Hi all, this is a spin off of the "Red Wine Vinaigrette wvo".
The process of removing the Free Fatty Acids from wvo using lye and water is something that I read a long time ago and can't really remember how it worked but I've been doing some tests and getting closer to getting it right.
The process as I remember it:
Mini batch
First mix 67 grams of lye with 1 liter of distilled water. Mark as lye stripper and keep it in an air tight container in the dark.
Next titrate your oil using your favorite technique and the result will be called "S"
Now multiply "S" by 10 to come up with the amount of milliliters of the lye stripper to use to treat 1 liter of the wvo.
Example:
Oil titrates to 12.3
12.3 x 10 = 123
Use 123 Ml of lye stripper in your 1 liter mini batch.
Mix the lye stripper into the wvo and agitate for 5 minutes. Let it stand until the soap separates to the bottom. Sometimes there is some soap floating on top that has to be skimmed off but the rest will be at the bottom. Usually the soap is slightly gelled and so it is easy to pour off the clean oil.

I recently did this process on some wvo that titrated over 18 ml. I treated it with the lye stripper as described above and it reduced the titration down to 2.9. The down side is 30% of the oil was converted to soap and it took 2 1/2 days to settle out.

In an effort to minimize the amount of oil lost in the process I did another test on some bad oil today. This is the same oil as above but I took the sample off the top of a 300 gallon tote and it titrated to 15.5. Still pretty bad. I divided my 1 liter test batch into 2 500 ml test batches. The first batch I treated just as I described above. I add 77.5 (155 divided by two because it is only 500ml) to the first 1/2 batch and shook it in a jar for 5 minutes. As soon as I was done shaking I poured 100 ml in a graduated cylinder so I can tell how much FFA turned to soap.
The second 1/2 liter was treated with 50 ml of the lye stripper. I used a wisk to agitate it for 5 minutes and also poured 100ml in another graduated cylinder. It separated out in just over an hour.


I produced 15 % soap but a titration showed that it only reduced the titration from 15.5 down to 11.2. It is a nice reduction but not really enough.
As you can see, the other sample is still an emulsion so I can't titrate it yet. I'm sure it will take a couple of days to settle. I think that the thin column of the graduated cylinder might hamper the settling. As soon as possible I will post the titration results

Just a note, the wvo that I cleaned before made some great biodiesel and the oil passed the water test (oil in fry pan) without so much as a single sputter.

I will continue to test until I get the best rate of lye/water for cleaning the oil.

I think your information about the maths is wrong. If your oil titrates by the usual method with NaOH to x ml you should use x grams of NaOH per litre of oil to react with the FFA.

The problem with this method is that it tends to make an emulsion which would take forever to settle out. In industry a centrifuge is used and it works well.

If you use less than the titration amount you will only partly reduce the FFA, as you found, but it appears to settle better than happens if you attempt a full extraction.

The question is: how much oil is lost in the emulsion? And how does this loss compare with the loss which occurs in the normal biodiesel base-only reaction.

It may turn out that a partial removal of FFA in this way will have the advantage of cleaning the oil better than simply settling or water washing. Looking forward to more results.

What is the purpose of this experiment if we are not making biodiesel? Is this a way of lowering the gelpoint of VO without going the biodiesel route?

I don't know that this removes FFAs, but what about a brine wash?
did some experimenting a while back and found that a solution of baking soda in water mixed w/ WVO and agitated (shook up) produces an emulsion that settles rapidly and completely and, I'm guessing, neutralizes some of the acid content of the WVO
worth trying a sample and titrating before and after and see what you get
no oil lost and baking soda is safer than lye

Form the similar washing research I did several years ago I suspect this may simply be removing/neutralizing water soluble acids.

quote:

Originally posted by EuDeMan:
I don't know that this removes FFAs, but what about a brine wash?
did some experimenting a while back and found that a solution of baking soda in water mixed w/ WVO and agitated (shook up) produces an emulsion that settles rapidly and completely and, I'm guessing, neutralizes some of the acid content of the WVO
worth trying a sample and titrating before and after and see what you get
no oil lost and baking soda is safer than lye

neutral, can a centrifuge be built? I don't know anything about them. By the name I assume something spins really fast but that's about it. In layman’s terms, how does a centrifuge work?
Cleaning the wvo this way seems to work, I assume that it will also lower the gel point of svo for those that run it.
I don't know what the highest titration is that can be used on the strait base method of making BD and I haven't had a chance to figure out the acid-base process. The bad oil I'm using seems to have something in it that keeps particles in suspension with every other method I have tried to use. This is slow but it seems to work. I plan to make BD from the two samples I treated yesterday and see how much difference there will be in the final production rate.
-mcguyver

When i need to reduce the FFA of wvo i use heat , methanol , sulfuric acid and time .

McGuyver...A centrefuge on the scale of what you probably want to do will very much resemble a carnaval ride. My thinking is to maybe use a diesel engine and using a connecting tranny to power the spinner pole. Then, connected to chains and a suitable metal container or basket to hold 5 gallon buckets (sealed of course) with wvo. An hour of spinning should do the job of seperating. Any thoughts????

quote:

Originally posted by Ivoryman:
McGuyver...A centrefuge on the scale of what you probably want to do will very much resemble a carnaval ride. My thinking is to maybe use a diesel engine and using a connecting tranny to power the spinner pole. Then, connected to chains and a suitable metal container or basket to hold 5 gallon buckets (sealed of course) with wvo. An hour of spinning should do the job of seperating. Any thoughts????

Your joking...right?

A backyard centrifuge? If designed like a carnival ride, turning at modest speed, it would have to be large. The industrial machine is quite small but turns at enormous speeds and is a continuous process, treating small amounts of material at any one time. It is not feasible to attempt to build one - the prior art is very far advanced.

