Process system for producing ultra-clean polypropylene

Abstract

The utility model discloses a process system for producing ultra-clean polypropylene. The process system comprises a polymerization system and a post-treatment system positioned at the downstream of the polymerization system, the polymerization system comprises a prepolymerization reactor, a first polymerization reactor and a second polymerization reactor; the post-treatment system comprises a flash evaporation unit, a steaming unit, a drying unit and a washing unit. By utilizing the process system, the ultra-clean polypropylene can be prepared.

Description

Technical Field

[0001] This utility model belongs to the field of polypropylene, and specifically relates to a process system for producing ultra-clean polypropylene. Background Technology

[0002] Polypropylene (PP) is one of the fastest-growing commercial plastics in recent years. It is a widely used polymer material and is known for its light weight, cleanliness, high rigidity, and high transparency among polyolefins.

[0003] Polypropylene powder obtained from polymerization reactors typically contains metallic substances from the main catalyst and co-catalyst, as well as low-molecular-weight polymers generated during the reaction. The presence of these metallic substances and low-molecular-weight polymers makes polypropylene susceptible to short circuits and even fires when used as an electrical material. Therefore, polypropylene must be purified in the production of electrical-grade polypropylene to obtain ultra-clean polypropylene (polypropylene isotacticity ≥98%, ash content ≤20ppm, and oligomers <0.5%).

[0004] The present invention aims to provide a process system for producing ultra-clean polypropylene. Utility Model Content

[0005] To improve the above-mentioned technical problems, this utility model provides a process system for producing ultra-clean polypropylene, including a polymerization system and a post-processing system located downstream of the polymerization system, wherein the post-processing system is used to process the polymerization product obtained by the polymerization system;

[0006] The polymerization system includes a prepolymerization reactor, a first polymerization reactor, and a second polymerization reactor;

[0007] The post-processing system includes:

[0008] A flash unit, located downstream of the second polymerization reactor, includes a flash tower for removing liquid propylene from the second polymerization product;

[0009] The steaming unit, located downstream of the flash unit and upstream of the drying unit, includes a steaming tower that uses steam to remove propylene entrained in polypropylene powder and simultaneously deactivate the catalyst.

[0010] The drying unit, located downstream of the steaming unit, includes a degassing tower. The degassing tower is provided with a polypropylene powder inlet and a nitrogen inlet. The positions of the polypropylene powder inlet and the nitrogen inlet meet the requirement of counter-current flow of polypropylene powder and nitrogen.

[0011] A washing unit, located downstream of the drying unit, is used to wash the polypropylene powder obtained from the drying unit, and includes a slurry premixing tank and a washing tank disposed downstream of the slurry premixing tank.

[0012] The slurry premixing tank is equipped with a polypropylene powder inlet and a washing solvent inlet, and the positions of the polypropylene powder inlet and the washing solvent inlet meet the requirements for co-current mixing of polypropylene powder and washing solvent.

[0013] According to an embodiment of this utility model, the prepolymerization reactor is provided with a raw material inlet, a catalyst (main catalyst and co-catalyst) inlet, an electron donor inlet, and a propylene prepolymer outlet. Alternatively, the prepolymerization reactor may further be provided with an activator inlet. Those skilled in the art can set the number of inlets as needed; for example, two or more of the catalyst inlet, electron donor inlet, and activator inlet can be combined into one inlet, or they can be set as independent inlets.

[0014] According to an embodiment of this utility model, the prepolymerization reactor is a batch reactor with an internal stirrer.

[0015] According to an embodiment of the present invention, the first polymerization reactor is provided with a propylene prepolymer inlet, a raw material inlet, and a first polymerization product outlet, wherein the propylene prepolymer outlet is connected to the propylene prepolymer inlet of the first polymerization reactor.

[0016] According to an embodiment of the present invention, the second polymerization reactor is provided with a first polymerization product inlet, a raw material inlet, and a second polymerization product outlet, wherein the first polymerization product outlet is connected to the first polymerization product inlet.

[0017] According to the embodiments of this utility model, both the first polymerization reactor and the second polymerization reactor are loop reactors.

