Thermodynamic modeling of iron and zinc reduction from B₂O₃ ‒ CaO ‒ Fe₂O₃ ‒ ZnО melt by СО ‒ CO₂ and H₂ ‒ Н₂О mixtures

The paper presents the thermodynamic modeling results of zinc and iron reduction from B₂O₃ ‒ CaO ‒ Fe₂O₃ ‒ ZnО melts by CO ‒ CO₂ and H₂ ‒ H₂O mixtures containing 0 – 60 % CO₂ (H₂O) at 1273 – 1673 K using a technique describing the reduction of metals from an oxide melt by gas in bubbling processes, under conditions that provide an approximation to real systems. Its originality is equilibrium determination for each individual portion of gas supplied into the working fluid. The reducible metals oxides content in each calculation cycle is taken from the previous data. During the calculations, changes in the content of zinc (С_ZnO ) and iron (С_Fe2O3 , С_Fe3O4 and С_FeO ) oxides in the melt and the degree of their reduction were estimated. When using CO or H₂ as a reducing agent, this process proceeds in three stages. In the first stage, Fe₂O₃ is reduced to Fe₃O₄ and FeO. C_Fe2O3 values decrease to almost zero, while C_Fe3O4 and C_FeO increase simultaneously. By the end of the stage, С_Fe3O4 reaches its maximum value. At the second stage, the Fe₃O₄ → FeO transition occurs, when С_FeO values reach its maximum. At these stages, there is a slight increase in the C_ZnO . At the third stage, the values C_FeO and C_ZnO decrease, and iron and zinc are reduced. An increase in temperature dramatically reduces the gas consumption for zinc reduction by 2 – 3 times, and the replacement of CO with H₂ reduces it by less than 20 %. In the presence of oxidizing agents (CO or H₂O), only zinc is reduced. The process ends when the final content of zinc oxide in the melt corresponds to the equilibrium with the initial gas composition. The higher the temperature, the less C_ZnO is. The obtained data are useful for the development of technologies for the selective recovery of metals.

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