Predicted effect of ore composition on slag formation in manganese ore reduction

Abstract

Previous work showed that manganese ore reduction rates are strongly influenced by the extent of slag phase formation. In this work, the effect of ore composition on slag formation during manganese oxide reduction was predicted using thermochemical calculations; FactSage 6?4 was used to calculate the equilibrium phase relations in the oxide system MnO-SiO 2 -CaO-MgOAl 2 O 3 . Practically observed differences in ore composition, even within the same orebody, are predicted to cause significant differences in slag formation during reduction, with large differences in ore reducibility expected.

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).…”

“…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.…”

Reduction Mechanisms in Manganese Ore Reduction

“…As discussed recently, liquid silicate formation is expected to decrease the rate of reduction, especially if monoxide phase (with a high MnO activity) is no longer present in the partially reduced mixture. [8] Carbon dissolved in the alloy plays an important role in the reduction of MnO from slag (liquid silicate phase) via FeO reduction. [9] The important role of FeO reduction is due to three effects: the Fe metal serves as a reservoir for Mn formed from MnO reduction and so limits manganese vaporization losses; the formation of this Fe-Mn alloy results in lowered activity of manganese, as compared to pure manganese formation, resulting in favorable thermodynamics to drive the MnO reduction reaction; and the Fe-Mn alloy is carburised after its initial formation and increases the number of MnO reduction sites as the alloy is carried throughout the slag via reductant gas product bubbles.…”

The Effect of Processing Parameters on Ferromanganese Alloy Carbon Content in Mamatwan Ore Reduction

“…Formation of low melting point slag phases will in part contribute to the absence of significant alloy carbon refinement according to reaction (1) because the liquid slag phase closed off original pores in the pre-reduced ore particles, and prevent CO 2 access to the alloy phases. In high carbon ferromanganese production in the SAF the bulk of manganese units in the feed mixture is made as lump ore so that slag formation is set by ore chemistry with little possibility of manipulating oxide melting behaviour in the feed mixture (Coetsee et al, 2014). Only when agglomerates such as pellets or sinters are used, may the oxide chemistry be manipulated to limit slag formation to facilitate gas access to alloy beads for reaction (1) to possibly drive carbon refinement.…”