Mixture Of Glass Beads Research Articles

Understanding the Changes in Hydraulic Conductivity Values of Coarse- and Fine-Grained Porous Media Mixtures

Low permeability clay-sand mixtures are often used to construct hydraulic barriers to prevent contaminated water leaching from landfills and other waste disposal sites from polluting local groundwater aquifers. In order to engineer effective hydraulic barriers, a proper knowledge of the hydraulic conductivity of clay-sand mixtures is required. While there are several empirical models available in the literature that can be used to predict reductions in hydraulic conductivity values of coarse sand due to the presence of clay and other fine minerals, all these models require measurement of multiple physical properties of the porous media. The resulting empirical expressions have several parameters that need to be individually evaluated using multiple soil characterization tests. In this study, we propose a single parameter model that can be used to capture the variations in hydraulic conductivity value of different types of porous media mixtures using a scalable modeling framework. Several laboratory tests were conducted to measure the hydraulic conductivity values of a variety of coarse and fine glass bead mixtures. The coarse glass beads were used to simulate sand and small glass beads were used to simulate fine minerals such as silt and clay. The model results were further validated using the data derived from experiments conducted with natural sand and clay mixtures, and also using multiple literature-derived datasets. Our results show that the proposed model is a useful tool for describing the hydraulic conductivity values of various types of coarse- and fine-grained porous media mixtures.

Intensification of vibration mixing of particulate solids by means of multi-layer loading of components

The objective of the study is to show how initial distribution of dissimilar particulate components influences the mixing time and mixture quality. The dissimilar components have a tendency to segregate in one another, and it is impossible to achieve the perfect mixture of them in industrial settings. Nevertheless, the situation can be improved if the components are loaded as a sequence of several sandwiches, each of these sandwiches containing layers of components that are proportional to their share in the mixture. In this case, a sort of pre-mixing occurs while still at the loading stage – which allows reducing the optimum mixing time and increasing the homogeneity of the mixture. The theory of Markov chains was used to simulate the mixing kinetics. It is shown that the number of loaded sandwiches has a very strong influence on the process efficiency. A loading device that can effectively realize multi-layer loading is proposed. The mixing kinetics for ternary mixture of glass beads was investigated experimentally at a lab scale vibration mixer. A one-time loading and a two-sandwich loading were compared. It was shown that the optimum mixing time and non-homogeneity of the mixture were reduced by half in the latter case.

Impact-induced compaction of primitive solar system solids: The need for mesoscale modelling and experiments

Primitive solar system solids were accreted as highly porous bimodal mixtures of mm-sized chondrules and sub-μm matrix grains. To understand the compaction and lithification of these materials by shock, it is necessary to investigate the process at the mesoscale; i.e., the scale of individual chondrules. Here we document simulations of hypervelocity compaction of primitive materials using the iSALE shock physics model. We compare the numerical methods employed here with shock compaction experiments involving bimodal mixtures of glass beads and silica powder and find good agreement in bulk material response between the experiments and models. The heterogeneous response to shock of bimodal porous mixtures with a composition more appropriate for primitive solids was subsequently investigated: strong temperature dichotomies between the chondrules and matrix were observed (non-porous chondrules remained largely cold, while the porous matrix saw temperature increases of 100’s K). Matrix compaction was heterogeneous, and post-shock porosity was found to be lower on the lee-side of chondrules. The strain in the matrix was shown to be higher near the chondrule rims, in agreement with observations from meteorites. Chondrule flattening in the direction of the shock increases with increasing impact velocity, with flattened chondrules oriented with their semi-minor axis parallel to the shock direction.

Effect of physical heterogeneity on the electromigration of nitrate in layered granular porous media

The effect of physical heterogeneity on the electrokinetic (EK) transport of nitrate, an electron acceptor frequently used for anaerobic biodegradation, was investigated experimentally within saturated granular porous media comprising two layers of high and low hydraulic conductivity (K) material. Two hypotheses were tested: firstly, that the presence of layered physical heterogeneity will generate non-uniformities in the electric field; and secondly that this would create non-uniform electromigration of ions resulting in an additional nitrate flux into the lower-K layer. Experiments were conducted in bench-top test cells that contained electrode and sediment chambers. An aqueous nitrate solution (0, 0.1, 1 and 5g-NO3L−1) was added at the cathode and the experiments run with an idealised mixture of glass beads and kaolinite, and natural sediment and kaolinite. A constant current (1.6Am−2) was applied in all experiments. Results showed elevated voltage differences between layers in heterogeneous experiments compared to equivalent homogenous experiments. Furthermore, nitrate concentrations are elevated in the low-K material in heterogeneous compared with homogeneous systems. Using predicted values this is shown to be a function of a transverse flux associated with the voltage difference between layers. The importance of this phenomena at field scale for delivery of an amendment (i.e., electron acceptor, donor or nutrient) by EK for bioremediation is presented in an electron balance model. Overall, this research establishes and quantifies a previously unreported important phenomenon in the electrokinetic transport literature that enhance the application of this technology for bioremediation of contaminated aquifers.

