Nearly a disaster, but luckily averted. After 18 months of making biodiesel and using a dry wash system which included a wood chip system, I came out to the garage to find a big problem.
First, let me say that I am not using a wood chip metal tower (I think that is going to change today!) I use a two poly barrels stacked upon on another with an upper barrel 1/2 full of redwood bark and the the lower barrel for the the bio to drain into. I have used this same set of chips for at least 18 months and ran about 350 - 750 gallons of bio through it. I usually demeth down to 0% methanol, measured by a breath-alyzer, but lately I got a little bit more lax and just didn't measure methanol content before running through the chips. (not sure this has any effect but I always worry about the excess methanol helping to cause spontaneous combustion and in this case could be a contributing factor.) Also, lately, I haven't let the bio settle as long (1 week instead of 2+ weeks) so there is a little more glycerin in the bottom of the bottom barrel than I have seen in the past. (Perhaps this is just the chips saturated, just not sure.)
Well I came out to the garage after running bio through the chips 3 days ago to work on the system and viola, smelled a heavy 'varnish' smell. For about 5-10 minutes I couldn't locate the smell and just set about my business. By accident, I put my hand on the top wood chip barrel and whoo! It was hot to the touch. No smoke in the garage, but I knew immediately the problem. After calling friends for assistance, I got the barrel outside and sprayed water over the chips. Smoke and steam came pouring out and upon further inspection, (EDIT: about 20% of the chips were burned black and were clumped together, while rest normal bark color.)
The top barrel was inverted with the base at the top and I had cut a semicircle out of the top (base) to be able to fill it with chips. I used hinges to attach the semi circle portion back on the barrel and had a large aluminum cookie sheet on top of that, so perhaps this limited the oxygen that got into the barrel.
Not telling people to avoid wood chips, but fire is a real possibility.
EDIT: Just wanted to add here for first time readers. My setup drained MOST of the bio out of the wood chips every time I ran a batch. This repeated wetting and drying of the wood chips combined with LONG exposure to air - weeks or even months between wood chip filtering led to the 'auto-ignition' of the wood chips. I promise to fix this set-up immediately and create a set-up that leaves the chips with little to no air and soaked in bio.This message has been edited. Last edited by: Doug Weiner,
Good save, Doug. Do you think the heat was generated by chemical oxidation or bacterial digestion? Time to change the chips, I think.
Doug, we've had that problem a few times. It is super scary that is for sure. Our set up is in metal barrels, but that still didn't stop it from getting things burning. I switched to an up flow set up with a check valve and a shut off on the bottom of the barrel. when I'm done filtering a batch, I just keep the chip barrel full of bio. so far, so good, no more combustion. the bottom is a 1" pipe welded into the side of the barrel, and the top has a 2" pipe welded in the side about 6" down from the lid. both are cut out so the fuel can get out the sides of the pipe. They are wrapped in window screen to keep the chips from running out. I did find out, that if you have too much flow, the 2" pipe can't keep up, and you will get leakage around the lid. I have some 2x8's screwed to the underside of the lid to hold down a piece of expanded metal that lays under the top pipe on top of the shavings. this keeps the shavings from being forced up against the lid and pipe. I really have got to get a camera.
2 bobcats, an excavator, and a ventrac mower. looking for a diesel weedeater!
RR, that's one of the best ways of avoiding the spontaneous combustion problem I've heard. Good work.
The way RolfQuo set up their wood chip drums is to fill 'em to capacity and then pack it down before putting the lid on. Then you need to keep the drum full at all times, so there is no avenue for an air.fuel mixture to ignite. RolfQuo straps their drums down to wood pallets; I have not done this part, but still have no problems so far.
On the farm there are regular wood chip dumps from a local tree guy, and often there is smoldering coming from the heeps. I am just waiting for the day some of that wood ferments and turns into wood alcohol (methanol) and things get really interesting. It will take time and the proper incubation temps for plain wood to spontaneously combust, but if you throw alcohol into the mix with it's extremely volatile nature you increase that potential many fold. So far no fires yet.
