Secondary aluminum dross(SAD),a by-product of aluminum extraction from primary aluminum dross,contains metallic aluminum particles coated with dense oxidized films,complicating the recovery of metallic aluminum using ...Secondary aluminum dross(SAD),a by-product of aluminum extraction from primary aluminum dross,contains metallic aluminum particles coated with dense oxidized films,complicating the recovery of metallic aluminum using traditional methods.Ball-milling was employed to break and alter the structure of these oxidized films.The results indicated that the films became thinner and stripped away,exposing the aluminum surface.Based on the in-situ observation of the structure evolution of milled SAD particles with temperature,the metallic aluminum liquid was efficiently recovered from SAD at 680℃via supergravity-enhanced separation,where the recovery ratio and mass fraction of Al in the separated aluminum phase were up to 95.72%and 99.10 wt.%,respectively.Moreover,the tailings can be harmlessly utilized in refractory,cement and ceramic fields with subsequent treatment,such as denitrification,dechlorination,and fluoride fixation.展开更多
A 3D model applying temperature-and carbon concentration-dependent material properties was developed to describe the scrap melting behavior and carbon diffusion under natural convection.Simulated results agreed reason...A 3D model applying temperature-and carbon concentration-dependent material properties was developed to describe the scrap melting behavior and carbon diffusion under natural convection.Simulated results agreed reasonably well with experimental ones.Scrap melting was subdivided into four stages:formation of a solidified layer,rapid melting of the solidified layer,carburization,and carburization+normal melting.The carburization stage could not be ignored at low temperature because the carburization time for the sample investigated was 214 s at 1573 K compared to 12 s at 1723 K.The thickness of the boundary layer with significant concentration difference at 1573 K increased from 130μm at 5 s to 140μm at 60 s.The maximum velocity caused by natural convection decreased from 0.029 m·s^(−1)at 5 s to 0.009 m·s^(−1)at 634 s because the differences in temperature and density between the molten metal and scrap decreased with time.展开更多
The phosphorus migration mechanism during melting separation of non-carbon-reduced high phosphorus iron ore was investigated.Firstly,the equilibrium compositions of hydrogen-reduced high phosphorus iron ore at differe...The phosphorus migration mechanism during melting separation of non-carbon-reduced high phosphorus iron ore was investigated.Firstly,the equilibrium compositions of hydrogen-reduced high phosphorus iron ore at different temperatures were simulated by the use of equilibrium composition module of HSC Chemistry software.Then,thermodynamic calculation was verified by the real heat treatment of simulated hydrogen-reduced high phosphorus iron ore with several pure reagents including self-made pure fluorapatite.The iron particles in the simulated samples gathered and grew up during heat treatment.Meanwhile,the hypoeutectic structure of Fe-P with grid shape of high phosphorus phase and circular shape of low phosphorus phase emerged within those iron particles.With the penetration of phosphorus from the periphery into the iron particles,the grid structure became denser and denser.It proves that the elemenlal phosphorus can be reduced from the gangue phase by metallic iron without solid carbon at high temperatures.展开更多
A new approach of removing the phosphorus-rich phase from high-phosphorous iron ore by melt separation at 1573 K in a super-gravity field was investigated. The iron？slag separation by super-gravity resulted in phosph...A new approach of removing the phosphorus-rich phase from high-phosphorous iron ore by melt separation at 1573 K in a super-gravity field was investigated. The iron？slag separation by super-gravity resulted in phosphorus being effectively removed from the iron-rich phase and concentrated as a phosphorus-rich phase at a temperature below the melting point of iron. The samples obtained by super-gravity exhibited obvious layered structures. All the iron grains concentrated at the bottom of the sample along the super-gravity direction, whereas the molten slag concentrated in the upper part of the sample along the opposite direction. Meanwhile, fine apatite crystals collided and grew into larger crystals and concentrated at the slag–iron interface. Consequently, in the case of centrifugation with a gravity coefficient of G = 900, the mass fractions of the slag phase and iron-rich phase were similar to their respective theoretical values. The mass fraction of MFe in the iron-rich phase was as high as 97.77wt% and that of P was decreased to 0.092wt%.展开更多
