Abstract:
A flow connector creates a fluid connection between a port in a wall of a reactor vessel and an axial flow path of the reactor vessel. The flow connector has a wall defining a flow path of the flow connector. The flow path terminates in a first end opening and a second end opening. The first end opening is configured to connect to the axial flow path of the reactor vessel, and the second end opening is configured to connect to the port in a wall of the reactor. The flow connector includes a passageway extending through the wall of the flow connector to provide access to the flow path of the flow connector. A cover is dimensioned for sealing the passageway. The passageway may be dimensioned such that a person may traverse the passageway to access the flow path of the flow connector.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to the contacting of fluids and particulate materials. Specifically, this invention relates to the internals of reactors used in the contact of fluids and solid particles. More specifically, this invention relates to the design of novel connectors for use in radial flow processes and apparatuses. 
     2. Description of the Related Art 
     A wide variety of industrial applications involves radial or horizontal flow apparatuses for contacting a fluid with a solid particulate. Representative processes include those used in the refining and petrochemical industries for hydrocarbon conversion, adsorption, and exhaust gas treatment. In reacting a hydrocarbon stream in a radial flow reactor, for example, the feed to be converted is normally at least partially vaporized when it is passed into a solid particulate catalyst bed to bring about the desired reaction. Over time, the catalyst gradually loses its activity, or becomes spent, due to the formation of coke deposits on the catalyst surface resulting from non-selective reactions and contaminants in the feed. 
     Moving bed reactor systems have therefore been developed for continuously or semi-continuously withdrawing the spent catalyst from the catalyst retention or contacting zone within the reactor and replacing it with fresh catalyst to maintain a required degree of overall catalyst activity. Typical examples are described in U.S. Pat. Nos. 3,647,680, 3,692,496, and 3,706,536. In addition, U.S. Pat. No. 3,978,150 describes a process in which particles of catalyst for the dehydrogenation of paraffins are moved continuously as a vertical column under gravity flow through one or more reactors having a horizontal flow of reactants. Another hydrocarbon conversion process using a radial flow reactor to contact an at least partially vaporized hydrocarbon reactant stream with a bed of solid catalyst particles is the reforming of naphtha boiling hydrocarbons to produce high octane gasoline. The process typically uses one or more reaction zones with catalyst particles entering the top of a first reactor, moving downwardly as a compact column under gravity flow, and being transported out of the first reactor. In many cases, a second reactor is located either underneath or next to the first reactor, such that catalyst particles move through the second reactor by gravity in the same manner. The catalyst particles may pass through additional reaction zones, normally serially, before being transported to a vessel for regeneration of the catalyst particles by the combustion of coke and other hydrocarbonaceous by-products that have accumulated on the catalyst particle surfaces during reaction. 
     The reactants in radial flow hydrocarbon conversion processes pass through each reaction zone, containing catalyst, in a substantially horizontal direction in the case of a vertically oriented cylindrical reactor. Often, the catalyst is retained in the annular zone between an outer particle retention device (e.g., an inlet screen) and an inner particle retention device (e.g., an outlet screen). The devices form a flow path for the catalyst particles moving gradually downward via gravity, until they become spent and must be removed for regeneration. The devices also provide a way to distribute gas or liquid feeds to the catalyst bed and collect products at a common effluent collection zone. In the case of radial fluid flow toward the center of the reactor, for example, this collection zone may be a central, cylindrical space within the inner particle retention device. Regardless of whether the radial fluid flow is toward or away from the center, the passage of vapor is radially through one (outer or inner) retention device, the bed of catalyst particles, and through the second (inner or outer) retention device. 
     Radial flow reactor design typically requires that the pressure drop across the vessel be minimized. This requires the use of large diameter inlet and outlet nozzles. Two typical, but non-limiting, radial flow reactor configurations include a top inlet, inward radial flow reactor and a top inlet, outward radial flow reactor. Both reactor configurations may include an elbow connector, which joins the central conduit to the inlet nozzle (for outward radial flow), or the outlet nozzle (for inward radial flow). The requirement for large diameter nozzles necessitates a restricted space between the interior surface of the vessel wall and the outside diameter of the elbow connector joining the nozzle to the central conduit. 
