Pre-Concentration of Vanadium from Stone Coal by Gravity Using Fine Mineral Spiral
Due to the low grade of V2O5 in stone coal, the existing vanadium extraction technologies face challenges in terms of large handling capacity, high acid consumption and production cost. The pre-concentration of vanadium from stone coal before the extraction process is an effective method to reduce cost. In this study, detailed mineral characterization of stone coal was investigated. It has been confirmed that the vanadium mainly occurs in muscovite and illite. A significant demand for an effective pre-concentration process with simple manipulation for discarding quartz and other gangue minerals is expected. Based on the mineralogical study, a new vanadium pre-concentration process using a fine mineral spiral was investigated. The experimental results showed that the separation process, which was comprised of a rougher and scavenger, could efficiently discard quartz, pyrite and apatite. A final concentrate with V2O5 grade of 1.02% and recovery of 89.6% could be obtained, with 26.9% of the raw ore being discarded as final tailings.
Synchronous activation of Si and Al in vanadium-bearing shale leaching residue via sodium carbonate additive
Abstract With increasing academic interest in geopolymers, research into the activation of geopolymer raw materials has become necessary. In this study, a novel activator sodium carbonate was used to activate vanadium-bearing shale leaching residues (VSLR). Under conditions of 15 wt% Na2CO3 addition, 450 °C activation temperature, and 60 min activation time, the (Si + Al) concentration in the activation residue leachate reached 1350.2 mg/L, which represents an increase of roughly 30% compared to that obtained by adding NaOH under the same conditions. Through thermodynamic and phase transformation analyses, it was found that the crystal minerals containing Si and Al in VSLR were synchronously activated at a lower temperature due to the presence of sodium carbonate. Therefore, the activation efficiency of Si and Al in VSLR was greatly improved and energy consumption reduced. The novel activator sodium carbonate is practically feasible, easy to operate, and highly efficient for VSLR activation compared to the traditional activator sodium hydroxide.
ROOM- AND HIGH-TEMPERATURE MAGNETIC PROPERTIES OF Sm(CobalFexCu0.088Zr0.025)7.5 (x=0.30) SINTERED MAGNETS
The effect of Fe content on room- and high-temperature magnetic properties of Sm(CobalFexCu0.088Zr0.025)7.5 (x=0-0.30) sintered magnets, prepared by the conventional powder metallurgy method, has been systematically studied. With increasing Fe content, the remanences BT and maximum energy products (BH)max at room temperature gradually increase and reach optimal values of 1.055 T with x=0.27 for BT, and 205 kJ/m3 with x=0.21 for (BH)max, respectively, and then drop sharply with further Fe increase. An excessive addition of Fe (x≥0.24) results in rapid deterioration of permanent magnetic properties due to the formation of a considerable amount of FeCo soft magnetic phase. It was found that the effect of Fe content on high temperature stability is huge. The lower the Fe content, the smaller the temperature coefficient of coercivity. When x=0.07, a temperature coefficient of coercivity of -0.14%/K (293-723 K) can be achieved, as compared with -0.23%/K for x=0.21. BT of 0.725 T, bHc of 517 kA/m, iHc of 764 kA/m, and (BH)max of 95 kJ/m3 at 723 K were obtained, and the B-H demagnetization curve remains a straight line.