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The effect of turbulence on the detachment between an air bubble and a glass bead (soda-lime) with different hydrophobicity was comprehensively researched. An experimental apparatus was designed to simulate the turbulent environment during the actual flotation process, which was used to research the detachment of different hydrophobic glass beads from bubble surfaces. It is indicated that three different hydrophobic glass beads detached from the bubble surfaces in the same way but at different speeds. The three-phase contact line (TPCL) shrank rapidly when the centrifugal detachment force of glass beads reached a critical value. The deformation of bubbles increased, and the three-phase contact (TPC) area continuously decreased. When the critical value was exceeded, the sliding and contraction speed around the TPCL further increased until a clear necking phenomena appeared near the TPC. Furthermore, the centrifugal detachment force, capillary force and total pressure force increased with increasing hydrophobicity in the detachment process. [Display omitted] • A special experiment was designed to simulate the turbulent conditions inside the flotation cell. • The bubble-particle detachment process was non-instantaneous. • The three-phase contact line rapidly shrank when the centrifugal detachment force of particles reached critical value. [ABSTRACT FROM AUTHOR]

This study presents a piezoelectric fast load cell (PFLC) as a novel device for testing single particle fracture energy under impact and proposes a collision model for measurement and calibration. The research examined various models, modifying the long-rod model to create a more practical short-rod model describing the contact dynamics during collision processes. Through back-calculating the Young's modulus of glass beads, the optimized measurement settings are calibrated for practical use based on the short-rod model, which is corroborated by comparison with fracture probabilities obtained from the drop weight tests and PFLC. It was verified that the observed fracture characteristics of ore align with established principles of fracture mechanics, validating the testing approach. The PFLC offers a cost-effective and compact substitute to classic ultra-fast load cell (UFLC), potentially enhancing the adoption of advanced comminution models like the Tavares Model. [Display omitted] • A device (PFLC) was developed to measure the fracture energy of a single particle under impact. • The short-rod model was established for the measurement and calibration. • A calibration technique was established through impact tests on regular glass beads. • The test results were aligned with the principles of fracture mechanics. [ABSTRACT FROM AUTHOR]

Knowledge of the shear behavior of landslide soil is very important for understanding landslide dynamics. This study investigated the shear behavior of base soil particle materials using ring shear tests with glass beads. Samples with varying particle sizes and distributions were examined to explore how particle size affects shear behavior at different shear velocities. Analysis of the samples included assessment of shear stress, displacement-shear stress fluctuations, and changes in the shear stress standard deviation. Results showed that with increasing shear displacement, shear stress fluctuations stabilize. Rather large difference particle size differences lead to more uniform particle mixing and a lower shear stress standard deviation. Conversely, when smaller particles predominate, particle mixing is less uniform, resulting in a higher shear stress standard deviation. Additionally, this study discussed the shear dilation and compaction mechanisms of samples under large displacement shear. [Display omitted] • TThe difference of particle size distribution in the upper and lower regions of glass microbeads was studied. • The changes of test parameters under different particle size distributions are analyzed. • The corresponding mechanism is proposed to explain the movement and parameter change of the sample. • The motion patterns of glass beads with different particle sizes were recorded by high-definition cameras. • Piv method was used to track the particle trajectory and demonstrate the velocity displacement. [ABSTRACT FROM AUTHOR]

Various industrial applications are performed in liquid-solid fluidized beds where drag force plays a significant role in affecting the expansion characteristics of granular-bed, and then determines the mass/heat transfer performance. This study employs dimensionless learning data-driven modeling method, which is derived from the principle of dimensional invariance, to automatically discover the relationship between the drag coefficient and hydraulic dimensionless numbers from the liquid-solid fluidization data. It is found that the Fr number (= u l 2 / gd s) also plays important role in improving the prediction accuracy of drag model except for Re number (= d s u l ρ l / μ l). The proposed data-driven modeling method has desired robustness, and the yielded drag model can be applicable to other liquid-solid systems, such as water-polystyrene spheres and water-coal particles, although it is derived from the fluidization of spherical glass beads in rising tap-water. The proposed drag model can also provide good CFD simulation results that agree very well with the experiment data with the relative error less than 5 %. [Display omitted] • A liquid-solid drag correlation was proposed by data-driven modeling method. • A dimensionless number group was found to characterize the drag coefficient well. • The yielded drag model is proved certainly universal. • The drag model was validated by various experimental data. [ABSTRACT FROM AUTHOR]

Liquid aerosols are found in many industrial sectors, particularly in the mechanical industry (oil mists). Granular bed (GB) filtration could be an interesting means for the removal of these liquid aerosols, due to their high storage capacity, robustness and low maintenance requirements. The aim of the study was to establish the filtration performance (filtration efficiency, pressure drop) of a fixed granular bed during filtration and its clogging by a liquid aerosol. Three grades of sand, obtained by sieving 100–200, 200–355 and 355–500 μm and glass beads of 140 μm diameter were used as the granular medium. The evolution of filtration efficiency and pressure drop of the GB was monitored during clogging with a DEHS aerosol of MMAD = 0.7 μm. Our measurements show that the filtration performance of granular beds during clogging was very similar to that observed for fibrous media. The fraction of the GB pore volume occupied by liquid when the drainage plateau is reached was between 28 and 33%. The GB reaches a drainage stage whose pressure drop can be correctly predicted using a model described for fibrous media. [Display omitted] • Sand-based granular beds are an efficient and inexpensive way to filter liquid aerosols. • During filtration the granular bed pressure drop increases steadily until a drainage level is reached. • A simple model, based on the grain Reynolds number, predicts the ΔP at the drainage stage. • The filtration performances are stabilized once the drainage stage is reached. [ABSTRACT FROM AUTHOR]

A vapor-liquid-solid three-phase closed thermosyphon (THPCT) with variable heating position at evaporation section is built by combining the fluidized bed heat transfer technology with the two-phase closed thermosyphon (TPCT). The effect of particle diameter and heating position on the thermal performance is investigated by varying the heating power (100–300 W) and solid holdup (5–15%). Results show that the addition of the glass beads with different diameters can enhance the heat transfer under certain conditions. The maximum reduction rates of the overall thermal resistance are 25.4% and 27.7% for L e = 200 mm and L e = 200 mm − up40, respectively. The upward movement of the heating position is beneficial to reducing the overall thermal resistances of the TPCT and the THPCT with small particles, but is not conducive to the heat transfer of the THPCT with large particles. A medium particle diameter and a low solid holdup are suggested for the THPCT with different heating positions. [Display omitted] • Fluidized bed heat transfer technology are combined with closed thermosyphon. • Glass beads particles are selected as the inert solid particles. • Effect of particle diameter and heating position on thermal performance is discussed. • Different diameters of particles can enhance the heat transfer of the thermosyhon. • Effect of heating position on thermal performance depends on particle diameter. [ABSTRACT FROM AUTHOR]

In this study, the effect of hydrophobic components was analyzed through single drop nucleation experiments on a particle bed. The particle bed's relative hydrophobicity/wettability was varied by changing the percentage composition of hydrophobic and hydrophilic glass beads. The generated nuclei were then isolated and tested using near-infrared spectroscopy and image analysis. The data collected from repeating the experiments were then processed using a random forest machine learning model to predict the probability of immersion and solid-spread nucleation. This model was used to indicate the nucleation mechanism of two formulations. The first contains a varying composition of Ibuprofen and Microcrystalline cellulose, and the second consists of varying compositions of Acetaminophen and Microcrystalline cellulose. The model was validated with experiments. At higher percentage composition of Acetaminophen, the model predicted a higher probability of immersion nucleation. At a higher concentration of Ibuprofen, the model predicted a high likelihood of solid-spread nucleation. [Display omitted] • Application of random forest method was used to predict type of nucleation. • NIR spectra and image analysis were used as predictors for the model. • A model system using glass beads was used as a proof of concept. [ABSTRACT FROM AUTHOR]

