Wet Particles Research Articles

Numerical Study on Effect of Aggregate Moisture on Mixing Process.

During the concrete mixing process, the transition of aggregates from a dry to a moist state introduces a crucial dynamic that significantly influences particle interaction, consequently impacting mixing homogeneity. In this paper, based on the discrete element method, the effect of aggregate moisture on the mixing process of sand and stone was investigated. The interaction between dry particles was described by the Hertz-Mindlin model, while the interaction between wet particles was calculated by the linear cohesion model considering the liquid bridge force. Additionally, a functional relationship between the moisture content and the parameters of the linear cohesive contact model was established. The results show that the numerical method can be employed to simulate the mixing process. Notably, when the moisture content of pebbles ranges from 0% to 0.75% and that of sand ranges from 0% to 10.9%, the linear cohesion model is deemed suitable. The standard deviation of the mixing homogeneity of wet particles is lower than that of dry particles for short mixing time, indicating that a small amount of liquid enhances mixing homogeneity. However, moisture has no obvious effect on mixing homogeneity for a long mixing time. This nuanced understanding of the interplay between moisture, particle interactions, and mixing duration contributes valuable insights to optimize concrete mixing processes.

Mechanistic Analysis of Temperature-Dependent Curcumin Release from Poly(lactic-co-glycolic acid)/Poly(lactic acid) Polymer Nanoparticles.

In this study, we investigated the mechanism of curcumin (CUR) release from poly(lactic-co-glycolic acid) (PLGA) and poly(lactic acid) (PLA) nanoparticles (NPs) by evaluating the temperature-dependent CUR release. NPs were prepared by the nanoprecipitation method using various PLGA/PLA polymers with different lactic:glycolic ratios (L:G ratios) and molecular weights. Increasing the polymer molecular weight resulted in a decrease in the particle size of NPs. The wet glass transition temperature (Tg) of PLGA/PLA NPs was lower than the intrinsic polymer Tg, which can be derived from the water absorption and nanosizing of the polymer. The reduction in Tg was more significant for the PLGA/PLA NPs with lower polymer L:G ratios and lower polymer molecular weight. The greater decrease of Tg in the lower polymer L:G ratios was possibly caused by the higher water absorption due to the more hydrophilic nature of the glycolic acid segment than that of the lactic acid segment. The efficient water absorption in PLGA/PLA NPs with lower molecular weight could cause a significant reduction of Tg as it has lower hydrophobicity. CUR release tests from the PLGA/PLA NPs exhibited enhanced CUR release with increasing temperatures, irrespective of polymer species. By fitting the CUR release profiles into mathematical models, the CUR release process was well described by an initial burst release followed by a diffusion-controlled release. The wet Tg and particle size of the PLGA/PLA NPs affected the amount and temperature dependence of the initial burst release of CUR. Above the wet Tg of NPs, the initial burst release of CUR increased sharply. Smaller particle sizes of PLGA/PLA NPs led to a higher fraction of initial CUR burst release, which was more pronounced above the wet Tg of NPs. The wet Tg and particle sizes of the PLGA/PLA NPs also influenced the diffusion-controlled CUR release. The diffusion rate of CUR in the NPs increased as the wet Tg values of the NPs decreased. The diffusion path length of CUR was affected by the particle size, with larger particle size resulting in a prolonged diffusion-controlled release of CUR. This study highlighted that for the formulation development of PLGA/PLA NPs, suitable PLGA/PLA polymers should be selected considering the physicochemical properties of PLGA/PLA NPs and their correlation with the release behavior of encapsulated drugs at the application temperature.

Numerical Prediction of Hydrodynamic Characteristics of Wet Particles and Power-Law Fluids in a Fluidized Bed Using the Dynamic Restitution Coefficient

Numerical Prediction of Hydrodynamic Characteristics of Wet Particles and Power-Law Fluids in a Fluidized Bed Using the Dynamic Restitution Coefficient

Energy and exergy analysis of drying of potash particles in a pulsation-assisted fluidized bed

Potash particles exhibit cohesiveness and hygroscopic behavior in the presence of moisture. During the drying of wet potash particles, solid bridges form, and the agglomeration behavior of such particles reduces the efficiency of drying. In this work, pulsed airflow was employed to break agglomeration and eliminate channeling in a fluidized bed with wet potash particles. The effect of different operating conditions including inlet drying gas temperature (40 °C, 50 °C, and 60 °C) and pulsation frequency (1.0 Hz and 2.0 Hz) on the energy and exergy efficiency of fluidized bed drying of potash particles was investigated. A drying model based on the thin-layer theory was employed to correlate the experimental data of drying of potash particles. The results showed that the highest energy and exergy efficiency of potash drying, 28.6% and 27.8%, respectively, was achieved when the fluidized drying of potash particles was operated at lower temperatures and close to the natural frequency of the fluidized bed system.

