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Post by Vortex on Dec 23, 2013 13:55:12 GMT -8
Anyone ever experimented with building a coal burning rocket stove? I know it's horrible dirty polluting stuff but a lot of people would like the efficiency of a rocket stove or masonry heater but have no access to wood or a place to season it. I've been asked several times recently if you can burn coal in one, I don't see why you couldn't build one to burn coal as it's main fuel. I tried doing some research and all I can find are several other people asking the same question. I've heard from two different sources that coal is burned in some masonry stoves in Germany. A grate would probably be necessary and top quality refractories, anything else that would need adapting?
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Post by Donkey on Dec 24, 2013 1:18:24 GMT -8
I don't know of anyone doing this.. Some first shots: With coal, unlike wood, it's the coal that you are burning.. The COAL itself. With wood, you are burning the gasses produced from heating wood.. This sounds trivial, but it's gonna mean a big difference in design. I don't think that things like the trip wire are going to help here.. I'm thinking that the burn tunnel should be eliminated too. You will want some kind of concentrated airflow right on the coal itself, like the tuyere of a forge, but in this case, the heat riser is creating the draft instead of a blower..
??
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Post by Vortex on Dec 24, 2013 9:40:18 GMT -8
That's surprising, I would have thought coal would be gasifying more than wood,,, don't they both go through the same stages of combustion? To get a clean burn you'd definitely need a good strong draw right across the coals, so a build with out to much resistance to the flow and a bypass for lighting. A smaller firebox as the fuel is more energy dense, and with so much heat in a small burn you'd want enough thermal mass to store a good proportion of it for slower release. Otherwise I cant see why this cant be done.
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Post by oboblomov on Dec 24, 2013 11:28:00 GMT -8
vortex & donkey: I'm a bit confused here. Surely the rocket stove is burning some charcoal all of the time during a wood burn?? Though perhaps only because charcoal burning is sustained by the concomitant combustion of wood-gas?? (These are both questions.) I use supplemental air provided by a hair-dryer to burn-out residual charcoal when it begins to choke out the flow of air in my 4" Dragon. Is that cheating? ;-)
Wiki-P says the coke is to coal as charcoal is to wood, so, vortex may have a point. I have a long standing aversion to coal but it would be interesting to know if one might use it to advantage in a rocket stove. (Have friends on Navajo & Hopi reservations who depend on coal for heat. They would definitely benefit from more efficient combustion techniques.)
I wish all here a very non-sectarian Happy Winter solstice season. Though mostly a lurker, I never the less truly benefit from and enjoy all of your comments and hope to contribute more to the discussions in the coming year.
obob
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Post by pinhead on Dec 24, 2013 12:56:42 GMT -8
I've got a pile of coal down the road from way back when the neighbors used to heat their houses with it. I'm tempted to put a layer of it on the bottom of my batch rocket and see how it burns. I stuck a fist-sized chunk in the burn tunnel of my J-tube rocket and then loaded and burned wood like normal. There was no coal left after the burn and the draft was phenomenal. It did burn really hot, though. I wouldn't load up a batch rocket with coal for fear of melting the barrel. Or maybe I would, just to watch the destruction.
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Post by Donkey on Dec 24, 2013 13:52:24 GMT -8
I got to admit that I'm pretty ignorant about coal.. My assumption is that MOST of what is a available to be burned there is the carbon. Like charcoal.. I don't have access to coal, but I make charcoal for my forge.. Again, my assumption is that most of the burn would be a lot like burning a big pile of charcoal left over inside the feed, after the wood-gas has burned off, just MUCH hotter.
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Post by treeclimber1 on Dec 24, 2013 20:16:06 GMT -8
I have used a regular heating grade of coal for doing little bit of forging. It seemed to off gas quite a bit. I don't know that much about it but if you can get all the smoke to burn I don't see why a rocket wouldn't work. Are there a lot of stuff in coal that goes up the chimney that can't be burnt? Do rocket stoves not like a lot of material that doesn't produce gas, just a lot of heat?
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Post by Donkey on Dec 25, 2013 0:08:52 GMT -8
Well... When you burn wood, SO MUCH of what's going on is about burning wood gas. I will stick my neck out a bit here to say that probably MOST of burning wood is about burning gas, which is why the tripwire matters and why all the work on P-channels for the batch box and all that.. Burning Gas.
