Reactors, systems and methods

Abstract

This suppresses the precipitation and accumulation of solid carbon on the walls of reactors used for the thermal decomposition of hydrocarbon gases. [Solution] In a reactor 100 for thermally decomposing hydrocarbon gas, provided in a system 10 that thermally decomposes hydrocarbon gas to produce hydrogen gas and solid carbon, the reactor comprises: a container body 102 provided with a cylindrical side wall 102a; a hydrocarbon gas introduction channel 104 provided on the central axis CA1 on the top side of the container body for introducing hydrocarbon gas into the container body from the top side; high-temperature gas introduction channels 106a and 106b provided on the upper end side of the side wall for introducing high-temperature gas from the horizontal direction to heat the hydrocarbon gas introduced from the hydrocarbon gas introduction channel and generating a swirling flow of high-temperature gas along the inner circumferential surface of the container body; and a discharge channel 108 provided on the central axis on the bottom side of the container body for discharging a mixed fluid of reaction gas containing hydrogen gas and solid carbon produced by thermal decomposition of hydrocarbon gas in the container body and high-temperature gas.

Description

Technical Field

[0001] The present invention relates to a reactor, a system, and a method.

Background Art

[0002] In order to achieve the prevention of global warming, it is required to reduce or even eliminate the CO2 emissions associated with energy consumption such as fossil fuels. From this perspective, technologies have been developed to produce hydrogen without emitting carbon dioxide by thermally decomposing hydrocarbon gases such as methane contained in natural gas to produce carbon as a solid.

[0003] As a related technology for thermally decomposing hydrocarbon gases such as methane to produce solid carbon and hydrogen gas, Patent Document 1 discloses a process in which methane gas is exposed to a molten salt medium and a solid catalyst within the volume of a reaction vessel under conditions effective for converting at least a portion of methane into hydrogen and solid carbon. On the other hand, Patent Document 2 discloses a hydrogen production apparatus that includes a steam supply unit for supplying steam to a first reaction unit that thermally decomposes hydrocarbons by the waste heat of a power generation device to produce solid carbon and hydrogen, thereby reducing the thermal energy required for hydrogen production and preventing clogging of the reactor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] When hydrocarbon gases are thermally decomposed under high-temperature conditions, the deposition and accumulation of solid carbon on the heated surface of the reactor where the hydrocarbon gas is decomposed can lead to concerns about rapid blockage of the pipeline system and shutdown of the system. Therefore, in systems that thermally decompose hydrocarbon gases to produce solid carbon and hydrogen gas, it is desirable to extend the continuous operation period of the system by suppressing the deposition and accumulation of solid carbon on the walls of the reactor where the hydrocarbon gas is decomposed.

[0006] This invention has been made in view of the above problems, and aims to suppress the precipitation and accumulation of solid carbon on the walls of a reactor used for the thermal decomposition of hydrocarbon gases. [Means for solving the problem]

[0007] One aspect of the present invention relates to a reactor for thermally decomposing a hydrocarbon gas, which is provided in a system for thermally decomposing a hydrocarbon gas to produce hydrogen gas and solid carbon, and comprises: a container body having a cylindrical side wall; a hydrocarbon gas introduction channel provided on the top side of the central axis of the container body for introducing the hydrocarbon gas into the container body from the top side; a high-temperature gas introduction channel provided on the upper end side of the side wall for introducing high-temperature gas from the horizontal direction to heat the hydrocarbon gas introduced from the hydrocarbon gas introduction channel, thereby generating a swirling flow of the high-temperature gas along the inner circumferential surface of the container body; and a discharge channel provided on the bottom side of the central axis of the container body for discharging a mixed fluid of the reaction gas containing hydrogen gas and solid carbon produced by thermally decomposing the hydrocarbon gas in the container body and the high-temperature gas.

[0008] According to one aspect of the present invention, since hydrocarbon gas introduced into the reactor from the top side is heated and thermally decomposed by a swirling flow of high-temperature gas generated along the inner circumferential surface of the container body, the deposition and accumulation of solid carbon on the walls of the reactor where the hydrocarbon gas is thermally decomposed can be suppressed.

[0009] Another aspect of the present invention relates to a system for producing hydrogen gas and solid carbon by thermal decomposition of a hydrocarbon gas, comprising: a reactor as described above; a hydrogen gas storage unit for storing the hydrogen gas produced by the thermal decomposition of the hydrocarbon gas in the reactor; and a control unit for controlling at least the temperature and flow rate of the hydrocarbon gas introduced into the reactor and the high-temperature gas introduced to heat the hydrocarbon gas in the reactor.

[0010] According to another aspect of the present invention, since hydrocarbon gas introduced into the reactor from the top side is heated and thermally decomposed by a swirling flow of high-temperature gas generated along the inner circumferential surface of the container body, the deposition and accumulation of solid carbon on the walls of the reactor where the hydrocarbon gas is thermally decomposed can be suppressed.

[0011] A further aspect of the present invention is a method for producing hydrogen gas and solid carbon by thermal decomposition of a hydrocarbon gas, wherein the hydrocarbon gas is introduced into the reactor from the top side of the reactor, which is provided with a cylindrical side wall, in the direction of the central axis, and a high-temperature gas that heats the hydrocarbon gas is introduced into the reactor from the upper end side of the side wall of the reactor, in a direction tangential to the vertical plane with respect to the central axis of the reactor, thereby generating a swirling flow of the high-temperature gas along the inner circumferential surface of the reactor, and the hydrocarbon gas is thermally decomposed while the swirling flow of the high-temperature gas comes into contact with the hydrocarbon gas introduced into the reactor from the top side.

