Hydrocarbon production apparatus and method for producing hydrocarbons

Abstract

To provide another technique for improving purity of a produced gas in a hydrocarbon production apparatus.SOLUTION: A hydrocarbon production apparatus comprises: a reactor that houses a catalyst containing a metal with hydrocarbon synthesis catalyst performance and a metal with carbon dioxide occlusion performance; a raw material gas supply unit that is connected to the reactor and supplies a raw material gas containing carbon dioxide to the reactor; a hydrogen supply unit that is connected to the reactor and supplies hydrogen to the reactor; a gas discharge unit that is connected to the reactor and discharges the gas inside the reactor by creating a negative pressure inside the reactor; and a control unit that controls the raw material gas supply unit, the hydrogen supply unit, and the gas discharge unit. The control unit causes the raw material gas supply unit to supply the raw material gas to the reactor, and then causes the gas discharge unit to discharge the gas inside the reactor, and then causes the hydrogen supply unit to supply the hydrogen to the reactor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the production of hydrocarbons. [Background technology]

[0002] Conventionally, hydrocarbon production apparatuses for producing hydrocarbon compounds from carbon dioxide and hydrogen have been known. For example, Patent Document 1 proposes a technology in which a carbon dioxide-containing gas is passed through a reactor containing activated ferritic iron oxide to adsorb the carbon dioxide, and then hydrogen is supplied to the reactor to recover methane. In this technology, if the methane concentration in the gas recovered in one reaction is low, a mixed gas of the product methane and unreacted hydrogen is supplied again to the reactor as methanation gas. That is, the technology discloses a technology in which the methane concentration in the recovered gas is increased by circulating the methanation gas multiple times. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-110731 Summary of the Invention [Problem to be solved by the invention]

[0004] In such a hydrocarbon production apparatus for producing hydrocarbon compounds from carbon dioxide and hydrogen, it is desired to improve the purity of the collected product gas.

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide another technique for improving the purity of the produced gas in a hydrocarbon production apparatus. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following aspects.

[0007] (1) According to one aspect of the present invention, there is provided a hydrocarbon production apparatus for producing hydrocarbons from carbon dioxide and hydrogen. The hydrocarbon production apparatus includes a reactor containing a catalyst including a metal having hydrocarbon synthesis catalytic activity and a metal having carbon dioxide occlusion activity, a raw material gas supply unit connected to the reactor and supplying a raw material gas including carbon dioxide to the reactor, a hydrogen supply unit connected to the reactor and supplying hydrogen to the reactor, and a gas discharge unit connected to the reactor and discharging gas within the reactor by creating a negative pressure within the reactor, wherein the control unit controls the raw material gas supply unit to supply the reactor with the raw material gas, the gas discharge unit to discharge the gas within the reactor, and then controls the hydrogen supply unit to supply hydrogen to the reactor.

[0008] According to this configuration, after the raw material gas is supplied to the reactor by the raw material gas supply unit, carbon dioxide is occluded by the catalyst in the reactor, and then the pressure inside the reactor is made negative by the gas exhaust unit, so that the gas remaining in the reactor (hereinafter also referred to as residual gas) can be discharged before hydrocarbon synthesis (before hydrogen is supplied). Therefore, when hydrogen is supplied to the reactor by the hydrogen supply unit, the amount of residual gas in the reactor is reduced. The residual gas after carbon dioxide is occluded contains nitrogen, oxygen, etc., and since the amount of residual gas in the reactor is reduced when hydrogen is supplied to the reactor, the purity of hydrocarbons in the product gas (hydrocarbon-containing gas) generated by supplying hydrogen to the reactor can be increased.

[0009] (2) The hydrocarbon production apparatus of the above aspect may further include a pressure acquisition unit that acquires a pressure value inside the reactor, and a reactor outlet valve that can open and close a gas outlet inside the reactor, and the control unit may close the reactor outlet valve and supply hydrogen to the reactor when the pressure value acquired by the pressure acquisition unit satisfies a low-pressure condition under which the hydrocarbon synthesis reaction in the reactor does not proceed easily. According to this configuration, the reactor outlet is sealed under a low-pressure condition under which the hydrocarbon synthesis reaction does not proceed easily, thereby suppressing the outflow of unreacted hydrogen. Furthermore, sealing the reactor outlet and increasing the pressure inside the reactor can improve the hydrocarbon conversion rate.

[0010] (3) The hydrocarbon production apparatus of the above aspect may further include a reactor outlet valve capable of opening and closing the gas outlet in the reactor, and the control unit may close the reactor outlet valve when supplying hydrogen to the reactor, supply hydrogen to the reactor for a predetermined time, and then open the reactor outlet valve to supply hydrogen to the reactor. When the gas in the reactor is discharged, the pressure in the reactor is low, so by supplying hydrogen while sealing the reactor for a predetermined time, the pressure in the reactor is increased. This also makes it possible to suppress the outflow of unreacted hydrogen and improve the hydrocarbon conversion rate.

[0011] (4) In the hydrocarbon production apparatus of the above aspect, the gas discharge unit may be disconnectably connected to a recovery tank that recovers the hydrocarbons, and the control unit may cause the gas discharge unit to recover the gas in the reactor into the recovery tank before supplying the raw material gas to the reactor. In this way, the product gas remaining in the reactor can be recovered and the reactor can be purged. As a result, the recovery rate of the product gas can be improved.

[0012] (5) According to another aspect of the present invention, a method for producing hydrocarbons is provided. This method for producing hydrocarbons includes a raw material gas supplying step of supplying a raw material gas containing carbon dioxide to a reactor containing a catalyst including a metal having hydrocarbon synthesis catalytic activity and a metal having carbon dioxide storage activity; a gas discharge step of discharging gas from the reactor by creating a negative pressure inside the reactor after the raw material gas supplying step; and a hydrogen supplying step of supplying hydrogen to the reactor after the gas discharge step. According to this method, carbon dioxide is occluded by the catalyst in the reactor in the raw material gas supplying step, and in the subsequent gas discharge step, the reactor is created under negative pressure to discharge residual gas from the reactor before hydrocarbon synthesis (before hydrogen is supplied). Therefore, when hydrogen is supplied to the reactor, the amount of residual gas (including nitrogen, oxygen, etc.) in the reactor has been reduced, and the purity of hydrocarbons in the product gas (hydrocarbon-containing gas) produced by supplying hydrogen to the reactor can be increased.

[0013] The present invention can be realized in various forms, for example, in the form of a system including a hydrocarbon production apparatus, a control method for the apparatus and system, a computer program for causing the apparatus and system to carry out hydrocarbon production, a server device for distributing the computer program, a non-transitory storage medium storing the computer program, etc. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing a schematic configuration of a hydrocarbon production apparatus 1 according to a first embodiment. [Figure 2] FIG. 1 is an explanatory diagram conceptually showing the reaction mechanism in a reactor 10. [Figure 3] 1 is a process diagram of a hydrocarbon production method in a hydrocarbon production apparatus 1. FIG. [Figure 4] FIG. 1 is a schematic diagram showing a schematic configuration of a hydrocarbon production apparatus 1A according to a second embodiment. [Figure 5] FIG. 2 is a process diagram of a hydrocarbon production method in a hydrocarbon production apparatus 1A. [Figure 6]FIG. 10 is a schematic diagram showing a schematic configuration of a hydrocarbon production apparatus 1B according to a third embodiment. [Figure 7] FIG. 2 is a process diagram of a hydrocarbon production method in a hydrocarbon production apparatus 1B. [Figure 8] FIG. 10 is a schematic diagram showing a schematic configuration of a hydrocarbon production apparatus 1C according to a fourth embodiment. [Figure 9] FIG. 2 is a process diagram of a hydrocarbon production method in a hydrocarbon production apparatus 1C. [Figure 10] FIG. 10 is a schematic diagram showing a schematic configuration of a hydrocarbon production apparatus 1D according to a fifth embodiment. [Figure 11] FIG. 2 is a process diagram of a hydrocarbon production method in a hydrocarbon production apparatus 1D. [Figure 12] FIG. 1 is a graph showing the relationship between the pressure inside the reactor and the hydrocarbon concentration under the first reaction conditions. [Figure 13] FIG. 10 is a graph showing the relationship between the pressure inside the reactor and the hydrocarbon concentration under the second reaction conditions. DETAILED DESCRIPTION OF THE INVENTION