Maybe there is some gas in coal, but I BET that MOST of the burn cycle is going to be about the carbon.. Burning a solid, directly.. Like charcoal.
so.. The thing to do is probably to look at a number of coal burning stoves to figure out if they're designed to maximize gas or solid burning.. Specifically the air intake(s)and how they are arranged.
Maybe someone who knows something about the subject could weigh in???
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Deleted
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Post by Deleted on Dec 25, 2013 4:13:51 GMT -8
Coal is partly decayed and by high pressure metamorphosed vegetation. The amount of volatile contend depends on the degree of metamorphosis. en.wikipedia.org/wiki/Coal
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Post by Vortex on Dec 25, 2013 10:41:05 GMT -8
Looking through a few pages of figures for coal and firewood, coal ranges from 7% - 65% volatiles and 60% - 91.5% carbon and an average for firewood of 80% volatiles and 20% carbon.
Most people who burn firewood do it in an open fire or woodstove, we've all seen how much that can be improved upon with a little knowledge, so I'm sure the same is probably true of coal. A lot of old and poor people around where I live burn coal as their main fuel source which has recently had a 20% carbon tax added on top of the 13.5% tax already charged on it. They would all love to have a more efficient way to burn it and save fuel. The solid fuel stoves for sale all seem to be Chinese imports which are of appalling quality and efficiency, it's like going to the new car showroom and finding all that's available are new 1970's cars but really badly made...
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morticcio
Full Member
"The problem with internet quotes is that you can't always depend on their accuracy" - Aristotle
Posts: 371
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Post by morticcio on Dec 26, 2013 10:03:54 GMT -8
The solid fuel stoves for sale all seem to be Chinese imports which are of appalling quality and efficiency I visited a customer last week. Their neighbour had a wood burner that was belching out stinking brown/black smoke every 5 minutes. The chimney cowl was coated in black soot. Next visit I'll pop next door and evangelize about clean burn efficient rocket stoves!
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Post by pluton5 on Dec 29, 2013 11:36:34 GMT -8
hello all It just so happens that I did try to coal combustion in rocket stoves but it turns out that it's not that simple. Wood and coal are two separate topics in the field of combustion. RS wood burns very rapidly causing huge pressure heat vertically and therefore does not require a classical stack, but will not cause such coal during the combustion and the pressure required , but , rather long funnel , which causes a vacuum in the furnace and allows for sufficient oxygenation of carbon by aeration holes . I do not want to dwell here on the subject because it is a separate issue. Overall I would say this , that burning coal produces huge amounts of smoke and is ineffective , vain results. You can slightly modify the combustion chamber in the RS to coal combustion , but THIS IS NOT IT . Personally, I'm burning coal in a house in the central heating boiler , but it is not RS . Coal fuel is not easy to smokeless combustion in the home . Interested give you a link to the issue in Polish unfortunately, but very interesting , Economic burning coal ,
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Post by Donkey on Dec 29, 2013 18:45:50 GMT -8
Yes please, pluton5.
Tak, proszę. Chciałbym zobaczyć.
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Deleted
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Post by Deleted on Dec 30, 2013 6:17:15 GMT -8
Wood and coal are two separate topics in the field of combustion. Wood is quite uniform, aside of density. Coals vary a lot more. Over 1200 coals have been classified. Coalification forms different coal types: (Peat) Lignite Bituminous coal Anthracite (Graphite) The biggest problem with coal combustion are tarry fumes, which need very high temperatures to burn clean. Preheating with wood or coke could help to avoid black smoke at the start.
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Post by pluton5 on Dec 30, 2013 10:11:43 GMT -8
Hey,hey, welcome all I've included the coordinates of the promised topic It is a huge forum for effective, economical combustion of hard coal and other solid fuels forum.muratordom.pl/showthread.php?100061-Ekonomiczne-spalanie-węgla-kamiennegoThe founder of the theme is a colleague Last Rico, who decided to teach people burn coal differently than is generally accepted for what belongs to him thanks. Due to the fact that I live in a country where coal (next to the wood, gas, coke) is the basic fuel for central heating boilers, the theme is very timely especially now when we started the heating season. Burning coal in a boiler, in which all the walls are flooded with water, are eternally cold, is not an easy task If something in the subject will not understand please ask, I will try to explain everything
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