Steve - You didn't offend me. I was merely appalled at the notion a professional woodworker would consider placing such a thing in a wood shop or any habitable building. I'm all for free heat, recycling, and such, but there is a limit.
It is curious that you are not insured because of the dust in the shop air. So now you are going to have a cherry red surface in contact with that air? My friend, do you have any idea how catastrophic your proposal looks to an observer?
There are accepted, proven ways to burn wood (even sawdust) for heat, and you need to understand that you are not going to uncover the Holy Grail of woodburning - there is none to discover - the science is all known.
I also have done quite a bit of research into accepted, tested and proven methods of burning sawdust, and it is done every day, 24 hrs a day, and all UL approved. I was searching for a way to recycle dust and scrap for heat in a 20,000 s/f shop after the conflagration described below. But the proper equipment used is nothing like your bona fide contraption.
I have seen what happens when the oxygen regulation fails on a home built heater (as GTO mentions). I once worked for a self made man (read: could not be reasoned with) and he decided to build an 8' x 8' x 20' 12" thick concrete box with a 12" x 12" chimney, to burn bundles of kiln dried rippings, dropped in from the top. He added two 8'x8' 1/2" thick plate steel lids on top, that could be opened with pulleys.
I suggested a small fire to see how the draft worked. This only spurred him on to load it up completely (he referred to me a 'college boy'). The fire was set thru a couple of 6x12 HVAC dampers (seriously), and it took off almost immediately. Once the 1/2" plate steel lids curled up and let in uncontrolled oxygen, the thing roared like the space shuttle. Fire departments from all around converged. They wouldn't put water on it, but sprayed down everything nearby to prevent ignition, while evacuating the area all around. The self-made man scurried about, mumbling about how we didn't do something or other correctly, the thing should work. The concrete cracked, the concrete pad turned to powder, the thing was nothing but expensive wreckage. We never mentioned it again.
Working the bugs out, indeed.