Process for olefin polymerization and olefin polymerization plant

Abstract

This invention relates to the field of olefin polymerization, and discloses a method and apparatus for olefin polymerization. The method includes three circulation loops and three switching modes. The method and apparatus provided by this invention can use the same liquid material, which can simultaneously serve as the solvent in the first reactor and the condensate in the second reactor of the olefin polymerization system. This method achieves a high degree of liquid utilization and eliminates the need for solvent separation and recovery processes.

Description

Technical Field

[0001] This invention relates to the field of olefin polymerization, and more specifically to a method and apparatus for olefin polymerization. Background Technology

[0002] Polyolefins have a wide range of applications in daily life, and their production processes mainly include slurry processing, gas-phase processing, and gas-liquid processing (condensation processing). It is known in the art that to achieve superior mechanical properties in polyolefin products, it is necessary to broaden the molecular weight distribution of the polyolefin or to prepare polyolefins with a bimodal or even multimodal molecular weight distribution. The low molecular weight fraction is used to improve processing performance, while the high molecular weight fraction is used to improve mechanical properties.

[0003] Traditional single reactors are not suitable for producing polyolefins with a wider molecular weight distribution. More complex structures or multiple reaction zones within the same reactor are needed to obtain polyolefins with broad or bimodal distributions. Alternatively, this can be achieved by connecting multiple reactors in series to produce polyolefins of different molecular weights in different reactors. Different reactors employ different production processes, requiring the addition of different materials to meet production requirements. For example, slurry processes require solvents as the reaction environment, while gas-liquid and gas-phase condensate processes require condensers to remove most of the heat of polymerization. Adding and using solvents and condensers separately will increase the need for additional separation and injection equipment and piping, significantly increasing energy consumption and potentially making it difficult to synchronously control the reactor's operating status.

[0004] CN200780013270.4 discloses a method for preparing ethylene polymers using multiple reactors arranged in series. This method creates different polymerization environments within different reactors to produce polymers of different molecular weights. However, this patent is only applicable to the production of polyolefins using a slurry process, and the types of polyolefins produced are limited.

[0005] CN201510674100.7 discloses a method and apparatus for olefin polymerization, which produces a wide distribution of polyolefins by connecting two or more reactors in series. However, the apparatus of this invention has a high coupling strength; if any loop is broken, it is difficult to maintain the other loop, thus its ability to withstand risks is low.

[0006] US7115687B discloses a process for connecting a first loop reactor and a second gas-phase fluidized bed reactor in series. However, it also has the problems of uneven residence time distribution of polymer particles in the two reactors and a large amount of resin fine powder produced by the first reactor.

[0007] CN200910222301.8 discloses a multi-zone circulating reactor and reaction method for olefin polymerization. This method requires four reactors, and the connection between the devices is complex, the operation is difficult, and the equipment investment is high.

[0008] Therefore, there is an urgent need for an olefin polymerization method and apparatus that can produce polyolefins with a wide molecular weight distribution, and which is simple to connect and easy to operate. Summary of the Invention

[0009] The purpose of this invention is to overcome the problems existing in the prior art where the production of polyolefins with a wide molecular weight distribution requires the separate addition and use of solvents and condensers, which increases the amount of additional equipment and piping, and also causes mutual interference in the production state of series-connected devices. This invention provides a method for olefin copolymerization and an olefin polymerization apparatus. When using this method to produce polyolefins with a wide molecular weight distribution, the liquid material serves as both the solvent in the first reactor and the condenser in the second reactor, which not only reduces the number of devices and shortens the process, but also avoids the adverse effects of the solvent and condenser interfering with each other.

[0010] To achieve the above objectives, a first aspect of the present invention provides an olefin polymerization method, the method comprising: introducing a mixture of a catalyst, an olefin monomer, a molecular weight regulator, a solvent, and a condenser into an olefin polymerization apparatus to carry out a polymerization reaction; the olefin polymerization apparatus comprising: a first reactor and a second reactor for olefin polymerization; the olefin polymerization apparatus comprising three circulation loops: circulation loop A, circulation loop B, and circulation loop C;

[0011] When circulation loop A, circulation loop B, and circulation loop C are all connected, the mixture and part of the product of the polymerization reaction pass through circulation A, circulation B, and circulation C in the olefin polymerization device;

[0012] When the circulation loop A is disconnected and the circulation loops B and C are connected, the mixture and part of the product of the polymerization reaction pass through circulation B and circulation C in the olefin polymerization device; the mixture in circulation B and circulation C respectively serves as the solvent of the first reactor and the condenser of the second reactor.

[0013] When the circulation loop B is disconnected from the circulation loop C and the circulation loop A is connected, the mixture and part of the product of the polymerization reaction pass through circulation A in the olefin polymerization device, and the mixture in circulation A serves as the condenser for the second reactor.

[0014] When the circulation loop C is disconnected and the circulation loop A and circulation loop B are connected, the mixture and part of the product of the polymerization reaction pass through circulation A and circulation B in the olefin polymerization device. The mixture in circulation A and circulation B respectively serves as the solvent of the first reactor and the condenser of the second reactor.

[0015] Wherein, loop A, loop B, and loop C are respectively:

[0016] Cycle A: The liquid material obtained by gas-liquid separation of gaseous and liquid materials enters the second reactor, where it is vaporized by the exothermic polymerization reaction as a condenser. The generated gas flows out of the second reactor, is pressurized and heat-exchanged, and then undergoes gas-liquid separation. The gaseous material and the remaining liquid material obtained after gas-liquid separation enter the second reactor again.

