dewatering problem

Collecting, filtering and dewatering of WVO SVO vegetable oil. For Biodiesel producers too.

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dewatering problem

Postby ajcbgray » Wed Apr 30, 2008 9:44 am

I'm finally getting my WVO dewatering setup going and need a little help. I have a 55-gal drum with a tap at the bottom and the top opened up. I have a 3"wide drum heater around the bottom of the drum. I heated the oil to about 140F and let it settle overnight... in the morning it was about 80F. I dipped some oil from the top of the tank and did a hot pan test only to find plenty of bubbles. I drained some oil out of the bottom and it looked clean and clear and a hot pan test revealed just as many bubbles as the oil taken from the top of the drum.
So, why is the water not settling out? Do I need to insulate the drum so that the oil cools more slowly?
Any suggestions would be great.
ben
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Postby SunWizard » Wed Apr 30, 2008 9:53 am

Where is the tap at the bottom? If you put a quart of water in the barrel does it all drain out the tap? If not there could be free water in a pool a the bottom recontaminating any dewatered VO.

You may have some soap or emulsifiers in the VO, which holds onto water. A mistwash before settling can remove that and make settling work. See the thread here about mistwash, and the thread about TDS meter to test as a way to see if you have soap/salt/acid/base in your VO.

Did you filter the VO yet? If it has food particles, those need to be removed since they hold onto water. Filter to 10 microns and try settling again. Insulating and slower cooling helps too.
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Re: dewatering problem

Postby canolafunola » Wed Apr 30, 2008 8:54 pm

ajcbgray wrote:I'm finally getting my WVO dewatering setup going and need a little help. I have a 55-gal drum with a tap at the bottom and the top opened up. I have a 3"wide drum heater around the bottom of the drum. I heated the oil to about 140F and let it settle overnight... in the morning it was about 80F. I dipped some oil from the top of the tank and did a hot pan test only to find plenty of bubbles. I drained some oil out of the bottom and it looked clean and clear and a hot pan test revealed just as many bubbles as the oil taken from the top of the drum.
So, why is the water not settling out? Do I need to insulate the drum so that the oil cools more slowly?
Any suggestions would be great.
ben


Did you filter before heat and settle? Heating thins the oil and allow the heavier water to settle. If you don't filter first, the lighter food particles has some water attached to it and will not settle. insulation (to decrease convection) is extremely important in order for the suspended water to settle. Think of a suspended water particle as a feather. If the feather is in a convective environment, it will never touch ground.
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Postby David » Wed Apr 30, 2008 10:08 pm

I have to admit, this fascinates me.

Are people here actually able to filter their oil, heat it and let it sit overnight and then get oil that passes a hot pan test just like that? Anyone have any pictures of the amount of bubbles they get in a HP test before they do this?

I have tried this a few times, my friends have tried it and none of us can see much if any difference at all. The oil I get will show a good amount of bubbles in a hot pan test but usually little ones that don't even crackle.

I checked some oil I have had sitting an an IBC for 6 months last weekend and it was still wet as far as a HP test went ( although quite good) And that was clear oil only taken off the top of cubees that had been already settling from 6 weeks to 3 months!
I dug out some oil the other week that had been sitting for 12 months I had forgotten about and it still wouldn't pass a HP either despite being some of the clearest, most sparkling oil I have seen.

I can understand this heat and settle process dropping free water in one night but as for passing a HP test, all I can say is the oil you guys get must be radically different to the stuff we get down under!
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Re: dewatering problem

Postby hheynow » Wed Apr 30, 2008 10:25 pm

I have a 55-gal drum with a tap at the bottom and the top opened up. I have a 3"wide drum heater around the bottom of the drum. I heated the oil to about 140F and let it settle overnight... in the morning it was about 80F. I dipped some oil from the top of the tank and did a hot pan test only to find plenty of bubbles. I drained some oil out of the bottom and it looked clean and clear and a hot pan test revealed just as many bubbles as the oil taken from the top of the drum.
So, why is the water not settling out? Do I need to insulate the drum so that the oil cools more slowly?
Any suggestions would be great.


Tap on bottom?
Did you de-head the bottom and now have two bungs on the bottom?
If so HERE is how I did my de-water drum.
Bottom drain is for water and sediment.
Standpipe drain is for dry oil once de-watered and s-l-o-w cooled.
Get a roll of R-13 fiberglass insulation and some good tape.
Leave the bottom eight inches of the drum uninsulated.
Cut a circle of insulation for the lid.
Band heater goes 3-4 inches from bottom of drum.
This allows a cool area under the heater for cold water to accumulate.
Creates a greater temperature range.
Proper de-watering takes place during s-l-o-w cooling.
If properly insulated the oil will drop to ambient in about 36 hours.
Heat to 160* instead of 140*
Remember that dry oil is crystal clear.
If the standpipe drain oil isn't dry (hot pan test) reheat to 160* again.
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Postby ajcbgray » Thu May 01, 2008 4:20 pm

Sorry for the delayed reply, work got in the way of my fun.

So the oil is already filtered and should have been dewatered by the guy who passed it on to me. I decided to check it and it didn't pass the hot pan test. The oil is slightly dark, but is clear and appears clean. I de-headed the bottom of the drum and have a drain coming out of the 3/4 inch bung that is now on the bottom. It is flush with the bottom (no standpipe). The problem is not water sitting on the bottom re-contaminating the oil because I first tried skimming a little oil from the top and that didn't pass the test either. I'll try insulating the drum this weekend and see if a slower cool-down does the trick.
ben
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Postby SunWizard » Thu May 01, 2008 4:34 pm

Did you filter it or are you relying on what the guy you got it from said?

Is the VO very old? (>1 year and exposed to air?) If so it could have a good amount of mono and di-glycerides from the oxidation process (see the polymerization thread here) which are good emulsifiers and could make it very hard to settle.
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Postby John Galt » Fri May 02, 2008 7:10 pm

Take a sample of the oil which you're having problems drying.
Place it in the fridge overnight.

Does anything settle out?

Test the clear oil from the top of the sample.
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