[0015] First Embodiment FIG. 1 is a schematic diagram showing the general configuration of a hydrocarbon production apparatus 1 according to a first embodiment. The hydrocarbon production apparatus 1 according to this embodiment produces methane (CH) as a hydrocarbon from carbon dioxide (CO) and hydrogen (H) recovered from a gas containing carbon dioxide (CO). The hydrocarbon production apparatus 1 according to the first embodiment includes a reactor 10, a raw material gas supply unit 20, a hydrogen supply unit 30, a gas discharge unit 40, a control unit 50, and a product gas tank 70.

[0016] The reactor 10 synthesizes CH4 through a methanation reaction therein. The reactor 10 accommodates a catalyst 12. The catalyst 12 includes a metal having methane synthesis catalytic performance and a metal having carbon dioxide occlusion performance. In this embodiment, the catalyst 12 is a compacted alumina powder supporting (Ru+CaO), in which the amount of ruthenium (Ru) supported is 5 parts by mass and the amount of calcium (Ca) supported is 10 parts by mass in terms of calcium oxide (CaO) per 100 parts by mass of alumina (Al2O3) powder. In addition to Ru, other metals that can be used as hydrocarbon synthesis catalytic performance include precious metals such as rhodium (Rh), platinum (Pt), and palladium (Pd), and transition metals such as nickel (Ni) and cobalt (Co). In addition to calcium oxide (CaO), metals with carbon dioxide storage capacity can include alkali metal oxides such as lithium oxide (Li2O), sodium oxide (Na2O), potassium oxide (K2O), rubidium oxide (Rb2O), and cesium oxide (Cs2O), as well as alkaline earth metal oxides such as magnesium oxide (MgO), strontium oxide (SrO), and barium oxide (BaO). Catalyst supports can also include alumina (Al2O3), titanium dioxide (TiO2), zirconia (ZrO2), cerium oxide (CeO2), and magnesium dioxide (MgO2).

[0017] The reactor 10 is connected to a raw material gas supply pipe 26 through which the raw material gas flows, a hydrogen supply valve 34 through which hydrogen gas flows, and a first gas flow pipe 61 through which gas discharged from the reactor 10 flows.

[0018] A carbon dioxide concentration sensor 62 is disposed in the first gas flow pipe 61. The carbon dioxide concentration sensor 62 detects the carbon dioxide concentration of the gas extracted from the reactor 10. The carbon dioxide concentration sensor 62 outputs a signal corresponding to the detected carbon dioxide concentration to the control unit 50.

[0019] Three pipes, namely, a second gas circulation pipe 63, a third gas circulation pipe 65, and a fourth gas circulation pipe 67, are connected to the downstream side of the first gas circulation pipe 61.

[0020] Furthermore, a dehydrator 14 is disposed in the first gas circulation pipe 61. The gas extracted from the reactor 10 flows through the first gas circulation pipe 61, is dehydrated by the dehydrator 14, and flows into the second gas circulation pipe 63. A first valve 64 and a compressor 66 are disposed in the second gas circulation pipe 63, and the downstream end of the second gas circulation pipe 63 is connected to a produced gas tank 70. The gas that flows into the second gas circulation pipe 63 is compressed by the compressor 66 and collected in the produced gas tank 70.

[0021] The raw material gas supply unit 20 supplies a raw material gas containing CO2, which is supplied from a "supply source" such as a combustion furnace or an internal combustion engine, to the reactor 10 via a raw material gas supply pipe 26. In this embodiment, the raw material gas supply unit 20 includes a raw material gas tank 22 and a raw material gas supply valve 24. The raw material gas tank 22 stores the raw material gas in a pressurized state. The raw material gas stored in the raw material gas tank 22 may contain O2, N2, H2O, etc. in addition to CO2. In this embodiment, the raw material gas tank 22 stores the raw material gas so that the temperature of the raw material gas is, for example, 350°C or less. Note that the configuration of the raw material gas supply unit 20 is not limited thereto, and gas discharged from a combustion furnace may be directly supplied to the reactor 10. In addition, the "supply source" is not limited to a combustion furnace or an internal combustion engine, and may be anything that generates a gas containing CO2.

[0022] The raw material gas supply valve 24 is disposed in the raw material gas supply pipe 26 and is electrically connected to the control unit 50. The opening degree of the raw material gas supply valve 24 is controlled in response to a command from the control unit 50. That is, the flow rate of the raw material gas supplied from the raw material gas tank 22 to the reactor 10 is adjusted by the raw material gas supply valve 24.

[0023] The hydrogen supply unit 30 supplies H to the reactor 10 via a hydrogen supply pipe 36. In this embodiment, the hydrogen supply unit 30 includes a hydrogen gas tank 32 and a hydrogen supply valve 34. In other embodiments, the hydrogen gas tank 32 may be replaced with, for example, a water electrolysis device.

[0024] The hydrogen supply valve 34 is disposed in the hydrogen supply pipe 36. The hydrogen supply valve 34 is, for example, a mass flow controller, and is electrically connected to the control unit 50, and its opening degree is controlled in response to a command from the control unit 50. That is, the flow rate of H supplied to the reactor 10 is adjusted by the hydrogen supply valve 34.

[0025] The gas discharge unit 40 discharges the gas inside the reactor 10 by creating a negative pressure inside the reactor 10. The gas discharge unit 40 has a second valve 42 and a vacuum pump 44, and is disposed in the third gas circulation pipe 65. In this embodiment, the vacuum pump 44 operates continuously while the hydrocarbon production apparatus 1 is in operation, and when the second valve 42 is opened in accordance with a command from the control unit 50, the gas inside the reactor 10 is discharged to the outside of the hydrocarbon production apparatus 1 via the first gas circulation pipe 61 and the third gas circulation pipe 65.

[0026] A third valve 68 is disposed in the fourth gas circulation pipe 67. The third valve 68 opens and closes in accordance with commands from the control unit 50. When the raw material gas is supplied to the reactor 10 with the third valve 68 open, gases (e.g., nitrogen, oxygen, etc.) that have not been occluded in the reactor 10 are discharged to the outside of the hydrocarbon production apparatus 1 via the first gas circulation pipe 61 and the fourth gas circulation pipe 67.

[0027] The control unit 50 is a computer including a ROM, a RAM, and a CPU, and performs overall control of the hydrocarbon production apparatus 1. The control unit 50 controls the raw material gas supply unit 20 and the hydrogen supply unit 30 by controlling the opening and closing of the raw material gas supply valve 24, the hydrogen supply valve 34, the first valve 64, and the third valve 68 based on a signal output from the carbon dioxide concentration sensor 62, thereby controlling the supply of raw material gas and hydrogen gas. The control unit 50 also controls the gas discharge unit 40 by controlling the opening and closing of the second valve 42. Details of the control by the control unit 50 will be described later. A program that realizes the control performed by the control unit 50 is pre-stored in the control unit 50. The program may also be provided by a program provider via a communication network. The program may also be stored in a commercially available portable storage medium. In this case, the portable storage medium may be set in an external or built-in reading device, and the program may be read and executed by the control unit 50. The portable storage medium can be of various types, such as a CD-ROM, a DVD-ROM, a flexible disk, an optical disk, a magneto-optical disk, an IC card, a USB memory device, etc. The program stored in such a storage medium is read by a reading device.

