What is the general thoughts on the oxidation of the BD we make?
I make small (50 l) batches that when completely washed and dried goes directly into the tank of the daily driver. The finished BD never gets stored. Every now and then, I make another batch that goes into a vehicle that only sees one or two trips per week.
Feedstock is soy WVO.
Even in the daily driver, I can smell the distinctive smell from oxidized BD when "sniffing" by the open fuel cap. Probably even worse in the vehicle that sits maybe a month without adding fresh fuel.
Concerned with the long term effects on the IP and overall fuel system.
Does anyone use the available anti-oxidation additives?
I think biodiesel oxidizes in part due to peroxides. If thin sheets of tin metal were put into stored biodiesel, then the peroxide would react preferentially with the tin metal rather than oxidise the biodiesel. The quicker the biodiesel is used the less it can oxidize during storage. I think metal cans of diethyl ether might be coated with tin on the inside to slow down or stop formation of peroxides. Thanks
Wesley, im very interested in your information about oxidation. My biodiesel is no problem, I have stored it for up to 6 months without any signs of degradation. I have recently been experimenting with thermal and catalytic cracking of waste plastics and the resultant diesel, especially that derived from polypropylene oxidizes very quickly. When I say quickly I mean clear, golden fuel turns almost black within a week.
I realize that the proper solution to this problem is to refine the catalytic action but would also be interested in any means of slowing the oxidation process. Could you point me in the direction of any journal articles or similar on the action of tin on peroxides?
I don't know of any scholarly articles on that subject. It seems obvious to me that peroxides will react with tin to form the metal oxide,. Tin has a lower electronegativity that carbon or hydrogen so it seems to me that it would react with peroxides forming the metal oxide. The tin would oxidise first. And the word oxidise can mean more than one thing, not just oxygen bonding to something else. I was referring to oxidation in fatty acid methyl esters that may be polyunsaturated. I don't know about pyrolytic degredation with catalysis of waste plastics. Might try burning finely divided plastic dust in the presence of adequate hot air to power a hot water heater.
When long chain polymers are cracked, the short hydrocarbon chains lack the extra two hydrogen atoms to seal the molecule so they are unsaturated. Without a catalyst to provide extra hydrogen they will seek any thing they can combine with, especially oxygen.
This seems a similar situation to the polyunsaturated fatty esters so might be well worth a try. i just happen to be an amateur tinker so getting tin in the form of tin plated steel is no problem, thanks for the info.
Biodiesel like any organic is prone to oxidation from oxygen and contact with certain materials.Your feedstock is the key. Peroxide value and iodine values of the oil have a direct correlation to the oxidative stability of the oil or biodiesel made from the oil.This effect is greatly excelarated when biodiesel is mixed with petro diesel,hince the many articles on Fallout, University of Idaho and Iowa State university have published several articles on oxidative satbility in biodiesel.Because of the fryer process Hi Heat water food particles damage the oil so any stabilzers or antioxidents that were in the oil are typicaly used up.So when we get the oil and make biodiesel peroxides are elavated which degrade the oil faster.Most home made biodeisel made with oil in excess of 2.5%FFA will not meet ASTM oxidative stability minimum of 3hrs.I use 2.5% ffas as a reference since generaly by that time the oil has been damaged enough to raise the peroxide value.I always add an Oxidative stabilzer to my finished fuel.Even though my fuel just meets the 3 hours I add enough stabilzer to triple that. Its not exspensive and keeps the fuel from degrading and bad biodiesel from falling out in my fuel system and casuing corrosion and filter plugging issues.I get my stabilzer in powder form from Heartland biodisel because it is non toxic and mixes easy with my fuel. I beleive Utah biodiesel also sells a stabilzer as well, but in a liquid form, however a friend read the contents and it was not a non toxic product or i would have bought it.Also some stabilzers work better with certain oils versus others.I typicaly dose mine at 300PPM to reach 9+hrs.
Good data lorgeme,
I just had this verified by a lab. Complete ASTM workup on some FAME B100, passed everything Except oxidation...
[Sample does not meet the following specification: oxidation stability.
Product would benefit from the addition of a stabilizer to pass the oxidation stability specification.]
Triglycerides measured approximately 0.2%, slightly better than a sample last year at .268%. Batch was 2 stage processed, passed 3/27 clear and bright "chilled", bubble washed and air dried. No oxidation stabilizer added.
Funny thing is this UVO feedstock titrated 3.25, and the fuel sample was tested within 5 days of production. Ya don't get much fresher.. So I'd have to agree with your 2.5% FFA limit since nothing else was flagged but oxidation stability. Was told yesterday by another producers lab tech that most BioD from UVO fail ASTM oxidation test without any stabilizer. Something I vaguely recall reading in some years past, but believe should be revisited by anyone looking to meet ASTM and avoid possible oxidation issues. Fresh fuel is not always good fuel...
I'm gonna resubmit another sample next week after adding some stabilizer to a batch in process now. It's also UVO, titration at 3.25 after glycerin pretreat. So we'll see how this plays out, better I'd hope.
Anyone have comments on ETHANOX 4760R, or any other stabilizers tailored for Biodiesel?
