Performance of the SRI fixed-element cooling crystalliser at Broadwater Mill

The fixed-element design of a horizontal cooling crystalliser is relatively new to the Australian industry and the installation at Broadwater Mill for the 2017 season proved to be an economical solution to refurbish the mill’s first unit in a continuous-flow station of three crystallisers. The crystalliser consists of 12 fixed cooling elements and 14 rotating paddles. A variable-speed drive was installed to allow a rotational speed of the paddles up to 1.45 r/min, depending on the massecuite viscosity and imposed torque. Apart from fabrication of the fixed elements, the mill’s staff undertook the complete installation. During the 2019 season, trials were undertaken to determine the heat-transfer performance and massecuite-exhaustion performance for different conditions of inlet massecuite composition, rotational speed of the paddles and cooling rate. The residence-time distribution for massecuite flow through the crystalliser was also measured. The results of this test program are reported and recommendations provided for maximising the exhaustion performance. The installation costs for this type of refurbishment and the financial implications for Australian factories are discussed. Key words Cooling crystallisation, fixed cooling elements, massecuite exhaustion, residence-time distribution