Hello charcoalers, I have done some experimenting with my clay lined charcoal kiln, but I have stopped up the holes, and Im using it as a pyramid kiln now. This seems to me to be maybe the best way I have yet tried to make charcoal without smoke. Here is a short video of me loading it.
The insulation makes it get really hot, so the burn is always quite clean. (Although I suspect it would do just fine without). I add wood every 15-30 minutes - as much as 5 gallons at a time. It does not really need to be tended, I did this batch today while backpack spraying, and would just toss on more wood when I was back to refill.
Once it gets up to the top, and mostly burned down, I put on a scrap of sheet metal to burn off the last woodgas without letting as much air in to the charcoal. This takes a little longer, but I feel like it is worth it. I weighed wood in and charcoal out on a small batch yesterday, and got an impressive 24% conversion by dry weight.
Todays batch took me 3 1/2 hours, but I got almost 3 hours of other work done, so it is pretty time efficient if you can work on something else nearby. I will weigh the yield of this batch tomorrow, but it should be in the neighborhood of 30 lbs - or roughly one 30 gallon steel garbage can full.
I am going to try and improve on the clay lining, as it has an annoying tendency to flake off little pieces, and it needs a bit of patching up after every couple of runs. Scooping out the finished charcoal is also kind of a pain, but not terrible. If I devise a more robust lining, it could maybe be tipped over. Otherwise, I feel like this is the best method I have tried so far. It is very similar to a cone kiln, but I like being able to partly cover the top at the end to finish the brands, and then cool it in place. No handling searing hot coals, or dousing with water.