Refining 101: Summer Gasoline
Posted by Robert Rapier on March 16, 2007 - 12:00pm
Just what is summer gasoline? Twice a year, in the fall and in the spring, you hear about the seasonal gasoline transition. However, most people probably don’t understand what this actually means. AAA has provided a Top 10 list explaining the seasonal rise in gasoline prices, and summer gasoline checked in at #7:
7. The summer blend switchover. This transition from winter-blend to summer-blend fuel, a concoction that causes less smog, occurs every spring. It causes a dip in gasoline supplies as refineries in the U.S. shut down temporarily to retool their production facilities.
That's only partially correct, and is probably the extent of most people's understanding of this transition. But given that I am very keen that people should understand the energy industry, it is worth a review, and a layman's explanation. I explained the details behind this transition in Refining 101: Winter Gasoline. But let’s review some concepts.
The RVP is based on a test that measures vapor pressure of the gasoline blend at 100 degrees F. Normal atmospheric pressure varies, but is usually around 14.7 lbs per square inch (psi). Atmospheric pressure is caused by the weight of the air over our heads. If a liquid has a vapor pressure of greater than normal atmospheric pressure, that liquid boils. For example, when you heat a pan of water, the vapor pressure increases until it reaches atmospheric pressure. At that point, the water begins to boil.
In the summer, when temperatures can exceed 100 degrees F in many locations, it is important that the RVP of gasoline is well below 14.7. Otherwise, it can pressure up your gas tanks and gas cans, and it can boil in open containers. Gas that is vaporized ends up in the atmosphere, and contributes to air pollution. Therefore, the EPA has declared that summer gasoline blends may not exceed 7.8 psi in some locations, and 9.0 psi in others. The particulars vary, but key considerations are the altitude and motor vehicle density of a specific location. The EIA summarizes the key points:
As gasoline evaporates, volatile organic compounds (VOC’s) enter the atmosphere and contribute to ozone formation. Gasoline’s propensity to evaporate is measured by Reid vapor pressure (RVP). In order to control VOC emissions, the Federal Clean Air Act Amendments of 1990 require that all gasoline be limited to an RVP maximum of 9.0 psi during the summer high ozone season, which the Environmental Protection Agency (EPA) established as running from June 1 to September 15. The Act also authorized the EPA to set more stringent standards for nonattainment areas. As a result, EPA limits areas designated as “high volatility non-attainment” to a maximum RVP of 7.8 psi during the high ozone season. Some States elected to require even more stringent restrictions to achieve local clean air goals, and require 7.2- and 7.0-psi gasolines.
Butane, which has an RVP of 52 psi, can be blended into gasoline in higher proportions in the winter because the vapor pressure allowance is higher. There are 2 advantages in doing this. First, butane is a cheaper blending component than most of the other ingredients. That makes fall and winter gasoline cheaper to produce. But butane is also abundant, so that means that gasoline supplies increase in the winter because more butane is thrown into the mix. Not only that, but this all takes place after summer driving season, when demand typically falls off. These factors normally combine each year to reduce gasoline prices in the fall (even in non-election years). The RVP is stepped back down to summer levels starting in the spring, and this usually causes prices to increase.
There are some misconceptions that I often seen repeated about this seasonal transition. One is that it is the reason that spring and fall maintenance are done. That is not the case. Most, if not all refineries can carry out this transition without shutting down or interrupting production. The reason that maintenance is done in the spring and fall is that it provides a combination of moderate weather (the inside of a vessel can be unbearable in the summer) and off-peak demand. Vessels must be inspected, new equipment must be installed, catalyst change-outs occur, etc. This is similar to tuning up your car to keep it in proper running condition. But the seasonal maintenance is unrelated to the gasoline transition. In fact, for reasons I won't get into here, seasonal maintenance often complicates the transition.
Another misconception that some have is that they can save money by buying cheap gas in the winter and storing it for the summer. Remember that winter gasoline will pressure up as the weather heats up, and the contained butane will start to vaporize out of the mix. You will end up with less gasoline than you paid for, and you will be contributing to the air pollution problem that summer gasoline was designed to avoid. If, on the other hand, you were to buy summer gasoline and try to store it until winter, you might find yourself having problems getting the fuel to ignite, due to the lower vapor pressure. This would be like putting a little bit of diesel in your gasoline – not very good for your car. So buy and use gasoline in the correct season.
The Politics of Ethanol Blending
I should also mention a bit about ethanol blending. The blending of ethanol into the gasoline pool has been controversial because (among other things) it increases the vapor pressure of gasoline blends. This has resulted in the need for a 1 psi waiver for ethanol-containing fuels. From the previously linked EIA report:
As a part of the Clean Air Act Amendments, conventional gasoline containing 10 percent ethanol was allowed to exceed the Federal RVP maximums by 1 psi.
