Vibratory Separation of Plastic Mixtures Using Triboelectric Charging

This article presents the results of experimental and analytical studies of the performance of a novel vibratory separator of plastic mixtures for recycling. The separator unit consists of a vibratory conveyor equipped with two plate electrodes. The principle behind the separation technique is based on the difference in Coulomb force acting on the plastic particles after triboelectric charging. The separation of a mixture of 50% polyvinylchloride (PVC) and 50% polyethylene terephthalate (PET) using this method was studied. An analytical model describing the relative distribution of the two types of plastic particles in the collection trays was developed. The effect of triboelectric charging time and electric-field strength on the separation efficiency was investigated.     

Vibratory Separation of Plastic Mixtures Using Triboelectric Charging

This article presents the results of experimental and analytical studies of the performance of a novel vibratory separator of plastic mixtures for recycling. The separator unit consists of a vibratory conveyor equipped with two plate electrodes. The principle behind the separation technique is based on the difference in Coulomb force acting on the plastic particles after triboelectric charging. The separation of a mixture of 50% polyvinylchloride (PVC) and 50% polyethylene terephthalate (PET) using this method was studied. An analytical model describing the relative distribution of the two types of plastic particles in the collection trays was developed. The effect of triboelectric charging time and electric-field strength on the separation efficiency was investigated.     

PARTICLE TRIBOELECTRIFICATION AND ITS USE IN THE ELECTROSTATIC SEPARATION PROCESS

Triboelectrification of solids is known since ancient times. Empirical experiments allow materials to be arranged in so-called “triboelectric series”. Reproducibility, however, is poor in most cases, and the basic mechanisms of the charge transfer are still a subject of speculation. The difference between tribocharging of conductors and insulators is discussed in this paper, and the basic equations for these effects are presented. Triboelectrification of solids has two aspects, one beneficial and one hazardous. The hazardous aspect manifests itself in electrostatic discharges (ESD), which can damage computer equipment, as well as causing fires and explosions during transport and storage of solids and liquids. The beneficial aspect triboelectrification is widely used in many industrial applications, such as the Xerox copying technique, powder coating, pre-charging of fabric filters, electrostatically enhanced cyclone separators, oil mist filtration, aerosol particle collection, and finally, the electrostatic separation of materials. The second part of this paper focuses on industrial electrostatic separation techniques using tribocharging of particles; the separation of potassium minerals, coal beneficiation, and polymer separation for waste processing are presented.     

Recent Development in Separators for High‐Temperature Lithium‐Ion Batteries

Lithium‐ion batteries (LIBs) are promising energy storage devices for integrating renewable resources and high power applications, owing to their high energy density, light weight, high flexibility, slow self‐discharge rate, high rate charging capability, and long battery life. LIBs work efficiently at ambient temperatures, however, at high‐temperatures, they cause serious issues due to the thermal fluctuation inside batteries during operation. The separator is a key component of batteries and is crucial for the sustainability of LIBs at high‐temperatures. The high thermal stability with minimum thermal shrinkage and robust mechanical strength are the prime requirements along with high porosity, ionic conductivity, and electrolyte uptake for highly efficient high‐temperature LIBs. This Review deals with the recent studies and developments in separator technologies for high‐temperature LIBs with respect to their structural layered formation. The recent progress in monolayer and multilayer separators along with the developed preparation methodologies is discussed in detail. Future challenges and directions toward the advancement in separator technology are also discussed for achieving remarkable performance of separators in a high‐temperature environment.     

