Thermochemical Effects of Flux and Coke Amount on the Smelting of Low-Grade Chromite Sand to Ferrochrome

Ferrochrome serves as a vital ferroalloy product, which functions as a fundamental alloying material in stainless steel production due to its corrosion resistance properties. However, its production needs high-grade chromite ore (46–48% Cr₂O₃) with a chromium-to-iron (Cr/Fe) ratio above 2.8, which creates problems because of declining reserves. To overcome the limitations of low-grade chromite, optimizing process parameters, such as basicity, becomes essential for achieving high metal yield and chromium recovery during smelting. This research investigates how flux type (basicity) and stoichiometric coke amount affect the thermochemical process of low-grade chromite sand (12.43% Cr₂O₃ with a chromium-to-iron ratio of 0,97) smelting using a DC Submerged Arc Furnace (DC SAF), which has a Ø200 mm × 400 mm, powered by a 60V and 100 kVA transformer. The research involved modifying basicity (0.4; 0.6; 0.8; 1; 1.2; 1.4) through silica and limestone flux additions and varying stoichiometric coke addition amounts (0.6; 0.8; 1; 1.2). Material characterizations via XRF, XRD, and SEM-EDX were used to confirm chromite and iron content, phase transformations, and product microstructure. The optimal results were achieved using a basicity of 0.6 with 20% stoichiometric coke addition, which produced 98.72% chromium recovery, 18.33% metal yield, and ferrochrome containing 45.78% chromium. The ferrochrome product meets the minimum low-grade ferrochrome standard (>45% Cr). However, achieving high-grade ferrochrome needs enhancement through chromite sand beneficiation before smelting to improve the Cr2O3 content and the chromium-to-iron ratio (Cr: Fe).