Online recovery system and method for carbon nanotube composite fiber acetone coagulating bath solution

Abstract

The invention discloses an on-line recovery system for a carbon nanotube composite fiber acetone coagulating bath solution. The system comprises a coagulating bath tank for bearing an acetone coagulating bath, an adsorption device for purifying the acetone coagulating bath, a liquid storage device for supplementing acetone and a corresponding circulation control unit, the control unit comprises a coagulating bath liquid level detection device, an acetone purity detection device, a circulating pump and a circulating controller. The method solves the problem that the coagulating bath gradually loses efficacy due to the reaction of chlorosulfonic acid and acetone during the batch preparation of the carbon nanotube fiber under the existing chlorosulfonic acid system, can realize the effective recovery of acetone, and reduces the cost. In addition, through systematic cooperative control, the preparation efficiency of the carbon nanotube fibers is improved, and large-scale preparation of the carbon nanotube fibers is promoted.

Description

Technical Field

[0001] This invention relates to the field of carbon nanotube fiber technology, and in particular to an online recovery system and method for carbon nanotube composite fiber coagulation bath solution. Background Technology

[0002] Carbon nanotubes possess excellent mechanical, electrical, and thermal properties. Their tensile strength can reach over 100 GPa, modulus reaches 1 TPa, room temperature thermal conductivity exceeds 3000 W / (m·K), and electrical conductivity exceeds that of copper by an order of magnitude. As its most promising assembly form, carbon nanotube fibers have applications spanning hundreds of billions of dollars in markets, including lightweight structures, high thermal conductivity components, conductive frameworks for new energy vehicles, and flexible electronic substrates. They are hailed as one of the strategic new materials of the "post-carbon fiber era" and are a key area of ​​focus for many countries. Among the methods for preparing carbon nanotube fibers, wet spinning technology has become the main technical solution for large-scale production due to its advantages of strong process scalability, low overall cost, and high stability and continuity. However, in the wet spinning process, to achieve effective dispersion and orientation control of the carbon nanotube spinning solution, it is often necessary to introduce systems such as chlorosulfonic acid and organic matter, which inevitably introduces a large number of heterogeneous components into the acetone solution in the coagulation bath. Furthermore, the metal catalysts and residual carbon carried by the carbon nanotubes themselves will gradually accumulate in the acetone solution of the coagulation bath. The above phenomena will affect the composition, flow state and micro-region dispersion characteristics of the coagulation bath solution, seriously interfering with the chemical potential gradient at the spinneret outlet, as well as the driving force and path stability of the non-equilibrium solid-liquid phase separation of the spinning solution. This not only aggravates the degree of carbon nanotube fiber forming a core-sheath structure, but also seriously interferes with the stability and continuity of the spinning process.

[0003] Chinese invention patent application CN202310721280.4 proposes a highly efficient recovery and recycling process for organic solvents in the wet spinning of meta-aramid fibers. Utilizing a step-by-step principle and considering the production parameter requirements of each process stage, it achieves recycling of extraction waste liquid, primary coagulation waste liquid, and secondary coagulation waste liquid, enabling the recycling of most organic solvents to save resources without affecting the quality of the aramid fibers. Chinese invention patent application CN202211073968.8 proposes an online sodium sulfate recovery device and method for polyvinyl alcohol fiber tows. Through wastewater recycling and sodium sulfate dissolution and purification, sodium sulfate is effectively recovered, thereby reducing sodium sulfate consumption during tow production. Chinese invention patent application CN202011192239.5 proposes a method and application for recovering zinc oxide from a cellulose urethane fiber coagulation bath. This method integrates and applies existing mature viscose fiber production equipment and processes, allowing all processes to be completed on existing viscose fiber production lines, facilitating industrial application and promotion. Chinese invention patent application number CN202110561421.1 proposes a simulation device, platform and method for the coagulation bath production site of carbon fiber precursor. Through the coordinated control of a host computer, multiple online sensors, raw liquid tank, coagulation bath simulation field, coagulation bath circulation tank and coagulation liquid recovery tank, the concentration in the coagulation bath is close to the ideal state, ensuring the deacidification effect and meeting the quality control of precursor.

