![]() ![]() These are recycled as a component of the anode production process. As the anode life in the electrolytic cells comes to an end, the residual anodes, called butts, remain attached to the rod. For this reason, the production of test specimen in bench scale is one of the methods used to assess the quality of the anodes within the composition of interest and subsequent evaluation of some of their properties 1. Finding out that the anodes have low quality when in use usually generates undesirable costs. Some methods, such as the bench scale method, are broadly used to measure anode reactivity with a quality control purpose. Good quality carbon anodes should be oxidation-resistant in gaseous environments in order to minimize losses due to air oxidation on the surface of the exposed piece (C + O 2→ CO 2) and carbon oxidation caused by the carbon dioxide generated during the aluminum production (CO 2 + C ↔ 2CO) 1. Molten aluminum is formed on the base of the carbon cathode in the pot, while oxygen ions released from the dissociation of the alumina react with the carbon anode blocks, generating carbon dioxide (CO 2). In this process, aluminum is produced in electrolytic pots into which alumina (Al 2O 3) is fed and dissolved in molten cryolite (Na 3AlF 6) at about 960 ☌. The Hall-Héroult process is the only method currently used to produce aluminum in the primary aluminum industry. Keywords: butt, aluminum, spent anode, anode reactivity The Fischer formula predicted a carbon specific consumption of - 48.47 kg.t -1 Al for baked carbon anodes with 127 ppm to 367 ppm of sodium content, showing that the sodium can cause relevant carbon losses and increase costs of the aluminum production. ![]() The quality-related figures varied from 1.34 to 1.12 for CO 2 and from 1.10 to 0.62 for air, showing quality loss in higher sodium content and higher impact on air reactivity. An average increase of 48 ppm of sodium from one to another formulation caused average increments of 3.38 and 2.72% for air and CO 2 reactivity, respectively. Six formulations with 0 to 25% butt powder were used. This paper evaluates the influence of sodium content on anode reactivity. The fragmentation of the butt generates some sodium-rich powder, which is captured and included in the recycled material. Spent anodes, denominated butts in the aluminum industry, are recycled as part of the raw material used to produce new anodes. IIFaculty of Chemical Engineering, Federal University of Pará - UFPA, R. Jefferson dos Santos Batista I Benedito Inácio da Silveira II, * Area Management, Alumínio do Norte do Brasil S.A. Influence of the sodium content on the reactivity of carbon anodes The Fischer formula predicted a carbon specific consumption of - 48.47 kg.t-1 Al for baked carbon anodes with 127 ppm to 367 ppm of sodium content, showing that the sodium can cause relevant carbon losses and increase costs of the aluminum production.īutt aluminum spent anode anode reactivity The quality-related figures varied from 1.34 to 1.12 for CO2 and from 1.10 to 0.62 for air, showing quality loss in higher sodium content and higher impact on air reactivity. An average increase of 48 ppm of sodium from one to another formulation caused average increments of 3.38 and 2.72% for air and CO2 reactivity, respectively. ![]()
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