Question about Prewash

[Michael David Junior Member Find all posts View Profile Close Michael David]

I have read in this forum about people doing a prewash, can someone please explain exactly how you do a prewash. (I hate asking dumb questions!)
Thanks & Regards Michael

[hdj80 Senior Member Find all posts View Profile Close hdj80]

Re: Question about Prewash

The idea is to add 5% water straight after you have completed your mixing/processing and before you drain off the Glycerol and mix the Bio/Glycerol and water for approx a further 15 minutes, settle as per normal and drain glycerol water mix.
It aids in removing the methanol from the bio and helps in the washing process, if you use NaOH the extra water will keep the Glycerol liquid.
I did not have good results the 3 times I tried this process but I am pretty much on my own on that one everyone that try's/does it seem to like the 5% Pre-Wash.

[Terry Syd Senior Member Find all posts View Profile Close Terry Syd]

Re: Question about Prewash

The most important thing to remember about the pre-wash is wait until the reaction is finished before adding the water. Once you add the water, the reacton stops.

You can use up to 15% water (in relation to the amount of oil used) and the glycerin will still drain without creating an emulsion. If you use too much water, you will end up with a complete mess. The 5% is the minimum you need to release the bound up biodiesel in the glycerin/soap. After 5% there is no more biodiesel released, however you can get a little bit better pre-wash of the biodiesel using more than 5%. You just have to figure out how to get rid of all that extra byproduct.

[dagwill Senior Member Find all posts View Profile Close dagwill]

Re: Question about Prewash

thanks all for info above.
i cream off golden oil on top to run on wco and when i have 200ltr of dreggs i turn that into bio. but ive slowly accumulated about 300ltr of glyc.
i hate to throw anthing out and scratched my head until reading above.
i wondered about burning it for some form of heating, trouble is its solid
now if i do a prewash in the future it sounds as though the waste glyc. will remain fluid.possibilities thanks