Polymerization in WVO

For discussing the modifications needed for diesel vehicles to run with 2 tank veggie oil conversions.

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Postby Welder » Fri May 30, 2008 10:54 pm

"This is because the bond affinity between aluminum and oxygen is much greater than between carbon and oxygen, so the hot aluminum strips oxygen from the carbon dioxide"

Thank you professor Burb! (LOL)

Okay, so now 3 questions spring to mind:

The first one, I already forgot, but the other two are:

1. Is mild steel (mostly iron) likely to exibit a similar affinity to oxygen as aluminum? IE, can we get by with mild steel and CO2 or will that give problems?

and

2. Is coolant temp considered high enough to cause this reaction? I mean, I know that heat only expedites what chemistry already wants to do, but will coolant temps (in an aluminum greasecar style heated veggie tank) cause CO2 to form CO1 and aluminum oxide until the veggie tank consumes itself dissolves into oxide powder? If so, would this take weeks or decades?



I'm betting that chucking a "chunk" of dry ice (liquid?) into a barrel of oil will result in oil that even a FASS can't pump. Good theoretical imagineering though!
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Postby Burbarian » Sat May 31, 2008 9:20 am

All metals will oxidize. In the case of steel, the bond strength between iron and oxygen is relatively weak. Typically water is needed as a catalyst. Scrapped cars parked in the desert under a 20% free oxygen atmosphere can last centuries, due to the low water vapour content of the air. At high temperature, red hot steel will indeed oxidize slightly even in a pure CO2 atmosphere, but this is due primarily to some of the CO2 being initially broken down into CO and O by the heat, and then the iron reacting with this. It doesn't 'strip' oxygen from CO2 like aluminum does. This allows CO2 to be used as a shield gas in welding steel, though welds made in CO2 have been found to be more brittle than those made in argon. For the purpose of vo storage, the problem isn't rust, but ionic nucleation sites for the formation of poly. A steel container flooded with dry CO2 will not rust, and I suspect CO2 saturated vo will not oxidize (need experimental verification). But oxidation is not polymerization. Polymerization is accelerated by oxidation, but polymerization per-se does not need free oxygen.

1. Considering the longevity of red hot turbocharger turbine housings (cast iron) and mufflers/tail pipes (mild steel) where hot CO2 rich exhaust gasses pass through, I'd say deterioration of steel coated in vo at boiling water temperature to be of very low concern. Specially well dewatered vo with no reactive salts in it.

2. Unlike rust, aluminum oxide forms a skin at the surface of aluminum and acts as a passivator, or barrier, greatly retarding further oxidation. Aluminum oxide is also relatively inert. However, if the surface is continually abraded or scoured, then the freshly exposed surface will oxidize also. What is of greater concern in such a situation is where the flaked-off aluminum oxide is going. Aluminum oxide is corundum, the same stuff rubies and sapphires (and anodized aluminum) is made of. It is very hard and highly abrasive. Aluminum oxide is harder than steel, and will do a serious number on your IP and injectors. However, its formation in significant quantity is highly unlikely, specially at the low temperatures in a heated fuel line or tank application.

Dry ice is solid carbon dioxide, available at many industrial gas suppliers as well as the meat packing and ice cream industry. It is available for purchase by the public in round wrapped 'cakes'. At STP it doesn't turn to liquid, instead sublimating from solid directly to gas. I figure tossing a chunk of solid carbon dioxide into the vo for storage will cause it to saturate the vo with co2, and as the co2 bubbles to the surface, will form a shield gas to displace oxygen and water vapor. With an air check valve, the top of a sealed tank will remain slightly pressurized with co2 at just below the check valve cracking pressure.

Admittedly, this is all just blue-sky hypothesis at this point. I wonder if the vo will solidify quickly enough around the ~-60C chunk of solid CO2 to be an issue. You'd likely see the solidified vo flakes coming up to the surface with the CO2 bubbles.
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Postby Welder » Sun Jun 01, 2008 1:14 am

Again I'm grateful for the free lecture Prof Burb. Very interesting tech details.

Anyway, regarding the fact that "polymerisation per-se does not need free oxygen.", I'm wondering how exposure to oxygen compares to either heat or metal ion catalytic action in the formation of vegpoly? I'm not sure if Joe Beatty tried purging his test samples with CO2 or inert gasses in his tests...

Basically, I'd like to know the order of priority in of the various factors in the formation of vegpoly. I always thought that oxygen exposure was the most significant. I guess that's a relative issue, since old style oil paint making was somewhat different than a SVO veggie tank (even a Greasecar tank isn't quite like making paint).



I'd like to hear that an entire tank of dry veggie can be repeatedly heated up to coolant temps in a mild steel veggie tank with no significant vegpoly formation, as long as a CO2 shield gas displaced the natural air. I know that a hot fox is usually ample to keep a small puddle of veggie liquified even in very cold weather, but I'm not sure whether hydrogenation totally prevents vegpoly formation by saturating all (or most) of the bonding sites, or whether hydrogenated veggie can still polymerise. (can lard or tallow?)

I'm also unsure of whether the term "partially hydrogenated" means that the factory hydrogenated the virgin veggie 100% and then blended it with non-hydro veggie, or if it means that they only hydrogenated part of the virgin veggie reacted? Is the term even considered to have an industry standard definition?

If you keep being this informative, Sunwizard may have to start charging fees to surf this forum (LOL)!!!

