Increasing Feed Pressure Research Articles

CO2/CH4 separation using mixed matrix membrane-based polyurethane incorporated with ZIF-8 nanoparticles

This study presents using zeolitic imidazolate framework-8 (ZIF-8) as porous filler dispersed phase and polyurethane (PU) as continuous phase to synthesis mixed matrix membranes (MMMs). ZIF-8 nanoparticles were synthesized using centrifugal method. The synthesized nanoparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA). In order to investigate the effect of ZIF-8 loading on the membrane performance in CO2/CH4 separation, different membranes were prepared with various amounts of ZIF-8 (0–50 wt%). Membranes properties were characterized by SEM, XRD, TGA, differential scanning calorimetry (DSC), and tensile analysis. SEM images exhibit that the ZIF-8 is dispersed uniformly in cross section of membrane. Thermal stability of membranes increases with addition of the ZIF-8 nanoparticles into the polymer matrix. Both tensile strength and strain at break in the MMMs increase with the ZIF-8 loading. To study the effect of feed pressure on CO2 and CH4 transport properties of the membranes, single gas experiments were conducted at 4, 8, and 12 bar feed pressures. Incorporation of ZIF-8 crystals into continuous PU matrix resulted in high-performance gas separation membranes. Increasing feed pressure, significantly, increased separation performances in all the membranes.

Scale-up of PEEK hollow fiber membrane contactor for post-combustion CO2 capture

Poly(ether ether ketone) (PEEK) hollow fiber membrane modules were scaled up from 2in. diameter and 16in. long to 4in. diameter and 58in. long (a factor of 90 increase in membrane area) for CO2 capture from flue gases using a membrane contactor process, which combines advantageous features of both absorption and membrane processes. Field tests of a 4-in.-diameter module with activated methyldiethanolamine (aMDEA) solvent demonstrated greater than 90% CO2 removal. The mass transfer coefficient in the absorption step was 1.2 (s)−1, which is over an order of magnitude greater than that of conventional column contactors. The membrane module was further scaled up from 4in. to 8in. diameter (a factor of 3 increase in membrane area). Single-gas permeation measurements indicated that 8-in. modules have an intrinsic CO2 permeance as high as 2150–2670 GPU. One 8-in.-diameter module was tested in membrane contactor mode for CO2 capture using a simulated flue gas. Carbon dioxide removal rate of 91.3% was achieved with a mass transfer coefficient of 1.5 (s)−1. Parametric tests indicated CO2 flux and capture rate increased with increasing feed pressure, solvent flow velocity and solvent temperature. PEEK hollow fiber membrane contactor is effective in capturing CO2 from low CO2-concentration feeds, showing its high potential for coal or natural gas flue gas CO2 capture.

Simulation Analysis of a Coanda-Effect Ejector Using CFD

This work presents the optimization of a Coanda-effect air ejector used widely in industry through computational fluid dynamics. This optimization was developed in ANSYS FLUENT® software V16.2. Two 3D models of the commercial ejector (ZH30-X185 by SMC®) were carried out for the simulation procedure, varying the size of the separation of 0.3 and 0.8 mm in the walls of the nozzle, which communicates the high-pressure region and the mixture zone. In the experiment designed, the feed pressure applied to the ejector take values of 0.20, 0.25, and 0.30 MPa and the dynamic fluid behavior was analyzed for the two geometries mentioned. For the numerical and fluid behavior analysis, a mesh study was conducted to guarantee the independence of the results with the number of discretization cells. The k-e RNG turbulence model was implemented with treatment of walls, solving in stationary manner [C1] the [C2] phenomenon occurring within it, given that the temporal evolution is quite rapid. Increased secondary mass flow (extracted) relations with respect to the primary mass flow (injected) were found when the separation communicating the high-pressure zone and the mixture zone diminished. With increased feed pressure of the primary flow, a decrease was found in the secondary mass flow relation with respect to the primary mass flow. [C1] Estacionaria [C2] ok

