JP4350507B2 - Improved fouling resistant fixed bed reactor - Google Patents

Description

  The present invention generally relates to a fixed bed reactor with one or more bypass devices for extending the operating life of the fixed bed reactor. One aspect of the present invention relates to a reactor including a fixed bed and a bypass device fixed in the bed. The bypass device divides the fixed bed into at least a first (or top) layer (or floor) and a second (or bottom) layer (or floor). The bypass device also allows the amount of fluid raw material that enters the floor and bypasses the first layer to be distributed to the second non-fouling layer when the fixed bed fouls. .

  One aspect of the present invention is a fixed bed having a bypass device disposed within a single fixed bed and providing a second virtual floor for optimal use of the fixed bed within the single fixed bed. Reactor related. Yet another embodiment of the present invention uses a multi-stage bypass device. This divides a single fixed bed into successive layers (or beds) and allows the reactor feed to bypass the continuous layers of the fixed bed when they foul. . The present invention also relates to a bypass device suitable for use with a fixed bed reactor and a method for extending the operational life of a fixed bed reactor using the bypass device of the present invention.

  During the operation of a fixed bed reactor, the top of the fixed bed is often fouled or clogged by the deposition of fouling material (also called particulates, particulate impurities or foulants) contained in the fluid feed flowing in the fixed bed. To do. Examples of fouling materials include organometallic compounds, polymeric materials, carbonaceous materials, organic particulates and inorganic particulates. Fixed bed clogging results in increased pressure drop, which may be accompanied by outages, reduced throughput and time consuming repairs and maintenance.

  Many bypass devices and methods have been devised to overcome this problem. Some require more than one fixed bed in each reactor, requiring complete bypassing of the fouled fixed bed. Examples of such a method are described in Patent Document 1 and Patent Document 2. One disadvantage of such a method is that it requires a spare fixed bed that can be bypassed. Therefore, it is not easy to apply the above method to a single fixed bed reactor.

  Other methods include the use of trash baskets. For example, Patent Literature 3 and Patent Literature 4 describe a fixed catalyst bed reactor comprising a hollow mesh basket made of a protective mesh material and extending into the fixed catalyst bed. Particulate impurities are removed by a hollow trash basket from the fluid stream flowing in the fixed catalyst bed.

  Although the trash basket removes some of the fouling material contained within the fluid feedstock, the effect of minimizing the increase in pressure loss due to fouling is generally negligible. This is partly because the fouling material closes the walls of the trash basket in a short time. Accordingly, the flow of the fluid feed is blocked and the pressure loss begins to rise, albeit at a somewhat slower rate than when the trash basket is not used. In general, it is desirable to maintain the fixed bed reactor for a long period of time, often for several years, without oil pressure increase without substantial increase in pressure loss. Thus, methods involving trash baskets do not adequately prevent increased pressure loss and other methods are needed to further extend the operating life of the fixed bed reactor. Existing methods for extending the operating life of fixed bed reactors involve other problems.

US Pat. No. 3,509,043 US Pat. No. 4,313,908 US Pat. No. 3,992,282 US Pat. No. 3,888,633

  One aspect of the present invention relates to a reactor for treating feedstock flowing therethrough. The reactor includes at least one fixed bed and at least one bypass device for processing the feedstock. One embodiment of the bypass device includes a cage disposed within the fixed floor. The cage has a top wall, sidewalls, and a substantially open or fully open lower end. The cage divides the fixed floor into a first top floor and a second virtual floor. The bypass device also includes a bypass tube in fluid communication with the cage. A bypass tube is disposed in the cage and protrudes from the cage onto the top surface of the fixed bed, increasing the amount of raw material around the first top floor that bypasses when the fixed bed fouls. The bypass tube is sized to control the bypass flow through the bypass device. The bypass tube is preferably sized to provide a pressure drop sufficient to prevent any significant bypass flow if the top layer of the floor is not fouled. This provides better use of the top floor. When the top layer fouls, the bypass flow is directed through the bypass tube into the cage and further out of the cage through its through hole, its open lower end, or a combination thereof, and the second virtual Head over the top surface of the floor. The cage has a substantially larger cross section than the bypass tube, and its velocity is effectively reduced when the bypass flow exits the tube.

  The bottomless bypass device may include a substantially open or fully open lower end to maximize the top surface area of the second virtual floor (where any bypassed foulant may be deposited here).

  Another aspect of the invention relates to a fixed bed reactor having a multi-stage bypass device. The multi-stage bypass device includes a cage having a plurality of consecutive chambers in fluid communication with each other. Each chamber may have a plurality of through holes so that any bypass flow entering the chamber can exit the chamber and enter a clean floor layer around the chamber. Each chamber may also have a fluid communication device (in the cage) to allow any bypass flow entering the chamber surrounded by the fouled layer to be routed into the next chamber. Except for the last chamber of). This process is repeated until the bypass flow enters the last chamber, exits through the side and / or bottom through holes, and reaches the last non-fouling layer of the floor. Preferably, the last chamber of the cage may have a substantially open or fully open lower end that provides a virtual second floor within the fixed floor.

  The multi-stage bypass device may also include a bypass tube in fluid communication with at least one chamber of the cage. The bypass tube may protrude from the cage onto the fixed bed and increase the amount of raw material bypassed around the fixed bed fouling layer. The bypass stream can be routed through the bypass tube into the cage chamber and out of the chamber through the chamber through-hole and into the clean bed layer. Multi-stage bypass devices effectively divide a single floor into multiple layers. This generally corresponds to the number of chambers in the cage.

