Stirring Intensity Research Articles

Study on the melting characteristics of steel scrap in molten steel

ABSTRACTSteel scrap is of great benefit for environmental protection. In converter steelmaking, bottom carbon injection was applied to enhance the scrap ratio and in EAF steelmaking, submerged carbon powder injection was used to accelerate the smelting of scrap. In these two cases, carbon powder is directly injected into molten metal to improve the scrap melting with effective carburization capacity and intense stirring effect. In this study, the induction furnace experiments were carried out to study the melting characteristics of steel scrap with different carbon contents and bottom-blowing gas flow rates. The results show that larger carbon content and faster fluid flow can promote scrap melting because the carburizing reaction can be accelerated by larger carbon concentration gradient and the heat transfer can be enhanced by larger stirring intensity. Finally, the convective mass transfer coefficient and heat transfer coefficient between steel bar and molten metal were also calculated.

In-situ activation of nano-silica and its foam stabilization mechanism

The in situ activation of silica nanoparticles (NPs) by adsorption of an anionic surfactant, nonylphenol-substituted decylsulfonate (C10-NPAS), has been studied. The mechanism whereby such NPs stabilize foams has been elucidated. Traditional static foam tests were carried out, focusing on the influence of stirring intensity on the stability characteristics of the foams. A freezing method has been applied for the first time to fix aqueous foams, and an anticipated mechanism has been verified. It was found that higher stirring intensity results in a finer foam and thinner foam lamellae, and the distribution of NPs is inhomogeneous therein. The foam stabilizing effect of NPs is more noticeable for thinner foam films. The anticipated mechanism, whereby partial aggregation of nano-SiO2 is beneficial to foam stability, has been verified by observing SEM images. Due to the strong hydrogen bonds interactions, C10-NPAS has the ability to activate NPs in situ and to stabilize negative charge thereon, making it potentially applicable in oilfields. The obtained results may expedite the development of super-long-term stable foams and potential application of NPs in enhanced oil recovery technology.

Solidification Structure and Segregation of High Magnetic Induction Grain-Oriented Silicon Steel

The solidification structure and centerline segregation of high magnetic induction grain-oriented silicon steel slabs were studied to describe the characteristics of solidification and compare the degree of centerline segregation of continuously cast slabs. Industrial experiments were conducted to investigate the solidification behavior of slabs by secondary cooling segment electromagnetic stirring. Three typical slabs were produced by S-EMS with current intensities of 0, 200, and 350 A. Molten steel cast at a low stirring intensity (0 A) resulted in a coarse structure relative to those cast at higher stirring intensities (200 and 350 A). The centerline segregation of carbon and silicon markedly increased with increases in S-EMS current intensity. Composition distribution by electron probe microanalysis identified segregation spots as the sources of centerline segregation. Experimental results indicate that to optimize the centerline segregation of grain-oriented silicon steel slabs, the columnar crystal zone should be enlarged and the equiaxed crystal zone be reduced.

Screening and Optimization of Demulsifiers and Flocculants Based on ASP Flooding-Produced Water

The water produced by alkaline–surfactant–polymer (ASP) flooding is difficult to treat due to the presence of residual chemicals. Therefore, research and development of efficient and low-cost methods for the treatment of ASP flooding produced water is necessary. Chemical destabilization is the most common and effective way to treat the produced water. This paper describes an optimization method for demulsification and flocculation. Some demulsifiers and flocculants commonly used in oilfields were screened, compounded, and optimized. Since the effect of treatment using only demulsifier or flocculant to treat the produced water is often not enough to meet the reinjection standard, an orthogonal experiment was carried out to study the demulsification–flocculation method to treat produced water. Five main influencing factors of the oil concentration were investigated. Based on the results of the range analysis and the relationship between the five factors and oil concentration, the order of significant factors was found to be demulsifier dosage > flocculant dosage > settling time > stirring time > stirring intensity, and the optimal demulsification–flocculation treatment conditions were successfully optimized.

