A Bilevel Decomposition Method for the Simultaneous Synthesis of Utility Systems, Rankine Cycles and Heat Exchanger Networks

This work tackles the simultaneous optimization of utility systems, Rankine cycles and heat exchanger networks (HEN). Thanks to the combination of two superstructures (Rankine cycle and HEN), all heat integration options between heat sources/sinks and Rankine cycle can be considered, and the trade-off between efficiency and plant costs is optimized. On the other hand, the resulting MINLP is extremely challenging due to its large number of binary variables and bilinear terms. We present an ad-hoc bilevel decomposition algorithm based on the McCormick relaxation with reinforcement constraints, piecewise linearization of the cost functions and “nested” integer cuts. The algorithm is applied to literature and real-world case studies to show its effectiveness compared to commercial MINLP solvers and metaheuristic algorithms.