[0018] According to the embodiments of this utility model, the raw material inlet is used to introduce fresh propylene and hydrogen into the polymerization reactor. It can be set as one inlet or as two independent inlets: a propylene inlet and a hydrogen inlet.

[0019] According to an embodiment of this utility model, the slurry premixing tank is equipped with an agitator for mixing polypropylene powder and washing solvent.

[0020] According to an embodiment of this utility model, the slurry premixing tank is provided with a premixed slurry outlet.

[0021] According to an embodiment of this utility model, the washing tank is provided with a premixed slurry inlet and connected to the premixed slurry outlet; furthermore, a heater can be provided on the connecting pipe between the premixed slurry inlet and the premixed slurry outlet to heat the premixed slurry, so that the temperature reaches the set washing temperature, thereby reducing the ash, oligomers, and other metal substances entrained in the polypropylene powder.

[0022] According to an embodiment of this utility model, the washing tank is equipped with an agitator, preferably a double-layer agitator, to ensure that the slurry and washing solvent are fully and evenly mixed.

[0023] According to an embodiment of this utility model, the flash tower is provided with a feed inlet, a gas phase outlet, and a solid phase outlet. The outlet of the second polymerization reaction product is connected to the feed inlet of the flash tower. The gas phase outlet collects unreacted propylene, and the solid phase outlet collects polypropylene powder. Furthermore, an antistatic agent inlet is provided on the connecting pipeline between the outlet of the second polymerization reaction product and the feed inlet of the flash tower. The antistatic agent can prevent static electricity buildup in the reaction products, improving product quality stability and safety during use.

[0024] According to the embodiment of this utility model, the steam tower is provided with a polypropylene powder inlet, a steam inlet and a polypropylene powder outlet. The polypropylene powder collected from the solid phase outlet of the flash tower enters the steam tower through the polypropylene powder inlet, and the propylene entrained in the powder is removed by water steam, while the catalyst is deactivated at the same time.

[0025] According to an embodiment of the present invention, the post-processing system further includes a centrifugation unit disposed downstream of the washing unit for separating polypropylene and washing solvent.

[0026] According to an embodiment of this utility model, the post-processing system further includes a conveying unit disposed downstream of the centrifuge unit, for conveying the polypropylene separated by the centrifuge unit to the next unit. For example, the conveying unit includes a screw conveyor.

[0027] According to an embodiment of this utility model, the post-processing system further includes a fluidized bed drying unit, which is located downstream of the conveying unit, for removing the small amount of residual washing solvent in the polypropylene, thereby preventing residual solvent from producing an odor.

[0028] According to an embodiment of the present invention, the post-processing system further includes a storage unit located downstream of the fluidized bed drying unit for buffering materials.

[0029] According to an embodiment of the present invention, the post-processing system further includes a granulation unit disposed downstream of the storage unit.

[0030] According to an embodiment of the present invention, the granulation unit includes an extrusion granulation system and an air conveying system.

[0031] According to a preferred embodiment of the present invention, the process system for producing ultra-clean polypropylene includes a polymerization system and a post-processing system located downstream of the polymerization system, wherein the post-processing system is used to process the polymerization product obtained by the polymerization system.

[0032] The polymerization system includes a prepolymerization reactor, a first polymerization reactor, and a second polymerization reactor;

[0033] The post-processing system includes:

[0034] A flash unit, located downstream of the second polymerization reactor, includes a flash tower for removing liquid propylene from the second polymerization product;

[0035] The steaming unit, located downstream of the flash evaporation unit, includes a steaming tower that uses steam to remove propylene entrained in polypropylene powder and simultaneously deactivate the catalyst.

[0036] The drying unit, located downstream of the steaming unit, includes a degassing tower. The degassing tower is provided with a polypropylene powder inlet and a nitrogen inlet. The positions of the polypropylene powder inlet and the nitrogen inlet meet the requirement of counter-current flow of polypropylene powder and nitrogen.

[0037] A washing unit, located downstream of the drying unit, is used to wash the polypropylene powder obtained from the drying unit. It includes a slurry premixing tank and a washing tank located downstream of the slurry premixing tank. The slurry premixing tank is provided with a polypropylene powder inlet and a washing solvent inlet. The positions of the polypropylene powder inlet and the washing solvent inlet meet the requirements for co-current mixing of polypropylene powder and washing solvent.

