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Recent Fuel Changes and How They Affect You: Part 2

Posted by: Erik Bjornstad

As a service to our customers, dealers and friends, Bell Performance hosts quarterly webinars on fuel topics of interest to their friends and their customers. This is Part 2 of a transcript of one of these recent webinars held on Fuel Changes & The Impact They Have On Your And Your Business. If you would like to watch the archived presentation, please click here. If you would like to read part 1, please click here.

Continued from Part 1.

storage-of-gasoline.jpgOkay, the first big change is that the storage life of fuels is completely different now than what it used to be. Back 20, 30, 40 years ago, the storage life of fuel was much longer. There was a study that was commissioned by the US Army in the 1960s. They wanted to study fuel storage life, what they found is very interesting. They found that the expected storage life of gasoline, just regular gasoline should be 2-5 years without any problems. Expected storage life of on road diesel fuel should be up to 10 years or more. That's what they found in the 1960s. The old storage life, 2-5 years or more.

What is the storage life like now? Well, not even close to what it used to be 20, 30 years ago. Now, storage life of gasoline, if it has any ethanol content, which virtually all on road gasoline does, expected shelf life for that is 90 days. For diesel fuel, #2 on road diesel fuel, you put it into storage. In one month, you can expect the storage quality of it to degrade about 25%. That can be anywhere up to 70, 80, 90% if you got things like water or microbes in that fuel.

What’s Changed to Decrease the Life Span of Stored Fuel?

Big difference is storage of fuel is way down compared to what it used to be. What changed? That's the question. What changed about it?

Well, in order to answer that question, we have to cycle back to the supply and demand issue. Demand is at an all-time high, the ability to fulfill that demand has been struggling to keep up, and so you've got greater and greater pressure for the refinery industry to get more gas, and more diesel out of crude oil. A barrel of crude oil, which is 42 gallons, they tend to get a certain amount of the main components out of this. You see, they take gas, they take diesel, jet fuels. They have heavy fuel oil, which is the residuals, the natural gas and then the asphaltines and the tars that are left over. What they want to do is, in order to meet this demand, they want to get as much gas, and as much diesel out of that crude as possible, but there are limitations as to what they're able to do. Right now, they're up to about 29 gallons out of every 42 gallons of crude oil becomes gasoline and diesel fuel. They would like it to be more than that.

buying-fuel.jpgWhat they have been able to do out of necessity really is petroleum chemists have developed what they call hydro cracking processes that they can use at the refinery to get even more gas, and even more diesel out of that crude oil. Now, in order to understand this better, you have to understand basically what we're talking about when we're talking about cracking. What is it all about and what do we mean by it? Consider that crude oil, when it comes out of the ground, it's a natural blend of a variety of large and small sized molecules. Those molecules are typically defined by the number of carbons that they have in them. Different sized molecules tend to be associated with different components. Gas and diesel fuels are made up of molecules that are between 8-21 carbons long. There's a sizable part of the crude oil that's even bigger than that. You can have molecules that are hundreds of carbons in size. What the petroleum industry did was they developed a process to crack those molecules, break them apart and turn them from large molecules into smaller ones. They were able to target this to get more molecules of the size that make up gas and diesel, and therefore, you get more gas and diesel out of it. That's great. That solves the problem to a certain extent, but it doesn't mean there aren't consequences that happen when you do this.

Cracked Feed Stock

The main consequences that if you have a fuel that has a certain amour of what they call cracked feed stock, because they will blend that in. They'll use that as a filler. The more cracked feed stock a fuel has in it, the more likely it is to react and to degrade and to lose stability over a given period of time. The reason why, is because when you take a long molecule like in this illustration, you take a long molecule and you do something and you break it apart into two smaller molecules, what you tend to get is, those smaller molecules tend to have double bonds in them. They're what they call alchemes, if you're a chemist. Double bonds tend to be more reactive. They're less stable and they're more reactive than single bonds are. What that means in practice is that those molecules, those cracked molecules now are in the fuel and they aren't going to go around. They're going to try to react with other molecules and they're going to start catalyzing reactions in that fuel that are eventually going to cause it to become unstable and break apart at a faster rate than if they weren't there.

