Polyolefin continuous slurry method production system and process based on wet crushing
By combining wet crushing technology with continuous slurry method, the problems of uneven particle size and thermal oxidative degradation of polyolefin powder in the existing technology have been solved, realizing efficient and continuous ultrafine particle size production, and improving production efficiency and product quality.
Patent Information
- Application Number
- CN202511147113.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-15
- Publication Date
- 2025-11-11
AI Technical Summary
Existing technologies make it difficult to efficiently, continuously, and non-destructively prepare high molecular weight polyolefin powders with uniform particle size. Furthermore, the dry grinding process is prone to thermal oxidative degradation and damage to particle morphology, which limits large-scale production and economic benefits.
The wet crushing technology combined with the continuous slurry method is adopted. A wet grinding unit is set up between the slurry dilution tank and the flash tank. The slurry circulation crushing is controlled by a three-way valve to ensure that the particle size meets the requirements. The grinding is carried out in a solvent to avoid heat accumulation.
It enables efficient and continuous production of ultrafine-particle-size high molecular weight polyolefins, reduces coarse particle loss, improves raw material utilization, ensures product consistency and performance, and avoids plasticization risks.
Smart Images
Figure CN120919918A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polyolefin production technology, specifically to a continuous slurry production system and process for polyolefins based on wet crushing. Background Technology
[0002] As a core raw material in the field of polymer materials, the uniformity of polyolefin powder particle size distribution directly affects the melt flowability, processing stability, and mechanical properties of the final product. Therefore, achieving high-quality polyolefin powders with controllable particle size distribution, especially ultra-high uniformity fine particle size powders required for high-end applications (such as high-performance medical devices, filter materials, and special films), has become a core goal of the industry. However, the preparation of polyolefin powders with both fine particle size and high molecular weight characteristics faces technical bottlenecks.
[0003] Currently, industrial production commonly uses the Ziegler-Natta catalyst slurry process to produce polyolefins. While this process is mature, it has drawbacks: the Ziegler-Natta catalyst is a multi-active-site catalyst, making it difficult to directly generate high-molecular-weight polymer particles with uniform particle size. Furthermore, olefin polymerization in a stirred reactor is a strongly exothermic reaction, easily generating localized "hot spots," leading to explosive polymerization and material agglomeration, resulting in lumps or large-diameter polymer particles. These large particles not only increase the difficulty of post-processing but also easily clog downstream pipelines. To control the final powder particle size distribution, post-processing techniques, including screening and homogenization, are needed to remove large particles. Vibrating screening is a common method for classifying polyolefin powder particles; however, the large particles generated during screening are usually sold as low-value-added products, increasing production costs and reducing economic efficiency.
[0004] Existing technologies can use grinding mills to crush large particles or lumps after screening. For example, patent CN220446923U discloses a polyolefin material separation and recovery device, which realizes the recovery of powder in polyolefin lumps through crushing mechanism and powder vibration screening mechanism, reduces the loss of qualified powder, and improves economic efficiency. However, this "dry grinding" method has the following defects: (1) It is mainly an intermittent small-scale operation, which is difficult to efficiently couple with the main line of large-scale continuous slurry polyolefin production, thus limiting the overall capacity and efficiency. (2) The dry grinding process generates intense frictional heat, which can easily lead to thermal oxidation degradation of high molecular weight polyolefins, and can easily produce plasticized materials due to overheating, destroying the molecular chain structure. (3) Strong mechanical grinding force may destroy the original morphology of particles and damage the consistency of product quality and performance.
[0005] Therefore, existing technologies based on screening to remove large particles, supplemented by dry grinding, still have significant shortcomings in the efficient, continuous, and non-destructive preparation of high-quality polyolefin powders with fine particle sizes. There is an urgent need to develop a novel slurry-based polyolefin production system and process that can operate continuously on a large scale and effectively control particle size distribution to overcome these technical deficiencies. Summary of the Invention
[0006] The purpose of this invention is to provide a continuous slurry production system and process for polyolefins based on wet crushing in order to solve the above-mentioned problems.
