Non-Chemical Why didn't Geo's chip incinerator explode?

[924T]

I have read about Geo pyrolizing chips in a Dutch Oven in a 55 gallon drum, using cut pieces of oak pallets
as the fuel, with the oak above and below the Dutch Oven.

What is puzzling me, and perhaps other students of the art, too, is after reading in several posts about
how explosive the black smoke is that comes off of the chips, and with Geo's Dutch Oven periodically
burping out some of that smoke, why didn't that cause an explosion?

My best guess is that the chip vapors/smoke, being totally surrounded by flame, didn't have a chance to
mix with Oxygen to be able to explode.

If that proves to be the correct reality of it, then I'm thinking that performing the same process with
a Dutch Oven in a 55 gallon steel drum, with oak pellets above and below the Dutch Oven, but with a
cyclonic burner head on the drum, with all the air being forced into the drum, there would probably
be an explosion when the Dutch Oven burped out some chip vapors.

Am I on the right track with that piece of theorization?

Cheers,

Mike

 

[Harold_V]

It is my opinion that you are on the right track in regards to the reason there is no explosion with the Dutch oven. The gasses that manage to escape are likely burned in the drum, but the lack of oxygen precludes any chance of the oven itself exploding.

I'd caution you against using forced air. If you're familiar with a cupola, you might understand my concern. Steel can be melted and converted to cast iron simply by blowing the cupola with air. Alternate layers of coke, steel (or iron) and limestone (flux) are used in the cupola. That means you are achieving a temperature in the range of 3,000°F. Cast iron, which is most likely the material from which the Dutch oven is made, melts at a much lower temperature, so you risk melting the device (along with the housing, unless it is refractory lined).

Harold

 

[Geo]

in a closed container (even lightly contained), without oxygen, there cant be an explosion. once i started the burn, i dont disturb anything until the next day. it leaves a lot of carbon behind to deal with though. ive stopped using it for chips but i still use it to pyrolize small copper coils.

forget about the forced air part. if you ventilate the bottom of the drum, the draw from the heat rising provides a good air flow.

 

[924T]

Harold_V,

Thanks for weighing in on this!

I'm not familiar with a cupola, but while on vacation in Kentucky last year, I came across a pre civil war
iron ore furnace (a massive stone structure, maybe 45 feet tall), and the historical marker showed how
the furnace had been filled with alternating layers of wood or coal, ore, and I believe something else, too.
I may have a picture of it somewhere.

So, your description of a cupola did make sense to me.

I didn't stumble across the several posts about the explosive potential of the smoke from I.C. chips on the
forum until about a month ago, and am I ever glad I asked the question about a forced air burning environment,
because I was planning to do that.

You've helped save a rookie from disaster!

Cheers,

Mike

 

[924T]

Geo,

Thanks to you, too, for weighing in on this!

I was thinking that if my suspicions were correct, since I'd already bought a 55 gallon steel drum, I'd just
make some holes around the bottom to provide air flow that way (would that correctly be called 'passive' air flow?).

So, thanks for warning me off about the forced air.

You mentioned you had a lot of Carbon to deal with from your process-----did you mean carbon from the
oak you used as fuel, or the Carbon left in the pyrolized chips?

Cheers,

Mike

 

[solar_plasma]

Considering a burning house is nothing else but some kind of pyrolysis and incineration oven, this article may provide some additional insights to this topic about the behaviour of smoke gas:

http://www.firetactics.com/FLASHOVER_answer.htm ...especially from chapter 7.

 

[Geo]

carbon from the chips. the wood burns clean leaving a fine white ash. the carbon left from the chips is very brittle and you can crumble them with your hands. if you mill and pan, it should still work ok with little problem. thats the main difference between pyrolizing and incinerating. incinerating leaves fine white ash due to the carbon being converted to carbon dioxide in the presence of oxygen. without the oxygen to oxidize the carbon, the chips are still black when you finish but all the oils and resins have been baked out leaving the brittle carbon behind.