[0012] According to yet another aspect of the present invention, since hydrocarbon gas introduced into the reactor from the top side is heated and thermally decomposed by a swirling flow of high-temperature gas generated along the inner circumferential surface of the container body, the deposition and accumulation of solid carbon on the reactor wall where the hydrocarbon gas is thermally decomposed can be suppressed. [Effects of the Invention]

[0013] According to the present invention, the deposition and accumulation of solid carbon on the walls of a reactor used for the thermal decomposition of hydrocarbon gases can be suppressed. [Brief explanation of the drawing]

[0014] [Figure 1] This block diagram shows an example of the overall schematic configuration of a system to which a reactor according to one embodiment of the present invention is applied. [Figure 2] This is a perspective view showing the schematic configuration of a reactor according to one embodiment of the present invention. [Figure 3] This is an explanatory diagram showing the CFD analysis results of the fluid velocity distribution inside a reactor when thermal decomposition is performed using a reactor according to one embodiment of the present invention. [Figure 4] This is an explanatory diagram showing the CFD analysis results of the temperature distribution inside a reactor when thermal decomposition is performed using a reactor according to one embodiment of the present invention. [Figure 5] This is an explanatory diagram showing the CFD analysis results of the solid carbon concentration distribution inside a reactor when thermal decomposition is performed using a reactor according to one embodiment of the present invention. [Figure 6] This is an explanatory diagram showing the CFD analysis results of the fluid streamline diagram inside a reactor when thermal decomposition is performed using a reactor according to one embodiment of the present invention. [Figure 7] (A), (B), and (C) are perspective views showing schematic configurations of modified examples of a reactor according to one embodiment of the present invention. [Modes for carrying out the invention]

[0015] Preferred embodiments of the present invention will be described in detail below. It should be noted that the embodiments described below are not intended to unduly limit the scope of the present invention as described in the claims, and not all of the configurations described in these embodiments are necessarily essential as solutions to the present invention.

[0016] In the following description, the terms "up," "down," "left," and "right" are used for explanatory purposes only and do not limit the method or manner of use. The terms "first" and "n" (where n is an integer) following "first" as described herein and in the claims are used as identifying terms to distinguish different elements and do not indicate any particular order or superiority.

[0017] The schematic configuration of a system to which a reactor according to an embodiment of the present invention is applied will be described while using the drawings. FIG. 1 is a block diagram showing an example of the overall schematic configuration of a system to which a reactor according to an embodiment of the present invention is applied.

[0018] The system 10 of the present embodiment is applied as a system for performing a method of thermally decomposing a hydrocarbon gas composed of a light hydrocarbon such as methane to produce hydrogen gas and solid carbon. The system 10 thermally decomposes, for example, a hydrocarbon gas composed of a light hydrocarbon having 4 or less carbon atoms such as methane contained in natural gas to produce hydrogen gas and solid carbon without discharging carbon dioxide. The system 10 shown in FIG. 1 includes a reactor 100 that serves as a reactor for thermally decomposing a hydrocarbon gas to produce hydrogen gas and solid carbon.

[0019] As shown in FIG. 1, the system 10 includes a reactor 100, a cooler 110, a cyclone separator 120, a first surge bin 122, and a first rotary valve 124. The system 10 further includes a gas cooler 130, a bag filter 140, a second surge bin 142, a second rotary valve 144, a solid carbon storage unit 150, and a hydrogen gas storage unit 160.

[0020] The reactor 100 functions as a reactor for thermally decomposing a hydrocarbon gas to produce hydrogen gas and solid carbon. In the present embodiment, the reactor 100 includes a container main body portion 102, a hydrocarbon gas introduction flow path 104, a high-temperature gas introduction flow path 106, and a discharge flow path 108.

[0021] The hydrocarbon gas introduction channel 104 has the function of introducing hydrocarbon gas to be thermally decomposed into the container body 102. In this embodiment, as shown in Figure 1, the hydrocarbon gas introduction channel 104 is positioned to stand upright at or near the top center of the container body 102 in order to introduce hydrocarbon gas into the container body 102 from the top side of the container body 102. The hydrocarbon gas introduced from the hydrocarbon gas introduction channel 104 is a light hydrocarbon such as methane, ethane, propane, and butane, which are alkanes with 4 or fewer carbon atoms and are thermally decomposed in a high-temperature range of about 1400 to 1600°C. The hydrocarbon gas is introduced from the outside by a hydrocarbon gas blower 170, heated to a desired temperature of, for example, 300 to 700°C by a hydrocarbon gas heating heater 171, and then introduced from the top side of the container body 102.

[0022] Thus, by preheating the hydrocarbon gas with the hydrocarbon gas heating heater 171 before introducing the hydrocarbon gas to the top of the container body 102 from the outside, the temperature and flow rate of the high-temperature hydrogen gas to be mixed can be reduced, which is desirable from the viewpoint of energy saving and the design of the hydrogen supply system's piping. However, in this embodiment, since light hydrocarbons consisting of alkanes with 4 or fewer carbon atoms, such as methane, ethane, propane, and butane, are used as the hydrocarbon gas introduced into the container body 102, thermal decomposition will occur if the temperature exceeds 800°C before it is introduced to the top of the container body 102. For this reason, in this embodiment, the temperature of the hydrocarbon gas introduced into the container body 102 from the outside is controlled so that it does not exceed 800°C.

