Centrifugal Granulation Research Articles

Characterization and pharmacokinetics of cinnamon and star anise compound essential oil pellets prepared via centrifugal granulation technology

Cinnamon and star anise essential oils are extracted from natural plants and provide a theoretical basis for the development and clinical application of compound essential oil pellets. However, cinnamon oil and star anise oil have the characteristics of a pungent taste, extreme volatility, poor palatability, and unstable physical and chemical properties, which limit their clinical use in veterinary medicine. In this study, the inhibitory effects of cinnamon oil and star anise oil on Escherichia coli and Salmonella were measured. Compound essential oil pellets were successfully prepared by centrifugal granulation technology. Subsequently, the in vitro dissolution of the pellets and their pharmacokinetics in pigs were investigated. The results showd that, cinnamon and star anise oils showed synergistic or additive inhibitiory effects on Escherichia coli and Salmonella. The oil pellets had enteric characteristics in vitro and high dissolution in vitro. The pharmacokinetic results showed that the pharmacokinetic parameters Cmax and AUC were directly correlated with the dosage and showed linear pharmacokinetic characteristics, which provided a theoretical basis for the development and clinical application of compound essential oil pellets.

Tritium release performance of biphasic Li2TiO3–Li4SiO4 ceramic pebbles fabricated by centrifugal granulation method

At present, the biphasic Li2TiO3–Li4SiO4 ceramic pebbles with high lithium content and crushing load have been viewed as promising tritium breeders for maintaining the safety-state operation of the D-T fusion reactor. The tritium release behavior of Li2TiO3–Li4SiO4 ceramic pebbles fabricated by centrifugal granulation method was investigated by using the Thermal Desorption Spectroscopy apparatus at Shizuoka University. It can be found that the Li2TiO3–Li4SiO4 ceramic pebbles show three tritium release peaks, and most of the tritium was released as HTO observed from T-TDS spectra, and the peaks at 581 K and 734 K are mainly due to tritium release from Li2TiO3 in core and shell. The peak at 813 K is mainly deemed as tritium release derived from the Li4SiO4 shell. The content of tritium release from biphasic Li2TiO3–Li4SiO4 ceramic is up to 11.5 MBq g−1, but the amount of gas species (HT) is only 0.126 MBq g−1. Besides, the isothermal heating experiment showed that the tritium release behavior was subject to diffusion process and de-trapping in defect sites. At the same time, the irradiation defects of E′-center, O-related center, and Ti3+ for breeding material can be found by using an ESR device, and the isochronous heating experiments have manifested that the amount of irradiated defect decreases as heating temperature increases, which indicates that the tritium release behavior is closely related to defect annihilation process. Therefore, the advanced Li2TiO3–Li4SiO4 ceramic breeder can be fabricated based on tritium release result, which will be conducive to meet the practical application of breeder in the future.

Computational Fluid Dynamics Numerical Simulation on Flow Behavior of Molten Slag–Metal Mixture over a Spinning Cup

Centrifugal granulation technology using a spinning cup opens a potential way to recycle steel slag that is currently difficult to reuse. The objective of this research was to study the flow characteristics of a molten slag–metal mixture that was produced during smelting reduction in molten steel slag, passing over a spinning cup, so as to explore the feasibility of using centrifugal granulation technology to treat the steel slag. This was achieved by developing and implementing a computational fluid dynamics (CFD) model that incorporated free-surface multiphase flow to predict the thickness of the liquid slag film at the edge of the spinning cup (slag film thickness for short), which was an important parameter for estimating the size of the slag particles resulting from centrifugal granulation of the molten slag–metal mixture. The influences of various relevant parameters, including spinning cup diameter, slag feeding rate, cup spinning speed, etc., on the slag film thickness were analyzed. Additionally, hot experiments on centrifugal granulation of a molten slag–metal mixture were conducted to verify the results of the numerical simulations. The experimental results indicated a progressive reduction in the Sauter mean diameter of the slag particles as the metallic iron content in the slag increased. Specifically, when the iron content rose from 5% to 15% at a cup spinning speed of 2500 RPM, the Sauter mean diameter decreased by 13.77%. The numerical simulation results showed that the slag film thickness had a positive relationship to the slag feeding rate but a negative relationship to the spinning cup diameter and the cup spinning speed. Furthermore, the ratio between the mean slag particle diameter and the slag film thickness decreased nearly linearly with the increase in the metallic iron content in slag, with the average ratio being approximately 4.25, and this relationship was useful for estimating the slag particle size from the slag film thickness. Therefore, the present research results can provide theoretical guidance for the industrial application of spinning cup centrifugal granulation technology to effectively treat and recycle steel slags.

