Answer:
Because they are different oxides.
Explanation:
In both processes they are involve Iron Oxides, but in the case of Ellingham diagrams, it is consider the Iron in combination with oxygen to form FeO, so the melting point is around 1600 ºC. In the case of blast furnace, the Fe that is present in the ores, are primary the hematite (Fe2O3) and the magnetite (Fe3O4).
