Bath Flow Research Articles

Discussion on “ Characteristics of the Instantaneous Kinetic Energy and Agitating intensity Index for the Bath Flow Under Various Bottom Regiment Configurations” Published in the Transactions of IIM, 2024, pp. 2073–2081

Discussion on “ Characteristics of the Instantaneous Kinetic Energy and Agitating intensity Index for the Bath Flow Under Various Bottom Regiment Configurations” Published in the Transactions of IIM, 2024, pp. 2073–2081

Variation in Flow Characteristics of Molten Baths at Different Blowing Stages in the Converter

The metallurgical tasks at different stages of converter blowing are different. The process operation and physical properties of molten baths are also different. It is very important to determine the flow characteristics of molten baths at different blowing stages for optimizing process operation. In this paper, a three-dimensional, full-scale model of a 120 t top–bottom combined blowing converter is established. Based on the parameters of oxygen lance position, bath temperature, bottom blowing intensity, and bath physical properties at different blowing stages, the changes in bath flow field, turbulent kinetic energy, impact depth, impact area, and wall shear force with blowing process are studied. The results show that at the initial stage of blowing, the lance position is high, the impact depth of the molten bath is 0.23 m, the impact area is 5.06 m2, the dead zone area of the longitudinal section is 0.40 m2, and the high-speed zone area is 2.73 m2. As the blowing time increases, the lance position decreases, the impact depth of the molten bath increases, the impact area decreases, and the internal velocity of the molten bath increases. In the later stage of tuyere blowing, the lance level decreases to its lowest, the impact depth increases to 0.42 m, the impact area decreases to 2.83 m2, the dead zone area of longitudinal section decreases to 0.18 m2, and the high-speed area increases to 3.34 m2. The area with the highest wall shear stress is situated within the gas–slag–metal three-phase region, where the lining experiences the most significant erosion. The fluctuation in the slag–metal interface is small, and the wall shear force is 2.80 Pa at the initial stage of blowing. From the early to late stages of blowing, the lance position decreases, the fluctuation range of the slag–metal interface increases, and the erosion of the furnace lining increases. In the later stage of blowing, the maximum wall shear force is 3.81 Pa.

A facile spinning approach towards the continuous production of aligned nanocellulose films

In this work, we present an alternative approach to cellulose nanofibril film (CNF) production, taking inspiration from the wet spinning of fibers to wet spin films. During the spinning process, a CNF suspension is injected into a coagulation bath, where the partially aligned CNF network is locked. The CNF alignment of the dry films is then detected by wide angle X-ray scattering (WAXS). The comparison between the ultimate strengths and strengths at breaks of the films produced with different process parameters, including the suspension injection rate, bath pH, and bath flow rate, indicated no significant change in mechanical properties, suggesting a reliable and constant outcome for large-scale film fabrication. Furthermore, the produced films demonstrated high total light transmittance of 93 % at the wavelength of 550 nm, making them suitable for optoelectronic applications. Polarized optical microscopy revealed that even a low degree of CNF alignment can lead to anisotropic optical properties. Moreover, an anisotropic response to humidity was observed, in which the films preferentially bend in the perpendicular direction of the CNF orientation, thus opening a way for humidity-driven actuators.

Effect of bottom stirring on bath mixing and transfer behavior during scrap melting in BOF steelmaking: A review

Abstract Basic oxygen furnace (BOF) steelmaking is a widely used method for steelmaking production, and the bath stirring has a significant influence on dynamics of bath flow and mixing. Therefore, the effect of bottom gas flowrate, nozzle number and configuration, and bottom gas distribution mode on bath stirring are summarized in this study. Reasonable matching of bottom gas flowrate, nozzle number and configuration, as well as intensive study on the coupling effect of gas flowrate gradient and exchange frequency on non-uniform stirring would receive more and more attention in the coming years. With wide concern on the low-carbon and high-efficient production for BOF steelmaking, as a kind of recyclable iron-containing resource, the rapid melting and reasonable utilization of scrap in converter bath were emphasized in recent works, which could be promoted with high-efficient bottom stirring. The effect of bottom stirring on heat and mass transfer during scrap melting process was reviewed in this work, and the influence mechanism of bottom stirring on coupled heat and mass transfer should be further investigated. In addition, an overview of recently published physical and numerical simulation describing the bottom stirring and its effect on scrap melting would provide an outlook for future work.

