Search

Electrolysis is an important way to produce manganese metal, but the low current efficiency and random growth of dendrites have always been challenging problems for enterprises. The lack of understanding of the dynamic system during the electrolysis process is the main reason for the accurate control of the electrolysis process. Based on this consideration, a new four-dimensional continuous hyperchaotic system with high Lyapunov exponents is designed. The amplitude control, frequency modulation, and offset boosting of the hyperchaotic system are obtained through the selection of feedback term. A circuit simulation and corresponding simplified circuit are established. In addition, the actual hyperchaotic circuit is applied to the manganese electrolysis process through the self-designed current amplification module (the amplification of w signal is realized by the offset boosting control). The experimental results of the hyperchaotic electrolysis of metal manganese showed that the hyperchaotic current can delay the occurrence time of electrochemical oscillation, and reduce the generation of cathode metal manganese dendrites. Furthermore, the results show that the hyperchaotic current can enhance the current efficiency and reduce the energy consumption. Based on the new experiment, it is suggested that the formation of anodic porous structures, whose primary phase compositions were PbSO4, MnO2, and Mn2O3, is one factor for the occurrence of electrochemical oscillations, while the conversion between Mn 3 + and Mn 4 + is another main factor for the mutation of electrochemical signal (manganese autocatalysis). [ABSTRACT FROM AUTHOR]

• The Mod-DI can destroy the symmetry flow field and induce more vortices. • The mixing time of the system could be shortened by equipping the Mod-DI. • The Mod-DI system reaches dynamic equilibrium before the Trad-DI system. • The intensification mechanism is due to the formation of metastable flow field. Process intensification is important for achieving efficient fluid mixing. In this study, the process intensification mechanism of mixing was investigated based on the evolution of sub-steady flow pattern. The results showed that the modified dual impeller (Mod-DI) could eliminate the isolation zone and symmetry of the flow pattern, which always appears in the traditional dual impeller (Trad-DI) system. Furthermore, the mixing time (t m) and dynamic equilibrium time (t de) of the Mod-DI system were significantly shorter than those of the Trad-DI system, which could be attributed to the enhancement of fluid flow fluctuations caused by the loss of stability of sub-steady flow field. In the presence of baffles, t m and t de could be further reduced. The shortening of time was at the expense of increasing power consumption. Overall, the intensification mechanism of the Mod-DI is mainly since the formation of sub-steady flow field, which enhances the instability of the fluid flow. [ABSTRACT FROM AUTHOR]

[Display omitted] • Combined with RGB brightness and quantitative area analysis, the mixing performance of the stirred reactor was evaluated. • There is an inherent axial mixing limit in traditional stirred reactors under laminar flow conditions. • The DSO mixing system exhibits enhanced mass transfer efficiency and overall mixing performance. • The flow pattern from radial flow to axial flow is adjusted by changing the interface evolution. Efficiently realizing laminar flow mixing of non-Newtonian fluids is a key challenge faced by conventional stirred reactors. In this study, an innovative strategy is proposed to regulate the flow pattern from radial to axial flow by changing the interface evolution of the flow field, so as to solve the problem of uneven mixing materials in laminar flow. An innovative combination of the RGB (Red, Green, Blue) brightness analysis and quantitative analysis area method was used to quantitatively describe the mixing performance of the three stirred reactor in the laminar flow. We found that the coloring area ratio of the dual shaft off-centred mixer (DSO) mixer was approximately 165.7 % and 93.8 % higher than that of the single shaft central (SSC) and single shaft off-centred mixer (SSO), respectively. Results showed that the DSO mixer can directionally adjust the stable interface of the flow field, and then obtain the ideal velocity distribution and flow pattern. Importantly, it is found that the mixer has an inherent axial mixing limit in the laminar flow. Increasing the Reynolds number can only shorten the time for the mixing system to reach the steady state, and cannot further improve the axial transport capacity of the system. Compared to the SSC and SSO systems, the DSO mixer demonstrated a reduction of nearly 20 % in overall mixing time and power consumption. Through comparative analysis of pressure distribution and Poincaré cross section, the DSO mixing system can switch chaos oscillation and realize the "globally chaotic mixing" from "locally chaotic mixing". Remarkably, this work highlights the potential of DSO mixer as a simple and efficient system for laminar flow mixing applications, such as polymerization processes, biological fermentation. [ABSTRACT FROM AUTHOR]

[Display omitted] A practical hyperchaotic circuit has been designed, which has further been successfully applied to the manganese metal electrolysis system, replacing the traditional direct current power to alter the dynamic system of electrolysis process. The results illustrate that the hyperchaotic current can significantly suppress the electrochemical oscillation. Therefore, the growth of manganese (Mn) dendrites in the cathode can be significantly suppressed by the ultra − wide chaotic current fluctuation because of the regulation of electronic dynamic system. In addition, the distribution of manganese dendrites is quantified for the first time through image analysis, processing, and calculation. Besides, the hyperchaotic current can also considerably improve the current efficiency with 2 % increasing and reduce the energy consumption about 0.3 kW·h/kg simultaneously. It also demonstrates some advantages of chaotic current electrodeposition technology by conducting a larger-scale chaotic current electrolysis experiment. [ABSTRACT FROM AUTHOR]

• Squeezing-induced chaotic advection mixing was proposed. • Mixing performance in rectangular stirred tanks was investigated. • Segregation region was eliminated in rectangular stirred tanks. • Mixing time decreased as Length-to-Width ratio increased. • Fluid mechanism in rectangular stirred tanks is similar to that in eccentric ones. The phenomenon of chaotic advection mixing in laminar stirred tanks, particularly when handling high-viscosity fluids, represents a common and challenging issue in various chemical and biochemical industrial processes. The effectiveness of these mixing processes is often constrained by the stretching, folding, and squeezing of fluid particles. Previous research efforts have predominantly concentrated on the design and/or optimization of impellers and operation modes to increase the stretching and folding of fluid particles. However, the mechanism of triggering chaos through the squeezing of fluid particles remains comparatively less explored. This study endeavors to address the intricate problem of laminar mixing by proposing the utilization of unbaffled rectangular stirred tanks. Via a combined approach of experimental and computational investigations, we illustrate that the implementation of rectangular stirred tanks yields significant improvements in chaotic mixing within laminar flow regimes. This type of tank not only enhances the convective transport of fluids but also distorts or completely eliminates the segregation regions by squeezing. Remarkably, as the tank L / W ratio increases from 1 to 2.5, the observed asymptotic area coverage from a frontal perspective escalates from approximately 55 % to about 85 %. Concurrently, the dimensionless mixing time decreased significantly from 1950 to 350. Of particular note, macroscopic homogeneous mixing is observed in stirred tanks with L / W ratios of 2 and 2.5 at R e = 29, with dimensionless mixing times of 550 and 350, respectively. This work highlights the potential of rectangular stirred tanks as a simple and cost-effective system for laminar mixing applications. Furthermore, it also hints at the broader applicability of the approach in various industrial mixing contexts, such as the suspension of floating granules, entrainment of air, and others. [ABSTRACT FROM AUTHOR]