Abstract:
An apparatus for preheating a batch ( 12 ) of glass cullet which is preferably enriched with raw materials for glass production, comprising a bunker ( 14 ) preferably having flow ducts for the passage of warm (off)gas. To discharge the preheated batch of glass cullet from the bunker, the apparatus has one or more discharge worms ( 26 ), by way of which the batch of glass cullet can be conveyed to at least one outflow opening ( 28 ) in the base region of the bunker ( 14 ).

Description:
STATEMENT OF RELATED APPLICATIONS 
     This application is based on and claims the benefit of German Patent Application No. 10 2009 019 454.1 having a filing date of 4 May 2009, which is incorporated herein in its entirety by this reference 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to an apparatus for preheating a batch of glass cullet which is preferably enriched with raw materials for glass production, comprising a bunker preferably having flow ducts for the passage of warm (off)gas. 
     2. Prior Art 
     An apparatus of this type is known, for example, from German Patent No. DE 34 16 317 C2. During the glass production process, this apparatus serves to utilize the thermal energy of the offgases produced during the combustion of the raw materials in the melting furnace for preheating the batch of glass cullet. For this purpose, the offgases are generally guided along flow ducts through the bunker, specifically through the batch of glass cullet—if appropriate in that they have preheated the combustion air required for the melting operation beforehand after they have passed through a heat exchanger. Within the bunker, at least some of the thermal energy of the offgas is transferred to the batch of glass cullet. The preheating of the batch of glass cullet ultimately reduces the amount of thermal energy needed for the downstream melting operation in the melting furnace. 
     After the batch of glass cullet has flowed through the bunker, it is discharged from the preheater apparatus and fed to the actual melting furnace. However, the discharge of the preheated batch of glass cullet from the preheater is problematic. 
     This is the case particularly when the batch of glass cullet is to be fed to a melting furnace having a so-called horseshoe fired furnace. This is because the doghouse of the horseshoe fired furnace—the batch feeder alcove of the melting end for feeding the batch of glass cullet—has comparatively small dimensions for design reasons. Therefore, as a rule only one individual chute of a batch feeder can open out into the doghouse of the horseshoe fired furnace, and this chute conveys the batch of glass cullet originating from the preheater apparatus into the doghouse. 
     In order to produce a continuous flow of material using only one chute, the material discharge capacity of the preheater has to be correspondingly high and constant. It is known in the prior art to use so-called vibrating bases for this purpose in the base region of the preheater. These perform oscillating motions and ensure that the material is discharged as uniformly as possible from the preheater apparatus or that the material discharge capacity of said apparatus is as high as possible. Here, the hoppers open out into the chute of the batch feeder, which in turn opens out into the doghouse. 
     A disadvantage of this prior art solution is that caking of the warm batch of glass cullet frequently occurs despite the oscillating motions of the vibrating bases. The hoppers accordingly become blocked. As a last consequence, the material discharge is stopped erroneously. 
     BRIEF SUMMARY OF THE INVENTION 
     Proceeding from this, it is an object of the present invention to improve the preheater apparatus mentioned in the introduction to such an extent that the batch of glass cullet, after it has passed or flowed through said apparatus, can be discharged as far as possible without any faults with high material discharge capacities. In particular, the aim is to prevent caking of the warm batch of glass cullet to the best possible extent. 
     This object is achieved by an apparatus of the type mentioned in the introduction for preheating a batch of glass cullet which is preferably enriched with raw materials for glass production, comprising a bunker preferably having flow ducts for the passage of warm (off)gas, characterized in that, in order to discharge the preheated batch of glass cullet from the bunker, the apparatus has one or more discharge worms, by way of which the batch of glass cullet can be conveyed to at least one outflow opening in the base region of the bunker. 
     Accordingly, in order to discharge the preheated batch of glass cullet from the bunker, the apparatus has one or more discharge worms, by way of which the batch of glass cullet can be conveyed to at least one outflow opening in the base region of the bunker. 
