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.
Flotation technology and adsorption mechanism of vanadium extraction from stone coal
In order to avoid the problems of pollution and low recovery in the conventional process,the flotation was adopted in the treatment of stone coal containing vanadium before leaching on the basis of mineralogical analysis.The proper flotation route was proposed based on condition experiments and closed-circuit test.The method of molecular dynamics simulation was used to study the adsorption process of the collector on roscoelite and quartz,providing a fundamental understanding of the flotation mechanism.The results show that the primary vanadium mineral in stone coal is roscoelite,while the main gangue is quartz.Roscoelite concentrate is eventually obtained with V2O5 grade of 3.20%(mass fraction) and the recovery of 74.50% by a flotation closed-circuit process.The collector is easy to be adsorbed on the surface of roscoelite(001),while hardly on that of quartz(001),which leads to the flotation separation of roscoelite and quartz in stone coal.
Experimental study on bond behavior between high-strength grout and deformed steel bars
Abstract Engineers use high-strength grout to connect precast concrete members for its low shrinkage and good fluidity. This paper designed 87 central pull-out specimens using the control variable method to investigate the influence of factors on the rebar-grout bond property such as compressive strength, steel grade, bar diameter, transverse stirrups, and bond length. The test result showed that improving grout compressive strength (85.8 MPa–122.7 MPa) cannot improve the bond strength, which was different from the previous conclusions of concrete pull-out tests. Simplified formulas were presented for calculating the characteristic values of bond strength, residual strength, peak slip, and relative slip of load-holding platform based on parameter analysis. Then, a constitutive model was proposed to predict the full-range bond stress-slip curve of high-strength grout and steel bar specimens from bearing to failure. Finally, FEA models were established to evaluate the applicability and accuracy of the constitutive model.