Polypropylene production system and method with flexibly combined reactors

Abstract

The invention provides a polypropylene production system and method with flexibly combined reactors, and belongs to the field of polypropylene production. The system comprises a prepolymerization reactor, a liquid phase body reactor, a gas phase reactor and a high-pressure separator, when homo-polypropylene or polypropylene random copolymer is produced, the prepolymerization reactor, the liquid phase body reactor and the gas phase reactor are communicated in sequence; when impact-resistant co-polypropylene is produced, the prepolymerization reactor, the liquid-phase body reactor, the high-pressure separator and the gas-phase reactor are sequentially communicated. According to the application, the reactor connection structure and the material path of the polypropylene production system are flexibly designed, so that the limitation of reactor combination rigidity in the traditional polypropylene production process is fundamentally broken through, and meanwhile, the energy consumption of the polypropylene production system is remarkably reduced through in-situ utilization of energy; therefore, the contradiction between the combination rigidity and high energy consumption of the reactor is solved.

Description

Technical Field

[0001] This application relates to the field of polypropylene production technology, and in particular to a polypropylene production system and method with flexible reactor combinations. Background Technology

[0002] Polypropylene, as one of the world's largest-produced and most widely used general-purpose plastics, relies on continuous innovation in its production processes as a core driving force for the development of the polymer materials industry. The production process of polypropylene is essentially an industrial process that transforms propylene monomers into polypropylene resins with different chain structures, molecular weights, and properties through polymerization under the action of a specific catalyst system. Depending on the reaction medium and phase, various technical routes have been developed, including solution polymerization, slurry polymerization, bulk polymerization, and gas-phase polymerization. Among these, liquid-phase bulk polymerization (also known as the bulk method or liquid-phase batch polymerization) has become the mainstream process since its industrialization in the 1970s due to its outstanding techno-economic advantages. The core feature of this technology is that liquid propylene itself acts as both the monomer and the reaction medium, undergoing polymerization under the action of a dedicated catalyst (such as a Ziegler-Natta catalyst or a metallocene catalyst). This design brings significant advantages: high reaction system concentration, good heat transfer efficiency, extremely high single-pass conversion rate, and simplified process flow due to the absence of additional inert solvents, resulting in higher product purity and relatively lower investment and operating costs.

[0003] To meet market demand for high-performance polypropylene materials, especially impact-resistant copolymer polypropylene, modern large-scale polypropylene plants generally employ a combined reactor design. A typical configuration involves connecting one or more dedicated gas-phase fluidized bed reactors in series after the homopolymerization reaction in the liquid-phase bulk reactor. In the production of impact-resistant copolymer products, homopolymer particles from the first reactor are transferred to the gas-phase reactor, where they copolymerize with introduced ethylene and propylene, forming a rubbery ethylene-propylene copolymer inside or on the surface of the homopolymer particles. This significantly improves the material's impact toughness, especially its low-temperature toughness. While this rigid "liquid-phase bulk + gas-phase copolymerization" process has successfully achieved the production of high-performance products, it also reveals significant limitations. When the plant only produces ordinary homopolymer polypropylene or random copolymer polypropylene, which have huge market demand, the subsequent dedicated gas-phase copolymerization reactor is often idle or operating at low load. This not only wastes expensive reactor equipment investment and increases fixed depreciation costs, but more importantly, it severely restricts the flexibility of the production plant to quickly adjust its product structure according to market demand. When scheduling production, factories must prioritize the production of impact-resistant products to amortize equipment costs, making it difficult to flexibly respond to market fluctuations in homopolymer / random products. Furthermore, although liquid-phase bulk polymerization technology itself has the advantage of high conversion rates, its overall energy efficiency still faces challenges. After the reaction, the slurry containing polypropylene particles needs to undergo a flash evaporation process to instantly vaporize and separate a large amount of unreacted liquid propylene monomers. This process consumes considerable energy to provide the heat of vaporization, and the subsequent compression, condensation, and recycling of monomers also constitute a significant portion of the plant's energy consumption.

[0004] Therefore, how to further optimize the process, achieve efficient in-situ energy utilization, and reduce energy consumption in separation and recovery units while ensuring or even improving process flexibility and product performance has become a key issue that urgently needs to be addressed in the development of polypropylene production technology. The industry has been exploring innovative process solutions that can break the fixed reactor combination mode, achieve flexible switching of reactor functions, and maximize the comprehensive energy utilization efficiency in different product production processes. Summary of the Invention

[0005] This application provides a polypropylene production system and method with flexible reactor combinations to solve the technical problem of the contradiction between rigid reactor combinations and high energy consumption in traditional polypropylene production processes.