[0004] Through the efforts of researchers in this field, a series of achievements have been made in the separation of heterogeneous solvents and impurities introduced into the coagulation bath during wet spinning, as well as in the recovery and recycling of the coagulation bath solution. However, existing treatment technologies still have the following problems: 1. It is difficult to coordinate the separation efficiency of polymer additives such as acetone coagulation bath, poly(p-phenylenebenzodioxazole), and polyimide with impurities such as residual carbon. The impurity components introduced during spinning are complex, and the interference mechanisms of each component on the spinning process and the physical processes required for impurity separation are also different. For example, the separation of residual carbon mainly relies on the adsorption effect, while chlorosulfonic acid mainly relies on acid-base neutralization for removal and requires limiting its reaction with the acetone coagulation solution, making conventional adsorption schemes difficult to apply. Reaction impurities are deposited at the bottom of the coagulation bath and continue to react with acetone. The high vapor pressure and low boiling point of acetone cause the coagulation bath to be lost quickly. Therefore, the separation effect of existing technologies fluctuates greatly over time, seriously interfering with the stability of fiber quality. 2. Challenges in steady-state control of the spinneret micro-region in the coagulation bath: Generally, the stability of the chemical potential and flow regime in the spinneret micro-region is crucial for fiber quality, structural stability, and continuous and stable fiber production. However, existing technologies inevitably affect the stability of boundary conditions in the mass transfer and solidification process of the spinneret micro-region during the extraction and circulation of the coagulation bath solution. This leads to fluid shear force fluctuations or turbulent disturbances, resulting in carbon nanotube fiber deformation and structural defects. 3. Challenges in automated control of the circulation system: Currently, coagulation bath circulation systems mostly rely on manual adjustment of circulation parameters. The isolation between devices makes stable circulation control difficult, severely impacting circulation efficiency and stability. Summary of the Invention

[0005] This invention addresses the problems of rapid coagulation bath failure, insufficient spinning continuity, and high acetone consumption in the wet spinning of carbon nanotube fibers under the existing chlorosulfonic acid technology system. It provides a carbon nanotube fiber tow production system that delays coagulation bath failure and improves spinning continuity by recycling and purifying acetone.

[0006] The online recovery system for acetone solution from carbon nanotube composite fiber coagulation bath provided by the present invention includes: an acetone coagulation bath, a coagulation bath tank, an adsorption device, a storage device, and a circulation control unit.

[0007] The coagulation bath is a rectangular stainless steel structure, including a cover plate, a tank body, an acetone outlet, an acetone inlet, and an observation window; the tank body is equipped with a temperature control jacket with a volume ratio of 15-30%, and the bottom of the tank body has an inclination angle of 1°-3° and is equipped with a V-shaped flow stabilizer.

[0008] The current stabilizer plate has evenly distributed circular holes with an area ratio of 30-60% and a diameter of 0.5-2 mm.

[0009] The acetone inlet is a grid structure located at the upper front end of the tank, and is equipped with a V-shaped flow stabilizer. The acetone outlet is a porous flow collection structure located at the bottom rear end of the tank, and is equipped with a combined filter.

[0010] The filter is composed of a ceramic carrier and an adsorbent. The ceramic carrier has pores with a porosity of 60-80% and an open porosity greater than 99.9% evenly distributed within it, with an average pore size of 80-120 μm. The adsorbent is one or more of silica gel, activated carbon, or a polymer.

[0011] The adsorption device consists of a detachable baffle, a pressure control device, a liquid distributor, a filter, and an outer temperature control jacket; wherein the detachable baffle has a multi-layer structure, the pressure control device is located at the top of the adsorption device, the filter is located at the bottom of the adsorption device, and a liquid distributor is provided between the top and each layer of the detachable baffle.

[0012] The liquid storage device is equipped with a liquid level monitoring device, an acetone leakage detection device, and a temperature and pressure control device.

[0013] The circulation control unit includes a liquid level detection device, an acetone purity detection device, a circulation pump, connecting pipes, and a circulation controller, which are used to connect to each device; the circulation controller can receive information from each device, display it, and centrally control the circulation pump to deliver the coagulated liquid.

[0014] In some embodiments, the coagulation bath is made of one of polytetrafluoroethylene, 316 stainless steel, 316L stainless steel or 904 stainless steel, preferably 904 stainless steel.

[0015] In some embodiments, the temperature control jacket has a temperature control range of 0-50 °C.

[0016] In some embodiments, the pressure control device has a control range of 10-300 kPa.

[0017] In some embodiments, the temperature control device has a temperature control range of 20±2℃.

[0018] In some embodiments, the acetone purification capacity is 0-100 L / h and the purity is controlled to be greater than 97%.

