Vegetable Oil SVO WVO waste cooking oil as biofuel

[SunWizard]

I have been using a Dieselcraft centrifuge (CF, designed originally for lube-oil bypass filtering, price= $200) to filter my waste vegetable oil (WVO) and it works great. I no longer need to buy replacement filters, and it dewaters the vegetable oil (which no filters can do - including "water block" types.). I put the oil sucked right from the dumpster through a 100 mesh screen into the rig, no settling needed. The oil needs to be heated to >120F and then pumped through it at 90psi and 0.9gpm. It spins at around 7000 rpms. The way I have the water heating elements, it is removing water both by centrifuge action (the best) and by Flash evaporation. I have sent samples to a testing lab and it showed good results, both for water and particle removal. Its easy to clean the rotor of the goop it removes. One operating trick I have learned is to capture the output of the rotor from the instant I shut off the pump, since it starts to dump oil with water and dirt as it slows. I run it all in a single barrel, and from my testing 4 passes seems to get most of the particles out, so it takes 2-3 hours for a 40-50 gallon batch. The longer you run, the more it removes. This works as a mobile rig very easily and is what I intend to use it for, as well as at home.

With any version of this you should make provisions to capture the output of the centrifuge right when you turn it off. The output at that time is often very dirty besides containing up to 4 oz. of water (if there was any water.) By doing this you are removing at least part of the water as a true centrifuge does, which is better than the Flash evaporating that this also does. This can also make it so you can avoid the mistwash step.

Diagram:

I used a closed top barrel with threads, cut off the bottom, put upside down so I could use the 3/4 threaded fitting. Note that I tilt the barrel towards the output so that any water on the bottom gets sent into the centrifuge. If you don't suck from the lowest point, there could be a pocket of water that settles out and keeps re-contaminating the dewatered oil. A cone bottom tank would be the best, but this was a lot cheaper. Here is a good way to test if you have a good barrel drain and tilt, pour an inch of water in the bottom and see if it all runs out the drain pipe. The suction should come from the lowest point, and the pipe should go continuously lower until the pump. Otherwise you could get a pocket of water in your pipes or drum. This the most common problem I see now that many have tried to copy my design and "improve" it.
(edit:)Now I have a Sandy Brae water in oil tester, and here are the results from a centrifuge run I did recently. Average quality WVO source, FFA=2.5%, settled for 4 months. Began at 700 PPM and end 270 PPM with sandy brae, also measured every 30 minutes with my capacitive water in oil meter (link: Homebrew capacitive water in oil meter testing) to make this chart, and temp. compensated.


How long I run it depends entirely on how dirty the oil is to begin with. I stop when a 50 gallon batch at 160F and 90psi has <1/16" layer in the bowl after 2 hours running since the last cleaning. All 5 of those numbers are important.

Reasons that I moved the centrifuge below the rim of the barrel (see 10-14-06 pics below in the timeline), was so it could be liquid tight if I sealed where the feed line perforates the drum with a bulkhead fitting, and using a solid lid with gasket, it could be run or at least carry a load of oil while traveling down the road. When I run a batch that's less than 45 gallons, like around 20-30g, it can splash a little and I set a lid on top, with it partially open by the centrifuge for water vapor to escape. A piece of window screen also works good to prevent splashes or debris getting in there. The only debris I ever got was insects flying into the oil. The centrifuge placement I used is also a better height for the window screen trick, which still allows the water vapor to escape.

Many have asked me why don't you use 2 barrels so you are sure that all the oil goes through the centrifuge each pass. I tried it, and so have many others, it doesn't reduce the number of passes, and it makes it much harder to run since you need to be there each time before the barrel runs out to prevent pump damage and capture the output of water and goo from the centrifuge. And you need to clean the rotor much more, each time it runs out. Its not worth it. That's too much babysitting for me, I like to start it up and come back 4 hours later when its done.

I kept all the text and dates so you can see its development as I went along:

25 September 2006

I just ran my first batch of 15 gallons of WVO straight from the restaurant barrel, 100 mesh (149 micron) screen on sucker, through the centrifuge with no other filtering and it works great. Easy to clean, no more filters to buy. Runs at 90psi, 1 gpm.

Here is my rig, it goes pump>heater>centrifuge>barrel: (This was before I added the fittings on the bottom of the barrel for the pump intake.)

