Coarse Solid Particles Research Articles

The effect of particle shape on the collapse characteristics of granular columns via the DEM

Granular flows that are composed of coarse solid particles are common in catastrophic events, such as landslides, rock avalanches, pyroclastic flows, or even turbidity currents. Understanding their complex dynamics is thus a key concern for risk assessment. The goal of the analyses in this study is to investigate the effects of particle shape on two-dimensional granular column collapses via the discrete element method (DEM). Specifically, three different particle shape types are constructed through three shape parameters (i.e., Sphericity S, Angularity α and roughness λ), the granular column mobility R* changes regularly with the evolution of the shape parameters at a specific aspect ratio. We investigate the effects of particle shape on the collapse of granular columns using a method that first selects an extreme shape and then transitions through a series shape evolution. Using this method, particle shape is shown to have an important effect on deposition morphology, energy evolution and the mechanical coordination number. Furthermore, the shape parameters that have the strongest impacts on granular column collapse are shown to be S and α, which can be used as macroscale factors to describe particle shape. Also, λ, which is a microscale factor that describes the particle surface, is shown to have a weaker influence. This study provides useful insights into the fluidity response of particle shape on granular column collapse.

SPH numerical model of wave interaction with elastic thin structures and its application to elastic horizontal plate breakwater

This paper develops a Smoothed Particle Hydrodynamics (SPH) model to simulate wave interaction with elastic thin structures. This is achieved by coupling the δ-SPH and the Total Lagrangian SPH (TL-SPH) models for solving the fluid and structure phases, respectively. To this aim, a multiresolution algorithm within the ghost particles framework is introduced in order to treat the thin elastic components of the structure. The main idea of the proposed technology is to evaluate the hydrodynamic forces acting on the structure and the elastic dynamic at the finest solid particle resolution. Then, the information is transferred to the coarse solid particles, which act as a non-penetrating boundary condition for the fluid phase. The present enforcement is introduced with the aim of overcoming the disadvantages in terms of CPU time for heavy SPH simulations, in which the choice of the initial spatial resolution is driven by the presence of elastic thin structures immersed in the fluid environment. The present elastic thin-wall boundary treatment is verified through several numerical cases, in which it is proved that the proposed technology can block non-physical interaction of fluid particles located at opposite sides of the elastic thin-wall boundary, ensures the stability of the fluid pressure field, and reasonably predicts the motion of elastic structures when these are subjected to hydrodynamic loads. Successively, the proposed numerical model is applied to simulate wave interaction with an elastic horizontal plate breakwater. The hydrodynamic performances of the breakwater, with focus on the reflection and transmission coefficients, are analyzed. The results of elastic and rigid horizontal plate breakwaters are compared in order to better understand the effects of the structure deformation on the hydrodynamics. Finally, an analysis of the structural deformation of the breakwater is also reported.

Improved dusty gas cleaning in open-cast automobile transport

Service life extension of internal combustion engines is an urgent task for open-cast automobile transport. Dust contamination of oil and constructive elements of the internal combustion engine accelerates its wear and tear, resulting in breakage. The authors developed a separation device with sections of double-T elements as a replacement for the first stage cleaning device in open-cast automobile transport. Numerical results show that the proposed separation device provides gas cleaning with high efficiency from fine, medium, and coarse solid particles. The use of this device improved the overall efficiency of gas cleaning and extended the service life of the fine filter, which has a positive effect on the internal combustion engine. Studies have shown that the separation device has an average efficiency of 81.2% with the following parameters: dust particle size 5–20 μm, dust particle density 1000–7000 kg/m3, inlet gas velocity 3–15 m/s.

