Particle Breakage Research Articles

Effects of particle breakage on the mechanical characteristics of geogrid-reinforced granular soils under triaxial shear: A DEM investigation

A series of numerically triaxial shear tests on crushable and uncrushable granular soils reinforced by geogrid were conducted using 3-Dimension Particle Flow Code. The macroscopic behaviors of crushable and uncrushable granular soil during shearing were compared. Also, the underlying macro–micro linkages were explored. The main findings are as follows: Particle breakage decreases the contact forces between soil particles to reduce the shear strength of granular soils; The reinforcement effect of geogrids on the shear strength of granular soils can be attributed to the increase in fabric and force anisotropies; The particle displacement distribution of crushable soil samples is more uniform than that of uncrushable samples, and the shear band of crushable samples is not obvious; The reinforcement effect of geogrid with the aperture size ratio of 4.4 is the highest among the samples because the number of crushed particles and the deformation of geogrids reaches a balance.

Analysis of the behavior of a high earth-core rockfill dam considering particle breakage

This paper presents a finite element analysis for the behavior of the Lianghekou high earth-core rockfill dam, which was just completed in construction in China. An elastoplastic constitutive model that can account for the degradation of rockfills due to particle breakage (hhu-SH-breakage model) was applied to simulate the mechanical behavior of the rockfills. The earth-core wall was analyzed by using the modified Cam-clay model combined with the Biot’s consolidation theory. Numerical results are in good agreement with in-situ measurements during construction, indicating the reasonability of the numerical analysis. Based on the breakage-packing concept, which is able to extract the breakage-induced deformation from the total deformation, numerical analysis showed that the breakage-induced settlement for the extra high rockfill dam is not negligible. Inspired by the sensitivity analysis using the hhu-SH-breakage model, engineering advices were proposed to reduce the settlement of high rockfill dams.

An Experimental Study on the Dilute Phase Pneumatic Conveying of Fat-Filled Milk Powders: Particle Breakage

Powder breakage during pneumatic conveying negatively affects the properties of dairy products and causes increased dusting, reduced wettability, and decreased product performance. In particular, particle breakage is a serious issue for fat-filled milk powder (FFMP) which, if it breaks, releases fat that causes odours and leads to sticky blocked pipes. In this work, a conveying rig (dilute phase, positive pressure) with 50 mm diameter food grade stainless steel pipes (1.5 m high and 5 m conveying distance with three 90° bends, two in the vertical plane and one in the horizontal plane) was built as the test system. The effects of operating conditions (conveying air velocity and solid loading rate) on the attrition of FFMP in a dilute phase conveying system were experimentally studied. Four quality characteristics were measured before and after conveying: bulk density, particle size distribution, wettability, and solubility, to access the influence of particle breakage. Conveying air speed shows a significant impact on powder breakage. As air speed increased, more breakage occurred, and the volume mean diameter D[4,3] decreased by around 50%, using the largest conveying air speed of 38 m/s. Bulk density increased accordingly whereas wettability decreased with an increase in air speed, resulting from the higher breakage rate. On other hand, improving the solid loading rate can further reduce the breakage level, but the positive effect is not as good as decreasing air speed.

Influences of input concentration, media particle size, metal cation valence, and ionic concentration on the transport, long-term release, and particle breakage of polyvinyl chloride nanoplastics in saturated porous media

The environmental impact of nanoplastics has gradually attracted widespread attention; however, nanoplastics of polyvinyl chloride, one of the most commonly used plastics, have not yet been studied. In this study, we investigated the transport, long-term release behavior, and particle fracture of polyvinyl chloride nanoplastics (PVC NPs) in saturated quartz sand with different metal cations, ionic concentrations, input concentrations, and sand grain sizes by determining breakthrough, long-term release, and particle size distribution curves. The breakthrough curves and retention profiles were simulated by a mathematical model. The transport of PVC NPs increased with increased input concentration and sand grain size, which could be predicted by the Derjaguin–Landau–Verwey–Overbeek (DLVO) and colloid filtration theories. Increased ionic concentration and metal cation valence could restrain the transport of PVC NPs in saturated quartz sand owing to the decreased energy barrier between PVC NPs and sand grains. The total released amount of PVC NPs in the long-term release tests with different experimental conditions ranged from 3.91 to 21.95%. Increased sand grain size and decreased metal cation valence and ionic concentration resulted in an increased released amount of retained PVC NPs in saturated quartz sand, indicating increased release ability and mobility. The particle fracture results indicated that the PVC NPs were not broken down during long-term release under the experimental conditions of this research. This opens up a completely new and meaningful study of whether nanoplastics are broken down into smaller nanoplastics during their long-term release under various conditions.

