Freeze drying VO?

Single Tank WVO systems and blending SVO WVO to thin it.

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Freeze drying VO?

Postby denson » Fri Apr 11, 2008 9:18 pm

Is it possible to bring a 55gal drum of VO down to freezing temps enough to freeze water and solidify fats. Then let it settle and thaw and just drain off the bottom of the 55gal. drum leaving the WVO dry and pre filtered? I ask this because I've put some samples in my freezer and they seemed to settle quicker. I'm not sure if it is water on the bottom of the samples or just fat.
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Postby John Galt » Fri Apr 11, 2008 9:41 pm

It happens to the oil I collect when it freezes in the winter. In the spring I pour the clear oil off the top of the cubies.
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Re: Freeze drying VO?

Postby SunWizard » Fri Apr 11, 2008 9:47 pm

denson wrote:Is it possible to bring a 55gal drum of VO down to freezing temps enough to freeze water and solidify fats.

Yes, but it could be slow, and expensive for the electricity to do this in Florida.
Then let it settle and thaw and just drain off the bottom of the 55gal. drum leaving the WVO dry and pre filtered?

It would be a good science project to try, take 2 samples of the same known, wet, pan tested VO, freeze 1, and the other heat to 120F and slowly settle overnight. Then drain off the bottom of both, and stir and pan test what remains. Both methods would take about 24 hours on a small amount, but the freezer method would take much longer than that on a 55g barrel.
I ask this because I've put some samples in my freezer and they seemed to settle quicker. I'm not sure if it is water on the bottom of the samples or just fat.

It could also be higher melt point VO. Thats one trouble with that method, since the higher melt point VO is great fuel if dewatered. In fact its the best fuel if you have a heated 2 tank rig, or weather warm enough that the VO is not clouding, since it has higher cetane and more BTUs.
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Postby denson » Sat Apr 12, 2008 6:40 pm

My (very crude) filtering sytem goes like this: Pump waste canola oil through a sock filter into ONE 55gal. drum with 2 through hull fittings one placed at the very bottom of the barrell, and one placed about 8" from the bottom through the side of the barrell. the bottom fitting is of course to drain off water, fats, crud, ect. the other goes through the pump, then 15-20 micron filter then 2-5 micron filter then through a goldenrod water block. Anyway to the point I remember in my younger days seeing a fridge that this guy had modifyed to hold a keg, the tap came out of the side of the fridge. so I was thinking of doing this with a 55gal barrel of oil and a freezer. oil would already be mixed with at least 50% ULSD among other thinning agents. I will do sun's science experiment first though to see if it is even worth pursueing. Any thoughts?
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Postby John Galt » Sat Apr 12, 2008 7:11 pm

That should work well to chill the mix and settle out any residual PHOs, fats and water. That's what happens in my final settling barrel of 50-50 mix, where I pump from 8" off the bottom through the final 5µ filter into the truck tank. When the temperature is 50°F or lower the layer of 'stuff' is solid in the bottom.
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Postby denson » Sat Apr 12, 2008 9:14 pm

That's what got me thinking about settling cold, when I pulled my samples out of the freezer the crud on the bottom was fairly solid while my useable fuel was still pretty fluid. Which would allow me to pump the useable fuel without disturbing the layer of crud on the bottom. Also once I let it thaw I noticed that there seemed to be more crud on the bottom or it expanded or possibly started to mix with my fuel again. Thanks for the feedback John.
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Postby WD8CDH » Mon Jun 02, 2008 1:53 pm

The cold will allow the fats to settle out but the suspended water will not settle out. You need to decrease the viscosity for the suspended water settle in a reasonable time.
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Postby zoochy » Mon Jun 02, 2008 7:54 pm

Water is most dense at 4C (40F) and would settle out best around that temp. Freezer to fridge perhaps?
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Postby Burbarian » Mon Jun 02, 2008 9:12 pm

While it is true that pure water is most dense at 4C, the low temperature will likewise increase the density and viscosity of the vo. For optimal settling, the ideal temperature would be that at which the vo would have the least viscosity while maximizing the DENSITY DIFFERENTIAL between the vo and h2o. The density of water at 1atm pressure varies only by about 4% between 4C and 100C. In contrast, the density of vegetable oils ranges from 0.93 to 0.91 g/cm3 between the temperatures of 15 °C and 25 °C. Though nonlinear, the thermal expansion gradient of oil is significantly wider than that of water. If the specific gravity of vo decreases with increasing temperature as one would normally expect, then as a first order conclusion the optimal temperature for settling out water from oil would be at just under the boiling point of water. This will ensure minimum viscosity of the oil, and maximal specific gravity delta between the oil and the water. Note that the entire solution must be at an even temperature, as uneven temps will give rise to convection currents which would be counterproductive to fluid separation.
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Postby WD8CDH » Tue Jun 03, 2008 7:06 am

