Membrane Reactor For Hydrogen Production Research Articles

Modeling analysis of water-gas-shift reaction on catalyst-packed ceramic-carbonate dual-phase membrane reactor for hydrogen production

Water-gas shift (WGS) reaction for hydrogen production and CO2 removal/capture in a catalyst-packed CO2-permselective membrane reactor is studied experimentally and simulated with a computational model. The reactor utilizes a tubular dense ceramic-carbonate dual-phase membrane with a commercial high-temperature WGS catalyst. Equations governing CO2 permeation through the membrane and WGS reaction kinetics on the catalyst were obtained through independent CO2 permeation experiments and a fixed-bed reaction kinetic study. The simulation results using the validated model are presented to examine the effects of feed gas composition, steam/CO ratio, gas hourly space velocity, temperature, reactor pressure, sweep to feed molar flow rate ratio, and the membrane area to catalyst volume ratio on the performance of the membrane reactor for WGS with CO2 removal. Under optimized conditions, the catalyst-packed membrane reactor for WGS demonstrates significantly enhanced CO conversion and product H2 purity by effectively removing/capturing CO2 from the WGS reaction side.

Solar-driven multichannel membrane reactor for hydrogen production from ammonia decomposition

Solar-driven ammonia decomposition is one of the most promising carbon-free pathways to release hydrogen from ammonia. Enhancing the heat and mass transfer processes within an ammonia decomposition membrane reactor is crucial to improve the hydrogen production rate. The multichannel reactors can reduce hydraulic diameters by raising the number of channels while the lateral surface areas of reactors keep the same, which can enhance heat and mass transfer without enlarging re-radiation losses. In this paper, a solar-driven multichannel membrane reactor for ammonia decomposition is proposed, which is promising to improve the conversion without deteriorating the efficiency. Models are developed to simulate the proposed multichannel membrane reactor under solar irradiation. A multichannel membrane reactor with three Pd membrane channels is designed and built. Experiments have been conducted to validate the reactor model. With the validated model, two consecutive parametric studies have been conducted for catalyst volume decreasing and increasing scenarios, respectively. The results show that enlarging permeation area by increasing membrane channels is worthwhile to improve the conversion although the catalyst volume decreases. Under the same solar flux and inlet ammonia properties, a six-channel membrane reactor can achieve a conversion of 0.76, while a single-channel membrane reactor can only achieve a conversion of 0.49. Additionally, the maximum temperature difference within the six-channel reactor is 47 °C lower than that within single-channel membrane reactor, which is favorable for the Pd membrane operating temperature range.

A Review: Membrane Reactor for Hydrogen Production: Modeling and Simulation

A membrane reactor is a multifactional vessel used for H2 production. Hydrogen's three spectrum colors are dependent on carbon present. Two types of membrane with high permeability to hydrogen (polymeric and metallic) Hydrogen is produced in two systems: conventional reactors and membrane reactors (which separate and purify hydrogen in a single vessel). There are many types of membrane reactors according to design (catalytic membrane reactor (CMR), fixed bed reactor (FBMR), fluidized bed reactor (FBMR), etc. The transport mechanism of H2 through the membrane by a "sorption-diffusion mechanism" and the government equations that are used for membrane reactor modeling and simulation, such as continuity, momentum, mass, and heat transfer equations of the CMR, and the thickness of the membrane. These equations are solved by MATLAB, COMSOL, and the Finite Element Method to simulate the MR at different parameters: rate of conversion, rate of sweep gas, temperature, pressure, rate of H2 permeation through a membrane, and activity of the catalyst. We summarized theoretical studies for membrane reactors, including the operation conditions, type of hydrocarbon feed, type of production method, kind of catalyst, and heat effect.

Self-catalytic nickel hollow fiber membrane reactor for hydrogen production via toluene steam reforming

Metal-nickel membrane exhibits good H2 separation performance and inherent catalytic activity, making it a promising candidate as a membrane reactor in the simultaneous catalytic reforming of hydrocarbons and H2 separation. In this work, nickel hollow fiber membranes were fabricated using a spinning/sintering technology and subsequently employed in a membrane reactor for toluene steam reforming and H2 separation. The catalytic H2 production and permeation performance of the toluene steam reforming (TSR) hollow fiber membrane reactor were investigated under varying conditions, such as temperature, feed flow rate, steam-to-carbon ratio (S/C). The results show that toluene can be fully converted with a toluene feed flow rate of 1.5 μL min−1. Increasing S/C can enhance the H2 production, but excessive steam will lead to a decrease of the H2 permeation flux. The H2 yield and H2 permeation flux are 24.2% and 4.35 mmol m−2 s−1, respectively, under the conditions of S/C = 3, Ar = 90 mL min−1 and N2 = 3 mL min−1 at a temperature of 950 °C. The H2 yield and H2 permeation flux of the TSR membrane reactor did not significantly decrease within 96 h. In addition, the membrane reactor can operate stably within 62 h in an atmosphere containing 1000 ppm H2S.