  Yet another aspect of the present invention relates to a method for extending the operating life of a fixed bed reactor. The method includes the steps of dividing the fixed bed into at least two successive layers or beds, introducing the hydrocarbon feedstock into the fixed bed, and the next non-fouled when each successive layer fouls. Increasing the amount of raw material bypassed to the layer. This method can use one or more of the bottomless and / or multi-stage bypass devices of the present invention.

  It has been surprisingly found that the use of one or more of the bypass devices of the present invention in a fixed bed reactor substantially reduces the increase in pressure loss of the fixed bed reactor. A method and system using a bypass device having a cage with a fully open lower end is preferred. However, the lower end of the cage may not be completely opened due to mechanical restrictions or restrictions peculiar to other reactors. Also, a wire mesh or grid may be used in the lower part of the cage that is almost completely or substantially open to the flow, as long as it does not significantly cover the top surface area of the virtual floor.

  A single larger cage, or several smaller cages, may be used to provide a second virtual floor and further maximize the top surface area of this virtual floor. Some of the cages may also have one or more chambers and one or more bypass tubes. Various other modifications may be made to provide a second virtual floor and further maximize its top surface area (which can be used for foulant deposition).

  These and other embodiments of the present invention will be better understood with reference to the following detailed description and considered in conjunction with the accompanying drawings, which are set forth below.

  One embodiment of the present invention is particularly applicable to increasing the cycle life (or operating life) of a fixed catalyst bed reactor, such as a hydroprocessing (or hydrogenation) reactor. Any of a number of reactions may be performed in the hydrotreating reactor to treat the hydrocarbon. The present invention is not limited to fixed catalyst bed reactors but can be applied to any fixed bed reactor and other fixed bed devices such as contactors and filters.

  For example, a fixed catalyst bed reactor can be used to convert or process hydrocarbons or chemical feedstocks in the presence of a gas phase, such as a hydrogen-containing process gas. More specific examples of reactors that can be used in the present invention include hydroconversion of heavy petroleum feeds to lower boiling products, hydrocracking of distillate boiling range feeds, light hydrocarbons, naphtha. And reactors used for the hydrogenation of various petroleum feedstocks such as distillate boiling range streams. The present invention is applicable to reactors having one or more catalyst beds, but is particularly useful for reactors having only one fixed catalyst bed. This is because it is possible in a single fixed catalyst bed to bypass one fouled catalyst layer or multiple fouled catalyst layers.

  For example, the bypass device of the present invention can be particularly advantageous in preventing fouling of a fixed catalyst bed used to contact a stream of hydrocarbon feed with a conventional reforming or hydroprocessing catalyst. One embodiment of the bypass device allows the feed to bypass the top or top layer of the catalyst bed when fouling occurs. This allows for substantially longer floor operation compared to operation without the bypass device. It can be easily implemented to equip existing or new reactors with one or more bypass devices so that they can be operated for longer periods of time.

  One embodiment of the present invention includes a first elongate hollow member or cage having a plurality of through holes or openings, and a second elongate hollow member ("" generally disposed within the cage and protruding above the top of the cage. Provided is a bypass device (also referred to as a “single layer bypass”) for bypassing a single bed of a catalyst bed, including a bypass tube ”when it fouls. The cage is partially or completely embedded in the floor, so that the compartment of the cage with an opening in it is bypassed in the floor, high above the fouled layer at the top of the floor. The hydrocarbon feedstock may be discharged and distributed. The cage may be closed at the top, except where the first hollow extension extends therethrough. However, depending on the application, all cage members (including top, side and bottom walls) may have openings. Preferably, the cage has a substantially open lower end or a fully open lower end. For example, FIG. 1 shows a cage having a top wall, side walls, and a bottom wall, and having openings at the bottom and bottom of the side walls. 2, 3 and 4 show a bottomless bypass device having no bottom wall.

  The placement of the bypass device within the fixed catalyst bed can vary. Preferably, however, the top wall of the cage is positioned well below the top surface of the catalyst bed and drilled to allow the top catalyst layer to be used completely for foulant deposition.

  The bypass tube is in fluid communication with the perforated cage and extends above the top of the perforated cage. A bypass device may be placed in the fixed catalyst bed so that the top of the bypass tube extends above the top surface of the fixed catalyst bed. When the top layer of the catalyst bed fouls due to impurities in the feed and loses flow permeability, it bypasses the top layer and enters the cage through the bypass tube, through holes and / or openings in the cage Increasing the amount of feed that exits the cage through the lower end and enters an unfouled or less fouled layer at the bottom of the catalyst bed.

  The bypass tube provides a pressure loss or flow resistance that is sufficiently higher than the pressure loss across the clean top layer of the floor, but lower than the pressure loss across the fouled bed (preferably the top fouling layer of the floor). Thus, the feed generally proceeds through the bypass tube only when the top layer of the floor has fouled. When the top layer is not fouling, the feed flows through the bed without significant bypass flow.