[0006] In a first aspect, embodiments of this application provide a polypropylene production system with flexible reactor combinations, the system comprising: a prepolymerization reactor, a liquid phase bulk reactor, a gas phase reactor, and a high-pressure separator; In the production of homopolymer polypropylene or random copolymer polypropylene, the prepolymer reactor, the liquid phase bulk reactor and the gas phase reactor are connected in sequence so that the discharge from the liquid phase bulk reactor is directly transported to the gas phase reactor. When producing impact-resistant copolymer polypropylene, the prepolymer reactor, the liquid phase bulk reactor, the high-pressure separator, and the gas phase reactor are connected in sequence so that the discharge from the liquid phase bulk reactor enters the high-pressure separator via a steam jacket pipeline for gas-solid separation, and the separated polypropylene powder is then transported to the gas phase reactor.

[0007] Optionally, the prepolymerization reactor is a stirred tank reactor or a loop reactor.

[0008] Optionally, the liquid phase bulk reactor is a stirred tank reactor or a loop reactor.

[0009] Optionally, the number of liquid phase bulk reactors is one or more reactors connected in series.

[0010] Optionally, the high-pressure separator is provided with a gasified propylene purging component at the bottom, which is used to purge the polypropylene powder in the high-pressure separator by introducing gasified propylene.

[0011] In a second aspect, embodiments of this application provide a method for producing polypropylene with flexible reactor combinations, the method being adaptable to the system described in any one of the first aspects, the method comprising: In a prepolymerization reactor, the polymerization catalyst and co-catalyst are subjected to a prepolymerization reaction with propylene to obtain a prepolymerization product; The prepolymer product is fed into a liquid phase bulk reactor and polymerized with propylene and / or ethylene in the presence of hydrogen to obtain a slurry product containing polypropylene and unreacted monomers. Select the subsequent aggregation process based on the target product type; When producing homopolymer polypropylene or random copolymer polypropylene, the slurry product is directly fed to a gas phase reactor. The heat of reaction released by the gas phase polymerization reaction in the gas phase reactor is used to vaporize the liquid propylene in the slurry product and continue the polymerization reaction in the gas phase reactor to obtain the final polypropylene product. When producing impact-resistant copolymer polypropylene, the slurry product is heated and flash-evaporated and then separated into gas and solid phases. The separated polypropylene powder is then purged to remove hydrogen and then transported to a gas phase reactor. Propylene and ethylene are introduced into the gas phase reactor to carry out a gas phase copolymerization reaction, thereby obtaining the final polypropylene product.

[0012] Optionally, in the production of impact copolymer polypropylene, the separated polypropylene powder is purged using vaporized propylene within the high-pressure separator.

[0013] Optionally, in the production of impact copolymer polypropylene, the pressure difference between the high-pressure separator and the gas phase reactor is 3 Bar to 6 Bar.

[0014] Optionally, in the production of random copolymer polypropylene, the mass of ethylene added to the liquid phase bulk reactor is 0% to 4% of the mass of propylene.

[0015] Optionally, in the production of random copolymer polypropylene, the mass of ethylene added to the gas phase reactor is 0% to 5.5% of the mass of propylene.

[0016] Optionally, when producing homopolymer polypropylene or random copolymer polypropylene, the operating temperature of the gas phase reactor is 70℃~85℃ and the operating pressure is 20 barg.

[0017] Optionally, the reaction temperature of the prepolymerization reaction in the prepolymerization reactor is 10℃~15℃, and the reaction time is 10min.

[0018] Optionally, the polymerization reaction in the liquid-phase bulk reactor is carried out at a temperature of 67°C to 75°C, and the reaction pressure is at least 2 bar higher than the saturated vapor pressure of propylene.

[0019] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a polypropylene production system with flexible reactor combinations. By flexibly designing the reactor connection structure and material path of the polypropylene production system, it fundamentally breaks the limitations of rigid reactor combinations in traditional polypropylene production processes. At the same time, it significantly reduces the energy consumption of the polypropylene production system through in-situ energy utilization, thereby resolving the contradiction between rigid reactor combinations and high energy consumption. The specific implementation method is as follows: To address the rigidity of reactor combinations in traditional processes, this application designs a dual-connection structure consisting of a gas-phase reactor, a liquid-phase bulk reactor, and a high-pressure separator, and constructs a material path switching mechanism based on product type. When producing homopolymer or random copolymer polypropylene, the polypropylene production system directly transports the polypropylene slurry from the liquid-phase bulk reactor to the gas-phase reactor, allowing the gas-phase reactor to handle subsequent polymerization and energy utilization. When producing impact copolymer polypropylene, the polypropylene production system transports the polypropylene slurry to the high-pressure separator via a steam-jacketed pipeline for processing, and then sends the polypropylene powder to the gas-phase reactor, allowing the gas-phase reactor to participate in the copolymerization reaction. This design ensures that the prepolymer reactor, liquid-phase bulk reactor, and gas-phase reactor fully participate in the reaction throughout all product production processes, with no core reactor idle, completely breaking the limitations of rigid reactor combinations in traditional processes.

