Drying bio with glycerin.

[Julian]

Has anyone tried this?

I've been glycerin washing recently with far more success than my first endeavours.  So, deranged as it is, my mind wandered to thinking about using glycerin to dry bio.

My thoughts were if glycerin has such an affinity for water it may only take a small quantity to dry quite a lot of bio.  It would surely be way cheaper to heat and dry a small quantity of glycerin than a large volume of bio.

[Bio-boy]

My only concern would be then removing the glycerin effectively post introduction. Have you carried out any trials? What were the results?

[Chug]

I thought of this when I was water washin but then I moved on to demeth n settle, so I would be interested in the outcome should any washers feel inclined try it.

[dgs]

It's not only the glycerine/glycerol removal that is the problem, it is the fact that the glycerine from the process contains roughly 35%+ soap.

Using 'cracked' glycerol also won't work unless it is dried, as it is very wet from the sulphuric acid treatment. It is also very acidic (around pH 2.5) so would need neutralising before drying.

Using pure glycerine would work. The trouble is it would only (probably) work once, then would have to be dried. I don't know the energy cost reqd to keep 20 litres of glycerine at 120degs for 1 hour.

Using it to de-soap however does work really well. It obviously depends on the original soap level in the bio and if it is de-methed, but I have found it works at least ten times at the 5% dosage level.

[Julian]

Little confused here, Dave ...

It's not only the glycerine/glycerol removal that is the problem, it is the fact that the glycerine from the process contains roughly 35%+ soap.

Are you saying that the soap will transfer form the glycerin to the bio, or that any glycerin left behind in the bio will contain circa 35% soap?  Surely that will settle out over time where as the water may not.

Also ...

Using it to de-soap however does work really well. It obviously depends on the original soap level in the bio and if it is de-methed, but I have found it works at least ten times at the 5% dosage level.

"it" being normal, untreated glycerin?


Soap issues aside, would you need a large volume of glycerin?  You would only be looking at a small volume of water could just a couple of litres dry say 100 ltrs of bio.

[dgs]

Sorry Julian, 'it' is either cracked or pure glycerine re the de-soaping method.

In a normal glycerol pre-treat method we add back the total amount of glycerol from the previous batch. From water tests I have done in the past this reduces the water in the oil from around the 850ppm level to about 350ppm.

Ex-process  bio contains about 600ppm water, so the amount of ex-process glycerol needed to dry it to a reasonable level would have to be a similar amount to the pre-treatment. I'm sure this would result in a situation where we would be back to settling again, so not really any advantage, plus there would be methanol contamination. This would mean that all the soap and glycerine would not settle out with time. ie
held in suspension because of the methanol.

Using either 'cracked' glycerol, suitably neutralised and dried or pure glycerine would be far more advantageous and may as you say require a much smaller amount.

[Julian]

I'm thinking in terms of economy rather than time.

If a small quantity of ex-process, ex-pre-treatment glycerin is heated to over 100°C for a reasonable period, surely that would eradicate most water and pretty much all methanol.

Soap surely wouldn't be too much of an issue with the methanol out of the picture and the glycerin should have a reasonable water capacity ... shouldn't it?

[dgs]

You could well be correct.

If you want to try it, I will do some before and after water tests for you. i don't have any new pure glycerine at the moment otherwise I could have sent you a couple of litres down.

When the pure glycerine is new it is really strange running it out of the bottom pipe as a colourless liquid, followed by normal coloured bio.

[Julian]

I will give it a go and take you up on your kind offer (need to find some cheap disposable containers ... posting jam jars gets a bit costly!).  What's the minimum size sample you need?

Oil I'm using at the moment is very low titration.  I'm down to around 4g/ltr NaOH and still getting a good conversion, so there should be very little soap.

I've also been banned from playing with bio in the kitchen, so will have to invest in a hot plate to dry the glycerin.

On another subject, did the sensor arrive safely?

[dgs]

Sorry I didn't say so julian, Yes it did- many thanks.

100mls per sample is fine, just in case I have to do a check.

[Julian]

OK, don't hold your breath, but I will do it.