Segregation of granular materials is often induced by differences in size, density, shape and surface properties. Density and size-induced mixing and segregation of binary mixtures of glass beads and/or resin particles in the FT4 powder rheometer are investigated experimentally using a new FT4 methodology. The proposed methodology allows for quantification of mixing and segregation of components based on a mixing index. It is observed that the mixing index increases with increasing density and size ratio. Variation of flow energy and torque is related to the mixing and segregation of the mixture components, thus demonstrating that the FT4 powder rheometer may be used as a predictive tool for the tendency of mixture components to segregate under various stress conditions. Numerical analysis by DEM shows that for non-cohesive systems mixing and segregation occur by sifting of fines through interstitial gaps formed between coarse particles in the dilated region. For the non-cohesive system, higher blade tip speeds reduce the rate of mixing and minimise the segregation of different-sized components. Increasing the interfacial energy reduces the rate of mixing and alleviates the segregation of particles. For the cohesive systems, mixing occurs by rupture of cohesive fine clusters with the mixing index increasing with increasing blade tip speed owing to the higher shear stresses that break the agglomerates. [Display omitted] • Mixing and segregation of binary mixtures in the FT4 were investigated. • A new FT4 methodology was developed to quantify mixing and segregation. • Effects of size and density ratios and surface energy were investigated. • Mechanisms governing mixing and segregation were evaluated. • Mixing and segregation rates were related to FT4 flow energy. [ABSTRACT FROM AUTHOR]

The quality of injection molded products is influenced by several factors: the geometry of the product, the polymer used, the mold, the technological parameters of processing and the injection molding machine itself. For this reason, modelling the process by computer is justified and widely used in the industry. Modelling, however, is complicated by the complex flow dynamic and thermal processes during injection molding, and the changes in the material structure of the polymer. Various fillers are used to modify the properties of the polymer, which is an additional challenge for simulation. Processing can cause variation in local filler content in the polymer, which influences several properties of the polymer, but available injection molding software cannot handle the distribution of fillers during the molding process yet, reducing the accuracy of simulations. In this project, we investigated the behavior of polypropylene filled with glass beads during injection molding. For the tests, we prepared mixtures of various filler contents and different bead sizes by extrusion. We also measured the effect of different injection molding parameters, and we examined the segregation of fillers. We modelled segregation numerically with Autodesk Moldflow, and calculated segregation from the results by discrete element modelling. [Display omitted] • We investigated and modelled the segregation of fillers during the injection molding. • Segregation increases considerably above the particle size of 125 μm. • Segregation is caused by partially embedded particles. • Spherical particle can be torn out of the frozen layer if it is embedded less deep than its radius. • The algorithm can describe the expected local glass bead concentration with high accuracy. [ABSTRACT FROM AUTHOR]

Powder rheology and its sensitivity to surrounding environmental condition by controlling the surface properties of the particles is one of the major challenges of the powder industries. Indeed, handling large quantities needs powders with good flowability, adequate compressibility and few electrostatic charges. We have performed a chemical treatment in order to obtain hydrophobic glass beads and its bulk behavior has been compared with raw glass beads depending on the humidity. We characterized flow properties under different processing equipments. We observed that by performing hydrophobic surface treatment sensitivity of glass beads reduced to the humidity. Furthermore, the influence of the electrostatic charges was an undeniable factor in increasing the viscosity of hydrophobic glass beads and consequently lowering its flowability in front of raw glass beads; at low shear rate. At high shear rate, the powders presented similar behaviors. [Display omitted] • At high shear rate, raw and hydrophobic glass beads had similar flowability. • At low shear rate, hydrophobic glass beads were less flowable than raw glass beads. • Hydrophobic formulation decreased sensitivity of glass beads to the humidity. • Hydrophobic formulation increased the electrostatic charge of glass beads. [ABSTRACT FROM AUTHOR]

This contribution proposes a methodology to measure the surface roughness of granular materials using the Gaussian filter. Artificially generated rough surfaces with known root mean square roughness (S q) combined with the spherical shape are analysed to determine the optimum cut-off wavelength (σ ∗) adopted in the Gaussian filter. Considering a combined dependency of S q and particle size (D) on σ ∗, an empirical regression equation is derived to describe their relationship. The regression equation is further found to be applicable for granular materials including glass beads and natural sand grains with irregular base shapes. To implement the proposed Gaussian filter method into practical use, a detailed guideline is given to determine S q including the selection of representative measurement area. Finally, quantitative comparisons of S q are made to distinguish the difference between the proposed method and motif method. [Display omitted] • A Gaussian filter method is proposed to evaluate the surface roughness. • A calibration process is developed to obtain the optimum cut-off wavelength (σ ∗). • A guidance is introduced to apply the proposed method in practical use. • Criteria are given to select a suitable measurement area of irregular particles. • Quantitative comparisons with the motif method are made. [ABSTRACT FROM AUTHOR]

The effects of bed size on the voidage in gas-solid bubbling fluidized beds were statistically studied. The experiments were conducted in plexiglass fluidized beds with different sections, and glass beads were used as bed materials. The voidage signals were measured at different axial positions in the beds. The average, standard deviation, skewness, and kurtosis of the voidage signals were analyzed. The results showed that the voidage and its dispersion degree decreased with increasing bed size, while the asymmetry and steepness degree increased. The bed size had a stronger effect on the voidage at lower axial positions. The relationship between the bed size and theoretical size of some bubbles was predicted. The transition gas velocity from local fluidization to complete fluidization was obtained. [Display omitted] • Statistical methods were used to evaluate the voidage signals. • The bed size had a stronger effect on the voidage at lower axial positions. • Distribution of voidage was almost right-skewed consistently. • Skewness and kurtosis under various experimental conditions showed similar trends. [ABSTRACT FROM AUTHOR]

The diffusion characteristics of three different granular materials in moving beds with different pipe arrangements are studied and compared. Diffusivities of glass beads are always the highest and coarse sands the lowest in all the zones in the beds with aligned pipes. The main flow diffusivity is 1.13 × 10−6, 5.49 × 10−7 and 1.78 × 10−7 m2/s for glass beads, corundum beads and coarse sands. In contrast, the main flow diffusivities of coarse sands and corundum beads are significantly enhanced in the beds with staggered pipes, but the change of glass beads is slight. The diffusivity of coarse sands is up to 5.95 × 10−6 m2/s. In addition, low diffusivity always remains in the region above pipes. Further studies of the dimensionless diffusivities for different materials show that the granular diffusion in aligned beds could be explained by the shear–induced diffusion theory. While the diffusion mechanisms are diversified in the staggered beds. [Display omitted] • The flow fields of three granular materials in two different beds are measured. • The granular diffusivities of different materials in different beds are studied. • The order of diffusivity is in accordance with flowability in the aligned bed. • The staggered pipes greatly affect the diffusion of granules with low flowability. • The dimensionless diffusivities are further calculated and analyzed. [ABSTRACT FROM AUTHOR]

Through particle dynamics simulations and experiments, we investigate the charging kinetics of a granular bed in a vibrating cell. The numerical method is based on a theoretical model combining an equation for charge transfer at the particle scale with a theoretical model of charge relaxation. Simultaneously, experiments are carried out to calibrate and validate the numerical model using a vibrated cell with glass beads. Specific charge per unit mass induced by vibrations initially increases before leveling off. Saturation specific charge and charging characteristic time decrease with increasing bed mass. Data collapse onto a master curve is observed when normalizing specific charges and times. At the particle scale, we find that charge saturation results from the balance between charge transfer and relaxation. Saturation specific charge correlates with the relative rate of collisions between particles and the vibrating plate. We introduce a simple expression for the average ballistic time based on single-particle dynamics and a restitution coefficient dependent on bed mass. The characteristic time is proportional to the ballistic time and decreases with increasing bed mass due to more inelastic collisions between particles. [Display omitted] • We introduce a model of triboelectric charging with charge relaxation. • We calibrate and validate this model using a vibrating setup. • DEM simulations with this model are used to analyze the charging kinetics. • The charging time is proportional to the ballistic time and decreases with bed mass. [ABSTRACT FROM AUTHOR]

