Polyethylene nitrogen circulating stripping, drying and solvent recovery device

Abstract

The utility model discloses a polyethylene nitrogen circulation blow -off, dry and solvent recovery device, including blow -off dry unit and recovery purification unit, the blow -off dry unit is including vertical fluidized bed, rotary unloader and cloth bag dust collector, the rotary unloader and cloth bag dust collector are connected with the both ends of vertical fluidized bed respectively through pipeline, the utility model discloses adopting plunger type movement double -deck vertical cylinder type fluidized bed, and the upper bed layer damp heat nitrogen gas convection blow -off material pentane solvent gasification evaporation, and the lower bed layer dry heat nitrogen gas convection dry material moisture gasification, and adopt condenser+adsorption tower's condensation+adsorption principle condenses the gaseous phase pentane in nitrogen gas into liquid phase pentane recycling, and the nitrogen gas recycling simultaneously purifies and reutilizes the mode, and makes the high molecular weight polyethylene material complete liquid phase pentane steam stripping blow -off in nitrogen circulation inert atmosphere protection's closed system in material, material dew point dry, gaseous phase pentane condensation liquid phase solvent recovery.

Description

Technical Field

[0001] This utility model mainly relates to the field of ultra-high molecular weight polyethylene production and solvent recovery technology, specifically a polyethylene nitrogen circulation stripping, drying and solvent recovery device. Background Technology

[0002] In the post-processing of ultra-high molecular weight polyethylene, nitrogen, as a special medium, not only serves as a process gas to carry solvent vapor and promote material drying, but also plays a safety protection role in avoiding the risk of dust explosion due to its inert properties. This type of nitrogen system, which needs to be circulated and controlled to achieve reuse, is a core element to ensure process safety and efficiency.

[0003] In the slurry process for preparing ultra-high molecular weight polyethylene (UHMWPE), solvent selection has evolved from the phasing out of gasoline and the maturation of hexane to the development of new pentane technologies. While pentane, as an emerging solvent, has attracted considerable attention due to its process potential, significant bottlenecks remain in related post-processing technologies. The pentane slurry suspension generated during polymerization requires filtration, pre-removal, and thermal drying to remove residual pentane. While filtration processes are relatively mature, the technical solutions for the stripping and drying stages are not yet perfected, and the supporting equipment is not adapted to the characteristics of pentane. Due to pentane's low boiling point and higher flammability and explosiveness, existing stripping processes struggle to achieve efficient solvent separation. If nitrogen is not fully utilized during the process, it will not only increase nitrogen consumption and energy consumption, but may also affect product quality due to excessive solvent residue. At the same time, the disconnect between the nitrogen circulation system and the pentane recovery process will lead to low solvent recovery rate, high tail gas treatment cost, and even safety hazards. Therefore, there is an urgent need in this field for a complete set of technologies that can integrate nitrogen circulation, pentane steam stripping, material dehumidification and drying, and solvent recovery to solve the problems of insufficient safety, high energy consumption, and low solvent recovery efficiency in material handling under the pentane solvent system, and promote the industrial application and technological upgrading of ultra-high molecular weight polyethylene pentane solvent process. Utility Model Content

[0004] This utility model addresses the problem of overly simplistic solutions in existing technologies by providing a polyethylene nitrogen circulation stripping, drying, and solvent recovery device. This device solves the technical problems mentioned in the background section regarding the imperfect stripping and drying technology and unsuitable equipment in the post-processing of ultra-high molecular weight polyethylene under a pentane solvent system. These problems result in low solvent separation efficiency, high nitrogen energy consumption, excessive solvent residue, and a disconnect between nitrogen circulation and pentane recovery, leading to low recovery rates, high costs, and safety hazards.

[0005] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows: A polyethylene nitrogen circulating stripping, drying, and solvent recovery device includes a stripping and drying unit and a recovery and purification unit. The stripping and drying unit includes a vertical fluidized bed, a rotary unloader, and a bag filter. The rotary unloader and the bag filter are connected to both ends of the vertical fluidized bed via pipes. A primary cooler and a secondary cooler are sequentially provided on one side of the bag filter. The secondary cooler is located on the side away from the bag filter. A circulating fan is provided on one side of the secondary cooler.

