A prepolymerization reactor for use in a polyolefin process

Abstract

This utility model discloses a prepolymerization reactor for polyolefin processes, comprising a shell, which is a double-cylinder structure consisting of an inner cylinder and an outer cylinder. The outer cylinder is equipped with a cooling jacket, and the inner cylinder is equipped with a heat exchange coil, both ends of which are connected to the heat exchange coil inlet and outlet outside the shell. The top of the inner cylinder has a monomer inlet, a mixture outlet, and an inner cylinder reagent inlet; the bottom of the outer cylinder has a discharge port and an outer cylinder reagent inlet; and the upper part of the outer cylinder has an outer cylinder reagent outlet, which is connected to the inner cylinder reagent inlet. This utility model provides a prepolymerization reactor for polyolefin processes. By adopting a double-cylinder structure, setting an outer cylinder heat exchange coil, and an outer cylinder jacket, the distance between the pre-contact and prepolymerization processes is greatly reduced, improving the overall temperature control of the prepolymerization system. This effectively reduces the risk of blockage in the connecting pipelines between the pre-contact and prepolymerization equipment and reduces the probability of temperature fluctuations in the prepolymerization reactor.

Description

Technical Field

[0001] This utility model relates to a reactor for a polyolefin process, belonging to the field of reactor design technology. Background Technology

[0002] Polymerization is the process of converting low-molecular-weight monomers into high-molecular-weight polymers. Polymers possess important properties not found in low-molecular-weight monomers, such as plasticity, fiber formation, film formation, and high elasticity, and are widely used in plastics, fibers, rubber, coatings, adhesives, and other applications. These materials are high-molecular-weight compounds composed of one or more structural units (monomers), synthesized from monomers through repeated reactions. Common polymers such as polypropylene and polyethylene are obtained through the polymerization of monomers propylene and ethylene.

[0003] In the production process of polyolefins, Ziegler-Natta (ZN) catalysts play a crucial role. ZN catalysts have high activity and produce polymers with excellent overall performance, making them a long-standing research hotspot in the field of olefin polymerization. However, due to their excessively high initial reactivity, high-temperature polymerization with high-concentration monomers can easily cause catalyst particles to break down into fragments, which then grow into fine polymer powder during polymerization. Furthermore, they are prone to generating localized hot spots, leading to polymer agglomeration in the reactor. These problems can affect the stable operation of the polymerization unit and may even lead to emergency shutdowns. A widely adopted industrial solution is to introduce prepolymerization technology, allowing the catalyst components to prepolymerize with olefin monomers under mild reaction conditions. This slows down the initial reactivity of polymerization, better controls the olefin polymerization process, prevents catalyst breakage, and improves the particle morphology of the polymer.

[0004] Prepolymerization refers to polymerization that occurs under mild conditions (relatively low temperatures and / or low monomer concentrations) before the main polymerization stage. In conventional olefin polymerization processes (e.g., ethylene polymerization, propylene polymerization, or copolymerization of ethylene, propylene, and other α-olefins), the main polymerization stage typically occurs at higher temperatures (65–80°C) and higher monomer concentrations. Therefore, the selection of the prepolymerization process mainly considers monomer concentration and prepolymerization temperature. Similar to main polymerization, prepolymerization methods include bulk, slurry, and gas-phase polymerization. However, slurry polymerization is typically used to ensure controllability of prepolymerization. This is because slurry polymerization has lower monomer concentrations; and for Zn catalysts, the reaction rate is faster at higher temperatures. Therefore, the prepolymerization temperature is much lower than the main polymerization temperature, typically 10–20°C.

[0005] Traditional prepolymerization uses a pre-contact tank + prepolymerization reactor process. A specific solvent carries the main catalyst, co-catalyst and electron donor, which are mixed and cooled in the pre-contact tank and then overflow out of the pre-contact tank to merge with the pre-cooled propylene in the prepolymerization reactor to react. The temperature of the prepolymerization reactor is controlled by a jacket, and the mixture after reaction overflows into the polymerization reactor.

