An integrated system for co2 capture and conversion to carbon nanofibers

Abstract

This invention discloses an integrated system for CO2 capture and conversion into carbon nanofibers, relating to the field of carbon nanofiber preparation technology. The system includes a CO2 capture unit and a carbon nanofiber preparation unit. The CO2 outlet pipe of the CO2 capture unit is connected to the CO2 inlet pipe of the carbon nanofiber preparation unit. The carbon nanofiber preparation unit includes a first fluidized bed reactor and a second fluidized bed reactor connected in series. The CO2 outlet pipe of the CO2 capture unit is connected to the CO2 inlet pipe of the first fluidized bed reactor. An exhaust pipe is connected to the outlet end of the second fluidized bed reactor, and the exhaust pipe is connected to a catalyst recovery device and a hydrogen recovery device. This system achieves continuous carbon nanofiber formation by connecting the CO2 capture unit, and simultaneously realizes the direct conversion of CO2 into carbon nanofibers. The process is simple, energy consumption is significantly reduced, and product performance is stable.

Description

Technical Field

[0001] This invention relates to the field of carbon nanofiber preparation technology, and specifically to an integrated system for capturing and converting CO2 into carbon nanofibers. Background Technology

[0002] Converting carbon dioxide into high-value-added nanomaterials has become a research hotspot. Chemical vapor deposition (CVD) is currently the mainstream process for preparing carbon nanofibers. This method achieves fiber growth by decomposing carbon-containing gases on the surface of a catalyst under specific conditions. In recent years, with the continuous growth of market demand for nanomaterials, the application scope of carbon nanofibers in aerospace, new energy vehicles, and high-end electronic devices has been expanding, placing higher demands on their yield and quality.

[0003] A typical process for preparing carbon nanofibers from carbon dioxide includes raw material pretreatment, catalytic reaction, product separation, and post-treatment. The raw material pretreatment stage requires precise proportioning and purification of carbon dioxide and hydrogen to ensure that the feed gas entering the reactor meets process requirements. The catalytic reaction is mostly carried out in a fixed-bed or fluidized-bed reactor, with the reaction temperature typically maintained at 500℃~800℃ and the pressure at 0.1MPa~2MPa. The catalyst is mainly transition metals and their alloys. In the product separation stage, multi-stage filtration and centrifugation are required to separate the carbon nanofibers from the catalyst. Finally, high-temperature treatment and surface modification are used to obtain the final product.

[0004] However, existing technologies suffer from the following prominent problems: First, traditional fixed-bed reactors have low mass and heat transfer efficiency and uneven gas distribution, resulting in reaction conversion rates generally below 60%, and severe localized catalyst overheating and deactivation. Second, while fluidized-bed reactors improve mass transfer conditions, they suffer from catalyst wear, low product purity, and catalyst lifespan typically not exceeding 200 hours. Third, existing processes are lengthy, with high energy consumption for material transfer between steps, and a lack of effective heat recovery systems, leading to high production costs. Finally, controlling product morphology is difficult, and the wide range of fiber diameter distributions affects product consistency and application performance. These problems severely restrict the industrial-scale promotion and application of carbon nanofiber preparation technology from carbon dioxide.

[0005] Patent document CN117470086A discloses a method for preparing carbon nanofibers based on in-situ growth of carbon nanotubes. This method constructs a carbon nanotube-carbon nanofiber composite structure through catalyst pyrolysis and carbon source pyrolysis. While this method achieves controllable preparation of carbon nanofibers, the preparation process requires multiple high-temperature treatments, resulting in high energy consumption. Furthermore, the use of traditional hydrocarbon gases as the carbon source fails to realize the resource utilization of carbon dioxide.

[0006] Patent document CN116791237A discloses a method for preparing transition metal telluride composite carbon nanofibers, which uses electrospinning and calcination processes to load transition metal telluride nanoparticles into carbon nanofibers. Although this method achieves a uniform distribution of active sites, the material preparation depends on polymer precursors, and the process is complex, making it difficult to achieve large-scale continuous production.

[0007] Therefore, current carbon nanofiber preparation systems still suffer from problems such as low mass transfer efficiency, short catalyst lifespan, difficulty in controlling product morphology, uneven fiber diameter distribution, complex process flow, high system energy consumption, low hydrogen utilization rate, and serious resource waste. These problems severely restrict the industrialization process of carbon dioxide resource utilization. Summary of the Invention

[0008] Given the problems of low hydrogen utilization and serious resource waste in current carbon nanofiber preparation systems, the purpose of this invention is to provide an integrated system for CO2 capture and conversion into carbon nanofibers. This system achieves continuous forming of carbon nanofibers by connecting a carbon dioxide capture unit, and at the same time realizes the direct conversion of carbon dioxide into carbon nanofibers. The process is simple, energy consumption is significantly reduced, product performance is stable, and it is suitable for various working conditions from atmospheric pressure to medium pressure.

[0009] This invention is achieved through the following technical solution:

[0010] This application provides an integrated system for CO2 capture and conversion into carbon nanofibers, including a carbon dioxide capture unit and a carbon nanofiber preparation unit. The carbon dioxide outlet pipe of the carbon dioxide capture unit is connected to the carbon dioxide inlet pipe of the carbon nanofiber preparation unit. The carbon nanofiber preparation unit includes a first fluidized bed reactor and a second fluidized bed reactor connected in series. The carbon dioxide outlet pipe of the carbon dioxide capture unit is connected to the carbon dioxide inlet pipe of the first fluidized bed reactor. CO2 is catalytically hydrogenated to generate mixed olefins, and the mixed olefins enter the first fluidized bed reactor to prepare carbon nanotubes. The outlet end of the second fluidized bed reactor is connected to an exhaust pipe, and the exhaust pipe is connected to a catalyst recovery device and a hydrogen recovery device.

[0011] The first and second fluidized bed reactors are each equipped with a product separation structure at their tops. The outlet pipe of the product separation structure is connected to the catalyst inlet of the second fluidized bed reactor, and a first injector is connected to the outlet pipe. The first injector is connected to a power pipe, which is connected to a power pump and is connected to the carbon source inlet pipe of the first fluidized bed reactor. A hydrogen inlet pipe is connected to the bottom of the first fluidized bed reactor. The product separation structure is a cyclone separator.

[0012] Both the first fluidized bed reactor and the second fluidized bed reactor are equipped with a fixed reactor. The fixed reactor is equipped with a porous gas distribution plate and a flow guide baffle is connected to the top of the fixed reactor.

[0013] Furthermore, the catalyst recovery device includes a cyclone separator, the top outlet of which is connected to a hydrogen recovery device, and the bottom of which is connected to a catalyst reuse pipeline. The catalyst reuse pipeline is connected to two catalyst reuse branch pipes, which are respectively connected to the first fluidized bed reactor and the second fluidized bed reactor, via a tee connector.

[0014] Furthermore, the hydrogen recovery device includes an ejector (second ejector) connected to a membrane separation unit, which is connected to a pressure swing adsorption (PSA) system. The top of the PSA system is connected to a first hydrogen recovery pipe, which is connected to the hydrogen inlet pipe of the first fluidized bed reactor. A hydrogen pipeline connects the first hydrogen recovery pipe to the desorption tower of the carbon dioxide capture unit. The bottom of the PSA system and the membrane separation unit is connected to a second hydrogen recovery pipe, which is connected to the hydrogen inlet pipe of the second fluidized bed reactor.