Optimizing heat transfer characteristics in dry centrifugal Granulation: Impact of particle population trajectory and cooling strategies

Efficient recovery of heat and utilize blast furnace slag resources are crucial for achieving energy savings and reducing consumption in the steel industry. This study focuses on applying dry centrifugal pelletizing technology for recovering waste heat from slag. A comprehensive two-dimensional model was developed to investigate heat transfer dynamics within particle clusters, considering the variable physical parameters of the slag, latent heat of the phase change, and slag particle characteristics. Through an extensive analysis of the heat exchange within the granulation bin, we examined the temperature variations of slag particles and the distribution of absorbed heat by the water-cooled and air. Findings underscore the significant influence of flight trajectory, residence time, air-inlet flow rate, and temperature on heat exchange efficiency. Additionally, we explored the impact of auxiliary cooling measures and investigated how slag particle characteristics affect the bin wall, highlighting their importance for safe operations. Our results provide valuable insights for enhancing waste heat recovery efficiency from blast furnace slag and optimizing the implementation of dry centrifugal granulation technology. It serves as a vital reference for promoting energy-saving initiatives and reducing consumption in the steel industry.

Heat transfer characteristics of high-temperature particle population in ultra-dilute phase: Particle-fluid-surface heat transfer during falling

In dry centrifugal granulation technology, the liquid slag is granulated in the granulator to produce a particle population with a high-temperature dilute-phase distribution. During the falling process, inadequate heat transfer can cause the droplets to fail to solidify completely, greatly reducing the safety of the heat recovery bed operation. In this work, A heat transfer model for a particle population of ultra-dilute phase slag was developed, to investigate the particle-fluid-surface heat transfer characteristics of the particle population around the tube, and obtain the changing law of particle population cooling and tube surface heat transfer characteristics. The conclusions of the study show that the fluid flows close to the tube, which is due to particle perturbation. The separation point is to be shifted back, from 180°∼210° to the top 90°∼120°, resulting in a local heat transfer coefficient maximum at the upper of the tube. The amplitude of the fluctuations in the local heat transfer coefficients exhibits the dominance of the different heat transfer types, the percentage of radiant heat transfer is above 60% in all cases. The extended particle residence time can effectively increase the particle cooling rate, the particle cooling rate is above 230 K/s. This study reveals the heat exchange mechanism between the gas-solid phase of the ultra-dilute particle population and the horizontal tube during the falling process, positive performance of horizontal tubes on heat transfer to particle populations was confirmed. Combined heat transfer between the surfaces of dilute-phase particle populations is proposed as a new research content in the field of high-temperature melt granulation, expanding the prospects of industrial applications of combined heat transfer between the surfaces of fluid-solid multiphase flows.

Composition-specific granulation characteristics of molten slag at improved throughput and high temperature of 1,723 K

Centrifugal granulation is one key step to enable waste heat recovery from the molten slag in the iron and steel industry. Yet, it remains unknown about the granulation characteristics of molten slag with different chemical compositions, especially at high throughput. In this work, we provided an experimental study on centrifugal granulation with four types of molten slags. The stage-specific centrifugal granulation was recorded and analyzed at first. Both effects of atomizer configuration and chemical compositions on granulation were investigated in detail. The cup-type atomizer favors film-mode disintegration and possesses better anti-adhesion capacity although the final granule size was not strongly affected by the atomizer configuration. Most importantly, centrifugal granulation has been demonstrated with appreciable adaptability to composition-specific blast furnace (BF) slag with binary basicity of 0.9–1.3. The present study not only sheds light on the modest effect of the chemical composition of molten slag on centrifugal granulation characteristics, but also gains credit for the adaptivity of CGATER.

