Method for monitoring state of carbon material preparation device

Abstract

The invention provides a method for monitoring the state of a carbon material preparation device. The method comprises the following steps: a) collecting initial data; b) real-time data collection: placing an electrode assembly on the outer wall surface of the reactor body, recording a capacitance value C measured by the electrode assembly, and converting the capacitance value C to obtain a mathematical signal; c) image reconstruction: carrying out algorithm iteration on the mathematical signal obtained in the step b) to calculate a dielectric constant of each unit, carrying out image reconstruction to obtain a void ratio P in the reactor at a corresponding moment, and calculating a required characteristic value theta through the void ratio P; and d) data adjustment: comparing the characteristic value theta obtained in the step c with a standard characteristic value theta s, and when the characteristic value theta is out of the range of the standard characteristic value theta s, adjusting parameters to enable the characteristic value to be within the range of the standard characteristic value theta s. According to the method provided by the invention, the characteristic value theta in the reaction process can be timely controlled within the set target range, so that the prepared carbon nanotube is more stable in performance and finer in control range.

Description

Technical Field

[0001] The present invention relates to a method for monitoring the state of a carbon material preparation device. The method provided by the present invention can timely control the characteristic value θ of the reaction process within a set target range, so that the performance of the prepared carbon nanotubes is more stable and the control range is more refined. Background Art

[0002] Carbon nanotubes are one-dimensional nanomaterials with excellent physical and chemical properties, such as good mechanical properties, thermal stability, special electrical properties, thermal conductivity, hydrogen storage, adsorption and catalytic properties, etc., and have broad application prospects in many fields such as nanoelectronic devices, catalyst carriers, electrochemical materials, composite materials, etc. At present, carbon nanotubes have been industrialized, which mainly depends on fluidized bed reactors. During the growth of carbon nanotubes, the reactor has not only a high temperature but also a large gas velocity, which leads to a complex state inside the reactor. And with the progress of the reaction batch, a carbon layer will gradually form on the tube wall of the fluidized bed, which will have a huge impact on the fluidization state, resulting in the need to adjust parameters for each production. At the same time, the fluidization quality determines the quality of carbon nanotube growth, so real-time display and monitoring of fluidization in a gas-solid fluidized bed is very necessary.

[0003] The industrial production of carbon nanotubes mainly depends on the reactor. During the growth process of carbon nanotubes, there is not only a high temperature inside the reactor but also a large gas velocity. After a long period of preparation of carbon nanotubes in the reactor, a carbon layer will form on the tube wall of the reactor, which will affect the fluidization state in the reactor. In order to maintain the stability of the performance of carbon nanotubes, parameters need to be adjusted according to the reactor status. Therefore, real-time display and monitoring of the reactor status is very necessary.

[0004] At present, there are two main monitoring technologies for reactors: one is to use the empirical formulas studied by predecessors and the prepared carbon nanotube structure to determine the change conditions between fluidization states; the other is to use some detection means, such as pressure sensors, thermocouples, etc. The existing monitoring technologies either have a certain hysteresis and are not targeted; or they do not need to destroy the reactor structure, which is easy to cause gas leakage.

[0005] Therefore, it is necessary to design a method that can monitor the internal state of the reactor in real time to achieve precise control of the reaction process in order to prepare carbon materials with more stable performance. Summary of the invention

[0006] The purpose of the present invention is to provide a method and device for continuously preparing carbon materials, which can solve the problem in the prior art that carbon materials cannot be grown continuously and uniformly in a fluidized field.

[0007] The present invention reduces the agglomeration of the growing carbon material by arranging the inert particles to space the catalyst, regulates the size of the carbon material agglomerates, and improves the fluidization quality. At the same time, the gas is controlled to separate the carbon materials of different masses from the inert substances, so that the batch continuous and stable preparation of carbon materials can be achieved. The carbon material preparation process of the present invention is simple and stable, and the process conditions are easy to control, so that batch preparation can be achieved. The carbon material obtained by the method and device of the present invention has the characteristics of high yield, large specific surface area, and high aspect ratio.

[0008] Another object of the present invention is to provide a method for monitoring the state of a reactor during the growth of carbon nanotubes. In view of the difference in the fluidization state of materials at different gas velocities during the growth of carbon nanotubes, the difference in capacitance values ​​measured by electrode sensors and an image reconstruction algorithm are combined to achieve real-time monitoring of the void fraction in the reactor, and then the reaction process is precisely controlled by adjusting the reaction parameters.

[0009] Therefore, one aspect of the present invention provides a method for continuously preparing a carbon material, the method comprising:

[0010] 1) providing an inert substance to a reactor, wherein the inert substance is a high temperature resistant substance and does not participate in the growth reaction of the carbon material;

[0011] 2) providing a catalyst and introducing a gas into a reactor, so that the inert substance and the catalyst are continuously moved under the action of the gas, and the catalyst and the gas interact with each other at a certain temperature to fluidize and grow into the carbon material, wherein the gas includes a carbon source gas, a reducing gas and a protective gas;

[0012] 3) controlling the gas to separate carbon materials of different qualities from inert substances;

[0013] 4) Maintaining the inert material at a certain level in the reactor and continuously discharging part of the carbon material;

[0014] 5) Repeat steps 2)-4) to achieve continuous preparation of carbon materials.

[0015] Another aspect of the present invention provides an apparatus for continuously preparing carbon materials, the apparatus comprising a main reactor for performing a CVD reaction and a collector for collecting carbon materials, the main reactor having an input end, an outflow end and a reactor body, the reactor body comprising a reaction zone and a separation zone, gas and catalyst are provided to the reaction zone through the input end; the outflow end is located at the upper part of the separation zone, and the separation zone is connected to the collector through the outflow end via a connecting pipe;

[0016] The collector comprises a filter, and the filter is used to separate the carbon material from the tail gas discharged from the main reactor.

[0017] Another aspect of the present invention provides a carbon material prepared by the method of the present invention.

[0018] Another aspect of the present invention provides a method for monitoring the state of the device for continuously preparing carbon materials according to the present invention, the method comprising the following steps:

[0019] a) Initial data collection: record the capacitance value C of the set gas source respectively m , the capacitance value C of carbon nanotubes n ;

[0020] b) real-time data collection: placing an electrode assembly on the outer wall of the separation zone of the reactor body, with the electrode assembly at a height H from the bottom of the reactor; recording the capacitance value C measured by the electrode assembly, and converting the capacitance value C into a mathematical signal;

[0021] c) Image reconstruction: the mathematical signal obtained in step b) is subjected to algorithm iteration to calculate the dielectric constant ε of each unit, and then image reconstruction is performed to obtain the void ratio P in the reactor at the corresponding time, and the characteristic value θ is calculated according to the void ratio P;

[0022] d) Data adjustment: Compare the eigenvalue θ obtained in step c with the standard eigenvalue θs. When the eigenvalue θ is outside the range of the standard eigenvalue θs, adjust the parameters so that the eigenvalue is within the range of the standard eigenvalue θs.

