Refining device and refining system for ultra-clean polypropylene

Abstract

The utility model discloses a refining device and a refining system for ultra-clean polypropylene. The refining device comprises a slurry premixing tank, a washing container, a centrifugal filter, a solvent recovery tower, a reflux tank, a fluidized bed dryer and a gas-liquid separator. According to the device, materials and energy are fully recycled, ash such as metal substances and oligomer entrained by polypropylene powder can be effectively reduced, and even electrical-grade polypropylene can be obtained. According to the utility model, on the premise of obtaining a refined polypropylene product, environment-friendly, low-consumption and stable long-period operation can be realized.

Description

TECHNICAL FIELD

[0001] The utility model belongs to polypropylene technical field relates to a kind of refining device and refining system of super-clean polypropylene. BACKGROUND

[0002] Polypropylene has the advantages of small relative density, good chemical resistance, good water resistance, etc., and also has good mechanical strength, electrical insulation and other characteristics, and can be applied to films, pipes, boards, various shaped products, wires and cables, etc., and has wide applications in agriculture, packaging, electronics, electrical, automotive, machinery, daily sundries and other fields.

[0003] Under certain temperature and pressure conditions, propylene monomer is polymerized into polypropylene powder through the action of main catalyst and cocatalyst. After the polypropylene powder comes out of the reactor, in addition to qualified polypropylene products, it also carries metal substances brought by the main catalyst and cocatalyst and low molecular polymers generated during the reaction. This low molecular polymer is compared with the molecular weight of polypropylene, usually with a molecular weight of several hundred to several thousand. These metal substances and low molecular weight products must be removed in the production of super-clean polypropylene, otherwise they can easily cause the filter screen of the extruder to be blocked, even cause short circuit when producing electrical products, and even cause fire.

[0004] Removing the ash and oligomers containing metal substances generated by the catalyst in polypropylene is a technical difficulty in the production of super-clean polypropylene products. Currently, China's imported high-end electrical film polypropylene uses washing to remove ash to obtain polypropylene raw materials with low ash content, and the ash content can be controlled below 20 ppm. Domestic polypropylene raw materials mainly reduce ash content through high-efficiency catalysts, optimized process conditions and additive formulations, and the ash content is usually controlled at 40-60 ppm, which cannot meet the requirements of high-end electrical special materials, resulting in long-term dependence on imports. Therefore, domestic research on washing devices is carried out to remove unnecessary ash from polymer powder. Currently, the most representative polypropylene powder washing devices are CN 114014960 B, CN 114011103 B, CN 117619286 A and CN 220425355 U, etc.

[0005] The washing devices of CN 114014960 B and CN 114011103 B are basically the same, both of which wash the polypropylene powder from the polymerization reaction with the washing solution in the washing tower in a countercurrent contact manner to achieve the purpose of removing ash. However, this flow mode causes high slurry concentration at the bottom of the washing container, which may block the bottom outlet of the washing container during continuous industrial operation, affecting the long-period stable operation of the device. In addition, the uneven distribution of slurry concentration affects the washing effect of polypropylene powder.

[0006] The washing and separation in the CN 117619286 A patent application are completed in a rotating filter press device. The polymerization process adopts a slurry method to produce polyolefin. The washing solvent and the polyolefin material from the polymerization reaction enter the washing filter press device together. Under the protection of nitrogen pressure, the washing and solid-liquid separation are completed. However, the filter press device is easily blocked by low molecular weight substances and polyolefin powder in the polymer, and needs to be cleaned regularly. The liquid used for cleaning is water. The sensitivity of the catalyst and the main catalyst to water is very high in the polyolefin process, which leads to an increase in the cost of the material refining system and a shortening of the operation cycle, and thus is not conducive to the continuous production of polyolefin.

