Analysis of HRSG Cold-end Design Options for Best Performance and Reliability

摘要

Maximizing the overall fuel efficiency of modern combined cycle power plants requires fine tuning all of the main components in concert to reach a common optimum. Experience shows that there exists a large potential for improvement in the so-called ‘cold-end’ of the HRSG comprised of the condensate preheater section, the deaerator, and the first economizer sections of the steam generator. Since these sections of the HRSG may also be subject to severe problems due to accelerated corrosion or flow instabilities if operated under extreme conditions, caution must be applied when looking for the optimal configuration. The paper studies and compares various commercially available configurations, designs and temperature control strategies of the HRSG cold-end. The study focuses on different configuration options to prevent potential problems with the sulphuric acid dew point and steaming in the low temperature economizer. It quantifies the impact of different fuel gas compositions, condensate inlet temperatures, duct firing loads and modes of operation for the deaerator on these key operational constraints. The study was performed using the EBSILON Professional heat and mass balance software to construct detailed thermodynamic models for both, design and off-design conditions in a typical 3-pressure level reheat HRSG. The study incorporates the extensive experience the authors have in power plant design, optimization, simulation and operations as well as available documentation, such as books, publications and patents by HRSG vendors.