  The cage is sized to provide the desired exit velocity for bypass flow into the non-fouling layer of the floor. Although the exact size of the cage and bypass tube can vary, the cage generally has a substantially larger cross-section than the bypass tube. The exact cage cross-sectional area / bypass tube cross-sectional ratio can vary, and those skilled in the art having read and understood the present disclosure will achieve the desired function of the bypass device of the present invention. It is easy to determine this. Typically, this ratio can be about 1.1 to about 20, preferably about 1.5 to about 16, more preferably about 2 to about 10, and most preferably about 3 to about 6.

  One or more bypass tubes can be used for each cage (not shown). For example, in one embodiment, a single bottomless bypass device having a plurality of bypass tubes disposed within a single large cage can be used. Preferably, the cage covers substantially the entire area of the fixed bed from one side wall of the reactor to the other side.

  In still other embodiments of the invention, the cage may include a top wall, sidewalls and an open lower end, as shown in FIGS. Preferably, the cage has through holes in the top and side walls. The bypass tube may protrude through the top wall of the cage, with the upper open end ending above the cage top wall and the lower open end ending in the cage. The bypass tube minimizes bypass if the top catalyst layer of the catalyst bed is not fouled, and diverts the feed flow if the top layer is fouled, bypasses the top layer of the catalyst bed, and Provides total pressure loss effective to enter.

  Preferably, one or more bottomless bypass devices are placed in a single fixed floor and the floor is a first top floor (or top floor) and a second lower floor (also referred to as a second virtual floor). Split effectively. The first top floor is generally the portion of the floor that is above the top wall of the bottomless bypass device. The second virtual floor is generally the portion below the floor bypass device, more specifically, the portion below the open lower end of the floor bottomless bypass device. The portion of the catalyst bed between the side walls of two consecutive bypass devices and the portion between the bypass device and the reactor wall may also be available for foulant deposition, but it is preferable to minimize this area. . The cage may also include a deflector plate that is generally located near the lower open end of the bypass tube. The deflector plate reduces the bypass flow exit velocity and better distributes the bypass flow to the top surface of the virtual second floor. The shape of the bottomless cage and bypass tube can vary. A preferred shape is one in which the top wall of the cage is minimized and the area of the lower open end of the cage is maximized. Such a design allows the top floor to be used well before the top floor fouls and maximizes the surface area of the second virtual floor top where the foulant is deposited.

  Yet another embodiment of the present invention relates to a multi-stage bypass device for bypassing successive layers of a fixed catalyst bed when they foul. The multi-stage bypass device may include a perforated cage having at least one internal plate that divides the cage into at least two compartments or chambers (upper chamber and lower chamber). The inner plate may include means for allowing fluid communication between the two chambers of the perforated cage. The fluid communication means may be any device that allows fluid communication between the two chambers, for example an opening, an orifice, a tube, a spring regulating valve, a rupture disk, etc., preferably an opening, an orifice or a tube. The pressure loss across the communication means connecting the first chamber to the second chamber is sufficiently higher than the pressure loss across the non-fouling catalyst layer (first catalyst layer) corresponding to the first cage chamber. Is designed to be lower than the pressure drop across the fouled first catalyst layer. Thus, any bypassed feed that enters the first cage chamber will generally enter the first catalyst layer not fouling out of the side cage through the first cage chamber, If the catalyst layer around the cage chamber is fouled, the amount of bypassed raw material entering the second cage chamber through the communication device increases.

  For example, the first communication means disposed on the first inner plate generally extrudes a bypass flow entering the first chamber through a through-hole disposed on the side wall of the first chamber and Provides a pressure drop effective for delivery to the first non-fouling layer of the catalyst bed (below the top layer of the bed) corresponding to the chamber. As this first layer gradually fouls, the pressure loss across the side through-hole becomes greater than the pressure loss across the first communication means, and the bypassed raw material flow enters the second cage chamber. Head.

  The multistage bypass device also includes a bypass tube. The bypass tube may protrude through the first or top chamber of the cage and extend above the top wall of the cage. The bypass tube provides a pressure loss or flow resistance that is well above the pressure drop across the clean bed but lower than the pressure drop across the fouled bed. Thus, the feed generally proceeds through the bypass tube only when the top layer of the floor has fouled. If the top layer is not fouled, the feed flows through the bed without significant bypass flow.

  In still another embodiment of the present invention, the cage divides the top wall, the side wall, the bottom wall, the plurality of through holes in at least a part of the side wall, and the interior into at least two chambers, an upper chamber and a lower chamber. At least one internal plate may be included. The inner plate may also include a fluid communication device to allow fluid communication between the upper and lower chambers. The bypass tube may protrude through the top wall of the cage and the upper open end may terminate in the upper chamber. The bypass tube minimizes bypass if the catalyst layer is not fouling, diverts the feed flow and bypasses the top layer of the catalyst bed into the upper chamber if the top bed is fouled. Provides effective total pressure loss. The fluid communication device provides a pressure loss effective to prevent the bypass flow entering the upper chamber from entering the lower chamber if the first catalyst layer corresponding to the upper chamber is not fouled. This also allows the bypass flow that entered the upper chamber to enter the lower chamber through the fluid communication device if the first catalyst layer is fouled.

  In still other embodiments of the present invention, the bypass tube may protrude through the top wall of the cage, with the upper open end ending on the cage top wall and the lower open end ending in the lower chamber. The bypass tube may have an intermediate opening disposed in the upper chamber and discharge the bypass flow into the upper chamber if the catalyst layer around the upper chamber is not fouled. 6, 7 and 8 show a multi-stage bypass device.

