Polypropylene production device flexible to operate

Abstract

A polypropylene production device flexible to operate, comprising a pre-polymerization kettle (1), a first reaction kettle (2), a second reaction kettle (3) and a third reaction kettle (5) which are sequentially connected, and an air lock (4) further arranged between the second reaction kettle (3) and the third reaction kettle (5). A first branch is further drawn from an outlet of the pre-polymerization kettle (1) to be connected to the second reaction kettle (3), and a second branch is further drawn from an outlet of the first reaction kettle (2) to be connected to the third reaction kettle (5). Different users can select an operation scheme on the basis of actual conditions, and different process combinations correspond to different propylene recovery systems.

Description

A polypropylene production device with flexible operation Technical Field

[0001] The utility model belongs to the technical field of polypropylene production, and relates to a polypropylene production device with flexible operation. Background Art

[0002] The polypropylene process produces a high-performance thermoplastic synthetic resin through the polymerization of propylene monomer in the presence of a catalyst. Polypropylene products primarily include homopolymers, random copolymers, terpolymers, and impact copolymers. These products exhibit excellent properties, including non-toxicity, chemical resistance, low relative density, heat resistance, and ease of processing and molding. They can be processed into woven and injection-molded products, films, and pipes, finding widespread application in various industrial and consumer plastics applications, including automotive, household appliances, packaging, engineering plastics, building materials, and medical applications.

[0003] There are three main types of foreign polypropylene production processes:

[0004] (1) Solvent process

[0005] Due to the development of catalyst systems and the significant increase in their activity, new large-scale polypropylene plants built after the 1990s have basically stopped using the solvent process. However, many solvent-based polypropylene plants are still in operation around the world to produce high-quality alloy-type specialty resins.

[0006] (2) Liquid phase bulk process

[0007] This process involves the polymerization of liquid propylene to produce polypropylene. Patented technologies are categorized by reactor type as follows: liquid-phase kettle reactors (Exxon, Mitsui, Shell, Sumitomo, Rexene, etc.); liquid-phase loop reactors (Spheripol, Hoechst, Solvay, Phillips, Borealis, etc.).

[0008] (3) Gas phase process

[0009] This type of process involves direct gas-phase polymerization of propylene to produce solid-phase polymer products. Based on the reactor type, the following patented technologies are available: gas-phase fluidized bed reactor: Unipol, Sumitomo process; gas-phase vertical stirred bed reactor: Novolen process; gas-phase horizontal stirred bed reactor: Innovene, Horizone process.

[0010] There are four main types of polypropylene processes in China:

[0011] Polypropylene batch bulk polymerization process, Sinopec loop polymerization process, SPG polypropylene continuous bulk polymerization process, HPP polypropylene continuous bulk polymerization process.

[0012] The representative processes of gas phase polypropylene and the combination of liquid phase bulk and gas phase polymerization that are similar to this patent are described as follows:

[0013] (1) Innovene gas phase polypropylene process

[0014] The Innovene gas-phase polypropylene process, developed by Ineos, utilizes a unique horizontal stirred reactor with a near-plug flow design. Utilizing two horizontal reactors in series, baffles, and a specialized agitator system, this process achieves a defined powder residence time distribution within a single reactor, effectively creating the effect of three fully mixed-flow reactors in series. A notable feature of this process is its ability to produce the full range of polypropylene products, including homopolymers, random copolymers, and impact copolymers, using a single catalyst. The Innovene process utilizes a gas lock system to rapidly stop the addition of the primary catalyst, ensuring a smooth and rapid shutdown, providing reliable assurance for safe plant operation.

[0015] (2) Hypol liquid phase bulk and gas phase polymerization combined process

[0016] Mitsui Chemicals' Hypol process combines liquid-phase bulk polymerization and gas-phase polymerization of propylene. Homopolymer is produced using two liquid-phase reactors equipped with stirred tanks and a gas-phase fluidized bed reactor equipped with agitating scrapers. A further gas-phase fluidized bed reactor is connected in series to produce impact copolymers. The liquid-phase reactor disperses the catalyst directly into liquid propylene, causing the polymerization reaction to occur. To produce impact copolymerized polypropylene, the polymer from the second homopolymerizer enters the fluidized bed gas-phase homopolymerizer. The resulting polymer powder is then fed to the connected gas-phase fluidized bed reactor for impact copolymerization. Operating at a pressure of 1.2 MPaG and a temperature of 70°C, the resulting impact copolymer is discharged to subsequent product processing systems.

