Session: 13-03: Thermal performance of HRSG and turbine adjustable nozzle guide vane

Paper Number: 152189

Impact of Flow Diverter Baffles on Flow Distribution and Thermal Performance of HRSGs 

Small gaps allowing bypass of turbine exhaust gas are at times overlooked in Heat Recovery Steam Generators (HRSG) inspection and maintenance programs, or perhaps in the original design. Accurately placed baffles redirect the gas into the intended path thereby allowing the heat transfer surfaces to absorb the maximum amount of thermal energy from the gas flow. Improper gas baffling can cause bypass around tube bundles, that can cause damage, exacerbate damage mechanisms as well as decreases performance. At one of ACWA Power’s Combined Cycle Power Plants (CCPP), the Centre of Excellence team conducted an investigation to enhance the heat transfer performance of the HRSGs. Inspections of the heat transfer surfaces in the gas path, as well as the upper and lower dead spaces of the units revealed that baffles between the tube harps and along the casing walls, were absent from the original design. Additional bypass susceptibilities were identified at the top and bottom of the modules between pressure part headers, where flue gas will bypass the heating surfaces by flowing into upper and lower dead spaces. Baffles implemented during construction in these dead spaces were found to be damaged, indicating signs of flue gas blow through, allowing gas to bypass entire modules in some regions. A 2-D Computational Fluid Dynamics analysis revealed that approximately five percent of the gas turbine exhaust flow was bypassing all the heat transfer surfaces in the HRSG, negatively impacting the overall heat rate. Following a comprehensive design review, flow diverter baffles were installed throughout the HRSGs to minimise these inefficiencies. Subsequent thermal performance evaluations demonstrated approximately three percent improvement in HRSG effectiveness, which corresponded to a heat rate improvement on average of 45 kJ/kWh across predominant operating loads in the CCPP. These findings highlight the significant potential of simple targeted modifications in HRSG design to enhance plant efficiency.

Presenting Author: Jalal Zia Acwa Power

Presenting Author Biography: Dr Jalal Zia has held lead technical roles in the Cryogenics Industry, Healthcare, R&D, Power Generation & Renewables across North America and the Middle East. He has a deep understanding of the technical challenge sustainable energy companies face in today’s turbulent energy landscape. In 2021 he built a startup company Energy Shift, to help companies minimize their carbon foot print by maximizing the performance, reliability and efficiency of their energy generation assets.

Since founding Energy Shift, Jalal’s passion is to help energy companies develop and maintain their lead in the global energy landscape through targeted development of key energy efficiency and sustainability technologies and innovations.

In 2023, Jalal joined ACWA Power as their Executive Director of Plant Monitoring and Prognostics. This role re-inforces Jalal’s passion for sustainable energy generation while minimizing the lifecycle carbon footprint of power generation for ACWA Power’s fleet.

Authors:

Ronald Abbas ACWA Power
Muhammad Azhar Janjua ACWA Power
Jalal Zia Acwa Power
Muhammad Adnan Saroosh ACWA Power
Matthew York Acwa Power