Carbon nanotube production device

Abstract

A carbon nanotube production device comprising: a first reaction tube to which a carbon nanotube starting material gas is supplied; a second reaction tube through which the starting material gas passes, and a heating chamber which heats the first reaction tube and the second reaction tube, wherein the first reaction tube and the second reaction tube are arranged in a straight line, and an end part of first reaction tube and an end part of the second reaction tube are connected.

Description

Carbon nanotube generation device

[0001] The present invention relates to a carbon nanotube producing apparatus for producing carbon nanotubes.

[0002] Carbon nanotubes (hereinafter sometimes referred to as "CNTs") are a new material that has attracted attention in many fields due to their excellent properties such as electrical conductivity, thermal conductivity, and mechanical strength. Patent Document 1 discloses a CNT manufacturing device that uses a chemical vapor deposition (CVD) method to generate CNTs by thermally decomposing a carbon-containing raw material (carbon source).

[0003] In a method for producing CNTs using chemical vapor deposition, for example, CNT raw materials and a carrier gas are supplied to a reaction tube heated to a high temperature, and CNTs are produced by passing the raw materials through the reaction tube for a certain period of time. The produced CNTs are discharged from the end of the reaction tube opposite the raw material supply side.

[0004] Japanese Patent Application Publication No. 2019-064918

[0005] In order to reduce the cost of CNT production, it is necessary to increase the amount of CNT produced per unit time to improve production efficiency. One possible method for increasing the amount of CNT produced per unit time is to increase the amount of raw material supplied to the reaction tube.

[0006] However, if the amount of CNT produced increases with an increase in the amount of raw material supplied, the reaction tube becomes more susceptible to clogging with CNTs. Therefore, in order to prevent clogging with CNTs, it is necessary to increase the flow rate of the carrier gas along with the increase in the amount of raw material supplied.

[0007] On the other hand, in order to control the quality of CNTs within a target range, it is necessary to carry out the CNT production process in an atmosphere set under appropriate conditions for an appropriate time. However, when the flow rate of the carrier gas is increased with the reaction tube length of the conventional apparatus, it is difficult to achieve appropriate processing conditions inside the reaction tube. In other words, when the flow rate of the carrier gas is increased with the conventional apparatus structure, CNTs of the target quality cannot be obtained. Therefore, in order to obtain CNTs of the target quality even when the flow rate of the carrier gas is increased, the reaction tube length must be extended according to the carrier gas flow rate.

[0008] However, there are several commonly used standards for the reaction tubes manufactured by reaction tube manufacturers, and manufacturing a reaction tube that does not meet these standards incurs significant costs. In other words, using a reaction tube longer than the standard reaction tube length leads to a significant increase in the cost of the CNT generation device. Therefore, conventional CNT generation devices have room for improvement in terms of increasing the amount of CNTs produced per unit time while maintaining CNT quality.

[0009] The present invention has been made in view of the above circumstances, and aims to provide a carbon nanotube production apparatus that increases the amount of carbon nanotubes produced per unit time while ensuring the quality of the carbon nanotubes.

[0010] The following are examples of aspects of the present invention that solve the above problems: (1) A carbon nanotube production apparatus for producing carbon nanotubes, comprising: a first reaction tube to which a raw material gas for the carbon nanotubes is supplied, a second reaction tube through which the raw material gas passes, and a heating chamber for heating the first reaction tube and the second reaction tube, wherein the first reaction tube and the second reaction tube are arranged in a straight line, and an end of the first reaction tube and an end of the second reaction tube are connected. (2) The carbon nanotube production apparatus according to (1), further comprising a connecting member connecting an end of the first reaction tube and an end of the second reaction tube, the connecting member having: a first insertion port through which the end of the first reaction tube is inserted, a second insertion port through which the end of the second reaction tube is inserted, and an intermediate wall portion provided between the first insertion port and the second insertion port, the intermediate wall portion having: a first surface facing an end face of the first reaction tube and parallel to the end face, a second surface facing an end face of the second reaction tube and parallel to the end face, and a through hole passing through the first reaction tube along the tube axis direction. (3) The carbon nanotube production apparatus according to (2), further comprising: a sealing material provided between the end face of the first reaction tube and the intermediate wall portion, and between the end face of the second reaction tube and the intermediate wall portion, or both. (4) The carbon nanotube generation apparatus according to (1), wherein an end of the first reaction tube on the second reaction tube side has a first outer diameter portion and a cylindrical second outer diameter portion having an outer diameter smaller than the first outer diameter portion, and an end of the second reaction tube on the first reaction tube side has a first inner diameter portion and a cylindrical second inner diameter portion having an inner diameter larger than the first inner diameter portion, and the second outer diameter portion is inserted inside the second inner diameter portion. (5) The carbon nanotube generation apparatus according to (4), wherein a sealant is provided between an end face of the first outer diameter portion and an end face of the second inner diameter portion. (6) The carbon nanotube generation apparatus according to (3) or (5), wherein the sealant is made of graphite. (7) The carbon nanotube generation apparatus according to any one of (3), (5), and (6), further comprising a pressing mechanism that brings the first reaction tube and the second reaction tube relatively close to each other to tightly contact the first reaction tube and the second reaction tube via the sealant.(8) The carbon nanotube generation apparatus according to (7), wherein an end of the first reaction tube opposite to the second reaction tube side is located outside the heating chamber, and the pressing mechanism comprises: a spring that expands and contracts in a direction parallel to the axial direction of the first reaction tube; a first member to which one end of the spring is fixed; and a second member to which the other end of the spring is fixed, wherein the first member is fixed to the first reaction tube, and the second member is fixed to the heating chamber, and the spring is fixed to the second member in a state where it is contracted from its natural length in a region opposite to the region of the first member on the second reaction tube side. (9) The carbon nanotube generation apparatus according to claim (8), wherein the second member is a rod inserted inside the spring. (10) The carbon nanotube generation apparatus according to (8) or (9), further comprising an adjustment mechanism for adjusting the amount of contraction of the spring. (11) The carbon nanotube generating apparatus according to (9), wherein the rod has a male thread portion, a nut is attached to the male thread portion, the spring is disposed between the nut and the first member, and the amount of contraction of the spring can be adjusted by rotating the nut. (12) The carbon nanotube generating apparatus according to any one of (1) to (11), wherein the end faces of the first reaction tube and the second reaction tube at the connecting portion between the first reaction tube and the second reaction tube each have an arithmetic mean roughness Ra of 0.2 to 6.3 μm.