Block copolyimide membranes for pure- and mixed-gas separation

Abstract A series of aromatic random and multiblock co-polyimides with varying block length was prepared from 2,2′-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride with m-phenylenediamine (6FDA-mPDA) and 2,3,5,6-tetramethyl-1,4-phenylenediamine (6FDA-durene). The permeability coefficients of pure gases (CO2, CH4, N2, He, O2, and H2) through the multiblock co-polyimide (6FDA-mPDA)-(6FDA-durene) membrane measured at various feed pressure (100–300 psi) and temperature (35 °C) were studied. The temperature dependence of permeabilities was also investigated over the permeation test range of 35–55 °C at 200 psi upstream pressure. The permeability properties of quaternary gas mixtures consisting of 10, 59, 30 and 1 vol% CO2, CH4, N2 and C2H6 respectively through the membrane were investigated at various feed pressures. In pure gas studies, permeability coefficients of all the penetrants stay relatively constant with increasing pressure. Different behaviour was however exhibited in the quaternary gas mixture studies as the permeability values of CO2 decrease with increasing feed pressure, whereas those of CH4, N2, C2H6 increase with increasing feed pressure. Unlike the pure gas studies that show constant CO2/CH4 and N2/CH4 selectivity values as a function of the feed pressure, the mixed gas studies did show some efficiency losses through a decrease of both CO2/CH4 and N2/CH4 selectivity. However C2H6/CH4 separation factor increases rapidly as the feed pressure is further increased.

Aromatic block co-polyimide membranes for sour gas feed separations

Permeation properties of pure and gas mixture consisting of CO2, H2S, CH4, N2 and C2H6 through dense films of the block co-polyimides (6FDA-mPDA)-(6FDA-durene) are studied at 35–55°C and pressures of 100–500psi for combined separation of CO2, H2S and N2 from acid gas streams. The H2S composition in the gas mixture is up to 20vol%. This rigid block copolymer exhibits relatively constant or slightly decrease in pure gas permeability with increasing feed pressure for most of the penetrants. The pure gas CO2/CH4 and N2/CH4 selectivities are up to 61 and 2.6 respectively. The mixed gas studies also show relatively constant or slightly decrease in permeability coefficients with increase in pressure for most of the penetrants. One significant fact is that, at feed pressure of 500psi and 20vol% H2S in feed gas mixture (consisting of CO2, N2, CH4 and H2S), H2S/CH4 and CO2/CH4 separation factors are 23 and 27 respectively. These values are within the same order of magnitude or even better than those obtained in other state-of-the-art polymeric membranes that have been reported. Another unique feature of this co-polyimide is that, in addition to being selective to acid gas, it is also more selective to N2 as compare to CH4. Moreover, the CO2/CH4 separation factor does not suffer significant loss to the same degree as in the case of cellulose acetate (CA), even under these much more aggressive environments. This stability at moderate pressures and high H2S concentration is quite remarkable, as most reported studies are focused on low H2S concentrations and low pressures.

Forward osmosis process for supply of fertilizer solutions from seawater using a mixture of draw solutions

Novel desalination approaches are required to provide both drinking and agricultural water as there is ever increasing stress upon precious freshwater resources. It was our hypothesis that a modified Forward Osmosis (FO) process had the potential for production of irrigation water comprising of appropriate concentrations of fertilizers from a seawater feed. Four agents, KNO3, Na2SO4, CaNO3, and MgCl2, plus 35 g/L seawater were used as the draw and feed solutions of the FO process. Net Driving Pressure (NDP) in the FO process was manipulated either by increasing the concentration of draw solution (FO process) or by increasing feed pressure (Pressure Assisted FO (PAFO) process). A series of nanofiltration (NF) and reverse osmosis (RO) membranes were used for the regeneration of draw solution. The results suggested that a PAFO process was more energy efficient than simple forward osmosis, provided the energy relating to the brine flow from the NF/RO membrane for pressurizing the feed solution of PAFO process was used. Furthermore, this study suggested using a mixture of a primary draw solution, MgCl2, and a secondary draw solution, KNO3, for NO3 supply into the irrigation water was preferable. As such, MgCl2 provided the driving force for fresh water extraction while KNO3 was the source of fertilizer in the irrigation water. Results showed that water quality provided by application of a MgCl2+KNO3 draw solution was better than that from KNO3 or Ca(NO3)2. The concentrations of NO3 and SO4 in irrigation water were within recommended levels when the diluted draw solution was regenerated by a dual stage low pressure RO process.

