A Numerical Study of Hydrogen Production via High-temperature and Low-temperature Water-Gas Shift Reactors’ System: The Multi-Scale Modeling Approach and Simulation

Abstract

The primary purpose of this study is to develop an advanced, and comprehensive multi-scale mathematical models of a packed bed reactors (PBRs) carrying out high and low temperature water-gas-shift reactions (WGSRs) for the hydrogen production. In industrial hydrogen generation applications, the water-gas-shift reactors are considered at high (called HTSR) and low (called LTSR) temperature stages with a cooling process between them. Therefore, detailed and advanced numerical studies on the HTSR and the LTSR in series are carried out to assess the overall performance of hydrogen production system. After completing a single-pellet, non-isothermal, steady-state simulation, we couple our model with a non-isothermal (adiabatic), steady-state packed-bed reactor model to form a hybrid multi-scale reactor model. The velocity, temperature and species’ concentration profiles along both the reactor length and the pellet radius are captured by using rigorously defined momentum, energy, and species transport models, accounting for the physical mechanisms involved in the system such as convection, conduction, and reaction-diffusion. The model’s equations are simultaneously solved for each domain: bulk gas domain and catalyst-pellet domain. The rigorous Maxwell-Stefan Model is applied on the reactor scale to account mass diffusion fluxes. On the other hand, Dusty Gas Model is considered to describe mass diffusion fluxes for the single pellet scale. Studies that include a broad range of the operating conditions and design parameters are carried out in this paper, in order to investigate the upper and lower limit conditions’ effects on the results.