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Research Papers: Gas Turbines: Cycle Innovations

# Combined Cycles With $CO2$ Capture: Two Alternatives for System Integration

[+] Author and Article Information
Nikolett Sipöcz

Department of Mechanical and Structural Engineering and Material Science, University of Stavanger, N-4036 Stavanger, Norwaynikolett.sipocz@uis.no

Department of Mechanical and Structural Engineering and Material Science, University of Stavanger, N-4036 Stavanger, Norway

J. Eng. Gas Turbines Power 132(6), 061701 (Mar 17, 2010) (6 pages) doi:10.1115/1.4000122 History: Received April 08, 2009; Revised April 14, 2009; Published March 17, 2010; Online March 17, 2010

## Abstract

As carbon capture and storage technology has grown as a promising option to significantly reduce $CO2$ emissions, system integration and optimization claim an important and crucial role. This paper presents a comparative study of a gas turbine cycle with postcombustion $CO2$ separation using an amine-based absorption process with monoethanolamine. The study has been made for a triple pressure reheated 400 MWe natural gas-fuelled combined cycle with exhaust gas recirculation (EGR) to improve capture efficiency. Two different options for the energy supply to the solvent regeneration have been evaluated and compared concerning plant performance. In the first alternative heat is provided by steam extracted internally from the bottoming steam cycle, while in the second option an external biomass-fuelled boiler was utilized to generate the required heat. With this novel configuration the amount of $CO2$ captured can be even more than 100% if the exhaust gas from the biofuelled boiler is mixed and cleaned together with the main exhaust gas flow from the combined cycle. In order to make an unprejudiced comparison between the two alternatives, the reduced steam turbine efficiency has been taken into consideration and estimated, for the alternative with internal steam extraction. The cycles have been modeled in the commercial heat and mass balance program IPSEPRO ™ using detailed component models. Utilizing EGR can double the $CO2$ content of the exhaust gases and reduce the energy need for the separation process by approximately 2% points. Using an external biomass-fuelled boiler as heat source for amine regeneration turns out to be an interesting option due to high $CO2$ capture effectiveness. However the electrical efficiency of the power plant is reduced compared with the option with internal steam extraction. Another drawback with the external boiler is the higher investment costs but nevertheless, it is flexibility due to the independency from the rest of the power generation system represents a major operational advantage.

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## Figures

Figure 1

Layout of the NGCC with EGR and CO2 separation by internal steam extraction

Figure 2

Layout of the NGCC with EGR and CO2 separation by the utilization of a biomass boiler

Figure 3

The effects on net combined efficiency and capture efficiency for increased steam generation by additional combustion of biomass fuel in the biomass boiler

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