Material Separation Processes Research Articles

Crack-tip cleavage/dislocation emission competition behaviors/mechanisms in magnesium: ALEFM prediction and atomic simulation

Structural properties and reliability of materials can be improved by increasing fracture toughness. At the atomic scale, the fracture is a material separation process, and the fracture toughness of materials is associated with the atomic-scale crack-tip behaviors/mechanisms. The crack-tip behaviors are relevant to the energy state of atoms in the system. Atomic thermal oscillation increases with increasing temperature, which may affect/alter the crack tip behaviors. This work is the first to investigate the temperature-dependent crack-tip cleavage/dislocation emitting competition in magnesium (Mg) using anisotropic linear elastic fracture mechanics theory, Density Functional Theory (DFT), and atomic simulation. Crack-tip behaviors are examined using a specially designed ‘K-field’ loads model. DFT calculations show that a single crystal system with lower entropy and higher Gibbs free energy implies stronger interatomic bonding that favors a higher KIc. Changes in the stress distribution initiate a brittle-ductile transition in crack-tip behavior. The ductile crack tip can be blunted by continuous crack-tip dislocations nucleation/slip, and the evolution of the ductile crack-tip geometry from sharp to semicircular structure significantly decreases the stress concentration at the crack tip. A new criterion of the crack-tip force vector is established, which reasonably explains the geometrical evolution of ductile crack tip where the angle θ between the crack plane and the slip plane is 0∘<θ<90∘ and θ=90∘. This work expands the atomic-scale brittle/ductile crack-tip behaviors/mechanisms of Mg, which provides a reference for crack-tip behavior analysis in engineering research.

In-situ repair of failed LiFePO4 cathode using residual Li- and C-containing impurities from active material separation process

Effectively recovering spent lithium-ion batteries can reduce resource waste and environmental pollution. LiFePO4 (LFP) batteries have been widely used in new energy vehicles. The main reason for the performance degradation of LFP cathodes is the loss of Li, oxidation of Fe, and the destruction of crystal structure and surface carbon layer. Here, an in-situ repair strategy of high-temperature calcination, using impurities remaining in cathode blackmass (e.g., LiPF6, LiPO3, Fe2O3, acetylene black, binder, and electrolyte) as raw materials, was proposed. During the calcination process, the residual LiPF6 is converted into Li, acting as a lithium source to fill the vacancies. The residual binder and electrolyte are pyrolyzed into amorphous carbon and carbon nanotubes, which deposit on the LFP particles to repair the missing carbon layer and enhance the conductivity of the electrode material. The pyrolytic carbon and residual acetylene black can provide a reducing atmosphere, converting Fe3+ to Fe2+. Additionally, the residual LiPO3 and Fe2O3 impurities undergo recrystallization forming new LFP. The failed LFP was restored to the same level as commercial LFP by calcining at 750 °C for 3 h. This in-situ repair strategy reduces the input of raw materials, providing a valuable reference for large-scale recycling of lithium batteries.

Degradation of organic pollutants accompanied by the ultrasonic separation of the spent lithium-ion battery cathode materials.

Since the majority of valuable components in spent lithium-ion batteries, such as lithium, exists in the electrode materials, common studies focused on the treatment of the cathode materials, which ignored the harm of residual electrolyte. The cavitation and thermal effects produced by ultrasonic can not only be used for the separation of electrode materials, but also have a wide range of applications in the field of sewage pollutant degradation. This work used ultrasonic to treat simulated electrolyte (propylene carbonate (PC)) solution of spent lithium-ion batteries, explored the effect of ultrasonic power, the addition amount of H2O2 solution (30 wt%) and reaction temperature on the degradation of electrolyte, and analysed the ultrasonic degradation reaction from the perspective of reaction kinetics. And the synchronous experiment of cathode material separation and electrolyte degradation was conducted under the optimal conditions. The results showed that the highest degradation efficiency of PC in the electrolyte was 83.08% under the condition of ultrasonic power of 900 W, the addition of H2O2 solution (30 wt%) of 10.2 mL, reaction temperature of 120°C and reaction time of 120 minutes, and the separation efficiency was 100%. This work reduced the environmental and health risks in the cathode material separation process and was conducive to the green development of spent lithium-ion battery recycling technology.

