| 341. |
- Zhang, Shunli, et al.
(författare)
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Intelligent liberation and classification of electronic scrap
- 1999
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Ingår i: Powder Technology. - 0032-5910 .- 1873-328X. ; 105:1, s. 295-301
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Tidskriftsartikel (refereegranskat)abstract
- Mechanical recycling of electronic scrap oriented towards overall materials recovery from obsolete electronics is being implemented worldwide. The main reason is that the amount of electronic scrap is increasing and that the content of the precious metals present is decreasing. In this context, an effective liberation of various materials like metals and plastics is a crucial step towards mechanical separation. In addition, classification of electronic scrap is also important to be able to provide an appropriate feed material for the subsequent separation process. In the present study, liberation and its impact on the separation of personal computer (PC) scrap and printed circuit board (PCB) scrap has been investigated in detail. A special equipment functioning as a shape separator and an aspirator was used for the classification of electronic scrap.
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| 342. |
- Zhang, Shunli, et al.
(författare)
-
Investigation of separability of particles smaller than 5 mm by eddy current separation technology. Part I : Rotating type eddy current separators
- 1999
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Ingår i: Magnetic and Electrical Separation. - : Hindawi Limited. - 1055-6915 .- 1029-0303 .- 1477-2876. ; 9:4, s. 233-251
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Tidskriftsartikel (refereegranskat)abstract
- Owing to the growing emergence of the end-of-life electrical and electronic products with complex material structures and an ever-diminishing particle size of the valuable metals involved, development of eddy current separators (ECS) has been targeting selective separation of small non-ferrous metal particles smaller than 5 mm. Separability of various materials smaller than 5 mm, including fine copper wires, has been investigated using ECS with various design concepts. The present research work is divided into two parts, with Part I focusing on the rotating type ECS which are today common in practice, and with Part II dedicated to the ECS with novel concepts such as wet ECS technology. In Part I, three rotating belted-drum ECS were employed, which are manufactured by Bakker Magnetics, the Netherlands, Huron Valley Steel Co., US, and Eriez Magnetics, UK respectively. It is found that the belted-drum ECS are effective for separating materials below 5 mm if the magnetic drum rotates in opposite direction to the conveyor belt. The separation principle, particularly the 'backward phenomenon' of the rotating type ECS for small particles has been unravelled in the present study. Moreover, separation of Al from the 0-10 mm fraction of electronic scrap has been conducted. The results obtained demonstrate that the belted-drum ECS with appropriate design may be applicable for separation of small aluminum particles from electronic scrap.
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| 343. |
- Zhang, Shunli, et al.
(författare)
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Mechanical recycling of electronics scrap : the current status and prospects
- 1998
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Ingår i: Waste Management & Research. - 0734-242X .- 1096-3669. ; 16:2, s. 119-128
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Tidskriftsartikel (refereegranskat)abstract
- Of the various mechanical metal recycling techniques employed in electronic scrap processing, air table separation, magnetic separation and eddy current separation technolo gies have proved to be the most commercially successful. In addition, it is very important, even indispensable, that, prior to the physical processing of electronic scrap, selective dis mantling and identification (if necessary) be employed. It is, however, recognized that problems such as process optimiza tion and organics handling remain and that in-depth charac terization of electronic scrap will be essential in this context.
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| 344. |
- Zhang, Shunli, et al.