[0020] To address the high energy consumption of traditional processes, this application innovatively utilizes the reaction heat of a gas-phase reactor to achieve in-situ energy utilization in the production of homopolymer or random copolymer polypropylene. When the polypropylene slurry from the liquid-phase bulk reactor directly enters the gas-phase reactor, the polypropylene production system does not rely on external steam heating. Instead, it uses the reaction heat generated by the polymerization reaction within the gas-phase reactor to directly vaporize the liquid propylene in the polypropylene slurry into gaseous monomers. This removes the reaction heat and meets the gas-phase reactor's requirements for raw material form, eliminating the additional energy consumption of "steam heating for vaporization" and "cooling water removal of reaction heat" in traditional processes. This reduces the overall energy consumption of the polypropylene production system from the energy utilization stage.

[0021] In summary, this application solves the problem of rigid reactor combination by "flexible reactor connection structure + product adaptation path switching" and solves the problem of high energy consumption by "in-situ utilization of reaction heat to gasify liquid propylene". The synergistic effect of improved reactor combination flexibility and reduced energy consumption effectively resolves the contradiction between rigid reactor combination and high energy consumption in traditional processes. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This application provides a schematic diagram of the structure of a polypropylene production system with flexible reactor combinations, as shown in the embodiments of the present application. Figure 2 A schematic diagram of the actual structure of a polypropylene production system with flexible reactor combinations provided in this application embodiment; Figure label: 1-Prepolymerization reactor, 2-Liquid phase bulk reactor, 3-High pressure separator, 31-Propylene gasification purging component, 4-Steam jacket pipeline, 5-Gas phase reactor. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1 to 6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0027] Figure 1 This application provides a schematic diagram of the structure of a polypropylene production system with flexible reactor combinations, as shown in the embodiments of the present application. Figure 2 This is a schematic diagram of the actual structure of a polypropylene production system with flexible reactor combinations, provided as an embodiment of this application.

[0028] like Figure 1 and Figure 2 As shown in the figure, this application provides a polypropylene production system with flexible reactor combination. The system includes: a prepolymerization reactor 1, a liquid phase bulk reactor 2, a gas phase reactor 5, and a high-pressure separator 3. When producing homopolymer polypropylene or random copolymer polypropylene, the prepolymer reactor 1, the liquid phase bulk reactor 2 and the gas phase reactor 5 are connected in sequence so that the output from the liquid phase bulk reactor 2 is directly transported to the gas phase reactor 5. When producing impact-resistant copolymer polypropylene, the prepolymer reactor 1, the liquid phase bulk reactor 2, the high-pressure separator 3 and the gas phase reactor 5 are connected in sequence so that the discharge from the liquid phase bulk reactor 2 enters the high-pressure separator 3 through the steam jacket pipeline 4 for gas-solid separation, and the separated polypropylene powder is then transported to the gas phase reactor 5.

[0029] In some embodiments, the prepolymerization reactor 1 is a stirred tank reactor or a loop reactor.

[0030] In some embodiments, the liquid phase bulk reactor 2 is a stirred tank reactor or a loop reactor.

[0031] In some embodiments, the number of liquid phase bulk reactors 2 is one or more reactors connected in series.

[0032] In some embodiments, the high-pressure separator 3 is provided with a gasified propylene purging component 31 at the bottom, which is used to purge the polypropylene powder in the high-pressure separator 3 by introducing gasified propylene.

[0033] The powder is equipped with a gasified propylene system for purging and dehydrogenating solid polypropylene. The high-pressure separation system isolates the reaction environments of the liquid phase reactor and the gas phase reactor, preventing material transfer and thus ensuring the reaction environment of the gas phase reactor. This effectively reduces the impact of hydrogen in the liquid phase reactor on the gas phase reactor.

[0034] In some implementations, the discharge destination of the liquid phase bulk reactor varies depending on the product type, requiring the installation of a discharge selection control system.

[0035] The polypropylene production system provided in this application achieves flexible combination and energy consumption optimization of the polypropylene production process through the synergistic effect of multiple key components.

[0036] The prepolymerization reactor 1 is the system start-up unit, used to activate and initially polymerize the catalyst under controlled low-temperature conditions, generating a stable prepolymer product that provides an efficient starting point for subsequent reactions. This reactor can be a stirred tank or a loop reactor.

