Cylindrical Particles Research Articles

Effect of particle characteristics, kinetics and transport phenomena on the prediction of particle mass loss and products yields during biomass fast pyrolysis

A low computational cost model for the pyrolysis of biomass anisotropic particles was used to study the effect of thermal conductivity of the particle, CRECK kinetic scheme implementation, intraparticle secondary reactions, heats of reaction, and advection on particle conversion prediction. The model considers a shrinking anisotropic cylindrical particle with biomass pseudo-components, the appearance of liquid intermediates, intra-particle mass and heat transport and secondary reactions of volatiles. The model was validated against oak and birchwood single particle experiments. More accurate predictions for mass loss evolution are found when considering the change of the particle thermal conductivity anisotropy with conversion and the temperature dependency of the thermal conductivities of the biomass and the gas phase, compared to ignoring these phenomena. The CRECK biomass pyrolysis reaction scheme provides insights into the effect of biomass composition on the evolution of the liquid intermediate phase allowing future studies about the presence of heavy compounds in the bio-oil and other phenomena such as aerosol ejection. Secondary intraparticle vapor phase reactions showed a negligible effect in volatiles conversion while heterogeneous reactions slightly overestimate its conversion. Heats of reaction and product advection are important for accurate prediction of particle mass loss.

Transient Electrophoresis of a Cylindrical Colloidal Particle

We develop the theory of transient electrophoresis of a weakly charged, infinitely long cylindrical colloidal particle under an application of a transverse or tangential step electric field. Transient electrophoretic mobility approaches steady electrophoretic mobility with time. We derive closed-form expressions for the transient electrophoretic mobility of a cylinder without involving numerical inverse Laplace transformations and the corresponding time-dependent transient Henry functions. The transient electrophoretic mobility of an arbitrarily oriented cylinder is also derived. It is shown that in contrast to the case of steady electrophoresis, the transient Henry function of an arbitrarily oriented cylinder at a finite time is significantly smaller than that of a sphere with the same radius and mass density as the cylinder so that a cylinder requires a much longer time to reach its steady mobility than the corresponding sphere.

Assessment of the Physical Properties of an Experimental Adhesive Dentin Bonding Agent with Carbon Nanoparticles

The present study was aimed at reinforcing the control adhesive (CA) with two concentrations (2.5% & 5%) of carbon nanoparticles (CNPs) and evaluating the impact of these additions on the adhesive’s properties. Scanning electron microscopy (SEM) and energy dispersive X-Ray (EDX) spectroscopy were utilized to examine the morphological characteristics and elemental mapping of the filler CNPs. To investigate the adhesive’s properties, rheological assessment, shear bond strength (SBS) testing, analysis of the adhesive–dentin interface, degree of conversion (DC) analysis, and failure mode investigations were carried out. The SEM micrographs of CNPs verified roughly hexagonal-shaped cylindrical particles. The EDX plotting established the presence of carbon (C), oxygen (O), and zirconia (Zr). Upon rheological assessment, a gradual reduction in the viscosity was observed for all the adhesives at higher angular frequencies. The SBS testing revealed the highest values for 2.5% CNP adhesive group (25.15 ± 3.08 MPa) followed by 5% CNP adhesive group (24.25 ± 3.05 MPa). Adhesive type interfacial failures were most commonly found in this study. The 5% CNP containing adhesive revealed thicker resin tags and a uniform hybrid layer without any gaps (compared with 2.5% CNP adhesive and CA). The reinforcement of the CA with 2.5% and 5% CNPs augmented the adhesive’s bond strength. Nevertheless, a diminished viscosity (at higher angular frequencies) and reduced DC were observed for the two CNP reinforced adhesives. CNP reinforced dentin adhesives are effective in enhancing the adhesive bond integrity of resin to dentin.