Low-temperature Cu/Zn/SBA-16 integrating carbon membrane reactor for hydrogen production and high CO conversion through water-gas shift reaction

The increasing demand for H2 energy has led to a great amount of research being conducted in a membrane reactor (MR), in which a membrane is applied during the water-gas shift (WGS) reaction. In this study, Cu/Zn/SBA-16 WGS catalysts and carbon molecular sieve (CMS) membranes were integrated into CMS MRs. To improve the CO conversion and H2 yield, C MRs were investigated, and different steam/CO (S/C) ratios were used to evaluate the conversion performance. In this study, a tubular CMS membrane was used as the membrane material for a MR. The as-prepared CMS membrane exhibited excellent selectivity of 185.64 for H2 and CO2 mixed gas, and an ideal H2 permeability of 9.7 × 10−9 mol m−2 s−1 Pa−1 when operated under low temperature/pressure conditions (300 °C/3 bar). The Cu/Zn/SBA-16 catalyst synthesized via coprecipitation was used in the WGS reaction. With a relatively low reaction temperature of 300 °C, 2500 h−1 gas hourly space velocity, and S/C equal to 1.5, the CO conversion efficiency of MR could reach up to 99%, and the recovery of H2 was approximately 76%. However, as the S/C increased to 2, the H2 recovery increased to 99%, whereas the CO conversion decreased to 89% because of the water vapor adsorbed on the active site. The hydrophobic Si/C-modified membrane was further synthesized and showed outstanding performance in CO conversion of over 99% with S/C equal to 2.

A Review of the CFD Modeling of Hydrogen Production in Catalytic Steam Reforming Reactors

Global demand for alternative renewable energy sources is increasing due to the consumption of fossil fuels and the increase in greenhouse gas emissions. Hydrogen (H2) from biomass gasification is a green energy segment among the alternative options, as it is environmentally friendly, renewable, and sustainable. Accordingly, researchers focus on conducting experiments and modeling the reforming reactions in conventional and membrane reactors. The construction of computational fluid dynamics (CFD) models is an essential tool used by researchers to study the performance of reforming and membrane reactors for hydrogen production and the effect of operating parameters on the methane stream, improving processes for reforming untreated biogas in a catalyst-fixed bed and membrane reactors. This review article aims to provide a good CFD model overview of recent progress in catalyzing hydrogen production through various reactors, sustainable steam reforming systems, and carbon dioxide utilization. This article discusses some of the issues, challenges, and conceivable arrangements to aid the efficient generation of hydrogen from steam reforming catalytic reactions and membrane reactors of bioproducts and fossil fuels.

Stable Ce0.8Gd0.2O2-δ oxygen transport membrane reactor for hydrogen production

Hydrogen production using oxygen transport membrane reactors has attracted widespread attention. However, the structural stability of membrane materials under harsh reducing atmospheres is still a significant challenge. Gadolinium doped cerium oxide (CGO) presents high ionic conductivity and good reducing resistance but is limited by its poor electronic conductivity. Herein, a 2 mol.% cobalt-doped Ce0.8Gd0.2O2-δ (CoCGO) ultrathin membrane was manufactured by thin-film technology and applied to hydrogen production from water splitting (WS) with simultaneous syngas production through partial oxidation of methane (POM). Two catalysts, La0.4Sr0.6CoO3-δ (LSC) and Ni/Al2O3, were utilized for promoting WS and POM, respectively. Hydrogen production rate above 1.8 mL min-1 cm-2 and methane conversion of around 80 % were achieved, and no noticeable degradation was detected during 100 h operation, suggesting its prospective stability advantages as a membrane reactor for hydrogen production from water.

Toward Minimal Complexity Models of Membrane Reactors for Hydrogen Production.

