Ultrahigh-purity polyolefin integrated separation and purification production process

Abstract

The invention relates to an ultra-pure polyolefin integrated separation and purification production process which comprises the following steps: (1) slurry polymerization reaction: carrying out slurry polymerization reaction in a reactor to generate slurry containing solid polyolefin; (2) diluting, flashing and degassing: inputting the obtained slurry into a diluting and flashing unit to separate and remove gas components; and (3) integrated separation and purification: pressurizing the degassed slurry, inputting the pressurized slurry into a rotary drum filter press, and carrying out integrated treatment of filtering, washing and drying. Compared with the prior art, the process has the advantages that the processes of filtering, washing and drying in polyolefin production are integrated into an integrated flow, the number of equipment and the occupied area are reduced, the operation and maintenance cost is reduced, and continuous production of ultra-clean high-purity polyolefin products is realized through multi-stage optimal combination of washing sections.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-high-purity polyolefins, and in particular to an integrated separation and purification production process for ultra-high-purity polyolefins. Background Art

[0002] As a core raw material in the field of polymer materials, polyolefins are widely used in manufacturing fields such as injection molding, film preparation, and pipe production. High-end polyolefins, represented by ultra-clean and high-purity products, are characterized by high technological content, high application performance, and high market value. They are used in various high-value applications, including medical fields, new energy battery separators, and high-end filter materials. For example, ultra-high-purity polyethylene (UHPPE) has important applications in semiconductor packaging, medical implants, and high-end optical devices, requiring it to meet stringent standards for purity and impurity content.

[0003] The slurry process is a relatively mature process for producing polyolefins. Specifically, raw materials such as monomers, comonomers, and hydrogen are added to an inert aliphatic hydrocarbon solvent. A catalyst is then used to generate polymers. Polymer particles form around the catalyst's active sites and gradually grow, forming solid polymer particles suspended in the solvent. This process, known as the slurry process, has become the mainstream production process due to its simple design, mild operating conditions, easy temperature control, uniform mixing, high monomer conversion, and relatively easy handling.

[0004] In the slurry synthesis process, the polymer slurry (containing the target product, solvent, oligomers, residual catalyst, co-catalyst, and other impurities) after the reaction is completed needs to be separated to obtain the final product. Currently, most processes use a centrifuge to remove part of the solvent, followed by nitrogen drying to remove and recover the remaining solvent in a step-by-step manner, such as Celanese's slurry process for producing ultra-high molecular weight polyethylene. However, centrifuges have high energy consumption, a high failure rate, and poor solid-liquid separation. They can only reduce the liquid content from 65% to below 30%, and a dryer is required afterwards, which affects the technical and economic efficiency of the slurry production equipment. In addition, to obtain a high-purity polymer product, steps such as washing, solid-liquid separation, and drying are usually required to remove impurities. To achieve these steps, multiple process units, such as washing kettles / wash tanks, centrifuges, and dryers / drying beds, are required. These units are usually connected by ancillary equipment such as transfer pumps, fans, and their corresponding pipelines, pipe fittings, and valves. This leads to a long process flow, numerous redundant operations, and a high risk of solvent leakage, posing a significant safety hazard. In addition, these devices are bulky, occupy a large area, and have high energy consumption. The more devices used, the greater the risk of device failure rate. It is difficult to ensure long-term continuous and stable operation of process production, and process improvements are needed. Summary of the Invention

[0005] The purpose of the present invention is to provide an integrated separation and purification production process for ultra-high purity polyolefins in order to solve the above problems.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] An integrated separation and purification production process for ultra-high-purity polyolefins comprises the following steps: (1) slurry polymerization reaction: a slurry polymerization reaction is carried out in a reactor to generate a slurry containing solid polyolefins; (2) dilution flash degassing: the obtained slurry is input into a dilution flash unit for separation and removal of gas components; and (3) integrated separation and purification: the degassed slurry is pressurized and then input into a rotary drum filter press for integrated filtration, washing and drying.

