Abstract:
A sealing apparatus adapted for use in a pressure vessel such as a synthesis gas cooler. The sealing apparatus is of a segmented plate construction formed around an outer wall section of a conduit means of the pressure vessel that defines at least part of a passage for receiving effluent from a gasification process. Pressure responsive mechanisms are provided on the plate segments to maintain the pressure difference across the sealing apparatus within the acceptable operating limits as well as to permit instantaneous pressure release to prevent damage to the pressure part assembly or cage. The seal is also maintained continuously through the differential growth movement between the conduit means and the pressure vessel during heat up and cool down cycles.

Description:
FIELD AND BACKGROUND OF THE INVENTION 
     The present invention relates in general to the field of coal gasification and, in particular, an apparatus for use with certain pressure vessels such as radiant syngas coolers (RSCs) to provide sealing between the hot syngas and the pressure vessel and to provide for instantaneous pressure relief against high differential pressures during transients. 
     A radiant syngas cooler (RSC) is a component of an integrated gasification combined cycle (IGCC) power plant. A stream of hot syngas and molten ash from the gasification process enters the top of the RSC, a vertical vessel. The RSC recovers heat from the syngas to generate steam, and removes most of the entrained solids. During normal operation, a seal must be maintained to prevent or minimize hot syngas from contacting certain parts of the vessel. During certain conditions, transient operating pressure excursions can occur which must be accommodated or relieved in order to protect conduit members which convey the synthesis gas within the vessel from being destroyed. 
     Various sealing devices with pressure release mechanisms have been developed. See, for example, U.S. Patent Application Publication No. US 2007/0119577, the text of which is hereby incorporated by reference as though fully set forth herein. None, however, disclose a sealing apparatus of a segmented ring construction positioned around an outer wall section of a conduit member with resiliently biased pressure device(s) or, pressure relief apparatus with resilient biased pressure for protection of the conduit member from high differential pressures. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a sealing apparatus for use in a pressure vessel for protection of the vessel shell and the back or outside of a conduit member from exposure to high syngas temperature and corrosive gases. The invention accommodates thermal and pressure differentials during operation. Another object of the present invention is to provide a pressure relief means for reducing pressure differential between opposite sides of a conduit member contained within the pressure vessel. 
     An exemplary sealing apparatus of the present invention comprises a flange member, ring segment retaining rods, ring segments, fastening members, and resilient members. 
     The flange member is preferably located concentric with and around the outer surface portion of the conduit member. The upper end of the flange member contains a slot for enclosing the segmented seal ring. The lower end is attached to the seal plate. Each seal ring segment is movably pressure loaded by at least one ring retaining rod. The plate segments are joined to each other preferably in a fluid tight manner, and are arranged around and overlap at least part of the conduit member along an axial direction as an elongated body or structure. 
     The retaining rods for the seal ring segments are held in position by fastening members that are attached in a fluid tight manner to the flange member. The resilient members are disposed between each fastening member and the respective ring segment to resiliently pressure or load the plate segments into a fluid tight relationship with the outer surface of the conduit member. 
     The pressure relief opening and a corresponding resiliently biased door are preferably provided on the flange member. The resiliently biased door is preferably located over and adapted to cover the pressure relief opening. 
     The other end of the plate segments is preferably attached in a fluid tight manner to a seal plate spaced at a distance from the conduit member. 
     The fluid tight connections formed between the various components of the sealing apparatus of the present invention and the pressure vessel provide a fluid tight seal between the opposite sides of the conduit member. 
     It is another object of the present invention to provide a pressure relieving apparatus with the resiliently biased door mounted on the flange member via at least one pair of spaced apart mounting assemblies. Each pair of door assemblies has one door each mounted on opposite sides of the flange member. The resilient members are arranged such that one door would open outwards and the opposite door would open inwards for opposite high differential pressure. Each mounting assembly preferably includes a rod member, a resilient member and a fastening member. One end of the rod member is attached to and extends outwardly from the surface of the plate segment. The resiliently biased door is movably mounted on each rod member, and the fastening member is mounted on the free end of the rod member to retain the resiliently biased door and the resilient member on the rod member. The mounting assemblies of each respective pair are preferably positioned opposite each other on opposite sides of the pressure relief opening. 
     The resiliently biased door is preferably adapted to close the pressure relief opening when the pressure differential is below a predetermined threshold value and to open and reduce the pressure differential when the pressure differential is equal to or exceeds the predetermined threshold value. 
     One problem solved by the present invention is the protection of the pressure vessel from the hot gas that contains corrosive compounds and protection of the heat absorbing pressure part cage (or conduit) from high differential pressures across the cage or between the hot gas volume and the annulus (or cavity) between the cage and the pressure vessel. The combination of the segmented seal ring with resiliently biased pressure and pressure relief doors with resiliently biased pressure responsive relief means is the complete assembly concept that prevents contact of the effluent gas with the inside wall of the pressure vessel, and allows for instantaneous pressure balance between the hot gas volume and the annulus. 