[0006] The recovery and purification unit includes a Roots blower, an adsorption tower, a solvent collection tank, and a vacuum pump, as well as a condenser group consisting of a primary condenser, a secondary condenser, and a tertiary condenser. The Roots blower is connected to a circulating fan via a nitrogen pipeline, the primary condenser is connected to the Roots blower via a pipeline, the tertiary condenser is connected to the adsorption tower via a pipeline, and the solvent collection tank is connected to the condenser group via a pipeline.

[0007] Furthermore, the vertical fluidized bed is a double-layer vertical cylindrical structure, including an upper bed layer and a lower bed layer. The bottom of the upper bed layer is provided with an annular distribution plate, and the bottom of the lower bed layer is provided with a conical distribution plate. The top of the vertical fluidized bed is provided with a mixed gas outlet connected to the inlet of a bag filter, and the bottom is provided with a material outlet connected to the inlet of a rotary unloader.

[0008] Furthermore, the bottom of the bag filter is provided with a powder return port, which is connected to the upper bed of the vertical fluidized bed through a pipe. The outlet of the bag filter is connected to the inlet of the primary cooler through a pipe. The outlet of the primary cooler is connected to the inlet of the secondary cooler through a pipe. The outlet of the secondary cooler is connected to the inlet of the circulating fan through a pipe.

[0009] And / or, the inlet of the primary cooler and the inlet of the secondary cooler are both connected to the outlet of the bag filter through pipes, and the outlet of the primary cooler and the outlet of the secondary cooler are both connected to the inlet of the circulating fan through pipes.

[0010] Furthermore, the stripping and drying unit also includes a heater. The outlet of the heater is divided into two pipelines. One pipeline is connected to the upper bed of the vertical fluidized bed, and the other pipeline is connected to the lower bed of the vertical fluidized bed. The outlet of the circulating blower is divided into two pipelines. One pipeline is connected to the inlet of the heater, and the other pipeline is connected to the inlet of the Roots blower.

[0011] Furthermore, the recycling and purification unit also includes a refrigeration unit and a solvent transfer pump. The refrigeration unit is connected to a secondary condenser via a refrigerant pipeline, and the outlet of the solvent collection tank is connected to the inlet of the solvent transfer pump via a pipeline.

[0012] Furthermore, the outlet of the first-stage condenser is connected to the inlet of the second-stage condenser via a pipe, and the outlet of the second-stage condenser is connected to the inlet of the third-stage condenser via a pipe.

[0013] And / or, the inlets of the first-stage condenser, the second-stage condenser, and the third-stage condenser are all connected to the outlet of the Roots blower via pipes.

[0014] Furthermore, the recovery and purification unit also includes a reheater, and the adsorption tower is a dual-tower parallel structure, including tower A and tower B, both of which are filled with activated carbon. The outlet of the adsorption tower is connected to the inlet of the reheater through a pipe, and the outlet of the reheater is connected to the lower bed of the vertical fluidized bed through a pipe.

[0015] Furthermore, the inlet of the vacuum pump is connected to the regeneration port of the adsorption tower via a pipe, and the outlet of the vacuum pump is connected to the inlet of the Roots blower via a pipe.

[0016] Compared with the prior art, the beneficial effects of this utility model are as follows: 1. This system employs a double-layer vertical cylindrical fluidized bed, integrating the two core processes of liquid-phase pentane stripping and material dehumidification and drying into a single unit. The upper bed utilizes an annular distribution plate to ensure uniform distribution of moist, hot nitrogen, which, combined with the circumferential plunger movement of the material, guarantees sufficient contact between nitrogen and wet material, enhancing the pentane vapor stripping effect. The lower bed, aided by a conical distribution plate, achieves uniform fluidization of dry, hot nitrogen while effectively preventing material blockage at the discharge port. A rotary discharger enables continuous discharge of the dried product. Simultaneously, the bag filter and the primary and secondary coolers can be connected in series or parallel. Series connection allows for stepped, deep cooling of the moist nitrogen, enhancing the condensation of water vapor and trace amounts of pentane; parallel connection allows for diverting gas flow, preventing equipment overload, and adapting to different operating conditions. The overall process eliminates the need for multiple, dispersed devices, simplifying the process structure and saving space. It also achieves continuous operation throughout the entire process from feeding, stripping, drying to discharge, solving the problems of disconnected stripping and drying equipment and low processing efficiency in traditional processes.