[0015] The pressure swing adsorption system is connected to a hydrogen supply pipe at the top. Both the first and second fluidized bed reactors are equipped with heating structures. These heating structures can utilize a molten salt heating system to achieve selective growth of carbon nanotubes by controlling the reaction temperature (500℃~800℃), catalyst concentration, and gas flow rate. The molten salt heating system maintains the reactor's internal temperature at the optimal reaction temperature.

[0016] Furthermore, the discharge port of the second fluidized bed reactor is connected to a feed pipe that communicates with the first fluidized bed reactor. The bottom of the first fluidized bed reactor is connected to a discharge pipe, which is connected to a carbon nanotube storage chamber. The carbon nanotube storage chamber is connected to a shearing structure, which is connected to a primary melter and a secondary melter connected in series. Carbon nanofibers are formed by spraying through the secondary melter.

[0017] The shearing structure includes a first shear connected to the carbon nanotube storage chamber, the first shear connected to an ejector, the ejector connected to a second shear, and the second shear connected to the molten structure. The second shear includes a rotary shear, and a shear material return pipe is connected between the second shear and the ejector.

[0018] Furthermore, both the primary melter and the secondary melter are connected to a heat source supplementation structure, and a heating structure for the substance to be melted is connected to the material transfer pipe connecting the shearing structure and the melting structure.

[0019] The heating structure for the material to be melted is a molten salt heating system.

[0020] The heat source supplementation structure includes hot air ducts connected to the primary and secondary melters. These hot air ducts are connected to fans and an air heating structure, which is a molten salt heating system. The temperature of the primary and secondary melters can be controlled by adjusting the fan speed to regulate the hot air flow. When the temperature in the melting zone deviates from the set value, the fan speed can be adjusted.

[0021] Furthermore, the carbon dioxide capture unit includes a carbon dioxide absorption tower. The bottom of the carbon dioxide absorption tower is connected to an intermediate buffer tower via a rich amine liquid delivery pipe. The bottom of the intermediate buffer tower is connected to a semi-lean liquid delivery pipe. The semi-lean liquid delivery pipe is connected to a first semi-lean liquid delivery pipe and a second semi-lean liquid delivery pipe via a tee connector. The first semi-lean liquid delivery pipe is connected to a carbon dioxide desorption tower, and the second semi-lean liquid delivery pipe is connected to the top of the carbon dioxide absorption tower.

[0022] The intermediate buffer tower is equipped with 3 to 5 sieve plates or packing materials to achieve preliminary gas-liquid separation and buffering, and to serve as a receiver for the reflux liquid at the top of the desorption tower.

[0023] Furthermore, a flash tank is connected to the bottom of the carbon dioxide desorption tower via a hot lean liquid delivery pipe; the bottom of the flash tank is connected to a liquid phase delivery pipe connected to the top of the carbon dioxide absorption tower, and a lean liquid pump and a heat exchanger are connected to the liquid phase delivery pipe.

[0024] Furthermore, a steam discharge pipe is connected to the top of the flash tank, and a vortex tube and a compressor are connected to the steam discharge pipe. The vortex tube is connected to a hot gas pipe leading to the bottom of the carbon dioxide desorption tower, and a cold gas pipe leading to the top of the carbon dioxide absorption tower. The compressor's outlet pressure is 0.8 MPa to 1.2 MPa.

[0025] Furthermore, the carbon dioxide absorption tower is connected to a reboiler.

[0026] Furthermore, a low-pressure flash distillation tower is connected to the top of the intermediate buffer tower via a gas pipe. The low-pressure flash distillation tower operates at a pressure of 0.1 MPa to 0.5 MPa and is used to directly obtain carbon dioxide product gas with a purity ≥ 99%.

[0027] The specific capture method of the carbon dioxide capture unit is as follows:

[0028] (1) Absorption process: The raw flue gas enters from the bottom of the carbon dioxide absorption tower and comes into countercurrent contact with the lean amine liquid entering from the top of the tower. The carbon dioxide in the flue gas is absorbed, and the purified fuel gas is discharged from the top of the tower. The carbon dioxide concentration drops to about 0.1%, and the carbon dioxide-enriched amine liquid is discharged from the bottom of the tower and enters the intermediate buffer tower. The pressure inside the carbon dioxide absorption tower is controlled at 0.1MPa~2.5MPa, and the temperature is controlled at 40℃~60℃.

[0029] (2) Gas-liquid separation and first-stage flash evaporation: In the intermediate buffer tower, the amine-rich liquid undergoes preliminary gas-liquid separation; the gas phase rich in carbon dioxide at the top of the tower enters the low-pressure flash evaporator for flash evaporation, and high-purity carbon dioxide gas product is obtained at the top of the tower, while the liquid phase at the bottom of the tower returns to the intermediate buffer tower; the semi-lean liquid at the bottom of the tower is divided into two streams.

[0030] (3) Desorption and regeneration: The semi-lean liquid from the bottom of the intermediate buffer tower is first returned to the carbon dioxide absorption tower as absorbent; the second stream is preheated by a heat exchanger and then enters the upper part of the carbon dioxide desorption tower; inside the desorption tower, the solution is heated by a reboiler, CO2 is desorbed and returned from the top of the tower to the lower part of the intermediate buffer tower; the regenerated hot lean liquid is discharged from the bottom of the desorption tower. The pressure inside the carbon dioxide desorption tower is controlled at 0.15MPa~0.25MPa, and the temperature is controlled at 110℃~130℃.

[0031] (4) Secondary flash evaporation and energy recovery: The hot lean liquid obtained in step (3) enters the flash tank for further flash evaporation. The liquid phase at the bottom of the flash tank is cooled by the heat exchanger and returned to the top of the carbon dioxide absorption tower as supplementary lean liquid. The gas phase flashed out from the top of the flash tank is pressurized by the compressor and then enters the vortex tube for energy separation.

[0032] (5) Comprehensive energy utilization: The high-temperature and high-pressure gas flowing out from the hot end outlet of the vortex tube returns to the bottom of the carbon dioxide desorption tower to provide part of the regeneration heat energy; the low-temperature gas flowing out from the cold end outlet of the vortex tube returns to the top of the carbon dioxide absorption tower for cooling of the absorption process.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] (1) The system in this invention achieves continuous molding of carbon nanofibers by connecting a carbon dioxide capture unit, and at the same time realizes the direct conversion of carbon dioxide into carbon nanofibers. The process is simple, energy consumption is significantly reduced, product performance is stable, and the raw materials are fully converted and resources are recycled. This improves the yield and quality of carbon nanofibers and is suitable for various working conditions from atmospheric pressure to medium pressure. The connected hydrogen recovery device and catalyst recovery device can separate unreacted gas through membrane separation and pressure swing adsorption and then return it to the fluidized bed reactor for reuse, which improves the utilization rate of raw materials. Through the synergistic effect of the dual reactor series and raw material recycling, the product quality and production efficiency are significantly improved. It has the advantages of high conversion rate and good product consistency. Compared with the traditional single reactor, the process investment cost of this system is reduced by more than 40% and energy consumption is reduced by more than 35% when applied, providing a reliable technical approach for the high-value utilization of carbon sources and catalysts.

