The main objective described in this paper is the optimization of technological parameters in the production of varistors based on recycled zinc oxide (ZnO). The content of this paper builds on our ...previous research aimed at proving that hydrometallurgically recovered ZnO material, from electric arc furnace dust, is suitable for applications in these semiconductors, an issue which has received very little attention at present. The focus of this research also corresponds to and supports the visions and strategies of environmental sustainability and the circular economy. Samples of ZnO varistors manufactured for this purpose were analyzed by scanning electron microscopy and then the electrical parameters were measured and calculated. Based on the results of the microstructural analysis and electrical properties, prerequisites for the optimal adjustment of technological parameters such as sintering temperature and sintering time were derived, which will be the starting point for further research.
•Manufacture of varistors from recycled zinc oxide (ZnO) product.•Optimization of technological parameters such as sintering temperature and sintering time.•Characterization of electrical properties of recycled ZnO varistors.•Towards the recovery and reuse of industrially significant materials.
The current global primary zinc stocks are estimated to last for approximately 20 years. For this reason, the recycling and processing of waste (especially steelmaking dust) containing zinc are ...currently necessary, and this will remain the case in the future. The main objective, we deal with in this article is the experimental research on electric arc furnace dust (EAFD) compounds which may potentially result in the commercial manufacture of products in the electrotechnical industry. In our work we focus on the production of ZnO-based varistors used in surge protection devices (SPD), which are the current trend in the world. ZnO, a resultant product of hydrometallurgical recycling of zinc-containing dust produced by the remelting of steel waste in an EAF, was used for this research. From the resulting product containing 79.04% Zn, five varistor samples were prepared. Subsequently, their electrical characteristics were measured and calculated on these samples. From the measured electrical parameters, the non-linear characteristic typical of voltage-dependent resistors–varistors is evident. Based on the results of the electrical characteristics, we conclude that the ZnO product, which is the output of hydrometallurgical recycling of EAFD, is a potentially suitable material for use in the production of ZnO varistors in the future.Graphic Abstract
This paper presents a literature review on the processing of used lithium-ion batteries in both industry and research. On an industrial scale, lithium-ion batteries are primarily processed through ...pyrometallurgical methods, leading to incomplete utilisation of lithium cells. On the other hand, the hydrometallurgical route of recycling lithium-ion batteries poses challenges, such as large-scale discharging or inert gas pretreatment, largely due to explosion hazards. Modern methods of lithium-ion battery recycling are oriented toward refining the leach liquor through solvent extraction methods using D2EHPA and Cyanex 272, to recover Co, Mn, and Ni. The final Li product is obtained through Na2CO3 precipitation.
The main objective of this work was to design and construct a device that would facilitate and reduce the intensity of work in the process of scanning surfaces with a Microflown PU Mini acoustic ...probe. Our proposed device will shorten the total time to scan the surface and improve the quality of data measurements. The device was designed to be able to perform movement along the
and
axes, thus achieving scanning of the entire sound field. Some components of the device are manufactured strictly according to particular specifications to suit our requirements. The most important step in the design of the scanning device we prepared for the particular acoustic sensor was the design for the linear connection that fulfills a supporting function for the entire device as well as provides movement along the
and
axes. The final step was the design for the automation of the entire system, for which we selected an Arduino Uno (ATmega328) controller. The actual device was tested in the final stages. The device is designed and tested as functional and able to work on what was intended for and is ready for further modifications or use in practice.
Copper anode furnace dust is waste by-product of secondary copper production containing zinc, lead, copper, tin, iron and many other elements. Hydrometallurgical Copper Anode Furnace dust recycling ...method was studied theoretically by thermodynamic calculations and the proposed method was verified experimentally on a laboratory scale. The optimum condition for leaching of zinc from dust was identified to be an ambient leaching temperature, a liquid/solid ratio of 10 and H2SO4 concentration of 1 mol/L. A maximum of 98.85% of zinc was leached under the optimum experimental conditions. In the leaching step, 99.7% of lead in the form of insoluble PbSO4 was separated from the other leached metals. Solution refining was done by combination of pH adjustment and zinc powder cementation. Tin was precipitated from solution by pH adjustment to 3. Iron was precipitated out of solution after pH adjustment to 4 with efficiency 98.54%. Copper was selectively cemented out of solution (99.96%) by zinc powder. Zinc was precipitated out of solution by addition of Na2CO3 with efficiency of 97.31%. ZnO as final product was obtained by calcination of zinc carbonates.
Sound visualization tools are now widely used in industry. As a tool, acoustic cameras are also well suitable for faster identification of errors as well as individual states when operating devices. ...The aim of this paper was to locate and quantify noise sources on a packet sorting line using an acoustic camera and then to propose noise reduction measures. Localization of noise sources was performed by an acoustic camera with a microphone ring array. The result of these measurements and analyzes was to sort the individual noise sources from less noisy to the noisiest, which gives a good assumption for better planning of spending on the implementation of noise reduction measures. The outputs of these measurements also give information on the character and frequency composition of the sound of individual sources, which will help out in the design of specific noise measures.
Waste generation is a part of every technological process, including galvanizing. The presented paper deals with the characterization of flue dust generated in the process of hot-dip galvanizing, and ...proposes possible methods for zinc recycling. The flue dust is released into the atmosphere as a white fume above the zinc bath, which is caused by the decomposition of ammonium chloride and zinc chloride present in the flux. This dust is classified as hazardous waste and is a material with a particle size below 90 µm. In addition to zinc and iron compounds, it contains water vapor and oils. The presented elemental, phase, and other characteristic methods of flue dust are important for the subsequent selection of a suitable method for processing the material. At present, this waste is not processed separately due to its low production, which is approximately 0.3 kg per 1 tonne of galvanized steel. The proposed hydrometallurgical recycling method enables the processing of flue dust on a small scale and enables the recovery of high-purity zinc in the form of metallic zinc or zinc oxide.
The main aim of the work described in this paper was to design and validate measures to reduce the noise levels in the training center. This training center serves for the practical training of ...students with the focus in the shaping and machining of engineering products. The reduction of noise in training center was mainly due to the clarity and hearing of the spoken word between the lecturer and the students, as well as to reduce the risk of hearing damage. In order to reduce noise levels, it was proposed to overlap the training center with a roof structure filled with sound absorbing material in two solutions. The noise absorption coefficient of the selected material was determined on the impedance tube. For verification of effectiveness, measurements of equivalent A sound levels were made before and after realization noise reduction measures. Reduction the equivalent A sound pressure levels after the noise reduction measures are between 15.5 dB and 17.5 dB depending on the measuring point and the operating mode. The effectiveness of the implemented measures reaches a good level, as noise has been reduced to the recommended legislative level.
Currently, emphasis is still placed on the risk evaluations of physical factors in workplaces. The aim of this paper was to evaluate objectively and subjectively the noise parameters and microclimate ...conditions near the conveyor systems at the workplace for the handling and sorting of postal items. Objective noise measurements were performed using the Norsonic 140 sound analyser, Class 1 and microclimatic conditions using the Testo 435 instrument. The subjective evaluation was performed by the questionnaire method (120; F: 66; M: 54). The result of the research was the assessment of health risks, depending on the sources of noise caused by conveyor systems.
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