Segregation of granular mixtures in a spherical tumbler.

Segregation of polydisperse granular materials in rotating containers is a ubiquitous but still not satisfactorily understood phenomenon. This study describes axial segregation of bidisperse granular mixtures of glass beads in a spherical container, rotating about its horizontal axis. Depending on the filling fraction of the mixer and on the composition of the mixture, qualitatively different spontaneously formed patterns are observed. For technical applications, the well-localized segregated bands allow a convenient separation of individual components of the mixtures. It is particularly surprising that the initial compositions of the granular mixtures have a fundamental influence on the location of the segregated bands. This evidences a collective pattern forming mechanism. The spontaneous formation of these bands cannot simply be traced back to individual particle dynamics. Existing models for segregation in spherical mixers are critically examined and extensions are suggested.

Bubbling to turbulent bed regime transition of ternary particles in a gas–solid fluidized bed

The transition from bubbling to turbulent flow regime of a wide particle size distribution (PSD) powder was investigated in a circulating fluidized bed riser with an internal diameter and a height of 0.1 and 3.7m, respectively. Iron ore and limestone particles were used as the wide PSD powder. To study the effect of particle size distribution on the flow regime transition, five types of mono size glass bead were used. Binary and ternary mixtures were made from the mixture of mono size glass beads. The regime transition of the wide PSD powder was studied by means of overall pressure drop and pressure fluctuation analysis. By gradually increasing the superficial gas velocity, a bed of a wide PSD powder changed from a fixed bed state to partial fluidization and then to complete fluidization. The transition from bubbling to turbulent fluidization occurred in the complete fluidization state. The effects of fine particle concentration, coarse particle size, and particle size distribution on bubbling-to-turbulent regime transition velocity were also studied. A correlation expressed in terms of Rec, Ar, and standard deviation of particle size distribution (σp) was proposed to predict the transition velocity (Uc). The predicted Uc values were in close agreement with the experimental data of mono, binary, and ternary mixtures.

Measuring two-phase particle flux with a multi-frequency acoustic Doppler profiler.

A methodology is developed and tested for simultaneously extracting time-resolved one-dimensional profiles of the mass-concentration and velocity of two different particle types in a mixed suspension, using a multi-frequency pulse-to-pulse coherent Doppler instrument. The technique involves inversion of a model for frequency-dependent acoustic backscatter amplitude and phase. Results are presented from a laboratory settling column experiment, measuring a mixture of polystyrene beads (slowly-settling, strongly-scattering) and glass beads (quickly-settling, weakly-scattering) in a vertical pipe section.

Exploring the relationship between critical state and particle shape for granular materials

The relationship between critical state and particle shape corresponds to the most fundamental aspect of the mechanics of granular materials. This paper presents an investigation into this relationship through macro-scale and micro-scale laboratory experiments in conjunction with interpretation and analysis in the framework of critical state soil mechanics. Spherical glass beads and crushed angular glass beads of different percentages were mixed with a uniform quartz sand (Fujian sand) to create a sequence of mixtures with varying particle shape. On the micro-scale, particle shape was accurately measured using a laser scanning technique, and was characterized by aspect ratio, sphericity and convexity; a new shape index, taken as the average of the three shape measures and referred to as overall regularity, was proposed to provide a collective characterization of particle shape. On the macro-scale, both undrained and drained triaxial tests were carried out to provide evidence that varying particle shape can alter the overall response as well as the critical states in both stress space and volumetric compression space. The mixtures of Fujian sand and spherical glass beads were found to be markedly more susceptible to liquefaction than the mixtures of Fujian sand and crushed angular glass beads. The change in liquefaction susceptibility was shown to be consistent with the change in the position of the critical state locus (CSL) in the compression space, manifested by a decrease in the intercept and gradient of the CSL due to the presence of spherical glass beads. Quantitative relationships have been established between each of the critical state parameters and each of the shape parameters, thereby providing a way to construct macro-scale constitutive models with intrinsic micro-scale properties built in.

