Membrane Separation System Research Articles

CFD Modelling of an Electrodialysis Cell

Electrodialysis (ED) cells are based on the selective transport of ions through membranes which ideally exclude the co-ions, so that when a potential difference is applied to the cell all ions are transported in solution but only the counter ions can cross the membrane. Thus, concentration polarization occurs in solutions adjacent to membrane surfaces due to the different transport number between the membrane and the solution. The concentration profiles formed in the solution near the membrane depends on the mass transport fluxes and hydrodynamic pattern in the channel; operating conditions and geometrical configuration of the cell affect greatly the concentration polarization [1]. Therefore, the performance of ED cells depends not only on the membrane properties but also on the electrolyte hydrodynamics being important to provide an adequate flow patter avoiding channeling, stagnant zones, jet formation, among others flow deviations. Keeping a homogeneous flow patter minimizes variations of mass transfer fluxes and current density over the membrane surface preventing high polarization zones that could give rise to water dissociation, low efficiency and premature membrane failure. The examination of relevant mass transport mechanisms by modelling can help to evaluate the effect of design characteristics and operating conditions on the performance of an electrodialysis cell through the analysis of concentration, potential and current density distributions. In this task, CFD has proven to be a valuable tool for the analysis of flow and mass transfer in membrane separation systems [2]. Therefore, this work presents the modelling of a laboratory ED cell coupling hydrodynamics and mass transport, taking into consideration changes of Donnan potential. The flow pattern inside channels of ED cell were obtained by 3D CFD modeling and the results were used to calculate the residence time distribution (RTD) to compare with experimental RTD. The hydrodynamic behavior was used then to solve the mass transport model to obtain a description of the concentration distribution of each of the ionic species in the cell, as well as of the amounts derived as fluxes of each of the components, current density and Donnan potentials at every point of the membrane.[1] Gurreri L., Tamburini A., Cipollina A., Micale G., Ciofalo M., CFD prediction of concentration polarization phenomena in spacer-filled channels for reverse electrodialysis J. Membr. Sci. 468, 133–148 (2014).[2] Fimbres-Weihs G.A., Wiley D.E., Review of 3D CFD modeling of flow and mass transfer in narrow spacer-filled channels in membrane modules, Chem. Eng. Process. 49 759–781 (2010).

Economic Estimation of Various Membranes and Distillation for Propylene and Propane Separation

The separation of propylene and propane is very costly due to similar physical-chemical properties. In this study, the effect of various membranes on the economic performance of the olefin unit was evaluated. The Robeson’s line cannot judge the economic performance of membrane separation systems. A precise model of cocurrent and counter-current hollow fiber membrane was developed and implemented in a commercial chemical engineering software to estimate the economics of the best inorganic (ZIF-8) and polymeric (6FDA-TrMPD) membranes compared with the existing distillation unit. At the same area, the cocurrent flows have higher recovery and the counter-current flows have higher purity. The use of the alternative polymer membrane results in a drastic increase in costs. The ZIF-8 membrane performance leads to a 30% increase in the total capital costs, while the annual cost considerably decreased by 46%. When the membrane performance is appropriate in terms of selectivity and permeability, the use of membrane ...

Treatment of natural rubber wastewater by membrane technologies for water reuse

A series of laboratory scale experiments were performed to investigate the feasibility of membrane separation technology for natural rubber (NR) wastewater treatment and reuse. Three types of spiral wound membranes were employed in the cross-flow experiments. The NR wastewater pretreated by sand filtration and cartridge filtration was forced to pass through the ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membranes successively. The UF retentate, which containing abundant proteins, can be used to produce fertilizer, while the NF retentate is rich in quebrachitol and can be used to extract quebrachitol. The permeate produced by the RO module was reused in the NR processing. Furthermore, about 0.1wt% quebrachitol was extracted from the NR wastewater. Besides, the effluent quality treated by the membrane processes was much better than that of the biological treatment. Especially for total dissolved solids (TDS) and total phosphorus (T-P), the removal efficiency improved 53.11% and 49.83% respectively. In addition, the removal efficiencies of biological oxygen demand (BOD) and chemical oxygen demand (COD) exceeded 99%. The total nitrogen (T-N) and ammonia nitrogen (NH4-N) had approximately similar removal efficiency (93%). It was also found that there was a significant decrease in the T-P concentration in the effluent, the T-P was reduced from 200 mg/L to 0.34 mg/L. Generally, it was considered to be a challenging problem to solve for the biological processes. In brief, highly resource utilization and zero discharge was obtained by membrane separation system in the NR wastewater treatment.

