neutral, the oil stays a liquid at 50F but I don't know how much lower. I'll have to do some checking on that. It's not homogenated at all. The whole test batch solidified pretty hard. Not quite the consistency of jello but close. If it is as Tilly suggest, (a trace of glycerin fell out and then the fuel was good enough to jell up), then reprocessing probably isn't necessary, Right?? I'm not sure how to prove this.
-mcguyver

I think that's right. The main reaction was good indicated by the lack of glycerine produced in the early stages of the reprocess test. According to Tilly's tests the gel which forms next is further indication of a good main reaction. I think whether or not this appears may depend on both the cloud point of the original oil and the temperature at the time of test, as the melting point of soap depends on the cloud point of the oil it is made from.

quote:

Originally posted by Tilly:

If you reprocess a litre of washed and dried biodiesel using the standard 1g NaOH in 50 ml methanol at room temp by putting the biodiesel in a 2 litre Dr Pepper bottle and giving it 20 good shakes and it forms a full gel within 5 minutes you have very high, probably ASTM conversion biodiesel.

Tilly et al - I appreciate this thread, like most of you am also on the search for good quality homemade fuel with quality testing to back it up. On my own I had decided reprocessing was one good way to go for quality testing but have only been confused by the gelling phenomina. Needless to say your input here is fascinating - and hopeful.

Can anyway tell me why the gelling happens with good fuel and doesn't with poorly reacted fuel? I assume gelling may be impeded by the presence of unreacted oil and/or x-glycerides but can anyone actually explain what's going on here? I'd appreciate that!

Thanks - Dave

I didn't get gel using KOH...but I did get about 6mL of glycerin to drop out of a 1L re-reacted batch.

I haven't seen much about the quantity of glycerin you can expect to drop out. There's a limit to the % of free glycerin (but it's not free glycerin until you react it). Does the % glycerin dropping out directly correlate to the % of unreacted oil?

I haven't been able to make that connection yet.

What am I doing wrong? I'm trying to do a gel test of finished bio. I mixed 10g NaOH with 500ml methanol to make my test 2% methanox. I put 10ml of the mixture into 200ml of finished (washed) bio and shook for awhile. And I wait.

Nothing happens. No gelling, no glycerin fallout - nothing. The mixture is at room temperature which is proably 68F. Do I need to warm the fuel first? I tried earlier with a smaller sample and nothing happened with that one either (although it did eventually form a skin on top and there was tiny bit of gel on the bottom - which I didn't notice until I poured it all out). Shouldn't there be more happening?

I also did Tilly’s gel test using samples from a KOH batch and NaOH batch. (Tilly your Royalty check is in the mail)

The KOH sample jelled but it took a good 10 to 15 minutes.

The NaOH in same time frame only got gelatinous.

My question is this test time sensitive? In Tillys post he says it should jell in 5 min. I’m wondering if the ambient temperature may effect the time it takes to jell. My room temp is also about 67-68 F.

quote:

Originally posted by Batch:
My question is this test time sensitive? In Tillys post he says it should jell in 5 min. I’m wondering if the ambient temperature may effect the time it takes to jell. My room temp is also about 67-68 F.

Hey - it's gelling. Be happy!! I've done some further testing and yes, when I heat up my samples they do whatever they're going to do better and faster. (Unfortunately that is still dropping out glycerin, not gelling!)

Re-reacting oil (1g NaOH & 50ml methanol per liter) is the same formula used for a gel test. What's to keep a tank full of fuel from gelling up? I mean, you'd certainly test a little first, but is this a concern? My experience with some fuel is that it drops glycerin on a re-react test, but may also form some 'gel-sheets' at the same time. Do you re-react such fuel?