     It has been found that the solution according to the invention solves the problems which have arisen to date, that of ensuring sufficient material discharge from the preheater, in an optimum manner. In particular, the discharge worms make it possible to prevent caking of the batch of glass cullet. 
     According to the invention, it is preferred for there to be a plurality of discharge worms which are each arranged above or on the base wall of the bunker. The discharge worms extend, in particular, parallel to one another and convey the batch of glass cullet to the at least one outflow opening. Expediently, all of the discharge worms act in the same direction. In this case, the discharge worms preferably cover substantially the entire base wall of the bunker, and therefore substantially the entire batch of glass cullet flowing from above in the direction of the base wall is conveyed to the at least one outflow opening. 
     The at least one outflow opening is generally arranged directly inside the base wall of the bunker or is embedded therein. It is preferably arranged in the region of the ends of the parallel discharge worms. 
     In a further embodiment of the invention, the outflow opening has an elongate design. In this case, it extends along a plurality of or all of the discharge worms transversely with respect to the direction in which they act, to be precise underneath them, in particular along their ends. 
     The discharge worms are advantageously arranged above or on the generally substantially rectangular base wall in such a way that the direction in which they act extends transversely to the longitudinal extent of the base wall. In this case, the at least one, advantageously strip-shaped outflow opening extends in the longitudinal direction of the base wall. In this case, the discharge worms convey the batch of glass cullet in the direction of this longitudinal opening. 
     The batch of glass cullet could then be fed from the at least one outflow opening directly to a batch feeder for feeding the batch into a doghouse of a melting end. 
     However, a further preferred embodiment of the invention provides for at least one conveyor worm to be arranged underneath the at least one outflow opening arranged in the base wall, and this worm acts at an angle, in particular perpendicularly or transversely, to the discharge worms arranged above the base wall of the bunker. In other words, the material flowing downwards from the outflow opening is conveyed on by the conveyor worm or worms in a direction at an angle or transversely to the direction in which the discharge worms act. 
     The at least one conveyor worm is preferably arranged directly underneath the outflow opening. Therefore, the material flows directly through the—in particular strip-shaped—outflow opening downwards, where it hits the at least one conveyor worm acting at an angle. 
     In a further embodiment of the invention, said conveyor worm finally conveys the batch, which generally flows in a wide material flow, to one or more obliquely or perpendicularly downwardly extending conveyor ducts which are arranged, in particular, in the region of the end of said conveyor worm. These conveyor ducts subsequently open out preferably into the region of the above-mentioned batch feeder, which conveys the batch of glass cullet to the doghouse of the burner tank. 
     The at least one conveyor duct preferably ends above an upper hopper opening of a hopper of the batch feeder or else within the upper hopper opening. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Further features of the present invention are apparent from the accompanying patent claims, from the following description of a preferred exemplary embodiment and from the accompanying drawing, in which: 
         FIG. 1  shows an oblique view, partially cut away, of an apparatus according to the invention for preheating batches of glass cullet. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows an apparatus  10  according to the invention for preheating a batch  12  of glass cullet, comprising a bunker  14 . The batch  12  of glass cullet to be preheated is fed to the bunker  14  through an upper opening  16 , in a manner which is not shown. The measures required for the feeding operation are known in the prior art. 
     The batch  12  of glass cullet generally flows approximately continuously from top to bottom in the bunker  14 , at least when the batch  12  of glass cullet is fed in continuously. In this case, the batch  12  of glass cullet is heated as it passes through the bunker  14 . Hot offgases which have been produced during a melting operation in a glass melting furnace (not shown) are fed to the bunker  14  in order to preheat the batch  12  of glass cullet therein. 