Microencapsulation of Purple-Fleshed Sweet Potato Anthocyanins with Chitosan-Sodium Tripolyphosphate by Using Emulsification-Crosslinking Technique

Anthocyanins extracted from purple-fleshed sweet potato were encapsulated using emulsification-crosslinking technique with chitosan acted as polymer and sodium tripolyphosphate as cross-linker. The parameters influencing microencapsulation were investigated i.e. stirring intensity and polymer concentration, pH of polymer and crosslinker solution, and also ratio of anthocyanins extract (core) to polymer concentration by characterizing the properties of obtained microcapsules. Stirring intensity of 1600 rpm achieved microcapsules with smaller mean diameter, narrower particle size distribution, and greater encapsulation efficiency than that of 1200 rpm for each similar polymer concentration. The research revealed that pH of 3.0 gave the greatest encapsulation efficiency and antioxidant activity of microcapsules. However, the different of mean diameter and particle size distribution of microcapsules for all of pH solution variation was not significant. Ratio of anthocyanins extract to polymer concentration 75% (w/w) possessed the greatest encapsulation efficiency, the biggest mean diameter and the widest particle size distribution between all of ratio variation. Meanwhile, ratio of 150% was selected for further analysis (microstructure and FT-IR) because it gave narrower particle size distribution and smaller mean diameter with its encapsulation efficiency was only little different from others ratio. Microstructure analysis by SEM revealed sphere and irregular microparticles. FT-IR analysis revealed that that there was bonding and interaction among anthocyanin, chitosan, and tripolyphosphate ion.

Efficient treatment of oil sands produced water: Process integration using ion exchange regeneration wastewater as a chemical coagulant

The potential of ion exchange regeneration wastewater (IERW) containing magnesium ions to act as a coagulant for steam-assisted gravity drainage (SAGD) boiler blowdown (BBD) water was investigated with the aim of reducing the water consumption in a SAGD plant. Conventional techniques for the treatment of BBD water require significant operational costs as they rely on the extensive use of chemical coagulants or electric power. Since the proposed process design in this study uses a wastewater stream for the treatment of the BBD water, operational costs and energy consumption are predicted to be minimized. The effect of temperature, the mixing ratio of BBD and the IERW water, and the stirring intensity on the removal of organic matter and dissolved minerals were investigated. Usage of IERW as the coagulant enhanced the removal of impurities; removal efficiency of 81.1% and 98.6% were obtained for organic matter and silica concentration, respectively. The treatment of BBD water by IERW, however, has led to an increase in the concentration of calcium in the effluent, which was effectively mitigated by soda ash softening. Furthermore, resource recovery from the coagulated sludge was explored by SEM, EDX, FTIR, XPS, and XRD, and revealed that the precipitated compounds were mostly composed of calcium, magnesium, and silica. Additionally, the successful usage of IERW for the treatment of another BBD wastewater with a higher concentration of organic matter was demonstrated. In conclusion, the IERW water proved to be highly effective in removing contaminants from SAGD produced water.

Vibrations of a laboratory-scale gas-stirred ladle with two eccentric nozzles and multiple sensors

During ladle stirring, a gas is injected into the steel bath to generate a mixing of the liquid steel. The optimal process control requires a reliable measurement of the stirring intensity, for which the induced ladle wall vibrations have proved to be a potential indicator. An experimental cold water ladle with two eccentric nozzles and eight mono-axial accelerometers was thus investigated to measure the vibrations. The effect of the sensors’ positions with respect to the gas plugs on the vibration intensity was analyzed, and experimental data on several points of the ladle were collected for future numerical simulations. It is shown that the vibration root-mean-square values depend not only on process parameters, such as gas flow rate, water, and oil heights, but also on the radial and axial positions of the sensors. The vibration intensity is clearly higher, close to the gas plumes, than in the opposite side. If one of the nozzles is clogged, the vibration intensity close to the clogged nozzle drops drastically (-,36 to -,59%), while the vibrations close to the normal operating nozzle are hardly affected. Based on these results, guidelines are provided for an optimized vibration-based stirring.

