EP0561181A2 - Tap pipe for a converter or an electric arc furnace - Google Patents

Abstract

A tap pipe for a converter or an electric arc furnace should achieve tapping times which are the same as far as possible during as many tappings as possible. For this purpose, the flow cross-sections at the various heights of the tap pipe (3) are, at least in the outflow zone (11) of the tap pipe (3), approximately equal to the cross-sections of that flow profile (So) of the melt which results at a vertical flow of the melt with a bath level of between 30% and 70% of the maximum bath level height (xm). <IMAGE>

Description

The invention relates to a tapping tube for a converter or arc furnace, with flow cross sections which are smaller at the height of the outlet zone than in the heights closer to the interior of the converter or arc furnace.

Such a tapping tube is described in EP 0 057 946 B1. In this case, the flow cross sections of the tapping tube taper in steps from the inlet zone close to the converter to the outlet zone of the tapping tube. As a result, the tapping channel should be adapted to the flow conditions of the tapping jet.

Wear of the tapping tube reduces its flow resistance. The result of this is that the cut-off time, that is to say the time in which the converter runs empty from its maximum bath level to its minimum bath level, changes accordingly. This is unfavorable because the respective cut-off time is the temperature that the melt has in the downstream vessel, influenced. With longer tapping times, the downstream melt temperature is lower than with shorter tapping times. In order to avoid the resulting metallurgical irregularities, the melt must be reheated. This requires a considerable amount of energy.

The object of the invention is to design a tapping tube of the type mentioned at the outset so that it has the same tapping time as possible in the tapping to be carried out with it.

According to the invention {ß the above object is achieved in a tapping tube of the type mentioned in that the flow cross-sections in the different heights of the tapping tube, at least in the outlet zone of the tapping tube, is approximately equal to the cross-sections of that flow profile of the melt at these heights, which is at a vertical flow of the melt at a bath level between 30% and 70% of the maximum bath level height.

rechenbar, wobei

A_(x)

der Strömungsquerschnitt in der Höhe x,

m

der Massenstrom der Schmelze pro Zeiteinheit,

r

die Dichte der Schmelze,

g

die Erdbeschleunigung und

x

die jeweilige Höhe ist.

It is thereby achieved that the flow profile of the tapping tube is adapted to the flow profile of the melt which is set at an average bath level - between 30% and 70% of the maximum bath level. This flow profile is calculated from the known formula

${\text{A}}_{\text{(x)}}{\text{= m / r (2gx)}}^{\text{1/2}}$

calculable, whereby

A _(x)

the flow cross section at height x,

m

the mass flow of the melt per unit of time,

r

the density of the melt,

G

gravitational acceleration and

x

the respective height is.

In accordance with the flow profile of the vertical melt flow which can be calculated from this in the case of a medium bath level, the flow cross sections which are adapted to the flow profile of the melt and differ in the different heights of the tapping tube can then be determined. The flow cross sections of the tapping tube are dimensioned accordingly at least in the outlet zone.

It is thereby achieved that the tapping tube, as long as it is good for tapping, ensures a fairly constant tapping time during these tapping, whereby a considerably improved constancy of the tapping time during the tapping can be seen here, for example during 80 When tapping through the same tapping tube, the tapping times only change between 3.5 min and 5.5 min.

Adjusting the flow cross-sections of the tapping tube in the outlet zone to the flow profile can suffice, since the outlet zone essentially determines the tapping time, at least as long as the length of the tapping tube is not reduced by wear of the lining of the converter itself.

Advantageous embodiments of the invention result from the subclaims and the following description.

Figur 1

einen Konverter in Ausgußstellung mit vertikaler Stellung seines Abstichrohres,

Figur 2

eine gegenüber Figur 1 vergrößerte Teilansicht,

Figur 3

eine Figur 2 entsprechende Ansicht eines dreiteiligen Abstichrohres bei einem noch nicht verschlissenen Konverter mit Schmelzen-Strömungsprofil bei maximaler Badspiegelhöhe,

Figur 4

das Schmelzen-Strömungsprofil bei einer mittleren Badspiegelhöhe zwischen 30 % und 70 % der maximalen Badspiegelhöhe,

Figur 5

ein dreiteiliges Abstichrohr für einen verschlissenen Konverter in einer Figur 3 entsprechenden Darstellung, wobei das Strömungsprofil bei maximaler Badspiegelhöhe mit durchgezogener Linie und das Strömungsprofil bei minimaler Badspiegelhöhe strich-doppelpunktiert angedeutet ist,

Figur 6

ein Diagramm der Abstechzeiten über der Anzahl der Abstiche und

Figur 7

die Intervalle der Auswechslung des Abstichrohres über den mit dem Konverter möglichen Abstichen bis zu dessen Erneuerung.

