Effect of Porous-Jump Model Parameters on Membrane Flux Prediction

2013 ◽  
Vol 734-737 ◽  
pp. 2210-2213
Author(s):  
Hong Hai Li ◽  
Yang Yang Cheng
Keyword(s):  
Porous Medium ◽  
Cfd Simulation ◽  
Membrane Separation ◽  
Membrane Surface ◽  
Model Parameters ◽  
Membrane Thickness ◽  
Pressure Jump ◽  
Medium Thickness ◽  
Membrane Flux ◽  
Jump Model

A three-dimensional computational fluid dynamics (CFD) simulation was performed to study the velocity distribution on membrane surface in membrane separation process, and the effect of face permeability, porous medium thickness, and pressure-jump coefficient of porous-jump model on membrane flux. The study shows that all the three factors have important impact on membrane flux. Membrane flux increases linearly with the increase of face permeability. When the membrane thickness is between 0.04~0.1mm, the membrane flux decreases with the increase of membrane thickness. The membrane flux decreases with the increase of pressure-jump coefficient. So that there must be a complex relationship between membrane flux and face permeability, porous medium thickness, and pressure-jump coefficient.

Optimization of the process of membrane separation of MSW landfill leachate with a high concentration of hardness salts

2021 ◽  
pp. 23-29
Author(s):  
М.Е. Ильина ◽  
И.Н. Курочкин
Keyword(s):  
Solid Waste ◽  
Reverse Osmosis ◽  
Membrane Separation ◽  
Sodium Tripolyphosphate ◽  
Membrane Surface ◽  
Feed Water ◽  
High Concentration ◽  
Waste Landfill ◽  
Membrane Flux ◽  
Sediment Formation

Рассмотрен вопрос оптимизации процесса мембранного обратноосмотического разделения имеющего повышенное содержание солей жесткости фильтрата полигона твердых бытовых отходов. Исследования проводились на экспериментальной двухступенчатой установке обратного осмоса. Для изучения возможности повышения эффективности процесса мембранного обратноосмотического разделения фильтрата и, в частности, удельной производительности мембраны в исходную осветленную фильтрационную воду (перед мембранным разделением) вводились различные ингибиторы осадкообразования: Avista Vitec 3000, Clarofos 381 и триполифосфат натрия. В качестве исследуемого водного раствора использовались фильтрационные воды полигона твердых бытовых отходов «Марьинский» (Владимирская область), которые имели повышенное содержание солей жесткости. По результатам проведенных исследований осуществлена оценка эффективности действия различных ингибиторов осадкообразования на процесс мембранного обратноосмотического разделения по показателю удельной производительности мембраны. Доказано положительное влияние на мембранное разделение введения в исходный осветленный фильтрат полигона ТБО ингибиторов процесса осадкообразования солей жесткости на поверхности мембран. Наилучшие результаты по увеличению удельной производительности мембраны при очистке осветленной фильтрационной воды были получены при использовании ингибитора Avista Vitec 3000. Проведенные исследования показали, что при выборе ингибитора осадкообразования необходимо учитывать особенности состава исходной воды, режим работы мембранного оборудования и особые требования технологии очистки. The aspects of optimizing the process of reverse osmosis membrane separation of the leachate of a municipal solid waste landfill with a high concentration of hardness salts is considered. The research was carried out in an experimental two-stage reverse osmosis unit. To study possible increasing the efficiency of the membrane reverse osmosis separation of the leachate and, in particular, of the membrane flux, various inhibitors of sediment formation were added to the feed clarified percolating water (before the membrane separation): Avista Vitec 3000, Clarofos 381, and sodium tripolyphosphate. Percolating water of the Mar’inskii solid waste landfill (Vladimir region) with a high concentration of hardness salts was used as a researchable aqueous solution. Based on the results of the executed studies, the effect of various inhibitors of sediment formation on the process of membrane reverse osmosis separation was estimated in terms of the membrane flux. The positive effect on membrane separation of the inhibitors of the sediment formation of hardness salts on the membrane surface added into the feed clarified leachate of the solid waste landfill has been proven. The best results in increasing the membrane flux during the purification of clarified percolating water were obtained with the use of the Avista Vitec 3000 inhibitor. The executed studies have shown that while choosing a sediment formation inhibitor, the specific composition of the feed water, the operating mode of the membrane equipment and the special requirements of the purification technology should be taken into account.

