Abstract:
The invention relates to a furnace slag door, comprising at least one panel which is moveable, in a mounted state of the slag door, from an opened position, in which the panel is remote from a corresponding slag discharge opening within the furnace wall to a closed position, in which the panel covers at least part of said slag discharge opening. The invention further comprises a corresponding furnace equipped with such slag door. The furnace is, in particular, an electric arc furnace (EAF) but may be as well of another type.

Description:
The invention relates to a furnace slag door, comprising at least one panel which is moveable, in a mounted state of the slag door, from an opened position, in which the panel is remote from a corresponding slag discharge opening within the furnace wall to a closed position, in which the panel covers at least part of said slag discharge opening. The invention further comprises a corresponding furnace equipped with such slag door. The furnace is, in particular, an electric arc furnace (EAF) but may be as well of another type. 
     As far the following description refers to any directions such as top, bottom, left, right, outside, inside etc. these refer to a regular melting position of a furnace equipped with a slag door (as shown in the figures). 
     The closed position describes a position of the respective panel, when said panel covers at least part of the corresponding slag discharge opening. In the opened position the panel is remote from this opening, so that slag and/or any other materials may be drawn off the furnace interior via said opening. 
     A slag door of the generic type mentioned is known i.a. from WO 2010/094584 A1. The slag door comprises two panels, an upper panel and a lower panel. While the upper panel is only forwarded from its opened to its closed position the lower panel may be further pushed through the slag discharge opening into the furnace and pulled back again. This is achieved by support means for the lower panel which follow a lever parallelogram. This additional movement of the lower panel allows slag scraping along corresponding surface areas next to the slag discharge opening. Because of the hinged movement of the lower panel its scraping path is limited with respect to its length and effectiveness. 
     SUMMARY OF THE DISCLOSURE 
     It is an object of the invention to provide a slag door and a corresponding furnace presenting improvements in closing, opening and use of said slag door for scraping any slag or other materials around a corresponding slag discharge opening. 
     The invention is based on the proposal to provide a slag door which allows an optimized scraping of slag and other materials which was deposited within the slag discharge opening and any areas in the vicinity of this opening. This is achieved by a telescopic slide-out structure which allows a corresponding panel (especially the lower panel of a multi part slag door) to be moved easily, along a long distance and alternating from its closed position into the furnace interior and back again, thereby contacting the corresponding bottom part of the opening and/or any furnace surfaces placed next to it. 
     This telescopic arrangement further allows to retract the respective panel not only up to its position closing the slag discharge opening but to a place (position) further ahead, that means to a position, where at least the lower edge of the panel being arranged outside the slag discharge opening, thereby allowing further contact of at least the lower edge of the panel to scrape any slag and/or other materials along corresponding surface sections in front of the opening. 
     At the same time the alternative movement by said telescopic slide-out allows reproducible and quick actions to free all areas in front, along and behind said slag discharge opening from any materials, mainly slag or scrap. 
     In its most general embodiment the invention provides a furnace slag door, comprising:
         at least one panel, moveable, in a mounted state of the slag door, from an opened position, in which the panel is remote from a corresponding slag discharge opening, to a closed position, in which the panel covers at least part of said slag discharge opening, wherein   the panel is part of a telescopic slide-out, allowing to push to the panel through said slag discharge opening into the associated furnace and pull it back again.       

     Depending on the size of the slag discharge opening it may be advantageous to provide a multi-part slag door. 
     According to one embodiment such a multi panel slag door may comprise:
         an upper panel,   moveable, in a mounted state of the slag door, along a path, from an opened position outside and above a corresponding slag discharge opening of the furnace to a closed position covering an upper part of the slag discharge opening,   a lower panel,   moveable, in a mounted state of the slag door, from an opened position outside and above the slag discharge opening to a closed a position covering a lower part of the slag discharge opening, wherein   the lower panel is part of said telescopic slide-out.       

     The movement (path) of said upper panel may by vertically or inclined with respect to a vertical plane, or a combination of a vertical and/or inclined and/or horizontal movement. It is possible to move the upper panel only along an inclined moving path from the opened into the closed position, for example along corresponding rails. 
