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CFD - Computational Fluid Dynamics in Minerals and Metallurgy
Teeming and Tundish Operation
CFD was used to estimate the grade change over time for a particular tundish. Flow distribution in the tundish has very critical influence on the casting process in terms of quality, productivity and economics. Use of CFD is becoming increasingly popular in designing and optimizing tundish internals (weirs, dams, and baffles). It is also possible to study the effects of various process parameters and practices and thereby optimize the process to achieve the minimum amount of intermixed grade steel. The images here show a free surface with bubbling effects and a snap shot during the progress of grade change over the course of the operation.
FLUENT© Left: Tundish model showing the free suface with bubbling effects,
Right: Concentration contours in a continuous casting tundish during a grade change operation
Vacuum Degassing Analysis
(Bethlehem Steel)
CFD simulation was used to improve the continuous-circulation vacuum-degassing process. Fluent software allows you to carry out a parametric study, investigating the effect of argon injection rate on the recirculating flow of steel and studying alternative designs that could improve process efficiency. The model of the degassing process consists of two vessels: the ladle, which holds the steel, and the degasser, which is dipped into the ladle through two cylindrical up-leg and down-leg snorkels. As the vacuum is applied in the degasser vessel, the steel rises into the degasser through the snorkels. The circulation of steel through the degasser is obtained by injecting argon gas into the up-leg snorkel
FLUENT© Particle paths illustrate the circulation of steel driven by argon gas injection.
CFD on SO2 Scrubber Problem - Primary Aluminum Smelter Plants
Computer simulation has helped to solve a challenging problem in scrubbers used to remove sulphur dioxide from gas in the production of aluminum at the Reynolds Metal Company, St. Lawrence Reduction Plant, Massena, N.Y. Tests showed that under conditions requiring high gas flow rates, the mist eliminators did not completely remove fine mist and liquor droplets in the gas stream. This resulted in potentially acidic moisture droplets being emitted to the atmosphere. Engineers simulated the operation of the scrubbers using CFD and discovered a significant gas maldistribution in the absorber. This was due to the geometry of the tower and inlet ducting. In further CFD work, they evaluated several alternate tower and ducting designs, with involvement of Hoogovens and Koch engineers, and selected one that solved the maldistribution problem at minimum expense.
FLUENT© SO2 Scrubber
Results showed there was a significant vapor maldistribution in the absorber due to the geometry of the tower and inlet ducting. One of the first things tried was removing the hood from the model and re-running the analysis. This change provided a major improvement in velocity distribution and reduced the maximum velocity to just below the limit for the mist eliminator.
Numerical Modelling of the Concentrate Burner in a Flash Smelting Furnace
(F. Guevara et al., Fourth Internatioal Conference, Copper 99 – Cobre 99)
The mathematical model consisted on the 3D averaged Navier-Stokes equations, turbulent kinetic energy and dissipation of turbulent kinetic energy considering the version of the Renormalization Group (RNG) theory for the k-e turbulence model. Computations were performed using FLUENT©, based in a finite-volume code.
The geometry of the concentrate burner was separated in the wind box and reaction tower. Results obtained in the exit of wind box were used as boundary conditions for the reaction shaft. Results of physical and numerical simulations show an asymmetry of the velocity field at the exit of wind box. This asymmetry is possibly due to existence of separated flow in the back of the exit ring. The fair agreement of physical and numerical results assess the capacity of the turbulence RNG k-e model to reproduce correctly the behavior of velocity field at the exit of the concentrate burner.
Left: Copper Smelting Flash Furnce Wind-Box, Right: Reaction shaft
Predicted velocity field at the exit of flash furnace burner for two different inlet velocity conditions
Water-Cooled-Hood Design
(Cade-Idepe Ing. Chile, Fith Internatioal Conference, Copper 03 – Cobre 03)
The model includes the volume within the gas handling system and the space within the building around the converters as well. Both sub domains, the one within the gas handling system (comprising converter, water-cooled hood, drop-out hopper, cyclones and ID fans.) and the building, are connected through some selected areas. Air leaks into the gas handling system through these areas and fugitive gas leaks out from the hood into the building. The air movement in the building is controlled by convection of the hot gas leaking from the converter hood, the dynamic pressure of the wind, the presence of the roof central openings and the presence of a tested air temperature gradient that sets up within the building. The results achieved are good because they include not only a detailed description of the gas movement within the gas handling system but a better estimate of the leaks. The latter are compatible with tests performed on the air within the building, to measure ambient SO2 concentrations and temperature.
A new design for the gas handling system was proposed including a new design for the hood and settling chamber. This new design was based basically on other solutions used in other smelters around the world. A CFD modeling was carried out for this new design to reinforce the modifications presented. The modifications proposed are:
 A new hood with a new refrigeration system, larger and inclined to 20º.
Alignment between the mouth angle and the walls of the hood.
A new settling chamber without infiltration of cold air and a water-cooled wall placed perpendicular to the gas flow at the middle of the chamber to precipitate the dust particles..
Lateral hood –converter seals without infiltration.
Lower gaps between the hood and the sliding gates attached to it.
Top: Physical layout converter & converter,
Bottom: Velocity vectors inside the converter hood.
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