Characteristics of the Instantaneous Kinetic Energy and Agitating Intensity Index for the Bath Flow under Various Bottom Regiment Configurations

Characteristics of the Instantaneous Kinetic Energy and Agitating Intensity Index for the Bath Flow under Various Bottom Regiment Configurations

FEA study on the TSV copper filling influenced by the additives and electroplating process

Through-Silicon Via (TSV) is a key technology of three-dimensional (3D) integration. However, Voids are usually found in the Cu filling process of TSV, and lead to lower reliability. Additives and optimized filling process are used to solve this problem. However, the comprehensive analysis of these affecting parameter needs many experiments and cost much time. Thus, the finite element analysis (FEA) for the mass transferring of electroplating is carried out by the COMSOL software in the work. Different inhibitor concentrations in filling process are first studied and the most suitable density of 64 mol/m2 is obtained. However, high inhibitor concentration will lead to much lower plating speed. Thus, the effect of filling process such as current density and plating bath flow velocity on the voids are investigated under the optimized concentrations above. The best filling quality is obtained at the inhibitor concentration of 64 mol/m2, current density of 1.4 ASD and the bath stirring velocity of 0.4 m/s. The underlying growth mechanism of these influencing factors are also analyzed and revealed.

Functional maturation of kidney organoid tubules: PIEZO1-mediated Ca2+ signaling.

Kidney organoids cultured on adherent matrices in the presence of superfusate flow generate vascular networks and exhibit more mature podocyte and tubular compartments compared with static controls (Homan KA, Gupta N, Kroll KT, Kolesky DB, Skylar-Scott M, Miyoshi T, Mau D, Valerius MT, Ferrante T, Bonventre JV, Lewis JA, Morizane R. Nat Methods 16: 255-262, 2019; Takasato M, Er PX, Chiu HS, Maier B, Baillie GJ, Ferguson C, Parton RG, Wolvetang EJ, Roost MS, Chuva de Sousa Lopes SM, Little MH. Nature 526: 564-568, 2015.). However, their physiological function has yet to be systematically investigated. Here, we measured mechano-induced changes in intracellular Ca2+ concentration ([Ca2+]i) in tubules isolated from organoids cultured for 21-64 days, microperfused in vitro or affixed to the base of a specimen chamber, and loaded with fura-2 to measure [Ca2+]i. A rapid >2.5-fold increase in [Ca2+]i from a baseline of 195.0 ± 22.1 nM (n = 9; P ≤ 0.001) was observed when microperfused tubules from organoids >40 days in culture were subjected to luminal flow. In contrast, no response was detected in tubules isolated from organoids <30 days in culture. Nonperfused tubules (41 days) subjected to a 10-fold increase in bath flow rate also exhibited a threefold increase in [Ca2+]i from baseline (P < 0.001). Mechanosensitive PIEZO1 channels contribute to the flow-induced [Ca2+]i response in mouse distal tubule (Carrisoza-Gaytan R, Dalghi MG, Apodaca GL, Kleyman TR, Satlin LM. The FASEB J 33: 824.25, 2019.). Immunodetectable apical and basolateral PIEZO1 was identified in tubular structures by 21 days in culture. Basolateral PIEZO1 appeared to be functional as basolateral exposure of nonperfused tubules to the PIEZO1 activator Yoda 1 increased [Ca2+]i (P ≤ 0.001) in segments from organoids cultured for >30 days, with peak [Ca2+]i increasing with advancing days in culture. These results are consistent with a maturational increase in number and/or activity of flow/stretch-sensitive Ca2+ channels, including PIEZO1, in tubules of static organoids in culture.

Numerical investigation of scrap melting in high-carbon hot metal

Abstract Scrap melting in the steelmaking process has recently attracted considerable attention. This study developed a mathematical model to investigate the effects of sizes, initial temperatures and carbon contents of scrap, and bath flow on its melting behaviors. The results showed that the volume of the solidified shell on the melting interface could be decreased or eliminated by increasing the initial temperature of the scrap. The initial carbon content also significantly influenced the melting behavior. The completion melting time decreased from 253 to 80 s when the carbon content increased from 0.10% to 0.30%. Importantly, the natural convection or driven flow formed in the bath significantly influenced the melting behaviors. Moreover, the dominating factors changed as the melting proceeded. Therefore this study provides more insights into the melting behavior of the scrap during the steelmaking process at different operating conditions.

