A supercritical reactor system

Abstract

The utility model discloses a kind of supercritical reaction kettle systems, belong to supercritical reaction equipment technical field.The system includes supercritical reaction kettle, temperature control jacket covered in the outside of reaction kettle, stirring device in kettle, material supply unit and pressure monitoring and automatic pressure relief unit.The stirring device adopts double-layer propeller blade structure, upper layer is folding blade, lower layer is propelling type paddle, can realize the efficient mixing of supercritical fluid and reaction material.The pressure monitoring and automatic pressure relief unit are by pressure transmitter on reaction kettle, PLC controller and the emptying pressure relief valve of connecting reaction kettle and pressure relief buffer tank composition.The utility model solves the problem of uneven mixing, insufficient temperature control accuracy and high pressure safety risk in supercritical reaction system through structural innovation, especially suitable for the synthesis of high-performance polymers such as PVDF.

Description

Technical Field

[0001] This utility model relates to the field of chemical synthesis equipment technology, specifically to a supercritical reactor system. Background Technology

[0002] Polyvinylidene fluoride (PVDF) is an important fluoropolymer. Due to its excellent chemical stability, heat resistance, weather resistance, UV resistance, as well as its outstanding mechanical strength and dielectric properties, it is widely used in key fields such as chemical corrosion protection, lithium-ion battery separators and adhesives, water treatment membranes, building coatings, and high-end wires and cables.

[0003] However, the performance of PVDF materials is highly dependent on their microstructure, particularly their crystal morphology, crystal size, distribution, and the regularity of molecular chain arrangement. Currently, traditional industrial processes for preparing PVDF (such as emulsion polymerization and suspension polymerization) have inherent limitations in precisely controlling the polymer's microstructure, resulting in products whose overall performance fails to meet the increasingly stringent demands of high-end applications. Specifically, existing technologies mainly suffer from the following problems: 1. Insufficient ability to control microstructure: In traditional polymerization processes, the dispersion uniformity and mass transfer efficiency of reactant monomers are limited, easily leading to uneven polymer chain growth and the generation of widely distributed crystalline and amorphous regions. This makes it difficult for the crystallinity of the final product to reach an ideal level, thus limiting further improvements in its tensile strength, impact toughness, and long-term creep performance.

[0004] 2. Bottlenecks in product performance: Due to defects in its microstructure, PVDF materials produced by traditional processes have insufficient corrosion resistance and stability when exposed to highly corrosive chemical media (such as concentrated acids, concentrated alkalis, and organic solvents). Simultaneously, the mechanical strength of the material often reaches a plateau, making it difficult to meet the extreme reliability requirements of materials in high-pressure pipelines or structural components subjected to dynamic loads.

[0005] 3. Energy consumption and environmental pressure in the process: Some traditional processes require the use of large amounts of organic solvents or additives, and the subsequent separation and recycling processes are complex, which not only increases production costs, but also brings challenges to environmental protection and safe production.

[0006] To overcome these bottlenecks, the industry has been exploring new preparation methods. Supercritical fluid technology, especially supercritical carbon dioxide (scCO2), has shown great potential in polymer science as a green and efficient medium. It combines the high permeability and diffusion of gases with the strong solubility of liquids, theoretically making it an ideal reaction medium to promote uniform monomer dispersion, improve mass transfer efficiency, and guide the orderly growth of polymer chains.

[0007] However, successfully applying supercritical fluid technology to the industrial preparation of PVDF still faces a series of severe challenges: First, it requires the design of specialized reaction equipment capable of withstanding high-temperature and high-pressure supercritical environments for extended periods; second, it necessitates solving the engineering challenge of achieving efficient and uniform mixing of supercritical fluids and reactants; and finally, it is essential to establish a highly reliable safety control system that matches the demanding process conditions. Currently, there are no publicly reported, mature, and reliable supercritical fluid-assisted preparation technologies that can systematically solve the above problems and achieve a comprehensive and significant improvement in PVDF performance.

