Jintao Gao

Process of Re-Resourcing of Converter Slag

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 (wTFe = 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.

Experimental study on solid state recovery of metallic resources from EAF dust

Abstract A new process to recover iron and zinc from electric arc furnace (EAF) dust in a solid state has been developed. It comprises three steps: (1) reduction of dust (<1000°C) using gas reductant with high H2 or CO content; (2) for the solid product of step (1), wet magnetic separation to separate Fe from gangue; and (3) for the condensed fumes collected in step (1), water washing to remove soluble compounds like KCl and enrich and recover the zinc oxide. The performance of this process indicates that four kinds of resources could be obtained, iron rich materials (TFeu200a=u200a92·3%); enriched zinc-rich materials (ZnOu200a=u200a83·7%); gangue produced in the wet magnetic separation, which can be used as a building material, and KCl solution. The process is greatly energy saving since it is carried out at low temperature so that sintering would not happen. This means that the iron can be separated directly by physical methods which avoid crushing and grinding.

Laboratory assessment of isothermal separation of V containing spinel phase from vanadium slag by centrifugal casting

Abstract V containing spinel phase was successfully separated from vanadium slag by centrifugal casting. With the process parameters of Gu200a=u200a900 (where normal gravity Gu200a=u200a1), tu200a=u200a20 min and Tu200a=u200a1557 K, almost all V containing spinel phase is enriched in the concentrate, while the tailing is made up of Fe2SiO4, Fe2TiO4 and Mn2VO4 phases. Under the hypothesis that the vanadium and silicon exist in the slag as V2O3 and SiO2, the mass fractions of V2O3 and SiO2 in the concentrate are 25·2 and 2·2%, while those of the tailing are 0·8 and 32·2% respectively. The recovery ratio of V in the concentrate is up to 97·4%, while the removal ratio of Si is 92·5% by centrifugal separation.

Separation of Anosovite from Modified Titanium-Bearing Slag Melt in a Reducing Atmosphere by Supergravity

The anosovite was effectively separated from the modified titanium (Ti)-bearing slag melt in a reducing atmosphere by supergravity. The slag melt went through the filter along the supergravity direction, whereas the high-purity rod-shaped anosovite crystals of size 200 to 4000 μm were intercepted by the filter and separated from the slag melt. Moreover, the effects of slag composition and gravity coefficient on the reduction, precipitation, and separation of anosovite crystals were investigated further.

Viscosity Measurement and Structure Analysis of Cr2O3-Bearing CaO-SiO2-MgO-Al2O3 Slags

In this study, the effects of different Cr2O3 contents and optical basicity (denoted by Λ) on the viscosity and structure of the Cr2O3-bearing CaO-SiO2-MgO-Al2O3 slag were investigated. The viscosities of Cr2O3-bearing CaO-SiO2-MgO-Al2O3 slags in the liquid phase below 1823xa0K (1550xa0°C) were measured by rotating-cylinder method, and the structures of the slags were examined via Raman spectroscopy. Three different parameters were used to characterize the structures of the slags. The results showed that the viscosity of the slags increased as the Cr2O3 content increased, but decreased as Λ increased. The Cr3+ ions acted as network formers and increased the degree of polymerization (DOP), and thus, the addition of Cr2O3 to the slag increased the number of bridging oxygen atoms in the silicate structural units. Generally, the viscosity increased by increasing DOP. In addition, there was a linear inverse relationship between the viscous activation energy (Eμ) and Λ. Furthermore, as the Cr2O3 content increased, the gradients of the plots of Eμ vs Λ decreased. This indicates that for a slag with a high Cr2O3 content, trying to improve the fluidity of the slag by increasing Λ has a limited effect.