[0011] According to the present invention, it is possible to provide a carbon nanotube production apparatus that increases the amount of carbon nanotubes produced per unit time while ensuring the quality of the carbon nanotubes.

[0012] FIG. 1 is an explanatory diagram showing a schematic configuration of a carbon nanotube production apparatus according to an embodiment; FIG. 2 is an explanatory diagram showing a schematic configuration of a carbon nanotube generation apparatus according to an embodiment; FIG. 3 is a perspective view showing a connection part between a first reaction tube and a second reaction tube; FIG. 4 is a diagram for explaining a connection structure between the first reaction tube and the second reaction tube; FIG. 5 is an explanatory diagram showing a schematic configuration of a pressing mechanism that presses the first reaction tube downward; FIG. 6 is an explanatory diagram showing another example of a connection structure between the first reaction tube and the second reaction tube; FIG. 7 is an explanatory diagram showing another example of a connection structure between the first reaction tube and the second reaction tube; FIG. 8 is an explanatory diagram showing another example of a connection structure between the first reaction tube and the second reaction tube;

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0014] 1 is an explanatory diagram showing a schematic configuration of a CNT production apparatus 1 for producing carbon nanotubes (hereinafter sometimes referred to as "CNT") according to this embodiment. In this specification, CNT refers to a tubular carbon allotrope (typically a cylindrical structure with a graphite structure), and includes so-called single-walled CNT, multi-walled CNT, or carbon nanohorns with horn-shaped tube tips. The CNT production apparatus 1 is particularly suitable for use in producing single-walled CNT.

[0015] The CNT manufacturing apparatus 1 includes a CNT production apparatus 10 that produces CNTs and a recovery apparatus 60 that recovers the CNTs.

[0016] The recovery device 60 is connected to the lower end of the CNT generation device 10. The recovery device 60 includes a recovery chamber 61, a roller 62 installed in the recovery chamber 61, and a motor 63 that rotates the roller 62. The CNTs generated in the CNT generation device 10 are wound around the rotating roller 62 to form a mass-like wound body. Once the wound body has reached a predetermined size, it falls from the roller 62 into the recovery chamber 61 by a separation mechanism (not shown), and is then recovered.

[0017] <Carbon Nanotube Generator> Figure 2 is an explanatory diagram showing the schematic configuration of a CNT generator 10 according to this embodiment. The CNT generator 10 is a device that generates CNTs using a chemical vapor deposition method (CVD method), which generates CNTs by thermally decomposing a raw material such as a catalytic metal or a catalytic metal compound. When CNT raw materials are supplied to the CNT generator 10, a carrier gas (e.g., hydrogen gas) is also supplied along with the raw materials. In this specification, the raw materials supplied together with the carrier gas are referred to as raw material gas.

[0018] The CNT generation device 10 includes a first reaction tube 11 to which a CNT raw material gas is supplied, a second reaction tube 12 connected to the lower end of the first reaction tube 11, and a heating chamber 13 for heating the first reaction tube 11 and the second reaction tube 12.

[0019] The tube axis of the first reaction tube 11 and the tube axis of the second reaction tube 12 are oriented in the vertical direction, and the first reaction tube 11 and the second reaction tube 12 are arranged in a straight line. In this embodiment, the reaction tubes 11 and 12 are arranged so that the tube axis direction of the first reaction tube 11 and the tube axis direction of the second reaction tube 12 are aligned.

[0020] The upper end of the first reaction tube 11 is located outside the heating chamber 13, and a raw material supply port (not shown) for supplying a CNT raw material gas is formed at the upper end of the first reaction tube 11. The lower end of the first reaction tube 11 and the upper end of the second reaction tube 12 are connected to each other, and the CNT raw material gas supplied to the first reaction tube 11 passes through the first reaction tube 11 and flows into the second reaction tube 12.

