The spontaneous combustion occurs because the biodiesel readily oxidizes and the sawdust acts as an insulator.
When the barrel was drained, the biodiesel was exposed to oxygen. The oxidation is exothermic and produces heat. With the sawdust acting as an insulator, the heat continues to buildup. At about 500°F (possibly less), the sawdust can self ignite.
The best demonstration I've seen of this phenomenon was with rags soaked in olive oil, squeezed out, then loosely packed in sawdust in a coffee can. Only took a few hours for it to burst into flames.
To guard against this repeating itself, I'd recommend forgoing the extended draining of the wood chips/sawdust and removed them as soon as possible after filtering. Even better would be to run water through them prior to disposal to help minimize heat buildup. Water turning to steam can absorb a significant amount of energy.
With most flammable materials, there is an ideal range of fuel/oxygen ratios where the material is explosive. Above and below that range the mixture is not explosive (doesn't mean it's not flammable).
Dusts are a weird beast in that when suspended in air, they follow similar rules for explosiveness. If you have an environment with an appropriate ratio of dust suspended in the air, the dust becomes flamable. There are entire books devoted to the subject so that manufacturing plants can protect their employees from such an event from happening.
One could re-enact such a scenario with ordinary flour. Try to light a handful of flour (not in your hand of course) and it really doesn't burn. Toss that handful of flour into the campfire and you get an unexpected response.
yeah, no doubt on the extended drain. i'm still voting for running through hot once. It seems to keep excess soap out of the drain tank. our demeth tank looks like a bad soap dish in the bottom. we have to hose it out with water on bad batches. cooking off the water on the wvo really helps to prevent the soaps. the current plan is to dump that load right into a burn barrel and touch it off with a lighter. this stuff would make great camping fire starters if your backpack wouldn't catch on fire and burn up the 12 pack of camping supplies!
2 bobcats, an excavator, and a ventrac mower. looking for a diesel weedeater!
These dusty hazardous areas are called Class II hazardous areas(gaseous hazardous areas are Class I). They are a big issue in wood, textile, grain, etc. shops and have killed and burned many over the years. Allot of static electricity is generated from the dust and is usually what ignites the mix. Any devices suitable to use in these environments will marked as such with the Class II rating in North America.
Simple schematic for a pump and heater control with a high limit
Sensor for the biodiesel/glycerin layer
I just tried sawdust instead of wood shavings for filtering the BD. I started with partially demethed BD and filled the bottom of a 20 gallon container with about 4 inches of sawdust. I mixed this together using a stick several times a day over the course of a couple of days.
I took a sample and shook it up with water. Mucho soap. So I transferred the BD to another container with a screen on it and used a little giant pump to recirculate the BD and drive off methanol. I let this run for about a day, but I didn't notice any soap dropout. Usually there will be soap on the pump. I transferred it back to the sawdust, stirred it up good and tested again. A little less soap. Then it dawned on me.
All sawdust is not created equal. Most of the sawdust that you will get from a cabinet shop comes from panel products i.e. plywood, chipboard, MDF, etc. Plywood cores can be from any type wood because the veneer is all you are going to see. In making plywood they lay up sheets of veneer using glues which sometimes even have formaldehyde in them. Most of the plywood on the market today comes from, you guessed it -- China.
China ply uses a lot of glue as their veneer core is usually still slightly green, which aids in warpage. So they over compensate by using extra glue.
So my solution was to filter the BD through maple shavings overnight and then run it through a 5 & 1 micron sock filter. After one pass through the filters, the BD is clean. Well at least it passed the shakemup test.
The conclusions that I reached from this test is that you need to know the source of the sawdust before even trying it. If it comes from solid wood, you should be ok. It appears that there is a lot more BD consumed by the sawdust vs. wood shavings. I may be able to get more to drain out later when I have time to deal with it. I will have to get some solid wood sawdust to see how long it takes to remove the soap. My findings were probably skewed by the glue content in the plywood sawdust.
I will make another attempt with sawdust, but I am very happy with wood shavings.
Does anyone have any clue about how long lets say a 55 gallon drum of wood chips would last. Meaning If I had a drum full of chips and pumped BD through it, how many gallons could I filter before the chips are rendered useless?
I don't have that answer yet but hope to soon enough, will post when I do.
** Biodiesel Glycerine Soap - The Guide
- on 5 continents helping people make & sell soap from the Biodiesel Glycerine.
Ok, here's another one.
If the 55 gallon drum proves to be a sufficient vessel, Can we turn it upside down and make or buy parts to have a 2"npt straining cartridge into the drum?
We can recycle the mistwashing/drying drums and use a long enuff standpipe to upflow or downflow.
I realize that with the bottoms cut open, we'd have to pull from the output of the drum and push it to the next vessel.
I wouldn't want to pressurize a poly drum.
I see most drywash towers use a strainer the full diameter of the tower, which makes perfect sense, But would a clever designed 2" strainer do the job?