[0038] A centrifuge unit, located downstream of the washing unit, is used to separate polypropylene and washing solvent;

[0039] A conveying unit, located downstream of the centrifuge unit, is used to convey the polypropylene separated by the centrifuge unit to the next unit;

[0040] A fluidized bed drying unit, located downstream of the conveying unit, is used to remove residual washing solvent from the polypropylene.

[0041] A storage unit is located downstream of the fluidized bed drying unit and is used to buffer materials;

[0042] The granulation unit is located downstream of the storage unit.

[0043] Those skilled in the art can install commonly used components such as pump bodies and valves on each connecting pipeline as needed.

[0044] The term "ultra-clean polypropylene" refers to polypropylene that meets the following parameter ranges:

[0045] a) The isotacticity of polypropylene is ≥98%;

[0046] b) Ash content in polypropylene ≤ 20 ppm;

[0047] c) The oligomer content in polypropylene is <0.5%.

[0048] Beneficial effects

[0049] The present invention provides a process system for producing polypropylene, consisting of a polymerization system and a post-processing system, which can produce ultra-clean polypropylene. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the process system for producing ultra-clean polypropylene in Example 1;

[0051] Figure reference numerals: 1-Prepolymerization reactor; 2-First polymerization reactor; 3-Second polymerization reactor; 4-Flash evaporator; 5-Steam evaporator; 6-Degassing evaporator; 7-Slurry premixing tank; 8-Washing tank; 9-Centrifuge unit; 10-Screw conveyor; 11-Fluidized bed drying unit; 12-Hopper; 13-Pneumatic conveying system; 14-Extrusion granulation system. Detailed Implementation

[0052] 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.

[0053] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0054] Example 1

[0055] like Figure 1 The process system for producing ultra-clean polypropylene shown consists of a polymerization system and a post-processing system located downstream of the polymerization system. The post-processing system is used to process the polymerization products obtained from the polymerization system.

[0056] The polymerization system includes a prepolymerization reactor 1, a first polymerization reactor 2, and a second polymerization reactor 3;

[0057] The prepolymerization reactor 1 is provided with a raw material inlet, a catalyst (main catalyst and co-catalyst) inlet, an electron donor inlet, and a propylene prepolymer outlet; or, the prepolymerization reactor 1 may further be provided with an activator inlet. Those skilled in the art can determine the number of inlets as needed; for example, two or more of the catalyst inlet, electron donor inlet, and activator inlet can be combined into one inlet, or they can be set as independent inlets.

[0058] Prepolymerization reactor 1 is a batch reactor with an internal stirrer;

[0059] The first polymerization reactor 2 is equipped with a propylene prepolymer inlet, a raw material inlet, and a first polymerization product outlet, with the propylene prepolymer outlet connected to the propylene prepolymer inlet;

[0060] The second polymerization reactor 3 is provided with a first polymerization product inlet, a raw material inlet, and a second polymerization product outlet, with the first polymerization product outlet connected to the first polymerization product inlet;

[0061] Both the first polymerization reactor 2 and the second polymerization reactor 3 are loop reactors;

[0062] The feed inlet is used to introduce fresh propylene and hydrogen into the polymerization reactor. It can be set as one feed inlet or as two independent feed inlets: a propylene feed inlet and a hydrogen feed inlet.

[0063] The post-processing system includes:

[0064] The flash evaporation unit, located downstream of the second polymerization reactor 3, includes a flash tower 4 for removing liquid propylene from the second polymerization product. The flash tower 4 has a feed inlet, a gas phase outlet, and a solid phase outlet. The outlet of the second polymerization product is connected to the feed inlet of the flash tower. The gas phase outlet collects unreacted propylene, and the solid phase outlet collects polypropylene powder. Furthermore, an antistatic agent inlet is provided on the connecting pipeline between the outlet of the second polymerization product and the feed inlet of the flash tower. The antistatic agent is used to deactivate the second polymerization product.