[0017] (3) Domestic polypropylene continuous bulk polymerization process

[0018] Currently, most domestic continuous bulk polymerization processes for polypropylene utilize a production method that combines liquid-phase bulk slurry polymerization of propylene with horizontal gas-phase polymerization. Polypropylene powder is produced through sequential slurry and gas-phase polymerization. The process consists of a propylene refining and feeding system, a catalyst addition system, a polymerization reaction system, a polypropylene drying and conveying system, a propylene recovery system, a hydrogen circulation system, and utility systems. This industrialized process boasts a 100% domestic production rate. Using the same catalyst, its advanced technology and economical operation have been verified and recognized by production users.

[0019] In the above three processes, if one of the reactors fails, the entire device usually needs to be shut down for maintenance, which has low operational flexibility and inevitably causes economic losses due to shutdowns.

[0020] In addition, Chinese patent CN217568664U discloses a continuous production process for polypropylene with one vertical and two horizontal processes and steam drying. The process adopts a continuous process of one vertical and two horizontal processes + polypropylene steam drying post-treatment. The entire device cannot be flexibly switched during operation. At the same time, the treatment of the subsequent process of propylene gas has not been optimized.

[0021] Utility Model Content

[0022] The purpose of the utility model is to provide a polypropylene production device with flexible operation, which adopts a prepolymerization kettle + three kettles in series mode, optimizes the process and flexibly uses it to realize a production mode of combining a prepolymerization kettle and different downstream reactors.

[0023] The purpose of the utility model can be achieved through the following technical solutions:

[0024] A polypropylene production device with flexible operation includes a prepolymerization kettle, a first reactor, a second reactor and a third reactor connected in sequence, an air lock is provided between the second reactor and the third reactor, the outlet of the prepolymerization kettle also leads to a first branch connected to the second reactor, and the outlet of the first reactor also leads to a second branch connected to the third reactor.

[0025] By switching the pipelines, the polypropylene production device of the utility model can realize a variety of combined production modes, such as one vertical and one horizontal, one vertical and two horizontal, and two horizontal kettles.

[0026] Furthermore, in order to reasonably and flexibly configure the subsequent propylene recovery system, produce homopolymer, random copolymer, and impact copolymer polypropylene products, and realize flexible operation and long-cycle operation of the polypropylene device, the polypropylene production device also includes a low-pressure bag filter, an oil washing tower and a dehydrogenation tower. The outlets of the second reactor and the third reactor are also connected to the low-pressure bag filter respectively, and the top gas phase outlet of the low-pressure bag filter is also connected to the oil washing tower and the dehydrogenation tower in sequence.

[0027] Furthermore, the unreacted gas outlet on the air lock is also connected to the dehydrogenation tower.

[0028] Furthermore, the second reaction kettle is provided with a second reaction gas cooling unit, which is connected to the top gas phase outlet of the second reaction kettle and is used to cool the reaction gas and return it to the second reaction kettle;

[0029] The third reaction kettle is provided with a third reaction gas cooling unit, which is connected to the top gas phase outlet of the third reaction kettle and is used to cool the reaction gas and return it to the third reaction kettle;

[0030] The non-condensable gas outlets on the second reaction gas cooling unit and the third reactor cooling unit are also connected to the dehydrogenation tower via pipelines respectively.

[0031] More preferably, the outlet of the oil washing tower also leads to a third branch which is returned and connected to the third reactor cooling unit arranged on the top of the third reactor.

[0032] Furthermore, a compressor is provided on the pipeline between the oil washing tower and the dehydrogenation tower.

[0033] Furthermore, the first reaction kettle is further provided with a first reaction gas cooling unit, which is connected to the first reaction kettle and forms a gas phase condensation circuit.

[0034] Furthermore, the first branch and the pipeline between the prepolymerization kettle and the first reactor are switched via a three-way valve.

[0035] Furthermore, the second reactor and the third reactor are also provided with an external steam heater.

