CA2037936A1 - Long lasting thermocouple for high temperature measurements of liquid metals, mattes and slags - Google Patents
Long lasting thermocouple for high temperature measurements of liquid metals, mattes and slagsInfo
- Publication number
- CA2037936A1 CA2037936A1 CA002037936A CA2037936A CA2037936A1 CA 2037936 A1 CA2037936 A1 CA 2037936A1 CA 002037936 A CA002037936 A CA 002037936A CA 2037936 A CA2037936 A CA 2037936A CA 2037936 A1 CA2037936 A1 CA 2037936A1
- Authority
- CA
- Canada
- Prior art keywords
- thermocouple
- cermet
- molten phase
- temperature
- dissimilar
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000002893 slag Substances 0.000 title claims description 10
- 238000009529 body temperature measurement Methods 0.000 title description 3
- 229910001338 liquidmetal Inorganic materials 0.000 title description 2
- 230000005923 long-lasting effect Effects 0.000 title description 2
- 239000011195 cermet Substances 0.000 claims abstract description 37
- 229910052751 metal Inorganic materials 0.000 claims abstract description 22
- 239000002184 metal Substances 0.000 claims abstract description 22
- 238000005259 measurement Methods 0.000 claims abstract description 7
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 15
- 229910052593 corundum Inorganic materials 0.000 claims description 15
- 229910001845 yogo sapphire Inorganic materials 0.000 claims description 15
- 238000006243 chemical reaction Methods 0.000 claims description 11
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 8
- 239000000919 ceramic Substances 0.000 claims description 6
- 229910052697 platinum Inorganic materials 0.000 claims description 3
- -1 Tio2 Chemical compound 0.000 claims description 2
- 229910052770 Uranium Inorganic materials 0.000 claims description 2
- 229910052804 chromium Inorganic materials 0.000 claims description 2
- 229910052746 lanthanum Inorganic materials 0.000 claims description 2
- 229910052750 molybdenum Inorganic materials 0.000 claims description 2
- 229910052758 niobium Inorganic materials 0.000 claims description 2
- 229910052763 palladium Inorganic materials 0.000 claims description 2
- 229910052702 rhenium Inorganic materials 0.000 claims description 2
- 229910052703 rhodium Inorganic materials 0.000 claims description 2
- 229910052707 ruthenium Inorganic materials 0.000 claims description 2
- 229910052709 silver Inorganic materials 0.000 claims description 2
- 229910052715 tantalum Inorganic materials 0.000 claims description 2
- 229910052719 titanium Inorganic materials 0.000 claims description 2
- 229910052721 tungsten Inorganic materials 0.000 claims description 2
- 229910052720 vanadium Inorganic materials 0.000 claims description 2
- 229910052727 yttrium Inorganic materials 0.000 claims description 2
- 229910052726 zirconium Inorganic materials 0.000 claims description 2
- 238000010348 incorporation Methods 0.000 claims 1
- 229910052748 manganese Inorganic materials 0.000 claims 1
- 150000002739 metals Chemical class 0.000 abstract description 9
- 238000000034 method Methods 0.000 abstract description 3
- 239000011449 brick Substances 0.000 description 8
- 230000005678 Seebeck effect Effects 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 3
- 230000003628 erosive effect Effects 0.000 description 3
- 238000009434 installation Methods 0.000 description 3
- 238000012423 maintenance Methods 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910003465 moissanite Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 230000005676 thermoelectric effect Effects 0.000 description 1
- 238000013519 translation Methods 0.000 description 1
Landscapes
- Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A thermocouple is disclosed for the continuous measurement of the temperature of a molten phase, which thermocouple comprises two cermet elements of dissimilar metals in which the thermoelectric circuit is closed by the medium, the temperature of which is being measured. The use of dissimilar cermet elements as opposed to conventional metallic wires imparts to the thermocouple sensor a superior resistance to high temperature, corrosive environments which allows it to be used for extended periods of time and for varied applications. A method of using the thermocouple is also disclosed.