CFD-DEM simulation of cyclone self-rotation drying: Particle high-speed self-rotation and heat transfer

Cyclone self-rotation drying (CSRD) has been demonstrated to have the outstanding advantage of low energy consumption in drying field due to the ability of non-phase change separation of liquid in wet particles. Particle high-speed self-rotation are key factors that affect the energy consumption and efficiency of CSRD, but their laws and regulation methods are still unclear. In this study, under the framework of Eulerian-Lagrangian method, Eulerian model and Reynolds Stress Model (RSM) were adopted, and computational fluid dynamics (CFD) and discrete element method (DEM) coupled simulation was established to systematically investigate the effects of operating parameters on sludge particle self-rotation and heat transfer in a 200-mm-diameter CSRD device. The particle self-rotation and revolution speeds were found to decrease with increasing particle size and feeding rate. An average self-rotation speed of 5217.8 rad/s was observed for 1 mm particles at a gas velocity of 10 m/s and a feeding rate of 50 kg/h, when the gas velocity increased to 20 m/s, the self-rotation speed increased about 888.4 rad/s. These operating parameters were also found to affect particle residence time and temperature, smaller particles have better heat transfer performance. This study provides theoretical support for application and optimization of CSRD devices.

ВЛИЯНИЕ УЛЬТРАЗВУКА НА ИЗМЕНЕНИЕ ОБЪЕМНОЙ ДОЛИ ЖИДКОСТИ В ПЕНЕ И ЕЕ УСТОЙЧИВОСТЬ

The wave method of acting on matter has long been an area of intense scientific and technological research. Ultrasonic dispersion allows to obtain various highly dispersed, homogeneous and chemically pure suspensions of solid particles in liquids; accelerates and improves the process of obtaining emulsions; ultrasonic waves of different frequencies create conditions for obtaining the structure of the material, which is characterized by isotropy of certain properties. However, the mechanism of action on dispersed systems, namely Pickering systems, is not well understood today. In this work, a study of the variation of liquid volume fraction and stability of bulk foam and its monolayers has been carried out to determine the features and nature of the failure of this dispersed system under wave action. The dependence of foam multiplicity and stability on the concentration and nature of solid particle-stabilizers (titanium oxide, clay, Aerosil-380), as well as on the content and structure of surfactant modifiers (anionic surfactant sodium decyl sulfate, cationic surfactants hexylamine and cetyltrimethylammonium bromide) is shown. The increase in the concentration of solid particles led to an increase in the resistance of foams to ultrasonic actions. The study of changes in the multiplicity and stability of foams at changing the concentration of water repellent showed that the maximum resistance to ultrasonic impacts was observed not at the maximum concentration of surfactant, but at the concentration corresponding to the maximum contact angle of wetting of particles (540). The use of long-chain surfactant cetyltrimethylammonium bromide increased the stability of the foam layer to ultrasonic action at a lower (compared to hexylamine) degree of modification of the surface of solid particles.

Numerical Simulation of Wet Particles Motion in a Vertical Powder Dryer

Numerical Simulation of Wet Particles Motion in a Vertical Powder Dryer

Microrheology of gemini surfactants at interfaces and in solutions in the dilute and semidilute regimes.

