Ok I built a small kiln for you guys as an example of how to build my version. There are no plans and you dont need them. You just need to understand the basic principal of it and you can scale this as big as you want. Here I built a small unit out of a 5 gallon steel bucket and a 10 gallon steel drum.
The basic construction I came up is very simple. You simply use threaded to fasten this system together and I used some steel 1 inch square tubing as stilts to hold the unit up so that you can fit a catch bucket under it to catch the charcoal as it is produced
So now you are ready to fire it up and make some charcoal. This small version did not run hot enough to close off the lid so I had to run it as an open top system.
I post vide of the larger kiln kit we offer with the closed top in action here. If you are successful this is how it should work.
For the grate I just bent some 3/8 rod into a triangle to fit inside the fire tube and rest the ledge. This is all you need for a grate, it must a very passive grate in order to allow the charcoal to fall through as it become brittle enough.
Next is to create the shroud. This guides the combustion gases along the fire tube to direct as much heat to it. This also shields the wind. This I simply cut out the bottom so it has an open top and bottom.
Next is to drills holes for mounting the fire tube inside this shroud using a threaded rod and then installing the support stilts.
Ok to start out the 5 gallon steel bucket in this example is the fire tube / fuel hopper. I cut out the bottom leaving a 1 inch ledge, this so you can install a grate that can sit on this ledge. Next I drilled an array of holes for the air intake for the oxidation zone. This feeds air in at the bottom to feed the primary combustion process. Next I drilled a second array of holes for the exhaust about 1/3 the way up from the bottom. This is to exhaust out the combustion along with pyrolysis gases produced from heating the fuel in the upper portion of the hopper. This is how you create the charcoal without fully burning it to ash.