[0023] The high-temperature gas introduction channel 106 has the function of introducing high-temperature gas horizontally to heat the hydrocarbon gas introduced from the hydrocarbon gas introduction channel 104 to the top side of the container body 102, thereby generating a swirling flow of high-temperature gas along the inner circumferential surface of the container body 102. Hydrogen gas stored in the hydrogen gas storage section 160, which stores hydrogen gas generated in system 10, is introduced into the high-temperature gas introduction channel 106. The hydrogen gas introduced into the high-temperature gas introduction channel 106 is introduced after being heat-treated as follows.

[0024] First, the first filter 161 is used to remove impurities such as dust and dirt from a portion of the hydrogen gas stored in the hydrogen gas storage unit 160. Then, the first hydrogen gas blower 162 is used to send the hydrogen gas from which impurities have been removed to the hydrogen gas heating heater 163, where it is heated to 1000-1600°C. The resulting high-temperature hydrogen gas is then introduced as high-temperature gas into the high-temperature gas introduction channel 106.

[0025] If the target gas reaction temperature after mixing is approximately 1400°C, and assuming a mass flow rate of 1 for the hydrocarbon gas to be treated, and a mass flow rate of 1.5 to 3 times that of high-temperature hydrogen gas is supplied, supplying a very large flow rate of hydrocarbon gas to the container body 102 would require increasing the size of the supply channel and thus the size of the first hydrogen gas blower 162, thus preventing overall space saving of the equipment. For this reason, in this embodiment, taking into consideration space saving of the equipment and equipment design, it is preferable to control the temperature of the high-temperature hydrogen gas used to heat the hydrocarbon gas to 1500°C or higher.

[0026] Thus, the high-temperature hydrogen gas used for heating hydrocarbon gases is recycled from hydrogen gas produced by the thermal decomposition of light hydrocarbon gases. Note that until a predetermined time has elapsed after the system 10 is started, a sufficient amount of hydrogen gas is not stored in the hydrogen gas storage unit 160. Therefore, other inert gases such as nitrogen may be heated and used as the high-temperature gas for heating the bicarbonate gas. Furthermore, electrical resistance heating using green electricity generated by the hydrogen gas produced in the system 10 may also be used to heat the hydrogen gas.

[0027] The discharge channel 108 has the function of discharging a mixed fluid of reaction gas containing hydrogen gas and solid carbon, which are produced by the thermal decomposition of hydrocarbon gas within the container body 102, and high-temperature gas. The discharge channel 108 is connected to the cooler introduction channel 114 of the cooler 110, which is located downstream of the reactor 100.

[0028] The cooler 110 has the function of cooling the mixed fluid discharged from the discharge channel 108 of the reactor 100 with a cooling gas. As shown in Figure 1, the cooler 110 comprises a cooler body 112, a cooler inlet channel 114, a cooling gas inlet channel 116, and a cooler discharge channel 118.

[0029] The cooler introduction channel 114 has the function of introducing the mixed fluid from the reactor 100 to be cooled into the cooler body 112. The mixed fluid introduced from the cooler introduction channel 114 is cooled to the desired temperature by the cooling gas introduced from the cooling gas introduction channel 116 located on the upper end side of the cooler body 112.

[0030] Similar to the high-temperature gas introduction channel 106 described above, hydrogen gas stored in the hydrogen gas storage unit 160 is introduced into the cooling gas introduction channel 116. The hydrogen gas introduced into the cooling gas introduction channel 116 is processed as follows. First, a second filter 164 is used to remove impurities such as dust and dirt contained in a portion of the hydrogen gas stored in the hydrogen gas storage unit 160. Then, a second hydrogen gas blower 165 is used to introduce the hydrogen gas from which impurities have been removed as a cooling gas into the cooling gas introduction channel 116. The mixed fluid, which has been rapidly cooled to a desired temperature of about 500-600°C after the reaction by the hydrogen gas introduced from the cooling gas introduction channel 116, is then discharged from the cooler discharge channel 118. In this example, the reactor 100 and the cooler 110 are configured as separate units, but the reactor 100 and the cooler 110 may be configured as a single main unit, with the cooling gas being introduced from around the middle of this main unit.

[0031] The mixed fluid cooled by the cooler 110 is separated into solid and gas in the subsequent cyclone separator 120. The mixed gas, mainly composed of hydrogen gas, obtained from the cyclone separator 120 is then cooled by the subsequent gas cooler 130 before being fed into the bag filter 140. The cooled mixed gas, mainly composed of hydrogen gas, is further separated into solid and gas in the bag filter 140 to remove excess solids such as solid carbon, resulting in higher purity hydrogen gas which is then stored in the hydrogen gas storage unit 160. In this way, the hydrogen gas produced through the thermal decomposition of hydrocarbon gas in the reactor 100 is stored in the hydrogen gas storage unit 160.

