Feed Pressure Research Articles

Comparative Performance Analysis of Catalysts for Syngas Production from Biogas: A Simulation Study Using DWSIM

This study explored how CH4/CO2 feed ratio, temperature, and pressure affect the conversion of carbon dioxide and methane and the H2/CO ratio of syngas using simulations for six catalysts: Rh/La2O3, Rh/La2O3-SiO2, Ru/La2O3, Ni-Co/Al-Mg-O, LaNiO3, and Ce-La-Ni-O2. Simulations with DWSIM© were conducted at CH4/CO2 feed ratios of 1–2, pressures of 1–5 bar, and temperatures of 550–750 °C. The effects showed that increasing the temperature by as much as 750 °C boosted the H2/CO ratio and improved CO2 and CH4 conversions because of the endothermic nature of the reactions. Higher pressure reduced conversion rates and H2/CO ratios across all catalysts, with a notable similarity between 2 and 5 bar, indicating thermodynamic limits. A higher feed ratio of CH4/CO2 decreased CH4 conversion while increasing the H2/CO ratio at the expense of reduced H2 yield. As the pressure decreases, the Ru/La2O3 and Rh/La2O3-SiO2 catalysts exhibited higher activity because of the kinetic factor. The current research focuses on the possibility of using dry reforming of biogas to synthesize syngas with suitable H2/CO ratios for different uses. The observations suggest that future studies should include techno-economic analysis to determine the least expensive catalysts that will ensure the dry reforming process yields the right composition of syngas.

Effects of extrusion process conditions on nutritional, anti‐nutritional, physical, functional, and sensory properties of extruded snack: A review

AbstractConsumers' demand for ready‐to‐eat extruded snack is increasing due to their convenience and time saving. Extrusion cooking is the most commonly used technology for manufacturing ready‐to‐eat snack products. However, improper management of extrusion parameters such as the barrel temperature, feed moisture content, pressure, and other parameters of the extruder can influence the quality of extruded snack foods. This paper aimed to review the effects of extrusion process conditions on the quality of the extruded snack. According to this review, most of the nutritional composition and anti‐nutritional factors are sensitive to the extruder's high barrel temperature. High barrel temperature decreased the anti‐nutritional factors of the extrudates. Low feed moisture content and high barrel temperature minimize the bulk density and hardness while increasing the extruded snack's expansion ratio and water solubility index. In contrast, low barrel temperature increased the color and appearance of the extrudates while decreasing the flavor and overall acceptability of the extrudates. In general, this review indicated that extrusion processing parameters need to be optimized to deliver nutrient‐rich extruded snack with appropriate physical, functional, and sensory properties.

Biogas purification using cellulose nanocrystals/polyvinyl alcohol coated facilitated transport hollow fiber membranes with L‐arginine as CO2 carrier

AbstractThe composition of biogas consists mainly of CH4 (~60%) and CO2 (40%). To be considered a clean fuel, CH4 concentration in biogas must be increased to over 95%. In this study, membranes which were stacked in a chamber were utilized to purify biogas by passing biogas over them. These membranes were composed of polyethersulfone hollow fiber substrate coated with a “selective layer” made of cellulose nanocrystals (CNC‐0–2 wt) in polyvinyl alcohol (PVA) and l‐arginine as a CO2 carrier. Of the different CNC concentrations in PVA‐LA, CNC1/PVA‐LA (1.0 wt% CNC in PVA‐LA) displayed the lowest water contact angle of 17° (corresponding to higher moisture absorbing ability). With further increase in CNC concentration, even though CNC1.5/PVA‐LA showed the higher crystallinity (66%), and water contact angle increased (20°); reducing the chances of facilitated transport of CO2 through it. Biogas separation experiments were conducted at 90% RH and different feed pressures (0.8–1 bar) for various CNC concentrations. Increasing the CNC concentration led to a thicker selective layer, enhancing the CO2 permeability and selectivity up to CNC1/PVA‐LA. However, with the further addition of CNC, both permeability and selectivity decreased. At 90% RH and 1 bar feed pressure, the CNC1/PVA‐LA setup demonstrated a CO2 permeability of 20,522 Barrer and a selectivity of 33, making it suitable for low‐pressure biogas storage systems with lower energy requirements.

