original post by julianf
Yes. But, of course, the glyc is hardly full of excess chem either.
I did try, a couple of batches back, adding some caustic to the glyc (dissolved in a tiny amount of meth) as it seems like a good idea... Im not sure it made much difference though, but then my oil is not all from the same place anyhow.
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The enhanced glycerol pre-wash can make a big difference, but we need to put it into perspective. The idea is to neutralise the FFA's 'in the prescence' of glycerol. This means the water produced from the neutralisation reaction plus any excess water in the oil will be absorbed into the glycerol. You will then in theory be able to complete the reaction in one further stage, using base amounts of chemicals.
Of course to do this pre-supposes you need to titrate. Also, depending on how much glycerol you use for the pre-treat, a 'normal' glycerol pre-treat is not going to neutralise oil that (say) titrates at 4.0
What I have found is that with my oil (titrating at 1.0 or thereabouts) just adding methanol to the glycerol will neutralise the FFA's and usually results in a 10/90 test of up to 20% conversion. The reason I only add methanol is that the residual chemicals left in the glycerol are biased in the favour of the catalyst. How do I know this? a Canadian guy on Infopop who used to advise a commercial producer ran some tests on enhancing glycerol with methanol and found it worked.
So, thats oil that titrates at 1.0 If your oil titrates at greater than that then to neutralise the FFA's the glycerol will also need some KOH. Probably 1.0 gm/litre for every 1.0 titration greater than 1.0
A while ago someone on here was processing oil that titrated at over 10.0 He was getting a yield of 68%. After he tried the enhanced glyc wash his yield went up to 88%.