[0032] As mentioned above, the hydrogen gas generated and stored in system 10 is partially heated by the hydrogen gas heating heater 163 and used as a high-temperature gas for thermal decomposition in reactor 100, and partially used as a cooling gas to cool the mixed fluid discharged from reactor 100. The remaining hydrogen gas, other than that reused as high-temperature gas and cooling gas, is utilized in renewable energy sources such as fuel cells and hydrogen power generation, as well as in the chemical industry and other fields.

[0033] On the other hand, the solid carbon obtained by solid-gas separation in the cyclone separator 120 is temporarily stored, for example, in the first surge bin 122, then the granular solid carbon is discharged by the first rotary valve 124 and transported to the solid carbon storage unit 150 using nitrogen gas blown from the nitrogen gas blower 172. Similarly, the solid carbon obtained by solid-gas separation in the bag filter 140 is temporarily stored, for example, in the second surge bin 142, then the granular solid carbon is discharged by the second rotary valve 144 and transported to the solid carbon storage unit 150 using nitrogen gas blown from the nitrogen gas blower 172. In this way, the solid carbon produced by the thermal decomposition of light hydrocarbon gas is separated and recovered as carbon black and can be used as a basic material for tire products, paints, conductive materials, etc.

[0034] The control unit 180 has the function of controlling all or part of the components of the system 10. The control unit 180 includes components such as a processor 181, a storage unit 182, and a connector 183, which are connected to each other via a bus. The processor 181 includes, for example, a CPU (Central Processing Unit). The storage unit 182 includes, for example, a hard disk, a ROM (Read Only Memory) for storing programs, and a RAM (Random Access Memory) as a work area. The control unit 180 communicates with each component of the system 10 via the connector 183. The control unit 180 may further include other components such as a display device such as a liquid crystal display or a touch panel, and an input device such as a keyboard, buttons, or a touch panel. The operation of the control unit 180 may be realized, for example, by having the processor 181 execute a program stored in the storage unit 182.

[0035] The control unit 180 has the function of controlling at least the temperature and flow rate of the hydrocarbon gas and high-temperature gas introduced into the reactor 100. Specifically, the control unit 180 controls the hydrogen gas heating heater 163 so that the hydrogen gas is heated to a temperature of 1400 to 1600°C. The control unit 180 also controls the hydrocarbon gas heating heater 171 so that the temperature of the hydrocarbon gas in the hydrocarbon gas introduction channel 104, which introduces the hydrocarbon gas into the reactor 100 from the top side of the container body 102, is 800°C or lower. Furthermore, the control unit 180 controls the first hydrogen gas blower 162 and the hydrocarbon gas blower 170 so that, for example, the flow rate of the hydrocarbon gas in the hydrocarbon gas introduction channel 104 is 5 to 25 m / s and the flow rate of the high-temperature gas in the high-temperature gas introduction channel 106 is 15 to 30 m / s, in order to achieve a desirable mixing flow rate ratio of the hydrocarbon gas and high-temperature gas introduced into the reactor 100.

[0036] Next, the details of the reactor 100 according to one embodiment of the present invention will be described with reference to the drawings. Figure 2 is a perspective view showing the schematic configuration of the reactor 100 according to one embodiment of the present invention.

[0037] The reactor 100 functions as a reactor for thermally decomposing hydrocarbon gas. As shown in Figure 2, the reactor 100 comprises a container body 102, a hydrocarbon gas introduction channel 104, a high-temperature gas introduction channel 106 (106a, 106b), and an exhaust channel 108.

[0038] The container body 102 functions as a reactor that thermally decomposes hydrocarbon gas introduced from the top of the container body 102 to produce hydrogen gas and solid carbon, and is provided with cylindrical side walls 102a. In this embodiment, the container body 102 as a whole has a cylindrical shape with a circular cross-section at the side walls 102a. Furthermore, since the container body 102 needs to have heat resistance that can withstand the high temperature of several hundred degrees Celsius at which thermal decomposition takes place, it is preferable that it be formed from a ceramic heat-resistant material such as alumina, zirconia, or zircon.

[0039] As shown in Figure 2, the container body 102 is provided with a tapered surface 102b that is formed so that the inner diameter of the container body 102 decreases toward the bottom. The tapered surface 102b is formed to have an inclination angle of 10 to 20 degrees with respect to the central axis CA1 in order to accelerate the flow while maintaining a swirling flow toward the outlet without generating a separating flow in the flow path. It is preferable that the entire container body 102 be made of a heat-resistant material such as alumina, but it is sufficient that the heat resistance of the part that comes into direct contact with the high-temperature gas is ensured, so it is sufficient that at least the inner surface is made of a heat-resistant material.

[0040] As described above, the hydrocarbon gas introduction channel 104 is a tubular member that has the function of introducing hydrocarbon gas to be thermally decomposed from the top side of the container body 102. The hydrocarbon gas introduction channel 104 is provided so as to be oriented vertically on the top side of the central axis CA1 of the container body 102, and is designed to allow hydrocarbon gas to be introduced from the top side of the container body 102 in the direction of the central axis CA1. Bicarbonate gas consisting of light hydrocarbons such as methane, heated to a desired temperature not exceeding 800°C, is introduced from the top side of the container body 102 via the hydrocarbon gas introduction channel 104.

