Circulation gas condenser and polypropylene production system

Abstract

The invention provides a recycle gas condenser and a polypropylene production system. The recycle gas condenser comprises a shell, a tube plate, a U-shaped heat exchange tube, a cavity dividing assembly and a flow guiding assembly. Wherein a plurality of shell pass inlets are formed in the shell; the cavity dividing assembly comprises a cavity dividing partition plate, a stopping part arranged on the periphery of the cavity dividing partition plate in a surrounding mode and extending upwards and a plurality of pipelines extending in the vertical direction, and a plurality of through holes are formed in the cavity dividing partition plate. The multiple shell pass inlets are designed to be distributed in the direction from top to bottom, the problem that the flow speed of the lower area in a traditional structure is too low is effectively solved, and therefore the utilization rate of the lower heat exchange area is remarkably increased, liquid accumulation in the heat exchange pipe can be reduced, and the overall heat exchange efficiency can be improved. By means of the optimized design of the sub-cavity assembly, under the action of the stop part on the sub-cavity assembly, the condensate can maintain a certain liquid level height on the sub-cavity partition plate, the spraying effect is achieved by means of hydrostatic pressure, and the condensate makes full contact with non-condensable gas and conducts efficient heat exchange.

Description

Technical Field

[0001] This invention belongs to the field of polypropylene production technology, specifically relating to a circulating gas condenser and a polypropylene production system. Background Technology

[0002] Polypropylene (PP) is a high molecular weight polymer produced by the polymerization of propylene monomers in a polymerization reactor. In a typical process using a fluidized bed reactor, the feed gas (mainly propylene) is introduced from the bottom of the reactor and polymerization continues under the action of a highly efficient catalyst. This reaction process is accompanied by a large amount of exothermic reaction, and the precise control of the reaction temperature has a decisive influence on the quality, molecular weight distribution, and catalyst activity of the final product.

[0003] To promptly remove reaction heat and maintain thermal equilibrium in the reaction system, circulating gas condensation technology is widely used in industry, with the circulating gas condenser being the core equipment. The high-temperature gas discharged from the top of the reactor (mainly containing unreacted propylene monomers, hydrogen, etc.) enters the circulating gas condenser after preliminary filtration. Inside the condenser, the circulating gas exchanges heat with the cooling medium (usually circulating cooling water) in the tubes, causing some of the gaseous propylene to condense into a liquid phase. The condensed liquid propylene is then returned to the reactor to continue participating in the reaction, thus achieving the recycling of materials and energy.

[0004] Existing circulating gas condensers mainly employ horizontal and multi-shell structures. Multi-shell heat exchangers, by incorporating semi-open longitudinal baffles internally, guide gas flow in an S-shape to enhance gas turbulence and improve the heat transfer coefficient. Adjusting the baffle spacing can further optimize the gas velocity distribution. However, although this type of structure improves the radial flow field distribution, the steam velocity exhibits a significant non-uniformity along the axial direction within the same flow channel, with higher velocity at the top and lower at the bottom. As the gas flows downwards along the axial direction, its volume decreases sharply due to condensation, resulting in ineffective utilization of the heat transfer area in the lower region, reduced local heat transfer performance, and a serious waste of heat transfer area.

[0005] Furthermore, as the gas releases heat during condensation and condenses into liquid on the surface of the heat exchange tubes, these liquid films gradually accumulate and thicken, creating additional thermal resistance. The continuous increase in liquid film thickness significantly reduces the heat transfer coefficient on the outside of the tubes, thereby further weakening the overall heat exchange efficiency.

[0006] The above background information is provided only to aid in understanding the concept and technical solution of this application. It does not necessarily belong to the prior art of this application, nor does it necessarily provide technical guidance. In the absence of clear evidence that the above information was disclosed before the filing date of this application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0007] The purpose of this invention is to provide a circulating gas condenser with high heat exchange efficiency and high heat exchange area utilization.

[0008] Another object of the present invention is to provide a polypropylene production system including the above-described circulating gas condenser.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] This invention provides a circulating gas condenser, comprising a shell, a tube sheet, and U-shaped heat exchange tubes. The shell includes an upper cover, a cylindrical body, and a lower cover. The tube sheet is disposed between the upper cover and the cylindrical body, and the U-shaped heat exchange tubes extending longitudinally into the cylindrical body are fixed thereon. The upper cover has a tube-side inlet and a tube-side outlet communicating with the U-shaped heat exchange tubes. The cylindrical body has a shell-side inlet, and the lower cover has a shell-side outlet.

