US 4,618,480 A · Recovery of alumina values from alunite ore

Abstract

A novel process for the recovery of alumina and potassium sulfate from alunite is provided comprising leaching the alunite with potassium hydroxide to which no sodium materials have been added, said leach solution being saturated with potassium sulfate. Aluminum values are solubilized into the leachate, and potassium and sulfur values are rendered soluble, but remain in the residue. The leachate is desilicated if necessary, preferably with lime, and aluminum trihydroxide is precipitated therefrom, followed by calcining to alumina product. The residue is leached to solubilize potassium sulfate in a secondary leach and the potassium sulfate product crystallized therefrom. Potassium hydroxide is regenerated from a portion of the potassium sulfate secondary leachate by several methods. Novel procedures for regenerating alkali metal hydroxides from the corresponding sulfates are also provided including routes involving formates and carbonates as intermediates and pyrohydrolysis.

Claims37

Dependent claims

A process for recovering aluminum and potassium values from alunite ore comprising:

(a) contacting said ore at a temperature above 60.degree. C. with potassium hydroxide saturated with potassium sulfate to which no Na has been added to form a potassium sulfate-saturated primary potassium hydroxide leach liquor containing said Al values and a primary leach residue containing said K values;
(b) separating said primary leach liquor from said primary leach residue;
(c) precipitating Al(OH).sub.3 crystals from the liquor of step (b) to recover the Al values therefrom;
and
(d) aqueous leaching said primary leach residue of step (b) to form a secondary leachate containing said K values.

2 more elements

A method of producing Al.sub.2 O.sub.3 and K.sub.2 SO.sub.4 from alunite ore using CaO as the only make-up reagent comprising:

(a) contacting said ore at a temperature above 60.degree. C. with a K.sub.2 SO.sub.4 -saturated KOH to which no Na has been added to form a K.sub.2 SO.sub.4 -saturated first KOH leach liquor containing said Al values and a first leach residue containing said K and S values;
(b) separating said first leach liquor from said first leach residue;
(c) desilicating said separated first leach liquor and separating the precipitated silicates from said liquor;
(d) precipitating Al(OH).sub.3 crystals from the desilicated liquor of step (c) to recover the Al values therefrom;
(e) calcining said Al(OH).sub.3 crystals to produce alumina;
(f) leaching of said first leach residue of step (b) with an aqueous solution to form a second leach liquor containing said K and S values;
(g) crystallizing K.sub.2 SO.sub.4 from at least a portion of said second leach liquor to form a spent liquid;
(h) regenerating KOH for recycle to step (a) by contacting a portion of said secondary leachate of step (f) with lime and hydrogen sulfide to form calcium sulfate and a potassium sulfide- and potassium hydrogen sulfide-containing liquor;
carbonating said liquor to form potassium carbonate;
and causticizing said potassium carbonates to produce potassium hydroxide;
(i) recycling at least a portion of the spent liquor of step (g) to step (f);
(j) controlling the level of KOH in said second leach liquor of step (g) by recycling to step (a) at least one of the streams selected from the group consisting of (1) at least a portion of the spent liquor of step (g);
and (2) at least a portion of said second leach liquor of step (f);
(k) controlling the build-up of impurities in the crystallization of step (d) by removing said impurities from at least a portion of said desilicated liquor;
(1) heating said CaCO.sub.3 of step (h) to form CaO and CO.sub.2 ;
and
(m) recycling said CaO to step (c) and step (h).

14 more elements

Dependencies are inferred from the claim text.

Recovery of alumina values from alunite ore

Life of this patent

Recovery of alumina values from alunite ore

Life of this patent

Abstract

Claims37