[0008] As a preferred technical solution of the present invention, the washing in step (3) is a multi-stage washing, which includes alkane solvent washing, acid solvent washing and post-washing in sequence.

[0009] As a preferred technical solution of the present invention, the alkane solvent washing adopts an inert alkane solvent to remove residual monomers, oligomers, and oil-like organic impurities; the acid solvent washing adopts a low-concentration acidic aqueous solution to complex and dissolve and remove metal ion impurities; the post-washing adopts ultrapure water, low-boiling point alcohols or an azeotrope of the two to remove residual acid and soluble metal salts.

[0010] As a preferred technical solution of the present invention, the alkane solvent is an inert alkane solvent, including hexane and pentane; the acid solvent is dilute nitric acid with a concentration of 0.1-0.5wt%; and the post-washing uses an azeotropic mixture of ethanol and ultrapure water.

[0011] As a preferred technical solution of the present invention, the rotary drum filter press includes a filtration process section, a washing process section, a drying process section and a unloading process section; the working pressure of the filtration process section, the washing process section and the drying process section is 0.1~0.8MPa, preferably 0.1~0.3MPa, and the working temperature is 60~70℃.

[0012] As a preferred technical solution of the present invention, the reactor in step (1) includes one or more reactors, and the multiple reactors are arranged in series or parallel; the reactor is a kettle agitator with a cooling jacket, and the cooling jacket is connected to a cooling circulation loop.

[0013] As a preferred technical solution of the present invention, the reactor is connected to a feeding system, which includes a solvent feeding pipeline, a reaction raw material feeding pipeline and a catalyst feeding pipeline, and a purification device is provided in the reaction raw material feeding pipeline.

[0014] As a preferred technical solution of the present invention, a circulating cooling subsystem for removing reaction heat through solvent phase change is provided on the top of the reactor, comprising: a condenser arranged on the top of the reactor, a buffer tank connected to the condenser, the bottom of the buffer tank is connected to the reactor through a pipeline, and the cooled and recovered solvent is returned to the reactor; a gas circulation pipeline with a circulating gas blower is connected to the top of the buffer tank, and the gas circulation pipeline is connected to the reactor.

[0015] As a preferred technical solution of the present invention, the dilution flash unit in step (2) includes a slurry dilution tank and a flash tank located downstream of the slurry dilution tank; the reactor is provided with an overflow discharge port, the slurry dilution tank is connected to the overflow discharge port of the reactor through an overflow pipe, and the upper part of the slurry dilution tank is connected to the kettle top of the reactor through a gas phase balance pipeline.

[0016] As a preferred technical solution of the present invention, the top of the flash tank is connected to a cooling circulation loop, including a condenser and a buffer tank connected by pipelines. The buffer tank is connected to the flash tank through a pipeline to return the cooled and recovered solvent to the reactor.

[0017] The present invention also provides an integrated separation and purification production system for ultra-high purity polyolefins, comprising:

[0018] A polymerization reaction unit, comprising a reactor, for slurry polymerization to produce polyolefin slurry;

[0019] a dilution flash unit, located downstream of the reactor, for separating gas components in the slurry;

[0020] The separation and purification unit includes a rotary drum filter press, which is arranged downstream of the dilution flash evaporation unit and is used for filtering, washing and drying the slurry in an integrated manner to obtain a clean and dry product.

[0021] As a preferred technical solution, along the rotation direction, the rotary drum filter press includes a filtration process section, a washing process section, a drying process section and a unloading process section in sequence; the filtration process section injects the pressurized polyolefin slurry from the dilution flash unit through the feed port; the washing process section includes a multi-stage segmented washing component, which at least includes an alkane solvent washing section, an acid solvent washing section and a post-washing section.

