Impacts of flexible operation on the service life of superheaters in heat recovery boilers: Analysis of creep–fatigue interaction in thermal power plants

This article investigates the impacts of flexible operation on Natural Gas-fired Combined-Cycle Power Plant (NGCCPP) equipped with Heat Recovery Steam Generator (HRSG), driven by the increasing integration of intermittent renewable energy sources into the power system. The objective is to assess the operational and structural limitations of these systems and to propose guidelines aimed at enhancing the safety and reliability of the Brazilian Integrated National Electrical System (INES). The methodology combines a systematic literature review and bibliometric analysis with modeling based on the Larson–Miller parameter and Miner's rule, incorporating creep–fatigue interaction to estimate the service life of critical components, particularly superheaters. The results indicate that creep-only assessments tend to overestimate component life, whereas more comprehensive models predict substantial reductions, with service life potentially decreasing to approximately 17 years under high-cycling conditions and extended load-hold periods. The analysis also shows that operational parameters, particularly the number of start-up/shutdown cycles and hold time, have a direct influence on degradation rates, while appropriate operational adjustments can extend component service life. Furthermore, existing assets may have limited remaining service life when subjected to the more demanding operating regime associated with increased flexibility requirements. These findings indicate that enabling flexible operation requires an integrated approach encompassing design, operation, maintenance, and regulatory frameworks. As a contribution, this study proposes improvements to the technical criteria adopted in capacity auctions, seeking greater alignment with actual operating conditions and enhanced reliability of the Brazilian power system.