Performance trials on the STG-FCB air-swept crystalliser

STG-FCB has developed an air-swept crystalliser for the processing of low-grade massecuites. This new technology relies on evaporative and convective cooling of massecuite by direct contact with air, with significant emphasis to maximise the evaporative cooling. This eliminates one of the major disadvantages of conventional indirect water-cooled crystallisers-maintaining the significant heat exchange area to ensure there are no water leaks in a corrosive environment. The plant is mechanically simple, easy to automate, has very low maintenance requirements and offers significant performance advantages over conventional water-cooled crystallisers. The first application of an STG-FCB air-swept crystalliser (provisional patent application PP0708) was in the Ord River Sugar Mill in 1995. This installation is a single vessel with a residence time of approximately 10 hours. A subsequent installation at an existing sugar factory in 1997 has converted one of three conventional crystalliser trains over to the STG-FCB air-swept technology. This latter installation has allowed side-byside comparison of this new technology with conventional technology. Mother liquor purity profiles have been measured from the entrance to the first crystalliser through to the final molasses leaving the low-grade centrifuges for all three crystalliser trains. This paper describes the results obtained for both installations and the implications for future crystalliser upgrades.