Thanx!
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Postby wydra » Mon Nov 03, 2008 7:58 pm

I have found that brass fittings like valves are OK where they aren't exposed to any oxygen.

I have brass fittings on the CF rig I just completed. Somebody on the frybrid forum mentioned that I should replace all the fittings due to the possibility of poly from the brass. I spent a lot of time building this thing and the last thing I want to do is tear it apart and rebuild.

Are you still using brass with your setup? If not what are you using instead?

Any thoughts on my system?
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The elbow is stainless and is no longer hard plumbed with stainless from the pressure gauge to T with the pressure relief valve
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Postby John Galt » Mon Nov 03, 2008 9:50 pm

The green coating that will develop on the copper and brass will make it look very environmental. Green is very big these days.
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Postby wydra » Mon Nov 03, 2008 10:50 pm

Well if it's green then it has to be good. :lol:
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aluminum?

Postby 3lr » Wed Oct 07, 2009 2:43 am

SunWizard wrote: alumininum


i had read various places that alu is a no-no and no alu tanks. have you had favorable results with aluminum. also what is the last word on black iron plumbing?
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Re: aluminum?

Postby SunWizard » Wed Oct 07, 2009 10:45 am

3lr wrote:i had read various places that alu is a no-no and no alu tanks. have you had favorable results with aluminum. also what is the last word on black iron plumbing?

Wherever you read that needs to be corrected. Aluminum has been well proven to be the best metal, especially for tanks, thats why frybrid, greasecar, and most other kits use it extensively. Early in this thread are links to several scientific studies by NREL and others proving that.

Black iron (and brass) is OK in plumbing where there isn't exposure to air. Alu or stainless is better.
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Re: aluminum?

Postby 3lr » Wed Oct 07, 2009 4:36 pm

SunWizard wrote:Wherever you read that needs to be corrected.


iirc the reference to coper was made. it is a popular alloying ingredient
for some grades of aluminum, usually used to add strength and hardness.
fuel tanks are generally not structural and a more inexpensive grade of
alu sheet can be used.
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Re: Polymerization in WVO

Postby MikeGoodman59 » Sun Jul 22, 2012 6:18 pm

Sun, following from the start. Looking at the "paint smell" you're talking about. I smell a "pungent" odor on older oil. Is that what you mean?
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Re: Polymerization in WVO

Postby MikeGoodman59 » Sun Jul 22, 2012 7:08 pm

Sun, when you say you try not to store your WVO for than 6 months do you mean your processed, ready-to-go fuel? I have oil that I have had for 3+ but I that's yet to be centrifuged. I know that when it's done with that I smell no "paint." This is an old post. I hope this gets to you.
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1982 VW Rabbit Truck (Custom Conversion, 12/09)
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Re: Polymerization in WVO

Postby SunWizard » Mon Jul 23, 2012 9:17 am

MikeGoodman59 wrote:Sun, following from the start. Looking at the "paint smell" you're talking about. I smell a "pungent" odor on older oil. Is that what you mean?

No, I mean just like oil based paint, since that is the same poly that occurs when paint dries. Pungent is too broad.
YVORMV - Your veg. oil results may vary.
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Re: Polymerization in WVO

Postby SunWizard » Mon Jul 23, 2012 9:23 am

MikeGoodman59 wrote:Sun, when you say you try not to store your WVO for than 6 months do you mean your processed, ready-to-go fuel?

That is total time. I try to process within a few months since it goes bad quicker due to water and food particles.
I have oil that I have had for 3+ but I that's yet to be centrifuged. I know that when it's done with that I smell no "paint."

The smell is only after opening a bung in a sealed barrel and only lasts a few seconds.
YVORMV - Your veg. oil results may vary.
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Re: Polymerization in WVO

Postby MikeGoodman59 » Mon Jul 23, 2012 9:58 am

Thanks. Guess I will have to use what I have. Would love to turn it over quicker. Have been storing as part of my "bunker". Practicing FIFO. CF 55-gal @ 180F @ CF inlte for 4+ hours until it drops to 147-150. that's the 4 passes required,no?

Will take advice and keep full and closed. Have not done that on my service fill barrel.

What do you say about no more than 20 gal in 60 gal tank unless on long trips to avoid oxidation due to oxidation and prolonged exposure to heat? OR ... is it better to keep full to avoid O2 at risk of prolonged heating? Heated pick up is where most the heat resides. Tank is TREKKER from GFS.

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Re: Polymerization in WVO

Postby SunWizard » Mon Jul 23, 2012 10:31 am

MikeGoodman59 wrote:What do you say about no more than 20 gal in 60 gal tank unless on long trips to avoid oxidation due to oxidation and prolonged exposure to heat? OR ... is it better to keep full to avoid O2 at risk of prolonged heating? Heated pick up is where most the heat resides. Tank is TREKKER from GFS.

Too hard to choose, since there are too many variables, like temp.of WVO in the tank, age and amount of use of WVO (measure FFA), how long it sits versus how much you drive, how much it splashes around in the part full tank. In most cases keeping it full is better since less air and less splashing inside, and lower temp in the tank since its more mass that get less heat transfer into it with short trips.

The easy thing I do is to smell every tank each time I open it, and each stored barrel. If you get a paint smell you know you have a problem and need to change something. Or if you start to get filter plugging problems.
YVORMV - Your veg. oil results may vary.
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