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Mick Maxen

Roasting ore

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For what is worth, there is a change in the spatial orientation of the Fe atoms ehen going from hematite to magnetite. Take that back, I should say ions instead of atoms since there is a need for an unbalanced number of protons and electrons in order for the Fe to have a charge. Either Fe++ or Fe+++. Going back to the explanation, there is a change in the spatial orientation of the Fe ions when going from Fe2O3 (hematite) to Fe3O4 (magnetite). Interestingly this spatial orientation of a Fe++ and a Fe+++ falls into a path that allows for transfer of electrons between the two. This electric path is responsible for generating a magnetic field.

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See now, I did not know that! I always said it was natural magic...

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Not smarter than you, Zeb. I have just read a bit more but given where you are at now at your age I am pretty sure you would have read more than I by the time you get to be as old as I am. ;)

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Back in 2000 or so I did some smelts with ore I got in central wisconsin. It had a large amount of granite mixed with very low quality iron...at the time it was all I could find.

It took many hits with a sledge to break up. After roasting and water quenching it crushed with just hand pressure.

 

That alone is reason enough to roast in a simple wood fire.

 

I now use 60% iron magnetite in near dust form and it is a struggle to get high yields of bloom due to the extra oxy.

Other ores are a better choice.

 

Ric

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Ric, Have you been baking your magnetite into some corn meal, for some sizing?

 

I found that helped me a bunch with the very fine magnetite.

 

Mark

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Ric is that the magnetite" flower" I used for arctic fire?

 

Zeb, thats a great little trick , Im gonna try that for sure.

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Ric, Have you been baking your magnetite into some corn meal, for some sizing?

 

I found that helped me a bunch with the very fine magnetite.

 

Mark

Mark I bulk it up in several ways..it does not blow out the stack.

 

Ric is that the magnetite" flower" I used for arctic fire?

 

Zeb, thats a great little trick , Im gonna try that for sure.

I assay in a carved out firebrick either in the forge or with a torch, but the wood seems a cheaper solution.

Yes..same ore that you used at Arctic Fire.

Ric

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If Fe203 is changing to Fe3O4, haematite to magnetite when we roast it. What is happening to Siderite ore that is Iron Carbonate FeCO3 when its roasted and turns magnetic ?

 

Mick.

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FeC03 + heat = Fe203 & C02 Then Fe203 more heat = Fe304? This is just a guess since I was comparing the process for turning calcium carbonate into lime.

Edited by brandon p

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I'm not sure, no time this morning to look it up-- but I think FeCO3 goes straight to FeO + CO2, and that's why siderite is considered easy to smelt (if it's rich enough, of course)--Lee

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OK , taken from the wealden iron magazine.....

As temp changes up to 400C.....FeCO3 to FeO+ CO2 followed by 3FeO + 1/2O2 to Fe3O4 siderite converts to magnetite}

As temps rise through 500C... 2fe3O4 + 1/2O2 goes to 3[ gamma-Fe2O3) or magnatite is converted to magnetic brown gamma-iron oxide (maghemite) ..

At around 600C maghemite starts converting to non magnetic Red Alpha-Fe2O3 (hematite) which is non magnetic.

 

Siderite also breaks down into limonite due to oxidisation and action of Rain (I guess acidic) ... somehow??? couldn't find an equation for that....

Edited by owen bush

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Ok found the weathering equation........

2FeCO3+H2O + 1/2O2 goes to 2Fe(OH) + 2CO2 or Siderite + water and a little oxygen goes to Geothite, liberating carbondioxide.

 

 

further weathering converts Geothite into brown Limonite otherwise known as clay-stone iron ore.....

guess there is yet another equation for that.

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OK , taken from the wealden iron magazine.....

As temp changes up to 400C.....FeCO3 to FeO+ CO2 followed by 3FeO + 1/2O2 to Fe3O4 siderite converts to magnetite}

As temps rise through 500C... 2fe3O4 + 1/2O2 goes to 3[ gamma-Fe2O3) or magnatite is converted to magnetic brown gamma-iron oxide (maghemite) ..

At around 600C maghemite starts converting to non magnetic Red Alpha-Fe2O3 (hematite) which is non magnetic.

 

That's interesting. if correct. It would seem like an argument against roasting siderite at all. (At least as far as the iron chemistry goes, leaving aside the sulfur issue, or ease of breaking to size.) It would at least make sense to roast it in as reducing or neutral a fire as possible.

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Might as well roast it, after-all you'll just be doing the same thing in the stack eventually, right?

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Thats how I recon it, its worth it from the rock breaking point of view if nothing else.

Edited by owen bush

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Might as well roast it, after-all you'll just be doing the same thing in the stack eventually, right?

 

Well, no. The equations Owen put up are for an oxidising fire, and say you're increasing the oxygen in the ore. maybe not a big deal in practice, but the opposite direction of where you want to go.

 

In the stack, you'd be in a reducing atmosphere. The FeCo3 to FeO + Co2 only needs heat. Then you're already at FeO.

 

Like I said, maybe not a big dealin the real world, but it would be an interesting thing to play with. Might need less stack height and/or charcoal if you didn't roast.

