Modelling of Multiphase Flow in Ironmaking Blast Furnace (original) (raw)

Modelling of the Solids Flow in a Blast Furnace

ISIJ International, 1998

A model to describe the solids flow under biast furnace conditions with countercurrent gas flow is developed on the basis of fluid mechanicsand the principles of solid mechanics. Thesurface stress resulting from the interaction among flowing particles is considered to be composed of two parts: rate-dependent and rate-independent. The concept of viscosity is extended to solids flow to represent the hydrodynamic particle-particle interaction (rate-dependent part), and the concept of solid plastic modulus and Coulomb frictional stress relation are employedto describe the frictional contact interaction (rate-independent part), Moreover, a method is proposed to determine the transition between moving and non-moving zones, i.e. the profile of stagnant zone, The validity of the model is demonstrated by the good agreement between the model predictions and measurements obtained from a cold physical model of a blast furnace under various flow conditions,

Model Study of Liquid Flow in the Blast Furnace Lower Zone

ISIJ International, 1997

Countercurrent gas-liquid interactions in the lower zone of a blast furnace play an important role in achieving stable operations with high productivity and efficiency. Previous gas-liquid flow models for the blast furnace did not adequately consider both the discrete nature of liquid flow and the strong, Iocalised gas-liquid interactions occurring in the cohesive zone, which have been elucidated experimentally. The present work details a two-dimensional numerical model and a cold two-dimensional physical mode[, used to study gas-liquid flow in the blast furnace cohesive zone. The numerical model utilises a force balance approach to describe the discrete liquid flow and a stochastic treatment to take into account the compiex packing structure. The validity of this model was demonstrated by the good agreement between model predictions and experimental observations. The model can be applied to simulate gas-liquid two-phase flow in a layered packing with multiple liquid sources, similar to the blast furnace lower zone condition.

Numerical simulation of solids flow in a blast furnace

Applied Mathematical Modelling, 2002

This paper presents a numerical study of the behavior of solids flow in a two-dimensional blast furnace. The investigation considers the layer-charging of materials (iron-bearing and coke) and solids consumption (e.g. coke combustion in the raceway) and is based on a previously developed solids flow model (Zhang et al., 1998). Input data includes the ore and coke profiles, productivity, and solids volume loss due to shrinkage, meltdown, reduction and combustion as determined from typical operating conditions. The results demonstrate that the mass loss strongly affects the solids flow pattern and deadman profile in a blast furnace.

Modelling of Multiphase Flow in a Blast Furnace: Recent Developments and Future Work

ISIJ International, 2007

An ironmaking blast furnace is a complex multiphase flow reactor involving gas, powder, liquid and solid phases. Understanding the flow behaviour of these phases is of paramount importance to the control and optimization of the process. Mathematical modelling, often coupled with physical modelling, plays an important role in this development. Yagi 1) gave a comprehensive review of the early studies in this area in 1993. Significant progress has since been made, partially driven by the needs in research but mainly as a result of the rapid development of computer and computational technologies. This paper reviews these developments, covering the formulation, validation and application of mathematical models for gas-solid, gas-liquid, gas-powder and multiphase flows. The need for further developments is also discussed.

Sophisticated Multi-phase Multi-flow Modeling of the Blast Furnace

ISIJ International, 2000

This article introduces an improvement of an existing blast furnace total model called the Four Fluid Flow Model, maintained by the last author. The derivation of solid phase motion in the former model is now replaced by an external numerical code, which implements a very specific granular flow theory called hypoplasticity. The calculation method in the external solid flow model is based on the finite element method (FEM), and differs from the method used in the fluid flow model (finite volume method or FVM), hence their separation. Both models are run one after the other by exchanging data such as solid velocity field, drag forces and solid voidage, until convergence. One major issue of the additional solid flow model is its ability to calculate the shape of the dead man (the name of the stagnant zone inside the blast furnace), whereas its shape was prescribed in the fluid model. The solid flow model also introduces stress state dependence on voidage, and takes into account source and sink terms related to solid phase physical and chemical transformations.