A new approach to model the influence of stirring intensity on ethanol production by a flocculant yeast grown on cashew apple juice

AbstractIn this work, a rigorous mathematical model was developed, aiming to address a major flaw inherent in most fermentation models found in the literature, which is the inability to accurately account for mass transfer effects. This model was based on the hypothesis of the existence of a stagnant film involving the cell where the mass transfer rate of the substrate flowing from the medium to the cell surface is equal to the rate of substrate consumption by the cells. The model was used to explore the influence of stirring speed, substrate, and initial cell concentrations and temperature on ethanol production by the flocculant yeast Saccharomyces cerevisiae CCA008, grown on cashew apple juice. Model parameters were estimated and validated against experimental data. The experimental data was divided into two sets: one for parameter optimization using non‐linear Marquardt least‐squares method; and the other to validate the final form of the model equations. Results have shown that the model herein proposed was capable of accurately describing the production of ethanol by S. cerevisiae flocculant yeast considering the influence of operational conditions, especially the effect of the stirring speed on the fermentation rate.

Magnetic Flocculation Treatment of Coal Mine Water and a Comparison of Water Quality Prediction Algorithms

In this study, laboratory-scale magnetic flocculation systems were set up and the optimal coagulant and flocculent dosage, magnetic seed immersion, pH, stirring intensity, and precipitation time were all evaluated. A total of 729 expansion reaction conditions were generated, and 700 of the expansion reaction conditions were used to train a back-propagation neural network (BPNN) and general regression neural network (GRNN). The other 29 conditions were used to verify the networks’ regression ability. The optimum coagulant was poly-aluminum chloride at a dosage of 100 mg/L; the optimum flocculent was anionic polyacrylamide at a dosage of 4 mg/L; the optimum size of the magnetic seed was 200 mesh at a dosage of 1 g/L; and the optimum stirring intensities were 300 r/min for the coagulation tank, 200 r/min for the mixing tank, and 100 r/min for the flocculation tank. Comparing BPNN and GRNN, the GRNN’s regression performance better matched the relationship between the reaction conditions and results.

Modelling of the microstructure formation during solidification of binary alloy Al–Si under stirring

The growth of primary crystals from a supercooled binary melt is modeled on the basis of the phase-field method with an approximate consideration for melt stirring. Changes in the concentration of the solute in the melt near the solidification region due to stirring are considered as the main reason for modifying the dendritic morphology of the crystals. The stirring effect results in a partial removal of the melt with an increased solute concentration from the region near the interface, which is called washout in the work. This effect is approximately modeled as a forced periodic replacement of the current high solute concentration in this region either at the initial concentration or at the averaged concentration in the melt. In this paper, we propose a new algorithm for choosing such a correction region, which can be used for a small intensity of stirring. A value is introduced to describe the washout intensity-the washout parameter. It is shown that when washed away dendritic morphology passes into a rosette morphology, depending on the intensity of stirring. A numerical analysis of the growth of perturbations on the surface of the initial embryo of a circular crystal is carried out. The main differences in the development of such perturbations are shown, which leads to a non-dendritic morphology of the crystal. The growth of additional branches is demonstrated due to a decrease in the solute concentration near the center of the crystal. Calculations have been performed for the case of crystal growth with a decrease in washout intensity with growth time. For this case, the secondary arms grow on additional branches growing from the center of the crystal. It is shown that at a constant value of the washout intensity near the surface of a growing crystal, only two types of morphology are possible from a small round embryo, dendritic and rosette. At the same time, if the crystal already has a rosette morphology, it is retained and with its further growth with a decrease in the washout intensity.

Microstructural Investigation of Semisolid Aluminum A356 Alloy Prepared by the Combination of Electromagnetic Stirring and Gas Induction

A three phase electromagnetic stirrer was used to agitate aluminum A356 slurry and a dry and oxygen free argon gas was introduced in to the slurry by a porous graphite core at a same time. The prepared semi-solid slurry was then transferred into a metallic mold and was compacted by a drop weight. Results demonstrated a favorable increase in shape factor, decrease in aspect ratio and average diameter size at different intensities of stirring. The intensity of stirring was changed by altering the current passed through the magnetic coil and also bubbling intensity via the porous graphite diffuser. Different time intervals for electromagnetic stirring and gas induction were applied. Agitating the slurry for 90 Sec. separately by electromagnetic stirrer and GISS method, gave better results in terms of shape factor, decrease in average diameter of the globules and aspect ratio.