[0007] The CN 220425355 U patent uses two vertically arranged screw rods to achieve the washing effect. The vertically arranged screw rod functions to mix and convey the mixture of polyolefin powder and washing solution. The horizontally arranged screw rod functions to heat, convey and wash. The disadvantages of the patent are that the vertically arranged screw rod is prone to sticking to low molecular weight polymers when conveying the slurry, and the rotation of the screw rod deteriorates with the extension of the running time, so that the device needs to be stopped for inspection and repair in time. In the horizontally arranged screw rod, the flow rate of the slurry is low, and the solid particles in the slurry are prone to accumulate on the wall, leading to a shortening of the running cycle. Practical new type content

[0008] To improve the above technical problems, the utility model provides a kind of refining device of super-clean polypropylene, comprising: slurry premixing tank, washing container, centrifugal filter, solvent recovery tower, reflux tank, fluidized bed dryer and gas-liquid separator;

[0009] The top of the slurry premixing tank is provided with a polypropylene powder inlet and a washing solvent inlet, and an internal agitator is arranged, and the bottom is connected with the slurry inlet of the washing container through a slurry circulating discharge pump;

[0010] The bottom of the washing container is connected with the centrifugal filter through a discharge pump;

[0011] The centrifugal filter comprises a solid phase outlet end and a liquid phase outlet end, the solid phase outlet end is connected with the fluidized bed dryer, and the liquid phase outlet end is connected with the solvent recovery tower;

[0012] The top of the solvent recovery tower is provided with the reflux tank, and the bottom of the reflux tank is connected with the washing solvent inlet;

[0013] The fluidized bed dryer comprises a gas phase outlet end, and the gas phase outlet end is connected with the gas-liquid separator;

[0014] The gas-liquid separator comprises a liquid outlet end, and the liquid outlet end is connected with the slurry premixing tank.

[0015] According to the embodiment of the utility model, the slurry circulating discharge pump is also connected to the top of the slurry premixing tank, that is, the slurry is circulated to make the polypropylene and the washing solution fully contact and mix; preferably, a first cooler is arranged on the connecting pipeline of the two.

[0016] According to the embodiment of the utility model, a first heater is arranged on the connecting pipeline of the bottom of the slurry premixing tank and the slurry inlet of the washing container, for heating the slurry to make the temperature of the washing container reach the set washing temperature, so as to ensure the washing effect. The slurry inlet of the washing container is arranged at the top of the washing container.

[0017] According to the embodiment of the utility model, a double-layer stirrer is arranged in the washing container to make the slurry and the washing solvent fully mix and uniformly.

[0018] According to the embodiment of the utility model, a second cooler is arranged on the connecting pipeline of the discharge pump and the centrifugal filter, for cooling the feed.

[0019] According to the embodiment of the utility model, the refining device further comprises a conveyor arranged at the solid-phase outlet end of the centrifugal filter, for conveying the solid-phase material to the fluidized bed dryer.

[0020] According to the embodiment of the utility model, the refining device further comprises a mother liquor collecting tank, one end of which is connected to the liquid-phase outlet end of the centrifugal filter, and one end of which is connected to the middle part of the solvent recovery column.

[0021] According to the embodiment of the utility model, the refining device further comprises a first condenser, one end of which is connected to the top of the solvent recovery column, and one end of which is connected to the reflux tank.

[0022] According to the embodiment of the utility model, the refining device further comprises a flash tank, the bottom of the solvent recovery column is connected to the flash tank, and preferably a second heater is arranged on the connecting pipeline of the two.

[0023] According to the embodiment of the utility model, the refining device further comprises a second condenser and a flash gas-phase condensing tank; one end of the second condenser is connected to the gas-phase outlet of the flash tank, and the other end is connected to the material inlet of the flash gas-phase condensing tank; the liquid-phase outlet of the flash gas-phase condensing tank is connected to the solvent recovery column.

