Estimation of TiO2-FeO-Na2O slag viscosity through molecular dynamics simulations for an energy efficient ilmenite smelting process

Abstract

Along with the increasing demand for the TiO2 pigment, the ilmenite smelting process has also become significant because it can utilize both rock- and sand-type ilmenite. However, due to the high liquidus temperature of the TiO2 slag system, the smelting process is highly energy consuming. In the present study, the viscosity of molten ilmenite slag was estimated using molecular dynamic simulations at a high temperature to achieve an appropriate and efficient slag design. To verify the validity of the simulation technique, experimental measurements were performed in parallel and their results were compared. The effects of FeO and Na2O addition on viscosity of TiO2 slag were also investigated. The addition of Na2O as a flux enhanced the ilmenite smelting process by not only lowering the liquidus temperature but also slowing the drastic viscosity increase. Statistical information obtained from the molecular dynamic simulations revealed a three-dimensional TiO6 octahedral network structure. The relationship between viscosity and structural change with varying FeO and Na2O concentrations was explored considering the coordination number of Ti and various bonding types.

Improving the production efficiency of high-titania slag in Ti extraction process: fluxing effect on formation of pseudobrookite

“…They also calculated the coordination number (CN) of titanium using molecular dynamic (MD) simulations, by which the CN of Ti in the TiO 2 -rich melts would be 6, i.e., the [TiO 6 ]-octahedron is main backbone structure of the melts 28,29 . The MD simulation and viscosity measurements were also performed by Kim and Park for the FeO-TiO 2 (-Na 2 O) systems 30 . They obtained the similar results with Hu et al 28 and Huang et al 29 for the FeO-TiO 2 system and additionally found that Na 2 O decreases the viscosity of the melts, resulting from a decrease in CN of titanium by Na 2 O addition.…”

“…They obtained the similar results with Hu et al 28 and Huang et al 29 for the FeO-TiO 2 system and additionally found that Na 2 O decreases the viscosity of the melts, resulting from a decrease in CN of titanium by Na 2 O addition. A decrease in CN of titanium means the network breaking event by Na 2 O, resulting in a decrease in viscosity 30 .…”

“…The experimental temperature was 1873 K and was controlled within ±2 K using a B-type (Pt-30%Rh/ Pt-6%Rh) thermocouple and a proportional integral differential controller. After the temperature stabilized, a mixture of ilmenite ore and flux (100 g) was quickly added onto the surface of the pre-melted iron bath and maintained for 1 h. Slag samples were collected at defined time intervals (5,7,10,15,20,30 and 60 min) using a steel rod dipped into the slag layer. The samples were quenched rapidly by flushing with high-purity (99.999%) Ar gas (flow rate of 25 L/min).…”

On the Application of the FactSage Thermochemical Software and Databases in Materials Science and Pyrometallurgy

“…The operation of high temperature pyrometallurgical processes nearly always involves the formation of chemically aggressive liquid phases (i.e., slag, matte, speiss, liquid metal, molten salts, etc). In specific cases such as ilmenite reduction in an electrical arc furnace, the liquid phase is so aggressive that the only option to contain it is by freezing it on the surface of the vessel using, for example, water-cooled copper plates [41]. Hence, the optimal selection of lining materials of high-temperature pyrometallurgical reactors is a critical task to limit shutdowns and prevent catastrophic accidents.…”

Viscosity Estimation of Multicomponent Slags of the CaO–SiO2–Al2O3–FexO System Based on Microstructure Analysis

“…According to the Eyring equation, Kondratiev − explored a quasi-chemical viscosity model by defining the “structure units of viscous flow”. In addition to the above theoretical models, there are some empirical or semiempirical formulas for viscosity estimation in terms of the relationship of composition and viscosity, , and some scholars also estimate the melt viscosity through molecular dynamics simulation. , …”