Search Results (53)

The roller press crushing of ore is a complex process involving the interplay of multiple factors. Roller dimensions, gap settings, and rotational speed all influence this process, which in turn affects the comprehensive crushing performance of the high-pressure grinding rolls (HPGR). Therefore, to simultaneously enhance the HPGR’s size reduction effectiveness (SRE) and throughput while controlling its energy consumption, wear, and edge effect, multi-objective parameter optimization of the HPGR is required. This study utilizes the Discrete Element Method (DEM) to simulate ore comminution within an HPGR. By first dividing the release zone into segments, the particle size distribution of the crushed product at different locations within this zone is investigated. Then, the influence of various factors on the SRE at different locations within HPGR is examined through single-factor experiments. Subsequently, the relative influence of roller diameter, roller width, roller speed, and roll gap on the comprehensive crushing performance of the HPGR is determined through signal-to-noise ratio (SNR) analysis and analysis of variance (ANOVA). Finally, multi-objective parameter optimization of the roller press crushing is conducted based on grey relational analysis (GRA), incorporating the weights assigned to different response target. The results indicate that the proportion of unbroken ore particles is relatively significant, primarily due to the edge effect. Further analysis reveals that along the horizontal diameter of the rollers, regions closer to the roller surface exhibit better SRE. Additionally, roller speed is identified as the most influential factor affecting the uniformity of SRE in the HPGR. The application of GRA to the multi-objective optimization of roller press crushing enables effective balancing of the comprehensive crushing performance in HPGR. Full article

To address the challenges of low permeability, high gas adsorption, and a fragile structure in coalbed methane reservoirs, this study developed a high-strength composite proppant with an activated carbon skeleton via nitric acid pretreatment, silica–alumina sol coating, and calcination. Orthogonal experiments optimized the preparation conditions: 30–40 mesh activated carbon, Si/Al molar ratio of 4:1, calcination at 650 °C for 2 h. The resulting proppant exhibited an excellent performance: a single-particle compressive strength of 55.5 N, porosity of 33.2%, crushing rate of only 2.3% under 50 MPa closure pressure, and permeability 48.5% higher than quartz sand. In simulated acidic coalbed environments (pH 3–5), its acid corrosion rate was <2.8%, and it enhanced methane desorption by 16.2% compared to pure coal. Additionally, the proppant showed a superior transport performance in fracturing fluids, with better distribution uniformity in fractures than ceramsite, and its hydrophobic surface (contact angle 115.32°) improved fracturing fluid flowback efficiency. This proppant integrates high strength, good conductivity, gas desorption promotion, and corrosion resistance, offering a novel material solution for efficient coalbed methane extraction. Full article

This study investigates the influence of particle morphology on two-dimensional (2D) single rock particle breakage using the combined finite-discrete element method (FDEM) coupled with fractal dimension analysis. Three key shape descriptors (elongation index EI, roundness index Rd, and roughness index Rg) were systematically varied to generate realistic particle geometries using the Fourier transform and inverse Monte Carlo. Numerical uniaxial compression tests revealed distinct morphological influences: EI showed negligible impact on crushing strength or fragmentation, and Rd significantly increased crushing strength and fragmentation due to improved energy absorption and stress distribution. While Rg reduced strength through stress concentration at asperities, suppressing fragmentation and elastic energy storage. Fractal dimension analysis demonstrated an inverse linear correlation with crushing strength, confirming its predictive value for mechanical performance. The validated FDEM framework provides critical insights for optimizing granular materials in engineering applications requiring morphology-controlled fracture behavior. Full article

This paper describes the complex process of rock crushing removal by AWJ impact from the microscopic perspective. The acceleration and deceleration mechanism of abrasive particles throughout the whole process of single abrasive particles impacting rocks, the spherical cavity expansion mechanism of the abrasive particles’ impact on the rock, and the elastic contact force of the collision between the abrasive particles and rock were investigated; a mathematical model of AWJ’s impact on the rock crushing removal conditions was established; and the threshold values of the jet impact parameters were obtained. The mathematical model of the rock crushing removal conditions was verified through numerical simulation and jet impact experiments. The research results show that the theoretical value of the jet impact velocity that meets the conditions for limestone crushing removal is greater than or equal to 36 m/s, and the theoretical value of the pressure is greater than or equal to 2.7 MPa. Numerical simulation was used to obtain the displacement of marked points, stress, and strain variation in marked elements of rock under different impact velocities. The effect of impact rock breaking obtained through the experiment demonstrates the correspondence between the test pressure and the theoretical pressure, which verifies the accuracy of the mathematical model of the rock crushing removal conditions. Full article

