Reduction and Dissolution Behaviour of Manganese Slag in the Ferromanganese Process

Abstract

The reduction and liquidus behaviour of manganese slag with different basicities were studied in non-isothermal experiments in the temperature range of 1400–1500 °C. Certain amounts of quartz were added to Assmang ore (South Africa), and lime was added to Comilog ore (Gabon), to adjust the charge basicity to 0.5, 0.8 and 1.2. The extent of manganese ore reduction as a function temperature were determined by thermo-gravimetric (TG) balance. Morphology of ores and its change in the course of reduction was examined by scanning electron microscopy (SEM). The results show that the reduction rate of Assmang slag decreases with decreasing basicity, as the liquidus temperature of slag decreases. When spherical MnO phase is present, the activity of MnO is high, and the reduction rate is rapid. Comilog slags show a much higher reduction rate than Assmang slags. The activation energies of MnO reduction between 1400 to 1500 °C are estimated in this study and found to be 230 kJ/mol for Assmang charges and 470 kJ/mol for Comilog charges. The dissolution behaviours of Assmang and Comilog slags were also studied by FactSage simulation and verified by experiments.

Phase Distribution During Slag Formation in Mn Ferroalloy Production

“…However, the dissolution of the monoxide solid solution is dependent on the composition of the ore and charge mixture as previously reported. [25][26][27] Comilog ore has negligible MgO content (Table I), and as such it forms a monoxide phase, which is purely MnO, as shown in FactSage calculated values presented in Table VIII, which are in close agreement with experimental values in Table II. This monoxide solid solution phase in Comilog completely dissolves in the liquid phase at 1623 K (1350 °C) as shown in Figure 7(b).…”

“…As such, FeO becomes stabilized in the monoxide solid solution. Contrastingly, previous studies [25,26,28] conducted in a relatively high and constant CO gas flow have shown the solid monoxide phase to be pure MnO or (Mn,Mg)O solid solution.…”

“…Laboratory investigations have been conducted extensively by several researchers to understand the formation of slag and the reduction to metal in the HCFeMn process. [17][18][19][20][25][26][27] The reduction behavior of different ore materials in the FeMn process is different as they possess different variations in ore chemistry, mineralogy and melting properties. Although information can be found in the literature [17][18][19][20][25][26][27][28] on phase development during slag formation in the FeMn process, some reduction behaviors from specific manganese ores require clarification.…”

“…[17][18][19][20][25][26][27] The reduction behavior of different ore materials in the FeMn process is different as they possess different variations in ore chemistry, mineralogy and melting properties. Although information can be found in the literature [17][18][19][20][25][26][27][28] on phase development during slag formation in the FeMn process, some reduction behaviors from specific manganese ores require clarification. As such, the main objective of this study is to investigate the smelting and reduction behavior of Comilog and Assmang ores in a setup that simulates the temperature gradient of industrial SAF processes.…”

Editorial for Special Issue “Metallurgical Slags”

“…Finally, the study of Li et al [14] focused on the reduction and liquidus behavior of manganese slags with different basicities. To study reduction rates, the authors performed experiments on two types of ores (Assmang ore from South Africa and Comilog ore from Gabon) with a continuous temperature increase under CO atmospheric pressure and fixed basicity.…”