Imidazole functionalized graphene oxide/PEBAX mixed matrix membranes for efficient CO2 capture

Abstract Mixed matrix membranes (MMMs) were composed of imidazole functionalized graphene oxide (ImGO), a CO 2 -philic nano-sheet inorganic material, and poly(ether- b -amide) (PEBAX) for CO 2 capture. MMM doped with 0.8 wt.% ImGO exhibits the best CO 2 separation performance, which shows the CO 2 /N 2 selectivity up to 105.5 combined with CO 2 permeability of 76.2 Barrer (1 Barrer = 10 −10 cm 3 (STP) cm cm −2 s −1 cmHg −1 ), surpassing the Robeson Upper Bound of 2008. The selectivity of MMM for CO 2 /N 2 increases by 46.0% compared to the Pristine PEBAX due to the interaction between CO 2 and imidazole groups. With the increase of feed pressure, CO 2 permeability increases significantly because of its higher solubility in polymer matrix and plasticization. It is effective to separation CO 2 from N 2 at lower temperature for MMMs because the apparent activation energy of the N 2 permeation process in ImGO/PEBAX MMMs is much higher than that of CO 2 . Tg of MMMs are increased gradually because the polymer chain mobility is restricted by the presence of ImGO and a rigidified interface generates between polymer and filler. The mechanical properties have been significantly enhanced by the ImGO sheet as expected because of the presence of H-bonding. Having distinct improvement of CO 2 separation performance, the ImGO/PEBAX MMMs indicates promising applications in CO 2 capture processes.

Pressure-dependent pure- and mixed-gas permeation properties of Nafion®

The permeation properties of Nafion® at 35°C are presented for pure gases H2, N2, O2, CH4, CO2, C2H6 and C3H8, as a function of pressure between 2 and 20atm. The effect of pressure on permeability and selectivity is analyzed to understand two observed phenomena: compression and plasticization. In pure-gas experiments, at increasing feed pressure, compression of the polymer matrix reduced the permeability of low-sorbing penetrants H2, N2, O2, and CH4. In contrast, permeabilities of more soluble penetrants CO2 and C2H6 increased by 18% and 46% respectively, as plasticization effects overcame compression effects. Permeability of C3H8 decreased slightly with increasing pressure up to 4.6atm as a result of compression, then increased by 3-fold at 9atm as a result of plasticization associated with high C3H8 solubility. Binary CO2/CH4 (50:50) mixed-gas experiments at total feed pressures up to 36atm quantified the effect of CO2 plasticization on separation performance. At 10atm CO2 partial pressure, CH4 permeability increased by 23% relative to its pure-gas value of 0.078 Barrer, while CO2 permeability decreased by 28%. Consequently, CO2/CH4 selectivity decreased to 19, i.e., 42% below its pure-gas value of 32.

Synthesis and characterization of poly (ether‐block‐amide) mixed matrix membranes incorporated by nanoporous ZSM‐5 particles for CO2/CH4 separation

AbstractIn this work, poly (ether‐block‐amide) (Pebax MH 1657) mixed matrix membranes (MMMs) were prepared using nanoporous ZSM‐5 as a filler. The fabricated membranes were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimeter (DSC) analysis, thermal gravimetric analysis (TGA) and X‐ray diffraction (XRD). Effects of zeoilte loading (5, 10 and 15 wt. %), and feed pressure (1, 3 and 5 bar) on CO2/CH4 separation of MMMs were investigated using constant volume/variable pressure system. SEM analysis represents a proper morphology along with proper dispersion of ZSM‐5 particles within the polymer matrix. TGA analysis demonstrated that the thermal degradation temperature (Td) of MMMs increased by increasing the ZSM‐5 loading. The obtained experimental results showed that both permeability and CO2/CH4 selectivity enhanced by addition of zeolite compared to neat Pebax. At low concentration of zeolite (5 wt. %), the CO2 permeability increased significantly from 122.4 Barrer to 217.9 Barrer at pressure of 1 bar. MMM that incorporated by 15 wt. % of zeolite showed the best CO2/CH4 selectivity of 33.9 at pressure of 1 bar. The CO2 permeability of MMM with 5 wt. % ZSM‐5 enhanced from 217.9 to 292.4 Barrer with increase in feed pressure from 1 to 5 bar. Copyright © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Mixed matrix membranes prepared from high impact polystyrene with dispersed TiO2 nanoparticles for gas separation

The current study presents synthesis and characterization of high impact polystyrene - TiO 2 nanoparticles mixed matrix membranes for separation of carbon dioxide from nitrogen. The solution-casting method was used for preparation of membranes. The nano mixed matrix membranes were characterized using scanning electron microscopy to ensure the suitable dispersion of nano particles in high impact polystyrene matrix. The effect of TiO 2 nanoparticles loading on membrane performance was investigated. The separation performance of synthesized membranes was investigated in separation of CO 2 from CO 2 /N 2 mixture. Effect of feed pressure and TiO 2 content on separation of CO 2 was studied. The results revealed that increase of feed pressure decreases flux of gases through the mixed matrix membrane. The results also confirmed that the best separation performance can be obtained at TiO 2 nanoparticles loading of 7 wt.%.

