Thinking about trying the prewash concept. How many subsequent mist washes does it take to complete and how much total water do you use?

sheesh, it depends on how much room you've got and how much soap your fuel contains, and whether your contaminated the fuel with glycerine before washing.

so, the famous biodiesel answer:
"it depends"

However, soap testing shows that you can reduce soap by half by doing the technique.

I did a sample test before I switched to prewashing.
the unprewashed samples required 12ml of HCL during the soap measurement..
the prewashed sample required 3ml of HCL during the soap measurement.

since that test I have always prewashed!!

the HCL solution was the same in both measurements. no don't try to convert that is PPM. its wasn't that accurate of a test. the prewashed had 25% of the soap the unprewashed.

I could also say that it used to take 4 days to process a batch thru my setup now it takes 2 at most.

also I haven't mist washed since then..that and using the 27/3 test have eliminated emulsions.

-dkenny

dkenny, are you saying that you only prewash and do no further type of washing?

I have no quantifiable information, only anecdotal. After switching to the 5% prewash (i actually do 7-10%) I only wash twice.

100 gallons oil
20% methanol
KOH- 7g base + titration (adjusted through spreadsheet for 90% purity)
React at 130* F for min. 2 hours, often 3hours

Add 7-10 gallons of water via methoxide tank
mix for 15-30 minutes

Let sit and drain glycerin

Use "gentle rain" pattern garden hose sprayer to wash water over biodiesel as the pump pumps it out and over the brass fire sprinkler head I use to diffuse it for drying. I wash with about 30 gallons.

I let this sit for at least 30 minutes, sometimes as much as 2 hours and drain water.

I repeat this again.

Then dry.

So far, (knock on wood) no emulsions, great separation, and just scrapes into passing the 3/27 test.

edited to add: My oil titrates regularly at less than 2

no prewash alone isn't enough to get out all the soap. It reduces the amount water washing necessary.


-dkenny

I agree with DKenny. Prewashing does a lot of good when it comes to washing, but you should still wash your fuel afterwords because there will definantly be some form of soaps/whatever left.

I personally do not pre-wash, only because I don't want to taint my glycerin with water before I run it through my Methanol Recovery System, but if I didn't do the Meth. Recovery, I'd definantly prewash.