Method and system for determining a temperature value of a molten metal bath

Abstract

The present invention relates to a method and a system for determining a temperature value of a molten metal bath. The method according to the invention has been proven to be especially suitable for installations of metallurgical vessels which are constantly moved during the metal making process.

Claims

1. A method for measuring the temperature of a molten metal bath in a furnace with a device comprising an optical cored wire and a detector, wherein the furnace has a furnace inclination, the method comprising: (a) providing a set of data relating furnace inclination values Fl to corresponding measurement profiles MP; (b) determining a furnace inclination value Fl(n) for a point in time t(n); (c) choosing a measurement profile MP(n) corresponding to the furnace inclination value Fl(n) from the provided set of data relating furnace inclination values Fl to corresponding measurement profiles MP; and (d) applying the measurement profile MP(n) at a point in time t(n) to obtain a measured temperature value.

2. The method according to claim 1, wherein a measurement profile MP defines at least a step of providing the leading tip of the optical cored wire at a first position p1 above the surface of the molten metal bath.

3. The method according to claim 1, wherein a measurement profile MP defines at least a step of feeding the leading tip of the optical cored wire from a first position p1 towards the molten metal bath to a second position p2.

4. The method according to claim 3, wherein the second position p2 is in an immersion depth il under the surface of the molten metal bath.

5. The method according to claim 1, wherein the set of data relating furnace inclination values Fl to corresponding measurement profiles MP relates the definition of at least one parameter in at least one step of a measurement profile MP to a furnace inclination value Fl.

6. The method according to claim 3, wherein the distance between the first position p1 and the second position p2 in the measurement profile MP(n) relates to the furnace inclination value Fl(n).

7. The method according to claim 3, wherein the distance between the first position p1 and the second position p2 is adapted by the same length for each degree of inclination of the furnace in a first direction and in a second direction from a predetermined initial position.

8. The method according to claim 3, wherein the distance between the first position p1 and the second position p2 is adapted by a first length for each degree of inclination of the furnace in a first direction and adapted by a second length for each degree of inclination of the furnace in a second direction from a predetermined initial position.

9. The method according to claim 3, wherein the distance between the first position p1 and the second position p2 is adapted by 2 cm to 20 cm for each degree of inclination of the furnace from a predetermined initial position.

10. The method according to claim 1, wherein the measurement profile MP defines at least a step within a stationary time period within two points in time t0 and t2, during which the feeding of the leading tip of the optical cored wire is paused with or the leading tip of the optical cored wire is fed with a low speed.

11. The method according to claim 1, wherein the measurement profile MP defines at least a step of obtaining temperature information within a measuring time period within two points in time t0 and t2.

12. The method according to claim 1, wherein the measurement profile MP defines at least one feeding velocity V.sub.fed with which the leading tip of the optical cored wire is fed to a second position p2 from a first position p1 towards the molten metal bath.

13. The method according to claim 1, wherein the set of data provided in step (a) further relates the level of the surface of the molten metal bath to the measurement profiles MP.

14. The method according to claim 1, wherein the set of data provided in step (a) further relates the position of the leading tip of the optical cored wire to the measurement profiles MP.

15. A system for determining a temperature value of a molten metal bath in a furnace in a method according to claim 1, the system comprising: a processing element P1 for determining the furnace inclination values Fl; a processing element P2 for choosing a measurement profile MP(n) corresponding to a furnace inclination Fl(n) from the provided set of data relating the furnace inclination values Fl to corresponding measurement profiles MP; and a controlling unit C comprising a controlling element C1 for applying the measurement profile MP(n) to obtain a measured temperature value.

16. The method according to claim 3, wherein the distance between the first position p1 and the second position p2 is adapted by 5 cm to 15 cm for each degree of inclination of the furnace from a predetermined initial position.

17. The method according to claim 3, wherein the distance between the first position p1 and the second position p2 is adapted by 8 cm to 12 cm for each degree of inclination of the furnace from a predetermined initial position.

Description

(1) The idea underlying the invention shall subsequently be described in more detail with respect to the embodiments shown in the figures. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. Herein:

(2) FIG. 1 shows schematic cross-sectional views of different designs of optical cored wires.

(3) FIG. 2 shows a schematic view of an exemplary installation with a molten metal bath, of which the temperature shall be determined.

(4) FIG. 3 shows a detailed schematic view of an electric arc furnace (EAF) with a typical installation to determine the temperature.

(5) FIG. 4 shows schematic views of an exemplary metallurgical vessel with different degrees of furnace inclination.

(6) FIG. 5 illustrates further exemplary vessel geometries in relation to the pivoting axis A.sub.P.