The pump is a free power steering pump off a 84 Mitsubishi montero, hooked to an old 1725rpm 3/4 hp motor I had. As small as 1/4 hp should work, this is what I had laying around:

This pump was easy since it had a rubber line going to the reservoir which I just turned upward and attached my inlet hose:

This goes into a 4500w 220v water heater element run at 110v (=1125w) in a tee in the bottom of the 1.25" vertical pipe. They are longer than an similar wattage 110v element, which means lower watt density, which means less chance of thermal polymerization (burning) of the oil. The oil started at 50 F and got up to 110 F first pass. An inline heater is more efficient since you don't have to heat up the entire barrel, it adds 20-30F right before the centrifuge. If you had to heat the entire barrel that much more means it takes much longer, and you get more heat loss. Plus you get better heat transfer with flow across the element, and its less likely to burn the oil on the element.

I did 3 passes with decreasing amounts filtered each pass, lots in the first pass, with almost no black sludge 3rd pass.
Here is the black gunk that stays in the rotor:

You guys working on the "holy grail" of mobile flash evaporator and filtering might want to look into this since with a little higher temp it might do both. Or you could do a flash or vacuum evaporation then right into this. At 120 F I was seeing small puffs of steam or atomized oil when pumping the hot oil through 2 small orifices at 90psi. This oil was water-free to begin with according to a pan test.

The oil I started with was black and you couldn't see through it at all. And here is the sweet iced tea drinkable looking WVO after only 15 mins for 15 gals:

Here is the makers website with a diagram of how it works: http://www.dieselcraft.com/productinfo_OC20.html

Its very easy to clean, you open it, take a nut off the rotor, and wipe inside parts with a rag. It makes a mess on the rag but not much else.

I think you could clean lots before the rotor fills. The dirt is really compressed. I could have done hundreds of gallons of the oil I had without cleaning it. But I wanted to clean it often just to see the goop.

It needs specific flow rates to work. The dieselcraft website gives info, but its about 0.9 gpm.

Design and operating this rig:

For the pump, you want a small gear or vane pump. I almost bought an Oberdorfer 1000BR gear pump on ebay for $80 until I realized that power steering pumps are the right size pumps. Most pumps are too big, you want a small one, this one is about 3"x3"x3" not counting the pulley and reservoir. You also want it to be easy to mount and to separate the reservoir to input directly to pump. Other models with the same pump I used is Dodge D50 and mitsubishi 2.5L truck from 80-89 and Monteros from 84-89. Test your pump with open flow, it should be about 1.5 gpm. This is the right open flow which will magically drop to about 0.9 gpm at 90psi. If its not the right flow, change the pulley size on the motor. My motor pulley is small so its reducing the slow 1725rpm motor some. Or you could use a variable speed motor if you wanted to be really cool.

Operating:
Turn on the pump to fill the lines before turning on the heater! I turn it on for just a few seconds, it self primes quick, until the first oil drips from the centrifuge, then shut off. You don't want cold oil going through. Then I turn on the heater element, wait about 1 minute, then start the pump. When you hear it whine you know its working.

For the 1st hour, I use both 1125watt inline heaters. This makes the first pass oil going through the centrifuge about 120F. After 1 hour, I usually stop, capture the output and clean the rotor. Then when I restart I use only 1 of the heaters, which heats the oil slowly to 160F by the end when I am done after 2-3 more hours.

Future ideas to test:
This is so close to a flash evaporator already, that I designed it to have a second 4500w heater element at the top T.

Idea #1. put a 3 way valve on just before the centrifuge, run it through a seperate orifice several times into the same barrel until its hot and flash evaporated. Then flip the valve to filter.

Idea #2. About a pint of water may be trapped in the rotor along with the gunk. Try putting a quart jar under the output just when I shut the centrifuge off to see if any water comes out. (edit- see page 12, this idea works,catches about 4 oz., it may be possible to remove sugars/acids without a mistwash if you capture the output at pump shutoff)

Idea #3. Run this thing hot enough to do the flash evaporation and centrifuge in one pass.

I had 2 heater elements in it at first, when the top one sprung a leak and sprayed a fine column about 30' straight up producing a warm golden shrimp smelling oil shower. I took it off until I solve the gasket issue.

29 September 2006

EUREKA! (is that what a wizard is supposed to say when an experiment succeeds?) I ran the same 15 gallons of oil which now after mistwashing had lots of water, visible water, left in there on purpose to see whether it can remove it. Mist washed in the same barrel the centrifuge runs in.

