[J-Rod]

This is a crosspost from open forum, I figured I'd try here as I didn't get any response, everyone is so busy with Katrina, but I think this has alot of bearing on our current situation.

Does anyone have numbers on this? I am curious to know, since I would think less gas could be refined from a lower grade product due to impurities, as well as increasing refining costs. If anyone has any links or ways to point me to a study showing the differences in refinability of the different crudes, I'd greatly appreciate it. -regards, JC

Since we are in a refining crisis right now, and seem to have peaked in sweet light, I am interested in how handling this sour might further affect our refining numbers.

[J-Rod]

80 views and nothing, heh. Maybe I am on my own on this one. I'll post back if I manage to find any real data I suppose.

[khebab]

This is an important problem, I've read that you need more quantity of sour crude oil as well as more energy to produce the same amount of distillates.

[J-Rod]

I dug up a little so far in my googling, more to come later as I find it.

Light, sweet crude is the grade of crude that the vast majority of
refineries are designed to process and there are a limited number of
refineries able to process the heavy sour crude. Heavy sour crude
consists of about 33% sulfur, six times above the limits for
gasoline under emmission control standards.

I don't know how much sulfur is in the sweet light, but 1/3 of your sour being thrown away sure sounds like alot to me.

3) the ratio of heavy sour crude in the US Strategic Petroleum
Reserve (SPR) has been steadilly increasing to the point that it now
represents anout two-thirds of the SPR (415 of 699mb)

I'm no expert but, AFAIK much of the refining process is the same
for all types of crude, but not all. The main defference with sour
crude is that there is a complicated process to remove most of the
33% sulfur content (generating huge yellow piles of sulfur discard)
before the oil can be refined into distilates. Although this is, in
effect, a separate process it would be extremely difficult to
retrofit a "sweet crude" refinery with the desulfuring process and
most such refineries do not have the space to do so anyway, thence
different refineries. Also it isn't such a discrete process that
you just tack it on the front. It would have to be integrated into
the flow of existing refining processes. And, yes, in theory, you
could run sour crude through a sweet crude refinery and end up with
distilates with 33% sulfur content. And I would honestly expect the
governments to move that way, back off their sulfur emmission
standards as the availability of light sweet diminishes with no new
capacity for sour crude being built leaving the only option "to keep
the economy rolling" to allow gasoline with 33% sulfur.

The above sounds really like exactly what I heard Bush say today. Relaxing restrictions on the refining of gasoline to keep some flowing, even if it's nasty.

It also looks like Energybulletin touches on it too, but there's a lack of actual data sets regarding the difference, other than the 33% sulfur I see popping around.

http://www.energybulletin.net/3639.html

[pup55]

There are some people on the board who are in this business and can tell us more authoritatively, but from what I understand, it is possible to run higher sulfur crude through the existing refineries, but, at a much lower throughput.

Also, one of the techniques for doing this is to add hydrogen to the oil to enhance the carbon/hydrogen ratio, which is the main driver in the ease with which fuel is made. Needless to say, the hydrogen is generated through use of natural gas.

I think another issue is the output ratio, that is, the product mix using the heavier crude is different, and this also impacts the economics of the operation.

So you have the prospect of having this heavy crude around, and being able to put it into the refinery, but actually less fuel output because of the product mix and throughput issues. So, if you are running the refinery, you do not want to do this because it impacts your economics, etc.

I will try to quantify some of this.

Others may feel free to comment.

[pup55]

Here it is:

