Simultaneous energy saving and production rate improvement in pelletizing process by solid fuel addition

• The production rate of induration machine was increased more than 30% by adding solid fuel to the initial mixture.
• The overall energy consumption of pelletizing process was reduced to at least 35% by adding solid fuel.
• The reducibility of pellets was noticeably increased by usage of anthracite as solid fuel.
• The strength properties of fired iron ore pellets were relatively improved by adding solid fuel.

Generally, in pelletizing process, the magnetite ore is oxidized to hematite during induration as an exothermic reaction; thereby the magnetite ore requires less energy compared to hematite ore. This form of heat generation inside the pellet is much more efficient than the transferred one from hot gases heated by external burners. This mechanism leads to higher production rates with lower total energy consumption. In order to achieve these improvements, different amounts of anthracite as the solid fuel (0 to 0.95 wt.%) were added to the initial mixture of hematite (60%) and magnetite (40%) ores. The portion of hematite was reduced to magnetite phase by anthracite, and then the produced magnetite re-oxidized again to secondary hematite. Afterwards, the studies of mechanical and reducibility behaviors of pellets were performed by the tumbler/abrasive indexes and the Linder experimental tests. Furthermore, the microstructural evaluation was carried out by scanning electron microscope (SEM). The results demonstrated that by anthracite addition to the mixture, the production rate was significantly increased (more than 30%) while the natural gas consumption was reduced at least 35%. Moreover, based on the strength and reducibility analyses, the anthracite addition up to 0.78% (as an optimal amount) caused considerably to the betterment of fired iron ore pellet properties.

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