Flexible rotating unit and kettle reactor for the synthesis of polyvinyl chloride

Abstract

The application discloses a flexible rotating unit arranged in a kettle type reactor for synthesizing polyvinyl chloride, which comprises at least a supporting main rod fixed at the bottom of the kettle type reactor, a rotating sleeve rod sleeved outside the supporting main rod and matched with the supporting main rod in a gap, a supporting auxiliary rod in an elongated clamping piece structure and extending along the radial direction of the rotating sleeve rod, one end of the supporting auxiliary rod being fixed on the rotating sleeve rod, the number of the supporting auxiliary rods being multiple and the supporting auxiliary rods being arranged in a spiral gap along the axial direction of the rotating sleeve rod, and a flexible blade in a spiral blade structure arranged around the rotating sleeve rod and clamped at the corresponding positions of the supporting auxiliary rods, wherein the flexible blade is in a free rotating state under the action of a flow field formed by a stirring device arranged at the upper portion of the kettle type reactor, and the bending direction of the flexible blade is the same as the bending direction of the blade of the stirring device. The application further discloses a kettle type reactor for synthesizing polyvinyl chloride and applying the aforementioned flexible rotating unit.

Description

Technical Field

[0001] This invention relates to the field of polyvinyl chloride (PVC) preparation technology, and particularly to a flexible rotating unit and a batch reactor for synthesizing PVC using the unit. Background Technology

[0002] The global annual production of polyvinyl chloride (PVC) is approximately 40 million tons, widely used in various industries. Industrially, a large portion of PVC homopolymer is produced through suspension polymerization (accounting for about 80% of total production). In suspension polymerization, water, dispersant, oil-soluble initiator, and other additives are first added to a batch reactor. After vacuuming and nitrogen purging to remove oxygen, monomers are added, and polymerization occurs at a predetermined temperature and pressure (50°C, 0.7 MPa). During the reaction, vinyl chloride monomer is suspended in water as small droplets, and the polymerization reaction takes place within these monomer droplets. Because the resulting PVC is insoluble in vinyl chloride monomer, it precipitates from the monomer and remains suspended in the batch reactor. The average particle size of PVC produced by suspension polymerization is 100–160 micrometers.

[0003] Molecular weight is one of the important quality indicators of polymer products. During the synthesis of polymer materials, it is necessary to strictly control the molecular weight range to meet the physicochemical property requirements of the product. The molecular weight of polyvinyl chloride (PVC) does not depend on the monomer conversion rate, but is mainly controlled by the reaction temperature and the monomer droplet size and dispersion. On the one hand, since the synthesis of PVC from vinyl chloride is an exothermic reaction with auto-acceleration, and the molecular weight of PVC increases with increasing reaction temperature, it is necessary to maintain a strictly constant temperature during the reaction, generally within ±0.5℃ of the target temperature. On the other hand, excessively large monomer droplets or the aggregation and coalescence of monomer droplets during the reaction can lead to excessive polymerization of vinyl chloride, forming long-chain PVC, thus affecting product quality. Therefore, it is necessary to maintain a high degree of dispersion of vinyl chloride monomer in water.

[0004] Suspension polymerization for polyvinyl chloride (PVC) production typically employs a large, batch reactor with a stirring and heat exchange jacket. Stirring and heat exchange maintain a constant temperature within the reactor, while nitrogen is introduced to assist in heat exchange. A dispersant is also added to the reaction system to form a protective film on the surface of the vinyl chloride monomer droplets, preventing droplet aggregation and agglomeration. Stirring also breaks up the vinyl chloride monomer droplets, maintaining a certain degree of monomer dispersion in the water.

[0005] However, there is an upper limit to the stirring speed of the agitator. On the one hand, excessively high stirring speeds can induce strong eddies, causing the suspended PVC to agglomerate and affecting the uniformity of the molecular weight of the synthesized polymer. On the other hand, as the synthesis reaction progresses, the suspended PVC will continuously increase the viscosity of the batch reactor system. The "climbing" effect of the polymer will hinder the rotation of the stirring blades, and excessively high stirring speeds can burn out the motor. Moreover, in order to reduce production costs and increase the stability of the synthesized polymer properties, the size of batch reactors is constantly expanding, with their volume increasing from the early 7–14 m³. 3 Increase to 25-150m 3 To facilitate cleaning of the stirring device during "boiling," the diameter of the stirring blades is smaller than the diameter of the upper end flange, resulting in a large dead zone in the radial direction of the batch reactor. Therefore, scaling up the batch reactor inevitably leads to a significant reduction in the unit heat transfer area, increasing the risk of explosive polymerization and "burning," and also affecting the dispersion of vinyl chloride monomer droplets. Furthermore, batch reactors generally do not have distributors; nitrogen gas typically enters the reactor through an inlet pipe on the side, making it difficult to ensure uniform dispersion within the reactor. Due to the strong corrosiveness of polyvinyl chloride, other internal components are usually not installed in the batch reactor; all materials are mixed solely by the stirring device. After polymerization, the dispersant is also difficult to remove from the polymerization product, affecting properties such as appearance and aging.

