Emulsion Zone Research Articles

Contribution of Emulsion Zone in Refining of Basic Oxygen Steelmaking Converter

Contribution of Emulsion Zone in Refining of Basic Oxygen Steelmaking Converter

Refining at the impact and emulsion zones of basic oxygen steel making process – a fundamental study

ABSTRACT Insights into the kinetics occurring during the combined blown (top and bottom blowing) oxygen steelmaking process, particularly at the impact and emulsion zones within separate reactors, can provide a deeper understanding of the refining mechanism in steelmaking. A dynamic model has been developed that can predict the contributions of various refining processes such as decarburization, desiliconization, demanganization, and dephosphorization. The model considers gas–metal interactions at the impact zone and slag–metal–gas interactions at the emulsion zone in an oxygen steelmaking converter. The model includes sub-models for lime dissolution and heat loss calculation. FactSage™ software and its macro programming facility were employed to integrate thermochemical and kinetic information into the model. The model predicts the temperature, composition, and volume of several phases involved in the process. The model predictions transient metal and slag compositions and metal bath temperature, were found to be consistent with the plant data.

Spongy all-in-liquid materials by in-situ formation of emulsions at oil-water interfaces

Printing a structured network of functionalized droplets in a liquid medium enables engineering collectives of living cells for functional purposes and promises enormous applications in processes ranging from energy storage to tissue engineering. Current approaches are limited to drop-by-drop printing or face limitations in reproducing the sophisticated internal features of a structured material and its interactions with the surrounding media. Here, we report a simple approach for creating stable liquid filaments of silica nanoparticle dispersions and use them as inks to print all-in-liquid materials that consist of a network of droplets. Silica nanoparticles stabilize liquid filaments at Weber numbers two orders of magnitude smaller than previously reported in liquid-liquid systems by rapidly producing a concentrated emulsion zone at the oil-water interface. We experimentally demonstrate the printed aqueous phase is emulsified in-situ; consequently, a 3D structure is achieved with flexible walls consisting of layered emulsions. The tube-like printed features have a spongy texture resembling miniaturized versions of “tube sponges” found in the oceans. A scaling analysis based on the interplay between hydrodynamics and emulsification kinetics reveals that filaments are formed when emulsions are generated and remain at the interface during the printing period. Stabilized filaments are utilized for printing liquid-based fluidic channels.

Design and Development of Solid SMEDDS and Liquisolid Formulations of Lovastatin, for Improved Drug Dissolution and In vivo Effects-a Pharmacokinetic and Pharmacodynamic Assessment.

Lovastatin (Lov) is a lipid-lowering agent, with 5% bioavailability (BA) due to extensive first pass metabolism and poor solubility. To enhance dissolution and in vivo effects, Lov solid self microemulsifying drug delivery system (SMEDDS) and liquisolid systems were developed and evaluated to select superior one. Solubilities were determined in oils, surfactants, and cosurfactants. Ternary phase diagrams were constructed and selected the one which showed maximum emulsion zone. In vitro dissolution, DSC, SEM and PXRD studies were used to characterize the developed formulations. In vivo studies were conducted on optimal formulations in wistar rats. Based on solubilities, Capmul PG8 and Capmul MCM were preferred as oils, Labrasol and Transcutol P as surfactant and cosurfactant. Here, Syloid XDP carrier showed better adsorption capacity among others, hence was used in optimal solid SMEDDS (SX) and liquisolid (LS) formulations. Dissolution study results showed significant improvement in release when compared to pure drug. DSC, SEM, and PXRD results indicated the loss of drug crystallinity in optimal formulations. In pharmacokinetic (PK) study, SX and LS showed 2.57 and 1.43 fold improvements in AUC, when compared to that of coarse suspension (CS). In pharmacodynamic (PD) study, hyperlipidemia was induced by Triton X-100. CS and LS treatments showed a decline in hyperlipidemic levels at 4h. But, SX-treated group showed early onset of decline at 2h. Further, the duration of anti-hyperlipidemia was at least 12h extra when compared to CS and LS. This study confirmed the superiority of SX over LS in PK and PD effects.

