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Research Papers: Gas Turbines: Cycle Innovations

# Process Analysis of Selective Exhaust Gas Recirculation for CO2 Capture in Natural Gas Combined Cycle Power Plants Using Amines

[+] Author and Article Information
Maria Elena Diego

Energy 2050,
Faculty of Engineering,
University of Sheffield,
Sheffield S10 2TN, UK
e-mail: m.diegodepaz@sheffield.ac.uk

Jean-Michel Bellas, Mohamed Pourkashanian

Energy 2050,
Faculty of Engineering,
University of Sheffield,
Sheffield S10 2TN, UK

1Corresponding author.

Contributed by the Cycle Innovations Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 5, 2017; final manuscript received July 6, 2017; published online August 16, 2017. Editor: David Wisler.

J. Eng. Gas Turbines Power 139(12), 121701 (Aug 16, 2017) (10 pages) Paper No: GTP-17-1284; doi: 10.1115/1.4037323 History: Received July 05, 2017; Revised July 06, 2017

## Abstract

Postcombustion CO2 capture from natural gas combined cycle (NGCC) power plants is challenging due to the large flow of flue gas with low CO2 content (∼3–4 vol %) that needs to be processed in the capture stage. A number of alternatives have been proposed to solve this issue and reduce the costs of the associated CO2 capture plant. This work focuses on the selective exhaust gas recirculation (S-EGR) configuration, which uses a membrane to selectively recirculate CO2 back to the inlet of the compressor of the turbine, thereby greatly increasing the CO2 content of the flue gas sent to the capture system. For this purpose, a parallel S-EGR NGCC system (53% S-EGR ratio) coupled to an amine capture plant (ACP) using monoethanolamine (MEA) 30 wt % was simulated using gCCS (gPROMS). It was benchmarked against an unabated NGCC system, a conventional NGCC coupled with an ACP (NGCC + carbon capture and storage (CCS)), and an EGR NGCC power plant (39% EGR ratio) using amine scrubbing as the downstream capture technology. The results obtained indicate that the net power efficiency of the parallel S-EGR system can be up to 49.3% depending on the specific consumption of the auxiliary S-EGR systems, compared to the 49.0% and 49.8% values obtained for the NGCC + CCS and EGR systems, respectively. A preliminary economic study was also carried out to quantify the potential of the parallel S-EGR configuration. This high-level analysis shows that the cost of electricity (COE) for the parallel S-EGR system varies from 82.1 to 90.0 $/MWhe for the scenarios considered, with the cost of CO2 avoided (COA) being in the range of 79.7–105.1$/ton CO2. The results obtained indicate that there are potential advantages of the parallel S-EGR system in comparison to the NGCC + CCS configuration in some scenarios. However, further benefits with respect to the EGR configuration will depend on future advancements and cost reductions achieved on membrane-based systems.

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## Figures

Fig. 1

Schematic of the EGR configuration in an NGCC power plant using amines

Fig. 2

Schematic of the (a) parallel and (b) series configuration in an NGCC power plant

Fig. 3

Process scheme of an NGCC power plant using the parallel S-EGR configuration

Fig. 4

Evolution of the O2 concentration at the inlet of the combustor, the CO2 content in the flue gas and the overall CO2 capture efficiency of the system of Fig. 3 with the S-EGR ratio for the parallel S-EGR configuration

Fig. 5

Sensitivity analysis on COE for the S-EGR plant under different scenarios that alter membrane cost, CO2 capture plant cost, and pressure difference across the membrane (black bold and dashed lines represent the costs of the NGCC + CCS and EGR systems, respectively)

Fig. 6

Sensitivity analysis on COA for the S-EGR plant under different scenarios that alter membrane cost, CO2 capture plant cost, and pressure difference across the membrane (black bold and dashed lines represent the costs of the NGCC + CCS and EGR systems, respectively)

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