Experimental investigation on centrifugal granulation of molten yellow phosphorus slag

Centrifugal granulation with waste recovery was proposed to recover the waste heat from the molten yellow phosphorus slag produced by an electric arc furnace and reduce pollution. The yellow phosphorus slag was heated to the same temperature as industrial electric furnaces and then granulated by centrifugal granulation. The study mainly investigated the effect of operating parameters on particle diameter distribution, flight distance distribution, and fiber mass fraction during the granulation process. The results showed that the average diameter was mainly 1.5–3 mm, and tended to decrease with the decrease of the mass flow rate, the increase of the rotating speed, and the increase of the rotary cup diameter. The particle diameter obeyed a log-normal distribution. As the rotating speed increased and the rotary cup diameter increased, the average flight distance and the distribution of flight distance were dispersed. The average flight distance was related to the linear velocity at the edge of the rotary cup. Increasing slag temperature, mass flow rate, and decreasing rotary cup diameter can reduce the fiber mass fraction. Re and We numbers can determine whether fibers produce.

On a mathematical model of the cooling and crystallization of metal drops during centrifugal granulation

A mathematical model has been developed for the crystallization of aluminum alloy granules under cooling conditions in an aqueous and water-steam media. The practical significance of the mathematical model lies in predicting the average value of the dendritic parameter of the obtained granules depending on the granulation method, the characteristics of the granulation process and the size of the obtained granules. The average value of the dendritic parameter makes it possible to predict the fineness of the granule structure and, consequently, the mechanical properties of the granular material. The mathematical model makes it possible to determine the speed of a melt drop in an aqueous media and takes into account the presence of a steam jacket effect, i.e., a vapor layer that appears between a crystallizing drop and an aqueous media, which significantly reduces the intensity of heat removal and the rate of crystallization. The application of the mathematical model was tested on the obtaining of granules of high-alloyed aluminum alloys (alloys D1 and D16 of the Al–Cu–Mg system, alloys V95 and V96Ts of the Al–Zn–Mg–Cu system), made by centrifugal spraying of the melt from a perforated rotating crucible and drip method during cooling in an aqueous media. The cooling rate and the crystallization rate of the granules obtained in real experiments were determined by measuring the dendritic parameter of the material structure. The mathematical model showed a high convergence of the simulation results and of real experiments of aluminum alloy granulation.

Effect of Equipment Parameters on Amount and Dispersion of Wetting Liquid in Planetary Centrifugal Granulation.

In planetary centrifugal wet granulation, the binder is often mixed into the formulation as a powder, followed by the addition of a wetting liquid, in a single step. Therefore, the amount and dispersion of the wetting liquid are important factors that determining granulation success and granules characteristics. In this study, granulation experiments, according to the Box-Behnken design, were performed. Further, the effects of equipment parameters, namely, processing speed, processing time, and vessel size, on the minimum amount of wetting liquid required to enable granulation and dispersion state in the vessel were statistically analyzed. Placebo granules were formulated with lactose hydrate and corn starch (7 : 3), using sodium carmellose as a binder. Results showed that the amount of wetting liquid decreased with increase in processing speed, processing time, and vessel size; however, the dispersion state of the wetting liquid was not significantly affected. Analysis of the effects of the equipment parameters on granule characteristics showed that a larger vessel size was proportional to a larger median diameter and smaller particle-size distribution width (span), and a faster processing speed was proportional to a smaller span. Furthermore, granules with the target properties could be prepared according to the parameters estimated from the model. In conclusion, the equipment parameters for controlling the amount of wetting liquid, which affected the granule properties, were clarified.