Boundaries of the Realizability Region of Membrane Separation Processes

The region of realizability of membrane separation systems having a constant total membrane area has been determined for a definite output of a final product at a definite composition of a mixture flow. The law of change in the pressure in the mixture, corresponding to the minimum energy required for its separation, was concretized for media close in properties to ideal gases and solutions.

Disinfection efficacy over yeast biofilms of juice processing industries

Membrane separation systems represent a hot – spot for biofilm formation in juice industries. Sodium hypochlorite (NaOCl) has been traditionally the disinfectant of choice; however, its effectiveness over well-established biofilms is limited. In this work the study of biofilm formation on ultrafiltration membranes was proposed. The effectiveness of cleaning and disinfection procedures commonly used in juice industry was tested on the removal and killing of cells. The species used (Rhodotorula mucilaginosa, Candida krusei, Candida kefyr and Candida tropicalis) were isolated from ultrafiltration modules of a clarified apple juice industry. Industrial concentrations of NaOCl (200mgCL∙L−1) showed to be effective against planktonic cultures with >4 log reductions, whereas their overall efficiency against adhered cells was smaller. Recovery of viable cell counts to initial numbers was evidenced regardless of the time of colonization. The topography of the surface showed to have an impact on the efficiency of the disinfectant, presenting membranes smaller log reductions than stainless steel (~1.09–1.53logCFU). At 200mgCl∙L−1 only membrane's cross flow recovery was reached with no long-term effect over the attached cells. The overall results demonstrated the recalcitrance of these biofilms to typical cleaning and disinfection process which may confer them with a selective advantage.

Economic response models for membrane design

Abstracts Membrane processes are typically analyzed to determine the most energy efficient and cost effective configurations and operating conditions. This can be achieved through simulation and optimization to identify the optimal designs for each case. In this study, a new approach is suggested for the visual analysis and comparison of the economic performance of different membrane configurations. The new methodology generates response surfaces for each configuration that can be used to show ranges of possible solutions. These solution surfaces can then be compared to show the conditions, under which each configuration become beneficial. This is demonstrated here through a case study using hollow fiber membrane separation systems to reduce the concentrations of CO 2 in natural gas.

Preliminary Study on the Manufacturing Process of a Membrane Filtration for Protein Concentration from the Recycled Materials

Jatropha curcas oil has become an important raw material in manufacturing biodiesel fuel because of its non-edible and rich-oil characteristics. After oil pressing, the recycled press cake of Jatropha curcas seed residue exhibited ample protein, and could be applied in bio-medical, bio-resources, or food industrial products. Protein concentration process using membrane module system combined with the control design has a significant advantage on energy saving compared to the heat drying of protein solution. However, fouling, large membrane area and frequent membrane cleaning will increase the energy consumption and operation cost for the protein concentration process with filter membrane. In this study, the membrane filtration for protein concentration will be conducted. The discussion of control factors, membrane pore size (X1), pH value (X2) and transmembrane pressure (X3), for protein concentration process with response surface methodology (RSM) were discussed. The results showed that R2R2 value for each model was close to one. Future investigation on the mechatronics integration of the membrane separation and purification system will be needed for commercial applications.

Designing an atmosphere controlling hollow fiber membrane system for mango preservation

We devised an atmosphere controlling facility to gain a longer life span for mango. A membrane module made of polyethersulfone/polydimethylsiloxane (PES/PDMS) composite membrane was applied to selectively permeate CO2 from the gas mixture of the fruit container. To design the membrane separation system, two models were introduced into our mathematical simulations: (1) an equilibrium model giving the optimal membrane area, the compositions of CO2 and O2 in the fruit container, feed flow rate and pressures on both the feed and permeate sides of the module, and (2) a dynamic model simulating the change in the gas composition of the fruit container with time. The pressure build-up in the bore side of the hollow fiber was also discussed using the Hagen-Poiseuille equation. The best membrane module configuration was obtained based on the pressure build-up analysis. That was (1) the vacuum pressure should be set at 0.1 bar, (2) the hollow fiber inner diameter should be 0.45 mm, and (3) the vacuum should be applied at both ends of the hollow fiber bore sides.

