Polymerization in WVO

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

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Polymerization in WVO

Postby SunWizard » Wed Mar 05, 2008 4:34 pm

WVO as it ages oxidizes (reacts with oxygen and decomposes) and polymerizes (forms long chains of molecules, a form of plastic) that can increase the viscosity of your WVO and plug your filters. It also makes what is called "chicken skin" on metal surfaces. It looks like slimy corn flakes if it makes it into your filters. And the oxidation reaction creates acidic suspended water in your WVO which can be very harmful to your IP and injectors.

Time, temp, air, type of WVO, and certain metals can all cause your WVO to oxidize and polymerize (in decreasing order of importance.) Its a chain reaction, that once started, is harder to stop. The metals you use is one easy thing to control, so thats one place to focus even though its the smallest factor. And the tank is the main place to focus since thats where there is lots of air, most use aluminum, stainless, or plastic. The other variables I list are harder to control and your results will vary hugely depending on how you control them. WVO sitting in a steel tank for a long time leads to many poly stories I have read, and have personal experience with.

Hydrolysis is one process that forms polymers. It requires no air, it only needs invisible amounts of water. It degrades the WVO triglycerides into mono and diglycerides, FFA, and polymers. This is why measuring your FFA is the best way to see if you have a poly reaction going on. Another indicator of poly is a paint type of smell when you open a stored barrel or tank of VO and take a good whiff. But a paint smell won't always be easy to detect, while FFA is. Here is an easy, cheap test for FFA that takes a few seconds:
WVO science project, FFA, standards and water testing

If you already have high FFA, an anti-oxidant and no reactive metals and no oxygen won't stop poly. Lowering the FFA is the way to slow or stop the poly chain reaction. This can be done with caustic stripping or Coorga Quik 'n' Free I simply reject WVO from sources with FFA > 3%. High FFA WVO holds onto more dissolved water (not removed at all by most peoples dewatering) which then makes more poly, FFA and acidic suspended water, then repeats faster and faster as FFA goes up.

I think if your FFA isn't too high, and you remove any polymerization by filtering or centrifuge, and then don't leave the fuel in storage or your vehicle tank for more than a few weeks, the poly doesn't have a chance to grow enough in that time to plug a filter, or create acidic byproducts. Except in cases where people have highly heated tanks which accelerate it. Or too large of tanks so it stays in there too long.

So I don't store my WVO for long periods, and keep it in sealed barrels with little air. If you need to store for longer than a few months, this might help:

Here is a link to a company already selling TBHQ as a commercial anti-oxidant for fuel use:
http://www.eastman.com/Markets/Agricultural/Biodiesel/Performance.htm

They also include a chelating agent which stops metal ions like copper which can accelerate the oxidation. There is some interesting performance data on that site also.

TBHQ has been proven most effective in many tests, and is readily available. Here are a large number of studies reviewed here by the NREL. The studies tested many additives on WVO as well as B100, and concluded that the oxidation and polymerization works the same in both. They even explain the chemistry of why they are the same, for those who want the details. Even though nearly all other research by the NREL is biased towards only Biodiesel.

BE30's active ingredient is 30% TBHQ. Its effectiveness is the same or slightly better than TBHQ alone since it also has 1.5% citric acid which slows copper and iron from accelerating poly. These are the same 2 chemicals they add to most new SVO as an antioxidant. All the cubies around here have those on the labels.
Last edited by SunWizard on Fri Jan 28, 2011 12:34 pm, edited 8 times in total.
YVORMV - Your veg. oil results may vary.
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Postby SunWizard » Wed Mar 05, 2008 6:03 pm

There are 2 types of polymerization, thermal and oxidative. We are mainly talking about oxidative here, because thermal requires high heat >300F.

If you start on cold VO, and some of it gets past your rings since they never seal well at startup, (worse on older and worn engines) this VO in your motor oil can polymerize and destroy your engine after many miles. This is why many recommend more frequent oil changes when using VO and biodiesel. This is independent of whether your VO had some poly before you put it in your tank.

