CN105217599B - A system and method for synthesizing carbon nanotubes - Google Patents

Abstract

The invention discloses a kind of system and method for synthesizing carbon nanotubes, described system includes circulation flame combustion domain, carbon source is pyrolyzed domain, CNT composite field, finished product collecting unit and chemical reaction raw material supply unit；And core reaction chamber, circulation flame combustion room, flame thrower, top umbrella；It is indoor that described circulation flame combustion domain is located at circulation flame combustion, described core reaction chamber is located at the center of circulation flame combustion room, described carbon source pyrolysis domain is located at core reaction intracavity bottom, described CNT composite field is located at core reaction intracavity top, the jet of described flame thrower is located at the side wall of circulation flame combustion room, described top umbrella is located at the top in core reaction chamber, described finished product collecting unit is located above the umbrella of top, and described chemical reaction raw material supply unit is to circulation flame combustion room and core reaction intracavity feed.

Description

A system and method for synthesizing carbon nanotubes

technical field

The invention belongs to the technical field of carbon nanotube synthesis, and in particular relates to a system and method for synthesizing carbon nanotubes.

Background technique

Carbon nanotubes are essentially an allotrope of carbon, which can be regarded as a nano-sized seamless hollow tubular structure formed by curling single-layer or multi-layer graphite sheets. The single-layered carbon nanotubes are called single-walled carbon nanotubes; the coaxial tubes rolled into multiple layers are called multi-walled carbon nanotubes, and the interlayer spacing is about 0.34nm. As a typical one-dimensional carbon nanomaterial, carbon nanotubes have unique electronic structures and physical and chemical properties. For example: extremely large aspect ratio and specific surface area, high elastic modulus and flexural strength, strong acid and alkali resistance, excellent heat transfer and electrical conductivity, self-lubrication, biocompatibility, etc. Comprehensive performance. Therefore, the application of carbon nanotubes in various fields has aroused widespread concern in the scientific community, and the prospects are very promising. The most important application areas include: supercapacitors, hydrogen storage materials, field emitters, atomic force microscope probes, lithium-ion batteries, chemical sensors, catalyst supports, reinforced composite materials, etc. In view of the various excellent properties of carbon nanotubes and the huge application value derived from them, how to synthesize carbon nanotubes with high efficiency, low cost, controllability and large scale has become the goal pursued by many scholars at home and abroad. In line with this purpose, the synthesis methods of carbon nanotubes are constantly being updated. There are many methods for synthesizing carbon nanotubes, mainly including: arc discharge method, laser evaporation method, chemical vapor deposition method (CVD method) and the relatively new flame method at present. The research of the first three methods is relatively mature, but they are greatly restricted in terms of scale, cost, equipment, operation and continuity. The various flame methods known today have basically achieved the goals of simple equipment, low cost, and convenient operation, but most of them have low output, low utilization rate of carbon source, and it is difficult to meet the requirements of controllable, batch-scale production. , Continuous production requirements.

To sum up, developing a method capable of efficiently, cheaply, controllably, batch-wise and continuously synthesizing carbon nanotubes is still the primary problem to be overcome in this technical field. The present invention is just a kind of brand-new solution proposed at this thorny problem.

Contents of the invention

The purpose of the present invention is to provide a brand-new solution for solving the above problems, that is, a system for efficiently and controllably synthesizing carbon nanotubes.

A system for synthesizing carbon nanotubes, including an annular flame combustion domain, a carbon source pyrolysis domain, a carbon nanotube synthesis domain, a product collection unit, and a chemical reaction raw material supply unit; and a core reaction chamber, an annular flame combustion chamber, and a flame injector , top umbrella; the circulation flame combustion domain is located in the circulation flame combustion chamber, the core reaction chamber is located in the center of the circulation flame combustion chamber, the carbon source pyrolysis domain is located in the lower part of the core reaction chamber, and the carbon nanotube synthesis domain Located in the upper part of the core reaction chamber, the injection port of the flame injector is located on the side wall of the circular flame combustion chamber, the top umbrella is located on the top of the core reaction chamber, the finished product collection unit is located above the top umbrella, and the chemical reaction raw material The supply unit supplies material to the circulating flame combustion chamber and the core reaction chamber.

Further, the finished product collection unit includes a bouncing finished product collection probe and a conveyor belt.

Further, the chemical reaction raw material supply unit includes carbon source supply equipment, auxiliary gas supply equipment, catalyst supply equipment, fuel supply equipment, and oxidant supply equipment.

Further, the core reaction chamber is in the shape of a circular tube, the shape of the circulating flame combustion chamber is a prism, and the cross-section of its outer wall is a polygon, and the injection ports of the flame injector are arranged on each end point or each side of the polygon.

