Efficient Purification Method of Carbon Nanotubes Based on Electromagnetic Heating and Waste Heat Recovery

Abstract

The present application discloses a method and device for efficient purification of carbon nanotubes based on electromagnetic heating and waste heat recovery. The method includes: collecting high-temperature waste liquid in a first reaction kettle, and using a heat exchanger for waste heat recovery to heat fresh acid liquid in the heating pipeline of the next-stage reaction kettle in combination with electromagnetic heating; pickling the raw materials with the acid liquid recovered by waste heat in the next-stage reaction kettle, and repeating the processes of waste heat recovery, heating and pickling until the raw materials are finally pickled by the last-stage reaction kettle to obtain purified carbon nanotubes; collecting multiple groups of pickling data, and constructing carbon nanotube purity curves and energy efficiency curves with different pickling times to optimize the number of reaction kettles set. Through the solution of the present application, secondary utilization of heat sources can be carried out, the number of reaction kettles can be optimized, energy waste can be reduced, and costs can be saved.

Description

Technical Field

[0001] This application relates to the field of carbon nanotube purification, and particularly to an efficient carbon nanotube purification method and device based on electromagnetic heating and waste heat recovery. Background Art

[0002] Carbon nanotubes exhibit great application potential in multiple fields due to their unique physical and chemical properties. However, impurities such as metal catalysts and amorphous carbon are inevitably introduced during their production process, which seriously affect the performance and applications of carbon nanotubes. Therefore, acid pickling purification of carbon nanotubes has become a crucial research topic. Acid pickling purification can not only effectively remove the residual metal catalysts and amorphous carbon in carbon nanotubes, but also improve the dispersibility and functionalization degree of carbon nanotubes, thus significantly enhancing their application effects in composite materials, electronic devices, energy storage and other fields. The importance of acid pickling purification lies in that it is a key step to obtain high-purity and high-quality carbon nanotubes, directly affecting the performance and reliability of subsequent applications.

[0003] Currently, the acid pickling purification of carbon nanotubes mainly adopts wet acid pickling technology. Its working principle is to use strong acids (such as sulfuric acid, nitric acid or their mixtures) to treat carbon nanotubes under high-temperature conditions, and dissolve metal catalysts and remove amorphous carbon through the oxidation of acids. However, this traditional acid pickling method has some significant problems: First, the acid pickling process takes a long time, usually several hours or even several days; Second, the operation under high-temperature and high-pressure conditions has safety hazards; Third, the use of a large amount of strong acids not only causes environmental pollution, but also increases production costs; Finally, the acid pickling process may cause a certain degree of damage to the carbon nanotube structure, affecting its inherent properties.

[0004] To solve the above problems, researchers have disclosed various improvement methods. For example, ultrasonic-assisted acid pickling can accelerate the reaction process and shorten the treatment time; microwave-assisted acid pickling can achieve rapid and uniform heating, improving the purification efficiency; electrochemical acid pickling enhances the oxidation ability of acids by applying an electric field, reducing the amount of acid used and the reaction temperature. However, these methods still have some defects. First, most of these methods only focus on the optimization of a single reaction kettle and fail to fully utilize the advantages of multi-stage reactions; Second, they often ignore the problem of energy utilization efficiency, especially the heat recovery and utilization in continuous production processes; Third, these methods require the introduction of additional equipment or energy input during implementation, increasing the complexity and cost of the process.

[0005] Therefore, there is an urgent need for a technical solution that can reuse heat sources, optimize the number of reaction kettles, reduce energy waste and save costs. Summary of the Invention

[0006] To address the deficiencies of the prior art, the embodiments of the present application provide a method and device for efficient purification of carbon nanotubes based on electromagnetic heating and waste heat recovery. The present application solves the technical problems such as energy waste caused by the heat source in the waste liquid discharged in the prior art.

[0007] The embodiments of the present application provide a method for efficient purification of carbon nanotubes based on electromagnetic heating and waste heat recovery, including: setting at least two reaction vessels for pickling, the reaction vessels being provided with a feed port, a discharge port, a liquid discharge port, a stirring device and / or a temperature sensor; configuring an independent electromagnetic heating pipeline for each reaction vessel, the electromagnetic heating pipeline being used for heating and transporting acid solution; adding carbon nanotube raw materials into the first reaction vessel, and heating the acid solution by using the electromagnetic heating pipeline to pickle the raw materials; collecting the high-temperature waste liquid in the first reaction vessel, and recovering waste heat by using a heat exchanger to heat the fresh acid solution in the heating pipeline of the next-stage reaction vessel in combination with electromagnetic heating; pickling the raw materials with the acid solution recovered from waste heat in the next-stage reaction vessel, and repeating the processes of waste heat recovery, heating and pickling until the raw materials are finally pickled through the last-stage reaction vessel to obtain purified carbon nanotubes; collecting multiple groups of pickling data, and constructing carbon nanotube purity curves and energy efficiency curves for different pickling times to optimize the number of reaction vessels set.

[0008] In one possible implementation, configuring an independent electromagnetic heating pipeline for each reaction vessel, the electromagnetic heating pipeline being used for heating and transporting acid solution, includes: configuring an electromagnetic heating pipeline system, including an electromagnetic heater, a stainless steel coil, a PTFE lining, a heat insulation layer, a temperature sensor and a flowmeter, wherein the electromagnetic heater uses high-frequency electromagnetic induction heating; setting the inner diameter of the stainless steel coil to 20 mm and the wall thickness to 2 mm, and coiling it into a spiral shape, coating a 1-mm-thick PTFE layer on the inner wall of the stainless steel pipe, and wrapping a 50-mm-thick glass wool heat insulation layer outside the coil; installing a temperature sensor at each of the inlet and outlet of the coil, and installing an electromagnetic flowmeter at the inlet of the coil; controlling the outlet temperature of the acid solution to be stable within a set range by adjusting the flow rate and heating power.

[0009] In one possible implementation, carbon nanotube raw materials are added to the first reaction kettle, and an electromagnetic heating pipe is used to heat the acid solution to pickle the raw materials, including: mixing the acid solution components in a pre-selected acid solution formula according to a predetermined volume ratio to prepare an acid solution, and heating it to a predetermined temperature through an electromagnetic heating pipe system; slowly adding the pre-weighed dry carbon nanotube raw materials to the acid solution heated to the predetermined temperature, and stirring at a predetermined rotation speed; continuously carrying out the pickling reaction at the predetermined temperature for a predetermined time, and intermittently sampling to detect the change of impurity content; stopping heating and stirring, and after the reaction mixture naturally cools to the predetermined temperature, carrying out solid-liquid separation on it through a centrifuge; repeatedly washing the separated carbon nanotubes with deionized water until the pH value of the washing liquid reaches a predetermined range; vacuum-drying the washed carbon nanotubes at a predetermined temperature for a predetermined time.

