JP6954564B2 - Nanocarbon manufacturing method and nanocarbon manufacturing system - Google Patents

Description

The present invention relates to a method for producing nanocarbon and a nanocarbon production system for producing nanocarbon using methane.

As a method for producing carbon nanotubes, a technique for producing nanocarbons using hydrocarbons in the presence of a catalyst is known.
For example, Patent Document 1 discloses a technique of bringing a metal-containing catalyst into contact with a hydrocarbon gas to catalytically convert at least a part of the hydrocarbon gas into hydrogen and carbon, as an example of the hydrocarbon gas. , Natural gas, coal seam gas, landfill gas, and biogas, and the composition of hydrocarbon gases is generally one or more light hydrocarbons from the group containing methane, ethane, ethylene, propane, and butane. It is said to contain hydrogen.

Further, Patent Document 2 discloses a method for synthesizing carbon nanotubes in which a raw material gas is methane or a mixture containing methane and the raw material gas is brought into contact with a catalyst at 500 to 1200 ° C. In Patent Document 2, the mixture containing methane is a mixed gas in which a gas other than methane is mixed, and is not particularly limited, but can be mixed with an inert gas, hydrogen, water vapor, carbon dioxide, or the like. , It is stated that it is preferable to mix with an inert gas.

In addition to these, there are known gas species other than methane that may affect the reaction when producing nanocarbons. For example, other hydrocarbons (saturated / unsaturated with C2 or higher) are known. _{Hydrocarbons), CO and CO 2} that may be used as raw materials, _{H 2} O (moisture) that may be intentionally _{added, H 2} and (CO) _{that reduce the catalyst, O 2} that oxidizes, etc. are used. ..
For example, in Patent Document 3, water is added, in Patent Document 4, CO and CO ₂ are added, and in Patent Document 5, reducing gas (H ₂ , CO) and oxidizing gas (O ₂ ) are added. There is. Further, Patent Document 6 describes that a hydrocarbon other than methane or CO is added, and Patent Document 7 describes that the mixture is mixed with another gas such as an alkyne.

Further, Patent Document 8 discloses a technique for improving the volume resistivity by using a raw material gas containing methane at a concentration of 10% by volume or less. Patent Document 9 discloses a method for producing nanocarbon having a high specific surface area by contacting a raw material gas having an adjusted carbon weight flux and a catalyst activator with a catalyst on a substrate.

JP-A-2018-528291 JP-A-2007-197304 Japanese Unexamined Patent Publication No. 2013-180913 Japanese Patent Application Laid-Open No. 2015-518461 Japanese Unexamined Patent Publication No. 2009-227470 Japanese Patent Application Laid-Open No. 2011-511809 Japanese Patent Application Laid-Open No. 2012-530663 JP-A-2010-006663 International Publication No. 2010/147193

As described above, it is known that methane is used as a raw material gas for nanocarbon. However, even if you say methane gas in a bite, the literature includes biomethane, natural gas (components differ depending on the production area, mining method, and liquefaction method to LNG), city gas, reaction synthesis (methanation) methane, and hide. It describes raid methane, a type of hydrocarbon gas, etc., and its purity varies from about 80%.
Patent Document 1 does not specifically describe the use of hydrocarbons. Further, in the examples of Patent Document 2, only those using methane and other mixed gases are shown. However, with these methods, it cannot be said that the production efficiency of nanocarbon and the characteristics of the obtained nanocarbon are sufficient.
In Patent Documents 3 to 7, since a gas other than methane is used, the configuration becomes complicated in order to achieve this, and sufficient reaction efficiency is not obtained.
Further, in Patent Document 8 and Patent Document 9, although it is possible to produce nanocarbon having excellent characteristics in some of the characteristics, there is no consideration for productivity and the balance of a plurality of characteristics is considered. There is a problem that there is no.

The present invention has been made against the background of the above circumstances, and by using pure methane having a higher purity than city gas containing methane, the productivity of nanocarbon is increased, and the characteristics of the produced nanocarbon are further enhanced. It is an object of the present invention to provide a nanocarbon production method and a nanocarbon production system capable of sufficiently improving the above.

That is, in the first form of the nanocarbon production method of the present invention, the boil-off gas (BOG gas) is derived, and the BOG gas is purified to make the purity of pure methane gas 99.9% or more by volume. Pure methane gas with a dew point of -72 ° C (water content 2 ppm) or less, a total impurity concentration of hydrocarbon components other than methane of l0 ppm or less, a carbon monoxide concentration of l ppm or less, a carbon dioxide concentration of lppm or less, and an oxygen concentration of 10 ppm or less. To produce nanocarbon by direct decomposition reaction using a catalyst in a heating environment in the range of 600 to 900 ° C.