[0017] Cycle B: The mixture and part of the liquid product of the polymerization reaction enter the first reactor. After circulating for a set residence time as a solvent, a stream is separated and enters the second reactor. As a condenser, it is vaporized by the exothermic polymerization reaction and then flows out of the second reactor. First, it is pressurized to liquefy part of the gas phase, and then heat is removed by heat exchange to obtain a gas-liquid mixture. Then, gas-liquid separation is performed. The gas phase material obtained after gas-liquid separation enters the second reactor, and the liquid obtained enters the first reactor.

[0018] Cycle C: The mixture and part of the liquid products of the polymerization reaction enter the first reactor, and after undergoing a set cycle as a solvent, it enters the second reactor, flows out of the second reactor together with the polyolefin particles, undergoes degassing and recovery to obtain the recovered liquid, and is then transported back to the first reactor to complete the cycle.

[0019] A second aspect of the present invention provides an olefin polymerization apparatus, comprising: a first reactor 2 and a second reactor 3 for olefin polymerization, wherein the outlet of the first reactor 2 is connected to the second reactor 3 via a fluid pipeline; the top outlet of the second reactor 3 is connected to the inlet of a gas-liquid separator 7 via a fluid pipeline, the liquid outlet of the gas-liquid separator 7 is connected to the bottom inlet of the first reactor 2 and the second reactor 3 via a fluid pipeline, a second liquid storage tank 8, and a second transfer pump 10, respectively; the gas outlet of the gas-liquid separator 7 is connected to the bottom inlet of the second reactor 3 via a fluid pipeline; a compressor 5 and a heat exchanger 6 are sequentially arranged between the top outlet of the second reactor 3 and the inlet of the gas-liquid separator 7; the second reactor 3 is provided with a liquid phase outlet for discharging liquid material from the second reactor 3, and the liquid phase outlet of the second reactor 3 is connected to the first reactor 2 via a fluid pipeline; a degassing and recovery unit 11, a first liquid storage tank 1, and a first transfer pump 9 are sequentially arranged between the liquid phase outlet of the second reactor 3 and the first reactor 2; wherein,

[0020] The device is equipped with loop A, loop B and loop C:

[0021] Circulation loop A includes the gas-liquid separator 7, the second storage tank 8, the second transfer pump 10, the second reactor 3, the compressor 5, and the heat exchanger 6 connected in sequence. The liquid material obtained by the gas-liquid separator 7 passes through the second liquid storage tank 8 and is then transported to the second reactor 3 by the second transfer pump 10. As a condenser, it is vaporized by the exothermic polymerization reaction. Then, the gaseous material is drawn out from the top outlet of the second reactor 3 and pressurized by the compressor 5. After passing through the heat exchanger 6 and the gas-liquid separator 7, the resulting gaseous material is injected into the second reactor 3 from below. The remaining liquid material is sent to the second reactor 3, completing the internal circulation of the second reactor system.

[0022] Circulation loop B includes the first reactor 2, the second reactor 3, the compressor 5, the heat exchanger 6, the gas-liquid separator 7, the liquid storage tank 8, and the second transfer pump 10, which are connected in sequence. The liquid is sent from the liquid storage tank 8 to the first reactor 2 via the second transfer pump 10. After circulating for a set residence time as a solvent, a stream is sent into the second reactor 3. As a condenser, it is vaporized by the exothermic polymerization reaction. Then, it is sent from the top outlet of the second reactor 3 to the compressor 5 for pressurization. After passing through the heat exchanger 6 to remove some heat, a gas-liquid mixture is obtained. Then, it passes through the gas-liquid separator 7. The resulting gaseous material enters the second reactor 3 from below, and the resulting liquid is sent back to the first reactor 2 to complete the cycle.

[0023] Circulation loop C includes the first reactor 2, the second reactor 3, the degassing and recovery unit 11, the first liquid storage tank 1, and the first transfer pump 9, which are connected in sequence. The liquid is sent from the first liquid storage tank 1 to the first reactor 2 via the first transfer pump 9. After undergoing a set cycle as a solvent, it is sent to the interior of the second reactor 3 and discharged from the outlet of the side wall of the second reactor 3 together with the polyolefin particles. After passing through the degassing and recovery unit 11, the recovered liquid is sent to the first liquid storage tank 1 to complete the cycle.

[0024] The loop A, loop B, and loop C are configured with the following three switching modes:

[0025] a. If the liquid outlet of the gas-liquid separator 7 is disconnected from the second reactor 3, then circulation loop A is disconnected, and circulation loop B and circulation loop C are connected. The liquid in circulation loop B and circulation loop C respectively serve as the solvent of the first reactor 2 and the condenser of the second reactor 3.

[0026] b. If the first reactor 2 and the second reactor 3 are disconnected, then circulation loop B and circulation loop C are disconnected, circulation loop A is connected, and the liquid in circulation loop A is used as the condenser for the second reactor 3.

[0027] c. The second reactor 3 is disconnected from the degassing and recovery unit 11, and / or the degassing and recovery unit 11 is disconnected from the first reactor 2. Then, the circulation loop C is disconnected, and the circulation loop A and circulation loop B are connected. The liquids in circulation loop A and circulation loop B are respectively used as the solvent of the first reactor 2 and the condenser of the second reactor 3.

