Chimney "Fires" from volatiles

Chimney "Fires" from volatiles

PostBy: steinkebunch On: Fri Dec 21, 2007 7:00 pm

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. :o Just fishing for info.

Anybody have this happen?

Steinke
steinkebunch
 
Stove/Furnace Make: Homemade Bituminous Hand-Fed
Stove/Furnace Model: Prill underfed stoker Model M8

Re: Chimney "Fires" from volatiles

PostBy: Berlin On: Sat Dec 22, 2007 10:15 am

no, it shouldn't happen, it seems that you're getting some fresh o2 into your chimney somewhere which is allowing the volitiles to flare slowly inside of the stovepipe. the soot will burn, however, it doesn't burn like creosote from wood, it will start glowing and burn very slowly only when there is lots of excess o2 in the stack (such as when the loading door is open) and stack temp must be above 500º F, it does not burn in such fashion that it would harm the chimney system through its own combustion and it extinguishes very easily; so yes, you can "burn out" the stove/chimney if you get a lot of buildup; infact, although i brush my chimney once/year for the hell of it, if i get a hot fire going, manage to slowly ignite some of the fluffy soot in the pipe close to my stove, ususally most of the soot in the rest of the chimney will just blow out.
Berlin
 
Hot Air Coal Stoker Furnace: Will-Burt Combustioneer 77B
Coal Size/Type: Ohio BITUMINOUS pea stoker coal

Re: Chimney "Fires" from volatiles

PostBy: steinkebunch On: Wed Dec 26, 2007 10:54 am

I checked outside at the chimney joint on top of the cleanout tee. Right around the joint feels cold, but the pipe above and below the joint feels warm. All the other joints that I can reach feel warm too. I used a candle to check for air leaks, and that joint did pull the candle flame toward it. I'm going to use some hi-temp caulking to seal that joint and see what happens. Maybe that will improve my draft as well. Also, one day I had a mini explosion in the stove after loading fresh coal (as bit stove can do), and I inadvertently blew my outside cleanout plug off. That reduced (or eliminated) my draft to my stove. Well, I didn't notice it for awhile, and smoke started coming out some of my stovepipe joints near the thimble, due to no draft. I'm thinking maybe I should seal those leaking joints as well. If it's sucking any air from places other than the stove, it seems like I'm wasting draft. Probably not enough to increase my draft significantly, but we'll see. I'll post results.

Steinke
steinkebunch
 
Stove/Furnace Make: Homemade Bituminous Hand-Fed
Stove/Furnace Model: Prill underfed stoker Model M8


Re: Chimney "Fires" from volatiles

PostBy: cokehead On: Tue Jan 01, 2008 3:11 pm

I was talking to a volunteer fire fighter and he said my chimney surface temp would have to hit 1500 degrees to start wood burning in contact with it. That number seemed high to me. I'd be worried long before that. He also suggester keeping some plastic bags of the dry chemical used in fire extinguishers to throw down the chimney in the event of a chimney fire. Water does a lot of damage to a HOT chimney. Maybe someone with more knowledge than me could chime in. My stove skin temp sometimes exceeds 900 degrees but I have sheilding around it. My chimney near the thimble sometimes gets hot enough so I don't want to hold my hand there long but not hot enough to burn skin.
cokehead
 
Stove/Furnace Make: Locke, Godin, Tarm in da works
Stove/Furnace Model: Warm Morning 617-A, 3721, 502

Re: Chimney "Fires" from volatiles

PostBy: steinkebunch On: Wed Jan 02, 2008 11:47 pm

Yesterday I had the stove rolling pretty well, but no fire up inside the chimney as described above. I put my ear up the the SS chimney joint above the cleanout tee. I could hear it sucking air in, and it readily pulled a candle flame in all around the joint. The joint was cold, but less than 6" above and below the joint it was hot, though you could hold your hand on it.

I'm going to wait until I get the manometer (loan program) and test the draft before and after I seal the joint.
I'll post results.