Catalytic Cracking. Earlier, we mentioned that one of main goals of the modern refinery is the production of automotive gasoline. Unfortunately, only a modest percentage of even high API gravity crude oils can be distilled to straight run gasoline. As the demand for gasoline rapidly increased in the early part of the 20th century, refinery engineers developed a process to break the larger hydrocarbon molecules found in heavy gas oils and residual fuels into much smaller, distillate fuel-range hydrocarbons. Early ‘cracking’ of hydrocarbons was accomplished by simply heating residual fuels to high temperatures to promote thermal breakdown and rearrangement of large hydrocarbon molecules. Today, the modern catalytic process is mediated by a free-flowing, recyclable catalyst in a refinery’s catalytic cracking unit (CCU). If carried out in the presence of excess hydrogen, the process is referred to hydrocracking. The useful products of catalytic cracking are cat cracked gasses, cat cracked gasoline, and cat cracked light and heavy fuel oils. These cat cracked distillates are used either for fuel blending or feedstocks to other refinery units. The residual of this process, called cycle oil, is continuously recycled as feed in the CCU. The type of cracking unit, the operating conditions of the cracker, the type and age of the catalyst used, and the nature of the feedstock to the CCU can result in different compositions of hydrocarbons in the cat cracked product stream. These differences in product stream chemistry can be used as potential markers in environmental forensics investigations.

Refining Process

From this, I would infer that most of the time, the factories have to handle various degrees of sour crude, and are set up with a certain sized CCU appropriate for the type of crude they expect to refine.

If they get in more heavy or sour crude than what they are set up for, the CCU runs at capacity, but the plant throughput is lower, because it can only run at the maximum rate of the CCU, therefore the CCU is a bottleneck. At some cost, this can be remedied by expanding or retrofitting whatever upstream equipment, such as the CCU, to handle a higher volume.

So, I think at some point in the day it's an economic decision.

[Aaron]

So, I think at some point in the day it's an economic decision.

I toured Valero's LA oil refinery last year, and this is exactly what they told me.

They can make more money in today's market refining sour, than sweet.

They actually sell the contaminates separately. (Sulfur etc...)

The retrogrades needed to convert from sweet to sour is quite expensive, but less than building it from scratch.

[azur]

but from what I understand, it is possible to run higher sulfur crude through the existing refineries, but, at a much lower throughput.

A refinery is a complex process system that has many constraints. Unless it is designed specifically to run sour crude, the ability to remove sulphur from the products will sverely limit the ability to run sour crude.

Moreover, sour crude is normally also heavy crude, which means that a refinery designed to process light Saudi oil will not be able to run at full capacity on heavier oil, as the bottom end products will constrain capacity.

The "economic decision" is therefore very local to each refinery, depending on the design crude slate, and may require a severe cut-back in nominal capacity to process heavier or more sour crude than it was designed for.

[MicroHydro]

I understand the sulfur piles outside the heavy sour refineries in central Asia are large enough to be seen from space.

[azur]

Not just there. Visit the Laque gas plant near Pau in France, which processes very sour gas (arond 15% H2S) and there are (or at least were a few years ago, not been back recently) sulphur hills.

There is a limited demand for sulphur, and it can not just be incinerated as it turns into SO2, forming acid rain.

On sweet refineries there are usually motlen sulphur pits, where the suplhur is kept in liquid form and then shipped in heated trucks.

[NTBKtrader]

Good uses for Sulphur:

Most of the sulphur produced is used to produce sulphuric acid, H2SO4, the most important manufactured chemical in the world. Sulphuric acid has many uses, including for the synthesis of fertilisers and polyamides. It is used in batteries ("battery acid").

Sulphur is a component of black gunpowder (a mixture of potassium nitrate, KNO3, carbon, and sulphur). It is used in the vulcanisation of natural rubber, as a fungicide, and as a fumigant.

Sulphur compounds are used in the bleaching of dried fruits and for paper products.

http://www.shell.ca/code/products/explo ... r_use.html

[FoxV]

I don't know how much sulfur is in the sweet light, but 1/3 of your sour being thrown away sure sounds like alot to me.

just to fill in this blank spot, sweet light crude (WTI and Brent) has 2% sulfur (sorry, no links but I found it from several googled sources)

so if that 33% sulfur content for heavy sour is true (which seems way to high), then it means we effectively have much less oil remaining than even ASPO states

personally I've always found "Peak oil" the wrong perspective, and it would be really nice to see "Peak Oil Products" charts

[Sparaxis]

Sulfur (sour) and heavy are two different issues for a refinery.

Heavy crudes means that the majority of the products that come from simple atmospheric distillation (up to 650F) doesn't boil off at that temperature, so the yield of light products is lower.