[0008] Therefore, developing a supercritical fluid-assisted PVDF preparation process that can precisely control the microstructure, significantly improve the overall performance of the product, and is suitable for safe industrial production has become a technical challenge that urgently needs to be solved in this field. Utility Model Content

[0009] To address the problems of uneven mixing, low temperature control accuracy, insufficient safety and reliability, and easy adhesion to the walls in existing supercritical reactor equipment, this invention provides a novel supercritical reactor system. Its purpose is to improve mixing efficiency and temperature uniformity through optimized structural design, enhance the system's safety protection capabilities under ultra-high pressure conditions, and improve anti-adhesion and discharge performance.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A supercritical reactor system, comprising: Supercritical reactor: The reactor is made of high-strength alloy material (such as INCONEL 625 alloy) to withstand high temperature and high pressure environments. Its inner wall is mirror polished and coated with a Teflon anti-stick layer to effectively prevent material adhesion.

[0011] Jacket: The jacket tightly covers the outside of the supercritical reactor and is provided with a heat transfer medium inlet and outlet. By circulating the heat transfer medium (such as heat transfer oil), the internal temperature of the reactor can be precisely and uniformly controlled.

[0012] High-efficiency stirring device: This device is located inside the reactor and its core feature is the use of a double-layer propeller structure. Specifically, the upper blade is a folding blade, mainly responsible for rapidly entraining the upper fluid and gas into the main liquid material; the lower blade is a propeller, mainly responsible for generating a strong axial flow to deeply shear and homogenize the materials. This structure ensures that the supercritical fluid and reactants achieve comprehensive and efficient mixing within the reactor.

[0013] Material supply unit: This unit includes a vinylidene fluoride monomer storage tank, an initiator solution storage tank, and a supercritical carbon dioxide storage tank. Each storage tank is connected to the supercritical reactor via independent pipelines (vinylidene fluoride monomer pipeline, initiator solution pipeline, and carbon dioxide pipeline) to achieve precise material addition.

[0014] Pressure monitoring and automatic pressure relief unit: This unit is the core guarantee for the safe operation of the system, including: A pressure transmitter is installed on the reactor to monitor the pressure inside the reactor in real time. The PLC controller is connected to the pressure transmitter signal and is used to receive and process pressure signals. The venting and pressure relief valve is installed on the pipeline connecting the reactor and the pressure relief buffer tank and is controlled by a PLC controller. The pressure relief buffer tank is filled with adsorbent material (such as activated carbon) to buffer and adsorb the released fluid. The tank is also equipped with a vent valve for final venting.

[0015] When the pressure transmitter detects that the pressure exceeds the preset safety threshold, the PLC controller immediately commands the venting and pressure relief valve to open, quickly releasing the supercritical fluid into the buffer tank, thereby achieving automatic and rapid safe pressure relief.

[0016] Compared with the prior art, the present invention has the following significant advantages: Significantly improved mixing efficiency: By adopting a double-layer stirring structure that combines an upper folding blade impeller with a lower propeller impeller, rapid dispersion and deep homogenization of supercritical fluids in reactants are achieved, effectively solving the mixing dead zone problem of traditional stirring in supercritical systems, and providing a guarantee for obtaining high-quality polymer products with uniform structure.

[0017] Precise and uniform temperature control: The external jacketed circulating temperature control design ensures the uniformity of heat exchange throughout the reactor, and can control the temperature fluctuation within a very small range, meeting the stringent requirements of supercritical polymerization reaction for temperature stability.

[0018] The system boasts extremely high safety: it integrates an automatic pressure relief system consisting of a pressure transmitter, a PLC controller, and a venting and pressure relief valve, which responds quickly and operates reliably. It is further supplemented by a pressure relief buffer tank with adsorption function, forming a double safety guarantee and greatly reducing the safety risks of ultra-high pressure operation.

[0019] Anti-sticking and easy maintenance: The mirror polishing and Teflon coating on the inner wall of the reactor effectively prevents the adhesion of polymer materials, ensuring product purity and making equipment cleaning and maintenance simple and quick, thus improving production efficiency and equipment lifespan.

[0020] High practicality: The system structure of this utility model is compact and reasonable, with good synergy among its units. It is particularly suitable for the synthesis of high-performance polymers such as PVDF in supercritical carbon dioxide medium and has good prospects for industrial application. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the supercritical reactor system described in this utility model.