     In order to inspect and maintain the vessel, a worker must be able to physically enter the vessel and then disconnect the elbow connector from the nozzle and central conduit. This type of maintenance is a challenge for typical radial flow reactor designs as a miter elbow needs to be removed from the reactor to access the inside of the center pipe, requiring disconnection (for example, by removing flange bolts or vessel shell welds) and removal of the upper portion of the vessel, which involves considerable downtime and expense. Therefore, one problem in the art is how to design radial flow reactors in order to improve accessibility during construction and maintenance of the vessels. Further, the mitered elbows in traditional radial flow reactors limit the possible location of vertical connecting flanges of the vapor transfer line, which in turn limits the possible locations of other reactor internals, such as, the transfer pipes. 
     SUMMARY OF THE INVENTION 
     Using a T-type connector to join the reactor top nozzle and the central conduit solves the aforementioned problems with radial flow reactor design. First, accessibility is improved through the use of interior flanges with bolting located on the inside of the various connections between the central conduit, connector and inlet/outlet (as opposed to standard, exterior flanges with bolting on the outside of the flange). Second, the T-type connector includes a passage to facilitate access to both the aforementioned connections and the central conduit itself. 
     According to an aspect, an apparatus for creating a fluid connection between a port in a wall of a reactor vessel and an axial flow path of the reactor vessel, the apparatus is provided. The apparatus includes a flow connector having a wall defining a flow path of the flow connector. The flow path terminates in a first end opening and a second end opening. The first end opening is configured to connect to the axial flow path of the reactor vessel and the second end opening is configured to connect to the port in a wall of the reactor. The flow connector includes a passageway extending through the wall of the flow connector to provide access to the flow path of the flow connector. The apparatus also includes a cover that is dimensioned for sealing the passageway. 
     According to an aspect, a system is provided for radial flow contact of a reactant stream with catalyst particles. The system includes a reactor vessel. The system also includes a flow connector having a wall defining a flow path. The flow path terminates in a first end opening and a second end opening. The first end opening is in fluid communication with an axial flow path of the reactor vessel. The second end opening is in fluid communication with a first port in a wall of the reactor. The flow connector includes a passageway extending through the wall of the flow connector to provide access to the flow path of the flow connector. The system further includes a cover dimensioned for sealing the passageway. 
     According to an aspect, a system for radial flow contact of a reactant stream with catalyst particles is provided. The system includes a reactor vessel. The system further includes a catalyst retainer disposed in the reactor vessel that has an inner particle retention device and an outer particle retention device. The inner particle retention device and the outer particle retention device are spaced apart to define a catalyst retaining space. The inner particle retention device defines the axial flow path of the reactor vessel. The outer particle retention device and an inner surface of a wall of the reactor vessel define an annular flow path of the reactor vessel. A flow connector has a wall defining a flow path of the flow connector that terminates in a first end opening and a second end opening. The first end opening is in fluid communication with an axial flow path of the reactor vessel. The second end opening is in fluid communication with a port in a wall of the reactor. The flow connector includes a passageway extending through the wall of the flow connector to provide access to the flow path of the flow connector. The system further includes a cover dimensioned for sealing the passageway. 