[0010] In one possible implementation, the high-temperature waste liquid in the first reaction kettle is collected, and a heat exchanger is used for waste heat recovery to heat the fresh acid solution in the heating pipe of the next-stage reaction kettle in combination with electromagnetic heating, including: discharging and collecting the high-temperature waste liquid after pickling in the first reaction kettle into a heat preservation tank with a preset capacity; setting a heat exchanger with a target material, a predetermined heat exchange area and a heat transfer coefficient in the heating system of the next-stage reaction kettle; using a corrosion-resistant pump to transport the waste liquid from the heat preservation tank to the heat exchanger at a preset flow rate to carry out heat exchange with the low-temperature fresh acid solution entering the next-stage reaction kettle, so that the waste liquid cools down and the fresh acid solution warms up; further heating the preheated fresh acid solution to the target temperature through the heating pipe system, and transporting the waste liquid after heat exchange to the waste liquid treatment system for neutralization treatment.

[0011] In one possible implementation, the raw materials are pickled with the acid solution recovered by waste heat in the next-stage reaction kettle, and the processes of waste heat recovery, heating and pickling are repeated until the raw materials are finally pickled by the last-stage reaction kettle to obtain purified carbon nanotubes, including: transferring the carbon nanotubes after primary pickling to the next-stage reaction kettle, and adding the newly prepared acid solution after waste heat recovery and electromagnetic heating for secondary pickling; repeating pickling, waste heat recovery and electromagnetic heating of the waste liquid until the product is transferred to the last-stage reaction kettle, and carrying out final pickling with a low-concentration acid solution; rinsing the carbon nanotubes with deionized water until the pH value is neutral, grinding the dried carbon nanotubes with a ball mill, and screening with a sieve with a preset mesh number to remove large-particle impurities to obtain purified carbon nanotubes.

[0012] In one possible implementation, multiple groups of pickling data are collected, and purity curves and energy efficiency curves of carbon nanotubes with different pickling times are constructed to optimize the set number of reactors, including: collecting multiple groups of carbon nanotube samples, and performing pickling treatments on each group of samples with different numbers of times, where the number of pickling times varies within a preset range; measuring the purity of carbon nanotubes, treatment quality, actual energy consumption, and waste heat recovery amount of the samples after each pickling, and recording the pickling operation parameters; using the non-linear regression method to fit the parameters of the purity prediction model, and plotting the curve of the purity of carbon nanotubes versus the number of pickling times; calculating the energy utilization efficiency of each group of experiments, and plotting the curve of energy efficiency versus the number of pickling times; constructing a comprehensive performance index, combining the purity improvement function and the energy efficiency function, and setting weight coefficients to determine the relative importance of purity and energy efficiency; calculating the corresponding comprehensive performance index values for each pickling time within the preset range; checking whether the purity requirements and the minimum energy efficiency constraint are met; among the pickling times that meet the constraint conditions, selecting the value that maximizes the comprehensive performance index as the optimal pickling time and the target configuration number of the reactor.

[0013] In one possible implementation, constructing a comprehensive performance index, combining the purity improvement function and the energy efficiency function, and setting weight coefficients to determine the relative importance of purity and energy efficiency, includes: where J(n) represents the comprehensive performance index of the pickling time n, w1 and w2 represent the weight coefficients, f(P(n)) represents the purity improvement function, g(η(n)) represents the energy efficiency function, P(n) represents the purity of the pickling time n, P initial represents the initial purity, P0 represents the theoretical maximum purity, η(n) represents the energy efficiency of the pickling time n, and η max represents the maximum energy efficiency observed in the experiment.

[0014] The embodiment of the present application also provides a high-efficiency purification device for carbon nanotubes based on electromagnetic heating and waste heat recovery, which is used to implement the high-efficiency purification method of carbon nanotubes as described in any one of the above embodiments, and is characterized in that it includes: at least two reactors, one or more electromagnetic heating pipes, and a heat exchanger; wherein, the reactor is provided with a feed port, a discharge port, a drain port, a stirring device, and / or a temperature sensor; each reactor is configured with an independent electromagnetic heating pipe; the electromagnetic heating pipe is used for heating and transporting the acid solution; the heat exchanger is used for waste heat recovery to heat the fresh acid solution in the heating pipe of the target reactor.

[0015] In a high - efficiency purification method and device for carbon nanotubes based on electromagnetic heating and waste heat recovery provided above, in the embodiments of the present application, by setting multiple reaction kettles and using electromagnetic heating technology, the efficient progress of the pickling process is realized. The application of electromagnetic heating technology not only improves the heating efficiency but also realizes the precise control of the reaction temperature, which is beneficial to improving the consistency of product quality. Secondly, through the waste heat recovery system, the heat energy in the waste liquid is fully utilized, improving the energy utilization efficiency and significantly reducing the energy consumption and production cost. Further, in some embodiments, by combining purity and energy efficiency ratio, the number of reaction kettles can be optimized to balance energy consumption and product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] To more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following - described drawings are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0017] Figure 1 It is a schematic flowchart of a high - efficiency purification method for carbon nanotubes based on electromagnetic heating and waste heat recovery provided by the embodiments of the present application;

[0018] Figure 2 It is a schematic diagram of a purity curve provided by the embodiments of the present application;

[0019] Figure 3 It is a schematic diagram of an energy efficiency curve provided by the embodiments of the present application;

[0020] Figure 4 It is a schematic block diagram of a high - efficiency purification device for carbon nanotubes based on electromagnetic heating and waste heat recovery provided by the embodiments of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Now, various exemplary embodiments of the present application will be described in detail with reference to the drawings. It should be noted that: unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application.

[0022] Those skilled in the art can understand that terms such as "first" and "second" in the embodiments of the present application are only used to distinguish different steps, devices or modules, etc., and neither represent any specific technical meaning nor indicate an inevitable logical order between them. It should also be understood that in the embodiments of the present application, "a plurality of" may refer to two or more, and "at least one" may refer to one, two or more. It should also be understood that for any component, data or structure mentioned in the embodiments of the present application, in the absence of a clear limitation or contrary indication in the context, it can generally be understood as one or more. In addition, the term "and / or" in the present application is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in the present application generally represents an "or" relationship between the associated objects before and after. It should also be understood that the present application emphasizes the differences between various embodiments in the description of each embodiment. Their similarities or similarities can be referred to each other. For the sake of brevity, they will not be elaborated one by one.

[0023] At the same time, it should be understood that for the convenience of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationship. The following description of at least one exemplary embodiment is actually only illustrative and in no way a limitation on the present application and its application or use. Technologies, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the said technologies, methods and devices should be regarded as part of the specification. It should be noted that like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, further discussion thereof is not required in subsequent drawings.

