Title of Invention | LOW COST SLAG DETECTION SYSTEM FOR MEASURING SLAG CARRY OVER TO THE MOLTEN STEEL DURING TAPPING |
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Abstract | The present invention relates to a low cost slag detection system for measuring slag carries over to the molten steel during tapping comprising a direct vision spectroscope (8) enclosed in a CCD camera (7) by which images from light source (4) are captured and processed through hardware card interface routines, a host PC (5) which generates intensity patterns of spectrum of steel and slag generated by said direct vision spectroscope, the classification of intensity distribution for steel and slag being carried out by the detection system via interfacing with the host PC (5) characterized in that the system can differentiate slag from steel during hot metal tapping from BOF and the identification is done in the visible region of the spectrum. |
Full Text | Field of Invention: The present invention relates to a development of low cost slag detection system during tapping to avoid slag carry over to the molten steel during tapping in steel manufacturing processes specifically in converter processes. Background of the invention: During primary refining in the BOF/EAF (Basic Oxygen Furnace/Electric ARC Furnace) converter, additions are made to form a slag to remove impurities such as sulphur and phosphorus from the steel. During converter tapping, in addition to the crude steel some converter slag is carried over into the steel-making ladle and impurities from the slag revert to the steel in the ladle. Thus me slag carried over into the ladle during tapping produce a negative influence on the quality of the melt. Iron oxide contained in the slag makes de-oxidation of the steel difficult and cause re-phosphorisation of the steel. The increasing demand for high quality standards, increased yield and higher production in steel making has necessitated the development of products and systems to provide a competitive advantage to steel business. For production of higher steel grades, secondary metallurgy is higher and growth in this area calls for more reliable methods avoiding slag carry over during tapping. It is in this area of development that slag-containing impurities from primary refining of steel should be desirably kept at Zero level of carry over to the steel in the ladle as variable levels of carryover slag cause undesirable variation in the ladle top slag composition which necessitates control of both the consistency and level of slag cany over. Presence of excess converter slag in ladle could raise the following problems: • Lower recoveries of alloys and conditioners (and thus increased alloying costs) as additions are hindered by presence of a slag layer. • Higher levels of FeO and MuO (slag constituents) result in high Oxygen content of steel leading to increased processing time and treatment costs. • Phosphorus and silicon reversal occurs. • Ladle desulpherization is hamped • High inclusion formation, • Increased risk of caster nozzle clogging. • High wear of Ladle refractory. • Increased consumption of Aluminium. • Lower yield To meet these disadvantages of slag carry over to the steel the present invention has proposed to develop a system to minimize the outflow of converter slag into a ladle and during hot metal transfer and thereby maximize the amount of steel removed from the vessel during further treatment thereby improving the quality of the steel and ensuring efficient process treatments of steel. A prior art patent CN1426146 discloses an invention "Signal transmission cable connector of slag detection system", the abstract of which recites that this invention discloses a slag detection system signal transmission cable connecting device including wire clipping components composed of clipping slots latches and quick connector base seat at right/left sides of a box. A T-shape clipping latch mounted in the clipping slot to fasten metal sheathed wire transducer wire at the left of the box, a wire connecting screw insulation base on the box bottom with four sets of screws, each two sets of which is connected with conducting plates and dust proof cover mounted outside of the quick connector base at the right of the box with the advantages of high stability of fine anti-mechanical, electric interface and small volume. Another prior patent GB1509746 discloses an invention entitled "Slag-metal interface detection system with a bottom pouring ladle", the abstract of which recites that a bottom pouring ladle 1 having a pair of axially aliened trunions 2 for suspending the ladle in a normally vertical position has a slag metal interface detector consisting of a pair of probes 13, 14 mounted in the wall of the ladle in the vertical plane passing through the trunions. The probes are connected by plug and socket connections to a circuit adapted to indicate when the metal surface lies between the two probes, this indication being unaffected by small angles of tilt. The cited prior specification discloses the inventions which is a direct method for slag detection in liquid steel. The present invention proposes a system development for detection of slag carry over in liquid steel while tapping from BOF vessel to ladle in an indirect method. In the past it was a common practice in the steel melting ships to visually detect slag carry over during tapping. Towards the end of tapping, experienced workers observe the