Session: 06-01 Carbon Capture Integration

Paper Number: 153625

Integrating Turbine Blade Cooling With Exhaust Gas Recirculation for Enhanced Carbon Capture in Combined Cycle Gas Turbine 

This paper investigates the feasibility of turbine blade cooling using Exhaust Gas from the Exhaust Gas Recirculation (EGR) in Combined Cycle Gas Turbine (CCGT) power plants for enhanced carbon capture (CC). The study has been performed due to the need to develop more economical solutions for carbon capture in current CCGTs during the transition towards net zero. Commercially mature CCGTs are the most efficient technology for power generation through fossil fuels and are widely used due to their higher flexibility, reliability and lower emissions compared to other power generation technologies. Post-combustion CC offers a solution to reduce CO₂ emissions from CCGTs. However, the low CO₂ concentration in flue gas results in a high CC energy demand, and the large volumetric exhaust flow rate requires large CC equipment, leading to high operating costs (OPEX) and capital costs (CAPEX). Based on theoretical studies, it is generally accepted that EGR should be applied in current CCGTs to reduce exhaust flow and increase exhaust CO₂ concentration. However, in this approach, the allowable recirculation of exhaust gas is limited by the minimum oxygen content required by the combustor, as EGR reduces oxygen concentration at the combustor inlet. In this study, we explore an innovative approach that uses exhaust gas for turbine blade cooling, as a potential solution for further CO₂ enrichment and reduction in exhaust mass flow without impact on combustion, leading to smaller CC units and lower CC energy consumption in existing utility-scale CCGTs, which are currently cooled using compressor bleed air. An existing H-class CCGT with three pressure level reheat bottoming cycle is modelled in WTEMP (Web-based Thermo-Economic Modular Program) software, a modular cycle analysis tool developed at the University of Genova. Carbon capture through exhaust gas is performed with a Monoethanolamine (MEA) based CC unit, modelled in ASPEN plus. A fraction of recirculated exhaust gas, compressed by an auxiliary compressor is used for cooling the turbine blades and the remaining is mixed with inlet air before gas turbine intake. Simulations are performed while maintaining an oxygen concentration of 16% (by vol.) at the combustor inlet. The impact of EGR based turbine cooling on CCGT performance is evaluated in terms of efficiency, specific work and economics of the carbon capture process. Results showed that for the same O₂ at combustor inlet, replacing compressor bleed air with exhaust gases for turbine cooling can allow a higher degree of recirculation and increase CO₂ exhaust concentration by around 8.5% with respect to EGR only. As a result, the size of the CC columns and their heat consumption were slightly reduced, resulting in a more economical carbon capture process.

Presenting Author: Abhishek Dubey University of Genova

Presenting Author Biography: Abhishek is an aerospace engineer from India. He obtained a Master's in aerospace propulsion from the Indian Institute of Technology Kanpur, India, in 2018 and subsequently worked at the Indian Institute of Science (IISc) Bangalore for three years before joining the INSPIRE program at the University of Genoa in January 2022. He has over five years of research experience in the field of gas turbine combustion, emission reduction technologies, laser diagnostics and the design of high-pressure optically accessible test rigs. He is passionate about developing more efficient and clean gas turbine technologies for propulsion and power generation.

Authors:

Abhishek Dubey University of Genova
Antoine Verhaeghe University of Mons (UMONS)
Ward De Paepe University of Mons (UMONS)
Alessandro Sorce University of Genova