Permeate Side Pressure Research Articles

Modeling of dual-skin asymmetric hollow fiber microporous membranes for predicting the skins parameters separately using gas permeation test

This study presented a comprehensive gas permeation model to predict the skin parameters of a complex system, specifically a hollow fiber membrane with an asymmetric structure consisting of two external and internal skin layers. According to the work of Haefer for n segments of pores connected in series as in hollow fiber membranes, applying the Wakao et al. model, a comprehensive model for the transition regime was derived. The model was examined against the various fabricated PES and PEI hollow fiber membranes. Unlike conventional models, the proposed method predicted the mean pore size and mean pore length independent of surface porosity for each skin layer. The study revealed valuable insights into i) the middle pressure, ii) the difference between the skin parameters of the two membrane skins, and iii) the impact of the feeding direction on gas permeation behavior. It was shown that the dependency of permeation behavior on the feeding direction is linked to the influence of middle pressure on viscous flow, which is closely related to surface porosities of each side. It is evident that even the slightest variations in the fabrication parameters can result in different structures. Furthermore, it is evident that the assumption of neglecting slip flow was reasonable within the experienced Knudsen number range. The model also highlighted that the skin parameters of the two skin layers may not be identical, a distinction not captured by the current models. The traditional approach of setting the middle pressure as the average of the upstream and downstream pressures has been improved by expressing it as a linear function of both pressures. In the feed side, higher pressures led to dominant viscous flow, whilst the permeate side was more influenced by the free molecular regime due to lower pressures. There existed a competition between the Knudsen flow and the viscous flow at a specific Knudsen number for the feeding side pores, whether it was the inner or outer surface. The finding emphasized the significance of porosity values on each side in determining the proximity of middle pressure to feed and permeate side pressures, underscoring the importance of accurate knowledge of surface porosities, mean pore sizes, and pore lengths for both skin layers in understanding processes involving porous dual-skin hollow fiber membranes.

Membrane properties overview in integrated forward osmosis/osmotically assisted reverse osmosis systems

Integration of forward osmosis (FO) and osmotically assisted reverse osmosis (OARO) provides low energy consumption and controlled fouling for brine treatment. This study explains the membrane properties required for cost–optimal OARO-based systems. A detailed model accounting for the relationship between burst pressure, permeate spacer gap, and structural parameters of OARO membranes was implemented with woven and non-woven spacers. Results indicate that the tradeoff between internal concentration polarization (ICP) and permeate–side pressure drop in OARO stages is a crucial consideration for optimal membrane element design. Due to the lower ICP of no-woven spacers, a system using non-woven spacers yielded lower levelized cost of water (LCOW) and specific energy consumption (5.83 $/m3 and 11.65 kWh/m3, respectively) as compared to the system with woven spacers (7.31 $/m3 and 9.90 kWh/m3, respectively) for dewatering a stream of 75 g/L salinity with 70 % water recovery. Sensitivity analysis shows that increasing the maximum pressure in OARO membranes requires a higher membrane structural parameter, aggravating ICP; however, the elevated driving force mitigates adverse effects of ICP. Moreover, a 15 % reduction in LCOW can be achieved if the membrane replacement factor of RO and OARO is reduced from 15 % to 5 %, which accounts for mitigated fouling.

Preparation ofZIF‐8—Pebax 1657 nanocomposite membranes forn‐hexane/nitrogen separation as a representative of gasoline vapour recovery

