CA1337245C - Method, device and probe for measuring a gas content of a bath of liquid metal - Google Patents
Method, device and probe for measuring a gas content of a bath of liquid metalInfo
- Publication number
- CA1337245C CA1337245C CA000590035A CA590035A CA1337245C CA 1337245 C CA1337245 C CA 1337245C CA 000590035 A CA000590035 A CA 000590035A CA 590035 A CA590035 A CA 590035A CA 1337245 C CA1337245 C CA 1337245C
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- Prior art keywords
- gas
- probe
- supply line
- line
- bath
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/20—Metals
- G01N33/202—Constituents thereof
- G01N33/2022—Non-metallic constituents
- G01N33/2025—Gaseous constituents
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- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Medicinal Chemistry (AREA)
- Physics & Mathematics (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating And Analyzing Materials By Characteristic Methods (AREA)
Abstract
A throw-away probe having a gas supply line and a gas removal line is connected to the lance by means of a quick-connection coupling having sections through which extend the ends of a gas circuit connected to the gas lines. The gas supply line contains drying means , is sealed at the bottom by a fusible stopper and is sealed in the coupling by a stopper which was pricked when installing the probe on the lance. The fusible stopper melts when the probe is immersed in the bath. The carrier gas which is pumped round through the gas detector in the circuit, is dried.
Description
-"Method, device and probe for measuring a gas content of a bath of liquid metal".
The invention relates to a method for measuring a gas content, in particular a hydrogen content, of a bath of liquid metal with a low partial pressure of oxygen, according to which method a probe with a gas supply line and a gas removal line, the lowermost ends of which are situated near each other, is immersed in the bath, a carrier gas is supplied via a gas line to the gas supply line, said carrier gas is collected again after exchanging with the bath the gas whose content is to be measured, and it is fed via the gas removal line of the probe and a gas line connected thereto through a gas detector in which the gas content is measured. A metal which a low partial pressure of oxygen is a metal with high H2/H20 ratio, such as, for example, steel.
A method of this type is described in the Belgian Patent No. 1,004,013 on November 22, 1988.
In said method, as indeed in other known methods for determining the hydrogen content, fairly large correction factors, which cannot always be clearly justified theoretically, have to be made in the actual measurement based on the hydrogen content which is obtained by exchange in the carrier gas. Although these correction factors produce a satisfactory result at high hydrogen concentrations, this is no longer so at low hydrogen concentrations.
The object of the invention is to remedy this defect and to provide a method which makes a more accurate measurement possible of the gas content, in particular of the hydrogen content, without such correction factors ,, ~
having to be used, which method can also be used at very low gas concentrations, in particular hydrogen concentrations, in the metal.
For this purpose, the carrier gas is dried.
Surprisingly, it has been found that water or moisture which is liberated when the probe is immersed in the bath from materials from which the probe is constructed can cause interferences in the measurement.
Liberated moisture can start to decompose at the high temperatures in the bath so that consequently, when the hydrogen content is measured, not only the hydrogen from the bath, but also the hydrogen produced from the moisture is measured.
The moisture liberated from the probe also proves to have a disadvantageous effect on the precision of the measurement in measuring other gas contents, such as nitrogen content.
By removing the moisture from the gas which is passed through the probe, a very correct measurement is obtained.
In a particular embodiment of the invention, the gas is passed during the measurement in a closed circuit through the probe and the gas detector, the drying being carried out during this circulation of the gas.
The drying may be carried out both in the probe and upstream or downstream of the probe.
The drying can be carried out in the usual man-ners, either by drying agents such as silica gel, or,if the drying is carried out outside the probe, by cooling and condensing the moisture.
The invention also relates to a device for measuring a gas content of a bath of liquid metal with a low partial pressure of oxygen, which device is particularly suitable for carrying out the method according to one of the preceding embodiments.
The invention thus relates to a device for measur-_ 3 - 1 3 3 724 5 ing a gas content, in particular a hydrogen content, of a bath of liquid metal with a low partial pressure of oxygen, which device contains a probe which is designed to be immersed in the liquid metal and which, in its turn, has a gas supply line, which debouches with an end on the end of the probe designed to be situated at the bottom, a gas removal line for collecting the gas which flows out of the gas supply line and has picked up a gas, whose content is to be measured, from the bath, the end of which removal line is situated in the vicinity of the lowermost end of the gas supply line, which device furthermore contains a gas circuit, one end of which connects to the gas supply line of the probe and the other end of which connects to the gas removal line of the probe, a gas detector installed in said circuit and means installed in or on said circuit for passing carrier gas around the circuit through the gas detector and the probe, characterized in that it contains drying means which is installed in or on the entity formed by the gas supply line of the probe, the gas removal line of the probe, the gas circuit and the gas detector.
In a particular embodiment of the invention, the drying means are installed in one of the gas lines in the probe.
