Utilization of waste heat for pre-heating of anodes
Peer reviewed, Journal article
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OriginalversjonLight Metals. 2020, 811-816. https://doi.org/10.1007/978-3-030-36408-3_108
Carbon anodes are replaced on a regular basis in Hall–Héroult cells as they are consumed by electrochemical reactions. Upon insertion of new anodes, bath will freeze locally as a result of low bath superheat and comparatively low anode temperature, creating an insulating layer on the anode surface, thereby delaying further production. In the current work the potential for pre-heating anodes directly utilizing waste heat from off-gas and spent anode butts is investigated using a numerical model realized in COMSOL and industrial measurements at the Alcoa Mosjøen smelter. Anode core temperatures over 150 ∘ C and surface temperatures over 250 ∘ C were found when using butts as a direct heat source. Frozen bath samples from both pre-heated and regular anodes were collected and analysed using computer tomography (CT) in order to assess how various heating strategies influences frozen bath morphology.