Apparatus and method for producing a polypropylene product

Abstract

The application relates to a production device and method of a polypropylene product, and belongs to the technical field of olefin polymerization. The production system comprises a catalyst providing unit, a propylene providing unit, a prepolymerization unit, a comonomer providing unit, a reaction unit, a flash evaporation unit, a medium-pressure separator, a low-pressure separator, a condensation recycling unit, a purification bin and a monomer recycling system. The polymer degassing and propylene and comonomer recycling section of the production system only comprises a flash evaporation process, a gas-solid separation process, a compression and condensation process, a purging process and a membrane recycling process. The gas-solid separation process is carried out in three steps in the medium-pressure separator, the low-pressure separator and the purification bin, the washing, steaming, drying and propylene / ethylene stripping separation processes in the original loop body polymerization process are cancelled, the polymer degassing and propylene / comonomer recycling section process is greatly simplified, the layout is more compact, and the equipment investment and wastewater discharge are reduced.

Description

Technical Field

[0001] This invention belongs to the field of olefin polymerization technology, and specifically relates to a production apparatus and method for polypropylene products. Background Technology

[0002] Currently, there is still a significant supply-demand gap for polyolefins in China. Many of the newly built large-scale oil refining and ethylene projects in the country have downstream polyolefin plants. Furthermore, with the construction boom in coal chemical projects in my country, the proportion of polyolefin capacity will gradually increase. It is expected that domestic polypropylene production capacity will continue to grow substantially in the future.

[0003] Currently, the world's major polypropylene production process technologies and patent holders include Lyondellbasell's Spheripol polypropylene process technology, Lyondellbasell's Spherizone polypropylene process technology, GRACE's Unipol gas-phase polypropylene process technology, INEOSCO's Innovene gas-phase polypropylene process technology, and CBI's Novolen gas-phase polypropylene process technology. Each of these processes has its own advantages; the bulk process offers high space-time yield and good heat dissipation, but requires more post-processing equipment. The gas-phase process is simple, requires fewer equipment units and has a compact layout, and easily controls the ethylene to propylene ratio. The rubber component in the polymer is not dissolved or swollen by the solvent, allowing for the production of high-impact copolymers. The stirred-bed gas-phase process removes the heat of reaction by utilizing the latent heat of vaporization from the sprayed liquid propylene, offering a wide operating range. However, the reactor and its agitator require high precision and are expensive. Fluidized-bed gas-phase reactors have lower equipment costs and no mechanical maintenance issues, but they are larger, have a smaller operating range, and require consideration of circulating compressor costs. Many competitors to the Unipol process argue that strongly backmixed reactors, compared to two-in-tandem reactor systems or plug flow reactors, result in uneven particle residence time distribution, leading to poorer flowability and rubber mass distribution in the impact copolymer product. Analysis of existing polypropylene processes suggests that the optimal solution for producing homopolymers and random copolymers is a bulk loop reactor; the optimal solution for producing high-impact copolymers is a hybrid approach, employing a combination of liquid-phase bulk and gas-phase processes.

[0004] The intermittent bulk polymerization (small bulk) polypropylene polymerization technology independently developed by my country in the late 1970s has low requirements for the quality of raw material propylene, the required catalyst is domestically guaranteed, the process is simple, the product grade conversion is flexible, and there is less waste. However, its production scale is small, making it difficult to generate economies of scale; the equipment requires a lot of manual operation, intermittent production, low level of automation control, and unstable product quality; the raw material consumption quota is relatively high; and the variety of product grades is limited, the quality is not high, and the applications are narrow.

[0005] To adapt to the requirements of large-scale plant development, Sinopec has independently developed a domestic loop polypropylene process technology (ST technology), which has basically replaced imported catalysts and greatly reduced production costs. However, its process flow is basically the same as the Spheripol process flow, and it inevitably has the disadvantages of the Spheripol process, such as having more post-processing equipment.

[0006] Based on the above technologies, patent CN 102399333 discloses an improved technology for propylene polymerization production using a loop reactor. By controlling the reaction pressure in the liquid-phase reactor to be 0.1–1.0 MPa higher than the saturation pressure of the material in the loop reactor, the loop reactor is ensured to be fully filled, eliminating the need for the reactor pressure stabilizing tank in existing production processes. Patent CN101787089 discloses a series reactor process for olefin polymerization, introducing a separation container between the series-connected two-phase gas reactors. This uses a liquid medium to isolate solid and gaseous materials, preventing cross-flow of reactants between the two reactors. Most of these patents represent technological improvements and have not yet formed new, proprietary process packages. Summary of the Invention

[0007] In view of the above problems, the present invention is proposed to provide an apparatus and method for producing polypropylene products that overcomes or at least partially solves the above problems.

[0008] The embodiments of the present invention provide

[0009] A production system for polypropylene products, the production system comprising:

[0010] A catalyst supply unit for preparing catalysts;

[0011] A propylene supply unit is used to supply propylene;

[0012] A prepolymerization unit is used to prepolymerize the catalyst and the propylene to obtain a catalyst slurry system; the prepolymerization unit is connected to the catalyst supply unit and the propylene supply unit respectively, and is used to receive the catalyst and the propylene;

[0013] Comonomer supply unit, used to supply comonomers;

[0014] The first reaction unit is used to react the catalyst slurry system with the reactant monomers propylene, comonomers and molecular weight regulators to obtain a primary slurry; the reaction unit is connected to the prepolymerization unit, the propylene supply unit, the comonomer supply unit and the molecular weight regulator supply unit respectively.

