Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
  • B01J8/02—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds
  • B01J8/04—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds the fluid passing successively through two or more beds
  • B01J8/0446—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds the fluid passing successively through two or more beds the flow within the beds being predominantly vertical
  • B01J8/0476—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds the fluid passing successively through two or more beds the flow within the beds being predominantly vertical in two or more otherwise shaped beds
  • B01J8/0484—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds the fluid passing successively through two or more beds the flow within the beds being predominantly vertical in two or more otherwise shaped beds the beds being placed next to each other
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
  • B01J8/02—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds
  • B01J8/0285—Heating or cooling the reactor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
  • B01J2208/00008—Controlling the process
  • B01J2208/00017—Controlling the temperature
  • B01J2208/00106—Controlling the temperature by indirect heat exchange
  • B01J2208/00115—Controlling the temperature by indirect heat exchange with heat exchange elements inside the bed of solid particles
  • B01J2208/00132—Tubes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/18—Details relating to the spatial orientation of the reactor
  • B01J2219/182—Details relating to the spatial orientation of the reactor horizontal

Definitions

• the present invention relates to fixed-bed, catalytic reactors and more particularly to a fixed-bed, catalytic, crossflow reactor.
• Reactors are devices or process vessels in which chemical reactions take place during a chemical conversion type of process. Reactors may be catalyzed or non- catalyzed. A catalyzed reactor may include a fixed bed of catalysts within the reactor. Because a reaction involved in a reactor may be exothermic or endothermic, a heat exchanger must frequently be included as part of the reactor design to provide heat or to absorb heat. For example, if an exothermic reaction is occurring, heat will generally need to be removed from the reactor to maintain the desired operating temperature because heat is given off during the process. If an endothermic reaction is occurring, heat will generally need to be supplied to properly sustain the reaction.
• the reactor of the present invention may be used for any number of exothermic or endothermic reactions, one example presented below involves a Fischer-Tropsch reaction, and therefore, some background on that reaction is provided.
• the Fischer-Tropsch process involves an exothermic catalytic reaction.
• the Fischer-Tropsch process or reaction refers to the synthetic production of hydrocarbons by the catalytic reaction of carbon monoxide and hydrogen. Numerous catalysts have been used in carrying out the reaction, and at relatively low to medium pressure (near atmospheric to 600 psig) and temperatures in the range of from about 300° F. to 600° F., both saturated and unsaturated hydrocarbons can be produced.
• the synthesis reaction is very exothermic and temperature sensitive whereby temperature control is required to maintain a desired hydrocarbon product selectivity.
• the Fischer-Tropsch reaction can be characterized by the following general formula:
• the two basic methods have generally been employed for producing the synthesis gas (“syngas”) utilized as feedstock in the Fischer-Tropsch reaction.
• the two methods are steam reforming, wherein one or more light hydrocarbons such as methane are reacted with steam over a catalyst to form carbon monoxide and hydrogen, and partial oxidation, wherein one or more light hydrocarbons are combusted sub-stoichiometrically to produce synthesis gas.
• the steam reforming reaction is endothermic and a catalyst containing nickel is often utilized.
• the hydrogen to carbon monoxide ratio of the synthesis gas produced by steam reforming of methane is approximately 3:1.
• Partial oxidation is the non-catalytic, sub-stoichiometric combustion of light hydrocarbons such as methane to produce the synthesis gas.
• the basic reaction is represented as follows: CHstay + M 0 2 ⁇ CO + 2H ?
• the partial oxidation reaction is typically carried out using high purity oxygen.
• High purity oxygen can be quite expensive.
• the hydrogen to carbon monoxide ratio of synthesis gas produced by the partial oxidation of methane is approximately 2:1.
• a combination of partial oxidation and steam reforming known as autothermal reforming, wherein air is used as a source of oxygen for the partial oxidation reaction has also been used for producing synthesis gas heretofore.
• autothermal reforming U.S. Patent Nos . 2,552,308 and 2,686,195 disclose low pressure hydrocarbon synthesis processes wherein autothermal reforming with air is utilized to produce synthesis gas for the Fischer-Tropsch reaction.
• Autothermal reforming is a simple combination of partial oxidation and steam reforming where the exothermic heat of the partial oxidation supplies the necessary heat for the endothermic steam reforming reaction.