High-speed mode movement of solid particles in turbomachines with radial blades

The introduction substantiates the relevance of research. The purpose of the work is to create and approbate a methodology for calculating the speed mode for movement of coarse solid particles along the radial blades of turbomachines. In the methodological part an analysis of the forces acting on a solid particle when sliding along the radial blades of turbomachines is carried out. A differential equation for motion of solid particles has been compiled and options for its solution have been considered. Analytical dependencies have been obtained that make it possible to determine the values of the relative and total velocities, as well as the angle between the corresponding vectors for the velocities of the particle as a function of time when it moves along the radius of the blade. A calculated estimate of the change in these parameters for a wide range variation of the friction coefficient of a particle on the rotor blade is carried out. It is shown that the total sliding velocity of the particle as well as its radial and transport components intensively increasing in the initial time range, asymptotically approach the linear functions of the particle coordinate, practically independent of its initial position, but linearly dependent on the angular velocity of the rotor rotation and nonlinearly – on the coefficient of friction of the particle on the blade. In this case, the exit angle of the particle does not depend on the radius and rotor angular velocity, but depends on the friction coefficient of the particle against the rotor blade. With an increase in the friction coefficient the relative and total velocities of particle motion decrease which leads to a decrease in the kinetic energy accumulated by the particles. Conclusions are drawn from the results of the study. It is noted that the results obtained can be used by design engineers when designing turbomachines with radial blades, as well as in the educational process when training mechanical engineers and process engineers.

Migration Behaviors of As, Se and Pb in Ultra-Low-Emission Coal-Fired Units and Effect of Co-Firing Sewage Sludge in CFB Boilers

The migration behaviors of As, Se and Pb in ultra-low-emission coal-fired units were investigated and the effect of co-firing of sewage sludge and coal was explored in circulating fluidized-bed (CFB) boiler units. Samples of feed fuel including coal and sewage sludge, fly ash, bottom slag and desulfurization slurry were collected from five CFB units with a capacity between 150 MW and 350 MW and two pulverized coal boiler (PC) units with a capacity of 350 MW and 600 MW. The majority of As, Se and Pb in coal is released during coal combustion and enriched in fly ash. As, Se and Pb in fly ash and bottom slag are associated with inorganic matter, of which As, Se and Pb associated with silicates and aluminosilicates account for more than 60%. In the wet flue gas desulfurization (WFGD) unit, more than half of the As, Se and Pb migrates to the solid fraction and the concentrations of As, Se and Pb in fine solid particles are much higher than those in coarse solid particles and the liquid fraction. The proportions of exchangeable As, Se and Pb or associated with organic matter in gypsum are higher than those of fly ash and bottom slag. According to the two studied CFB units with blending ratios of sewage sludge below 10%, co-firing with sewage sludge has little effect on the migration and transformation characteristics of As, Se and Pb. Under a long-term acidic leaching environment, Pb in combustion by-products is in the range of low risk, while As and Se are in the range of medium risk.

Experimental investigation of critical suction velocity of coarse solid particles in hydraulic collecting

Hydraulic collecting and pipe transportation are regarded as an efficient way for exploiting submarine mineral resources such as the manganese nodules and ores. Coarse particles on the surface of the sea bed are sucked by a pipe during the mining and crushing of the mineral. In this paper, the critical suction velocity for lifting the coarse particles is investigated through a series of laboratory experiments, and the solid–liquid two-phase flow characteristics are obtained. Based on the dimensional analysis, the geometric similarity is found between actual exploitation process and model test with the same kind of material. The controlling dimensionless parameters such as the hydraulic collecting number, the relative coarse particle diameter, the relative suction height, and the density ratio are deduced and discussed. The results show that the logarithm in base 10 of the hydraulic collecting number increases approximately linearly with the increase of the relative suction height, while decreases with the relative particle diameter. A fitting formula for predicting the critical suction velocity is presented according to the experimental results.

Validation of friction factor predictions in vertical slurry flows with coarse particles

Abstract The paper presents validation of a mathematical model describing the friction factor by comparing the predicted and measured results in a broad range of solid concentrations and mean particle diameters. Three different types of solids, surrounded by water as a carrier liquid, namely Canasphere, PVC, and Sand were used with solids density from 1045 to 2650 kg/m3, and in the range of solid concentrations by volume from 0.10 to 0.45. All solid particles were narrowly sized with mean particle diameters between 1.5 and 3.4 mm. It is presented that the model predicts the friction factor fairly well. The paper demonstrates that solid particle diameter plays a crucial role for the friction factor in a vertical slurry flow with coarse solid particles. The mathematical model is discussed in reference to damping of turbulence in such flows. As the friction factor is below the friction for water it is concluded that it is possible that the effect of damping of turbulence is included in the KB function, which depends on the Reynolds number.

