System for producing hydrogen via nebulizer thermal CVD decomposition

Abstract

[Problem] To produce hydrogen with high production efficiency together with a high-value-added carbon nanotube thin film. [Solution] A system that is for producing hydrogen via nebulizer thermal CVD decomposition and that comprises a vertical thermal CVD device and a nebulizer device which contains a mixed Fe-ethanol liquid. Into the vertical thermal CVD device, the inside of which is set at 800-1000°C, the mixed Fe-ethanol liquid is nebulized via the nebulizer device, and a natural gas which has methane as a main component is fed as a carrier gas. The methane in the natural gas is brought into contact with the nebulized Fe or a catalyst, so as to achieve decomposition into carbon nanotubes and gas components including hydrogen. After the gas components including hydrogen are filtered, the hydrogen is removed via a gas filter and stored in an externally provided tank, the remaining gas components are returned to the carrier gas to be reused, and the collected carbon nanotubes are subjected to purification treatment.

Description

Hydrogen production system using nebulizer thermal CVD decomposition

[0001] The present invention relates to a system for producing hydrogen by nebulizer thermal CVD decomposition.

[0002] Natural gas is an extremely abundant petrochemical fuel resource. The world's proven natural gas reserves total 14,211 trillion cubic meters, with an energy content equivalent to 914.3 billion barrels of crude oil. Projected reserves range from 250 to 350 trillion cubic meters. Because methane is the primary component of natural gas, many countries around the world place great importance on its processing and utilization. Furthermore, with the current worsening problem of global warming, the production of hydrogen from methane is attracting increasing attention. While various processes exist for producing hydrogen (H2), the current industrial production method primarily relies on by-product hydrogen from petroleum, chemical, and steel plants, as well as natural gas reforming.

[0003] The main methods are direct decomposition of methane: CH4 → solid carbon + 2H2 and steam reforming of methane (SRM): CH4 + 2H2O → CO2 + 4H2. Other methods that have been used include partial oxidation of methane (POM) and autothermal reforming of methane (ATR).

[0004] Patent Publication No. 2022-169379

[0005] However, these conventional methods have problems in terms of stable production of hydrogen.

[0006] First, in the case of the direct methane decomposition method and SRM, it is necessary to first activate the methane molecules. Because methane molecules are very inactive, the reaction conditions are very harsh, and methane can only be decomposed in high yield at temperatures above 900°C.

[0007] Direct methane decomposition has the great advantage that no CO2 is emitted during the reaction, but on the other hand, it has the problem that the amount of hydrogen obtained from the same amount of methane is small. Also, steam reforming emits CO2 when hydrogen is produced, so to make it carbon neutral, a device is required to capture and fix the generated CO2.

[0008] Furthermore, these conventional methods have the problem that they have low hydrogen production capacity, and the carbon by-products obtained are of low added value and are only of practical value.

[0009] Furthermore, there is a problem of catalyst poisoning, that is, the catalyst deteriorates due to the pores being blocked by carbon deposition on the surface of the catalyst, and the catalyst must be replaced frequently, which naturally increases production costs.

[0010] These have been described for the direct methane decomposition method and the SRM method, but the POM method and the ATR method also have certain advantages, but their problems have not been resolved.

[0011] In view of the above circumstances, the present invention provides a vertical thermal CVD apparatus including a heating furnace provided on the outer periphery of a quartz tube, the inside of which is provided with a catalyst storage basket having a number of holes at the bottom, and a nebulizer device storing an Fe-based element / alcohol mixed solution, the storage basket storing one or more catalysts carrying Fe, Ni, Co, Cu, Pd, Pt, Rh, Ru, Ir, and other transition metals and precious metals, and the Fe-based element / alcohol mixed solution is atomized by the nebulizer device in the vertical thermal CVD apparatus, the interior of which is set to 800°C to 1000°C by the heating furnace, We propose a hydrogen production system using nebulizer thermal CVD decomposition, characterized in that natural gas, whose main component is methane, is fed as a carrier gas, and the methane in the natural gas is brought into contact with atomized Fe-based elements or a catalyst to decompose it into gas components containing carbon nanotubes and hydrogen.The hydrogen-containing gas components are passed through a filtration tank to filter out the carbon nanotubes contained therein, and the hydrogen is extracted through a gas filter in a separation tank and stored in an external tank, and the remaining gas components are returned to the carrier gas for recycling.

