Efficient separation of copper and lead is a difficult part in crude lead refining process, in which the copper dross generally contains significant amounts of lead due to the limitations of current slagging extractor equipment. Therefore, a new method was proposed for in-situ efficient removal of copper and minimization of lead loss in crude lead refining process via supergravity separation. The crystallization behavior of copper indicated that for crude lead with a copper content of 2 wt%, copper particles precipitated significantly at 600–330 ℃ and the precipitation rate reached 96.2 % at 330 ℃. Thus, copper removal from crude lead could be carried out via supergravity separation at 330 ℃ and the results indicated that 99.9 % of copper particles were removed and the copper content in the lead liquid could be lowered to 0.0773 wt%, which could be directly transferred to the electrolytic refining process. Meanwhile, the lead content in copper particles was reduced to 21.7 wt%, which was far superior to existing processes. For further reducing the lead loss in the copper removal process, the separation behavior of copper was investigated which suggested that the lead content in copper particles dropped from 21.7 wt% to 1.4 wt% as the temperature increased from 330 to 600 ℃. Hence, a two-step separation was used to further reduce the lead content in the copper particles to 4.5 wt% by supergravity separation at 500 ℃ and 330 ℃, respectively. Finally, a new process route was proposed for efficient in-situ removal copper from crude lead.
Reports the selective crystallization and separation of V in V-bearing slag. The selective crystallization behavior of V-containing spinel in FeO–SiO2–V2O3–TiO2–CaO–MgO system is reported in Sect. 7.1. The study on selective separation of V in V-bearing slag, including the motion and separation behaviors of V-containing spinel in molten V-bearing slag, is included in Sect. 7.2.
Rare-earth concentrate obtained through mineral processing of rare-earth ore was characterized by a high rare-earth content and various rare-earth minerals. To effectively recover rare earth from the rare-earth concentrate, a novel method of enriching rare-earth elements and separating the RE-rich phases from Bayan Obo rare-earth concentrate by super gravity was proposed in current study. The mineral evolutions of rare-earth phases and the migrations of rare earth in various phases with temperature rising were investigated. The variations of mineralogical compositions and microstructures indicated the rare-earth phases transformed into fine britholite, cerium oxyfluoride, rare-earth ferrate and monazite particles at a low temperature range of 1423 K–1523 K, which transformed further into lager equiaxed cerium oxyfluoride crystals and most rare-earth elements enriched into the cerium oxyfluoride phase significantly at a higher temperature range of 1573 K–1773 K. Consequently, separation of the RE-rich phases was carried out at the high temperature range in a super-gravity filed, and the cerium oxyfluoride phase and the britholite containing slag phase were effectively separated by super gravity.
In this study, the investigation on the isothermal enrichment of P-concentrating phase from CaO-SiO 2 -FeO-MgO-P 2 O 5 melt with super gravity was carried out.The results show that there was an obvious stratification appearing in the sample after centrifugal enrichment.The upper part of the sample is loose and porous, while the lower part is smooth and compact.With the help of metallographic microscopy and X-ray diffraction, it is found that the P-concentrating phase gathered in the upper part, while it is hard to find any P-concentrating phase in the lower part of the sample.In addition, the volume fraction and equivalent diameter of P-concentrating phase present gradient distribution along the direction of super gravity.After centrifugal enrichment, the mass fraction of P 2 O 5 in the concentrate is up to 4.92%, while that in the tailing is just 1.08%.The recovery ratio of P 2 O 5 in the concentrate is up to 72.62% with the gravity coefficient G = 600, time t = 20 minutes and temperature T = 1 623 K.
Class III medical devices are defined as those which are implanted inside the human body and applied to maintain normal life and retain original tissue or organic functions. Because these devices are associated with high risk, their effectiveness and safety should be strictly monitored and clinically investigated. The aim of clinical investigation of these medical devices is to ensure the acceptability of their effectiveness and safety levels. On designing the clinical trial, the investigator should determine the indices to assess the effectiveness and safety of medical devices, select reasonable data-analyzing methods, and pay attention to several other issues. Although some guidelines on specific class III medical devices have illustrated those aspects in detail, there is still no comprehensive report that details all those principles and methodologies. This article aims to summarize the common features among the instruction principles and provide technological support for the clinical study of class III medical devices.
