Claims
- 1. An improved process for producing pure aluminum oxide of the type wherein clay or clay- containing minerals undergo a two-stage treatment with sulfuric acid under the use of pressure and increased temperature, separation of the insoluble residue, reduction of the iron, hydrolysis of the aluminum sulfate solution to solid basic aluminum sulfate, and decomposition of the hydrolysis product to aluminum oxide, said improvement comprising the steps of providing in the first leaching stage an Al.sub.2 O.sub.3 excess in the starting material of 60-120% related to the Al.sub.2 O.sub.3 component to be leached; adding to the filtrate of the first leaching stage which is supplied to the hydrolysis, to obtain a weight ratio SO.sub.3 :Al.sub.2 O.sub.3 of 2.0-2.86, sufficient magnesium sulfate for the solution supplied to hydrolysis to contain 30-90 g/l MgSO.sub.4 ; carrying out the hydrolysis under pressure with the exclusion of oxygen and without the addition of active clay, basic aluminum sulfate or other chemicals which increase the basicity; and from the hydrolysis solution precipitating basic aluminum solfate at 220.degree.-280.degree.C. which is calcined to obtain alumina.
- 2. The process of claim 1, wherein the solution supplied to hydrolysis contains 50-110 g/l Al.sub.2 O.sub.3, the weight ratio SO.sub.3 :Al.sub.2 O.sub.3 is set at 2.65 and the hydrolysis is carried out at 240.degree. C.
- 3. The process of claim 1, wherein a second leaching stage can be operated at normal pressure.
- 4. The process of claim 1 further comprising the step of cooling down the hydrolysis residue, said cooling being carried out in the temperature range of 140.degree.-80.degree. C. in less than 10 minutes, whereby the reverse solution effect on precipitated basic aluminum sulfate is avoided.
Priority Claims (1)
Number |
Date |
Country |
Kind |
203210 |
Jan 1978 |
DDX |
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CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of my co-pending application Serial No. 001,159, filed January 4, 1979 now abandoned, said application entitled:
US Referenced Citations (5)
Foreign Referenced Citations (1)
Number |
Date |
Country |
883311 |
Nov 1961 |
GBX |
Non-Patent Literature Citations (1)
Entry |
Scott, "Research", vol. 14, Feb. 1961, pp. 50-54. |