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Will W.

Questions about a charcoal retort

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Hello all. I've been thinking about making a charcoal retort for a while now, because I prefer charcoal to coal, and it's expensive to buy. I would rather put the time and energy into making my own. I found a picture of what I was thinking of making. 58e91700bb32f_charcoalretort2.thumb.PNG.9cfb019b119a67d39388a31f2f34ce04.PNG

This. My main design change would be a ball valve placed halfway on the vertical section of pipe, to close off once the charcoal is finished burning off. 

Now, does anyone have experience making and using a retort similar to this? My main concerns are if the 3/4" pipe and 1/4" holes recommended here will be large enough to properly vent and burn the gas (I don't want to build a pipe bomb) and what exactly would stop the fire made by the combustible gases from traveling back through the pipe and into the charcoal chamber? It seems to be an efficient design, in my mind anyways. Once the gases become mostly combustible and the water vapor is mostly gone, the process would feed itself, requiring less sacrificial wood. Yes, I've read the stickies, and the designs there were different from this one. Also, all of the pics in the stickies, I was unable to pull up. It said "file not found." Not entirely sure why, but I'm not very technologically savvy. 

Thanks for looking!

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If I were building a charcoal retort, I would probably look at the Hookway design, which (like the one you describe above) reburns the gasses from carburization, but feeds them into a central firebox/chimney. The basic idea is that you build the initial fire, which then is augmented and replaced with the fire from the combustible gasses. Once carburization is complete, the fire goes out, and (since there is no air inlet into the retort to cause the charcoal itself to ignite) the fire goes out.

I posted a thread about this last year; take a look: https://www.iforgeiron.com/topic/43490-hookway-charcoal-retort/

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The pipe complicates things and the amount of volatiles produced add little to the combustion process.

A plain flat lid with a hole to vent it and some weights to seal it works fine, When it stops steaming and starts smoking just offer it a flame and it'll burn off the volitiles, when the flame goes out it's an indication that the process is complete, coer the hole to stop any air entering and you can damp the fire or let it burn down.

I just use two cans, a slightly smaller one with the charge and a larger one (as near a fit as you can find) as a lid, I sit it in the fire and the gases vent at the bottom of the up turned lid. Any sizes of can works and if you can only find smaller ranges of cans (which are easier to handle) you can stack a number of "mini" retorts if your fire is big enough.

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JHCC 

I actually stumbled upon that design. I considered it for a while, but then thought up this design (obviously wasn't the first though!) It seemed like it would make a burner almost like a propane BBQ underneath the barrel, but I'm not sure exactly how effective it would be. I'll reconsider my options. I kind of forgot about the Hookaway design so thank you for re introducing me. 

Smoggy

My whole thought process is to use the gas that you're offering a flame to. Once it's burning, use that heat to make more gas, more flame, more heat, yada, yada, so you don't have to keep sacrificing wood for your heat. This design just seemed pretty efficient *on paper.*

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if your worried about flame travelling back up the pipe just put a piece of wire mesh into one of the joints to act as a flame stopper. the gas will pass through it but flame won't go back other way.

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On 4/9/2017 at 4:26 AM, PapaDooks said:

just put a piece of wire mesh into one of the joints to act as a flame stopper.

I could be wrong about this, but fire is a plasma, so I don't see how wire mesh would stop it. It seems, in my head, like pouring water over a grate. It just goes around the grate. Could you explain more? Is there something I'm missing?

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Yes there is something you are missing.  You may want to look at how a Davy Safety Lamp works. It's use in coal mines saved many lives!

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Mr. Powers is correct,

A wire gauze lowers the temperature dramatically. So the flame does not propagate through and past the gauze or mesh.

This idea is counterintuitive, but it works.

SLAG.

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Got a lecture on it when we toured a coal mine in Wales, (also pit ponies, etc...).  Then I found a complete Davy's safety lamp at the fleamarket in Las Cruces NM...

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No, fire is NOT plasma, it's fast oxidization. In a retort there is no oxy so flame can NOT travel back up the pipe. Using the volatiles from pyrolization has been the norm for a couple millenia at least. A screen or bend in the tube will prevent a backfire IF there's a chance it might happen.

What you draw is pretty much the norm for home build retorts. I recommend you use a drum with a lid and lock ring. just replace the rubber gasket with stove rope and it's converted. Look for the lids with a 2" bung. screw a street elbow in the bung, screw on a nipple that clears the side by enough to add another elbow for another nipple. Drill your burner holes in the long nipple I like them alternating off center down the length spaced maybe 6".

Then you want the "oven."  This retort is intended to lay on it's side with the burner tube under it. Stand it on a couple bricks or in a hole and cover it with light sheet metal, a saber saw and another 55gl drum makes a fine "oven."

Load the drum, dry split wood of reasonably uniform size works best. Lathes to separate staves is good it allows heat and volatiles to circulate and escape. Large chunks aren't desirable as the smaller wood will turn to dust before large wood pyrolizes. Leave room under the drum for combustion air so the volatiles from pyrolization can burn. The cover will help contain the heat and exhaust can escape from the end with the drum lid and plumbing.

Start the process with brush or other small wood it takes a decent fire to get the process working but once it does it's self supporting. When the flammable volatiles are cooked off the flame will go out. Let it cool before you open the drum!

People been doing this for thousands of years. This is called the "Indirect Method" of coaling wood. If you don't want to go to the hassle of a self sustaining retort flame just remove the bung plug, pile wood around the drum, light it off and when the flame at the bung hole goes out, rake the firewood away, cover the bung hole or stuff fiberglass insulation in it to prevent combustion air entering as it cools.

This is an easy process but can be fun to try inventing some high performance retort. IF you wish.

Frosty The Lucky.

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Thank you guys for explaining the wire mesh idea to me. I looked into it, and learned a lot about it. I had no idea. 

Frosty

My old chemistry teacher would be disappointed in me. Upon further research, flame is itself the chemical reaction occurring from the re-ox process. I don't know why I beleived it was a plasma. Amazing how some things must be re-learned! 

Anyways, thank you for the knowledge about the retort. Laying the drum on its side does seem more beneficial. If it were stood up as drums typically are, the wood on the bottom would be receiving far more heat than the wood on the top. I'll also add a cover ("oven") of some sort to contain the heat to my design. Again, the knowledge is appreciated. 

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Ah we all get stuck on a thought and they often turn out wrong. I could see exactly what you were thinking but a flame only looks like another state of matter. It's not so much a matter of needing to relearn as it is editing, I typically edit a post 3-4 times before sending. Since the TBI I'm a TYPO machine.

Oddly enough the retort seems to hold a pretty even temp top to bottom being closed. I prefer laying them on their side to increase the surface area of flame contact and the rising heat will follow the curve of the drum much more closely than vertical side. The vent doesn't need to be on top either the volitiles aren't leaving the room because of convection it's pressure differential.

Frosty The Lucky.

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That's sort of what I figured. The pressure differential will cause it to exhaust no matter what position the vent is in. Sorry to hear about the TBI. I hope it wasnt too bad, all things considered. Thank you again for the knowledge. Now I just to find a drum that is in halfway decent shape. 

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