A thermocouple is disclosed for the continuous measurement of the temperature of a molten phase, which thermocouple comprises two cermet elements of dissimilar metals in which the thermoelectric circuit is closed by the medium, the temperature of which is being measured. The use of dissimilar cermet elements as opposed to conventional metallic wires imparts to the thermocouple sensor a superior resistance to high temperature, corrosive environments which allows it to be used for extended periods of time and for varied applications. A method of using the thermocouple is also disclosed.
Description
203 ~
This invention relates to an improved thermocouple. More particularly, the invention relates to a thermocouple designed to measure the temperature of molten phases (metals, mattes, speiss' or slags) in metallurgical operations within an accuracy of +/- 2C without the need for maintenance or calibration over significant periods of time.
Hitherto, the high temperature of metallurgical melts has usually been measured by conventional wire thermocouples or optical pyrometers. However, there is presently a widespread need within the metallurgical industry for an instrument capable of accurately measuring the temperature of molten phases over extended periods of time without the need for maintenance or recalibration.
Pyrometers are inadequate in this respect as they are only accurate in the order of +/- 20C and are subject to periodic recalibration. Moreover, conventional thermocouples fabricated of dissimilar metal wires, although of sufficient precision, have a limited practicable lifespan in corrosive, high temperature environments; the lifespan being a function of the dissolution rate of the thermocouple sleeve or protection tube.
Cermets are a composite of a ceramic and a metal and have hitherto been used to a limited extent in pyrometers and thermocouples. For example~ United States Patent No. 3,473,968 (Rinesch et al.) teaches a thermocouple device for measuring the temperature of hot media in reaction vessels comprising a tube of heat-proof material which penetrates the wall of the vessel and is sealed at its inner end by a replaceable cermet plug within which is mounted the conventional metal wire thermocouple.
United States Patent No. 4,686,320 (Novak et al.) describes a composite article comprising a porous cermet electrode on a solid electrolyte suitable for use in thermoelectric generators and Canadian Patent No. 859,993 2 ~
(Strohmeier et al.) discloses a thermoelectric device for measuring the temperature of corrosive media such as me~al melts which comprises a cermet element body in which the hot junctions of the thermocouples together with their insulating means are enclosed by either pressing or sintering means. Finally, a translation of the German article "Application of Cermets in the Iron and Steel Industry", 1967 by Strohmeier et al. describes the use of Cr- Mo and Al2O3 based materials for measuring purposes in the copper industry. However, no mention is made of the use of two dissimilar cermets as a thermocouple.
It is an object of the present invention to provide a long-lasting thermocouple for high temperature measurements of molten phases in metallurgical operations and in particular of liquid metals, mattes and slags.
It is a further object of the invention to provide a thermocouple which is resistant to corrosive, high temperature environments and allows accurate measurements for extended applications and periods of time without the need for maintenance or recalibration.
Accordingly, the invention provides a thermocouple for the continuous measurement of the temperature of a metal-containing medium, the thermocouple comprising two cermet elements of dissimilar metals adapted for use in conjunction with a molten phase, such as-a matte, metal, speiss or slag, in which the thermoelectric circuit is closed by the molten phase, the temperature of which is being measured.
The invention also provides a method of using the thermocouple device which comprises incorporating the thermocouple into a wall of a metallurgical reaction vessel, the molten phase, the temperature of which is being measured in said vessel, closing the thermoelectric circuit of the thermocouple.
2 ~
Due to the characteristic properties of cermets, a thermocouple comprising two cermets of which the metal components are dissimilar will not only provide an accurate measurement of temperature but will also afford increased resistance to a corrosive environment in which measurements are being carried out. The increased resistance to corrosion, of course, allows for increased durability of the thermocouple. Furthermore, depending on the geometry of the application, such a thermocouple can be incorporated in the brick lining of a furnace or vessel wall, and continuously expose new surface to the medium being measured while progressively wearing out or eroding, along with the brick furnace lining, but while continuing to be operative. Thus, the life of the cermet thermocouple of the invention can be expected to be approximately the same as the life of the vessel itself.