[0041] As described above, the high-temperature gas introduction channels 106 (106a, 106b) have the function of introducing high-temperature gas into the container body 102 from a horizontal direction to heat the hydrocarbon gas introduced from the top side of the hydrocarbon gas introduction channel 104. As shown in Figure 2, the high-temperature gas introduction channels 106a and 106b are hollow, rectangular cylindrical channels, but other shapes of channels may also be used. Furthermore, the high-temperature gas introduction channels 106a and 106b introduce high-temperature gas from the tangential direction of the periphery of the container body 102 in a vertical plane (orthogonal plane) with respect to the central axis CA1 of the container body 102. The high-temperature gas introduction channels 106a and 106b are provided as a pair on the upper end side of the side wall 102a of the container body 102 so as to be rotationally symmetrical, i.e., point-symmetrical, with respect to the central axis CA1 of the container body 102. Therefore, the high-temperature gas introduction channels 106a and 106b have the function of introducing high-temperature gas into the container body 102 while generating a swirling flow F1 (see Figure 6) of the high-temperature gas along the inner circumferential surfaces 102a1 and 102b1 (see Figure 4) of the container body 102.

[0042] The discharge channel 108 has the function of discharging a mixed fluid of reaction gas containing hydrogen gas and solid carbon, which are produced by the thermal decomposition of hydrocarbon gas within the container body 102, and high-temperature gas. The discharge channel 108 is located on the bottom side of the central axis CA1 of the container body 102. That is, the discharge channel 108 is positioned coaxially with the hydrocarbon gas introduction channel 104 and the central axis CA1.

[0043] As described above, in this embodiment, the reactor 100, which functions as a reactor that thermally decomposes hydrocarbon gas to produce hydrogen gas and solid carbon, is configured to allow the introduction of high-temperature light hydrocarbon gas to be thermally decomposed from the top side of the main body 102 of the reactor 100 along the central axis CA1. Furthermore, the reactor 100 in this embodiment is configured to allow the introduction of heated high-temperature hydrogen gas symmetrically from the side of the reactor 100. As a result, a swirling flow of high-temperature hydrogen gas is generated along the inner circumferential surfaces 102a1 and 102b1 of the main body 102 of the reactor 100, thereby suppressing contact between the light hydrocarbon gas introduced from the top side of the main body 102 and the inner wall of the main body 102, while enabling the direct mixing of the light hydrocarbon gas to be thermally decomposed and the high-temperature hydrogen gas within the reactor 100 for reaction thermal decomposition.

[0044] Furthermore, in this embodiment, the hydrocarbon gas introduced into the reactor 100 from the top side of the container body 102 is heated by a swirling flow of high-temperature hydrogen gas generated along the inner circumferential surfaces 102a1 and 102b1 of the container body 102 of the reactor 100, while the hydrocarbon gas is thermally decomposed. As a result, the solid carbon produced by the thermal decomposition of the hydrocarbon gas is blown away by the swirling flow of high-temperature hydrogen gas, thereby suppressing its adhesion to the inner circumferential surfaces 102a1 and 102b1.

[0045] Next, the results of the CFD (Computational Fluid Dynamics) analysis inside the reactor when thermal decomposition is performed using the reactor according to one embodiment of the present invention will be explained with reference to the figures. Figure 3 is an explanatory diagram showing the CFD analysis results of the fluid velocity distribution inside the reactor when thermal decomposition is performed using the reactor according to one embodiment of the present invention, and Figure 4 is an explanatory diagram showing the CFD analysis results of the temperature distribution inside the reactor. Furthermore, Figure 5 is an explanatory diagram showing the CFD analysis results of the solid carbon concentration distribution inside the reactor, and Figure 6 is an explanatory diagram showing the CFD analysis results of the fluid streamline diagram inside the reactor.

[0046] In order to solve the problem of suppressing the deposition and accumulation of solid carbon on the walls of a reactor used for the thermal decomposition of hydrocarbon gases, the inventors diligently investigated the fluid velocity distribution, temperature distribution, solid carbon concentration distribution, and fluid streamline diagram within the reactor when thermal decomposition was performed using the reactor of this embodiment, and discovered the following phenomenon.

[0047] In this embodiment, the main body 102 of the reactor 100 is φ200 (outer diameter 200 mm), the hydrocarbon gas introduction channel 104 is φ50 (outer diameter 50 mm), the length of one side of the high-temperature gas introduction channels 106a and 106b is □50 (50 mm), and the discharge channel 108 is φ100 (outer diameter 100 mm). Figure 3 shows the fluid velocity distribution inside the reactor 100 when methane gas at 500°C is introduced at a rate of 2.5 kg / h from the hydrocarbon gas introduction channel 104 and hydrogen gas at 1600°C is introduced at a total rate of 5.0 kg / h from the high-temperature gas introduction channels 106a and 106b.

[0048] As shown in Figure 3, it can be seen that the fluid velocity increases from the inner circumferential surface 102a1 of the side wall 102a of the container body 102 to the inner circumferential surface 102b1 of the tapered surface 102b. In this embodiment, by introducing high-temperature hydrogen gas horizontally from the high-temperature gas introduction channels 106a and 106b, a swirling flow of high-temperature hydrogen gas is generated along the inner circumferential surfaces 102a1 and 102b1 of the container body 102, and the velocity of the swirling flow is accelerated at the inner circumferential surface 102b1 of the tapered surface 102b on the bottom side of the container body 102. From this, it can be seen that the swirling flow of high-temperature hydrogen gas accelerates and flows along the inner circumferential surfaces 102a1 and 102b1 of the container body 102, causing the solid carbon produced by thermal decomposition to be blown away by the swirling flow. Therefore, it is presumed that the solid carbon produced by thermal decomposition will be less likely to adhere to the inner circumferential surfaces 102a1 and 102b1 of the container body 102.