CFD-DEM modelling of hydraulic conveying of solid particles in a vertical pipe

This paper presents a numerical study of hydraulic conveying of coarse solid particles by means of the combined approach of Computational Fluid Dynamics (CFD) for the liquid phase and Discrete Element Method (DEM) for particles. Via the model validation, it proves the reasonability of applying the CFD-DEM method in the simulation of this flow system, where the lift force acting on a particle needs to be considered. Numerical results show that particles tend to concentrate in the middle of the vertical pipe. Increasing feed solid concentration and conveying speed gives a more dispersed distribution of particles and leads to an increase of pressure drop. In contrast, particle diameter has a negligible influence on instantaneous flow regimes and pressure drop. Under all the operating conditions considered, time-averaged variables including solid volume fraction, axial liquid velocity, and axial solid velocity all present maximum values in the middle of the pipe, which decline gradually in the radial direction toward the wall. These results are expected to shed light on the optimization of hydraulic conveying.

Study on transient dynamics of piers under the impact of debris flow

Because of the climate warming and the serious ecological damage of the valley slope, the frequency of debris flow in the valley is increasing frequently. The solid deposits in the debris flow are, transported at high speed under the action of water flow and self-gravity, have a great impact on the piers along the line, which greatly destroys the integrity and stability of the pier. Through the theoretical analysis and numerical simulation of debris flow, the transient dynamic response of the pier under the impact of debris flow is analyzed. It is concluded that the pier is subjected to the punching and shearing form load, and the impact damage of the coarse solid particles in the debris flow to the pier is more obvious. The pier displacement reaches the maximum at the second impact of the debris flow; the maximum displacement is 10.9mm, which appears at the 5m above the bottom of the pier. A tensile stress concentration zone appears at the bottom of the pier, and the maximum tensile stress is 1.84MPa, which exceeds the concrete strength of the pier and so we can take corresponding measures to guard against this problem so as to ensure the safety of bridge structure.

Coupling of material point method and discrete element method for granular flows impacting simulations

SummaryGranular debris flows are composed of coarse solid particles, which may be from disaggregated landslides or well‐weathered rocks on a hill surface. The estimation of agitation and the flow process of granular debris flows are of great importance in the prevention of disasters. In this work, we conduct physical experiments of sandpile collapse, impacting 3 packed wooden blocks. The flow profile, run‐out distance, and rotation of blocks are measured. To simulate the process, we adopt a material point method (MPM) to model granular flows and a deformable discrete element method (DEM) to model blocks. Each block is treated as comprising 9 material points to couple the MPM and DEM, and the acceleration of grid nodes arising from the contacts between granular material and blocks is projected to the discrete element nodes working as body forces. The contacts between blocks are detected using the shrunken point method. The simulation results agree well with the experimental results. Thus, the coupling method of MPM and DEM developed in this work would be helpful in the damage analysis of buildings under impact from the debris flows.

Experimental study of hydraulic transport of coarse basalt

In many industrial applications, as in dredging or deep sea mining, coarse solid particles (typical size in the order of millimeters or tens of millimeters) are transported hydraulically in mixture with water through pipelines. This paper discusses experimental results obtained for flows of water-based slurries of three fractions of coarse basalt pebbles in a 100-mm pipe of the laboratory loop of the Institute of Hydrodynamics in Prague. The collected experimental database includes concentration distributions measured in the horizontal section of the pipe loop. The data are used to evaluate friction mechanisms of slurry flow and their relation to the internal structure of the flow. Measured frictional pressure drops are analysed and compared with existing predictive formulae. A theoretical background is proposed for a modified predictive formula for the frictional pressure drop in horizontal flow of slurry carrying coarse grains transported in saltation or as a sliding bed. The relative excess pressure drop in such flow is found to be sensitive primarily to the slip ratio, the thickness of a sliding bed and the solids friction coefficient. An accurate determination of frictional energy losses is essential to a successful assessment of an economy of hydraulic transport and to an optimisation of operations of slurry pipelines conveying very coarse solids.

