Numerical Simulation Study of a Flexible Ammonia Synthesis Process with a Two-Stage Fixed-Bed Reactor
Huang Weirong1, Tian Qingyun1, Ao Jiyuan1, Huang Yangqiang2, Luo Xiao2, Chen Hao2
1. Hunan Chemical Engineering Design Institute Company Limited, Changsha 410007, China;
2. College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
Abstract：Conventional ammonia synthesis processes are characterized by high energy consumption and high emissions, making them poorly suited to the intermittency and variability of renewable energy and thereby hindering the development of green ammonia technologies. To address this issue, a numerical study was conducted on a flexible ammonia synthesis process employing a two-stage fixed-bed reactor. A one-dimensional steady-state mathematical model coupling multicomponent reaction kinetics, mass transfer, and heat transfer was established. COMSOL Multiphysics was employed to systematically simulate the first- and second-stage reactors packed with iron-based and ruthenium-based catalysts, respectively. The model was validated against experimental data reported in the literature and showed good accuracy in predicting the axial distribution of ammonia mole fraction and the outlet ammonia mole fraction. The results indicate that the first-stage adiabatic reactor experiences a pronounced temperature rise of up to 117.4 ℃, suggesting a risk of excessive temperature rise within the catalyst bed and highlighting the need for strict temperature monitoring during practical operation. In the second-stage heat-exchange reactor, when the cold-stream flow rate varies from 50 kmol/h to 180 kmol/h, the maximum outlet ammonia mole fraction reaches 15.05%, while the ammonia yield remains stable, demonstrating good adaptability to fluctuations in operating conditions. This study elucidates the coupled multiphysics behavior within the two-stage fixed-bed reactor used in a flexible ammonia synthesis process and provides a theoretical basis for its industrial design and safe and efficient operation.
Huang Weirong,Tian Qingyun,Ao Jiyuan et al. Numerical Simulation Study of a Flexible Ammonia Synthesis Process with a Two-Stage Fixed-Bed Reactor[J]. Chemical Reaction Engineering and Technology, 2026, 42(4): 360-370.