I hooked up a 2x6 concentrating parabolic solar panel to add the equivalent heat of my 2nd 1125w heater element which I don't have installed until the seal is fixed. Plus I just like solar and had it laying around.

Right away it formed a terrible emulsion, with 1" of beer foam looking head, and I thought I just ruined the cleanest WVO I had seen (clean since it had previously been through the centrifuge for about 2 hours = 6 passes.) The milky emulsion cleared up in about 15 minutes of running. It started puffing out many clouds of steam really quick at about 120 F, much more than the first time I ran the oil. Note -it had not puffed any steam after 15 minutes into the original run a few days ago, which is another thing that made me suspect this was steam and not atomized oil. It also fits Tim's description of how his flash evaporator steam releases, you can hear little random puffs just before each steam cloud is visible.

So I left it run for about 2 hours, it slowly got up to about 200 F, and I waited until it was not puffing anymore, then did the pan test. No bubbles at all, EUREKA! no water. This thing just might be the holy grail! More testing to come...

07 October 2006

I just ran my second batch through this centrifuge, and it worked great. This batch was 30 gallons, totally black and smelled like french fries, and I ran it for about 30 minutes. The amount of gunk in the rotor was large, around 1/4" thick all around, but still easy to wipe out, kind of a plastic mud texture to the gunk.

I added the pressure relief valve suggested earlier in this thread from graingers. It popped off and released some pressure at first with cold oil since at startup the pressure is higher, and then closed and didn't pop again.

11 October 2006

I solved the sealing of the water heater elements. Use a 1/16" thick by 1.25" ID metal washer first on the element, then a 1.5" ID washer with a 1/8" x 1.25" O-ring inside. The bigger washer acts like a retainer, preventing blowout. This seals great and has handled the high temp and pressure used with my rig.

So now I am using 2 - 4500 watt heater elements which gets the WVO hot real quick and makes both the centrifuge and the flash evaporator functions work better.

14 October 2006

I had an email asking for more detailed pics so here are some more. Centrifuge in the barrel. The Tee before it is the pressure relief valve with a plastic elbow over it to direct the flow down:

Here is the first heater element:

Second heater element (showing the metal washers that hold the o-ring in place):

Parabolic concentrating 2x6' solar collector (not needed with the 2 water heaters, but fun!)


Here is how I do my pan test for water (link)

Removing suspended water in 1 pass
23 October 2006

A major development to report today. This rig does remove suspended water as a true centrifuge! (but it keeps it in the rotor) With only a simple change to how you operate it: you must capture all the output right after turning off the pump. Several times half the rotor contents were dirty water! (even while the output was close to passing the pan test) It will remove and collect up to 4 oz. water each time you do this. This makes for very fast dewatering, and may solve the issue of requiring a mistwash beforehand which has been discussed so much.

I ran tests today which are getting sent to the lab for testing. I started with 12 gallons right from the dumpster, and on purpose sucked up some crud from the bottom of the barrel. And then I added 1/4 cup vinegar to make sure we got lots of acid, and then I sucked up a thick emulsion layer in an old settling barrel that wouldn't seperate after about a month of heat & settle. These are all things I would normally avoid but I was going for bad conditions. Then I ran it through all the rig without the centrifuge circulating it well and suspending it all in a nice mess. Saved a gallon of this for testing labeled #1. Saved 5 gallons of #1 to process later below. This was dangerous to do a pan test on it pops so bad. And the water/acid is suspended, it hasn't settled out after 12 hours of heat & settle.

Ran the centrifuge only (no mistwash) for 4 passes on 5 gallons of this mess. Labeled as sample #2. The rotor captured about 2 oz. water with acid PH. And removed lots of black goo. It removed all traces of water in the pan test.

Then cleaned out the rig, and pumped into it and heated the other 5 gallons I had saved of #1 to 120F, and did a mistwash with a mistpro nozzle, adding about 1 gallon of water. Then I ran the rig without the centrifuge for about 15 minutes, which turned this into and even worse emulsion looking like chocolate milk, and also really washed it. Then I let this settle only for about 30 minutes, and drained the free water from the bottom which looked like white milk, and had acid PH. There was still a large amount of water suspended and on the walls of the barrel. Then ran the rig for 6 passes on this mess. Lots of steam puffing out, and when I stopped midway 2 times, the rotor contained 4 oz. of free water which I captured the output when I turned it off. And about the same amount of black goo. Tested water free with the pan test, labeled samples as #3.

