ALUMINA FINES’ JOURNEY FROM CRADLE TO GRAVE

Alumina product quality is a priority for all refineries. Chemical purity of alumina is controlled on the red side whilst physical quality control happens largely within precipitation, with great care taken to meet customer specification. SSA, Alpha alumina and LOI are controlled in calcination.

Particle size is controlled in precipitation. Excessive nucleation, poor size control and particle breakage across calcination result in increased fines in product. Refineries and smelters alike understand size but not strength and the customers insist on certain size numbers. Yet, considerable particle breakage occurs in smelters questioning if the achievement of a spec at the refinery boundary is the best parameter to work to.

This papers looks at alumina quality aspects in a holistic way, from precipitation to smelter reduction cells, with a major emphasis on fines – from ‘cradle to grave’. The industry as a whole needs to define, understand and measure particle ‘strength’. Although being mentioned for years, has the time come to find ways to eliminate addition of fine alumina and ESP dust to product? Smelters need to consider particle breakage during in-plant transfers in order to reduce dusting, particulate emissions and improve reduction cell efficiency. By working together refineries and smelters can bring about improvements in HSEC issues as well as the bottom line. It is possible that re-defining the quality specification for alumina will improve refinery efficiency whilst better meeting smelter demands.