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 B 2 O 3 ‒ CaO ‒ Fe 2 O 3 ‒ ZnО melts by CO ‒ CO 2 and H 2 ‒ H 2 O mixtures containing 0 – 60 % CO 2 (H 2 O) 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 H 2 as a reducing agent, this process proceeds in three stages. In the first stage, Fe 2 O 3 is reduced to Fe 3 O 4 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 Fe 3 O 4 → 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 H 2 reduces it by less than 20 %. In the presence of oxidizing agents (CO or H 2 O), 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.