Highly proton conductive membranes based on carboxylated cellulose nanofibres and their performance in proton exchange membrane fuel cells

2019 ◽  
Author(s):  
Valentina Guccini ◽  
Annika Carlson ◽  
Shun Yu ◽  
Göran Lindbergh ◽  
Rakel Wreland Lindström ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Surface Charge ◽  
Proton Exchange Membrane ◽  
Membrane Surface ◽  
Proton Exchange ◽  
Membrane Thickness ◽  
Fuel Cell Performance ◽  
Cellulose Nanofibres ◽  
Exchange Membrane

The performance of thin carboxylated cellulose nanofiber-based (CNF) membranes as proton exchange membranes in fuel cells has been measured in-situ as a function of CNF surface charge density (600 and 1550 µmol g<sup>-1</sup>), counterion (H<sup>+</sup>or Na<sup>+</sup>), membrane thickness and fuel cell relative humidity (RH 55 to 95 %). The structural evolution of the membranes as a function of RH as measured by Small Angle X-ray scattering shows that water channels are formed only above 75 % RH. The amount of absorbed water was shown to depend on the membrane surface charge and counter ions (Na<sup>+</sup>or H<sup>+</sup>). The high affinity of CNF for water and the high aspect ratio of the nanofibers, together with a well-defined and homogenous membrane structure, ensures a proton conductivity exceeding 1 mS cm<sup>-1</sup>at 30 °C between 65 and 95 % RH. This is two orders of magnitude larger than previously reported values for cellulose materials and only one order of magnitude lower than Nafion 212. Moreover, the CNF membranes are characterized by a lower hydrogen crossover than Nafion, despite being ≈ 30 % thinner. Thanks to their environmental compatibility and promising fuel cell performance the CNF membranes should be considered for new generation proton exchange membrane fuel cells.<br>

Modeling of Hydrogen-Air Detonations in the TONUS CFD Code and Its Application to the FLAME F-19 Test

2008 ◽  
Author(s):  
Eveliina Takasuo
Keyword(s):  
Cfd Simulation ◽  
Hydrogen Combustion ◽  
Severe Accident ◽  
Parameter Study ◽  
Model Parameters ◽  
Gas Detonation ◽  
Global Rate ◽  
Detonation Structure ◽  
Mesh Resolution ◽  
Post Shock

In severe accident management, the ability to predict pressure and thermal loads resulting from hydrogen combustion is important since they may threaten containment integrity. In computational modeling, different combustion regimes have to be accounted for and state-of-the-art techniques developed for reliable analysis. In the present study, the focus is on computational fluid dynamics code validation for reactive flows in the detonation regime. The FLAME hydrogen combustion test F-19 performed at the Sandia National Laboratories has been simulated by using the gas detonation model implemented in the TONUS CFD code which is developed by CEA and IRSN (France). In this model the reactive Euler equations are solved and the reaction rate is obtained by the Arrhenius global rate equation. Several simulations were run in order to examine the effect of modifying the parameters of the chemistry model. A mesh convergence study was performed for the purpose of finding out the necessary mesh resolution which could capture the detonation propagation with adequate accuracy. In addition, Chapman-Jouguet post-shock equilibrium conditions and the ZND detonation structure for the present gas mixture were examined by chemical kinetics calculations. The CFD simulation results were compared to the test results and the Chapman-Jouguet post-shock conditions. It was observed that the computational results differ from the C-J results with the C-J velocity being slightly exceeded. The model parameter study showed that it is not possible to significantly affect the flame propagation by adjusting the model parameters.

A Wall Film Model for Membrane Fouling

2018 ◽  
Author(s):  
Sina Jahangiri Mamouri ◽  
Volodymyr V. Tarabara ◽  
André Bénard
Keyword(s):  
Multiphase Flow ◽  
Membrane Fouling ◽  
Oil And Gas ◽  
Membrane Separation ◽  
Film Formation ◽  
Membrane Surface ◽  
Permeate Flux ◽  
Water Separation ◽  
Wall Film ◽  
Oil Water

Deoiling of produced or impaired waters associated with oil and gas production represents a significant challenge for many companies. Centrifugation, air flotation, and hydrocyclone separation are the current methods of oil removal from produced water [1], however the efficiency of these methods decreases dramatically for droplets smaller than approximately 15–20 μm. More effective separation of oil-water mixtures into water and oil phases has the potential to both decrease the environmental footprint of the oil and gas industry and improve human well-being in regions such as the Gulf of Mexico. New membrane separation processes and design of systems with advanced flow management offer tremendous potential for improving oil-water separation efficacy. However, fouling is a major challenge in membrane separation [2]. In this study, the behavior of oil droplets and their interaction with crossflow filtration (CFF) membranes (including membrane fouling) is studied using computational fluid dynamics (CFD) simulations. A model for film formation on a membrane surface is proposed for the first time to simulate film formation on membrane surfaces. The bulk multiphase flow is modeled using an Eulerian-Eulerian multiphase flow model. A wall film is developed from mass and momentum balances [3] and implemented to model droplet deposition and membrane surface blockage. The model is used to predict film formation and subsequent membrane fouling, and allow to estimate the actual permeate flux. The results are validated using available experimental data.