     These and other features, aspects, and advantages of the present invention will become better understood upon consideration of the following detailed description, drawings and appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional profile of a top-inlet radial flow reactor with inward radial flow and having an outlet nozzle in communication with the central conduit via an elbow connection′ 
         FIG. 2  is a cross-sectional profile of a top-inlet radial flow reactor with outward radial flow and having an inlet nozzle in communication with the central conduit via an elbow connection; 
         FIG. 3  is a cross-sectional plan view of a radial flow reactor taken along lines  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a cross-sectional profile of a top-inlet radial flow reactor with inward radial flow and having an outlet nozzle in communication with the central conduit via a T-type connection of the present invention; 
         FIG. 5  is a cross-sectional profile of a top-inlet radial flow reactor with outward radial flow and having an inlet nozzle in communication with the central conduit via a T-type connection of the present invention; and 
         FIG. 6  is a cross-sectional plan view of a radial flow reactor taken along lines  6 - 6  of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The features referred to in  FIGS. 1-4  are not necessarily drawn to scale and should be understood to present an illustration of the invention and/or principles involved. Some features depicted have been enlarged or changed in view relative to others, in order to facilitate explanation and understanding. Particle retention devices such as screens, as well as radial flow fluid/solid contacting apparatuses and processes utilizing such apparatuses, as disclosed herein, will have configurations, components, and operating parameters determined, in part, by the intended application and also the environment in which they are used. The processes and apparatus described herein can be utilized in various hydrocarbon conversion processes. Some specific examples of hydrocarbon conversion processes are provided below. 
     In an example, the hydrocarbon conversion process is a reforming process. The reforming process is a common process in the refining of petroleum, and is usually used for increasing the amount of gasoline. The reforming process comprises mixing a stream of hydrogen and a hydrocarbon mixture and contacting the resulting stream with a reforming catalyst. The usual feedstock is a naphtha feedstock and generally has an initial boiling point of about 80° C. and an end boiling point of about 205° C. The reforming reactors are operated with a feed inlet temperature between 450° C. and 540° C. The reforming reaction converts paraffins and naphthenes through dehydrogenation and cyclization to aromatics. The dehydrogenation of paraffins can yield olefins, and the dehydrocyclization of paraffins and olefins can yield aromatics. 
     Reforming catalysts generally comprise a metal on a support. The support can include a porous material, such as an inorganic oxide or a molecular sieve, and a binder with a weight ratio from 1:99 to 99:1. The weight ratio is preferably from about 1:9 to about 9:1. Inorganic oxides used for support include, but are not limited to, alumina, magnesia, titania, zirconia, chromia, zinc oxide, thoria, boria, ceramic, porcelain, bauxite, silica, silica-alumina, silicon carbide, clays, crystalline zeolitic aluminasilicates, and mixtures thereof. Porous materials and binders are known in the art and are not presented in detail here. The metals preferably are one or more Group VIII noble metals, and include platinum, iridium, rhodium, and palladium. Typically, the catalyst contains an amount of the metal from about 0.01% to about 2% by weight, based on the total weight of the catalyst. The catalyst can also include a promoter element from Group IIIA or Group IVA. These metals include gallium, germanium, indium, tin, thallium and lead. 
     The hydrocarbon conversion process may be a dehydrocyclodimerization process wherein the feed comprises C2 to C6 aliphatic hydrocarbons which are converted to aromatics. Preferred feed components include C3 and C4 hydrocarbons such as isobutane, normal butane, isobutene, normal butene, propane and propylene. Diluents, e.g. nitrogen, helium, argon, and neon may also be included in the feed stream. Dehydrocyclodimerization operating conditions may include a reaction temperature from about 350° C. to about 650° C.; a pressure from about 0 kPa(g) to about 2068 kPa(g); and a liquid hourly space velocity from about 0.2 to about 5 hr −1. Preferred process conditions include a reaction temperature from about 400° C. to about 600° C.; a pressure from about 0 kPa(g) to about 1034 kPa(g); and a liquid hourly space velocity of from 0.5 to 3.0 hr −1. It is understood that, as the average carbon number of the feed increases, a reaction temperature in the lower end of the reaction temperature range is required for optimum performance and conversely, as the average carbon number of the feed decreases, the higher the required reaction temperature. Details of the dehydrocyclodimerization process are found for example in U.S. Pat. No. 4,654,455 and U.S. Pat. No. 4,746,763. 
