Various approaches to batch evaporating crystallizer control have been utilized in the sugar industry for many years with varying degrees of success and ability to produce a consistent massecuite quality. The development of improved and more reliabledevices for the measurement of mother syrup dry substance (DS) concentration (refractometric measurement) and overall massecuite DS concentration (microwave density measurement) during the sugar crystallization process have enabled a more or less complete control of the crystallization process to manage both syrup concentration (supersaturation) and crystal content (massecuite; concentration relative to syrup concentration) during the crystallization cycle. This paper discusses the theory, development and application of refractometric and microwave measurement for the automatic and self-optimizing computerized control of the batch crystallization process developed and installed at the Mini-Cassia Factory of the Amalgamated Sugar Company, LLC, USA. Operator interaction and selection of various input set points allow adjustment for seeding optimization and final grain size while the control system offers feed-back for seeding set point adjustment relative to standard liquor purity (sucrose solubility) and processing conditions to maintain consistent massecuite quality and uniform crystal size distribution. Multiple operating modes allow for continued operation in the event of necessary refractometer or microwave measurement maintenance and calibration.
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