Evaluate the suitability of the fixed element crystalliser for widespread adoption in Australian sugar factories : final report 2019/202

Abstract

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 which demonstrated good overall performance with respect to heat transfer, residence time distribution and molasses exhaustion. The good performance is attributed to the paddles providing strong flow of massecuite transversely and also longitudinally to generate flow across the cooling surface. Torque control of the variable speed drive is recommended as this allows rotation of the paddles at maximum speed for the prevailing viscosity of the massecuite, while limiting the stresses on the drive components.

The fixed-element design proved to be an economical solution for Broadwater Mill to refurbish their No 1 crystalliser. The design is well suited for new crystallisers and to replace the internals of horizontal crystallisers at all positions within the crystalliser station.