THE SRI continuous A pan was installed and commissioned at Tully Sugar Mill for the
1998 season. During the 2002 season, the performance of the pan was evaluated in
terms of: exhaustion performance and crystal quality; heat transfer coefficients in the
four calandria modules; circulation measurements in one of the 10 cells; and tracer
studies of the flow behaviour and residence time of the crystals in the continuous pan.
The operation of the continuous A pan enables tight control of the massecuite properties and allows good exhaustion to be achieved consistently. The tracer studies demonstrated that the overall flow of crystals through the 10 cells of the continuous pan approximates plug flow and no short-circuiting occurs. A narrow crystal size distri-bution is achieved in the product massecuite. Circulation velocities were measured in one cell of the pan using anemometer probes at locations within the downtake and underneath the calandria. A strong volumetric flow of massecuite was measured in the pan in comparison to batch vacuum pans. The flow patterns produced within the pan are
detailed. The heat transfer data show the highest heat transfer coefficients exist in the
latter half of the pan which boils the heavier material. This finding contradicts the
results and general trends observed for batch vacuum pans and other continuous pans.
The operation of the pan is highly automated and the methods for pan control are
described. Effective cleaning procedures, which make use of the modular construction
of the pan, have been developed by factory staff and these allow the cleaning program
to be implemented with minimal disruption to factory processing. These procedures,
and the incorporation of the pan into the overall pan stage operations, are discussed.