Simplified Absorption-Enhanced Haber-Bosch Process for Green Ammonia Recovery: Aspen Plus® Simulation, Separation Optimization and Energy Assessments

This work presents an Aspen Plus simulation of an ammonia recovery subsystem based on NH3 absorption in water followed by solvent regeneration via distillation. The study focuses on the absorber-distillation loop with water recycle, analyzed independently from the full Haber-Bosch gas recycle to isolate intrinsic separation behavior. A parametric analysis was performed for absorber pressures between 40 and 70 bar, and reflux ratios between 1.2 and 2.5. Near complete NH3 purity 100 mol% was achieved with an overall recovery of 97% under optimal conditions P = 50 bar, R = 1.5. However, the process is strongly constrained by thermodynamic limitations of the NH3–H2O system. At low pressure, reduced NH3 solubility leads to increased solvent circulation and dilution, resulting in a sharp rise of reboiler duty up to 60 MW. Energy analysis shows that the distillation reboiler accounts for 98% of total thermal demand. Comparison with literature confirms the trends and highlights the critical role of thermal integration. The study provides a detailed, reproducible framework for analyzing and optimizing NH3 recovery subsystems.