EP1183506A1

EP1183506A1 - Measuring system for determining the physical quantity of a hot liquid

Info

Publication number: EP1183506A1
Application number: EP00940252A
Authority: EP
Inventors: Heinz-Dieter Hannes; Franz Walter Hellmanns; Friedhelm Paulus; Wolfgang Schönbrenner
Original assignee: Zimmermann and Jansen GmbH
Current assignee: SCHOENBRENNER, WOLFGANG
Priority date: 1999-06-04
Filing date: 2000-05-16
Publication date: 2002-03-06
Also published as: WO2000075614A1; AU5524700A; DE19925685A1

Abstract

The invention relates to a system (1) for determining the physical quantity and/or for the chemical analysis of a hot liquid (3), especially of a steel melt or slag by optical means. Said system comprises an observation tube (4) that contacts the hot liquid and is fire-proof, an imaging device (6) that is mounted inside the observation tube or on its end and a measuring or analytical device (9) that is optically allocated to the imaging device. The observation tube (4) is freely arranged above the liquid level and from this position dips into the liquid (3).

Description

Measuring arrangement for determining a physical quantity of a hot liquid

Description

The invention relates to an arrangement for determining a physical quantity, in particular the temperature, and / or for the chemical analysis of a hot liquid by optical means according to the preamble of claim 1.

With a large number of metallurgical and chemical processes, the reliable and precise recording of physical parameters of a liquid at a very high temperature, in particular of metal melts or of liquid reaction mixtures, is necessary for the ongoing quality assurance of the corresponding products.

For the temperature measurement of molten metal, a cardboard sleeve equipped with a thermocouple is placed on a metal tube according to a known and widespread method. The contact elements of the thermocouple are located at the tip of the metal tube. The metal tube with the cardboard sleeve and the thermocouple at the end is brought into the melt, and a temperature measurement is possible before the thermocouple is destroyed by the melt.

The disadvantage of this method is that it can only be carried out discontinuously, ie it does not permit permanent monitoring of the melt temperature. In addition, a thermocouple is used for each measurement. For certain applications ( for example, when measuring the temperature of precious metal or other high-purity melts), the contamination of the melt associated with this procedure is also unacceptable. In addition, experience has shown that there are often contact difficulties between the metal tube and the thermocouple, so that the reliability of the measurements leaves something to be desired.

In a second common method of measuring the temperature of a molten metal, a ceramic tube which is closed at the end is used, in which a commercially available thermocouple is accommodated. The ceramic tube is immersed in the melt and a continuous temperature measurement is possible via the thermocouple. If the ceramic tube breaks, which occurs relatively often when measuring in a metallurgical plant, the thermocouple is also destroyed.

Optical measurement methods have long played a major role in metallurgy and chemical engineering, including radiation thermometry in particular - often referred to as "pyrometry" in connection with high-temperature processes - and spectroscopic methods, especially emission photometry, atomic absorption spectroscopy and infrared spectroscopy. In the case of these optical methods, the actual measuring devices are relatively complicated and costly devices which must not be directly exposed to the high temperatures of the hot liquids to be examined and which must therefore be arranged some distance away from them. Care must be taken to ensure that the radiation of the liquid (melt) used for parameter determination or analysis reaches the optical input of the measuring or analysis device as unadulterated as possible.

In order to avoid falsification by the surrounding atmosphere or parts of the system, the use of an observation tube in contact with the hot liquid has proven itself which - at the necessary distance from the liquid - the measuring device is also arranged.

From US-A-3, 747, 408 a temperature measuring arrangement for use in a converter for steel production is known, in which a tube is provided in the nozzle bottom of the converter, in which on the one hand a two-color radiation pyrometer and on the other hand with a plasma gun connected gas generating device is housed. About this tube is heated by the plasma gun with a temperature of about 1000 ° C at the

Radiation pyrometers are blown past at high pressure into the molten steel, thereby opening up a sufficient observation area for the pyrometer in which the melt temperature can be detected.