Conventional thermocouples comprise metallic wires which are susceptible to corrosion and thus require protection from the environment. Such protection is usually in the form of a protective sleeve and the rate of deterioration thereof determines the lifespan of the measuring system.
Cermets possess some properties of ceramics, e.g.
good resistance to oxidation, and some properties of metals, in particular electrical conductivity. A
thermocouple based on two cermets of dissimilar metals does not comprise metallic wires in a thermoelectric circuit;
instead, the cermets carry the current and the circuit is closed by the molten matte, metal, spPiss or slag phase, the temperature of which is being measured. The physical and chemical properties of the cermet rods provide resistance to the eroding effects of a corrosive environment which substantially reduces the rate of the thermocouple system deterioration. Specifically, the ceramic content of a cermet acts to provide oxidation resistance while the metallic content provides electrical 20,~ 3 conductivity. Moreover, since the thermoelectric circuit is closed by the medium being measured, even significant erosion of the cermet rods would not destroy the measuring system as the circuit will not be broken.
Accordingly, with the correct design and implementation, the life of the thermocouple sensor could be equal to the life of the refractory lining of the reaction vessel in a metallurgical installation. The cermet thermocouple of the present invention is particularly applicable to metallurgical installations such as, inter alia, furnaces, refractory brick linings, ladles and forehearths.
The dissimilar cermet thermocouple of the invention can be based on a range of differing pairs of cermets, for instance those formed from a ceramic selected from Al203, ZrO2 and SiC and a metal selected from Mo, Cr, Ir and Ni. One preferred embodiment comprises Mo-Al203 and Cr-Al203. Another preferred cermet thermocouple is based on Mo-ZrO2 and Cr-Al203. Operable cermets could also potentially be synthesized from ceramics including Tio2, MgO, Y203, La203, SCZO3 and B4C and metals including Zr, Ti, V, Nb, Ta, W, Re, Ru, Rh, Co, Pt, Au, Os, Ag, Pd, U, La, Y
and Mn. In each case, resulting cermet could be paired with any other if the thermoelectric effect were great enough to provide a practical thermocouple.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure l is a graph plotting electromotive force (millivolt) against temperature (C) for both a pure Mo wire vs. a pure Ir wire and an Mo-Al203 cermet vs. a pure Ir wire;
Figure 2 is a schematic illustration of a preferred form of cermet thermocouple sensor;
2037f Figure 3 is a plot of electromotive force (millivolt) against temperature (C) for a thermocouple of two dissimilar cermets (Mo-Al203 vs. Cr-Al203);
Figure 4 is a schematic diagram illustrating an embodiment of invention in which the thermocouple device is incorporated in the wall of a reaction vessel; and Figure 5 illustrates a variation of the embodiment depicted in Figure 4.
Referring now to the drawings, a preferred form of cermet-based thermocouple of the present invention is shown in Figure 2. The thermocouple is defined by two dissimilar cermets 10 each adjacent to the other and in parallel relationship. At one end of each cermet is disposed a lead 20 while the other end is exposed to a molten matte, metal, speiss or slag phase 30, which melt acts to close the thermoelectric circuit. Generally speaking, the invention is more relevant to slags of high ionic conductivity as slags of lower conductivity may possess too high a resistance to complete a circuit.
In general, when two wires composed of dissimilar metals are joined at both ends and one of the wires is heated, a continuous current flow will occur in the thermoelectric circuit which has been created. This phenomenon, which is the basis of thermocouples, is known as the Seebeck Effect. In the thermocouple of the present invention, two cermets of dissimilar metals function in place of the standard metallic wires. As can be seen in Figure 1, the Seebeck Effect occurs to the same extent and in the same manner in both the conventional Mo vs. Ir wire thermocouple and in a thermocouple comprising a cermet (Mo-Al203) and a metallic wire, Ir. The fact that the Seebeck Effect in the all-wire thermoelectric circuit is similar for a metal wire and a cermet containing the said metal indicates the suitability of using cermets in the place of metallic wires in a thermocouple.