Performance of a medical oxygen concentrator using rapid pressure swing adsorption process: Effect of feed air pressure

The effects of feed air pressure on the steady‐state performance of a medical oxygen concentrator (MOC) were experimentally evaluated using a novel design of a MOC unit which produced a continuous stream of ∼90% O2 employing a rapid pressure swing adsorption (RPSA) process scheme. Dry, CO2 free air containing ∼1% Ar at different feed gas pressures was used in the tests in conjunction with a commercial sample of LiLSX zeolite as the N2 selective adsorbent in the process. The bed size factor (BSF) can be systematically reduced by increasing the feed air pressure for any given total cycle time. The effect of feed air pressure on the oxygen recovery (R) is, however, more complex; it increases with increasing feed pressure only at longer cycle times while the effect is marginal at shorter cycle times. The BSF cannot be indefinitely reduced by lowering total process cycle time at any pressure—a minimum is exhibited in the BSF‐cycle time plot. The minimum value of the BSF decreases as the feed pressure is increased. The cycle time for the minimum BSF is, however, not significantly altered by the feed pressure in the data range of this work. © 2015 American Institute of Chemical Engineers AIChE J, 62: 1212–1215, 2016

Poly(amide-6-b-ethylene oxide)/[Bmim][Tf2N] blend membranes for carbon dioxide separation

Poly(amide-6-b-ethylene oxide) (Pebax1657)/1-butyl-3-methylimidazo-lium bis[trifluoromethyl)sulfonyl]-imide ([Bmim][Tf2N]) blend membranes with different [Bmim][Tf2N] contents were prepared via solution casting and solvent evaporation method. The permeation properties of the blend membranes for CO2, N2, CH4 and H2 were studied, and the physical properties were characterized by differential scanning calorimeter (DSC) and X-ray diffraction (XRD). Results showed that [Bmim][Tf2N] was dispersed as amorphous phase in the blend membranes, which caused the decrease of Tg (PE) and crystallinity (PA). With the addition of [Bmim][Tf2N], the CO2 permeability increased and reached up to approximately 286 Barrer at 40 wt% [Bmim][Tf2N], which was nearly double that of pristine Pebax1657 membrane. The increase of CO2 permeability may be attributed to high intrinsic permeability of [Bmim][Tf2N], the increase of fractional free of volume (FFV) and plasticization effect. However, the CO2 permeability reduced firstly when the [Bmim][Tf2N] content was below 10 wt%, which may be due to that the small ions of [Bmim][Tf2N] in the gap of polymer chain inhibited the flexibility of polymer chain; the interaction between Pebax1657 and [Bmim][Tf2N] decreased the content of EO units available for CO2 transport and led to a more compact structure. For Pebax1657/[Bmim][Tf2N] blend membranes, the permeabilities of N2, H2 and CH4 decreased with the increase of feed pressure due to the hydrostatic pressure effect, while CO2 permeability increased with the increase of feed pressure for that the CO2-induced plasticization effect was stronger than hydrostatic pressure effect.

Relationship between polymer–filler interfaces in separation layers and gas transport properties of mixed matrix composite membranes

To systematically explore polymer–filler interface and its influence, a series of mixed matrix composite membranes were fabricated by coating the mixture comprised of polyvinylamine(PVAm) and different inorganic nanofillers on polysulfone(PS) flat ultrafiltration membranes. Multiwalled carbontube(MWCNT), SiO2 and ZSM-5 were chosen as pristine inorganic nanofillers, and MWCNT–NH2, SiO2–NH2 and ZSM-5–NH2 were used as modified inorganic nanofillers. Possible gas transport mechanisms are discussed. A method of assessing the size of interface voids is developed by analyzing a trend in gas permeance with increasing feed pressure. The effect of feed pressure on gas permeance of the mixed matrix composite membranes was investigated. For PVAm–pristine inorganic nanofiller/PS membranes, membrane compaction, void-filling effect, surface flow and interface void channels affect its N2, O2 or CH4 permeance change with increasing feed pressure. The size of interface voids varies in the order of PVAm–ZSM-5 interface voids>PVAm–MWCNT interface voids>PVAm–SiO2 interface voids. Furthermore, gas permeance of PVAm-modified inorganic nanofiller/PS membrane is lower than that of the corresponding PVAm–pristine nanofiller/PS membrane. The result suggests that surface modification of inorganic nanofillers with compound containing the same functional groups as polymer is an effective way to improve the interface compatibility between polymer chains and modified inorganic nanofillers.

