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Vanadium concentrate

Carbon Reduction. The production of ferrovanadium by reduction of vanadium concentrates with carbon has been supplanted by other methods. An important development has been the use of vanadium carbide as a replacement for ferrovanadium as the vanadium additive in steelmaking. A... [Pg.382]

Silicon Reduction. The preparation of ferrovanadium by the reduction of vanadium concentrates with ferrosiUcon has been used but not extensively. It involves a two-stage process in which technical-grade vanadium pentoxide, ferrosiUcon, lime, and fluorspar are heated in an electric furnace to reduce the oxide an iron alloy containing ca 30 wt % vanadium but undesirable amounts of siUcon is produced. The siUcon content of the alloy is then decreased by the addition of more V2O5 and lime to effect the extraction of most of the siUcon into the slag phase. An alternative process involves the... [Pg.383]

The particuiar magnesium compound seiected for inhibition is dependent upon fuei characteristics. For iow-vanadium concentrations (beiow 50 ppm), an oii-soiubie compound such as magnesium suifonate is added in the correct proportion to the vanadium present. The cost of oii-soiubie inhibitors becomes prohibitive above concentrations of 50 ppm. [Pg.450]

In general, vanadium concentrations above 2,000 ppm on the E-Cat can justify passivation. [Pg.65]

Vanadium and sodium neutralize catalyst acid sites and can cause collapse of the zeolite structure. Figure 10-5 shows the deactivation of the catalyst activity as a function of vanadium concentration. Destruction of the zeolite by vanadium takes place in the regenerator where the combination of oxygen, steam, and high temperature forms vanadic acid according to the following equations ... [Pg.325]

A somewhat more detailed study of vanadium atoms and dimers has also appeared 108). Figure 1 shows the UV-visible spectra of V and V2 as a function of vanadium concentration. Figure 2 shows a tjqiical, metal-concentration plot illustrating the aforementioned kinetic anal-... [Pg.83]

The quantity E is eliminated in favor of the total vanadium concentration which is measurable,... [Pg.679]

The singly and doubly protonated decamers predominate under most conditions (10, 32). The percentage concentration of the unpro-tonated decavanadate ion is strongly dependent on the ionic strength. For instance, calculations show that its maximum concentration in ionic medium 0.15 M NaCl is less then 10% of the total vanadium concentration (0.02 M), but in 3.0 M NaC104 medium it amounts to about 50% (28). [Pg.139]

Where uranium and vanadium concentrations are in pg/L and potassium and bi-carbonate are in mg/L. Where the CSI is equal to zero then groundwater chemistry and carnotite saturation are in equilibrium and the mineral has the potential to be present. The assessment of groundwater chemistry in the vicinity of calcrete-hosted carnotite deposits indicates that a wide geochemical halo exists and that this halo can be identified during exploration. In Australia direct analysis of groundwater and the CSI have been demonstrated as suitable methods for exploration. In Namibia, in reality although the approach may be useful for... [Pg.429]

Absorbed vanadium is primarily excreted in the urine, and it was detectable in 12 of the workers for periods of up to 2 weeks. Urinary vanadium concentrations were elevated in workers exposed to mean air concentrations of 0.1-0.28mg/m but there was no correlation between the air and urinary concentrations. Although most absorbed vanadium was excreted within 1 day after cessation of exposure, increased excretion relative to unexposed controls continued for more than 2 weeks among chronically exposed workers. ... [Pg.727]

As was already mentioned, the narrow lines at 692 and 710 nm in the luminescence spectrum of zoisite have been connected with element emission, while Cr and were considered as the possible candidates (Koziarsca et al. 1994). Laser-induced time-resolved luminescence spectra of zoisite reveal the same lines (Fig. 4.59). We are inclined to connect these lines with for the reason that vanadium concentration in our sample is much higher than the chromium concentration. [Pg.187]

Some of the metallic constituents were somewhat soluble in the propane-oil portion, but all tended to be concentrated in the asphaltic portion. Although vanadium (0.02% by weight in the original crude petroleum) was present in all fractions, the greater part was found in the cyclohexane and benzene fractions. From the similarity of the absorption spectra of the vanadium concentrates from petroleum and those of synthetic vanadium porphyrin complexes, Skinner arrived at the conclusion that vanadium compounds from the petroleum of the Santa Maria Valley Field in California exist as porphyrin complexes. Additional metallic constituents were detected by Skinner as these became concentrated in the various solvent fractions, including aluminum, titanium, calcium, and molybdenum. [Pg.339]

Figure 1 Potential versus pH diagram for the vanadium-water system at 25 °C. The dashed lines indicate the domains of relative predominance of the dissolved forms of the metal, but the various dissolved forms for each oxidation state are not explicit. The solid lines correspond to saturated solutions with a total vanadium concentration of 0,51 gdm-3. The long dashed lines correspond to oxidation and reduction of water (for E° values of 1.23 and 0.00 V respectively) (adapted from E. Deitombe, N. Zoubov and M. Pourbaix, in Atlas d Equilibres Electrochimiques , ed. M. Pourbaix,... Figure 1 Potential versus pH diagram for the vanadium-water system at 25 °C. The dashed lines indicate the domains of relative predominance of the dissolved forms of the metal, but the various dissolved forms for each oxidation state are not explicit. The solid lines correspond to saturated solutions with a total vanadium concentration of 0,51 gdm-3. The long dashed lines correspond to oxidation and reduction of water (for E° values of 1.23 and 0.00 V respectively) (adapted from E. Deitombe, N. Zoubov and M. Pourbaix, in Atlas d Equilibres Electrochimiques , ed. M. Pourbaix,...
To determine the vanadium concentration in a sample of steel, 2g of the steel is dissolved in an acid medium and 1 pg of 50V is added to the resulting solution. [Pg.326]