I got from all of your previous posts that you got to keep the wood chips 'wet' with bio otherwise they will dry out and cause this problem. I just got done going through the burnt wood chips. I was mistaken, only abut 15% burned, the rest no problem. I actually had two kinds in there, hardwood planer chips (small) and the red-wood bark. Only pockets of both kinds of chips burned, probably due to the rest of chips being wet. The ones that were burnt were almost pure 'ashes", but fused together.
As for a new setup, I have a spare fiberglass water softening tank that a I will use instead and use it in an upflow set up so it always 'full' of bio. Later I will probably purchase and arbor fuel chip tower.
Just wanted to let others know of the eventual danger.
I am not sure how to tell the difference. My guess is chemical oxidation, but if you know otherwise, please let me know.
doug, how big is the softener tank? That might work pretty well if it big enough to hold a large volume of chips.
Most of the fires we have had (4) have been caught quickly the largest was the size of soccer ball, and similar to what you describe. the first one, we had, we took the whole thing out side on the sidewalk and just let it go to see what happens, it eventually got going and burned completely up with low flames. I do think stirring it up investigating the fire gave it more air to get going though. I king of miss processing in front of the house, we were such a sideshow for the community.
if you can mig weld, the barrel set up is pretty easy to make. ours is made of 55 gallon drums and sit on top of a 250 gallon tank, but you could scale that down pretty easily to a 10 or 20 gallon drum that sat on top of a 55 gallon drum. I just use a hole saw bit on a drill to cut the holes so they are very close fitting to the pipe you are putting through the hole. Just don't use the cheap hole saws, they don't cut the mustard. even the good ones wear out quickly cutting holes in metal. I use a nothern tool 1" red pump to circulate, but that would be too much flow and pressure for anything less than a 55 gallon filter barrel. if you use one of those, I'd say you'd need a bypass valve or pressure relief valve in the plumbing to slow down the flow and pressure, or pick a smaller flow pump.
2 bobcats, an excavator, and a ventrac mower. looking for a diesel weedeater!
I already use a fiberglass water softner tank for my Thermax resin. Softner Tank is 10"x35" I use a gravity flow with little to no pressure in the tank by simply drilling a hole in the top of the softener tank and piping the overflow back into the source. (I also have the tank upside down and plumbed in reverse, so that the bio goes up through the center tube and then drains via gravity at the bottom. That way, I can drain most of the bio from Thermax.) I too use the HF pump, but added a throttle system to it: HERE is the basic idea. I will post pictures later. Its far from accurate, but I can really slow the flow down.
For the wood chip tank, I will just plumb another one of these tanks, however I will make it an upflow setup, so the chips always stay wet. The only real hassle I imagine will be the loading and unloading of the chips themselves.
PS. If I could weld, I would build a lot more stuff CHEAPLY. I have a little mig welder fro HF, and built one stand for a cone barrel I have. Every time I look at that stand, I wonder if today is the day it collapses. So no more welding for me.
The whole idea of a reverse flow tank is best understood by the common fuel filter. When you look at the inside of the head there are two ports; the short port (inlet) drops the fuel onto the part of the filter that has the holes, the fuel then seeps down through the media and then returns via the center of the filter to then outlet from the other port (the one that screws into the can).
The water filter tanks work exactly the same way; the fuel comes in and drops onto the resin/wood chips and then gravity feeds down to the bottom and then migrates up the center tube following the path of least resistance and out of the tank. I posted some photos of my tank's set up on my site. The head of the water filter tank is exactly like that of a fuel filter wit the center tube going right down to the bottom of the tank and coming up to attach in the middle of the head. The other port is where the fuel comes in to then gravity feed. With the top sealed it creates a very slight pressure in the tank that forces the fuel up the center tube (path of least resistance). This way the tank is always full.