• the autothermal reforming process can be carried out in a relatively inexpensive refractory lined carbon steel vessel whereby low cost is typically involved.
• the autothermal process results in a lower hydrogen to carbon monoxide ratio in the synthesis gas than does steam reforming alone. That is, as stated above, the steam reforming reaction with methane results in a ratio of about 3:1 while the partial oxidation of methane results in a ratio of about 2:1.
• the optimum ratio for the hydrocarbon synthesis reaction carried out at low or medium pressure over a cobalt catalyst is 2:1.
• the feed to the autothermal reforming process is a mixture of light hydrocarbons such as a natural gas stream, some form of additional control is required to maintain the ratio of hydrogen to carbon monoxide in the synthesis gas at the optimum ratio of about 2:1.
• syngas Once the syngas is produced, it is treated and delivered to a synthesis reactor, where heavier hydrocarbons are formed.
• the synthesis reaction is typically very exothermic and temperature sensitive.
• a traditional reactor design which is presently used, includes a vertical reactor having tubes containing catalysts into which the syngas may be introduced. The syngas passes over or through the catalyst in the tubes and then exits the reactor. A fluid for removing or adding heat, such as boiling water, flows around the tubes. Some of these reactors have 10,000 or more tubes and might be 30 or 40 feet long. Frequently it is difficult to load the tubes of a vertical reactor design. Also, this design has another shortcoming by being difficult to add additional reactant or other substances at an intermediate point in the vertical reactor vessel. Additionally, in reactor vessels with this design, it is generally difficult to vary the flow rate and to establish discrete flow zones within the vertical reactor. This type of design has a further disadvantage of being relatively difficult to build and to operate .
• a fixed-bed, catalytic, crossflow reactor that includes a cylindrical body having a process fluid inlet for receiving a process fluid and a process fluid outlet for removing the process fluid, a first hemispherical end cap attached to a first end of the cylindrical body having a heat-exchange-fluid inlet, a second hemispherical end cap attached to a second end of the cylindrical body and having a heat -exchange- fluid outlet, a first tube sheet coupled within the first hemispherical end cap, a second tube sheet coupled to the second hemispherical end cap, a plurality of heat-exchange tubes coupled to and running between the first tube sheet and the second tube sheet such that a heat-exchange fluid introduced into the heat-exchange-fluid inlet may flow into and through the plurality of heat -exchange tubes into the second
• the reactor may further include a plurality of separators for removing condensates or other liquid fluids from the reactor, the plurality of separators coupled to the cylindrical body, and at least one separator of the plurality of separators associated with the process fluid outlet.
• the reactor may include a plurality of separators and at least one conduit for transporting the process fluid exiting one of the plurality of separators to an opposite side of the cylindrical body where it is reintroduced into the body.
• a technical advantage of the present invention is that the reactor may be easier to load catalyst than previously known designs. Another technical advantage of the present invention is that additional substances may be readily introduced into the reactor at points in between the feedstock fluid inlet and process fluid outlet. Another technical advantage of the present invention is that the crossflow of the process fluid relative to heat-exchange fluid provides more efficient heat transfer allowing lower fluid flow rates. Another technical advantage of the present invention is that the geometry within the reactor may be readily varied to provide multiple flow zones with the same or different fluid flow rates in each flow zone. Another technical advantage of the present invention may be that it is relatively easier to manufacture than most prior art reactors .
• Another aspect of the present invention includes providing a reactor having a generally cylindrical body with a longitudinal axis extending substantially horizontal and one or more separators or boots extending from a lower portion of the cylindrical body to receive condensate or other liquids from the reactor.
• the separators may be maintained at a different temperature as compared to the temperature of the cylindrical body. By maintaining the separators at a different temperature, one or more substances may be added to the separators to initiate a reaction which is different from the reaction carried out within the cylindrical body.
• the separators may be maintained at a suitable temperature such that hydrogen can be introduced into the separator to initiate cracking of the hydrocarbon condensate and/or liquids contained therein.
• a further aspect of the present invention includes providing a primary reactor having a generally cylindrical body with a longitudinal axis extending substantially horizontally therethrough.
• One or more separators or boots extending from a lower portion of the cylindrical body to receive condensate or other liquids from the primary reactor.
• One or more secondary reactors communicating with an upper portion of the cylindrical body to provide a chamber for a secondary vapor phase reaction such as oligomerization of reactants flowing from one fluid flow zone or pathway to the next fluid flow zone or pathway.