Steinke
steinkebunch
 
Stove/Furnace Make: Homemade Bituminous Hand-Fed
Stove/Furnace Model: Prill underfed stoker Model M8

Re: Chimney "Fires" from volatiles

PostBy: murphyslaw On: Tue Dec 13, 2011 1:21 pm

I have a brand new type A system. Have been burning in if for two months. Friday I had 10' flames coming out the top of my pipe that melted the cap. The stove temp was 350*. WTF!!! Had to tear a good bit of ceder off the ceiling to inspect the thimble and pipe. According to the TIC 20min after the flames were gone my pipe was 1300*......


I thought Chimney fires were a wood thing. This has my other half scared *censored* less of the stove now. We have used and abused a wood stove for years and never had a chimney fire.
murphyslaw
 
Stove/Furnace Make: Hitzer
Stove/Furnace Model: Model 82

Re: Chimney "Fires" from volatiles

PostBy: Berlin On: Tue Dec 13, 2011 3:00 pm

I don't see any way you could get a chimney fire from bit or subbit coal, I burned both and even illinois basin high vol (40+) for a long time. What is possible is that your stove was distilling volitiles slowly and an air leak in the pipe allowed the smoke to begin combustion in the pipe itself.

Have you been burning wood? Coal stoves with lots of underfire air tend to create more creosote buildup when they are used for wood.

for that much flame and heat, you had LOTS of air entering the stack somewhere it shouldn't have been.

It might be possible that with the alaska subbit high moisture coal, extended slow burns, and extremely cold outside temps (and thus low flue temps) there is some condensation of flue gas tars. IF this is the case (and I don't think it is, I've burned subbit before) than a daily HOT fire to burn out the soot/tar accumulation at small intervals would be a good precaution.
Berlin
 
Hot Air Coal Stoker Furnace: Will-Burt Combustioneer 77B
Coal Size/Type: Ohio BITUMINOUS pea stoker coal

Re: Chimney "Fires" from volatiles

PostBy: Rob R. On: Tue Dec 13, 2011 3:02 pm

Berlin wrote:for that much flame and heat, you had LOTS of air entering the stack somewhere it shouldn't have been.


A barometric damper?
Rob R.
 
Stoker Coal Boiler: EFM DF520
Hand Fed Coal Stove: Hitzer 50-93
Other Heating: Dad's 1953 EFM Highboy

Re: Chimney "Fires" from volatiles

PostBy: rockwood On: Tue Dec 13, 2011 3:04 pm

Wow. I've never heard of this before when only burning coal. I have seen soot burn in hand fired stoves when recharging the fire but never any flames, just glowing sparks that slowly dance around for a brief time where the soot is accumulated.
Have you noticed excessive soot build-up in the stove? Were you tending the stove when this happened?
Are/were you using a baro damper? If not, there must have been another source of air entering the chimney for the soot to ignite and burn like that...?
I have experienced a chimney fire when burning wood but I was able to stop it just by closing the draft on the stove and the stove pipe damper.

Edit: I see some of these points were already covered while I typed and submitted. :oops:
rockwood
 
Hot Air Coal Stoker Furnace: Stokermatic coal furnace
Hand Fed Coal Stove: Rockwood Stoveworks Circulator
Baseburners & Antiques: Malleable/Monarch Range
Coal Size/Type: Soft coal: Lump and stoker (slack coal)

Re: Chimney "Fires" from volatiles

PostBy: Berlin On: Tue Dec 13, 2011 3:13 pm

Rob R. wrote:
Berlin wrote:for that much flame and heat, you had LOTS of air entering the stack somewhere it shouldn't have been.


