Using chips/ion exchange in a lead/lag configuration is a logical approach.
The chips 'protect' the expensive resin and if the soap level is monitored after the chips the resin is protected (it doesn't then have to do any work and is just there as a safeguard)
I have actually taken to acid washing my bio recently. After an initial wash/washes when the soap level is no more than about 200ppm I introduce a small amount of acetic acid to the wash water, it makes washing so easy.
If this introduces about 200ppm of ffa's into the bio I feel it is of little significance.
Just a little information re the water tests. a member on the UK biopowered forum assembled a capacitance sensor comprised of 51 brass plates. i did some comparison tests between the results it gave coupled to a arduino programmed for capacity.
it worked really accuratley for a while, just immersing it in the bio for about 3 mins and taking the reading. The intention was to produce a graph so the capacity as indicated with the arduino could be read as ppm water.
All was going well, then after a few weeks the range started to alter. We realised it was due to corrosion on the plates. The comparison between samples was still present but the range altered so much it just turned out not to be a usable method.This message has been edited. Last edited by: Dgs,
Have you considered the 5% prewash before processing finishes? What about Graham Laming's high voltage electrostatic process?
The acetic acid in this situation might push the TAN over the limit. Incidentally you can replicate the TAN test with an ordinary tumeric titration kit. you will need a 1ml syringe or pipette and add the titration fluid very slowly .1ml at a time. the EN4104 limit is .5.
The EN TAN test is done by mass not volume so there is a small discrepancy in the result but its close enough to be useful as a field test.
Paulus, I had forgotten about the 5% prewash. I used it religiously for years before I moved on to drywashing with my woodchips. It will be interesting to compare results between the mist wash method and the 5% prewash.
Ive looked at Graham Lamings system before but I dont think it would be usable at this scale of 750 litres per day.
Thank you for your reply. Why did you decide to skip the caustic stripping process? - because really this has what has brought on the problem with excess soap. How have you been doing the caustic stripping?
I've had a go at Tim C Cook's baking soda process with really old WVO that has animal fat and is simply gravy. If everything is kept heated, and the quantities adhered to in proportion, all the gunk drops out in a matter of hours including flour. Quite impressive. I have not titrated it yet.
What do your clients do with their glycerol, and is there no effort to recover MeOH? No chance of vacuum de-mething?
For what it's worth, I also have some really old BD that's gone acidic. I tried the baking soda treatment on that, and got good results in that the water coloured up and the tendency to form web-like emulsion at the water/BD interface vanished. I burn this in our wood burner fireplace mixed with sawdust and rolled up in newspaper sheets to form "sausage rolls" which make excellent firewood extenders. But I do digress.This message has been edited. Last edited by: Paulus,
In the particular batch where we ran into trouble, the titration was 4ml KOH which I thought was low enough to proceed without caustic stripping. The batch processed easily and we got good conversion but the test results came back a failure on the TAN with a result of 1.2 if I remember correctly.
After that we caustic stripped every batch so that the titration was <1 ml koh. We had no further problem with TAN on subsequent batches.
The development of the method we used to caustic strip is described in detail here on this forum under the thread caustic stripping. My only complaint with caustic stripping is the loss of yield and the extra time involved. My experiments with mist wash are to see can we avoid caustic stripping and still pass TAN.
In this case the glycerol disposal is taken care of by the French client and I dont know what they do with it. When the unit returns home to Ireland the glycerol will most likely be collected by one of my other clients who manufactures several industrial products from it . He recovers methanol and biodiesel from the raw glycerol before further processing.
At the risk of chewing the fat longer than it's worth, you're using KOH and not methylate? It would seem the water component of your KOH is producing the added soap. And you can't over-allow KOH because it will increase soap.
I know this will be contentious, but Stephen Boyd, who is a super-switched-on PhD chemist in Long Island, says NaOH is the only reagent to use, chiefly because of its higher reactivity but also because it doesnt have the added water contamination in its structure.
We dont use methylate simply on cost grounds, its way too expensive here. I have no particular opposition to using NaOH, I use it for caustic stripping because of the better reactivity and would agree that you have to be precise in dosing the catalyst during transesterification to avoid extra soap production. Do you have a link to this chemists info, Id be interested to read it , although what works best in a beaker sometimes isnt the most practical solution, KOH is much easier to mix on cold mornings, and our free glycerol collection service only applies to liquid KOH glycerol.
Im also interested in Tim Cooks Baking soda method as my next commission is to design a commercial unit to prepare large quantities of Trap grease for conversion to biodiesel.
Using a 50/50 mix of KOH and NaOH can be advantageous. The glycerol is still liquid and the residual soaps will fall faster than just using KOH. If the KOH is mixed first with the methanol, the heat of the methoxide then helps dissolve the NaOH portion and it dissolves a lot quicker.
For most of my processing I now use a mix of 65/35 ASM KOH. The glycerol is still liquid and the soaps noticeably less (about 250ppm after bubbling 12 hours and settling for 6 hours) so then easy to deal with whichever way you choose.
Using this mix of catalysts the yield is around the 103% but it depends on the methanol quality.
I have recently achieved 100% yield using the above mix of catalysts with the 97% (min) reclaimed methanol that Trinity offer. I tested the water on this methanol and it is 9000ppm (0.9%)This message has been edited. Last edited by: Dgs,
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