  Preferably, the cage of the multi-stage bypass device has a shape that minimizes the top wall of the cage and maximizes the lower open end of the cage, for example, the shape of the inverted cup shown in the embodiment of FIG.

Referring now to FIG. 1, there is shown a fouling resistant reactor 6 having a fixed catalyst bed 5 and a single layer bypass device or equipment 10 embedded in the catalyst bed 5 of one embodiment of the present invention. Although only one bypass device is shown, the present invention may include a plurality of bypass devices spaced throughout the catalyst bed. Each bypass device 10 may extend to different bed depths in the catalyst bed.

The bypass device 10 is also referred to as elongated hollow member 2 (cage member or cage with top wall 10a, side walls 10b, and a plurality of through-holes 9 lower end portion or arranged in the lower compartment 4 near the bottom wall 10c and generally cage 2 ) Is included. However, the position of the through hole can vary. For example, all cage walls may have through holes. The bypass device 10 further includes another elongated hollow member 1 (also referred to as a bypass tube) that is disposed in the cage 2 and protrudes above the catalyst bed 5 from the top wall 10a of the cage 2. The bypass tube 1 extends above the catalyst bed 5. The cage 2 has an upper surrounding part 3 (top wall and upper side wall) and a lower porous part 4 (bottom wall and lower side wall). The bypass tube 1 may optionally have a cap 7 on its top end or on a portion extending above the catalyst bed 5. An inert material layer 8 may optionally be disposed around the porous compartment 4 of the cage 2 in the catalyst bed 5.

  The elongate hollow members 1 and 2 may be tubular members, and the elongate hollow member 1 may be positioned or disposed within the elongate hollow member 2 in the form of concentric circles as shown in FIG. However, it should be understood that the elongated hollow members 1 and 2 may have other geometric shapes and relative configurations. However, preferably, the cage member (cage) 2 has a substantially larger cross section than the bypass member 1 (bypass tube). Also preferably, the cage has an open end or bottom, as shown in the embodiment of FIGS.

  In operation, the bypass tube 1 receives a part of the raw material and sends it to the cage 2, from which the raw material is discharged through the through-hole 9 of the cage 2 and sent to the lower layer of the catalyst bed 5 that is not fouled. can do. The top wall of the bypass device of FIG. 1 is level with the top surface of the floor. However, the position of the bypass device in the floor can vary. Preferably, the bypass device 10 is inserted into the catalyst bed 5 so that the cage 2 is buried in the bed. However, the location and dimensions of the bypass device can vary. For example, the bypass device is embedded in the catalyst bed, the cage lower part is included in the catalyst bed, and the bypass flow is distributed to the bed layer disposed below the top layer where substantial bed fouling has occurred. You may do it. Typically, fixed catalyst bed reactors that may benefit from the arrangement of the bypass device of the present invention include hydroprocessing and reforming reactors used in petroleum refining. However, any fixed bed that uses a solid packing for contact with the raw material, filtration of the raw material, or reaction of the raw material may benefit from the use of the bypass device of the present invention. For a typical commercial scale hydroprocessing and reforming reactor, the top layer may extend from about a few inches to about 5 feet (150 cm) from the top surface of the bed. Accordingly, the bypass device may be designed to bypass flow to the catalyst layer below the fouled top layer.

  In the embodiment shown in FIG. 1, the second elongate member extends through the first hollow elongate cage and terminates in a portion having substantially a through-hole in the cage. However, other forms are within the scope of the present invention. For example, the second elongate member may end before the through hole or may extend to a region in the portion having the through hole of the cage. The bottom of the cage may be sealed, and the lower part of the cage may have a through hole only on the side wall. In one embodiment, the cage is fully embedded in the catalyst bed below the surface of the bed and has an opening over the entire length of the cage. In a catalyst bed in which only the top layer is fouled, the bypassed feed can be sent directly below the fouled top layer.

  The cage through-hole 9 can be produced by various methods such as producing a part of the cage from a mesh material. The area with the cage opening can vary. For example, only the side wall may have a through hole, and other regions of the cage such as the top and the bottom wall may similarly have a through hole. Alternatively, all the walls of the cage may be perforated. Also, the size of the cage through-holes can vary. For example, in one embodiment of the present invention, the through-holes are large enough to allow fine particles mixed in the bypass flow to exit the cage and be distributed into the floor, even in small quantities. can do. Alternatively, the through-hole 9 of the cage may be sufficiently small so that any foulant particulates that are bypassed are retained in the cage. However, preferably, the through-holes in the cage are of a size that allows larger size particles to be retained and allows smaller size particles to exit the cage. In general, bypass foulant particulates are small particles contained within the hydrocarbon feedstock, bypassed through a bypass tube, and contribute to catalyst bed fouling. Typically, the cage opening may be a hole or slit in the size range of about 1/8 inch (0.31 cm) to about 1/2 inch (1.25 cm) wide. The region around the cage opening may be filled with a solid material larger in size than the catalyst particles to prevent the catalyst particles from passing through the through holes and into the cage.

