The sugar manufacturing process based on cooling crystallisation of concentrated raw juice is considered. Micro-filtration and softening of raw juice makes it possible to obtain white sugar by three-or four-stage cooling crystallisation. Prior to crystallisation, raw juice should be concentrated by multistage evaporation in a pressure range below the atmospheric pressure. The preferred evaporator arrangement is backward feed. As the temperature of vapours and condensates leaving the evaporator station is low, the opportunities for heat recovery are limited. In order to save energy, vapour recompression can be applied. For a given evaporator structure, the energy consumption depends on the parameters of the evaporation process. The minimum energy consumption of the novel process should thus be determined by, simultaneously carrying out energy targeting and optimisation of evaporation. It is assumed that the consumption of utilities in the sugar factory is balanced with the supply of heat and power from the factory's own power plant. Energy systems employing various CHP technologies and various evaporator stations optionally combined with vapour compressors are studied. A range of feasible solutions is defined in terms of minimum energy consumption and combined heat transfer area of the evaporator station and the heat exchanger network. (C) 2001 Elsevier Science Ltd. All rights reserved.
