A solution process for producing polyolefins

Abstract

The application belongs to the technical field of solution preparation device, and provides a reaction device for preparing polyolefin by solution method.The reaction device comprises a barrel and a stirrer, the axis center of the barrel of the reaction device is provided with the stirrer, at least two groups of first heat exchangers are arranged in the barrel of the reaction device in a ring shape, the first heat exchanger comprises at least two vertical heat exchange pipes, the inlet and outlet of the first heat exchanger are located at the bottom of the reaction device, the outer wall of the barrel of the reaction device is attached with a second heat exchanger, and a baffle pipe is axially inserted into the gap between the first heat exchanger and the inner wall of the barrel of the reaction device, and the baffle pipe can destroy the flow boundary layer on the surface of the first heat exchanger and the inner wall of the barrel of the reaction device.The application aims to solve the problems of low mass transfer and heat transfer efficiency, uneven mixing, local overheating, wall hanging, fouling and poor discharge of the high viscosity solution polymer, and the problems of large number of heat exchange components in the reactor and difficult structure design.

Description

Technical Field

[0001] This invention relates to the field of chemical production technology and provides a reaction apparatus for preparing polyolefins using a solution method. Background Technology

[0002] In the solution-based preparation of polyolefins, the inlet reactants, catalyst, and outlet product of the reactor are all solutions. Problems include low mass and heat transfer efficiency, uneven mixing, and localized overheating in high-viscosity solution polymer systems; scaling, fouling, and poor discharge in high-viscosity solution polymer systems; a large number of internal heat exchange components, leading to structural design difficulties; and difficulty in cleaning the reactor interior. Existing technology CN 223096746U describes a polymerization reactor with a dry powder catalyst feeding system, including: a polymerization reactor, a feeding system, a venting system, a nitrogen feeding system, a raw material feeding system, and a vacuum system. The feeding system includes a catalyst sampler and a catalyst feeder connected via a first catalyst feed pipe. Both the catalyst sampler and the catalyst feeder are connected to the first catalyst feed pipe via a first pipe joint. The catalyst feeder and the polymerization reactor are both connected to a second catalyst feed pipe via a second pipe joint. The polymerization reactor and the catalyst feeder are both connected to a venting system. A nitrogen feeding system is connected to both the catalyst feeder and the polymerization reactor. A raw material feeding system is connected to both the polymerization reactor and the catalyst feeder. A vacuum system is connected to the polymerization reactor. The inventors of the prior art catalyst believe that the prior art has significant room for improvement. Summary of the Invention

[0003] The purpose of this invention is to solve the problems of low mass and heat transfer efficiency, uneven mixing, and localized overheating in high-viscosity solution polymer systems. Secondly, it addresses the issues of wall adhesion, scaling, and poor discharge in high-viscosity solution polymer systems; it also solves the problems of a large number of heat exchange components inside the reactor, making structural design difficult, and the difficulty of cleaning the reactor interior.

[0004] A reaction apparatus for preparing polyolefins by solution method includes a cylinder and a stirrer. The stirrer is located along the axis of the cylinder. At least two sets of first heat exchangers are arranged circumferentially inside the cylinder. Each first heat exchanger includes at least two vertical heat exchange tubes. The inlet and outlet of the first heat exchanger are located at the bottom of the reaction apparatus. A second heat exchanger is attached to the outer wall of the cylinder. A baffle tube is inserted axially into the gap between the first heat exchanger and the inner wall of the cylinder. The baffle tube can disrupt the flow boundary layer on the surface of the first heat exchanger and the inner wall of the cylinder. With the above configuration, the top of the heat exchange tubes of the first heat exchanger are connected by elbows. The first heat exchanger is a U-shaped tube, with one end of the U-shaped tube bundle fixed and the other end freely expandable and contractible. This compensates for the thermal expansion difference caused by temperature changes below 300℃, eliminates the thermal stress caused by the difference in thermal expansion coefficients between the tube bundle and the shell, and solves the thermal compensation problem of the tube bundle cooling system. The cooling medium inside the first heat exchanger is usually demineralized water. The heat exchange tubes are high-flux tubes with microporous structures or other structures that increase the surface area for heat dissipation, which greatly promotes the boiling heat transfer of the solution outside the tubes. A second heat exchanger is installed outside the reaction device. Different circulating media are introduced into the second heat exchanger according to different stages of the reaction. Before the reaction and at the beginning of the reaction, low-pressure steam is introduced to heat the reaction device, accelerating the reaction device to reach the reaction temperature. After the reaction stabilizes and... After the reaction, the circulating medium in the second heat exchanger is demineralized water, which, together with the first heat exchanger, removes heat from the reaction solution. This simultaneous heat removal inside and outside the reaction apparatus improves heat transfer efficiency and ensures there are no dead zones at the bottom and top of the apparatus. Four to eight baffles are installed between the first heat exchanger and the inner wall of the reactor cylinder. The outer wall of each baffle has at least two finger-shaped rods. When the baffles rotate, they disrupt the flow boundary layer near the inner wall surface, preventing the formation of micro-adhesives and maintaining the heat transfer effect of the cylinder. They also prevent these micro-adhesives from growing into scale. If material adheres to the heat exchanger tube walls or the reactor inner wall, as the adhesion thickness increases, scale forms, increasing the thermal resistance of the adhered material layer. This wall adhesion will significantly reduce heat transfer efficiency, and the product of the reaction apparatus may fail to meet standards due to a high residual monomer content. The residual monomer content refers to the content of remaining reactant monomers.

