Cleaner Production

A novel and efficient method for resources recycling in waste photovoltaic panels: High voltage pulse crushing Pengfei Zhao 1,a, Junwei Guo a, Guanghui Yan a, Guangqing Zhu a, Xiangnan Zhu b, Zhenxing Zhang a, Bo Zhang a,c,*,1 aKey Laboratory of Coal Processing and Efficient Utilization of Ministry of Education, China University of Mining&Technology, Xuzhou, Jiangsu, 221116, China bCollege of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao, Shandong, 266590, ChinacResearch Center of Coal Resources Safe Mining and Clean Utilization, Liaoning Technical University, Fuxin, Liaoning, 123000, China article info Article history: Received 16 September 2019 Received in revised form 4 January 2020 Accepted 4 February 2020 Available online 7 February 2020 Handling editor: Bin Chen Keywords: High-voltage pulse Photovoltaic panels Recycling Selective crushing Enrichment abstract Photovoltaic power generation technology has developed rapidly in the past decade due to its clean and efficient characteristics. However, with the development of photovoltaic power generation technology, a large number of waste photovoltaic panels are generated, but there is no clean and effective method for resources recycling in waste photovoltaic panels. High-voltage pulsing tends to cause fractures at in- terfaces of materials with different dielectric constants, which has a satisfactory recovery effect on layered materials like photovoltaic panels In this paper, high voltage pulse crushing is used to dissociate and enrich waste photovoltaic panels, the experimental results show that there are differences in the selectivity of different components during high-voltage pulse crushing (selectivity: Ag>Si>glass). This makes high voltage pulse crushing have good enrichment effect on photovoltaic panels. Most of the high- value elements are enriched to lower grain size, the glass purity of 0.5~4 mm grain size can be directly recycled while it reaches over 98%. High-voltage pulse crushing has the most obvious enrichment effect on silver, Selectivity increases with the decrease offield strength and pulse number. The enrichment rate of silver in the lowerfield strength and pulse can reach 3.08, and the recovery rate is 54.07%. As thefield strength and pulse number increase, the enrichment rate of silver drops to 1.67 but the recovery rate increases to 89.41%. The silver recovery can be effectively improved by adjusting the electrode gap. High- voltage pulse crushing can effectively enrich and recover the silver in the waste photovoltaic panels, providing convenience for subsequent sorting. ©2020 Elsevier Ltd. All rights reserved. 1. Introduction Photovoltaic power generation is a reliable and clean technol- ogy, which has become an active area of research in various countries as fossil fuel derived energy is increasingly exhausted. Globally, photovoltaic-based energy supply doubled in 2016 compared to 2015. With the development of photovoltaic energy, it is estimated that 9.6 million tons of waste photovoltaic panels will be generated by 2050 (Nevala et al., 2019). If the waste photovoltaic panels are directly treated by landfill, it will lead to the leaching anddiffusion of toxic elements and the loss of traditional resources and high-value elements (Pagnanelli et al., 2017). Therefore, it is necessary to recycle waste photovoltaic panels. To date, many scholars have carried out relevant studies of the recycling of photovoltaic panels. Some scholars, for example, pro- posed the use of a mechanical crushing method to extract and recycle the useful components of photovoltaic panels (Granata et al., 2014;Pagnanelli et al., 2017). Other scholars used chemical etching to recover silicon from photovoltaic panels (Klugmann- Radziemska et al., 2010a,2010b). Others have tried to remove the ethylene-vinyl acetate copolymer (EVA) used in photovoltaic panels by organic reagent (Doi et al., 2001;Kim et al., 2012) or thermo- chemistry (Zhang et al., 2016), resulting in the panels breaking apart, allowing them to be recycled. However, each of these recycling methods has its own short- comings. Such as poor dissociation, high treatment cost, reagent *Corresponding author. Key Laboratory of Coal Processing and Efficient Utiliza- tion of Ministry of Education, China University of Mining&Technology, Xuzhou, Jiangsu, 221116, China. E-mail addresses:[email protected],[email protected](B. Zhang). 