Modeling fluid-particle interactions in flowing film type gravity concentrators

Understanding of particle motion through water and the particle sedimentation as well as distribution mechanism in an open channel flow is of considerable engineering importance. In an effort to test the extent to which fundamental fluid mechanics can provide a prediction of particle concentration profile and the fluid velocity profile, a study on a simple inclined rectangular channel has been carried out using glass bead and ilmenite mixtures at various particle concentrations and flow rates. Great care was taken to devise a flow splitter at the end of the channel that permitted accurate measurement of the fluid flow profile and collection of slurry samples, allowing evaluation of the particle species concentration profiles for model validation purpose. The resulting predictions of particle separation are shown to be a strong function of the settling velocities of the particles used and the resulting predictions of particle separation are remarkably good, which ultimately validates the modelling methodology.

Prediction of Pressure Drop and Holdup for Homogeneous Ternary Mixtures of Spherical Glass Bead Particles in a Three-Phase Fluidized Bed

Hydrodynamic characteristics, viz. bed pressure drop and gas holdup, have been studied for ternary mixtures of homogeneous regular particles in a co-current three-phase fluidized bed. For this, a series of experiments have been carried out in a 5-cm diameter column with air as the gas phase, water as the liquid phase, and ternary mixtures of glass beads (1.54, 1.3, and 1.1 mm) as the solid phase. The dependence of bed pressure drop on the average particle diameter, superficial gas velocity, and initial static bed height has been discussed. Based on the dimensional and statistical analyses, correlations have been developed with the system parameters, for both bed pressure drop and gas holdup. Experimental values of bed pressure drop and gas holdup have been found to agree well with those calculated from developed correlations.

Effects of superficial gas velocity and temperature on entrainment and electrostatics in gas–solid fluidized beds

The effects of superficial gas velocity and temperature on particle entrainment and electrostatic charges in fluidized binary mixtures of glass beads were investigated in a column of 150mm inner diameter and 2m height. The degree of electrification in the bed was measured by four collision ball probes at different levels. The charge density of entrained particles in the freeboard was determined by a freeboard sampler constructed as a Faraday cup. An instrumented pipe coated with Ni in the reactor exit line measured the electrical current transferred from entrained fine particles by collisions. The particle entrainment flux and electrostatic charge inside the bed and freeboard region increased with increasing superficial gas velocity. Temperature had negligible effect on the entrainment flux over the limited range studied. However, electrostatic charges decreased and the charge polarity reversed as the bed temperature increased from 20 to 75°C.

Discharge flow of a bidisperse granular media from a silo.

The discharge flow in a cylindrical and a rectangular silo using both monodisperse and bidisperse mixtures of spherical glass beads is studied experimentally. The flow rate is measured using a precision balance for a large range of particle diameters, size ratios, and outlet diameters. A simple physical model is proposed to describe the flow of bidisperse mixtures. It gives an expression for the flow rate and predicts that the bulk velocity follows a simple mixture law. This model implies that a mixture diameter cannot be simply defined. Moreover it is shown that bidisperse granular media allow for the transport of coarse particles below their jamming conditions.

고온 고압 스팀을 주입하는 SAGD 공정에서 CO2주입이 오일샌드 역청 회수율에 미치는 영향

오일샌드에서 비투맨(bitumen)을 회수하는 지하회수방식 중 가장 많이 사용하는 기술인 SAGD (steam assisted gravity drainage)공정으로부터 비투맨의 회수율을 향상시키고자 스팀과 함께 주입한 첨가제의 효과와 매커니즘에 대해서 연구하였다. 실제 광구에서 쓰이는 SAGD공정을 150 : 1로 축소한 실험실 규모의 모사장비가 사용되었으며, 지하 박층을 모사할 수 있는 장치(이하 GM, geological model)가 사용되었다. 초중질유와 글래스비드(glass bead 1.5 mm)의 혼합물은 오일샌드의 모사재료로 사용되었다. 첨가제로서 <TEX>$CO_2$</TEX>가 사용되었으며, 스팀 챔버(steam chamber)의 성장 변화를 비교 분석하였다. <TEX>$CO_2$</TEX>의 주입방식에 따른 효과를 확인하기 위하여 스팀과 <TEX>$CO_2$</TEX>를 연속 주입하는 실험(<TEX>$cCO_2$</TEX>-SAGD)과 순차적으로 주입하는 실험(<TEX>$sCO_2$</TEX>-SAGD)을 실시하였다. 그 결과 <TEX>$sCO_2$</TEX>-SAGD 실험의 경우 Control 실험 대비 오일 회수율은 60.2%에서 69.3%로 향상되었으며 cSOR의 경우 7.1에서 6.0으로 낮아졌다. 반면에 <TEX>$cCO_2$</TEX>-SAGD 실험의 경우 60.2%에서 57.6%, 7.1에서 7.3으로 증가 되었다. SAGD (steam assisted gravity drainage) process is the most commonly used in-situ technology for the recovery of bitumen from oil sand. It was investigated that the effects of different additives on bitumen recovery rate from oil sand in SAGD process among many possible mechanisms studied throughout the study. Bitumen recovery from thin layer oil sand reservoirs was simulated by using an experimental SAGD apparatus with scale of 150:1. To improve the simulation accuracy of thin layer oil reservoir, we have attached geological model (GM). Oil sand was simulated by using a mixture of extra heavy oil and glass beads with a diameter of 1.5 mm. <TEX>$CO_2$</TEX> was used as an additive and the evolution of steam chambers were closely monitored, and the effects of <TEX>$CO_2$</TEX> as an additive was investigated. Two types of injection methods were tested; continuous (<TEX>$cCO_2$</TEX>-SAGD) and sequential interruption (<TEX>$sCO_2$</TEX>-SAGD) <TEX>$CO_2$</TEX> injection. For the <TEX>$sCO_2$</TEX>-SAGD experiment, it was observed that the recovery rates and CSOR were efficiently improved control experiment from 60.2% to 69.3% and 7.1 to 6.0, respectively, whereas <TEX>$cCO_2$</TEX>-SAGD experiment decreased from 60.2% to 57.6% and 7.1 to 7.3.

