CN1784500A - Gas bubbling element and corresponding bubbling device - Google Patents

Abstract

The invention relates to a refractory ceramic gas bubbling element for a metallurgical crucible and to a corresponding gas bubbling system comprising such a gas bubbling element.

Description

Gas flushing elements and associated gas flushing devices

The invention relates to a refractory ceramic gas flushing element for a metallurgical hearth and an associated gas flushing device with such a gas flushing element.

Gas flushing elements of the described type have been known for many years. It is used to blow gases, such as argon or nitrogen, into a metallurgical melt. The gas has a different effect: it is used to homogenize the molten metal. In addition, the oxidation process can be accelerated. One purpose of the gas treatment may also be the removal of non-metallic impurities in the melt or, for example, the desulfurization or dephosphorization of the steel melt.

Metallurgical hearths in which such gas flushing elements are used may for example be ladle or ladle furnaces. Gas flushing elements of the described type are also used in the vacuum treatment of steel.

In this case, the gases are each guided along the gas flushing elements between a first end at which the gas is supplied and a second end at which the gas is discharged into the melt. The gas is generally guided through corresponding channels. These channels can be formed directly in the ceramic material, for example by a burnable material. However, the channels can also be formed by tubes (capillaries) distributed in the ceramic material. These channels have different cross-sectional shapes. The flow cross section is, for example, circular or slot-shaped. The passages can be straight, ie axial, but also labyrinthine from one end to the other.

It is also known to provide a so-called breakthrough protection at the first end of the gas flushing element or in the gas flushing element itself. Such a breakout protection serves to prevent molten metal from penetrating into the gas flushing element.

The known gas flushing elements have, for example, a continuous circular cross section. In addition, a frusto-conical gas flushing element is known, which is used as a so-called exchangeable flushing device. The gas flushing element may be encased in a fire resistant frame member. The frame member is a component of a smelting plant, such as an electric arc furnace or an open hearth furnace. This flushing element is especially installed in the bottom or side wall of the metallurgical hearth. The flushing elements in the bottom can be arranged in such a way that the gas is sprayed into the melt more or less perpendicularly to the bottom surface. However, it is also known that the flushing element is arranged obliquely in order to guide the gas to a defined point in the melt. This also applies to the side wall mounting of the flushing element. This installation can be carried out more or less horizontally, ie perpendicular to the inner wall of the metallurgical vessel or inclined towards the horizontal (melt pool surface).

The supply of flushing gas can be continuous or discontinuous. In any case it must be ensured that the gas flushing device is always functional if required. This requires corresponding safety measures in order to prevent, for example, the ventilation channels from being blocked by molten metal or slag.

In addition, it must be ensured in particular that the already mentioned breakthrough of the molten metal is prevented.

Accordingly, the object of the present invention is to provide a gas flushing element and an associated gas flushing device, which have a high safety standard, allow a safe and regular supply of gas into the molten metal and can meet unlimited Desired metallurgical features.

In order to achieve this object, the invention proposes a refractory ceramic gas flushing element for metallurgical hearths, the flushing element having the following sections, namely at a first end on which the gas is supplied and on which the gas is discharged Between the second ends of:

- at least one gas supply pipe opens into the first end,

- the gas supply pipe opens into a first gas distribution chamber,

- a plurality of capillary channels extending from the first gas distribution chamber to a second gas distribution chamber,

- At least one air channel extending from the second gas distribution chamber up to the second end of the gas flushing element, said air channel having a larger cross-section than the capillary channel.

One such gas flushing element has the following features and advantages:

Although the gas flushing element is divided into different, axially interconnected segments, a continuous gas supply from the (so-called cold) first end to the (so-called hot) second end can be ensured. In this way gas can be introduced into the flushing element via the gas supply tube. From there the gas reaches a first gas distribution chamber, from where the gas then flows through a plurality of capillary channels towards the second end and then reaches a second gas distribution chamber. From there the gas is conducted via the larger channel mentioned to the second end of the gas flushing element and exits there.

One such gas flushing element has several safety features:

If molten metal infiltrates into the gas channel extending from the second end toward the first end, the second gas distribution chamber acts as a "barrier" to prevent further intrusion of molten metal. The gas distribution chamber has a larger cross section than the sum of the gas channels, so that the penetrating molten metal can spread out, cool down and solidify. Further penetration towards the cold (first) end of the gas flushing device can also be prevented in that the capillary channel is connected at the other end of the second gas distribution chamber. These capillary channels have a significantly smaller flow cross-section than the gas channels in the second end region, so that the penetration of the molten metal into the capillary channels is additionally made more difficult for this alone.

