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Dry wash with wood chips

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July 03, 2010, 03:44 PM
Dry wash with wood chips
Thanks Jehu!!
The Amberlite was in place and part of the processor platform when purchased.
Wanting to protect the investment there as well as be able to improve the process and produce consistent quality.
You think ok to drill holes in the half pipe that rests over the pipe ??

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July 03, 2010, 09:05 PM
The half pipe idea is ok so long as there is no flow restriction to the filter. If the only route to the filter is thru small holes the flow will stop in no time. If the half pipe is open ended there shouldnt be a problem, and it wont promote channelling since the fuel has to pass down thru the sawdust to reach it. Channelling is only a problem with upflow set ups.
May 27, 2011, 02:13 PM
Hello guys,

I have a big problem last weeks, and I am thinking to go back to water washing.

My wood chips column after the chips replacements, works very well. But when I am not using my column for 2 weeks, and I start the new batches, the results of water test are very bad.
I can understand why this happens...

Any suggestions?

May 27, 2011, 03:20 PM
After a batch has run through the chips the chips will have a certain amount of bio and the soap that was soaked into the chips, over time this stuff will drain out of the chips and collect at the bottom of your tank.
When you make a new batch this stuff will be flushed into the new bio, especially if your bio is hot or even warm, hot bio will dissolve the soap in used chips and put it back into suspension in your new batch.
May 27, 2011, 03:39 PM
Doug Weiner
Fabricator, interesting, I never had this problem. I wonder what kind of chips he is using. Perhaps a soft wood.
May 27, 2011, 05:37 PM
I use red oak sawdust and chips that I build with my own cnc router.
I left the unwashed biodiesel 2 weeks to settle so it is cool(without any other processing).If I understand, you propose to empty my sawdust column after use? or could you propose, any other solution?

May 27, 2011, 07:12 PM
It all depends on the size of your batch of bio and the size of your column, your starting soap level and your ending soap level, it is possible your chips are used up after one batch.
May 27, 2011, 07:39 PM
Doug Weiner
A few things:

1. Way too much soap per batch like over
7000pppm... That's a lot if soap. This is not my first guess but possible.

2. Wrong kind of wood. I think Jeru recomended red oak, but double check.

3. Chips are not small/fine enough. The more surface area, the better. The chips should not be planer chips, but routing remanants should be small enough.

4. Some kind of resin is in the wood.

All I know for sure is that every kind of wood works. I got bags of chips from a yard that did custom hardwood molding, and those didn't work.
A quick test is to put some chips in a jar, add unwashed bio and shake. Let it sit for a few minutes. Then pour the bio through a paper towel into another jar. An do a shak'em test. It should more or less give clear water. The chips that worked for me was 'red wood bark.". I am now using a bag of eco2pure.

This message has been edited. Last edited by: Doug Weiner,
May 27, 2011, 08:29 PM
I use poplar shavings, from Tractor Supply, it usually takes four bags to get 350 gallons from 1200 ppm to 35-40 ppm, I don't do the shake up thing, I do the soap titration.
May 27, 2011, 08:55 PM
Legal Eagle
One key element in a dry wash system is a proper demething of the biodiesel prior to chips and/or resin. The demething process, accompanied with an after settling time, will drop most soaps out of solution, and the the wood chips do the rest.

I have started with 2800ppm soaps before demething and passed ASTM for free and total glycerin at .024 after demething but after chips and resin my soaps are ZEROppm. Values were checked in a lab.

To get a good grip on the science of this check out Graham Laming's website. He has shown conclusively that once the residual methanol is removed then whatever soaps were in suspension will then fall out on their own, although this process consumes time as natural settling times must run their course. The demething followed by a day or so's settling will get most of the soap to drop out, and then the finalization of the process is accelerated with chips and/or resin. The end result is the same; biodiesel that is free of residual soaps and of very high quality.


