Stirring Mode Research Articles

Electrochemical removal of ethylene glycol monobutyl ether in aviation industry wastewater using a porous Ti4O7/Ti electrode

Titanium alloy chemical milling wastewater contains a significant amount of ethylene glycol monobutyl ether (EGBE), which is toxic and difficult to be degraded by microorganisms, and the emission will lead to severe environmental pollution. To solve this problem, the electrocatalytic oxidation method was employed to remove EGBE in the wastewater, in which a porous Ti4O7/Ti electrode were prepared and employed as the anode, while stainless steel acted as the cathode. The effects of current density, interelectrode distance, and stirring mode on the COD removal rate were also investigated. Results show that the COD of the wastewater significantly decreases from 12410 to 15 mg L−1 after 16 h of electrolysis at 10 mA cm−2 and electrode spacing of 1.0 cm as well as aeration stirring at 100 mL min−1. Moreover, pilot-plant scale testing reveals that the COD decreasing from 11980 to 183 mg L−1 after 24 h of electrolysis. Consequently, the utilization of porous Ti4O7/Ti electrode as anode in the electrocatalytic oxidation method presents significant potential in removal of EGBE in aviation industry wastewater.

Numerical Simulation of Segregation in Slabs under Different Secondary Cooling Electromagnetic Stirring Modes.

Secondary cooling electromagnetic stirring (S-EMS) significantly impacts the internal quality of continuous casting slabs. In order to investigate the effects of S-EMS modes on segregation in slabs, a three-dimensional numerical model of the full-scale flow field, solidification, and mass transfer was established. A comparative analysis was conducted between continuous electromagnetic stirring and alternate stirring modes regarding their impacts on steel flow, solidification, and carbon segregation. The results indicated that adopting the alternate stirring mode was more advantageous for achieving uniform flow fields and reducing the disparity in solidification endpoints, thus mitigating carbon segregation. Specifically, the central carbon segregation index under continuous stirring at 320 A was 1.236, with an average of 1.247, while under alternate stirring, the central carbon segregation index decreased to 1.222 with an average of 1.227.

Significance of homogeneous operation in light-assisted fixed-bed bioprocess under ammonia stress: Optimization, long-term operation and metagenomic analysis

Activating microbes with light is a promising strategy for addressing ammonia-stressed anaerobic digestion (AD). However, as a critical in-process parameter, homogenous operation, in light-assisted AD amended by bio-fixed bed has received limited attention. This research endeavors to establish a uniform-illuminated biosystem and assess its practical feasibility through a 90-day semi-continuous operation at pilot scale under solar light illumination. With optimal stirring mode (intermittent stirring for 3 min every 15 min), robust methane yields were achieved across various organic loads, reaching 88.7–94.3% of theoretical yield under high ammonium stress (3500 mg/L). The metagenomic analysis unveiled that uniform illumination triggered synergistic effects in AD, fostering a diversified microbial consortium, enhancing carbohydrate and methane metabolism, and facilitating the formation of an electroactive bio-cluster. This study underscores the significance of homogenous illumination in AD systems for efficient waste-to-energy conversion, highlighting the implementation of solar light as a greener approach for scale-up application.

Fabric phase sorptive extraction as a sustainable sample preparation procedure to determine synthetic musks in water

