The recoveries of vanadium, chromium, and titanium are much low in the current process of high-chromium vanadium–bearing titanomagnetite. The gas-based direct reduction followed by melting separation process was proposed because the valuable elements including iron, vanadium, chromium, and titanium can be utilized simultaneously and all the recoveries should increase. The melting separation study was carried out in the present work, and the behavior as well as mechanism during melting separation process was investigated. The effect of temperature on the melting separation kinetic was more considerable than thermodynamic. As increased basicity, the area of liquid phase was enlarged and the solubility of Al2O3 in slag was increased. The main mineral in separation slag was anosovite (MgTi2O5), besides a small number of pseudobrookite (Fe2TiO5), perovskite (CaTiO3), and spinel (Ca3Al2O6). The melting separation was improved by the increasing C/O, temperature, time, additive of CaF2, and basicity. The rational melting separation parameters for high-chromium vanadium–bearing titanomagnetite contained a C/O of 1.2, a melting temperature of 1625°C, a melting time range of 40–50 min, an additive CaF2 of 2%, and a basicity of 1.1. Under these conditions (melting time of 50 min), the melting separation was achieved successfully. Both the titanium-bearing slag together with the iron containing vanadium and chromium was obtained. The recoveries of Fe, V, Cr, and TiO2 could reach around 99%, 97%, 92%, and 94%, respectively; and the mass fraction of Fe, V, Cr, and TiO2 were 93.50%, 0.90%, 0.69%, and 37.52%, respectively.
Abstract Based on the fundamental characteristics of high chromium vanadium-titanium magnetite (HCVTM), the effects of roasting temperature and roasting time on the phase transition and oxidation consolidation during the oxidation were investigated systematically. It was shown that the oxidation of HCVTM pellet was not a simple process but complex. With increasing roasting temperature and time, the compressive strength of oxidized pellet was improved. The phase transition during oxidation was hypothesized to proceed as follows: (1) Fe 3 O 4 → Fe 2 O 3 ; (2) Fe 2.75 Ti 0.25 O 4 → Fe 9 TiO 15 + FeTiO 3 → Fe 9 TiO 15 + Fe 2 Ti 3 O 9 ; (3) Fe 2 VO 4 → V 2 O 3 → (Cr 0.15 V 0.85 ) 2 O 3 ; (4) FeCr 2 O 4 → Cr 2 O 3 → Cr 1.3 Fe 0.7 O 3 + (Cr 0.15 V 0.85 ) 2 O 3 . The oxidation consolidation process was divided into three stages: (1)oxidation below 1,173 K; (2) recrystallization consolidation at 1,173 – 1,373 K; (3) particle refining recrystallization-consolidation by the participation of liquid phase at 1,373 – 1,573 K. To obtain the HCVTM oxidized pellet with good quality, the rational roasting parameters included a roasting temperature of 1,573 K and a roasting time of 20 min.
The gas content and permeability of coal reservoirs are the main factors affecting the productivity of coalbed methane. To explore the law of gas content and permeability of coal reservoirs in the Zhijin area of Guizhou, taking No.16, No.27 and No.30 coal seams in Wenjiaba mining area of Guizhou as the engineering background, based on the relevant data of coalbed methane exploration in Wenjiaba block, the geological structure, coal seam thickness, coal quality characteristics,coal seam gas content and permeability of the area were studied utilizing geological exploration, analysis of coal components and methane adsorption test. The results show that the average thickness of coal seams in this area is between 1.32 and 1.85 m; the average buried depth of the coal seam is in the range of 301.3-384.2 m; the gas content of No.16 and No.27 coal seams is higher in the syncline core. The gas content of the No.30 coal seam forms a gas-rich center in the south of the mining area. The buried depth and gas content of coal seams in the study area show a strong positive correlation. Under the same pressure conditions, the adsorption capacity of dry ash-free basis is significantly higher than that of air-dried coal. The permeability decreases exponentially with the horizontal maximum principal stress and the horizontal minimum principal stress. The horizontal maximum primary stress and the flat minimum prominent stress increase with the increase of the buried depth of the coal seam. The permeability and coal seam burial depth decrease exponentially. This work can provide engineering reference and theoretical support for selecting high-yield target areas for CBM enrichment in the block.
Abstract Due to the inherent brittleness and low mechanical strength, it is still a challenge for calcium phosphate (Ca‐P) ceramics to be used in load‐bearing bone defect repair. To achieve a good balance between mechanical strength and osteogenic activity, hollow‐tube‐whisker‐modified biphasic calcium phosphate (BCP) ceramics (BCP‐HW) are successfully fabricated by an in situ growth process in the present study. Compared to the initial BCP ceramics (BCP‐C) and those with solid whiskers, BCP‐HW exhibits larger specific surface area (3.9 times vs BCP‐C) and higher mechanical strength (3.4 times vs BCP‐C), endowing it with stronger stimulation on adhesion, proliferation, and osteogenic differentiation of bone marrow mesenchymal stem cells. In an intramuscular implantation model of canine, BCP‐HW shows excellent osteoinductivity and promotes the maturation of new bone, and the resultant compressive strength of the implant increases to ≈12 MPa at 3 months postoperatively. In another critical‐sized segmental bone defect model of rabbit femur, BCP‐HW has the best repairing effect. After implantation for 6 months, much more new bone ingrowth and higher bending load are observed in BCP‐HW than BCP‐C. Collectively, these findings suggest that the in situ hollow‐tube whisker construction possesses immense potential in expanding the applications of Ca‐P ceramics to load‐bearing bone defect repair.
The empirical mode decomposition (EMD) combines with Hilbert Transform is a common method of nonlinear and non-stationary signal time frequency analysis. Signal can be decomposed into different intrinsic mode functions (IMF) through the EMD. Each IMF represents a simple oscillation which provides meaningful instantaneous frequency through Hilbert transform. The mode mixing of IMF is a critical problem which limits the performance of EMD. There are several reasons to cause mode mixing, the common reason is one IMF contains several periodic components. In order to solve this type of mode mixing, we propose an algorithm to detect and separate the periodic components from IMF. Each resulting periodic component can provide meaningful instantaneous frequency, and IMF can be replaced by the assemblage of all periodic components and the residuum. Our algorithm bases on the correlation coefficient between IMF slope segment and pure tone segment. The time resolution of this method depends on the duration of segment. We use three mode mixing examples to illustrate the good performance of our algorithm, includes the performance under additive white Gaussian noise.
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