[0024] According to some embodiments of the present application, the refining device further comprises a cyclone separator arranged above the fluidized bed dryer, a gas phase outlet end of the fluidized bed dryer is connected with a material inlet of the cyclone separator, a gas outlet of the cyclone separator is connected with the gas-liquid separator, and a solid outlet of the cyclone separator is communicated with the fluidized bed dryer. Preferably, a third cooler is arranged on a connecting pipeline between the gas outlet of the cyclone separator and the gas-liquid separator.

[0025] According to embodiments of the present application, the gas outlet of the gas-liquid separator is connected with the fluidized bed dryer, and preferably a circulating nitrogen air blower and / or a third heater are arranged on a connecting pipeline between the two.

[0026] According to embodiments of the present application, a pump body can be arranged on the pipeline as needed by those skilled in the art.

[0027] The present application also provides a refining system for super-clean polypropylene, which comprises the above refining device and a polypropylene powder preparation device. Further, the refining system further comprises a preparation device for washing solvent.

[0028] Beneficial effects:

[0029] The present application provides a refining device for super-clean polypropylene powder, which can make the polypropylene powder and the washing solvent enter a slurry premixing tank in a co-current manner, i.e., by gravity. The agitator in the slurry premixing tank prevents the accumulation of solid materials in the tank, which causes poor discharge and uneven mixing. The premixed slurry is discharged by a slurry circulating discharge pump, which not only solves the problem that the slurry cannot enter the washing container by gravity, but also circulates the slurry to make the polypropylene and the washing solvent fully contact and mix. At the same time, the arrangement of the centrifugal filter, the solvent recovery tower, the reflux tank, the fluidized bed dryer and the gas-liquid separator realizes the full recovery and recycling of materials and energy, and effectively reduces the ash content, oligomers and other metal substances carried by the polypropylene powder, and even super-clean polypropylene can be obtained.

[0030] In summary, the present application can realize long-period stable operation with low energy consumption and environmental protection on the premise of obtaining super-clean polypropylene products. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The structure diagram of the refining device for super-clean polypropylene provided for the embodiments is shown in the figure.

[0032] Reference numerals: 1. Slurry premixing tank; 2. Agitator; 3. First cooler; 4. Slurry circulation discharge pump; 5. First heater; 6. Double-layer agitator; 7. Washing container; 8. Washing container discharge pump; 9. Second cooler; 10. Centrifugal filter; 11. Conveyor; 12. Mother liquor collection tank; 13. Solvent recovery tower feed pump; 14. Preheater; 15. Solvent recovery tower; 16. First condenser; 17. Reflux tank; 18. Solvent recovery tower top reflux pump ; 19. Solvent recovery tower bottom discharge pump; 20. Second heater; 21. Flash tank; 22. Second condenser; 23. Flash vapor phase condenser discharge pump; 24. Flash vapor phase condenser; 25. Solvent recovery tower bottom circulation pump; 26. Solvent recovery tower reboiler; 27. Fluidized bed dryer; 28. Cyclone separator; 29. ​​Third heater; 30. Circulating nitrogen blower; 31. Gas-liquid separator; 32. Third cooler; 33. Gas-liquid separator discharge pump;

[0033] a-Polypropylene powder, b-Washing solvent. Detailed Implementation

[0034] The technical solution of this utility model will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only illustrative and explanatory of this utility model, and should not be construed as limiting the scope of protection of this utility model. All technologies implemented based on the above content of this utility model are covered within the scope of protection intended by this utility model.