We could follow it with reusable spin-on particle filters.
And if one could elevate the drum high enuff, he could use gravity, you know, the free energy.
Hmm, that would make changing the wood easier as well.
I just had this thought when I read Wal's question. 'just shooting at shadows.
For that matter we could mimic John Galt's cold upflow drum diagram and use gravity.
Something just tells me that residence time is key, and not to really force the fuel through the wood chips.
I cold upflow my oil with crude glycerin in the bottom and my down tube is only .5" and flows 20liters of clean, dryer oil in 18 minutes.
Thoughts?.... or is there a good design for the drum version already?
1996 K2500 4x4 6.5TD
sorry i haven't been on in a while. Sinbad you asked how it worked. could be 2 things Hardwood has tanic acid that they used to tan hides or it simply could be that soap gets caught on the rough surface.
Andew M you asked chips or bark. Bark works best but chips are are more available.. mix them together. Wood does not need to be kiln dried.. no wood is 100% dry. we have used wet chips and it just requires a little me drying but still takes the soap out.
I have tested both sawdust and chips and the chips are definatelly better. They don't necessarily have to be shavings they can be a little larger.
I find that if the wood is dry you will loose a litte fuel the first batch.
As for how long do they last. that depends on how much soap you have to start with. At first it will take the soap out in an hour of sitting in the chips. then it goes to 2hrs then 3hrs. I guess it depends on how much time you have. If you have a week the will last a very very long time.
we have passed all astm testing using this method. Just a note, we let sit not flow thru.
Tilt1 when you say bark do you mean the stuff you can get at the local landscape supply place? As far as chips,would chainsaw chips be the right size? Or are planer chips better? Sawdust I assume means the stuff that comes out of my table saw? I wonder how many motors I could burn out just filling a tower? I can make, obtain free, or purchase at reasonable cost any of these.
It's what you learn after you know it all that counts.
Lowes carries hardwood mulch;
I'm going to look at it in person to see that it has no treatments to it.
It definitely looks like it has to be sifted thru a screen.
I could use the finer stuff around the house anyway.
It may not be cheaper than water, but my time is worth more.
I'll probly just get 4 bags @ 3CF each for a 100 liter batch, on deck to brew to prep the mulch
---If I find that it's pure wood.
1996 K2500 4x4 6.5TD
Weldshop, I have been playing with wood chips all weekend long. My tests show some problems. I tested bark mulch, maple chips, burr oak chain saw chips and red oak planer shavings. The red oak when titrated for soap, showed no soap at all. But when water was applied to the same sample significant quantities of soap washed out. I have no way of confirming this but I believe that the tannic acid in the oak neutralized the soap while removing only some of the soap. I believe this because when comparing to a control samples, I could not get an emulsion in the chip washed fuel.
It's what you learn after you know it all that counts.
I just got back with 1 bag of mulch. It seem loaded with mud-dirt. Very moist.
I filled a 2 gallon bucket of the mulch and poured in about a half gallon of methanol as suggested.
I had forgotten that we have a hardwoods mill in the next town. I will visit them when we have some dry weather.
I will let the batch settle and bubble of methanol- they say some soap will fall out.
My towers are not complete yet so I got time. Maybe a week.
Also this will be my first big batch at home, 100L. Rick's two stage calc. NaOH. Titrate 2ml.
Also, the fuel will go thru Purolite and the 5 micron bag after the wood. I'm only going to try this 2 gallons of mulch to see how it goes. I have my doubts.
Thanks for the testing. One day we will get this down with something that works.
I dont have any wood working tools, just a skillsaw and jigsaw.
Keep this thread going,
1996 K2500 4x4 6.5TD
Mike, what were your testing methods?
I just figured out how to post photos on this forum. I guess I don't have permissions, so if you want to see my dry wash setup click on the following link:
This is really a simple setup. There is absolutely no need for fancy steel towers to use wood chips. Notice also that I have two small PVC columns as part of my resin purification system. I have used them for a year with no problems. I think the PVC is a problem with larger diameter pipe.
Oops. Still new at posting photos. Try this link:
Go figure. Now both links work.
Wow that shake test looks really good. I have got to find some time so I can configure a chip tower.
I believe this is what I am going to try to construct this weekend. I intend to gravity feed the BD through the t from the settle tower. The vent tube should stop any accident/spills. When the barrel is full I can let it sit with the basket being full of chips. An occassional stir with the pump will pull from the pooling BD at the bottoma nd run it back over the top of the chips. One more valve I i can pull off a sample to test for the drop in soap. When finished I can run the BD to a wash tank of my choosing to finish out with a water wash. I also intend to get a double bubbler in the settle tower to run off some of the methanol while waiting to go to the chips. Kick it around and give me some ideas.
Hey Wal I cant wait to here how your setup works. I think it will be great.
I am now at 150 gallons and wood chips still good.
Lisa 2006 Ford F250 6.0L Powerstroke with 12 inch lift