Shell pass structure of tubular reactor

Abstract

The utility model discloses a shell side structure of a tubular reactor, which comprises a grating component, a shell side plate and a shell side plate, the grating component is integrally of a tubular structure and comprises a grating ring and grating strips, the grating ring integrally encloses tubes to form a wall surface of the tubular structure, and the grating strips are arranged in a layered manner, are arranged in a latticed manner and are used for isolating and supporting the tubes; the baffle assembly is arranged at the inlet and the outlet of the shell pass of the heat removal fluid and forms an annular space channel in the reactor. The shell pass structure of the tubular reactor can effectively solve the problems that in the prior art, the temperature distribution in the reactor is not uniform, and the resistance drop of heat removal fluid is large, is preferably used in the process of synthesizing vinyl acetate, and is more suitable for the large-scale requirement of a device.

Description

Technical Field

[0001] The utility model relates to the field of fixed bed reactors, in particular to a shell-side structure applied to large-diameter tubular reactors. Background Art

[0002] The structure of a shell-and-tube reactor is similar to a vertical fixed tubesheet heat exchanger. Catalysts are loaded into each reaction tube. Under the combined effects of the catalyst, temperature, and pressure, the reaction medium within the tubes undergoes a chemical reaction, releasing a large amount of heat. Heat is removed between the tubes, i.e., along the shell side, making reaction temperature control easier. Therefore, shell-and-tube reactors are primarily suitable for highly exothermic gas-liquid-solid reactions using solid catalysts and gas / liquid phase reaction media.

[0003] Taking the synthesis of vinyl acetate as an example, the ethylene process involves mixing ethylene, oxygen, and acetic acid vapor. Under certain temperature and pressure conditions, this mixture is passed through a fixed-bed reactor equipped with a precious metal catalyst, where a gas-phase oxidation reaction occurs to produce vinyl acetate, along with small amounts of byproducts such as acetaldehyde, ethyl acetate, and methyl acetate. Because the production of vinyl acetate by the ethylene process is a highly exothermic reaction, the heat released must be removed promptly to maintain the required temperature and pressure. Consequently, shell-and-tube reactors are widely used in chemical plants for vinyl acetate production.

[0004] Chinese patent CN202893319U discloses a shell-side structure and a shell-and-tube vinyl acetate synthesis reactor including the shell-side structure. The upper and lower ends of the reactor shell-side structure are respectively provided with annular distributors similar to a draft tube structure along the circumferential direction of the outer side of the reactor shell. The reactor shell is provided with multiple distribution holes uniformly distributed along the circumferential direction and of uniform size. The heat removal fluid enters / exhausts the reactor shell through the distribution holes, continuously removing the reaction heat to meet the reaction temperature control requirements. However, when the reactor diameter is large, the number of distribution holes on the shell at the annular distributors at the upper and lower ends also increases. On the one hand, this weakens the strength of the reactor shell at this location and increases the difficulty of manufacturing the reactor. On the other hand, since the heat removal fluid needs to enter / exhaust the reactor shell through the various distribution holes on the shell after passing through the annular distributor from the external pipeline, the resistance drop of the heat removal fluid is increased. In addition, discs and annular baffles are set in the shell side of this type of reactor, and no pipes are laid in the center and edge areas to enhance the turbulence of the shell side fluid and increase the heat transfer coefficient. However, since the setting of the baffles causes the fluid to flow horizontally perpendicular to the axis of the tube, dead zones are inevitably generated in the center and edge areas of the baffles. Moreover, the horizontal flow of the shell side fluid is also the main reason for inducing tube vibration.

[0005] As production scale continues to expand, the diameter of the reactor also increases according to demand. If the deflection facilities in the above-mentioned prior art are still used, the dead zone of the shell-side heat removal fluid will further increase, making it difficult to achieve uniform distribution of the shell-side heat removal fluid in the reactor. The reaction heat cannot be removed in time, resulting in uneven temperature distribution in the reactor and even causing local temperature runaway. In severe cases, it causes premature deactivation of the catalyst, affects the yield of the vinyl acetate product, and also brings safety risks to the stable operation of the vinyl acetate unit.