Statistical numerical investigation of translational-rotational ultrafast image-based dynamic light scattering to measure a bimodal Gaussian sample of cylindrical nanoparticles

In a translational-rotational ultrafast image-based dynamic light scattering (TR-UIDLS) experiment, nanoparticles in Brownian motion in a solvent are illuminated by a focused Gaussian beam and scatter the light toward a camera. If both vertical-vertical and vertical-horizontal polarization geometries are recorded at the same time, using a polarization camera, a distribution of “equivalent cylindrical particles” is determined from the cross-correlation coefficients between the pairs of pictures recorded by the camera in both polarization geometries. The equivalent cylindrical particles are the monodisperse cylindrical particles that scatter the same light fluctuations as the polydisperse particles in the measurement volume. The distribution of equivalent cylindrical particles is not strictly the distribution of the particles in the sample, and our purpose is to measure characteristic information about the size and shape of the particles in the sample from the distribution of the equivalent cylindrical particles. With this purpose, we propose in the present paper a model of numerical simulation of the TR-UIDLS experiment for polydisperse arbitrary distributions of cylindrical particles. The TR-UIDLS has been simulated for the bimodal Gaussian distribution of gold cylindrical nanorods immersed in water. In view of these simulations, a strategy is discussed to retrieve characteristic information about the bimodal Gaussian distribution of cylindrical particles.

Research on a New Drag Force Model for Cylindrical Particles in Fixed Bed Reactors

Fixed bed reactors play an important role in converting solid wastes to high-quality products. The solid wastes, as well as the corresponding catalysts, are often made into cylindrical particles. However, research on the drag force for cylindrical particles is still rarely reported. In this work, the fixed bed porosity was firstly predicted with the unresolved CFD-DEM method and validated against experimental data. Then, the Ergun model, Di Felice model, and Ganser model were evaluated against the reported pressure drop data for both the spherical and cylindrical particles, so that a more solid drag force theory could be selected as a candidate for cylindrical particles. Finally, a new Ganser model was proposed for cylindrical particle drag force prediction based on the reported experimental results and validated by other experimental data. It was found that, for the spherical particle bed, the relative prediction errors of the Di Felice model are approximately 10%, while those of the Ergun model are approximately 15%. For the cylindrical particle bed, the relative prediction errors of the Ganser model are approximately 10%, while those of the Di Felice model are much higher than 10%. With the new Ganser model proposed in this work, the maximum error between the predicted pressure drop and the experimental data can be lowered to approximately 5%. The research is of reference value for drag force model selection when simulating similar FBRs with cylindrical particles.

Modeling of slurry-type photocatalytic reactors containing core-shell particles for predicting transient behaviours based on Langmuir-Hinshelwood kinetics

Governing equations were derived for photocatalytic batch reactors and CSTR (Continuously Stirred Tank Reactor) containing photocatalytic pellets to obtain numerical solutions of the concentration in bulk medium and intra-particle concentration based on Langmuir-Hinshelwood kinetics. Numerical solutions could be obtained by finite element method under proper initial and boundary conditions to solve coupled reaction-diffusion equations using partial and ordinary differential equations. Effects of Thiele modulus, Biot number, Langmuir—Hinshelwood parameter and photocatalyst loading were investigated by predicting the performance of batch reactor. Effects of residence time and initial reactant concentration were studied for CSTR. In addition to conventional morphologies of pellets such as sphere, cylinder and slab, mathematical modeling of core-shell particles was also conducted to study the effect of thickness of inert core. Although the performance of spherical pellets was the best, cylindrical pellets also showed good activity for removing reactant by photocatalytic decomposition. In core-shell spherical pellets, there was little effect of thickness of inert core on the reduction rate of reactant concentration and steady-state concentration in batch and CSTR, respectively, compared to core-shell cylindrical and slab-type particles. The cascade connection of photocatalytic CSTRs and fixed bed reactors with back mixing could be also analysed by finite element method. Experimental data about the removal of methylene blue using silica-titania core-shell particles in batch photocatalytic reactor were compared with numerical solutions to estimate reaction parameters.

