Search

The effective recovery and utilization of elemental sulfur in the direct leach residue (DLR) from zinc oxygen pressure leaching poses a significant challenge. This study analyzes the distribution characteristics of sulfur in DLR and determines its solubility in n -decane at various temperatures. Results indicate a gradual increase in sulfur solubility with temperature, reaching a maximum of 6.84 g/100 mL at 150 °C Utilizing the Apelblat model, a fitting equation of ln X = 88.3–7155.9/ T − 12.0ln T is derived. Under conditions of 130 °C, a liquid–solid ratio of 8:1, a reaction time of 3 min, and a stirring speed of 300 rpm, 99.2% of sulfur in the residue can be dissolved in n -decane. Additionally, this separation process naturally enriches other valuable elements in the residue. The cooling rate significantly influences sulfur purity, with elemental sulfur forming high-quality crystals exhibiting a positive octahedral rhombic morphology at a cooling rate of 0.018 °C/s. Finally, the dissolution mechanism of sulfur in n -decane involves sulfur complexation, and the reliability of the sulfur solubility model is verified. • Achieving good separation of sulfur in direct leaching residue from zinc oxygen pressure leaching. • Realize the harmless and resourceful treatment of direct leaching residue. • Crystallization by slow cooling gives better crystalline ortho-octahedral sulfur. • Analysis of sulfur dissolution mechanism in direct leaching residue. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a comparison is made between the leaching associated with microwave heating (MHL) and electric heating (EHL) of converter vanadium slag in an autoclave under an oxygen pressure of 0.4 MPa. The comparative study of the leaching processes showed that the vanadium leaching efficiency reached 46% in 20 min using EHL, whereas it reached 96% under the same condition when MHL was used. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses of MHL residue showed that decomposition of the spinel phase in the converter vanadium slag can be accelerated through this process. In addition, MHL can reduce the granularity and make the surface of the particles more porous. In general, using MHL is more effective than EHL, for the leaching of converter vanadium slag in pressure leaching process. Through kinetic studies of MHL and EHL, the activation energies of vanadium leaching were determined to be 14.8 and 40.5 kJ/mol, respectively. The reaction rate depends on acid concentration as well as oxygen partial pressure. The order of reaction with respect to H 2 SO 4 concentration was found to be 0.99 for MHL and 2.21 for EHL. The order of reaction with respect to the oxygen partial pressure was found to be 0.51 and 0.65 for MHL and EHL, respectively. The kinetic equations are derived and reported for MHL and EHL processes. Highlights • A novel resource utilization and extraction method of the converter vanadium slag • An efficient leaching process for converter vanadium slag using microwave heating • Advantage of microwave heating illustrated by analysis of leaching kinetics and characterization of solids. • The new technology achieves the objective of "efficient green production technology". [ABSTRACT FROM AUTHOR]

Abstract This study investigated the effects of various types of paddles on the oxygen gas holdup in different regions at a temperature of 403 K, oxygen partial pressure of 0.6 MPa, and agitation rate of 500 r/min. The results illustrate that the application of a self-priming agitator can significantly promote a bubble holdup in a solution. Furthermore, experiments determining the effects of the agitation rate, temperature, and oxygen partial pressure on the gas holdup were carried out, where the gas holdup increased from 0.03% to 1.59% with an agitation rate of 200 to 700 r/min, from 0.83% to 1.06% with a temperature of 363 to 423 K, and from 0.50% to 1.27% with an oxygen pressure of 0.1 to 0.8 MPa. The kinetics of oxygen pressure acid leaching of marmatite using various types of paddles were also studied. The activation energies of Zn leaching when using various types of paddles were determined to be 53.23, 56.30, 59.76, and 67.58 kJ mol−1, which shows that the processes were controlled through the surface chemical reactions. Based on a comparison of the activation energies, the self-priming type agitator was shown to be optimal. Finally, a similar criteria relationship of a self-priming agitator was established using the principle of homogeneity and Buckingham's theorem. Comprehensively, an empirical equation of a gas holdup was deduced based on experimental data and a similarity theory, where the criterion equation was determined to be ε = 7.20 × 10−10 n 2.63 T -1.52 P g 0.45. It can be seen from the formula that the agitation rate has the greatest impact on the gas holdup during the pressure leaching process using a self-priming agitator. Highlights • A transparent quartz autoclave and various types of paddle were used to study the gas holdup. • The gas holdup was studied under the condition of high temperature and high pressure. • The high-speed camera was used to investigate the bubble behavior at different condition. • The application of self-priming agitator could significantly promote bubble holdup and kinetics in solution. • The similar criteria relationship of self-priming agitator was established by Homogeneous Principle and Buckingham's theorem. [ABSTRACT FROM AUTHOR]