[0028] The product gas tank 70 stores, at high pressure, the product gas containing the hydrocarbons synthesized in the reactor 10. The product gas stored in the product gas tank 70 is supplied to, for example, a device (not shown) that uses CH, such as a combustion furnace.

[0029] FIG. 2 is an explanatory diagram conceptually illustrating the reaction mechanism in the reactor 10. When the feed gas is supplied to the reactor, CO2 chemically reacts with the metal with CO2 storage capacity, resulting in the catalyst absorbing and retaining the CO2 in the carbonate state. After the metal with CO2 storage capacity has absorbed sufficient CO2, H2 gas is switched to the reactor. Activated H2 on the catalyst surface reacts with CO2 in the carbonate state via the metal with hydrocarbon synthesis catalytic performance, synthesizing hydrocarbons. The chemical CO2 absorption reaction, which has high CO2 retention capacity, enables CO2 capture under conditions that are relatively difficult to achieve with physical adsorption, such as high temperatures (e.g., 300°C) and low CO2 partial pressures using a vacuum pump. In this embodiment, the Sabatier reaction (CO2 + 4H2 → CH4 + 2H2O) occurs in the reactor 10.

[0030] FIG. 3 is a process diagram of a hydrocarbon production method in the hydrocarbon production apparatus 1. In this embodiment, the control unit 50 executes a program stored in advance in the control unit 50, thereby realizing the hydrocarbon production method. The hydrocarbon production process shown in FIG. 3 can be executed at any timing in the hydrocarbon production apparatus 1. In this embodiment, for example, the process starts in the raw material gas supply unit 20 when a sufficient amount of raw material gas containing CO2 discharged from the combustion furnace is stored in the raw material gas tank 22 for hydrocarbon production in the reactor 10. In the hydrocarbon production method of this embodiment, hydrocarbons can be continuously produced by repeating the process shown in FIG. 3.

[0031] In the hydrocarbon production method of this embodiment, as shown in Fig. 3, an occlusion step in which a feed gas containing carbon dioxide is brought into contact with a catalyst 12 contained in a reactor 10 to occlude carbon dioxide, and a reduction step in which hydrogen is supplied to reduce the occluded carbon dioxide are alternately repeated. In addition, a purging step is included between the occlusion step and the reduction step to prevent gas mixing between the two steps. In this embodiment, vacuum purging using a vacuum pump is performed as the purging step.

[0032] First, the control unit 50 closes the first valve 64 and the second valve 42 and opens the third valve 68 (step P102), thereby supplying the raw material gas to the reactor 10 (step P104). Specifically, in step P104, the control unit 50 increases the aperture of the raw material gas supply valve 24, causing the raw material gas stored in the raw material gas tank 22 to flow into the reactor 10 via the raw material gas supply pipe 26. In the reactor 10, CO2 contained in the flowing raw material gas is occluded by the catalyst 12, thereby removing CO2 from the raw material gas. The residual gas, which is the raw material gas remaining after CO2 removal, flows through the first gas flow pipe 61 and is dehydrated in the dehydrator 14. Since the first valve 64 and the second valve 42 are closed in step P102, the dehydrated residual gas is released to the outside of the hydrocarbon production apparatus 1 via the fourth gas flow pipe 67.

[0033] When the supply of the raw material gas starts, the control unit 50 acquires the concentration value of the carbon dioxide concentration of the gas extracted from the reactor 10, i.e., the residual gas, from the carbon dioxide concentration sensor 62 (step P106). Specifically, the carbon dioxide concentration sensor 62 detects the carbon dioxide concentration of the residual gas flowing through the first gas flow pipe 61, and sends a corresponding signal to the control unit 50.

[0034] The control unit 50 continues to supply the raw material gas and repeatedly acquires the concentration value from the carbon dioxide concentration sensor 62 until the concentration value acquired from the carbon dioxide concentration sensor 62 becomes greater than 100 ppm (NO in step P108). When the carbon dioxide concentration of the residual gas is 100 ppm or less, it is expected that the amount of carbon dioxide occluded by the catalyst 12 is still less than the saturation amount of the catalyst 12, and therefore the control unit 50 continues to supply the raw material gas.

[0035] When the concentration value acquired from the carbon dioxide concentration sensor 62 is greater than 100 ppm, the control unit 50 closes the raw material gas supply valve 24 to stop the supply of raw material gas, and proceeds to step P110. This is because when the carbon dioxide concentration of the residual gas is greater than 100 ppm, it indicates that the amount of CO2 occluded per unit time by the catalyst 12 has begun to decrease, and it is expected that the amount of carbon dioxide occluded by the catalyst 12 is approaching the saturation amount of the catalyst 12. Note that the threshold value in step P108 is not limited to this embodiment. As shown in the figure, steps P102 to P108 are the occlusion step.

[0036] Next, the control unit 50 opens the second valve 42 and closes the third valve 68 (step P110). As described above, the vacuum pump 44 is operating while hydrocarbon production is being carried out in the hydrocarbon production apparatus 1. Therefore, when the second valve 42 is opened, the vacuum pump 44 extracts the residual gas remaining in the reactor 10 from the reactor 10 and passes through the first gas circulation pipe 61 and the third gas circulation pipe 65 to be discharged to the outside of the hydrocarbon production apparatus 1. At the end of the occlusion step, the residual gas remaining in the reactor 10 contains carbon dioxide, nitrogen, oxygen, water, etc. Note that, in step P110, the carbon dioxide occluded in the catalyst 12 of the reactor 10 is not discharged. Here, the residual gas discharged to the outside of the hydrocarbon production apparatus 1 has been dehydrated by the dehydrator 14 arranged in the first gas circulation pipe 61. Step P110 is a purging step.

[0037] After a predetermined time (e.g., 10 seconds) has elapsed, the control unit 50 opens the first valve 64, closes the second valve 42, and increases the opening of the hydrogen supply valve 34 to supply hydrogen gas to the reactor 10 (step P112). In the reactor 10, the catalyst 12 is activated for methane synthesis, and CH is synthesized by a methanation reaction between CO2 occluded in the catalyst 12 and H2. The methane-containing gas containing the methane synthesized in the reactor 10 flows into the first gas flow pipe 61, is dehydrated by the dehydrator 14, flows into the second gas flow pipe 63, is compressed by the compressor 66, and is collected in the product gas tank 70. After a predetermined time (e.g., 50 seconds) has elapsed, the control unit 50 closes the hydrogen supply valve 34 to stop the supply of hydrogen. Step P112 is a reduction step. The time for vacuum purging and the time for supplying hydrogen can be set as appropriate.

[0038] Thereafter, the control unit 50 opens the second valve 42 and closes the first valve 64 (step P113). As described above, the vacuum pump 44 operates while hydrocarbons are being produced in the hydrocarbon production apparatus 1. Therefore, when the second valve 42 is opened, the residual gas remaining in the reactor 10 is removed from the reactor 10 by the vacuum pump 44 and discharged to the outside of the hydrocarbon production apparatus 1 through the first gas circulation pipe 61 and the third gas circulation pipe 65. At the end of the reduction step, the residual gas remaining in the reactor 10 contains hydrogen not used in the reduction, methane produced in the reduction step, and the like. The residual gas removed from the reactor 10 in step P113 has a different composition from the residual gas removed from the reactor 10 in step P110. Here, the residual gas discharged to the outside of the hydrocarbon production apparatus 1 has been dehydrated by the dehydrator 14 arranged in the first gas circulation pipe 61. Step P113 is a purging step.