Diffusiophoresis of a cylindrical colloidal particle oriented parallel to an electrolyte concentration gradient field.

We derive the general expression for the diffusiophoretic mobility of a cylindrical particle oriented parallel to an applied electrolyte concentration gradient field in a symmetrical electrolyte solution. From the general mobility expression as combined with an approximate analytic expression with negligible error for the electric potential distribution around a cylinder, an accurate analytic mobility expression is obtained, which is applicable for arbitrary values of the particle zeta potential and the electrical double layer thickness. It is also found that the low zeta potential approximation is an excellent approximation for low-to-moderate values of the particle zeta potential.

Numerical modeling for particulate flow through realistic microporous structure of microfiltration membrane: Direct numerical simulation coordinated with focused ion beam scanning electron microscopy

In this study, the focused ion beam scanning electron microscope (FIB-SEM) technique is utilized to obtain a realistic microstructure geometry of mullite and α-alumina membranes, which are commercially available microfiltration (MF) membranes, for implementation in a high-resolution numerical simulation model based on coupled direct numerical simulation (DNS) and the discrete element method (DEM). The flow and particle permeation through the membrane pores are evaluated for different particle sizes. The developed simulation model is a powerful tool for enhancing our understanding of the MF process because it introduces the realistic microporous structure of an actual MF membrane rather than the simplified membrane model structures such as straight cylindrical pores and particle packing structures that have been used in previous numerical studies. The application of the developed model is discussed for the prediction of the rejection curve, which shows the importance of considering a realistic microporous structure for the accurate prediction of the MF process. The results showed different rejection curves for the mullite and α-alumina membranes, which mainly contributed to the difference in the local pore size distributions of the two membranes. Furthermore, detailed particle permeation through the membrane is evaluated, which is not feasible in experimental analyses for realistic MF membranes. • Realistic microfiltration geometry was obtained using FIB-SEM technique. • High resolution DNS-DEM was developed for detailed particle permeation analysis. • Different rejection curve for mullite and α-alumina membranes was obtained. • Membrane microstructure affected the particle permeation behavior and rejection. • Image analysis of microstructure supported the DNS-DEM results.

DEM study on discharge behavior of ternary cylindrical activated coke particles

The discharge behavior including segregation of ternary cylindrical activated in a funnel is numerically studied through DEM. A variety of variables (e.g., particle shape, the filling method, mass fraction, and filling sequence) are investigated. The results show that whether it is layered or mixed filling, the discharge velocity of spherical particles is higher than that of cylindrical particles. The contact number of medium-sized particles under layered filling is larger than that of mixed filling conditions. The discharge velocity decreases with the increase of the mass fraction of the large particles and the segregation of the small particles decreases. For different filling sequences, the discharge behaviors are different, while the change characteristics of the discharge mass fraction of the same layer particles are not obvious. When there are medium-sized particles at the top layer, small particles in the middle layer, and large particles at the bottom layer, the small particles will form a protective film for large particles and hinder the unloading of large particles. • DEM study of discharge behavior of ternary cylindrical activated coke particles is presented. • Cylinder shape affects the descending velocity and segregation. • Influence of some key variables on discharge behavior is quantitatively investigated.

Settling of heavy cylindrical particles in granular beds

The way a rigid cylindrical particle falls through a viscous Newtonian liquid into a loosely packed granular bed of smaller and lighter particles has been studied numerically. This solid-liquid flow system has been solved with the lattice-Boltzmann method combined with an immersed boundary method for explicitly imposing no-slip at the particle surfaces. We study the effect of the orientation of the cylinder (vertical and horizontal), its settling speed (the Reynolds numbers at impact is of the order of 100), and its density (relative to liquid and bed density) on the depth of penetration into the granular bed. The simulation results are particularly sensitive to the friction between particles as parameterized through friction coefficients (varied in the range 0.15 – 0.50). The results have practical relevance for particles getting immobilized – or even buried – in granular beds. More importantly, the simulation cases have been designed such as to allow for straightforward experimentation the results of which would be valuable for further numerical model development.