[0021] Although the detailed description of the connection structure between the first reaction tube 11 and the second reaction tube 12 will be given later, it is preferable that the lower end surface of the first reaction tube 11 and the upper end surface of the second reaction tube 12 have an arithmetic mean roughness Ra of 0.2 to 6.3 μm as specified in JIS B 0601:2001. This can improve the sealing performance at the connection part between the first reaction tube 11 and the second reaction tube 12.

[0022] Each of the reaction tubes 11, 12 is a straight tube, but the shape of each of the reaction tubes 11, 12 is not particularly limited. The cross-sectional shape of each of the reaction tubes 11, 12 perpendicular to the tube axis may be a rounded shape such as a circle, an ellipse, or an egg, or a polygonal shape. The material of each of the reaction tubes 11, 12 is selected taking into consideration heat resistance to the heating temperature during CNT production, thermal shock resistance, weather resistance to the atmospheric gas at that temperature, corrosion resistance, and the like. Examples of materials that can be used include alumina (Al2O3), mullite, silicon carbide (SiC), quartz glass, Kanthal (iron-chromium-aluminum alloy), Inconel, and carbon.

[0023] The length of each of the reaction tubes 11 and 12 is, for example, 0.5 to 4.0 m, preferably 1.0 to 3.0 m, and more preferably 2.0 to 2.5 m. The inner diameter of each of the reaction tubes 11 and 12 is, for example, 10 to 300 mm, preferably 50 to 200 mm, and more preferably 80 to 120 mm. The number of reaction tubes is not limited to two and may be three or more. Even in the case where the number of reaction tubes is three or more, the reaction tubes are arranged in a straight line.

[0024] The heating chamber 13 is, for example, a cylindrical housing, and a heat insulating material 14 is provided on the inner side of the wall of the heating chamber 13. A space 15 is formed inside the heat insulating material 14 and around each of the reaction tubes 11, 12. A heater 16 for heating each of the reaction tubes 11, 12 is installed in this space 15.

[0025] The shape and heating method of the heater 16 are not particularly limited as long as they can heat the reaction tubes 11 and 12 to a temperature suitable for CNT growth. For example, a tungsten heater capable of heating the reaction tubes 11 and 12 to 500°C to 2000°C, or a carbon heater or silicon carbide heater (SiC heater) capable of heating the reaction tubes 11 and 12 to 600°C to 1600°C can be used as the heater 16.

[0026] Thermocouples 17 for measuring the temperature in the space 15 are installed on the side wall of the heating chamber 13. A plurality of thermocouples 17 are installed at intervals along the height direction of the heating chamber 13, and thus the temperature distribution in the axial direction of each reaction tube 11, 12 can be measured.

[0027] A shielding gas supply pipe 18 that communicates with the aforementioned space 15 is provided on the bottom wall of the heating chamber 13. An inert gas, for example, is supplied to the shielding gas supply pipe 18 as a shielding gas, and an inert gas atmosphere is created inside the space 15 during CNT production. An exhaust pipe 19 that communicates with the space 15 is provided on the ceiling wall of the heating chamber 13, and the exhaust pipe 19 is connected to, for example, an exhaust system of a factory. During CNT production, an inert gas is supplied and exhausted, and if any raw material gas leaks from a gap between the first reaction tube 11 and the second reaction tube 12, it is exhausted from the exhaust pipe 19.

[0028] (Connection structure of reaction tubes) Fig. 3 is a perspective view showing the connection part between the first reaction tube 11 and the second reaction tube 12. Fig. 4 is a diagram for explaining the connection structure between the first reaction tube 11 and the second reaction tube 12. Fig. 4(a) is an exploded view of the connection structure, showing a cross section when the connection part of the reaction tubes 11 and 12 is cut along the vertical direction. Fig. 4(b) is a diagram showing the connection state between the first reaction tube 11 and the second reaction tube 12, showing an end face when the connection part of the reaction tubes 11 and 12 is cut along the vertical direction.

[0029] Between the lower end of the first reaction tube 11 and the upper end of the second reaction tube 12, a connection holder 20 is provided as a connecting member for connecting the first reaction tube 11 and the second reaction tube 12.

[0030] The connection holder 20 has a cylindrical side wall portion 21, a first insertion opening 22 into which the end of the first reaction tube 11 is inserted, and a second insertion opening 23 into which the second reaction tube 12 is inserted.

[0031] The inner diameter of the side wall portion 21 is slightly larger than the outer diameter of each reaction tube 11, 12, and the outer peripheral surfaces of the ends of each reaction tube 11, 12 inserted into the connection holder 20 are supported by the inner peripheral surface of the side wall portion 21.

[0032] An intermediate wall 24 is provided between the first insertion inlet 22 and the second insertion inlet 23, protruding inward from the inner circumferential surface of the side wall 21. The intermediate wall 24 has an upper surface (first surface) facing the lower end surface of the first reaction tube 11 and parallel to the lower end surface, and a lower surface (second surface) facing the upper end surface of the second reaction tube 12 and parallel to the upper end surface. The intermediate wall 24 is located at the center of the side wall 21 in the vertical direction, but the position of the intermediate wall 24 in the vertical direction is not particularly limited as long as it can support each of the reaction tubes 11, 12.