2 ~13 r~/ ~J ~ sj With reference to Figure 3, it can be seen that the voltage generated in a thermocouple based on dissimilar cermets (Mo-Al203 vs. Cr-Al2O3) is proportional to the temperature of the hot junction. The cermets employed in this instance were Metamic 829 (Al203 19.4~, Mo 77.7%, ZrO2 2.8%) and Metamic 612 (Al2O3 24~, sio2 4~, Cr 72%). This clearly indicates that the inherent relationship between voltage and temperature necessary to the functioning of a thermocouple does in fact exist in a thermocouple comprising two dissimilar cermets. The voltage generated is in the same order of magnitude as he conventional platinum type thermocouple.
The preferable method of using the thermocouple comprises incorporating the thermocouple sensor into the interior refractory wall of a metallurgical reaction vessel such as, inter alia, a furnace, ladle or forehearth. The metal-containing melt within the installation closes the thermoelectric circuit allowing an accurate measurement of the melt temperature to be effected in the order of +/-2C. The characteristic physical and chemical properties of cermets provide superior resistance to the corrosive -` effects of molten phases such as metals, mattes and slags, substantially extending the operable life of the thermocouple. Since the molten phase closes the thermoelectric circuit, any deterioration of the cermets has no significant effect upon the accuracy of the temperature measurements.
For example, Figure 4 depicts the physical embodiment of a thermocouple comprising two dissimilar cermet elements 110 and 120 incorporated into the interior refractory wall, for instance refractory brick 100, of a reaction vessel. The cool ends of the cermet rods 111 and 121, which extend outside of and beyond one edge of the refractory brick, are available for connection to a suitably calibrated temperature readout device 160. The "hot" ends of the cermet rods 112 and 122, which are level ~ ft~ ~J ~
. `
with the other edge of the brick, would be exposed to the molten phase.
The means of connecting the cermet thermocouple described above to a readout meter are readily seen in Figure 4. In order for the cermet thermocouple to yield accurate temperature readings, the temperature of the cool ends of the cermets must be known. This may be accomplished by connecting a conventional thermocouple to the cold end of each cermet. Hence, a knowledge of the temperature of the cool end of each cermet enables the determination of the temperature of the molten phase. As can be seen in Figure 4, the conventional metallic thermocouple leads 150 from the cermet elements 110 and 120 connect the cermet elements to a thermocouple readout meter 160. The leads 150 are not exposed to the corrosive molten phase but, as noted above, act to measure the temperature of the cool end of each cermet element thereby providing a basis of comparison from which to determine the molten phase temperature; this also being necessary to conventional thermocouple operation.
With reference to Figure 5, a variation of the reaction vessel of Figure 4 is depicted. In this embodiment, the wall of the reaction vessel 100 is composed of two layers, the outer layer 105 is composed of insulating brick and the inner layer 103 is composed of fire brick.
This invention relates to an improved thermocouple. More particularly, the invention relates to a thermocouple designed to measure the temperature of molten phases (metals, mattes, speiss' or slags) in metallurgical operations within an accuracy of +/- 2C without the need for maintenance or calibration over significant periods of time.
Hitherto, the high temperature of metallurgical melts has usually been measured by conventional wire thermocouples or optical pyrometers. However, there is presently a widespread need within the metallurgical industry for an instrument capable of accurately measuring the temperature of molten phases over extended periods of time without the need for maintenance or recalibration.
Pyrometers are inadequate in this respect as they are only accurate in the order of +/- 20C and are subject to periodic recalibration. Moreover, conventional thermocouples fabricated of dissimilar metal wires, although of sufficient precision, have a limited practicable lifespan in corrosive, high temperature environments; the lifespan being a function of the dissolution rate of the thermocouple sleeve or protection tube.
Cermets are a composite of a ceramic and a metal and have hitherto been used to a limited extent in pyrometers and thermocouples. For example~ United States Patent No. 3,473,968 (Rinesch et al.) teaches a thermocouple device for measuring the temperature of hot media in reaction vessels comprising a tube of heat-proof material which penetrates the wall of the vessel and is sealed at its inner end by a replaceable cermet plug within which is mounted the conventional metal wire thermocouple.