[0035] (2) By connecting a molten structure at the back end of a two-stage fluidized bed reactor, the present invention integrates the carbon dioxide conversion and fiber preparation process, solving the technical problems of separation of reaction and molding processes and complex process in traditional processes. It realizes the direct conversion and continuous molding of carbon nanofibers, with a simple process flow, significantly reduced energy consumption, stable product performance, and is suitable for various working conditions from normal pressure to medium pressure, providing a new technical path for the resource utilization of carbon dioxide.

[0036] (3) The melting structure of the present invention consists of two-stage melters connected in series, so that the carbonaceous product completes basic melting and homogenization in the first stage melter, and then enters the second stage melter for fine conditioning and spinning. Both melters are equipped with a spinning system, which realizes continuous and stable molding of carbon nanofibers, and at the same time can obtain carbon nanofiber products with ideal morphology and consistency.

[0037] (4) The molten structure of the present invention achieves precise control of the microstructure of carbon nanofiber products through the synergistic effect of hot air, thereby improving the quality of the prepared carbon nanofiber products.

[0038] (5) This invention realizes the stepwise catalytic conversion of mixed carbon sources through a two-stage fluidized bed reactor, and realizes the efficient utilization of raw materials by using interstage separation and circulation units. It realizes the direct conversion of mixed carbon sources to carbon nanotubes, improves the conversion rate of mixed carbon sources, and also improves the quality of products. The process is simple, energy consumption is significantly reduced, and product performance is stable. The system is suitable for various working conditions such as negative pressure to medium pressure, and provides a new technical path for the resource utilization of mixed carbon sources.

[0039] (6) In this invention, the first and second fluidized bed reactors connected in series can achieve continuous feeding. The first fluidized bed reactor achieves catalytic activation of the mixed carbon source to obtain carbon nanotubes and some intermediate products. The formed intermediate products enter the second fluidized bed reactor to continue the reaction and generate carbon nanotubes. The reaction is completed through continuous feeding and discharging. The gas-solid separation is achieved through the interstage separation structure, and the separated catalyst is returned to the reaction system for reuse.

[0040] (7) The fluidized bed reactor of the present invention is equipped with a porous gas distribution plate to ensure that the reaction gas is uniformly distributed in the bed. At the same time, the staggered flow guide plates inside the reactor can effectively prolong the gas-solid phase contact time and improve the raw material conversion efficiency. Meanwhile, the flow guide baffles enhance the airflow disturbance, enabling the reactants to diffuse rapidly to the catalyst active sites. This strong turbulent environment ensures high mass transfer efficiency, allowing the carbon source gas to be rapidly cracked and deposited, thereby achieving high-speed growth of carbon nanotubes.

[0041] (8) The ejector in this invention is the core power structure. It uses a high-pressure power gas source to generate a vacuum effect, providing stable gas flow power for the entire reaction system. The ejector ensures that the reactants form a stable sulfidation state in the fluidized bed reactor by precisely controlling the gas flow rate and pressure parameters, while realizing the efficient recycling of unreacted gas.

[0042] (9) The system in this invention is stable, energy-efficient, safe and reliable. It can process mixed carbon source raw materials of different concentrations. The system has wide raw material adaptability and high operational flexibility. It is suitable for various process conditions such as negative pressure, normal pressure, pressurization or vacuum. The preparation system is flexible in regulation and has high production efficiency.

[0043] (10) The present invention achieves fully enclosed material transportation through a complete pipeline network, which effectively prevents pollution and improves the purity of the product.

[0044] (11) The carbon dioxide capture system of the present invention includes a multi-stage flash regeneration process and a high-efficiency energy recovery network, which solves the problems of high energy consumption and easy degradation of absorbent in traditional carbon dioxide capture systems.

[0045] (12) The carbon dioxide capture system of the present invention constructs a complete system including an absorption unit, a regeneration unit and an energy recovery unit. The absorption unit achieves efficient capture of carbon dioxide through an absorption tower. The regeneration unit significantly reduces energy consumption by combining flash evaporation and desorption. The energy recovery unit realizes the recycling of energy within the system through heat exchange between lean and rich liquids and energy separation by vortex tubes. Ultimately, the carbon dioxide capture process achieves high efficiency, energy saving and long-term stable operation.

[0046] (13) The absorption unit of the carbon dioxide capture system of the present invention consists of a carbon dioxide absorption tower and an intermediate buffer tower. The high-efficiency packed tower structure ensures that the absorbent and flue gas are in full contact. The regeneration unit includes a low-pressure flash tower and a carbon dioxide desorption tower. By connecting a reboiler with zoned temperature control, the heat of the desorption process is utilized in stages. The energy recovery unit consists of a lean and rich liquid heat exchanger, a compressor and a vortex tube energy separation device, forming a multi-level heat recovery network.

[0047] (14) The carbon dioxide capture system of the present invention adopts an absorption-flash evaporation-regeneration-re-flash evaporation structure, wherein the low-pressure flash evaporation tower directly produces high-purity carbon dioxide products, significantly reducing the regeneration load of the desorption tower. The system achieves gas-liquid separation and material distribution by setting an intermediate buffer tower. The gas phase at the top of the tower enters the low-pressure flash evaporation tower to obtain carbon dioxide products, and the semi-lean liquid at the bottom of the tower is divided into two paths. One path returns to the absorption tower for recycling, and the other path enters the regeneration system. This multi-stage separation design greatly improves the system's operational flexibility and energy utilization efficiency.

[0048] (15) The energy recovery unit configured in the carbon dioxide capture system of the present invention, wherein the vortex tube effectively separates the energy of flash steam into two streams of hot and cold fluids, which are respectively used for heating at the bottom of the desorption tower and cooling at the top of the absorption tower, forming an energy recycling mode inside the system. The lean and rich liquid heat exchanger realizes the heat exchange between the hot and cold streams, further reducing the external energy input of the system. This multi-level energy recovery design reduces the system energy consumption by 25% to 35% compared with the traditional method.

[0049] (16) Compared with traditional carbon capture systems, the carbon dioxide capture system of the present invention achieves a dual reduction in system energy consumption and operating costs through the synergistic effect of flash evaporation structure and energy recovery network. Compared with traditional single-stage regeneration, the flash evaporation structure in the present invention reduces regeneration energy consumption by more than 30%; compared with traditional simple heat exchange, the energy recovery network improves system thermal efficiency by more than 25%; compared with traditional amine carbon capture system, the operating cost is reduced by 35%~40%, achieving a unity of high efficiency, stability and economy in the carbon capture process.

[0050] (17) The carbon dioxide capture system of the present invention is applicable to various industrial applications such as coal-fired power plants, gas-fired power plants, steel plants, and cement plants. The system is stable in operation, precise in control, and has significant energy-saving effect. It can handle flue gas of different concentrations and flow rates, achieve optimal operating conditions, and has strong adaptability. It can be used for the treatment of various carbon emission sources. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 This is a schematic diagram of the structure of an integrated system for capturing and converting CO2 into carbon nanofibers according to the present invention.