[0037] The liquid-phase bulk reactor 2 is the main reaction zone, receiving the prepolymerized product and introducing propylene (or propylene and ethylene) and hydrogen for bulk polymerization to produce polypropylene slurry. It can be configured individually or in series to adapt to different production scales.

[0038] The high-pressure separation system is an "environmental isolation unit" specifically designed for the production of impact-resistant copolymer polypropylene products. The system consists of two parts: a steam jacketed pipeline 4 and a high-pressure separator 3. The steam jacketed pipeline 4 connects the liquid phase reactor 2 and the high-pressure separator 3, and its function is to heat the polypropylene slurry discharged from the liquid phase reactor 2 to a vaporized state using steam. The high-pressure separator 3 receives the vaporized material from the steam jacketed pipeline 4 and separates the gaseous monomer from the solid polypropylene powder through gas-solid separation. The core value of this system lies in physically isolating the reaction environments of the liquid phase reactor 2 and the gas phase reactor 5, preventing the high hydrogen content in the liquid phase reactor 2 from entering the subsequent gas phase reactor 5.

[0039] The vaporized propylene purging component 31 is integrated at the bottom of the high-pressure separator 3 and serves as a "purification unit" to ensure the quality of impact-resistant products. Its function is to introduce clean vaporized propylene into the polypropylene powder at the bottom of the high-pressure separator 3, and through airflow purging, completely replace and remove the hydrogen entrained in the solid polypropylene powder.

[0040] The gas-phase reactor 5 is the system's "flexible functional unit." When producing homopolymer or random copolymer polypropylene products, the gas-phase reactor 5 is directly connected to the liquid-phase bulk reactor 2, receiving the polypropylene slurry discharged from the liquid-phase bulk reactor 2. At this time, the gas-phase reactor 5 utilizes the heat generated by its own polymerization reaction to vaporize the liquid propylene in the polypropylene slurry. When producing impact-resistant copolymer polypropylene products, the gas-phase reactor 5 is connected to the high-pressure separator 3, receiving the polypropylene powder processed by the high-pressure separation system, and introducing a mixture of propylene and ethylene monomers into it to carry out a copolymerization reaction to generate impact-resistant polypropylene products.

[0041] Meanwhile, the system provided in this application achieves a comprehensive improvement in the flexibility, energy efficiency, and product quality of polypropylene production through the high degree of coordination among its components and intelligent path selection.

[0042] (1) Component synergy during the production of homopolymer / random copolymer polypropylene: When producing homopolymer or random copolymer polypropylene products, the components within the system form a coherent collaborative chain: "prepolymerization reactor 1 - liquid phase bulk reactor 2 - gas phase reactor 5". Prepolymerization reactor 1 conveys the prepolymerized product to liquid phase bulk reactor 2; after generating polypropylene slurry, liquid phase bulk reactor 2 directly conveys the polypropylene slurry to gas phase reactor 5. Gas phase reactor 5 receives the polypropylene slurry, utilizes its own heat of reaction to vaporize the liquid propylene in the slurry, and completes the subsequent polymerization reaction. Finally, gas phase reactor 5 conveys the reacted mixture to the downstream separation unit.

[0043] (2) Component coordination during the production of impact-resistant copolymer polypropylene: When producing impact-resistant copolymer polypropylene, the system component collaboration path switches to "prepolymer reactor 1 - liquid phase bulk reactor 2 - high-pressure separation system - gas phase reactor 5". After the liquid phase bulk reactor 2 generates polypropylene slurry, it is transported to the high-pressure separator 3 through the steam jacket line 4. The steam jacket line 4 heats the polypropylene slurry to vaporize it, and the high-pressure separator 3 completes the gas-solid separation. Simultaneously, the propylene vaporization purging unit 31 is activated to purge and dehydrogenate the polypropylene powder. The purified polypropylene powder is then transported to the gas phase reactor 5, where propylene and ethylene monomers are introduced to complete the copolymerization reaction. Finally, the gas phase reactor 5 transports the reaction mixture to the downstream separation unit.

[0044] (3) Global energy and material synergistic optimization: From a system-wide perspective, the interaction of each component optimizes the utilization of energy and materials. Regarding energy utilization, when producing homopolymer / random products, the gas-phase reactor 5 utilizes its own reaction heat to vaporize the liquid propylene monomer output from the liquid-phase bulk reactor 2, thus removing the heat of reaction and reducing the external steam energy consumption required for additional propylene monomer vaporization. The combination of structural flexibility and collaborative adaptability of each component allows the entire system to be flexibly adjusted according to production needs.

