Copper matte smelting slag inevitably entrains amounts of copper droplets, which brings about a high loss of copper in copper slag. In this study, a new method was proposed to continuously recover copper droplets from copper matte smelting slag via super-gravity. Motion behavior of copper droplets indicated that a long time of 60–120 min was needed for settling of copper droplets in copper matte smelting slag at 1573–1673 K under gravity. In contrast, copper droplets were directionally separated from copper matte smelting slag within 3–5 min at 1523–1573 K via super-gravity with a high Cu recovery ratio of 97.98%. Moreover, the application experiment of continuous recovery of copper droplets from copper matte smelting slag was carried out in a laboratory-scale apparatus. On this basis, this study provides a cleaner approach to efficiently recover copper resources in copper matte smelting slag with no additives and no additional heat.
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-SiO 2 -CaF 2 -P 2 O 5 -Fe 3 O 4 -RE 2 O 3 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.
The anosovite was effectively separated from the modified titanium (Ti)-bearing slag melt in a reducing atmosphere by supergravity. The slag melt went thro
Massive copper slag containing heavy metals is produced in copper making and 0.5 - 8.0 wt% Cu is lost into it, deserving to be recovered. In this study, the waste coke and gypsum were employed to clean the copper slag, the lost copper was reduction-sulfurized and enriched to the matte droplets. However, the free-settling of matte droplets under normal gravity needed a higher temperature of 1350 ℃. On this basis, the matte droplets were efficiently separated from the cleaned slag via super-gravity at a low temperature of 1200 ℃ within 3 min, the recovery ratio of Cu was up to 99.56%, and the grade of Cu in the matte phase and cleaned slag was 85.84 wt% and 0.08 wt%, respectively. Moreover, the migration, distribution and leaching behavior of heavy metal elements (Pb, Zn, Ni, etc.,) were performed and analyzed, and the treatment and utilization of volatilized vapors and tailings were also discussed. This study proposed a green method to clean the copper slag and simultaneously recover copper resources via reduction-sulfurizing smelting and super-gravity separation at a low temperature, providing scientific guidance and application prospects for the synergistic treatment of hot copper slag with waste coke and gypsum.
Bayer red mud is a kind of solid waste generated during the production of alumina, which is hazardous to environment due to the high alkalinity caused by soluble sodium. Therefore, a green method for solidification and recovery of soluble sodium from red mud through stepwise separation via super-gravity was developed in this research. Firstly, the Na was completely enriched into the Na-rich slag through the separation of FeAl 2 O 4 phase from the red mud via super-gravity. Subsequently, the Na was solidified and recovered further as NaAlSiO 4 from the Na-rich slag via super-gravity separation at its single crystallization temperature of 1423-1323 K. Accordingly, the soluble sodium was recovered stepwise into Na-rich slag and then to the stable phase (NaAlSiO 4 ) from red mud with a high recovery ratio of 78.14%. Moreover, the low leaching ratio of Na + in NaAlSiO 4 confirmed that the soluble sodium in red mud was efficiently solidified and recovered friendly to the environment.
Bayer red mud, a solid waste that is generated during the production of alumina, is classified as an industrial solid waste because of the high alkalinity
The process of “re-resourcing of converter slag” was put forward based on the analysis of the existing steel slag treatment process. The converter slag obtained from Jinan steel plant was studied. After grinding, the slag contained 3.3% of iron particles, 54.84% of magnetic part (ωTVe = 20%), and 41.84% of non-magnetic part, which could be used for making cement directly. At a temperature below 1000 °C, the non-magnetic Fe2 O3 in the slag could be efficiently reduced to magnetic iron by pure H2 and CO. The slag after precise reduction had high degree of dispersion and did not get sintered, which provided an optimum condition for the separation of iron and impurities. To separate the slag and enrich the iron after reduction, the laboratory-scale device of magnetic separation was designed and made. The process of slag re-resourcing, which included magnetic sorting, precise reduction, magnetic separation, and removal of free calcium oxide (f-CaO), was proposed to obtain iron-rich magnetic materials and cement adulterant materials. Through this process, 33 kg iron particles, 150 kg iron-rich material and 700 kg cement could be obtained in each ton slag. Besides, this process to recycle converter slag had a lower energy and material consumption and no pollutant emission.
