Retrofitting the natural gas combined cycle through integration with chemical looping hydrogen generation and ammonia synthesis toward a carbon-neutral trigeneration system

The global electricity sector is currently dominated by fossil fuels, posing a significant challenge to achieving net-zero emissions targets. Decarbonizing the power sector while utilizing existing fossil fuel-based power plants is essential. Natural gas (NG), the second-largest source of electricity globally, can be partially replaced with hydrogen (H 2 ) and/or ammonia (NH 3 ). A 50:50 M mixture of H 2 and NH 3 offers a promising solution, providing a flame speed comparable to NG while addressing these limitations. Despite this potential, H 2 production is still predominantly reliant on fossil fuel-based grey H 2 . In this study, the integration of biomass CLHG, NH 3 synthesis, and an existing 500 MW NGCC power plant was investigated through process simulation and off-design analysis. This approach addressed key limitations of conventional H 2 and NH 3 production pathways and assessed necessary modifications to accommodate H 2 -NH 3 co-firing while maintaining efficiency. The CLHG system achieved an H 2 production efficiency of 75 %, while the NH 3 synthesis process exhibited an efficiency of 63 %. When NG was replaced by the H 2 -NH 3 mixture, the overall efficiency of the system decreased from 56.19 % to 47.1 %, primarily due to fuel production processes. Under partial load conditions, the efficiency trends of NGCC were comparable to those observed in conventional NGCC systems, except at 40 % load, due to the high steam flow rate in the heat recovery steam generator. The calculated levelized cost of electricity for the integrated system was 0.1075 USD/kWh, lower than that of imported fuels. Additionally, the levelized costs of H 2 and NH 3 were 1.439 USD/kg-H 2 and 0.365 USD/kg-NH 3 , respectively. By leveraging a steady-state CLHG-NH 3 system with flexible NGCC operation, this study presents a viable pathway for decarbonizing NGCC plants while ensuring cost competitiveness in a transitioning energy market. • Chemical looping and NH 3 synthesis are integrated into NGCC, yielding 47.1 % efficiency. • H 2 -NH 3 blends slightly reduce NGCC power in off-design simulations. • Partial load (40 %) is not advised for H 2 -NH 3 due to efficiency issues. • The estimated LCOE is 0.1075 USD/kWh, within the H 2 -NH 3 import price range. • Without integration, LCOH and LCOA 1.439 USD/kg-H 2 and 0.365 USD/kg-NH 3 .