I have never used any other method than water washing in my BD making process. Now it takes a 7-ish% pre-wash & 4 more 15 litre water washes (v. occasionally 5) to get a clear pass on 140L of BD. I use one machine for the entire process from beginning to end. I always use cold water for all water washing. You can do this ww process at any temperature & I usually do it at ambient.
What I've learned:
I suppose it's obvious but always bear in mind it's the process that creates the problems, so be scrupulous in following the basic rules & you will eliminate many of the problems rather than create them.
I used to try to make a batch of BD too quickly, sometimes in one long day. Now I have broken the process up into several days.
Day 1 - Drying the oil is very important. I get my oil from 2 sources & they decant from their fryers the morning after they used the oil for the last time the night before so it's pretty water free. I crank the machine with 140L of WVO up to about 70 degrees & leave it for 2 hours then drain off what little water there is. I then turn on the pump to get the WVO in the pipes, pump etc into the body of the machine & leave it for another 2 hours, then drain. There's usually no water coming out at this stage.
Then Stage 1 followed by Stage 2
DO NOT over dose with chemicals, if anything be conservative on Stage 1 & accurate in your calculations for Stage 2. Doing this will save on chemicals & save an enormous amount of time & frustration in sorting out overdoses, emulsions etc. Ask me how I know this.
I do the 7% pre-wash & I usually do it immediately after stage 2 without stopping or checking my BD is fully converted. I've done this process so many times I know it's 100% (or as near as dammit) converted. The thing to be careful of here to avoid an emulsion is the speed in which the pre-wash water is introduced. Too quickly & you risk an emulsion so take your time. I introduce the water for the pre-wash slowly through the venturi, the same way & speed I introduce methoxide, & once it's safely in I open all the valves & pump wash with the same ferocity as I use when converting feedstock to BD. It can take 7 or 8 minutes to add 15L of water. I run the pre-wash for 15ish minutes full blast & then shut the thing down for the night.
Day 2 - Water washing day. After sitting overnight following the pre-wash I drain away a lot of potential issues when I drain the pre-wash water. In the next wash I pour the 15 litres in the top of the machine at a gentle rate (not just dumping it as fast as I can) while it runs at about 40% speed, then when it's all in I close the lid & crank it up to max. After that the risk of emulsion seems to be eliminated & I can just dump 15 litres straight out of a bucket into the machine.
I run each ww for about 20-25 mins & then leave it a couple of hours to settle.
After the 3rd ww I test & can usually tell whether I'll be done with 1 or 2 more washes. When I have a pass with a clear separation & clear water in a jar after shaking vigorously & settling I let the converted & now clean BD sit in the processor for a day or 3 to allow the water to drop out, then I dry it by heat.
I've often wondered if just how dirty their BD is is a concern for people who don't water wash. Seeing the stuff that comes out in my water washes I have to say that even though it can be a time consuming PITA I wouldn't make BD any other way.
I do not make BD from about October until the beginning of May, making enough in the warmer months to last me through the colder ones. I NEVER have any glyc, soap, water or anything else in the bottom of the 25L containers I use to store made fuel, even if they've been sitting in my fuel reserve for 6-8 months.
