Read an article somewhere about bubbling air through unwashed bio to get more Glycerine to drop out. Thought I would see what happens. I ran the air for several hours, shut it off, and let it settle out overnight as usual. Yesterday when I went to drain it, there was a layer of less transparent bio between the clearer bio on top and the glycerine that settled out on the bottom. Some Glycerine also formed on the wood bubbler, and there seemed to be a little more Glycerine dropping out this way, just wondering if the other will clear up. Will look after work. Anyone else do this?
I've tried it a couple of times, and didn't like it. The "transparent" layer is most likely soap. Bubbling air through the unwashed bio will usually result in soap formation. As long as you pass the 3/27 test you shouldn't have any glycerol left in your bio.
Get mine in 50 lb bags from DudaDiesel. He also carries sock filters. I stack mine 25,5,1 micron. Most seems to be caught by the 25 micron. I then pump through a 10 micron spin on filter (Chemtek, would like to find a finer one)
I demeth my fuel by spraying it through a pump for 4-6 hours (75 gallon batches) and then settle for as long as I can - 2 days if I need the fuel and longer if I have some completed. Keep in mind that the settling and demething takes places after the initial settling and draining of glycerin from the reacted fuel.
I am not a chemist, but this is my experience: I think the methanol in the fuel keeps the glycerin in suspension. I have sampled my fuel hourly during aeration and found that it clears up immediately once the methanol is gone (fast enough to amaze you). In fact it clears to the point that you can read print through the beaker and does not appear to need washing. This allows me to use much less magnesol to finish the fuel. Glycerin "jelly" is left in the bottom of the tank when I decant.
I believe the soap is formed during aeration by humidity; after all, it takes water to form the soap. During very dry days I get almost no soap and on cloudy high humidity days I some soap is formed.
In short, I think it is a very viable component of making fuel and makes washing with magnesol a finishing step. I hate to think of the cost of removing a few liters of glycerin and soap through media washing or with magnesol. Plus it is FREE.
In the pictures notice one contains soap in the settled glycerin and the others contain such a small amount that it is not obvious. Humidity was the only variable in the process. Compressors used to aerate also collect moisture if a water trap is not used.