AbstractGasoline vapour emission is hazardous to both human health and the ecosystem and also results in capital loss, altogether revealing the necessity of its recovery. Some ZIF‐8–Pebax flat nanocomposite membranes were fabricated by the method of solution casting and used for gasoline vapour recovery as represented byn‐hexane vapour/nitrogen separation. Microporous ZIF‐8 nanoparticles were synthesized and characterized by Fourier transform infrared (FTIR) and Brunauer–Emmett–Teller (BET) analysis. BET results revealed specific surface area, total volume, and average pore diameter of 940.8 m2 · g−1, 0.36 cm3 · g−1, and 1.54 nm, respectively. Pure nitrogen andn‐hexane vapour/nitrogen gas mixture permeabilities were measured through the membranes. There was a decline in both permeation rate and selectivity up to 5.0 wt.% of ZIF‐8 loading and the next increment at their higher loadings to considerably more values that the pristine membrane. The maximumn‐hexane vapour permeability and selectivity at 10.0 wt.% loading of ZIF‐8 nanoparticles, the feed flow rate of 173 mL · min−1, and permeate side pressure of −200 mbar were observed as 280.1 Barrer and 106.7, respectively, revealing 60.0% and 36.9% improvements compared with those of the pristine Pebax membrane. Observed 86%–92%n‐hexane vapour recovery approves the successful application of the ZIF‐8–Pebax nanocomposite membranes forn‐hexane/nitrogen separation. The long‐term separation performance of 5.0 wt.% ZIF‐8 loaded nanocomposite membrane was improved by 76.5% compared with that of the pristine Pebax membrane.

Thermodynamic performance analysis of a novel air conditioning system integrating solar absorption compression refrigeration and vacuum membrane-based dehumidification (SACV)

For solar absorption cooling systems, it is difficult to generate lower chilled water for dehumidifying and cooling, as well as facing intermittency problems. In this work, the novel SACV system for indoor temperature and humidity control is proposed, which integrates the SSAR subsystem, the VCR subsystem, and the VMD subsystem. The VMD subsystem and the VCR subsystem solve the dehumidification difficulty and all-weather heating and cooling problems, respectively. This work also proposes a method for determining the collector area that avoids frequent start-ups and shutdowns of the VCR subsystem. Besides, a thermodynamic model of the SACV system is established and validated, and a systematical performance analysis of the SACV system is carried out. For the SACV system, the sensitivity of the parameters to the MCOP is also discussed. Results indicate that the outdoor air temperature, the latent heat load ratio, and the solar radiation intensity are the key parameters for designing the SACV system; further, the evaporation temperature and the permeate side pressure are the key parameters for the SACV system optimization. The SACV system is more suitable for high-humidity environments. Moreover, during the cooling season, the SACV system of a commercial building can realize a power saving rate of 39.82% compared to the conventional VCR system. The proposed SACV system of a commercial building can reduce 19653.59 kg/year carbon emission compared to the conventional VCR system in Nanjing. The carbon reduction rate of the SACV system in the selected cities is rather similar, about 36.78%–39.79%.

Optimization of Small-Scale Hydrogen Production with Membrane Reactors

In the pathway towards decarbonization, hydrogen can provide valid support in different sectors, such as transportation, iron and steel industries, and domestic heating, concurrently reducing air pollution. Thanks to its versatility, hydrogen can be produced in different ways, among which steam reforming of natural gas is still the most commonly used method. Today, less than 0.7% of global hydrogen production can be considered low-carbon-emission. Among the various solutions under investigation for low-carbon hydrogen production, membrane reactor technology has the potential, especially at a small scale, to efficiently convert biogas into green hydrogen, leading to a substantial process intensification. Fluidized bed membrane reactors for autothermal reforming of biogas have reached industrial maturity. Reliable modelling support is thus necessary to develop their full potential. In this work, a mathematical model of the reactor is used to provide guidelines for their design and operations in off-design conditions. The analysis shows the influence of temperature, pressures, catalyst and steam amounts, and inlet temperature. Moreover, the influence of different membrane lengths, numbers, and pitches is investigated. From the results, guidelines are provided to properly design the geometry to obtain a set recovery factor value and hydrogen production. For a given reactor geometry and fluidization velocity, operating the reactor at 12 bar and the permeate-side pressure of 0.1 bar while increasing reactor temperature from 450 to 500 °C leads to an increase of 33% in hydrogen production and about 40% in HRF. At a reactor temperature of 500 °C, going from 8 to 20 bar inside the reactor doubled hydrogen production with a loss in recovery factor of about 16%. With the reactor at 12 bar, a vacuum pressure of 0.5 bar reduces hydrogen production by 43% and HRF by 45%. With the given catalyst, it is sufficient to have only 20% of solids filled into the reactor being catalytic particles. With the fixed operating conditions, it is worth mentioning that by adding membranes and maintaining the same spacing, it is possible to increase hydrogen production proportionally to the membrane area, maintaining the same HRF.