Dynamic Characteristics Analysis for Fluid-Solid Coupling of Vertical Lifting Pipe in Transporting Coarse Particles

Fluid-solid coupling dynamic characteristics analysis of vertical cantilever lifting pipe in transporting coarse solid particles was conducted by adopting ADINA. Firstly, finite element models of pipe and fluid were built, which was solved by using ADINA/FSI module. Secondly dynamic characteristics of pipe vibration for different run-time, constrain conditions, volume concentration and transporting velocities were studied. Thirdly the stress and displacement characteristics were discussed under above conditions. The results were shown that stress and displacement will increase with transporting concentration and velocity rising; the shorter run-up time is, the bigger stress and displacement will be; stress and displacement of lifting pipe supportive anchor in weak constrain were greater than that in fixed connect condition. Analysis results have certain directive significance in future structure design, check, reducing vibration study for lifting pipeline in the ocean mining.

Critical Flow Velocity in Slurry Transporting Horizontal Pipelines

A new empirical equation is proposed for predicting critical flow velocity in slurry-transporting horizontal pipelines. An analysis of the settling velocity of solid particles, including the effect of solid particle concentration, is undertaken because of this parameter's importance. This study builds on a previous study carried out to consider the settling velocity of a single solid particle in clear-water condition, which is actually different from the real physics of the hydrotransport phenomenon of the solid particles. Two earlier proposed methods are applied to the calculation of the settling velocity of a solid particle, including the effect of solid particle concentration within the suspending fluid. The most appropriate method for slurry transportation among these two methods is discussed and used in the analysis of critical flow velocity. The new proposed equation is based on analysis of data from the experiments as well as data from the earlier studies. A unique feature of the proposed equation is that it can be applied to noncohesive, uniform, and nonuniform coarse solid particles. In a comparison of prediction accuracy with four existing relationships, the proposed equation was found to give significantly better agreements with the observed data. Therefore, it can be stated that the new equation can safely be used by designers in the problems of slurry transportation.

Drying of Porous Solid Particles in Various-Shaped Spouted Bed with a Draft-Tube.

Spouted beds are often used for drying of coarse solid particles. In this study, the spherical porous solid particles of activated alumina were dried in three types of spouted beds with a draft-tube, an ordinary spouted bed, a screen-bottomed spouted bed and a top-sealed spouted bed, by using dry air at room temperature. Drying ability was defined as moisture evaporated per unit mass of solid particles per unit volume of air, being averaged during the time until moisture content reaches one-half of its initial value. The screen-bottomed spouted bed provided the highest drying ability and the ordinary spouted bed provided the lowest of all three spouted beds.

Distribution characteristics of the mass concentration of coarse solid particles in a two-phase turbulent jet

In the paper the results of the mathematical modelling a horizontal two-phase turbulent round jet carrying coarse solid particles are presented. The numerical results are compared with the experimental data obtained in our laboratory. The goal of these investigations is to describe the distribution characteristics of the mass concentration of particles moving with a velocity lag which starts from the pipe outlet. These features are based on the intensive diffusion of particles with the rapid decrease of their concentration from the initial stage of the jet (scattering effect) and the less intensive diffusion giving a wave-like distribution of the mass concentration along the axis of the jet (intermediate effect). Such particle distributions in the jet are related to the specific motion of coarse particles in the pipe expressed by their lagging behind the gas. For the mathematical description, an algebraic model for the closure of the equations for the dispersed phase which is based on the inter-particle collision is used since the solid admixture in our experiments is a polydispersed powder. Along with the inter-particle collision, turbulent interaction between the phases resulting in the Reynolds stresses in the dispersed phase is also taken into account. In addition, the Magnus lift force contributes to the model due to the particle rotation and the velocity lag of the particles which enter the jet.