[0005] Preferably, the top and bottom of the cylinder are hemispherical, and the middle part is cylindrical. The second heat exchanger includes a semi-tube structure, which is a tubular structure cut along its extension direction. The open surface of the semi-tube structure is the heat-conducting surface, and the closed surface is the heat-dissipating surface. The heat-conducting surface is in contact with the outer wall of the cylinder. The circulating medium inside the semi-tube structure exchanges heat with the reaction solution inside the cylinder through the heat-conducting surface. Because the heat-conducting surface of the semi-tube structure is open and has a large heat dissipation area, and is separated from the reaction solution only by the cylinder, the heat transfer efficiency of the semi-tube structure is high, and the heat transfer efficiency between the semi-tube structure and the reaction solution is also high.

[0006] Preferably, the semi-tube structure includes a spiral semi-tube, a manifold semi-tube, and a vertical semi-tube connected to the manifold semi-tube at both ends. The top and bottom of the cylinder are fitted with the heat-conducting surfaces of the spiral semi-tube, while the middle part of the cylinder is fitted with the heat-conducting surfaces of the manifold semi-tube and the vertical semi-tube. The semi-tube structure covers all surfaces of the reactor cylinder, and the different shapes of the semi-tubes are designed to accommodate the different flow fields in different parts of the reactor, thus avoiding heat transfer dead zones at the bottom and top of the cylinder.

[0007] Preferably, the outer wall of the baffle is equipped with finger-shaped rods, with the angle between the finger-shaped rods and the outer wall of the baffle being 15-90°. Each finger-shaped rod ends in a rotating nozzle. With this configuration, the baffle can receive hot solvent that does not participate in the reaction but has a temperature close to the reaction temperature. The hot solvent is sprayed out using the rotating nozzles. The finger-shaped rods not only act as flow-tightening elements but also work in conjunction with the hot solvent to purge, generating continuous fluid shear force to clean the inner wall of the reactor cylinder and the outer surface of the heat exchange tubes of the first heat exchanger. The polymers used in the production of polyolefins are high-viscosity systems with poor flowability, easily leading to problems such as wall adhesion and vessel sticking. The fluid shear force can peel off the material adhering to the inner wall of the reactor cylinder and the outer surface of the heat exchange tubes of the first heat exchanger, preventing it from growing into scale. This solves the problem that after scaling, the increased thickness of the adhered material layer leads to increased thermal resistance, resulting in decreased heat transfer efficiency and high residue content in the product. The hot solvent is separated from the reaction products in subsequent processes.

[0008] Preferably, the cylinder is provided with at least two discharge ports, including a first discharge port and a second discharge port, with the first discharge port located in the middle of the cylinder and the second discharge port located at the top of the cylinder. When the reactor is not full, the operator discharges the material through the first outlet located on the side wall of the reactor body. Compared to the traditional outlet located at the bottom, this method utilizes fluid kinetic energy and gravity to guide the product out smoothly while reducing backmixing. Specifically, it reduces the phenomenon where, after the fluid in the reactor body flows upward axially under the action of the stirrer, some of the fluid flows backward and mixes on the cross-section of the flow channel due to the influence of fluid kinetic energy and gravity. When the material height is equal to the first outlet, backmixing occurs almost non-existently. When the material height is slightly higher than the first outlet, backmixing only occurs in the portion of the material above the first outlet. Furthermore, when the reactor is full, the operator discharges the material through the second outlet located at the top of the reactor body. Compared to the traditional outlet located at the bottom and the aforementioned outlet located on the side wall of the reactor body, the second outlet located at the top of the reactor body significantly reduces backmixing, resulting in a more complete and uniform reaction, while also shortening the material residence time and improving reaction efficiency.