[0022] As a preferred technical solution, the alkane solvent washing section is connected to the alkane solvent storage unit via a pipeline; the acid solvent washing section is connected to the acid solvent storage unit via a pipeline; and the post-washing section is connected to the detergent storage unit via a pipeline. The alkane solvent storage unit is filled with an inert alkane solvent, such as hexane or pentane; the acid solvent storage unit is filled with a low-concentration acidic aqueous solution, preferably dilute nitric acid with a concentration of 0.1-0.5wt%. Dilute nitric acid can achieve targeted removal of metal impurities. The oxidizing property of dilute nitric acid can decompose the organometallic compounds in the residual catalyst, releasing metal ions. At the same time, nitrate ions form water-soluble complexes with metal ions, which, under pressure osmosis, clean the particle surface and internal pores, significantly reducing the ash and metal content of the product. The detergent storage unit is filled with ultrapure water, a low-boiling point alcohol solvent, or an azeotrope of ultrapure water and a low-boiling point alcohol solvent, for example, an azeotropic mixture of ethanol and ultrapure water (the ethanol content in the azeotropic mixture is 95.57wt% and the water content is 4.43wt%). The azeotropic mixture of ethanol and water has a boiling point of 78.15°C, which is lower than the boiling points of pure ethanol and pure water, facilitating subsequent rapid drying.

[0023] As a preferred technical solution, the drying process section is connected to the air supply unit via a pipeline, and pressurized drying gas is injected into the drying process section through an inlet.

[0024] As a preferred technical solution, the rotary drum filter press includes a shell, a drum rotatably arranged in the shell, and a plurality of isolation seals arranged at intervals along the circumference of the shell; the isolation seals divide the annular chamber between the shell and the drum into a plurality of independent compartments in sequence, and a plurality of flow pipes connecting the compartments are provided in the rotary drum.

[0025] As a preferred technical solution, the isolation seal is a pneumatic isolation seal, which includes an isolation plate. The isolation plate is made of chemically resistant plastic. A filter plate is provided on the surface of the drum, and a support net and a filter cloth are laid on the filter plate in sequence.

[0026] As an optimal technical solution, a flow hole is provided at the bottom of the compartment chamber, a control head is provided in the drum, one end of the flow pipe is connected to the flow hole at the bottom of the corresponding compartment chamber, and the other end is connected to the control head. The control head discharges the media of different process sections independently and is collected into an independent recovery unit; the unloading process section is provided with a scraper mechanism and a flushing nozzle, and the scraper mechanism is made of non-metallic material to avoid the introduction of metal impurities.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention integrates the filtering, washing, drying and unloading functions of a rotary drum filter press to achieve continuous processing of polyolefin slurry, shorten the process flow, reduce equipment investment and floor space. A multi-stage segmented washing (alkane solvent → acid solvent → post-washing) is adopted to remove organic residues, metal ions and acidic impurities in a targeted manner, and combined with a solvent washing system, the product purity is synergistically improved. By sequentially arranging an alkane solvent washing section, an acid solvent washing section and a post-washing section, the classification and targeted removal of different types of impurities in polyolefin particles are achieved: the alkane solvent washing section effectively dissolves and elutes residual monomers, oligomers, oil-based organic impurities and some catalyst residues; the acid solvent washing section efficiently complexes, dissolves and removes metal ion impurities (such as catalyst residual metals), significantly reducing the ash and metal content of the product; the post-washing section removes residual acid, soluble metal salts and low-molecular polymer microparticles, etc., to achieve extreme purification of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the production process system structure of the present invention;

[0030] Figure 2 Schematic diagram of the structure of the separation and purification unit of the present invention;

[0031] Figure numerals: 1-reactor; 2-slurry dilution tank; 3-flash tank; 4-drum filter press; 5-recovery unit; 6-condenser; 7-buffer tank; 8-circulating air fan; 9-purification device; 10-alkane solvent storage unit; 11-acid solvent storage unit; 12-detergent storage unit; 13-air supply unit; 401-shell; 402-drum; 403-isolating seal; 404-compartment chamber; 405-flow pipe; 406-scraper mechanism; 407-flushing nozzle; 408-flow hole. DETAILED DESCRIPTION

[0032] The present invention is described in detail below. All matters not described in detail in the present invention are technical solutions disclosed in the art.