[0007] The objective of this invention is achieved through the following technical solution:
[0008] A continuous slurry production system for polyolefins based on wet crushing, the system comprising:
[0009] Polymerization reaction unit;
[0010] A dilution flash evaporation unit is located downstream of the polymerization reaction unit and includes a slurry dilution tank and a flash evaporation tank.
[0011] Wet grinding unit I is located between the slurry dilution tank and the flash tank;
[0012] The feed inlet of the wet grinding unit I is connected to the discharge outlet of the slurry dilution tank via a pipeline. The discharge pipeline of the wet grinding unit I is connected to a three-way valve. One outlet of the three-way valve is connected to the upper part of the slurry dilution tank via a pipeline, and the other outlet is connected to the flash tank via a pipeline.
[0013] This system incorporates a wet grinding unit in the discharge pipeline of the slurry dilution tank. This unit wet-crushes the slurry containing large polymer particles to eliminate them. The liquid level in the dilution tank is maintained by controlling the opening of a three-way valve. The three-way valve can also be used to circulate and crush the slurry until the particle size meets the specified requirements. The fine-particle slurry is then sent to a flash tank for further processing. This system can operate continuously and stably on a large scale, offering high efficiency and output. Furthermore, wet grinding in a solvent generates minimal heat, preventing the formation of plasticized materials and preserving the product's shape.
[0014] As a preferred technical solution, the discharge pipe of the flash tank is connected to the wet grinding unit II, and the crushing particle size of the wet grinding unit II is smaller than that of the wet grinding unit I.
[0015] Furthermore, the particle size of the wet grinding unit I is 200-500 μm, and the particle size of the wet grinding unit II is 30-200 μm. Wet grinding unit II employs ultrafine grinding, requiring a small particle size in the input material. Therefore, this can be achieved through a series connection to ensure that the particle size of the powder at the shear pump inlet meets the requirements. By setting a wet grinding unit downstream of the flash tank, slurry classification and crushing are achieved, ensuring that the slurry does not contain large particles, thus enabling the production of products with finer particle sizes.
[0016] Furthermore, the wet grinding unit I and wet grinding unit II include a shear pump and a booster pump connected to the shear pump. Both the shear pump and the booster pump are connected to a motor via a coupling.
[0017] Furthermore, the shear pump is an adjustable particle size shear pump used to produce grade products with different particle size distributions. The particle size of the shear pump can be adjusted by adjusting the power through a frequency converter, or a mechanically adjustable shear pump can be used (by adjusting the gap between the rotor and stator in the shear pump).
[0018] As a preferred technical solution, the system also includes a separation unit, which employs a centrifuge or a rotary drum filter press to achieve solid-liquid separation of the polyolefin slurry.
[0019] As a preferred technical solution, the polymerization reaction unit includes at least one reactor for slurry polymerization reaction to generate polyolefin slurry. The reactor is provided with an overflow port, which is connected to the slurry dilution tank through a pipeline. The reaction products leave the reactor by overflow and continuously enter the slurry dilution tank, which is used to separate the gas in the slurry.
[0020] As a preferred technical solution, the reactor is a stirred tank with a cooling jacket. The tank preferably uses a plate-and-frame agitator. Heat removal from the reactor is achieved through solvent vaporization and heat exchange via the cooling jacket, ensuring the stable progress of the polymerization reaction. The reactor is connected to a feeding unit, into which solvent, reactants, and catalyst are fed for the polymerization reaction.
[0021] As a preferred technical solution, the polymerization reaction unit includes multiple reactors, which are arranged in parallel or in series.
[0022] As a preferred technical solution, the top of the slurry dilution tank is provided with a gas phase balance pipeline that communicates with the polymerization reaction unit, so as to return the separated gas to the polymerization reaction unit.
[0023] A continuous slurry production process for ultrafine polyolefins based on wet crushing is disclosed. The production system described above is used for production. This process is based on wet crushing and achieves efficient, continuous, and non-destructive production of ultrafine-particle-size high molecular weight polyolefins.
