Abstract:
A reactor vessel system includes a reactor vessel including a first port in fluid communication with an interior of the reactor vessel and an outlet port connected in fluid communication with the interior of the reactor vessel. A base supports the reactor vessel. A first coil of tubing is connected in fluid communication with the first port and disposed around a perimeter of the reactor vessel. A method of operating a reactor vessel system includes providing a reactor vessel including a first port in fluid communication with an interior of the reactor vessel and an outlet port connected in fluid communication with the interior of the reactor vessel, providing a first coil of tubing connected in fluid communication with the first port and disposed around a perimeter of the reactor vessel, and flowing steam through the first coil and into the reactor vessel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to U.S. Provisional Patent Application Ser. No. 60/951,095 filed Jul. 20, 2007, the contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    A reactor vessel that operates at elevated temperatures can expand (e.g., elongate in length along an axial length of the vessel) as the reactor vessel heats from a non-operational, cool state to an operational, heated state. Such reactor vessels are typically mounted by mounting the base thereof at a fixed location, and can be interconnected by piping connections to one or more other components. However, the other components may operate under different thermal conditions and/or be subject to different expansion/contraction configurations than the reactor vessel. The inventions have determined that such relative positional shifts between components in such a system can create stresses in the piping connections, which can cause failure or hasten fatigue failure in the piping connections. 
       BRIEF SUMMARY OF THE INVENTION 
       [0003]    In an effort to eliminate the above problems, the inventors have constructed a coil piping system as described below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0004]    A more complete appreciation of the invention and many of the attendant advantages thereof will become readily apparent with reference to the following detailed description, particularly when considered in conjunction with the accompanying drawings, in which: 
           [0005]      FIG. 1A  is a front perspective view of a coil piping system for a water gas shift reactor according to the present invention; 
           [0006]      FIG. 1B  is a rear perspective view of the coil piping system for a water gas shift reactor according to the present invention; 
           [0007]      FIG. 2A  is a front elevational view of the coil piping system for a water gas shift reactor according to the present invention; 
           [0008]      FIG. 2B  is a side elevational view of the coil piping system for a water gas shift reactor according to the present invention; 
           [0009]      FIG. 2C  is a top view of the coil piping system for a water gas shift reactor according to the present invention; 
           [0010]      FIG. 3A  is an exploded, perspective view of the natural gas preheater depicted in  FIGS. 1A-1B  and  2 A- 2 C; 
           [0011]      FIG. 3B  is an assembled, cross-sectional view of the natural gas preheater depicted in  FIGS. 1A-1B  and  2 A- 2 C; 
           [0012]      FIG. 3C  is a reduced, assembled, perspective view of the natural gas preheater depicted in  FIGS. 1A-1B  and  2 A- 2 C; 
           [0013]      FIG. 3D  is a reduced, assembled, bottom elevational view of the natural gas preheater depicted in  FIGS. 1A-1B  and  2 A- 2 C; 
           [0014]      FIGS. 4A and 4B  are diagrams depicting a coil in a compressed state and in a non-compressed state, respectively; and 
           [0015]      FIGS. 5A and 5B  are perspective views of a reactor system showing the coil piping system of the present invention connected to a water gas shift reactor vessel with a natural gas preheater, a hydrogen desulfurizer vessel, and a steam reformer reactor vessel having an air-preheater. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    Embodiments of the present invention are described hereinafter with reference to the accompanying drawings. In the following description, the constituent elements having substantially the same function and arrangement are denoted by the same reference numerals, and repetitive descriptions will be made only when necessary. 
         [0017]    A reactor vessel that operates at elevated temperatures can expand (e.g., elongate in length along an axial length of the vessel) as the reactor vessel heats from a non-operational, cool state to an operational, heated state. Such reactor vessels are typically mounted by mounting the base thereof at a fixed location, and can be interconnected by piping connections (e.g., inlet piping, outlet piping, etc.) to one or more other components (e.g., another reactor vessel, a preheater assembly, etc.). However, the other component(s) may operate until different thermal conditions and/or be subject to different expansion/contraction configurations than the reactor vessel. Thus, the expansion of the vessel during operating conditions may shift the position of one or more ports thereof (e.g., inlet port, outlet port, etc.) with respect to the base, and the positional shift of the port(s) of the reactor vessel may not correspond to positional shifts in the ports of the other component(s) to which the piping connection(s) is mounted. Thus, the relative positional shifts in the port(s) of the reactor vessel and the port(s) of the other component(s) to which the reactor vessel is interconnected by the piping connection(s), can create stresses in the piping connection(s), which can cause failure or hasten fatigue failure in the piping connection or port(s). Also, if one or more ports of the reactor vessel is connected via connection piping to port(s) of one or more other components that do not shift in position (i.e. do not expand or contract) and thus remain in a fixed position, then the positional shift of the port(s) of the reactor vessel will create stresses in the piping connection(s), which can cause failure or hasten fatigue failure in the piping connection or port(s) or support structure(s). 
