Search

With the continuous evolution and development, smelting technology has gradually matured. After the tungsten is extracted through the smelting process, a large amount of tungsten smelting slag is piled up, which has a negative impact on human production and life. The composition of tungsten smelting slag is complex, and there is leaching agent remaining on the surface, which is rich in valuable metals, so the selection of suitable process to recover the valuable metals in tungsten smelting slag can not only reduce the solid waste emission, reduce the pollution of soil and water resources, but also improve the resource utilization rate of valuable metals and reduce the cost of tungsten smelting slag treatment. The reduction, environmental protection and resource treatment of tungsten smelting slag are the key parts of carbon emission reduction in the tungsten industry. The recovery of metal tin out of a mixed tungsten smelting slag from treatment of wolframite and scheelite was experimentally studied. In this slag about 87.59% of the tin in the tungsten smelting slag was distributed in the -0.045 mm particle size, which was difficult to sort. The Knelsen vertical centrifugal separator was selected as the roughing equipment, and the optimal conditions for the roughing process were determined by step-by-step optimization experiments, which were 78.15% -0.038 mm of the grinding fineness, 15% of the feed concentration, 90 G/s of separation cone speed, and 2.60 L/min of backflush water flow. In order to further improve the tin grade of the rough concentrate, the four selection methods were compared and tested, and finally with the gravity separation process of "one roughing and one cleaning centrifugal separation, shaking table and centrifugal separation after classification", under the feed concentration 15%, the speed of the separation cone 90 G/s and the backflush water flow rate 2.75 L/min, the tin grade of tin concentrate was 4.03% and the tin recovery was 52.41%, which realized the effective recovery of valuable metal tin in tungsten smelting slag, and provided a certain reference for the reduction and resource utilization of the tungsten smelting slag. [ABSTRACT FROM AUTHOR]

Copyright of Archeologia Postmedievale is the property of Edizioni all'Insegna del Giglio and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The treatment of spent cemented carbides using the conventional alkali-acid leaching process results in the generation of hazardous solid waste tungsten leaching residue. This study proposed an alternative process using the alkali-treated tungsten leaching residue (AW-residue) without the acid leaching step, preserving Co in the residue. By using photovoltaic silicon kerf waste (SKW) as a reducing agent, heavy metals (Co, Ni, W, Nb, and Ta) were efficiently extracted from AW-residue and a Co-rich alloy was obtained. The silicothermic reduction process facilitated the recovery of iron group metals (Co, Ni, and Fe) and effectively captured trace refractory metals (W, Ta, and Nb). Phase separation occurred through reduction reaction and viscosity-driven processes between the Co-rich alloy and the slag. Optimal conditions were identified as 20% SKW addition, MgO crucible, and a holding time of 120 min, achieving a total recovery yield of 95.5%, with specific yields for Co (97.7%), Ni (97.0%), W (82.5%), Nb (76.3%), and Ta (70.5%). A 20 kg pilot-scale experiment confirmed the feasibility of the process, yielding 47.0% Co-rich alloy from AW-residue compared to 48.3% in lab-scale experiment, and producing a harmless slag phase. This environmentally friendly approach promotes sustainable recycling of valuable metals in the tungsten industry. [Display omitted] • A silicothermic reduction was applied to extract heavy metals from AW-residue. • Photovoltaic silicon kerf waste was used as a low-cost and high-efficient reductant. • The AW-residue was converted to a Co-rich alloy and a harmless slag phase. • The total recovery yield of valuable metals (Co, Ni, W, Nb and Ta) was up to 95.5%. • The Co-rich alloy yield reached 47.0% in a 20 kg pilot-scale experiment. [ABSTRACT FROM AUTHOR]