The mineral industry uses tremendous amounts of water every year in the processing of ores. Sustainable practices associated with the processing of ores are, therefore, of critical importance. The project described herein is the first step toward producing a dry, particle-separation process based upon control and exploitation of adhesive forces. In this research, the goal is to determine the surface energy of particles, and further, whether the solid surface energy can be used to understand the adhesion between these particles and surface-modified substrates. Glass spheres were chosen to represent silicate minerals, the most abundant type of minerals found in mineral deposits. The solid surface energy was found by using contact angle measurements and by applying the van Oss-Good-Chaudhury (VOGC) method. The VOGC method utilizes three-liquid triads to determine the Lifshitz-van der Waals, Lewis acid and Lewis base surface energy components. Surface energies from plasma-cleaned glass were between 40.2 and 60.2 mJ/m2; for the same glass with a hydrophobic chemical surface treatment, trichloro(octadecyl)silane (TCOD), the surface energy was between 20.8 and 20.9 mJ/m2; and for the glass with a hydrophilic chemical surface treatment (n1-(3-trimethoxysilylpropyl) diethylenetriamine (TMPA)) the surface energy was between 46.3 and 61.6 mJ/m2. The particle-substrate adhesion was also measured using a mechanical impact tester. Glass disks and beads were used, cleaned and surface treated with TCOD and TMPA. A custom horizontal impact tester was designed and used to measure the adhesion force between the glass spheres and a glass disk substrate. Impact of the disk/particle puck causes particle removal as tensile forces act on the particles. The tensile detachment force and adhesive force are equal at a critical particle size. Johnson-Kendall-Roberts (JKR) theory was used to determine the interfacial energy between the particles and the surface. The average interfacial energy of plasma cleaned glass, glass treated with TCOD and with TMPA were 44.8 mJ/m2, 21.6 mJ/m2, and 40.1 mJ/m2, respectively. These values are in good agreement with the literature values and with the interfacial energy determined using the VOGC method described above, demonstrating that two approaches compare favorably, despite the dramatically different methods (molecular vs mechanical) utilized. [Display omitted] • The surface energy of substrates was measured using a molecular approach. • The interfacial energy between particles and substrates was mechanically measured. • Molecular and mechanical methods to calculate surface energy compare favorably. • This data will be applied to develop a sustainable dry system to separate minerals. [ABSTRACT FROM AUTHOR]

A new component of the combined finite-discrete element method (FDEM) is employed to estimate the effects of geometrical features, friction and energy dissipation parameters on the bulk properties of rigid pellet packs. This work constitutes the first systematic validation of the Solidity FDEM code for rigid particles. The experimental and numerical axial and radial packing density profiles and orientation distributions have been compared, confirming that the numerical simulations of packing of cylindrical catalyst supports, glass beads and trilobe pellets deposited in a cylindrical container match the corresponding emergent bulk properties obtained from X-Ray CT scans. The presented results are a first confirmation of the applicability of FDEM based methods to the simulation of this class of multi-body problems. The assessment of the accuracy of the simulated topology of the pellet pack that is established in this work is encouraging for further investigations of the multi-physical engineering systems of interest for catalyst pellets involving hydro-thermo-mechanical, fracturing and fragmentation interactions using coupled FDEM formulations. Unlabelled Image • A combined finite-discrete element method (FDEM) is used in packing simulations. • The mesh, contact, friction, damping parameters influence on packs is shown. • FDEM packs of cylinders, beads, trilobes match X-Ray scans emergent properties. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach to the determination of the coalescence kernel for population balance modelling of a general class of batch fluidised bed aggregation systems, using a continuous sprayed-in liquid binder. Coalescence requires inter-particle collisions, the wetting of the contact surfaces and the dissipation of particle kinetic energy by the viscous squeezing of the binder film. These three sub-processes in principle depend both on the size of the contacting particles and on time. A new time-dependent aggregation rate constant of the coalescence kernel has been formulated by considering the general evolution of inter-particle collision behaviour with time. The model is implemented in MATLAB and its numerical output compared to two sets of experimental data: the granulation of glass beads with polyethylene glycol as a binder and the granulation of semolina with water. The evolution of mean and standard deviation in diameter versus time are examined as is the state of the size distribution at different stages in the process. The time-averaged aggregation rate for the glass beads evaluated as 7.59 × 10−9 m-0.5 s−1 while for the semolina it was 3.86 × 10−9 m-0.5 s−1. The agreement between numerical predictions and experiment is shown to be good, demonstrating the validity of the approach. Whilst conceptually simple, the model generates realistic output and provides a powerful insight into the underlying mechanisms of granulation. Unlabelled Image • A new time-dependent rate constant of the coalescence kernel has been derived from inter-particle collision behaviour. • The novel approach is applied to model batch fluidised bed granulation and requires only one adjustable parameter. • The model is integrated with an existing size-dependency methodology using a discrete PBM form. • The agreement between model (solved by MATLAB) and two experimental case-studies is good. • Output from the model reveals and helps explains underlying trends in batch FBG systems. [ABSTRACT FROM AUTHOR]

The powder flow was influenced by carrier gas in the unit operation, such as pneumatic conveying and hopper discharge, in the pressurized entrained flow gasification technology. Carrier gases play a vital role in fluidization/ defluidization of powders. In this paper, we investigate the fluidization/ defluidization of absorbent Fluid Catalytic Cracking (FCC) and non-absorbent glass bead with two different carrier gases, N 2 and CO 2. The flowability of aerated powders with different carrier gases were obtained in the fixed bed region whose superficial gas velocity was lower than minimum fluidization gas velocity and fluidization region. The powder flowability was characterized by basic flow energy, flowability rate index and aeration energy with the help of FT4 powder Rheometer. The influence of different carrier gases on fluidization/ defluidization of powder bed was further discussed. Transition line of A/C powders with different carrier gases was revealed. Effect of gas type and interparticle force were calculated, compared with the flowability of aerated powder bed. In addition, combined with bed stress analysis, different bed fluidization mechanism with different gas velocities were revealed. Our findings might help people understand the influence of carrier gases on the fluidization/ defluidization of powders in the relative chemical unit operations. Unlabelled Image • Bed stress with different carrier gases was analyzed. • Fluidization and rheology of powder bed was studied. • The mechanism of carrier gases on bed was revealed. [ABSTRACT FROM AUTHOR]

A down-flow circulating fluidized bed evaporator is designed and built to investigate the liquid–solid two-phase flow pressure drop. With POM, 20%PA66 and glass bead particles as the solid phase, the effects of the amount of added particles, circulation velocity and particle types are investigated by pressure sensors. The research results show the pressure drop of liquid–solid two-phase flow is always greater than that of single-liquid-phase flow in the downer. The maximum pressure drop ratio ranges from 16.9% to 32.0% for the selected particles. The pressure drop of the liquid–solid two-phase flow increases with the increase in circulation velocity in the down-flow bed. The pressure drop ratio fluctuates with the increase of the amount of added particles, circulation velocity and settling velocity of the particles. The difference in pressure drop ratio generally decreases with the increase in circulation velocity, and decreases or fluctuates with the increase in the amount of added particles, depending on circulation velocity. Three dimensional diagrams are established to display the variation ranges of the operating parameters for the pressure drop and pressure drop ratio in the down-flow bed. The research results can provides some reference to the application of the fluidized bed heat transfer technology in industry. Unlabelled Image • The pressure of liquid-solid two-phase flow is investigated in the down-flow bed. • The addition of the particles increases the pressure drop. • Pressure drop ratio fluctuates with the operating parameters. • Difference in pressure drop ratio decreases as circulation velocity increases. • Three dimensional diagrams of pressure drop and pressure drop ratio are established. [ABSTRACT FROM AUTHOR]

