Papers by Keyword: Comminution

Abstract: In the year 2016 alone, more than 1.35 billion smartphones were manufactured globally. These smartphones contain up to 60 different chemical elements and the summarized metal weight of the 2016 production may have well exceeded 50,000 metric tons. At present, most elements contained in this very complex “mixture” represented by a smartphone have recycling rates well below 50%, and the recycling rates of rare earths, indium, tantalum or gallium are even below 1%. The major challenge of mobile phone recycling is the complex composition of the devices made of many individual components – and the lack of transparent information as to the composition of these components. This is aggravated by the fact that many elements occur in traces only and / or are located in highly complex material composites. To enable more effective recycling of mobile phones, it is thus imperative to characterize the constituent components, the presence of elements in it, as well as their behavior during comminution. In a pilot study, a Nokia mobile phone Model 5228 Type RM-625, crushed with a granulator UG300, was examined by Mineral Liberation Analysis. The analysis of three particle size fractions of the comminuted material was carried out in an automated measurement mode with a grid of energy-dispersive X-ray spectra. A total of 130 different phases were detected during this analysis. More than 100 of these phases occur at levels <1% by weight. This strongly illustrates the very complex composition of smartphones. A comparison of the modal content of the three particle size fractions showed good liberation of certain components and an enrichment of some components in specific fractions. These observations reveal the potential to successfully separate different technical components from one another with the goal to increase the resource efficiency of the recycling process.

Abstract: Since the metallic elements are covered with or encapsulated by various plastic or ceramic materials on printed circuit boards (PCBs), a pre-treatment process allowing their liberation and separation is first needed in order to facilitate proficient extraction. In this work, a fundamental study has been carried out to recover metallic concentrates from PCBs scraps. The most important step is to separate or release particles from the associated gangue minerals at the possible liberation particle size. The samples of printed circuit boards were separated into the magnetic and non-magnetic fractions by Rare-earth Roll Magnetic Separator. Then, the magnetic and non-magnetic fractions were separated to heavy fraction (metallic elements) and light fraction (plastic) by Mozley Laboratory Table Separator. Results show that the unliberated particles still remain in the comminution fines PCBs. The use of Rare-earth roll magnetic separation was clarified that the Fe, Ni and Zn element tend to be condensed in magnetic particles. Meanwhile Cu element tends to be release in non-magnetic particles. Mozley Laboratory Table Separation was capable to obtain fractions with relatively high concentrations of metallic elements. This study is expected to provide useful data for the efficient physical separation of metallic components from printed circuit boards scraps.

Abstract: The dry crushing of wasted printed circuit boards (PCBs) can make secondary contamination. In this paper, a wet comminution process is put forward to solve the difficulties. For the comminution product, the distributions of particle size, liberation degree and metal grade are analyzed, and for the product below 1mm, a wet metal beneficiation process combined with shaking table and flotation is employed. The results show that the Whole PCBs could be comminuted by the MX wet impact crusher, and the cumulative yield, liberation degree, total metal content and its copper grade of the product below 1mm is 83.49%, 97%, 83.46% and 20.50%respectively, and that metal concentrates could be beneficiated by XZY wet shaking table, and the yield, total metal weight, copper grade of the metal concentrate, the recovery of total metal and copper is 34.87%, 88.99%, 50.73%,79.90% and 78.07% respectively keeping the feeding concentration at 20% and water consumption in 1100L/h. For these metals included by shaking-table middling, the separation of both flotation and shaking table is carried out, and the total metal content and its copper grade, recovery in metal concentrate 2′ is 72.07% , 31.59% and62.04% respectively, meanwhile the copper grade of tailings in flotation and shaking table are decreased to 1.26% and 2.94%. The wet treatment process can effectively concentrate these valuable metals from waste PCBs.

Abstract: Nanoparticles usually prepared through chemical synthetic method. In our study, nanoCoenzyme Q10 was prepared by water jet comminution process. The results were characterized with scanning electron microscope (SEM) and the color change of the water solution. The color becomes lighter when the particles have a smaller size. The effect of comminution is related to the number of process cycles. nanoCoenzyme Q10 water solution (particle size less than 50nm) was obtained through water jet comminution at 50Mpa with five cycles. This new method not only solves the problem of physical comminution collection, but also gives an effective way to prepare natural nanoparticles.

Abstract: Aimed principally at increasing the impact velocity of the particle assuming a given circumferential velocity and to achieve collinear collision of particles by a mechanical method with a consideration on energy saving for comminution, a prototype dual cone impact mill was designed and built. This dual cone impact mill mainly consists of two cone disks with the same geometrical dimensions, and the same rotational speeds rotating in opposite directions. There are no grinding media in the dual cone impact mill. The dependence of the comminution effect on two parameters, cone disk speed and air flow rate, was experimentally investigated. The results obtained from grinding quartz and cement clinker indicate that this prototype mill can be used for grinding materials of Mohs hardness up to of 6-7, while achieving mean particle sizes of 10  m.