A rapid sample preparation fabric phase sorptive extraction (FPSE) methodology followed by gas chromatography coupled to tandem mass spectrometry is proposed for the first time to determine 12 synthetic musks including nitro-, polycyclic and macrocyclic musk in environmental water and wastewater. An asymmetric screening design of experiments was used to evaluate the influence of nine parameters affecting FPSE in only 16 experiments. The factors included the sol–gel sorbent coating, stirring mode (both extraction and desorption), extraction and desorption time, salting-out effect, sample volume, type of solvent, and desorption solvent volume. The selected conditions imply the use of the sol–gel PDMS sorbent coating, 15 min extraction by ultrasound energy employing 10 mL of sample and 0.5 mL of ethanol as desorption solvent during 5 min. Accuracy and precision were assessed in different real water samples. Matrix effects were evaluated performing recovery studies in several aqueous matrices: river, sea, spring, laundry washing place, and wastewater at different concentration levels (0.1, 2, 10 µg L−1) demonstrating method accuracy (results ranged between 82 and 110%) and good precision (relative standard deviation, RSD < 12% in all cases). Limits of detection (LODs) were below 8 ng L−1 for the analyzed synthetic musks. As extraction was quantitative (exhaustive extraction), calibration was carried out using solvent standards without the need of repeating the extraction step, which is required in most microextraction methods, improving sample throughput, and reducing costs. Finally, the analysis of real contaminated samples revealed the presence of 11 out of the 12 target synthetic musks at concentrations up to 30 µg L−1, three of them banned in cosmetic regulation (musk tibetene, ambrette, and moskene). The developed FPSE based methodology uses low volume (0.5 mL) of a Generally Recognized as Safe (GRAS) solvent (ethanol), as well as minimum energy and time consumption, demonstrating to be a sustainable alternative to detect these microcontaminants in environmental waters and wastewaters.

Effect of Magnet Alternate Stirring on the Internal Quality of Sn-Pb Alloy

A permanent magnet stirrer was built to study the effect of different magnetic field stirring modes on the solidification quality of Sn-20 wt-% Pb alloy ingots. The internal quality of the ingot can be improved by adjusting both the stirring speed and the modes. When the continuous magnetic stirring mode was adopted, the higher the stirring speed, the higher the flutter height at the ingot edge. When the stirring speed was 200 rpm, the flutter height reached 4.12 mm. The rotating magnetic field can significantly refine the grain size of the ingot. When the stirring speed of the magnetic field was increased from 0 rpm to 200 rpm, the grain size of the ingot reduced from 301 μm to 241 μm. By fixing the magnetic field stirring speed to 200 rpm and adjusting the mode to the alternate stirring process, the flutter height at the ingot edge reduced to 1.86 mm, which stabilized the liquid level of the molten alloy in the crucible. In addition, the grain size of the ingot was shortened to 223 μm, and the elemental homogeneity within the ingot was optimized.

Effect of magnetic alternate stirring on solidification structure of the round billet

ABSTRACT In this study, a permanent magnet stirrer was constructed for the implementation of experiments on different magnetic field stirring modes. Through experiments, it can be observed that when the fixed speed of 200 rpm and the alternate stirring mode of magnetic field was adopted, the loose area in the core of ingots was reduced from about 72 mm2 to 21 mm2, which significantly improved the density and element uniformity of the ingot. A Φ220 mm SAE1527 round billet was selected as industrial trial steel. When the stirring current and frequency was 350 A and 3 HZ, the electromagnetic stirring of the mold was adjusted from continuous stirring to alternate stirring mode. The solidification structure of the billet has been improved to a certain extent. Furthermore, the number of spot segregation larger than 0.5mm2 was reduced from 43 to 26, thereby improving the uniformity of internal elements in the billet.

Regulation of friction pair to promote conversion of mechanical energy to chemical energy on Bi2WO6 and realization of enhanced tribocatalytic activity to degrade different pollutants

Recently, friction-induced tribocatalysis has received tremendous attention through converting mechanical energy to chemical energy. However, its efficiency is much lower than those of photocatalysis and piezocatalysis, and its environmental application is limited in dye degradation. Herein, we developed a facile approach to improve the tribocatalytic activity of Bi2WO6 via adding trace polymer powders to form friction pairs with Bi2WO6. Among various polymers, PTFE was demonstrated to be the best counterpart of Bi2WO6. Subsequently, the PTFE dosage, stirring rate, magnetic bar size and number, and stirring mode were further optimized. The PTFE-promoted Bi2WO6 tribocatalysis was verified to possess excellent performance not only for removing different dyes, but also for degrading chlorophenols that are typical persistent organic pollutants. Multiple uses of the recycled catalysts indicated its good stability and prominent tribocatalytic durability. EPR measurements suggested the generation of hydroxyl radical and superoxide radical, which were determined to be continuously generated within 12 h at the rates of 0.88 μM h−1 and 85 μM h−1, respectively. Subsequently, a possible mechanism was proposed to explain the enhanced performance of the PTFE-promoted Bi2WO6 tribocatalysis. Finally, on basis of the detected intermediates, the degradation pathways of Rhodamine B and 2,4-Dichlorophenol during tribocatalysis were suggested.