In studies on rabbit alveolar macrophage cultures, Waters and coworkers (133) presented data suggesting that vanadium oxides may adversely affect pulmonary defense. The cytotoxicity of the oxides studied were directly related to their solubility, i.e., V2O5 > V203 > V02. Ambient vanadium concentrations in urban regions have been reported to correlate with mortality incidence from bronchitis and pneumonia, especially in males (134). Likewise, industrial exposure to airborne manganese has been shown to correlate with increased incidence of bronchitis, caused in part by increased susceptibility to infection (135). [Pg.210]

An effect of pore diffusion in residuum demetallation is illustrated in Figure 9, which shows nickel and vanadium concentration profiles measured through a catalyst pill after residuum desulfurizing service. The catalyst originally contained neither of these metals. These profiles confirm that the rate of reaction of the metal-containing molecules in the feed (particularly the vanadium compounds) is high compared with their rate of diffusion. [Pg.130]

Vanadyl and nickel reactivity differences resulting from the chemistry of the oxygen ligand on vanadium were discussed in Section IV,A,l,c. Enhanced V reactivity could also arise from molecular size constraints. Beuther and co-workers (Beuther and Schmid, 1963 Larson and Beuther, 1966) speculate that nickel concentrates in the interior of asphaltene micelles while vanadium concentrates on the exterior. Thus a combination of stronger adsorption due to the oxygen ligand and inhibition of Ni reaction, coupled with the exposed position at the periphery of the asphaltene, may all contribute to the enhanced vanadium reactivity relative to nickel. [Pg.193]

Tamm et al. (1981) measured the maximum concentration of vanadium buildup in the catalyst at various reactor positions and times on stream. Near the reactor inlet, maximum vanadium concentrations increased rapidly with time before leaveling off. The catalyst in this portion of the bed has apparently reached its capacity and lost nearly all activity for HDM at about 80% of the run length. The catalysts in the reactors midsection and at the outlet have lower maximum concentrations, which increase more slowly with time. The lower zones of the catalyst bed are protected somewhat from metals deposition by the catalyst in the inlet region. This phenomenon continues until the catalyst bed does not have enough activity... [Pg.231]

Metals accumulate more slowly on the catalyst surfaces because the inlet concentrations of metals are lower than for coke precursors. The accumulation of metals can be even greater than coke, for example the vanadium concentration can reach 30-50 wt% of the catalyst on a fresh catalyst basis (Thakur and Thomas, 1985). Demetallization reactions can be considered autocatalytic in the sense that once the surface of the catalyst is covered with metal sulfides the catalyst remains quite active and continues to accumulate metal sulfides. The final loss of catalyst activity is usually associated with the filling of pore mouths in the catalyst by metal sulfide deposits. [Pg.209]

If a reacting solution is acid quenched then a small amount of hydrazine, derived probably from an intermediate reduction product, is formed. The rate of ammonia formation is linear in PN2 and depends on the square of vanadium concentration, but the actual rate is a function of dioxygen pressure, metal contaminants, etc. The mechanism is believed to follow the pattern discussed above, with dinitrogen bound between two dinuclear pairs of vanadium(II) ions (232, 233), but the precise identity of the fixing species remains a mystery. [Pg.268]

XRD, XPS, and Raman characterization of V supported on pseudoboehmite alumina or on amorphous aluminosilicate gels (metal loaded with a solution of V0+z Naphthenate in benzene) have indicated the presence of tetrahedrally and octahedrally coordinated vanadium (31) having speciation and dispersion that depends on vanadium concentration (and surface area) present on the steamed (760°C/5h) samples. [Pg.270]

Although NMR is a notoriously insensitive technique, vanadium is a highly responsive nucleus, and it is quite feasible to get spectra from a few micromolar concentration of vanadium in solution. Frequently, there is no necessity for such low concentrations, and more typically NMR studies utilize 0.5 mM, and above, total vanadium concentrations. [Pg.8]

Pettersson, L., B. Hedman, A.-M. Nenner, and I. Andersson. 1985. Multicomponent polyanions. 36. Hydrolysis and redox equilibria of the H+-HV042 system in 0.6 M Na(Cl). A complementary potentiometric and 51-V NMR study at low vanadium concentrations in acid solution. Acta Chem. Scand. A 39 499-506. [Pg.29]


See other pages where Vanadium concentrate is mentioned: [Pg.102]    [Pg.65]    [Pg.691]    [Pg.275]    [Pg.77]    [Pg.133]    [Pg.55]    [Pg.337]    [Pg.623]    [Pg.31]    [Pg.252]    [Pg.382]    [Pg.385]    [Pg.387]    [Pg.387]    [Pg.459]    [Pg.478]    [Pg.896]    [Pg.112]    [Pg.125]    [Pg.290]    [Pg.290]    [Pg.290]    [Pg.20]    [Pg.26]   
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