水平輸送管路における水力勾配の算定式 堆積層を伴うスラリーの流動機構に関する理論的考察

Many attempts to date have been directed to develop a relationship for the prediction of the hydraulic gradient im in heterogeneous flow of settling slurry having coarse solid particles. This fact indicates clearly that existing correlations lack the universality, and often provide poor im prediction results due to the great diversity of flow conditions.In this paper a heterogeneous suspentions model was developed for the flow simulation and scale-up of slurry pipelines in the deposit regime. Our analytical work has two main steps: In the first part, the modified O'Brien's equation for distribution of suspended particles above the bed was derived, and solved mathematically. Secondly, the mean velocity-hydraulic gradient correlation was determined in theory.The predictions for the concentration distributions and the hydraulic gradient from the model were in good agreement with experimental results taken from the published literature for a variety of flow conditions of slurries. Based on the above analyses, we also discussed specific energy, Batchelor's dimensionless number, and Durand-Condolios equation.As a result, it was confirmed that in the design of slurry pipelines for the commercial transportation of any materials our study made possible to predict the hydraulic gradients precisely in the deposit regime without laboratory flow loon tests.

堆積層上の粒子群の流動について

Contrary to the most investigators' opinions that the deposit regime is uneconomical, some papers have reported this regime to be not necessarily uneconomic since the power requirement may decrease for velocities below the limit deposit velocity. Also, it is said that in all applications of industrial significance the system should be designed to prevent occurrence of this unsafe region because there is imminent danger of pipe blockage. Nevertheless, for the slurry pipeline system transporting coarse solid particles and involving difficulties in controling operational variables rigorously such as hydraulic dredging or hydraulic conveying of run-of-mine coal, it is inevitable for some or all of solids to deposit temporarily on the bottom of the pipe.On these bases there is an immediate need for relationships to use in estimating both the bed thicknesses and the hydraulic gradients under the flow conditions in the deposit regime.This paper presents results of investigations of design methods in this regime. Experiments were conducted to support the theoretical modeling effort for the particle size range 1.71-3.10 mm using a 25.9mm (ID) transparent plastic pipeline, with total length of approximately 10 m, mounted on the frame horizontally.The correlation of experimental data has shown that the ratio hr of the bed thickness to the pipe diameter D and the hydraulic gradient im of slurry flow may be determined from following equations if the functions of f1 (Cv) and f2 (Cv) are given experimentally:_??_in which: Va=apparent mean velocity of slurry flow; g=gravitational constant; Cv=delivered volumetric concentration of solids; v=kinematic viscosity of water; R, R0=hydraulic radii of the free flow section above the bed and of the pipe; Vt=terminal settling velocity of single particle;δ=specific gravity of solids.

Emission Standards for the Control of Solid Particles, A New Approach by New Jersey

Existing chapters of the New Jersey Air Pollution Control Code are described, followed by an explanation of a proposed new chapter to control emissions of coarse solid particles and fine solid particles from industrial processes. The chapter is designed to limit dustfall of coarse particles off the premises of the emitter to WO tons per square mile per year, and the methods used to relate this criterion to stack emissions are explained. Fine particles, suspended in the air off the premises, are limited to 0.615 milligrams per cubic meter during average weather conditions. Measures taken for the protection of buildings, where the plant property line is less than 10 stack heights from the base of the stack, are described.

A technique for contacting gases with coarse solid particles

AbstractAlthough coarse, uniformly sized particles are not amenable to fluidization, it has been found possible by use of either gases or liquids to impart a regular cycling motion to a bed of this type of material in which the solids are rapidly carried upward by the fluid in a central well‐defined core within the bed. The particles move uniformly downward in the annular space surrounding the core, thus providing dense‐phase countercurrent contact between the fluid and the solids. There is no wall separating the core from the annulus. This method is called the spouted‐bed technique. The effect of column diameter, fluid inlet diameter, bed depth, and physical properties of solids and fluids on spouting behavior has been investigated. The minimum fluid velocity required for spouting has been correlated, and the flow pattern of the fluid and of the solids has been stuided. The technique has been applied to the drying of wheat.