Slotted Pore Membrane Research Articles

Modelling of transmembrane pressure using slot/pore blocking model, response surface and artificial intelligence approach

This work investigates the application of empirical, statistical and machine learning methods to appraise the prediction of transmembrane pressure (TMP) by oscillating slotted pore membrane for the treatment of two kinds of deformable oil drops. Here, we utilized the previous experimental runs with permeate flux, shear rate and filtration time as features, while TMP of crude oil and Tween-20 were two distinct targets. For 87 experimental runs, Response surface methodology (RSM) and Artificial Neural network (ANN) modelling were opted as statistical and machine learning tools, respectively, which were comprehensively compared with empirical slot-pore blocking model (SBM) considering accuracy and generalization. ANN with 10 neurons in the hidden layer could approximate the TMP of both oils better than RSM and SBM, which is reflected by computed performance metrics. Under the given conditions, almost similar analysis were predicted for TMP of both oils except changes in magnitude which were interpreted by (1) line plots, which showed that TMP of crude oil and Tween-20 were linearly related to flux rate and filtration time, and there was an inverse relationship between TMP and shear rate, (2) contour plots, which illustrated the strong interaction effect of flux rate and time on TMP, and (3)- sensitivity analysis, which revealed the influential sequence of variables on TMP as; flux rate > filtration time > shear rate, for both cases. The optimisation of the process showed that minimum TMP can be attained by maintaining higher shear rate and lower flux rate and time. Conclusively, the current findings indicate the utilization of ANN for the accurate assessment of TMP and can be helpful for the process designing and scale up.

Crude Oil Drop Penetration into Permeates Using a Slotted Pore Membrane.

The primary focus of the presented research is to come up with a model that could be utilized to evaluate the permeate content (concentration) of oil drops using a straight (nonconverging) slotted microstructured membrane. The content (concentration) of crude drops in the permeate with a nonconverging slit structure membrane has not been studied before, and the study presented would be a good contribution to the literature. A comparison between the use of a converging (narrowing toward the inside) and a nonconverging slotted pore microstructured membrane is made for the purpose of removing oil content from the produced water. Due to the drag force, the droplets pass through the membrane slots; however, the static force acts in the opposite direction and tries to reject droplets by the membrane. At a certain point, these two forces balance the effect of each other, which is known as “100% cutoff through the membrane”. A linear line is obtained by joining the 100% cutoff or rejection point to the 0% rejection point, which is referred to as the “linear fit” in this paper. The linear fit approach could be utilized for estimating rejection below the 100% cutoff point. Various types of crude oil drops obtained from different locations were analyzed experimentally, and the results were compared with the presented model. The proposed model was found to be in agreement with the different types of oil drops. Experimental and predicted results showed that the nonconverging slotted microstructured membrane provided low friction to oil drops through the membrane as compared to the converging slots. Furthermore, the developed model can be utilized to predict the overall oil content in the permeate. This research has great importance and will allow researchers around the globe to estimate crude oil concentration within the allowable limits.

Membrane oscillation and slot (pore) blocking in oil–water separation

Deformable oil drops of two interfacial tensions (namely, 4 and 30mNm−1) were filtered through a slotted-pore membrane (with pore dimensions of 4×400μm) at four vibrational shear rates (namely, 0, 1200, 3200 and 8000s−1) and two permeate fluxes (namely, 200 and 1000lm−2h−1). The membrane material was made of nickel. The membrane surface was modified with Poly tetra fluoroethylene (PTFE)F for better performance in-terms of higher flux rate rejection. The oil with the lower interfacial tension was more deformable, because the increase in TMP was less due to the passage of even larger drops to the slot opening, also the permeate quality was lower as a result of the higher concentration of the oil in the permeate. The impact of interfacial tension was more significant under the following conditions; first at lower shear rates, the particle back-transport effects become more dominant than the deformability effects at higher shear rates, and secondly at the higher permeate flux, the higher permeate drag enhances the deformability effects. Discrepancies were observed between experimental results and model predictions based on circular membrane pores and non-deformable foulants. In the future, it is expected that a better agreement of the experimental results and the analytical model could be obtained if the model is modified for the slotted pore membrane.