[0045] Based on a general inventive concept, embodiments of this application provide a method for producing polypropylene with flexible reactor combinations, the method being adaptable to any of the systems described above, the method comprising: S1. In prepolymerization reactor 1, the polymerization catalyst and co-catalyst are subjected to a prepolymerization reaction with propylene to obtain a prepolymerization product. S2. The prepolymerized product is fed into the liquid phase bulk reactor 2 and polymerized with propylene and / or ethylene in the presence of hydrogen to obtain a slurry product containing polypropylene and unreacted monomers. S3. Select the subsequent aggregation process based on the target product type; S301. When producing homopolymer polypropylene or random copolymer polypropylene, the slurry product is directly transported to the gas phase reactor 5. The heat of reaction released by the gas phase polymerization reaction in the gas phase reactor 5 is used to vaporize the liquid propylene in the slurry product and continue the polymerization reaction in the gas phase reactor 5 to obtain the final polypropylene product. S302. When producing impact-resistant copolymer polypropylene, the slurry product is heated and flash-evaporated and separated into gas and solid phases. The separated polypropylene powder is purged to remove hydrogen and then transported to the gas phase reactor 5. Propylene and ethylene are introduced into the gas phase reactor 5 to carry out a gas phase copolymerization reaction to obtain the final polypropylene product.

[0046] It should be noted that in the production of homopolymer or random copolymer polypropylene products, the polymerization catalyst and co-catalyst are mixed and fed into the prepolymerization reactor along with cold propylene for reaction. The resulting slurry then enters the liquid-phase bulk polymerization reactor directly based on the pressure difference, where it continues to react with propylene or propylene + ethylene. The reaction products, along with propylene, enter the gas-phase reactor in slurry form for further reaction. The heat of reaction in the gas-phase reactor vaporizes the liquid propylene from the liquid-phase bulk reactor. The polypropylene powder discharged from the gas-phase reactor, along with unreacted monomers, enters the downstream separation unit.

[0047] The polypropylene slurry discharged from the liquid phase reactor is vaporized through a flash pipeline and then enters a high-pressure separator. Unreacted monomers, including propylene, ethylene, and hydrogen, are discharged from the top of the high-pressure separator. The solids are purged and dehydrogenated by the vaporized propylene and then enter the gas phase reactor, where they continue to react with the added propylene and ethylene to produce impact-resistant polypropylene.

[0048] More importantly, the production of homopolymer or random copolymer polypropylene achieves energy-efficient utilization and continuous reaction through a unique subsequent polymerization step. The core of this step lies in directly feeding the polypropylene slurry from the liquid-phase bulk reactor 2 into the gas-phase reactor 5, where the heat generated by the polymerization reaction inside the gas-phase reactor 5 instantly vaporizes the liquid propylene in the slurry. The vaporized propylene then directly serves as a monomer, continuing the polymerization reaction in the gas-phase reactor 5.

[0049] This step is particularly advantageous for random copolymer products: it completely overcomes the limitation of ethylene solubility in liquid propylene, allowing the amount of ethylene added to be directly adjusted in the gas phase reactor 5, thereby enabling more flexible and precise control of the ethylene content in the final product, providing a key technical path for the production of random copolymer polypropylene products with high ethylene content.

[0050] In some embodiments, during the production of impact copolymer polypropylene, the separated polypropylene powder is purged using vaporized propylene within the high-pressure separator 3.

[0051] In the high-pressure separator 3 used in the production of impact-resistant copolymer polypropylene, the separation of polypropylene powder is purged using gasified propylene. This is a crucial operation to ensure the quality of the subsequent gas-phase copolymerization reaction. Gasified propylene, as a clean purging medium, can efficiently replace and remove impurities such as hydrogen entrained in the polypropylene powder. This prevents impurities such as hydrogen from negatively impacting the copolymerization efficiency of ethylene and propylene after entering the gas-phase reactor 5, ensuring a uniform and stable rubber phase formation process within the gas-phase reactor 5. This, in turn, guarantees that the core performance indicators of the impact-resistant product, such as impact strength, meet the required standards.

[0052] In some embodiments, during the production of impact-resistant copolymer polypropylene, the pressure difference between the high-pressure separator 3 and the gas phase reactor 5 is 3 Bar to 6 Bar.

[0053] During the production of impact-resistant products, maintaining a pressure difference of 3 Bar to 6 Bar between the high-pressure separator 3 and the gas-phase reactor 5 is crucial for ensuring orderly material flow and isolating the reaction environment. This pressure difference propels the polypropylene powder in the high-pressure separator 3 smoothly and unidirectionally into the gas-phase reactor 5, while effectively preventing the ethylene and propylene mixture in the gas-phase reactor 5 from flowing back into the high-pressure separator 3. This avoids material interference between the two systems, creating independent and stable environments for the separation and purification process in the high-pressure separator 3 and the copolymerization reaction in the gas-phase reactor 5.