In the invention of the second aspect of the nanocarbon production method, in the invention of the above-described embodiment, the catalyst is non-supporting and may be any one or a combination of iron-based, nickel-based, alumina-based, and cobalt-based. be.

In the invention of the third embodiment of the nanocarbon production method, in the invention of the above-described embodiment, the nanocarbon contains a pure carbon crystal, and the pure carbon crystal is graphene, graphite, single-walled or multi-walled carbon nanotube, carbon. It is characterized by containing one or more of nanofibers and graphene.

Among the nanocarbon production systems of the present invention, the first mode is a BOG gas transfer path for transferring BOG gas, and a BOG gas transfer path.
The BOG gas provided in the middle of the BOG gas transfer path is purified to increase the methane concentration to 99.9% or more by volume and the dew point to -72 ° C. (moisture 2 ppm) or less. , A purification unit that sets the total concentration of impurities of hydrocarbon components other than methane to l0 ppm or less, carbon monoxide concentration to lppm or less, carbon dioxide concentration to lppm or less, and oxygen concentration to 10 ppm or less.
A reactor in which a catalyst is housed, the BOG gas transfer path is connected, and pure methane gas introduced through the BOG gas transfer path is directly decomposed and reacted by the catalyst.
A heating unit that heats the inside of the reactor and
The nanocarbon receiving part for receiving the nanocarbon taken out from the reactor is provided.
The invention of the nanocarbon production system of the second embodiment includes a BOG gas transfer path for transferring BOG gas and a BOG gas transfer path.
A reactor in which a catalyst is housed, the BOG gas transfer path is connected, and the BOG gas introduced through the BOG gas transfer path is directly decomposed and reacted by the catalyst.
A heating unit that heats the inside of the reactor and
A nanocarbon receiving part for receiving the nanocarbon taken out from the reactor is provided.
It has a gas discharge path for transferring residual methane and hydrogen discharged from the reactor.
It has a heat exchanger that exchanges heat between the BOG gas transfer path to which a relatively low temperature BOG gas is transferred and the gas discharge path to which a relatively high temperature residual methane and hydrogen are transferred.
The gas discharge passage, the downstream side of the heat exchanger shall be the being connected to energy supply

In the invention of the third embodiment, the invention of the nanocarbon production system includes a screw feeder type moving bed in the reaction furnace and a catalyst inlet for charging a catalyst into the moving bed.

The invention of the nanocarbon production system of the fourth embodiment includes a liquid storage tank in which BOG is generated, or a container in which at least BOG is stored, in the invention of the above-described embodiment.

Invention of the nanocarbon manufacturing system of the fifth embodiment of the present invention, in the form, a liquid storage tank LNG storage tank or a liquid methane storage tank which BOG is generated, said liquid storage tank Ground tanks, underground It is one of a tank, a cold evaporator (CE) of satellite equipment, a liquid gas container; and a portable ultra-low temperature container (LGC).

The invention of the nanocarbon production system of the sixth embodiment is characterized in that, in the invention of the above-described embodiment, a liquid storage tank in which BOG is generated or at least a container in which BOG is stored is configured to be movable.

In the invention of the seventh aspect of the nanocarbon production system, in the invention of the above-described embodiment, the liquid storage tank in which BOG is generated is an LNG liquid storage tank or a liquid methane liquid storage tank, and the liquid storage tank fuels the stored matter. It is used for energy, and a part or all of hydrogen gas and unreacted methane taken out from the reactor are used for the fuel energy.

That is, according to the present invention, nanocarbon can be produced with high productivity by a direct decomposition reaction using pure methane, and the characteristics of the obtained nanocarbon are well-balanced. For example, since nanocarbon is produced from BOG gas that is naturally vaporized by heat input from an LNG liquid storage tank or a liquefied methane liquid storage tank, it is compared with a nanocarbon production method that does not mention the conventional raw material supply method. Dramatically improve productivity and economy. Further, the characteristics of nanocarbon are improved by using high-purity methane gas derived from BOG as a raw material.