[0006] Existing industrial strategies involve installing a series of baffles on the walls or stirring devices of the batch reactor. However, this approach does not significantly improve the aforementioned problems and instead increases the dead zones in the flow field within the batch reactor. Chinese patent application CN113368803A provides a batch reactor that replaces the traditional central stirring device with an eccentric stirring device that revolves around the center of the batch reactor, thereby enhancing material mixing at the reactor's edges. The reactor includes a main body with a drive motor mounted on top. The output shaft of the drive motor is connected to a stirrer located inside the reactor body. The stirrer includes a central longitudinal shaft, an eccentric side rod, and an eccentric main shaft connected in sequence. One end of the central longitudinal shaft is connected to the output shaft of the drive motor, and the other end is fixedly connected to the eccentric side rod. The eccentric side rod and the eccentric main shaft are connected by bearings. A gear is mounted on the eccentric main shaft, and a rack meshing with the gear is installed on the inner wall of the reactor body. Upper and lower helical blades with opposite helical directions are fixed on the eccentric main shaft. The batch polymerization reactor of this scheme can effectively shorten the mixing time of the gas and liquid phases, enhance the mixing effect, improve the reaction efficiency, and save energy consumption. It is especially suitable for gas-liquid interface reactions with high viscosity.

[0007] Such eccentric stirring devices can only be used in small-scale batch reactors. When the device is scaled up, the length of the eccentric side rod also increases accordingly, and over long-term operation, it will gradually deviate from its original rotation trajectory under the influence of blade gravity. Furthermore, the climbing effect of the polymer will cause it to stick to the gears on the eccentric main shaft and the reactor wall. Therefore, this type of design reduces the operating time of the rotating device and lowers its safety.

[0008] In large-scale batch reactors used for suspension polymerization of polyvinyl chloride (PVC), limitations in stirring rate, reduced heat transfer area per unit volume due to reactor enlargement, the existence of self-accelerating reaction, and the adhesion and aggregation of suspended PVC monomers make it essential to address how to remove the heat of polymerization, precisely control the reactor temperature, and control the particle size and dispersion of PVC monomers in water during the design of PVC batch reactors.

[0009] Therefore, there is an urgent need to install a flexible rotating unit in a large batch reactor for polyvinyl chloride, which can effectively improve the dispersion uniformity of the polymer monomers while enhancing heat transfer, thereby improving the above-mentioned problems in the existing technology.

[0010] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0011] The purpose of this invention is to provide a flexible rotating unit and a batch reactor for synthesizing polyvinyl chloride using this unit. By setting a flexible rotating unit at the bottom of a large batch reactor, the heat transfer process can be effectively enhanced by the rotation of the flexible blades, and the uniformity of temperature distribution can be controlled. It can also enhance the uniform distribution of vinyl chloride monomer droplets in the batch reactor, avoiding the problem of product quality degradation caused by uneven distribution of vinyl chloride monomer droplets and / or excessively large droplet diameter.

[0012] To achieve the above objectives, according to a first aspect of the present invention, a flexible rotating unit is provided, disposed in a batch reactor for synthesizing polyvinyl chloride, comprising at least: a supporting main rod fixed to the bottom of the batch reactor; a rotating sleeve sleeved on the outside of the supporting main rod and clearance-fitted with the supporting main rod; a supporting secondary rod, which is a slender clamping structure extending radially along the rotating sleeve, one end of the supporting secondary rod being fixed to the rotating sleeve, and the supporting secondary rods being multiple in number and spirally spaced along the axial direction of the rotating sleeve; and flexible blades, which are helical blade structures arranged around the rotating sleeve, the flexible blades being clamped at corresponding positions on the supporting secondary rods; under the action of the flow field formed by the stirring device disposed at the top of the batch reactor, the flexible blades are in a free rotating state; the bending direction of the flexible blades is the same as the bending direction of the stirring device blades.