Membrane reactors are inherently two-dimensional systems that require complex models for an accurate description of the different transport phenomena involved. However, when their performance is limited by mass transport within the reactor rather than by the selective product permeation across the membrane, the 2D model may be significantly simplified. Here we extend results previously found for methane steam reforming membrane reactors to show that such simplified two-dimensional model admits either a straightforward analytical solution for the cross-section averaged concentration profile, or can be reduced to a 1D model with an enhanced Sherwood number, depending on the stoichiometry of the reaction considered. Interestingly, the stoichiometry does not affect the expression of the enhanced Sherwood number, indicating that a versatile tool has been developed for the determination of membrane reactor performance at an extremely low computational cost and good degree of accuracy.

CFD analysis and scale up of a baffled membrane reactor for hydrogen production by steam methane reforming

Catalytic membrane reactor (CMR) represents an intensified process that combines the reaction and separation steps. For a high level of productivity, multiple membrane tubes are placed in a CMR, which can lead to the problem of concentration and temperature gradients. This study explores the idea of placing baffles inside the CMR, which is called baffled membrane reactor (BMR). Representative CMR and BMR are compared using computational fluid dynamics (CFD) simulations. First, the CFD model of a single-tube CMR is validated with the published experimental data. The results for a 4-tube CMR and BMR (with 14-baffles) reveal that the baffles lead to complex flow patterns, regions with elevated pressure, reduced concentration gradients and reduced temperature drops. The BMR’s performance is less sensitive to an increase in gas hourly space velocity than that of the CMR. Simulations of a larger-scale BMR shows that the performance improvement over the CMR is retained.

Optimization and improvement of a conventional tri-reforming reactor to an energy efficient membrane reactor for hydrogen production

This study represents a numerical investigation of methane tri-reforming process with full computational fluid dynamics (CFD) in a conventional and a novel membrane fixed-bed reactor. A 2-D non-isothermal axisymmetric model is stablished to analyze the influence of relevant parameters. Three single objective optimization are conducted to maximize the H2 purity, energy efficiency and CO2 conversion, individually. The decision variables are the molar ratios of CO2/CH4, H2O/CH4 and O2/CH4 and the reactor inlet temperature. The optimization results indicate that the maximum value of energy efficiency in the conventional reactor is 73.29%. Moreover, when the H2 purity is maximum, the energy efficiency is almost 2% lower than its maximum value. Therefore, the novel membrane reactor is simulated using the first optimal conditions to achieve an energy efficient process for H2 production. A “hot-spot”, which is beneficial for the high endothermic reactions, is observed near the reactor entrance. It is proved that the hotter and greater “hot-spot” is in favor of the H2 production and energy efficiency. The counter-current configuration is more efficient due to its higher “hot-spot”. Finally, it is found that as the sweep gas velocity increases, the H2 purity and H2 recovery increase due to the “hot-spot” increment.

Study of Static and Dynamic Behavior of a Membrane Reactor for Hydrogen Production

The paper investigates the stability and bifurcation phenomena that can occur in membrane reactors for the production of hydrogen by ammonia decomposition. A simplified mixed model of the membrane reactor is studied and two expressions of hydrogen permeation are investigated. The effect of the model design and operating parameters on the existence of steady state multiplicity is discussed. In this regard, it is shown that the adsorption-inhibition effect caused by the competitive adsorption of ammonia can lead to the occurrence of multiple steady states in the model. The steady state multiplicity exists for a wide range of feed ammonia concentration and reactor residence time. The effect of the adsorption constant, the membrane surface area and its permeability on the steady state multiplicity is delineated. The analysis also shows that no Hopf bifurcation can occur in the studied model.

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

The most widely used process for hydrogen production is steam methane reforming. It can be carried out using a membrane reactor in which simultaneous hydrogen production and purification occur. Mathematical modeling of these reactors plays a key role in the selection of the design and operating parameters that yield high performance for the reactor. This review study discusses, synthesizes, and compares different mathematical modeling studies on the packed bed membrane reactors for hydrogen production from methane found in the literature. Different approaches used in these modeling studies for the hydrogen permeation steps, reaction kinetic expressions, phases involved (pseudo-homogeneous and heterogeneous), and spatial dimensions (one, two, and three dimensional) are given.