Influence of the Geometrical Features of the Cutting Edges of Abrasive Grains on the Removal Efficiency of the Ti6Al4V Titanium Alloy.

The shape of the cutting blades of the abrasive grains has an influence on the material separation process in the machining zone. The paper analyzes the influence of the geometrical parameters of the abrasive grains (rake angle γ, apex angle ε, opening angle α), as well as width bz and length bb of the cutting zone on the material removal efficiency. The material removal efficiency was determined taking into account the volume of the removed material VG and the volume of lateral piles-up VR. The analyses were carried out on the basis of the results of experimental and simulations using the finite element method. The relationship between the selected geometric parameters characterizing the cutting zone and the coefficient characterizing the efficiency of the material removal process was determined. A strong influence of the opening angle α as well as the width bz and length bb of the cutting zone on the material removal process by abrasive grain was demonstrated. It was observed that the wide cutting edge, and thus the large opening angle α of the grain, reduced the size of the pile-ups and more effectively removed the chip material.

Ergonomic aspects of material separation process modeling on stationary screw surfaces

The motion of material particles on gravitational surfaces, ie the motion of particles on surfaces under the action of its own weight, is used in special devices for their separation by physical and mechanical properties. For this purpose stationary screw surfaces of a steady step are applied. A number of papers have now considered the relationship between the kinematic parameters of motion, the coefficient of friction and the design parameters of the separator, when its surface is a deployable helicoid. The purpose of the study is to investigate helical surfaces with different design parameters in order to improve their separation ability through mathematical and geometric modeling of the process without making surface models. The problem of finding the trajectory of a material particle on the surface under the action of its own weight is preceded by the problem of finding the trajectory on an inclined plane. If a material particle with a certain initial velocity vо and a certain angle of inclination to the horizon falls on an inclined plane, it will move along a certain curve (in the absence of friction and air resistance, the trajectory will be a parabola). A system of equations is obtained, which describes the motion of a material point on the gravitational surface in the general case. If it is created for a specific surface, nonlinear and numerical methods must be used to integrate it. Modern software products allow not only to find the trajectory of the particle, but also to show it on the surface and even make an animation that essentially replaces high-speed shooting. This approach makes it possible to study the kinematic parameters of motion on different helical surfaces without full-scale samples of these surfaces, which significantly reduces the cost of finding the right surfaces. The motion of particles along a helical conoid and a deployable helicoid is considered. Simulation of the motion of a material particle on helical surfaces and its study by modern means of numerical integration and visualization have shown that for different surfaces the nature of the motion of the particle will also be different. When moving on the surface of the helical conoid, the particle in the presence of friction first accelerates, and then stops at a considerable distance from its axis. To prevent this, you need to take a limited compartment of the conoid both in height and on its periphery. When a particle moves on the surface of a deployed helicoid, its velocity becomes constant over time, and the trajectory after that will be a helical line. Key words: particle motion, helical surfaces, helical conoid, deployable helicoid, simulation

Математичне моделювання процесу розділення матеріалу на стаціонарних гвинтових поверхнях

The motion of material particles on gravitational surfaces is used in special devices for their separation by physical and mechanical properties. For this purpose stationary screw surfaces of a constant step are applied. The purpose of the study is to investigate helical surfaces with different design parameters in order to improve their separation ability through mathematical and geometric modeling of the process without making surface models. The problem of constructing the trajectory of a material particle on the surface under the action of its own weight is preceded by the problem of finding the trajectory on an inclined plane. Modern software products make it possible not only to find the trajectory of the particle, but also to show it on the surface and even make an animation, which essentially replaces high-speed camera recording. This approach makes it possible to study the kinematic parameters of motion on different helical surfaces without full-scale samples of these surfaces, which significantly reduces the cost of finding the desired surfaces. The trajectories of the particle on the surface of the helical conoid and the deployable helicoid are obtained. It is established that when moving on the surface of a helical conoid, the particle in the presence of friction first accelerates, and then stops at a considerable distance from its axis. To prevent this, its need to take a limited compartment of the conoid both in height and on its periphery. When a particle moves on the surface of a helicoid, its velocity becomes constant over time, and the trajectory after that will be a helical line. The developed approaches make it possible to study the process of material separation not only after stabilization of motion, but also during the transition process, as it became possible to visualize it. This will allow you to choose the surface compartment of the optimal size, which will provide the desired productivity of separation due to the dispersion of particles with different coefficients of friction on its surface. Key words: material particle, trajectory, material separation, helical conoid, helicoid