[0013] Furthermore, in the above technical solution, the flexible blades are preferably made of polytetrafluoroethylene with a molecular weight of 100,000.

[0014] Furthermore, in the above technical solution, the number of flexible blades can be 1 to 5 and they have the same structure; multiple flexible blades are arranged alternately around the rotating sleeve.

[0015] Furthermore, in the above technical solution, the main support rod can be fixed to the bottom of the reactor via a base; the top of the main support rod can be provided with a limiting component to restrict the rotating sleeve rod within the range of the main support rod and allow the rotating sleeve rod to rotate relative to the main support rod.

[0016] Furthermore, in the above technical solution, the base, main support rod, rotating sleeve rod, secondary support rod, and limiting component can all be made of polytetrafluoroethylene with a molecular weight of millions, and form an integral whole with the flexible blade.

[0017] Furthermore, in the above technical solution, the end of the support rod closer to the rotating sleeve rod is the fixed end, and the end farther from the rotating sleeve rod is the free end; the fixed end and the free end of the slender clamping plate structure are both in a clamping state relative to the flexible blade, or the fixed end of the slender clamping plate structure is in a clamping state relative to the flexible blade, while the free end is in an open state relative to the flexible blade.

[0018] Furthermore, in the above technical solution, strip-shaped holes can be evenly distributed on the flexible blade. The length of the strip-shaped holes can be from 19mm to 74mm, and the width can be from 4mm to 6mm.

[0019] Furthermore, in the above technical solution, the length of the main support rod can be 150mm to 200mm, and the diameter can be 5mm to 8mm; the rotating sleeve rod has a hollow structure and a length of 140mm to 190mm, with an inner diameter of 6mm to 9mm that is larger than the diameter of the main support rod; the length of the secondary support rod can be 25mm to 80mm, and the thickness can be 1mm to 2mm. The angle between the flexible blade and the horizontal plane can be 30° to 60°, and the pitch can be 20mm to 30mm.

[0020] According to a second aspect of the present invention, the present invention provides a batch reactor for synthesizing polyvinyl chloride, employing the aforementioned flexible rotating unit, which is disposed at a corresponding position on the lower end cap at the bottom of the batch reactor and distributed in an array in the radial direction of the reactor.

[0021] Furthermore, in the above technical solution, the net spacing between adjacent flexible rotating units can be 2mm to 5mm.

[0022] Furthermore, in the above technical solution, there is a dead zone in the flow field near the bottom wall of the batch reactor; the arrayed flexible rotating units can be arranged with their height increasing sequentially from the inside to the outside in the radial direction. Preferably, the upper edge of the flexible rotating unit located in the dead zone is higher than the tangent of the lower head.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) By setting a flexible rotating unit at the bottom of the batch reactor for synthesizing polyvinyl chloride, the present invention can enhance the mass and energy exchange between the dead zone at the bottom of the batch reactor and the main body, and make up for the deficiency of insufficient fluid kinetic energy transferred by the upper stirring device to the bottom of the batch reactor. This results in a more uniform temperature distribution and better dispersion of vinyl chloride monomer in the batch reactor, thereby improving product quality.

[0025] 2) This invention sets a flexible rotating unit at the bottom of the polyvinyl chloride synthesis reactor. Due to the "spiral" arrangement of the flexible blades of the flexible rotating unit, the flexible blades are integrated along the axis of the rotating sleeve. The local force on the flexible blades will drive the entire component to rotate, thereby creating agitation in the "dead zone".

[0026] 3) During the polymerization of polyvinyl chloride (PVC), vinyl chloride monomer droplets may coalesce to form long-chain PVC. If rigid blades are used, the long-chain PVC is difficult to detach from the blades, and once the amount of PVC entangled reaches a certain level, the rigid blades may lose their rotational function. This invention uses flexible blades, which, on the one hand, can entangling the long-chain PVC formed by the coalescence of vinyl chloride monomer droplets during polymerization onto the flexible blades, separating it from the main body and preventing further polymerization, thus ensuring the stability of the PVC product's molecular weight; on the other hand, a certain "vibration and shaking" effect is created during rotation, preventing a large amount of long-chain PVC from remaining entangled on the blades for an extended period. Once entangled to a certain extent, it can easily detach and settle to the bottom of the reactor.

[0027] 4) By using the flexible rotating unit of the present invention, the height-to-diameter ratio of the batch reactor can be appropriately increased, thereby increasing the heat transfer area between the unit mass of heat medium in the batch reactor and the cooling medium in the wall jacket, and further enhancing the heat transfer rate between the batch reactor and the jacket; at the same time, the increase in the height-to-diameter ratio of the batch reactor can also reduce the floor space occupied by the batch reactor.

