Gas Separation Systems Research Articles

Computational Analysis of Permeance Prediction for Gas Separation Membrane Using Countercurrent Flow Model

Gas separation polymeric membranes have gained significant attention in various industries, including gas processing, petrochemicals, and environmental applications. Accurately predicting the permeance of these membranes is crucial for optimizing their design and performance. This paper presented a numerical prediction model for the permeance of a binary gas mixture under various process conditions, using only algebraic equations to minimize the calculation effort. The model considers input parameters such as feed and permeate flow rates, feed pressure, feed and permeate mole fraction, and membrane area. It demonstrates the behavior of permeance and selectivity in this study. The study also presented two case studies that utilize predicted selectivity to model counter-current flow and compare the results with experimental data from the literature. The first case study involves recovering helium from natural gas using an asymmetric high-flux membrane. The second case study separates air using nano-porous carbon as the membrane material. The numerical analysis successfully accurately predicted the permeance of gas separation polymeric membranes. The model accounted for variations in membrane thickness, feed composition, and operating conditions, providing valuable insights into the overall performance of the membrane system. It also allowed for the optimization of membrane design and operational parameters to enhance separation efficiency and productivity. The study showcased the effectiveness of numerical techniques in accurately predicting membrane performance. The developed model can be a valuable tool for membrane designers and engineers, enabling them to optimize the design and operation of gas separation systems.

Improving gas separation performance by boron nitride nanotubes

The performance of boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs) in multiple gas separation systems was systematically compared using molecular simulation methods. Findings reveal that under conditions of 298 K and 2 MPa, BNNTs generally show higher adsorption selectivities than CNTs for CH4/N2, CO2/CH4, and CO2/N2 mixtures. Notably, in the CO2/CH4 system, BNNTs exhibit a selectivity of up to 350 at a radius of 0.48 nm, significantly surpassing the 14 observed for CNTs; in the CO2/N2 system, selectivity can reach as high as 969 for BNNTs, contrasting with the 69 for CNTs. Furthermore, BNNTs achieve saturation adsorption for CF4 at 0.04 MPa with a capacity of 2.7 mmol/g, while CNTs show a higher adsorption capacity for N2, reflecting the superior selective adsorption capability of BNNTs for specific gases. Analysis of nanotubes with different chiral configurations led to the recommendation of (11,11) and (7,7) chiralities as optimal structures for efficient gas separation. Fluctuations in energy contributions from fluid-wall interactions in BNNTs, are closely related to their selectivity fluctuations. The results demonstrate that BNNTs, due to their unique structural characteristics, possess significant potential in the field of gas adsorption and separation, particularly in enhancing the selective adsorption of CO2 and CF4.

Membrane Separation Technology in Direct Air Capture.

Direct air capture (DAC) is an emerging negative CO2 emission technology that aims to introduce a feasible method for CO2 capture from the atmosphere. Unlike carbon capture from point sources, which deals with flue gas at high CO2 concentrations, carbon capture directly from the atmosphere has proved difficult due to the low CO2 concentration in ambient air. Current DAC technologies mainly consider sorbent-based systems; however, membrane technology can be considered a promising DAC approach since it provides several advantages, e.g., lower energy and operational costs, less environmental footprint, and more potential for small-scale ubiquitous installations. Several recent advancements in validating the feasibility of highly permeable gas separation membrane fabrication and system design show that membrane-based direct air capture (m-DAC) could be a complementary approach to sorbent-based DAC, e.g., as part of a hybrid system design that incorporates other DAC technologies (e.g., solvent or sorbent-based DAC). In this article, the ongoing research and DAC application attempts via membrane separation have been reviewed. The reported membrane materials that could potentially be used for m-DAC are summarized. In addition, the future direction of m-DAC development is discussed, which could provide perspective and encourage new researchers' further work in the field of m-DAC.