Designing of trimetallic-phase ternary metal sulfides coupled with N/S doped carbon protector for superior and safe Li/Na storage

Traditional transition metal sulfides (TMSs) have shown favorable potentials in energy storage. Nevertheless, its further usage is plagued by the issues of particle breakage and large volume change. In this work, the nanostructured ternary TMSs coupled with N/S doped carbon protector (NiCoFe-S@NSC) is delicately designed via compositional regulation and spatial structure protection strategies. As lithium ion batteries anode, this electrode gives an impressive capacity of 995.7 mAh/g after running 1000 cycles at 1 A/g. More importantly, NiCoFe-S@NSC electrode still shows a discharge capacity of 221.94 mAh/g after running 20,000 cycles at 10 A/g, reflecting an extremely-low capacity decay rate of 0.0377 ‰ per cycle. As sodium ion batteries anode, a high initial discharge capacity of 896.4 mA h g−1 can be found. Even after running 400 cycles at 5 A/g, the electrode still displays a reversible capacity of 334.5 mAh/g with outstanding coulombic efficiency above 98.0 %. Impressively, LiNixCoyMn1-x-yO2//NiCoFe-S@NSC full cell gives incipient discharge/charge capacities of 186.89/240.18 mAh/g. Moreover, the discharge capacities for the following 100 cycles remain above 150 mAh/g. Thermal runaway tests also demonstrate the higher thermal safety of cells with NiCoFe-S@NSC electrode, accompanying with the promoted activation energy.

Experimental investigation of the particle breakage of coarse-grained materials under impact loading

Particle breakage is commonly observed in coarse-grained materials (CGMs) when subjected to external loads. In this study, the evolution of the particle size distribution of CGMs was systematically investigated by conducting a series of impact loading tests with respect to different influencing factors: initial grading, water content, and compaction coefficient. The extents of particle breakage based on the gradings before and after the tests were analysed. Particle breakage under impact loading was found to be non-negligible. The gradings after tests were observed to shift away from the initial gradings. Coarse-grained materials with less water content were subject to more particle breakage. In addition, irrespective of the initial gradings and water content, an increase in the extent of particle breakage with an increase in the compaction coefficient was observed under impact loading.

Collision characteristics and breakage evolution of particles in fluidizing processes

Fluidized beds are widely used in chemical reactors. Particles in fluidized bed usually circulate between reactors, and therefore, particle attrition cannot be avoided. Catalyst particle attrition in the fluidized bed significantly shortens their lifespan and raises operating costs. This study established an irregular polyhedron model of the particles to acquire their motion and force characteristics by the Euler-Lagrangian method and then employed the Ab-T10 breakage model to predict the particle's breakage process. The collision frequency and stress characteristics of the three-dimensional surface of a single particle were explored, as well as the time-dependent variations in the collision frequency and impact power between particles. The breakage and elutriation processes of a single particle were observed. The investigation found that the velocity differential between particles was the main factor that caused impact power. The particles were typically crushed one to six times before becoming completely fine powder, and their size evolution can be summarized in three stages. The complete process of particle breakage was revealed by tracing the size evolution of a single particle. This work would contribute to a deeper understanding of particle collision behavior and breakage mechanisms in fluidized beds.

