A bit of interesting biodiesel conversion chatter.

[dgs]

David Smith
Believe it or not there used to be a bio conversion method where the NaOH was dissolved in water before adding the methanol. There was a discussion about it when it was posted on the Aussie forum years ago. Bearing in mind that KOH has 10% water, if the water % is no more than 10% w/w of the NaOH why wouldn't it work.
Reply6 h
Paul Gobert
David Smith I am the person who originated that method. It has to be a saturated solution of NaOH. ( 111g Naoh dissolved in 100ml of water giving 120ml of concentrated solution) Multiply grams of NaOH required for batch by 1.2 to give the volume of conc solution required. GC tests on three batches using a) Metalic Sodium dissolved in Methanol b) Solid NaOH disso;ved in methanol c) Conc aqueous NaOH added to methanol all gave similar results. The advantage is that the conc solution can be stored ( in airtight containers ) and mixes instantly with the methanol.
Reply3 h
David Smith
Paul Gobert WOW, Paul, thanks for that. Nice to know that I can recall things reasonably accurately! Are you also the person that mentioned the "polymerisation at the interface" that Neutral had noticed. I must admit I thought it was a load of rubbish until you mentioned Neutrals name, then I took it more seriously. Just going back to the above, is example (a) ASM that you are referring to. Cheers, Dave.

[countrypaul]

I can understand the reason for using that approach, but without the rest of the process (it might be elsewhere on their thread) it is unclear to me how different it is. I could, perhaps, see that if the process is relatively quick - ie carried out at an elevated temperature that the catalysis of soap formation might be quite low, but if carried out at ambient (especialy in this country) I could easily see significant soap production. If the oil was dry and free from FFA then using ASM would result in no soap formation, as soon as NaOH and water is present some soap will be formed.

[dgs]

Hi Paul, what do you think about the comment that came from Neutral, where he says to get the glycerol out of the processor quickly otherwise there could be polymerisation.

[countrypaul]

Hi Dave,

I was not sure what interface the comment in the section you posted was refering to, nor is there anything about removing the glycerol quickly - do I assume you have read more of the thread than the section you posted.

I know some on the VegOil forum have posted about doing a whole batch demeth without removing the glycerol at all - that appears to conflict with the idea  of having to remove the glycerol quickly. It appears even with surplus glycerol and catalyst present the reverse reaction is either very slow or non-existant.

I know polymerisation is very dependant on the oil used (any idea what they were using?), for example linseed oil will polymerise easily where as coconut oil is much less interested. Linseed has a lot of highly unsaturated fatty acids where as coconut has predominately saturated fatty acids.

Do you have a link to the original discussion?

[dgs]

No, sorry Paul. I've searched the Aussie Biofuels forum for the original thread but could never find it. It was only when Paul Gobert posted about it on the facebook group and mentioned Neutrals name that got me interested. If Chug reads this he may remember something. The subject may have been discussed on Infopop and I know Chug used to be involved with discussions with Neutral on there.

As some on here will probably know I am not a great believer in methanol recovery or indeed the concept of the g/l  style processor.

If an average amount of soap is produced in the process it takes with it double this amount of biodiesel into the glycerol. This equates to between  4 and 5 litres of bio in a 20 litre cubie of glycerol.  So why put time effort and energy into recovering only methanol when glycerol pre-washing (at ambient) will recover most of both.

[countrypaul]

There was a thread on the vegoil forum about dissolving NaOH in water, but I can't locate it, I can find a link to wherre it used to be but it appears to have been broken when the forum software was updated, iirc Chug made a significant contribution to that thread.

I wasn't thinking about the recovered methanol in the WBD method, more around the fact polymerisation was never mentioned - may never have been considered or seen. Different people may view quick removal of glycerol in differing ways though. If once processing has finished and a 100L batch is left for an hour to sttle out most glycerol is that considered quick? How about overnight? Does choice of catalyst influence the process? How was the polymerisation detected - could it be due to some other material present? More questions than answers I'm afraid 

I agree with the glycerol prewash, it removes FFA, water, soap (from the FFA) and lots of BCBs, as well as releasing bio and methanol into the Oil, and can also contribute to some conversion. Oil cleaned up by glycerol prewash usually needs much less reagents to process and creates glycerol that has less soap etc. (especially if using ASM!) so cleans up the next batch better.

[Chug]

You remember correctly Paul, I started threads on Infopop and on VOD, I was a man possessed doing lots of experiments and trying lots of different things to try and find a simple way to process oil into bio, the aqueous method worked ok and it was my method for a few batches but I can't really remember anything significantly good or bad about it, other than I moved on to different methods so it couldn't have been that good.

The WBD came about after another of my experiments to see if the theory was correct about reversing the reaction, but I've done many WBD's and never managed it. But as said a glyc wash is a simpler way to reclaim the meth and you get an easy conversion after too.