Understanding the performance of RHO type zeolite membrane for CH4/N2 separation based on molecular dynamics and deep neural network methods

This study shows a molecular dynamics (MD) simulation study on the performance of the RHO zeolite membrane for separating nitrogen from methane/nitrogen gas mixtures. The contamination of natural gas, predominantly composed of methane, with nitrogen diminishes its value. Zeolite membranes offer promising prospects for gas separation due to their stability, rigid pore structure, and molecular sieving properties. The study investigates the impact of pressure difference (up to 30 MPa), feed composition, and membrane thickness on the separation rate at a system temperature of 298 K. Results demonstrate that the RHO zeolite membrane exhibits high permeability and selectivity for N2 separation, surpassing the upper limit defined by Robson with a maximum permeability of 2.14 × 105 GPU (Gas Permeation Units). Exceptional selectivity of N2 over CH4 molecules is observed. Additionally, altering the feed composition and membrane thickness positively influences the membrane's separation performance, thereby enhancing its efficiency. The findings contribute to the advancement of separation technologies, providing valuable insights into the potential application of zeolite membranes for efficient N2 separation from CH4/N2 gas mixtures in natural gas processing. Furthermore, the study explores the use of Deep Neural Network (DNN) models to predict the membrane's performance under diverse operating conditions. The DNN models, trained using simulation data from MD simulations, exhibit high accuracy with a coefficient of determination (R2) exceeding 0.9, ensuring reliable predictions. The integration of DNN models facilitates the optimization of zeolite membrane-based gas separation systems, improving their design and operation.

Understanding the Heat Transfer Performance of Zeolitic Imidazolate Frameworks upon Gas Adsorption by Molecular Dynamics Simulations.

Metal-organic frameworks (MOFs) with ultrahigh specific surface area and porosity have emerged as promising nanoporous materials for gas separation, storage, and adsorption-driven thermal energy conversion systems such as adsorption heat pumps. However, an inadequate understanding of the thermal transport of MOFs with adsorbed gases hampers the thermal management of such systems in practical applications. In this work, an in-depth investigation on the mechanistic heat transfer performance of three topological zeolitic imidazolate frameworks (ZIFs) upon hydrogen, methane, and ethanol adsorption was carried out by molecular dynamics simulations. It is revealed that the trade-off between the additional heat transfer pathway and phonon scattering resulting from adsorbed gases determines the thermal conductivity of ZIFs. It is found that the increased thermal conductivity with the increased number of adsorbed gases is correlated with the overlap energy between the vibrational density of states of gases and Zn atoms, suggesting the additional heat transfer pathways formed between gas molecules and frameworks. Moreover, the gas spatial distribution and diffusion also impose remarkable impacts on the heat transfer performance. Both the homogeneous gas distribution and the fast gas diffusion are conducive to form effective heat transfer pathways, leading to enhanced thermal conductivity. This study provides molecular insight into the mechanism of the improved thermal conductivity of ZIFs upon gas adsorption, which may pave the way for effective thermal management in MOF-related applications.

Research on Erosion Characteristics of the Sleeve-Type Blowdown Valve in the Shale Gas Gathering and Transportation Station

Summary In the shale gas separation and sewage system, the separator removes the sand and sewage in the produced gas and releases the sand-carrying sewage to the blowdown pipeline. As an important throttling component in this system, the sleeve-type blowdown valve is severely eroded during operation. To address the problem, this paper carries out numerical research on the erosion characteristics during the real opening and closing process of the sleeve-type blowdown valve based on the FLUENT fluid simulation software. The change of the erosion at different velocities, sand mass flow, sand size, and shape coefficient is analyzed, and the main factor affecting the erosion characteristics is evaluated. Based on the above research, a novel blowdown valve is proposed, and the erosion characteristics and flow performance before and after improvement are compared. The results show that when the velocity is 8 m/s, the maximum erosion rate after improvement is 4.79×10−5 kg/(m2·s). Compared with the maximum erosion rate before improvement of 1.22×10−2 kg/(m2·s), the erosion inhibition rate reaches 99.6%. Moreover, the pressure loss is obviously reduced after the improvement, and the flow capacity is enhanced. This provides useful guidance for the improvement of blowdown valves and ensures the safe operation of shale gas production.