This is some very interesting results which leads to a new way to run this where you could remove the water much faster which I will test next time: Run 1 pass, empty the rotor of water, repeat until no more steam puffs which in every case has been a simple and accurate indicator that it will pass the pan test.

This also means with any version of this you should make provisions to capture the output of the rotor right when you turn it off. The output of the rotor at that time is often very dirty besides containing water (if there was suspended or free water.)

Operating like this could lead to the holy grail - an at home and mobile version that doesn't require a mistwash.

24 October 2006

I just ran the first test of my new capture method, on my bad #1 oil from above that I had saved, which had lots of suspended water according to a pan test. And the filtered oil passed the pan test with no bubbles after 1 pass at only 120F temps. And the stuff I captured from the rotor is horrible on the pan test, very crackly and dangerous, and I see some small globules of free water in the bottom even.

Lab test results
07 November 2006

Lab test results are in for the first samples I sent.

Sample 1 was the original oil, sucked from dumpster with 100 mesh screen.
Sample 2 was 1 pass, 55-120F.
Sample 3 was heated, mistwash, 6 passes, 120-180F. I did some calcs. on the particle numbers, % reduction:

>14 micron, >10 micron
1 pass = 60.0%, 32.4%
6 pass = 98.5%, 93.7%

The >10 micron reduction looks very good, and that is the size that most people are filtering to. Although a 10 micron nominal filter won't come close to this, since they often only remove 50% > 10 microns.

I am surprised at the no reductions in <10 micron category. Maybe it was because of the mistwash which I didn't settle out, which put a lot of water in the rotor (4 oz), making the small particles not remove. Or the mistwash broke the particles down to smaller size, or sampling errors.

Interesting results for water reduction. #1= 708ppm, #2= 545ppm, #3=478ppm by Karl Fischer ASTM D6304.

It removed my suspended water, even with 1 pass, when I captured the output at shutdown. This shows the pan test is not detecting water below 545ppm. I ran 2 pan tests on each sample separated by several hours. #1 showed lots of bubbles. #2 and 3 had no bubbles. When I shutdown after 1 pass and captured the output, I tested the captured oil and it was very bad on the pan test (lots of crackles.) This showed it was removing the water by true centrifuge in the rotor, not by evaporative means.

Here are the # of particles per ml by HIAC HL-1185 method:
sample 1,2,3
06-10, 23483, 29230, 23438
10-14, 18067, 14542, 1560
14-25, 8559, 3482, 129
>25, 132, 58, 5

More testing is needed to determine the best way if you want to remove <10 microns (more passes, leave mistwash water settle?) My truck is a 10 micron stock filter so I am happy with the 94% reduction to 10 micron. We now have more public testing data for this than for any other filter method. I would like to see the same test run on a 2 micron absolute or 10 micron nominal filter as a comparison, but I can't find anyone who has published this data for any fluid, much less oil.

Parts List

Qty...Description...Cost
1 Dieselcraft OC-20 centrifuge from http://www.dieselcraft.com $220 (now $299 with relief and guage and tees)
Pump/motor:
1 -Power Steering Pump from junkyard $20
1 -¼ HP or greater 110v electric motor 1725rpm (Junkyard or Harbor Freight cheapie) $20
1 -1.5” pulley wheel for the electric motor $5
1 -0.5" V-belt
Or for an off the shelf pump/motor:
http://www.mcmaster.com/nav/enter.asp?pagenum=330
pump only look at look at part# 4271K1 $197
These should work with an OC-20 or 50, and ff25 and 60:
pump only look at look at part# 4271K12 $196
pump/motor ready to go part# 4272K31 $396


1 pressure relief valve 25-250psi (http://www.grainger.com part 6D915) $5 or mcmaster part# 8088K14 $21
5ft Length of hydraulic hose (get it from the car you pull the PS pump from)
8ft Length of ¾” or bigger hi-temp hose to attach to input of PS pump
1 -24” x 1.25” steel pipe (for heating element) ~$5
1 -4500KW 240v water heater heating element (at 110v = 1125W) ~$8
1 -1.25” steel T (use 2 tees if you’re putting 2 heating elements in) ~$4
1 -8” x 1/2” steel tube to attach to centrifuge input ~$4
1 Reducer to attach centrifuge 1/2" to 1.25” ~$5
1 Reducer to attach PS output to 1.25” input ~$10

Plumbing fittings to attach to the bottom of the barrel to flow to the input of the PS pump ~$15
1 Pressure Gauge (grainger #5WZ34, $8.58) ~$9
1/16" thick by 1.25" ID metal washer first on the element, then a 1.5" ID washer with a 1/8" x 1.25" O-ring inside (to seal the heating element) Tractor parts counter is where I got mine.

