Hi,
Secondary combustion is a proven concept, but the manufacturers dont want us to know how both because they want to sell us a thousand dollar stove, and because there is no way we could afford to have a DIY UL tested for "legal" installation.
In order to get secondary combustion we need the following:
A consistently hot primary fire. To get this a larger woodstove is helpful, something with about 10 cu ft or a little larger. Full firebrick lining of the combustion chamber is another way to keep it hot. Two methods used by the commercial guys are pre heated combustion air and non-airtight design. To preheat primary combustion air, they usually force the air to pass through a foot or longer pipe/passage that is heated by the fire. Non airtight design means that you cant(or wont) completely shut down the primary air supply. Always let in enough air so the fire has some healthy flames to it.
A way to introduce heated secondary combustion air to the smoke. This air must also be heated. Smoke wont burn much below 500f, so cold air almost never works. The DIY crowd likes using black steel water/gas pipe like they sell at Lowe's. This stuff is heavy enough to weld easily and holds a lot of heat to warm the air passing thru. I use 1/2 in pipe and drill 3/16 holes about every inch to introduce the air to the hot smoke. Will need some kind of valve to control the amt of air entering the secondary combustion area.
A secondary combustion chamber: Not all commercial stoves use a separate chamber for secondary combustion, but for us it increases the chances for success. One easy way is to include a smoke baffle that is sealed at the back and sides, and forces the smoke to travel to the front area of the stove before going up and out the pipe. The baffle is full width, and 2-4 inches from the stovetop. I make the secondary combustion chamber the width of a firebrick to make it easier to insulate. Many commercial stoves insulate the inside of the stovetop also, but this is difficult to do and usually just falls off anyway. If you want to try, ceramic wool is what they use, but there is really no effective glue so you might weld on some kind of wire or mesh to hold it up. I use 1/4 in. plate for the top so it takes a long time for it to burn through.
The heated secondary combustion air is introduced to the smoke on the bottom of the baffle, with the holes pointing down. In theory this allows the smoke to be burning by the time it gets to the chamber on top of the baffle and done burning by the time it hits the flue so it doesnt melt the flue pipe. In my last creation I uses 4 pieces of 1/2 in steel pipe welded to the bottom of the baffle, and passing out the sides of the stove.
A very good article is hearth.com/.../index.php/wiki/convert_your_old_1970_stove_to_secondary_burnHow_To_DIY. (If I copied this wrong search DIY secondary burn and it should come up.)
I havent been able to install my latest creation, but will soon and I'll let you know how/if it works.
Okiezeke