[0039] After a predetermined time (for example, 10 seconds) has elapsed, the control unit 50 returns to step P102 and repeats the hydrocarbon production process. The time for performing vacuum purging can be set appropriately. In the hydrocarbon production apparatus 1, for example, when the remaining amount of raw material gas in the raw material gas tank 22 becomes equal to or less than a predetermined threshold, the control unit 50 terminates the production of hydrocarbons.

[0040] As described above, according to the hydrocarbon production apparatus 1 of this embodiment, after the raw material gas is supplied to the reactor 10 by the raw material gas supply unit 20 and carbon dioxide is occluded by the catalyst 12 in the reactor 10, the residual gas in the reactor 10 is sucked by the gas exhaust unit 40 without supplying a purge gas, thereby creating a negative pressure in the reactor 10. This allows the residual gas (nitrogen, oxygen, etc.) remaining in the reactor 10 to be discharged before hydrocarbon synthesis (before hydrogen is supplied). Therefore, when hydrogen is supplied to the reactor 10 by the hydrogen supply unit 30, the amount of residual gas in the reactor 10 is reduced. For example, if a method of circulating a predetermined amount of nitrogen (N2) is used in the purging step, the reactor 10 will be filled with a large amount of nitrogen gas, and this nitrogen gas will mix with the product gas during the reduction step, reducing the purity of the product gas. In contrast, in this embodiment, vacuum purging is used in the purging step, which allows the purity of hydrocarbons in the product gas (hydrocarbon-containing gas) produced by supplying hydrogen to the reactor 10 in the reduction step to be increased.

[0041] Furthermore, according to the hydrocarbon production apparatus 1 of this embodiment, a line (third gas circulation pipe 65) is provided to purge the inside of the reactor 10 using a vacuum pump 44, and the circulation lines for the outlet gas are different for each of the absorption process, purge process, and reduction process, so that it is possible to prevent nitrogen, oxygen, etc. (residual gas) from being mixed into the produced gas.

[0042] Furthermore, according to the hydrocarbon production method of this embodiment, carbon dioxide is occluded in the catalyst 12 in the reactor 10 in the raw material gas supply step, and in the subsequent gas discharge step, the residual gas remaining in the reactor 10 is discharged before hydrocarbon synthesis (before hydrogen is supplied). Therefore, when hydrogen is supplied to the reactor 10 in the hydrogen supply step, the amount of residual gas in the reactor 10 has been reduced, and the purity of hydrocarbons in the product gas (hydrocarbon-containing gas) produced by supplying hydrogen to the reactor 10 can be increased.

[0043] Second Embodiment Fig. 4 is a schematic diagram showing the general configuration of a hydrocarbon production apparatus 1A of the second embodiment. The hydrocarbon production apparatus 1A of the second embodiment differs from the hydrocarbon production apparatus 1 of the first embodiment (Fig. 1) in that it does not include the fourth gas circulation pipe 67 and the third valve 68, and that a control unit 50 controls the vacuum pump 44. In the embodiments described below, the same components as those of the hydrocarbon production apparatus 1 of the first embodiment are denoted by the same reference numerals, and reference is made to the preceding description.

[0044] 5 is a process diagram of a hydrocarbon production method in the hydrocarbon production apparatus 1A. In the hydrocarbon production method of this embodiment, a control unit 50 controls the ON / OFF of a vacuum pump in a purging step. In the hydrocarbon production method described below, the same steps as in the first embodiment are denoted by the same reference numerals.

[0045] First, the control unit 50 closes the first valve 64 and opens the second valve 42 (step P102A), and supplies the raw material gas to the reactor 10 (step P104). In the reactor 10, CO2 contained in the inflow raw material gas is occluded by the catalyst 12, so that CO2 is removed from the raw material gas. The residual gas, which is the raw material gas remaining after CO2 has been removed, flows through the first gas circulation pipe 61 and is dehydrated in the dehydrator 14. In step P102A, because the first valve 64 is closed and the second valve 42 is open, the dehydrated residual gas is released to the outside of the hydrocarbon production apparatus 1 via the third gas circulation pipe 65. At this time, because the vacuum pump 44 is not operating, the residual gas is discharged as the raw material gas is supplied to the reactor 10.

[0046] When the supply of raw material gas starts, the control unit 50 acquires the concentration value of the carbon dioxide concentration of the gas extracted from the reactor 10, i.e., the residual gas, from the carbon dioxide concentration sensor 62 (step P106), and while continuing the supply of raw material gas, repeatedly acquires the concentration value from the carbon dioxide concentration sensor 62 until the concentration value acquired from the carbon dioxide concentration sensor 62 becomes greater than 100 ppm (NO in step P108).

[0047] When the concentration value acquired from the carbon dioxide concentration sensor 62 is greater than 100 ppm, the control unit 50 closes the raw material gas supply valve 24 to stop the supply of raw material gas, and proceeds to step P110A. As shown in the figure, steps P102A to P108 are absorption steps.

[0048] Next, the control unit 50 starts the vacuum pump 44 to start discharging the residual gas in the reactor 10 (step P110A). At this time, the residual gas remaining in the reactor 10 is extracted from the reactor 10 by the vacuum pump 44 and is discharged to the outside of the hydrocarbon production apparatus 1 through the first gas circulation pipe 61 and the third gas circulation pipe 65. At the end of the storage step, the residual gas remaining in the reactor 10 contains carbon dioxide, nitrogen, oxygen, water, etc. Note that in step P110A, the carbon dioxide stored in the catalyst 12 of the reactor 10 is not discharged.

[0049] After a predetermined time (for example, 10 seconds) has elapsed, the control unit 50 closes the second valve 42 and stops the vacuum pump 44 (step P111). The vacuum purging ends at step P111. Steps P110A to P111 constitute the purging step. The time for performing the vacuum purging can be set appropriately.

[0050] Thereafter, the control unit 50 opens the first valve 64 and increases the opening of the hydrogen supply valve 34 to supply hydrogen gas to the reactor 10 (step P112A). In the reactor 10, the catalyst 12 is activated for methane synthesis, and CH is synthesized by a methanation reaction between CO2 occluded in the catalyst 12 and H2. The methane-containing gas containing the methane synthesized in the reactor 10 flows into the first gas circulation pipe 61, is dehydrated by the dehydrator 14, flows into the second gas circulation pipe 63, is compressed by the compressor 66, and is collected in the product gas tank 70. After a predetermined time (e.g., 50 seconds) has elapsed, the control unit 50 closes the hydrogen supply valve 34 to stop the supply of hydrogen. Step P112A is a reduction step.

[0051] Next, the control unit 50 closes the first valve 64, opens the second valve 42, and starts the vacuum pump 44 to start discharging the remaining gas in the reactor 10 (step P114). At this time, the remaining gas remaining in the reactor 10 is removed from the reactor 10 by the vacuum pump 44 and is discharged to the outside of the hydrocarbon production apparatus 1 through the first gas circulation pipe 61 and the third gas circulation pipe 65. At the end of the reduction step, the remaining gas remaining in the reactor 10 includes hydrogen that was not used in the reduction, methane produced in the reduction step, and the like.

[0052] After a predetermined time (for example, 10 seconds) has elapsed, the control unit 50 stops the vacuum pump 44 (step P116), and the process returns to step P102, where the hydrocarbon production process is repeated. The vacuum purging ends at step P116. Steps P114 to P116 constitute the purging process. The time for performing the vacuum purging can be set appropriately.

