Biopowered - vegetable oil and biodiesel forum
Biodiesel => Chemistry and process => Topic started by: neisel on May 14, 2023, 10:51:52 AM
-
145L of beautiful oil, left in processor untouched for 3-4 days for any water to drop out. Got a thimble full.
16L of virgin, 950gs of KOH resulted in a 90% conversion, 2.3L + whatever amount of KOH the no tit calculator told me to use. Bingo, all done.
Pre wash resulted in a thicker than normal drop out but it was the same amount as the water I used so went to first water wash which resulted in a mild emulsion. Added some 36% Hydrochloric Acid which cleared emulsion but left the water crystal clear with a v. definite delineation between it & the BD. I knew something was up so did another water was & left it for 48 hours. achieving the same result.
(https://i.postimg.cc/dDZBbQjY/DSCF7250.jpg) (https://postimg.cc/dDZBbQjY)
Because I knew something was odd I did another water wash this a.m. - water wash should have resulted in cloudy water clearing a bit after each wash & crystal after 4 or so washes. It
Anyhoo, emulsion came back so I added a little acid & now once again have crystal water & a v. definite delineation between it & the BD.
Any idea whats up here?
I know this isn't what I usually see but on the other hand I know loads of you don't water wash at all & your 'dirty' fuel doesn't seem to cause your vehicles any issues. Should I just dry it & use it or what?
P.S. All ^^^ done at ambient temps.
-
I forgot to mention, the 145L was glyc washed TWICE with 2 lots of virgin stage 1 KOH glyc, each of approx 15 litres.
-
Hi neisel, I don't know what is wrong with the batch but just a few comments.
Is the emulsion through the whole batch or a layer between the water and bio. Whole batch is soap, layer is monoglycerides.
Have you never had a mono emulsion, even with a clear 10/90 there can be quite an amount present which really cocks up the water washing.
I would suggest that 1.0 ml dropout in your 10/90 ( S1) is too far away from the reaction end point to get an accurate reaction end point after S2 for water washing. With a clear 10/90 you never know if there would be a small dropout if you had left it to settle longer at a cooler temperature, OR if its clear how much have you over reacted by. For this reason I get my penultimate reaction to show a dropout of ideally 0.3mls.
I've never used the no tit calculator, I work out chems for myself between every stage, then do the small o/d on K before the last reaction.
It's not a good idea adding acid. If you have soap you will make ffa's and if you have mono's they seem to be removed for the acid wash but re-appear when you use water only ( I wonder if you have the mono problem)
-
dge,
Thanks.
The emulsion (pre acid introduction) was throughout the batch, there was no water level. The picture shows the split AFTER acid with clear water & un-emulsified BD.
I don't understand how soap could have formed in this when the oil was dry (it comes straight out of the fryers hot) & almost like new, it was double glyc washed & chemical use was very light (12% methanol).
The question now is what to do with it? Do I need to do anything or just dry it and use it?
-
A couple of points:
As soon as you dissolve KOH in methanol you produce water - every 56g of KOH will produce 18g of water in the methanol. This water will then catalyse the formation of soap, so the transesterication and saponification reactions take place at the same time and in competition. Whilst the tansesterification does not use up the potash, the saponification does (the KOH is purely a catalyst for the transesterification). Using an excess of methanol will ensure that the saponification is kept to a minimum. The reason many of us like ASM is that it is completely free of water so no need to wory about soap formation (provided the oil was glyc washed to remove all FFA). Alas getting ASM now is not at all easy.
Bio should be completely miscible with methanol, whilst we often check for fallout on a 3/27 or 10/90 methanol test, if the reaction has completed, you souls be able to do 20/90, 30/90 40/90 without seeing any dropout if your reaction has completely converted - even then there may be some monoglycerides that are still present.
You should be able to split the emulsion by adding methanol (though I have never tried as I don't normally water wash). You might want to try a Dr Pepper type test on some emulsion and adding methanol to try and split the water/bio. This would avoid the acid which itself will convert both Bio and Veg oil (inclding di and monos) to FFA. If you intend on carrying out a further stage after splitting the emulsion you may want to titrate and find out how much FFA is present and allow for that with extra KOH, or even perform a glyc wash before the further processing.
-
I dumped in & mixed about 10L of virgin KOH glyc & left overnight. Did a w/w after draining it & even though there was tons more soap than I would have expected it looks to be on the path of a normal batch now.
I use this oil from this source all the time & have never had this soap issue before. I still am unclear as to where it all came from.