A better idea for the backyard would be to do the FFA stripping not with water but with the glycerine from the previous batch. It is too hard to dissolve NaOH in glycerine but KOH will do it. The high density of glycerine ensures that separation will occur without the need for a centrifuge, just as happens with the biod reaction. Due to the high viscosity of the glycerine this must all be done at high temp and drained hot.

It is all a substantial work load however and I think the preferred route for high FFA oil is the two stage acid/base process. This has the added advantage that it permits the recovery of the FFA so that they may be included in the next batch, thus eliminating them from the waste stream, an option not available with any other process. This is a substantial saving as for every litre of FFA (in soap) that goes down the drain there will be two litres of perfectly good biodiesel going down the drain with it.

DN
I haven't had a chance to learn about the acid-base method yet. I haven't built a good mini batch vessel that I can heat and stir while sealed. Do you think you could greatly reduce the ffa of wvo with a titration of 17 or 18? It is really bad oil and seems to hold tremendous amounts of water in suspension. It's been filtered through a 20 micron sock filter and smells terrible.

Ivoryman
I'm beginning to get the idea of how it works. I assume the "crud" and water is heavier than the oil so it settles to the bottom of the bucket. Right??
I don’t know if running an engine for an hour for just 10 gallons of wvo is the best means but it might be a stepping stone to building something better. I’m going through about 120 gallons per week so I’d probably have to have something a little bigger or something with a continuous supply. Does a small continuous unit exist or is it even possible?
After your description, I see a wheel with 5 or 6 vials spinning and the vials swing further and further out as the rpms increase.

danalinscott
You mentioned something about some research about brine wash? Is this something that could be done on real bad oil?

I've been super busy this week and haven’t had a chance to update my results on the two test batches. So far, both have settled but I haven't titrated the second sample yet.
-Mcguyver

Check out this thread called "DIY centrifuge". the 8th post down from top has a link to an actual experimental centrigug built by john o. (here).

There is another post HERE indicating someone was having success with a "spinner" type centrifuge but the post never went anywhere. Don't know if the "spinner" refered to in this post is the "spinner on-board oil filter" for diesel engines or not.

I have been monitering centrifuges on ebay for some time now, lots and lots of the small testube lab centrifuges but I have not yet seen a large continious feed unit.

I am told by employees of the local Humco/Kraft vegoil processing plant that these large continious units are what is used there to seperate different weight vegoils and water from oil.

http://biodiesel.infopop.cc/eve/forums/a/tpc/f/919605551/m/341102225/p/2

I haven't worked with this lately, but maybe there's potential??

After reading about hydrocyclones in the above link I was wondering -- What if we combined the idea of the hydrocyclone and a centrifuge, Yes - a bit outside the box thinking -BUT- Start with a fairly large centrifugal pump, say 6-8 inches in diameter, mount it so the input opening (center) is pointing straight up, hook the shaft to a motor like normal. A centrifugal pump can have its output flow completely blocked with no problems, it just makes some amount of pressure and then spins the fluid round and round. What if now we use another smaller pump to push fluid BACKWARDS through the centrifugal pump so that fluid is being forced into what is normaly the OUTLET of this pump, This fluid is going to go round and round at 1750 or 3450 rpm or whatever, as fluid is pushed into the outlet other fluid near the center HAS to be forced up and out of what is normaly the INLET -- If we choose a pump with a flat backplate it would be fairly easy to remove the outer housing to remove the solids that should get deposited on the inside wall of the pump housing, actualy would not be to difficult to fab a flat sided housing with a small center outlet (original inlet) as this is not a crucial part of the pump and nothing is moving about it. The impeller can be increased or reduced in diameter as might be nescicary, this is one of the ways used to control the G/M flowrate of a centrifugal pump anyway. This should also seperate the free water or heavy oil from the lighter oil, just put another outlet in the outer wall and control the output flow rate of this outlet to match the amount of water or heavy oil being seperated, maybe several outlets across the face of the outer housing from the center to the outside edge, each outlet would be for a different weight fluid.

Continuous feed and seperation, High "G" forces, no balance problems, sealed shaft, scalable, small and mobile, could be powered by a 12 volt DC motor -- Sounds to good to be true... OH YAH -- Pat. Pend.

The problem in continuous centrifugation is that you need not only immense G forces but also an environment without churning so that settling can occur. The industrial machines have a central stack of discs so that the oil has to move in a constrained way through tiny slits.

Neutral -- Ok, we may have to machine a custom impeller that has a stack of closely spaced thin plates with small radial slits, may not need the radial slits ? May not be perfect but this is the first idea I have come up with to give mobile filtering at least a glimmer of hope. I invisioned the feed to be at a very slow rate, I would think this would allow the time needed for seperation and migration of the thinner fluid to the center outlet ? will need to do lots of testing.

May take two of these units in series, the first one using a normal impeller to force the particulates to adhere to the outer housing and a second unit to seperate water ? Maybe several ?

It would be wise to have a look at a centrifuge before doing anything I think. And if the chemistry is right do you really need a centrifuge?

Nahh -- just dive in - you have already shortened my initial research and testing time considerably.

To bad you don't burn straight vegoil, you are stuck in a biodiesel frame of mind. There is not a lot of chemistry to consider in cleaning straight vegoil, just a lot of filter clogging.

McGuyver...I was talking about 5-10 buckets swinging which would make it worth while. The thing we need to figure out is the speed the revolution needs to be for separation as well as the time. My wife uses a centrifuge for blood work as a doctor. The revolutions per minute on the machine she uses is staggering. I don't think it has to be blinding speed to get the layers started on the wvo. Any more thoughts???

Tim...do you see this as a way to collect directly from the collection bins? I still would do extensive filtering but it sure would make it easier to initially separate water and gunk.