[0033] An integrated separation and purification production process for ultra-high purity polyolefins comprises the following steps: (1) slurry polymerization reaction: a slurry polymerization reaction is carried out in a reactor to generate a slurry containing solid polyolefins; (2) dilution flash degassing: the obtained slurry is input into a dilution flash unit to separate and remove gas components; (3) integrated separation and purification: the degassed slurry is pressurized and then input into a drum filter press for integrated filtration, washing and drying. The washing is a multi-stage segmented washing process, which includes alkane solvent washing, acid solvent washing and post-washing in sequence. The alkane solvent washing uses an inert alkane solvent to remove residual monomers, oligomers, and oil-like organic impurities; the acid solvent washing uses a low-concentration acidic aqueous solution to complex, dissolve and remove metal ion impurities; and the post-washing uses ultrapure water, low-boiling point alcohols or an azeotrope of the two to remove residual acid and soluble metal salts. The alkane solvent is an inert alkane solvent, including hexane and pentane; the acid solvent is dilute nitric acid with a concentration of 0.1 to 0.5 wt%. The post-washing step uses an azeotropic mixture of ethanol and ultrapure water. The rotary drum filter press includes a filtration process section, a washing process section, a drying process section, and a discharge process section. The operating pressure of the filtration process section, the washing process section, and the drying process section is 0.1 to 0.8 MPa, preferably 0.1 to 0.3 MPa, and the operating temperature is 60 to 70°C.

[0034] Reference Figure 1 A system for an integrated separation and purification production process of ultra-high-purity polyolefins includes a polymerization reaction unit, a dilution flash unit, and a separation and purification unit. The polymerization reaction unit is provided with a reactor 1 for slurry polymerization reaction to generate polyolefin slurry, the dilution flash unit is provided with a slurry dilution tank 2 and a flash tank 3 located downstream of the slurry dilution tank 2, for separating gas components in the slurry, and the separation and purification unit is provided with a rotary drum filter press 4 for filtering, washing, and drying the slurry in an integrated manner to obtain a clean and dry product.

[0035] Reactor 1 is connected to the feed system, which includes a solvent feed line, a reaction raw material feed line, and a catalyst feed line. A purification device 9 is provided in the reaction raw material feed line. Taking the production of ultra-high purity high molecular weight polyethylene as an example, the feed system includes a hydrogen feed line a (for adding hydrogen), an ethylene feed line b (for adding ethylene), a catalyst feed line d (for adding catalyst), and a circulating hexane line c (for adding hexane). A purification device 9 is provided in the ethylene feed line b, which includes equipment such as a packing refining tower and an adsorption tower to deeply purify the incoming ethylene raw material to ensure the cleanliness of the ethylene. The reaction raw materials undergo polymerization in reactor 1 at a certain operating pressure and temperature. Taking the production of polyethylene as an example, the pressure is controlled between 0.25 and 0.7 MPaG and the operating temperature is between 60 and 90°C. The reaction product leaves the reactor 1 with a stirrer by overflow. Solvents such as hexane serve as both dispersants and vaporization heat removal agents. The polymerization reaction is a highly exothermic reaction, and the heat removal of the reactor is mainly carried out by solvent vaporization. The circulating gas composed of the hexane gas phase evaporated from the top of the reactor 1 and unreacted ethylene, hydrogen and inert gas components such as methane, ethane, nitrogen and other media is cooled to 38-40°C by the condenser 6 and then enters the buffer tank 7 for liquid separation. A wire mesh demister is provided on the top of the buffer tank 7 to prevent liquid from being carried at the inlet of the circulating gas blower 8. The liquid phase of the buffer tank 7 is circulated to the reactor 1 as circulating hexane; the gas phase is pressurized by the circulating gas blower 8 and returned to the reactor 1 for recycling. Fresh ethylene and hydrogen are added to the outlet gas pipeline of the circulating gas blower 8. The reactor 1 is equipped with a cooling jacket, which is connected to the cooling circulation loop and is used to remove heat from the reactor through the jacket water pump, further removing the reaction heat to ensure the stable progress of the polymerization reaction.