It is a schematic diagram of the nanocarbon production system of one Embodiment of this invention. It is a block diagram of the nanocarbon manufacturing system in another embodiment. It is a figure which shows the modification of the embodiment of FIG. It is a figure explaining a plurality of supply forms of pure methane in embodiment of this invention. It is a figure which shows the structure of the reactor used in the Example of this invention. It is a figure which shows the XRD pattern of the produced carbon obtained from the city gas (13A) in an Example. It is a figure which shows the XRD pattern of the produced carbon obtained from the high-purity methane of 3N in an Example. It is a figure which shows the XRD pattern of the produced carbon obtained from the ultra-high purity methane of 6N in an Example. It is a figure which shows the pore diameter distribution of the produced carbon obtained from the city gas (13A) in an Example. It is a figure which shows the pore diameter distribution of the produced carbon obtained from the high-purity methane of 3N in an Example. It is a figure which shows the pore diameter distribution of the produced carbon obtained from the ultra-high purity methane of 6N in an Example. It is a drawing substitute photograph which shows the SEM image of the produced carbon obtained from the city gas (13A) in an Example. It is a drawing substitute photograph which shows the SEM image of the produced carbon obtained from the high-purity methane of 3N in an Example. It is a drawing substitute photograph which shows the SEM image of the produced carbon obtained from the ultra-high purity methane of 6N in an Example.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a schematic example of the nanocarbon production system of the present invention.
The nanocarbon production system 1 has a production apparatus 5 in which pure methane is introduced through the pure methane transfer path 10C and nanocarbon is produced by a direct decomposition reaction, and the nanocarbon NC taken out from the production apparatus 5 is nano. It is taken out by the carbon receiving unit 6. A catalyst (not shown) is arranged in the manufacturing apparatus 5. As the catalyst, any one or a combination of iron, nickel, alumina, and cobalt can be used. The manufacturing apparatus 5 corresponds to the reactor of the present invention.

A supply unit 4 is provided on the upstream side of the pure methane transport path 10C, and can be configured by providing a pressure and flow rate, an inlet gas temperature adjusting device, a pump, and the like.
A pure methane transport path 10B is connected to the upstream side of the supply section 4, and a purification section 3 is provided on the upstream side of the pure methane transport path 10B. The purification unit 3 increases the purity of pure methane transported from the upstream side, and can be composed of known substances such as distillation, adsorption, and permeation membrane.
A pure methane transport path 10A is connected to the upstream side of the purification unit 3. The upstream side of the pure methane transport path 10A is connected to the upper space 21 of the liquid storage tank 2 including the LNG liquid storage tank or the liquid methane liquid storage tank.

In the upper space 21, there is LNG stored in the liquid storage tank 2 and BOG (boil-off gas) evaporated from liquid methane. BOG gas has a high methane concentration as pure methane. Although not shown in the figure, a relief valve may be provided in the upper space of the liquid storage tank 2. The relief valve is a mechanism provided for the purpose of keeping the pressure in the storage tank constant, and thereby removes impurity gases such as nitrogen and oxygen contained in the liquid storage tank 2 having a boiling point different from that of methane from the upper space 21. can do.
The type of the liquid storage tank 2 is not particularly limited, and an LNG underground tank, an LNG satellite cold evaporator (CE), a liquid methane satellite evaporator (CE), an LGC (liquid gas container; a portable ultra-low temperature container), or the like should be used. Can be done.

In this embodiment, the BOG gas has been described as being supplied from the liquid storage tank 2 to the purification unit 3, but is directly transferred from the upper space 21 of the liquid storage tank 2 to the supply unit through the pure methane transport path 11A. It may be a thing. Through the purification unit 3, the concentration of pure methane can be, for example, 99.9% or more in volume%, and further 99.99999% or more (6N). The purity can be the desired purity.

Further, the BOG gas and the pure methane via the purification unit 3 are temporarily stored in the cylinder 7 or reliquefied and stored in the LGC, and then transferred to the purification unit 3 via the pure methane transfer path 11B connected to the cylinder 7. It may be transferred to the supply unit 4 via the pure methane transfer path 11C. The BOG gas may be a gas that has been moved from another place, or may be a gas that stores the BOG generated from the liquid storage tank.

The LNG and liquid methane in the liquid storage section 20 of the liquid storage tank 2 can be used as fuel energy in factories and the like, and hydrogen generated by the production of nanocarbon in the manufacturing apparatus 5 and reactions. Unreacted methane, which was not involved in the production, can also be used as fuel energy for factories and the like.

FIG. 2 shows the nanocarbon manufacturing system 1A installed in the satellite, which will be described below.
The nanocarbon production system 1A has a liquid storage tank 2A for storing LNG or liquid methane, and the liquid storage tank 2A is provided with a supply path 22 from a lorry, and LNG or liquid methane is provided at an appropriate time. Can be replenished. In the liquid storage tank 2A, for example, LNG or liquid methane is stored at −150 ° C. to −160 ° C., depending on the pressure inside.
As the liquid storage tank 2A, a tank of satellite equipment, a cold evaporator, a liquid gas container, or the like can be used.
In the liquid storage tank 2A, a relief valve 28 communicating with the upper space 21A is provided so that the pressure in the upper space can be released, and further, impurity gas having a boiling point lower than that of pure methane is excluded from the upper space 21A. be able to.