Hydrodynamics of Liquid-Solid Semi-fluidized Bed with Regular Homogenous Ternary Mixture

Hydrodynamics studies in Semi-fluidized bed relating to bed pressure drop, height of top packed bed, minimum and maximum semi-fluidization velocities with regular (spherical glass beads) homogeneous ternary mixtures, have been made in 0.01, 0.025, 0.037, 0.05, and 0.065 m internal diameter Perspex columns, with water as the fluidizing medium. Ternary mixtures of glass beads of different sizes (-8+10, -10+12 and -12+14 BSS) have been used as the semi-fluidized solids. Experimental studies relate to establish the effect of system parameters viz. column diameter, average particle size of semi-fluidized solid and initial static bed height and operating parameters viz. superficial liquid velocity and bed expansion ratio on the above mentioned system variables. Empirical and semi-empirical models have been developed using dimensional as well as statistical analyses. The calculated values from the predicted models have been compared with their experimental counterparts and fairly good agreement has been obtained. The results have also been compared with those available in the literature for irregular homogenous ternary mixtures.

Experimental investigation of residual saturation in mixed-wet porous media using a pore-scale approach

Wettability is an important factor in terms of flow distribution and the amount of oil left behind in a petroleum reservoir after primary, secondary, and tertiary recovery processes. In fact, most alkaline flooding operations are aimed at wettability reversal. Therefore, a good understanding of how wettability, and other relevant factors (e.g., fluid saturation and porosity), affects displacement efficiency and fluid distribution at the pore-scale can lead to successful predictions of flow properties at the macroscale. In this study, pore-scale two-phase fluid flow in a synthetic mixed-wet granular media was investigated using X-ray microCT. Analysis of residual fluid structures in granular media composed of a mixture of glass and plastic beads (ranging from 0.4 to 0.6 mm in diameter) showed that the number of trapped water blobs was 2.4 times greater than that of oil, whereas most of the blobs were between 0.0001 and 0.001 mm3 in size (i.e., 100 times smaller than in the case of uniform wettability), and were smaller than the mean pore volume (0.03 mm3). The ratio of surface area to blob volume showed a slight tendency of water blobs to wet a higher surface area of the grains than oil blobs, for blob volumes larger than the mean pore size; this phenomenon can be attributed to stronger wetting affinity of the glass grains to the water phase than that of the plastic grains to the oil phase. Furthermore, statistical analysis of the distance between residual oil and water blobs to each solid surface confirms preferential wetting affinity of oil and water to plastic and glass surfaces, respectively.

The Study of Water-Sediment Two Phase Flow Field Measurement Based on Particle Image Velocimetry

Internal flow field of water-sediment two phase flow was hardly observed by PIV system, due to poor light transmittance. To improve this situation, the glass particle was used in experiment instead of sediment particle. According to the experiment results, the light transmittance of the mixture of glass beads and water was better than the mixture of sediment and water; so the relatively clear internal image of the two-phase flow could be obtained by PIV system. According to the experiment, the glass beads movement was similar to sediment in water.