  The tube (tube-cage bypass) in the cage design of the present invention offers many advantages over prior art bypass devices. For example, “tube-cage” bypass generally allows for a lower outlet velocity of the bypass stream entering the catalyst bed, so that the “tube-cage” bypass preserves the integrity of the catalyst particles. In general, high outlet speeds can erode and upset the floor, increase its pressure drop, and degrade the overall reactor performance. In the bypass device of the present invention, the cage has a substantially larger cross-section than the bypass tube, making it possible to effectively reduce the outlet velocity of the bypass flow. There are other advantages as well. For example, a larger cross section cage allows for a larger surface area and deposits any foulant found in the bypass flow. Also, more bypass flow can be sent faster through the bypass tube, reducing the cross section of the tube and allowing the top surface of the floor to be better utilized before fouling.

  Reactor 6 can be operated by introducing feedstock 11 to be reacted in catalyst bed 5 such as hydrocarbons, optionally with any suitable process gas and chemicals such as hydrogen. The raw material 11 may be a liquid, a gas, or a mixture thereof. The reactor 6 may be operated at any suitable process conditions. Such conditions are well known in the art and are generally not changed by using the bypass device of the present invention. The feedstock 11 may undergo any desired chemical reaction as it moves through the catalyst bed. In the early stages when the catalyst bed 5 is clean and no or little foulant is deposited on the top of the bed, the flow mostly proceeds through the catalyst bed 5 instead of the bypass device 10. This is because the bypass tube 1 is sized to have a higher pressure loss than a clean floor. The flow thus takes the least resistance flow path through the non-fouling catalyst bed 5. Generally, the bypass tube 1 is sized to provide a pressure loss of about 2 to about 100 times, preferably about 5 to about 80 times, more preferably about 10 to about 50 times the pressure loss of the fouling top layer prior to fouling. It can be. During operation, as the top of the floor fouls, the resistance to flow through the floor increases and the amount of flow that bypasses the top of the floor through the bypass device 10 increases.

  For example, in a typical commercial scale hydroprocessing reactor, the pressure drop through a clean (non-fouling) 4 foot top layer of the catalyst bed can typically be 2 psi. For such reactors, depending on the method of operation, the bypass tube 1 is about 5 to about 200 psi, preferably about 10 to 160 psi, more preferably about 20 to about 200, relative to the total feed stream in the tube 1. The size can have a flow resistance of 100 psi. In general, by using one or more bypass devices, the pressure loss through the top 4 foot section of the floor may not exceed about 50 psi over time. If the bypass device 10 of the present invention is not used, the pressure loss during fouling can be significantly higher than 50 psi and it may be necessary to shut down the reactor or reduce the throughput.

  The bypass device of the present invention may be made from any material that is compatible with the operating conditions of the reactor. Suitable materials include metals such as carbon steel, stainless steel, ceramic materials and other composite materials such as carbon fiber reinforcement.

  The bypass tube 1 has the feedstock bypassed therethrough, but its diameter or width depends on the amount and rate of bypass flow to the non-fouling bed of the catalyst bed and the desired pressure drop. It may be a value. Such a diameter can be readily determined by one skilled in the art. For example, typically, the diameter of the bypass tube 1 is from about 0.25 inches (0.625 cm) to about 12 inches (30 cm), more preferably from about 0.5 inches (1.25 cm) to about 6 inches ( 15 cm), most preferably from about 0.5 inches (1.25 cm) to about 3 inches (7.5 cm). Cage 2 may have any diameter as well, but in order to be able to prevent the bed from being excessively disturbed in order to make the exit velocity of the bypass flow entering the bed sufficiently low, It has a substantially larger diameter or cross section than the bypass tube 1. For example, the cage diameter is from about 3 inches (7.5 cm) to about 20 inches (50 cm), more preferably from about 4 inches (10 cm) to about 12 inches (30 cm), and most preferably from about 4 inches to about 10 inches. It can be.

  One or more bypass devices can be used. The number of bypass devices used can generally depend on the size of the reactor and the flow rate of the feed in the reactor. The design and number of bypass devices should allow the bypass device to provide a higher flow resistance than a clean bed and a lower flow resistance than a fouled bed. In determining the number and arrangement of bypass devices, those skilled in the art may consider local speed, residence time and temperature distribution, among others. The number and arrangement of bypass devices for any reactor can be selected to maintain the overall performance of the device.

  The compartment 4 of the cage 2 distributes the bypassed feed into the catalyst bed. The area surrounding the through-hole 9 of the cage may include a layer of packing 8 that is sized to assist in the distribution of the feedstock through the catalyst bed. The use of fillers is optional. The filling 8 may allow particulates flowing in the bypass device 10 to disperse as they exit the cage through-holes 9. A suitable packing material 8 can be any inert material such as alumina spheres and is typically used to support catalyst particles in a fixed bed. The filling material 8 may be any other material, and may be catalyst particles as long as it has a size larger than the through hole 9. Therefore, when selecting catalyst particles as the packing material 8, it is preferably of an appropriate size for distributing the bypassed feedstock. Typically, the particles are about 0.25 inches (0.625 cm) to about 4 inches (10 cm) in size. In addition to alumina spheres, several other packing materials, such as those typically used in packed towers, can also be used.