This of course means that ethanol will exacerbate smog at certain times of the year, and has resulted in a campaign by Senator Diane Feinstein to limit ethanol blending in California:
California contends its refineries can make clean-burning gasoline without oxygenates such as ethanol or MTBE. In fact, California’s Sen. Diane Feinstein contends ethanol’s volatility may be the cause for increasing smog levels in Southern California since the waiver was denied and more ethanol was added to the state’s gasoline supply.However, it looks like she is losing this battle for political reasons:Recently, Feinstein asked the EPA and the California Air Resources Board to investigate the impact of ethanol-blended gasoline on California’s air quality.
She said air quality in the South Coast Air Quality Management Zone has gotten worse this year compared to last and "the switch to ethanol-blended gasoline is considered one of the main culprits in increased ozone."
"Since ethanol’s volatility increases smog, particularly in the summer, I believe we need to look carefully at its impact on air quality," said the senator.
In the face-off between California and Corn Belt states over ethanol, California lost again this month. Federal officials concede that the corn-based fuel additive can increase smog and soot pollution from vehicles. But in a ruling shocking in its disregard for public health, the U.S. Environmental Protection Agency refused for a second time to scrap the rule requiring California to blend ethanol in its gasoline.The EPA conceded that California air quality officials are right about ethanol's polluting effect in summer. Nonetheless, in its tortured ruling, the federal agency said California had not "clearly demonstrated" that the ethanol requirement would delay or interfere with the state's ability to meet federal clean air standards. Incredibly, the ruling said that even if California had demonstrated that the ethanol rule prevented the state from meeting clean air standards, the EPA "would deny the waiver." Why? "This reduction in the use of ethanol would undermine the potential benefits vis a vis energy security and support for rural and agricultural economy that Congress expected" from its ethanol rule.
The EPA ruling's effect is to increase payouts to one special interest, Midwest corn producers. For that California endures higher gasoline prices and dirtier air.
California cannot afford to let this assault on public health, fairness and common sense stand. U.S. Sen. Dianne Feinstein, D-Calif., has persuaded the Senate Energy Committee to add a clause to a pending energy bill that would exempt California from the ethanol rule during summer months. All the state's elected officials should join her in that fight.
All energy issues seem to be completely entangled with politics, and the sad fact is that the politics often trump the science. Ethanol blending is a perfect example where we are willing to exempt certain pollution issues "for the greater good."
Conclusion
Hopefully that was an easy-to-understand explanation of the seasonal gasoline transition in the U.S. The purpose of the transition is to curb pollution, but as the last section demonstrates the politics often interfere with the original intent. Now the next time you hear "season gasoline transition", you will know exactly what they are talking about and what the expected impact on supply and price will be.
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Come on folks, hit reddit and digg, and send this link to your linkfarms (on as many posts as you are inclined to).
Please do so, it really does help us in the long run in improving the discourse on energy...
This is the first time I've posted here, and being a layman (totally) I have not understood a lot of the "rock oil" industry and what we are possibly facing-at all. Thanks to everybody here at theoildrum.com for posting such articles as this one (special tip of the hat to you Robert!!!) that really help explain the nuts and bolts not only what is going on, but fascinating reasons for those questions like "what IS Summer Blend?"
On that track, what usually goes into Summer and Winter Blends? Butane in winter of course, but what about other components, such as straight run, naptha, and the like? (Yes I've been reading here for awhile!) This ties in nicely with the post awhile back about Crude assays (also very informative for newbies!)
thanks again,
Franc (penguinzee)
On that track, what usually goes into Summer and Winter Blends? Butane in winter of course, but what about other components, such as straight run, naptha, and the like?
Well, first of all welcome to TOD. I hope you enjoy your stay.
The simplest explanation to give to anyone regarding summer and winter blends is: Summer blends contain 2% butane, and winter blends contain 10% butane. That right there sums up almost the entire difference. The same ingredients can go into summer and winter blends (cracked gas, alkylate, naphtha, straight run, etc.) but you just juggle the amounts. Naphtha, for instance, has a very low vapor pressure. Therefore, it would be useful for bringing down the vapor pressure of the blend, which would make it more of a summer component. But, it also has a very low octane, so you can’t put much in there without putting in some high octane components to compensate.
Now, some process units tend to get run differently in the summer and winter, but even then that often involves them being allowed to shift the product spectrum toward more butane in the winter and less in the summer. Butane is what it’s all about.
Naphtha does not necessarily have a low RVP. I've had light naphthas pass through my hand that were being sold because they could not blended into even 11 PSI gas. (pentane hexane rich streams)
The component LA refiners most prize as they try to make the strictest RVP (5 PSI in the old days) is alkylate as it has high octane and can have very low RVP. As a trader, that was the juice you tried to cobble together in winter to send to the US in summer.
The key to all of this isn't just butane. In summer you have to cut the front end off of all the components to keep light ends out of the blend by adjusting cutpoints in all the fractionators. The entire distillation specification shifts heavier.
Glad to see you point out though just how much butane can be fit into winter gas. The double whammy of extra production capabitily on top of lower demand in winter is the main reason prices fall hard in fall (despite election year conspiracy theories).
What happens to the light fractions in summer. Are they sold for plastic manufacture ?