Chitosan-polyethersulfone mixed matrix composite membranes utilizing amine and non-amine hafnium-MOFs for enhanced CO2 separation

Exploring the realm of advanced membranes with customizable separation capabilities holds great promise in CO2 separation. A particularly exciting path is the utilization of mixed matrix membranes (MMMs) to surpass the performance of commonly used polymeric membranes. In recent times, there has been a surge of interest in hafnium (Hf) metal–organic frameworks (MOFs) due to their multiple potential sites for CO2 adsorption. These MOFs feature four bridging hydroxyl groups (μ3-OH) positioned at the corners of the tetrahedral cavity, electronegative linker moieties, and Bronsted acid sites arising from undercoordinated metals. In this study, we synthesized task-specific UiO-66(Hf) and UiO-66-NH2(Hf) MOFs and integrated them into a chitosan (CS) matrix to explore their effects on CO2 separation performance of MMMs. Comprehensive analyses using various analytical techniques were conducted on synthesized MOFs and MMMs. At an optimal loading of 5 wt% of UiO-66-NH2(Hf) under humid conditions, the MMMs demonstrated a remarkable 408 % increment in CO2 permeance and a 113 % improvement in CO2/N2 selectivity compared to unfilled CS membranes. Notably, the UiO-66-NH2(Hf) MOF, enriched with amino ligands, exhibited superior dispersibility and enhanced CO2 separation ability compared to the UiO-66(Hf) MOF within the CS matrix. These findings not only approach the 2008 Robeson upper bound curve but also demonstrate consistency in the CO2 separation performance for over 120 hours of exposure at elevated temperatures (85°C) and a feed pressure of 2.21 bar under humid conditions. These challenging conditions, mirroring real-world applications, highlight the stability of the synthesized MMMs as efficient gas separation technologies.

Advanced Two-Stage Nanocomposite Membrane System for Methane and Carbon Dioxide Separation from Atmospheric Air

This paper presents an advanced two-stage nanocomposite membrane system designed to efficiently separate and capture methane (CH4) and carbon dioxide (CO2) from atmospheric air and water sources. The membrane system comprises a CO2-selective primary membrane and a CH4-selective secondary membrane, utilizing a hierarchical nanomaterials and polymers structure. The proposed system demonstrates unprecedented versatility, operating effectively across an extensive range of gas concentrations (>20% to <0.02%) and reducing CH4 levels from 100-500 ppm to 5-10 ppm in both aerobic and anaerobic conditions. Performance metrics specify CO2 permeances of 200-2000 GPU and CO2/N2 selectivities of 30-500 at 57 °C and 1 atm feed pressure, surpassing the Robeson upper bound for traditional polymer membranes. The CH4-selective membrane achieves 500-2000 GPU permeances with CH4/CO2 selectivities >50. Furthermore, experimental validation over 1000 hours of continuous operation demonstrated 92% methane capture efficiency under challenging conditions (55 tons/hour methane content at 30 °C). The system's energy consumption of 0.3 kWh/kg of CH4 captured underscores its efficiency compared to traditional methods. This innovative membrane technology offers a promising solution for addressing critical ecological and industrial challenges associated with greenhouse gas emissions in the 21st century.

Dehydration by Pervaporation of an Organic Solution for the Direct Synthesis of Diethyl Carbonate

Pervaporation has been a central subject in the research community within the scope of the further development of energy- and cost-efficient alternatives to conventional liquid–liquid separation technologies. The potential eligibility of four commercial membranes (ZEBREX ZX0, PERVAPTM 4155-80, PERVAPTM 4100, PERVAPTM 4101) for use in an integrated dehydration application of a diethyl carbonate/water/ethanol mixture by pervaporation was assessed experimentally. The impact of feed concentration, operating temperature, pressure, and sweep gas flow rate on membrane separation performance, including permeation flux, permeate quality, selectivity, and permeance, was thoroughly investigated. Applying the ZX0 membrane delivered the best qualities of all tested membranes of the permeate stream, with a water concentration of mostly >98%. In comparing the water flux, the ZX0 membrane remained reasonably competitive with the polymer membranes. Furthermore, the sweep gas volume flow rate and the operating temperature were identified as influencing the flux significantly but not the product composition. At the same time, the feed concentration of water also influenced the water purity within the permeate. The experiments were monitored with a partial least squares model, allowing a quick assessment of obtained samples while delivering accurate results.

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.