[0028] The beneficial effects of the present invention through the above technical solution are:

[0029] When producing polyolefins with a wide molecular weight distribution using the olefin polymerization method and apparatus provided by this invention, the liquid material serves as both the solvent in the first reactor and the condenser in the second reactor, avoiding the operational complexity and lengthy process caused by the separate addition and utilization of solvents and condensers. This invention employs a series connection of slurry and gas-liquid (condensation) processes, reducing the need for circulating pumps and other equipment, shortening the process, and enhancing the process's resilience through appropriate equipment combinations. Even if some material flow is interrupted, a circulation loop can still maintain operation. This not only shortens the process and improves the comprehensive utilization of circulating liquids while producing polyolefins with a wide molecular weight distribution, but also effectively reduces equipment investment, increases operational flexibility, reduces energy consumption, eliminates the need for solvent separation and recovery, and avoids the complexity of separation and recovery caused by using two or more liquids. Furthermore, by comprehensively utilizing the liquids, the olefin polymerization method and apparatus provided by this invention can also prepare polyolefins with different melt indexes, densities, and other properties. Attached Figure Description

[0030] Figure 1 This is an olefin polymerization apparatus provided according to a preferred embodiment of the present invention.

[0031] Explanation of reference numerals in the attached figures

[0032] 1. First liquid storage tank 2. First reactor

[0033] 3. Second reactor; 4. Gas distribution plate

[0034] 5. Compressor 6. Heat exchanger

[0035] 7. Gas-liquid separator; 8. Second liquid storage tank

[0036] 9. First transfer pump 10. Second transfer pump

[0037] 11. Degassing and recovery unit Detailed Implementation

[0038] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0039] The first aspect of the present invention provides an olefin polymerization method, the method comprising: introducing a mixture of a catalyst, an olefin monomer, a molecular weight regulator, a solvent, and a condenser into an olefin polymerization apparatus to carry out a polymerization reaction; the olefin polymerization apparatus comprising: a first reactor and a second reactor for olefin polymerization; the olefin polymerization apparatus comprising three circulation loops: circulation loop A, circulation loop B, and circulation loop C;

[0040] When circulation loop A, circulation loop B, and circulation loop C are all connected, the mixture and part of the product of the polymerization reaction pass through circulation A, circulation B, and circulation C in the olefin polymerization device;

[0041] When the circulation loop A is disconnected and the circulation loops B and C are connected, the mixture and part of the product of the polymerization reaction pass through circulation B and circulation C in the olefin polymerization device; the mixture in circulation B and circulation C respectively serves as the solvent of the first reactor and the condenser of the second reactor.

[0042] When the circulation loop B is disconnected from the circulation loop C and the circulation loop A is connected, the mixture and part of the product of the polymerization reaction pass through circulation A in the olefin polymerization device, and the mixture in circulation A serves as the condenser for the second reactor.

[0043] When the circulation loop C is disconnected and the circulation loop A and circulation loop B are connected, the mixture and part of the product of the polymerization reaction pass through circulation A and circulation B in the olefin polymerization device. The mixture in circulation A and circulation B respectively serves as the solvent of the first reactor and the condenser of the second reactor.

[0044] Wherein, loop A, loop B, and loop C are respectively:

[0045] Cycle A: The liquid material obtained by gas-liquid separation of gaseous and liquid materials enters the second reactor, where it is vaporized by the exothermic polymerization reaction as a condenser. The generated gas flows out of the second reactor, is pressurized and heat-exchanged, and then undergoes gas-liquid separation. The gaseous material and the remaining liquid material obtained after gas-liquid separation enter the second reactor again.

[0046] Cycle B: The mixture and part of the liquid product of the polymerization reaction enter the first reactor. After circulating for a set residence time as a solvent, a stream is separated and enters the second reactor. As a condenser, it is vaporized by the exothermic polymerization reaction and then flows out of the second reactor. First, it is pressurized to liquefy part of the gas phase, and then heat is removed by heat exchange to obtain a gas-liquid mixture. Then, gas-liquid separation is performed. The gas phase material obtained after gas-liquid separation enters the second reactor, and the liquid obtained enters the first reactor.

[0047] Cycle C: The mixture and part of the liquid products of the polymerization reaction enter the first reactor 2, and after undergoing a set cycle as a solvent, it enters the second reactor, flows out of the second reactor together with the polyolefin particles, is degassed and recovered to obtain a recovered liquid, and is then transported back to the first reactor to complete the cycle.

[0048] In this invention, the liquid circulating in the polymerization apparatus can serve as both a solvent in the first reactor and a condenser in the second reactor. By controlling the circulation loop of the liquid materials in the polymerization process, the process's resilience and operational flexibility are improved, promoting the comprehensive utilization of the liquid and avoiding the complexity of separation and recovery caused by using two or more liquids.

[0049] According to the present invention, preferably, the solvent is selected from at least one of C3-C8 saturated straight-chain alkanes, C4-C8 saturated branched-chain alkanes, and C4-C8 cycloalkanes.

[0050] According to the present invention, preferably, the temperature of the solvent is 20-90°C.

[0051] According to the present invention, preferably, the distribution ratio of the liquid circulating in the first reactor and the second reactor system is (0.1:0.9) to (0.9:0.1). Different distribution ratios, i.e., different amounts of liquid in different reactors, will affect the mass transfer and heat transfer processes, thereby affecting the reaction and ultimately resulting in different properties of the final product.

[0052] According to the present invention, preferably, the pressure of the first polymerization reaction carried out in the first reactor is 1-10 MPa and the temperature is 0-120°C, and the pressure of the second polymerization reaction carried out in the second reactor is 1-10 MPa and the temperature is 30-150°C.

[0053] According to the present invention, preferably, the catalyst is selected from at least one of chromium-based catalysts, Ziegler-Natta catalysts, metallocene catalysts, and post-transition metal catalysts.

[0054] According to the present invention, preferably, the olefin monomer is ethylene and / or C3-C 18 α-olefins.

[0055] According to the present invention, preferably, the first polymerization reaction and the second polymerization reaction are carried out in the presence of an antistatic agent.

