Granular Mixtures Research Articles

Fluorescence in the assessment of the share of a key component in the mixing of feed

AbstractThis paper presents the results of the mixing of a multicomponent feed for cattle. Three types of mixtures with different proportions of individual components and granulometric composition were selected. After the mixing process, the fraction of the key component (tracer) was determined. Tracer consisted of crushed grains of yellow maize, which was wet treated with a 0.01% solution of Rhodamine B. A tracer with two different average particle sizes d1 = 2.0 mm and d2 = 1.25 mm was introduced into the mixture. Then, the sample was illuminated with UV light, and the content of the tracer in the sample was evaluated using the computer image analysis. In addition, the tracer was separated to determine its fraction using a laboratory scale. From the obtained results, the high reliability of the fluorescence optical method for the evaluation of the homogeneity of granular multicomponent mixtures was proved. It was also observed that slightly better results were obtained for a tracer with a larger average particle size (d = 2.0 mm), although the comparative analysis did not indicate a significant statistical difference in the results in each series of tests.

Potential of Natural and Recycled Concrete Aggregate Mixtures for Use in Pavement Structures

This study investigates the feasibility of using recycled concrete aggregate (RCA) as a partial substitution of natural aggregate in pavement engineering. Despite RCA’s good properties, such as polishing value and freeze-thaw resistance, its use is limited by low resistance to fragmentation and high-water absorption. This paper parent the experimental results of mineralogical-petrographic and physical-mechanical properties of RCA, natural stone (dolerite) and their combination (RCA content—15%, 30%, 45%, and 60%). The tested granular mixtures showed good resistance to fragmentation and wear (LA 22–27%, MDE 14–15%), as well as satisfactory Polished Stone Value of 55–57, which means they can be used in different layers of pavement structures. According to the obtained testing results, the application of RCA is possible in different flexible and rigid pavement layers and for various traffic loads.

A particle tracking velocimetry method to measure size and charge distributions in tribocharged powder particles

Simultaneous charge and size of tribocharged particles suspended in a gas stream are measured using image analysis. Under the action of a homogeneous electric field, drag, and electric forces are the main factors influencing particle trajectory, from which electric charge and polarity are derived. We could check that the system operates in a laminar gas regime inside the analysis cell since high flow turbulences would alter the particle “electrical” path, thus invalidating the measurement. Single component granular materials and binary mixtures are studied, all cases showing bipolar distributions and dependence on particle size. Mixture composition affects the overall charge polarity in the dispersed powder, and this effect can not solely be attributed to the weight proportion of the components. PTV is a powerful tool in techniques used for triboelectric dry separation of organic and inorganic products since their efficiency relies much on the charge to mass ratio.

Computations of mixing/segregation of binary mixtures in supercritical water fluidized bed

Numerical simulations are performed for investigating the mixing/segregation of flotsam component (FC) and jetsam component (JC) of binary mixture in supercritical water fluidized bed (SCW FB). The collisional interactions of FC and JC are modeled by means of the unequipartition of granular energies-based kinetic theory of granular mixture (KTGM). The distributions of segregation index are predicted at different SCW pressures and temperatures. Four regions named as the segregation (SE), dense (DE), transition (TR) and freeboard (FR) are defined along bed height. The synergy angle is proposed to measure the compromise in competition of mixing/ segregation of FC and JC along bed height. The synergy angles are determined from volume fractions of FC and JC in the DE region. The effect of SCW temperature and pressure on synergy angle and segregation index is investigated. The simulated results are analyzed according to the SCW pressure and temperature as well as inlet SCW fluidizing velocities. The simulated results suggest that the increase of SCW temperature and fluidizing velocity contribute the mixing of FC and JC binary mixture along bed height of SCW FBs.

