Search Results (10)

The objective of this work was to study the possibility of upgrading the control system of the drum shear mechanism by using neural network PI controllers to improve the efficiency of the sheet-metal cutting process. The developed detailed model of the mechanism, including a dual DC electric drive with three subordinate control loops for the voltage of the thyristor converter, current and speed of the motors, a 6-mass kinematic system with viscoelastic connections as well as a model of the metal cutting process, made it possible to uncover that the interaction of electric drives with the mechanical part leads to significant speed fluctuations during the cutting process, which worsens the quality of the sheet-metal edge. A modified system of current and speed controllers with built-in three-layer fitting neural networks as nonlinear components of proportional-integral channels is proposed. An algorithm for the fast learning of neural controllers using the gradient descent method in each cycle of calculating the controller signal is also proposed. The developed neuro-regulators make it possible to reduce the amplitude of speed fluctuations during the cutting process by four times, ensuring the effective damping of oscillations and reducing the duration of transient processes to 0.1 s. Full article

The integration of solar generation into national energy balances is associated with a wide range of technical, economic, and organizational challenges, the solution of which requires the adoption of innovative strategies for energy system management. The inherent variability of electricity production, driven by fluctuating climatic conditions, complicates system balancing processes and necessitates the reservation of capacities from conventional energy sources to ensure reliability. Under modern market conditions, the pricing of generated electricity is commonly based on day-ahead forecasts of day energy yield, which significantly affects the economic performance of solar power plants. Consequently, achieving high accuracy in day-ahead electricity production forecasting is a critical and highly relevant task. To address this challenge, a physico-statistical model has been developed, in which the analytical approximation of daily electricity generation is represented as a function of a random variable—cloud cover—modeled by a β-distribution. Analytical expressions were derived for calculating the mathematical expectation and variance of daily electricity generation as functions of the β-distribution parameters of cloudiness. The analytical approximation of daily generation deviates from the exact value, obtained through hourly integration, by an average of 3.9%. The relative forecasting error of electricity production, when using the mathematical expectation of cloudiness compared to the analytical approximation of daily generation, reaches 15.2%. The proposed forecasting method, based on a β-parametric cloudiness model, enhances the accuracy of day-ahead production forecasts, improves the economic efficiency of solar power plants, and contributes to strengthening the stability and reliability of power systems with a substantial share of solar generation. Full article

Magnesium is a valuable industrial metal prized for its strength and reactivity. Traditionally, magnesium was extracted from seawater and brines. However, to meet the rising global demand, it is now primarily sourced from mineral deposits. This shift has sparked renewed interest in extracting magnesium from non-saline sources, including carbonates, silicates, halides, oxides, and hydroxides. This review examines the extraction technologies currently used for these mineral-based resources, including pyrometallurgical, hydrometallurgical, and electrometallurgical methods. Each method is assessed based on the reactions involved in the transformation, operational principles, efficiency, and energy requirements. The review emphasizes the importance of mineral pretreatment—thermal, mechanical, and chemical—in improving magnesium recovery, especially from refractory silicates. By summarizing recent advancements and process innovations, the review aims to inform future research and industrial practices, and support the development of sustainable, cost-effective, and scalable magnesium extraction strategies. Full article

This study presents a comprehensive mathematical model of a semiconductor structure based on vanadium dioxide (VO₂), specifically in its conductive phase. The model was developed using the finite element method (FEM), enabling detailed simulation of the formation of a conductive channel under the influence of low-frequency alternating voltage (50 Hz). The VO₂ structure under investigation exhibits pronounced electric field concentration at the surface, where the field strength reaches approximately 5 × 10⁴ V/m, while maintaining a more uniform distribution of around 2 × 10⁴ V/m within the bulk of the material. The simulation results were validated experimentally using a test circuit. Minor deviations—no greater than 8%—were observed between the simulated and measured current values, attributed to magnetic core saturation and modeling assumptions. A distinctive feature of the model is its ability to incorporate the nonlinear dependencies of VO₂’s electrical properties on frequency. Analytical expressions were derived for the magnetic permeability and resistivity of VO₂, demonstrating excellent agreement with experimental data. The coefficients of determination (R²) for the frequency dependence of magnetic permeability and resistance were found to be 0.9976 and 0.9999, respectively. The current version of the model focuses exclusively on the conductive phase and does not include the thermally induced metal–insulator phase transition characteristic of VO₂. The study confirms that VO₂-based structures exhibit high responsiveness and nonlinear switching behavior, making them suitable for applications in electronic surge protection, current limiting, and switching elements. The developed model provides a reliable and physically grounded tool for the design and optimization components based on VO₂ in power electronics and protective circuitry. Full article