[0017] 2. Nitrogen is fed from the stripping and drying unit to the recovery and purification unit and then back to the fluidized bed, with no external discharge or loss throughout the process. Only a small amount of nitrogen needs to be added, which reduces the cost of purchasing fresh nitrogen and prevents the oxidation and degradation of ultra-high molecular weight polyethylene materials by isolating oxygen through an inert atmosphere, thereby improving product purity. In terms of solvent recovery, a combination of three-stage condensation and dual-tower adsorption process is adopted, which enables a pentane recovery rate of over 95%. The recovered liquid pentane can be directly reused in the polymerization process, reducing solvent waste. In terms of energy utilization, the heater and reheater use low-pressure steam, and the refrigerant in the cooling system is recycled, further reducing energy consumption. The entire circulation system not only solves the problems of nitrogen waste and solvent emission in traditional processes, but also improves product quality through inert protection, effectively achieving the dual benefits of energy saving and quality improvement.

[0018] The present invention will be explained in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0019] Figure 1 This is a connection diagram of the process equipment of this utility model; Figure 2 This is a process flow diagram of the present invention.

[0020] Numbering on the map: 1. Stripping and drying unit; 2. Recovery and purification unit; 3. Vertical fluidized bed; 4. Rotary unloader; 5. Bag filter; 6. Primary cooler; 7. Secondary cooler; 8. Circulating fan; 9. Heater; 10. Roots blower; 11. Primary condenser; 12. Secondary condenser; 13. Tertiary condenser; 14. Refrigeration unit; 15. Solvent collection tank; 16. Solvent transfer pump; 17. Adsorption tower; 18. Reheater; 19. Vacuum pump. Detailed Implementation

[0021] To facilitate understanding of this utility model, a more comprehensive description of the utility model will be given below with reference to the accompanying drawings, which show several embodiments of the utility model. However, the utility model can be implemented in different forms and is not limited to the embodiments described in the text. On the contrary, these embodiments are provided to make the disclosure of the utility model more thorough and comprehensive.

[0022] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0023] Please refer to the appendix carefully. Figure 1-2A polyethylene nitrogen circulating stripping, drying and solvent recovery device includes a stripping and drying unit 1 and a recovery and purification unit 2. The stripping and drying unit 1 includes a vertical fluidized bed 3, a rotary unloader 4 and a bag filter 5. The rotary unloader 4 and the bag filter 5 are respectively connected to the two ends of the vertical fluidized bed 3 through pipes. A primary cooler 6 and a secondary cooler 7 are sequentially provided on one side of the bag filter 5. The secondary cooler 7 is located on the side away from the bag filter 5. A circulating fan 8 is provided on one side of the secondary cooler 7.

[0024] The recovery and purification unit 2 includes a Roots blower 10, an adsorption tower 17, a solvent collection tank 15, and a vacuum pump 19, as well as a condenser group consisting of a primary condenser 11, a secondary condenser 12, and a tertiary condenser 13. The Roots blower 10 is connected to the circulating fan 8 through a nitrogen pipeline. The primary condenser 11 is connected to the Roots blower 10 through a pipeline. The tertiary condenser 13 is connected to the adsorption tower 17 through a pipeline. The solvent collection tank 15 is connected to the condenser group through a pipeline.

[0025] In some embodiments, such as Figure 1 and Figure 2 As shown, the vertical fluidized bed 3 is a double-layer vertical cylindrical structure, including an upper bed layer and a lower bed layer. The bottom of the upper bed layer is provided with an annular distribution plate, and the bottom of the lower bed layer is provided with a conical distribution plate. The top of the vertical fluidized bed 3 is provided with a mixed gas outlet connected to the inlet of the bag filter 5, and the bottom is provided with a material outlet connected to the inlet of the rotary unloader 4.

