Publications

Influence of Particle Size Distribution on Agglomeration/defluidization of Iron Powders at Elevated Temperature

The effects of particle size distribution (narrow, Gaussian, binary and flat) on high-temperature defluidization behavior of iron powder were investigated. The fluidization characteristics were studied involving minimum fluidization velocity, bubbling velocity and bed voidage. The thermo-mechanical analysis was applied to examine the sintering temperature and surface viscosity of iron powder due to surface softening. The results indicated that the effects of PSD on defluidizaton were dependent on temperature. The Gaussian distribution was favorable to fluidization and presented better fluidization quality at lower temperatures. However, at higher temperatures, the narrow distribution exhibited a higher defluidization temperature and thus a lower agglomeration tendency due to a larger apparent viscosity and lower particle stickiness. Therefore, the PSD apparently affected not only hydrodynamic behavior, but also particle adhesion of bed materials for defluidization.

Effect of Basicity on the Solid Solution Behavior of Phosphorus and In Situ Separation of nC2S–C3P Solid Solution from Molten Steelmaking Slag via Super-Gravity

Residual phosphorus (P) is one of the main factors limiting the recycling of steelmaking slag from the steelmaking process. In this study, the effect of ba

Effects of super-gravity field on precipitation and growth kinetics of perovskite crystals in CaO–TiO₂–SiO₂–Al₂O₃–MgO melt

The precipitation and growth behaviours of perovskite crystals from CaO–TiO2–SiO2–Al2O3–MgO melt in a super-gravity field with different gravity coefficients at different cooling rates were investigated in this study. In a super-gravity field, the first precipitated perovskite crystals migrated quickly along the super-gravity direction, and gradually concentrated and grown into larger crystals in the bottom area, while the new perovskite crystals keep precipitating and concentrating towards the bottom area simultaneously. Furthermore, by simplifying the layered samples obtained by super-gravity into three areas along super-gravity direction: slag-rich area, interface area and perovskite-rich area, the variations in volume fractions and equivalent diameters of perovskite crystals against gravity coefficients and cooling rates were obtained by weighting the values of the three areas. And the results indicated that increasing gravity coefficient was not only beneficial for the precipitation but also for the growth of perovskite crystals in the slag melt. Afterwards, the effects of super-gravity field on the precipitation and growth kinetics of perovskite crystals were further discussed.

Nucleation and Growth of Iron Whiskers during Gaseous Reduction of Hematite Iron Ore Fines

A high-temperature confocal scanning laser microscope and an online reduction–water quenching experiment system were used to systematically study the generation of iron whiskers during the reduction of hematite ore particles with CO/CO2 gas. The "blooming" phenomenon of the surface during the reduction of iron ore particles was found in this experiment. The orientation of the grain on the longitudinal section of an iron whisker was measured to be uniform by applying the electron back-scattered diffraction technique, which proved that the iron whiskers are most likely to exist in single crystal form. According to the in-situ online experimental video, the average diffusion flux of iron atoms when the layered iron completely covers the surface of the ore particle is about 0.0072 mol/(m2·s). While the iron atom diffusion flux at the root of the iron whisker during the pre-growth process is much larger than the flux when the layered iron is produced, which are defined to be 0.081 mol/(m2·s), 0.045 mol/(m2·s), 0.013 mol/(m2· s), and 0.0046 mol/(m2·s), respectively during the four stages of the growth of an iron whisker. The quantitative relationship between the chemical driving force and the whisker growth is established as Δ G θ + R T ln p CO 2 p CO + 2 n 0.056 r ρ E s T = 0 .

