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US 4,246,239 AGranted
Alumina production by nitric acid extraction of clay
AssigneeReynolds Metals Company
InventorsJohn L. Dewey, Charles E. Scott, James F. Kane, Claud L. Stratton, John C. Rushing, Robert H. Spoonts
Life of this patent
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Abstract
Alumina values are extracted from clay by the steps of pelletizing into spherical particles, calcining the pellets in a fluidized bed reactor, extracting the clay in about 30-40% nitric acid, purifying the basic aluminum nitrate produced, crystallizing aluminum nitrate nonahydrate, decomposing the nonahydrate in at least three steps, calcining the produced alumina and reconstituting the NO.sub.x gases to nitric acid.
Claims12
A process for the extraction of alumina values from clay using nitric acid comprising the steps of:
- (i) pelletizing the clay into generally spherical particles having a diameter of between about 1 and about 8 mm and a free moisture content of between about 17 and 22%;
- (ii) calcining the pellets formed in step 1 at a temperature of between about 1100.degree. and 1550.degree. F. in a fluidized bed reactor;
- (iii) extracting the calcined clay pellets obtained in step (ii) in about 30 to about 40% nitric acid for a period of between about 1 and about 4 hours at about atmospheric pressure and a temperature of between about 220.degree. and about 270.degree. F. to produce basic aluminum nitrate product solution comprising between about 8 and 13 weight percent alumina and between about 5 and about 20% less nitric acid than required by stoichiometry to form aluminum nitrate;
- (iv) purifying the basic aluminum nitrate product of step (iii) by
- (a) precipitating iron oxide by holding the product of step (iii) for a period of at least about 2 hours and at a temperature of between about 80 and about 120.degree. C. in the presence of a small amount (about 1 to about 3%) of iron oxide seed material;
- and
- (b) filtering the liquor derived from step (iv)(a) to remove silicaceous impurities;
- (v) crystalizing aluminum nitrate nonahydrate from the product of step (iv)(b);
- (vi) converting the crystalized aluminum nonahydrate produced from step (v) to an infusible basic aluminum nitrate in an at least two-step process comprising:
- (a) evaporating nitric acid from the crystals in molten form to provide a solution of basic aluminum nitrate containing at least about 16.5 by weight alumina and recovering of the heat of condensation of the vapors thus produced;
- (b) decomposing of the basic aluminum nitrate liquor to infusible basic aluminum nitrate solids;
- (vii) further decomposing the infusible basic aluminum nitrate solids in one or two stages at a temperature of between about 600.degree. and 1300.degree. F. for a period of from about 2 to about 7 hours;
- (viii) calcining the residual metallurgical grade alumina at a temperature of between about 1900.degree. and 2200.degree. F., and
- (ix) reconstituting to nitric acid the NO.sub.X gases from step (xii).
11 more elements
Dependencies are inferred from the claim text.