Classical Filtration Research Articles

Анализ фильтрационного процесса в угольном пласте, отрабатываемом длинными столбами по простиранию

The underground coal field mining is inevitably associated with coal oxidation process accompanied with the thermal energy emission and the formation of coal self-heating spots. The self-heating spots can emerge in both coal dust accumulations deposited in the excavations and in the excavated coal seams. It is known that self-heating is caused by both chemical processes accompanied with heat emission and physical processes, primarily the filtration of gas-air mixtures through porous and fractured layers of rocks and coal seams. Although the filtration processes accompanying oil and gas field exploration have been thoroughly studied, similar processes accompanying coal mining have been studied less. The article focuses on the mathematic problem concerning the filtration process in the coal seam when excavated by long pillars. In this system, both fresh airflows and worked out flows move in opposite directions and under different pressures along the mine roadway and the ventilation opening. This causes so-called air suctions due to air infiltration through the coal seam. In theory, this problem has not been solved yet and thus is considered urgent. Based on the classic filtration theories and assumptions regarding the coal seam isotropy and homogeneity, the one-dimensional initial value problem describing the non-stationary air filtration process through the coal seam was formulated. The solution provided explicit formulas to determine the pressure and rate of air-gas mixture filtration and identified several regularities of the filtration process in the coal seam. Particularly, it was established that the filtration rate increases significantly in the direction towards the ventilation opening, especially at the initial stages of filtration. In process of time, however, the filtration rate aligns and after 5 days, the rate difference is not so significant.

GPF Filtration Characteristics Considering Fractal Characteristics of Particles and Filters

Abstract To reduce the emission of fine particulate matter (PM) from gasoline engines, a gasoline particulate filter (GPF) filtration model that considers the fractal characteristics of both particulate matter and filters is designed and its filtration characteristics are analyzed based on several GPF filtration models. Based on the GPF filtration mechanism, a new mathematical model of fiber efficiency filtration is established after correcting the classical filtration formula based on correcting the particle size of particles and considering the relationship between the porosity of the fiber filter and the fractal dimension of the filter. Simulation of the filtration efficiency of the established mathematical filtration model is carried out to obtain visual filtration efficiency curves. The filtration efficiency and pressure drop of the model are analyzed, and the effects of parameters such as particle fractal dimension, filter fractal dimension, filter thickness, flow rate, and fiber diameter on filtration efficiency are also comprehensively analyzed. The results show that when the fractal dimension of particles is in the range of 1.8-2.8, the most penetrating particle size decreases with the increase of the fractal dimension of particles. When the particle size is small, the effect of fractal dimension on filtration efficiency is not obvious. When the particle size is larger than the most penetrating particle range, the larger the fractal dimension, the filtration efficiency increases obviously. Considering the relationship between the fractal dimension of the filter body and the porosity and the influence of each on the filtration efficiency, the optimal fractal dimension of the filter body should be between 1.82 and 1.925, and the thickness of the filter has some influence on the filtration efficiency. The slower the gas flow rate is, the better the trapping effect will be. However, considering the problem of automobile emission, a lower exhaust speed can be chosen. Increasing the fiber diameter can improve the trapping efficiency of the model, but will reduce the porosity of the trapping collective. Therefore, the fiber diameter should not be too large under the combined action.

