Electrode Technology for Aluminum Production: Session II
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Stephan Broek, Kensington Technology Inc; Dmitry Eskin, Brunel University
Tuesday 8:00 AM
March 1, 2022
Room: 208A
Location: Anaheim Convention Center
Session Chair: Derek Santangelo, Hatch
8:00 AM
Dynamics of Anode Baking Furnace VOC Emissions through a Firing Cycle: Ole Kjos1; Thor Aarhaug1; Heiko Gaertner1; Anders Brunsvik1; 1Sintef As
The anode baking process produces significant amounts of volatile organic compounds (VOC) and polyaromatic hydrocarbons (PAH). Measuring the full range of these emissions is costly and time consuming. However, VOC and lighter PAH components that exists mainly in gas phase can be measured by simpler means. Establishing a known ratio between the components could enable estimates of the total emissions by following certain proxy components. To document the distribution, and time profiles, of VOC and light PAH components different sampling methodologies with time resolution better than 30 minutes were evaluated. Measurements using TD tubes, a PID instrument and a GC-FID were conducted up and downstream the gas treatment center. Removal efficiencies of selected VOC were calculated. In addition, dynamics between different gas components during the firing cycle was shown, indicating high initial load of light VOC just after the onset of the firing cycle while heavier components emerged later.
8:25 AM
NOW ON-DEMAND ONLY – Anode Rod Tracking: A New Marking Method for Optimized Implementation: Pascal Cote1; Jean-Pierre Gagné1; Rémi St-Pierre1; 1Stas Inc.
Process optimization by applying the industry 4.0 principles is now on the roadmap of most of the aluminium producers. Especially, the anode assembly loop has shown interest. Gradually, the operational technologies required to allow for the introduction of process intelligence are being developed and deployed. Automated stub and butt inspection, anode and anode rod tracking are gaining adoption. In the past decade, STAS has implemented anode rod tracking systems using a dual marking approach, that is datamatrix codes for automated reading and alphanumeric marking for human-reading. Although the original code implementing technique proved to be effective and robust, it involved to divert the rods from their regular route. To address this issue, STAS has now developed and deployed a new technique based on laser engraving that has the advantage of being easily installed along the aerial conveyor. This opens the door to a wider adoption of the technology.
8:50 AM
Plate Yokes. Anode Assembly without Cast Iron: Jorund Hop1; Vidar Hjelle1; Per Johnny Teigen1; Inge Arild Vee1; Bjarte Øye2; Grzegorz Stefanski1; 1Hydro Aluminium AS; 2SINTEF
Anode assemblies typically consist of steel stubs locked into holes in the anode carbon using cast iron. The contact resistance between the cast iron and carbon and the necking of the amperage in the anode top contribute to electrical resistance. In the anode assembly presented here the cast iron is replaced by steel shots and the stubs replaced by plates. The assembly is held together with eight L-locks machined into the carbon anode. The steel shots sinter during an anode cycle, but can after an anode cycle be stripped off, crushed and re-used. The area of the yoke-carbon-connection is increased by using plates instead of stubs. A reduction of 50 mV-100 mV in 11 kA anode assemblies was measured. The contact area and therefore the electrical resistance is less affected when changing plate thickness. The heat loss of such an assembly is therefore easier to design. The rodding operation without liquid cast iron will be safer. The footprint, investment cost and operation cost of such a rodding station will probably be significantly reduced.
9:15 AM
Bio-binders and Its Carbonization and Interaction with Petroleum Coke during Baking: Goril Jahrsengene1; Stein Rørvik1; Anne Støre1; Liang Wang2; Øyvind Skreiberg2; 1SINTEF Industry; 2SINTEF Energy Research
To reduce the carbon footprint in aluminium production, bio-based binders are suggested to replace some or all coal tar pitch in the carbon anodes. In this study, bio-binders based on Norwegian spruce and birch woods were produced in a laboratory set-up, which were studied in terms of wetting properties towards petroleum coke. The binders were mixed with petroleum coke and baked to three different temperatures. Graphitization of the binders were investigated on pure carbonized binders by XRD. Optical light microscopy was used to investigate the structures and interactions between coke and binder after baking. The bio-based binders appeared to adhere well to the coke particles, indicating excellent wetting behaviour during mixing. The optical structure of the carbonized bio-binder seemed to be affected by strain due to shrinkage of the bio-binder around the coke grain boundaries.