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Grain comminution is commonly observed in numerous geological settings. To elucidate the role of grain comminution in dry granular friction, we sheared breakable halite (NaCl) grains using a ring‐shear configuration at a constant slip rate under various normal stresses. We observed transient frictional behaviors: a constant regime exhibiting a high friction coefficient at small slip displacements, and a weakening regime showing a substantial decay in friction at large slip displacements. The characteristic slip lengths for both regimes decreased with normal stress and were characterized by similar exponents. Micro‐X‐ray tomography revealed the evolution of microstructure from distributed grain comminution to progressive shear localization for these two regimes. We propose that the filling processes of comminuted fine particles, during which fine particles saturate and then overflow the shear zone, define transient frictional behaviors. This study may hold significant implications for natural shear systems, given the ubiquity of comminution and localization phenomena. Plain Language Summary: Grain comminution and structural evolution are common phenomena in natural settings, including earthquake faults and landslides. However, their role in granular friction remains unclear. To investigate this, we experimentally sheared breakable NaCl grains to simulate the processes within growing fault zones and visualized microstructural evolution using micro‐X‐ray computed tomography (CT). We observed two distinct frictional behaviors: a constant regime exhibiting a high friction coefficient at small slip displacements, and a weakening regime showing a substantial decay in friction at large slip displacements. The characteristic slip lengths for both regimes decreased with normal stress. Micro‐observations revealed drastic grain comminution and segregation processes in the constant regime, while the weakening regime showed progressive shear localization evolving from multiple discontinuous shear planes to one extremely localized shear plane. The higher constant friction appeared to result from large grain contacts, while the substantially lower steady‐state friction arose from comminuted fine particle contacts. We propose that grain comminution generates fine particles, gradually filling the pores within the shear zone in the constant regime, ultimately leading to frictional weakening by effectively reducing large grain contacts. The characteristic lengths defining transient behavior may be influenced by geometrical complexities and boundary conditions in various geological settings. Key Points: Sheared granular halite exhibits constant friction at small slip displacement and substantial weakening at large displacementCharacteristic slip lengths for constant friction and weakening decrease with normal stress and are characterized by similar exponentsThe production, saturation, and overflow of comminuted fines in the shear zone are key factors determining transient frictional behavior [ABSTRACT FROM AUTHOR]

In granular media, the crushing of individual particles is influenced by the number of contacts with neighbouring particles. This well-known phenomenon of "cushioning" shields the individual particles from crushing when the number of contacts is high. However, in open systems that involve extensive granular flow and bulk motion, like those found in industrial mills, the neighbouring particles continually exchange positions due to segregation and mixing, thereby altering the number of neighbouring contacts and their sizes, affecting the crushing of individual particles. Therefore, a critical challenge for properly modelling comminution in such systems lies in tracking the fluxes of the various particle size classes. Here, we explore the physics that governs the mechanisms of segregation and mixing within the multiscale heterarchical modelling paradigm. Building upon the framework developed in Part I, which integrated the heterarchical aspects of the physics of crushing along streamlines, we further account for segregation and mixing, and demonstrate their impact on the comminution efficiency of autogenous grinding mills. In particular, segregation is shown to greatly enhance the extent of particle crushing within the mill. Accordingly, we posit that this mechanism cannot be ignored. In summary, the new model sheds light on previously obscured dynamics within industrial mills, as well as enables the field to predict the time evolution of the particle size distribution at any point in the mill domain. This modelling capability opens the doors to new developments for estimating and improving milling efficiencies. [ABSTRACT FROM AUTHOR]

Rotary mills aim to effectively reduce the size of particles through a process called comminution. Modelling comminution in rotary mills is a challenging task due to substantial material deformation and the intricate interplay of particle kinematics of segregation, mixing, crushing, and abrasion. Existing particle-based simulations tend to provide predictions that cannot cope with the large number of particles within rotary mills, their wide range of sizes, and the physics dictating the crushing of individual particles. Similarly, there is currently no deterministic modelling means to determine the evolving population of particle sizes at any point in time and space within the mill. The aim of this two-part contribution is to address these gaps by advancing a framework for a novel stochastic comminution model for rotary mills, which has a well-defined deterministic continuum limit and can cope with arbitrarily large numbers of particles. This work describes the basic physics and structure of the new model within a heterarchical framework for ball and autogenous grinding mills. The primary focus of this Part I paper is to develop a computational model for the integration of motion of material along streamlines inside a mill. Coupled to this process is the kinetic physics dictating particle crushing. In a subsequent work, Part II, segregation and mixing will be added to this model such that realistic behaviour from the mill can be observed. [ABSTRACT FROM AUTHOR]

The article focuses on the review of HPGR operation mainly from a technological point of view. A critical review of recent achievements in HPGR technology was carried out, and major research areas and interests were distinguished and characterized. The economic potentials of HPGR presses were analyzed from the scope of the energy consumption. The HPGR researches were grouped into the following subjects: construction and design of HPGR machines, HPGR feed characterizations, the process course and assessment of comminution operations in HPGR devices, modeling and optimization of HPGR operation, HPGR-based technological circuits, and impact of HPGR operation on effectiveness of beneficiation processes. Apart from that, quantitative and qualitative analyses of the publications registered in the Web of Science database were performed. The evaluation has been performed according to the most frequently published institutions, countries, and journals. The analysis of merit content was performed through a critical review of research areas and investigative topics characterized by keywords. [ABSTRACT FROM AUTHOR]