The hot dip galvanizing dross is a valuable by-product because it contains high levels of zinc, motivating a search for processes or technologies to allow the cost-effective recovery of the zinc content. In this work, the feasibility of recovering zinc from an industrial galvanizing dross by a novel method of super-gravity separation was investigated. The effects of gravity coefficient (G), separation time (t) and separation temperature (T) on the separation efficiency were evaluated. When the gravity coefficient was higher than 15, the galvanizing dross samples were separated into two parts, i.e. the upper residue and the lower filtered zinc. The majority of the dross particles were retained in the upper residue and the filtered zinc was purified significantly. At G ≥ 500, t ≥ 180 s and T = 510 °C, over 79 wt% zinc was recovered with a high purity of about 99 wt%. Increasing gravity coefficient and separating time favored the zinc recovery, but at G ≥ 500 and t ≥ 60 s, the zinc recovery increased at a very limited rate. Increasing separating temperature benefited the zinc recovery but reduced the iron removal. Also, cake mode filtration was determined to be the dominant mechanism of the super-gravity separation of galvanizing dross in this work.
A method of selective precipitation, <italic>in situ</italic> separation and <italic>ex situ</italic> characterization of rutile crystals from slag melt under super-gravity is proposed.
The Bayan Obo rare-earth concentrate was obtained through mineral processing and massively disposed at the tailing dams. For efficient extraction of the rare earth elements (REEs) from the rare-earth concentrate, a novel approach was proposed to selectively enrich and separate REEs as rare earth oxide fluoride ([Ce,La,Pr,Nd]OF) phase under super gravity. Firstly, the mineral reconstruction behavior of the rare-earth concentrate revealed that REEs were selectively enriched into the rare earth oxide fluoride phase with the temperature’s rising to 1473 K–1773 K under a reductive atmosphere. Subsequently, selective separation of the rare earth oxide fluoride phase was conducted under super gravity at the enriching temperature range, where the REEs were enriched as the single Re-rich phase while other minerals formed the molten slag. Accordingly, high-purity rare earth oxide fluoride phase with a high ∑ReO content of 90.35 wt.% was efficiently separated from the rare-earth concentrate under super gravity at 1773 K with G = 1000 for 10 min, which was accurately characterized for the first time to supplement some lacking data for the Re-rich phase. In addition, this manuscript provided a novel physical separation method for mineral processing.
A green method was proposed for respectively recovering rare earths (REEs) under super-gravity from rare-earth tailings which are massively stockpiled in the Bayan Obo tailings dams. Firstly, the REEs (Ce, La, Pr, Nd) were discovered to be precipitated as the rare earth oxyfluoride, rare earth ferrate and britholite phases respectively at various temperature ranges of 1773–1673 K, 1673–1473 K and 1473–1373 K. However, the Re-rich phases were intimately intertwined with each other in the normal-gravity. Consequently, respective recovery of REEs (Ce, La, Pr, Nd) at their corresponding precipitation temperatures was conducted under the super-gravity. 98.38% of (Ce) were firstly enriched into the rare earth oxyfluoride and separated from the tailings as driven by the super-gravity, 97.70% of (La) were enriched into the rare earth ferrate and separated subsequently, and the residual REEs were precipitated further into britholite. Accordingly, high-purity of rare earth oxyfluoride, rare earth ferrate and britholite phases were attained respectively, achieving the green and efficient recovery of REEs (Ce, La, Pr, Nd) from the tailings with no additives, no hazardous wastes and no secondary pollution.
With the wide application and consumption of rare earths (REs), the secondary resources of RE-bearing blast furnace slag are being investigated as viable resources for the recovery of these critical elements. In this study, the crystallisation behaviour including nucleation and growth kinetics of the RE-phase in RE-bearing blast furnace slag was studied and the optimal precipitation conditions for the RE-phase during the cooling process was obtained, providing an important reference and guidance for the efficient extraction and subsequent functionalised reuse of REs. Subsequently, the supergravity enhanced separation of RE-phase from the slag system was conducted in the optimal precipitation conditions of cooling rate (2 °C/min), experiment temperature (1200 °C), and holding time (100 min). At G = 1000, the RE-phase was successfully separated from molten slag, and the mass fraction of CeO 2 in the separated sample increased from the original 20.51% to 74.85%, and the recovery ratio reached 92.06%. This indicated that the supergravity separation technology is considered to be an effective technology for the enrichment and recovery of REs from RE-bearing blast furnace slag.
