ALUMINA LIQUOR CLARIFICATION: FILTER MEDIA CLASSIFICATION AND DEVELOPMENT USING IN-LINE, PORTABLE PILOT SCALE, TWIN CHAMBER, PRESSURE FILTER TESTING EQUIPMENT

Downie, R.W., Glen, S.J., and Neate, M.J.

Development of new media for pressure filtration has traditionally relied heavily on full-scale filter vessel trials. To overcome this Albany International pioneered the use of a custom built, portable pressure filter testing unit, first presented at the 6th International Alumina Quality Workshop. This allowed for results to be gained under real process conditions, without relying exclusively on physical media parameters tested in the laboratory and intrusive full-scale trials. While the unit was used successfully to accelerate new product development at refineries throughout Australia, comparisons between developmental filter media and existing filter media often became distorted by process variations between different timeframes of each pilot test.

To overcome this, Albany International has developed and implemented a new twin chamber pilot pressure filter testing unit to test new filter media in the clarification circuits of several alumina refineries in Australia. The new unit allows developmental filter media and current filter media to be comparatively tested simultaneously, ensuring identical liquor feed conditions and eliminating process variations. In addition each chamber is independently capable of instigating pressure control or flow control, replicating the process control conditions specific to each refinery. Development of the twin chamber pilot scale test unit has significantly improved the effectiveness of pilot scale filter media testing using ‘live process liquor’.

This paper presents the findings acquired through the utilisation of the twin chamber unit at alumina refineries around Australia, and illustrates the improvements this method has over the old single chamber unit. It demonstrates how these findings are utilised in implementing and progressing design improvements to filter media.