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Yuu S.,Ootake R. and D. Consulting Office | Umekage T.,Kyushu Institute of Technology
ISIJ International | Year: 2013

The particle and the air motions in the nearly full scale sintering bed have been simulated to elucidate the void (crack) formation mechanism and the crack growth mechanism. The simulation results showed that the contraction force produced the large scale cracks in the wide area in the fixation zone above the melting zone. Since the contraction force acts toward the particle center from each contact point, the resultant force in the inhomogeneous configuration of contact point moves the particles in the melted liquid. This migration produced the agglomerate which grew continuously. The bed weight in the sintering particle bed disrupted the large agglomerate. Through the process the cracks (voids) further grew and merged to a large scale crack. Large scale cracks developed taking account of the contraction force well represented the measured large scale cracks in the full scale sintering bed obtained using CT scan. In the case that the liquid volume produced by melting was large such as 88% of particle volume, the distance between the neighboring particles in the melted liquid became large and the liquid film between particles became thick. Thus it became hard for particle to move by the resistance force in the liquid. Therefore the agglomerate and the void did not grow to the large scale crack. The agglomeration of particles for 88% of particle volume melted was not so fast that the sintering bed in which the agglomerate particles uniformly distributed was formed. © 2013 ISIJ. Source


Yuu S.,Ootake R. and D. Consulting Office | Umekage T.,Kyushu Institute of Technology
Materials | Year: 2011

Granular flows of 200 μm particles and the pile formation in a flat-bottomed hopper and bin in the presence of air and in a vacuum were predicted based on three-dimensional numerically empirical constitutive relations using Smoothed Particle Hydrodynamics and Computational Fluid Dynamics methods. The constitutive relations for the strain rate independent stress have been obtained as the functions of the Almansi strain including the large deformation by the same method as Yuu et al. [1]. The constitutive relations cover the elastic and the plastic regions including the flow state and represent the friction mechanism of granular material. We considered the effect of air on the granular flow and pile by the two-way coupling method. The granular flow patterns, the shapes of piles and the granular flow rates in the evolution are compared with experimental data measured under the same conditions. There was good agreement between these results, which suggests that the constitutive relations and the simulation method would be applicable for predicting granular flows and pile formation with complex geometry including free surface geometry. We describe the mechanisms by which the air decreases the granular flow rate and forms the convergence granular flow below the hopper outlet. © 2011 by the authors. Source


Yuu S.,Ootake R. and D. Consulting Office | Umekage T.,Kyushu Institute of Technology | Ishiyama O.,Nippon Steel & Sumitomo Metal Corporation
ISIJ International | Year: 2012

The formation and the growth of void (crack) in the sintering bed have not been explored. In this study the motions of particles and the air in the nearly actual scale sintering bed were simulated to elucidate the void formation and the growth mechanisms to large scale crack by the simultaneous calculation of Navier-Stokes equations and the Lagrangian DEM equations based on the simple sintering model in which the phase change of particles, the cohesion force due to the liquid film between particles and the fixation process above the melting zone were considered. The air flow among particles facilitated to grow the crack and finally to produce the large scale crack. The cohesion force by the liquid film caused the agglomeration among particles and grew the voids in the melting zone. In the fixation zone the large cohesive force which was 10 or 30 times larger than that in the melting zone in this study advanced the agglomeration and grew the void. Therefore the cohesion force between particles mainly affects the occurrence of the large scale crack. The decrease of mobility of particle motion by the fixation process in the fixation zone generated the locally large contact force which was about 250 times larger than the usual cohesion force between particles in the agglomerate and the large velocity difference between agglomerates. They broke down the agglomerate particle. Through the fixation zone the cracks (voids) further grew and merged to a large scale crack. © 2012 ISIJ. Source


Yuu S.,Ootake R. and D. Consulting Office | Umekage T.,Kyushu Institute of Technology | Matsuzaki S.,Nippon Steel & Sumitomo Metal Corporation | Kadowaki M.,Nippon Steel & Sumitomo Metal Corporation | Kunitomo K.,Nippon Steel & Sumitomo Metal Corporation
ISIJ International | Year: 2010

The computational program for the particle and the air flows in an actual blast furnace using Distinct Element Method (DEM) for the coke and the iron ore particles of which number was about 16 million and the Finite Difference Method of which computational cell number was about 3 million for the numerical analysis of Navier-Stokes equations with the interaction terms between the air and the particles has been developed. The motions of coke and iron ore particles and the air flow in the blast furnace have been simulated using this program. The computational domain in the tangential direction was 1/4, which was 90 degree of the region of the horizontal plane and in which 10 tuyeres were arranged, of the actual blast furnace. The simulation results showed that the model softening melting cohesive zones, which were formed by the model that 50% volume of the ore particle melted and the diameter Dp reduced to 0.794 Dp by melting the particle surface at the 1200°C line and the residue of the ore particle melted down completely at the 1400°C line, largely affected the air and the coke particle flows and caused the non-homogeneous and unstable flows. The air was divided into two flows at the softening melting cohesive zones. The one was the flow with the slope angle nearly 45° from the horizontal toward the furnace wall in the central region and the other is vertically upward flow in the region near the furnace wall. The coke and ore particle velocities on the wide region of the furnace wall became very low. These nearly quiescent solid particle layers might cause the scaffold of the solid particle bed on the furnace wall. The results also showed that the interaction between tuyeres affected the shape and the stability of the raceway and influenced the particle and the air flows in the wide region on the raceway. Hereafter we will continue to calculate the air and the particle motions, and present the various unstable motions which would bring about an extraordinary event in the actual blast furnace. © 2010 ISIJ. Source


Yuu S.,Ootake R. and D. Consulting Office | Umekage T.,Kyushu Institute of Technology | Kadowaki M.,Kyushu Institute of Technology
ISIJ International | Year: 2010

Flows of solid particles and air in a model blast furnace have been simulated using Distinct Element Method (DEM) for the particles and Finite Difference Method for the numerical analysis of Navier-Stokes equations with the interaction terms between the air and the particles. The flow of solid particles, the air flow, the raceway and the packing fraction distribution are presented. The raceway depth, the diameter of particle inflow area and the raceway height which quantitatively represent a raceway are also presented and compared with the experimental data [CAMP-ISIJ, 16 (2003)). The fairly good agreement obtained by the comparison indicates that our simulation results are sound and the simulation results would represent the flow mechanisms of the solid particles and the air in the model blast furnace, and the simulation method that the Lagrangian motion of particles and the Eulerian motion of the air are simultaneously solved is a useful tool for predicting the flow fields of particles and the gas in a blast furnace. Unsteady state solutions of these flows suggest that dynamical characteristics in the model blast furnace are unstable and fluctuate, and that an unusual phenomenon would happen under some conditions even in the small scale model blast furnace. © 2010 ISIJ. Source

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