Gas-permeable fluorine-substituted poly(diphenylacetylene)s: Effect of number and position of fluorine atoms on gas permeability

Poly(diphenylacetylene)s are ideal for fabricating gas-permeable membranes in gas separation systems. We previously reported the superior gas permeability of fluorine-substituted poly(diphenylacetylene)s compared to their fluorine-free counterparts. In this study, novel poly(diphenylacetylene)s were synthesized by varying the number of fluorine atoms from three to five in the repeating unit (2a, 2b, and 2c). Comparing the gas permeability for 2a–c, the highest value was achieved for poly(diphenylacetylene) with three fluorine atoms in a repeating unit (2a). The oxygen permeability coefficient was 8,100 barrers for 2a, remarkably higher than that of the previously reported poly(diphenylacetylene) with two fluorine atoms in the repeating unit. The density and X-ray diffraction analyses revealed a decrease in the free volume of the membranes with an increase in the number of fluorine atoms. Additionally, 2a–c did not show desilylation because the trimethyl silyl groups were substituted on the benzene ring possessing an electron-withdrawing fluorine atom.

Analysis of Factors Causing Air Pollution on Ships

Air pollution on ships is a serious problem that can affect human health, the environment, and the operational safety of the ship itself. The aim of this study is to identify and understand the factors that contribute to air pollution on ships, as well as provide a better understanding of its impact on human health and the environment. This study used the research method of literature review. Data collection techniques are carried out by literature studies, data obtained through Google Schoolar. The results showed that poor air quality inside the ship can be caused by exhaust emissions from the engine, inefficient fuel use, the presence of an inadequate exhaust gas separation system, shipping in traffic-heavy areas or routes often used by large ships, fuel combustion processes, and weather factors. The impact of air pollution on human health includes respiratory disorders, cardiovascular disorders, to skin health problems. While the impact on the environment includes air pollution in the port area, water pollution, and soil pollution.

Development of new technological processes based on supersonic flow of natural gas

The article is devoted to the study of supersonic movement of natural gas in a pipeline and the possibility of developing new technological processes for cooling, drying and separating liquid hydrocarbons. Technological processes and a set of equipment created using the supersonic movement of natural gas are studied, their advantages and disadvantages are analyzed. It is known that a change in the process of gas injection into UGS facilities in a wide range of pressure during the season creates opportunities for more efficient use of compressor equipment. The thermobaric parameters of gas cooling due to supersonic motion in various designs have been calculated, and the existence of ample opportunities for creating new technological processes has been proved. Recommendations have been developed on the throughput capacity of gas installations to ensure the regulation of cooling systems created for underground gas storage facilities. It was noted that the cooling and gas separation systems created on the basis of thermobaric parameters and principles of regulation will be useful not only for underground gas storages, but also for other sub-sectors of the gas industry. Keywords: natural gas; supersonic movement; laval nozzle; underground gas storage; gas cooling; separation; compressor.

