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Microscopic analysis of Hopper flow with ellipsoidal particles

AIP Conference Proceedings 2013年第1期1542卷 694-697页

作者： Sida Liu Zongyan Zhou Ruiping Zou David Pinson Aibing Yu Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering The University of New South Wales Sydney NSW 2052 Australia Steelmaking Technology and Planning BlueScope Steel P.O. Box 202 Port Kembla NSW 2505 Australia

Hoppers are widely used in process industries. With such widespread application, difficulties in achieving desired operational behaviors have led to extensive experimental and mathematical studies in the past decades. Particularly, the discrete element method has become one of the most important simulation tools for design and analysis. So far, most studies are on spherical particles for computational convenience. In this work, ellipsoidal particles are used as they can represent a large variation of particle shapes. Hopper flow with ellipsoidal particles is presented highlighting the effect of particle shape on the microscopic properties.

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Discrete modelling of the packing of ellipsoidal particles

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AIP Conference Proceedings 2013年第1期1542卷 357-360页

作者： Zongyan Zhou Ruiping Zou David Pinson Aibing Yu Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering The University of New South Wales Sydney NSW 2052 Australia Steelmaking Technology and Planning BlueScope Steel P.O. Box 202 Port Kembla NSW 2505 Australia

Particle shape affects the packing characteristics significantly. Such a topic has been investigated extensively in the literature by physical experiments or mathematical modelling. In this paper, we give a summary of packing of ellipsoidal particles using discrete element method. As ellipsoidal particles can represent a large number of shapes, e.g. from platy to elongated, the relationships between packing properties (such as packing fraction, coordination number and radial distribution function) and aspect ratios are established. Flow and force structures are also presented to illustrate how the shape affects those microscopic properties for further fundamental understanding. The results demonstrate that discrete element method provides a useful method to investigate the packing dynamics of ellipsoidal particles.

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Numerical investigation of burden distribution m a blast furnace bell -less top

Numerical investigation of burden distribution m a blast fur...

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第五届宝钢学术年会

作者： LIU Sida ZHOU Zongyan YU Aibing PINSON David TSAIAPATIS John Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engin Steelmaking Technology and Planning BlueScope SteelP. O. Box 202Port KemblaNSW 2505Australia OneSteel Whyalla SA 5600Australia

Burden distribution plays an important role in achieving the stable and efficient operation in a modem ironmaking blast furnace ( BF).Granular materials such as coke and ore are discharged from hoppers,descend to rotating chutes,and generate impaction on the burden *** efforts have been made to investigate this *** this work,a 3D DEM - based model framework is established and used to study burden distribution in the scaled OneSteel BF top *** results are compared with experiments,showing a good *** indicates that the proposed DEM is capable of the investigation of BF burden distribution for further fundamental understanding.

关键词： blast furnace bell - less top burden distribution discrete element method

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Impaction of particle streams on a granular bed

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AIP Conference Proceedings 2013年第1期1542卷 634-637页

作者： Sida Liu Zongyan Zhou Kejun Dong Aibing Yu John Tsalapatis David Pinson Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering The University of New South Wales Sydney NSW 2052 Australia OneSteel Whyalla SA 5600 Australia Steelmaking Technology and Planning BlueScope Steel P.O. Box 202 Port Kembla NSW 2505 Australia

Impaction of particle streams on granular beds can be observed in various processes. One typical example is the burden distribution in an ironmaking blast furnace. The stream of heavy iron-bearing pellets impacts the pre-formed coke surface at the blast furnace throat region. The coke layer then can move and collapse. The formed burden profile is important in controlling the radial distribution of gas flow, and hence productivity and stability. In this paper, the impaction of pellets on the coke surface is investigated using discrete element method. A 90 degree sector is modelled with a pre-formed coke surface impacted by pellets flowing from a rotating chute. Microscopic analysis on the flow and force structures is carried out to examine the impaction with different chute angles and discharge rates.

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Discrete particle simulation of particle flow in a stirred mill: Effect of mill properties and geometry

Discrete particle simulation of particle flow in a stirred m...

