SIMULTANEOUS-OPTIMIZATION MODELS FOR HEAT INTEGRATION .3. PROCESS AND HEAT-EXCHANGER NETWORK OPTIMIZATION

In this paper, the proposed heat integration representation of Part I (Yee et al., Computers & Chemical Engineering 14, 1151, 1990) is used for the simultaneous optimization or synthesis of the process and its heat exchanger network. The basic idea involves embedding the proposed representation into a given process flowsheet or superstructure and optimize the combined superstructure simultaneously, where flows and temperatures of the potential heat integrated streams are treated as variables. The proposed model accounts for capital and operating costs of the heat exchange network. It does not require the specification of a heat recovery approach temperature (HRAT) and can easily handle constraints for heat integration. Synthesis examples of a distillation sequence and of a process flowsheet are presented to illustrate the capabilities of the simultaneous model which can be formulated as an NLP problem or as an MINLP problem when the structure of the network is to be determined explicitly.