Crystal growth and vacuum pan productivity

The sugar industry in Australia, as in many other parts of the world, has expanded rapidly in recent years greatly increasing the burden on processing stations in sugar factories. Consequently, boiling houses and centrifugal stations have often become production bottlenecks, requiring installation of new equipment, or significant upgrades of existing plant. Meanwhile, of course, sugar quality and recovery must be maintained, which requires (amongst other things) optimisation of crystal growth rates, Thus, the SRI embarked on a rigorous analysis of growth rates, and the effects of factors such as grade of massecuite, stages in the boiling operation and variations in pan design, aiming to establish benchmark figures for factory performance. Further research has centred on the use of model-based control, using growth equations derived from laboratory and factory experiments to enhance efficiency, and the comparison of such systems with conventional conductivity control. Productivity gains of 10% are anticipated when model-based control schemes are applied to batch pans with good circulation and heat transfer properties. Important work now underway seeks to determine circulation velocities and flow directions, allowing batch and continuous pan designs to be evaluated quantitatively, and to validate and refine computational fluid dynamics predictions.