Influence of microbubble two-phase feed flow on reverse osmosis desalination using different salt concentrations

This study aims to implement microbubble two-phase flow in the feed stream to improve mass transfer and achieve improved reverse osmosis (RO) process performance. The swirl-flow microbubble generator (MBG), which can effectively generate microbubbles, is integrated into the conventional RO system and has experimentally proven its performance under various operating conditions. To investigate the influence of microbubbles in the feed stream on the RO process depending on the feed concentration, real seawater and two types of artificial brackish water were used as the feed solution. The formation of microbubble two-phase flows in the feed stream had a positive impact on the transmembrane flux and distillate water quality of the RO process; this demonstrates that improved mass transfer due to microbubbles introduced into the feed can effectively attenuate the concentration polarization effect in the RO process. MBG-RO performance using seawater as the feed solution was found to be more pronounced at lower feed pressures and higher airflow rates, with an improvement in permeation flux of up to 16 %. Meanwhile, the MBG contribution to RO performance was lower when using artificial brackish water with relatively low concentration than that when using seawater.

Simulation of a System to Simultaneously Recover CO2 and Sweet Carbon-Neutral Natural Gas from Wet Natural Gas: A Delve into Process Inputs and Units Performances

The growing need for carbon-neutral energy solutions necessitates the development of efficient systems for carbon dioxide (CO2) recovery and the production of sweet carbon-neutral natural gas (CNNG) from wet natural gas. Despite existing approaches, limitations in process optimization, solvent efficiency, and output purity persist. This study aims to address these gaps by simulating a system for simultaneous recovery of CO2 and CNNG using an integrated three-stage process, modeled in Aspen Plus V8.8. The unique aspect of this work lies in employing the ENRTL-RK base model, coupled with sensitivity analyses to optimize input parameters across 13 interconnected process units, including compressors, heat exchangers, and extraction columns. Key innovations include the novel configuration of units, yielding a recovery efficiency of 95.94% for CNNG and a CO2 purity of 93.185% at optimal conditions, surpassing conventional methods. The performance of the monoethanolamine (MEA) solvent was enhanced by careful adjustment of input parameters, improving its absorption efficiency by 12% compared to standard operational settings. Sensitivity analysis revealed critical parameters such as feed pressure and solvent flow rate as primary drivers for maximizing output efficiency. This study also provides a detailed quantitative assessment of power requirements, with a compressor brake horsepower (BHP) of 18,2605 watts at 110 bar discharge pressure. It addresses the existing research gap by introducing a systematic approach to process optimization, significantly improving the purity and recovery of CNNG and CO2 while minimizing energy consumption. The results not only demonstrate the viability of this process but also provide a foundation for further refinement in sustainable gas processing technologies.

Clarification of apple juice using cold plasma treated mixed cellulose esters membrane: flux modeling, membrane fouling, and juice physicochemical properties evaluation

This study aimed to clarify apple juice using unmodified and low-pressure cold plasma (gas: air, power: 10 W, and exposure time: 180 s) surface-modified mixed cellulose esters (MCE) microfiltration membranes. The effect of feed pressure (20, 40, and 60 kPa), feed flow rate (10, 15, and 20 mL/s), and feed temperature (27 and 40°C) on the permeate flux was evaluated using response surface methodology (RSM). The binary interaction of feed pressure and temperature and the second-order (non-linear) interaction of feed pressure and flow rate had a significant effect on the permeate flux (P<0.05). Generally, the process at 60 kPa, 15 mL/s, and 40 °C resulted in the maximum permeate flux. The cold plasma surface modification of the MCE membrane increased the permeate flux by about 45% at the optimum process conditions. Evaluation of membrane fouling showed that the cake formation was the predominant membrane fouling mechanism during both membrane processing. The physicochemical properties evaluation revealed that the surface-modified membrane produced clarified apple juice with antioxidant activity, reducing sugars, total sugars, phenolic, and vitamin C contents about 18.87%, 12.9%, 15.49%, 24.53%, and 45.15% more than clarified apple juice produced with unmodified MCE membrane, respectively.

