Glycerol prewash temperature.

[rumple]

I use KOH for processing and I use glycerol from my previous batch to treat my oil. The wiki on prewash suggests heating the mix to 65C. As I use a plastic conical I have been heating it to 50. The question I have is what temperature do others who do a prewash use? Can I get away with lower temps and use less electricity and still have the benefits of prewashing. I think DGS does an ambient prewash but my pump struggles with cold oil and more so with cold glycerol so it would probably need some heat. I'd prefer to prewash a few days before processing to allow as much KOH glycerol as possible to drop out. What do others do/think?

[countrypaul]

I use sodium catalyst, which can be solid especially in winter. I tend to start heating the oil and use the warm oil/glyc to dissolve the solid glycerol, leaving it to circulate until the oil is up to about 60C. I then leave it to settle for 30 mins (sometimes a little longer) before draining the glyc and processing (2 stage). I see no point in tryig to get all the glyc out, after all the first step in processing creates more. Again, for the second stage, I only tend to leave the glyc from the first for about 30 mins before draining. I usually process about 125L at a time in a GL processor.

On some occasions I have added warm glyc to the oil at ambient whist it is still in drums and left it, especially if the oil has free water or lots of BCBs. It usually makes it much easier to take the oil off with dragging all the unwanted stuff into the processor. I then still do a gylc prewash in the processor.

[rumple]

Thanks for the reply Countrypaul. I was just curious to know if a prewash at lower temps works as well as at higher temps. Then I'd try two stage no tit at a lower temp and see how it goes. It may be false economy of course, if I end up up with a load of mono's causing problems when  water washing. Maybe I should stick to my tried and tested higher energy method.

[Chug]

It will be fine at lower temps, and some folks do it without any heat as long as it can be mixed.

[Vijay]

always done mine at 50c

[Mr Tickle]

I always heat up my oil first (65) and then dry it for 3 hours.
Whilst the oil is warm I then do my Glyc pre-wash.
I thought everyone dried their oil first?

[countrypaul]

I always heat up my oil first (65) and then dry it for 3 hours.
Whilst the oil is warm I then do my Glyc pre-wash.
I thought everyone dried their oil first?

The glyc prewash is a way of drying the oil as glycerol absorbs the water. As said above is the oil is liquid and the glyc is liquid it does not have to be heated, although a higher temperature can make everything less viscous so pumping, mixing and settling can be quicker a can the processing that follows if the oil is still warm.

[Mr Tickle]

So are you saying that I have been wasting my time and money by drying first and I should just do the gylc wash only?

[dgs]

So are you saying that I have been wasting my time and money by drying first and I should just do the gylc wash only?

Indeed you have been wasting your time. From expts I have done in the past, glycerol will still 'dry' oil if it contains 10% water. Well settled oil that was 850 ppm water was 350ppm after glyc washing.

You can glyc wash at ambient temps but the glyc just takes longer to fall. Trick is to allow yourself plenty of time to process.

I glyc wash at ambient, I process at ambient, I do julians intermittant pumping method so the pump runs only 8 mins per stage.

if you bubble & settle you can finish the batch using no heat at all. I water wash but with fine tuning with a turbo dryer I have reduced the heat to 35degs. 5 hours drying and its at <200ppm water.

as our energy prices rocket its important to use as little elec as possible. I've now got a lot of the lads on the facebook group on ambient temps.

rumple, use a more powerful pump like a tam 120 its 1500watts but as said then you can use it for 4 x 2 min bursts per stage. Its a saving over a 105 for 1 hour.

[countrypaul]

It works for some of us, but try it for yourself. If the oil is very wet, it might needs two lots of glyc to get it ready. If the previous batch was high titrating there is likely to be more soap and water in the glyc and it may not work quite as well. Dave (DGS) has posted on this in the past along with figres for the actual water content.

OK Dave beat me to it..

[dgs]

Thanks for the reply Countrypaul. I was just curious to know if a prewash at lower temps works as well as at higher temps. Then I'd try two stage no tit at a lower temp and see how it goes. It may be false economy of course, if I end up up with a load of mono's causing problems when  water washing. Maybe I should stick to my tried and tested higher energy method.

rumple, use about 30gms of KOH extra per 100 litre batch after you have just achieved a clear 10/90 pass. This will convert your mono's even with ambient processing. There can be several % of mono's present even with a clear 10/90 that is just a pass.

[rumple]

Thanks for all the replies. I hoped there was scope for reducing the temperatures and my electricity bill. I always add extra catalyst to the second stage to hopefully reduce the monos. I tended to heat the second stage to 50F believing it was necessary to convert the monos but it's good to know doesn't need to go that high. I'm hoping for a bit warmer weather to raise the ambient temperature of the oil. Might be waiting a while.

[dgs]

I processed a batch on that very warm day, without heating the processing temperature was about 39degs.

[rumple]

So on 30th September I decided to take the plunge and do a low temperature glyc wash. I raised to oil temp from an ambient 11 deg C to 20 and added 40 litres of KOH glyc from previous batches so that the pump was quite happy and ran it for 30 minutes. Normally I do this at 50 deg and the glyc settles well after a couple of hours and the viscosity is noticeably increased when draining it off. Normally I'll take out roughly 30 litres after the wash. Two weeks after doing the low temp wash the glycerol layer is at the 50 litre mark and is reluctant to drop any further. Yesterday I warmed the mix up to 40 deg C. The immersion heater is roughly at the 25 litre mark so some of the heat went into the glycerol but I didn't try circulating the mix as my pump is only a 370W one so not really happy with cold glyc.  This morning it's dropped very very slightly. I'll probably leave it for another week or so then drain  off the 50 litres into cubies and let it settle. I'm lucky enough to have had my oil from the same place for the last six years and it's consistently good so I doubt it's anything to do with the oil. I've read that KOH glyc can be slow to settle but other than cold ambient temperatures recently I'm not sure what's happened.

[neisel]

That too has been my problem with ambient glyc washing. It takes forever to separate & never does it cleanly, with a clear line between oil & glyc (I've got a viewing window in my processor).

I went back to heating to between 45 -50 for the glyc wash & as you, it's all dropped after a couple of hours. With the exciting new leccy prices imminent I'll try it at 40 when I start making BD in the Spring.