[0036] Furthermore, the prepolymerization kettle is a vertical stirring reactor; the first reactor is a vertical stirring reactor; the second reactor and the third reactor are horizontal stirring reactors.

[0037] Compared with the existing technology, the utility model adopts a prepolymerization kettle + three kettles in series mode, and through process optimization and flexible application, realizes a production mode of combining the prepolymerization kettle and different downstream reactors: one vertical and one horizontal, one vertical and two horizontal, and two horizontal kettles. It is a production process that takes the above three combination modes into consideration, and at the same time reasonably and flexibly configures the subsequent propylene recovery system to produce homopolymerization, random copolymerization, and impact copolymerization polypropylene products, thereby realizing flexible operation and long-term operation of the polypropylene device. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a schematic structural diagram of the present invention;

[0039] Explanation of the marks in the figure: 1-prepolymerization kettle; 2-first reactor; 3-second reactor; 4-air lock; 5-third reactor; 6-low-pressure bag filter; 7-oil washing tower; 8-dehydrogenation tower; 9-first reaction gas cooling unit; 10-second reaction gas cooling unit; 11-third reaction gas cooling unit. DETAILED DESCRIPTION

[0040] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0041] In the following implementation manners or examples, unless otherwise specified, functional components or structures are conventional components or conventional structures in the art for realizing corresponding functions.

[0042] In order to achieve flexible switching between reactors to meet different production product requirements, the present invention provides a flexible polypropylene production device, the structure of which can be seen in Figure 1, including a prepolymerization reactor 1, a first reactor 2, a second reactor 3 and a third reactor 5 connected in sequence, and an air lock 4 is also provided between the second reactor 3 and the third reactor 5. The outlet of the prepolymerization reactor 1 also leads to a first branch connected to the second reactor 3, and the outlet of the first reactor 2 also leads to a second branch connected to the third reactor 5.

[0043] By switching the pipelines, the polypropylene production device of the utility model can realize a variety of combined production modes, such as one vertical and one horizontal, one vertical and two horizontal, and two horizontal kettles.

[0044] In some specific embodiments, in order to reasonably and flexibly configure the subsequent propylene recovery system, produce homopolymerization, random copolymerization, and impact copolymerization polypropylene products, and realize flexible operation and long-term operation of the polypropylene device, the polypropylene production device also includes a low-pressure bag filter 6, an oil washing tower 7 and a dehydrogenation tower 8, and the outlets of the second reactor 3 and the third reactor 5 are also respectively connected to the low-pressure bag filter 6, and the top gas phase outlet of the low-pressure bag filter 6 is also connected to the oil washing tower 7 and the dehydrogenation tower 8 in sequence.

[0045] In a more specific embodiment, the unreacted gas outlet on the air lock 4 is also connected to the dehydrogenation tower 8 .

[0046] In a more specific embodiment, a second reaction gas cooling unit 10 is provided on the second reaction kettle 3. The second reaction gas cooling unit 10 is connected to the top gas phase outlet of the second reaction kettle 3 and is used to cool the reaction gas and return it to the second reaction kettle 3.

[0047] The third reaction kettle 5 is provided with a third reaction gas cooling unit 11, which is connected to the top gas phase outlet of the third reaction kettle 5 and is used to cool the reaction gas and return it to the third reaction kettle 5;

[0048] The non-condensable gas outlets on the second reaction gas cooling unit 10 and the third reactor cooling unit are also connected to the dehydrogenation tower 8 through pipelines, respectively.

[0049] More preferably, the outlet of the oil washing tower 7 also leads to a third branch line which is returned and connected to the third reactor cooling unit arranged on the top of the third reactor 5 .

[0050] In a more specific embodiment, a compressor is further provided on the pipeline between the oil washing tower 7 and the dehydrogenation tower 8 .

[0051] In a more specific embodiment, a first reaction gas cooling unit 9 is further provided on the first reaction kettle 2 . The first reaction gas cooling unit 9 is connected to the first reaction kettle 2 and forms a gas phase condensation circuit.

[0052] In some specific embodiments, the first branch and the pipeline between the prepolymerization kettle 1 and the first reactor 2 are switched via a three-way valve.

[0053] In some specific embodiments, the second reactor 3 and the third reactor 5 are further provided with an external steam heater.

