Gas washing device with reduced gas flow upon wear of gas sink

A gas washing device for supplying gas through a metallurgical vessel to molten metal therein includes a gas permeable sink positioned to extend through a wall of the metallurgical vessel. The sink has an inner end to be exposed to the molten metal and subject to wear thereby and an outer end. A gas inlet supplies an operational flow of gas from a gas supply to the outer end of the sink. A device is operatively mounted with respect to the sink and is responsive to a temperature rise indicative of a predetermined extent of wear of the inner end of the sink by the molten metal, to reduce the flow of the gas to a reduced flow less than the operational flow upon the inner end of the sink being worn or eroded to the predetermined extent. A detector detects or measures the reduced flow of gas.

BACKGROUND OF THE INVENTION 
The present invention relates to a gas purging system or gas washing device 
for supplying gas through a metallurgical vessel to molten metal therein 
and of the type having a refractory purging brick or sink as well as a gas 
inlet for supplying an operational flow of gas from a gas supply to the 
purging or washing brick or sink such that the gas flows through the brick 
or sink into the molten metal. The present invention more particularly is 
directed to such a gas purging or washing device improved to respond to a 
temperature rise indicative of a predetermined extent of wear of the gas 
permeable brick or sink by the molten metal to reduce the flow of gas to a 
reduced flow less than the operational flow, thereby maintaining the 
ability to continue the supply of gas even upon substantial wear of the 
brick or sink, as well as means for detecting such reduced gas flow. 
In such gas purging or washing devices it is necessary to prevent the 
danger of molten metal breakthrough upon substantial wear or erosion of 
the gas permeable brick or sink. West German DE-OS No. 32 40 097 discloses 
a gas purging system including a layer of granular filler material having 
a melting point below the temperature of the molten metal. When molten 
metal has eroded or worn the brick or sink to a point such that the molten 
metal enters the filler material, the filler material melts with the 
result that a barrier is formed to prevent the molten metal from breaking 
through. However, due to this barrier the gas purging or washing operation 
itself also is stopped. 
Copending application Ser. No. 877,971 filed June 23, 1986 discloses a gas 
purging or washing system wherein upon extensive wear of the brick or sink 
the total gas flow increases. This arrangement enables continuing gas feed 
but in practice is difficult to employ since it is inappropriate to pass 
an increased quantity of gas to a highly eroded brick or sink. 
West German DE-OS No. 34 24 466 discloses a gas purging system in which 
electrodes of an electric circuit are provided in the gas purging brick. 
When the temperature rises due to erosion of the brick, contacts of the 
electrodes are intended to fuse, as a result of which the electric circuit 
is closed. However, the purging process ceases if the purging brick has 
been worn down substantially. Moreover, it is disadvantageous if the 
electrodes in the purging brick must be located in a probe. European No. 
EP-82,078 Al discloses an electric wear indicator wherein molten metal, 
due to its electrical conductivity, is to connect electrodes of an 
electrical circuit placed at different heights in the purging brick. In 
this case also the total flow rises with increasing wear of the purging 
brick so that continued purging is not possible after substantial erosion. 
Moreover, this arrangement requires that no electrically insulating layers 
be formed around the electrodes, and this is difficult to achieve in 
practice. 
SUMMARY OF THE INVENTION 
With the above discussion in mind, it is an object of the present invention 
to provide a improved gas purging or washing device whereby it is possible 
to overcome the above and other prior art disadvantages. 
It is a further object of the present invention to provide such a device 
whereby it is possible to detect substantial erosion of a purging or 
washing brick while preventing molten metal breakthrough but while still 
enabling continued flow of the purging or washing gas. 
These and other objects are achieved in accordance with the present 
invention by the provision of means, operatively mounted with respect to 
the brick or sink and responsive to a temperature rise indicative of a 
predetermined extent of wear or erosion thereof, i.e. indicative of the 
fact that the brick or sink has been worn down to a residual height, for 
reducing the flow of the gas to a reduced flow less than the operational 
flow upon the inner end of the brick or sink being worn to the 
predetermined extent. More specifically, upon a temperature rise 
indicative of such predetermined extent of erosion or wear the cross 
sectional area available for the supply of the gas is reduced 
automatically, thereby reducing the gas flow. There is provided means 
operatively associated with the gas inlet for detecting the reduced flow, 
thereby giving an indication of erosion of the gas permeable brick or sink 
to a substantial extent. The brick or sink however need not be replaced 
immediately, and it is possible to wait for a convenient time for 
replacement. The total gas flow is reduced to a minimum value, but since 
the gas flow is not stopped completely it is possible to continue the 
purging or washing operation. Additionally, to continue a practical 
purging or washing operation the gas pressure at the gas inlet may be 
increased to thereby raise the overall gas flow to the molten metal. 