New aggregate grading models for low-binder self-consolidating and semi-self-consolidating concrete (Eco-SCC and Eco-semi-SCC)

In this study, the characteristics of the granular skeletons of 38 low-binder self-consolidating concrete mixtures were investigated to minimize the binder content and volume of paste (VP). 20 granular mixtures were proportioned using 5 different Fuller-Thompson distribution moduli (q) of 0.4 to 0.5 and 4 different volumetric sand-to-total aggregate ratios (S/A) of 0.45–0.60. The investigated Eco-SCC mixtures with a water-to-binder ratio (w/b) of 0.60 and VP of 29% were classified based on their flowability, passing ability, and static stability results. The volume of paste was reduced in two successive steps to 26% and 24% using the Eco-SCC mixtures proportioned with the optimized granular skeletons.Using 3D image analysis of the aggregate shapes, modified versions of Funk-Dinger model and new grading models as functions of natural logarithm of the particle sizes were proposed for the optimized granular skeletons. The new proposed models were validated with the Eco-SCC mixtures containing the minimum VP of 24% and 2 new aggregate sources. The results showed that considering the realistic dimensions of aggregate using the new proposed logarithmic grading model with q of 2.6212 and S/A of 0.55 can result in a significant reduction in binder content and volume of paste from 309 kg/m3 to 256 kg/m3 and 29% to 24%, respectively, with equivalent workability performance. These also led to decrease the global warming potential values from 206 to 172 e-CO2 kg/m3 of concrete, while higher eco-efficiency indices and workability characteristics, as well as an appropriate compressive strength for housing application were achieved.

Experimental investigation of a tribo-electrostatic separation device using linear moving electrodes

The aim of this paper is to carry out an experimental analysis of a triboelectrostatic separation device constituted of two “back-and-forth” moving horizontal plate electrodes supplied by two high-voltage DC supplies of opposite polarities. The experiments were performed using samples of micronized white pure virgin PolyVinyl Chloride particles (WPVC) and gray PolyVinyl Chloride particles (GPVC) of average size 100 µm. Moreover, a homemade method was developed to estimate the purity of the separated products. It was deduced that the separation outcome, in terms of recovery and purity, is efficient and depends on several factors: the high-voltage level, the movement speed of the electrodes, the fluidization rate and the composition ratio of the granular mixture.

Behavior of density-induced segregation with multi-density granular materials in a thin rotating drum

In this study, the effect of multi-density particles on granular segregation was experimentally investigated in a rotating drum. Optical cameras were used to record the motions of the granular materials. Particle tracking methods and image processing technology were used to determine the angle of repose, segregation index, and the velocities and granular temperatures of white POM (polyformaldehyde) beads (tracer particles). The experimental results showed that the final steady-state segregation index increases with the density ratio in a binary granular mixture. The results indicated that the final steady state segregation index is smaller with multi-density granular materials compared with those of materials with the binary granular mixture. The behavior of density-induced segregation is mitigated upon the addition of glass beads into the binary granular mixture. The relation between granular temperature and density-induced segregation was also discussed in this study.

Size segregation of bidisperse granular mixtures in rotating drum

Size segregation of granular mixtures is one of the common types of segregation in a rotating drum. This phenomenon occurs in process equipment such as mixers, ball-mills and rotary-kilns. Here, we studied the segregation of bidisperse spherical glass-beads with size ratio ranging from 0.1 to 0.9 in a rotating drum by experiment and DEM modelling. In the experimental part, solidified-bed sampling was applied. For size ratios larger than the transition amount (0.26), the smaller component tended to accumulate in the core region with a maximum core-shell segregation around the size ratio 0.5, whereas in the opposite case (smaller size-ratios), they percolated near the drum wall. At ratios around the transition ratio (0.26) and at size ratios approaching unity, the most uniform concentration of beads was attained based on the relative standard deviation (RSD).

