SIMULATION OF THE HIPOWAR GAS-STEAM POWER GENERATION SYSTEM USING AMMONIA AS FUEL

This work presents a simulation activity on an innovative power generation cycle, developed within the EU Horizon 2020 project HiPowAR, using ammonia as fuel for an oxy-combustion process in a membrane reactor. The key advantages of the system are the low compression requirement, typical of steam cycles, and the large expander inlet temperature, typical of gas turbine cycles. The analysis explores the options of cooled or uncooled expander, either adopting a steam-cooled turbine made of conventional Ni-based alloys or using high temperature-resistant ceramic matrix composite (CMC) materials. The simulations show that, with a reactor outlet temperature of 1350°C, a cooled system could reach up to 48.2% efficiency, with limited additional advantages when further increasing the temperature. At the same temperature level, the uncooled system could instead achieve 52.5% efficiency, allowing also a substantial system simplification. However, since the expanded mixture contains nearly 90%mol steam, the use of CMC materials is made difficult by degradation issues and would require the development of suitable barrier coatings.