Types of Iron Ore: Hematite vs. Magnetite

Iron ore pellets are made from both magnetite and hematite ores. Hematite ores are concentrated using a flotation process. Pellets include a mineral binder that represents about 2% by weight. Much of the ore in pellets made from magnetite is oxidized to hematite during the high-temperature induration process that sets the binder. Induration is necessary to instill the durability necessary to support a blast furnace burden, and to mitigate fines generation during shipping & handling. Direct shipping lumpy ore is now very scarce. Fine iron ore must be agglomerated before being fed to a blast furnace either by pelletizing or sintering, which is normally done at the steel mill. Fine iron ore cannot be fed to a blast furnace, or it will plug. The burden b=must be sufficiently porous to allow the wind to penetrate the birden. Sintering also provides a means to recycle steel mill wastes, including pellet chips, pit scrap and BOF dust.

Iron ore pellets are made from both magnetite and hematite ores. Hematite ores are concentrated using a flotation process. Pellets include a mineral binder that represents about 2% by weight. Much of the ore in pellets made from magnetite is oxidized to hematite during the high-temperature induration process that sets the binder. Induration is necessary to instill the durability necessary to support a blast furnace burden, and to mitigate fines generation during shipping & handling. Direct shipping lumpy ore is now very scarce. Fine iron ore must be agglomerated before being fed to a blast furnace either by pelletizing or sintering, which is normally done at the steel mill. Fine iron ore cannot be fed to a blast furnace, or it will plug. The burden b=must be sufficiently porous to allow the wind to penetrate the birden. Sintering also provides a means to recycle steel mill wastes, including pellet chips, pit scrap and BOF dust.

Atomic weights of Fe at 56 and oxygen at 16. In chemically pure minerals the percentage Fe in hematite Fe2O3 is 112/(112+48)=70%. Percentage Fe in magnetite Fe3O4 is 168/(168+64)=72.4%. In nature magnetite often contains impurities in the ore which makes the Fe content of mined ore lower than hematite. As stated the impurities in magnetite can be removed via processing often resulting in an Fe percentage higher than hematite.

Atomic weights of Fe at 56 and oxygen at 16. In chemically pure minerals the percentage Fe in hematite Fe2O3 is 112/(112+48)=70%. Percentage Fe in magnetite Fe3O4 is 168/(168+64)=72.4%. In nature magnetite often contains impurities in the ore which makes the Fe content of mined ore lower than hematite. As stated the impurities in magnetite can be removed via processing often resulting in an Fe percentage higher than hematite.

If I remember my chemistry, %Fe in (pure) magnetite is 70% and is actually higher than the %Fe in (pure) haematite which is 67.5%. So the opening line in the section on magnetite above is perhaps misleading since it is not the chemical composition which is the difference. The difference is the level of impurities in magnetite deposits which are removed by magnetic seperation and then pelletising is needed to agglomerate the fine magnetite material. This gives a pellet which is more expensive than high grade haematites but with a higher %Fe as the author then correctly states.

If I remember my chemistry, %Fe in (pure) magnetite is 70% and is actually higher than the %Fe in (pure) haematite which is 67.5%. So the opening line in the section on magnetite above is perhaps misleading since it is not the chemical composition which is the difference. The difference is the level of impurities in magnetite deposits which are removed by magnetic seperation and then pelletising is needed to agglomerate the fine magnetite material. This gives a pellet which is more expensive than high grade haematites but with a higher %Fe as the author then correctly states.

The author has not done her research thoroughly enough : processing magnetite ores result in a significantly higher carbon footprint than with the processing of hematite ores.

The author has not done her research thoroughly enough : processing magnetite ores result in a significantly higher carbon footprint than with the processing of hematite ores.