APCI- LNG single mixed refrigerant process for natural gas liquefaction cycle: Analysis and optimization

In this paper, a typical single mixed refrigerant (SMR) with low energy consumption is analyzed to determine the optimum operating conditions. Genetic Algorithm (GA) tool is used to minimize the total required work by optimizing eleven variables including the outlet pressures of all compressors and throttling valves and the molar flow rate of the MR components. The results of the process simulation show that the total work is varied linearly by the compositions. It is observed that to have a minimum work, when the ambient temperature increases, the compositions of both methane and ethane should be decreased, while those of nitrogen, propane and n-butane should be increased. Moreover, optimized values of the total required work at different ambient temperatures were correlated with a second order polynomial. Increasing feed pressure has small effect on the MR compositions, but significant effect on the total work.

Application of nanofiltration as a tertiary treatment in a polyester production industry for wastewater reuse

Membrane technology is one of the most efficient approaches for the treatment of industrial wastewater and reuse. In this study, the influence of influential parameters, including pH, feed pressure, sulfate concentration, and chemical oxygen demand (COD) on the simultaneous removal efficiency of pollutants in Polyacryl Iran Company, were investigated by applying a commercial TFC polyamide nanofilter. The three leveled factors of sulfate and COD concentration, feed pressure, and pH were considered in the range of 550–1,283 mg L−1, 85–198 mg L−1, 0.5–0.9 MPa, and 5–9, respectively. By increasing pH from 5 to 9, the sulfate and COD removal efficiency increased up to 90%, and also by increasing feed pressure from 0.5 to 0.8 MPa, the removal rate of COD increased to 92%, whereas the effect of feed pressure on the sulfate removal was found insignificant. Results also indicated that an increase in the COD concentration resulted in a reduction in the removal efficiency of COD from 96 to 82%. On the other hand, by increasing the sulfate concentration to 800 mg L−1, an increase in the sulfate removal efficiency from 94 to 96% was observed. A further increase in the sulfate concentration resulted in the reduction of sulfate removal efficiency.

Beer dealcoholization using non-porous membrane distillation

In this present work, performance of non-porous membrane distillation method is investigated during beer dealcoholization process. A thin-film composite polyamide membrane is used as membrane module while a commercial beer product with 5%-volume ethanol is used as feed. The results indicate that non-porous membrane distillation can be used to dealcoholize beer without losing the other nutrients and flavoring components such as maltose and glycerol. The increase of feed pressure and vacuum pressure can improve membrane flux due to higher permeability. However, membrane selectivity is decreased with the increase of vacuum pressure. The membrane flux and ethanol concentration in permeate are 0.15–0.76L/m2h and 3.66–4.64%-vol., respectively. Meanwhile, there are no specific sequences on the maltose concentration in the effect of operating conditions. The slight loss of maltose in the dealcoholized beer can be attributed to adsorption phenomena in membrane surface thus membrane flushing may be conducted to recover it. The glycerol behavior in dealcoholization process is similar to maltose. Some glycerol compounds are found in the permeate stream but all of them are less than 0.005%-vol. At 3000mbar feed pressure and 580mbar vacuum pressure, the flux of membrane is 0.69L/m2h with 3.70%-vol. and 4.60%-vol. of ethanol concentration in dealcoholized beer and permeates side respectively, no maltose and only 0.001%-vol. glycerol in permeate side. A long run operation for beer dealcoholization using these operating conditions can reduce the alcohol content from 5%-vol. to 2.45%-vol. in 6h.

Modeling, Simulation, and Economic Assessment of Membrane-Based Gas Dehydration System and Comparison with Other Natural Gas Dehydration Processes

An economic assessment of natural gas dehydration using polymeric membranes was made through modeling and simulation and the results were compared with those conducted through absorption and adsorption. A diagram of the economic boundaries between different natural gas dehydration processes was also introduced. The effects of the membrane properties, membrane module cost, feed pressure, and natural gas wellhead price on the cost of water vapor removal were examined. It has been concluded that at low feed pressures and at feed flow rates more than 0.85 MMSCMD the membrane-based gas dehydration system is not competitive with the absorption process. An increase in the feed pressure increases the cost of the absorption and adsorption processes, while decreases that of the membrane system. At feed flow rates higher than 3.4 MMSCMD and inlet pressures less than about 4100 kPa, the total separation cost of the adsorption unit was lower than that of the membrane system.