[0028] 5) By setting a flexible rotating unit at the bottom of the polyvinyl chloride synthesis reactor, the present invention can also perform secondary crushing of nitrogen and vinyl chloride monomer droplets after they are broken by the stirring device, ensuring the heat exchange area between nitrogen and fluid, and preventing the generated polymer from having an excessively large molecular weight, thereby improving the quality of the product.

[0029] 6) When a flexible rotating unit of the present invention is equipped with multiple flexible blades, the multiple flexible blades can be arranged alternately around the rotating sleeve. Through this arrangement, the number of blades in the flexible rotating unit can be flexibly adjusted according to the viscosity of the reaction system. When the system viscosity is high, more flexible blades can be used to enhance the heat and mass transfer process; when the system viscosity is low, fewer flexible blades can be used to reduce the energy consumed by rotation and equipment investment.

[0030] 7) The support rod of the present invention can adopt a slender clamping structure. When its free end is open relative to the flexible blade, that is, the upper and lower clamping plates at the free end do not clamp the flexible blade. This allows the flexible blade to form a local "swing" at this point. This local swing can further enhance the aforementioned "vibration and shaking" effect during the rotation of the flexible blade, prevent a large amount of long-chain polyvinyl chloride from being wrapped around the blade for a long time, and at the same time, it can more effectively break up vinyl chloride monomer droplets and / or nitrogen.

[0031] 8) By opening the strip-shaped holes, this invention can not only further enhance the function of breaking up vinyl chloride monomer droplets and / or nitrogen, but also further increase the separation ability of flexible blades for long-chain polyvinyl chloride. Therefore, the amount of dispersant added can be reduced, thereby improving the effect of dispersant on the appearance, aging and other properties of the polymer product.

[0032] 9) Due to the dead zone in the flow field near the bottom wall of the batch reactor, this invention applies an array of flexible rotating units to the batch reactor. On the one hand, the upper stirring device transfers greater kinetic energy to the fluid at the center of the batch reactor, causing the flexible rotating unit at the center of the bottom of the batch reactor to start rotating first. Subsequently, the flexible rotating unit at the center transfers kinetic energy radially to the flexible rotating units at the side walls. On the other hand, as long as the flexible rotating unit at the side wall is higher than the tangent of the lower head, the streamline can act on the upper part of the flexible rotating unit. Since the flexible blades of the flexible rotating unit are a whole, the upper part can be driven to start rotating after being subjected to the force of the fluid. Driven by the kinetic energy from both sides, the flexible rotating unit 1 in the "dead zone" can also rotate efficiently, thereby enhancing the mass and energy exchange between the dead zone at the bottom of the batch reactor and the main flow field. In addition, the array arrangement is more conducive to the uniform distribution of vinyl chloride monomer droplets in the batch reactor, avoiding the decline in product quality caused by uneven distribution of vinyl chloride monomer droplets and / or excessively large droplet diameter.

[0033] 10) The flexible rotating units arranged in an array inside the reactor of the present invention are preferably arranged with increasing height from the inside to the outside in the radial direction. With this arrangement, the flexible rotating units in the "dead zone" are easier to rotate.

[0034] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, and to make the above and other objects, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings. Attached Figure Description

[0035] Figure 1 is a three-dimensional structural schematic diagram of the flexible rotating unit of the present invention (wherein) Figure 1-A A flexible blade is installed in the middle; Figure 1-B Two flexible blades are installed in the middle; Figure 1-C Three flexible blades are installed in the middle; Figure 1-D Four flexible blades are installed in the middle; Figure 1-E (Five flexible blades are installed in the middle).

[0036] Figure 2 This is a schematic diagram of the arrangement of the supporting auxiliary rods in the flexible rotating unit of the present invention.

[0037] Figure 3 is a partially enlarged schematic diagram of the free end of the supporting auxiliary rod of the present invention (wherein) Figure 3-A The clamping structure at the free end of the middle support rod is in a clamping state relative to the flexible blade; Figure 3-B The clamping structure at the free end of the middle support rod is in an open state relative to the flexible blade.

[0038] Figure 4 This is a three-dimensional structural schematic diagram of another embodiment of the flexible blade in the flexible rotating unit of the present invention (showing the strip-shaped through hole opened on the flexible blade).

[0039] Figure 5 This is a three-dimensional schematic diagram of the arrangement of the flexible rotating unit of the present invention in a batch reactor.