[0024] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0025] Figure 1 It is a schematic flow chart of a high-efficiency purification method of carbon nanotubes based on electromagnetic heating and waste heat recovery provided for the embodiments of the present application. This method aims to solve the problems of energy waste and high cost in the existing carbon nanotube purification process. Through the process design and equipment configuration combining electromagnetic heating and waste heat recovery, high efficiency and low energy consumption in the carbon nanotube purification process are achieved.

[0026] First, it needs to be understood that carbon nanotubes are a type of nanomaterial with a unique structure and excellent properties, and their purification process is crucial for improving the material quality and performance. Pickling purification is a key step in the production of carbon nanotubes, aiming to remove impurities and impure substances on the surface of carbon nanotubes, thereby improving their purity and performance. Traditional pickling purification methods are usually carried out in a heating environment, such as carrying out the pickling reaction at a temperature of about 70°C. However, this method has the problem of low energy utilization efficiency because the temperature of the discharged waste liquid usually still remains at about 50°C, and this part of the thermal energy is not fully utilized, resulting in energy waste and an increase in production costs.

[0027] The technical solution disclosed in this application aims at the above problems and designs an efficient purification method for carbon nanotubes based on electromagnetic heating and waste heat recovery. The core idea of this method is to improve energy utilization efficiency by setting up multiple reaction kettles and utilizing the waste heat of the waste liquid. Specifically, this method includes but is not limited to the following key steps.

[0028] As Figure 1 shown, at step S101, at least two reaction kettles for pickling are set up, and the reaction kettles are provided with a feed port, a discharge port, a liquid discharge port, a stirring device and / or a temperature sensor. These reaction kettles are the main containers for carbon nanotube pickling purification. Each reaction kettle is provided with a feed port, a discharge port, a stirring device and / or a temperature sensor, and a liquid discharge port is provided at the bottom. The feed port is used to add carbon nanotube raw materials and acid solution into the reaction kettle; the discharge port is used to take out the purified carbon nanotubes; the stirring device is used to ensure sufficient and uniform reaction during pickling; the temperature sensor is used to monitor the reaction temperature in real time; and the liquid discharge port is used to discharge the waste liquid after the reaction. This design ensures the efficient progress and precise control of the pickling process.

[0029] Before obtaining the target configuration quantity, the method for determining the number of reaction kettles may include: where N represents the required number of reaction kettles, C i represents the initial impurity concentration, C f represents the target final impurity concentration, k represents the reaction rate constant, t represents the reaction time of a single reaction kettle, T represents the reaction temperature, V represents the volume of the reaction kettle, represents the ceiling function.

[0030] The formula of the embodiment of this application is based on the first-order reaction kinetics, assuming that the impurity removal follows the exponential decay law. The impurity removal efficiency of each reaction kettle is related to the reaction time, temperature and volume. Specifically, C i : the initial impurity concentration, determined according to the purity of the raw material carbon nanotubes. For example, a purity of 95% corresponds to C i =50000mg / L. C f: Target impurity concentration, determined according to the product purity requirement. For example, for a purity of 99.9%, C f = 1000 mg / L. k: Reaction rate constant, depending on the type and concentration of the acid. For example, for 3M sulfuric acid, k ≈ 0.005 L / (mol·min·K). t: Reaction time of a single reactor, usually set to 120 - 180 minutes. T: Reaction temperature, generally in the range of 353 - 373 K. V: Reactor volume, for example, taking 500 L.

[0031] This formula is based on the principles of chemical kinetics, assuming that impurity removal follows first-order reaction kinetics. In each reactor, the impurity concentration decays exponentially with time. The log(1 + ktT / V) in the formula represents the impurity removal efficiency of a single reactor, where ktT / V represents the dimensionless reaction extent. By taking the logarithmic ratio log(C i / C f ), the total reaction extent required to achieve the target purity can be calculated. Dividing the total reaction extent by the efficiency of a single reactor gives the number of reactors required.

[0032] For example, based on the fitting parameters of the experimental data in Table 1 below (3M sulfuric acid, T = 363 K, V = 500 L), C i = 50000 mg / L, C f = 1000 mg / L, k = 0.005 L / (mol·min·K), t = 150 min, T = 363 K, V = 500 L.

[0033] Table 1 - 3M sulfuric acid

[0034]

[0035]

[0036] Therefore, in this case, 4 reactors are required to achieve the target purity.

[0037] In an implementation scenario, usually setting 2 - 3 reactors can meet most purification requirements. The purpose of setting multiple reactors is to perform multiple pickling operations to gradually improve the purity of carbon nanotubes. The determination of the specific number of reactors depends on the following factors: 1) The initial purity of the raw carbon nanotubes. The lower the purity, the more pickling times are required. 2) The purity requirement of the target product. The higher the requirement, the more pickling times are required. 3) The production scale. The larger the scale, the number of reactors can be considered to be increased to improve efficiency. 4) Economic considerations. The number of reactors needs to be balanced with the investment cost and operating cost.

[0038] Taking a typical medium-scale production line as an example, 3 reactors can be set up, which are respectively used for primary pickling, secondary pickling and final pickling. The volume of each reactor can be designed to be 500L, made of 316L stainless steel, and lined with polytetrafluoroethylene (PTFE) to resist acid corrosion. The top of the reactor is provided with a feed inlet, a discharge outlet, a stirring device and a temperature sensor. The bottom is provided with a liquid discharge port.

[0039] The reactor is used to carry out the pickling and purification reaction of carbon nanotubes. In an acidic environment and under heating conditions, the acid can dissolve or oxidize impurities such as metal catalyst residues and amorphous carbon on the surface of carbon nanotubes, thereby improving the purity of carbon nanotubes.

[0040] At step S102, an independent electromagnetic heating pipeline is configured for each reactor, and the electromagnetic heating pipeline is used to heat and transport the acid solution. The electromagnetic heating pipeline not only heats the acid solution, but also undertakes the function of transporting the acid solution. Compared with the traditional heating method, the electromagnetic heating technology has the advantages of fast heating speed, high energy conversion efficiency, accurate temperature control, etc. By applying the electromagnetic heating technology in the pipeline, the acid solution can be heated to the required temperature before entering the reactor, thereby improving the reaction efficiency and energy utilization rate.

[0041] Specifically, it includes: configuring an electromagnetic heating pipeline system, including an electromagnetic heater, a stainless steel coil, a PTFE lining, a heat insulation layer, a temperature sensor and a flowmeter, wherein the electromagnetic heater uses high-frequency electromagnetic induction heating; setting the inner diameter of the stainless steel coil to 20mm, the wall thickness to 2mm, and coiling it into a spiral shape, coating a 1mm-thick PTFE layer on the inner wall of the stainless steel pipe, and wrapping a 50mm-thick glass wool heat insulation layer outside the coil; installing a temperature sensor at each of the inlet and outlet of the coil, and installing an electromagnetic flowmeter at the inlet of the coil; by adjusting the flow rate and heating power, controlling the outlet temperature of the acid solution to make it stable within the set range.

