The Corex certainly looks an impressive bit of engineering. Just the height of the Chinese one (126 metres!!!) is amazing. Imagine having to go up the top to get a gas sample every shift!
The main difference that I can tell is that the Siemens design reduces the ore in a moving bed (continuously dropping slowly down a packed column), whereas the APG process uses a bed of fluidized ore particles. The first is completely countercurrent. This packed bed can create difficulties with nonuniform gas flow.
The APG bed is known as a CSTR (continous stirred tank reactor). This gives excellent gas/solid contact and ease of control of operating conditions.
The Siemens design requires the gasification of coal prior to reduction of the iron, whereas APG allows the coal to be thrown in with the oxide. The coal gasification step requires tight control of coal size. This is probably less important in the APG process due to the low density of coal compared to iron oxide.
I think the Siemens design requires pure oxygen (correct me if I am wrong), whereas the APG process just uses air with all the nitrogen included.
The Siemens process produces molten iron, so probably would be coupled with a steelmaking plant. The APG design is more suited to supplying smaller, geographically distributed EAF's.
All in all, I would imagine that the APG process would end up simpler and more compact.
Energy...???? Bit hard to tell from the outside looking in... especially since we don't have public figures for any energy balances from APG. If Siemens use pure oxygen, that is likely to reduce energy losses.
I would imagine that the capital cost per unit production capacity would be higher for Corex though due to the engineering sophistication and support structure necessary.
But I could be misguided...:)
APG Price at posting:
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