The treatment and management of textile waste is an ever-growing issue worldwide, due to the continuously changing trends and the popularity of fast-fashion brands. There are numerous waste management methods besides simple landfilling, including reuse, open-loop or closed-loop recycling options. The described research explores the applicability of an open-loop recycling method, the processing of end-of-life textiles to produce fibres for fibre-reinforced geopolymers, to combine various waste streams for the production of an environmentally friendly binder system. By the examination of different textile waste processing methods, the most valuable fibrous material was produced with the application of a rotary shear and a vertical cutting mill, eliminating the necessity of manual cutting. As the most common base material of the textiles was found to be polyester and cotton, these were deemed useful for fibre reinforcement. The flexural strength showed a significant increase with the addition of 5 wt.% fibres, indicating the possibility of more than doubling the flexural strength of geopolymer specimens. Based on the microstructural analysis, however, even though there was good adhesion between the fibre and the geopolymer matrix, the latter showed inhomogeneities with higher fibre addition, indicating the need to further optimise the production steps, such as mixing time, vibration time, etc. [ABSTRACT FROM AUTHOR]

The development of mining projects in the exploration and pre-feasibility stages involves challenges related to geological and processing heterogeneity and uncertainty due to variability in their primary and response attributes. Therefore, the objective of this research is to develop the geometallurgical model of the Bond work index. For this purpose, linear regression models were developed in Jupyter Notebook considering 790 samples of uniaxial compressive strength of rock (UCS), lithologies, mineral zones and Bond work index (BWi) in a porphyry copper deposit. The results indicate a directly proportional linear relationship between BWi and UCS, generating modeling with acceptable R2 performances between 0.76 and 0.90. In addition, the lithologies and ore zones in the deposit studied are relevant characteristics related to comminution. Finally, according to rock competence, the rock is classified as medium to hard, hard and very hard in the oxide, mixed and primary sulfide zones, respectively.

The Geopyörä breakage test uses two counter-rotating wheels to nip and crush rock specimens with a tightly controlled gap between rollers. This paper presents the detailed measures conducted to evaluate the accuracy and precision of energy measurements across various ore types using the Geopyörä. Force measurement was assessed just for its precision. The outputs were compared directly to the drop weight test (DWT) measures of fragmentation at the same energy and fitted A and b parameters. Test reproducibility was evaluated using a Round-Robin methodology, testing several samples in multiple laboratories. The results confirmed that the new test has sufficient accuracy to match DWT results and excellent precision to assure reproducibility. [ABSTRACT FROM AUTHOR]

In the manufacturing process of ship propellers, large quantities of grinding chips are generated. These grinding chips result from the finishing of the blade surfaces after the primary casting process of the propeller. The aim of this study was to investigate and compare different preparation processes used to produce chip powders with sufficient powder quality for the additive manufacturing process of directed energy deposition. The preparation of the samples was performed through different sieving, milling and re-melting processes. For the characterization of the prepared samples, powder analysis according to relevant industry standards was carried out. It was found that the re-melting processes result in superior powder quality for additive manufacturing in terms of particle size, morphology, and flowability. For some characteristics, the powder exhibits even better properties than those of commercial powders. Furthermore, the powder properties of the milled samples demonstrate a promising potential for use in additive manufacturing. [ABSTRACT FROM AUTHOR]

The role of subglacial abrasion in sustaining subglacial microbiomes is an area of growing interest. It is likely that subglacial abrasion produces a range of bioutilisable compounds, some released from fluid inclusions in the confines of the mineral matrix and some produced via the surface free radicals that crushing produces in a variety of different minerals. As yet, the geochemical reactions which are initiated by abrasion remain poorly understood. This is largely because of the multiple potential sources and sinks of free radicals that occur in even the most simple of multi-mineralic system during crushing and subsequent wetting of the mixture. We illustrate this assertion by conducting a series of laboratory experiments where common, "simple" silicate minerals, such as quartz and feldspar, are abraded and incubated with ultra-pure water. Gaseous reaction products included CH4, H2 and CO2. The concentrations of major ions (including Na+, K+, Mg2+, and Ca2+), dissolved silicate, dissolved iron and pH of the solution during incubation are reported. These results were used to calculate HCO3- in solution and the saturation index with respect to various minerals using PHREEQCi. We found that abrasion of silicates produces bio-available gases and has the potential to increase the concentration of various weathering products in solution. Further, we found that even trace amounts of carbonates, an impurity in many natural rocks and minerals, may significantly affect the reaction products, making it challenging to concretize the reactions taking place. These results highlight the importance of conducting abrasion experiments utilising natural samples to better understand how apparently negligeable changes in mineralogy might affect the reaction products of abrasion and crushing. [ABSTRACT FROM AUTHOR]

The engineered artificial mineral (EnAM) lithium aluminate (LiAlO2) is a promising candidate for the recycling of lithium from slags, which can originate from the reprocessing of batteries, for example. Derivatives of the natural product Punicine (1-(2′,5′-dihydroxyphenyl)-pyridinium) from Punica granatum have been proven to be effective switchable collectors for the flotation of this mineral as they react to light. In the present study, three Punicines were added to a planetary ball mill before grinding LiAlO2 to particle sizes suitable for flotation. We investigated the influence of Punicine and two derivatives with C10 and C17 side chains on the grinding results at different grinding times and conditions as well as on the yields in flotations. SEM images of the particles, IR and ICP–OES measurements provided insights into the Punicine–particle interactions. They showed that Punicines not only prevent the formation of hydrophilic and thus undesirable lithium aluminate hydroxide hydrate (LiAl2(OH)7 ▪ x H2O) surfaces in this process, as is unavoidable in aqueous flotation without this pretreatment, they also prevent the undesired release of lithium cations into the aqueous phase. Due to considerable hydrophobization of the particle surface of LiAlO2, nearly quantitative recovery rates of this engineered artificial mineral are achieved using the process described here. [ABSTRACT FROM AUTHOR]

