Hello Doug, I have been asking myself the same question. I got busy this week but I wanted to go a friend of mine who is a chemical engineer. I want to show him and present the question to him. Why does this work so well?
My gut instinct on this is that it is removing methanol below .2% and then the soap just so wants to drop out and it gets stuck to the wood. (That decimal point I am unsure of because someone is using a breathalyzer to measure methanol content and I am unsure what scale they are using) Regardless, it appears through Graham Lanming's research and those using the breathalyzer, that when you get below this point, the soap does just drops out regardless of wood chip filtering. I have never experienced this myself yet even though I am using the push/pull process because of either one of two reasons: 1) I am using Koh and that is an un-researched variable or 2) I have not got lower than the 2% yet. Because of those using the breathalyzer research can get their Bio to just drop soap, I am beginning to suspect more and more that is the way to go. Which is why I make this connection to this thread. Am I right? I could be but at the same time, still just a guess until we have some real testing. I think I need to buy a breathalyzer and run this methanol test before and after wood chip filtering to see.
DougThis message has been edited. Last edited by: Doug Weiner,
I am sure if you drive off the methanol and just let the BD sit the soap will fall out. The factor here is time. Time is the one thing I do not have the pleasure of owning. No b%tchin, that is just how it is. I have a machinist bud of mine and I intend to give him the dimension for the venturi. When he is done I should be able to take the old pipe out and use two junctions on either end of the venturi to put it on. With recovering the bulk of the methanol and running through the chips I should be able to speed up the process. I have to make 300 to 400 gallons a month to stay away from the dino pumps. I can't brew 80 gallons and wait for the soap to fall out. I need to push it out as fast as I can.
I think Graham in the GL-1 write-up states that the soap settling process doesn't seem to work as well with KOH. I am sure the soap settles out of the BD, but it is not as obvious as in BD made with NaOH.
I look forward to the results of your testing.
Generally you have the right data relative to methanol removal and biodiesel's immiscibility with glycerin and soap. Fortunately the glycerin is a great scavenger of other undesirable elements, as well. We found dropping glycerin through fluids was a great way to knock done total particulate count - this is why some original work with biodiesel production (Van Gerpen) said filtering to <100 microns might not be necessary because once the glycerin is produced in the reaction process it will strip out particulate matter during the settling process (note however this same particulate matter can be primarily starch and in this case not filtering can be disasterous since these kinds of particles can hold excessive amounts of water and other side reaction problems).
Anyway the wood fibers have a capillary action which tends to trap the glycerin and the glycerin in turn traps the soap. Additionally if the biodiesel does have a low methanol content then the soap naturally becomes slimy and stringy and the wood sawdust/chips act as a mechanical filter (which is why we really like the sawdust or Eco2Pure in our process because we use it as a serious contaminate KNOCK down media and don't rely on it to produce ASTM fuel).
Methanol content is still the tricky element in this though since methanol isn't really being removed - like resins it may trap some finite amount but it isn't a lot and as the methanol passes through, it will take dissolved soaps the most readily - right through the bed of sawdust; that is unless there is sufficient quantities of glycerin already adsorbed in the wood fiber capillaries.
PS did Jehu say BUTT ... HEH HEH HEH
Causing a Regenerative Economy
I've been water washing(and washing, and washing) and really bumming about all this water I'd like to be reclaiming. I'm thinking about switching to a wood chip wash. I have a bunch of questions....
Is there a preferred size of chip? sawmill dust?; wood chipper size from a tree company?
Is there a preferred moisture level? is right out of the chipper OK?
I saw that hardwood was preferred to softwood. I have access to seasoned hardwood from a firewood producer. Is that good enough?
Lot's of questions I know. whatever help you could be would be great!
Sawdust is better machine shavings, and chipper stuff would be less effective still, but they all work if the biodiesel is left in long enough.
Hardwood is much better than softwood.
Dampness is to be avoided, so get dried stuff. You can let damp stuff sit in methanol for a while then air dry it afterwards.
Remember that hardwood also contains a fair bit of resin, tho its flushed out with the first batch of biodiesel.