Contribution of Hot-Spot Zone in Decarburization of BOF Steel-Making: Fundamental Analysis Based upon the FactSage-Macro Program

An improved computational model to describe the decarburization process in basic oxygen furnaces for steel making is presented in this work. A dynamic model was thus developed to calculate the decarburization rate and its breakup as a contribution coming from the hot-spot zone (under jet impact) and emulsion zone (by droplet and slag reactions). In this work, multiple interconnected equilibrium/adiabatic stoichiometric-reactor-based approaches are used to describe the overall basic oxygen steel-making process. The macroprogramming facility of FactSage™ software was used to understand the thermodynamics and kinetics of basic oxygen steel-making processes. The temperature, compositions, and volumes of various phases are estimated with the use of this model. Hot-spot temperatures in the range from 2000 to 3000 °C as a benchmark was considered for calculations. The major contribution of decarburization was established to come from hot-spot reactions in the major part of the blow, except in the last part when emulsion phase reactions govern it. This development represents an original contribution to our understanding of the BOF steel-making process.

Modeling the motion of fuel particles in a fluidized bed

A semiempirical model for the mixing of fuel particles in a fluidized bed is presented and validated against experimental data from the literature regarding lateral fuel mixing. The model of fuel particle mixing categorizes the fluidized bed into three mixing zones: a rising bubble wake solid zone, an emulsion zone with sinking bulk solids, and a splash zone located above the dense bed. In the emulsion zone, the axial motion of the fuel particle is described by a force balance, applying a viscoplastic stress model, i.e., with a dominant yield stress and only a minor contribution of the shear stress, using an empirical expression from the literature. In the lateral direction, the model is divided into so-called ‘recirculation cells’, which are crucial for the lateral mixing.Comparisons of the modeled and measured lateral dispersion coefficients of different fuel types measured in three different large-scale fluidized bed units under both hot and cold conditions (covering a broad range of coefficients: 10−4–10−1 m2/s) reveal satisfactory agreement. The validated model was used to investigate how the lateral mixing of fuel particles depends on the excess gas velocity, the bed height, and the lateral distribution of bubbles over the bed cross-section (which is typically uneven in industrial FB furnaces), as well as the size and density of the fuel particles.

Application of Pseudohomogeneous and Heterogeneous Models in Assessing the Behavior of a Fluidized-Bed Catalytic Reactor

Comparative analysis of the steady-state and transient properties of a bubbling fluidized-bed catalytic reactor obtained according to different mathematical models of the emulsion zone was performed to verify the commonly used assumption regarding the pseudohomogeneous nature of this zone. Four different mathematical models of the fluidized-bed reactor dynamics were formulated, based on different thermal and diffusional conditions at the gas-solid interface and within the catalyst pellet, namely the model based on the assumption of pseudohomogeneous character for the emulsion zone, and a group of two-scale models accounting for the heterogeneous character of this zone. It was demonstrated that, while the pseudohomogeneous model of the emulsion zone predicts almost identical behavior of the reactor at steady-state as the proposed heterogeneous models, it may fail in the prediction of the reactor start-up behavior, especially when dealing with highly exothermic processes run at relatively high fluidization velocity.

Dynamic Modeling and Simulation of Basic Oxygen Furnace (BOF) Operation

Basic oxygen furnaces (BOFs) are widely used to produce steel from hot metal. The process typically has limited automation which leads to sub-optimal operation. Economically optimal operation can be potentially achieved by using a dynamic optimization framework to provide operators the best combination of input trajectories. In this paper, a first-principles based dynamic model for the BOF that can be used within the dynamic optimization routine is described. The model extends a previous work by incorporating a model for slag formation and energy balances. In this new version of the mathematical model, the submodel for the decarburization in the emulsion zone is also modified to account for recent findings, and an algebraic equation for the calculation of the calcium oxide saturation in slag is developed. The dynamic model is then used to simulate the operation of two distinct furnaces. It was found that the prediction accuracy of the developed model is significantly superior to its predecessor and the number of process variables that it is able to predict is also higher.

