System for producing hydrogen by nebulizer thermal CVD decomposition

Abstract

To provide a system for producing hydrogen at high production efficiency together with a carbon nanotube thin film having high added value.SOLUTION: A system for producing hydrogen by nebulizer thermal CVD decomposition that comprises a vertical thermal CVD device 1 and a nebulizer device 6 storing an Fe / ethanol mixture, is configured such that an Fe / ethanol mixture liquid is atomized by the nebulizer device and natural gas mainly composed of methane is fed as carrier gas into the vertical thermal CVD device set at an internal temperature of 800°C to 1000°C, methane in the natural gas is brought into contact with atomized Fe or a catalyst for decomposition into carbon nanotubes 9 and a gas component containing hydrogen, the gas component containing hydrogen is filtered, hydrogen is taken out through a gas filter 14 and stored in a tank 17 provided externally, the remaining gas component is returned to the carrier gas for circulating use, and the collected carbon nanotubes are purified.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Natural gas is an extremely abundant petrochemical fuel resource, with the world's confirmed natural gas reserves of 14,211 trillion cubic meters, the equivalent of 914.3 billion barrels of crude oil. The estimated reserves are 250-350 trillion cubic meters. As methane is the main component of natural gas, many countries around the world attach great importance to the treatment and utilization of methane, and as the problem of global warming worsens, the production of hydrogen from methane is drawing increasing attention. There are various processes for producing hydrogen (H2), but the current mainstream hydrogen production in the industrial sector is by-product hydrogen from petrochemical plants and steel plants, and natural gas reforming.

[0003] The main methods are direct decomposition of methane: CH4 → C solid + 2H2 and steam reforming of methane (SRM): CH4 + 2H2O → CO2 + 4H2. Other methods that have been used up to now include partial oxidation of methane (POM) and auto thermal reforming of methane (ATR). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-169379 Summary of the Invention [Problem to be solved by the invention]

[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, the methane molecule must first be activated. Because the methane molecule is very inactive, the reaction conditions are very harsh, and methane can only be decomposed in high yields at temperatures above 900°C.

[0007] Direct methane decomposition has the great advantage that no CO2 is emitted during the reaction, but the problem is that the amount of hydrogen obtained from the same amount of methane is small. Also, steam reforming emits CO2 during the production of hydrogen, so in order to be carbon neutral, a device is required to capture and fix the generated CO2.

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

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

[0010] These are 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. [Means for solving the problem]

[0011] In view of the above circumstances, the present invention provides a vertical thermal CVD apparatus having a heating furnace provided around the outside of a quartz tube, a catalyst storage basket having a number of holes at its bottom, and a nebulizer device storing an Fe-based element / alcohol mixture, 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 mixture is atomized by the nebulizer device in the vertical thermal CVD apparatus, the inside 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, which is characterized by the following: natural gas, whose main component is methane, is sent 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 gas components containing hydrogen 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. The remaining gas components are returned to the carrier gas and recycled for reuse. Effect of the Invention

[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] Furthermore, the present invention has the advantage that no CO2 is emitted during the hydrogen production process, and therefore no CO2 capture and fixation equipment is required.

[0014] Furthermore, in the present invention, the catalyst or its storage cage is constantly vibrated to discharge the carbon nanotubes synthesized on the catalyst through multiple 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 making it possible to produce hydrogen at low production costs.

[0015] In this case, the means for constantly vibrating the catalyst or the basket containing it is a method in which the basket containing the catalyst is supported and rotated by a rotating shaft bearinged at the bottom, thereby constantly vibrating the catalyst inside the basket.

[0016] Alternatively, a method can be adopted in which an agitating blade is disposed inside the storage cage and the agitating blade is rotated by a rotating shaft to constantly vibrate the catalyst inside the storage cage. [Brief description of the drawings]