The effect of evaporation section setting on the thermal performance of a closed thermosyphon combined with the fluidized bed heat transfer technology is experimentally investigated by varying the solid holdup (10–20%) and input power (50–300 W). Pure water and glass beads are chosen as the working media in a smooth copper tube. The results show that the particle addition may enhance the heat transfer of the thermosyphons under different evaporation section settings. The maximum reduction rate of the overall thermal resistance is 23.5% with a evaporation section length of 200 mm at solid holdup of 15% and input power of 300 W. The overall thermal resistances of the two-phase and three-phase thermosyphons decrease with the increase in evaporation section length. The upward movement of the evaporation section is beneficial to the heat transfer of the two-phase closed thermosyphon, but is not conducive to that of the three-phase closed thermosyphon. Unlabelled Image • Closed thermosyphon is combined with fluidized bed heat transfer technology. • Effect of evaporation section setting on the thermal performance is examined. • Addition of glass beads may enhance heat transfer at certain conditions. • The evaporation section setting obviously influences the enhancing effect. • Three-dimensional diagrams are established to determine the optimal parameters. [ABSTRACT FROM AUTHOR]

The granular materials involved in industrial moving beds vary widely, and the corresponding flow characteristics differ. This paper compares the flow characteristics of three kinds of typical granular materials, namely, glass beads, corundum beads, and coarse sand. The repose, internal friction, and particle-wall friction angles of these materials are measured, and the flow characteristics of these materials in near 2D silos, in moving beds with aligned pipes and staggered pipes are studied by particle image velocimetry (PIV). Detailed results regarding the vertical velocity distributions, horizontal velocity distributions, local velocity field surrounding pipes, and dimensionless tangential velocity distribution around pipes of the three granular materials are revealed and compared. The mass flow index of silos, the kinetic energy correction factor in certain cross sections and average dimensionless tangential velocities around pipes are calculated to reveal the similarities and differences of flow characteristics for different granular materials in moving beds. Three kinds of typical granular materials are selected to compare their flow characteristics in a near 2D silo and moving beds with aligned and staggered pipes by PIV. In addition to horizontal and vertical velocity, the local velocity field and tangential velocity distribution around pipes are revealed and compared. Unlabelled Image • Three kinds of typical granular materials are selected to compare their flow characteristics. • The repose, internal friction, and wall friction angles of these materials are measured. • Flow characteristics of these materials in a near 2D silo are studied by PIV. • Flow characteristics in moving beds with aligned and staggered pipes are revealed. [ABSTRACT FROM AUTHOR]

A vast majority of widely accepted granular segregation mechanisms are attributed to dynamic phenomena such as percolation, kinetic sieving, convection-induced segregation, condensation, inertia and granular temperature gradients. We distinguish the ballistics of the particles from such dynamic and material properties and show that the former is a dominant mechanism in the segregation of particles sedimented in a container. We first perform granular sedimentation experiments with glass beads in water that exhibit size-segregation of bidisperse grains. We then show through simulations using a simple, first-order model that the ballistics of the particles alone is sufficient to qualitatively predict this segregation. Segregation of a bidisperse sample poured through different geometries. The segregation observed in experiments is reproduced in a simulation that considers only ballistics of the particles. Thus, isolating geometric effects shows that the confinement, pouring source and the topology of filled particle contribute to the dominant segregation mechanism. Unlabelled Image • Geometric cuases of granular segregation in water is studied in isolation. • A ballistic event driven simulation predicts the outcome of segregation experiment. • The confinement and the pouring source geometry influences segregation. • Material and dynamic properties and angle of repose are less relevant for this segregation mechanism. [ABSTRACT FROM AUTHOR]

Discrete Element Method (DEM) simulations coupled with shear cell experimental results have been used to investigate the flow behaviour of a dry particle assembly of glass beads in the quasi-static regime. Experimental studies have been undertaken using an FT4 powder shear cell apparatus, in parallel with extensive DEM simulations of both homogeneous simple shear and the FT4 shear cell itself. The findings show that it is not possible to accurately predict the bulk friction coefficient with homogeneous simple shear simulations unless both rolling and sliding friction are considered. There are, however, multiple pairs of sliding and rolling friction coefficients which can reproduce the experimental bulk friction coefficient. Sliding test experiments were conducted to yield the coefficient of sliding friction, and hence minimise the set of potentially correct pairs. Simulations of the full FT4 shear cell with two different calibration pairs, along with a pair without rolling friction, were then undertaken to understand the effect of their selection on realistic wall-bounded shearing conditions. Discrepancies were mainly found in the obtained radial contact number and velocity profiles, with increasing friction coefficients - particularly sliding friction - found to inhibit packing and particle velocity in the shear deformation zone. Comparison between homogeneous simple shear and shear cell simulation results showed a significant effect of the wall on the obtained force network, with almost a complete absence of the weakest structures which were seen supporting the strong structures in the simple shear scenario. Unlabelled Image • FT4 shear cell experiments and sliding tests were carried out. • DEM shows sliding and rolling friction coefficient pairs of correct bulk friction. • Many friction pairs exist, sliding tests allow the correct pair to be determined. • Simple shear simulations show the importance of rolling friction on flow behaviour. • Shear cell simulations showed a significant effect of wall on the force network. [ABSTRACT FROM AUTHOR]

Bubble dynamics (i.e., bubble shape, bubble size, bubble rise velocity) and bed voidage in a semi-cylindrical gas-solid fluidized bed at various superficial gas velocities and particle sizes were measured by fiber optic probe and image analysis. Measurements in the semi-cylindrical bed were compared with those in the cylindrical bed to investigate the similarity of two fluidized beds and verifying whether a semi-cylindrical bed can be used for measuring hydrodynamic properties of fluidized beds. Experiments were carried out in two Plexiglas semi-cylindrical and cylindrical fluidized beds of 14 cm in diameter at ambient pressure and temperature. Glass beads of various sizes (120, 290 and 450 μm) were used as the bed material. The superficial gas velocity was varied in the range of 0.2–0.8 m/s and both beds were operating in the bubbling fluidization regime. It was shown that increase in the particle size leads to decrease in the emulsion phase fraction while increases the fraction of bubble phase. At low gas velocity, the semi-cylindrical fluidized bed contains normal bubbles while at higher superficial gas velocity, elongated bubbles with normal rising velocity can be found. Increase in the particle size leads to increase in the aspect ratio of bubbles. It was found that the average bubble size and rise velocity increases with increasing particle size and superficial gas velocity. Results indicated that the gas-solid distribution, bubble rise velocity and bubble size in both beds are similar and geometry of the cross-section of column (semi-circular and circular) has no significant effect on these parameters. It was shown that the hydrodynamics of both beds are very similar and the difference is negligible. Since measuring the bubble size and rise velocity in the semi-cylindrical bed can be easily done by visual observation compared to those in a cylindrical bed, using a semi-cylindrical fluidized bed instead of two dimensional fluidized bed in the laboratory scale is the preferred choice which provides bubble dynamics close to that in a three-dimensional bed. Unlabelled Image • No effect of column cross-section (semi-circular and circular) on the gas-solid distribution and bubble dynamics was observed. • Increase in the particle size leads to increase in the bubble phase fraction, aspect ratio, size and rise velocity of bubble. • Semi-cylindrical fluidized bed contains spherical bubbles at low gas velocity but elongated ones appear at higher velocities • Semi-cylindrical fluidized bed is useful for hydrodynamics investigation of fluidized bed instead of two dimensional [ABSTRACT FROM AUTHOR]