I'm assuming that its hard to get the yield of light fractions down below a certain point.
Some refiners have polymerization plants that take c4-c6 and make longer molecules. We did haul light naphthas around to ethylene crackers as well. Third place I saw them disappear was into 3rd world markets where blenders loaded them up with lead and sold it as gasoline (Nigeria, Vietnam eg).
Butanes can also be left in the refinery fuel gas streams to some extent backing out purchased nat gas.
And you are right, there isn't much you can do to lessen lifht end yield except reduce severity in your cracking units which is the wrong direction in high demand season.
Naphtha does not necessarily have a low RVP. I've had light naphthas pass through my hand that were being sold because they could not blended into even 11 PSI gas. (pentane hexane rich streams)
I know that I shouldn't generalize, but that makes it easier to understand without getting bogged down into details. When we start getting into fine details, the eyes of the audience start to glaze over. I have personally never seen high RVP naphthas, but this is of course based on numerous factors. Where are your cut points defined? Are you calling something naptha that someone else would call light straight run? What I have seen is that the RVP of straight run naphtha is very low - down in the 2-3 psi range.
The key to all of this isn't just butane. In summer you have to cut the front end off of all the components to keep light ends out of the blend by adjusting cutpoints in all the fractionators. The entire distillation specification shifts heavier.
It isn't all about butane, but it is about shifting lighter components out in the summer and back in during the winter, and butane tends to be the most important component. But if you were of a mind to, and the economics supported it, you could run your units exactly the same year round and just add butane in the fall and take it back out in the spring.
Glad to see you point out though just how much butane can be fit into winter gas. The double whammy of extra production capabitily on top of lower demand in winter is the main reason prices fall hard in fall (despite election year conspiracy theories).
Exactly. You can always have a fall hurricane screw up this trend, but more often than not it is very cyclical: In the fall you have lower demand and higher supplies because of the butane addition, and in the spring it is the reverse.
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.
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.
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.
Thanks Robert, that does clarify it quite a bit. And indeed, the EPA ruling is stunning in its political audacity. So much for Environmental Protection....
A somewhat related question: When I try to explain to people about what is going on in the oil patch (potential peak, potential export problems, gas is really cheap, etc), the response is always that I'm wrong and it's just Big Oil gouging us. It really seems to gear up this time of year as the gas price goes up. How would you recommend responding to these people? Or is it pointless? It seems that some of them so WANT to believe this that they won't consider any data points.
Cheryl
When I try to explain to people about what is going on in the oil patch (potential peak, potential export problems, gas is really cheap, etc), the response is always that I'm wrong and it's just Big Oil gouging us. It really seems to gear up this time of year as the gas price goes up. How would you recommend responding to these people? Or is it pointless?
It is almost pointless, but I try anyway. If people think that high oil prices are all about Big Oil gouging them, they are never going to understand the problem we face. They will point fingers at Big Oil until they realize that there’s more to it than meets the eye.
So, the question I always ask someone who says something like this are: 1). What is gouging? Please define. 2). How much money should a company be allowed to make? 3). Should it depend on the size of the company? 4). Do you think a major oil company has a higher risk profile than a major software company? 5). Did you know that they oil company earns on average under a dime per dollar of sales, while the software company earns almost $0.30 per dollar of sales? 6). Did you know that oil company profits would plunge if we all drove 10% less?
Those are the kinds of questions I use to frame the discussion. Ask them if they believe demand increases in the summer. Then, ask what they think would happen if prices did not go up as demand increased. There is a limit to how much we can crank up production. This can help them understand a little bit about the supply and demand pictures, and then you can explain that other things affect supply and demand, and it isn’t just a summer issue. Next, you may be ready to hit them with oil depletion and ask them what they think is going to happen when supply starts going down while demand is still rising.
But they have to get past “It’s all an oil company conspiracy” and start understanding the effects of supply and demand.
Thanks Robert, those are excellent responses.
I've known for some time that the profit margins for big oil are very low compared to most big businesses, but for some reason people expect big oil to give their product away rather than profit from it as other companies do.
The risks that oil producers face are also some of the biggest: From drilling expensive dry holes, to sabotage, to equipment failures/replacements, to mother nature's wrath, to explosions and fires...
There is just no comparison to a company that pushes paper for a profit, but the public, as a whole, doesn't seem to get it. It's a very weird mindset. They complain more about the price of gasoline, which isn't essential to life itself, than they do about the price of food. Go figure.
This layperson appreciated the presentation.
It may be hard for ADHD afflicted consumers to consider their own demand, let alone omnipresent supply constraints.
How would you recommend responding to these people? Or is it pointless?
I just jumped over to the Digg thread where this article is being discussed. Look at that, and fear for what we are up against. A sampling of comments:
Menthol Hydrate? Is it any wonder that educating people on energy is such an uphill struggle? This the mindset of the majority of Americans, and our politicians are trying to pander to this sort of nonsense. That's why our energy policy is so screwed up. The one comment just typified the average person: I didn't read the article, but I am going to share my uninformed opinion anyway.