Dont be sparing with wood, the bigger your filter drum/tower the better. Actually a drum is better than a tower, which is awkward to empty, and besides gravity is better than pumping.
This thread is back alive. Good.
1. All wood chips are not created equal. I collected small planer shavings from a shop that does custom hardwood cabinets. I sifted out the fines and viola - nothing. These chips were a mixture of hardwood so I cannot swear what they were. I was later informed that the finer the better and the fines I sifter out with a colander, was a bad idea. The only problem is that this fine dust clogged my mesh screen - which might have been too small at 200x200.
2. Using Redwood shredded bark works wonders. I left my wood chips in the bottom of my 55 gallon barrel and put 2 bags of red wood bark on top. I left the old wood chips as a buffer to hopefully pull out some of the fines of the red wood bark. Circulating the bio through this stuff (barrel on the bottom filled with soapy bio and barrel full of chips/shredded bark in a barrel placed on top and just gravity drained back into the bottom) I can cut the bio from about 1500 ppm soap to 250 ppm in a few passes. I don't think it will go much lower than that, like maybe down to 210, but I have left that thing running for hours (by accident) and soap levels never got below 210ppm. I then run it through 24 inches of Thermax resin in a 4 foot tower and the bio gets down to around 100. My pipette size is 25mm, so its a little tough to calculate these differences when my HCL drop sizes are relatively big (even though it feels small to me.)
I just built 2 four foot towers for a friend who will use Redwood and Resin in a continuous lead-lag configuration and I will know next week if this is enough wood chips to make this set up work.
It is important to note 2 things. One is that there is little to no methanol in the bio I have been using and I let it sit for a minimum of 1 week. At the point, soap ppm is around 1600-1800. Also I really do think it is unsafe to circulate bio laden with a lot of methanol in the wood chips. Too many stories of auto-ignition of Methanol rags. If one of theses towers heats up in the sun and meth is trapped in a glob of wood chips... Maybe just keeping the towers out of the sun is enough, but just a word of caution.
PS. To measure methanol content. I simply bought a Alco-hawk breathalyzer off e-bay. I got one that reads up to .4% Simply drilled 2 holes in the top of a mason jar lid. One just big enough for an air bubbler hose for an aquarium bubbler i have, and a 2nd (like 1/2") to put a barb fitting that takes a 3/8" pieces of hose attached to it. Take a sample of bio in the mason jar. Screw on the lid with the holes. Put the bubbler hose in the jar. Switch on the air bubbler. Turn on the breathalyzer and when its ready, shove the mouthpiece into the 3/8" tube. Viola you get a reading. The reading is a littler higher than what the true measure is, but you get a close approximation.
Thanks Doug and Jehu!
We're going to install a meth-recovery port on the processor and do a 5%-10% water wash before we go into the wood chip wash. Do we need to dry the bio before sending it through the wood (I'm thinking of a drum filled w/chips and a shower head to feed it and let it drain by gravity. Or would you suggest getting a tower kit?
Do either of you wet wash at all?
I'm using KOH.
What's a good soap test?
So far, I have only used a 55 gallon drum over drum and I know it works. You are going to need to find some mesh to keep the wood particles from falling through. In this upside down upper barrel, I plumbed a 3/4" pvc pipe horizontally (using a female 90 degree on the inside of the barrel and piece of 3/4" pipe that went all the way through the bung cap.) I channeled the horizontal pipe with a dremel (tops and sides 0- NOT the bottom) and wrapped it in some coarse mesh, like 20x20.
As for using wet bio, I have no idea how that will effect things. I imagine its not good. Could you then air dry the bio first, just so it as least clear. That might be enough.
Also, I use KOH and this process works for that.
One last thing, I think you are going to get a mess if you water wash the bio after demething. I have found that anything over 1000ppm tends to emulsify but will break up on its on over a few days. However about 1500ppm, its worse. If you are doing that to save replacing the wood chips more frequently, well you are on the cutting edge so try it. In my opinion, not worth the effort. Now if you want ATSM perfect bio, water wash and dry after the resin tower. Then assuming you made good bio, you will virtually ATSM stuff now.