stream and subjectively determine the time when the converter vessel is to be titled back to its upright position. Due to different experience personal skills of the melting personnel, the slag carried over always varies. To overcome these problems presently different methods were applied like ball and dart arrangement, electromagnetic coils etc. Presently all over the world the most favored way to detect slag carry over during hot metal tapping is using Thermal Imaging Camera. This concept is based on the existence of difference between the emissivities of hot metal (steel) and slag at higher wavelengths. The detection is possible only in the Infrared region. The system uses an Infrared (IR) camera that captures the thermal image of the hot metal stream and calculates the slag percentage. The same system is in use in four BOF vessels of Tata Steel. The system uses a long wave Infrared camera (7-14 micron), Image grabber card, Special Processing unit, and related accessories. One of the main disadvantages associated with this system is the high cost. It takes generally two years to recover the cost of investment. Another disadvantage associated with this system is the non-availability and maintainability of the hardware, specially me Infrared camera. As the infrared (IR) cameras are considered sensitive for defense applications it requires special Government sanctions to procure such cameras. Again whenever the camera stops functioning it has to be sent to OEM (Original Equipment Manufacturer) for repair as the camera is a proprietary item and can be repaired by OEM only. According to the main objective of the present invention it is proposed a system to differentiate slag from steel during hot metal tapping from BOF vessel to ladle in die visible region of the spectrum. According to another objective of the present invention it is proposed an automated assessment and decision making system based on a spectral imaging principle which will be of very low cost, in-house maintainable, and operator friendly. According to a further objective of the present invention there is proposed a low cost area scan CCD camera based system to view the spectrum. According to a still further objective of the invention it is proposed to generate intensity distribution pattern for slag and steel and identify slag phase by providing a system units for spectrum generation, image capturing and processing, camera enclosure with water cooler and system cabling and accessories. DESCRIPTION FO THE INVENTION: Spectroscopy is the use of absorption, emission or scattering of electromagnetic radiations by atoms or molecules (or atomic or molecular ions) to qualitatively or quantitatively study the atoms or molecules, or to study physical processes. The present invention in this case depends on spectroscopy. In this process atoms or molecules excited to high energy levels, decay to lower levels by emitting radiation (emission or luminescence). For atoms excited by a high temperature energy source, this light emission is commonly called atomic or optical emission. When a matter is being heated (or excited) to 1700 Degree Celsius it luminescence's in the visible range. The spectrum so generated varies characteristically for materials of different atomic composition. Though the composition of steel is grade dependent but mainly the constituents of steel are Carbon, Manganese, Phosphorus, Sulphur, Silica, Nickel, and Chromium While steel slag mainly comprises of oxides of different materials like Ca0, Si02, Fe0, Mn0, Mg0, Al203, P205, Sulphur and Metallic Fe. Thus steel and slag generate different spectra when heated to about 1700°C. The crux of the system development lies in to register the spectral constituents of incoming light onto a normal CCD (charged coupled device) plane with the help of a direct view spectroscope and men to determine the presence of the slag by its specific signature. The system operates as a computer assisted visual decision system, using efficient Image Processing techniques. High-resolution areas scan CCD camera captures the spectrum generated by the direct vision spectroscope and behaves like intelligent eyes of the system. The captured images are sent to the computers in the control room for fiirther processing. The processing is done with Image Processing Hardware and by supporting software. The software generates an array of pixel intensities along a line within the image of the spectrum. The intensity distribution of the spectrum generated by the steel and slag are different By using the thermal imaging based system as reference, classification was done for the intensity pattern of steel as well as slag. Different classification algorithms were tried like Support Vector Machines (SVM), K-Nearest Neighbors (KNN) etc and most suitable one was found to be K Nearest Neighbors. After the classification, when this algorithm is used to test the real and mixed data pattern of steel and slag, the test accuracy was found to be 96% repeatedly. The algoritlim testing was done using MATLAB. 1MAGE CAPTURING AND PROCESSING The image Processing System consists of the following: 1. High- resolution area scan camera with environmental enclosure installed just below the tapping pulpit. 2. High-speed frame grabber and Image processing card (PCVision) for real-time processing. 