The Significance of Stage Efficiency in a Cane Milling Tandem

The history of the sugar industry in Natal has shown that enormous advances have taken place both in capacity and te2hnology of plants. Recent years in particular have seen a marked upward surge in the graph of production an achievement due in no small way to the dedicated efforts of chemists and engineers in charge of the operation and expansion of sugar factories. It is perhaps typical of such conditions of rapid expansion that sugar technologists, with their attention fixed on rapidly rising production targets, have had little enough time to contemplate the wcalth of process data inherited from their own considerable experience let alone the application of the more fundamental techniques of modern chemical engineering. So often the necessity to contemplate the view on the horizon causes the scene in the foreground to go unnoticed. During this period of tremendous growth the sugar industry has developed its own empirical approach to performance figures and design calculations and the progress in this direction can be viewed as one of the achievements of sugar technologists. However, in pursuing this specialised approach to process technology the dangers of seclusion from the rapidly expanding fundamentals of chemical engineering should not be overlooked. It is possible for example that opportunities could be missed for advancement due to our failure to assess the merits of changes in process and units on a more general and fundamental basis. recovery of crystal product~jnvolves almost every unit operation of chemical engineering with one exception -distillation. Hence it is unfortunate that so few chemical engineers are employed at sugar factories. The more general use of heat and mass transfer coefficients, stage efficiencies, transfer units and dimensionless numbers would for example provide a more rational basis for scale-up problems in design and specification of new units and a better insight into the performance and mechanism of unit processes.