[0035] Example 1

[0036] like Figure 1 The purification apparatus for ultra-clean polypropylene shown includes:

[0037] The slurry premixing tank 1, washing container 7, centrifugal filter 10, conveyor 11, mother liquor collection tank 12, solvent recovery tower 15, first condenser 16, reflux tank 17, flash tank 21, second condenser 22, fluidized bed dryer 27, cyclone separator 28 and gas-liquid separator 31;

[0038] The top of the slurry premixing tank 1 is equipped with a polypropylene powder inlet and a washing solvent inlet. An agitator 2 is installed inside. The bottom is connected to the slurry inlet of the washing container 7 via a slurry circulation pump 4. A first heater 5 is installed on the connecting pipeline between the slurry circulation pump 4 and the slurry inlet of the washing container 7 to heat the slurry, ensuring the washing container reaches the set washing temperature and guaranteeing the washing effect. The slurry circulation pump 4 is also connected to the top of the slurry premixing tank 1, circulating the slurry to ensure thorough contact and mixing of the polypropylene and the washing solution. Furthermore, a first cooler 3 is installed on the connecting pipeline between the slurry circulation pump 4 and the top of the slurry premixing tank 1.

[0039] The inside of the washing container 7 is provided with a double-layer agitator 6 to mix the slurry and the washing solvent thoroughly. The bottom of the washing container 7 is connected with a centrifugal filter 10 through a washing container discharge pump 8. A second cooler 9 is arranged on the connecting pipeline between the washing container 7 and the centrifugal filter 10 to cool the feed.

[0040] The centrifugal filter 10 comprises a solid phase outlet end and a liquid phase outlet end. The solid phase outlet end is connected with a fluidized bed dryer 27 through a conveyor 11. The liquid phase outlet end is connected with a mother liquor collecting tank, which is connected with a solvent recovery tower 15 through a solvent recovery tower feed pump 13 and a preheater 14.

[0041] A first condenser 16 is arranged at the top of the solvent recovery tower 15. One end of the first condenser 16 is connected with the top of the solvent recovery tower 15, and the other end is connected with a reflux tank 17. The bottom of the reflux tank 17 is connected with the washing solvent inlet through a solvent recovery tower top reflux pump 18.

[0042] A solvent recovery tower tank discharge pump 19 is arranged at the bottom of the solvent recovery tower 15, which is connected with a flash tank 21 through a second heater 20.

[0043] A solvent recovery tower tank circulation pump 25 and a solvent recovery tower reboiler 26 are arranged at the bottom of the solvent recovery tower 15 to form a loop at the bottom.

[0044] A second condenser 22 is arranged at the top of the flash tank 21 (i.e. the gas phase outlet). One end of the second condenser 22 is connected with a flash gas phase condensing tank 24, and the other end is connected with the material inlet of the flash gas phase condensing tank 24.

[0045] The bottom of the flash gas phase condensing tank 24 (i.e. the liquid phase outlet) is connected with the solvent recovery tower 15 through a flash gas phase condensing tank discharge pump 23.

[0046] A cyclone separator 28 is arranged above the fluidized bed dryer 27. The gas outlet of the fluidized bed dryer 27 is connected with the material inlet of the cyclone separator 28. The gas outlet of the cyclone separator 28 is connected with a gas-liquid separator 31. The solid outlet of the cyclone separator 28 is connected with the fluidized bed dryer 27. A third cooler 32 is arranged on the connecting pipeline between the gas outlet of the cyclone separator 28 and the gas-liquid separator 31. The liquid outlet end of the gas-liquid separator 31 is connected with the slurry pre-mixing tank 1 through a gas-liquid separator discharge pump 33, so as to realize the recycling and utilization of the washing solvent. The gas outlet of the gas-liquid separator 31 is connected with the fluidized bed dryer 27. A circulating nitrogen blower 30 and a third heater 29 are further arranged on the connecting pipeline between the gas-liquid separator 31 and the fluidized bed dryer 27.

