Slag-Metal Separation in Mn Ferroalloy Production

The separation of slag and metal in the ferroalloy production process is an important issue that has an impact on both the ecological and environmental considerations of the entire production process. The extensive mixing of metal and slag during the tapping into ladles leads to the formation of a considerable amount of metal droplets in slag due to interfacial interaction and turbulence of the molten flow from the tap-hole. The entrainment of metal droplets into the slag phase causes ferroalloy losses with the slag, creating additional difficulties in the removal of metal from the slag. It is known that the separation of metal and slag is strongly influenced by interfacial phenomena and for this reason they were studied in this thesis, and the influence of interfacial tension and surface tension were also discussed for ferroalloy-slag systems. The main goal of this research work was to understand interfacial phenomena between ferroalloy and slag. This has been achieved by developing a methodology for investigating the interfacial interaction in ferroalloy-slag systems, modelling the separation of molten slag and metal in OpenFOAM, and assessing operational parameters and physical properties affecting the formation of metal-slag emulsion and metal droplets in slag. The microstructure of slag and metal phases under different conditions has also been extensively addressed. This thesis demonstrates a novel methodology for estimating the interfacial tension between metal and slag which combines experiments in the sessile drop furnace and multiphase modelling in OpenFOAM. It was concluded that the interfacial interaction can be significantly altered by surface-active elements such as sulfur in ferroalloy-slag systems, as well as by changing the composition of the slag, which causes to the transfer of species or elements across the interface, creating interfacial instability and reducing the interfacial tension. As a consequence, the significant instability of the interface leads to higher losses of metal with the slag

Numerical Simulation of Phase Transitions in Porous Media with Three-Phase Flows Considering Steam Injection into the Oil Reservoir

This study focuses on the analysis of an approach to the simulation of the phase transition in porous media when hot steam is injected into the oil reservoir. The reservoir is assumed to consist of a porous medium with homogeneous thermal properties. Its porous space is filled with a three-phase mixture of steam, water, and oil. The problem is considered in a non-stationary and non-isothermal formulation. Each phase is considered to be incompressible, with constant thermal properties, except for the dynamic viscosity of oil, which depends on the temperature. The 1D mathematical model of filtration, taking into account the phase transition, consists of continuity, Darcy, and energy equations. Steam injection and oil production in the model are conducted via vertical or horizontal wells. In the case of horizontal wells, the influence of gravity is also taken into account. The Lee model is used to simulate the phase transition between steam and water. The convective terms in the balance equations are calculated without accounting for artificial diffusion. Spatial discretization of the 1D domain is carried out using the finite volume method, and time discretization is implemented using the inverse (implicit) Euler scheme. The proposed model is analyzed in terms of the accuracy of the phase transition simulation for various sets of independent phases and combinations of continuity equations. In addition, we study the sensitivity of the model to the selected independent phases, to the time step and spatial mesh parameters, and to the intensity of the phase transition. The obtained results allow us to formulate recommendations for simulations of the phase transition using the Lee model

Numerical Simulation of Phase Transitions in Porous Media with Three-Phase Flows Considering Steam Injection into the Oil Reservoir

This study focuses on the analysis of an approach to the simulation of the phase transition in porous media when hot steam is injected into the oil reservoir. The reservoir is assumed to consist of a porous medium with homogeneous thermal properties. Its porous space is filled with a three-phase mixture of steam, water, and oil. The problem is considered in a non-stationary and non-isothermal formulation. Each phase is considered to be incompressible, with constant thermal properties, except for the dynamic viscosity of oil, which depends on the temperature. The 1D mathematical model of filtration, taking into account the phase transition, consists of continuity, Darcy, and energy equations. Steam injection and oil production in the model are conducted via vertical or horizontal wells. In the case of horizontal wells, the influence of gravity is also taken into account. The Lee model is used to simulate the phase transition between steam and water. The convective terms in the balance equations are calculated without accounting for artificial diffusion. Spatial discretization of the 1D domain is carried out using the finite volume method, and time discretization is implemented using the inverse (implicit) Euler scheme. The proposed model is analyzed in terms of the accuracy of the phase transition simulation for various sets of independent phases and combinations of continuity equations. In addition, we study the sensitivity of the model to the selected independent phases, to the time step and spatial mesh parameters, and to the intensity of the phase transition. The obtained results allow us to formulate recommendations for simulations of the phase transition using the Lee model