The significant increase in global consumption of rare earth elements (REEs) has attracted more attention to the separation of REEs from complex rare-earth systems. Bayan Obo ore is the world’s largest rare-earth deposit, where REEs are mainly transfered to RE-concentrate which contains various species of REEs (mainly includes lanthanide: Ce, La, Pr, and Nd). This study reported a new finding and technology for selective separation of different REEs from Bayan Obo RE-concentrate system. The basic data on phase transformation of different REEs in CaO-SiO2-CaF2-P2O5-Fe3O4-RE2O3 systems were reported, and firstly found that different REEs of Ce, La, Pr and Nd could be selectively enriched into cerium oxide, lanthanum ferrate, praseodymium apatite and neodymium apatite, respectively. A novel technology of separating RE-phases via super gravity was proposed, various high-purity RE-phases containing different REEs were separated and characterized, and the crystal information missing in the current database were supplemented.
Al dross is a hazardous solid waste produced in the smelting of electrolytic Al and contains amounts of metallic Al droplets encapsulated by dense oxidized films. The conventional Al recycling processes from Al dross are either inefficient or prone to producing harmful gases and salt cake. In this study, equimolar amounts of KCl and NaCl were employed to attack and erode the solid oxidized films and the metallic Al and molten salt were recovered simultaneously via super-gravity separation. The erosion behavior of salt flux on Al dross indicated that the Al–Al2O3 interface structure was changed, and the cracks and fractures were formed on the oxidized films, which provided the prerequisite conditions for the movement of Al liquid. On this basis, the metallic Al and molten salt were efficiently recovered from Al dross by the enhanced separation of super-gravity with recovery ratios of 98.51 % and 99.03 %, respectively, preventing the production of hazardous gases and unmanageable salt cake. The recovered molten salt was reused in the process of erosion on oxidized films and Al separation from Al dross, where the recovery ratios of metallic Al and molten salt were also up to 94.87 % and 98.58 % after five cycles of recycling. The final residue can also be utilized in appropriate ways and further provides a sustainable method for Al recovery and resource recycling from Al dross.
In situ observation on the morphology evolution and phosphorous migration of gaseous-reduced, high-phosphorous oolitic iron ore during the melting process
A thermodynamic model was developed to associate the agglomeration tendency with the inherent properties of bed materials. Solid surface energy of metallic iron was calculated by the elastic modulus and lattice constant. Based on the relationship between solid surface energy and temperature, the thermodynamic spontaneity for particle agglomeration was explained, and the limiting temperature to defluidize was determined in a good agreement with the experimental data. Consequently, a criterion for the defluidization was proposed as a reference to select the bed materials.
A new approach to enriching perovskite phase from CaO–TiO2–SiO2–Al2O3–MgO melt by super gravity was investigated. The samples obtained by the gravity coefficient G≥600, time t≥20 min and temperature T≥1578 K appear significant layers and perovskite phase present gradient size distribution in the sample along the super gravity. The layered sample was central cut and characterized by metallographic microscopy, and it is hardly to find any perovskite particles in the upper area of the sample and the perovskite phase gathers at the middle and bottom areas of the sample. The mechanism of moving speed of perovskite particles in super gravity field was also discussed, and the conclusion indicates that the moving speed of perovskite particles is proportional to the square of the perovskite particle size. As a result, large size perovskite particles move a farther distance than the small ones and gather at the bottom of the sample, while small size perovskite particles accumulate in the middle of the sample. Under the hypothesis that the titanium exists in the slag in terms of TiO2, with the gravity coefficient G=600, time t=20 min and temperature T=1578 K, the mass fraction of TiO2 in the concentrate is up to 34.97%, while that of the tailing is just 11.16%. Considering that the mass fraction of TiO2 is 22.34% in the parallel sample, the recovery ratio of Ti in the concentrate is up to 74.16% by centrifugal enrichment.
Bayan Obo is the second largest niobium deposit in the world, and has been developed and utilized as iron ore for a long time because of its low niobium co