[0053] As described above, according to the hydrocarbon production apparatus 1A of this embodiment, the control unit 50 links the ON / OFF control of the vacuum pump 44 with the switching control of each process, so it is possible to perform an exhaust operation equivalent to that of the first embodiment while reducing the number of valves and lines (gas distribution pipes) compared to the hydrocarbon production apparatus 1 of the first embodiment. This makes it possible to simplify the configuration of the hydrocarbon production apparatus 1A, contributing to size reduction and cost reduction.

[0054] <Third embodiment> Fig. 6 is a schematic diagram showing the general configuration of a hydrocarbon production apparatus 1B of the third embodiment. The hydrocarbon production apparatus 1B of the third embodiment differs from the hydrocarbon production apparatus 1 of the first embodiment (Fig. 1) in that it is provided with a fourth valve 69 immediately below the reactor 10, a pressure gauge 46 that measures the internal pressure of the reactor 10, and the control details by the control unit 50. In this embodiment, the fourth valve 69 is also referred to as the "reactor outlet valve," and the pressure gauge 46 is also referred to as the "pressure acquisition unit."

[0055] Fig. 7 is a process diagram of a hydrocarbon production method in the hydrocarbon production apparatus 1B. In the hydrocarbon production method of this embodiment, the control unit 50 controls the methanation reaction in the reactor 10 by opening and closing the fourth valve 69 in accordance with the internal pressure of the reactor 10 acquired from the pressure gauge 46. In the hydrocarbon production method shown in Fig. 7, the same steps as in the first embodiment are denoted by the same reference numerals.

[0056] First, the control unit 50 performs the occlusion process (steps P102 to P108) and then the purge process (step P110) in the same manner as in the first embodiment. After performing the purge process (step P110) for a predetermined time (for example, 10 seconds), the control unit 50 proceeds to step P112B.

[0057] In step P112B, the control unit 50 closes the second valve 42 and the fourth valve 69 and increases the opening of the hydrogen supply valve 34 to supply hydrogen gas to the reactor 10. When the vacuum purge is completed, the reactor 10 is in a low-pressure state, which reduces the probability of gas contact with the catalyst surface and may result in low reactivity of the supplied hydrogen. In step P112B of this embodiment, the fourth valve 69 is closed, which prevents unreacted hydrogen from flowing out under low pressure.

[0058] The control unit 50 acquires the pressure value P in the reactor 10 from the pressure gauge 46 and continues supplying hydrogen gas while keeping the fourth valve 69 closed until the pressure value P becomes equal to or greater than a predetermined threshold value Th (NO in step P113). As hydrogen is supplied to the reactor 10 while keeping the fourth valve 69 closed, the pressure in the reactor 10 increases. Since the hydrocarbon synthesis reaction in this embodiment is the Sabatier reaction (CO + 4H → CH + 2H O), the increase in reaction pressure caused by closing the fourth valve 69 is advantageous for progressing the reaction. The predetermined threshold value Th can be set by experimentally determining in advance a pressure value at which the hydrocarbon concentration in the recovered product gas becomes equal to or greater than a predetermined concentration (e.g., 70%). In this embodiment, the predetermined threshold value Th may be set to, for example, −0.02 (MPaG).

[0059] When the pressure value acquired from the pressure gauge 46 is equal to or greater than the predetermined threshold value Th, the control unit 50 opens the first valve 64 and the fourth valve 69. The methane-containing gas (product gas) containing methane synthesized in the reactor 10 flows through the first gas flow pipe 61 into the second gas flow pipe 63, is compressed by the compressor 66, and is collected in the product gas tank 70 (step P118). As shown in the figure, steps P112B to P118 constitute the reduction step. The time for the reduction step can be set appropriately. In this embodiment, the condition "that the pressure value acquired from the pressure gauge 46 is less than the predetermined threshold value Th" is also referred to as the "low-pressure condition." At the end of the purge step (step P110), as described above, the inside of the reactor 10 is in a low-pressure state, and the condition "that the pressure value acquired from the pressure gauge 46 is less than the predetermined threshold value Th" is satisfied.

[0060] Thereafter, the control unit 50 opens the second valve 42 and closes the first valve 64 (step P120). As described above, the vacuum pump 44 is operating while hydrocarbons are being produced in the hydrocarbon production apparatus 1B. Therefore, when the second valve 42 is opened, the vacuum pump 44 removes the residual gas remaining in the reactor 10 from the reactor 10 and discharges it to the outside of the hydrocarbon production apparatus 1B through the first gas circulation pipe 61 and the third gas circulation pipe 65. As shown in the figure, step P120 is a purging step.

[0061] After a predetermined time (for example, 10 seconds) has elapsed, the control unit 50 returns to step P102 and repeats the hydrocarbon production process. The time for which vacuum purging is performed can be set appropriately.

[0062] As described above, according to the hydrocarbon production apparatus 1B of this embodiment, the fourth valve 69 is provided immediately below the reactor 10, and the pressure gauge 46 for measuring the internal pressure of the reactor 10 is also provided, and the control unit 50 opens and closes the fourth valve 69 in accordance with the internal pressure of the reactor 10. When the vacuum purge is completed, the inside of the reactor 10 is in a low pressure state, and there is a possibility that the reaction efficiency when hydrogen is supplied is not high. Therefore, by closing the fourth valve 69 when the vacuum purge is completed and the supply of hydrogen gas is started, it is possible to prevent the hydrogen gas from flowing out unreacted under low pressure.

[0063] Furthermore, as hydrogen is supplied to the reactor 10 with the fourth valve 69 closed, the pressure inside the reactor 10 increases. Since the hydrocarbon synthesis reaction in this embodiment is the Sabatier reaction (CO + 4H → CH + 2H O), the reaction can be accelerated by increasing the reaction pressure caused by closing the fourth valve 69. Therefore, the purity of the hydrocarbons in the product gas recovered in the product gas tank 70 can be further improved.

[0064] <Fourth embodiment> 8 is a schematic diagram showing the general configuration of a hydrocarbon production apparatus 1C of the fourth embodiment. The hydrocarbon production apparatus 1C of the fourth embodiment differs from the hydrocarbon production apparatus 1 of the first embodiment (FIG. 1) in that it is provided with a fourth valve 69 immediately below the reactor 10, a fifth gas circulation pipe 48 connecting the vacuum pump 44 and the compressor 66, a fifth valve 82 provided in the fifth gas circulation pipe 48, and a sixth valve 84 in the third gas circulation pipe 65 downstream of the vacuum pump 44, as well as in the control contents by the control unit 50.

[0065] Fig. 9 is a process diagram of a hydrocarbon production method in a hydrocarbon production apparatus 1C. In the hydrocarbon production method of this embodiment, the control unit 50 controls the methanation reaction in the reactor 10 by opening and closing the fourth valve 69 according to time. Furthermore, the residual gas extracted from the reactor in the purging step after the reduction step is recovered in the product gas tank 70. In the hydrocarbon production method shown in Fig. 9, the same steps as in the first embodiment are denoted by the same reference numerals.

[0066] First, the control unit 50 performs the occlusion process (steps P102C to P108) as in the first embodiment. However, in step P102C of this embodiment, the control unit 50 closes the first valve 64, the second valve 42, and the fifth valve 82, and opens the third valve 68 and the fourth valve.

[0067] Next, the control unit 50 opens the second valve 42 and the sixth valve 84, and closes the third valve 68 (step P110C). As described above, since the vacuum pump 44 is operating while hydrocarbons are being produced in the hydrocarbon production apparatus 1, the residual gas remaining in the reactor 10 is removed from the reactor 10 by the vacuum pump 44 and discharged to the outside of the hydrocarbon production apparatus 1C through the first gas circulation pipe 61, the third gas circulation pipe 65, and the fourth gas circulation pipe 67. After performing the purging step (step P110C) for a predetermined time (e.g., 10 seconds), the control unit 50 proceeds to step P112C.