Modelling the film fragmentation of industrial-scale centrifugal granulation of high-temperature molten slag

Centrifugal-granulation-assisted thermal energy recovery (CGATER) is one of the most promising routes to enable waste heat harvest from molten slags. However, it remains a grand scientific and technological challenge to produce fine particles from the bulk high-temperature molten slag, especially at large slag throughput. In this work, we established an improved model to simulate the centrifugal granulation at the large flowrate comparable to the laboratory- pilot-scale trials. For the first time, film fragmentation has been successfully reproduced by modelling. On this basis, we elucidated the intricate film fragmentation by quantifying the off-atomizer film characteristics at various operational conditions, with a strong focus on the metrics of the off-atomizer slag film. The present study provides an important and valuable CFD model to approach the underlying physics of film fragmentation. Most importantly, it opens up new possibilities for predicting slag droplet formation at experimentally unavailable operational conditions.

Mass fabrication of Li2TiO3–Li4SiO4 ceramic pebbles with high strength by facile centrifugal granulation method

AbstractThe bi‐phase Li2TiO3–Li4SiO4 ceramic pebbles have been considered a promising breeder to realize the tritium self‐sustainment in the blanket. However, up to now, the reported ceramic pebbles have the disadvantages of low yield, poor crushing load, and loose internal structure, which cannot meet the practical application requirements. In this work, the Li2TiO3–Li4SiO4 ceramic pebbles with excellent mechanical properties were fabricated successfully via the centrifugal granulation method with the assistance of introducing a spray‐drying process, simulating particle trajectory by discrete element software and improving bonding interface between core and shell with ethylene glycol. The composition, microstructure, and inner structure of the Li2TiO3–Li4SiO4 ceramic pebbles were investigated, respectively, through X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and X‐ray computed tomography (CT). It can be found that the employment of the ethylene glycol solution on the surface of Li2TiO3 can make the core and the shell combine well. Moreover, the effect of the rolling speed of the Li2TiO3–Li4SiO4 ceramic pebbles was investigated via discrete element method (EDEM) simulation and experiments. The experimental results displayed that the Li2TiO3–Li4SiO4 ceramic pebbles sintered at 1100°C for 2 h have a uniform diameter of 1 mm, a good sphericity of 0.97, and an excellent crushing load of 82.4 N, which are superior to those pebbles that obtained by using the traditional wet methods. Moreover, the CT results showed that the appropriate porosity of the core was 3.21% and of the shell was 10.73%. Therefore, the simple centrifugal granulation method can be applied to prepare the Li2TiO3–Li4SiO4 ceramic pebbles in a large scale and shed a light to investigate the relevant advanced biphasic tritium breeder materials in the future.

CFD Numerical Simulation on the Mode of Ligament Disintegration during Centrifugal Granulation of Molten Slag by Using a Spinning Cup

In order to study the behavior of molten blast furnace slag ligament breakup into droplets by centrifugal granulation with a spinning cup, three-dimensional transient CFD model simulations were performed in the present work to study the process of the slag deformation into ligaments upon leaving the spinning cup, which eventually disintegrate into droplets. The formation of molten slag ligaments at the edge of the spinning cup and their disintegration into droplets were numerically revealed so that the behavior and mechanism of the slag ligament breakup into droplets could be investigated. This work specifically examined the influence of cup spinning speed on the diameter and length of the molten slag ligaments around the cup periphery and the diameter of the droplets produced. The simulation results show that, for the same slag flowrate, with the increase in cup spinning speed, the slag film thickness at the cup edge decreases, the number of molten slag ligaments increases, and the diameter of the ligaments decreases, thus reducing the diameter of slag droplets. Moreover, as the number of molten slag ligaments increases as a result of the increased cup spinning speed, the flowrate of a single ligament decreases, so that the ligament disintegrates in a shorter radial distance, that is, the length of the ligament is shortened. In addition, this work also investigated the behavior and mechanism of a single molten slag ligament breakup into droplets. It was found that the process of molten slag ligament breakup into droplets under the action of centrifugal force and surface tension can also be approximately explained by the theory of the Rayleigh disintegration mechanism.