Solid crystalline suspensions (SCSs) containing submicron particles were introduced as a competitive solution to increase dissolution rates and the bioavailability of poorly water-soluble drugs. In an SCS, poorly water-soluble drug crystals are finely dispersed in a hydrophilic matrix. Lately, melt milling as an adapted wet milling process at elevated temperatures has been introduced as a suitable batch manufacturing process for such a formulation. In this work, the transfer from batch operation to a two-step continuous process is demonstrated to highlight the potential of this technology as an alternative to other dissolution-enhancing methods. In the first step, a powder mixture of a model drug (griseofulvin) and a carrier (xylitol) is fed to an extruder, where a uniform suspension is obtained. In the second step, the suspension is transferred to a custom-built annular gap mill, where comminution down to the submicron region takes place. The prototype's design was based on batch grinding results and a narrow residence time distribution, intended to deliver large quantities of submicron particles in the SCS. The throughput of the mill was found to be limited by grinding media compression. By inclining the mill at an angle, the grinding media position was manipulated, such that compression was avoided. Different states of the grinding media in the grinding chamber were identified under surrogate conditions. This strategy allows the maintenance of an energy-optimized comminution without adaption of the associated process parameters, even at high throughputs. Using this new process, the production of an SCS with 80–90 % submicron particles in a single passthrough was demonstrated. [ABSTRACT FROM AUTHOR]

Feedstock heterogeneity is a fundamental obstacle to cost-competitive biobased products. Agricultural products like corn stover have anatomical components that vary in their chemical composition, mechanical properties, structure, and response to chemical and biological treatments. A technique that can enrich streams in select anatomical fractions would allow a tailored deconstruction approach to increase overall process efficiency. Air classification can be leveraged for such refining; however, fundamental characterization and understanding of the particle properties that underly the physics of air classification are only modestly documented. Here, we determine fundamental particle properties including mass-to-area ratio, drag coefficient, and partition velocity that describe how anatomical tissues of corn stover behave during air classification. Mass-to-area ratios of anatomical tissues vary by nearly two orders of magnitude from 2.3 mg/mm2 for cob to 0.04 mg/mm2 for leaf. Drag coefficients of longer, fibrous materials (i.e., rind, husk, and sheath) are shown to correlate with particle area (p-value < 0.001) whereas granular tissues (i.e., cob, pith, and leaf) correlate better with mass-to-area ratio (p-values < 0.001). When compared to experimental observations, a simulated two-stage air classification and size reduction scenario predicts the overall partitioning of anatomical tissues within 15% for pith, husk, rind, and cob tissues. The model predicts an air-classified fraction preferentially enriched in cob (purity = 20%), rind (purity = 74%), and pith (purity = 4.5%) with a mass yield of 47%. Empirical relations for these properties can be used to predict the partitioning of corn stover during air classification based on anatomical type and size. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to introduce a new classification system for paediatric femoral neck fractures (PFNFs) and to evaluate its reliability. Methods: Two hundred and eight unilateral PFNFs (mean patient age: 9.0 ± 4.8 years) were included. Based on preoperative radiographs, the new classification system distinguished PFNFs without anterior or posterior translation (Type I), PFNFs with anterior (Type II) or posterior (Type III) translation, PFNFs with a comminuted medial or posterior column (Type IV), and subtrochanteric femoral fractures (SFFs; Type V). Radiographs were evaluated twice with an interval of two weeks by 19 raters with different specialties, experiences and geographical origins. The results were compared with a selection of 50 patient age-matched unilateral PFNFs and SFFs (mean patient age: 9.1 ± 4.9 years). These were graded twice by the same graders according to the Delbet-Colonna (D-C) classification. Results: Four radiologists and 15 paediatric orthopaedic surgeons from Europe and Asia graded the radiographs. Fair agreement was found between radiologists (κ = 0.296 ± 0.01) and surgeons (κ = 0.3 ± 0.005) (P = 0.17), although more experienced surgeons performed better than less experienced ones; a similar fair assessment was found for raters from Europe (κ = 0.309 ± 0.021) and Asia (κ = 0.3 ± 0.006) and for type II, III and IV fractures; the κ value in the first evaluation (0.309) was similar to that in the second evaluation (0.298). The overall κ value of the D-C classification subtypes was significantly higher (0.599 ± 0.217) than that of the new classification, 0.326 ± 0.162 (t = 3.190 P = 0.005). Conclusions: The new classification system showed fair reliability relative to the D-C classification. The reliability of the new classification system was not affected by the specialty or geographic origin of the rater or the evaluation round, only by rater experience level. The concordance was worse for PFNFs with anterior or posterior translation or with a comminuted medial or posterior columns. [ABSTRACT FROM AUTHOR]