[0017] [Figure 1] Process diagram of hydrogen production according to the present invention [Diagram 2] Illustrated diagram of hydrogen decomposition and carbon nanotube (CNT) synthesis in a catalytic cage [Diagram 3] FIG. 1 shows an embodiment of vibrating a catalyst in a storage cage [Figure 4] FIG. 13 is a diagram showing another embodiment of vibrating the catalyst in the storage cage. [Diagram 5] A diagram showing the separation of H2 gas, CO, and CH4 gas in the present invention. [Figure 6] SEM images of multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) [Figure 7] TEM images of multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) [Figure 8] Raman spectroscopy of multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotube nets (SWNTs) [Figure 9] Diagram of a hydrogen station constructed using produced H2 gas DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The system is equipped with a vertical thermal CVD apparatus and a nebulizer device containing an Fe / ethanol mixed liquid, and the inside of the vertical thermal CVD apparatus is set to 800℃-1000℃. The nebulizer device atomizes the Fe / ethanol mixed liquid, and natural gas, mainly composed of methane, is sent into the vertical thermal CVD apparatus as a carrier gas. The methane in the natural gas is brought into contact with the atomized Fe or catalyst to decompose it into gaseous components containing carbon nanotubes and hydrogen. The gaseous components containing hydrogen 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 circulating use, and the collected carbon nanotubes are purified. EXAMPLES

[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 cage 4 having holes 4a... at its bottom is provided within the quartz tube 2, and the storage cage 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 cage 4 is constantly vibrated by an externally installed vibration device.

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

[0023] In FIG. 4, an agitating blade 22 is disposed within a catalyst storage basket 4, and the agitating blade 22 is rotated by a rotating shaft 21 driven by a motor 23 to vibrate 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] Also, natural gas such as methane is injected into a gas tank 8 and sent as a carrier gas to the nebulizer device 6 , where the Fe / ethanol mixture is atomized and sent into the quartz tube 2 .

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

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

[0029] As shown in Fig. 2, by vibrating the catalyst storage cage 4, the synthesized CNTs 9 are constantly rolled over and discharged from the holes 4a, etc. in the bottom plate without being attached or 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] The carbon nanotubes (CNTs) deposited in the lower collector 10 of the vertical thermal CVD apparatus 1 and the carbon nanotubes (CNTs) filtered in the filtration tank 11 are sent to a purification chamber 13 and purified.

[0032] The gas components (H2, CO, and 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 a conceptual diagram showing how gas components such as H 2 , CO, and CH 4 are separated by the gas filter 14.

[0034] When gas components such as H2, CO, and CH4 enter the separation tank 15, a pressure difference is created at both ends of the gas filter 16 by the suction force of the pump 16. H2 molecules are smaller than gas molecules such as CO and CH4, so the 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), the SEM image of MWNTs of CNTs shows a thick MWNTs layer, and it is possible to synthesize a large amount of MWNTs. (b) shows the SEM image of SWNTs of CNTs, and thin-film CNTs are clearly observed from the SWNTs.

[0039] As shown in Figure 7(a), the TEM images of MWNTs of CNTs are shown. In order 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 of the single-walled carbon tubes are bundled together, and only a few show a single state.

[0040] Figure 8. Raman spectroscopy of MWNTs (a) and SWNTs (b). The Raman spectrum of CNTs shows 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, along with a Fano-type spectrum resonating with metal. 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 CNTs.

[0041] Figure 9 shows an image of a hydrogen station. Fuel cell vehicles (FCVs), the next-generation automobiles that run on hydrogen (H2), are the subject of a development race underway by automakers both in Japan and overseas, and Japan began selling mass-produced vehicles in 2014, ahead of the rest of the world. The penetration rate of hydrogen stations is extremely important, and is directly proportional to the number of FCVs. Currently, 164 commercial hydrogen stations are in operation across the country, and 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 may be modified within the scope of the claims. [Industrial Applicability]

[0043] In summary, compared with the commonly used SRM, POM, and ATR methods, this invention not only has the advantage of more efficient hydrogen production, but also produces economical CNTs, and contributes to reducing greenhouse gas emissions and realizing a decarbonized society. [Explanation of symbols]

[0044] 1 is a vertical thermal CVD device 2 is a quartz tube 3 is an electric furnace 4 is the catalyst storage cage 4a, ... are holes provided on the bottom plate of the storage cage 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 collector of CNTs 11 is the filter tank 12 is a filter 13 is the refining room 14 is a gas filter 15 is a separation tank 16 is a pump 17 is H2 gas tank 18 is a hydrogen concentration measuring instrument 19 is a pressure gauge 20 is a circulation pump 21 is the axis of rotation 22 is a stirring blade 23 is the 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. 2. The hydrogen production system according to claim 1, wherein the Fe-based element / alcohol is Fe / ethanol.

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

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

5. 5. The 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. 6. The hydrogen production system according to claim 5, wherein 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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