A liquid feeding path 23 is provided in the liquid storage section 20A of the liquid storage tank 2A. An evaporator 24 and a warmer 25 are sequentially provided in the liquid feeding path 23. LNG and liquid methane contained in the liquid storage unit 20A of the liquid storage tank 2A are sent out to the liquid supply passage 23, evaporated by the evaporator 24, and heated by the warmer 25 to be heated by the warmer 25, such as a business establishment such as a factory or a house. It can be used for energy supply in such cases.

The BOG gas taken out from the liquid storage tank 2A containing LNG has a methane purity of 99% or more, a dew point of −72 ° C. (moisture of 2 ppm) or less, and a total impurity of hydrocarbon components other than methane of l0 ppm or less. It is desirable to have it.
By purifying the above BOG gas, the methane purity is 99.9% or more by volume, the total impurity of hydrocarbon components other than methane is l0 ppm or less, and carbon monoxide and carbon dioxide are each 1 ppm by volume. Hereinafter, it can be assumed that the volume fraction of oxygen is 10 ppm or less and the dew point is −72 ° C. (moisture 2 ppm) or less.
Further, the BOG gas generated by storing the liquid methane obtained by liquefying the BOG gas can have a higher purity, for example, a purity of 4N5 or more can be obtained.
Further, the ultra-high purity methane obtained by highly distilling and purifying the pure methane derived from the BOG gas can have a purity of (6N or more).
In the present invention, the purity of BOG gas is not limited to the above.

The above values for pure methane will be described below.
-The dew point is -72 ° C (moisture 2ppm) or less Moisture is removed at the stage of cryogenic liquefaction of mined natural gas to make it LNG. Since the BOG gas has this LNG (about −160 ° C.) gas phase, it contains almost no water in principle. By using this pure methane derived from BOG gas, the amount of water in the pure methane can be reduced as much as possible. By directly decomposing using pure methane with reduced water content, an efficient reaction can be carried out and a superior effect can be obtained in terms of characteristics.
For methane gas derived from other sources such as biomethane and domestic natural gas (for example, domestic methane gas calculated in Chiba and Niigata prefectures), the methane purity is expected to be about 2N, but since it is methane separated from groundwater. The dew point (moisture) is considerably bad.

-The total amount of impurities of hydrocarbon components other than methane is l0 ppm or less. By suppressing the amount of hydrocarbons other than methane, a good reaction can be performed. If a large amount of hydrocarbons other than methane is contained, the reaction temperature is affected and the reaction efficiency is lowered. In addition, at the catalyst temperature that matches the direct reaction conditions of methane gas, the presence of a hydrocarbon component different from methane is thought to affect the quality of carbon crystals.

-Carbon monoxide is lppm or less Carbon monoxide is a gas with reducing properties and is considered to affect the activity of the catalyst. In addition, since it is a gas in which carbon (C) is present, it is considered that it also affects the quality of carbon crystals.

-Carbon dioxide is lppm or less Carbon dioxide is inactive at room temperature, but is considered to act as an oxidizing agent at high temperatures with a catalyst. Therefore, when it exists as an impurity in methane gas, it is considered that it also affects the quality of carbon crystals. It may also oxidize the catalyst and oxidize methane gas and carbon crystals depending on the temperature.

-Oxygen is 10 ppm or less Oxygen components may oxidize the catalyst and oxidize methane gas and carbon crystals at high temperatures.

The BOG gas evaporated in the upper space 21A of the liquid storage tank 2A is sent out to the pure methane transfer path 13 connected to the upper space 21A of the liquid storage tank 2A. The downstream end of the pure methane transfer path 13 is connected to the nanocarbon production apparatus 5. A warmer 26 is provided in the middle of the pure methane transfer path 13 to heat pure methane of low temperature BOG (about -100 ° C. at the pipe port) to room temperature (for example, 10 ° C. or higher) to achieve the pure methane transfer path. Prevents dew condensation of piping such as 13. In addition, pure methane may be transferred to the downstream side without going through the warmer 26.

In this embodiment, the BOG gas is sent to the nanocarbon production apparatus 5 as it is, but as described above, a purification unit may be provided in the middle of the pure methane transfer path to increase the methane purity. For example, pure methane of about 2N may be highly purified to a purity of 3N or more, or pure methane of about 4N5 may be highly purified. Further, it may be ultra-highly purified to a purity of 6N or more by advanced distillation purification or the like.

When the liquid methane is contained in the liquid storage tank 2A, the liquid methane may be taken out, the liquid methane may be evaporated, and the liquid methane may be sent to the pure methane transfer path 13. The pure methane evaporated from the liquid methane may be used alone, or may be mixed with BOG gas and supplied to the nanocarbon production apparatus 5.