CFD Modeling and Cold Physical Model Simulation on Single Molten Slag Ligament Disintegration into Droplets

Aiming at the mode of liquid ligament disintegration into droplets in the process of the centrifugal granulation of molten blast furnace slag using a spinning cup, in order to gain an in-depth understanding of the behavior and mechanism of droplet formation by liquid ligament disintegration and to obtain appropriate conditions to control the size of the produced slag granules, a three-dimensional CFD model describing water–air two-phase flow with a free surface was established in this work for simulating the process of a single water ligament breakup into droplets under the action of gravity, surface tension and inertial forces, so as to compare with the process of a molten slag ligament disintegration into droplets due to centrifugal force exerted by the spinning cup. By studying the disintegration behavior and mechanism of a single water ligament, the similar phenomenon of a molten slag ligament disintegration is examined. The numerical simulation results on the breakup of a single water ligament show that the length of the ligament before its disintegration and the diameter of the droplets formed both increase with the increase of the velocity of the ligament initially exiting a capillary nozzle. In addition, an experimental set-up was established in the laboratory to conduct cold physical model simulation experiments on single water or liquid paraffin ligament disintegration. The experimental results are compared with the numerical simulation results so that the reliability of the CFD model is verified. The results of the present study show that, in the centrifugal granulation process of blast furnace slag using a spinning cup operated in the ligament disintegration mode, the breakup of a single molten slag ligament is very similar to that of a single water or liquid paraffin ligament, and both approximately follow the Rayleigh Disintegration Mechanism, which provides a theoretical basis for analyzing the breakup process of the ligaments of different liquids as references for guiding the operation of centrifugal granulation of molten slag.

Numerical study of inlet eccentricity on liquid film spreading and splitting in centrifugal granulation assisted thermal energy recovery

Centrifugal granulation assisted thermal energy recovery(CGATER) is a method of recovering waste heat from molten slag by centrifugal granulation on a rotating disc. Disturbance and positioning errors can cause the incoming liquid column to deviate from the center of the disc. In this study, numerical simulation was conducted to investigate the effect of inlet eccentricity on liquid film flow spreading, liquid filament formation and fragmentation, and droplet size distribution during CGATER. The study shows that the eccentric granulation results in a new splitting pattern in which the liquid filament grows to a certain length with the rotation of the disc and then breaks from the bottom; the thickness of the liquid film on the eccentric granulation disc is consistent with the radial velocity distribution of the liquid film. Finally, the general dimensionless prediction correlation of particle median diameter is established for the eccentric situation. • A simulation of centrifugal granulation under eccentric entry was carried out. • Eccentric entry creates a new mode of liquid filament splitting. • Consistent liquid film thickness and radial velocity distribution on the disc. • A dimensionless particle size prediction equation with eccentricity was proposed.

Feasibility Study on A Novel Waste Heat Recovery Process of Industrial Waste Salt Based on High Temperature Melting Dry Method

Industrial waste salt is mainly produced by industrial production processes of pesticides, drug synthesis, printing and dyeing, as well as solid-liquid separations, concentration and crystallization of solution, and sewage treatment, etc. At the present stage, the annual output of waste salt in China has exceeded 2.0×107 tons and the high-temperature melting method is considered to be a promising treatment method, but there are problems such as molten salt adhesion and agglomeration, unused high-temperature sensible heat, and waste of water resources. A novel process for waste heat recovery by high temperature melting dry method is proposed in this paper, using a combination of centrifugal granulation and waste heat recovery to dispose high-temperature molten salt and effectively recover heat. Through thermal equilibrium analysis and calculation, the waste heat recovering efficiency of the waste heat recovery using the novel process can reach up to 98%. Taking the annual treatment of 100,000 tons of waste salt as an example, the benefits of effective heat recovery converted to standard coal could be approximately 5 billion. While efficiently utilizing waste heat resources, the novel process brings considerable economic benefits to enterprises, has good industrial application prospects, and helps to advance the process of national hazardous waste solid waste treatment.

