Patent Publication Number: US-2007101913-A1

Title: Refractory burner brick

Description:
The present invention relates to a refractory furnace brick and to burners utilizing a grid of such bricks e.g. in blast furnaces and the like.  
      Conventional blast furnace stoves utilize burners made up of successive courses of bricks, each course comprising bricks of different sizes, the courses forming overlapping grids which facilitate combustion of the furnace gases.  
      Such burners are subjected to extremely high temperatures and are also impacted by solid debris which can result in failure, particularly of the smaller bricks.  
      An object of the present invention is to provide a simpler construction which can overcome or alleviate at least some of the above disadvantages.  
      The present invention provides a refractory furnace brick having a longitudinal central bore surrounded by sidewalls, the brick having a transverse cross-section in which corner regions of the junctions of the sidewalls are shaped externally to interface with external corner regions of neighbouring furnace bricks when disposed in a regular two dimensional grid of such bricks.  
      An advantage of such a construction is that relatively small bricks which are correspondingly more susceptible to breakage can be eliminated. Furthermore the manufacturing requirements are simplified.  
      Preferably said corner regions are chamfered to form mating faces. The chamfering reduces the pressure at the interfacial regions, thereby reducing the risk of fracturing of the bricks, and also stabilizes the arrangement.  
      Preferably the interfacial regions comprise ridge portions which can interlock with the ridge portions of neighbouring bricks in said regular two dimensional grid. This feature further stabilizes the construction and obviates the requirement for cement joints.  
      Preferably the refractory furnace brick is so shaped and dimensioned that the transverse cross-section of said upright central bore is substantially the same as that of each neighbouring bore defined by the spacing between opposed external brick surfaces in such a regular two dimensional grid. This feature ensures that the grid openings are of a uniform size and facilitates good combustion.  
      Preferably the area of said transverse cross-section of said upright central bore is within ±20% of that of each said neighbouring bore. More preferably each dimension of said transverse cross-section of said upright central bore is within ±10% of the corresponding dimension of said neighbouring bore.  
      Further preferred features are defined in the dependent claims. 
    
    
      A preferred embodiment of the invention is described below by way of example only with reference to FIGS.  1  to  8  of the accompanying drawings, wherein:  
       FIG. 1  is a perspective view from below of a refractory furnace brick in accordance with the invention and intended for use in the top capping course of a burner;  
       FIG. 2  is a perspective view from below of a further refractory furnace brick in accordance with the invention which is intended for use in the capping course immediately beneath the top capping course of a burner;  
       FIG. 3  is a perspective view from below of the furnace brick of  FIG. 1  showing one half cut away in order to reveal the longitudinal cross-section of each of the longer sidewalls;  
       FIG. 4  is a perspective view from below showing the top two capping courses of a burner utilizing the furnace bricks of  FIGS. 1 and 3  and  FIG. 2 ;  
       FIG. 5  is a diagrammatic horizontal section of either of the capping courses in  FIG. 4 ;  
       FIG. 5A  is a magnified view of the interfacial region of the two furnace bricks shown in  FIG. 5 ;  
       FIG. 6  is a longitudinal diametrical cross-section through a furnace utilizing the capping courses shown in  FIG. 4 ;  
       FIG. 6A  is a magnified partial view showing the gap between the outer wall of the furnace and the burner grid of  FIG. 6 ;  
       FIG. 7  is a transverse cross-section through the upper capping course of  FIG. 6 ; and  
       FIG. 8  is a transverse cross-section through the lower capping course of  FIG. 6 . 
    
