Abstract:
An apparatus is for directing a fluid into a radial reactor is and which maintains a bed of solid particulate material within a reactor. The apparatus comprises a duct for directing fluid into a reactor and has a screenless face for the egress of the fluid, while providing for the retention of solid particles.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a Division of copending Application Ser. No. 11/743,904 filed May 3, 2007, the contents of which are hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to the contacting of fluids and solid materials. Specifically, this invention relates to the internals of reactors used in the contact of fluids and solid particles with respect to conduit design for the radial flow of fluids in fluid solid contacting. 
       BACKGROUND OF THE INVENTION 
       [0003]    A wide variety of processes use radial flow reactors to provide for contact between a fluid and a solid. The solid usually comprises a catalytic material on which the fluid reacts to form a product. The processes cover a range of processes, including hydrocarbon conversion, gas treatment, and adsorption for separation. 
         [0004]    Radial flow reactors are constructed such that the reactor has an annular structure and that there are annular distribution and collection devices. The devices for distribution and collection incorporate some type of screened surface. The screened surface is for holding catalyst beds in place and for aiding in the distribution of pressure over the surface of the reactor to facilitate radial flow through the reactor bed. The screen can be a mesh, either wire or other material, or a punched plate. For a moving bed, the screen or mesh provides a barrier to prevent the loss of solid catalyst particles while allowing fluid to flow through the bed. Solid catalyst particles are added at the top, and flow through the apparatus and removed at the bottom, while passing through a screened-in enclosure that permits the flow of fluid over the catalyst. The screen is preferably constructed of a non-reactive material, but in reality the screen often undergoes some reaction through corrosion, and over time problems arise from the corroded screen or mesh. 
         [0005]    One type of inlet distribution device is a reactor internal having a scallop shape and is described in U.S. Pat. No. 6,224,838 and U.S. Pat. No. 5,366,704. The scallop shape and design provides for good distribution of gas for the inlet of a radial flow reactor, but uses screens or meshes to prevent the passage of solids. The scallop shape is convenient because it allows for easy placement in a reactor without concern regarding the curvature of the vessel wall. The screens or meshes used to hold the catalyst particles within a bed are sized to have apertures sufficiently small that the particles cannot pass through. A current inlet duct design, OptiMiser™ by United States Filter Corp., WO 01/66239 A2, has an improved shape, but still uses a screen comprised of wires having a sufficiently narrow spacing to prevent the passage of catalyst. A significant problem is the corrosion of meshes or screens used to hold catalyst beds in place, or for the distribution of reactants through a reactor bed. Corrosion can plug apertures to a screen or mesh, creating dead volumes where fluid does not flow. Corrosion can also create larger apertures where the catalyst particles can then flow out of the catalyst bed with the fluid and be lost to the process increasing costs. This produces unacceptable losses of catalyst, and increases costs because of the need to add additional makeup catalyst. 
         [0006]    The design of reactors to overcome these limitations can save significantly on downtime for repairs and on the loss of catalyst, which is a significant portion of the cost of processing hydrocarbons. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides for a new screenless inlet duct for the flow of fluid into a radial reactor. The invention comprises an inlet flow duct that is vertically oriented when disposed within a radial reactor. The duct comprises a front face oriented toward the catalyst bed, two side faces, and a rear face oriented toward the exterior wall of a radial reactor. The front face comprises a plate having apertures defined therein, and louvers that are affixed to the front face. The louvers have a leading edge and a trailing edge, where the leading edge is affixed to the front face at a position above the apertures, and the trailing edge extends away from the front face and in a downward direction. 
         [0008]    In one embodiment, the invention comprises a new radial reactor that uses the screenless inlet ducts, where the screenless inlet ducts are arrayed in a circumferential manner around the inside of the reactor housing exterior wall. 
         [0009]    Other objects, advantages and applications of the present invention will become apparent to those skilled in the art from the following drawings and detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a diagram of a louvered inlet duct; 
           [0011]      FIG. 2  is a diagram of the louvered inlet ducts arrayed around the inside of a reactor housing; and 
           [0012]      FIG. 3  is a diagram of a recessed embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    A problem exists with radial flow reactors where a catalyst flows down an annular region, and the annular region is defined by an inner screened partition and an outer screened partition, which defines the catalyst bed, or a particle retention volume for holding a granular solid. In a typical radial reactor, a fluid, usually a gas, flows into an annular region surrounding the reactor, flows across the partitions and catalyst bed, and exits into a centerpipe where the resulting effluent is withdrawn. The fluid reacting with the catalyst to produce a product fluid, also usually a gas. The reactor holds the catalyst in with screens where the gas flows through. The partitions need holes sufficiently small to prevent catalyst particles from passing, but the holes are subject to plugging and creating dead spaces where the gas doesn&#39;t flow, as well as the partitions are subject to erosion and corrosion, creating holes that allow for catalyst to spill out. 