[0006] The pre-contact tank and the prepolymer reactor are connected by pipelines. Due to the specific solvent forming a slurry with the main catalyst, co-catalyst and electron donor in the pre-contact tank, it overflows into the prepolymer reactor. Moreover, the connecting pipeline is relatively thin, which can easily cause pipeline blockage and poor flow. At the same time, the pre-contact tank and the prepolymer reactor are two separate temperature control systems, and the temperature of the pre-contact tank directly affects the temperature control of the prepolymer reactor.

[0007] Prepolymerization can be carried out in both batch reactors and tubular reactors, but it is generally much smaller in scale than the main reactor and can be operated continuously or intermittently. Summary of the Invention

[0008] The technical problem to be solved by this utility model is: to reduce the connecting pipes between the pre-contact tank and the prepolymer reactor, thereby reducing the risk of pipe blockage; and to reduce the probability of temperature fluctuations in the prepolymer reactor by unifying the temperature control of the pre-contact tank and the prepolymer reactor.

[0009] To address the aforementioned technical problems, this utility model provides a prepolymer reactor for polyolefin processes, comprising a shell, which is a double-cylinder structure consisting of an inner cylinder and an outer cylinder. The outer cylinder is provided with a cooling jacket, and the inner cylinder is provided with a heat exchange coil. The two ends of the heat exchange coil are connected to the heat exchange coil inlet and heat exchange coil outlet outside the shell. The top of the inner cylinder is provided with a monomer inlet, a mixture outlet, and an inner cylinder reagent inlet. The bottom of the outer cylinder is provided with a discharge port and an outer cylinder reagent inlet. The upper part of the outer cylinder is provided with an outer cylinder reagent outlet, which is connected to the inner cylinder reagent inlet.

[0010] Preferably, the top of the outer cylinder is provided with flange one, the upper end of flange one is provided with flange cover, and the lower end is an elliptical end cap; the top of the inner cylinder is provided with inner cylinder plate, the upper and lower sides of the inner cylinder plate are respectively connected and fixed to flange cover and flange one, and the lower end of the inner cylinder is an elliptical end cap; the monomer inlet, the mixture outlet, and the inner cylinder reagent inlet are provided on the flange cover.

[0011] Preferably, the shell is a cylindrical structure vertically aligned along a central axis, consisting of an inner and outer cylinder. The upper end has a flat end cap, and the lower end has an elliptical end cap. The aspect ratio of the outer cylinder is not less than 2, and the aspect ratio of the inner cylinder is not less than 1.5, with the aspect ratio of the outer cylinder not being less than that of the inner cylinder. The inner cylinder functions as a prepolymerization reactor, and the space between the inner and outer cylinders functions as a pre-contact tank.

[0012] Preferably, the cooling jacket provided on the outside of the outer cylinder has a jacket inlet at the lower part and a jacket outlet at the upper part; a heat exchange coil is provided on the outside of the inner cylinder, and the heat exchange coil is connected to the inlet and outlet of the inner coil on the outer cylinder through flanges.

[0013] Preferably, the inner cylinder is equipped with a stirrer, and the top of the stirrer is connected to the motor through a stirrer connection port.

[0014] More preferably, the motor is a variable frequency motor. The main function of the stirrer is to promote the fusion of monomers and reagents and improve the conversion rate of the reaction. The stirring power comes from the motor located at the top, and the stirring speed can be adjusted according to the specific reaction degree.

[0015] Preferably, the inlet of the single unit is connected to a lower deep pipe, which extends to the lower part of the inner cylinder.

[0016] Preferably, the reagent inlet of the outer cylinder is connected to the interior of the outer cylinder through a static mixer. The reagent inlet of the outer cylinder is the inlet for a mixture of the main catalyst, co-catalyst, electron donor, and specific solvent. A static mixer is installed between the inlet and the equipment to ensure that the non-uniformity of the mixture is minimized and to guarantee a stable output of the reagent.

[0017] Preferably, the outer cylinder's agent outlet is connected to the inner cylinder's agent inlet via a pipeline, and the pipeline is equipped with two shut-off valves. The outer cylinder's agent flows into the inner cylinder by gravity due to pressure differential.

[0018] Preferably, the heat exchange coil inlet and outlet are connected to both ends of the heat exchange coil via flange two and flange three, respectively; the lower end of the heat exchange coil is the inlet end, and the upper end is the outlet end.