Further, one set of the flame injectors is installed at the same height of the side wall of the circular flame combustion chamber or multiple sets are installed at different heights, and each of the same group of flame injectors is installed on the side wall of the circular flame combustion chamber at the same height.

Further, the fuel and the oxidant are sprayed out after being premixed inside the flame injector, or sprayed out from respective channels in the flame injector, and then meet in the annular flame combustion chamber.

Further, the outlet air flow of the flame injector is a straight jet or a rotating jet, and the geometric axis of the air flow is tangent to the outer wall of the circular tube-shaped core reaction chamber; after the air flow ejected from each flame injector merges, A flame that burns violently and flows rapidly around the outer wall of the core reaction chamber will be formed in the central area of the circular flame combustion chamber.

Further, when the bouncing finished product collection probe reaches directly above the carbon nanotube synthesis domain, it pops up automatically and extends into a predetermined position in the carbon nanotube synthesis domain. At the same time, the conveyor belt stops running immediately so as to collect the finished product Carbon nanotubes; when the probe's residence time reaches the preset finished product collection time, the probe will automatically spring back to its original position, and the conveyor belt will continue to run immediately.

Further, the carbon source supplied by the carbon source supply device is gas, liquid, solid or plasma carbon-containing raw material.

The auxiliary gas supplied by the auxiliary gas supply device refers to hydrogen and inert gas or low activity gas.

The catalyst supplied by the catalyst supply equipment is a simple substance or alloy of a transition metal element or a compound of a transition metal element or a mixture of the above-mentioned simple substance, alloy or compound.

The fuel supplied by the fuel supply equipment is gas, liquid or solid combustibles with high calorific value.

The oxidant supplied by the oxidant supply device is air, pure oxygen or oxygen-nitrogen mixed gas.

Further, the system also includes:

(1) Bypass system. When the bypass system needs to change the operating conditions or the system needs to be shut down due to problems, the gas with cooling function can be directly put into the system, and the gas is an inert gas or a low-activity gas;

(2) Temperature sensor and digital instrument connected with it: used to monitor the temperature of carbon source pyrolysis domain and carbon nanotube synthesis domain;

(3) Digital timer: used in conjunction with the temperature sensor, it can realize the automatic pop-up and reset action of the finished product collection probe, as well as the stop operation and continuous operation action of the conveyor belt;

(4) Igniter: When the system starts to operate, it is used to ignite the fuel sprayed from the flamethrower;

(5) The impeller and deflector capable of providing swirl conditions, so that the outlet airflow of the flamethrower forms a swirling jet, so as to cooperate with the control of the combustion characteristics of the flame;

(6) Cold ash hopper: In coal-fueled systems, it is installed at the bottom of the circulating flame combustion chamber to collect ashes.

The present invention also provides a method for synthesizing carbon nanotubes using the above system, comprising the following steps:

(1) Start the fuel supply equipment and oxidant supply equipment, deliver fuel and oxidant to the flamethrower, and prepare for ignition;

(2) Start the auxiliary gas supply equipment to deliver cooling gas (such as helium, nitrogen, etc., in order to save costs, directly use air) into the core reaction chamber, so as not to burn out the core reaction chamber with high-temperature flames after ignition;

(3) Start the igniter to ignite the mixture of fuel and oxidant sprayed from the flamethrower;

(4) After the circulating flame in the combustion chamber is formed, adjust the consumption of fuel and oxidant to the required value;

(5) After the circulating flame burns stably, and the temperature of the circulating flame at different heights in the circulating flame combustion chamber reaches the design value, start the carbon source supply equipment and the catalyst supply equipment, and transport the carbon source and the catalyst to the core reaction chamber;

(6) Increase the amount of carbon source and catalyst to the design parameters, so that the carbon source begins to pyrolyze;

(7) After the temperature of the carbon source pyrolysis domain and the carbon nanotube synthesis domain both reach the design value, start the finished product collection unit;

(8) When the first bouncing-type finished product collection probe arrives directly above the carbon nanotube synthesis domain along with the conveyor belt, it will automatically pop up and extend into the predetermined position in the carbon nanotube synthesis domain to start collecting the synthesized carbon nanotubes. tube; at the same time, the conveyor belt will stop running immediately;

(9) After the residence time of the first probe in the carbon nanotube synthesis domain reaches the preset product collection time, the probe will automatically spring back to its original position, and the conveyor belt will continue to run immediately;

(10) Repeat the steps of (8) and (9) for the continuous bouncing finished product collection probe in turn until the system stops running;

When it is necessary to change the operating conditions or the system needs to be shut down due to problems, follow the steps below:

