Abstract:
A refractory anchoring system that mitigates the effects of the thermo-mechanical stresses that arise from the furnace temperature gradient and varying thermal expansions of the refractory and casing. This anchoring system provides independent movement which may be important for maintaining the refractory lining stability and its ability to contain the furnace processes. The invention relates more specifically to the metallic member that is configured in a specific spring-like manner. This invention also relates to the specific design of the non-metallic member (refractory anchor) to work in conjunction with the metallic member.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates generally to the refractory arts, more particularly to a support system that attaches the refractory to a furnace casing so that each can move independently of each other with the thermal expansion of the refractory in a furnace environment. This independent movement may be important for maintaining the refractory lining stability and its ability to contain the furnace processes. This invention maybe found applicable to other structures in which the advantages hereinafter pointed out would be useful. 
       BACKGROUND OF INVENTION 
       [0002]    Refractories are heat resistant materials that are used as a means to contain a process and/or used as insulation to reduce heat loss (increase efficiency) in industrial applications requiring high temperatures such as metallurgical processing, incineration, refining, cement manufacturing, power generation, glass manufacturing, ceramic/brick manufacturing, etc. The refractory generally lines the interior of a metal casing which provides support for the process and refractory. The refractory is secured to the casing utilizing the casing geometry (arch type construction) or with various types of support devices (anchors). The anchors consist of a metallic alloy assembly secured to the shell by means of welding, bolting, clipping, etc. and can be used independently or in conjunction with a refractory (ceramic) anchor. 
         [0003]    Ceramic anchors are generally required for most applications when, the temperature exceed the limitations of alloy anchors, corrosive atmospheres limit alloy anchors, supplemental anchor holding power is required, multiple component linings or support surface area is needed to hold the refractory during installation. Anchors made like a pre-cast castable shape are also considered as ceramic anchor even though they do not have ceramic bonding. Ceramic anchors are often viewed as a “necessary evil”. This is due to the multitude of refractory lining failures that have been blamed on the anchor and/or its orientation. The thermal conditions within a furnace environment impart stresses into the refractory and the refractory support system which ultimately leads to refractory failures. This application provides a utilitarian design of an anchoring system that mitigates the effects of the thermo-mechanical stresses that arise from the furnace temperature gradient and varying thermal expansions of the refractory and casing. 
       SUMMARY OF THE INVENTION 
       [0004]    This application discloses a furnace wall assembly comprising: an exterior wall having an inner face; an interior refractory wall comprising: an insulating layer adjacent to the exterior wall inner face; and a hotface layer adjacent to the insulating layer such that the insulating layer is disposed between the exterior wall inner face and the hotface layer, the hotface layer movable from a first position to a second position when subjected to thermal energy; an anchor having a first end and a second end, the anchor first end adjacent to the exterior wall inner face and the anchor second end extending into the hotface layer of the interior refractory wall, wherein the anchor is movable from a first lateral position to a second lateral position when the hotface layer moves from the hotface layer first position to the hotface layer second position; and a support having a first end rigidly coupled to the exterior wall inner face and slidingly engaging the anchor in the anchor first lateral position, and wherein the support further engages the anchor when the anchor is moved to the second anchor position. 
         [0005]    This application also discloses a furnace wall assembly comprising: an exterior wall having an inner face; an interior refractory wall adjacent to the exterior wall inner face, the interior refractory wall movable from a first position to a second position when subjected to thermal energy; an anchor having a first end and a second end, the anchor first end adjacent to the exterior wall inner face and the anchor second end extending into the interior refractory wall, wherein the anchor is movable from a first lateral position to a second lateral position when the interior refractory wall moves from the interior refractory wall first position to the interior refractory wall second position; and a support having a first end rigidly coupled to the exterior wall inner face and slidingly engaging the anchor in the anchor first lateral position, and wherein the support further engages the anchor when the anchor is moved to the second anchor position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The invention may take physical form in certain parts and arrangements of parts, an illustrative embodiment of which will be described in detail in the specification and illustrated in the accompanying drawings with form a part hereof, and wherein: 
           [0007]      FIG. 1  is perspective view of partial refractory line wall structure illustrating an embodiment of the present invention. 