[0042] In one embodiment, the electromagnetic heating pipeline system can be composed of, but not limited to, the following parts: 1) Electromagnetic heater: adopting high-frequency electromagnetic induction heating technology, with adjustable power and a maximum power of 50kW. 2) Stainless steel coil: with an inner diameter of 20mm, a wall thickness of 2mm, a total length of about 30m, and coiled into a spiral shape. 3) PTFE lining: coating a 1mm-thick PTFE layer on the inner wall of the stainless steel pipe to prevent acid solution corrosion. 4) Heat insulation layer: wrapping a 50mm-thick glass wool heat insulation layer outside the coil to reduce heat loss. 5) Temperature sensor: installing a PT100 temperature sensor at each of the inlet and outlet of the coil. 6) Flowmeter: installing an electromagnetic flowmeter at the inlet of the coil to measure the flow rate of the acid solution.

[0043] The working principle of the electromagnetic heating pipeline is to utilize the high-frequency alternating magnetic field to generate eddy currents in the metal pipe wall. The eddy currents generate Joule heat to directly heat the pipe wall, and then heat the acid solution in the pipe through heat conduction. This heating method has the advantages of fast heating, precise temperature control, and low energy consumption.

[0044] The flow of the acid solution in the pipeline can precisely control the outlet temperature of the acid solution by adjusting the flow rate and heating power, ensuring that the pickling reaction proceeds at the optimal temperature. Among them, controlling the outlet temperature of the acid solution by adjusting the flow rate and heating power includes: Q1 = v·A·(T out -T in )·ρ·c p , where Q1 represents the heating power without waste heat recovery, v represents the flow velocity, A represents the cross-sectional area of the pipeline, T out represents the outlet temperature, T in represents the inlet temperature, ρ represents the density of the acid solution, and c p represents the specific heat capacity of the acid solution.

[0045] At step S103, add the carbon nanotube raw material into the first reaction kettle, and use the electromagnetic heating pipeline to heat the acid solution to pickle the raw material. This step includes adding the carbon nanotube raw material into the first reaction kettle, heating the acid solution using the electromagnetic heating pipeline, and then transporting the heated acid solution into the reaction kettle to pickle the raw material. In this process, the role of the electromagnetic heating pipeline is fully exerted, ensuring that the acid solution reaches the optimal reaction temperature when entering the reaction kettle.

[0046] Specifically, it includes: mixing the acid solution components in the pre-selected acid solution formula according to the predetermined volume ratio to prepare the acid solution, heating it to the predetermined temperature through the electromagnetic heating pipeline system; slowly adding the pre-weighed dry carbon nanotube raw material into the acid solution heated to the predetermined temperature, and stirring at the predetermined rotation speed; continuously performing the pickling reaction at the predetermined temperature for the predetermined time, and intermittently sampling to detect the change in impurity content; stopping heating and stirring, and after the reaction mixture naturally cools to the predetermined temperature, performing solid-liquid separation on it through a centrifuge; repeatedly washing the separated carbon nanotubes with deionized water until the pH value of the washing solution reaches the predetermined range; vacuum drying the washed carbon nanotubes at the predetermined temperature for the predetermined time.

[0047] Taking the first pickling of the first reaction kettle as an example, the specific operation steps are as follows:

[0048] Prepare the acid solution: Select a suitable acid solution formula according to the type and impurity situation of the carbon nanotubes. Commonly used acid solutions include sulfuric acid, nitric acid, or a mixture of both. For example, a mixed solution of concentrated sulfuric acid (98%) and concentrated nitric acid (65%) with a volume ratio of 3:1 can be used. The total volume of the acid solution should be 80% of the effective volume of the reaction kettle, that is, 400L.

[0049] Preheat the acid solution: Heat the prepared acid solution to 70°C through an electromagnetic heating pipeline system. During the heating process, control the flow rate at 20 L / min. The power of the electromagnetic heater is initially set at 40 kW and then automatically adjusted according to the PID control algorithm.

[0050] Add carbon nanotubes: When the temperature of the acid solution stabilizes at 70°C, slowly add 50 kg of dry raw material carbon nanotubes. Keep stirring during the feeding process, and the stirring speed is 100 rpm.

[0051] Reaction process: Continuously react at 70°C for 4 hours. During the reaction process, maintain the temperature constant through the electromagnetic heating pipeline system. Take samples for detection every 30 minutes to monitor the change of impurity content.

[0052] End of reaction: Stop heating after 4 hours and turn off the stirring. Let the reaction mixture cool naturally to 50°C. It should be noted that the reason for first naturally cooling the reaction mixture to 50°C and then performing solid-liquid separation is that the strong acid solution at 70°C has high corrosiveness and volatility. Lowering the temperature can reduce the operation risk. The lower temperature can also reduce the thermal stress and corrosion on the centrifugal separation equipment. In addition, the decrease in temperature can help improve the efficiency of solid-liquid separation.

[0053] Separation: Perform solid-liquid separation on the reaction mixture through a centrifuge. The rotation speed of the centrifuge is set at 5000 rpm, and the centrifugation time is 30 minutes.

[0054] Washing: Wash the separated carbon nanotubes repeatedly with deionized water until the pH value of the washing liquid is close to neutral (pH 6 - 7).

[0055] Drying: Dry the washed carbon nanotubes in a vacuum drying oven at 60°C.

[0056] At step S104, collect the high-temperature waste liquid in the first reaction kettle and use a heat exchanger for waste heat recovery to heat the fresh acid solution in the heating pipeline of the next-stage reaction kettle in combination with electromagnetic heating. After the first reaction kettle completes pickling, collect the high-temperature waste liquid in it. Although this waste liquid can no longer be used for pickling, it still has a relatively high temperature and contains a large amount of thermal energy. In order to make full use of this part of thermal energy, the embodiment of the present application introduces a heat exchanger for waste heat recovery. Specifically, introduce the high-temperature waste liquid into the heat exchanger to preheat the fresh acid solution in the heating pipeline of the next-stage reaction kettle. This way of waste heat recovery not only reduces energy waste but also reduces the additional heating energy consumption required for the second pickling.