Gemini surfactants are ideal systems to study a wide range of rheological behaviours in soft matter, showing fascinating analogies with living polymers and polyelectrolytes. By only changing the concentration, the shear viscosity can vary by 7 orders of magnitude in the bulk when transitioning through the semidilute regime. In order to elucidate on the intrinsic shear viscosity profile at the interface in soft matter systems manifesting various concentration regimes and morphological transitions, we performed microrheology and adsorption experiments under a wide range of experimental conditions. The surface shear viscosity has been characterized by passive microrheology, tracking Brownian particles trapped at the air-solution interface, under particle wetting conditions precisely characterized by interferometry. We observe that a steep increase in bulk shear viscosity as a function of the concentration does not translate at the interface, which may show a negative surface shear viscosity. By comparing macrorheology and microrheology, we measure significant differences both at the interface and in the bulk in the semidilute regime, where wormlike micelles start to entangle. The disparity in rheological measurements can be attributed to notable depletion effects near both the air-solution and particle-solution interfaces.

Numerical simulation of collision dynamics between a dry particle and a liquid-coated wet particle

A comprehensive understanding of wet particle collisions in the presence of a liquid film is essential for industrial processes. In this study, we conduct a numerical investigation into the dynamics of both normal and oblique collisions between a dry particle and a liquid-coated wet particle. In normal collisions, the gas flow velocity near the stretching liquid bridge increases significantly, while oblique collisions exhibit no such increase. The wetting area of particles reaches its maximum when solid particles come into contact, at which point the viscous and capillary forces acting on the particles also reach their peaks. The capillary force causes kinetic energy dissipation to be one magnitude greater than viscous energy dissipation. The normal wet restitution coefficient rises with the logarithm of the modified Stokes number, reflecting energy dissipation effects. As the collision angle increases, the normal wet restitution coefficient gradually increases and surpasses the tangential wet restitution coefficient.

The force and dynamic response of low-velocity projectile impact into 3D dense wet granular media

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.

Study on the mechanism of surfactant droplet wetting and coagulation of respiratory dust: The case of AEO-9

In industrial production, spraying is the most widely used dust control method. However, the traditional pure water spray has poor dust removal effect, and the principles of droplet wetting and dust encapsulation are unclear, resulting in poor dust removal effect. In this study, based on the CLSVOF method, we investigated the dynamic wetting and coalescence process of surfactant droplets and dust particles from a microscopic perspective. By changing the size ratio between the droplets and dust particles, as well as the initial velocity of the droplets, we simulated the spreading and wetting of surfactant droplets on the dust surface and found the optimal parameter range for encapsulating respirable dust. Through the experimental determination of spray atomization characteristics, it was found that the spray pressure of 6 MPa and the use of a 1.2 mm fine atomization nozzle produced a spray field with droplet sizes ranging from 14 to 21 μm, accounting for approximately 62.4 % of the distribution. Around 60 % of the droplets had velocities between 20 and 30 m/s. Dust settling efficiency experiments were conducted under these optimal spray parameters, and the settling efficiency of respirable dust reached 84.33 % within the favorable parameter range. Numerical simulations of the dynamic wetting process of dust-fog coupling at the microscopic level, as well as macroscopic spray experiments, were carried out to validate the reliable results. This method has significant implications for the control of respirable dust.

Mixing Behaviors of Dry and Wet Particles in a Pulsating Fluidized Bed

Mixing Behaviors of Dry and Wet Particles in a Pulsating Fluidized Bed

Wettability, flowability and core bending strength of wet silica sand particles based on the interfacial properties of liquid silicate binders

The flowability of wet silica sand particles containing liquid binders, which are among the new moulding materials for green casting, must be further improved. Herein, we conducted an in-depth study on the interface characteristics of silicate binders with the addition of anionic surfactants. Through particle flow experiments and sand core bending fracture experiments, the influence of anionic surfactants on the flow characteristics of wet sand particles and the mechanical properties of silicate-bonded sand was explored. The experimental results showed that the addition of 0.10 wt% of an anionic surfactant significantly reduced the surface tension and contact angle of solutions, from 78.99 to 28.53 mN/m, and from 49.9° to 34.4°. Moreover, compared with unmodified wet particles, the flowability of wet particles modified with 0.10 wt% of the anionic surfactant was improved to some extent. However, the flexural strength of silicate-bonded sand was also reduced to a certain extent.