1Co-first author: These authors contributed equally to this work. Contents lists available atScienceDirect Journal of Cleaner Production journal homepage:www.elsevier.com/locate/jclepro https://doi.org/10.1016/j.jclepro.2020.120442 0959-6526/©2020 Elsevier Ltd. All rights reserved. Journal of Cleaner Production 257 (2020) 120442 harm, high energy consumption and pollution. Therefore, it is necessary to explore other methods of photovoltaic panel recycling. In thefield of mineral processing, mineral recovery is mainly based on gravity separation (Li, Z. et al., 2019),flotation and dry separation (Zhu et al., 2019;Zhang B et al., 2020;Yan et al., 2019a,b). However, a new method for mineral recovery has emerged in recent years, namely high voltage pulsing. High-voltage pulsing tends to cause fractures at interfaces of materials with different dielectric con- stants, which has a satisfactory recovery effect on layered materials like photovoltaic panels In this paper, Research into high voltage pulse technology began in the 1930s with capacitor discharge X- rays (Anders, 2010). The crushing effect of high voltage pulsing was found in the 1950s, when in the process of using high voltage pulses for the decomposition of water, a shock wave was produced that could crush ore (Wang et al., 2012). In 1971, Andres conducted the first systematic comparison test of apatite using high-voltage pulse technology (Anders, 2010;Anders et al., 1999). After this, high voltage pulse technology was applied to crushing and recycling in manyfields. For example, high voltage pulse technology is used to improve the permeability of coalbed methane (Yan et al., 2016a,b), pre-weaken the ore (Zuo et al., 2015;Wang et al., 2011), and enrich copper ore (Yan et al., 2018;Yan et al., 2019a,b). Then high-voltage pulse technology has also been applied to the recycling of circuit boards, with excellent results (Duan et al., 2018; Zhao et al., 2015;Veit, H.M. et al., 2006). Scholars have also begun to study whether high-voltage pulse technology is suitable for photovoltaic panel recycling. Some scholars use the characteristics of high-voltage pulse crushing to recover the waste photovoltaic panels, through the gravity separation and electrolysis of the crushed powder, the noble metal components in the photovoltaic panel were successfully recovered, which proved the feasibility of using high-voltage pulse crushing to recover waste photovoltaic panels (Yuta et al., 2018). Later, other scholars studied the differ- ence between high-voltage pulse crushing and mechanical crush- ing for photovoltaic panels, and found an enrichment advantage when using high-voltage pulse crushing (Nevala et al., 2019). In previous studies, the advantages of high-voltage pulse tech- nology over mechanical crushing technology in the recycling of photovoltaic panels were elaborated. However, the selective crushing effect of high-voltage pulses on photovoltaic panels and enrichment of each component of photovoltaic panels were not fully explored. This paper describes a study of the effect of various factors on degree of crushing and selective crushing rule of photovoltaic panels using high voltage pulses. In this paper, the effects of various factors on the selective crushing rule of photo- voltaic panels and the recovery and enrichment effect of Ag under high voltage pulse were studied. 2. Experimental methods 2.1. Materials The waste polycrystalline silicon photovoltaic panels used in this study were provided by local photovoltaic manufacturers. The general structure of the panels is shown inFig. 1. Their internal structure can be divided intofive layers. From top to bottom, the layers are glass, EVA, cell layer, EVA, and the backboard layer. EVA refers to“ethylene-vinyl acetate copolymer ”an organic material with the molecular formula (C2H4) x.(C4H6O2) y.The backboard layer is mainly composed of TPT, it is a polyvinylfluoride composite film, consisting of two polyvinylfluoridefilms (Tedlar made by Dupont company) sandwiched with a polyethylene terephthalate (PET)film. After the glass on the photovoltaic panel is manually stripped, the remaining material is heated in a muffle furnace (650
