Heat removal device for preparing polyolefin by slurry method

Abstract

The utility model relates to a heat removal device for preparing polyolefin by a slurry method, which is characterized in that an inner jacket heat removal mechanism is arranged on the inner wall of a reactor shell of a kettle type reactor body, the inner jacket heat removal mechanism comprises a heat exchange wall surface, and a gap is formed between the heat exchange wall surface and the inner wall of the reactor shell at an interval; and mutually communicated cavities are formed between the flow guide supporting pieces as well as among the flow guide supporting pieces, the heat exchange wall surface and the inner wall of the reactor shell and are used for introducing a heat exchange medium. The heat exchange wall surface is in direct contact with reaction materials in the reactor for heat exchange, a spiral heat exchange medium flowing direction is formed, the flow channel structure is optimized, the flow field state is improved, effective circulation of fluid between the flow guide supporting piece and the heat exchange wall surface is ensured, and the heat removal efficiency is high.

Description

Technical Field

[0001] The utility model relates to the technical field of polyolefin preparation, in particular to a heat removal device used for preparing polyolefin by a slurry process. Background Art

[0002] The polyolefin production process includes solution method, slurry method and gas phase method. Among them, the slurry method is relatively mature and has good product quality. It is the main method for producing polyolefins (especially high-density polyethylene and ultra-high molecular weight polyethylene). The slurry method is to fuse aliphatic hydrocarbon solvents and ethylene to generate polymers under the action of catalysts, and the polymers are suspended in the solvent. According to the different forms of reactors, the slurry method is divided into tubular slurry method and kettle slurry method. When preparing polyolefins, such as ultra-high molecular weight polyethylene, by the kettle slurry method, since ethylene polymerization is a strongly exothermic reaction, when the heat removal effect is not ideal, there are local hot spots inside the reactor, and polyethylene (especially ultra-high molecular weight polyethylene) is prone to swelling in the solvent, resulting in agglomeration and other phenomena. Therefore, timely removal of reaction heat is a key process to ensure smooth polymerization.

[0003] In the prior art, Chinese patent CN 117482875 A discloses a production device for synthesizing 1-octene, and discloses an inner and outer jacket heat exchange method, wherein a heat exchange inner coil is installed between the stirring paddle and the outer wall of the reactor for heat exchange, but the inner coil has a complex structure in the reactor, which easily causes the inner coil to stick to the wall and agglomerate. Chinese patent CN218834527U discloses a reaction device for preparing 1-octene by ethylene polymerization, wherein an inner jacket gas lift pipe is arranged inside the reactor, and the reaction heat is promptly and effectively withdrawn by passing cooling water, however, the inner jacket gas lift pipe of the patent is arranged in the middle of the reactor, which will occupy part of the space in the reactor, and requires large consumption to maintain the circulation of gas and liquid. Chinese patent CN 110918018 A discloses a combined heat removal method for a kettle slurry polyethylene reactor, and discloses three combinations of removing the polymerization reaction heat by adopting solvent evaporation, slurry external circulation and reactor jacket, however, the patent adopts an outer jacket, and due to the problem of reactor shell wall thickness, the heat exchange efficiency is low. Patent CN205046027U discloses a kettle-type slurry olefin continuous polymerization device, which is provided with an inner jacket for filling liquid hexane and is arranged on the inner wall of the first reactor. However, the patent does not disclose the specific structure of the inner jacket. The heat exchange medium flow field in the inner jacket may have dead corners and short circuits, and the heat exchange efficiency still needs to be further improved. Utility Model Content

[0004] The purpose of the utility model is to solve the above problems and provide a heat removal device for preparing polyolefins by slurry process.

[0005] The purpose of the utility model is achieved through the following technical solutions:

[0006] A heat removal device for preparing polyolefins by a slurry process comprises a kettle reactor body, wherein the inner wall of the reactor shell of the kettle reactor body is provided with an inner jacket heat removal mechanism.

[0007] The inner jacket heat removal mechanism comprises a heat exchange wall surface, a gap is formed between the heat exchange wall surface and the inner wall of the reactor shell, and a flow guide support is spirally arranged in the gap.

[0008] Interconnected chambers are formed between the flow guiding supports, between the flow guiding supports and the heat exchange wall surface and the inner wall of the reactor shell, and are used for introducing heat exchange medium.

