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Alumina miniplant operations - separation of aluminum chloride liquor from leach residue solids by classification and thickening.

Sorensen RT; Sawyer DL Jr.; Turner TL
Boulder City, NV: U.S. Department of the Interior, Bureau of Mines, RI 8805, 1983 Jan; :1-23
The Bureau of Mines has investigated the recovery of cell-grade alumina by HCl leaching of calcined kaolin in the alumina miniplant at its Boulder City, Nevada, Engineering Laboratory. Classification and thickening were used for separating aluminum chloride leach liquor from the siliceous residue generated in the acid leaching step of the clay-HCl process. Coarse solids were classified from fines at 115 mesh and countercurrently washed in three additional spiral classifiers. Fines were treated in a conventional five-thickener, countercurrent decantation circuit. When this method was applied to the solids-liquid separation of slurry from HCl leaching of minus 10- mesh calcined kaolin, 75 pct of the residue reported as classifier sands and 25 pct as thickener underflow. Predicted individual classifier and thickener area requirements were 6 and 25 ft2/tpd, respectively. Total thickener circuit flocculant requirement was 2.4 Lb/ton solids. Aluminum chloride pregnant liquor was produced that analyzed 8.4 pct Al2O3, and contained more than 97 pct of the alumina in the liquid phase of the slurry. Bench-scale settling tests were used to correlate fines content of leach residue to thickener area and flocculant requirements.
Materials-recovery; Aluminum-oxide; Separation; Leaching; Hydrochloric-acid; Classifiers; Thickening; Kaolinite; Flocculants; Process-charting; Design-criteria; Performance-evaluation; Clays; Aluminum-chloride; Clay-HCl-process
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IH; Report of Investigations
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Boulder City, NV: U.S. Department of the Interior, Bureau of Mines, RI 8805
Page last reviewed: November 12, 2021
Content source: National Institute for Occupational Safety and Health Education and Information Division