I use 2 extension cords going to 2 different 20 amp circuit breakers, 1 has the 10 amp heater and a 5 amp pump, the other has the other 10 amp heater.

Got a new pump
26 January 2007

Several people have reported the vanes sticking in their power steering pumps, making it not work until its disassembled and cleaned. A gear pump is better since it won't have that problem. Here is my new pump/motor combo, its an Oberdorfer 991N gear pump close coupled to a 1/3hp 1725rpm motor that I got on ebay for $23.00 which is working nicely:


Added a switch panel:

I added a switch panel with extension cords and 4 switches connected to 4 outlets, which I use to turn on and off the pump and 2 heaters separately. This saves me from unplugging those 3 plugs each time I shut down. With an extra switch and outlet for future ideas.

[SunWizard]

Mobile "Holy Grail" version of this rig:

I made a mobile unit out of this same rig, to use when I am travelling long distances so I don't have to carry hundreds of gallons of Veg. Oil. I run it with a little, quiet honda 2000watt generator, or plugin power if I am stopped where I have it, which I prefer since then its easier to check and clean the CF rotor. I put a sealed lid on the barrel so it can carry VO while moving, or have the CF running to process it. This is why I have the CF mounted below the rim of the barrel.

With the lid, it dewaters at about 30-50% of the speed of when the lid is off the barrel.

[canolafunola]

Originally posted by canolafunola:
I did the same test with salt 2 weeks ago and just did it with vinegar. I am happy to report that whatever is in vinegar (acetic acid? ascorbic acid?) is heavier than oil and will be spun out and captured in a centrifuge (or by settling).

The test:

Pic below of 12 oz distilled white vinegar emulsified in approx 2 gal of previously filtered WVO. I did a mini wash of a small sample of this emulsion (using distilled water) and the TDS reading was 40. I also tasted it and it was a little sour.



I CF’ed this emulsion for approx 1 hour starting at 60F and ending at 205F. Pic below is what was in the rotor. Note the small droplets of water in the bottom of the pot. This is very little water that was captured of the 12 oz of vinegar that I introduced, which according to the bottle was 5% acidity ( that means the rest of it , 95%, was water). So, most of the water was flash evaporated.



Here’s a close up of the rotor capture. The white stuff was very sour tasting (Vitamin C?). The brown stuff is rust I believe. The acid must have reacted with the rotor. It tasted like rust and was a little sour but nowhere as sour as the white stuff. I had to use a Scotch Bright abrasive pad and soap and lots of elbow grease to get the rust off.. Imagine what acid will do to your IP and injectors?



I did a mini wash of the rotor capture (just the oil from the rotor, not the white stuff) and the TDS reading was 430! This makes sense since the TDS of the emulsion was 40 prior to CF and has gotten much higher post CF due to it being concentrated. Note: TDS reading of vinegar straight from the bottle was 640.



I then ran the CF again for another 30 min or so and captured the rotor. There was very little debris. I did a mini wash of this capture and the TDS reading was 20.

Comments anyone?

[sacveggieguy]

Hi to all.

Nice forum here, looks like a breath of fresh air. I will be setting up my centrifuge rig very soon what pressure regulator are you guys using where do you get them and if so do you guys have a part # I will be trying to copy Sunwizards set up with p/s pump elec motor etc.

Thanks Paul aka Sacveggieguy

[SunWizard]

From my parts list above:
1 pressure relief valve 25-250psi (http://www.grainger.com part 6D915) $5 or mcmaster part# 8088K14 $21

Or you can get one in the plumbing dept. at home depot, any model that is adjustable to 90psi will work.

[SunWizard]

A frequent question about making this a mobile rig, can I use a DC motor?

Yes you could use a DC motor but they are much more expensive than AC ones. You need at least 1/3 HP and 1725 rpm.

Or you could use an inverter which converts the 12vdc to 110vac, but the <$500 chinese ones won't last very long with this large a load.

With either one, you would need to keep your vehicle engine running for the 4 or more hours needed which is a waste of fuel and could cause long term trouble like coking by so much idling. If you set it up right (sealed from sloshing), you could run the CF while driving.

I use a small quiet honda EU2000i generator to run mine, which is useful for many other things on the road too.

