Multiscale modelling in ammonia synthesis: Integrating CFD and process simulation - A review

Ammonia synthesis is a crucial industrial process, but its high energy consumption and greenhouse gas emissions highlight the need for advanced modelling to optimise and develop sustainable pathways. This review provides a comprehensive analysis of multiscale modelling in ammonia synthesis, specifically integrating Computational Fluid Dynamics (CFD) and process simulation. A systematic literature review of Web of Science and Scopus databases, up to March 31, 2025, was conducted, focusing on kinetic models, CFD applications, and process simulation studies. The findings reveal the widespread use of various kinetic models (Temkin-Pyzhev, LHHW, microkinetic) to describe reaction rates, while CFD simulations primarily focus on reactor-level details like flow, heat, and mass transfer, evaluating geometry and operating conditions. Process simulation is extensively applied for plant-wide analysis, techno-economic assessment, and dynamic studies, often utilising simplified reactor representations. A significant gap identified is the absence of published studies explicitly integrating CFD and process simulation for ammonia synthesis, despite its demonstrated value in other chemical engineering contexts. Addressing this critical gap through future research is crucial for a more comprehensive understanding and the effective optimisation of sustainable ammonia production. • First systematic review (100 + papers, 1940-2025) mapping kinetics, CFD and process-simulation studies for ammonia synthesis. • Reveals zero published CFD–flowsheet integrations, exposing a key multiscale research gap. • Shows prevailing use of Temkin-Pyzhev/Dyson macroscopic kinetics and near-absence of microkinetic or Ru-specific rate laws. • Synthesises CFD evidence that spherical radial-flow reactors boost N 2 conversion by ∼30 % over tubular beds, steering intensified designs. • Outlines a future agenda—CFD–process co-simulation, ML surrogates, and greener PtA/BtA routes—to cut energy and CO 2 , matching the journal’s PI focus.