Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Involving measuring – analyzing – or testing during synthesis
Reexamination Certificate
2006-11-14
2006-11-14
Bell, Bruce F. (Department: 1746)
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Involving measuring, analyzing, or testing during synthesis
C205S337000, C205S372000, C205S374000, C205S392000, C205S394000, C205S396000, C374S139000
Reexamination Certificate
active
07135104
ABSTRACT:
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 (AlF3) determined by the following equation: Q(p)=Qint(p)−Qc1(p)+Qt(p), where Qint(p) is an integral (or “self-adaptive”) term which represents the total actual AlF3requirements of the cell and which is calculated from a mean Qm(p) of the actual AlF3supplies made during the last N periods, Qc1 is a compensating term corresponding to the so-called “equivalent” quantity of AlF3contained 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 AlF3content greater than 11%.
REFERENCES:
patent: 4446350 (1984-05-01), Mizukawa et al.
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patent: 5094728 (1992-03-01), Entner
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patent: 6183620 (2001-03-01), Verstreken
patent: 2106435 (1998-03-01), None
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Peter M. Entner: “Control of AIF3Concentration”, Light Metals, 1992, pp. 369-374.
M. J. Wilson: “Practical Considerations Used in the Development of a Method for Calsulating Aluminium Fluoride Additions Based on Cell Temperatures”, Light Metals, 1992, pp. 375-378.
Bonnardel Oliver
Vanvoren Claude
Aluminum Pechiney
Baker Donelson Bearman Caldwell & Berkowitz PC
Bell Bruce F.
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