Pickering emulsions stabilized by chitosan-flaxseed gum-hyaluronic acid nanoparticles for controlled topical release of ferulic acid

Chitosan (CS) based nanoparticles (NPs) were fabricated via an ionic gelation reaction modified by flaxseed gum (FG) or sodium tripolyphosphate (STPP). The average particle size, morphology, interfacial tension, and wettability of NPs were characterized. The particle size of CS-STPP-HA (hyaluronic acid)-FA (ferulic acid) NPs and CS-FG-HA-FA NPs was 400.8 nm and 262.4 nm, respectively under the optimized conditions of CS/STPP = 5:1 (w/w) or CS/FG = 1:1 (v/v) with HA concentration of 0.25 mg/mL and FA dosage of 25 μM. FG acted as a good alternative for STPP to form particles with CS in stabilizing Pickering emulsion with an internal diacylglycerol (DAG) phase of 50–80 % (v/v). The complex nanoparticles had high surface activity and contact angle close to 90 °C, being able to tightly packed at the droplet surface. The emulsions had high thermal, ionic and oxidative stability. With the aid of moisturizing polysaccharides and DAG oil, the emulsions had a good sustained-release ability for FA with deeper penetration and retention into the dermis of the skin. Thus, FG and HA-based NPs serve as green vehicles for the fabrication of novel Pickering emulsions and possess great potential to be applied as a delivery system for lipophilic active agents in functional food and cosmetic products.

Surfactant-Mediated Effects on Hydrological and Physical Soil Properties: Data Synthesis.

Soils are under the threat of a multitude of anthropogenic factors affecting the complex interplay of various physical and hydrological soil processes and properties. One such factor is the group of surface-active compounds. Surfactants have a broad range of applications and can reduce solid-liquid interfacial forces and increase wettability and dispersion of particles. Surfactant effects are context-dependent, giving rise to a wide range of reported effects on different soil processes and properties. Here, we evaluate the evidence base of surfactant research on 11 hydrological and physical soil variables. Our goal was to identify knowledge gaps and test the robustness of the proposed surfactant effects. We found that the current knowledge base is insufficient to reach strong data-backed conclusions about the effects of surfactants in soils. We identified a unique case of bias in the data as a result of conflated patterns from laboratory and field studies. We could not support the hypothesis that the surfactant charge determines soil effects for any of the tested soil variables. We believe that further experiments on surfactant-mediated effects on soil properties and processes are urgently required, paying attention, in particular, to improving experimental design and data reporting standards.

Tunable rheological properties of high internal phase emulsions stabilized by phosphorylated walnut protein/pectin complexes: The effects of pH conditions, mass ratios, and concentrations

The current study reported high internal phase emulsions (HIPEs) stabilized by phosphorylated walnut protein/pectin complexes (PWPI/Pec) and elucidated how their rheological properties were modulated by pH conditions, mass ratios, and concentrations of the complexes. At pH 3.0, the HIPEs stabilized by PWPI/Pec exhibited smaller oil droplet sizes, as well as higher storage modulus (G') and flow stress, in comparison to those stabilized by the complexes formed at pH 4.0–6.0. These observations can be directly linked to pH-dependent changes in particle size, surface hydrophobicity, and wettability of the PWPI/Pec complexes. Rheological analysis revealed that all generated HIPEs displayed weak strain overshoot behavior, irrespective of pH conditions. Notably, HIPEs stabilized by PWPI/Pec at mass ratios of 2:1 and 4:1 showed enlarged oil droplet sizes, lower G' and flow stress but higher flow strain with unaffected loss factor compared to those stabilized by PWPI/Pec 1:1. However, reducing the concentration of PWPI/Pec led to a simultaneous decrease in G', flow stress, and flow strain, along with a significant increase in the loss factor of the HIPEs. Furthermore, the HIPEs formed with 1% PWPI/Pec 1:1 at pH 3.0 demonstrated excellent stability against heat treatment and long-term storage. These results provide valuable insights into the modulation of rheological characteristics of HIPEs and offer guidance for the application of walnut protein-based stabilizers in HIPE systems.