Preferably, the device contains a lance and the probe is a throw-away probe which is installed on the lance by means of a quick-connection coupling, of which quick connection coupling a section is installed on the probe and a section on the lance, and which quick-connection coupling connects the gas supply line and the gas removal line of the probe in a gastight manner to both ends of the gas circuit, the drying means are installed in one of the gas lines in the probe, the lowermost end of at least one of the gas lines in the _ 4 _ 1 33 72 45 probe is sealed in a moisture-tight manner by a seal which is opened when the probe is immersed in the metal bath and the uppermost end of said gas line in the probe is likewise sealed in a moisture-tight manner by a seal which is opened by coupling the sections of the quick-connection coupling to each other.
The invention finally also relates to a throw-away probe obviously designed to be used in the device according to one of the preceding embodiments.
The invention therefore also relates to a throw-away probe for measuring a gas content, in particular a hydrogen content, of a bath of liquid metal with a low partial pressure of oxygen, which probe has a gas supply line, which debouches with one end on the end designed to be situated at the bottom, and a removal line for collecting a gas which flows out of the gas supply line, the end of which is situated in the vicinity of the lowermost end of the gas supply line, and which is characterized in that it contains drying means in at least one of the gas lines and said gas line is sealed in a moisture-tight manner at both ends by breakable seals.
Other features and advantages of the invention will emerge from the description, which follows below, of a method, device and probe for measuring a gas content of a bath of liquid metal according to the invention;
this description is given solely as an example and does not restrict the invention; the reference numerals relate to the accompanying drawings.
Figure 1 represents a block diagram of a device for measuring the hydrogen content of liquid steel according to the invention.
Figure 2 is partly a section and partly a front view of the lowermost section of the probe from the device according to figure 1.
_ 5 _ 1 3 3 7245 Figure 3 is partly a section and partly a front view of the uppermost section of the probe from figure 1, but drawn on a larger scale than figure 2.
In the three figures, the same reference numerals relate to the same elements.
The device in figure 1 contains essentially a probe 1 , a gas circuit 2, both ends of which connect to the probe and in which a filter 4, a katharometer 5,a pump 6, a four-way stopcock 7 and a flow meter 8 are installed consecutively in the flow direction of the gas which is indicated in figure 1 by the arrow 3.
The probe 1 is a throw-away probe, is connected by means of a quick-connection coupling 9, 10 detachably to a lance 11 through which ends of the gas circuit 2 extend, and is connected by means of the same quick-connection coupling 9, 10 to said two ends of the circuit 2.
A bottle 12 containing pressurized nitrogen is connected by means of a supply line 13 to the four-way stopcock 7.
Said four-way stopcock 7 closes, in one position, the gas circuit 2, the supply line 13 being connected to the open atmosphere. The bottle 12 is, of course, then closed. In another position, the four-way stopcock interrupts the gas circuit 2 and it connects, on the one hand, the supply line 13 to the section of the gas circuit 2 which connects to the probe 1 via the flow meter 8 and it connects, on the other hand, the section of the gas circuit 2 which comes from the pump 6 to the open atmosphere.
The katharometer 5 is also of a construction known per se and is not described in detail here. Said katha-rometer determines the hydrogen content of the inert carrier gas by measuring the thermal conductivity of the gas.
The probe 1 contains, as depicted in figures 2 and 3, at one end a gas collection section which is formed by a bell 14 of porous refractory stone and at the other end, one section 9 of the quick-connection coupling 9, 10 mentioned above.
The opening of the bell 14 is directed away from the section 9 and the bell is held at a distance from said section 9 by a quartz tube 15, to the ends of which the bell 14 and the section 9 are attached by means of cement 16.
Extending axially through the quartz tube 15 is a narrow quartz tube 17 which, on the one hand, projects into the section 9 and, on the other hand, extencls through the bell 14 and is attached to said bell 14 with cement.
A limb of a narrower fine quartz tube 18, bent through 180 , is attached by means of the cement 19 in the open end of the narrow quartz tube 17 extending outside the bell 14. The other limb of said fine quartz tube 18 is directed with its free end towards the open-ing of the bell 14. Said end is sealed by a plug 38 of a material which melts at the temperature of the steel bath and which seals the gas supply line 17, 18, 27 in a moisture-tight manner before the probe 1 is immersed in the metal bath. The cement 19 seals the narrow tube 17 around the fine tube 18 in a gastight manner.
In the quartz tube 15, the narrow quartz tube 17 is additionally surrounded by a tube 20 of A12O3.
The end of the quartz tube 15 remote from the bell 14 and especially the section 9 of the quick-connec-tion coupling 9, 10 are surrounded by a sheath consisting of three concentric tubes adjacent to each other, namely an innermost tube 21 of paperboard, a middlemost tube 22 of paperboard and an outermost tube 23 of resin-bonded sand.