     The dehydrocyclodimerization catalyst may be a dual functional catalyst containing acidic and dehydrogenation components. The acidic function is usually provided by a zeolite which promotes the oligomerization and aromatization reactions, while a non-noble metal component promotes the dehydrogenation function. Exemplary zeolites include ZSM-5, ZSM-8, ZSM-11, ZSM-12, and ZSM-35. One specific example of a catalyst disclosed in U.S. Pat. No. 4,746,763 consists of a ZSM-5 type zeolite, gallium and a phosphorus containing alumina as a binder. Multiple reactors or reaction zones may be used to manage the heat of reaction. The dehydrocyclodimerization process regeneration zone pressure may range from about 0 kPa(g) to about 103 kPa(g). In a particular embodiment, the regeneration conditions may include a step comprising exposing the catalyst to liquid water or water vapor as detailed in U.S. Pat. No. 6,657,096. 
     In an example, the hydrocarbon conversion process is a dehydrogenation process for the production of olefins from a feed comprising a paraffin. The feed may comprise C2 to C30 paraffinic hydrocarbons and in a preferred embodiment comprises C2 to C5 paraffins. General dehydrogenation process conditions include a pressure from about 0 kPa(g) to about 3500 kPa(g); a reaction temperature from about 480° C. to about 760° C.; a liquid hourly space velocity from about 1 to about 10 hr −1; and a hydrogen/hydrocarbon mole ratio from about 0.1:1 to about 10:1. Dehydrogenation conditions for C4 to C5 paraffin feeds may include a pressure from about 0 kPa(g) to about 500 kPa(g); a reaction temperature from about 540° C. to about 705° C.; a hydrogen/hydrocarbon mole ratio from about 0.1:1 to about 2:1; and an LHSV of less than 4. Additional details of dehydrogenation processes and catalyst may be found for example in U.S. Pat. No. 4,430,517 and U.S. Pat. No. 6,969,496. 
     Generally, the dehydrogenation catalyst comprises a platinum group component, an optional alkali metal component, and a porous inorganic carrier material. The catalyst may also contain promoter metals and a halogen component which improve the performance of the catalyst. In an embodiment, the porous carrier material is a refractory inorganic oxide. The porous carrier material may be an alumina with theta alumina being a preferred material. The platinum group includes palladium, rhodium, ruthenium, osmium and iridium and generally comprises from about 0.01 wt % to about 2 wt % of the final catalyst with the use of platinum being preferred. Potassium and lithium are preferred alkali metal components comprising from about 0.1 wt % to about 5 wt % of the final catalyst. The preferred promoter metal is tin in an amount such that the atomic ratio of tin to platinum is between about 1:1 and about 6:1. A more detailed description of the preparation of the carrier material and the addition of the platinum component and the tin component to the carrier material may be obtained by reference to U.S. Pat. No. 3,745,112. The dehydrogenation process regeneration zone pressure may range from about 0 kPa(g) to about 103 kPa(g). 
     Aspects of the invention relate to novel T-type connectors for use in apparatuses for contacting fluids (e.g., gases, liquids, or mixed phase fluids containing both gas and liquid fractions) with solids that are typically in particulate form (e.g., spheres, pellets, granules, etc.). The maximum dimension (e.g., diameter of a sphere or length of a pellet), for an average particle of such particulate solids, is typically in the range from about 0.5 mm (0.02 inches) to about 15 mm (0.59 inches), and often from about 1 mm (0.04 inches) to about 10 mm (0.39 inches). An exemplary solid particulate is a catalyst used to promote a desired hydrocarbon conversion reaction and normally containing a catalytically active metal or combination of metals dispersed on a solid, microporous carrier. Catalysts and other solid particulates are retained in particle retention devices when the smallest widths of the flow channels, for passage of fluid in the radial direction, are less than the smallest dimension (e.g., diameter of a sphere or diameter of the base of a pellet), for an average particle of a particulate solid. Typical smallest or minimum flow channel widths (e.g., formed as gaps or openings between adjacent, spaced apart profile wires or windings of profile wires) are in the range from about 0.3 mm (0.01 inches) to about 5 mm (0.20 inches), and often from about 0.5 mm (0.02 inches) to about 3 mm (0.12 inches). A representative apparatus containing a particle retention device according to the present invention is therefore a radial flow reactor that may be used in a number of chemical reactions including hydrocarbon conversion reactions such as catalytic dehydrogenation and catalytic reforming. 