[0065] The steaming unit, located downstream of the flash unit, includes a steaming tower 5. The steaming tower 5 is equipped with a polypropylene powder inlet, a steam inlet, and a polypropylene powder outlet. The polypropylene powder collected from the solid phase outlet of the flash tower 4 enters the steaming tower through the polypropylene powder inlet. Water vapor is used to remove propylene entrained in the powder and deactivate the catalyst at the same time.

[0066] The drying unit, located downstream of the steaming unit, includes a degassing tower 6. The degassing tower 6 is equipped with a polypropylene powder inlet and a nitrogen inlet. The positions of the polypropylene powder inlet and the nitrogen inlet meet the requirement of countercurrent flow of polypropylene powder and nitrogen. For example, the polypropylene powder inlet is located at the top of the degassing tower, and the nitrogen inlet is located at the bottom of the degassing tower.

[0067] The washing unit, located downstream of the drying unit, is used to wash the polypropylene powder obtained from the drying unit, and includes a slurry premixing tank 7 and a washing tank 8 disposed downstream of the slurry premixing tank.

[0068] The slurry premixing tank 7 is equipped with a polypropylene powder inlet and a washing solvent inlet. The positions of the polypropylene powder inlet and the washing solvent inlet meet the requirements for co-current mixing of polypropylene powder and washing solvent. The slurry premixing tank 7 is equipped with an agitator inside for mixing polypropylene powder and washing solvent. The slurry premixing tank 7 is also equipped with a premixed slurry outlet.

[0069] The washing tank 8 is provided with a premixed slurry inlet and a premixed slurry outlet; furthermore, a heater can be provided on the connecting pipe between the premixed slurry inlet and the premixed slurry outlet to heat the premixed slurry and bring the temperature to the set washing temperature, thereby reducing the ash, oligomers, and other metal substances entrained in the polypropylene powder; the washing tank 8 is equipped with an agitator, preferably a double-layer agitator, to ensure that the slurry and washing solvent are fully and evenly mixed.

[0070] Centrifuge unit 9, located downstream of the washing unit, is used to separate polypropylene and washing solvent;

[0071] A conveying unit, located downstream of the centrifugal unit, includes a screw conveyor 10 for conveying the polypropylene separated by the centrifugal unit to the next unit.

[0072] The fluidized bed drying unit 11 is located downstream of the conveying unit and is used to remove the remaining washing solvent from the polypropylene.

[0073] A storage unit, located downstream of the fluidized bed drying unit, includes a silo 12 for buffering materials;

[0074] The granulation unit is located downstream of the storage unit and includes an extrusion granulation system 14 and an air conveying system 13.

[0075] Compared to other polymerization reaction systems or processes, this system has the following advantages:

[0076] 1. It has a higher reactor time-space production rate;

[0077] 2. The reactor has a simple structure and is easy to design and manufacture;

[0078] 3. The reactor has a small volume and short residence time, facilitating product switching;

[0079] 4. The polymer particles are suspended in the propylene liquid, and there is excellent heat transfer between the polymer and propylene;

[0080] 5. The slurry in the loop reactor is circulated at high speed using an axial flow pump, resulting in uniform distribution of polymer slurry and catalyst system, more precise control of reaction conditions, and more consistent product quality;

[0081] 6. The high polymer slurry concentration in the reactor results in a higher single-pass conversion rate, making it more suitable for the production of homopolymers.

[0082] Example 2

[0083] Ultra-clean polypropylene was prepared using the process system of Example 1:

[0084] Step 1: Propylene from the propylene oxide unit is used as the monomer raw material for polymerization. The propylene monomer is thoroughly mixed with the main catalyst, external electron donor and activator and then fed into the prepolymerization reactor 1 to generate polypropylene prepolymer.

[0085] The residence time (i.e., the reaction time in the prepolymerization reactor 1) is 5 to 15 minutes;

[0086] The addition rate of propylene monomer is 3.4 kg / h;

[0087] The main catalyst is a Ziegler-Natta catalyst. The solid main catalyst is uniformly dispersed in a mixture of industrial white oil and petrolatum (the mass ratio of white oil to petrolatum is 2:1) to form a paste catalyst. The concentration of the main catalyst is controlled at 22.1-53.5 g / L, and the addition flow rate is 0.5 g / h.

