branchburner said:
In a way it's really not surprising there is more creosote with extra-dry wood in a conventional stove. Without a mechanism for sustained secondary combustion, the fire cannot consume quite as much of the increased level of gases - those gases are more rapidly released from the drier wood.
But the table sure shows why old timers who burnt hot preferred burning green oak to dry pine. The numbers are really fascinating.
So, is the whole idea for the secondaries to catch the smoke that escapes the primary burn zone and burn it before it escapes the stove entirely? Or is it to generate a dense as smoke as possible in order to have awesome secondary flame displays? Just because you have a high-tech vacuum system doesn't mean you shouldn't wipe your feet before you come into the house.
I can see no practical advantage to deliberately generating super dense smoke just because you have an EPA stove. You have to burn that smoke or let it up the flue, no getting around that. If you have too much smoke, you need to add a lot more air to burn it, and that will make too much heat. If you don't give it enough air, it will not burn at all and will end up as wasted heat plastered to the walls of your flue.
All devices that burn gases (and that is really what any stove is doing) rely on getting the the right air:fuel ratio. Too much air just may burn everything, but much heat will be lost up the stack in the process. Too much fuel and there will surely be air-starved pockets that escape combustion, and those gases will be carried away into the outside air. Maybe someday someone will invent a device that automatically feeds specially made, highly compressed tiny cylinders of very low moisture content wood fiber at a precise rate into a carefully designed burn pot that is fed the ideal amount of air, but until that day...
I think this info is fascinating as well, and unlike the above poster, I feel it is entirely relevant to a discussion on secondary burns. It's quite obvious to me why that is so, or I wouldn't have included it here. The pine thing was of particular interest to me because I recently came upon a reference in an old wood burning manual about pine creating more smoke/creosote. I thought we had laid that one to rest, but it appears the old manual had it right.
As far as the old timers, most of them were out to lunch. They liked green oak because they could burn it real
slow and get heat all through the night. As the table shows, oak makes more creosote at higher moisture contents only during a low burn. It's cleaner at medium to high burn rates. Many old timers were stingy with their wood and burned low and slow all the time. Besides, additional moisture will only help up to a point, unless you have an incinerator. As wood continues to rise in moisture beyond 30% MC, it suffers increasingly more sluggish burns until you get to a point where it won't burn at all and will just sit there and smolder. The table only shows up to 25% MC, hardly green. In fact, wood at that moisture content is well within the range an EPA stove is designed to handle. OTOH I'm sure green oak (80% MC) in any stove will produce a long, smokey, creosote-laden burn, and that's what used to be the norm. That, and a good ol' chimney fire every morning to clean out the plumbing.
