Bunker oil?

[veggie]

ooops !
Missed the part about abrasives and salts.
Yes... Nasty stuff.

BTW....I live so far inland that Bunker fuel is just a myth here, so I won't be chasing that form of fuel any time soon 

veggie

[BioHazard]

So if this stuff is so nasty...how do ships get away with running it in engines that cost more than any of us will probably ever make in our lives?

[mike90045]

So if this stuff is so nasty...how do ships get away with running it in engines that cost more than any of us will probably ever make in our lives?

Steam turbines, not diesels.

[AdeV]

So, Cognos, you reckon this stuff is as abrasive as ash? Or not so much...?

I think you'll find the ash is FAR worse 

[BioHazard]

Steam turbines, not diesels.

ALL of them...or just the modern versions?

From the wikipedia article:

MDO (Marine diesel oil) - A blend of heavy gasoil that may contain very small amounts of black refinery feed stocks, but has a low viscosity up to 12 cSt so it need not be heated for use in internal combustion engines

Marine diesel oil contains some heavy fuel oil, unlike regular diesels. Also, marine fuel oils sometimes contain waste products such as used motor oil.

So it's diluted...but it sounds like it's used or once was used as engine fuel. How do they keep them from wearing out at 2000 hours? What design factors do these giant engines have that allow them to use these fuels without issue?

Also, what about filtering/centrifuging the oil?

The density is also an important parameter for fuel oils since marine fuels are purified before use to remove water and dirt from the oil. Since the purifiers use centrifugal force, the oil must have a density which is sufficiently different from water

Not saying I'm going to go fill a Kubota with bunker oil, but as always I see this as another source of information pertaining to what we like to do here...
(my attitude is rarely "it can't be done", but rather, "think outside the box - how can I do it and prove everyone wrong?" )

However, its undesirable properties make it very cheap. In fact, it is the cheapest liquid fuel available.

I do know about the use of shotguns for cleaning boilers...I used to have an "industrial" Remington 10 gauge designed for that.

[LowGear]

Partial Research Report:

I was reading about the use of Palm Oil at HELCO (Hawaiian Electric Company) and their using it in a boiler situation rather than an internal combustion engine.  The same boilers burn bunker oil with little modification.  It takes a few more gallons per minute but does burn cleaner.  We're talking megawatt programs here.  Unfortunately Palm Oil has almost doubled in price in the last couple of years.  "Unfortunately" unless you're raising Oil Palms in Malaysia or Indonesia.

Casey

[rcavictim]

The rise in price of palm oil is easily explained. Because of rampant greed it now takes more palm oil to grease those same palms.

[cognos]

Fluid Catalytic Cracking Catalyst is many, many times more abrasive than what's called "ash" derived from burning a fuel... then again, not all ash is created equal, either!

Very simply put, cat cracker catalyst is a grain of glorified sand - we start with aluminum silicate - think sand - we end up with something called a trace-metal zeolite molecular sieve. A typical cat unit processing 40,000 barrels per day has about 200 tons of the stuff going around in circles, and loses about 6 tons of catalyst a day, mostly up the stack... but a significant amount ends up in the Heavy Catalytic Gas Oil cut.

Alone, it is seriously abrasive. Don't park downwind of a refinery with a cat unit - it will put microscratches in the paint of your car every time you wash it... Under a microscope, a grain looks just like a tiny sponge, with thousands of holes, and the edges of the holes are literally razor sharp. It is designed like this, in order to maximize contact area with the oil it mixes with, to maximize the catalytic area available.

You can take a handfull of this stuff and just rub it on a rusty pipe - you'll have a shiny spot in no time. I've done it many times, bored, while unloading a truck of the stuff...

Mind you, I'm describing what it's like when it's new. After it's "spent", some of it it ends up in heavy catalytic gas oil - a blendstock component for various heavier products, one of which may be a "Bunker." HCGO can contain up to 5% catalyst "fines."

Spent catalyst is nastier than fresh, it now contains coke, nickel, copper, vanadium, iron, acids, and some powdered concrete from the production vessels thrown in. Rock dust and all...

Back in the good ole' days, when crude was cheap, bunker may have been made with higher-quality feedstock components. Not anymore. If crap is allowed in the end product, then crap will be in the end product, up to the maximum allowed specification for crap. Removing crap from feedstock is expensive. Refineries don't spend money removing crap out of the goodness of their hearts...

There is "bunker" for disesel engine use. I would *guess* that it doesn't contain any heavy gas oil blendstock from the FCCU unit. There are several other production units that make heavy gas oils that *may* contain less abrasive contaminants than FCCU catalyst fines - but not by much... HGO derived from a Crude Distillation Unit will contain actual sand and clay that was originally in the crude oil as it was pumped out of the ground...

I've seen "Bunker 2C" and "Bunker 6C" in refineries. Again, I'd *guess* that these are internal specification designations. I'd guess 2c was lighter and "cleaner" than 6C. I'd *guess* 2C was for the large diesel engines.

I'm also going to *guess* that steam turbine powered ships, and those powered by gas turbines, are more common than those powered primarily by large diesel engines. I'd guess that those large diesel engines are designed to handle the particulate contamination in heavy fuels that would quickly kill a smaller diesel engine. Or they specifically purchase a spec of "bunker" that is designed specially for large diesels. Probably do both.

I know I'm weaselling out a bit on this one, but I don't know a lot about marine fuels - the refineries I've spent the majority of my time in are mostly inland, and don't make much ship fuel. When we did, we'd run off around 100,000 barrels or so - takes a few days - and then the tank guys would blend it per the customer's instructions. I didn't get too involved with that kind of stuff. What I do know about is how and what is made on the various production units, and what is contained in the various products.

[BioHazard]

I'd guess that those large diesel engines are designed to handle the particulate contamination in heavy fuels that would quickly kill a smaller diesel engine.

That's what I want to know more about. What design factors do they have that allow them to burn dirty fuel? (besides being the size of a house  ) Can a centrifuge remove the catalyst?

[cognos]

Yes, a centrifuge wil remove catalyst fines - and other particulate contamination. The trick is to do it economically, since you need to heat bunker 6C up to around 350 - 450°G to get the viscosity down low enough for a centrifuge to be effective, and in real life, heat costs money. So does the imparted cyclonic energy.

In the refinery, catalyst fines are removed to the greatest extent necessary by the use of large liquid/liquid multi-stage cyclonic separation - very like those used in a Dyson-type vacuum cleaner - but with liquid.

I have no idea what design elements are incorporated into any size engine to allow it to burn any type of fuel - wrong specialty, for me.

[Thob]

The rise in price of palm oil is easily explained. Because of rampant greed it now takes more palm oil to grease those same palms.

Thanks for the laugh of the day - 

[DanG]

Seems the biggest Marine diesels have at least three lubrication subsystems - system oil engine crankcase lubricant, cylinder head oil and medium-speed engine oil for piston lubrication. The biggest lubrication requirements are anti-acid additives since bunker can be 0.5% -3.5% sulfur and extreme anti-water emulsion formulation.

How they keep wear down is the pistons have their own pressurized recirculating lubrication and oil-cooling passages  - and the oil contains potassium hydroxide in suspension to check sulfuric acid combustion by-products - so the cylinder bore is continually wiped with a fresh lubrication film that burns off so resists ash build-up.

For the biggest engines you have an engine that can burn a dollar-plus of fuel every second so I imagine they can afford separate small vacuum filtration plant that runs continually for each of the three oiling systems...