[0068] In step P112C, the control unit 50 closes the fourth valve 69 and increases the opening of the hydrogen supply valve 34 to supply hydrogen gas to the reactor 10. When the vacuum purge is completed, the inside of the reactor 10 is in a low-pressure state, and there is a possibility that the reaction efficiency when hydrogen is supplied will be low. In step P112C of this embodiment, because the fourth valve 69 is closed, it is possible to prevent unreacted hydrogen from flowing out under low pressure, as in the third embodiment.

[0069] The control unit 50 supplies hydrogen while keeping the fourth valve 69 closed for a predetermined time (e.g., 10 seconds), and then opens the first valve 64 and the fourth valve 69. As a result, a methane-containing gas (product gas) containing methane synthesized in the reactor 10 flows through the first gas flow pipe 61 into the second gas flow pipe 63, where it is compressed by the compressor 66 and collected in the product gas tank 70 (step P118C). The time for supplying hydrogen while keeping the fourth valve 69 closed can be set by experimentally determining in advance the time required for the pressure to be reached so that the hydrocarbon concentration of the collected product gas reaches a predetermined concentration (e.g., 70%) or higher. When the time is set in this manner, it can also be said that the control unit 50 opens and closes the fourth valve 69 depending on the pressure. As shown in the figure, steps P112C to P118 constitute the reduction step. The time for the reduction step can be set as appropriate.

[0070] Thereafter, the control unit 50 opens the second valve 42 and the fifth valve 82 and closes the first valve 64 (step P120C). As described above, the vacuum pump 44 is operating while hydrocarbon production is being carried out in the hydrocarbon production apparatus 1C. Therefore, when the valves are opened and closed as described above in step P120C, the residual gas remaining in the reactor 10 is removed from the reactor 10 by the vacuum pump 44, passes through the first gas circulation pipe 61 and flows into the third gas circulation pipe 65, passes through the vacuum pump 44 and the fifth gas circulation pipe 48 and flows into the compressor 66, is compressed by the compressor 66, and is recovered in the product gas tank 70 through the second gas circulation pipe 63. As shown in the figure, step P120C is a purging step.

[0071] After a predetermined time (for example, 10 seconds) has elapsed, the control unit 50 returns to step P102C and repeats the hydrocarbon production process. The time for which vacuum purging is performed can be set appropriately.

[0072] As described above, according to the hydrocarbon production apparatus 1C of the present embodiment, like the hydrocarbon production apparatus 1B of the third embodiment, the fourth valve 69 is provided immediately below the reactor 10, but the pressure gauge 46 for measuring the internal pressure of the reactor 10 is not provided. However, the control unit 50 opens and closes the fourth valve 69 depending on time, and by closing the fourth valve 69 when the vacuum purge ends and the supply of hydrogen gas starts, it is possible to prevent unreacted hydrogen gas from flowing out under low pressure, like the third embodiment.

[0073] Furthermore, in this embodiment, the control unit 50 supplies hydrogen to the reactor 10 while keeping the fourth valve 69 closed for a predetermined time, so that, similarly to the third embodiment, the pressure inside the reactor 10 increases and the methanation reaction can be promoted. Therefore, similarly to the third embodiment, the purity of hydrocarbons in the product gas recovered in the product gas tank 70 can be improved.

[0074] Furthermore, in this embodiment, in the purge step after the reduction step, the residual gas in the reactor 10 is removed and recovered in the product gas tank 70. Since the residual gas in the reactor 10 at the end of the reduction step contains methane produced in the reduction step, the recovery rate of the produced methane can be improved. Also, in this embodiment, in step P120C, both purging of the reactor 10 and recovery of methane can be achieved simultaneously.

[0075] Fifth Embodiment FIG. 10 is a schematic diagram showing the overall configuration of a hydrocarbon production apparatus 1D of the fifth embodiment. The hydrocarbon production apparatus 1D of the fifth embodiment differs from the hydrocarbon production apparatus 1C of the fourth embodiment (FIG. 8) in that it includes two reactors 10. In FIG. 10, the same components as those in the hydrocarbon production apparatus 1C of the fourth embodiment are designated by the same reference numerals, and the preceding description is referred to. In FIG. 10, in order to distinguish between the two reactors 10, the reactor 10 on the left side of the page in FIG. 10 is shown as reactor 10M, and the reactor 10 on the right side is shown as reactor 10N. Similarly, the gas flow pipes, valves, carbon dioxide concentration sensors, etc. are also designated by the suffixes "M" and "N," respectively, to enable distinction. In the following description, when distinction is not necessary, the suffixes "M" and "N" are omitted.

[0076] Fig. 11 is a process diagram of a hydrocarbon production method in the hydrocarbon production apparatus 1D. In the hydrocarbon production method of this embodiment, carbon dioxide (CO2) is recovered and methane (CH4) is produced in each of two reactors 10M and 10N in parallel. In the flowchart shown in Fig. 11, either reactor 10M or reactor 10N is referred to as "one reactor," and either reactor 10M or reactor 10N is referred to as "the other reactor."

[0077] 11, when methane production is started, a raw material gas is supplied to one reactor (reactor 10M) (steps P202 to P208), and a vacuum purge is performed in the other reactor (reactor 10N) (steps P302 to P304). Specifically, the control unit 50 closes the first valve 64M, the second valve 42M, and the fifth valve 82, and opens the third valve 68M and the fourth valve 69M (step P202), and increases the aperture of the raw material gas supply valve 24M to allow the raw material gas in the raw material gas tank 22 to flow into the reactor 10M (step P204). As in the above-described embodiment, the control unit 50 acquires the concentration value of the carbon dioxide concentration of the residual gas extracted from the reactor 10M from the carbon dioxide concentration sensor 62M (step P206), and while continuing to supply the raw material gas, repeatedly acquires the concentration value from the carbon dioxide concentration sensor 62M until the concentration value acquired from the carbon dioxide concentration sensor 62M becomes greater than 100 ppm (NO in step P208). Steps P202 to P208 are the absorption step in the reactor 10M.

[0078] Meanwhile, the control unit 50 sets the aperture of the raw material gas supply valve 24N to 0, closes the first valve 64N and the third valve 68N, and opens the second valve 42N, the fourth valve 69N, and the sixth valve 84 (step P302). As in the above-described embodiment, since the vacuum pump 44 is operating while hydrocarbon production is being carried out in the hydrocarbon production apparatus 1D, the residual gas in the reactor 10N is extracted and discharged to the outside of the hydrocarbon production apparatus 1D through the first gas circulation pipe 61N, the third gas circulation pipe 65N, and the third gas circulation pipe 65 (step P302). Steps P302 to P304 are purging steps in the reactor 10N.

[0079] When the concentration value acquired from the carbon dioxide concentration sensor 62M becomes greater than 100 ppm (YES in step P210), the control unit 50 switches the supply destination of the raw material gas (step P210). Specifically, the control unit 50 closes the second valve 42N and the fifth valve 82, opens the third valve 68N, increases the aperture of the raw material gas supply valve 24N, and causes the raw material gas in the raw material gas tank 22 to flow into the other reactor (reactor 10N) (step P308). As in the occlusion step in reactor 10M, the control unit 50 acquires the concentration value of the carbon dioxide concentration of the residual gas extracted from reactor 10N from the carbon dioxide concentration sensor 62N (step P308), and repeatedly acquires the concentration value from the carbon dioxide concentration sensor 62N while continuing to supply the raw material gas until the concentration value acquired from the carbon dioxide concentration sensor 62N becomes greater than 100 ppm (NO in step P310). Steps P306 to P310 are the absorption steps in the reactor 10N.

