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The handling of off-gases is an important part of pyrometallurgical operations, involving the removal and recycling of flue dust, the recovery of thermal energy, and the removal of environmentally hazardous compounds such as SOx and NOx (Offerman, 2019a).
Some of the treatment equipment used includes:
- Wet scrubbers (e.g., Venturi scrubbers): used to remove gaseous compounds such as SOx and fine dust.
- Cyclones: These use centrifugal forces to remove particulate matter.
- Bag filters: These filter systems use fabric filters to trap particulate matter.
- Electrostatic precipitators (ESPs): for dust removal, with a total dust removal efficiency that can reach 95% to 98%.
Here are some advantages of treating pyrometallurgical off-gases:
- Other chemical products, such as sulfuric acid (H₂SO₄), can be produced from the flue gases of sulfide smelting processes.
- Energy recovery as high-pressure steam, and thus electricity, is common in pyrometallurgical smelters. Many sulfides smelters function as small power plants, often capable of partly providing the power required to operate the entire smelter. They also produce steam, which can be used for various heating purposes. Energy recovery is achieved through various heat exchangers, e.g., hot stoves for blast furnace ironmaking and waste-heat boilers (WHBs) for sulfide smelting.
It is worth noting that the off-gas treatment system is often larger than the smelting furnace, and the total investment in the off-gas handling system accounts for 25% to 50% of the total plant investment (Offerman, 2019b).
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Reference:
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Offerman, S. E. (2019a). Critical Materials: Underlying Causes and Sustainable Mitigation Strategies (Vol. 05). WORLD SCIENTIFIC. https://doi.org/10.1142/11007
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Offerman, S. E. (2019b). Critical Materials: Underlying Causes and Sustainable Mitigation Strategies (Vol. 05). WORLD SCIENTIFIC. https://doi.org/10.1142/11007
