I didn't have luck with the search feature, so sorry- no links

Basically, the old concept, that I've tried and definitely works, is doing a 10% glycerin "wash" on your feedstock to reduce FFA and settle out the heavier fats. It works well, but then you've got that crude glycerin/FFAs/heavy fats stew to deal with.

I've been trying to think of a way to adapt this to commercial scale, because I've seen how well it works on smaller scale. The stuff that settles is gross, thick, and sticky, but I wonder if you could acid esterify it, glycerin and all? You would essentially be acidulating the glycerin at the same time, right? Hm.

Anybody already tried (or want to try) this?

I tried the glycerin prewash. Not sure I did it right, as when I tested the finished biodiesel, it clouded & gelled at the same temp as the previous batch(no glycerin prewash) made from the same oil stock.

The stuff I did drain off, had a bunch of the white congealment. I was wondering what to do with it. I'm willing to give it a go, but all I have for acid is drain cleaner sulphuric(Though I did a titration, and assuming my work wasn't too sloppy and my chemistry&math correct, it's 18M), and maybe some battery acid(again sulphuric)- don't know its concentration.

You make any progress with the glycerin cracking/separating?

I think this is the thread which discussed this process ...

http://biodiesel.infopop.cc/eve/forums/a/tpc/f/419605551/m/9441081511/p/1


Regards,

Thanks Graham.

quote:

You make any progress with the glycerin cracking/separating?

Not anything beyond what I've reported so far.

Kumar ,
I do find this idea an interesting one , but at the moment have no time to try it out . Most of the homebrew ideas for reducing FFA's do not work well in my opinion because they are sacrificing too much valuable feedstock and thus increasing the end cost of the fuel produced if the feedstock does come at a price . If I could find a better way than the typical acid / base /base meathod I would be really interested , but I am not willing to give up a huge amout of yeild to get a easier process . I suspect your thinking is likely the same . If I get caught up with the ADA stuff any time soon I will try to devote some time to this idea , it does sound promising .

I have used this method with really nasty oil - it seems the worse it is, the better this works. I had some pretty rank leftovers ( after settling out and removing the good stuff) in a 45 gallon drum, and threw in 10% by volume crude glycerin (not with methanol removed), gave it a quick stir, and left it overnight.

The next morning i had lovely clear oil on top, and after a couple of days, i carefully siphoned off the top two thirds - ensuring not to disturb the crud in the bottom.

From what i remember from the other discussion link, it does not do too much to lower the FFA. However, if you have high cloud point fats or tallow, they seem to settle out to the bottom, leaving whats left on top with lower cloud point properties.

I was amazed when i first did this at just the difference in the look of the oil. However, it seems that if you start with half decent oil (without fats and tallows), you wont notice any difference with the cloud point using this method.

Regarding 'huge' losses of yield. If all you do is remove the FFA then you will not lose what I would call a huge amount of feedstock; I personally would not remove tallows as they have more energy content than an equivelant amount of veg oil.

Furthermore the FFA you remove will not make soap in the transestrification reaction. Hence they will not remove three times thier own amount of biodiesel into the byproduct. Hence a net saving in yield of three times what you have removed and what you have removed would be lost anyway as soap.

Of course if you want to estrify to save that small volume of feedstock represented by the FFA that is up to you.

To me the only justification for estrification is with exceptionally high FFA content or to make oil usable for transestrification without inordinate soap production.

Estrification or even Acid catalysed methanolisis transestrification and estrification combined al la the CSP 6 hour process, is still the best method I am aware of for very high FFA content oil but caustic stripping as Rick de tech calls it seems the best for removing relatively small amounts of FFA that would otherwise form soap and trap bio.
Estrification is much more work than caustic stripping and does not seem justified unless the FFA is very high.

I guess it depends on what you consider high FFA content . I have about 1000 gallons of oil that titrates at 42 right now . That to me would indicate a huge loss of feedstock if I simply remaove the FFA's instead of using the acid meathod .

I think you would lose about 5% which is not all that huge but maybe worth the trouble of estrifying to save the 50 US gallons involved. Not sure I would bother for 170 something litres myself.

You could try the CSP six hour jobby if you can decipher the method with the help of the rest or the thread and the links.

The biggest benefit of this method is that it not only uses the "catalyst" portion of the caustic to neutralise some FFA, and binds the High Melting Point oils, it also removes water from the oil.
The glycerol absorbs water! This means that if you have a small amount of free water, or any dissolved water, the glycerol can absorb some or all of the water from the oil.

If you have any significant amount of free water, you will produce a proportionately large amount of soap during this process.

Tony

I have been useing the oil prewash with glycerol for several months now with great results.If I put in 4 cubbies of glycerol I get back 4 cubbies plus about 1 lt.In about 40 gals oil that usually titrates 26-28 koh.This gives me a drop to around 10 titration.Less byproduct when processing.No major loss of oil.