[0054] In some specific embodiments, the prepolymerization kettle 1 is a vertical stirring reactor; the first reactor 2 is a vertical stirring reactor; the second reactor 3 and the third reactor 5 are horizontal stirring reactors.

[0055] In some specific embodiments, independently controlled valves are also provided in each section of the pipeline in the entire production device. For example, a three-way valve (i.e., valve 1) is provided between the prepolymerization kettle 1 and the first reactor 2, and a three-way valve (i.e., valve 2) is provided between the first reactor 2 and the second reactor 3, etc.

[0056] The above embodiments may be implemented individually or in any combination of two or more.

[0057] The above implementation is described in more detail below with reference to specific examples.

[0058] Example 1:

[0059] This embodiment provides a polypropylene production device with flexible operation, the structure of which can be seen in Figure 1. It includes a prepolymerization kettle 1, a first reactor 2, a second reactor 3 and a third reactor 5 connected in sequence. An air lock 4 is also provided between the second reactor 3 and the third reactor 5. The outlet of the prepolymerization kettle 1 also leads to a first branch connected to the second reactor 3, and the outlet of the first reactor 2 also leads to a second branch connected to the third reactor 5.

[0060] Prepolymerization vessel 1 is a vertical stirred reactor with a relatively small volume. The residence time is controlled between 4 and 15 minutes, and the reaction pressure is 3.15 and 4.2 MPaG. Prepolymerization is performed at a low temperature of approximately 15°C, with a prepolymerization dosage of 50 to 100 g / g of catalyst. The prepolymerization slurry concentration is controlled at 30 to 50 g / l. The catalyst reacts with a small amount of propylene for a short, low-speed reaction. A pre-coated outer layer surrounds the active catalyst region, primarily controlling the initial particle growth rate and morphology. This outer layer prolongs the catalyst's active period when polymerization conditions are met, preventing the generation of local hot spots that accelerate the reaction and reduce the regularity of the polypropylene. Prepolymerization vessel 1 is operated full, and the heat released by the reaction is carried away by chilled water in the jacket and the material outflow. The prepolymerized catalyst and propylene enter the first reactor 2 under self-pressure.

[0061] The first reactor 2 is a vertical stirring reactor (i.e., a vertical reactor) with a reaction pressure of 3.0 3.6 MPaG, reaction temperature around 70°C. Liquid propylene undergoes slurry polymerization within the reactor, with the heat released by polymerization being carried away by vaporization of the liquid propylene. Most of the gaseous propylene and hydrogen leaving the first reactor 2 enters the external circulation condenser for condensation, while a small amount serves as external circulation bypass gas and does not enter the condenser. The condensate flows back to the first reactor 2 by gravity, while the non-condensable gases return to the first reactor 2 via the circulating fan. The polymerization product, polypropylene slurry, enters the second reactor 3 or the third reactor 5 under self-pressure.

[0062] The second reactor 3 is a horizontal stirred reactor (i.e. horizontal reactor), with a reaction pressure of 2.1 2.8MPaG, reaction temperature The reaction takes place at 80°C. The reaction takes place in the reactor, where the heat released by the reaction is removed by condensation and cooling of the unreacted propylene gas through a heat exchanger. The condensed liquid propylene is then pressurized and returned to the second reactor 3 via a propylene condensate pump to control the reaction temperature.

[0063] The structure and heat extraction method of the third reactor 5 are the same as those of the second reactor 3. The polypropylene in the second reactor 3 enters the airlock 4, where the excess ethylene and hydrogen are stripped and recycled back to the second reactor 3. The airlock 4 then pressurizes the polypropylene powder and pumps it into the third reactor 5 for a gas-phase reaction to form an impact copolymer. This prevents the subsequent copolymerization reaction from preventing the material in the third reactor 5 from flowing back into the second reactor 3. This ensures the independence of the gas-phase systems of the second and third reactors 3, preventing unnecessary gas emissions from the second reactor 3 from causing disturbances in the H2 concentration within the reactor, and enabling precise control of the process parameters of each reaction system.

[0064] During the production process, the main catalyst, the co-catalyst and the electron donor can all be added to the first reactor 2. When producing impact-resistant products, ethylene is only added to the third reactor 5.