Experimental and numerical study on thermodynamic characteristics of a vacuum membrane distillation system based on mechanical vapor recompression for sulfuric acid waste

Energy conservation and emission reduction in the field of industrial wastewater treatment have attracted worldwide attention. This study focused on the concentration and recovery of industrial sulfuric acid waste by a vacuum membrane distillation system based on mechanical vapor recompression (VMD-MVR). Mathematical models were built considering the mass and energy conservation principles and relevant thermal equilibrium theory, and an experimental platform, which was suitable for sulfuric acid solution, with excellent corrosion resistance was also constructed. Initially, the performance of VMD-MVR from the energetic and exergetic standpoints was evaluated based on the experimental data. Furthermore, the effects of critical parameters on compression and condensation heat transfer in VMD-MVR were simulated and revealed, and exergy destruction analysis was conducted using various selected parameters. The obtained experimental results indicated that VMD-MVR exhibited a membrane flux of 1.7 kg·m−2·h−1, separation efficiency of 99.9%, and performance coefficient (COP) of 7.88 under the following conditions: feed concentration: 5%; feed temperature: 353.0 K; feed velocity: 1.6 m·s−1; permeate side pressure: 45 kPa; heat transfer temperature difference (ΔThex): 2 K; and compressor frequency: 40 Hz. The exergy input, exergy destruction, exergy output, and exergy efficiency were 4.95 kW, 4.691 kW, 0.259 kW, and 5.24%, respectively. Moreover, according to the numerical simulation results, with a decrease in the feed concentration and ΔThex or with an increase in the feed temperature, feed velocity, and permeate side pressure, the compression ratio and exergy destruction in VMD-MVR decreased, whereas the COP increased.

Permeability and Stability of Hydrophobic Tubular Ceramic Membrane Contactor for CO2 Desorption from MEA Solution.

Ceramic membrane contactors hold great promise for CO2 desorption due to their high mass transfer area as well as the favorable characteristics of ceramic materials to resist harsh operating conditions. In this work, a hydrophobic tubular asymmetric alpha-alumina (α-Al2O3) membrane was prepared by grafting a hexadecyltrimethoxysilane ethanol solution. The hydrophobicity and permeability of the membrane were evaluated in terms of water contact angle and nitrogen (N2) flux. The hydrophobic membrane had a water contact angle of ~132° and N2 flux of 0.967 × 10−5 mol/(m2∙s∙Pa). CO2 desorption from the aqueous monoethanolamine (MEA) solution was conducted through the hydrophobic tubular ceramic membrane contactor. The effects of operating conditions, such as CO2 loading, liquid flow rate, liquid temperature and permeate side pressure, on CO2 desorption flux were investigated. Moreover, the stability of the membrane was evaluated after the immersion of the ceramic membrane in an MEA solution at 373 K for 30 days. It was found that the hydrophobic α-Al2O3 membrane had good stability for CO2 desorption from the MEA solution, resulting in a <10% reduction of N2 flux compared to the membrane without MEA immersion.

Performance analysis of a vacuum membrane distillation system coupled with heat pump for sulfuric acid solution treatment

This paper proposed a vacuum membrane distillation system coupled with heat pump (VMD-HP) for the treatment of sulfuric acid solution, in which the evaporator was employed to cool secondary vapor from the VMD process while the condenser was used to heat feed sulfuric acid solution. Mathematical models were first established in view of mass and energy conservation principles, and then validated through a conventional VMD experimental system with polytetrafluoroethylene (PTFE) membrane material. Furthermore, the effects of operating parameters on system performance were investigated comprehensively. The results showed that the combined system could achieve the evaporation process with lower temperature of 318.15 K–333.15 K. Decreasing feed concentration or increasing feed temperature, feed velocity and permeate side pressure, was effective to reduce the specific heating energy consumption (SHEC) and elevate the performance coefficient (COP). Taking the treatment concentration of 20% for instance, feed temperature, feed flow rate and evaporation rate were fixed at 333.15 K, 2 t•h−1and 1 t•h−1, respectively. The SHEC and COP for the VMD-HP system were 181.47 kWh•t−1 and 3.44, respectively. The specifics evaporation cost was found to be 15.56 $•t−1, with a reduction amplitude of 58.74% than that of conventional VMD system.

