Almasfuzitoi Timfoldgyar

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Femipari Kutato Intezet

Aluterv Aluminiumipari Tervezo Vallalat

Aluminiumipari Troszt

Tibor Ferenczi

Karoly Solymar

Jozsef Matyasi

Jozsef Zoldi

Janos Zambo

Peter Siklosi

Laszlo Lengyel

Istvan Voros

Kalman Wentzely

Jozsef Boros

Bela Toth

Tihamer Pinter

Ivan Feher

Ferenc Lazar

Gyorgy Sigmond

Gyula Horvath

Zsolt Csillag

Tibor Kalman

Pal Toth

Maria Orban Nee Kelemen

Istvan Sajo

Ferenc Orban

Ildiko Tassy Nee Varju

Gyorgy Banvolgyi

Marika Orban Nee Kelemen

Erno Bujdoso

T Anna Csordas

Zoltan Ozvald

Lajos Toth

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.

Process for producing alumina

An improved process for accelerating the digestion process in the Bayer alumina process is provided which promotes both the goethite-hematite conversion and a more perfect and quick dissolution of the diaspore. The above is achieved by carrying out the digestion in the process of 5-20% by weight calculated on the dry weight of the bauxite of a novel hydrogarnet catalyst.

Process for accelerating the digestion and sedimentation steps on the

The invention relates to an improved process for the production of alumina according to the Bayer technology, of bauxites containing goethite and especially of boehmitic or diasporic bauxites, for the acceleration of the digestion process, for the transformation of goethite into hematite, for the increase of alumina yield and for the reduction of the caustic soda losses, the essence of which consists in carrying out the digestion in the presence of 2-6% CaO and 0.2-2.0% Mg.sup.++, Fe.sup.++, Mn.sup.++ Co.sup.++ ions based on the weight of the dry bauxite or of compounds or ores containing these ions in the indicated quantities.

Process for digesting goethite-containing bauxites according to the

A method for processing bauxites according to the Bayer technology, with an increased yield in Al.sub.2 O.sub.3 and with decreased caustic soda losses, starting particularly from goethite bauxites of boehmite and/or diaspore type and carrying out the digestion at 180.degree.C to 300.degree.C using an aluminate liquor containing Na.sub.2 O.sub.caustic in a concentration of 80 to 300 g./l. The digestion is carried out in the presence of a calcium compound in an amount corresponding to 2 to 6 % of CaO calculated for the dry weight of bauxite and of a sulfate salt in an amount corresponding to 1.0 to 7.0 g./l. of sulfate ion concentration, whereby the goethite content of the bauxite is converted into hematite. The process provides advantageous conditions for the complete dissolution of the boehmite and diaspore content of bauxite in the vicinity of the equilibrium molar ratio, and enables to recover efficiently the caustic soda losses in the Bayer process itself, requiring no supplementary operation.

Method for processing bauxites

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Budapest, Hungary

Tibor Ferenczi