[canolafunola]

Originally posted by canolafunola:
Well, I finally found my TDS meter and was able to test the "cleaned" oil from the salt test with a mini wash of the bottom of the cubie after settling for a week or so. TDS was 2, according to Sunwizard, below 5 would be considered a success. To read about my vinegar test, go
here.

Originally posted by canolafunola:
I ran a test on the CF today. I mixed 2 heaping tablespoon of salt into 12 oz hot water and poured it into a ½ full cubie of previously filtered WVO and shook it up till emulsified. I tasted a droplet of the concoction on the tip of my tongue and could definitely taste the salt. I then CF this ½ cubie of wvo salt water emulsion at 160F till there was no more water vapors from flash evaporation. Then captured rotor on shutdown and this is what I drained out of it.


The white flakes tasted very salty. There was very little free water. Most of the 12 oz of salt water was flash evaporated, not captured in the rotor.


I took the rotor apart and found more salt.


I ran the CF for another 45 min to see how much more salt would be captured and got a little more.

This is good news.

I was going to do sugar next but I know what the outcome would be so I think I am going to skip it and do vinegar next.

Edit:
I drained the CF'ed oil into a clean cubie and will let it settle then taste the bottom and see if any more salt.

[sacveggieguy]

Hi Sunwizard,

What pressure relief valve are you using? And in your pics of your rig it showa a Tee where the veg comes in then tees off is this where you install the relief valve and then it just dumps back into the 55 gal drum before it get to the CF?

Thanks Paul aka Sacveggieguy

[SunWizard]

I am using a pressure relief valve 25-250psi (www.grainger.com part 6D915) $5 from my post above. Yes its right before the CF as shown in the diagram and pics.

[sacveggieguy]

Does the pressure relief valve you show in the pics screw right on to the plumbing it looks like it does not come right off the tee at a 90 degree angle? And I guess it adjustable?

Thanks Paul aka Sacveggieguy

[SunWizard]

Yes it screws into standard plumbing, and its adjustable 25-250psi as I said in my last post.

[sheryco]

Sunwizard, I have noticed that you have your heater outside the tank and in a metal pipe so to say. I was wondering which way is more efficient in heating the oil your setup or a setup where the heating element is in the tank itself. If you setup is more efficient can you elaborate how and why? If efficiency isn't the point what is the point of that type of setup? (of course apart from heating the oil). Thanks

[SunWizard]

In a pipe is more efficient since you don't have to heat up the entire barrel, it adds 20-30F right before the CF. Heating the entire barrel that much more means it takes much longer, and you get more heat loss. Plus you get better heat transfer with flow across it, and its less likely to burn the VO on the element.

[SkySkiJason]

As I read this thread again I noticed a very significant point.

The lightened color of the VO after the CF is possibly indication of early stages of polymerization. In Joe Beatty's experiments, we saw a lightening of the oil samples simultaneous to an increase in peroxide free radicals. The peroxide value is a measurement of the amount of oxidation that has occurred in the VO.

This is likely due to the amount of oxygen introduced as the (hot) VO is sprayed into the CF. Ever notice how its almost foamy as it falls out? I've seen what looks like poly in the CF after extended use on same oil...

On a practical level, what does this mean? I think it basically reduces the shelf life of the VO. Maybe significantly depending on what happens to it next. (ie, If ya put it in a steel fuel tank w/a copper HE and drive around w/that same VO in the tank for several days) Same VO may last years stored in cubie full to the top.

Think of poly as a recipe. The more poly-causing ingredients you add (pro-oxidents, heat, oxygen and time) the sooner you get to the reaction. Meanwhile, once you introduce the free radicals into the oil, the reaction has begun.

I realize that suggesting the CF is not a good idea is not going to be popular, but considering how 'new' they are to VO as a fuel - it is very possible we are yet to learn the 'long term' effects.

[SunWizard]

I have been using my CF for 2 years now, and haven't had any troubles with poly, even on VO that was stored for 12 months after CF. Thats about as long term as I care about.

CF probably does increase the oxidation of the VO, but only a tiny amount, much less than it being used in a fryer for another 4 hours. All VO we get has begun the oxidation process already, unless it wasn't used. Remember in a fryer its at 350F (versus 160F in the CF) and its got air being bubbled through it all the time as food is fryed, and there is usually water introduced in the fryer too. Oxidation doubles with each increase of 10C (18F), so that means in a fryer its oxidizing at around 1000 times as fast as in the CF from the temp. difference alone.