[0054] In some embodiments, when producing random copolymer polypropylene, the mass of ethylene added to the liquid phase bulk reactor 2 is 0% to 4% of the mass of propylene.

[0055] In some embodiments, when producing random copolymer polypropylene, the mass of ethylene added to the gas phase reactor 5 is 0% to 5.5% of the mass of propylene.

[0056] When producing random copolymer products using multiple reactors connected in series, the addition of ethylene to the gas phase reactor is not limited by the solubility of liquid propylene. This allows for the control of different ethylene and propylene ratios between the liquid phase reactor and the gas phase reactor, thereby enabling the production of random copolymer polypropylene products with high ethylene content.

[0057] In the production of random copolymer polypropylene, the ethylene mass in the liquid-phase bulk reactor 2 accounts for 0%–4% of the propylene mass, while the ethylene mass in the gas-phase reactor 5 accounts for 0%–5.5% of the propylene mass. The ethylene addition ratios in the liquid-phase bulk reactor 2 and the gas-phase reactor 5 are designed to fully adapt to the characteristics of different reaction environments. In the liquid-phase bulk reactor 2, the ethylene ratio is adapted to the solubility limitations of the liquid-phase system, ensuring that ethylene can be uniformly dispersed in the reaction system of the liquid-phase bulk reactor 2 to achieve stable copolymerization. In the gas-phase reactor 5, there are no solubility constraints, and the ethylene ratio can be flexibly increased. Through the differentiated design of ethylene addition in the two stages of the liquid-phase bulk reactor 2 and the gas-phase reactor 5, both the stability of the copolymerization reaction and the precise control of the total ethylene content in the product can be guaranteed.

[0058] In some embodiments, when producing homopolymer polypropylene or random copolymer polypropylene, the gas phase reactor 5 operates at a temperature of 70°C to 85°C and an operating pressure of 20 barg.

[0059] When producing homopolymer or random copolymer products, the gas phase reactor 5 is set at 70~85°C and 20 barg. This condition not only connects well with the upstream liquid phase reaction, but its key role is to achieve in-situ energy utilization: the heat of gas phase polymerization is used to directly vaporize the incoming liquid propylene, eliminating the need for an external heating source, and simultaneously achieving heat removal and efficient utilization of monomers.

[0060] In some embodiments, the reaction temperature of the prepolymerization reaction in the prepolymerization reactor 1 is 10°C to 15°C, and the reaction time is 10 min.

[0061] Prepolymerization is carried out at 10-15°C for 10 minutes, mainly to provide an environment for the mild activation of the catalyst and to ensure the formation of prepolymer products with uniform activity and regular morphology, thus laying the foundation for subsequent main polymerization.

[0062] In some embodiments, the polymerization reaction in the liquid-phase bulk reactor 2 is carried out at a temperature of 67°C to 75°C and at a pressure at least 2 bar higher than the saturated vapor pressure of propylene.

[0063] The liquid-phase bulk polymerization is controlled at 67~75°C and the pressure is at least 2 bar higher than the saturated vapor pressure of propylene. The core purpose is to maintain a pure liquid-phase reaction environment, so as to achieve high conversion rate and polymer isotacticity, while also providing a stable slurry feed for flexible switching of subsequent logistics.

[0064] In summary, the polypropylene production system and method provided in this application exhibit significant advantages in multiple dimensions, with the core being the deep integration of production flexibility, energy consumption optimization, product quality and scope expansion, and improved equipment utilization.

[0065] In terms of production flexibility, the system achieves efficient adaptation to different types of polypropylene products through modular component design and intelligent path switching mechanism. Whether producing homopolymer, random copolymer, or impact copolymer products, production can be completed using the same core equipment: when producing homopolymer or random copolymer products, the slurry from the liquid phase bulk reactor can be directly fed into the gas phase reactor; when switching to impact copolymer products, only the high-pressure separation system needs to be activated to create an independent gas phase copolymerization environment, without the need to idle any reactors. Simultaneously, both the prepolymer reactor and the liquid phase bulk reactor can flexibly utilize stirred tank or loop structures. The liquid phase bulk reactor can also be connected in series according to the scale of the plant, further adapting to different production capacities and process requirements, significantly improving the plant's responsiveness to diverse market demands.

[0066] The optimization of energy consumption is a prominent feature of this application. The system innovatively realizes in-situ recovery and efficient utilization of energy. When producing homopolymer and random copolymer products, the heat generated by the polymerization reaction in the gas phase reactor is used to directly vaporize the liquid propylene in the slurry discharged from the liquid phase bulk reactor into reaction monomers, eliminating the need for additional steam heating and circulating water heat removal in traditional processes, thus reducing energy consumption from the source.