A paint smell when you first open a VO container often indicates you have a high level of oxidation going on. Oxidation of VO doubles with each increase of 10C temp. This is one reason you only want to heat the pickup in your VO tank, not the entire tank (another is that it takes too long to heat the entire tank.) And why its not good to keep your VO sitting in warm barrels in the sun for very long. And keep containers full and sealed when possible so there is less oxygen for the reaction.

Here is a good article from the NREL (National Renewable Energy Lab) which has studied biodiesel thoroughly and much of this info applys to VO as well.

One paragraph from it that applys to this topic:

Brass, bronze, copper, lead, tin, and zinc may accelerate the oxidation of diesel and biodiesel fuels and potentially create fuel insolubles (sediments) or gels and salts when reacted with some fuel components. Lead solders and zinc linings should be avoided, as should copper pipes, brass regulators, and copper fittings. The fuel or fittings will tend to change color and insolubles may plug fuel filters. Affected equipment should be replaced with stainless steel, carbon steel, or alumininum.

I have found that brass fittings like valves are OK where they aren't exposed to any oxygen. I have seen brass and copper inside fuel tanks create a mess of poly buildup (ask a Greasecar owner if they ever looked at their tranny cooler dipped into their hot VO tank after a year.)
Last edited by SunWizard on Fri Mar 21, 2008 4:37 pm, edited 3 times in total.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
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Storage in plastic is better than in metal

Postby JohnO » Wed Mar 05, 2008 9:41 pm

I'll add that long term storage of SVO in plastic totes or plastic barrels is better than in steel barrels. In cold weather, when I can't easily process oil into fuel, I dry it (boil dry at 250F) and pump unfiltered into a sealed tote. The dry oil doesn't turn rancid, despite the presence of cooking residue, and smells "fresh" after 6 months. The same oil stored in a sealed 55-gallon steel drum had a definite "paint" smell after only about 3 months. The drum was filled after the tote was full, so some of the tote oil was older yet. I've repeated this exercise each winter for the last few years, and can only get about 6 months storage life in steel. My oldest oil in a tote is 2 years old now, but it was dried and filtered first, and is starting to smell stale, but not like paint.
I suspect that dry, filtered oil with an anti-oxidant, stored in a well sealed plastic container might have a useful life as SVO fuel or biodiesel feedstock for 3-5 years.

Do we want to discuss checking viscosity? It's a sensitive indicator of polymerization beginning.
Cheers,
JohnO
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Postby SunWizard » Wed Mar 05, 2008 9:52 pm

I agree about plastic versus steel that matches my experience and I only store in plastic anymore.

Yes lets discuss checking viscosity. I just got a visgage pocket oil comparator from ebay:
Image

http://www.visgage.com/page_2.htm
It looks like a high precision antique.
YVORMV - Your veg. oil results may vary.
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BE30

Postby WyoSam » Thu Mar 06, 2008 7:41 am

Where do you buy BE30? I can't find a place on Eastman's site.
Not that I have any signs of polymerization, but if BE30 is cheap enough it might be a good prevention.

Some folks are saying it is cheaper and easier to just add a few gallons of diesel to your tank and you'd get the same benefit as BE30. I'm wondering if turpentine also does the same, turpentine is a strong anti-oxidant.

The polymerization issue seemed pretty hot last summer, but then died pretty quickly. Maybe it will come back up with warmer weather, ummm warm weather - that's pretty well faded from my memory now <g>.

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Postby SunWizard » Thu Mar 06, 2008 9:42 am

Its hard to find BE30, someone on Frybrid after reading my posts about this got price quotes but it was only available in large quantities. I think a better and cheaper way would be to get the active ingredient TBHQ which is available from most chemical supply houses. I haven't done it since I try not to store my VO for more than 6 months.

I don't think adding diesel gives you any protection against poly. In fact diesel itself oxidizes and ages faster than VO, but with different byproducts. This is why they always add anti-oxidant additives to diesel. I haven't seen anyone do any scientific testing of it yet. The only tests I saw was heating VO/diesel mixes in an oven which isn't a fair test of poly.
YVORMV - Your veg. oil results may vary.
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Postby WyoSam » Thu Mar 06, 2008 10:37 am

Yes, pretty much as I figured.

Seems the best test for an anti-polymerizing additive would be to test it in a drying oil, like linseed or tung oil.