Separation of oil-in-water emulsion using slotted pore membrane

Nowadays, oil-in-water (O/W) emulsion has become an important topic in many industries. Petroleum industry is one of these industries. O/W emulsion produced in crude oil recovery causes problems at different stages in petroleum industry. Produced water can not be injected again into the well, because it contains high concentrations of oil, grease and suspended particles. Recently, membrane technology has been applied in separation of O/W emulsion. One membrane that has been developed special for oil filtration is slotted true surface filter. This research investigated influences of pore size and initial concentration of feed emulsion during oil filtration using slotted pore membrane. From the experiment, oil rejection will be higher if we use membrane with smaller pore size, emulsion with high stability and small trans membrane pressure. Based on the slot width it can be concluded that 33 microns membrane gives better oil rejection than 80 microns membrane. Initial concentrations of challenge emulsion also influence value of flux and oil rejection, which will also influence our decision to choose suitable membrane in relation with hydrophilicity of the membrane. During microfiltration process, there was deformation of oil particle through slot of membrane, which can be analyzed by observing size of oil drops in feed and permeate sides. Keywords: emulsion, microfiltration, slotted pore membraneAbstrakSaat ini penanganan limbah emulsi minyak dalam air menjadi topik penting di berbagai industri. Salah satunya adalah industri perminyakan. Emulsi yang dihasilkan dalam proses penambangan minyak mentah menimbulkan masalah pada beberapa tahapan proses di industri. Air yang mengandung minyak tidak dapat digunakan kembali untuk meningkatkan perolehan minyak karena mengandung minyak, lemak dan partikel tersuspensi dalam konsentrasi tinggi. Sehingga dibutuhkan proses pemisahan emulsi minyak dalam air. Akhir–akhir ini teknologi membran telah digunakan untuk memisahkan emulsi tersebut. Salah satu membrane yang dikembangkan adalah membrane berslot seperti yang digunakan dalam penelitian ini. Penelitian ini telah berupaya mengamati pengaruh variasi ukuran pori dan konsentrasi umpan terhadap performa membrane berslot dalam memisahkan emulsi minyak dalam air. Dari percobaan, diperoleh hasil bahwa rejeksi membran terhadap minyak meningkat jika digunakan membrane dengan ukuran ori lebih kecil, emulsi dengan kestabilan yang tinggi, dan beda tekanan yang kecil. Disimpulkan bahwa membrane dengan ukuran pori 33 mikrometer memberikan rejeksi membrane lebih tinggi dibandingkan membrane dengan ukuran pori 80 mikrometer. Konsentrasi awal umpan mempengaruhi fluks dan rejeksi serta mempengaruhi pilihan kita dalam memilih jenis membran yang digunakan. Selama proses filtrasi, terjadi perubahan bentuk atau deformasi partikel minyak melewati slot atau pori membrane yang diamati melalui distribusi ukuran partikel.Kata kunci: emulsi, mikrofiltrasi, membran berslot

The critical pressure for microfiltration of oil-in-water emulsions using slotted-pore membranes

The influence of fluid properties on the critical pressure of permeation of an oil micro-droplet into a slotted pore is studied numerically by solving the Navier-Stokes equations. We consider a long slotted pore, which is partially blocked by the oil droplet but allows a finite permeate flux. An analytical estimate of the critical permeation pressure is obtained from a force balance model that involves the drag force from the flow around the droplet and surface tension forces as well as the pressure variation inside the pore. It was found that numerical results for the critical pressure as a function of the oil-to-water viscosity ratio, surface tension coefficient, contact angle, and droplet radius agree well with theoretical predictions. Our results show that the critical permeation pressure depends linearly on the surface tension coefficient, while the critical pressure nearly saturates at sufficiently large values of the viscosity ratio or the droplet radius. These findings are important for an optimal design and enhanced performance of microfiltration systems with slotted pores.