** Biodiesel Glycerine Soap - The Guide
- on 5 continents helping people make & sell soap from the Biodiesel Glycerine.

May 27, 2011, 09:27 PM
True, I vacuum distill the methanol out of the bio before running it through chips, if you run a new batch of bio through chips that were previously used, the methanol in the new bio will cause the soap to go back into suspension in the new batch causing a very high soap level.
May 27, 2011, 09:32 PM
Also when you use KOH in your process even very low ppm amounts of methanol will cause soaps to stay in suspension for a LONG time, soap will eventually settle out but it can take weeks.
May 28, 2011, 01:51 AM
After your thoughts , I think that it is wrong to feed the column from the upper side because soaps go to bottom after a weeks of not in use..
May 28, 2011, 02:25 AM
I concur with Fab and Luc

Get the methanol out. Ive had batches that looked very pulpy after demething.
At home I let it sit till its clear and use kiln dried poplar shavings, same product as Fabricator.
Well worth the $3-5 bag. check KoeterSmith.

At home I settle till its clear fuel and I get a cookie of glyc-like layer on the bottom of my white poly drum. used to be my old water wash tank with a 6" standpipe. Some times it takes over a week after demeth. im in no hurry

At work I distill under vacuum and if it is soapy, i see stringy pulp swirling when stirred.
We water wash once after that. distill bound water and fuge and still send it thru poplar wood loaded totes with a Z shaped snorkel pipe thru a Roper gear pump and on to final particulate filtering.

Run it cold for sure.


1996 K2500 4x4 6.5TD
June 17, 2011, 04:17 PM
demething is optional. It will greatly extend the life of the wood by giving it less to do. Wood will do the job though; at the cost of shortened lifespan.

I use a three barrel system to avoid demething. The first barrel takes a hammering, second cleans most of whats left, third barrel polishes it clean and shiny.

Purolite etc is not needed at all anymore and is mostly used by people who already had the setup before wood tech matured.

Lifespan is dependent on methanol and soap saturation of the wood.

Allowing meth to evaporate or washing it and soap out of the wood with water will extend/renew life of media.

Demething obviously removes both methanol and soap before bio reaches the wood so greatly extends lifespan.

The wood works by demething the bio then acting as a depth filter for the precipitated soaps.

mathematical elegance -- desired result achieved with minimal complication
March 11, 2014, 10:38 PM
Originally posted by Jehu:
Originally posted by flapjack:
I'm presently water washing but want to change to wood shaving dry washing now. I have a 45 gallon drum with a drain tap near the bottom, which I intend to half fill with either woodchips or sawdust. Then add the biodiesel. Would it be adviseable to stir the mixture a few times, or just let it work it's way down through the woodchips? Also, would it be better to use large chips rather than sawdust, as I have a feeling that sawdust would compact too much and block the biodiesel from working it's way down to the bottom of the tank and out through the drain tap? I would really appreciate any ideas on the best way to do this!! David.

You will need some sort of fine grid with a fairly large surface area to have a decent flow rate; the sawdust will block a tap. And yes sawdust does compact; this results in air being trapped and reducing washing efficiency and flow rate. I use a long thin rod to probe thru the sawdust, but generally some air gets trapped. For a 45 gallon drum 2/3 - 3/4 filled with sawdust a flow rate of 1 - 2 L/min is fine. The last few gallons will come thru very slowly - its sometimes best to leave it in and get it with the next batch so that youve always got a half decent flow rate.

Jehu. Please some advice.

In my town i can only get pine woodchips and sawdust.
I have two 55 gal drums.
What do you recommend for preparing the woodchips set?
Let Biodiesel set over night and drain the resin after?
What to do with that resin stuff is still good for another batch?
Also, i have an issue. Town is ver hot always 95F.
Im worried about the internal combustion issue.

What do you recommend? Always keep bio on te drum?
Keep it with the close lid and the vent closed?

Thanks in advance.