[0015] A flash evaporation unit is used to evaporate unreacted liquid hydrocarbon monomers in the initial slurry to obtain initial powder. The flash evaporation unit is connected to the reaction unit.

[0016] A medium-pressure separator is used to perform gas-solid separation on the primary powder to obtain primary polymer powder and first reuse gas. The medium-pressure separator is connected to the flash evaporation unit.

[0017] A low-pressure separator is used to further separate the gas and solid components of the polymer powder to obtain polymer powder and second recycled gas. The low-pressure separator is connected to the medium-pressure separator.

[0018] A condensation recovery unit is used to recover the first and second recovered gases. The input of the condensation recovery unit is connected to the medium-pressure separator and the low-pressure separator, respectively, and the output of the condensation recovery unit is connected to the propylene supply unit.

[0019] The purification chamber is used to purge polymer powder with hot nitrogen to obtain polypropylene product and purging exhaust gas. The purification chamber is connected to the low-pressure separator and the hot nitrogen pipeline.

[0020] The monomer recovery system is used to separate the purge tail gas to obtain reusable nitrogen and reusable olefins. The input end of the monomer recovery system is connected to the purification chamber, the nitrogen output end of the monomer recovery system is connected to the hot nitrogen pipeline, and the olefin output end of the monomer recovery system is connected to the reusable olefin pipeline.

[0021] Optionally, the catalyst providing unit includes:

[0022] The main catalyst preparation tank is used to prepare the dry powder main catalyst and solvent to obtain the main catalyst slurry;

[0023] A pre-activation tank is used to mix and activate the main catalyst slurry, co-catalyst, and catalyst modifier to obtain a catalyst. The input end of the pre-activation tank is connected to the main catalyst preparation tank, and the output end of the pre-activation tank is connected to the pre-polymerization unit.

[0024] Optionally, the production system further includes:

[0025] The second reaction unit is used to copolymerize the polymer powder from the first reaction unit with propylene, comonomers, and hydrogen to obtain a copolymer precursor. The second reaction unit is connected to the medium-pressure separator to receive the polymer powder precursor discharged from the medium-pressure separator. The second reaction unit is also connected to the low-pressure separator to intermittently discharge the copolymer precursor to the low-pressure separator.

[0026] A raw material supply unit is provided to supply propylene, comonomers, and hydrogen; the raw material supply unit is connected to the second reaction unit;

[0027] A recycling unit is used to recycle the gas in the second reaction unit and the low-pressure separator. The input end of the recycling unit is connected to the second reaction unit and the low-pressure separator, the solid output end of the recycling unit is connected to the second reaction unit, and the gas output end of the recycling unit is connected to the raw material supply unit.

[0028] Loosening pipelines are used to loosen the bottom of the bed of the second reaction unit, the loosening pipelines being connected to the bottom of the second reaction unit.

[0029] Optionally, the production system further includes:

[0030] A propylene gas purging line is used to purge clean propylene gas into the medium-pressure separator, and the propylene gas purging line is connected to the bottom of the medium-pressure separator.

[0031] Based on the same inventive concept, embodiments of the present invention also provide a method for producing a polypropylene product, the method comprising:

[0032] Catalyst preparation;

[0033] The catalyst and propylene were prepolymerized to obtain a slurry system;

[0034] The slurry system is reacted with the reactive monomer propylene, the comonomer, and the molecular weight regulator to obtain the initial slurry.

[0035] The initial slurry is subjected to flash evaporation and gas-solid separation to obtain initial polymer powder and first reuse gas.

[0036] The initial polymer powder is subjected to gas-solid separation to obtain polymer powder and second recycled gas.

[0037] The first and second reused gas are reused;

[0038] The polymer powder was purged with hot nitrogen to obtain polypropylene product and purging exhaust gas.

[0039] The purge tail gas is separated to obtain reusable nitrogen and reusable olefins;

[0040] The recycled nitrogen and recycled olefins are reused.

[0041] Optionally, the preparation of the catalyst specifically includes:

[0042] The dry powder main catalyst and solvent are mixed to obtain the main catalyst slurry;

[0043] The main catalyst slurry, co-catalyst, and catalyst modifier are mixed and activated to obtain the catalyst.

[0044] Optionally, the main catalyst includes a Zn catalyst, the solvent includes white oil, the co-catalyst includes triethylaluminum, and the catalyst modifier includes a silane electron donor.

[0045] Optionally, the comonomer includes ethylene and / or butene-1; the molecular weight regulator includes hydrogen.

[0046] Optionally, the method further includes:

[0047] The liquid in the initial slurry is evaporated, followed by gas-solid separation to obtain the initial polymer powder.

[0048] The polymer powder primary product is copolymerized with propylene, comonomer and hydrogen in a gas phase reactor to obtain the copolymer primary product.

[0049] The copolymer primary product is subjected to gas-solid separation to obtain copolymer third reuse gas;

[0050] The third type of recycled gas will be reused.

[0051] Optionally, the reaction pressure in the step of reacting the slurry system with the reactive monomer propylene, the comonomer, and the molecular weight regulator to obtain the initial slurry is 3.2-4.6 MPaG.

