A decomposition approach for retrofit design of energy systems in the sugar industry

Sugar factory retrofit often includes improvements in the factory's energy system comprising power plant. multiple-effect evaporator and process heati ng equipment. To reduce the energy consumption, the evaporator subsystem an d the process heating subsystem should be retrofitted to make improved heat recovery possible. The retrofit design procedure includes two stages: targ eting for various options of the evaporator structure and selecting the mos t promising one, and designing both subsystems for targets so determined, A t the targeting stage, one is confronted with the problem of designing the evaporation process and simultaneously considering the energy consumption. This constitutes an extension of the established targeting approach that as sumes process conditions to be fixed. The problem can be transformed by dec omposing the energy system, that is, conceptually separating the evaporator (in which vapours and condensates are generated) from the process heating subsystem (in which these heat carriers call be regarded as utilities), The transformed problem is one of targeting under constraints and can be solve d iteratively by combining pinch analysis algorithm with evaporator simulat or. The second stage of the retrofit design procedure requires defining the details of process heating subsystem that includes a heat exchanger networ k. This problem is conveniently solved using the network pinch approach. (C ) 2000 Elsevier Science Ltd. All rights reserved.