Im working on the next version of the kiln. This is also going to be kit I offer. So basically what Im trying to do with this is integrate a TLUD concept into this kiln but with a bell over the top to contain the smoke and also reclaim more heat . I have few issues but I think the concept was working. I have a few issues I need to fix, one is there is interferance with the grate as thing gets hot grows or warps or what ever its doing. haha. I just cant shake the grate, I think the centering is too deep and is grinding on the grate bars. The grate spacing I think is too tight. So Ill address both when I re build this grate. Right now it has 4 inch spare spacing. Im going to measure the proto type and build to that spec and then cut down that center ring and hope that fixes that issue.
Ok I fixed the interference issue and widened the grate. Started test running and there was just too much smoke!! So opened up the second stage air feed by a lot! Went from four 3/4" tubes to twelve 2 inch holes; It worked but still a bit of smoke. So pulled it outside and took the top off. After running it that way I think I was just fiddling with it too much!! Need to just let it be and do its thing haha.
On the outside run I easily got a 1;2 yield I would say thats pretty good considering this is factoring in the energy to produce the fuel? I still had fuel in the fire tube when I harvested the barrel;. So 20 gallons of chunked wood in and 10 gallons usable charcoal out. Further development and automation Im sure will improve this.
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This here I think is before I started tuning the second stage air feed !
Hi Matt
between the first version and the last version, you have moved the series of holes for the secondary air inlet from the top of the barrel to the middle of the barrel
for what purpose did you do this?
The holes in the first version in the video are irrelevant and serve no purpose. The barrel was re used from an earlier outdoor kiln and they were used at the lower intake air feed. When I built this first version with the bell I flipped the barrel as the grate has the inlet holes for the primary air feed.
Now the second or I guess maybe the third version, those holes are exhaust vents for the gas to bypass the fuel in the hopper so to not oxidize it. the top of the barrel is closed off and the gas exhaust out those holes and heat the hopper.
Yeah I am now processing the fuel a bit finer now and I am easily getting back 60 to 70% of what I feed into it. Oh and plus I get plenty of heat for the shop in that process. I ran it for five hours today. Fed that thing Roughly 30 gallons of roughly 4 inch X 4 inch slat wood and I harvested 20 gallons. This is with the damper throttle down so I dont know if this will change in the convertible mode or not. I know it processes a lot faster in that mode though, Its about two to three times faster in convertible mode where the bell and chimney set up is a lot more restrictive.
Also note I revised the second stage air feed as well. The four pipes you see are not nearly enough air supply to feed that second stage. Not even close, I removed them and ended up drilling big two inch holes all the way around the top of the base in an array that is between the fire tube and the shroud barrel.
Exactly, its a BLUD though. Primary air feeds into the grate for primary combustion. The resulting combustion gases migrate out the exhaust holes of the fire tube and then the second stage air feeds through the big holes I drilled for the second stage combustion process. Then this gas flows between the fire tube and the shroud barrel to apply heat the hopper. Only 1’/3 of the fuel is subjected to oxidizing in the process.
Matt. I built a stove inspired by yours. I can collect charcoal and cook the grain of our pigs, but I cannot achieve a smokeless burn. I have tried different primary air adjustment without results. I cannot adjust the secondary air. My wood is dry but it is very humid here (100% H / R). Could atmospheric humidity be the cause of the lack of secondary combustion?
Thierry
Is that lid covering all the way to the outer barrel? That wont work that way, you only want to cover the fire tube / hopper barrel. The outer barrel needs to be open.
If you are only covering the center fire tube. Then I would suspect you are not getting enough air in through the grate to feed the primary combustion. To much secondary air feed will cause a bias flow favoring the second stage air. So it is probably a balancing issue.
Can you post some detailed pictures? I cant see what you got going there. Need to see how it is built and need to see your fire tube with exhaust holes .location, size of them in relation to the secondary air feed.
You may need to create openings that vent into the grate. Air does not feed directly through my grate, there are air holes around it it needs to be very passive so the second stage air does not overcome this air feed.
here are some pictures as requested. I hope they answer your questions.
The primary air passes entirely through the grid. This is the space between the charcoal pot and the grid that allows me to adjust the primary air P_20210427_181300|666x500
Oh wow that is a nice build. I think you just need bigger holes for the fire tube exhaust. Also how is air feeding the bottom of the second outer barrel?
Edit: I see through the chimney. Yeah just open those exhaust holes up. But looks like you are making charcoal with it.
This is a video about how I make charcoal fuel. When I set the phone up on something to record the grinding and sifting it only shot the top half of me so the grinder spitting out pieces and the sifting are audio only while you get a view of the Northern Michigan sky. Probably just as well. Sometimes I forget to wear pants. I made some better still photos of the metal parts that shows in the video. I am rebuilding it in all metal. It works well enough that I’m not going to bother building anything more elaborate.
Pictures of the actual grinding mechanism of the above video. Also the screen for sifting. That is just a wooden frame with expanded metal nails onto it. I pour the ground char into it and stick the rotohammer on the edge of the frame. No real work involved.
Pictures of the actual grinding mechanism of the above video. Also the screen for sifting. That is just a wooden frame with expanded metal nails onto it. I pour the ground char into it and stick the rotohammer on the edge of the frame. No real work involved.
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