14.4% conversion

[Tony]

I found this one quite interesting...

I did a 125l batch at the weekend.  Made methoxide with 17l methanol + 1.1kg NaOH (more than required - excess catalyst - 8.8g/l).

I also had 2l recovered methanol to use from the last batch.

Stage 1

Put in all but 4l of the methoxide + 2l of recovered methanol.

Totals: 15l methanol or 12% by volume, and 840g of NaOH (6.7g/l)

Mixed and drained glyc.

Stage 2

Put in remaining 4l of the methoxide mix.

Mixed, got clear pass, and drained glyc (there wasn't much, just a few litres).

Finishing

Demethed remaining bio phase, recovered 1l before it was up at 95C (didn't take very long, not much meth present in the final mix).

Conclusions

Total methanol consumed by the reaction process was 14.4%, and much less energy spent recovering methanol than normal.

It does suggest that in stage 1 when the glycerol is drained there is very little methanol in it.  Perhaps because 12% is below the average stoichiometric ratio for oil and plenty of catalyst is present, almost all methanol is consumed by the reaction?

Then stage 2 there is excess methanol, but because there isn't much glycerol dropped not much unconsumed methanol is lost with it, leaving most in the biodiesel phase for recovery.

I've not done WBD for the last few batches (not much point as very little methanol left in the glycerol), instead tinkering with the ratios for the two stages when excess catalyst is present.  This one has been the best so far in terms of using minimum methanol to get a clear pass.

[julianf]

I have also wondered if there isnt a safeguard, with regard to soaps, in the 2 stage process, when minimal methanol is used -

Ie. if there are soaps produced in S1, do they stay with the methylester / tryglyceride mix (in to which they are insoluable) or are they removed with the glycerol?

We all know that its the methanol that keeps the soaps in solution with the methylester, so is the prior concept of excess methanol at all times really such a good plan?


Ive been impressed with using 10% methanol (to triglyceride ratio) on both stages.  I use 5g / ltr on stage one, but maybe i should try 6g /ltr and see what becomes of it?

[julianf]

ps.

A few days ago, someone told my (by pm) that with the 10% they found that active demething was not even required - that bubbling for 24hrs seemed to do the trick alone.

[willbuild]

Did you put back first stage glyc and do a wash after the clear pass?

[Tony]

No I don't wash, settle only.  WATER

[Jamesrl]

14.4%! as much as that, I'd be a little peeved at that amount.

I regularly get a total consumption of 12.5 - 13%, must be your crappy ol'oil.

[Glycer-rides]

ps.

A few days ago, someone told my (by pm) that with the 10% they found that active demething was not even required - that bubbling for 24hrs seemed to do the trick alone.

I've done this twice now. Let me elaborate on my last brew:
 
160L of whites were given an insubstantial (just 20L) glyc wash.
S1 used 16L That's 10% meth and 4.5 g/l naoh = an unsurprising 60% conversion.
My meth comes in 20L containers, so S2 = 4L. That works out as 6.25% meth, which should not work. OK, it was a cloudy pass.

No demeth. The bio was bubbled off for 24 hrs as usual. The next evening, I redid the 10/90 - same result. I noticed the S2 glyc. was as solid as WBD glyc and way more fudge-coloured.
There you have it, 20 L meth for 160L batch size, 12.5%.

Someone else verify, please!

[Tony]

14.4%! as much as that, I'd be a little peeved at that amount.

I regularly get a total consumption of 12.5 - 13%, must be your crappy ol'oil.

It's some right slimy shite at the moment.

12.5-13% I might be about to achieve with WBD and nice oil, but the energy cost of recovering the last bits of meth I suspect would approach the cost of the meth itself (not to mention risking reverse reaction).

With WBD I would typically hit 16% so this is definitely an improvement on process for me.

[Tony]

ps.

A few days ago, someone told my (by pm) that with the 10% they found that active demething was not even required - that bubbling for 24hrs seemed to do the trick alone.

I've done this twice now. Let me elaborate on my last brew:
 
160L of whites were given an insubstantial (just 20L) glyc wash.
S1 used 16L That's 10% meth and 4.5 g/l naoh = an unsurprising 60% conversion.
My meth comes in 20L containers, so S2 = 4L. That works out as 6.25% meth, which should not work. OK, it was a cloudy pass.

No demeth. The bio was bubbled off for 24 hrs as usual. The next evening, I redid the 10/90 - same result. I noticed the S2 glyc. was as solid as WBD glyc and way more fudge-coloured.
There you have it, 20 L meth for 160L batch size, 12.5%.

Someone else verify, please!

Did you keep your cloudy pass to see if it got drop out?

[Jamesrl]

14.4%! as much as that, I'd be a little peeved at that amount.

I regularly get a total consumption of 12.5 - 13%, must be your crappy ol'oil.

It's some right slimy shite at the moment.

12.5-13% I might be about to achieve with WBD and nice oil, but the energy cost of recovering the last bits of meth I suspect would approach the cost of the meth itself (not to mention risking reverse reaction).

With WBD I would typically hit 16% so this is definitely an improvement on process for me.

I haven't WBD'd for years bio only for me.

I use a gross volume of 16 -17% and after demething between 3.5 & 4.5% in approx 80mins at 85c I end up with a nett 12.5%, mind you I am using ASM so no generated water in the methoxide.

[Tony]

I haven't WBD'd for years bio only for me.

I use a gross volume of 16 -17% and after demething between 3.5 & 4.5% in approx 80mins at 85c I end up with a nett 12.5%, mind you I am using ASM so no generated water in the methoxide.

I'm not sure water generated by the methoxide mix would account for the extra methanol consumption.  But I understand that different oil types have different stoichiometric ratios and that may account for it - rapeseed at 11.3% through to 16.3% for coconut oil.  I've no idea what I've currently got but it's quite nasty.  I think one place in particular I'm going to stop collecting from.

[Jamesrl]

I'm brewing 95% rape 5% palm, I'm guesstimating the palm content as I settle and syphon off the best liquid but it almost certainly holds palm, plus a small pickup at the interface..

[Glycer-rides]

ps.

A few days ago, someone told my (by pm) that with the 10% they found that active demething was not even required - that bubbling for 24hrs seemed to do the trick alone.

I've done this twice now. Let me elaborate on my last brew:
 
160L of whites were given an insubstantial (just 20L) glyc wash.
S1 used 16L That's 10% meth and 4.5 g/l naoh = an unsurprising 60% conversion.
My meth comes in 20L containers, so S2 = 4L. That works out as 6.25% meth, which should not work. OK, it was a cloudy pass.

No demeth. The bio was bubbled off for 24 hrs as usual. The next evening, I redid the 10/90 - same result. I noticed the S2 glyc. was as solid as WBD glyc and way more fudge-coloured.
There you have it, 20 L meth for 160L batch size, 12.5%.

Someone else verify, please!

Did you keep your cloudy pass to see if it got drop out?

Aye, I did. (It was actually my usual 'end of process' syringe 1/9).
I was fully expecting to see drop out, proportional to the S2 under-dose of meth, appear the next day.

After 5 days nothing extra had dropped.

Something new I didn't mention. My plant now runs a 70 lpm pump with the 2 stage educator, so on a batch this size there's vigorous mixing going on.

Anyone else like to try a serious under-dose on their next S2? If it fails badly, all you need do is add more meth and mix

[Glycer-rides]

My latest project. I like to delegate, as appropriate 

[kamaangir]

How cute is that!