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Different oil no separation problem
19-01-2020, 12:18 PM
Post: #1
Different oil no separation problem
Hi, I make biodiesel for a few years now , always one stage and usually get lightly used fresh soy oil.
Now I got some free rapeseed oil which has been sitting for a while but otherwise seemed ok. I titrated it and it came a bit higher than usual ,I usually get 0.5 ml titration and this time it was more like 1.5 ml so I added more NaOH.
When the methoxide went in the processor there seemed to be a normal reaction (I have clear tubing) . But coming back this morning I noticed there was no separation at all and it seemed like the oil just got a bit thinner and darker .
Besides the different oil and more NaOH every thing else was the same. I would assume most of the methanol is still present?
Is there a way I can try and fix this situation? Titrate again ? I would hate to use a lot more methanol but NaOH is not a problem .
Another option is some how to use it on my older hilux ? But I guess it will be a hard time getting rid of the soap if the oil is like this.

Thanks!
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19-01-2020, 05:25 PM
Post: #2
RE: Different oil no separation problem
Just warm it, pump it and add some more glycerol, it will then separate.

Location York.
Enhanced Glycerol pre-wash, then 1 more stage (usually)
De-meth, water wash and dry to <200ppm.
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FOC Water testing by S/B or KF for forum members.
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19-01-2020, 05:41 PM
Post: #3
RE: Different oil no separation problem
Did you dry the oil before trying to use it? If not and if it had lots of water present you might have produced lots of soap and little bio.
First step is to try what Dave has suggested and see if if then splits.

Paul
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19-01-2020, 07:38 PM
Post: #4
RE: Different oil no separation problem
Whatever you do prove it off by doing a jug sample and then scale it up to your batch size.Cool

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20-01-2020, 06:51 AM (This post was last modified: 20-01-2020 06:52 AM by WesleyB.)
Post: #5
RE: Different oil no separation problem
Take about 300 milliliters of the unsplit product and put a tablespoon of table salt into it . Might warm it up . See if any lower layer forms . Doing this in a glass heat shock resistant beaker would work .
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20-01-2020, 09:04 AM
Post: #6
RE: Different oil no separation problem
Thank you all , oil was crystal clear but I dont check for water if it is clear since I assume it is below 1000 ppm . After I finish with the bio I do soap titrate it and check it with the sandy brae water tester .

It is a good idea to do small batch tests for the salt and glycerin mixing. I will check it . Just for understanding better , why would adding glycerin or salt help it separate?
Thanks!
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20-01-2020, 10:04 AM (This post was last modified: 20-01-2020 10:08 AM by dgs.)
Post: #7
RE: Different oil no separation problem
You will have produced biodiesel with your failed batch and therefore glycerol. Why the glycerol has not dropped I'm not sure, it could be something to do with the differential densitys.

However if you add more glycerol it will increase the average density of the glycerol and it will drop.

Although bio can only hold about 1000ppm water in a dissolved state, oil can hold more (how much I'm not sure but certainly more than 1500ppm) so being clear isn't a good assumption of low water.

I'm not sure that salt would work, Its usually used to break emulsions during water washing.

I'm impressed that you also have a Sandy Brae.

Location York.
Enhanced Glycerol pre-wash, then 1 more stage (usually)
De-meth, water wash and dry to <200ppm.
2x 2.0 HDI's both on B100.
2x ransomes mowers both on B100.
FOC Water testing by S/B or KF for forum members.
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20-01-2020, 04:29 PM
Post: #8
RE: Different oil no separation problem
Yep get some more glyc into there it will usually split it

Be prepared for doing more stages as wet batches like that often get low conversion
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20-01-2020, 06:49 PM (This post was last modified: 20-01-2020 06:54 PM by WesleyB.)
Post: #9
RE: Different oil no separation problem
Putting plain sodium chloride salt into maybe 250 milliliters of unsplit product should not disslove if it's dry . But if it was dry it should have split . It may reveal if there's a water problem . When seperation occurs the lower layer is more dense and polar , there's hydrogen bonding occurring in the lower layer more than in the upper layer . Salt might cause a separation to occur by increasing the density and polarity of a portion of the unsplit product .
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27-01-2020, 02:54 PM
Post: #10
RE: Different oil no separation problem
For future batches, maybe you can 'pre-dry' your oil by using some of your previous batch 1st stage glycerol & pumping that around for 15 mins or so; this removes a lot of water from any oil. Of course I use KOH - not sure if NAOH glycerol can be used like this - I have heard that it goes solid when cold? But the principle is there - get your oil as dry as possible first then process it...

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