The drawing shows:

Figure 1

a converter in the pouring position with its tapping tube in the vertical position,

Figure 2

2 shows a partial view enlarged compared to FIG. 1,

Figure 3

2 shows a view corresponding to FIG. 2 of a three-part tapping tube in a converter which has not yet been worn and has a melt flow profile at a maximum bath level,

Figure 4

the melt flow profile at an average bath level between 30% and 70% of the maximum bath level,

Figure 5

a three-part tapping tube for a worn converter in a representation corresponding to FIG. 3, the flow profile at maximum bath level height being indicated by a solid line and the flow profile at minimum bath level height being indicated by dash-double-dots,

Figure 6

a graph of cut-off times versus number of cuts and

Figure 7

the intervals of changing the tapping tube over the tapping possible with the converter until it is renewed.

A converter 1 has a lining 2, in which a tapping tube 3, which projects above it, is seated. Intermediate layers 4, 5 are provided between the tapping tube 3 and the lining 2.

If the converter 1 is pivoted about its axis 6 so that the tapping tube 3 is vertical, then a maximum bath level height xm is set in the converter 1. The outlet opening 7 of the tapping tube 3 is at a height x2.

When the lining 2 of the converter 1 is not yet worn, the inlet opening 8 of the tapping tube 3 is at the inlet height x1. There is a tapping tube 3 with a length 11 between the inlet height x1 and the outlet height x2.

If the lining 2 is worn as a result of the tapping, as shown in FIG. 2 by the wear line 9, then the tapping pipe 3 is also worn, so that its current inlet opening 10 is at the inlet height x3, the tapping tube 3 being between the inlet height x3 and the outlet height x2 only has a length 12 that is less than length 11.

The level of the bath level drops during parting off. In an average bath level, the bath level height x0 results, which is 30% to 70%, preferably 40% to 50%, of the maximum bath level height xm above the minimum bath level height xu.

The flow profile thus established at this average bath level height xo - without the tapping tube 3 - is from the Above formula can be calculated for the different heights between the inlet height x1 and the outlet height x2. According to this calculation, the flow cross sections A1, A3, A2 in the heights x1, x3, x2 and also in the intermediate heights can be dimensioned in such a way that they are as equal as possible to the cross sections of the flow profile So of the melt in each case.

This adjustment of the flow cross-sections to a melt flow from the average bath level x0 ensures that the cut-off times during the taps 3 possible with a specimen of a tapping tube are within narrow limits, that is to say they are as equal as possible. Figure 6 illustrates this:

FIG. 6 shows a maximum cut-off time To with, for example, 5.5 min and a minimum cut-off time Tu with about 3.5 min. Cut-off times between these cut-off times are not metallurgically problematic.

FIG. 6 shows the course of the parting times over 80 partitions when using one of the parting tubes according to the invention with a solid line. With one example of the tapping tube 3 according to the invention, 80 taps are possible without the tapping time permissible between the limits Tu and To being exceeded.

For comparison, the corresponding course for tapping through a cylindrical tapping tube is shown in FIG. 6 with "-ooo". The cut-off times for the initial cut-offs - up to about the 10th cut-off - are above the maximum cut-off time To and are then already less the minimum parting-off time Tu at the 50th tapping. In addition, the characteristic "- + - + - +" is shown for comparison in FIG. 6, which corresponds to the course of a stepped or a purely conical tapping tube according to the prior art. In this case too, the cut-off time is above the maximum allowable cut-off time To for many initial taps and then is already about 65 taps below the minimum allowable cut-off time Tu.

