Modelling of a milk powder falling film evaporator for predicting process trends and comparison of energy consumption

In this study, two commonly used types of milk powder evaporators: a conventional five-effect falling-film evaporator without mechanical vapour recompression (MVR), and a three-effect evaporator with MVR were modelled in a commercial process simulator. The objectives were to predict the process variable trends (temperature profile along the tube side and the shell side of the evaporator) and to compare energy consumption for the two types of evaporators. Heat-recovery processes were integrated into the model so that energy consumption could be compared for the two processes. The size of the evaporator required was also estimated so that so that operating and capital costs could be assessed. The model prediction results were validated using industrial data from a local milk powder plant. The developed model successfully predicted temperature profiles similar to industrial evaporator. Furthermore, energy comparison between two types of evaporators was consistent with a known fact that a three-effect falling-film evaporator with MVR could consume 60% less energy than a conventional five-effect evaporator. These developed models in a commercial process simulator are novel in the dairy industry and can be used for simulating heat-recovery integrated evaporation processes but they still remain sufficiently generic and flexible to be applied to other production processes.