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THE PROCESS
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Char production .
The reductant for the process is produced by the devolatisation of thermal coal. The volatiles (off-gases) are recovered from this stage and fed into the oxidiser for combustion. The devolatised coal is then milled to sub 2mm size. |
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Recipe formulation and blending.
The fine iron oxide and milled char are added according to the required blend recipe via a weigh hopper, and mixed. The blend recipe is dependant on ore type and quality, and properties of the char (fixed carbon, reactivity). |
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Reduction.
The heart of the process, reduction proceeds in 2 stages – pre-heating and reduction in externally heated rotary kilns. The gaseous reduction products (primarily CO with CO2) are extracted to the oxidiser for combustion. |
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Oxidiser.
Gases from the coal devolatisation and ore reduction processes are combusted in the oxidiser. The hot output gas is then cascaded around the reduction, pre-heating, and ore drying units as the primary energy source for these processes. The amount of energy available from these gases is a function of the properties of the coal (volatile content, CV of volatiles), recipe (amount of carbon addition), quality of the feed ore (% Fe2O3 or Fe3O4 in the ore), the reduction efficiency, and thermal design efficiencies (maximising energy transfer to product & minimizing heat losses to atmosphere). |
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Cooler.
The reduced Fe powder is cooled to approximately 80°C under reducing conditions to prevent re-oxidation, before further treatment. |
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Magnetic separation.
This beneficiation step of the reduced Fe powder removes excess carbon and gangue (from the ore and char ash), giving a higher total and metallic Fe content in the product. Recovered carbon is recycled into the reductant feed. |
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Final product options.
The reduced iron powder can now be i) melted directly by feeding into a DC arc furnace or ii) briquetted for use as a feedstock into traditional electric steelmaking processes. Depending on requirements, the product can be hot or cold (with binder) briquetted – the final form being a HBI or DRI product. |
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