(Invited) Electrochemical Gas Separation

Electrochemical gas separators are electrically powered systems that selectively remove a targeted gas species from a mixture of gases by virtue of electrochemical reactions. Electrochemical separation is an attractive option owing to its higher efficiency and lower cost compared to incumbent technologies like pressure swing adsorption, cryogenic processes, and selective permeation. This work focuses on two specific electrochemical separation processes – (1) separation of hydrogen from a mixture of gases to help develop the hydrogen distribution infrastructure, and (2) nitrogen separation from air for aircraft fuel tank inerting.Reductions in CO2 emission since the beginning of this century by the US electric power sector are mainly attributed to the replacement of coal by natural gas in power plants. Nevertheless, the combustion of natural gas still contributes heavily to global warming and climate change. It is imperative to find alternatives to combustion-based energy technologies and nurture the growth of renewable energy systems. In this scenario, hydrogen is a leading candidate as a carbon-free fuel with high energy density and is expected to play a key role in future energy systems. However, hydrogen faces serious obstacles in its distribution due to the lack of a nationwide hydrogen pipeline network. Developing a dedicated hydrogen pipeline network will be quite expensive, therefore, it is worthwhile to examine whether existing natural gas pipelines could be effectively deployed for hydrogen distribution. This would be accomplished by directly injecting a prescribed amount of hydrogen at the point of production into a natural gas pipeline. Such a mixture of hydrogen and methane is labeled as hythane. While this enables the convenient transport of hydrogen across large distances, the process can only be completed by separating hydrogen from methane at the destination point. Electrochemical hydrogen separation (ECHS) systems built around proton-selective polymer electrolyte membranes (PEMs) represent an effective platform to separate and simultaneously compress hydrogen in a continuous operation. Furthermore, ECHS ensures that the resulting gas is not contaminated by lubrication oil as observed in conventional systems. In ECHS, the hythane mixture enters the anode compartment wherein the hydrogen is selectively dissociated to protons and electrons. The protons are then driven across the PEM by an externally applied voltage to recover hydrogen at the cathode.The first part of this study demonstrates hydrogen purification using low-temperature PEM-based ECHS from various gas mixtures including methane/hydrogen, carbon dioxide/hydrogen, water gas shift effluent, and hythane. ECHS performance is first investigated for pure hydrogen as a function of membrane thickness, cell temperature, and relative humidity of the anode stream. In the second set of experiments, various ratios of methane/hydrogen and carbon dioxide/hydrogen are introduced to examine the effect of hydrogen concentration in the feed gas mixture on ECHS performance. Finally, experiments are performed for hydrogen purification from a water gas shift (WGS) effluent mixture as well as a practical hythane gas feed. ECHS performance for all gas mixtures was benchmarked against the pure hydrogen case. The purity of the separated hydrogen gas was measured to confirm the effectiveness of the method. The results show that ECHS represents a good solution to separate hydrogen from the hythane mixture at the downstream end of the pipeline.Pertinent to the second electrochemical separation process examined here, after the TWA flight 800 disaster due to a fuel tank explosion in 1996, inerting of aircraft fuel tanks became a priority. During fuel tank inerting, an inert gas like nitrogen is supplied to the tank to reduce its flammability. An electrochemical gas separation and inerting system (EGSIS) is a device that generates nitrogen enriched air (NEA) from ambient air by the application of electrical power. EGSIS combines a PEM electrolyzer anode wherein water is dissociated to release oxygen, and a PEM fuel cell cathode where atmospheric air is converted to NEA. Aircraft tank inerting requires varying NEA flowrates (low during takeoff and ascent, and high during descent). In conventional hollow fiber membrane air separation modules typically used in current aircraft, the total membrane surface area is determined by the maximum required NEA flow rate which results in large and expensive modules. On the other hand, the NEA flow rate can be easily controlled in EGSIS by simply adjusting the applied voltage. This portion of the study focuses on results for a single EGSIS cell and its optimization. Various EGSIS stack configurations are also described in order to develop a practical system. Finally, a techno-economic analysis of EGSIS is presented to show that EGSIS can compete favorably with incumbent technologies in terms of fuel usage and cost.