[0088] The external electron donor was (DONOR-C), the concentration of the external electron donor was 10 wt%, and the flow rate of the external electron donor was 0.9 g / h;

[0089] The activator was triethylaluminum (TEAL), with a concentration of 100% and a flow rate of 8.7 g / h.

[0090] Step 2: The polypropylene prepolymer obtained in Step 1, along with fresh propylene and hydrogen, is introduced into the first loop reactor 2 to continue the polymerization reaction, yielding the first polymerization product.

[0091] The residence time in the first loop reactor 2 is 55 min. The hydrogen concentration in the first loop reactor 2 is 200–500 ppm, the hydrogen flow rate is 15.5 g / h, the temperature is 70℃, the pressure is 3.4 MPa, and the propylene content is 56 wt%. The density of the first loop reactor is 540–550 kg / m³. 3 The fresh propylene flow rate was 73.9 kg / h.

[0092] Step 3: The polymer reactants obtained in Step 2, along with fresh propylene and hydrogen, are introduced into the second loop reactor 3 to continue the polymerization reaction, yielding the second polymerization product. The residence time in the second loop reactor 3 is 35 min, the hydrogen concentration is 200–500 ppm, the hydrogen flow rate is 8.0 g / h, the temperature is 70℃, the pressure is 3.4 MPa, and the propylene content is 46 wt%. The density of the second loop reactor is 540–550 kg / m³. 3 The fresh propylene flow rate is 40.1 kg / h.

[0093] Step 4: The second polymerization product obtained in Step 3 enters flash tower 4, where liquid propylene is removed by flash evaporation. Simultaneously, antistatic agent Atmer-163 (1000 ppm) is added during the flash evaporation process. The polypropylene powder collected from the solid phase outlet of flash tower 4 then enters steam tower 5 through the polypropylene powder inlet. Water vapor is used to remove propylene entrained in the powder and simultaneously deactivate the catalyst. The polypropylene powder then enters degassing tower 6, where it is dried using counter-current hot nitrogen to obtain polypropylene powder. Throughout the entire polymerization reaction, the total polymerization load is 62.5 kg / h, and the polymerization load ratio between the first loop reactor in Step 2 and the second loop reactor in Step 3 is 54:46.

[0094] Step 5: Add 62.5 kg / h of polypropylene powder (containing 1% oligomer and 63 ppm ash) and 187.5 kg / h of washing solution co-currently to the slurry premixing tank 7 equipped with a stirrer. Mix thoroughly for approximately half an hour until homogeneous under the action of the stirrer and the premixing tank circulation pump. Then, pump the mixture through the premixing tank circulation pump to the washing tank 8 equipped with a double-layer stirrer. Set the washing temperature to 80℃ and wash for a total of 3 hours. Use a washing solution with a hexane:butanol ratio of 3:1 (by mass). The slurry leaving the washing tank enters the centrifuge unit 9. The resulting liquid material is collected, and the solid material is sent to the fluidized bed drying unit 11 for drying to obtain the ultra-clean polypropylene product.

[0095] The polypropylene product was sampled and analyzed, and the results are shown in Table 1. The ash content of the polypropylene product was 17 ppm, the oligomer content was 13 ppm, and the isotacticity was 99.2%. It fully meets the technical specifications of the national standard for high-grade electrical grade polypropylene.

[0096] Table 1

[0097]

[0098] The embodiments of this utility model have been described above. However, this utility model is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A process system for producing ultra-clean polypropylene, characterized in that, The process system includes a polymerization system and a post-processing system located downstream of the polymerization system; The polymerization system includes a prepolymerization reactor, a first polymerization reactor, and a second polymerization reactor; The post-processing system includes: A flash unit, located downstream of the second polymerization reactor, includes a flash tower; A steaming unit, located downstream of the flash unit and upstream of the drying unit, includes a steaming tower; The drying unit, located downstream of the steaming unit, includes a degassing tower. The degassing tower is provided with a polypropylene powder inlet and a nitrogen inlet. The positions of the polypropylene powder inlet and the nitrogen inlet meet the requirement of counter-current flow of polypropylene powder and nitrogen. A washing unit, located downstream of the drying unit, is used to wash the polypropylene powder obtained from the drying unit, and includes a slurry premixing tank and a washing tank disposed downstream of the slurry premixing tank. The slurry premixing tank is equipped with a polypropylene powder inlet and a washing solvent inlet, and the positions of the polypropylene powder inlet and the washing solvent inlet meet the requirements for co-current mixing of polypropylene powder and washing solvent.