[0009] Preferably, the centerline of the first discharge port has a downward angle of 15-75° with the horizontal plane. With this configuration, the structure can fully utilize fluid kinetic energy and gravity to guide the product smoothly out of the outlet, effectively preventing polymer accumulation and blockage in the outlet area.

[0010] Preferably, the stirrer includes a vertical stirring rod and a blade mechanism sleeved outside the stirring rod. The blade mechanism includes radial flow blades and at least one layer of axial flow blades. The radial flow blades are located at the end of the stirring rod and at the bottom of the reaction device. The rotation of the radial flow blades generates radial turbulence perpendicular to the stirring rod. The axial flow blades are arranged sequentially along the extension direction of the stirring rod, and their rotation generates axial flow parallel to the stirring rod. The stirrer has multiple layers of stirring blades from bottom to top. The bottom layer consists of large-bladed radial flow blades perpendicular to the stirring plane, used to generate strong radial turbulence at the bottom of the reaction device, achieving rapid and uniform mixing of the liquid catalyst and reactant solution. Above the bottom layer are axial flow blades with an angle or curvature to the stirring plane. The axial flow blades can push the polymer in the reaction device to flow upward axially as a whole, cooperating with the radial turbulence at the bottom to form a flow field covering the inside of the reaction device.

[0011] Preferably, the second heat exchanger is coupled with a blade mechanism, in which a collection half-pipe is provided on the plane of the blade mechanism, which has radial flow blades and axial flow blades respectively. During the stirring process, the heat generated by the friction between the blade mechanism and the reaction solution due to stirring friction and the blades driving the reaction solution is higher than that at other locations in the flow field. The collection half-pipe at this plane position shortens the heat exchange path. Secondly, compared with the vertical half-pipe, the open surface of the collection half-pipe surrounds the annular surface of the reactor body at this plane position. There is a wall thickness between adjacent vertical half-pipes, while the collection half-pipe has no discontinuity. Thirdly, although the axial flow blades mainly generate axial fluid, they also generate some radial fluid rotating in the same plane as the radial flow blades. The open surface of the collection half-pipe can also better adapt to the horizontal flow field. In addition, through the above configuration, the vertical half-pipe is connected to the collection half-pipe at both ends, and the vertical half-pipe can also efficiently dissipate heat in the area where the axial flow blades mainly generate axial flow. The open surface of the vertical half-pipe can better adapt to the axial flow field. Both the collection half-pipe and the vertical half-pipe of the second heat exchanger can effectively dissipate heat.

[0012] Preferably, the surfaces of the radial and axial flow blades of the impeller mechanism are coated with a 30-50 μm low surface energy fluoropolymer. Furthermore, the fluoropolymer can be polytetrafluoroethylene (PTFE) or Teflon-based coatings. Utilizing their low surface energy, the adhesion between the impeller mechanism and the polymer is reduced, preventing overloading of the impeller mechanism due to excessive resistance from the agitated material, and ensuring a stable flow field in the stirred reaction solution, thus promoting complete reaction.

[0013] Preferably, the surface roughness Ra of the outer surfaces of the reactor cylinder inner wall and the heat exchange tubes in contact with the reaction solution in the solution method is 0.2 μm. All key metal surfaces in contact with the polymer solution, such as the reactor cylinder inner wall and the outer walls of the internal heat exchange tubes, are precision mechanically polished to control the surface roughness Ra at 0.2 μm. This high polishing degree significantly reduces polymer adhesion to the walls.

[0014] This invention solves the problems of low mass and heat transfer efficiency, uneven mixing, and localized overheating in high-viscosity solution polymer systems; it also solves the problems of wall adhesion, scaling, and poor discharge in high-viscosity solution polymer systems; it addresses the challenges of numerous internal heat exchange components and complex structural design in reactors; and it resolves the difficulty of cleaning the reactor interior. Furthermore, it offers the following advantages: it compensates for thermal expansion differences caused by temperature changes below 300°C, eliminating thermal stress caused by the difference in thermal expansion coefficients between the tube bundle and the shell; it maintains the cleanliness of the inner wall of the reaction device and the outer wall of the first heat exchanger, preventing incomplete reaction of reactant monomers due to increased thermal resistance, and preventing the product from failing to meet standards due to high residual monomer content; it reduces the adhesion force between the impeller mechanism and the polymer, preventing overload of the impeller mechanism due to excessive resistance from the stirred material, and it ensures that the stirred reaction solution forms a stable flow field, promoting complete reaction. Attached Figure Description

[0015] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the external structure of a reaction apparatus for preparing polyolefins using a solution method.

