Granular flow in rotating drums exhibits complex phenomena which are further complicated by the presence of liquids. This paper reviews our recent work on flow of wet particles in rotating drums based on the discrete ...
Granular flow in rotating drums exhibits complex phenomena which are further complicated by the presence of liquids. This paper reviews our recent work on flow of wet particles in rotating drums based on the discrete element method (DEM) simulations. The DEM model was validated by comparing the simulation results with experimental measurements. Particle flow at quasi-static and dynamic states was investigated. In the quasi-static state with the drum rotating at low speeds, wet particle bed failed through avalanche and slow structural change was identified prior to the avalanches. In the dynamic state, flow transited from continuous to avalanche flow with increasing liquid surface tension and a plug flow was developed on the bed surface. Particle mixing in both transverse and axial directions was studied. While cohesion in general reduced transverse mixing, enhanced mixing of wet particles was also observed, which was explained by a theory based on particle circulation period. On the other hand, the axial mixing was well described by Fick’s law of diffusion and particle diffusivity decreased with increasing cohesion. A correlation was observed between particle diffusivity and granular temperature.
This paper presents a numerical study on the piling processes of mono-sized wet particles by the discrete element method (DEM). The capillary force between particles due to liquid bridge is implemented in an existing ...
This paper presents a numerical study on the piling processes of mono-sized wet particles by the discrete element method (DEM). The capillary force between particles due to liquid bridge is implemented in an existing DEM model. The effects of moisture content on the repose angle and structure of a pile are studied by a series of controlled numerical experiments. It is confirmed that the structure of a pile is similar to that of a packing for cohesive particles. Moreover, the averaged local porosity and repose angle have similar changes with the moisture content and can be linearly correlated. Therefore, the relationship between the repose angle and the cohesive force can be established based on the previous correlation between the porosity and the force ratio of the cohesive force to gravity developed in the packing of cohesive particles.
A three-dimensional CFX-based mathematical model is developed to describe the flow-heat transfer-chemical reactions behaviours of gas-solid-liquid phases in an ironmaking blast furnace (BF), where the raceway cavity i...
A three-dimensional CFX-based mathematical model is developed to describe the flow-heat transfer-chemical reactions behaviours of gas-solid-liquid phases in an ironmaking blast furnace (BF), where the raceway cavity is considered explicitly. The typical in-furnace phenomena of an operating blast furnace, in particular, the liquid flow in the lower part of a blast furnace is simulated in aspects of velocity and volume fraction. This model offers a cost-effective tool to understand and optimize blast furnace operation.
In order to understand the complex phenomena of pulverized coal injection (PCI) process in blast furnace (BF), mathematical models have been developed at different scales: pilot-scale model of coal combustion and indu...
In order to understand the complex phenomena of pulverized coal injection (PCI) process in blast furnace (BF), mathematical models have been developed at different scales: pilot-scale model of coal combustion and industry-scale model (in-furnace model) of coal/coke combustion in a real BF respectively. This paper compares these PCI models in aspects of model developments and model capability. The model development is discussed in terms of model formulation, their new features and geometry/regions considered. The model capability is then discussed in terms of main findings followed by the model evaluation on their advantages and limitations. It is indicated that these PCI models are all able to describe PCI operation qualitatively. The in-furnace model is more reliable for simulating in-furnace phenomena of PCI operation qualitatively and quantitatively. These models are useful for understanding the flow-thermo-chemical behaviors and then optimizing the PCI operation in practice.
The pulverized charcoal (PCH) combustion in ironmaking blast furnaces is abstracting remarkable attention due to various benefits such as lowering CO2 emission. In this study, a three-dimensional CFD model is used to ...
The pulverized charcoal (PCH) combustion in ironmaking blast furnaces is abstracting remarkable attention due to various benefits such as lowering CO2 emission. In this study, a three-dimensional CFD model is used to simulate the flow and thermo-chemical behaviours in this process. The model is validated against the experimental results from a pilot-scale combustion test rig for a range of conditions. The typical flow and thermo-chemical phenomena is simulated. The effect of charcoal type, i.e. VM content is examined, showing that the burnout increases with VM content in a linear relationship. This model provides an effective way for designing and optimizing PCH operation in blast furnace practice.
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....
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.
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...
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.
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 rota...
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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.
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 ...
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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