• FIGURE 1 is a schematic diagram of a reactor according to one aspect of the present invention.
• FIGURE 2 is a longitudinal cross-section of the reactor of FIGURE 1 ;
• FIGURE 3 is a radial cross-section of the reactor of FIGURES 1 and 2 taken along line 3-3;
• FIGURE 4 is a schematic diagram of a second embodiment of the present invention
• FIGURE 5 is a schematic diagram of a third embodiment of the present invention.
• FIGURES 1-5 like numerals being used for like and corresponding parts of the various drawings.
• Reactor 10 may be generally described as a fixed-bed, cross-flow, gas-phase or two phase catalytic reactor that is suitable for conducting most exothermic or endothermic chemical reactions typically carried out using a fixed-bed catalyst .
• Examples of reactions that may occur in reactor 10 may include a Fischer-Tropsch reaction, synthesis gas reaction producing methanol and ammonia, and the like.
• Reactor 10 has a housing 12 that includes a main cylindrical body 14, and a first hemispherical end 16 and a second hemispherical end 18, which are attached to body 14.
• Reactor 10 has a heat- exchange-fluid inlet 20 and a heat-exchange-fluid outlet 22. The fluid flow path between inlet 20 and outlet 22 will be explained in more detail in connection with FIGURE 2.
• Reactor 10 has a process inlet 24 and a process outlet 26.
• Various reactants or feedstocks may be introduced into reactor 10 through inlet 24.
• the feedstock may contain one or more substances depending upon the intended use of reactor 10.
• the feedstock will preferably include synthesis gas suitable for use in a Fischer-Tropsch reaction.
• Process fluid which originates as feedstock at inlet 24 travels through reactor 10 and contains varying levels of feedstock, desired product, unreacted synthesis gas, water, and inert compounds depending upon the location of the process fluid within reactor 10.
• Near inlet 24, the process fluid will consist almost entirely of feedstock and near outlet 26 the process gas is greatly depleted of reactants.
• one or more additional substances or reactants may be added at selected locations in accordance with teachings of the present invention.
• Reactor 10 may have a first manway 28 and a second manway 30 for allowing access to the internal portion of reactor 10 for the purposes of loading catalysts and removing spent catalysts from reactor 10.
• Reactor 10 may also have a plurality of separators or boots such as separators 32, 34, 36, and 38. Separators 32, 34, 36, 38 may be attached to reactor 10 when reactor 10 is to be used for reactions involving the production of condensate such as in a Fischer-Tropsch reaction.
• the number of separators 32, 34, 36 and 38 included with reactor 10 depends on the number of pathways or zones desired through reactor 10 as will be described further below.
• Reactor 10 is preferably mounted horizontally as shown in FIGURE 1; that is, with the longitudinal axis of housing 12 extending generally perpendicular to the direction of gravitational forces. As such, reactor 10 has a top side 40 and a bottom side 42. The flow is generally vertical in each pathway or zone. A plurality of pathways or zones for the process fluid are defined within reactor 10. For purposes of illustration only, the reactor 10 is shown with four pathways: first flow pathway 44, second flow pathway 46, third flow pathway 48, and fourth flow pathway 50, which will be described below in connection with FIGURE 2.
• a feedstock having one or more reactants enters inlet 24.
• the feedstock is converted from feedstock into desired liquid hydrocarbon products exiting through a conduit 78.
• the process fluid which originates as feedstock, first travels through the first pathway 44 until reaching first separator 32.
• the process fluid is returned to topside 40 of reactor 10 through process fluid return conduit 52.
• Conduit 52 delivers the process fluid to second pathway 46, and after flowing through pathway 46, the process fluid arrives at second separator 34.
• Second separator 34 returns the process fluid to the topside 40 through second process fluid return conduit 54 on topside 40 at reactor 10.
• Process fluid then flows through third pathway 48 until reaching third separator 36.
• Third separator 36 delivers the process fluid to third process fluid return conduit 56 for delivery to topside 40 of reactor 10 and into fourth pathway 50.
• Process fluid return conduits 52, 54, and 56 are shown on an external surface of reactor 10, but they may be included internally in some embodiments.
• the process fluid is passed through a fourth pathway
• Condensate exiting separator 66 is then delivered to storage 68 through conduit 70.