[0011] The shell-side inlets are multiple and arranged in a top-to-bottom direction;

[0012] The circulating gas condenser further includes a chambering assembly and a flow guiding assembly. The chambering assembly is provided for each pair of adjacent shell-side inlets and connected to the inner wall of the cylinder between the two adjacent shell-side inlets, dividing the cylinder into multiple heat exchange chambers. Each heat exchange chamber corresponds to one shell-side inlet and has at least one non-condensable gas outlet. The chambering assembly includes a chambering partition, a stop portion surrounding the periphery of the chambering partition and extending upward, and several pipes extending in the vertical direction. The chambering partition has multiple through holes, some of which are first through holes for condensate to pass through; others are second through holes connected to the pipes. The height of the pipes is not less than the height of the stop portion to allow non-condensable gas to pass through.

[0013] The flow guiding components are in multiple sets, each corresponding to multiple heat exchange chambers. Each set of flow guiding components includes multiple flow guiding plates arranged alternately in the corresponding heat exchange chamber and extending in the vertical direction. The spacing between adjacent flow guiding plates may be the same or different.

[0014] In some embodiments, along the gas flow direction within the heat exchange chamber, the plurality of through holes are formed in the partition plate region between the downstream guide plate and the inner wall of the cylinder. Preferably, the plurality of through holes on each partition plate are located on a first side of the cylinder. The shell-side inlet of each heat exchange chamber is located on a second side of the cylinder. More preferably, the first side and the second side are opposite to each other.

[0015] In some embodiments, the first through hole and the second through hole are staggered on the partition plate.

[0016] In some embodiments, the chamber assembly is positioned adjacent to the lower shell-side inlet of its two corresponding adjacent shell-side inlets.

[0017] In some embodiments, the noncondensable gas outlet is located at the upper part of its corresponding heat exchange chamber.

[0018] In some implementations, the non-condensable gas outlet on the uppermost heat exchange chamber is located on the tube sheet.

[0019] In some embodiments, the shell-side inlets have 3 to 5, and the distance between two adjacent shell-side inlets may be equal or unequal.

[0020] In some embodiments, the guide vanes in the flow guiding assembly are arranged at unequal intervals; for any flow guiding assembly, the spacing between its plurality of guide vanes gradually decreases along the direction extending from its corresponding shell-side inlet into the shell-side interior.

[0021] The present invention also provides a polypropylene production system, including a polymerization reactor and a circulating gas condenser as described above.

[0022] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0023] This invention, by designing multiple shell-side inlets distributed from top to bottom, effectively avoids the problem of excessively low flow velocity in the lower region of traditional structures, thereby significantly improving the utilization rate of the lower heat exchange area. Simultaneously, this structure also reduces liquid accumulation within the heat exchange tubes, contributing to improved overall heat exchange efficiency.

[0024] Furthermore, through optimized design of the compartment components, the condensate can maintain a certain liquid level on the compartment partition under the action of the stop section, and achieve a spraying effect with the help of hydrostatic pressure, allowing the condensate to fully contact the non-condensable gases and carry out efficient heat exchange. This mechanism not only enhances the heat transfer process, but also further improves the system's heat exchange performance and energy utilization efficiency. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of a circulating gas heat exchanger provided by the present invention;

[0026] Figure 2 A schematic diagram of the distribution of a cavity partition and a flow guide plate provided by the present invention (the through holes of the cavity partition are not shown);

[0027] Figure 3 A schematic diagram of the structure of a cavity assembly provided by the present invention;

[0028] Figure 4 This is a schematic diagram of a cavity assembly from another angle provided by the present invention;

[0029] Figure 5 A schematic diagram of a polypropylene production system provided by the present invention;

[0030] Among them, 1. Shell; 11. Top cover; 12. Cylinder; 13. Bottom cover; 14. Shell-side inlet; 15. Shell-side outlet; 16. Tube-side inlet; 17. Tube-side outlet; 18. Non-condensable gas outlet; 19. Header;

[0031] 2. Chamber assembly; 21. Chamber partition; 211. First through hole; 22. Stop; 23. Pipe;

[0032] 3. Tube sheet; 4. Baffle plate; 5. U-shaped heat exchange tube; 6. Polymerization reactor; 7. Separator; 8. Flash tank; 9. Storage tank. Detailed Implementation

[0033] The present invention will be further described below with reference to embodiments, but the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0034] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the embodiments of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0035] In the description of the embodiments of the present invention, it should be understood that the terms "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the appendix. Figure 1 The orientations or positional relationships shown, such as the upper cover 11 being located above, the lower cover 13 being located below, the shell-side inlet 14 being located to the right, and the non-condensable gas outlet 18 being located to the left, are merely for the purpose of facilitating the description of embodiments of the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the embodiments of the present invention.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0037] The following disclosure provides many different implementations or examples for carrying out different structures of the embodiments of the present invention. To simplify the disclosure of the embodiments of the present invention, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the embodiments of the present invention. Furthermore, reference numerals and / or reference letters may be repeated in different examples of the embodiments of the present invention; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed.

