Simulation and energetic assessment of the ammonia synthesis loop with ionic liquid-Based ammonia recovery from recycle gas

Abstract

Ammonia (NH3) synthesis by Haber-Bosch process is recognized as the most important pathway for NH3 production. However, NH3 recovery from recycle gas using conventional condensation separation is still an energy-intensive process. Ionic liquids (ILs) have been proved to be effective solvents for NH3 separation and recovery due to their unique properties. In this work, a novel IL-based ammonia synthesis loop (IL-HB) was proposed, taking the protic IL [Bim][NTf2] as the absorbent to separate and recover NH3 from recycle gas, aiming to reduce the energy consumption and increase the NH3 production capacity of the synthesis tower. Then, a systematic methodology that considers reliable thermodynamic models as well as process simulation and assessment was established to evaluate the feasibility of the IL-HB. Furthermore, two entire processes (ILa-HB and ILb-HB) that integrate the optimal sections of IL-based NH3 recovery from recycle gas with the ammonia synthesis loop as a whole were simulated, taking the conventional Haber-Bosch ammonia synthesis loop (HB) as the benchmark. The simulation results prove great techno-economic potentials of the proposed ILa-HB and ILb-HB. Compared with the HB, the energy consumption and CO2 emissions of ILb-HB can be reduced by 16.01% and 29.44%, respectively, presenting enormous energy-saving and environment-friendly superiority.