[0006] Therefore, there is an urgent need for a shell-side structure suitable for large-diameter shell-and-tube reactors, which can not only make the temperature distribution in the reactor more uniform, but also effectively reduce the resistance drop of the heat removal fluid.

[0007] The information disclosed in this background technology section is only intended to increase the understanding of the overall background of the present invention, and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art. Utility Model Content

[0008] The purpose of the utility model is to provide a shell-side structure suitable for large-diameter tubular reactors, thereby overcoming the problems of uneven temperature distribution in the reactor and large resistance drop of the heat removal fluid in the prior art.

[0009] To achieve the above-mentioned objectives, the present invention provides a shell-side structure of a shell-and-tube reactor, comprising: a grid assembly, which is a cylindrical structure as a whole and includes a grid ring and grid bars, the grid ring enclosing the tubes as a whole and forming the wall of the cylindrical structure, the grid bars being arranged in layers and each layer being arranged in a grid shape, for isolating and supporting each tube; a baffle assembly, which is arranged at the shell-side inlet and outlet positions of the heat removal fluid and forms an annular gap channel in the reactor.

[0010] Furthermore, in the above technical solution, the baffle assembly may include: a first annular baffle, which is arranged above the lower tube plate in the reactor, including a first vertical section and a horizontal section, and a first annular gap is formed between the lower edge of the first vertical section and the lower tube plate; a second annular baffle, which is arranged below the upper tube plate in the reactor, including a second vertical section and an inclined section, and a second annular gap is formed between the upper edge of the second vertical section and the upper tube plate.

[0011] Furthermore, in the above technical solution, the gap between the grid bars and adjacent tubes can be set to 0.2-1.0 mm; the distance between the grid bars of adjacent layers, and the distance between the grid bars and adjacent baffles can be set to 800-1600 mm.

[0012] Furthermore, in the above technical solution, the shell-side inlet of the heat removal fluid is arranged on the reactor wall and distributed circumferentially along the first annular baffle, and the number of shell-side inlets can be 2 to 10; the shell-side outlet of the heat removal fluid is arranged on the reactor wall and distributed circumferentially along the second annular baffle, and the number of shell-side outlets can be 2 to 36.

[0013] Furthermore, in the above technical solution, the first vertical section of the first annular baffle is a circular side plate, and the horizontal section is a circular cover plate. The side plate and the cover plate and the inner wall of the reactor form a first annular channel, and the upper end of the first annular channel is closed and the lower end is open.

[0014] Furthermore, in the above technical solution, the second vertical section of the second annular baffle is a circular side plate, and the inclined section is a circular bottom plate. The side plate and the bottom plate and the inner wall of the reactor form a second annular channel, and the upper end of the second annular channel is open and the lower end is closed.

[0015] Furthermore, in the above technical solution, the height of the first annular gap can be set to 30-300 mm; the height of the second annular gap can be set to 20-200 mm.

[0016] Furthermore, in the above technical solution, the width of the first annular channel may be 1% to 10% of the reactor diameter, and the ratio of the height of the first annular channel to the shell-side inlet pipe diameter may be 1.1 to 3.

[0017] Furthermore, in the above technical solution, the ratio of the width of the second annular channel to the width of the first annular channel can be 0.5-1, and the ratio of the height of the second annular channel to the shell-side outlet pipe diameter can be 1.1-3.

[0018] Furthermore, in the above technical solution, the grille ring and the grille bars can both be made of metal plates and fixed by welding; the width of the metal plates is 10 to 150 mm, and the thickness is 0.1 to 3.0 mm.