[0053] Figure label:

[0054] 01-Carbon dioxide absorption tower, 02-Rich amine liquid conveying pipe, 03-Intermediate buffer tower, 04-Semi-lean liquid conveying pipe, 05-Second semi-lean liquid conveying pipe, 06-First semi-lean liquid conveying pipe, 07-Flash tank, 08-Hot lean liquid conveying pipe, 09-Liquid phase conveying pipe, 10-Heat exchanger, 11-Lean liquid pump, 12-Steam discharge pipe, 13-Compressor, 14-Vortex tube, 15-Cold gas pipe, 16-Hot gas pipe, 17-Carbon dioxide desorption tower, 18-Reboiler, 19-Low-pressure flash tower, 20-Carbon dioxide outlet pipe, 21-Hydrogen inlet pipe, 22-Heating structure, 23-First fluidized bed reactor, 24-Porous gas distribution plate, 25-Fixed reactor, 26-Baffle plate, 27-First Cyclone separator, 28-First hydrogen recovery pipe, 29-Catalyst recovery pipe, 30-Second cyclone separator, 31-Hydrogen replenishment pipe, 32-Pressure swing adsorption system, 33-Secondary membrane separation unit, 34-First-stage membrane separation unit, 35-Second hydrogen recovery pipe, 36-Second ejector, 37-Second fluidized bed reactor, 38-First ejector, 39-Power pump, 40-Power pipe, 41-Carbon source inlet pipe, 42-Feeding pipe, 43-Carbon nanotube storage bin, 44-First shearer, 45-Ejector, 46-Shear material return pipe, 47-Second shearer, 48-First-stage melter, 49-Second-stage melter, 50-Material return pipe, 51-Fan, 52-Hot air pipe, 53-Hydrogen pipe. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0056] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known materials or methods have not been specifically described in order to avoid obscuring the invention.

[0057] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described herein, as well as the features of those different embodiments or examples.

[0058] In this application, unless otherwise stated, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "middle," "vertical," "horizontal," "lateral," and "longitudinal," etc., generally refer to the directions shown in the drawings or describe the relative positional relationships of the components in a vertical, perpendicular, or gravitational direction. They are used only to describe the relative positional relationships between the components or constituent parts and do not specifically limit the specific installation orientation of each component or constituent part. "Inner" and "outer" generally refer to the interior or exterior of the cavity relative to the chamber or the radial interior or exterior relative to the center of a circle. The above directional terms are defined for ease of understanding of the present invention and therefore do not constitute a limitation on the scope of protection of the present invention.

[0059] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0060] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0061] Furthermore, the structures, proportions, sizes, etc., drawn in the accompanying drawings of this application are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which this application can be implemented. Therefore, they have no substantial technical significance. Any modification to the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects and purposes that this application can produce, should still fall within the scope of the technical content disclosed in this application.

[0062] Example

[0063] like Figure 1 As shown, this embodiment provides an integrated system for CO2 capture and conversion into carbon nanofibers, including a carbon dioxide capture unit and a carbon nanofiber preparation unit. The carbon dioxide outlet pipe 20 of the carbon dioxide capture unit is connected to the carbon dioxide inlet pipe of the carbon nanofiber preparation unit. The carbon nanofiber preparation unit includes a first fluidized bed reactor 23 and a second fluidized bed reactor 37 connected in series. The carbon dioxide outlet pipe 20 of the carbon dioxide capture unit is connected to the carbon dioxide inlet pipe of the first fluidized bed reactor 23. CO2 is catalytically hydrogenated to generate mixed olefins, and the mixed olefins enter the first fluidized bed reactor 23 to prepare carbon nanotubes. The outlet end of the second fluidized bed reactor 37 is connected to an exhaust pipe, and the exhaust pipe is connected to a catalyst recovery device and a hydrogen recovery device.

[0064] The continuous molding of carbon nanofibers is achieved by connecting a carbon dioxide capture unit, simultaneously realizing the direct conversion of carbon dioxide into carbon nanofibers. The process is simple, energy consumption is significantly reduced, and product performance is stable. It achieves full conversion of raw materials and recycling of resources, improving the yield and quality of carbon nanofibers. It is suitable for various operating conditions from atmospheric to medium pressure. The connected hydrogen recovery unit and catalyst recovery unit allow unreacted gases to be separated by membrane separation and pressure swing adsorption before being returned to the fluidized bed reactor for reuse, improving raw material utilization. Through the synergistic effect of the dual-reactor series connection and raw material recycling, product quality and production efficiency are significantly improved. It boasts advantages such as high conversion rate and good product consistency. Compared to traditional single reactors, this system reduces process investment costs by more than 40% and energy consumption by more than 35%, providing a reliable technical approach for the high-value utilization of carbon sources and catalysts.

[0065] Specifically, the discharge port of the second fluidized bed reactor 37 is connected to a feed pipe 42 that communicates with the first fluidized bed reactor 23. The bottom of the first fluidized bed reactor 23 is connected to a discharge pipe, which in turn connects to a carbon nanotube storage chamber 43. The carbon nanotube storage chamber 43 is connected to a shearing structure, which in turn connects to a melting structure. Carbon nanofibers are formed by spraying through the melting structure. Multiple feed pipes can be connected to the carbon nanotube storage chamber 43 to replenish the carbon nanotube material within it.

[0066] Specifically, the shearing structure includes a first shearer 44 connected to the carbon nanotube storage chamber 43, a jet injector 45 connected to the first shearer 44, a second shearer 47 connected to the jet injector 45, and a molten structure connected to the second shearer 47. The second shearer 47 is a rotary shearer, and a shearing material return pipe 46 connects the second shearer 47 and the jet injector 45. The jet injector 45 is a high-speed jet injector 45.

[0067] Specifically, the melting structure includes a primary melter 48 and a secondary melter 49 connected in series. Both the primary melter 48 and the secondary melter 49 are connected to a heat source supplementation structure. A material transfer pipe connecting the shearing structure and the melting structure is connected to a heating structure 22 for the substance to be melted. The heating structure 22 for the substance to be melted is a molten salt heating system. The heat source supplementation structure includes a hot air duct 52 connected to the primary melter 48 and the secondary melter 49. A fan 51 is connected to the hot air duct 52, and an air heating structure 22 is connected to the hot air duct 52. The air heating structure 22 is also a molten salt heating system.

[0068] The molten structure consists of two series-connected melters. The carbonaceous product undergoes basic melting and homogenization in the first melter 48, followed by fine conditioning and spinning in the second melter 49. Both melters are equipped with spinnerets, enabling continuous and stable formation of carbon nanofibers and yielding carbon nanofiber products with ideal morphology and consistency. Through the synergistic effect of hot air, the molten structure achieves precise control over the microstructure of the carbon nanofiber product, improving the quality of the prepared carbon nanofiber product.

[0069] Specifically, both the first fluidized bed reactor 23 and the second fluidized bed reactor 37 are connected to a product separation structure at their tops. The outlet pipe of the product separation structure is connected to the catalyst inlet of the second fluidized bed reactor 37, and a first injector 38 is connected to the outlet pipe. The first injector 38 is connected to a power pipe 40, and a power pump 39 is connected to the power pipe 40. The power pipe 40 is connected to the carbon source inlet pipe 41 of the first fluidized bed reactor 23. A hydrogen inlet pipe 21 is connected to the bottom of the first fluidized bed reactor 23. The product separation structure is a cyclone separator.