Sam
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Postby hheynow » Thu Mar 06, 2008 5:26 pm

My steel drums originally had virgin olive oil in them. The inside is coated in a mustard yellow paint or sealer. This must be the coating all drums that contain food products have. I'm using them for long term storage where they're filled to the top, sealed tight and stored in a dark cool place. So far so good.
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Postby WyoSam » Thu Mar 06, 2008 7:33 pm

hheynow wrote:The inside is coated in a mustard yellow paint or sealer. This must be the coating all drums that contain food products have. I'm using them for long term storage where they're filled to the top, sealed tight and stored in a dark cool place. So far so good.


Hi Richard,

Have you tried to heat oil in one of those drums? I'd like to know how well the paint holds up?

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Postby SunWizard » Thu Mar 06, 2008 7:38 pm

*raises hand* I can answer that one. I have a similar painted barrel on my CF and I always heat the VO to 160F, sometimes higher to 180F and its held up just fine. Mine is a maroon red color paint and the barrels originally held glycerine.

And I agree with hheynow, the paint (as long as its not chipped or scratched) has been working fine to stop rust and poly for me. But I haven't used any for long term since I have lots of plastic barrels available.

The brass valve before my CF has built up some nice green slimey chicken skin poly since its repeatedly exposed to air and VO for almost 2 years now. And this fits right in with the topic of this thread, since this is now another experiment that shows brass and copper (main ingredient in brass) accelerates poly, and the black iron pipe fittings right next to the brass haven't developed a poly layer under the same conditions.
YVORMV - Your veg. oil results may vary.
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Postby hheynow » Thu Mar 06, 2008 8:04 pm

WyoSam wrote:Have you tried to heat oil in one of those drums? I'd like to know how well the paint holds up?


Yes to 150*F. The paint is perfect after six months of intermittent heat, but these were brand new drums when I got them. I used THESE PLANS to make my de-water standpipe drum which is well insulated with aluminum bubble wrap and heated by a band heater.
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Postby SunWizard » Fri Mar 07, 2008 8:35 pm

VO varies quite a bit in how fast it makes poly. Soy will poly faster than canola or most any other VO except the ones used for paint. Too bad its by far the most common VO in the US.

Here is a good chart comparing the different oils, the Iodine Value in the last column is the way they are compared (the lower the better):
http://www.the-soap-dish.com/oil-properties-chart.htm
and another:
http://journeytoforever.org/biodiesel_yield2.html#fuelfats

Note that soy is only slightly better than flax/linseed oil, which has been the main ingredient in oil based paint and stain for centuries, because it dries (makes poly) so quickly. They make boiled linseed oil so it makes completely hard plastic like poly really quick when exposed to air (<24 hours) by heating it, bubbling air through it, and adding tiny amounts of copper or other reactive metal powders.

Poly the same basic process as paint for any VO, just varying speeds.
YVORMV - Your veg. oil results may vary.
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Postby HoldOnTight » Fri Mar 07, 2008 10:12 pm

hheynow wrote:
WyoSam wrote:Have you tried to heat oil in one of those drums? I'd like to know how well the paint holds up?


Yes to 150*F. The paint is perfect after six months of intermittent heat, but these were brand new drums when I got them. I used THESE PLANS to make my de-water standpipe drum which is well insulated with aluminum bubble wrap and heated by a band heater.


hheynow and any others planning on the same thing. I have almost exactly that setup for dewatering. I have a heating element a couple inches off the bottom, but the interesting part is this: put a U turn on the end of that standpipe so as you dewater, the falling water molecules won't go into the standpipe, since the opening is facing down. It seems to work well for me.

:)
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Postby hheynow » Fri Mar 07, 2008 10:17 pm

Since 80% of my collected oil is rice bran oil I did a search on its iodine value. According to HERE...

The much lower linolenic acid content of rice bran oil makes it more stable to oxidation than soy oil.


So in addition to a low iodine number being desirable so is a low linolenic acid content number.
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Postby SunWizard » Fri Mar 07, 2008 10:25 pm

The low linolenic aspect is probably reflected in the IV, rice bran has one of the best IV, better than canola even.
YVORMV - Your veg. oil results may vary.
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