Chemistry of inorganic compounds – Oxygen or compound thereof – Metal containing
Reexamination Certificate
2007-03-20
2007-03-20
Bos, Steven (Department: 1754)
Chemistry of inorganic compounds
Oxygen or compound thereof
Metal containing
Reexamination Certificate
active
10333211
ABSTRACT:
An improved process for the production of tricalcium aluminate (TCA) filter aid for use in an alumina refinery is described. Quicklime is slaked in a slaker tin using a suitable slaking solution to form a slaked lime slurry (10). A suitable surface-active agent is added to the slaking solution prior to slaking of the lime. Alternatively, the surface-active agents can be added to the slaked lime either during slaking or after slaking. The slaked lime slurry is then transferred to a stirred storage/transfer tank (12) before it is pumped to a lime aging tank (14). A concentrated Bayer liquor and steam are added to the tank (14) to provide a caustic aluminate solution that reacts with the slaked lime. Sufficient residence time is allowed in the lime aging tank (14) for the initial product of the reaction to “age” before use, forming relatively pure particles of the thermodynamically stable TCA. The addition of a suitable surface-active agent or agents at the appropriate concentration will significantly improve TCA formation in the lime aging facility. These improvements include a narrower and more symmetric sized distribution, and a more crystalline structure, leading to substantially improved filtration characteristics.
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Whittington, B.I. , Fallows, T.M., and Willing, M.J., “Tricalcium aluminate hexahydrate (TCA) filter aid in the Bayer industry: factors affecting TCA preparation and morphology,” International Journal of Mineral Processing, vol. 49 (1997), pp. 1-29, no month.
Rosenberg Steven P.
Wilson Darrel J.
Bos Steven
Edell Shapiro & Finnan LLC
Worsley Alumina Pty. Ltd.
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