[0019] The functions of each component in this utility model are as follows:

[0020] Outer shell: The outer shell of the equipment. The space between the outer shell and the inner shell can serve as a functional replacement for the traditional pre-contact tank. Within this space, the main catalyst, co-catalyst, and electron donor are fully mixed.

[0021] Inner cylinder: used for the prepolymerization reaction of monomers, and can serve as a functional replacement for traditional prepolymerization reactors;

[0022] Inner cylinder reagent inlet: The inner cylinder inlet, which carries the main catalyst, co-catalyst, and specific solvent of the electron donor, flows out of the pre-contact tank by itself. Through this port, the uniformly mixed mixture between the inner and outer cylinders is sent to the inner cylinder to catalyze the prepolymerization reaction. The lower part of the inlet is connected to the lower deep pipe, which goes directly to a certain distance from the bottom of the cylinder.

[0023] Monomer inlet: Used for feeding monomers after external precooling. The monomers enter the inner cylinder through this inlet to carry out the prepolymerization reaction. The lower part of the inlet is connected to the lower deep pipe, which leads directly to the bottom of the cylinder.

[0024] Mixed material outlet: This is used for the outlet of the material after the reaction. The material obtained after prepolymerization in the inner cylinder flows by gravity to the main reactor through this outlet.

[0025] Agitator connection port: used to connect the inner cylinder agitator. Since the prepolymerization of monomers in the inner cylinder is a reaction in a slurry environment, in order to ensure a full reaction, an agitator is needed to stir the reactants and promote thorough mixing between the materials. The agitator is driven by a motor with a variable frequency drive.

[0026] Outer cylinder reagent inlet: The outer cylinder inlet is used for the slurry mixture of main catalyst, co-catalyst, electron donor and specific solvent. A static mixer is set between this inlet and the outer cylinder to minimize the non-uniformity of the three reagents and achieve contact.

[0027] Static mixer: Through the internal components of the mixing unit fixed inside the tube, the slurry mixture of main catalyst, co-catalyst, electron donor and specific solvent is subjected to fluid cutting, shearing, rotation and remixing, so as to achieve good dispersion and full mixing between the fluids.

[0028] Discharge port: Used for discharging materials from inside the outer cylinder during inspection and maintenance;

[0029] Jacket inlet: The inlet for regulating the internal temperature of the outer cylinder;

[0030] Jacket outlet: The outlet for the medium used to regulate the internal temperature of the outer cylinder;

[0031] Heat exchanger coil inlet: The medium inlet used to regulate the temperature of the inner and outer cylinders, which is connected to the inner cylinder heat exchanger coil flange;

[0032] Heat exchanger coil outlet: The medium outlet used to regulate the temperature of the inner and outer cylinders, which is connected to the inner cylinder heat exchanger coil flange;

[0033] Heat exchanger coil: The outer coil is located outside the inner cylinder and is connected to the inlet and outlet of the heat exchanger coil via flanges. It is used to regulate the temperature between the inner cylinder and the inner and outer cylinders.

[0034] Outer cylinder reagent outlet: The slurry mixture for the main catalyst, co-catalyst, electron donor, and specific solvent flows by gravity from the outer cylinder into the inner cylinder, and is connected to the inner cylinder reagent inlet via a pipeline.

[0035] Pipeline: Used to connect the outer cylinder reagent outlet and the inner cylinder reagent inlet. The purpose is to allow the uniformly mixed reagent to enter the inner cylinder from the outer cylinder to catalyze the prepolymerization reaction of the monomer. Two shut-off valves are installed on the pipeline for isolation between the inner and outer cylinders. The pipeline should be as short as possible.

[0036] In the monomer prepolymerization process, this invention employs a double-cylinder structure. The outer cylinder approximates a pre-contact tank, while the inner cylinder approximates a prepolymerization reactor. A pipeline connecting the two cylinders delivers a uniformly mixed slurry catalyst and other agents to the inner cylinder for prepolymerization. Due to the inner and outer cylinder structure, the connection length between the pre-contact and prepolymerization processes is significantly shortened, reducing the risk of pipeline blockage. Simultaneously, a heat exchange coil is installed outside the inner cylinder. This coil can regulate both the temperature inside the inner cylinder and the temperature between the inner and outer cylinders, greatly improving temperature consistency between them. Furthermore, the outer cylinder is equipped with a jacket as a backup for temperature regulation. When the coil's regulating capacity decreases, it supplements the temperature regulation inside the outer cylinder, thereby affecting the temperature of the inner cylinder and reducing the probability of temperature fluctuations in the prepolymerization reactor. Attached Figure Description