Optimization of an Electrochemical Gas Separation and Inerting System

Aircraft fuel tank inerting is typically accomplished by supplying nitrogen enriched air (NEA) into the ullage (volume of air above the fuel level in the tank). We have developed a novel on-board electrochemical gas separation and inerting system (EGSIS) to generate NEA for fuel tank inerting. EGSIS is an electrically powered system that functionally combines a proton exchange membrane (PEM) fuel cell cathode with an electrolyzer anode. Water management is important in such a PEM-based system because proton transfer requires proper hydration of the membrane. Extremes of both dryout and flooding conditions should be avoided for optimal EGSIS performance. Previous single-cell EGSIS experiments revealed that supplying liquid water at the anode will maintain sufficient membrane hydration even when the system is operated under dry cathode conditions. However, it was difficult to avoid flooding at low cathode air stoichiometries when parallel flow field channels were employed. Here, we implement various strategies to optimize EGSIS performance such as using serpentine and interdigitated flow field channels, as well as a double-layer gas diffusion layer with graded hydrophobicity to mitigate flooding and improve water management. We also present a theoretical analysis of various stack configurations for a practical EGSIS module.

Assessing Chemical Migration from Plastic Food Packaging into Food Simulant by Gas and Liquid Chromatography with High-Resolution Mass Spectrometry.

Some components of plastic food packaging can migrate into food, and whereas migration studies of known components are required and relatively straightforward, identification of nonintentionally added substances (NIAS; unknowns) is challenging yet imperative to better characterizing food safety. To this aim, migration was investigated across 24 unique plastic food packaging products including plastic wrap, storage bags, vacuum bags, and meat trays. Gas and liquid chromatography separation systems coupled with Orbitrap mass analyzers were used for comprehensive nontargeted screening of migrants. Tentative identifications of features were assigned by searching commercial databases (e.g., NIST, MZCloud, ChemSpider, Extractables and Leachables) and filtering results based on mass accuracy, retention time indices, and mass spectral patterns. Several migrants showed elevated levels in specific food packaging types, particularly meat trays and plastic wrap, and varying degrees of migration over the 10 days. Eleven putative migrants are listed as substances of potential concern or priority hazardous substances. Additionally, migration amounts of an Irgafos 168 degradation product determined by semiquantitation exceeded proposed theoretical maximum migration values.

3D Computational Model for an Electrochemical Gas Separation and Inerting System

Aircraft fuel tank inerting is employed to reduce the flammability of the fuel vapor in the ullage (air volume above the fuel) by restricting its oxygen concentration to a safe value—12% for commercial aircraft and 9% for military aircraft. Inerting is typically accomplished by displacing oxygen in the ullage with an inert gas like nitrogen. Electrochemical gas separation and inerting system (EGSIS) is an on-board method to generate and supply nitrogen-enriched air (NEA) to the fuel tank. EGSIS combines a polymer electrolyte membrane (PEM) electrolyzer anode which dissociates water to evolve oxygen, and a PEM fuel cell cathode which reduces oxygen from atmospheric air to produce NEA at its outlet. This paper represents the first attempt to model and simulate EGSIS using a three-dimensional, steady state, isothermal model. Various EGSIS performance indicators such as current density, reactant concentration distribution, and polarization curves are studied as a function of operating conditions and design parameters. The results from the computational model are validated against our previous experimental results for various operating conditions. The simulation results reveal the effects of temperature, reactant flowrates, and material property optimization on EGSIS performance. Different operating strategies are explored with the goal of improving system performance.

Optimization of channel structure in micro networked gas separator utilizing the Soret effect

In recent years, hydrogen energy, which does not emit carbon dioxide when used, has been attracting attention as a candidate solution to environmental issues. Hydrogen is produced as a mixture of hydrogen and carbon dioxide or other gases, mainly using fossil fuel reforming. Therefore, in order to use hydrogen as an energy source, the gas mixture must be separated and purified to a high-purity hydrogen. The methods currently used require advanced technology, leading to increased costs. This research has developed a gas separation system utilizing the Soret effect, a thermal diffusion phenomenon caused by a temperature gradient, as a simple and low-cost method to extract hydrogen from a hydrogen and carbon dioxide mixture. Since the separation caused by the Soret effect is very small at one time, previous studies have employed network separation structures to achieve high efficiency. This time, we succeeded in improving the separation performance by optimizing the size of the partition structure inserted at the gas branching area.