Polymeric membrane materials selection for high-pressure CO2 removal from natural gas

A quick qualitative comparison of membrane materials is often necessary in the early phases of membrane separation process design. This comparison and final material selection can be complex when a large number of materials and performance properties are involved. In such cases, a model-based material selection method is a very important tool that is needed by the engineers who are responsible for designing membrane separation systems. Therefore, a new performance criterion was proposed in terms of productivity loss. This criterion was used along with other membrane properties such as plasticization pressure, CO2 permeability, and CO2/CH4 selectivity to carry out a multi-objective optimization of membrane material selection for high-pressure membrane gas separation. Results from the analysis revealed that the productivity loss is very essential in evaluating the property of plasticization-resistant membrane materials. It was also shown that membrane material selection can be efficiently optimized using the multi-objective optimization approach.

Cellulose Nanofibril Based-Aerogel Microreactors: A High Efficiency and Easy Recoverable W/O/W Membrane Separation System

Hereby we report a novel cellulose nanofirbril aerogel-based W/O/W microreactor system that can be used for fast and high efficient molecule or ions extraction and separation. The ultra-light cellulose nanofibril based aerogel microspheres with high porous structure and water storage capacity were prepared. The aerogel microspheres that were saturated with stripping solution were dispersed in an oil phase to form a stable water-in-oil (W/O) suspension. This suspension was then dispersed in large amount of external waste water to form W/O/W microreactor system. Similar to a conventional emulsion liquid membrane (ELM), the molecules or ions in external water can quickly transport to the internal water phase. However, the microreactor is also significantly different from traditional ELM: the water saturated nanocellulose cellulose aerogel microspheres can be easily removed by filtration or centrifugation after extraction reaction. The condensed materials in the filtrated aerogel particles can be squeezed and washed out and aerogel microspheres can be reused. This novel process overcomes the key barrier step of demulsification in traditional ELM process. Our experimental indicates the novel microreactor was able to extract 93% phenol and 82% Cu2+ from external water phase in a few minutes, suggesting its great potential for industrial applications.

A computational fluid dynamics (CFD) approach for the modeling of flux in a polymeric membrane using finite volume method

The computational fluid dynamics (CFD) modeling in this study observes steady-state mass transfer in a polymeric membrane. The efficiency, robustness, and reliability of recent numerical methods for finding solutions to flow problems have given rise to the implementation of CFD as a broadly used analysis method for engineering problems like membrane separation system. This study is novel due to the implementation of user-defined scalar diffusion equation by using user-defined functions in finite volume method (FVM). During the implementation of governing equation and boundary conditions important details of the FVM are discussed in detail. In this research, the flux profile is reported calculated from the pressure gradient for a steady-state problem.

Possibilities of application of advanced oxidation–membrane separation system for treatment and reuse of laundry wastewater

Possibilities of application of advanced oxidation–membrane separation system for treatment and reuse of laundry wastewater

Computational fluid dynamics (CFD) modeling of heat transfer in a polymeric membrane using finite volume method

The efficiency, robustness and reliability of recent numerical methods for finding solutions to flow problems have given rise to the implementation of computational fluid dynamics (CFD) as a broadly used analysis method for engineering problems like membrane separation system. The CFD modeling in this study observes steady and unsteady (transient) heat flux and temperature profiles in a polymeric (cellulose acetate) membrane. This study is novel due to the implementation of user defined scalar (UDS) diffusion equation by using user-defined functions (UDFs) infinite volume method (FVM). Some details of the FVM used by the solver are carefully discussed when implementing terms in the governing equation and boundary conditions (BC). The contours of temperature due to high-temperature gradient are reported for steady and unsteady problems.

