Absorption-enhanced Haber-Bosch for small-scale green NH3 production. A feasibility study

In the context of energy transition, ammonia (NH₃), traditionally used as a fertilizer, represents a promising carbon-free energy vector due to its high hydrogen density (around 17.8 wt%). Nevertheless, the huge carbon intensity of NH₃ synthesis calls for an intensification of the conventional, fossil fuel-based Haber-Bosch process. Flexibility, small-scale plants, modularity and mild operating pressures become fundamental requirements for sustainable NH₃ production, obtained by green H₂ from water electrolysers. To achieve these objectives, this work presents a feasibility study for intensifying the Haber-Bosch process, performed by Aspen Plus® V14 simulation software. Lowering the operating pressure, the NH₃ condensation downstream the reactor is replaced by NH₃ absorption in water. Performances of the novel layout are assessed by means of an energy analysis, based on pinch technology and NH₃ equivalent method. Due to the lower power requirement than the traditional scheme and the absence of thermal energy requirement, the proposed configuration is proved to be a promising pathway towards sustainable and decentralized ammonia, supporting global efforts for transition to a low-carbon future.