Characterization and flocculation evaluation of a novel carboxylated chitosan modified flocculant by UV initiated polymerization

In this work, carboxylated chitosan modified flocculant (CC-g-PCD) was prepared by graft copolymerization technique to enhance the charge-attracting and adhesion of bridges and net-sweeping capacity of flocculants. The dimethyldiallylammonium chloride (DMDAAC), carboxylated chitosan (CMCS), and 3-chloro-2-chloropropyltrimethylammonium chloride (CTA) were utilized for synthesis of CC-g-PCD via photopolymerization techniques. The synthesized CC-g-PCD was characterized by 1H NMR, SEM, XRD, and FTIR, and the characteristic groups on the main chain and surface morphological structure of CC-g-PCD were investigated. The obtained results indicated that CTA and DMDAAC were successfully grafted into the CPCTS. In ordered to evaluate the flocculation performance of CC-g-PCD at various dosages, stirring intensity (G value), and pH value by detecting Chl a, COD, and turbidity, the actual lake water that contains algae was used for flocculation assessment tests. The experimental results of the water sample with flocculation showed that the maximum flocculation efficiency of turbidity (91.1%), Chl a (97.2%), and COD (97.0%) can be achieved by CC-g-PCD at pH 7, G value 200 s−1, and 4.0 mg/L. The comparison results demonstrated that CC-g-PCD had better flocculation efficiency than commercial flocculants. Finally, based on the analysis of algae removal in combination with Zeta potential measurements, the flocculation mechanisms in actual lake water at various dosages and pH values were adsorption bridging and electrical neutralization.

Direct estimation of microalgal flocs fractal dimension through laser reflectance and machine learning

The pre-concentration of microalgal cultures through flocculation can be applied to reduce the harvesting costs of biomass. The microalgal flocs induced through flocculation must have the optimal size and geometry to enhance the performance of subsequent concentration operations. In this work, we propose a new method to estimate the average fractal dimension of Chlorella sorokiniana flocs based on correlating the suspension chord length distribution with the flocs average geometry through a machine learning random forest regression model. To obtain the data required for training the machine learning model, a set of virtual flocs of prescribed fractal dimension was generated through a computer software. The virtual flocs were subject to chord length data acquisition by means of another piece of software simulating the operation of a focused beam reflectance probe. With the chord length data generated the random forest regression model was trained and optimized and then satisfactorily validated with data of real suspensions of known average geometry. The method developed may be used to implement flocculation control systems capable of adjusting the geometry of flocs to the requirements of subsequent concentration operations by actuating on the process stirring intensity.

The influence of travelling magnetic field on phosphorus distribution in n-type multi-crystalline silicon

The influence of different melt streams on the distribution of phosphorus in multi-crystalline silicon ingot was studied. Phosphorus-doped multi-crystalline silicon (mc-Si) ingots were directionally solidified using travelling magnetic fields (TMF) to alter axial phosphorus profiles. Resistivity distributions in the crystallized n-type ingots were measured along the ingot length. Different Lorentz forces were applied in order to enhance melt stirring and with that to transport phosphorus more rapid towards the melt surface. A new rectangular setup was developed, which enables simultaneous directional solidification of 4 G0-sized mc-Si ingots (80x80x60 mm3) under the influence of TMF. 900 g ingots with different initial level of phosphorus doping were grown, and dopant concentrations in ingots were related to stirring intensities. The phosphorus evaporation rate significantly affects axial dopant profile of mc-Si material, thus this approach can be used as a powerful tool to control and tailor resistivity distribution along phosphorus-doped mc-Si ingots.