(11) Turn off the fuel supply equipment and oxidant supply equipment, stop delivering fuel and oxidant to the flame injector, and extinguish the flame in the combustion chamber;

(12) Turn off the carbon source supply equipment and catalyst supply equipment, stop transporting carbon source and catalyst to the core reaction chamber, and avoid wasting raw materials;

(13) close the finished product collecting unit, make it stop running;

(14) Open the bypass system, deliver cooling gas (such as helium, nitrogen, etc., in order to save costs, directly use air) into the flamethrower and the core reaction chamber, and spray the cooling gas into the combustion chamber for cooling Flame injectors, combustion chambers and core reaction chambers, to avoid damage to them by the residual high temperature after flameout in the combustion chamber;

(15) After the temperature in all parts of the combustion chamber drops below 200°C, turn off the auxiliary gas supply equipment.

By applying the system and process for synthesizing carbon nanotubes in the present invention, high-quality carbon nanotubes and arrays thereof can be synthesized efficiently, cheaply, controllably, in batches, and continuously.

Description of drawings

Fig. 1 is a schematic diagram of a carbon nanotube synthesis system of the present invention.

Figure 2 shows three reference examples of flamethrower arrangements.

Fig. 3 shows the approximate temperature distribution on a certain cross-section in the combustion zone of the circulating flame after numerical simulation of the reference example in Fig. 2(a).

FIG. 4 is a high-magnification transmission electron micrograph of the single-walled carbon nanotubes prepared in Example 1. FIG.

FIG. 5 is a Raman spectrum of the single-walled carbon nanotubes prepared in Example 1 in the range of 0-2500 cm ^-1 Raman shift.

FIG. 6 is a scanning electron micrograph of the carbon nanotube array prepared in Example 2.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Fig. 1 is a schematic diagram of a carbon nanotube synthesis system of the present invention. It is described with a preferred embodiment of the present invention. For easy distinction, in Figure 1, the theoretical components of the system are marked with the number 1 at the beginning, and the physical structural components of the system are marked with the number 2 at the beginning.

In FIG. 1 , the circular flame combustion domain is represented by 101 , the carbon source pyrolysis domain is represented by 102 , and the carbon nanotube synthesis domain is represented by 103 . This representation method is only to illustrate the approximate positions of the carbon source pyrolysis domain and the carbon nanotube synthesis domain in the core reaction chamber. In fact, there is no clear boundary between the carbon source pyrolysis domain and the carbon nanotube synthesis domain. In addition, 104 represents a finished product collection unit, and 105 represents a chemical reaction raw material supply unit.

In Fig. 1, 201 represents the core reaction chamber, 202 represents the circulating flame combustion chamber, 203 represents the flame injection port, 204 represents the top umbrella, 205 represents the finished product collection probe, 206 represents the bouncing probe conveyor belt, 207 represents the carbon source supply equipment, and 208 represents Auxiliary gas supply equipment, 209 denotes catalyst supply equipment, 210 denotes fuel supply equipment, and 211 denotes oxidant supply equipment. Wherein, the flame injection port (203) refers to the outlet of the flame injector, that is, the interface between the flame injector and the circulating flame combustion chamber.

Figure 2 shows three reference examples of flamethrower arrangements. Among them, (a) is a regular square arrangement, (b) is a regular hexagonal arrangement, and (c) is a special arrangement. In this arrangement, the core reaction chamber is a square tube, and the cross-section of its outer wall is Rectangular, the cross-section of the combustion chamber is circular, and the flamethrowers are arranged on the four endpoints of any two mutually perpendicular diameters of the circle.

A system for synthesizing and synthesizing carbon nanotubes by a circular flame, including: a circular flame combustion domain, a carbon source pyrolysis domain, a carbon nanotube synthesis domain, a finished product collection unit, and a chemical reaction raw material supply unit. The relationship between them is shown in Figure 1 Show.

In addition, the system may also include some other auxiliary components. For example, when the operating conditions need to be changed or the system needs to be shut down due to system problems, the bypass system is set up to cool the flame injector, combustion chamber and core reaction chamber in time to ensure the safety of the equipment.

In terms of physical structure, the main components of the system are: core reaction chamber, circulating flame combustion chamber, flame injector, top umbrella, finished product collection equipment and chemical reaction raw material supply equipment.

In addition, the system may also include some other auxiliary construction components. For example, a cold ash hopper for collecting ashes; an impeller and a deflector provided to make the outlet airflow of the flamethrower form a rotating jet.

The combustion area of the circulating flame is the distribution range of the circulating flame in space. The combustion process of the circulating flame is mainly carried out in the circulating flame combustion chamber.

