Recovered a lot of fuel from glycerol

[Tony]

So I did a batch with a lot of recovered Methanol, and well, I'd left the top off one of the drums so it must have absorbed water from the wet winter air.

That batch of 125l dropped 40l of glycerol.  I wasn't impressed as the resulting yield was terrible.

The next batch, however, I glyc pre-treated with this 40l - mixed at 60C for an hour.  The glycerol then drained came to 25l, so 15l of it had "returned" as oil/bio.

The rest of that batch went as normally expected with no issues and is settling now.

I've heard of this effect before but not seen it so dramatically demonstrated.  Nore do I quite understand the chemistry behind it...

[dgs]

Hi Tony, There could be a few things going on here.

Your batch that produced the excess glycerol because of the watery methanol couldnt have produced any more glycerine than the glycerine molecules contained in the original oil. Most of the excess volume will be due to soap and an amount of this soap will have been absorbed into the oil during your pre-wash.

Don't take this as being dead accurate but I think the volume of actual glycerine in a 125 litre batch is something like 10 litres. I realise there is also methanol, water and bio in the glycerol, but the amount of soap will be very high (probably over 50%) and as said some of this will have been absorbed by the oil.

When I did the anhydrous methoxide test on dry, neutral oil I produced only 16 litres of glycerol from a 190 litre batch.

Also there will still be some glycerol retention in the oil, it can take weeks for it all to drop out.

I have recently done some soap tests on glyc washed oil that showed no conversion and the soap content is suprisingly high.

[dgs]

Just to divert onto a related subject here.

I have recently noticed after I have done a glycerol pre-wash on oil to use for the c/heating with glycerol that has been used already to pre-wash oil for road fuel, there is a considerable retention of oil in the glycerol.

When I say considerable, after settling for 3 or 4 days, then running off the glycerol into cubies and leaving another week, up to 5 litres of oil has formed on top of the glycerol. To avoid this I have set up a 400 litre cone bottom poly tank in my polytunnel. I poured about 230 litres of glycerol into it about 1 week ago and now the top 40 litres is oil.

This effect seems to be more since I started to use my ASM/KOH mix as the catalyst.

[Chug]

I found with using reclaimed meth that once you start getting below 95% purity you make too much soap which is what I think you have found Tony, once it gets below 90% purity is not worth using in my experience.


I only glycwash if the oil is really whites n crap, most of the time I cant be bothered and just sacrifice a little extra catalyst and accept a little more soap

[Head Womble]

Hi Tony, There could be a few things going on here.

Your batch that produced the excess glycerol because of the watery methanol couldnt have produced any more glycerine than the glycerine molecules contained in the original oil. Most of the excess volume will be due to soap and an amount of this soap will have been absorbed into the oil during your pre-wash.

Don't take this as being dead accurate but I think the volume of actual glycerine in a 125 litre batch is something like 10 litres. I realise there is also methanol, water and bio in the glycerol, but the amount of soap will be very high (probably over 50%) and as said some of this will have been absorbed by the oil.

When I did the anhydrous methoxide test on dry, neutral oil I produced only 16 litres of glycerol from a 190 litre batch.

Also there will still be some glycerol retention in the oil, it can take weeks for it all to drop out.

I have recently done some soap tests on glyc washed oil that showed no conversion and the soap content is suprisingly high.

If I understand this correctly, it will explain why from time to time (generally after processing wet oil) I find it better to start afresh, as in discard the gly from the last batch and do without the prewash, thus removing the stage of introducing excess soap at the start of the process.

[dgs]

This 'accumulative' effect of re mixing oil with soapy glycerol I'm sure can be a big disadvantage, although Tony said his batch processed normally. It probably depends on how long the oil is left to settle before processing.

I removed about 10 litres of glycerol yesterday from my tank that feeds the processor. The oil in this tank has been left about 1 month after pre-washing and that is after settling in the actual pre-wash tank for several days.

That works out to a 3% glycerol retention even after it has settled for 3 days or so.