EVALUATION OF A MAGNETIC ION EXCHANGE (MIEX®) RESIN FOR DECOLORISATION APPLICATIONS WITHIN A RAW SUGAR FACTORY

DECOLORISATION OF sugar syrup prior to crystallisation improves the quality of raw sugar produced and reduces costs in further refining processes. The use of ion exchange resins for this purpose has been discussed in many publications and specialised resins are used in sugar refineries. This paper describes laboratory and mill prototype trials to evaluate the potential of a magnetic ion exchange resin (MIEX®) for application within a raw sugar factory to decolorise syrup. Simple jar tests proved that MIEX® resin outperforms an existing industry resin when used at equal capacity. Further detailed laboratory testing showed that logarithmic relationships exist whereby decolorisation efficiency decreases with increasing brix and with resin contact time, but increases with higher dry resin doses. Simulated long-term stability studies showed that the MIEX® resin retained similar efficiency under factory treatment conditions (70°C with 50 brix syrup) than it did under extended testing (ambient temperature) with drinking water, and did not suffer significant physical degradation. A prototype reactor unit was constructed for sugar factory testing and was capable of treating up to 30 m3/h of 45 brix syrup in a fluidised bed system with a 5 minute resin contact time. Higher brix solutions could not be used within the fluidised bed design due to viscosity problems and resin overflow. Typical experiments to examine resin exhaustion showed initial decolorisation rates of around 70% which dropped slowly to 20% after just over 200 tonnes of syrup (or around 90 tonnes syrup brix) had been processed. A series of tests designed to produce average decolorisation efficiencies of around 50% were conducted and were successful with no apparent drop in this efficiency until around 80 m3 syrup had been treated, which required a 4 hour run. These results showed that the initial laboratory experiments could be replicated on a factory prototype scale with the resin showing acceptable and reproducible performance.