The semi-autogenous grinding (SAG) mill, renowned for its high efficiency, high production capacity, and low cost, is widely used for crushing and grinding equipment. However, the current understanding of the overall particle behavior influencing its efficiency remains relatively limited, particularly the impact of the shape of SAG mill liners on material behavior. This study employs discrete element method (DEM) simulation technology to investigate the effects of different liner structures on particle trajectories and collision energy, systematically investigating the impact of lifter bars angle, height, and the number of lifter bars on grinding efficiency. The results of single-factor simulations indicate that when the lifter bars height (230 mm) and the number of lifter bars (36) are fixed, the total collision energy dissipation between steel balls and ore, as well as among ore particles, reaches a maximum of 526,069.53 J when the lifter bars angle is 25°. When the lifter bar angle is fixed at 25° and the number of lifter bars is set to 36, the maximum collision energy dissipation of 627,606.06 J occurs at a lifter bars height of 210 mm. When the angle (25°) and height (210 mm) are fixed, the highest energy dissipation of 443,915.37 J is observed with 12 lifter bars. Results from the three-factor, three-level orthogonal experiment reveal that the number of lifter bars exerts the most significant influence on grinding efficiency, followed by the angle and height. The optimal combination is determined to be a 20° angle, 12 lifter bars, and a 210 mm height, resulting in the highest total collision energy dissipation of 700,334 J. This represents an increase of 379,466 J compared to the original SAG mill liner configuration (320,868 J). This research aims to accurately simulate the motion of discrete particles within the mill through DEM simulations, providing a basis for optimizing the operational parameters and structural design of SAG mills. Full article

The conventional spent lithium-ion batteries (LIBs) recycling method suffers from complex processes and excessive chemical consumption. Hence, this study proposes an electrochemical strategy for achieving reductant-free leaching of high-valence transition metals and efficient separation of valuable components from spent cathode sheets (CSs). An innovatively designed sandwich-structured electrochemical reactor achieved efficient reductive dissolution of cathode materials (CMs) while maintaining the structural integrity of aluminum (Al) foils in a dilute sulfuric acid system. Optimized current enabled leaching efficiencies exceeding 93% for lithium (Li), cobalt (Co), manganese (Mn), and nickel (Ni), with 88% metallic Al foil recovery via cathodic protection. Multi-scale characterization systematically elucidated metal valence evolution and interfacial reaction mechanisms, validating the technology’s tripartite innovation: simultaneous high metal extraction efficiency, high value-added Al foil recovery, and organic removal through single-step electrochemical treatment. The process synergized the dissolution of CM particles and hydrogen bubble-induced physical liberation to achieve clean separation of polyvinylidene difluoride (PVDF) and carbon black (CB) layers from Al foil substrates. This method eliminates crushing pretreatment, high-temperature reduction, and any other reductant consumption, establishing an environmentally friendly and efficient method of comprehensive recycling of battery materials. Full article

Most grinding operations are the process of reducing the particle size of ore materials under the combined action of impact and abrasion. The action mechanism of impact damage and abrasion damage of materials in the grinding process is different, and the ability of each constituent mineral of ore to resist impact damage and abrasion damage is different. In order to study the independent action mechanism and interaction law of impact and abrasion in grinding, mineral ores calcite, chalcopyrite, and sphalerite are studied in this paper. The JK drop weight test method and batch grinding test method are used to study the changes and laws of various indexes of three mineral ores under a single impact condition, a single abrasion condition, and the coexistence of the two effects. The results show that the impact crushing parameters of the three mineral ores and the corresponding hardness grade of the ores are related to the particle size. The smaller the particle size of the material, the smaller the value of the impact crushing capacity parameter A × b. The order of impact crushing resistance of the three mineral ores is consistent with the characterization results of ore Mohs hardness. Under the same particle size condition, the order of impact crushing parameter A × b of the three mineral ores is calcite > sphalerite > chalcopyrite. The first-order linear model can better fit the grinding kinetics in the cascading state, and its kinetic parameters are related to ore hardness and feed particle size. The t₁₀ is more suitable to characterize the grinding effect in the dropping state than in the cascading state. Full article

