Stuff boiling out of mankey oil.

[julianf]

I know bio diesel isnt in fashion at present, but... : )

I have a batch in at present, that is about 1/3 prep, 2/3 standard oil, and then the rest (i said "about" : ) mankey slops that have got cold over winter, been rained on (in buckets) etc. etc.

So, most of the batch is ok, but then theres some right stuff in there too - its only actually in there as i wanted to throw out the containers, and there was probably too much in them to go in the bin.


Anyhow, i had this happen some years back - something in the oil is boiling in the inline when the batch is up to about 70c.  I need to swap my pumps over again, as the multistage is getting blocked, so the flow rate through the heater isnt huge, but its certainly behaving oddly.

The fumes off the batch (when i was running oil over the solids to melt them) stung my eyes some.


Its at 70c now, and im leaving it overnight to settle.  Ill change the pump tomorrow, and load up some glyc.


The last time this happened, i did two glyc washes, and the oil ended up light and clear, and all the eye stinging stopped (the batch before was much worse though).


Anyhow, troubled as it will be, its unusual - anyone else encountered this, and got any idea what may be causing the boiling?  Ive heated and settled plenty of wet batches before, but this boiling / eye stinging thing is different.

[greasemonkey]

What boils at 70c? Some kind of alcohol?
Some kind of cleaning agent, maybe used when servicing the fryers?
Maybe not the alcohol it self causing the stinging eyes, but it could be carrying a cleaning agent out with it.
Other than that, some exotic spice used in the cooking? Some of these chillies and that will rip your head off.
Actually, are some chillies stored in alcohol?
That would do it. The food place would probably have to keep a separate cooker for them, because they are so strong. Any oil coming from the fryer would be some pretty wild stuff.
Just guessing really.

[julianf]

Im not sure -

The rotten stuff was dreggs from cans id processed before. Id tipped out the liquid, and left the gloop, and kind of forgotten about it.

So i would have thought that if it was somthing from source, it would have been in the rest of the stuff - and, whilst i dont remember processing it, the fact that i dont remember it probably means it was fairly uneventful.

I reckon its some sort of product of decay that you get with wet oil.  But then ive processed wet oil thats been left before too.

And there wasnt even much in this batch - im guessing less than 10% of batch volume.


Im tempted to settle out what water there is in there, and then fill it up with fresh water from the tap, and turn it over for a while.   Ive not heard of people water washing raw oil, but you would think that it would take out any water soluble acids etc?

Im not planning on adding caustic till its dry.

[julianf]

Settled overnight.

Took out about 6% of the batch volume as black water.   Added about 8% of the batch volume back in in glycerol.  Heating back up now.  Id add more glycerol, but, unusually, i have none suitable.

Three observations -

The interface between the water and oil was sharp.  Draining the water, and then the switch to oil coming from the drain was sudden.
After settling, the oil was clear at 35c.  Fairly dark, but nothing unusual.  No milkyness though.
When melting in the glycerol at 40c, the oil still made my eyes sting.


Predictions -

Gycerol will make a slight improvement, and then ill have a troubled S1.

[kamaangir]

I have had similar and i would hazard a guess that its bacteria in the watery crap. When dewatering batches like that I would easily lose a 3rd to evaporation, thats with no visible water droping out.

Glyc washing and if you have the time do a 3 stage underdosing the 1st stage, droping the glyc on it which should get rid of lots of crap.

If it is the above you have to be vigilant with your finished fuel. I used to use mine on a long run. Its not as cold so you may be ok.

[julianf]

Disappointing, but not terrible S1 -

10% of batch in meth, and 5g ltr gave only 30% converted, and a fraction less glyc out than meth in.

S2 processing now - 10% and 5g ltr for the unconverted.

I predict a whole load of glycerol out, and a tiny amount still unconverted.  Will see in an hour.

[julianf]

S2 gave over 20% of the batch volume in glycerol, and left 15% still unconverted.

I finished up with a S3 to give a clear pass.


The 10% / 5g combination is supposed to be meth limiting, and it usually is, however, in this case, i suspect it was catalyst limited.  The unusual amount of crude glycerol was, i suspect, by volume, meth rich.

It was an expensive batch (i dont care how much caustic i use, but methanol is 50p / ltr or there abouts) but its converted now.


Another glyc wash may have saved me some of this bother, or, possibly, a 'seeded' glyc wash, as per DGS's posts on the other channel.  Or just titrating - which i should get back into the habit of doing on suspect batches.

[Tony]

What is a seeded glyc wash?

[julianf]

I have not tried it, but -

You mix an amount of caustic with a small amount of meth, and add it to the glycerol pre-wash.

The idea being that the additional caustic does the neutralisation reaction, without all the other bits of the process going on.

There's a thread by DGS about it on the other channel, and more talk on infopop about it too.

Seems like a good idea to me.

[Tony]

I guess that will work so long as there's little or no water present in the source oil?  Otherwise risk of soap/gelling surely.

[julianf]

Some people, it seems, have been using water to dissolve the caustic - so it cant be that critical.

[julianf]

By its very nature, there will be some water, as the acid + base reaction creates water.

I think the idea is that you do the neutralisation reaction at the start (as has always been the partial intention of the glyc wash anyway) and strip out both the FFAs and the resultant water (from the neutralisation) leaving you a clearer slate to start with.

[Chug]

I tried the Aqueous methoxide method a few years back, seemed alright at first but after more tests my general conclusion then was, as we all now know, is that adding water inevitably makes more soap.
However things are different when there's glyc in the equation too.

http://www.vegetableoildiesel.co.uk/mybbforum/showthread.php?tid=9317&highlight=aqueous

[therecklessengineer]

Some people, it seems, have been using water to dissolve the caustic - so it cant be that critical.

Back when I was first starting homebrewing, I used this method. Must have been 2004 ish. Pre- 3/27 or soap tests so can't comment on the quality - but it ran the car fine.

[julianf]

I didn't mean dsolving the catalyst in water for the trans esterification - I only meant that I've read of people using a little water for dissolving the chem for the pre main reaction neutralisation phase.