| Carbon capture for CCGT


Integrating exhaust gas recirculation for reduced CO2 emissions from combined cycle power plants


CO2


towards climate friendly-energy production. The latest Asme Turbo Expo conference took place in London and attracted 2500 plus turbomachinery and propulsion engineering leaders from industry, academia, and government. In this context, SINTEF Energy Research presented research results demonstrating how the efficiency and costs of a natural gas combined cycle (NGCC) power plant with CO2


by adopting an innovative approach: namely hydrogen-assisted exhaust gas recirculation (EGR) Elettra Vantaggiato MSc researcher, Luca Riboldi research scientist, Mario Ditaranto chief scientist SINTEF, Norway


The SINTEF group is one of Europe’s largest independent research institutes. SINTEF Energy Research specialises in originating and advancing innovative energy solutions, with strong foundations in research-based knowledge and industry collaboration, both in Norway and internationally. It has been working on carbon capture for decades. Today, SINTEF conducts research on the whole value chain for CO2


of Florence, TotalEnergies, Baker Hughes, CERFACS and DLR) to achieve further advancements in carbon-neutral power generation from natural gas fired power plants using gas turbines. To do this, access to a highly efficient carbon capture process is crucial. When capturing CO2


from the exhaust capture, transport


captured from flue gases and placed in permanent geological storage, can speed up the reduction of GHG emissions. In the European research project TRANSITION (grant nr. 101069665), SINTEF is collaborating with research and industry partners (University


and storage for various industrial and power sectors. When the substitution of fossil fuels by renewable electricity is not possible or too expensive, carbon capture and storage (CCS), with CO2


gases of a natural gas fuelled combined cycle power plant, it is necessary to provide energy to the CO2


capture system, often in the form of heat. This heat is typically taken from the combined cycle process itself. As a result, the overall efficiency of the system is reduced because some of the energy that would have been used for generating electricity is diverted to the CO2


capture process. In other


words, finding ways to minimise the energy consumption of the capture process means minimising efficiency penalties. One important factor affecting capture efficiency is the


capture from flue gases is recognised as part of the strategy for climate change mitigation. Consequently, power plants based on natural gas with CO2


capture are expected to maintain a role in the transition capture can be improved


SINTEF carbon capture test rig (Photo: SINTEF)


carbon dioxide concentration in the exhaust gas. The higher the concentration gets, the less thermodynamically demanding becomes separation of CO2


from the other gases and


the lower the energy requirement for the CO2 capture process.


Typical CO2 concentrations in the exhaust


gases of gas turbines are around 3–5% due to low carbon intensity of natural gas and the very high operating air-to-fuel ratio in these engines. A way to increase the CO2


concentration is the


implementation of exhaust gas recirculation (EGR). EGR is based on recycling a portion of the exhaust gases to the compressor inlet of the gas turbine, while the remaining part is directed to the CO2


capture system. EGR is a


well-established technique in diesel engines for NOx


Increasing the carbon dioxide concentration in combined cycle power plant exhaust gases offers the potential to minimise CO2


capture energy penalties (Source: SINTEF)


control, but not commercially adopted for gas turbines. Mixing the recycled exhaust gas with air at the compressor inlet results in a working fluid richer in CO2


. Another effect of EGR is to reduce the volumes of exhaust gas www.modernpowersystems.com | October 2024 | 25


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