[0026] The above structure employs a plunger-type moving double-layer vertical cylindrical fluidized bed, integrating the liquid-phase pentane stripping and dehumidification drying processes of ultra-high molecular weight polyethylene wet materials through upper and lower bed partitioning. This simplifies the structure and saves space. The annular distribution plate at the bottom of the upper bed ensures uniform distribution of moist hot nitrogen gas, which, combined with the circumferential plunger movement of the material, guarantees gas-material contact efficiency to improve the pentane stripping effect. Meanwhile, the conical distribution plate at the bottom of the lower bed achieves uniform distribution of dry hot nitrogen gas and fluidizes and loosens the material, preventing blockage at the bottom connection with the rotary unloader 4. The top of the fluidized bed connects to the bag filter 5, quickly introducing nitrogen containing powder to complete gas-solid separation and reduce material loss. The bottom connection with the rotary unloader 4 enables continuous discharge of dried products, ultimately achieving continuous production of feeding, stripping, drying, and unloading.

[0027] In some embodiments, such as Figure 1 and Figure 2 As shown, the bottom of the bag filter 5 is provided with a powder return port, which is connected to the upper bed of the vertical fluidized bed 3 through a pipe. The outlet of the bag filter 5 is connected to the inlet of the primary cooler 6 through a pipe. The outlet of the primary cooler 6 is connected to the inlet of the secondary cooler 7 through a pipe. The outlet of the secondary cooler 7 is connected to the inlet of the circulating fan 8 through a pipe.

[0028] In some embodiments, the inlet of the primary cooler 6 and the inlet of the secondary cooler 7 are both connected to the outlet of the bag filter 5 via pipes, and the outlet of the primary cooler 6 and the outlet of the secondary cooler 7 are both connected to the inlet of the circulating fan 8 via pipes.

[0029] With the above structure, the connection of bag filter 5, primary cooler 6, and secondary cooler 7 can be flexibly selected according to the working conditions. The series cooling path is realized by connecting the outlet pipe of primary cooler 6 to the inlet pipe of secondary cooler 7. The wet nitrogen gas passes through two stages of cooling in sequence, which can achieve step-by-step deep cooling, enhance the condensation effect of water vapor and trace amounts of pentane, and ensure the dryness of the subsequent circulating nitrogen gas.

[0030] The parallel cooling path is achieved by connecting the inlets of the primary cooler 6 and the secondary cooler 7 to the outlet pipes of the bag filter 5, and connecting the outlets to the inlet pipes of the circulating fan 8. This allows for the diversion and treatment of wet nitrogen, increasing the overall cooling capacity, avoiding excessive load on a single cooler, and ensuring system continuity by allowing one cooler to continue operating while the other is under maintenance.

[0031] It can also be equipped with independent heat exchange for refrigerants at different temperatures by configuring refrigerants of different temperatures for the two coolers. For example, the first-stage cooler 6 uses a slightly higher-temperature refrigerant for initial cooling, while the second-stage cooler 7 uses a lower-temperature refrigerant for deep cooling. This can accurately adapt to the cooling requirements of different wet nitrogen components. Through three connection methods, it works in conjunction with the gas-solid separation function of the bag filter 5. The condensate generated during cooling is all connected to the solvent collection tank 15 for resource recovery. Ultimately, this ensures the stability of nitrogen recycling and improves the recovery efficiency of materials and solvents, adapting to different working conditions for ultra-high molecular weight polyethylene material processing.

[0032] In some embodiments, such as Figure 1 and Figure 2 As shown, the stripping and drying unit 1 also includes a heater 9. The outlet end of the heater 9 is divided into two pipelines. One pipeline is connected to the upper bed of the vertical fluidized bed 3, and the other pipeline is connected to the lower bed of the vertical fluidized bed 3. The outlet end of the circulating blower 8 is divided into two pipelines. One pipeline is connected to the inlet of the heater 9, and the other pipeline is connected to the inlet of the Roots blower 10.

[0033] With the above structure, the outlet of the circulating blower 8 is divided into two paths. It can transport part of the nitrogen to the heater 9 to provide a heat source for stripping and drying, and can also directly transport the other path of pentane-containing nitrogen to the Roots blower 10 to enter the recovery and purification unit 2. There is no need to add additional nitrogen transport power equipment, which reduces energy consumption. At the same time, the outlet of the heater 9 is divided into two paths to connect the upper and lower beds of the vertical fluidized bed 3. The heated nitrogen can be accurately distributed to the upper bed where wet hot nitrogen stripping of pentane is required and the lower bed where dry hot nitrogen drying of materials is required. This achieves synchronous adaptation of a single heat source to two processes. Through the centralized distribution and recycling of nitrogen, nitrogen exhaust loss is reduced, and an inert atmosphere is maintained in the vertical fluidized bed 3 to prevent material oxidation and degradation.