         [0014]    The inlet annular region comprises a series of channels for directing the fluid into the reactor. The channels comprise vertically elongated ducts where each duct has a front face, two side faces, and a rear face. The duct, as shown in  FIG. 1 , has a substantially trapezoidal cross-section, such that when the ducts are arrayed in a cylindrical reactor housing, as shown in  FIG. 2 , the ducts form a toroidal structure with the rear faces of the ducts facing the reactor housing  40 , and the front faces of the ducts facing a reaction zone that holds the catalyst bed. The front face  12  of the duct  10  comprises a plate with apertures  14  defined therein. The apertures  14  are spaced over the front face  12  to provide for a uniform distribution of inlet fluids to the catalyst in the reaction zone. The apertures  14  are covered with louvers  16  to prevent the flow of catalyst through the apertures  14 . The louvers  16  have a leading edge  18  affixed to the front face  12  and a trailing edge  20  extending away from the front face  12  and into the zone for containing catalyst. For purposes of this invention, the terms leading edge  18  and trailing edge  20  are with respect to the flow of solid particles through the reactor. The leading edge  18  is the upstream edge with respect to the direction of flow of the solid particles, and the trailing edge  20  is the downstream edge. The particles flow through the reactor, and particles flowing along the front face  12  will contact the leading edge  18  first, flow along the louver  16  and contact the trailing edge  20 . 
         [0015]    This design reduces fouling tendencies and problems associated with corrosion, such as plugging, or destruction of the mesh that lets catalyst through the face of the inlet duct. The apertures  14  are sized sufficiently large to provide a free flow of fluid through the apertures  14 , and preferably are substantially larger than the size of the catalyst particles in the reactor. The front face  12  with apertures  14  can be fabricated according to any method known to those skilled in the art, include drilling holes or punching holes. The invention also reduces the pressure drop across the front face of the inlet duct. 
         [0016]    The louvers  16  are disposed at an angle between 1° and 89° from vertical, where an angle of 0° means the louvers  16  would lay flat along the surface of the front face  12 , and an angle of 90° means the louvers  16  would be oriented perpendicularly to the front face  12 . However, the greater the angle, the greater the chance of creating a hold up of the catalyst, and an angle greater than 60° would present potential problems with catalyst hold up. It is preferred that the louvers  16  are oriented at an angle between 10° and 30° from vertical. The angle, as used herein is the angle formed by the louver  16  with the front face  12  of the duct. 
         [0017]    In one embodiment, the louvers  16  have a length defined as the distance between the leading edge  18  and the trailing edge  20  of the louver  16 . The apertures  14  in the front face  12  have an upper edge and a lower edge, where the upper edge is the point on the aperture that is highest on the front face  12 , and the lower edge is the point on the aperture that is lowest on the front face  12 , where the duct  10  is oriented in a vertical direction. A louver  16  in the present embodiment extends to a distance of at least the lower edge of the apertures that it covers. In a preferred embodiment, the length of the louvers  16  is sufficient to have the louver trailing edge  20  extend a distance below the aperture lower edge equal to the distance of the gap between the louver  16  and the front face  12 . 
         [0018]    In another embodiment, the louvers  16  have side edges, and the louvers  16  further comprises extensions  26 , where each extension  26  is affixed to one edge of the louver  16  and to the front face, forming an awning like structure over the apertures  14 . 
         [0019]    The structure of the ducts  10  have a substantially trapezoidal cross-section. When the ducts  10  are arrayed around the inside of the reactor housing  40 , the side faces  22  would lie on radial lines that go from the center of the reactor housing  40  to the reactor housing walls. In one embodiment, the front face  12  and the rear face  24  are substantially flat surfaces, with the front face  12  comprising a surface with apertures  14 . This provides for convenient construction of the ducts  10 , where the louvers  16  are affixed to the front face  12  after the apertures  14  are made. In fabricating the ducts  10 , the louvers  16  can be affixed to the front face  12  before attachment to the side faces  22 , or the louvers  16  can be affixed to the front face  12  after the front face  12  is attached to the side faces  22 . The side faces  22  and the rear face  24  can be fabricated from a single sheet of metal formed into an open box before the attachment of the front face  12 . 
         [0020]    In one embodiment, the ducts  10  have a substantially trapezoidal cross-section as described above, but with the front face  12  and the rear face  24  having a curvature to equal the radius of curvature of a circle with the circle&#39;s center at the center of the reactor housing  40  and the radius equal to the distance of each face from the center. A variation on these two embodiments is that one of either the front face  12  or rear face  24  is curved. 