The tubes 22 and 23 of said sheath are attached to the quartz tube 15 by means of cement 24.
The sheath 21, 22, 23 extends at the side facing away from the bell 14 to appreciably beyond the section 9. The inside diameter of the innermost tube 21 corres-ponds to the outside diameter of the lance 11 whose end projects into said sheath when the lance is connected to the probe 1.
The sheath 21, 22, 23 forms a thermal shield for this lowermost end of the lance 11 and particularly for the quick-connection coupling 9, 10.
As is especially evident from figure 3, the section 9 of the quick-connection coupling 9, 10 consists of a body which, on the immersion side, i.e. the side directed towards the bell 14 is provided with a collar 25 in which the quartz tube 15 is secured and is centrally provided with a hole 26 into which an end of the narrow quartz tube 17 projects.
An axial hole 27, which forms a gas supply line together with the quartz tubes 17 and 18, extends through said body.
The uppermost end of the axial hole 27 is sealed by a rubber stopper 39 which seals the hole 27 and therefore the gas supply line 17,18, 27 in a moisture-tight manner before the sections 9 and 10 of the quick-connection coupling are coupled and therefore before the probe 1 is installed on the lance 11.
Next to the axial hole 27, there extend through the body of the section 9 four holes 28 which debouch into the space between the quartz tube 15 and the narrow quartz tube 17 and which together with the last-mentioned space form a gas removal line which is closed at the immersion side by the porous bell 14 which forms a diaphragm, allows gas through but holds back liquid metal.
The diameter of the body of the section 9 of the quick-connection coupling 9, 10 decreases stepwise in the direction facing away from the quartz tube 15 and, specifically, in a manner such that three inwardly indented collars 29, 30 and 31 are formed.
The innermost tube 21 of the sheath 21, 22, 23 are up against the collar 29 situated most outwardly and nearest the quartz tube 15 and is also up against the outside of the cylindrical section of the section 9 which is situated between the collars 29 and 30.
The section of the body with a smaller diameter which is situated between the collars 30 and 31 is surrounded by an O-ring 32 partially recessed therein.
The abovementioned holes 28 debouch in the collar 31.
The cylindrical section extending outside the collar 31 is also surrounded by an O-ring 33 partially recessed therein.
The collars 30 and 31 and the O-rings 32 and 33 interact with parts of the section 10 of the quick-connection coupling 9, 10, which section 10 forms a piece which is installed on the end of the lance 11.
This section 10 is provided at its end with an axial circular hole 34 into which the cylindrical section, situated between the collars 30 and 31, of the section 9 fits and is provided with a smaller axial hole 35 which,on the one hand, debouches at the base of the hole 34 and, on the other hand, connects to the end of the gas circuit 2 which is situated downstream of the flow meter 8.
Around the hole 35 there extends, in the section 10, a channel 36 which, on the one hand, debouches at the base of the hole 35 and, on the other hand, connects to the other end of the gas circuit 2 which just like the previous end, is attached in said section 10 .
These two ends of the gas circuit therefore ex-tend through the metal lance 11.
In the smallest hole 35 of the section 10 of thequick-connection coupling 9, 10 there is attached a mechanical connecting piece 37 which has four sprung legs 41 provided at their ends with thicker parts which, when the lance 11 is pushed into the sheath 21, 22, 23, snap in a sprung manner over the thickened head on the end of the section of the section 9 projecting outside the collar 31.
Connected to the connecting piece 37 is a hollow needle 40 which extends axially between the legs 41 and whose hollow part connects to an axial channel 42 transversely through the connecting piece 37.
When installing the probe 1 on the lance 11, the needle 40 is forced through the rubber stopper 39 into the hole 27 of the section 9 so that if the legs 41 of the section 10 are snapped over the thickened head of the section 9, the needle 40 projects through the stopper 39 and connects the hole 35 of the gas supply line 17, 18, 27 with one end of the circuit 2 situated in the centre of the lance and downstream of the flow meter 8.
As is especially evident from figure 2, the narrow quartz tube 17 of the gas supply line 17, 18, 27 is partly filled with silica gel 43.
Because said gas supply line are sealed in a moisture-tight manner at both ends, respectively by the fusible plug 38 and the rubber stopper 39 by mounting the probe 1 on the lance 11, the drying means formed by the silica gel 43 does not absorb any moisture from the air.
The entity formed by the quartz tube 15 with possibly - lo - ~ 33 7 2 4 5 the bell 14, the projecting end of the narrow quartz tube 17 and the fine quartz tube 18 may also be surrounded by a cap of metal which, for the sake of simplicity, is not depicted in the figures and is attached to the sheath 21, 22, 23 and which is surrounded by a cap of paperboard, likewise not shown in the figures.
