Liquid-carrying cooling element for shaft furnaces
BACKGROUND OF THE INVENTION 
     FIELD OF THE INVENTION 
     The invention relates in general to furnace wall construction and in particular to a new and useful liquid-carrying cooling element for shaft furnace walls especially blast furnace walls. 
     The inventive construction includes a plate body made of cast iron or similar metal with coolant-carrying tubes which are arranged inside it, which extend substantially parallel to the hot side of the associated furnace, and exit on the cold side. The wall is advantageously equipped with predominantly horizontally extending brickwork supports on the hot side. 
     Such cooling elements are usually arranged between the steel jacket of the furnace and the furnace lining and are connected to the cooling system of the shaft furnace. On the side facing the inside of the furnace, the cooling elements are provided with refractory material. 
     In the case of a shaft furnace, the life of a furnace depends mainly on the service life of the refractory lining. Besides the selection of resistant grades of refractory materials, good cooling of the refractory material contributes to the prolongation of the service life. 
     The cooling method involving the use of liquid-carrying cooling elements has proved to be particularly successful. Contrary to other methods, it brings about uniform, whole-surface cooling of the shaft furnace wall and consequently of the furnace lining as well. 
     The first lining or the relining of a furnace was previously performed by first mounting the cooling elements, i.e., the metallic plate bodies, on the inner surface of the steel jacket of the furnace and subsequently installing a refractory lining from bottom to top. The annular gap formed was carefully pointed with mortar for heat transfer between the refractory lining and the plate bodies. 
     The wear on the refractory lining is determined mainly by chemical, mechanical, and thermal stresses. The thermal stress on the plate bodies increases with progressive wear of the lining. Finally, the chemical and mechanical stresses on the plate body reach their maxima on complete loss of the refractory lining. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention the furnace life is prolonged by intensifying cooling and reducing the time needed for installation of the cooling elements both for the initial lining and/or the relining of a shaft furnace. 
     The inventive construction makes it possible to have a shorter time for lining the shaft furnace and consequently a reduction of the downtime, a better connection between the refractory brickwork and the metallic plate bodies, a guaranteed improvement in heat dissipation and optimal cooling of the brickwork, and consequently also prolonged service life of the cooling elements. 
     The integrally cast nose of the plate body, due to being arranged on the lower narrow side of the plate body, forms a firm support for the refractory brickwork. 
     In case of destruction and loss of a layer of bricks after prolonged operating time, this damage is usually limited by the nose according to the present invention to a single cooling element, so that the adjacent cooling elements are not affected. 
     The predetermined breaking notches provided in the refractory bricks prevent the entire refractory lining from being lost. Instead any deterioration takes place layer by layer and is retarded. Pre-lining within the furnace is dispensed with. The lining operations are carried out in the shop under favorable ergonomic conditions. The mode of operation, and the elimination of time pressure are condutive to improved quality of work. 
     Since the expansion characteristics of the refractory lining have been known to differ from those of the plate bodies, small bricks are selected for the cooling element according to the present invention. Both thermal and mechanical stresses can be eliminated by standard joints. If this is not sufficient in the case of certain grades of refractory material, additional expansion joints are provided in the refractory part of the cooling element. 
     Corresponding to the stress in the individual concentric ring layers, it is possible to select bricks with different expansion characteristics and different resistance to mechanical abrasion and chemical corrosion. For example, it is possible to use a material with high thermal conductivity, e.g., for the first layer that is close to the plate body, and a material with lower thermal conductivity for the layers more remote from the plate. It is obvious that the brick material should be as resistant to abrasion and chemical corrosion as possible. 
     In certain areas of the shaft furnace with low stress, the refractory brickwork according to the present invention can also be supported on shorter holding noses. The use of such cooling elements is possible, for example, in the upper shaft of the furnace. It is also possible to completely dispense with the installation of holding noses on the plate bodies of the cooling elements, e.g., in the belly of the shaft furnace. 
     In accordance with the invention a cooling element for a furnace particularly a shaft furnace is provided which includes a metallic plate which is formed with a cooling conduit therein and is provided with a nose formation at its inner furnace facing hot side which forms a support for refractory brick which is formed on a cooling element. 