Barium Titanate as a Highly Stable Oxygen Permeable Membrane Reactor for Hydrogen Production from Thermal Water Splitting

Hydrogen production from water splitting by a mixed ionic-electronic conducting membrane is an efficient and promising technology; however, it is severely impeded by the poor reduction tolerance of the existing cobalt- or iron-containing membrane materials. In this work, a novel BaMg0.1Zr0.05Ti0.85O3−δ (BMZ-Ti) perovskite was synthesized by combining citric acid and ethylenediaminetetraacetic acid methods. The new membrane is characterized by its superior chemical stability in a wet H2 atmosphere as well as with environment-responsive mixed conductivity, generating from the mild reduction of Ti4+ at low oxygen partial pressure. Benefiting from these combined properties, the BMZ-Ti membrane showed an oxygen permeation flux larger than 0.3 mL min–1 cm–2 under a H2O/(CH4–CO2) gradient, more than 50 times larger than that under an air/He gradient, which was able to be used for coupling methane reforming with water dissociation to efficiently produce hydrogen with a production rate of 0.8 mL min–1 cm–2. Furthermore, no performance degradation was observed during an over 100 h test. These results highlight the potential of the BMZ-Ti membrane, with both environment-responsive mixed conductivity and excellent chemical stability, as a novel oxygen permeable membrane for hydrogen production from water.

Experimental validation of a pilot membrane reactor for hydrogen production by solar steam reforming of methane at maximum 550 °C using molten salts as heat transfer fluid

An innovative steam reformer for hydrogen production at temperatures lower than 550 °C has been developed in the EU project CoMETHy (Compact Multifuel-Energy To Hydrogen converter). The steam reforming process has been specifically tailored and re-designed to be combined with Concentrating Solar plants using “solar salts”: a low-temperature steam reforming reactor was developed, operating at temperatures up to 550 °C, much lower than the traditional process (usually > 850 °C). This result was obtained after extensive research, going from the development of basic components (catalysts and membranes) to their integration in an innovative membrane reformer heated with molten salts, where both hydrogen production and purification occur in a single stage. The reduction of process temperatures is achieved by applying advanced catalyst systems and hydrogen selective Pd-based membranes. Process heat is supplied by using a low-cost and environmentally friendly binary NaNO3/KNO3 liquid mixture (60/40 w/w) as heat transfer fluid; such mixture is commonly used for the same purpose in the concentrating solar industry, so that the process can easily be coupled with concentrating solar power (CSP) plants for the supply of renewable process heat. This paper deals with the successful operation and validation of a pilot scale reactor with a nominal capacity of 2 Nm3/h of pure hydrogen from methane. The plant was operated with molten salt circulation for about 700 h, while continuous operation of the reactor was achieved for about 150 h with several switches of operating conditions such as molten salts inlet temperature, sweep steam flow rate and steam-to-carbon feed ratio. The results obtained show that the membrane reformer allows to achieve twice as high a conversion compared to a conventional reformer operating at thermodynamic equilibrium under the same conditions considered in this paper. A highly pure hydrogen permeate stream was obtained (>99.8%), while the outlet retentate stream had low CO concentration (<2%). No macroscopic signs of reactor performance loss were observed over the experimental operation period.

Exploration of ceramic supports to be used in membrane reactors for hydrogen production and separation

The objective of this study is to develop ceramic supports employed in the preparation of catalytic membrane reactor using less catalyst and lower temperature and enabling H2 production and separation together through the dry reforming of methane. For this reason, nine different ceramic supports are fabricated by using three different types of activated alumina (acidic, basic and neutral) and three different Si/Al molar ratios at two different calcination temperatures in order to investigate the surface acidity and basicity effect of supports to be used with impregnated Rh catalyst for rising the activity to CH4, CO2 and sensitivity to coke formation encountered with Ni-based catalysts. Subsequently, the effect of those variations on supports is determined by using XRD, SEM and BET instruments, in addition to this, H2 permeability test of five supports having high BET surface areas is also performed with using constant volume-variable pressure technique at the temperatures of between 25 and 250 °C. Acidic alumina sintered at 600 °C and containing Si/Al ratio of 0.648 represented the highest hydrogen permeability with higher activity, whereas, neutral alumina calcined at the temperature of 600 °C having Si/Al ratio of 0.555 gave the highest activity with the lower hydrogen permeability, while basic alumina sintered at the temperature of 600 °C and including Si/Al ratio of 0.648 imparted lower activity with higher hydrogen permeability.

Sensitivity analysis and optimization of a membrane reactor for hydrogen production through methane steam reforming

Hydrogen is one of most studied sources for clean power generation in the near future. Nowadays, hydrogen is mainly produced through methane steam reforming in packed bed reactors, with a promising alternative to this technology being the implementation of hydrogen-selective membrane reactors. This work compares the isothermal mathematical models of both designs by assessing the effects of multiple design variables on methane conversion, while also providing recommended operating conditions for maximum efficiency of the membrane reactor over the packed bed technology. Additionally, an optimization study is carried by dividing the reactor length in isothermal segments to achieve higher efficiency. Results showed that the membrane technology considerably increases hydrogen production, with temperature being the most influential variable on methane conversion. While the temperature profile optimization provided similar conversions compared to the isothermal models, the membrane reactor’s efficiency was increased, further justifying its implementation.