To carry out a measurement, the probe 1 is installed by means of the quick-connection coupling 9, 10 on a lance 11, which lance is therefore pushed into the sheath 21, 22, 23 of the probe 1, as a result of which the seal formed by the rubber stopper 39 of the uppermost end of the gas supply line 17, 18, 27 is opened by the needle 40 as described above.
The four-way stopcock 7 is set in the position in which the supply line 13 connects to the gas circuit 2 so that nitrogen flows from the bottle 12 to the probe 1.
Because the lowermost end of the gas supply line 17, 18, 27 is still sealed by the fusible plug 38, nitrogen will no longer flow once said line has been filled and a relatively high pressure, which corresponds to the pressure of the gas bottle 12, will prevail in said line.
As soon as the probe 1 is immersed in the bath of liquid steel, the plug 38 melts and nitrogen bubbles through the liquid metal, which nitrogen is collected in the bell 14 and is drawn off via the gas removal line 14, 15, 28 and the circuit 2 via the filter 4 and the katharometer 5 by the pump 6 which has been started in the meantime.
For a few seconds, the gas drawn off escapes at the position of the four-way stopcock 7 into the open atmosphere as a result of which any impurities which when the probe 1 is immersed in the metal bath, for example by combustion of the constituents of the probe, are removed.
After flushing for ten seconds, when the catharo-meter no longer measures any impurities, the position of the four-way stopcock changes to that depicted in figure 1, and the nitrogen therefore flows in a closed circuit around the circuit 2 and the probe 1, and the actual measurement begins.
Already during the flushing, but also still while nitrogen is circulating, any moisture which is still released, for example, from the probe 1, is absorbed by the silica gel 43 in the narrow tube 17 so that no moisture is fed into the metal bath with the nitrogen and neither is any additional hydrogen consequently produced by liberated moisture.
After the dried nitrogen which has exchanged hydrogen with the metal bath has been pumped round for a short time, an equilibrium is established in relation to the hydrogen and the katharometer 5 indicates the correct hydrogen content.
As a result of the absence of additional hydrogen which has been formed by moisture, no correction factor has to be applied and it is also possible for very low hydrogen contents to be measured.
The invention is by no means restricted to the embodiment described above and within the scope of the patent application, many alterations on the described embodiment may be made, inter alia, in relation to the shape, the structure, the arrangement and the number of the components which are used to implement the invention.
In particular, the silica gel does not necessarily have to be located in the gas supply line of the probe and the drying means do not necessarily have to be formed by silica gel.
The drying means may, for example, also be provided in the gas removal line of the probe or in both gas lines of the probe.
The said gas lines in which the drying means are present should always be sealed in a moisture-tight manner at both ends before the probe is installed on the lance in order to avoid absorption of moisture from the atmosphere.
The drying means may, however, also be provided outside the probe in the gas circuit. For example, the filter from the circuit may be filled with silica gel or another drying means instead of with filter material.
The drying means may also be provided, for example in the katharometer.
Insofar as drying means are provided in the circuit, they may also, for example, be formed by cooling means which remove the moisture from the gas in the circuit by condensation.
The invention relates to a method for measuring a gas content, in particular a hydrogen content, of a bath of liquid metal with a low partial pressure of oxygen, according to which method a probe with a gas supply line and a gas removal line, the lowermost ends of which are situated near each other, is immersed in the bath, a carrier gas is supplied via a gas line to the gas supply line, said carrier gas is collected again after exchanging with the bath the gas whose content is to be measured, and it is fed via the gas removal line of the probe and a gas line connected thereto through a gas detector in which the gas content is measured. A metal which a low partial pressure of oxygen is a metal with high H2/H20 ratio, such as, for example, steel.
A method of this type is described in the Belgian Patent No. 1,004,013 on November 22, 1988.
In said method, as indeed in other known methods for determining the hydrogen content, fairly large correction factors, which cannot always be clearly justified theoretically, have to be made in the actual measurement based on the hydrogen content which is obtained by exchange in the carrier gas. Although these correction factors produce a satisfactory result at high hydrogen concentrations, this is no longer so at low hydrogen concentrations.
The object of the invention is to remedy this defect and to provide a method which makes a more accurate measurement possible of the gas content, in particular of the hydrogen content, without such correction factors ,, ~
having to be used, which method can also be used at very low gas concentrations, in particular hydrogen concentrations, in the metal.
For this purpose, the carrier gas is dried.
Surprisingly, it has been found that water or moisture which is liberated when the probe is immersed in the bath from materials from which the probe is constructed can cause interferences in the measurement.
Liberated moisture can start to decompose at the high temperatures in the bath so that consequently, when the hydrogen content is measured, not only the hydrogen from the bath, but also the hydrogen produced from the moisture is measured.
The moisture liberated from the probe also proves to have a disadvantageous effect on the precision of the measurement in measuring other gas contents, such as nitrogen content.