Experimental investigation on the mechanical vapor recompression evaporation system coupled with multiple vacuum membrane distillation modules to treat industrial wastewater

• A multiple vacuum membrane distillation modules system (MVMD) was constructed. • A mechanical vapor recompression system coupled with MVMD was constructed. • An experimental study of the MVMD and MVR-MVMD systems was conducted. • Economic assessment of the MVMD and MVR-MVMD systems was made. • The MVR-MVMD system can save 79.24% energy than that of the MVMD system. Excessive population growth has increased the importances of industrial wastewater treatment as well as energy conservation. This paper presented an experimental study of a mechanical vapor recompression evaporation system coupled with multiple vacuum membrane distillation modules (MVR-MVMD) for energy saving in the wastewater treatment process. For this aim, the MVMD system was constructed to investigate the water production performance in the VMD process, and then the MVR was joined to the MVMD system to examine the energy-saving performance. The experiment results showed that: In the experiment of the MVMD system, an excellent water production performance was observed with the sodium chloride solution as evaporation object, and the parameters that significantly affected the water production performance were obtained as follows: feed temperature was the highest effect, and then permeate side pressure, feed flow rate, and feed concentration had the lowest effect through an orthogonal multi-factor experiment. In the experiment of the MVR-MVMD system, the specific heating energy consumption was 81.95 kWh t −1 , which could save 79.24% energy than that of the conventional MVMD system, at conditions of feed concentration of 5%, feed flow rate of 25 m 3 /h and membrane area of 200 m 2 . Finally, a detailed economic assessment had been made concerning the capital investment, operation, and environment costs compared to the MVMD system. From a long-term perspective, the MVR-MVMD system showed excellent economic performance comparable to the MVMD system.

Research on thermodynamic performance of a novel building cooling system integrating dew point evaporative cooling, air-carrying energy radiant air conditioning and vacuum membrane-based dehumidification (DAV-cooling system)

In this work, a novel building cooling system is proposed, namely DAV-cooling system, which integrates dew point evaporative cooling, air-carrying energy radiant air conditioning and vacuum membrane-based dehumidification. The DAV-cooling system does not use any organic refrigerants, and can naturally provide fresh air indoors to prevent managers from arbitrarily reducing fresh air, and can be flexibly adjusted to meet different cooling requirements. In addition, the thermodynamic model of the DAV-cooling system is established, and some systematical analysis of parameters of the DAV-cooling system is carried out. The results indicate that there is an optimal ratio of fresh air to primary air for the DAV-cooling system, and the optimal value of this ratio should be in the range of 0.2–0.4. When the DAV-cooling system operates under the condition of a higher flow of primary air, the requirements for the dehumidification efficiency of the vacuum membrane-based dehumidification device can be reduced. Moreover, the relationship between COP and cooling capacity ratio is revealed, and it is found that COP decreases as the cooling capacity ratio increases, but they are not in an absolutely one-to-one relationship. Outdoor temperature and humidity also have a greater impact on the performance of the DAV-cooling system. For Singapore and Changsha in the period from June to August, the COP of the DAV-cooling system is about 5–7 and 4.5–9 respectively when the permeate side pressure is 20 kPa. Finally, the engineering design methods of the DAV-cooling system are discussed, and it is found that the DAV-cooling system can be designed as a temperature and humidity independent control air conditioning system through the proposed design method and the established model. This work can provide a complete solution reference and some new insights for the application of next-generation HVAC systems.