INVERSE MODELLING OF INTERFACIAL TENSION BETWEEN FERROALLOY AND SLAG USING OPENFOAM

The entrainment of molten ferroalloy droplets in slag during tapping operations is strongly related to turbulence and interfacial forces between alloy and slag. Therefore, interfacial phenomena are of great importance for the ferroalloys industry and a better understanding of entrainment mechanisms can reduce ferroalloy losses with slag flow. The interfacial tension plays an important role in the interaction between ferroalloy and slag due to the ability to modify droplets shape and the flow regime. However, the measurement of interfacial tension between two molten phases is challenging due to high temperatures and complex composition. In particular, surface active elements significantly influence the interfacial tension. Available methods for determining the interfacial tension are often based on using complex equipment (e.g. a furnace equipped with an X-ray camera) and tend to have significant uncertainty in measurements. In this study, a methodology for inverse modelling of interfacial tension between ferroalloys and slag was developed and investigated by combining experimental measurements, reduced order modelling and simulations in OpenFOAM. The proposed method relies upon experimental determination of the shape of single droplets, from which surface tension can be determined using numerical procedures such as elliptic fitting and the low-bond axisymmetric drop shape technique. Given relevant material properties for single phases, parameters governing the interactions between the phases, e.g. interfacial tension, can be determined by comparing parametric simulations to experiments in which interactions are present. Simulations are realized using multiphaseInterFoam for a slag droplet at rest on molten metal in an inert atmosphere. The current work describes the modelling strategy and demonstrates its applicability to recent experiments for the FeMnslag system. The uncertainty and sensibility of the method are assessed by comparing different available simulation settings, resolution and the uncertainty in the experimental data

Inverse modelling of interfacial tension between ferroalloy and slag using openfoam

The entrainment of molten ferroalloy droplets in slag during tapping operations is strongly related to turbulence and interfacial forces between alloy and slag. Therefore, interfacial phenomena are of great importance for the ferroalloys industry and a better understanding of entrainment mechanisms can reduce ferroalloy losses with slag flow. The interfacial tension plays an important role in the interaction between ferroalloy and slag due to the ability to modify droplets shape and the flow regime. However, the measurement of interfacial tension between two molten phases is challenging due to high temperatures and complex composition. In particular, surface active elements significantly influence the interfacial tension. Available methods for determining the interfacial tension are often based on using complex equipment (e.g. a furnace equipped with an X-ray camera) and tend to have significant uncertainty in measurements. In this study, a methodology for inverse modelling of interfacial tension between ferroalloys and slag was developed and investigated by combining experimental measurements, reduced order modelling and simulations in OpenFOAM. The proposed method relies upon experimental determination of the shape of single droplets, from which surface tension can be determined using numerical procedures such as elliptic fitting and the low-bond axisymmetric drop shape technique. Given relevant material properties for single phases, parameters governing the interactions between the phases, e.g. interfacial tension, can be determined by comparing parametric simulations to experiments in which interactions are present. Simulations are realized using multiphaseInterFoam for a slag droplet at rest on molten metal in an inert atmosphere. The current work describes the modelling strategy and demonstrates its applicability to recent experiments for the FeMn-slag system. The uncertainty and sensibility of the method are assessed by comparing different available simulation settings, resolution and the uncertainty in the experimental data