Metallic materials play a vital role in the economic life of modern societies; hence, research contributions are sought on fresh developments that enhance our understanding of the fundamental aspects of the relationships between processing, properties, and microstructures. Disciplines in the metallurgical field ranging from processing, mechanical behavior, phase transitions, microstructural evolution, and nanostructures, as well as unique metallic properties, inspire general and scholarly interest among the scientific community. Three of the most important elements are included in unit operations in non-ferrous extractive metallurgy: (1) hydrometallurgy (leaching under atmospheric and high-pressure conditions, mixing of a solution with a gas and mechanical parts, neutralization of a solution, precipitation and cementation of metals from a solution aiming at purification, and compound productions during crystallization), (2) pyrometallurgy (roasting, smelting, and refining), and (3) electrometallurgy (aqueous electrolysis and molten salt electrolysis). Advances in our understanding of unit operations in non-ferrous extractive metallurgy are required to develop new research strategies for the treatment of primary and secondary materials and their application in industry. Full article

Recovery of metals from e-waste forms a major focus of circular economy thinking and aligns well with the Sustainable Development Goals (SDG). While hydrometallurgical extraction from electronic printed circuit boards (PCBs) is well established, the separation of metals from the leach liquors, which are complex mixtures, remains a challenge. To achieve selective separation, ion exchange resins with chelating functional groups were employed in the present study. Batch and column studies for selective recovery of Cu²⁺ from a given mixed metals leach solution were conducted using Dowex M4195 resin, and both the adsorption isotherm and kinetics were studied. The process involves three major steps: selective recovery of Cu²⁺ by M4195 at low pH and elution with H₂SO₄; sorption of Ni²⁺ from the raffinate by Dowex M4195 at pH 2 and removal of Fe³⁺ from raffinate. The batch experimental results showed appreciable and selective recovery of copper (51.1%) at pH 0.7 and 40.0% Ni²⁺ was sorbed from raffinate at pH 2.0 with co-adsorption of Fe³⁺ as impurity. The batch adsorption data could be fitted with both Langmuir and Freundlich isotherms and exhibited pseudo-second-order kinetics. Column studies agreed with the Yoon–Nelson model and indicated that Cu²⁺ break-through time in the column decreased with an increase in flowrate from 3.0 to 10.0 min/mL and decreased in sorption capacity, while it was delayed with increased bed heights from 20 to 30 mm. Complete elution of Ni²⁺ was obtained with 2.0 M H₂SO₄ after selective elution of trace impurities with dilute HCl. Iron in the raffinate was removed via the addition of Ca (OH)₂ at pH 4.0 leaving Zn-Al in the solution. Full article

Polysaccharide-based natural polymer electrolyte membranes have had tremendous consideration for the various energy storage operations including wearable electronic and hybrid vehicle industries, due to their unique and predominant qualities. Furthermore, they have fascinating oxygen functionality results of a higher flexible nature and help to form easier coordination of metal ions thus improving the conducting profiles of polymer electrolytes. Mixed operations of the various alkali and alkaline metal–salt-incorporated biopolymer electrolytes based on different polysaccharide materials and their charge transportation mechanisms are detailly explained in the review. Furthermore, recent developments in polysaccharide electrolyte separators and their important electrochemical findings are discussed and highlighted. Notably, the characteristics and ion-conducting mechanisms of different biopolymer electrolytes are reviewed in depth here. Finally, the overall conclusion and mandatory conditions that are required to implement biopolymer electrolytes as a potential candidate for the next generation of clean/green flexible bio-energy devices with enhanced safety; several future perspectives are also discussed and suggested. Full article