EXPRESS METHOD FOR CHEMICAL REAGENTS SELECTION FOR INCREASING OIL RECOVERY OF LOW-PERMEABILITY RESERVOIRS

The choice of hard-to-recover reservoir (HRR) engineering technologies is one of the actual problems facing oil companies in the Russian Federation and the World. In order to increase the efficiency of the development of such fields various methods for production intensification are used to obtain an economically profitable industrial oil inflow. It is possible to use surfactant flooding to solve this problem. The surfactant efficacy results from the fact that aqueous surfactants solutions even at low concentrations dramatically decrease the oil/water/rock interfacial tension that results to changing wettability, allowing to increase the oil inflow.The purpose of this work is to study an alternative method of testing the effect of surfactant solutions on oil recovery. The method consists in mass testing using a laboratory petrophysical centrifuge to identify the most promising solutions, followed by the classical filtration method. The method of centrifugation is based on the substitution of one fluid in the pores of the core sample by another, occurring at a pressure difference at the boundary of the two phases under the action of centrifugal force. The suggested method will allow massively and in a short time to identify the most effective solutions for specific geological conditions.To carry out this work, three surfactant solutions were selected that were tested for resistance to mineral aggression and temperature, surface tensions and phase behaviors were determined. The object of the study was the core material of the formations of the AS, BS and YuS groups of one of the deposits of Western Siberia. Two series of experiments were carried out: classical filtration tests and centrifugation of core samples under conditions of initial and residual oil saturation.The results of the experiments have shown the effectiveness and prospects of using the centrifugation method for mass testing of surfactant solutions as displacing agents. The described method is express and cannot completely replace the classical filtration experiment due to non-compliance with an important criterion – the thermobaric conditions of the reservoir.

Study on filtration equations based on filtrate viscosity

ABSTRACT Classical filtration equations incorporate microscopic parameters, which pose challenges when applied in industrial settings. Previous extensive research has established the impact of filter cake thickness and variations in filtration pressure on the filtration rate. Moreover, the thickness of the filter cake is influenced by various factors, such as the filtration chamber’s design dimensions and the coal slurry’s properties. Thus, by expressing the properties of the coal slurry at a macroscopic level, it becomes possible to achieve a macroscopic representation of the filtration rate. This study presents the derivation of a macroscopic filtration equation that relies on the viscosity of the filtrate. The derivation process is mainly based on Darcy’s law, analyzing the relationship between the permeability of each layer and the permeability of cake under constant pressure and explaining and analyzing the method of determining the equation parameters.

Biomarkers in acute kidney injury - the search for the "renal troponin"

The prognosis of acute kidney injury (AKI) is poor, partly due to significant limitations of the current functional marker-based definition, which results in too small therapeutic window to treat AKI. Therefore, AKI biomarkers are needed to detect AKI earlier. Classical filtration markers are serum creatinine and cystatin C, which, however, show clear limitations for AKI prediction. Early AKI markers are divided into damage markers and "stress" markers. The latter indicate a pre-injury phase with increased AKI risk. The one "renal troponin" will probably never be found because of heterogeneous renal structure and heterogeneous causes of AKI. However, AI-based models with inclusion of biomarkers could significantly improve AKI prediction and prognosis.

Clarification of Limed Sugarcane Juice by Stainless Steel Membranes and Membrane Fouling Analysis.

The performance of stainless steel membranes with pore sizes of 100 and 20 nm in clarifying limed sugarcane juice was investigated under different operating conditions. An increase in transmembrane pressure (TMP) for the 20 nm membrane from 2 to 5 bar led to an increase in the average flux from 146.6 Lm−2 h−1 to 187.8 Lm−2 h−1 (approximately 9 h). The increase in crossflow velocity from 2 to 5 m/s led to an increase in the average flux from 111.9 Lm−2 h−1 to 158.1 Lm−2 h−1. The increase in temperature from 70 °C to 90 °C caused an increase in the average flux from 132.8 Lm−2 h−1 to 148.6 Lm−2 h−1. Simultaneously, the test produced a high-quality filtered juice with an average of 1.26 units of purity rise. The purity increased with time, and a 99.99% reduction in turbidity and an average 29.3% reduction in colour were observed. In addition, four classic filtration mathematical models and scanning electron microscopy (SEM) analyses suggested that cake formation is the main mechanism for flux decline. Fourier transform infrared (FTIR) spectrometry and energy-dispersive X-ray (EDX) spectrometry indicated that organic fouling is the main foulant. This study demonstrates the potential of stainless steel membranes as filters for the clarification of raw sugarcane juice.

