Author Topic: Sawed off cupola  (Read 39543 times)

Offline vtsteam

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Re: Sawed off cupola
« Reply #225 on: January 06, 2018, 02:44:11 PM »
All photos restored after Photobucket broke links.
« Last Edit: January 07, 2018, 10:55:43 AM by vtsteam »
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Sawed off cupola
« Reply #226 on: January 07, 2018, 11:25:14 AM »
Having revisited this thread now several years later, I think I understand the charcoal fuel problem better. And possible solutions.  :coffee:

I think I missed the point that though charcoal may be hotter burning, it is also much less dense than coke. So to melt the same amount of iron (with the same amount of heat -- regardless of burn temperature) I would have needed the same weight of charcoal per unit weight of iron. And the burning zone would have needed to be proportionately larger to produce the same amount of local heat.

There are two ways to increase the amount of charcoal available to the burning zone -- increase the diameter of the cupola, or increase the height.

Increasing the diameter would increase fuel mass as the square of  the dimensional increase. Increasing the height would increase the mass of fuel linearly.

Since the burn time was so short, more height would help with that. A sawed-off cupola isn't ideal for much burn time. Even with the short extension, it wasn't adequate, although better.

Increasing the diameter would increase the temperature of the hot area. And this would have possibly been a benefit in melting sufficient metal to fill the well and keep it hot. It's also more efficient with less proportionate heat loss to insulation.

The proportion of charcoal to metal in a charge would probably needed to be higher than with coke (even by weight).
As the metal charge and fuel drops down the cupola barrel, it basically determines metal feed rate to the molten puddle. With a fast burning fuel like charcoal, that metal feed rate is faster as well, since the iron is dropping into the heat zone faster, coming along for the ride with the charcoal.

So, in general, I'm going to say, a specifically designed charcoal cupola might better be taller even than a conventional coke cupola, and the fuel to metal ratio would likely need to be higher. Blast will likely need to be be lower since the charcoal is less dense, and the weight of oxygen needed is proportionate to the weight consumed of a less dense fuel.

Anyway, I think I can see what might have needed changing.  :smart:  :wack:
I love it when a Plan B comes together!
Steve
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Offline RotarySMP

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Re: Sawed off cupola
« Reply #227 on: January 09, 2018, 09:11:17 AM »
Thanks for reposting the photos to your thread. It is a great thread.

Another avenue which springs to mind would be using smaller lumps of iron. Smashing up iron small is a PITA, but might help. It would be cool to you have another go with the larger lunps of charcoal, and smaller iron.
Mark

Offline vtsteam

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Re: Sawed off cupola
« Reply #228 on: January 12, 2018, 04:57:02 PM »
I think if I tried again, I might use the same cupola with anthracite. It is obtainable here. And I already have some.

Anthracite requires a hot blast to work, as I understand it, so the blast would have to be routed through the exhaust gasses. You'd need some other fuel to heat it to start with, as well. Maybe load wood, charcoal or charcoal briquets in the cupola first, then when the exhaust and  intake gets up to temp, add the anthracite. Once that's going, add the iron charge.

The other possibility, for a true charcoal cupola would be to build a much taller and possibly wider cupola. Better insulation and a softer blast would seem to be advantages. The melting capacity would be in proportion to the weight of the charcoal, which is considerably less dense than coke.
I love it when a Plan B comes together!
Steve
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Offline RotarySMP

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Re: Sawed off cupola
« Reply #229 on: January 13, 2018, 07:15:48 AM »
How about a mix of charcoal and coal? Could you turn coal to coke in you charcoal burner?
Mark

Offline vtsteam

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Re: Sawed off cupola
« Reply #230 on: January 13, 2018, 03:19:49 PM »
Neither would work with anthracite.
I love it when a Plan B comes together!
Steve
www.sredmond.com