Laboratory-scale production of ferrosilicon using amorphous siliceous sedimentary rocks

Amorphous silica-rich sedimentary rocks, including diatomite, opoka, and tripoli, demonstrate significant potential as alternative raw materials for ferrosilicon production due to their enhanced reactivity compared to conventional quartzite. This study presents comprehensive laboratory-scale smelting trials utilizing these materials for ferrosilicon synthesis. Experimental procedures involved arc furnace melting of a charge mixture containing 77.2% SiO₂, 7.1% Al₂O₃, 3.8% CaO, 4.3% Σ(Na₂O+K₂O), 1.3% MgO, and 3.3% other oxides, with a total charge mass of 35-37 kg comprising sedimentary rocks, steel shavings, and coke. The smelting process yielded either FeSi50 ferrosilicon (47.2% Si) or a Fe-Si-Al alloy (46.5% Si, 4.6% Al), depending on furnace power settings and charge composition. Silicon recovery rates reached 90.7% for FeSi50 production, while the Fe-Si-Al alloy process achieved 89.7% silicon recovery and 78.8% aluminum recovery. These results indicate the technical feasibility of substituting traditional quartzite with more reactive amorphous silica sources in industrial ferrosilicon production. The findings suggest broader applications for amorphous silica-containing rocks in manufacturing other silicon alloys, including ferrosilicomanganese, ferrosilicochromium, and ferrosilicocalcium, potentially improving process efficiency and reducing energy consumption in metallurgical operations.