Modeling Axial Mixing of Fuel Particles in the Dense Region of a Fluidized Bed

A semi-empirical model for the axial mixing of fuel particles in the dense region of a fluidised bed is presented and validated against experimental magnetic particle tracking in a fluid-dynamical, down-scaled fluidised bed that resembles hot, large-scale conditions. The model divides the bottom region into three mixing zones: a rising bubble wake solids zone; a zone with sinking emulsion solids; and the splash zone above the dense bed. In the emulsion zone, which is crucial for the mixing, the axial motion of the fuel particle is shown to be satisfactorily described by a force balance that applies experimental values from the literature and an apparent emulsion viscosity of Newtonian character. In contrast, the values derived from the literature for key model parameters related to the bubble wake zone (such as the upwards velocity of the tracer), which are derived from measurements carried out under cold laboratory-scale conditions, are known to underestimate systematically the measurements relevant to h...

The Decarburization Kinetics of Metal Droplets in Emulsion Zone

A mathematical model has been developed to predict the decarburization rate within individual droplets in the emulsion zone. All the chronological events pertaining to the life cycle of a metal droplet in the emulsion zone like oxygen supply (from slag), external and internal decarburization have been modeled dynamically and validated against experimental data available in open literature. The bloating behavior of metal droplets in the emulsion was represented theoretically by incorporating an escape function dependent on internal CO gas generation. The model is able to predict the onset of bloating and the residence time of metal droplets in the emulsion zone. The residence time of droplet containing 2.6 wt pct C and 0.007 wt pct S is in the range of 10 to 13 seconds. The contribution of decarburization rate in the emulsion zone to the overall decarburization rate is studied using the industrial data reported by Cicutti et al. The model predicts 5 to 75 pct of total decarburization takes place in the emulsion zone. It is found that the extent of decarburization of a metal droplet depends on its initial carbon content rather than its oxygen content for slag containing FeO greater than 10 wt pct.

Dynamic Model of Basic Oxygen Steelmaking Process Based on Multizone Reaction Kinetics: Modeling of Manganese Removal

In the earlier study, a dynamic model for the BOF process based on the multizone reaction kinetics has been developed. In the preceding part, the mechanism of manganese transfer in three reactive zones of the converter has been analyzed. The study predicts that temperature at the slag–metal reaction interface plays a major role in the Mn reaction kinetics. Further, mathematical treatments to simulate the transient rate parameters associated with each reaction interface have been developed. The model calculations of Mn removal rate obtained from different zones of the converter predicts that the first stage of the blow is dominated by the oxidation of Mn at the jet impact zone, albeit some additional Mn refining has been observed as a result of the oxidation of metal droplets in emulsion phase. The simulation result shows that the reversion of Mn from slag to metal primarily takes place at the metal droplet in the emulsion due to an increase in slag–metal interface temperature during the middle stage of blowing. In the final stage of the blow, the competition between simultaneous reactions in jet impact and emulsion zone controls the direction of mass flow of manganese. Further, the model prediction shows that the Mn refining in the emulsion is a strong function of droplet diameter and the residence time. Smaller sized droplets approach equilibrium quickly and thus contribute to a significant Mn conversion between slag and metal compared to the larger sized ones. The overall model prediction for Mn in the hot metal has been found to be in good agreement with two data sets obtained from different size converters reported in the literature.

The Effect of Sulfur Concentration in the Metal on the Mass Transfer of Phosphorus in Bloated Metal Droplets

In Basic Oxygen Steelmaking, metal droplets created by the impact of the oxygen jet will swell due to internal decarburization when they react with oxidizing slag in the emulsion zone. In this study, the dephosphorization behavior of bloated metal droplets containing different sulfur concentrations is investigated in the temperature range from 1813 to 1913 K using X‐ray fluoroscopy coupled with constant volume pressure change measurements and chemical analysis of quenched samples. The results show that higher sulfur droplets (>0.017 wt%) have a much longer incubation period for swelling than those with lower sulfur (<0.017 wt%). Due to this different swelling behavior, the dephosphorization rate for high sulfur droplets is found to be not heavily affected by the experimental temperature compared to the case of lower sulfur droplets. Employing a mixed control model including mass transfer and chemical reaction, the effect of temperature on dephosphorization kinetics is further discussed. The mass transfer coefficient in the metal, km, is found to increase slightly with increasing temperature for droplets with 0.021 wt% sulfur. It is also found that lower rates of CO formation result in less stirring in the droplet and lower mass transfer rates of phosphorus for high sulfur droplets.