Indian Oil lets contracts for new units at Barauni, Haldia refineries

In this work, a novel building cooling system is proposed, namely DAV-cooling system, which integrates dew point evaporative cooling, air-carrying energy radiant air conditioning and vacuum membrane-based dehumidification. The DAV-cooling system does not use any organic refrigerants, and can naturally provide fresh air indoors to prevent managers from arbitrarily reducing fresh air, and can be flexibly adjusted to meet different cooling requirements. In addition, the thermodynamic model of the DAV-cooling system is established, and some systematical analysis of parameters of the DAV-cooling system is carried out. The results indicate that there is an optimal ratio of fresh air to primary air for the DAV-cooling system, and the optimal value of this ratio should be in the range of 0.2–0.4. When the DAV-cooling system operates under the condition of a higher flow of primary air, the requirements for the dehumidification efficiency of the vacuum membrane-based dehumidification device can be reduced. Moreover, the relationship between COP and cooling capacity ratio is revealed, and it is found that COP decreases as the cooling capacity ratio increases, but they are not in an absolutely one-to-one relationship. Outdoor temperature and humidity also have a greater impact on the performance of the DAV-cooling system. For Singapore and Changsha in the period from June to August, the COP of the DAV-cooling system is about 5–7 and 4.5–9 respectively when the permeate side pressure is 20 kPa. Finally, the engineering design methods of the DAV-cooling system are discussed, and it is found that the DAV-cooling system can be designed as a temperature and humidity independent control air conditioning system through the proposed design method and the established model. This work can provide a complete solution reference and some new insights for the application of next-generation HVAC systems.

Thermodynamic performance assessment of vacuum membrane-based dehumidification and air carrying energy radiant air-conditioning system (VMD-ACERS)

Temperature and humidity independent control (THIC) air-conditioning system is a promising technology. In this work, a novel temperature and humidity independent control (THIC) system is proposed, namely VMD-ACERS, which integrates vacuum membrane-based dehumidification and air carrying energy radiant air-conditioning system. This work establishes a novel coefficient of performance (COP) model of VMD-ACERS. The main parameters affecting the COP of conventional fan coil unit cooling system (FCUCS) and VMD-ACERS are investigated. The performance of FCUCS and VMD-ACERS are compared, and the energy-saving potential of VMD-ACERS is proved. Results indicate that, for FCUCS, the importance ranking of parameters is basically stable. However, for VMD-ACERS, the importance ranking will be affected by FCU and refrigerant. The most important parameters of VMD-ACERS are condensation temperature and permeate side pressure. On the contrary, superheating, subcooling are relatively less important parameters. For VMD-ACERS, it is not necessary to pursue the membrane with very high selectivity, because the selectivity of membrane would also be a less important parameter when it reaches 500. The COP of VMD-ACERS is higher than that of FCUCS when the permeate side pressure is higher than 8 kPa. The VMD-ACERS solves two technical problems about power-saving and thermal comfort of conventional THIC, and can extend the application of THIC air-conditioning system.

Rate determining step in SDC-SSAF dual-phase oxygen permeation membrane

Dense mixed ionic-electronic conducting (MIEC) dual-phase Ce0.85Sm0.15O1.925–Sm0.6Sr0.4Al0.3Fe0.7O3-δ (SDC-SSAF) represents one of the most attractive oxygen-selective membrane materials for oxygen separation from air above 700 °C. Its high phase stability in reducing atmosphere and CO2 resistance allows its potential direct integration into oxyfuel combustion and membrane reactor applications. In this work, the oxygen permeation parameters and properties of SDC-SSAF are evaluated theoretically using the Zhu model, which analyses the role of interfaces in electrochemical oxygen permeation. The model produced good correlation with the experimental data (R2 = 0.9990), with the calculated resistance constants indicating higher resistance encountered at the feed side interface as compared to the permeate side. An analysis of the characteristic thickness indicates increasing influence of surface exchange reactions with decreasing temperature, feed side pressure, and permeate side pressure. Although oxygen permeation is dependent upon various operating conditions, our parametric study reveals that temperature effect surpasses oxygen partial pressure difference effect in enhancing the oxygen permeation flux. Oxygen permeation is limited by surface reactions between 800 and 850 °C and mixed bulk diffusion and surface exchange reactions between 850 and 875 °C. Above 875 °C, the rate determining step shifts to bulk diffusion.

