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.