Dim light at night unmasks sex-specific differences in circadian and autonomic regulation of cardiovascular physiology

Shift work and artificial light at night disrupt the entrainment of endogenous circadian rhythms in physiology and behavior to the day-night cycle. We hypothesized that exposure to dim light at night (dLAN) disrupts feeding rhythms, leading to sex-specific changes in autonomic signaling and day-night heart rate and blood pressure rhythms. Compared to mice housed in 12-hour light/12-hour dark cycles, mice exposed to dLAN showed reduced amplitudes in day-night feeding, heart rate, and blood pressure rhythms. In female mice, dLAN reduced the amplitude of day-night cardiovascular rhythms by decreasing the relative sympathetic regulation at night, while in male mice, it did so by increasing the relative sympathetic regulation during the daytime. Time-restricted feeding to the dim light cycle reversed these autonomic changes in both sexes. We conclude that dLAN induces sex-specific changes in autonomic regulation of heart rate and blood pressure, and time-restricted feeding may represent a chronotherapeutic strategy to mitigate the cardiovascular impact of light at night.

Highly plasticization-resistant Tröger’s base polymer–MOF mixed-matrix membranes for stable gas separation

The plasticization phenomenon, characterized by polymer chain swelling when exposed to highly soluble gas at high feed pressure, has been a major problem for polymer membranes. To address this, we prepared Tröger’s base (TB) polymer-based metal–organic framework (MOF) mixed-matrix membranes (MMMs), which are highly plasticization-resistant membranes. Three different highly porous MOF nanoparticles (ZIF-8, UiO-66-NH2, and MIL-101(Cr)) were prepared in small particle sizes. The corresponding MMMs were formed with a 30 wt% MOF loading to study the effects of MOF species, particle size, chemical functionality, and MOF–polymer interfacial interaction on gas-transport properties and plasticization behavior. The TB polymer-based MOF MMMs exhibited significantly higher H2 and CO2 permeabilities (fourfold to eightfold) than the TB polymer membrane owing to the porous nature and high gas adsorption capacity of the MOF. Additionally, the TB-based MOF MMMs, particularly the UiO-66-NH2 MMM, displayed exceptional CO2 plasticization resistance. This is attributed to the interfacial interaction of the strong hydrogen bonding between the amine group of the TB polymer and the amino group of UiO-66-NH2, as confirmed by small-angle X-ray scattering characterization. This TB polymer-based MOF MMM approach provides a feasible and effective route for enhancing gas-transport properties and CO2 plasticization resistance to achieve energy-efficient and stable gas separation.

Simulation and experimental demonstration of helium purification from He/N2 mixtures by pressure swing adsorption

Terrestrial helium is an indispensable non-renewable resource used in medicine, space, electronics, and nuclear research. This paper reports a high-pressure five-step pressure swing adsorption (PSA) cycle using Zeolite 5A for purification of He from dilute He/N2 mixtures. A Dual-Site Langmuir (DSL) model fitted both the low-pressure N2 and high-pressure N2 isotherm data. Dynamic column breakthrough (DCB) experiments were used to confirm volumetric equilibrium loadings. The DCB model predicted the experimental breakthrough curves for a wide range of feed compositions (100% N2, 74.5% N2, and 51.5% N2) and feed pressures (1 bar and 11.2 bar). A large experimental campaign studied the impact of various operating conditions on the He purity and recovery achievable from the PSA process. The study showed that a single-stage PSA experiment could enrich He up to 13% purity with greater than 90% recovery from a feed containing 1% He. Helium purity of 95% and a recovery of 90% can be achieved from a feed containing 10% He. All trends were predicted well by numerical simulations. A multi-objective optimization was performed to maximize helium purity and recovery for various He feed compositions. The study also showed that points from the Pareto curve can be realized experimentally.

The performance of nanofiltration membranes in seawater and desalination brine applications: Saudi Water Authority experience

The process of dual brine concentration employs an NF-RO-MBC configuration as its fundamental setup. Understanding the ion rejection capabilities of NF in seawater is crucial within this framework. Testing of fourteen commercial NF membranes using Jubail seawater revealed variations in ion rejection capabilities. Twelve membranes operated at a consistent feed pressure of 17.7 bar. The results categorized membranes based on their TDS rejection into high (≥ 45 %), medium (25–45 %), and low (< 25 %) rejection membranes. When concentrating the NF-treated SWRO brine, NF membranes can be utilized in the MBC system. Eight commercial NF membranes were evaluated with SWRO brine, where Na and Cl constituted over 96 % of the TDS. The investigation assessed the concentration performance and secured solid quantity in the reject relative to the feed by applying pressures of up to 40 bar for the conventional NF membranes and up to 65 bar for the newly introduced HPNF membranes. Among these membranes, two conventional and two HPNF membranes exhibited promise for concentrating SWRO brine. In addition, the ion rejection performance of five commercial NF membranes on SWRO brine was examined for a potential RO-NF-MBC configuration, suggesting suitable NF membranes for SWRO brine separation. Lastly, the ion rejection performance was studied in a multistage NF system with varying feed compositions at each stage and compared with projected performance. The accumulated NF membrane performance database will be utilized to optimize the overall membrane system configuration for seawater and brine separation and concentration.

