Multi-objective optimization for work-integrated heat exchange network coupled with interstage multiple utilities

Heat exchange networks and work-heat exchange networks have been effective manners for energy integration. However, the utility system is only considered at the end of streams in traditional work-heat exchange networks, which requires high-level steam and limits the possibility of using multiple utilities. To address the issue, aiming at the coupling of compression, heat exchange network and utility system, this paper proposes an extended superstructure considering inter-stage multiple utilities configuration optimization and both compression and heat exchange on branch streams. A mixed integer nonlinear programming model is established based on the superstructure, which performs multi-objective optimization with the objectives of minimum exergy consump-tion and minimum total annualized cost. The optimal Pareto solution is obtained by the epsilon-constraint method. An example with different cases is studied to illustrate the feasibility and efficacy of the proposed model, where the preferable network configurations to weigh the thermodynamic and economic performances are obtained.