(författare)
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Mechanical separation-oriented characterization of electronic scrap
- 1997
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Ingår i: Resources, Conservation and Recycling. - 0921-3449 .- 1879-0658. ; 21:4, s. 247-269
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Tidskriftsartikel (refereegranskat)abstract
- The ever-increasing amount of electronic scrap and the steadily-decreasing contents of the precious metals used in electronics, as well as the ever-growing environmental awareness, challenges such conventional precious-metal-oriented recycling techniques as pyrometallurgy. Separation and beneficiation of various materials encountered in electronic scrap might provide a correct solution ahead. In this context, mechanical separation-oriented characterization of electronic scrap was conducted in an attempt to evaluate the amenability of mechanical separation processes. Liberation degrees of various metals from the non-metals, which are crucial for mechanical separation, were analyzed by means of a grain counting approach. It is found that the metallic particles below 2 mm achieve almost complete liberation. Particle shapes were also quantified through an image processing system. The results obtained show that the shapes of the particles, as a result of shredding, turn out to be heterogeneous, thereby complicating mechanical separation processes. In addition, separability of various materials was ascertained by a sink–float analysis. It has been shown that density-based separation techniques shall be viable in separating metals from plastics, light plastics (ABS, PS and PVC, etc.) from glass fiber reinforced resins and aluminum from heavy metals. Specifically, a high quality copper concentrate can be expected by density-based separation techniques. Moreover, FT-IR spectra of plastics pieces from the light fractions after the sink–float testing show that PC scrap primarily contains ABS, PS and PVC plastics with the density range of +1.0–1.5 g/cm3, whereas PCB scrap mainly contains glass fiber reinforced epoxy resins plastics with the density range of +1.5–2.0 g/cm3.
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| 345. |
- Zhang, Shunli, et al.
(författare)
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Optimization of electrodynamic separation for metals recovery from electronic scrap
- 1998
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Ingår i: Resources, Conservation and Recycling. - 0921-3449 .- 1879-0658. ; 22:3-4, s. 143-162
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Tidskriftsartikel (refereegranskat)abstract
- The performance of an electrodynamic separator has been optimized in the present study for metals recovery from electronic scrap. Eight variables involved in the system was investigated by a 2IV8-4 fractional factorial design in an attempt to determine the significant variables. The effects of those variables were detailed with glass, polyvinyl chloride (PVC) as a representative of plastics, copper wires, copper and aluminum granulates. For various binary mixtures of copper wires and glass or PVC plastic, the electrodynamic separator is able to produce copper products with the grade ranging from 93 to 99%, and recovery from 95 to 99%, respectively, under the optimized conditions. Further, one sample which is a middling fraction resulting from air table separation was also tested. For a single pass, copper and aluminum was upgraded approximately from 11 and 7% to 34 and 22%, while maintaining the corresponding recovery of 87 and 99%, respectively.
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| 346. |
- Zhang, Shunli, et al.
(författare)
-
Particle trajectory simulation of two-drum eddy current separators
- 1999
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Ingår i: Resources, Conservation and Recycling. - 0921-3449 .- 1879-0658. ; 26:2, s. 71-90
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Tidskriftsartikel (refereegranskat)abstract
- Particle trajectories of the newly-developed two-drum eddy current separators are simulated by the ECSIM software package. The simulation results have been substantiated by measuring the horizontal displacements of the particles to be investigated under the same conditions. It is shown that the simulation results are in good agreement with the experimental ones. Further, on the basis of the simulation results obtained, the potential for improving the design of two-drum eddy current separators is discussed. It appears that the performance of two-drum eddy current separators, when processing small particles, may be enhanced by strengthening the magnetic field intensity and simultaneously increasing the maximum drum speed.
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| 347. |
- Zhang, Shunli, et al.
(författare)
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Separation mechanisms and criteria of a rotating eddy-current separator operation
- 1999
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Ingår i: Resources, Conservation and Recycling. - 0921-3449 .- 1879-0658. ; 25:3, s. 215-232
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Tidskriftsartikel (refereegranskat)abstract
- Much work has so far been done for modelling the magnetic deflecting (repulsive) force of eddy current separators. However, selective separation of various materials by eddy current separation depends not only on magnetic deflecting forces but also on competing forces like the gravitational force and the centrifugal force. Co-acting forces on a particle leaving the external drum are analyzed and evaluated in this study. Separation mechanisms of metal/non-metal and metal/metal separation systems have been investigated by a newly-developed High-Force® eddy-current separator. Further, a separation model governing an effective separation among various materials is presented. Based on this separation model, four practical separation criteria for metal/metal separation systems are put forward and have been substantiated experimentally.
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