  In a preferred embodiment of the present invention, the bypass tube 1 may have on its top a device or cap 7 that facilitates the separation of particulates from the bypassed hydrocarbon feed, as shown in FIG. The hydrocarbon feed moving downwards from the reactor inlet is redirected by the cap 7 so that it moves upwards and then enters the bypass device 10. The direction of the raw material flow can be changed by the cap 7, but due to the inertia of these fine particles, the flow direction of the fine particles does not change. These particulates are separated and accumulate at the top of the bed. Thus, the cap 7 can remove a significant number of particulates and minimize fouling of the compartment inside the floor. Separation cap 7 (or separation device) generally removes larger size particulates. Depending on the size of the incoming particles, some of the very small particles may not be separated by the separation cap 7. These particulates are very small in size and therefore often pass through the catalyst bed 5 without clogging. The inert filler 8 surrounding the cage through-holes 9 can facilitate the dispersion of these small sized particulates within the layer of inert material and further minimize the increase in pressure loss. Other separation devices can also be used. Examples of suitable separation devices can include small centrifuges or cyclones attached to the top of each bypass tube 1.

  In one embodiment of the invention shown in FIG. 2, a fixed bed reactor 51 is provided that includes a fixed bed 56 and a plurality of bottomless bypass devices 50. Each bypass device 50 includes a bypass tube 53 disposed within the bottomless cage 54. The bottomless cage 54 has a top wall 50a and a side wall 50b, but does not have a bottom wall. That is, the cage 54 has an open lower end 57. The side wall 50b of the bottomless cage 54 has a through hole so that at least some of the bypass flow is discharged into the region of the bed between the two continuous bypass devices 50 and between the bypass device 50 and the side wall 51b of the reactor 51. Is done. Preferably, the plurality of bottomless bypass devices 50 are embedded in a single catalyst bed 56 and a virtual second bed 59 is provided in the single catalyst bed 56. The first top floor 58 is generally defined as the catalyst bed above the top wall 50 a of the bypass device 50, and the second virtual bed 59 is brought under the open lower end 57 of the bypass device 50. The area of the catalyst bed between the bypass device and between the bypass device and the wall 51b of the reactor 51 is generally also useful for foulant deposition. However, it is preferred that this region be minimized so that the bypass flow exits the cage 54 through its lower open end 57. The deflector plate 60 is preferably arranged in the vicinity of the lower open end 53 b of the bypass tube 53 to reduce the outlet velocity of the bypass flow, which is better distributed by the top surface of the virtual second floor 59. This configuration promotes deposition on the top surface of the second virtual floor 59 rather than the gap in the second virtual floor 59 if there is a foulant contained in the bypass flow. Optionally, a cap 61 may be placed over the top end 53a of the bypass tube 53 as in the embodiment of FIG.

The shape of the bottomless cage 54 can vary. For example, the cage can be truncated cone, truncated pyramid or cylindrical. One alternative design is shown in FIG. Here, each bottomless cage 64 has an inverted conical cup shape. This design maximizes the surface area of the open lower end 67 of the cage 64 and thus the top surface area of the second virtual floor 69 available for foulant deposition. Preferably, the cage 64 has a perforated top 64a and side walls 64b. The amount, size and position of the through holes can vary. The embodiments of FIGS. 2, 3 and 4 provide virtual second beds (59, 69 and 89, respectively) for foulant deposition in a single fixed bed. If the foulant is included in the bypass flow, it is deposited on the top surface of the second virtual floor without being deposited in the gap between the floors. Also, as in the embodiment shown in FIGS. 2, 3 and 4, a deflector plate 70 and a cap 71 may be used.

FIG. 4 shows yet another embodiment of the present invention. This includes a reactor 81 that includes a fixed bed 86 and two bottomless bypass devices 80. Each bypass device 80 includes a bypass tube 83 fixed in the bottomless cage 84. The bottomless cage 84 has a top wall 80a, a side wall 80b, and a fully open lower end 87. Side wall 80b and the top wall are perforated. The cage 84 covers substantially the entire area of the fixed bed, leaving little space between the cages and between each cage and the side wall 81b of the reactor 81. Thus, when the top floor 88 fouls, substantially all of the bypass flow enters the bypass device 81 through the opening 83a of the bypass tube 83 and exits the cage 84 through its open lower end 87. The bypass device 80 also includes a deflector plate 90 and a cap 91 as in the embodiment of FIGS.

  It has been unexpectedly found that the bottomless cage bypass device reduces the pressure increase. While not wishing to limit the present invention, it is theorized that the bottomless cage in any case promotes foulant deposition on the surface of the bed rather than the interstitial space between the catalyst particles. FIG. 5 shows increased pressure drop data obtained in a laboratory scale fixed catalyst bed reactor. The reactor was fouled by contaminating the gas feed with finely crushed walnut shells. The crushed walnut shell mimics the typical size of a foulant found in commercial raw materials and has an average particle size of about 250 μm. The reactor does not include a bypass device. FIG. 5 shows that initially, pressure loss increases rapidly as foulant particles fill the gap near the top of the bed. Later, as the catalyst bed gap near the top of the bed was filled and the particles began to deposit on the bed, the rate of increase in pressure loss decreased dramatically.

  Unlike the bypass device shown in FIG. 1, the bottomless bypass device does not have a bottom wall at all. An example of a bottomless bypass device is shown in FIGS. By using multiple bottomless bypass devices, it is possible to provide a virtual second bed in a single bed reactor. The bottomless bypass device allows the foulant contained in the bypass flow to deposit on the top surface of the virtual floor rather than on the floor gap. In general, the increase in pressure loss obtained using a bottomless bypass device can be somewhat slow. Thus, a much longer operating period of the reactor can be achieved.

