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Mark Wilf - One of the best experts on this subject based on the ideXlab platform.
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effect of feed temperature on Permeate Flux and mass transfer coefficient in spiral wound reverse osmosis systems
Desalination, 2002Co-Authors: Mattheus F A Goosen, Shyam S Sablani, Salha Saleh Almaskari, R Albelushi, Mark WilfAbstract:The objective of the present study was to analyze and model concentration polarization in spiral-wound seawater membrane elements. In particular, the influence of feed temperature, salinity and flow rate on Permeate flow and salinity was evaluated. Membrane lifetime and Permeate Fluxes are primarily affected by the phenomena of concentration polarization (accumulation of solute) and fouling (i.e., microbial adhesion, gel layer formation and solute adhesion) at the membrane surface. Results show that the polymer membrane is very sensitive to changes in the feed temperature. There was up to a 60% increase in the Permeate Flux when the feed temperature was increased from 20 to 40°C. This occurred both in the presence and absence of solute. Surprisingly, the Permeate Flux appears to go through a minimum at an intermediate temperature. There was up to a 100% difference in the Permeate Flux between feed temperatures of 30 and 40°C. The differences were statistically significant (p<0.05). A doubling of the feed flow rate increased the Permeate Flux by up to 10%, but only at a high solute concentration. Membrane parameters were estimated using an analytical osmotic pressure model for high salinity applications. A combined Spiegler-Kedem/film theory model described the experimental results. The modeling studies showed that the membrane transport parameters were influenced by the feed salt concentration and temperature.
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Effect of feed temperature on Permeate Flux and mass transfer coefficient in spiral-wound reverse osmosis systems☆
Desalination, 2002Co-Authors: Mattheus F A Goosen, Shyam S Sablani, Salha Saleh Al-maskari, R. Al-belushi, Mark WilfAbstract:The objective of the present study was to analyze and model concentration polarization in spiral-wound seawater membrane elements. In particular, the influence of feed temperature, salinity and flow rate on Permeate flow and salinity was evaluated. Membrane lifetime and Permeate Fluxes are primarily affected by the phenomena of concentration polarization (accumulation of solute) and fouling (i.e., microbial adhesion, gel layer formation and solute adhesion) at the membrane surface. Results show that the polymer membrane is very sensitive to changes in the feed temperature. There was up to a 60% increase in the Permeate Flux when the feed temperature was increased from 20 to 40°C. This occurred both in the presence and absence of solute. Surprisingly, the Permeate Flux appears to go through a minimum at an intermediate temperature. There was up to a 100% difference in the Permeate Flux between feed temperatures of 30 and 40°C. The differences were statistically significant (p
R J Wakeman - One of the best experts on this subject based on the ideXlab platform.
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shear stress based modelling of steady state Permeate Flux in microfiltration enhanced by two phase flows
Chemical Engineering Journal, 2004Co-Authors: Petr Pospíšil, R J Wakeman, I O A Hodgson, Petr MikulášekAbstract:Abstract Crossflow microfiltration experiments without intensification and with two-phase gas–liquid flow were performed on aqueous titanium dioxide dispersions using an alumina tubular membrane. The influence of gas flow velocity on Flux was studied. The empirical model for steady state Permeate Flux and cake thickness prediction was developed. The results of experiments show positive effects of constant gas–liquid two-phase flow on the Flux. It was found that there are no operating conditions at which air injection has no effect on the Permeate Flux. From analysis of the experimental results without gas flow, the empirical model based on Darcy’s Law and on mass balance over a membrane module was derived. The model is based on dimensionless numbers regression of all basic operating conditions that influence Permeate Flux and cake thickness. The results showed good agreement between model prediction and experimental data with gas injection tested on the same apparatus. When the data from a different system (membrane type, membrane material) were taken, the agreement was not so good.