[0057] Specifically, the high-temperature waste liquid after pickling in the first reactor is discharged and collected into a heat-insulated tank with a preset capacity; a heat exchanger made of the target material, having a predetermined heat exchange area and heat transfer coefficient, is provided in the heating system of the next-stage reactor; a corrosion-resistant pump is used to transport the waste liquid from the heat-insulated tank to the heat exchanger at a preset flow rate for heat exchange with the low-temperature fresh acid liquid entering the next-stage reactor, so as to cool the waste liquid and heat up the fresh acid liquid; the preheated fresh acid liquid is further heated to the target temperature through a heating pipeline system, and the waste liquid that has completed heat exchange is transported to a waste liquid treatment system for neutralization treatment.

[0058] This step is the core point of the embodiment of the present application, and realizes the efficient utilization of energy through waste liquid waste heat recovery. The specific implementation scheme is as follows:

[0059] Waste liquid collection: After pickling is completed in the first reactor, the waste liquid at about 50 °C is discharged through the bottom drain port and collected in a 300L heat-insulated tank.

[0060] Heat exchanger design: A plate heat exchanger is added to the electromagnetic heating pipeline system of the second reactor. The heat exchanger is made of 316L stainless steel, and the heat exchange area is 10m 2 , and the heat transfer coefficient is 2000W / (m 2 ·K).

[0061] Waste liquid pumping: A corrosion-resistant magnetic drive pump is used to pump the waste liquid from the heat-insulated tank into the heat exchanger, and the flow rate is controlled at 15L / min.

[0062] Heat exchange process: The waste liquid exchanges heat with the fresh acid liquid about to enter the second reactor in the heat exchanger. The waste liquid is cooled from 50 °C to 30 °C, while the fresh acid liquid is preheated from 20 °C to 27 - 33 °C.

[0063] Temperature control: The fresh acid liquid after heat exchange is further heated to 70 °C through the electromagnetic heating pipeline system. Due to preheating, the required additional heating power will be reduced.

[0064] Waste liquid treatment: The waste liquid that has completed heat exchange is sent to a waste liquid treatment system for neutralization and treatment.

[0065] The heat transfer in the heat exchange process can be described by the following formula: Q = U * A * LMTD, where Q is the heat transfer amount (W), U is the total heat transfer coefficient (W / (m 2 ·K)), A is the heat exchange area (m 2), where LMTD is the log mean temperature difference (K). LMTD = ((T_h1 - T_c2) - (T_h2 - T_c1)) / ln((T_h1 - T_c2) / (T_h2 - T_c1)), where T_h1 and T_h2 are the inlet and outlet temperatures of the hot fluid (waste liquid), and T_c1 and T_c2 are the inlet and outlet temperatures of the cold fluid (fresh acid solution). Through this secondary utilization scheme of the heat source, the heating energy consumption required for the second pickling can be significantly reduced, and the energy efficiency of the entire purification process can be improved.

[0066] Therefore, the preheated fresh acid solution is further heated to the target temperature through the heating pipe system, including: Q2 = Q1 - U·B·LMTD, where Q2 represents the heating power after waste heat recovery, Q1 represents the heating power without waste heat recovery, U represents the overall heat transfer coefficient, B represents the heat transfer area, and LMTD represents the log mean temperature difference.

[0067] At step S105, the raw material is pickled with the acid solution recovered by waste heat in the next-stage reactor, and the processes of waste heat recovery, heating, and pickling are repeated until the raw material is finally pickled by the last-stage reactor to obtain purified carbon nanotubes. This step makes full use of the waste heat of the waste liquid from the first pickling, improves the energy utilization efficiency, and ensures the reaction temperature of the secondary pickling. It should be noted that this process of waste heat recovery and pickling can be repeated multiple times as needed until the raw material is finally pickled by the last-stage reactor to obtain a high-purity carbon nanotube product.

[0068] It includes: transferring the carbon nanotubes after the initial pickling to the next-stage reactor, adding the newly prepared acid solution recovered by waste heat for secondary pickling; repeating the pickling and waste heat recovery of the waste liquid until the product is transferred to the last-stage reactor and finally pickled with a low-concentration acid solution; rinsing the carbon nanotubes with deionized water until the pH value is neutral, grinding the dried carbon nanotubes with a ball mill, and screening with a sieve of a preset mesh number to remove large-particle impurities to obtain purified carbon nanotubes.

[0069] In an implementation scenario, the carbon nanotubes after the first pickling are transferred to the second reactor, and a newly prepared acid solution (the acid solution concentration can be adjusted according to the results of the first pickling) is added. The pickling process in the third step is repeated, but the reaction time can be shortened to 3 hours.

[0070] If necessary, the last pickling can be carried out in the third reactor. This time, a milder acid solution, such as 1M hydrochloric acid, can be used, and the reaction time is 2 hours.

[0071] After the last pickling, the carbon nanotubes are rinsed with a large amount of deionized water until the pH value is close to 7. A pH meter can be used to monitor the pH value of the washing solution in real time.

[0072] If further improvement in the dispersion of carbon nanotubes or an increase in specific functional groups is needed, functionalization can be carried out at this stage. For example, the carbon nanotubes can be treated with H2O2 solution at 60 °C for 2 hours to introduce hydroxyl and carboxyl groups.

[0073] The treated carbon nanotubes are dried in a vacuum drying oven at 80 °C for 24 hours to ensure complete drying.

[0074] The dried carbon nanotubes are slightly ground using a ball mill to break up the agglomerates. Ball milling parameters: ball-to-material ratio of 10:1, rotation speed of 200 rpm, and time of 30 minutes. Screening is carried out using a 100-mesh sieve to remove any large particle impurities that may be present. The final product is packed into an anti-static and moisture-proof aluminum foil bag and sealed under vacuum for storage.

[0075] At step S106, multiple sets of pickling data are collected, and based on the carbon nanotube purity curves and energy efficiency curves for different pickling times, the target configuration quantity of the reaction kettle is determined. This includes: collecting multiple sets of carbon nanotube samples and performing pickling treatments with different numbers of times on each set of samples, where the number of pickling times varies within a preset range; measuring the carbon nanotube purity, treatment quality, actual energy consumption, and waste heat recovery amount for each sample after pickling, and recording the pickling operation parameters; fitting the purity prediction model parameters using the non-linear regression method and plotting the curve of carbon nanotube purity versus the number of pickling times; calculating the energy utilization efficiency for each set of experiments and plotting the curve of energy efficiency versus the number of pickling times; constructing a comprehensive performance index by combining the purity improvement function and the energy efficiency function, and setting weight coefficients to determine the relative importance of purity and energy efficiency; calculating the corresponding comprehensive performance index values for each pickling time within the preset range; checking whether the purity requirements and the minimum energy efficiency constraint are met; and among the pickling times that meet the constraint conditions, selecting the value that maximizes the comprehensive performance index as the optimal pickling time and the target configuration quantity of the reaction kettle.