[0070] Both the first fluidized bed reactor 23 and the second fluidized bed reactor 37 are equipped with fixed reactors 25. Each fixed reactor 25 contains a porous gas distribution plate 24, and a flow guide baffle 26 is connected to its top. The porous gas distribution plate 24 ensures uniform distribution of the reactant gas within the bed. Simultaneously, the staggered flow guide plates inside the reactor effectively extend the gas-solid phase contact time, improving feed conversion efficiency. The flow guide baffle 26 enhances airflow turbulence, allowing reactants to rapidly diffuse to the catalyst active sites. This highly turbulent environment ensures high mass transfer efficiency, enabling rapid cracking and deposition of the carbon source gas, thus achieving high-speed growth of carbon nanotubes. Furthermore, the surface of the flow guide baffle 26 forms a synergistic interaction surface with the reactor inner wall, increasing the reaction interface area, enhancing the mass and heat transfer efficiency within the system, and significantly improving energy utilization efficiency.

[0071] Specifically, the outlet end of the first cyclone separator 27 on the second fluidized bed reactor 37 is connected to an exhaust pipe, which is connected to a catalyst recovery device and a hydrogen recovery device.

[0072] The catalyst recovery device includes a second cyclone separator 30. The top outlet of the second cyclone separator 30 is connected to a hydrogen recovery device, and the bottom is connected to a catalyst reuse pipe 29. The catalyst reuse pipe 29 is connected to two catalyst reuse branch pipes that are respectively connected to the first fluidized bed reactor 23 and the second fluidized bed reactor 37 via a tee connector.

[0073] Specifically, the hydrogen recovery device includes a second injector 36, which is connected to a membrane separation unit, and the membrane separation unit is connected to a pressure swing adsorption system 32; the top of the pressure swing adsorption system 32 is connected to a first hydrogen recycling pipe 28, which is connected to the hydrogen inlet pipe 21 of the first fluidized bed reactor 23, and a hydrogen pipeline 53 is connected between the first hydrogen recycling pipe and the desorption tower of the carbon dioxide capture unit; the bottom of the pressure swing adsorption system 32 and the membrane separation unit is connected to a second hydrogen recycling pipe 35, which is connected to the hydrogen inlet pipe 21 of the second fluidized bed reactor 37.

[0074] The membrane separation unit consists of a primary membrane separation unit 34 and a secondary membrane separation unit 33, forming a two-stage membrane separation structure. It can recover and purify more than 95% of the hydrogen in the reaction tail gas and return it to the reaction system for recycling.

[0075] This hydrogen recovery device can perform membrane separation and pressure swing adsorption separation on unreacted gases and then return them to the fluidized bed reactor for reuse, thus improving the utilization rate of raw materials. Through the synergistic effect of dual reactors in series and raw material recycling, it significantly improves product quality and production efficiency, and has the advantages of high conversion rate and good product consistency. Compared with traditional single reactors, this reactor reduces the process investment cost by more than 40% and energy consumption by more than 35% when applied, providing a reliable technical approach for the high-value utilization of mixed carbon sources.

[0076] The ejector is the core power structure. It uses a high-pressure power gas source to generate a vacuum effect, providing stable gas flow power for the entire reaction system. The ejector ensures that the reactants form a stable sulfidation state in the fluidized bed reactor by precisely controlling the gas flow rate and pressure parameters, while realizing the efficient recycling of unreacted gases.

[0077] Specifically, a hydrogen supply pipe 31 is connected to the top of the pressure swing adsorption system 32. The purpose of connecting the hydrogen supply pipe to the top of the pressure swing adsorption system 32 is that when the hydrogen in the pressure swing adsorption system 32 cannot meet the hydrogen requirements of the second fluidized bed reactor 37, hydrogen can be added from the outside to the pressure swing adsorption system 32 to meet the reaction requirements of the second fluidized bed reactor 37.

[0078] Specifically, both the first fluidized bed reactor 23 and the second fluidized bed reactor 37 are connected to a heating structure 22. This heating structure 22 is a molten salt heating system, which controls the reaction temperature in the first fluidized bed reactor and the second fluidized bed reactor 37, so that carbon nanotubes are prepared within a suitable temperature range, thereby improving product quality.

[0079] Specifically, the carbon dioxide capture unit includes a carbon dioxide absorption tower 01. The bottom of the carbon dioxide absorption tower 01 is connected to an intermediate buffer tower 03 via an amine-rich liquid delivery pipe 02. The bottom of the intermediate buffer tower 03 is connected to a semi-lean liquid delivery pipe 04. The semi-lean liquid delivery pipe 04 is connected to a first semi-lean liquid delivery pipe 06 and a second semi-lean liquid delivery pipe 05 via a tee connector. The first semi-lean liquid delivery pipe 06 is connected to a carbon dioxide desorption tower 17, and the second semi-lean liquid delivery pipe 05 is connected to the top of the carbon dioxide absorption tower 01.

[0080] The intermediate buffer tower 03 is equipped with 3 to 5 sieve plates or packing materials to achieve preliminary separation and buffering of gas and liquid, and to serve as a receiver for the reflux liquid at the top of the desorption tower.

[0081] Specifically, a flash tank 07 is connected to the bottom of the carbon dioxide desorption tower 17 via a hot lean solution delivery pipe 08. The bottom of the flash tank 07 is connected to a liquid phase delivery pipe 09, which connects to the top of the carbon dioxide absorption tower 01. A lean solution pump 11 and a heat exchanger 10 are connected to the liquid phase delivery pipe 09. A steam discharge pipe 12 is connected to the top of the flash tank 07. A vortex tube 14 and a compressor 13 are connected to the steam discharge pipe 12. The vortex tube 14 is connected to a hot gas pipe 16 leading to the bottom of the carbon dioxide desorption tower 17, and also to a cold gas pipe 15 leading to the top of the carbon dioxide absorption tower 01. The outlet pressure of the compressor 13 is 0.8 MPa to 1.2 MPa.

[0082] The hot lean liquid discharged from the bottom of the carbon dioxide desorption tower 17 enters the flash tank 07 for secondary flash evaporation. The liquid phase at the bottom of the flash tank 07 is cooled by the lean and rich liquid heat exchanger 10 and then returns to the top of the carbon dioxide absorption tower 01. The flash vapor generated at the top of the flash tank 07 is pressurized by the compressor 13 and then enters the vortex tube 14. The vortex tube 14 separates the flash vapor into hot and cold fluids. The hot end fluid returns to the bottom of the carbon dioxide desorption tower 17 to provide an auxiliary heat source, while the cold end fluid is used to cool the top of the carbon dioxide absorption tower 01.

[0083] Specifically, the carbon dioxide desorption tower 17 is connected to a reboiler 18, where thermal desorption is performed through the combined action of hydrogen and the reboiler. The semi-lean liquor from the intermediate buffer tower 03 is preheated by the lean-rich liquor heat exchanger 10 and then enters the upper part of the carbon dioxide desorption tower 17. Under the action of the heat energy provided by the reboiler 18, carbon dioxide is desorbed from the amine liquor, and the fully regenerated lean amine liquor is discharged from the bottom of the tower into the flash tank 07.

[0084] Specifically, the top of the intermediate buffer tower 03 is connected to a low-pressure flash tower 19 via a gas pipe. The low-pressure flash tower 19 operates at a pressure of 0.1MPa to 0.5MPa and is used to directly obtain carbon dioxide product gas with a purity of ≥99%.