Toward the Bath Flow Interaction of a 250 t Combined Top and Bottom Blowing Converter Based on a Mathematical Modeling

Herein, the fluid mechanical aspects involving flow interactions between flows formed by the top impinging jet and bottom blowing bubbles in a combined blowing converter bath are focused on. The effects of different operation conditions on the flow field and the kinetic energy of the bath are investigated to examine different roles of the blowing operations with the help of numerical model. It is found that the stirring intensity in the region near the bath wall is decreased even though the flow is more active in the vicinity of the impact cavity when the top lance declines. For the combined blowing converter, the bottom blowing plumes normally dominate the bath flow. However, the bath stirring intensity is increased slightly when the bottom blowing flowrate is higher than a critical value (0.08 Nm3 min−1 t−1). In addition, the results of energy dissipation demonstrate that higher flowrate of bottom blowing causes more intensive interaction between flows formed by the top and the bottom blowing, which, in turn, causes more energy dissipation.

CFD Investigation of Bath Flow and Its Related Alumina Transmission in Aluminum Reduction Cells: Slotted Anodes and Busbar Designs

Alumina is an indispensable raw material for the modern aluminum electrolysis industry. The distribution and transmission of alumina within the bath is of great significance to maintain stable operation and reduce energy consumption. In this study, a computational fluid dynamics (CFD) model was developed to investigate the bath flow and its related alumina transmission in aluminum reduction cells. The bath flow driven by bubbles, electromagnetic force, and aluminum flow presented two different sized vortices in the horizontal plane of the anode–cathode distance (ACD). Both numerical results and industrial data show that the average alumina concentration in the half-cell at the duct end is slightly larger than that of the tap end. With the application of slotted anodes, the maximum velocity of the bath flow increased and the average velocity decreased slightly in the horizontal plane, resulting in a more uniform distribution of alumina than that in the use of unslotted anodes. The symmetrical nature of the bath flow vortices became more obvious with the upgrade of the busbar design and the alumina concentration gradient became smaller within the bath.

Self-induced flows enhance the levitation of Leidenfrost drops on liquid baths

In a study of the Leidenfrost levitation of a droplet on a hot liquid bath, rather than, classically, on an extremely hot plate, an existential feedback is revealed. The droplet induces a bath flow, whose fickle structure is explored both experimentally and theoretically. In turn, the flow drastically enhances the heat transfer to the droplet by convective means, thus ensuring such an evaporative levitation despite the poorly conducting liquid medium of the bath.

Numerical Simulation of the Melting Behavior of Steel Scrap in Hot Metal

The current study focuses on the melting behavior of a scrap bar with low carbon content in hot metal which contains high carbon concentration by applying experiments and mathematical modelings. The experiments suggest that higher temperature is favorable for the melting of the bar and the melting rate of the bar is initially high while decreased to a relative stable level after 90 s in the current conditions. It can be found from the mathematical results that the bar temperature is increased near to bath temperature in about 20 s after it was immersed into the bath, and the temperature in the axis of the bar is not distributed evenly during the temperature increase stage. Moreover, the mathematical results shows that a bath circulation flow would be formed in the bath under the effects of temperature and carbon distribution during the melting process. The bath flow near the melting interface would influence the carbon concentration of the molten phase, in turn, affects the melting rate of the bar in the vertical direction. Both the experimental and mathematical results show that the melting rate in the upper part, which is in the upstream of the bath flow, is higher than that of the middle part, followed by the down part of the bar in the downstream of the flow, in which the carbon concentration is much lower than that of the bath. At this period, the main factor that dominate the bar melting is not the temperature but the carbon distribution at the melting interface after the bar temperature is increased to the bath temperature.

Physical and Mathematical Modeling of Swirling Gas Jets Impinging onto a Liquid Bath Using a Novel Nozzles‐Twisted Lance

Physical and mathematical modeling is performed in a 10:1 scaled‐down basic oxygen furnace (BOF) steelmaking vessel to study impingement onto a bath of swirling gas jets from a novel nozzles‐twisted lance. The particular aspects with respect to the swirling jets‐induced cavity characteristic, jets’ stirring efficiency, and bath flow field are focused upon, and their discrepancies with those created by conventional oxygen lance jets are assessed. Results show that compared with the conventional jets, the swirling jets strike a greater impact area with a shallower but wider cavity and facilitate bath surface flow. Due to a more intensive bath horizontal flow, which shows an increase in intensity by 0.34–1.66 times than that of conventional jets, the swirling jets shorten bath mixing time by 11–60%, depending on the nozzle twist angle of the lance. These results suggest that the lance height of the nozzles‐twisted lance is operated more flexibly than that of the conventional one. This not only enables sufficient bath stirring efficiency and improves slagging but also contributes to postponing lance tip erosion and prolonging its life span in plant operations, whereas the enhanced flows in the regions near the sidewall accelerate refractory erosion there.