[0017] Figure 2 This is a schematic diagram of the internal structure of a reaction apparatus for preparing polyolefins using a solution method.

[0018] Figure 3 This is a diagram showing the connection of the first heat exchanger.

[0019] Figure 4 This is a schematic diagram showing the arrangement of the first heat exchanger and its inlet and outlet.

[0020] Figure 5 This is a diagram showing the heat exchanger tube layout for the first heat exchanger.

[0021] Figure 6 This is a schematic diagram of the second heat exchanger.

[0022] Figure 7This is a partially enlarged view of the second heat exchanger.

[0023] Figure 8 This is a schematic diagram of the connection structure between the combined half-pipe and the vertical half-pipe.

[0024] Figure 9 This is a magnified view of a portion of the first discharge port.

[0025] Figure 10 This is a schematic diagram of the stirrer in Example 2.

[0026] Legend: 1 Second heat exchanger; 11 Spiral half-pipe; 12 Collector half-pipe; 13 Vertical half-pipe; 14 Open surface; 15 Closed surface; 2 First heat exchanger; 21 Elbow; 22 Heat exchange tube; 3 Agitator; 31 Axial flow blade; 32 Radial flow blade; 4 First discharge port; 5 Second discharge port; 6 Cylinder; 7 Baffle; 71 Finger rod; 72 Rotary nozzle. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0028] Example 1

[0029] Combination Figure 1 and Figure 2 As shown, a reaction apparatus for preparing polyolefins by solution method includes a cylinder 6 and a stirrer 3. The stirrer 3 is located along the axis of the cylinder 6. Five sets of first heat exchangers 2 are arranged circumferentially inside the cylinder 6. The first heat exchangers 2 include at least two vertical heat exchange tubes 22. The inlet and outlet of the first heat exchangers 2 are located at the bottom of the reaction apparatus. A second heat exchanger 1 is attached to the outer wall of the cylinder 6. A baffle tube 7 is inserted axially into the gap between the first heat exchangers 2 and the inner wall of the cylinder 6. The baffle tube 7 can disrupt the flow boundary layer on the surface of the first heat exchangers 2 and the inner wall of the cylinder 6.

[0030] Through the above settings, combined with Figure 2 , Figure 3 , Figure 4 and Figure 5As shown, the reaction device is equipped with five sets of first heat exchangers 2. The top of the heat exchange tubes 22 of the first heat exchangers 2 are connected by elbows 21. The first heat exchangers 2 are U-shaped tubes. One end of the U-shaped tube bundle is fixed, and the other end can be freely extended and retracted. This can compensate for the thermal expansion difference caused by temperature changes below 300℃, eliminate the thermal stress caused by the difference in thermal expansion coefficients between the tube bundle and the shell, and solve the thermal compensation problem of the tube bundle cooling system. The cooling medium in the first heat exchangers 2 is usually demineralized water. The heat exchange tubes 22 are high-flux tubes. The surface of the heat exchange tubes 22 has a microporous structure or other structures that increase the surface area for heat dissipation, which can greatly promote the boiling heat transfer of the solution outside the tube. Each group of first heat exchangers 2 has an inlet pipe N1 and an outlet pipe N2. N1a corresponds to N2a, N1b corresponds to N2b, N1c corresponds to N2c, N1d corresponds to N2d, and N1e corresponds to N2e. The cooling medium enters the head through the inlet pipe and then flows evenly into the heat exchange tubes 22. The tops of every two first heat exchangers 2 are connected by elbows 21. The first heat exchanger 2 has 36 heat exchange tubes 22 inside, and the included angle of the lines connecting the centers of the heat exchange tubes 22 is 60°.

