Abstract:
The present invention relates generally to furnace systems and more particularly, but not by way of limitation, to a split-ring assembly for sealing a junction between a catalyst tube and a furnace. In one aspect, the present invention relates to a ring-seal assembly. The ring-seal assembly includes a housing ring coupled to an outer surface of a furnace. The housing ring is disposed around a circumference of a tube proximate a junction with the furnace. The ring seal assembly further includes a brush seal that is at least partially disposed within the housing ring. The brush seal is disposed around the circumference of the tube. A plurality of brushes extend radially inwardly from the brush seal towards the tube.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to, and incorporates by reference for any purpose, the entire disclosure of U.S. Provisional Patent Application No. 61/903,770, filed Nov. 13, 2013. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present application relates generally to furnace systems and more particularly, but not by way of limitation, to a split-ring assembly for sealing a junction between a catalyst tube and a furnace. 
         [0004]    2. History of the Related Art 
         [0005]    Furnaces used in the refining and petro-chemical industries are designed to operate with interior temperatures in excess of 1600 degrees Fahrenheit. Factors of economy and safety dictate the these interior temperatures be controlled with a high degree of precision. It is thus, imperative that any penetration of ambient air into the interior of the furnace and leakage of heat and hot flue gases from the furnace be minimized with a sealing device. 
         [0006]    In many cases, the area near the top of the furnace is a primary location for leakage of flue gases and furnace heat. The area near the top of the furnace is highly congested with numerous hardware including, for example, catalyst tubes, catalyst tube flanges, inlet piping, tube-support assemblies, and associated hardware. Such congestion limits the space available for installation of a sealing device. Because furnace components and associated hardware are often metallic, any sealing device must allow vertical growth, due to thermal expansion, of, for example, a catalyst tube. In addition, a sealing device must facilitate installation and replacement without altering or removing the associated hardware. 
       SUMMARY 
       [0007]    The present invention relates generally to furnace systems and more particularly, but not by way of limitation, to a split-ring assembly for sealing a junction between a catalyst tube and a furnace. In one aspect, the present invention relates to a ring-seal assembly. The ring-seal assembly includes a housing ring coupled to an outer surface of a furnace. The housing ring is disposed around a circumference of a tube proximate a junction with the furnace. The ring seal assembly further includes a brush seal that is at least partially disposed within the housing ring. The brush seal is disposed around the circumference of the tube. A plurality of brushes extend radially inwardly from the brush seal towards the tube. 
         [0008]    In another aspect, the present invention relates to a method of sealing a junction between a tube and a furnace. The method includes installing housing ring to an outer surface of a furnace. The housing ring is installed about a circumference of a tube proximate a junction with the furnace. The method further includes installing a brush seal around the circumference of the tube. The brush seal is at least partially disposed within the housing ring. A plurality of brushes extending radially inwardly from the brush seal and contact an outer surface of the tube. The brush seal is seated within the housing ring. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    For a more complete understanding of the present invention and for further objects and advantages thereof, reference may now be had to the following description taken in conjunction with the accompanying drawings in which: 
           [0010]      FIG. 1  is a perspective view of a prior-art catalyst tube arrangement; 
           [0011]      FIG. 2  is an exploded view of a ring seal according to an exemplary embodiment; 
           [0012]      FIG. 3  is a perspective view of the ring seal of  FIG. 2  in an installed configuration according to an exemplary embodiment; 
           [0013]      FIG. 4A  is a cross-sectional view of the ring seal of  FIG. 2  in an installed configuration according to an exemplary embodiment; 
           [0014]      FIG. 4B  is a top view of the ring seal of  FIG. 2  in an installed configuration according to an exemplary embodiment; and 
           [0015]      FIG. 5  is a flow diagram of a process for sealing a catalyst tube according to an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Various embodiments of the present invention will now be described more fully with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. 