STIRRING OF METAL MELTS FOR IMPROVING THE EFFICIENCY OF THE “LADLE – FURNACE” UNITS Message 2. NEW METHOD FOR ELECTROMAGNETIC STIRRING OF METALLIC MELT IN “LADLE – FURNACE” UNIT

The features of refractory lining’s wear of “ladle – furnace” unit at work on metallurgical mini-plant with intensive stirring of liquid metal by gas and electromagnetic field is studied. It was established that the most affected areas are slag zone, ladle’s bottom, as well as side wall, near which the electromagnetic stirrer is located. The stability of these areas determines the duration of the ladle working between repairs. Recommendations for recovery of the lining’s working layer have been developed. Also, there are formulated the requirements for rationalization of melt stirring modes. Theoretical studying of influence of electromagnetic stirring on heat &amp; mass transfer processes in liquid metal bath of metallurgical aggregates (in particular, during homogenization of alloy in free turbulence mode at input of additives) was investigated. New electromagnetic stirrer was designed in the PTIMA NASU, and it is proposed for technologies of melting and finishing of alloys. The stirrer creates the pulsating magnetic field, and its force lines spread equally intensively both in the horizontal and vertical planes. It is shown that design of developed stirrer, its power supply by industrial frequency 50 Hz, and physical nature of the generated field’s action provide the simplicity of its making and operation. So, new stirrer has essential technical, economic and technological advantages in comparison with known stirrers of travelling magnetic field at the same parameters of electromagnetic systems. Joint research performed by specialists of the PTIMA NASU and IED NASU with using mathematical modeling and experiments on aluminum melt showed the following. It is possible to realize a wide range of stirring modes, both intensity and melt movement directions. Thus, the application of developed electromagnetic stirrer in the “ladle – furnace” units will allow to significantly expand the possibilities for finishing liquid alloys on chemical composition and temperature, especially at small metallurgical plants.

Study on the effect of mould alternate stirring on the internal quality of the round billet

ABSTRACT In this paper, the effects of mold alternate stirring and single-direction continuous stirring on the internal quality of the billet were compared. When the mold alternate electromagnetic stirring was adopted, with the increase of stirring current form 260A to 350A, the central shrinkage cavity of the billet was disappeared, and the proportion of central equiaxed crystal zone increased gradually from 18.67% to 25.00%. The number of spot segregation larger than 1.0 mm2 in the billet was reduced from 18 to 10, and the maximum positive segregation of carbon and manganese decreased from 1.059 and 1.020 to 1.029 and 1.012, and the maximum negative segregation increased from 0.959 and 0.989 to 0.972 and 0.991, which improved the uniformity of elements distribution of the round billet. Through the above analysis, it can be seen that the mold alternate stirring mode with suitable parameters can improve the internal quality of the billet.

Significance of Low Stirring Modes on the Kinetics of Methane Hydrate Formation

Significance of Low Stirring Modes on the Kinetics of Methane Hydrate Formation

CFD Simulation of a New Dynamic-Static Stirred Model and Its Application in the Leaching Process of Chromite

In the liquid phase oxidation leaching process of chromite salt, a new dynamic-static combined stirred mode is proposed. That is, a static cylindrical baffle is fixedly installed at a certain radius from the stirred blade to control the vicinity of the blade. The CFD numerical simulation method is mainly used to investigate the effect of dynamic-static combined mode on the flow field distribution. Meanwhile, the velocity distribution and trailing vortex near the blade are analyzed. Finally, the differences between traditional stirred blade and dynamic-static combined stirred blade in the oxidation leaching process of chromite are compared. The results show the new dynamic-static combined stirring mode can effectively improve the flow field distribution, reduce the occurrence of “dead zones” in the flow, and increase the chromite leaching efficiency. The leaching time can be reduced from 300 to 240 min, and the chromium-leaching rate has reached up to 99%.