[0076] Furthermore, constructing a comprehensive performance index by combining the purity improvement function and the energy efficiency function, and setting weight coefficients to determine the relative importance of purity and energy efficiency, includes: Where J(n) represents the comprehensive performance index for pickling times n, w1 and w2 represent the weight coefficients, f(P(n)) represents the purity improvement function, g(η(n)) represents the energy efficiency function, P(n) represents the purity for pickling times n, P initial represents the initial purity, P0 represents the theoretical maximum purity, η(n) represents the energy efficiency for pickling times n, η max represents the maximum energy efficiency observed in the experiment.

[0077] Specifically, to determine the optimal configuration quantity of the reactor (i.e., the optimal pickling times), it is necessary to collect multiple sets of pickling data and plot the carbon nanotube purity curve and energy efficiency curve based on these data. The specific steps are as follows: Prepare multiple batches of carbon nanotube samples, and perform pickling treatments on each batch with different numbers of times, which can range from 1 to 6 times. After each pickling, measure the following parameters: carbon nanotube purity (P), mass of carbon nanotubes processed (m), total energy actually consumed (E_total), energy saved through waste heat recovery (E_recovered), and record the operating parameters of each pickling, such as acid concentration, temperature, time, etc. Repeat the experiment multiple times to ensure the reliability and consistency of the data, and remove outliers and extreme values.

[0078] The purity prediction model as shown below (as Figure 2 shown) can be used to analyze the purity data: P_final = P_0 - (P_0 - P_initial) * e^(-k * n), where P_final: final purity (%), P_0: theoretical maximum purity (%), P_initial: initial purity (%), k: purification efficiency coefficient for each pickling, n: pickling times.

[0079] Using the experimental data, determine the best - fit values of the parameters P_0 and k through non - linear regression method. Using the determined parameters, plot the curve of purity varying with pickling times.

[0080] Then the energy efficiency formula as shown below (as Figure 3 shown) can be used to analyze the energy efficiency data: η = (m * ΔH) / (E_total - E_recovered), where η: energy utilization efficiency, m: mass of carbon nanotubes processed (kg), ΔH: theoretical energy required for purifying per unit mass of carbon nanotubes (kJ / kg), E_total: total energy actually consumed (kJ), E_recovered: energy saved through waste heat recovery (kJ).

[0081] Calculate the energy utilization efficiency η for each set of experimental data. Plot the curve of energy utilization efficiency η varying with pickling times.

[0082] To determine the optimal pickling times, two factors, namely purity improvement and energy efficiency, need to be considered. A comprehensive optimization model can be constructed to combine these two factors. By defining a comprehensive performance index J, which is expressed as a function of purity improvement and energy efficiency: J(n) = w_1 * f(P(n)) + w_2 * g(η(n)), where: J(n) is the comprehensive performance index, n is the pickling times, w_1 and w_2 are weight coefficients reflecting the relative importance of purity and energy efficiency, f(P(n)) is the purity improvement function, and g(η(n)) is the energy efficiency function. Specifically, f(P(n)) = (P(n) - P_initial) / (P_0 - P_initial) and g(η(n)) = η(n) / η_max can be defined, where η_max is the maximum energy efficiency observed in all experiments.

[0083] In one embodiment, the purity constraint is: P(n) ≥ P_required, where P_required is the required minimum purity. The energy efficiency constraint is: η(n) ≥ η_min, where η_min is the acceptable minimum energy efficiency.

[0084] The integer constraint is: n is a positive integer.

[0085] Since the pickling times n is discrete, the enumeration method or dynamic programming can be used to solve for the optimal value of n: For each possible value of n (from 1 to the maximum allowed pickling times), calculate J(n). Check whether all constraint conditions are satisfied. Among the n values that satisfy the constraint conditions, select the n value that maximizes J(n) as the optimal pickling times.

[0086] First, use the experimental data to fit the parameters of the purity prediction model: P(n) = P_0 - (P_0 - P_initial) * e^(-k * n), and estimate the values of P_0 and k using the nonlinear least squares method. For each pickling times n, calculate the corresponding energy efficiency η(n): η(n) = (m * ΔH) / (E_total(n) - E_recovered(n)), where E_total(n) and E_recovered(n) are the actual energy consumption and recovery amount after n pickling times. Determine the weight coefficients w_1 and w_2. This can be set according to product requirements and production cost considerations. For example, w_1 = 0.6 and w_2 = 0.4. For each possible value of n (e.g., from 1 to 6), calculate the comprehensive performance index J(n): J(n) = w_1 * ((P(n) - P_initial) / (P_0 - P_initial)) + w_2 * (η(n) / η_max). Check the constraint conditions: P(n) ≥ P_required and η(n) ≥ η_min. Only consider the n values that satisfy these constraints, and among the n values that satisfy the constraints, select the n that maximizes J(n) as the optimal pickling times.

[0087] For example, there are the following experimental data: P_initial = 80%, P_required = 95%, η_min = 0.5. Through data fitting, it can be obtained that: P_0 = 99.9%, k = 0.8. For n = 1 to 5, the following are calculated:

[0088] n = 1: P(1) = 95.98%, η(1) = 0.60

[0089] n = 2: P(2) = 98.72%, η(2) = 0.65

[0090] n = 3: P(3) = 99.52%, η(3) = 0.68

[0091] n = 4: P(4) = 99.79%, η(4) = 0.70

[0092] n = 5: P(5) = 99.89%, η(5) = 0.71

[0093] Let η_max = 0.71, w_1 = 0.6, w_2 = 0.4, and calculate J(n):

[0094] J(1) = 0.6 * (0.7990 / 0.999) + 0.4 * (0.60 / 0.71) = 0.6784

[0095] J(2) = 0.6 * (0.9360 / 0.999) + 0.4 * (0.65 / 0.71) = 0.7975

[0096] J(3) = 0.6 * (0.9760 / 0.999) + 0.4 * (0.68 / 0.71) = 0.8457

[0097] J(4) = 0.6 * (0.9895 / 0.999) + 0.4 * (0.70 / 0.71) = 0.8684

[0098] J(5) = 0.6 * (0.9945 / 0.999) + 0.4 * (0.71 / 0.71) = 0.8768

[0099] All values of n satisfy the constraint conditions. J(n) reaches the maximum value when n = 5. Therefore, the optimal pickling times is 5 times. In addition, when n is less than 2, the optimal pickling times is taken as 2.

[0100] This method can be used to determine the optimal number of pickling times based on actual experimental data, taking into account purity improvement and energy efficiency. This method takes into account the two key factors of purity and energy efficiency and is able to strike a balance between the two. By adjusting the weight coefficient, it can flexibly adapt to different production strategies and market demands.

[0101] Finally, it should be emphasized that the accuracy and effectiveness of this model largely depends on the quality and quantity of experimental data. Therefore, in practical applications, a large number of experiments and data collection should be carried out, and the model parameters should be updated regularly to ensure that the model can accurately reflect the actual situation of the production process.