[0056] According to the present invention, preferably, the antistatic agent is selected from at least one of aluminum distearate, ethoxylated amine, polysulfone copolymer, polymeric polyamine, and oil-soluble sulfonic acid.

[0057] According to the present invention, preferably, the first polymerization reaction and the second polymerization reaction are carried out in the presence of a co-catalyst and an inert gas.

[0058] A second aspect of the present invention provides an olefin polymerization apparatus, comprising: a first reactor 2 and a second reactor 3 for olefin polymerization, wherein the outlet of the first reactor 2 is connected to the second reactor 3 via a fluid pipeline; the top outlet of the second reactor 3 is connected to the inlet of a gas-liquid separator 7 via a fluid pipeline, the liquid outlet of the gas-liquid separator 7 is connected to the bottom inlet of the first reactor 2 and the second reactor 3 via a fluid pipeline, a second liquid storage tank 8, and a second transfer pump 10, respectively; the gas outlet of the gas-liquid separator 7 is connected to the bottom inlet of the second reactor 3 via a fluid pipeline; a compressor 5 and a heat exchanger 6 are sequentially arranged between the top outlet of the second reactor 3 and the inlet of the gas-liquid separator 7; the second reactor 3 is provided with a liquid phase outlet for discharging liquid material from the second reactor 3, and the liquid phase outlet of the second reactor 3 is connected to the first reactor 2 via a fluid pipeline; a degassing and recovery unit 11, a first liquid storage tank 1, and a first transfer pump 9 are sequentially arranged between the liquid phase outlet of the second reactor 3 and the first reactor 2; wherein,

[0059] The device is equipped with loop A, loop B and loop C:

[0060] Circulation loop A includes the gas-liquid separator 7, the second storage tank 8, the second transfer pump 10, the second reactor 3, the compressor 5, and the heat exchanger 6 connected in sequence. The liquid material obtained by the gas-liquid separator 7 passes through the second liquid storage tank 8 and is then transported to the second reactor 3 by the second transfer pump 10. As a condenser, it is vaporized by the exothermic polymerization reaction. Then, the gaseous material is drawn out from the top outlet of the second reactor 3 and pressurized by the compressor 5. After passing through the heat exchanger 6 and the gas-liquid separator 7, the resulting gaseous material is injected into the second reactor 3 from below. The remaining liquid material is sent to the second reactor 3, completing the internal circulation of the second reactor system.

[0061] Circulation loop B includes the first reactor 2, the second reactor 3, the compressor 5, the heat exchanger 6, the gas-liquid separator 7, the liquid storage tank 8, and the second transfer pump 10, which are connected in sequence. The liquid is sent from the liquid storage tank 8 to the first reactor 2 via the second transfer pump 10. After circulating for a set residence time as a solvent, a stream is sent into the second reactor 3. As a condenser, it is vaporized by the exothermic polymerization reaction. Then, it is sent from the top outlet of the second reactor 3 to the compressor 5 for pressurization. After passing through the heat exchanger 6 to remove some heat, a gas-liquid mixture is obtained. Then, it passes through the gas-liquid separator 7. The resulting gaseous material enters the second reactor 3 from below, and the resulting liquid is sent back to the first reactor 2 to complete the cycle.

[0062] Circulation loop C includes the first reactor 2, the second reactor 3, the degassing and recovery unit 11, the first liquid storage tank 1, and the first transfer pump 9, which are connected in sequence. The liquid is sent from the first liquid storage tank 1 to the first reactor 2 via the first transfer pump 9. After undergoing a set cycle as a solvent, it is sent to the interior of the second reactor 3 and discharged from the outlet of the side wall of the second reactor 3 together with the polyolefin particles. After passing through the degassing and recovery unit 11, the recovered liquid is sent to the first liquid storage tank 1 to complete the cycle.

[0063] The loop A, loop B, and loop C are configured with the following three switching modes:

[0064] a. If the liquid outlet of the gas-liquid separator 7 is disconnected from the second reactor 3, then circulation loop A is disconnected, and circulation loop B and circulation loop C are connected. The liquid in circulation loop B and circulation loop C respectively serve as the solvent of the first reactor 2 and the condenser of the second reactor 3.

[0065] b. If the first reactor 2 and the second reactor 3 are disconnected, then circulation loop B and circulation loop C are disconnected, circulation loop A is connected, and the liquid in circulation loop A is used as the condenser for the second reactor 3.

[0066] c. The second reactor 3 is disconnected from the degassing and recovery unit 11, and / or the degassing and recovery unit 11 is disconnected from the first reactor 2. Then, the circulation loop C is disconnected, and the circulation loop A and circulation loop B are connected. The liquids in circulation loop A and circulation loop B are respectively used as the solvent of the first reactor 2 and the condenser of the second reactor 3.

[0067] According to the present invention, a second liquid storage tank 8 and a second transfer pump 10 are provided on the fluid pipeline connected to the liquid outlet of the gas-liquid separator 7, for transporting a portion of the liquid separated by the gas-liquid separator 7 to the first reactor 2 and the other portion to the second reactor 3.

[0068] According to the present invention, preferably, a gas distribution plate 4 is provided inside the second reactor 3.

[0069] According to the present invention, preferably, a nozzle is provided at the end of the pipe connecting the outlet of the first reactor 2 and the second reactor 3, for feeding the reaction slurry in the first reactor 2 into the second reactor 3 under the action of pressure difference.

[0070] Preferably, the nozzle is positioned above the gas distribution plate 4, and the ratio of the distance between the nozzle and the gas distribution plate 4 to the height of the straight section of the second reactor 3 is (0.1-0.8):1. The feed position is controlled by controlling the distance between the nozzle and the gas distribution plate 4.