The Fe-bearing phase and P-bearing phase were successfully separated from a steelmaking slag by the super gravity and the separated efficiency was improved with increasing the separated time. The P-bearing phase precipitating at 1663 K was intercepted by the filter, while most residual melt went through the filter into the lower crucible to form calcium iron and aluminum and solid solution of iron, magnesium and manganese (RO phase) after centrifugal separation. Under the condition of gravity coefficient G=600 g, T=1663 K and t=15 minutes, the mass fraction of P2O5 in the P-bearing slag increased from 2.49 wt% before separation to 3.56 wt% and that of FetO in the Fe-bearing slag from 23.99 wt% to 38.67 wt%. The recovery ratio of P2O5 and FetO accounted for 82.2% and 68.5%, respectively.
The fluidized bed ironmaking technology has attracted the attention of many researchers for decades as a direct reduction ironmaking method with many advantages. This process has been applied as a pretreatment method in many non-blast furnace ironmaking processes. However, the sticking problem hindered its development greatly. Defining the essential cause of sticking, and fundamentally solving this problem are the key steps encountered by this process. The research works related to the prevention of sticking problem during fluidized bed reduction of fine iron ore are comprehensively summarized in this article. The causes of sticking, the influencing factors of sticking and the solution of sticking are firstly discussed, followed by the analysis on the possible development direction of future fluidized bed ironmaking technology.
The mechanisms of agglomeration and defluidization and fluidization characteristic of iron oxide particles were investigated based on the theory of surface diffusion, interface reaction, surface nano/microeffect, and phase transformation. Moreover, a mathematical model was developed to predict the high-temperature defluidization behavior by the force-balance and plastic-viscous flow mechanism, and the fluidization phase diagram was obtained. On these bases, a control method of defluidization and its inhibition mechanism were proposed. As a result, the theoretical system of agglomeration/defluidization in the gas-solid fluidization was developed, and thus afforded theory support and technological bases for the solution of defluidization in industrial fluidized-bed reactors.
Bayan Obo ore has abundant rare earth (RE) reserves, and RE elements (REEs) are mainly transferred into the RE‐bearing slag. However, the utilization of RE‐bearing slag is greatly limited due to the serious lack and ambiguity of RE crystals. In this study, in situ separation of RE crystals from RE‐bearing slag via supergravity was developed, and the high‐purity crystals of britholite with various REEs contents were selectively separated from the CaO–SiO 2 –CaF 2 –P 2 O 5 –Ce 2 O 3 system with a high REEs recovery ratio of 95.58%–98.65%. On this basis, the chemical formula, the crystal structure, and the formation mechanism of britholite were characterized from the high‐purity crystals through a combination of the Rietveld refinement and DFT calculation. It was found that the britholite was verified to be evolved from Ca 5 (PO 4 ) 3 F, there would be an SiO 4 4− instead of a PO 4 3− when a Ce 3+ replaced a Ca 2+ , the chemical formula changed from Ca 5 (PO 4 ) 3 F to Ca 4.377 Ce 0.623 Si 0.6 P 2.4 O 12 F, Ca 3.956 Ce 1.044 Si 1.01 P 1.99 O 12 F, and Ca 3.176 Ce 1.824 Si 1.93 P 1.07 O 12 F with the increase of REEs content, and the substitution range of REEs was between 0 and 2. This study supplements some necessary basic data of RE crystals, which provides the theoretical reference for efficient recovery of RE resources and sustainable utilization of RE‐bearing slag.
Selective precipitation and concentrating of perovskite crystals from titanium-bearing slag melt in the supergravity field was investigated in this study.
Red mud produced in the Bayer process is an ultrafine solid waste containing various metallic elements, which is hazardous to the environment because of its high alkalinity caused by the soluble sodium (Na). In this study, a green method for efficiently solidification and recovery of soluble sodium to eliminate high alkalinity of red mud via super-gravity was developed. Iron-slag melting separation from red mud was firstly conducted at 1523 K, where the Fe was fully recovered into metallic iron and almost all the Na was enriched into the Na-rich slag. Subsequently, the Na was selectively solidified into a stable phase of anorthite at 1373–1323 K, all of which were efficiently separated from the Na-rich slag at 1323 K via super-gravity, where the recovery ratio of Na in anorthite was up to 97.09%. Compared to the red mud, the leaching rates of Na+ in the anorthite and residue were significantly decreased to 0.01% and 0.05%, and the pH of both products was decreased to 8.1–8.4. It was confirmed that the high soluble sodium in red mud was efficiently solidified and recovered into a stable phase of anorthite, and the high alkalinity was fully eliminated in both products which are environmentally friendly.
