Aluminum Pechiney

Oliver Bonnardel

Claude Vanvoren

The invention relates to a regulation method for an electrolytic cell for the production of aluminium by means of reduction of alumina dissolved in a molten cryolite bath, wherein a solidified bath ridge is formed on the internal walls of the pot, a quantity B, referred to as the 'ridge variation indicator', which is sensitive to the variation of said solidified bath ridge, is determined and at least one of the setting means of the pot (such as the anode-metal distance) and/or at least one control operation (such as the addition of AlF) is modified as a function of the value obtained for said indicator. The indicator may be determined from electrical measurements on the pot and/or from measurements of the liquid metal surface area. The method according to the invention makes it possible to regulate an electrolytic cell effectively at currents of up to 500 kA with an electrolyte bath with an AlFcontent greater than 11% and reduce the number of AlFcontent measurements in the bath considerably.

Method for regulating an electrolytic cell

The invention relates to a regulation method for an electrolytic cell for the production of aluminium by means of reduction of alumina dissolved in a molten cryolite bath and comprises the addition, in the electrolyte bath, during pre-determined time intervals p referred to as 'periods', of a determined quantity Q(p) of aluminium trifluoride (AlF) determined by the following equation: Q(p)=Qint(p)&#x2212;Qc1(p)+Qt(p), where Qint(p) is an integral (or 'self-adaptive') term which represents the total actual AlFrequirements of the cell and which is calculated from a mean Qm(p) of the actual AlFsupplies made during the last N periods, Qc1 is a compensating term corresponding to the so-called &#x201c;equivalent&#x201d; quantity of AlFcontained in the alumina added to the cell during the period p, and Qt(p) is a corrective term which is a typically increasing function of the difference between the measured bath temperature T(p) and the set-point temperature To. The method according to the invention makes it possible to regulate effectively the acidity of an electrolytic cell at intensities of up to 500 kA with an electrolyte bath having an AlFcontent greater than 11%.

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Saint Martin D'arc, France

Oliver Bonnardel