[0067] The stability of product quality and the expansion of its application range are fully guaranteed. For impact copolymer products, the synergistic effect of the high-pressure separation system and the propylene gasification purging component creates a strictly isolated environment between the liquid and gas phase reaction zones. By removing hydrogen entrained in the powder, the copolymerization reaction of ethylene and propylene in the gas phase reactor is ensured to be uniform and stable, facilitating the high-quality formation of the rubber phase and significantly improving the product's impact resistance. For random copolymer products, the system overcomes the limitation of ethylene solubility in the liquid phase environment. Through differentiated ethylene ratio control between the liquid and gas phase reactors, products with high ethylene content can be flexibly produced, enriching the product performance gradient. At the same time, the prepolymerization step provides a stable and active catalytic starting point for subsequent reactions, and the precise control of the liquid phase bulk reactor ensures the uniformity of quality for various products.

[0068] Furthermore, the system completely solves the problem of idle gas-phase reactors in traditional processes. Through a "full-condition operation" design, the gas-phase reactor performs core functions in the production of various products, significantly improving equipment utilization and return on assets. Overall, this application, through component collaboration, path optimization, and detailed design, achieves a comprehensive upgrade in the flexibility, energy efficiency, and product competitiveness of polypropylene production, providing an economical and adaptable solution for industrial production.

[0069] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards / industry standards / the disclosure herein; if there are no corresponding national standards / industry standards / the disclosure herein, they are performed according to generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer.

[0070] Example 1 This embodiment provides a method for producing polypropylene using a flexible reactor combination system, including the following steps.

[0071] Prepolymerization step: The polymerization catalyst and co-catalyst are mixed and fed into prepolymerization reactor 1 along with cold propylene. The temperature of the cold propylene is controlled at 10℃~15℃, the residence time in prepolymerization reactor 1 is controlled at 10min, and the reaction temperature in prepolymerization reactor 1 is controlled at 18℃~22℃.

[0072] Liquid-phase bulk polymerization step: The prepolymerized product discharged from prepolymerization reactor 1 is fed into liquid-phase bulk reactor 2. The residence time in liquid-phase bulk reactor 2 is controlled to be 40 min to 90 min, and the residence time needs to be set according to the catalyst activity profile. A certain amount of catalyst activity needs to be reserved for the subsequent gas-phase reactor 5. The reaction temperature in liquid-phase bulk reactor 2 is controlled to be 67℃ to 75℃, and the reaction pressure in liquid-phase bulk reactor 2 is controlled to be at least 2 bar higher than the saturated vapor pressure of propylene at the operating temperature.

[0073] Subsequent aggregation and path selection steps: When producing homopolymer or random copolymer polypropylene: the polypropylene slurry discharged from the liquid phase bulk reactor 2 is directly transported to the gas phase reactor 5 through the first discharge pipeline. The reaction temperature of the gas phase reactor 5 is controlled at 70℃~85℃, and the reaction pressure of the gas phase reactor 5 is controlled at 20 BarG. The gas phase reactor 5 uses its own heat of reaction to vaporize the liquid propylene in the polypropylene slurry and carry out a gas phase polymerization reaction.

[0074] When producing impact-resistant copolymer polypropylene: The polypropylene slurry discharged from the liquid phase bulk reactor 2 is transported to the steam jacket line 4 through the second discharge pipeline. The steam jacket line 4 heats the polypropylene slurry, causing the liquid propylene in the slurry to vaporize. The vaporized gas-solid mixture enters the high-pressure separator 3 for separation. The gaseous monomer is discharged from the top of the high-pressure separator 3, and the solid polypropylene powder is discharged from the bottom of the high-pressure separator 3. The vaporized propylene purging component 31 installed at the bottom of the high-pressure separator 3 purges the polypropylene powder, and the purging gas flow rate of the vaporized propylene purging component 31 is controlled to be 4% of the polypropylene powder production. The purged polypropylene powder is sent to the gas phase reactor 5, and the pressure difference between the high-pressure separator 3 and the gas phase reactor 5 is controlled to be 3 Bar to 6 Bar. Propylene and ethylene are introduced into the gas phase reactor 5, causing the polypropylene powder to undergo a gas phase copolymerization reaction with propylene and ethylene to produce the impact-resistant copolymer polypropylene product.

[0075] Terminal separation step: The polypropylene product discharged from gas phase reactor 5 and the unreacted monomers are transported to the downstream separation system.

[0076] Furthermore, one or more technical solutions in the embodiments of this application have at least the following technical effects or advantages: (1) Homopolymer and random copolymer polypropylene products are produced by connecting multiple reactors in series. The reaction heat of the gas phase reactor is used to vaporize the liquid propylene discharged from the liquid phase bulk reactor, thereby saving a lot of steam and circulating water and reducing the energy consumption of the polypropylene production unit.

