Thermodynamics of a Karatau and Aktobe phosphorites mixture interaction when producing phosphorus, calcium carbide and ferrosilicon

Abstract

Relevance. Associated with the need to increase the level of comprehensive use of phosphorites during their electrothermal processing and to reduce the amount of slag waste generated during the production of phosphorus and polluting the environment. Aim. To conduct computer thermodynamic modeling of the effect of temperature and amount of iron on technological parameters of interaction of a Karatau and Aktobe phosphorites mixture with carbon and iron to produce phosphorus, calcium carbide and ferrosilicon. Objects. Phosphorites of the Karatau and Aktobe phosphorite-bearing basins. Methods. Thermodynamic computer modeling using the HSC Chemistry 6.0 software; rotatable second-order experiment planning technique; geometric optimization of technological parameters. Results. It has been established that depending on temperature in a mixture of Karatau and Aktobe phosphorites with carbon and iron, they participate in interaction:  CaSiO3, SiO2, Si, SiC, SiO(g), MgSiO3, Al2SiO5, Na2SiO3 , Ca(g), CaO, CaC2, CaF2, CaS, Fe, FeSi, FeSiO3, FeP, Fe2P, Fe3P, FeP2, FeO, Fe3Si; Ca3(PO4)2, P2(g), P4(g). An increase in iron amount leads to an increase in the degree of silicon extraction into the alloy, and at 2000 °C reduces the extraction degree of calcium in CaC2 and the silicon concentration in the alloy. Branded calcium carbide with a volume of more than 230 dm3/kg and ferrosilicon FeSi25 are formed from a mixture of phosphorites, carbon and iron at 2077...2088 °C in the presence of 20...21.4 % iron and 43 % carbon (in this case, phosphorus is completely distilled off into the gas phase). Using our proposed method of electric smelting of phosphorites with phosphorus distillation and associated production of ferroalloy, in comparison with the traditional method, the indicator of integrated use of raw materials increases from 43.9 to 62.7...73.6 %, that is 1.43...1 ,67 times. The proposed processing technology helps to increase active reserves of phosphorites and bring low-grade phosphorites of the Aktobe basin into production.