What happens when you throw a lump of coal on your wood stove?

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MountainStoveGuy

Minister of Fire
Jan 23, 2006
3,654
Boulder County
Out west, there is very little coal avalible for burning, and its actually illeagle in my state. Im courious, why are coal stoves so specific? If i could buy coal why cant i put a pice on my wood fire? If the answer is yes, that you can throw coal on your wood fire, does stove type make a difference? Type meaning steel, cast iron, or soapstone?
 

MountainStoveGuy

Minister of Fire
Jan 23, 2006
3,654
Boulder County
even though it is a illeagle fuel here, i did find a source of bituminous coal, i know its not as good as anthracite (sp?0 coal, but do people burn it? the vendor that i found that carries it sells it by the piece for people that want to play jokes on people for christmas, but he will sell the bags (70lbs) for 20 bucks.
 

MountainStoveGuy

Minister of Fire
Jan 23, 2006
3,654
Boulder County
I just found on hearthstones website that the sulfur in coal will etch your glass, coal stoves dont use glass? And it also says that coal burns at very high temps, i dont see a problem with that with the soapstone, but it might wreck the burn tubes. Do coal stoves not use secondary burn systems?
 

roac

New Member
Dec 8, 2005
227
Nampa, Idaho
Illegal? Why bother making it illegal if you can't get it? By the way I think Montana is the closest for us in Idaho (same in Colorado?) to get coal but I'm sure shipping it here for residential use would be cost prohibitive. I'm sure it isn't commercially illegal to burn. A lot of big industry uses coal for their process. As far as home use I think coal stoves are built more robust for the higher heat source. Not sure on the glass but it isn't really glass either so who knows.
 

MountainStoveGuy

Minister of Fire
Jan 23, 2006
3,654
Boulder County
I dont want to burn it, i have lots of customers that ask about it. I am just trying to educate myself on coal. I would consider trying a piece or two on my established fire at night to hold it over, and your right, i use the glass term loosely, its ceramic. And i dont want to ruin my nice hearthstone ceramic glass, it has that nice IR coating on the inside that relflects a lot of heat back in the box, and most glass shops dont carry it. I hate to order one from hearthstone.
Ryan
 

MountainStoveGuy

Minister of Fire
Jan 23, 2006
3,654
Boulder County
I think i have found enough information to discourage my customers from using coal in there woodstove LOL, there are some real horror stories on the net.
 

precaud

Minister of Fire
Jan 20, 2006
2,307
Sunny New Mexico
With the right appliance, coal is a wonderful heat source. In the 80's I used to buy truckloads of coal from somewhere is CO, 23 tons at a time. It was bituminous but harder and cleaner than most. I sold enough in 100lb bags to pay for what I used and a little extra. I was a Jotul dealer at the time, and the Jotul 404 coalstove was great, as well as the Surdiac coalstoves that Jotul was distributing at the time that were super nice. The Godin stoves are excellent for coal as well, and still available new here. The only thing I didn't like about coal was the sulfury smell it gave to the house. If the anthracite mine 15 miles south of here ever opens again, I'll get a coal burner immediately!
 

webbie

Seasoned Moderator
Nov 17, 2005
12,178
Western Mass.
MountainStoveGuy said:
Out west, there is very little coal avalible for burning, and its actually illeagle in my state. Im courious, why are coal stoves so specific? If i could buy coal why cant i put a pice on my wood fire? If the answer is yes, that you can throw coal on your wood fire, does stove type make a difference? Type meaning steel, cast iron, or soapstone?

In general, here is what happens.

1. It surely could screw up a cat stove, so forget about that one!
2. Coal burns slower than wood, so the coal will usually not be consumed totally, while the wood around it may.
3. Coal produces 10X the ash of wood, so mixing a lot of it can really mess up the bed of charcoal in a wood stove.

All that said, there is little problem with throwing, as you say; a couple lumps of coal onto the red hot embers of a wood stove. In fact, in TN back in the early 70's - when I started using stoves, it was a treat for us to have a lump or two on expecially cold nights.

Of course, we get into the hard coal and soft coal thing - hard coal being tough to ignite in any stove without grates and air from underneath.
 

Martin Strand III

New Member
Nov 20, 2005
763
NW MI near nowhere
Hey MSG:

You do pretty good having a conversation with yourself.