Triboelectric separation of a starch-protein mixture – Impact of electric field strength and flow rate

Triboelectric separation is a method for separating dry particulate systems due to their different electrostatic chargeability. Previous applications are limited to the separation of coarse powders. The aim of the present study is to examine the influence of the flow conditions and the influence of the electric field strength on the separation efficiency of starch and protein particles. Very fine organic powders are separated in a simple bench scale electrostatic separator to extend this technique to powders below 50?µm. The influence of different gas flow rates in the turbulent flow regime on particle charging and subsequent separation is investigated.As an organic model substrate, a mixture of barley starch and whey protein was used. The tribocharger consists of a PTFE charging tube and a rectangular separation chamber where an electric field is applied between two electrodes. The particles are conveyed through the charging tube and charged by frictional contact with the tube wall. It is shown that different gas flow rates at a turbulent flow regime in the charging tube did not change the separation characteristics. In contrast, increasing electrical field strength increases separation efficiency of protein particles regardless of gas flow conditions. The proportion of starch at the anode is the same for all the investigated parameters.     

Engineering development of high gradient magnetic separators

The commercial development of high gradient magnetic separation began in 1969 when the first industrial, cyclic high gradient magnetic separators were sold to the J.M. Huber Corporation by Magnetic Engineering Associates, Sala's predecessor, for processing high grade paper coating clays. Since that time, high gradient magnetic separation for the processing of high quality clays has come to be fully accepted in the United States kaolin industry. A number of large cyclic separators of the Sala design, with capacity ratings above 60 tph have been constructed under license from Sala and installed in major U.S. clay producers' facilities. Applications of high gradient magnetic separation technology to mineral processing and water treatment have been explored(1,2,3,4). The cyclic high gradient magnetic separators utilized in the clay industry may be employed for most water treatment applications since the volume of magnetic material to be removed is a relatively small percentage of the total flow volume through the machine. In the majority of mineral separation and beneficiation problems, the feed percentage of magnetics is more than 1 to 2 percent and to solve this problem efficiently a continuous high gradient magnetic separator has been developed by us. A 15 tph continuous pilot separator is now operating in our Cambridge pilot plant and is able to process ores with the effectiveness of the cyclic high gradient magnetic separators.     

Triboelectric Separation of Three-Component Plastic Mixture

The results of an experimental study on the triboelectric separation of one type of plastic from a three-component plastic mixture are presented. A triboelectric separator, which consists of a vibratory conveyor equipped with two electrodes, was used. The separation method makes it possible to avoid the adhesion of oppositely charged particles. Separation tests were performed on two kinds of mixtures. The effect of operating parameters such as electric field strength, polarity of applied voltage, and triboelectric charging time on the separation efficiency was examined. In the case of the separation of a mixture of 50% polyvinyl chloride (PVC), 50% polyethylene terephthalate (PET), and 50% polyethylene (PE), the purity of the extracted PVC was larger than 99% for a recovery rate of 94.9%. In the case of the separation of a mixture of 50% acrylonitrile butadiene styrene (ABS), 50% polypropylene (PP), and 50% polystyrene (PS), the purity of the extracted ABS was larger than 99% for a recovery rate of 89.4%.     

AIR FLOW AND PARTICLE TRANSPORT IN A TRIBOELECTRIC COAL/ASH CLEANING SYSTEM-COUNTER FLOWING STRAIGHT DUCT DESIGN

ABSTRACT

The process of triboelectric coal/ash cleaning is outlined and a new design for scale-up to industrial systems is described. A straight rectangular duct forms the mixing chamber and the main body of this triboelectric separator. To improve mixing and to generate a uniform concentration in the main electrostatic separator duct, the mixture enters the mixing box in the form of two opposing jets. The stress transport model of the FLUENT code is used for simulating the mean gas flow and to guide the overall design of the electrostatic coal/ash separator. The three-dimensional computational grid covers the mixing chamber with the opposing inlets and the upper part of the main separator duct. The gas flow field conditions including the directional intensities of turbulence are evaluated. The instantaneous fluctuating velocity field was simulated by a Gaussian filtered white noise model. A recently developed computational model for Lagrangian particle tracking is used to study the transport of particles from the inlets to the main body of the separator duct. The model accounts for the drag and lift forces acting on the particle, in addition to the Brownian motion and gravitational sedimentation effects. The particles are also dispersed by the action of the high level of turbulence that is generated in the mixing chamber. The computational results show that the new design generates roughly uniform flow conditions in the triboelectric separator duct. Furthermore, the larger 100 µm particles will have a more uniform distribution when compared with the smaller (40 µm) particles.

