Apparatus and method for measuring temperature of molten metal

• US 20040174922A1
• Filed: 01/27/2004
• Published: 09/09/2004
• Est. Priority Date: 07/27/2001
• Status: Active Grant

• Current Assignee: Nittetsu Plant Designing Corp. (Government of Japan), Nippon Steel Corporation
• Original Assignee: Nittetsu Plant Designing Corp. (Government of Japan), Nippon Steel Corporation
• Inventors: Tanaka, Tomoaki, Yamashita, Kosuke, Sumi, Makoto, Sugiura, Masato, Horikoshi, Kiyomi
• Granted Patent: US 6,923,573 B2
• Time in Patent Office: Days
• US Class Current: 374/131
• CPC Class Codes: C21C 2005/5288 Measuring or sampling devices
• CPC Class Codes: C21C 5/4673 Measuring and sampling devices
• CPC Class Codes: F27D 21/0014 Devices for monitoring temperature
• CPC Class Codes: F27D 21/02 Observation or illuminating devices
• CPC Class Codes: G01J 5/041 Mountings in enclosures or in a particular environment
• CPC Class Codes: G01K 1/125 for siderurgical use
• CPC Class Codes: Y02P 10/20 Recycling

Abstract

The invention provides a cooling system for protecting an image fiber and an imaging device from thermal influences and a temperature measurement apparatus, for a molten metal, capable of being easily controlled and stably measuring the temperature. The temperature measurement apparatus for a molten metal comprises four connectable portions of a nozzle portion a purge/cooling gas introduction portion, an image fiber fitting portion with a window glass and an image fiber to a double pipe nozzle protection tube. A distance from a nozzle distal end as an introduction portion of thermal radiation light to a light reception portion at an image fiber distal end becomes short so that a greater amount of thermal radiation light can be received.

Claims

1. An apparatus for measuring a temperature of a molten metal by disposing a nozzle penetrating through a wall of a vessel accommodating a molten metal, guiding out thermal irradiation light of the molten metal facing a distal end of said nozzle through an image fiber (image transfer fiber) and measuring the temperature of the molten metal from said thermal radiation light so guided out, wherein;

said nozzle has a double pipe structure, said thermal radiation light of the molten metal is observed while a purge gas is passed through an inner pipe and a protective cooling gas for protecting melting loss of said nozzle is passed through an outer pipe;

a construction of a fitting portion between said nozzle and said image fiber comprises four connectable portions of a nozzle portion, a purge/cooling gas introduction portion, an image fiber fitting portion with window glass and an image fiber protection tube;

at least one joint portion is disposed on said purge/cooling gas introduction portion so that centering of an optical axis can be made for connecting said thermal radiation light of the molten metal to said image fiber;

an imaging device such as a CCD camera for measuring the two-dimensional distribution of thermal radiation luminance is connected to a rear end of said image fiber; and

said imaging device is accommodated in a sealed box having a cooling structure and is disposed in the proximity of an outer wall of the vessel for accommodating the molten metal.

2. An apparatus for measuring a temperature of a molten metal as defined in claim 1, further including an AD conversion device for converting image signals generated by said CCD camera to digital signals, a computer, a nozzle gas control device and a camera control device, said personal computer having a function of computing the temperature of the molten metal from luminance of a high luminance region (molten metal image) on a screen, wherein:

said personal computer judges a hole open state at a distal end of said nozzle from the images and sends a signal indicating a gas kind or a gas flow rate to said nozzle gas control device.

3. An apparatus for measuring a temperature of a molten metal as defined in claim 2, wherein, when the temperature of the molten metal is computed from luminance of the high luminance region (molten metal image) on the screen inputted to said personal computer, the high luminance region (molten metal image) is extracted from inside a region designated in advance and the temperature of the molten metal is estimated from its luminance value.

4. An apparatus for measuring a temperature of a molten metal as defined in claim 1, wherein the temperature of a main body of said imaging device or an atmospheric temperature inside said sealed box is measured by a thermo-couple, or the like, and a flow rate and a pressure of a cooling gas or cooling water charged into said sealed box, for keeping the temperature below an allowable upper limit temperature of said imaging device, are controlled.

5. An apparatus for measuring a temperature of a molten metal as defined in claim 1, which has a triple structure of an inner pipe flexible hose for inserting and protecting an image fiber cable and an image fiber protective tube for inserting and protecting said inner pipe flexible hose, and has a structure such that a cooling/purge gas can be passed through said inner pipe flexible hose and through said image fiber protective tube, and when the cooling/purge gas is emitted outside, a portion at a distal end of the image fiber corresponding to a lens portion at the distal end of said image fiber can be cooled by said gas from outside.

6. An apparatus for measuring a temperature of a molten metal as defined in claim 1, wherein, in the fitting structure of said nozzle and said image fiber, said purge/cooling gas introduction portion and/or said image fiber fitting portion with a window glass has a water cooling structure.

7. An apparatus for measuring a temperature of a molten metal as defined in claim 5 or 6, wherein the temperature of an image fiber or its atmospheric temperature is measured by a thermo-coupled, etc, the flow rate or/and pressure of said purge/cooling gas or/and said cooling water are controlled for keeping the temperature below an allowable upper limit temperature of said image fiber and said lens.

8. An apparatus for measuring a temperature of a molten metal as defined in claim 2, wherein, when an area of a high luminance region (molten metal image) due to thermal radiation light on the image decreases and accuracy of the temperature of the molten metal converted from the luminance value gets deteriorated, a gas containing high concentration oxygen is blown from said nozzle and melts a base metal (solidified metal) formed at a distal end portion of said nozzle.

9. In a method for removing a base metal adhering to a distal end of a nozzle having a double pipe structure and dipped into a molten metal inside a refining furnace, a method for measuring a temperature of a molten metal involving the steps of;

bringing a refining furnace in operation into an empty furnace state;

flowing a hydrocarbon type gas, a liquid fuel or an inflammable gas either individually or in mixture of two of more kinds through a flow path in a space between an outer pipe and an inner pipe of a nozzle having a double pipe structure;

flowing a gas containing an oxygen gas adjusted to a concentration range in which the oxygen gas is combustible through the inner pipe of said nozzle;

melting and removing away a base metal adhering to a distal end of said nozzle while the refining furnace in operation is under the empty state; and

charging a molten metal into the refining furnace and measuring a temperature of the molten metal;

said method comprising the steps of;

taking thermal radiation light of the molten metal facing a distal end portion of said nozzle into an imaging device through an image fiber while an inert gas for preventing invasion of the molten metal into said nozzle is pressure-fed;

converting image signals outputted from said imaging device into digital image data;

executing a processing on the basis of the digital image data; and

measuring the temperature of the molten metal on an imaging screen.