Robert,
Thanks so much for posting the article...very interesting, and presented in a format that a layman(me) could understand. Thanks also for posting the responses on Digg...another reason I believe that we will not do what's necessary until it's too late.
Robert,
Now to an issue dear to my own heart, Diesel fuel, and in particular, Ultra Low Sulfur Diesel (ULSD).
Several months ago, here on TOD, and in several other forums, including at my own small energy group, I made the argument that Diesel fuel would never again be as cheap as gasoline on a sustained basis, due to the need for increased hydrogen consumption extracted from natural gas, thus in effect making Diesel fuel now a "bi-fuel" in that it's price and supply is relient on both crude oil and natural gas.
So far, my argument has been born out. I have not seen Diesel at the pump cheaper than gasoline since ULSD was introduced (once or twice it has been dead equal in price, but only for a matter of hours).
The real test will be in the summer, when gasoline demand goes up, and Diesel prices usually fall, due to the decline in distillant production for heating oil. I have, by the way, also argued, as opposed to those who say we cannot possibly make any type of hydrogen industry work, that the refineries are already operating a hydrogen industry on a large scale, for the purpose of "de-sulfering" Diesel and even gasoline if the source crude is "sour" high sulfer.
What's your take on this discussion? I want to make sure everyone understands that I am in favor of clean Diesel and ULSD, I just feel that the EPA misjudged (as did everyone) what the price of natural gas would be now, back when they originally laid out the ULSD plan back in the late 1990's.
(brief aside, for the financial folks in the audience....did anyone see the twin wild spikes up in crude oil prices today (March 16) followed by a drop right back down the mean price for the day.....any guesses.....speculator longs trying to get a rally going and prop the price back up maybe?
If so the effort failed for the day.....what does this portend for outlying bets by speculators (over the next quarter, let's say?) Can they hold $50....which way will Saudi bet? Will the Saudi strong arm tactics on new member Angola and other older members be able to sustain oil above $50, or are we seeing the "bubble" pop, at least for awhile? Thoughts? :-)
Roger Conner Jr
Remember, we are only one cubic mile from freedom
I made the argument that Diesel fuel would never again be as cheap as gasoline on a sustained basis
All bets are off in times of shortage. On Canada's west coast, ULS diesel today is several cents a litre less than regular. My local stations have regular for C$1.10, up eleven cents since the last time I bought gas. As with you, our diesel prices have previously been above regular for some time. However, a refinery fire in Ontario a few weeks back created gasoline shortages there and raised prices across the country, despite the West coast's independence of physical supply from Ontario.
I've also noticed those two oil price spikes and then the step down. It does look weird.
Diesel has been lower than regular gasoline here in Northern California for several weeks. I've wondered why as my assumption has been that the world wide mix of more heavy, sour oil would cause a long term increase in low sulfer diesel. Any ideas?
Refiners do indeed make a lot of hydrogen. First source is reformers that take low octane naphthas and rearrange the molecules to make branched and ringed molecules with much higher octanes. Lots of hydrogen excessed.
Second source for refineries with sour/heavy feeds is usually a steam reformer though a few have partial oxidation plants. Reformers feed nat gas or refinery made gas only if it is cheaper than some other feed like butane or light naphtha. Catalysts are optimized for specific feeds but you can get away with some fuel switching.
So nat gas is not a critical element in production of ULSD, but rather a cheaper feedstock only.
ULSD doesn't really take that much more H2 to make anyway. When you are starting with Arab Light diesel of 1.3% sulfur, knocking 13,000 PPM to 15 PPM vs 500 really isn't that big an increment on hydrogen (though it's larger than the straight ratio as you get other cracking as well when you go that severe). The problem refiners had was insufficient severity capability. You have to hit it pretty hard to get that last bit out.
I have heard that winter gas has about 1 or 2 percent less energy per gallon. Is this true, and if so, is it due to the increased amount of relatively low energy density butane in the winter gas?
Perhaps we are getting some of the added expense of summer gas back due to the greater energy density of summer gas?
I have heard that winter gas has about 1 or 2 percent less energy per gallon. Is this true, and if so, is it due to the increased amount of relatively low energy density butane in the winter gas?
Yes and yes. I don't know if the number is 2%, but the higher the butane in the gas, the lower the energy content. But the primary reason for the added expense in summer is that butane is considerably less expensive (most of the time) than gasoline. So, the more butane you can put in there, the lower the cost to produce the gasoline.
Minor quibble. Butane actually has a higher btu/lb heat of combustion than iso-octane. But butane lowers the density per gallon of the blend so you end up behind. Premium gas is usually quite a bit more dense so you get more lbs/gallon and mileage there. Not enough to cover the cost delta though in my mind.
Summer gas is more expensive mostly because there are more buyers than sellers. Demand is up, production capacity is down relative to winter (RVP constrained). Add to that speculation pressures (hard to have fear driven price spikes in winter) and up up and away on mogas prices.