The effect of the presence of an electric field perpendicular to the flow direction is also studied. It is shown that the charged particles are significantly deflected by the action of the electrostatic forces. As a result, the system could separate coal and ash particles that carry different charges. The simplicity and effectiveness of the straight duct separator makes it a prime candidate for scale-up for use in industrial applications for online coal beneficiation and separation of minerals from ash in combustion product.     

AIR FLOW AND PARTICLE TRANSPORT IN A TRIBOELECTRIC COAL/ASH CLEANING SYSTEM-COUNTER FLOWING STRAIGHT DUCT DESIGN

The process of triboelectric coal/ash cleaning is outlined and a new design for scale-up to industrial systems is described. A straight rectangular duct forms the mixing chamber and the main body of this triboelectric separator. To improve mixing and to generate a uniform concentration in the main electrostatic separator duct, the mixture enters the mixing box in the form of two opposing jets. The stress transport model of the FLUENT code is used for simulating the mean gas flow and to guide the overall design of the electrostatic coal/ash separator. The three-dimensional computational grid covers the mixing chamber with the opposing inlets and the upper part of the main separator duct. The gas flow field conditions including the directional intensities of turbulence are evaluated. The instantaneous fluctuating velocity field was simulated by a Gaussian filtered white noise model. A recently developed computational model for Lagrangian particle tracking is used to study the transport of particles from the inlets to the main body of the separator duct. The model accounts for the drag and lift forces acting on the particle, in addition to the Brownian motion and gravitational sedimentation effects. The particles are also dispersed by the action of the high level of turbulence that is generated in the mixing chamber. The computational results show that the new design generates roughly uniform flow conditions in the triboelectric separator duct. Furthermore, the larger 100 µm particles will have a more uniform distribution when compared with the smaller (40 µm) particles.

The effect of the presence of an electric field perpendicular to the flow direction is also studied. It is shown that the charged particles are significantly deflected by the action of the electrostatic forces. As a result, the system could separate coal and ash particles that carry different charges. The simplicity and effectiveness of the straight duct separator makes it a prime candidate for scale-up for use in industrial applications for online coal beneficiation and separation of minerals from ash in combustion product.     

Study of Gas Core Behavior of Passive Cyclonic Two-Phase Separator for Microgravity Applications

Separating gas-liquid two-phase flow is of practical importance for many space engineering systems. While droplet and bubble removal is a naturally occurring phenomenon in most terrestrial situations, the absence of buoyancy in a microgravity environment often results in situations where two disparate phases have no distinct inclination to separate from one another. Passive cyclonic separators can perform this task without moving parts and the reliability concerns of active separators. In such separation devices, separation efficiency is strongly influenced by the gas core behavior. Based on experimental and numerical investigations, the behavior of the gas core with two-phase injection is studied. A control-volume model is developed to capture the relevant physics of the flow in the separator. It is shown that the injection nozzle design, swirl number, and volumetric gas quality all have a major influence on the core size. The present investigation covers a range of volumetric quality from 0 to 0.75, and a range of swirl number from 17 to 28. Both homogeneous and non-homogeneous nozzles are used. The implications of the results are discussed in detail.     

动力/储能锂离子电池隔膜制备先进技术及研究进展

锂离子电池主要由电极、隔膜、电解液三大部分构成。其中隔膜作为电池的关键部件之一,极大地影响着电池的综合性能。商业聚烯烃隔膜由于润湿性与耐温性差、孔隙率低等缺点,很难满足高性能锂离子电池隔膜的要求。因此,隔膜的制备技术与材料急需进行深入的研究与探索。本文从近期隔膜的研究热点出发,分别从商业聚烯烃隔膜的改性、静电纺丝法及相分离法制备等方面对动力/储能锂离子电池隔膜最新研究成果进行综述,并指出了未来隔膜的发展方向。     