The nanocarbon manufacturing apparatus 5 has a screw feeder 50, and includes a screw 51 that is rotationally driven by a motor 52. A pure methane transport path 13 is connected to the carry-in side of the screw feeder 50 so that pure methane can be supplied to the carry-in side, and a catalyst charging section 54 is provided on the carry-in side.
In the screw feeder 50, the pure methane introduced to the carry-in side and the catalyst sent from the catalyst charging section 54 come into contact with each other while being sent by the screw 51, and are sent while being agitated by the screw 51 to cause a direct decomposition reaction of pure methane. It is produced, and nanocarbon and hydrogen are produced. Since the catalyst is conveyed while being agitated by the screw 51, it can be unsupported, and since it is conveyed while being agitated, a decrease in catalytic activity is suppressed during the reaction, and the temperature inside the furnace is made uniform and the catalyst is conveyed. The reaction efficiency can be kept high due to the effect of preventing the flow of gas that does not come into contact with the catalyst and increasing the contact probability between the gas and the catalyst. The reaction may be carried out by adding a co-catalyst to the catalyst.

Examples of the catalyst charged from the catalyst charging unit 54 include iron-based, nickel-based, and alumina-based catalysts, and more specifically, cobalt-based catalysts can be shown. The type of catalyst is not particularly limited in the present invention, but iron-based, nickel-based, alumina-based, cobalt-based, and the like can be preferably used.

A heater 53 is arranged as a heating unit on the outer peripheral side of the screw feeder 50 to heat the inside of the screw feeder 50. As the heating temperature, for example, 600 to 900 ° C. can be a suitable temperature. The reaction temperature differs depending on the type of catalyst, and is preferably around 650 ° C. for nickel-based catalysts, around 750 ° C. for iron-based catalysts, and around 850 ° C. for cobalt-based catalysts.

However, in the present invention, the heating temperature is not limited to the above range. The configuration of the heating unit is not limited to the heater, and an appropriate heating configuration such as gas burning or radiant heating can be adopted, and the configuration is not particularly limited in the present invention.
The amount of pure methane supplied to the screw feeder 50 is preferably introduced at an appropriate flow rate, and for example, a flow rate of 5 to 50 L / min is a preferable example.
When the flow rate is small, the reaction efficiency becomes high, the hydrogen conversion rate becomes high, and the nanocarbon diameter becomes large. When the flow rate is high, the hydrogen conversion rate decreases, but the diameter decreases.
However, the present invention is not limited to the flow rate.
In the screw feeder 50, nanocarbon is efficiently produced. For example, nanocarbon is produced at 12 L / min or more, and high productivity is obtained.

The screw feeder 50 has a discharge unit 55 for discharging nanocarbon, a nanocarbon receiving part 6 at the discharge destination of the discharge part 55, and the nanocarbon is stored in the nanocarbon receiving part 6. The configuration of the nanocarbon receiving unit 6 is not particularly limited, and the nanocarbon may be retained as it is, may be conveyed to an appropriate place by a conveyor or the like, and further, an apparatus using nanocarbon may be used. It may be configured to be input.
At the outlet of the screw feeder 50, hydrogen as a product and residual methane that did not contribute to the reaction are further discharged. These residual methane and reactive hydrogen can be used as fuel energy for factories and the like.

The nanocarbon housed in the nanocarbon receiving portion 5 has excellent properties, and has well-balanced properties in terms of average diameter, electrical resistivity, and specific surface area. Specifically, it can be expected that the average diameter is 90 nm or less, the electrical resistivity is 0.70 Ω · cm or less, and the specific surface area is 115 m ^{2 / g or more.} It should be noted that the present invention is not required to have these characteristics.

In the above embodiment, the screw feeder is used as the reactor, but the present invention is not limited to the reactor configured by the screw feeder.

The obtained nanocarbon can be used as an additive auxiliary material as it is for improving various material properties such as rubber, resin, building materials, batteries, paints and inks, and can also be used as a dispersant and a binder (binding). It can be widely applied to the above-mentioned applications as a compound mixed with other substances such as wood). The uses of the present invention that can be usefully used are not particularly limited.

Since the hydrogen and residual methane discharged from the screw feeder 50 are high-temperature gases exceeding 500 ° C. at the outlet, for example, the gas is exchanged with a low-temperature BOG at about -100 ° C. at the outlet pipe of the liquid storage tank. After the temperature is set to normal temperature, it is introduced into the fuel energy piping. Further, since the BOG entering the reactor is also preheated, the reaction efficiency for carbon production is improved.
The nanocarbon manufacturing system 1B of this modified example is shown in FIG. The same components as those of the embodiment shown in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted or simplified.

