•The electric arc furnace process was analyzed using machine learning methods.•The data-centric approach improved performance on test sets for four models.•Quantitative and qualitative correlations ...between parameters and target are shown.•An increase in natural gas decreases electricity consumption up to 40 kWh/t.•Electricity consumption increases by about 1.5 kWh/t per operating minute.
The electric arc furnace has been the subject of extensive research due to its complex and chaotic nature. Machine learning methods provide a powerful forensic examination of industrial processes as they exclude numerous assumptions and involve irregularities present in industrial conditions. In this study, different machine learning and data processing methods were used to evaluate the energy efficiency parameters of the electric arc furnace process. The dataset was collected over five years, in a steelmaking factory, with 42 features. This data was split into training and test sets, which were used for training and evaluation, respectively. With extensive data management, the data quality and machine learning model performance were improved. It was found that selected models display similar performance, yet the artificial neural network shows greater flexibility when changing targets. The results indicate that a data-centric rather than model-centric approach is better for improving model performance. Using the partial dependence plot and SHAP method, insight was gained into each parameter’s correlation with the target. It was found that the amount of hot heel (melted steel left in the furnace, to be re-heated) was the main factor disturbing the data quality and model performance. It was also demonstrated that data for total oxygen consumption should be divided from the oxygen used into refining and natural gas. This highly improves model performance. Employing a data-centric machine learning model to control and optimize main process parameters (with a small capital investment) leads to lower energy consumption for industrial processes.
Reuse of waste is one of the main principles of sustainable development and circular economy. Secondary alkaline lead slag is a hazardous waste generated in the recycling process of lead-acid ...batteries that may be suitable in construction materials. The environmental impact of the use of lead slag as a partial replacement of fine aggregates in the cement-based stabilization/solidification (S/S) process for the preparation of concrete was studied in this paper. Solidified products containing 10%, 15%, 20%, and 25% slag were laboratory tested by unconfined compressive strength (UCS) analyses and the Toxicity Characteristic Leaching Procedure (TCLP). At the same time, the leachability of toxic elements from solidified products with a high percent of slag was evaluated under environmental conditions for during one year. The results of the UCS and TCLP indicated that utilization of this type of slag in cement-based applications may be justified with its controlled addition. However, the described application of the slag was disputed due to the high release of As under high alkaline environmental conditions. Eh-pH analyses and the geochemical modeling using the software PHREEQC were evaluated, as well as the mechanism of pollutant (Pb, As) immobilization (precipitation, adsorption) as a function of pH conditions.
This paper presents thermochemical synthesis of copper/alumina nanocomposites in a Cu-Al2O3 system with 1–2.5 wt.% of alumina and their characterization, which included: transmission electron ...microscopy: focused ion beam (FIB), analytical electron microscopy (AEM) and high resolution transmission electron microscopy (HRTEM). Thermodynamic analysis was used to study the formation mechanism of desirable products during drying, thermal decomposition and reduction processes. Upon synthesis of powders, samples were cold pressed (2 GPa) in tools dimension 8 × 32 × 2 mm and sintered at temperatures within the range 800–1000 °C for 15 to 120 min in a hydrogen atmosphere. Results of characterization showed that dispersion-strengthened compacts could be produced by sintering of thermo-chemically prepared Cu-Al2O3 powders with properties suitable for material application, such as a contact material exhibiting high strength and high electrical conductivity at the same time. Additional research was carried out in order to analyze the application of the obtained nanocomposite powders for the synthesis of copper/alumina nanocomposites by a new method, which is a combination of a thermochemical procedure and mechanical alloying. The measured values of an electric conductivity and hardness were compared with ones in literature, confirming an advantage of the proposed combined strategy.
By-products from zinc hydrometallurgy are classified as hazardous waste with strong leaching toxicities. Even though numerous research papers are dedicated to valorizing valuable metals in it, the ...primary management route is still disposal or partial reuse, such as the Waelz process. Presented experimental research investigates possibilities of sulfidization and further processing as a technologically sustainable route for valuable metals valorization from non-standard jarosite-PbAg sludge. The comprehensive thermodynamic analysis was done by HSC Chemistry®, through optimizing process parameters, i.e., temperature, sulfur addition, and selection of possible additives. Technological possibility of magnetic separation, flotation, and smelting of sulfidized material was also investigated; the results were below the values that allow practical application, due to the obtained texture of sulfidized jarosite, which does not allow the liberation of minerals. Smelting tests were performed on sulfidized jarosite with sulfur and without and with carbon as additive. By smelting sulfidized jarosite-PbAg sludge with added carbon in sulfidization stage at 1375 °C, obtained products were matte, slag, raw lead, and dust in which base, critical, and slag forming components were valorized. Valuable metals were concentrated in smelting products so as to enable further processing, which also could be interesting in the case of treatment of complex, polymetallic, and refractory primary materials, which represent a significant contribution to the circular economy.
