Method for observing inside of molten iron refining furnace and tuyere for observing inside of furnace

Abstract

It is possible to stably observe the temperature and/or composition of molten iron in a refining furnace by opening a tuyere for observation at all times according to the state of refining. There is provided a method of observing the inside of a molten metal refining furnace comprising the steps of: using a single tube tuyere for observing the temperature and/or composition of molten iron in the refining furnace via a tube penetrating refractories of a furnace wall and/or furnace bottom of the molten iron refining furnace by detecting electromagnetic waves radiated from molten metal at a forward end of the tuyere under a non-contact condition; and using an inert gas or an oxidizing gas, alone or mixed, according to the opening condition of the forward end of the tuyere.

What is claimed is:  
     
         1 . A method of observing the inside of a molten metal refining furnace comprising the steps of: using a single tube tuyere for observing the temperature and/or composition of molten iron in the refining furnace via a tube penetrating refractories of a furnace wall and/or furnace bottom of the molten iron refining furnace by detecting electromagnetic waves radiated from molten metal at a forward end of the tube under a non-contact state; and using an inert gas or an oxidizing gas alone or mixed with each other according to the opening condition of the forward end of the tube.  
     
     
         2 . A method of observing the inside of a molten metal refining furnace according to  claim 1 , wherein a mixed gas of an inert gas with an oxidizing gas or only an oxidizing gas is supplied in the case where the ratio (%) of opening of the tube is not higher than α which is calculated by the inner diameter r (mm) of the tube according to Equation (1), and only inert gas is supplied in the case where the ratio of opening is higher than α.  
       α=765/ r   2   (1)  
     
     
         3 . A method of observing the inside of a molten metal refining furnace comprising the steps of: using a single tube tuyere for observing the temperature and/or composition of molten iron in the refining furnace via a tube penetrating refractories of a furnace wall and/or furnace bottom of the molten iron refining furnace by detecting electromagnetic waves radiated from molten metal at a forward end of the tube under a non-contact state; and controlling a flow rate of an inert gas according to the opening condition of the forward end of the tube.  
     
     
         4 . A method of observing the inside of a molten metal refining furnace according to  claim 3 , wherein a flow rate of inert gas is controlled according to the temperature and composition of molten iron so that the ratio (%) of opening of the single tube can be not less than α, which is calculated from the inner diameter r (mm) of the tube according to Equation (1), and not more than 95%.  
     
     
         5 . A tuyere for observing the inside of a molten metal refining furnace having a single tube for observing the temperature and/or composition of molten iron in the refining furnace via a tube penetrating refractories of a furnace wall and/or furnace bottom of the molten iron refining furnace by detecting electromagnetic waves radiated from molten metal at a forward end of the tube under a non-contact state, the tuyere for observing the inside of a molten metal refining furnace comprising a control function by which an inert gas or an oxidizing gas can be used alone, or mixed with each other, according to a state of opening of the forward end of the tuyere tube, the inner diameter of which is 2 to 6 mm.  
     
     
         6 . A method of observing the inside of a molten metal refining furnace in which the temperature and/or composition of molten iron in the molten iron refining furnace is observed via a tube penetrating refractories of a furnace wall and/or furnace bottom of the molten metal refining furnace in a non-contact state by detecting electromagnetic waves radiated from molten iron at the forward end of the tube, the method of observing the inside of the molten metal refining furnace comprising the steps of: using a twin tube tuyere; detecting a ratio of opening of the forward end of the inner tube tuyere; and controlling a size of a mushroom at the forward end of tuyere by changing gas flow rate and/or gas composition of which is supplied through the inner and the outer tube according to a change in the ratio of opening so as to keep the ratio of opening necessary for observation.  
     
     
         7 . A method of observing the inside of a molten metal refining furnace according to  claim 6 , further comprising the steps of: estimating the size of the mushroom at the forward end of tuyere according to the temperature and composition of molten iron; and controlling the size of the mushroom at the forward end of tuyere by changing the gas flow rate of and/or gas composition of LPG inert gas, an inert gas and an oxidizing gas which are supplied through the outer tube according to the result of the estimation so as to keep the ratio (%) of opening of the inner tube in a range from not less than α (%), which is calculated by Equation (5), to not more than 95%.  
       α=850/ r   2   (5)  where r is an inner diameter (mm) of the inner tube.    
     
     
         8 . A method of observing the inside of a molten metal refining furnace according to  claim 6 , further comprising the steps of: supplying mixed gas, in which an inert gas and an oxidizing gas are mixed, or only an oxidizing gas, from the inner tube so as to increase the ratio of opening in a tube opening period in the case where the ratio of opening of the inner tube is lower than α (%) in Equation (5); and supplying only an inert gas from the inner tube in a period except for the tube opening period.  
     
     
         9 . A method of observing the inside of a molten metal refining furnace according to one of  claims 6  to  8 , further comprising the steps of: supplying an inert gas from the inner tube at all times; supplying a mixed gas, in which an inert gas and an oxidizing gas are mixed with each other, or only an oxidizing gas from the outer tube so as to increase the ratio of opening of the inner tube in a tube opening period in the case where the ratio of opening of the inner tube is lower than α (%) in Equation (5); and supplying tuyere cooling gas or an inert gas alone through the outer tube or supplying a mixed gas, in which tuyere cooling gas and an inert gas are mixed, from the outer tube in a period except for the tube opening period.  
     
     
         10 . A tuyere for observing the inside of a molten metal refining furnace which is double tube tuyere for observing the temperature and/or composition of molten iron in the refining furnace via a tube penetrating refractories of a furnace wall and/or furnace bottom of the molten iron refining furnace by detecting electromagnetic waves radiated from molten metal at a forward end of the tube under a non-contact state, the tuyere for observing the inside of a molten metal refining furnace comprising: a piping structure; and a control system capable of independently controlling a gas flow rate and/or gas composition which is supplied through each of the inner and the outer tube.  
     
     
         11 . A tuyere for observing the inside of a molten metal refining furnace according to  claim 10 , wherein inner diameter r of the inner tube is 5 to 20 mm.