[0033] A through-hole 25 is formed in the radial center of the intermediate wall portion 24, penetrating along the tube axial direction of the first reaction tube 11. The diameter of the through-hole 25 is smaller than the inner diameter of each reaction tube 11, 12, whereby the lower end surface of the first reaction tube 11 is supported by the upper surface of the intermediate wall portion 24, and the lower surface of the intermediate wall portion 24 is supported by the upper end surface of the second reaction tube 12.

[0034] If the size of the through-hole 25 is excessively small, the flow of the raw material gas may be obstructed by the intermediate wall portion 24, which may result in deposition of CNTs on the upper surface of the intermediate wall portion 24 or clogging of the through-hole 25 with CNTs. Therefore, it is preferable that the size of the through-hole 25 is as large as possible within a range in which each of the reaction tubes 11, 12 inserted into the connection holder 20 can maintain a stable posture. Specifically, it is preferable that the diameter A of the through-hole 25, the inner diameter B of the first reaction tube 11, and the inner diameter C of the second reaction tube 12 satisfy the relationship A≧B=C.

[0035] The material of the connection holder 20 described above is not particularly limited as long as it is a material that is heat-resistant to the heating temperature during CNT generation, but carbon or silicon carbide (SiC) can be used, for example. Note that, since outside air can flow into the space 15 shown in FIG. 2 where the shielding gas is supplied, if the purity of the shielding gas in the space 15 is low, oxygen will be contained in the atmosphere in the space 15. For this reason, for example, if the connection holder 20 is made of carbon, it will be prone to oxidation due to contact with oxygen that may be present in the space 15 in a high-temperature environment. On the other hand, if the connection holder 20 is made of silicon carbide, such oxidation is suppressed, enabling the connection holder 20 to have a longer life.

[0036] Furthermore, for example, when the thermal expansion coefficient of the connection holder 20 is excessively small compared to the thermal expansion coefficient of each of the reaction tubes 11, 12, the expansion rate of each of the reaction tubes 11, 12 becomes faster than that of the connection holder 20 when the temperature is increased in the heating chamber. Therefore, each of the reaction tubes 11, 12 may further expand in a state where the outer circumferential surface of each of the reaction tubes 11, 12 and the inner circumferential surface of the side wall portion 21 of the connection holder 20 are in contact with each other. Furthermore, for example, when the thermal expansion coefficient of the connection holder 20 is excessively large compared to the thermal expansion coefficient of each of the reaction tubes 11, 12, the contraction rate of the connection holder 20 becomes faster than that of each of the reaction tubes 11, 12 when the temperature is decreased in the heating chamber. Therefore, the connection holder 20 may further contract in a state where the outer circumferential surface of each of the reaction tubes 11, 12 and the inner circumferential surface of the side wall portion 21 of the connection holder 20 are in contact with each other.

[0037] In any of the above cases, there may be damage to the reaction tubes 11, 12 or the connection holder 20. Therefore, it is preferable that the material of the connection holder 20 has a thermal expansion coefficient that is approximately the same as that of the material of each of the reaction tubes 11, 12, and it is more preferable that the material of the connection holder 20 and the material of each of the reaction tubes 11, 12 are the same material.

[0038] An annular packing 30 is provided as a sealing material between the lower end surface of the first reaction tube 11 and the upper surface of the intermediate wall portion 24, and between the upper end surface of the second reaction tube 12 and the lower surface of the intermediate wall portion 24. The provision of this packing 30 suppresses leakage of the source gas from the gap between the first reaction tube 11 and the connection holder 20 or the gap between the second reaction tube 12 and the connection holder 20.

[0039] The material of the packing 30 is not particularly limited as long as it can ensure the desired sealing properties, but examples thereof include metal oxides and carbon-based materials, specifically alumina and graphite. Parts containing carbon can deteriorate when in contact with the CNT raw material gas in a high-temperature environment, but because the reaction tubes 11, 12 and the intermediate wall portion 24 of the connection holder 20 are in close contact with each other, the packing 30 is unlikely to be exposed to the raw material gas atmosphere. Therefore, even if the packing 30 is made of graphite, stable sealing properties can be ensured for a long period of time.

[0040] The packing 30 is expected to exhibit high sealing performance by being made of a material that deforms under load. Furthermore, if the packing 30 has a laminated structure in which multiple layers of such materials are stacked, the sealing performance will be further improved. A suitable laminated structure is, for example, a laminated structure of sheet-like graphite films.

[0041] 4, the packings 30 are provided both between the first reaction tube 11 and the intermediate wall portion 24 and between the second reaction tube 12 and the intermediate wall portion 24, but the packings 30 may be provided only on one of the two sides as long as the required sealing performance can be ensured. Furthermore, the packings 30 may not be provided as long as the required sealing performance can be ensured.

[0042] The above has described the connection structure between the first reaction tube 11 and the second reaction tube 12. The shapes of the connection holder 20 and the packing 30 are appropriately changed depending on the horizontal cross-sectional shapes of the reaction tubes 11, 12.

