Dynamic Analysis of Gas and Solid Flows in Blast Furnace with Shaft Gas Injection by Hybrid Model of DEM-CFD

Abstract

where, e, n n, p, r g and m g denote the void fraction, velocity vector, pressure, density, and viscosity of a fluid, respectively. The local void fraction is obtained from the particle locations calculated by DEM. The source term f g takes into account the interaction force between fluid and particles.The gas flow equations are common to the gas from ordinal tuyere and auxiliary tuyere at shaft gas injection. Particle-Fluid InteractionWhen the calculation region is divided into microscopic cells in order to calculate the gas flow in the blast furnace, the fluid velocity is treated as superficial velocity in Eqs.(12) and (13). In this study, the void fraction in the packed bed is calculated from the location of the particles obtained as a result of the particle movement analysis by DEM. The pressure drop is expressed by the multi-dimensional Ergun's equation for a packed bed. 13,14) In this study, only the gas velocity is considered, as it was assumed that the particle velocity in the packed bed is sufficiently small in comparison with the gas velocity.... (14) where, d p denotes the representative particle diameter in a cell. The pressure drop in the cell is considered to be the total of the momentum exchange of the particles. Therefore, a cluster particle used in DEM receives the total drag forces of the actual particles which are included in the cluster, as shown in Fig. 2 (18) where, N i , n n pi and n n g denote the number of actual particles included in a cluster particle and the velocity vectors of the particle and the gas, respectively. Procedure of Simulation DEM-CFD Model for the Blast FurnaceA blast furnace of 5 000 m 3 inner volume with 40 tuyeres was taken as the object for present simulation. The profile of the blast furnace is shown in Fig. 3. In order to decrease number of particle in DEM, semicircle model which has a flat wall in front with no friction was employed. However, this model is based on the three dimensional structure.Raceways are represented by 20 spheres with 1.6 m in diameter which placed equally-spaced on wall at tuyere level. Particles of coke entrained in the raceway disappeared at arbitrarily-specified interval. The pig iron and slag layer in the hearth are not considered. The curved line which denotes melting zone was placed from 1.0 to 7.4 m over tuyere level as shown in Fig. 3, and particles of ore disappeared on the line. The top surface of burden descends with consumption of ore at melting zone and coke at raceways. When surface of burden places at 1 m below from stock line, coke and ore particles are charged alternately. Gas phase was assumed to be isothermal and incompressible.Motion of burden particles was calculated by the DEM and, then distribution of voidage was derived from position of particles. Depending on the voidage in blast furnace, gas flow was calculated by CFD. Gas drag force on particle in DEM was generated from gas flow. The details of the DEM-CFD model were described in the previous papers. 8) In this study, the method based on numeric strict technique (...

Wettability Model Considering Three-Phase Interfacial Energetics in Particle Method

“…As measurement of gasliquid surface tension in high temperature fields is important for clarifying the relationship between the physical properties of the melt and wettability phenomena, measurements of surface tension in high temperature fields have been made widely, and much knowledge has been obtained by performing simulations of the distribution of liquid phases dripping in packed beds based on the physical property values obtained thereby. 4,5) However, there have been few examples of analysis of wetting phenomena accompanying dispersion/bonding of droplets in packed bed processes from the viewpoint of hydrodynamics.…”

Evaluation of Coke Mixed Charging Based on Packed Bed Structure and Gas Permeability Changes in Blast Furnace by DEM-CFD Model

“…The authors have conducted research on simultaneous analysis of burden descent behavior and the gas flow in the blast furnace by coupling the Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD). 12,13) In DEM, it is possible to reproduce various types of packed bed structures, irrespective of whether layered charging or mixed charging is assumed, and a DEMbased element model that expresses permeability changes such as shrinkage of the ore layer has also been reported. 14) In the present research, this element model of softening under load is applied to coke mixed charging.…”

Recent Progress on Advanced Blast Furnace Mathematical Models Based on Discrete Method

“…30,31) Figure 17 shows the results of a 3-dimensional gas flow calculation during shaft gas injection in large-scale blast furnace and small-scale blast furnace. A region which is influenced by the gas flow injected from an auxiliary tuyere at the bottom part of the shaft can be confirmed, and it can be understood that this region of influence differs depending on the inner volume of the blast furnace.…”