The major resource for recycling Ti is currently in-house Ti scrap generated in smelting and fabrication processes instead of postconsumer Ti products, and the actual recycling rate including cascade ...recycling in the smelting and fabrication industry is high. The major impurities in Ti scrap are O and Fe. High-grade Ti scrap with low O and Fe concentrations is remelted to obtain Ti and its alloys. On the other hand, low-grade Ti scrap with high O and Fe concentrations is used as ferrotitanium for the steel industry. However, if demand for Ti drastically increases, the amount of low-grade Ti scrap generated would exceed the demand for ferrotitanium. Before this happens, technologies for anti-contamination or for efficient O and Fe removal must be developed for efficient utilization of Ti. Herein, the current status of Ti scrap generation and its recycling flow are reviewed. New developments in Ti recycling technology are also discussed.
Fundamental experiments are conducted with the aim of developing an efficient recycling process for rare earth elements (REEs) from neodymium-iron-boron (Nd-Fe-B) permanent magnet scrap. Molten ...magnesium dichloride (MgCl
2
) was chosen as an extraction medium, which can selectively chlorinate and extract REEs in magnet alloys. Dysprosium-containing Nd-Fe-B magnet alloy was immersed in molten MgCl
2
at 1273 K (1000 °C) for 3 to 12 hours. The results of the experiments clearly show that the REEs in the magnetic alloy were successfully extracted into the molten salt, while the Fe-B alloy remained in a solid form. The extraction ratios of Nd and Dy were at most 87 and 78 mass pct, respectively. After the extraction experiment, excess MgCl
2
and Mg were removed by vacuum distillation and the rare earth chlorides were recovered. Thus, the feasibility of this method for efficient recovery of rare earths using molten MgCl
2
is demonstrated.
Recent Progress in Titanium Extraction and Recycling Takeda, Osamu; Ouchi, Takanari; Okabe, Toru H.
Metallurgical and materials transactions. B, Process metallurgy and materials processing science,
08/2020, Letnik:
51, Številka:
4
Journal Article
Recenzirano
Odprti dostop
This paper presents a brief review of the history of titanium smelting and the current trends in related research and development. Presently, both electrolytic and metallothermic reduction processes ...utilizing various feed materials such as titanium oxide are widely studied. However, many challenges remain to be addressed before realizing the practical application of smelting processes utilizing oxide feed. To make titanium a “common metal”, a new reduction process that is high speed, energy-efficient, low cost, and of low environmental impact is required. The current status of titanium recycling is likewise outlined, and the development of the recycling process is discussed. Low-grade titanium scraps heavily contaminated by oxygen and iron are currently used for producing additive alloys (ferro-titanium) in the steel industry. In the near future, if the demand for titanium metal increases dramatically, there could be an oversupply of low-grade titanium scraps in the market. Therefore, the development of anti-contamination and efficient removal processes for oxygen and iron is essential for the efficient utilization of titanium. The development of these technologies is vital for expanding the titanium industry through innovation in both titanium smelting and recycling technologies.
Abstract Titanium (Ti) is an attractive material, abundant in nature and possessing superior mechanical and chemical properties. However, its widespread use is significantly hampered by the strong ...affinity between titanium and oxygen (O), resulting in elevated manufacturing costs during the refining, melting, and casting processes. The current work introduces a high-throughput technique that effectively reduces the oxygen content in molten titanium to a level suitable for structural material applications (1000 mass ppm, equivalent to 0.1 mass%). This technique aspires to streamline the mass production of titanium by seamlessly integrating the refining, melting, and casting processes. The developed method leverages the high affinity of rare-earth metals, such as yttrium (Y), for oxygen. This method utilizes the formation reaction of their oxyhalides (YOF) to directly remove oxygen from liquid titanium, resulting in titanium with a significantly reduced oxygen content of 200 mass ppm. This technique enables the direct conversion of titanium oxide feeds into low-oxygen titanium without requiring conversion into intermediate compounds. Additionally, this process offers a pathway for the upgrade recycling of high-oxygen-content titanium scrap directly into low-oxygen titanium. Consequently, this technology holds the potential to dramatically lower titanium production costs, thereby facilitating its more widespread utilization.
Background
Previous studies have reported that patients undergoing oesophagectomy in high‐volume hospitals experience lower mortality rates. However, there has been ongoing discussion regarding the ...validity of evidence for this association. The purpose of this study was to investigate the relationship between hospital volume and risk‐adjusted mortality following oesophagectomy in Japan, using a nationwide web‐based database.
Methods
The study included patients registered in the database as having undergone oesophagectomy with reconstruction between 2011 and 2013. Outcome measures were 30‐day and operative mortality rates. Logistic regression analysis was used to adjust for hospital volume, surgeon volume and risk factors for mortality after oesophagectomy.
Results
A total of 16 556 oesophagectomies at 988 hospitals were included; the overall unadjusted 30‐day and operative mortality rates were 1·1 and 3·0 per cent respectively. The unadjusted operative mortality rate in hospitals performing fewer than ten procedures per year (5·1 per cent) was more than three times higher than that in hospitals conducting 30 or more procedures annually (1·5 per cent). Multivariable models indicated that hospital volume had a significant effect on 30‐day (odds ratio 0·88 per 10‐patient increase; P = 0·012) and operative (odds ratio 0·86 per 10‐patient increase; P < 0·001) mortality.
Conclusion
In Japan, high‐volume hospitals had lower risk‐adjusted 30‐day and operative mortality rates following oesophagectomy compared with low‐volume hospitals.
Volume outcome effect evident in Japan
Oxygen removal from metallic Ti is extremely difficult and, currently, there is no commercial process for effectively deoxidizing Ti or its alloys. The oxygen concentration in Ti scraps is normally ...higher than that in virgin metals such as in Ti sponges produced by the Kroll process. When scraps are remelted with virgin metals for producing primary ingots of Ti or its alloys, the amount of scrap that can be used is limited owing to the accumulation of oxygen impurities. Future demands of an increase in Ti production and of mitigating environmental impacts require that the amount of scrap recycled as a feed material of Ti ingots should also increase. Therefore, it is important to develop methods for removing oxygen directly from Ti scraps. In this study, we evaluated the deoxidation limit for β-Ti using Y or light rare earth metals (La, Ce, Pr, or Nd) as a deoxidant. Thermodynamic considerations suggest that extra-low-oxygen Ti, with an oxygen concentration of 100 mass ppm or less can be obtained using a molten salt equilibrating with rare earth metals. The results presented herein also indicate that methods based on molten salt electrolysis for producing rare earth metals can be utilized for effectively and directly deoxidizing Ti scraps.
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