[0049] As shown in Figure 4, the CFD analysis results of the temperature distribution inside reactor 100 show that both the inner circumferential surface 102a1 of the side wall 102a and the inner circumferential surface 102b1 of the tapered surface 102b of the container body 102 are at the temperature of high-temperature hydrogen gas. Therefore, it can be seen that the hydrocarbon gas introduced from the hydrocarbon gas introduction channel 104 located on the top side of the container body 102 flows only along the central axis CA1 of reactor 100. From this, it can be inferred that only a swirling flow of high-temperature hydrogen gas flows on the inner circumferential surfaces 102a1 and 102b1 of reactor 100, and that the hydrocarbon gas flowing from the top side of the container body 102 along the central axis CA1 is heated and thermally decomposed by the swirling flow of high-temperature hydrogen gas.

[0050] Furthermore, as shown in Figure 5, the CFD analysis results of the solid carbon concentration distribution within the reactor 100 show that the solid carbon concentration is high on the central axis CA1 of the reactor 100, while the solid carbon concentration is low on the inner circumferential surfaces 102a1 and 102b1 of the container body 102. From this, it can be seen that the solid carbon generated by the thermal decomposition of hydrocarbon gas within the reactor 100 flows along the central axis CA1 of the reactor 100, thus reducing the adhesion of solid carbon to the inner circumferential surfaces 102a1 and 102b1 of the container body 102.

[0051] Furthermore, as shown in Figure 6, the CFD analysis results of the fluid stream diagram inside reactor 100 show that a swirling flow F1 of high-temperature hydrogen gas is generated along the inner circumferential surfaces 102a1 and 102b1 of the container body 102. This indicates that when high-temperature hydrogen gas is introduced from the high-temperature gas introduction channels 106a and 106b provided on the upper end of the side wall 102a of the container body 102 of reactor 100, a swirling flow is generated along the inner circumferential surfaces 102a1 and 102b1 of the container body 102. Therefore, the hydrocarbon gas flowing from the top of the container body 102 along the central axis CA1 of reactor 100 is heated and thermally decomposed by the generated swirling flow, thus suppressing the deposition and accumulation of solid carbon on the walls of reactor 100.

[0052] Note that the configuration of the reactor 100 in this embodiment is not limited to the configuration shown in Figure 2. A modified configuration of the reactor 100 in this embodiment will be described with reference to Figures 7(A) to 7(C).

[0053] For example, as shown in Figure 7(A), compared to the reactor 100 shown in Figure 2, the reactor 200 has a cylindrical shape overall, with the main body 202 of the container not having a tapered surface on the bottom side. With this configuration, the high-temperature gas introduced from the high-temperature gas introduction channels 206a and 206b generates a swirling flow along the inner circumferential surface of the main body 202 of the container. As a result, the hydrocarbon gas flowing along the central axis of the reactor 200 from the hydrocarbon gas introduction channel 204 located at the top of the main body 202 is heated and thermally decomposed by the high-temperature gas introduced from the high-temperature gas introduction channels 206a and 206b, thus suppressing the deposition and accumulation of solid carbon on the walls of the reactor 200. Although not shown in Figure 7(A), two pairs of gas introduction channels may be provided. In other words, the pair of high-temperature gas introduction channels 206a and 206b and the other pair of gas introduction channels may be arranged on the same plane as the plane in which the high-temperature gas introduction channels 206a and 206b are provided, such that they are 90° apart from each other with respect to the central axis CA1.

[0054] Furthermore, the other pair of gas introduction channels may be provided on a different plane from the pair of high-temperature gas introduction channels 206a and 206b. That is, for example, the other pair of gas introduction channels may be provided in the middle or lower section of the container body 202. By providing the other pair of gas introduction channels on a different plane in this way, the flow velocity of the swirling flow of the introduced high-temperature gas can be re-accelerated by the high-temperature gas introduced from the other pair of gas introduction channels, thereby suppressing the decrease in the flow velocity of the swirling flow. Alternatively, a single gas introduction channel may be provided instead of the other pair of gas introduction channels. By adjusting the number of gas introduction channels provided, the degree of re-acceleration of the swirling flow can be adjusted.

[0055] Furthermore, as shown in Figure 7(B), compared to the reactor 100 shown in Figure 2, the reactor 300 has a high-temperature gas introduction channel 306 provided on the upper end side of the side wall 302a of the container body 302, and is arranged so that high-temperature gas can be introduced from the tangential direction of the periphery of the container body 302 within a vertical plane with respect to the central axis of the container body 302. With this configuration, the high-temperature gas introduced from the high-temperature gas introduction channel 306 generates a swirling flow along the inner circumferential surface of the side wall 302a and tapered surface 302b of the container body 302, heating the hydrocarbon gas flowing along the central axis from the hydrocarbon gas introduction channel 304 located on the top side of the reactor 300, thereby thermally decomposing the hydrocarbon gas and discharging it from the discharge channel 308, thus suppressing the deposition and accumulation of solid carbon on the walls of the reactor 300.

