Porosity Of Filter Cake Research Articles

Slurry filtration process and filter cake formation during shield tunnelling: Insight from coupled CFD-DEM simulations of slurry filtration column test

The slurry infiltration process plays a crucial role in the slurry shield tunneling process, during which a filter cake is expected to form on the tunnel face to transmit the support pressure. This paper proposed a coupled computational fluid dynamics (CFD)-discrete element method (DEM) numerical approach to investigate the slurry infiltration and filter cake formation by modeling the slurry filtration column test, which incorporates the particles, fluid phase, and their interactions. The Simplified Johnson-Kendall-Roberts (SJKR) model was employed to consider the cohesion effect between slurry particles. The validity of the current approach was verified based on the Kozeny-Carman Equation modified by Ergun (1952). The slurry filtration process was divided into four stages with different characteristics of filter cake porosity and pressure drop. Influences of some key model parameters including externally-applied pressure, friction coefficient and cohesion energy density on filter cake formation were investigated and the underlying mechanisms were explored. The law of pressure variation within the filter cake was proposed. A linear relationship between pressure drop ratio and porosity of filter cake was established, which will be useful for predicting the effectiveness of support pressure transmission due to slurry filtration.

Impact of Clay Minerals on the Dewatering of Coal Slurry: An Experimental and Molecular-Simulation Study

The cleaning process of coals is challenging due to the existence of clay minerals. The overall objective of this study is to investigate how the dewatering of coal slurry is impacted by the presence of clay minerals, i.e., kaolinite and montmorillonite. Filtration tests were first conducted to investigate the effect of kaolinite and montmorillonite on the dewatering efficiency of coal. Specifically, we measured the filtration velocity, moisture, average specific resistance, and porosity of filter cakes for six slurry samples, in which different amounts of kaolinite and montmorillonite were contained. Filtration tests show that a small amount of kaolinite and montmorillonite leads to a significant reduction in the filtration velocity and porosity, and a big increase in the average specific resistance and the moisture of the filter cake. We observe that most kaolinite existed in the top and middle layers of the filter cake, while most montmorillonite existed in the top layer; on the contrary, little montmorillonite is observed in the middle and bottom layers of the filter cake. Montmorillonite results in a much more deteriorative effect than kaolinite. Considering that the interactions between clay minerals and water may play a key role, we then further investigate the effect of such interactions using molecular simulations. Simulation results show that water molecules could hardly diffuse into kaolinite from the edge, while they could readily penetrate into the montmorillonite layers from the edge surface. This result can be explained by the hydrated cation in montmorillonite. The adsorption density of water on the octahedral surface of kaolinite is higher than that of water on the tetrahedral surface of kaolinite. Furthermore, the adsorption density of water on the double surfaces of kaolinite is higher than that of water on the montmorillonite surface. This research is expected to provide benefits or contributions to the dewatering of clay-rich coal tailings.

Investigation of mud density and weighting materials effect on drilling fluid filter cake properties and formation damage

Drilling fluid density/type is an important factor in drilling and production operations. Most of encountered problems during rotary drilling are related to drilling mud types and weights. This paper aims to investigate the effect of mud weight on filter cake properties and formation damage through two experimental approaches. In the first approach, seven water-based drilling fluid samples with same composition are prepared with different densities (9.0–12.0 lb/gal) and examined to select the optimum mud weight that has less damage. The second approach deals with investigating the possible effect of the different weighting materials (BaSO4 and CaCO3) on filter cake properties. High pressure/high temperature loss tests and Scanning Electron Microscopy (SEM) analyses were carried out on the filter cake (two selected samples).Data analysis has revealed that mud weigh of 9.5 lb/gal has the less reduction in permeability of ceramic disk, among the seven used mud densities. Above 10.5 ppg the effect of the mud weight density on formation damage is stabilized at constant value. Fluids of CaCO3-based weighting material, has less reduction in the porosity (9.14%) and permeability (25%) of the filter disk properties than the BaSO4-based fluid. The produced filter cake porosity increases (from 0.735 to 0.859) with decreasing of fluid density in case of drilling samples of different densities. The filtration loss tests indicated that CaCO3 filter cake porosity (0.52) is less than that of the BaSO4 weighted material (0.814). The thickness of the filter cake of the BaSO4-based fluid is large and can cause some problems.The SEM analysis shows that some major elements do occur on the tested samples (Ca, Al, Si, and Ba), with dominance of Ca on the expense of Ba for the CaCO3 fluid sample and vice versa. The less effect of 9.5 lb/gal mud sample is reflected in the well-produced inter-particle pore structure and relatively crystal size. A general recommendation is given to minimize the future utilization of Barium Sulfate as a drilling fluid.