[0009] The utility model arranges an inner jacket heat removal mechanism on the inner wall of the kettle reactor, and the heat exchange wall surface of the inner jacket heat removal mechanism directly contacts the reaction material on the inner wall of the reactor for heat exchange. Through the arrangement of the flow guide support, not only can the thin-sized heat exchange wall surface be effectively supported to enhance its pressure resistance, but also the heat exchange wall surface is spirally arranged to form a spiral upward heat exchange medium flow direction, optimize the flow channel structure, help to improve the flow field state, ensure the effective circulation of the fluid between the flow guide support and the heat exchange wall surface, avoid dead corners and short circuit phenomena, and improve the heat transfer coefficient.

[0010] As a preferred technical solution of the utility model, the angle between the flow guide support and the reactor shell along the axial direction is 30-90°, preferably 30-60°, for example, it can be 30°, 35°, 40°, 45°, 50°, 55°, 60°, etc., and further preferably 45°.

[0011] As a preferred technical solution of the utility model, the distance between the adjacent flow guide supports is 2-20 cm, preferably 2-10 cm, and more preferably 3-6 cm. The gap thickness of the inner jacket heat removal mechanism along the radial direction of the reactor shell is 2-8 cm, preferably 3-5 cm.

[0012] Arranging the guide support in this way forms a spirally inclined flow direction of the heat exchange medium, optimizes the flow channel structure, improves the flow field state, ensures effective circulation of the fluid between the guide support and the heat exchange wall, avoids dead corners and short circuits, and helps to improve the heat transfer coefficient.

[0013] As a preferred technical solution of the utility model, the irregular side surfaces of the flow guide support are used to increase the spoilers for the turbulent flow of the heat exchange medium. The setting of the spoilers increases the Reynolds number of the heat exchange medium, enhances the turbulent flow conditions, and helps to further improve the heat exchange efficiency.

[0014] As a preferred technical solution of the utility model, the spoiler is a metal thorn edge, including a stick-like metal needle.

[0015] As a preferred technical solution of the utility model, the heat exchange wall is made of thin-walled stainless steel. Selecting stainless steel with good thermal conductivity and corrosion resistance can greatly improve the heat exchange performance.

[0016] As a preferred technical solution of the utility model, the upper part of the reactor shell is provided with a heat exchange medium outlet connected to the chamber, and the lower part is provided with a heat exchange medium inlet. The cooling medium flows from bottom to top through the inner jacket heat removal mechanism. The heat exchange fluid enters from bottom to top and exits from top to bottom, which helps to improve the heat exchange effect. The heat exchange medium outlet and the heat exchange medium inlet are provided with one or more groups.

[0017] As a preferred technical solution of the utility model, in order to improve the heat exchange efficiency, the chambers are distributed up and down along the reactor shell to form a multi-stage parallel passage structure, and multiple groups of heat exchange medium inlets and outlets are set.

[0018] As a preferred technical solution of the utility model, a stirring device is provided inside the kettle reactor body, and the stirring device includes a three-blade swept-back agitator, a turbine agitator, a plate-and-frame agitator, etc. The specific form can be selected according to actual needs. Preferably, a plate-and-frame agitator is adopted, including a stirring shaft and a stirring paddle installed on the stirring shaft. The excellent heat transfer and mass transfer effects of the plate-and-frame agitator are utilized to improve the reaction efficiency, and the problems of uneven stirring, dead corners, easy sedimentation, uneven heat dissipation, etc. in the polymerization process can be alleviated to a certain extent.

[0019] As a preferred technical solution of the utility model, the bottom of the reactor of the kettle reactor body is equipped with a bottom bearing through a bracket, and the bottom bearing is installed at the end of the stirring shaft to stabilize the stirring equipment.

[0020] The utility model optimizes and improves the heat removal mechanism of the kettle reactor based on the heat transfer principle. The heat transfer principle is calculated according to the heat transfer rate equation (Formula I) and the total heat transfer coefficient (Formula II).

[0021] Q=K·A·Δt Formula I

[0022] K=1 / (1 / α1+δ / λ+1 / α2) Formula II

[0023] In formula I, Q represents the heat transfer amount; K represents the total heat transfer coefficient; A represents the heat transfer area; Δt represents the average temperature difference between the two heat exchange fluids;

[0024] In formula II, α1 represents the heat transfer coefficient of the hot fluid; α2 represents the heat transfer coefficient of the cold fluid; δ represents the wall thickness, and λ represents the thermal conductivity of the wall material.

