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Research Papers: Gas Turbines: Cycle Innovations

# Qualitative and Quantitative Comparison of Two Promising Oxy-Fuel Power Cycles for $CO2$ Capture

[+] Author and Article Information
Wolfgang Sanz

Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology, Graz 8010, Austriawolfgang.sanz@tugraz.at

Herbert Jericha, Bernhard Bauer, Emil Göttlich

Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology, Graz 8010, Austria

J. Eng. Gas Turbines Power 130(3), 031702 (Apr 02, 2008) (11 pages) doi:10.1115/1.2800350 History: Received May 24, 2007; Revised May 25, 2007; Published April 02, 2008

## Abstract

Since the Kyoto conference, there is a broad consensus that the human emission of greenhouse gases, mainly $CO2$, has to be reduced. In the power generation sector, there are three main alternatives that are currently studied worldwide. Among them oxy-fuel cycles with internal combustion with pure oxygen are a very promising technology. Within the European project ENCAP (enhanced CO2 capture) the benchmarking of a number of novel power cycles with $CO2$ capture was carried out. Within the category oxy-fuel cycles, the Graz Cycle and the semiclosed oxy-fuel combustion combined cycle (SCOC-CC) both achieved a net efficiency of nearly 50%. In a second step, a qualitative comparison of the critical components was performed according to their technical maturity. In contrast to the Graz Cycle, the study authors claimed that no major technical barriers would exist for the SCOC-CC. In this work, the ENCAP study is repeated for the SCOC-CC and for a modified Graz Cycle variant as presented at the ASME IGTI Conference 2006. Both oxy-fuel cycles are thermodynamically investigated based on common assumptions agreed upon with the industry in previous work. The calculations showed that the high-temperature turbine of the SCOC-CC plant needs a much higher cooling flow supply due to the less favorable properties of the working fluid. A layout of the main components of both cycles is further presented, which shows that both cycles rely on the new designs of the high-temperature turbine and the compressors. The SCOC-CC compressor needs more stages due to a lower rotational speed but has a more favorable operating temperature. In general, all turbomachines of both cycles show similar technical challenges and are regarded as feasible.

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## Figures

Figure 1

Principle flow scheme of the modified Graz Cycle power plant with condensation/evaporation in 1bar range (5)

Figure 2

Principle flow scheme of SCOC-CC

Figure 3

Arrangement of the main turbomachinery for a 400MW Graz Cycle plant

Figure 4

C1 compressor with titanium blisk and radial last stage

Figure 5

Design of the C2 drum rotor with cooling steam flow arrangement, combustor, and HTTC

Figure 6

Design of the two-stage HTTC and 50Hz HTTP

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