My Honda Insight, which is extremely sensitive to mileage-determining parameters, will drop about 10-15% in gas mileage in the winter. The Honda technicians nod and say yeah, it's the winter gasoline blend. I figure there is some additional drop because of rainy weather (additional rolling resistance), but the mileage difference is significant and noticeable for me.
seems extreme.
http://www.eia.doe.gov/oiaf/1605/gg96rpt/btabs.html#tblb02
density delta winter/summer is only about 2%. Old data but doubt the delta is changing that fast.
"If, on the other hand, you were to buy summer gasoline and try to store it until winter, you might find yourself having problems getting the fuel to ignite, due to the lower vapor pressure"
Is this why after storing gasoline over a couple winters, it is so much harder to get my lawn mower to start? I have such a small lot that my 2.5 gallon tank will last me 3 or 4 summers. Maybe it's not a new lawn mower I need, I just need to buy a small amount of summer fuel at the beginning of each summer.
Also, wondering about the butane, is it generally obtained from nat gas, oil or both?
Oh, and thanks Robert for another nice post that makes the petroleum industry more understandle to the layperson.
Is this why after storing gasoline over a couple winters, it is so much harder to get my lawn mower to start? I have such a small lot that my 2.5 gallon tank will last me 3 or 4 summers. Maybe it's not a new lawn mower I need, I just need to buy a small amount of summer fuel at the beginning of each summer.
Yeah, not only will the vapor pressure go down as butane evaporates, but some of the components get slowly oxidized over time to compounds that don't combust very well. I am guilty of the same; in fact I have half a gallon of gas in the garage that I bought for my mower in August. But I won't be surprised if I have trouble running it through my mower in the spring. Actually, this year that will be my wife's problem since I am in Scotland. :-)
What's the shelf life of diesel? It's much longer, correct? I've talked to old farmer types around here who have run 5 year old diesel in their equipment... supposedly to no ill effect.
depends on how clean the system is. Sometimes long held diesel that has a water in the system will start growing bacteria -- bad news. European strategic fuel stocks are rotated periodically to avoid this sort of problem. Biocieds help but aren't foolproof. Some Russian supplies were effectively unusable from all the bugs back a decade or two ago. (fouls filters).
Old gas isn't necessarily bad either. Usually the light ends have evaporated so hard to get engines to start. Also, if the gas had a lot of unsaturated components, it can get gummy over time.
Hi Robert, another great article contributing to the education of the great unwashed like me.
I run a diesel car and I have been wondering for some time why gasoline cannot be put into it (because gasoline is often cheaper as noted elsewhere in the replies). The fuel is injected when the piston is at top dead centre so it seems that it has nothing to do with early ignition because diesel fuel ignites then too.
The two explanations I can think of are:
1. The differing viscosity of the two fuels will result in the fuel pump metering the wrong amount of fuel to inject; and
2. Various seals and gaskets not being compatible with gasoline
But this raises an interesting question. Diesel cycle engines are more efficient than otto cycle engines. I have heard that the military have "multi fuel capable" vehicles.
So why have vehicle manufacturers not designed engines to run on gasoline using the diesel cycle?
Diesels have much higher compression ratios. With ordinary gasoline, they'd knock like h--l.
think those multi fuel military beasts are diesel and jet. Not gasoline.
Gasoline is injected prior to compression, so knocking is an issue in Otto cycle engines, whereas in the diesel cycle the fuel is injected at the point of maximum compression , so knocking should not be an issue if gasoline were used instead.
Also the lighter petroleum grades would not be an issue in a diesel cycle gasoline engine.
then you tell me why no one does it?
doesnt lubricity have something to do with it?
Gasoline is injected prior to compression, so knocking is an issue in Otto cycle engines, whereas in the diesel cycle the fuel is injected at the point of maximum compression , so knocking should not be an issue if gasoline were used instead.
What I would guess might happen is that the gasoline would ignite before it reaches maximum compression in the cylinder. You could also have ignition upstream of where you want it.
I have heard people suggest that ethanol or butanol could be run in diesel engines.
The 2 1/2 ton truck used by the U.S. in the Vietnam era was a multi-fuel that in theory would burn Gasoline, Diesel, Jet fuel etc. It used the "Continental LDS-465" engine which as far as I know was a 4 cycle, carberated (not injected) compression ignition i.e."Diesel cycle" engine.
I think it relied on a mechanical gizmo in the fuel line, linked to the carb. which sensed fuel viscosity to vary the fuel air mixture on the theory that energy content of the fuels likly to be used is related to viscosity.
The Lepard tank was also multi-fuel, a big 800+ hp V10 engine.
There are other examples.
The idea here is that whatever fuel that was found "by the side of the road" could be dumped in the tank and the vehicle would continue to operate. Fuel economy and other factors that you would want to maximise for environmental / peak oil reasons were not top considerations.
Good stuff JM and glad to have your expertise here OilcoEx. Or is it back here? Very informative.
On the knocking thing; detonation (as oppossed to run-on) is caused when an independent flame front occurs in the combustion chamber b/c fuel octane dosen't stand the pressure rise uniformly. This makes a spike in combustion pressure (two fires, one not at the plug} and a short duration burn resulting in less total work under the curve.