Extrapolation-Based Scale Effect Model for Granular Heap Modulus

The numerical analysis was used to predict the rockfill dam displacement, and the model parameters were calibrated using the triaxial experiments on scale-down rockfill samples. Due to the scale effect of rockfill material, the displacements were usually underestimated in the design phase. This study focused on the scale effect of rockfill material and an extrapolation model was proposed to extrapolate the prototype modulus from the laboratory modulus. By conducting confined compression experiments, the size effect was investigated using ball heaps. Based on the experimental findings, considering a granular heap as a cumulative particle structure, the structural mechanics approach was introduced to establish the size effect model. Then, the boundary constrain effect model was speculated using the elastic mechanics analysis. By conducting the confined experiments on ball heaps, the modulus variation with particle breakage was investigated and the breakage effect model was established consequently. Finally, via combining the effects from the size, boundary constrain, and particle breakage, a scale effect model was established for extrapolating prototype modulus from the laboratory modulus. The proposed model was evaluated through numerical analysis of an actual dam. The experimental results revealed that the compressive modulus decreased as the initial void ratio increased; under the same initial void ratio, the compressive modulus decreased as the ratio of the specimen width to particle size increased; the compressive modulus decreased as the particle breakage increased. The numerical analysis results showed that prediction accuracy for rockfill dam displacement was improved by 8%–10%. The proposed model represents a new approach for investigating the scale effect of rockfill material, which could be adopted by engineers to improve the prediction of rockfill dam displacement.

Simulation and experimental study on milling mechanism and tool wear of low volume SiCp/Al composites

Silicon carbide particles reinforced aluminum matrix composites are widely used in national defense and related high-end technology fields due to their excellent mechanical properties. To explore the milling mechanism and tool wear mechanism of low-volume SiCp/Al composites in high velocity milling, the milling experiments for 20% volume SiCp/Al2009 composites were performed using a polycrystalline diamond (PCD) tools. A three-dimensional milling model of SiCp/Al composite was established considering the random distribution of SiC particles, the influence of milling parameters on surface quality was comprehensively analyzed and its cutting mechanism was described, and the wear forms and mechanism of PCD tools were revealed during milling of SiCp/Al composites. The result showed that the cutting depth is the main factor affecting the machined surface quality, followed by the spindle speed, and the feed rate has the smallest effect on it. It was observed that when spindle speed ( n) was 17,000 r/min, the feed rate ( f) was 8 mm/min, the depth of cut ( ap) was 0.04 mm, the surface roughness value was the smallest, Ra was 0.056 μm. The surface morphology was mainly manifested as pits, cracks, burrs, and so on, subsurface defects included particle breakage, peeling, and matrix cracks, and the tool wear forms included chipping, flaking, and bond wear.

Fines generation from South African manganese ores during preheating in a rotary kiln

Manganese ores are the major source of manganese for the production of manganese ferroalloys. There is a gap in the knowledge of the decrepitation behaviour of manganese ores, which presents a problem in the operation of smelters. Decrepitation, which is the breakage of the ore particles upon heating, is an important quality parameter for these ores. The purpose of this investigation was to determine the extent to which South African manganese ores decrepitate during preheating in a rotary kiln. The effects of temperature, rotational speed, and particle size decrepitation were investigated. Manganese ores were heated in a laboratory-scale rotary kiln at temperatures of 600, 800, and 1000°C, and rotational speeds of 3, 6, and 12 r/min. The size ranges were +6-20, +20-40, and +40-75 mm and the residence time was constant at 30 minutes. The decrepitation index (DI) is quantified as the ratio of the mass of <6 mm particles after pre-heating to the total mass of the sample. It was found that the DIs for all ores used were proportional to the temperature and the rotational speed and inversely proportional to the particle size range with temperature being the most important parameter. Ore A was the most susceptible to decrepitation followed by ore C and ore B; this was mainly to the decomposition of kutnohorite, the content of which was the highest in ore A and the lowest in ore B.

Numerical simulation of mechanical compaction and pore evolution of sandstone considering particle breakage