[0080] While the absorption step is being performed in the other reactor (reactor 10N), the purge step, reduction step, and purge step are performed in this order in one reactor (reactor 10M). Specifically, the control unit 50 opens the second valve 42M and the sixth valve 84 and closes the third valve 68M. As described above, while hydrocarbon production is being performed in the hydrocarbon production apparatus 1D, the vacuum pump 44 is operating, so that the residual gas in the reactor 10M is extracted and discharged to the outside of the hydrocarbon production apparatus 1D through the first gas circulation pipe 61M, the third gas circulation pipe 65M, and the third gas circulation pipe 65 (step P212). At the end of the absorption step, the residual gas remaining in the reactor 10M contains carbon dioxide, nitrogen, oxygen, water, etc. Step P212 is the purge step in the reactor 10M.

[0081] Thereafter, a reduction step similar to that of the fourth embodiment is performed. Specifically, the control unit 50 closes the fourth valve 69M and the sixth valve 84, increases the opening of the hydrogen supply valve 34M, and supplies hydrogen gas to the reactor 10M (step P214). After supplying hydrogen for a predetermined time (e.g., 10 seconds) while keeping the fourth valve 69M closed, the control unit 50 opens the first valve 64M and the fourth valve 69M. Then, a methane-containing gas (product gas) containing methane synthesized in the reactor 10M flows through the first gas flow pipe 61M and the second gas flow pipe 63M into the second gas flow pipe 63, where it is compressed by the compressor 66 and collected in the product gas tank 70 (step P216). As shown in the figure, steps P214 to P216 constitute a reduction step. In the reduction step in the reactor 10M, as in the fourth embodiment, it is possible to prevent unreacted hydrogen from flowing out under low pressure, thereby improving the reactivity of the methanation reaction.

[0082] Thereafter, a purging step similar to that of the fourth embodiment is performed, and the residual gas in the reactor 10M at the end of the reduction reaction is vacuum-recovered. Specifically, the control unit 50 opens the second valve 42M and the fifth valve 82 and closes the first valve 64M (step P218). As described above, the vacuum pump 44 operates while hydrocarbon production is being carried out in the hydrocarbon production apparatus 1D. Therefore, when the valves are opened and closed as described above in step P218, the residual gas remaining in the reactor 10 is removed from the reactor 10 by the vacuum pump 44, passes through the first gas circulation pipe 61M and the third gas circulation pipe 65M, flows into the third gas circulation pipe 65, passes through the vacuum pump 44 and the fifth gas circulation pipe 48, flows into the compressor 66, is compressed by the compressor 66, and is collected in the product gas tank 70 through the second gas circulation pipe 63. As shown in the figure, step P218 is a purging step.

[0083] On the other hand, when the absorption process in the reactor 10M is completed (YES in step P310), the control unit 50 switches the supply destination of the raw material gas (step P312) and performs the absorption process in the reactor 10N as described above (steps P202 to P208). While the absorption process is being performed in one reactor (reactor 10N), the purge process, reduction process, and purge process are performed in this order in the other reactor (reactor 10N). Specifically, the control unit 50 opens the second valve 42N and the sixth valve 84 and closes the third valve 68N. As described above, while hydrocarbons are being produced in the hydrocarbon production apparatus 1D, the vacuum pump 44 is operating, so that the residual gas in the reactor 10N is extracted and discharged to the outside of the hydrocarbon production apparatus 1D through the first gas circulation pipe 61N, the third gas circulation pipe 65N, and the third gas circulation pipe 65N (step P212). At the end of the absorption step, the residual gas remaining in the reactor 10N contains carbon dioxide, nitrogen, oxygen, water, etc. Step P314 is a purging step in the reactor 10N.

[0084] Thereafter, a reduction step similar to the reduction step in reactor 10M is performed in reactor 10N. Specifically, the control unit 50 closes the fourth valve 69N and the sixth valve 84, increases the opening of the hydrogen supply valve 34N, and supplies hydrogen gas to reactor 10N (step P316). After supplying hydrogen for a predetermined time (e.g., 10 seconds) while keeping the fourth valve 69N closed, the control unit 50 opens the first valve 64N and the fourth valve 69N. Then, a methane-containing gas (product gas) containing methane synthesized in reactor 10N flows through the first gas flow pipe 61N and the second gas flow pipe 63N into the second gas flow pipe 63, where it is compressed by the compressor 66 and collected in the product gas tank 70 (step P318). As shown in the figure, steps P316 to P318 constitute the reduction step. In the reduction step in the reactor 10N, similarly to the reduction step in the reactor 10M, it is possible to prevent unreacted hydrogen from flowing out under low pressure, thereby improving the reactivity of the methanation reaction.

[0085] Thereafter, a purging step similar to the purging step (step P218) in the reactor 10M is performed in the reactor 10N, and the gas remaining in the reactor 10N at the end of the reduction reaction is vacuum-recovered. Specifically, the control unit 50 opens the second valve 42N and the fifth valve 82 and closes the first valve 64N (step P320). As described above, the vacuum pump 44 operates while hydrocarbon production is being performed in the hydrocarbon production apparatus 1D. Therefore, when the valves are opened and closed as described above in step P320, the residual gas remaining in the reactor 10N is removed from the reactor 10N by the vacuum pump 44, passes through the first gas circulation pipe 61N and the third gas circulation pipe 65M, flows into the third gas circulation pipe 65, passes through the vacuum pump 44 and the fifth gas circulation pipe 48, flows into the compressor 66, is compressed by the compressor 66, and is collected in the product gas tank 70 through the second gas circulation pipe 63. As shown, step P320 is a purge step.

[0086] After a predetermined time (for example, 10 seconds) has elapsed, the control unit 50 ends the purging step. When the absorption step is completed in one reactor (reactor 10M), the control unit 50 switches the supply destination of the raw material gas, and performs the absorption step in the other reactor (reactor 10N) (steps P306 to P310), thereby repeating the hydrocarbon production step.

[0087] In the hydrocarbon production apparatus 1D of this embodiment, the two reactors 10M and 10N are arranged in parallel with respect to the raw material gas supply unit 20D. As a result, when the raw material gas is continuously supplied, by switching the supply destination of the raw material gas, it is possible to recover CO from the raw material gas in one reactor while producing CH in the other reactor. Therefore, it is possible to effectively utilize CO contained in the raw material gas. [Example]

[0088] The present invention will be explained in more detail with reference to examples. Using the hydrocarbon production apparatus of the example of the above embodiment and the hydrocarbon production apparatus of the comparative example, tests were carried out under the reaction conditions described below, and the hydrocarbon concentrations of the recovered product gases were compared.

[0089] FIG. 12 is a diagram showing the relationship between the pressure inside the reactor and the hydrocarbon concentration under the first reaction conditions. Example 1 shows the results of producing hydrocarbons using the hydrocarbon production method shown in FIG. 3 in the hydrocarbon production apparatus 1 of the first embodiment (FIG. 1). Examples 2 to 4 show the results of producing hydrocarbons using the hydrocarbon production method shown in FIG. 7 in the hydrocarbon production apparatus 1B of the third embodiment (FIG. 6). In Examples 2 to 4, switching was performed based on time in step P113 of FIG. 7. Comparative Example 1 shows an example in which nitrogen (N2) purging was performed as the purging method. The hydrocarbon production apparatus of the comparative example is equipped with a purge gas supply unit having a nitrogen gas tank, and performs nitrogen gas purging instead of the purging step in Examples 1 to 4.