Integration of multi-stage membrane carbon capture processes to coal-fired power plants using highly permeable polymers

Membrane separation systems could be a feasible option as post combustion carbon capture technologies in coal-fired power plants. Recent advancement on membrane materials based on microporous super glassy polymers could improve significantly the capture process but the properties of the materials have to guide the design of the separation stage. In this study an advanced hybrid two-stage membrane process employing one of the most permeable polymer known (PIM-1) is retrofitted to a coal fired power plant and the process is analysed in terms of energy requirement and cost performance. The results are based on the use of an in-house detailed membrane module model implemented in UniSim Design®, the Honeywell process flowsheet simulator. The study indicates the need for advanced configuration in order for highly permeable membranes to be competitive with more mature technologies in terms of capture cost. The effect of ageing and impurities on the material is also investigated in order to predict the decline in process performance over time and suggest a timeproof design.

Techno-economical evaluation of membrane based biogas upgrading system: A comparison between polymeric membrane and carbon membrane technology

A shift to renewable energy sources will reduce emissions of greenhouse gases and secure future energy supplies. In this context, utilization of biogas will play a prominent role. Focus of this work is upgrading of biogas to fuel quality by membrane separation using a carbon hollow fibre (CHF) membrane and compare with a commercially available polymeric membrane (polyimide) through economical assessment. CHF membrane modules were prepared for pilot plant testing and performance measured using CO2, O2, N2. The CHF membrane was modified through oxidation, chemical vapour deposition (CVD) and reduction process thus tailoring pores for separation and increased performance. The post oxidized and reduced carbon hollow fibres (PORCHFs) significantly exceeded CHF performance showing higher CO2 permeance (0.021 m3(STP)/m2 h bar) and CO2/CH4 selectivity of 246 (5 bar feed vs 50 mbar permeate pressure). The highest performance recorded through experiments (CHF and PORCHF) was used as simulation basis. A membrane simulation model was used and interfaced to 8.6 V Aspen HYSYS. A 300 Nm3/h mixture of CO2/CH4 containing 30–50% CO2 at feed pressures 6, 8 and 10 bar, was simulated and process designed to recover 99.5% CH4 with 97.5% purity. Net present value (NPV) was calculated for base case and optimal pressure (50 bar for CHF and PORCHF). The results indicated that recycle ratio (recycle/feed) ranged from 0.2 to 10, specific energy from 0.15 to 0.8 (kW/Nm3feed) and specific membrane area from 45 to 4700 (m2/Nm3feed). The high recycle ratio can create problems during start-up, as it would take long to adjust volumetric flow ratio towards 10. The best membrane separation system employs a three-stage system with polyimide at 10 bar, and a two-stage membrane system with PORCHF membranes at 50 bar with recycle. Considering biomethane price of 0.78 $/Nm3 and a lifetime of 15 years, the techno-economic analysis showed that payback time for the best cascade is 1.6 months.

CO2/CH4 separation by means of Matrimid hollow fibre membranes

CO2/CH4 mixtures separation was investigated using Matrimid®5218 hollow fibre membranes and measuring the membrane flux feeding singly CH4 and CO2 and their mixtures, with CH4 concentration ranging from 5 to 70 %molar. Specific attention was paid to membrane properties at a high temperature (up to 75 °C) and feeding humidified streams, not yet particularly investigated, in a pressure range 400–600 kPa. The membrane properties were restored when water vapour was removed and temperature decreased stating the excellent hydro-thermal stability of these membranes. Maps of the separation performance were also calculated for a range of operating conditions wider than the experimental one paying specific attention to the feed/permeate pressure ratio further to membrane selectivity and permeance. Single and multi-stage membrane separation systems were investigated using these maps. The prepared Matrimid®5218 hollow fibres showed very good performance in terms of flux and selectivity for temperatures up to 60 °C, also in steam saturated conditions, allowing a methane concentration meeting the specification for its injection into the grid.