[0071] According to the present invention, preferably, the liquid phase outlet of the second reactor 3 is disposed above the gas distribution plate 4, and the ratio of the distance between the liquid phase outlet of the second reactor 3 and the gas distribution plate 4 to the height of the straight section of the second reactor 3 is (0.05-0.6):1.

[0072] According to the present invention, preferably, the first reactor 2 is a loop reactor or a stirred tank reactor, and the second reactor 3 is a fluidized bed reactor.

[0073] According to a preferred embodiment of the present invention, such as Figure 1 The device is provided with loop A, loop B and loop C:

[0074] Circulation loop A includes the gas-liquid separator 7, the second liquid storage tank 8, the second transfer pump 10, the second reactor 3, the compressor 5, and the heat exchanger 6 connected in sequence. The liquid material obtained by the gas-liquid separator 7 is transported to the second liquid storage tank 8, and then sent to the second reactor 3 by the second transfer pump 10. As a condenser, it is vaporized by the exothermic polymerization reaction. Then, the gaseous material is drawn out from the top outlet of the second reactor 3 and pressurized by the compressor 5. After passing through the heat exchanger 6 and the gas-liquid separator 7, the resulting gaseous material is injected into the second reactor 3 from below the gas distribution plate 4. The remaining liquid material is sent to the second liquid storage tank 8 and injected into the second reactor 3 from above the gas distribution plate 4, completing the internal circulation of the second reactor system.

[0075] Circulation loop B includes the first reactor 2, the second reactor 3, the compressor 5, the heat exchanger 6, the gas-liquid separator 7, the second liquid storage tank 8, and the second transfer pump 10, which are connected in sequence. The liquid is sent from the first liquid storage tank 1 to the first reactor 2 via the first transfer pump 9. After circulating for a certain residence time as a solvent, a stream is sent into the second reactor 3. As a condenser, it is vaporized by the exothermic polymerization reaction. Then, it is sent from the top outlet of the second reactor 3 to the compressor 5 for pressurization. After passing through the heat exchanger 6 to remove some heat, a gas-liquid mixture is obtained. Then, it passes through the gas-liquid separator 7. The resulting gaseous material enters the second reactor 3 from below the gas distribution plate 4. The resulting liquid is sent to the second liquid storage tank 8 and then sent back to the first reactor 2 via the second transfer pump 10 to complete the circulation.

[0076] Circulation loop C includes the first liquid storage tank 1, the first transfer pump 9, the first reactor 2, the second reactor 3, and the degassing and recovery unit 11, which are connected in sequence. Liquid enters the first liquid storage tank 1, is pumped to the first reactor 2 by the first transfer pump 9, and after a certain cycle as a solvent, is transported to the second reactor 3. There, it is discharged from the outlet on the side wall of the second reactor 3 along with the polyolefin particles. After passing through the degassing and recovery unit 11, the recovered liquid is sent back to the first liquid storage tank 1 to complete the cycle. In addition, to compensate for the loss of the recovered liquid, fresh liquid needs to be replenished to the first liquid storage tank 1 in a timely manner.

[0077] The following three switching modes are configured for loop A, loop B, and loop C:

[0078] a. If the second delivery pump 10 is disconnected from the second reactor 3, then circulation loop A is disconnected, and circulation loop B and circulation loop C are connected. The liquids in circulation loop B and circulation loop C are respectively used as the solvent of the first reactor 2 and the condenser of the second reactor 3.

[0079] b. If the first reactor 2 and the second reactor 3 are disconnected, then circulation loop B and circulation loop C are disconnected, and circulation loop A is connected. The liquid in circulation loop A serves as the condenser for the second reactor 3. In addition, fresh liquid can be added to the second liquid storage tank 8.

[0080] c. Disconnect the second reactor 3 from the degassing and recovery unit 11, and / or disconnect the degassing and recovery unit 11 from the first liquid storage tank 1. In this case, circulation loop C is disconnected, and circulation loops A and B are connected. The liquids in circulation loops A and B respectively serve as the solvent for the first reactor 2 and the condensate for the second reactor 3. Additionally, fresh liquid can be added to the first liquid storage tank 1 and / or the second liquid storage tank 8.

[0081] In this invention, the material composition of the polymerization environment in the first reactor 2, the material composition of the polymerization environment in the second reactor 3, and the content and composition of the condensate in the second reactor 3 can be adjusted by controlling the distribution ratio of the liquid circulating in the first reactor 2 and the second reactor system and the temperature of the liquid. When the liquid has more than one component, the material composition of the polymerization environment in the first reactor 2, the material composition of the polymerization environment in the second reactor 3, and the content and composition of the condensate in the second reactor 3 can also be adjusted by controlling the content of various components in the liquid.

[0082] The present invention will be described in detail below through examples and comparative examples. Unless otherwise specified, the following examples and comparative examples are all conventional methods; the reagents and materials used are commercially available unless otherwise specified.

[0083] Example 1

[0084] use Figure 1 The polymerization apparatus shown has a distance between the nozzle and the gas distribution plate, and a height ratio of the straight section of the second reactor of 0.4:1; the distance between the liquid outlet of the second reactor and the gas distribution plate is 0.2:1.

