Electrode Technology for Aluminum Production: Anode Assembly and Cathodes
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Duygu Kocaefe, University of Quebec at Chicoutimi
Wednesday 8:30 AM
February 26, 2020
Room: 3
Location: San Diego Convention Ctr
Session Chair: Houshang Darvishi Alamdari, Laval University
8:30 AM Introductory Comments
8:40 AM
Energy Saving in Hall-Héroult Cell by Optimization of Anode Assembly Design: Abdul-Majid Shamroukh1; S. A. Salman2; William Berends3; W. Abdel-Fadeel4; G.T Abdel-Jaber5; 1Aluminium compny of Egypt (Egyptalum); 2Mining and Metallurgy Engineering Division, Faculty of Engineering, Al-Azhar University, Cairo, Egypt; 3AluCellTech Inc. Canada; 4Faculty of Energy Engineering, Aswan, Egypt; 5Faculty of Engineering, Mechanical Design and Production Dept. South Valley University, Egypt
Abstract Over the past few decades, intensive research was carried out on developing anode assembly designs to reduce energy consumption in aluminum reduction cell. The present research work was carried out in the aluminum company of Egypt (Egyptalum) smelter. A new anode assembly design was developed by inserting multiple steel nails into stub hole. The total anode voltage drop of the current anode design and that of the proposed design have been studied using thermo-electrical analysis via ANSYS simulation software. The developed model was validated by comparing predictions with the measurements from in-situ experiments. A significant improvement of the electrical contact resistance (ECR) between cast iron thimble and carbon was achieved by this new design. The mean voltage drop reduction reached 30 mV, which can achieve estimated annual cost saving of $1,228,800 USD/year for a smelter producing 320k tons of aluminum. Keywords: Hall-Héroult, Anode voltage drop, Electrical contact resistance, Steel nails, Thermo-electrical model.
9:05 AM
Redesigning of Current Carrying Conductor - The Energy Reduction Initiative in Low Amperage Hall-Héroult Cell: Ved Rai1; Vibhav Upadhyay1; 1Hindalco Industries Limited
To decrease specific energy consumption, we worked on Variable Stub and Solid Busbar project. In Variable Stub project, we changed the geometry of the stub, which decreased stub-to-carbon voltage drop. Our smelter has busbars of small cross-section. The busbar voltage drop is very high, which could be reduced by increasing the cross-sectional area. One pot has three sets of new welded busbars: one set on anode ring attached to the superstructure, two sets of half cathode ring welded to anode riser. This change-over requires shunting the next pot for 3 to 4 hours which is taken back into the circuit after job completion. This paper will discuss the new modified pots, benefits, way forward, gain obtained after implementing the variable stub and solid busbar in the pots and also all the steps which are adopted to change the busbar without shunting the plotline.
9:30 AM
Ready-to-Use Cathodes for the Hall-Héroult Process: Markus Pfeffer1; Louis Bugnion2; Laure Von Kaenel2; Oscar Vera Garcia1; 1COBEX GmbH; 2NOVALUM
Ready-to-Use Cathode (RuC™) blocks based on copper-inside-cathode concept have been implemented in many aluminum smelters since 2015. The concept and key performance parameters are presented, along with measurements of cathode resistance, collector bar current distributions and temperatures at the cell start-up as a function of cell age. Today, more than 500 RuC cathodes are in operation and more RuC™ cells are started every day. Significant energy savings and improvement of the cell magneto-hydrodynamic state are achieved. The reduction of the maximum cathode surface current density should lead to longer cathode life. The concept allows to avoid cast iron rodding and recovery of copper at the relining time. A new generation of cathode is ready to be implemented.
9:55 AM Break
10:15 AM Cancelled
High Temperature Creep Behaviour of Carbon-based Cathode Material for Aluminum Electrolysis: Wei Wang1; Kai Sun1; 1Henan University of Science and Technology
The creep strain of the semi-graphitic commercial cathode material used for aluminum production was measured on solid cylinder sample. Experimental results were obtained using a modified Rapoport equipment for the cathode material during aluminum electrolysis with a cryolite ratio (NaF [mole]/AlF3 [mole]) of 2.5 and at temperature of 950 ℃ under different stress levels. The coincident method proposed previously was applied to model the creep strain of carbon-based cathode material for aluminum electrolysis. The test data was processed, and the creep characteristics of the cathode material were determined based on Graham creep equation. A relationship between creep coefficients and stress has been developed. Then, the creep characteristics of the cathode material were obtained by finite element numerical simulations. The model results were in accordance with the experimental ones. This work will contribute to controlling the quality of the carbon cathode and improving the cell design.
10:40 AM Cancelled
Mechanism Understanding of Sodium Penetration into Anthracite Cathodes: A Perspective from Diffusion Coefficients: Jiaqi Li1; Hongliang Zhang1; Jingkun Wang1; Yunrui Wang1; 1Central South University
Sodium penetration into carbon cathodes is an important cause of cell failure and efficiency loss, but it is a formidable task to unravel the detailed mechanism experimentally. Combined with MD simulation and DFT calculation, several diffusion coefficients were acquired to quantitatively analyze the behaviors of sodium penetration for the first time. Especially, the transport diffusion coefficient of sodium vapor in the large-scale realistic anthracite cathode model was calculated as 6.132*10-10 m2/s, which was in outstanding agreement with experimental results. Owing to lower diffusion energy barrier, sodium was found to be faster along the grain boundaries than the other two solid diffusion pathways. The striking difference of corresponding diffusion coefficients in the order of magnitude indicated that sodium may migrate predominantly by vapor migration, rather than through solid diffusion, at least in anthracite cathodes with high porosity. This fundamental research would contribute to the understanding of sodium penetration mechanism and the optimization of cathode industry in the future.