Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Russia:

A. S. Vusikhis, Senior Researcher, Candidate of Technical Sciences, e-mail: vas58@mail.ru
E. N. Selivanov, Head of the Laboratory, Doctor of Technical Sciences
L. I. Leontiev, Principal Researcher, Doctor of Technical Sciences
S. N. Tyushnyakov, Senior Researcher, Candidate of Technical Sciences

For predicting the results of sparging processes to understand how much metal can be reduced from oxide melt, a method of thermodynamic modelling has been developed that ensures approximation to real systems in which the metallic phase and gases are removed from the liquid at a certain interval. The key principle of this method is that equilibrium is determined for every single portion of introduced gas, and the concentration of oxides of the reduced metals in each cycle is taken from the previous data. Such approach enables a very close simulation of real processes so that one can have an idea about the quality of reactions taking place in pyrometallurgical units. When the thermodynamic modelling method was applied to the processes of iron and nickel reduction, the obtained results well matched the experimental data. A comparative analysis was carried out to understand how the temperature T and the amount of introduced gas V_СО or V_Н2 influence the process of zinc reduction from oxide melt. For the purposes of modelling, a B₂O₃ – CaO – ZnO melt was used with the B₂O₃/CaO ratio equal to 3 (which corresponds to the eutectic composition) and with the initial ZnO concentration in the range from 3 to 12 %; the temperature range used was 1273–1673 K. The concentration of zinc oxide С_ZnO in the melt, as well as the reduction degree Zn were analyzed. The correlation dependences С_ZnO, φ_Zn = f(C₀, T, V_CO or V_H2) are presented in the form of second order polynomials. Reduction of zinc with hydrogen is a more intense process than when zinc is reduced with carbon monoxide. Therefore, less gas is required to reach a similar reduction degree. A higher temperature facilitates the reduction of zinc while less СО or Н₂ is required to achieve the target reduction degree Zn. Irrespective of the initial composition of the melt, it takes 1.5 times less hydrogen that carbon monoxide to obtain the unit mass of zinc with the process temperature being the same. The obtained data explain the changing zinc distillation performance when changing the temperature. The established relationships between C_ZnO and φ_Zn and the temperature and the amount of introduced gas are useful for predicting the zinc distillation performance and can be used as basic relationships for analyzing experimental data.
This research was funded by the Russian Foundation for Basic Research under the Project No. 18-29-24093мк.

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