Water removal in WVO

[SCOTT]

Dana

As the resident expert on Veg oil use, could you comment on the various ways to dewater WVO?

I am particularly interested in centrifuge and flash evaporation.  I am sure this info is avaliable in other forums, could you just give a bref explanation and some links to the indepth discussions on the other threads

Thanks
Scott

[Geno]

This crackle test was in my WVO folder. I'm pretty sure its from Dana. You should be able to find dewatering techniques here. 
http://biodiesel.infopop.cc/6/ubb.x?a=cfrm&s=447609751


Crackle test is explained on teh Frybrid website.

I delveloped the HotPan Test several years ago so those using wvo for fuel had a simple, cheap, but very accurate test for water even at very low levels ( under 100ppm) in WVO.

It continues to be developed.

The  test as it stands currently is:
Smear an oil dampened finger of wvo accross a cool cast iron fry pan.
This will serve to indicate when the pan is reaching test temperature.

Keep the sample of wvo to be tested handy. Enough for 1/4"-3/8" thickness covering the bottom works best.
Heat the pan on medium high temp until the smear begins to produce smoke then pour in the sample.

Observe  the sample where the oil contacts the pan surface. Very small bubbles forming on the pan/oil interface indicate suspended water in the sample.
The density of bubbles indicates how much water is present in suspended form.
Many large bubbles indicate  the sample contains at leas 1000 ppm of water in the sample.
Many small bubbles indicate the sample contains 500-1000 ppm of water in the sample.
3-4  bubbles per square inch indicate 200-300 ppm of water in the sample.
1-2  bubbles per square inch indicate under 100 ppm of water in the sample.
If crackling or popping is heard..over 1000ppm of water is present in the sample.
Optimumly you want to use VO fuel that contains less than 100ppm of water for maximum  injector pump and injector life.


NOTES:
Do not pour in a sample with any visible water.
If water droplets are visible no testing is needed. There is water present in your sample.
Visible droplets of water will spatter hot oil out of the pan and may cause burns or fire.
Do not average bubble count. The visibility of bubbles is dependent on the temp of the underlying pan and this may be regionalized depending on your heat source.
If the pan has been washed or not used previously it must be "seasoned"   to make certain that no moisture is trapped in the pores on the surface of cast iron.
False positive results (bubbles) can be obtained if the pan is WAY too hot..or if solvents are mixed in the WVO.
False negative  results (no bubbles)  are possible if the suspended water has high concentrations of salt/sugar/ acids.

[ronmar]

Well i am not Dan, but I wil jump in:) two basic methods would be a centrifuge and vacume distillation.

Water in the oil will naturally separate over time, just set a WVO sample on a shelf undisturbed for a few months and see what happens.  A bit of heat will accelerate this process as the separation occurs easier with warmer oil.  A centrifuge speeds up this process by applying several thousand "G"s(2000-4000) to the oil in a spinning bowl or basin.  The bowl has a top lip which contains the oil that is slung out to the sides of the spinning bowl.  As more oil is added the level eventually reaches a point where it flows over this lip to be slung against the outer case.  The contaminated oil is added to the bottom of the bowl where it is accelerated outward and the tremendous G force is applied.  This separates the heavier elements/particles and of course water is heavier than oil so it travels to the outside of the spinning bowl.  The oil slowly travels from the bottom to the top, shedding it's heavier contaminants outward untill it reaches the bowl lip and is slung off the bowl to be recovered.  Again, heat also helps with this process.  The bowl must be stopped from time to time to clean out the water and separated contaminants lest they fill the bowl to the lip and spill over along with the cleaner oil.  There are self cleaning units such as those made by Alfl-Laval but they are fairly complex and very expensive. Check out the videos section at www.simplecentrifuge.com. They have a pretty good animation that shows how the process works.

Water boils at different temperatures based on the pressure.  The lower the pressure, the lower the boiling point.  If you apply enough vacume to a sample of WVO, you could in theory boil the water out of the oil at room temperature.  Typically a lesser vacume and some moderate heat is applied to cause the separation.  The water turns to steam/vapor and must be drawn out of the chamber.  This is done by circulating air(under the same vacume) thru the chamber top to a dessicant filter to absorb the moisture or to a condenser where it is cooled and the water can reform outside the oil chamber. This dried air is then returned to the chamber to pickup more water vapor.  Agitation of the oil helps to get the vaporised water out of the oil. Depending on the vacume and temp used and the ammount of water in the oil, the boiling process could also be quite violent, but far safer than doing it at atmospheric pressure and 212 degrees F. 

There are companies that specialize in doing this to installed hydraulic systems where the working temp of the oil in use provides enough heat to boil off the water under vacume. 

If I recall the freshwater evaps I used to work with, the first stage was under 17" of vacume and boiled at 133 degrees F.  We recovered enough heat from the distilled freshwater in the first stage to boil the sea water in the second stage under about 24" of vacume(forget the temp).

Ron       

[SCOTT]

rommar
I have seen the simple centrifuge, I am working on a design that is similar (but improved of course) I am thinking of integrating a heating element so evaporative dewatering can be accomplished at the same time as particulate separation.  I think the idea of using a high G centrifuge is very versatile, you can use it on WVO, motor oil, transmission fluid... and depending on the dwell time you can control the level of cleaning.  The only slight problem is getting one made for a reasonable price; the materials alone are expensive not to mention the machine work.  This is not something a home shop can handle, when dealing with 2000 G’s + high precision is a must.  I should have some drawings for the machine shop in a week or two, it will be interesting to see what price they come back with.

Scott

[ronmar]

Be carefull, evaporative de-watering at atmospheric pressure can be hazardous.  Just as Geno mentioned with the frying pan metod of water detection.  A little too much heat with a high concentratin of water and you have a possibly explosive situation with potential for steam and hot oil burns.  The centrifuge should spin the water out of the warm oil safely.  I would like to see your centrifuge plan.

Good Luck
Ron