         [0018]    The present invention provides a method and system for providing piping connections for a reactor vessel that can alleviate negative consequences resulting from such stresses. The piping system preferably provides one or more piping connections to a vessel that allows for minimization or elimination of stresses in the piping connections during operation of the vessel. 
         [0019]      FIGS. 1A-1B  and  2 A- 2 C depict an embodiment of a coil piping system according to the present invention. The coil piping system  10  depicted includes an inlet coil  30  and an outlet coil  60 ; however, note that the system can alternatively include only one of the inlet coil  30  or the outlet coil  60  (i.e., the system need not include both), or can alternatively include coils in addition to the inlet coil and the outlet coil, for example, for connection to other ports (not shown) in the vessel. The coil piping system  10  depicted in  FIGS. 1A-1B  and  2 A- 2 C is connected to a water-gas shift reactor (WGS) vessel  20 ; however, the invention can be applied to any other type of vessel or housing subject to expansion and contraction during the lifetime thereof.  FIGS. 5A and 5B  are perspective views of an exemplary reactor system incorporating the coil piping system of the present invention connected to the WGS vessel  20  with a natural gas preheater  40 , a hydrogen desulfurizer (HDS) vessel  100 , a steam reformer reactor vessel  110 , and an air-preheater  120  for the steam reformer reactor  110 . 
         [0020]    The WGS vessel  20  includes a lower potion  22  rigidly mounted to a base  12 , which is rigidly affixed to a floor or to a packaging unit or housing, for example. The WGS vessel  20  has an inlet port  28  on a side of an upper portion  26  thereof and an outlet port  24  on a side of the lower portion  22 . Within the WGS vessel  20  is a packed bed of catalyst material, such as a low-temperature water-gas shift catalyst. Thus, fluid (in this case, reformate from a steam reformer reactor vessel) enters the upper portion  26  of the WGS vessel  20  through the inlet port  28 , then travels downward through the packed bed of catalyst material, and then exits the lower portion  22  of the WGS vessel  20  through the outlet port  24 . 
         [0021]    The WGS vessel  20  depicted in  FIGS. 1A-1B  and  2 A- 2 C is connected to a natural gas preheater assembly (or NG preheater)  40 ; however, the invention can be applied to any vessel or housing, and need not be connected to such a preheater, or can be connected to any other type of component. A conduit  25  is attached to the side of the lower portion  22  of the WGS vessel at the outlet port  24 . The conduit  25  provides a fluid interconnection between the outlet port  24  and an inlet  42  of the NG preheater  40 . The conduit  25  also provides a structural interconnection between the WGS vessel  20  and the NG preheater  40  by providing a cantilevered support of the NG preheater  40 . 
         [0022]    In this embodiment, the NG preheater  40  uses reformate exiting the WGS vessel  20  to preheat a natural gas feed before the natural gas feed is sent to and used in a hydrogen desulfurizer (HDS) vessel  100  (see  FIGS. 5A and 5B ). The NG preheater  40  is used, for example, to increase the temperature of the natural gas feed to an appropriate level to ensure that the desulfurization reaction takes place in the HDS vessel  100 . In addition to the depictions of the NG preheater in  FIGS. 1A ,  1 B,  2 A, and  2 C,  FIGS. 3A-3D  depict the details of the internal and external structures of the NG preheater. 
         [0023]    The NG preheater  40  includes two shell-and-tube heat exchangers; a first shell-and-tube heat exchanger provided within section  44  and a second shell-and-tube heat exchanger provided within section  48 . The reformate exiting the WGS vessel  20  is provided shell-side as it travels through the NG preheater  40 , while the natural gas feed is provided tube-side as it travels through the NG preheater  40 . 
         [0024]    The reformate exiting the WGS vessel  20  through outlet port  24  travels through conduit  25  and enters the inlet  42  of the NG preheater  40 . The reformate then travels shell-side upward through the first shell-and-tube heat exchanger provided within section  44 , then travels through curved section  46  (which does not include a tube array for the natural gas, as will be explained below), then travels shell-side downward through the second shell-and-tube heat exchanger provided within section  48 , and then exits the NG preheater  40  through an outlet port  50 . 