[0023] In a preferred embodiment, the electrode assembly converts the measured capacitance value C into a voltage signal, and performs analog-to-digital conversion on the voltage signal through phase-sensitive demodulation and a low-pass filter to obtain a mathematical signal.

[0024] In a preferred embodiment, the value range of H is 10D≤H≤30D, wherein D is the diameter of the reaction zone of the reactor.

[0025] In a preferred embodiment, the characteristic value θ is calculated as follows:

[0026]

[0027] Where P is the void ratio of the reactor and H0 is the height of the reactor.

[0028] In a preferred embodiment, for wound carbon nanotubes, the standard characteristic value θs is [2, 7], and for arrayed carbon nanotubes, the standard characteristic value θs is [5, 10].

[0029] In a preferred embodiment, P is calculated according to the C normalization formula and the image reconstruction formula,

[0030] The normalization formula of C is:

[0031] C r =(CC m ) / (C n -C m ) Formula (3)

[0032] The image reconstruction formula is:

[0033]

[0034] In formula (4), C r is the normalized value of capacitance C, g(i) is the pixel grayscale value of the dielectric constant distribution image in the measured field, S(i) is the average sensitivity of the medium at microelement i, δ i is the area of ​​infinitesimal element i. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention is described below in conjunction with the accompanying drawings.

[0036] In the attached figure:

[0037] Figure 1 is a schematic diagram of a conical fluidized bed main reactor according to one embodiment of the present invention, wherein the separation zone and the reaction zone have different pipe diameters;

[0038] Figure 2 is a schematic diagram of a conical fluidized bed main reactor according to one embodiment of the present invention, wherein the separation zone has the same pipe diameter as the reaction zone;

[0039] Figure 3 is a schematic diagram of a cylindrical fluidized bed main reactor according to one embodiment of the present invention, wherein the separation zone and the reaction zone have different pipe diameters, and the reaction zone has a distribution plate;

[0040] Figure 4 is a schematic diagram of a conical fluidized bed main reactor and a continuous collection device according to one embodiment of the present invention;

[0041] Figure 5 It is a schematic diagram of the fluidization of spherical particles in a conical fluidized bed with a distribution plate and the continuous growth of carbon nanotubes;

[0042] Figure 6 It is an experimental statistical graph reflecting the change of the characteristic value θ of the reactor state over time;

[0043] Figure 7 Schematic diagram of the structure of a device for monitoring the status of a reactor according to one embodiment of the present invention. DETAILED DESCRIPTION

[0044] A method for continuously preparing a carbon material, the method comprising:

[0045] 1) providing an inert substance to a reactor, wherein the inert substance is a high temperature resistant substance and does not participate in the growth reaction of the carbon material;

[0046] 2) providing a catalyst and introducing a gas into a reactor, so that the inert substance and the catalyst are continuously moved under the action of the gas, and the catalyst and the gas interact with each other at a certain temperature to fluidize and grow into the carbon material, wherein the gas includes a carbon source gas, a reducing gas and a protective gas;

[0047] 3) controlling the gas to separate carbon materials of different qualities from inert substances;

[0048] 4) Maintaining the inert material at a certain level in the reactor and continuously discharging part of the carbon material;

[0049] 5) Repeat steps 2)-4) to achieve continuous preparation of carbon materials.

[0050] The following is a description of the method for continuously preparing carbon materials:

[0051] In the present invention, the term "carbon material" includes at least one carbon nanotube or graphene. The preparation of different carbon materials can be achieved by fine-tuning the catalyst elements and reaction conditions.

[0052] (1) Provide inert substances

[0053] The inert material is a high temperature resistant material and does not participate in the growth reaction of the carbon material. The present invention reduces the agglomeration of the growing carbon material by arranging the inert material particles to space the catalyst, regulates the size of the carbon material, such as the carbon nanotube agglomerate, and increases the fluidization quality. The inert material includes spherical particles or non-spherical materials, and the non-spherical materials include porous medium materials, which are in a whole or dispersed state, and reciprocate along the length direction of the fluidized bed or are in a free fluidization state under the action of the gas source.

[0054] The rock includes but is not limited to marble, granite, etc. The high temperature resistant metal includes but is not limited to refractory metals such as tungsten, molybdenum, tantalum, niobium, vanadium, chromium, titanium, zirconium, etc. The high temperature alloy includes but is not limited to chromium-nickel-molybdenum alloy, chromium-manganese-molybdenum alloy, etc. The high carbon material includes but is not limited to graphene, carbon black, CNT, activated carbon. The light aggregate can be divided into industrial waste residue light aggregate according to its source, such as fly ash ceramsite, self-igniting coal gangue, expanded slag beads, coal slag and its light sand; natural light aggregate, such as pumice, volcanic slag and its light sand; artificial light aggregate, such as shale ceramsite, clay ceramsite, expanded perlite and its light sand. The inert material can also include composite materials, such as carbon-carbon composite materials or ceramic-based composite materials, minerals or processed minerals, such as perlite, pumice, etc.

[0055] Most preferably, the inert substance is at least one substance selected from the group consisting of high carbon substances, coconut shell carbon, alumina particles, floating beads particles and perlite particles.

[0056] In a preferred embodiment, the average bulk density of the inert substance is at least 1.5 times that of the carbon material. Since the inert substance has a high bulk density and a large weight, while the generated carbon material has a low density and a light weight, the inert substance and the carbon material can be separated by gas control in the separation step.

[0057] In a preferred embodiment, the inert substance is a porous medium with a porosity of 30-90%.

[0058] In a preferred embodiment, the inert substance is a non-spherical or spherical particle with an average particle size of 0.1 μm-5000 μm, preferably 100-2000 μm. Preferably, the inert substance is a non-spherical or spherical particle, and a stepped stratified fluidization can be formed in the fluidized bed by adjusting the shape, density and size of the spherical particles.

[0059] In a preferred embodiment, the inert substance is uniform spherical particles of various sizes, and the size is 30-150 mesh.

[0060] (2) providing a catalyst and introducing a gas into a reactor, so that the inert substance and the catalyst are continuously moved under the action of the gas, and the catalyst and the gas interact with each other at a certain temperature to fluidize and grow into the carbon material, wherein the gas includes a carbon source gas, a reducing gas and a protective gas.