Adsorption equilibrium and kinetics of maxilon blue GRL on cotton fiber

<title>Abstract</title> The adsorption interaction between cotton fibers and dye maxilon blue GRL was systematically investigated under varying contact times, initial dye concentrations, agitation speeds and temperatures; and the adsorption capacity of dyes increases with the increase of those four parameters. Analysis of adsorption isotherms revealed superior fit with the Langmuir model compared to the Freundlich model, and both the saturated adsorption capacity <italic>q</italic>_m and adsorption capacity <italic>K</italic>_F exhibited temperature-dependent enhancement. The adsorption of dye onto cotton fibers could be described satisfactorily by the pseudo-second-order rate model, where both the equilibrium adsorption amount <italic>q</italic>_e and the apparent rate constant <italic>k</italic>₂ increase with elevated agitation speeds and temperatures. Thermodynamic analysis yielded an enthalpy change Δ<italic>H</italic>* of 63.5 kJ·mol⁻¹ and Gibbs energy change Δ<italic>G</italic>* of 8.7 kJ·mol⁻¹, collectively indicating a non-spontaneous endothermic process. The negative entropy change (Δ<italic>S</italic>* = ⎼209.3 J·mol^{− 1}·K^{− 1}) suggested reduced molecular randomness at the solid-liquid interface during adsorption. The low activation energy (<italic>E</italic>ₐ = 11.34 kJ·mol⁻¹) and adsorption enthalpy change confirmed physical adsorption mechanisms dominated by hydrogen bonding. Understanding the interaction between fiber and dye is helpful for optimizing dye utilization in industrial processes and engineering modified cotton fibers for wastewater decolorization.

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 17 min treatment at 900°C produces an iron product of ∼92%Fe and a zinc product of ∼86%Zn.

Recovery of Potassium from K-Feldspar by Thermal Decomposition with Flue Gas Desulfurization Gypsum and CaCO₃: Analysis of Mechanism and Kinetics

The thermal decomposition mechanism of K-feldspar with industrial waste of FGD gypsum to produce soluble potassium (K) salt was investigated. Effects of the reaction temperature and the amount of reagents used on the recovery of K were studied. The results showed that increasing the reaction temperature and mass ratio of CaCO3/KAlSi3O8 and CaSO4/KAlSi3O8 was beneficial to the decomposition of K-feldspar. The recovery ratio of K was higher than 90% with the mass ratio of KAlSi3O8:CaSO4:CaCO3 = 1:1:3 at 1373 K for 40 min, and the product K2SO4 with a purity of 91.3% was obtained. A crystal structure disintegration mechanism for KAlSi3O8 was proposed on the basis of the characterization of phase transformation sequences by XRD, FTIR, and SEM/EDS. It was found that two product layers formed successively during the KAlSi3O8 decomposition process. K was enriched in the outer product layer, and the decomposition rate was controlled by Ca diffusion through the inner one. Based on the experimental results, a kinetics model of K-feldspar decomposition was established using the Crank-Ginstling-Brounshtein equation, and the apparent activation energy was determined.

Efficient recovery of metallic aluminum from hazardous secondary aluminum dross via ball-milling and supergravity-enhanced separation

Viscosity of RE-bearing slag systems and kinetics of nucleation and growth for RE-phases

The RE-bearing slag with a considerable concentration of rare earths have attracted widespread attention in recent years, while the serious lack of basic data greatly limits its development and utilization. The viscosity of RE-bearing slag and kinetics for nucleation and growth of RE-phase are basic data which closely related to the mass transfer, separation and recovery of rare earths in the slag. However, the current reports on viscosity of RE-bearing slags are extremely scanty, and the existing viscosity models also have limitations due to the lack of thermodynamic data of rare earths. In this study, the viscosities of various RE-bearing slag systems (CaO–SiO2–Ce2O3, CaO–SiO2–CaF2–Ce2O3 and CaO–SiO2–CaF2–P2O5–Ce2O3) were firstly measured by the rotating cylinder method, and the change rules of viscosity for RE-bearing slag with CaF2 and P2O5 were reported. Moreover, the nucleation and growth kinetics of various RE-phases (calcium cerite, cefluosil, and britholite) were comprehensively studied, and the crystallization ability of RE-phases in RE-bearing slag was found to be cefluosil, followed by britholite and calcium cerite. The basic data reported in this study provide the necessary reference and guidance for recovery and utilization of rare earths in RE-bearing slag.

Selective Crystallization and Separation of P in P-Bearing Slag

Reports the selective crystallization and separation of P in P-bearing slag. The solid solution behavior of P and selective crystallization behavior of C2S-C3P in CaO–SiO2–FeO–MgO–P2O5 system are reported in Sect. 6.1. The study on motion and separation of C2S–C3P in CaO–SiO2–FeO–MgO–P2O5 system and steelmaking slag is included in Sects. 6.2 and 6.3, respectively.

