Mathematical Modeling of Iron and Steel Making Processes. Modeling the Liquid Levels in the Blast Furnace Hearth.

Brännbacka, Johnny; Saxén, Henrik

doi:10.2355/isijinternational.41.1131

Cited by 44 publications

(28 citation statements)

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“…Furthermore, the deadman floating model will be used in a more detailed study of instantaneous liquid level tracking. 15,22,23) Estimated deadman floating degrees will also be compared with the floating indices developed in earlier work. 21 …”

Section: Conclusion and Future Prospectsmentioning

confidence: 99%

“…The assumptions about the outflow behavior of iron and slag are motivated by results from an earlier study of measurements of instantaneous slag and iron tap rates. 15) The moment at which slag starts to flow out was selected on the basis of results from both from physical and mathematical modeling reported in the literature, 13,14,[16][17][18] as well as findings from statistical tests on data from a large number of tap cycles. 15) Assumption d) is motivated especially in studies of the over-all behavior of the liquid levels during the tap cycle.…”

Section: Simplifying Assumptionsmentioning

confidence: 99%

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Model Analysis of the Operation of the Blast Furnace Hearth with a Sitting and Floating Dead Man

Brännbacka

Saxén

2003

ISIJ International

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The phenomena in the blast furnace hearth are extremely complex and the possibilities to directly measure its internal state are practically non-existent. In order to control the process to achieve smooth operation and long campaigns, a thorough understanding of the conditions in the hearth is required. Such knowledge can be gained through mathematical modeling of the internal conditions. Since the properties of the dead man are known to considerably affect the hearth conditions, a model describing the operation of the hearth with a sitting, partially or completely floating dead man has been developed. Simulation of the tap cycle of a one-taphole blast furnace shows the effect of boundary conditions, hearth geometry, coke voidage and dead-man floating state on the evolution of the liquid levels and the slag delay. On the basis of the computed inner geometry of the hearth, the model has been applied to data from a six-year period of a Finnish blast furnace, and it has been found to accurately predict the long-term variations in the slag delay.KEY WORDS: blast furnace hearth; tap cycle; dead man floating; slag delay. scend further to a certain (given or calculated) level below the taphole at the end of each tap. Under these assumptions, the voidage of the dead man can be estimated once in every tap cycle from produced and tapped quantities of iron.According to Zulli, 13) a coke-free zone at the bottom of the hearth does not influence the cyclic behavior of the liquid levels as long as its volume is constant and it does not extend above the surface of the iron phase. However, if a coke-free zone below the dead man exists, the reason must be that the dead man is (at least partially) floating, so the position of the dead man, and thus also the size of the free space below it, depends on the volume of the liquids in the hearth. From this it follows that it is likely that the volume of the free space varies and affects the liquid levels. Therefore, the methods for estimating the dead-man voidage reviewed above apply only for a hearth with a sitting dead man. This is one of the motivations behind the modeling effort presented in the present paper, where the effect of a floating dead man on the liquid levels is investigated. In particular, the implications of dead-man floating on the slag delay, t sl , i.e., the time of iron-only flow in the beginning of the tap, is studied. Modeling The Tap CycleIn blast furnaces with one taphole, the tapping of iron and slag from the hearth follows a typical cycle, schematically illustrated in Fig. 1. When the taphole is closed both iron and slag accumulate in the hearth because of the progress of reduction and smelting of iron and slag formation. In the hearth the two liquids form separate layers, the dense iron on the bottom and the light slag layer floating on top of the iron bath. The taphole is generally kept plugged for at least 20-30 min to let the injected taphole mud solidify properly. Thus, as the tapping begins the iron-slag interface, henceforth called the iron level, is us...

