| Carbon capture and storage
How steam integration and EGR can reduce CCS costs for combined cycle plants
Exhaust gas recirculation, which increases the concentration of carbon dioxide in gas turbine exhaust gas, coupled with a high degree of integration between the combined cycle steam systems and the carbon dioxide capture plant, can greatly improve the economics of carbon capture when applied to natural gas fuelled combined cycle power plants. These measures can also be combined with gas turbine upgrades and advanced control systems (for both gas turbines and capture systems). The end result is the prospect of significant reduction in the size and the cost of the carbon capture systems required for combined cycle applications, with smaller and/or fewer absorber towers, improved power plant efficiency and flexibility, and the potential for increased power output. A FEED study focused on retrofitting post combustion carbon capture to the James M. Barry unit 6 combined cycle power plant in Mobile County, Alabama, USA, has demonstrated these benefits
Majed Sammak, John Sholes, Parag Kulkarni, Matt Davidsaver GE Vernova
The carbon dioxide emissions produced by power generation account for more than 40% of total world CO2
emissions but due
to their capacity to adapt to fluctuations in grid demand, gas fuelled power plants are projected to continue to play a significant role in power generation, with gas turbine based power plants being extensively used for the purpose of mitigating grid volatility and meeting fluctuating power demand, as well as power generation per se.
emitted per unit of electricity generated) of gas turbine based power plants. This involves implementing measures such as enhancing plant efficiency, reducing carbon
GE Vernova is working with power plant operators and partners to create strategies for reducing the CO2 CO2
intensity (amount of
content in fuel by using low-carbon fuel alternatives like hydrogen, and adopting carbon capture and storage/utilisation technologies (Figure 1).
GE Vernova strengthens the commercial viability and visibility of carbon capture plant integration with combined cycle power plants through the implementation of strategies such as steam integration, exhaust gas recirculation, gas turbine upgrades, and advanced control systems.
Steam integration is the extraction of steam from the combined cycle steam turbine crossover rather than using an auxiliary boiler (the ‘bolt-on’ solution). Steam integration not only improves site fuel consumption but also lowers the carbon capture plant’s capex and footprint by reducing CO2
site emissions.
Figure 1. Basic principles of a carbon capture system installed on a natural gas fuelled combined cycle power plant (Image: GE Vernova)
Exhaust gas recirculation sends a portion of the stack flue gas to the gas turbine, hence elevating the flue CO2
concentration and
reducing the volume of flue gas directed to the carbon capture plant. The CO2
capture rate is directly influenced by the CO2
partial pressure, which is directly proportional to the concentration of CO2
flue gas. The cost of CO2 in the capture is influenced by
concentrations in exhaust gas from different sources show significant variations, which directly affect the performance, design, and selection of capture plant technologies, as well as the capital expenditure and operating expenditure.
the partial pressure, since it directly impacts the dimensions of the equipment, power consumption, and the selection of the capture method. The CO2
CONCENTRATE: exhaust gas recirculation COOL: direct contact cooler CAPTURE: absorption system COLLECT: stripper system COMPRESS: carbon dioxide compression train
www.modernpowersystems.com | November/December 2024 | 13
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