| 摘要 |
<p>An improved precipitation system is provided for the Bayer process production of alumina hydrate. In order to produce coarse and strong alumina hydrate at high yield, supersaturated Bayer process sodium aluminate liquor is seeded with a relatively small seed charge in a first precipitator at a relatively low temperature and the produced slurry is transferred to a second precipitator where without additional seeding, the solids content of the slurry is allowed to increase to about 250-700 g/l by accumulating solids in the line until the desired solids content is reached. After a suitable residence time, a coarse, strong product hydrate can be recovered in yields of or exceeding 80 g/l based on the alumina (Al2O3) content of the supersaturated sodium aluminate liquor subjected to precipitation. The process not only produces the desired product at high yield but also, due to the use of a single, small seed charge, the precipitation system requires fewer precipitators and classifiers for a given residence time. Additionally, it allows significant energy savings by eliminating the need for cooling during the precipitation cycle due to the lower than conventional temperatures which can be utilized in the first precipitator.</p> |