         [0021]    In another embodiment, the ducts  10  have a substantially rectangular cross-section. The creates a small gap between adjacent ducts  10 , with the front faces  12  touching the edges of neighboring front faces  12 . By fabricating the ducts  10  with substantially rectangular cross-sections, the ducts are more easily fabricated and provide for room fitting the ducts into the reactor housing  40 . In addition, the ducts  10  can be placed within the reactor housing  40  with a small gap between the ducts  10 , and a covering plate (not shown) can be placed over the gap to prevent the catalyst from entering the space between the ducts  10 . In a variation of the covering plates, the ducts  10  can be fabricated with overlaying flange portions (not shown). The flange portions would be attached to only one side of the duct  10 , such that when the ducts  10  are positioned inside the reactor housing  40  a flange portion will cover an edge of the front face  12  of a neighboring duct  10 . The use of overlaying flange portions allows for room to fit the ducts  10  within the reactor housing  40  without requiring an exact fit with no room for thermal expansion and contraction of the ducts  10  during any heating and cooling cycles of the reactor. 
         [0022]    In another embodiment, the ducts  10  have a substantially trapezoidal cross-section, and the ducts  10  are as described above. However, the trapezoidal cross-section is such that the width of the front face  12  is greater than the width of the rear face  24 . This embodiment creates void spaces between neighboring ducts  10 , and requires the use of a covering plate to cover any gap between neighboring front faces  12 , or the use of an overlaying flange portion with each duct  10  to cover any gap. The covering plate or flange portion prevent the movement of catalyst particles into the void spaces between the neighboring ducts  10 . 
         [0023]    A further feature that can be included in the ducts  10  include support bars, disposed within the duct  10 , or on the exterior of the ducts  10  that provide structural rigidity to the ducts. 
         [0024]    In one embodiment, the invention comprises an improved radial flow apparatus. The apparatus can be an adsorber, a reactor, or any operations unit requiring radial flow. The apparatus comprises a vertically oriented and substantially cylindrical vessel having a fluid inlet and a fluid outlet. Inside the apparatus, a vertically oriented centerpipe is disposed within the vessel and is located substantially in the center of the cylindrical vessel. The center pipe can be either a fluid inlet or a fluid outlet, where the wall of the centerpipe include openings, or apertures, for the fluid to pass through the wall of the centerpipe. The apparatus further includes a plurality of vertical ducts arranged circumferentially around the cylindrical vessel, and along the inside of the cylindrical vessel wall. The ducts have a transverse cross-section having a substantially trapezoidal or rectangular shape. The ducts have a front face facing toward the centerpipe, a rear face facing the inside surface of the cylindrical vessel wall, and in contact with the vessel wall, and two side faces connecting the front face to the rear face. The front face further includes apertures defined therein to allow for the flow of fluid across the front face. The apertures are covered by a louver that prevents catalyst particles flowing through the reactor from passing through the apertures in the front face of the ducts. The ducts with the louvers are as described above. 
         [0025]    The ducts are separated from the centerpipe to define a space for holding solid particles, and in a particular embodiment, the solid particles are catalyst particles. 
         [0026]    The apparatus provides for a fluid that is flowing into the apparatus to be directed into the vertically arrayed ducts. The fluid flows down the ducts and through the apertures in the front face, then across the solid particle, or catalyst, bed to the centerpipe. The fluid flows through the openings in the centerpipe, and is carried out of the apparatus. 
         [0027]    In one embodiment, the improved inlet flow devices comprise a recessed front face as shown in  FIG. 3 . The apparatus comprises a vertically elongated inlet duct  10  having a front face  12 , two side faces  22 , and a rear face  24 . The front face  12  is disposed between the two side faces  22  and recessed from the edges  28  of the side faces  22 . The front face  12  has apertures  14  defined in the front face  12 , where fluid entering the duct  10  can exit through the apertures  14  and flow across a reactor volume. Affixed to the front face  12  are a plurality of louvers  16  extending outwardly from the front face  12 . The louvers  16  have a leading edge  18  affixed to the front face  12  at a position above at least one aperture  14 , and the trailing edge  20  extending away from the front face  12  and in a downward direction. The louvers  16  extend across the front face  12  from one side face  22  to the other side face  22 , and are affixed to the side faces  22  along the edge of the louvers  16 . The louvers  16  extend away from the front face  12  at an angle between 1° and 89° from vertical, and preferably at an angle between 10° and 30° from vertical. The recessed front face design allows for convenient insertion of the apparatus in existing cross-flow reactors, where the reactors might have screens, but the screens have corrosion or erosion problems and would normally need to be replaced. The use of this invention obviates the need for replacing corroded screens and allows for bringing a reactor on line faster. 
         [0028]    While the invention has been described with what are presently considered the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.