[0037] Figure 1 A schematic diagram of the reactor provided by this utility model. Detailed Implementation

[0038] To make this utility model more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0039] Example

[0040] like Figure 1 As shown, this utility model provides a prepolymerization reactor for a polyolefin process, including a shell. The shell is a vertical, straight, double-cylinder structure with inner and outer sections. The outer cylinder 1 has a flange 22 at the top, a flange cover 24 at the upper end, and an elliptical end cap at the lower end. The inner cylinder 2 is fixed at the top by an inner cylinder plate 23 via the flange 22 and the flange cover 24, and has an elliptical end cap at the lower end. The flange cover 24 is provided with an inner cylinder reagent inlet 19, a monomer inlet 9, a mixture outlet 8, and a stirrer connection port 25. The bottom end cap of the outer cylinder 1 is provided with an outer cylinder reagent inlet 18 and a discharge port 17. The lower part of the side of the outer cylinder 1 is provided with a heat exchange coil inlet 14, and the upper part is provided with a heat exchange coil outlet 13 and an outer cylinder reagent outlet 12. A cooling jacket 3 is provided outside the outer cylinder 1, with a jacket inlet 16 at the lower part and a jacket outlet 15 at the upper part.

[0041] The main body of the shell is a cylindrical shape with a central axis, consisting of inner and outer cylinders. The upper end is a flat end cap structure connected by a flange cover 24, and the lower end is an elliptical end cap. The length-to-diameter ratio of the outer cylinder 1 is ≥2, and the length-to-diameter ratio of the inner cylinder 2 is ≥1.5. Furthermore, the length-to-diameter ratio of the outer cylinder 1 is ≥ the length-to-diameter ratio of the inner cylinder 2.

[0042] The outer cylinder 1 of the twin-cylinder system is provided with a cooling jacket 3, and the inner cylinder 2 is provided with a heat exchange coil 4 for system temperature regulation. The lower end of the heat exchange coil 4 is the inlet end, and the upper end is the outlet end. The two ports are respectively connected to the heat exchange coil inlet 14 and heat exchange coil outlet 13 on the outer cylinder 1 through flange 20 and flange 3 21.

[0043] The stirrer connection port 25 and the stirrer 5 are mainly used to promote the fusion of monomers and reagents and improve the conversion rate of the reaction. The stirring power comes from the motor 6 set at the top. The motor 6 is frequency-converted and the stirring speed can be adjusted according to the specific reaction degree.

[0044] The monomer inlet 9 is the inlet for polymer monomers, which is a liquid feed. The lower part of the inlet is connected to a deep pipe that extends directly to the bottom of the inner cylinder.

[0045] The inner cylinder drug inlet 19 and the outer cylinder drug outlet 12 are connected by a pipeline 10, which is equipped with two shut-off valves 11 for isolation between the inner cylinder 2 and the outer cylinder 1. The pipeline is kept as short as possible, and the drug in the outer cylinder 1 flows into the inner cylinder 2 by gravity through the pressure difference.

[0046] The agent inlet 19 is connected to a lower deep pipe at the lower part of the inlet, which extends directly to near the bottom of the inner cylinder.

[0047] The outer cylinder reagent inlet 18 is the inlet for the mixture of main catalyst, co-catalyst, electron donor and specific solvent. A static mixer 7 is installed between the inlet and the equipment to ensure that the non-uniformity of the mixture is minimized and to ensure stable output of the reagent.

[0048] The static mixer 7 connects the outer cylinder reagent inlet 18 with the outer cylinder 1. Through the mixing unit internals fixed inside the tube, the slurry mixture of the main catalyst, co-catalyst, electron donor and specific solvent is subjected to fluid cutting, shearing, rotation and remixing, so as to achieve good dispersion and full mixing between the fluids.

[0049] The discharge port 17 is used to discharge the material inside the outer cylinder 1 during inspection and maintenance.

