Investigations of the effect of continuous fugal operations on shipment sugar quality

Current high-grade fugal installations in the Australian sugar industry tend to be mostly batch with a few continuous units; thus, optimisation of the continuous machines is often a low priority. Invicta Mill is in a unique position in that it has fully continuous production of shipment massecuite followed by a fully continuous fugal stage. Expansion of the production rate at Invicta was carried out with more than the usual amount of risk in order to achieve the benefits of a fully continuous operation. The mill has since experienced problems with sugar quality, prompting a thorough study of the pan and fugal station to pinpoint the causes. Early problems with the continuous pans were overcome but quality problems, particularly high fine grain in the product sugar, persisted. The crystal mean aperture profile was measured across the pan, fugal and drier stations in an attempt to identify the exact mechanism of crystal size degradation. The use of a bench fugal enabled very quick measurement of baseline conditions, namely, the massecuite crystal mean aperture (MA). Pan product crystal MA and fine grain levels were generally satisfactory. The incremental change in mean aperture and coefficient of variation acroSS the fugals was found to be substantial for some combinations of fugal operational parameters. A very large dataset obtained in these experiments enabled suggestions for optimal running conditions for the Invicta fugal stage, with possible extension of the principles to other installations.