2. The process system according to claim 1, characterized in that, The prepolymerization reactor is provided with a raw material inlet, a catalyst inlet, an electron donor inlet, and a propylene prepolymer outlet; or, the prepolymerization reactor is further provided with an activator inlet.

3. The process system according to claim 1, characterized in that, The prepolymerization reactor is a batch reactor with an internal stirrer; Both the first polymerization reactor and the second polymerization reactor are loop reactors.

4. The process system according to claim 1, characterized in that, The first polymerization reactor is provided with a propylene prepolymer inlet, a raw material inlet, and a first polymerization product outlet, wherein the propylene prepolymer outlet is connected to the propylene prepolymer inlet of the first polymerization reactor; The second polymerization reactor is provided with a first polymerization product inlet, a raw material inlet, and a second polymerization product outlet, with the first polymerization product outlet connected to the first polymerization product inlet.

5. The process system according to claim 1, characterized in that, The slurry premixing tank is equipped with a premixed slurry outlet and has an agitator inside. The washing tank is provided with a premixed slurry inlet and connected to the premixed slurry outlet, and an agitator is provided inside the washing tank; furthermore, a heater is provided on the connecting pipeline between the premixed slurry inlet and the premixed slurry outlet.

6. The process system according to claim 4, characterized in that, The flash tower is provided with a feed inlet, a gas phase outlet and a solid phase outlet, and the outlet of the second polymerization product is connected to the feed inlet of the flash tower. Alternatively, an antistatic agent inlet can be installed on the connecting pipeline between the outlet of the second polymerization product and the inlet of the flash tower.

7. The process system according to claim 6, characterized in that, The steam tower is equipped with a polypropylene powder inlet, a steam inlet, and a polypropylene powder outlet. The polypropylene powder collected from the solid phase outlet of the flash tower enters the steam tower through the polypropylene powder inlet.

8. The process system according to claim 1, characterized in that, The post-treatment system also includes a centrifugation unit, located downstream of the washing unit; The post-processing system also includes a conveying unit located downstream of the centrifugation unit; The post-processing system also includes a fluidized bed drying unit, located downstream of the conveying unit; The post-processing system also includes a storage unit located downstream of the fluidized bed drying unit; The post-processing system also includes a granulation unit located downstream of the storage unit.

9. The process system according to claim 8, characterized in that, The granulation unit includes an extrusion granulation system and an air conveying system.

10. A process system for producing ultra-clean polypropylene, characterized in that, The process system for producing ultra-clean polypropylene includes a polymerization system and a post-processing system located downstream of the polymerization system. The polymerization system includes a prepolymerization reactor, a first polymerization reactor, and a second polymerization reactor; The post-processing system includes: A flash unit, located downstream of the second polymerization reactor, includes a flash tower; A steaming unit, located downstream of the flash steaming unit, includes a steaming tower; The drying unit, located downstream of the steaming unit, includes a degassing tower. The degassing tower is provided with a polypropylene powder inlet and a nitrogen inlet. The positions of the polypropylene powder inlet and the nitrogen inlet meet the requirement of counter-current flow of polypropylene powder and nitrogen. A washing unit, located downstream of the drying unit, is used to wash the polypropylene powder obtained from the drying unit. It includes a slurry premixing tank and a washing tank located downstream of the slurry premixing tank. The slurry premixing tank is provided with a polypropylene powder inlet and a washing solvent inlet. The positions of the polypropylene powder inlet and the washing solvent inlet meet the requirements for co-current mixing of polypropylene powder and washing solvent. A centrifugal unit is located downstream of the washing unit; A conveying unit is located downstream of the centrifuge unit; A fluidized bed drying unit is located downstream of the conveying unit; A storage unit is located downstream of the fluidized bed drying unit; The granulation unit is located downstream of the storage unit.

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