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

V containing spinel phase was successfully separated from vanadium slag by centrifugal casting. With the process parameters of G = 900 (where normal gravity G = 1), t = 20 min and T = 1557 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.

Selective Crystallization and Separation of B in B-Bearing Slag

It reports the selective crystallization and separation of B in B-bearing slag. The competitive crystallization behavior of B, Si, and Mg in B-bearing slag is reported in Sect. 3.1. The study on two-stage separation of olivine and suanite, the selective separation of last precipitated suanite, and the crystalline phase transformation and one-step separation of suanite in molten B-bearing slag are included in Sect. 3.2, 3.3, and 3.4, respectively.

Separation of Rare Earth and Fluorite Phases from Bayan Obo Ore at Low Temperature by Super-Gravity

The iron-slag separation of gaseous reduced Bayan Obo ore was conducted at a low temperature by super-gravity for the aim of separating rare earth and fluorite phases. Driven by the super-gravity, the slag melt went through the filter, whereas the iron grains were effectively intercepted by the filter. Moreover, the fluorite remained in solid particles and migrated to the lower slag, while all REEs precipitated into Ca3(Ce,La,Pr,Nd)2[(Si,P)O4]3F crystals and concentrated in the bottom slag at 1373 K–1473 K.

Recovery of Zinc from Zn–Al–Fe Melt by Super-gravity Separation

The removal of iron-containing dross particles and recovery of zinc from galvanizing dross by super-gravity separation was investigated using a model Zn–Fe–Al alloy. After super-gravity separation, the high purity molten zinc went through the filter, while the residue mainly consisting of dross particles was intercepted by the filter and separated from the molten zinc. The effects of gravity coefficient and separating temperature on zinc recovery and iron removal were investigated. The preliminary results show the super-gravity separation is a promising method of recovering zinc from galvanizing dross.

A new method for efficient recovery of rare earth resources from NdFeB waste via selective oxidation and supergravity separation

NdFeB waste is both a secondary resource rich in rare earth elements and a hazardous waste, posing significant recycling potential alongside environmental concerns. However, conventional recycling methods face significant challenges due to high separation temperatures and limited product purity. In response to these issues, this study introduces a novel recycling approach that integrates selective oxidation with a supergravity separation technique, enabling the efficient recovery of rare earth resources from NdFeB waste. Experimental results demonstrate that the addition of 14 wt% carbon powder effectively modulates the oxygen partial pressure within the system, facilitating the formation of rare earth oxides while maintaining iron in its metallic state. Following this, supergravity separation is employed within a temperature range of 1260°C to 1350°C to achieve effective segregation of iron from REEs-rich slag. The findings reveal that, when compared to the rare earth slag produced by traditional slag-iron separation methods at 1550°C, the new process at 1320°C yields a REEs-rich slag with a rare earth content increase from 67.3 wt% to 82 wt% and an improvement in the RE extraction rate from 82.7 % to 99.9 %. These results highlight the potential of this low-temperature, highly efficient process for the recovery of high-purity REEs-rich slag, offering a promising technological pathway for the environmentally sustainable recycling of NdFeB waste.

Selective Crystallization and Separation of REEs in RE-Bearing Slag

It reports the selective crystallization and separation of REEs in RE-bearing slag. The selective crystallization behaviors of RE in RE-bearing slag, including the isothermal phase diagram of CaO–SiO2–CaF2–Ce2O3 system, the phase equilibria of RE-phase, and the isothermal crystallization and growth kinetics of RE-phase are reported, respectively, in Sect. 4.1. The study on selective separation of RE in RE-bearing slag, including the motion and separation behaviors of cefluosil in molten RE-bearing slag, is included in Sect. 4.2.

Phosphorus migration mechanism between iron and high phosphorus gangue phase at high temperatures

The phosphorus migration mechanism during melting separation of non-carbon-reduced high phosphorus iron ore was investigated. Firstly, the equilibrium comp

Mechanism and Prevention of Agglomeration/Defluidization during Fluidized-Bed Reduction of Iron Ore

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.