Open Journal of Energy Efficiency, 2018, 7, 33-52 http://www.scirp.org/journal/ojee ISSN Online: 2169-2645 ISSN Print: 2169-2637 DOI: 10.4236/ojee.2018.72003 May 17, 2018 33 Open Journal of Energy Efficiency Process Simulation of a 620 Mw-Natural Gas Combined Cycle Power Plant with Optimum Flue Gas Recirculation Ahmed Badr Al Hashmi, Abdel Aziz Abdulla Mohamed, Zin Eddine Dadach * Chemical & Petroleum Engineering Department, Abu Dhabi Men’s College, Higher Colleges of Technology, Abu Dhabi, UAE Abstract The main objective of this investigation is to obtain an optimum value for the flue gas recirculation ratio in a 620 MW-Natural Gas Combined Cycle (NGCC) power plant with a 100% excess air in order to have a composition of the exhaust gas suitable for an effective absorption by amine solutions. To reach this goal, the recirculated flue gas is added to the secondary air (dilution air) used for cooling the turbine. The originality of this work is that the opti- mum value of a Flue Gas Recirculation (FGR) ratio of 0.42 is obtained from the change of the slope related to the effects of flue gas recirculation ratio on the molar percentage of oxygen in the exhaust gas. Compared to the NGCC power plant without flue gas recirculation, the molar percentage of carbon dioxide in the flue gas increases from 5% to 9.2% and the molar percentage of oxygen decreases from 10.9% to 3.5%. Since energy efficiency is the key para- meter of energy conversion systems, the impact of the flue gas recirculation on the different energy inputs and outputs and the overall efficiency of the power plant are also investigated. It is found the positive effects of the flue gas recirculation on the electricity produced by the steam turbine generator (STG) are more important than its cooling effects on the power output of the com- bustion turbine generator (CTG). The flue gas recirculation has no effects on the water pump of the steam cycle and the increase of energy consumed by the compressor of flue gas is compensated by the decrease of energy con- sumed by the compressor of fresh air. Based on the Low heating value (LHV) of the natural gas, the flue gas recirculation increases the overall efficiency of the power plant by 1.1% from 57.5% from to 58.2%. Keywords Natural Gas Combined Cycle (NGCC), Flue Gas Recirculation, Absorption by Amine, CCS How to cite this paper: Al Hashmi, A.B., Mohamed, A.A.A. and Dadach, Z.E. (2018) Process Simulation of a 620 Mw-Natural Gas Combined Cycle Power Plant with Optimum Flue Gas Recirculation. Open Journal of Energy Efficiency, 7, 33-52. https://doi.org/10.4236/ojee.2018.72003 Received: March 17, 2018* Accepted: May 14, 2018 Published: May 17, 2018 Copyright © 2018 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Open Access