Sinterização de finos de manganês: como reduzir custos e consumo de combustível sólido
Sintering of ore fines reduces costs, improves energy efficiency, and increases operational safety in submerged arc furnaces.
In ore beneficiation, a large quantity of fines (fraction smaller than 10 mm) is generated. These cannot be used directly in furnaces due to permeability issues, dust entrainment, and low reactivity.
To economically valorize this material, different agglomeration methods can be employed, among which sintering stands out.
What is sintering?
The sintering process consists of the thermal agglomeration of ore fines — focusing on manganese fines (sinter-feed) — mixed with other inputs such as:
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Coke fines (fuel);
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Limestone (flux);
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Return material.
The final product is a porous material with a structure suitable for blast furnaces and electric furnaces. It also exhibits excellent reducibility due to the partial pre-reduction of manganese oxides.
The impact of variable costs
In manganese ferroalloy production, from the variable cost perspective, the approximate distribution is as follows:
| Input | Share |
|---|---|
| Ores | 45% |
| Energy | 25% |
| Reductants (coke) | 25% |
| Other inputs | 5% |
Therefore, proper electric furnace performance is extremely important to keep these costs under control and ensure company competitiveness and profitability.
Benefits of using sinter in electric furnaces
Considering these aspects, the use of sinter in manganese ferroalloy production in submerged arc furnaces can bring significant operational benefits:
1. Improved burden resistivity
In submerged arc furnaces, electrode positioning is critical for proper operation. The presence of sinter in the burden increases the electrical resistivity of the bed, favoring proper electrode immersion and promoting greater heat transfer through ohmic resistance, leading to better energy utilization.
2. Reduction of "blows" and increased operational safety
The improved burden permeability, provided by the sinter's particle size and porosity, allows process gases to percolate through the mass easily, preventing the formation of gas "pockets" that, when suddenly released, cause undesirable "blows." This results in furnace stability and, most importantly, operational safety.
3. Reduced coke consumption
Sinter, being a pre-reduced material (with lower chemically bound oxygen content), reduces the coke demand for the manganese oxide reduction reaction, decreasing the amount of reductant required per ton of alloy produced.
4. Reduced specific energy consumption (MWh/t)
The combination of the above factors — better resistivity, greater permeability, and fewer endothermic reduction reactions — results in a thermally stable operation with less heat loss through gases and reduced exposure time of the burden to electrical power, thus lowering specific energy consumption per ton of ferroalloy produced.
Conclusion
Manganese ore fines sintering proves to be not only a viable solution for utilizing tailings and previously discarded materials but also a technically advantageous strategy for ferroalloy production in submerged arc furnaces.
The benefits range from improving furnace electrical and thermal parameters to reducing critical input consumption, such as coke and electricity, directly impacting variable costs, which represent the largest share of operational expenses.
Additionally, gains in operational stability and safety reinforce the positive nature of using sinter in the operation.
Therefore, investing in sinter quality control and its proper burden dosing is a promising path to:
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Increase production efficiency;
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Reduce emissions (through lower use of fossil reductants);
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Improve the economic and environmental sustainability of the manganese alloy production process.
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