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crossflow microfiltration behaviour of a double chain cationic surfactant dispersion in water i the effect of process and membrane characteristics on Permeate Flux and surfactant rejection
Chemical Engineering Science, 1994Co-Authors: G. Akay, R J WakemanAbstract:Abstract Microfiltration of a double-chain cationic surfactant, dioctadecyldimethylammonium chloride, in water has been studied using 1 or 0.2 μm track-etched polycarbonate membranes. A computer-controlled filter rig was used, in which the process conditions of crossflow velocity u , transmembrane pressure drop Δ p and temperature T were changed independently. In addition, Permeate Flux J and in some cases surfactant concentration in the feed c f and Permeate c p , were monitored during filtration. The effects of process and material variables on the Permeate Flux decay, steady-state Permeate Flux J ∞ and the Permeate surfactant concentration were assessed. It was found that fouling of the membrane by surfactant is very rapid (within tens of seconds) although high crossflow veclocity, large memebrane pore size and low feed surfactant concentration reduced the rate of surfactant deposition. Steay-state Permeate Flux increases significantly with crossflow velocity provided the surfactant is in a rigid chain (gel) lamellar dispersion state ( T J ∞ decays linearly with ln ( c f ) provided the feed concentration is less than the so-called gel concentration ( c g ) which is obtained by extrapolating the linear portion of the curves J ∞ vs ln ( c f ) so that c f = c g when J ∞ 0. Although the gel concentration, which is independent of pore size and the process variables, is found to be 20 gl −1 , experiments conducted at feed concentration well above c g still yield a reasonable Permeate Flux, albeit at a reduced level. Surfactant rejection studies indicate that 0.2 μm membranes yield lower rejection than 1 μm membranes while rejection is greater at 30°C than at 60°C. Other process variables do not have any significant influence on rejection. The effectiveness of a membrane and the processing conditions can be quantified by considering the variation of J ∞ with c p /c f . It is found that a 1 μm membrane is more effective than a 0.2 μm membrane, crossflow velocity increase the effectiveness of the process, and that temperature has no significant influence.
Mattheus F A Goosen - One of the best experts on this subject based on the ideXlab platform.
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effect of feed temperature on Permeate Flux and mass transfer coefficient in spiral wound reverse osmosis systems
Desalination, 2002Co-Authors: Mattheus F A Goosen, Shyam S Sablani, Salha Saleh Almaskari, R Albelushi, Mark WilfAbstract:The objective of the present study was to analyze and model concentration polarization in spiral-wound seawater membrane elements. In particular, the influence of feed temperature, salinity and flow rate on Permeate flow and salinity was evaluated. Membrane lifetime and Permeate Fluxes are primarily affected by the phenomena of concentration polarization (accumulation of solute) and fouling (i.e., microbial adhesion, gel layer formation and solute adhesion) at the membrane surface. Results show that the polymer membrane is very sensitive to changes in the feed temperature. There was up to a 60% increase in the Permeate Flux when the feed temperature was increased from 20 to 40°C. This occurred both in the presence and absence of solute. Surprisingly, the Permeate Flux appears to go through a minimum at an intermediate temperature. There was up to a 100% difference in the Permeate Flux between feed temperatures of 30 and 40°C. The differences were statistically significant (p<0.05). A doubling of the feed flow rate increased the Permeate Flux by up to 10%, but only at a high solute concentration. Membrane parameters were estimated using an analytical osmotic pressure model for high salinity applications. A combined Spiegler-Kedem/film theory model described the experimental results. The modeling studies showed that the membrane transport parameters were influenced by the feed salt concentration and temperature.
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Effect of feed temperature on Permeate Flux and mass transfer coefficient in spiral-wound reverse osmosis systems☆
Desalination, 2002Co-Authors: Mattheus F A Goosen, Shyam S Sablani, Salha Saleh Al-maskari, R. Al-belushi, Mark WilfAbstract:The objective of the present study was to analyze and model concentration polarization in spiral-wound seawater membrane elements. In particular, the influence of feed temperature, salinity and flow rate on Permeate flow and salinity was evaluated. Membrane lifetime and Permeate Fluxes are primarily affected by the phenomena of concentration polarization (accumulation of solute) and fouling (i.e., microbial adhesion, gel layer formation and solute adhesion) at the membrane surface. Results show that the polymer membrane is very sensitive to changes in the feed temperature. There was up to a 60% increase in the Permeate Flux when the feed temperature was increased from 20 to 40°C. This occurred both in the presence and absence of solute. Surprisingly, the Permeate Flux appears to go through a minimum at an intermediate temperature. There was up to a 100% difference in the Permeate Flux between feed temperatures of 30 and 40°C. The differences were statistically significant (p
