What It Is:
This method involves “pre-washing” Biodiesel with a little water after it’s reacted but before the glycerin is removed. Adding the water before glycerin separation aids in removing the water soluble methanol, glycerol, and other contaminants. This has been shown to significantly reduce the amount of soap, glycerin, and methanol left in the Biodiesel once the glycerin has separated.
5% Pre-Wash Benefits:
– Faster glycerin separation from reacted Biodiesel
– Better removal of methanol from Biodiesel
– Results in less soap formation during waster washing
– Requires less water to completely water wash the Biodiesel
– When dry-washing, reduced methanol levels allow for better soap removal with ion exchange resins
– Results in ion exchange resins lasting longer (because there’s less soap to be removed)
How To Do It:
1) Figure out how much 5% of your total batch size would be (oil + methoxide).
2) Mix your oil & methoxide together as normal
3) Just before you normally shut down your pump, add the 5% water
4) Continue mixing for about 15-20 minutes
5) Shut the mixing down and allow the glycerin to separate as normal
6) Commence washing your fuel
40 gal oil + 8 gal methoxide = 48 gal liquid
48 x 0.05 = 2.4 gallons
After reacting for your normal period of time, add 2.4 gallons of water to the processor. Allow it to mix into the batch for 15 to 20 minutes. Then separate the glycerin.
1) Ensure Fuel Is Reacted Before Adding Water
It’s important that you ensure your fuel is well reacted before adding the water. Once the water hits the oil/methoxide mixture, it’ll stop the reaction dead in it’s tracks. Some people pull a sample of their mixing fuel prior to adding the water, quickly separate the glycerin (allow it to settle in a vial), and run a 3/27 Conversion Test on it.
If it passes, they go ahead & add the water. If it doesn’t they continue to let the reaction run and pull a test again a few minutes later.
2) Adding Water To Glycerin Makes It Difficult To Recover Methanol
When adding water to the process before glycerin separation, a large majority of the water will end up in the glycerin. This will mix with the methanol in the glycerin and can cause problems when trying to recover methanol from the glycerin.
3) 80/20 Method Notes
– Don’t add water until the “20% Reaction” part
– When adding the water, also re-add all the glycerin removed during the 80% part
– Otherwise, too little glycerin in the mix can allow emulsions to occur