In complex geological environments, the discontinuous dynamic response behavior of jointed rock masses under the coupled effects of in situ stress and transient dynamic disturbances significantly exacerbates the risk of surrounding rock instability. This study establishes three-dimensional numerical models of various jointed rocks under uniaxial–biaxial–triaxial split Hopkinson pressure bar (SHPB) experimental systems through the coupling of the finite difference method (FDM) and discrete element method (DEM). The models adhere to the one-dimensional stress wave propagation assumption and satisfy the dynamic stress equilibrium requirements, demonstrating dynamic mechanical responses consistent with physical experiments. The results reveal that the synergistic–competitive effects between joint configuration and initial pre-compression jointly dominate the dynamic mechanical response of rocks. Multiaxial pre-compression promotes the development of secondary force chain networks, enhances rock impact resistance through multi-path stress transfer mechanisms, significantly improves strain energy storage density during peak stages, and drives failure modes to evolve from macroscopic through-going fractures to localized crushing zones. The spatial heterogeneity of joint configurations induces anisotropic characteristics in principal stress fabric. Single joint systems maintain structural integrity due to restricted weak plane propagation, while cross/parallel joints exhibit geometrically induced synergistic propagation effects, forming differentiated crack propagation paths that intensify frictional and kinetic energy dissipation. Through cross-scale numerical model comparisons, the evolution of force chain fabric, particle displacement distribution, microcrack propagation, and energy dissipation mechanisms were analyzed, unveiling the synergistic regulatory effects of the stress state and joint configuration on the rock dynamic response. This provides a theoretical basis for impact-resistant structure optimization and dynamic instability early warning in deep engineering projects involving jointed surrounding rock. Full article

In order to find a short, economically feasible process for chalcopyrite preconcentration and to provide a reference for the preconcentration of similar copper sulfide ores, the particle size characteristics of the crushed products from a high-pressure grinding roller (HPGR) and jaw crusher (JC) were analyzed, as well as the liberation degree and fracture characteristics of the chalcopyrite. The float–sink test (FST) was carried out on the crushed products, and the effects of the two crushing methods on the FSTs of the crushed products were compared. The research results show that at the same crushing fineness, the chalcopyrite liberation in HPGR products can be enhanced by 14%~18% compared with the JC. The single-particle crushing of the JC tends to produce intergranular fracturing of chalcopyrite, while the lamination crushing of the HPGR produces more transgranular fracturing of chalcopyrite; the chalcopyrite in the −5 + 0.5 mm size fraction mainly produces intergranular fracturing, and the chalcopyrite in the −0.5 mm size fraction mainly produces transgranular fracturing. The FST results show that heavy media preconcentration was suitable for chalcopyrite, and, in the optimal conditions of a size fraction of −3 + 0.5 mm and separation density of 2.55 g/cm³, the grade and distribution rate of Cu in the sinks obtained by HPGR-FST were 0.35% and 89.86%, respectively, and the floats yield was 24.76%, with a better enrichment of sinks and higher floats yields, which was better when compared with that of the JC-FST. Full article

The morphology of an individual particulate refers to its shape characteristics and size properties, which both play important roles for granular matter in physics, mechanics, chemistry, and biology. In this study, ellipsoidality is defined as a 3D shape index for evaluating particle roundness, and an explicit calculation method is applied. The dependences of 3D shape characteristics (aspect ratios, sphericity, and ellipsoidal degree) on particle size (ranges from 0.063 mm to 5.0 mm) are adequately investigated with the X-ray micro-computed microtomography (uCT) imaging for hundreds of thousands of particles of crushed and natural sands. This study focuses on comparing and evaluating the specific surface area and equivalent diameter, suggesting that particle segregation and changes in surface area may explain the strong dependence of particle shape on size. The correlation between different shape metrics was analyzed by comparing crushed sand with natural sand to provide theoretical support for material filling and mechanical behaviour. The significant differences in the microscale particle size indexes of different sands by single grading are used to provide data references for further analyses of the effect of material microscale on material properties in future discrete element particle simulations. Full article

A recent study reported the rapid growth of SiC single crystals of ~1.5 mm/h using high-purity SiC sources obtained by recycling CVD-SiC blocks used as materials in semiconductor processes. This method has gained attention as a way to improve the productivity of the physical vapor transport (PVT) method, widely used for manufacturing single crystal substrates for power semiconductors. When recycling CVD-SiC blocks by crushing them for use as sources for growing SiC single crystals, the properties and the particle size distribution of the material differ from those of conventional commercial SiC powders, making it necessary to study their effects. Therefore, in this study, SiC single crystals were grown using the PVT method with crushed CVD-SiC blocks of various sizes as the source material, and the growth behavior was analyzed. Simulation results of the temperature distribution in the PVT system confirmed that using large, crushed blocks as the SiC source material generates a greater temperature gradient within the source compared to conventional commercial SiC powder, making it advantageous for rapid growth processes. Additionally, when the large, crushed blocks were vertically aligned, good crystal quality was experimentally achieved at high growth rates, even under non-optimized growth conditions. Full article