[0036] The overflow port of reactor 1 flows out the polyethylene slurry after polymerization, and the slurry content is as high as 35%. The medium overflowing from the overflow port will entrain a large amount of gas due to the strong back mixing in the reactor. A slurry dilution tank 2 is set to separate the gas in the slurry to avoid long-distance gas-liquid two-phase transportation. The separated gases are returned to the top of the reactor through the gas phase balance pipeline. The stable polyethylene slurry from the slurry dilution tank 2 enters the flash tank 3 to flash out non-condensable gas. The flash gas from the flash tank 3 is cooled by the condenser 6, and the condensate is collected in the buffer tank 7 and then returned to the flash tank 3. The non-condensable gas enters the next process for further treatment. The slurry after flashing is sent to the rotary drum filter press 4 through the slurry delivery pump for integrated filtration, washing and drying of the slurry.

[0037] Reference Figure 2The separation and purification unit includes a rotary drum filter press 4, which comprises a housing 401, a rotary drum 402 rotatably mounted within the housing 401, and multiple isolation seals 403 spaced circumferentially along the housing 401. The isolation seals 403 sequentially divide the annular chamber between the housing 401 and the rotary drum 402 into multiple independent compartments 404, serving as different process sections. Multiple flow tubes 405 are provided within the rotary drum 402, connecting the compartments 404. Flow holes 408 are defined at the bottoms of the compartments 404. A control head is located within the rotary drum 402. One end of the flow tube 405 is connected to the flow hole 408 at the bottom of the corresponding compartment 404, and the other end is connected to the control head. The control head independently discharges the media from the different process sections, which are then collected in independent recovery units 5. Centrally located within the control head is a control core integrated with the rotary drum. The outlets for all filtrate tubes within the rotary drum are sequentially distributed on the surface of the control core. The annular cavity between the rotating control core and the housing where the control head is fixed is divided into several independent chambers by several isolation blocks. These chambers correspond one-to-one to the process sections on the filter housing, and respectively receive the filtrate or medium from the corresponding process sections, thereby achieving the separation and independent discharge of different filtrates.

[0038] Isolation seal 403 is a pneumatic isolation seal consisting of an isolation plate made of chemically resistant plastic. A filter plate is positioned on the surface of drum 402, which is then covered with a support mesh and filter cloth. Isolation seal 403 is designed to contact drum 402 and divide the annular chamber into multiple zones, sealing each zone relative to the others. In one embodiment, the long edge of isolation seal 403 on the side in contact with drum 402 extends axially along housing 401. In actual design, isolation seal 403 is designed to contact drum 402 with a relatively suitable pressure to seal adjacent zones from each other without affecting the normal rotation of drum 402 during operation. The isolation plate of isolation seal 403, under the action of air pressure, adheres tightly to the drum surface, separating the two process sections on either side into independent zones that do not interfere with each other and prevent material from flowing through. The isolation plate is a long-wear component made of high-grade, chemically resistant plastics such as PTFE and PEEK. Multiple compartments 404 are arranged on the surface of the drum 402 for accommodating materials to be processed; a filter element is arranged at the bottom of each compartment 404; and multiple flow pipes 405 are arranged in the inner cavity of the drum 402 and communicate with corresponding compartments 404.