[0065] Prepolymerization involves a short, low-speed reaction with a small amount of olefin before olefin polymerization in the presence of a catalyst and an aluminum alkyl under mild conditions. This results in a polymer coating on the catalyst surface. Low-temperature prepolymerization allows for better control of catalyst activity. The first reactor 2 is a vertical, liquid-phase bulk polymerization reactor with stirring. The heat of reaction is removed by evaporating the liquid propylene in the reactor, and the vaporized propylene is partially condensed and then reflowed back into the reactor. The second and third reactors 3 and 5 are horizontal reactors with stirring. The polymer slurry exiting the liquid-phase reactor enters the second reactor 3, where the liquid propylene in the polymer slurry evaporates due to the polymerization heat. The evaporated propylene gas is cooled, and the liquid phase returns from the top of the reactor to control the reaction temperature. The vapor phase returns from the bottom of the reactor to the reactor, further loosening the polymer within the reactor. When producing impact-resistant products, the polymer powder exiting the second reactor 3 is stripped and pressure-fed through an airlock 4 before being transferred to the third reactor 5, where it undergoes polymerization with a specific ratio of ethylene and propylene. The heat extraction method is the same as for the second reactor 3.

[0066] The second reactor 3 and the third reactor 5 are also equipped with external steam heaters for heating the reactors in the initial stage of operation. Compared with other domestic processes that adopt jacket design, the cancellation of the jacket greatly reduces the manufacturing difficulty of the reactor, reduces the purchase cost of the reactor, saves project costs, and also speeds up the manufacturing cycle of the reactor.

[0067] The combined process flow can be switched flexibly, as follows:

[0068] Based on the above pipeline arrangement, the production process flow of the polypropylene production device of this embodiment can be flexibly switched, as follows:

[0069] (1)Polymerization reaction process can be selected:

[0070] Process 1: Prepolymerization kettle 1 + first reactor 2 + second reactor 3 or third reactor 5, producing homopolymer and random copolymer polypropylene products, with the third reactor 5 being a standby. The pipeline between the prepolymerization kettle 1 and the first reactor 2 and the first branch are switched via a three-way valve (i.e., valve 1). At this time, valve 1 can be controlled to open for entering the first reactor 2, and closed across the line for entering the second reactor 3. Valve 2 can be selectively opened to allow the flow to enter either the second reactor 33 or the third reactor 55. Valve 3 is closed, valve 4 is open, and valve 7 is closed.

[0071] Process 2: Prepolymerization kettle 1 + first reactor 2 + second reactor 3 + airlock 4 + third reactor 5, producing homopolymer, random copolymer, and impact copolymer polypropylene products. Valve 1 entering first reactor 2 is open, valve 1 entering second reactor 3 is closed across the line, valve 2 is fully open, valve 4 is closed, valve 3 is open, and valve 7 is open.

[0072] Process 3: Prepolymerization reactor 1 + second reactor 3 + airlock 4 + third reactor 5, producing homopolymer, random copolymer, and impact copolymer polypropylene products. Valve 1 entering the first reactor 2 is closed, valve 1 entering the second reactor 3 is open across the line, valve 2 is fully closed, valve 4 is closed, valve 3 is open, and valve 7 is open.

[0073] (2) Propylene gas recovery process configuration

[0074] The process consists of a low-pressure bag filter 6, an oil washing tower 7, and a dehydrogenation tower 8. The propylene gas after polymer separation in the low-pressure bag filter 6 is sent to the oil washing tower 7, where oligomers, alkyl aluminum, and fine powder are washed away. The gas is then pressurized by a compressor and sent to the dehydrogenation tower 8 to separate propylene and hydrogen for recycling.

[0075] The propylene recovery process corresponding to process 1: the oil washing tower 7 + compressor is operated in series with the dehydrogenation tower 8, the valve 6 is opened, and the valve 5 is closed.

[0076] The propylene recovery process corresponding to process 2: the oil washing tower 7 + compressor and the dehydrogenation tower 8 are operated independently in parallel, the valve 6 is closed, and the valve 5 is opened.

[0077] The propylene recovery process corresponding to process 3: the oil washing tower 7 + compressor and the dehydrogenation tower 8 are operated independently in parallel, the valve 6 is closed, and the valve 5 is opened.

