Metal droplet entrainment by solid particles in slags : a combined phase field-experimental approach

This doctoral work investigated metal droplet entrainment by solid particles in slags with a combination of two experimental set-ups and two phase field models. The binary model with limited complexity already clarified our view of the interaction between metal droplets and nonreacting solid particles to a great extent. For example, the fact that the movement of one phase with respect to the others influenced the apparent wetting regime is very interesting for the interpretation of experimentally obtained results. Moreover, the two different types of experiments confirmed that a chemical reaction might lay at the origin of the attachment, but that it requires nucleation sites in the form of metal droplets before it takes place. However, the first phase field model assumed nonreactive solid particles. Thus, a model concerning the growth of the solid phase in a realistic quaternary oxide system was also considered. Future work needs to consider the interaction of reacting metal droplets with reacting solid particles in a realistic liquid slag

Interactive industrial application to represent isothermal sections of multi component phase diagram

“Make the slag and the steel will make itself” is an old phrase in steelmaking. The converter or basic oxygen furnace (BOF) process is a necessary step in the steel production during which carbon, phosphorus and other impurities present in the hot metal, coming from the blast furnace, are removed and steel is produced. This steel is tapped from the converter and further refined, next cast, rolled and finished. The BOF process is complex due to many reasons: high temperatures, multiple phases present, interactions of kinetics and thermodynamics, etc. Emphasis in this work is put upon the BOF steelmaking slag. Yet, even though this has been topic of many research projects no full understanding of all the slag related phenomena has been far from achieved. One of the difficulties is the multi-component nature of the slag. In its most simplified form, the slag is a three component system consisting of CaO, SiO2 and FeOn. However, in practical applications this slag contains more than three components, making graphical representations of equilibria complex and difficult. This work shows the potential to apply CALPHAD based data for industrial applications via an interactive visual tool. Isothermal sections of multi-components phase diagrams were constructed with Factsage 7.1 software. Addition of extra components to the calculated isothermal sections, gives a graphical representation which can be used to gain insight in certain observed phenomena in the BOF process. To illustrate that the interactive visualisation yields an interesting tool to integrate CALPHAD based calculations in industry two case studies from steelmaking are discussed: the effect of MgO upon the refractory wear and the effect of MgO upon dephosphorization

Influence of rigid body motion on the attachment of metallic droplets to solid particles in liquid slags - a phase field study

Metallic droplets can remain attached to solid particles within liquid slags, resulting in production losses in several pyrometallurgical industries. This study shows the extension of a recently developed phase field model to include the movement of solid particles in the liquid slag in a system, considering the attachment of liquid metal droplets to solid particles in slags. The influence of this movement on the wetting of the metal droplets to the solid particles in the slag and on the resulting microstructures is investigated as a function of the velocity of the particles. For all wetting regimes, the apparent contact angle in the final microstructures was clearly larger than without particle movement. For the amount of metal attached to the particle, a clear trade-off was found between the speed of motion of the solid particle and the wetting regime

Heat transfer considerations on the spontaneous triggering of vapor explosions : a review

Vapor explosions have been investigated both theoretically and experimentally for several decades, focusing either on the vapor film, or on mechanical aspects. Where the main interest for industry lies in the safety risks of such an event, fundamental research is focusing on all partial processes that occur during a vapor explosion. In this paper, vapor explosions are discussed from a heat transfer point of view. Generally accepted knowledge of heat transfer between hot surfaces and liquids is compared to early investigations regarding the origin of vapor explosions. Both steady state and transient models are discussed. The review of available literature suggests that vapor explosions trigger spontaneously by the collapse of the boiling film. Better understanding of the fundamental aspects of vapor explosions might give rise to future ideas on how to avoid them

Metal droplet entrainment by solid particles in slags : an experimental approach

This study investigates the origin of the attachment of metal droplets to solid spinel particles in liquid slags. Previous research hinted a reactive origin: the spinel particles form by a chemical reaction together with a new droplet or alongside a droplet that was already present in the system. In this study, a smelting experiment was used to investigate this hypothesis. For such a study of the mechanism, a simple chemical system was used to avoid complex reactions. However, performing smelting experiments in simple slag systems requires an adaptation of the previously developed experimental methodology, resulting in a new 'partial melting' methodology. During the experiment, the atmosphere of the system was first set as oxidative, to dissolve the metallic copper in the slag and then a reductive atmosphere was used to actuate the reaction. Moreover, Ag was added to the metallic phase to act as a tracer element. The results show that the amount and size of copper droplets increase over the duration of the experiment. The fact that silver is present in the attached copper droplets in a smaller concentration than in the master alloy in this study indicates that the origin of the attachment is not purely dispersive, and either a purely reactive or a dispersion-reaction combination is possible, which confirms the hypothesis