This arrangement is complex and costly both in manufacture and in operation and must also be taken into account from the outset when designing the converter, and cannot therefore be easily retrofitted.

EP-B-0 160 359 discloses a pyrometer arrangement for continuously measuring the temperature of the melt in metallurgical plants via nozzle arrangements there. In this case, a periscope arrangement with a glass fiber cable is inserted into the nozzle body, the light inlet opening of which is aligned with the longitudinal axis of the nozzle opening and can thus collect the radiation of the metallic melt directed through the nozzle. The radiation is then fed to a fiber-optic temperature sensor or two-color pyrometer. This arrangement does not require any structural modification of the metallurgical plant as extensive as the first one, but its use is restricted to plants in which corresponding nozzle bodies are provided. In the case of the known solutions mentioned, the measurement accuracy is also limited in that the radiation from the melt is detected directly in an injection region, in which it is naturally reduced by the cooling effect of the injected gas compared to the mean melt temperature.

The invention is therefore based on the object of specifying an improved arrangement of the generic type, which is particularly simple and inexpensive to manufacture and use, and yet should allow reliable measurements.

This object is achieved by an arrangement with the features of claim 1.

The invention includes the essential idea of a departure from the previously established fixed assignment of an optical measuring or analysis device to air inlet openings of a metallurgical plant, especially to the nozzle bottom of a converter. It also includes the idea that an observation tube is not below or to the side of the hot liquid (melt), ie. H. to be arranged in the wall of the melting tank or the reaction vessel, but to immerse it in the liquid level. With this positioning, the use of the arrangement is not restricted to systems with certain structural requirements or complex modifications, but is possible with little effort in practically any metallurgical or chemical system.

Ultimately, a variant of the invention includes the idea of keeping the free end of the observation tube closed by a material with sufficient thermal conductivity, which assumes the temperature of the liquid to a good approximation. The measuring or analysis device then in turn scans the temperature of this heat transfer element. The slight deviation from the real temperature of the liquid can determined by calibration and taken into account in the output of the measurement result by a constant.

In an embodiment that can be retrofitted, the heat transfer element is designed as a thin plate with high thermal conductivity, in particular as a pressed or sintered ceramic plate. This ensures sufficient mechanical stability with a small thickness. Highly heat-conductive ceramics are preferably used as the material for the plate. In another embodiment, the tube is closed at the end from the outset.

In contrast to the open measuring tube arrangement, the closed end absolutely prevents the penetration of liquid (or foam or slag or the like) into the interior of the observation tube, so that the measuring arrangement is on the one hand extremely low-maintenance and on the other hand no additional technical measures to prevent it liquid intrusion must be taken.

In addition, since in particular a fire-resistant observation tube is used and therefore does not necessarily have to be measured in the area of a cooling gas stream, the actual mean temperature of the liquid is recorded and a fundamentally more reliable measurement result is provided than with known arrangements.

In a practically particularly important embodiment, the measuring or analysis device has a temperature measuring device, which is designed in particular as an IR (infrared) radiation pyrometer. Such temperature measuring devices are known as such, and a special embodiment is also described in EP-B-0 160 359, so that a detailed description of the actual measuring device is not necessary here. In a further important embodiment, the measuring or analysis device has a photometric or spectroscopic analysis device for qualitative and / or quantitative chemical analysis of the liquid (melt). The term “liquid” is also intended to refer to individual layers of a liquid bath, for example a slag layer on a molten steel. It is therefore also possible within the scope of the invention to immerse the observation tube only into such a slag layer and thus physical parameters or in particular It is also within the scope of the invention to use the proposed arrangement in chemical reaction vessels with a fluid content, for example in a reactor for calcium carbide production or in reactors in which there are hot, pseudofluidic beds of granular material Especially in such applications, the use of a spectroscopic - for example laser spectroscopic - analysis device is of high process value.

