Optimization of Heat Networks for CO2 Capture from Combined Cycle Gas Turbine Power Plant

Abstract

Electricity generation through fossil fuel power plants significantly impacts greenhouse gases (GHGs), especially with the projected increase in global energy demand. Therefore, reducing GHGs emissions is crucial to mitigate climate change and effective strategies must be adopted. However, decarbonizing power plants can be energy intensive, leading to substantial power losses and increased electricity costs. This study evaluates the thermodynamic and economic performance of integrating a 727 MW natural gas combine cycle (NGCC) power plant with a post-combustion carbon capture (PCCC) unit. An equation-oriented NGCC model is developed in gPROMS© and validated against an equivalent model presented by the Department of Energy (DOE). Subsequently, a surrogate model is constructed for a rigorous rate-based PCCC unit. This facilitates integrating and optimizing the NGCC power and PCCC unit within the same software environment. The integrated system is evaluated using multiple key performance indicators (KPIs), such as LCOE, COE, and efficiency penalty. Following this, the integration of NGCC and various PCCC process configurations is assessed. The results showed that response surface methodology (RSM) can accurately represent the base case PCCC unit. The single-objective optimization of the integrated NGCC and PCCC system showed trade-offs between the cost and efficiency penalty. Thus, bi-objective optimization is used to visualize the trade-offs between COA and efficiency penalty in a Pareto front diagram. In the case of 90% capture, the Pareto front diagram shows that COA ranges from 72.2 $/tCO2 to 80.8 $/tCO2 and efficiency penalty ranges from 7.69%-points to 8.04%-points. Subsequently, implementing the PCCC process configuration reduces the integrated system's cost and efficiency penalty, where the integration of NGCC with the triple PCCC process configuration has the lowest LCOE (63.1 $/MWh), COA (73.61 $/tCO2), and efficiency penalty (7.73%-points), compared to the base case PCCC, which has LCOE (67.9 $/MWh), COA (89.5 $/tCO2), and efficiency penalty (8.84%-points). Overall, the study highlights the importance of evaluating the integrated NGCC and PCCC system, both thermodynamically and economically, to ensure accurate and informative outcomes.

Date of Award	19 Jul 2024
Original language	American English
Supervisor	AHMED ALHAJAJ (Supervisor)