(7) FIG. 6 shows a position-time graph indicating the immersion of the leading tip of the optical cored wire during the application of a representative measurement profile.

(8) FIG. 7 shows a position-time graph indicating the immersion of the leading tip of the optical cored wire during the application of another representative measurement profile.

(9) FIG. 8 shows a schematic view of a system according to an embodiment of the invention.

(10) FIG. 9 shows a schematic view of a module according to an embodiment of the invention.

(11) FIG. 1 shows schematic cross-sectional views of different designs of optical cored wires in accordance with exemplary embodiment of the invention. FIG. 1A shows an optical cored wire 1 which comprises an optical fiber 2 surrounded by a metal tube 3.

(12) FIG. 1 B shows an optical cored wire 1 which comprises an optical fiber 2 surrounded by a metal tube 3. A second metal tube 4 additionally surrounds metal tube 3. The void space between the two metal tubes 5 is not filled with a solid material; i.e. the void space may comprise a gas or a gas mixture.

(13) FIG. 1 C shows an optical cored wire 1 which comprises an optical fiber 2 surrounded by a metal tube 3 and a second metal tube 4. The void space between the two metal tubes 5 is filled with a filler material, for example fibers from an organic material or e-glass.

(14) FIG. 2 shows a schematic view of an exemplary installation 6 with a molten metal bath 7, of which the temperature shall be determined.

(15) The installation 6 comprises an optical cored wire 1 which is located at least partly on a coil 8 and is at least in part unwound from the coil 8 for conducting a measurement. One end of the optical cored wire 9 is connected to a detector 10 which in turn could be connected to a computer system (not shown) to process the data obtained with the optical cored wire 1 and the detector 10.

(16) The molten metal bath 7 is contained in a vessel 11 which may be part of an electric arc furnace (EAF) or a converter known to those skilled in the art for the processing of molten metal. The optical cored wire 1 is led by moving means 12 through a guide tube 13 in the vessel 11 having an entry point 14. The moving means 12 comprises rollers for moving the optical cored wire 1 and may include a servo motor to drive at least one of the rollers. The shown configuration is used as an example, a lid 22 with a respective entry point 14 is not a pre-requisite for the present invention.

(17) The shown configuration illustrates an exemplary measurement position p2 of the optical cored wire 1 with the leading tip 15 immersed below the surface of the molten metal bath MB.sub.S. The angle of immersion of the optical cored wire 1 with respect to the surface of the molten metal bath MB.sub.S is 90 in the presented embodiment. However, the angle can vary depending on the construction details of the metallurgical facility.

(18) The temperature of a part of the optical cored wire 1 extending from the coil 8 to the entry point of the vessel 14 can be considered to be low, which could be a temperature ranging from room temperature up to 100 C. Once passing the entry point 14 in the direction of the molten metal bath 7, a hot atmosphere of up to 1700 C. or even higher is first encountered, followed by a slag layer 17 which is in turn followed by the molten metal bath 7. The entry point 14 to the vessel could be equipped with a blowing lance 18 to prevent metal and slag penetration into the guiding tube 13.

(19) The optimal level of the molten metal bath MB.sub.S may be approximately known for each metallurgical vessel by its design and mode of operation.

(20) To obtain a temperature measurement, the optical cored wire 1 is fed with its leading tip at the immersion end 15 towards the molten metal bath 7 to the required immersion depth at position p2. In order to obtain reliable temperature measurements, it may be desired to measure at a more or less fixed immersion depth in the molten metal bath. A suitable feeding system 12 will accurately control the feeding velocity of the optical cored wire 1.

(21) After a measurement sequence, the part of the optical cored wire immersed in the molten metal bath 19 will be molten and thereby consumed. The length of this part is indicated with L.sub.C. It is to be understood, that the length L.sub.C correlates to the immersion depth, to which the optical cored wire is fed. After the measurement is taken, the part of the optical cored wire 20 located in the hot atmosphere and extending through the slag layer can be fed back into the direction of the coil 8 and can be reused for the next measurement. The length L.sub.D correlates to the length of the optical cored wire, which has been located inside the vessel but has not been consumed during a measurement. The total length of the optical cored wire L.sub.T which has been fed into the metallurgical vessel is the sum of the length which has been consumed Land the length L.sub.D of the optical cored wire, which has been located inside the vessel.

(22) FIG. 3 shows a detailed schematic view of furnace 110, in particular an EAF, with a typical installation comprising an optical cored wire 1 for temperature measurements. An EAF used for steelmaking usually comprises a vessel 11 containing the molten metal bath 7, a removable lid 22 through which one or more electrodes 23 can enter the furnace and a platform 24 arranged on the side of the vessel 11. As shown in the view of the EAF, the body containing the molten metal bath 7 is not necessarily symmetrical to a central axis A.sub.P but can also be designed asymmetrical. The electrodes 23 employed to heat the metal are typically arranged above the vessel 11.