United States Patent No. 4,686,320 (Novak et al.) describes a composite article comprising a porous cermet electrode on a solid electrolyte suitable for use in thermoelectric generators and Canadian Patent No. 859,993 2 ~
(Strohmeier et al.) discloses a thermoelectric device for measuring the temperature of corrosive media such as me~al melts which comprises a cermet element body in which the hot junctions of the thermocouples together with their insulating means are enclosed by either pressing or sintering means. Finally, a translation of the German article "Application of Cermets in the Iron and Steel Industry", 1967 by Strohmeier et al. describes the use of Cr- Mo and Al2O3 based materials for measuring purposes in the copper industry. However, no mention is made of the use of two dissimilar cermets as a thermocouple.
It is an object of the present invention to provide a long-lasting thermocouple for high temperature measurements of molten phases in metallurgical operations and in particular of liquid metals, mattes and slags.
It is a further object of the invention to provide a thermocouple which is resistant to corrosive, high temperature environments and allows accurate measurements for extended applications and periods of time without the need for maintenance or recalibration.
Accordingly, the invention provides a thermocouple for the continuous measurement of the temperature of a metal-containing medium, the thermocouple comprising two cermet elements of dissimilar metals adapted for use in conjunction with a molten phase, such as-a matte, metal, speiss or slag, in which the thermoelectric circuit is closed by the molten phase, the temperature of which is being measured.
The invention also provides a method of using the thermocouple device which comprises incorporating the thermocouple into a wall of a metallurgical reaction vessel, the molten phase, the temperature of which is being measured in said vessel, closing the thermoelectric circuit of the thermocouple.
2 ~
Due to the characteristic properties of cermets, a thermocouple comprising two cermets of which the metal components are dissimilar will not only provide an accurate measurement of temperature but will also afford increased resistance to a corrosive environment in which measurements are being carried out. The increased resistance to corrosion, of course, allows for increased durability of the thermocouple. Furthermore, depending on the geometry of the application, such a thermocouple can be incorporated in the brick lining of a furnace or vessel wall, and continuously expose new surface to the medium being measured while progressively wearing out or eroding, along with the brick furnace lining, but while continuing to be operative. Thus, the life of the cermet thermocouple of the invention can be expected to be approximately the same as the life of the vessel itself.
Conventional thermocouples comprise metallic wires which are susceptible to corrosion and thus require protection from the environment. Such protection is usually in the form of a protective sleeve and the rate of deterioration thereof determines the lifespan of the measuring system.
Cermets possess some properties of ceramics, e.g.
good resistance to oxidation, and some properties of metals, in particular electrical conductivity. A
thermocouple based on two cermets of dissimilar metals does not comprise metallic wires in a thermoelectric circuit;
instead, the cermets carry the current and the circuit is closed by the molten matte, metal, spPiss or slag phase, the temperature of which is being measured. The physical and chemical properties of the cermet rods provide resistance to the eroding effects of a corrosive environment which substantially reduces the rate of the thermocouple system deterioration. Specifically, the ceramic content of a cermet acts to provide oxidation resistance while the metallic content provides electrical 20,~ 3 conductivity. Moreover, since the thermoelectric circuit is closed by the medium being measured, even significant erosion of the cermet rods would not destroy the measuring system as the circuit will not be broken.
Accordingly, with the correct design and implementation, the life of the thermocouple sensor could be equal to the life of the refractory lining of the reaction vessel in a metallurgical installation. The cermet thermocouple of the present invention is particularly applicable to metallurgical installations such as, inter alia, furnaces, refractory brick linings, ladles and forehearths.
