Patrick Rohan

Optimisation of ingot casting wheel design using SPH simulations

Performance improvements of a new filling system for aluminium ingot casting resulting from a combination of Smoothed Particle Hydrodynamic (SPH) modelling and pilot scale testing are reported in this paper. The SPH modelling was used as the primary design tool, passing through several design iterations to understand the flow fundamentals and to progressively improve performance. The best concept from the simulation design stage was then refined through a detailed programme of pilot scale testing and a final round of SPH simulation. The results of this development programme will be described, with the new wheel design now able to operate at 50% higher throughput with an expected reduction in the oxide content by about 53% compared to that of the original design.

Predicting dross formation in aluminium melt transfer operations

Aluminium melt transfer operations can lead to significant amounts of dross formation as a result of chemical oxidation and physical entrapment processes. It has been suggested that these activities may contribute up to 50% of the total metal loss of ~1% in a typical primary aluminium smelter (i.e. 2,500 tonne/annum (tpa) in a smelter of 500,000tpa output). This is a large financial loss to any company, and also, in the new CO2-conscious era, it also represents a significant carbon footprint to ameliorate. A significant proportion of this metal loss may be prevented by adopting more efficient melt transfer strategies that reduce splashing and turbulence thereby resulting in reduced oxide and therefore dross formation. Optimisation of such systems is normally achieved by trial-and-error approaches, however a clear opportunity exists for rapid optimisation by employing computational modelling to explore the effects of changed equipment design and process conditions, such as tilt speed, spout height, spout geometry, etc. In the present paper, the Smoothed Particle Hydrodynamics (SPH) modeling method is used to predict the amount of oxide generated during molten metal transfers from a 500kg capacity tilting crucible furnace into a heated sow mould. Various conditions were tested. An oxidation model based on skimming trials performed in a laboratory-scale (8kg) oxidation rig is employed in the simulation. The predicted oxide from the simulations is compared against those of the experimental pours. It is anticipated that the validated model will be used for modifying the design and optimizing the operation of various melt transfer operations occurring in the aluminium industry.

Safety Enhancement in Ingot Casting at Tomago Aluminium

Tomago Aluminium experienced problems with the boiling of cooling water in ingot casting machines, where water splashed onto molten aluminium after mould filling. The boiling problem was particularly severe when new standard moulds were installed. This paper describes the experiments and modelling employed to analyse and identify the cause of the problem and based on the results, modifications to mould geometry were suggested. Subsequent testing in lab and field trials showed that the boiling was suppressed. The first set of modified moulds in service at Tomago Aluminium showed mould life was improved as predicted. Other issues with the modified mould design, which arose in service, are also discussed.

Implementation of CASTfill Low-Dross Pouring System for Ingot Casting

Producing low-dross ingots has been a long-term goal in aluminium cast houses. The patented CASTfill technology [1] is a low-dross and high-productivity pouring system developed to fulfil this demand. This paper describes the research methods used during the development of CASTfill; now in service at Boyne Smelters Limited (BSL) since August 2009. The importance of combining scientific modelling and testing procedures with process operability, maintainability and durability to ensure the success of new technology in a production facility is also highlighted. Ingot assessments showed that the latest CASTfill design greatly reduced dross generated during mould filling. Improved ingot packaging and reduced variation of ingot weights were also observed as the results of a more tranquil flow of molten aluminium through CASTfill and its uniquely modular design.