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

Attenuation of polarization echoes in NMR: A study of the emergence of dynamical irreversibility in many-body quantum systems

The reversal of the time evolution of the local polarization in an interacting spin system involves a sign change of the effective dipolar Hamiltonian which refocuses the 'spin diffusion' process generating a polarization echo. Here, the attenuation of these echo amplitudes as a function of evolution time is presented for cymantrene and ferrocene polycrystalline samples, involving one and two five spin rings per molecule respectively. We calculate the fraction of polarization which is not refocused because only the secular part of the dipolar Hamiltonian is inverted. The results indicate that, as long as the spin dynamics is restricted to a single ring, the non-inverted part of the Hamiltonian is notable by itself to explain the whole decay of the polarization echoes. A cross over from exponential (cymantrene) to Gaussian (ferrocene) attenuation is experimentally observed. This is attributed to an increase of the relative importance of the spin dynamics, as compared with irreversible interactions, which favors dynamical irreversibility.Comment: 6 pages in Revtex, 11 Postscript figures. Final versio

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

An examination of the accuracy of the activity-based travel simulation against smart card and navigation data

Activity-based travel simulators have been experiencing difficulty obtaining high quality activity-travel data and network information, which limits the applicability of the simulator to real world problems. For example, accurate information regarding travel time, link traffic volume and trip distribution is essential for sensitivity analysis using an activity-based travel simulator. Survey data, which relies on respondents’ memories, is typically inaccurate. The recent development of big data engineering has enabled us to use passively collected big data such as from smartcards and navigation devices; their travel time and spatial information is highly accurate. Activity-based travel simulation based on the household travel survey (HTS) can therefore identify inaccuracies in simulated travels by comparing smartcard and navigation device data. This paper aims to examine the accuracy of journeys simulated by an activity-based travel simulator, FEATHERS Seoul (FS), against smartcard and car navigation device data collected in Seoul. The analysis found that the activity-based simulator performs well and reproduces individual travel decisions, as reflected by the overall trip frequency and distance, but it partly fails to correctly reproduce geographical distributions in flexible, non-work trip destinations. The results imply that an activity-based travel simulator needs to improve its incorporation of geographical characteristics using big data engineering to enhance the simulated travel accuracy

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