[0024] Compared with the prior art, the present invention has the following beneficial effects:
[0025] This invention achieves efficient, continuous, and non-destructive production of ultrafine-particle-size high-molecular-weight polyolefins by combining wet crushing with a continuous slurry process. Employing wet shear crushing technology ensures product consistency while effectively mitigating the risk of plasticization, thus protecting the integrity of the polyolefin chain structure and its mechanical properties. This process eliminates the need for vibrating screening and dry grinding, reducing coarse particle loss and significantly improving raw material utilization. Furthermore, the circulation and crushing path of the slurry can be dynamically controlled via a three-way valve, and combined with the continuous flow design of the flash evaporation and separation units, continuous and stable large-scale production operation is ultimately achieved. Attached Figure Description
[0026] Figure 1 This is a schematic diagram of the production system shown in Example 1;
[0027] Figure 2 This is a top view of the wet grinding unit;
[0028] Figure 3 for Figure 2 Front view diagram;
[0029] Figure 4 A photograph of the actual sample to be processed;
[0030] Figure 5 Here is an electron microscope image of the powder after crushing in the example;
[0031] Figure 6 This is a schematic diagram of the production system shown in Example 2;
[0032] Figure 7 This is a schematic diagram of the production system shown in Example 3. Detailed Implementation
[0033] The present invention will now be described in detail. Any technical solutions not described in detail herein are those already disclosed in the art.
[0034] Example 1
[0035] Reference Figure 1A continuous slurry production system for polyolefins based on wet crushing is disclosed. The system includes a polymerization reaction unit, a dilution flash evaporation unit, a wet grinding unit I4, and a separation unit. The polymerization reaction unit is equipped with a reactor 1 for slurry polymerization to generate polyolefin slurry. The dilution flash evaporation unit is located downstream of the polymerization reaction unit and includes a slurry dilution tank 2 and a flash evaporation tank 3. The reactor 1 is equipped with an overflow port, which is connected to the slurry dilution tank 2 through a pipeline. The reaction products leave the reactor 1 by overflow and continuously enter the slurry dilution tank 2. The medium overflowing from the overflow port carries a large amount of gas due to strong backmixing in the reactor. The slurry dilution tank 2 separates the gas in the slurry to avoid long-distance gas-liquid two-phase transportation. The separated gas can be returned to the top of the reactor 1 through a gas phase balance pipeline.
[0036] Wet grinding unit I4 is located between slurry dilution tank 2 and flash tank 3. The inlet of wet grinding unit I4 is connected to the outlet of slurry dilution tank 2 via a pipeline. The outlet pipeline of wet grinding unit I4 is connected to a three-way valve 6. One outlet of the three-way valve 6 is connected to the upper part of slurry dilution tank 2 via a pipeline, and the other outlet is connected to flash tank 3 via a pipeline. Wet grinding unit I4 continuously wet-crushes the slurry containing polymer particles from slurry dilution tank 2 to eliminate large particles. By controlling the opening of the three-way valve 6, the liquid level in slurry dilution tank 2 is maintained. The three-way valve 6 can also be controlled to circulate and crush the slurry as needed until the particle size meets the specified requirements. The crushed fine-particle slurry is then sent to flash tank 3 for flash evaporation. This system achieves large-scale continuous and stable operation with high production efficiency. Furthermore, because wet grinding is performed in a solvent, the heat generation is low, avoiding the production of plasticized materials and preserving the product's morphology.
[0037] As a preferred implementation scheme, refer to Figure 1 The discharge pipe of flash tank 3 is also connected to wet grinding unit II 5, wherein the particle size of wet grinding unit II is smaller than that of wet grinding unit I. Furthermore, the particle size of wet grinding unit I 4 is 200-500μm, for example, the particle size of the product can be set to 500μm, 400μm, 300μm, 200μm, etc., and the particle size of wet grinding unit II 5 is 30-200μm, for example, the particle size of the product can be set to 200μm, 150μm, 120μm, 100μm, 50μm, 40μm, 30μm, etc. The wet grinding unit II5 uses ultra-fine crushing, with small particle size of the incoming material. This series connection ensures that the particle size of the powder at the inlet of the shear pump meets the requirements, realizes slurry classification and crushing, fully guarantees that the slurry does not contain large particles, realizes fine particle size product preparation, effectively solves the problem of blockage of the system pipeline caused by the generation of lumps in the reactor, and reduces the pressure of the vibrating screen in processing powder.