[0039] Along the rotation direction, the drum filter press 4 includes a filtration process section A, a washing process section B, a drying process section C and a discharging process section D in sequence. The filtration process section A is connected to the flash tank 3 through a pipeline, and the pressurized polyolefin slurry is injected through the feed port; the washing process section B includes a multi-stage segmented washing component, specifically including an alkane solvent washing section B1, an acid solvent washing section B2 and a post-washing section B3, wherein the alkane solvent washing section B1 is connected to the alkane solvent storage unit 10 through a pipeline; the acid solvent washing section B2 is connected to the acid solvent storage unit 11 through a pipeline; the post-washing section B3 is connected to the alkane solvent storage unit 10 through a pipeline. The pipeline is connected to the detergent storage unit 12, and the alkane solvent storage unit 10 is filled with an inert alkane solvent, such as hexane, pentane, etc.; the acid solvent storage unit 11 is filled with dilute nitric acid with a concentration of 0.1 to 0.5 wt%; the detergent storage unit 12 is filled with ultrapure water, a low-boiling point alcohol solvent, or an azeotrope of ultrapure water and a low-boiling point alcohol solvent, preferably an azeotropic mixture of ethanol and ultrapure water (the ethanol content in the azeotropic mixture is 95.57 wt% and the water content is 4.43 wt%). The azeotropic mixture of ethanol and water has a low boiling point, which facilitates subsequent rapid drying. By sequentially configuring the alkane solvent washing section, acid solvent washing section, and post-washing section, different types of impurities in polyolefin particles can be graded and targeted for removal. Specifically, the alkane solvent washing section effectively dissolves and elutes residual monomers, oligomers, oil-based organic impurities, and some catalyst residues; the acid solvent washing section efficiently complexes, dissolves, and removes metal ion impurities, significantly reducing the product's ash and metal content; and the post-washing section removes residual acid, polar soluble metal salts, and fine particles, ensuring the final product is free of acid residues and achieving extreme product purification. Drying process section C is connected to the gas supply unit 13 (e.g., a nitrogen network) via a pipeline to inject pressurized dry gas. During operation, dry gas from the outside, such as compressed nitrogen, is injected into the cavity of drying process section C and dries the material to be dried therein. The filter element, including a filter plate, is fixed in the filter cake trough of the rotary drum, responsible for releasing liquids and intercepting solids. The filter plate has a filtrate channel, a support mesh, and a filter cloth. Depending on the process requirements, the filter cloth can be made of synthetic fiber or sintered metal. In practical applications, the appropriate material can be selected according to the temperature of the material to be filtered.

[0040] In this embodiment, the chamber area of ​​the unloading process section D is equipped with a discharge port and a flushing port. Unloading is carried out at atmospheric pressure. A scraper mechanism 406 is provided at the discharge port, and filter cake unloading is achieved in combination with gas backflushing. Multiple flushing nozzles 407 are provided at the flushing port to clean the drum surface after unloading and, in combination with gas backflushing, to regenerate the filter cloth. In the unloading area, the filter cake is unloaded at atmospheric pressure with the help of air or nitrogen backflushing. A spring-controlled, passive scraper assists in unloading. A filter cloth flushing device is provided at the lower rear of the unloading area for continuous or on-demand flushing of the filter cloth. Preferably, the scraper mechanism 406 is made of a non-metallic material, and a discharge screw is provided downstream of the scraper mechanism 406 to break up any lumps of filter cake to facilitate the next process step.

[0041] The operating pressure of filtration process section A, washing process section B, and drying process section C is 0.1-0.8 MPa. Drum filtration is performed under a certain pressure to enhance the solvent's penetration capacity and washing efficiency, ensuring deep displacement and elution of impurities, which facilitates the removal of impurities from dense particles. Furthermore, the temperature of the filtration, washing, and drying process sections is controlled at 60-70°C to prevent oligomer precipitation. As a preferred embodiment, drying process section C can be configured as a multi-stage drying section, for example, using two drying sections, to further improve the drying effect.