DanielFP, do you have any information on wash water? We have a septic tank, and I don't want to destroy its equilibrium. Someone suggested adding muriatic acid until the water becomes a pH of 7, at which point it will render a ton of salt. But I need to know more about this solution and possible adverse consequences as it drains thru the septic tank, leach field, and into the surrounding land.
Thanks.

quote:

Originally posted by danielfp:
I am currently studying for a major in chemistry and had a recent project involving biodiesel. I would like to answer some of the questions you have asked. First, the ecological impact of methanol evaporation is none, as the oxidation reaction methanol + oxygen -> carbon dioxide + water is spontaneous and has a short life. Nonetheless, if animals were to breath the methanol while it is in the atmosphere it would cause intoxication because of its partial oxidation to formaldehyde in the animal's liver. Second, as it was pointed out in the last post, there is a precise amount of catalyst which would provide the highest convertion ratio, but this amount, is based on many different variables. The two most important, are the equilibriumm (NaOH+alcohol-> methoxide + water), which, if pushed too far into the products can encourge soap formation and the free fatty acid content of the oil which would indeed, consume catalyst to form soap. In our study, our goal was to develop a solid catalyst, which could be used by a home producer, and would take care of all this complications. One of our most promising catalysts was made from CaCO3 and BaOH. From which we achieved 98% convertion and complete reutilization of the catalyst.

quote:

added

b100 supply has the folowing description of the reprocess test:

quote:

In this test you reprocess a sample batch to see if any more glycerine falls out. This test can give false indications. While glycerine does fall out if you are very badly under reacted, not having glycerine fall out does not mean the sample is anywhere near ASTM spec. The excess methanol in the reprocessed biodiesel will tend to keep any glycerine freed up by transesterification suspended in solution and undetectable to the naked eye.

The JTF Reprocess Test
-- Useful to identify grossly under reacted biodiesel.
-- Not sensitive enough to identify high quality fuel.

It is true that he is refering to the JTF site, but I am wondering how you feel this critcism relates to your reprocess test.

Thank you Joseph for pointing out what is essentially a third reprocess test.

The test you quoted refers only to the JTF version of the test. It is a completely different test. In the JTF version they call for processing as if it were "virgin veg oil" The JTF recipe for virgin oil calls for 200mL of methanol per Liter of biodiesel. Neutral and Tilly are calling for 50mL.

In this post neutral is using KOH and looking for glycerine to fall out in the same way as the JTF test. He notes that in one case the methanol is keeping the glycerine in solution. Thats with only 50mL. Using 200mL would have a much more dramatic effect at keeping the glycerine in solution. neutral's response to the methanol causing a false indication was to remove the methanol before judging how much glycerine was present. The JTF test does not call for removing the methanol.

Tilly's version using NaOH does not depend on a visual detection of glycerine so is not at all the same test.

Yes, I understand that Neutral's reprocess test has a much lower chance of suspending glycerol, because it uses so much less methanol.

My concern is this: if 1-3% methanol in biodiesel can suspend so much soap in our biodiesel, then it seems like if only a small amount of glycerine was produced in the reprocess test, at least some of the glycerine would remain suspended.

Neutral's recommendation is to:

quote:

For an indication, add 1g NaOH in 50ml methanol per litre of washed and dried biodiesel. If you use too much methanol the density of the glycerine may be too low to settle. Warm, shake and settle, as for making biodiesel. Separate the glycerine and evaporate the methanol from it and weigh the residue.

Clearly, it is important to evaporate out the methanol from the glycerine, but it seems like invariably the excess methanol will still hold at least some glycerine suspended in the biodiesel, thus making the test innaccurate.

I am unsure how much glycerine it would hold, which is why I am posing the question to the forums. Perhaps it is not enough to make much of a difference.

A proposed alternative is to boil out all of the methanal in the biodiesel BEFORE draining the glycerine (see the "GL's 1 Day Process" forum for more thoughts on this).

Once methanol is evaporated, any previously suspended glycerine should fall out of solution.

From there it would not be a problem to measure the glycerine percentage as Neutral recommends.

I look forward to hearing your thoughts on this idea.

This seems like a really important question as far as quality testing is concerned. Does anybody have any more thoughts?