Innovation in comminution is expected to continue unabated to address the inefficiencies that are inherent in comminution circuits. The rotary offset crusher (ROC) is a new comminution device with a promising performance potential in terms of throughput due to the enhanced speed of transportation induced by the centrifugal force of the discs. However, the processes driving the comminution of particles trapped in the conical space between the two discs of the crusher are not fully understood. To gain a better insight into the comminution process in this device, discrete element modeling (DEM) simulations were conducted to study the breakage of a single particle for the crusher operated under two different dynamic conditions, i.e., (1) a stationary top disc and (2) both discs rotating at the same speed. For both scenarios, the speed of the discs was varied between 550 and 2350 rpm. Experimental testwork was also conducted with the laboratory prototype to generate the data that were used to calibrate the breakage parameters of the Ab × t10 breakage model. Simulations were performed using polyhedral UG2 ore particles that were generated with the in-built particle generator in the DEM simulator. The simulated ROC, which is operated with both discs rotating, outperformed the ROC with a stationary top disc in terms of the specific input energy and throughput. The crusher with a stationary top disc is characterized by high shear forces (suggesting a higher wear rate), specific input energies greater than 1 kWh/t, and low throughputs (<50 kg/h). The ROC operated with a stationary disc is not recommended for hard rock applications due to expected excessive wear of crushing surfaces and higher energy consumption. The freewheeling discs are recommended, but there is scope to optimize the crusher performance in terms of the power draw, size reduction, and throughput by manipulating the difference between the speeds of the discs. There is also scope to optimize the crusher performance when it is simulated with many particles. Once the full performance potential of the ROC is established, it will then be important to benchmark it against the existing crushers in the minerals industry as well as other industries where crushers are used. [ABSTRACT FROM AUTHOR]

Abstract Grain comminution is commonly observed in numerous geological settings. To elucidate the role of grain comminution in dry granular friction, we sheared breakable halite (NaCl) grains using a ring‐shear configuration at a constant slip rate under various normal stresses. We observed transient frictional behaviors: a constant regime exhibiting a high friction coefficient at small slip displacements, and a weakening regime showing a substantial decay in friction at large slip displacements. The characteristic slip lengths for both regimes decreased with normal stress and were characterized by similar exponents. Micro‐X‐ray tomography revealed the evolution of microstructure from distributed grain comminution to progressive shear localization for these two regimes. We propose that the filling processes of comminuted fine particles, during which fine particles saturate and then overflow the shear zone, define transient frictional behaviors. This study may hold significant implications for natural shear systems, given the ubiquity of comminution and localization phenomena.

Due to their increasingly high demand, lithium-ion batteries (LIBs) will encounter a scarcity of essential resources if recycling is not prioritized. The current pretreatment methods for spent LIBs used in industrial production are inefficient, costly, and hazardous. The study aimed to maximize the yield of lithium and cobalt from the black mass of spent Lithium-ion batteries through an optimized high-temperature thermal pretreatment process, which combined mechanical (direct crushing) and thermal treatments to facilitate the subsequent recovery of these valuable metals. Sieve analysis showed that direct crushing for 2 min resulted in 40.81 % of the anode material in the 4750 + 2500 μm size range, while 5 min of crushing led to a more even distribution, with 28.57 % in the smallest size range (−75 μm). Heat treatment followed by 2 min of crushing concentrated 52.38 % of the anode material in the 4750 + 2500 μm range. For the cathode material, 2 min of direct crushing distributed 24.49 % in the −2500 + 1250 μm range, while 5 min of crushing accumulated 38.80 % in the −75 μm range. Heat treatment and 2 min of crushing resulted in 56.05 % of the cathode material in the −75 μm range, indicating improved liberation. The combination of heat treatment and mechanical treatment effectively liberates and reduces the size of the active materials, resulting in a higher cumulative mass fraction of finer particles (≤630 μm). Heat treatment at 600 °C for 15 min, followed by 2 min of crushing, dissociated current collectors (Al) from the cathode material, minimized the harmful gas emissions and produced fine particles (630 μm) with minimal Al content (0.8 wt%). The optimal heat treatment condition of 600 °C for 35 min achieved complete decomposition of PVDF and enriched 73.49 wt% cobalt and 5.41 wt% lithium in the black mass, superior to previous studies.

For the effective comminution and subsequent enrichment of mineral ores, comprehensive knowledge of their mineralogical and physical properties is required. Using an integrated methodology, this study evaluated samples of polymetallic Ni-Cu ore from Zapolyarnoe, Russia. Several analytical techniques were utilised, including optical microscopy, microindentation with Vickers geometry, the Point Load Test, and Mineral Liberation Analysis (MLA). The purpose of this study was to determine mineral associations, physical features, and enrichment during jaw crusher comminution. The acquired properties included the Point Load Strength Index, Vickers Hardness Number, and fracture toughness. The MLA method characterised seven fractions in terms of particle size distribution, degree of liberation, association, and modal mineralogy. Magnetite, pyrrhotite, pentlandite, and chalcopyrite were calculated in terms of wt% and their textural features. The enrichment of each ore phase in fractions with particle sizes smaller than 400 µm was determined. The influence of this enrichment was discovered to be correlated with various textural and structural parameters, such as intergrowth, grain size, and crack morphologies after indentations. In addition, the chromium content of magnetite contributed to an increase in the fracture toughness values. Despite the complexities involved, even limited samples of materials provide valuable insights into processing behaviour, emphasising the importance of considering mineralogical parameters in comminution studies. [ABSTRACT FROM AUTHOR]

The increasing amount of electronic waste (e-waste) has placed significant burdens on society and the environment, particularly with regards to waste printed circuit boards (WPCBs), which are essential in electronics manufacturing. As natural resources become scarce, it is crucial to effectively recycle and reclaim WPCBs due to their high value and large output. Comminuting printed circuit boards is a crucial step in enabling the recovery of valuable materials, and this review provides an in-depth analysis of WPCB comminution. It explores the structure, types, and composition of the WPCBs, including their mechanical properties. The review thoroughly surveys conventional mechanical comminution machinery and also discusses emerging technologies such as innovative pretreatment approaches, electrodynamic disintegration, high voltage electrical pulses, and abrasive waterjet cutting. The literature has been critically examined to identify research gaps and inconsistencies, and future directions for increased efficiency and sustainability are proposed. [ABSTRACT FROM AUTHOR]

