Thermochemical Performance Analysis of the Steam Reforming of Methane in a Fixed Bed Membrane Reformer: A Modelling and Simulation Study

Abstract

Pd-based membrane reformers have been substantially studied in the past as a promising reformer to produce high-purity H2 from thermochemical conversion of methane (CH4). A variety of research approaches have been taken in the experimental and theoretical fields. The main objective of this work is a theoretical modelling to describe the process variables of the Steam Reforming of Methane (SRM) method on the Pd-based membrane reformer. These process variables describe the specific aims of each equation of the mathematical model characterizing the performance from reformer. The simulated results of the mole fractions of components (MFCs) at the outlet of the Fixed Bed Reformer (FBR) and Packed-Bed Membrane Reformer (PBMR) have been validated. When the H2O/CH4 ratio decreases in PBMR, the Endothermic Reaction Temperature (ERT) is notably increased (998.32 K) at the outlet of the PBMR’s reaction zone. On the other hand, when the H2O/CH4 ratio increases in PBMR, the ERT is remarkably decreased (827.83 K) at the outlet of the PBMR’s reaction zone. An increase of the spatial velocity (Ssp) indicates a reduction in the residence time of reactant molecules inside PBMR and, thus, a decrease of the ERT and conversion of CH4. In contrast, a reduction of the Ssp shows an increase of the residence time of reactant molecules within PBMR and, therefore, a rise of the ERT and conversion of CH4. An increase of the H2O/CH4 ratio raises the conversion rate (CR) of CH4 due to the reduction of the coke content on the catalyst particles. Conversely, a reduction of the H2O/CH4 ratio decreases the CR of CH4 owing to the increase of the coke content on the catalyst particles. Contrary to the CR of CH4, the consumption-based yield (CBY) of H2 sharply decreases with the increase of the H2O/CH4 ratio. An increase of the ERT raises the thermochemical energy storage efficiency (ηtese) from 68.96% (ERT = 1023 K), 63.21% (ERT = 973 K), and 48.12% (ERT = 723 K). The chemical energy, sensible heat, and heat loss reached values of 384.96 W, 151.68 W, and 249.73 W at 973 K. The selectivity of H2 presents higher amounts in the gaseous mixture that varies from 60.98 to 73.18 while CH4 showed lower values ranging from 1.41 to 2.06. Our work is limited to the SRM method. In terms of future uses of this method, new works can be undertaken using novel materials (open-cell foams) and the physical-mathematical model (two-dimensional and three-dimensional) to evaluate the concentration polarization inside membrane reactors.

Mathematical modelling of the residence time distribution of CO2 tracer in a three-phase micro-packed bed reactor: An experimental analysis

“…It is possible to transform the equations system, Equations ( 1)-( 14), applying Equations ( 20)-( 21) using the boundary conditions of each EDP (Medeiros et al, 2021). Thus, transformed equations are reported as follows.…”

A review on mathematical modeling of packed bed membrane reactors for hydrogen production from methane

“…The results showed that when the reaction and separation sections are decoupled such as RMM, the overall conversion of methane is increased by nearly 30%, which in turn improves the system efficiency. de Medeiros et al 108 conducted a modeling and simulation study to evaluate the thermochemical performance analysis of fixed bed reformer (FBR) and packed‐bed membrane reformer (PBMR). The developed models were validated with experimental data.…”

Design and multiobjective optimization of membrane steam methane reformer: A computational fluid dynamic analysis

“…The membrane reactor has attracted significant attention owing to its compactness, fast response time, and high hydrogen yield 6‐9 . This latter can be affected by the chemical equilibrium shift in the SMR and the involved side reactions, especially the water gas shift (WGS) reaction that is deemed very weak in conventional reactors 10‐12 . Thus, the membrane helps to decentralize the system by reducing the number of separation modules and affords fast response times.…”

“…They showed an increase in the hydrogen recovery and methane conversion by 6.8% and 19.8%, respectively. Medeiros et al 43 conducted a parametric study on packed and fixed‐bed membrane reactors for SMR operations. The results showed several impacts of the operating conditions, that is, lowering the steam‐to‐carbon ratio can decrease the reactor outlet temperature and prompt carbon formation on the catalyst particles.…”

“…[6][7][8][9] This latter can be affected by the chemical equilibrium shift in the SMR and the involved side reactions, especially the water gas shift (WGS) reaction that is deemed very weak in conventional reactors. [10][11][12] Thus, the membrane helps to decentralize the system by reducing the number of separation modules and affords fast response times. Similarly, the autothermal reforming (ATR) of steam and methane helps in reducing the heating modules.…”