         [0017]      FIG. 1  is a perspective view of a prior-art catalyst tube arrangement. A furnace  100  includes a plurality of catalyst tubes  102  extending outwardly therefrom. A fabric seal  104  is placed around each tube of the plurality of catalyst tubes near a junction with an outer wall of the furnace  100 . The fabric seal  104  is flexible and must be installed with sufficient slack to allow room for thermal expansion of the plurality of catalyst tubes  102  during operation. The excess material required to accommodate thermal expansion is constrained by available space thus making installation and maintenance difficult. 
         [0018]      FIG. 2  is an exploded view of a ring seal  200 . The ring seal  200  includes a brush seal  204  that is disposed between a housing ring  202  and a retaining ring  206 . The housing ring  202  includes a first split-ring section  202 ( a ) coupled to a second split-ring section  202 ( b ). In other embodiments, however, ring seals utilizing principles of the invention may include a single-piece housing ring or a hinged housing ring. A rabbet  214  is formed around an interior circumference of the first split-ring section  202 ( a ) and the second split-ring section  202 ( b ). 
         [0019]    Still referring to  FIG. 2 , the brush seal  204  includes a first brush-seal ring  205 , a second brush-seal ring  207 , and a third brush-seal ring  209  disposed within the housing ring  202 . In other embodiments, however, ring seals utilizing principles of the invention may include any number of brush-seal rings. The first brush-seal ring  205  includes a first joint  216 , the second brush-seal ring  207  includes a second joint  218 , and the third brush-seal ring  209  includes a third joint  220 . When installed, the first brush-seal ring  205 , the second brush-seal ring  207 , and the third brush-seal ring  209  are arranged such that the first joint  216 , the second joint  218 , and the third joint  220  are staggered such that the first joint  216 , the second joint  218 , and the third joint  220  are not aligned thereby inhibiting transmission of gases through the first joint  216 , the second joint  218 , and the third joint  220 . 
         [0020]    Still referring to  FIG. 2 , the first brush-seal ring  205  includes support ring  210 ( a ) and a plurality of brushes  212 ( a ) extending radially inwardly from the support ring  210 ( a ). The second brush-seal ring  207  includes support ring  210 ( b ) and a plurality of brushes  212 ( b ) extending radially inwardly from the support ring  210 ( b ). The third brush-seal ring  209  includes support ring  210 ( c ) and a plurality of brushes  212 ( c ) extending radially inwardly from the support ring  210 ( c ). 
         [0021]    Still referring to  FIG. 2 , the retaining ring  206  is disposed above the brush seal  204 . The retaining ring  206  includes a first section  222  and a second section  224 . In other embodiments, however, ring seals utilizing principles of the invention may include a single-piece retaining ring or a hinged retaining ring. The retaining ring  206  is secured to the housing ring  202  by a plurality of screws  208  thereby securing the brush seal  204  between the housing ring  202  and the retaining ring  206 . 
         [0022]      FIG. 3  is a perspective view of the ring seal  200  in an installed configuration. The ring seal  200  is secured around a circumference of an outer wall  304  of a tube  302  at a junction between the tube  302  and a furnace arch or a furnace roof (not shown in  FIG. 3 ). In a typical embodiment, the tube  302  is, for example, a catalyst tube; however, in other embodiments, the ring seal  200  may be used to seal any type of furnace-inlet or furnace-outlet tube. 
         [0023]    Referring to  FIGS. 2-3 , the first brush-seal ring  205 , the second brush-seal ring  207 , and the third brush-seal ring  209  are secured within the housing ring  202 . The brushes  212 ( a )-( c ) extend radially inwardly from the support rings  210  ( a )-( c ) and contact the outer wall  304  of the tube  302  thereby inhibiting the transmission of gases between the outer wall  304  and the ring seal  200 . The tube  302 , however, is not connected to the brushes  212 ( a )-( c ). Thus, the tube  302  may move, for example, in an axial direction relative to the ring seal  200 . Such movement of the tube  302  may be, for example, due to thermal expansion and/or thermal contraction of the tube  302 . 
