Simultaneous Multiperiod Optimization of Rankine Cycles and Heat Exchanger Networks

This work addresses the multiperiod synthesis and optimization of integrated Heat Exchanger Networks (HEN) and Rankine cycles for plants with demanding operational flexibility requirements. A general and systematic synthesis methodology has been developed to optimize simultaneously the utility systems, Rankine cycles and HENs considering different expected operating modes, seeking for the solution with the minimum Total Annual Costs (TAC). Heat exchangers have been modelled with different approaches depending on the type of control measure (with/without by-pass) in off-design operation. The problem is formulated as a challenging nonconvex MINLP and solved with a bilevel decomposition method, specifically developed to address this class of problems. We present the results of the proposed methodology applied to an extremely challenging problem, with 35 streams and 2 operating modes (periods), consisting in the design of an Integrated Gasification Combined Cycle (IGCC).