Clariant and Lummus awarded contract for one of the world[StQuote]s largest PDH units

Nanoparticles (NPs) are particles of less than or equal to 100 nm in diameter. Due to their size, they have a significant effect on health and safety of people. Capture of these NPs in general ventilation systems by filters remains one of the most widely used means of protection due to its relative simplicity of implementation and its effectiveness for capturing various size of particles. In North America, filters used in general ventilation systems are tested by the ANSI/ASHRAE Standard 52.2 and are graded according to their efficiency, which is a function of particle diameter. However, the current standard limits the filtration efficiency assessment for particles between 0.3 and 10.0 µm. There is therefore a significant lack of knowledge about the behavior of these filters with respect to the particle diameter below 0.3 µm considering the overall filter used in general ventilation. The main objective of this study was to develop a measurement procedure to evaluate the effectiveness of mechanical filters used in general ventilation systems against NPs. In this regard, a small setup was designed, build and qualified. Then measurement procedure was validated by comparing the penetration measurements with those obtained on qualified big loop setup for nanoparticles, which was inspired by ASHRAE. One type of mechanical filter rated (MERV 8) in three depth sizes (2.54, 5.08 and 10.16 cm) was used to compare the penetrations. The obtained results are consistent with the classical filtration theory for mechanical media and with previous experimental measurements on media. The data presented in this study show that the penetration range of 0.7–1.0 obtained for particle range 22.1–294.3 nm and at 1.00 and 0.75 m/s gives a fairly good correlation (R2 = 0.898) between the two setups. The outcome results validate the methodology used to evaluate the effectiveness of one mechanical filter used in general ventilation systems against nanoparticles by using the small setup.

Albemarle undertakes strategic review of catalyst business

Nanoparticles (NPs) are particles of less than or equal to 100 nm in diameter. Due to their size, they have a significant effect on health and safety of people. Capture of these NPs in general ventilation systems by filters remains one of the most widely used means of protection due to its relative simplicity of implementation and its effectiveness for capturing various size of particles. In North America, filters used in general ventilation systems are tested by the ANSI/ASHRAE Standard 52.2 and are graded according to their efficiency, which is a function of particle diameter. However, the current standard limits the filtration efficiency assessment for particles between 0.3 and 10.0 µm. There is therefore a significant lack of knowledge about the behavior of these filters with respect to the particle diameter below 0.3 µm considering the overall filter used in general ventilation. The main objective of this study was to develop a measurement procedure to evaluate the effectiveness of mechanical filters used in general ventilation systems against NPs. In this regard, a small setup was designed, build and qualified. Then measurement procedure was validated by comparing the penetration measurements with those obtained on qualified big loop setup for nanoparticles, which was inspired by ASHRAE. One type of mechanical filter rated (MERV 8) in three depth sizes (2.54, 5.08 and 10.16 cm) was used to compare the penetrations. The obtained results are consistent with the classical filtration theory for mechanical media and with previous experimental measurements on media. The data presented in this study show that the penetration range of 0.7–1.0 obtained for particle range 22.1–294.3 nm and at 1.00 and 0.75 m/s gives a fairly good correlation (R2 = 0.898) between the two setups. The outcome results validate the methodology used to evaluate the effectiveness of one mechanical filter used in general ventilation systems against nanoparticles by using the small setup.

Relation of the Modern Theory of Disperse Systems with the Classical Filtration Theory

Relation of the Modern Theory of Disperse Systems with the Classical Filtration Theory

Filtration resistance during pressure filtration tests of liquid aluminium alloys

Abstract Prefil Footprinter, a portable pressure filtration instrument, is usually employed to detect liquid metal quality. However, no investigations have ever been done to determine overall filtration resistance and resistance of the “clean” filter media. Based on the identification of flow behaviour using the derivative methods, classic filtration equations have been effectively used to estimate total filtration resistance for the first time. The variations of overall resistance during filtration provide a new approach to understand filtration behaviour. The resistance values of the “clean” filter media have been obtained for the first time. An innovative method has been developed to obtain the resistance of the “clean”' filter media through the backward extrapolation of the overall filtration resistance versus filtrate weight or filtration time curves over the steady stages operating in incompressible cake mode.

