MOISTURE REDUCTION AND ENHANCEMENT OF FILTRATION PROCESSES FOR ALUMINA TRIHYDRATE AND RED MUD SLURRIES

Chester, R., Kildea, J., Urbani, C.

Filtration processes are used extensively throughout the Bayer process. A variety of filtration devices and methods are used across the industry with a range of process slurries, most notably those containing alumina trihydrate and red mud, being filtered. While a number of filter aids for both trihydrate and red mud have been used in the industry over a number of years, recent advances in product development have identified a new class of filter aid (FilterMaxTM) which acts to increase the porosity of the solid filter cake. It is effective on both trihydrate and red mud slurry with application delivering both improved filter performance (flow rate) as well as a reduction in moisture content of the final cake solids. As a result, the FilterMax products can be effectively used to improve filtration outcomes across a broad range of process areas.

In addition, a parallel development has identified and developed a new class of alumina trihydrate dewatering aid (PowerDryTM). This new product provides a step change in performance above existing dewatering aid technologies and operates using a mechanism that is substantially different to the FilterMax material. When used together, the mechanisms of FilterMax and PowerDry complement each other and enable cake moisture to be significantly reduced. Potential energy savings that calcination of low moisture trihydrate would deliver are discussed, together with potential and delivered benefits of FilterMax use across a range of trihydrate and red mud applications.