[0077] (2) The multi-reactor series operation technology not only solves the problem of idle gas phase reactors used to produce impact copolymer polypropylene in most processes when producing homopolymer polypropylene and random copolymer polypropylene, but also provides a suitable platform for the design and development of new bimodal polypropylene or multimodal polypropylene products.

[0078] (3) When producing impact-resistant copolymer polypropylene products, a gasification system and a high-pressure separation system are set between the liquid phase bulk reactor and the gas phase reactor. The gasification system and the high-pressure separation system effectively isolate the reaction components of the liquid phase bulk reactor and the gas phase reactor, ensuring the generation of the rubber phase in the gas phase reactor.

[0079] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A reactor flexible combined polypropylene production system, characterized by, The system includes: a prepolymerization reactor (1), a liquid phase bulk reactor (2), a gas phase reactor (5), and a high-pressure separator (3); When producing homopolymer polypropylene or random copolymer polypropylene, the prepolymer reactor (1), the liquid phase bulk reactor (2) and the gas phase reactor (5) are connected in sequence so that the discharge from the liquid phase bulk reactor (2) is directly transported to the gas phase reactor (5). When producing impact-resistant copolymer polypropylene, the prepolymer reactor (1), the liquid phase bulk reactor (2), the high-pressure separator (3) and the gas phase reactor (5) are connected in sequence so that the discharge from the liquid phase bulk reactor (2) enters the high-pressure separator (3) via the steam jacket pipeline (4) for gas-solid separation, and the separated polypropylene powder is then transported to the gas phase reactor (5).

2. The system of claim 1, wherein, The prepolymerization reactor (1) is a stirred tank reactor or a loop reactor.

3. The system of claim 1, wherein, The liquid phase bulk reactor (2) is a stirred tank reactor or a loop reactor.

4. The system of claim 1, wherein, The number of liquid phase bulk reactors (2) is one or more reactors connected in series.

5. The system of claim 1, wherein, The high-pressure separator (3) is provided with a gasified propylene purging component (31) at the bottom. The gasified propylene purging component (31) is used to purge the polypropylene powder in the high-pressure separator (3) with gasified propylene.

6. A process for producing polypropylene by flexible combination of reactors, characterized by, The method is adapted to the system according to any one of claims 1 to 5, and the method includes: In the prepolymerization reactor (1), the polymerization catalyst and the co-catalyst are subjected to a prepolymerization reaction with propylene to obtain a prepolymerization product; The prepolymer product is fed into a liquid phase bulk reactor (2) and polymerized with propylene and / or ethylene in the presence of hydrogen to obtain a slurry product containing polypropylene and unreacted monomers. Select the subsequent aggregation process based on the target product type; When producing homopolymer polypropylene or random copolymer polypropylene, the slurry product is directly transported to the gas phase reactor (5). The heat of reaction released by the gas phase polymerization reaction in the gas phase reactor (5) is used to vaporize the liquid propylene in the slurry product and continue the polymerization reaction in the gas phase reactor (5) to obtain the final polypropylene product. When producing impact-resistant copolymer polypropylene, the slurry product is heated and flashed and separated into gas and solid. The separated polypropylene powder is purged to remove hydrogen and then transported to the gas phase reactor (5). Propylene and ethylene are introduced into the gas phase reactor (5) to carry out gas phase copolymerization reaction to obtain the final polypropylene product.

7. The method of claim 6, wherein, In the production of impact copolymer polypropylene, the separated polypropylene powder is purged using gasified propylene inside the high-pressure separator (3).

8. The method of claim 6, wherein, In the production of impact copolymer polypropylene, the pressure difference between the high-pressure separator (3) and the gas phase reactor (5) is 3 Bar to 6 Bar.

9. The method of claim 6, wherein, In the production of random copolymer polypropylene, the mass of ethylene added to the liquid phase bulk reactor (2) is 0% to 4% of the mass of propylene.

10. The method of claim 6, wherein, In the production of random copolymer polypropylene, the mass of ethylene added to the gas phase reactor (5) is 0% to 5.5% of the mass of propylene.

11. The method of claim 6, wherein, When producing homopolymer polypropylene or random copolymer polypropylene, the operating temperature of the gas phase reactor (5) is 70℃~85℃ and the operating pressure is 20 barg.

12. The method of claim 6, wherein, The reaction temperature of the prepolymerization reaction in the prepolymerization reactor (1) is 10℃~15℃, and the reaction time is 10min.

13. The method according to claim 6, characterized in that, The polymerization reaction in the liquid phase bulk reactor (2) is carried out at a temperature of 67°C to 75°C and the reaction pressure is at least 2 bar higher than the saturated vapor pressure of propylene.

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