[0040] Figure 6 This is a plan view of the arrangement of the flexible rotating unit of the present invention in a batch reactor.

[0041] Figure 7 This is a schematic diagram of the flow field under the action of the stirring device inside the reactor of the present invention.

[0042] Explanation of key figure labels:

[0043] 1- Flexible rotating unit (1A, 1B, 1C, 1D, 1E are flexible rotating units with different heights), 11- Rotating sleeve rod, 12- Supporting auxiliary rod, 12A- Upper clamping piece, 12B- Lower clamping piece, 13- Flexible blade, 13A- First flexible blade, 13B- Second flexible blade, 13C- Third flexible blade, 13D- Fourth flexible blade, 13E- Fifth flexible blade, 131- Strip-shaped through hole, 14- Base, 15- Limiting component;

[0044] 100-Stirred reactor, 101-Inlet, 102-Outlet, 103-Exhaust port, 104-Stirring device, 105-Lower head, 106-Nitrogen inlet. Detailed Implementation

[0045] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0046] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0047] In this document, for ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” “above,” “upper,” etc., are used to describe the relationship of one element or feature to another element or feature in the accompanying drawings. It should be understood that spatial relative terms are intended to encompass different orientations of an object in use or operation, in addition to those depicted in the figures. For example, if an object in the figure is flipped, an element described as “below” or “under” another element or feature would be oriented “above” that element or feature. Thus, the exemplary term “below” can encompass both the downward and upward orientations. An object may also have other orientations (rotated 90 degrees or other orientations), and the spatial relative terms used herein should be interpreted accordingly.

[0048] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0049] First, it should be noted that traditional batch reactors for synthesizing polyvinyl chloride (PVC) are equipped with a stirring device. The rotation of this device drives the material to rotate radially. Under the influence of the pressure difference between the upper and lower parts of the stirring blades, the material also circulates axially. Specifically, the material moves downwards in the main area below the stirring blades, and upwards near the sidewalls, before returning to the upper part of the stirring blades, forming an axial circulation (see reference). Figure 7(The arrows in the diagram indicate the direction of the reaction). However, due to the high viscosity of the polymerization reaction in the synthesis of polyvinyl chloride (PVC), the kinetic energy transmitted to the fluid by the stirring device is dissipated into heat energy by the fluid viscosity. Therefore, the kinetic energy of the fluid gradually decreases with the increase of the distance from the stirring device. Furthermore, since the streamlines of the flow field cannot make 90° right-angle turns, a large dead zone exists at the bottom of the batch reactor, especially near the wall. The heat and mass transfer rates are slow at this point, and PVC is prone to explosive polymerization, forming long-chain PVC, which affects product quality. This invention addresses the problem of the "dead zone" by setting a flexible rotating unit at this height. This not only effectively enhances the heat transfer process at the bottom of the batch reactor, making the temperature distribution inside the batch reactor more uniform, but also effectively enhances the uniform distribution of vinyl chloride monomer droplets in the batch reactor, avoiding the decline in product quality caused by uneven distribution of vinyl chloride monomer droplets and / or excessively large droplet diameter.

[0050] As shown in Figures 1 and 2, the present invention provides a flexible rotating unit 1, which is disposed in a batch reactor for synthesizing polyvinyl chloride, and includes at least a main supporting rod, a rotating sleeve 11, a secondary supporting rod 12, and flexible blades 13. The main supporting rod is fixed to the bottom of the batch reactor 100 (see reference). Figure 5 The length of the main support rod can be 150mm to 200mm, and the diameter can be 5mm to 8mm. The rotating sleeve 11 is fitted around the main support rod with a clearance fit (i.e., the rotating sleeve can rotate outside the main support rod, therefore the main support rod is not shown in the figure). The rotating sleeve 11 is a hollow structure with a length of 140mm to 190mm and an inner diameter of 6mm to 9mm, which is larger than the diameter of the main support rod. The secondary support rod 12 is a slender clamping structure and extends radially along the rotating sleeve 11 (see reference). Figure 2 One end of the supporting rod 12 is fixed to the rotating sleeve rod 11. Multiple supporting rods 12 are arranged at intervals along the axial direction of the rotating sleeve rod 11 (specifically, in a helical arrangement). The length of the supporting rod 12 can be 25mm to 80mm, and the thickness can be 1mm to 2mm. The flexible blade 13 is a helical blade structure arranged around the rotating sleeve rod 11, and the flexible blade 13 is clamped at corresponding positions on the supporting rod 12 (i.e., at different heights of the helix). Under the action of the flow field formed by the stirring device 104 installed at the top of the batch reactor 100 (refer to...), Figure 5 and Figure 7 The flexible blade 13 is in a free-rotating state. The bending direction of the flexible blade 13 is the same as the bending direction of the blades of the stirring device 104. The angle between the flexible blade 13 and the horizontal plane can be 30° to 60°, and the pitch can be 20mm to 30mm.

