Gas Turbine Combined Cycle System Integration with Carbon Capture Plant for Improved Value

Abstract The aim of this study is to analyze methodologies that can reduce performance impact on natural gas combined cycle (NGCC) plant when integrated with carbon capture plant (CCP) and lower the capital expenditure (CapEX) associated with carbon capture. The conventional approach of providing steam to the carbon capture reboiler for CO2 regeneration is the use of a bolt-on system, which entails an external auxiliary boiler. The study presented four promising technologies that can enhance the integration of NGCC with CCP: steam integration, exhaust gas recirculation (EGR), gas turbine improvement, and enhanced control system. The paper analyzes how EGR can decrease CCP CapEX and footprint, focusing on equipment with the most significant CapEX reductions. The steam integration approach refers to extracting steam from various locations in the steam cycle such as the crossover between the intermediate pressure (IP) and low pressure (LP) sections of the steam turbine using a throttle and control valve. The EGR method refers to recirculating a part of the flue gas from the stack back into the gas turbine inlet, where it is combined with ambient air. The analysis reveals that EGR contributes to an increase in the concentration of CO2 in exhaust while simultaneously decreasing the amount of flue gas directed to the CCP. This dual effect is expected to result in a reduction in both the overall CCP CapEX and its footprint. The study delves into the impact of EGR return temperature and EGR ratio on the output of gas turbine and combined cycle systems. NGCC performance has been evaluated utilizing GE’s internal mass and heat balance tools. CCP performance and cost were assessed using commercial tools ProMax and Aspen Process Economic Analyzer. The study demonstrates that providing steam to CCP through a steam integration solution is more effective than using a bolt-on solution. The steam integration solution has a potential to achieve up to 30% decrease in CCP CapEX compared to the bolt-on solution utilizing an auxiliary boiler. In addition, using a 30% EGR in the steam integration solution decreases the CapEx for the CCP by an additional 7%. EGR return temperatures ranging from 27°C to 44°C at 1°C intervals are considered, alongside studied EGR ratios of 10%, 20%, 30%, and 40%. The analysis demonstrates that the output of the studied NGCC increases at all studied EGR return temperatures and EGR ratios, reaching a peak at a 35% EGR ratio before leveling off.