Haber-Bosch process intensification: A first step towards small-scale distributed ammonia production

Abstract

High operating pressures are needed in the Haber-Bosch process to push up the NH3 conversion, which is limited by the thermodynamic equilibrium. This evidence hinders the application of distributed renewable ammonia production on small-scale. One possible solution to overcome this problem is the NH3 removal downstream the reaction stage. Ammonia separation from unconverted gases can be performed either with solid-state species (i.e., metal halides or borohydrides), that react reversibly with gas phase NH3, or liquid solvents. Among liquid solvents, traditional NH3 absorption technologies (water, aqueous acids or NH4H2PO4) or novel absorption technologies (ionic liquids or deep eutectic solvents) can be applied. In this respect, the aim of this work is to analyse the NH3 production process intensification, introducing the NH3 removal section through absorption with a phosphate solution downstream the reaction stage. The use of absorption for ammonia separation may open the door to moderate pressure synthesis loop and may pave the way for a down-scalable process based on renewable energy sources.