Electronic scrap, especially wasted printed circuit boards (PCBs), is regarded as an environmental challenge. At present, the physical separation is thought to be the environmental friendly and economical method of tr...Electronic scrap, especially wasted printed circuit boards (PCBs), is regarded as an environmental challenge. At present, the physical separation is thought to be the environmental friendly and economical method of treating and reutilizing electronic waste. An effective liberation of metals from non metallic components is a crucial step towards mechanical separation and recycling of wasted PCBs. In this paper, the selective shredding theory and mechanics characteristics of wasted PCBs were analyzed, and the shredded experiments of wasted PCBs by hammer mill were investigated. The result shows that the selective shredding exists in the wasted PCBs shredded process by hammer mill. The shredding velocity of non metallic components is far greater than that of metals in the wasted PCBs shredding, which makes the metals concentrate in the coarser fraction. And the impact force of hammer mill is superior to metal liberation from non metallic components, a satisfied metal liberation degree can be achieved in the wasted PCBs shredding by hammer mill.展开更多
Physical methods show great potential and advantages on comprehensive reutilization of waste printed circuit boards (PCBs) because of lower investment and operation cost, higher efficiency and environment friendliness...Physical methods show great potential and advantages on comprehensive reutilization of waste printed circuit boards (PCBs) because of lower investment and operation cost, higher efficiency and environment friendliness. However, metals contained in fine fraction of PCBs cannot be recovered effectively by conventional equipments such as high tension electrostatic separator or shaking table. In the paper, this conundrum was resolved successfully with the enhanced Falcon SB concentrator. The separation mechanism of Falcon SB concentrator was analyzed and main factors affecting separation efficiency such as magnitude of rotation frequency of bowl, water counter pressure and slurry concentration of feed were studied and interaction of factors above also were investigated using Design-Expert software. Experiment results show that complete liberation degree and great difference of density between metals and nonmetals are suitable to recover metals from -74 μm PCBs using enhanced Falcon SB concentrator and 80.77 % integration efficiency can be achieved when slurry concentration of feed is 40 g/L with the water counter pressure of 0.01 MPa and rotation frequency of 50 Hz.展开更多
Research on recycling waste Printed Circuit Boards(PCB) is at the forefront of preventing environmental pollution and finding ways to recycle resources.The Tapered Column Separation Bed(TCSB) is invented aiming at dis...Research on recycling waste Printed Circuit Boards(PCB) is at the forefront of preventing environmental pollution and finding ways to recycle resources.The Tapered Column Separation Bed(TCSB) is invented aiming at disposing the problem that fine particles of waste printed circuit boards cannot be separated efficiently so as to obtain further insight about the underlying mechanisms and demonstrate the separation feasibility in the tapered column separation bed.In this work,a Computational Fluid Dynamics(CFD) coupled with Discrete Element Method(DEM) model for two-phase flow has been extended to simulate the fluid-solid flow in the tapered column separation bed.Its validity is demonstrated by its successful capturing the key features of particles' flow pattern,velocity,the pressure distribution,the axial position with time and axial force for particles with different densities.Simulation results show that the plastic particles and resin particles become overflow,while copper particles,iron particles and aluminum particles successively become underflow,with a discharge water flow rate of 1 m^3/h,an obliquity of 30°.The simulated results agree reasonably well with the experimental observation.Using this equipment to separate waste PCBs is feasible,theoretically.展开更多
文摘Electronic scrap, especially wasted printed circuit boards (PCBs), is regarded as an environmental challenge. At present, the physical separation is thought to be the environmental friendly and economical method of treating and reutilizing electronic waste. An effective liberation of metals from non metallic components is a crucial step towards mechanical separation and recycling of wasted PCBs. In this paper, the selective shredding theory and mechanics characteristics of wasted PCBs were analyzed, and the shredded experiments of wasted PCBs by hammer mill were investigated. The result shows that the selective shredding exists in the wasted PCBs shredded process by hammer mill. The shredding velocity of non metallic components is far greater than that of metals in the wasted PCBs shredding, which makes the metals concentrate in the coarser fraction. And the impact force of hammer mill is superior to metal liberation from non metallic components, a satisfied metal liberation degree can be achieved in the wasted PCBs shredding by hammer mill.
基金Project 200360290015 supported by the Doctoral Program of Higher Education, China Ministry of Education
文摘Physical methods show great potential and advantages on comprehensive reutilization of waste printed circuit boards (PCBs) because of lower investment and operation cost, higher efficiency and environment friendliness. However, metals contained in fine fraction of PCBs cannot be recovered effectively by conventional equipments such as high tension electrostatic separator or shaking table. In the paper, this conundrum was resolved successfully with the enhanced Falcon SB concentrator. The separation mechanism of Falcon SB concentrator was analyzed and main factors affecting separation efficiency such as magnitude of rotation frequency of bowl, water counter pressure and slurry concentration of feed were studied and interaction of factors above also were investigated using Design-Expert software. Experiment results show that complete liberation degree and great difference of density between metals and nonmetals are suitable to recover metals from -74 μm PCBs using enhanced Falcon SB concentrator and 80.77 % integration efficiency can be achieved when slurry concentration of feed is 40 g/L with the water counter pressure of 0.01 MPa and rotation frequency of 50 Hz.
基金the National Key Basic Research Program of China(No.2012CB214904)the National Natural Science Foundation of China for Innovative Research Group(No.51221462)+2 种基金the National Natural Science Foundation of China(Nos.51304196,51134022,and 51174203)the Natural Science Foundation of Jiangsu Province of China(No. BK2012136)the Specialized Research Fund for the Doctoral Program of Higher Education(No.20120095130001)
文摘Research on recycling waste Printed Circuit Boards(PCB) is at the forefront of preventing environmental pollution and finding ways to recycle resources.The Tapered Column Separation Bed(TCSB) is invented aiming at disposing the problem that fine particles of waste printed circuit boards cannot be separated efficiently so as to obtain further insight about the underlying mechanisms and demonstrate the separation feasibility in the tapered column separation bed.In this work,a Computational Fluid Dynamics(CFD) coupled with Discrete Element Method(DEM) model for two-phase flow has been extended to simulate the fluid-solid flow in the tapered column separation bed.Its validity is demonstrated by its successful capturing the key features of particles' flow pattern,velocity,the pressure distribution,the axial position with time and axial force for particles with different densities.Simulation results show that the plastic particles and resin particles become overflow,while copper particles,iron particles and aluminum particles successively become underflow,with a discharge water flow rate of 1 m^3/h,an obliquity of 30°.The simulated results agree reasonably well with the experimental observation.Using this equipment to separate waste PCBs is feasible,theoretically.