[0025] It can be seen from the above formula that when the reactor is determined, the heat exchange area A is basically determined. If the heat transfer rate is to be increased, the heat transfer coefficient K should be increased. The technical solution of the utility model can greatly improve the total heat transfer coefficient K and improve the heat removal efficiency by arranging an inner jacket heat removal mechanism on the inner wall of the reactor and using the thin-walled stainless steel heat exchange wall to directly contact the slurry reaction material inside the reactor (reducing the wall thickness δ and increasing the thermal conductivity λ of the wall material).

[0026] At the same time, the spirally arranged flow guide support plays the role of reinforcing rib support on the one hand, which can support the stress of thin-walled steel plates under pressure resistance conditions. On the other hand, the spirally arranged flow guide support forms a spirally upward heat exchange medium channel. When the heat exchange medium (such as cold water) flows through, the flow field state is good, and it can circulate effectively, avoiding dead corners and short circuits, and removing heat in time. In addition, the spoiler is also arranged on the flow guide support to further increase the turbulent flow conditions of the heat exchange medium, which helps to improve the heat exchange efficiency.

[0027] Compared with the prior art, the utility model has the following beneficial effects:

[0028] 1. By setting an inner jacket heat removal mechanism on the inner wall of the kettle reactor, the heat exchange wall is made of thin-walled stainless steel material, which is directly in contact with the slurry reaction materials inside the reactor. Compared with the existing technology (usually an outer jacket), the total heat transfer coefficient K can be greatly improved and the heat removal efficiency can be improved.

[0029] 2. The spirally arranged guide support plays a supporting and guiding role, which can support the force of the thin-walled steel plate under the pressure-resistant condition, and at the same time forms a spiral upward heat exchange medium channel. When the heat exchange medium (such as cold water) flows through, the flow field state is good, and it can circulate effectively, avoiding dead corners and short circuits, and removing heat in time.

[0030] 3. A spoiler is arranged on the guide support to increase the turbulent flow condition of the heat exchange medium and further improve the heat exchange efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the overall structure of the utility model;

[0032] Figure 2 It is a schematic diagram of the arrangement of the flow guide support along the reactor cylinder;

[0033] Figure 3 for Figure 1 A partial enlarged view of point I in the middle;

[0034] In the figure: 1-motor; 2-reducer; 3-bracket; 4-manhole; 5-feeding port; 6-support; 7-barrel; 8-agitation shaft; 9-agitation paddle; 10-heat exchange medium inlet; 11-discharge port; 12-bottom bearing; 13-flow guide support; 14-chamber; 15-heat exchange wall; 16-reactor shell; 17-spoiler; 18-heat exchange medium outlet. DETAILED DESCRIPTION

[0035] The present invention is described in detail below in conjunction with the accompanying drawings. All matters not described in detail in the present invention are technical solutions disclosed in the art.

[0036] The following discloses a variety of different implementation methods or embodiments of the subject technical solution. To simplify the disclosure, specific examples of each element and arrangement are described below. Of course, these are only examples and are not intended to limit the scope of protection of the utility model. For example, the first feature subsequently recorded in the specification is formed above or on the second feature, which may include an implementation method in which the first and second features are formed in a directly connected manner, and may also include an implementation method in which an additional feature is formed between the first and second features, so that the first and second features may not be directly connected. In addition, the figure marks and / or letters may be repeated in different examples in these disclosures. This repetition is for simplicity and clarity, and does not itself represent the relationship between the various implementation methods and / or structures to be discussed. Further, when the first element is described in a manner connected or combined with the second element, the description includes an implementation method in which the first and second elements are directly connected or combined with each other, and also includes the use of one or more other intervening elements to indirectly connect or combine the first and second elements.

[0037] In addition, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the utility model and simplifying the description. Unless otherwise stated, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the utility model; the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself, and the use of words such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above words have no special meanings, and therefore cannot be understood as limiting the scope of protection of the utility model.

