Making charcoal with the Twin-Turbo Thermowoodclear Fission Reactor
Equipment: 1. 55 gal drum, no top, bottom optional. Pinholes and rust ok. 2. 2" pipe, 4' long 3. 2" pipe, 4' or longer 4. high volume blower. Old vacuum cleaner works good. 5. low volume blower. An old computer fan, 4 or 5" dia., or a blow dryer. 6. welding gloves 7. retort. fancy chemist name for "cooker" 8. grate for retort to sit on in the barrel. or three sacrificial bricks 9. 8" concrete block 10. flamethrower, weedburner, or other suitable lighting device.
Safety precautions: 1. Don't be too drunk. Things are going to get pretty hot. 2. Remove all flammable materials for four feet all around the drum. This includes grass, leaves, and dirt. 3. Stretch out a hose with a good nozzle, and turn the water on. 4. Don't do this under a tree, or in the carport.
The Retort No, it's not a smart answer. It's a sturdy container that can stand being red hot for a few hours. It needs a tight fitting lid, and holes for gas to escape. a 15 gal grease drum will work a few times before burning out. No paint, galvanizing, grease or other contaminates can be inside the retort. It also needs a means to be made airtight at the end of the process. This can be as simple as setting it in a bed of sand, if the holes are in the bottom. Mine is made from an old water heater, 16" in dia, cut down to 24" long. The rim of the original top is flared out with a hammer to fit down over the sides snugly. Three 1" wide steel straps are welded onto the lid, and screwed into the sides. The original 3/4" pipe connections remain, to let the gas out. I cut a 4" hole in the top and bottom for a 4" thinwall steel chimney. The fit between the retort and chimney is very good, with only a tiny crack. A gas water heater would have been ideal. The barrel is 22" I.D., leaving 3" between the retort and barrel sides. Four 3" long 3/4" pipe stubs are welded to the bottom edge of the retort, to maintain this gap and keep the retort centered in the barrel.
The Grate This keeps the retort about 5" above the bottom of the barrel. Three bricks on edge in a radial pattern will accomplish the same thing, but the operating procedure will be slightly different. Either way, don't use something irreplaceable. Things are going to get hot.
The Barrel The barrel serves to contain the coals that start the reaction, the resulting gas, and direct the flame around the retort. Make a hole in the side at the bottom edge to insert the longer 2" pipe. Make another hole 1/3 of the way up the side for the 4' long 2" pipe. Insert the pipe, and use it to bend the barrel so that the pipe is tangential to the barrel. This is real easy with a rusty barrel.
Charging the Retort Stack your char wood tightly in the retort. Small gaps between pieces are needed to allow gas to escape, but the wood doesn't need to be loose. Small chunks, about 1x3x3 work well. End grain pieces tend to crumble. Any hardwood will work, but stay away from pine or sweetgum. Don't make it too heavy to handle. Mine weighs 120# loaded, and that's as much as I care to fool with.
Charging the barrel Stack fuel wood closely in the bottom of the barrel, under the grate or on top of the bricks. Leave a passage at the bottom hole for the lighter flame and air to enter. I make four or five layers of 1x3 boards stacked at right angles, with about 1/4" between boards in each layer. Set the retort on top of the grate (or wood, if you're using bricks), vent holes down. Yes, my retort has holes in the top, so it goes upside down. The four pipe stubs at the bottom make good handles, and keep it from tipping over. Poke the 4' pipe into the upper hole, and rest the end on an 8" block. This causes it to point up at a slight angle. Add a few pieces of fuel wood all around the retort. Don't pack it.
Firing the reactor Light the weedburner, and poke it into the bottom hole in the barrel. Give it about ten minutes to start the wood, then pull it out, and poke in the pipe. Apply the high volume blower until the barrel begins to glow. There should be some smoke and a little flame coming out of the barrel. Move the high volume blower to the upper pipe, and apply the low volume blower to the bottom pipe. Air from the upper pipe will direct flame around the retort in a spiral, heating it all the way to the top. When the wood in the retort heats up, it produces water vapor and combustible gas. The gas is heated by the wood coals at the bottom of the barrel, and burns when more air is added by the upper pipe. The coals burn down, more and more gas is produced, until the process is fueled by wood gas alone. If you can peek in through the hole at the bottom of the barrel, you will see jets of flame coming out the vent holes. Do not allow the wood coals to burn completely out. Add a little more wood, if necessary. These coals will be needed later. After about an hour and a half, all the more volatile compounds in the wood have been driven off. You may notice black, sooty smoke and the smell of creosote. More heat is needed to combust the gas, so add some fuel wood around the retort. The last remaining wood coals will help light this new fuel wood. By the time this wood is burned up, the charcoal will be finished. Don't add too much wood, or you'll have to wait unnecessarily. When the fuel wood coals are burned out, let the retort cool enough to remove from the barrel. Use the welding gloves, and be careful! Seal up the retort by setting it in sand. Wait several hours for it to cool before opening it up. If you open it hot, or any air leaks in, your charcoal will burn up! Be patient. After the retort cools, open it, and spread the charcoal out on a non-flammable surface to cool completely. A sheet of roofing tin works well, and can be folded up to funnel the charcoal into a container. Check carefully for any hot spots that might ignite, then store it away. Don't discard the "fines"; they'll burn quite well when added on top of a good thick bed of burning coals.
Conclusions: A 50 # charge of hardwood yielded 22# of charcoal. A 20# bag of commercial lump goes for about seven bucks. Was it worth it? I think so. I took waste material that would have been needlessly landfilled, and created a useful product, with less emissions than many commercial kilns. I also know exactly what went into this charcoal, which is important - what you burn is what you eat, and I've found some nasty stuff in bought bags of lump. There's also the pyrotechnic entertainment value, as well. Run a batch at night, and I think you'll agree!