Computational Model for Electrochemical Gas Separation and Inerting System

In July 1996, TWA flight 800 crashed into the Atlantic Ocean only 12 minutes after takeoff killing all 230 people on board. After a 4-year investigation into this catastrophe, the National Transportation Safety Board concluded that the accident was probably caused by the explosion of flammable fuel vapor in the Boeing 747’s center fuel tank. Following this landmark incident new regulations for aircraft fuel tank inerting were developed to prevent such explosions. Fuel tank inerting is the process of reducing the flammability of the fuel vapor by restricting the oxygen concentration in the ullage (air volume above the fuel) to a safe value – 12% for commercial aircraft and 9% for military aircraft. Generally, inerting is carried out by driving oxygen out the ullage using an inert gas like nitrogen.Existing inerting technologies include systems like liquid nitrogen, explosion suppressant foam, halon extinguishment, and on-board inert gas generation systems (OBIGGS). Compared to other techniques, OBIGGS is seen as viable option since nitrogen enriched air (NEA) can be produced during flight by supplying pressurized air into separation modules that preferentially retain nitrogen while allowing oxygen to escape. However, such systems are expensive and consume substantial amounts of energy, while also undergoing premature failure. Additionally, the NEA generation rate is fixed in such systems, whereas the actual NEA requirement depends on the aircraft’s flight stage. Thus, incumbent technologies are designed based on the highest demand making them overweight and expensive.Here, we propose a novel on-board electrochemical gas separation and inerting system (EGSIS) to overcome such problems. EGSIS is an electrically powered system that can be used to produce and supply NEA to the fuel tank. It combines a polymer electrolyte membrane (PEM) electrolyzer anode wherein water is dissociated to generate oxygen, and a PEM fuel cell cathode where oxygen from the inlet air inlet is reduced to produce humidified NEA as the output gas. After proper dehumidification, the NEA can be supplied directly to the ullage to reduce its oxygen concentration. Unlike current technologies, the NEA production rate in EGSIS can be easily varied with demand just by controlling the voltage applied to the system. Experimental investigations of EGSIS have been previously conducted by our group. This paper represents the first attempt to model and simulate EGSIS.We present a two-dimensional mathematical model of a single cell EGSIS that provides a foundation for the simulation and analysis of a full-scale EGSIS module. A single phase, two-dimensional, steady state, isothermal model is implemented in an EGSIS cell using COMSOL. Various EGSIS performance parameters such as current densities, reactant concentration distributions, and polarization curves are investigated as a function of operating voltage and temperature. The model involves the material properties of the various components including the polymer electrolyte membrane, the catalyst later and gas diffusion media; the transport of water vapor and air in the anode and cathode flow field channels, respectively; the transport of protons and water in the catalyst layer and the membrane; and the transport of electrical charge in the solid phase. The governing equations include continuity and steady-state incompressible Navier-Stokes equations. Additionally, species transport is modeled using the generalized Stefan-Maxwell equations whereas the Butler-Volmer equation is employed for charge transport. All of these coupled model equations are solved by the finite element method using the COMSOL Multi physics software package. The results from the computational model are then compared and validated with our experimental results for various operating conditions. Different operating strategies are explored with the goal of improving system performance. The simulated results reveal the influence of temperature, reaction flowrate, and optimized material properties on EGSIS performance. This model also provides a base for future research into the effect of alternate catalysts and gas diffusion media. It also serves as a foundation for the analysis of a practical EGSIS stack.

Holistic review on the recent development in mathematical modelling and process simulation of hollow fiber membrane contactor for gas separation process

Hollow fiber membrane contactor (HFMC) has been widely studied for gas separation process due to its process intensification capability of combining conventional contactors with membrane technology. In the area of modeling and simulation of HFMC, the development of mathematical model for non-ideal conditions, that is incorporated into process design is key to accurately reflect actual industrial gas separation process. This article aims to review the modelling and simulation techniques, the capabilities and the limitations of different mathematical models in predicting gas separation performance in HFMC for both laboratory analysis and industrial applications. The approach of incorporating the HFMC models into gas separation system and the current progress of process simulation works to develop industrial scale gas separation process will be highlighted. Future works and challenges towards developing comprehensive model in HFMC for industrial gas separation process would also be presented to portray the potential of modelling and simulation in designing and optimizing the HFMC system.

