h a l f b a k e r yYeah, I wish it made more sense too.
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It's about as simple as the summary: construct a small wood gasifying stove (a reverse downdraft gasifier), put a glass shade (similar to the shade on a kerosene lamp) on it to protect it from the wind, and hang a piece of lime inside it, above the flame. The heat causes the lime to glow.
It won't
be as bright as if lit by an oxyhydrogen torch, but it won't be as heavy or as dangerous, either.
Plus, it could probably be made as small as a kerosene lantern (I can't imagine a *small* oxyhydrogen limelight)
Some science demonstration thingy about thermoluminescence
http://www.chem.lee...emonstration_19.htm
[goldbb, Mar 18 2009]
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Sounds like something Sir Humphrey Davy would've came up with. |
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Good stuff! Could you also pipe it around a building like gaslights? Another thought is, is it possible to make a woodburning stove from materials which are transparent to visible light, stand up to the heat and also act as good insulators? To an extent, that can clearly be done because they have windows (can't think of a joke here so i'll leave it hanging). The initial combustion itself would provide light too. Whereas the amount of lighting available might be the same, sending it round in pipes would compensate for that by lighting other places. |
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Is it possible that an oxy-hydrogen flame is so much hotter than any others ? |
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Here's a quote I found on the web (see link for the full page) |
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/C.H. Pfaff [5] says if the light of a wax candle be unity, the light emitted by a cylinder of lime one-fifth the diameter of the flame of the candle is 153 when heated by the oxy-hydrogen flame; 76 by the ether-oxygen flame; 69 by the alcohol-oxygen flame; and 19 by the oxygen-coal gas flame./ |
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The author of the page I found, was quoting a publication from 1837. I'd be happy if someone could find some more modern info regarding the brightness of limelight, using various heat sources. |
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I would assume that wood gas and coal gas have approximately the same energy content. Of course, since air, not pure oxygen is used, the temperature will surely be cooler, and the brightness of the lime lesser. |
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nineteenthly, yes, you could pipe woodgas around your house like gaslights, but it wouldn't be any cheaper than using gas from the utility company. Also, if you're producing it yourself, it's going to come out of the gasifier burning hot, so you have to cool it before piping it (or else very thoroughly insulate the pipes). Also, don't forget that woodgas (just like coal gas aka producer gas, which *used* to be what the utility companies provided) contains significant quantities of carbon monoxide, so you have to be very careful to avoid co poisoning. Gas from your (modern day) utility company is mostly methane; you only have to worry about it catching fire / exploding, not poisoning you. |
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Electricity is a much safer and more efficient way of lighting your home. |
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But if you're a camper/survivalist, and you're going on a long trip in the woods, a woodgas lantern might possibly be a better pick than an oil/kerosene lantern, or a battery lantern. |
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It would be less fragile than a mantle system. |
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I messed around last winter with directly heating lime on an open fire, using a small electric fan to increase the temperature. My goal was to increase the radiant energy, visible or not, into the room. It lit up the room well enough to read at some distance from the fire. The light was a yellowish colour, not the usual orange-red of a fire, but far from the dazzling white of true limelight. |
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I'm guessing that your system would produce a similar temperature, and therefore a similar quality and quantity of light, but with better control over the brightness and placement. The luminous efficiency would be low, but that might not matter much, especially if the heat were used. |
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[Goldbb], i'm aware of the carbon monoxide content, but i'd take issue with the question of cost. If it's actually wood gas, as opposed to producer gas from a non-biomasse source such as coal, it's potentially free because of the ready availability of discarded wood. However, fire provides light in itself, so to me it would make more sense to pipe the light around through fibre optics than the potentially dangerous CO stuff. Even so, i would also question how hazardous that is, since that would depend more on how good the plumbing is. Electric current is also dangerous, but with good wiring that can be ignored most of the time. What's the essential difference in risk between good wiring and good plumbing? Doesn't the hazard essentially depend on how well the pipes are sealed? I've assumed the whole thing is sealed from the inside and vents to the outside.
The issue of my apparently unusual colour perception comes up again here, as i would be concerned about the colour of the light. Orange and yellow light is depressing and trying to me, so i would hope that this would be less saturated at least. Firelight is intolerable for more than a minute or so. It seems that others don't have this. I would want some form of blue or violet light rather than stuff from the other end of the visible spectrum. Are we talking about dull colours? |
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Regarding the safety of piping around carbon monoxide: Coal gas was in common use until the middle of the 20th century... people did occasionally become sick or die due to leaks or due to an accidentally extinguished pilot light. Not *regularly*, but it did happen. |
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Regarding using fiber optics to route the light through your house: If you're going to do *that*, I suspect that it would be more fuel efficient to make the gas, burn it in an diesel engine, generate electricity, and use the electricity to light up LEDs. |
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As for the color... I don't know. The heated lime will doubtless glow white, but some of the light's color will also come from the burning gas itself, whose color I don't know. |
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ahh the myth of "free" firewood. |
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I'm old enough to remember "town gas", which is effectively the same thing, and i think it burns reddish-orange. That's also what the gas looked like in the cruddy illegally-let house i used to live in. It was useful if you couldn't sleep! Concerning the lime, i presume you're talking about quicklime, and there i think you might run into a problem. I think you might end up with calcium carbonate because of the carbon monoxide, but i don't know enough about what would happen. Maybe it should be kept separate, so it gets heated but can't combine with the actual gas. Calcium carbonate would melt, i think. |
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We once tried something similar in school, getting lime to glow just from the heat of several (methane) Bunsen burners. The light was measly at best, and the metal tongs holding the lime were glowing about the same brightness as it. |
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A few things I do remember playing around with in science classes are firstly, if you dip a piece of wood in water before putting it in a Bunsen flame, you get a nice white glow. Also, if you take a piece of thin pencil lead (such as from a mechanical pencil) and connect it to a 12 volt source, it glows white and very hot, enough to burn a hole in a table. |
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Also, try plugging a Bunsen burner into a tap. |
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Were you actually using calcium oxide? It's the temperature rather than the chemical reaction, i think. |
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The thermoluminesence of lime should not play a role after the initial heating, and so the lime will only glow as any non-metallic object would, so hanging any type of non-splintering stone, ceramics, whatever in there would have the same effect, no? |
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It seems that zinc oxide does the same thing, though i may be wrong. |
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[loonquawl] the lime absorbs the IR and emits visible-light spectra.
hmm... wonder what the energy>visible-light efficiency is compared to a lightbulb. |
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As far as I can tell, the useful property of CaO is that it doesn't readily melt or react at high temperatures. Ca(OH)2 and CaCO3 both decompose to CaO at red heat. |
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