[0019] Furthermore, in the above technical solution, the shell-and-tube reactor is a large-diameter reactor that can be used to synthesize vinyl acetate.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1) Compared with the shell-side structure of disc-shaped and annular baffles used in the prior art, the present invention avoids the problems of slow flow velocity and lateral flow at the center of the disc-shaped baffle and the edge of the annular baffle, which lead to the inability to remove the reaction heat in time, uneven radial temperature distribution of the reactor, occurrence of over-temperature hot spots, and further occurrence of temperature runaway and increased reaction by-products. The present invention uses a multi-layer grid arranged in a grid pattern, which can not only effectively isolate and support the tubes of a large-diameter reactor, but also minimize the radial flow of the heat removal fluid to avoid dead zones. The grid structure allows the heat removal fluid to flow axially along the length of the reactor tubes, which can remove the reaction heat generated in the tubes in time; the grid structure divides the tubes in the shell side of the reactor into units of equal cross-sectional area along the radial direction of the reactor to ensure uniform distribution of the heat removal fluid, thereby minimizing the radial temperature difference of the reactor; the grid structure allows the heat removal fluid to flow axially along the outside of the tubes, and also effectively prevents the vibration of the tubes induced by the lateral flow of the heat removal fluid;

[0022] 2) Compared with the conventional method of providing external flow guide devices at the upper and lower ends of the reactor shell, the first and second annular gaps constructed in the present invention structurally eliminate the flow dead zone between the through holes on the shell and the adjacent tube sheets caused by the heat removal fluid entering / exiting the shell side through the through holes opened in the reactor shell from the external flow guide devices. The first and second annular baffles are located inside the reactor shell, which not only reduces the resistance drop of the heat removal fluid and facilitates the uniform distribution of the heat removal fluid, but also greatly reduces the difficulty of equipment manufacturing because no through holes are required in the shell. It also avoids the weakening effect of the shell strength caused by opening multiple through holes at the same height section of the shell, thereby ensuring the smooth operation and safety of the equipment.

[0023] 3) The shell-and-tube reactor of the present invention is preferably used in the process of synthesizing vinyl acetate and is more suitable for the large-scale requirements of the device; the shell-side structure of the present invention solves the problems of the complex shell-side structure of the shell-and-tube reactor for producing vinyl acetate in the past and the large flow dead zone of the heat removal fluid in the shell-side, and has a better heat removal effect for large-diameter reactors.

[0024] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and to implement it according to the contents of the specification, and to make the above and other purposes, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the shell-side structure of the tubular reactor of the utility model.

[0026] Figure 2 It is a top view schematic diagram of the grid assembly in the shell-side structure of the utility model.

[0027] Description of main reference numerals:

[0028] 1-grid, 11-grid ring, 12-grid bar, 2-first annular gap, 20-first annular channel, 21-first vertical section of the first annular baffle, 22-horizontal section of the first annular baffle, 3-second annular gap, 30-second annular channel, 31-second vertical section of the second annular baffle, 32-inclined section of the second annular baffle;

[0029] 100 - reactor, 101 - vessel wall, 102 - tube array, 103 - shell-side inlet for heat removal fluid, 104 - lower tube sheet, 105 - shell-side outlet for heat removal fluid, 106 - upper tube sheet, 107 - reaction gas inlet, 108 - synthesis gas outlet. DETAILED DESCRIPTION

[0030] The specific implementation of the present invention will be described in detail below with reference to the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation.

[0031] Unless expressly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising” will be understood to include the stated elements or components but not to exclude other elements or components.

[0032] In this document, for ease of description, spatially relative terms such as "below," "beneath," "down," "above," "above," etc. may be used to describe the relationship of one element or feature to another element or feature in the accompanying drawings. It should be understood that the spatially relative terms are intended to encompass different orientations of an object in use or operation in addition to the orientation depicted in the drawings. For example, if the object in the figure is turned over, the element described as being "below" or "below" other elements or features will be oriented "above" the element or feature. Therefore, the exemplary term "below" can include both below and above directions. Objects may also have other orientations (rotated 90 degrees or other orientations) and the spatially relative terms used herein should be interpreted accordingly.

