Model construction and techno-economic analysis of current-assisted mild synthesis of green ammonia

Ammonia (NH₃) as an essential chemical is produced on a large scale by Haber-Bosch process at high temperature and pressure. The realization of mild green NH₃ production is of great significance to environmental protection. In this study, three one-dimensional steady-state models were developed for the study of current-assisted NH₃ synthesis reactor, including adiabatic quench cooling reactor (AQCR), adiabatic indirect cooling reactor (AICR), and auto-thermal reactor (ATR). The axial distributions of temperature, pressure, conversion and NH₃ mole fraction of the three reactors were obtained. Meanwhile, the performance of three reactors with different heat transfer forms were compared. When the NH₃ output were consistent, the temperature and pressure changes of ATR along the catalytic bed were the most moderate. The conversion of AICR and ATR were significantly higher than AQCR, at 0.1616 and 0.1580. In addition, six NH₃ synthesis loops under mild conditions were constructed by coupling the three reactors with condensation unit (CON) or ionic liquid (IL) absorption unit (ABS), and the techno-economic analysis was carried out. In three NH₃ synthesis loop coupled to condensation unit, the LCOA of ATR-CON was the lowest, at 795.76 $ t_NH3⁻¹, which indicated that ATR has great advantages in energy consumption and cost in the NH₃ synthesis loop constructed with the condensation unit. However, LCOA was obviously reduced in all in three NH₃ synthesis loop coupled to IL absorption unit. Compared to AICR-ABS loop, the LCOA of AQCR-ABS and ATR-ABS are lower, at 654.70 and 654.59 $ t_NH3⁻¹ respectively.