[0012] The present invention not only has the advantage of producing hydrogen more efficiently than the commonly used SRM, POM, and ATR methods, but also produces carbon nanotubes (CNTs) with high economic efficiency.

[0013] In addition, in the process of hydrogen production, CO ２ is not emitted, and therefore CO ２ It has the advantage that no recovery or fixing device is required.

[0014] Furthermore, in the present invention, the catalyst or its storage basket is constantly vibrated to discharge the carbon nanotubes synthesized on the catalyst through the numerous holes at the bottom, so that the synthesized carbon nanotubes do not remain on the catalyst surface for long, thereby extending the catalyst's lifespan and enabling hydrogen to be produced at low production costs.

[0015] In this case, the catalyst or its storage basket is constantly vibrated by supporting and rotating the catalyst storage basket on a rotating shaft bearing at the bottom, thereby constantly vibrating the catalyst inside the storage basket.

[0016] Alternatively, a method can be adopted in which an agitating blade is placed inside the storage basket and the agitating blade is rotated by a rotating shaft to constantly vibrate the catalyst inside the storage basket.

[0017] Process diagram for hydrogen production according to the present invention. Image diagram of hydrogen decomposition and synthesis of carbon nanotubes (CNTs) in a catalyst storage basket. Diagram showing one embodiment of vibrating the catalyst in the storage basket. Diagram showing another embodiment of vibrating the catalyst in the storage basket. Diagram showing separation of H2 gas from CO and CH4 gas in the present invention. SEM diagram of multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs). TEM diagram of multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs). Raman spectroscopy diagram of multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotube net (SWNTs). Diagram of a hydrogen station constructed using produced H2 gas.

[0018] This hydrogen production system uses nebulizer thermal CVD decomposition to produce hydrogen. The system is equipped with a vertical thermal CVD apparatus and a nebulizer device containing an Fe / ethanol mixture, and the interior of the vertical thermal CVD apparatus is set to 800-1000°C. The nebulizer device atomizes the Fe / ethanol mixture, and natural gas, primarily composed of methane, is fed into the vertical thermal CVD apparatus as a carrier gas. The methane in the natural gas is brought into contact with atomized Fe or a catalyst, decomposing it into gaseous components containing carbon nanotubes and hydrogen. The hydrogen-containing gaseous components are filtered, and then hydrogen is extracted through a gas filter and stored in an external tank. The remaining gaseous components are returned to the carrier gas for recycling, and the collected carbon nanotubes are purified.

[0019] FIG. 1 shows a nebulizer thermal CVD decomposition hydrogen production system according to one embodiment of the present invention, in which reference numeral 1 denotes a vertical thermal CVD apparatus having an electric furnace 3 attached to the outer periphery of a quartz tube 2.

[0020] A catalyst storage basket 4 having holes 4a at the bottom is provided inside the quartz tube 2, and the storage basket 4 stores one or more types of spherical catalysts 5 carrying Fe, Ni, Co, Cu, Pd, Pt, Rh, Ru, Ir, and other transition metals and precious metals.

[0021] The catalyst storage basket 4 is constantly vibrated by an externally provided vibrating device.

[0022] In FIG. 3, the catalyst storage basket 4 is supported by a rotary shaft 21 journaled at the bottom, and rotational vibration is imparted to the storage basket 4 itself to vibrate the catalyst inside.