Functionalized separator for next-generation batteries

Advancements in battery technology have dramatically increased demand for improvements in separator design, as the separator plays a critical role in ensuring the safety and electrochemical performance of the cells. Current separators, either in commercial usage or under investigation, have yet to meet the high stability and lifespan performance standards necessary to prevent deterioration in the efficiency and reliability of the battery technologies. Recently, considerable effort has been devoted to developing functionalized separators, ranging from designing a variety of new materials and modification methods, and increasingly, to optimizing advanced preparation processes. In order to understand how the mechanisms of separator performance are affected by different properties, we will first summarize recent research progress and then have in-depth discussions regarding the separator’s significant contribution to enhancing the safety and performance of the cell. We then provide our design strategy for future separators, which not only meets the requirements of different type of batteries, but also aims for multifunctionality. We hope such a perspective could provide new inspiration in the development of separator research for future battery technologies.     

锂离子电池用纤维素材料及其隔膜制备技术的研究进展

随着新能源行业的快速兴起,高性能锂离子电池成为当下的研究热点。作为锂离子电池的重要组成部分之一,隔膜不仅决定了电池的内部结构和内阻,而且对电池的容量、循环和安全性能起着至关重要的作用。纤维素材料来源丰富、环境友好,由纤维素制备的隔膜具有高孔隙率、高比表面积和高离子电导率,有希望成为传统聚烯烃隔膜的优良替代品。概括了不同种类的纤维素在锂离子电池膈膜中的应用进展,对纤维素膈膜的制备技术及其性能进行了全面的讨论和总结,最后,提出了纤维素锂离子电池隔膜领域有待解决的问题以及纤维素在隔膜领域的发展前景。     

A new two-roll electrostatic separator for recycling of metals and nonmetals from waste printed circuit board

The electrostatic separation is an effective method for recycling waste electrical and electronic equipment (WEEE). The efficiency of electrostatic separation processes depends on the ability of the separator. As a classical one, the roll-type corona-electrostatic separator has some advantages in recycling metals and plastics from waste printed circuit board (PCB). However, its industry application still faces some problems, such as: the further disposal of the middling products of the separation process; the balance of the production capacity and the good separation efficiency; the separation of the fine granular mixture and the stability of the separation process. A new "two-roll-type corona-electrostatic separator" was built to overcome the limitation of the classical one. The experimental data were discussed and the results showed that the outcome of the separation process was improved by using the new separator. Compared with the classical machine, the mass of conductive products increases 8.9% (groups 2 and 3) and10.2% (group 4) while the mass of the middling products decreases 45% (groups 2 and 3) and 31.7% (group 4), respectively. The production capacity of the new machine increases, and the stability of the separation process is enhanced.     

空调用高效旋流油分离器仿真优化与实验

为了提高空调系统中旋流油分离器的分离效率、降低压力损失,本文对其结构参数进行了优化设计,通过流体仿真研究了油分离器内部各参数对分离效率和压力损失的影响,得到最佳的参数尺寸比例,并据此制作了一款新型油分离器,安装在空调系统中进行实验测试。实验结果表明:新型油分离器在回油工况(最低制冷剂流速)下分离效率由95.5%提高到99.0%,名义制冷工况下分离效率由97.3%提高到99.6%;名义制冷工况下压力损失由55.2 k Pa降低至23.1 k Pa;同时获得了油滴颗粒的分布函数。     

Optimization of key factors of the electrostatic separation for crushed PCB wastes using roll-type separator

For the electrostatic separation process, the separator is most crucial. As a classical one, the roll-type corona-electrostatic separator has some advantages in recycle of waste electrical and electronic equipment (WEEE). Some researches have been done in this field and shown that there was a complex correlation between its configuration and the efficiency of the separation. In this paper, a fractional factorial design (2v1-5) was built and 32 tests were performed on a roll-type corona-electrostatic separator. The sample of granular mixture got from crushed PCB wastes (size 0.3-0.45 mm, containing 25% metal and 75% nonmetal). The experimental data were discussed and used to analyze the factors' main effect, interaction and optimization of the process. Three liner-interaction mathematical models were derived to describe the mass of middling fraction (M), conductor fraction (C) and Nonconductor fraction (NC), respectively. The results show that the efficiency of the PCB waste electrostatic separation process has a significant correlation with not only factors' main effects, but also the interaction between them.     