[0052] The process of flash evaporation and gas-solid separation of the initial slurry to obtain initial polymer powder and first reuse gas involves a gas-solid separation pressure of 2.0-3.0 MPaG.

[0053] The copolymerization process involves reacting the polymer powder with propylene, comonomers, and hydrogen to obtain a copolymer precursor. The copolymerization pressure is 1.8-2.2 MPaG.

[0054] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0055] The polypropylene production system provided in this embodiment of the invention includes: a catalyst supply unit for preparing a catalyst; a propylene supply unit for supplying propylene; a prepolymerization unit for prepolymerizing the catalyst and the propylene olefin to obtain a catalyst slurry system; the prepolymerization unit is connected to both the catalyst supply unit and the propylene supply unit to receive the catalyst and propylene; and a first reaction unit for reacting the catalyst slurry system with the reactive monomer propylene, a comonomer, and a molecular weight regulator to obtain a primary slurry; the reaction unit is connected to both the prepolymerization unit and the propylene supply unit. The system comprises: a supply unit, a comonomer supply unit, and a molecular weight regulator supply unit; a flash evaporation unit for evaporating unreacted liquid hydrocarbon monomers in the initial slurry to obtain initial powder, the flash evaporation unit being connected to the reaction unit; a medium-pressure separator for gas-solid separation of the initial powder to obtain initial polymer powder and first recycled gas, the medium-pressure separator being connected to the flash evaporation unit; a low-pressure separator for further gas-solid separation of the initial polymer powder to obtain polymer powder and second recycled gas, the low-pressure separator being connected to the medium-pressure separator; and a condensation and recycling unit for recycling the first and second recycled gas. The condensation and reuse unit has its input connected to the medium-pressure separator and the low-pressure separator, and its output connected to the propylene supply unit. A purification chamber is used to purge the polymer powder with hot nitrogen and steam to deactivate the catalyst and triethylaluminum activity in the polymer powder, obtaining polypropylene product and purge tail gas. The purification chamber is connected to the low-pressure separator and the hot nitrogen pipeline. A monomer recovery system separates the purge tail gas to obtain recycled nitrogen and recycled olefins. The input of the monomer recovery system is connected to the purification chamber, and its nitrogen output is connected to the propylene supply unit. The hot nitrogen pipeline connects to the olefin output of the monomer recovery system, which is linked to the recycled olefin pipeline. Additionally, the second reaction unit is a gas-phase reaction unit used to copolymerize the polymer powder from the first reaction unit with propylene, comonomers, and hydrogen to obtain a preliminary copolymer product. This second reaction unit is connected to the medium-pressure separator to receive the polymer powder product discharged from the separator. It is also connected to the low-pressure separator to intermittently discharge the preliminary copolymer product to the separator. A raw material supply unit provides propylene, comonomers, and hydrogen; this unit is connected to the second reaction unit. The polymer degassing and propylene and comonomer recovery sections of this production system only include flash evaporation, gas-solid separation, compression condensation, purging, and membrane recovery processes. The gas-solid separation process is carried out in three steps in the medium-pressure separator, low-pressure separator and purification chamber. This eliminates the washing, steaming, drying and propylene / ethylene stripping separation processes in the original loop polymerization process, greatly simplifying the polymer degassing and propylene / comonomer recovery process. The layout is more compact, reducing equipment investment and wastewater discharge.

[0056] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 This is a schematic diagram of the production system provided in an embodiment of the present invention;

[0059] Figure 2 This is a flowchart of the production method provided in Embodiment 1 of the present invention;

[0060] Figure 3 This is a flowchart of the production method provided in Embodiment 2 of the present invention;

[0061] Figure reference numerals: 1-Catalyst supply unit, 2-Propylene supply unit, 3-Prepolymerization unit, 4-First reaction unit, 5-Flash evaporation unit, 6-Medium-pressure separator, 7-Low-pressure separator, 8-Condensation and reuse unit, 9-Purification chamber, 10-Monomer recovery system, 11-Main catalyst preparation tank, 12-Pre-activation tank, 13-Second gas phase reaction unit, 14-Raw material supply unit, 15-Reuse unit, 16-Loosening pipeline, 17-Propylene gas purging pipeline. Detailed Implementation

[0062] The present invention will be described in detail below with reference to specific embodiments and examples, thereby making the advantages and various effects of the present invention more clearly apparent. Those skilled in the art should understand that these specific embodiments and examples are for illustrative purposes only and are not intended to limit the present invention.

[0063] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any conflict, this specification shall prevail.

[0064] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0065] The technical solution of this application embodiment is to solve the above-mentioned technical problems, and the general idea is as follows:

[0066] According to a typical embodiment of the present invention, a production system for polypropylene products is provided.

[0067] The production system includes:

[0068] A catalyst supply unit for preparing catalysts;

[0069] A propylene supply unit is used to supply propylene;

[0070] A prepolymerization unit is used to prepolymerize the catalyst and the propylene to obtain a catalyst slurry system; the prepolymerization unit is connected to the catalyst supply unit and the propylene supply unit respectively, and is used to receive the catalyst and propylene;

[0071] Comonomer supply unit, used to supply comonomers;

[0072] The first reaction unit is used to react the catalyst slurry system with the reactant monomers propylene, comonomers and molecular weight regulators to obtain a primary slurry; the reaction unit is connected to the prepolymerization unit, the propylene supply unit, the comonomer supply unit and the molecular weight regulator supply unit respectively.