INVERSE MODELLING OF INTERFACIAL TENSION BETWEEN FERROALLOY AND SLAG USING OPENFOAM

The entrainment of molten ferroalloy droplets in slag during tapping operations is strongly related to turbulence and interfacial forces between alloy and slag. Therefore, interfacial phenomena are of great importance for the ferroalloys industry and a better understanding of entrainment mechanisms can reduce ferroalloy losses with slag flow. The interfacial tension plays an important role in the interaction between ferroalloy and slag due to the ability to modify droplets shape and the flow regime. However, the measurement of interfacial tension between two molten phases is challenging due to high temperatures and complex composition. In particular, surface active elements significantly influence the interfacial tension. Available methods for determining the interfacial tension are often based on using complex equipment (e.g. a furnace equipped with an X-ray camera) and tend to have significant uncertainty in measurements. In this study, a methodology for inverse modelling of interfacial tension between ferroalloys and slag was developed and investigated by combining experimental measurements, reduced order modelling and simulations in OpenFOAM. The proposed method relies upon experimental determination of the shape of single droplets, from which surface tension can be determined using numerical procedures such as elliptic fitting and the low-bond axisymmetric drop shape technique. Given relevant material properties for single phases, parameters governing the interactions between the phases, e.g. interfacial tension, can be determined by comparing parametric simulations to experiments in which interactions are present. Simulations are realized using multiphaseInterFoam for a slag droplet at rest on molten metal in an inert atmosphere. The current work describes the modelling strategy and demonstrates its applicability to recent experiments for the FeMnslag system. The uncertainty and sensibility of the method are assessed by comparing different available simulation settings, resolution and the uncertainty in the experimental data.published Versio

Interfacial Behaviour in Ferroalloys: The Influence of Sulfur in FeMn and SiMn Systems

The present study has investigated the influence of sulfur content in synthetic FeMn and SiMn from 0 to 1.00 wt pct on interfacial properties between these ferroalloys and slags. The effect of experimental parameters such as temperature and holding time was evaluated. Interfacial interaction between ferroalloys and slags was characterized by interfacial tension and apparent contact angle between metal and slag, measured based on the Young–Laplace equation and an inverse modelling approach developed in OpenFOAM. The results show that sulfur has a significant influence on both interfacial tension and apparent contact angle, decreasing both values and promoting the formation of a metal-slag mixture. Despite the fact that sulfur was added only to the ferroalloys, most of sulfur is distributed into slag after reactions with the metal phase. Increasing the maximum experimental temperature in the sessile drop furnace also resulted in a decrease of both interfacial properties, resulting in higher mass transfer rates and intensive reactions between metal and slag. The effect of holding time demonstrated that after reaching equilibrium in FeMn-slag and SiMn-slag systems (both with and without sulfur), interfacial tension and apparent contact angle remain constant.publishedVersio

Slag-metal interactions in the FeMn tapping process: Interfacial properties and wetting

FeMn-alloys are produced by transforming ore and carbon materials into FeMn and slag at high temperatures in a furnace. Entrainment of FeMn in slag during tapping reduces the yield. Entrainment and subsequent separation are strongly influenced by slag-metal interfacial properties. In the current work, interfacial properties, including the contact angle, in the FeMn-slag graphite system have been investigated using the sessile drop technique at temperatures above 1573 K. Two experimental configurations are proposed: (a) slag and metal placed beside each other on graphite; and (b) slag placed on top of the metal layer. The average interfacial tension between slag and metal over the temperature interval was found to be 1.08±0.10 N/m for slag-to-metal weight ratio 0.19, and 1.30±0.32 N/m for slag-to-metal weight ratio 0.28. In addition, wetting properties are considerably influenced by the variation of slag-metal weight ratio in the range from 0.25 to 1.50 and only marginally by temperature.publishedVersio

Interfacial Behaviour in Ferroalloys: The Influence of FeMn Slag Composition

The present study investigated the interfacial interaction between FeMn alloy and slags of different compositions and basicity from 0.4 to 1.2 in a sessile drop furnace. Interfacial tension between the FeMn alloy and the slags was measured, and the results were analyzed to assess the sensitivity of the applied methodology. The measurement of the interfacial tension was based on combining the results from experiments, multiphase flow simulations in OpenFOAM, equilibrium calculations in FactSage, and calculation of slag density and surface tension based on numerical models. The results demonstrate that the interfacial tension between the FeMn alloy and slag increases with the slag basicity. It was found that the addition of Al2O3 to the slag with basicity of 0.8 and 1.2 increases the interfacial tension, while increasing MnO content from 30.0 to 45.0 wt pct does not have any statistically significant influence on the interfacial tension. EPMA analysis of slag and FeMn phases showed that slags at lower basicities and the FeMn alloy form a metal–slag emulsion due to the destabilization of the interface induced by chemical reactions, partial reduction of SiO2 in the slag and the mass transfer of Si across the metal–slag interface