Lots of interesting thoughts, I don't have many answers though. From what I've gathered, the air needs to be preheated. I don't think it's enough to just bring it through the load door, as lots of stoves do that, but few are truly successful at burning volatiles until things really get hot, and then you have to really keep things hot to continue to burn them.
I read a really old publication on industrial applications for reducing smoke in stokers, and they were eyeing the 350F to 400F range for preheated air temps. I guessed it would have to be hotter than that, but I'm not sure.
Yes - we all know we can get ignition of the gasses when you open the load door after a fresh load, but it's hard to maintain that situation with my stove and my coal. Things above the fresh coal cool too much after a fresh load, and it takes an hour or so to get the "boom". Lots of soot and smoke occurs during that hour. Hence some bank the coal bed to avoid the boom. But I still wonder even with banking if you do a good job of burning volatiles, or if they just go out the stack.
Pete69 wrote:What about the idea of adding combustion air into a preheated secondary burn chamber/heat exchanger like the Vermont castings vigilant that is rated to burn low to mid vol ital bitt. coal
Or using your existing design with the addition of a secondary preheated burn chamber?
I guess I thought I was trying to do what you are describing, my burn chamber being all the piping I've drawn.
Regarding your statement about passing secondary air through passages on the outside or back of the stove - with all the firebrick in the stove to direct the heat back to the coal bed, it seems that any outer pipes would remain relatively cool compared with pipes "inside the firebrick".
I'll chew on it all awhile yet, and hopefully others will chime in with even more knowledge. Thanks for the replies.