The pure methane transfer path 13 connected to the upper space 21A of the storage tank 2A is connected to the screw feeder 50 of the nanocarbon production apparatus 5 via the first path for heat exchange of the heat exchanger 26. On the other hand, an exhaust gas transfer path 27 is connected to the discharge side of the screw feeder 50, and the exhaust gas transfer path 27 discharges residual methane and hydrogen having a high temperature, for example, about 500 ° C., in the screw feeder 50. NS. The exhaust gas transfer path 27 is connected to the evaporator 24 in the example of the figure via a second path for heat exchange of the heat exchanger 26.
In the heat exchanger 26, the BOG gas at about -100 ° C. transferred through the pure methane transfer path 13 and the residual methane + hydrogen at about 500 ° C. sent through the exhaust gas transfer path 27 are heat-exchanged, and the BOG gas is heated. Then, the residual methane + hydrogen is calculatedly cooled to about 100 to 200 ° C. and transferred. Since each gas is transferred along with the reaction, heat exchange can be performed efficiently.

In the description of FIGS. 2 and 3 above, an example used in a satellite facility for LNG or liquid methane has been described, but various supply systems applicable to the present invention will be described with reference to FIG.
In the liquid storage tank 200 such as an LNG terminal, an above-ground tank, and an underground tank, pure methane is used in various usage forms.
In one of them, the LNG in the liquid storage tank 200 is transported by the LNG lorry 300, and is housed in a satellite cold evaporator 600 or the like at a factory or the like. The LNG contained in the cold evaporator 600 is used as fuel for factories and the like. The BOG gas generated by the cold evaporator 600 is supplied to the nanocarbon production apparatus 5, and nanocarbon is produced as described above.

The BOG gas generated in the liquid storage tank 2 is distilled in the distillation column 401 in the distillation / reliquefaction column 400, and the gas distilled in the reliquefaction column 402 is reliquefied. The reliquefied pure methane is stored as liquid methane in the liquid storage tank 403. The liquid methane in the liquid storage tank 400 is transferred by the liquid methane lorry 310 and stored in a cold evaporator 610 or the like that stores the liquid methane in the factory 500. The liquid methane in the cold evaporator 610 can be evaporated and supplied as pure methane to the nanocarbon production apparatus 5 for use in the production of nanocarbon. The BOG gas generated by the cold evaporator 610 can also be supplied to the nanocarbon production apparatus 5 and used for producing nanocarbon.

In the liquid storage tank 403, the liquid methane is transferred to the movable tank 320 and moved, and in the factory, nanocarbon can be produced by the nanocarbon production apparatus 5 using pure methane obtained by evaporating the liquid methane.
The BOG gas generated in the liquid storage tank 403 is stored in a cylinder 330 as high-purity methane having a purity of 3N, and is used in the nanocarbon production apparatus 5 at the factory 500 for producing nanocarbon.

Further, the BOG gas generated in the liquid storage tank 200 is transferred to the purification unit 410, refined in, for example, an ultra-high distillation column, stored in a movable cylinder 330 as pure methane having a purity of 6N, and stored in the factory 500. It is carried and used in the nanocarbon NC production apparatus 5.
As described above, in the production of nanocarbon, there are various supply forms for pure methane, and the present invention includes not only a fixed portion but also a form in which nanocarbon is produced by satellite with movement. Is done.

Although the present invention has been described above based on the above-described embodiment, the technical scope of the present invention is not limited to the contents described in the above-described embodiment, and the above-mentioned embodiment is not limited to the scope of the present invention. Appropriate changes to the form are possible.

Next, examples of the present invention will be described.
As reaction gases, city gas (13A), 3N-purity high-purity methane (CH ₄ ), and 6N-purity ultra-high-purity methane (CH ₄ ) were prepared. 3N high-purity methane and 6N ultra-high-purity methane are purified pure methane derived from BOG used in the examples of the present invention. The methane purity of general city gas (13A) made from natural gas is about 90% by volume, and is used as a comparative example with respect to the example of the present invention.
High-purity methane and ultra-high-purity methane use methane derived from BOG, and high-purity methane and ultra-high-purity methane are obtained by purifying BOG gas to purify methane.
The high-purity methane gas and ultra-high-purity methane used, which were purified from BOG gas, had a total impurity of hydrocarbon components other than methane of l0 ppm or less, carbon monoxide and carbon dioxide of l ppm or less, and oxygen of 10 ppm or less, respectively. The dew point is −72 ° C. (moisture 2 ppm) or less.

As a reaction furnace using each of the above gases, as shown in FIG. 5, a quartz reaction tube 55A having an inner diameter of 26 mm was used. The quartz reactor 55A was placed horizontally, the catalyst 56 was housed inside, the inside of the tube was replaced with methane, and then the mixture was heated to 750 ° C. As a catalyst, 1 g of an iron-based catalyst was used. The reaction gas was sent into the quartz reactor 55A to directly carry out the decomposition reaction. By this decomposition reaction, the produced carbon of nanocarbon and the produced gas were obtained. The flow rate of the reaction gas was 100 ml / min, and the reaction time was 180 minutes.
Hydrogen activity declined over time. There was no significant difference in hydrogen activity in each reaction gas.