[0073] A flash evaporation unit is used to evaporate unreacted liquid hydrocarbon monomers in the initial slurry to obtain initial powder. The flash evaporation unit is connected to the reaction unit.

[0074] A medium-pressure separator is used to perform gas-solid separation on the primary powder to obtain primary polymer powder and first reuse gas. The medium-pressure separator is connected to the flash evaporation unit.

[0075] A low-pressure separator is used to further separate the gas and solid components of the polymer powder to obtain polymer powder and second recycled gas. The low-pressure separator is connected to the medium-pressure separator.

[0076] A condensation recovery unit is used to recover the first and second recovered gases. The input of the condensation recovery unit is connected to the medium-pressure separator and the low-pressure separator, respectively, and the output of the condensation recovery unit is connected to the propylene supply unit.

[0077] The purification chamber is used to purge polymer powder with hot nitrogen to obtain polypropylene product and purging exhaust gas. The purification chamber is connected to the low-pressure separator and the hot nitrogen pipeline.

[0078] The monomer recovery system is used to separate the purge tail gas to obtain reusable nitrogen and reusable olefins. The input end of the monomer recovery system is connected to the purification chamber, the nitrogen output end of the monomer recovery system is connected to the hot nitrogen pipeline, and the olefin output end of the monomer recovery system is connected to the reusable olefin pipeline.

[0079] As an optional implementation, the production system also includes:

[0080] The second reaction unit, which is a gas-phase reaction unit, is used to copolymerize the polymer powder from the first reaction unit with propylene, comonomers, and hydrogen to obtain a preliminary copolymer product. The second reaction unit is connected to the medium-pressure separator to receive the polymer powder preliminary product discharged from the medium-pressure separator. The second reaction unit is also connected to the low-pressure separator to intermittently discharge the preliminary copolymer product to the low-pressure separator.

[0081] A raw material supply unit is provided to supply propylene, comonomers, and hydrogen; the raw material supply unit is connected to the second reaction unit;

[0082] A recycling unit is used to recycle the gas in the second reaction unit and the low-pressure separator. The input end of the recycling unit is connected to the second reaction unit and the low-pressure separator, the solid output end of the recycling unit is connected to the second reaction unit, and the gas output end of the recycling unit is connected to the raw material supply unit.

[0083] The refined fresh liquid propylene and refined ethylene are added to the separator. The liquid in the separator (i.e., the raw material supply unit) is injected from the top of the gas-phase fluidized bed as a coolant to absorb the reaction heat in the horizontal gas-phase reactor. The unreacted gas passes through the dome at the top of the horizontal gas-phase reactor and the circulating cyclone separator for gas-solid separation. The circulating gas is partially condensed by the circulating gas condenser and then returned to the separator for recycling.

[0084] The loosening pipeline is used to loosen the bottom of the bed in the gas phase reaction unit. The loosening pipeline is connected to the bottom of the gas phase reaction unit. In specific implementation, the loosening pipeline is connected to the raw material supply unit. The uncondensed circulating gas discharged from the raw material supply unit is compressed by the circulating gas compressor and added from the bottom of the reactor together with the purified hydrogen to loosen the bottom of the bed and prevent the polymer from sticking to the reactor.

[0085] When producing impact copolymers, the horizontal gas-phase reactor (i.e., the gas phase reactor) and the liquid-phase bulk reactor (i.e., the reaction unit) use different raw material feeding systems, circulating gas condensation equipment, and circulating gas paths. This ensures that unreacted gases are fully recovered while maintaining the difference in reactant concentrations, especially hydrogen concentrations, between the liquid-phase bulk loop reactor and the horizontal gas-phase reactor, thus ensuring the performance of the impact copolymer.

[0086] As an optional implementation, the production system further includes a propylene gas purging line for purging clean propylene gas into the medium-pressure separator, the propylene gas purging line being connected to the bottom of the medium-pressure separator.

[0087] According to another typical embodiment of the present invention, a method for producing a polypropylene product is provided, characterized in that the production method includes:

[0088] S1. Obtain the catalyst;

[0089] Specifically, S1.1. The dry powder main catalyst and solvent are mixed to obtain a main catalyst slurry;

[0090] S1.2. The main catalyst slurry, co-catalyst, and catalyst modifier are mixed and activated to obtain the catalyst;

[0091] S2. Prepolymerize the catalyst and propylene to obtain a slurry system;

[0092] S3. React the slurry system with the reactive monomers propylene, comonomers, and molecular weight regulators to obtain the initial slurry;

[0093] S4. The initial slurry is subjected to flash evaporation and gas-solid separation to obtain the initial polymer powder and the first reuse gas;

[0094] S5. Perform gas-solid separation on the initial polymer powder to obtain polymer powder and second recycled gas;

[0095] S6. Reuse the first and second reused gas;

[0096] S7. The polymer powder is purged with hot nitrogen to obtain polypropylene product and purging exhaust gas;

[0097] S8. Separate the purge tail gas to obtain recycled nitrogen and recycled olefins;

[0098] S9. The recycled nitrogen and recycled olefins are recycled;

[0099] The specific implementation includes the following steps:

[0100] 1) Catalyst preparation: The dry powder main catalyst and solvent are prepared in the main catalyst preparation tank, and then mixed and activated with the co-catalyst and catalyst modifier in the pre-activation tank through a metering system;

[0101] 2) Raw material feeding and prepolymerization: Propylene from the boundary area is purified by the propylene refining system to remove impurities and then enters the propylene feed tank (i.e., propylene supply unit). After cooling, one stream directly enters the prepolymerization reactor (i.e., prepolymerization unit), and the other stream is used as flushing liquid to flush the catalyst slurry into the prepolymerization reactor for prepolymerization.

