EXPERIENCE AND UTILISATION OF AN ON-LINE SUGAR COLORIMETER IN A RAW SUGAR MILL

AN ON-LINE sugar colour instrument was installed on the wet sugar screw directly downstream of the raw sugar centrifugals at Harwood Mill. The device accurately and reliably measured raw sugar colour in the process environment and provided valuable, real time indications of its pol. Reduced recirculation of sucrose to the boiling house by minimising over-washing in the centrifugals was achieved while maintaining sugar quality. The sugar stream discharged from each centrifugal was continuously measured, permitting the identification and diagnosis of problems within and between machines and the subsequent optimisation of each centrifugal. Broadcast of the instrument output across the plant SCADA system provided information to process supervisors and other operators. The raw sugar boiler operator was able to monitor raw sugar colour for immediate feedback of massecuite quality, and that information was used to assist with decisions on boiling formulation adjustments. The mill supplies raw sugar directly to the back-end refinery. A more uniform and tighter colour feed to the back-end refinery reduced colour load and improved operational stability. Raw sugar colour and pol deviations from standard had previously caused problems in the refinery. The refinery operators were able to use the raw sugar colour data to proactively adjust clarification and decolourisation operating parameters to suit the incoming raws and keep their process within specification. The accurate real time colour measurements have contributed to labour cost savings and assisted the training of new supervisors and operators.