Investigation of LCM soaking process on fracture plugging for fluid loss remediation and formation damage control

When drilling through naturally fractured reservoirs, the remediation of drill-in fluid loss needs to be designed by taking both fracture plugging and formation damage into account. Lost circulation materials (LCMs) should be implemented efficiently to minimize the solid-laden fluid invasion into the fractures during the development of fracture plugs. This study investigated the effects of three LCM deployment factors: injection rate, soaking time, and soaking pressure, on the total fluid invasion volume and plug breaking pressure. Full factorial experimental design and statistical analysis were conducted to study the statistical significance of each factor. Scanning Electron Microscope (SEM) and Micro Computed Tomography (MicroCT) were applied to visualize the plug structures for the understanding of the soaking effects.Different combinations of LCMs were tested in a permeability plugging apparatus with a slotted disk. For granular LCM mixtures, the soaking pressure and time did not have a significant impact on total fluid invasion volume or ultimate plug breaking pressure. For mixtures blended with fibrous LCMs, longer soaking time contributed to reducing fluid loss and increasing plug breaking pressure. A lower LCM pill injection rate led to less fluid invasion upon the establishment of an effective seal. The SEM and MicroCT images indicated that a longer soaking time could lead to a less porous and strengthened plug structure.The results and conclusions from this study provide new insights into the identification of optimal LCM implementation scheme with better formation damage control.

DEM investigation of macro- and micro-mechanical properties of rigid-grain and soft-chip mixtures

We investigated the macro- and micro-mechanical properties of rigid-grain and soft-chip mixtures (GCMs) through numerical simulations using the discrete element method. We present a novel framework for the discrete modeling of soft chips and rigid grains in conjunction with calibration processes. Several numerical triaxial tests were also performed on GCMs with 0%, 10%, 20%, and 30% volumetric chip contents, P. The simulation results demonstrate that increasing P leads to higher GCM toughness, higher deviatoric peak stress, and higher corresponding shear strain. Higher P also contributes to more volume contraction and less dilation. The friction angles at both the peak and residual state significantly increase with increasing P. In view of the micro-mechanical features, strong contact force chains develop along the loading direction, which results in considerable anisotropy in the peak and residual states. Both the formation of strong force chains and rotation of grains decrease with increasing P, whereas the grain sliding percentage increases. The tensile force is mobilized with shearing and higher P leads to less mobilization of the tensile force. These findings are useful for better understanding the internal structure of GCMs with different soft-chip contents, especially in granular mixture mechanics and geomechanics.

Texture Properties of a-2D Granular Mixture of an Angular Particle under Bi-axial Compression

Utilizing Discrete Element Modeling (DEM), we investigate the shear strength properties and microstructure of 2D granular mixture composed of various regular polygonal particles (from triangle to icosagon and disk) under biaxial compression. Three cases were considered: 1) increase of proportion and angularity started from disk (S1); 2) increase of proportion by decreasing the angularity started from triangle (S2); 3) increase of proportion by random angularity started from disk (S3) and polygons (S4). The results show that the shear strength changes with the mean angularity. On the other hand, the packing fraction slightly varies with the mean angularity. At the microscopic scale, the granular texture in term of the force, the contacts transmitted the force higher than the average force (strong force) are oriented in the direction of externally applied loading but they represent only 40% of the total number of contacts. Besides, the tangential contact forces direction tend to be consistent with the maximum shear strength direction.

Numerical Validation of Heat Conduction in 2D Binary Granular Mixtures under Mechanical Loading

This study set out to investigate numerical simulations of heat conduction to validate existing experimental results of two-dimensional binary granular mixtures subjected to mechanical loading. Data for this study were collected using molecular dynamics (henceforth MD) method. Three different configurations of the granular composite samples were systematically prepared under similar experimental conditions. A confined mechanical loading was applied to the granular samples. The fields of normalized temperature change of each particle were plotted for an individual sample. The results were statistically analyzed under a static equilibrium condition. The results indicate that simulation is in good correlation with the experiments in terms of statistical analysis via the probability of the distributions of the normalized temperature change. It also revealed that the normalized temperature changes which are greater than the average temperature distributes as an exponential decreasing for all tested samples. This study is in line with other studies that are related to force distribution of law. Less than 50% of particle numbers that have the normalized temperature changes, which are greater than the average value, is also explored. Besides, localizations of the temperature were found in the individual sample.

