Processing of phosphorites with extraction of phosphorus, obtaining calcium carbide and ferroalloy

The article considers the results of studying the thermodynamic computer modeling of the interaction of phosphorite (Karatau basin, Kazakhstan) with carbon and coke performed using the HSC-10 software package and electric smelting of the phosphorite with coke and steel shavings in an arc furnace. The modeling allowed us to determine the equilibrium extraction degrees of phosphorus into gas (Р₂, Р₄), silicon into ferroalloy in the form of iron silicides (FeSi₂, FeSi, Fe₃Si, Fe₅Si₃, Si) and calcium into CaС₂. At temperatures above 1500 °C, regardless of the amount of iron, the extraction degree of phosphorus into gas is more 99%. The resulting ferroalloy contains 21.2-23.8% of Si, 1.6-2.8% of Al; the calcium carbide has a capacity of 288-325 dm³/kg. The extraction degree of silicon into the alloy was 89.8%, calcium in CaC₂ – 72.5%, phosphorus into gas – 99.4%. The ferroalloy, formed at the electric smelting of the Chulaktau phosphorite together with coke and steel shavings and containing 24.9-29.8% of Si, is FS25 grade ferrosilicon, and the formed calcium carbide has a capacity of 278-290 dm³/kg and belongs to the third and second grades. The developed technology makes it possible to increase the degree of phosphorites’ comprehensive use two times (up to 87.5%).