     Use of the term “particle retention device” is understood to refer to devices that retain, or restrict the flow of, a solid particulate in at least one direction (e.g., radially), but do not necessarily immobilize the solid particulate. In fact, contemplated applications of the particle retention devices include their use in radial flow reactors in which the solid particulate, often a catalyst used to promote a desired conversion, is in a moving bed that allows the catalyst to be intermittently or continuously withdrawn (e.g., for regeneration by burning accumulated coke) and replaced in order to maintain a desired level of catalytic activity in the reactor. Therefore, the particle retention device may, for example, confine the catalyst in the radial direction (e.g., from the center of the reactor to an outer radius of a cylindrical retention zone or otherwise between an inner radius and an outer radius of an annular retention zone) but still allow the catalyst to move axially in the downward direction. 
     As discussed above, however, the use of both outer and inner particle retention devices can be advantageous for not only distributing the inlet fluid such as a hydrocarbon-containing feed stream to, but also for collecting the outlet fluid such as a hydrocarbon-containing product stream as it exits the particle retention zone. Particle retention devices described herein can also be combined with conventional screens, for example, in the case of radial fluid flow toward the central axis of the vessel, an outer particle retention device as described herein may be used to effectively distribute the inlet fluid feed, and a conventional inner screen may be used to collect outlet fluid product, whereby solid particulate is retained in an annular particle retention zone between the outer particle retention device and the screen. 
     Representative embodiments of the invention are directed to radial flow reactors, including moving bed reactors, comprising a vessel, a particle retention device and a novel T-type connector, as described herein, that is disposed in the vessel to promote ease of access for inspection and maintenance of the vessel internals. In many cases, the T-type connector will be T-shaped with cylindrical arms or connections. Other connector geometries, for example, a connector with a rectangular cross-section, are possible. 
     Referring now to the Figures, like elements are indicated with like numbers between  FIGS. 1-4  with the 100 series elements of  FIG. 1  analogous to the 200 series elements of  FIG. 2 , and so forth. For example, central conduit  170  in  FIG. 1  is analogous to central conduit  270  in  FIG. 2 , etc. Certain exceptions to the aforementioned numbering scheme are specifically noted where elements may not be analogous. 
       FIGS. 1 and 2  show a sectional view of a typical top-inlet inward radial flow reactor and a top-inlet outward radial flow reactor, respectively. An understanding of the construction and operation of a typical top-inlet inward/outward radial flow reactor provides context and motivation for replacing the typical elbow fitting, which connects the central conduit with the inlet (outward radial flow) or outlet (inward radial flow) nozzle, with the novel T-type connection of the present invention. Referring first to  FIG. 1 , catalyst particles (not shown) are transferred by a series of transfer conduits  150  into a particle retaining space  152  in the interior space of the vessel  124 . A bed of catalyst particles is formed in retaining space  152  immediately below the lower extent of transfer conduits  150 . A vessel partition  154  defines a catalyst collection space  151  below the lower extent of retaining space  152  and the catalyst bed. An inner particle retention device  174  and an outer particle retention device  158  define the extent of the catalyst bed in retaining space  152 , which has a generally annular cross section. Catalyst particles are withdrawn from the bottom of retaining space  152  into the catalyst collection space  151  and then through another series of transfer conduits (not shown) that transfer the catalyst particles from the vessel  124 . 