For example, the gas channel in the second end region has an inner diameter >2 mm or >3 mm, while the inner diameter of the capillary channel is chosen to be <1 mm.

However, even if the molten metal flows into and passes through the capillary channel, the gas flushing element according to the invention provides an additional safety mechanism by means of the first gas distribution chamber, in which a gas distribution chamber similar to that already described by means of the second gas distribution chamber similar effect.

Finally, the present invention provides a fourth safety measure in one embodiment. This safety measure consists in that the gas supply line leading into the first gas distribution chamber has a length which is greater than the axial distance between the first end of the gas flushing element and the first gas distribution chamber. In other words: the gas supply line should not run in a straight line, but have at least one, preferably several curved (bent) sections to extend the flow path. The gas supply line can be bent, for example, helically, helically and/or meander-like. Through multiple "branches", the gas flow path is extended on the one hand, which in principle has no adverse effects, but also the path of the possibly intrusive molten metal is extended, so that it is forced to cool and solidify.

In this case, the gas supply line can consist of a material which melts at a temperature below the temperature of a metallurgical melt to be treated. If molten metal invades this area the gas supply pipe will melt. If the gas supply line is embedded in a loose material, as provided in another embodiment, then the molten metal can diffuse, ie branch, in this section of the gas flushing element, thereby accelerating the solidification behavior again. It goes without saying that the bulk material must be arranged in a corresponding outer container (for example made of metal or dense ceramic) so that the melt cannot spread uncontrollably radially. The vessel is also encased in refractory material.

Insofar as segments along the longitudinal axis are in question, they do not have to be physically separated. This concept should be understood more in terms of functionality. The individual segments can thus have an identical cross-sectional shape, for example designed as a circular cross-section, so that overall an outer cylindrical shape results for the gas flushing element. The individual segments can be interconnected. However, it is also possible for all segments to be assembled in a common refractory basic body. In this case, the gas flushing element can have a constant cross-section over its entire length, for example a circular cross-section. The cross-section may also vary, eg taper, from the first end to the second end, such that a frusto-conical shape results. In this way the gas flushing element can be used in particular as a replaceable flusher.

For a constant cross section, in particular a circular cross section, it is possible for the associated gas flushing device to move the gas flushing element axially and/or to rotate. For this purpose, the gas flushing device is designed with a corresponding drive. This drive can be used for an alternating axial and/or rotational movement of the gas flushing element. For example the flushing element may alternately be moved axially back and forth a few millimeters (eg +/- 3mm), or rotated by an angle of a few degrees in one direction or the other. The drive can also be used to push the flushing element axially backwards, that is to say forwards towards the melt, for example if the flushing element is partially worn in the region of the first end.

As already mentioned, the cross-section of the first and second gas distribution chambers is greater than the sum of the cross-sectional areas of the connected capillary channels in order to form a diffusion space for any intrusive melt and to ensure that the gas is introduced into or out of the capillary channels .

According to one embodiment, the flow cross-section of a capillary channel (ie fluid-technically effective cross-section) is at least 50% smaller than the flow cross-section of a gas supply line at the first end or a gas channel at the second end. In this case, the flow cross-section of each capillary channel can also be significantly smaller than the stated 50%, for example 70%, 80% or 90%, relative to the gas supply line or gas channel.

According to one embodiment, the gas channels at the second end are slot-shaped, that is to say they have a rectangular cross section. The gas channel can likewise be designed with a triangular or drop-shaped flow cross-section. In this case, it has proven to be advantageous if, in the case of a drop-shaped cross-sectional geometry, the channels (thin tubes) are arranged such that the narrower end is oriented towards the central longitudinal axis of the gas flushing element, as described in the following description of the figures.

The gas distribution chamber can be formed in situ in the ceramic base material of the gas flushing element. The gas distribution chamber can also be formed by a metal cavity, into which cavity the associated gas channels or capillary channels open.