         [0024]      FIG. 4A  is a cross-sectional view of the ring seal of  200  in an installed configuration.  FIG. 4B  is a top view of the ring seal  200  in an installed configuration. Referring to  FIGS. 4A and 4B , the first split-ring section  202 ( a ) is coupled to the second split-ring section  202 ( b ) to form the housing ring  202  around the outer wall  304  of the tube  302 . Use of the first split-ring section  202 ( a ) and the second split-ring section  202 ( b ) allows the ring seal  200  to be utilized with existing furnaces without need for significant equipment removal. The housing ring  202  is secured to an outer wall  402  of a furnace  404  via a process such as, for example, welding, brazing, or the like. 
         [0025]    Still referring to  FIGS. 4A and 4B , the first brush-seal ring  205 , the second brush-seal ring  207 , and the third brush-seal ring  209  are disposed within the housing ring  202  above the rabbet  214 . The brushes  212 ( a )-( c ) extend radially inwardly from the support rings  210 ( a )-( c ) and contact the outer wall  304  of the tube  302  thereby inhibiting the transmission of gases between the outer wall  304  of the tube  302  and the ring seal  200 . The tube  302 , however, is not connected to the brushes  212 ( a )-( c ). Thus, the tube  302  may move, for example, in an axial direction relative to the ring seal  200 . Such movement of the tube  302  may be, for example, due to thermal expansion and/or thermal contraction of the tube  302 . The retaining ring  206  is positioned above the first brush-seal ring  205 , the second brush-seal ring  207 , and the third brush-seal ring  209 . The retaining ring is secured to the housing ring  202  by the plurality of screws  208 . 
         [0026]      FIG. 5  is a flow diagram of a process  500  for sealing a catalyst tube. The process  500  starts at step  502 . At step  504 , the first split-ring section  202 ( a ) and the second split-ring section  202 ( b ) are assembled around a base region of the tube  302 . The first split-ring section  202 ( a ) and the second split-ring section  202 ( b ) are coupled together to form the housing ring  202  via the screws  406 . Use of the first split-ring section  202 ( a ) and the second split-ring section  202 ( b ) allow the housing ring  202  to be installed without removal or alteration of the tube  302  or the furnace  404 . At step  506 , the first brush-seal ring  205 , the second brush-seal ring  207 , and the third brush-seal ring  209  are wound around the outer wall  304  of the tube  302  to form the brush seal  204 . The first joint  216 , the second joint  218 , and the third joint  220  are arranged in a staggered configuration such that the first joint  216 , the second joint  218 , and the third joint  220  are not aligned. Such a configuration improves the sealing properties of the brush seal  204  by inhibiting transmission of gas through the first joint  216 , the second joint  218 , and the third joint  220 . At step  508 , the brush seal  204  is disposed within the housing ring  202  and seated on the rabbet  214 . At step  510 , the first section  222  and the second section  224  are secured around the tube  302 . The first section  222  and the second section  224  are coupled to each other to form the retaining ring  206 . At step  512 , the retaining ring  206  is secured to the housing ring  202  via the plurality of screws  208 . The process  500  ends at step  514 . 
         [0027]    Referring now to  FIGS. 2-5 , during operation, the brush seal  204  creates a sufficient barrier so as to inhibit infiltration of ambient air into the furnace  404  as well as to inhibit escape of flue gas from the furnace  404 . The plurality of brushes  212 ( a )-( c ) contain many bristles that create a tortuous flow path for escape of internal heat and flue gases from the furnace  404 . Further, use of the first brush-seal ring  205 , the second brush-seal ring  207 , and the third brush-seal ring  209  creates multiple air layers around the perimeter of the tube  302 . The multiple air layers isolate internal heat and flue gases within the furnace  404  and, thus, provide effective sealing. The ring seal  200  permits axial movement of the tube  302  therethrough. Thus, axial expansion and contraction of the tube  302  due to, for example, thermal expansion, is facilitated. In addition, use of the housing ring  202  and the retaining ring  206  allows the ring seal  202  to be installed, maintained, and replaced without removal or alteration of the furnace  404  or the tube  302 . 
         [0028]    Although various embodiments of the method and system of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Specification, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substitutions without departing from the spirit and scope of the invention as set forth herein. It is intended that the Specification and examples be considered as illustrative only.