Dynamic Model of Basic Oxygen Steelmaking Process Based on Multi-zone Reaction Kinetics: Model Derivation and Validation

A multi-zone kinetic model coupled with a dynamic slag generation model was developed for the simulation of hot metal and slag composition during the basic oxygen furnace (BOF) operation. The three reaction zones (i) jet impact zone, (ii) slag–bulk metal zone, (iii) slag–metal–gas emulsion zone were considered for the calculation of overall refining kinetics. In the rate equations, the transient rate parameters were mathematically described as a function of process variables. A micro and macroscopic rate calculation methodology (micro-kinetics and macro-kinetics) were developed to estimate the total refining contributed by the recirculating metal droplets through the slag–metal emulsion zone. The micro-kinetics involves developing the rate equation for individual droplets in the emulsion. The mathematical models for the size distribution of initial droplets, kinetics of simultaneous refining of elements, the residence time in the emulsion, and dynamic interfacial area change were established in the micro-kinetic model. In the macro-kinetics calculation, a droplet generation model was employed and the total amount of refining by emulsion was calculated by summing the refining from the entire population of returning droplets. A dynamic FetO generation model based on oxygen mass balance was developed and coupled with the multi-zone kinetic model. The effect of post-combustion on the evolution of slag and metal composition was investigated. The model was applied to a 200-ton top blowing converter and the simulated value of metal and slag was found to be in good agreement with the measured data. The post-combustion ratio was found to be an important factor in controlling FetO content in the slag and the kinetics of Mn and P in a BOF process.

Modeling of Droplet Generation in a Top Blowing Steelmaking Process

Quantification of metal droplets ejected due to impinging gas jet on the surface of liquid metal is an important parameter for the understanding and for the modeling of the refining kinetics of reactions in slag-metal emulsion zone. In the present work, a numerical study has been carried out to critically examine the applicability of droplet generation rate correlation previously proposed by Subagyo et al. on the basis of dimensionless blowing number (N B). The blowing number was re-evaluated at the impingement point of jet with taking into account the temperature effect of change in density and velocity of the gas jet. The result obtained from the work shows that the modified blowing number N B,T at the furnace temperature of 1873 K (1600 °C) is approximately double in magnitude compared to N B calculated by Subagyo and co-workers. When N B,T has been employed to the Subagyo’s empirical correlation for droplet generation, a wide mismatch is observed between the experimental data obtained from cold model and hot model experiments. The reason for this large deviation has been investigated in the current study, and a theoretical approach to estimate the droplet generation rate has been proposed. The suitability of the proposed model has been tested by numerically calculating the amount of metals in slag. The study shows that the weight of metals in emulsion falls in the range of 0 to 21 wt pct of hot metal weight when droplet generation rate has been calculated at ambient furnace temperature of 1873 K (1600 °C).

The Research for Work Roll Thermal Deformation of Cold Rolling Mill with Plastic Materials

In this article, the factors which have influence on the work roll thermal deformation in cold strip rolling and the heat transferring mechanism are discussed. It is considered that there are three direc-tions, radial、axis and circumference, for heat transferring for work roll thermal deformation with plastic materials. Therefore, it is a three dimensions unstable system for work roll temperature field of cold strip rolling. The plastic deformation work and friction heat are calculated by the divided element and digital integration method. The simplified calculation model is built for the heat trans-ferring along work roll. There are four zones for work roll heat transferring: roll gap zone、air zone、emulsion zone、rolls contact zone. The heat transferring between the zones is decided by the temperature difference. The inter temperature field and thermal deformation of work roll can be calculated by two-dimension finite difference method. The work roll temperature and thermal crown of actual application cold rolling mill are analyzed by the model. By the comparison between calculated values and measured values, the work roll thermal calculation model can meet the accu-racy requirement of on-line control.

Population Balance Model for Batch Gravity Separation of Crude Oil and Water Emulsions. Part I: Model Formulation

A population balance model for the separation of emulsions in a batch gravity settler is presented. Within the context of the model development, possible methodologies were elucidated for incorporating a) the physical properties of the bulk liquids, b) the physical properties of the phase interface, and c) the presence and functioning of interfacially active compounds. The model presented explicitly accounts for interfacial coalescence and the deformation of the emulsion zone due to the dynamic growth of the resolved dispersed phase; interfacial coalescence is modeled in terms of physically meaningful film drainage models and an approach for incorporating the accumulated buoyancy force in the dense packed layer is also discussed. Hydrodynamically hindered sedimentation is also considered in the model. The model is well suited to predict experimental batch settling data, especially data obtained from low-frequency NMR measurements of emulsion destabilization. The model predicts the evolution of the volume fraction of the dispersed phase at any axial position and time in the separator. Furthermore, the model predicts the location of the resolved dispersed phase interface as a function of time. Additionally, for any axial position and time in the settler, the model predicts the evolution of the average number density of droplets, the average volume/radius of droplets, the standard deviation of the droplet volume/radius, and the rate of growth of the droplets. The model is compared directly with experimental data for crude oil separations in Part II of this article.