The term "liquid" is also intended to refer to individual layers of a liquid bath, for example a slag layer on a molten steel. It is therefore also possible within the scope of the invention to immerse the observation tube only into such a slag layer and thus to record physical parameters or in particular the chemical composition of this slag layer. It is also within the scope of the invention to use the proposed arrangement in chemical reaction vessels with a fluid content, for example in a reactor for calcium carbide production or in reactors in which there are hot, pseudofluidic beds of granular material.

For most important applications, especially the use in molten metals, there is a ceramic observation tube expedient. In the context of the invention, this includes tubes made of silicate ceramic, oxide ceramic or non-oxide ceramic, for example made of silicon or boron carbide or graphite. The observation tube must have adequate mechanical stability. However, the use of complex special manufacturing processes, such as isostatic pressing, can be dispensed with.

In an advantageous embodiment, the imaging device provided in the observation tube or at its end remote from the hot liquid has an optical fiber arrangement. Because of the short length and the low demands on the optical transmission material, this can be a cost-effective implementation, as is available for industrial measurement technology; however, it is important to ensure that the temperature resistance is adequate and appropriate for the specific application.

Particularly when the imaging device is designed as a light guide arrangement, the additional provision of a gas supply device for purging the observation tube with gas, in particular inert gas (e.g. argon), for cooling the imaging device is expedient.

Such a gas supply device can also be useful in connection with another embodiment of the imaging device, namely with a deflecting mirror arrangement, although such a mirror arrangement is less temperature sensitive than a glass fiber arrangement. This is because it also leads to the evacuation of gases escaping from the pipe wall and interfering with the measurement.

A special, controllable version of the gas purging of the observation tube is especially for the use of the proposed arrangement with an open tube in metal melts on which there is a slag layer - for example in steel melts of particular advantage. After immersion of the observation tube into the melt from above, it enables the interior of the observation tube to be "blown free", that is to say, to push out the slag / molten metal mixture contained therein. After the pressure has subsequently been lowered, the end of the Observation tube up to a level determined by the residual pressure with the metal melt again - but now without a slag layer, which makes it possible to measure the actual melt temperature even in slag-containing metal melts.

This process is expediently repeated at certain time intervals during operation, so that the measuring tube is filled with fresh material, in particular fresh melt.

Another possibility for designing the observation tube for this application is to provide the observation tube with a closure element or a protective cap for the immersion process, which is either destroyed with a certain time delay by the immersion or subsequently removed. This also makes it possible to keep the observation tube free of slag, since after the cap has been destroyed or removed, pure metal melt penetrates into the tube end.

From the above comments it already follows that the arrangement is expediently provided with a height adjustment device for lowering or raising the observation tube (or the whole

Measuring arrangement, if this is firmly connected to the observation tube).

Advantages and expediencies of the invention result from the subclaims and the following Description of preferred exemplary embodiments using the figures. Of these show:

1 is a schematic cross-sectional representation of a first embodiment,

FIG. 2 shows a cross-sectional illustration of a second embodiment analogous to FIG. 1, FIGS. 3a-3c show sketch-like cross-sectional illustrations for

Explanation of a special training according to a third embodiment;

Fig. 4 is a schematic cross-sectional view of a fourth embodiment.

In Fig. 1, a temperature measuring arrangement 1 for detecting the surface temperature of a metal melt 3 contained in a melting tank 2 is shown in a sketch-like manner. The temperature measuring arrangement 1 comprises a sintered ceramic observation tube 4 which plunges vertically into the molten metal 3 from the surface and which is positioned horizontally by means of an angle piece 5 in which a 90 ° deflection mirror 6 is held

Support tube 7 (also made of ceramic or metal) is connected, at the end of which a measuring device chamber 8 is flanged, which receives an IR radiation pyrometer 9. An evaluation and display unit 10 is connected to the IR radiation pyrometer 9.