Effect of SiO2 coating on polyethylene separator with different stretching ratios for application in lithium ion batteries

To enhance the properties of polyethylene separators in lithium ion batteries, we tested separators with uni-axial stretching ratios of 180% and 300%. We also tested stretched separators coated with SiO₂ ceramic substance to increase ionic conductivity and thermal stability without sacrificing mechanical properties. To test the thermal and tensile properties, thermomechanical analyzer (TMA) is employed. CR 2032-type coin cells are prepared by sandwiching pristine and coated stretched separators, respectively, between the Li anode and Li[Ni_1/3Co_1/3Mn_1/3]O₂ cathode to evaluate the AC impedance and cycling performance. The coated separators are observed with superior ionic conductivity, thermal and tensile properties. The cells prepared with coated separator have slightly higher discharge capacity and a better capacity retention ratio than the cells with pristine separators. These results suggest that the coated separator is a better option for lithium ion batteries.     

Performance evaluation of industrial large-scale cyclone separator with novel vortex finder

This paper presents an experimental and numerical study on an industrial large-scale tangential-inlet cyclone separator with a novel and easy-to-implement vortex finder. The vortex finder was designed with slots on the side wall to improve cyclone performance. The collection efficiency, pressure drop, and interior flow field were analyzed. The proposed device provides an effective gas flow pathway and a coupled swirl-inertia separation mechanism, which eliminates short circuit flows under the bottom inlet of the slotted vortex finder to reduce the swirling intensity and minimize the flow instability in the separator. The pressure drop was reduced up to 27.9% compared to the conventional separator and the maximal increase in collection efficiency was 5.45%. The results presented here may provide a workable reference regarding the effects of vortex finders on improving flow fields and corresponding performance in industrial large-scale cyclone separators.     

Precombustion Cleaning of Coal By Triboelectric Separation of Minerals

In one method of electrostatic beneficiation, pulverized coal is tribocharged by contact with electrically grounded copper. Coal maceral and mineral particles charge with positive and negative polarities, respectively. The charged particles are passed through a separator consisting of two plate electrodes, across which a high voltage is applied, and the positively charged coal particles are separated from the negatively charged mineral particles. The efficiency of separation is dependent upon coal bulk and surface composition, and fineness of grind. Analyses of total sulfur and ash content of the charge-separated particles were used to evaluate beneficiation success of the Illinois No. 6 and Pittsburgh No. 8 coals studied. Two-stage beneficiation demonstrated improved separation. Exposing coal powders to chemical vapors of SO 2 , NH 3 , or acetone prior to beneficiation did not enhance beneficiation.     

页岩灰与催化裂化催化剂细粉旋风分离性能的对比试验研究

试验测定和对比页岩灰和流化催化裂化三旋灰(FCC三旋灰)的旋风分离器性能,考察入口气速、入口浓度对分离效率和分离器压降的影响.结果表明,在相同操作条件下,同一台旋风分离器上,粒度小于75 μm的页岩灰与FCC三旋灰的分离效率和分离器压降曲线差别显著;页岩灰的分离效率与分离器压降都明显低于FCC三旋灰,且入口浓度增大,页岩灰分离器压降的下降幅度高于FCC三旋灰;页岩灰分离效率最高的入口气流速度也低于FCC三旋灰.颗粒特性对旋风分离器的分离性能有明显影响,页岩灰和三旋灰的颗粒特性与形状差别是导致其旋风分离特性不同的一个基本原因;油页岩旋风分离器的设计应当考虑油页岩颗粒特性的影响.