The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 31, 1987
Filed:
May. 05, 1986
Michel Leroy, Saint-Jean-de-Maurienne, FR;
Aluminium Pechiney, Paris, FR;
Abstract
A process is disclosed for accurately maintaining a low alumina content of between 1 and 4.5% in a cell for the production of aluminum by electrolysis in the Hall-Heroult process. According to the invention, a control parameter P=-1/D(dR.sub.1 /dt), is determined, wherein D is the variation in the alumina content of the electrolytic bath in % weight per hour, R.sub.1 is the internal resistance of the cell, and t is the time. A series of operations is then carried out in a repeated cycle, starting with the cell being fed alumina at a nominal rate which is substantially equal to the quantity consumed by electrolysis. At periodic intervals, an over-supply of alumina is added in order to enrich the bath, and the over-supply is continued for a preset time during which dR.sub.1 dt is negative. The feed rate is then reduced to less than the nominal feed rate, during which time dR.sub.1 dt passes through zero to become positive and the regulation parameter P, the value of which tends to rise, is measured often. The successive values of P are compared with a required preset value Po. As soon as P equals Po, the feed rate is returned to the nominal feed rate and a new cycle is recommenced.