  The length of the bottomless bypass device can vary, but is preferably less than the total length of the floor, as shown in FIGS. Typically, the length of the bottomless bypass device can be from a few inches to about 5-8 feet.

  Referring to FIG. 6, a cross-sectional side view of a fouling resistant reactor 620 having two multi-stage bypass devices 621 is provided. Reactor 620 can be any of a number of well-known fixed bed catalyst reactors having single or multiple fixed catalyst beds. Preferably, the multistage bypass device is embedded in the first catalyst bed 622a. However, it should be understood that the bypass device 621 may be embedded within the second catalyst bed 622b if desired. The bypass device 621 may be embedded such that the top wall of the cage member 624 is substantially flush with the top surface of the catalyst bed, as shown in FIG. However, preferably, each bypass device 621 is embedded in the floor 622a with the top wall of the cage member 624 below the top surface of the catalyst layer. Although only one bypass device 621 may be used, it is preferable to use a plurality of bypass devices that substantially cover the entire cross section of the catalyst bed. The cage 624 of each bypass device 621 may extend the entire depth of the catalyst bed 622a and may end at some desired depth within the catalyst bed 622a. The cage 624 is one or more that divides the cage into a plurality of chambers (opening 738 (shown in FIG. 7) or other fluid communication means through some communication means (tube, rupture disk, spring adjustment valve, etc.). An internal plate 625 may be included. Bypass tube 623 is secured to cage 624 and is in fluid communication with the first chamber of cage 624. The length and diameter of the bypass tube 623 prevents any significant bypass flow if the top layer of the floor is not fouled, but allows bypass flow when the top layer of the floor is fouled. It can vary to provide an effective pressure drop across the tube. A cap 627 or other separation device may also be used. Multi-stage bypass devices can effectively divide the catalyst bed into a plurality of successive layers. For example, if a multi-stage bypass device is buried in the catalyst bed, the next layer can be seen. That is, a top layer that is generally above the cage top wall of the bypass device, and a plurality of catalyst layers corresponding to the chambers of the multi-stage bypass device (e.g., a first layer commonly referred to as a catalyst layer around the first chamber of the cage, A second layer commonly referred to as a catalyst layer around the second chamber of the cage).

Referring to FIG. 7, one embodiment of a multi-stage bypass device 720 is provided. The multistage bypass device includes a bypass tube 723 disposed within the cage 724. The cage 724 has two internal plates or walls 725 that divide the cage 724 into three chambers (724a, 724b, and 724c). The bypass tube 723 protrudes through the top wall of the cage 724, the upper open end 736 ends above the top wall of the cage 724, and the lower open end 737 ends in the first chamber 724a of the cage 724. A plate 726 may be placed near the open end 737 of the bypass tube 723 to deflect the bypass flow when exiting the bypass tube 723. Each internal plate has an opening 738. This is a size that provides an effective pressure drop to direct the bypass flow from one chamber to the next when the catalyst layer around the chamber fouls. Thus, during operation, when the top catalyst layer fouls, more feed flow passes through the bypass tube 723 and enters the first chamber 724a through the open end 737 of the bypass tube 723. The bypass flow exits the first chamber 724a through the side through hole 733a and enters the first catalyst layer disposed around the side wall of the first chamber 724a. When the first catalyst layer fouls, more bypass flow enters the second chamber 724b through the first opening 738 and further passes through the side through hole 733b of the second chamber 724b. Through there and into the second catalyst layer corresponding to the second chamber 724b. Similarly, when the second catalyst layer fouls, more bypass flow passes through the second opening 738 to the third chamber 724c and further to the side of the third chamber 724c and Exit through the lower through-hole 733c, exit the cage 724 and enter the remaining catalyst bed. Separation cap 727 or some other separation device may be used to facilitate separation of large particulates 739 from bypass hydrocarbon stream 729a.

  For example, for a catalyst bed that has a pressure loss of about 2 psi if not fouled at the 4 foot top layer, preferably a multistage bypass device 720, a pressure loss across a tube 723 of about 20 to about 80 psi, and With a pressure drop across each opening 738 of about 10 to about 40 psi, the total pressure drop across bypass device 720 is designed to be about 40 to about 160 psi.

Referring to FIG. 8, another embodiment of a multi-stage device 840 that includes a bypass tube 843 disposed within a cage 844 is provided. The cage 844 has two internal walls 845. This divides the cage 844 into three chambers (844a, 844b and 844c). The bypass tube 843 protrudes through the top wall of the cage 844, the upper open end 846 ends above the top wall of the cage 844, and the lower open end 847 ends in the lower chamber 844c of the cage. The bypass tube 843 has two intermediate openings 848a and 848b. One intermediate opening 848a is disposed in the first upper chamber 844a, and the other intermediate opening 848b is disposed in the second chamber 844b. Intermediate openings 848a and 848b divert bypass flow and provide effective pressure loss from the upper chamber through the bypass tube 843 to the next lower chamber when the catalyst layer around the upper chamber fouls. Size. Thus, during operation, when the top catalyst layer fouls , more feed flow passes through the first section 843a of the bypass tube 843 and further through the first intermediate opening 848a to the second of the cage 844. Enters one chamber 844a, exits through a side through hole 849a in the first chamber 844a, and enters a first non-fouling catalyst layer corresponding to the first chamber 844a in the cage 844. When the first catalyst layer fouls , the bypass flow then passes through the second section 843b of the bypass tube 843 and further through the second intermediate opening 848b to the second chamber 844b of the cage 844. And exits through the side through-hole 849b of the second chamber 844b and enters the second non-fouling catalyst layer corresponding to the second chamber 844b.