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作者： Jayasundara, C.T. Yang, R.Y. Yu, A.B. Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering University of New South Wales Sydney NSW 2052 Australia

Particle flow in a stirred mill was modeled using discrete element method, focusing on the effect of mill properties and stirrer configurations, such as particle-wall friction, the size of disc holes, distance between stirrers, and stirrer shape, on the flow properties of grinding media. The flow properties were analyzed in terms of velocity field, porosity distribution, collision frequency, collision energy, impact energy, and power draw. The results indicate that although particle-wall sliding friction coefficient affects the energy transfer from discs to particles, too high a sliding friction may lead to a decrease in energy efficiency. The distance between discs significantly affects the circulation of grinding media between discs. Among the different stirrer types considered, energy transfer is more effective when disc holes are present. Pin stirrer shows increased grinding rates which also results in relatively high power consumption. Although different collision environments exist with different stirrer types, it is shown that the grinding rate can be determined by the first-order kinetics where the rate constant is dependent on the impact energy, for a given material. Grinding efficiency has been compared for different grinding materials under different operating conditions. The results suggest that selection of stirrer geometry also depends on the feed size and the type of material to be ground. Discussion has also been made of the usefulness of particle scale information in the design and control of stirred mills of different types. © 2011 American Chemical Society.

关键词： Grinding (machining)

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Effect of the size of media on grinding performance in stirred mills

Effect of the size of media on grinding performance in stirr...

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This work investigated the effect of grinding medium size on the wet milling performance in stirred mills using a combined numerical and experimental approach. Physical experiments were performed in a 1.4L stirred mill with the discs rotating at different speeds to grind aluminium hydroxide powders with different sized glass beads. The results showed that the grinding process followed the first order kinetics and the grinding rate increased with increasing disc speeds. While 4 mm glass beads had slightly larger grinding rates than 2 mm and 6 mm glass beads, the differences were generally within 5%, indicating their weak dependence. On the other hand, the energy consumption increased significantly for the large grinding media. simulations based on the combined discrete element method (DEM) and computational fluid dynamics (CFD) approach were performed under similar conditions. The simulated flow patterns and power draws were comparable to those measured. The total impact energy, which is the summation of all collision energy, had a unified power law relationship with the grinding rate for all grinding conditions. It is expected that the ratio of total impact energy and input power, which decreased for larger grinding media in the present study, can be used to describe the grinding efficiency. © 2011 Elsevier Ltd. All rights reserved.

关键词： Computational fluid dynamics

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modelling in-furnace phenomena of pulverized coal injection in ironmaking blast furnace: Effect of coke bed porosities

Modelling in-furnace phenomena of pulverized coal injection ...

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作者： Shen, Yansong Yu, Aibing Austin, Peter Zulli, Paul Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering University of New South Wales Sydney NSW 2052 Australia BlueScope Steel Research P.O. Box 202 Port Kembla NSW 2505 Australia

In order to understand the complicated in-furnace phenomena of pulverized coal injection in ironmaking blast furnaces, a three-dimensional CFD model has been developed to simulate the gas-particle behaviors in not only raceway cavity but also the surrounding coke packed bed under practical conditions. The model considers two different fuels, pulverized coal and coke bed. The model is validated against the measurements in terms of coal burnout and gas composition, respectively. The typical in-furnace phenomena are simulated. Then an array of parametric study is carried out to evaluate the effects of local porosities of different coke bed zones. The qualitative and quantitative analysis is conducted. The results indicate that the local porosities of different coke bed zones can affect the coal burnout and gas composition differently: significantly in the deadman zone but insensitive in the dripping zone. In addition, the present model is able to provide a more reliable indicator to describe coal burnout, i.e. burnout over raceway surface, rather than burnout only along the centerline. The model is expected to be useful for understanding the flow-thermo-chemical behaviors and then optimizing the PCI operation in full-scale blast furnaces. © 2011 Elsevier Ltd. All rights reserved.