The carbon source pyrolysis domain is the spatial range where the carbon source is pyrolyzed under high temperature conditions to generate carbon atoms. The pyrolysis process of carbon source is mainly carried out in the middle and lower part of the core reaction chamber.

The carbon nanotube synthesis domain is the spatial range in which carbon atoms synthesize carbon nanotubes under suitable conditions (such as temperature, catalyst, etc.). The synthesis process of carbon nanotubes is mainly carried out in the middle and upper part of the core reaction chamber and near the outlet periphery. In some implementation cases, the synthesis process of carbon nanotubes can even be carried out in the top umbrella.

The finished product collection unit is a module used to collect the synthesized carbon nanotubes, which includes a series of equipment, and the specific equipment will be introduced later.

The chemical reaction raw material supply unit is a module used to provide various chemical raw materials (such as carbon sources, catalysts, fuels, etc.) A series of equipment, specific equipment will be introduced later.

From the perspective of engineering thermodynamics, the core reaction chamber can be regarded as an open system that exchanges matter and energy with the outside world and contains chemical reactions, providing a series of continuous processes from carbon source pyrolysis to carbon nanotube synthesis. required space. From the pyrolysis of carbon source to the synthesis of carbon nanotubes is a series of continuous processes. This series of continuous processes are all carried out in the core reaction chamber. There is no gap between the pyrolysis domain of carbon source and the synthesis domain of carbon nanotubes. Clear boundaries. Usually, the middle and lower parts of the core reaction chamber provide carbon source pyrolysis domains, while the middle and upper parts and the periphery of the outlet provide carbon nanotube synthesis domains.

In order to match the hydrodynamic characteristics of the external circulating flame, the core reaction chamber should be made into a circular tube, so that the best heating effect can be obtained. Of course, it is also possible to make the core reaction chamber into other shapes.

The bottom of the core reaction chamber is connected to the chemical reaction raw material supply unit, and chemical reaction raw materials such as carbon source, catalyst, and auxiliary gas required for the synthesis of carbon nanotubes are input into the core reaction chamber.

In order to monitor the temperature of carbon source pyrolysis domain and carbon nanotube synthesis domain, several temperature measurement points should be set along the height direction near the inner wall of the core reaction chamber, which requires temperature sensors to be set at these places and connected to on the external digital gauge.

The surrounding flame combustion chamber provides the required space for the combustion of the surrounding flame. It can also be regarded as an open system that exchanges matter and energy with the outside world and includes chemical reactions.

The shape of the circulating flame combustion chamber is not completely fixed, and it can be made into a cylindrical shape, a prismatic shape, a conical shape, a pyramid shape, etc. according to specific working conditions. For non-special occasions, in order to facilitate the installation of flamethrowers, a prismatic annular flame combustion chamber should be used.

In order to monitor the temperature of the circulating flame at different heights in the combustion chamber, multiple temperature measuring points should be set along the height direction near the outer wall of the core reaction chamber, which requires setting temperature sensors at these places and connecting them to external digital instruments superior.

The flame injector is used to inject fuel and oxidant into the combustion chamber, so as to form a circular flame around the core reaction chamber in the combustion chamber, so as to provide required energy for a series of chemical reactions of synthesizing carbon nanotubes. The inlet of the flame injector is connected with the chemical reaction raw material supply unit, through which the chemical raw materials such as fuel and oxidant required for the combustion process of the circulating flame are input, and then sprayed into the interior of the combustion chamber through the outlet. After the fuel and oxidant are sprayed out from the flame injector, they start to burn, forming the most intense combustion circular flame in the center of the combustion chamber (that is, around the outer wall of the core reaction chamber).

Flame throwers are mounted on the side walls of the combustion chamber. One set can be installed at a certain height of the combustion chamber (single-layer arrangement), or multiple sets can be installed along the height direction of the combustion chamber (multi-layer arrangement), depending on the needs of the embodiment.

The fuel and the oxidant can be premixed in the flame injector before spraying out, or they can be sprayed out from their respective channels in the flame injector, and then meet in the combustion chamber. Different mixing methods can be selected in different implementation cases.

In order to control the combustion characteristics of the flame, the outlet air flow of the flamethrower can be either a straight jet or a rotating jet, and different jet modes can be selected in different implementation cases. In order to realize the rotating jet, some auxiliary components that can provide swirling conditions should be installed, such as impellers, deflectors, etc.

In addition, auxiliary components such as an igniter must be arranged at the outlet of one (or more) flame injectors. When the system starts to operate, the igniter will ignite the fuel sprayed from the flame injector.

The top umbrella is a part installed on the top of the core reaction chamber. It has a large cross-sectional area and can even cover the top of the circulating flame combustion chamber, hence the name. Through it, multiple purposes and effects can be achieved.