Hello Joseph

I suspect you will find that the 2-3% of methanol remaining in the biodiesel will have no glycerine in it.
If it did it would settle out and not stay with the biodiesel.
It may however , take a week or two for all the glycerine to settle out of the biodiesel.

Hi Joseph,

Just to clarify, I recommend you drain glycerol following the reaction, and THEN extract the Methanol from the biodiesel.

Any little remaining glycerol and the remaining soaps will then fall out more easily.

Don't try to drive off the methanol from your biodiesel while the glycerol is still in abundance, or I believe there is a risk of the reaction reversing, and glyceride levels rising.

Tilly:
It seems that Grahams demeth washing system wouldn't work unless glycerol stays dissolved in a very small ammount of methanol and water.

It also seems that the reprocessing test would leave a slight ammount of excess methanol (which could hide the slight ammount of glycerine which would indicate an incomplete reaction)

Boiling off the excess methanol after a reprocessing test seems absolutely essential.

This question is important...any thoughts anybody?

Reprocessing,

I reprocessed according to Tilly's Dr. Pepper method (add royalty fee to my acct. Tilly).

I started to get gelling within 5-10 min and by morning I had a gell that encompassed the entire liter. However, the outside 1/4" was liquid. So was it a pass or fail? Oh, a tiny amount of gly dropped out. "bubbles" about 1/4-3/8" in diameter at the bottom

Reprocessing: 1.55gr NaOH 50cc Methanol sample of bio-D (feedstock was soy-pho) was unwashed and heated to 100-110deg F. It was stored in the celler where temps are ~50deg F. and when I poured the sample from the jug, it had "floaties" you know the kids you get when your olive oil is cold.

So I guess the gel means high conversion? gly that dropped out was like 10cc total!?!

I reprocessed this batch because I was having trouble making soap from the gly and wanted to see if the fuel portion was any good.

Lastly, what do I do with the gell? dump it? or can I get it back to fuel?

C.

quote:

Originally posted by neutral:
mwr,

There are two aspects to this query: 1. why is there a dropout of glycerine on reprocess and 2. does it matter.

1. My test shows that with ASTM conversion (approx 98%) there should be no more than a trace of glycerine on reprocessing. You don't mention how you do the reaction so I cannot judge what your level of conversion is. You may be losing methanol to evaporation, doing it not hot enough, too briefly, or not agitating correctly.

2. The question about whether degree of converion matters is one that plagues this industry. In the early days of biodiesel I called repeatedly for people to show me scientific studies that showed how the impurities in poorly made biodiesel harmed motors. None were presented. Of course we all know that free water in fuel is bad for a diesel but what about the other impurities?

Methanol. Present at 2% to 3% in unwashed biod. Lowers flash point but is apparently harmless to motors. Keeps gums, soap and glycerine from depositing. May aid combustion.

Unconverted oil. Present at 2% to 4% in below spec biodiesel. Some users are blending in 50% apparently without harm.

Partially converted oil, mainly diglyceride. Maximum possible about 4%. Will clog a filter but will not harm motor. If the fuel is clear at the lowest temperature likely to be encountered it cannot clog the filter.

Soap. Can only be present at low levels. Can clog a filter. If fuel is clear at low temp it cannot clog a filter.

Free glycerol. Can only be present at 0.15% in unwashed biodiesel. Oil Can Harry makes a special fuel which contains about 8% free glycerol, which apparently burns perfectly well in the motor. The only problem with free glycerol appears to be that, with unwashed fuel, some can come out of solution as the methanol evaporates. This can be prevented by adding a little alcohol to the fuel in the tank.

Water. After washing, water will be present. As long as the fuel is clear at low temp it is dry enough.

At least for indirect injection motors, and for those direct injection motors shown to tolerate vegetable oil, there appears to be no reason to aim for a high conversion from the point of view of the motor. There appears to be no need to wash the fuel.

If you are washing the fuel it is better to aim for a reasonably high conversion to minimize diglycerides and hence reduce the tendency to form emulsions during washing.

