An enhanced superstructure-based model for work-integrated heat exchange network considering inter-stage multiple utilities optimization

Abstract Deterministic and heuristic approaches have been widely applied to synthesize work/heat exchange network, including direct/indirect work exchange and classified/unclassified heat exchange. The network synthesis with minimizing hot and cold utility consumption can achieve considerable energy savings. However, this process is heavily dependent on using single hot/cold utility at stream ends, without the consideration of multiple utilities optimization. To address this issue, an enhanced superstructure-based model with inter-stage multiple utilities optimization is proposed for synthesis of work-integrated heat exchange network. The optimized selection of multi-grade steams is performed for preferable trade-off between power/heat generation of the utility system and work/heat allocation of pressure-change streams. A comprehensive mixed-integer nonlinear programming model is established to obtain the economically preferable configurations with better utilities placement. Two examples are studied to illustrate the feasibility and efficacy of the proposed model, where the optimal network configurations with lower total annual cost are obtained.