scholarly journals Biofouling Characteristics of Graphene Oxide Membrane in a Protein-rich Environment

2021 ◽  
Author(s):  
Richard P Rode ◽  
Saeed Moghaddam
Keyword(s):  
Graphene Oxide ◽  
Self Assembly ◽  
Membrane Surface ◽  
Water Flux ◽  
Polymer Membrane ◽  
Blood Protein ◽  
Separation Processes ◽  
Sem Images ◽  
Membrane Flux ◽  
Protein Rich

Membrane biofouling has inhibited permselective separation processes for decades, requiring frequent membrane backwash treatment or replacement to maintain efficacy. However, frequent treatment is not viable for devices with a continuous blood flow such as a wearable or implantable dialyzer. In this study, the biofouling characteristics of a highly hemocompatible graphene oxide (GO) membrane developed through a novel self-assembly process is studied in a protein-rich environment and compared with performance of a state-of-the-art commercial polymer membrane dialyzer. The studies are conducted in phosphate-buffered saline (PBS) environment using human serum albumin (HSA), which represents 60% of the blood protein, at the nominal blood protein concentration of 1 g L-1. Protein aggregation on the membrane surface is evaluated by monitoring the change in the membrane flux and SEM imaging. The GO membrane water flux declined only ~10% over a week-long test whereas the polymer membrane flux declined by 50% during the same period. The SEM images show that HSA primarily aggerates over the graphitic regions of nanoplatelets, away from the charged hydrophilic edges. This phenomenon leaves the open areas of the membrane formed between the nanoplatelets edges, through which the species pass, relatively intact. In contrast, HSA completely plugs the polymer membrane pores resulting in a steady decline in membrane permeability.

The Effect of Flow Pulsation on Ultrafiltration System Limiting Flux Behavior

2013 ◽  
Author(s):  
Chyouhwu Brian Huang ◽  
Hung-Shyong Chen
Keyword(s):  
Membrane Filtration ◽  
Concentration Polarization ◽  
Membrane Separation ◽  
Membrane Surface ◽  
Paper Industry ◽  
Surface Concentration ◽  
Permeate Flux ◽  
Filtration Time ◽  
Protection Systems ◽  
Oil Water

Ultrafiltration (UF) is an important industrial operation and is found in the food industry, separation of oil-water emulsions, treatment effluents from the pulp and paper industry, and environmental protection systems. Despite being widely used in these areas, UF systems exhibit a limiting flux behavior caused by concentration polarization on the membrane surface. Concentration polarization can be severe in macromolecular solutions due to low diffusivity on membrane separation and both mechanical and chemical methods have been used to reduce this phenomenon. This study introduces a new mechanical method that improves the performance of membrane separation and decreases concentration polarization. It involves pulsing the feed flow discontinuously and based on our results, feed flow velocity and solution bypass/membrane filtration time ratio are two vital factors when it comes to improving permeate flux. The proposed method is expected to find wide application, particularly in the processing of macromolecular solution.

scholarly journals Experimental and Computational Analysis of NOx Photocatalytic Abatement Using Carbon-Modified TiO2 Materials

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1366
Author(s):  
Tatiana Zhiltsova. ◽  
Nelson Martins ◽  
Mariana R. F. Silva ◽  
Carla F. Da Silva ◽  
Mirtha A. O. Lourenço ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Kinetic Model ◽  
Photocatalytic Oxidation ◽  
Cfd Simulation ◽  
Emission Spectra ◽  
Chemical Kinetic ◽  
Solar Light ◽  
Model Parameters ◽  
Chemical Kinetic Model ◽  
Simulated Solar Light

In the present study, two photocatalytic graphene oxide (GO) and carbon nanotubes (CNT) modified TiO2 materials thermally treated at 300 °C (T300_GO and T300_CNT, respectively) were tested and revealed their conversion efficiency of nitrogen oxides (NOx) under simulated solar light, showing slightly better results when compared with the commercial Degussa P25 material at the initial concentration of NOx of 200 ppb. A chemical kinetic model based on the Langmuir–Hinshelwood (L-H) mechanism was employed to simulate micropollutant abatement. Modeling of the fluid dynamics and photocatalytic oxidation (PCO) kinetics was accomplished with computational fluid dynamics (CFD) approach for modeling single-phase liquid fluid flow (air/NOx mixture) with an isothermal heterogeneous surface reaction. A tuning methodology based on an extensive CFD simulation procedure was applied to adjust the kinetic model parameters toward a better correspondence between simulated and experimentally obtained data. The kinetic simulations of heterogeneous photo-oxidation of NOx carried out with the optimized parameters demonstrated a high degree of matching with the experimentally obtained NOx conversion. T300_CNT is the most active photolytic material with a degradation rate of 62.1%, followed by P25-61.4% and T300_GO-60.4%, when irradiated, for 30 min, with emission spectra similar to solar light.