[0047] The product polypropylene powder a from the polymerization reaction entrains metal substances, oligomers, propylene, etc., which is fed into the slurry premix tank 1, and the prepared washing solvent b is fed into the slurry premix tank 1 in a countercurrent manner with the polypropylene powder a, and the slurry premix tank 1 is provided with a stirrer 2 and a slurry circulating discharge pump 4 for sufficient contact and mixing. The slurry is fed into the washing vessel 7 by the slurry circulating discharge pump 4, and a first heater 5 is provided on the washing vessel feed line to maintain the required temperature for washing, and the slurry is heated to 70-100°C before entering the washing vessel 7. The washing vessel 7 is provided with a double-layer stirrer 6 for sufficient mixing, and after the required washing time of 2-4h is reached, the slurry formed is discharged from the washing vessel 7 into the washing vessel discharge pump 8, which is fed into the centrifugal filter 10 for centrifugal drying. The liquid material separated from the centrifugal filter 10 is fed into the mother liquor collecting tank 12, and is fed into the solvent recovery tower 15 by the solvent recovery tower feed pump 13, and the washing solvent is evaporated in the solvent recovery tower. The overhead material of the solvent recovery tower 15 is the clean washing solvent, which is cooled by the first condenser 16 and fed into the reflux tank 17, and is returned to the slurry premix tank 1; the bottom material of the solvent recovery tower 15 is heated by the second heater 20 to flash evaporation, and is separated in the flash tank 21, and the gaseous washing solvent is cooled and fed into the flash gas phase condenser tank 24, and is returned to the solvent recovery tower 15 by the flash gas phase condenser tank discharge pump 23 for recycling; the liquid phase slurry is discharged into the waste liquid collecting tank, and is discharged or treated by the corresponding treatment facilities outside the device. The solid material separated from the centrifugal filter 10 is fed into the fluidized bed dryer 27, and hot nitrogen gas is used to further dry the polypropylene powder in the fluidized bed dryer 27, so as to completely separate the washing solvent entrained in the polypropylene powder from the polypropylene. The nitrogen gas used in the fluidized bed dryer 27 needs to be recycled. The make-up nitrogen gas and the recycled nitrogen gas are heated to 100-130°C by the third heater 29 and are fed into the bottom of the fluidized bed dryer 27, and the hot nitrogen gas evaporates the washing solvent entrained in the polypropylene, so as to achieve the separation purpose. The hot nitrogen gas separated from the washing solvent is first fed into the cyclone separator 28, and the hot nitrogen gas entrained polypropylene fine powder is filtered out, and the polypropylene fine powder returns to the fluidized bed dryer 27 by gravity flow. The filtered gas is cooled by the third cooler 32, and the washing solvent entrained in the nitrogen gas is condensed and fed into the gas-liquid separator 31, and the liquid phase in the gas-liquid separator 31 is the washing solvent, which is returned to the slurry premix tank 1 by the gas-liquid separator discharge pump 33; the gas phase in the gas-liquid separator 31 is pressurized by the circulating nitrogen gas blower 30 and is heated to 100-130°C by the third heater 29, and is returned to the fluidized bed dryer 27, so as to achieve the purpose of recycling. The dried powder in the fluidized bed dryer 27 is the polypropylene product almost free of washing solvent, which is fed into the downstream extrusion granulation system through the solid material conveying pipeline.The device can effectively reduce the ash such as metal substances and oligomers entrained by the polypropylene powder, and realizes full recycling and reuse of the material and energy.

[0048] Embodiment 2

[0049] Use Figure 1 The device is used for mixing 75kg / h polypropylene powder (with 1% oligomer content and 63ppm metal substance content) and 225kg / h washing solvent in the slurry premixing tank under the action of the stirrer and the premixing tank circulating discharge pump, and then the mixture is sent to the washing container through the premixing tank circulating discharge pump, the washing temperature is set to 80℃, and the washing process lasts for 3h. The mass ratio of the polypropylene powder to the washing solvent is 1:3, and the washing solvent is n-hexane:isopropyl alcohol=3:1 (mass ratio). After the slurry leaving the washing container passes through the separation, drying and recycling units, the product polypropylene is sampled and analyzed, and the obtained results are as follows: the metal substance content in the washed polypropylene is 17ppm, the oligomer content is 13ppm, and the isotacticity is 98.3%. The technical indexes of the product polypropylene completely reach the technical indexes of the superior product of the electrical grade polypropylene required by the state.

