Multiperiod optimization of heat exchanger networks with integrated thermodynamic cycles and thermal storages

Abstract

This work proposes a multiperiod synthesis methodology to optimize simultaneously the utility systems, Rankine cycles and Heat Exchanger Networks considering different expected operating modes and off-design operating conditions. Heat exchangers are modeled with different approaches depending on the type of off-design control measure. The problem is formulated as a nonconvex MINLP. Being too challenging for general purpose MINLP solvers, a bilevel decomposition algorithm is specifically developed. One case study consists in designing a flexible Organic Rankine Cycle able to deal with different operating modes, and the returned solution shows a considerable improvement in economics compared to a single-period design. The other two case studies are an Integrated Gasification Combined Cycle able to operate in two different modes, and a flexible Integrated Solar Combined Cycle power plant. Despite the large number of hot/cold streams and technical design/operational constraints, the proposed method can find very good solutions featuring cost-effective designs.