Good info' Kenr.
We use ethanox with very good results, around 250ppm is increasing our ox stab by 2-3 hours. I'm not sure about the oxidative stability based on the %FFA though. Possibly only with the oil you have. Up here (Canada) most of my oil comes from canola so even the kitchen grease stuff we have is testing at almost 5 hours ox stab. I would note that we used to have a few copper fittings that the bio went through and the ox stab tested at 1.5 hours on actual canola not the used stuff. Copper has a HUGE effect on this number.
Any good sources for home-brewer quantity purchase?
2004 Motorhome CatC7
1987 Mercedes 190D 2.5 Turbo(possibly for sale)
1983 VW Pick-up (Caddy) 1.6 Turbo
So far I've not located any, but I was thinking maybe some guys could get together on a drum. Have a call with a company CSR for details on Monday.
BWilder, the copper reaction is an interesting topic. Was gonna say we don't use any copper parts in our setup, then I realized we actually have a massive heat exchanger in the mixing line on the reactors. It's normally in bypass status unless we are recovering heat, like right after we gly pre-treat the incoming UVO.. That puppy has copper heat transfer tubes for it's core.
Things that make you go Hmmm..
Yeah that is exactly what we had one big solid copper heat exchanger. When I arrived at the company couldn't figure out what was causing the low ox stab. (1.5h) Then I scratched the paint off the sucker and the light went on. Now we never get one under 4.5 hours even on straight WVO. Still use the ethanox as a precaution though.
Yeah I'd say that exchanger is gonna have to go. What's your thoughts on brass since we're on the subject?
I hear brass is not as bad as cooper, but read where it can also cause OX issues. We do have a few brass housing ball valves in the system, as does probably 99% of the small scale producers out there.
Wish I had the exact time from this stability test, but the lab involved only gives ya pass / fail results along with some "hints" listed above. Unless ya wanta file a FOIA request.. Would be nice to see numbers before and after stabilizer, and then after we remove the exchanger. Guess I'll hunt down a lab with a petroOXY to perform the specif OX Stab testing.
Well don't know if you will have access to it but there is the article
'corrosion characteristics of copper and leaded bronze in palm biodiesel'
They get into the actual chemical reactions that occur due to the copper and bronze and what acids are created that cause the increase in acid # that is also seen.
Bronze does effect it much like copper but to a lesser degree.... how 'much' bronze fittings will effect it I couldn't say. From a homebrew perspective if you are using the bio right away I don't think it should matter provided you aren't using enough of them to see a noticeable colour change in the bio (green). I'd like to have zero bronze myself but even we have a few of them due to financial constraints. Although none on the direct process lines.
They don't give ya full access to article for free, but I could see the graph comparisons from all the tests. Looks like B100 is less corrosive on brass than copper, however when it comes to the change to the total acid number or oxidation of the fuel, the results look dead even.
I'd agree the normal home brewer who uses fuel fast as it's made, oxidation from high FFA or a couple brass fittings will probably never become an issue. But after some review of our process start to finish I can see where it could be easy to amplify the problem. As in our use of the heat exchanger during UVO pretreatment. Basically doubling the exposure time.
Look closely at the UVO in the top of the sight tube below. These tubes have bronze fittings top an bottom. If we leave pretreated oil in the tank for week before processing, the top 1/2 inch of oil in the site tube develops a green tint where it slowly drains down past the top bronze fitting. This had caught my eye before, sometimes more noticeable than the pic, but figured whats 10ml in a 1000ltr batch... Only happens when oil is pretreated.
Sometimes the more I learn the less I know.
Removed the copper exchanger from our mixing system, boy was it shinny inside...
I received a sample of Ethanox stabilizer for testing last week. Looks like it's available in 42 gallon drums, no delivered price yet but am working with a distributor on that. We submitted another sample of fuel to the lab last week for ASTM testing [before removing the copper parts] that was treated with off the shelf Stabil Diesel Formula. Looking forward to those results.
Also arranged to have fresh fuel samples tested to determine the baseline times along with Ethanox PPM requirement to the reach 6-7hr level. So should have some good data to calculate the cost per gallon increase of each treatment. Below you can see the difference between these two products, Ethanox is visibly darker and thicker, guessing also more concentrated than Stabil so hopefully cheaper in the long run.
Update on the additives.
Received the oxidation stability results back on the latest B100 from UVO samples we submitted. The sample we treated with Stabil Biodiesel formula showed NO noticiable time improvement and came in at 1 hour, same as our untreated B100. Sent another sample out to a private lab to estimate the Ethanox treatment required to pass, here are those results.
Treated a full batch at 750 PPM, sent sample of it back our friends in DC. Received an email on Thursday saying you PASSED ASTM.
Now we our testing the feedstock to see if the low times are related to suppliers or our equipment. We removed all the copper from the process, now onto the brass valves. A lab tech did mention that FFA value along with the oils total metal contact time does impact the stability times of finished fuel.
So there ya go, I'll post what we find on the feedstock and maybe we can compile this data into something usable.
Excellent info Ken thank you....
that's some low stability oil you guys have down there
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