[0061] Gas and catalyst are provided into the reactor from the input end, and the gas and catalyst can be independently input from the input end, or the gas and catalyst can be mixed and then input. The independent input method of the catalyst includes at least one of the following methods: direct input, spray input mixed with liquid, and gas co-introduction. The independent input means that the catalyst and the gas source are input separately through their own pipelines. Direct input means that the catalyst is input separately, spray input mixed with liquid means that the catalyst is mixed with liquids such as water and then input into the fluidized bed in a spray form, and gas co-introduction means that the catalyst is mixed with inert gases such as nitrogen and then input into the fluidized bed. The present invention has no particular restrictions on the input method of gas and catalyst, and can be carried out by conventional input methods in the field, as long as the purpose of the present invention can be met.

[0062] The gas includes a carbon source gas, a reducing gas and a protective gas. The carbon source gas is a hydrocarbon or alcohol mobile phase. Preferably, the carbon source gas includes at least one gas selected from the group consisting of propylene, ethylene, propane, carbon monoxide, carbon dioxide and methane; more preferably propylene or ethylene. Preferably, the reducing gas includes at least one gas selected from the group consisting of hydrogen and carbon monoxide. Preferably, the protective gas includes nitrogen and argon. In the present invention, the gas may also include a gasified liquid phase substance.

[0063] The catalyst may be a catalyst commonly used in the art for catalyzing a carbon source to generate a carbon material through a CVD reaction. The catalyst includes a powder catalyst and a liquid catalyst. The powder catalyst includes at least one of iron, cobalt, nickel and their precursors, and the liquid catalyst precursor includes a metallocene organic compound and / or a carbonyl metal organic compound, preferably ferrocene, pentacarbonyl iron, tetracarbonyl nickel, and octacarbonyl dicobalt. In a preferred embodiment of the present invention, the catalyst includes at least one compound selected from the group consisting of a metallocene organic compound and / or a carbonyl metal organic compound, preferably ferrocene, pentacarbonyl iron, tetracarbonyl nickel, and octacarbonyl dicobalt. The metallocene organic compound and / or the carbonyl metal organic compound are dispersed in a low temperature zone to form uniform nano-scale catalyst particles, and a few-wall or single-wall carbon material can be obtained without consuming more processes and costs to prepare the catalyst.

[0064] In a preferred embodiment, the catalyst enters the reaction zone in a gaseous form. In a preferred embodiment, the catalyst enters the reaction zone in a gaseous form after being heated to 120-500°C.

[0065] The certain temperature is at least the temperature at which the carbon material grows. A heating device may be provided outside the reaction zone to provide the set temperature required for the growth of the carbon material. The temperature range is 500-1500° C. In the presence of an inert substance in a fluidized state, the catalyst and the gas interact with each other under the temperature range to fluidize and grow into the carbon material.

[0066] (3) controlling the gas to separate carbon materials of different masses from inert substances;

[0067] Since the generated carbon material and inert substance have different weights, the carbon material and the inert substance can be separated by controlling the gas, and the lighter carbon material leaves the reactor under the entrainment of the gas flow, while the heavier inert substance remains in the reactor body.

[0068] In the present invention, the separation of the carbon material from the inert particles can be achieved by controlling the flow rate or changing the diameter of the main tube.

[0069] The flow rate control refers to achieving different separation effects by changing different intake speeds, including setting pulse intake and sinusoidal function intake.

[0070] Changing the main body tube diameter means setting fluidized bed tube diameters of different diameters under the condition of constant gas source flow rate to achieve separation of the carbon material from the inert substance. Preferably, the separation zone tube diameter is set larger than the reaction zone diameter, which is conducive to separation and sedimentation.

[0071] 4) Maintain inert materials in the reactor and continuously discharge part of the carbon material

[0072] The inert material is kept in the reactor, and the generated carbon material is discharged from the reactor through the outflow end. The outflow end can be connected to the collector through a connecting pipe to achieve a better separation effect.

[0073] 5) Repeat steps 2)-4) to achieve continuous preparation of carbon materials.

[0074] Repeat steps (d)-(f) to maintain continuous feeding of the catalyst and gas and continuous discharge of the carbon material in the reactor to achieve continuous preparation of the carbon material.

[0075] Another aspect of the present invention provides an apparatus for continuously preparing carbon materials, the apparatus comprising a main reactor for performing a CVD reaction and a collector for collecting carbon materials, the main reactor having an input end, an outflow end and a reactor body, the reactor body comprising a reaction zone and a separation zone, gas and catalyst are provided to the reaction zone through the input end; the outflow end is located at the upper part of the separation zone, and the separation zone is connected to the collector through the outflow end via a connecting pipe;

[0076] The collector comprises a filter, and the filter is used to separate the carbon material from the tail gas discharged from the main reactor.

[0077] The specific components of the device for continuously preparing carbon materials are described below:

[0078] (1) Main Reactor

[0079] In the present invention, the main reactor refers to a reactor suitable for preparing carbon nanotubes by CVD reaction using a catalyst to catalyze the cracking of a carbon source. In this reactor, at a suitable temperature, such as 500-1100°C, preferably 650-900°C, and more preferably 700-800°C, the carbon source grows carbon nanotubes on a catalyst carrier under the action of the catalyst.

[0080] In the present invention, the main reactor may be a fluidized bed reactor. Preferably, the aspect ratio of the height to the diameter of the reactor is 5-25:1, preferably 10-20:1, and more preferably 12-15:1. The reactor may be a cylindrical reactor or a conical reactor. Preferably, the fluidized bed reactor is a conical reactor with a conical bottom structure, and the cone angle of the cone bottom is preferably 5° to 50°.

[0081] The main reactor comprises an input end, an outflow end and a reactor body, wherein the reactor body comprises a reaction zone and a separation zone. The input end can be respectively set as a gas input end and a catalyst input end, the gas input end can be set at the bottom of the reactor, and the catalyst input end can be combined with the gas input end or set separately.

[0082] The gas enters the main reactor through a gas input port located at the bottom of the main reactor. There is no particular restriction on the form of the input gas, and the carbon source gas, reducing gas and / or protective gas can be introduced in the form of a mixed gas, or a certain volume of carbon source gas, reducing gas and / or protective gas can be introduced in sequence.

[0083] In the present invention, the protective gas input end and the carbon source gas input end can be separately arranged, or combined for feeding. Preferably, the gas inlet includes a carbon source gas input end and a protective gas input end, wherein the carbon source gas input end and the protective gas input end are arranged at multiple points at the bottom of the main reactor, which is conducive to fluidized reaction and heat conduction.