     A large number of horizontally extending flow ducts (not shown for the sake of simplicity) are located within the main part of the bunker  14 , which, in the present case, is rectangular and formed by upright side walls  20 . The flow ducts, which are arranged one above another, are connected to one another and positioned within the bunker  14  in such a way that the warm offgas can be fed in in the lower region of the bunker  14  and can be guided upwards within the bunker  14  in crosswise countercurrent. The batch  12  of glass cullet is thereby heated by the warm or hot offgas flowing past in the manner of a heat exchanger. Further details relating to the way in which such a preheating apparatus works can be gathered, for example, from German Patent No. DE 34 16 317 C2, the content of which is hereby integrated in the present application. 
     After the batch  12  of glass cullet has passed through the bunker  14 , the preheated batch of glass cullet has to be removed from said bunker. 
     For this purpose, the bunker  14  narrows towards the bottom and has, in the lower region, a funnel-shaped region  14   a . The funnel-shaped region  14   a  of the bunker  14  is adjoined by a bunker base pan  14   b  with a rectangular cross section, upright side walls  24  and a base wall  22  which closes off the bunker  14  and the base pan  14   b  at the bottom. 
     In the present example, ten discharge worms  26  are arranged in the base pan  14   b  transversely to the longitudinal extent of said pan. These discharge worms cover substantially the entire, rectangular base wall  22  and, at each of their ends  26   a ,  26   b , each adjoin the upright side walls  24  of the base pan  14   b . The ten discharge worms  26  are arranged in parallel, and therefore the directions in which they act likewise extend in a parallel manner. The directions in which the discharge worms  26  act in the base pan  14   b , these directions extending transversely to the base wall  22 , are shown by way of example by a corresponding arrow in  FIG. 1 . 
     As a rule, the preheated batch  12  of glass cullet flows continuously from above onto the discharge worms  26  and is conveyed, in the direction in which the respective discharge worms  26  act, in the direction of the longitudinal side wall, at the front in  FIG. 1 , of the base pan  14   b . A strip-like outflow opening  28  or outflow recess  28 , which extends transversely to the directions in which the worms  26  act and also in the longitudinal direction in relation to the base wall  22 , is arranged in the base wall  22 , in the region of the ends  26   a  of the discharge worms  26  which adjoin the front longitudinal side wall. 
     The batch  12  of glass cullet conveyed by the worms  26  in each case in the direction of said longitudinally extending outflow opening  28  flows through said outflow opening downwards out of the base pan  14   b.    
     Two mutually aligned, further conveyor worms  30   a  and  30   b  are arranged directly underneath the strip-shaped outflow opening  28  parallel to the longitudinal extent of the latter, and therefore transversely to the directions in which the discharge worms  26  act. These conveyor worms each convey the batch  12  of glass cullet in the opposite direction, to be precise towards upper inlet openings of vertically downwardly extending conveyor ducts  32   a ,  32   b . These upper inlet openings of the conveyor ducts  32   a ,  32   b  are arranged in the region of the ends of the worms  30   a ,  30   b , directly underneath the latter. 
     The conveyor ducts  32   a ,  32   b  have a square cross section and each open out into the upper opening  34  of a hopper  36  of a so-called batch feeder  38 . 
     The batch feeder  38  subsequently ensures that the batch  12  of glass cullet is conveyed to the doghouse  40  of a horseshoe fired furnace of the glass melting furnace (not shown). For this purpose, after it has flowed through the hopper  36  the batch of glass cullet flows to a vibrating chute  42  of the batch feeder  38 , and this chute in turn opens out directly into the doghouse  40 . 
     LIST OF REFERENCE SYMBOLS 
     
         
           10  Preheating apparatus 
           12  Batch of glass cullet 
           14  Bunker 
           14   a  Funnel-shaped portion 
           14   b  Base pan 
           16  Upper opening 
           20  Side wall 
           22  Base wall 
           24  Side wall 
           26  Discharge worm 
           26   a  End 
           26   b  End 
           28  Longitudinal recess 
           30   a  Conveyor worm 
           30   b  Conveyor worm 
           32   a  Conveyor duct 
           32   b  Conveyor duct 
           34  Opening 
           36  Hopper 
           38  Batch feeder 
           40  Doghouse