Figure 7 shows another advantage of the invention. This is based on the fact that in the tapping tube according to the invention the permitted tapping time is essentially the same over a large number of taps. In Figure 7 it is assumed that after about 800 taps, converter 1 or its lining 2 must be replaced. The lines shown correspond to FIG. 6. It can be seen that the tapping tube 3 according to the invention only has to be replaced 9 times at 800 taps, whereas a conventional tapping tube with a purely cylindrical flow cross section has to be replaced 17 times and a tapping tube with a stepped cross section 13 times during the 800 taps should be. It is also favorable that in the tapping tube 3 according to the invention the intervals between the replacement of the tapping tube 3 are the same and can be determined in each case for an equal number of taps, 80 taps in the example, so that the personnel until the converter 1 or its lining 2 is renewed the tapping tube 3 can be renewed again and again after an equal number of taps, whereas with the tapping tubes according to the prior art these periods are continuously shortened, so that the staff has to replace a tapping tube according to the prior art in the case of a more worn converter, than with an even less worn converter.

In the exemplary embodiment according to FIGS. 3 to 5, the tapping tube 3 consists of three components 11, 12, 13.

The block 11 forms the outlet zone of the tapping tube 3. It is dimensioned in the flow cross sections in its height H1 in such a way that it corresponds to the flow profile So of the melt at this height at an average bath level height x0 with a free melt outlet (see FIG. 4).

The building block 12 forming the inlet zone of the tapping tube 3 is dimensioned in the different heights of its flow cross-section so that its flow cross-sections correspond over its height H2 to the flow profile which occurs at a minimum or lower bath level height xu (cf. and that when the lining 2 of the converter 1 has been used up so far that the wear of the wear line 9 has approximated.

The block 13 is designed as a transition block. Transition modules 13 with different heights H3 are available, in each case the transition module 13 being designed in such a way that it forms the smoothest possible transition between the modules 11, 12 on the flow or inside side.

FIGS. 3 and 5 each show blocks 11 of the same size for the outlet zone and blocks 12 of the same size for the inlet zone. Only the building blocks 13 of the transition zone are designed differently. The different design of the building blocks 13 lies in their height H3, which progresses in the direction of the wear line 9 Wear of the lining 2 of the converter 1 is adjusted. In the event that, as in the example according to FIG. 7, nine replacements of the tapping tube 3 are provided for a converter trip of 800 taps, transition modules 13 nine or ten different lengths H3 are accordingly provided, which flow-side can be adjusted as smoothly as possible in all cases Connect the same blocks 11 and 12 of the outlet zone and the inlet zone.

This simplifies the repair or replacement of the tapping tube 3 with simple components. This design is also favorable because the manufacturer's comparatively few and easily producible block formats are sufficient to provide the tapping tubes required for a converter trip, which guarantee approximately the same parting times.

Claims (4)

Tapping tube for a converter or arc furnace, with flow cross-sections that are smaller at the height of the outlet zone than at heights closer to the interior of the converter or arc,
characterized,
that the flow cross-sections in the different heights of the tapping tube (3), at least in the outlet zone (11) of the tapping tube (3), is approximately equal to the cross-sections of that flow profile (So) of the melt at these heights, which changes with a vertical flow of the melt with a bath level between 30% and 70%, in particular between 40% and 50%, the maximum bath level height (xm). Tapping tube according to claim 1,
characterized,
that the flow cross sections in the different heights of the inlet zone (12) of the tapping tube (3) is approximately equal to the cross section of the flow profile (So) of the melt at these heights, which is between 30% and 70% with a vertical flow of the melt at a bath level , in particular between 40% and 50%, of the maximum bath level height (xm) and a length (12) of the tapping tube (3) that is reduced due to wear of the converter (1). Tapping tube according to claim 1 or 2,
characterized,
that the tapping tube is composed of at least three modules (11, 12, 13), in the first (11) the outlet zone, in the second (12) the inlet zone and in the third (13) the transition zone between the first and the second module (11, 12) lies. Tapping tube according to claim 2 or 3,
characterized,
that between the inlet zone and the outlet zone of the tapping tube (3) a smoothly connecting transition zone (13) is provided, the length of which is adapted to the wear of the converter (1).

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