[0102] 3) Liquid-phase bulk polymerization: The slurry system after prepolymerization continuously enters the liquid-phase bulk reactor (i.e., the reaction unit) from the prepolymerization reactor. The reactant monomer propylene, along with the molecular weight regulator hydrogen and / or the comonomer ethylene, is added from the bottom of the liquid-phase bulk reactor to produce homopolymers or random copolymers. When producing ternary random copolymers, the comonomer 1-butene needs to be added. The liquid-phase bulk reactor is equipped with an axial flow circulation pump to ensure slurry circulation.

[0103] 4) Liquid phase bulk polymer post-treatment and circulating gas recovery: The polymer degassing and propylene and comonomer recovery section only includes flash evaporation, gas-solid separation, compression and condensation, purging and membrane recovery processes; the gas-solid separation process is carried out in three steps in the medium-pressure separator, low-pressure separator and purification chamber; the gas separated in the low-pressure separator is compressed by the propylene recovery compressor and enters the circulating gas path loop A, and together with the gas separated in the medium-pressure separator, it is condensed and recovered by the propylene condenser to the propylene feed tank.

[0104] As an optional implementation method, the main catalyst is a Zn catalyst, the prepolymer catalyst preparation solution is white oil, and the main catalyst modifier is triethylaluminum.

[0105] As an optional implementation, the pre-activation tank and the prepolymerization reactor are kept at a low temperature using a refrigerant jacket, preferably chilled water.

[0106] As an optional implementation, the prepolymerization reactor is a vertical stirred tank reactor or a loop reactor, preferably a vertical stirred tank reactor; the liquid phase bulk reactor is a stirred tank reactor or a loop reactor, preferably a loop reactor.

[0107] In practice, both prepolymerization and liquid-phase bulk polymerization are carried out continuously. The prepolymerization reactor and the liquid-phase bulk reactor are operated with full liquid, while the liquid-phase bulk reactor is operated with continuous discharge.

[0108] In actual operation, when producing homopolymers or random copolymers, the medium-pressure bag separator to the low-pressure separator adopts a continuous discharge mode.

[0109] As an alternative implementation, in the production of impact copolymers, the horizontal gas-phase reactor controls the reaction pressure by adjusting the temperature of the circulating gas condenser and controls the bed temperature by adjusting the flow rate of the injected propylene liquid.

[0110] As an optional implementation, the method further includes:

[0111] S10. Evaporate the liquid of the initial slurry, and then perform gas-solid separation to obtain the initial polymer powder;

[0112] S11. The polymer powder primary product is copolymerized with propylene, comonomer and hydrogen to obtain copolymer primary product;

[0113] S12. Perform gas-solid separation on the copolymer primary product to obtain copolymer third reuse gas;

[0114] S13. The third reuse gas is reused.

[0115] The specific implementation includes the following steps:

[0116] 5) Gas-phase copolymerization: When producing copolymers, the homopolymer powder generated in the liquid-phase bulk reactor evaporates the liquid in a shell-and-tube heat exchanger (i.e., flash unit), and then achieves gas-solid separation in a medium-pressure bag separator (i.e., medium-pressure separator). The homopolymer powder separated by the medium-pressure bag separator is directly discharged into the horizontal gas-phase reactor (i.e., gas-phase reaction unit) to undergo gas-phase copolymerization with the vaporized propylene, ethylene, and hydrogen. The gas in the separator (i.e., raw material supply unit) is compressed by the circulating gas compressor and added from the bottom of the horizontal gas-phase reactor along with the purified hydrogen to loosen the bottom of the bed in the horizontal gas-phase reactor. While ensuring the full recovery of unreacted gas, the difference in reactant concentration, especially hydrogen concentration, between the liquid-phase bulk reactor and the horizontal reactor is maintained to ensure the performance of the copolymer.

[0117] 6) Post-processing of gas-phase copolymer and recovery of circulating gas: The impact copolymer generated in the horizontal gas-phase reactor enters the low-pressure separator. The polymer powder after low-pressure gas-solid separation enters the purification chamber for further processing. The unreacted gas separated is compressed by the recovery propylene compressor and then switched to the circulating gas path loop B. Together with the unreacted gas separated by the cyclone separator, it enters the circulating gas condenser for condensation and is added to the separator for recycling.

[0118] In the production of impact copolymers, homopolymer powder is continuously discharged from a medium-pressure bag separator to a horizontal gas phase reactor, where the discharge from the horizontal gas phase reactor to a low-pressure separator is controlled by a level gauge.

[0119] In actual operation, the operating pressure of the liquid phase bulk reactor is 3.2-4.6 MPaG; the operating pressure of the medium-pressure bag separator is 2.0-3.0 MPaG, preferably 2.4 MPaG; and the operating pressure inside the horizontal gas phase reactor is 1.8-2.2 MPaG.