 

[bswartzwelder]

The initial load in your Dutch Oven consists of chips and the air surrounding them. As the Dutch Oven heats in the fire, the air inside will heat up and expand. Since this air contains approximately 21% oxygen, if it mixes with the gasses given off by the chips, it is possible bad things could happen. Another forum member, Deano (aka NoIdea) has quite a bit of experience pyrolyzing/incinerating chips. He recommends adding a small amount of water to the chips before you put their container in the fire. The water will flash to steam and drive out all the oxygen in the container. No oxygen, no explosion. To me, this seems like a really simple, cheap, yet effective means of getting rid of the oxygen which could cause major problems. Once the gasses generated by the pyrolyzing chips escape the Dutch Oven, they can mix with oxygen drawn into the fire from the atmosphere and burned safely thereby greatly diminishing the risk of an explosion. Two added benefits: burning these gasses cleans a lot of the nasty chemicals found in them and acts somewhat like an afterburner, and since the gasses burn, they add fuel to the fire surrounding them. One of Deano's pyrolyzer units used propane as a fuel and once everything got nice and hot, he turned off the propane, thereby saving fuel until the process was almost completed. He did have to turn the propane back on near the end of the process when there simply wasn't enough off gassing to continue the burning process without additional fuel. From all the Dutch Ovens I've seen, they do not have airtight or pressure tight lids like in a pressure cooker. Pressure cookers also have a gasket around the rim to seal in the pressure. With a Dutch oven, as any pressure builds up inside, it would cause the lid to lift slightly allowing the gasses to expel (burp off) as there is no gasket to seal the top and bottom of the Dutch Oven. It is even possible the lid and the body of the Dutch Oven have small gaps whereby the gasses can escape. I don't think Dutch Ovens and their lids are machined to close tolerances. Hope this helps.

 

[924T]

bswartzwelder,

Yours is a really good in-depth explanation of the process----thanks!

I do have another question--------the other reason I bought the cyclonic burner head was that in the
manufacturer's (Elastec Marine) literature, it described how they safely and routinely incinerate plastics, as
well as other trash, with it.

I was theorizing that, if nothing else, I could incinerate the plastic surrounds from IDE cable sockets,
such as are found on mother boards, floppy drive boards, CD/DVD boards, hard drive boards, etc.,
leaving the pins free of plastic, to then further treat them electrolytically or in a stripping solution.

Having gone far enough in my learning curve, courtesy of the forum, to realize that any assumption
could be injurious or fatal, I would welcome any and all commentaries on this.

If it turns out I'm off target, at least I'll be able to burn trash and yard waste, with vigor.

Cheers,

Mike

 

[FrugalRefiner]

I do have another question--------the other reason I bought the cyclonic burner head was that in the
manufacturer's (Elastec Marine) literature, it described how they safely and routinely incinerate plastics, as
well as other trash, with it.

GSP safely and routinely recovered gold with cyanide because he had the proper equipment and the knowledge to use it correctly. That doesn't mean it would be a safe process for me. Many burners can be used, but whether the system is safe depends on many factors beyond the burner.

I was theorizing that, if nothing else, I could incinerate the plastic surrounds from IDE cable sockets,
such as are found on mother boards, floppy drive boards, CD/DVD boards, hard drive boards, etc.,
leaving the pins free of plastic, to then further treat them electrolytically or in a stripping solution.

My first comment would be that incinerating any plastic presents the same problems as incinerating chips. They will all put off varying quantities of toxic fumes. That's why I advise pyrolyzing plastics first, then incinerating the carbonacious remains.

Having said that, it seems like the pins might be adversely affected by the heat, melting of the plastic, pyrolyzation, incineration, etc. during the process, resulting in some "dirty" pins at the end. The heat could cause the base metals and the plating to become more of an alloy than plating, making recovery more difficult. I've never tried it, but it may not be the best way in the end.

Dave