Numerical Assessment on Effects of Longitudinal Slots and Its Application in Aluminium Reduction Cells

The effects of longitudinal slots on gas evolution and bubble-driven flow in Hall–Heroult cells by a computational fluid dynamics (CFD) model have been investigated. A similar flow pattern in the anode-to-cathode distance (ACD) or spacing was shown between unslotted and slotted cases, but more complex local flow and gas evolution behavior beneath the anodes are derived from the slots. The gas accumulates in the slots/anode gaps and is released from these paths, and over 50% of gas bubbles escape from the slot tops in the slotted case. The design of the current applied slots in smelters was optimized based on CFD simulations, and it was shown that a trisected slotted design along the width direction produced the minimum ‘gas holdup’ in the ACD regions. The effects of the slot-inclined direction on bath flow and gas holdup were further investigated to quantitatively evaluate the easily made mis-operation in the anode change process during commercial production. Based on the findings of this analysis, using the horizontal slot design instead of the current typical inclined slot design is recommended, as it avoids the issue of operator error while still providing a similar benefit to the inclined slots. At the end of this paper, an industrial application of slotted anodes is discussed as an example to indicate that the slotted anode technology should be carefully applied, especially for smelters with poor quality anodes.

Modeling of Mixing Behavior in a Combined Blowing Steelmaking Converter with a Filter-Based Euler–Lagrange Model

A filter-based Euler–Lagrange multiphase flow model is used to study the mixing behavior in a combined blowing steelmaking converter. The Euler-based volume of fluid approach is employed to simulate the top blowing, while the Lagrange-based discrete phase model that embeds the local volume change of rising bubbles for the bottom blowing. A filter-based turbulence method based on the local meshing resolution is proposed aiming to improve the modeling of turbulent eddy viscosities. The model validity is verified through comparison with physical experiments in terms of mixing curves and mixing times. The effects of the bottom gas flow rate on bath flow and mixing behavior are investigated and the inherent reasons for the mixing result are clarified in terms of the characteristics of bottom-blowing plumes, the interaction between plumes and top-blowing jets, and the change of bath flow structure.

State and Parameter Estimation in Hall-Héroult Cells using Iterated Extended Kalman Filter

The measurement of individual anode currents in the Hall-Héroult process provides localized information that can be used to improve cell operation. One promising application is to estimate the local cell conditions, which are impracticable to measure regularly during the cell operation. This paper presents an approach to estimation of localized state variables and process variables, including the alumina concentration, anode-cathode distance and bath flow rate. This is achieved by using the Iterated Extended Kalman Filter (IEKF) with a discretized Hall-Héroult cell model. The results show that the proposed IEKF can produce more accurate estimation of the state variables and parameters compared to the conventional Extended Kalman Filter thanks to its robustness to ill-set initiation conditions.

Numerical Modeling of Flow Dynamics in The Aluminum Smelting Process: Comparison Between Air–Water and CO2–Cryolite Systems

Air–water models have been widely applied as substitutes for CO2–cryolite systems in the study of the complex bubble dynamics and bubble-driven flow that occurs in the molten electrolyte phase in the aluminum electrolytic process, but the detailed difference between the two systems has not been studied. This paper makes a numerical comparison between the bubble dynamics for the two systems. Simulations of both single bubble and continuous bubbling were conducted using a three-dimensional computational fluid dynamics (3D CFD) modeling approach with a volume of fluid (VOF) method to capture the phase interfaces. In the single bubble simulations, it was found that bubbles sliding under an anode in a CO2–cryolite system have a smaller bubble thickness and a higher sliding velocity than those in the air–water system for bubbles of the same volume. Dimensionless analysis and numerical simulation show that contact angle is the dominant factor producing these differences; the effects of kinematic viscosity, surface tension, and density are very small. In the continuous bubbling simulations, the continuous stream of air bubbles detaches from the anode sidewall after a period of climbing, just as it does in the single bubble simulation, but bubbles have less tendency to migrate away from the wall. Quasi-stable state flow characteristics, i.e., time-averaged bath flow pattern, turbulence kinetic energy, turbulence dissipation rate, and gas volume fraction, show a remarkable agreement between the two systems in terms of distribution and magnitude. From the current numerical comparisons, it is believed that the air–water model is a close substitutive model for studying bubble-driven bath flow in aluminum smelting processes. However, because of the difference in bubble morphologies between the two systems, and also the reactive generation and growth of bubbles in the real system, there will likely be some differences in bubble coverage of the anode in the anode–cathode gap.