[0078] Specifically, according to different needs, the process selection of the polypropylene production device in this embodiment is as follows:

[0079] (1) When producing homopolymers and random copolymers, process 1, process 2 or process 3 can be used.

[0080] Using process 1: prepolymerization reactor 1 + first reactor 2 + second reactor 3 (or third reactor 5), when producing homopolymer, propylene is added to both first and second reactors 2 and 3. When producing random copolymers, propylene and ethylene are added simultaneously to first and second reactors 2 and 3 in a specific ratio. This process offers advantages such as reduced operating energy consumption, a shorter process flow, and ease of operation. In this configuration, the second reactor (i.e., second reactor 3) and the third reactor (i.e., third reactor 5) can serve as backup units, eliminating the need for a complete system shutdown in the event of a failure in either the second or third reactor system.

[0081] Using process 2: prepolymerization reactor 1 + first reactor 2 + second reactor 3 + airlock 4 + third reactor 5. When producing homopolymer, propylene is added to the first reactor 2, second reactor 3, and third reactor. When producing random copolymers, propylene and ethylene are added simultaneously to the first reactor 2, second reactor 3, and third reactor in a specific ratio. This process has the advantage of increasing the production capacity of homopolymer or random products.

[0082] Using Process 3: Prepolymerization Reactor 1 + Second Reactor 3 + Airlock 4 + Third Reactor 5, when producing homopolymers, propylene is added to both the second and third reactors. When producing random copolymers, propylene and ethylene are added simultaneously to the second and third reactors in a specific ratio. In this process, the first reactor 2 is inactive. This process has the advantages of reducing operating energy consumption, avoiding the transition between liquid-phase and gas-phase reactions, and providing a short process flow and convenient operation. Both reactors operate in gas-phase, resulting in smoother operation and relatively easy control of product quality. It also allows for the possibility of a failure in the first reactor system without shutting down the entire plant.

[0083] In the above homopolymerization and random working conditions, the corresponding gas recovery system for processes 1, 2, and 3 is an oil scrubber 7 and a dehydrogenation tower 8 operated in series, without the need to isolate the respective propylene and hydrogen recovery systems. The polypropylene exiting the second reactor 3 (process 1) or the third reactor 5 (process 2 and process 3) is first subjected to gas-solid separation by a low-pressure bag filter 6. The propylene gas exiting the top of the low-pressure bag filter 6 is washed with white oil in the oil scrubber 7 to remove triethylaluminum and oligomers carried in the propylene gas. The cleaned propylene gas is pressurized by a compressor and then enters the dehydrogenation tower 8 together with the unreacted gas from the air lock 4. The liquid propylene separated by the propylene is pressurized and recycled, and the non-condensable gas containing hydrogen is sent to the hydrogen circulation system for reuse.

[0084] (2) When producing impact-resistant copolymer products, process 2 or process 3 can be used.

[0085] Using process 2: prepolymerization reactor 1 + first reactor 2 + second reactor 3 + airlock 4 + third reactor 5, propylene is added to first and second reactors 2 and 3, and propylene and ethylene are added to third reactor 5 in a certain ratio. This process makes it difficult to control the consistency of the homopolymer product performance produced by first and second reactors 2 and 3, which has a certain impact on the stability of the operating parameters of the subsequent third reactor 5, requiring a high level of operational skill.

[0086] Flow 3: Prepolymerization reactor 1 + second reactor 3 + airlock 4 + third reactor 5. In this case, propylene is added to the second reactor 3, and propylene and ethylene are added to the third reactor 5 in a certain ratio. In this case, the first reactor 2 is inactive. The advantages are reduced operating energy consumption, avoiding the transition between liquid and gas phase reactions, and a short process flow for easy operation. The second reactor 3 produces a homopolymer product that provides feed for the third reactor 5, producing an impact-resistant product. In this case, operation is more stable and product quality is relatively easy to control. It is also suitable for the situation where a failure in the first reaction system will not cause a complete shutdown of the entire unit.