Role of P2O5 in the viscous behavior and structure of yellow phosphorus slag

To clarify the role of P2O5 in the fluidity of yellow phosphorus slag during the centrifugal granulation process, the viscosity and structure of slag with various P2O5 contents were researched. It showed that increasing P2O5 content from 1.38wt% to 5.80wt% enhanced the slag viscosity and activation energy for viscous flow, which reduced the slag fluidity. P2O5 in slag existed as QP0 and QP1 units whose proportions were about 0.89 and 0.11, respectively, irrespective of the P2O5 contents. The introduced P2O5 promoted the polymerization of silicate structure because the metal cations coordinated by non-bridging oxygens in silicate structure became connected with the phosphate structure. P2O5 addition encouraged the conversion of [AlO4] units into [AlO5] units and reduced the polymerization degree of aluminate structure. The variations in the polymerization degree of silicate and aluminate structure played a competitive role in determining the slag viscosity, and the silicate structure was the dominant factor.

Effect of batch size on the granule properties in planetary centrifugal granulation.

A granulation method using a planetary centrifugal mixer, called planetary centrifugal granulation, has been developed for small-scale production, such as extemporaneous preparation in pharmacies. Although the impact of its operational parameters on granulation is described, the scale effect has not been investigated. Therefore, we aimed to reveal the effects of vessel size and vessel filling rate on granule properties. In this study, ibuprofen 20% granules consisting of lactose, cornstarch, sodium carmellose, and talc were used as model granules. Granulation was performed using geometrically similar containers, 6-58 mL, with a filling rate of 20-70%. After granulation, we monitored the granule properties, for example, median diameter (d50), span of particle size distribution, and sphericity. At filling rates of 40% and 50% in the 58-mL vessel, the granules grew larger in diameter, and at a rate of 30%, the granules showed a higher sphericity. When the filling rate was 30%, d50 became larger and the span decreased as the vessel size increased. The yields of the granules were higher than 95% when using the 12-58 mL vessel. Lastly, the drug content uniformity and drug dissolution behavior of the granules produced in different vessel size were examined. The granules showed similar drug consistencies and drug dissolution profiles. In conclusion, the quality of the products was not affected by changes in vessel size. Thus, pharmacists could prepare and compound the granule formulations with high yield and appropriate quality using an adequate vessel in the same manner.

Flow Characteristics of the Liquid Film During Centrifugal Granulation of Liquid Slag on the Surface of Rotary Cup

Flow Characteristics of the Liquid Film During Centrifugal Granulation of Liquid Slag on the Surface of Rotary Cup

Cooling and phase evolution of a molten blast furnace slag particle

In the dry centrifugal granulation process to treat liquid blast furnace slag, it is critical to clarify the cooling and crystallization characteristics of slag particles, which greatly determine their subsequent reutilization and waste heat recovery. Here, we investigated the cooling characteristics of a single slag particle by simulation in terms of crystal phase content variation, temperature and velocity distributions, average cooling rate, etc. The most influential operating parameter was demonstrated to be the particle size and the dimensionless average cooling rate was determined, thereby helping regulate the cooling process more effectively. Moreover, the exploration in the slag composition indicated that reducing the corrected optical basicity was extremely beneficial to promote the particle quality. In the selection of thermophysical parameters, we concluded that constant viscosity was feasible, while density, conductivity and heat capacity should keep temperature-dependent. These results are expected to provide guidance for the application of dry centrifugal granulation technology.

Numerical simulation analysis of rotary cup centrifugal blast furnace slag

In the process of centrifugal dry granulation of blast furnace slag, the thickness of the liquid film at the outlet of the rotor will have a significant impact on the degree of crushing of the slag after leaving the rotor and the size of the solid particles formed. Therefore, this paper uses the VOF method to analyse the flow of molten slag inside the cup. The results have shown that the slag flow has a significant effect on the thickness of the liquid film and the linear relationship is obvious; the thickness of the liquid film decreases with the increase of the diameter of the rotary cup and the rotation speed, and the negative correlation with the diameter of the cup is more obvious; Secondly, as the depth of the cup increases, the thickness of the liquid film decreases first and then increases. The inclination angle of the cup wall has little effect on the thickness of the liquid film.