[0120] As an optional implementation, the bottom of the medium-pressure bag separator is equipped with hot clean propylene gas purging to displace the hydrogen gas entrained in the material discharged from the liquid phase reactor, thereby isolating the gas phase of the two reactors, the liquid phase reactor and the horizontal gas phase reactor.

[0121] In actual operation, the horizontal gas phase reactor and the medium-pressure separator are arranged vertically; the low-pressure separator and purification chamber can be arranged on the roof of the extrusion granulation plant. The degassed polymer powder directly enters the extrusion granulation system, reducing the need for a pneumatic conveying system and thus saving a powder conveying system, making the layout more compact.

[0122] The production apparatus and method for polypropylene products of this application will be described in detail below with reference to embodiments, comparative examples and experimental data.

[0123] Example 1

[0124] The main catalyst, namely the ZN catalyst, is prepared in a main catalyst preparation tank using prepolymerized catalyst preparation liquid white oil, in which the catalyst accounts for about 25% by weight.

[0125] Subsequently, it is mixed and activated in a pre-activation tank with the co-catalyst triethylaluminum and the catalyst modifier silane via a main catalyst metering pump. The reaction temperature in the activation tank is 10℃, the reaction pressure is 3.2-4.6MPaG, and the tank is cooled by jacketed chilled water. The amount of triethylaluminum added is 0.1-0.2kg per ton of polypropylene, and the amount of silane added is 0.01-0.1kg per ton of polypropylene.

[0126] Propylene from the boundary area undergoes impurity removal treatment in the propylene refining system before entering the propylene feed tank, where it is pumped by a propylene feed pump. Approximately 3% by mass of the propylene is used for prepolymerization, with the prepolymerization reactor temperature maintained at 10-25°C; the remainder is used for liquid-phase bulk polymerization. The propylene used for prepolymerization is cooled by a propylene cooler. Approximately 40% by mass of the low-temperature propylene is used as a flushing fluid to carry the catalyst system into the prepolymerization stirred tank for prepolymerization, while the remainder serves as a solvent within the prepolymerization stirred tank, maintaining the stirred tank at full liquid level.

[0127] The prepolymerized catalyst slurry system continuously enters the liquid-phase bulk loop reactor from the top of the prepolymerization stirred tank. The operating pressure of the liquid-phase bulk loop reactor is 3.2-4.6 MPag, and the operating temperature is 67-71℃. The polymerization monomer propylene, along with the molecular weight regulator hydrogen, is added from the bottom of the liquid-phase bulk loop reactor to produce homopolymers. The molar concentration of hydrogen varies from tens to tens of thousands of ppm. When producing random copolymers, comonomers such as ethylene and butene-1 are also added. The liquid-phase bulk loop reactor uses an axial flow pump to ensure slurry circulation. Both the prepolymerization stirred tank and the liquid-phase bulk loop reactor utilize jacketed refrigerant (cooling water) to remove the heat of reaction.

[0128] A portion of the high-speed circulating polymer slurry is continuously discharged from the bottom of the liquid phase bulk loop reactor and passes through a shell-and-tube heat exchanger, where the pressure is about 2.4 MPa and the temperature is 80-90℃, where flash evaporation is performed to vaporize the liquid phase monomers.

[0129] The flash-evaporated gas is separated from trace amounts of polymer powder by a medium-pressure bag separator, which operates at a pressure of 1.9-2.4 MPaG and a temperature of 90°C. The gas is then condensed by a propylene condenser, which uses circulating cooling water as a refrigerant. After condensation, the gas is pumped to a propylene feed tank via a propylene recovery pump and mixed with the refined fresh propylene feedstock.

[0130] In the medium-pressure bag separator, polymer solid powder continuously enters the low-pressure separator, where the operating pressure is 0.02-0.05 MPa and the operating temperature is 80°C. The further separated gases, propylene and hydrogen, are compressed by the propylene recovery compressor and enter the loop A. Valve 1 is normally open (NO) and valve 2 is normally closed (NC). Together with the gas separated from the medium-pressure bag separator, they are condensed and recovered by the propylene condenser to the propylene feed tank.

[0131] The polymer solid powder separated by the low-pressure separator enters the purification chamber to remove the small amount of propylene monomer contained in the polymer, so that the residual propylene monomer content in the polymer is below 0.01%.

[0132] Hot nitrogen gas at 60-110℃ is injected into the bottom of the purification chamber to purge the polymer powder. Water vapor, mixed with the nitrogen gas at a mass percentage of 2%-3%, is used to completely deactivate residual catalysts and co-catalysts in the powder. The purge exhaust gas containing nitrogen and olefins is sent to the membrane recovery system for recycling. The recovered nitrogen is mixed with replenishing fresh nitrogen and heated by a nitrogen heater to be used as purge gas. The recovered olefins are sent outside the boundary for recycling. The purification chamber is located on the roof of the extrusion granulation plant. The degassed polymer powder enters the extrusion granulation system directly under gravity, thus reducing the need for a pneumatic conveying system and saving on a powder conveying system, resulting in a more compact equipment layout. The gas outlet at the top of the purification chamber is equipped with a filter to prevent powder entrained in the purge exhaust gas from clogging the membrane recovery system.