[0038] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "some embodiments" mentioned twice or more in different positions in this specification do not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0039] like Figure 1 As shown, it is a schematic diagram of the overall structure of the heat removal device for preparing ultra-high molecular weight polyethylene by the slurry method of the utility model, including a kettle reactor body, the main body of the kettle reactor body is a cylindrical stirred reactor, and a stirring device is arranged inside the stirred reactor. The stirring device preferably adopts a plate-frame stirrer, including a stirring shaft 8 and a stirring paddle 9 installed on the stirring shaft 8. The excellent heat transfer and mass transfer effect of the plate-frame stirrer is utilized to improve the reaction efficiency, and the problems of uneven stirring, dead angle, easy sedimentation, and uneven heat dissipation in the polymerization process can be alleviated to a certain extent. A reducer 2 is installed at the upper end of the stirred reactor through a bracket 3, and a motor 1 is installed at the upper end of the reducer 2. The motor 1 is connected to the reducer 2 in transmission, and the output end of the reducer 2 is connected to the stirring shaft 8 of the stirring device through a connecting shaft and drives the stirring device to rotate, so as to stir and disperse the reaction materials in the kettle. In order to improve the stability of the stirring device and avoid the formation of a dead zone at the bottom of the kettle, the utility model installs a bottom bearing 12 at the bottom of the stirred reactor through a bracket, and the bottom bearing 12 is installed at the end of the stirring shaft 8 of the stirring device, which plays a stabilizing role on the stirring device. In addition, a support 6 for installation is provided on the upper part of the reactor, a manhole 4 and at least one feed port 5 are provided on the top, and at least one discharge port 11 is provided at the lower end. These are necessary facilities of the kettle reactor and will not be described in detail.

[0040] Since the preparation of polyethylene by slurry process, especially the preparation of ultra-high molecular weight polyethylene, is a highly exothermic reaction, timely removal of reaction heat is the key to ensure the production of high-quality products. In order to improve the reaction heat removal efficiency of the device, the utility model adopts the design of the inner jacket heat removal mechanism, and especially optimizes the structure of the inner jacket. The specific technical solution is as follows:

[0041] An inner jacket heat removal mechanism is arranged close to the inner wall of the kettle reactor shell. The inner jacket heat removal mechanism mainly includes a heat exchange wall 15 whose shape is adapted to the reactor barrel 7. The heat exchange wall 15 is arranged at an interval with the inner wall of the reactor shell 16, and is supported and connected by a guide support 13, that is, a guide support 13 is arranged between the heat exchange wall 15 and the inner wall of the reactor shell 16. The guide support 13 is arranged in a spiral shape. On the cylindrical surface of the barrel, the guide support 13 is arranged in a spiral shape and tilted downward (such as Figure 2As shown in the figure, the angle between the guide support 13 and the shell along the axial direction is 30-60°, for example, in a specific embodiment, a 45° tilt setting is adopted. At the lower head of the reactor, the guide support 13 is arranged in a concentric circle. In practical applications, it is difficult to set the structure of the inner jacket at the upper and lower heads due to too many openings and great manufacturing difficulty. The inner jacket can be replaced by an outer jacket or a half-tube jacket.

[0042] In this embodiment, the flow guide supports are arranged at an interval of 2-20 cm, preferably 2-10 cm, more preferably 3-6 cm, for example, 5 cm in a specific embodiment. The width of the flow guide support is 2-8 cm, preferably 3-5 cm, for example, 4 cm in a specific embodiment, and the gap width of the formed inner jacket cavity is the same as the width of the flow guide support. In addition, a channel or notch for the heat exchange medium to pass through is provided on the flow guide support 13, and mutually connected chambers 14 are formed between the flow guide support 13 and the flow guide support 13, and between the flow guide support 13 and the heat exchange wall 15 and the inner wall of the reactor shell 16. A heat exchange medium outlet 18 connected to the chamber 14 is provided at the upper end of the inner jacket, and a heat exchange medium inlet 10 connected to the chamber 14 is provided at the lower end. When working, the heat exchange medium (preferably cooling water) is introduced from the lower end inlet, and the heat exchange medium flows through each chamber 14, and finally flows out from the heat exchange medium outlet 18 at the upper end, and the heat exchange medium is connected to the external heat exchange equipment to complete the cyclic heat exchange. By setting in this way, a spiral upward heat exchange medium channel can be formed on the surface of the reactor. This optimized flow channel structure helps to improve the flow field state, ensure that the fluid effectively exchanges heat between the flow guide support and the heat exchange wall, avoid dead corners and short circuits, and improve the heat exchange efficiency. In addition, compared with the internal coil heat exchange, the heat exchange wall surface that is in direct contact with the reaction materials in the reactor, that is, the effective heat exchange contact area, is larger, so the heat removal efficiency is also higher.