Improving the Reverberation Chamber Performance Using a Reconfigurable Source Stirring Antenna Array

An antenna array composed of 16 asymmetric distributed monopoles on a circular dielectric substrate is proposed to use as a reconfigurable source stirrer in a reverberation chamber (RC). The distance between antennas is above λ2 to ensure the isolation between antennas below −15 dB. In order to ensure the mutual independence of the stirring modes of the antenna array, the 16 monopoles are asymmetrically distributed on both sides with X and Y as axes. The stirring efficiency of a stirrer is related to its size, and usually a higher stirring efficiency means a larger stirrer. The source stirring technique can achieve high efficiency, but the rotation of a source stirring antenna is limited to the radius of the turntable in an RC. To solve this problem, we propose to use an antenna array as a reconfigurable source stirrer, which can achieve a high efficiency of source stirring. As the antenna array can achieve source stirring and mechanical stirring at the same time, the source stirring section is not limited to the radius of the turntable; the switch between the selected antennas of the antenna array can increase the actual stirring samples of the stirring. Thus, the efficiency can be improved significantly and has been verified by the measurement results. The volume occupied by the conventional mechanical stirrer is reduced, which improves the working volume. The figures of merit, such as the field uniformity (FU), the independent sample numbers, the average K-factor, and the total scattering cross-section (TSCS), are measured and compared to the conventional mechanical stirring, mechanical stirring, and source stirring of the antenna array. Measurement results of the reconfigurable stir are illustrated below. FU has the best convergence and the lowest value, below 0.5 dB. The independent sample number is the largest. K-factor is the lowest, and most ranges are below −15 dB. Additionally, the proposed method has the largest TSCS, above 2 m2. These confirm that the proposed reconfigurable source stirring technique outperforms other three stirring techniques significantly. The antenna array can be easy to disassemble and install in different RC. With a wide range of working band, the proposed method can be applied to 5G OTA testing.

Microstructure, Properties, and Numerical Simulation of Semi-Solid Aluminum Alloy under Planetary Stirring Process

In order to solve the problem of insufficient convective heat transfer of uniaxial stirred melt, the temperature field and shear rate of melt under planetary stirring were studied based on CFD simulation. The microstructure and properties of this technology were also experimentally studied. The results show that compared with the uniaxial stirring semi-solid technology, the convective heat transfer ability of aluminum alloy, semi-solid slurry in planetary stirring mode is stronger. In addition, its temperature field can be reduced to the semi-solid range faster and more evenly, which is conducive to a large number of nucleation and improves the nucleation rate. The temperature difference of the whole melt is small, so the preferred direction growth and uniform growth of dendrites are avoided, and the morphology is improved. Properly increasing the revolution and rotation speed of the stirring shaft can refine the grains of semi-solid aluminum alloy parts, improve the grain morphology, and improve the tensile strength. The planetary stirring semi-solid process is very suitable for rheological high-pressure casting.

Hydrothermal Microwave-Assisted Fabrication of Nanohydroxyapatite Powder and Optimization of Its Nanocomposite Coatings on Magnesium Alloy for Orthopedic Applications.

Developing appropriate protecting coatings for Mg alloy applications is a challenging issue. Herein, nanohydroxyapatite (nanoHAP) powder was first fabricated by the simple hydrothermal microwave-assisted method. A direct current electrophoresis deposition (EPD) of nanoHAP composite coatings on Mg–3Zn–0.8Ca magnesium alloy was successfully executed. Three suspensions with HAP-dispersive resin solution (ETELAC) ratios (in wt %) of 5–5, 5–2.5, and 2.5–2.5 were chosen for optimizing the effect of applied voltage, deposition time, and stirring mode and rates on the EPD process. NanoHAP composite coatings were applied on each sample in single- and double-run depositions. The results revealed that the maximum weight gain on the coated samples was obtained in 5–5 suspension at 50 V under 150 rpm mechanical stirring rate. Surface examination indicated crack-free coating formation with varying grain sizes. Adhesion tests demonstrated high interconnection between the obtained nanocomposite coatings and the alloy substrate. Electrochemical evaluation measurements in SBF at 37 °C indicated that the corrosion resistance of any coated sample is always superior compared to that of the uncoated bare substrate. It was suggested that the EPD of nanoHAP/ETELAC composite coatings on Mg–Zn–Ca alloy can be a good solution for protecting the alloy from the attack of the aggressive ions bound in the SBF environment.

