Experimental Studies of Slag Flow in the Blast Furnace Hearth during Tapping Operation

Abstract

I n order to clarifY the causes of the excess accumulation of mollen materials in the blast furnace hearth which gives rise to a trouble in the blast furna ce operation , such as hanging and slillping, the behaviour of .flowing out and accumulating of slag in the hearth have been studied by m~ans of model eXlleriments. The results of th~ model experiments were analyz ed as the scale-up problem based on the th~ories of .fluid dynamics. The in.fluential fa ctors such as the porosity 0, the shape fac tor <jJ, and the mean diameter d of the coke bed in the hearth, the viscosity fJ., the density p and the superficial velocity Vo of the slag , the depth of slag layer at the beginning of its .flow-out H and the h~arth diameter D were combined to give the dim ensionless" flow-out coefficient " F L) F = 180 (l-0)2 1 I' Vo [ H J' I. 03 , ? d l , 0 g D w hich is f oulld 10 be closely related to th e ratio of res idual slag (f , i .e. , th e ratio of the amount of residual slag at the end of tallping to that accumulated at lh~ bgginning , in sllch a manner thal an increase in F,. causes an increase in rr (Fig. 8). The ranges of exlJerimental conditiollJ were selecled so as to cove r the flow conditions in the hearth in order to make it Ilossible to a/JP1y Ihe experimental results directly to the slag flo w in Ihe blas t furna ce hearlh. The amount of res idual iron is estimated to be less than one-tenth of the amounl of residual slag at the end of tap/Jillg .

Off-line Model of Blast Furnace Liquid Levels

“…5) The slag viscosity also gives rise to a downward bending of the slag-gas interface toward the taphole, which leaves considerable amounts of residual slag in the hearth as the tap ends when gas bursts out from the taphole. 6,7) These phenomena make the time evolution of the liquid levels during the tap cycle complex. Furthermore, in large furnaces the liquid levels may be fundamentally different in the region close to the draining taphole and on the opposite side, particularly if the deadman voidage is low, e.g., due to impermeable zones 8,9) caused by poor coke quality or by coke fines that accumulate in the bed because of improper combustion of excessive injection rates of pulverized coal.…”

“…They applied a slot model with two immiscible liquids to demonstrate the theory and also discussed the bending of the slag surface at the end of the tapping, revising the original findings of Fukutake and Okabe. 6,7) Zulli 11) further refined the expression of the residual slag, considering the motion of the iron-slag and slag-gas interfaces. Later, Nouchi et al 12) experimentally studied the influence of different deadman voidages, including cases where the core of the deadman was clogged, on hearth drainage and the outflow rates of the two liquids.…”

“…To estimate when this happens, several investigators have studied the system in laboratory scale and proposed correlations, e.g., for the flow-out coefficient. [5][6][7]11) Factors affecting the amount of residual slag are the slag outflow rate, slag viscosity, deadman voidage and coke diameter. As most of these (local) properties are unknown in the practical operation of the blast furnace, a simplified tap-end condition was applied here where ω is a model parameter and subscript j* denotes the draining pool.…”

Dynamic model of liquid levels in the blast furnace hearth

“…2 these measurement points have been indicated by small circles. As for the slag level, it can be estimated at the end of each tap, t end , from the relationship between the residual slag ratio and a dimensionless flow‐out coefficient [13–15], as indicated by squares in Fig. 2.…”

Physical modelling of hot metal flow in a blast furnace hearth

“…Fukutake & Okabe [2,3] studied the effect of the rate of tapping, the viscosity of slag and the number of tapping operations on drainage of viscous liquids and developed an empirical relationship between the amount of residual slag and the above-mentioned parameters. Tanzil, Pinczewski and co-workers in Australia extended the modelling work, e.g.…”