[0038] Example 1

[0039] A circulating gas condenser, such as Figures 1 to 4 As shown, it includes a shell 1, a tube sheet 3, a U-shaped heat exchange tube 5, a cavity assembly 2, and a flow guiding assembly.

[0040] like Figure 1 As shown, the shell 1 includes an upper cover 11, a cylindrical body 12, and a lower cover 13. A tube sheet 3 is disposed between the upper cover 11 and the cylindrical body 12, dividing the shell 1 into two independent upper and lower spaces. The upper space is the cooling medium space, and the lower space is the heat exchange space. U-shaped heat exchange tubes 5 (not fully shown in the figure) extending longitudinally towards the cylindrical body 12 are fixed on the tube sheet 3. The specific arrangement of the U-shaped heat exchange tubes 5 can be found in existing technology. The upper cover 11 has a tube-side inlet 16 and a tube-side outlet 17 connected to the U-shaped heat exchange tubes 5. The tube-side inlet 16 is used to introduce the cooling medium, such as circulating cooling water; the tube-side outlet 17 is used to exit the cooling medium. The cylindrical body 12 has a shell-side inlet 14 for introducing circulating gas (i.e., the substance to be condensed), and multiple shell-side inlets 14 are arranged from top to bottom. The lower cover 13 has a shell-side outlet 15 for exiting condensate.

[0041] The chamber-splitting assembly 2 is provided for each pair of adjacent shell-side inlets 14 and connected to the inner wall of the cylinder 12 between the two adjacent shell-side inlets 14, thereby dividing the cylinder 12 into multiple heat exchange chambers. Each heat exchange chamber corresponds to one shell-side inlet 14 and is provided with at least one non-condensable gas outlet 18. Specifically, as shown... Figure 3 and Figure 4As shown, the chamber assembly 2 includes a chamber partition 21, a stop portion 22 surrounding the periphery of the chamber partition 21 and extending upward, and several pipes 23 extending in the vertical direction. The chamber partition 21 has multiple through holes, some of which are first through holes 211 for condensate to pass through; others are second through holes connected to the pipes 23. The height of the pipes 23 is not lower than the height of the stop portion 22 to allow non-condensable gases (such as hydrogen) to pass through. Multiple sets of flow guiding assemblies are provided, each corresponding to a multiple heat exchange chamber. Each set of flow guiding assemblies includes multiple flow guide plates 4 staggered within the corresponding heat exchange chamber and extending in the vertical direction, dividing the heat exchange chamber into multiple shell-side sections. The spacing between adjacent flow guide plates 4 may be equal or unequal.

[0042] In existing technologies, the shell-side inlet 14 of a circulating gas condenser is typically located only at the top of the cylinder 12. After the circulating gas enters through this inlet, as the condensation process proceeds from top to bottom, the gas phase composition gradually decreases, leading to a continuous reduction in volumetric flow rate and a decrease in flow velocity along the axial direction. This phenomenon results in a significant decrease in the heat transfer coefficient of the lower heat exchange tube region, leaving a large amount of heat exchange area unutilized. Simultaneously, liquid phase accumulation easily occurs in the low-velocity region, covering the surface of the heat exchange tubes and further weakening the heat transfer performance, forming "stagnant zones" and "dry wall zones," thus restricting the overall heat exchange efficiency of the equipment.

[0043] The multi-shell-pass inlet, compartmentalized structural design of this invention effectively improves the utilization rate of the heat exchange area, enhances the heat exchange effect, and increases the heat exchange efficiency by nearly 25%. Specifically, by opening multiple shell-pass inlets 14 axially in the shell body 12, the entire shell pass is divided into several heat exchange chambers, and a shell-pass inlet 14 is provided in each heat exchange chamber. This allows the circulating gas, which originally entered from only one shell-pass inlet 14, to be split into multiple streams, each entering its corresponding heat exchange chamber through its respective shell-pass inlet 14. This arrangement significantly increases the gas throughput in the lower heat exchange tube area, making the axial velocity distribution more uniform, thereby significantly improving the utilization rate of the heat exchange area and effectively alleviating liquid accumulation, ensuring that the heat exchange tubes operate at high efficiency throughout. The flow rate of the circulating gas entering from different shell-pass inlets 14 can be adjusted independently and can be specifically designed according to actual conditions.

