Green ammonia production via the integration of a solid oxide electrolyser and a Haber-Bosch loop with a series of solid electrolyte oxygen pumps

A conceptual design for a small-scale green ammonia plant is presented in which ammonia synthesis was realised via a Haber-Bosch loop using hydrogen produced by a solid oxide electrolyser and nitrogen purified from air with a series of solid electrolyte oxygen pumps. The system operated with an energetic efficiency of 52.12%, very close to a cryogenic ASU reference system where an efficiency of 52.89% was achieved. The specific energy consumption was 9.94 kWh/kgNH3. Whilst these were encouraging results, opportunities exist to improve system design further. For example, greater heat integration could allow for steam required by the electrolyser to be raised using waste heat from the series of oxygen pumps.