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Spontaneous combustion?
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I have been following this discussion on using wood shavings for drying for a while now and was wondering what are the chances or probability of this occurring when using chips or shavings?And if anyone has had it happened what was the situation to make it happen?Is it caused by running the Bio too hot into the chips or what?Thanks
 
Registered: September 16, 2005Reply With QuoteReport This Post
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So far,

I've seen a post of a tote that spontaneously combusted (presumably), not observed, and it actually also spontaneously extinguished itself.

http://biodiesel.infopop.cc/ev...98101761?r=398101761

There has also been notes of many rag fires, and perhaps washing machine fires.

I haven't heard of a Drywash Column burning. Well, maybe I missed it... there was a note about using barrels with chips as a dry wash catching fire. See comments starting in the middle of the page by Road Runner.
http://biodiesel.infopop.cc/ev...01332/m/22710751/p/2

Comments about keeping the shavings covered with oil if planning to reuse sound good.
I'd be wary about the suggestion of washing the shavings with water, unless keeping them submerged with detergent and water.

Spontaneous combustion typically needs:
  • Some kind of organic combustable material
  • Oxygen
  • Water
  • Bacteria (usually)
  • Heat, Confinement, or Insulation
  • Gasses are a special case that essentially require oxygen/gas concentration between LEL and UEL
I would think that your column itself would be rather safe.

However... I'd encourage the following:
  • All Steel Column (if possible). All steel pipes, perhaps with strategically placed Pressure Relief system if there is a possibly of building pressure. Note, of course, comments about Road Runner above about wanting to disassemble the system.
  • Keep it Moisture Free. Bacteria like moisture & don't like 100% oil.
  • Heat is ok. It should cut down on the bacteria. Keep in mind the flash points of what you have at different stages of your processing... Flash point of Methanol vs Flash point of Biodiesel.
  • Keep the column full of oil between batches. Don't introduce oxygen (except the little dissolved in the oil, or inherently in the wood).
Your biggest risk is likely in draining and cleaning your column.

How are people disposing of the wood chips? Storing them? I assume most people eventually burn the chips, but I would think the storing of the waste chips would be the most problematic.
 
Location: Oregon | Registered: October 17, 2007Reply With QuoteReport This Post
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I don't think there is reason to get overly worried about it. I would just keep the oxygen from being able to circulate. That's pretty much a given in most of the designs I've seen so far. I wouldn't use plastic on anything in contact with the wood chips. It could build up enough heat to melt plastic.

The process here is chemical oxidation of the oil and wood. I would expect it would consume the oxygen in the tower pretty quickly then stop. Watch for smoke exiting the vent when adding oil. That would be your best indication that it's a problem.

Your biggest concern would be during disposal. A pile of oil soaked wood chips could be a big problem. If you want to drain the last bit of biodiesel out of them, spread out the chips so they can't act like insulation and build up heat. Personally, I would burn the spent wood chips as soon as possible.
 
Location: Cowboy Country | Registered: December 06, 2004Reply With QuoteReport This Post
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I've often thought about this. I keep my spent sawdust which I use for heating batches in a sawdust burner in a 100L blue solvent drum, and the sawdust which is in current use is open to the atmosphere, but so far I havent seen the slightest sign of heat being generated. If it does go up in flames it'll hit the national news Eek
 
Location: Scotland | Registered: March 19, 2006Reply With QuoteReport This Post
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we did at one time have some problems with combustion. I came to the conclusion that the finished fuel was hot during the intitial filtering, and that gave the shavings a bit of a heat boost to get combustion going. we now settle for at least a week, and have had no problems since. I'll soon be going to a sealed drum system similar to what has been written about on this site.


powering
2 bobcats, an excavator, and a ventrac mower. looking for a diesel weedeater!
 
Location: morgantown wv | Registered: June 18, 2008Reply With QuoteReport This Post
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From memory I think most of the posts about this in the last year or two,involved pure cotton rags soaked in bio and then left in the sun-from memory some people could reproduce the effect by doing this-metal trash cans out of the sun seemed ok
 
Location: UK | Registered: October 14, 2008Reply With QuoteReport This Post



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Yes, the wood shavings column/drum will spontaneously combustion, if you dont keep it saturated or air-tight, perhaps. Mine did.

After using my first batch of shavings from last summer, I decided to drain all the fuel out of the shavings and change the media. Perhaps try my hand at glycerin logs.

After a few days the wood shavings began to smoke. This was all the way down near the steel/mesh strainer and being a white poly drum, I could see a black melting spot near the bottom.
It happened quick once it started and I only let it go until the smoke was getting carried away.

I was/am very aware of the possibility of this and had placed the filter rig in a safe area to drain.
It was not in the sun, nor was it hot weather. It was 3 weeks ago.

I also suggest steel construction, keep the wood media submerged-always (install a bottom valve).
When you want to change the media, drain, dump and contain/process/burn the wood in one labor session.

I extinguished the potential meltdown by turning on the circulation pump. I had maybe 6-8 gallons left in the catch drum. The fuel came out black and smelled like a smoker grill. Not a bad smell at all, just smokey. The fuel was pretty much beyond salvage.

I hope that helps someone understand the potential of the process. Be aware of what you do in any part of bio homebrewing, dont be a statistic to outlaw this art.


1996 K2500 4x4 6.5TD
 
Location: Southern Indiana USA | Registered: June 20, 2008Reply With QuoteReport This Post
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Was your drain valve was open to the air?
 
Location: Cowboy Country | Registered: December 06, 2004Reply With QuoteReport This Post
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Yes it was.
The top is wide open upside down 30g poly drum. I wish I could share exactly how long it took, but I cant remember now.


1996 K2500 4x4 6.5TD
 
Location: Southern Indiana USA | Registered: June 20, 2008Reply With QuoteReport This Post
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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, most of the chips are charred black with about 10% still 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.

Doug
 
Location: Los Angeles | Registered: March 25, 2008Reply With QuoteReport This Post
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