The shape of the top umbrella does not have a completely fixed pattern, and it can be made into a disc shape, a fan shape, a bowl shape, a fin shape, a figure-eight shape, an inverted figure-eight shape, a double figure-eight shape, a double inverted figure-eight shape, and a petal shape according to specific working conditions. Wait.

The finished product collection unit is a general term for a series of equipment used to collect synthesized carbon nanotubes. It mainly includes: finished product collection probe, bouncing probe conveyor belt.

The finished product made in the carbon nanotube synthesis domain is taken out by the collection probe, which can not only go deep into the core reaction chamber to collect carbon nanotubes, but also collect carbon nanotubes in the top umbrella.

The bouncing probe conveyor belt is set up for the requirements of batch and continuous production, and the finished product collection probes are arranged on the conveyor belt according to the designed interval and sequence.

When the finished product collection probe on the conveyor belt reaches the top of the carbon nanotube synthesis domain, it will automatically pop up and extend into the predetermined position in the carbon nanotube synthesis domain. At the same time, the conveyor belt will stop running immediately to collect the finished product carbon nanotubes. When the dwell time of the probe reaches the preset finished product collection time, the probe will automatically spring back to its original position, and the conveyor belt will continue to run immediately.

The automatic pop-up and reset action of the finished product collection probe, as well as the stop operation and continuous operation action of the conveyor belt are realized by auxiliary components such as temperature sensors and digital timers.

The chemical reaction raw material supply equipment is a general term for all equipment used to provide various chemical raw materials required for a series of chemical reactions for synthesizing carbon nanotubes and the combustion process of the circular flame. Mainly include: carbon source supply equipment, catalyst supply equipment, auxiliary gas supply equipment, fuel supply equipment, oxidant supply equipment, etc.

The carbon source supply device is used to provide the system with the necessary carbon source for synthesizing carbon nanotubes. The carbon source can be gas, liquid or solid, even plasma, such as: carbon monoxide, methane, ethanol, benzene, coke, carbon nanoplasma.

The catalyst supply device is used to provide the system with catalysts corresponding to the types of carbon nanotubes required for synthesis. The catalyst can be a simple substance (or alloy) composed of Fe, Co, Ni, Mo, Cr, Cu, Pt and other transition metal elements and its compound or mixture. For example: iron element, nickel element, ferrocene, cobalt nitrate, ferric oxide, iron pentacarbonyl, etc. The appropriate catalyst can be selected according to the technical requirements such as the thickness and wall number of the required carbon nanotubes.

The auxiliary gas supply equipment is used to provide the system with various auxiliary gases required for synthesizing carbon nanotubes. Auxiliary gases are beneficial for the synthesis of carbon nanotubes, each of which plays a different role. For example: hydrogen can promote the adsorption and dissociation of carbon sources, clean up impurities on the surface of carbon tubes, and keep catalysts active; inert gases or low-activity gases (such as helium, neon, argon, nitrogen, etc.) can dilute The catalyst can also play a role in reducing the temperature locally, preventing the carbon nanotubes from being burned at an excessively high temperature. In addition, it can also be used as a carrier for carrying the catalyst in the case of using iron pentacarbonyl as the catalyst.

The fuel supply equipment is used to provide the system with fuel required for combustion. The fuel can be gas, liquid or solid, for example: acetylene, hydrogen, methane, gasoline, diesel, coal powder, sawdust, sulfur, etc.

The oxidant supply device is used to provide the system with the combustion oxidant required for combustion. In order to save costs, the oxidant is first considered to use air. In the case where a higher heating temperature is required, the oxidant can also use a 21:79, 3:7 or 1:1 equal ratio of oxygen-nitrogen mixture, or even pure oxygen.

All the auxiliary components and auxiliary construction parts in this system serve for the above-mentioned composition parts and physical construction parts. For example: the igniter is used to ignite the fuel sprayed from the flamethrower when the system is started; the temperature sensor and digital timer are used for the automatic ejection and reset action of the finished product collection probe. A cold ash hopper installed at the bottom of the combustion chamber to collect ashes; an impeller and a deflector to make the outlet airflow of the flamethrower form a rotating jet.

There are many ways to arrange the flamethrower, and several reference examples are given in Figure 2. The most easy to manufacture, install and use is the regular four-corner arrangement (as shown in Figure 2(a)). In this arrangement, the cross-section of the combustion chamber is a square, and the flamethrowers are arranged on the four corners of the square. The geometric axes of the outlet airflows of the flame injectors are all tangent to the outer wall of the circular tube-shaped core reaction chamber. Numerical simulations have been carried out on the flame combustion in this arrangement, and the approximate temperature distribution on a certain cross-section in the circulating flame combustion zone is shown in Figure 3.