Traditional dissolution of geologic samples often requires a significant time investment. Here, we present an alternative method for the dissolution of geologic materials using laser-driven hydrothermal processing (LDHP). LDHP uses laser energy directed onto a submerged sample, which increases the temperature and pressure at the liquid–sample interface and drives the hydrothermal dissolution coupled with photomechanical spallation, an ablative process. This uses focused 527 nm laser energy at 40 W average power, 1 kHz pulse repetition rate, and 115 ns pulse duration. When LDHP is performed on basalt geostandards (BCR-2 and BHVO-2) using the conditions outlined, we show that LDHP does not produce significant elemental fractionation and, thus, can be considered an alternative processing method to traditional mechanical crushing and acid digestion. Additionally, it is possible using LDHP to utilize the spatially confined beam to target and selectively isolate individual phases in a rock, potentially alleviating the need for mechanical separation of inclusions that are difficult to physically isolate. Furthermore, using this outlined method of LDHP, we demonstrate full dissolution of 120 mg of obsidian in 85 minu, meaning that LDHP is a potentially very useful method when sample processing is time sensitive. [ABSTRACT FROM AUTHOR]

Objective: To compare the treatment outcome for reconstruction plates and mini plates in treating comminuted mandibular fracture. Study Design: Randomized Controlled Trial. Setting: Department of Oral and Maxillofacial Surgery, Allama Iqbal Medical College/Jinnah Hospital, Lahore. Period: October 2021 to April 2023. Methods: All subjects presented for treatment of comminuted fractures of the mandible fulfilling the inclusion criteria at Jinnah Hospital Lahore Maxillofacial surgery department were included in the study, and were randomly allocated into group A and group B. The mini-plate osteosynthesis technique was used on Group A and Group B was treated by fixation with reconstruction plate. Results: A total of (n=30) patients were included in this study. Fifteen of these patients received mini-plate fixation (group A) and the remaining fifteen were treated with reconstruction plates (group B). The mean age was 29.4± 10.5 years. 80% of study subjects were male n=24. All patients of (group A) were treated via an intraoral approach. However, n=10 (66.6%) patients were treated by intraoral approach in (group B). Whereas the rest of the subjects (n=4) were treated with extra oral approach and (n=1) through combined intraoral and extra oral approach.100% stability at the fracture site was observed in both groups. Comparative occlusion status showed a nonsignificant p-value (p=1.000). Pearson chi-square value=0.0000a for plate exposure between both groups also shows a non-significant difference. The contour of the mandible was improved in 38.89% of (group A) population and 61.11% of group B patients. Conclusion: Mini-plate and reconstruction plate osteosynthesis are equally effective for the fixation of comminuted fractures of the mandible, considering postoperative occlusion status, stability of the fracture segment, and the possibility of plate exposure. [ABSTRACT FROM AUTHOR]

Advances in high-pressure grinding roll (HGPR) technology since its first commercial application in the cement industry include new roll wear protection techniques and new confinement systems. The latter contribute to reductions in the edge effects in an attempt to reach a more homogenous product size along the rolls. Additional advances in this technology have been made in recent years, while modeling and simulation tools are also reaching maturity and can now be used to subject such novel developments to detailed scrutiny. This work applies a hybrid approach combining advanced simulations using the discrete element method, the particle replacement model and multibody dynamics to a phenomenological population balance model to critically assess two recent advances in HPGR technology: spring-loaded cheek plates and the offset roller press. Force and torque controllers, included in the EDEM 2022.1 software, were used to describe the responses of the geometries in contact with the granular material processed. Simulations showed that while the former successfully reduced the lateral bypass of the material by as much as 65% when cheek plates became severely worn, the latter demonstrated lower throughput and higher potential wear but an ability to generate a finer product than the traditional design. [ABSTRACT FROM AUTHOR]

The rare-earth elements (REEs) have gained enormous economic and scientific attention due to their distinct properties and new applications. Nepheline syenite rock is an important primary source of rare earth minerals. The nepheline syenite rocks from the Rairakhol area, western Odisha, have been characterized for their rare earth mineralogical and textural characteristics. Preliminary beneficiation studies of these rocks were carried out to upgrade the REE values using falcon gravity separation and floatation technique. Hornblende, biotite, K-feldspar, albite, and nepheline are the major mineral constituents of the nepheline syenite where REE-bearing minerals occur as accessory minerals. The REE mineral phases present are zircon, sphene, apatite, allanite, britholite, and REE phosphate, with grain sizes ranging from 10 to 50 microns. Allanite and britholite occupy the intergranular spaces of major mineral phases and occur as thin lines or veins whereas sphene and zircon occur as inclusions within major mineral phases. The flotation study shows that the total REE content of the froth product could be enriched to 1696 ppm, which is three times more than the total REE content (563 ppm) of the feed sample. [ABSTRACT FROM AUTHOR]

Mineral deposits have shown decreasing ore grade and increasing complexity, which has led mining projects to experience increased capital and operating costs. Preconcentration is an alternative to minimize such costs. Notwithstanding the resulting rise in ore grade and reduction in feed mass, the generated tailings may contain significant amounts of the material of interest. In order to improve the mineral liberation at this stage, selective comminution proposes to explore different comminution mechanisms. This investigation compared three different crushing methods (jaw crusher, impact crusher, and high-pressure roller mill) for three different types of ores and the response of their products to pre-concentration, using a gravity method that was evaluated through heavy-liquid separation of the -6.35+3.35 mm crushed fraction. This fraction represents approximately 15% of the total sample, and is used as an indication of the gangue rejection potential for the -12+1.18 mm fraction. Copper and polymetallic ores showed good pre-concentration results for this size range at laboratory scale, with metallurgical recoveries greater than 90% and a rejection of over 20% of mass. Iron ore showed a 97% metallurgical recovery and 10% mass rejection. The impact crusher proved to be the best option for selective comminution for the polymetallic ore, with the highest metallurgical recovery. Finally, no significant differences were observed when using any of the three crushing mechanisms for the copper and iron ore. [ABSTRACT FROM AUTHOR]