In accordance with one preferred embodiment of the present invention the 
gas permeable brick or sink is in the form of a inner brick and an outer 
brick confronting each other at a joint area, the inner and outer bricks 
abutting each other at a first portion of the joint area and being spaced 
from each other by a chamber at a second portion of the joint area. The 
reducing means comprises a material which is meltable upon being subjected 
to the temperature rise, and this material is positioned within the 
chamber such that upon the material being melted it forms a barrier to the 
flow of the gas at the second portion of the joint area, with the gas then 
flowing only at the first portion of the joint area. Preferably the 
meltable material is a granular or granulated material. Further 
preferably, the area of the first portion is smaller than the area of the 
second portion, and particularly the first portion extends 
circumferentially or peripherally and surrounds or encloses the second 
portion. In this arrangement, the temperature of the granulate meltable 
material rises upon erosion of the inner brick, thereby gradually melting 
the material and reducing the total gas flow. When only the second portion 
of the joint area is available for the flow of gas, the quantity of gas 
supplied through the sink is at a minimum, but nevertheless permits 
continuation of the gas purging or washing operation. The reduction of the 
quantity of gas being passed can be indicated on a flow meter to show the 
advanced state of erosion. 
In accordance with a further preferred embodiment of the present invention, 
the reducing means is in the form of a valve incorporated in the gas 
inlet, the valve including a valve seat and a valve body movable between a 
first position spaced from the valve seat and a second position toward the 
valve seat. Temperature sensitive means prevents the valve body from 
moving to the second position prior to the gas permeable brick or sink 
being worn to the predetermined extent. The valve body may be in the form 
of a gas permeable member seated tightly on the valve seat in the second 
position thereof, and the valve body may be bonded to the valve seat when 
in the second position. Alternatively, the valve body may be in the form 
of a gas impermeable member defining with the valve seat a gas passageway 
in the second position. In this embodiment the valve body also may be 
bonded to the valve seat in the second position. 
The temperature sensitive means may be in the form of a meltable fuse 
provided between a rod member contacting or connected to the valve body 
and a locating sleeve mounted on and preferably embedded in the gas 
permeable brick or sink. The sleeve may be connected to a star-shaped base 
member supporting the sink. The fuse may be in the form of a meltable 
portion of the rod member. 
The temperature sensitive means alternatively may be in the form of a 
meltable fuse provided between a first rod member connected to the gas 
permeable brick or sink and a second rod member contacting or connected to 
the valve body. The fuse preferably may be formed between inclined 
confronting end surfaces of the first and second rod members. 
The temperature sensitive means still further may be in the form of a 
bimetallic strip having a first end fixed relative to the gas permeable 
brick or sink and a second end blocking the valve body from moving to the 
second position before the temperature rise and deflective or deflectable 
at the temperature rise to allow the valve body to move to the second 
position. 
In accordance with a further aspect of the present invention there is 
provided a spring urging the valve body toward the valve seat either in 
the direction of gas flow or in a direction opposite to the direction of 
gas flow.

DETAILED DESCRIPTION OF THE INVENTION 
In FIG. 1, illustrating a first embodiment of the present invention, there 
is shown schematically the bottom 1 of a metallurgical vessel adapted to 
contain therein molten metal. A gas purging or washing brick or sink 2 has 
a metal, for example steel, cladding 3 and is mounted within an opening in 
bottom 1 of the vessel. Below sink 2 is provided a gas distributing space 
4 having a gas feed or inlet 5 connected to gas line 6 for supplying an 
operational flow of gas from a gas supply such that the gas passes through 
sink 2. Particularly, brick or sink 2 is intended to be formed of a gas 
permeable ceramic material of known composition. A gas flow meter 7 is 
installed in gas line 6, a manometer 8 is connected to gas line 6, a 
pressure booster 9 with a pressure limiter is installed upstream of gas 
flow meter 7, and a warning device 10 is connected to pressure booster 9. 
The devices 7-10 are illustrated only in FIG. 1, but it is to be 
understood that such devices are intended to be included in the 
arrangements of the other embodiments of the present invention. 
In the particular embodiment of FIG. 1, the gas purging or washing brick or 
sink 2 is in the form of an inner, conically tapered wear resistant 
refractory brick 11 and an outer similarly configured brick 12 serving as 
a safety brick. Brick 12 has on its inner end a recess 13 forming a 
chamber 14 between bricks 12, 11. Chamber 14 is filled with a granulate 
meltable material 15. The bricks 11, 12 abut each other along a first, 
peripheral area 16, such area surrounding the area of chamber 14. The 
cross-sectional area occupied by chamber 14 is substantially larger than 
the cross-sectional area occupied by abutting rim area 16. 
