I'm using KOH at the standard 7g + titrate value and each batch ends up with a thin emulsion layer during washing that is hard to remove (keeps sticking to the sides of my tank) 3/27 test has a few tiny droplets falling out after about 5min.
Am I correct to assume that I should bump up the KOH in my calculations?

I'm losing alot of fuel in the wash process

Thanks!

The emulsion could be soap or monoglycerides (and to a lesser extent diglycerides).

If it is soap, then you may not have enough methanol.

If it is monoglyceride, then you may not have reacted long enough.

The "few tiny droplets" are a sure sign of under-reacted fuel.

Under-reaction may be caused by: too little methanol, too low temperature; too short reaction time; too little mixing; or whatever?

Can you describe your process so the cause of your problem can be narrowed down.

Sure:

I using 20% methanol to oil (in this case 4 gal. meth. to 20 gal. oil)

Heating in barrel to 130F, transfer to Processor tank, mixing for 2 hrs, settle for 24 hours, drain off glycerin and transfer to wash tank.

Is the processor tank sealed? Is it possible for methanol vapors (they are clear and, virtually, odorless) to escape from the processor. Is it insulated?

The layer is normal for me, it has to do with washing and I suppose it has something to do with processing also. Just drain the top of it below your standpipe and then drain the BD off. Every now and then drain the wash tank fully into a barrel and after awhile it will turn into BD. Let that collect in the barrel till you can reach in with a can and skim it off and add it to your next wash.

There will be those that say they never get this layer but it happens for me and others.

Processor tank is Poly Cone Bottom tank - screw on top, but I suppose it's possible that some vapors are escaping, It's insulated with some foil backed bubble wrap insulation.

I'm using an identical tank for washing for now.

It's not your processor leaking fumes IMHO.

One more quick question. Is your wash water hard or soft? If it is hard, could it considered to be very hard?

Water could be considered very hard - it's well water right out of the spigot - also high in sodium.

Assuming: 1) your reagents are fresh; 2) the titration was performed correctly; 3) your oil was dry; and, 4) your methanol was dry (if unsure about any of these points, then you should check them out and be sure they are all OK before proceeding) then there could be three, easily correctable items that could be causing “a thin emulsion layer during washing that is hard to remove (keeps sticking to the sides of my tank)”, and “3/27 test has a few tiny droplets falling out after about 5min”.

Solution one: Process for another 2 hours. Even though you are processing in an insulated processor you could be loosing heat during product transfer and during the two hours the reaction is now taking. Lengthening the reaction time will allow more of the triglycerides to convert to biodiesel. This will cause your fuel to pass the 3/27 test.

Solution two: However, lengthening the reaction time will allow more time for your methanol to evaporate. Therefore, if you are not absolutely positive that your processor lid is sealed tight I would recommend wrapping the seal with a couple of wraps of duct tape just to be sure. If there is a leak of methanol vapors then the adhesive on the tape will quickly deteriorate. Of course BD splashing on the tape will cause the same problem. In either case a leak would be indicated. So, try taping the lid tight at least once and process a batch. You will quickly learn how tight your lid is.

Solution three: The “sticky emulsion” could be from soap formed because you washed with hard water instead of soft, or from monoglycerides formed from an under reacted batch mixing with the wash water. If you are washing with hard water, then switch to soft water. Otherwise, extending the processing time will reduce the triglycerides to acceptable levels.

I would not add more KOH yet until the other issues are addressed. Too much KOH can cause emulsion problems also.

If you are washing with cold water that would be suspect. I think that is what causes mine. I don't worry about the layer, BD passes 3/27, I just deal with it as described above.

One of the first things that happens when the oil and catalyst mixture are added together at the beginning of the reaction is the formation of soap.

A single molecule of FFA combines with a single K+ ion (Na+ if using NaOH) to form soap.

K+ (an Na+) based soaps are soluble in soft water. When soft water is used to wash, almost all of soap is washed out by the second wash.

Hard water, by definition, has a high concentration of, primarily, Ca and to a lesser extent Mg.

Both Ca and Mg are more active than K or Na. Therefore, if you wash with hard water, the Ca and Mg replace the K or Na.

Ca or Mg based soap include a single Ca+ ion (Mg+) and 2 fatty acid tails. So one ion of Ca will combine with two molecules of K (Na) soap to form 1 molecule of Ca (Mg) soap. This renders the Ca (Mg) soaps insoluble in water. The resultant soap is insoluble and tends to fall out of solution and stick to any solid surface it comes in contact with. You have seen bathtubs rings when bathing with hard water. This is where it comes from.

Raftens's above point is valid, if you don't mind the sticky soap remaining in your equipment, then the resulting biodiesel should have a very low soap concentration.

Also, washing with hard water will cause very few emulsions.

Thanks for the quick responses - it gives me some things to try to eliminate this nagging problem (not a big problem - just hate losing any of my precious fuel - I think I'll drain out the emulsiong layer and let it sit for a few days to see if it seperates. I had been just dumping it out with the wash water.

When do you add your methanol? In the barrel at the same time you heat your oil, or in the processor when you transfer your oil?

I have the same white layer. Sealed reactor, all oil titrates at 1, NaOH. I have only hard well water. Cold, warm, or hot water all result the same. I figured it was the hard water. I rinse the wash tank after use. After drying, (my 35 gallon batches usually dry in an open drum in 24 hours) I can see the bottom of the dry tank clearly. No dropout or white layer has made its way to the drying or storage drum.

IMHO, if your process is correct, it is normal. Wash your equipment between batches.

Excellent write-up producer, very informative.

I add the methanol to a seperate 15 gallon tank that is plumbed into my reactor, this way I can mix the caustic soda together with the methanol 1st.

I realize this is an old topic but relevant to my issue.

We have been washing using water run through water softener in main house. We just started taking water from an outside spigot. On the most recent batch I got a thin emulsion on wash #1 and #2 which I drained off. We bubblewash.

On the 3rd and 4th wash, when I added the water it immediately emulsified. I put a vibrating aquarium bubbler on top of the tank and it settled out perfectly within 30 minutes. The 4th wash ran overnight and was still fine this morning.

I don't know if its the temperature of the water more than the hardness. the water from the house coming through the softener was heated. Guess I'll just go back to using that for now.

Freesoul is your bio hot when you first wash. It is much hearder to c reate an emulsion with hot bio.


Mike

Mike is right. Hot BD and hot water is best. Maybe you need to wash a little more with the spigot water before bubbling. Sometimes bubbling to soon will cause an emulsion..

Its as hot as it stays after we drain the glycerin- using a poly cone tank. We usually drain the glycerin about 5 hours after we shut off the processor. I guess we'll just go back to using water from the main house. Even after the semi-emulsions the batch turned out fine- 70 gallons after drying.