Claims
- 1. In a process for precipitating alumina hydrate from a stream of Bayer process liquor, wherein the stream is first divided into a major portion and a minor portion, the minor portion fed to an agglomeration stage and seeded with fine seed to induce precipitation and formation of a slurry, and the major portion cooled and charged with coarse seed and directed to a growth stage to induce formation of alumina hydrate product;
- the steps of:
- separating solids from the minor portion after formation of the slurry;
- cooling, to a temperature of between about 45.degree. C. and about 60.degree. C., the liquid remaining after separating solids from the slurry formed in the agglomeration stage;
- adding an amount of coarse seed of about 80 to about 100 microns in median particle size to the remaining liquid to generate a slurry of fresh hydrate nuclei; and
- recombining the slurry of fresh hydrate nuclei with the major portion of the stream.
- 2. A process in accordance with claim 1, wherein the slurry of fresh hydrate nuclei are recombined with the major portion of the stream beyond the growth stage.
- 3. A process in accordance with claim 2, wherein the slurry of fresh hydrate nuclei are recombined with the major portion of the stream in a classification stage.
- 4. A process in accordance with claim 3, wherein the remaining liquid is cooled to a temperature no greater than about 50.degree. C.
- 5. A process in accordance with claim 4, wherein the remaining liquid is cooled to a temperature of about 45.degree. C. to about 50.degree. C.
- 6. A process in accordance with claim 3, wherein the fresh hydrate nuclei are recombined with the major portion of the stream in a secondary classification circuit which removes coarse product particles and passes nucleated fine particles to a tertiary classification stage.
- 7. A process in accordance with claim 6, wherein the process is run in a continuous mode.
- 8. A process in accordance with claim 6, wherein the process is run in a batch mode.
- 9. A process in accordance with claim 4, wherein the remaining liquid has an alumina to caustic ratio of between about 0.4 to about 0.5.
- 10. A process in accordance with claim 3, wherein the solids are separated from the remaining liquid in a separating device.
- 11. A process in accordance with claim 10, wherein the separating device is a gravity settler, a filter or a hydrocyclone.
- 12. A process in accordance with claim 10, wherein the separating device is a hydrocyclone.
- 13. In a process for precipitating alumina trihydrate from a stream of Bayer process liquor, wherein the stream is first divided into a major portion and a minor portion, the minor portion fed to a series of tanks constituting an agglomeration stage, and the major portion cooled, charged with coarse seed, and directed to a series of tanks constituting a growth stage to induce formation of product;
- the steps of:
- separating solids from liquid in the slurry formed in the agglomeration stage;
- cooling, to a temperature of less than about 50.degree. C., liquid remaining after separating solids from the slurry formed in the agglomeration stage;
- adding an amount of coarse seed of about 80 to about 100 microns in median particle size to the remaining liquid to generate a slurry of fresh hydrate nuclei; and
- recombining the slurry of fresh hydrate nuclei with the major portion of the stream.
- 14. A process in accordance with claim 13, wherein the remaining liquid is cooled to a temperature of about 45.degree. C. to about 50.degree. C.
- 15. A process in accordance with claim 14, wherein the slurry of fresh hydrate nuclei are recombined with the major portion of the stream in a classification stage.
RELATED APPLICATIONS
This application is a continuation-in-part of U.S. patent application Ser. No. 665,430, filed Mar. 6, 1991, now U.S. Pat. No. 5,158,577 which is in turn a continuation-in-part of Ser. No. 480,059, filed Feb. 14, 1990, now U.S. Pat. No. 5,102,426. The entire contents of these parent applications are incorporated by reference with the same force and effect as if fully set forth herein.
US Referenced Citations (10)
Foreign Referenced Citations (3)
Number |
Date |
Country |
3219288 |
Jun 1983 |
DEX |
49-4696 |
Jan 1974 |
JPX |
55-51720 |
Apr 1980 |
JPX |
Non-Patent Literature Citations (1)
Entry |
Brown, N. "The Production of Coarse Mosaie Aluminum Trihydroxide from Ball-Milled Seed," Light Metals 1990 (C. Bechert, ed.), pp. 131-139. |
Continuation in Parts (2)
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Number |
Date |
Country |
Parent |
665340 |
Mar 1991 |
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Parent |
480059 |
Feb 1990 |
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