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:
Jun. 16, 1992
Filed:
May. 29, 1990
Gyorgy Banvolgyi, Budapest, HU;
Jozsef Zoldi, Budapest, HU;
Peter Siklosi, Budapest, HU;
Tibor Ferenczi, Budapest, HU;
T Anna Csordas, Budapest, HU;
Ivan Feher, Budapest, HU;
Ildiko Tassy nee Varju, Budapest, HU;
Istvan Sajo, Budapest, HU;
Aluminiumipari Troszt, Budapest, HU;
Abstract
An improvement in the process for extracting alumina from gibbsitic bauxites, wherein the basic, known process comprises mixing the bauxites with a sodium hydroxide-sodium aluminate digestion liquor, digesting the bauxites at a temperature in the range of 100.degree.-180.degree. C., diluting the resulting slurry, separating the red mud therefrom, precipitating alumina hydrate by cooling and agitation of the sodium aluminate liquor, and calcining the alumina hydrate precipitate to obtain alumina, wherein the improvement is characterized by so controlling the process that, in the liquid phase of the slurry leaving the digestion reactor, the reactive hydroxide ion concentration is maintained below 6 g/l, and preferably between 0 and 2 g/l, where the reactive hydroxide ion concentration is defined by the following formula: ##EQU1## where: C.sub.Al.sbsb.2 O.sub.3,gi.sup.eq is the equilibrium solubility of Al.sub.2 O.sub.3 for gibbsite, in g/l.