The infrared radiation emanating from the surface of the hot molten metal 3 reaches the deflecting mirror 6, shielded by the observation tube 4 from disturbing ambient radiation, and is deflected by the latter to the entrance optics of the IR radiation pyrometer 9 arranged away from the molten metal at normal working temperature. There, after passing through an entrance window and an objective (which are not shown separately), the radiation is analyzed in a manner known per se, for example by comparing the radiation intensity at two predetermined wavelengths, and from the Analysis result obtained a temperature value displayed on the evaluation and display unit 10.

FIG. 2 shows a modified temperature measuring arrangement 1 'which largely has the same structure as the temperature measuring arrangement 1 according to FIG. 1 and in which corresponding components are therefore designated with the same reference number as in FIGS. 1 and 4 and are not described again .

Instead of the deflecting mirror 6, a light guide cable 6 'is provided as the imaging device, the entry surface of which is centered on the end of the observation tube 4 facing away from the molten metal 3 and the opposite end of which is slightly different from an entry optic (compared to the embodiment according to FIG modified) IR radiation pyrometer 9 'is connected. Furthermore, a modified support tube 1 'is used, which is connected to an inert gas source (for example a nitrogen or argon bottle) 11 via a gas inlet connection (not shown separately) via a controllable valve 12.

In this arrangement, the IR radiation reaches the entrance pupil of the optical fiber cable 6 'from the surface of the molten metal 3 and is transmitted to the IR radiation pyrometer 9' practically without loss. Nitrogen or argon is blown into the support tube 7 from the nitrogen or argon bottle 11 to cool the glass fiber cable via the controllable valve 12. This can escape again through openings in the area of the elbow 5 or the upper part of the ceramic tube 4 facing away from the melt after it has fulfilled its task of cooling the optical fiber cable.

In a further development of this embodiment it is provided that the nitrogen or argon pressure can be increased via the controllable valve 12 to such an extent that the pressure in the lower end of the ceramic Mikrohrs 4 standing liquid is completely pushed out of the ceramic tube. As already mentioned briefly above, this version is particularly suitable for determining the temperature of molten metals on which a layer of slag is floating. By subjecting the ceramic tube 4 to high nitrogen pressure, the melt containing slag after immersion in the ceramic tube is pressed out of it, and the slag constituents float outside the ceramic tube to the surface of the melt. If the nitrogen pressure is then lowered again via the controllable valve 12, only pure metal melt flows into the end of the ceramic tube 4, so that unadulterated radiation reaches the light guide cable 6 'and finally the IR radiation pyrometer 9' from the metal melt.

It goes without saying that the design of the support tube with gas supply is also possible in the variant outlined in FIG. 1 with a deflecting mirror arrangement.

Another possibility is sketched in FIGS. 3a-3c, how an unadulterated measurement of a physical quantity or analysis of the chemical composition of a liquid bath (for example a molten metal) can also be achieved if there is an impurity layer (for example slag) on the surface thereof. 1 and 2 are also the same here

Parts again with the same reference numbers as there.

In this modified temperature measuring arrangement 1 ″, a closure cap 13 made of a material is attached to the lower end of the ceramic observation tube 4, which cap is destroyed with a certain time delay when immersed in the melt 3, for example a metal with a melting point just below that Temperature of the melt. There is a slag layer 3a on the molten metal 3. When lowering the observation tube by means of a lowering device 14, the sealing cap penetrates the slag layer and penetrates into the molten metal 3 and is subsequently destroyed (for example by melting). At this time, since the lower end of the observation tube 4 is below the lower edge of the slag layer 3a in the area of the molten metal 3, molten metal then flows into the ceramic tube 4, so that its interior (as in the case above with reference) solution described in FIG. 2) is free of slags. If a temperature measurement is then carried out via the observation tube 4, this correctly gives the desired measured value of the temperature of the molten metal 3.