• separators 32, 34, 36, and 38 do not include separators 32, 34, 36, and 38 because no condensation is produced by the process carried out in the reactor 10; for example, if a low-alfa catalyst is used in a Fischer- Tropsch process, there should be little or no condensation and, therefore, no need for separators 32, 34, 36 and 38.
• the process fluid exiting outlet 26 is delivered to heat exchanger 72, which may remove heat, and then on through conduit 74 to a separator 76.
• the desired liquid hydrocarbon products exit separator 76 and are introduced through conduit 78 to storage 80.
• Separator 76 may return tail gas, which consists of unreacted feedstock, though conduit 75 to inlet 24 for possible reintroduction into first flow pathway 44 for further reaction or to other locations within the process for energy recovery.
• first flow pathway 44 is defined by first tube sheet 88 and first baffling 82.
• the second flow pathway 46 is defined by first baffling 82 and second baffling 84.
• the third pathway is defined by second baffling 84 and third baffling 86.
• the fourth pathway 50 is defined by third baffling 86 and second tube sheet 90.
• baffling 82, 84, and 86 is secured in place at the time of manufacturing of reactor 10. Baffling 82, 84, and 86 may be, for example, welded to body 14.
• Another important aspect of the present invention is that the multiple pathways allow for flexibility in introducing additional catalysts or substances at points in between inlet 24 and outlet 26. For example, it may be desirable in some situations to add hydrogen or olefins or other substances to one particular flow path to control the reactions.
• the additional substances may be introduced into a flow path by a simple T-fitting on one of the product-return conduits 52, 54, or 56; for example, conduit 56 is shown with a T-fitting 55 for introducing a substance such as hydrocarbon or another reactant after flow path 48 and before flow path 50.
• first tube sheet 88 and second tube sheet 90 In between first tube sheet 88 and second tube sheet 90 are a plurality of heat-exchange tubes generally referenced by numeral 92.
• the tubes are shown substantially perpendicular to the flow paths 44, 46, 48 and 50.
• the heat-exchange tubes 92 carry a heat-exchange fluid for removing or providing heat to the product flowing between inlet 24 and outlet 26.
• the heat-exchange fluid is delivered to inlet 20 and is distributed into tubes 92 by tube sheet 88.
• the heat-exchange fluid exits tubes 92 at second tube sheet 90 and then exits reactor 10 through outlet 22.
• This cross-flow, tube-and-shell arrangement provides effective and efficient heat transfer between the process product and the heat-exchange fluid passing through the plurality of heat exchange tubes 92.
• This embodiment shows a single pass arrangement of the plurality of tubes 92, but in other embodiments a multiple pass arrangement could be utilized.
• First, second, third, and fourth distribution baffles or manifolds 94, 96, 98 and 100, respectively, are provided to evenly distribute the product into the flow paths 44, 46, 48, and 50, respectively. In other embodiments, this may be a single integral distributor.
• a first, second, third and fourth catalyst bed 102, 104, 106, and 108 are used to hold catalyst 110 (FIGURE 3) .
• the catalyst bed is formed as a single integral bed. Referring now to FIGURE 3, a radial cross-section taken along line 3-3 of FIGURE 2 is shown. The cross flow of path 46 through the plurality of heat-exchange tubes 92 is reflected in this cross-sectional view.
• a portion of catalyst 110 which is loaded onto catalyst bed 104 is shown in the lower right-hand corner of FIGURE 3.
• internal sidewalls 120 and 122 are attached to the first tube sheet 88 and second tube sheet 90 and run the longitudinal length of body 14.
• Internal sidewalls 120 and 122 help to provide a more consistent and even flow through paths 44, 46, 48 and 50.
• the space between internal sidewalls 120 and 122 and the inner surface of body 14 may be filled with an insulating material.
• sidewalls 120 and 121 may be removed such that pipes may be extended to the inner surface of body 14 or if the catalyst is not sensitive to flow rate, the catalyst may fill the entire zone.
• catalyst pellets may be introduced from topside 40 onto the plurality of heat-exchange tubes 92.
• the catalyst pellets 110 will interact with the plurality of heat-exchange tubes 92 until they arrive on catalyst bed 104 and are built up back towards the top of the tubes 92.
• This arrangement allows for the catalyst 110 to be quickly and easily loaded into reactor 10 without damage to catalyst 110 from free falling great distances.