The recycling of spent lithium-ion batteries (Li-ion Batteries) has drawn a lot of interest in recent years in response to the rising demand for the corresponding high-value metals and materials and the mounting concern emanating from the detrimental environmental effects imposed by the conventional disposal of solid battery waste. Numerous studies have been conducted on the topic of recycling used Li-ion batteries to produce either battery materials or specific chemical, metal or metal-based compounds. Physical pre-treatment is typically used to separate waste materials into various streams, facilitating the effective recovery of components in subsequent processing. In order to further prepare the recovered materials or compounds by applying the principles of materials chemistry and engineering, a metallurgical process is then utilized to extract and isolate pure metals or separate contaminants from a particular waste stream. In this review, the current state of spent Li-ion battery recycling is outlined, reviewed, and analyzed in the context of the entire recycling process, with a particular emphasis on hydrometallurgy; however, electrometallurgy and pyrometallurgy are also comprehensively reviewed. In addition to the comprehensive review of various hydrometallurgical processes, including alkaline leaching, acidic leaching, solvent (liquid-liquid) extraction, and chemical precipitation, a critical analysis of the current obstacles to process optimization during Li-ion battery recycling is also conducted. Moreover, the energy-intensive nature of discussed recycling process routes is also assessed and addressed. This study is anticipated to offer recommendations for enhancing wasted Li-ion battery recycling, and the field can be further explored for commercialization. Full article

Unit operations (UO) are mostly used in non-ferrous extractive metallurgy (NFEM) and usually separated into three categories: (1) hydrometallurgy (leaching under atmospheric and high pressure conditions, mixing of solution with gas and mechanical parts, neutralization of solution, precipitation and cementation of metals from solution aiming purification, and compound productions during crystallization), (2) pyrometallurgy (roasting, smelting, refining), and (3) electrometallurgy (aqueous electrolysis and molten salt electrolysis). The high demand for critical metals, such as rare earth elements (REE), indium, scandium, and gallium raises the need for an advance in understanding of the UO in NFEM. The aimed metal is first transferred from ores and concentrates to a solution using a selective dissolution (leaching or dry digestion) under an atmospheric pressure below 1 bar at 100 °C in an agitating glass reactor and under a high pressure (40–50 bar) at high temperatures (below 270 °C) in an autoclave and tubular reactor. The purification of the obtained solution was performed using neutralization agents such as sodium hydroxide and calcium carbonate or more selective precipitation agents such as sodium carbonate and oxalic acid. The separation of metals is possible using liquid (water solution)/liquid (organic phase) extraction (solvent extraction (SX) in mixer-settler) and solid-liquid filtration in chamber filter-press under pressure until 5 bar. Crystallization is the process by which a metallic compound is converted from a liquid into a crystalline state via a supersaturated solution. The final step is metal production using different methods (aqueous electrolysis for basic metals such as copper, zinc, silver, and molten salt electrolysis for REE and aluminum). Advanced processes, such as ultrasonic spray pyrolysis, microwave assisted leaching, and can be combined with reduction processes in order to produce metallic powders. Some preparation for the leaching process is performed via a roasting process in a rotary furnace, where the sulfidic ore was first oxidized in an oxidic form which is a suitable for the metal transfer to water solution. UO in extractive metallurgy of REE can be successfully used not only for the metal wining from primary materials, but also for its recovery from secondary materials. Full article

Magnetite is an essential iron-bearing mineral. The primary method of magnetite ore beneficiation involves successive steps of crushing, grinding, and magnetic separation. Reverse cationic flotation is used at the final stage to remove silicate and aluminosilicate impurities from the magnetite concentrate and reduce silica content to 1–3%, depending on metallurgical processing route (electrometallurgy, direct iron reduction). In view of the stringent demands of the magnetite concentrate grade, before flotation, the ore is currently routinely ground down to a particle size below 35 µm, and magnetite particles are ground to a size below 10 µm. This significantly reduces the efficiency of flotation and increases iron loss in the tailings due to the hydraulic report in froth being up to 15–25%. Combined microflotation (CMF) looks to be a promising method of increasing fine-particle flotation efficiency, as it uses relatively small amounts of microbubbles alongside conventional coarse bubbles. Microbubbles act as flotation carriers, collecting gangue particles on their surface, which then coarse bubbles float. The purpose of this study is to explore the effectiveness of CMF for processing a model mixture that contained magnetite particles smaller than 10 µm and glass beads (Ballotini) below 37 µm in size when the initial iron content in the mixture was 63.76%. Commercial reagent Lilaflot 821M was used as both collector and frother. The flotation procedure, which included the introduction of 15 g/t of the collector before the start of flotation, and the addition of 5 g/t of the collector in combination with a microbubble dose of 0.018 m³/t 6 min after starting flotation, ensured an increase in the concentrate grade to 67.63% Fe and iron recovery of 91.16%. Full article