Expanding interfacial polymerization for gas separation beyond water purification

Extending interfacial polymerization (IP) to gas separation is challenging due to microdefects in dry conditions, despite its attractive and straightforward processability. This study presents a systematic defect-tailoring approach for highly reproducible polyamide (PA) thin film composite (TFC) membranes with precise size-sieving ability. The approach combines highly porous polyethylene support, extended IP reaction time (60 min), and post-thermal/solvent treatments, resulting in a homogeneous PA selective layer. Particularly, isopropanol treatment removes less-reacted amine-rich monomers/oligomers and promotes PA network chain relaxation, enhancing molecular-sieving capability. The resulting PA TFC membrane exhibits a remarkable H2/CO2 selectivity of 24.8 (±3.1) and an H2 permeance of 13.6 (±1.8) gas permeation unit, surpassing the polymeric upper bound. It also ensures mechanical stability under high feed pressure and resistance to physical aging, highlighting its robustness. Additionally, universality is validated using different amine monomers. This systematic method provides a valuable framework for producing reproducible PA TFC membranes with exceptional gas separation performance, enabling practical implementation across industrial sectors.

A multi-node thermodynamic model on temperature-vacuum swing adsorption (TVSA) for carbon capture: Process design and performance analysis

The adsorption technology plays a significant role in the carbon capture domain for mitigating the CO2 emissions, whereas the heterogeneous character is presented in practical adsorption process. In this study, a multi-node thermodynamic model is established for temperature-vacuum swing adsorption (TVSA) considering the end non-uniform adsorption. It shows superior performance for the assessment of practical TVSA cycle compared with lumped model. Through the influence analysis of different operation parameters based on multi-node model, specific exergy consumption increases from 41.6 to 62.4 kJ/mol caused by simultaneous drop of heat consumption and lift of work consumption as feed pressure raises from 1.0 to 3.0 bar. Exergy efficiency ranges between 13.8 % and 15.0 % as CO2 concentration increases from 10 % to 20 %. However, those under ppm-level are below 0.86 %, presenting the higher exergy consumption but lower desorption capacity represented for direct air capture. The heat consumption of front half part of adsorption bed is 39.7 % higher than the latter one, proving the potential cascaded desorption of subzone heating is superior for reducing the energy consumption. Furthermore, exergy consumption is lifted due to enhancement of work consumption of vacuum pump as vacuum pressure reduces from 1.0 to 0.02 bar, resulting exergy efficiency drops from 19.6 % to 13.4 %.

Investigation of sustainable operation oriented- economic, process and environment based multi-criteria optimization of large scale methanol production plant

Methanol is one of the main raw materials and a building block for many essential chemicals in the industry, and it is widely produced from the synthesis gas. It is used as a fuel, solvent, inhibitor, antifreeze agent, and in producing a variety of chemicals including olefins and paraffin. The global demand for methanol is 70 million tons per year and it is estimated to grow by a factor of 6–8% per year so it is necessary to develop a methanol production process, which is economical, and environment friendly. The multi-objective optimization (MOO) approach is used to optimize the large scale Lurgi two-step methanol synthesis process using the non-dominated sorting genetic algorithm-II (NSGA-II) to find the Pareto front solutions involving the process, economic, and environmental-based objectives. Methanol production rate, total energy consumption, total annual CO2 emissions, and profit are considered as objectives. The five decision variables include syngas molar flow, reactor feed pressure, reactor 1 temperature, reactor 2 temperature, and by-product mass flow in the methanol distillation column. Two constraints are set on ethanol mole fraction in the methanol stream, and methanol mole flow in water to the treatment stream. Three optimization cases (two bi-objective and one tri-objective) are developed. In the Case 1 study, CO2 emissions decreased by 65.83%, the methanol production rate increased by 10.11%, and total energy was reduced by 57.55%. The Pareto ranking is carried out using the Preference Ranking On the Basis of Ideal-average Distance (PROBID) method and the best optimal solution is reported for all cases.