The accurate modeling of single-particle breakage based on three-dimensional (3D) images is crucial for understanding the particle-level mechanics of granular materials. This study aims to propose a systematic framework incorporating single-particle breakage experiments and numerical simulations based on a novel 3D particle reconstruction technique for fractal analysis of particle size and morphology in single-particle breakage. First, the vision foundation model is used to generate accurate particles from 3D images. The numerical approach is validated by simulating the single-particle breakage test with multiple Fujian sand particles. Then, the breakage processes of reconstructed sand particles under axial compression are numerically modeled. The relationship between 3D fractal dimensions and particle size, particle crushing strength, and morphology is meticulously investigated. Furthermore, the implications of these relationships on the particle breakage processes are thoroughly discussed, shedding light on the underlying mechanisms that govern particle breakage. The framework offers an effective way to investigate the breakage behavior of single sand particles, which will enhance understanding of the mechanism of the whole particle breakage process. Full article

A complementary characterisation of the Al-alloy EN AW-5454 was carried out, intended for obtaining the laser hybrid welding parameters of subassemblies in the automotive industry. The investigation included a microstructural examination and the determination of the alloy’s properties using several analytical methods (HV5 hardness measurement, tensile test, Charpy impact toughness, fracture mechanics analysis). Samples were prepared in the longitudinal and transverse directions of a cold-rolled sheet of EN AW-5454 with thicknesses of 3.5 mm and 4 mm. The measured hardness on the thinner sheet was 5% higher than on the thicker sheet. The tensile and yield strength were nominal, while the elongations were smaller by 2.2–3.2% for the longitudinal samples and by 2.7–13.7% for the transverse samples. The smaller deviations from the nominal values are for the thinner sheet metal. A precise topographical analysis showed the brittle fractures of the samples. The Charpy impact toughness results on the thicker plate showed a 20% greater work needed to break it in the longitudinal direction than in the transverse direction. With the thinner sheet metal, 40% greater work was needed. SEM (scanning electron microscope) analysis has shown that the intermetallic Al₆(Mn,Fe) particles in the longitudinal samples were mostly intact, with evidence of tough areas on the upper part of the fracture, indicating a better toughness than the specimens in the transverse direction. More crushed intermetallic particles were observed at the fractures of the transverse samples, and their distribution appeared to be more oriented in the direction of rolling. Fracture mechanics SENB (single edge notch bending) tests and their analysis showed that the resistance of the material to crack propagation in the longitudinal sample was about 50% greater than that in the transverse sample. SEM analysis of the fractures showed that the state of the intermetallic particles in the fracture mechanics testing and the fracture mechanism differed from the one in the Charpy fractures. Full article

Calcareous sand is a crucial construction material for island and reef development and reinforcing it using Microbially Induced Calcite Precipitation (MICP) technology is a promising new method. This study employed 3D scanning technology to assess changes in the particle size and morphology of MICP-treated, coated calcareous sand particles. Single-particle crushing tests were conducted to analyze their crushing strength, crushing energy, crushing modes, and fragment fractal dimensions. The results indicated that MICP treatment significantly increased particle size, surface area, and volume, while reducing flatness. At a cementation solution concentration of 1 mol/L, both crushing strength and crushing energy were optimized. The coated particles exhibited three crushing modes: explosive crushing, mixed crushing, and splitting crushing. Thicker coatings led to a tendency for particles to break into larger fragments through the mixed and splitting crushing modes. Fractal analysis revealed that coating thickness directly affects the local crushing characteristics of the particles. Full article

Proppant is one of the key materials for hydraulic fracturing. For special situations, such as middle-deep reservoirs and closure pressures ranging from 40 MPa to 60 MPa, using a single proppant cannot solve the contradiction between performance, which means crushing rate and fracture conductivity, and cost. However, using combined proppants is an economically effective method for hydraulic fracturing of such special reservoirs. Firstly, for different types, particle sizes, and proportions of combined proppants, various contact relationships between proppant particles are considered. The random phenomenon of proppant particle arrangement is described using the Monte Carlo method, and the deterministic phenomenon of proppant particles is processed using an optimization model, achieving computer simulation of the microscopic arrangement of proppant particles. Secondly, a mathematical model for the force analysis of combined proppant particles is established, and an improved singular value decomposition method is used for numerical solution. A computational model for the crushing rate and fracture conductivity of combined proppants is proposed. Thirdly, the numerical calculation results are compared and discussed with the test values, verifying the accuracy of the computational model. Finally, the application of combined proppants is discussed, and a model for optimizing the proportion of combined proppants is proposed. The onsite construction technology is introduced, and the cost and economic benefits of combined proppants are compared with those of all ceramic particles and excessive all-quartz sand. It is proved that combined proppants can balance performance and price, and are an economically effective method for hydraulic fracturing of special reservoirs. The research results can select the optimal proppant material and optimize the combination of different proppant types, which can help achieve cost reduction and efficiency increase in oil and gas development. Full article