Mechanical compaction is an important diagenetic process in sandstone reservoirs. Particle breakage, which commonly occurs during mechanical compaction, plays a significant role in controlling the physical properties of the reservoir. However, existing numerical simulation methods have limitations in simulating mechanical compaction when considering particle breakage. In this study, a discrete element simulation method of mechanical compaction was proposed based on particle cutting, and the experimental results reported in the literature were used to calibrate the simulation parameters. Finally, this method was applied to the simulation of the mechanical compaction of sandstone to analyze the pore evolution process. The results show that the new simulation method has high computational efficiency and can reflect the process of particle breakage. The simulation results coincide well with the experimental results. In the simulated mechanical compacted process of coarse sandstone, particle breakage is strong in the high-stress stage with a vertical stress of 30 MPa–50 MPa. The porosity and mean radii of pores and throats decreased rapidly, and the number of pores and throats increased rapidly in the high-stress stage. When the vertical stress reached 50 MPa, compared to the simulation results without considering particle breakage, the porosity difference rate caused by particle breakage was 4.63%; the radius difference rates of pores and throats were 2.78% and 6.8%, and the number difference rates of pores and throats were 4.95% and 8.74%, respectively. In the process of mechanical compaction, the pore evolution of the reservoir is controlled by the filling of the pre-existing pore space by the fragments generated through particle breakage and the generation of microfractures. Additionally, the simulation method presented in this study can be applied to complex geological conditions and can be combined with other reservoir simulation methods. The simulation results can provide rich training samples for artificial intelligence and other emerging technologies.

Critical Dynamic Stress and Cumulative Plastic Deformation of Calcareous Sand Filler Based on Shakedown Theory

Calcareous sand is a special marine soil rich in calcium carbonate minerals, characterized by brittle particles. It is, therefore, widely used as a filling material in the construction of islands and reefs. In this study, a series of cyclic tri-axial tests were conducted on calcareous sand taken from a reef in the South China Sea under different confining pressures and cyclic stress ratio (CSR). Then, applying the shakedown theory, the cumulative deformation of calcareous sand under a long-term cyclic load of aircraft was evaluated. Results showed that with the increase in the effective confining pressure, the stress–strain curves of calcareous sand showed a change from the strain-softening to the strain-hardening state; the volumetric strain of calcareous sand showed a change from shear shrinkage and then shear expansion to continuous shear shrinkage. Calcareous sand showed three different response behaviors under cyclic load: plastic shakedown, plastic creep and incremental plastic failure. With the plastic strain rate as the defining index, this study determined the critical CSR of calcareous sand under different shakedown response statuses and found them to increase with the effective confining pressure. The empirical formula for critical stress was established based on the fitting analysis of critical CSR under different confining pressures, taking the confining pressure as the variable. At the early stage of the cyclic load, calcareous sand samples were under compression. When the resilient modulus grew rapidly and the number of loading cycles continued to increase, the particles of calcareous sand samples were crushed, causing the fine particles to fill the voids among coarse particles, further compacting the samples and increasing the resilient modulus of calcareous sand samples. Hardin’s breakage potential model was adopted to quantitatively describe the particle breakage of calcareous sand samples before and after tests. The results indicated that calcareous sand samples produced obvious particle breakage when the CSR was small. As the CSR increased, the extent of the breakage of the sample particles first increased and thereafter stabilized. This study provides a theoretical reference for the assessment of the dynamic stability of calcareous sand subgrade subjected to traffic loads.

Comminution and Classification as Important Process Steps for the Circular Production of Lithium Batteries

Lithium-ion batteries (LIBs) provide the largest source of electrical energy storage today. This paper covers the use of comminution processes and, thus, crushers and mills for particle breakage and dispersing, as well as classifiers for particle separation within the process chain, from the raw material to the final lithium battery cell and its recycling at end of life. First of all, the raw materials for the active material production have to be produced either by processing primary raw materials, or by recycling the spent lithium batteries. The end-of-life battery cells have to be shredded, the materials separated and then milled in order to achieve the so-called black mass, which provides a secondary material source with very valuable components. Using these materials for the synthesis of the cathode active materials, milling has to be applied in different stages. The natural graphite, increasingly used as anode material, has to be designed in mills and classifiers for achieving targeted properties. Nanosized silicon is produced by nanomilling using stirred media mills as a primary option. Conductive additives for LIBs, like carbon black, have to be dispersed in a solvent with machines like planetary mixers, extruders or stirred media mills. In the future, mechanochemical synthesis of solid electrolytes will especially require additional application of comminution processes.