A study of zinc borne waste water treatment with dispersion supported liquid membrane

This paper based on a theoretical study of the supported liquid membrane separation technology, explores the appropriate liquid membrane separation system, makes a study on the Pb (II) transmission behavior in the PC-88A-kerosene-HCl dispersion supported liquid membrane system and reviews influence of the feed liquid pH value, volume ratio between the membrane liquid and analytic agent, HCI concentration during analytic phase and initial Pb (II) transmission concentration. The results show that the migration of Pb (II) is well completed for 190 min with the migration rate being up to 95% on the premise that the feed liquid pH is equal to 6.0, Pb (II) initial concentration of 3.0 × 10−3 mol/L, HCl concentration during the stripped and dispersed phase is 4.0 mol/L, volume ratio between the stripped liquid and organic phase is 40:160 and that of the conventional supported liquid membrane is only 72.4%. The dispersion supported liquid membrane is characterized by higher transmission efficiency, stable membrane system and long membrane service life. The procedure has provided accurate results with zinc borne waste water treatment.

Preliminary Investigation of an Anaerobic Membrane Separation Process for Treatment of Low-Strength Wastewaters

As a result of an evaluation of biomass reduction technologies, anaerobic treatment was found to have potential for the lowest level of biomass production in the treatment of municipal and industrial wastewaters. A limitation of anaerobic wastewater treatment processes for dilute wastewaters and at cold temperatures is the ability to maintain a significant level of methanogenic organisms in the reactor to sustain efficient treatment. A process consisting of an anaerobic baffled reactor followed by membrane separation was proposed for the treatment of low strength wastewaters at colder temperatures. A 4 gpm pilot plant facility was assembled and installed at the West Point wastewater treatment plant in Seattle, to test the feasibility of the anaerobic/membrane separation treatment system. During a 7 month period, 3 different attempts were made for system start up with the result of little methanogenic activity in the anaerobic baffled reactor system. The temperatures during the start up ranged from 10 to 15°C and may have been a significant factor in the inability to generate a significant methanogenic population within the time available. Another aspect of this continuing study to investigate biomass reduction was a cost analysis to evaluate the potential for an anaerobic/membrane process for biomass reduction. The cost analysis showed that the significant capital expenditure for adding a membrane reactor to retrofit an existing secondary treatment system resulted in a greater annual amortization costs than the significant operational cost savings realized by less sludge production, less aeration hp, and excess methane gas production. Because the membrane separation system represented about 90% of the retrofit costs, the cost analysis suggests that a less expensive method be pursued for liquid solids separation after anaerobic treatment of low strength wastewaters. This title belongs to WERF Research Report Series ISBN: 9781843397298 (eBook)

Crude biodiesel refining using membrane ultra-filtration process: An environmentally benign process

Ceramic membrane separation system was developed to simultaneously remove free glycerol and soap from crude biodiesel. Crude biodiesel produced was ultra-filtered by multi-channel tubular membrane of the pore size of 0.05μm. The effects of process parameters: transmembrane pressure (TMP, bar), temperature (°C) and flow rate (L/min) on the membrane system were evaluated. The process parameters were then optimized using Central Composite Design (CCD) coupled with Response Surface Methodology (RSM). The best retention coefficients (%R) for free glycerol and soap were 97.5% and 96.6% respectively. Further, the physical properties measured were comparable to those obtained in ASTMD6751-03 and EN14214 standards.

Separation of lipid mixtures using a coupled supercritical CO 2 –membrane technology system

Abstract Supercritical CO 2 was used as a solvent for the separation of a triacylglycerol/oleic acid (TAG/OA) model mixture at different pressure conditions employing five commercially available polymer reverse osmosis membranes, AK, SG, HL, CE, and DL. Equal amounts of OA and TAG (%, w/w) were placed in the high pressure vessel. Contributions of SC-CO 2 extraction and membrane separation steps on the final OA concentration in the permeate mixture were investigated. TAG and OA separation factors for each membrane were determined at 120 and 280 bar. HL exhibited the best separation factors at 120 bar whereas both SG and HL had the highest OA separation factor at 280 bar. When the pressure was increased from 120 bar to 280 bar, total lipid yield in the permeate stream of SG membrane was increased by 7 fold. Feed pressure of 280 bar resulted in fouling of the membranes after 4 h of processing. Pure CO 2 addition did not delay the decrease in CO 2 flux. Feed pressure was found to be an important parameter affecting yield and final composition after separation by using the coupled SC-CO 2 extraction–membrane separation system.