(23) The entry point 14 through which the optical cored wire 1 enters the vessel 11 is arranged on the platform 24 in the shown configuration. The immersion device comprising the moving means 12 is also arranged on the platform 24 (not shown for the sake of clarity). The configuration shown illustrates the vessel 11 in a representative neutral position; i.e. without a tilting.

(24) In such an EAF configuration in operation, i.e. with a load of metal which has been molten to a molten metal bath, the depth of the molten metal bath is in the range of 1 m and the distance from the entry point 14 to the surface of the molten metal bath in the range of 1-1.5 m. The typical inner diameter of such a vessel is between 6 m to 7 m, but larger installations with up to 9 m inner diameter are also common. The distance from the center of the EAF to the entry point 14, installed on a platform is in the range of 3 m-3.5 m. The numbers emphasize, that all Figures are not drawn to scale, but the items are shown in size ratios to clarify the circumstances leading to the present invention.

(25) FIG. 4 shows schematic views of an exemplary furnace 110 with a metallurgical vessel 11 with different degrees of furnace inclination. It may be understood that the elements and their proportions to each other are not drawn to scale, but to illustrate the invention in further detail. Typically, the tilting of the vessel is within the range of +3 to 3, the tilting of 10 as shown in the figure was chosen for better clarification.

(26) The optical cored wire 1 is guided into the vessel 11 through an entry point 14, which is located near a side wall of the vessel. The entry point 14 may also be at the same position as a first position p1, from which the feeding of the optical cored wire is initiated in exemplary measurement profiles. The position to which the leading tip of the optical cored wire is fed is marked with p2 in FIG. 4A, the marking was omitted in FIGS. 4 B and C for better clarity.

(27) FIGS. 4A-C illustrate the relationships between the surface of the molten metal bath MB.sub.S, a centered pivoting axis A.sub.P and a tilting axis A.sub.T the furnace inclination value is referred to and an horizontal plane P.sub.H which can also be used to define the furnace inclination value in different configurations of the vessel 11. Furthermore, the total length of the optical cored wire L.sub.T entering the vessel 11, being defined as the sum of the length L.sub.C of the optical cored wire immersed under the surface of the molten metal bath MB.sub.S and the length L.sub.D of the optical cored wire entering the vessel 11 but not being immersed under the surface of the molten metal bath MB.sub.S are shown for the different furnace configurations.

(28) FIG. 4A shows the vessel 11 in a representative neutral position, referring to a furnace inclination value of 0. The pivoting axis A.sub.P is configured perpendicular to the bottom of the vessel 11 and is aligned with the tilting axis A.sub.T. Both axes are perpendicular to a horizontal plane P.sub.H which is aligned with the bottom of the vessel 11.

(29) FIG. 4 B shows the vessel 11 in a position tilted to one side by 10. The furnace inclination value is defined by the angle between the pivoting axis A.sub.P and the tilting axis A.sub.T. Alternatively, the furnace inclination value can be defined by the angle between horizontal plane P.sub.H and the bottom of the vessel 11.

(30) FIG. 4 C shows the vessel 11 in a position tilted to the other side by 10, per definition the furnace inclination value has a negative mathematical sign.

(31) FIGS. 4A-C illustrate configurations, in which the total length of the optical cored wire L.sub.T entering the vessel 11 is constant. The tilting of the furnace influences the immersion depth of the leading tip of the optical cored wire 1, represented by the length L.sub.C of the optical cored wire immersed under the surface of the molten metal bath MB.sub.S. The object of the present invention was to take this varying immersion depth with the moving furnace 110 into consideration when conducting a temperature measurement.

(32) FIG. 5 illustrates further exemplary vessel geometries of metallurgical furnaces in relation to the pivoting axis A.sub.P. Additional parts are not shown for clarity. FIG. 5A shows a furnace 110 with a round-bottomed vessel 11 with the pivoting axis A.sub.P centrally arranged in neutral position. In FIG. 5 B, a furnace 110 with a non-symmetrical vessel 11 is shown. When the vessel 11 is tilted from the pivoting axis A.sub.P, the level of the molten metal bath MB.sub.S will move to a different extend relative to the entry point 14 when tilted to one side or the other side.

