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So, the process used in the article is molten oxide electrolysis - using a raw iron oxide ore in molten form in a bath with its other (oxygen-bound) impurities

by tofof 5y ago

So, the process used in the article is molten oxide electrolysis - using a raw iron oxide ore in molten form in a bath with its other (oxygen-bound) impurities - aluminum oxide, burnt lime (CaO), etc. The neat thing here is that the impurities stay behind in the electrolyte bath after the iron is removed (unsure if it's a gravity mechanism or a cathode attraction, but the molten iron ends up on the bottom of the electrolytic cell). As the article explains, this means that even cheap, low-grade ore with lots of impurities can be used with this technique. The other advantage is that the direct chemical reduction of iron eliminates the multi step (ore in a blast furnace to get pig iron, pig iron + coke, etc) procedure in traditional production. 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.

rocqua 5y ago
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.
baybal2 5y ago
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
- scythe 5y ago
  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/ https://pubmed.ncbi.nlm.nih.gov/23657254/ So, that's why MOE wasn't around before 2013.
  - baybal2 5y ago
    MOE wasn't, but colocating blast furnaces with steel converters is a very old idea.
kragen 5y ago
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.
- kragen 5y ago
  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.)
londons_explore 5y ago
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.

by tofof 5y ago

rocqua 5y ago

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.

baybal2 5y ago

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

scythe 5y ago
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/ https://pubmed.ncbi.nlm.nih.gov/23657254/ So, that's why MOE wasn't around before 2013.
- baybal2 5y ago
  MOE wasn't, but colocating blast furnaces with steel converters is a very old idea.

kragen 5y ago

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.

kragen 5y ago
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.)

londons_explore 5y ago

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.