[0034] In some embodiments, such as Figure 1 and Figure 2 As shown, the recycling and purification unit 2 also includes a refrigeration unit 14 and a solvent transfer pump 16. The refrigeration unit 14 is connected to the secondary condenser 12 through a refrigerant pipeline, and the outlet of the solvent collection tank 15 is connected to the inlet of the solvent transfer pump 16 through a pipeline.

[0035] With the above structure, the refrigeration unit 14 is connected to the secondary condenser 12 through refrigerant pipelines, which can stably provide the secondary condenser 12 with refrigerant suitable for pentane condensation, ensuring the efficient condensation effect of the secondary condenser 12 on gaseous pentane in nitrogen. In turn, it can work with the condenser group to achieve the recovery of more than 95% of pentane in nitrogen. At the same time, the connection between the outlet of the solvent collection tank 15 and the inlet of the solvent transfer pump 16 can promptly pressurize and transport the buffered liquid pentane in the collection tank back to the solvent storage tank of the ultra-high molecular weight polyethylene polymerization process, realize solvent recycling and reuse, and reduce pentane waste.

[0036] In some embodiments, such as Figure 1 and Figure 2 As shown, the outlet of the first-stage condenser 11 is connected to the inlet of the second-stage condenser 12 via a pipe, and the outlet of the second-stage condenser 12 is connected to the inlet of the third-stage condenser 13 via a pipe.

[0037] In some embodiments, the inlet of the primary condenser 11, the inlet of the secondary condenser 12, and the inlet of the tertiary condenser 13 are all connected to the outlet of the Roots blower 10 via pipes.

[0038] With the above structure, when using a series connection, the outlet of the Roots blower 10 is connected to the inlet of the first-stage condenser 11 via pipelines, the outlet of the first-stage condenser 11 is connected to the inlet of the second-stage condenser 12, and the outlet of the second-stage condenser 12 is connected to the inlet of the third-stage condenser 13, forming a continuous condensation path. Combined with the -50℃ refrigerant supplied to the second-stage condenser 12 by the refrigeration unit 14, the nitrogen containing pentane undergoes a stepped cooling process, which can deeply remove gaseous pentane from the nitrogen, ensuring a pentane recovery rate of over 95%, thus meeting the requirements for high-efficiency recovery.

[0039] When using a parallel configuration, the inlets of the three condensers are all connected to the outlet of the Roots blower 10 via pipelines, and the outlets are all connected to the inlet of the subsequent adsorption tower 17 via pipelines to achieve split condensation. This can increase the nitrogen processing capacity, avoid excessive load on a single condenser, and ensure that the other equipment can operate normally while one condenser is under maintenance, thus ensuring continuous system operation and adapting to working conditions with large fluctuations in nitrogen volume.

[0040] Alternatively, when using separate heat exchange methods with different refrigerants at different temperatures, the three condensers can be configured with cooling media of different temperatures. For example, liquid nitrogen can be used for the first-stage condenser 11, -50℃ refrigerant for the second-stage condenser 12, and other temperature refrigerants for the third-stage condenser 13. Whether connected in series or in parallel, the changes in pentane content in nitrogen can be precisely matched, taking into account both recovery efficiency and energy saving.

[0041] In some embodiments, such as Figure 1 and Figure 2 As shown, the recovery and purification unit 2 also includes a reheater 18, and the adsorption tower 17 is a dual-tower parallel structure, including tower A and tower B. Both tower A and tower B are filled with activated carbon. The outlet of the adsorption tower 17 is connected to the inlet of the reheater 18 through a pipe, and the outlet of the reheater 18 is connected to the lower bed of the vertical fluidized bed 3 through a pipe.