Process simulations can be used to improve grinding circuit performance, which efficiently reduces operating costs. The population balance model (PBM) is widely accepted for grinding modeling because it can reproduce breakage events in tumbling mills, as described by Austin et al. (1984). In this study, a pseudodynamic model is introduced, integrating the PBM with the Monte Carlo Method to stochastically simulate variables in an industrial grinding circuit. This integrated approach enabled circuit simulations over a period of 2 hours, representing the operational variables as seen in historical data. Model validation showed a correlation of 0.74 in the product size distribution when comparing simulated outcomes with the original population. [ABSTRACT FROM AUTHOR]

In conventional fish soup processing, valuable aquatic resources like fish skins, bones, and scales are often squandered. This study was aimed at investigating if comminution combined with pressure-conduction treatment has the potential to enhance the reutilization of cooking residues. The different blending ratios of original soup (OS), made from the initial cooking of fish, and residue soup (RS), produced from processed leftover fish parts, were alternatively investigated to satisfy the new product development. Comminution combined with pressure-conduction treatment significantly increased the nutrient contents of calcium, soluble proteins and total solids in crucian carp soup (p < 0.05). With the increase in RS ratio, the decomposition of inosine monophosphate (IMP) and free amino acids was accelerated, but the accumulation of aromatic compounds was promoted simultaneously. In addition, the Maillard reaction may lead to a reduction in aldehydes, causing a diminution in the characteristic flavor of fish soup, while the formation of 1-octen-3-ol can enhance the earthiness of the fish soup. The electronic tongue test results and the sensory results showed that the blend ratio of OS and RS at 7:3 had a more significant umami and fish aroma (p < 0.05). Under this condition, the mixed soup has better nutritional values and flavor characteristics. [ABSTRACT FROM AUTHOR]

To clarify the mechanism of liberation in the comminution process of electronic scrap (e-scrap), we attempted to express the degree of liberation by first-order kinetic equation related to impact energy. Breakage energy measurements, comminution experiments, and discrete element method (DEM) simulations were conducted on two types of e-scrap with relatively simple structures. The mechanism of the liberation was estimated from the observation of the fractions in the comminution experiments. The results of the breakage energy measurements and DEM simulations supported the mechanism in terms of impact energy. The results of fitting first-order kinetic equations based on the cumulative specific impact energy from the DEM simulations and the degree of liberation in the experiments showed a high correlation. The fitting parameters of the firstorder kinetic equations were compared confirmed to be consistent with the mechanism of liberation and the breakage energy measurements, suggesting the numerical validity of the equations. In conclusion, it was shown that for e-scrap with relatively simple structures, the first-order kinetic equations of the cumulative specific impact energy calculated by DEM simulations can be used to evaluate the degree of liberation.

High Pressure Grinding Rolls (HPGR) have been used in the mining industry for decades. However, there are limited quantifications of the particle properties after comminution. Furthermore, the influence of microcracks in grinding provided by this technology has not been extensively quantified. In the recent work, there were two comminution paths tested: 1 (Jaw crusher + cone crusher + ball mill) and 2 (Jaw crusher + HPGR + ball mill). The possible weakening effect aiding ball mill grinding due to microcracks of HPGR path was shown via specific energy, fines generation and breakage rate measurements. To achieve a quantification about the impact of microcracks and the high rate of reduction rate of HPGR technology, first the product was reconstructed using Rosin Rammler's Weibull double formula and the similar particle size distribution was obtained by a conventional cone crusher. By this way the feed size distribution to the grinding stage remained constant regardless of the type of crushing process (HPGR or cone crusher). The results showed that the microfractures generated by the HPGR technology influence the specific energy consumption, fines generation and breakage rates. Ball mill after HPGR consumed 12.46 kWh/t of specific energy, however ball mill after cone crusher consumed 14.36 kWh/t of specific energy. The experimental methodology proposed in this paper maintains a consistent feed size range (-1500 to +41.31 µm) to show that the size reduction observed in the sample undergoing HPGR grinding is not the primary factor contributing to reduced energy consumption and increased fines generation. Instead, it is predominantly associated with the microfractures generated through the compression in HPGR technology; the energy reduction (optimization) of a grinding path is shown in the study. [ABSTRACT FROM AUTHOR]

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The aim of this study was to use landscape grass from species-rich orchards for biogas production, thus preserving these very valuable areas for future generations. Since these grass clippings have high lignocellulose content, the substrate has to be pretreated before being fed into the biogas digester. In this study, three different mechanical treatment processes (cross-flow grinder, ball mill and a mounted mower) were investigated and compared with untreated grass clippings. Chemical composition, specific methane yield, degradation kinetics and microscopic images were analyzed. In order to derive recommendations, the harvesting and pretreatment processes were examined in terms of energy demand, additional methane yield, and suitability of the substrate for use in biogas plants, taking into account conservation aspects. Within the pretreatment process, ball milling leads to the highest significant increase in specific methane yield of up to 5.8% and the fastest gas formation kinetics (lag time λBM: 0.01 ± 0.0 d; duration to reach half of total gas production ½M(x)BM: 5.4 ± 0.2 d) compared to the untreated variant (λUT: 1.02 ± 0.2 d; ½M(x)UT: 6.5 ± 0.2 d). A comparison of the energy required for the mechanical disintegration of the substrates with the increased yield of methane during the digestion process shows that the mechanical processing of these substrates appears to be useful. A positive energy balance was achieved for the cross-flow grinder (12.3 kWh tVS−1) and the ball mill (21.4 kWh tVS−1), while the Amazone Grasshopper left a negative balance (−18.3 kWh tVS−1), requiring more energy for substrate pretreatment than was generated as methane surplus. In summary, the pretreatment of landscape management grass is a suitable approach for utilizing agricultural residues efficiently in a biogas plant and thus contributing to sustainable energy production. [ABSTRACT FROM AUTHOR]