[0050] This invention provides a novel prepolymerization reactor for polyolefin processes. By adopting a double-cylinder structure, setting an inner cylinder with an outer heat exchange coil, and a spare outer cylinder jacket, the distance between the pre-contact and prepolymerization processes is greatly reduced, the overall temperature control of the prepolymerization system is improved, the risk of blockage in the connecting pipelines between the pre-contact and prepolymerization equipment is effectively reduced, and the probability of temperature fluctuations in the prepolymerization reactor is reduced.

Claims

1. A prepolymerization reactor for use in polyolefin processes, characterized in that, The shell includes a double-cylinder structure consisting of an inner cylinder (2) and an outer cylinder (1). The outer cylinder (1) is provided with a cooling jacket (3), and the inner cylinder (2) is provided with a heat exchange coil (4). The two ends of the heat exchange coil (4) are connected to the heat exchange coil inlet (14) and heat exchange coil outlet (13) outside the shell. The top of the inner cylinder (2) is provided with a single inlet (9), a mixed material outlet (8), and an inner cylinder agent inlet (19). The bottom of the outer cylinder (1) is provided with a discharge port (17) and an outer cylinder agent inlet (18). The upper part of the outer cylinder (1) is provided with an outer cylinder agent outlet (12), which is connected to the inner cylinder agent inlet (19).

2. The prepolymerization reactor for polyolefin processes as described in claim 1, characterized in that, The outer cylinder (1) is provided with a flange (22) at the top, and a flange cover (24) is provided at the upper end of the flange (22) and an elliptical end cap at the lower end; the inner cylinder (2) is provided with an inner cylinder plate (23) at the top, and the upper and lower sides of the inner cylinder plate (23) are respectively connected and fixed to the flange cover (24) and the flange (22), and the lower end of the inner cylinder (2) is an elliptical end cap; the monomer inlet (9), the mixture outlet (8), and the inner cylinder reagent inlet (19) are provided on the flange cover (24).

3. The prepolymerization reactor for polyolefin processes as described in claim 1, characterized in that, The shell is a cylindrical shape with a central axis, consisting of inner and outer cylinders. The upper end is a flat end cap structure, and the lower end is an elliptical end cap structure. The aspect ratio of the outer cylinder (1) is not less than 2, and the aspect ratio of the inner cylinder (2) is not less than 1.

5. Furthermore, the aspect ratio of the outer cylinder (1) is not less than the aspect ratio of the inner cylinder (2).

4. The prepolymerization reactor for polyolefin processes as described in claim 1, characterized in that, The cooling jacket has a jacket inlet (16) at the bottom and a jacket outlet (15) at the top; the heat exchange coil (4) is connected to the inlet and outlet of the inner coil on the outer cylinder (1) by flanges.

5. The prepolymerization reactor for polyolefin processes as described in claim 1, characterized in that, The inner cylinder (2) is equipped with a stirrer (5), and the top of the stirrer (5) is connected to the motor (6) through the stirrer connection port (25).

6. The prepolymerization reactor for polyolefin processes as described in claim 5, characterized in that, The motor (6) is a variable frequency motor.

7. The prepolymerization reactor for polyolefin processes as described in claim 1, characterized in that, The inlet of the single unit (9) is connected to the lower deep pipe, which extends to the lower part of the inner cylinder (2).

8. The prepolymerization reactor for polyolefin processes as described in claim 1, characterized in that, The outer cylinder reagent inlet (18) is connected to the interior of the outer cylinder (1) through a static mixer (7). The outer cylinder reagent inlet is the inlet for a mixture of main catalyst, co-catalyst, electron donor and specific solvent. A static mixer is installed between the inlet and the equipment to ensure that the non-uniformity of the mixture is minimized and to ensure stable output of the reagent.

9. The prepolymerization reactor for polyolefin processes as described in claim 1, characterized in that, The outer cylinder drug outlet (12) is connected to the inner cylinder drug inlet (19) via a pipeline (10), and two shut-off valves (11) are provided on the pipeline (10).

10. The prepolymerization reactor for polyolefin processes as described in claim 1, characterized in that, The heat exchange coil inlet (14), heat exchange coil outlet (13) and the two ends of the heat exchange coil (4) are connected by flange two (20) and flange three (21) respectively; the lower end of the heat exchange coil (4) is the inlet end and the upper end is the outlet end.

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