Glycerol Pre-Treating in Bulk.

[Fluffle-Valve]

Is all this pretreating done at ambiant temps?

[dgs]

Is all this pretreating done at ambiant temps?

Yes it is. In the midsts of Winter it doesn't work quite as well but as long as the temp is 10degs or over it works fine (maybe not quite as well as heating it but not far off) Many energy saving advantages to this method though as no heat reqd and I now mix it only with the 1/2hp compressor instead of the TAM120 so only 25% of the electric is used.

[neisel]

24 hours ago I treated 150 litres of WVO with glyc at ambient temps for the 1st time.

The glyc has still not separated.

I imagine the cure is to heat it up, pump it around for a while & then wait for it to settle, which is what I'd normally do anyway.

Just wondering why I've got no split.

[dgs]

That is really strange. I have always had separation even at less than 10degs although the colder the temp the longer it takes.

I actually did a glyc wash a short time ago, 450 litres of oil and 80 litres of glyc. Compressor has been stopped 45mins after 1 hour of mixing. Already I can see the glycerol pooling at the bottom of the 600 litre IBC.

[dgs]

I know this sounds really stupid but for the last few glyc washes I have added some of my 50/50 glyc /water from the 5% prewash method. The resultant oil seems to be lighter in colour.

So today the mix was;

450 litres oil (already glyc washed in the 600 litre IBC)

Added 100 litres of oil

Added 70 litres of ex process glycerol.

Added 30 litres of wet glycerol.

Mix temp was 19degs. It was mixed for 1 hour.

All this added as it was being mixed by the compressor. I will take a sample tomorrow and test for conversion and water. I've tested glyc washed oil for water before when mixed with wet glycerol and it has always been <500ppm. However this mix had 15 litres of water in 85 litres of glycerol.

[dgs]

Tested the oil today:

Dropout using 10/90 was 7.5mls

Water 380ppm (even though it was washed with glycerol containing at least 17% water)

[Chug]

Good stuff Dave,

Its times like this I wish I had kept notes instead of putting it online and it getting lost in forum upgrades, anyway I think it was Frank the chemist "Neutral" on infopop who did tests on the amount of water glyc can absorb, I did some basic throw amounts of water into glyc and see tests and found it has an amazing ability to suck water up, so I'm not surprised that your water laden glyc still has little affect on its cleaning ability, especially mixed witha large amount of dry glyc.

Why not try a small test with just some water laden glyc and cruddy wvo, I bet it still does a good job

[dgs]

Thanks Chug, I'll do that.

[julianf]

One point about conversion that I have been intending to make-

Ive begun to think that ex process glycerol, even when well settled, contains locked up bio.

If I ever add ex process glycerol to a prewash, I only ever get about 50% back out again, even if I settle for days..

I've never done the sums as to the volume that stays in the reactor, and the conversion test of the feedstock, but I would be interested to know how they compare?

I have also thought that there should really be no catalyst left in the glycerol of a well calculated process, so, again I wonder about conversion?

This sounds like I'm disagreeing, but it's more of a comment - it's interesting stuff to get to the bottom of, and, as with all of this, there are so many variables that it's all just "sometimes" or "most of the time" etc anyhow!

[dgs]

Hi Julian, Yes I think you are correct on most points.

There is certainly tied up bio in glycerol, even if it doesn't show on the surface. I dried some glyc in a tea urn for several hours (this was an expt that didn't work) then added it to some oil. The oil went really dark. HC2 said the retained bio in the glyc had been burnt during the long drying process, I'm sure he is correct.

There is more catalyst in the glycerol than realised. Because we tend to skimp on the methanol the chemicals left in the glycerol are biased towards the catalyst. Under certain circumstances a fair degree of conversion can be achieved by enhancing the glycerol with methanol only.

A lot of the volume retention noticed when glyc pre-treating is due to 1; soap. (glyc contains around 40% and some of this will remain suspended in the oil. For those who have ever re-titrated after glyc pre-treating the soap retention will affect the titration so the oil may still actually titrate higher than it seems. and 2; the glycerol itself is partially retained in the oil, I have found this is very roughly 2 1/2 litres in a 200 litre batch after 24 hours.

Because of my larger volumes when glyc washing in the 600 litre IBC I never notice any increase in volume and as the treated oil is pumped into the processor any increase is never taken into consideration when measuring yield.

Just to add, the way I do it (using mostly other peoples ex process glyc) to achieve around a 20% conversion before processing, leaves me using a maximum of 12% methanol and equivalent to about 6.5 gms KOH/litre for full conversion.

Nowadays I would never attempt to convert any oil that had a positive titration. what would be the point in wasting my own chemicals when I can use the residual chemicals in other peoples glycerol to do the same thing.

[DavidShinn]

Hi Dave

All very interesting as always and you have me itching to have a go at treating in bulk. I have a 600litre ibc that I can use with a decent tap at the bottom. I gather from this thread that you favour bubbling air in at the bottom rather than circulating with a pump. I take it that even a large aquarium bubbler would be too small for the job but I wonder what sort of compressor would be suitable? I have a little Clarke piston compressor but that would be in pieces if I left it running for an hour and it’s so noisy. What type of compressor is yours please?

Kind regards to all

David (Leeds)

[K.H]

Ive used a compressor from a fridge before

[dgs]

I use a Broom Wade small compressor (like the one Tony had at the bbb 3 years ago) he rekoned the output was 2 to 3 cu ft/min which equates to between 57 and 86 litres/min. It seems to be as efficient as the tam120 at mixing glyc and oil. As the IBC is outside any methanol fumes arn't an issue.

I started using it as it is only 0.5HP so uses 1/4 of the electric consumed by the 120

I've never tried a fridge compressor but obviously worked for KH

My IBC faces South and with the good Weather we have been having the last mix was done at nearly 30degs.

I think an aquarium pump would be too weak, the compressor really churns it up.