Filtration of Submicron Soot Particles, Oil Droplets, and their Mixtures on Single- and Multi-layer Fibrous Filters

The dynamics of filtration efficiency and pressure drop during the simultaneous filtration of soot and oil aerosols on single- and multi-layer filters were investigated, and the determined filtration efficiency was compared with the theoretical efficiency obtained via the classical filtration theory. Additionally, the influence of liquid-phase aerosols on the morphology of the formed deposits was investigated. It was concluded that the addition of oil aerosols decreased the filtration efficiency and lowered the pressure drop increase rate for multi-layer filters. Additionally, for the filtration of aerosols containing soot and high oil concentrations, once maximum filtration efficiency was reached, an efficiency decrease occurred. The system imperfection factor was proposed as a mean to predict the efficiency of multi-layer filters. The modified version of the single fibre efficiency method was used to calculate filter mass change with reasonable accuracy.

Development of a novel model by combining the intermediate blocking and cake filtration models for assessment of the prevailing fouling mechanism in a microbial fuel cell-facilitated membrane bioreactor

This study was carried out on a membrane bioreactor (MBR) facilitated with an electric field provided by a microbial fuel cell (MFC), which effectively reduced membrane contamination and extended the operation time of the MBR from 18 to 24 days. To understand the theory of membrane fouling in the MFC-MBR, a novel model based on the operation of the MFC-MBR was proposed with the modification of the classical filtration models to assess the membrane fouling. With this model, a two-phase membrane fouling development was observed, which was initially dominated by the intermediate-blocking model and then gradually changed to cake filtration. In the combined model of two-phase development, fouling was significantly mitigated by the electric field in phase 1, but its function was barely observed in phase 2. The combined model fit well with the experimental data, which could predict membrane fouling in the application of the MFC-MBR.

Probing the Effective Diffusion Coefficient and Filtration Performance of Micro/Nanofibrous Composite Layered Filters

Diffusion is an important filtration mechanism of fibrous filters for removing fine particles from gas streams. An analytical model is proposed in this work, based on fractal theory, to quantify the effective diffusion coefficient (EDC) across micro/nanofibrous filters with a layered structure. To show the influence of macroscopic parameters of fibrous filters on EDC, the present models are expressed in terms of fiber diameter. Polyacrylonitrile (PAN) nanofibers were prepared by electrospinning on melt-blown polypropylene (PP) microfiber filter materials to form micro/nanofibrous filters. To validate this model, a three-dimensional (3D) fiber model with physical parameters of the samples was reconstructed using the GeoDict code, and the Brownian movement of nanoparticles was simulated to calculate the EDC. Two kinds of pore size distributions for the layer-structured fibrous filters have been identified, which also shows the internal heterogeneity of the filter media. With decreasing fiber diameter, the tortuosity of the pore channel increases, while the EDC decreases. Compared with the numerical simulation and the experimental data reported in the literature, the current model gives a better theoretical prediction. In addition, the diffusion mechanism in classical filtration theory was modified to reduce the deviation between theoretical prediction and experimental results.

On a Space-Fractional Generalization of the Black Oil Model

Classical multiphase filtration models, which are based on Darcy's law, are well studied and actively used in modern oil engineering. However, such models do not allow efficient describing of processes with power-law memory effects or with spatial non-locality effects. In recent years, there has been a significantly increasing interest in models with fractional derivatives and integrals that allow such effects to be taken into account.The article considers the space-fractional generalization of the two-phase Black Oil model. This model is built on the basis of a fractional modification of the Darcy’s law with the Riesz potential, which is one of the possible generalizations of a fractional integral to the case of a multidimensional space. The use of such a modification of Darcy's law allows efficient describing of filtration processes in heterogeneous fractured porous media with the effects of spatial non-locality.For the numerical solution of the system of equations from the obtained model, the use of the IMPES method is proposed. For this purpose, from the presented system of equations, one equation is selected that describes the evolution of pressure. This equation is written provided that the capillary pressure variation within the time step is neglected.A special case of the pressure equation with the Riesz potential of radial function is considered, which describes the pressure variation in the case of a radial plane flow. For this equation, a self-similar solution is constructed using the Mellin integral transform method. A representation of this solution in the form of the Mellin-Barnes contour integral was obtained, which made it possible to write it in terms of the Fox functions. It is shown that in the limiting case of a zero degree of the Riesz potential, this solution coincides with the self-similar solution of the classical heat equation. The constructed self-similar solution can be further used in the software implementation of the numerical solution of the model presentedThe main line of further research is to develop and implement a software computing system based on the proposed fractional generalization of the two-phase Black Oil model.