A discrete element method (DEM) based approach is used to study the relationships between material attributes (MAs), processing parameters (PPs), and quality attributes (QAs) for the knife milling of maize stalks. An approximate DEM shape model was conceptualized based on real maize stalks and calibrated based on experimental bending test data for flexural properties (elastic bending stiffness, elastic bending angle limit, elastoplastic ratio, etc.). DEM simulations of maize stalk comminution in a Jordan Reduction Solutions ("JRS") knife mill were performed to investigate the relationships between the MAs (maize stalk size and breakage stress limit), PPs (impeller rotational speed), and QAs (mass throughput and output particle size distribution (PSD)). The DEM results suggest that stalk length has little influence on mass throughput and PSD, whilst stalks with larger cross sections tend to generate larger sizes of milled particles given the same breakage stress limit. Both the DEM and experimental results show that faster impeller rotation (or higher power) does not necessarily generate higher throughput or smaller output PSD, especially for maize stalks of higher breakage stress limit. The correlations between these MAs, PPs and QAs are found highly stochastic, though breakage stress limit dictates mass throughput, regardless of stalk size. The DEM-predicted output particle size tended to match the experimental data with coarse PSDs based on sieve size but showed weakened fidelity with finer material, indicating the potential for further model improvement. [Display omitted] • Novel DEM model is introduced for simulation of knife milling of maize stalks. • Stalk shell breakage stress limit dictates mass throughput, regardless of stalk size. • Milled particle size is influenced by stalk cross-section area but not stalk length. • Faster impeller rotation may not produce higher throughput or smaller particle size. • DEM predictions match experiments on higher end of milled particle size distribution. [ABSTRACT FROM AUTHOR]

Comminution is the most power-demanding stage, and the lack of geometallurgical testing, often for financial reasons, may result in an inefficient operation. The Geopyörä rock breakage test was developed with the objective of making mineral variability data more accessible by providing both standard comminution parameters and rock mechanical properties at low cost and with a modest sample size, allowing a larger number of samples to be tested to reduce uncertainties and assure productivity. The objective of this work is to present the results of an extensive validation of this new rock breakage method against two of the main tests currently in use, namely the SMC and Bond ball mill work index tests. More than 100 samples have been tested and the results compared, showing that the new method can accurately estimate the parameters of the traditional tests. This confirms that the new test is a reliable tool for performing comminution and geometallurgical tests. [ABSTRACT FROM AUTHOR]

A particle scale model based on a full two-way coupling of the Discrete Element Method (DEM) and Smoothed Particle Hydrodynamics (SPHs) methods is applied to SAG mills. Motion and collisions of resolved coarser particles within an SAG mill are performed by the DEM component. Fine particles in the feed combine with the water to form a slurry, which is represented by the SPH component of the model. Slurry rheology is controlled by solid loading and fine particle size distribution for each volume of slurry. Transport, dispersion, and grinding of the slurry phase particle size distribution are predicted by solving additional coupled advection–diffusion equations in the SPH component of the model. Grinding of the finer particles in the slurry due to collisions and shear of the coarser particles (rocks and grinding media) is achieved via the inclusion of population balance terms in these equations for each SPH particle. This allows prediction of the transport of both coarser and finer material within the grinding and pulp chambers of an SAG mill, including the discharge performance of the mill. This particle-scale model is used to investigate the relative performance (throughput, product size distribution, resident particle size distribution, net power draw, wear) for an SAG mill at a pilot scale and a 36 ft industrial scale. The 36′ SAG mill considered is a geometrically scaled-up version of the 1.8 m Hardinge pilot scale mill but with a longer belly length, reflecting current SAG mill design preferences. The belly lifters are scaled to a lesser degree with a larger number of lifters used (but still many fewer liners than would typically be used in a large SAG mill based on conventional liner selection rules). The model shows that despite reasonable qualitative similarities, many aspects of the charge structure, slurry transport, coarse particle and slurry discharge through the grates, and the collision energy spectra vary in important ways. This demonstrates that a near purely geometric scale-up of an SAG mill is not sufficient to produce a comparable performance at the two physical mill scales. [ABSTRACT FROM AUTHOR]

Abstract Process simulations can be used to improve grinding circuit performance, which efficiently reduces operating costs. The population balance model (PBM) is widely accepted for grinding modeling because it can reproduce breakage events in tumbling mills, as described by Austin et al. (1984). In this study, a pseudo-dynamic model is introduced, integrating the PBM with the Monte Carlo Method to stochastically simulate variables in an industrial grinding circuit. This integrated approach enabled circuit simulations over a period of 2 hours, representing the operational variables as seen in historical data. Model validation showed a correlation of 0.74 in the product size distribution when comparing simulated outcomes with the original population.