[0019] In some embodiments, the circulating pump needs to be resistant to acetone and chlorosulfonic acid, and is one or more of a peristaltic pump, diaphragm pump, or magnetic pump.

[0020] In some embodiments, the liquid level detection device is used for detecting the liquid level in the coagulation bath, where the liquid level change is less than 5 mm.

[0021] In some embodiments, the loop controller has a universal data interface that can be used for integrated control and system upgrades.

[0022] This invention also provides a method for online recovery of acetone solution used in the coagulation bath of carbon nanotube composite fibers, employing the online recovery system described above, the method comprising the following steps:

[0023] (1) Acetone pumping: Acetone is pumped from the storage device into the coagulation bath to the specified level under the control of the control system.

[0024] (2) Acetone pumping out: Under the control of the control system, the circulating pump is used to steadily pump the coagulated liquid out from the bottom of the coagulation bath and inject it into the acetone purification device.

[0025] (3) Acetone purification: The coagulated bath liquid comes into full contact with the adsorbent through the liquid distributor, and the clean acetone is pumped out from the bottom of the purification device.

[0026] (4) Acetone reflux: After purification, the acetone flows through the acetone purity detection device and then refluxes back into the coagulation bath. The control system replenishes acetone from the acetone storage device through the liquid level detection and flow detection devices to maintain a stable liquid level.

[0027] The carbon nanotube composite fiber bundles described in this invention have a diameter of 30~400 μm, a tensile breaking strength of 1~8 GPa, a tensile modulus of 50~600 GPa, a breaking elongation of 1~10%, and a thermal conductivity of 50-700 W / mK.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The online recovery system and method for carbon nanotube composite fiber coagulation bath solution provided by this invention can realize the steady-state and continuous preparation of high-performance uniform carbon nanotubes and their composite fibers. Through the systematic design of technologies such as steady-state laminar flowout, coupling of adsorption, neutralization and hybridization reactions, and systematic steady-state recovery, the problems of rapid coagulation bath failure and poor fiber uniformity during carbon nanotube fiber spinning are solved. In addition, by reserving a standardized data interface, it is conducive to the introduction of intelligent systems, providing a potential solution for intelligent and high-throughput preparation.

[0030] (2) The online recovery system and method for the coagulation bath solution of carbon nanotube composite fibers provided by this invention produce carbon nanotube composite fibers with strong uniformity, high density, high orientation, and excellent mechanical and thermal properties. By controlling the stability of the chemical potential and flow state in the micro-region of fiber emergence, the stability of the bidirectional permeation process of solvent and coagulation liquid in the coagulation bath is greatly optimized. This not only helps to reduce the disturbance of fiber orientation and densification behavior caused by the interference of mass transfer and solidification process in the micro-region of fiber emergence, but also reduces the deformation and structural defects of carbon nanotube fibers, thus realizing the preparation of fibers with high strength, high toughness, high thermal conductivity and high electrical conductivity.

[0031] (3) The online recovery system and method for carbon nanotube composite fiber coagulation bath solution provided by the present invention are low in cost, simple in process, and easy to realize industrial production. The present invention proposes relevant technical solutions based on standardized and mature industrial technology, and realizes the batch preparation of carbon nanotubes and their composite fibers with high stability and high yield. This not only greatly reduces the preparation cost of existing carbon nanotube fibers, but also facilitates their subsequent industrial transformation and production. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the acetone recovery system for carbon nanotube composite fiber bundles as shown in an embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram of the coagulation bath inlet structure shown in an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the coagulation bath outlet structure shown in an embodiment of the present invention;

[0035] in:

[0036] 1-1-Inlet to the coagulation bath;

[0037] 1-2-Coagulation bath;

[0038] 1-3-Condensation bath outlet;

[0039] 1,4-acetone storage device;

[0040] 1-5-Flow valve;

[0041] 1-6- Metering pump;

[0042] 1-7-Purification device;

[0043] 1-8-Cycle Control Device;

[0044] 1-9-Circulation pump;

[0045] 2-1-Flow stabilizer;

[0046] 2-2-Flange interface;

[0047] 3-1 filter hole;

[0048] 3-2-Flow stabilizer;

[0049] 3-3-Flange interface. Detailed Implementation

[0050] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the claims of this application.

[0051] One embodiment of the present invention provides a design scheme for an acetone recovery system of carbon nanotube composite fiber bundles, such as... Figure 1 As shown in the figure. The following describes this embodiment in further detail with reference to the examples:

[0052] Example 1

[0053] (1) The treated carbon nanotubes and chlorosulfonic acid were mixed to obtain a spinning solution of 0.6 wt%.

