1) the Tm of Fe203 Haematite is 1838 K and for Fe3O4 Magnetite is 1867 K. The melting point of a substance is only dependant on the temperature not on the environment.
2) the reduction of Iron can take place in the presence of CO as it does in the blast furnace (800 - 1050oC) so the formation of iron micro spheres in the system could depend on the flue gas composition; as the formation of Iron would only happen with sufficient CO. Excess O2 would result in the oxidation of the iron formed back to Iron oxide