Tungsten leaching residues are industrial wastes that are largely generated during commercial tungsten production. The residues have been classified as hazardous solid wastes due to the presence of toxic elements. On the other hand, the residues contain valuable elements, such as W, Mn, and Fe which can be recovered for economic benefit. To utilize the residue, a carbothermic reduction process was studied to achieve the effective utilization of the residue and sustainable development of the tungsten industry. Fe-W-Mn alloys and nontoxic slags were obtained successfully at 1450°C, and can be used to produce wear-resisting iron materials and glass–ceramics, respectively. The more effective metal–slag separation was achieved by controlling the MnO concentration of the slag, which impacted the liquidus temperature and the viscosity of the slag. This study confirmed a method for utilizing the tungsten residues, which could be a step toward practical industrial-scale techniques. [ABSTRACT FROM AUTHOR]

Hardmetals intended to perform in harsh operating conditions are developed with the use of metallic powders, in particular, tungsten powders. The growing consumption of tungsten in industry necessitates the improvement of techniques employed to produce it from industrial waste. The objective of this research effort was to reduce metallic tungsten (as a powder) from chloride and chloride–fluoride melts and determine the factors influencing its particle size. The starting material was tungsten oxide (WO3) produced electrochemically from processed raw material (VK-6 tungsten carbide pseudoalloy). The melts were KCl–NaCl–CsBr and NaCl–KCl–CsBr–Na3WO3F3 eutectic mixtures. When the melt with a high WO2F42− content was subjected to electrolysis, tungsten precipitated as a superfine powder. The precipitate morphology showed that the tungsten particle size was dependent on electrolysis conditions. A relatively inexpensive and effective method of producing tungsten powders was developed upon the research. [ABSTRACT FROM AUTHOR]

Taking the waste tungsten tailing sand as the main raw material, using its intrinsic mineral composition and particle gradation, ceramic permeable bricks were prepared by adding binder, and the experimental research on the preparation of high-performance ceramic permeable bricks was carried out, and an effective way for the comprehensive utilisation of tungsten tailing sand was also sought.Permeable ceramic bricks were prepared with waste tungsten tailings and ball clay by a two-stage calcination technology, which involves rapid sintering at high temperature (900–1215 °C) and slow crystallisation at low temperature (<900 °C). The pore structure and flexural strength of permeable bricks were improved synthetically. The composition and sintering parameters were optimised, including the ratio of large (>2 mm) to small (1–2 mm) aggregates (1:1 w/w), content of waste ceramic (20 wt%), binder content (10 wt%), sintering temperature (1215 °C), and sintering time (holding time at the maximum sintering temperature; 60 min). The optimised water-permeable ceramic bricks had high permeability (2.53 × 10−2 cm/s) and excellent flexural strength (4.62 MPa). Therefore, through the recovery of tungsten tailing sand and waste ceramics can protect the environment, save resources, and achieve high-value comprehensive utilisation of tungsten tailing sand, with significant economic and environmental benefits, which is conducive to the sustainable development of the tungsten industry. [Display omitted] • The permeable brick with reasonable porosity was designed by using tungsten tailings through particle grading and binder. • Adoption of two-stage calcination technology, control quartz crystal transformation and interface strength was obtained. • The relationship between microstructure and properties of tungsten tailings permeable brick was expounded. [ABSTRACT FROM AUTHOR]

Tungsten leaching residue (W-residue), a hazardous waste generated from the industrial recovery of the spent tungsten carbides, poses a threat to the environment. The W-residue contains high grades of SiO 2 and TiO 2 oxides, and low grades of high-value metal oxides such as WO 3 , CoO, Ta 2 O 5 , and Nb 2 O 5. Herein, a smelting reduction process was proposed to effectively recover the high-value metals from the W-residue and obtained a medium-entropy carbide (MEC) composite. During the smelting process, the valuable metals were recovered as alloy consisting of (Fe, Co)-rich silicide, (Fe, Cr, W)-rich silicide, and (W, Ta, Nb, Ti)C, respectively. The addition of flux CaO lowered the liquidus temperature of the molten slag, and effective alloy-slag phase separation was achieved by adding Fe as a metal collector to capture the alloy droplets entrapped in the slag. Under the optimal conditions, the total recovery rate reached 86.8%. Moreover, the obtained (W, Ta, Nb, Ti)C as MEC exhibited a Vickers hardness of over 19 GPa and can be used as a wear-resistant alloy. This study proposed a strategy for extracting high-value metals from hazardous tungsten residue, which could complement existing recycling processes towards a closed-loop process in the tungsten industry. [Display omitted] • Clean extraction of high-value metals from W-residue was proposed. • A slag system was designed for the smelting reduction of W-residue. • The CaO-Fe capture agent was effective for the collection of alloy droplets. • More than 86% W, Co, Ta, and Nb are recovered during the smelting process. • The average Vickers hardness of the obtained MEC exceeds 19 GPa. [ABSTRACT FROM AUTHOR]