SIMULATION-DRIVEN DEVELOPMENT FOR COARSE COMMINUTION PROCESS - A CASE STUDY OF GEITA GOLD MINE, TANZANIA USING PLANTSMITH PROCESS SIMULATOR

AbstractA comminution process is a material size reduction and separation process which is primarily used in the aggregates and the minerals processing industry. Knowledge related to equipment’s operation, raw material properties, operational strategies, control system, maintenance, etc. is needed to design a capable plant. New needs are arising from the industry for existing operational crushing plants such as investigation for improvements, upscaling, and downscaling of the capacity. The paper presents an application of simulation-driven development for a crushing plant in an existing gold processing plant. Due to the change in ore characteristics and the need for optimizing the cost of operation, it is required to investigate the opportunities for improvement and alternative options for downscaling the capacity of the plant. A systematic process for configuring, developing, and evaluating alternative concepts using a process simulation tool is presented. The results show the process of generating knowledge for alternative crushing plant operation settings and how the choices can be selected and eliminated using boundary conditions. The evaluation presents possible improvements and alternative concepts with their opportunities and pitfalls.

Development of Material Separation Process for Recycling Waste Coffee Capsules

Development of Material Separation Process for Recycling Waste Coffee Capsules

Separation and Purification of Hydrocarbons with Porous Materials

AbstractThis Minireview focuses on the developments of the adsorptive separation of methane/nitrogen, ethene/ethane, propene/propane mixtures as well as on the separation of C8 aromatics (i.e. xylene isomers) with a wide variety of materials, including carbonaceous materials, zeolites, metal–organic frameworks, and porous organic frameworks. Some recent important developments for these adsorptive separations are also highlighted. The advantages and disadvantages of each material category are discussed and guidelines for the design of improved materials are proposed. Furthermore, challenges and future developments of each material type and separation processes are discussed.

Design and Fabrication of Faulty Product Detection and Separation System

With recent advances in industrial technologies, automation has become an indispensable part in the manufacturing world. Industrial environments are adopting more and more aspects of automation to increase product quality, accuracy, and reduce product costs. Conveyor systems are used wildly in manufacturing industries. This automated conveyor system works by detecting the size of the material in the conveyor using ultrasonic sensors. The microcontroller analyses this data from the ultrasonic sensor and then directs the pneumatic cylinder material to different directions, height-wise, depending on the height of the material. The position of the conveyor is indicated by a 16X2 liquid crystal display and LED. This project thus automates the material separation process in the conveyor to improve efficiency and increase productivity.

A Particle-Based Cohesive Crack Model for Brittle Fracture Problems.

Numerical simulations of the fracture process are challenging, and the discrete element (DE) method is an effective means to model fracture problems. The DE model comprises the DE connective model and DE contact model, where the former is used for the representation of isotropic solids before cracks initiate, while the latter is employed to represent particulate materials after cracks propagate. In this paper, a DE particle-based cohesive crack model is developed to model the mixed-mode fracture process of brittle materials, aiming to simulate the material transition from a solid phase to a particulate phase. Because of the particle characteristics of the DE connective model, the cohesive crack model is constructed at inter-particle bonds in the connective stage of the model at a microscale. A potential formulation is adopted by the cohesive zone method, and a linear softening relation is employed by the traction–separation law upon fracture initiation. This particle-based cohesive crack model bridges the microscopic gap between the connective model and the contact model and, thus, is suitable to describe the material separation process from solids to particulates. The proposed model is validated by a number of standard fracture tests, and numerical results are found to be in good agreement with the analytical solutions. A notched concrete beam subjected to an impact loading is modeled, and the impact force obtained from the numerical modeling agrees better with the experimental result than that obtained from the finite element method.

Mathematical Modeling of Kinetics and Optimization of Grain Material Separation Processes on Sieve Classifiers

A mathematical model of the kinetics of thin-layer separation of granular materials on multiple-deck sieve classifiers was constructed based on the theory of Markovian processes. We identified the kinetic models using the oversize residues from sieves. The problem of optimization is formulated and solved in a multi-criteria formulation, where the criteria are selected device performance and the separation efficiency on its sieves.