3D-Tracking of Sand Particles in a Wave Flume Using Interferometric Imaging

We report the 3D-tracking of irregular sand particles in a wave flume using a cylindrical interferometric particle imaging set-up. The longitudinal position of each particle is deduced from the ellipticity of its speckle-like interferometric image. The size of a particle is determined from the analysis of the 2D Fourier transform of its defocused image. It is further possible to identify some rotation of the particles. Simulations accurately confirm the experimental determination of the different parameters (3D position and size of each particle).

Experiments and simulations of settling cylinders over a wide range of Archimedes numbers

AbstractQuantitative visualization experiments and particle‐resolved simulations of rigid cylindrical particles settling in a Newtonian liquid have been conducted. By varying the viscosity of the liquid—a glycerol‐water mixture—as well as the density of the cylinders, we were able to cover an Archimedes number range that spans almost six orders of magnitude in the experiments. The length over diameter aspect ratio of the cylinders ranged from 2.5 to 20. Cylinders were released vertically and rotated to a stable horizontal orientation in most of the lower viscosity solutions. The time required for reaching a horizontal orientation, as well as the Reynolds number at that stage, scale with the Archimedes number and only weakly depend on the aspect ratio. Particle‐resolved numerical simulations based on the lattice‐Boltzmann method complement the experimental study and illustrate the relevance of the experimental data as a benchmark for numerical approaches to solid–liquid flow with non‐spherical particles.

Enhanced settling of microplastics after biofilm development: A laboratory column study mimicking wastewater clarifiers

The settling of microplastics (MPs) is crucial for their removal from municipal wastewater treatment plants (WWTPs) and sedimentation in static waterbodies, where they can accumulate in bottom sediments. Biofilm formation on MPs enhances their aggregation with other particles, thereby changing their density and size and altering their settling rates. However, only a few studies have investigated the settling of MPs of different sizes and materials. Specifically, the settling of small-sized MPs (<150 μm) has been poorly documented. In this study, cylindrical and fragmented particles of four polymer types (high-density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), and poly(ethylene terephthalate) (PET)) were used to investigate the settling or floating of reference MPs (20–130 μm) in a custom-made column that simulated a primary sedimentation tank in a typical WWTP before and after incubation in wastewater influent. The settling velocity of the reference MP particles was strongly influenced by the particle size and density. The settled fractions of all the cylindrical reference MPs increased significantly (up to 5 times) due to biofilm formation at overflow velocities of 0.15, 0.26, and 0.40 mm s−1. This was observed even for HDPE and PP (density <1 g cm−3) after biofilm formation. The fragmented reference MPs showed complex and rather unpredictable behavior, possibly due to their irregular shape. Generally, the settling of pristine PS and PET in the laboratory tests was consistent with the theoretical predictions obtained using Stokes’ law. The experimental findings of this study can be used to develop models that predict the removal efficiencies of MPs in WWTPs and to estimate the sinking of MPs to bottom sediments of static waterbodies.

Scrap computer keyboards a sustainable resource for silver (Ag) and low density oil (L D Oil)

Most neglected part of the scrap computers are the keyboards, which are generally incinerated by the informal recycling sectors creating environmental pollution and leads to the wastage of precious metallic contents present in it. Present paper is focused on a novel chemical processing technique developed to recover silver (Ag) as value added product and low density oil (L D Oil) from the computer keyboards. Initially, scrap keyboards were manually dismantled to separate Mylar sheets and the same were pyrolysed at 300 °C for 2 h to recover L D Oil. The obtained pyrolysed Mylar sheets was further crushed, milled and homogenized to reduce particle size (−100 mesh). The crushed sample was leached using 2 M HNO3 at 60 °C in mixing time of 20 min and pulp density of 100 g/L to achieve maximum dissolution of Ag. The leaching kinetics for Ag dissolution well fitted with chemical reaction control dense constant size cylindrical particles, 1-(1-X)1/2 = kct. The obtained leach liquor was put to cementation process using metallic copper (Cu). Almost 99% of Ag gets cemented as Ag powder in 15 min at a constant solution temperature of 60 °C and pH 1.1. The developed bench scale process has application orientation to the industry after piloting the process.