     The reactant stream enters the vessel  124  through a nozzle  162  and flows into an outer chamber  164  defined by an interior surface of the outer wall  160  of the vessel  124  and an exterior surface of the outer particle retention device  158 . A base plate  166  extends across the bottom of chamber  164  to separate it from the catalyst collection space  151 . Chamber  164  communicates the reactants with the interior of the retaining space  152  through the outer particle retention device  158 . The reactants pass across retaining space  152 , through the inner particle retention device  174 , and are collected by a central conduit  170  defined by the interior space of the inner particle retention device  174 . Central conduit  170  has a closed bottom and transports the effluent vapors from retaining space  152  upward and out of the vessel  124  through a nozzle  172  via elbow connector  171 . Elbow connector  171  may be joined to central conduit  170  and outlet nozzle  172  by various means. One possible means would be the use of an elbow connector  171 , which is flanged, such as a standard, exterior flange that is bolted on the outside. The vessel  124  of  FIG. 1  is depicted with an exterior flange  132  for connection to the central conduit  170  and an exterior flange  134  for connection to the outlet nozzle  172 . 
     Means are provided for supporting the particle retention devices  158  and  174  in place within the vessel  124 . The particle retention devices  158  and  174  may be supported from the bottom. For example, in  FIG. 1 , a support  173  positioned near the bottom of the vessel  124  contacts the lower end of the outer particle retention device  158  in order to hold the outer particle retention device  158  in place. 
     Flow arrows in the Figures illustrate radial fluid flow through inner and outer particle retention devices (e.g.,  174 ,  158  in  FIG. 1 ), and also through catalyst particle retaining space (e.g.,  152  in  FIG. 1 ), but an overall axial flow of feed distributed to, and product collected from, the particle retaining space (e.g.,  152  in  FIG. 1 ). 
       FIG. 2  shows a sectional view of an embodiment of a typical top-inlet outward radial flow reactor. The construction and operation of the top-inlet outward radial flow reactor of  FIG. 2  share several similarities with the top-inlet inward radial flow reactor depicted in  FIG. 1 . For example, catalyst particles (not shown) are transferred by a series of transfer conduits  250  into a particle retaining space  252  in the interior space of the vessel  224 . A bed of catalyst particles is formed in retaining space  252  immediately below the lower extent of transfer conduits  250 . A vessel partition  254  defines a catalyst collection space  251  below the lower extent of retaining space  252  and the catalyst bed. An inner particle retention device  274  and an outer particle retention device  258  define the extent of the catalyst bed in retaining space  252 , which has a generally annular cross section. Catalyst particles are withdrawn from the bottom of retaining space  252  into the catalyst collection space  251  and then through another series of transfer conduits (not shown) that transfer the catalyst particles from the vessel  224 . 
     The differences between the vessels  124  and  224  of  FIGS. 1 and 2 , respectively, include the location and elevation of the inlet and outlet nozzles, and the design of supports for the particle retention devices. Referring again to  FIG. 2 , the reactant stream enters the vessel  224  through a nozzle  272 . The reactant stream passes from the nozzle  272  into the central conduit  270  via elbow connector  271  and intermediate conduit  269 . Elbow connector  271  may be joined to intermediate conduit  271  and inlet nozzle  272  by various means. The vessel  224  of  FIG. 2  is depicted with an exterior flange  232  for connection to the intermediate conduit  271  and an exterior flange  234  for connection to the inlet nozzle  272 . Furthermore, intermediate conduit  272  may be joined to central conduit  270  with connection means such as external flange  236 . 
     The central conduit  270  is defined by the interior space of the inner particle retention device. A base plate  266  extends across the bottom of central conduit  270  to separate it from the catalyst collection space  251 . The conduit  270  communicates the reactants with the interior of the retaining space  252  through the inner particle retention device  274 . The reactants pass across the retaining space  252 , through the outer particle retention device  258 , and are collected in an outer chamber  264 , which is defined by an interior surface of the outer wall  260  of the vessel  224  and an exterior surface of the outer particle retention device  258 . Outer chamber  264  has a closed bottom defined by base plate  266  and transports the effluent vapors from retaining space  252  upward and out of the vessel  224  through a nozzle  262 . 