Back to your query about burning coal in wood stoves. Can it be done? Sure, but I wouldn't do it routinely for a few reasons:

1. To burn well, coal needs in-air from underneath - wood likes it at and above the level of the fire. Most stoves can't do both.
2. Soft coal (bituminous) burns dirty with lots of toxic pollutants; hard coal (anthracite) burns clean and hot with sulfur residue which forms sulfuric acid with moisture and can corrode your system unless cleaned out periodically (which you should be doing anyway).
3. Coal burns hotter than wood but is not good when outside temps are about 40* F or higher (poor draft then).
4. Coal is a limited resource and wood is not, if managed properly.

But you said "a lump of coal on your wood stove", not burning lots of coal and wood together, so pardon the diversion.

Aye,
Marty
 

wg_bent

Minister of Fire
Nov 19, 2005
2,248
Poughkeepsie, NY
Marty was right on track. If you want to understand the difference between coal and wood stoves, Take a look at the parts schematic of the Morso 1410. It can be configured as a coal or wood stove. The wood version has a single air inlet, secondary burn tubes, and a somewhat different baffle system, I think to support the secondary burn tubes. The Coal verson has a second air inlet that allows the primary air to come in from below the coal, thus directing the air through the coal bed. No secondary burn tubes, since the top air inlet allows air to ignite the gasses coming off the coal when you first put coal on the fire. The baffle system looks a bit beefier and simpler. A coal stove will burn wood but not as completely as a wood stove, and will not meet the EPA limits. Throwing a lump or two of coal seems like it might work but I'm not sure that the coal will continue to burn after the wood coals are gone. Never tried it. Also, the coal will be sitting directly on the fire brick and will be very hot. Not sure that's all that good for the brick.
 

MountainStoveGuy

Minister of Fire
Jan 23, 2006
3,654
Boulder County
Im almost a expert now, thanks! i do tend to talk to myself alot, it must be the one hour commute each way to work. I will look closely at coal stoves this year at the show in salt lake. I dont think i will be throwing any type of coal in my hearthstone even if i could get it. It was all hypothetical anyway, and i appreciate all the information! My customers wont think im such a idiot when they ask me about coal and i have that blank look in my face, we all hate that look.
 

webbie

Seasoned Moderator
Nov 17, 2005
12,178
Western Mass.
MountainStoveGuy said:
I just found on hearthstones website that the sulfur in coal will etch your glass, coal stoves dont use glass? And it also says that coal burns at very high temps, i dont see a problem with that with the soapstone, but it might wreck the burn tubes. Do coal stoves not use secondary burn systems?

Since coal stoves use similar glass as wood stoves, the glass thing is not a big deal....sure, it might cloud up after a numner of years, but in my experience it does not break or wear.

Coal does have a secondary burn, but vastly smaller than wood and it often does not have to be designed into coal stoves. For instance, Russo stoves just had a little spacer around the door glass which allowed a tiny bit of air above the fire.

Think of it this way - with coal the heat is mostly in the red coal bed (pure carbon?), whereas with wood, the heat is as much as 50/50 in the embers and the gases. I think coal, depending on type, is 90/10 or 95/5, etc.

So, there are vastly fewer gases to burn, hence secondary burn is not as important.
 

Martin Strand III

New Member
Nov 20, 2005
763
NW MI near nowhere
Craig:

I agree except the "heat" (energy) from burning wood comes from the wood solids:wood gases at about 1/3 : 2/3 (not 1/2 : 1/2 or 50/50). There is about 1% non-combustible component to wood which results in ash.

Aye,
Marty
 

webbie

Seasoned Moderator
Nov 17, 2005
12,178
Western Mass.
Marty S said:
Craig:

I agree except the "heat" (energy) from burning wood comes from the wood solids:wood gases at about 1/3 : 2/3 (not 1/2 : 1/2 or 50/50). There is about 1% non-combustible component to wood which results in ash.

Aye,
Marty

I think it depends on the wood - like pines and such have a lot more gases and oaks might have a lot more coals????? Or something like that.....working from memory here, so the percentages are just gueses - again from memory wood results in as little as 1/10 of one percent ash and perhaps as much as 1% or more - and coal can be 4% to as much as 10% ash. I'm talking weight here, not vol.....

Anyhow, that's the big diff between coal and wood. Fixed carbon vs a mixture of all kinds of jazz!

Here's some drivel that seems to say gases are even more than 50% (but that's one reason I DIDN'T go to college)

---------------
Volatiles

Wood and other types of biomass contain approx. 80% volatiles (in percentage of dry matter). This means that the component part of wood will give up 80% of its weight in the form of gases, while the remaining part will be turned into charcoal. This is one reason why a sack of charcoal seems light compared to the visual volume. The charcoal has more or less kept the original volume of the green wood, but has lost 80% of its weight.

