Crystallization Of CaO.SiO2 In A CaO-Al2O3-SiO2 Melt: Computer Simulations And In-situ Experiments

Abstract:

Partial or full solidification of metallurgical slags occurs in many industrial pyrometallurgical processes. To enhance the fundamental knowledge of this phenomon, this research focuses on the simulation and in-situ observation of crystallizing minerals in oxide melts. The isothermal crystallization of Wollastonite (CaO.SiO2) in a ternary CaO-Al2O3-SiO2 melt is investigated. We used a confocal laser microscope (CLSM) to observe the dendritic crystallization and measured the dendrite tip radius and its velocity as a function of undercooling. The phase field method is chosen to model and simulate the crystallization, because it has proven its power for phase transformations in metals. The phase field model uses a vast number of physical input data, such as Gibbs energies of the phases, diffusion coefficients of the components and the interfacial energy of the solid-liquid interface. The thermodynamic data is retrieved from the FACTSage database for oxide systems. Diffusion coefficients are taken from literature, while surface energies are estimated from both Molecular Dynamics data and wetting experiments. By comparing experimental values for the dendrite tip velocity with values obtained with simulations, the influence of surface energy and diffusion coefficients on the crystallization behavior can be assessed.

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