[0102] Figure 2 A schematic diagram of a purity curve provided in the embodiment of the present application. Figure 2 As shown in the figure, the purity curve shows a typical exponential growth shape, which is consistent with the mathematical form of the model. The purity increases rapidly in the initial stage (the first few acid washes), and then the growth rate gradually slows down, and finally approaches the theoretical maximum purity P_0. This trend reflects the common situation in the purification process: the initial purification effect is significant, but as the purity increases, further improvement becomes increasingly difficult.

[0103] Figure 3 A schematic diagram of an energy efficiency curve provided in an embodiment of the present application. For the energy efficiency curve, the embodiment of the present application draws three lines: a) electromagnetic heating (with waste heat recovery): using a circular mark ('-o'), b) electromagnetic heating (without waste heat recovery): using a cross mark ('-x'), c) direct pickling: using a square mark ('-s'). Figure 3 As shown in the figure, electromagnetic heating (with waste heat recovery) has the highest energy efficiency, because the waste heat recovery system can reduce energy loss. The energy efficiency of electromagnetic heating (without waste heat recovery) is second, but still higher than the direct pickling method. This may be due to the high energy conversion efficiency of electromagnetic heating. Direct pickling has the lowest energy efficiency, which may be due to the large heat loss and the lack of a waste heat recovery system. All curves show that the energy efficiency increases with the increase in the number of pickling times. This may be because the subsequent pickling process can utilize the waste heat of the previous process, or the operating parameters have been optimized.

[0104] Comparing the purity curve and the energy efficiency curve, it can be obtained that: in the initial stage, the purity increases rapidly, while the energy efficiency is relatively low. This may be because a large amount of impurities need to be removed in the initial stage, and the energy consumption is large. As the number of pickling times increases, the purity improvement rate slows down, but the energy efficiency continues to improve. This may be because in the subsequent pickling process, fewer impurities need to be removed, and energy can be more effectively used to remove target impurities. This relationship proves that in actual production, the method described in the previous embodiment can be used to find a balance between purity and energy efficiency.

[0105] Generally speaking, the high-efficiency purification method of carbon nanotubes based on electromagnetic heating and waste heat recovery provided in this embodiment significantly improves the energy utilization efficiency of the purification process through the heating method and energy recovery technology, and optimizes the configuration of the number of reaction kettles, that is, the number of pickling times. This method not only improves the purity of carbon nanotubes, but also reduces the production cost and energy consumption, and has good economic and environmental benefits.

[0106] Figure 4 The figure is a schematic block diagram of a high-efficiency purification device for carbon nanotubes based on electromagnetic heating and waste heat recovery provided by an embodiment of the present application. It should be understood that the device shown in the figure is exemplary rather than restrictive. This means that the involved system architecture is not limited to a specific form or design, but is presented as an example. In other words, the architecture shown in the figure can be regarded as a way of expression to clearly describe relevant concepts and relationships, and does not exclude other forms of architecture. Therefore, when explaining the architecture in the said figure, it should be understood that the model has flexibility and diversity, and its purpose is to provide an exemplary description rather than a restrictive regulation of a specific form.

[0107] The present application discloses a high-efficiency purification device for carbon nanotubes based on electromagnetic heating and waste heat recovery that applies the high-efficiency purification method described in any one of the above embodiments, including: at least two reaction kettles, one or more electromagnetic heating pipes, and a heat exchanger; wherein, the reaction kettle is provided with a feed port, a discharge port, a liquid discharge port, a stirring device, and / or a temperature sensor; each reaction kettle is configured with an independent electromagnetic heating pipe; the electromagnetic heating pipe is used for heating and transporting acid solution; the heat exchanger is used for waste heat recovery to heat the fresh acid solution in the heating pipe of the target reaction kettle.

[0108] It should be understood that the technical solution of the present application is not limited to the above steps, and can also be flexibly adjusted and optimized according to actual production requirements. For example, parameters such as the number of reaction kettles, the number of pickling times, and the reaction temperature can be adjusted according to the characteristics of the carbon nanotube raw material and the purification requirements. In addition, an automatic control device can be added to the system to realize the intelligent management of the entire purification process, and further improve the production efficiency and the stability of product quality.

[0109] The technical solution of this application has many advantages. First, by setting up multiple reactors and using electromagnetic heating technology, the pickling process is carried out efficiently. The application of electromagnetic heating technology not only improves the heating efficiency but also enables precise control of the reaction temperature, which is conducive to improving the consistency of product quality. Second, through the waste heat recovery system, the heat energy in the waste liquid is fully utilized, significantly reducing energy consumption and production costs. This recycling method not only has significant economic benefits but also has a good environmental protection effect. Moreover, the design of the entire system fully considers the continuity and automation of the process flow, which is conducive to improving production efficiency and reducing manual operation costs.

[0110] In addition, the technical solution of this application also has good scalability and adaptability. For example, the number and capacity of the reactors can be adjusted according to the actual production scale; the number of pickling times and reaction conditions can be adjusted according to the purification requirements of different types of carbon nanotubes; and this technical solution can also be combined with other purification technologies, such as ultrasonic-assisted purification, microwave-assisted purification, etc., to further improve the purification effect and efficiency.

[0111] Generally speaking, the efficient carbon nanotube purification method and device based on electromagnetic heating and waste heat recovery provided by this application, through reasonable process design and equipment configuration, effectively solve the problems of energy waste and high costs existing in the traditional carbon nanotube purification process. This method not only improves the efficiency and quality of carbon nanotube purification but also realizes the efficient utilization of energy, with significant economic and environmental benefits. The application of this technical solution will contribute to the sustainable development of the carbon nanotube industry and provide new ideas and directions for technological progress in related fields.

[0112] Furthermore, the embodiment of this application also provides an efficient carbon nanotube purification device based on electromagnetic heating and waste heat recovery, including: a processor, a memory, and a system bus; the processor and the memory are connected through the system bus; the memory is used to store one or more programs, and the one or more programs include instructions, and when the instructions are executed by the processor, the processor executes any one of the above methods.

[0113] Furthermore, the embodiment of this application also provides a computer program product, which, when running on a terminal device, enables the terminal device to execute any one of the above methods.

[0114] As can be seen from the description of the above embodiments, those skilled in the art can clearly understand that all or part of the steps in the above-described embodiment methods can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product, which can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network communication device such as a media gateway, etc.) to execute the methods described in each embodiment or some parts of the embodiments of the present application.

[0115] It should be noted that the various embodiments in this specification are described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method part.

[0116] It should also be noted that in the embodiments of the present application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0117] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined in the embodiments of the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the embodiments of the present application, but will conform to the widest scope consistent with the principles and novel features disclosed in the embodiments of the present application.