         [0025]    The natural gas feed enters the NG preheater  40  through an inlet  52 , then travels upward tube-side through a tube array of the second shell-and-tube heat exchanger to an upper end of the section  48  for a first pass through section  48 , then turns and travels downward tube-side through the tube array of the second shell-and-tube heat exchanger for a second pass through section  48 , then travels from a lower end of section  48  to a lower end of section  44  via tube  55  (the J-shaped tube), then enters the lower end of section  44  through an inlet  56 , then travels upward tube-side through a tube array of the first shell-and-tube heat exchanger to an upper end of the section  44  for a first pass through section  44 , then turns and travels downward tube-side through the tube array of the first shell-and-tube heat exchanger for a second pass through section  44 , and then exits the NG preheater  40  through outlet  58 . The preheater natural gas feed exiting outlet  58  travels via a conduit to the HDS vessel  100  for use therein. 
         [0026]    The inlet coil  30  of the present invention has an inlet end  32  that is connected to an outlet port  130  of a steam gas reformer vessel  110  via rigid piping. The inlet coil  30  includes a rigid connection piping portion  34  that generally can include any combination of straight and curved sections of piping needed to connect the inlet end  32  (and the outlet port of the steam gas reformer vessel  110 ) to an end of a coil portion  36  of the inlet coil  30 . The opposite end of the coil portion  36  has an outlet end  38  connected to the inlet port  28  of the WGS vessel  20 . 
         [0027]    The outlet coil  60  of the present invention has an inlet end  62  that is connected to the outlet port  50  of the NG preheater  40  for receiving the reformate exiting the NG preheater  40 . The inlet end  62  of the outlet coil  60  is connected to an end of a coil portion  64 . The opposite end of the coil portion  64  is connected to a rigid piping connection portion  66  having an outlet  68 . The rigid connection piping portion  66  generally can include any combination of straight and curved sections of rigid piping needed to connect the outlet  68  to another component, which in this case is a preheater  120  used to preheat air before the air is used in the steam gas reformer vessel  110 . 
         [0028]    The coil portion  36  of the inlet coil  30  is made of tubing or piping that is bent to form a helical coil. In the embodiment depicted, the coil portion  36  of the inlet coil  30  wraps around the WGS vessel  20  about four times; however, the coil portion  36  of the inlet coil  30  can alternatively wrap around the WGS vessel  20  more times or less times than in the embodiment depicted. The coil portion  36  forms a coil spring. 
         [0029]    The coil portion  64  of the outlet coil  60  is made of tubing or piping that is bent to form a helical coil. In the embodiment depicted, the coil portion  64  of the outlet coil  60  wraps around the WGS vessel  20  five times; however, the coil portion  64  of the outlet coil  60  can alternatively wrap around the WGS vessel  20  more times or less times than in the embodiment depicted. The coil portion  64  forms a coil spring. 
         [0030]    As can be seen in  FIGS. 2A and 2B , the inlet port  28  of the WGS vessel  20  is providing at an elevation that is a distance d 1  away from the upper surface of the base  12 , within which the WGS vessel  20  is mounted. Additionally, the outlet port  24  of the WGS vessel  20  is providing at an elevation that is a distance d 2  away from the upper surface of the base  12 . During operation of the WGS vessel  20 , the WGS vessel  20  will become heated, which will cause thermal expansion of the WGS vessel  20  and elongation of the WGS vessel  20  along the axial length thereof. Thus, the distance d 1  and the distance d 2  will vary from a cold, non-operational state to a hot, operational state, such that d 1(OPERATIONAL STATE) &gt;d 1(NON-OPERATIONAL STATE) , and d 2(OPERATIONAL STATE) &gt;d 2(NON-OPERATIONAL STATE) . 
         [0031]    In addition to the variation in the positions of the inlet port  28  and the outlet port  24  of the WGS vessel  20 , the ports of the components to which the inlet port  28  and the outlet port  24  are connected can also vary in position due to thermal expansion/contraction of those components. The relative positional shifts in the ports  24  and  28  of the WGS vessel  20  and the ports of the other components to which the WGS vessel  20  is interconnected by piping connections, can create stresses in the piping connections, which can cause failure or hasten fatigue failure in the piping connection or ports. Also, if one or more ports of the WGS vessel  20  is connected via connection piping to port(s) of one or more other components that do not shift in position (i.e. do not expand or contract) and thus remain in a fixed position, then the positional shift of the port(s) of the WGS vessel  20  will create stresses in the piping connection(s), which can cause failure or hasten fatigue failure in the piping connection or port(s). 
         [0032]    Based on experimentation or calculation, the relative positional shift between the inlet port  28  of the WGS vessel  20  and the outlet port of the component to which it is connected can be determined between a non-operational state and an operational state of the WGS vessel  20  and that component. Once this relative positional shift has been determined, the coil portion  36  of the inlet coil  30  can be configured to absorb the relative positional shift between the inlet port  28  of the WGS vessel  20  and the outlet port of the component to which it is connected. 
