Method for discharging reduced product from a moveable-hearth furnace and a discharging device

Abstract

A method for discharging a reduced product produced on a movable hearth of a movable-hearth furnace uses a discharging device. The discharging device includes a removal unit for removing the reduced product from the movable hearth, a separation unit for separating the reduced product from a solid reductant, a leaving-returning unit for either leaving substances other than the reduced product on a solid reductant layer or returning the substances onto the solid reductant layer, and a discharge unit for discharging the reduced product to the outside of the movable-hearth furnace.

What is claimed is:  
     
         1 . A method for discharging a reduced product produced on a movable hearth of a movable-hearth furnace, comprising: 
 removing the reduced product from the movable hearth;    separating the reduced product from a solid reductant;    either leaving substances other than the reduced product on the solid reductant layer or returning the substances onto the solid reductant layer; and    discharging the reduced product to the outside of the movable-hearth furnace.    
     
     
         2 . The method according to  claim 1 , wherein removing the reduced product from the movable hearth comprises attracting the reduced product with a magnetic force to thereby remove the reduced product from the movable hearth.  
     
     
         3 . The method according to  claim 2 , further comprising: 
 cooling the reduced product before attracting the reduced product.    
     
     
         4 . The method according to  claim 1 , wherein removing the reduced product from the movable hearth comprises: 
 scooping the reduced product and the solid reductant with a screen; and    separating the reduced product from the solid reductant comprises sifting the reduced product and the solid reductant according to the grain size of the reduced product and the solid reductant with the screen.    
     
     
         5 . The method according to  claim 4 , wherein sifting the reduced product and the solid reductant according to the grain size of the reduced product and the solid reductant with the screen such that the reduced product and the solid reductant having smaller grain sizes are left on the movable hearth, comprises selecting the reduced product having a larger grain size with a rotary drum which substantially spans the movable hearth of the movable-hearth furnace in the widthwise direction of the movable hearth and is provided with a plurality of net-shaped or comb-shaped screens each extending radially outwardly from the rotary drum from the periphery thereof.  
     
     
         6 . The method according to  claim 4 , wherein sifting the reduced product and the solid reductant according to the grain size of the reduced product and the solid reductant with the screen such that the reduced product and the solid reductant having smaller grain sizes are left on the movable hearth, comprises removing the reduced product having a larger grain size from the solid reductant layer and discharging the reduced product with a screw feeder having an axis of rotation which substantially spans the movable hearth in the widthwise direction of the movable hearth and extends outwardly of the movable-hearth furnace, and which operates in such a manner that a part of the solid reductant is left on the solid reductant layer by controlling the position of the axis of the screw feeder with respect to the movable hearth.  
     
     
         7 . The method according to  claim 6 , wherein a plurality of apertures are formed in a casing substantially surrounding the screw feeder, the apertures being arrayed substantially along the axis of the screw feeder, such that the reduced product and the solid reductant having smaller grain sizes are left on the solid reductant layer.  
     
     
         8 . The method according to  claim 7 , wherein the casing provided with the plurality of apertures is a cylindrical screen which substantially covers the screw feeder.  
     
     
         9 . The method according to  claim 6 , further comprising: 
 classifying the reduced product and the solid reductant according to grain size; and    returning the reduced product and the solid reductant having smaller grain sizes either onto the solid reductant layer formed on the movable hearth of the movable-hearth furnace or to a layer of mixed raw materials formed on the solid reductant layer.    
     
     
         10 . A discharging device for discharging a reduced product produced on a movable hearth of a movable-hearth furnace, comprising: 
 removal means for removing the reduced product from the movable hearth;    separation means for separating the reduced product from a solid reductant;    leaving-returning means connected to either leaving substances other than the reduced product on the solid reductant layer or returning the substances onto the solid reductant layer; and    discharge means connected to discharge the reduced product outwardly of the movable-hearth furnace.    
     
     
         11 . The discharging device according to  claim 10 , wherein the removal means, the separation means and the discharge means comprise a belt conveyor which opposes the movable hearth at at least one portion of the belt conveyor and extends outwardly of the movable-hearth furnace, and at least one magnet provided within a loop formed by a belt of the belt conveyor at least at a position opposing the movable hearth and adjacent to the position outside the movable-hearth furnace, the at least one magnet attracting the reduced product from the movable hearth, thereby separating the reduced product from the solid reductant.  
     
     
         12 . The discharging device according to  claim 11 , wherein the at least one magnet is disposed at a position opposing the movable hearth with the belt of the belt conveyor therebetween.  
     
     
         13 . The discharging device according to  claim 11 , wherein the at least one magnet is fixed to a rear face of the belt of the belt conveyor.  
     
     
         14 . The discharging device according to  claim 10 , wherein the removal means, the separation means and the discharge means comprise a first belt conveyor which opposes the movable hearth at at least one portion of the first belt conveyor and extends outwardly of the movable-hearth furnace, a second belt conveyor which is provided within a loop formed by a belt of the first belt conveyor and is disposed at a position opposing the movable hearth with a lower portion of the belt of the first belt conveyor therebetween, rotation of the first belt conveyor and the second belt conveyor being substantially synchronized with each other, and having at least one magnet which is mounted on a rear face of the belt of the second belt conveyor.  
     
     
         15 . The discharging device according to one of  claims 10  to  14 , further comprising: 
 a scraper disposed adjacent a portion of the belt conveyor to which a magnetic force is not applied and which is outside the movable-hearth furnace, the scraper adapted to scrape the reduced product adhered to a front face of the belt of the belt conveyor.  
 
