comments top
So when were bumping along the sub 85 plateu; How important is the energy lost in refining progressively heavier crude? Is it significant? Or is it that the energy lost in cracking/refining is provided from burning fractions that aren't useful?

I guess what I'm asking is: Is there, after cracking/refining, as much gasoline in a light sweet barrel as in a hevy crude barrel?

(Im not dumb, Oil is just not my trade....)

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TJ on March 26, 2006 - 6:44pm Permalink | Subthread | Parent | Comments top
Two points:

  1. Cracking is an endothermic reaction.  It does take heat to raise the feed and catalyst temperatures (providing by burning the coke), but most of that energy goes into making the more energetic short chain molecules.  The only energy lost in the sense I think you mean in the cracking is actual heat loss from the equipment to ambient.  Insulation and heat recovery techniques take care of a lot of it.

  2. About the only thing you can generalize is that you will get more distillate and gasoline and less residual from any crude if you use an FCC than if you don't.
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zero CO2 on March 26, 2006 - 7:32pm Permalink | Subthread | Parent | Comments top
Checking out what FCC was on the wikipedia lead to some enlightening reading....

One way of phrasing what Im getting at is:
When the gasoline is in the hummers tank ready to be consumed; Is there already a larger CO2 price tag on the gasoline derived from Heavy than on gasoline from light sweet.

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TJ on March 26, 2006 - 7:51pm Permalink | Subthread | Parent | Comments top
Heavies have more carbon and less hydrogen than lights, so more CO2.  It's not a gigantic difference, though.
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TJ on March 26, 2006 - 7:58pm Permalink | Subthread | Parent | Comments top
And wikipedia is a good source if you want a quick look at the unit operations in an oil refinery.
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28 comments on Cracking oil is not a funny business

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