Numerical Investigation of the Effects of Particle Density and Dimensionless Acceleration on Segregation in 2D Vertically Vibrated Binary Granular Mixtures

The present work aims to investigate the influences of particle density and dimensionless acceleration on segregation phenomena in 2D binary granular mixtures by using contact dynamics method. The granular samples were prepared by randomly depositing two species of regular pentagonal particles inside a rectangular container. These two particle species are the same in size, but differ in terms of particle density. Different levels of vertical vibration were then applied to the mixtures. The simulation results were systematically analyzed by using segregation coefficient (H), segregation pattern, and velocity field related to convection mechanism. It was found that segregation phenomena are not observed in this study. This could be explained by the fact that a value of friction coefficient between interparticle and that value between wall and particle is set to be the same, that is why no segregation was found in the present study. Due to the friction, only convection rolls were observed for all the density ratios when dimensionless acceleration is greater than 2.

Dynamic properties of the two-dimensional density-driven segregation

We discuss some dynamic properties of the segregation in vertically vibrated binary granular mixtures with the same size. We present a method that can accurately calculate the order parameter in the simulation. By use of the time evolution of the order parameter, we have found that the convergence of the segregated state depends at least on the vibration amplitude, the total mass of the particles, and also the density difference between the lighter and heavier particles. The convergence is quicker for larger vibration amplitude, lighter total mass of the particles and more density difference between the lighter and heavier particles. We have also found that the fluctuation is larger even after the steady state is reached for lighter total mass of the particles and less density difference between the lighter and heavier particles.

Thermal percolation in mixtures of monodisperse spheres

The connectivity of individual species in a locally heterogeneous granular mixture strongly influences assembly-scale behavior. A behavioral transition is observed at the percolation threshold for a given constituent; that is, the mixing fraction at which the constituent has statistical connectivity between two opposing boundaries. This behavior is particularly evident in conductivity phenomena, e.g., the percolation of conductive particles (thermal, electric) or the relative degree of connectivity of the void space (hydraulic). Hard-core (first nearest-neighbor or lattice) percolation has been extensively studied experimentally, theoretically, and numerically. That hard-core percolation occurs in dense randomly packed bi-phasic mixtures of monodisperse spheres occurs at a mixing fraction of 0.15 v/v is well-accepted. Radiant conduction (e.g., heat), however, is influenced by hard-core “soft-shell” percolation, which is an nth-nearest neighbor problem and less well-studied. In the current work, we use discrete element method simulations coupled with a thermal network model that leverages a robust domain decomposition algorithm to simulate large assemblies of spheres to investigate soft-shell percolation numerically. Our results show that the thermal conductivity of a randomly packed assembly obeys a power law with respect to volume fraction of conductive particles while percolation threshold follows a power law with respect to coordination number. The ability of the pore fluid to transmit heat over a longer distance results in an increase of thermal conductivity and a decrease in thermal percolation threshold. Moreover, we observe that, contrary to previous findings, critical percolation density is not a dimensional invariant and depends on the microstructure of the assembly.

Особенности накопления йода в мышцах кроликов на фоне использования антиоксидантов в липосомальной форме

Abstract. The problem of iodine saturation of livestock products for residents of most regions of our country requires a detailed study. One of the factors is the obtaining of livestock products enriched with organic iodine. The study of the degree of accumulation of iodine in the muscle tissue of rabbits at the background of the use of liposomal form of antioxidants enriched with organic iodine (LFA) was the main purpose of the research. Methods. An experiment on rabbits of the California breed were used. The first control group received the main diet (MD) in the form of a granular mixture. The experimental second group was given LFA based on White sea laminarias at the rate of 250 g per ton of feed mixture of MD. The third experimental group was injected with MD the LFA with Black sea Cystoseira. The formation of meat indicators, chemical analysis of muscle tissue, the level of accumulation of trace elements, including iodine in muscle tissue was studied indicators. Results. Based on the somatometric method of evaluating rabbits, it was found that the young animals of the experimental groups form a more eirisomus-type body (from 60 to 70 % of the total population). All indicators of the interactions of somatic parameters in the young groups II and III positive and highly significant correlation, and the correlation index of the density of the body correlated positively with body length (r = +0,67, p ≤ 0.01), chest girth (r = +0,86, p ≤ 0.001), length of loin (r = +0,61, p ≤ 0,01), the length of the backside (r = +0.71, p ≤ 0.001) and head measurement (r = +0,57, p ≤ 0.05). An improvement of the indicators of slaughter of experimental groups of young animals was stated. The slaughter weight increases by 12.2 %, and the mass of internal organs responsible for digestion by 4.5–43.8 %. A percentage of increase in muscle tissue during boning by 10.0–15.9 % and a decrease in the proportion of low-value parts in the carcass-bone tissue by 8.6–9.9 % was stated. Iodine in the average sample of muscle tissue of the experimental groups increases by 91.8 mcg (p ≤ 0.05) in animals of the second group and by 113.3 mcg (p ≤ 0.05) of the third group.