Diesels have a single flame front originating from the nozzle so lower octane fuel (with higher BTU's) will burn. (Still kinda makes a sorta knocking noise, huh?)
I work at a 'training center' & have had diesel engines ruined by burning gasoline and gas engines ruined by burning diesel. Too much heat generated in the gas engine, melted parts, washing fuel oil in the crankcase. The problem with running gasoline in the diesel is the injector pump (unless specially built) is lubricated internally by the diesel and it's hard on the cylinder walls and rings. That 'multi' had an extended combustion chamber (a hyper-cycle ?? been a while) and many had the density sensor bypased later to make it 'conventional' diesel.
You can cruise on a mixture of gas and diesel but it'll be tough to start with too much gas. Winter will allow you to go 20% gasoline or in an emergency but with the price of the parts it's probably not a good idea.
I did have an old model B John Deere made in 1936 that ran on either gasoline or a heated diesel mix in a carburetor but it only had 6.5 to one compression and 1100 RPM's was screaming for it :)
"hyper-cycle" was, I think, Continentals name for a technology developed by MAN known by them as "Whisper", a spherical shaped pit in the top of the piston in which most of the combustion took place. I think this was the workaround for the knock issues with Gas as the fuel
Ah yes. I remember seeing that cut out pocket in the center of the piston. The injector stream was directed there.
back in the olden days, that was the 1950's, the international wd-9 (farm tractor) was started on gasoline and then swithced to diesel after it warmed up
With a lawn that small consider getting a push mower. Quiet.
Or get rid of the lawn turf entirely and put in a garden.
Thought about getting a push mower. I have scores of small branches that fall onto my lawn from mine and neighbors trees. I've read that I would have to rake those up before mowing each time.
Also, my gardening efforts have not succeeded in the past for the same reason. Too much shade from the trees.
Another question for Robert...
Yesterday, I had someone start trying to argue with me that the fuel crisis has been solved, and that someone has invented some type of small hydrogen device that greatly increases mileage and will take care of all of our problems since it works off water. I'm not sure, but he made it sound like this somehow magically works with a gasoline engine. To my knowledge, this is a bunch of total bunk.
He made it sound like this is available and doable now. Bear in mind, this is a normally intelligent person. I don't know enough about this stuff to argue on any real basis except to say that my readings indicate that any real-world hydrogen solution is at least a decade away -- not sitting on our back porches.
Do you know what he is talking about?
Last year I had this guy convinced about the energy crisis and the need to take action. He was going to have solar PV installed. But after gas prices came down, he decided I was nuts and now he's on this hydrogen kick. I just don't know how to respond. I care about this family and would like them to consider RATIONAL solutions, not some pill you drop in your gas tank.
Sounds like cold fusion and look how well that took off.
I sent him an email and asked him what the name of this device is or for some links to info on this device that will save mankind's happy motoring days. He has yet to respond. Of course, I did not word it that way.
Yeah, if prices keep going up I'm gonna have to sell my car and get a bike!
http://www.DCguide.com
"To my knowledge, this is a bunch of total bunk."
pretty much.
water is a combustion product so not much chemical energy left. Maybe you can sell your friend some stock in a perpetual motion machine company?
Maybe. It rains a lot here, maybe I could make and sell those gadgets. He really seemed convinced, but didn't answer my questions since he had to go...
Last I knew, gasoline combustion engines weren't too terribly fond of water.
He mentioned something about NASA. There was a comment yesterday about some guy who worked on a secret project for the govt. It was either about hydrogen or cold fusion and is supposed to be the trick we pull out of our hats for energy salvation. I didn't follow the link and don't remember what it was about, but maybe that was what he was talking about. I'll believe it when I see it actually work, but I'll not likely ever believe it will work with our current crop of autos.
Hi Cheryl,
First time post for me. Sounds like your friend saw a video clip from a news story that claimed an inventor had hooked up a "Brown's gas" generator to an automobile and had "driven 100 miles on just 4oz of H2O". Didn't say how much GASOLINE he used though :-). The Wikipedia entry ( http://en.wikipedia.org/w/index.php?title=Special:Log/delete&page=Brown%...) for Brown's gas has been deleted but Google will sell? tell you much!
Thank you Robert and WT for your fine posts.
Edit
An illuminating link:
http://www.phact.org/e/bgas.htm
video link:
http://peswiki.com/energy/Directory:Hydrogen_Technology_Applications_Inc...
Welcome Spaceman!
I think you are right. I recall he made some claim about 100 miles on 4oz of H2O. Thanks, NOW I can follow up.
Cheryl
hmmm wonder where there's a road of 100 miles all down hill....some people are so gullible. I always loved the guys who sold magnets to put on your fuel line because if you lined up the molecules (or some other bull crap) you got more mileage. (oh and by the way, we tuned your engine and put air in your tires so you got 10% from other things)....
Yesterday, I had someone start trying to argue with me that the fuel crisis has been solved, and that someone has invented some type of small hydrogen device that greatly increases mileage and will take care of all of our problems since it works off water. I'm not sure, but he made it sound like this somehow magically works with a gasoline engine. To my knowledge, this is a bunch of total bunk.
