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Aluminum and calcium have substantially stronger affinities for oxygen than iron does, so they'll tend to stay in oxide form even when you're successfully reducing the oxygen.

This is mentioned in the article:

> All of these oxides are more stable than iron oxide, so the iron oxide is the first to separate when exposed to electric charge, breaking down into pure oxygen and iron. The iron, still liquified, sinks to the bottom where it can be tapped out and turned to steel.

There are other elements in ore that will tend to reduce before the iron, like nickel, cobalt, lead, and copper, but they're a lot less abundant than iron and may not be harmful to the iron produced.

I meant when you're successfully reducing the iron. (And the answer for why it goes to the bottom is that it's two or three times as dense as the oxides.)

The higher temperature doesn't consume more energy theoretically as long as there is some way to use the heat of the produced iron and oxygen to help heat up the incoming iron oxide.

Not many heat exchangers can survive 1100 degrees C, but even a rudimentary 'fan blows air over the produced iron and then directs that through a ceramic pipe and through the incoming iron ore' heat recovery system should extract a large percentage of the thermal energy.

You don't target cheap steel market with this, you go after VAR, and ESR steel.

> Among other benefits, you're now only heating the material once instead of 2-3 times, and as a result, you actually consume less total energy in this process even though you have to reach a higher temperature in the single heating.

Combined steel+iron plants were around 60+ years

The key development that allowed this was the 2013 development of chromium anodes that tolerate the insane conditions of the process:

https://pubmed.ncbi.nlm.nih.gov/23657254/

So, that's why MOE wasn't around before 2013.

MOE wasn't, but colocating blast furnaces with steel converters is a very old idea.

I imagine the carbon content of the final steal output might still be hard to control. In which case further treatment would be required, though perhaps that could be done directly with the molten output from the cell (e.g. by blowing CO or O2 through the molten iron depending on whether carbon should be added or removed.