  Similarly, when the second catalyst layer fouls, the bypass flow passes through the final section 843c of the bypass tube 843 into the cage lower chamber 844c, through the side of the chamber 844c and through the lower through-hole 849c. Then exit the cage 844 and enter the remaining catalyst bed.

The bypass tube section 843b prevents most bypass flow from entering the second chamber 844b unless the first catalyst layer corresponding to the first chamber 844a is fouled. Is designed to have a pressure drop effective to allow most of the bypass flow to enter the second chamber 844b. Generally, the bypass tube section 843b is sufficiently higher than the total pressure loss across the first intermediate opening 848a and the side through-hole 849a of the first chamber 844a if the first catalyst layer is not fouled. When the first catalyst layer fouls, it provides a pressure loss sufficiently lower than the pressure loss across the flow path. Similarly, the bypass tube section 843c has a second intermediate opening 848b and a side through hole 849b in the second chamber 844b unless the second catalyst layer corresponding to the second chamber 844b is fouled. Provides a pressure drop sufficiently higher than the total pressure drop across. The pressure loss in the bypass tube section 843c is also sufficiently lower than the pressure loss across the flow path when the second catalyst layer fouls.

  Yet another aspect of the invention relates to a method for extending the operating life of a fixed bed reactor. The method includes dividing the fixed bed into a top layer and a lower layer. The pressure drop across the top bed of the fixed bed increases due to fouling during raw material processing. The method further includes the step of introducing a hydrocarbon feedstock into the fixed bed of catalyst material, and when the top layer of the fixed bed fouls, the bypass device of the present invention is used to bypass to the lower layer of the fixed bed. Increasing the amount of raw material to be included.

  Yet another embodiment of the present invention relates to a method for extending the operating life of a fixed bed reactor comprising the steps of providing a fixed bed reactor and dividing the fixed bed into a plurality of successive layers. The method further includes the steps of introducing the raw material into the fixed bed and increasing the amount of raw material bypassed to the next non-fouled layer when each successive layer fouls. In a specific embodiment, the bypass step may include a step of placing at least one of the multistage bypass devices of the present invention in a fixed bed.

  Many modifications may be made to the above exemplary embodiments by those skilled in the art without departing from the scope of the appended claims.

1 illustrates a fouling resistant fixed catalyst bed reactor having a single layer bypass device of one embodiment of the present invention. FIG. 4 illustrates a fouling resistant fixed catalyst bed reactor having a plurality of bottomless bypass devices according to another embodiment of the present invention. FIG. FIG. 4 illustrates a fouling resistant fixed catalyst bed reactor having a plurality of bottomless bypass devices according to another embodiment of the present invention. FIG. Fig. 4 shows a fouling resistant fixed catalyst bed reactor having two bottomless bypass devices according to yet another embodiment of the present invention. Figure 5 shows pressure loss enhancement data obtained in a laboratory scale reactor. Fig. 3 shows a fouling resistant fixed catalyst bed reactor having a multi-stage bypass device according to another embodiment of the present invention. 1 shows a multi-stage bypass device according to an embodiment of the present invention. 3 shows a multi-stage bypass device according to another embodiment of the present invention.

Claims (5)

A reactor for reacting flowing raw materials,
The reactor, a fixed catalyst bed for processing the raw material; wherein and the disposed fixed catalyst bed cage and is located in at least one fixed catalyst bed, continuously of the fixed catalyst bed At least one bypass device for bypassing the two or more successive layers when two or more layers are fouled;
The bypass device includes: (i) a plurality of stacked and continuous chambers separated from each other by an internal plate and in fluid communication with each other by a fluid communication device, each having a plurality of through holes; and (ii) a top wall of the cage. Comprising a bypass tube extending through and in fluid communication with the uppermost chamber of the cage;
The bypass tube is continuous to the at least one chamber of the cage through the bypass tube and around the fouling layer of the fixed catalyst bed when the bed of the fixed catalyst bed fouls. In order to increase the amount of feedstock that bypasses into the continuous non-fouling layer of the fixed catalyst bed through the through holes in a chamber, an open end projects from the cage and above the fixed catalyst bed. Is over,
The bypass tube minimizes the bypass if the uppermost layer of the fixed catalyst bed is not fouled, and the upper chamber if the first catalyst layer of the fixed catalyst bed corresponding to the upper chamber is not fouled. The bypass flow entering the lower chamber is prevented, and if the first catalyst layer of the fixed catalyst bed is fouled, the bypass flow entering the upper chamber passes through the fluid communication device. A reactor characterized in that it provides a pressure drop effective to allow entry into the second chamber . The reactor according to claim 1, wherein the bypass tube has an intermediate opening disposed in the upper chamber. The reactor according to claim 1, wherein a ratio of a cross-sectional area of the cage / a cross-sectional area of the bypass tube is 1.1-20. The reactor according to claim 1, wherein the last chamber of the cage has an open lower end. The reactor according to claim 1, wherein the cage has a larger diameter than the bypass tube.

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