<p>Despite the improvement of sulfuric-acid leaching of vanadium quartzites, this technology is associated with the formation of dump waste cake containing up to 75–85% SiO₂. The paper presents the research results on this cake use for ferrosilicon smelting with coke replacement to coal tailings. In thermodynamic modeling of the cake mixture with coal tailings’ interaction, the HSC-6.0 software package and the second-order rotatable research planning method were used. It was found that the interaction products at 500–1900&#xa0;°C are SiO, CO_(g), FeSi, Al₂SiO₅, SiO_(g), FeSiO₃, CaSiO₃, Si, SiC, MgSiO₃, FeO, S, CaS, CS_2(g), H_2(g), Al, Fe₃Si, FeSi_2.33, FeSi₂, COS_(g), BaSiO₃, S_2(g), CS(g), CO_2(g), Mg_(g), H₂O_(g), Fe₅Si₃. An increase in the iron amount in the charge has a positive effect on increasing the silicon extraction into the alloy and reduces the silicon transition into undesirable SiC and SiO_(g). Iron is also a regulator of the silicon content in the ferroalloy (reducing it with an increase in the silicon extraction in the charge). Using the obtained mathematical models of the temperature and iron influence on the Si extraction into the alloy and its concentration in the alloy, it was found by the graphical optimization method that the FeSi45 ferrosilicon formation (with 60–71% Si extraction) occurs at 29–51% Fe and 1705–1900&#xa0;°C, FeSi50 (with 55.7–67% Si extraction)–at 25–35.5% Fe and 1816–1900&#xa0;°C. The possibility of obtaining FeSi45 ferrosilicon containing 44% silicon from the mixture of cake and coal tailings is confirmed by electric smelting in an arc furnace. Replacing quartzite and coke with leaching cake and coal tailings allows to reduce the ferrosilicon production costs by 20%.</p>