[0033] In this document, the terms "first", "second", etc. are used to distinguish two different elements or parts, and are not used to limit specific positions or relative relationships. In other words, in some embodiments, the terms "first", "second", etc. can also be interchangeable with each other.

[0034] like Figure 1 、 2As shown, the present invention provides a shell-side structure of a tubular reactor, which replaces the traditional baffle structure and changes the traditional structural form of the shell-side inlet and outlet of the heat removal fluid, and is particularly suitable for large-diameter reactors in gas-solid strong exothermic reactions. The shell-side structure includes at least a grid assembly and a baffle assembly. Among them, the grid assembly (i.e., the grid 1) is a cylindrical structure as a whole and includes a grid ring 11 and grid bars 12. The grid ring 11 encloses the tubes 102 as a whole and forms the wall of the cylindrical structure. The grid bars 12 are arranged in layers and each layer is arranged in a grid shape, which is used to isolate and support each tube 102. The baffle assembly is arranged at the corresponding positions of the shell-side inlet 103 and the shell-side outlet 105 of the heat removal fluid, and forms an annular gap channel in the reactor 100 (i.e., a channel for the reactor for the heat removal fluid to enter and exit). The present invention adopts a different concept from the prior art. Through the grid arranged in a multi-layer grid shape, it can not only effectively isolate and support the tubes of the large-diameter reactor, but also minimize the radial flow of the heat removal fluid to avoid dead zones. The grid structure allows the shell-side medium (i.e., heat removal fluid) to flow axially along the length of the reactor tubes, which can promptly remove the reaction heat generated in the tubes; secondly, the grid structure divides the tubes in the reactor shell into units of equal cross-sectional area along the radial direction of the reactor to ensure uniform distribution of the heat removal fluid, thereby minimizing the radial temperature difference of the reactor; thirdly, the grid structure allows the heat removal fluid to flow axially along the outside of the tubes (i.e., Figure 1 It also effectively prevents the tube vibration caused by the lateral flow of the heat removal fluid.

[0035] Specifically, the grid 1 of the present invention is composed of a plurality of grid bars 12 welded to a circular grid ring 11. Both the grid ring 11 and the grid bars 12 can be made of ordinary metal sheets with a width of 10 to 150 mm and a thickness of 0.1 to 3.0 mm. The grid bars 12 are arranged in a grid pattern so that each tube is isolated and supported by grid bars on all sides. Preferably, but not restrictively, the gap between the grid bars 11 and the reaction tubes is 0.1 to 2.0 mm, and more preferably, it is in the range of 0.2 to 1.0 mm. In a multi-layer grid, the distance between adjacent layers of grids, as well as the distance between the grid and adjacent baffles (i.e., the first annular baffle and the second annular baffle), is 500 to 2000 mm, and more preferably, it is in the range of 800 to 1600 mm. The inventors have found through experimental research that with the above-mentioned structure and dimensions, the grid has a more significant effect in isolating and supporting the tubes, and the heat removal fluid flows more smoothly and evenly along the axial direction of the tubes, completely avoiding dead zones.