[0031] like Figure 1 As shown, a second heat exchanger 1 is provided outside the reaction device. The second heat exchanger 1 is supplied with different circulating media according to different stages of the reaction. Before the reaction and at the beginning of the reaction, low-pressure steam is introduced to heat the reaction device and accelerate the reaction device to reach the reaction temperature. After the reaction stabilizes and after the reaction is completed, the circulating media of the second heat exchanger 1 is demineralized water, which, together with the first heat exchanger 2, removes heat from the reaction solution. Heat is removed from both inside and outside the reaction device at the same time, which improves the heat transfer efficiency and ensures that there are no dead zones for heat transfer at the bottom and top of the reaction device.

[0032] like Figure 2As shown, the stirrer 3 includes a vertical stirring rod and a blade mechanism sleeved outside the stirring rod. The blade mechanism includes radial flow blades 32 and two layers of axial flow blades 31. The radial flow blades 32 are located at the end of the stirring rod and at the bottom of the reaction device. The rotation of the radial flow blades 32 generates radial turbulence perpendicular to the stirring rod. The axial flow blades 31 are arranged sequentially along the extension direction of the stirring rod, and the rotation of the axial flow blades 31 generates axial flow parallel to the stirring rod. The stirrer 3 has multiple layers of stirring blades from bottom to top. The bottom layer consists of large-bladed radial flow blades 32 perpendicular to the stirring plane, used to generate strong radial turbulence at the bottom of the reaction device to achieve rapid and uniform mixing of the liquid catalyst and reactant solution. Above the bottom layer are axial flow blades 31 with an angle or curvature to the stirring plane. The axial flow blades 31 can push the polymer in the reaction device to flow upward axially as a whole, cooperating with the radial turbulence at the bottom to form a flow field covering the inside of the reaction device. Four to eight baffles 7 are installed between the reactor tubes. The outer wall of each baffle 7 has at least two finger-shaped rods 71. When the baffles 7 rotate, they disrupt the flow boundary layer near the inner wall surface, preventing the formation of micro-adhesives and maintaining the heat transfer effect of the reactor body 6. They also prevent the micro-adhesives from growing into scale. If material adheres to the walls of the heat exchange tubes 22 and the reactor interior, as the thickness of the adhesion increases, it grows into scale, increasing the thermal resistance of the adhered material layer. This wall adhesion will lead to a significant decrease in heat transfer efficiency, and the product of the reactor may fail to meet standards due to a high residual monomer content. The residual monomer content refers to the content of residual reactant monomers.

[0033] The surfaces of the radial flow blades 32 and axial flow blades 31 of the blade mechanism are coated with a 40 μm low surface energy fluoropolymer. Furthermore, the fluoropolymer can be polytetrafluoroethylene (PTFE), utilizing its low surface energy to reduce the adhesion between the blade mechanism and the polymer, preventing the blade mechanism from being overloaded due to excessive resistance from the stirred material, and ensuring that the stirred reaction solution forms a stable flow field, promoting complete reaction.

[0034] like Figure 2As shown, the cylinder 6 is provided with two discharge ports N3 and N4. N3 is the first discharge port 4 and N4 is the second discharge port 5. The first discharge port 4 is located in the middle of the cylinder 6 and the second discharge port 5 is located at the top of the cylinder 6. When the reactor is not full, the operator discharges the product through the first outlet 4 located on the side wall of the reactor body 6. Compared to the traditional outlet located at the bottom, this method utilizes fluid kinetic energy and gravity to guide the product out smoothly while reducing backmixing. This reduces the phenomenon where some of the fluid flowing upwards axially under the action of the stirrer 3 reverses flow and mixes on the cross-section of the flow channel due to the influence of fluid kinetic energy and gravity. When the material height is equal to the first outlet 4, backmixing occurs almost non-existently. When the material height is slightly higher than the first outlet 4, backmixing only occurs in the portion of the material above the first outlet 4. Furthermore, when the reactor is full, the operator discharges the product through the second outlet 5 located at the top of the reactor body 6. Compared to the traditional outlet located at the bottom and the aforementioned outlet located on the side wall of the reactor body 6, the second outlet 5 located at the top of the reactor significantly reduces backmixing, making the reaction more complete and uniform, while shortening the material residence time and improving reaction efficiency.