4 shows a further temperature measuring arrangement 1 ″ ″ for detecting the surface temperature of the metal melt 3 contained in the melting tank 2. The temperature measuring arrangement 1 '' 'comprises a cast ceramic observation tube 4' '' which plunges vertically into the molten metal 3 from the surface and which (analogous to the arrangement according to FIG. 1) via the angle piece 5 in which the 90 ° deflection mirror 6 is held , is connected to the horizontally positioned support tube 7 (also made of ceramic or metal). At its end facing away from the observation tube 4, the measuring device chamber 8 is flanged, which receives the IR radiation pyrometer 9. The evaluation and display unit 10 is connected to the IR radiation pyrometer 9.

The end of the sintered ceramic observation tube 4 '' 'protruding into the molten metal 3 is tightly sealed by a thin pressed ceramic plate 4a with high thermal conductivity.

The metal melt transfers its heat almost without inertia to the thin (and therefore low heat capacity) ceramic plate 4a, and the infrared radiation emanating from it passes through the observation tube 4 '''shielded from disturbing ambient radiation, to the deflecting mirror 6. It is deflected by the latter to the entrance optics of the IR radiation pyrometer 9 arranged at a normal working temperature away from the molten metal and evaluated there in a manner known per se.

In the case of a modified temperature measuring arrangement, the ceramic tube is cast with the closed end, so that the ceramic plate does not have to be closed to close it.

The implementation of the invention is not limited to the examples described above, but is also possible in a variety of modifications that are within the scope of specialist trade.

B e z u g s z e i c h e n l i s t e

; 1'; 1 V "temperature measuring arrangement

Melting furnace

Molten metal a slag layer; 4 '"ceramic observation tube aa ceramic plate

Elbow

6 90 "deflecting mirror

6 'fiber optic cable; 7 'support tube 8 8 measuring device chamber

9; ^' 9' IR radiation pyrometer

10 evaluation and display unit

11 inert gas source (nitrogen bottle;

12 controllable valve 1 133 sealing cap

14 lowering device

Claims

Expectations

1. Arrangement (1; 1 '; 1' '; 1' '') for determining a physical quantity, in particular the temperature, and / or for the chemical analysis of a hot liquid (3), in particular a molten steel and / or slag (3a), optically, with an observation tube (4) that contacts the hot liquid, in particular a refractory tube, an imaging device (6; 6 ') arranged in the viewing tube or at its end and one measuring or measuring device optically assigned to the imaging device. Analysis device (9; 9 '), characterized in that the observation tube (4; A' '') is arranged freely above the liquid level and from there is immersed in the liquid (3) and in particular is closed at its free end.

2. Arrangement according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the observation tube is a closed end molded

Is ceramic tube.

3. Arrangement according to claim 1, characterized in that the observation tube (4 ''') carries at its free end a tightly placed heat transfer element (4a).

4. Arrangement according to claim 3, so that the heat transfer element is designed as a thin plate (4a) with high thermal conductivity, in particular as a pressed or cast ceramic plate.

5. Arrangement according to one of the preceding claims, that the measuring or analysis device has a temperature measuring device which is in particular designed as an IR radiation pyro meter (9).

6. Arrangement according to one of the preceding claims d a d u r c h g e k e n n z e i c h n e t that the measuring or analysis device has a photometric or spectroscopic analysis device.

7. Arrangement according to one of the preceding claims, that the imaging device has a light guide arrangement (6 ') or a deflecting mirror arrangement (6).

8. Arrangement according to one of the preceding claims, that the observation tube is assigned a gas supply device (11, 12) for purging with a gas, in particular inert gas, for cooling the imaging device (6 ') and / or for cleaning foreign substances.

9. Arrangement according to one of the preceding claims, g e k e n n z e i c h n e t d u r c h a height adjustment device for controlled lowering and raising of the observation tube (4).