[0051] This invention enhances the mass and energy exchange between the dead zone at the bottom of the reactor and the main body by setting a flexible rotating unit at the bottom of the reactor for synthesizing polyvinyl chloride. This compensates for the deficiency of insufficient kinetic energy transferred to the fluid at the bottom of the reactor by the rotation of the upper stirring device, resulting in a more uniform temperature distribution and better dispersion of vinyl chloride monomer within the reactor, thereby improving product quality.

[0052] This invention utilizes a flexible rotating unit at the bottom of a reactor for synthesizing polyvinyl chloride (PVC). The flexible blades of this rotating unit are spirally arranged, forming a single unit along the axial direction of the rotating sleeve, with each radial direction of the flexible blades forming an angle with the horizontal plane. Therefore, incoming flow from all directions causes the flexible rotating unit to rotate, and the localized force on the flexible blades drives the entire unit to rotate, creating agitation in the "dead zone." During the polymerization of PVC, vinyl chloride monomer droplets may coalesce to form long-chain PVC. If rigid blades are used, the long-chain PVC becomes entangled and difficult to detach. Once the entangled PVC reaches a certain level, the rigid blades may lose their rotating function. This invention employs flexible blades, which, on the one hand, can wrap the long-chain PVC generated during the polymerization process by the polymerization of vinyl chloride monomer droplets around the flexible blades, separating them from the main body and preventing further polymerization, thus ensuring the stability of the PVC product's molecular weight. On the other hand, the rotation process creates a certain "vibration and shaking" effect, preventing a large amount of long-chain PVC from being wrapped around the blades for an extended period. After being wrapped to a certain extent, it can easily detach and settle to the bottom of the batch reactor. In addition, by using the flexible rotating unit of this invention, the height-to-diameter ratio of the batch reactor can be appropriately increased, thereby increasing the heat transfer area per unit mass of heat medium and cooling medium in the wall jacket of the batch reactor, further enhancing the heat transfer rate between the batch reactor and the jacket. At the same time, the increased height-to-diameter ratio of the batch reactor can also reduce the footprint of the batch reactor.

[0053] This invention, by incorporating a flexible rotating unit at the bottom of the batch reactor for synthesizing polyvinyl chloride (PVC), further breaks up nitrogen and vinyl chloride monomer droplets after they have been broken up by a stirring device. This ensures sufficient heat exchange area between nitrogen and the fluid and prevents the resulting polymer from having excessively large molecular weight, thereby improving product quality. In the suspension polymerization process for producing PVC, nitrogen is introduced to assist heat exchange. However, the batch reactor lacks a distributor, and nitrogen enters directly from a pipeline on the side of the reactor (see reference). Figure 7The nitrogen gas is circulated to various areas of the batch reactor via a stirring device. Due to the high viscosity of the polymerization system and the decrease in kinetic energy of the fluid with increasing distance from the stirring device, the average kinetic energy of the fluid at the bottom of the batch reactor is the lowest. Therefore, the small nitrogen bubbles formed by the stirring device will coalesce into larger bubbles at the bottom of the batch reactor, correspondingly reducing their heat and mass transfer area with the fluid. This invention, by incorporating a flexible rotating unit at the bottom of the batch reactor, can further break up the large bubbles that have coalesced into smaller bubbles through its rotation. Similarly, vinyl chloride monomer droplets at the bottom of the batch reactor are also prone to coalescence, and the flexible rotating unit of this invention can also further break up the vinyl chloride monomer droplets into smaller droplets.

[0054] Furthermore, preferably but not limitingly, the flexible blade 13 is preferably made of polytetrafluoroethylene (PTFE) with a molecular weight of 100,000 to ensure excellent flexibility. The supporting main rod, rotating sleeve 11, and supporting auxiliary rod of the present invention can be made of PTFE with a molecular weight of millions to ensure that these components have sufficient strength and that the flexible rotating unit forms a unified whole.