[0036] Further Figure 1As shown, the baffle assembly includes a first annular baffle and a second annular baffle. The first annular baffle is positioned above the lower tube sheet 104 within the reactor 100 and comprises a first vertical section 21 and a horizontal section 22. A first annular gap 2 is formed between the lower edge of the first vertical section 21 and the lower tube sheet 104. The second annular baffle is positioned below the upper tube sheet 106 within the reactor 100 and comprises a second vertical section 31 and an inclined section 32. A second annular gap 3 is formed between the upper edge of the second vertical section 31 and the upper tube sheet 106. The height of the first annular gap is preferably 30 to 300 mm; the height of the second annular gap is preferably 20 to 200 mm. The first annular gap and the second annular gap constructed in the present invention structurally eliminate the flow dead zone (i.e., the flow dead zone between the through-holes in the shell and the adjacent tube sheets) caused by the heat removal fluid entering / exhausting the shell side from the external flow guide device through the through-holes opened in the reactor shell, compared with the conventional method of arranging external flow guide devices at the upper and lower ends of the reactor shell; the first annular baffle and the second annular baffle (which function as annular baffle-type distributors) are located in the reactor shell, which not only reduces the resistance drop of the heat removal fluid and is conducive to the uniform distribution of the heat removal fluid, but also greatly reduces the difficulty of equipment manufacturing because there is no need to open through-holes in the shell, and avoids the weakening effect of the shell strength caused by opening multiple through-holes at the same height section of the shell, thereby ensuring the smooth operation and safety of the equipment.

[0037] Further Figure 1 As shown, the first vertical section 21 of the first annular baffle is a circular side plate, and the horizontal section 22 is a circular cover plate. The side plate and cover plate, together with the inner wall of the reactor 100, form a first annular channel 20. The first annular channel 20 is closed at the top and open at the bottom. The gap between the open end and the lower tube sheet 104 is the first annular gap 2. Similarly, the second vertical section 31 of the second annular baffle is a circular side plate, and the inclined section 32 is a circular bottom plate. The side plate and bottom plate, together with the inner wall of the reactor 100, form a second annular channel 30. The second annular channel 30 is open at the top and closed at the bottom. The gap between the open end and the upper tube sheet 106 is the second annular gap 3. The provision of the inclined section 32 can serve to guide the heat removal fluid. Preferably, but not limiting, the width of the first annular channel can be designed to be 1% to 10% of the reactor diameter, and the ratio of the first annular channel height to the shell-side inlet pipe diameter can be designed to be 1.1 to 3. The ratio of the width of the second annular channel to the width of the first annular channel may be 0.5-1, and the ratio of the height of the second annular channel to the shell side outlet pipe diameter may be 1.1-3.

[0038] Further Figure 1As shown, shell-side inlets 103 for the heat removal fluid are provided on the reactor wall and distributed circumferentially along the first annular baffle. The number of shell-side inlets 103 can be designed to be 2 to 10. Shell-side outlets 105 for the heat removal fluid are provided on the reactor wall and distributed circumferentially along the second annular baffle. The number of shell-side outlets 105 can be designed to be 2 to 36. With more than two shell-side inlets and outlets, the heat removal fluid from the first annular gap 2 and the second annular gap 3 can be quickly introduced into and out of the reactor.

[0039] refer to Figure 1 , using the shell-side structure of the tubular reactor of the utility model, the reaction raw materials (i.e. Figure 1 The reaction gas in the reaction gas) enters the catalyst bed composed of each reaction tube 102 from the reaction gas inlet 107 through the gas distributor, and the reaction product (i.e. Figure 1 The synthesis gas in the reactor 100 flows out of the reactor 100 from the synthesis gas outlet 108; the heat removal fluid enters the first annular channel 20 from the shell side inlet 103, passes through the first annular gap 2, and then enters the shell side of the reactor, exchanges heat with the reaction heat generated in each reaction tube 102, and removes the heat generated by the reaction in a timely and continuous manner. After heat exchange, the heat removal fluid enters the second annular channel 30 through the second annular gap 3 and then flows out of the reactor 100 from the shell side outlet 105.

[0040] The shell-and-tube reactor of the present invention is preferably a large-diameter reactor for synthesizing vinyl acetate. The shell-side structure of the present invention solves technical problems such as the complex shell-side structure of conventional shell-and-tube reactors for producing vinyl acetate, the presence of large dead zones in the heat removal fluid within the shell, uneven radial temperature distribution in the reactor shell, and the subsequent localized overheating of the catalyst bed, increased by-products, and poor equipment safety and process stability. The shell-side structure of the reactor is compact, dead zones are eliminated, and experiments have shown that reaction heat can be removed promptly and continuously, resulting in a more uniform radial temperature distribution in the shell, thereby ensuring product quality, achieving long-term stable operation of the equipment, meeting the requirements for large-scale equipment, and achieving excellent technical results.