     According to one embodiment the slag door provides a lower panel which, in the mounted state of the slag door, is moveable along a path, inclined with respect to the vertical plane, from the opened position to the closed position. In this case the lower panel follows only one movement direction. Again, similar to the movement path of the upper panel, this movement of the lower panel may as well be a combination of a vertical and/or inclined and/or horizontal movement, the latter especially for movement of the lower panel toward the slag discharge opening or into the slag discharge opening. The same is true if the slag door comprises only one panel. 
     An inclined path for movement of the lower panel may be parallel to the path along which the upper panel (and/or any other panel) being moved between the positions mentioned. This design is especially advantageous when the respective panels are commonly moved between their respective closed and opened positions (strokes). This common move may be achieved by a mechanical link between the respective supports of the panels. The panels may be guided along rail-like guiding means (arranged with a distance to each other at lateral ends of the panels) between these positions. Connecting bars and/or supports may serve to arrange the respective panel(s). 
     Corresponding movement direction and guiding means may be used in an embodiment with only one panel. 
     The guidance (movement) between closed and opened position of at least one panel may be achieved by hydraulic actuator means, especially hydraulic piston-/cylinder combinations. 
     A (further) hydraulic actuator may also be used to push the panel, used for scraping purposes, from its closed position into the furnace interior and/or to pull it back again, including further pulling/pushing into a position outside the slag discharge opening. In other words: The telescopic slide-out, to which this panel is mounted, may be moved as well by hydraulic actuator means. This additional movement is typically independent from any movement of any further panel between respective closed and opened positions. This additional movement is responsible for the scraping action which is carried out by this panel. 
     The scraping action may be further improved by additional scraping means at the circumference of the panel, especially along its lower edge, next to the surface to be cleaned. This scraping means may be discrete teeth, pins or the like as well as traverse bars with a corresponding profiled scraping edge. 
     The telescopic slide-out arrangement may be realized in different embodiments allowing the corresponding panel to be moved, when it reached its position right in front or within the slag discharge opening (the closed position), in a general horizontal movement into the furnace interior and back again. The term “horizontal movement” includes all patterns by which the panel is directed from a position in front of the slag discharge opening or a position within the slag discharge opening into a position behind the slag discharge opening and vice versa. Insofar it may be designed in such a way that a corresponding longitudinal movement of the panel may be effected along at least one of the following patterns: wavelike, saw tooth like, involute like, zigzag, linear, dredger like. These non-linear movements are all summerized under the term “horizontal movement”. 
     Such “linear and/or non-linear” movement has the advantage that the lower panel may be used effectively to scrape all slag and/or other solid and viscous materials deposited along the corresponding motion (way of movement) of the panel. It may further follow any irregularities of the surface of such deposits and provide a “cleaned” surface after it has been moved at least once in the way described. It becomes clear from the task of this scraping panel (besides its function to close the slag discharge opening in its closed position) that an alternating movement improves this function, i.e. that the lower panel may be moved in an alternating fashion several times between a forwarded and a retracted position. During its way into the furnace and back again its may be agitated by only one pattern, for example the wave-like pattern or by several patterns of the type mentioned. 
     Insofar the movement of the lower panel may be characterized by at least two subsequent patterns. 
     The telescopic suspension of the scraping panel may be realized, according to one embodiment of the invention, in a part of a panel support which part extends mostly horizontally (when the slag door is in its mounted state). This part can comprise a guide rail, hollow bar or the like, cooperating with a corresponding piston, bar or the like, to which the panel is mounted (at its end) and along which a corresponding actuator, for example a piston-/cylinder means and corresponding bearings is arranged to move the associated panel in the desired way. In order to achieve the respective pattern the support to which the panel is mounted, may be guided along corresponding guiding means, for example corresponding slits (for example wavelike slits) in the side walls of said bar/rail. The panel can (further) be attached to the piston of a piston/cylinder unit by a cardan joint or similar connecting means allowing the desired non-linear movement. 