[0056] Furthermore, as shown in Figure 7(C), the configuration of reactor 400 differs from that of reactor 300 shown in Figure 7(B) in that the container body 402 does not have a tapered surface, but otherwise the configuration is the same. That is, reactor 400 does not have a tapered surface on the bottom side of the container body 402 where the inner diameter of the container body 402 decreases, and has a cylindrical shape with a constant inner diameter. With this configuration, the high-temperature gas introduced from the high-temperature gas introduction channel 406 generates a swirling flow along the inner circumferential surface of the container body 402. By heating and thermally decomposing the hydrocarbon gas flowing along the central axis from the hydrocarbon gas introduction channel 404 located at the top of reactor 400, the deposition and accumulation of solid carbon on the walls of reactor 400 can be suppressed.

[0057] Next, the operation and effects of the reactor, system, and method according to this embodiment will be described.

[0058] The inventors of this invention diligently investigated the problem of suppressing the precipitation and accumulation of solid carbon on the walls of reactors used for the thermal decomposition of hydrocarbon gases, and discovered the following phenomenon.

[0059] In other words, the inventors have found that when high-temperature hydrocarbon gas is introduced from the top side of the reactor's central axis, and then heated high-temperature gas is introduced horizontally from the side of the reactor, a swirling flow of high-temperature gas is generated along the inner circumferential surface of the container body. Furthermore, the inventors have found that by directly mixing the hydrocarbon gas introduced from the top side of the reactor with the swirling flow of high-temperature gas, and then thermally decomposing the hydrocarbon gas while heating it, the thermal decomposition reaction can be carried out while suppressing contact between the hydrocarbon gas to be heated and the inner circumferential surface of the reactor container body. According to these findings, by generating a swirling flow of high-temperature gas introduced from the side of the reactor, contact between the hydrocarbon gas being thermally decomposed while heating the hydrocarbon gas introduced from the top side of the reactor and the inner circumferential surface of the reactor container body, which forms the flow path wall, is suppressed, and the accumulation of solid carbon on the wall surface can be reduced. As a result, it becomes possible to prevent the reactor from becoming blocked.

[0060] In related technologies for thermally decomposing light hydrocarbon gases such as methane to produce hydrogen gas and solid carbon, heating methods include introducing the process gas into a heating tube or bringing it into direct contact with a high-temperature heating element. However, both methods have the problem of solid carbon precipitation and accumulation on the heating surface, leading to rapid blockage of the pipeline system and shutdown of operations, as well as the need for a process to remove the precipitated carbon.

[0061] In contrast, the system and method of this embodiment for thermally decomposing hydrocarbon gas to produce hydrogen gas and solid carbon involves direct mixing of light hydrocarbon gas such as methane with high-temperature hydrogen gas in a cyclone-type flow field. This allows the thermal decomposition reaction to be carried out while preventing contact between the bicarbonate gas and the reactor wall. This suppresses the deposition and accumulation of solid carbon on the pipeline wall on the inner circumferential side of the reactor, thereby extending the continuous operation period.

[0062] Furthermore, in this embodiment, a high-temperature gas introduction channel is provided on the upper end of the side wall of the reactor, in a vertical plane with respect to the central axis of the container body, to introduce high-temperature gas from the tangential direction of the periphery of the container body. As a result, a swirling flow of high-temperature gas is easily generated along the inner circumferential surface of the container body, and as hydrocarbon gas introduced from the top of the reactor is heated with the high-temperature gas, the solid carbon produced by thermal decomposition can be suppressed from adhering to the inner circumferential surface of the container body. In particular, by providing a pair of high-temperature gas introduction channels arranged rotationally symmetrically with respect to the central axis of the container body, a swirling flow of high-temperature gas is easily generated along the inner circumferential surface of the container body, thereby suppressing the adhesion of the generated solid carbon to the inner circumferential surface of the container body.

[0063] Furthermore, according to the system and method of this embodiment, in order to generate a thermal decomposition reaction of hydrocarbon gas, the hydrogen gas generated by thermal decomposition is circulated and reheated and used as a high-temperature gas. In this way, since the generated hydrogen gas is reused as a high-temperature gas or cooling gas, it becomes possible to achieve a circulating hydrocarbon gas detoxification treatment while generating hydrogen gas and solid carbon without using extra raw materials or emitting carbon dioxide.

[0064] Furthermore, according to the system and method of this embodiment, a swirling flow of high-temperature gas introduced along the inner circumferential surface of the reactor vessel body having cylindrical side walls is generated, and the hydrocarbon gas introduced from the top of the reactor is mixed with and brought into contact with it in a simple manner, thereby performing thermal decomposition of hydrocarbon gas. For this reason, compared to other thermal decomposition methods discussed as related technologies mentioned above, it is possible to realize an apparatus configuration under low-pressure conditions without requiring pressure vessels or pressure piping.

[0065] Although one embodiment of the present invention has been described in detail above, it will be readily apparent to those skilled in the art that many modifications are possible without substantially departing from the novel aspects and effects of the present invention. Therefore, all such modifications are included within the scope of the present invention.

