Temps required for a clean burn

[Adios Pantalones]

'at's all true, but you need some extra. Stove aint gonna burn all the fuel with exactly the amount of air needed for combustion- there's an inefficiency that will mean you need a bit more air.

Introducing air under the fuel charge would help out probably, but then the air intake gets all clogged with ash and such.

In my kiln I introduce air above the wood charge so that the air gets sucked through the burning fuel. wood burns upside down. Pretty cool. Too much air is a serious issue in a kiln where you need to heat a large mass of bricks and pots to almost 2400F.

 

[Pagey]

But in a non-cat stove, that smoke needs to hit around 1,100F up there by the baffle to combust and thus burn off MOST of the organic/volatile materials before they can even get to the flue.

SO wouldn't that translate to a potentially lower flue gas temperature? Since all the VOCs and such are burned, there is theoretically less creosote forming materials to condense on the chimney walls. I just installed a probe thermometer on my double wall stove pipe, and the temps were reading around 500*F 18" up from the collar while my stove top was ~650*F. If i turned down the primary air to a point where all i saw was ghost flames coming from the re-burn tubes the flue temps decreased to ~400*F... is this considered a "clean" burn if i have good secondary burn? The stove top temp dropped slightly to ~600*F...

I would say a flue gas temp of 400F is fine. I think creosote condenses best at 250F and under. Again, someone please correct me if I am spouting off BS.

 

[mnowaczyk]

Measuring 'stove top' or flue temps just above the stove are meaningless to determine this since the critical stack temperature for creosote formation is many feet away. Of course, if one is way off base and burns wood only by 'smoldering', creosote will form in the chimney closer to the stove and maybe there too.

Here's a composite photo I took last year of my old stove during a starting burn using three progressively smaller intakes air openings, each one 1/2 of the one before. No flue pipe temperature data because I din't use a flue thermo back then, but all I can say is that the stove was warm to the touch when I began and the flue pipe was scathingly hot before I started to reduce the air. Each time I halved the air, you could hear the stove accelerate and see the temperature inside the burn zone increase by the change in color. At 1/8 air, the coals inside were yellow-white... well over 2000ºF. Unfortunately, the fire was so bright that I had to make adjustments in the exposure to prevent it from blowing out the photo, so you really can't see what it looked like in person.

Maybe I'm missing the point here, but it looks like you are saying the stove got hotter with less and less air, meaning that the air cools the fire if there is too much. Is this the point? If so, are you saying too much air can cause creosote because the flue temp and chimney will be too cool? Maybe the air would move too quickly to burn off the smoke before it cooled?

Well, the real reason I'm responding is because I would assume that the reason the fire got hotter with less and less air would have been the turbulent flow that results with a smaller intake in this type of stove where the air doesn't have to pass throuogh channels that heat and slow it down on the way in... which i'd assume leades to less turbulent air flow. Maybe it's my chimney, but I've never been able to get flames that look like turbulent flow in my stove. I think it's basically designed to make laminar air flow down around the wood before hitting the afterburner chamber at the back of the stove. I'm sure everyone has seen their stove stoke right up if they crack the door a little bit, but we all understand we are loosing heat right up the chimney, albeit it's not a bad way to warm up a cool shimney and get some coals in a cold stove. Right?

So is there a possibility that the stove was getting hotter due to turbulent air flow (i.e. mixing) so your full load could burn instead of just the hottest spots with the wider opening?

Just more thoughts. So freaking complicated. I do like the way somebody here put it: no smoke, clean glass, nothing but steam out the top of the chimney... then you've got clean burning. I guess that's the answer I really needed.

Add to that I will find out how clean the chimney is tomorrow when I pull the stove.

I'VE LEARNED SO MUCH WITH EVERYONE'S HELP! THANK YOU! I can't believe how clean my glass is now that i'm burning right!