[0085] Working principle: First, high-purity carbon dioxide is prepared through the carbon dioxide capture unit. The prepared carbon dioxide enters the first fluidized bed reactor 23 of the carbon nanofiber preparation unit to participate in the reaction to prepare carbon nanofibers.

[0086] The specific capture method for carbon capture is as follows:

[0087] (1) Absorption process: The raw flue gas enters from the bottom of the carbon dioxide absorption tower 01 and comes into countercurrent contact with the lean amine liquid entering from the top of the tower. The carbon dioxide in the flue gas is absorbed, and the purified fuel gas is discharged from the top of the tower. The carbon dioxide concentration drops to about 0.1%, and the carbon dioxide-enriched amine liquid is discharged from the bottom of the tower and enters the intermediate buffer tower 03.

[0088] (2) Gas-liquid separation and first-stage flash evaporation: In the intermediate buffer tower 03, the amine-rich liquid undergoes preliminary gas-liquid separation; the gas phase rich in carbon dioxide at the top of the tower enters the low-pressure flash tower 19 for flash evaporation, and a high-purity carbon dioxide gas product is obtained at the top of the tower, while the liquid phase at the bottom of the tower returns to the intermediate buffer tower 03; the semi-lean liquid at the bottom of the tower is divided into two streams.

[0089] (3) Desorption and regeneration: The semi-lean liquid coming out from the bottom of the intermediate buffer tower 03 first returns to the carbon dioxide absorption tower 01 as the absorbent; the second liquid is preheated by the heat exchanger 10 and enters the upper part of the carbon dioxide desorption tower 17; inside the desorption tower, the solution is heated by the reboiler 18, CO2 is desorbed and returned from the top of the tower to the lower part of the intermediate buffer tower 03; the regenerated hot lean liquid is discharged from the bottom of the desorption tower.

[0090] (4) Secondary flash evaporation and energy recovery: The hot lean liquid obtained in step (3) enters the flash tank 07 for further flash evaporation. The liquid phase at the bottom of the flash tank 07 is cooled by the heat exchanger 10 and returned to the top of the carbon dioxide absorption tower 01 as supplementary lean liquid. The gas phase flashed out from the top of the flash tank 07 is pressurized by the compressor 13 and then enters the vortex tube 14 for energy separation.

[0091] (5) Comprehensive energy utilization: The high-temperature and high-pressure gas flowing out from the hot end outlet of the vortex tube 14 returns to the bottom of the carbon dioxide desorption tower 17 to provide part of the regeneration heat energy; the low-temperature gas flowing out from the cold end outlet of the vortex tube 14 returns to the top of the carbon dioxide absorption tower 01 for cooling of the absorption process.

[0092] In step (1), the operating pressure of the carbon dioxide absorption tower 01 is 1.5 MPa to 2.5 MPa, and the operating temperature is 40℃ to 60℃; in step (2), the operating pressure of the low-pressure flash tower 19 is 0.1 MPa to 0.5 MPa. The operating pressure of the carbon dioxide desorption tower 17 is 0.15 MPa to 0.25 MPa, and the temperature of the reboiler 18 is 110℃ to 130℃; in step (4), the outlet pressure of the compressor 13 is 0.8 MPa to 1.2 MPa.

[0093] This carbon dioxide capture unit incorporates a multi-stage flash regeneration process and a high-efficiency energy recovery network, solving the problems of high energy consumption and easy degradation of absorbents in traditional carbon dioxide capture systems. By constructing a complete system comprising an absorption unit, a regeneration unit, and an energy recovery unit, the absorption unit achieves efficient carbon dioxide capture through an absorption tower. The regeneration unit significantly reduces energy consumption by combining flash evaporation and desorption. The energy recovery unit achieves energy recycling within the system through lean-rich liquid heat exchange and energy separation via vortex tube 14, ultimately achieving high efficiency, energy saving, and long-term stable operation of the carbon dioxide capture process. The absorption unit consists of a carbon dioxide absorption tower 01 and an intermediate buffer tower 03, employing a high-efficiency packed tower structure to ensure sufficient contact between the absorbent and the flue gas. The regeneration unit includes a low-pressure flash tower 19 and a carbon dioxide desorption tower 17, connected to a zone-controlled reboiler 18 to achieve cascaded utilization of heat from the desorption process. The energy recovery unit consists of a lean-rich liquid heat exchanger 10, a compressor 13, and an energy separation device via vortex tube 14, forming a multi-layered heat recovery network. The system employs an absorption-flash-regeneration-re-flash structure, where the low-pressure flash tower 19 directly produces high-purity carbon dioxide, significantly reducing the regeneration load on the desorption tower. The system utilizes an intermediate buffer tower 03 for gas-liquid separation and material distribution. The gaseous phase at the top of the buffer tower enters the low-pressure flash tower 19 to obtain carbon dioxide, while the semi-lean liquid at the bottom is divided into two paths: one returns to the absorption tower for recycling, and the other enters the regeneration system. This multi-stage separation design greatly improves the system's operational flexibility and energy utilization efficiency. The system's energy recovery unit, with its vortex tube 14, effectively separates the energy of the flash steam into hot and cold fluids, which are respectively reused for heating the bottom of the desorption tower and cooling the top of the absorption tower, forming an internal energy recycling mode. The lean-rich liquid heat exchanger 10 enables heat exchange between the hot and cold streams, further reducing external energy input. This multi-level energy recovery design reduces system energy consumption by 25% to 35% compared to traditional methods. Compared to traditional carbon capture systems, this invention achieves a dual reduction in system energy consumption and operating costs through the synergistic effect of a flash evaporation structure and an energy recovery network. The flash evaporation structure in this invention reduces regeneration energy consumption by more than 30% compared to traditional single-stage regeneration; the energy recovery network improves system thermal efficiency by more than 25% compared to traditional simple heat exchange; and compared to traditional amine-based carbon capture systems, operating costs are reduced by 35% to 40%, achieving a balance between high efficiency, stability, and economy in the carbon capture process. This carbon dioxide capture system is suitable for various industrial applications such as coal-fired power plants, gas-fired power plants, steel plants, and cement plants. The system operates stably, with precise control, significant energy-saving effects, and can handle flue gas of different concentrations and flow rates, achieving optimal operating conditions. The system is highly adaptable and can be used for the treatment of various carbon emission sources.