[0133] Example 2

[0134] When producing impact copolymers, the homopolymer powder generated in the liquid phase bulk loop reactor evaporates the liquid through a shell-and-tube heat exchanger, and then achieves gas-solid separation in a medium-pressure bag separator. The solid powder is continuously discharged into the horizontal gas phase reactor for gas-phase copolymerization through a pressure control system, relying on the pressure difference between the liquid phase bulk loop reactor and the horizontal gas phase reactor. The operating pressure in the horizontal gas phase reactor is 2.2 MPa and the operating temperature is about 70°C.

[0135] A stream of hot, clean propylene gas is injected into the bottom of the medium-pressure bag separator to displace the gaseous components in the material discharged from the liquid phase reactor, while preventing cross-contamination of the gas phase composition between the two reactors.

[0136] The horizontal gas-phase reactor and the liquid-phase bulk loop reactor employ different raw material feeding systems, circulating gas condensation equipment, and circulating gas paths. This ensures the full recovery of unreacted gases while maintaining the difference in reactant concentrations, especially hydrogen concentration, thus ensuring the performance of the impact copolymer.

[0137] The refined fresh liquid propylene and refined ethylene are added to the separator. The propylene liquid and ethylene liquid are injected from the top of the bed of the horizontal gas phase reactor to absorb the heat of gas phase polymerization reaction. The unreacted gases (including propylene, ethylene and hydrogen) in the horizontal gas phase reactor are separated into gas and solid by passing through the dome at the top of the horizontal gas phase reactor and the circulating gas cyclone separator. The gases are condensed to about 45°C by the circulating gas condenser and then returned to the separator for recycling.

[0138] Uncondensed gas in the separator is compressed by the circulating gas compressor and then added along with refined hydrogen from the bottom of the horizontal gas-phase reactor to loosen the bed and prevent sticking. Cooling water is used as the refrigerant in the circulating gas condenser. The reactor pressure is controlled by adjusting the circulating gas condensation temperature, and the bed temperature is maintained at 65-70℃ by adjusting the flow rate of injected propylene liquid.

[0139] The impact copolymer generated in the horizontal gas-phase reactor is intermittently discharged into the low-pressure separator via a level gauge. The separated unreacted gas is compressed by the propylene recovery compressor and then enters the loop B. Valve 1 is normally closed (NC), and valve 2 is normally open (NO). Together with the unreacted gas separated by the circulating gas cyclone separator, the gas enters the circulating gas condenser and is condensed to approximately 45°C. It is then added to the separatory tank for recycling. The polymer powder after low-pressure gas-solid separation enters the purification chamber for further processing.

[0140] Comparative Example 1

[0141] Impact copolymer products are produced using the Spheripol process.

[0142] It should be noted that the polypropylene plant used in Example 2 and Comparative Example 1 both have a production capacity of 300,000 tons / year. Compared with the Spheripol process, the method provided by the present invention has a shorter process, a smaller plant area, and the ethylene mass percentage in the obtained impact copolymer product can reach 25%.

[0143] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0144] (1) This invention provides a method for producing polypropylene using a prepolymer-liquid phase bulk-gas phase combined method, which develops domestic independent technology and reduces dependence on foreign countries. This invention preferentially adopts a vertical stirred tank prepolymer reactor and a plug-flow horizontal gas phase reactor, eliminating the washing, steaming, drying and propylene / ethylene stripping separation processes in the original loop bulk polymerization process, greatly simplifying the polymer degassing and propylene / comonomer recovery process. It has the advantages of simple process, low equipment cost, compact equipment layout, good impact resistance, wide process operation range, and the ability to produce impact resistance products with a wide range of ethylene content.

[0145] (2) In the production of impact copolymers, the method provided in this embodiment of the invention uses different raw material feeding systems, circulating gas condensation equipment and circulating gas paths in the horizontal gas phase reactor and the liquid phase bulk reactor. While ensuring the full recovery of unreacted gas, it maintains the difference in reactant concentration, especially hydrogen concentration, in the two reactors, the liquid phase bulk loop reactor and the horizontal gas phase reactor, so as to ensure the performance of the impact copolymer.

[0146] (3) The impact-resistant polypropylene produced by the method provided in this embodiment of the invention has a high comonomer content, good rigidity and impact resistance, and the ethylene content can be controlled between 5% and 25%. At the same time, since the gas phase reaction adopts a similar plug flow reactor, the product has better uniformity and a better balance between rigidity and toughness.

