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Will coal work for a rocket stove?

Dale Schlehuber


Joined: Jan 20, 2013
Posts: 9
We are building a RMH on my friends ranch in SE Montana. Lots of cactus and some sagebrush, just a little wood in the creek bottom. However, he has a 3 foot seam of coal on the ranch that the original homesteaders used to heat their houses. Question is, will the coal burn (much hotter I assume) be a way for him to warm his buns? Any forseeable problems in so doing?
tel jetson
steward

Joined: May 17, 2007
Posts: 3097
Location: woodland, washington
    
  53
I've never tried it, but I think it would work. the optimum dimensions will be substantially different than the more common stoves tuned for burning wood, though.


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Dale Schlehuber


Joined: Jan 20, 2013
Posts: 9
Why would the dimensions be different? Longer burn chamber? Would the intake require more oxygen because of the increased heat? If so, any idea what the variants are?
K Nelfson


Joined: Nov 07, 2012
Posts: 124
Should work fine. If anything, it'll be easier to manage. The fuel is more energy dense and you won't have a problem with creepy crawlies that tend to accompany wood piles.

I would suggest a grill to promote airflow from under the coals. But lots of RMH designs include that, so maybe you already know...

An open vein of coal is a fire risk, though. Lightning and grass fires can set it off and it could burn for decades.

tel jetson
steward

Joined: May 17, 2007
Posts: 3097
Location: woodland, washington
    
  53
Dale Schlehuber wrote:Why would the dimensions be different? Longer burn chamber? Would the intake require more oxygen because of the increased heat? If so, any idea what the variants are?


they're just very different materials. just like gasoline doesn't burn the same as a pile of leaves, wood and coal burn differently. more oxygen is necessary for coal, but not because of the increased heat. it's because coal is a richer source of fuel. toss coal in a stove designed for wood and a disgusting smoky mess will be the result.

I don't know exactly what the changes necessary would be, but I would guess that you would want to design for less coal burning than would be the case with wood, but more air supply. some experimentation is certainly in order, and I do hope you discuss your progress here.
R Scott


Joined: Apr 13, 2012
Posts: 2433
Location: Kansas Zone 6a
    
  28
Look at what Rob did to get a rocket to burn wood pellets: http://www.permies.com/forums/posts/list/40/18515#166077

Similar issues, but you will need an even better grate and burn tunnel and possibly barrel. A rocketing rocket will be a FORGE hot fire breathing dragon melting most metal and lesser refractories in its path.


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jay kenny


Joined: Jan 24, 2013
Posts: 1
iv been burning coal in a rocket stove i made from a large gas cylinder. the fire box and riser are lined with vermiculite board and are holding up well as this stove gets good and hot it does smoke from the chimney with coal however not a wisp with wood i find a mixture of both to be best



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Kari Gunnlaugsson
volunteer

Joined: Jun 22, 2011
Posts: 308
    
    8
I burn coal in a blacksmith forge, and the blower doesn't seem much stronger than the draft on my rocket stove. So it could get HOT, especially if you stoke it right up. I just used regular brick for my burn tunnel and i have a steel heat riser, so I've been wary of burning coal as i'm not sure if my stove would stand up to it... Do you think proper firebrick would be needed?
Ernie Wisner
volunteer

Joined: Oct 16, 2009
Posts: 788
Location: Tonasket washington
    
  23
you can burn coal you do need to allow for more air since coal is a much denser energy source.

the best way i have so far found is to mix coal and wood chips with a dung binder press till it all sticks together and burn the resulting briquette. With a seam of coal i would defiantly make the feed bigger and get some sort of grate that would stand the heat. this would mean the burn portion of the system would need to be masonry or it will burn out. As to the fan for a forge it is a stronger draft than you usually get on an RMH and far more focused. however it is also stoking the coals to make a much higher heat in a smaller area.

the normal draft so far works ok for coal. if you dont want to build a press i would try just mixing with dung and drying in some sort of log (haven't tried this one yet).


Need more info?
Ernie and Erica
Wood burning stoves, Rocket Mass Heaters, DIY,
Stove plans, Boat plans, General permiculture information, Arts and crafts, Fire science, Find it at www.ernieanderica.info


Kari Gunnlaugsson
volunteer

Joined: Jun 22, 2011
Posts: 308
    
    8
Thanks Ernie. I guess I'll have to stay away from it with my steel heat riser.
Dale Schlehuber


Joined: Jan 20, 2013
Posts: 9
Thanks Ernie (not Eric, sorry about that!)