I've been saying this for some time now, and was glad to see neutral already mentioned it years back!

Years can go by between posts on this thread. It appears that there is renewed interest in this topic. I copy here an email I received today. I think this is better than responding to a private post.

SWMSGoodman

posted May 06, 2013 08:06 AM
http://biodiesel.infopop.cc/ev...5551/m/892103409/p/2

I am new to BD, old to WVO. I've always wondered about the effects of quality. To read this, there are a LOT fewer concerns. There are many smart, SMART people on this site and you seem to be one of them. I am a degreed engineer with a lot of field experience but BD is not what I've been trained in.

Do you mind explaining your qualifications so I know you can be sure of this stuff. Even if you've been doing home research and have a lot of field smarts, I trust that.

Mike Goodman
High Point, NC

83 MB 300SD (2 tank)
82 Rabbit Truck (2 tank, my design) - SOLD
98 Dodge 2500, 2 tank Golden Fuels
Diesel Craft CF process in enclosed shed
BD first batch 9/23/12
6-4x10 solar hot water panels and 500 gallon wood-burning water stove
2.8 kW PV grid-tie w/batt b/u commissioned March 2011

Here is my response. My PhD is on organic free radical chemistry. This gave me some knowledge of oxidation of oils and the use of antioxidants. While working for the WA Dept of Agriculture I was involved in a project extracting oil from Canola. This occurred during the 1970s, a time when OPEC was jacking up the market price of oil, including diesel fuel. We did some experiments using diesel, diesel blended with veg oil and biodiesel, in a lighting plant. We were able to show that the motor ran with the same efficiency on diesel and on biodiesel. On a blended fuel of similar viscosity to biodiesel the motor ran briefly with the same efficiency but soon deteriorated. The injector nozzle was found to have a build-up of carbon. When this was removed the efficiency was restored, briefly. This was a direct injection motor. My conclusion was that the only convenient way to safely run a direct injection motor on veg oil was to convert it into methyl esters.

Since then I have acted as a consultant, and have given advice on the manufacture and use of biodiesel. I have conducted many laboratory scale experiments to determine the optimum conditions for manufacture of biodiesel in batch systems.

My main interest now is to challenge the nightmareish regulations. Most people making biodiesel are doing so for their own use. Most are using the fuel in indirect injection motors, motors with pre-combustion chambers. It is clear that these motors do not have such critical requirements. Under these circumstances, one by one, we can cross off the ASTM requirements.

1. Removal of glycerine. The standard way to do this is by washing with water. All diesels have a warning light which tells you if there is water in the oil. It will also tell you if there is glycerine in the oil. When the light comes on, drain the filter. I have fitted a cheap pre-filter in the fuel line, which catches the crud which is likely to come out of the fuel tank when you change to biodiesel. If your car does not have a good hand pump to assist bleeding the system, it is a good idea to fit an additional filter from a Toyota or a Nissan. These have a float for a warning light for water, and provide additional protection.

2. Removal of methanol. This can be done by distillation or washing. Distillation requires surprisingly high temperatures or vacuum. It is costly and a nuisance. If it is washed out it is wasted. Why waste a good fuel?

So, if you can tolerate a little glycerine and methanol in the fuel, you don't need to wash. If you don't wash, your yield will be higher as the excess methanol will be preserved and used as fuel, as will the small amount of soap that does not go out with the glycerine. If you don't wash you will have no problems with emulsions formed by the mono and diglycerides which are prevalent in low conversion fuel.

3. Achieving 98% conversion. Can anyone tell me why this is a good idea? Are there some vehicles which play up on low conversion fuel but not on high conversion fuel? If you cut back the conversion by cutting back on the methanol, you can cut back on the amount of catalyst required in proportion. You can't cut back on the amount of caustic needed to neutralize the FFA of course.

I am going for the easy life: I use KOH because it dissolves easier and the glycerine does not solidify when it cools. I don't wash and I save money.

Peugeot SRDT.