On-line monitoring of cake layer structure during fouling on porous membranes by in situ electrical impedance analysis

The structure of a fouling cake layer building up during membrane filtration can have a decisive influence on the performance of the membrane process. Hence a comprehensive description of the cake layers structure is mandatory. In this work we report a new methodology of simultaneously recording hydraulic resistance and electrical impedance during a membrane filtration experiment for flat sheet as well as hollow fiber membranes. An equivalent circuit model is derived to describe the development of the measured impedance during filtration. In situ e.g filter cake height and filter cake porosity as a function of time can be extracted from the experimental data for flat sheet as well as for hollow fiber membranes. The extracted data support traditional filtration theories for dead-end filtration on flat sheet membranes predicting an increase of cake layer porosity with proceeding filtration. However, the data obtained from inside-out filtration using a hollow fiber membrane reveal an apparent decrease of cake layer porosity during filtration. So the decreasing deposition area for the particles in inside-out filtration apparently results in a higher packing density of the particles and thus lower cake layer porosity. The electrical impedance data give an additional correlation allowing us to characterize the fouling cake layer structure or composition.

Effect of Sand Content on the Filter Cake Properties and Removal During Drilling Maximum Reservoir Contact Wells in Sandstone Reservoir

The drilling mud program contains many tests such as filtration rate and filter cake properties to select the proper drilling fluid additives that yield the standard ranges of the viscosity, filtration rate, etc. However, the physical and chemical changes in the mud composition during the mud circulating will cause changes to the filter cake properties. The changes in the filter cake properties should be considered in the mud design program to prevent the problems associated with the change in the drilling fluid properties. For long horizontal wellbores penetrating plastic formations, the two sources of solids in filter cake are drilling chemical additives and formation cuttings (sand particles in the case of sandstone reservoir). This study focuses on the effect of introducing sand particles from the drilled—formations on the filter cake properties. Real drilling fluid samples from the field were collected at different location during drilling a 3600 ft of the horizontal section of a sandstone formation. Calcium Carbonate (CaCO3) was used as weighting material in this filed. The drilling fluid samples were collected at two different points: the flow line coming from the well after shale shaker and the flow line going to the well to verify the effect of separation stages on filter cake properties. The primary drilling fluid properties of the collected samples were measured such as density and rheological parameters. High pressure high temperature (HPHT) filter press was used to perform the filtration and filter cake experiments at 300 psi differential pressure and room temperature (25 °C). The mineralogy of the external filter cake formed by fluid loss cell is determined using SEM (scanning electron microscopy) and XRD (X-ray diffraction). Finally, solubility test was conducted to evaluate the effect of sand particles on filter cake removal (containing Calcium Carbonate as weighting material) using chelating agent: glutamic diacetic acid (GLDA) at pH 4. The results showed that for long horizontal sections, the effect of introducing sand particles to the composition of the filter cake can cause significant change to the properties of filter cake such as mineralogy, thickness, porosity, and permeability. For instant the thickness of filter cake increased about 40% of its original thickness when drilling sandstone formation in horizontal well due to fine sand particle settling. The filter cake porosity and permeability increment in the first 2000 ft part of the horizontal section was observed clearly due to the irregular shape of the drilling particles. However for the points after the first 2000 ft of horizontal lateral, the porosity and permeability almost remained constant. Increasing the sand content up to 20% degrade the dissolution rate of calcium carbonate in the GLDA (pH = 3.8) to 80% instead of 100%.

Can filter cake porosity be estimated based on the Kozeny–Carman equation?