[0055] Further details are shown in Figure 1 (including...) Figures 1-A to 1-E The number of flexible blades 13 in this invention is preferably 1 to 5 and they have the same structure; when there are multiple flexible blades 13, the multiple flexible blades are arranged alternately around the rotating sleeve 11. Figure 1-A This illustrates a flexible blade 13 arranged in a spiral configuration; Figure 1-B The illustration shows a first flexible blade 13A and a second flexible blade 13B arranged in a spirally interlocked configuration. Figure 1-C The illustration shows three spirally interwoven first flexible blades 13A, second flexible blades 13B, and third flexible blades 13C. Figure 1-D The diagram illustrates four spirally interleaved flexible blades: a first flexible blade 13A, a second flexible blade 13B, a third flexible blade 13C, and a fourth flexible blade 13D. Figure 1-E The diagram illustrates five helically staggered flexible blades: a first flexible blade 13A, a second flexible blade 13B, a third flexible blade 13C, a fourth flexible blade 13D, and a fifth flexible blade 13E. This arrangement allows the number of flexible rotating unit blades to be flexibly adjusted according to the viscosity of the reaction system. When the system viscosity is high, more flexible blades can be used to enhance heat and mass transfer processes; when the system viscosity is low, fewer flexible blades can be used to reduce the energy consumed by rotation and equipment investment.

[0056] As further shown in Figures 1 and 2, the main support rod can be fixed to the bottom of the reactor via the base 14; a limiting member 15 is provided at the top of the main support rod to restrict the rotating sleeve 11 within the position range of the main support rod and allow the rotating sleeve to rotate relative to the main support rod. The base 14 and the limiting member 15 can also be made of polytetrafluoroethylene with a molecular weight of millions.

[0057] As further shown in Figure 3, the slender clamping structure of the supporting rod 12 can serve to "fix" the flexible blade 13 segment by segment. (Reference) Figure 2 The end of the supporting rod 12 closest to the rotating sleeve rod 11 is the fixed end, and the end furthest from the rotating sleeve rod 11 is the free end. In one embodiment, both the fixed end and the free end of the elongated clamping structure are clamped relative to the flexible blade 13 (see reference). Figure 3-A In other words, both ends of the upper clamp 12A and the lower clamp 12B are clamped to the flexible blade; in another embodiment, the fixed end of the elongated clamp structure is clamped relative to the flexible blade 13, while the free end is open relative to the flexible blade 13 (see reference). Figure 3-B This means that one end is fixed while the other end is not, allowing the flexible blade to partially "oscillate" (the upper clamp 12A and lower clamp 12B are open at this end). This partial oscillation can further enhance the aforementioned "vibration and shaking" effect during rotation, preventing a large amount of long-chain PVC from being wrapped around the blade for a long time, while also more effectively breaking up PVC monomer droplets and / or nitrogen.

[0058] Further as Figure 4 As shown, the flexible blade 13 can be uniformly distributed with strip-shaped holes 131. The opening of these strip-shaped holes not only further enhances the breaking function of vinyl chloride monomer droplets and / or nitrogen gas, but also further increases the separation capacity of the flexible blade for long-chain polyvinyl chloride. Therefore, the amount of dispersant added can be reduced, thereby improving the effect of the dispersant on the appearance, aging, and other properties of the polymer product. The length of the strip-shaped holes is preferably 19 mm to 74 mm, and the width is preferably 4 mm to 6 mm.

[0059] like Figures 5 to 7As shown, the present invention also provides a batch reactor 100 for synthesizing polyvinyl chloride, employing the aforementioned flexible rotating unit 1. The flexible rotating unit 1 is disposed at a corresponding position on the lower end cap at the bottom of the batch reactor and distributed in an array in the radial direction of the reactor. Further, the net spacing between adjacent flexible rotating units is preferably 2 mm to 5 mm. Since there is a flow field dead zone near the bottom wall of the batch reactor, by using the array-distributed flexible rotating units 1, on the one hand, the upper stirring device 104 transfers greater kinetic energy to the fluid at the center of the batch reactor 100, causing the flexible rotating unit 1 at the bottom center of the batch reactor 100 to start rotating first, and then the flexible rotating unit 1 at the center transfers the kinetic energy radially to the flexible rotating units at the side walls; on the other hand, as long as the flexible rotating units at the side walls are higher than the tangent of the lower end cap, the streamlines can act on the upper part of the flexible rotating unit. Since the flexible blades of the flexible rotating unit 1 are a whole, the upper part can be driven to start rotating after being subjected to the force of the fluid. Driven by two kinetic energies, the flexible rotating unit 1, located in the "dead zone," can also rotate efficiently, thereby enhancing the mass and energy exchange between the dead zone at the bottom of the batch reactor and the main flow field. In addition, the array arrangement is more conducive to the uniform distribution of vinyl chloride monomer droplets in the batch reactor, avoiding the decline in product quality caused by uneven distribution of vinyl chloride monomer droplets and / or excessively large droplet diameter.

