(355a) Real-Time Monitoring of Nucleation and Growth Rates in An Industrial Semi-Batch Sugar Crystallizer

The process of boiling sugar cane syrup to produce refined sugar crystals was first performed in India around 300 AD. Although sugar manufacturing has evolved dramatically since that time, the basic methods of sugar crystallization in vacuum pans have been unchanged for almost two hundred years. Still, even in one of the oldest industrial processes, there is room for improving process efficiency and maximizing production capacity. As with many batch and semi-batch crystallization processes, the formation of large quantities of fine crystals ? through nucleation events ? can significantly reduce downstream separation efficiency and overall throughput.

A METTLER TOLEDO FBRM® crystallization monitor (model D600) was installed directly in a White Pan semi-batch crystallizer at The Amalgamated Sugar Company (Twin Falls, ID). Data were collected from 35 consecutive batches to monitor normal batch operation, to characterize batch-to-batch variability and to provide direct real-time analysis of how modifications to the batch recipe would impact the final crystal product.

In-line monitoring of the crystal population with FBRM permitted the calculation of relative nucleation and growth rates that were used to assess batch to batch variability and were able to pinpoint periods of intense secondary nucleation. The identification of factors and disturbances that promoted nucleation enabled adjustments to the operation of the sugar crystallizer that minimized nucleation events in subsequent batches - as confirmed with the inline particle size measurement.