Summary In this study, a two‐dimensional mathematical model is proposed for modeling the hollow fiber membrane (HFM) separators for hydrogen (H2) recovery unit implemented in the Razi Petrochemical Company (Imam Khomeini Port, Iran) to capture hydrogen from ammonia (NH3) purge gas. In this regard, computational fluid dynamics is applied to solve the equations of momentum and mass transfer in the laminar flow conditions. Axial and radial diffusion for mass transfer inside the membrane fibers and axial diffusion within the shell side of separator were considered. The distributions of concentration, velocity, and mass transfer fluxes were achieved by the model. As the new insights, the effects of feed flow rate and feed gas concentration on mass transfer of H2 were investigated. Moreover, fluid velocity profile and H2 fluxes in the tube (fiber), membrane, and shell sides of the HFM separator were studied. The results of simulation were compared with the industrial data and showed that the present developed model has excellent agreement with the experimental data with a low mean deviation value of 3.5%.

a b s t r a c tIn the current research, simulation of chemical oxygen demand (COD) removal process from a high saline refinery wastewater using a membrane bioreactor equipped with a hollow fiber membrane, named as a hollow fiber membrane contactor (HFMC) was investigated using computational fluid dynamics method. A two-dimensional mathematical model was proposed to investigate COD transfer. This model describes the diffusion in the axial and radial directions of the HFMC. The model also examines the momentum transfer toward the tube and the shell. Comparing the model results with the experimental data, a deviation of 7.35% attained which reflects the proper reliability of the proposed model to predict the absorption of COD in the HFMC.