Application of the Kozeny–Carman equation for estimating the porosity of filter cakes formed in filtration is examined. It is shown that the Kozeny–Carman equation belongs to a class of relationships relating the pressure gradient and flow rate for fluid flow through porous media and is applicable to unconsolidated randomly packed media composed of spherical or nearly spherical particles. In contrast, filter cakes formed under pressure may be compressible and are not homogeneous. Furthermore, the question whether filter cakes may be considered as unconsolidated remains unresolved. These complicating factors plus the fact that the calculated porosity values based on the Kozeny–Carman equation tend to be exceedingly low as compared with those obtained from independent measurements strongly suggest that using the Kozeny–Carman equation for determining cake porosity is questionable and not appropriate.

Analysis of the Porosity of Filter Cakes Obtained by Filtration of Colloidal Suspensions

AbstractThe filtration of suspensions in the colloidal regime is part of many processes. It is necessary due to the widespread use of nano‐size particles in many applications. In nano‐scale particle systems, the huge specific surface of the particles is dominating the processes. The question is whether the well‐known filter theory is applicable for such type of products. The experiments in this study were conducted by gas‐driven filtration. The analysis of the filter cake was done globally according to the Darcy equation and locally by the use of magnetic resonance imaging (MRI) techniques. Due to the very high resistances during filtration for colloidal suspensions, comparatively thin filter cakes with an approximate height of 0.5–3 mm were investigated. The overall porosities determined by the different techniques are in good agreement. The MRI technique allows an in situ measurement of the porosity gradient within a filter cake formed by compressible material.

Simulation of filter cake porosity in solid/liquid separation

A simulation of filter cake formation as a random process has been conducted. The random packing occurs after spherical particles are generated at a randomly selected coordinate above the cake. The force balance of the particles considers the driving force of filtration, skeleton forces due to virtually overlying particle layers, and adhesive forces. The factors for determining when a particle stops are defined as follows: a. Adhesion to the contacting particles based on the force balance. b. Finding a steady position if contacting three or more particles of the cake. The calculations deliver local porosities, mean porosities and size distributions of the pores dependent on the filtration parameters. The results confirm observations made in filtration experiments.

フロートを用いたヌッチェ型真空ろ過試験による圧縮透過特性の推算

Vacuum filtration tests of Korean kaolin slurry were conducted under various filtration pressures using a nutsche equipped with a floating disk. The floating disk was used to determine the filtrate volume by its displacement. The average porosity of filter cake was obtained based on the principle of sudden reduction of filtration area during filtration. Compression-permeability cell data such as the local specific filtration resistance and the local porosity were evaluated as functions of the local solid compressive pressure on the basis of vacuum filtration data. The expression characteristics of slurry under relatively large expression pressure conditions were well evaluated based on the compression-permeability cell data determined from the vacuum filtration data under low pressure conditions. In addition, an approximate method has been developed for obtaining the permeability data on the basis of expression data.

Porosity Investigations of Fine-Grained Filter Cake

Conventional filtration theory states that the filtrate flow rate depends on the porosity of the filter cake, so that its prediction requires advance knowledge of the porosity. A previous paper proposes a new theoretically supported approach to the prediction of the porosity of fine-grained filter cake. This approach considers the agglomeration phenomena in the filter cake determined by the adhesive forces between the particles on the one hand, and the disruption of the agglomerates by the drag force of filtrate flow on the other. The model is derived from the balance of forces and includes common filtration parameters (pressure difference, particle size and filter cake height) as well as the free specific surface energy of the particles as a measure of the agglomeration activity. In order to verify the model, porosity measurements were compared with porosity predictions. The results of this validation study are presented in this paper.

Experimental results of solid monodisperse particle clogging of fibrous filters

An apparatus is shown which provides useful filtration performance responses of flat fibrous filter media to aerosol challenges of solid particles of practical monodispersity (geometric standard deviation less than 1.25). Examples are given of the changes in the instantaneous penetration and pressure drop of filter papers of different structures from the initial stages to the final filter cake formation states of filter loading. For filters of large pore diameter, the plots of pressure drop against mass loading display three regions: an initial region of slow increase, a transition region and a final linear region of cake filtration. The changing responses of penetration and pressure drop with particle loading are both sensitive to the effective pore diameter of the filter structure. After filter cake formation, the slopes of pressure drop with mass loading were identical for a specific particle diameter regardless of the filter structure, yielding a technique for determining the porosity of filter cakes for different particle size challenges.

