Potentials for Decarbonizing Ammonia Synthesis Plants: Retrofitting of Novel Process Configurations

Abstract Decarbonizing ammonia production is crucial for reducing industrial greenhouse gas emissions; however, steam methane reforming (SMR) remains the dominant, carbon-intensive pathway. This study proposes a retrofit strategy for large-scale ammonia plants (1,268 tons/day) by replacing the conventional reformer with an advanced dual-reactor system that enables CO₂ utilization and carbon valorization. The novel configuration co-produces synthesis gas and multi-walled carbon nanotubes (MWCNTs), integrating ammonia and CNT production in a single process. Aspen Plus® simulations compare the baseline SMR process with the retrofitted configuration, assessing energy demand, feedstock consumption, CO₂ emissions, and economic performance. The retrofitted system achieves a 76% reduction in lifecycle CO₂-equivalent emissions and a 31% decrease in total energy demand, despite a 2.6-fold increase in methane input. At 25% MWCNT recovery, the Levelized Cost of Ammonia (LCOA) increases to $680.90/ton; however, substantial co-product revenue yields a 3.2-fold increase in Net Present Value (NPV), 56% Internal Rate of Return (IRR), and a 4.5-year payback period. Sensitivity analyses support the robustness of the economic potential, confirming the viability of integrated CNT-ammonia production as a pathway for sustainable, low-carbon manufacturing.