[0023] In FIG. 4, an agitating blade 22 is placed in a catalyst storage basket 4, and the agitating blade 22 is rotated by a rotating shaft 21 driven by a motor 23, thereby vibrating the catalyst inside.

[0024] On the other hand, 6 is a nebulizer device containing an Fe / ethanol mixture, 7 is a storage tank for natural gas such as methane, and 8 is a gas tank.

[0025] When the system is operated, the temperature of the quartz tube 2 is set to 800°C to 1000°C by the electric furnace 3.

[0026] Furthermore, natural gas such as methane is injected into a gas tank 8 and sent as a carrier gas to the nebulizer 6 , which then atomizes the Fe / ethanol mixture and sends it into the quartz tube 2 .

[0027] Methane in natural gas is decomposed into carbon nanotubes (CNTs) 9 and gas components (H2, CO, undecomposed CH4) by contacting with the atomized Fe or catalyst 5 in the storage basket 4.

[0028] Carbon nanotubes (CNts) 9 pass through holes 4 a, . . . in the bottom plate of the storage basket and are deposited on a CNTs collector 10 provided at the bottom of the vertical thermal CVD apparatus 1 .

[0029] As shown in Figure 2, by vibrating the catalyst storage basket 4, the synthesized CNTs 9 are constantly rolled over and discharged from the holes 4a in the bottom plate without adhering or being fixed to the catalyst surface. Therefore, the catalyst surface is not poisoned, and the catalyst life can be maintained for a long time.

[0030] On the other hand, the gas components (H2, CO, undecomposed CH4) are sent to a filtration tank 11, and while passing through a filtration filter 12, the carbon nanotubes (CNTs) 9 contained therein are filtered out.

[0031] Carbon nanotubes (CNTs) deposited in the lower collector 10 of the vertical thermal CVD apparatus 1 and carbon nanotubes (CNTs) filtered in the filtration tank 11 are sent to a purification chamber 13 where they are purified.

[0032] The gas components (H2, CO, undecomposed CH4) that have passed through the filtration tank 11 are sent to a separation tank 15 equipped with a gas filter 14.

[0033] FIG. 6 is an image diagram showing how gas components such as H 2 , CO, and CH 4 are separated by the gas filter 14.

[0034] H 2 and CO, CH 4 When gas components such as H enter the separation tank 15, a pressure difference is created between both ends of the gas filter 16 due to the suction force of the pump 16. 2 H2 molecules are smaller than gas molecules such as CO2 and CH4, and H2 molecules pass through the gas filter 16 and are injected into the H2 gas tank 17.

[0035] A sufficient amount of H2 cannot be collected with a single pump 16. Therefore, in this embodiment, a plurality of separation tanks 15 and corresponding pumps 16 are provided.

[0036] The hydrogen concentration and pressure in the H2 gas tank 17 are measured by a hydrogen concentration measuring device 18 and a pressure gauge 19.

[0037] The remaining gas components (CO, undecomposed CH4) are sucked into the circulation pump 20 and sent to the gas tank 8 for recycling.

[0038] As shown in Figure 6(a), an SEM image of MWNTs from CNTs shows a thick MWNT layer, indicating that a large amount of MWNTs can be synthesized. (b) shows an SEM image of SWNTs from CNTs, clearly showing thin CNTs growing from the SWNTs.

[0039] As shown in Figure 7(a), this is a TEM image of MWNTs of CNTs. To confirm the characteristics of MWNTs, they were placed in a microgrid and observed using a transmission electron microscope (TEM). Multi-walled and single-walled carbon tubes are clearly observed. Most single-walled carbon tubes are bundled together, with only a few showing a single state.