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Section: Conclusion and Future Prospectsmentioning

confidence: 99%

Section: Simplifying Assumptionsmentioning

confidence: 99%

Model Analysis of the Operation of the Blast Furnace Hearth with a Sitting and Floating Dead Man

Brännbacka

Saxén

2003

ISIJ International

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“…Especially, the slag flow behavior should be understood precisely. [1][2][3][4][5][6][7] Fukutake and Okabe proposed 'flow out coefficient', F L , and they concluded that their correlation can be used to estimate residual slag volume in a blast furnace. [1][2][3] At the same time, the effect of the iron phase below the taphole was not considered.…”

Section: Introductionmentioning

confidence: 99%

A Three-dimensional Mathematical Modelling of Drainage Behavior in Blast Furnace Hearth

2005

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Stable blast furnace operation is required to reduce energy consumption in iron and steelmaking industry. For the stable blast furnace operation, precise controlled drainage is one of the important factors. However, the effects of the various in-furnace conditions on the stable operation were not examined well. Therefore, in this work, basic characteristic features of drainage in a blast furnace hearth were examined.Two-and three-dimensional mathematical model were developed based on the finite difference method to simulate molten iron and slag flow in a hearth of a blast furnace. Pressure drop evaluation model in a taphole was developed to reflect pressure variation in a blast furnace hearth on drainage rate of molten iron and slag for the three-dimensional mathematical model.The two-dimensional mathematical model results were validated with measured interfaces shapes obtained using an experimental model. The three-dimensional mathematical model results were validated with measured total, iron and slag drainage rate of Chiba No. 6 blast furnace. The results indicate that the drainage behavior and residual iron and slag volume were affected by the conditions in the hearth. The taphole conditions dominate the total drainage rate under the term of assumed blast furnace conditions. In order to reduce the residual slag volume, the taphole diameter change during the tap should be controlled. The decrease of the coke diameter causes increase of the residual slag volume, decrease of the residual iron volume.KEY WORDS: iron and slag flow; residual slag volume; numerical simulation; VOF method; blast furnace hearth; ironmaking.faces shapes of immiscible fluids having different properties. Two-dimensional Mathematical ModellingThe governing equations for fluid flow used in the twodimensional mathematical model are based on the HSMAC method, 8) ... (3) where u is the horizontal velocity (m/s), v is vertical velocity (m/s), x and y are coordinates (m), t is time (s), r is density of fluids (kg/m 3 ), p is pressure of fluids (Pa), m is viscosity (Pa · s), g is acceleration due to gravity (m/s 2 ), and S is an interaction force between fluid and 2 flat parallel plates (m/s 2 ). In the two-dimensional mathematical model, gas, slag and iron were treated as one fluid having local properties, which correspond to each phase. Representation of InterfacesFor the determination of the fluid properties in each computational cell, it is necessary to compute the proportion of gas, iron and slag in each cell. Therefore, gas-slag and slag-iron interfaces should be identified exactly. To distinguish the interfaces, the VOF method 9) was applied for the calculation of interfaces (gas-slag, slag-iron). Generally, the VOF method is used to track free boundaries in two-or three-dimensional meshes. Although, in this work, VOF is also used to identify slag-iron interface, as shown in Fig. 1. A unit value of VOF 1 would correspond to a cell full of liquid. A unit value of VOF 2 would correspond to a cell full of iron. Cells with VOF 2 values betw...

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“…6. 3) Hearth of a blast furnace is a receptacle for temporary storage of liquid (metal and slag) generated in the blast furnace. The hearth is filled up with coke and only 30-35 % of the total volume is available as void for liquids.…”

Section: Application Casementioning

confidence: 99%

Process Visualization and Diagnostic Models Using Real Time Data of Blast Furnaces at Tata Steel

2010

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Mathematical Modeling of Iron and Steel Making Processes. Modeling the Liquid Levels in the Blast Furnace Hearth.

Cited by 44 publications

References 2 publications

Model Analysis of the Operation of the Blast Furnace Hearth with a Sitting and Floating Dead Man

Model Analysis of the Operation of the Blast Furnace Hearth with a Sitting and Floating Dead Man

A Three-dimensional Mathematical Modelling of Drainage Behavior in Blast Furnace Hearth

Process Visualization and Diagnostic Models Using Real Time Data of Blast Furnaces at Tata Steel

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