The granulate material 15 may be in the form of porcelain bodies, hydrous 
or water-containing glass rocks, metals or alloys. For example, obsidian 
with a water content of 1-2 weight percent, perlite with a water content 
of 3-4 weight percent or pitchstone with a water content of more than 4 
weight percent are suitable as glass rocks. Sn, Pb, Zn, Mg, Al, Cu or 
other metals may be employed to form the granulate material 15. 
Particularly, a granulate material with a melting point lower than that of 
the molten metal within the metallurgical vessel is provided. 
When, during operation of the metallurgical vessel and the gas purging or 
washing device, the inner brick 11 has become worn down or eroded (in a 
known manner), its height or thickness with regard to the thickness of the 
vessel bottom decreases. This causes a temperature rise of the granulate 
material 15, such that material 15 melts gradually, thereby causing the 
melted granulate material to penetrate into brick 12 or even into brick 
11. As a result, the melted granulate forms a closure or barrier in the 
region of chamber 14, and this greatly reduces the area available for the 
supply of the gas through the sink 2 to the molten metal. After the 
granulate material 15 has melted, the gas continues to flow only through 
the rim area 16. As a result, there will be a greatly reduced quantity of 
gas passed through sink 2, and this will be detected by or read on the gas 
flow meter 7 as an indication that the brick 11 has been eroded or worn 
down to a predetermined extent or to a residual height. To continue the 
desired or washing operation, the gas pressure can be raised by pressure 
booster 9 within certain limits, such that the purging or washing of the 
molten metal can be continued if necessary. 
FIGS. 2 through 4 illustrate a second embodiment of the present invention 
wherein the gas purging or washing brick or sink 2 is seated or supported 
on a star-shaped supporting member 17 which in turn rests on or is 
supported by a gas impermeable ceramic base plate 18 within which is 
formed the gas distributing space 4. An opening, defining a valve seat 19, 
extends through base plate 18 and communicates with gas feed inlet 5. The 
star-shaped supporting member 17 has, as shown in FIG. 6, a plurality of 
radial arms 20 and an outer ring 21. A locating sleeve 22 is formed at the 
center of member 17 and is embedded within sink 2. A rod member 24 is 
secured within locating sleeve 22 by a meltable fuse, such as a soldered 
joint 23. Rod member 24 is mounted on a valve body 25 formed of a gas 
permeable ceramic material. Valve seat 19 preferably is provided with a 
glaze, and likewise the outer surface of valve body 25 directed toward 
valve seat 19 also can be provided with a glaze. 
Star-shaped supporting member 17 is formed of a relatively heat conductive 
material, for example aluminum, steel or an alloy. Locating sleeve 22 may 
be formed of the same material or of SiC, Si-metal or cermets. The same is 
true for rod member 24 Soldering joint 23 may be in the form of a solder 
of a suitable melting point. However, joint 23 also may be in the form of 
organic hot-melt adhesives or inorganic substances, such as As, AlF.sub.3, 
MoS, NH.sub.4 Cl with a well-defined sublimation temperature. Phosphate 
glasses, for example, are suitable as the glaze. It would be understood to 
one skilled in the art however, that other materials than those mentioned 
above may be provided for the above materials. 
In the nonworn or slightly worn state of gas purging or washing brick or 
sink 2, the fuse or joint 23 holds rod member 24 in such a manner that the 
valve body 25 is maintained at an open position spaced from valve seat 19. 
The purging or washing gas therefore can flow without impediment into the 
gas distributing chamber 4 and then through the brick or sink 2 to the 
molten metal. However, when the brick or sink 2 has been eroded or worn 
down to a predetermined extent, i.e. to a residual height, there will be a 
temperature rise at the heat conducting star-shaped supporting member 17 
of an extent such as to cause the soldered joint or fuse 23 to melt. As a 
result, the valve body 25 will be pressed against valve seat 19, either 
under the action of a pressure spring 26 or due to the pressure of the 
washing gas alone. As a result, the gas flow is abruptly reduced. The gas 
flow is not completely stopped, since the valve body 25 is gas permeable. 
The glaze leads to the bonding of valve body 25 to valve seat 19, thereby 
providing an additional safety measure against the breakthrough of molten 
metal. 
The gas flow meter 7 (FIG. 1) detects or indicates the abrupt reduction of 
the quantity of gas passed. The gas pressure can be increased by booster 9 
to continue the operation of washing or purging of the molten metal. The 
increase of the gas pressure can be monitored on manometer 8, and the 
raised pressure can be limited to a maximum value by means of the warning 
device 10 and the pressure limiter. 
