“Charcoal!”, he retorted.
This is my first foray into high-tech low-tech clean charcoal production but I am stoked to try it out.
For background information on fuel alternatives, see the post entitled: Sustainable ‘Smithing?. For this project, I visited the good folks at Demxx and picked up a steel drum along with a 6″ diameter steel pipe about the same length as the barrel is high, intending to build my own version of some of the retorts I have seen online.
The construction is similar to a rocket stove, but with an additional chamber around the combustion chamber. The steel pipe is the combustion chamber and the charcoal wood will be around it, inside the drum. Air will enter through holes around the bottom and be drawn into the pipe by the heat draft. Wood gas produced by the heat of the fire in the combustion chamber will be forced out through the bottom of the barrel and drawn up into the pipe where it will become fuel to sustain the reaction until the charcoal is fully ready. That is the theory…
My design had to be simple to assemble and disassemble, and had to require no welding and very light-duty torch work at most. I used the mini oxy-propane torch to cut a circle in the top of the drum and carefully enlarged it until the pipe fit snugly. I cut a smaller hole in the bottom and heated and hammered it into a lip that will catch and centre the bottom of the pipe and direct wood gas up into the combustion chamber. Next I cut off the bottom with a cold chisel and cleaned it up with hammer and shears.
The drum was dented on one side so I pushed it out with a jack and hammered it closer to round again. The drum formerly contained palm kernal oil and there was about 2 litres of it left, about the consistency of butter, so I scraped it out into a container (soap making, anyone?).
I cut 2 lengths of angle iron and matching triangular slots on the bottom sides of the drum. The angle iron will slide under the bottom lid of the drum, holding it and the pipe up, and the triangular openings will provide air to the combustion chamber.
After the burn is complete it will be simple to seal the air intakes with soil but the one concern I have is whether there will be a correct flow volume ratio during the burn to keep wood gas coming out of the charcoal chamber without allowing oxygen in. I think I have a connection for some pine scraps to produce charcoal from so tomorrow will hopefully be a test run day on the charcoal retort 0.9 beta.
Find out about the construction and operation of our new and improved charcoal kiln: Charcoal Kiln V.3