Development on a small scale industrial CFB boiler with an evaporating loop seal

Most of the small scale industrial CFB (SICFB) boilers in China work at low operating pressure. Compared with the big scale CFB boiler in power plant, the heat ratio of water evaporation is higher in the SICFB boiler. Consequently, evaporating submerged tubes are always installed in the furnace emulsion zone in order to avoid overheating of flue gas at the furnace outlet. The boiler metal consumption could also be reduced because of the higher heat transfer coefficient of submerged tubes. But serious erosions are brought to the submerged tubes as the furnace emulsion zone always works at turbulent fluidized bed state with higher fluidization velocity. In the study, for alleviating the erosion to the submerged tubes, all the evaporating submerged tubes are set in the loop seal instead of in the furnace emulsion zone, and the loop seal is enlarged accordingly to be an evaporating loop seal (ELS). An 11t/h SICFB boiler with an ELS has been put into industrial application, the design consideration and operating characteristics of the boiler are systematically discussed in the paper.

Comprehensive Model of Oxygen Steelmaking Part 2: Application of Bloated Droplet Theory for Decarburization in Emulsion Zone

The development of a global model for oxygen steelmaking and its validation against industrial data was reported in Part 1 of this paper. This paper focused on the development of one sub-model on the decarburization reaction in the emulsion zone incorporating the bloated droplet theory. This paper also critically evaluated the current knowledge on the kinetics of decarburization reaction in the emulsion phase and discussed the repercussions of the new model for industrial practices. The decarburization model, in conjunction with the industrial data, indicates that the decarburization rates in the emulsion phase reaches up to approximately 60% of the overall decarburization rate during the main blow. It was found that the residence time of droplets as well as decarburization reaction rate via emulsified droplets was strong function of bloating behavior of metal droplets in the emulsion phase. The estimated residence times of the metal droplets in the emulsion were between 0.4 to 45 s throughout the blow. The influence of variations in droplet size and ejection angle on residence time and decarburization rates via emulsified droplets was also investigated. It was shown in this study that the decarburization rates in the emulsion were accelerated if droplet size was decreased or if the ejection angle was decreased.

Work Roll Thermal Deformation Calculation Model of Cold Rolling Mill

In this article, the factors which have influence on the work roll thermal deformation in cold strip rolling and the heat transferring mechanism are discussed. It is considered that there are three directions, radial, axis and circumference, for heat transferring for work roll thermal deformation. Therefore, it is a three dimensions unstable system for work roll temperature field of cold strip rolling. The plastic deformation work and friction heat are calculated by the divided element and digital integration method. The simplified calculation model is built for the heat transferring along work roll. There are four zones for work roll heat transferring: roll gap zone, air zone, emulsion zone, rolls contact zone. The heat transferring between the zones is decided by the temperature difference. The inter temperature field and thermal deformation of work roll can be calculated by two-dimension finite difference method. The work roll temperature and thermal crown of actual application cold rolling mill are analyzed by the model. By the comparison between calculated values and measured values, the work roll thermal calculation model can meet the accuracy requirement of on-line control.

Batch Drying Kinetics in a Two-Zone Bubbling Fluidized Bed

This article deals with investigation and modeling of batch drying process of solids in fluidized bed apparatus. There has been used model of fluidized bed drying, which consists two zones: emulsion zone and bubbling zone with taking into consideration the presence of solid particles in the bubbles. The results of theoretical expectations that arise from simulation calculations have been verified with experimental data obtained with the use of fluidized bed dryer 0.225 m in diameter. A drying process of silica gel, sand, and ammonium sulfate has been tested. To verify the model, the concept of a generalized drying curve has also been employed.