     In addition, the annulus is continuously purged with an inert gas to positively remove harmful gases from contacting the pressure vessel and to prevent the gases from entering the annulus volume. Too much purge flow is not desirable. The positive seal provided by the sealing apparatus of the present invention allows for placement of purge flow orifices to control the amount of inert purge gas. 
     The advantages offered by the segmented ring sealing apparatus with spring plate pressure relief of the present invention include but are not limited to: 
     There is a positive seal between the hot gas volume and the annulus between the cage and the pressure vessel, which keeps harmful gasification products away from the pressure vessel for corrosion protection and reduced exposure of high temperature gases on the pressure vessel; 
     The seal is maintained continuously through the differential growth movement between the cage and the pressure vessel during heat up and cool down cycles of the cooler; in addition, the seal is maintained for any lateral movement of the cage assembly that can be caused by ambient wind pressure loading on the outside of the pressure vessel; 
     The pressure differential between the hot gas volume and the annulus is minimized by the instantaneous pressure relief devices, which maintains the structural integrity of the cage; and 
     The amount of annulus purge flow is controlled and access is provided for inspection and replacement of the devices. 
     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 preferred embodiments of the invention are illustrated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a sectional view of a sealing apparatus of the present invention installed inside a synthesis gas cooler; 
         FIG. 2  is a sectional side view of a sealing apparatus of the present invention; 
         FIG. 3  is a top plan view of a sealing apparatus of the present invention; 
         FIGS. 4A ,  4 B and  4 C are a sectional views of  FIG. 3  viewed in the direction of arrows  4 - 4  of  FIG. 3 , and illustrate various spring configurations; 
       and 
         FIG. 5  is a partial sectional side view of a plate segment of the present invention with a pressure release assembly. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, in which like reference numerals are used to refer to the same or similar elements,  FIG. 1  shows a sealing apparatus  9  and pressure relief apparatus  8  of the present invention operatively installed in a pressure vessel  10  such as a synthesis gas cooler (SGC)  10 . The pressure relief apparatus  8 is adapted to reduce the pressure difference between opposite sides of a conduit member or cage  28  when a predetermined pressure differential is reached, and the sealing apparatus  9  is adapted to provide a fluid tight seal between a flue  11  defined by the conduit member  28  and an inner cavity  42  located between the conduit member  28  and an outer shell  30  of the SGC. The flue  11 , as is shown in  FIG. 1 , is defined by the conduit member or cage  28 , and typically comprises heat exchange elements such as fluid cooled tubes and/or radiant heat transfer surfaces. Synthesis gas or effluent  12  such as that produced by a gasification process is introduced into the flue  11  provided within the synthesis gas cooler  10 . A purge gas may be selectively introduced into the cavity  42  defined by the conduit member  28  and the outer shell  30  to remove any effluent  12  that might enter the cavity  42  to prevent or reduce corrosion and exposure to high gas temperatures of the wall of the outer shell  30  or the surfaces disposed within the cavity  42 . 
     As shown in  FIG. 1 , although other arrangements are possible, the sealing apparatus  9  contacts on one end to a lower outer surface portion of the conduit member  28  and is mounted to a seal plate  13  on the other end.  FIGS. 4A ,  4 B and  4 C show by way of non-limiting example a conduit member  28  with a lower header  32  attached to its inner surface and the sealing apparatus  9  attached its outer surface. Other possible arrangements for the sealing apparatus  9  are shown in  FIGS. 2 and 4A ,  4 B and  4 C. 
     Referring to  FIG. 1 , while other arrangements are possible, the pressure relief apparatus  8  is mounted on a flange member  15  of the sealing apparatus  9 . 
     The predetermined threshold pressure value at which the pressure relief apparatus  8  activates is preferably selected such that the pressure differential across the sealing apparatus  9  does not impair or compromise the structural integrity of the conduit member or cage  28  and/or the seal plate  13 . Alternatively, the predetermined threshold pressure value may be selected such that the pressure differential does not cause the walls of the conduit member or cage  28  and/or the seal plate  13  to fail and release the effluent  12  into the cavity  42 . 
     The conduit member  28  preferably has a cross sectional shape corresponding to that of the outer shell  30 . However, the conduit member  28  may have any suitable shape or configuration, and any suitable dimension for its intended application. 
     Referring now to  FIGS. 2 and 4A ,  4 B and  4 C, there are shown sectional side views of the sealing apparatus  9  of the present invention which comprises a flange member  15 , spaced apart plate retaining rods  17 , seal ring segments  18 , fastening members  16 , resilient members  14 , one or more pressure relief openings  21 , and door plate assemblies with resiliently biased doors  19 . 
     The seal ring segments  18  are preferably located on and extend around a lower outer surface portion of the conduit member  28  in a plane perpendicular to the central conduit axis  22  (see  FIG. 1 ). The ring retaining rods  17  are preferably attached to and extend outwardly from the peripheral surface  38  of the seal ring segments  18 . The flange member  15  preferably has a slot  23  formed on one end thereof for receiving the seal ring segments  18  and at least one fastening bore  25  opening into the groove  23  for receiving one of the retaining rods  17 . Each seal ring segment  18  is movably mounted on at least one plate retaining rod  17 . 