[0084] The catalyst input end can be arranged at any position of the reaction zone of the main reactor, and the catalyst input end can be arranged in multiple layers and / or multiple points in the same layer in the main reactor, which is conducive to fluidized reaction and heat conduction. In the main reactor of the present invention, the reaction zone and the separation zone are connected, the separation zone is located above the reaction zone, and the diameter of the separation zone is at least equal to that of the reaction zone. Preferably, the diameter of the separation zone is larger than the diameter of the reaction zone. Preferably, the diameter of the separation zone is 1-5 times the diameter of the reaction zone.

[0085] The outflow end is arranged at one side of the separation zone of the main reactor, located at the upper part of the separation zone, and the separation zone is connected with the collector through the outflow end via a connecting pipe.

[0086] In the present invention, there is no particular limitation on the types of the input end, the outflow end, and the feeding device, as long as it is a feeding device suitable for feeding the catalyst and the gas.

[0087] The main reactor of the present invention is preferably a fluidized bed reactor with a distribution plate, wherein the inert substance and the carbon material are located on the same side of the distribution plate. The aperture of the distribution plate is at least smaller than that of the inert substance, so that the inert substance is located above the distribution plate, and the fluid is distributed or dispersed on the plate in a predetermined manner. In a cylindrical or conical fluidized bed with a distribution plate, it is preferred to input the catalyst and the gas independently, and the input ends of the two substances are respectively located on both sides of the distribution plate, the catalyst input is located on the upper side of the distribution plate, and the gas input is preferably located on the lower side of the distribution plate.

[0088] Preferably, the main reactor further comprises a cone bottom, and the cone bottom is a conical structure. Preferably, the main reactor is a cone bottom with a conical structure at the bottom, and the cone bottom is a conical structure, and preferably the angle of the cone bottom is 5° to 50°.

[0089] Preferably, a heating device is provided outside the reaction zone to provide a set temperature required for the growth of the carbon material.

[0090] (2) Collector

[0091] In the present invention, the carbon material is continuously collected in the collector from the separation zone of the reactor through the connecting pipe. The collector includes at least a filter, and the filter is used to separate the carbon material from the tail gas discharged from the main reactor. The filter includes a filter screen, a metal filter, a ceramic filter, etc.

[0092] There is no particular limitation on the collector and filter suitable for use in the present invention, including but not limited to temperature-resistant filter bags, stainless steel filters, etc., as long as the purpose of collecting and filtering carbon materials of the present invention can be achieved.

[0093] The present invention reduces the agglomeration of the growing carbon material by setting inert particles to space the catalyst, regulates the size of the carbon nanotube agglomerates, and improves the fluidization quality; at the same time, it is conducive to cleaning the distribution plate to avoid clogging; further increases the uniformity of the contact temperature between particles, making the growth more uniform; because the particle size or density of the inert material particles is greater than the carbon material agglomerates, the small particles can be better fluidized under the drive of the large particles, and the gas source is controlled to separate materials of different masses to achieve the continuity of the carbon material. The technical solution of the present invention can solve the problem that the prior art cannot uniformly grow the carbon material continuously.

[0094] The carbon material prepared by the method of the present invention has the advantages of high yield, large specific surface area and high aspect ratio. The process of the present invention is simple, the conditions are easy to control, the product stability is good, the production efficiency is significantly improved, and continuous batch production can be realized.

[0095] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings:

[0096] Figure 1 A schematic diagram of a conical fluidized bed main reactor according to an embodiment of the present invention is shown, wherein the conical fluidized bed main reactor includes a main body 102 and a conical bottom 101, the main body 102 includes a reaction zone 1022 and a separation zone 1021, the reaction zone 1022 and the separation zone 1021 are connected, the diameter of the separation zone 1021 is larger than the diameter of the reaction zone 1022; a heating device 15 is provided on the outside of the reaction zone 1022 to provide the set temperature required for the growth of the carbon material.

[0097] Figure 2 A schematic diagram of a conical fluidized bed main reactor according to an embodiment of the present invention is shown, wherein the conical fluidized bed main reactor includes a main body and a conical bottom 11, the main body includes a reaction zone 1022 and a separation zone 1021, the reaction zone 1022 and the separation zone 1021 are connected, and the diameter of the separation zone 1021 is the same as that of the reaction zone 1022.

[0098] Figure 3 A schematic diagram of a cylindrical fluidized bed main reactor according to one embodiment of the present invention is shown, wherein the separation zone and the reaction zone have different pipe diameters, wherein the reaction zone has a distribution plate 104 , and gas and catalyst are input into the reactor from an input end 11 .

[0099] Figure 4 A schematic diagram of a conical fluidized bed main reactor and a continuous collection device according to one embodiment of the present invention is shown, wherein the diameter D1 of the separation zone in the fluidized bed reactor 10 is larger than the diameter D2 of the reaction zone, the input end 11 is arranged as a gas input end 111 and a catalyst input end 112, the separation zone is connected to the collector 13 through a connecting pipe 12, and the collector 13 has a filter 131.

[0100] Figure 5 A schematic diagram is shown of the fluidization of spherical particles and the continuous growth of carbon nanotubes in a conical fluidized bed with a distribution plate, wherein the fluidized bed reactor 10 is divided into a conical bottom 101, a reactor body 102, an outflow end 103, spherical inert particles 14 are loaded in the reaction zone, and the carbon material obtained by the reaction enters the collector 13 from the outflow end 103 through a connecting pipe.

[0101] In a specific embodiment, an inert substance is placed in the reaction zone, an inert gas is introduced into the fluidized bed through the input end, the temperature is raised to a set temperature, catalyst particles are continuously input and gas is introduced to continuously grow the carbon material; the gas source velocity is controlled to separate the carbon material from the inert substance; the carbon material enters a collector through the outflow end of the fluidized bed, and the carbon material is continuously collected.

[0102] The following describes the method of monitoring the device status:

[0103] Figure 6The experimental statistical graph of the characteristic value θ of the growth state of carbon nanotubes in the reactor changing with time is shown. According to the statistical graph, the characteristic value θ can be used to judge the state of the fluidized bed. After a large number of experimental statistics, the standard characteristic value θs is set within a specific range (θ1≤θs≤θ2). When preparing carbon nanotubes, if the θ value calculated in real time is within the range of θs, there is no need to adjust the parameters. If the θ value calculated in real time is outside the range of θs, the θ value is restored to the range of θs by adjusting parameters such as temperature, pressure, and airflow volume V2. By adjusting various parameters, the characteristic value θ is always within the set specific range, which can promote the growth of carbon nanotubes and prepare carbon nanotubes with more stable performance.