     Another difference between the radial flow reactor of  FIG. 1  and the radial flow reactor of  FIG. 2  is the inlet nozzle  272  is positioned at a higher elevation than the outlet nozzle  262 . The outlet nozzle  262  may be positioned above the catalyst retaining space  252 , as illustrated in  FIG. 2 , or lower at a position generally adjacent to the catalyst retaining space. Means are provided for supporting the particle retention devices  258  and  274  in place within the vessel  224 . However, based on the configuration of the inlet and outlet nozzles  272 ,  262  of a top-inlet outward radial flow reactor of the present invention, the particle retention devices  258  and  274  may be supported from the top. For example, in  FIG. 2 , a support  273  positioned near the top of the vessel  224  contacts the upper end of the outer particle retention device  258  in order to hold the outer particle retention device  258  in place. 
     For radial flow reactors, and particularly in reforming reactors, it is usually desirable to limit pressure drop across the vessel  124 ,  224 . Furthermore, in fluid particle contacting in general, it is preferred to avoid excessive pressure drop through fluid distributors. For example, it is known in the art that appreciable pressure drops will form fluid jets that can impinge upon and damage the contacted particles. One advantage of the design and operation of the vessel  224  of  FIG. 2  results from the outward radial flow of the reactant stream. First, as the volume that may be occupied by the reactant stream increases in the outward radial direction, the linear flow rate of the reactant stream is lower at the surface of the outer particle retention device  258  as compared with the surface of the inner particle retention device  274 . Therefore, potential issues with catalyst pinning are alleviated as compared with an inward radial flow reactor design. 
     Another advantage of the outward radial flow scheme relates to wear and tear on the vessel  124 ,  224 . Catalyst particles will collide with the particle retention device in the direction of flow of the reactant stream. For inward radial flow, catalyst particles collide more frequently with the surface of the inner particle retention device  274 . However, for outward radial flow, as the surface area of the outer particle retention device  258  is greater than the surface area of the inner particle retention device  274 , wear and tear due to catalyst particles colliding with the surface of the outer particle retention device is distributed over a greater area, thereby increasing the amount of time the vessel  224  may be operated before maintenance is required. 
       FIG. 3  illustrates a cross-sectional plan view of the reactor of  FIG. 1  taken along line  3 - 3 . While  FIG. 3  will be described with regard to the reactor of  FIG. 1 , it should be understood that the reactor of  FIG. 2  has a similar arrangement of the elements described with regard to  FIG. 3 . As illustrated in  FIG. 3 , a plurality of transfer pipes  150  are arranged about the generally central inner particle retention device  174 . The inlet nozzle  172  as illustrated includes the miter elbow  171  providing communication between the inlet nozzle  172  and the inner particle retention device. As the inlet nozzle  172  has a relatively large diameter, one or more of the catalyst transfer pipes  150  typically passes through a portion thereof, as shown. The miter elbow  171  includes one or more welds  149  for connecting portions of the elbow. Due to the welds  149  and the configuration of the miter elbow  171 , the flange  134  is located at a relatively large distance from a central portion of the vessel  124 . Because the transfer pipes  150  typically cannot pass through a weld  149  or flange  134 , the positioning of the transfer pipes  150  passing through the inlet  172  is limited, typically radially outside of the flange  134 . The arrangement of the miter elbow illustrated in  FIGS. 1-3  may also restrict the design and location of other reactor internals as well. 
       FIGS. 4 and 5  show a sectional view of a top-inlet inward radial flow reactor and a top-inlet outward radial flow reactor, respectively. The reactors in  FIGS. 4 and 5  each show a possible implementation of the novel T-type connection. Referring to  FIG. 4 , operation and design of the vessel  324  is similar to the vessel  124  of  FIG. 1 . The reactor of  FIG. 4  implements a T-type connector  371 , which joins the central conduit  370  to the outlet nozzle  372 . The T-type connector  371  may include connection means such as flanges, socket joints, butt welds and the like. In  FIG. 4 , the T-type connector  371  includes an interior flange  332  for connection to the central conduit  370  and an interior flange  334  for connection to the outlet nozzle  372  which has an inside diameter in the range of 1 feet to 15 feet. The interior flanges  332 ,  334  may be bolted on the inside as opposed to a traditional exterior flange. The inside diameter of the T-type connector  371  where the interior flanges  332 ,  334  are located is in the range of 1 feet to 15 feet. The T-type connector  371  may further include a resealable passage  340  having an inside diameter in the range of 1 feet to 15 feet. The passage  340  may be resealable with cover  337 , wherein the cover  337  is connected to the T-type connector  371  with an exterior flange  338 . Pipes  371  and  372  may include a variety of cross-sectional shapes, including but not limited to circular, square, rectangular, and elliptical. 