3. High-End PC. 4. Sophisticated software, coded in Microsoft Visual C++ Ver. 6.0, using specific Image processing routine of MVTOOLS ver. 6.0 and HEX routine for card interface. Mvtools is a set of C type routines for building short and elegant yet reasonably complex code in fewer liues. And 1TEX library is adopted for accessing the PCVision frame grabber card functions. The library consists of routines for image grabbing and acquisition. 5. The algorithm for classification and testing was done on MATLAB. Each data is a vector of length 720. Through PCA (Principle Component Analysis) me dimensionality is reduced to 10. Training set consisting of 1200 samples of steel spectrums and 373 samples of slag (steel + slag) spectrums are recorded. The first test set consisting of 580 samples of steel spectrum and 300 samples of slag (steel + slag) spectrums are computed from the training set. The same kinds of tests were carried out for different set of samples. CAMERA ENCLOSURE: The camera assembly is specially designed and packaged to face the harsh plant conditions, and has protective enclosure for dust. The camera and the direct vision spectroscope are mounted inside the enclosure, equipped with air- cooling. The complete enclosure assembly is mounted on a rigid structure below the tapping pulpit. According to the invention there is provided a low cost slag detection system for measuring slag carry over to the molten steel during tapping comprising a direct vision spectroscope enclosed in a CCD camera by which images are captured and processed through hardware card interface routines consisting of MVTools and ITEX, a host PC, the ITEX routine being adopted for accessing the PC vision card functions, the whole system being supported by a software to generate intensity patterns of spectrum generated by the direct vision spectroscope of steel and slag, the classification of intensity distribution for steel and slag being measured through a algorithm MATLAB with set of rules specifying a sequence of actions carried out by the detection system via interfacing with the PC to identify slag phase in the molten steel during tapping. DETAIL DESCRIPTION OF THE ACCOMPANYING DRAWINGS The nature of the invention, its objective and further advantages residing in the same will be apparent from the following description made with reference to non-limiting exemplary embodiments of the invention represented in the accompanying drawing, in which: Fig.1 : represents a schematic diagram of the Slag Detection System. Fig.2 : represents a schematic diagram of the Direct Vision Spectroscope. Fig.3 : represents a flow chart of slag detection via software. Fig 4: represents the graphical representation of the experimental results on MATLAB for support vector machines method In Fig 1 spectrum is generated of the tapping stream (4) by direct vision spectroscope (8) enclosed in a camera (7) through a software (1) developed for this purpose. The spectrum is pointed directly at a light source (4). The captured images in a high resolution area scan CCD camera are sent to a PC vision (2) for further processing of the said captured images through image processing hardware interface such as ITEX interline transfer and supporting software (1). The software generates an array of pixel intensities along a line within the image of the spectrum. Classification of intensity distribution of metal and slag are carried through different classification algorithms such as SVM, (Support Vector Machines) KNN (K- Nearest Neighbors) and MVT tools (9). Algorithm testiqg is carried through MATLAB (3). The Host PC (5) save records of the image processing classification and generates report and display through the in home built hardwares (6 and 9) and software (1). The test accuracy after the classification is found to be 96% repeatedly. In fig 2 the spectroscope is shown which is an hand held instrument consisting of a small tube (10) which is pointed at the light, which passes through a slit (11), a collimating lens (12), a prism train consisting of two crown glass prisms (13) and one flint glass prism (14) being cemented together, and exiting through a plain glass cover (15). The instrument consists of two concentrical cylinders (16 and 17). The collimator lens and prism assembly is mounted in the inner cylinder (17) and the slit is in the outer cylinder (16). The focus of the spectrum can be adjusted by moving these cylinders and sharpness of (lie spectrum is adjusted by varying me slit width (not shown). Fig 2 also shows the normal CCD plane (18) on which the spectral constituents of incoming light fall. Fig 3 in a flow chart illustrates the strategy used for detection of slag. Any error in captured images in PCVision (2) is corrected through resending the images in PCVision card and camera again. Train set of samples of sloel and slag spcctrurus are fontted through die software (1) coded in Microsoft visual f>+ vcr 6.0 (9) and UEX roulinet- (6) for card interface to form n File Maintained Phase which is transmitted to the re?:;j!tiric accumulated phase. Hie said phase is then classified and tested i>y MAT'lAls ('/?i to identify slag phase h ottt the linked dabi oisV-ru of steel and slag. Fig 4 the graphical representation of classification of intensify pattern of steel and mixed intensity pattern of steel and slag are shown. The said pattern is obtained through support vector machines (SVM) (9) by using thermal imaging based system as reference via support vector for first and second principle components. The graph generated through the image processing system clearly distinguish