Experimental research on the influence of different factors on the behaviour of broken coal and rock particles during compaction

Broken coal-rock masses are a major part of the goaf. The breaking of coal and rock particles in the compaction process affects various aspects including control of strata motion, prediction of surface subsidence, and backfill mining. Therefore, isotropic compaction experiments on broken coal-rock mass were carried out by utilising the loading part of the seepage test system for coal-rock mass to analyse influences of particle strength, particle size, mixed type, stress, and loading and unloading times on breakage of particles in the compaction process. The test results show that the crushing behaviour of coal and rock particles in the compaction process can be divided into three stages: the structural re-arrangement and crushing of particles under a low stress, particle breakage under moderate stress, and compression of particles under a high stress. The reduction rate of porosity decreases with the increase of particle strength and increase of loading and unloading times, increases with the increase of particle size, has nothing to do with two mix types of coal-rock mass after compaction. Under the same stress unloading conditions, the recovery amounts of particles from compression deformation were similar, which was not related to unloading times. Research results is significant to those analysing overlying strata motion, predicting surface subsidence, optimising the material ratio for backfill mining, etc.

Degradation suppression effect of amorphous-hard-carbon-bundled Si-based negative electrode

To improve the electrode calendar life of high-capacity Si, a non-core–shell type Si negative electrode was investigated for preventing volume changes and particle breakage of nano-sized Si particles.

Critical states observed in triaxial compression tests on volcanic pumice soil related to debris flow in the 2008 Iwate-Miyagi Nairiku Earthquake

The Iwate-Miyagi Nairiku Earthquake (M7.2) that occurred on June 14, 2008, caused a slope failure in Dozo-zawa River near the summit of Mt. Higashi-Kurikoma. The debris flow caused by the slope failure flowed for about 10 km and took the lives of 7 people. The mechanisms of the slope failure and long-distance debris flow have not yet been well understood. In this study, a series of triaxial compression tests was conducted using a highly crushable pumice soil collected from the collapsed area, and shear behavior and particle breakage were discussed. Both reconstituted specimens and intact specimens showed contractancy and reached critical states that implies high flow potential. However, intact specimens preserved looser structure during consolidation and showed stronger contractancy during shearing than the reconstituted specimens, due to their natural soil structure. Significant particle breakage was observed in the tests with reconstituted specimens.

Lightweight shear stiffening gel with enhanced mechanical and thermal-insulating performance for advanced fire suit

A lightweight and thermal-insulating shear stiffening gel (LT-SSG) with anti-impact was developed via introducing hollow glass microspheres BR20 into shear stiffening gel (SSG). It was lightweight enough to be placed on a leaf. LT-SSG showed the ability to resist impact. Finally, a multifunctional Kevlar safeguarding suit (MKSS) with flame retardant property was fabricated. It exhibited good adiabatic effect which could isolate heat at high temperatures and prevent heat loss at low temperatures. • LT-SSG with lightweight, heat-insulation and anti-impact properties was prepared. • LT-SSG showed enhanced protective effect due to the existence of BR20 particles. • A multifunctional Kevlar safeguarding suit (MKSS) was assembled. • MKSS was capable to resist fire combustion and displayed good adiabatic effect. • MKSS effectively prevented the heat loss from humans in cold environment. Herein, a lightweight and thermal-insulating shear stiffening gel (LT-SSG) with anti-impact was prepared by introducing insulating glass microspheres BR20 into SSG. The density of LT-SSG was 48.97% lower than that of SSG. Meantime, LT-SSG showed excellent energy absorption effect. The remained impact force of LT-SSG was only 0.23 kN compared with 0.41 kN of SSG when impacted from 20 cm. Moreover, LT-SSG with good thermal insulation performance could effectively isolate surrounding temperature to 42.6 ℃ at 80 ℃ and block external cold temperature to protect the heat loss from human body. While SSG as well as the breakage of BR20 particles absorbed and dissipated much impact energy, proving its excellent protective properties. Finally, a multifunctional Kevlar safeguarding suit (MKSS) was developed. It showed the ability to resist low-speed drop hammer and high-speed ballistic impact. To this end, the reported LT-SSG showed promising application in fire suit and body armors.

