Hi, after making batches of 60L biodiesel from WVO. I water wash at least twice - usually until water is clean(ish). Then I dry by circulation through a spray bar at about 65 deg C for at least 2 hours.
After this, the bio looks good and clear. I then put it into 25L poly drums. After a few days quite a bit of black glycerin drops out; maybe half a litre maybe less, so I decant the biodiesel to another container before using.
Does anyone know how I can minimise this glycerin drop-out.
I have tried running the process in a single stage. As a two stage process: 80% of methoxide first pass and 20% second pass. I've also used the 27/3 test for residual oil and then run a second process using KOH according to the wvo dropout in the 27/3 test.
Any help ?
Basically your wash process is not aggressive enough. Glycerol readily mixes with water, so if the bio/water is mixed hard enough and enough washes are done so the wash water is clear, no way will you get the small glyc dropout in your bio.
I mix my 200 litre batches with a compressor and use only 8 litres of water per wash and build up the wash times from around 2 mins to 20 mins over 5 washes.
my soap level (a good indication to see if glycerol is also present) after this is max 20ppm.
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