Manufacturing of open-cell aluminum foams via infiltration casting in super-gravity fields and mechanical properties

Replicated open-cell aluminum foams were produced by infiltration casting in super-gravity fields. Infiltration of preforms packed by NaCl particles with different sizes was conducted to demonstrate the technical feasibility of this method. The relative densities between 0.25 and 0.34 of the aluminum foams were obtained by varying the NaCl particle size of the preform from 600 to 200 μm. Increasing the gravity coefficient (G) increased the centrifugal pressure (Pc) and correspondingly improved the relative densities and structural integrity of the resulting foams. As Pc increased, the aluminum foam exhibited a transition from a structure of smooth struts to a relatively complex structure where many protrusions extended inside the pores from the surface of the struts. Also, the specific relationship between the minimum centrifugal pressures necessary to produce self-standing aluminum foams and the NaCl particle size of the preform was established. The minimum centrifugal pressures of 32, 49 and 83 kPa were required for aluminum foams with pore sizes of 600, 400 and 200 μm, respectively. Preliminary results show that super-gravity infiltration is promising to be a practical manufacture process for replicated open-cell aluminum foams.

Selective precipitation and in situ separation of rutile crystals from titanium bearing slag melt in a super-gravity field

This manuscript proposes a novel method of selectively precipitating and separating rutile (TiO2) crystals from titanium bearing slag melt using super-gravity, and also develops a new approach for investigating a specified crystal from various melts through selective precipitation, in situ separation and ex situ characterization in a super-gravity field. The precipitation behaviors of titanium bearing slag melt with decreasing temperature indicate that the titanium precipitated selectively into rutile crystals under the conditions of a slag basicity of 0.5 and a TiO2 content of 22–25 wt%, with 1573–1473 K as the optimum precipitation temperature range. Consequently, in situ separation of rutile crystals from the slag melt was conducted in a super-gravity field at the precipitation temperature, where rutile crystal was the only solid phase and other minerals formed molten slag. The slag melt went through a filter as driven by super-gravity, whereas the rutile crystals were overall intercepted by the filter and separated from the slag. In addition, the efficiency of the rutile-slag separation and purity of the separated rutile crystals were enhanced significantly with increasing the gravity coefficient. Accordingly, the high-purity rutile crystals with a dendritic structure were attained with G = 600 at T = 1553 K for 5 min, and the mass fraction of TiO2 in the separated rutile phase was up to 95.56 wt%.

Evolution of microstructure, mechanical and magnetic properties of electrodeposited 50% Ni-Fe alloy foil after thermal treatment

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 6 h.

Rapid Separation of Copper Phase and Iron-Rich Phase From Copper Slag at Low Temperature in a Super-Gravity Field

A novel approach for quickly separating a metal copper phase and iron-rich phase from copper slag at low temperature is proposed based on a super-gravity method. The morphology and mineral evolution of the copper slag with increasing temperature were studied using in situ high-temperature confocal laser scanning microscopy and ex situ scanning electron microscopy and X-ray diffraction methods. Fe3O4 particles dispersed among the copper slag were transformed into FeO by adding an appropriate amount of carbon as a reducing agent, forming the slag melt with SiO2 at low temperature and assisting separation of the copper phase from the slag. Consequently, in a super-gravity field, the metallic copper and copper matte were concentrated as the copper phase along the super-gravity direction, whereas the iron-rich slag migrated in the opposite direction and was quickly separated from the copper phase. Increasing the gravity coefficient (G) significantly enhanced the separation efficiency. After super-gravity separation at Gu2009=u20091000 and 1473 K (1200u2009°C) for 3 minutes, the mass fraction of Cu in the separated copper phase reached 86.11 wt pct, while that in the separated iron-rich phase was reduced to 0.105 wt pct. The recovery ratio of Cu in the copper phase was as high as up to 97.47 pct.

Gaseous reduction of ultrafine metallurgical dust in rotary furnace

A laboratory scale rotary furnace has been developed for gaseous reduction of ultrafine metallurgical dusts to produce iron, zinc and other metal resources at submelting point temperatures. The kinetics of this process is much higher than say static or moving bed systems. By way of example, using dust with 38%Fe and 10%Zn, a 17u200amin treatment at 900°C produces an iron product of ∼92%Fe and a zinc product of ∼86%Zn.