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Reclaiming metal from slag


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HI guys first post on the forum but I've been a member for a while. Anyway quick introduction my name is will and I've been blacksmithing for a while at living history museums and in the past few years smelting iron as well. I've run a lot of Aristotle and evenstad style furnaces for remelting metal.

 I've been wondering if it's possible to use the slag from Full smelts to run through the remelting furnaces as a way of reclaiming iron. My most recent run I used an evenstad style furnace with a tap hole and had a liquid slag run but wasn't able to keep it going and the furnace clogged however I did end up with a frozen slag bowl and what looks to be iron on top of it. The picture is the largest piece of what i got out and some of the slag that did run. has anyone had decent success with this.

Thanks

Will

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It's theoretically possible, but I don't know anyone who has done it (that I know of!).  I do know that medieval and later iron smelters used the slag from Roman furnaces as part of the ore charge because it was high enough in iron to act as an ore itself.  The trouble is the slag is already at its happy place in terms of composition, and just running hot carbon monoxide over and through it is not going to reduce the iron oxide as much as it should ordinarily.  If you can powder it and run it through a shaft furnace slowly that might be your best bet, especially if you add some rich ore to start out with a high balance of iron.  Iron likes other iron, and practically speaking you're never going to get the slag down to less than around 30% iron, so if the slag is barely 50% now adding some 60+% ore will adjust things into the side of the equation that tends to result in iron rather than just more slag.

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To be clear I am using mostly the mother(iron and slag that doesn't weld to the main bloom) from short stack bloomery furnaces and other highly magnetic slag as charges through the evenstad style open hearth furnaces that Lee sauder and mark have spoken about on the forum.

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Would you think that a typical 3 ft shaft furnace would do this well or since the mother and slag are already reduced a smaller furnace would suffice. I seem to remember Lee talking about a furnace built in scale to the short stack furnaces but in a lower height but I can't seem to find that post anymore.

Your essentially referring to seeding a furnace with iron from ore and then trying to add slag as an ore source after a point if I'm reading correctly

Edited by Will Urban
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That is what I was saying, yes.  And yes, I'd stick with the 3-ft shaft and 10" bore.  You could possibly go to a 2-ft shaft and 8" bore.  Keep in mind I am no expert, though!  Lee is, and Mark is pretty darned good himself.  As long as the slag is highly magnetic you can treat it as ore.  

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  • 2 weeks later...

Will- yes you can remelt it in your evenstad hearth, or a little aristotle size furnace, to reclaim any metal that has already been reduced, but couldn't get into a bloom. You just need a decent avenue to keep draining the slag away until you've got enough bloom there.

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Thanks for the reassurance Lee. I used a half inch hole for this attempt and got slag to tap liquid almost like a regular smelt. The problem I had was that it froze over immediately after. Next try I was going to use a larger area for tapping slag any suggestions.  I also wanted to ask about the height of the walls I typically build the evenstad hearths about six inches tall from the floor should I build these taller to keep in more heat?

Thanks

Will 

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