Welcome, Rick.
I am concerned by the number of 90 degree turns you're demanding the exhaust stream make. I also don't think you need such an elaborate approach to heat your retort, although I do think one thing might have been omitted that you might want to consider.
I am unsure why you don't just stack the barrel retort atop the barrel drum, as heat rises. I think you'd need to insulate the retort heavily, and I would wonder about the long-term viability of any sheet metal in the exhaust stream, but if your insulated drum oven with biomass pyrolising inside sat atop the bell, perhaps with the bottom quarter or third exposed to the exhaust stream at the top of the bell (sitting inside a depression at the top of the bell made for it), it would cook nicely.
All that would be required is a couple of one-way pressure relief valves, with repurposed bbq venturi tubes taking the retort's
wood gas exhaust to the burn tunnel. You could even have a mechanism by which you raise or lower the frame holding the retort up or down in the exhaust stream, to raise or lower the temperature, and to allow for easier lighting at the start.
You could even have a bbq or oven thermometer installed into the top of the retort, so you know how hot the coldest part of the retort is getting.
No masonry shrapnel bombs, no undercooked charcoal. And to move, or to empty, you could at least arrange something, a yoke or framework, to catch and lower the vertical retort ninety degrees for loading or emptying. If it was already suspended from a frame for raising or lowering, it could easily swivel from it's centre point at the highest extent of its travel ninety degrees and then be lowered to rest across its socket, which could be designed to have two rests cut for the drum in its loading/unloading horizontal state, corresponding with semicircular plugs of whatever mineral insulation on the top drum, probably that oven insulation stuff, shaped to fit together in the vertical orientation.
Having dealt with complex exhaust streams in the past, I am just concerned about how you'll get it started. That's a lot of twists and turns for the exhaust stream, a distinctly non-rockety thing at the beginning of a system.
Do let us know, though. The advice offered regarding capacity is sound. I would worry about safety with regards to the metal involved using any larger than an 8" system. If everything metal melts, that's a bad day for your
project. Unless you get it on video and monetize it somehow. But imagine a retort of cooked charcoal melting into the top of the riser and falling into the burn tunnel, all that ambient oxygen rushing into that previously oxygen-starved pyrolysis environment. I have never seen it happen, but I know charcoal is explosive as all hell, and a 55 gallon barrel collapsing would generate a lot of charcoal dust.
Charcoal is dangerous on its own, in a traditional artisanal setting. Please be very careful in your experimentations, whatever you do. Keep us posted, and good luck.
-CK
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
-Robert A. Heinlein
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