Reusable Amberlyst 16 catalyst for acetic acid esterification relevant for pyrolysis bio-oil upgrading process

The current research article addresses the ability of heterogeneous Amberlyst 16 to catalyze the esterification reaction between acetic acid and ethanol, as well as the modelling of the chemical kinetics. The effects of pretreatment, reaction temperature, ethanol-to-acid molar ratio, catalyst dose and time on the rate of ethyl acetate production were systematically investigated. Furthermore, the recyclability of Amberlyst 16 to accelerate the esterification reaction was carefully examined. Amberlyst 16 was found to be a suitable catalyst for this process giving a final acid conversion of 93.3% using reaction temperature of 60 °C, ethanol-to-acid molar ratio of 6:1, catalyst dose of 10 wt% and 200 rpm stirring intensity after 1680 min, and can be successfully utilized for 4 recycle tests. A detailed kinetic model has been developed and tested for the described process, which was based on a four-step mechanism equivalent to the Langmuir–Hinshelwood one. It was found that that the esterification reaction occurred between ethoxide ions and acetic acid chemisorbed on the neighboring catalytic surfaces, whereas, the overall process was controlled by the surface reaction step.

Experimental and Kinetic Study of Magnesium Extraction and Leaching from Laterite Nickel Ore by Roasting with Ammonium Sulfate

Laterite-nickel ore was roasted with ammonium sulfate to extract magnesium by a single-factor experiment, and an orthogonal test was employed to optimize the conditions. The optimum roasting conditions were: calcination temperature, 450°C; calcination time, 120 min; molar ratio of reactants, 2 : 1; granularity <80 µm. The kinetics of the roasting process were also studied. The experimental results showed that the extraction rate of magnesium increased as the calcination temperature increased. The reaction rate of magnesium is in accordance with the shrinking non-reacted nuclear model for the solid product formation reaction. The roasting reaction is controlled by internal diffusion. The apparent activation energy is E = 18.96 kJ mol–1. The kinetic equation is $${\text{1}} + {\text{2}}\left( {{\text{1}} - {\alpha\text{}}} \right) - {\text{3}}{{\left( {{\text{1}} - {\alpha\text{}}} \right)}^{{{{\text{2}} \mathord{\left/ {\vphantom {{\text{2}} {\text{3}}}} \right. \kern-0em} {\text{3}}}}}} = {\text{0}}{\text{.05061exp}}\left[ { - {{{\text{18}}{\text{963}}} \mathord{\left/ {\vphantom {{{\text{18}}{\text{963}}} {\left( {RT} \right)}}} \right. \kern-0em} {\left( {RT} \right)}}} \right]t.$$ A single factor experiment and orthogonal test were carried out to optimize the magnesium leaching process reaction conditions. The optimum conditions of the leaching process were: leaching temperature, 60°C; leaching time, 60 min; liquid to solid ratio, 2.5 : 1; stirring intensity, 400 r min–1. The kinetic equation is 1 – (1 – α)2/3 = 0.3991exp(–8632/RT)t. The apparent activation energy is E = 8.63 kJ mol–1. The reaction rate of the leaching process was controlled by external diffusion.

Numerical simulation of flow and solidification in continuous casting process with mold electromagnetic stirring

The magnetic, heat transfer and flow phenomenon occurring in the continuous casting process under the mold electromagnetic stirring was further analyzed by solving the 3-D electromagnetic field mathematical model and flow solidification model with finite element method and finite volume method, respectively. The results indicate that the solidified shell thickness located in the effective stirring region fluctuates because of the unsteady scouring under the mold electromagnetic stirring. The maximum rotational velocity is a key parameter to the solidification of the billet when controlling the stirring intensity. When the rotational velocity reaches 0.32 m/s, the mush zone enlarges significantly and the solidification rate is further accelerated. The number of vortexes in the lower recirculation zone is not only two and depends on the stirring parameters. Besides, the secondary flow is closely associated with the solidification. Compared with the results of the model ignoring the influence of solidification on the flow of molten steel, the flow pattern within the lower recirculation region changes dramatically, and thus a coupling analysis of the flow, heat transfer, and solidification is essential when simulating the electromagnetic continuous casting process.