[0041] The foregoing descriptions of specific exemplary embodiments of the present invention are for illustrative and illustrative purposes. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations are possible based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize the various exemplary embodiments of the present invention and various options and variations. Any simple modifications, equivalent variations, and modifications made to the above exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. A shell-side structure of a tubular reactor, characterized in that: include: The grid assembly has a cylindrical structure and includes a grid ring and grid bars. The grid ring encloses the tubes as a whole and forms the wall of the cylindrical structure. The grid bars are arranged in layers and each layer is arranged in a grid pattern to isolate and support each tube. The baffle assembly is arranged at the shell inlet and outlet positions of the heat removal fluid and forms an annular gap channel in the reactor.

2. The shell-side structure of the tubular reactor according to claim 1, characterized in that: The baffle assembly comprises: a first annular baffle, which is arranged above the lower tube plate in the reactor and comprises a first vertical section and a horizontal section, wherein a first annular gap is formed between the lower edge of the first vertical section and the lower tube plate; The second annular baffle is arranged below the upper tube plate in the reactor and comprises a second vertical section and an inclined section. A second annular gap is formed between the upper edge of the second vertical section and the upper tube plate.

3. The shell-side structure of the tubular reactor according to claim 1, characterized in that: The gap between the grid bars and adjacent tubes is 0.2-1.0 mm; the distance between the grid bars of adjacent layers and the distance between the grid bars and adjacent baffles are 800-1600 mm.

4. The shell-side structure of the tubular reactor according to claim 2, characterized in that: The shell-side inlet of the heat removal fluid is arranged on the reactor wall and distributed circumferentially along the first annular baffle, and the number of shell-side inlets is 2 to 10; the shell-side outlet of the heat removal fluid is arranged on the reactor wall and distributed circumferentially along the second annular baffle, and the number of shell-side outlets is 2 to 36.

5. The shell-side structure of the shell-and-tube reactor according to claim 2, characterized in that: The first vertical section of the first annular baffle is an annular side plate, and the horizontal section is an annular cover plate. The side plate, the cover plate and the inner wall of the reactor form a first annular channel, which is closed at the upper end and open at the lower end.

6. The shell-side structure of the shell-and-tube reactor according to claim 2, characterized in that: The second vertical section of the second annular baffle is an annular side plate, and the inclined section is an annular bottom plate. The side plate, the bottom plate and the inner wall of the reactor form a second annular channel with an open upper end and a closed lower end.

7. The shell-side structure of the shell-and-tube reactor according to claim 2, characterized in that: The height of the first annular gap is 30 to 300 mm; the height of the second annular gap is 20 to 200 mm.

8. The shell-side structure of the shell-and-tube reactor according to claim 5, characterized in that: The width of the first annular channel is 1% to 10% of the diameter of the reactor, and the ratio of the height of the first annular channel to the diameter of the shell-side inlet pipe is 1.1 to 3.

9. The shell-side structure of the shell-and-tube reactor according to claim 8, characterized in that: The ratio of the width of the second annular channel to the width of the first annular channel is 0.5-1, and the ratio of the height of the second annular channel to the shell side outlet pipe diameter is 1.1-3.

10. The shell-side structure of the shell-and-tube reactor according to claim 1, characterized in that: The grille ring and grille bars are both made of metal plates and are fixed by welding; the width of the metal plates is 10 to 150 mm and the thickness is 0.1 to 3.0 mm.

11. The shell-side structure of the shell-and-tube reactor according to claim 1, characterized in that: The reactor is a large-diameter reactor used for synthesizing vinyl acetate.

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