Removal of manganese from water using combined chelation/membrane separation systems

2005 ◽  
Vol 51 (6-7) ◽  
pp. 349-355 ◽  
Author(s):  
S.-C. Han ◽  
K.-H. Choo ◽  
S.-J. Choi ◽  
M.M. Benjamin
Keyword(s):  
Membrane Separation ◽  
Membrane Surface ◽  
Feed Solution ◽  
Operating Conditions ◽  
Acidic Ph ◽  
Nitrate Ions ◽  
Manganese Removal ◽  
Regeneration Cycle ◽  
Manganese Hydroxides ◽  
Volumetric Flux

The addition of the chelating polymer polyacrylic acid (PAA) to assist in the removal of manganese from groundwater by membranes was investigated using membranes with different pore sizes under various operating conditions. Negligible manganese removal was achieved with the UF and NF membranes at acidic pH values, but removals exceeding 90% could be achieved at elevated pH (pH 9), presumably due to the formation of manganese hydroxides. Mn removal increased substantially when PAA was added to the feed solution, due to chelation of Mn by the PAA and rejection of the chelates by the membranes. The chelate could be broken at acidic pH, releasing free PAA that could then be separated from the Mn ions and reused. Smaller PAA molecules were lost in the first regeneration cycle, but negligible PAA was lost in subsequent cycles. In the systems with PAA, nitrate ions were rejected more efficiently than in the PAA-free systems, presumably because of electrical repulsion between nitrate ions and PAA sorbed on the membrane surface. With increasing PAA dose, the volumetric flux first decreased and then increased; the latter result was accompanied by a change in the physical-chemical form of the polymers, as indicated by an increase in turbidity.

scholarly journals Ceramic Membranes Photocatalytically Functionalized on the Permeate Side and Their Application to Water Treatment

Membranes ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 64 ◽  
Author(s):  
André Ayral
Keyword(s):  
Organic Molecules ◽  
Membrane Separation ◽  
Functional Performance ◽  
Membrane Surface ◽  
Scale Up ◽  
Ceramic Membranes ◽  
Membrane Surface Area ◽  
Small Organic Molecules ◽  
Different Types ◽  
Specific Degradation

This work deals with direct coupling of membrane separation and photocatalytic degradation by using photocatalytic ceramic membranes. An unusual configuration is considered here, with the irradiation applied on the permeate side of the membrane in order to mineralize small organic molecules not retained by the membrane. Different types of such membranes are presented. Their functional performance is quantified thanks to a simple experimental method enabling the estimation of the specific degradation rate δ, i.e., the quantity of destroyed organic molecules per unit of time and of membrane surface area. The relevance of δ for the design and scale-up of purification units is then illustrated. Finally, current technological challenges and potential solutions concerning the industrial implementation of such photocatalytic membranes are discussed.

Replacement of Secondary Clarification by Membrane Separation—Results with Tubular, Plate and Hollow Fibre Modules

1999 ◽  
Vol 40 (4-5) ◽  
pp. 311-320 ◽  
Author(s):  
Berthold Günder ◽  
Karlheinz Krauth
Keyword(s):  
Activated Sludge ◽  
Suspended Solids ◽  
Membrane Separation ◽  
Membrane Surface ◽  
Hollow Fibre ◽  
Stable Operation ◽  
Membrane Systems ◽  
Process Technology ◽  
Mixed Liquor ◽  
Activated Sludge Processes

Membrane separation systems can replace the final clarification step to separate mixed liquor suspended solids (MLSS) in the activated sludge processes. Mixed liquor suspended solids concentrations as high as 20 g/l can be obtained compared with the typical 3-4 g/l for conventional activated sludge/secondary clarifier systems. This leads to much smaller reactor volumes. In addition, excellent, solids free effluent qualities can be achieved with this process technology. This paper reports about the parallel investigation of three membrane systems installed within or outside bioreactors of 7 to 9 m3 volume and flow rates from 1 to 3 m3/h. The different membrane modules were investigated: plate module (80 m2 membrane surface), hollow fibre module (80 m2) and tubular module (45 m2). At MLSS concentrations up to 25 g/l and water temperatures from 10 to 25°C a stable operation of the membrane systems was achieved for a period of more than one year. The energy consumption was approximately 1.5 kWh/m3 for the plate and hollow fibre and 3.0 kWh/m3 for the tubular module system.

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