An experimental study is conducted on a pilot-scale zigzag air separator (ZZS) to study the effects of varying the solid feed mass stream, the mean channel air velocity, and the number of channel segments onto the grade efficiency. Spherical glass beads are classified. A straight pipe separator model (PSM) is modified for the ZZS and fitted to the experimental data to estimate the relative cut-point settling velocity, the separation sharpness, the relative rise velocity, the diffusion coefficient, and the particle loading. The proposed model is thoroughly investigated with regard to all important parameters, e.g. the estimated particle loading is shown to be more precise than the ratio of the solid and air mass stream, used in many publications. Finally, the relative rise velocity is shown to be only a function of the particle loading, making the experimental results within the model collapse. Unlabelled Image • Experimental study and one-dimensional model for a zigzag air separator. • Varying feed mass stream, mean channel air velocity and number of channel segments. • Estimation of grade efficiency, particle loading and relative rise velocity. • Relative rise velocity is a key characteristic of the grade efficiency function. • Relative rise velocity solely depends on the particle loading. [ABSTRACT FROM AUTHOR]

In the rotary dryers with flights, the drying occurs mainly in the active region where the material comes into direct contact with the air stream. The design of these flights is a complex task and studies are necessary to gain an in-depth understanding of the particle dynamics. This work aims to investigate the effects caused by angulations in flights of two and three segments on the particle dynamics, especially in the active region. The prediction of the solids flow was investigated by simulation using a Discrete Element Method (DEM) approach in an open-source software LIGGGHTS®. The simulated results were compared with experimental data using glass beads, with the rotary drum operating with 12 flights. The active region characteristics were analyzed using the responses variables: mass of solids in active phase, percentage of active region area occupied by the particles and the dispersion of the particles in the active region. Unlabelled Image • The particle dynamic behavior in the active region was studied. • The effects of angulations in flights of two and three segments were analyzed. • Open-source LIGGGHTS® 3.8.0 solver was used in simulations. • The best angles combinations for flights with two and three segment were obtained. [ABSTRACT FROM AUTHOR]

In this paper, lignite and glass beads with different particle size were selected as experimental materials. These powder materials were discharged from hoppers in the situations of without insert (No In), with confined insert (Con In) and with unconfined insert (Ucon-In), respectively. The discharge processes were first discussed in detail and consequently, the solid flow rate of powders was obtained and analyzed. The flow zones in hoppers were divided based on the radial flow model of powder flow and the effects of inserts on the flow zone evolution were revealed. Experimental results show that both confined and unconfined inserts are beneficial to the increase of the solid flow rate, especially for the weaker flowability powders. The lignite, with the worst flowability, shows the largest increment of solid flow rate giving a value of 58% under Con In. Considering characteristics of the inserted hopper structure as well as the development of flow zones, a modified model derived from the minimum energy theory was developed. The model was able to predict the solid flow rate through both the traditional hoppers and the inserted hoppers, with the deviation below than 10%. Unlabelled Image • Special flow phenomena in insert-hopper were described. • Con-In and Ucon-In improved the solid flow rate. • Insert had a better effect on powders with weaker flowability. • A novel solid flow rate prediction method was proposed. [ABSTRACT FROM AUTHOR]

In tablet manufacturing, a lubricant is added in a tumbling mixer prior to compression to ensure that the tablet is ejected smoothly without sticking or breakage. Control and monitoring of this process is critical as process parameters can negatively affect final tablet properties. Inline monitoring methods including passive vibration measurements could be implemented to improve process efficiency. This method is non-invasive, non-destructive, and has a reduced cost compared to other monitoring techniques. Using an accelerometer affixed to the lid of a V-blender, magnesium stearate was added to glass beads and granule formulations and monitored to determine the effect of lubricant concentration, particle size, and particle size distribution on vibration measurements. Mixing end-points were identified and changes in mixing profiles were reflected in signal amplitude and variation. This research indicates that passive vibration measurements have the potential to be used as a real-time inline monitoring method for lubricant addition. Unlabelled Image • Measured vibrations from particle collisions provide information about the particle. • Lubricant forms a layer around the particles thereby altering energy dissipation upon impact. • Particle surface morphology alter the development of the lubricant layer. • The mixing end-point of lubricant dispersal can be identified through measured vibrations. • Mixing profiles were affected by particle size and size distribution, surface morphology and amount of lubricant. [ABSTRACT FROM AUTHOR]

At moderate stresses, shear cells are the preferred method of powder flow measurement. However, several industrial processes operate at low stresses, where the determination of unconfined yield strength by the shear cell technique may be inconsistent, or found not to correlate with observed behaviour. Alternatively, ball indentation can be used, which directly measures hardness; related to unconfined yield strength by the constraint factor. However, it is not known how constraint factor is influenced by particle properties. Here, ball indentation and shear cell methods are applied for glass beads of various size distributions, and the influence of particle size distribution on the constraint factor is explored. The constraint factor is shown to be independent of the pre-consolidation stress, though reduces as the d 10 , d 50 or d 90 are increased. Unconfined yield strength inferred from indentation measurements suggest that extrapolation of shear cell data to low stresses overestimates the unconfined yield strength. Unlabelled Image • Extrapolating shear cell data from high to low stress overestimates yield strength. • Ball indentation measures hardness; equal to yield strength times constraint factor. • Constraint factor is independent of applied stress. • Constraint factor decreases with increasing particle size and distribution width. • Constraint factor increases with fines content, though reduces with added coarse. [ABSTRACT FROM AUTHOR]

Experiments on continuously operated spray fluidized bed agglomeration are presented in this work. The process is conducted with glass beads and water-based binder hydroxypropylmethylcellulose (HPMC). By varying the process parameters, the results show that by the decrease of air temperature or feed rate and by the increase of binder concentration, larger particles can be achieved. Larger particle size also results in higher bed mass and more fluctuations in the process. Besides parameters variations, different internal and outlet weir configurations are used. Tracers are used in the experiments to characterize the particle residence time distribution. The separation effect can be decreased and the particle residence time can be optimized by the installation of internal weirs and lower height of outlet weir. The results show that the jets from the spray nozzles are increasing the motion and mixing of particles significantly. Unlabelled Image • Experimental investigation of continuously operated spray agglomeration in a pilot horizontal fluidized bed. • Influences of fluidization air temperature, feed rate, binder concentration and weir configurations were investigated. • Evolution of particle size and process stability were illustrated and compared. • Particle residence time distributions were measured by tracer method. [ABSTRACT FROM AUTHOR]

Surface roughness plays a critical role in flotation, as it has a marked impact on bubble-particle interaction, i.e., attachment and detachment. In the present study, the effect of surface roughness on the detachment between bubble and glass beads with different contact angles was investigated using a home-built system for measuring bubble-particle detachment. By applying a simple harmonic oscillation to a bubble-particle aggregate, the critical detachment force could be calculated from the critical amplitude based on Newton's second law. Smooth and rough glass beads were hydrophobized simultaneously using octadecyl trichlorosilane vapor to ensure that they have the same local contact angle in parallel experiments. The results show that the detachment force of a smooth particle was higher than that of a rough particle when the local contact angle with the particle surface was below 90° (hydrophilic). However, the detachment force of a rough particle was higher than that of a smooth particle when the local contact angle was above 90° (hydrophobic). Surface roughness rendered the hydrophilic bubble-particle aggregate less stable while hydrophobic bubble-particle aggregate more stable. The decrease in apparent contact angle and contact line length decreased the detachment force of the hydrophilic particles, while an increase in these parameters increased the detachment force of the hydrophobic particles. Unlabelled Image • Effect of surface roughness on detachment of glass beads was studied. • Roughness rendered the hydrophilic bubble-particle aggregate less stable. • Roughness rendered the hydrophobic bubble-particle aggregate more stable. • Roughness affects the apparent contact angle and contact line length. [ABSTRACT FROM AUTHOR]