The high content of volatiles means that the combustion air should generally be introduced above the fuel bed (secondary air), where the gases are burnt, and not under the fuel bed (primary air).

Structural Elements of Wood

The structural elements (ultimate analysis) of the organic portion of wood are carbon (45 - 50 percent), oxygen (40 - 45 percent), hydrogen (4.5- 6 percent) and nitrogen (0.3 - 3.5 percent). The distinct advantage of woody biomass over fossil fuels is the small amount of sulphur. The ultimate analysis of some tree species show that carbon and hydrogen contents are rather uniform among species. Bark has a higher percentage of carbon and hydrogen than wood. This is most visibly the case with birch and alder.

In the proximate analysis the amount of volatiles is 65- 95 percent, fixed carbon 17 -25 percent and ash content 0.08- 2.3 percent. Please note that the information of the properties of wood fuels has been collected from several different sources. The most comprehensive data of wood fuel properties was available from ECN laboratories from Netherlands.
--------------

OK, so let's not repeat that swirling smoke stuff - I think we all agree that wood varies, but in any case has vastly more gases to burn than coal.
 

wg_bent

Minister of Fire
Nov 19, 2005
2,248
Poughkeepsie, NY
Webmaster said:
Marty S said:
Craig:

I agree except the "heat" (energy) from burning wood comes from the wood solids:wood gases at about 1/3 : 2/3 (not 1/2 : 1/2 or 50/50). There is about 1% non-combustible component to wood which results in ash.

Aye,
Marty

I think it depends on the wood - like pines and such have a lot more gases and oaks might have a lot more coals????? Or something like that.....working from memory here, so the percentages are just gueses - again from memory wood results in as little as 1/10 of one percent ash and perhaps as much as 1% or more - and coal can be 4% to as much as 10% ash. I'm talking weight here, not vol.....

Anyhow, that's the big diff between coal and wood. Fixed carbon vs a mixture of all kinds of jazz!

Here's some drivel that seems to say gases are even more than 50% (but that's one reason I DIDN'T go to college)

---------------
Volatiles

Wood and other types of biomass contain approx. 80% volatiles (in percentage of dry matter). This means that the component part of wood will give up 80% of its weight in the form of gases, while the remaining part will be turned into charcoal. This is one reason why a sack of charcoal seems light compared to the visual volume. The charcoal has more or less kept the original volume of the green wood, but has lost 80% of its weight.

The high content of volatiles means that the combustion air should generally be introduced above the fuel bed (secondary air), where the gases are burnt, and not under the fuel bed (primary air).

Structural Elements of Wood

The structural elements (ultimate analysis) of the organic portion of wood are carbon (45 - 50 percent), oxygen (40 - 45 percent), hydrogen (4.5- 6 percent) and nitrogen (0.3 - 3.5 percent). The distinct advantage of woody biomass over fossil fuels is the small amount of sulphur. The ultimate analysis of some tree species show that carbon and hydrogen contents are rather uniform among species. Bark has a higher percentage of carbon and hydrogen than wood. This is most visibly the case with birch and alder.

In the proximate analysis the amount of volatiles is 65- 95 percent, fixed carbon 17 -25 percent and ash content 0.08- 2.3 percent. Please note that the information of the properties of wood fuels has been collected from several different sources. The most comprehensive data of wood fuel properties was available from ECN laboratories from Netherlands.
--------------

OK, so let's not repeat that swirling smoke stuff - I think we all agree that wood varies, but in any case has vastly more gases to burn than coal.

I believe they must be talking about Sumac. :cheese: Ever throw a peice of that on a fire? It's like the stuff is soaked in Gasoline. Then in 10 minutes there's nothing left.
 

Martin Strand III

New Member
Nov 20, 2005
763
NW MI near nowhere
Dylan:

If the difference between "50/50 vs 33/67 is ‘splitting hairs’." (17% in my book), your bank account would get virtually no interest, profit margins in business would disappear, burning wet or dry wood wouldn't matter, global warming would not exist, all knowledge bases would need to be re-written, etc "ad nauseum".