In the regular hexagonal arrangement (as shown in Figure 2(b)), the cross-section of the combustion chamber is a regular hexagon, and the flamethrowers are arranged on the six corners of the regular hexagonal shape. The geometric axes are all tangent to the outer wall of the circular tubular core reaction chamber.

What Fig. 2 (c) shows is a kind of special arrangement mode, in this arrangement mode, the core reaction chamber is a square tube, the cross-section of its outer wall is a rectangle, the cross-section of the combustion chamber is a circle, and the flame injector is arranged On the four endpoints of any two mutually perpendicular diameters of the circle, the geometric axes of the outlet airflows of the four flamethrowers are all tangent to an imaginary circle whose diameter is the diagonal of the rectangle.

The present invention utilizes the method for synthesizing carbon nanotubes of above-mentioned system to comprise the following steps:

S1. Start the fuel supply equipment and oxidant supply equipment, deliver fuel and oxidant to the flamethrower, and prepare for ignition;

S2. Start the auxiliary gas supply equipment, and deliver cooling gas (such as helium, nitrogen, etc., in order to save costs, directly use air) into the core reaction chamber, so as not to burn out the core reaction chamber due to high-temperature flames after ignition;

S3. Start the igniter to ignite the mixture of fuel and oxidant sprayed from the flamethrower;

S4. After the circulating flame in the combustion chamber is formed, adjust the consumption of fuel and oxidant to the required value;

S5. After the circulating flame burns stably, and the temperature of the circulating flame at different heights in the combustion chamber reaches the design value, start the carbon source supply equipment and the catalyst supply equipment, and deliver the carbon source and the catalyst to the core reaction chamber;

S6. Increase the amount of carbon source and catalyst to the design parameters, so that the carbon source begins to pyrolyze;

S7. After the temperature of the carbon source pyrolysis domain and the carbon nanotube synthesis domain both reach the design value, start the finished product collection unit;

S8. When the first finished product collection probe on the conveyor belt reaches the direct top of the carbon nanotube synthesis domain, it will pop up automatically, extend into the predetermined position in the carbon nanotube synthesis domain, and begin to collect the synthesized carbon nanotubes; At the same time, the conveyor belt will stop running immediately;

S9. After the residence time of the first probe in the carbon nanotube synthesis domain reaches the preset product collection time, the probe will automatically spring back to its original position, and the conveyor belt will continue to run immediately;

S10. All subsequent finished product acquisition probes will repeat the steps of S8 and S9 in turn until the system stops running;

When it is necessary to change the operating conditions or the system needs to be shut down due to problems, follow the steps below:

S11. Close the fuel supply equipment and oxidant supply equipment, stop delivering fuel and oxidant to the flame injector, and make the combustion chamber extinguish;

S12. Turn off the carbon source supply equipment and the catalyst supply equipment, stop transporting the carbon source and the catalyst to the core reaction chamber, and avoid wasting raw materials;

S13. Close the finished product collection unit to make it stop running;

S14. Open the bypass valve, deliver cooling gas (such as helium, nitrogen, etc., in order to save costs, directly use air) into the flamethrower and the core reaction chamber, and spray the cooling gas into the combustion chamber to cool the flame Injectors, combustion chambers and core reaction chambers, to avoid damage to them by the residual high temperature after flameout in the combustion chamber;

S15. After the temperature of all parts of the combustion chamber drops below 200°C, turn off the auxiliary gas supply equipment.

The content of the present invention will be further described below with reference to the accompanying drawings and preferred embodiments. It must be pointed out that the invention may be embodied in many different specific forms and should not be construed as limited to the embodiments described herein. On the contrary, these embodiments are provided to make the content of the present invention more clear and complete, fully convey the scope of the present invention to those skilled in the art, and convey other objects not mentioned above.

In the following two preferred embodiments, the general method and steps for synthesizing carbon nanotubes using the system of the present invention are as described above, while the catalyst preparation method and some conventional operating steps are well known to those skilled in the art, Therefore, no more details will be given here, and only the key technical parameters will be described here.

Example 1

The present embodiment provides a kind of preparation method of single-wall carbon nanotube, and its technical parameter is as follows:

(1) The shape of the circulating flame combustion chamber is a quadrangular prism, and its cross section is a square; the flame injectors are arranged on the four corners of the square, and three groups (multi-layer arrangement) are installed along the height direction of the combustion chamber; the core The reaction chamber is in the shape of a circular tube; the top umbrella is in the shape of a bowl;

(2) Co/Mo/MgO catalyst is prepared by sol-gel method in advance, wherein the ratio of Co, Mo and Mg is 1:2:30, and the calcination temperature is 850°C;

(3) Using methane gas as the carbon source, hydrogen and helium as auxiliary gases, wherein the volume flow ratio of CH ₄ , H ₂ , and He is 3:4:5;

(4) Use acetylene gas as fuel, and 21:79 oxygen-nitrogen mixture as oxidant, and its volume flow ratio is 1:13; fuel and oxidant are ejected from their respective channels in the flame injector, and then burn Meeting indoors, the outlet airflow of the flamethrower is a straight jet;

(5) The finished product collection time is 6 minutes.