[0043] (Pressing Mechanism) Next, there will be described a pressing mechanism 40 which is preferably provided to improve the sealing property of the connecting portion between the first reaction tube 11 and the second reaction tube 12. Fig. 5 is an explanatory view showing a schematic configuration of the pressing mechanism 40 which presses the first reaction tube 11 downward.

[0044] The pressing mechanism 40 includes an annular plate 41 fixed to the upper end of the first reaction tube 11 located outside the heating chamber 13, an annular plate 42 fixed to the lower surface of the plate 41, and an annular plate 43 fixed to the lower surface of the plate 42.

[0045] The pressing mechanism 40 also has an annular plate 44 fixed to the ceiling wall 13a of the heating chamber 13, a cylindrical wall 45 fixed to the inner peripheral end of the plate 44, and an annular plate 46 fixed to the upper end of the cylindrical wall 45.

[0046] A bellows 47 is provided as a flexible member between the plate material 43 and the plate material 46. The bellows 47 is disposed such that the extension / contraction direction is parallel to the axial direction of the first reaction tube 11. The upper end of the bellows 47 is fixed to the plate material 43, and the lower end of the bellows 47 is fixed to the plate material 46.

[0047] The upper end of the first reaction tube 11 is surrounded by plates 41 to 43, a cylindrical wall portion 45, a plate 46, and a bellows 47, thereby forming a space 48. For example, an inert gas is supplied to the space 48 from a shielding gas supply pipe (not shown), and the space 48 becomes an inert gas atmosphere during CNT production. The inert gas filled in the space 48 flows into the heating chamber 13 through a through-hole 13b formed in the ceiling wall portion 13a of the heating chamber 13 and is exhausted from an exhaust pipe (e.g., exhaust pipe 19 shown in FIG. 2 ) (not shown). Appropriate sealing materials are provided on the contact surfaces between the plates to prevent leakage of the shielding gas from the space 48 to the outside.

[0048] When the temperature of the heating chamber 13 is increased, the first reaction tube 11 and the second reaction tube 12 are expanded along the tube axis direction due to thermal expansion, and in this case, the bellows 47 is also expanded. On the other hand, when the temperature of the heating chamber 13 is decreased, the expanded first reaction tube 11 contracts, and therefore the first reaction tube 11 contracts along the tube axis direction, and in this case, the bellows 47 is also contracted.

[0049] That is, since the bellows 47 expands or contracts depending on the expansion or contraction amount of the first reaction tube 11, it is possible to suppress the occurrence of breakage of parts such as the plate members 41 to 43 fixed directly or indirectly to the upper end portion of the first reaction tube 11 and the reaction tubes 11, 12 themselves during thermal expansion or contraction of the first reaction tube 11.

[0050] It is preferable that the pressing mechanism 40 has a structure in which the bellows 47 expands or contracts in response to the change in the axial length of the first reaction tube 11 as described above, but such a structure may be provided as a mechanism independent of the pressing mechanism 40.

[0051] A spring 49 is provided above the plate material 43 on the side of the bellows 47. The spring 49 is arranged so that the extension / contraction direction is parallel to the axial direction of the first reaction tube 11, and a lower end 49 a of the spring 49 is fixed to the upper surface of the plate material 43.

[0052] A rod 50 is inserted inside the spring 49, passes through the plate 43, and has its lower end fixed to the upper surface of the plate 46. The rod 50 is a hollow or solid material such as a tube. An external thread is formed on the upper end of the rod 50, and a nut 51 is attached to the external thread.

[0053] The lower surface of the nut 51 is in contact with the upper end 49b of the spring 49, and by tightening the nut 51, the upper end 49b of the spring 49 moves downward and the spring 49 contracts. That is, the upper end 49b of the spring 49 is fixed to the rod 50 by the nut 51. In other words, the spring 49 is located between the nut 51 and the plate 43, and the upper end 49b of the spring 49 is fixed to the rod 50 in a region of the plate 43 on the opposite side to the second reaction tube 12 side.

[0054] There are provided a plurality of structures each consisting of the above-described spring 49, rod 50, and nut 51. Here, if a member to which a lower end 49a, which is one end of the spring 49, is fixed is referred to as a first member, and a member to which an upper end 49b, which is the other end of the spring 49, is fixed is referred to as a second member, the first member corresponds to the plate material 43, and the second member corresponds to the rod 50.

[0055] As described above, the plate 43 is fixed to the plate 42, the plate 42 is fixed to the plate 41, and the plate 41 is fixed to the upper end of the first reaction tube 11. That is, the plate 43 as the first member is indirectly fixed to the upper end of the first reaction tube 11 via another member.

[0056] On the other hand, the rod 50 serving as the second member is fixed to a plate 46. The plate 46 is fixed to the cylindrical wall 45, the cylindrical wall 45 is fixed to a plate 44, and the plate 44 is fixed to the ceiling wall 13a of the heating chamber 13. In other words, the rod 50 serving as the second member is indirectly fixed to the heating chamber 13 via another member.