By removing the moisture from the gas which is passed through the probe, a very correct measurement is obtained.
In a particular embodiment of the invention, the gas is passed during the measurement in a closed circuit through the probe and the gas detector, the drying being carried out during this circulation of the gas.
The drying may be carried out both in the probe and upstream or downstream of the probe.
The drying can be carried out in the usual man-ners, either by drying agents such as silica gel, or,if the drying is carried out outside the probe, by cooling and condensing the moisture.
The invention also relates to a device for measuring a gas content of a bath of liquid metal with a low partial pressure of oxygen, which device is particularly suitable for carrying out the method according to one of the preceding embodiments.
The invention thus relates to a device for measur-_ 3 - 1 3 3 724 5 ing a gas content, in particular a hydrogen content, of a bath of liquid metal with a low partial pressure of oxygen, which device contains a probe which is designed to be immersed in the liquid metal and which, in its turn, has a gas supply line, which debouches with an end on the end of the probe designed to be situated at the bottom, a gas removal line for collecting the gas which flows out of the gas supply line and has picked up a gas, whose content is to be measured, from the bath, the end of which removal line is situated in the vicinity of the lowermost end of the gas supply line, which device furthermore contains a gas circuit, one end of which connects to the gas supply line of the probe and the other end of which connects to the gas removal line of the probe, a gas detector installed in said circuit and means installed in or on said circuit for passing carrier gas around the circuit through the gas detector and the probe, characterized in that it contains drying means which is installed in or on the entity formed by the gas supply line of the probe, the gas removal line of the probe, the gas circuit and the gas detector.
In a particular embodiment of the invention, the drying means are installed in one of the gas lines in the probe.
Preferably, the device contains a lance and the probe is a throw-away probe which is installed on the lance by means of a quick-connection coupling, of which quick connection coupling a section is installed on the probe and a section on the lance, and which quick-connection coupling connects the gas supply line and the gas removal line of the probe in a gastight manner to both ends of the gas circuit, the drying means are installed in one of the gas lines in the probe, the lowermost end of at least one of the gas lines in the _ 4 _ 1 33 72 45 probe is sealed in a moisture-tight manner by a seal which is opened when the probe is immersed in the metal bath and the uppermost end of said gas line in the probe is likewise sealed in a moisture-tight manner by a seal which is opened by coupling the sections of the quick-connection coupling to each other.
The invention finally also relates to a throw-away probe obviously designed to be used in the device according to one of the preceding embodiments.
The invention therefore also relates to a throw-away probe for measuring a gas content, in particular a hydrogen content, of a bath of liquid metal with a low partial pressure of oxygen, which probe has a gas supply line, which debouches with one end on the end designed to be situated at the bottom, and a removal line for collecting a gas which flows out of the gas supply line, the end of which is situated in the vicinity of the lowermost end of the gas supply line, and which is characterized in that it contains drying means in at least one of the gas lines and said gas line is sealed in a moisture-tight manner at both ends by breakable seals.
Other features and advantages of the invention will emerge from the description, which follows below, of a method, device and probe for measuring a gas content of a bath of liquid metal according to the invention;
this description is given solely as an example and does not restrict the invention; the reference numerals relate to the accompanying drawings.
Figure 1 represents a block diagram of a device for measuring the hydrogen content of liquid steel according to the invention.
Figure 2 is partly a section and partly a front view of the lowermost section of the probe from the device according to figure 1.
_ 5 _ 1 3 3 7245 Figure 3 is partly a section and partly a front view of the uppermost section of the probe from figure 1, but drawn on a larger scale than figure 2.
In the three figures, the same reference numerals relate to the same elements.
The device in figure 1 contains essentially a probe 1 , a gas circuit 2, both ends of which connect to the probe and in which a filter 4, a katharometer 5,a pump 6, a four-way stopcock 7 and a flow meter 8 are installed consecutively in the flow direction of the gas which is indicated in figure 1 by the arrow 3.
The probe 1 is a throw-away probe, is connected by means of a quick-connection coupling 9, 10 detachably to a lance 11 through which ends of the gas circuit 2 extend, and is connected by means of the same quick-connection coupling 9, 10 to said two ends of the circuit 2.
A bottle 12 containing pressurized nitrogen is connected by means of a supply line 13 to the four-way stopcock 7.
Said four-way stopcock 7 closes, in one position, the gas circuit 2, the supply line 13 being connected to the open atmosphere. The bottle 12 is, of course, then closed. In another position, the four-way stopcock interrupts the gas circuit 2 and it connects, on the one hand, the supply line 13 to the section of the gas circuit 2 which connects to the probe 1 via the flow meter 8 and it connects, on the other hand, the section of the gas circuit 2 which comes from the pump 6 to the open atmosphere.
