2 stage bother : (

[julianf]

Feedstock -

Mix of real grim kebab fat (semi liquid) and some beef tallow (very hard)

Process -

Preheated in water heated pre-heat tank.  No pumping, so the water / bits of meat fall out nicely.
Into reactor.  Added 60 ltrs of virgin koh glyc.  Pumped for longer than normal / drained.  Remember being surprised at how clear the glyc looked, and thinking what a good job the new preheat drum was doing.  Oil after the glyc was quite dark, but nice and clear.

300 ltr batch.


Normally i try and maximise the first stage, but, this time, i thought id do a smaller first stag, and larger 2nd.  So -

40 ltrs of virgin meth
1600g of koh

(ie i was looking at reacting 200 ltrs of imaginary titration 1 oil - ie 20% of 200 / 200 x 8g)



At that point its all gone wrong.

I thought maybe my venturi had got blocked (again) so i took that apart, and its clear.
So i think its a flow issue.  Either something is wrong with the pump, or it cant handle the oil that now seems to look like whites, even though the temp is still 64c.


Some of this tallow needs to be real hot to flow, but the oil was clear before i added the methoxide, so im confused.  Ive got the batch climbing to 70c, to see what happens then.

I have more methoxide mixed, such as to make it a 1 stage / 300 ltr batch, but with the venturi not sucking, im going to have issues getting it in the reactor.

[Jamesrl]

Sounds to my like an ineffective dry regime, adding the lye may have created a form of emulsion/soap.

WHY do people rely so heavily on glyc pre-wash.

IF or when I do do a glyc wash I always dry my oil first to gain the greatest advantage from the phase. 

[julianf]

Preheated in water heated pre-heat tank.  No pumping, so the water / bits of meat fall out nicely.

[julianf]

Oil has cleared again now, so im sure it was just a temperature issue.

Your venturi, however, still is not sucking, and i have no idea why.

[Jamesrl]

If a venturi doesn't work it'll be down to the pump or pipework.

[1958steveflying]

Not sure if this is the problem but I have found a first stage of at least 75% conversion is needed in my instances to get any glyc to drop at all. if your first stage was only aiming at 60 odd percent then maybe this could be causing issues.

[Jamesrl]

Not sure if this is the problem but I have found a first stage of at least 75% conversion is needed in my instances to get any glyc to drop at all. if your first stage was only aiming at 60 odd percent then maybe this could be causing issues.

I have to agree with you there Steve, had a 70% first stage on my last batch and the glyc separation took quite a while, any less and I don't think it would have split.

I'm using the cruddy WVO I couldn't use in the colder weather.

[nigelb]

Sounds to my like an ineffective dry regime, adding the lye may have created a form of emulsion/soap.

WHY do people rely so heavily on glyc pre-wash.

IF or when I do do a glyc wash I always dry my oil first to gain the greatest advantage from the phase.

I rely totally on glyc washing to dry my oil....but I have the advantage of knowing my oil, as I suspect many homebrewers do. Having another drying method in the process, would to me, be a complete waste of time and effort. Others are different, I know, but there are many like me who just use glyc washing.

Every now and again though a spanner gets lodged in the works...just like Julian was experincing when he opened the thread.

[Head Womble]

My last batch was heated and settled, then condensed off at 95°, then gly washed,
and I still had damp oil, it looked good but gave only a fraction of the convertion I was expecting,
no gly dropped either, I had to add more gly (another 20L) to get anything to drop.
This was mostly the crud I've stockpiled over winter.

So sometimes no matter what you do you can't remove all the water.

In the end I had to do three stages but ended up with good bio.

[julianf]

Ive now got pretty much 100% conversion, but the glyc wont drop.

I do wonder if its the silly amount of meth that ive put in (30% in total - multiple stages) holding the glyc in suspension.

I now have about 400ltrs of this *stuff* - i think it may be time to give up, and can it (and then feed it into later batches if it still does not settle)

I have considered bringing in a sample to demeth on the cooker (to see if that makes the glyc drop) but, to be honest, i dont much like that idea.

[1958steveflying]

Ive now got pretty much 100% conversion, but the glyc wont drop.

I do wonder if its the silly amount of meth that ive put in (30% in total - multiple stages) holding the glyc in suspension.

I now have about 400ltrs of this *stuff* - i think it may be time to give up, and can it (and then feed it into later batches if it still does not settle)

I have considered bringing in a sample to demeth on the cooker (to see if that makes the glyc drop) but, to be honest, i dont much like that idea.

I once had a conversation with Graham laming and excess meth is a reason for glyc to stay in suspension, perhaps if you were to demeth the batch a bit then it may drop.

[Head Womble]

Ive now got pretty much 100% conversion, but the glyc wont drop.

I do wonder if its the silly amount of meth that ive put in (30% in total - multiple stages) holding the glyc in suspension.

I now have about 400ltrs of this *stuff* - i think it may be time to give up, and can it (and then feed it into later batches if it still does not settle)

I have considered bringing in a sample to demeth on the cooker (to see if that makes the glyc drop) but, to be honest, i dont much like that idea.

I once had a conversation with Graham laming and excess meth is a reason for glyc to stay in suspension, perhaps if you were to demeth the batch a bit then it may drop.

Or add some more gly, this should swing the balance in your favor.

[julianf]

Ive split the batch and left about 150 ltrs in the reactor, which i am now WBD'ing.

Ill take a sample in a while, and see if the glyc falls.  If it does, ill settle and drain, and then continue with normal demeth.

Thank you to everyone for the comments so far.  Will update as i progress.

[julianf]

I promised an update...

Bad to worse.

I split the batch and started WBD on half of it.  I came back to carnage.

My conclusion was that the batch thickened as demeth progressed, which lowered the flow, caused the inline heater to cavitate, and the 'pulsing' caused the pipework to 'blow' off the venturi inlet.


We have sackfulls of sawdust / bio mix now.

[nigelb]

What a mess!