Recent advances in the modelling of solid flows in the blast furnace

Revue de Métallurgie, 2004

The solid flow inside a blast furnace is modelled using a standalone finite element program and a constitutive equation called hypo-plastic, in order to better simulate the granular material behaviour. The parameters of this constitutive equation are calibrated using data obtained from simple soil mechanics tests on coke and sinter materials, such as triaxial and oedometric devices. Steady velocity, stress and void fraction fields are obtained after several iterations of the code. Knowledge of the solids velocity field makes it possible to determine the dead man profile, as well as its renewal kinetics. Burden trajectories and time lines are also computed. Knowledge of the stress field makes it possible to compute pressures acting on the burden as well as on the walls. Finally, knowledge of void fraction field makes it possible to determine gas paths. The solid flow model was validated on 20 and 30 small-scale cold blast furnaces, but the simulations never required any tuning parameter. This code is in fact an invaluable tool to determine the effect of blast furnace profile on solid flow conditions, and reciprocally.

Numerical Investigation of the Transient Multiphase Flow in an Ironmaking Blast Furnace

ISIJ International, 2010

Discrete particle simulation (DPS) has been applied to multiphase flow modelling in an ironmaking blast furnace (BF), including burden distribution at the top, gas-solid flow in the BF shaft and raceway, and liquid-solid flow in the hearth. In this work, the approach is further extended to take into account the transient features of gas and particle flow coupled with liquid tapping operation. In the simulation, two types of particles of coke and ore with different physical properties are considered, together with different shapes of the cohesive zone and the shrinkage of size of ore particles in the cohesive zone to present ore reduction. The simulated results show that the flow of both solid and gas phases varies spatially and temporally, particularly in the cohesive zone. Gas flow is strongly affected by the layered structure of ore and coke particles in the cohesive zone. A coke-free zone can form in the hearth, and the boundary profile between the coke-free zone and the coke bed depends on the amount of liquid accumulated in the hearth, gas and solid flow rates in the raceway, and coke consumption in different regions at the interface of liquid and the coke bed. The results show that the complicated transient multiphase-flow in a BF can be captured by the present approach which may be extended to account for heat transfer and chemical reaction in the future.

Validation of a Blast Furnace Solid Flow Model Using Reliable 3-D Experimental Results

ISIJ International, 2000

The finite element method (FEM) is used in conjunction with plasticity theory in granular materials to derive the stress field and velocity field inside a small experimental apparatus reproducing the blast furnace. The theory used, called hypo-plasticity, gave satisfactory agreement between numerical and experimental time lines, and was able to predict the shape of the stagnant region in the bottom part, the so called dead man, without any adjustable parameters. Specific numerical methods, like iterative remeshing, allowed it to reach steady flow conditions in an Eulerian frame. The stress field is characterized by a plastic active state in the upper part, and a plastic passive state in the lower part. The velocity field is characterized by a plug flow in the upper part, and a funnel flow in the lower part. This model can also simulate granular flows in all type of vessels, like silos. In modeling blast furnaces, its usefulness lies in its connection with a multi-phase total model.

Gas–solid flow in an ironmaking blast furnace-II: Discrete particle simulation

Powder Technology, 2011

This paper presents a numerical study of the gas-solid flow in an ironmaking blast furnace by combining discrete particle simulation (DPS) with computational fluid dynamics (CFD). The conditions considered include different gas and solid flow rates, asymmetric conditions such as non-uniform gas and solid flow rates in blast furnace raceways, and existence of scabs on the side walls. The obtained results show that main gas-solid flow features under different conditions can be captured by this approach. The computed results are consistent with the experimental observations. Microscopic structures including the force structure are examined to analyze the effect of gas flow on the solid flow at a particle scale. Further, macroscopic properties such as solid pressure and porosity are obtained from the corresponding microscopic properties by an averaging method. It is shown that the solid pressure-porosity relationship in a blast furnace is complicated, varying with different flow zones. None of the literature correlations considered can fully describe such a feature. Based on the simulated results, two correlations are formulated to describe the solid pressureporosity relationship covering different flow regimes. But their general application needs further tests in future work.

A simplified mathematical model for gas?solid flow in a blast furnace

Progress in Computational Fluid Dynamics, An International Journal, 2004

This paper presents a numerical study of the behaviour of solid flow in a two-dimensional blast furnace with or without gas flow. The mathematical model, as a simplified version of the more detailed model developed earlier, is similar to the so-called viscous flow model but the method to determine the stagnant zone profile is similar to that used in the kinematic model. The study shows that the simplified model is able to capture the key flow characteristics of solid flow in a blast furnace and describe reasonably the effects of gas and solid flowrates, and particle properties, although the predicted quasi-stagnant zone may be smaller. The advantage of the present approach is that it can be readily implemented in a full process model that needs to have a quick response to change for the purpose of control and optimisation.