Computer simulation of equilibrium relations in managanese ferroalloy production

Abstract

The complex heterogeneous equilibria associated with the production of manganese ferroalloys have been simulated using recently developed thermochemical databases. Over 600 measured equilibrium data have been used to verify and calibrate the model calculations. Good agreement is obtained for many important technical relations such as carbon solubility, equilibrium diagrams and phase relations, and element distribution as a function of temperature and composition. Experimental slag/metal and slag/metal/gas equilibria in MnO-SiO 2 binary, MnO-SiO 2 -CaO and MnO-SiO 2 -Al 2 O 3 ternary, MnO-SiO 2 -CaO-Al 2 O 3 quaternary, and MnO-SiO 2 -CaO-Al 2 O 3 -MgO quinary systems can be reproduced within experimental uncertainties. The influence of temperature, CO partial pressure, and slag chemistry on the Mn-and Si-distribution equilibria has been quantitatively evaluated. This leads to a sound basis for optimizing the manganese ferroalloy production processes.

Carbide Capacity of CaO–SiO2–MnO Slag for the Production of Manganese Alloys

“…1) Graphite is the stable phase in the lower Si range, whereas silicon carbide (SiC) becomes the stable phase at higher Si content, e.g. 22 mass% Si when [C]ϭ1.0 mass% at 1 773 K. 4) Therefore, the addition of Si decreases the solubility limit of carbon in SiMn alloy melt, resulting in a nucleation and growth of SiC particles in the melt. The carbide particles are believed to float up and partly dissolve into the slags at slag/metal interface.…”

Insights into the potential for reduced refractory wear in silicomanganese smelters

“…It was found that the carbon solubility predicted with FactSage is very similar to that predicted by Tang and Olsen (2006), if slightly lower (see Figure 2). Most importantly for this discussion, the silicon content at double saturation of the metal (saturation with both graphite and silicon carbide) is essentially the same; see Table III.…”

“…In the cases where solid precipitation was allowed to proceed to equilibrium (Figure 5), the proportion of graphite-saturated melts was even smaller (Table VIII); this is because SiC precipitation (which would occur in SiC-saturated melts) would remove carbon from solution, moving the metal composition even further from graphite saturation. Where the calculations were based on the Tang and Olsen (2006) database, the calculated activities of SiC and C, were lower than for FSstel (Table VIII).…”

“…The average slag and metal compositions, and standard deviations between analyses normalized, were calculated per furnace, and are reported in Table I, Table II, and Table VII. Thermodynamic calculations were conducted in FactSage 6.4, using the FToxid, FSstel, and FactPS databases, and the liquid Mn-Fe-Si-C database of Tang and Olsen (2006). Process temperatures between 1530°C and 1600°C are required to produce Mn7FeSiC sat containing 17% Si in equilibrium with slag where the SiO 2 activity ranges between 0.2 and saturation, at 1 atmosphere pressure (Olsen, Tangstad, and Lindstad, 2007).…”

Modelling of the Refining Processes in the Production of Ferrochrome and Stainless Steel

“…Batra, 2003;Slizovskiy & Tangstad, 2010;Tang & Olsen, 2004) Concerning the modelling of these processes, it is necessary -as it is in the production of ferrochrome -to know the influence of the electric current on the physical and chemical properties and phenomena within the furnace. In the thermodynamic modelling of the ferroalloys production systems, the most important phases to be modelled are the liquid slag and the metal alloy itself (Tang & Olsen, 2004). Despite the existing similarities, production of each ferroalloy has also its own characteristic features that needs to be taken into account in the modelling of these processes.…”