[0060] Further as Figure 5 As shown, preferably but not limitingly, the arrangement height of the arrayed flexible rotating units 1 increases sequentially from the inside to the outside in the radial direction, that is... Figure 5 The overall height of the flexible rotating units 1A, 1B, 1C, 1D, and 1E increases sequentially. This arrangement makes it easier for the flexible rotating units in the "dead zone" to rotate.

[0061] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. Any simple modifications, equivalent changes, and alterations made to the foregoing exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. A flexible rotating unit, characterized in that, Set in a batch reactor for synthesizing polyvinyl chloride, including: The main support rod is fixed to the bottom of the reactor. A rotating sleeve rod is sleeved outside the main support rod and has a clearance fit with the main support rod. The supporting auxiliary rod is a slender clamping structure that extends radially along the rotating sleeve rod. One end of the supporting auxiliary rod is fixed to the rotating sleeve rod. There are multiple supporting auxiliary rods arranged spirally at intervals along the axial direction of the rotating sleeve rod. The flexible blade is a helical blade structure arranged around the rotating sleeve rod, and the flexible blade is clamped at the corresponding position of the supporting auxiliary rod; under the action of the flow field formed by the stirring device arranged at the top of the batch reactor, the flexible blade is in a free rotation state; the bending direction of the flexible blade is the same as the bending direction of the stirring device blade.

2. The flexible rotating unit according to claim 1, characterized in that, The flexible blades are made of polytetrafluoroethylene with a molecular weight of 100,000.

3. The flexible rotating unit according to claim 1, characterized in that, The number of flexible blades is 1 to 5 and they have the same structure; multiple flexible blades are arranged alternately around the rotating sleeve.

4. The flexible rotating unit according to claim 1, characterized in that, The main support rod is fixed to the bottom of the reactor via a base; a limiting component is provided at the top of the main support rod to restrict the rotating sleeve rod within the range of the main support rod and allow the rotating sleeve rod to rotate relative to the main support rod.

5. The flexible rotating unit according to claim 4, characterized in that, The base, main support rod, rotating sleeve rod, secondary support rod, and limiting component are all made of polytetrafluoroethylene with a molecular weight of millions, and form an integral whole with the flexible blade.

6. The flexible rotating unit according to claim 1, characterized in that, The end of the support rod closest to the rotating sleeve is a fixed end, and the end furthest from the rotating sleeve is a free end; both the fixed end and the free end of the slender clamping structure are clamped relative to the flexible blade, or the fixed end of the slender clamping structure is clamped relative to the flexible blade, while the free end is open relative to the flexible blade.

7. The flexible rotating unit according to claim 1, characterized in that, The flexible blade has uniformly distributed strip-shaped holes.

8. The flexible rotating unit according to claim 1, characterized in that, The length of the strip hole is 19mm to 74mm, and the width is 4mm to 6mm.

9. The flexible rotating unit according to claim 1, characterized in that, The main support rod has a length of 150mm to 200mm and a diameter of 5mm to 8mm; the rotating sleeve rod has a hollow structure with a length of 140mm to 190mm and an inner diameter of 6mm to 9mm, which is larger than the diameter of the main support rod; the secondary support rod has a length of 25mm to 80mm and a thickness of 1mm to 2mm.

10. The flexible rotating unit according to claim 9, characterized in that, The flexible blade has an angle of 30° to 60° with the horizontal plane and a pitch of 20mm to 30mm.

11. A batch reactor for synthesizing polyvinyl chloride, characterized in that, The flexible rotating unit as described in any one of claims 1 to 10 is used, wherein the flexible rotating unit is disposed at a corresponding position on the bottom lower head of the batch reactor and is distributed in an array in the radial direction of the reactor.

12. The flexible rotating unit according to claim 11, characterized in that, The net spacing between adjacent flexible rotating units is 2mm to 5mm.

13. The flexible rotating unit according to claim 11, characterized in that, The bottom wall of the reactor has a dead zone in the flow field; the flexible rotating units arranged in an array increase in height from the inside to the outside in the radial direction.

14. The flexible rotating unit according to claim 13, characterized in that, The upper edge of the flexible rotating unit located within the dead zone of the flow field is higher than the tangent of the lower head.

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