[0085] The first reactor is a loop reactor, and the second reactor is a fluidized bed reactor. Both use a magnesium-titanium Ziegler-Natta catalyst, with ethylene as the olefin monomer, 1-hexene as the comonomer (molar ratio of 1-hexene to ethylene is 0.019:1), and isobutane and isopentane as solvents / condensers. In the loop reactor, ultra-high molecular weight polyethylene (UHMWPE) is produced under reaction conditions of 65°C and 4.0 MPa (low-molecular-weight polyethylene is produced first to reduce the entanglement of UHMWPE). Then, the reaction slurry is directly injected into the fluidized bed reactor under differential pressure, where homopolymerization occurs at 88°C and 2.3 MPa to produce high-density polyethylene (HDPE). The ethylene mass flow rate is 3411 kg / h, the 1-hexene mass flow rate is 612 kg / h, the catalyst feed rate is 3.77 kg / h, and the liquid distribution ratio circulating between the first and second reactors is 0.722:1.

[0086] In this embodiment, the total production capacity of grade A is 18.75 t / h, of which 5 wt% is detangled ultra-high molecular weight polyethylene produced by the loop reactor and 95 wt% is high-density polyethylene produced by the fluidized bed reactor. The resulting polyethylene has a melt index of 0.11 g / 10 min and a density of 0.953 g / cm³ under a load of 2.16 kg. 3 .

[0087] Example 2

[0088] Polyethylene was produced using the apparatus and method of Example 1, except that 1-butene was used as the comonomer (the molar ratio of 1-butene to ethylene was 0.071:1), and the reaction temperature in the loop reactor was 70°C, as detailed below:

[0089] The first reactor is a loop reactor, and the second reactor is a fluidized bed reactor. A magnesium-titanium Ziegler-Natta catalyst is used, with ethylene as the olefin monomer, 1-butene as the comonomer (molar ratio of 1-butene to ethylene is 0.071), and isobutane and isopentane as solvents / condensers. Ultra-high molecular weight polyethylene (UHMWPE) is produced in the loop reactor under reaction conditions of 70°C and 4.0 MPa (low-molecular-weight polyethylene is produced first to reduce the entanglement of UHMWPE). Then, the reaction slurry is directly injected into the fluidized bed reactor under differential pressure, where homopolymerization occurs at 88°C and 2.3 MPa to produce high-density polyethylene (HDPE). The ethylene feed rate is 3259 kg / h, the butene feed rate is 533 kg / h, the catalyst feed rate is 3.78 kg / h, and the liquid distribution ratio circulating between the first and second reactors is 0.716:1.

[0090] In this embodiment, the total production capacity of grade B is 18.75 t / h, of which 10 wt% is detangled ultra-high molecular weight polyethylene produced by the loop reactor and 90 wt% is high-density polyethylene produced by the fluidized bed reactor. The resulting polyethylene has a melt index of 0.22 g / 10 min and a density of 0.958 g / cm³ under a load of 2.16 kg. 3 .

[0091] Example 3

[0092] Polyethylene was produced using the apparatus and method of Example 1, except that 1-butene and 1-hexene were used as comonomers (the molar ratio of 1-butene to ethylene was 0.034, and the molar ratio of 1-hexene to ethylene was 0.009), and the reaction temperature in the loop reactor was 70°C, as detailed below:

[0093] use Figure 1The polymerization apparatus shown has a loop reactor as the first reactor and a fluidized bed reactor as the second reactor. A magnesium-titanium Ziegler-Natta catalyst is used, with ethylene as the olefin monomer, 1-butene and 1-hexene as comonomers (molar ratio of 1-butene to ethylene is 0.034, and molar ratio of 1-hexene to ethylene is 0.009), and isobutane and isopentane as solvents / condensers. Ultra-high molecular weight polyethylene (UHMWPE) is produced in the loop reactor under reaction conditions of 70°C and 4.0 MPa (low molecular weight polyethylene is produced first to reduce the entanglement of UHMWPE). Then, the reaction slurry is directly injected into the fluidized bed reactor under pressure differential, where homopolymerization occurs at 88°C and 2.3 MPa to produce high-density polyethylene (HDPE). The feed flow rate for ethylene is 3122 kg / h, the feed flow rate for 1-butene is 514 kg / h, the feed flow rate for 1-hexene is 774 kg / h, the catalyst feeding rate is 3.64 kg / h, and the liquid distribution ratio circulating in the first reactor and the second reactor system is 0.798:1.

[0094] In this embodiment, the total production capacity of grade C is 18.75 t / h. Of this total capacity, 15 wt% is produced by the detangled ultra-high molecular weight polyethylene from the loop reactor, and 85 wt% is produced by the high-density polyethylene from the fluidized bed reactor. The resulting polyethylene has a melt index of 2.5 g / 10 min and a density of 0.950 g / cm³ at a load of 2.16 kg. 3 .

[0095] Example 4

[0096] Polyethylene was produced using the apparatus and method described in Example 1, except that only loop A was retained, i.e., a fluidized bed reactor was used for polyethylene production. This production process used ethylene as the olefin monomer, 1-hexene as the comonomer (molar ratio of 1-hexene to ethylene was 0.188:1), and isopentane as the condenser. The reactants were fed into the fluidized bed reactor, where polymerization occurred at 2.3 MPa and 82.35 °C. The ethylene mass flow rate was 14000 kg / h, the 1-hexene mass flow rate was 2632 kg / h, and the magnesium-titanium Ziegler-Natta catalyst feeder speed was 400 rpm.

[0097] In this embodiment, when producing grade D polyethylene, the production capacity is 11,000 kg / h. The resulting polyethylene has a melt index of 2.1 g / 10 min and a density of 0.916 g / cm³ under a load of 2.16 kg. 3 .