Abstract Mineral deposits have shown decreasing ore grade and increasing complexity, which has led mining projects to experience increased capital and operating costs. Preconcentration is an alternative to minimize such costs. Notwithstanding the resulting rise in ore grade and reduction in feed mass, the generated tailings may contain significant amounts of the material of interest. In order to improve the mineral liberation at this stage, selective comminution proposes to explore different comminution mechanisms. This investigation compared three different crushing methods (jaw crusher, impact crusher, and high-pressure roller mill) for three different types of ores and the response of their products to pre-concentration, using a gravity method that was evaluated through heavy-liquid separation of the -6.35+3.35 mm crushed fraction. This fraction represents approximately 15% of the total sample, and is used as an indication of the gangue rejection potential for the -12+1.18 mm fraction. Copper and polymetallic ores showed good pre-concentration results for this size range at laboratory scale, with metallurgical recoveries greater than 90% and a rejection of over 20% of mass. Iron ore showed a 97% metallurgical recovery and 10% mass rejection. The impact crusher proved to be the best option for selective comminution for the polymetallic ore, with the highest metallurgical recovery. Finally, no significant differences were observed when using any of the three crushing mechanisms for the copper and iron ore.

This study aimed to explore the effects of different comminution degrees and the incorporation of a natural antioxidant on the quality attributes and oxidative reactions of turkey meat. Four distinctive turkey meat systems were established, namely: 3 mm minced treatment (M), 3 mm minced treatment with the addition of 200 ppm gallic acid equivalent Aloe vera (Aloe barbadensis Mill.) extract (MA), fine-ground treatment (FM), and fine-ground treatment with the addition of 200 ppm gallic acid equivalent Aloe vera extract (FMA). The evaluation encompassed an in-depth analysis of various quality parameters and the assessment of lipid-protein oxidation reactions throughout the storage period. The inclusion of Aloe vera extract (AE) increased the pH and b* values while simultaneously decreasing the L* and a* values. Conversely, increasing the degree of comminuting manifested an elevation in L* values, concomitant with a decline in a* values. Increased comminuting degree ratios were found to contribute to an exacerbation of oxidative reactions. Nonetheless, the strategic utilization of AE demonstrated its potential to effectively mitigate oxidative reactions during storage.

The Geopyörä breakage test uses two counter-rotating wheels to nip and crush rock specimens with a tightly controlled gap between rollers. This paper presents the detailed measures conducted to evaluate the accuracy and precision of energy measurements across various ore types using the Geopyörä. Force measurement was assessed just for its precision. The outputs were compared directly to the drop weight test (DWT) measures of fragmentation at the same energy and fitted A and b parameters. Test reproducibility was evaluated using a Round-Robin methodology, testing several samples in multiple laboratories. The results confirmed that the new test has sufficient accuracy to match DWT results and excellent precision to assure reproducibility.

In the manufacturing process of ship propellers, large quantities of grinding chips are generated. These grinding chips result from the finishing of the blade surfaces after the primary casting process of the propeller. The aim of this study was to investigate and compare different preparation processes used to produce chip powders with sufficient powder quality for the additive manufacturing process of directed energy deposition. The preparation of the samples was performed through different sieving, milling and re-melting processes. For the characterization of the prepared samples, powder analysis according to relevant industry standards was carried out. It was found that the re-melting processes result in superior powder quality for additive manufacturing in terms of particle size, morphology, and flowability. For some characteristics, the powder exhibits even better properties than those of commercial powders. Furthermore, the powder properties of the milled samples demonstrate a promising potential for use in additive manufacturing.

The engineered artificial mineral (EnAM) lithium aluminate (LiAlO2) is a promising candidate for the recycling of lithium from slags, which can originate from the reprocessing of batteries, for example. Derivatives of the natural product Punicine (1-(2′,5′-dihydroxyphenyl)-pyridinium) from Punica granatum have been proven to be effective switchable collectors for the flotation of this mineral as they react to light. In the present study, three Punicines were added to a planetary ball mill before grinding LiAlO2 to particle sizes suitable for flotation. We investigated the influence of Punicine and two derivatives with C10 and C17 side chains on the grinding results at different grinding times and conditions as well as on the yields in flotations. SEM images of the particles, IR and ICP–OES measurements provided insights into the Punicine–particle interactions. They showed that Punicines not only prevent the formation of hydrophilic and thus undesirable lithium aluminate hydroxide hydrate (LiAl2(OH)7 ▪ x H2O) surfaces in this process, as is unavoidable in aqueous flotation without this pretreatment, they also prevent the undesired release of lithium cations into the aqueous phase. Due to considerable hydrophobization of the particle surface of LiAlO2, nearly quantitative recovery rates of this engineered artificial mineral are achieved using the process described here.

Innovation in comminution is expected to continue unabated to address the inefficiencies that are inherent in comminution circuits. The rotary offset crusher (ROC) is a new comminution device with a promising performance potential in terms of throughput due to the enhanced speed of transportation induced by the centrifugal force of the discs. However, the processes driving the comminution of particles trapped in the conical space between the two discs of the crusher are not fully understood. To gain a better insight into the comminution process in this device, discrete element modeling (DEM) simulations were conducted to study the breakage of a single particle for the crusher operated under two different dynamic conditions, i.e., (1) a stationary top disc and (2) both discs rotating at the same speed. For both scenarios, the speed of the discs was varied between 550 and 2350 rpm. Experimental testwork was also conducted with the laboratory prototype to generate the data that were used to calibrate the breakage parameters of the Ab × t10 breakage model. Simulations were performed using polyhedral UG2 ore particles that were generated with the in-built particle generator in the DEM simulator. The simulated ROC, which is operated with both discs rotating, outperformed the ROC with a stationary top disc in terms of the specific input energy and throughput. The crusher with a stationary top disc is characterized by high shear forces (suggesting a higher wear rate), specific input energies greater than 1 kWh/t, and low throughputs (