Is my Bio getting Burnt.

[dgs]

After glyc washing my oil up to several times in my 600 litre IBC and resulting in oil that virtually has the colour of new oil I've noticed my finished bio has a darker colour than the starting colour of the oil. This is before I 'bleach' it in the sun.

I've probably mentioned this before, but a little experiment a few years ago where I dried glycerol for about 4 hours in my tea urn prior to pre washing with it resulted in the oil colour increasing considerably. HC2 (VOD) came to the conclusion that the small amount of bio left in the glycerol had been burnt by the constant heating, this burnt bio was left in the oil after the pre wash resulting in much darker oil.

I think that when the wet bio is in my wash tank after washing, being heated up to 60degs to dry it, the immersion element is slightly burning the bio, especially with the drying head in place and being bubbled.

Dawson (DB off VOD) came to see me this last week and after a 5% prewash he then dries his bio at 105degs! he has been using the venturi to dry. What he has assumed as water vapour exiting the vent was probably bio vapour resulting in him leaving the immersion on for several hours. He has also noticed very dark bio.

I have just ordered a 1KW immersion for the wash tank and I intend to dry for longer at a lower temperature.

Is it really possible that the heat of a 3KW immersion can burn the bio if left for long enough.

Any thoughts would be appreciated, Cheers.

[Jamesrl]

You don't need to mess about changing immersions, just half the voltage.

A 110v transformer will run a 240v 3kw immersion at 750w output.

[dgs]

You don't need to mess about changing immersions, just half the voltage.

A 110v transformer will run a 240v 3kw immersion at 750w output.

Good to know Jim but I've ordered the 1KW immersion now.

I don't think the burning will take place so much if the bio is being circulated, but when it is static I'm sure it takes place. I wonder what the surface temperature of the element is?

[Tony]

It is a thought, since the elements are really designed to heat water.

I'm wondering if your 1kW element will have a lower surface area because it's only 1kW.  IE the energy delivered per unit of surface area may be the same.

Running a 3kW one off a site transformer would at least have the element surface area of a 3kW element but at lower output power.

The other alternative is to put two 3kW elements in series, then you'll get 1.5kW split as 750W per element.

Of course there are all manner of series and parallel connections you could make, 4x 3kW elements with 2x 2 in series is back up to 3kW of heat delivery but with 4x the element surface area.

I'm sure there is something that could be done with three phase elements too if you were feeling creative.

[photoman290]

i have found that the donut cooker will burn the oil if i have it above 200C probably not at all relevant to the present conversation. have you processed the oil you got from me yet dave? that will be well heated as it has been at 200C for around 9 hours. that oil is soya with no additives.  different oils will have different smoke points plus you wont know how long it has been used for. i did get some tests done on my oil but nothing conclusive about burnt sugar came up. the only to tell is to try some new oil and see if that shows anything.

[dgs]

Thanks for the info Tony, if I find the !KW doesn't work well the other alternatives are an option.

Bob, I'm doing a process with 50/50 your oil and what was in the IBC. The mix is very light coloured. I will report when the batch is finished as to the end colour.

The 11" 1KW immersion that I have ordered is just 1 loop, so about 2/3 of the length of a normal 3KW one which has 1 1/2 loops. Hopefully this means that the surface temperature of the element is considerably less than normal.

[photoman290]

you can get oval profile elements that are supposed to help in not burning the oil. don't suppose it would make a lot of difference at bio temperatures plus they are designed for fryers not immersion elements.

[dgs]

In the absence of the new immersion (assumed still in transit) I made up an adapter lead and used one of the immersions powered from the 110 transformer. It took 2 hours to heat up by 10degs from 27 to 37 which is not so much of a problem if I hadn't started this 2 hours ago.

I will see what it is at just before I go to bed at 12, then switch it off. The silica drying head is in place so with a bit of luck the water content will not be too high. I'll check it tomorrow and see if i need to re-heat, hopefully not.

If I find the heat up isn't quick enough maybe Tonys suggestion of the 2 immersions in series would be the best option.

[dgs]

Last night I 'cheated' a little and plugged in the immersion on 3KW for the last 7 degs just to get the temp  up to 50degs. I set the timer for the drying head to stop bubbling at 2am.

I centrifuged 60 litres this morning (before magnesol treating the 140 litres left in the tank) and the colour is noticeably lighter than the previous batch from the same oil. It really does seem that a 3kw heater left switched on in static bio (not pumped or bubbled) does cause some burning of the bio, increasing the colour.

I've just completed a water test on this batch as it was dried at only 50degs, it was 485ppm. I will now start a water test on the magnesol treated portion just to see if it really does lower the water content as the Dallas Corporation claim.

[dgs]

Isn't it just great when tests work out the way you want them to!

I've just completed the water test on the magnesol treated bio and it has reduced to 315ppm.

Just to recap, 500gms (1 litre) of magnesol, mixed by compressor at 28degs in 140 litres of biodiesel for 30 mins reduced the water from 485ppm to 315ppm.

[Bio-boy]

I would have thought convection currents would prevent this until temperatures had become consistent within your processor and those convection currents would have slowed. At that point I would have thought pump activation would again mitigate any burning.

I don't dewater my oil and so never just have my immersion heater on without my pump. I now react my oil from cold with the heat element on and heat to 55 deg whilst circulating my batch. I then settle without the heat on and then complete stage 2 in the same manner. The only time the bio is not circulated is when washing and then the action of the water I would have thought would prevent any burning.

[dgs]

I'm confused here Bio Boy, in a previous thread you stated that you reacted at ambient, yet above you say you heat the oil after methoxide addition to 55degs.

I didn't take photo's of the bio using the immersion on 750 watts but the bio was lighter in colour.

My present batches start at 20degs, after methoxide addition and mixing for about 1 hour the temperature reaches 35degs or so.

[Tony]

i have found that the donut cooker will burn the oil if i have it above 200C

Probably no coincidence then that domestic fryers seem to top out at 190C.

[kamaangir]

I can tell you from previous experience that an immersion heats up to beyond the flashpoint of oil, the thermocouple is not sensitive enough to react quick enough. What prevents it from igniting the oil is the large mass of oil that it had to take beyond flashpoint for ignition and thermal losses to atmosphere.

I used to dry my oil in a metal drum with an immersion and if the oil level was low enough it would reach smoke point/pyrolysis in about 10 minutes, I would then dump lumps of solids into it to melt them. I have come close to the oil being almost the colour of used engine oil and smoking profusely.

 

[Bio-boy]

I'm confused here Bio Boy, in a previous thread you stated that you reacted at ambient, yet above you say you heat the oil after methoxide addition to 55degs.

Dave, I react my Bio depending on what side of the bed I get out of. lol