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Author: Subject: Super-high temperature carbon-steel furnace
neutrino
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cool.gif posted on 5-1-2005 at 20:17
Super-high temperature carbon-steel furnace


This is sort of a random idea I had a little while ago and was wondering if it could be put to practical use.

A normal gas-air flame will heat something up to about red/orange heat—about 700*C lower than the flame temperature because of the cooling effects of the flowing gas. A charcoal fire will do something similar. The question remains: how do you heat things of significant size (not just something like a thin wire) to white heat for a long period of time?

Reading about the Bessemer process, I got an idea. In the process, iron with a good deal of carbon and silicon in it is melted and air is blown through it. The reaction of these elements to form their oxides heats up the iron from barely molten at the start of the reaction to completely molten and white hot (coke furnaces couldn’t even melt the stuff half-decently). Here, you have a large pool of extremely hot material to heat that retort to distill your phosphorus or whatever else would require prolonged ungodly temperatures.

Theoretically, all you’d have to do to keep the reaction going is add carbon (charcoal). This poses two questions: how fast will it dissolve in the iron and is the silicon (described by Bessemer as a major heat-producing element) really necessary?
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rikkitikkitavi
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[*] posted on 6-1-2005 at 07:08


well actually it is not the gas that cools only, it is quite a lot of radiant cooling aswell.

The effect versus area is not so good for a "small " flame compared to a larger flame, so it is easy to build a oven , heated by gas that reaches 14-1500 C (if the air is preheated) if it is just large enough.

If done as you say, yes, adding charcoal would dissolve the carbon in the iron, but at the same time iron is oxidized so you would eventually burn away everything.
The trick is to stop in time, before to much iron is lost.

Silicon is present in the ore, and is definately an unwanted alloy element in the iron/steel (except from some special alloys) . The dissolving of carbon would probably be quite quick , and if the air is blown into the molten iron so it bubbles through then the agitation is good, which increases the dissolving rate substantially.
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Cyrus
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[*] posted on 6-1-2005 at 18:03


Hmm, this sounds a bit awkward when ordinary wood will get plenty hot for phosphorus. I just don't see the Bessemer process being useful for heating. When you cool the furnace down you'll be left with a huge chunk of iron- Do you want to remelt this every time the furnace needs to be fired up. This is just my mostly uninformed pessimistic opinion. :)

Coal/Coke/Wood/Charcoal/Nat. Gas/Propane/Waste oil are all plenty hot, and if that's too messy, there's always electrical heating, and then there are arc furnaces. :)




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neutrino
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[*] posted on 6-1-2005 at 19:14


For some preparations of phosphorus, you need to heat a retort to a steady white heat.

I was thinking of the following startup/shutdown procedure: Start a small thermite reaction to get a small amount of very hot molten iron. Add charcoal and more iron while blowing air through the mass of liquid iron, thus steadily building up the mass. When you’re finished, turn off the air supply, add as much charcoal as will dissolve, and pour ingots. The high carbon content should make the next startup easier.

The thing I’m not sure about is the burning of the iron itself. I’m guessing that this shouldn’t be too much of a problem as long as there’s enough carbon in the melt, but this is only a guess.
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[*] posted on 7-1-2005 at 20:12


I'm sure you'll BAT get a nice steady white heat from coal/charcoal. :) Do you have a furnace or anything currently?

Also, what are you using for the retort? Slip-cast zircon or something?




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jimwig
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[*] posted on 8-1-2005 at 13:12


more heat

1. more insulation surrounding the fire box

2. add a blast of air to the hot box

3. make firebox just large enough

4. gain experience with using furnaces. take a sculpture course using molten metal techniques

my commercial kiln (small about 12x12x8";)goes to 2000F and my two small (antique) dental furnaces will melt gold.
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neutrino
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[*] posted on 8-1-2005 at 15:09


No, I currently have nothing. What you are saying is that this will only be a marginal improvement over the standard furnace? I thought it would have been more because Mr. Bessemer said that the standard coke furnaces of his day could only get steel partially molten, while the Bessemer process would make it completely fluid.
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neutrino
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[*] posted on 11-1-2005 at 17:36


I did a little more research and found some more information about this. I was wrong about the ‘partially molten steel’ thing, he said it would only get steel up to a pasty mass in the most powerful furnaces, although he was probably referring to large amounts (several tons) being processed at once. In his description of the process, he said that the carbon is first burned off, then the reduced carbon content allows some oxidation of the iron. So, as long as the carbon content is high enough there should be no problem with this. The silicon wasn’t even mentioned here, so it should be insignificant.
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[*] posted on 11-1-2005 at 19:27


You could melt and heat the iron white hot using an induction heater, provided you had sufficient insulation.
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[*] posted on 12-1-2005 at 14:01


>Do you want to remelt this every time the furnace needs to be fired up<

if I am hearing this right you cannot remelt this "plug" of iron. when small cupola furnaces are shut down the bottom is dropped leaving nothing in the fire box. i am not familiar with the Bessemer method but the energy necessary to remelt a sizable chunk will be enormous. and btw this is all to do with cast iron and not for steel.
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FrankRizzo
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[*] posted on 12-1-2005 at 22:18


Why not just go all-out and make an arc furnace? ;)
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