FIG. 4 is a high-magnification transmission electron micrograph of carbon nanotubes prepared in Example 1. FIG. It can be clearly seen from Figure 4 that there are many single-walled carbon nanotubes with a large aspect ratio, uniform diameter distribution, and very high purity, with only very little amorphous carbon present.

FIG. 5 is a Raman spectrum diagram of the carbon nanotubes prepared in Example 1 in the range of 0-2500 cm ^-1 Raman shift. It can be seen from Figure 5 that there is a G-band spectrum peak around 1550-1600cm ^-1 , and its spectrum peak is very strong, indicating that the product has a high degree of graphitization; while D mode appears around 1250-1450cm ^-1 Mode (D-band) spectral peak, its spectral peak is quite weak, shows that the content of amorphous carbon in the product is negligible. In addition, there is a very obvious radial breathing peak (RBM) around 180cm ^-1 , which indicates that there are a large number of high-quality single-walled carbon nanotubes in the product.

Example 2

This embodiment provides a method for preparing a carbon nanotube array, and its technical parameters are as follows:

(1) The shape of the circulating flame combustion chamber is cylindrical, and its cross section is circular; the flame injectors are arranged on the four ends of the two diameters perpendicular to each other, and three groups are installed along the height direction of the combustion chamber. (multi-layer arrangement); the core reaction chamber is in the shape of a circular tube; the top umbrella is in the shape of a petal;

(2) Pre-preparing Fe/Mo/Al ₂ O ₃ catalysts by sol-gel method, wherein the ratio of the amount of Fe, Mo, and Al is 5:1:60, and the calcination temperature is 900°C;

(3) Carbon monoxide gas is used as the carbon source, and hydrogen and helium are used as auxiliary gases, wherein the volume flow ratio of CO, H ₂ and He is 2:3:3;

(4) With acetylene gas as fuel and air as oxidant, its volume flow ratio is 1:13; fuel and oxidant are sprayed out after being premixed inside the flame injector first, and the outlet air flow of the flame injector is a rotating jet;

(5) Apply an electric field with a potential difference of not less than 60V to the inside of the core reaction chamber along the height direction of the core reaction chamber;

(6) The finished product collection time is 5 minutes.

FIG. 6 is a scanning electron micrograph of the carbon nanotube array prepared in Example 2. It can be seen from Figure 6 that the carbon nanotubes grow directionally in clusters and are arranged in a neat array, with thinner tube diameters, straighter tubes, and very few impurities.

The specific implementation above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the present invention. within the scope of protection.

Claims (9)

1. a kind of system of synthesizing carbon nanotubes is it is characterised in that include circulation flame combustion domain, carbon source pyrolysis domain, carbon nanometer Pipe composite field, finished product collecting unit and chemical reaction raw material supply unit；And core reaction chamber, circulation flame combustion room, fire Flame ejector, top umbrella；Described circulation flame combustion domain is located at circulation flame combustion interior, and described core reaction chamber is located at circulation The center of flame combustion room, described carbon source pyrolysis domain is located at core reaction intracavity bottom, and described CNT composite field is located at core Heart reaction chamber internal upper part, the jet of described flame thrower is located at the side wall of circulation flame combustion room, and described top umbrella is located at The top in core reaction chamber, described finished product collecting unit is located above the umbrella of top, and described chemical reaction raw material supply unit is to ring Erysipelass flame combustor and core reaction intracavity feed.

2. system according to claim 1 is it is characterised in that described finished product collecting unit includes the collection spy of flip-over type finished product Head and conveyer belt, automatic spring when described flip-over type finished product acquisition probe reaches the surface of CNT composite field, it extend into Precalculated position in CNT composite field, meanwhile, conveyer belt is out of service immediately, so that the finished product carbon that collection is obtained is received Mitron；After the time of staying of probe reaching default finished product acquisition time, probe will reply position by appliance for releasing single, and conveyer belt also can Immediately continue with operation.

3. system according to claim 1 is it is characterised in that described chemical reaction raw material supply unit includes carbon source supply Equipment, assists gas supply equipment, catalyst supply equipment, fuel facility, oxidant supply equipment.

