Looking for what chemically goes on when using wood-chips for dry-washing.
I understand the ion-exchange principle using resins, where the Na+ ion is exchanged with a H+ ion, turning the soap/salts into FFA's again. This of course would make the fuel too acid if starting out with too much soap.
Do wood-chips work in a different way? What happens to the Na soaps/salts? Does dry-washing with wood-chips increase the acidity of the fuel?
They work in a different way than the resin.
The wood chips just absorb the soap (think kitty litter on an oily floor).
No ion exchange occurs.
Thanks. That helps.
Now for another question. What do most people do for drying after the wood-chips?
I would like to get well below 500 ppm water by the time the BD flows into my storage drum.
Currently, I water-wash using a pump method - seems to work well, but I am looking into building a dry wash system. I only do 13 gallon batches, and have time. I was thinging of the following process set-up:
Trans-estrification followed by 5% water pre-wash. May even do one more 5% pump wash to get more methanol and gross soaps out. Bubble drying to get clear BD (probably more than 1000 ppm water still).
Two 5 feet by 6 inch wood-chip towers in series (currently have nice hickory kiln-dried chips) followed by macro Thermax in same size tower and then Quick-and-Dry in a fourth tower. 1 micron filtration into storage barrel.
I'll flow at about 0.7 gallon/hour with metering pump.
Do I really need the Thermax? I assume the wood-chips will not take the water out, so some kind of drying would be required, thus the fourth tower with Quick-and-dry.
Generally people use drywash systems to completely eliminate water washing. I'm actually not sure what the benefits of doing both would be (although someone correct me if i'm wrong obviously). It seems like you would still have all that wash water to dispose of which is the main benefit of dry wash to begin with.
Several people, ours included, simply use wood chips in front of a resin tower such as purolite, dudadiesel, or thermax, of course there must also be a demeth step in there.
Ours is very similar to what legal eagle is doing. A set of wood chips in front of a ion exchange resin tower. Wood chips remove the bulk of the soaps, ion exchange remove the last traces and glycerin.
You would also need a demeth step in there as well. I have found that if you never water wash and your oil is dry to begin with demething will also dewater. For info mine typically tests about 100-200ppm water after the demeth. We've had a few times where we failed methanol (not demething enough) and the water was still a pass at ~300ppm. Anecdotal but leads me to believe if it's demethed it's also dewatered.
So in short if you are comfortable with your demething procedure then completely eliminating water shouldn't be a problem. The tricky part then is limiting soaps into the ion exchange to keep acid #'s down and ensuring all the glycerin is gone.
It reduces the amount of water required, so one does not have "all that wash water to dispose of".
Disposing wash water isn't a problem for everyone.
Thanks for the replies.
The reason I still would use water for pre-wash and maybe one more pump wash is to de-meth. I don't really have another good way. Waste water is not a problem. Looking into dry-wash to reduce labor and making consistent quality BD.
So should I use something like Quick-and-Dry to "polish" of remaining water before my storage drum?
Anyone have thoughts or experience using dry corn cobs?
Don't use water.
The wood works by demething the bio and depth filtering the precipitated soaps.
I use three barrels of wood in series to get soap free bio without water or demeth.
Not demething shortens the life of the media but it is free,recycled and easier to change than demething bio.
You don't need water, thermax, purolite or anything but wood to get soap free bio.
Most people who use ion exchange made the investment before wood got going properly.
I was the first person to tell everyone here what ecopure was made from (obvious when you see it but back then not many people had). Since then I have used a lot of sawdust to clean bio without demething and I get bio with no detectable soap.
mathematical elegance -- desired result achieved with minimal complication