Sensitivity analysis and Taguchi application in vacuum membrane distillation

In this work, desalination experiments were performed on vacuum membrane distillation (VMD). Process parameters such as feed flow rate, vacuum degree on permeate side, feed bulk temperature and feed salt concentration were optimized using sensitivity analysis and Taguchi method. The optimum values of process parameters were found to be 2 lpm of feed flow rate, 60 degree Celsius of feed bulk temperature, 5.5 kPa of permeate-side pressure and 5000 ppm of salt concentration. The permeate flux at these conditions was obtained as 26.6 kg/m2⋅hr. The rejection of salt in permeate was found to be 99.7%. The percent contribution of various process parameters using ANOVA results indicated that the most important parameter is feed bulk temperature with its contribution of 95%. The ANOVA results indicate that the percent contribution of permeate pressure gets increased to 5.384% in the range of 2 to 7 kPa as compared to 0.045% in the range of 5.5 to 7 kPa.

Separation of benzo[a]pyrene and n-tetradecane mixtures using pervaporation technique and optimization

Benzo[a]pyrene is a carcinogen often present in diesel. For pervaporative removal of benzo[a]pyrene from n-tetradecane, representing a model diesel composition, both conventional as well as statistically designed experimental methods have been carried out. The effect of membrane composition, thickness, the effect of membrane pretreatment time and operating temperature on pervaporative separation have been investigated by response surface methodology, RSM for efficient permeation of target compound. The suitable membrane has been further used to study the effect of different physico-chemical parameters on permeation conventionally. RSM has also been applied to optimize the operational conditions of pervaporation process to maximize the response, i.e., the pervaporation separation index. With the design of experiments, the quadratic response surface models have been developed to link the response with input variables via mathematical relationships. The maximum value of Pervaporation Separation Index obtained is 1.9654 kg m−2 h−1. The optimized process condition’s run time is 10.79 h, the feed PAH concentration is 166.34 ppm with a permeate side pressure of 0.73 mmHg and an operating temperature of 451.25 K.

Dehydration of Industrial Byproduct Solutions for Recycling via Pervaporation–Adsorption Hybrid Process

Dehydration of used solvents in the printing and packaging industry is required in order to reuse or increase the commercial value of the solvents. In this study, a pervaporation–liquid-phase adsorption hybrid process for dehydration of a low-value byproduct solution obtained from a real operation was examined. The byproduct solution contained water varying in the range of 1–11.5 wt %, and the majority of the rest is ethanol and isopropanol with minor components such as ethyl acetate and methoxy propanol. We measured the flux and separation factor of two commercial membranes as a function of process parameters such as feed and membrane module temperature, feed flow rate, and permeate side pressure in addition to the feedwater and ethyl acetate concentration. We observed higher flux and separation factors at high temperatures and low permeate side pressures. PERVAP 2201 membranes showed higher flux with a reasonable separation factor toward water. PERVAP 2211 showed higher water separation factor but lower...

Properties of methane autothermal reforming to generate hydrogen in membrane reactor based on thermodynamic equilibrium model

Methane reforming reaction is one of the most important industrial chemical processes for hydrogen production. Membrane reactor has better performance of methane reforming reaction, can effectively increase methane conversion and hydrogen yield. To utilize this technology more effectively, it is necessary to develop a better understanding of the process of hydrogen generation and the effects of various parameters on the performance of membrane reactor. The characteristics of methane autothermal reforming to generate hydrogen in membrane reactor are studied with the thermodynamic equilibrium model. The results show that increasing permeate side pressure leads to reducing methane conversion and hydrogen permeability. Retentate side pressure has little effect on methane autothermal reforming reaction. The increase of air-methane molar ratio leads to a lower hydrogen production. The hydrogen production increases firstly and then decreases with the elevated steam-methane molar ratio. The H2/CO molar ratio can be regulated by the steam-methane molar ratio. Methane autothermal reforming occurs much more easily when temperature of 973 K, retentate side pressure and permeate side pressure of 0.1 MPa and 0.02 MPa, and the molar ratio of air-methane and steam-methane of 1 and 2 respectively.