Aye,
Marty

Grandma used to say, "Non illegitimi carborundum."
 

smirnov3

Feeling the Heat
Feb 7, 2006
439
Eastern Ma
One concern about burning coal for home heat is the amount of mercury in it. Mercury is a neurotoxin, and may (emphasis on MAY) trigger autism

a study in Texas found a 1:1 correlation between atmospheric mercury levels and autism rates in the local schools, and another study found that the number of new cases of autism in Californai has dropped for the first time when a mercury preservative was was withdrawn from use in infant vaccines (it took them 6 years to notice, because CA only officially diagnoses Autism when the kids enter elementary school)
 

Corey

Minister of Fire
Nov 19, 2005
2,588
Midwest
Well, I guess we've done enough theorizin' now it's time to get to experimentin'. So nothing left to do but build us a nice cozy wood fire, grab a couple of lumps of Wyoming's finest, and chuck them in the fire (red arrows). We will call the start of the experiment time = 0 or T=0.
 

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Corey

Minister of Fire
Nov 19, 2005
2,588
Midwest
In the interest of brevity, let's just say you have to wait until about T=30 minutes for anything "exciting" to happen. The coal is well involved right now. A fine layer of white ash is starting to form and flames are coming from the coal, although not much (if any) visible smoke. One lump on the outer edge of the fire (red arrow) hasn't really caught on yet and is still pretty much intact.
 

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Corey

Minister of Fire
Nov 19, 2005
2,588
Midwest
T=45 minutes, things are starting to perk right along now. The coals are really burning like...well, coal! The glass has not etched into a frosted masterpiece, the stove has not melted and everything appears normal. The fire does have somewhat a radioactive glow in the photo, but I think that is due to the CCD in the camera actually picking up some of the near infra-red light and converting it to visible. Bizarre!
 

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Corey

Minister of Fire
Nov 19, 2005
2,588
Midwest
T=50 minutes. Our experiment is drawing to a close. The lumps of coal have been reduced to ...coals, along with most of the wood - I just used some small splits to get the fire going. Everything from this point on seems pretty peaceful!
 

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JAred

New Member
Nov 18, 2005
125
Interesting,

I'm not gonna say I want to burn coal all the time but it would be fun to experiment. Theirs a pile of coal in the grandpa's basement thats been there for decades I would'nt mind trying it just for kicks. My wood pile is getting boring....Time to find some apple wood or somthing else. Somthing stronger, the pine is not doin it anymore. Iwant more Flames I want more heat burn! Burn! Burn! Burn! I need somthing stronger This pine stuff is'nt as strong as it used to be I can't help my self. I need to burn somthing.

I think I'm addicted.
 

MountainStoveGuy

Minister of Fire
Jan 23, 2006
3,654
Boulder County
This thread has been very helpfull, that was a cool experement. I wonder long term if it would hurt anything? what do you think? that glow LOOKS HOT! wich is good. Maybe i will buy a bag of this crap soft coal and see what happens. Hopefully none of the neighbors wont call the smoke police on me. Its a good thing that i dont have any real close neighbors anyway. Can i expect smoke out of my chimney? will it smell funny? more importanly, will it be possible to tell that im burning coal?
 

Corey

Minister of Fire
Nov 19, 2005
2,588
Midwest
MountainStoveGuy said:
This thread has been very helpfull, that was a cool experement. I wonder long term if it would hurt anything? what do you think? that glow LOOKS HOT! wich is good. Maybe i will buy a bag of this crap soft coal and see what happens. Hopefully none of the neighbors wont call the smoke police on me. Its a good thing that i dont have any real close neighbors anyway. Can i expect smoke out of my chimney? will it smell funny? more importanly, will it be possible to tell that im burning coal?

MSG - If you are looking at long term as in tons of coal per year for many years, you may want to study the differences in coal and wood stoves (or the combo) stoves, and see how it applies to your model. If you are talking a couple of 40# bags a year just for fun, I can't see that it would be too much difference from wood. I know the glow looks hot on the photo, but in reality, it's just your standard orange-red coal glow. The camera is picking up some of the infra-red light and converting it to visible. I've attached a shot looking at a remote control LED. The LED is invisible to the naked eye, but emits strongly in the IR. The camera picks it up as if it were white.

As far as smoke, if you are burning coal in a pure wood stove, my experience is the bigger chunks, the better. I am limited to hand stoking, so the whole black art of keeping a coal fire going and all the air flow and feed rates don't really apply. This is really on the level of a wood fire burning coal. If you load up with a huge pile of coal, or really fine coal, it will probably smoke some. But if you keep the load small and the pieces relatively big for good air flow, the smoke is minimal. Although the neighbors will still know you are burning coal...at least if they have any sense of smell!

Corey
 

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