That would be red, unless you have something else in it. But it is actually about turning iron ore, which is basically dirty iron oxide, into pure iron:
Hmmm I heard of studies/prototyping/research to completely overhaul steel production in order to reduce the (gigantic) carbon footprint. It might be linked?
Not just heating it differently, really change the process..
Searching for source, will update.
Using hydrogen instead of coal, not for heating but for the reaction actually creating iron.
I remeber reading about rotating furnace, like the one used to create cement.
