I'm full of questions and few answers. Burning Wyoming Bit. coal in a handfed. Twice this year I have noticed that after adding a fresh load of coal and getting the fire rolling real good, I could hear some rumbling in the smokepipe. I shut the combustion air (primary and secondary) and the rumbling would cease, or stop after a few minutes. I went outside and felt the SS chimney pipe and it was too hot to touch. Once when I heard the chimney rumbling I shut the air and went outside, and could even hear the rumbling in the chimney outside. Looked up the chimney from the outside cleanout cap and caught sight of a few of the last flames before they stopped.
So it seems that I'm getting flames in my chimney, though not from creosote like wood, but most likely burning volatiles from the new coal. These flames are not necessarily just an extension of a flame in the firebox, but are igniting gases in the chimney.
Chimney is clean too, though I've read the soot doesn't burn, and that seems to be true in my firebox. Soot doesn't burn, just builds.
What would cause the volatiles to burn in the chimney? Too high volatile content in the coal? Shouldn't they burn up in the stove? I had flames in the firebox both times this happened, so it's not like they couldn't ignite earlier. Could this be related to draft? Too strong, too weak? Double-wall stovepipe is in the house, so is too much heat being maintained so that temps are higher in stovepipe and allow ignition?
It scares me when the chimney gets this hot.
Just fishing for info.
Anybody have this happen?