This paper presents an experimentally-proved hydrometallurgical process for selective metals recovery from the waste-printed circuit boards (WPCBs) using a combination of conventional and time-saving ...methods: leaching, cementation, precipitation, reduction and electrowinning. According to the results obtained in the laboratory tests, 92.4% Cu, 98.5% Pb, 96.8% Ag and over 99% Au could be selectively leached and recovered using mineral acids: sulfuric, nitric and aqua regia. Problematic tin recovery was addressed with comprehensive theoretical and experimental work, so 55.4% of Sn could be recovered through the novel physical method, which consists of two-step phase separation. Based on the results, an integral hydrometallurgical route for selective base and precious metals recovery though consecutive steps, (i) Cu, (ii) Sn, (iii) Pb and Ag, and (iv) Au, was developed. The route was tested at scaled-up laboratory level, confirming feasibility of the process and efficiencies of metals recovery. According to the obtained results, the proposed hydrometallurgical route represents an innovative and promising method for selective metals recovery from WPCBs, particularly applicable in small scale hydrometallurgical environments, focused on medium and high grade WPCBs recycling.
This paper describes the synthesis of tungsten disulfide (WS2) powder by the sulfurization of tungsten trioxide (WO3) particles in the presence of additive potassium carbonate (K2CO3) in nitrogen ...(N2) atmosphere, first at lower temperature (200 °C) and followed by reduction at higher temperature (900 °C). In addition, the ultrasonic spray pyrolysis of ammonium meta-tungstate hydrate (AMT) was used for the production of WO3 particles at 650 °C in air. The HSC Chemistry® software package 9.0 was used for the analysis of chemistry and thermodynamic parameters of the processes for WS2 powder synthesis. The crystalline structure and phase composition of all synthesized powders were analyzed by X-ray diffraction (XRD) measurements. The morphology and chemical composition of these samples were examined by scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX).
The aim of this research was to study the effect of graphite addition in the process of synthesis of tribological materials based on tin sulphides. The tin sulphides powders were synthesized from ...selected precursors by pyrometallurgical method in rotary tilting tube furnace. The thermodynamic parameters of the synthesis were determined using HSC Chemistry software modelling package. In addition, the synthesis process was also characterized by the thermal analysis method: simultaneous differential scanning calorimetry and thermogravimetry (DCS-TGA). The characterization of the synthesized tin sulphides powders included analysis of chemical composition by optical emission spectroscopy, phase composition identification by X-ray diffraction (XRD) and examination of morphology, as well as elemental composition by scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). The hexagonal SnS2 and orthorhombic Sn2S3 phases were formed after the thermal treatment of starting powders in nitrogen atmosphere. The obtained results indicate the positive effects of the graphite addition which enables the synthesis of tin sulphide powders with appropriate content of sulphide phases with minimal loss of sulphur.
Secondary alkaline lead slag (SALS), generated during lead–acid batteries recycling, is a hazardous waste due to its high reactivity, solubility, and migration of toxic elements. After pulverization ...caused by storage under atmospheric condition for 30 days, the SALS was sieved and coarse fraction (+ 1 mm) was returned to the recycling process. Finer fraction (− 1 mm) was treated by water leaching to remove soluble compounds. SALS compositions prior and after the pre-treatment and effects of liquid-to-solid ratio, stirring rate, and temperature on Na, S, Fe, As, and Pb leaching from SALS were analyzed. The results show that maximal leaching degrees were 95.78%, 75.32%, and 79.89% for Na, S, and As, respectively (20 l kg
−1
, 600 min
−1
, 333 K, 120 min). Leachability of Na and S from SALS was controlled by dissolution of Na
2
SO
4
that could be recovered from leaching solution. Isothermal As leaching is described by diffusion mechanism with activation energy of 15.5 kJ mol
−1
. Insoluble Pb and Fe sulfates, sulfides, and oxides remained in the SALS. Pre-treated SALS, with reduced mass up to 32%, was solidified in cement matrix. The results of toxicity characteristic leaching procedure and unconfined compressive strength confirmed effectiveness of As removal from SALS by water leaching and Pb immobilization in cement matrix containing 20% of SALS.
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