[0094] When the carbon dioxide captured by the carbon capture unit enters the first fluidized bed reactor 23 of the carbon nanofiber preparation unit, high-purity carbon dioxide participates in the reaction. Simultaneously, a mixed carbon source is introduced into the first fluidized bed reactor 23 through a carbon dioxide inlet pipe connected to it, and hydrogen is introduced into the first fluidized bed reactor 23 through a hydrogen inlet pipe 21 connected to it. At the same time, a catalyst is introduced into the first fluidized bed reactor 23 through its catalyst inlet. Both the mixed carbon source and hydrogen entering the first fluidized bed reactor 23 are first heated by a molten salt heating system connected to the carbon dioxide and hydrogen inlet pipes 21 before entering the reactor. The mixed carbon source and hydrogen in the first fluidized bed reactor 23 are first uniformly distributed through a porous gas distribution plate 24 to form a stable fluidized state. Simultaneously, the temperature is controlled by a molten salt heating system connected to a fixed reactor 25. After the raw gas reacts fully in the fixed reactor 25, carbon nanotubes and some intermediate products are generated. After separation by a cyclone separator connected to the top of the first fluidized bed reactor 23, the carbon nanotubes fall downwards through the channel formed between the guide baffle 26 and the wall of the first fluidized bed reactor 23, and are then discharged from the outlet at the bottom of the first fluidized bed reactor 23. The generated intermediate products or remaining gas enter the second fluidized bed reactor 37 through an inlet pipe. Before entering the second fluidized bed reactor 37, the gas enters the first ejector 38. The first ejector 38 utilizes a high-pressure power gas source to generate a vacuum effect, providing stable gas flow power for the entire reaction system. Simultaneously, through precise control of gas flow rate and pressure parameters, it ensures that the reactants form a stable sulfidation state within the fluidized bed reactor.The intermediate products or residual gas generated in the first fluidized bed reactor 23 are introduced into the second fluidized bed reactor 37 through the first injector 38 for further catalytic reaction. Simultaneously, a mixed carbon source is introduced into the second fluidized bed reactor 37 through the carbon dioxide inlet pipe. The hydrogen required in the second fluidized bed reactor 37 comes from the hydrogen recovery system. After the feed gas fully reacts in the second fluidized bed reactor 37, carbon nanotubes are formed, and some intermediate products or residual hydrogen may also be formed. The generated carbon nanotubes can be directly discharged from the bottom outlet of the second fluidized bed reactor 37, or a feed pipe can be connected to the outlet of the second fluidized bed reactor 37 to introduce the carbon nanotubes generated in the second fluidized bed reactor 37 into the first fluidized bed reactor 23, and then discharged together from the bottom outlet of the first fluidized bed reactor 23. The carbon nanotubes are then transported through the feed pipe 42. The material is transported to the carbon nanotube storage chamber 43. When carbon nanofibers need to be prepared, the carbon nanotubes in the storage chamber are first transported to the first shear 44 for primary dispersion, and then enter the high-speed jet injector 45. After being dispersed again in the high-speed jet injector 45, the material enters the second shear 47 (rotary shear) for deep processing. Some of the material returns to the high-speed jet injector 45 through the shear material return pipe 46 for further processing. The homogenized material enters the first-stage melter 48 and the second-stage melter 49 in sequence. The material is first plasticized in the first-stage melter 48 and then enters the second-stage melter 49. With the assistance of hot air, the material is deeply melted. The melted material is directly sprayed through the pipe to form carbon nanofibers, and then enters the pressing device to complete the final shaping before the carbon nanofiber product is output.

[0095] If there is any material that is not completely melted during the carbon nanofiber spraying process, it can be passed through the material return pipe 50 into the primary melter 48 and the secondary melter 49 for remelting.

[0096] In addition, the residual gas after the reaction in the second fluidized bed reactor 37 is separated by a cyclone separator and enters the second cyclone separator 30. The second cyclone separator 30 separates the hydrogen and catalyst. The separated hydrogen is then fed into a hydrogen recovery device. The hydrogen first enters the second injector 36, and then enters the primary membrane separation unit 34 and the secondary membrane separation unit 33 for separation and purification, achieving efficient hydrogen recovery. The hydrogen after being processed by the membrane separation unit enters the pressure swing adsorption system 32. When hydrogen needs to be introduced into the second fluidized bed reactor 37, the hydrogen separated in the pressure swing adsorption system 32 can be used, achieving efficient resource utilization. The separated catalyst is then reintroduced into the first fluidized bed reactor 23 and the second fluidized bed reactor 37 for use.

[0097] The carbon nanofiber preparation unit of this invention integrates carbon dioxide conversion and fiber preparation processes by connecting a melting structure at the rear end of a two-stage fluidized bed reactor. This solves the technical problems of separation between reaction and molding processes and complex procedures in traditional methods, achieving direct conversion and continuous molding of carbon nanofibers. The process is simple, energy consumption is significantly reduced, product performance is stable, and it is suitable for various working conditions from atmospheric to medium pressure, providing a new technical path for the resource utilization of carbon dioxide. Compared with traditional stepwise preparation systems, the uniformity of fiber diameter is improved by about 40%, tensile strength is increased by about 35%, and production energy consumption is reduced by about 45%. The high-speed jet injector 45 effectively improves the dispersion uniformity of materials through strong turbulent flow; two sets of shears perform secondary shearing treatment on carbon nanotubes, further improving the nanoscale dispersion effect of the material; the secondary melt strengthening unit optimizes the plasticization process of the material through stepped temperature control; and the direct spraying of molten carbon nanotubes enables continuous preparation of carbon nanofibers. This integrated design not only significantly improves production efficiency but also significantly reduces energy consumption and raw material consumption.

[0098] Furthermore, in the preparation of carbon nanotubes, a two-stage fluidized bed reactor was used to achieve the stepwise catalytic conversion of mixed carbon sources. The interstage separation and recycling units enabled efficient utilization of raw materials, achieving direct conversion from mixed carbon sources to carbon nanotubes. This improved the conversion rate of mixed carbon sources and the quality of the product. The process is simple, energy consumption is significantly reduced, and product performance is stable. This system is suitable for various operating conditions, from negative pressure to medium pressure, providing a new technical path for the resource utilization of mixed carbon sources. In addition, the first fluidized bed reactor 23 and the second fluidized bed reactor 37, connected in series, can achieve continuous feeding. The first fluidized bed reactor 23 catalytically activates the mixed carbon source to obtain carbon nanotubes and some intermediate products. The formed intermediate products enter the second fluidized bed reactor 37 to continue the reaction and generate carbon nanotubes. The continuous feeding and discharging ensures complete reaction. The interstage separation structure achieves efficient gas-solid separation, and the separated catalyst is returned to the reaction system for reuse. Moreover, the system is stable, energy-efficient, safe, and reliable. It can handle mixed carbon source raw materials of different concentrations, has wide raw material adaptability, and high operational flexibility, making it suitable for various industrial conditions. Compared to traditional single-reactor carbon source conversion processes, this reaction system achieves directional pyrolysis and efficient conversion of different carbon source raw materials, improving the yield of carbon nanotubes. The system boasts strong raw material adaptability, a short process flow, and energy consumption that is 25-35% lower than traditional reaction beds. Furthermore, the product exhibits uniform structure and stable quality, making it suitable for large-scale conversion of various mixed carbon source raw materials. The system achieves fully enclosed material transport through a sophisticated pipeline network, effectively preventing contamination and improving product purity.

[0099] Experimental Example 1

[0100] The carbon capture unit processes 25 kg / h of flue gas with a CO2 concentration of 10%. The absorption tower operates at a pressure of 0.15 MPa and a temperature of 45°C; the desorption tower operates at a pressure of 0.18 MPa and a reboiler temperature of 115°C. The CO2 capture rate is 92%, and the purity is 99.5%. A fluidized bed system is used to convert CO2 into carbon nanotubes. The first fluidized bed has a diameter of 280 mm, and the second fluidized bed has a diameter of 150 mm. The influent gas velocity is 0.2 m / s, and the H2 / CO2 molar ratio is 5:1. The resulting carbon nanotubes have a diameter of 50 nm, a purity of 40%, a yield of 1800 g / h, and a carbon fiber length of 60 μm.