关键词： Computational fluid dynamics

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Particle scale modelling of the multiphase flow in a dense medium cyclone: Effect of fluctuation of solids flowrate

Particle scale modelling of the multiphase flow in a dense m...

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作者： Chu, K.W. Kuang, S.B. Yu, A.B. Vince, A. Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering University of New South Wales Sydney NSW 2052 Australia Elsa Consulting Group Pty. Ltd. PO Box 8100 Mt. Pleasant QLD 4740 Australia

Dense medium cyclone (DMC) is widely used to upgrade run-of-mine coal in the coal industry. The flow dynamics/fluctuation in a DMC is important but has not been studied previously. In this work, the dynamics is studied by numerically with special reference to the effect of the fluctuation of solid mass flowrate. The simulation is carried out by use of a combined approach of Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM). In the model, the motion of discrete mineral particle phase is obtained by DEM which applies Newton's equations of motion to every individual particle and the flow of medium (mixture of water, air and fine magnetites) phase by the traditional CFD which solves the Navier-Stokes equations at a computational cell scale. The simulated results are analysed in terms of medium and coal flow patterns, and particle-fluid, particle-particle and particle-wall interaction forces. It is shown that under high fluctuation frequency and current conditions, the performance of DMC is not sensitive to both the fluctuation amplitude and period of coal flow at the DMC inlet. However, under low fluctuation frequency, as fluctuation amplitude increases, the separation performance deteriorates slightly and the flow is obviously affected at the spigot. A notable finding is that the near-gravity particles that tend to reside at the spigot and/or have longer residence time in the DMC would be affected more than other particles. The work shows that this two-way coupled CFD-DEM model could be a useful tool to study the dynamics of the flow in DMCs. © 2011 Elsevier Ltd. All rights reserved.

关键词： Computational fluid dynamics

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Some Challenging Problems in Discrete Element modelling of particulate systems

Some Challenging Problems in Discrete Element Modelling of P...

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中国力学学会2012颗粒材料计算力学学术会议

作者： Yu Ai-Bing Laboratory for Simulation and Modelling of Particulate Systems (Simpas)School of Materials Science and Engineering The University of New South Wales Sydney NSW 2052 Australia

Particle science and technology is a rapidly developing interdisciplinary research area with its core being the understanding of the relationships between micro-and macro-scopic properties of particulate/granular matter-a state of matter that is widely encountered but poorly *** macroscopic behaviour of particulate matter is controlled by the interactions between individual particles as well as interactions with surrounding fluids and wall.

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Aggregation Kinetics of Inclusions in Swirling Flow Tundish for Continuous Casting

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Journal of Iron and Steel Research International 2010年第5期17卷 6-10页

作者： YUE Qiang ZOU Zong-shu HOU Qin-fu School of Materials and Metallurgy Northeastern University Shenyang 110004 Liaoning China Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering University of New South Wales Sydney NSW 2052 Australia

The mechanism of inclusion aggregation in liquid steel in swirling flow tundish is analyzed by applying the theory of flocculation which was developed in the field of colloid engineering. The gas bridge forces due to the micro bubbles on hydrophobic inclusion surfaces were responsible for the inclusion collision and agglomeration, which can avoid the aggregation to breakup. The quantity of micro bubbles on hydrophobic inclusion particle is more than that on hydrophilic one. The trend of forming gas bridges between micro bubbles on particles is strong in the course of collision. The liquid film on hydrophobic particles is easy to break during collision process. Hydrophobic particles are liable to aggregate in collision. According to the analysis of forces on a nonmetallic inclusion particle in swirling chamber, the chance of inclusion collision and aggregation can be improved by the centripetal force. Hydropbobic particles in water are liable to aggregate in collision. Hydrophilic particles in water are dispersed although collision happens. The wettability can be changed by changing solid-liquid interface tension. The nonmetallic inclusion removal in swirling flow tundish is studied. The result shows that under certain turbulent conditions, *** concentration and the wettability between particles and liquid steel are the main factors to induce collision and aggregation.

关键词： collision aggregation wettability inclusion swirling chamber continuous casting tundish

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