Electrode Technology for Aluminum Production: Anode and Cathode Process Improvements
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Roy Cahill, Rio Tinto; Stephan Broek, Kensington Technology Inc
Wednesday 2:00 PM
March 22, 2023
Room: 31A
Location: SDCC
Session Chair: Roy Cahill, Rio Tinto Aluminium
2:00 PM
Investigation of the Stacking Effects on the Electrical Resistivity of Industrial Baked Anodes: Thierno Saidou Barry1; Donald Picard2; Guillaume Gauvin1; Julien Lauzon-Gauthier3; Houshang Alamdari1; 1REGAL Aluminium Research Center; 2Eddyfi; 3Aloca
Producing Anodes with the highest uniformity and consistent properties is essential to improve the energy efficiency and productivity of the Hall-Héroult process. One of the production parameters which may affect the anode quality is the position of the anodes in the baking furnace on their final properties. During the baking process, the anodes are stacked in the pits of the furnace and baked according to predefined temperature profiles. Stacking the anodes may generate mechanical stress on the lower anodes. This additional stress state could affect the rearrangement of the anode coke particles, leading to internal structure anisotropy. To investigate the effect of this parameter, we measured the electrical resistivity and density of the anodes baked at different positions in the furnace. The results show a statistically meaningful variation of the electrical resistivity as a function of anode position in the furnace.
2:25 PM
New Generation Anode Baking Furnace: Use of Prefabrication for Additional Conversions at Bell-Bay Plant: Sandra Besson1; David Deneef1; Anthony Reeve2; Youcef Nadjem2; Meaghan Noonan3; Roy Cahill3; 1Rio Tinto Aluminium Technology Solutions; 2Bell Bay Aluminium; 3Rio Tinto Transformation and Technical Support - Pacific Operations
The anodes used for aluminium production are baked in order to reach the resistivity, mechanical resistance and reactivity adequate for the electrolysis process. The anodes are baked in pits that are usually separated from each other by fluewalls and headwalls made of dense refractory material. In 2017, an industrial prototype of the new generation anode baking technology was installed at the Bell Bay smelter with 6 sections converted to this patented technology. The headwalls were partially removed to allow a productivity increase by 15 % and gas consumption reduction by 30 %. After the success of this first trial, the conversion of five additional 6-sections zones by the end of 2025 has been decided for Bell-Bay’s furnace. The use of prefabrication has been developed and implemented for the installation of the second generation of walls to: 1. shorten the construction duration and limit the production loss, 2. improve the ergonomics and safety for the construction workers and, 3. improve the overall brick assembly quality.This paper reviews the process that led to an optimized second NG zone construction through prefabrication.
2:50 PM
AHEX Full Scale Experiences at TRIMET Aluminium SE: Anders Sorhuus1; Vrauke Zeibig2; Eivind Holmefjord1; Oemer Mercan2; Elmar Sturm3; 1REEL Norway AS; 2TRIMET Aluminium SE; 3ESC-Consulting
The new AHEX technology for treating the off gas fumes from the anode baking furnaces has been successfully demonstrated since 2018 for a complete new FTC at TRIMET Hamburg. With this new technology, the fumes are cooled in an indirect heat exchanger with water in a closed loop. Thereby, many issues with corrosion and deposits inside the traditional FTC based on the conditioning tower designs are avoided. Alumina is injected into the AHEX to keep the surfaces clean, and at the same time the alumina absorbs and removes part of the undesired components from the off gas stream. The less sticky and less humid gas due to the AHEX improves the operation conditions for the filter bags. The paper will present performance results achieved including operational and maintenance experiences over time after the start up of the first full scale AHEX FTC installed at TRIMET’s Hamburg anode bake furnace.
3:15 PM
Inline Modal Detection System of Anodes and Cathodes Measuring Cracks and Physical Properties: Dag Herman Andersen1; 1Hydro Aluminium
An anode and cathode quality system based on modal analysis has been developed. The modal detection system finds the resonances of the item tested by measuring the movements of the item caused by an input force from a hammer or shaker. The modal method is verified by measurements and modelling of anodes and cathodes to find cracks and the elastic property, Youngs Modulus (YM). Measurement times around 60 s/item can be achieved. For an inline station to measure YM and find crack plane orientations, the resonances need to be identified by mode shapes. The method has a huge potential of detecting items with cracks that can cause unstable cell operation and early cathode failures. In addition, the modal test can provide feedback to production plants of anodes and cathodes to produce those items which are closest the reference spectrum of resonances from a crack free homogeneous product.
3:40 PM Concluding Comments