[0054] (2) The above spinning solution is extruded into a coagulation bath 1-2 containing acetone. The extrusion speed is 0.75 mL / h and the draw ratio is 1.5 to complete the double diffusion process of solvent and non-solvent. Chlorosulfonic acid and acetone partially react. At this time, the temperature of the coagulation bath jacket is 10.2℃ and the temperature of acetone is 10.9℃. The coagulation bath is made of 904 stainless steel.

[0055] (3) The coagulation bath is drawn out from the bottom outlet 1-3 at the rear end of the coagulation bath tank 1-2 using the circulation pump 1-9. The bath liquid is filtered through the filter hole 3-1 and stabilized by the flow stabilizer plate 3-2. The outlet is equipped with a flange interface 3-3 for easy connection to the pipeline. After the acetone is drawn out, it is pumped into the upper port of the acetone purification device 1-7 at a flow rate of 2 L / h. The fluid is evenly distributed by the distributor and fully contacts the ion exchange resin adsorption material to remove residual chlorosulfonic acid, water and reaction products. The temperature jacket temperature is controlled at 20℃ and the pressure is 130kPa. Then the purified acetone is pumped out from the lower port, flows through the flow control valve 1-5 and the acetone circulation monitoring and control device 1-8 and is pumped back into the coagulation bath tank. The acetone purity is 99.5%. The pipeline is made of PTFE material and the circulation pump is a diaphragm pump.

[0056] (4) Use the acetone circulation monitoring and control device to control the circulation speed of the coagulation bath and keep the liquid level of the coagulation bath at 110 mm. At this time, the maximum fluctuation of the liquid level of the coagulation bath is 2 mm. The acetone is pumped from the acetone storage device 1-4 through the flow control valve 1-5 and the acetone circulation monitoring and control device 1-8 into the coagulation bath through the acetone inlet 1-1. The total flow rate is 2.4 L / h. The inlet is equipped with a flow stabilizer 2-1 to stabilize the fluid and is equipped with a flange interface 2-2 for easy pipeline connection.

[0057] Example 2

[0058] Spinning was performed with a spinning solution concentration of 0.9 wt%, an extrusion speed of 0.75 mL / h, and a draw ratio of 1.4. At this time, the coagulation bath liquid level was 108 mm, the maximum liquid level fluctuation was 3 mm, the acetone purity was 99.1%, the acetone pump outflow rate was 4 L / h, the pump return flow rate was 4.5 L / h, the coagulation bath jacket temperature was 10.1℃, the acetone temperature was 11.2℃, the temperature control jacket temperature was 21℃, and the pressure was 135 kPa.

[0059] Example 3

[0060] Spinning was performed with a spinning solution concentration of 1.3 wt%, an extrusion speed of 0.70 mL / h, and a draw ratio of 1.3. At this time, the coagulation bath liquid level was 114 mm, the maximum liquid level fluctuation was 4 mm, the acetone purity was 98.4%, the acetone pump outflow rate was 6 L / h, the pump return flow rate was 6.5 L / h, the coagulation bath jacket temperature was 10.0℃, the acetone temperature was 10.8℃, the temperature control jacket temperature was 20℃, and the pressure was 150 kPa.

[0061] Table 1. Coagulation bath circulation in Examples 1-3

[0062] Example spinning solution concentration Extrusion speed Stretch ratio coagulation bath temperature Coagulation bath level Acetone purity Pumping speed Pump return speed 1 0.6 wt% 0.75 mL / h 1.5 10.9 11.0 cm 99.5% 2 L / h 2.5 L / h 2 0.9 wt% 0.75 mL / h 1.4 11.2 10.8 cm 99.1% 4 L / h 4.5 L / h 3 1.3 wt% 0.70 mL / h 1.3 10.8 11.4 cm 98.4% 6 L / h 6.5 L / h

[0063] In summary, this invention proposes a technical solution combining flow stabilization and separation to address the problem of efficient and stable online recovery of acetone solution from carbon nanotube composite fiber coagulation baths. To address the difficulty in coordinating the separation efficiency of various components, a structure with a top inlet for flow stabilization, a bottom plate for auxiliary flow, and a bottom outlet for filtration is designed. By creating a gentle laminar flow at the bottom of the coagulation bath, the reaction products are separated and discharged with low disturbance under gravity assistance. To address the challenge of steady-state control of coagulation bath components, an acetone purification system and online circulation method are designed, effectively solving problems related to acetone purification, level control, and impurity separation. In particular, regarding the coordinated control of the circulation system, this invention, based on existing industrial technology, utilizes a unified communication protocol framework to achieve overall coordinated control of coagulation bath reagent reaction, separation, long- and short-range order, and fluid parameters, improving circulation control efficiency and process stability. The technical solution provided by this invention is of great significance for solving the problem of acetone failure and high-efficiency recovery from coagulation baths.