Burbarian wrote:While it is true that pure water is most dense at 4C, the low temperature will likewise increase the density and viscosity of the vo. For optimal settling, the ideal temperature would be that at which the vo would have the least viscosity while maximizing the DENSITY DIFFERENTIAL between the vo and h2o. The density of water at 1atm pressure varies only by about 4% between 4C and 100C. In contrast, the density of vegetable oils ranges from 0.93 to 0.91 g/cm3 between the temperatures of 15 °C and 25 °C. Though nonlinear, the thermal expansion gradient of oil is significantly wider than that of water. If the specific gravity of vo decreases with increasing temperature as one would normally expect, then as a first order conclusion the optimal temperature for settling out water from oil would be at just under the boiling point of water. This will ensure minimum viscosity of the oil, and maximal specific gravity delta between the oil and the water. Note that the entire solution must be at an even temperature, as uneven temps will give rise to convection currents which would be counterproductive to fluid separation.


Hi Burbarian,

There is one other factor: Dissolved Water. If there is free or suspended water present, dissolved water increases with temperature.

Free water is like rain, it will fall out easily with gravity.

Suspended water is like fog. Convection and Brownian motion keeps it suspended.

Dissolved water is like Humidity. Invisable and won't settle out. Just like Fog and Humidity, Dissolved water and Suspended water can go back and forth between states depending on temperature.

If you try to remove water with the temperature too high, the Dissolved water may be high enough that it becomes Suspended (un-dissolved) water when the temperature decreases.

When you are using settling to remove water, you need GRAVITY and TIME. The higher the viscosity, the more TIME that you need. It becomes a compromize between too hot allowing more Dissolved water and too cold making the settling time too long.

I settle at 100F with very even heat to prevent convection currents.
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Since '81 former WVO conversions:
'83 240D
'80 Audi 4000D
'83 Isuzu Pup
'86 Golf
'76 Honda Civic with Kubota engine
Prior to the cars, several generators
Kubota Tractor
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Postby David » Tue Jun 03, 2008 7:15 am

In my settling barrels I very rarely get any free water, it is all disolved in the grey looking crap in the bottom. I have heated this and find I can still get no free water to drop out and the oil is still very wet. I have tried filtering and drying this liquid fat for fuel but the amount of water in it makes drying such a drawn out process it simply isn't worth the effort.
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Postby zoochy » Tue Jun 03, 2008 11:47 am

So basically… water will settle out as long as the oil remains liquid at a temperature constant enough to prevent convective mixing. That and constant warmer would be quicker than constant cooler, but not too warm as to prevent suspended water from becoming dissolved.

So, cool the oil, let it warm up and sit at a constant temp
for a few weeks, then siphon all but the bottom dregs?

Is it worth the extra step of chilling the oil though? Won’t the heavy oil settle to the bottom either way? I’m curious as chilling naturally happens outdoors at my latitude.

Good experiment to perform; Denson, let us know the results.
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>160,000 km on:
88% canola WVO
11% old gasoline
.6% turpentine
.3% acetone
.1% eye of newt
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Postby WD8CDH » Tue Jun 03, 2008 3:02 pm

I have seen no advantage of cooling the oil unless you want to remove the fats that are still liquid at your particular ambient temperature.

Personally I don't want to remove the fats. Fats are usable energy that I can run in my vehicle any time of the year. If I don't remove them I don't have to dispose of them.

Either holding the oil at a constant temperature with very even heat or heating up the oil and allowing it to cool very very slowly by being well insulated is the best way to settle out water and most of the contaminants.

My settling is effective enough that a 2 micron Racor 1000 filter element lasts for about a year of processing oil. :D
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Since '81 former WVO conversions:
'83 240D
'80 Audi 4000D
'83 Isuzu Pup
'86 Golf
'76 Honda Civic with Kubota engine
Prior to the cars, several generators
Kubota Tractor
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Postby denson » Tue Jun 03, 2008 4:16 pm

That is exactly what I'm trying to do, remove the fats. Ambient tempuratures here in southwest florida are around 80F and climbing. I do not want to burn the fats because I do not use a heated system. There are currently no conversions to my truck, so I want my fuel closer to diesel or bio than SVO.
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Postby John Galt » Tue Jun 03, 2008 5:04 pm

Removing the fats was why I adopted Ron's heated upflow to cold upflow:
I have the advantage of temperatures below 50°F for much of the year, so the fats tend to settle nicely.

What temperature is the cold tap water? One could make a cold water jacket with a 30 gal barrel in a 55 gal barrel to chill the oil enough to drop the fats if one had a source of cold water.

The other option is to get an old fridge or freezer and put the upflow barrel in it.
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