Zinc-dust cementation of silver from alkaline cyanide solutions — analysis of Merrill-Crowe plant data

The direct recovery of precious metals from alkaline cyanide solution is frequently accomplished by the well-established Merrill-Crowe process involving zinc-dust cementation. This is particularly true for silver. Plant data from two operations are presented and analyzed in terms of intrinsic reaction features. In such Merrill-Crowe plants a plate-and-frame filter press acts as a semicontinuous fixed-bed reactor with a distribution of particle retention times. For the plants studied, 99% of the silver is recovered with a solution retention time of less than 2 min. Differences in plant operating conditions and product characteristics can be related to the nature of the surface deposit of silver which forms on the zinc particles. From laboratory experiments and plant samples it has been found that the presence of lead in the system activates a change in the silver deposit morphology to the dendritic state which affects the rate of silver deposition as well as the filter cake porosity. Finally the plate-and-frame press is considered from an engineering perspective as a semi-continuous fixed-bed reactor to describe the behavior of the system.

A Filtration Mechanism of Electrostatically Stabilized Calcite Suspension

The filtration behavior of calcite/water su spension containing various amount of Sodium hexameta-phoshate (NaPOM3)6, were observed and the specific filter cake resistance was analized in a view point of interfacial electrochemical phenomenon.In the filtration experiment, the relation between filtrate volume and filtration time, and also the porosity of filter cake were measured, using a vacuum type filtration apparatus.Two kinds of average specific filter cake resistances, denoted as α and α' were determined from the filtration data. Here, the α is a resistance calculated by the filtration equation derived from Hagen-Poiseuialle's law and α' is one calculated by Kozeny-Carman's equation.The resistance α takes larger value than α', and a dependence on zeta-potential of the electrical double layer which is elevated to be dispersive by increasing the addition amount of (NaPO3)6 is quite different between them, as like increasing α, against decreasing α'.The value of relative viscosity η'/η equivalent to α'/α increases gradually accompanied with zeta-potential until maximum value of about 8, where η and η' are viscosity of water in bulk and in filter cake respectively. The η'/η is also changed “thixotropically” by the flowing velocity of the fluid through the micro porous filter cake.For these results, it is discussed that the electrical double layer and oriented water molecules surrounding the suspended particle will originate the large porosity due to keep far the particle-particle distance, and high viscous water film at the interface.

Investigation of the fundamental assumptions relating compression‐permeability data with filtration

AbstractA recently reported investigation indicates several inaccuracies in the methodology of compression‐permeability (C‐P) testing which suggest that previously reported agreement between C‐P and filtration data may be fortuitous. Until now, there has been no separate and direct confirmation of each of the two assumptions necessary to obtain a unique correspondence between C‐P and filtration data.The first assumption that the specific filtration resistance is a function solely of cumulative‐drag‐stress is generally accepted. Direct proof requires that the parabolic filtration equation, which is derived primarily on this assumption, describes both incompressible and compressible cake behavior. Most materials produce compressible cakes and “a priori” screening to find an incompressible cake requires identification of a material (Geon) that produces a cake with a linear axial pressure distribution. Results show that the parabolic filtration equation fits both types of cake behavior but an equation based on constant filtration resistance describes only incompressible cake behavior. To engineering accuracy and for dilute slurries, the assumption is verified.The second assumption that the cumulative‐drag‐stress equals the cake pressure drop is a macroscopic force balance and experimental verification requires a filter chamber designed to measure both of these quantities. A theoretical development, based on integral averaging, and experimental results both indicate that the ratio of cumulative‐drag‐stress to cake pressure drop correlates extremely well with cake porosity.A unique one‐to‐one correspondence between C‐P and filtration data is not possible without “a priori” knowledge of filter cake porosity. Previously reported agreement between C‐P and filtration data can probably be attributed to the L/D dependence of C‐P specific filtration resistances. Consequently, C‐P data can be used as a research tool to simulate filtration data but predicted filtration times based solely on C‐P data can be in considerable error.