A guy gave me a sample of really, really bad oil to see what I can do with the stuff. He says that his brother bought a whole bunch of this stuff to make biodiesel out of, but all it makes is glop. I titrates out at 90 ml of KOH. I compute this to mean that the oil is nearly 50% FFAs. I have sucessfully done this before with 25 titrating oil using 2ml/L of 95% sulphuric acid. But, with oil this bad, I doubt that 2ml/L of acid will be enough. Is there any set equations to compute how much sulphuric one needs per titration amount? I currently have a minibatch in process and I computed the acid requirment based off of 5% of total weight of FFA per sample, but I would like to cross check this calculation with someone that knows more about this than I do. Is there a simpler formula out there anywhere?

Bought???

Yea, he bought the stuff from a rhenderer, which is fooling in my opinion. I know the rhenderers separates the good stuff and gives it the lipstick outfits and leaves the bad stuff for everyone else to buy at the same price. I assume that he didn't titrate the oil before he bought, I know looks like crap and smells like it too.

Mgrant - what did you end up doing, if anything?

If nothing so far, then, yes, you'll want to kick the acid up a little bit but do so by adding it in two or more parts. The reason is not because the acid gets "used up" - it's a catalyst, here - but because H2SO4 is a strong dehydrator. Too much all at once will "burn" some of the oil and FFAs. On the other hand, the conversion of FFAs to FAMEs (eg, biodiesel) produces water as a byproduct, so more H2SO4 is needed to prevent it becoming so diluted it no longer mixes/reacts with the FFAs.

I'm curious to hear your results!