     The seal ring segments  18  are preferably joined to each other in a fluid tight manner, and are arranged around and overlap at least part of the conduit member  28  along a lengthwise direction as an elongated body or structure. The flange member  15  may be provided with one or more port holes  26  to provide a flow path for the purge gas. Pressure applied to seal ring segments  18  may be applied by either compressing or extending the resilient member  14  from its neutral position when the pressure differential is lower than the predetermined threshold value. The neighboring seal ring segments  18  are preferably joined to each other via a tongue and groove interlocking structure, as illustrated in  FIG. 3 . 
     The fastening members  16  are mounted on the flange member  15  and are adapted to retain the seal ring plate segment  18  with the slot  23  on the retaining rod  17 . Preferably, the fastening member  16  is threadably mounted on the retaining rod  17  and is axially displaceable along the retaining rod  17  for adjusting biasing force exerted by the resilient member  14  against the seal ring segments  18 . It will be appreciated that instead of using the fastening member  16  to adjust the tension or force of the resilient member  14 , a tension adjusting member  24 , disposed between the fastening member  16  and the flange member  15  may be used. 
     The resilient members  14  are disposed between each fastening member  16  and the respective seal ring segment  18  to resiliently pressure or load the seal ring segments  18  into a fluid tight relationship with the outer surface of the conduit member  28 . Examples of resilient members include coil springs made of metal, plastic or other suitable material for the pressure and temperature conditions expected. 
     Referring to  FIG. 5 , the pressure relief opening  21  and the corresponding resiliently biased door  19  are preferably provided on the flange member  15 . The resiliently biased door  19  is preferably located over and adapted to cover the pressure relief opening  21 . 
     The other end of the flange member  15  is preferably attached in a fluid tight manner to a seal plate  13  spaced at a distance from the conduit member  28 . Preferably, the seal plate  13  is arranged perpendicular to the central conduit axis  22 . 
     The fluid tight connections formed between the various components of the sealing apparatus  9  of the present invention and conduit  28   10  provide a fluid tight seal between the opposite sides of the conduit member  28 , at least when the pressure difference across the conduit member  28  is within or below a predetermined threshold value(s). 
     The resiliently biased door plate assembly allows immediate pressure release during pressure excursions by means of the spring assemblies allowing the door  19  to open as required. Labyrinth seals may be employed to create additional sealing capabilities when the door  19  is in the closed position. Additional plate sleeves or stud sleeves may be used to act as a load leveling device in the event a twist in the door action becomes an issue (see  FIG. 5 ). The resiliently biased door  19  of the door plate assembly is preferably adapted to close the pressure relief opening  21  when the pressure differential is below a predetermined threshold value and to open and reduce the pressure differential when the pressure differential is equal to or exceeds the predetermined threshold value. 
     In an embodiment, the conduit member  28  has a substantially circular cross section and the seal ring segments  18  are provided with an arcuate configuration with a rectangular configuration in cross-section to conform to the outer surface of the conduit member  28 . Although the number of seal ring segments  18  can vary, depending on, for example, the cross sectional size of the conduit member  28  or the operating parameters of the sealing apparatus  9 , the preferred number of seal ring segments  18  ranges from 2 to 10. It will be appreciated that more or fewer seal ring segments  18  can also be used. The seal ring segments  18  may all be substantially the same width or may comprise a variety of different widths. A sealing apparatus  9  of the present invention with  8  such seal ring segments  18  is shown in  FIG. 3 . 
     Referring now to  FIG. 5 , the resiliently biased doors  19  are preferably mounted on the flange member  15  via at least one pair of spaced apart mounting assemblies  27 . Each mounting assembly  27  preferably includes a rod member  29 , a resilient member  31  (e.g., a coil spring) and a fastening member  33 . One end of the rod member  29  is attached to and extends outwardly from the surface of the flange member  15 . The resiliently biased door  19  is movably mounted on the rod member  29  via opening  35 , and the fastening member  33  is mounted on the free end of the rod member  29  to retain the resiliently biased door  19  and the resilient member  31  on the rod member  29 . The mounting assemblies  27  of each respective pair are preferably positioned opposite each other on opposite sides of the pressure relief opening  21 . The resiliently biased door  19  preferably overlaps the edge extending around the pressure relief opening  21  and/or is in intimate surface contact with the outer surface of the flange member  15 . 
     As shown in  FIG. 5 , a stud/guide sleeve  34  may be inserted between the resilient member  31  and the rod member  29  to permit even movement of the resiliently biased door  19 . A sleeve member  36  may also be provided on the side/surface of the door  19  facing the flange member  15 . The sleeve member  36  preferably abuts against a portion  39  of the pressure relief opening  21  to allow even movement of the resiliently biased door  19 . The stud/guide sleeve  34  or the sleeve member  36  may be used alone or together, as required. 
     While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.