G. Akay - One of the best experts on this subject based on the ideXlab platform.
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Permeate Flux decay during crossflow microfiltration of a cationic surfactant dispersion
Filtration & Separation, 1994Co-Authors: G. Akay, Richard J. WakemanAbstract:Abstract The transient Permeate Flux and rejection behaviour of a cationic surfactant dispersion during crossflow microfiltration is studied using membranes with different degrees of hydrophobicity which is characterised by the solubility parameter. It is found that the transient Permeate Flux behaviour is strongly affected by the membrane hydrophobicity if the feed concentration is low. The mechanism of crossflow membrane filtration is evaluated by studying, in addition to transient Permeate Flux and rejection, the deposition of the surfactant on the membrane and within its pores. It is shown that the surfactant deposition results in the formation of a secondary membrane supported by the primary membrane. To a large extent, the secondary membrane controls the Permeate Flux and rejection of the surfactant. The secondary membrane is formed on the surface of the membrane, and penetrates into the pores forming a region of high surfactant concentration which is an order of magnitude higher than the so-called gel concentration.
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mechanisms of Permeate Flux decay solute rejection and concentration polarisation in crossflow filtration of a double chain ionic surfactant dispersion
Journal of Membrane Science, 1994Co-Authors: G. Akay, R J WakemaAbstract:Abstract The mechanism of crossflow membrane filtration of an ionic double chain surfactant dispersion is evaluated by studying the deposition of the surfactant on the membrane and within its pores, together with the transient behaviour of the Permeate Flux and Permeate concentration. It is shown that the surfactant deposition results in the formation of a secondary membrane supported by the primary membrane. To a large extent, the secondary membrane controls the Permeate Flux and rejection of the surfactant. The secondary membrane is formed on the surface of the membrane and penetrates into the pores forming a region of high surfactant concentration which is an order of magnitude higher than the so-called (pseudo) gel concentration. The structure of the secondary membrane, evaluated from cold field emission scanning electron microscopy, differs from that expected on the basis of phase behaviour of the surfactant at the prevailing concentration, temperature and pressure.
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crossflow microfiltration behaviour of a double chain cationic surfactant dispersion in water i the effect of process and membrane characteristics on Permeate Flux and surfactant rejection
Chemical Engineering Science, 1994Co-Authors: G. Akay, R J WakemanAbstract:Abstract Microfiltration of a double-chain cationic surfactant, dioctadecyldimethylammonium chloride, in water has been studied using 1 or 0.2 μm track-etched polycarbonate membranes. A computer-controlled filter rig was used, in which the process conditions of crossflow velocity u , transmembrane pressure drop Δ p and temperature T were changed independently. In addition, Permeate Flux J and in some cases surfactant concentration in the feed c f and Permeate c p , were monitored during filtration. The effects of process and material variables on the Permeate Flux decay, steady-state Permeate Flux J ∞ and the Permeate surfactant concentration were assessed. It was found that fouling of the membrane by surfactant is very rapid (within tens of seconds) although high crossflow veclocity, large memebrane pore size and low feed surfactant concentration reduced the rate of surfactant deposition. Steay-state Permeate Flux increases significantly with crossflow velocity provided the surfactant is in a rigid chain (gel) lamellar dispersion state ( T J ∞ decays linearly with ln ( c f ) provided the feed concentration is less than the so-called gel concentration ( c g ) which is obtained by extrapolating the linear portion of the curves J ∞ vs ln ( c f ) so that c f = c g when J ∞ 0. Although the gel concentration, which is independent of pore size and the process variables, is found to be 20 gl −1 , experiments conducted at feed concentration well above c g still yield a reasonable Permeate Flux, albeit at a reduced level. Surfactant rejection studies indicate that 0.2 μm membranes yield lower rejection than 1 μm membranes while rejection is greater at 30°C than at 60°C. Other process variables do not have any significant influence on rejection. The effectiveness of a membrane and the processing conditions can be quantified by considering the variation of J ∞ with c p /c f . It is found that a 1 μm membrane is more effective than a 0.2 μm membrane, crossflow velocity increase the effectiveness of the process, and that temperature has no significant influence.
