(393n) CFD Modeling and Simulation of a Protonic Membrane Reformer Using Experimental Data

Hydrogen plays a critical role in the global transition to clean and renewable energy. Currently, 98% of global hydrogen production relies on fossil fuel-based technologies. Among various hydrogen production methods, steam methane reforming (SMR) accounts for nearly 50% of global hydrogen production [1]. Traditional SMR technologies require large-scale industrial plants, leading to significant capital costs associated with steam methane reforming reactions, water-gas shift reactions, hydrogen separation, and compression [2]. To address these challenges, protonic membrane reformers (PMRs) offer an integrated approach, combining SMR reactions, hydrogen production, and separation in a single unit, providing advantages over conventional SMR technologies.

To gain deeper insights into PMR performance, in this work, a two-dimensional transient CFD simulation is developed based on the realistic dimensions and operating conditions of an experimental-scale PMR constructed at UCLA. Specifically, an axisymmetric computational domain is implemented in the CFD simulation based on the cylindrical geometry of the PMR tube, saving computational cost while capturing variables distributions along axial and radial directions. The CFD model has been validated against experimental data under two operating conditions: with hydrogen extraction through the membrane and without. Specifically, to accurately capture the impact of temperature and catalyst loading on PMR performance, the temperature and catalyst weight in the CFD simulation are calibrated to match experimental measurements. To correctly account for reaction kinetics, a global SMR kinetic model developed by Xu and Froment [3] is implemented in the CFD simulation using User-Defined Functions (UDFs). Hydrogen separation is modeled based on Faraday’s Law of electrolysis, incorporated as a source term. The flow domain is characterized as incompressible, laminar fluid flow, consistent with the operating conditions of the experimental system. The pseudo-steady-state mole fractions of methane, carbon dioxide, carbon monoxide, and hydrogen are validated against steady-state experimental data obtained under identical conditions. This study provides critical insights into mass transport, reaction kinetics, and temperature distribution within the PMR by analyzing the spatial profiles of species mole fractions, temperature, velocity, and reaction rates along the axial direction.

References:

[1] Soltani, S. M., Lahiri, A., Bahzad, H., Clough, P., Gorbounov, M., & Yan, Y. (2021). Sorption-enhanced steam methane reforming for combined CO2 capture and hydrogen production: a state-of-the-art review. Carbon Capture Science & Technology, 1, 100003.

[2] Malerød-Fjeld, H., Clark, D., Yuste-Tirados, I., Zanón, R., Catalán-Martinez, D., Beeaff, D., ... & Kjølseth, C. (2017). Thermo-electrochemical production of compressed hydrogen from methane with near-zero energy loss. Nature Energy, 2, 923-931.

[3] Xu, J., & Froment, G. F. (1989). Methane steam reforming, methanation and water-gas shift: I. Intrinsic kinetics. AIChE journal, 35, 88-96.