[0044] Furthermore, by installing flow guiding components in each heat exchange chamber, the circulating gas is guided to flow along a preset S-shaped path, enhancing airflow disturbance and turbulence, extending the residence time of the circulating gas in the shell side, promoting full contact with the heat exchange tube surface, and improving condensation efficiency. In addition, the stop portion 22 on the partition plate 21 maintains a certain liquid level of condensate above the partition plate, forming a liquid seal. Under static pressure, the condensate is uniformly sprayed through a specific distribution structure, making countercurrent contact with the relatively low-temperature non-condensable gas flowing upwards, further facilitating heat exchange. Preferably, the height of the stop portion 22 is 50mm to 80mm, such as 50mm, 60mm, 65mm, 70mm, or 90mm, and can be designed according to actual needs. The diameter of the through hole is 5mm to 22mm, such as 5mm, 6mm, 8mm, 10mm, 12mm, 16mm, 18mm, or 22mm, and can be designed according to the amount of condensate or other requirements.

[0045] In this embodiment, the first through hole 211 and the second through hole are staggered on the cavity partition 21 (e.g., Figure 3 (As shown). Furthermore, along the gas flow direction within the heat exchange chamber, multiple through holes are formed in the area of ​​the partition plate 21 between the downstream guide plate 4 and the inner wall of the cylinder 12. Figure 4 The upper region shown is the area of ​​the partition plate 21 on the opposite side of the shell-side inlet 14. This facilitates efficient countercurrent heat exchange between the gas and liquid phases. Preferably, the multiple through holes of the different partition plates 21 are located on the first side of the shell 12, and the shell-side inlets 14 of each heat exchange chamber are located on the second side of the shell 12, with the first side and the second side opposite each other. The partition assembly 2 is arranged adjacent to the lower shell-side inlet 14 of its two adjacent shell-side inlets 14. The non-condensable gas outlet 18 is located in the upper part of its corresponding heat exchange chamber. The non-condensable gas outlet 18 on the uppermost heat exchange chamber is opened on the tube sheet 3, and the non-condensable gas outlet 18 can be collected in the header 19 on the outside of the shell 1 through a pipe.

[0046] As the circulating gas flows along an S-shaped path within the heat exchange chamber, its volume decreases with the condensation process, leading to a reduction in gas velocity in the downstream channel. Therefore, to maintain a consistent gas velocity within the heat exchange chamber, the guide vanes 4 in the flow guiding assembly are preferably arranged at unequal intervals. The spacing between multiple guide vanes 4 gradually decreases along the direction extending from their corresponding shell-side inlet 14 into the shell-side interior. By adjusting the spacing between the guide vanes 4, the heat exchange chamber can be divided into multiple shell-side sections with gradually decreasing spacing, thereby ensuring approximately equal radial flow velocities. The spacing can be designed according to actual requirements.

[0047] Furthermore, the guide plate 4 can be fixed using a frame and baffle rods, with the length of the lowest guide plate 4 extending to the bottom wall of the U-shaped heat exchange tube 5. One end of the guide plate 4 is sealed to the inner wall of the cylinder 12 by a sealing strip, while the other end is a certain distance away from the inner wall of the cylinder 12. The specific distance is not limited and can be designed according to actual conditions. The guide plate 4 is preferably made of austenitic stainless steel such as S30408, S30403, S31608, or S31603, with a thickness preferably of 10mm to 15mm. The sealing strip can be an elastic spring sheet with a thickness preferably of 0.2mm to 0.8mm.

[0048] Example 2

[0049] A polypropylene production system, such as Figure 5 As shown, it includes a polymerization reactor 6, a separation device, a circulating gas heat exchanger, a flash tank 8, and a storage tank 9. The circulating gas heat exchanger is the type described above, and its specific structure and working principle are as described previously and will not be repeated here.

[0050] The polymerization reactor 6 is equipped with a circulating gas outlet and a circulating gas inlet. The feed gas (mainly propylene) is introduced through the circulating gas inlet and undergoes a polymerization reaction under the action of a catalyst within the reactor. Unreacted feed gas is discharged through the circulating gas outlet, undergoes preliminary separation by a separation device, and then enters a circulating gas heat exchanger for condensation. The polymerization reactor 6 can be a common reactor type in the art, such as a batch reactor, a loop reactor, or a fluidized bed gas-phase reactor.