Sorption Properties of ZrO2-Analcime Composites in Relation to Cs(I) and Sr(II)

Composite zeolite sorbents based on analcime with inclusions of hydrated zirconium dioxide (ZrO2-analcime) have been obtained by hydrothermal treatment of coal fly ash cenospheres with a high glass phase content in the presence of a zirconium compound and an alkaline activating agent at 150 °C and different stirring modes of the reaction mixture. The synthesis products were characterized by XRD, SEM-EDS, STA and low-temperature nitrogen adsorption; their sorption properties with respect to Cs+ and Sr2+ were studied in the pH range of 2–10. It was found that the ZrO2-analcime compositions surpass unmodified analcime by 2–5 times in terms of sorption of Cs+ and Sr2+ and by two orders of magnitude in terms of the distribution coefficient value (KD ~106 ml/g). The process of high-temperature solid-phase transformation of Cs+/Sr2+-exchanged forms of the compositions was studied, which simulates the process of conversion of water-soluble forms of Cs‑137 and Sr‑90 radionuclides into a mineral-like form. It was shown that at 1000 °C the ZrO2-analcime compositions with sorbed Cs+ and Sr2+ undergo the phase transformation resulting in polyphase systems of similar composition based on nepheline, tetragonal ZrO2, and glass phase

Study of the factors that determine the transfer of water and organic compounds into the gas phase from aqueous solutions in a discharge with a liquid cathode

A study was performed to investigate the transfer of organic compounds and water from an aqueous solution to the gas phase under the action of a direct current discharge, in which an aqueous solution that contains organic compounds plays the role of a cathode. The effect of the area of the free surface of a liquid in various reactors, as well as the effect of the stirring mode of a solution near the surface of a liquid on the rate of transfer of water and organic compounds under the action of a discharge of this type, have been investigated. It is shown that a change in the area of the free surface of a liquid has no significant effect on the rate of transfer of water and organic compounds from solution to the gas phase under the action of a direct current discharge with a liquid cathode. It is shown that the stirring mode and the temperature of the solution, on the contrary, have a very significant effect on the rate of nonequilibrium transfer of both water and organic compounds from solution to the gas phase under the action of a discharge with a liquid cathode.

Horizontal CCMs in small-capacity metallurgy

Production of light-section rolled products and wire rods of alloyed steel grades differs by small volume of yearly output and wide range of smelted grades. To organize production of light-section rolled products of alloyed steel grades in small volumes, OJSC “Spetsmash” elaborated concept of small-capacity production, which was implemented at several plants. It was shown that horizontal CCM can be effectively applied in the small-capacity production within complexes of light-section rolled stock of alloyed steels production. At the plant “Ferrotrade” (Beloretsk) when creating a complex for production wire rods of 6.5 mm diameter of austenite class steels and nickel-based alloys, a horizontal CCM was constructed. Production of 60 mm diameter billets by the machine was mastered, which enabled to apply a rolling mini-mill, characterizing by small dimensions and power. The horizontal CCM, constructed in 2016 at the steelmaking shop of CJSC “Izhevsk pilot-mechanical plant”, was equipped by electromagnetic stirrer (EMS). It was noted that EMS was applied for the first time in domestic metallurgy at the industrial CCM of horizontal type. In the process of this CCM mastering, more than 60 heats were casted into billets of 80, 200 and 120 mm diameter. EMS application resulted in improving average point on the central porosity to 1.2—1.8 depending on the stirring modes. In 2018 the OJSC “Spetsmash” for the Research Center “Thermodeform” (Magnitogorsk) constructed an experimental horizontal CCM, designed for casting of billets of 40—60 mm diameter by direct casting of melt from the crucible of 60 kg induction furnace into the metal reservoir 776 of the machine. Development of a project of horizontal CCM for PJSC “PlasmaTek” (Ukraine, Vinnitsy) finished, designed for production of billets of 50 and 60 mm diameter within a complex of equipment for manufacturing welding electrodes not only of alloyed but also of carbon steel grades. The designed productivity of the complex is 12,000 t/year. Basic technical characteristics of the CCM presented. Small-capacity production with horizontal CCMs can be organized as independent objects and within existing steel-works for expanding product range.