[0042] Taking the slurry process to produce ultra-high purity ultra-high molecular weight polyethylene as an example, the specific working process of the drum filter press is as follows:

[0043] The flashed polyethylene slurry is pumped to the drum filter press 4 (the drum 402 keeps rotating in the working state) through the slurry pump, and the slurry is injected into the cavity area of ​​the filtration process section A at a certain pressure (about 0.3 MPa). The solid-liquid mixed slurry entering the cavity area quickly fills the cavity area. Due to the pressure difference between the compartment 404 and the flow pipe 405, and on both sides of the filter element in the compartment 404 (along the circumferential direction of the drum 402), the liquid solvent in the slurry in the compartment 404 passes through the filter element, enters the flow pipe 405 through the flow hole 408 of the filtration process section A, and is discharged from the flow pipe 405 through the control head and collected in the independent recovery unit 5. It can be recycled after subsequent treatment, while the solid components are retained on the filter element on the surface of the drum in the form of filter cake.

[0044] As the drum 402 rotates, the drum 402 loaded with the filter cake enters the cavity of the washing process section B and undergoes multi-stage graded washing: (1) In the alkane solvent washing section B1, clean hexane from the alkane solvent storage unit 10 is injected into the cavity of the alkane solvent washing section B1 at a certain pressure (about 0.3 MPa) to clean the filter cake on the filter element in the compartment chamber 404. Residual monomers, oligomers, oils and other organic impurities and some catalyst residues that are easily soluble in hexane in the filter cake are eluted. The hexane carries these impurities into the flow pipe 405 through the flow hole, and is discharged from the flow pipe 405 through the control head and collected in the independent recovery unit 5. After subsequent treatment, it can be recycled. (2) The drum 402 continues to rotate, and the filter cake after being washed with hexane enters the acid solvent washing section B2. The dilute nitric acid (about 0.35wt%) in the acid solvent storage unit 11 is injected into the cavity of the acid solvent washing section B2 at a certain pressure (about 0.3MPa) to clean the filter cake. The dilute nitric acid has a certain oxidizing property and can complex, dissolve and remove the metal ion impurities (mainly including catalyst residual metals) in the polyethylene filter cake. The dilute nitric acid reacts with the metal element chemical substances remaining in the polyethylene powder, significantly reducing the ash content and metal content of the product. The acid solvent carrying impurities enters the flow pipe 405 through the flow hole, and is discharged from the flow pipe 405 through the control head and is collected in the independent recovery unit 5. It can be recycled after subsequent treatment. (3) Drum 402 continues to rotate, and the filter cake after acid washing enters the post-washing section B3. The azeotropic mixture of ethanol and water in the detergent storage unit 12 is injected into the cavity of the post-washing section B3 at a certain pressure (about 0.3 MPa) to clean the filter cake, remove residual acid, soluble metal salts, and fine particles, and ensure that the final product is free of acid residue, achieving extreme product purification. The waste liquid carrying impurities enters the flow pipe 405 through the flow hole, and is discharged from the flow pipe 405 through the control head and collected in the independent recovery unit 5 for subsequent processing.

[0045] The drum 402 continues to rotate, and the washed filter cake enters the cavity area of ​​the drying process section C. Drying gas (such as hot nitrogen) is injected into the cavity area of ​​the drying process section C at a certain pressure (such as 0.1-0.3 MPa) to dry the filter cake. The drying gas passes through the filter cake and removes the moisture in the filter cake. The gas enters the flow pipe 405 through the flow hole and is discharged from the flow pipe 405 to be collected in the independent recovery unit 5.

[0046] The drum 402 continues to rotate, and the dried filter cake enters the unloading process section D. The unloading is carried out under normal pressure. At the discharge port of the unloading process section D, the dried filter cake in the compartment 404 is broken under the stirring of the scraper mechanism 406, and the filter cake is unloaded in combination with gas backflushing. The obtained polyethylene dry powder slides out of the drum 402 and is collected. As the drum 402 continues to rotate, the drum 402 is rotated to the flushing port. A plurality of flushing nozzles 407 are provided at the flushing port to clean the drum surface after unloading and regenerate the filter cloth in combination with gas backflushing. It is then rotated to the cavity area of ​​the filtration process section A for the next "filtration-washing-drying" cycle. Through this device, ultra-clean and high-purity ultra-high molecular weight polyethylene (metal content less than 1ppm, non-volatile residue less than 0.01%) is produced on a large scale and continuously, which can meet the needs of high-end application scenarios such as semiconductor photoresist, medical filter materials, and medical implants.