• a person may enter manway 28 to help distribute catalyst 110 onto the plurality of tubes 92.
• Manway 30 allows access to a lower portion of reactor 10 to assist with removal of spent catalyst 110.
• Reactor 210 is analogous in most respects with the embodiment shown in FIGURES 1-3. In this embodiment, however, flow pathways 244, 246, 248 and 250 alternate direction without requiring a product-return conduit. This arrangement may be appropriate where the process occurring in reactor 210 does not produce condensate or produces only an insubstantial amount of liquids.
• baffling 282 does not run the full width of reactor 10 but stops short to provide a flow path, and additional baffle 283 is added to direct the flow as indicated by flow path 246.
• the reorienting of path 246 over to third path 248 is accomplished using baffling 284 with an opening 285 and with an additional baffling 287.
• the reorientation of flow path 248 over to flow path 250 is accomplished using baffling 286 to form opening 287 and with the use of an additional baffling 289.
• the plurality of heat -exchange tubes 292 run between first tube sheet 288 and second flow sheet 290.
• Reactor 310 is analogous in most respects with the embodiment shown in FIGURES 1-3.
• heat sources 433, 435, 437, and 439 are added to separators 332, 334, 336, and 338 to maintain them at a different temperature than the flow paths 344, 346, 348, and 350.
• one or more substances may be added to the separators to initiate a reaction which is different from the reaction carried out within the cylindrical body.
• the separators may be maintained at a suitable temperature such that hydrogen can be introduced into the separator to initiate cracking of the hydrocarbon condensate, e.g. wax, contained therein.
• Fischer-Tropsch reactions occur at a temperature substantially lower than that of hydrocracking.
• separators 332, 334, 336, and 348 in conjunction with heat sources 444, 446, 448 and 450 allows for elevated temperatures in the separators while maintaining lower temperatures in flow paths 444, 446, 448, and 450.
• the separators eliminate water generated in the Fischer-Tropsch reactions, the presence of which would generally prevent hydrocracking.
• the addition of hydrocracking of the hydrocarbon condensate reduces the amount of heavy hydrocarbons in line 60 and increases the amount of lighter, liquid hydrocarbons.
• Such liquid hydrocarbons are separated in separator 366 and delivered through conduit 371 to storage 369 for storage.
• the rate of hydrogen addition should be controlled to prevent liquid carryover back into the previous flow path, such as flow path 344 for separator 332.
• the additional hydrogen may be added, for example, through conduit 325, which receives hydrogen from the feedstock.
• a portion of the hydrogen in the feedstock may be separated from the feedstock by hydrogen membrane 327.
• This hydrogen may also be added to the various flow paths
• FIGURE 2 As discussed above, the addition of reactants into the various flow paths is useful in controlling the quantity, quality and volume of desired liquid hydrocarbon products at conduit 378 and conduit 370.
• the embodiment of the present invention as previously described with respect to FIGURE 5 may be generally described as a secondary liquid phase reaction occurring at the bottom of cylindrical body 314.
• a secondary vapor phase reaction may occur at the top of cylindrical body 314.
• one or more secondary reaction chambers similar to separators 332, 334, 336 and 338 may be mounted on the upper portion of cylindrical body 314.
• an appropriate catalyst (not expressly shown) may be disposed within each secondary reaction chamber.
• appropriate heating or cooling may be provided for each secondary reaction chamber depending upon the desired vapor phase reaction.
• a secondary reaction chamber may be provided in conduit 352 to allow oligomerization of any olefins contained within the process fluid as it travels between flow paths or zones 344 and 346. Adding one or more secondary reaction chambers as part of cylindrical body 314 to carry out an oligomerization process because the resulting polymers would be generally unaffected as they travel through the remainder of cylindrical body 314 and would result in an increased in the desired liquid hydrocarbon product at conduit 378.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=21810400

Family Applications (1)

Country Status (3)

Families Citing this family (6)

Family Cites Families (4)

• 1997
  • 1997-06-20 EP EP97930165A patent/EP0914200A1/de not_active Withdrawn
  • 1997-06-20 AU AU34062/97A patent/AU3406297A/en not_active Abandoned
  • 1997-06-20 WO PCT/US1997/010732 patent/WO1998004342A1/en not_active Application Discontinuation

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events