[0042] With the above structure, the adsorption tower 17 adopts a dual-tower structure with tower A and tower B connected in parallel. When one tower adsorbs nitrogen containing trace amounts of pentane, the other tower is regenerated by vacuum pump 19 and purged with compressed nitrogen, which can realize the switching operation from adsorption to regeneration, ensuring the continuity of nitrogen purification. The activated carbon filling can specifically adsorb the 5% trace amount of pentane remaining in the nitrogen at the outlet of the three-stage condenser 13, realizing deep purification of nitrogen. The purified nitrogen is heated to 80-90°C by reheater 18 and directly sent back to the conical distribution plate of the lower bed of vertical fluidized bed 3 as dry hot nitrogen for reuse. This reduces the amount of fresh nitrogen replenishment and energy consumption, and ensures the stability of the heat source for the fluidized bed drying process. Finally, it provides a high-purity gas source for the nitrogen circulation system, which meets the dual requirements of ultra-high molecular weight polyethylene process for inert atmosphere and energy saving.

[0043] In some embodiments, such as Figure 1 and Figure 2 As shown, the inlet of vacuum pump 19 is connected to the regeneration port of adsorption tower 17 through a pipe, and the outlet of vacuum pump 19 is connected to the inlet of Roots blower 10 through a pipe.

[0044] With the above structure, the pentane saturated in the activated carbon pores of the adsorption tower 17 can be efficiently desorbed by vacuum pumping through the connection between the inlet of vacuum pump 19 and the regeneration port of adsorption tower 17, thus thoroughly cleaning the adsorbent and quickly restoring the deep purification performance of adsorption tower 17. At the same time, the gaseous pentane generated by vacuum pumping can be directly sent back to the multi-stage condensation system of recovery and purification unit 2 through the connection between the outlet of vacuum pump 19 and the inlet of Roots blower 10. The solvent can be recovered for the second time without the need for additional pentane treatment equipment. This avoids pentane loss and external pollution, and can be completed by relying on the existing condensation channel. At the same time, nitrogen is added to the system, which takes into account the regeneration efficiency of adsorption tower 17, solvent recovery and utilization rate, and the overall airtightness and energy saving of the system.

[0045] The specific operating procedure of this utility model is as follows: It should be noted that this fluidized bed adopts a plunger-type moving double-layer vertical cylindrical fluidized bed. Its core function is to achieve efficient processing through stratification and plunger motion. An annular distribution plate is installed at the bottom of the upper bed for introducing moist hot nitrogen. After the material enters from one side of the bed, it undergoes circumferential plunger motion under the action of the moist hot nitrogen and the distribution plate components, similar to piston pushing, which avoids localized material accumulation. Through sufficient contact between the moist hot nitrogen and the material, the vaporization and stripping of liquid pentane are completed. A conical distribution plate is installed at the bottom of the lower bed for introducing dry hot nitrogen. The material stripped from the upper layer enters the lower layer through the inner cylinder opening. The conical distribution plate ensures uniform distribution of dry hot nitrogen, fluidizes and loosens the material, and prevents blockage at the discharge port, ultimately completing the dehumidification and drying of the material.

[0046] First, turn on the circulating fan 8 and the refrigeration unit 14 to bring the nitrogen circulation path and condenser group into a ready-to-operate state, ensuring that there are no leaks in the pipeline and the pressure is stable.

[0047] After sludge filtration, the ultra-high molecular weight polyethylene wet material, with a temperature of approximately 25℃ and a moisture content of 20-30% (wt), is continuously and uniformly fed into the upper part of the vertical fluidized bed 3 through an external feeding device. The nitrogen output from the circulating fan 8 is divided into two paths. The main path enters the heater 9 and is indirectly heated to 80-90℃ by saturated steam at 0.3MPa and 145℃, providing a heat source for stripping and drying. A small amount of saturated steam is mixed into the heated nitrogen to humidify it, forming humid hot nitrogen with a temperature of 90-100℃ and a relative humidity of 80-90%. This humid hot nitrogen enters the upper part of the vertical fluidized bed 3 through the annular distribution plate of the upper bed. The material undergoes circumferential plunger motion under the push of the humid hot nitrogen. The water vapor in the humid hot nitrogen condenses and releases heat, causing the liquid pentane in the material to vaporize, completing the steam stripping.

[0048] In the heated nitrogen, another stream of dry hot nitrogen enters the lower bed of the vertical fluidized bed 3 through the cone-shaped distribution plate of the lower bed. After the material is blown off from the upper layer, it enters the lower layer, where the dry hot nitrogen directly contacts the material, blowing away and carrying away the moisture to form a dried product. Finally, the dried product is continuously discharged through the rotary unloader 4 and sent to the next stage.