The capillary channels are arranged essentially axially, ie parallel and spaced apart from one another, whereas the gas channels in the second end region of the gas flushing element can be arranged in different ways:

For example, for a gas channel with the described droplet geometry, one embodiment provides that the channel is distributed "symmetrically" in cross-section. For example with three channels, individual channels - compared to a clock - can be set at the 6 o'clock, 10 o'clock and 14 o'clock positions.

In another embodiment, in particular when gas channels or slit-shaped channels with a circular cross section are selected, these channels can extend separately from each other along an imaginary straight line, wherein for example in a This line runs horizontally in the washer on the wall.

Channels and cavities are always surrounded by refractory ceramic material (matrix material). This material can be cast or extruded. A shell is not necessary. Ceramic flushing elements can be installed this way.

Further features of the invention are the subject matter of the dependent claims as well as the rest of the application material.

The invention is described below diagrammatically with the aid of various figures, the figures being purely schematic for better explanation.

Shown here:

Figure 1: A side view of a gas flushing element according to the invention,

Figure 2: Section along the line A-A according to Figure 1,

Fig. 3: an alternative structure according to the embodiment of Fig. 2,

Figure 4: Section along line B-B in Figure 1,

Figure 5: Section C-C in the longitudinal direction of the region of the first end of the flushing element with the connected first gas distribution chamber,

Figure 6: Section D-D through the second gas distribution chamber in the longitudinal direction,

Figure 7: Side view of a gas flushing device with a flushing element guided on a bearing,

FIG. 8 : A view of a gas flushing device with a gas flushing element movable axially by a drive.

Components that are identical or have the same effect are identified with the same reference symbols in the figures.

A gas flushing element according to the invention is depicted in FIG. 1 . The structure of the gas flushing element (from right to left) is as follows:

A gas supply pipe 5 enters a first section 3 at E1 , which is bounded at the end by a steel plate 30 and at the circumference by a steel tube 14 . The gas supply line 5 runs helically behind the steel plate 30 , the helix being indicated by the reference numeral 13 . The spiral 13 extends in a space filled with a loose material 15 , for example on an expanded pearlite basis, and is delimited at a distance from the steel plate 30 by another steel plate 31 through which the spiral 13 passes.

A first gas distribution chamber 32 is connected to the steel plate 31 , and the periphery of the gas distribution chamber is limited by the extended steel pipe 14 .

In the flow direction of the gas there follows a section 2 , the cross-section of which is shown in FIG. 4 . In a cylindrical steel frame 12 (extension of tube 14 ) there is a refractory ceramic material in which capillary channels 10 are distributed in the axial direction of the flushing element. The capillary channel (formed of a thin steel tube) has a circular cross-section with an inner diameter of 0.5 mm.

By the gas supply pipe 5 and the screw 13, the gas guided through the first gas distribution chamber 32 flows through the capillary channel 10 into a next first gas distribution chamber 16 (Fig. 6), which is internally limited by a pipe body 33, which The body is housed in a housing 17. The tube body 13 and the shell 17 can be made of metal or refractory ceramics.

The gas guided through the second gas distribution chamber 16 then reaches the gas channels 6, which are distributed axially and separately from each other in a ceramic matrix material 8 (Fig. 2, 3) and up to the second end of the gas flushing element The end face of part E2.

According to FIG. 2, three gas channels 6 with a circular cross section are arranged along an imaginary horizontal line. Each of the gas channels 6 has an inner cross section of 2 mm. FIG. 3 shows an alternative embodiment, in which the three channels 6 each have the shape of a drop, wherein the gas channels 6 - compared to a clock - are arranged at the 6 o'clock, 10 o'clock and 14 o'clock positions. The orientation of the gas channels 6 is such that the narrow, approximately triangular ends each point inwards.

This section 1 of the flushing element is likewise delimited on the circumferential side by a metal tube 9 .

The housings (pipes) of the individual segments, each made of ceramic or metal parts, are mechanically connected to one another, wherein the end segments are stepped and have corresponding threads. The flushing element depicted in FIG. 1 is completely encased in refractory material. It is likewise possible to fit the entire gas flushing element in a continuous tubular housing or to dispense with the housing entirely. In this case the gas distribution chambers 16 , 32 and the various channels are designed in a ceramic matrix material.

Not only the gas supply pipe 5, but also the capillary channel 10 and the gas channel 6 are formed by thin metal tubes, but they can also be formed in situ, for example during production, by inserting at their positions a material with a corresponding cross section. Incinerated material that will later be incinerated. The same applies if cavities (gas distribution chambers) are formed in the ceramic base body.

