HRSGs and boilers |
Evolution of HRSGs for advanced combined cycle power plants
A GE Vernova perspective Helga Kremer Product Line Leader HRSG at GE Vernova
Since the commercial operation of the world’s first industrial gas turbine, in Neuchâtel, Switzerland, in 1939, GE Vernova and its predecessor companies have developed and deployed several generations of gas turbines (GTs), steam turbines (STs), generators, and heat recovery steam generators (HRSGs). GE Vernova is a supplier of all major equipment within a gas fired power plant and builds on know-how across GT, ST & HRSG as well as plant controls to provide optimal solutions.
HRSG technology has evolved over time together with the evolution of GT technology and is a critical component that makes the mighty combined cycle power plant (CCPP) possible, as the connective tissue between the gas turbine and the steam turbine. HRSG designs were derived from fired boiler design (utility boiler) experience and know-how and the first generation HRSGs were mostly vertical gas flow, horizontal tube forced circulation designs, both with and without supplemental firing. In the 90s, HRSGs saw various product changes and improvements as a new fleet of large frame gas turbines, the F-Class, entered the
marketplace. The higher exhaust temperature and flow of these GTs enabled higher combined cycle efficiency and triple pressure with reheat HRSGs became the standard, while going to horizontal gas flow and transitioning from bottom to top supported pressure parts to accommodate the larger thermal expansions that came with the higher GT exhaust gas energies. Water–steam cycle parameters through much of the 1990s were below 540°C/120 bar; however, by the late 1990s the 565°C/165 bar water steam cycle became standard in the industry. This required the application of advanced materials such as 9% chromium alloys previously used in utility boilers. During this time GE Vernova’s Once Through (OT) HRSG technology was developed and introduced to the marketplace, with 33 units installed across the US and Mexico behind GT24 gas turbines.
The 2000s started out with the “gas-bubble” and very low natural gas prices in the US driving the build out of many CCPPs powered by mostly F-Class GTs. The horizontal gas flow HRSG with natural circulation, established in the late 90s and early part of 2000s, became the technology of
choice moving forward for most applications in both 50 Hz and 60 Hz markets. Supplementary firing capability was introduced in the USA to capitalise on high electricity prices and to this day most combined cycle power plants in the USA have supplemental firing. Also, during this time US regulatory requirements led to the introduction of emission control equipment in HRSGs for NOx
and CO, which have become
standard for most advanced combined cycle power plants.
In the early 2000s HRSGs were engineered with limited capability for cycling as the plants were intended to be base loaded. However, with the increase in gas prices in the mid 2000s there was a change of operating regime to more cycling operation as daily starts and stops became more the norm. This is where GE Vernova’s innovative single row harp arrangement originated and today all of our HRSGs, regardless of the operating profile specified in RFQs, utilise single row harps in the front end. This configuration provides more flexibility to support reliable high- cycling duty and produces three times less stress than conventional multi-row harps, while capable of fast starts, high ramp rates and enhanced operational flexibility.
Also, during this period in the USA, constructability of HRSGs became a big driver and consequently GE Vernova started to offer various constructability options, from loose harps to pressure part modules, C-frame, supermodules, and fully assembled HRSGs delivered by boat, enabling customers to choose the degree of prefabrication that best fits the site-specific project requirements and logistics constraints. Today, GE Vernova’s advanced combined cycle power plants with OT HRSGs for high fuel hour regions represent a new era of high efficiency combined cycle power plant where the OT HRSG technology is a key enabler. These HRSGs are paired with GE Vernova’s highly efficient H-class GTs, which have pushed exhaust gas temperatures beyond 650°C. GE Vernova’s OT HRSG technology has more than 2.5 million operating hours and enables:
Goi power station project. Three GE Vernova 1x1 9HA.02 GTs with HRSGs each delivered in only three prefabricated supermodules assembled in South Korea then transported across the ocean to Japan. Each supermodule weighs approximately 2500 metric tons and is between 43 to 46 m high, almost as tall as the Arc de Triomphe or a 15-floor building. Photo: GE Vernova
10 | October 2025|
www.modernpowersystems.com
higher operating steam pressures resulting in higher thermal efficiencies at base load; superior off design and part load performance due to the ability to vary feedwater flow, resulting in increased thermal efficiencies;
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