(476f) Design, Modeling, and Eco-Technoeconomic Analysis of Ammonia Co-Firing in a Natural Gas Combined Cycle Plant

Alternative fuels have drawn attention for their potential to reduce greenhouse gas (GHG) emissions in the power generation sector [1]. Ammonia, as an alternative fuel and a hydrogen carrier, has advantages such as high hydrogen density, ease of long-distance transportation and storage, and compatibility for co-firing with natural gas (NG) [2-4]. However, the feasibility of large-scale application of ammonia co-firing with NG, in terms of techno-economics and life cycle emissions, remains uncertain. In this study, we investigated the viability of both greenfield and retrofit designs of ammonia co-firing in a natural gas combined cycle plant (NGCC) in India through model simulations using Aspen Plus, techno-economic analyses, and life cycle assessments. We explored cases ranging from substituting 20% of NG (in terms of heating value) with ammonia up to 100% pure ammonia combustion, using ten different upstream ammonia production pathways (including grey, blue, and green pathways). For our baseline case, which is greenfield 20% ammonia co-firing in NGCC in India, by using blue ammonia produced via autothermal reforming using air combustion with carbon capture and sequestration in Australia, the levelized cost of electricity (LCOE) and life cycle GHG emission were estimated at $64/MWh (in 2019 U.S. dollars) and 417 kg-CO₂e/MWh, respectively. Increasing the proportion of ammonia co-firing to 80% resulted in an LCOE of $121/MWh and a life cycle GHG emission of 324 kg-CO₂e/MWh. The cost of life cycle CO₂ avoided (CCA) for the 20% and 80% ammonia co-firing cases compared to the original NGCC were $631/tonne-CO₂e and $617/tonne-CO₂e, respectively. Despite the significant onsite GHG emission reduction achievable with ammonia co-firing (e.g., 80% ammonia co-firing would result in around 80% onsite GHG emission reduction), the CCA remained high due to life cycle GHG emissions or high upstream ammonia costs ($397/tonne-NH₃ including production and transportation as our baseline case). Considering the anticipated advancements in renewable energy in the future, ammonia co-firing stands to benefit from a reduction in upstream ammonia costs (via green pathways) and its potential as dispatchable power. If the upstream costs of green ammonia (produced via low temperature electrolyzers) reduced to around $200/tonne-NH₃, the CCA for 20%-80% ammonia co-firing cases can be reduced to around $100/tonne-CO₂e.

[1] Sánchez, A., Castellano, E., Martín, M., & Vega, P. (2021). Evaluating ammonia as green fuel for power generation: A thermo-chemical perspective. Applied Energy, 293, 116956.

[2] Xiao, H., Howard, M., Valera-Medina, A., Dooley, S., & Bowen, P. J. (2016). Study on reduced chemical mechanisms of ammonia/methane combustion under gas turbine conditions. Energy & Fuels, 30(10), 8701-8710.

[3] Ito, S., Uchida, M., Suda, T., & Fujimori, T. (2020). Development of ammonia gas turbine co-generation technology. IHI Eng. Rev, 53(1), 6.

[4] Ito, S., Uchida, M., Suda, T., & Fujimori, T. (2022). Demonstration Tests of Ammonia/Natural Gas Co-firing Power Generation with a 2-MW-Class Gas Turbine. In CO2 Free Ammonia as an Energy Carrier: Japan's Insights (pp. 515-522). Singapore: Springer Nature Singapore.