           [0008]      FIG. 2  is perspective view of the metallic and ceramic anchor system mounted on a furnace sidewall. The refractory lining is not shown for clarification. 
           [0009]      FIG. 3  is a sectional view of the metallic anchor and ceramic anchor configuration before and after attachment. 
           [0010]      FIG. 4  is a perspective view of a representation of the prior art. 
           [0011]      FIG. 5  is a sectional view of the prior art shown in  FIG. 4 . 
           [0012]      FIG. 6  is a sectional view of the prior art and illustrates movement due to thermal strain. 
           [0013]      FIG. 7  is a sectional view of an embodiment and illustrates movement due to thermal strain. 
           [0014]      FIG. 8  shows examples of how a spring-like assembly claimed in this invention can be used in conjunction with prior art and other configurations 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Referring now to the drawings wherein the drawings are for the purpose of illustrating an embodiment of the invention only, and not for the purpose of limiting the same. 
         [0016]      FIG. 1  is a perspective view of a partially assembled furnace wall structure  10 , illustrating an embodiment of the present invention. Furnace wall structure  10  depicted in the drawing shows a refractory wall structure that could represent the interior of any industrial furnace application. The furnace wall structure  10  is comprised of a metallic panel  100  that form the outer casing of the structure and a two-component refractory wall  20  that is formed by an insulating layer of refractory  30  and a hotface layer of refractory  40 . The refractory is attached to the furnace wall with a metallic spring support  50  and a ceramic anchor  60 .  FIG. 1  also shows a layer of compressible material  70  wrapped around the spring support to provide an area within the refractory for movement to occur. 
         [0017]      FIG. 2  is an isolated, perspective view of the embodiment consisting of a metallic spring support  50  and ceramic anchor  60  system mounted on a furnace casing  100 . The refractory lining is not shown for clarity. 
         [0018]      FIG. 3  is a sectional view of the metallic spring support  50  and ceramic anchor  60  configuration before and after the ceramic anchor  60  is mounted into the support.  FIG. 3  illustrates the mating of a corrugated spiral  110  formed in the configuration of a ceramic anchor  60  with a metallic spring support  50 . The base of the metallic spring support is shown so that the attachment point (weld)  115  is located on either the outer diameter of the spring  120  and on the inner diameter of the spring  125 . 
         [0019]      FIG. 4  is a perspective view of a representation of the prior art consisting of a metallic furnace wall panel  100  with a C-shaped member alloy support “C-clip”  300  that contains a standardized shape ceramic anchor  310 . 
         [0020]      FIG. 5  is a sectional view of the prior art shown in  FIG. 4 . This view shows the gap  240  between the ceramic anchor  310  and the C-clip  300 . A wedge  245  must be installed in the gap  240  to support the ceramic anchor  310  in the proper position prior to the refractory installation. 
         [0021]    The present invention thus provides a unique apparatus for supporting the refractory lining to the interior of a furnace and allows the refractory to move independently from the furnace casing. The invention allows for any and all movement in any direction parallel to the furnace casing and also movement away from the casing (toward the furnace interior). The amount of movement allowed may be limited by the characteristics of the spring support system. 
         [0022]      FIG. 6  represents a is a sectional view of the furnace wall structure  10  that is comprised of a metallic panel  100  that form the outer casing of the structure and a two-component refractory wall  20  that is formed by an insulating layer of refractory  30  and a hotface layer of refractory  40 . The refractory is attached to the furnace wall with the prior art consisting of a C-clip  300  and a standardized ceramic anchor  310 . A thermal strain  200  resulting from the furnace environment (shown as arrows) causes a deflection  205  in the refractory lining. The deflection  205  can cause a unidirectional, bi-directional or shear load on the ceramic anchor  310 . In this prior art, this stress is transferred to the “ears”  285  of the ceramic anchor  310  creating a bending moment (tension) and ultimate failure  272  as ceramics are extremely brittle and have little tensile strength. The amount of stress in the ceramic anchor ear  285  is related to the total amount of deflection  205  beyond the deflection  208  that is allowed for in the C-clip. This type of failure is very common in many refractory installations. 