     A further object of the invention is to provide a cooling element which may be pre-fabricated before installation in a furnace such as a shaft furnace and which may be positioned in the furnace with the refractory already secured thereto. 
     A further object of the invention is to providing a cooling element for furnaces which comprises forming a cooling plate with at least one cooling conduit formed in the interior of the plate and with a furnace facing hot side which has an outwardly projecting nose and securing a refractory to the plate hot side over the nose and which is advantageously provided with refractory brick securing recesses on the hot side face. 
     A further object of the invention is to provide a cooling element for a shaft furnace which is simple in design, rugged in construction and economical to manufacture. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated. 
    
    
     BRIEF DESCRIPTION OF THE PREFERED EMBODIMENT 
     In the drawings: 
     FIG. 1 is a sectional view of a cooling element constructed in accordance with the invention. 
     FIG. 2 and 3 similar to FIG. 1 indicating various embodiments of the invention; and 
     FIG. 4 is an elevational view of the cooling element shown in FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE PREFERED EMBODIMENT 
     Referring to the drawings inparticular the invention embodied therein comprises a cooling element generally designated 1 which may be completely pre-fabricated in a manner such that it may be fitted into a shaft furnace or similar furnace in an easy and inexpensive manner. 
     The cooling element, generally designated 1 includes metallic plate bodies 2 with the coolant-carrying tubes 5 and 6 and a refractory lining 7. Said plate body 2 preferably consists of cast iron. The coolant tubes 5 and 6 are preferably made of steel. 
     The plate body 2 has, at its lower edge a holding nose 4 projecting toward the hot side or inside the furnaces as shown by the arrow 40, which serves to support the small bricks of refractory lining 7. The entire end face of plate body 2 facing the inside of the furnace is provided with recesses and projections forming brickwork supports 3. 
     FIGS. 1-3 show longitudinal sections of one of the main cooling tubes 5 with inlet and outlet, as well as the nose cooling tubes 6 for cooling the holding nose 4. In FIG. 4, both the nose and the main cooling tube are shown in an elevation and on a larger scale, with inlets and outlets. The nose cooling tube 6 has the shape of a horizontal figure eight, as a result of which uniform cooling of the area of the holding nose is achieved. 
     The other main cooling tubes not shown in the drawings are arranged in parallel to the cooling tube represented. A single nose cooling tube 6 is normally sufficient to cool said holding nose 4. However, it is also possible to arrange additional cooling tubes if desired. 
     The refractory lining 7 is composed of small bricks which are assembled, after casting, then into the one-piece cooling element 1 by adhesion or cementing. 
     This preferred cooling wall unit or element 1 can be considered to be a principal advantage of the cooling element according to the present invention over the prior-art cooling plates. The cooling elements according to the present invention can be manufactured as complete, ready-to-install products, i.e., including the refractory lining, in a shop, without time pressure and furnace downtime and under favorable ergonomic conditions. After installation of the complete cooling elements in the furnace wall, only the horizontal and vertical joints toward the adjacent cooling elements are to be sealed subsequently with mortar. Each cooling element is designed according to the present invention in such a way that long service life in the shaft furnace is guaranteed, and the separately cooled holding nose arranged on the lower side of the plate body reliably supports the refractory lining of the cooling element. 
     The refractory bricks of the brickwork 7, which are provided with grooves and extending in a circumferential direction (laterally along the face of the plate body 2), have notches or recesses 8 on one side, which serve to cause better interengagement and provide predetermined breakage or separation of only one ring layer of the refractory lining rather than breaking off of the entire refractory lining of the cooling element. These or prepositional breaking notches 8 may also be provided on both sides of the bricks. 
     The bricks of the brickwork 7 have all-around joints by which the mechanical and thermal stresses are compensated. In addition, as is apparent from FIG. 2, horizontal expansion joints 9 on opposite brick sides or faces may also additionally be provided in the refractory lining 7. 
     Different crosshatching in FIG. 3 indicates that refractory bricks of different qualities can be used to line the hot side of said cooling element 1. This permits better adjustment to locally different temperatures, and mechanical and chemical stresses. For example, bricks made of a material with high abrasion resistance and lower thermal conductivity are selected for the surface of the cooling element facing the inside of the furnace, whereas bricks made of a material with high thermal conductivity are preferably selected for the layer close to the plate body.