Claims

1. A method for efficiently purifying carbon nanotubes based on electromagnetic heating and waste heat recovery, characterized in that: include: At least two reaction kettles for pickling are provided, wherein the reaction kettles are provided with a feed inlet, a discharge outlet, a liquid discharge outlet, a stirring device and / or a temperature sensor; Each reactor is equipped with an independent electromagnetic heating pipeline, which is used to heat and transport the acid solution; Adding carbon nanotube raw materials into the first reaction kettle, and heating the acid solution by using an electromagnetic heating pipe to acid-wash the raw materials; The high-temperature waste liquid in the first reactor is collected and the waste heat is recovered by using a heat exchanger, so as to heat the fresh acid liquid in the heating pipe of the next reactor in combination with electromagnetic heating; In the next stage reactor, the raw material is pickled with acid liquid recovered from waste heat, and the waste heat recovery, heating and pickling process are repeated until the raw material is finally pickled by the final reactor to obtain purified carbon nanotubes; Multiple sets of pickling data were collected, and the purity curves and energy efficiency curves of carbon nanotubes with different pickling times were constructed to optimize the number of reactors to be set.

2. The method for efficiently purifying carbon nanotubes according to claim 1, characterized in that: in, Each reactor is equipped with an independent electromagnetic heating pipeline, which is used to heat and transport the acid solution, including: Configure electromagnetic heating pipeline system, including electromagnetic heater, stainless steel coil, PTFE lining, insulation layer, temperature sensor and flow meter, where the electromagnetic heater adopts high-frequency electromagnetic induction heating; The inner diameter of the stainless steel coil is set to 20 mm, the wall thickness is set to 2 mm, and it is coiled into a spiral shape. A 1 mm thick PTFE layer is coated on the inner wall of the stainless steel tube, and a 50 mm thick glass wool insulation layer is wrapped around the outside of the coil. Install a temperature sensor at the inlet and outlet of the coil, and install an electromagnetic flowmeter at the inlet of the coil; By adjusting the flow rate and heating power, the acid liquid outlet temperature is controlled to be stable within the set range.

3. The method for efficiently purifying carbon nanotubes according to claim 1, characterized in that: in, Adding carbon nanotube raw materials into a first reaction kettle and heating acid solution by using an electromagnetic heating pipe to acid wash the raw materials, including: The acid solution prepared by mixing the acid components in the pre-selected acid solution formula according to a predetermined volume ratio is heated to a predetermined temperature through an electromagnetic heating pipeline system; Slowly adding a pre-weighed amount of dry carbon nanotube raw material into the acid solution heated to a predetermined temperature, and stirring at a predetermined speed; Continue to carry out the pickling reaction at the predetermined temperature for a predetermined time, and intermittently take samples to detect changes in impurity content; Stop heating and stirring, wait for the reaction mixture to cool naturally to a predetermined temperature, and then separate the solid from the liquid by a centrifuge; Repeatedly washing the separated carbon nanotubes with deionized water until the pH value of the washing solution reaches a predetermined range; The cleaned carbon nanotubes are vacuum dried at a predetermined temperature for a predetermined time.

4. The method for efficiently purifying carbon nanotubes according to claim 1, characterized in that: in, The high-temperature waste liquid in the first reactor is collected and the waste heat is recovered by using a heat exchanger, so as to heat the fresh acid liquid in the heating pipe of the next reactor in combination with electromagnetic heating, including: The high-temperature waste liquid after pickling in the first reactor is discharged and collected into a heat preservation tank with a preset capacity; A heat exchanger of target material, with a predetermined heat exchange area and heat transfer coefficient is provided in the heating system of the next-stage reactor; The waste liquid is transported from the insulation tank to the heat exchanger at a preset flow rate using a corrosion-resistant pump, and heat is exchanged with the low-temperature fresh acid entering the next-stage reactor, so that the waste liquid is cooled and the fresh acid is heated; The preheated fresh acid liquid is further heated to the target temperature through the heating pipe system, and the waste liquid after the heat exchange is transported to the waste liquid treatment system for neutralization treatment.

5. The method for efficiently purifying carbon nanotubes according to claim 1, characterized in that: in, The raw material is pickled using acid liquid recovered from waste heat in the next stage reactor, and the waste heat recovery, heating and pickling process are repeated until the raw material is finally pickled by the final stage reactor to obtain purified carbon nanotubes, including: The carbon nanotubes after the initial pickling are transferred to the next-stage reactor, and the newly prepared acid solution after waste heat recovery and electromagnetic heating is added for secondary pickling; Repeat pickling, waste heat recovery and electromagnetic heating of waste liquid until the product is transferred to the final reactor and finally pickled with low-concentration acid solution; The carbon nanotubes are rinsed with deionized water until the pH value is neutral, and the dried carbon nanotubes are ground with a ball mill, and sieved with a sieve with a preset mesh number to remove large particle impurities to obtain purified carbon nanotubes.

6. The method for efficiently purifying carbon nanotubes according to claim 1, characterized in that: in, Collect multiple sets of pickling data and construct carbon nanotube purity curves and energy efficiency curves for different pickling times to optimize the number of reactor settings, including: Collecting multiple groups of carbon nanotube samples, and performing different times of acid washing on each group of samples, wherein the number of acid washings varies within a preset range; The purity, treatment quality, actual energy consumption and waste heat recovery of carbon nanotubes were measured for each sample after pickling, and the pickling operation parameters were recorded; The nonlinear regression method was used to fit the parameters of the purity prediction model, and the curve of the change of carbon nanotube purity with the number of acid washings was plotted; the energy utilization efficiency of each group of experiments was calculated, and the curve of the change of energy efficiency with the number of acid washings was plotted; Construct a comprehensive performance index that combines the purity improvement function with the energy efficiency function, and set weight coefficients to determine the relative importance of purity and energy efficiency; For each pickling number within the preset range, calculate the corresponding comprehensive performance index value; check whether the purity requirements and the minimum energy efficiency constraints are met; among the pickling times that meet the constraints, select the value that maximizes the comprehensive performance index as the optimal pickling number and the target configuration number of reactors.

7. The method for efficiently purifying carbon nanotubes according to claim 6, characterized in that: in, Construct a comprehensive performance index that combines the purity improvement function with the energy efficiency function, and set weight coefficients to determine the relative importance of purity and energy efficiency, including: Where J(n) represents the comprehensive performance index of pickling times n, w1 and w2 represent weight coefficients, f(P(n)) represents the purity improvement function, g(η(n)) represents the energy efficiency function, P(n) represents the purity of pickling times n, P initial represents the initial purity, P0 represents the theoretical maximum purity, η(n) represents the energy efficiency of pickling times n, η max represents the maximum energy efficiency observed in the experiment.

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