C for 1 h)to constant weight. This procedure causes the EVA and backboard layers to be pyrolyzed, leaving behind less than 1% of the materials in these layers, which for the purposes of this study can be regarded as complete removal. The resulting material can be regarded as a pure cell layer. The compositions of the glass and cell layers are determined using X-rayfluorescence spectrometry, as shown in Table 1andTable 2. The photovoltaic panels used in this test are removed from their aluminum alloy frames in advance, and cut into 5050 mm pieces of to meet the requirements of the crushing equipment. 2.2. Theory of high voltage pulse crushing The main condition of high voltage pulse crushing solid insu- lation material is the material internal dielectric breakdown, and the condition of internal dielectric breakdown is that the electric field intensity inside the insulation material reaches the breakdown condition, and the electricfield intensity of the external material should not reach the breakdown condition. When the voltage rises for a short time (Si>Glass. (3) The enrichment rate of Ag was higher under the condition of lowerfield strength and pulse number. However, the decrease in voltage and pulse number has a greater impact on the recovery rate. Therefore, in order to ensure the re- covery effect of Ag, electrode gap can be appropriately increased. (4) A sorting test was performed on the0.5 mm particle size product, and the pure glass product (rate 98.99%) was ob- tained; the0.5 mm particle size crushed product was processed by a Falcon sorter, 93.78% of silver and 94.22% of copper was successfully recovered. Credit author statement Pengfei Zhao: Methodology, Investigation, Formal analysis, Writing - Original Draft. Bo Zhang: Conceptualization, Visualiza- tion, Supervision, Writing - Review&Editing. Junwei Guo: Re- sources, Writing - Review&Editing, Supervision, Data Curation. Guanghui Yan: Resources, Writing - Review&Editing, Supervision, Data Curation. Guangqing Zhu: Writing: Review&Editing. Xian- gnan Zhu: Writing: Review&Editing. Zhenxing Zhang: Writing: Review&Editing. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgement The authors acknowledge thefinancial support by the ResearchFund for the postdoctoral Program (No.2018M630638), China; the National Nature Science Foundation of China (51974306, 51774283, U1903132); Open Projects of Research Center of Coal Resources Safe Mining and Clean Utilization LNTU (LNTU17KF16), China. References Duan, C., Han, J., Shen, Z., et al., 2018. The stripping effect of using high voltage electrical pulses breakage for waste printed circuit boards. Waste Manag. 77, 603e610. Andres, U., 1977. Liberation study of apatite-nepheline ore comminuted by pene- trating electrical discharges. Int. J. Miner. Process. 4 (1), 33e38. Andres, U., 1989. Parameters of disintegration of rock by electrical pulses. Powder Technol. 58 (4), 265e269. Andres, U., 2010. Development and prospects of mineral liberation by electrical pulses. Int. J. Miner. Process. 97 (1e4), 31e38. Andres, U., Jirestig, J., Timoshkin, I., 1999. Liberation of minerals by high-voltage electrical pulses. Powder Technol. 104 (1), 37e49. Bluhm, H., Frey, W., Giese, H., et al., 2000. Application of pulsed HV discharges to material fragmentation and recycling. IEEE Trans. Dielectr. Electr. Insul. 7 (5), 625e636. Dal Martello, E., et al., 2012. Electrical fragmentation as a novel route for the refinement of quartz raw materials for trace mineral impurities. Powder Technol. 