Probabilistic Approach to the Separation of Grain Material

Possible ways to improve operating elements of grain cleaning machines due to mobilization factors directly influence on qualitative and quantitative aspects of separation are presented. In relation to sieve grain cleaning machine the technological process of grain mixture separation on the sieve is presented as a block diagram. Some variants of mathematical description (models) consideration of grain material separation process are also given. The dependencies between parameters of grain material and uniformity of seed distribution on sieve area are given. Calculation formulas and schemes of definition probability of a particle entering the hole are presented. It is established, that in the range β from 0 to 30° probability of particle passage increases from 0.315 to 0.548, that is 1.74 times.

Evaluating carbon footprint of municipal solid waste treatment: Methodological proposal and application to a case study

This paper applies the Life Cycle Assessment methodology to develop a simple method to calculate the carbon footprint of the municipal solid waste treatment stage. This simple and structured methodological procedure takes into account: i) direct greenhouse gas emissions produced in waste treatment, taking place within the city boundary (scope 1 of international carbon footprint standards); ii) indirect greenhouse gas emissions related to the use of grid-supplied electricity, as well as fuel production and distribution (scopes 2 and 3 emissions as per international carbon footprint standards); and iii) avoided greenhouse gas emissions as a result of the products obtained (if any) that can replace other products or the raw materials used to produce them. Madrid City (a representative European city), the capital of Spain, was used as a case study to prove the validity and usefulness of the proposed methodology. In this city, 344 kg of municipal solid wastes were produced per inhabitant in 2013. These wastes were collected separately in different fractions (packaging, glass, paper/cardboard and mixed waste, including organic material). Mixed waste and packaging fractions were processed at the Valdemingómez Technology Park. The current treatment stage was compared with several alternative scenarios which describe hypothetical management routes for the different waste fractions. The carbon footprint for the current situation is equal to 224 kg CO2 eq/twaste. In comparison to the worst situation, corresponding to the scenario in which municipal wastes were landfilled without energy recovery, the current scenario reduces its carbon footprint by 1597 kg CO2 eq/twaste (a reduction of 88%). Improvements in the material separation and recovery processes, along with the implementation of biological treatments for the organic fraction, clearly contribute to reducing the carbon footprint of the municipal solid wastes handled in the city of Madrid.According to the obtained results, the scenarios based on a total recovery of valuable materials and waste-to-energy or anaerobic digestion treatments present the lowest carbon footprint because burden avoided is more important than direct and indirect emissions from treatments. In addition, the consumption of electricity and the emissions derived from its generation (mix of generation), can increase the carbon footprint of power-intensive treatments.

Rolling contact fatigue and wear in rail steels: An overview

Rolling contact fatigue (RCF) and wear of rails are two critical failure generating problems of railway transport system worldwide. This paper presents an overview of investigations and state of the art knowledge on the mechanisms of RCF and wear studies revealed till date. Notably, majority of railway accidents are found to be promoted by RCF induced rail fracture and train derailments. The operational mechanism of wheel/rail contact introduces varied proportion of stick-slip formation from the involved rolling-sliding phenomenon. Sliding induced friction contributes many variety of defects of which wear is a prominent material separation process that in severity can also promote crack initiation. In view of the gravity of RCF and wear present study, as a first step, overviews their characterisation approaches. This understanding will help to formulate strategies in investigating the problems to evolve scientific and technological strategies for their mitigation.

Numerical evaluation of blast resistance of RC slab strengthened with AFRP

In this study, in order to precisely evaluated the retrofitting effectiveness of the Aramid Fiber Reinforced Plastic (AFRP) sheet on the blast response of reinforced concrete (RC) slab, a refined non-linear finite element model is proposed for simulating of the structural response of RC slab strengthened with AFRP under blast loads. The complicated material models are applied in the simulation considering the high strain rate effects of the materials as well as the dynamic interfacial behavior between AFRP and concrete. Also, a appropriate erosion criterion technique is specially applied to capture the fracture and material separation process during the detonation of the explosive. At first, the numerical model of an actual laboratory sample of a conventional RC slab subjected to blast loads was simulated and verified using available experimental results. Then with the calibrated model, numerical simulations of RC slabs strengthened with AFRP to blast loadings are carried out. The numerical results of strengthened and non-strengthened RC slab (i.e., conventional slab) are compared to investigate the retrofitting effectiveness of AFRP on blast-resistant performance of RC slabs. In addition, a comprehensive investigation on the blast responses of FRP-strengthened RC slabs affected by these parameters, i.e. different AFRP layer, FRP type, strengthening mode, FRP bond strength and TNT mass, are also reported.