[0066] For example, any term that appears at least once in the specification or drawings alongside a broader or synonymous term may be replaced with that different term anywhere in the specification or drawings. Furthermore, the reactor configuration and operation are not limited to those described in this embodiment, and various modifications are possible. [Explanation of symbols]

[0067] 10 Systems 100 reactors 102 Container body 102a side wall 102a1 Inner surface (of the side wall) 102b Tapered surface 102b1 Inner surface (of tapered surface) 104 Hydrocarbon gas introduction channel 106 High-temperature gas introduction channel 106a High-temperature gas introduction channel 106b High-temperature gas introduction channel 108 Discharge channel 110 Cooler 112 Cooler body 114 Cooler introduction channel 116 Cooling gas introduction channel 118 Cooler discharge channel 120 Cyclone Separator 122 First surge bin 124 First Rotary Valve 130 Gas Cooler 140 Bug Filters 142 Second surge bin 144. Second Rotary Valve 150 Solid carbon storage unit 160 Hydrogen gas storage unit 161 First filter 162 First hydrogen gas blower 163 Hydrogen gas heating heater 164 Second filter 165 Second hydrogen gas blower 170 Hydrocarbon gas blower 171 Hydrocarbon gas heating heater 172 Nitrogen gas blower 180 Control Unit 181 processors 182 Memory section 183 Connector 200 reactors 202 Container body 204 Hydrocarbon gas introduction channel 206a High-temperature gas introduction channel 206b High-temperature gas introduction channel 300 reactors 302 Container body 302a side wall 302b Tapered surface 304 Hydrocarbon gas introduction channel 306 High-temperature gas introduction channel 308 Discharge channel 400 reactors 402 Container body 404 Hydrocarbon gas introduction channel 406 High-temperature gas introduction channel CA1 center axis F1 swirl flow

Claims

1. In a reactor for thermally decomposing hydrocarbon gas, provided in a system that thermally decomposes hydrocarbon gas to produce hydrogen gas and solid carbon, A container body having cylindrical side walls, A hydrocarbon gas introduction channel is provided on the top side of the central axis of the container body and introduces the hydrocarbon gas into the container body from the top side, A high-temperature gas introduction channel is provided on the upper end side of the side wall and introduces high-temperature gas, which heats the hydrocarbon gas introduced from the hydrocarbon gas introduction channel, from a horizontal direction to generate a swirling flow of the high-temperature gas along the inner circumferential surface of the container body, A discharge channel is provided on the bottom side of the central axis of the container body for discharging a mixed fluid of reaction gas containing hydrogen gas and solid carbon, which is produced by thermal decomposition of the hydrocarbon gas within the container body, and the high-temperature gas. A reactor equipped with the following features.

2. The reactor according to claim 1, wherein the high-temperature gas introduction channel is provided to introduce the high-temperature gas from a direction tangential in a vertical plane with respect to the central axis of the container body.

3. The reactor according to claim 1, wherein a pair of high-temperature gas introduction channels are provided so as to be rotationally symmetric with respect to the central axis of the container body.

4. The reactor according to claim 1, wherein the container body is provided with a tapered surface formed such that the inner diameter of the container body decreases toward the bottom side.

5. The reactor according to claim 4, wherein the tapered surface has an inclination angle of 10 to 20 degrees with respect to the central axis.

6. The reactor according to any one of claims 1 to 5, wherein at least the inner surface of the container body is formed of a heat-resistant material.

7. In a system that thermally decomposes the hydrocarbon gas to produce hydrogen gas and solid carbon, The reactor according to claim 1, A hydrogen gas storage unit for storing the hydrogen gas produced by the thermal decomposition of the hydrocarbon gas in the reactor, A control unit that controls at least the temperature and flow rate of the hydrocarbon gas introduced into the reactor and the high-temperature gas introduced to heat the hydrocarbon gas within the reactor, A system equipped with these features.

8. The system according to claim 7, wherein a cooler is provided for cooling the mixed fluid discharged from the reactor with the hydrogen gas stored in the hydrogen gas storage unit.

9. The system according to claim 7, wherein the high-temperature gas is a high-temperature hydrogen gas produced by heating a portion of the hydrogen gas stored in the hydrogen gas storage unit.

10. The system according to claim 9, wherein the control unit heats the hydrogen gas and controls it so that the high-temperature hydrogen gas reaches 1400 to 1600°C.

11. The system according to any one of claims 7 to 10, wherein the control unit controls the temperature of the hydrocarbon gas in the hydrocarbon gas introduction channel for introducing the hydrocarbon gas into the reactor to be 800°C or less.

12. The system according to claim 11, wherein the control unit controls the flow velocity of the hydrocarbon gas in the hydrocarbon gas introduction channel to be 5 to 25 m / s, and the flow velocity of the high-temperature gas in the high-temperature gas introduction channel for introducing the high-temperature gas into the reactor to be 15 to 30 m / s.

13. In a method for producing hydrogen gas and solid carbon by thermal decomposition of hydrocarbon gas, The hydrocarbon gas is introduced into the reactor from the top side of the reactor, which is provided with cylindrical side walls, in the direction of the central axis. A high-temperature gas that heats the hydrocarbon gas is introduced into the reactor from the upper end of the side wall of the reactor in a tangential direction in a vertical plane with respect to the central axis of the reactor, thereby generating a swirling flow of the high-temperature gas along the inner circumferential surface of the reactor. A method for thermally decomposing a hydrocarbon gas while bringing the swirling flow of the high-temperature gas into contact with the hydrocarbon gas introduced into the reactor from the top side.

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