Hoppers and silos are widely used in storing powders in various industries, such as agricultural, chemical, food and pharmaceutical industries. It is of practical importance to design hoppers and silos to ensure smooth discharge of bulk solids from these devices, and to minimise the occurrence of arching, blockage and build-up of materials around the walls. However, due to the complex nature of bulk solids, arching behaviour of bulk solids in silos and hoppers is still not well understood. In this study, a combined experimental and numerical study was performed to explore the transition from non-flow to flow of bulk solids from a flat bottom hopper. Glass beads of various sizes were considered and the minimal orifice size through which these materials can be discharged was determined experimentally using a Flodex™ tester and numerically with discrete element modelling (DEM). The dependency of the minimal orifice size on the particle size was explored. Both the experimental and numerical results showed that the minimal orifice size is a function of the particle size, which can be well described using a modified Beverloo equation. It was also interesting to find that, even for spherical particles, dead zones could be formed during the discharge from the flat bottom hopper. Moreover, mono-layered dead zones were created when large particles were used. Unlabelled Image • Monolayer dead zones were observed for hopper discharge with large particles. • The effects of orifice size and particle size on the discharge rate and the dead zone profile were investigated. • A modified Beverloo equation was proposed to predict both the discharge rate and the critical orifice size. [ABSTRACT FROM AUTHOR]

The goal of this work was to investigate the impact of pressure and the presence of fine particles (i.e., a surrogate for pulverized fuel) on the overall surface-to-bed heat transfer coefficient in relation to an oxygen-fired pressurized fluidized bed combustor. Experiments were conducted in a pilot-scale fluidized bed with an inner diameter of 0.15 m under cold flow conditions. A tube bundle consisting of five horizontal staggered rows was completely submerged in the bed. One of the tubes was replaced by a heating cartridge housed in a hollowed copper rod. Five thermocouples distributed at 45° intervals along the copper rod circumference measured the surface temperature and ensured that local effects were included. The bed material was glass beads of 1.0 mm in diameter while the fines were glass beads of 60 μm in diameter and thus susceptible to entrainment. The fine particles were continuously fed to the fluidized bed and then captured downstream by a filter system. Fluidization was conducted at 101, 600 and 1200 kPa (abs) with excess gas velocities (U g -- U mf) of 0.21, 0.29 and 0.51 m/s. Fine particle feed rates were 0, 9.5 and 14.4 kg/h. Two heating rod positions (2nd row and 4th row) were studied. Overall, the heat transfer coefficient approximately doubled when pressure was increased from 101 to 1200 kPa. At atmospheric conditions, where the slug flow regime occurred, the maximum heat transfer coefficient was at the bottom of the rod, while it moved to the side of the rod at high pressures where the bubbling regime occurred. When the heating rod was moved from the 2nd row to the 4th row, the averaged heat transfer coefficient increased by 18%, 9% and 6% at 101, 600 and 1200 kPa. The addition of fine particles decreased the average heat transfer coefficient by 10 to 20 W/m2 K, where the averaged coefficients were approximately 220 and 450 W/m2 at 101 and 1200 kPa respectively, but there was no effect on the angular heat transfer profile around the tube surface. The results showed that average heat transfer coefficients matched the correlation developed by Molerus et al. (1995) within a 5% difference across all conditions when fines were not present. • Heat transfer was studied in a pressurized fluidized bed with continuous addition of fines. • A horizontal tube bundle consist of 5 staggered rows was used with one tube replaced by a heater. • Study was carried out in relation to oxygen-fired pressurized fluid bed combustors. • Overall surface-to-bed heat transfer coefficient doubled as the pressure elevated to from 101 to 1200 kPa. • The addition of fines (up to 5 wt%) reduced the average heat transfer coefficient. [ABSTRACT FROM AUTHOR]

The wetting kinetics of powder-liquid systems represent an important factor with regards to many practical applications, such as coating, granulation, agglomeration or powder reconstitution. Wetting as the first step during food powder reconstitution strongly depends on the interactions of the wetting liquid and the particle surface, expressed by the contact angle. Due to the heterogeneous composition of food materials including hydrophilic and hydrophobic surfaces, also the wetting process heterogeneous in nature. Furthermore, the solubility of food ingredients, such as sugars, increases the complexity of understanding and describing the wettability. We investigated the liquid penetration into heterogeneous, soluble model food powders using a Washburn setup. Soluble sucrose was used as hydrophilic food component and silanized glass beads were prepared as hydrophobic, inert material. Both materials were characterized in terms of contact angle and powder properties. Different mixtures of hydrophilic, soluble sucrose and hydrophobic glass beads were produced and their wetting performance was determined. For predicting the liquid penetration into food powders, the model developed in our previous study (Kammerhofer et al., 2018a [1]) about the penetration of aqueous solutions into food powders was extended. It now considers solute concentration-dependent liquid properties and the heterogeneity of solid surfaces. The model is based on the solution of a coupled system of two differential equations representing capillary rise into a pore network and the mass transfer equation. Two main factors were identified as having a major influence on the wetting kinetics: the viscosity and the contact angle. Increasing either of these factors reduces the penetration performance, but each of them is dominant in a different concentration range. Our adapted model predicts penetration rates which are close to the experimental data. Thus, we can conclude that it is suitable for predicting the capillary penetration into heterogeneous, soluble food powders. Unlabelled Image • Viscosity increase due to dissolution has main effect on penetration performance. • Development of model predicting penetration into heterogeneous, soluble powders. • Fair agreement of experimental and modelled penetration behaviour. [ABSTRACT FROM AUTHOR]

A DEM model incorporating realistic sand shape was developed to simulate sand-clay mixture (SCM) behaviour based on CT images acquired during uniaxial compression of a SCM containing quartz sand (SCM_R) and a SCM containing glass beads (SCM_S) with in-situ X-ray micro-tomography scanning. The influences of shape, size and content of sand grains on the uniaxial behaviour of SCM were studied. SCM_R revealed a higher peak strength and elastic modulus than SCM_S with the same sand content, sand size and initial void ratio. Increasing sand content led to significantly reduced peak strength for both SCM, and remarkably increased and unnoticeably changed elastic modulus for SCM_R and SCM_S, respectively. Meanwhile, increasing sand size resulted in dramatically decreased yet insignificantly varied peak strength and elastic modulus for SCM_R and SCM_S, respectively. The different phenomenon between SCM_R and SCM_S were attributed to the significantly different sand-clay bond intensities and interface interlocking effects between them. [Display omitted] • CT image-based DEM model incorporating realistic sand shape of sand-clay mixtures. • Sand-clay mixtures (SCM) uniaxially compressed with in-situ X-ray μCT scanning. • DEM model calibration with both macro- and micro-mechanical experimental data. • Lower peak strength and elastic modulus of SCM with spherical sand grains (SCM_S). • Different effects of sand content and size between SCM with irregular sand and SCM_S [ABSTRACT FROM AUTHOR]

The presence of liquid bridges between particles in a wet granular media gives rise to capillary forces at the microscopic scale that dramatically alters the material's microstructure and macroscopic responses. Previous experimental studies show significant differences in the penetration depth of the projectile into assemblies of dry or wet particles. Still, there is a lack of fundamental understanding of the difference induced by the presence of liquid bridges in dynamic regimes. In this study, the contact model parameters of wet glass beads are calibrated employing the angle of repose tests and cylinder lifting tests, and a series of three-dimensional discrete element method simulations of spheres impact into wet granular packings are conducted. The dynamic characteristics of the projectile are obtained numerically and found to be in good agreement with the experimental data. The analyses indicate that the final penetration depth in the wet granular media is linearly related to the initial velocity and has a power function relationship with the impact energy. The generalized Poncelet law is suitable for wet granular materials, but the presence of liquid significantly affects the values of the parameters. There is a velocity "stagnation zone" at the initial stage of the wet granular impact, and the final penetration depth and the duration interaction time are smaller than that of the dry case. The difference can be attributed to the resistance evolution of the projectile exerted by particles and gives the parameter scaling law of the peak impact force. Further, a macro-micro transition technique is employed to characterize the velocity field, pressure field, and stress field inside the wet granular media and the spatial distribution is quantified based on stress theory. [Display omitted] • Micro mechanical parameters of wet glass beads were calibrated by laboratory tests. • Liquid bridge forces caused the final penetration depths less than dry case. • The peak force on the projectile is a quadratic function of the initial velocity. • Macroscopic field data for the granular media were obtained by the coarse-graining. • The mean stress and equivalent shear stress distribution around the projectile. [ABSTRACT FROM AUTHOR]