[0087] For the above-mentioned processes 2 and 3 under the impact resistance working condition, the corresponding gas recovery systems are the oil washing tower 7 series and the dehydrogenation tower 8 series, which are operated independently in parallel. In order to prevent the ethylene-containing gas discharged from the second reactor 3 from returning to the second reactor 3, it is necessary to isolate the respective propylene and hydrogen recovery systems. The polypropylene coming out of the third reactor 5 is first separated into gas and solid by the low-pressure bag filter 6. The propylene gas coming out of the top of the low-pressure bag filter 6 is washed with white oil in the oil washing tower 77 to remove the trace polypropylene powder, triethyl aluminum and oligomers carried by it, and then pressurized by the compressor and returned to the third reactor 5. The mixed gas discharged from the second reactor 3 and the unreacted gas from the air lock 4 enter the dehydrogenation tower 8 together. The liquid propylene separated by the propylene is pressurized and recycled, and the non-condensable gas containing hydrogen is sent to the hydrogen circulation system for reuse.

[0088] Example 2:

[0089] Based on the polypropylene production apparatus of Example 1, as shown in Figure 1, this embodiment adopts process 1. Specifically, propylene feed enters the prepolymerization reactor 1 through the fresh propylene pipeline 101. The total polypropylene production capacity of the production line is 8750 kg / h. The catalyst enters the prepolymerization reactor 1 through the catalyst pipeline 102. The feed rates of the main catalyst, auxiliary catalyst, and external electron donor are adjusted according to different production grades. The main catalyst flow rate is generally 0.03-0.04 kg / tPP. The prepolymerization amount is 50-100 gPP / g catalyst. The PP output in the discharge pipeline 103A of the prepolymerization reactor 1 is 35 kg / h. In the homopolymerization and random operation mode, the second reactor 3 or the third reactor 5 is selectively used. The production capacity of the first reactor 2 is 30%, and the production capacity of the second reactor 3 or the third reactor 5 is 70%. The vertical reactor discharge 104A or 104B produces 2625 kg / h of polypropylene. The horizontal reactor discharge 105A or 105B contains 8750 kg / h of polypropylene and 1600 kg / h of entrained propylene gas. The propylene gas 107 after polymer separation is 1450 kg / h, and the separated polypropylene powder material 106 is 8900 kg / h (with 150 kg / h of entrained propylene gas).

[0090] Example 3:

[0091] As shown in Figure 1, the polymerization reaction system adopts process 1. Propylene feed enters the prepolymerization reactor 1 through the fresh propylene pipeline 101. The total polypropylene production capacity of the production line is 8750 kg / h. The catalyst enters the prepolymerization reactor 1 through the catalyst pipeline 102. The feed amounts of the main catalyst, auxiliary catalyst, and external electron donor are adjusted according to different production grades. The main catalyst flow rate is generally 0.03-0.04 kg / tPP, the prepolymerization amount is 50-100 gPP / g catalyst, and the PP output in the discharge pipeline 103A of the prepolymerization reactor 1 is 35 kg / h. Under low-impact operating conditions, the vertical reactor (i.e., first reactor 2) and the horizontal reactor (i.e., second reactor 3) produced homopolypropylene. No ethylene feed was used. The horizontal reactor (i.e., third reactor 5) was fed with ethylene to produce low-impact polypropylene. The vertical reactor capacity was 26.25%, the horizontal reactor capacity was 61.25%, and the horizontal reactor capacity was 12.5%. The vertical reactor discharge 104A produced 2625 kg / h of polypropylene. The horizontal reactor discharge stream 112 contained 7656.25 kg / h of polypropylene powder, along with 650 kg / h of entrained propylene gas, which entered airlock 4. Propylene replacement gas stream 115 at the bottom of airlock 4 flowed at 1423 kg / h, while unreacted gas discharge 113 at the top of airlock 4 flowed at 2073 kg / h. Fresh propylene, ethylene, and hydrogen were introduced into the third reactor 5. The horizontal reactor discharge stream 105B contained 8750 kg / h of polypropylene, along with 1750 kg / h of entrained propylene gas. The propylene gas 107 after polymer separation is 1650kg / h, and the separated polypropylene powder material 106 is 8850kg / h (entrained propylene gas 100kg / h). After the propylene gas is washed by the oil washing tower 7, since the gas contains ethylene, it cannot be recycled to the vertical kettle and the horizontal kettle for reuse. After being pressurized by the compressor, valve 6 is closed, valve 5 is opened, and returned to the horizontal kettle 5.

