M. Segatz’s research while affiliated with Hydro Aluminium and other places

Hydro's HAL Ultra cell technology development has achieved a major milestone to demonstrate greener aluminium production by operating two different electrolysis cell platforms at energy consumption levels below 12 kWh/kg. Two cells based on HAL300 and HAL4e technology have been rebuild with newly developed solutions to reduce cell resistance, enhance heat conservation and further improve standard operational procedures. Applying Hydro's portfolio of modelling tools, materials knowledge, process know-how and operational competence enabled the development team to design high performance cell components and methods to reduce process variability. These elements were pre-tested on several cells before merging into full demonstrators. The HAL4e and HAL4e Ultra cell technologies will be installed as part of the Karmøy technology pilot plant.

Numerical simulation of coupled bath/metal magnetohydrodynamics (MHD) and MHD stability analysis allow the optimization of anode set pattern with respect to minimal cell disturbance. The contribution of anode gas-induced forces and the impact on the flow field are discussed. During a complete anode set cycle, the anode current distribution changes significantly due to varying anode resistances, frozen bath and different metal pad heights. Typically the largest disturbance to cell stability occurs during a short time span after the anode change. With steady-state MHD simulations immediately before and after each anode change - following the sequence of the underlying set pattern - the relevant cell current and ACD distribution are determined. The impact of these parameters on cell stability is predicted with a linear MHD stability analysis for a complete anode change cycle.

Modernization of the 210,000 tpy VAW Rheinwerk smelter includes installation of point feeder, alumina conveying system, state-of-the-art pot control system and foresees an increase in amperage of up to 175 kA. For the modernized pots concepts for the potlining as well as for improvements of the busbar system were developed based solely on computer simulations. For the layout of the potlining a new three-dimensional thermoelectric cell model was applied that allows prediction of side ledge contours as well as heat and voltage balances. Based on this model the choice of semi-graphitic vs. fully graphitized cathode blocks was evaluated with respect of the anticipated increase in system amperage. Temperature fields and side ledge contours predicted are in good agreement with measurements. The busbar system, designed originally for a current load of 110 kA, was improved in a very efficient manner to cope with the higher amperage. Magneto-hydrodynamic simulations predicted and plant measurements demonstrated significant improvements in cell stability and performance.

Hydro’s HAL Ultra cell technology development has achieved a major milestone to demonstrate greener aluminium production by operating two different electrolysis cell platforms at energy consumption levels below 12 kWh/kg. Two cells based on HAL300 and HAL4e technology have been rebuild with newly developed solutions to reduce cell resistance, enhance heat conservation and further improve standard operational procedures. Applying Hydro’s portfolio of modelling tools, materials knowledge, process know-how and operational competence enabled the development team to design high performance cell components and methods to reduce process variability. These elements were pre-tested on several cells before merging into full demonstrators. The HAL4e and HAL4e Ultra cell technologies will be installed as part of the Karmøy technology pilot plant.

The growth rate, period of oscillation, and spatial shape of interface waves in Hall-Héroult cells are determined from a linear stability analysis in the three-dimensional domain of liquid bath and metal. The linearized Maxwell and momentum equations together with the demand for hydrostatic balance at the interface describe a self-exciting oscillator. The corresponding eigenvalue problem for the interface movement is solved numerically. The resulting periods of typically 20–40s are in good agreement with measurements. Both the steady-state as well as the oscillating component of the three-dimensional magnetic field and current density pattern are included. This gives a consistent description of different instability-driving mechanisms. The spatial distribution of the electromagnetic to kinetic energy transfer is used to localize the regions in the cell which mainly cause instabilities . The influences of current intensity, ACD, metal pad height, and density ratio on strength and type of instability are demonstrated.

In the context of global climate change and Hydro's focus on reducing its greenhouse gas footprint, Hydro's Primary Metal Technology (PMT) department has been focusing on low energy pot development for the last decade. Disclosing some of the development is meant as one of Hydro's contributions to the industry's effort in reducing greenhouse gas production. This paper presents Hydro's PMT experiences with the use of external potshell insulation. It presents its early uses as a tool to improve pots having cold spots, to a solution for maintaining a cathode free from bottom deposits on pots where heat input is sharply decreased, opening the door to cheap retrofitting of smelters for low energy consumption. Hie authors also mention recent development where external insulation is becoming part of pot design, which, along with other efforts in reducing voltage drops, allows stable pot operation below 12kWli/kg. All rights reserved.

In the context of global climate change and Hydro’s focus on reducing its greenhouse gas footprint, Hydro’s Primary Metal Technology (PMT) department has been focusing on low energy pot development for the last decade. Disclosing some of the development is meant as one of Hydro’s contributions to the industry’s effort in reducing greenhouse gas production. This paper presents Hydro’s PMT experiences with the use of external potshell insulation. It presents its early uses as a tool to improve pots having cold spots, to a solution for maintaining a cathode free from bottom deposits on pots where heat input is sharply decreased, opening the door to cheap retrofitting of smelters for low energy consumption. The authors also mention recent development where external insulation is becoming part of pot design, which, along with other efforts in reducing voltage drops, allows stable pot operation below 12kWh/kg.

Introduction MHD Stability Analysis of Anode Set Pattern Optimization of Anode Set Pattern Effect of Gas Bubbles Conclusion

Modernization of the 210,000 tpy VAW Rheinwerk smelter includes installation of point feeder, alumina conveying system, state-of-the-art pot control system and foresees an increase in amperage of up to 175 kA. For the modernized pots concepts for the potlining as well as for improvements of the busbar system were developed based solely on computer simulations. For the layout of the potlining a new three-dimensional thermoelectric cell model was applied that allows prediction of side ledge contours as well as heat and voltage balances. Based on this model the choice of semi-graphitic vs. fully graphitized cathode blocks was evaluated with respect of the anticipated increase in system amperage. Temperature fields and side ledge contours predicted are in good agreement with measurements. The busbar system, designed originally for a current load of 110 kA, was improved in a very efficient manner to cope with the higher amperage. Magneto-hydrodynamic simulations predicted and plant measurements demonstrated significant improvements in cell stability and performance. © 2013 The Minerals, Metals & Materials Society. Published 2013 by John Wiley & Sons, Inc.