Increasing our understanding of supersaturation and the use of massecuite dry substance in pan control – part 3

Australian factories use, almost exclusively, the measurement of massecuite conductivity to regulate the feed of syrup/molasses to batch and continuous pans. In recent years, the dry substance of massecuite as measured by microwave transducers is being used increasingly in overseas factories. Following investigations into the supersaturation levels typically experienced in the various boiling duties in Australian factories, the profiles of massecuite dry substance values have been determined during run-up and heavy-up prior to pan drop. As for the use of massecuite conductivity, the massecuite dry substance must be regulated tightly through all stages of the pan cycle to achieve fast enough crystal growth rates to suit the required production rate, but not so high as to form nucleation (fine grain). This paper examines the profiles of massecuite dry substance in typical high-grade seed, A, B and C massecuite boilings, C seed production, magma preparation and fine-grain washing. Comparison is made between the use of conductivity and massecuite dry substance as the process variable for the control of the feeding rate of syrup/molasses.