An XRD pattern was obtained by X-ray diffraction of the produced carbon. The obtained patterns are shown in FIGS. 6 to 8. Each pattern has a peak at about 26 degrees, and the peak at about 45 degrees indicates α-Fe. α-Fe is obtained by changing iron oxide, which is a catalyst, into metallic iron, which is an active species, in a high temperature of a reducing atmosphere.
In each reaction gas, high intensity was obtained at a diffraction angle corresponding to carbon. In particular, in 3N high-purity methane and 6N ultra-high-purity methane, higher X-ray intensity is obtained at the diffraction angle of C as compared with the X-ray intensity of Fe, and carbon is crystallized.
Further, the carbon strength of 6N ultra-high-purity methane is higher than that of 3N high-purity methane, and by increasing the purity of pure methane, highly crystalline carbon can be obtained.
As the X-ray diffractometer, a sample horizontal multipurpose X-ray diffractometer Ultima IV (manufactured by Rigaku Electric Co., Ltd.) was used, and the measurement was performed under the conditions of 40 Kv and 20 mA (CuKα).

Next, the pore size distribution of the produced carbon was measured by the nitrogen adsorption method using Sortomatic 1990 (manufactured by ThermoQuest), and the specific surface area and pore volume were calculated by the BET plot and the BJH method. The results are shown in FIGS. 9 to 11.
In city gas (13A), the specific surface area was 111 m ² / g and the pore volume was 0.75 mg / g, the specific surface area was relatively small, and the pore volume was slightly large.
The 3N high-purity methane had a specific surface area of 116 m ² / g and a pore volume of 0.73 mg / g, which was larger than that of city gas (13A) and had a smaller pore volume.
Further, the 6N ultra-high purity methane had a specific surface area of 131 m ² / g and a pore volume of 0.61 mg / g, which was larger than that of the 3N high-purity methane and had a smaller pore volume. By increasing the purity of pure methane, the specific surface area of the produced carbon was increased and the pore volume was smaller.

Next, the obtained produced carbon was observed with a scanning electron microscope to obtain an SEM image (20,000 times). Each SEM image is shown in FIGS. 12-14. In the observation, the acceleration voltage was 20 kV and the working distance was 11 mm. The resulting nanocarbon is linear.
In each SEM image, the diameters of linear nanocarbons were randomly measured at 15 locations each from the two images, for a total of 30 locations, and the diameter of the nanocarbons was obtained from the average value. The nanocarbon diameter value is shown on each screen.
The city gas (13A) had a diameter of 95.2 nm, the 3N high-purity methane had a diameter of 85.0 nm, and the 6N ultra-high-purity methane had a diameter of 80.6 nm. The diameters of high-purity methane and ultra-high-purity methane were smaller than those of city gas (13A), and the diameter of ultra-high-purity methane was smaller than that of high-purity methane. That is, it can be seen that the diameter of the linear nanocarbon becomes smaller by increasing the purity of pure methane.

Table 1 summarizes the characteristics of nanocarbon based on each gas used. The amount of carbon produced is calculated by subtracting the weight of the catalyst from the amount of recovered carbon. As for the amount of carbon produced, higher-purity methane and ultra-high-purity methane produce more carbon than city gas. By increasing the purity of pure methane rather than city gas, the crystallinity of the produced carbon is increased.

Further, the electrical resistivity of the produced carbon (powder) of nanocarbon obtained by each gas used was calculated by the four-terminal method using an electrical resistance measuring device (Imoto Seisakusho IMC-0240 type). The electrical resistivity of high-purity methane and ultra-high-purity methane is smaller than that of city gas (13A), and that of ultra-high-purity methane is smaller than that of high-purity methane.
That is, it can be seen that the electrical resistivity of the produced carbon becomes smaller by increasing the purity of pure methane. That is, the nanocarbon-generated carbon produced from a gas having better methane purity has better conductivity.
As described above, the nanocarbon produced by the method of the present invention has well-balanced properties in terms of average diameter, electrical resistivity, and specific surface area. That is, the average diameter is 90 nm or less, the electrical resistivity is 0.70 Ω · cm, and the specific surface area is 115 m ² / g or more.

Further, as shown in Table 2, all of the commercially available nanocarbons have a higher electrical resistivity than the nanocarbons produced in the present invention, and the present invention has a higher electrical resistivity than the commercially available ones. Nanocarbon can be effectively used as an electric member such as a conductive auxiliary material for a lithium ion battery, an electrode auxiliary material for a fuel cell, and a wiring material.

