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Abstract
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The production of alumina from nepheline
syenite via lime sintering generates significant waste
due to the presence of silica. In this study, a
carbothermal reduction process was proposed to
simultaneously produce alumina and ferrosilicon,
optimizing conditions using response surface
methodology and the Box-Behnken design. The
maximum conversion of silica to ferrosilicon
was achieved at 1125 °C with a soaking time of
14.86 minutes, a graphite-to-nepheline syenite mass
ratio of 0.53, and a ferric oxide-to-nepheline syenite mass ratio of 0.72. The ferrosilicon produced was separated magnetically, leaving
alumina, sodium, and potassium in the nonmagnetic fraction with efficiencies of 90.85%, 91.98%, and 92.01%, respectively. Following
leaching, the overall extraction efficiencies were 77.1% for alumina, 68.4% for sodium, and 82.6% for potassium. This process provides a
cleaner, more efficient alternative to lime sintering by minimizing waste and producing a valuable ferrosilicon by-product for industrial
applications.
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