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blogfast25
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What makes you think keeping the shells in a crucible will make one iota of difference? You burn charcoal (or pine cones) and use the hot combustion
gases, rich in CO<sub>2</sub>, to heat furnace and crucible in it. How can a crucible make a difference there/
[Edited on 25-9-2014 by blogfast25]
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Little_Ghost_again
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Quote: Originally posted by blogfast25  |
What makes you think keeping the shells in a crucible will make one iota of difference? You burn charcoal (or pine cones) and use the hot combustion
gases, rich in CO<sub>2</sub>, to heat furnace and crucible in it. How can a crucible make a difference there/
[Edited on 25-9-2014 by blogfast25] |
As I stated above, Nothing at all " I doubt that is going to make any difference with CO2 though"
It was more of I hope I am wrong and it will make a difference kind of thing  .
Slight fly in the ointment at the moment, the last one used a leisure battery to power 12V air source, this one uses a 240V airblower from a bouncy
castle, the problem is I have started building the MK2 15 meters too far for the power extension lead .
So I will have to drag the small petrol generator around the back when I want to use it 
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macckone
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A crucible with a lid will keep contaminants out while allowing CO2 to escape. I mean do you really want to be picking
chunks of CaO out of ashes? It is more of a cleanliness thing.
The CaO doesn't care if it is in a crucible or not as it is formed.
In fact the crucible will slow down the reaction because the
heat must penetrate the calcium carbonate mass through
the crucible.
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WGTR
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One thing that I haven't seen mentioned so far is the effect of carbon monoxide on the equilibrium of the reaction. I've calcined small pieces of
limestone in a charcoal kiln before. It was an updraft design, with forced air coming from below. The kiln was loaded with charcoal and lit.
After everything heated up, more charcoal was loaded, and the limestone was placed on top of the charcoal. A lid was placed over the kiln, with a
hole for the exhaust gasses. Most of the oxygen would get consumed at the bottom of the pile, with the heat and CO2 rising through the rest of the
hot charcoal. The CO2 would be mostly CO by the time it got to the lime. This gas could be easily ignited at the exhaust vent. With the kiln
insulated with fire brick, the atmosphere was glowing bright orange under the lid. With .25" pieces of limestone, they were calcined after about
15-20 minutes. For cool-down, more charcoal is loaded in the kiln, and the air holes plugged until things were no longer glowing, and the lime could
be removed.
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blogfast25
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| Quote: Originally posted by macckone | In fact the crucible will slow down the reaction because the
heat must penetrate the calcium carbonate mass through
the crucible. |
Assuming equilibrium temperature is achieved fairly quickly the crucible will not hinder the process. It's only temperature that matters.
| Quote: Originally posted by WGTR | | One thing that I haven't seen mentioned so far is the effect of carbon monoxide on the equilibrium of the reaction. |
CO should not affect CaCO<sub>3</sub>(s) < === > CaO(s) + CO<sub>2</sub>(g)
[Edited on 26-9-2014 by blogfast25]
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Little_Ghost_again
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Thanks guys and thanks Blogfast for the equation, I have to redo the MK2 because of my lack of the whole measure twice cut once thing . I got switched the wrong way round lol.
yeah the crucible is mostly to keep it clean and out the ash, also I want powder the shells first, I found a really old Darkroom film developer
machine in one the buildings. Dad says he had it a long time ago when he was into photography. A few mods and I should have a ball mill , my wrists are getting weaker so crushing things with a P&M hurts a fair bit.
My first batch of Ethanol got messed up today , so I have to get another batch
going.
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WGTR
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My intended meaning, though poorly phrased, is that the presence of CO lowers the partial pressure of CO2, helping drive the reaction to
the right. With the right kiln design and fuel loading, little CO2 should be exiting from the kiln.
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blogfast25
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| Quote: Originally posted by WGTR | | My intended meaning, though poorly phrased, is that the presence of CO lowers the partial pressure of CO2, helping drive the reaction to
the right. With the right kiln design and fuel loading, little CO2 should be exiting from the kiln. |
If you burn the fuel completely to CO then yes, the partial pressure of CO<sub>2</sub> will basically be that of air and the equilibrium
will not be affected by the off gases.
But the combustion to CO runs less hot than to CO<sub>2</sub>:
C + 1/2 O<sub>2</sub> === > CO is less exothermic than ('all other things being equal'):
C + O<sub>2</sub> === > CO<sub>2</sub>
[Edited on 27-9-2014 by blogfast25]
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