[0022] In the diagram: 1-Supercritical reactor; 2-Stirring device; 3-Jacket; 4-Pressure relief buffer tank; 4.1-Vent and pressure relief valve; 4.2-Pressure transmitter; 5-PLC controller; 6-Supercritical carbon dioxide storage tank; 6.1-Carbon dioxide pipeline; 7-Initiator solution storage tank; 7.1-Initiator solution pipeline; 8-Vinyl fluoride monomer storage tank; 8.1-Vinyl fluoride monomer pipeline. Detailed Implementation

[0023] The specific embodiments of this utility model will now be described in detail with reference to the accompanying drawings. This description is intended to enable those skilled in the art to understand and implement this utility model, and is not intended to limit the scope of protection of this utility model.

[0024] Example 1: This embodiment provides a supercritical reactor system specifically designed for PVDF synthesis, the structure of which is as follows: Figure 1 As shown.

[0025] The system mainly includes the following components: Supercritical Reactor 1: In this embodiment, the reactor body is forged from INCONEL 625 high-strength nickel-based alloy, with a design pressure of 35 MPa and a design temperature of 150°C. The reactor body is cylindrical with a volume of 50 liters. Its inner surface is precision mirror-polished (surface roughness Ra≤0.2μm) and uniformly coated with a 50μm thick polytetrafluoroethylene (Teflon) non-stick coating. The reactor lid has multiple interfaces for connecting various pipes, sensors, and stirring shafts.

[0026] Jacket 3: This jacket is made of carbon steel and is tightly welded to the outside of the reactor 1. A heat transfer oil inlet is located at the bottom of the jacket, and a heat transfer oil outlet is located at the top. The jacket is connected via pipeline to an external high-precision circulating oil bath (not shown in the figure) to form a closed-loop circulation circuit. The temperature control accuracy of the oil bath is ±0.5℃.

[0027] Mixing Device 2: This device includes a 5.5kW variable frequency drive motor, a mixing shaft passing through a mechanical seal, and double-layer propeller blades fixed to the shaft. The upper layer consists of six folding blades installed at a 45° angle, primarily designed to break up the gas / liquid interface and rapidly entrain supercritical carbon dioxide fluid into the bulk liquid phase. The lower layer consists of three propeller blades with a pitch-to-diameter ratio of 1.5:1, mainly used to generate a strong downward axial flow for deep circulation and shear mixing of the material, ensuring no dead zones throughout the entire process. The mixing speed can be steplessly adjusted within the range of 0-300 r / min via a frequency converter.

[0028] Material supply unit: Vinylidene fluoride single-unit storage tank 8: It is a pressurized storage tank made of 304 stainless steel with a volume of 100 liters. It is equipped with an external coil cooling system to maintain the internal temperature at 5-10℃ and is continuously filled with 0.3MPa of high-purity nitrogen for protection.

[0029] Initiator solution storage tank 7: A glass-lined storage tank with a stirrer, with a volume of 20 liters.

[0030] Supercritical carbon dioxide storage tank 6: This is a high-pressure stainless steel storage tank equipped with a refrigeration unit and a plunger-type booster pump. It can store carbon dioxide in liquid form (5℃, 8MPa) and instantly vaporize it to a supercritical state through an electric preheater.

[0031] Each storage tank is connected to reactor 1 via high-pressure stainless steel pipelines (8.1, 7.1, 6.1), and each pipeline is equipped with a precision metering pump and a shut-off valve.

[0032] Pressure monitoring and automatic pressure relief unit: Pressure transmitter 4.2: The selected model is ROSEMOUNT 3051S, with a range of 0-40MPa and an accuracy of ±0.075%FS. It is directly installed on the interface at the top of the reactor.

[0033] PLC controller 5: It adopts Siemens S7-1200 series PLC and is connected to pressure transmitter 4.2 through a 4-20mA analog input module.

[0034] Venting and pressure relief valve 4.1: A pneumatic high-pressure shut-off valve from VELAN (USA), nominal pressure PN400, is selected and installed on the DN25 pipeline connecting reactor 1 and pressure relief buffer tank 4. This valve is connected to the digital output module of PLC controller 5 via a solenoid valve.

[0035] Pressure relief buffer tank 4: 75 liters in volume (1.5 times the volume of the reactor), designed pressure 15 MPa. Its interior is filled with ceramic rings in the lower layer and granular activated carbon in the upper layer, with the total filling volume occupying approximately 2 / 3 of the tank's volume. A DN15 manual vent valve is installed on the top of the tank.