[0043] As a specific implementation method, in order to further improve the heat exchange efficiency, the chambers 14 are distributed up and down along the reactor shell 16 to form a multi-stage parallel passage structure, and each is provided with an inlet and outlet of the heat exchange medium. With this arrangement, the heat exchange effect is better. At the same time, for working conditions that require heat preservation, hot water can be introduced as needed to meet more complex operation and use requirements. As a specific implementation method, the heat exchange wall 15 is made of thin-walled stainless steel, and stainless steel with good thermal conductivity and corrosion resistance is selected. While meeting the slurry polymerization reaction, the heat exchange performance is improved. At the same time, due to the supporting effect of the guide support 13, the pressure bearing capacity per unit area of ​​the heat exchange wall 15 is improved, and it can still withstand very high pressure in a relatively thin state, meeting the use requirements of the slurry method under higher pressure.

[0044] As a specific preferred embodiment, refer to Figure 3, a spoiler 17 is arranged on the flow guide support, for example, a plurality of metal thorns are arranged irregularly on the side of the flow guide support 13, specifically, a bar-shaped metal fine needle can be arranged, and these spoilers 17 increase the Reynolds number of the heat exchange medium when the heat exchange medium flows through, increase the turbulent flow state of the heat exchange medium, and further improve the heat exchange efficiency. When in use, the reaction raw materials are polymerized under stirring in the polymerization kettle, and the inner jacket heat removal mechanism can remove the reaction heat in a timely and efficient manner.

[0045] The above description of the embodiments is to facilitate the understanding and use of the utility model by those skilled in the art. It is obvious that those familiar with the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the utility model is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the utility model without departing from the scope of the utility model should be within the scope of protection of the utility model.

Claims

1. A heat removal device for preparing polyolefins by a slurry process, comprising a kettle reactor body, characterized in that: The inner wall of the reactor shell (16) of the kettle reactor body is provided with an inner jacket heat removal mechanism. The inner jacket heat removal mechanism comprises a heat exchange wall surface (15), a gap is formed between the heat exchange wall surface (15) and the inner wall of the reactor shell (16), and a flow guide support (13) is spirally arranged in the gap. Interconnected chambers (14) are formed between the flow guide supports (13) and between the flow guide supports (13) and the heat exchange wall surface (15) and the inner wall of the reactor shell (16).

2. The heat removal device according to claim 1, characterized in that: The angle between the flow guide support (13) and the reactor shell (16) along the axial direction is 30-90 degrees.

3. The heat removal device according to claim 2, characterized in that: The flow guide supports (13) are arranged adjacent to each other at a distance of 2-20 cm, and the gap thickness of the inner jacket heat removal mechanism along the radial direction of the reactor shell (16) is 2-8 cm.

4. The heat removal device according to claim 1, characterized in that: The side surfaces of the flow guide support (13) are irregularly provided with spoilers (17) for increasing the turbulent flow of the heat exchange medium.

5. The heat removal device according to claim 4, characterized in that: The spoiler (17) is a metal thorn edge, including a metal needle in the shape of a stick.

6. The heat removal device according to claim 1, characterized in that: The heat exchange wall surface (15) is made of thin-walled stainless steel.

7. The heat removal device according to claim 1, characterized in that: The upper part of the reactor shell (16) is provided with a heat exchange medium outlet (18) connected to the chamber (14), and the lower part is provided with a heat exchange medium inlet (10). The heat exchange medium outlet (18) and the heat exchange medium inlet (10) are provided with one or more groups, and the cooling medium flows from bottom to top through the inner jacket heat removal mechanism.

8. The heat removal device according to claim 1, characterized in that: The chambers (14) are distributed up and down along the reactor shell to form a multi-section parallel passage structure, and are provided with multiple groups of heat exchange medium inlets and outlets.

9. The heat removal device according to claim 1, characterized in that: A stirring device is arranged inside the kettle reactor body. The stirring device includes a three-blade swept stirrer, a turbine stirrer, a plate-frame stirrer, and includes a stirring shaft (8) and a stirring paddle (9) mounted on the stirring shaft (8).

10. The heat removal device according to claim 9, characterized in that: The bottom of the reactor of the kettle reactor body is provided with a bottom bearing (12) through a bracket, and the bottom bearing (12) is installed at the end of the stirring shaft (8).

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