[0038] Reference Figure 2 , Figure 3 The wet grinding unit I4 and wet grinding unit II5 include a shear pump 401 and a booster pump 402 connected to the shear pump 401. Both the shear pump 401 and the booster pump 402 are connected to the motor 404 via a coupling 403. The slurry dilution tank 2 discharges through a pipeline into the inlet 405 and is discharged through the outlet 406 after crushing. As a preferred technical solution, the shear pump 401 is an adjustable particle size shear pump, so as to produce product grades with different particle size distributions according to actual needs. The particle size is adjusted by adjusting the shear pump power through a frequency converter, or a mechanically adjustable shear pump can be used, that is, the crushed particle size can be adjusted by adjusting the gap between the rotor and stator in the shear pump.
[0039] In this embodiment, the selection of shear pumps in wet grinding unit I and wet grinding unit II can be based on commercially available models that meet the requirements. It is preferable to use a wet shear pump with adjustable outlet particle size, which can achieve precise control of product particle size and enable the development of multiple grades of products.
[0040] In this embodiment, the separation unit uses a centrifuge 7 for solid-liquid separation. The pipeline between the centrifuge 7 and the flash tank 3 can be equipped with a slurry delivery pump as needed to increase the slurry delivery capacity. After solid-liquid separation by the separation unit, the slurry enters the subsequent processing steps.
[0041] In practical implementation, reactor 1 can be a stirred reactor equipped with a cooling jacket. A plate-and-frame agitator is preferred. Heat removal from the reactor is achieved through solvent vaporization and heat exchange via the cooling jacket, ensuring stable polymerization. Reactor 1 is connected to a feeding unit, which delivers solvent, reactants, and catalyst to the reactor for polymerization. Taking the production of ultra-high molecular weight polyethylene as an example, the feeding unit includes a hydrogen feed line (for adding hydrogen), an ethylene feed line (for adding ethylene), a catalyst feed line (for adding catalyst), and a circulating hexane line (for adding hexane). The pressure in reactor 1 is controlled between 0.25 and 0.7 MPaG, and the operating temperature is between 60 and 90°C.
[0042] To verify the wet crushing effect of this system, a wet crushing experiment was conducted using a simulation experimental device. The material processed was 4 million molecular weight polyethylene powder provided by Puxijing New Energy Materials (Shanghai) Co., Ltd., and screening was performed to remove materials containing a large number of large particles (see actual photos). Figure 4 Water was used as a solvent in the slurry.
[0043] In the experiment, approximately 50 kg of polyethylene powder and water were added to a mixing tank to form a polyethylene suspension (simulating the slurry formed by slurry polymerization). The mixing tank was connected to a wet grinding unit to wet crush the polyethylene slurry. The particle size distribution of the crushed polyethylene powder was tested using a laser particle size analyzer. The D10, D50, and D90 of the samples were tested respectively, and the particle size distribution width was calculated as (D90-D10) / D50. During the experiment, the wet grinding was carried out with a crushing particle size of 500 μm. Experiment 1 involved one crushing, and Experiment 2 involved a second crushing. The specific experimental results are detailed in Table 1.
[0044] Table 1
[0045] Group D10 / μm D50 / μm D90 / μm Particle size distribution width Percentage of particles with a diameter ≥500μm Original sample 113 480 783 1.4 64.09％ Experiment 1 81 330 740 2.0 41.63％ Experiment 2 89 280 497 1.5 19.78％
[0046] As shown in Table 1, the content of large particles in the powder was significantly reduced after wet crushing. The D50 (median particle size) decreased from 480 μm in the original sample to 330 μm in Experiment 1 (single crushing), and further to 280 μm in Experiment 2 (secondary crushing), indicating that the process can effectively reduce the average particle size. Simultaneously, the proportion of coarse particles (≥500 μm) decreased from 64.09% in the original sample to 41.63% in Experiment 1, and further to 19.78% in Experiment 2, confirming that wet crushing can significantly reduce the content of coarse particles. The particle size distribution width (1.5) in Experiment 2 was significantly narrower than that in Experiment 1 (2.0), and approached the level of the original sample (1.4), indicating that multiple crushing processes not only effectively eliminated large particle components but also improved the uniformity of the powder.
