I recently needed some bio in a hurry so I mixed some up, removed glyc, then heated a small amount (8 litres, just enough to get me back and forth to work a couple of times) to 120 degrees... I assumed this would evaporate any methanol or water and should remove soap - I let the bio cool then did a shake 'em up test - no soap. Strangely enough however, there was no residue in the bottom of the pot I cooked the bd in, yet the bd appeared to be soap free? I got good conversion as this batch passed 27/3. I'm using NaOH.

I put it in the car and it ran ok, no obvious residue in filters etc.

So I'm intruigued as to where did the soap go? Is this a valid method to wash/dry biodiesel? Wouldn't want to do this on a regular basis but would be handy to know that it works.

Any comments appreciated.

Cheers,
Ben

Ben
It looks like your titration was spot-on, the oil was loww FFA and the small amount of soap produced in neutralising the FFAs went out with the byproduct.

Just because some people have issues with soap in the biodiesel and the evidence of that showing up when the methanol is removed (skin on top of the biodiesel), this oes not necessarily occur in all cases. Low FFA oil produces small amounts of soap, high FFA oil produces much more than in proportion to the titration ,due to the saponification of the FFA having water as a byproduct, which can cause some oil to form soap instead of biodiesel.

What was your titration?

Regards,
Tony

Hi Tony, thanks for that - I just assumed that I would always have some soap but your post makes sense. All the other batches I have made have produced some soap, I do the 5% prewash and then generally 2 washes cleans it up nicely. It is pretty good canola oil, certainly makes tasty fish and chips. Titration was 0.8 or 0.9 from memory so maybe I fluked it exactly this time. I don't think my titration skills are that good, I get different results from the same oil from multiple titrations, usually within 0.2 or so of each other, but I also got it quite wrong recently when I made an emulsion.

Cheers,
Ben