You dont need to water wash, tho you can sprinkle in 5 - 10% hot water without mixing and leave it overnight - that takes out a lot of soap without getting the biodiesel wet.
Dont use a tower, theyre really hard to clean out. Use a garden water drum or something with a tap on the bottom and put an internal mesh in it to stop the sawdust coming out - easy to load, empty and clean out, and hold much more sawdust/shavings.
Thanks again. How are you getting your soap numbers?
I know all about making bio-snot with the water wash. If we heat it and let it sit, it will separate over time. It seems time and gravity solve most problems. The problem is we don't have enough time so we're trying to push the process.
Don't use any prewash, you don't need any water at all, if you do a prewash and go through the wood you will just end up with a mess.
Why don't you just vacuum the water out of the biodiesel?
I ran a test some time back using Fir Planer shavings in a pvc column about 4" diameter x 4' high.
The fuel was water washed through two or three cycles then ran through the shavings. A significant amount of water was removed from the fuel. Not perfectly dry but clear enough to read through it at room temperature.
I've been thinking (ok I know thats dangerous) but theres two aspects to how dampness might affect the shavings: damp shavings would absorb soap and glycerol better as these are much more soluble in water than biodiesel. The problem is that damp shavings is likely to prevent the biodiesel from coming into proper contact with the wood fibres for good absorption to take place. However, I havent tested this theory in practice, and since the dry sawdust works wonders anyway I cant be bothered doing it.
So you are using sawdust? How are you managing to screen it out of the bio either at the bottom of your column or barrel? Any way to post a pic of the dry dust you are using so we can a see its size.
DougThis message has been edited. Last edited by: Doug Weiner,
OK everybody, thanks for your thoughtful responses. I'll try to address everybody in one shot.
First JRogo: Vacuum? I'm not sure what that means. centrifuge?
Double D: Thanks for your input!
Jehu and Doug: I'm just starting to plan how I might experiment with this and have scored some of the firewood cutter's chips which i think are the perfect size. If you've ever used a (properly sharpened)chainsaw - that's what I'm talking about - nice small chips with lots of surface area. I'll take a picture tomorrow and show you what I'm thinking of for a membrane to isolate the chips. I'm thinking of cutting the bottom out of a drum and then turning it over so I can plumb out the bung holes which will then be at the bottom. I did a wash tank like that a few generations ago. I'll then drill (or burn w/ a torch) some large-ish holes in the lid and sit it inside on some stone risers which will sit on the bottom of the tank.
Jehu: Does anything get dry in Scotland?
Am I to assume you have run fuel right from the processor into the chips then into the Thermax? No water at all? I set aside a few gallons off my last batch and will do a test run tomorrow....hopefully I'll have pics.
No water. I currently I do not run a continuous lead/lag method. Just run the bio through the chips over and over. Then when that's done, through a 10 micron filter as the bio heads into the tower full of Thermax. Be aware if you use the Thermax, soak the the resin first in clean bio. I didn't and My first batch came out like coffee. I freaked but was told that was normal in the beginning if you don't pre-soak. I simply reprocessed that batch. The resin darkens the fuel a little so it turns out golden brown. Lowest Soap content I am getting is approximately 100 ppm. Not sure if my 25mm pipettes are to blame for my high count or my processing techniques.
PS. Also don't forget to drive off all the methanol and let settle for about a week before doing the wood chip filtering. After a week, I drain off from my cone bottom settling tank about four 800ml mason jars (2.5L) of glycerin and soap before I even hit the bio - and that bio is quite soapy - much soapier than the top bio which measures about 1600-1800ppm soap. This is using KOH. NaOH I think drops out much more soap but dealing with the thick glycerin is such a pain.
I screen out the sawdust with a large stainless steel car air filter attached to a bin lid which fits onto the bottom inside of the sawdust drum, leaving about an inch of free space for the biodiesel to drain thru the tap. My sawdust is about the size of ground oatmeal. Of course a lot of very fine stuff gets thru at first, which is filtered out using a RO filter.
I'll get round to posting a pic sometime, once i get round to clearing away all the junk thats littering the place.