Tube-wall catalytic membrane reactor for hydrogen production by low-temperature ammonia decomposition

Ammonia has attracted great interest as a chemical hydrogen carrier. However, ammonia decomposition is limited kinetically rather than thermodynamically below 400 °C. We developed a tube-wall catalytic membrane reactor that could decompose ammonia with high conversion even at temperatures below 400 °C. The reactor had excellent heat transfer characteristics, and thus nearly 100% conversion for an NH3 feed of 10 mL/min at 375 °C was achieved with a 2-μm-thick palladium composite membrane, and hydrogen removal from the decomposition side resulted in a large kinetic acceleration.

ANOVA analysis of an integrated membrane reactor for hydrogen production by methane steam reforming

Steam methane reforming is an endothermic reaction and it used to produce hydrogen and syngas. In this research, a factorial design is developed for an integrated Pd-based membrane reactor, producing hydrogen by methane steam reaction. In literature, no analogous works are present, because a simple sensitivity analysis is carried out without finding significant factors for the process. The reactor is modelled in MATLAB software using the Numaguchi kinetic. The reactor does not use conventional catalysts, but a Ni(10)/CeLaZr catalyst supported on SSiC ceramic foam. In ANOVA analysis, inlet temperature (550 K-815 K), methane flow rate in the feed (0.1 kmol/h-1 kmol/h), hydrogen permeability (1000 m3μmm−2hrbar0.5–3600 m3μmm−2hrbar0.5), the thickness of membrane (0.003 m-0.02 m) are the chosen factors. The analyzed responses are: hydrogen yield, carbon dioxide conversion and methane conversion. Results show that only inlet temperature, methane flow rate, their interaction and the thickens of membrane are significant. Also, the optimal operating conditions are obtained with inlet temperature, methane flow rate, hydrogen permeability and thickness of membrane equal to 550 K, 0.1 kmol/h, 3600 m3μmm−2hrbar0.5 and 0.003 m.

Module design of silica membrane reactor for hydrogen production via thermochemical IS process

The potential of the silica membrane reactors for use in the decomposition of hydrogen iodide (HI) was investigated by simulation with the aim of producing CO2-free hydrogen via the thermochemical water-splitting iodine-sulfur process. Simulation model validation was done using the data derived from an experimental membrane reactor. The simulated results showed good agreement with the experimental findings. The important process parameters determining the performance of the membrane reactor used for HI decomposition, namely, reaction temperature, total pressures on both the feed side and the permeate side, and HI feed flow rate were investigated theoritically by means of a simulation. It was found that the conversion of HI decomposition can be improved by up to four times (80%) or greater than the equilibrium conversion (20%) at 400 °C by employing a membrane reactor equipped with a tubular silica membrane. The features to design the membrane reactor module for HI decomposition of the thermochemical iodine-sulfur process were discussed under a wide range of operation conditions by evaluating the relationship between HI conversion and number of membrane tubes.

Life Cycle Assessment and Economic Analysis of an Innovative Biogas Membrane Reformer for Hydrogen Production

This work investigates the environmental and economic performances of a membrane reactor for hydrogen production from raw biogas. Potential benefits of the innovative technology are compared against reference hydrogen production processes based on steam (or autothermal) reforming, water gas shift reactors and a pressure swing adsorption unit. Both biogas produced by landfill and anaerobic digestion are considered to evaluate the impact of biogas composition. Starting from the thermodynamic results, the environmental analysis is carried out using environmental Life cycle assessment (LCA). Results show that the adoption of the membrane reactor increases the system efficiency by more than 20 percentage points with respect to the reference cases. LCA analysis shows that the innovative BIONICO system performs better than reference systems when biogas becomes a limiting factor for hydrogen production to satisfy market demand, as a higher biogas conversion efficiency can potentially substitute more hydrogen produced by fossil fuels (natural gas). However, when biogas is not a limiting factor for hydrogen production, the innovative system can perform either similar or worse than reference systems, as in this case impacts are largely dominated by grid electric energy demand and component use rather than conversion efficiency. Focusing on the economic results, hydrogen production cost shows lower value with respect to the reference cases (4 €/kgH2 vs 4.2 €/kgH2) at the same hydrogen delivery pressure of 20 bar. Between landfill and anaerobic digestion cases, the latter has the lower costs as a consequence of the higher methane content.