[0098] Comparative Example 1

[0099] Polyethylene was produced using the slurry process disclosed in CN101421317A in two fluidized bed reactors connected in series. A magnesium-titanium Ziegler-Natta catalyst was used. Hydrogen, nitrogen, ethylene, and hexene were introduced into the first reactor, with isobutane added as a diluent. The ethylene to hexene concentration ratio in the first reactor was controlled at 1:3, and the hydrogen concentration was maintained at a low level. The ethylene concentration ratio between the first and second reactors was controlled at 1:4, and the hydrogen concentration was 2% (volume fraction). The reaction temperature was 83-88℃. The resulting product had a melt index of 0.53 g / 10 min and a density of 0.9478 g / cm³ under a 2.16 kg load. 3 .

[0100] Comparative Example 2

[0101] Polyethylene was produced in a single fluidized bed reactor using the gas-phase process disclosed in CN106957382B. A highly active titanium-based Ziegler-Natta catalyst was employed. Hydrogen, nitrogen, ethylene, and 1-butene were introduced into the fluidized bed reactor, with the hydrogen-to-ethylene ratio controlled at 0.18:1. The polymerization temperature was 90℃ and the pressure was 2.3 MPa. The produced polyethylene product had a melt index of 1.2 g / 10 min and a density of 0.9267 g / cm³ under a 2.16 kg load. 3 .

[0102] As can be seen from the results of the polyethylene production in the above embodiments and comparative examples, the polyethylene produced in Examples 1-4 using the olefin polymerization method and apparatus provided by the present invention, based on the comprehensive utilization of liquids, exhibits significantly different product properties such as melt index and density compared to the polyethylene produced in Comparative Examples 1-2. This demonstrates that the olefin polymerization method and apparatus provided by the present invention, through the comprehensive utilization of liquids, can create different reaction environments without adding different liquid processing procedures, and can also produce polyethylene with different product properties to meet new demands.

[0103] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for olefin polymerization, characterized in that, The method includes: introducing a mixture of catalyst, olefin monomer, molecular weight regulator, solvent and condenser into an olefin polymerization apparatus to carry out a polymerization reaction; the olefin polymerization apparatus includes: a first reactor and a second reactor for olefin polymerization; the olefin polymerization apparatus includes three circulation loops: circulation loop A, circulation loop B and circulation loop C; When circulation loop A, circulation loop B, and circulation loop C are all connected, the mixture and part of the product of the polymerization reaction pass through circulation A, circulation B, and circulation C in the olefin polymerization device; When the circulation loop A is disconnected and the circulation loops B and C are connected, the mixture and part of the product of the polymerization reaction pass through circulation B and circulation C in the olefin polymerization device; the mixture in circulation B and circulation C respectively serves as the solvent of the first reactor and the condenser of the second reactor. When the circulation loop B is disconnected from the circulation loop C and the circulation loop A is connected, the mixture and part of the product of the polymerization reaction pass through circulation A in the olefin polymerization device, and the mixture in circulation A serves as the condenser for the second reactor. When the circulation loop C is disconnected and the circulation loop A and circulation loop B are connected, the mixture and part of the product of the polymerization reaction pass through circulation A and circulation B in the olefin polymerization device. The mixture in circulation A and circulation B respectively serves as the solvent of the first reactor and the condenser of the second reactor. Wherein, loop A, loop B, and loop C are respectively: Cycle A: The liquid material obtained by gas-liquid separation of gaseous and liquid materials enters the second reactor, where it is vaporized by the exothermic polymerization reaction as a condenser. The generated gas flows out of the second reactor, is pressurized and heat-exchanged, and then undergoes gas-liquid separation. The gaseous material and the remaining liquid material obtained after gas-liquid separation enter the second reactor again. Cycle B: The mixture and part of the liquid product of the polymerization reaction enter the first reactor. After circulating for a set residence time as a solvent, a stream is separated and enters the second reactor. As a condenser, it is vaporized by the exothermic polymerization reaction and then flows out of the second reactor. First, it is pressurized to liquefy part of the gas phase, and then heat is removed by heat exchange to obtain a gas-liquid mixture. Then, gas-liquid separation is performed. The gas phase material obtained after gas-liquid separation enters the second reactor, and the liquid obtained enters the first reactor. Cycle C: The mixture and part of the liquid products of the polymerization reaction enter the first reactor, and after undergoing a set cycle as a solvent, it enters the second reactor, flows out of the second reactor together with the polyolefin particles, undergoes degassing and recovery to obtain the recovered liquid, and is then transported back to the first reactor to complete the cycle.

2. The method according to claim 1, characterized in that, The solvent is selected from at least one of C3-C8 saturated straight-chain alkanes, C4-C8 saturated branched-chain alkanes, and C4-C8 cycloalkanes; And / or, the temperature of the solvent is 20-90°C.

3. The method according to claim 1 or 2, characterized in that, The first polymerization reaction in the first reactor is carried out at a pressure of 1-10 MPa and a temperature of 0-120°C; the second polymerization reaction in the second reactor is carried out at a pressure of 1-10 MPa and a temperature of 30-150°C.

4. The method according to claim 3, characterized in that, The catalyst is selected from at least one of chromium-based catalysts, Ziegler-Natta catalysts, metallocene catalysts, and post-transition metal catalysts; and / or the olefin monomers are ethylene and / or a-olefins of C3-C 18 ; and / or the olefin monomers are ethylene and / or a-olefins of C3-C 18 ; and / or the olefin monomers are ethylene and / or a-olefins of And / or, the first polymerization reaction and the second polymerization reaction are carried out in the presence of an antistatic agent; And / or, the antistatic agent is selected from at least one of aluminum distearate, ethoxylated amine, polysulfone copolymer, polymeric polyamine, and oil-soluble sulfonic acid; And / or, the first polymerization reaction and the second polymerization reaction are carried out in the presence of a co-catalyst and an inert gas.