[0035] Combination Figure 1 and Figure 2 As shown, the second heat exchanger 1 cooperates with the impeller mechanism, which has a radial flow impeller 32 and an axial flow impeller 31 respectively, and a collection half-pipe 12 is provided on the plane. During the stirring process of the stirrer 3, the heat generated by the stirring friction and the impeller driving the reaction solution in the part of the impeller mechanism that is in direct contact with the reaction solution is higher than that in other parts of the flow field. The collection half-pipe 12 is located at this plane position, which shortens the heat exchange path. Secondly, compared with the vertical half-pipe 13, the open surface 14 of the collection half-pipe 12 surrounds the annular surface of the reaction device cylinder 6 at this plane position. There are gaps between adjacent vertical half-pipes 13, while there is no discontinuity in the collection half-pipe 12. Furthermore, although the axial flow impeller 31 mainly generates axial fluid, it also generates some radial fluid rotating in the same plane as the radial flow impeller 32. The open surface 14 of the collection half-pipe 12 can also better adapt to the horizontal flow field. Furthermore, through the above configuration, the vertical half-pipe 13 is connected to the manifold half-pipe 12 at both ends, and the vertical half-pipe 13 can also efficiently dissipate heat from the axial flow area generated by the axial flow blade 31. The open surface 14 of the vertical half-pipe 13 can better adapt to the axial flow field. Both the manifold half-pipe 12 and the vertical half-pipe 13 of the second heat exchanger 1 can effectively dissipate heat.

[0036] Combination Figure 1 and Figure 8As shown, the top and bottom of the cylinder 6 are hemispherical, and the middle part of the cylinder 6 is cylindrical. The second heat exchanger 1 includes a semi-tube structure, which is a tubular structure cut along its extension direction. The open surface 14 of the semi-tube structure is a heat-conducting surface, and the closed surface 15 of the semi-tube structure is a heat-dissipating surface. The heat-conducting surface is in contact with the outer wall of the cylinder 6. The circulating medium inside the semi-tube structure exchanges heat with the reaction solution inside the cylinder 6 through the heat-conducting surface. Since the heat-conducting surface 14 of the semi-tube structure is an open surface with a large heat dissipation area, and it is separated from the reaction solution only by the cylinder 6, the heat transfer efficiency of the semi-tube structure is high, and the heat transfer efficiency between the semi-tube structure and the reaction solution is also high.

[0037] Combination Figure 6 and Figure 7 As shown, the semi-tube structure includes a spiral semi-tube 11, a manifold semi-tube 12, and a vertical semi-tube 13 connected to the manifold semi-tube 12 at both ends. The top and bottom of the cylinder 6 are fitted with the heat-conducting surfaces of the spiral semi-tube 11, and the middle part of the cylinder 6 is fitted with the heat-conducting surfaces of the manifold semi-tube 12 and the vertical semi-tube 13. The semi-tube structure covers all surfaces of the cylinder 6 of the reaction device to avoid heat transfer dead zones at the bottom and top of the cylinder 6. The size of the manifold semi-tube 12 is DN50~DN100, and the size of the vertical semi-tube 13 is DN25~DN50. In this embodiment, the sizes of the manifold semi-tube 12 and the vertical semi-tube 13 are DN50 and DN25, respectively.

[0038] like Figure 2 and Figure 9 As shown, the outer wall of the baffle 7 is provided with finger-shaped rods 71, and the angle α between the finger-shaped rods 71 ​​and the outer wall of the baffle 7 is 15-90°. Each finger-shaped rod 71 has a rotating nozzle 72 at its end. In this embodiment, the angle α between the finger-shaped rods 71 ​​and the outer wall of the baffle 7 is 45°. With the above configuration, the baffle 7 can input a hot solvent that does not participate in the reaction but has a temperature close to the reaction temperature. The hot solvent is sprayed out using the rotating nozzle 72. The finger-shaped rods 71 ​​not only act as flow-tightening elements but also work in conjunction with the hot solvent to purge, forming a continuous fluid shear force to clean the inner wall of the cylinder 6 and the outer surface of the heat exchange tubes 22 of the first heat exchanger 2. The polymers used in the production of polyolefins are high-viscosity systems with poor fluidity, easily leading to problems such as wall adhesion and vessel sticking. Fluid shear force can peel away the material adhering to the inner wall of the reactor shell 6 and the outer surface of the heat exchange tube 22 of the first heat exchanger 2, preventing it from growing into scale. This solves the problem that after scaling, the increased thickness of the material adhesion layer leads to increased thermal resistance, resulting in decreased heat transfer efficiency and high residue content in the product. The hot solvent is separated from the reaction product through subsequent processes.