[0047] To verify the product morphology, the electron microscopy morphology of the powder after pulverization in Experiment 2 was further tested. Figure 5 The results showed that the particles had uniform surfaces and good morphology, indicating that the crushing process did not damage the product integrity. In conclusion, this wet crushing process can be effectively used to produce ultrafine polyolefin powder.
[0048] Example 2
[0049] Reference Figure 6 Compared with Example 1, in this example, reactor 1 is set up in two groups and is set up in parallel. Each group of reactor 1 is equipped with a slurry dilution tank 2 and a wet grinding unit I4 downstream. The slurry after being crushed by the wet grinding unit I4 is sent to the flash tank 3 for further processing. In this example, the separation unit uses a centrifuge 7 to separate solid and liquid, and then proceeds with subsequent operations.
[0050] Example 3
[0051] Reference Figure 7Compared with Example 2, the separation unit of this example adopts a rotary drum filter press 9, and a buffer tank 8 is set upstream of the rotary drum filter press 9. Compared with the centrifuge separation process, the rotary drum filter press 9 can realize the integrated processing of "filtration-washing-drying", which has higher separation efficiency and is conducive to the production of higher quality polyolefin products.
[0052] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.
Claims
1. A continuous slurry production system for polyolefins based on wet crushing, characterized in that, The system includes: Polymerization reaction unit; A dilution flash evaporation unit is located downstream of the polymerization reaction unit and includes a slurry dilution tank and a flash evaporation tank. Wet grinding unit I is located between the slurry dilution tank and the flash tank; The feed inlet of the wet grinding unit I is connected to the discharge outlet of the slurry dilution tank via a pipeline. The discharge pipeline of the wet grinding unit I is connected to a three-way valve. One outlet of the three-way valve is connected to the upper part of the slurry dilution tank via a pipeline, and the other outlet is connected to the flash tank via a pipeline.
2. The continuous slurry production system for polyolefins based on wet crushing according to claim 1, characterized in that, The discharge pipe of the flash tank is connected to the wet grinding unit II, and the crushing particle size of the wet grinding unit II is smaller than that of the wet grinding unit I.
3. The continuous slurry production system for polyolefins based on wet crushing according to claim 2, characterized in that, The particle size of the wet grinding unit I is 200-500μm, and the particle size of the wet grinding unit II is 30-200μm.
4. The continuous slurry production system for polyolefins based on wet crushing according to claim 2, characterized in that, The wet grinding unit I and wet grinding unit II include a shear pump and a booster pump connected to the shear pump. Both the shear pump and the booster pump are connected to a motor via a coupling.
5. A continuous slurry production system for polyolefins based on wet crushing according to claim 4, characterized in that, The shear pump is an adjustable particle size shear pump.
6. The continuous slurry production system for polyolefins based on wet crushing according to claim 1, characterized in that, The system also includes a separation unit, which is a centrifuge or a drum filter press.
7. A continuous slurry production system for polyolefins based on wet crushing according to claim 1, characterized in that, The polymerization reaction unit includes at least one reactor, which is provided with an overflow port, which is connected to the slurry dilution tank through a pipeline.
8. A continuous slurry production system for polyolefins based on wet crushing according to claim 7, characterized in that, The reactor is a stirred reactor equipped with a cooling jacket, and the reactor is connected to a feeding unit.
9. A continuous slurry production system for polyolefins based on wet crushing according to claim 7, characterized in that, The polymerization reaction unit includes multiple reactors, which are arranged in parallel or in series.
10. A continuous slurry production process for ultrafine polyolefins based on wet crushing, characterized in that, Production is carried out using the production system described in any one of claims 1-9.