Diesel Refining Question

[casteld73]

I have been researching the percentages of petroleum products dervied from a "barrel" of crude.
Assumptions:

1 Barrel = 42 Gallons
The barrel is of Crude is Constant. Let's not complicate the matter with different types of crude.

Question:
I have a single barrel of let's say "North Brent" crude. I am going to gear a lab to extract as much diesel as possible from that single barrel. And on the contrary, what is the mimimum amount of gasoline that can be produced.

What is the maximum amount of diesel that can be extracted from that single barrel?

Some simple google searches have left me with 19 gallons gas and 9 gallons diesel.

So, the way I understand this, the chemistry of diesel is such that it is impossible (chemically) to extract as many gallons of diesel form a barrel as it is gasoline.

Does anone have refining experience who can answer this?

Does refining a barrel always result in some percentage of gasoline and diesel? I assume yes.

Anyone have some laymans terms for the chemial composition of the two products and an explaination as to why you wind up with both?

 

[Hansi]

not sure if you tried this site but I find it to be very informative , www.eia.doe.gov then click on petroleum

 

[casteld73]

go there all the time. "kids corner" touches ont he issue. Just doesn't directly address shifts in refining-etc.

 

[Ski in NC]

The product spread from a barrel of crude can be adjusted more towards gasoline or diesel as needed by the market. But it is expensive to do this as it requires chemical processing beyond simple distillation. And crude from different sources has different balances between gas and diesel. Light- more gasoline. Heavy- more diesel and other longer chain hydrocarbons. No expert here, just basing this off what I have read.

 

[rodejetta]

Some crudes have very high percentages of diesel, others low ones. Keep in mind that simply put a crude consists of carbon atoms hooked together to chains (there are some rings, but those are minor). Also, crude oils vary enormously in composition, even within one reservoir the bottom part is different from the top of the accumulation underground.
Gasoline has 8 to 10 carbon atom chains, diesel 14 to 18 and kerosene sits in between. To get each out, there are several ways. One is simply distilling, heating up, and the volatile gasoline comes out at a lower temperature than diesel. That leaves a huge amount of unused crude material. That can be changed into these fuels for a large part also. One is by heating the remaining crude to a higher temperature, and heating is nothing else than making the molecules vibrate more and more. To the point where they break apart into smaller chains. That then can be distilled again.
Another way is put materials in there that are catalysts (somewhat similar to enzymes) and requires less heat (cheaper!); those catalysts are materials that speed up this breaking apart of those much longer molecules, and then the result is distilled again. A refinery has to tune for all these complex things, and that is why they like a crude that is as similar as possible over the long run.
The short end for us is that it is really impossible to generalise how much diesel or gasoline crude oil will produce, sorry.

 

[casteld73]

Let me try to ask this another way:

If I could choose a Crude that is best suited for Diesel, would I be able to produce more or at least as much gasloine?

In addition, is gasoline ALWAYS a product of refining crude or could I potentially refine other products and not get out a drop of gas?

TIA

 

[rodejetta]

Let me try to ask this another way:

If I could choose a Crude that is best suited for Diesel, would I be able to produce more or at least as much gasloine?

In addition, is gasoline ALWAYS a product of refining crude or could I potentially refine other products and not get out a drop of gas?

TIA

Let's take as an example the crude that comes from Norman Wells in the NWT. That smells as if it can be put in a helicopter with just filtering it. Distilling that will produce mostly diesel, some gasoline. Now if you would crack that crude by heating or using catalysts, you could make more gasoline out of it than diesel. Crudes that come from a reservoir that is somewhat leaky, especially for methane and so, often have little gasoline left in them. You could also make diesel out of a gasoline crude by combining those carbon chains again, but that take large amounts of energy.

In theory you could crack virtually all the crude to natural gas, that being methane, and some ethane, butane and propane, and leave no gasoline. You could crack also the gasoline to those. In nature, what I described above with the leaking, that happened likely offshore Nova Scotia with the Sable Island gas. That gas leaked off the main reservoir deeper down, and when that gas gets to the surface at lower temperatures and pressures, butane and propane condense out of it.