Two-dimensional density-driven segregation in vertically vibrated binary granular mixtures

Two-dimensional segregation effect in vertically vibrated binary granular mixtures with same size is studied by molecular dynamic simulation. The results show that the lighter and mixed state, in which the lighter particles tend to rise and form a pure layer on top of the system while the heavier particles and some of the lighter ones stay at the bottom and form a mixed layer, also exists in the two-dimensional system. The validity of the scheme of the lighter and mixed state is testified by comparing the distribution profiles implied by the scheme with that of the real simulated state. We further propose to use twice the ratio of the thickness of the top layer to that of the whole system as an order parameter to describe the degree of the segregation quantitatively, and present a method that can accurately calculate the order parameter in the simulation. By use of the order parameter, we show that the order parameter is a convex monotonic function of the density ratio between the heavier and lighter particles.

Measuring segregation characteristics of industrially relevant granular mixtures: Part II – Experimental application and validation

To apply an existing transport model to industrially relevant granular mixtures and flows, we demonstrate an approach to experimentally measure the segregation coefficient, S, and the flowing layer thickness, δ, using a modified quasi-2D bounded heap. During heap formation, the flowing layer velocity is characterized using particle image velocimetry, which determines δ and other kinematics. After formation, the heap is sampled to determine the concentration of each species along its length. The difference between measured and model-predicted concentration profiles is minimized by varying S, which gives the experimental estimate of S for the mixture of interest. The methodology is tested for bidisperse combinations of Cellets — industrially relevant and roughly spherical microcrystalline-cellulose particles. Variation of S with particle-size-ratio matches previous DEM results for glass particles. Further validation of the approach is provided by tests with different flow rates and mixtures, including glass particles and Cellets, and a tridisperse Cellets mixture.

Improving the recovery of copper from electric cable waste derived from automotive industry by corona-electrostatic separation

The aim of this work is to demonstrate the possibility of using electric field forces for the recovery of copper from a fine PVC/Cu granular mixture of low metal content (less than 15%), obtained as “PVC fraction” in the recycling process of electric cable waste from automotive industry, using vibrating table technology. Electrostatic separation of copper granules which are “impurities” in the PVC fraction, increased the overall recovery of copper close to 100%. Granular size classification proved to be a very useful operation in the electrostatic separation process of a particular mixture. The −0.63 mm size class contains the majority of the copper granules and the electrostatic separation allows the recovery of up to 95% copper contained in the granular waste, at purity higher than 99.8%. Copper represents less than 1% in the +0.63 mm size class and can also be recovered with high purity by improving the chopping technology of the cable waste, as well as the separation between the copper and the high conductivity rubber granules.

Measuring segregation characteristics of industrially relevant granular mixtures: Part I – A continuum model approach

We present a method to estimate the segregation parameter, S, a key input in a continuum transport model of particulate flows. S is determined by minimizing the difference between measured and model-predicted concentration profiles. To validate the approach, we conduct discrete element method simulations of size-bidisperse mixtures in quasi-2D bounded heap flow; the resulting data show that S calculated from concentration profiles is consistent with the directly measured value. The method's accuracy depends critically on the velocity profile during filling, but only weakly on the diffusion coefficient. When the velocity profile is nominally spanwise invariant, the error between estimated and measured S is 10%. This method is intended for practical application (described in Part II), so we restrict characterization of the velocity profile to that which can be readily determined experimentally, and explore the sensitivity of concentration profiles to variation of the gap between the sidewalls of the heap.