[0049] After the upper bed is stripped, the nitrogen gas containing pentane at a temperature of 80-90℃ and the nitrogen gas containing water vapor after the lower bed is dried converge at the top of the vertical fluidized bed 3 and enter the bag filter 5 together. The solid powder in the nitrogen gas is intercepted by the filter bag, and the powder flows back into the upper bed of the vertical fluidized bed 3 by gravity to avoid material loss.

[0050] The wet nitrogen gas purified by the bag filter 5 enters the primary cooler 6 and the secondary cooler 7 in sequence. It is indirectly condensed by using chilled water with a pressure of 0.4 MPa, a temperature of -15℃ and a concentration of 50% ethylene glycol aqueous solution (when the primary cooler 6 and the secondary cooler 7 are used in series, the chilled water return pressure is 0.2 MPa and the temperature is -10℃) to reduce the temperature of the nitrogen gas to 0-5℃, and precipitate trace amounts of water and a small amount of pentane.

[0051] The cooled nitrogen gas returns to the inlet of the circulating fan 8 and re-enters the circulation. The trace amounts of water and small amounts of pentane mixture generated by condensation flow into the solvent collection tank 15 for buffering through a pressure valve.

[0052] Of the nitrogen output from the circulating fan 8, another stream of pentane-containing nitrogen directly enters the Roots blower 10. After being further pressurized by the Roots blower 10, it is sent to the condensation system. The pressurized nitrogen is sequentially fed into the first-stage condenser 11, the second-stage condenser 12, and the third-stage condenser 13. The second-stage condenser 12 is supplied with -50℃ refrigerant by the refrigeration unit 14. The first-stage condenser 11 and the third-stage condenser 13 are cooled in cascade with liquid nitrogen at a temperature of -100℃ (liquid nitrogen first enters the third-stage condenser 13, and after heat exchange, it enters the first-stage condenser 11 with liquid nitrogen at a temperature of -60℃). More than 95% of the gaseous pentane in the nitrogen is condensed into liquid phase and flows into the solvent collection tank 15 for buffering through pipelines.

[0053] After three-stage condensation, nitrogen gas containing 5% trace pentane enters adsorption tower 17 through a pressure valve. Adsorption tower 17 is a dual-tower parallel structure, filled with activated carbon. It operates by switching between adsorption and regeneration in one tower to ensure continuous purification.

[0054] After adsorption and purification, the nitrogen enters the reheater 18 and is indirectly heated to 80-90°C by saturated steam at a pressure of 0.3 MPa and a temperature of 145°C. The nitrogen is then returned to the conical distribution plate of the lower bed of the vertical fluidized bed 3 through a pipeline. When a certain adsorption tower, such as tower A, becomes saturated, the system switches to regeneration mode and starts the vacuum pump 19. The saturated pentane in the pores of the activated carbon is vacuum-extracted through the regeneration port of the adsorption tower 17. The extracted gaseous pentane is returned to the inlet of the Roots blower 10 and re-enters the condensation system for recovery.

[0055] After vacuum suction is completed, the adsorption tower 17 is purged with compressed nitrogen gas at a pressure of 0.6 MPa and a temperature of 25°C. The purging gas is also returned to the inlet of the Roots blower 10, and the nitrogen gas lost in the system is replenished at the same time. After regeneration, it is ready for use.

[0056] When the liquid pentane in the solvent collection tank 15 reaches the set level, the solvent transfer pump 16 is started to pressurize the recovered liquid pentane and send it back to the solvent storage tank of the ultra-high molecular weight polyethylene polymerization process through the pipeline, thus completing the recycling of pentane solvent and reducing raw material waste.

[0057] The present invention has been described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvement made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, shall be within the protection scope of the present invention.

