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How is ferroniobium made from pyrochlore concentrate?
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niobium processing
Four one-millimetre thick samples of niobium metal foil.
Ferroniobium is produced from pyrochlore concentrate through an aluminothermic process. The production involves the following steps:
- Preparation: The pyrochlore concentrate is mixed with hematite (iron ore), aluminum powder, and small amounts of fluorspar and lime fluxes in a rotary mixer.
- Reaction: The mixture is placed in steel containers lined with magnesite refractory bricks, which are set within circular concave pits made of lime, fluorspar, and silica sand. The reaction is initiated by igniting a mixture of aluminum powder and sodium chlorate or barium peroxide.
- Reduction: An exothermic reaction occurs, reaching temperatures of approximately 2,400 °C (4,350 °F) over 15 to 30 minutes. During this process, gangue impurities—including all thorium and uranium oxides—are separated into the molten slag.
- Finishing: Once the reaction concludes, the slag is tapped off, and the vessel is lifted to allow the metal to solidify in the sand. The resulting ferroniobium alloy is then crushed into particles of approximately 10 millimetres for marketing.1