[0101] Experiment Example 2

[0102] The carbon capture unit processes 30 kg / h of flue gas with a CO2 concentration of 25%. The absorption tower operates at a pressure of 0.12 MPa and a temperature of 55°C; the desorption tower operates at a pressure of 0.15 MPa and a reboiler temperature of 105°C. The CO2 capture rate is 90%, and the purity is 99%. A fluidized bed system is used to convert CO2 into carbon nanotubes. The first fluidized bed has a diameter of 300 mm, and the second fluidized bed has a diameter of 160 mm. The influent gas velocity is 0.2 m / s, and the H2 / CO2 molar ratio is 6:1. The resulting carbon nanotubes have a diameter of 80 nm, a purity of 45%, a yield of 2200 g / h, and a melt-blown carbon fiber length of 56 μm.

[0103] Experimental Example 3

[0104] The carbon capture unit processes 50 kg / h of flue gas with a CO2 concentration of 5%. The absorption tower operates at a pressure of 0.18 MPa and a temperature of 55°C; the desorption tower operates at a pressure of 0.12 MPa and a reboiler temperature of 108°C. The CO2 capture rate is 90%, and the purity is 95%. A fluidized bed system is used to convert CO2 into carbon nanotubes. The first fluidized bed has a diameter of 320 mm, and the second fluidized bed has a diameter of 150 mm. The influent gas velocity is 0.4 m / s, and the H2 / CO2 molar ratio is 8:1. The resulting carbon nanotubes have a diameter of 15 nm, a purity of 55%, a yield of 4000 g / h, and a melt-blown carbon fiber length of 65 μm.

[0105] Finally, it should be noted that the specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. For those skilled in the art, it is obvious that this application is not limited to the details of the above exemplary embodiments, and that the present application can be implemented in other specific forms without departing from the spirit or basic characteristics of the present application. Furthermore, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe various possible combinations separately. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of this application is defined by the appended claims rather than the foregoing description, and therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included within this application.

Claims

1. An integrated system for capturing and converting CO2 into carbon nanofibers, characterized in that, The system includes a carbon dioxide capture unit and a carbon nanofiber preparation unit. The carbon dioxide outlet pipe (20) of the carbon dioxide capture unit is connected to the carbon dioxide inlet pipe of the carbon nanofiber preparation unit. The carbon nanofiber preparation unit includes a first fluidized bed reactor (23) and a second fluidized bed reactor (37) connected in series. The carbon dioxide outlet pipe (20) of the carbon dioxide capture unit is connected to the carbon dioxide inlet pipe of the first fluidized bed reactor (23). CO2 is catalytically hydrogenated to generate mixed olefins, and the mixed olefins enter the first fluidized bed reactor (23) to prepare carbon nanotubes. The outlet end of the second fluidized bed reactor (37) is connected to an exhaust pipe, and the exhaust pipe is connected to a catalyst recovery device and a hydrogen recovery device.

2. The integrated system for CO2 capture and conversion into carbon nanofibers according to claim 1, characterized in that, The catalyst recovery device includes a cyclone separator. The top outlet of the cyclone separator is connected to a hydrogen recovery device, and the bottom is connected to a catalyst reuse pipe (29). The catalyst reuse pipe (29) is connected to two catalyst reuse branch pipes that are respectively connected to the first fluidized bed reactor (23) and the second fluidized bed reactor (37) through a tee connector.

3. The integrated system for CO2 capture and conversion into carbon nanofibers according to claim 1, characterized in that, The hydrogen recovery device includes an injector connected to a membrane separation unit, which is connected to a pressure swing adsorption system (32). The top of the pressure swing adsorption system (32) is connected to a first hydrogen recycling pipe (28) connected to the hydrogen inlet pipe (21) of the first fluidized bed reactor (23). A hydrogen pipeline (53) is connected between the first hydrogen recycling pipe (28) and the desorption tower of the carbon dioxide capture unit. The bottom of the pressure swing adsorption system (32) and the membrane separation unit is connected to a second hydrogen recycling pipe (35) connected to the hydrogen inlet pipe (21) of the second fluidized bed reactor (37).

4. The integrated system for CO2 capture and conversion into carbon nanofibers according to claim 1, characterized in that, The discharge port of the second fluidized bed reactor (37) is connected to a conveying pipe (42) that communicates with the first fluidized bed reactor (23). The bottom of the first fluidized bed reactor (23) is connected to a discharge pipe, which is connected to a carbon nanotube storage chamber (43). The carbon nanotube storage chamber (43) is connected to a shearing structure, which is connected to a primary melter (48) and a secondary melter (49) connected in series. Carbon nanofibers are formed by spraying through the secondary melter (49).

5. The integrated system for CO2 capture and conversion into carbon nanofibers according to claim 4, characterized in that, Both the primary melter (48) and the secondary melter (49) are connected to a heat source supplementation structure, and a material transfer pipe connecting the shearing structure and the melting structure is connected to a material heating structure (22) for the substance to be melted.

6. The integrated system for CO2 capture and conversion into carbon nanofibers according to claim 1, characterized in that, The carbon dioxide capture unit includes a carbon dioxide absorption tower (01). The bottom of the carbon dioxide absorption tower (01) is connected to an intermediate buffer tower (03) via an amine-rich liquid delivery pipe (02). The bottom of the intermediate buffer tower (03) is connected to a semi-lean liquid delivery pipe (04). The semi-lean liquid delivery pipe (04) is connected to a first semi-lean liquid delivery pipe (06) and a second semi-lean liquid delivery pipe (05) via a tee connector. The first semi-lean liquid delivery pipe (06) is connected to a carbon dioxide desorption tower (17), and the second semi-lean liquid delivery pipe (05) is connected to the top of the carbon dioxide absorption tower (01).

7. The integrated system for CO2 capture and conversion into carbon nanofibers according to claim 6, characterized in that, The bottom of the carbon dioxide desorption tower (17) is connected to a flash tank (07) via a hot lean liquid delivery pipe (08); the bottom of the flash tank (07) is connected to a liquid phase delivery pipe (09) connected to the top of the carbon dioxide absorption tower (01), and a lean liquid pump (11) and a heat exchanger (10) are connected to the liquid phase delivery pipe (09).

8. The integrated system for CO2 capture and conversion into carbon nanofibers according to claim 7, characterized in that, The top of the flash tank (07) is connected to a steam discharge pipe (12), and the steam discharge pipe (12) is connected to a vortex tube (14) and a compressor (13). The vortex tube (14) is connected to a hot gas pipe (16) leading to the bottom of the carbon dioxide desorption tower (17), and the vortex tube (14) is connected to a cold gas pipe (15) leading to the top of the carbon dioxide absorption tower (01).

9. The integrated system for CO2 capture and conversion into carbon nanofibers according to claim 6, characterized in that, The carbon dioxide absorption tower (01) is connected to a reboiler (18), and thermal desorption is carried out through the combined action of hydrogen and the reboiler.

10. The integrated system for CO2 capture and conversion into carbon nanofibers according to claim 6, characterized in that, The top of the intermediate buffer tower (03) is connected to a low-pressure flash tower (19) via a gas pipe.

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