Slacking of Gate Adsorption Behavior on Metal-Organic Frameworks under an External Force.

As flexible metal-organic frameworks (MOFs) and their gate adsorption behaviors are increasingly expected to be used in gas storage and separation systems, evaluating their performance by considering their usage patterns in actual processes is becoming increasingly important. Herein, we show that the shaping of the elastic layer-structured MOF-11 (ELM-11; [Cu(BF4)2(4,4'-bipyridine)2]) into pellet forms using polymer binders smears its stepwise uptake associated with the CO2 gate adsorption. This is a critical problem because the superior adsorption properties of flexible MOFs are highly dependent on the sharpness of the step. Free energy analysis by molecular simulations revealed that the slacking of the gate adsorption is natural from a thermodynamic point of view. In other words, the external force exerted by the polymer binders, which prevents the expansion of MOF particles upon the gate opening, changes the free energy landscape of the system. This causes the flexible motifs within the MOF particles to undergo a structural transition at slightly different pressures from each other. The force profile dependence of the slacking phenomenon on both adsorption and desorption isotherms was also investigated. It was revealed that controlling the force profile applied to MOF particles is important to mold MOF pellets that satisfy the robustness and sharpness of the gate adsorption. Finally, we examined the coating of pellets to verify the relationship between the force profile and the degree of slacking and discussed possible strategies to improve the sharpness of the gate adsorption on MOF pellets considering the revealed mechanism.

Influence of external mass transfer and support resistances for hydrogen permeation through composite palladium membranes

AbstractPalladium membranes represent a suitable alternative to obtain high purity hydrogen for industrial applications. The modeling of hydrogen permeation through composite membranes is important to understand gas separation systems. Here, experimental and calculated hydrogen flux data through composite palladium/alumina membranes were compared. A dense palladium film of 2.4 μm thick was deposited on a porous support and the produced composite membrane presented infinite hydrogen/nitrogen selectivity. Experimental molecular hydrogen flux at 100 kPa and 723 K was 0.1015 ± 0.0009 mol m−2 s−1. Calculated molecular hydrogen fluxes with the conventional permeation model, without considering external mass transfer and support resistances, were at least 5.7 times greater than experimental data. However, calculated hydrogen flux was only 6.7% lower than the experimental flux at 100 kPa and 723 K when external mass transfer and support resistances were included in the conventional permeation model. Thus, external mass transfer resistances and the permeation through the porous support should be considered for a suitable description of hydrogen fluxes through composite palladium membranes.

High-performance Gas Separation System Using Gate-type Adsorbents

High-performance Gas Separation System Using Gate-type Adsorbents

Electrochemical gas separation and inerting system

Following the TWA 800 flight disaster in 1996 which was attributed to an explosion in the fuel tank, inerting of the ullage (air volume above the fuel in the tank) has gained prominence. Fuel tank inerting is the process of reducing the flammability of the ullage by supplying it with an inert gas like nitrogen. Current inerting techniques are expensive, consume large amounts of energy, and fail prematurely. Here, we propose a novel in-flight electrochemical gas separation and inerting system (EGSIS) to produce and supply nitrogen-enriched air (NEA). EGSIS combines a polymer electrolyte membrane (PEM) fuel cell cathode with a PEM electrolyzer anode to generate humidified NEA as the cathode output which can be dehumidified and supplied directly to the fuel tank. The required rate of NEA varies during a typical flight and a major advantage of EGSIS is that the rate of NEA generation can be conveniently controlled by varying the voltage applied to the system. Here, we report on the performance of a single-cell EGSIS apparatus and evaluate its suitability for aircraft fuel tank inerting.