224, 209e216. Doi, T., Tsuda, I., Unagida, H., et al., 2001. Experimental study on PV module recy- cling with organic solvent method. Sol. Energy Mater. Sol. Cells 67 (1), 397e403. Granata, G., Pagnanelli, F., Moscardini, E., et al., 2014. Recycling of photovoltaic panels by physical operations. Sol. Energy Mater. Sol. Cell. 123, 239e248. Kim, Y., Lee, J., 2012. Dissolution of ethylene vinyl acetate in crystalline silicon PV modules using ultrasonic irradiation and organic solvent. Sol. Energy Mater. Sol. Cell. 98, 317e322. Klugmann-Radziemska, E., Ostrowski, P., 2010a. Chemical treatment of crystalline silicon solar cells as a method of recovering pure silicon from photovoltaic modules. Renew. Energy 35 (8), 1751e1759. Klugmann-Radziemska, E., Ostrowski, P., Drabczyk, K., et al., 2010. Experimental validation of crystalline silicon solar cells recycling by thermal and chemical methods. Sol. Energy Mater. Sol. Cell. 94 (12), 2275e2282. Li, Z., Fu, Y., Zhou, A., et al., 2019. Effect of multi-intensification on the liberation of maceral components in Coal. Fuel 237, 1003e1012. Nevala, S.M., Hamuyuni, J., Junnila, T., et al., 2019. Electro-hydraulic fragmentation vs conventional crushing of photovoltaic panelseimpact on recycling. Waste Manag. 87, 43e50. Pagnanelli, F., Moscardini, E., Granata, G., et al., 2017. Physical and chemical treat- ment of end of life panels: an integrated automatic approach viable for different photovoltaic technologies. Waste Manag. 59, 422e431. Veit, H.M., et al., 2006. Recovery of copper from printed circuit boards scraps by mechanical processing and electrometallurgy. J. Hazard Mater. 137 (3), 1704e1709. Wang, E., Shi, F., Manlapig, E., 2011. Pre-weakening of mineral ores by high voltage pulses. Miner. Eng. 24 (5), 455e462. Wang, Y.B., Wang, S.W., Zeng, X.W., et al., 2012. A semiempirical model for the prebreakdown-heating process in the underwater discharge acoustic source. IEEE Trans. Plasma Sci. 40 (1), 98e111. Yan, F., Lin, B., Zhu, C., et al., 2016a. Experimental investigation on anthracite coal fragmentation by high-voltage electrical pulses in the air condition: effect of breakdown voltage. Fuel 183, 583e592. Yan, F., Lin, B., Zhu, C., et al., 2016b. Using high-voltage electrical pulses to crush coal in an air environment: an experimental study. Powder Technol. 298, 50e56. Yan, G., et al., 2018. Enrichment of chalcopyrite using high-voltage pulse discharge. Powder Technol. 340, 420e427. Yan, G., Zhang, B., Duan, C., et al., 2019a. Beneficiation of copper ores based on high- density separationfluidized bed. Powder Technol. 355, 535e541. Yan, G., Zhang, Z., Zhang, B., Zhu, G., Yao, H., Zhu, X., Han, J., Liu, R., Zhao, Y., 2019b. Preferential sequence crushing of copper ore based upon high-voltage pulse technology. Miner. Eng. 131, 398e406. Yuta, A., Atsushi, I., Etsuro, S., 2018. High-voltage pulse crushing and physical separation of polycrystalline silicon photovoltaic panels. Miner. Eng. 125, 1e9. Zhang, L., Xu, Z., 2016. Separating and recycling plastic, glass, and gallium from waste solar cell modules by nitrogen pyrolysis and vacuum decomposition. Environ. Sci. Technol. 50 (17), 9242e9250. Zhang, B., Zhang, Z., Ma, Z., et al., 2020. Oil shale upgrading by gas-solid high density separationfluidized bed under secondary accumulation distribution. Fuel 262, 116468. Zhao, Y., Zhang, B., Duan, C., et al., 2015. Material port fractal of fragmentation of waste printed circuit boards (WPCBs) by high-voltage pulse. Powder Technol. 269, 219e226. Zhu, G., Zhang, B., Zhao, P., Duan, C., Zhao, Y., et al., 2019. Upgrading low-quality oil shale using high-density gas-solidfluidized bed. Fuel 252, 666e674. Zuo, W., Shi, F., 2015. A t10-based method for evaluation of ore pre-weakening and energy reduction. Miner. Eng. 79, 212e219. Table 3 Enrichment rate bvalue of Ag under different operating parameters. Level operating parameter Electrode gap Pulse Voltage 1 1.79 1.24 1.59 2 1.73 2.37 3.08 3 2.06 1.55 2.22 4 1.92 1.28 2.54 5 2.67 1.67 2.38 P. Zhao et al. / Journal of Cleaner Production 257 (2020) 120442 8