Evaluation of the influence of a dimensionless threshold pressure gradient on deviation of filtration from classical filtration law

Depletion of hydrocarbon reserves in reservoirs with high and medium permeability increases the proportion of low permeability reservoirs in which nonlinear filtration effects are observed: at low pressure gradients, filtration does not obey the classical filtration law (Darcy’s law). One of the methods to describe the nonlinear filtration effects is to apply the filtration law with a threshold pressure gradient (TPG). The influence of this parameter on the deviation of filtration from Darcy's law has not been previously analyzed. The aim of this work is to evaluate this effect of the TPG. Piezoconductivity equations are nondimensionalized and solved according to the classical filtration law and the filtration law with TPG for plane radial flow and constant well pressure. In the framework of the classical filtration law, the piezoconductivity equation is solved by applying a self-simulated variable. Using the filtration law with TPG, the conductivity equation solution is solved by the method of integral relations. Relations between dimensionless production rate and dimensionless time for both filtration laws are found from the solved piezoconductivity equations. To prove the identity of the obtained solutions, a comparative analysis is performed for a threshold pressure gradient equal to zero. Comparison of production decline curves for classical filtration law and filtration law with TPG at various values TPG is carried out. The relation between the shapes of the production decline curves shape and various dimensionless TPG values is analyzed. With increasing dimensionless TPG, the influence of nonlinear effects on filtration increases: the nonlinear filtration effects become apparent earlier, and the production decline curves for the filtration law with TPG deviate greater from the production decline curve for the classical filtration law.

Particle Track and Trace during Membrane Filtration by Direct Observation with a High Speed Camera.

A methodology was developed for direct observation and analysis of particle movements near a microfiltration membrane. A high speed camera (1196 frames per second) was mounted on a microscope to record a hollow fiber membrane in a filtration cell with a transparent wall. Filtrations were conducted at varying pressure and crossflow velocities using synthetic core–shell particles (diameter 1.6 μm) of no and high negative surface charge. MATLAB scripts were developed to track the particle positions and calculate velocities of particle movements across and towards the membrane surface. Data showed that the velocity of particles along the membrane increases with distance from the membrane surface which correlates well with a fluid velocity profile obtained from CFD modelling. Particle track and trace was used to calculate the particle count profiles towards the membrane and document a higher concentration of particles near the membrane surface than in the bulk. Calculation of particle velocity towards and away from the membrane showed a region within 3–80 μm from the membrane surface with particle velocities higher than expected from the velocity of water through the membrane, thus the permeation drag underpredicts the actual velocity of particles towards the membrane. Near the membrane, particle velocities shift direction and move away. This is not described in classical filtration theory, but it has been speculated that this is an effect of particle rotation or due to membrane vibration or change in flow pattern close to the membrane.

MATHEMATICAL MODELING OF WATER PURIFICATION WITH FILTER

Purpose. To analyze the effectiveness of water purification in water treatment systems, an important task is the development of mathematical models that allow determining the degree of water purification at the design stage. The main purpose of the work is to construct numerical models for calculating the filtration process and mass transfer in the filter. Methodology. The calculation of the filtering process of contaminated water in the filter is carried out in two stages. At the first stage, the flow rate field in the filter is calculated. To solve this problem, the classical filtration equations are used. At the second stage of the calculation, the flow of contaminated water in the filter is simulated. To solve this problem, the mass transfer equation is used, which expresses the law of mass conservation. This equation takes into account the transfer of impurities by the filtration flow, the transfer of impurities due to dispersion and the sorption of impurities in the filter material. The solution of the filtration equation is carried out using the alternating triangular method of A. A. Samarskyi. The unknown pressure value based on this method is determined by the explicit formula of point-to-point computation. For numerical integration of the mass transfer equation in the filter, a difference splitting scheme is used. Findings. The current trend in the field of water supply and sanitation is the creation of multidimensional and multifactor mathematical models. Such models make it possible to replace a physical experiment with a computational one. The complex of water treatment facilities necessarily includes water purification filters. The filter efficiency affects the efficiency of other treatment facilities of the technological treatment scheme. A mathematical model has been developed that allows analyzing the water purification process in the filter. Based on the developed numerical model, a package of application programs has been developed for computer simulation of the filter water purification process. The results of a computational experiment on modeling the filtering process of contaminated water in a filter are presented. Originality. The paper proposes a numerical two-dimensional filter model based on the filtration equation and the mass transfer equation. A feature of the developed mathematical models is the possibility of modeling the velocity field and the process of impurity transfer taking into account the geometric shape of the filter. Practical value. The calculation time for one variant of the task based on the developed numerical model is several seconds, which is important for conducting serial calculations in practice. Models can be used as an alternative to laboratory experiments.