Rotating Cylinder Microfiltration of Oil–in–Water Emulsion Using Novel Slotted Pore Filter

Nowadays, oil–in–water emulsion has become an important topic in petroleum industry, which produces oil–inwater emulsion in the recovery of crude oil. Oil–in–water emulsion produced in crude oil recovery causes problems at different stages of the production in the petroleum industry. Recently, microfiltration has been applied in the separation of oil from water. In filtration of oil–in–water emulsion, there is the possibility of oil drops deforming and squeezing through the slot of membrane so the separation efficiency will decrease. This research has studied cross flow filtration of oil–in–water emulsion in a rotating system and also visualized the interaction of oil drops and slot shaped membrane pores. The drop or bubble–slot experiment used a slot with different width. It has been found that the squeezing of an oil drop in the slot is really determined by the pressure applied and velocity of the surrounding fluid. Cross flow microfiltration experiment was conducted using tubular slotted pore membrane with rotation to generate shear on the surface of membrane. Kerosene and crude oil were tested using 5.3 and 7.5 microns membrane at different rotation speed and permeate velocity. Experimental results indicated that in a no blocking condition, the movement of oil drops was determined by shear force and permeate drag force. While in blocking condition, the rejection of oil drops was determined by the formation and characteristic of the secondary membrane formed on the surface of membrane. Blocking will improve the filtration performance in relation to oil rejection, but it will increase the pressure needed or decrease the flux rate through the membrane.

Investigation of membrane fouling at the microscale using isopore filters

Investigations of membrane fouling at the pore-scale have long been of limited interest due to microstructural defects of the commercial membranes that prevent any quantitative analysis of the experimental results. In this paper, we employed novel microengineered membranes with regular pore size to investigate the effect of the membrane pore geometry on the fouling mechanisms during filtration of micron-sized particles. For particles larger than the membrane pore size, the fouling mechanism was pore blockage followed by the cake filtration, while pore narrowing was the dominant mechanism when particles were smaller than the membrane pore size. Filtration with the slotted pore membrane offers some interesting advantages comparing to the filtration with circular pores. The rate of flux decline was slower for the membrane with slotted pores compared with the membrane with circular pores since the initial particle deposition only covered a small fraction of the pores. It was also found that the flow resistance of the slotted pore membrane is much lower than the circular one because a slotted pore has a smaller perimeter than several circular pores with the same total surface area. We can conclude that by proper selection of membrane pore geometry, flux decline can be hindered while maintaining a high selectivity during microfiltration. These findings can be useful also for researchers who are using microfluidic platforms with integrated isopore filters for various applications such as stem cell enrichment, cancer cell isolation, blood fractionation and pathogen removal.

Prediction of size distribution of crude oil drops in the permeate using a slotted pore membrane

Size distribution of crude oil drops in the permeate has been predicted using the ‘linear fit’ approach with, and without oscillating the membrane. Without membrane oscillation (without shear rate), static and drag forces are taken into account and their balance is assumed as 100% cut-off or rejection point. With the membrane oscillation, ‘inertial lift’ model available in the literature is considered and in this case 100% cut-off is assumed when away migration and convection velocities becomes equal. Three types of crude oil drops with different °API values and interfacial tensions are analysed experimentally, the results are compared with the presented model and the model is an agreement with the experiments. The study has been validated with the genuine size distribution of oil drops obtained from oil companies operating at Kuwait at various locations in order to investigate the industrial applicability of the model. Overall oil concentration of the permeate can be calculated using the proposed model that provides an idea whether the concentration of oil in the permeate is within the standard set by international regulatory authorities.

Passage and deformation of oil drops through non-converging and converging micro-sized slotted pore membranes

The model presented in the paper is the continuation of the previous work where a mathematical model was developed for the passage and deformation of micro-sized oil drops through a 4μm converging slotted pore membrane. In the previous work, it was assumed that drops deform from a spherical shape to a prolate spheroid when pass through a converging slot. In the present study, it has been assumed that drops deform into an oblate spheroid while passing through a non-converging slot and a mathematical model is developed for the deformation of drops through non-converging slots. After extending the idea of static and drag forces, it is readily seen that the magnitude of static force (Fcx) for the non-converging slotted pore membrane is higher than the static force (Fcx∗) for the converging slotted pore membranes. This is because of drops deform suddenly in the non-converging slots, while, in case of converging slots, the drops deform gradually. Micro-sized oil drops of two systems with different interfacial tensions (4 and 9mN/m) have been used in the study and it is observed that a higher interfacial tension leads to a higher rejection rate for both converging and non-converging slotted pore membranes at various in-pore filtration velocities.