Performance evaluation of material separation in a material recovery facility using a network flow model

In this paper, we model the recycling process for solid waste as performed in a material recovery facility. The intent is to inform the design and evaluation of a material recovery facility (MRF) in order to increase its profit, efficiency and recovery rate. We model the MRF as a multi-stage material separation process and develop a network flow model that evaluates the performance of the MRF through a system of linear equations. We estimate the parameters of the network flow model from historical data to find the best fit. We validate the model using a case-study of a light-packaging recovery section of an MRF in Spain. Additionally, we examine how uncertainty in the input material composition propagates through the system, and conduct a sensitivity analysis on the model parameters.

Computer-aided drug design to explore cyclodextrin therapeutics and biomedical applications.

Cyclodextrin (CD) is a subset of the macrocyclic structural class, which is an important class of small organic agents that are useful functional excipients. They have wide range application possibilities in different fields of sciences such as material preparation, medicine, analytical chemistry, and separation processes. They are used widely in pharmaceutical formulations and drug delivery for increasing the water solubility of low soluble drugs and drug candidates. Due to the ring structure, they behave differently than smaller molecules and may be capable of hitting new classes of targets. A macrocyclic molecule presents varied functionality and stereochemical complexity in a pre-organized conformation of the ring structure. This can result in high selectivity and affinity for protein targets while conserving enough bioavailability to arrive at intracellular locations. Regardless of these valuable features, and the verified success of several marketed macrocycle drugs isolated from natural compounds, this class has been little explored in drug development. This study describes some of the key features of the CDs therapeutic discovery. Also, the application of computational chemistry approaches such as QSAR/QSPR, molecular docking, and molecular/quantum mechanics for modeling of CD-drug system is reviewed briefly.

Scalability and extensionality of innovative Chinese medicine preparation under guidance of component structure theory

Chinese medicine preparation is a science to study how to make raw material into suitable dosage forms to be used in clinical operations. Its study scope is significantly different from traditional chemical drugs. As is known, the ingredients of Chinese medicine are complex and various, as a result, the composition of the ingredients is not clear and the property is not unified. The pre-treatment process is the key factor to affect the druggability, safety and efficacy of the Chinese medicine. The connotation of Chinese medicine is a huge systematic project, not only including the traditional dosage form design process but also including the components structure optimization process on material basis, components extraction, separation and purification process, components characterization process as well as the pharmacological and toxicological study processes which aim to select suitable dosage form to exert the maximum drug efficacy and evaluate the properties of preparations. Therefore, according to the requirement of modern innovative preparations and based on the integrity and systematicness of Chinese medicine, in this paper we will explore the scalability and extensionality of modern Chinese medicine, including the material basis of Chinese medicine based on component structure theory; separation, refining and purification of components; component structure optimization and network pharmacology and regulation, as well as biopharmaceutics properties of representative components, and we will construct the multi-unit drug delivery system and Chinese medicine multi-dimensional dynamic quality control system. This paper elaborates the scientific connotation and systematicness of modern Chinese preparation, and provides ideas and methods for the development of modern innovative Chinese preparations.

Numerical simulation of damage evolution for ductile materials and mechanical properties study

This paper presents results of a numerical modelling of ductile fracture and failure of elements made of 5182H111 aluminium alloys subjected to dynamic traction. The analysis was performed using Johnson-Cook model based on ABAQUS software. The modelling difficulty related to prediction of ductile fracture mainly arises because there is a tremendous span of length scales from the structural problem to the micro-mechanics problem governing the material separation process. This study has been used the experimental results to calibrate a simple crack propagation criteria for shell elements of which one has often been used in practical analyses. The performance of the proposed model is in general good and it is believed that the presented results and experimental-numerical calibration procedure can be of use in practical finite-element simulations.