Development of a hybrid membrane through coupling of high selectivity zeolite T on ZIF-8 intermediate layer and its performance in carbon dioxide and methane gas separation

This work demonstrated a novel hybrid membrane development through coupling of zeolite T membrane on ZIF-8 intermediate layer. ZIF-8 which acted as an intermediate layer was firstly grown on a macroporous α-alumina support via vacuum seeding. Pure phase zeolite T membrane was then synthesized on ZIF-8 which was pre-grown on the α-alumina support. Single gas permeation of standing free zeolite T membrane showed a CO2/CH4 selectivity of 68 with CO2 and CH4 gas permeances of 6.08×10−8 and 0.09×10−8mol/m2.s.Pa, respectively. On the other hand, the CO2/CH4 selectivity of the hybrid membrane was 3 folds as compared to standing free zeolite T membrane, giving the highest CO2/CH4 selectivity of 182 and the CO2 and CH4 gas permeances of 5.46×10−8 and 0.030×10−8mol/m2.s.Pa, respectively. Both gas permeances of CO2 and CH4 increased with increasing feed pressure from 1 to 4bar with a slight decrease in the selectivity observed at the feed pressure of 4bar. While for the effect under increasing temperature, CO2 showed an increasing trend of its gas permeability from 5.46×10−8 to 6.12×10−8mol/m2.s.Pa while CH4 gas permeability increased slightly from 0.03×10−8 to 0.042×10−8mol/m2.s.Pa due to greater mobility of gas molecules promoted by higher temperature.

Mixed matrix membranes of Pebax-1657 loaded with 4A zeolite for gaseous separations

Mixed matrix membranes (MMMs) made from selective inorganic fillers and polymers have received extensive attention in the field of gas separation. In this work, poly(ether-block-amide), (Pebax)/zeolite 4A MMMs were prepared using ethanol/water as solvent mixture. The concentration of zeolite 4A in membrane was varied from 5 to 30wt.% of the polymer. The membranes were characterized by SEM, FTIR and XRD to study the morphologies, the effect of zeolite 4A incorporation on intermolecular interactions and degree of crystallinity, respectively. The pure gas permeabilities were recorded at the ambient temperature, using an indigenously built high-pressure gas separation manifold. The permeabilities of Pebax-1657/zeolite 4A membranes were enhanced from 71.4 to 155.7 Barrers for CO2, 2.2–19.6 Barrers for CH4, 5.8–17.9 Barrers O2 and 1.4–12.0 Barrers for N2. The ideal selectivity of 10wt.% zeolite 4A MMM enhanced from 54.1 to 94.2 for the CO2/N2 gas pair with increase in feed pressure from 5 to 25kg/cm2, whereas the corresponding values for CO2/CH4 and O2/N2 were found to rise from 26.4 to 41.3 and 4.3 to 4.9, respectively. The Pebax/zeolite 4A membranes thus provide a potentially promising means for separation of CO2/N2, CO2/CH4, and enrichment of O2 and N2 from air.

Analysis of gas transport in laminated semi-infinite solid: Novel method for complete membrane characterization during highly transient state

Gas transport in a two-layer membrane system, subjected to a step increase in feed pressure, is modeled under highly transient state in which the Layer 2 behaves as a semi-infinite solid. The system of governing partial deferential equations is solved using Laplace transforms, and the solution is used to obtain the expression for the pressure decay in the upstream volume. Accordingly, the pressure decay at short and long times is directly proportional to the square root of time, where the early and late slopes are dependent on the properties (i.e., diffusivity and solubility) of the materials of Layer 1 and Layer 2, respectively. Knowing the properties of the material of Layer 2, the material of Layer 1 can be fully characterized based on the early slope and the rate at which this early slope changes once the penetrant enters Layer 2. Since the thickness of Layer 1 in the two-layer system can be orders of magnitude smaller than that of a stand-alone membrane, the approach presented in this paper may allow characterizing barrier materials, which otherwise could not be characterized in a reasonable timeframe by traditional integral, permeation and sorption techniques. In addition, the new method may be used for characterization of the selective layer in thin film composite membranes.