[0104] Theoretically, the relationship between the capacitance and the dielectric constant is as shown in formula (1):

[0105] C=K·ε=F(ε) Formula (1)

[0106] In formula (1), C represents the capacitance value, K is the characteristic constant, and ε is the dielectric constant of the carbon nanotube when it is fluidized, where K depends on the electrode structure. The dielectric constant can be calculated from the measured C value.

[0107] ε can also be expressed as:

[0108] ε=(V1 / V)*ε1+(V2 / V)*ε2=ε2+(V1 / V)*(ε1-ε2) Formula (2)

[0109] In formula (2), ε1 and ε2 are the dielectric constants of the discrete phase carbon nanotubes and the continuous phase gas flow, respectively, V1 and V2 are the volumes of the discrete phase carbon nanotubes and the continuous phase gas flow, respectively, V = V1 + V2; where ε1 is the dielectric constant of the carbon nanotubes, which is a known value, and ε2 is related to C m Related, is a known value, V2 can be measured, and the volume V1 of the carbon nanotube can be calculated by this formula.

[0110] Theoretically, V1 / V is the porosity (P) of the reactor, which is related to the characteristic value θ. Therefore, the state of the reactor can be monitored by measuring the capacitance value C using the electrode assembly, and precise control of the reaction process can be achieved by adjusting the reaction parameters.

[0111] During the real-time monitoring process, the electrode sensor converts the measured capacitance value C into a voltage signal, and converts the signal from analog to digital through phase-sensitive demodulation and a low-pass filter, and then transmits it to the image reconstruction computer to obtain a mathematical signal. The mathematical signal is iterated by an algorithm to calculate the dielectric constant of each unit, and then image reconstruction is performed to obtain the void ratio of the fluidized bed at different times, and the required characteristic value is calculated through the void ratio.

[0112] The normalization formula of C is:

[0113] C r =(CC m ) / (C n -C m ) Formula (3);

[0114] The image reconstruction formula is:

[0115]

[0116] In formula (4), C r is the normalized value of capacitance C, g(i) is the pixel grayscale value of the dielectric constant distribution image in the measured field, assuming that each microelement i has the same sensitivity, then g(i)=(δ i -ε1) / (ε2-ε1), g(i)∈[0,1], S(i) is the average sensitivity of the medium at the microelement i, s(i)=(C - C m ) / δ i , δ i is the area of ​​the microelement i. The microelement i can be a small rectangle, δ i =dxdy, the average sensitivity of the medium at the microelement i is a known value, and the area of ​​the microelement i is a known value. According to formula (4), we can get The derivation process of the image reconstruction formula is detailed in page 17 of Liu Xiaomin's master's thesis "Capacitance Tomography Algorithm and Its Application in Two-Phase Flow Detection".

[0117] After algorithm iteration, the void ratio P of the reactor is:

[0118]

[0119] Where g(i) is the pixel grayscale value of the dielectric constant image at position i; the reactor is divided into Z equal parts along the longitudinal direction, and each part is used to display the proportional relationship between carbon nanotubes and gas in the form of an image, so the sum should be divided by the number of parts Z to obtain the porosity value of the entire reactor.

[0120] The calculation formula of the characteristic value θ is:

[0121]

[0122] Where θ is the characteristic value, H0 is the reactor height;

[0123] For the arrayed carbon nanotubes, the void fraction P is about 50%, and for the entangled carbon nanotubes, it is about 20%, both of which are statistically calculated results.

[0124] After a large number of experimental statistics, it is found that for wound carbon nanotubes, the standard characteristic value θs is [2, 7], and for array carbon nanotubes, the standard characteristic value θs is [5, 10]. That is, for wound carbon nanotubes, when the characteristic value θ obtained by real-time measurement and calculation is within the range of 2≤θ≤7, there is no need to adjust the parameters. When the characteristic value θ obtained by real-time measurement and calculation is outside this range, the θ value is restored to the above range by adjusting parameters such as temperature, pressure, and airflow volume; for array carbon nanotubes, when the characteristic value θ obtained by real-time measurement and calculation is within the range of 5≤θ≤10, there is no need to adjust the parameters. When the characteristic value θ obtained by real-time measurement and calculation is outside this range, the θ value is restored to the above range by adjusting parameters such as temperature, pressure, and airflow volume V2.

[0125] The method for monitoring the state of a reactor provided by the present invention utilizes an electrical capacitance tomography device to monitor the state inside the reactor, which can not only obtain the state of the material in the reactor in real time, including gas velocity, fluidization state, etc., to monitor the reaction process, but also calculate the void ratio of the carbon nanotubes during the fluidization process to achieve precise flow control, thereby avoiding the "temperature runaway" phenomenon caused by rapid reaction in industrial production, improving the efficiency and safety of the reaction process, and achieving good economic and practical benefits.

[0126] The present invention also provides a device for monitoring the state of a reactor, the device comprising at least a main reactor, an electrode assembly, a capacitance test module, a data processor and an image reconstruction computer. The electrode assembly is composed of four parts: a test electrode, an insulating pipe, a radial electrode and a grounding shield. The test electrode comprises at least one of a rectangular sensor, a rotating electrode sensor and a micro sensor. The number of the test electrodes is n, and the value range of n is n≥6. The electrode assembly converts the measured capacitance value C into a voltage signal, and performs analog-to-digital conversion on the voltage signal through phase-sensitive demodulation and a low-pass filter to obtain a mathematical signal.

[0127] like Figure 7 As shown, the device for monitoring the state of the reactor includes a main reactor, an electrode assembly 17, a capacitance test module 15, a data processor 8 and an image reconstruction computer 7, wherein the main reactor includes a reactor cone bottom 11, a reactor reaction zone 18 and a reactor separation zone 6, a heating system 16 is arranged outside the reaction zone, an inert substance 14 is located at the bottom of the reactor, a gas source enters the reactor through an air intake system 9, an electrode assembly 17 is placed on the outer wall of the reactor, and the height of the electrode assembly 17 from the bottom of the reactor is H, the capacitance test module 15 displays the measured capacitance value C, after the data processor 8 performs data processing, the data is transmitted to the image reconstruction computer 7 for algorithm iteration and image reconstruction, and the real-time porosity and characteristic value of the fluidized bed are obtained.

[0128] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. For the experimental methods in the following examples where specific conditions are not specified, conventional conditions are usually used, or the conditions recommended by the manufacturer. Ratios and percentages are based on molar amounts unless otherwise specified.