The preparation of ultra-fine tungsten carbide (WC) is a difficult and hot topic in tungsten industry. The industrial production process requires the need to transform tungsten concentrates to produce ammonium paratungstate (APT) intermediate products followed by hydrogen reduction to produce W, and finally carburization to produce WC. Due to the formation of H 2 O in the hydrogen reduction process, it is difficult to obtain <100 nm tungsten powder materials. Therefore, in this study, a novel method was introduced that synthesizes ultrafine WC via hydrothermal synthesis of ZnWO 4 followed by a carbothermic reduction–carburization process. The findings of this study showed that ZnWO 4 with a particle size of 29 nm was synthesized from Na 2 WO 4 solution. This can solve the problem of ammonia‑nitrogen wastewater discharge in the process of APT preparation, and prepare nano-scale raw material. In addition, zinc is volatile at high temperature, which has been widely used in the field of recycling waste cemented carbide. Based on this, the W C mixed powder was obtained by carbothermic reduction of ZnWO 4 under the condition of excess C addition, which can inhibit the agglomeration of particles and avoid the production of H 2 O. Then the single-phase WC with a particle size of 60 nm was obtained by a carburization reaction process at 1300 °C for 3 h. The research intersects tungsten metallurgy with tungsten material preparation, shortens the production process and reduces waste water discharge. [Display omitted] • Tungsten in the Na 2 WO 4 leaching solution was recovered as ZnWO 4. • Nanometer ZnWO 4 was obtained by hydrothermal method. • W C mixture was produced by carbon reduction of ZnWO 4. • Ultrafine WC was synthesized by a carburization process. • The particle size of the synthesized WC powder is <100 nm. [ABSTRACT FROM AUTHOR]

• W and Mo were separated from peroxotungstic acid solution with TBP and TRPO. • 81 % Mo and 1 % W was extracted using TBP and TRPO. • A maximum single-stage separation coefficient of 400 was reached. • Mo can be separated efficiently from peroxotungstic acid solution. An increasing problem facing the tungsten industry is developing an effective separation of molybdenum from peroxotungstic acid solutions due to the similarities of these two metals. This study herein separates molybdenum from peroxotungstic acid solution for the selective production of tungsten from scheelite acid decomposition residue using hydrogen peroxide. Solvent extraction was the main method employed, and the feed was peroxotungstic acid solution containing peroxomolybdic acid. The concentration of tungsten and molybdenum in the feed and the raffinate were measured by Inductively Coupled Plasma (ICP) to characterize the separation efficiency. The results showed that in the peroxide solution, an organic phase of tributyl phosphate (80 %), trialkyl phosphine oxide (2 %), and sulfonated kerosene (18 %) was used effectively to separate molybdenum from tungsten in acid leach solutions. A maximum single-stage separation coefficient of 400 was reached under the following extraction conditions: temperature, 25 °C; contact time 4–6 min; separation time 4 min; and organic to aqueous ratio, 1.2. Using ammonium bicarbonate as the stripping agent, the stripping ratio of molybdenum and tungsten were 83 % and 33 %, respectively, and the corresponding separation coefficient was 10. [ABSTRACT FROM AUTHOR]