[0051] The separation device is used for preliminary separation and purification, separating out unreacted gases that are basically free of solid powder, and sending the unreacted gases to the circulating gas heat exchanger. The device mainly includes a separator 7 (refer to the prior art), whose inlet is connected to the circulating gas outlet of the polymerization reactor 6, and whose outlet is connected to multiple shell-side inlets 14 of the circulating gas heat exchanger through multiple branch pipes, thereby realizing airflow distribution and parallel input.

[0052] Flash tank 8 is used to treat the condensate flowing from the shell-side outlet 15 of the circulating gas heat exchanger. In this device, the liquid material is flash-evaporated under reduced pressure, where unreacted propylene gas is separated and returned to the polymerization reactor 6 to participate in the reaction, while the remaining polymer mother liquor is transported to the storage tank 9 as polypropylene product. The structure and operation of flash tank 8 can be implemented with reference to existing technology.

[0053] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

Claims

1. A circulating gas condenser comprising a shell (1), a tube sheet (3) and U-shaped heat exchange tubes (5), the shell (1) comprising an upper cover (11), a barrel (12) and a lower cover (13), the tube sheet (3) being arranged between the upper cover (11) and the barrel (12) and having the U-shaped heat exchange tubes (5) fixed thereon and extending longitudinally into the barrel (12), the upper cover (11) having a tube pass inlet (16) and a tube pass outlet (17) formed therein and communicating with the U-shaped heat exchange tubes (5), the barrel (12) having a shell pass inlet (14) formed therein, and the lower cover (13) having a shell pass outlet (15) formed therein, characterized in that: the shell pass inlet (14) is in plurality and arranged in a top-down direction; the circulating gas condenser further comprises a compartment dividing assembly (2) and a flow guiding assembly; the compartment dividing assembly (2) is arranged corresponding to every two adjacent shell pass inlets (14) and connected to the inner wall of the barrel (12) between the two adjacent shell pass inlets (14), thereby dividing the barrel (12) into a plurality of heat exchange chambers, each heat exchange chamber corresponding to one shell pass inlet (14) and being provided with at least one non-condensable gas outlet (18); the compartment dividing assembly (2) comprises a compartment dividing baffle (21), a stopper (22) extending upward around the periphery of the compartment dividing baffle (21) and a plurality of pipes (23) extending in a top-down direction, the compartment dividing baffle (21) having a plurality of through holes formed therein, a part of the through holes being first through holes (211) for condensate to pass through, and the other part of the through holes being second through holes to which the pipes (23) are connected, the height of the pipes (23) being not less than the height of the stopper (22) so as to allow non-condensable gas to pass through; the flow guiding assembly has a plurality of groups corresponding to the plurality of heat exchange chambers, each group of flow guiding assembly comprising a plurality of flow guiding plates (4) arranged in a staggered manner in the corresponding heat exchange chamber and extending in a top-down direction, the distance between adjacent two flow guiding plates (4) being equal or unequal. The plurality of through holes are formed on the compartment dividing baffle (21) region between the most downstream flow guiding plate (4) and the inner wall of the barrel (12) in the flow direction of gas in the heat exchange chamber. The plurality of through holes on each compartment dividing baffle (21) are located on a first side of the barrel (12); and / or, The shell pass inlets (14) of each heat exchange chamber are located on a second side of the barrel (12). The first side is opposite to the second side.

2. The cycle gas condenser of claim 1, wherein: The first through holes (211) and the second through holes are staggered on the compartment dividing baffle (21).

3. The cycle gas condenser of claim 2, wherein: The compartment dividing assembly (2) is arranged adjacent to the lower shell pass inlet (14) of the corresponding two adjacent shell pass inlets (14). The non-condensable gas outlet (18) is arranged at the upper part of the corresponding heat exchange chamber; and / or, 4. The cycle gas condenser of claim 3, wherein: The non-condensable gas outlet (18) on the uppermost heat exchange chamber is formed on the tube sheet (3).

5. The cycle gas condenser of claim 1, wherein: The shell pass inlet (14) is in 3-5 in number, and the distance between adjacent two shell pass inlets (14) is equal or unequal.

6. The cycle gas condenser of claim 1, wherein: ​ 7. The cycle gas condenser of claim 1, wherein: ​ ​ 8. The cycle gas condenser of claim 1, wherein: ​ 9. The cycle gas condenser of claim 1, wherein: The guide vanes (4) in the guide vane assembly are arranged at unequal intervals; for any guide vane assembly, the intervals between the plurality of guide vanes (4) thereof gradually decrease along a direction extending from the corresponding shell side inlet (14) to the inside of the shell side.

10. A polypropylene production system comprising a polymerization reactor (6) and a recycle gas condenser, characterized in that: The cycle gas condenser is the cycle gas condenser according to any one of claims 1 to 9.

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