Hydrodynamics of three-phase fluidization of a homogeneous ternary mixture of regular particles—Experimental and statistical analysis

Abstract In the present study, a series of experiments were carried out for homogeneous well-mixed ternary mixtures of glass beads of varying compositions in a three-phase fluidized bed. The hydrodynamic characteristics determined included the bed pressure drop, bed fluctuation and bed expansion ratios. The individual and combined effects of operating parameters such as superficial gas velocity, superficial liquid velocity, initial static bed height, average particle size and column diameter on the responses have been analyzed using response surface methodology (RSM). A 25 full factorial central composite experimental design has been employed. Analysis of variance (ANOVA) showed a high value coefficient of determination and a satisfactory prediction of second-order regression model. The synergetic and antagonistic effect of the system parameters on the above three responses are analyzed from the developed regression models. The coefficient of correlations for bed pressure drop, bed expansion and fluctuation ratios are found to be 0.9642, 0.9483 and 0.9423 respectively. Thus, the experimental values of the above three hydrodynamic parameters have been found to agree well with those calculated from the developed correlations.

Constitutive behavior of binary mixtures of kaolin and glass beads in direct shear

Composite soils having a wide range of particle size may be the most commonly encountered materials in geotechnical engineering practice. This study involves 21 direct shear tests to investigate the constitutive behavior of composite soils within the normal stress range from 50 to 200 kPa. The samples are mixtures of fine (kaolin) and coarse (glass beads) fractions at various proportions. The properties of the samples considered in the investigation are particle size distribution, water content of sheared specimens, structural features of shear surface and residual shear strength. It is shown that the particle size distribution influences the void ratio produced with the same compaction effort. Increasing fine fraction from zero to a threshold value (approximately 20–30%) causes a decrease in void ratio of the mixture. Beyond this threshold, a further increase of fine fraction causes an increase in void ratio. High proportion of fine fraction causes: (1) lower water content of shear zones relative to outer zones, (2) densification process within shear zone, (3) well slickensided shear surfaces, and (4) shearing in sliding mode and hence low residual shear strength.

Definition of the New Mean Particle Size Based on the Settling Velocity in Liquid

New analysis and a definition of the new mean particle size have been discovered by rediscussing theory of the buoyancy weighing-bar method, which is a type of sedimentation methods. This paper proposes a new mean particle size based on the settling velocity in liquid. The velocity mean size of all particles [equation], which is the new mean particle size defined in this paper by the buoyancy weighing-bar method, is given as follow.[equation]ΔGi is the buoyancy difference mass of particles xi. Homogenous particles and a ternary mixture of spherical glass beads are used as the samples. Although the buoyancy weighing-bar method is also time-consuming, the maximum particle size and the mean particle size can be derived within a short time after initiating measurement.

Occurrence dePseudomonas aeruginosadans les réseaux intérieurs : présentation d’un protocole adapté à la collecte du biofilm présent dans la robinetterie sanitaire

Pseudomonas aeruginosa is an opportunistic pathogen that naturally occurs in aquatic environments. This bacterium is adapted to oligotrophic environmental conditions and could be detected in drinking water systems. Although, water for human consumption is required to be free of any bacteria that might pose a health risk, P. aeruginosa is not included in parameters to be analyse and in a recent report the ANSES conclude that there is no proof that the normal use of contaminated drinking water can be a source of infection by oral route in the general population. This bacterium is mostly harmless for healthy people but must be regarded as a relevant opportunistic pathogen for sensitive human population especially for hospitalized people in intensive care unit. This bacterium is responsible for almost 10% of the hospital-borne infections and drinking water network inside the building is suspected to be a source and a reservoir of P. aeruginosa . Although the target level to achieve is the absence of P. aeruginosa at terminal point-of-use, several studies showed that 4.5 in 97% of water samples taken in intensive care units are contaminated by P. aeruginosa . The origin of patients’ contamination remained discussed but among exogen sources of contamination, tap water is often suspected to be a source and a reservoir for these opportunistic pathogens. Nevertheless control strategies are limited for drinking water and recurrent contamination of tap water remained unsolved. Water contamination could be explained by retrograde contamination and by colonization of taps. To better characterize the populations of P. aeruginosa present in biofilm drinking water networks, we developed a protocol to sample biofilm from taps. Assays were performed on biofilms established inside taps and on the surface of tap swirls. Mechanical action of glass beads was compared with swabbing and proved to have more efficiency in sampling biofilm on surface of tap swirls. The protocol was then adapted to sample biofilm in faucets. It consists in filling the tap to study with a mixture of sterile distilled water and borosilicate glass beads of 1 mm in diameter and then to perform a mechanical shaking of 3 minutes with a vortex. This protocol will be used to collect biofilm on terminal point-of-use and to compare occurrence of P. aeruginosa in this type of biofilm and in the biofilm established on plumbing material.