[0129] Raw material source and preparation:

[0130] (1) Inert substances:

[0131] Ceramic spherical particles (particle size 500μm-1000μm), products of Shandong Qitai Industrial Ceramics Co., Ltd., specifications: 0.5-1mm;

[0132] High carbon material (particle size 200 μm-400 μm), product of Shandong Dazhan Nanomaterial Co., Ltd., number: GTY-301;

[0133] Alumina (particle size 0.2mm-3mm), product of Shandong Qitai Industrial Ceramics Co., Ltd., specifications: 0.5-1mm, 1mm, 2mm, 3mm;

[0134] Floating beads 40-100 mesh, products of Dongying Wanjia Energy Saving Materials Co., Ltd., specifications: 40-100 mesh;

[0135] Perlite 70-90 mesh, a product of Xinyang City Shihe District Houpu Mining Materials Factory, specification: 70-90 mesh;

[0136] The particle size of coconut shell carbon particles is 10-60 mesh, and it is a product of Changge Tanernuo Catalytic Technology Co., Ltd. with a specification of 30-110 mesh.

[0137] (2) Catalyst

[0138] Iron nitrate, cobalt nitrate, aluminum nitrate, ammonia water, and ammonium carbonate were all purchased from Zibo Aiken Economic and Trade Co., Ltd.; purified water was produced by Shandong Dazhan Nanomaterials Co., Ltd. after distillation and purification.

[0139] The micronized catalyst was prepared by the following method:

[0140] Mix ferric nitrate, cobalt nitrate, aluminum nitrate and purified water according to the proportion and dissolve them until they are uniform and free of particles to form an acid solution;

[0141] Ammonia water, ammonium carbonate and purified water are mixed according to the proportions, dissolved evenly and without particles, to form lye;

[0142] Precipitation titration: Control the pH titration by controlling the flow rate of the acid and alkali solution. After the titration is completed, age for 2-4 hours;

[0143] Filter pressing: The mixture after the titration reaction is passed through a plate and frame or centrifuge to filter out most of the water and collect the filter cake;

[0144] Drying and roasting: The filter cake is dried and roasted at high temperature. After roasting, it is crushed into particles with uniform particle size and packaged.

[0145] (3) Gas:

[0146] Hydrogen: purchased from Zibo Anze Special Gas Co., Ltd.

[0147] Propylene: purchased from Shandong Jingbo Petrochemical Co., Ltd.

[0148] Nitrogen: purchased from Praxair (Qingdao) Industrial Gas Co., Ltd.

[0149] (4) Device

[0150] The device for monitoring the reactor status adopts the capacitance tomography ECVT produced by Tech4Imaging Company of the United States.

[0151] Embodiment 1:

[0152] Example 1 uses Figure 4 The device shown in the figure is used to place ceramic spherical particles (particle size 100 μm-300 μm) into the fluidized bed. Then, nitrogen is introduced into the fluidized bed 10 from the gas input end 111 for 5-20 minutes (1000 L / min) to drive away the residual oxygen in the fluidized bed, so that the ceramic spherical particles are in a continuous fluidized state, the temperature is raised to the set temperature of 660 degrees Celsius and stabilized, the fluidized bed is controlled to be set to input a micro-powdered catalyst (50-80 mesh) from the catalyst input end 112, and then a mixed gas of hydrogen, propylene and nitrogen in a ratio of 1:6:7 is input from the gas source input end 111, and the gas speed is controlled to be 320 L / h to realize the fluidized growth of carbon nanotubes, and separation is realized in the separation zone. The carbon nanotubes leave the fluidized bed from the outflow end and enter the collector 13 through the connecting pipe 12 to collect the carbon nanotubes. The tail gas leaves the collector through the filter 131. The continuous introduction of catalyst and gas source realizes the continuous and uniform preparation of carbon nanotubes.

[0153] Embodiment 2:

[0154] Example 2 uses Figure 4The device shown in the figure is used to put 20 kg of high carbon material (particle size 200 μm-400 μm) into the fluidized bed, and then nitrogen is input into the fluidized bed 10 from the gas source input end 111 for 5-20 minutes (500 L / min) to drive away the residual oxygen in the fluidized bed, so that the high carbon material is in a continuous fluidized state, and the temperature is raised to the set temperature of 660 degrees Celsius and stabilized, and the fluidized bed is controlled to input (80-100 mesh) micro-powdered catalyst from the catalyst input end 112, and then a mixed gas of hydrogen, propylene and nitrogen in a ratio of 1:7:10 is input from the gas source input end 111, and the gas velocity is controlled to realize the fluidized growth of carbon nanotubes, and separation is realized in the separation zone, and the carbon nanotubes leave the fluidized bed from the outflow end, and enter the collector 13 through the connecting pipe 12 to collect the carbon nanotubes. The tail gas leaves the collector through the filter 131. The catalyst (0.9-1.1 Kg / h) and gas source (900 L / min) are continuously introduced to achieve continuous and uniform preparation of carbon nanotubes.

[0155] Embodiment 3:

[0156] Example 3 uses Figure 4 The device shown in the figure is used to put 1-30g of aluminum oxide (particle size 0.2mm-3mm) into the fluidized bed. Then, nitrogen is input into the fluidized bed 10 from the gas source input end 111 for 5-20 minutes (100L / h) to drive away the residual oxygen in the fluidized bed, so that the aluminum oxide is in a continuous fluidized state, and the temperature is raised to the set temperature of 670 degrees Celsius and stabilized. The fluidized bed is controlled to input (80-100 mesh) micro-powdered catalyst from the catalyst input end 112, and then a mixed gas of hydrogen, propylene and nitrogen in a ratio of 5:8:10 is input from the gas source input end 111. The gas velocity is controlled to realize the fluidized growth of carbon nanotubes, and separation is realized in the separation zone. The carbon nanotubes leave the fluidized bed from the outflow end and enter the collector 13 through the connecting pipe 12 to collect the carbon nanotubes. The tail gas leaves the collector through the filter 131. The catalyst and gas source (230L / h) are continuously introduced to realize the continuous and uniform preparation of carbon nanotubes.

[0157] Embodiment 4:

[0158] Example 4 uses Figure 4The device shown in the figure is used to carry out the process, and floating beads of 40-100 mesh (total mass 10g) are placed in the fluidized bed. Then, nitrogen is input into the fluidized bed 10 from the gas source input end 111 for 5-20 minutes (100-200L / h) to drive away the residual oxygen in the fluidized bed, so that the alumina is in a continuous fluidized state, and the temperature is raised to the set temperature of 670 degrees Celsius and stabilized. The fluidized bed is set to input a micro-powdered catalyst (80-100 mesh) from the catalyst input end 112, and then a mixed gas of hydrogen, propylene and nitrogen in a ratio of 5:8:10 is input from the gas source input end 111, and the gas velocity is controlled to realize the fluidized growth of carbon nanotubes, and separation is realized in the separation zone. The carbon nanotubes leave the fluidized bed from the outflow end and enter the collector 13 through the connecting pipe 12 to collect the carbon nanotubes. The tail gas leaves the collector through the filter 131. The catalyst and gas source (280L / h) are continuously introduced to realize the continuous and uniform preparation of carbon nanotubes.