         [0033]    Similarly, the relative positional shift between the outlet port  24  of the WGS vessel  20  and the inlet port of the component to which it is connected can be determined between a non-operational state and an operational state of the WGS vessel  20  and that component. And, once this relative positional shift has been determined, the coil portion  64  of the outlet coil  60  can be configured to absorb the relative positional shift between the outlet port  24  of the WGS vessel  20  and the inlet port of the component to which it is connected. 
         [0034]    In the preferred embodiment of the present invention, the coil portions  36  and  64  are configured such that low or no stress is present in the inlet coil  30  and outlet coil  60  during an operational state of the WGS vessel  20  and the components connected thereto. Thus, the helical springs formed by the coil portions  36  and  64  are in an unstressed, uncompressed state during the operational state of the WGS vessel  20  and the components connected thereto. However, when the WGS vessel  20  and the components connected thereto are in a cold, non-operational state, the thermal contraction of the WGS vessel  20  and the components connected thereto will cause relative positional shifts between the respective inlet and outlet ports, which will axially compress the helical springs formed by the coil portions  36  and  64 . Thus, in the cold, non-operational state, the helical springs formed by the coil portions  36  and  64  will be in a compressed state. 
         [0035]      FIGS. 4A and 4B  are diagrams depicting a coil in a compressed state and in a non-compressed state, respectively, in order to provide an explanation of how to configure the coil portions  36  and  64  of the present invention. The coil portions can be constructed such that the coil has an axial length d 3  when in a non-compressed state as depicted in  FIG. 4B , and an axial length d 4  when in a compressed state as depicted in  FIG. 4A . Once the relative positional shifts are determined for the inlet port  28  and the outlet port  24  and the components to which they are connected, then the positional shift value for the inlet port and the positional shift value for the outlet port  24  can each be used as a distance d 5 , which is the respective distance by which the coil portions  36  and  64  should be compressed during mounting in the non-operational state. Thus, during the operational state, the relative positional shifts will uncompress the helical springs, such that the piping connections are in an unstressed condition. 
         [0036]    Alternatively, the coil portions can be configured such that the helical coils are in a compressed configuration in the operational state, and in a non-compressed configuration during the non-operational state. Further alternatively, the coil portions can be configured such that the helical coils are in tension, rather than compression, when in a stressed state. Alternatively, the coil portions can be configured such that the helical coils are in compression in the operational state, in tension in the non-operational state, and in an unstressed state during a point in time when the system is heating up from the cold, non-operational state to the heated, operational state, and during a point in time when the system is cooling down from the heated, operational state to the cold, non-operational state. Further alternatively, the coil portions can be configured such that the helical coils are in tension in the operational state, in compression in the non-operational state, and in an unstressed state during a point in time when the system is heating up from the cold, non-operational state to the heated, operational state, and during a point in time when the system is cooling down from the heated, operational state to the cold, non-operational state. 
         [0037]    Thus, the coil system of the present invention advantageously can be configured to reliably absorb stresses without failure, can be configured to reduce the magnitude of stresses caused by thermal expansion/contraction changes in the overall system, and/or can be configured to provide either a non-stressed operational, state or a non-stressed, non-operational as desired. By taking into account the changes in the relative positions of inlets and outlets of the various components in the system due to thermal expansion/contraction, the coil system of the present invention can provide a robust piping system. If desired, the coil(s) can be manufactured in a prestressed state and maintained in that prestressed state during shipping, such that the piping system would be unstressed under normal operating conditions. For example, if it is determined that a shift in relative position from cold state to hot operating state will be 0.75 inches, the coil can be prestressed with 0.75 inches of axial compression. 
         [0038]    In the preferred embodiment, the coils are not attached to the outer walls of the WGS vessel, but rather a minimum spacing is maintained between the outer surface of the WGS vessel and the inner diameter of the coils under both operating and non-operating conditions. Preferably, the spacing provided is large enough to allow for a layer of insulation to be provided around the outer surface of the WGS vessel. Additionally, the coils are preferably insulated and intended to be adiabatic. 
         [0039]    The WGS vessel is depicted as including a lifting lug at a top surface thereof, and an upper thermowell and a lower thermowell are depicted as extending from side surfaces thereof for thermocouples used to measure temperatures within the WGS vessel. 
         [0040]    It should be noted that the exemplary embodiments depicted and described herein set forth the preferred embodiments of the present invention, and are not meant to limit the scope of the claims hereto in any way. Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.