[0040] Figure 8. Raman spectroscopy of MWNTs (a) and SWNTs (b). The Raman spectrum of CNTs contains a peak at 1,340 cm -1 The D-band was observed near 1,600 cm -1 A G-band is observed near the center, accompanied by a Fano-type spectrum with metal resonance. The ratio of these peaks can be used to evaluate the crystalline purity and defect ratio of carbon. (a) is the Raman spectrum of MWNTs, where a high D-band is observed, which is due to the high crystalline purity and defect ratio of some CNTs, resulting in an amorphous state. (b) is the Raman spectrum of SWNTs, where a low D-band is observed, which is due to the low crystalline purity and defect ratio of the CNTs.

[0041] Figure 9 shows an image of a hydrogen station. Fuel cell vehicles (FCVs), next-generation vehicles that run on hydrogen (H2), are the subject of a development race between automakers both in Japan and overseas, with Japan becoming the first country in the world to begin selling mass-produced vehicles in 2014. The penetration rate of hydrogen stations is extremely important, and is directly proportional to the number of FCVs. Currently, there are 164 commercial hydrogen stations in operation nationwide, but this number is expected to increase by several tens of times in the future.

[0042] The present invention is not limited to the above-described implementation process, but can be modified within the scope of the claims.

[0043] In summary, compared to the commonly used SRM, POM, and ATR methods, this method not only has the advantage of producing hydrogen more efficiently, but also produces CNTs that are more economical, and contributes to reducing greenhouse gas emissions and realizing a decarbonized society.

[0044] 1 is a vertical thermal CVD apparatus, 2 is a quartz tube, 3 is an electric furnace, 4 is a storage basket for the catalyst, 4a, ... are holes in the bottom plate of the storage basket, 5 is a spherical catalyst, 6 is a nebulizer device containing an Fe / ethanol mixture, 7 is a storage tank for natural gas such as methane, 8 is a gas tank, 9 is carbon nanotubes (CNTs), 10 is a CNTs collector, 11 is a filtration tank, 12 is a filtration filter, 13 is a purification chamber, 14 is a gas filter, 15 is a separation tank, 16 is a pump, 17 is an H2 gas tank, 18 is a hydrogen concentration measuring device, 19 is a pressure gauge, 20 is a circulation pump, 21 is a rotating shaft, 22 is a stirring blade, 23 is a motor

Claims

1. A hydrogen production system using nebulizer thermal CVD decomposition, comprising: a vertical thermal CVD apparatus having a heating furnace attached to the outer periphery of a quartz tube, and a nebulizer device storing an Fe-based element / alcohol mixture, the storage basket storing one or more types of catalysts carrying Fe, Ni, Co, Cu, Pd, Pt, Rh, Ru, Ir, and other transition metals and precious metals, the nebulizer device atomizing the Fe-based element / alcohol mixture into the vertical thermal CVD apparatus, the interior of which is set to 800°C to 1000°C by the heating furnace, natural gas containing methane as a carrier gas, the methane in the natural gas being brought into contact with the atomized Fe-based element or catalyst to decompose it into gaseous components containing carbon nanotubes and hydrogen, the hydrogen-containing gaseous components being passed through a filtration tank to filter out the carbon nanotubes contained therein, and hydrogen being extracted through a gas filter in a separation tank and stored in a tank provided outside, and the remaining gaseous components being returned to the carrier gas for circulating use.

2. The hydrogen production system according to claim 1, wherein the Fe-based element / alcohol is Fe / ethanol.

3. The hydrogen production system according to claim 1, wherein the carbon nanotubes collected in the production system are purified in a purification chamber.

4. A hydrogen production system according to claim 1, wherein the catalyst or the cage housing the catalyst is constantly vibrated to discharge the carbon nanotubes synthesized on the catalyst through a number of holes at the bottom.

5. A hydrogen production system according to claim 4, wherein the catalyst storage cage is supported and rotated by a rotating shaft journaled at the bottom thereof to constantly vibrate the catalyst within the storage cage.

6. A hydrogen production system according to claim 5, in which an agitating blade is disposed within the storage cage and the catalyst within the storage cage is constantly vibrated by rotating the agitating blade using a rotating shaft.

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