Do I understand correctly, a grate? As in the bottom portion of the feed chamber, to hold it off the bottom? Will the increased heat also effect the riser metal?
Ernie Wisner
volunteer

Joined: Oct 16, 2009
Posts: 788
Location: Tonasket washington
    
  23
the heat riser will need to be brick as well. Should be brick in anycase if it's to be a long term stove. the temps 2/3rd of the way up the heat riser are very very high and even with soft wood it will burn out the steel over time.
Andrew Parker


Joined: Feb 13, 2012
Posts: 350
Location: Salt Lake Valley, Utah, hardiness zone 6b/7a
    
    4
It is true that wood and coal burn differently. It is also true that all coal is not created equal and adjustments must be made for each type of coal. It may be enough to be able to adjust both the primary and secondary air, which can be problematic with the basic rocket and RMHdesign. There are designs at Donkey's forum that could probably be adapted to burn coal efficiently.
Dale Schlehuber


Joined: Jan 20, 2013
Posts: 9
Thank you for the information about the riser. If the metal is not long term, why do all the videos show a 6" pipe insulated with clay and vermiculite and a 10" pipe? Could have saved some money not buying an insulated stove pipe and just built up the fire bricks!

If the feed, burn and riser are all made of fire brick, do I have to worry about the extra heat of coal, and just have to worry about getting adequate oxygen for the burn?
Mike Kimble


Joined: Nov 28, 2012
Posts: 21
Tried the coal in the stove last night, without any definitive results. Got a good bed of coals, put in a cast iron grate, and started putting in coal a few pieces at a time. The coal took right off; but as it was getting late and very cold, I didn't stay too long to see the results. It seemed to fire up, then start cooling. I cut down the air supply, and gave it up for the night. Here's my conclusions:

1. We all know that wood fires are made a lot differently in rocket mass stoves; I think coal fires offer the same challenge. Could take a lot of time to figure out the best way for burning coal
2. Coal burns dirty and smelly; nothing as beautiful as wood.
3. I used to burn quite a bit of coal in a US stove wood/coal furnace, so I am somewhat familiar with coal's burning properties. After the coal fires, you cannot poke/mess with it. That makes clinkers, so it's a bit hard to add wood after the coal. Since the coal is burning so hot; it makes the wood steam; even wood that appears completely dry.

I will probably mess around a little more this weekend with it, but am thinking that coal is not that great in a rocket mass stove; at least in my application.

Mike

PS I think Ernie's idea of wood chips/coal and dung would work, but am wondering if something can be used instead of dung. I used all my dung in the compost pile.
Andrew Parker


Joined: Feb 13, 2012
Posts: 350
Location: Salt Lake Valley, Utah, hardiness zone 6b/7a
    
    4
Coal burns dirty and smelly


No fuel will burn dirt or smelly, if it is being burned properly.
Dale Schlehuber


Joined: Jan 20, 2013
Posts: 9
Will I have to worry about "klinkers" with a rocket stove?
Mike Kimble


Joined: Nov 28, 2012
Posts: 21
Dale Schlehuber wrote:Will I have to worry about "klinkers" with a rocket stove?


Hi Dale,

I still had some klinkers when I burned a small amount of coal...

Mike
Andrew Parker


Joined: Feb 13, 2012
Posts: 350
Location: Salt Lake Valley, Utah, hardiness zone 6b/7a
    
    4
Review this project for some ideas on how to burn coal cleanly. I mentioned it in an earlier thread on coal, "First RMH in Mongolia".

You may also want to look into using a p-channel (described at Donkey's Stove Forum).
Mike Kimble


Joined: Nov 28, 2012
Posts: 21
Andrew Parker wrote:Review this project for some ideas on how to burn coal cleanly. I mentioned it in an earlier thread on coal, "First RMH in Mongolia".

You may also want to look into using a p-channel (described at Donkey's Stove Forum).


Andrew,

Thanks for the info. Great pics and explanations.

Mike
Paul Casserly


Joined: Feb 01, 2014
Posts: 1
I've recently completed my RMH, it works nicely. I used all quality refractory material, intending to burn coal. No problems with wood, but coal is very difficult. I can get a nice mass of coal glowing but can't maintain it. I have a grate beneath it. Seems to be a draft issue
 
I agree. Here's the link: http://stoves2.com
 
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