Studies of the Aluminum-Melt Stirring Mode in an Induction System with Permanent Magnets

Studies of the Aluminum-Melt Stirring Mode in an Induction System with Permanent Magnets

Dynamics of interfacial interaction between components during mixing

. The effect of mechanical action on the mixing and whipping of a mixture of components contributes to the establishment of a three-dimensional sponge-mesh continuous structure of the gluten framework, as it determines the elastic and elastic properties of the medium and is relevant in the dispersion of gas in a liquid. The purpose of the work was to establish the relationship between the gas retention capacity of the medium and the energy consumed for the hydration of the components. The experiments performed the task of determining the gas retention capacity of the medium with variable parameters of the height of the liquid phase from the intensity of mixing, the time of the transient processes of the formation of the full volume of the gas-liquid medium, the time of the transient process of the dispersed gas phase. The difference in levels before the gas phase generation and the stirring mode determines the value of gas retention capacity. Therefore, it was concluded that it is expedient to completely destabilise the steady-state regimes by changing the modes of action of the working body in the flow system. An additional impact on the system is the change of hydrodynamic regimes due to the unstable dynamics of the dispersed gas phase generation. The generation of this phase means the presence of energy costs for the interfacial surface establishment, which must be considered in the overall energy balance. In addition, a part of the gas phase, which existed and continues to exist in the new regime after mixing, enters the transient regime. Therefore, the most effective mixing occurs in case of compliance with the shifted mode of dosing components in a suspended state and the mechanical impact of the working body. Considering the tasks and conditions for mixing the dough, the requirements for the design of the mixer are determined, and it is established that the supply of components should last at least 45 seconds. During this period, there is hydration and a reduction in energy consumption. Such an approach intensifies mass transfer and biochemical processes under conditions of thermodynamic equilibrium with appropriate desorption bonds of the dissolved part of the gas phase and liquid, which covers a new method of mixing and allows further use in the design calculations of working chambers

INFOGEST inter-laboratory recommendations for assaying gastric and pancreatic lipases activities prior to in vitro digestion studies

In vitro digestion studies often use animal digestive enzyme extracts as substitutes of human gastric and pancreatic secretions. Pancreatin from porcine origin is thus commonly used to provide relevant pancreatic enzymes such as proteases, amylase and lipase. Rabbit gastric extracts (RGE) have been recently introduced to provide gastric lipase in addition to pepsin. Before preparing simulated gastric and pancreatic extracts with targeted enzyme activities as described in in vitro digestion protocols, it is important to determine the activities of enzyme preparations using validated methods. The purpose of this inter-laboratory study within the INFOGEST network was to test the repeatability and reproducibility of lipase assays using the pH-stat technique for measuring the activities of gastric and pancreatic lipases from various sources. Twenty-one laboratories having different pH-stat devices received the same protocol with identical batches of RGE and two pancreatin sources. Lipase assays were performed using tributyrin as a substrate and three different amounts (50, 100 and 200 µg) of each enzyme preparation. The repeatability results within individual laboratories were satisfactory with coefficients of variation (CVs) ranging from 4 to 8% regardless of the enzyme amount tested. However, the inter-laboratory variability was high (CV > 15%) compared to existing standards for bioanalytical assays. We identified and weighted the contributions to inter-laboratory variability of several parameters associated with the various pH-stat equipment used in this study (e.g. reaction vessel volume and shape, stirring mode and rate, burette volume for the automated delivery of sodium hydroxide). Based on this, we established recommendations for improving the reproducibility of lipase assays using the pH-stat technique. Defining accurate and complete recommendations on how to correctly quantify activity levels of enzyme preparations is a gateway to promising comparison of in vitro data obtained from different laboratories following the same in vitro digestion protocol.