[0092] Example 4:

[0093] As shown in Figure 1, the polymerization reaction system process 1, propylene feed enters the prepolymerization reactor 1 through the fresh propylene pipeline 101, the total production capacity of the production line is 8750kg / h of polypropylene, the catalyst enters the prepolymerization reactor 1 through the catalyst pipeline 102, the main catalyst, auxiliary catalyst, and external electron donor are adjusted according to different production grades. The main catalyst flow rate is generally 0.03-0.04kg / tPP, the prepolymerization amount is 50-100gPP / g catalyst, the prepolymerization reactor 1 discharge pipeline 103A is closed, the first branch 103B is opened, and the PP output is 35kg / h. The vertical reactor can be cut out, and the production capacity of the two horizontal reactors is 60% and 40% respectively. The horizontal reactor discharge 105A produces 5250kg / h of polypropylene. Valve 4 is closed and valve 3 is open. The gas lock 4 does not need to be used for homopolymerization or random operation. The horizontal reactor discharge 105B stream contains 8750kg / h of polypropylene and 1757kg / h of entrained propylene gas. The propylene gas 107 after polymer separation is 1600 kg / h, and the separated polypropylene powder material 106 is 8907 kg / h (with 157 kg / h of entrained propylene gas).

[0094] The above description of the embodiments is intended to facilitate understanding and use of the utility model by those skilled in the art. Those skilled in the art will readily be able to make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the utility model is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of this utility model without departing from the scope of this utility model should be within the scope of protection of this utility model.

Claims

1. A polypropylene production device with flexible operation, comprising a prepolymerization kettle, a first reaction kettle, a second reaction kettle and a third reaction kettle connected in sequence, and an air lock is further provided between the second reaction kettle and the third reaction kettle, characterized in that, Another first branch is led out from the outlet of the prepolymerization kettle and connected to the second reaction kettle, and another second branch is led out from the outlet of the first reaction kettle and connected to the third reaction kettle.

2. The flexible operation polypropylene production device according to claim 1, wherein It further includes a low-pressure bag filter, an oil scrubber tower and a dehydrogenation tower. The outlets of the second reaction kettle and the third reaction kettle are respectively connected to the low-pressure bag filter, and the top gas-phase outlet of the low-pressure bag filter is sequentially connected to the oil scrubber tower and the dehydrogenation tower.

3. An operationally flexible polypropylene production device according to claim 2, characterized in that, The unreacted gas outlet on the air lock is also connected to the dehydrogenation tower.

4. An operationally flexible polypropylene production device according to claim 2, characterized in that, A second reaction gas cooling unit is provided on the second reaction kettle. The second reaction gas cooling unit is connected to the top gas-phase outlet of the second reaction kettle and is used to cool the reaction gas and then return it to the second reaction kettle. A third reaction gas cooling unit is provided on the third reaction kettle. The third reaction gas cooling unit is connected to the top gas-phase outlet of the third reaction kettle and is used to cool the reaction gas and then return it to the third reaction kettle. The non-condensable gas outlets on the second reaction gas cooling unit and the third reactor cooling unit are respectively connected to the dehydrogenation tower through pipelines.

5. An operationally flexible polypropylene production device according to claim 4, characterized in that, A third branch is led out from the outlet of the oil scrubber tower and returns to be connected to the third reactor cooling unit arranged on the top of the third reaction kettle.

6. The flexible polypropylene production device according to claim 2, wherein, A compressor is also provided on the pipeline between the oil scrubber tower and the dehydrogenation tower.

7. An operationally flexible polypropylene production device according to claim 2, characterized in that, A first reaction gas cooling unit is also provided on the first reaction kettle. The first reaction gas cooling unit is connected to the first reaction kettle and forms a gas-phase condensation loop.

8. An operationally flexible polypropylene production device according to claim 1, characterized in that, The switching between the first branch and the pipeline between the prepolymerization kettle and the first reaction kettle is realized through a three-way valve.

9. The flexible operation polypropylene production device according to claim 1, characterized in that External steam heaters are also provided on the second reaction kettle and the third reaction kettle.

10. An operationally flexible polypropylene production device according to claim 1, characterized in that, The prepolymerization kettle adopts a vertical stirring reactor; the first reaction kettle is a vertical stirring reactor; the second reaction kettle and the third reaction kettle are horizontal stirring reactors.

Images