CFD modelling of a membrane reactor for hydrogen production from ammonia

Despite the growing use of hydrogen (H2) as a transport fuel, one of the major barriers still remaining is efficient and inexpensive fuel distribution and storage. Current approaches, such as compression, liquefaction or metal hydride formation, incur a significant energy penalty. Ammonia (NH3) has long been considered a prospective H2 medium, exhibiting a higher volumetric H2 density than liquid H2, through liquid-phase storage at mild pressure. Decomposition of NH3 into H2 and N2 can be achieved via use of catalytic reactors and fuel-cell-grade H2 can be produced using metal membranes at H2 distribution sites.In this study, a 3-Dimensional (3D) Computational Fluid Dynamics (CFD) model has been developed to understand the performance of the H2 separation process in gas mixtures derived from an NH3-cracking reaction. The reactor consists of 19 tubular membrane tubes, each 470 mm long, inside a tubular shell with an inner diameter of 130 mm. Standard transport and energy equations governing a 3D, pressure-based, steady-state model were derived from the laws of conservation of mass, momentum and energy. The governing equations were solved using commercial CFD software ANSYS Fluent 18.0. Gas flow and mixing were modelled by the two-equation standard k-epsilon model for closure. Coupled solver was used for pressure-velocity coupling, enabling a pseudo-transient option with pseudo time steps of 0.01 s. To estimate H2 permeation through the metal membrane, a constant H2 permeability of 3.0E–07 mol.m−1 s−1 Pa−0.5 derived from series of experiments tested under a range of industrial conditions, was used. Model simulations were conducted for an adiabatic temperature of 300 °C, a feed-side pressure of 7.8 bara and a permeate side pressure of 0.1 bara. A parametric analysis was carried out to explore the effects of variation in total feed-gas flow and effects of changes in NH3-cracking efficiency on H2 production rates and H2 yields. The model estimated that 4.6–11.6 kg H2/day can be produced from a 30-70 L min−1 NH3 inlet flow with 80-90% NH3-cracking efficiency. At lower NH3 inlet flow rates, higher H2 yields can be obtained within a shorter distance of the membrane tubes due to relatively slower velocities and longer residence times. At high inlet flow rates, H2 yields were significantly lower due to their faster velocities and shorter resident times, but high yields (>95%) were still observed at the membrane reactor outlet. A sensitivity analysis of the model showed that even if metal membranes functioned at only 50% of the maximum permeability, a high H2 yield similar to that estimated using 100% permeability can still be achieved at the H2 outlets.

New experimental setup for continuous mass flux measurement in pervaporation

Pervaporation is a separation process of liquid mixtures through a thin non-porous membrane. In vacuum pervaporation, the global mass flux is classically estimated by weighing the mass of permeate collected in cold traps. In this work, we propose a new experimental setup that allows a continuous measurement of the mass flux. The new mass flux method measurement was validated for single component permeation (ethanol and water) by comparing mass of permeate collected in cold traps with the level decrease of feed liquid measured with a pressure sensor. This new setup can be useful for laboratory studies dealing with the evolution of mass flux according to different parameters of the process as, for example, the permeate side pressure level or temperature of liquid feed.

Effects of hydrophilic silica nanoparticles and backing material in improving the structure and performance of VMD PVDF membranes

Effects of hydrophilic silica nanoparticles and Non-Woven Fabric (NWF) backing material on the properties and performance of the Polyvinylidene Fluoride (PVDF) membrane have been studied in this work. The nanocomposite membranes were prepared by the phase inversion method and characterized in terms of surface pore size, cross-sectional morphology, thickness, porosity, surface roughness and hydrophobicity. The fabricated membranes were subjected to Vacuum Membrane Distillation (VMD) experiments and their performance was evaluated through measuring the pure water flux and salt rejection. According to the results, effects of the hydrophilic nano-additives and NWF polyester enabled much higher VMD flux than the neat PVDF membrane when an appropriate amount of the nano-filler was added, possibly due to increase in the surface pore size and the reduction of the sponge-like layer thickness. The supported nanocomposite membranes possessed appropriate Liquid Entry Pressure (LEPw) and mechanical strength, which make the membrane applicable in VMD process. When 7.0 wt.% of the silica nanoparticles was incorporated in a NWF supported membrane, the pure water flux became 12749.6 g/m2 h at feed temperature of 27.5 °C and permeate side pressure of 1.2 kPa, representing a 2456% increase from the neat PVDF membrane. Almost complete NaCl rejection was also achieved when tested with 35 g/L NaCl aqueous solution.