Reduction Thermodynamics for Iron Oxides

There are several different views about the reduction process of iron oxides and their mixtures. According to the principle so-called transportation stage-by-stage, the reduction of iron oxides is from the oxide of high valence to low valences in turn as follows  

According to Fe-O state diagram (see Fig. 4.4 in Chapter 4), not only metal and oxide with low valance but also the solid solution can be generated in the system. 

The thermodynamic region of the stable iron oxide has been shown in Fig. 3.2 in Chapter 3. 

For the reduction of fused iron catalysts, the reduction temperature is lower than 570°C, regardless of iron oxide in catalysts is Fes04, FeO or their mixtures (of the Fe +/Fe + 0.5, Fe20s does not exist in this system), therefore they can be directly reduced to Fe.  

In general, when H2 and CO are used as reductants, the possible reduction reaction of iron oxides is as follows  

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