The dissimilar cermet thermocouple of the invention can be based on a range of differing pairs of cermets, for instance those formed from a ceramic selected from Al203, ZrO2 and SiC and a metal selected from Mo, Cr, Ir and Ni. One preferred embodiment comprises Mo-Al203 and Cr-Al203. Another preferred cermet thermocouple is based on Mo-ZrO2 and Cr-Al203. Operable cermets could also potentially be synthesized from ceramics including Tio2, MgO, Y203, La203, SCZO3 and B4C and metals including Zr, Ti, V, Nb, Ta, W, Re, Ru, Rh, Co, Pt, Au, Os, Ag, Pd, U, La, Y
and Mn. In each case, resulting cermet could be paired with any other if the thermoelectric effect were great enough to provide a practical thermocouple.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure l is a graph plotting electromotive force (millivolt) against temperature (C) for both a pure Mo wire vs. a pure Ir wire and an Mo-Al203 cermet vs. a pure Ir wire;
Figure 2 is a schematic illustration of a preferred form of cermet thermocouple sensor;
2037f Figure 3 is a plot of electromotive force (millivolt) against temperature (C) for a thermocouple of two dissimilar cermets (Mo-Al203 vs. Cr-Al203);
Figure 4 is a schematic diagram illustrating an embodiment of invention in which the thermocouple device is incorporated in the wall of a reaction vessel; and Figure 5 illustrates a variation of the embodiment depicted in Figure 4.
Referring now to the drawings, a preferred form of cermet-based thermocouple of the present invention is shown in Figure 2. The thermocouple is defined by two dissimilar cermets 10 each adjacent to the other and in parallel relationship. At one end of each cermet is disposed a lead 20 while the other end is exposed to a molten matte, metal, speiss or slag phase 30, which melt acts to close the thermoelectric circuit. Generally speaking, the invention is more relevant to slags of high ionic conductivity as slags of lower conductivity may possess too high a resistance to complete a circuit.
In general, when two wires composed of dissimilar metals are joined at both ends and one of the wires is heated, a continuous current flow will occur in the thermoelectric circuit which has been created. This phenomenon, which is the basis of thermocouples, is known as the Seebeck Effect. In the thermocouple of the present invention, two cermets of dissimilar metals function in place of the standard metallic wires. As can be seen in Figure 1, the Seebeck Effect occurs to the same extent and in the same manner in both the conventional Mo vs. Ir wire thermocouple and in a thermocouple comprising a cermet (Mo-Al203) and a metallic wire, Ir. The fact that the Seebeck Effect in the all-wire thermoelectric circuit is similar for a metal wire and a cermet containing the said metal indicates the suitability of using cermets in the place of metallic wires in a thermocouple.
2 ~13 r~/ ~J ~ sj With reference to Figure 3, it can be seen that the voltage generated in a thermocouple based on dissimilar cermets (Mo-Al203 vs. Cr-Al2O3) is proportional to the temperature of the hot junction. The cermets employed in this instance were Metamic 829 (Al203 19.4~, Mo 77.7%, ZrO2 2.8%) and Metamic 612 (Al2O3 24~, sio2 4~, Cr 72%). This clearly indicates that the inherent relationship between voltage and temperature necessary to the functioning of a thermocouple does in fact exist in a thermocouple comprising two dissimilar cermets. The voltage generated is in the same order of magnitude as he conventional platinum type thermocouple.
The preferable method of using the thermocouple comprises incorporating the thermocouple sensor into the interior refractory wall of a metallurgical reaction vessel such as, inter alia, a furnace, ladle or forehearth. The metal-containing melt within the installation closes the thermoelectric circuit allowing an accurate measurement of the melt temperature to be effected in the order of +/-2C. The characteristic physical and chemical properties of cermets provide superior resistance to the corrosive -` effects of molten phases such as metals, mattes and slags, substantially extending the operable life of the thermocouple. Since the molten phase closes the thermoelectric circuit, any deterioration of the cermets has no significant effect upon the accuracy of the temperature measurements.