The katharometer 5 is also of a construction known per se and is not described in detail here. Said katha-rometer determines the hydrogen content of the inert carrier gas by measuring the thermal conductivity of the gas.
The probe 1 contains, as depicted in figures 2 and 3, at one end a gas collection section which is formed by a bell 14 of porous refractory stone and at the other end, one section 9 of the quick-connection coupling 9, 10 mentioned above.
The opening of the bell 14 is directed away from the section 9 and the bell is held at a distance from said section 9 by a quartz tube 15, to the ends of which the bell 14 and the section 9 are attached by means of cement 16.
Extending axially through the quartz tube 15 is a narrow quartz tube 17 which, on the one hand, projects into the section 9 and, on the other hand, extencls through the bell 14 and is attached to said bell 14 with cement.
A limb of a narrower fine quartz tube 18, bent through 180 , is attached by means of the cement 19 in the open end of the narrow quartz tube 17 extending outside the bell 14. The other limb of said fine quartz tube 18 is directed with its free end towards the open-ing of the bell 14. Said end is sealed by a plug 38 of a material which melts at the temperature of the steel bath and which seals the gas supply line 17, 18, 27 in a moisture-tight manner before the probe 1 is immersed in the metal bath. The cement 19 seals the narrow tube 17 around the fine tube 18 in a gastight manner.
In the quartz tube 15, the narrow quartz tube 17 is additionally surrounded by a tube 20 of A12O3.
The end of the quartz tube 15 remote from the bell 14 and especially the section 9 of the quick-connec-tion coupling 9, 10 are surrounded by a sheath consisting of three concentric tubes adjacent to each other, namely an innermost tube 21 of paperboard, a middlemost tube 22 of paperboard and an outermost tube 23 of resin-bonded sand.
The tubes 22 and 23 of said sheath are attached to the quartz tube 15 by means of cement 24.
The sheath 21, 22, 23 extends at the side facing away from the bell 14 to appreciably beyond the section 9. The inside diameter of the innermost tube 21 corres-ponds to the outside diameter of the lance 11 whose end projects into said sheath when the lance is connected to the probe 1.
The sheath 21, 22, 23 forms a thermal shield for this lowermost end of the lance 11 and particularly for the quick-connection coupling 9, 10.
As is especially evident from figure 3, the section 9 of the quick-connection coupling 9, 10 consists of a body which, on the immersion side, i.e. the side directed towards the bell 14 is provided with a collar 25 in which the quartz tube 15 is secured and is centrally provided with a hole 26 into which an end of the narrow quartz tube 17 projects.
An axial hole 27, which forms a gas supply line together with the quartz tubes 17 and 18, extends through said body.
The uppermost end of the axial hole 27 is sealed by a rubber stopper 39 which seals the hole 27 and therefore the gas supply line 17,18, 27 in a moisture-tight manner before the sections 9 and 10 of the quick-connection coupling are coupled and therefore before the probe 1 is installed on the lance 11.
Next to the axial hole 27, there extend through the body of the section 9 four holes 28 which debouch into the space between the quartz tube 15 and the narrow quartz tube 17 and which together with the last-mentioned space form a gas removal line which is closed at the immersion side by the porous bell 14 which forms a diaphragm, allows gas through but holds back liquid metal.
The diameter of the body of the section 9 of the quick-connection coupling 9, 10 decreases stepwise in the direction facing away from the quartz tube 15 and, specifically, in a manner such that three inwardly indented collars 29, 30 and 31 are formed.
The innermost tube 21 of the sheath 21, 22, 23 are up against the collar 29 situated most outwardly and nearest the quartz tube 15 and is also up against the outside of the cylindrical section of the section 9 which is situated between the collars 29 and 30.
The section of the body with a smaller diameter which is situated between the collars 30 and 31 is surrounded by an O-ring 32 partially recessed therein.
The abovementioned holes 28 debouch in the collar 31.
The cylindrical section extending outside the collar 31 is also surrounded by an O-ring 33 partially recessed therein.
The collars 30 and 31 and the O-rings 32 and 33 interact with parts of the section 10 of the quick-connection coupling 9, 10, which section 10 forms a piece which is installed on the end of the lance 11.
This section 10 is provided at its end with an axial circular hole 34 into which the cylindrical section, situated between the collars 30 and 31, of the section 9 fits and is provided with a smaller axial hole 35 which,on the one hand, debouches at the base of the hole 34 and, on the other hand, connects to the end of the gas circuit 2 which is situated downstream of the flow meter 8.
Around the hole 35 there extends, in the section 10, a channel 36 which, on the one hand, debouches at the base of the hole 35 and, on the other hand, connects to the other end of the gas circuit 2 which just like the previous end, is attached in said section 10 .
These two ends of the gas circuit therefore ex-tend through the metal lance 11.