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I roast with a gas burner, in a big make shift forge.....kind of un rootzy but the last time I roasted with wood I had neighbours complaining about the smoke... so I probably roast at near neutral (ish).

 

 

I am torn between the "want" to learn more about this process and the "fact" that i have done just fine knowing very little and relying on some stats (for the sake of repetition) and gut feeling backed up with very limited chemistry.

 

Its complicated for sure, much more complicated than in practice. I had an interesting day smelting with the wealden group who "know" an awful lot more than I do, and have not had any good results ( from a making iron point of view, which is kind of the point .....isn't it)

 

 

 

so what would the chemistry for the reduction from finely broken down un roasted siderite be.......

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Well, no. The equations Owen put up are for an oxidising fire, and say you're increasing the oxygen in the ore. maybe not a big deal in practice, but the opposite direction of where you want to go.

 

In the stack, you'd be in a reducing atmosphere. The FeCo3 to FeO + Co2 only needs heat. Then you're already at FeO.

 

Like I said, maybe not a big dealin the real world, but it would be an interesting thing to play with. Might need less stack height and/or charcoal if you didn't roast.

 

Isn't it quite oxidizing at the bottom? I thought down where all the real action takes place you would be having excess oxygen touching the ore at about the melt point due to the small amount of charcoal between the ore and the tuyer (simply due to lack of space). Where is the melting actually happening in relation to the air blast? I have really got to try this just so I can know more, but at the same time this stuff is helping me prep SO much! Y'all are a bunch of fun!

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Hey Owen

 

Yeah, I smelted next to the Wealden guys at the HMS brouhaha in 2010. I tried to convince them to be less timid about the whole thing- seems to me they just needed to crank it up and go at it with more air, and more overall vigor!


So if the equations above accurately describe things- it would make sense to try unroasted siderite (if it hasn't already weathered to goethite/limonite). When you heat it and knock off the CO2, you're at FeO already. If you start with Fe2O3 (or Fe3O4), your first step in the stack is to reduce to FeO, then you go to Fe. So if you start with FeO, you're already halfway there. That's why it might need less stack height or less charcoal.

 

But maybe it don't mean diddly in real life, can't know 'til you try.

 

I understand your reluctance to get into a bunch of comparative experiments, when you've got something good going. But I love that stuff, so maybe that's the next excuse for us to get together ! -- try to tackle both the siderite roasting issue and the sulfur issue?

 

Lee

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Isn't it quite oxidizing at the bottom? I thought down where all the real action takes place you would be having excess oxygen touching the ore at about the melt point due to the small amount of charcoal between the ore and the tuyer (simply due to lack of space). Where is the melting actually happening in relation to the air blast? I have really got to try this just so I can know more, but at the same time this stuff is helping me prep SO much! Y'all are a bunch of fun!

 

Jerrod, it seems to me, from lots of watching, that the the oxidising zone at the tuyere ain't much bigger than your fist. Maybe two fists.

The rest of the stack is strongly reducing (depending somewhat on charcoal:ore ratio). A thing to remember in this situation- above a red heat, CO2 in the presence of more C immediately goes to CO (Boudouard reaction, or as my buddy Skip like to call it , the Boudoir reaction). So if you have enough charcoal, it's hard to have much oxidising zone.

Edited by Lee Sauder

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Jerrod, it seems to me, from lots of watching, that the the oxidising zone at the tuyere ain't much bigger than your fist. Maybe two fists.

The rest of the stack is strongly reducing (depending somewhat on charcoal:ore ratio). A thing to remember in this situation- above a red heat, CO2 in the presence of more C immediately goes to CO (Boudouard reaction, or as my buddy Skip like to call it , the Boudoir reaction). So if you have enough charcoal, it's hard to have much oxidising zone.

Thanks Lee. I just would have thought the zone would be bigger. Again, it is so good to learn this all before my first smelt (it WILL happen... eventually).

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The oxy zone depends upon the air in and tuyer shape and fuel and such

If you have a 1/4" tuyer outlet and are pushing in 1,000CFM with an electric blower you get an oxy lance that can chew a hole through anything in the furnace (including the furnace) in front of the tuyer. The up side is it never clogs..the down said is you tend not to make iron/steel.

If you have a 1" tuyer and have two hand bellows then you get a collapse of the oxy zone at every hesitation in the puff.

 

If you have a steady flow and all is well for the tuyer and such then I would think the zone projects a bit down bubble below the tuyer and then washes up into the fuel and is overtaken about 4-5" inches up the stack by the carbon.

 

Ric

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Personally I think over thinking is realy deep wolf hole where any can step in to...

 

In todays light roasting to bog, lake ores ( limonites) is ok..others like Fe2O3 or Fe3O4 would not see the benefit.

Also in all reactions in side the different zones are more or less in our control...mostly less.

 

One huge reaction that need to keep in mind is exotermic reaction...this is seen in flame, like other indicators too.

 

Over thinking leads us totally wrong path´s...keep it simple, think like they did at ancinet times and all will be way easyer ;D

 

 

Niko

Edited by Niko Hynninen

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