     The term telescopic slide-out further includes other constructions/layouts and/or other actuator means by which a corresponding “horizontal” and alternating movement of the scraping panel may be achieved. The telescopic slide-outs are generally independent from any other movement means for said panels, especially those for transferring the panels from their opened position into their closed position. 
     While the scraping panel is moved from its opened position (so called “opening stroke”) to its closed position (so called “home position”) in a linear way its scraping movement typically follows any of the patterns mentioned. 
     The telescopic slide out allows to move the corresponding panel in a predetermined fashion during its scraping action and thus to adapt the panel movement to any individual construction, design and local situation. It further allows to predetermine any desired shape of a final surface of those areas, along which the scraping panel has been moved. 
     In a two panel embodiment the upper panel may be moved by the same means from its opened into its closed position as used for the lower panel. Both may be moved commonly or independently from each other. 
     The invention further provides a furnace, especially an EAF, comprising
         a refractory lined lower shell,   a cooled upper shell,   a metal charge opening,   a slag discharge opening within the cooled upper shell, and   a slag door, mounted externally (at the outer periphery of the furnace shell) adjacent to the slag discharge opening, wherein   the slag door is a slag door as described above.       

     At least one panel may be dimensioned such that a gap remains between an outer periphery of the respective panel and a corresponding outer frame portion of the discharge opening when the respective panel is in its “closed position”, also called “home position”. That means that the panel(s) not necessarily close the slag discharge opening hermetically, although it (they) may do so. Any clearance between the respective slag door panel and the corresponding frame of the slag discharge opening (the tunnel-like opening in the furnace wall) does not influence the function of the EAF negatively as the metal melt is always arranged in the lower shell of the furnace, i.e. below the bottom of the slag discharge opening. In contrary: Any clearance secures an unrestricted (unhindered) movability of the slag door. 
     The upper panel of the multi-part slag door may be arranged, in its closed position, such that its lower edge lies within the tunnel space defined by the slag discharge opening, while its upper edge lies outside of said tunnel space, i.e. the upper panel is inclined, for example by up to 15 degrees with respect to an imaginary vertical plane, but a vertical arrangement is as well possible (meaning 0 degrees with respect to said imaginary vertical plane). 
     Further features of the invention may be apparent from the sub-claims and the other applications documents, including the figures and corresponding explanations. 
     In the attached drawings the following is shown schematically: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1   a : a 3-dimensional view of a slag discharge area of an electric arc furnace and its associated slag door in its opened position 
         FIG. 1   b : a side view according to  FIG. 1   a    
         FIG. 2 : same as  FIG. 1  with the slag door in its home position 
         FIG. 3 : same as  FIG. 2  with a lower panel of the slag door in its scraping position 
         FIG. 4 : a 3-dimensional view onto the inner side of the slag discharge area when the slag door is in its position according to  FIG. 3   
     
    
    
     DETAILED DESCRIPTION 
     All Figures show a partly view onto that part of an electric arc furnace  10 , comprising a so called slag discharge opening  12 , which may be closed (partly or completely) by a corresponding slag door  20 . 
     They further show part of a lower shell  14  and an upper shell  16  of said electric arc furnace. While the lower shell  14  is lined with a refractory material (either bricks or a monolithic lining) the upper shell  16  is characterized by cooling panels. As said refractory lining of that part of the furnace, comprising a metal melt, and the upwardly extending cooling panels (which serve as a barrier against slag and onto which a solidified slag layer is built up during processing of the furnace) belong to common prior art these features are not further shown and described. 
     The same is true with respect to any corresponding opening in the furnace to charge metal and the design of the slag discharge opening  12 , forming a tunnel-like opening within the upper shell  16 . Said discharge opening  12  is limited by a bottom portion  12   b , provided by the upper end of the lower shell  14  and/or a corresponding metal/slag layer formed thereon, two frame portions  12   l,r  extending perpendicularly from said bottom portion  12   b  and a top portion  12   t  opposite to bottom portion  12   b.    
     During melting, i.e. especially when scrap is melted in the electric arc furnace  10 , slag door  20  predominantly is arranged in a position called “home position” shown in  FIG. 2 . 