Importance of liquid bridge forces in dynamics of rock-ice avalanches: insights from discrete element simulations

Rock-ice avalanches imminently threaten high-mountain and glacierized regions. The wet rock-ice particle flow exhibits dependence on pendular liquid bridges; however, its mechanisms are unclear. This paper focuses on the influence of interstitial water in the pendular regime on the dynamics of rock-ice avalanches. A scheme was proposed to incorporate capillary and viscous liquid bridge forces into the discrete element method (DEM) for simulating the wet rock-ice particle flow. Numerical results indicate that the proposed scheme could well reproduce the key experimental outcomes of small flume tests. The liquid bridges could reduce the mixture mobility remarkably via pseudo-cohesion, which was mainly attributed to the capillary force. The pseudo-cohesion effect could alter the collision-dominant flow regime to the shear-dominant regime through buffering collisions and suppress the segregation through impeding the downward penetration of gravels. A very small amount of water, too little to form liquid bridges, could lubricate the sliding surface, and increase the mixture mobility. The role of the critical inter-element separation distance was deterministic in DEM for wet particles. This paper demonstrated the crucial impact of the liquid bridges in the dynamics of rock-ice avalanches and offered a promising scheme for deeply understanding the solid–liquid interactions in wet rock-ice avalanches.

Improved physical and structural properties of high-protein powders by fluidized-bed agglomeration.

High-protein powders (milk protein isolate (MPI) and soybean protein isolate (SPI)) were treated with maltodextrin solution (10% or 20%) or water as a binder and then subjected to fluidized-bed agglomeration. The MPI agglomerates were compared with the SPI agglomerates as a function of maltodextrin (MD) concentration. The particle size, wettability, and porosity values of SPI agglomerates were much higher than those of the raw powder when compared to the MPI agglomerates. The agglomerated protein powders with MD binder showed significantly higher solubility values than the raw powders. These tendencies were discernible in the morphological examination via SEM analysis. The dynamic modulus values of SPI agglomerates decreased with an increase in MD concentration from 10 to 20% whereas those of MPI agglomerates increased. These findings indicate that the physical, structural, and rheological properties of agglomerated high-protein powders are greatly influenced by the type of protein and the addition of MD binder.

Modeling of multiphase heat and mass transport and drying behavior of potash particles in a packed bed: Experiments and simulation

The drying behavior of potash particles was experimentally investigated in a convective packed bed dryer under different operating conditions, including inlet gas temperature of 40 °C, 50 °C, and 60 °C, moisture content of 2.8 wt%, and superficial gas velocity of 0.3 m/s. When the temperature increased from 40 °C to 50 °C and then to 60 °C, the drying time decreased from 930 s to 870 s and then to 720 s, respectively. The thermal conductivity and specific heat capacity of potash particles as a function of moisture content and porosity of the packed bed was determined at a 95 % confidence interval to have R2 values of 0.94 and 0.91, respectively. During drying of potash particles, solid bridges form, and the whole bed behaves like a porous medium with void spaces that expand. In this work, a conjugate heat and mass transfer model was developed for batch packed bed drying of wet potash particles. Computational fluid dynamics was used to simulate the momentum, mass, and energy transport in a porous medium based on the physical properties of potash particles. The model successfully correlated the experimental particle moisture content versus time with average absolute deviation percentage values of 14.8, 3.2, and 14.7 for the inlet gas temperatures of 40 °C, 50 °C, and 60 °C, respectively.

Solubility and Bioavailability Enhancement of a Novel Liquisolid Compact of Gliclazide

The study investigates the use of liquisolid compacts, a revolutionary pharmaceutical formulation technique, to improve the dissolution rate of weakly water-soluble medicines, with gliclazide as a case study. Nonvolatile solvents such as polyethylene glycol (PEG) 400, tween 80, and propylene glycol were used to make liquidsolid tablets, together with carrier ingredients such as Avicel PH102, starch, or HPMC, and Aerosil 200 as a coating material. The drug-excipient interaction was studied utilizing techniques such as differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The produced tablets were tested for appearance, weight fluctuation, hardness, friability, drug content, and in-vitro drug release before being compared to traditional tablets (control) to determine the improvement in dissolution rate. The optimum formulation was subjected to stability tests. FTIR and DSC investigations revealed no significant drug-excipient interactions. All pill formulations met the requirements. Liquisolid tablets significantly increased gliclazide dissolving when compared to conventional tablets, which was ascribed to improved wetting qualities and particle effective surface area. According to the study, the liquisolid technique is a potential approach for increasing the dissolving rate of poorly soluble pharmaceuticals. The tablets remained stable at accelerated settings for three months, demonstrating the efficacy and feasibility of the liquisolid approach in increasing gliclazide dissolving rates.