         [0023]      FIG. 7  is a sectional view of the embodiment showing a furnace wall structure  10  that is comprised of a metallic panel  100  that form the outer casing of the structure and a two-component refractory wall  20  that is formed by an insulating layer of refractory  30  and a hotface layer of refractory  40 . The refractory is attached to the furnace wall with a metallic spring support  50  and a ceramic anchor  60 . A layer of compressible material  70  wrapped around the spring support to provide an area of growth.  FIG. 7  illustrates that the as the hotface refractory layer  40  is subjected to thermal strain  200  and movement as represented as arrows, the invention allows for movement of the metallic spring  50  and ceramic anchor  60  in the direction of the force. The shadow drawing  215  represents the original position of the anchor system. The compressible material  70  is compressed  72  in the direction of the refractory movement. 
         [0024]    In addition to allowing the movement of the refractory lining, an advantage of the present invention is that the spring supports will distributes stresses developed from the thermal expansion of the lining throughout the entire length of the spring support and across many corrugations of the ceramic anchor rather than create a bending moment at one ear as does the prior art allows. Another advantage is that the spring support is active in holding the ceramic anchor along the entire length of the spring. This results in a larger surface area where the anchor meets the spring support which reduces the amount of localized stress between the anchor and the support. 
         [0025]    The closer the anchor retention point is to the working environment of the furnace the hotter the anchor becomes. As the metallic anchor becomes hotter the strength properties of the metal substantially decrease thus creating a weaker support. In the prior art, the anchor retention area is fixed at about 3″ away from the furnace casing compared the present invention where the anchor retention extends from 3″ away from the casing to the casing proper. This provides a larger section of the metallic anchor in contact with the ceramic anchor that is at a substantially cooler and stronger condition. 
         [0026]    The illustrative ceramic anchor is this invention has a rounded cross-section. The round shape will induce less stress and resulting cracking of the refractory than the prior art of square cross-sectional ceramic anchors which tend to induce stress riser in the corners especially on the furnace interior. The rounded cross-section of the ceramic anchor in the illustrative embodiment can help eliminate voids and shadows when installing the refractory as compared to the square configuration of the prior art. 
         [0027]    In this embodiment, the overall apparent length of the anchor (and thus the thickness of the refractory lining) is adjustable as the ceramic anchor does not have to be tightened all the way to the furnace casing. In this embodiment, the metallic anchor support and ceramic anchor are additive and can be joined in multiple sections to achieve various lining thicknesses. 
         [0028]    Because of the C-clip gap in the prior art, the ceramic anchor has to be wedged into place to hold it securely during the refractory installation. Typically two small wooden wedges are used. Many applications the wooden wedge does not get hot enough to burn and continues to hold the brick tightly against the ears of the C-clip thus giving rise to additional stress in the prior art. No wedges are necessary with the illustrative embodiment which eliminates this source of stress and facilitates the installation. 
         [0029]    The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. For example, as illustrated in  FIG. 8  shows examples of how a spring-like assembly claimed in this invention can be used in conjunction with prior art, namely standardized ceramic anchors and the support clips to increase the utility of the prior system. Spring design modifications may include changes to the number of coils, curvatures, flat springs, dimensional springs, orientation, Hooke&#39;s law constants, alloys, diameters, and attachment methods. Ceramic anchor modifications may include changes to the anchor dimensions, corrugations dimensions, spiral dimensions, methods to attach to the spring clip, internal (male) springs, external (female) springs, anchor material composition, anchor fabrication method, metallic anchors, pre-cast blocks, brick anchors or interlocking tiles. Installation practices may be modified to include changes to the application of the compressible material, composition of the compressible material, anchor spacings, use of multiple anchors type in conjunction with the invention, various applications, various furnace configurations or non-refractory applications.