Claims

1. A polyethylene nitrogen circulation stripping, drying and solvent recovery device, comprising a stripping and drying unit (1) and a recovery and purification unit (2), characterized in that: The stripping and drying unit (1) includes a vertical fluidized bed (3), a rotary unloader (4) and a bag filter (5). The rotary unloader (4) and the bag filter (5) are connected to both ends of the vertical fluidized bed (3) through pipes. A primary cooler (6) and a secondary cooler (7) are arranged in sequence on one side of the bag filter (5). The secondary cooler (7) is located on the side away from the bag filter (5). A circulating fan (8) is arranged on one side of the secondary cooler (7). The recycling and purification unit (2) includes a Roots blower (10), an adsorption tower (17), a solvent collection tank (15), and a vacuum pump (19), as well as a condenser group consisting of a primary condenser (11), a secondary condenser (12), and a tertiary condenser (13). The Roots blower (10) is connected to a circulating fan (8) through a nitrogen pipeline. The primary condenser (11) is connected to the Roots blower (10) through a pipeline. The tertiary condenser (13) is connected to the adsorption tower (17) through a pipeline. The solvent collection tank (15) is connected to the condenser group through a pipeline.

2. The polyethylene nitrogen circulation stripping, drying, and solvent recovery device according to claim 1, characterized in that: The vertical fluidized bed (3) is a double-layer vertical cylindrical structure, including an upper bed layer and a lower bed layer. The bottom of the upper bed layer is provided with an annular distribution plate, and the bottom of the lower bed layer is provided with a conical distribution plate. The top of the vertical fluidized bed (3) is provided with a mixed gas outlet connected to the inlet of the bag filter (5), and the bottom is provided with a material outlet connected to the inlet of the rotary unloader (4).

3. The polyethylene nitrogen circulating stripping, drying, and solvent recovery device according to claim 1, characterized in that: The bottom of the bag filter (5) is provided with a powder return port, which is connected to the upper bed of the vertical fluidized bed (3) through a pipe. The outlet of the bag filter (5) is connected to the inlet of the primary cooler (6) through a pipe. The outlet of the primary cooler (6) is connected to the inlet of the secondary cooler (7) through a pipe. The outlet of the secondary cooler (7) is connected to the inlet of the circulating fan (8) through a pipe. The inlet of the primary cooler (6) and the inlet of the secondary cooler (7) are connected to the outlet of the bag filter (5) through pipes, and the outlet of the primary cooler (6) and the outlet of the secondary cooler (7) are connected to the inlet of the circulating fan (8) through pipes.

4. The polyethylene nitrogen circulation stripping, drying, and solvent recovery device according to claim 1, characterized in that: The stripping and drying unit (1) also includes a heater (9). The outlet end of the heater (9) is divided into two pipelines. One pipeline is connected to the upper bed of the vertical fluidized bed (3) and the other pipeline is connected to the lower bed of the vertical fluidized bed (3). The outlet end of the circulating fan (8) is divided into two pipelines. One pipeline is connected to the inlet of the heater (9) and the other pipeline is connected to the inlet of the Roots blower (10).

5. The polyethylene nitrogen circulating stripping, drying, and solvent recovery device according to claim 1, characterized in that: The recycling and purification unit (2) also includes a refrigeration unit (14) and a solvent transfer pump (16). The refrigeration unit (14) is connected to the secondary condenser (12) through a refrigerant pipeline, and the outlet of the solvent collection tank (15) is connected to the inlet of the solvent transfer pump (16) through a pipeline.

6. The polyethylene nitrogen circulating stripping, drying and solvent recovery device according to claim 1, characterized in that: The outlet of the first-stage condenser (11) is connected to the inlet of the second-stage condenser (12) via a pipe, and the outlet of the second-stage condenser (12) is connected to the inlet of the third-stage condenser (13) via a pipe. The inlet of the primary condenser (11), the inlet of the secondary condenser (12), and the inlet of the tertiary condenser (13) are all connected to the outlet of the Roots blower (10) via pipes.

7. The polyethylene nitrogen circulating stripping, drying and solvent recovery device according to claim 1, characterized in that: The recycling and purification unit (2) also includes a reheater (18). The adsorption tower (17) is a dual-tower parallel structure, including tower A and tower B. Both tower A and tower B are filled with activated carbon. The outlet of the adsorption tower (17) is connected to the inlet of the reheater (18) through a pipe. The outlet of the reheater (18) is connected to the lower bed of the vertical fluidized bed (3) through a pipe.

8. The polyethylene nitrogen circulating stripping, drying and solvent recovery device according to claim 1, characterized in that: The inlet of the vacuum pump (19) is connected to the regeneration port of the adsorption tower (17) through a pipe, and the outlet of the vacuum pump (19) is connected to the inlet of the Roots blower (10) through a pipe.

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