1, 1A, 1B Nanocarbon production system 2, 2A Liquid storage tank 3 Purification unit 4 Supply unit 5 Manufacturing equipment 7 Bomb, LGC, etc. Container 10A, 10B, 10C, 11A, 11B, 11C Pure methane transfer path 13 Pure methane transfer path 20, 20A Liquid storage unit 20 Liquid storage unit 20A Liquid storage unit 21 Upper space 21A Upper space 22 Supply path 23 Liquid supply path 24 Evaporator 25 Heater 26 Heater 27 Exhaust gas transfer path 28 Relief valve 50 Screw feeder 51 Screw 54 Catalyst input 55 Discharge section 200 Liquid storage tank 300 LNG lorry 310 Liquid methane lorry 320 Tank 330 Bomb 400 Distillation / reliquefaction tower 400 Liquid storage tank 401 Distillation tower 402 Reliquefaction tower 403 Liquid storage tank 410 Purification unit 500 Factory 600 Cold Evaporator 610 Cold Evaporator NC Nanocarbon

Claims (10)

Derived from boil-off gas (BOG gas), the BOG gas is purified to make the purity of pure methane gas 99.9% or more by volume, the dew point is -72 ° C (moisture 2 ppm) or less, and hydrocarbon components other than methane. A catalyst was used in a heating environment in the range of 600 to 900 ° C. using pure methane gas having a total impurity concentration of l0 ppm or less, a carbon monoxide concentration of lppm or less, a carbon dioxide concentration of lppm or less, and an oxygen concentration of 10 ppm or less. A method for producing nanocarbon, which produces nanocarbon by a direct decomposition reaction. The method for producing nanocarbon according to claim 1, wherein the catalyst is non-supported and is any one or a combination of iron-based, nickel-based, alumina-based, and cobalt-based. The nanocarbon contains a pure carbon crystal, wherein the pure carbon crystal contains one or more of graphene, graphite, single-walled or multi-walled carbon nanotubes, carbon nanofibers, and fullerenes. Item 2. The method for producing nanocarbon according to Item 1 or 2. BOG gas transfer path for transferring BOG gas and
The BOG gas provided in the middle of the BOG gas transfer path is purified to increase the methane concentration to 99.9% or more by volume and the dew point to -72 ° C. (moisture 2 ppm) or less. , A purification unit that sets the total concentration of impurities of hydrocarbon components other than methane to l0 ppm or less, carbon monoxide concentration to lppm or less, carbon dioxide concentration to lppm or less, and oxygen concentration to 10 ppm or less.
A reactor in which a catalyst is housed, the BOG gas transfer path is connected, and pure methane gas introduced through the BOG gas transfer path is directly decomposed and reacted by the catalyst.
A heating unit that heats the inside of the reactor and
A nanocarbon manufacturing system including a nanocarbon receiving unit that receives nanocarbon taken out from the reactor. BOG gas transfer path for transferring BOG gas and
A reactor in which a catalyst is housed, the BOG gas transfer path is connected, and the BOG gas introduced through the BOG gas transfer path is directly decomposed and reacted by the catalyst.
A heating unit that heats the inside of the reactor and
A nanocarbon receiving part for receiving the nanocarbon taken out from the reactor is provided.
It has a gas discharge path for transferring residual methane and hydrogen discharged from the reactor.
It has a heat exchanger that exchanges heat between the BOG gas transfer path to which a relatively low temperature BOG gas is transferred and the gas discharge path to which a relatively high temperature residual methane and hydrogen are transferred.
A nanocarbon manufacturing system characterized in that the gas discharge path is connected to an energy supply side on the downstream side of the heat exchanger. The nanocarbon production system according to claim 4 or 5, wherein the reaction furnace is provided with a screw feeder type moving bed and has a catalyst charging section for charging a catalyst into the moving bed. The nanocarbon production system according to any one of claims 4 to 6, further comprising a liquid storage tank in which BOG is generated, or at least a container in which BOG is stored. BOG is liquid storage tank LNG storage tank or a liquid methane storage tank which occurs, the reservoir is ground-based tank, underground tanks, satellite equipment cold evaporator claim is either Liquid Gas Container 7. The nanocarbon production system according to 7. The nanocarbon production system according to claim 7 or 8, wherein the liquid storage tank in which the BOG is generated, or at least the container in which the BOG is stored, is configured to be movable. The liquid storage tank in which BOG is generated is an LNG liquid storage tank or a liquid methane liquid storage tank, and the liquid storage tank uses the stored matter as fuel energy. The nanocarbon production system according to any one of claims 4 to 9, wherein a part or all of the reaction methane is used for the fuel energy.

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