Towards a coupled multi-scale, multi-physics simulation framework for aluminium electrolysis

Aluminium metal production through electrolytic reduction of alumina in a cryolite bath is a complex, multi-physics, multi-scale process, including magneto-hydrodynamics (MHD), bubble flow, thermal convection, melting and solidification phenomena based on a set of chemical reactions.Through interactions of the different forces applied to the liquid bath combined with the different time and length scales, self-organised fluctuations occur. Moreover, the MHD behaviour causes a complex metal pad profile and a series of surface waves due to the meta-stable condition of the metal/cryolite interface.The large aspect ratio of an industrial cell, with a footprint of 20 by 4m and at the same time having dimensions approaching just 30mm of height for the reaction zone, prevents an integrated approach where all relevant physics are included in a single mathematical model of this large degree of freedom system. In order to overcome these challenges, different modelling approaches have been established in ANSYS® FLUENT®; Three models are used to predict details of specific physics: one to predict the electro-magnetic forces and hence the metal pad profile, a second that resolves details of the local bubble dynamics around a single anode and a third for the full cell bath flow. Results from these models are coupled to allow integration of the different phenomena into a full cell alumina distribution model. The current paper outlines each of the approaches and presents how the coupling between them can be realized in a complete framework, aiming to provide new insight into the process.

Research and Analysis on the Physical and Chemical Properties of Molten Bath with Bottom-Blowing in EAF Steelmaking Process

Bottom-blowing technology is widely adopted in electric arc furnace (EAF) steelmaking to promote the molten bath fluid flow, accelerate the metallurgical reaction, and improve the quality of molten steel. In this study, a water model experiment and a computational fluid dynamics model were established to investigate the effects of bottom-blowing gas flow rate on the fluid flow characteristics in the EAF molten bath. The results show that the interaction among the bottom-blowing gas streams influences the molten bath flow field, and increasing the bottom-blowing gas flow rate can accelerate the fluid flow and decrease the volume of the dead zone. Based on industrial application research, the physical and chemical properties of the molten bath with bottom-blowing were analyzed. Compared with traditional melting conditions without bottom-blowing, bottom-blowing technology demonstrates obvious advantages in promoting the heat transfer and metallurgical reactions in the molten bath. With the bottom-blowing arrangement, the dephosphorization and decarburization rates are accelerated, the contents of FeO and T. Fe in endpoint slag are decreased, and the endpoint carbon-oxygen equilibrium of molten steel is improved.

Anodic Bubble Behavior and Voltage Drop in a Laboratory Transparent Aluminum Electrolytic Cell

The anodic bubbles generated in aluminum electrolytic cells play a complex role to bath flow, alumina mixing, cell voltage, heat transfer, etc., and eventually affect cell performance. In this paper, the bubble dynamics beneath the anode were observed for the first time from bottom view directly in a similar industrial electrolytic environment, using a laboratory-scale transparent aluminum electrolytic cell. The corresponding cell voltage was measured simultaneously for quantitatively investigating its relevance to bubble dynamics. It was found that the bubbles generated in many spots that increased in number with the increase of current density; the bubbles grew through gas diffusion and various types of coalescences; when bubbles grew to a certain size with their surface reaching to the anode edge, they escaped from the anode bottom suddenly; with the increase of current density, the release frequency increases, and the size of these bubbles decreases. The cell voltage was very consistent with bubble coverage, with a high bubble coverage corresponding to a higher cell voltage. At low current density, the curves of voltage and coverage fluctuated in a regularly periodical pattern, while the curves became more irregular at high current density. The magnitude of voltage fluctuation increased with current density first and reached a maximum value at current density of 0.9 A/cm2, and decreased when the current density was further increased. The extra resistance induced by bubbles was found to increase with the bubble coverage, showing a similar trend with published equations.