4. system according to claim 1 it is characterised in that described core reaction chamber be tubular, circulation flame combustion The profile of room is prismatic, and its external wall cross-section is polygon, and the jet of flame thrower is arranged in each end polygonal On point or on each bar side.

5. system according to claim 1 is it is characterised in that described flame thrower is in circulation flame combustion room side wall Install one group at sustained height or install multigroup at differing heights, each of same group of flame thrower is installed in ring At sustained height on erysipelass flame sidewall of combustion chamber.

6. system according to claim 5 is it is characterised in that the exit flow of described flame thrower is direct jet, Or rotating jet, and the geometrical axis of air-flow is all tangent with the outer wall in tubular core reaction chamber；Each flame thrower sprays After the air-flow going out converges, the central area in circulation flame combustion room is formed vigorous combustion and cincture core reaction cavity outer wall is fast The flame of fast rotational flow.

7. system according to claim 3 is it is characterised in that the carbon source of described carbon source supply equipment supply is gas, liquid The carbon raw material of body, solid or plasma；The auxiliary gas of described auxiliary gas supply equipment supply refers to hydrogen and lazy Property gas；The catalyst of described catalyst supply equipment supply is transition metal simple substance or alloy or transition metal The mixture that compound or above-mentioned simple substance, alloy or compound are constituted；The fuel of described fuel facility supply be gas, The high calorific capacity combustibles of liquid or solid；The oxidant of described oxidant supply equipment supply is air, pure oxygen or oxygen-nitrogen Gas gaseous mixture.

8. system according to claim 1 is it is characterised in that described system also includes：

(1) bypath system, described bypath system is needing change operating condition or system to go wrong when needing to shut down, and can will have The gas having refrigerating function direct plunges into system, and described gas is noble gases or low activity gas；

(2) temperature sensor and coupled digital instrument：It is pyrolyzed domain and CNT composite field in order to monitor carbon source Temperature；

(3) digital timer：Use cooperatively with temperature sensor, the automatic spring of achievable finished product acquisition probe moves with resetting Make, and conveyer belt out of service with continue to run with action；

(4) lighter：When system brings into operation, to be lighted the fuel spraying from flame thrower by it；

(5) impeller and the air deflector of Swirl Condition can be provided, make the exit flow of flame thrower form rotating jet, so that Cooperation controls the combustion characteristics of flame；

(6) furnace hopper：In system with solid as fuel, in the bottom of circulation flame combustion room, furnace hopper is installed, for collecting Ashes.

9. the method utilizing the system synthesis CNT described in any one of claim 1-8, comprises the following steps：

(1) starting fluid supply equipment and oxidant supply equipment, conveying fuel and oxidant into flame thrower, for igniting Prepare；

(2) start auxiliary gas supply equipment, convey cooling gas to core reaction intracavity；

(3) initial igniter, lights the mixture of the fuel from flame thrower ejection and oxidant；

(4) after the indoor circulation flame formation of circulation flame combustion, the consumption adjusting fuel with oxidant is to desirable value；

(5) burn with treating circulation flame stabilization, and the circulation flame temperature at the differing heights of circulation flame combustion interior all reaches To after design load, start carbon source supply equipment and catalyst supply equipment, convey carbon source and catalyst to core reaction intracavity；

(6) consumption of carbon source and catalyst is tuned up to design parameter, make carbon source start to be pyrolyzed；

(7) after the temperature in carbon source pyrolysis domain and CNT composite field all reaches design load, start finished product collecting unit；

(8) when first flip-over type finished product acquisition probe reaches the surface of CNT composite field with conveyer belt, appliance for releasing single Go out, extend into the precalculated position in CNT composite field, start to gather the CNT of synthesis；Meanwhile, conveyer belt stops Only run；

(9) treat that the time of staying in CNT composite field for first flip-over type finished product acquisition probe reaches default finished product and adopts After the collection time, appliance for releasing single replys position, and conveyer belt continues to run with；

(10) step that the flip-over type finished product acquisition probe continuing is repeated in (8th), (9) two steps, until system is out of service； When needing change operating condition or system to go wrong when needing to shut down, then follow the steps below：

(11) close fuel facility and oxidant supply equipment, stop conveying fuel and oxidant into flame thrower, Make burning indoor flame-out；

(12) close carbon source supply equipment and catalyst supply equipment, stop conveying carbon source and catalyst to core reaction intracavity；

(13) close finished product collecting unit so as to out of service；

(14) open bypath system, convey cooling gas to flame thrower with core reaction intracavity, and by cooling gas to combustion Burn indoor injection；

(15) temperature throughout the room to be combusted is all down to 200 DEG C, closes auxiliary gas supply equipment.