For example, Figure 4 depicts the physical embodiment of a thermocouple comprising two dissimilar cermet elements 110 and 120 incorporated into the interior refractory wall, for instance refractory brick 100, of a reaction vessel. The cool ends of the cermet rods 111 and 121, which extend outside of and beyond one edge of the refractory brick, are available for connection to a suitably calibrated temperature readout device 160. The "hot" ends of the cermet rods 112 and 122, which are level ~ ft~ ~J ~
. `
with the other edge of the brick, would be exposed to the molten phase.
The means of connecting the cermet thermocouple described above to a readout meter are readily seen in Figure 4. In order for the cermet thermocouple to yield accurate temperature readings, the temperature of the cool ends of the cermets must be known. This may be accomplished by connecting a conventional thermocouple to the cold end of each cermet. Hence, a knowledge of the temperature of the cool end of each cermet enables the determination of the temperature of the molten phase. As can be seen in Figure 4, the conventional metallic thermocouple leads 150 from the cermet elements 110 and 120 connect the cermet elements to a thermocouple readout meter 160. The leads 150 are not exposed to the corrosive molten phase but, as noted above, act to measure the temperature of the cool end of each cermet element thereby providing a basis of comparison from which to determine the molten phase temperature; this also being necessary to conventional thermocouple operation.
With reference to Figure 5, a variation of the reaction vessel of Figure 4 is depicted. In this embodiment, the wall of the reaction vessel 100 is composed of two layers, the outer layer 105 is composed of insulating brick and the inner layer 103 is composed of fire brick.
Claims (11)
1. A thermocouple for the continuous measurement of the temperature of a molten phase, the thermocouple comprising two dissimilar cermet elements adapted for use in conjunction with a molten phase, in which the thermoelectric circuit is closed by the molten phase, the temperature of which is being measured.
2. A thermocouple as claimed in claim 1, wherein the thermocouple is adapted for incorporation into the refractory lining of a metallurgical reaction vessel so as to communicate with the molten phase contained within the interior of said reaction vessel.
3. A thermocouple as claimed in claim 2, wherein the metallurgical reaction vessel is a furnace, ladle or converter or other means of containing a molten phase.
4. A thermocouple as claimed in claim 1, 2 or 3, wherein the molten phase is a metal.
5. A thermocouple as claimed in claim 1, 2 or 3, wherein the molten phase is a matte.
6. A thermocouple as claimed in claim 1, 2 or 3, wherein the molten phase is a slag.
7. A thermocouple as claimed in claim 1, 2 or 3, wherein the molten phase is a speiss.
8. A thermocouple as claimed in claim 1, 2 or 3, wherein one element is a Mo-Al2O3 cermet and the other element is a Cr-Al2O3 cermet.
9. A thermocouple as claimed in claim 1, 2 or 3, wherein one element is a Mo-ZrO2 cermet and the other element is a Cr-A1203 cermet.
10. A thermocouple as claimed in claim 1, 2 or 3, wherein the dissimilar cermet elements are each composed of a different metal selected from the group consisting of Zr, Mo, Cr, Ti, V, Nb, Ta, W, Re, Ru, Rh, Co, Pt, Au, Os, Ag, Pd, U, La, Y, and Mn, and a ceramic selected from the group consisting of A1203, ZrO2, Tio2, MgO, Y203, La203, Sc203, Sic and B4C.
11. In combination, a furnace or other vessel having incorporated into the interior refractory wall thereof a thermocouple comprising two dissimilar cermet elements.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002037936A CA2037936A1 (en) | 1991-03-11 | 1991-03-11 | Long lasting thermocouple for high temperature measurements of liquid metals, mattes and slags |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002037936A CA2037936A1 (en) | 1991-03-11 | 1991-03-11 | Long lasting thermocouple for high temperature measurements of liquid metals, mattes and slags |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2037936A1 true CA2037936A1 (en) | 1992-09-12 |
Family
ID=4147161
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002037936A Abandoned CA2037936A1 (en) | 1991-03-11 | 1991-03-11 | Long lasting thermocouple for high temperature measurements of liquid metals, mattes and slags |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2037936A1 (en) |
-
1991
- 1991-03-11 CA CA002037936A patent/CA2037936A1/en not_active Abandoned
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |