Non-ferrous Metal Particles Research Articles

Generation mechanism and empirical model of eddy current force and torque in drum-type eddy current separation

Enhancing the recovery efficiency of non-ferrous metals in eddy current separation is of great significance. In this study, the accuracy of the simulation model was verified by comparing the eddy current force. The transformation mechanism of the Lorentz forces into the eddy current force and torque in non-ferrous metal particles was revealed by analyzing various physical fields. Then, the influence of magnetic field parameters on eddy current, eddy current force, and torque was studied. It shows that the eddy current force and torque are affected by the vector gradient of the magnetic field and the magnetic flux density, respectively. Additionally, the time derivative of the magnetic field impacts the magnitude of the eddy current force and torque by controlling the eddy current. On this basis, the empirical models of eddy current force and torque were established by similarity theory. The results obtained can improve and expand the application of eddy current separation.

A novel TMR sensor based on digital lock-in amplifier technology for portable oil multipollutant detection system

Metal particles identification in lubrication oil has become a popular technology to perform the fault diagnosis and health monitoring of machinery equipment. Unfortunately, the magnetic signals induced by particles are generally weak or even submerged in heavy noise. The sensitivity of conventional inductive sensors for detecting non-ferrous particles can still be improved to better distinguish between different non-ferrous particles. Based on the above issues, this paper proposed a novel tunnel magnetoresistance (TMR) sensor based on digital lock-in amplifier (DLIA) technology to detect ferrous and multiple nonferrous metallic particles in oil under noisy conditions. Moreover, compared to conventional inductive sensor structures, the proposed method can effectively reduce the sensor volume, which is particularly necessary when considering the design of portable oil multipollutant detection system. Owing to the high resolution of TMR and outstanding versatility of DLIA for extracting weak signal overwhelmed in noise, the detection sensitivity can be improved tremendously. Extensive simulation and experimental results validated that the proposed approach was practical and effective. Based on the experimental results, the minimum values of detectable diameter could be computed as 24.76 µm for iron particles, 81.34 µm and 82.32 µm for copper and aluminium particles respectively.

Optimal design of a new Halbach array magnetic roller with axial eddy current force

Non-ferrous metal recovery is of great significance to the sustainable development of resources. Small-sized nonferrous metal particles account for a large proportion of nonferrous metals in solid waste, but the recovery efficiency is low. Eddy current separation is an important technology for physical recovery of non-ferrous metals. Optimizing its magnetic roller is extremely important for improving the recovery efficiency and economy of small-sized non-ferrous metals. In this study, COMSOL Multiphysics is used to establish a three-dimensional transient simulation model of the vertical rotary-drum ECS. On the basis of the two-dimensional Halbach array magnetic roll, the magnetic system of the magnetic roll is designed in the axial direction, so that the particles are subjected to the axial eddy current force opposite to the direction of gravity for the first time. This force can slow down the falling velocity of particles, increase the difference in falling trajectory and repulsion distance, improve recovery efficiency. In addition, due to the generation of axial eddy current force, the interlayer dislocation type magnetic roller can achieve the same recovery effect by only using 1/3 of the length of the basic type magnetic roller. Based on the electromagnetic theory and particle dynamics, by comparing the axial magnetic density distribution of different magnetic rollers, the axial eddy current force and the trajectory of non-ferrous metal particles, the generation mechanism of the axial eddy current force and the magnetic system structure that can generate the axial eddy current force are clarified.

Copper particle detection method by in-situ resistance background implemented in conductance-path recognition algorithm (iRB-CPR) among dominant aluminum particles

Copper particle has been detected among dominant aluminum particles by in-situ resistance background implemented in conductance-path recognition algorithm (iRB-CPR). The iRB is a particle volume fraction prediction from a resistance background database measured by shifted-four-wire measurement (SRM) in various particle arrangements. The CPR is adopted from a decision tree algorithm to predict the particle conductance path by comparing the real-condition resistances classified by iRB. The selected resistance background is used as a denominator to normalize the resistance measurement by SRM under unknown particle arrangement in the real condition. Finally, Cu is detected by comparing the normalized resistances with the normalized spatial-mean resistance. The iRB-CPR successfully suppress the resistance deviation ratio in the simulation 〈r〉sim 93.8% and experiment 〈r〉exp 73.9%. Moreover, the Cu detection by iRB-CPR satisfies give a low error ES = 6.11% at S = 180 under α = 10%. This research opens a new detection modality as a part of non-ferrous metal particles recovery.

A Highly Sensitive In-Line Oil Wear Debris Sensor Based on Passive Wireless LC Sensing

This paper presents ${a}$ new, and efficient, wear debris detection sensor based on passive wireless LC sensing approach. This sensor enables online monitoring of metal debris in hydraulic flow tubes with large thickness, employed in high-pressure applications. In conventional inductive debris sensors, the coil is kept outside the tube. $(i)$ Hence, for thick tubes, the sensitivity is extremely low. If the coil is kept inside the tube, holes are required to connect it to the measurement unit (MU). (ii) This limits the pressure withstanding capacity. The proposed sensor solves these two problems using the wireless LC sensor approach, wherein the MU is connected to an outer coil (outside the thick tube), and an inner coil is kept close to the oil, with debris. Thus, it is highly sensitive to the debris. It requires no electrical connection to the MU. The outer coil is energized from an AC signal at the parallel resonance frequency of the system, drawing minimum current from the source. The change in phase of this current, due to the change in inductance of the inner coil as debris passes, is measured using ${a}$ phase-sensitive detector. This highly sensitive measurement approach together with the fact that the inner coil is close to the oil, helps to achieve high sensitivity, and enables monitoring flow tubes with large diameter and thickness. ${A}$ prototype of the proposed wireless LC debris sensor has been developed (inner and outer diameters of 25.4 mm and 80 mm respectively), integrated into ${a}$ hydraulic circuit and tested. The output was not only very sensitive to ferrous and non-ferrous metallic particles but also helps in distinguishing them.

A new model of trajectory in eddy current separation for recovering spent lithium iron phosphate batteries

Eddy current separation (ECS) is an environment-friendly technology for separating nonferrous metallic particles whose size was from 2 mm to 10 mm. No wastes are generated in ECS. ECS quality of nonferrous metals from solid wastes is rather low in the production practice of spent lithium iron phosphate (LFP) batteries recovering. Repeating separation even manual sorting is required in the production. The traditional method of falling point prediction based on eddy current mechanics uses equivalent acceleration to replace separation motion curves. These curves have low precision and are unsuitable for predicting the motion trajectory of small particle size of sorted materials. In this work, eddy current separation of positive and negative plates in a crushed product of spent lithium iron phosphate battery is used as an example to establish the force and kinematics models of different materials in the eddy current separation. An iterative method, rather than average speed method, is used to improve the accuracy of the model. Displacement interval replaces disengagement angle as a separating index to improve the model’s intuitiveness and practical guidance. In the range of 2–20 mm, test results are consistent with simulation results. The copper and aluminium foils at a magnetic roller speed of 800r/min can be separated to a maximum particle size ratio of 1.72, and the maximum particle size ratio of copper and positive electrode sheets can be large. This paper provided an environmental-friendly and effective technology for separating nonferrous metals from crushed spent LFP batteries.

Electrodynamic Concentration of Non-ferrous Metallic Particles in the Moving Gas-powder Stream: Mathematical Modeling and Analysis

The paper presents theory, modeling, and analysis of a novel electrodynamic concentration approach for submillimeter-sized conductive metal particles focusing in moving gas-powder stream. Such method is of particular interest in blown-powder feeding fabrication industry (e.g., powder-fed additive manufacturing) to generate a tightly focused powder stream. Conceptual design of a concentration generator is proposed with two different configurations: The doublet Halbach permanent magnet quadrupoles (doublet-Halbach-PMQs) and the doublet electromagnet quadrupoles (doublet-EMQs). Analytical models for magnetic forces and concentration angles were built. Numerical calculations were conducted for pure aluminum particles with a radius of <math xmlns='http://www.w3.org/1998/Math/MathML'> <mrow> <mn>50</mn><mo><</mo><msub> <mi>R</mi> <mi>p</mi> </msub> <mo>≤</mo><mn>500</mn><mtext> </mtext><mi>μ</mi><mi>m</mi></mrow> </math>. It was found that the magnetic force and the concentration angle increase with an increase of the particle size. The numerical results indicate that the proposed concentration generator with doublet-Halbach-PMQs configuration cannot be effectively used for small-size particle concentration. By contrast, the concentration generator with doublet-EMQs configuration under high frequency is capable to concentrate particles with a radius of <math xmlns='http://www.w3.org/1998/Math/MathML'> <mrow> <msub> <mi>R</mi> <mi>p</mi> </msub> <mo>></mo><mn>150</mn><mtext> </mtext><mi>μ</mi><mi>m</mi></mrow> </math>. The particles with a radius of <math xmlns='http://www.w3.org/1998/Math/MathML'> <mrow> <msub> <mi>R</mi>

Solid particles, water drops and air bubbles detection in lubricating oil using microfluidic inductance and capacitance measurements

The contaminants in lubricating oil can be used to judge the operating conditions of a machine, which can be divided into solid, liquid and gas depending on the form. Microfluidic devices based on the electrical technique are presented to detect ferrous metal particles, different kinds of non-ferrous metal particles, non-metallic particles, water drops and air bubbles. The ferrous metal particle and nonferrous metal particle can be detected by the inductance pulses and differentiated by the directions of inductance pulses based on the permeability of particles; a method that calculates the electrical conductivity of a particle is introduced to differentiate different kinds of nonferrous metal particles by measuring the inductance changes caused by the particles. Continuously and evenly distributed tiny ferromagnetic metal particles are introduced to detect non-metallic particles. Water drops and air bubbles can be detected by the capacitance pulses and differentiated by the directions of capacitance pulses.

Differentiation of nonferrous metal particles in lubrication oil using an electrical conductivity measurement-based inductive sensor.

A method that measures the electrical conductivity of metal based on monitoring the inductance changes of coils via an inductive sensor is introduced in this work to differentiate metal particles in lubrication oil. Theoretical analysis coupled with experimentation is employed to differentiate varieties of nonferrous metal particles, including copper and aluminum particles, ranging from 860 μm to 880 μm in diameter. The results show that the inductive sensor is capable of the identification and differentiation of nonferrous metal particles in lubrication oil based on the electrical conductivity measurement. The concept demonstrated in this paper can be extended to inductive sensors in metal particle detection and other scientific and industrial applications.

Performance Determination of Novel Design Eddy Current Separator for Recycling of Non-Ferrous Metal Particles

Improvements were made in the study for the design of the conventional Eddy Current Separator (ECS) used for separating small sized non-ferrous particles in the waste. These improvements include decreasing the air gap between the material and magnetic drum, making the drum position adjustable and placing the splitter closer to the drum. Thus, small particles were separated with high efficiency. The magnetic drum was removed from inside the ECS conveyor belt system as design change and was placed as a separate unit. Hence, the force generated on the test material increased by about 5.5 times while the air gap between the non-ferrous materials and drum decreased from 3 mm to 1 mm. The non-metal material in the waste is separated before the drum in the novel design. Whereas non-ferrous metal particles are separated by falling into the splitter as a result of the force generated as soon as the particles fall on the drum. Every material that passes through the drum can be recycled as a result of moving the splitter closer to the contact point of the drum. In addition, the drum can also be used for the efficient separation of large particles since its position can be adjusted according to the size of the waste material. The performance of the novel design ECS was verified via analytical approaches, finite element analysis (FEA) and experimental studies.

Key factors of eddy current separation for recovering aluminum from crushed e-waste

Recovery of e-waste in China had caused serious pollutions. Eddy current separation is an environment-friendly technology of separating nonferrous metallic particles from crushed e-waste. However, due to complex particle characters, separation efficiency of traditional eddy current separator was low. In production, controllable operation factors of eddy current separation are feeding speed, (ωR−v), and Sp. There is little special information about influencing mechanism and critical parameters of these factors in eddy current separation. This paper provided the special information of these key factors in eddy current separation of recovering aluminum particles from crushed waste refrigerator cabinets. Detachment angles increased as the increase of (ωR−v). Separation efficiency increased with the growing of detachment angles. Aluminum particles were completely separated from plastic particles in critical parameters of feeding speed 0.5m/s and detachment angles greater than 6.61deg. Sp/Sm of aluminum particles in crushed waste refrigerators ranged from 0.08 to 0.51. Separation efficiency increased as the increase of Sp/Sm. This enlightened us to develop new separator to separate smaller nonferrous metallic particles in e-waste recovery. High feeding speed destroyed separation efficiency. However, greater Sp of aluminum particles brought positive impact on separation efficiency. Greater Sp could increase critical feeding speed to offer greater throughput of eddy current separation. This paper will guide eddy current separation in production of recovering nonferrous metals from crushed e-waste.

Optimization of wet shaking table process using response surface methodology applied to the separation of copper and aluminum from the fine fraction of shredder ELVs

With the purpose of reducing the waste generated by end-of-life vehicles (ELVs) by enhancing the recovery and recycling of nonferrous metals, an experimental study was conducted with the finest size fraction of nonferrous stream produced at an ELV shredder plant. The aim of this work was to characterize the nonferrous stream and to evaluate the efficiency of a gravity concentration process in separating light and heavy nonferrous metal particles that could be easily integrated in a ELV shredder plant (in this case study the separation explicitly addressed copper and aluminum separation). The characterization of a sample of the 0–10mm particle size fraction showed a mixture of nonferrous metals with a certain degree of impurity due to the present of contaminants such as plastics. The majority of the particles exhibited a wire shape, preventing an efficient separation of materials without prior fragmentation. The gravity concentration process selected for this study was the wet shaking table and three operating parameters of the equipment were manipulated. A full factorial design in combination with a central composite design was employed to model metals recovery. Two second order polynomial equations were successfully fitted to describe the process and predict the recovery of copper and aluminum in Cu concentrate under the conditions of the present study. The optimum conditions were determined to be 11.1° of inclination, 2.8L/min of feed water flow and 4.9L/min of wash water flow. All three final products of the wet shaking table had a content higher than 90% in relation to one of the metals, wherein a Cu concentrate product was obtained with a Cu content of 96%, and 78% of Cu recovery and 2% of Al recovery.

Metal Enrichment of Finely Ground Electronic Waste using Eddy Current Separation

The applicability of Eddy Current Separation (ECS) in the processing of relatively fine (−1.0 mm) electronic waste is investigated. An in-depth understanding of the influences of the operating variables in the ECS is obtained by experimentation and optimization exercise. It is established that a high quality product can be generated with a high recovery of metal values in single stage operation of the ECS even for finely ground electronic waste. A high rotor speed helps in generating a purer product albeit with a lower mass yield. Conveyer belt speed does not have a substantial effect on the quality of the product but the mass yield increases with an increase in the belt speed. The mass yield improves when the feed rate increases but the product grade deteriorates. Material related variables such as particle size and specific gravity play significant roles in the horizontal deflection of the nonferrous metallic particles. It was established that below a size of 0.1 mm effective separation of metals is not possible in the ECS. Although particle shape plays a role, it may not be feasible to achieve separation based on shape in this size range. Mathematical models for the mass yield and product grade were established.

Real-time monitoring of wear debris in lubrication oil using a microfluidic inductive Coulter counting device

A microfluidic device based on an inductive Coulter counting principle to detect metal wear particles in lubrication oil is presented. The device detects the passage of ferrous and nonferrous particles by monitoring the inductance change of an embedded coil. The device was tested using iron and copper particles ranging in size from 50 to 125 μm. The testing results have demonstrated that the device is capable of detecting and distinguishing ferrous and nonferrous metal particles in lubrication oil; such particles can be indicative of potential machine faults in rotating and reciprocating machinery.

Characterization of shredded television scrap and implications for materials recovery

Characterization of TV scrap was carried out by using a variety of methods, such as chemical analysis, particle size and shape analysis, liberation degree analysis, thermogravimetric analysis, sink-float test, and IR spectrometry. A comparison of TV scrap, personal computer scrap, and printed circuit board scrap shows that the content of non-ferrous metals and precious metals in TV scrap is much lower than that in personal computer scrap or printed circuit board scrap. It is expected that recycling of TV scrap will not be cost-effective by utilizing conventional manual disassembly. The result of particle shape analysis indicates that the non-ferrous metal particles in TV scrap formed as a variety of shapes; it is much more heterogeneous than that of plastics and printed circuit boards. Furthermore, the separability of TV scrap using density-based techniques was evaluated by the sink-float test. The result demonstrates that a high recovery of copper could be obtained by using an effective gravity separation process. Identification of plastics shows that the major plastic in TV scrap is high impact polystyrene. Gravity separation of plastics may encounter some challenges in separation of plastics from TV scrap because of specific density variations.

Dry Magnus separation

The Magnus effect is the lift force on a body moving through a fluid as a result of the rotation of that body. In theory, the Magnus effect can be used to recover small non-ferrous metal particles from dry bulk streams. The Magnus separation process would consist of passing a feed stream next to a fast-spinning magnet in order to create a selective rotation of the non-ferrous particles so as to deflect them away from the stream by the Magnus effect. The present work shows the experimental deflection for flat and granular particles with a size between 1 and 3 mm and gives a theoretical background of the separation. It is also shown that the measured deflections relate well to values from numerical simulations.

Future trends in automatic particle sorting

Automation of the sorting of non-ferrous metallic scrap particles is not generally applied, despite the availability of a number of sorting systems. This contribution highlights the components of a sorting system, their state-of-the-art, and their prospects regarding farther improvements. Advanced data processing and the combination of different sensors are expected to gain in importance in future applications, and increase the automation of sorting. A prototype system developed at Delft University demonstrates the advantages of this approach.

Eddy-current separation by permanent magnets part I: Theory

In eddy-current separation, forces are exerted on non-ferrous metal particles to separate these metals from solid material mixtures. These forces depend on the magnetic field inducing the eddy currents as well as on the electric conductivity and the shapes and sizes of the particles. The present paper provides model calculations of the forces exerted in a vertical eddy-current separator. A quality factor was developed by which the magnetic configuration of these systems can be optimized. The quality factor was also used to design rotating disc separators. In both separation systems the magnetic fields are produced by permanent magnets. The validity of the model calculations was tested by measurement of the exerted forces.

Developments in analytical ferrography

Recent work at the Foxboro Analytical ferrography laboratory on the recognition of non-ferrous metal particles, particles from lead-, tin- and Pb- Sn-based alloys, ferrous oxide particles and corrosive wear debris is described. An explanation of polarized light microscopy as it applies to ferrography is given. Ferrograms made from conductive substrates which can be used in a scanning electron microscope without requiring coating are discussed.