5. An olefin polymerization apparatus, characterized in that, The apparatus includes a first reactor (2) and a second reactor (3) for olefin polymerization. The outlet of the first reactor (2) is connected to the second reactor (3) via a fluid pipeline. The top outlet of the second reactor (3) is connected to the inlet of a gas-liquid separator (7) via a fluid pipeline. The liquid outlet of the gas-liquid separator (7) is connected to the bottom inlet of the first reactor (2) and the second reactor (3) via a fluid pipeline, a second liquid storage tank (8), and a second transfer pump (10), respectively. The gas outlet of the gas-liquid separator (7) is connected to the second reactor via a fluid pipeline. The bottom inlet of the second reactor (3) is connected to the top outlet of the second reactor (3) and the inlet of the gas-liquid separator (7) are sequentially provided with a compressor (5) and a heat exchanger (6); the second reactor (3) is provided with a liquid phase outlet for discharging liquid materials from the second reactor (3), and the liquid phase outlet of the second reactor (3) is connected to the first reactor (2) through a fluid pipeline; a degassing and recovery unit (11), a first liquid storage tank (1) and a first transfer pump (9) are sequentially provided between the liquid phase outlet of the second reactor (3) and the first reactor (2); wherein, The device is equipped with loop A, loop B and loop C: Circulation loop A: includes the gas-liquid separator (7), the second liquid storage tank (8), the second transfer pump (10), the second reactor (3), the compressor (5), and the heat exchanger (6) connected in sequence. The liquid material obtained by the gas-liquid separator (7) passes through the second liquid storage tank (8) and is then transported to the second reactor (3) by the second transfer pump (10). As a condenser, it is vaporized by the exothermic polymerization reaction. Then, the gaseous material is drawn out from the top outlet of the second reactor (3) and pressurized by the compressor (5). After passing through the heat exchanger (6) and the gas-liquid separator (7), the resulting gaseous material is injected into the second reactor (3) from below. The remaining liquid material is sent to the second reactor (3), completing the internal circulation of the second reactor system. Circulation loop B includes the first reactor (2), the second reactor (3), the compressor (5), the heat exchanger (6), the gas-liquid separator (7), the second liquid storage tank (8), and the second delivery pump (10) connected in sequence. The liquid is sent from the second liquid storage tank (8) to the first reactor (2) via the second delivery pump (10). After circulating for a set residence time as a solvent, a stream is sent into the second reactor (3) as a condenser and vaporized by the exothermic polymerization reaction. Then, it is sent from the top outlet of the second reactor (3) to the compressor (5) for pressurization. After passing through the heat exchanger (6) to remove some heat, a gas-liquid mixture is obtained. Then, it passes through the gas-liquid separator (7). The resulting gaseous material enters the second reactor (3) from below, and the resulting liquid is sent to the first reactor (2) to complete the cycle. Circulation loop C: includes the first reactor (2), the second reactor (3), the degassing and recovery unit (11), the first liquid storage tank (1), and the first transfer pump (9) connected in sequence, so that the liquid is sent from the first liquid storage tank (1) to the first reactor (2) via the first transfer pump (9), and after undergoing a set cycle as a solvent, it is sent to the interior of the second reactor (3), and discharged from the outlet of the side wall of the second reactor (3) together with the polyolefin particles. After passing through the degassing and recovery unit (11), the recovered liquid is obtained and sent to the first liquid storage tank (1) to complete the cycle; The loop A, loop B, and loop C are configured with the following three switching modes: a. If the liquid outlet of the gas-liquid separator (7) is disconnected from the second reactor (3), then the circulation loop A is disconnected, and the circulation loop B and circulation loop C are connected. The liquid in the circulation loop B and circulation loop C respectively serve as the solvent of the first reactor (2) and the condenser of the second reactor (3). b. If the first reactor (2) and the second reactor (3) are disconnected, then the circulation loop B and circulation loop C are disconnected, and circulation loop A is connected. The liquid in circulation loop A is used as the condenser of the second reactor (3). c. Set the second reactor (3) to be disconnected from the degassing and recovery unit (11), and / or set the degassing and recovery unit (11) to be disconnected from the first reactor (2), then the circulation loop C is disconnected, the circulation loop A and the circulation loop B are connected, and the liquid in the circulation loop A and the circulation loop B respectively correspond to the solvent of the first reactor (2) and the condenser of the second reactor (3).

6. The apparatus according to claim 5, characterized in that, The second reactor (3) is equipped with a gas distribution plate (4).

7. The apparatus according to claim 6, characterized in that, A nozzle is provided at the end of the pipe connecting the outlet of the first reactor (2) and the second reactor (3) for feeding the reaction slurry in the first reactor (2) into the second reactor (3) under the action of pressure difference.

8. The apparatus according to claim 7, characterized in that, The nozzle is positioned above the gas distribution plate (4), and the ratio of the distance between the nozzle and the gas distribution plate (4) to the height of the straight section of the second reactor (3) is (0.1-0.8):

1.

9. The apparatus according to any one of claims 6-8, characterized in that, The liquid phase outlet of the second reactor (3) is located above the gas distribution plate (4), and the ratio of the distance between the liquid phase outlet of the second reactor (3) and the gas distribution plate (4) to the height of the straight section of the second reactor (3) is (0.05-0.6):

1.

10. The apparatus according to any one of claims 5-8, characterized in that, The first reactor (2) is a loop reactor or a stirred tank reactor, and the second reactor (3) is a fluidized bed reactor.

11. The apparatus according to claim 9, characterized in that, The first reactor (2) is a loop reactor or a stirred tank reactor, and the second reactor (3) is a fluidized bed reactor.

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