Others have gotten to it already, but I get this question on a fairly regular basis. In fact, my Mom sent me an e-mail not too long ago asking about the same thing. This might be worth a quick essay at some point.
When hydrogen is burned, it combines with oxygen and makes water. A lot of heat is released. Now, one can take that water, crack it back to hydrogen and oxygen, and repeat the cycle. So, I could in fact run a car off of water.
BUT, the laws of thermodynamics say that you must put more energy into cracking the water than you can get out of burning the hydrogen. So, it is a losing proposition. Where do you get this excess energy? Let's say I devised an engine where I derive the energy from gasoline, and then use the hydrogen I produce to run the car. I am in fact going to use more gasoline than if I just ran it directly through the engine.
Now, there are a couple of cases where you might be able to pull this off. If you have some source of excess energy, it may not matter that you are getting less out than you put in. Here is an example. Let’s say you have solar panels on your roof, and you generate more electricity than you can use. You could take the excess and use that to turn water back into hydrogen and oxygen, and then run a car off of that. It would be less efficient than if you could use the solar electricity to directly power the vehicle, but it might be workable. The same holds true for a nuclear reactor. If you can produce more power than needed, you could crack water and produce hydrogen. You could have a hydrogen car, but it would be indirectly nuclear.
Gary Bridge
BUT, the laws of thermodynamics say that you must put more energy into cracking the water than you can get out of burning the hydrogen. So, it is a losing proposition. Where do you get this excess energy? Let's say I devised an engine where I derive the energy from gasoline, and then use the hydrogen I produce to run the car. I am in fact going to use more gasoline than if I just ran it directly through the engine.
•••••••••••••••••
Robert,
Your comment above is interesting. Even though this discussion is moving off the subject of summer/winter gasoline... However, the last sentence in your thermodynamics statement above may be rather confusing to some folks. What's he mean by using more gasoline here? I think that you are indicating that H2 would be {reformed} out of gasoline and this is the inefficiency of isolating H2 from a fossil carrier source such as gasoline.
And to this specific element, I agree.
Most folks don't realize aspects of chemical reactions such as reformation which is utilized to isolate H2 from fossil petroleums OR gasification of coal to isolate hydrogen instead of syngas OR even gathering and scrubbing H2 isolated from natural decomposition and biological breakdown of any sort of biomass, even composting.
And the typical consequences of isolating H2 is that is co-produced stream of CO2 simultaneously occurs when hydrogen is isolated from carbonaceous sources with the exception (to my knowledge) being the electrolysis of water yielding two Hydrogen's and one Oxygen.
Multiple experts have repeatedly displayed statistics in the last few years of debates concerning hydrogen hallucinations -- which clearly indicate that the direct electrolysis of water to isolate H2 consumes more electrical energy from a power plant than the resulting H2 is intrinsically worth as a source of energy.
Thus H2 gathered from electrolysis may be the most expensive method to isolate it. This source of H2 would be very clean, yet still as dangerous (ever hear of a hydrogen bomb?) even clean H2 was isolated from water using solar generated electricity.
But back to reality for a minute. I've never been a fan of dangerously compressed hydrogen utilized in any manner whatsoever with the transportation sector. And I'm speaking of combusting H2 (bottled up to 15,000 psi) in gasoline-type internal combustion engines OR utilizing H2 when plucked across PEM membranes in hydrogen fuel cells.
The entire mechanism to bottle and use highly pressurized H2 for transportation fuel is patently silly. It is simply too dangerous and anybody who works with hydrogen would very likely agree. H2 utilized within industrial processes is typically bolted to terra-firma or the H2 is anchored tightly within pipeline infrastructures.
There is one more comment I'd like to make while speaking of hydrogen. The only element which I've witnessed through videos and research reports which seems on the surface to break the 2nd lawsof thermodynamics is something very much akin to the Brown's gas as was linked earlier in this thread.
I've learned that a few inventors have clearly demonstrated using water as the substrate from which to isolate hydrogen PLUS keep it bound to magic oxygen such as with the Brown's gas 2H2O2 recipe. And this technique somehow involves using far, far less electricity, (only a few milli-amps) than would be utilized to normally electrolyze water using a simple anode and cathode setup as a means of electrical current transfer through the H2O.
I've witnessed plastic tank devices which have been engineered to hold about 20 oz. of water. This tube of water is intersected by a series of metal tubes and plates with holes drilled into them. And somehow, the science is to create and direct "the exact resonant frequency" of water back into the 20 oz. of water held within this tank.
The H2O then boils into gray cloud of swirling bubbles which are collected as a 2H2O2 Brown's gas mixture of hydrogen and oxygen. The tank of swirling, bubbling water doesn't get hot and heat up. The resulting Brown's gas is fed at fairly low pressures as it is being produced to a combustion engine which conventionally powers a dune buggy.