 

[casteld73]

Ok-

So is this a fair statement:

Depending on the crude oil used (raw material), the refining process, and energy used to process, varying amounts of gasoline and/or diesel can be produced. In some cases more diesel can be refined than gasoline or vice versa. The process design of the refinery is best matched to a single source of crude since the chemistry of each barrel of crude can be vastly different. This process would be such that the oil company can maximize profits out of the material they are refining. Obviously, they would not want to expend so much energy(and money) creating a product that is produce cheaper by another refinery using a different process/raw material source.

Based on the sources of crude, the world as a whole, will have for consumption some gasoline and some diesel. Bascially, if we wanted to make just diesel from all the crude left it would not be possible. So as long as there is crude there will always be gasoline and the "need" for ICE that run on gasoline.

TIA Again...

 

[rodejetta]

Yes, it is.

 

[naturist]

Yes, that is so, practically speaking.

 

[wolfskin]

Ok-

Bascially, if we wanted to make just diesel from all the crude left it would not be possible.

It would be possible, the technology exists to convert any hidrocarbon (even complex organic material) into simple chains of any desired weight, but it would be expensive (in energy).
Probably it would be even less energy-efficient overall than burning the gasoline in the Otto engines.

 

[TDIMOFO]

http://www.eia.doe.gov/bookshelf/brochures/diesel/index.html


This site really explains a lot about the topic.
Interesting how they get more than 42 gallong of product (not only diesel) out of a barrel of crude... Call me crazy.

Really have a look here.
TDIMOFO

 

[Keith_J]

http://www.eia.doe.gov/bookshelf/brochures/diesel/index.html


This site really explains a lot about the topic.
Interesting how they get more than 42 gallong of product (not only diesel) out of a barrel of crude... Call me crazy.

Really have a look here.
TDIMOFO

And when they "crack" heavier distillates like kerosene and diesel into gasoline, they get MORE gallons of diesel than the combination of kero and diesel. The energy required to do this is a consideration but most refineries have tight energy efficiencies. Flaring of gas products is only done in emergencies where such products, usually gaseous, cannot be stored. Everything from propane up can be liquified and stored.

When crude is high enough in price, the residual from atmospheric distillation goes to a vacuum distillation unit. Resid from that is further reacted until no further product is available. Instead of asphalt, the final product is petroleum coke, something that resembles coal in that is has no melting point and is a glowing solid. It is then quenched, producing CO, methane etc and a bit of hydrogen , all of which go back into the process. Petroleum coke is a marketable product, used in batteries, metal refining and as a fuel.

 

[Powder Hound]

That hydrogen and methane would be really valuable to the refinery, since the cracking process requires hydrogen as an input. When the long hydrocarbon chains are broken, the breaks need hydrogens to fill the now empty bonds if you want a normal hydrocarbon to come out of the end.

 

[Joe_Meehan]

With cracking and reformulation you can convert all the crude to diesel. However it is not economical to do that. The further you push the process one way or another, the more expensive it becomes.

As for the some of the parts being greater than the total, that is easy. But consider this, the total weight will not change the total volume can, some products are lighter per unit of volume than others, which is why fuel floats on water, it is lighter.

Another difference is the total potential energy of the products can vary as well however the total energy including the energy used to crack or reformulate will never be more than the original total energy.

 

[nicklockard]

http://www.eia.doe.gov/bookshelf/brochures/diesel/index.html


This site really explains a lot about the topic.
Interesting how they get more than 42 gallong of product (not only diesel) out of a barrel of crude... Call me crazy.

Really have a look here.
TDIMOFO

The finished, refined products have a lower average specific density **when separated from one another** than they do when they all cohabitate together in one barrel. That is why the final refined volume is greater than the crude volume. That fact merely proves that some of the components are cosolvents to one another, nothing else.

Of course, the mass of oil in a barrel of crude must exactly equal the total mass of all the refined products from that crude. Mass doesn't change; volume and densities do though.

 

[wolfskin]

Try mixing water and ethanol, you get the same result: the volume of the mix is less than the sum of volumes of the water and ethanol. Seen it in high school when they explained solution.