[0064] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions conceived without creative effort should be included within the scope of protection of the present invention.

Claims

1. An online recovery system for acetone solution from a carbon nanotube composite fiber coagulation bath, characterized in that: include: Acetone coagulation bath, coagulation bath tank, adsorption device, storage device and circulation control unit; The coagulation bath is a rectangular stainless steel structure, including a cover plate, a tank body, an acetone outlet, an acetone inlet, and an observation window; the tank body is equipped with a temperature control jacket with a volume ratio of 15-30%, and the bottom of the tank body has an inclination angle of 1°-3° and is equipped with a V-shaped flow stabilizer. The current stabilizer plate has evenly distributed circular holes with an area ratio of 30-60% and a diameter of 0.5-2 mm. The acetone inlet is a grid structure located at the upper front end of the tank, and is equipped with a V-shaped flow stabilizer. The acetone outlet is a porous flow collection structure located at the bottom rear end of the tank, and is equipped with a combined filter. The filter is composed of a ceramic carrier and an adsorbent. The ceramic carrier has pores with a porosity of 60-80% and an open porosity greater than 99.9% evenly distributed within it, with an average pore size of 80-120 μm. The adsorbent is one or more of silica gel, activated carbon, or a polymer. The adsorption device consists of a detachable baffle, a pressure control device, a liquid distributor, a filter, and an outer temperature control jacket. The removable baffle has a multi-layer structure, the pressure control device is located at the top of the adsorption device, the filter is located at the bottom of the adsorption device, and a liquid distributor is provided between the top and each layer of the removable baffle. The liquid storage device is equipped with a liquid level monitoring device, an acetone leakage detection device, and a temperature and pressure control device. The circulation control unit includes a liquid level detection device, an acetone purity detection device, a circulation pump, connecting pipes, and a circulation controller, which are used to connect to each device; the circulation controller can receive information from each device, display it, and centrally control the circulation pump to deliver the coagulated liquid.

2. The online recycling system according to claim 1, characterized in that: The coagulation bath is made of one of the following materials: polytetrafluoroethylene, 316 stainless steel, 316L stainless steel, or 904 stainless steel.

3. The online recycling system according to claim 1, characterized in that: The temperature control jacket has a temperature control range of 0-50 ℃.

4. The online recycling system according to claim 1, characterized in that: The pressure control device has a control range of 10-300 kPa.

5. The online recycling system according to claim 1, characterized in that: The temperature control device has a temperature control range of 20±2℃.

6. The online recycling system according to claim 1, characterized in that: The acetone purification capacity is 0-100 L / h, and the purity is controlled to be greater than 97%.

7. The online recycling system according to claim 1, characterized in that: The circulating pump must be resistant to acetone and chlorosulfonic acid, and is one or more of the following: peristaltic pump, diaphragm pump, or magnetic pump.

8. The online recycling system according to claim 1, characterized in that: The liquid level detection device is used for detecting the liquid level in the coagulation bath, and the liquid level change range is less than 5 mm.

9. The online recycling system according to claim 1, characterized in that: The loop controller has a universal data interface, which can be used for integrated control and system upgrades.

10. A method for online recovery of acetone solution used in a coagulation bath for carbon nanotube composite fibers, characterized in that: The method using the online recycling system as described in any one of claims 1-9 includes the following steps: (1) Acetone pumping: Acetone is pumped from the storage device into the coagulation bath to the specified level under the control of the control system. (2) Acetone pumping out: Under the control of the control system, the circulating pump is used to steadily pump the coagulated liquid out from the bottom of the coagulation bath and inject it into the acetone purification device. (3) Acetone purification: The coagulated bath liquid comes into full contact with the adsorbent through the liquid distributor, and the clean acetone is pumped out from the bottom of the purification device. (4) Acetone reflux: After purification, the acetone flows through the acetone purity detection device and then refluxes back into the coagulation bath. The control system replenishes acetone from the acetone storage device through the liquid level detection and flow detection devices to maintain a stable liquid level.

Images