Michael Dance

William Bronson wrote:I think your stovepipe should be plenty good enough and that much copper is more valuable elsewhere,  even if only as scrap!

It’s a fraction of the total copper I have from the still parts, and large kettles for reducing cane juice for panela, or rum 😉. I’d rather make use of it as is than scrap it.

Based on observations in another forum, on the function of chimneys, and ratio of air intake area to chimney outflow area, the copper chimney seems a better fit.

Though I am still open to further suggestions, with supporting data.

Before I had any other kiln options, I experimented with making small batches in a ceramic cauldron, inside a wood-burning pizza oven. Worked OK. Better results than my first batch in a 55gal drum.

Having trouble attaching photos to post. Just figured out how to minimize the file size. Let’s see if this works.

Can anyone share the advantages/disadvantages of wider/narrower, or taller/shorter chimneys?

As I’ve mentioned in previous post(s), I’m putting together a modified tin-man, a brick-man, if you will. Outer oven/kiln of fire bricks, with inner stainless steel retort.

I have two possible chimneys on hand. One is a stove chimney (either galvanized or stainless), 5 1/4” (13.3cm) diameter by 34” (86.4cm) tall. The other is a copper chimney from a still, 12 1/2” (31.75cm) diameter by 38” (96.5cm) tall.

My inner stainless retort is about 15” (38cm) diameter. And the brick kiln interior dimensions will be 25.6” (65cm) length x 20.5” (52cm) width x 35.8” (91cm) height.

None of the above. I don’t really have a lawn, but I have a lot of grass to cut, some of which is lawn-like once cut. I use gas weed-whacker with string, gas weed-whacker/brush cutter with blade, and/or a machete, depending on conditions.

John Suavecito wrote:I hope you take pictures so others can try this design or develop their own version.  I look forward to seeing it.

I will try to take photos while building it. And depending on how it turns out, maybe a video with description and a burn, incorporating those photos.

John Suavecito wrote:I agree with William about how much extra work it would be to continually move bricks each time…

The retort is great if your priority is to be able to leave it and let it go out by itself. That isn't my priority.   My problem was that it didn't make enough biochar for my needs in my garden.

Thanks John.

I’m not planning on moving the bricks. They will be a permanent structure making up the outer “drum” of the kiln. The stainless drum will be placed inside. Then a metal lid and chimney on top. Only have to remove the chimney and lid and lift the inner drum out. I expect the inner drum to be less than 8kg, empty, maybe double that when full of processed biochar.

My rainy season is most the year. So I want to be able to fill the retort and outer kiln with material and light it up, when I have a couple hour dry window. Then it doesn’t matter if it starts raining while it’s going.

William Bronson wrote:I think removing a barrel from inside of a brick chimney would be a pain in the butt.
This design would be easier to unload:

https://www.google.com/amp/s/www.instructables.com/How-to-Make-some-Charcoal/%3famp_page=true

As built, they use cement board.
I am not sure how durable that proved to be.
Your bricks  should be fine.

Something that is close to your initial idea is this :
https://youtu.be/NrTaISI9fm4?si=vf3I2S0aCyq87OjY

Thanks. Not really interested in the first method. For my climate I think the fully enclosed kiln would work better.

I based my idea on the method in the video you shared. The video is 8 years old. They haven’t responded to questions, which is why I asked here. That brick chimney design has a lot more space between the brick outer oven and inner retort bucket for filling in fuel, than does a 55/30 gallon tin man. It seems excessive. I’m trying to find a happy medium. With some input from people who have used these types of retorts.

I’m not going to be using a 30 gallon steel drum, but a custom made stainless inner retort. I can have handles fastened to the upper sides, or one on top. I don’t think it will be too difficult lifting it out when it’s finished and cooled. As long as I have sufficient space between the inner retort and the brick chimney.

Happy New Year Permie Biochar enthusiasts!

I tried a simple flame cap burn in a 55 gallon drum on its side with a panel cut out of it. Not real happy with the results. A lot of partially burnt wood, not fully pyrolyzed. I think my very damp climate makes it difficult to get the wood dry enough for this method to achieve the heat it needs. And also some user error, as this was my first time with this method. And a few other cons I won’t go into.

Anyway, I’d prefer a kiln retort like a tin man. However, I don’t have a ready source of 55 or 30 gallon drums to replace as they break down from oxidation. I want something more permanent.

I will have a craftsman here make an inner retort drum of stainless steel, so it lasts a lot longer. And build my outer chamber with fire bricks, for better insulation.

Two questions.

The common tin man uses a 30 gallon inside a 55 gallon drum. I don’t have a 30 gallon to measure, but online sources say the standard size is about 46cm diameter by 70-75cm height. Based on a standard 55gal, that only leaves about 5cm between the inner and outer drum and about 15 cm on top of the inner drum to squeeze in the wood fuel to fire up this process.

Seems a bit scant to me to achieve temps of 550ºF+ for pyrolysis.

I can have my retort fabricated to any size, and also build the outer brick kiln to any size.

Is there an optimum size, or space between the inner and outer drums, to get a sufficient but efficient burn?

And how many holes are recommended for the bottom of inner drum? I’ve seen suggestions of five 1/2” holes in the 30gallon. Would more holes of smaller diameter, say seven to ten 3/8” allow a more balanced release of pyrolysis gases, less chance of bursts, but still prevent oxygen from entering?

Thanks for your input.