The effects of particle property on gas-solid flow in the diameter-varying riser are experimentally examined using the optical fiber probe in this research. Local flow features are obtained by signal analysis method under the operating conditions of 3–7 m/s and 8–63 kg/m2s. The results show that solid holdup distribution of glass beads is wider than that of catalyst particle particles in the wall region but is narrow in the center region. Solid holdup fluctuations tend to decrease with the increase of particle density under low-concentration conditions but increase at high-concentration conditions. The results from power spectrum density (PSD) show that the increase in particle density strengthens the periodic flow features in the enlarged section. The motion intensity decreases at the particle level but increases at the cluster level for high-density particles. Additionally, as particle density rises, the solid concentration discrepancies between the straight section and the enlarged section widen. In contrast to the upper straight section, the effects of particle density on gas-solid flow are minimal in the enlarged section. Particle property and riser configuration are significant factors for investigating complex gas-solid two-phase flow in the riser. In this work, the combined effects of the expanding riser segment and particle density on local gas-solid flow were studied be means of various analysis methods. Gas-solid flow mechanisms in the diameter-varying riser were deeply clarified. [Display omitted] • The increase in particle density strengthens the periodic flow structure. • High-density particle exhibits large sensitivity on operating condition. • Particle density has small effects on local flow in the enlarged section. • High-density particle enlarges axial solid holdup discrepancy in the riser. [ABSTRACT FROM AUTHOR]

Glass beads and fragments were selected as different shape materials to investigate bubble-particle detachment behavior under ultrasound-assisted detachment tests. The oscillation of the unloaded bubble was also observed. The results showed that the changing trend of projected area of a fixed unloaded bubble under ultrasound-assisted detachment test looked like a harmonic wave. The oscillation frequency of bubble was determined by the ultrasonic frequency while the oscillation amplitude of bubble increased with the increase of ultrasonic amplitude. The particles were pre-attached to the bubble surface forming a loaded bubble. The detachment behavior of particles from the bubble was evaluated using the changes of bubble-particle angle (BPA). When the initial BPA was nearly the same, the irregular glass fragments had lager final BPAs than that of glass beads under the same ultrasonic amplitude. The detachment of glass fragments from the fixed bubble needed larger ultrasonic amplitude than that of glass beads. Unlabelled Image • Bubble-particle angle (BPA) under various ultrasonic amplitudes was investigated. • BPA of glass particles decreased with the increase of the ultrasonic amplitude. • Glass fragments are more difficult to detach from bubble than glass beads. • Attachment force of bubble-glass fragment is larger than that of bubble-glass bead. [ABSTRACT FROM AUTHOR]

Rehydration of biopolymer powders is influenced by dissolution, viscosity development and swelling. Associated dynamic changes of powder characteristics correlate with their rehydration properties. Especially floating and particle aggregation negatively affect the rehydration process and powder quality. A deeper knowledge about these dynamics is crucial with regard to product development and quality improvement. The dynamics of swelling and viscosity development are of special importance. Controlling these parameters by a targeted modification will improve the rehydration process. Within this study the rehydration behavior of xanthan gum, guar gum and alginate was analyzed. Focus was on investigating their dynamic behavior and providing a detailed description of the rehydration process. Experiments were carried out using a model system, consisting of biopolymer coated glass beads. Rehydration was investigated experimentally and by simulation. The importance of dynamic effects and their mutual interaction was demonstrated. Results explain the mechanisms of the dynamic rehydration process of food powders. Rehydration of biopolymer powders was studied using a model system. A physical based simulation approach was established to simulate rehydration in terms of capillary liquid rise. By a parameter variation study the interrelation between dynamic changing powder characteristics was demonstrated and the mechanisms of the rehydration dynamics were explained. Unlabelled Image • Biopolymer rehydration was investigated based on a coated glass beads system. • Delay of capillary liquid rise is associated with surface-related dynamic processes. • A coating layer of 0.5 μm is enough to delay capillary liquid rise. • Viscosity development is restricted to the hydrated, swollen surface layer. • Simulation explains the relation between powder properties and rehydration. [ABSTRACT FROM AUTHOR]

Prediction of granular mass discharge-rate and velocity of particles at the outlet of hoppers and silos is critical in industry which are handling and processing granular material. This work is focused on prediction of gravity driven granular mass discharge-rate through different orifice shapes (circular, square and triangular) with same opening area at discharge of a flat-bottomed cylindrical silo using DEM-based open-source software: LIGGGHTS. The basic idea behind this work was to use three orifice shapes and compare the steady-state (mean) mass discharge-rate (Q) for spherical glass beads, and calculation of Beverloo equation constants (k & C) and their dependence on orifice shape. Velocity contours along radial direction were plotted at different bed-heights showing the velocity distribution and dependence of velocity on orifice shape for funnel flows. Unlabelled Image • Study of effect of orifice area on particle flow through a flat-bottom silo. • Comparison of particle flow through different orifice shapes with same area. • Study of particle frequency through different orifice shapes and dimensions. • Study of effect of orifice shape on particle velocities along radial direction. • Study of velocity distribution at different silo heights. [ABSTRACT FROM AUTHOR]

An experimental study was conducted in a large scale circulating fluidized bed (0.3 m diameter×15.5 m tall) equipped with nonmechanical L-valve (0.25 m diameter×1.52 m long) varying the riser superficial gas velocity (U g), bed inventory (m), L-valve aeration velocity (U Lvalve), and standpipe aeration velocity (U move). The effects of these operational parameters on pressure drop were investigated in each of the different components in the CFB and on the solid circulation rate with two different Group B particles (180 μm glass bead and 750 μm phosphorescent polyethylene beads, PPE). Tests were carried out at ambient temperature and pressure conditions using air as the fluidization gas. The operating parameters were shown to significantly affect pressure drops across various sections of the CFB due to redistribution of solids within the system. The pressure drop in the horizontal section of the L-valve was affected by aeration rates in addition to the solid flow rate reported in previous studies of smaller L-valves without aeration. A new dimensionless semi-empirical correlation was able to explain >98% of the variance between pressure drop across the horizontal section of the L-valve and operating parameters for these Group B particles. The results of present study indicated that the nonmechanical L-valve cannot be isolated from the CFB system for performance evaluation. Unlabelled Image • A statistical study was conducted on Group B materials in a large cold flow CFB • The pressure balance and circulation rate were analyzed around this CFB loop • The L-valve aeration had the greatest influence for this large L-valve • A general relationship for the pressure drop across the L-valve is proposed • The model predictions show good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Acoustic emission (AE) methods have been proposed for on-line size measurement of pneumatically conveyed particles in recent years. However, there is limited research on the fundamental mechanism of the AE-based particle sizing technique. In order to achieve more accurate measurement of particle size, the impact between particles and a waveguide should be described in a more realistic way. In this paper, an improved model based on the Stronge impact theory is presented to establish the relationship between the resulting AE signal and the particle size being measured. The improved model is validated with experiments on a single-particle test rig. A total five sets of glass beads with a mean diameter of 0.4, 0.6, 0.8, 1.0 and 1.2 mm, respectively, are used as the test particles with an impact velocity ranging from 22 m/s to 37 m/s. It is proven that the Stronge impact theory is more accurate to describe the collision process than the Hertzian impact theory and is thus more suitable for the particle size inversion, which is validated by comparing the inversion results using these two impact theories. Meanwhile, a good agreement is observed between the measured and reference particle sizes under different experimental conditions. The mean relative error between the measured and reference diameters is mostly within 12%. Unlabelled Image • An on-line particle sizing approach considering plastic deformation is presented. • Experiments were conducted on a single-particle test rig. • The particle collision process is modelled using the Stronge impact theory. • The Stronge impact theory is applied to particle size inversion. [ABSTRACT FROM AUTHOR]