[0036] The system works as follows: Feeding and Initialization: Metered vinylidene fluoride monomer and initiator solution are added to reactor 1 from storage tanks 8 and 7 respectively via metering pumps. All feed valves are closed, and the circulating oil bath is started to preheat the materials in the reactor through jacket 3.

[0037] Supercritical fluid injection and reaction: Start the stirring device 2, setting the initial speed to 150 r / min. Then, open the outlet valve and metering pump of the supercritical carbon dioxide storage tank 6 to inject supercritical carbon dioxide into the reactor 1. The PLC controller 5 dynamically adjusts the jacket oil temperature and carbon dioxide injection rate based on feedback from the pressure transmitter 4.2, stabilizing the reactor temperature at 55℃ and the pressure at 15 MPa, ensuring that the fluctuation range meets the process requirements of ±2℃ for temperature and ±0.5 MPa for pressure. Subsequently, increase the stirring speed to 250 r / min to begin the polymerization reaction.

[0038] Safety Monitoring and Pressure Relief: Throughout the reaction process, the PLC controller 5 continuously monitors the pressure inside the reactor. In this embodiment, the safety pressure relief threshold is set to 28 MPa. If the pressure transmitter 4.2 detects a pressure of 28.5 MPa, the PLC controller 5 will immediately send an opening signal to the venting and pressure relief valve 4.1. The valve will open rapidly within 1-2 seconds, releasing the high-pressure fluid into the pressure relief buffer tank 4. The activated carbon inside the tank adsorbs any trace organic matter that may be entrained, buffering the energy and stabilizing the pressure drop. Finally, the treated gas can be slowly vented through the vent valve on the top of the tank.

[0039] Discharge and Maintenance: After the reaction is complete, depressurize normally. Due to the excellent anti-stick properties of the inner wall of reactor 1, the generated PVDF powder can be easily and completely discharged from the bottom outlet without any residue sticking to the wall, facilitating the next batch production and equipment cleaning.

[0040] Example 2: In another embodiment, the double-layer propeller structure of the stirring device 2 can be modified. The upper blades adopt Brumatin blades to further enhance gas containment capacity; the lower blades adopt serrated disc turbine blades to provide stronger shearing action under high viscosity conditions. The remaining structure is the same as in Embodiment 1, which can also achieve efficient mixing of supercritical fluids and materials and is suitable for different polymer synthesis systems.

[0041] The above description is merely a preferred embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in this utility model, based on the technical solution and inventive concept of this utility model, should be included within the protection scope of this utility model.

Claims

1. A supercritical reactor system, characterized in that, include: Supercritical reactor (1), the reactor being made of high-strength alloy material; A jacket (3) is provided on the outside of the supercritical reactor (1). The jacket (3) is provided with a heat transfer medium inlet and a heat transfer medium outlet for circulating the heat transfer medium to maintain the temperature inside the reactor. A stirring device (2) is installed inside the supercritical reactor (1) for mixing materials; The material supply unit includes a vinylidene fluoride monomer storage tank (8), an initiator solution storage tank (7), and a supercritical carbon dioxide storage tank (6), each of which is connected to the supercritical reactor (1) via a pipeline. The pressure monitoring and automatic pressure relief unit is used to monitor the pressure inside the reactor in real time and automatically relieve pressure when overpressure occurs; it includes: A pressure transmitter (4.2) is installed on the supercritical reactor (1) for real-time monitoring of the pressure inside the reactor; The PLC controller (5) is connected to the pressure transmitter (4.2) via signal. The pressure relief buffer tank (4) has its inlet connected to the venting and pressure relief valve (4.1) via a pipe, and the interior of the pressure relief buffer tank (4) is filled with adsorbent material; The venting and pressure relief valve (4.1) is installed on the pipeline connecting the supercritical reactor (1) and the pressure relief buffer tank (4), and is connected to the PLC controller (5) for control.

2. The supercritical reactor system according to claim 1, characterized in that, The stirring device (2) includes a drive motor, a rotating shaft driven by the drive motor, and double-layered propeller blades fixed on the rotating shaft.

3. The supercritical reactor system according to claim 2, characterized in that, The upper blade of the double-layer propeller is a folding blade, and the lower blade is a propulsion blade.

4. The supercritical reactor system according to claim 1, characterized in that, The pressure relief buffer tank (4) is equipped with a vent valve for venting the gas inside the tank.

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