[0039] like Figure 9As shown, the centerline of the first discharge port 4 forms a downward angle β with the horizontal plane of 15-75°. In this embodiment, the angle β between the centerline of the first discharge port 4 and the horizontal plane is 30°. With the above configuration, this structure can fully utilize fluid kinetic energy and gravity to guide the product to discharge smoothly, effectively avoiding the accumulation and blockage of polymer in the outlet area.

[0040] The surface roughness Ra of the outer surfaces of the reactor cylinder 6 and the heat exchange tube 22 that come into contact with the reaction solution in the solution method is 0.2 μm. All key metal surfaces in contact with the polymer solution, such as the inner wall of the reactor cylinder 6 and the outer wall of the internal tube heat exchange tube 22, are precision mechanically polished to control the surface roughness Ra at 0.2 μm. The high polishing degree can significantly reduce polymer adhesion to the walls.

[0041] Example 2

[0042] like Figure 10 As shown, in this embodiment, unlike Embodiment 1, the stirring rod of the stirrer 3 is provided with finger-shaped rods 71. The finger-shaped rods 71 ​​form an angle with the outer wall of the stirring rod, causing the finger-shaped rods 71 ​​to rotate and generate a cone angle γ. The spatial projection of the finger-shaped rods 71 ​​covers the impeller mechanism below. The stirring rod of the stirrer 3 has a hollow structure, allowing the input of hot solvent that does not participate in the reaction but has a temperature close to the reaction temperature. Similar to Embodiment 1, the finger-shaped rods 71 ​​can output this hot solvent, which is sprayed out using a rotating nozzle 72. The finger-shaped rods 71 ​​not only cooperate with the hot solvent for purging but also form a continuous fluid shear force on the outer surface of the impeller mechanism. The polymers in the reaction producing polyolefins are high-viscosity systems with poor fluidity, easily leading to problems such as wall adhesion and vessel sticking. The fluid shear force can peel off the material adhering to the impeller mechanism, avoiding increased rotational load on the impeller mechanism and preventing the impeller gaps from being filled with material, thus reducing the stirring effect of the impeller mechanism.

[0043] In another embodiment, to avoid the influence of the finger rod 71 on the stirring rod and the hot solvent purging on the axial flow field generated by the stirring of the axial flow blade 31, the finger rod 71 is adjusted to an inclined nozzle on the stirring rod. The included angle of the inclined nozzle is the same as that of the finger rod 71 in Embodiment 2. The hot solvent sprayed from the inclined nozzle has a weaker purging effect on the blade mechanism than the finger rod 71. However, at a lower stirring speed, the inclined nozzle has a weaker influence on the axial flow field generated by the stirring of the axial flow blade 31, which is beneficial to the fluid flow inside the reaction device.

[0044] This invention solves the problems of low mass and heat transfer efficiency, uneven mixing, and localized overheating in high-viscosity solution polymer systems; it also solves the problems of wall adhesion, scaling, and poor discharge in high-viscosity solution polymer systems; it addresses the challenges of numerous internal heat exchange components and complex structural design in reactors; and it resolves the difficulty of cleaning the reactor interior. Furthermore, it offers the following advantages: it compensates for thermal expansion differences caused by temperature changes below 300°C, eliminating thermal stress caused by the difference in thermal expansion coefficients between the tube bundle and the shell; it maintains the cleanliness of the inner wall of the reaction device and the outer wall of the first heat exchanger 2, preventing incomplete reaction of reactant monomers due to increased thermal resistance, and preventing the product from failing to meet standards due to high residual monomer content; it reduces the adhesion force between the impeller mechanism and the polymer, preventing overload of the impeller mechanism due to excessive resistance from the stirred material, and ensuring that the stirred reaction solution forms a stable flow field, promoting complete reaction.

[0045] The above embodiments and / or implementation methods are merely illustrative of preferred embodiments and / or implementation methods for realizing the technology of the present invention, and are not intended to limit the implementation methods of the technology of the present invention in any way. Any person skilled in the art may make some modifications to other equivalent embodiments without departing from the scope of the technical means disclosed in the content of the present invention, but these should still be regarded as the technology or embodiments that are substantially the same as the present invention.