slag phase in the molten steel and the system of identification of slag phase thus enables to take precautionary measure to minimise the outflow of the converter slag into the ladle containing molten metal and thus enables to produce quality steel to maintain its physical characteristics as specified for various industrial applications. The invention as herein described and illustrated should not be read in a restrictive manner as various adaptations, modifications and changes are possible as encampused within die scope of appended claims: WE CLAIM 1. A low cost slag detection system for measuring slag carry over to the molten steel during tapping comprising a direct vision spectroscope (8) enclosed in a CCD camera (7) by which images from light source (4) are captured and processed through hardware card interface routines, a host PC (5) which generates intensity patterns of spectrum of steel and slag generated by said direct vision spectroscope, the classification of intensity distribution for steel and slag being carried out by the detection system via interfacing with the host PC (5), characterized in that the system can differentiate slag from steel during hot metal tapping from BOF and the identification is done in the visible region of the spectrum. 2. A detection system as claimed in claim 1, wherein an array of pixel intensities are generated along a line within the image of the spectrum and the host PC (5) records image processing classification and generates reports. 3. A detection system as claimed in claim 1, wherein each data of the pixel intensities along a line within the image of the spectrum formed is a vector of length 720. 4. A detection system as claimed in claim 1, wherein the said vector is dimensionally reduced to 10 through PCA. 5. A detection system as claimed in the proceeding claims wherein the record saving and report generation for intensity distribution for steel and slag are carried through the host PC (5) via graphical representation through first and second principle components of support vectors. 6. A detection system as claimed in the proceeding claims wherein the spectra] constituents of incoming light from the tapping stream (4) is registered onto a CCD plane with the help of a direct view spectroscope and then the presence of slag is determined by its specific characteristics. 7. A detection system as claimed in the proceeding claims wherein the high- resolution area scan camera (7) with protective enclosure mounted on a rigid structure is installed just below the tapping point 8. A detection system as claimed in claim 7 wherein the camera and the direct vision spectroscope are provided with air-cooling arrangement 9. A detection system as claimed in the proceeding claims wherein the low cost direct vision spectroscope (8) comprises of a small tube (10) consisting of two concentric cylinders (16 and 17) pointed at the light source (4) which passes through a slit (11), a collimating lens (12), a prism train consisting of two glass prisms (13) and one flint glass prism (14) and exiting through a plain glass cover (15). 10. A low cost slag detection system for measuring slag carry over to the molten steel during tapping as herein described and illustrated with reference to the accompanying drawings. The present invention relates to a low cost slag detection system for measuring slag carries over to the molten steel during tapping comprising a direct vision spectroscope (8) enclosed in a CCD camera (7) by which images from light source (4) are captured and processed through hardware card interface routines, a host PC (5) which generates intensity patterns of spectrum of steel and slag generated by said direct vision spectroscope, the classification of intensity distribution for steel and slag being carried out by the detection system via interfacing with the host PC (5) characterized in that the system can differentiate slag from steel during hot metal tapping from BOF and the identification is done in the visible region of the spectrum. |
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00480-kol-2006-correspondence others-1.1.pdf
00480-kol-2006.correspondece others.pdf
00480-kol-2006.description (complete).pdf
480-KOL-2006-CANCELLED DOCUMENT.pdf
480-kol-2006-correspondence.pdf
480-KOL-2006-DESCRIPTION COMPLETE.pdf
480-kol-2006-examination report.pdf
480-kol-2006-granted-abstract.pdf
480-kol-2006-granted-claims.pdf
480-kol-2006-granted-description (complete).pdf
480-kol-2006-granted-drawings.pdf
480-kol-2006-granted-form 1.pdf
480-kol-2006-granted-form 2.pdf
480-kol-2006-granted-specification.pdf
480-kol-2006-reply to examination report-1.1.pdf
480-KOL-2006-REPLY TO EXAMINATION REPORT.pdf
Patent Number | 246130 | |||||||||||||||
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Indian Patent Application Number | 480/KOL/2006 | |||||||||||||||
PG Journal Number | 07/2011 | |||||||||||||||
Publication Date | 18-Feb-2011 | |||||||||||||||
Grant Date | 15-Feb-2011 | |||||||||||||||
Date of Filing | 22-May-2006 | |||||||||||||||
Name of Patentee | TATA STEEL LIMITED | |||||||||||||||
Applicant Address | RESEARCH AND DEVELOPMENT AND SCIENTIFIC SERVICES DIVISION, JAMSHEDPUR 831 001, INDIA | |||||||||||||||
Inventors:
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PCT International Classification Number | B22D 2/00 | |||||||||||||||
PCT International Application Number | N/A | |||||||||||||||
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