A novel model of pressure drop for airflow penetrating randomly packed cylindrical particles

Pressure drop is the key factor related to performance and energy consumption of fixed bed. However, the packing of cylindrical particles produces anisotropic gaps and an extremely complex airflow field and makes the formation mechanism of flow resistance undefined. This study conducted a comprehensive investigation on how such factors as the void fraction, diameter, and aspect ratio of cylinders on the flow resistance, in terms of experimental and numerical methods. With the DEM-CFD simulation, the laminar and transitional flow pattern was acquired, and the critical Reynolds number was determined. The expression of void fraction in the inertia term of the original Ergun equation was confirmed not applicable to cylindrical particles, which was proved to be the reason why previous predictions cannot accurately give the flow resistance of packed cylindrical particles. Finally, a new prediction model for the pressure drop of airflow penetrating the packed cylindrical particles was developed.

Investigation of flow field and pollutant particle distribution in the aquaculture tank for fish farming based on computational fluid dynamics

Hydrodynamics is important for fish survival in the aquaculture tank systems, as it can directly affect the behaviour of farmed fish and the self-cleaning property of culture tank systems. The present study designs a new tank configuration, rectangular single-side arc angle tanks, to improve the performance of aquaculture vessels. The tank hydrodynamics was investigated by solving the Reynolds-Averaged Navier–Stokes (RANS) equations and combined with the discrete phase model (DPM) model to study particle motion. The velocity at the monitoring point and the discharge rate of particles from the tank were separately measured using Acoustic Doppler Velocimetry and the MATLAB image recognition method to validate the numerical model. We numerically tested the effect of culture tank configurations and the horizontal distance from the inlet pipe to the sidewall on hydrodynamics parameters, including velocity magnitude and uniformity, turbulence region and vortex distribution. Subsequently, to further understand the self-cleaning property of the culture tank systems for settleable particles, 300 cylindrical particles with a uniform size of 2.5 mm are tracked in the Lagrangian frame. Meanwhile, velocity distribution and pressure gradient have been employed to quantitatively evaluate the effects of hydrodynamics on the collection and discharge regularity of particles. Through CFD-assisted design verification, the tank configuration and the position of the inlet pipe layout have a considerable impact on the removal of particles from the tank and the energy to sustain the flow in the tank. Some key findings are found that 1) the hydrodynamics was improved significantly after rounding two right-angle edges in the rectangular culture tank, in which the configuration tanks of η = 0.2 and η = 0.3 could establish the strengthened rotational flow with better uniformity; 2) the inlet pipes proper far from the sidewall can enhance the self-cleaning property of the tank and the inlet pipe layout position of δ = 0.02–0.04 is the preferred interval.

Correlations Based on Numerical Validation of Oscillating Flow Regenerator

Stirling regenerator is one of the emerging heat exchanger systems in the area of cryogenic cooling. Many kinds of research have been conducted to study the efficiency of Stirling regenerators. Therefore, the principles and related knowledge of Stirling refrigerators must be thoroughly understood to design a regenerator with excellent performance for low-temperature and cryogenic engineering applications. In this study, an experimental setup is developed to estimate the pressure drop of the oscillating flow through two different wire-mesh regenerators, namely, 200 mesh and 300 mesh, for various operating frequencies ranging from 3 (200 RPM) to 10 Hz (600 RPM). Transient, axisymmetric, incompressible, and laminar flow governing equations are solved numerically, and source terms are added in the governing equations with the help of the porous media model and the Ergun semiempirical correlation, assuming that the wire meshes are cylindrical particles arranged uniformly. Simulation results show that the numerical predictions of temporal pressure variation are in reasonably good agreement with those of experimental findings. It is also found that the Ergun correlation works more accurately for higher flow rate conditions.