Claims

1. A reaction apparatus for preparing polyolefins by solution method, comprising a cylinder (6) and a stirrer (3), characterized in that, A stirrer (3) is provided along the axis of the cylinder (6) of the reaction device. At least two sets of first heat exchangers (2) are arranged circumferentially inside the cylinder (6). The first heat exchanger (2) includes at least two vertical heat exchange tubes (22). The inlet and outlet of the first heat exchanger (2) are located at the bottom of the reaction device. A second heat exchanger (1) is attached to the outer wall of the cylinder (6) of the reaction device. A baffle tube (7) is inserted axially into the gap between the first heat exchanger (2) and the inner wall of the cylinder (6) of the reaction device. The outer wall of the baffle tube (7) is provided with finger rods (71). The angle between the finger rods (71) and the outer wall of the baffle tube (7) is 15-90°. The end of each finger rod (71) is provided with a rotating nozzle (72). When the baffle tube (7) rotates, it can destroy the first heat exchanger (2) and the reaction device. The flow boundary layer on the inner wall surface of the cylinder (6); the top of the heat exchange tube (22) of the first heat exchanger (2) is connected by an elbow (21). The first heat exchanger (2) is a U-shaped tube. One end of the U-shaped tube bundle is fixed and the other end can be freely extended and retracted; the stirring rod of the stirrer (3) is provided with a finger rod (71). The finger rod (71) has an angle with the outer wall of the stirring rod. The angle causes the finger rod (71) to rotate and generate a cone angle γ. The spatial projection of the finger rod (71) covers the blade mechanism below; a second heat exchanger (1) is provided outside the reaction device. The second heat exchanger (1) is supplied with different circulating media according to different stages of the reaction. Before the reaction and at the beginning of the reaction, low-pressure steam is supplied to heat the reaction device and accelerate the reaction device to reach the reaction temperature. After the reaction stabilizes and after the reaction ends, the circulating media of the second heat exchanger (1) is demineralized water.

2. The reaction apparatus for preparing polyolefins by solution method according to claim 1, characterized in that, The top and bottom of the cylinder (6) are hemispherical, and the middle part of the cylinder (6) is cylindrical. The second heat exchanger (1) includes a semi-tube structure, which is a tubular structure cut along the extension direction. The open surface (14) of the semi-tube structure is a heat-conducting surface, and the closed surface (15) of the semi-tube structure is a heat-dissipating surface. The heat-conducting surface is in contact with the outer wall of the cylinder (6).

3. The reaction apparatus for preparing polyolefins by solution method according to claim 2, characterized in that, The semi-tube structure includes a spiral semi-tube (11), a collection semi-tube (12), and a vertical semi-tube (13) connected to the collection semi-tube (12) at both ends. The top and bottom of the cylinder (6) are attached to the heat-conducting surfaces of the spiral semi-tube (11), and the middle part of the cylinder (6) is attached to the heat-conducting surfaces of the collection semi-tube (12) and the vertical semi-tube (13).

4. The reaction apparatus for preparing polyolefins by solution method according to claim 1, characterized in that, The cylinder (6) is provided with at least two discharge ports, including a first discharge port (4) and a second discharge port (5). The first discharge port (4) is located in the middle of the cylinder (6), and the second discharge port (5) is located at the top of the cylinder (6).

5. The reaction apparatus for preparing polyolefins by solution method according to claim 4, characterized in that, The centerline of the first discharge port (4) has a downward angle of 15-75° with the horizontal plane.

6. The reaction apparatus for preparing polyolefins by solution method according to claim 3, characterized in that, The stirrer (3) includes a vertical stirring rod and a blade mechanism sleeved outside the stirring rod. The blade mechanism includes radial flow blades (32) and at least one layer of axial flow blades (31). The radial flow blades (32) are located at the end of the stirring rod and at the bottom of the reaction device. The rotation of the radial flow blades (32) generates radial turbulence perpendicular to the stirring rod. The axial flow blades (31) are arranged sequentially along the extension direction of the stirring rod. The rotation of the axial flow blades (31) generates axial flow parallel to the stirring rod.

7. The reaction apparatus for preparing polyolefins by solution method according to claim 6, characterized in that, The second heat exchanger (1) cooperates with the blade mechanism, and the blade mechanism has a radial flow blade (32) and an axial flow blade (31) on its plane and a collection half-pipe (12).

8. The reaction apparatus for preparing polyolefins by solution method according to claim 6, characterized in that, The surfaces of the radial flow blades (32) and axial flow blades (31) of the blade mechanism are coated with a fluoropolymer with a low surface energy of 30-50 μm.

9. The reaction apparatus for preparing polyolefins by solution method according to claim 1, characterized in that, The surface roughness Ra of the inner wall of the cylinder (6) and the outer wall of the heat exchange tube (22) of the reaction device in contact with the reaction solution of the solution method is <0.2μm.

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