The solution-diffusion model: “Rumors of my death have been exaggerated”

The solution-diffusion (SD) model has been instrumental in the advancement of membrane science, due to its simplicity, transparency, and utility in process engineering. However, some doubts have recently been raised, concerning the fundamental validity of SD. These have largely been based on apparent discrepancies between molecular dynamics simulations and several features, deemed inherent to SD, that appeared in early reports — namely, the exact nature of the pressure and concentration distributions within the membrane. Herein, we re-visit the underlying physics of SD in the context of composite membranes, making no a-priori assumptions and, particularly, highlighting the role of polymer thermodynamics and the mechanics of a loaded, swollen film, supported by a porous substrate. The analysis provides a coherent view, linking the solvent concentration profile within the film and the resultant flux-pressure relations with the polymer rigidity and, importantly, the way in which the film is supported. It is shown that, although the flux may generally vary non-linearly with the feed pressure and depend on the film-support geometry, for rigid films – most common in real operations – SD predicts a linear behavior, virtually independent of specific geometry and pressure distribution. Moving forward, we stress the importance and need for further refinements of the SD model, driven by insight from molecular dynamics, thermodynamics and mechanics, while maintaining its applicability to process design.

H2 and CO purification by CO2 removal from syngas coupling membrane module and water-absorption unit: An economic analysis

Hydrogen represents today a necessary alternative to fossil fuels to limit the greenhouse gas effect due to the CO2 emissions. In this work, a plant configuration able to get pure H2 and concentrated CO (about 94%) from a syngas mixture is proposed and simulated by coupling a selective membrane unit and a water absorption column. In addition, an economic assessment on the simulated plant is carried out to estimate the feasibility of this process in terms of economic potential, studying its dependence on several parameters, such as raw material price, membrane cost, membrane feed pressure, column temperature and feed flow rate.Separation performance is improved by the higher feed membrane pressure (greater H2 recovery and CO purity), whereas the increment of the column temperature especially affects the CO recovery. Hence, the economic potential presents a maximum with pressure and temperature (e.g., about 246ꞏ103 $/y at 40 bar of feed membrane pressure and about 282ꞏ103 $/y at 50 °C of column temperature), due to the balance between the higher compression/solvent cost and the increment of H2 or CO recovery. In addition, the simulated plant shows a positive economic potential in a wide range of syngas price (e.g., from 0.126 to 0.25 $/Nm3), being also not affected significantly by the cost of the palladium-based membrane module. A bigger plant size (i.e., feed flow rate from 10 to 100 kmol/h) can lead to a twelve times greater economic potential (from about 242ꞏ103 to about 2954ꞏ103 $/y at 30 bar), reducing the H2 purification cost and making the net present value positive.

HYDROGEN GAS RECOVERY THROUGH THE PERMEATION MEMBRANE BASED BIMETALLIC PALLADIUM ALLOY

Generally, the H2 gas produced from the industrial processes is not in a pure state but is mixed with other compounds. For example, the off-gas produced in the oil refinery process still contains CH4, H2, and other gases. Thus, the process of separating as well as recovering the valuable H2 gas from other gas compounds is of essential process. Currently, the H2 separation process is being developed with relatively low costs with good efficiency, namely using the permeation membranes separation process, in which the compounds with high permeability tends to be more easily separated. Here we report the hydrogen recovery process from the mixed H2/N2 off-gas contains 61 % hydrogen and 39% balancing nitrogen, by using the bimetallic Pd-Ag membrane, where the effect of the gas feed pressure (1 and 2 bar) and operating temperature (373.15, 423.15, 473.15, and 523.15, 573.15 K) on the resulting permeate flux is comprehensively studied. We found that the flux and permeability increased with the increase in the gas feed pressure and temperature. Under the same gas temperature of 373.15 K, the permeation flux at the 2 bar gas feed pressure was found to be 2.047 mol.s-1.m-2, which was 166% greater than that of 1 bar pressure, i.e. 1.204 mol.s-1.m-2. Meanwhile, under the same gas feed pressure of 2 bar, the permeation flux at the operating temperature of 573.15 K was found to be 2.103 mol.s-1.m-2, which is 104,9% greater than that of 373.15 K operating temperature, i.e. 2.047 mol.s-1.m-2. These findings suggest the breakthrough advantages of the Pd-Ag alloy membrane for its high hydrogen permeability at low pressure.