The wood chip drum is not a reverse flow set up so it must be looked at differently. So, the drum is filled to capacity with chips and patted down so that the chips are tight in there when the lid is fastened. A vent tube allows air to escape while it is being filled. Once biodiesel starts coming out the vent port it gets closed and the drum is full. I have ball valves set up at the feed point (the pump) and also just before the inlet to the chip drum as this controls any potential for back draft suction when the pump is turned off. Another BV is placed at the outlet point at the floor level of the drum (the drain) to isolate it should I need to move the drum when it is full without loosing anything. Another BV is placed just before the inlet to the lead/lag water filter tanks with the Purolite PD206 resin. This stops any potential for suction causing a vacuum and reverse flow when the pump is turned off. I leave the fill tube open and inside a container when I close the pump so that if there is any pressure build up it will slowly drain without emptying the tanks.The tanks therefore stay full all the time. I have never had a spontaneous combustion occur to date.
This setup looks like a gravity drain. Bio pumped in from top, mesh drain at the bottom.
How do you prevent all the bio from draining out? Or do you just use volume to decide when
to shut off the ball valve on the outlet side?
Legal, is the 55g drum one of your food-grade drums with the epoxy lining, or just plain steel?
The drum of chips that is pump fed is controlled by ball valves. When the pump is turned off the valves are closed to stop any backward suction; this keeps the drum full.The primary valve is right at the pump's outlet,as is the by-pass return control valve. (you can see it in the pics on the dry wash side on my site - here ). And the pump's valve set up is the same as when I water washed. That set up is here. The settling tank is the same and the wash tank was converted to the demething tank. Everything else is the same. The cross over was not that big a deal, and the main benefit for me was to be able to produce even in winter as I was dependent on a hose for water and it is not operational in the winter. Also another benefit for me was to get rid of the wash water disposal dilemma.
On the outlet side, right at the floor level, I have another ball valve and yet another right before the resin tanks; this later is also shut, so now the drum is isolated and neither pressure nor suction can have any effect on it. Should I need to move the drum I close the floor level valve and can then remove the resin tanks without emptying the drum.
The path is this; the biodiesel gets pushed into the top of the drum, it filters down to the bottom and then comes back up to the top to enter the first resin tank. From there is reverse flows back up into the second resin tank and the reverse process is repeated. The final polish is done via a 2 micron CAT fuel filter can (when first installing the CAT can do not fill it first,let the flow do it. I split the filter material inside on a couple of these by filling it first before screwing in on).
The resin water softener tanks are reverse flow and stay full as soon as the drum is isolated. The little bit of pressure built up in the resin tanks is quickly eliminated by the open drip tube and goes into a container.
The chip drum is a standard open head steel drum with a bolt type closure. Like mentioned before it is 100% filled with chips and patted down before the lid is affixed to it. The drum will soak up a batch of biodiesel one its first run but after that it is clear sailing.
RolfQuo`s drums, mentioned in the interview (thanks for pointing out the text repeat Paulus), have had over 1/2 million liters put through them and were still working fine last time I checked (about 2 months ago). The only addition there was a drum of Purolite PD206 after the chips, but this only happened last year. The end result in both RolfQuo and my set up is ZERO ppm soaps. My biodiesel can sit through the winter with thaw and freeze several times and still not show any residual drop out on the bottom of the containers. I use canola feedstock that titrates between 2 and 2.5 NaOH; I cannot vouch for other types of feedstock and how they will react, but the results should be the same or close to it.
Legal (no e)
Got it. Missed that you then send the bio back up to a resin tank, thus the wood chip barrel never empties.
Also, your link for BETE and 120 degree sprayer, links to the shurflo pump page by mistake I think. Quick google search led me here:
I am using this one from McMaster Carr for about $25 in brass but they are also on Bete sight as well. Hollow Full Cone
1) What material are these made from and how much do they cost?
2 I added the Pig mats. How flammable are they?
The Bete fittings are offered generally in two materials; one is plastic (don't bother for biodiesel) and the other (my fav) is stainless steel (the ones I got). They each ran me about $50/ea. Not cheap, but then you buy them once. I recently posted some pics from my demething tank, but can't remember which thread. I opened it all up to refasten the heat spear and plumbing.