A barometric damper?



well, if that's true then I just don't see room air (feeding the flue at a nice pace and thus lowering the dew point) mixed with hot exhaust gasses leading to tars in the flue in the first place. Soot itself, aside from tars can begin to glow and "burn" when present in very high amounts, but it doesn't get very hot, needs a LOT of heat to start the burn, and tends to die out without creating any substantial elevation in flue pipe temp.
Berlin
 
Hot Air Coal Stoker Furnace: Will-Burt Combustioneer 77B
Coal Size/Type: Ohio BITUMINOUS pea stoker coal

Re: Chimney "Fires" from volatiles

PostBy: rockwood On: Tue Dec 13, 2011 3:43 pm

Berlin wrote:needs a LOT of heat to start the burn

Maybe volatile gasses burning up into the flue caused the soot to ignite..? If that were true though, there would need to be lots of fresh air for volatile gasses and soot to burn so intensely. I would think the soot build-up would have to be extreme for that to happen.
rockwood
 
Hot Air Coal Stoker Furnace: Stokermatic coal furnace
Hand Fed Coal Stove: Rockwood Stoveworks Circulator
Baseburners & Antiques: Malleable/Monarch Range
Coal Size/Type: Soft coal: Lump and stoker (slack coal)

Re: Chimney "Fires" from volatiles

PostBy: murphyslaw On: Tue Dec 13, 2011 4:23 pm

I have a baro. And the only wood that has been in that thing was a few pieces to start the fire two months ago. I was not tending the stove. There is a lot of build up(looks like creosote) on the inside of the stove, I scrap it off every now and then.
murphyslaw
 
Stove/Furnace Make: Hitzer
Stove/Furnace Model: Model 82

Re: Chimney "Fires" from volatiles

PostBy: Berlin On: Tue Dec 13, 2011 4:35 pm

rockwood wrote:
Berlin wrote:needs a LOT of heat to start the burn

Maybe volatile gasses burning up into the flue caused the soot to ignite..? If that were true though, there would need to be lots of fresh air for volatile gasses and soot to burn so intensely. I would think the soot build-up would have to be extreme for that to happen.


The soot buildup would have to be extreme because powdery soot just doesn't contain very much energy. Tarry creosote does, soot does not.

since there seems to be some tarry creosote, is the coal extremely wet? are the sizes large lumps or small pieces? and when you load the stove, does it smother the fire and smoulder for hours on end or are there visable flames above the fuelbed?


*** well, if all else fails, or the stove's burning well for you otherwise, just get rid of the baro then it won't matter whether you have anything in the flue or not, there won't be any oxygen or any danger.
Berlin
 
Hot Air Coal Stoker Furnace: Will-Burt Combustioneer 77B
Coal Size/Type: Ohio BITUMINOUS pea stoker coal

Re: Chimney "Fires" from volatiles

PostBy: murphyslaw On: Wed Dec 14, 2011 3:36 am

It's lump(stove) it's dry and warm. Keep one ton at a time in the garage in the trailer at 55f. I don't load it up but 50% at a time. I make sure there is a flame on reload. I have had a few puff backs when I first started. But now know how to avoid those. The stove temp will drop about 100* for 20-30min then come right back up.

It is tary, just don't get it. I need to get on the roof and look down it to see what it looks like.
murphyslaw
 
Stove/Furnace Make: Hitzer
Stove/Furnace Model: Model 82

Re: Chimney "Fires" from volatiles

PostBy: oros35 On: Wed Dec 14, 2011 12:55 pm

I had something similar happen when I tried to burn straight Bit coal in an Ant parlor stove. I was able to almost completely plug up the exhaust pipe and filled about 6 feet of 6" pipe with I'd say 75% full of black stringy soot. All this soot in about 36 hours.

The fire would start off hot and smokey, then sit and smoulder for the rest of the time. Wasn't enough draft to suck the heavy stringy black soot out and it collected. And what did make it up the chimney stuck to the screen on the cap and plugged it. When I tried to revive the fire, the soot caught and lit. It didn't last long, but I did verify the chimney pipe was way hotter than the stove temp. I killed it by opening up the chimeny cleanout breaking the draft from the stove and smothering the fire.

It was like the tar that gets released from the bit coal didn't burn but it did vaporize and then re-collected on the soot making it heavy and stringy. Which stuck to the walls of the pipe. It didn't have enough air to burn. But when I tried to revive the fire, it got enough air to catch, and create enough draft to suck enough air to keep burning.
oros35
 
Baseburners & Antiques: 1912 Smith & Anthony Hub Heater #215
Stove/Furnace Make: Smith & Anthony Co.
Stove/Furnace Model: #215 Hub Heater