[0147] Finally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0148] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0149] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A production system for polypropylene products, characterized in that, The production system includes: A catalyst supply unit for preparing catalysts; A propylene supply unit is used to supply propylene; A prepolymerization unit is used to prepolymerize the catalyst and the propylene to obtain a catalyst slurry system; the prepolymerization unit is connected to the catalyst supply unit and the propylene supply unit respectively, and is used to receive the catalyst and propylene; a comonomer supply unit is used to supply comonomers; The first reaction unit is used to react the catalyst slurry system with the reactant monomers propylene, comonomers and molecular weight regulators to obtain a primary slurry; the reaction unit is connected to the prepolymerization unit, the propylene supply unit, the comonomer supply unit and the molecular weight regulator supply unit respectively. A flash evaporation unit is used to evaporate unreacted liquid hydrocarbon monomers in the initial slurry to obtain initial powder. The flash evaporation unit is connected to the first reaction unit. A medium-pressure separator is used to perform gas-solid separation on the primary powder to obtain primary polymer powder and first reuse gas. The medium-pressure separator is connected to the flash evaporation unit. A low-pressure separator is used to further separate the gas and solid components of the polymer powder to obtain polymer powder and second recycled gas. The low-pressure separator is connected to the medium-pressure separator. A condensation recovery unit is used to recover the first and second recovered gases. The input of the condensation recovery unit is connected to the medium-pressure separator and the low-pressure separator, respectively, and the output of the condensation recovery unit is connected to the propylene supply unit. The purification chamber is used to purge polymer powder with hot nitrogen to obtain polypropylene product and purging exhaust gas. The purification chamber is connected to the low-pressure separator and the hot nitrogen pipeline. A monomer recovery system is used to separate purge tail gas to obtain reusable nitrogen and reusable olefins. The input end of the monomer recovery system is connected to the purification chamber, the nitrogen output end of the monomer recovery system is connected to the hot nitrogen pipeline, and the olefin output end of the monomer recovery system is connected to the reusable olefin pipeline. The second reaction unit is used to copolymerize the polymer powder from the first reaction unit with propylene, comonomers, and hydrogen to obtain a copolymer precursor. The second reaction unit is connected to the medium-pressure separator to receive the polymer powder precursor discharged from the medium-pressure separator. The second reaction unit is also connected to the low-pressure separator to intermittently discharge the copolymer precursor to the low-pressure separator. The prepolymerization unit is a vertical stirred tank reactor; the first reaction unit is a tank reactor or a loop-type liquid phase reactor; the second reaction unit is a horizontal gas phase reactor. A propylene gas purging line is used to purge clean propylene gas into the medium-pressure separator, and the propylene gas purging line is connected to the bottom of the medium-pressure separator; The low-pressure separator and purification chamber are located on the roof of the extrusion granulation plant. The gas-solid separation process takes place in a medium-pressure separator, a low-pressure separator, and a purification chamber; The monomer recovery system is a membrane recovery system.

2. The polypropylene product production system according to claim 1, characterized in that, The catalyst supply unit includes: The main catalyst preparation tank is used to prepare the dry powder main catalyst and solvent to obtain the main catalyst slurry; A pre-activation tank is used to mix and activate the main catalyst slurry, co-catalyst, and catalyst modifier to obtain a catalyst. The input end of the pre-activation tank is connected to the main catalyst preparation tank, and the output end of the pre-activation tank is connected to the pre-polymerization unit.

3. The polypropylene product production system according to claim 1, characterized in that, The production system also includes: A raw material supply unit is provided to supply propylene, comonomer, and hydrogen; the raw material supply unit is connected to the second reaction unit; A recycling unit is used to recycle the gas in the second reaction unit and the low-pressure separator. The input end of the recycling unit is connected to the second reaction unit and the low-pressure separator, the solid output end of the recycling unit is connected to the second reaction unit, and the gas output end of the recycling unit is connected to the raw material supply unit. Loosening pipelines are used to loosen the bottom of the bed of the second reaction unit, the loosening pipelines being connected to the bottom of the second reaction unit.

4. A method for producing polypropylene products using the production system according to any one of claims 1-3, characterized in that, The production method includes: Catalyst preparation; The catalyst and propylene were prepolymerized to obtain a slurry system; The slurry system is reacted with the reactive monomer propylene, the comonomer, and the molecular weight regulator to obtain the initial slurry. The initial slurry is subjected to flash evaporation and gas-solid separation to obtain initial polymer powder and first reuse gas. The initial polymer powder is subjected to gas-solid separation to obtain polymer powder and second recycled gas. The first and second reused gas are reused; The polymer powder was purged with hot nitrogen to obtain polypropylene product and purging exhaust gas. The purge tail gas is separated to obtain reusable nitrogen and reusable olefins; The recycled nitrogen and recycled olefins are reused; The reaction of the slurry system with the reactive monomers propylene, comonomers, and molecular weight regulators to obtain the initial slurry occurs at a reaction pressure of 3.2-4.6 MPaG. The process of flash evaporation and gas-solid separation of the initial slurry to obtain initial polymer powder and first reuse gas involves a gas-solid separation pressure of 2.0-3.0 MPaG. The copolymerization process involves reacting the polymer powder with propylene, comonomers, and hydrogen to obtain a copolymer precursor. The copolymerization pressure is 1.8-2.2 MPaG.

5. The method for producing polypropylene products according to claim 4, characterized in that, The preparation of the catalyst specifically includes: The dry powder main catalyst and solvent are mixed to obtain the main catalyst slurry; The main catalyst slurry, co-catalyst, and catalyst modifier are mixed and activated to obtain the catalyst.

6. The method for producing polypropylene products according to claim 5, characterized in that, The main catalyst includes a Zn catalyst, the solvent includes white oil, the co-catalyst includes triethylaluminum, and the catalyst modifier includes a silane electron donor.

7. The method for producing polypropylene products according to claim 4, characterized in that, The comonomers include ethylene and / or butene-1; the molecular weight regulators include hydrogen.

8. The method for producing polypropylene products according to claim 4, characterized in that, The method further includes: The liquid in the initial slurry is evaporated, followed by gas-solid separation to obtain the initial polymer powder. The polymer powder primary product is copolymerized with propylene, comonomer and hydrogen in a gas phase reactor to obtain the copolymer primary product. The copolymer primary product is subjected to gas-solid separation to obtain copolymer third reuse gas; The third type of recycled gas will be reused.

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