The consequences of this for where you're at, in the real world, as we said, is poor storage life. Cracked fuels leave the refinery with greater numbers of unstable molecules and these molecules are reacting, and when they react, they don't just react without consequences. What happens is that they tend to join, and they tend to form longer and longer and bigger molecules as they react. What you start getting is the formation of longer and longer polymers in the fuel, and eventually, if you give it enough time, these molecules become big enough that they are too big to stay dissolved in the fuel. They start to drop out of solution, and when that happens, you get color change in the fuel. The fuel starts to darken, things like sludge and varnish and gums start to form. Those are the things that are going to be causing some of the problems that we're going to talk about.

Stored Fuel Problems

1aboom_truck_cnij.jpgWhat does this look like in the field? What that question means is, if you are a fuel user where you are at, what problems is this going to cause for you where you are at?

To a certain extent, the problems are universal, but how you use the fuel basically, whether you are a fleet user, for transportation, or whether you use it in emergency backup generation, that is going to influence the problems that are going to most impact you where you are at. What does this look like in the field? Cracked fuel instability, well, if you are a fleet operator or if you are a driver, then what you're going to get is things like, fuel's not going to burn as completely, or burn as well as it would if it was fresh and that's going to lower the MPGs that you're going to get out of it. It's not going to burn as completely which means that you're going to get more soot and more smoke production from that. You're going to get injector deposits and you're also going to get shortened life and shorter surface intervals for your DPS, your diesel particular filter system. All of these happen because the unstable fuel, because of the cracked molecules in it, the unstable fuels breaking apart, it's not burning cleanly, it's not burning completely in the engine. You're not getting the full energy value out of them.

Injector Deposits

You're getting all of these problems. The big one to be concerned about if you're a fleet or a driver is these injector deposit issues. Injector deposits happen because you're running fuel through them that already has sludge or gum, or heavy polymer components dropping out of it. Those are going to collect in that injector. They're going to cook. They're going to react with the heat and the pressure that's already inherent in an injector kit and you're going to get deposits formed in that injector tip.

The problem this causes for the trucks is that it affects the way the fuel animizes. You don't get the best, most efficient functioning of that fuel injection system, and injector deposits are the single biggest influencer for mileage for any fuel injected vehicle apart from of course, driver behavior. Those are the ways that cracked fuel affects fleets and drivers.

Stored Fuel for Generators and Emergencies

010dieselstorage_compressed-resized-600.jpgOn the other side of the coin, you've got people who tend to store the fuel, and they use it for generators and emergencies. Those people are going to have similar problems again because it's reacting in the same way to them as it is for the fleet and the truck driver. They're going to get sludge formation in the tank, because that fuel is sitting there, all those heavy polymers that are forming, until that fuel is used, they're just going to be sitting there.

It's going to drop out and it's going to collect in the bottom of the tank. The reason this is a problem is because first of all, sludge, those molecules used to be part of the fuel. They used to be dissolved soluble in the fuel. Now they're not, and that means that part of the energy value that those would have contributed, it's not being contributed to anymore so the amount of work they're getting out of it, we would say MPGs, but it's basically the amount of work that it can do, is not going to be as much as it was before. The system's not going to be as efficient because it's lost energy value, and that sludge will plug filters and if it happens to get drawn into an engine to be used, well, it's going to cause the same kind of deposits that it's going to cause in diesel truck engines. Second thing, black smoke, as you can see from the illustration. That is a backup generator that is being load tested. All that black smoke and particles are particles of partially burned fuel. They're partially burned because large polymer molecules do not-. Diesel engines are not designed to burn huge, large polymer molecules.

They're designed to burn molecules that are 10, 15, 20 carbons in length, not 250. All of that is partially burned fuel. Unreliable system operation, that's a big one for emergency assistance for standby generators, for critical use systems and we're going to touch on that a couple of times more later, but that is a big one. They store the fuel motor for it to do a job, but if the fuel is unstable, it's not going to burn as well and that means you've got a greater chance of that system not running like you need it to when you need it to. The bottom line for all this talk about cracked fuels, greater demand means there's more pressure on getting more gas and diesel out of a finite amount of oil, and that means that the fuels that they are producing are dirt. They burn dirtier. They burn less completely, and they do not store anywhere near as well as they used to. That's the first big change. Greater use of cracked fuel, cracked feed stocks in diesel. The second big one is one that everyone is probably well familiar with by now, ultra-low sulfur diesel, or the market reduction in sulfur content that diesel fuel today has over how it used to be 15, 20 years ago.

Continue reading Recent Fuel Changes and How They Affect You: Part 3

The Essential Fuel Tests You Need to Know About


This post was published on May 26, 2016 and was updated on March 27, 2018.

Topics: Fuel Storage