This once was my wash tank and used the same Bete MP187 MaxiPass nozzle (120degree full cone) as I've installed in the demething tank.
This same nozzle has seen several years of service for water and hot biodiesel w/ methanol and came out looking brand new; all clean and highly polished. The drum, an int'l food grade metal thing, still had its liner in place with no signs of chipping or peeling.
I have no idea what a "pig mat" is.
Update; I dropped by RolfQuo today and asked about their chip drum set up. It is still the original chips they set up a couple years ago. I asked whatthe readings were after the chips but before the resin and was told that they start out with a soap count of between 800 -1000ppm and by the time it gets to the single resin drum they use the soap count is down to between 100 and 200ppm. After the Purolite PD206 the soap count is ZERO ppm. The flow rate is just over 4liters/minute.
Another bad link? Crap! that two in the same day. If this keeps up you guys will give me a perfectly coded site, hehe. Thanks for pointing that out, it is now fixed.
Legal, how does your demeth setup work please?
A picture is worth a thousand words. I don't know if this is what Legal is using, but it would work.
The vent in the drain tank acts as a vacuum breaker preventing the sawdust tank from emptying. You just have to make sure you don't put more in the top tank than you have room for in the drain tank.
What was my wash tank has been converted to a demething tank. I have it fitted with one of Joe_M's heat spears and the drum itself has a standpipe in it (same deal as the wash tank).
My ShurFlo pump does the work of circulating from the floor drain of the tank and returning it to the top where the flow is split in two; one goes to the Bete MP187 spray head and the other is free flowing. This configuration is used until the demething is done, and then the floor drain is swapped out for the standpipe outlet for a couple minutes and then the flow is turned off and the biodiesel is allowed to settle at least overnight but sometimes longer if I can't get back to it straight away.
Once it has cooled and settled out most of the residual soaps, which drop to the bottom of the tank, I can then draw from the standpipe and cajoling the right ball valves run the fuel to the dry media with the excess returning to the main tank. Occasionally it is necessary to open the floor drain and remove the accumulation of soaps, but that is only after 4-5 batches or so. When loading the demething tank from the settling drum (same ShurFlo pump) I open the floor drain of the demething tank first and draw out the soapy mix and start it circulating, then the flow from the settling tank joins it. The soaps helps draw out some of the methanol from the incoming batch.
To close the top I use one of these and plenty of duct tape to seal it. I don`t recommend this method as it is too prone to allowing leaks and the type of leaks that it gives are methanol fumes, so it has to be done just right and if anyone follows my method the responsibility is on you to make it safe.
A much better tank would be a water heater turned upside down a-la-apple-turnover. Joe_M made a really neat bushing from a burned out water heater element that allows a 1/2" pipe to be inside the tank as well as a 1/2" screw on the outside. The bushing is already made for the heater element port so a tight fit is guaranteed. This allows for a Bete nozzle to be attached to a short nipple and angled down for atomization to help in the vaporizing of the methanol and what was the drain port to be used as the condenser port.
The secret is using a good quality cutting oil, liberally! Also low RPM is important, if the chips are blue its turning too fast.
A quality bi-metal hole saw will last for along time as long as its never run dry or over heated.
Simple schematic for a pump and heater control with a high limit
Sensor for the biodiesel/glycerin layer
OK, I am getting started in wood chip dry washing. They will be gravity fed. Full all the time, no air allowed in. Fed from the top and drained from the top. No holes made in drum to be a potential leak point. Comments? Critiques?
Perforared metal to allow space for introducing BD.
Nearly full of oak chips.
Lid on. Haven't decided if out put will be the 3/4 inch bung or the 2 inch.
Blessings. Joe 1999 Chevy Suburban w/new optimizer 6500 TD and 1995 Chevy Cube van 6.5L. WWW.RillaBioFuels.com