Glyc pretreatment, all is forgiven!

[Tony]

Hated it when I pre-treated oil with NaOH glyc, but now I'm on KOH I thought I'd give it a whirl.

Normally I heat the oil to 105C to dewater, but this time just I added back the glyc from the last batch, heated to 60C, mixed and settled.

Sure enough the glyc I put in was more than the glyc I got out, and the reaction I did after that completed to clear pass with a single stage.

Might be doing that again then

[Twenty4Seven]

Why didn't you get on with NaOH glyc Tony? Is it the viscosity?

I found it was very thick and took ages to draw in. Adding hot oil didn't help because it separates out so quickly - so now I just add a litre of watery methanol I happen to have laying around - which does thin it down enough to go in easily.

Nick

[Tony]

I'm trying to remember, I think it was both the viscosity, and that it set in the pipes quickly when settling.

[dgs]

It's hard to believe a man like you hasn't done any potassium glyc washing before Tony!

[Tony]

I've been a sodium man exclusively for years.  But I'm just about coming around to the idea that potassium, despite being more expensive, is considerably easier to work with.  I like being able to leave a batch too!

Batch before last, I dewatered the oil the night before, it had fallen to reaction temp by the morning, so in went the stage 1 potassium methoxide via venturi, and I just turned everything off left it standing static while I went to work.

I got back and it had mostly completed the reaction without any mixing.

Ran the pump for an hour and got back up to temp, and no further reaction took place - first stage had gone as far as it was going to go just by sitting there, fantastic!

Couldn't do that with sodium hydroxide, would spend hours unblocking the pipes...

[Manfred]

Does that mean you are going back to overdosing single stage to completion ?

[Keef]

If I remember correctly, you used to WBD? Now no need to?

[Bio-boy]

If I remember correctly, you used to WBD? Now no need to?

?

[neisel]

http://www.biopowered.co.uk/wiki/Acronyms

[Bio-boy]

http://www.biopowered.co.uk/wiki/Acronyms

 

[Tony]

If I remember correctly, you used to WBD? Now no need to?

Stopped doing WBD a fair while ago in favour of http://www.biopowered.co.uk/wiki/Two_stage_methanol_starvation_process

But now I'm on KOH I'm definitely going to give glyc pre-treatment a good run to see how that pans out too.  I guess it works so long as the oil isn't ridiculously wet to start with (some of mine does come in sometimes with free rainwater!)

[dgs]

Tony, as long as it doesn't have free water present (in which case you need to get rid of it) adding the normal amount of glycerol back in (that the process makes) will result in oil that is <500ppm water.

To make sure the glycerol absorbs as much water as it can you need to mix at
 60degs for 1 hour.

[Tony]

That's good to know. I've done several batches this way now and getting a clear pass is very easy.  Plus I'm not heating the oil to 105c to get water out with the condenser.

[dgs]

Thats correct. The 105 degree thing is ok if you are running veg but for bio it's a waste of time, the glyc wash will simply remove the water.

[Head Womble]

Thats correct. The 105 degree thing is ok if you are running veg but for bio it's a waste of time, the glyc wash will simply remove the water.

This is mainly true, however there is a limit to the amount of water the gly can remove.

I suffered with processing wights some time ago, due to the capacity wights have to hold on to water the gly wash just could not remove enough of it.