[0047] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. 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 present invention, should be within the scope of protection of the present invention.

Claims

1. An integrated separation and purification production process for ultra-high purity polyolefins, characterized in that: The following steps are involved: (1) Slurry polymerization: Slurry polymerization is carried out in a reactor to generate a slurry containing solid polyolefin; (2) Dilution flash degassing: The resulting slurry is fed into a dilution flash unit to separate and remove gas components; (3) Integrated separation and purification: The degassed slurry is pressurized and fed into a rotary filter press for integrated filtration, washing, and drying.

2. The integrated separation and purification production process for ultra-high purity polyolefin according to claim 1, characterized in that: The washing in step (3) is a multi-stage washing, which includes alkane solvent washing, acid solvent washing and post-washing in sequence.

3. The integrated separation and purification production process for ultra-high purity polyolefin according to claim 2, characterized in that: The alkane solvent washing uses an inert alkane solvent to remove residual monomers, oligomers, and oil-based organic impurities; the acid solvent washing uses a low-concentration acidic aqueous solution to complex, dissolve, and remove metal ion impurities; and the post-washing uses ultrapure water, low-boiling point alcohols, or an azeotrope of the two to remove residual acid and soluble metal salts.

4. The integrated separation and purification production process for ultra-high purity polyolefin according to claim 3, characterized in that: The alkane solvent is an inert alkane solvent, including hexane and pentane; The acid solution solvent is dilute nitric acid with a concentration of 0.1 to 0.5 wt%; The post-washing adopts an azeotropic mixture of ethanol and ultrapure water.

5. The integrated separation and purification production process for ultra-high purity polyolefin according to claim 1, characterized in that: The rotary drum filter press includes a filtration process section, a washing process section, a drying process section and a discharging process section; The working pressure of the filtration process section, the washing process section and the drying process section is 0.1-0.8 MPa, preferably 0.1-0.3 MPa, and the working temperature is 60-70°C.

6. The integrated separation and purification production process for ultra-high purity polyolefin according to claim 1, characterized in that: The reactor in step (1) includes one or more reactors, and the multiple reactors are arranged in series or in parallel; The reactor is a kettle-type agitator with a cooling jacket, and the cooling jacket is connected to a cooling circulation loop.

7. The integrated separation and purification production process for ultra-high purity polyolefin according to claim 1, characterized in that: The reactor is connected to a feeding system, which includes a solvent feeding pipeline, a reaction raw material feeding pipeline and a catalyst feeding pipeline. A purification device is provided in the reaction raw material feeding pipeline.

8. The integrated separation and purification production process for ultra-high purity polyolefin according to claim 7, characterized in that: The top of the reactor is provided with a circulating cooling subsystem for removing reaction heat through solvent phase change, which includes: a condenser arranged on the top of the reactor, a buffer tank connected to the condenser, the bottom of the buffer tank is connected to the reactor through a pipeline, and the cooled and recovered solvent is returned to the reactor; The top of the buffer tank is connected to a gas circulation pipeline provided with a circulating gas blower, and the gas circulation pipeline is communicated with the reactor.

9. The integrated separation and purification production process for ultra-high purity polyolefin according to claim 1, characterized in that: The dilution flash unit in step (2) includes a slurry dilution tank and a flash tank located downstream of the slurry dilution tank; The reactor is provided with an overflow discharge port, the slurry dilution tank is connected to the overflow discharge port of the reactor through an overflow pipe, and the upper part of the slurry dilution tank is connected to the kettle top of the reactor through a gas phase balance pipeline.

10. The integrated separation and purification production process for ultra-high purity polyolefin according to claim 9, characterized in that: The top of the flash tank is connected to a cooling circulation loop, which includes a condenser and a buffer tank connected by pipelines. The buffer tank is connected to the flash tank through a pipeline to return the cooled and recovered solvent to the reactor.

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