[0057] The spring 49 fixed to the plate material 43 and the bar material 50 is fixed to the plate material 43 and the bar material 50 in a state where it is contracted from its natural length by tightening the nut 51. Therefore, a restoring force is generated in the spring 49 in the contracted state, but the bar material 50 to which the nut 51 is attached is fixed to the heating chamber 13 via the plate material 46, the cylindrical wall portion 45, and the plate material 44, so the bar material 50 is in a restrained state.

[0058] Therefore, the restoring force of the spring 49 acts in a direction toward the lower end 49a of the spring 49, and a downward load is applied to the upper surface of the plate material 43. Since the plate material 43 is fixed to the upper end of the first reaction tube 11 via the plate material 42 and the plate material 41, the downward load input to the plate material 43 presses the first reaction tube 11 downward.

[0059] 4 is pressed against the upper surface of the intermediate wall portion 24 of the connection holder 20, and the lower surface of the intermediate wall portion 24 is pressed against the upper end surface of the second reaction tube 12. This increases the adhesion between the lower end surface of the first reaction tube 11 and the upper surface of the intermediate wall portion 24, and between the lower surface of the intermediate wall portion 24 and the upper end surface of the second reaction tube 12, thereby improving the sealing performance of the packing 30.

[0060] The amount of contraction of the spring 49 can be adjusted by the tightening pressure of the nut 51, but if the tightening pressure of the nut 51 is excessive, it will hinder the expansion of the bellows 47. For this reason, the tightening pressure of the nut 51 is set appropriately taking into consideration the expansion of the bellows 47, and is, for example, 6 to 50 MPa.

[0061] The pressing mechanism 40 that presses the first reaction tube 11 downward has been described above, but the pressing mechanism 40 is not limited to the configuration shown in Fig. 5. For example, the plate material 43 serving as the first member to which one end of the spring 49 is fixed may be directly fixed to the first reaction tube 11. Similarly, the rod material 50 serving as the second member to which the other end of the spring 49 is fixed may be directly fixed to the heating chamber 13.

[0062] Furthermore, for example, the rod 50 that was disposed inside the spring 49 may be disposed outside the spring 49. In this case, by providing a plate (not shown) that connects the upper end 49b of the spring 49 to the rod 50, it is possible to fix the upper end 49b of the spring 49 to the rod 50 in a state in which the spring 49 is contracted from its natural length. However, from the viewpoint of reducing the number of parts and making the pressing mechanism 40 smaller, it is preferable to dispose the rod 50 inside the spring 49.

[0063] The mechanism for adjusting the amount of contraction of the spring 49 by rotating the nut 51 is provided as needed, and this adjustment mechanism is not limited to a configuration using the nut 51.

[0064] Furthermore, the pressing mechanism 40 is not limited to a configuration that presses the first reaction tube 11 downward, and may be configured, for example, to press the second reaction tube 12 upward. That is, the pressing mechanism 40 may have a configuration that brings the first reaction tube 11 and the second reaction tube 12 relatively close to each other.

[0065] The above has described the CNT generator 10 according to this embodiment. In this CNT generator 10, the first reaction tube 11 and the second reaction tube 12 are arranged in a straight line, and in this state, the lower end of the first reaction tube 11 and the upper end of the second reaction tube 12 are connected by a connection holder 20.

[0066] As a result, when the supply rate of the raw material gas supplied to the first reaction tube 11 is increased, the raw material gas can be sufficiently heated in the second reaction tube 12 to produce CNTs. Furthermore, because the raw material gas flow path is longer than when there is only one reaction tube, even when the supply rate of the raw material gas is increased, it is easier to control the processing conditions inside each reaction tube 11, 12 to be suitable for CNT production, and the quality of the CNTs can be maintained. Therefore, with the CNT production apparatus 10 according to this embodiment, it is possible to increase the amount of CNTs produced per unit time while ensuring the quality of the CNTs.

[0067] Although the connection holder 20 is provided in the above embodiment, the first reaction tube 11 and the second reaction tube 12 may be connected without providing the connection holder 20 as will be described below.

[0068] (Other Examples of Connection Structure) Hereinafter, other examples of the connection structure will be described with reference to Figs. 6 to 8. (a) in each figure is an exploded view of the connection structure, showing a cross section when the connection part of the reaction tubes 11 and 12 is cut along the vertical direction. Also, (b) in each figure is a view showing a connected state of the first reaction tube 11 and the second reaction tube 12, showing an end face when the connection part of the reaction tubes 11 and 12 is cut along the vertical direction.

[0069] Fig. 6 is a diagram showing a connection structure of each reaction tube 11, 12 having a stepped end. As shown in Fig. 6, the lower end of the first reaction tube 11 is composed of a first outer diameter portion 11a and a cylindrical second outer diameter portion 11b having an outer diameter smaller than that of the first outer diameter portion 11a, and the second outer diameter portion 11b is located below the first outer diameter portion 11a. On the other hand, the upper end of the second reaction tube 12 is composed of a first inner diameter portion 12a and a cylindrical second inner diameter portion 12b having an inner diameter smaller than that of the first inner diameter portion 12a, and the second inner diameter portion 12b is located above the first inner diameter portion 12a. When connecting the first reaction tube 11 and the second reaction tube 12, the second outer diameter portion 11b is inserted into the second inner diameter portion 12b.

