Recipe-based 1-D dynamic modeling of an integrated NH3-synthesis-sorption reactor

Long-term green hydrogen storage can be realized via flexible and efficient ammonia (NH3) synthesis. Process intensification via a sorbent-integrated, ideally recycle-less NH3-synthesis unit enables milder pressure and temperature levels during NH3 synthesis, while shifting the single-pass conversion beyond the thermodynamic equilibrium. Understanding the process behavior of this novel, integrated synthesis-sorption reactor (SSR) requires an analysis and choice of suitable materials for catalysis and sorption based on the chemical equilibrium and kinetics of both the sorption and reaction phenomena. This study first proposes an equilibrium thermodynamic analysis to provide an initial performance assessment of a desired SSR, evaluating several sorbent material candidates. On this basis, a novel, pressure-driven dynamic model is developed to rigorously assess the inherently transient dynamics of a fixed-bed SSR in cyclic batch-wise operation under a predefined operation recipe. By consistent formulation of the conservation equations to describe the interplay of flow, reaction, and sorption phenomena, a physically accurate model is derived. Given the operation recipe, the simulation results highlight an NH3 yield of 60.9%, substantially exceeding the single-pass conversion of 10 - 15 %, typically achieved in state-of-the-art Haber–Bosch reactors. Additionally, a sensitivity analysis reveals that sorbent kinetics, rather than catalyst kinetics, should be the primary focus of material development to mitigate the effects of back-reaction in the presence of catalyst material during desorption. While the need for further material development is highlighted, this study provides the first rigorous dynamic evaluation of an integrated SSR for ammonia synthesis.