Process for keeping a tuyere passing through a metallurgical vessel free of a skull

Abstract

The present invention relates to a process for keeping a tuyere passing through a metallurgical vessel free of a skull by intermittendly passing an oxygen-containing gas through the tuyere to dissolve the skull, wherein it is determined that an interval for passing said oxygen-containing gas through the tuyere needs to be started by detecting electromagnetic radiation emanating from a spot in the interior of the melt by means of a dual wavelength pyrometer and comparing the intensity of the pyrometer signals with the ratio of the pyrometer signals, and initiating said interval for passing said oxygen-containing gas through the tuyere, upon the condition that the combined intensity of the signals falls below a predetermined threshold value and that the ratio of the signals remains substantially constant.

1 . A method of keeping a tuyere passing through a metallurgical vessel free of a skull, the method comprising intermittently passing an oxygen-containing gas through the tuyere to dissolve the skull, wherein it is determined that an interval for passing said oxygen-containing gas through the tuyere needs to be started by detecting electromagnetic radiation emanating from a spot in the interior of the melt by means of a dual wavelength pyrometer and comparing the intensity of the pyrometer signals with the ratio of the pyrometer signals, and initiating said interval for passing said oxygen-containing gas through the tuyere, upon the condition that the combined intensity of the signals falls below a predetermined threshold value and that the ratio of the signals remains substantially constant.  
   
   
       2 . The method of  claim 1  wherein said threshold value is determined by using a video camera which is arranged with the pyrometer along one optical path and by setting into relation the intensity of the pyrometer signal with the image of the video camera, deciding on the basis of the video image whether a status of clogging is reached and determining the corresponding intensity value of the combined pyrometer signals.  
   
   
       3 . A method of measuring electromagnetic radiation emanating from the interior of a metallurgical vessel, the method comprising adjusting the optical axis of a measuring unit including a video detector and an instrument for measuring the electromagnetic radiation through a tuyere having a first end facing the interior of the metallurgical vessel and a second end facing the instrument, wherein said measuring unit is arranged along an optical path, and the adjustment is carried out on the basis of the video image by varying the orientation of the measuring unit such that the first end and second end in the video image form concentric circles.  
   
   
       4 . The method of  claim 3  wherein said instrument for measuring electromagnetic radiation is a pyrometer.  
   
   
       5 . The method of  claim 3  wherein said instrument for measuring electromagnetic radiation is a spectrometer.  
   
   
       6 . A method for measuring the length of a tuyere passing through a metallurgical vessel having a first end facing the interior of said metallurgical vessel and a second end facing the exterior of said metallurgical vessel by means of an autofocus video camera, wherein the lens system of the autofocus video camera is adjusted so that the first end of the tuyere facing the interior of said metallurgical vessel is in focus and the length of said tuyere is determined on the basis of the distance of the focus and the known position of said second end of the tuyere with respect to the camera.  
   
   
       7 . An apparatus for carrying out the method of  claim 1 , the apparatus comprising: 
 (a) a dual wavelength pyrometer,    (b) an autofocus video camera which is aligned with said dual wavelength pyrometer along one optical path, and    (c) means for varying the orientation of the optical path.    
   
   
       8 . The apparatus of  claim 7  further comprising a laser device suitable for creating a plasma in the interior of said metallurgical vessel, and wherein the further detector is a spectrometer capable of detecting electromagnetic radiation emanating from said plasma.  
   
   
       9 . The apparatus of  claim 7  which is connected to the interior of said metallurgical vessel by means of a tube which is passed through the tuyere.  
   
   
       10 . The apparatus of  claim 7 , further comprising: 
 (d) a further detector for measuring electromagnetic radiation emanating from the interior of the vessel.    
   
   
       11 . An apparatus for carrying out the method of  claim 3 , the apparatus comprising: 
 (a) a dual wavelength pyrometer,    (b) an autofocus video camera which is aligned with said dual wavelength pyrometer along one optical path, and    (c) means for varying the orientation of the optical path.    
   
   
       12 . The apparatus of  claim 11  further comprising a laser device suitable for creating a plasma in the interior of said metallurgical vessel, and wherein the further detector is a spectrometer capable of detecting electromagnetic radiation emanating from said plasma.  
   
   
       13 . The apparatus of  claim 11  which is connected to the interior of said metallurgical vessel by means of a tube which is passed through the tuyere.  
   
   
       14 . The apparatus of  claim 11 , further comprising: 
 (d) a further detector for measuring electromagnetic radiation emanating from the interior of the vessel.    
   
   
       15 . An apparatus for carrying out the method of  claim 6 , the apparatus comprising: 
 (a) a dual wavelength pyrometer,    (b) an autofocus video camera which is aligned with said dual wavelength pyrometer along one optical path, and    (c) means for varying the orientation of the optical path.    
   
   
       16 . The apparatus of  claim 15  further comprising a laser device suitable for creating a plasma in the interior of said metallurgical vessel, and wherein the further detector is a spectrometer capable of detecting electromagnetic radiation emanating from said plasma.  
   
   
       17 . The apparatus of  claim 15  which is connected to the interior of said metallurgical vessel by means of a tube which is passed through the tuyere.  
   
   
       18 . The apparatus of  claim 15 , further comprising: 
 (d) a further detector for measuring electromagnetic radiation emanating from the interior of the vessel.