What I'm wondering about is how these thermodynamic laws seem to be broken herein... Because so very, very little electricity is somehow utilized to power this special type of electrolysis reaction and thus the cleanly explosive 2H2O2 gasses released from water don't cost very much at all to produce. It seems like the key here is to somehow map, engineer and properly focus "the resonant frequency" of water itself back into itself.
I still would not drive any H2 powered vehicle IF that H2 were highly pressurized and bottled in the trunk. Yet combusting 2H2O2 from water as it may be alternatively produced through a keener method of electrolysis and under very little pressure -- sure sounds like it could be a physical paradigm-shift in the worlds of alternative energies.
I wonder if you could hook up such a device to a restaurant such that you produce free bubble up and rainbow stew?
The first test of any of this sort of claim is:
where the hell are the production units?
If you could do this, do you think the Japanese (who have nil home production of petroleum) wouldn't be producing nice little h2o/electric cars?
Ditto the Chinese, the French, Korea etc etc. Big oil doesn't have the whole world under its thumb. And US engineering doesn't have a lock on engineering brainpower.
America (and the planet ftm) is so diverse...temperature, climate, seasons, geography, altitude, attitude...and certainly as has been pointed out there is no "one size fits all" fuel, fossil or alternative. Transportation and feedstock costs and availability, tariffs, subsidies, air quality goals and Im sure Ive missed many...the point is that there will not or cannot be a "one policy fits all" either. But there does need to be a coherent policy, not this mishmash dictated by "free-markets" and "free-marketeers" (ie speculators, lobbyists, their clients and fiefdoms among others)
I have never known this part of the equation in determining gasoline prices. This is a truly great post!
I am making this as the "Post of the Day" for my "Post Awards" blog. It is also in the running for the "Post of the Week".
Post Awards - Post of the Day
Robert, I think this is a very well written article and is interesting and informative.
I have a question regarding butane. By part of this reasoning that summer gasoline costs more because butane is cheap and in the summer there is much less added to the gasoline blend, why doesn't the price of L.P.G. drop in the summer? If your argument regarding summer gasoline prices being due to supply and demand, wouldn't there be a price decrease in L.P.G. in the summer?
Or does increased summer gasoline usage not create an actual surplus of butane?
In Canada, there were a lot of propane conversions of gasoline engines being done 10-15 years ago, but the price of L.P.G. increased and it isn't really feasible anymore.
By part of this reasoning that summer gasoline costs more because butane is cheap and in the summer there is much less added to the gasoline blend, why doesn't the price of L.P.G. drop in the summer? If your argument regarding summer gasoline prices being due to supply and demand, wouldn't there be a price decrease in L.P.G. in the summer?
Butane price is very cyclical. If you plot the price over the years, you will see it climbing from late summer through mid winter, and falling back in the summer. I know because I have looked at the economics of installing extra tankage to load up on butane during the summer when it is cheap. Somewhere I have the average summer price and average winter price, and I used that to work out the economics.
Locally at least, butane pricing isn't reflected to consumer pricing of L.P.G. and I haven't seen any price reduction at the consumer level during summer. I was interested in converting my camper to propane (440 Dodge), which has horrible fuel economy, but we only use it in the summer and the mileage is limited. Due to the low annual mileage and the increase in L.P.G. price, it doesn't make the propane conversion feasible. In agriculture, we used large quantities of L.P.G. for grain drying and it used to be a relatively cheap fuel, it's not anymore.
I'm not sure if this is an accurate source, but this chart shows a 3x price increase of L.P.G. as a commodity over the last 10 years:
http://www.tfc-charts.w2d.com/chart/PR/M
If butane and L.P.G. are essentially a by-product of gasoline refining, why isn't the summer surplus of butane and lower price passed down to consumers?
i think lpg is closer to a by-product of natural gas production (than refining)
and now for a really important question : what is the winter and summer composition of all those bic lighters?
and what type of fuel is used in a zippo ?
lpgs are more a byproduct of nat gas production. the summer swoon in price is limited by companies that store large amounts in salt domes for use in winter.
In the cargo market the price swings can be extreme. I once saw Med LPG quotes drop from $600/MT to about $50 over 60 days at the end of winter. Extreme shortage (plus probably a squeeze) followed by a collapse.
The retail price for butane is probably not all that competitive. Retailers are selling small lots with hand filling etc. They sell it for what they can get not a constant profit. For all the complaining you see, gasoline price variance is far more competitive than most consumer products. How do people think Retailer X can offer 2 for 1 sales? Maybe they had a 100% markup originally???
Thank you very much for all this information.
I have an Associate Degree in Automotive Technology and interestingly enough engine fuels have never been discussed in any of the courses I have taken. Oh sure they talk about octane rating and that higher octane reduces pinging but that's just about the extent of it. Almost everybody that owns a car knows that! It wasn't until this past year that I really learned something about oil and liquid fuel, how it's made, the oil business, etc. thanks in a large part to The Oil Drum.
By the way I am also a five thousand mile a year bicyclist and eighty percent of that is commuting and running errands, NOT using oil! (most of the oil I do use for transportation is riding the bus).