Petr Mikulášek - One of the best experts on this subject based on the ideXlab platform.
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shear stress based modelling of steady state Permeate Flux in microfiltration enhanced by two phase flows
Chemical Engineering Journal, 2004Co-Authors: Petr Pospíšil, R J Wakeman, I O A Hodgson, Petr MikulášekAbstract:Abstract Crossflow microfiltration experiments without intensification and with two-phase gas–liquid flow were performed on aqueous titanium dioxide dispersions using an alumina tubular membrane. The influence of gas flow velocity on Flux was studied. The empirical model for steady state Permeate Flux and cake thickness prediction was developed. The results of experiments show positive effects of constant gas–liquid two-phase flow on the Flux. It was found that there are no operating conditions at which air injection has no effect on the Permeate Flux. From analysis of the experimental results without gas flow, the empirical model based on Darcy’s Law and on mass balance over a membrane module was derived. The model is based on dimensionless numbers regression of all basic operating conditions that influence Permeate Flux and cake thickness. The results showed good agreement between model prediction and experimental data with gas injection tested on the same apparatus. When the data from a different system (membrane type, membrane material) were taken, the agreement was not so good.
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Hydrodynamic based calculation of steady state Permeate Flux in microfiltration process
2003Co-Authors: Petr Pospíšil, Petr Mikulášek, Petr DolečekAbstract:Crossflow microfiltration experiments were performed with aqueous titanium dioxide dispersions and alumina tubular membranes. Intensification effect of two-phase gas-liquid flow was studied on this system. The results ofexperiments show a positive effect of constant gas-liquid two-phase flow on the Permeate Flux values; both the immediate and steady state ones. The maximum increase inFlux values up to 90 % was reached during the experiments in the slug flow regime of gas-liquid flow, which was found the most efficient regime applied during intensification experiments. The empirical model for steady state Permeate Flux and cake thickness prediction was developed from analysis of experimental results without gas flow. This model is based on Darcy's Law and on Mass balance over a membrane module. Dimensionless numbers covering all the basic operating conditions that influence Permeate Flux and cake thickness were introduced, and from their regression in the range of experimental feed concentrations final equations were derived. The results show good agreement between model prediction and experimental data with gas-liquid flow tested on the same apparatus.
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Effects of backflushing conditions on Permeate Flux in membrane crossflow microfiltration of oil emulsion
Desalination, 2000Co-Authors: Jiří Cakl, Petr Doleček, I. Bauer, Petr MikulášekAbstract:The paper reports results of experiments with oil-in-water emulsion, which were carried out in a laboratory crossflow microfiltration unit equipped with backflushed zirconia ceramic membranes. The results demonstrate that the membrane backflushing can maintain the Permeate Flux at a level which is nearly three-fold over the long-term Flux in the absence of membrane backflushing. It was observed that the effect of backflushing was the more pronounced when the backpulse duration was shorter, the transmembrane pressure difference was higher, and the retentate velocity was lower in forward filtration. An optimum backflushing frequency which maximized the average Permeate Flux was found to be in the range of 1 to 50 s depending on the operating conditions. The magnitude of the transmembrane pressure difference in the reverse flow had a relatively small effect. Attempt has also been made to explain the results in terms of a simple semiempirical model of the process. Parameters evaluated from dynamic and steady state experiments without membrane backflushing were shown to be useful in estimating the performance of the process with membrane backflushing. The influence of backflushing duration and frequency, transmembrane pressure difference, and retentate velocity on average Permeate Flux were well predicted using this model.
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Effect of Fluidized Bed on Permeate Flux in Ceramic Membrane Cross-Flow Microfiltration
Collection of Czechoslovak Chemical Communications, 1995Co-Authors: Petr MikulášekAbstract:The microfiltration of a model fluid on an α-alumina microfiltration tubular membrane in the presence of a fluidized bed has been examined. Following the description of the basic characteristic of alumina tubular membranes, model dispersion and spherical particles used, some comments on the experimental system and experimental results for different microfiltration systems are presented. From the analysis of experimental results it may be concluded that the use of turbulence-promoting agents resulted in a significant increase of Permeate Flux through the membrane. It was found out that the optimum porosity of fluidized bed for which the maximum values of Permeate Flux were reached is approximately 0.8.