A new correlation for the heat transfer of liquid–solid two-phase flow is established and validated. The numerical investigation on the heat transfer of liquid–solid two-phase flow in an up-flow multi-tube circulating fluidized bed heat exchanger is performed by hooking the new correlation to the corresponding computational domain. Operational conditions are optimized by examining the effects of the operating parameters on the heat transfer enhancing factors of the particles including SiC particles, glass bead and POM particles. The results indicate that the amount of added particles and wall temperature are more important to enhance heat transfer than inlet velocity. The enhancing factor of SiC particle is superior to those of the other particles due to great collision intensity with the wall. The enhancing factors of POM particles are significantly raised at the great amount of added particles of 3% and the high wall temperature of 360 K. [Display omitted] • A new correlation for heat transfer is established and validated. • Conduct a numerical investigation on heat transfer in circulating fluidized bed. • The effects of the operational parameters on the heat transfer are surveyed. • Enhancing factor of SiC particles is the greatest among three types of particles. • Competitive behaviors of two opposing factors determine the heat transfer. [ABSTRACT FROM AUTHOR]

Three types of slurries (two single-sized glass-bead slurries 0.44 mm and 0.125 mm in diameter and a multi-sized mixture containing the two sizes in equal fraction by mass) transported by a 54.9-mm-diameter horizontal pipe are modeled using a steady three-dimensional hydrodynamic multiphase model based on the kinetic theory of granular flow. The effect of interaction of particles with different sizes on particle kinetics—such as particle concentration distribution, velocity distribution, granular pressure distribution, wall shear stress distribution, flow regime, and their change trends—are investigated for particles of different sizes for varying efflux solid concentration and flow conditions in a multi-sized slurry by comparing it with those in single-sized slurries under the same conditions. The results reveal the different transport properties and regularly changing trend of equal-sized particles in multi-sized and single-sized slurries under the same conditions with varying solid concentrations and flow velocities. Additionally, a lubrication layer forms from fine particles near the bottom of a multi-sized slurry, which is a key factor affecting the performance of coarse particles especially at low flow velocity, and changes the coarse particles' flow regime from saltation to a sliding bed, thereby reducing the collision energy consumption and pressure drop. The solid-concentration distribution in the simulation results agrees with published experimental data. [ABSTRACT FROM AUTHOR]

The flotation process of minerals is influenced by the shape of the particle. In this paper, the glass beads and fragments are selected as different shape materials. The effect of particle shape on bubble-particle attachment behavior is investigated by the bubble-particle attachment angle tests and flotation tests. The bubble-particle attachment angle (BPA) is introduced to quantify the mass of particles. The results show that the irregular glass fragments have a lager BPA than that of glass beads. The addition of collector improves floatability of glass particles and then weakens the influence of particle shape on the BPA. The flotation results show the cumulative flotation recovery corresponds to the BPA and the addition of collector also weakens the role of the shape in the cumulative recovery. Glass fragments with shape edges can accelerate the thinning and rupture of the water film between bubble and particle and hence enlarge the BPA and flotation recovery. [ABSTRACT FROM AUTHOR]

Experimental investigation on transversal thermal bed mixing was conducted in a batch rotary drum with a diameter of 0.6 m and a length of 0.45 m. The drum was filled with two fractions of granular material with different thermal conditions and the mixing temperature in the solid bed was measured with thermocouples located at different radial positions inside the bed. The thermal mixing behavior was analyzed for various materials such as quartz sand, glass beads, expanded clay and steel spheres with different disperse system. The parameters such as particle size, bed thermal properties and particle size ratio were varied and the influence of these parameters on thermal mixing time was evaluated. Furthermore, the thermal mixing behavior was shown in terms of time constant, number of bed revolution, bed revolution time and mixing number. [ABSTRACT FROM AUTHOR]

The dynamic wetting behavior as first step in reconstitution of heterogeneous model food powders was investigated in the present work. Therefore, we studied the capillary rise of water into single pores and pore systems containing hydrophilic and hydrophobic walls. A two-wall setup was developed to realize the capillary rise in a single gap containing walls with two different contact angles but a constant pore size. The equilibrium penetration height was measured and compared to calculated heights using advancing contact angles inserted in a model equation. Wetting experiments in a Washburn setup were performed with respect to the investigation of water penetration into a heterogeneous pore network which leads to a variable pore size during the rise. In order to determine the effect of contact angle, three different glass materials at varied levels of hydrophobicity were prepared. Furthermore, a focus was put on understanding the impact of the pore network on the wetting kinetics by mixing two size fractions of glass beads. The equilibrium heights determined in heterogeneous single gaps fit well with the calculated heights by inserting advancing contact angles into the model equation. The results of the powder systems show a significant impact on the wetting with an increasing hydrophobic fraction, while an increased hydrophobic contact angle further increased the wetting time only at higher quantities of the hydrophobic component in the sample. Furthermore, our findings emphasize the complexity of wetting into a system with heterogeneity in pore size and contact angle. [ABSTRACT FROM AUTHOR]

The use of inserts in the hopper provides a reliable way to improve the quality of powder flow. In this work, glass beads, fluidized catalytic cracking catalyst (FCC), lignite and polyvinyl chloride (PVC) were used as experimental materials and the flow properties of powders were characterized by the FT4 powder rheometer and the PT-X powder tester. Discharge experiments on a Perspex hopper at a laboratory scale are presented in this paper, comparing the flow characteristics of fine powders discharged from a plain hopper and from hoppers modified with the use of inserts of different geometries. Effects of insert and powder properties on powder flow rate are discussed. A mechanism model is developed to describe the hindering effect to the discharge consequent to the powder expansion at the hopper outlet. Mechanisms of insert on powder flow are analyzed. It is demonstrated that the higher flow rates of the hopper operating with a solid insert are due to the anticipated expansion of the material generated by the presence of the insert. The hopper with a hollow insert shows a flow sequence and the values for the powder flow rates are averaged values between two regimes. Based on understanding above mechanisms, powder flow rates for plain hopper and hoppers modified with insert are successfully predicted. [Display omitted] • Powder flow rates from hoppers with different inserts were examined. • Flow promotion by inserts in powder discharge from the hopper was determined. • Mechanism of the use of inserts in powder discharge from the hopper was revealed. • Regimes of discharge with different inserts were discussed. [ABSTRACT FROM AUTHOR]

The water retention curve (WRC) is a key material function to define the unsaturated behaviour of natural and artificial particulate media. In many circumstances, it is necessary to have the estimate of the WRC in the early stage of a project or a research activity. This paper presents an empirical method to predict the moisture characteristics of artificial porous media, glass beads with diameters between 0.5 mm and 3 mm, on the base of the particle size distribution. The proposed method allows to estimate the parameters of the van Genuchten equation, a frequently used model. Homogeneous spheres, binary mixtures and ternary mixtures are analyzed and several experiments have been performed on a Tempe cell, modified to work in the desired suction range during the drying process. The proposed equations have been fitted to experimental data with a fairly good agreement, in particular for homogeneous spheres. The uncertainty analysis is performed and some limitations of the model are discussed. [ABSTRACT FROM AUTHOR]

The size of particle is a relevant parameter in the study of the granular material behaviour. For wet granular materials, it affects the capillary force and the number of liquid bridges. We present quantitative and qualitative investigations of the effect of the particle size on the steady-state shear behaviour of partially wet granular material. Two sizes of glass beads have been used: 12–40 μm and 70–110 μm in diameter and the shear behaviour was studied using an annular shear cell. The results show different regimes of the shear-normal stresses relationship depending on the particle size, with a general increase of the magnitude of the shear stress for a decrease in the particle size. Most studies of wet granular material behaviour have focused on the pendular state of saturation with liquid bridge formed between particles. In this study, the states of saturation are explored going up to completely filling the space between beads of 70–110 μm. Different regimes are identified depending on the liquid fraction and the applied normal stress. A theoretical approach was used to estimate the tensile strength for the different states of saturation. An agreement between both experimental and theoretical data was observed and discussed. [ABSTRACT FROM AUTHOR]