[0070] Between the lower end surface of the first outer diameter portion 11a and the first inner diameter portion 12a, a ring-shaped packing 31 is provided as a sealing material. The material of the packing 31 is the same as the material of the packing 30 described in the above embodiment.

[0071] 6, the packing 31 is not exposed to the inner peripheral surface of each reaction tube 11, 12 through which the raw material gas passes, and therefore it is possible to suppress deterioration of the packing 31. Furthermore, when the above-mentioned pressing mechanism 40 is applied to this connection structure, it is possible to improve the sealing property.

[0072] In addition, when the outer diameter and the inner diameter of the first outer diameter portion 11a and the outer diameter and the inner diameter of the first inner diameter portion 12a are the same as the outer diameter and the inner diameter of each reaction tube 11, 12 shown in Fig. 4, the area of ​​the packing 31 has to be made smaller than the area of ​​the packing 30. Therefore, from the viewpoint of sealing property, the structure provided with the connection holder 20 shown in Fig. 4 is superior in sealing property.

[0073] 7 shows an example of the connection structure shown in FIG. 6 in which the packing 31 is not provided. In this example, a liquid sealant is applied between the outer peripheral surface of the second outer diameter portion 11b and the inner peripheral surface of the second inner diameter portion 12b, thereby bonding the second outer diameter portion 11b and the second inner diameter portion 12b. Therefore, the connection structure of the reaction tubes 11, 12 shown in FIG. 7 has excellent sealing properties. Furthermore, since this connection structure does not require a sealing material such as a packing, the aforementioned pressing mechanism 40 is not required, and the structure of the CNT generation device 10 can be simplified.

[0074] Fig. 8 is a diagram showing a connection structure of the reaction tubes 11 and 12 whose end portions are tapered. As shown in Fig. 8, the first reaction tube 11 is formed at its lower end with a first tapered portion 11c whose outer diameter gradually decreases downward, and the second reaction tube 12 is formed at its upper end with a second tapered portion 12c whose inner diameter gradually increases upward.

[0075] The first reaction tube 11 and the second reaction tube 12 are connected by inserting the first tapered portion 11c into the second tapered portion 12c. The outer peripheral surface of the first tapered portion 11c and the inner peripheral surface of the second tapered portion 12c are bonded by applying a liquid sealant. Therefore, the connection structure of the reaction tubes 11 and 12 shown in FIG. 8 has excellent sealing properties. Furthermore, because this connection structure does not require a sealant such as a packing, the aforementioned pressing mechanism 40 is not required, and the structure of the CNT generation apparatus 10 can be simplified.

[0076] 6 to 8, the end processing of the reaction tubes 11 and 12 is required, but in the case where the connection holder 20 shown in Fig. 4 is provided, the end processing is not required. That is, in the connection structure using the connection holder 20, for example, commercially available tubes without end processing can be used as the reaction tubes 11 and 12 as they are, and therefore, this structure is advantageous in terms of cost reduction.

[0077] (Regarding the Tube Axis Direction of the Reaction Tubes) In the above examples, the tube axis direction of each of the reaction tubes 11 and 12 is vertical, but the tube axis direction may be horizontal or another direction. When the tube axis direction is a direction other than vertical, for example, by replacing the "upper end of the first reaction tube 11" with the "end of the first reaction tube 11 opposite to the second reaction tube 12 side," the "lower end of the first reaction tube 11" with the "end of the first reaction tube 11 on the second reaction tube 12 side," the "upper end of the second reaction tube 12" with the "end of the second reaction tube 12 on the first reaction tube 11 side," and the "lower end of the second reaction tube 12" with the "end of the second reaction tube 12 opposite to the first reaction tube 11 side," a CNT generator that exhibits the same effects as the CNT generator 10 described in the above examples can be obtained.

[0078] Although the present invention has been described above by way of example, it is understood that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and that such modifications and alterations are also within the technical scope of the present invention.

[0079] For example, the components of the above-described embodiments can be combined in any manner, and such combinations will naturally provide the functions and effects of the individual components involved in the combination, as well as other functions and effects that will be apparent to those skilled in the art from the description herein.

[0080] In the CNT generating apparatus according to the embodiment of the present invention, a performance test was carried out to evaluate the airtightness of the connecting portion between the first reaction tube and the second reaction tube.

[0081] The CNT generation apparatus according to the embodiment has the structure shown in Figures 2 to 4, and the first and second reaction tubes are connected by a connection holder. Each reaction tube is 1 m long. In addition, packing is provided on the lower end surface of the first reaction tube and the upper end surface of the second reaction tube as a sealing material. A supply space for shielding gas is formed around each reaction tube, and a heater is installed in this space.

[0082] In the CNT generation apparatus having the above structure, the heater temperature was set to 1200°C, and hydrogen gas as a carrier gas was supplied from the upper end of the first reaction tube at a flow rate of 50 L / min. The internal pressure (gauge pressure) of the reaction tube and the hydrogen concentration in the supply space of the shielding gas were measured to evaluate the airtightness of the reaction tube.