So refineries that process heavy crudes have additional equipment that use low pressures to achieve an effective higher temperature (>650F), then take the streams from that unit and further crack under high temperatures and pressures in the presence of a catalyst to create the shorter molecules that make up gasoline, kerosene, diesel, etc. So compared to light crudes, it takes a lot more energy to make the same amount of gasoline from heavy crudes, but it can be done.

If it's also sour, then the equipment has to be made from stainless steel that isn't corroded by the sulfur. And additional equipment such as hydrotreaters are needed to remove the sulfur from the products. This is also done under pressure, with hydrogen, so the energy consumption is even more.

So heavy, sour crude processing is much more energy intensive than light crude processing, but you can still achieve the same yield as a light crude processing plant if you have all the upgrading equipment.

The 33% number is a typo, error, or miscopy. No crude contains that much sulfur. Sour is generally higher than 1.5%, and few crudes have as much as 5%. Maya crude..the benchmark heavy sour from Mexico, is 3.5% sulfur.

Every refinery daily runs a linear programming (LP) model that is a detailed description of all their units, with yields, energy use, costs, catalyst use, water use, steam use etc. all included. It is driven by what the cost of crude is versus what can be earned by selling the products based on that day's prices. The severity, volume, type of crude, product slate, can all be varied based on profit maximization (or cost minimization). These days, with the light crude margin over heavy crudes at record highs, and product prices also at record highs, refining heavy crude has become much more profitable.

[Antimatter]

Is it easier to produce diesel than gasoline from heavier crudes? Seems like it would need less cracking and isomerization, or is the difference minimal?

[Sparaxis]

Is it easier to produce diesel than gasoline from heavier crudes? Seems like it would need less cracking and isomerization, or is the difference minimal?

It depends how the refinery is configured and how you chose to run it. The Chinese, for example, produce twice as much diesel as gasoline, but rely on catalytic crackers to make the gas oil processed into diesel. In the US, those same catalytic crackers are run to maximize gasoline production. Both use the same heavy bottom feed from heavy crudes.

Also what your target product specification is matters. In China, cat-cracker based diesel has a fairly low cetane value (the diesel equivalent of octane), but that's acceptable there, so it's pretty straightforward. In the US, we require high cetane, so that same stream would have to be further processed to raise the cetane value. So here we tend to favor hydrocrackers which are much more energy intensive than cat crackers to produce diesel, so in that sense diesel is more challenging.

All in all, if you have to use secondary equipment to upgrade heavy bottoms, you can't really generalize about one product over another, since you have to make them all simultaneously anyway. It all takes a lot more energy than with light crudes.

[Tanada]

Is it easier to produce diesel than gasoline from heavier crudes? Seems like it would need less cracking and isomerization, or is the difference minimal?

It depends how the refinery is configured and how you chose to run it. The Chinese, for example, produce twice as much diesel as gasoline, but rely on catalytic crackers to make the gas oil processed into diesel. In the US, those same catalytic crackers are run to maximize gasoline production. Both use the same heavy bottom feed from heavy crudes.

Also what your target product specification is matters. In China, cat-cracker based diesel has a fairly low cetane value (the diesel equivalent of octane), but that's acceptable there, so it's pretty straightforward. In the US, we require high cetane, so that same stream would have to be further processed to raise the cetane value. So here we tend to favor hydrocrackers which are much more energy intensive than cat crackers to produce diesel, so in that sense diesel is more challenging.

All in all, if you have to use secondary equipment to upgrade heavy bottoms, you can't really generalize about one product over another, since you have to make them all simultaneously anyway. It all takes a lot more energy than with light crudes.

OK here is a really dumb question, if you run a mix of waste cooking oil, used motor oil and heavy sour crude through a refinery would it be more or less efficient than biodiesel production through transesterification? I have always wondered why bio oil is converted to bio-diesel instead of just dumping it through a refinery like petroleum. Same goes for any animal or plant derived fats and oils. Why not just add it to the refinery stream?

[MrBill]

You guys are great. Thanks. I have learnt some new things. In any case, if you can direct me to any other sites or links with further background reading on this subject, I would very much appreciate it. Thanks. Cheers.