Thermodynamic modeling of nickel and iron reduction from multicomponent silicate melt in bubbling process. Report 2. Reducing agent – a mixture OF Н2 – Н2О

Abstract

A number of technologies in ferrous and non-ferrous metallurgy  are based on bubbling processes. For prediction of melting parameters  including the reduction of metals from oxide melt by a reducing gas  in a bubbling layer in industrial aggregates, a thermodynamic modeling technique is proposed based on calculation of the equilibrium in  oxide-melt-metal-gas system. Originality of the technique is that equilibrium is determined for each unit dose of gas introduced into the  working body, with the contents of oxides of metals being reduced in  each subsequent design cycle equal to the equilibrium in the previous  one. For the analysis NiO (1.8  %) – FeO (17.4  %) – CaO (13.5  %)  –  MgO  (1.9  %) – SiO2 (58.0  %) – Al2O3 (7.4  %) oxide system was  taken, closely corresponding to composition of oxidized nickel ore.  The ratio of Н2О/Н2 in gas mixture varies between 0 and 1.0. (1823  K),  amount and composition of formed metal (ferronickel), as well as the  indices (the ratio of slag and metal, the degree of reduction of metals)  are important in implementation of the process under commodity conditions. The increase in hydrogen consumption monotonously reduces  the content of nickel oxide in the melt, while the content of iron oxide  initially increases, and then decreases.  When H2 is introduced in an  amount of about 50 m3 per ton of the melt, the content of nickel oxide  in it is reduced to 0.017  %, and of iron oxide to 16.7  %. Resulting ferronickel contains 61  % Ni, ratio of slag and metal – 42  units. Further  increase in H2 consumption leads to preferential iron reduction. An increase in H2O/H2 ratio worsens the results of reduction of metals from  the melt: decrease in degree of reduction of nickel and iron, increase  in nickel content in the alloy, and the ratio of slag and metal. However,  even with a H2 / H2O ratio of 1.0, which corresponds to 50  % of H2O  in the gas mixture, reduction process does not stop. For comparison,  the work presents data on change in content of nickel and iron oxides,  when metals are restored from similar melts with carbon monoxide.  At a nickel recovery rate of 98  %, indicators are close in case of using  both H2 and CO. However, to achieve them, it is required 2.5  times less hydrogen, and 1.36 times less mixture in which H2O/H2  =  0.11  (H2  –  90  %) than carbon monoxide.