THE FORMING OPEN ZONE ON A PHASE-TO-PHASE’S BORDER AT THE AFFINAGE HOT METAL IN A LADLE

For results analysis experiments from research hydro- and gas dynamics bath in the ladle installed, that when rotated submersible lance around the axis best dispersion and dispersal by volume formed gas bubbles is provided at the speed rotation, which does not exceed 2,17 s-1, at specific gas consumption up to 0,018 m3/min.Performed by authors current article calculations of values specific power mixing using the expressions given (under constant conditions regarding bath temperature,mass of melt and gas consumption showed that the quantities vary greatly among themselves. This does not allow you to recommend expressions for mechanical transfer on condition of ladle processing of a melt, including using a rotary lance.From the analysis results calculations by expressions, it follows that the power mixing, mainly determined by the work Archimedes taking into account the forces on isothermal expansion of the gas bubble.With increasing speed submersible lance the gas saturation of the bath is reduced, which may be related with the formation exit channels gas volumes on the surface bath. It affects both the power mixing, and on all processes that accompany the blowing bath with gas.Impact of size, lifting speed and the trajectory movement up to the surface bath bubbles the power mixing is determined by the power Archimedes.To take into account the impact rotation submersible lance around the axis is necessary quantification dissipated energy gas jet which depends on its length and the speed lance. When using two nozzles submersible lance, with nozzles located at an angle 900 to the axis lance the length jets decreases in accordance with the increase rotational speed lance.Proposed expressions to calculate the power mixing the bath in the ladle with a rotary submersible lance. It is shown that condition increase in mixing power there is an increase in size pop up to the surface bath bubbles, which in turn can negatively affect on the degree assimilation reagents to remove impurities at ladle refining hot metal. Dependence is determined dissipation energy gas jets from the rotational speed the submersible lance.The way to increase stirring intensity may be combined use mechanical stirring with additional dispersion gas volumes. Under such circumstances should be expected increase in intensity mass-exchange processes in a bath.

Magnetic ion exchange resin for effective removal of perfluorooctanoate from water: study of a response surface methodology and adsorption performances.

This research exhibited the use of magnetic ion exchange (MIEX) resin as an effective adsorbent for the removal of perfluorooctanoate (PFOA) in aqueous solution. The adsorption performance of PFOA was investigated by a batch experiment. All kinds of factors affecting the adsorption of PFOA, including adsorbent dosage, initial concentration, adsorption time, temperature, stirring intensity, coexistent anions, initial solution pH, natural organic matter, ion strength, and bed volume were studied. Moreover, the response surface methodology was put into use to know the key parameters affecting PFOA removal efficiency. The sorption equilibrium and kinetic data could conform well to the Langmuir and pseudo-second-order model, respectively. Thermodynamic parameters were obtained, and it was observed that the adsorption of PFOA onto MIEX resin was an endothermic and spontaneous process at the temperatures under investigation. It was summarized that both chemical absorption and physical adsorption were involved in the PFOA sorption onto the MIEX resin. Moreover, the MIEX resin could be effectively regenerated using a saturated sodium chloride solution. A series of batch experiments and characterizations demonstrated that the MIEX resin possessed a strong adsorption ability with the removal efficiency exceeding 90%, allowing a possible practical application in future water treatment.

Effects of M-EMS Magnetic Field Intensity on MnS Precipitate in Rail

The process contrast tests with M-EMS stirring intensity was carried out, MnS inclusion scanned and statistics with Aspex, make comparison among the different process for the same testing area after conversion and unified the results that about the length of single inclusion and ratio of inclusion area. Result shows possibility of big size pure MnS separate increased with the greater stirring intensity; besides, nucleation possibility of compound state MnS increased, formation of bigger size compound MnS was promoted at the same time. Conclude that add nucleating agent while smelting and choose 210Gs as the proper stirring intensity is helpful for MnS inclusion separate control, and improve the technological level of inclusion control in rail at last.