[0083] Furthermore, a performance test was carried out on a conventional CNT device in which a single 2 m reaction tube was installed instead of the first reaction tube, second reaction tube, and connection holder described above, under the same temperature and gas supply conditions as in the examples.

[0084] As a result of the above performance tests, in both the CNT device according to the example and the CNT device according to the comparative example, the internal pressure of the reaction tube was 0 to 2 kPaG, and the hydrogen concentration in the shielding gas supply space was 0 ppm. In other words, even a CNT generation device with a structure in which the first and second reaction tubes are connected has the same airtightness as a conventional CNT generation device with a single tube structure, and is capable of performing CNT generation processing.

[0085] Furthermore, the effects described herein are merely descriptive or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that are apparent to those skilled in the art from the description of this specification, in addition to or in place of the above-described effects.

[0086] The present invention can be applied to a carbon nanotube production device.

[0087] REFERENCE SIGNS LIST 1 CNT production apparatus (carbon nanotube production apparatus) 10 CNT production apparatus (carbon nanotube production apparatus) 11 First reaction tube 12 Second reaction tube 13 Heating chamber 13a Ceiling wall portion 13b Through hole 14 Heat insulating material 15 Space 16 Heater 17 Thermocouple 18 Shielding gas supply pipe 19 Exhaust pipe 20 Connection holder 21 Side wall portion 22 First insertion port 23 Second insertion port 24 Intermediate wall portion 25 Through hole 30 Packing 40 Pressing mechanism 41 Plate material 42 Plate material 43 Plate material 44 Plate material 45 Cylindrical wall portion 46 Plate material 47 Bellows 48 Space 49 Spring 49a Lower end of spring 49b Upper end of spring 50 Rod material 51 Nut 60 CNT recovery device (carbon nanotube recovery device) 61 recovery chamber 62 roller 63 motor

Claims

1. A carbon nanotube production apparatus for producing carbon nanotubes, comprising: a first reaction tube to which a raw material gas for the carbon nanotubes is supplied; a second reaction tube through which the raw material gas passes; and a heating chamber for heating the first reaction tube and the second reaction tube, wherein the first reaction tube and the second reaction tube are arranged in a straight line, and an end of the first reaction tube and an end of the second reaction tube are connected.

2. A carbon nanotube production apparatus as described in claim 1, comprising a connecting member connecting an end of the first reaction tube and an end of the second reaction tube, the connecting member having: a first insertion port into which the end of the first reaction tube is inserted; a second insertion port into which the end of the second reaction tube is inserted; and an intermediate wall portion provided between the first insertion port and the second insertion port, the intermediate wall portion having: a first surface facing the end face of the first reaction tube and parallel to the end face; a second surface facing the end face of the second reaction tube and parallel to the end face; and a through hole passing through the first reaction tube along the axial direction of the tube.

3. A carbon nanotube production apparatus as described in claim 2, wherein a sealant is provided between the end face of the first reaction tube and the intermediate wall portion, and / or between the end face of the second reaction tube and the intermediate wall portion.

4. The carbon nanotube generating apparatus according to claim 1, wherein the end of the first reaction tube on the side of the second reaction tube has a first outer diameter portion and a cylindrical second outer diameter portion having an outer diameter smaller than that of the first outer diameter portion, the end of the second reaction tube on the side of the first reaction tube has a first inner diameter portion and a cylindrical second inner diameter portion having an inner diameter larger than that of the first inner diameter portion, and the second outer diameter portion is inserted inside the second inner diameter portion.

5. The carbon nanotube generating apparatus according to claim 4, wherein a sealant is provided between the end face of said first outer diameter portion and the end face of said second inner diameter portion.

6. The carbon nanotube generating apparatus according to claim 3, wherein the sealing material is made of graphite.

7. A carbon nanotube production apparatus as described in claim 3, further comprising a pressing mechanism that brings the first reaction tube and the second reaction tube relatively close to each other and tightly seals the first reaction tube and the second reaction tube together via the sealing material.

8. The carbon nanotube production apparatus according to claim 7, wherein the end of the first reaction tube opposite to the second reaction tube side is located outside the heating chamber, the pressing mechanism comprises: a spring that expands and contracts in a direction parallel to the axial direction of the first reaction tube; a first member to which one end of the spring is fixed; and a second member to which the other end of the spring is fixed, the first member being fixed to the first reaction tube, the second member being fixed to the heating chamber, and the spring being fixed to the second member in a state where it is contracted from its natural length in an area opposite to the area of ​​the first member on the second reaction tube side.

9. The carbon nanotube generating apparatus according to claim 8, wherein the second member is a rod inserted into the inside of the spring.

10. The carbon nanotube generating apparatus according to claim 8, further comprising an adjusting mechanism for adjusting the amount of contraction of the spring.

11. A carbon nanotube production apparatus as described in claim 9, wherein the rod has a male threaded portion, a nut is attached to the male threaded portion, the spring is arranged between the nut and the first member, and the amount of contraction of the spring can be adjusted by rotating the nut.

12. The carbon nanotube production apparatus according to claim 1, wherein the end faces of the first reaction tube and the second reaction tube at the connection between the first reaction tube and the second reaction tube each have an arithmetic mean roughness Ra of 0.2 to 6.3 μm.

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