(33) FIG. 6 shows a position-time graph indicating the immersion of the leading tip of the optical cored wire during the application of an exemplary measurement profile. The x-axis shows the time, whereas the y-axis indicates the position of the leading tip. The position of the surface of the molten metal bath MB.sub.S is indicated for orientation. Prior to the start of a measurement; i.e. prior to t0, the leading tip is positioned at a starting point, referred to as first position p1. This may be inside the metallurgical vessel and proximate the entry point; i.e. close to the point where the optical cored wire enters the vessel. The optical cored wire is fed for a duration from to t2 with a feeding velocity towards and into the molten metal bath to a second position p2. This duration is typically in the range of seconds. The leading tip of the optical cored wire enters the molten metal bath at a point in time t1, i.e. t1 is the point in time from which the leading tip is immersed below the surface of the molten metal bath. In the shown graph, a single feeding velocity is applied, but the feeding may comprise several phases with different feeding velocities. Even a phase without feeding; i.e. a stationary phase, can be included during the conduction of a measurement as indicated in the graph shown in FIG. 7, representing another preferred embodiment. The temperature measurement is obtained during a measurement time period during t1 to t2. The leading tip has to be immersed under the surface of the molten metal bath to obtain reliable measurements. It has been found, that providing the leading tip in a constant immersion depth at this point allows obtaining the most accurate results. Temperature values obtained in an early phase of the feeding may often be not representative for the bulk temperature of the molten metal bath. After t2, the optical cored wire is retracted from the molten metal bath back to a position above the surface. Ideally, the part of the optical cored wire immersed under the surface of the molten metal bath L.sub.C is consumed until t2.

(34) For the given reasons, it is advantageous that the parameters of the feeding scheme are adjusted to the physical configuration of the metallurgical vessel which influence the relationship of the surface level of the molten metal bath and the positions of the leading tip of the optical cored wire from which a measurement sequence is initiated and to which it is fed when to obtain a measurement.

(35) Applying the method according to the present invention will furthermore minimize the amount of optical cored wire which is consumed during a measurement sequence, since the immersion depth can be chosen in such a way, that only the minimal amount of optical cored wire is immersed under the surface of the molten metal bath and therefore consumed.

(36) It has been observed that different parameters applied to obtain a temperature value during the application of a measurement profile deliver varying measurement qualities. The measurement quality of a measurement profile refers to different measurement accuracies compared to measurement values obtained by using a stationary installed standard thermocouple. The idea underlying the present invention is an adaption of the specific measurement profile to the circumstances present inside a metallurgical vessel at the point in time during which a measurement is taken.

(37) FIG. 8 shows a schematic view of a system 30 according to an embodiment of the invention. The system 30 is configured to perform the method according to the invention. In particular, it is configured to provide a set of data, relating data for the furnace inclination with measurement profiles which deliver optimal measurement qualities for the respective configuration of the furnace. The system 30 is further configured to determine the configuration, i.e. the inclination value of the furnace. Additionally, the system 30 is configured to choose a measurement profile from the provided set of data. Furthermore, the system 30 is configured to apply this measurement profile and obtain a temperature.

(38) The system comprises a device 40, wherein the device 40 comprises an optical cored wire and a detector. Furthermore, the system comprises a module 50. Device 40 and module 50 are adapted to interact with each other; i.e. the module is configured to carry out the method according to the invention with the device 40, resulting in the measurement of temperature values of a molten metal bath.

(39) FIG. 9 shows a schematic of the module 50 in more detail. The module 50 comprises a storage unit S, a processing unit P and a controlling unit C.

LIST OF REFERENCE NUMERALS

(40) 1, 1, 1, 1 Optical cored wire 2, 2, 2 Optical fiber 3, 3, 3 Metal tube 4, 4 Second metal tube 5, 5 Void space between metal tubes 6 Installation 7 Molten metal bath 8 Coil 9 Opposite end (end of cored wire connected to detector) 10 Detector 110, 110, 110, 110 Furnace 11, 11, 11 Vessel; metallurgical container 12 Moving Means 13 Guide tube 14 Entry point 15 Leading tip of optical cored wire MB.sub.S Surface of molten metal bath 17 Slag layer 18 Blowing lance 19 Part of the cored wire immersed in the molten metal bath Part of cored wire subjected to hot atmosphere and slag 22 Removable Lid 23 Electrodes 24 Platform 30 System 40 Device 50 Module S Storage unit P Processing unit C Controlling unit L.sub.C Length of optical cored wire immersed in the molten metal bath L.sub.D Length of optical cored wire located inside the vessel L.sub.T Total length of optical cored wire fed into the vessel p1 Initial position of the leading tip of the optical cored wire p2 Position to which the leading tip of optical cored wire is fed to under surface of molten metal bath A.sub.P Pivoting axis A.sub.T Tilting axis P.sub.H Horizontal Plane