[0050] Embodiment 3

[0051] The polypropylene refining system comprises the refining device of embodiment 1 and a polypropylene powder preparation device.

[0052] In some embodiments, the refining system further comprises a washing solvent preparation device connected with the slurry premixing tank.

[0053] The above describes the embodiments of the present application. However, the present application is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A finishing device for super-clean polypropylene, characterized in that, The refining device comprises a slurry premixing tank, a washing vessel, a centrifugal filter, a solvent recovery column, a reflux tank, a fluidized bed dryer and a gas-liquid separator; The top of the slurry premixing tank is provided with a polypropylene powder inlet and a washing solvent inlet, and an internal agitator is arranged therein, and the bottom is connected with the slurry inlet of the washing vessel through a slurry circulating discharge pump; The bottom of the washing vessel is connected with the centrifugal filter through a discharge pump; The centrifugal filter comprises a solid phase outlet end and a liquid phase outlet end, the solid phase outlet end is connected with the fluidized bed dryer, and the liquid phase outlet end is connected with the solvent recovery column; The top of the solvent recovery column is provided with the reflux tank, and the bottom of the reflux tank is connected with the washing solvent inlet; The fluidized bed dryer comprises a gas phase outlet end, and the gas phase outlet end is connected with the gas-liquid separator; The gas-liquid separator comprises a liquid outlet end, and the liquid outlet end is connected with the slurry premixing tank.

2. The finishing apparatus according to claim 1, characterized by The slurry circulating discharge pump is also connected with the top of the slurry premixing tank, and a first cooler is arranged on the connecting pipeline between the two. And / or, a first heater is arranged on the connecting pipeline between the bottom of the slurry premixing tank and the slurry inlet of the washing vessel.

3. The finishing apparatus according to claim 1, characterized by A double-layer agitator is arranged in the washing vessel.

4. The finishing apparatus according to claim 1, wherein A second cooler is arranged on the connecting pipeline between the discharge pump and the centrifugal filter; And / or, the gas outlet of the gas-liquid separator is connected with the fluidized bed dryer, and a circulating nitrogen air blower and / or a third heater are arranged on the connecting pipeline between the two.

5. The finishing apparatus according to claim 1, wherein The refining device further comprises a conveyor arranged at the solid phase outlet end of the centrifugal filter; And / or, the refining device further comprises a mother liquor collecting tank connected with the liquid phase outlet end of the centrifugal filter at one end and connected with the middle part of the solvent recovery column at the other end; And / or, the refining device further comprises a first condenser connected with the top of the solvent recovery column at one end and connected with the reflux tank at the other end.

6. The finishing apparatus according to claim 1, wherein The refining device further comprises a flash tank, and the bottom of the solvent recovery column is connected with the flash tank, and a second heater is arranged on the connecting pipeline between the two.

7. The finishing apparatus according to claim 6, wherein The refining device further comprises a second condenser and a flash gas phase condensing tank; one end of the second condenser is connected with the gas phase outlet of the flash tank, and the other end is connected with the material inlet of the flash gas phase condensing tank; the liquid phase outlet of the flash gas phase condensing tank is connected with the solvent recovery column.

8. The finishing apparatus of claim 1, wherein The refining device further comprises a cyclone separator arranged above the fluidized bed dryer, the gas phase outlet end of the fluidized bed dryer is connected with the material inlet of the cyclone separator, the gas outlet of the cyclone separator is connected with the gas-liquid separator, and the solid outlet of the cyclone separator is in communication with the fluidized bed dryer.

9. The finishing apparatus of claim 8, wherein A third cooler is arranged on the connecting pipeline between the gas outlet of the cyclone separator and the gas-liquid separator.

10. A finishing system for super-clean polypropylene, characterized by, The refining system comprises the refining device of any one of claims 1-9 and a polypropylene powder preparation device, or further comprises a washing solvent preparation device.

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