    
      Referring to  FIG. 1 , the refractory furnace brick  1  is substantially rectangular in cross-section and has a substantially rectangular upright central bore A as shown. The two longer sidewalls have rounded ridge portions R 1  which project beyond flat faces F 4  at the bottom of the two shorter sidewalls. The longer sidewalls have external faces F 1  which define substantially rectangular bores between the bricks when disposed in a grid as described below with reference to  FIG. 4 . The outer faces F 2  of the shorter sidewalls constitute the other internal faces of the neighbouring bores in the grid as will become apparent from  FIG. 4 .  
      It will be noted that the shorter sidewalls have longitudinal ridges R whose extremities are defined by faces F 2 . The upright longitudinal edges of these ridges enable the furnace bridge to interlock when assembled into a grid, and lie adjacent chamfered surfaces F 3  at the four corners of the block which interface with the chamfered corners of neighbouring bricks as will become apparent from the discussion of  FIG. 5  below.  
      As best seen in  FIG. 3 , all four sidewalls are tapered in transverse cross-section at their upper extremities to form ridges R 2  which are also shown in  FIG. 4 .  
      The refractory furnace brick  2  showing in  FIG. 2  is intended to be assembled into a grid supporting an upper capping course composed of bricks  1  and it will be noted that the longer sidewalls and upper ridges r 1  which are similar to ridges R 1  of brick  1  and that the shorter sidewalls have upper end faces f 4  which are similar to flat faces F 4  of furnace brick  1 . As will become apparent from  FIG. 4 , when the furnace bricks  1  are inverted they can be placed on the furnace bricks  2  with the ridges R 1  sitting on end faces f 4  and the ridges r 1  contacting the faces F 4 . This arrangement enables the upper capping course to be displaced horizontally relative to the lower capping course as necessary since there is no interlocking between the flat faces f 4 /F 4  and the ridges R 1 /r 1 . The lower end portions of the sidewalls have flat faces (not shown) unlike the ridged portions of the bricks  1  since they rest on flat surfaces of a lower grid. The bricks  2  are otherwise similar to the bricks  1 , in particular by including external sidewall faces f 1  and f 2  which define neighoburing bores in the lower grid of  FIG. 4 , by incorporating a ridge R′ similar to the ridge R of brick  1  which ensures interlocking between neighbouring bricks and by incorporating chamfered mating surfaces f 3  at the respective corners.  
      Turning now to  FIG. 4 , it will be seen that an upper layer of furnace bricks  1  can be assembled to form a regular grid with each brick contacting neighbouring bricks as its chamfered faces F 3  and at the edge portions of its ridges R, and that the bricks  2  of the lower grid similarly define a lower grid.  
      It will be seen that the two grids are mutually offset by half a brick width along the direction of the shorter sidewalls, enabling airstreams a and gas streams b to be bifurcated and mixed to ensure efficient combustion.  
      In order to provide a distributed expansion allowance, the chamfered faces F 3 /f 3  of the bricks  1 / 2  are spaced apart by ceramic fiber pads P having a thickness e.g. 1.5 mm to 2 mm corresponding to the brick spacing as best seen in  FIG. 5A . These pads are relatively thin compared to the height of the ridges R, again as best seen in  FIG. 5A  and hence do not prevent interlocking between the sides of the ridges and the faces F 1 /f 1 .  
       FIG. 6  shows the complete burner in cross-section, which is typically part of a blast furnace or other high temperature combustion unit. As shown in  FIG. 6A , a further expansion gap G is provided at the periphery of the burner grid. The tapered upper extremities of the sidewalls prevent debris from catching on the grid walls which might otherwise lock the grid openings. The tapered lower extremities of the furnace bricks  1  facilitate a smooth gas flow through the burner assembly.  
      As best seen in  FIG. 7 , the bores A within the interior of the respective bricks  1  are of essentially the same transverse cross-section as the bores B defined by the faces F 1  and F 2  of surrounding bricks. The corners of the bores A are however rounded slightly to avoid weak points at these regions.  
      The outer bricks are cut in half where necessary in order to provide a roughly circular shape which can be confined within the outer walls W of the burner.  
       FIG. 8  shows a similar arrangement of the furnace bricks  2  of the lower grid and again it will be seen that the bores A′ are of a similar transverse cross-section to the bores B′ defined by the faces f 1  and f 2  of surrounding bricks  2 .  
      In a ceramic burner (as described above) the composition of the firebricks is suitably as follows:  
                                                   Firebrick Option (brick   Monolithic Option (brick           formed by pressing)   formed by moulding)           Chemical Analysis   Chemical Analysis                          Al 2 O 3  - 61.5%   Al 2 O 3  - 60%           SiO 2  - 34%   CaO - 1.9%           Fe 2 O 3  - 1.2%   Fe 2 O 3  - 1.4%           Bulk Density - 2450 kg/m 3     Bulk Density - 2420 kg/m 3                        
 
 The bricks of the invention can also be used in units such as: 
          Acid Drying Towers,     Thermal Oxidisers,     Blast Furnace Stoves,     Reactor Vessels.        

      In these applications the following compositions are suitable:  
                                   Firebrick Option (brick   Monolithic Option (brick       formed by pressing)   formed by moulding)       Chemical Analysis   Chemical Analysis                  Al 2 O 3  - 42 to 80.5%   Al 2 O 3  - 39 to 98%       SiO 2  - 53 to 11.8%   CaO - 3.2 to 1.4%       Fe 2 O 3  - 2 to 1.6%   Fe 2 O 3  - 2.3 to 0.1%       Bulk Density - 2220 to 2780 kg/m 3     Bulk Density - 2250 to 3100 kg/m 3                    
 
 The above compositions are exemplary and not limiting.