The effect of the hot top height on the formation of positive and negative macrosegregation patterns, the ingot quality, and the material yield during solidification of a 12 MT cast ingot made of a Cr-Mo-low alloy steel was investigated. A 3D numerical simulation of the process was conducted using finite element modeling. A full-size 12 MT ingot was cut off from its center in the longitudinal direction, and a large cross-section was sliced into small samples. The chemical mapping of all the elements in the steel composition was obtained for all samples and compared with the model predictions for validation purposes. The influence of the increase in hot top height on the liquid metal velocity field, size and shape of vortexes, cooling rate of the liquid, and liquidus temperature was determined. Results revealed that increasing the hot top height by 165 mm increased the solidification time, fluid velocity in regions including the hot top and ingot bottom, and decreased the local liquidus temperature. The combination of all the above resulted in an overall decrease in positive and negative macrosegregation of more than 6% and an increase in ingot quality. The results are interpreted based on the interactions between the transport of solute and heat coupled with the flow driven by thermo-solutal convection and shrinkage-induced flow.

Large numbers of carbon anodes are used in aluminum industry. The manufacture of carbon anodes involves the preparation of a paste (a mixture of coke, pitch, and recycled material), the production of green anodes via mixing and compaction of this paste, followed by cooling and baking of the green anodes. Anode baking is carried out in large furnaces. Any modification to design or operation would require a careful study of its impact on anode quality. In recent years, mathematical models have been used effectively to complement the experimental work in order to improve furnace operation and design. A design model and a process model are being developed to study the behavior of a horizontal anode baking furnace and to determine the necessary improvements. In this article, these models and their use for the study of a furnace will be described, and the results of the numerical simulations will be presented.

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In aluminum industry, carbon anodes are consumed continuously during alumina reduction in the electrolysis cells. Anodes are made of calcined coke, butt, and recycled anode particles and pitch as the binder. Green anodes are baked in large furnaces where they attain specific properties in terms of density, mechanical strength, and electrical conductivity. Baking is an important and costly step in carbon anode production. The proper operation of the furnace provides the required anode quality. Mathematical modeling allows the prediction of the heating profile of anodes during baking. Taking into account all the important phenomena, a 3-dimensional transient mathematical model was developed to reproduce numerically the different stages of the baking process in the furnace. The predictions give a detailed view of the furnace operation and performance. In this article, the 3D model is described, and the results on the impact of various parameters on furnace behavior are presented.