Microstructure and phase evolution of micronized ceramic colorants from a pilot plant for inks production

The advent of inkjet printing as digital decoration of ceramic materials has irreversibly modified the industrial decoration technology, imposing companies to change the colorant production process. The inkjet application requires micronized particles in the ultrafine particle size range (smaller than 1 μm). Particles size reduction of ceramic colorants is performed by a high-energy comminution process in wet-operated bead mills, affecting colorants properties. Since a deep knowledge of milling-induced microstructural changes is still lacking, the micronization effects on a set of five industrial ceramic colorants are thoughtfully investigated in this work by simulating the industrial process at a pilot plant. Particle size distribution and energy consumption are monitored during the comminution process. The compositional (including crystallite size and microstrain analysis of the main phases) and morphological variation of four ceramic pigments (yellow zircon, brown spinel, pink malayaite, and green eskolaite) and one dye (blue olivine) is investigated by XRPD (Rietveld method) and SEM analyses. The analytical approach combined with a physical/semiempirical modelling of the colorants elastic features versus the energy demand for particle reduction has yielded details on the nature of the micronization-induced microstructural changes in ceramic colorants. Specifically, the comminution efficiency as well as the crystalline phase stability are related to the intrinsic properties of each colorant. Brittle breakage rather than plastic deformation on comminution are also system dependent. When an euhedral to subhedral crystal habit is maintained a brittle fracture is preserved throughout the comminution progress, while the formation of flake-like particles and particle agglomeration are strong evidences of plastic deformation. The last evidence deals with the material elastic features. Materials with high bulk modulus convert the grinding energy to lattice defects that lead to particle breakage by brittle fractures, while materials with lower bulk modulus convert/dissipate part of the supplied energy in plastic deformations, drastically decreasing the comminution process efficiency.

Particle attrition-breakage model for CFD-DEM simulation based on FRM and WPM: Application in blast furnace raceway

In the raceway of blast furnace, the coke attrition would cause the blockage of the nearby area. Small particles move to the deadman and gather, which affects the smoothness of gas-liquid flow and worsens the circumstance in the furnace. In this study, a comprehensive attrition-breakage model is developed with high accuracy and efficiency. For breakage, the unequal volume probability breakage model is established based on the experimental results and fragment replacement model (FRM) method. The wear-equivalent particle method (WPM), which satisfies the mass conservation, is proposed to improve accuracy through replacing wear loss with equivalent particles. The validity and efficiency of the attrition-breakage model are verified through experiments and simulations. In the industrial blast furnace raceway, the application of the model enables a good description of the breakage and wear characteristics of raceway. This study deepens the research on the blast furnace raceway, and proposes an effective attrition-breakage model suitable for large-scale simulations of industrial scale. • Fragment replacement method to simulate particle breakage. • Generate small particles on the particle surface to simulate wear. • Particle attrition-breakage model used in numerical simulation. • Further subdivision of the blast furnace raceway. • Blockage in blast furnace with breakage and wear.

Reinforcement of Calcareous Sands by Stimulation of Native Microorganisms Induced Mineralization

Calcareous sand is a special soil formed by the accumulation of carbonate fragments. Its compressibility is caused by a high void ratio and breakable particles. Because of its high carbonate content and weak cementation, its load-bearing capacity is limited. In this study, the optimal stimulation solution was obtained with response surface methodology. Then, the effect of reinforcing calcareous sand was analysed with unconfined compressive strength (UCS) tests, calcium carbonate content tests, microscopy and microbial community analyses. The components and concentrations of the optimal stimulation solution were as follows: sodium acetate (38.00 mM), ammonium chloride (124.24 mM), yeast extract (0.46 g/L), urea (333 mM), and nickel chloride (0.01 mM), and the pH was 8.75. After the calcareous sand was treated with the optimal stimulation scheme, the urease activity was 6.1891 mM urea/min, the calcium carbonate production was 8.40%, and the UCS was 770 kPa, which constituted increases of 71.41%, 35.40%, and 83.33%, respectively, compared with the initial scheme. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses showed that calcium carbonate crystals were formed between the particles of the calcareous sand after the reaction, and the calcium carbonate crystals were mainly calcite. Urease-producing microorganisms became the dominant species in calcareous sand after treatment. This study showed that biostimulation-induced mineralization is feasible for reinforcing calcareous sand.