ORALS

SESSION: MoltenWedPM1-R11	Kipouros International Symposium (8th Intl. Symp. on Sustainable Molten Salt, Ionic & Glass-forming Liquids & Powdered Materials)
Wed. 30 Nov. 2022 / Room: Game
Session Chairs: Inessa Novoselova; Session Monitor: TBA

14:00: [MoltenWedPM105] OS
Continuous monitoring and control of the AlF3 content of the cryolitic melt in aluminium electrolysis
Vicky Vassiliadou¹ ; Antonis Peppas² ; Maria Taxiarchou³ ; Ioannis Paspaliaris³ ; ¹Mytilineos Holdings S.A, Agios Nikolaos, Greece; ²National Technical University of Athens, Zografos Campus, Greece; ³National Technical University of Athens, Athens, Greece;
Paper Id: 378 [Abstract]

The aim of this paper is to summarize the mathematical equations applied to the modelling of the physicochemical properties of the aluminium electrolysis cryolite melts and the study of the effect on the properties of its aluminium fluoride content and the development of a methodology for the direct determination of its concentration in the electrolysis bath that can be applied in industrial scale electrolysis cells.<br />The AlF₃ content of the electrolyte melt is one of the most important parameters affecting the physicochemical properties of the electrolysis bath. In the current industrial practice, the determination of AlF₃ concentration in the bath is performed through periodic sampling, chemical analysis of the selected samples and, based on the chemical analysis results, the appropriate quantity of AlF₃ addition is determined. This procedure is time consuming, and its major disadvantage is that between the time of sampling and analysis until the addition of the corrective AlF₃ quantity, the AlF₃ content of the bath has changed. This creates a serious problem in the proper control of the AlF₃ concentration in the electrolysis bath and the stable operation of the electrolysis cell.<br />A methodology for the real time determination of the AlF₃ content of the electrolysis bath has been developed based on the measurement of the bath resistance. According to the proposed methodology, a given change in the anode cathode distance is applied and the corresponding change in the bath resistance is measured and, from its value, the bath electrical resistivity is determined. The value of the electrical resistivity is correlated to the value of the theoretical electrical resistivity of the bath and through an appropriate algorithm the AlF3 content of the bath is determined in real time with sufficient accuracy.

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