Thermoeconomic Optimization of Heat Recovery Steam Generators: A Modular Approach to Define the Layout of Heat Exchange Sections

Abstract

One of the most efficient energy conversion systems in state-of-the-art electricity generation technology are combined cycle gas turbines. As is well known, the heat recovery steam generator (HRSG) configuration has a major impact on the overall performance of a combined-cycle power plant. Thus providing a tool for optimizing design parameters and layout of a HRSG is an important issue. The present study focuses on HRSG optimization, employing an exergoeconomic methodology. This is based on the minimization of the total cost of HRSG, including capital costs of heat exchanger sections and operating costs related to exergy destruction. The decision variables of the proposed optimization method are the HRSG operating parameters, as well as the layout of the heat exchanger sections. To predict behavior and performance, the HRSG is regarded as a modular structure, i.e. as a set of elementary components, interacting through nodes affected by mass and energy flows. The modular approach proposed makes the optimization methodology particularly flexible, as the configuration of the HRSG can be identified defining an “interaction matrix” to characterize the mode of interaction of the elementary components.