Performance analysis of selective exhaust gas recirculation integrated with fogging cooling system for gas turbine power plants

Abstract

Selective exhaust gas recirculation (S-EGR) is a proposed alternative for enhancing the CO2 capture units applied in power plants. Most previous studies focused on the correlation between S-EGR and CO2 capture unit efficiency. Nevertheless, the S-EGR system without pre-cooling considerably influences the gas turbine output power due to its relatively high temperature. Hence this study aims to investigate the influence of the integration of fogging cooling systems with S-EGR on gas turbine performance. This combination could reduce the adverse effects of the S-EGR system in power plants as well as increase the effectiveness of the fogging cooling system in hot, humid regions. A three-dimensional Euler–Lagrange CFD model is employed to simulate the mutual effect between S-EGR and fogging cooling systems under different operation conditions. The impact of output condition from combined fogging and S-EGR system (cooled CO2 enriched air) on the gas turbine performance is then investigated. Results illustrate that applying the fogging cooling approach after mixing the inlet air and S-EGR reduces the moisture content of the inlet air and augments the cooling capacity of the fogging system. When the CO2-enriched stream is pre-cooled to the same ambient temperature, the fogging system outlet temperature drops more, especially at high S-EGR ratios. Applying the S-EGR system could increase the inlet mixture density (CO2-enriched air) by about 12% at an S-EGR ratio of 35%, which is increased to 18% after incorporating the fogging cooling system. Regarding gas turbine performance, using CO2-enriched air without pre-cooling leads to a significant deterioration in performance, notably at high S-EGR ratios. On the other hand, the amalgamation of S-EGR with fogging cooling could boost gas turbine output power from 11.7 to 19.2%, with an efficiency gain of half a percentage point.