The reduction behavior of single iron ore particle was investigated at high temperatures(above 1373 K)with CO/CO2 mixture.A high-temperature laser scanning confocal microscope for in situ observation and a vertical qu...The reduction behavior of single iron ore particle was investigated at high temperatures(above 1373 K)with CO/CO2 mixture.A high-temperature laser scanning confocal microscope for in situ observation and a vertical quenching furnace for offline characterization were designed.The reduction process of ore particles at different temperatures and in different atmospheres was videoed using the confocal microscope.In the temperature range studied,the transformation of Fe2O3-FeO firstly occurred in the ore particles,and there was no metallic iron until the ore particles completely converted to FeG phase.During the formation of FeO phase,its crystal lattice transforms along the most close-packed direction of its close-packed plane(111).The gangue-rich area firstly melts during reduction around 1573 K.Above 1673 K,the iron ore particles melt and form spherical liquid drops with metallic iron in the center.The gas-based reduction behavior of iron ore particles above 1373K is deduced and graphically presented.展开更多
Experiments on the solid-state reaction between iron ore particles and MgO were performed to investigate the coating mechanism of MgO on the iron ore particles＇ surface during fluidized bed reduction. MgO powders and...Experiments on the solid-state reaction between iron ore particles and MgO were performed to investigate the coating mechanism of MgO on the iron ore particles＇ surface during fluidized bed reduction. MgO powders and iron ore particles were mixed and compressed into briquettes and, subsequently, roasted at different temperatures and for different time periods. A Mg-containing layer was observed on the outer edge of the iron ore particles when the roasting temperature was greater than 1173 K. The concentration of Fe in the Mg-containing layer was evenly distributed and was approximately 10wt%, regardless of the temperature change. Boundary layers of Mg and Fe were observed outside of the iron ore particles. The change in concentration of Fe in the boundary layers was simulated using a gas–solid diffusion model, and the diffusion coefficients of Fe and Mg in these layers at different temperatures were calculated. The diffusion activation energies of Fe and Mg in the boundary layers in these experiments were evaluated to be approximately 176 and 172 k J/mol, respectively.展开更多
In order to expand the application of the electrodeposited Ni-Fe alloy foil,their mechanical and magnetic properties were studied after heat treatment.The development of grain growth during annealing was in-situ onlin...In order to expand the application of the electrodeposited Ni-Fe alloy foil,their mechanical and magnetic properties were studied after heat treatment.The development of grain growth during annealing was in-situ online investigated using a heating stage microscope,and the texture was analyzed via X-ray diffraction（XRD）and electron back-scattered diffraction（EBSD）.The results indicated that abnormal grain growth usually occurred during annealing at 1000-1050°C.The{111}oriented grains preferentially grew as the annealing temperature and holding time increased.The plasticities of the electrodeposited Ni-Fe alloy foils after heat treatment were better than those of the original samples.The excellent ductility was obtained without a loss in magnetic properties after annealing at 1100°C for 6h.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52304342,52174275,51774037)the China Postdoctoral Science Foundation(No.2021M700393)。
文摘Secondary aluminum dross(SAD),a by-product of aluminum extraction from primary aluminum dross,contains metallic aluminum particles coated with dense oxidized films,complicating the recovery of metallic aluminum using traditional methods.Ball-milling was employed to break and alter the structure of these oxidized films.The results indicated that the films became thinner and stripped away,exposing the aluminum surface.Based on the in-situ observation of the structure evolution of milled SAD particles with temperature,the metallic aluminum liquid was efficiently recovered from SAD at 680℃via supergravity-enhanced separation,where the recovery ratio and mass fraction of Al in the separated aluminum phase were up to 95.72%and 99.10 wt.%,respectively.Moreover,the tailings can be harmlessly utilized in refractory,cement and ceramic fields with subsequent treatment,such as denitrification,dechlorination,and fluoride fixation.
基金the National Key R&D Program of China(No.2019YFC1905701)the National Natural Science Foundation of China(Nos.51674022,51734003)the Key projects of NSFC(No.U1960201).
文摘A 3D model applying temperature-and carbon concentration-dependent material properties was developed to describe the scrap melting behavior and carbon diffusion under natural convection.Simulated results agreed reasonably well with experimental ones.Scrap melting was subdivided into four stages:formation of a solidified layer,rapid melting of the solidified layer,carburization,and carburization+normal melting.The carburization stage could not be ignored at low temperature because the carburization time for the sample investigated was 214 s at 1573 K compared to 12 s at 1723 K.The thickness of the boundary layer with significant concentration difference at 1573 K increased from 130μm at 5 s to 140μm at 60 s.The maximum velocity caused by natural convection decreased from 0.029 m·s^(−1)at 5 s to 0.009 m·s^(−1)at 634 s because the differences in temperature and density between the molten metal and scrap decreased with time.
基金the China Postdoctoral Science Foundation(2017M610768)the Open Projects of State Key Laboratory of Advanced Metallurgy(No.41617013)the National Key Research and Development Plan of China(2016YFB0601304).