[0159] Example 5

[0160] Example 5 uses Figure 4 The device shown in the figure is used to place pearlite of 70-90 mesh (total mass 10g) into the fluidized bed, and then nitrogen is input into the fluidized bed 10 from the gas source input end 111 for 5-20 minutes (150L / h) to drive away the residual oxygen in the fluidized bed, so that the alumina is in a continuous fluidized state, the temperature is raised to the set temperature of 670 degrees Celsius and stabilized, the fluidized bed is controlled to input (80-100 mesh) micro-powdered catalyst from the catalyst input end 112, and the reducing gas (hydrogen) is input for 5min (50L / h), after reduction, the mixed gas of propylene and nitrogen in a ratio of 8:15 is input from the gas source input end 111, the gas velocity is controlled to realize the fluidized growth of carbon nanotubes, and separation is realized in the separation zone, the carbon nanotubes leave the fluidized bed from the outflow end, and enter the collector 13 through the connecting pipe 12 to collect the carbon nanotubes. The tail gas leaves the collector through the filter 131. The catalyst and gas source (230 L / h) were continuously introduced to achieve continuous and uniform preparation of carbon nanotubes.

[0161] Example 6

[0162] Example 6 uses Figure 4The device shown in the figure is carried out, coconut shell carbon particles (particle size 10-60 mesh) are placed in the fluidized bed, and then nitrogen is input into the fluidized bed 10 from the gas source input end 111 for 5-20 minutes (1000L / min) to drive away the residual oxygen in the fluidized bed, ensure an oxygen-free environment and make the unloaded catalyst particles in a continuous fluidized state, increase the temperature to a set temperature of 660 degrees Celsius and stabilize, control the fluidized bed setting to input (50-80 mesh) micro-powdered catalyst from the catalyst input end 112, and then input a mixed gas of hydrogen, propylene and nitrogen in a ratio of 1:6:7 from the gas source input end 111, control the gas velocity to achieve fluidized growth of carbon nanotubes, and achieve separation in the separation zone, the carbon nanotubes leave the fluidized bed at the first end 103 of the fluidized bed, and enter the collector 13 through the connecting pipe 12 to collect the carbon nanotubes. The tail gas leaves the collector through the filter 131. Continuous introduction of catalyst and gas source realizes the continuous and uniform preparation of carbon nanotubes.

[0163] Comparative Example

[0164] The comparative example also uses Figure 4 The device shown is carried out, nitrogen is input into the fluidized bed 10 from the gas source input end 111 for 5-20 minutes (100L / h) to drive away the residual oxygen in the fluidized bed, the temperature is raised to the set temperature of 670 degrees Celsius and stabilized, the fluidized bed is set to input (80-100 mesh) micro-powdered catalyst from the catalyst input end 112, and then a mixed gas of hydrogen, propylene and nitrogen in a ratio of 5:8:10 is input from the gas source input end 111, the gas velocity is controlled to achieve fluidized growth of carbon nanotubes, and separation is achieved in the separation zone, the carbon nanotubes leave the fluidized bed at the first end 103 of the fluidized bed, and enter the collector 13 through the connecting pipe 12 to collect the carbon nanotubes. The tail gas leaves the collector through the filter 131. The catalyst and gas source (230L / h) are continuously introduced to achieve continuous and uniform preparation of carbon nanotubes.

[0165] Product performance testing

[0166] (1) Four-probe resistivity:

[0167] The resistivity of the product is tested according to the national standard GB / T 39978-2021 Nanotechnology Carbon Nanotube Powder Resistivity Four-Probe Method;

[0168] (2) Specific surface area test:

[0169] According to the national standard GB / T 10722, the specific surface area of ​​the product is tested using a nitrogen physical adsorption instrument;

[0170] (3) Microscopic morphology test:

[0171] The diameter of carbon nanotubes was determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM);

[0172] (4)Magnification

[0173] The ratio is calculated by the output of carbon material product / the input of carbon source material.

[0174] The performance tests of the products obtained in Examples 1-6 and Comparative Examples were performed, and the results are shown in the following table:

[0175]

[0176] From the above results, it can be seen that the addition of inert substances plays a role in fluidization. Without the addition of inert substance particles, the yield of carbon materials is extremely low. After adding inert substances, the yield increases, the specific surface area increases, and the resistivity decreases. The best results are obtained by using high carbon substances, alumina, floating beads, perlite and coconut shell carbon as inert substances.

[0177] Embodiment 7:

[0178] Example 7 uses Figure 1 The device shown in the figure is carried out, coconut shell carbon particles (particle size 10-60 mesh) are introduced into the fluidized bed, and the coconut shell carbon particles at the cone bottom 101 of the main reactor are in a continuous fluidized state under the action of gas. The heating device 15 raises the temperature to the set temperature of 660 degrees Celsius and stabilizes it. The fluidized bed is controlled to input a micro-powdered catalyst (50-80 mesh) from the catalyst input end, and a mixed gas of hydrogen, propylene and nitrogen in a ratio of 1:6:7 is input from the gas source input end. The gas rate is controlled to be 320L / h, so that the fluidized growth of carbon nanotubes is realized, and separation is realized in the separation zone. The catalyst and the gas source are continuously introduced to realize the continuous and uniform preparation of carbon nanotubes. The reaction lasts for 120 hours, and each group of experiments is repeated 5 times to detect the reaction process, the mass content of H2 in the tail gas, and the performance of the carbon nanotube product.

[0179] In this series of embodiments, the wound carbon nanotubes use a catalyst with an iron-cobalt active component and an alumina ball carrier; the arrayed carbon nanotubes use a catalyst with an iron-cobalt active component and a flaky alumina carrier.