     
     
         16 . The discharging device according to  claim 10 , wherein the removal means and the separation means comprise a rotary drum which substantially spans the movable hearth of the movable-hearth furnace in the widthwise direction of the movable hearth and is provided with at least one magnet at least at a portion of the rotary drum opposing the movable hearth, for attracting the reduced product disposed on the movable hearth, and 
 the discharge means comprises transfer means disposed substantially parallel to the axis of the rotary drum, and which receives the reduced product attracted to and falling from the rotary drum and transfers the reduced product outwardly from the movable-hearth furnace.    
     
     
         17 . The discharging device according to  claim 16 , wherein the rotary drum has a rotational direction and comprises an outer drum and an inner roller disposed inside the outer drum and which is provided with the at least one magnet fixed to a cylindrical surface of the inner roller, said at least one magnet extending in the rotational direction of the rotary drum from a lower portion of the cylindrical surface to a portion thereof associated with the discharge means.  
     
     
         18 . The discharging device according to one of claims  16  and  17 , wherein the discharge means comprises a belt conveyor disposed substantially parallel to the axis of the rotary drum, and which receives the reduced product attracted to and falling from the rotary drum, and extends from the movable hearth and outwardly from the movable-hearth furnace.  
     
     
         19 . The discharging device according to one of claims  16  and  17 , further comprising a plurality of protrusions on a peripheral face of the rotary drum.  
     
     
         20 . The discharging device according to one of claims  16  and  17 , wherein the rotary drum is formed as a cylinder having a smaller diameter at an intermediate portion in an axial direction of the cylinder.  
     
     
         21 . The discharging device according to one of claims  16  and  17 , further comprising a cooling member which cools the reduced product before the reduced product has a magnetic field applied thereto to be attracted and removed from the movable hearth by the magnetic force.  
     
     
         22 . The discharging device according to  claim 10 , wherein the removal means and the separation means comprise a classifying member including at least one net-shaped or comb-shaped screen protruding from a drum in a radial direction thereof, the drum substantially spanning the movable hearth of the movable-hearth furnace in the widthwise direction of the movable hearth, and 
 the discharge means comprises a transfer conveyor which transfers the reduced product scooped from the movable hearth by the classifying member.    
     
     
         23 . The discharging device according to  claim 22 , wherein the transfer conveyor is disposed in the vicinity of the drum provided with the classifying member and substantially parallel to a rotational axis of the drum, the transfer conveyor being disposed at a position in which the transfer conveyor receives the reduced product falling from the classifying member.  
     
     
         24 . The discharging device according to  claim 22 , wherein the transfer conveyor is disposed to pass through the drum in an axial direction thereof, and the drum is provided with at least one opening formed in the drum in the vicinity of the net-shaped or comb-shaped screen such that the reduced product scooped by the at least one net-shaped or comb-shaped screen is received by the transfer conveyor through the at least one opening.  
     
     
         25 . The discharging device according to one of  claims 22  to  24 , further comprising: 
 side plates individually disposed at sides of the movable hearth along the direction of movement of the movable hearth and adapted to prevent a deposited substance from collapsing.  
 
     
     
         26 . The discharging device according to  claim 10 , wherein the removal means, the separation means and the discharge means comprise a screw feeder which substantially spans the movable hearth in the widthwise direction thereof and extends outwardly from the movable-hearth furnace, and a casing disposed at a downstream side of the screw feeder in the direction of movement of the movable hearth, the casing being formed with a sidewall extending along a rotational axis of the screw feeder and a bottom plate extending from the sidewall substantially parallel to the movable hearth.  
     
     
         27 . The discharging device according to  claim 26 , wherein the casing has a plurality of apertures.  
     
     
         28 . The discharging device according to  claim 10 , wherein the removal means, the separation means and the discharge means comprise a screw feeder which substantially spans the movable hearth in the widthwise direction thereof, a reductant-discharging shooter disposed at a position associated with an end portion of the screw feeder protruding outwardly from the movable-hearth furnace, a reduced-product-discharging shooter disposed toward an outer side of the movable-hearth furnace from the reductant-discharging shooter, and a cylindrical screen which covers the end portion of the screw feeder associated with the position at which the reductant-discharging shooter is disposed, rotation of the cylindrical screen being substantially synchronized with that of the screw feeder; and 
 wherein the reduced-product-discharging shooter is positioned at an open end of the cylindrical screen.    
     
     
         29 . The discharging device according to  claim 10 , wherein the removal means, the separation means and the discharge means comprise a guide plate disposed in a discharge section of the movable hearth, for reducing the width of an accumulative layer of the reduced product and the solid reductant, and a screw feeder disposed in a direction substantially perpendicular to the direction of movement of the movable hearth and provided with a tapered portion toward a discharge end of the screw feeder on the movable hearth, an end portion of the screw feeder from the tapered portion to the end thereof protruding outwardly from the movable-hearth furnace being formed as a reduced-diameter part; and 
 wherein a conical collecting shooter is disposed at the tapered portion of the screw feeder, a discharge cylinder is disposed about the reduced-diameter portion of the screw feeder toward the discharge end thereof from the conical collecting shooter, the discharge cylinder being provided with a net-shaped screen at a portion of the discharge cylinder associated with the movable hearth, and a reduced-product-discharging shooter is provided at an open end of the discharge cylinder disposed outwardly from the movable-hearth furnace.