In the embodiment of FIGS. 5 and 6, locating sleeve 22 is embedded in sink 
2 which is supported on a ring 27. A fusable pin or rod member 28 is 
positioned within sleeve 22 and contacts a ball-shaped valve body 29, 
thereby holding valve body 29 in an open position away from a valve seat 
30 against the force of a pressure spring 26. In this position, the valve 
is opened such that there is an unrestricted flow of gas into distributing 
chamber 4. 
When the brick or sink 2 has been eroded or worn down to a predetermined 
extent or to a residual height, the temperature in the area of sleeve 22 
and of pin or rod member 28 rises to an extent such that fusable pin or 
rod member 28 melts. As a result, spring 26 forces valve body 29 against 
valve seat 30. Valve seat 30 has a star-shaped or irregular configuration 
as shown in FIG. 6, such that even when valve body 29 seats on valve seat 
30 the flow of gas will be abruptly reduced but not stopped. The gas 
purging or washing operation thereby can be continued, for example by 
increasing the gas pressure in the manner discussed above. 
FIG. 7 illustrates an embodiment similar to FIG. 5, but wherein a pin or 
rod member 31 is formed on or contacts ball-shaped valve body 29 and is 
retained in sleeve 22 by a fuse, for example a soldered joint 23. This 
renewable fuse melts when the temperature rises due to the erosion or 
wearing of the sink 2. Upon melting of the fuse, the spring 26 presses the 
valve body 29 against toothed or star-shaped valve seat 30, and pin or rod 
member 31 is pushed into sleeve 22. 
In the embodiment of FIG. 8, a bolt 32 having an inclined end face 33 is 
secured or embedded in sink 2, i.e. without the provision of sleeve 22. A 
pin or rod member 31 has a complementarily inclined end face 34. End faces 
33, 34 are fused to each other by a soldered joint 23. Accordingly, when 
the sink 2 has been eroded or worn down to a predetermined extent or 
residual height, fuse 23 melts such that under the action of pressure 
spring 26 or under the action of the gas pressure alone the two faces 33, 
34 are displaced relative to each other ball-shaped valve body 29 is 
allowed to seat on toothed or star-shaped valve seat 30. 
In the embodiment of FIG. 9, a bimetallic strip 35 is provided in place of 
a fuse. Thus, one end of bimetallic strip 35 is attached externally to a 
locating sleeve 22 embedded in sink 2. The other end of bimetallic stri 35 
supports a locking or blocking bolt 36 which extends through an aperture 
in sleeve 22 and forms a stop for pin or rod member 31 of ball-shaped 
valve body 29. Pin or rod member 31 abuts bolt 36 to maintain valve body 
29 in the open position spaced from valve seat 30. When the temperature 
rises as a result of erosion or wear, bimetallic strip 35 expands, thereby 
causing bolt 36 to be withdrawn from the opening in sleeve 22, thereby 
releasing pin or rod member 31 such that spring 26 urges valve body 29 to 
seat against valve seat 30. Here also, as in the embodiments of FIGS. 2-8, 
the total gas flow is reduced abruptly upon the occurrence of a 
predetermined extent of wear of brick or sink 2. 
FIG. 10 illustrates an embodiment substantially similar to the embodiment 
of FIG. 8. However, in the embodiment of FIG. 10 the valve seat 37 is on 
the side of ball-shaped valve body 29 spaced away from sink 2. 
Accordingly, pressure spring 38 is provided on the side of valve body 29 
adjacent sink 2. As long as soldered joint or fuse 23 is not melted, the 
valve body, attached to the rod member, is maintained in the open position 
spaced from valve seat 37, thereby allowing an unrestricted flow of gas. 
However, when the temperature rises such that fuse 23 melts, then the rod 
member and valve body 29 are allowed to drop and are urged by the force of 
spring 38 against valve seat 37, thereby causing the total gas flow to be 
reduced to a low value. Spring 38 is dimensioned such that the valve 
arrangement opens again to a reduced extent for continued purging when the 
gas pressure is increased. Also, it of course would be possible to provide 
valve seat 37 of a construction similar to that of valve seat 30. 
Although the present invention has been described and illustrated with 
respect to preferred features, it is to be understood that various 
modifications and changes may be made to the specifically described and 
illustrated features without departing from the scope of the present 
invention. Further, it readily would be understood by one skilled in the 
art the manner in which a particular installation could be designed to 
cause reduction of the gas flow upon a temperature rise at a given 
position indicative of a given extent of erosion or wear of the gas 
purging or washing brick or sink.