[0180] Analysis of relevant properties of wound carbon nanotubes

[0181]

[0182] During the growth of carbon nanotubes in different experiments, the volume content of H2 in the tail gas was sampled and analyzed every 1 hour, and the results were as follows:

[0183]

[0184]

[0185] Analysis of related properties of array carbon nanotubes

[0186]

[0187] During the growth of carbon nanotubes in different experiments, the volume content of H2 in the tail gas was sampled and analyzed every 1 hour, and the results were as follows:

[0188]

[0189]

[0190] Example 8

[0191] Example 8 uses Figure 7 The device shown is carried out, that is, Figure 1 On the basis of the invention, a device for monitoring the state of the reactor is added, coconut shell carbon particles (particle size 10-60 mesh) are placed in the fluidized bed, the coconut shell carbon particles 14 at the cone bottom 11 of the main reactor are in a continuous fluidized state under the action of gas, the heating device 16 raises the temperature to the set temperature of 660 degrees Celsius and stabilizes it, the fluidized bed is controlled to input a micro-powdered catalyst (50-80 mesh) from the catalyst input end, and a mixed gas of hydrogen, propylene and nitrogen in a ratio of 1:6:7 is input through the air intake system 9 to realize the fluidized growth of carbon nanotubes, and the electrode The component 17 is placed on the outer wall of the reactor, and the height of the electrode component 17 from the bottom of the reactor is H=10m. The capacitance value Cm of the gas source and the capacitance value Cn of the carbon nanotubes are recorded, and these initial values ​​are input into the data processor. The capacitance test module 15 displays the real-time measured capacitance value C, and the dielectric constant ε is calculated and input into the computer. The data processor automatically converts the capacitance C value and transmits the converted corresponding data to the image reconstruction computer, and transmits s(i) to the reconstruction computer to obtain the real-time porosity and characteristic value of the fluidized bed.

[0192] When preparing the entangled carbon nanotubes, observe whether the characteristic value θ displayed by the image reconstruction computer is within the range of 2≤θ≤7. When it exceeds this range, adjust the volume V2 parameter of the gas source to make θ return to the above range. The reaction is continued for 100 hours. The properties of the entangled carbon nanotubes prepared by the reaction are as follows:

[0193] Analysis of relevant properties of wound carbon nanotubes

[0194]

[0195]

[0196] During the growth of carbon nanotubes in different experiments, the volume content of H2 in the tail gas was sampled and analyzed every 1 hour, and the results were as follows:

[0197] Repeat the experiment <![CDATA[C H11 ]]> <![CDATA[C H12 ]]> <![CDATA[C H13 ]]> <![CDATA[C H14 ]]> <![CDATA[C H15 ]]> F 58 56 56 58 57 G 60 57 58 55 57 H 56 55 58 57 56 I 55 58 59 56 56 J 58 57 56 55 57

[0198] When preparing array carbon nanotubes, observe whether the characteristic value θ displayed by the image reconstruction computer is within the range of 5≤θ≤10. When it exceeds this range, adjust the temperature T of the reactor to make θ return to the above range, and continue the reaction for 150 hours.

[0199] Analysis of related properties of array carbon nanotubes

[0200]

[0201]

[0202] During the growth of carbon nanotubes in different experiments, samples were taken every hour to analyze the volume content of H2 in the exhaust gas.

[0203] Repeat the experiment <![CDATA[C H11 ]]> <![CDATA[C H12 ]]> <![CDATA[C H13 ]]> <![CDATA[C H14 ]]> <![CDATA[C H15 ]]> F 51 53 52 54 53 G 50 52 53 51 53 H 53 53 54 54 55 I 52 55 53 53 52 J 55 54 52 55 53

[0204] The standard deviations of various parameters of entangled carbon nanotubes and arrayed carbon nanotubes were calculated, and the results are as follows:

[0205]

[0206] By comparing the performance of the carbon nanotubes prepared in Example 7 and Example 8, it can be seen that since Example 8 adds a device for monitoring the reactor status to the reactor device used in Example 7, the characteristic value θ of the reaction process can be timely controlled within the set target range. Therefore, the standard deviation of each property of the carbon nanotubes prepared in Example 8 is more stable and the control range is finer than that in Example 7.

[0207] The process method for preparing carbon materials of the present invention, the amount of raw materials used and the process parameters are not limited to the above-mentioned embodiments. After reading the above teaching content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A method for monitoring the status of a carbon material preparation device, characterized in that: The method comprises the following steps: a) Initial data collection: record the capacitance value Cm of the set gas source and the capacitance value Cn of the carbon nanotube respectively; b) real-time data collection: placing an electrode assembly on the outer wall of the device, with the height of the electrode assembly from the bottom of the device being H; recording the capacitance value C measured by the electrode assembly, and converting the capacitance value C into a mathematical signal; c) Image reconstruction: the mathematical signal obtained in step b) is subjected to algorithm iteration to calculate the dielectric constant of each unit, and then image reconstruction is performed to obtain the void ratio P in the reactor at the corresponding time, and the required characteristic value θ is calculated through the void ratio P; d) Data adjustment: Compare the eigenvalue θ obtained in step c with the standard eigenvalue θs. When the eigenvalue θ is outside the range of the standard eigenvalue θs, adjust the parameters so that the eigenvalue is within the range of the standard eigenvalue θs.

2. The method according to claim 1, characterized in that The electrode assembly converts the measured capacitance value C into a voltage signal, and performs analog-to-digital conversion on the voltage signal through phase-sensitive demodulation and a low-pass filter to obtain a mathematical signal.

3. The method according to claim 1, characterized in that The characteristic value calculation formula is: Wherein, P is the porosity of the reactor and is the height of the reactor.

4. The method according to claim 1, characterized in that For the wound carbon nanotubes, the standard eigenvalue θs is [2, 7], and for the arrayed carbon nanotubes, the standard eigenvalue θs is [5, 10].

5. The method according to claim 1, characterized in that P is calculated according to the C normalization formula and the image reconstruction formula. The normalization formula of C is: C r =(CC m ) / (C n -C m ) Formula (3) The image reconstruction formula is: In formula (4), is the normalized value of capacitance C, is the pixel gray value of the dielectric constant distribution image in the measured field, is the average sensitivity of the medium at microelement i, and is the area of ​​microelement i.

6. The method according to claim 1, characterized in that The device comprises a main reactor for performing CVD reaction and a collector for collecting carbon materials, wherein the main reactor has an input end, an outflow end and a reactor body, wherein the reactor body comprises a reaction zone and a separation zone, and gas and catalyst are provided to the reaction zone through the input end; The outflow end is located at the upper part of the separation zone, and the separation zone is connected with the collector through the outflow end via a connecting pipe; The collector is used to collect the carbon material.

7. The method according to claim 1, characterized in that The collector comprises a filter, and the filter is used to separate the carbon material from the tail gas discharged from the main reactor.

8. The method according to claim 6, characterized in that The main reactor is a conical reactor with a conical bottom structure, and the angle of the cone bottom is 5° to 50°.

9. The method according to claim 6, characterized in that The electrode assembly is disposed on the outer wall surface of the separation zone of the reactor body.

10. The method according to claim 1, characterized in that The value range of H is 10D≤H≤30D, wherein D is the diameter of the reaction zone of the reactor.

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