In the smallest hole 35 of the section 10 of thequick-connection coupling 9, 10 there is attached a mechanical connecting piece 37 which has four sprung legs 41 provided at their ends with thicker parts which, when the lance 11 is pushed into the sheath 21, 22, 23, snap in a sprung manner over the thickened head on the end of the section of the section 9 projecting outside the collar 31.
Connected to the connecting piece 37 is a hollow needle 40 which extends axially between the legs 41 and whose hollow part connects to an axial channel 42 transversely through the connecting piece 37.
When installing the probe 1 on the lance 11, the needle 40 is forced through the rubber stopper 39 into the hole 27 of the section 9 so that if the legs 41 of the section 10 are snapped over the thickened head of the section 9, the needle 40 projects through the stopper 39 and connects the hole 35 of the gas supply line 17, 18, 27 with one end of the circuit 2 situated in the centre of the lance and downstream of the flow meter 8.
As is especially evident from figure 2, the narrow quartz tube 17 of the gas supply line 17, 18, 27 is partly filled with silica gel 43.
Because said gas supply line are sealed in a moisture-tight manner at both ends, respectively by the fusible plug 38 and the rubber stopper 39 by mounting the probe 1 on the lance 11, the drying means formed by the silica gel 43 does not absorb any moisture from the air.
The entity formed by the quartz tube 15 with possibly - lo - ~ 33 7 2 4 5 the bell 14, the projecting end of the narrow quartz tube 17 and the fine quartz tube 18 may also be surrounded by a cap of metal which, for the sake of simplicity, is not depicted in the figures and is attached to the sheath 21, 22, 23 and which is surrounded by a cap of paperboard, likewise not shown in the figures.
To carry out a measurement, the probe 1 is installed by means of the quick-connection coupling 9, 10 on a lance 11, which lance is therefore pushed into the sheath 21, 22, 23 of the probe 1, as a result of which the seal formed by the rubber stopper 39 of the uppermost end of the gas supply line 17, 18, 27 is opened by the needle 40 as described above.
The four-way stopcock 7 is set in the position in which the supply line 13 connects to the gas circuit 2 so that nitrogen flows from the bottle 12 to the probe 1.
Because the lowermost end of the gas supply line 17, 18, 27 is still sealed by the fusible plug 38, nitrogen will no longer flow once said line has been filled and a relatively high pressure, which corresponds to the pressure of the gas bottle 12, will prevail in said line.
As soon as the probe 1 is immersed in the bath of liquid steel, the plug 38 melts and nitrogen bubbles through the liquid metal, which nitrogen is collected in the bell 14 and is drawn off via the gas removal line 14, 15, 28 and the circuit 2 via the filter 4 and the katharometer 5 by the pump 6 which has been started in the meantime.
For a few seconds, the gas drawn off escapes at the position of the four-way stopcock 7 into the open atmosphere as a result of which any impurities which when the probe 1 is immersed in the metal bath, for example by combustion of the constituents of the probe, are removed.
After flushing for ten seconds, when the catharo-meter no longer measures any impurities, the position of the four-way stopcock changes to that depicted in figure 1, and the nitrogen therefore flows in a closed circuit around the circuit 2 and the probe 1, and the actual measurement begins.
Already during the flushing, but also still while nitrogen is circulating, any moisture which is still released, for example, from the probe 1, is absorbed by the silica gel 43 in the narrow tube 17 so that no moisture is fed into the metal bath with the nitrogen and neither is any additional hydrogen consequently produced by liberated moisture.
After the dried nitrogen which has exchanged hydrogen with the metal bath has been pumped round for a short time, an equilibrium is established in relation to the hydrogen and the katharometer 5 indicates the correct hydrogen content.
As a result of the absence of additional hydrogen which has been formed by moisture, no correction factor has to be applied and it is also possible for very low hydrogen contents to be measured.
The invention is by no means restricted to the embodiment described above and within the scope of the patent application, many alterations on the described embodiment may be made, inter alia, in relation to the shape, the structure, the arrangement and the number of the components which are used to implement the invention.
In particular, the silica gel does not necessarily have to be located in the gas supply line of the probe and the drying means do not necessarily have to be formed by silica gel.
The drying means may, for example, also be provided in the gas removal line of the probe or in both gas lines of the probe.
The said gas lines in which the drying means are present should always be sealed in a moisture-tight manner at both ends before the probe is installed on the lance in order to avoid absorption of moisture from the atmosphere.
The drying means may, however, also be provided outside the probe in the gas circuit. For example, the filter from the circuit may be filled with silica gel or another drying means instead of with filter material.
The drying means may also be provided, for example in the katharometer.
Insofar as drying means are provided in the circuit, they may also, for example, be formed by cooling means which remove the moisture from the gas in the circuit by condensation.
