ADVANCES IN CONTROL OF TRIHYDRATE CLASSIFICATION USING HIGH PERFORMANCE FLOCCULATION

Aboagye, A., Chester, R., Kildea, J., O’Brien, K., Phillips, E. and Wang, J.

Productivity in the Bayer process is often directly related to the efficient capture and classification of trihydrate particles into various size fractions. Efficient size classification can often be achieved using cyclones but in many plants a series of settling classifiers are still used. In such cases, the use of trihydrate flocculants can be advantageous in a number of ways. In addition to faster settling enabling higher throughput, flocculants can also capture solids that may otherwise be lost and recycled to digestion with spent liquor. However, a critical advantage that is often overlooked is the use of trihydrate flocculants to enhance underflow rheology, thus preventing premature tank failures due to excessive rake torques, “rat-holing” and scale formation in classification vessels. While a range of trihydrate flocculants have been accepted and used by the industry for more than a decade, recent work has resulted in the development of an enhanced range of trihydrate flocculants. These products provide a variety of properties that allow for further optimization and improvements in process productivity.