Thermo-Mechano-Electrochemical Analysis in Cylindrical Electrode Particles of Lithium-Ion Battery

A thermo-mechano-electrochemical model is proposed in this paper to study the coupled effect on diffusion induced stresses (DISs) in cylindrical electrode particles. The traditional heating model, Bernardi’s model, is modified to be practical in particle dimension. And the finite deformation theory as well as stress-induced diffusion hypothesis are also adopted to establish equations of the whole coupled system. By means of numerical simulation, the result of incipient thermal behavior shows significant dependence on both initial concentration of lithium-ion in the particle and capacity of heat interchange at particle surface. The DISs influenced by thermal behavior display amplification that is small (about 2% in 3C condition) but tend to increase with higher charging and discharging rate. Moreover, when temperature increase reaches 220 K, the result of DISs in the adiabatic model demonstrates prominent amplification which exceeds 12%. Therefore, thermal behavior is supposed to be taken into consideration when dealing with a quick-charging problem.

Lateral migration of cylindrical particle in a constricted microchannel—A numerical study

AbstractInertial migration of a single cylindrical particle in a constricted microchannel is addressed in this work. A computational model (two‐dimensional) has been constructed with the assistance of the immersed boundary finite volume method. The feedback forcing strategy is utilized for the simulation of lateral migration. The parameters like equilibrium position, migration time, and shortest equilibrium distance are computed to analyze the inertial migration characteristics of the particle. Also, a comprehensive parametric study has been performed on the migration behaviour of particles inside the constricted channel by addressing the effects of Reynolds number, diameter, initial release position, and constriction clearance. The parametric study shows that the equilibrium position changes with variations in the initial release position and particle diameter. On the other hand, it stays unaffected by changes in Reynolds number and constriction clearance. The parameters like the shortest equilibrium distance and migration time increase with a rise in Reynolds number and particle diameter. On the other hand, it reduces with the reduction in constriction clearance. Inspired by the parametric study results, in the following stage, a prediction model is created with an artificial neural network algorithm. This is used for an effective forecast of equilibrium position, migration time, and shortest equilibrium distance. Further, the computational model is utilized to check for the existence of a critical Reynolds number for the particle movement in a constricted microchannel. It is observed that the critical Reynolds number remains unchanged with a change in particle diameter. However, it increases linearly with an increase in constriction clearance.

CFD-DEM numerical study on air impacted packing densification of equiaxed cylindrical particles

A CFD-DEM model was developed to reproduce the packing densification process of mono-sized equiaxed cylindrical particles under air impact. The effects of operating parameters on packing density were firstly studied. Then various microscopic properties of packing structures such as coordination number (CN), contact types, particle orientations, pore features were characterized and compared. And corresponding densification mechanisms were analysed based on particle motion behaviour, local structure evolution, and forces. Results indicate that the air impact can realize the packing densification of cylindrical particles under appropriate conditions. The pore size distribution in the packing of cylindrical particles shows a tail at larger pore sizes compared with that in the packing of equal spheres. Both the size and the sphericity of the pores decrease in the final dense packing; also, more surface-surface and less surface-edge contacts between two particles therein can be formed. More cylindrical particles tend to be in parallel or perpendicular contact with each other to form more stable local structures during air impact. Most particles at higher position move down (direction of gravity/air impact) with about one particle length during the densification process and most particles exhibit translational motion to realize the local rearrangement for pore filling through air impact induced inter-particle forces.