The gas flows from the first end E1 through the interconnected segments up to the gas outflow-side end, which is marked E2 in FIG. 1 .

The function of the flushing element has already been explained while explaining the invention. It should also be mentioned that the thread 13 here is made of copper, ie a metal with a relatively low melting point.

According to FIG. 7 the flushing element is guided by bearings 18 , 19 . The bearings mentioned here are rolling bearings. The tubular flushing element can be rotated by means of a motor M and a transmission 20 , ie alternately to the left and to the right. The drive is outside the hearth.

In the exemplary embodiment according to FIG. 8 , a transmission 22 is described, with which a continuous vibrating movement (for example a sinusoidal movement) can be transmitted to the flushing element in order to move the flushing element axially, for example back and forth, by several millimeters.

It goes without saying that the gas flushing element must be arranged in the bottom or side wall of an associated metallurgical vessel in a corresponding refractory frame, and also in the embodiment according to FIGS. 7 and 8, so that the flushing element can be guaranteed rotational and axial movements. The refractory material of the side walls or bottom of the metallurgical vessel is indicated by reference numeral 35 in FIGS. 7 and 8 .

Claims (16)

1. Refractory ceramic gas flushing element for a metallurgical hearth between a first end (E1) on which gas is supplied and a second end (E2) on which gas is discharged With segments (3, 2, 4, 1) following each other: a) at least one gas supply pipe (5) opens into said first end E1, b) said gas supply pipe (5) leads into a first gas distribution chamber (32); c) a plurality of capillary channels (10) extending from the first gas distribution chamber (32) up to a second gas distribution chamber (16), d) At least one gas channel (6) whose flow cross-section is larger than the flow cross-section of a capillary channel (10) extends from the second gas distribution chamber (16) to the second end (E2) of the gas flushing element. 2. The gas flushing element as claimed in claim 1, wherein the first and the second gas distribution chamber (32, 16) each have a cross-section that is greater than the sum of the cross-sectional areas of the capillary channels (10). 3. The gas flushing element according to claim 1, wherein the gas supply pipe (5) leading to the first gas distribution chamber (32) has a length that is greater than the first end (E1) and the first gas Axial distance between distribution chambers (32). 4. The gas flushing element as claimed in claim 3, wherein the gas supply line (5) is bent in a helical, threaded and/or meandering manner. 5. The gas flushing element as claimed in claim 3, wherein the gas supply line (5) consists of a material which melts at a temperature below the temperature of a metallurgical melt to be treated. 6. The gas flushing element as claimed in claim 3, wherein the gas supply line (5) is embedded in a bulk material (15). 7. The gas flushing element as claimed in claim 1, wherein the capillary channels (10) each have a flow cross section which is smaller than the gas supply line (5) at the first end (E1) or at the second end The flow cross-section of the gas channel (6) at the two ends (E2) is at least 50% smaller. 8. The gas flushing element as claimed in claim 1, wherein the capillary channels (10) each have a flow cross section which is larger than a gas supply tube (5) at the first end (E1) or at the The flow cross-section of the gas channels (6) at the second end (E2) is at least 90% smaller. 9. The gas flushing element according to claim 1, wherein the individual, interconnected segments (3, 2, 4, 1) are each arranged in a tube (14, 12, 17 made of steel or refractory ceramic material) , 9). 10. The gas flushing element as claimed in claim 1, wherein the segments (3, 2, 4, 1) are arranged in a common tube made of steel or refractory ceramic material. 11. The gas flushing element as claimed in claim 1, wherein the gas channel (6) at the second end (E2) has a slit-shaped, triangular or drop-shaped flow cross section. 12. The gas flushing element according to claim 1, which has a plurality of gas channels (6) on the second end (E2), which are separated from each other along a virtual straight line in the second gas distribution The cavity (16) extends between the second end (E2). 13. The gas flushing element according to claim 1, which has a circular cross section over its entire length. 14. The gas flushing element as claimed in claim 13, the cross section of which decreases from the first to the second end (E1, E2). 15. Gas flushing device having a gas flushing element according to claim 1 and a drive (M) for the axial and/or rotational movement of the gas flushing element. 16. The gas flushing element as claimed in claim 15, wherein the drive (M) is designed for an alternating movement of the gas flushing element.

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