     Referring to  FIG. 5 , operation and design of the vessel  424  is similar to the vessel  224  of  FIG. 2 . The reactor of  FIG. 4  implements a T-type connector  471 , which joins the intermediate conduit  479  to the inlet nozzle  472 . In turn, intermediate conduit  479  is joined to central conduit  470 . The T-type connector  471  may include connection means such as flanges, socket joints, butt welds, and the like. In  FIG. 5 , the T-type connector  471  includes an interior flange  432  for connection to the intermediate conduit  479  and an interior flange  434  for connection to the inlet nozzle  472 . Intermediate conduit  479  also includes an interior flange  436  for connection to central conduit  470 . The interior flanges  432 ,  434 ,  436  may be bolted on the inside as opposed to an exterior flange. The T-type connector  471  may further include a resealable passage  440 . The passage  440  may be resealable with cover  437 , wherein the cover  437  is connected to the T-type connector  471  with an exterior flange  438 . 
     Using a T-type connector  371 ,  471  results in an improvement to the top-inlet inward radial flow reactor and top inlet outward radial flow reactor designs of  FIGS. 4 and 5 , respectively, as well as other reactor configurations not described herein, including, but not limited to bottom inlet and/or outlet inward or outward radial flow reactors. In  FIG. 4 , accessibility is improved through the use of interior flanges  332 ,  334  and passage  340  to facilitate access to the interior flanges  332 ,  334  and the central conduit  370  itself. For example, the central conduit may be accessed by removing the cover  337  rather than disconnecting and removing the top of the reactor vessel as was necessary in the designs illustrated in  FIGS. 1-3  in order to remove the miter elbow. Similarly, in  FIG. 5 , accessibility is improved through the use of interior flanges  432 ,  434 ,  436  and passage  440  to facilitate access to the interior flanges  432 ,  434 ,  436  and the central conduit  470  itself. 
     Further, referring to  FIG. 6 , because there is no inclined miter elbow, the possible locations of the flange  334  and  434  are increased, providing for improved reactor internals design, for example the location of the catalyst transfer pipes  350 . For example, as illustrated in  FIG. 6 , the T-type connector  371  may avoid the need for a weld that is offset radially outward from the central conduit  370 . Similarly, the flange  334  or other connector may be located at different radial positions, including closer to the central conduit  370  than what was possible in the designs of  FIGS. 1-3 . For these reasons, greater freedom is provided for designing the reactor internals, including the transfer pipes  350  and  450 , which can be positioned further radially inward than in previous designs. 
     Overall, aspects of the invention are associated with novel T-type connectors for use in radial flow reactors and regenerators. While use of the radial flow apparatus is not limited to any process, the radial flow apparatus can be particularly beneficial in: (i) the catalytic reforming of a hydrocarbon feedstream (e.g., a naphtha feedstream) to produce aromatics (e.g., benzene, toluene and xylenes) (see, e.g., U.S. Patent Application Publication Nos. 2012/0277501, 2012/0277502, 2012/0277503, 2012/0277504, and 2012/0277505); and (ii) the catalytic dehydrogenation of a paraffin stream to yield olefins (see, e.g., U.S. Pat. No. 8,282,887). 
     Those having skill in the art, with the knowledge gained from the present disclosure, will recognize that various changes could be made in the above devices, as well as radial flow fluid/solid contacting apparatuses and processes utilizing these devices, without departing from the scope of the present disclosure. Therefore, the scope of the appended claims should not be limited to the description of the embodiments contained herein.