文摘The phosphorus migration mechanism during melting separation of non-carbon-reduced high phosphorus iron ore was investigated.Firstly,the equilibrium compositions of hydrogen-reduced high phosphorus iron ore at different temperatures were simulated by the use of equilibrium composition module of HSC Chemistry software.Then,thermodynamic calculation was verified by the real heat treatment of simulated hydrogen-reduced high phosphorus iron ore with several pure reagents including self-made pure fluorapatite.The iron particles in the simulated samples gathered and grew up during heat treatment.Meanwhile,the hypoeutectic structure of Fe-P with grid shape of high phosphorus phase and circular shape of low phosphorus phase emerged within those iron particles.With the penetration of phosphorus from the periphery into the iron particles,the grid structure became denser and denser.It proves that the elemenlal phosphorus can be reduced from the gangue phase by metallic iron without solid carbon at high temperatures.
基金financially supported by the National Natural Science Foundations of China(Nos.51404025 and 51234001)the Fundamental Research Funds for the Central Universities of China(FRF-TP-15-009A2)
文摘A new approach of removing the phosphorus-rich phase from high-phosphorous iron ore by melt separation at 1573 K in a super-gravity field was investigated. The iron？slag separation by super-gravity resulted in phosphorus being effectively removed from the iron-rich phase and concentrated as a phosphorus-rich phase at a temperature below the melting point of iron. The samples obtained by super-gravity exhibited obvious layered structures. All the iron grains concentrated at the bottom of the sample along the super-gravity direction, whereas the molten slag concentrated in the upper part of the sample along the opposite direction. Meanwhile, fine apatite crystals collided and grew into larger crystals and concentrated at the slag–iron interface. Consequently, in the case of centrifugation with a gravity coefficient of G = 900, the mass fractions of the slag phase and iron-rich phase were similar to their respective theoretical values. The mass fraction of MFe in the iron-rich phase was as high as 97.77wt% and that of P was decreased to 0.092wt%.
文摘The reduction behavior of single iron ore particle was investigated at high temperatures(above 1373 K)with CO/CO2 mixture.A high-temperature laser scanning confocal microscope for in situ observation and a vertical quenching furnace for offline characterization were designed.The reduction process of ore particles at different temperatures and in different atmospheres was videoed using the confocal microscope.In the temperature range studied,the transformation of Fe2O3-FeO firstly occurred in the ore particles,and there was no metallic iron until the ore particles completely converted to FeG phase.During the formation of FeO phase,its crystal lattice transforms along the most close-packed direction of its close-packed plane(111).The gangue-rich area firstly melts during reduction around 1573 K.Above 1673 K,the iron ore particles melt and form spherical liquid drops with metallic iron in the center.The gas-based reduction behavior of iron ore particles above 1373K is deduced and graphically presented.
基金supported by the Fundamental Research Funds for the Central Universities (FRF-TP-15-009A2)the Project Funded by China Postdoctoral Science Foundation (2015M570931)+1 种基金the National Natural Science Fund Project of China (91534121)the National Major Scientific Instruments Special Plan (2011YQ12003907)
文摘Experiments on the solid-state reaction between iron ore particles and MgO were performed to investigate the coating mechanism of MgO on the iron ore particles＇ surface during fluidized bed reduction. MgO powders and iron ore particles were mixed and compressed into briquettes and, subsequently, roasted at different temperatures and for different time periods. A Mg-containing layer was observed on the outer edge of the iron ore particles when the roasting temperature was greater than 1173 K. The concentration of Fe in the Mg-containing layer was evenly distributed and was approximately 10wt%, regardless of the temperature change. Boundary layers of Mg and Fe were observed outside of the iron ore particles. The change in concentration of Fe in the boundary layers was simulated using a gas–solid diffusion model, and the diffusion coefficients of Fe and Mg in these layers at different temperatures were calculated. The diffusion activation energies of Fe and Mg in the boundary layers in these experiments were evaluated to be approximately 176 and 172 k J/mol, respectively.
基金funded by National Natural Science Foundation of China(51234001)
文摘In order to expand the application of the electrodeposited Ni-Fe alloy foil,their mechanical and magnetic properties were studied after heat treatment.The development of grain growth during annealing was in-situ online investigated using a heating stage microscope,and the texture was analyzed via X-ray diffraction（XRD）and electron back-scattered diffraction（EBSD）.The results indicated that abnormal grain growth usually occurred during annealing at 1000-1050°C.The{111}oriented grains preferentially grew as the annealing temperature and holding time increased.The plasticities of the electrodeposited Ni-Fe alloy foils after heat treatment were better than those of the original samples.The excellent ductility was obtained without a loss in magnetic properties after annealing at 1100°C for 6h.