     Slag door  20  comprises an upper panel  22  (made of water cooled pipe sections  22   p ) and a lower panel  24 . Upper panel  22  is mounted by levers  22   s  to a rod  26 , extending between supports  28   a , 28   b  guided along rail-like guiding bars  30   a ,  30   b , which bars  30   a , 30   b  are inclined (arrow I in  FIG. 1   b ) with respect to a vertical plane (arrow V in  FIG. 1   b ) when the said slag door  20  is mounted on the outer wall of upper shell  16  of furnace  10 . These rail-like guiding bars  30   a , 30   b  are secured at their respective bottom end in a pivot bearing  31 . 
     A further bracket  34  serves to pivotally fasten a cylinder  38  of a hydraulic piston-/cylinder unit, the piston of which is marked by numeral  38   b  and pivotally secured at its upper free end to an arm  40 , which carries, at its opposite end, support  28   a  (fixed to support  28   a ). 
     A first part  41  of a support  42  for lower panel  24  is pivotally fastened onto said rod  26  (between levers  22   s ) and extends downwardly with a part  42   a  into a second part  42   b  of said support  42 , which second part  42   b  extends mostly horizontally. This lower end  42   a  of part  41  is slidably guided within said second part  42   b , which provides a U like cross section with an upper opening of smaller width than in an associated inner section. The lower end  42   a  of upper part  41  is shaped correspondingly to allow the desired alternating sliding movement. The lower panel  24  is mounted at the inner free end of part  42   b  ( FIG. 4 ) and may be moved from its closed position ( FIG. 2 ) through the slag discharge opening  12  into the furnace interior by (non illustrated) hydraulic actuator means, pushing part  42   b /lower panel  24  into the furnace interior and pulling them back again. During the return way the lower panel  24  may be retracted into a position behind the closed position, i.e. into a position in front of the slag discharge opening  12 . 
     This movement of lower panel  24  serves to scrape any slag, metal/slag mixtures and/or other substances from the corresponding inner wall portions of said electric arc furnace  10  and/or the tunnel area, formed by the slag discharge opening  12  and/or any surfaces in front of the slag discharge opening  12 . 
     As these formations of mostly solid material have in most cases an irregular shape the invention provides for a lower panel  24  able to move not only in a substantially linear direction into the furnace  10  and back again but along totally different patterns. 
     For this purpose the guiding means for scraping movement of the lower panel  24  are adapted accordingly as described in the general part above. 
     According to one embodiment the said hydraulic actuator for the lower panel may be hingedly secured by a cardan joint, which allows lower panel  24  to follow any wavelike or other non-linear movement on its way into furnace  10  and back again. 
     In other words: lower panel  24  is part of a telescopic slide-out, allowing to push to lower panel  24  through the slag discharge opening  12  into the associated electric arc furnace  10  an pull it back again up to a position outside slag discharge opening  12 . On its way lower panel  24  may contact the corresponding bottom part  12   b  of slag discharge opening  12  and/or any associated surface areas on both sides of this opening  12 . 
     For scrapping purposes the invention provides additional scraping means especially at the lower edge of lower panel  24 , i.a. shaped as teeth, shaped as a comb, a rake, a brush or the like, symbolized by reference numeral  24   s.    
     The motion of the scraping panel (in the embodiment according to the Figures: the lower panel  24 ) may be supported by a further movement of the guiding means to which the upper panel  22  and/or the first part  42   a  of the lower panel are mounted, for example a tilting movement (arrow T in  FIG. 1   b ). This tilting movement may be realized by corresponding pivot joints for fastening the panels  22 , 24  and/or parallelogram-like lever arrangements and indicated in the figures by reference numeral  35 . 
     As may be seen from  FIGS. 1   a,b  and  2  upper panel  22  and lower panel  24  are forwarded in a common movement from their opened position ( FIG. 1   a,b ) into their closed position ( FIG. 2 ), This movement is linear (arrow I  FIG. 1   b ) according to the corresponding linear guide-rails (guiding bars)  30   a ,  30   b  along which the corresponding panel supports  28   a , 28   b  are moved.