Shear enhanced microfiltration and rejection of crude oil drops through a slotted pore membrane including migration velocities

Shear enhanced microfiltration of crude oil/water emulsion is investigated and the effect of an applied shear rate on the rejection of droplets by the membrane is reported. Applying vibration provides shear rate at the membrane surface leading to shear-induced migration and an inertial lift of drops/particles. Both phenomena tend to move the droplets away from the membrane surface. The shear-induced migration and inertial lift increase with increasing of the shear rate. A mathematical model is presented to account for the presence of both phenomena. The developed model is used for theoretical prediction of 100% cut-off of crude oil droplets by the membrane with, and with-out, vibration applied. A satisfactory agreement of the model predictions with experimental data shows that the model can be successfully used for a theoretical prediction of 100% cut-off of droplets by slotted pore membranes. Rejection of droplets increased with applying shear rate: at 8000 s-1 shear rate and 200 l m-2 hr-1 flux rate 3 to 4 μm radius droplets were almost completely rejected reducing 400 ppm of crude in the feed to 7 ppm in the permeate.

Stability and deformation of oil droplets during microfiltration on a slotted pore membrane

The effect of interfacial tension between two fluids, on the passage and rejection of oil droplets through slotted pore membranes is reported. A mathematical model was developed in order to predict conditions for 100% cut-off of oil droplets through the membrane as a function of permeate flux rate. Good agreement of theoretical predictions with experimental data shows that the model can be applied to the filtration of deformable droplets through slotted pore membranes. At high interfacial tension (40mN/m) with lower flux (200lm−2hr−1)droplets of crude oil (27 API) were 100% rejected at droplet diameter 4.3μm using a 4μm slotted pore membrane. At lower interfacial tension (5mN/m), with the same flux rate, 100% rejection occurred at 10μm droplet diameter using the same membrane. It was also found that the droplet rejection efficiency below the 100% cut-off was roughly linear with drop size, down to zero rejection at zero drop diameter. Hence, the model, coupled with this approximate correlation, can be used to predict dispersed oil drop concentration from a known feed drop size distribution.

Microfiltration of deforming oil droplets on a slotted pore membrane and sustainable flux rates

Oil droplets from an emulsion were filtered using a slotted pore membrane with a 4 μm slot width and 400 μm slot length. Droplets up to 15 μm in diameter were filtered at various flux rates (200–1200 l m −2 h −1) using oscillatory membrane microfiltration. Surface shear rates at the membrane of various intensities (0, 1200, 3200 and 8100 s −1) were applied and the effect on permeate flux rate and trans-membrane pressure were investigated. Near constant filtration flux was obtained for all the tests. Without shear the trans-membrane pressure increased quickly, but at the highest shear rate (8100 s −1) nearly constant trans-membrane pressure and flux rate were observed and may be described as sustainable, or weak form of critical flux. A filtration membrane blocking model was used to investigate the filtration and identify when sustainable, or critical, flux was achieved.

Effects of membrane pore geometry on fouling behavior during yeast cell microfiltration

The effects of the pore geometry on yeast cell fouling during microfiltration were studied using novel micro-patterned membranes having well-defined slot-shaped or circular pores. Normal flow filtration experiments were performed with Baker's yeast suspensions. The flux decline data were consistent with initial fouling by pore blockage followed by cake filtration. The specific resistance of the cake layer was a function of both the pore geometry and the overall membrane porosity. The initial rate of flux decline was slower for the membrane with slotted pores compared to the membrane with circular pores since the initial cell deposition only covered a small fraction of the slotted pore due to its high aspect ratio. The data then show a transition to cake filtration, with the nature of the transition also a function of the underlying pore geometry. A simple geometric model was developed to describe the cake growth phenomenon on slotted pore membranes. These results provide important insights into the effects of pore geometry on membrane fouling.