Claims (9)
1. A method for measuring a gas content, in parti-cular a hydrogen content, of a bath of liquid metal with a low partial pressure of oxygen, according to which method a probe with a gas supply line and a gas removal line, the lowermost ends of which are situated near each other, is immersed in the bath, a carrier gas is supplied from a gas line to the gas supply line, said carrier gas is collected again after exchanging with the bath the gas whose content is to be measured, and it is fed via the gas removal line of the probe and a gas line connected thereto through a gas detector in which the gas content is measured, characterized in that the carrier gas is dried and in that the gas is passed during measurement in a closed circuit through the probe and the gas detector, the drying being carried out during this circulation of the gas.
2. A device for measuring a gas content, in particular a hydrogen content, of a bath of liquid metal with a low partial pressure of oxygen, which device contains a probe which is designed to be immersed in the liquid metal and which, in its turn, has a gas supply line, an end of which debouches at the end of the probe designed to be situated at the bottom, and a gas removal line for collecting the gas which flows out of the gas supply line and which has picked up gas, whose content is to be measured, from the bath, the end of which removal line is situated in the vicinity of the lowermost end of the gas supply line,which device furthermore contains a gas circuit, one end of which connects to the gas supply line of the probe and the other end of which connects to the gas removal line of the probe, a gas detector installed in said circuit and means installed in or on said circuit for passing carrier gas around the circuit through the gas detector and the probe, characterized in that it contains drying means which are installed in the entity formed by the gas supply line of the probe , the gas removal line of the probe, the gas circuit and the gas detector.
3. The device according to claim 2, characterized in that the drying means are installed in one of the gas lines in the probe.
4. The device according to claim 2, characterized in that it contains a lance and the probe is a throwaway probe which is installed on the lance by means of a quick-connection coupling of which quick-connection coupling a section is installed on the probe and a section on the lance, and which quick-connection coupling connects the gas supply line and the gas removal line of the probe in a gastight manner to both ends of the gas circuit, the drying means are installed in one of the gas lines in the probe and the lowermost end of at least one of the gas lines in the probe is sealed in a moisture-tight manner by a seal which is opened when the probe is immersed in the metal bath and the uppermost end of said gas line in the probe is likewise sealed in a moisture-tight manner by a seal which is opened by coupling the sections of the quick-connection coupling to each other.
5. The device according to claim 4, characterized in that the gas supply line of the probe is sealed at both ends, respectively by a seal which is opened during immersion and a seal which is opened by coupling the probe to the lance.
6. The device according to claim 4, characterized in that the seal which is opened by coupling the probe to the lance is an elastic stopper which seals the channel in the section of the quick-connection coupling which forms part of the probe, there being installed on the section of the quick-connection coupling which forms part of the lance, a hollow needle which connects to the circuit and is pierced through the elastic stopper.
7. A throw-away probe for measuring a gas content, in particular a hydrogen content, of a bath of liquid metal with a low partial pressure of oxygen, which probe has a gas supply line, one end of which debouches at the end designed to be situated at the bottom, and a gas removal line for collecting the gas which flows out of the gas supply line the end of which is situated in the vicinity of the lowermost end of the gas supply line, characterized in that it contains drying means in at least one of the gas lines and said gas line is sealed in a moisture-tight manner at both ends by breakable seals.
8. The throw-away probe according to claim 7, characterized in that the gas line in which drying means are provided is sealed at its lowermost end by a fusible stopper which melts at the temperature of the liquid metal.
9. The throw-away probe according to claim 7, characterized in that the gas line in which the drying means are provided is sealed at its uppermost end by an elastic stopper which can be pierced by a hollow needle.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| BE08800154 | 1988-02-10 | ||
| BE8800154A BE1001447A4 (en) | 1988-02-10 | 1988-02-10 | METHOD, DEVICE AND PROBE FOR MEASURING A gas content of A BATH LIQUID METAL. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1337245C true CA1337245C (en) | 1995-10-10 |
Family
ID=3883257
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000590035A Expired - Lifetime CA1337245C (en) | 1988-02-10 | 1989-02-03 | Method, device and probe for measuring a gas content of a bath of liquid metal |
Country Status (4)
| Country | Link |
|---|---|
| BE (1) | BE1001447A4 (en) |
| CA (1) | CA1337245C (en) |
| ES (1) | ES2012643A6 (en) |
| ZA (1) | ZA89960B (en) |
-
1988
- 1988-02-10 BE BE8800154A patent/BE1001447A4/en not_active IP Right Cessation
-
1989
- 1989-02-03 CA CA000590035A patent/CA1337245C/en not_active Expired - Lifetime
- 1989-02-08 ZA ZA89960A patent/ZA89960B/en unknown
- 1989-02-10 ES ES8900486A patent/ES2012643A6/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| BE1001447A4 (en) | 1989-10-31 |
| ES2012643A6 (en) | 1990-04-01 |
| ZA89960B (en) | 1989-10-25 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |