Biopowered - vegetable oil and biodiesel forum
Biodiesel => Chemistry and process => Topic started by: willbuild on August 22, 2015, 07:15:45 PM
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After the 5% wash I drain off glycerol then do an acid wash using 1ml of vinegar per gram of Kohl used to process with water at 10% of fuel being washed.
I then do 3 or 4 10% water washes.
Was tempted the other day to add the acid to the first 5% wash but thought about the recent posts about learning by your mistakes. ???
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Pretty much what I do, except my acid wash is usually 0.12 * weight of NaOH used to give the ml vol of conc. sulfuric acid, but added to 5% water.
There's no point in adding acid to the prewash I think it would just be neutralised by what's left in the glycerin. To that end, to make the acid wash have the most effect, it's best to have several hits at draining every last drop of glycerin. I usually drain the bulk in the evening and drain the remnants the following morning.
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You could do a titrated acid wash (I'm sure the info is on the wiki), this way you only add the required amount of acid for each batch, it takes all the guess work out of it.
That said I don't routinely acid wash anymore as I rarely need to, if the first wash does form an emulsion it's easily split with acid anyway, and you get to know how the reaction has gone and if it's likely to give washing problems.
I add 30ml of acetone to my wash water as this reduces the amount of washes needed, I normally only need to do two pump washes.
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You have mentioned the acetone addition before and I intend to give it a go when I get some. The only thing I worry about is that is the acetone 'holding on' to something in the bio that should really be washed out.
I never acid wash as I don't want the formation of any FFA's.
I can imagine doing an acid wash when the 5% water/glycerol is present will produce lots of them.