Morphology of Shear-Induced Colloidal Aggregates in Porous Media: Consequences for Transport, Deposition, and Re-entrainment.

Colloid deposition in granular media is relevant to numerous environmental problems. Classic filtration models assume a homogeneous pore space and largely ignore colloid aggregation. However, substantial evidence exists on the ubiquity of aggregation within porous media, suggesting that deposition is enhanced by it. This work studies the deposition process in relation to aggregate size and structure. We demonstrate that aggregation is induced at typical groundwater velocities by comparing the repulsive DLVO force between particle pairs to the hydrodynamic shear force opposing it. Column experiments imaged with high-resolution X-ray computed tomography are used to measure aggregate structure and describe their morphology probability distribution and spatial distribution. Aggregate volume and surface area are found to be power-law distributed, while Feret diameter is exponentially distributed with some flow rate dependencies caused by erosion and restructuring by the fluid shear. Furthermore, size and shape of aggregates are heterogeneous in depth, where a small number of large aggregates control the concentration versus depth profile shape. The range of aggregate fractal dimensions found (2.22-2.42) implies a high potential for restructuring or breaking during transport. Shear-induced aggregation is not currently considered in macroscopic models for particle filtration, yet is critical to consider in the processes that control deposition.

Transport of graphene quantum dots (GQDs) in saturated porous media

Graphene quantum dots (GQDs), a new type of carbon-based nanoparticles are widely used in scientific applications in the recent years. With the size less than 10 nm, and the strong hydrophilic characteristics GQDs exhibit high mobility in the environment, and can easily transmit to the groundwater environment. Hence, a good understanding of the transport behaviors of GQDs in porous media can provide guidance for assessment and prediction of its environmental risks. Saturated packed column experiments were conducted to investigate the effect of ionic strength (IS,1 and 100 mM), pH (4,7 and 9) and initial concentration (9 and 18 mg L−1) on the fate and transport of GQDs in saturated porous media. Advection-dispersion-reaction model with the second-order kinetics simulated the process well. The retention of GQDs was promoted with increased ionic strength in sand column, which could be explained with classic filtration and XDLVO theories. The increase of pH slightly reduced the GQDs deposition in saturated porous media, due to that there were no secondary minima in XDLVO calculation, and GQDs still showed high mobility. Higher input concentration slightly increased the GQDs retention due to the ripening process. The recovery rate of GQDs were more than 90 % in the environment with low salt content, exhibiting extremely high migration capacity.

Regulation of precoating filtration process based on SERS detection technology

The factors affecting a precoating filtration process and its regulation are studied through lab scale and pilot scale tests combined with surface-enhanced Raman spectroscopy. In the classic filtration process, the diatomite filter aids are introduced for precoating to regulate the specific resistance of the filter cake during the filtration process. This approach solves the fast termination of filtration caused by the rapid increase of the specific resistance of filter cake in classic filtration process. Moreover, surface-enhanced Raman spectroscopy is introduced to detect the trajectory of the filter particles moving with the filtrate in different precoating. The key factors, such as median particle size, thickness, and suspension mass concentration of precoating in the filter aids, are determined using lab scale and pilot scale tests. This study provides a foundation for industrial application of precoating filtration processes.