[0090] The first reaction conditions in the test were as follows: Raw material gas composition: CO2 (10%), N2 (90%) Raw gas flow rate: 15 L / min (SV=450 / hr) Reducing gas composition: H2 (100%) Reducer gas flow rate: 9L / min (SV=270 / hr) Supply time ratio of raw gas to reducing gas = 7:5 Reaction temperature: 320℃ Purge time: 10 seconds where SV is the space velocity.

[0091] The composition of the purge gas used in Comparative Example 1 was N2 (100%), and the flow rate of the purge gas was 15 L / min.

[0092] In Example 1, the reactor internal pressure was -0.1 (MPaG) after vacuum purging because the area directly below the reactor outlet, which corresponds to the fourth valve in Examples 2 to 4, was always open. The hydrocarbon concentration of the product gas recovered in Example 1 was 69%. As described above, Examples 2 to 4 had the same configuration of hydrocarbon production apparatus 1B and production method, but the pressure at the time the fourth valve was opened (the switching time of the fourth valve) was changed. As shown in the figure, as the switching time of the fourth valve increased, the reactor internal pressure when the fourth valve was open increased, and the resulting hydrocarbon concentration increased. When the reactor internal pressure was 0.15 (MPaG), the hydrocarbon concentration reached a maximum of 74%. In contrast, in Comparative Example 1, the reactor internal pressure, which corresponds to the fourth valve, was always open because the area directly below the reactor outlet, which corresponds to the fourth valve, was always open, so the reactor internal pressure was slightly positive (0.02 MPaG) due to the supply of nitrogen gas, and the resulting hydrocarbon concentration was 48%. As shown in the figure, in Examples 1 to 4, even without valve operation (Example 1), the hydrocarbon concentration was higher than that of the N2 purging method (Comparative Example 1), and the hydrocarbon concentration became even higher when the fourth valve was operated. Furthermore, the hydrocarbon concentration increased depending on the pressure inside the reactor when the fourth valve was opened.

[0093] Figure 13 is a diagram showing the relationship between the pressure inside the reactor and the hydrocarbon concentration under the second reaction conditions. In the example shown in Figure 13, the amount of catalyst inside the reactor is the same as in the example shown in Figure 12, but the flow rate is doubled (SV is doubled) compared to the example shown in Figure 12. That is, the second reaction conditions are as follows: Raw material gas composition: CO2 (10%), N2 (90%) Raw gas flow rate: 30 L / min (SV=900 / hr) Reducing gas composition: H2 (100%) Reducer gas flow rate: 18 L / min (SV=540 / hr) Supply time ratio of raw gas to reducing gas = 7:5 Reaction temperature: 320℃ Purge time: 10 seconds

[0094] The composition of the purge gas used in Comparative Example 1 was N2 (100%), and the purge gas flow rate was 30 L / min. Compared to Comparative Example 1 shown in Figure 12, the flow rate was doubled, resulting in a slightly higher internal pressure in the reactor. Furthermore, the hydrocarbon concentration of the product gas recovered in Comparative Example 1 was 48% in the example shown in Figure 12, but improved to 62% in the example shown in Figure 13. This is thought to be because the increased flow rate and resulting increased amount of product gas reduced the impact of gas contained in voids and the like within the reactor.

[0095] Furthermore, in Examples 1 to 5, even without valve operation (Example 1), the hydrocarbon concentration was higher than that obtained with the N2 purging method (Comparative Example 1), and the hydrocarbon concentration increased further when the fourth valve was operated. Also, when combined with the example shown in Fig. 12, it can be said that the hydrocarbon concentration increases depending on the pressure inside the reactor when the fourth valve is opened.

[0096] 12 and 13, in the hydrocarbon production method, by performing vacuum purging after carbon dioxide absorption and before hydrogen supply, the hydrocarbon concentration in the produced gas can be improved compared to when N2 purging is performed. Furthermore, when performing vacuum purging, the longer the time hydrogen is supplied with the fourth valve located immediately below the reactor outlet closed, and the higher the pressure inside the reactor when the fourth valve is opened, the more the hydrocarbon concentration in the produced gas can be improved.

[0097] The predetermined threshold value Th in the third embodiment can be appropriately set by examining in advance the relationship between the reactor internal pressure, the closing time of the fourth valve, and the hydrocarbon concentration of the produced gas as described using Figures 12 and 13.

[0098] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0099] In the above-described embodiment, the hydrocarbon production apparatus produces methane (CH4) as the "hydrocarbon." However, the hydrocarbons produced by the hydrocarbon production apparatus are not limited to methane (CH4), and may include, for example, compounds composed of carbon and hydrogen, such as ethane and propane, compounds composed mainly of carbon and hydrogen, such as methanol, and compounds composed of carbon, hydrogen, and other atoms.

[0100] In the above embodiment, the Sabatier reaction (CO2 + 4H2 → CH4 + 2H2O) is exemplified as the hydrocarbon synthesis reaction, but hydrocarbons may be synthesized by other hydrocarbon synthesis reactions. For example, direct alcohol synthesis from CO2 (methanol: CO2 + 3H2 → CH3OH + H2O, ethanol: 2CO2 + 6H2 → C2H5OH + 3H2O), or Fischer-Tropsch reaction (nCO + 2nH2 → (CH2)) via reverse water gas shift reaction (CO2 + H2 → CO + H2O) n +nH2O). When hydrocarbons are synthesized by such a hydrocarbon synthesis reaction, the hydrocarbon synthesis reaction can be further advanced by increasing the internal pressure of the reactor in the reduction step, as in the third to fifth embodiments described above. Furthermore, hydrocarbon synthesis reactions other than those described above may also be used.

[0101] In the third embodiment, the control unit 50 opens the fourth valve 69 in response to the pressure value from the pressure gauge 46. However, the third embodiment may not include the pressure gauge 46 and may instead open the fourth valve 69 in response to time.

[0102] In the fourth and fifth embodiments, an example was shown in which a pressure gauge 46 was not provided and the control unit 50 opened the fourth valve 69 in accordance with time. However, as in the third embodiment, a pressure gauge 46 may be provided and the control unit 50 may open the fourth valve 69 in accordance with the pressure value from the pressure gauge 46.

[0103] In the above embodiment, the hydrogen supply valve is a mass flow controller, and the flow rate of H2 supplied to the reactor is controlled by controlling the opening degree in response to a command from the control unit. However, the method for controlling the flow rate of H2 supplied to the reactor is not limited to this. For example, H2 may be supplied to the reactor from multiple conduits that can supply a constant gas flow rate through one or more valves.

[0104] In the above-described embodiment, when supplying H2 to the reactors 10 and 60, the control unit supplies H2 at an initial flow rate that is 60% or less of the generation flow rate, and then supplies H2 at the generation flow rate. However, the relationship between the initial flow rate and the generation flow rate is not limited to this. The initial flow rate may be any rate as long as it is smaller than the generation flow rate.

[0105] In each of the above embodiments, some of the configurations implemented by hardware may be replaced with software, and conversely, some of the configurations implemented by software may be replaced with hardware. Furthermore, if some or all of the functions of the present disclosure are implemented by software, the software (computer program) may be provided in a form stored on a computer-readable recording medium. The term "computer-readable recording medium" is not limited to portable recording media such as floppy disks and CD-ROMs, but also includes internal computer storage devices such as various RAMs and ROMs, and external storage devices fixed to a computer such as a hard disk. In other words, the term "computer-readable recording medium" has a broad meaning, including any recording medium capable of storing data packets non-temporarily.

[0106] In the above embodiments, the supply of the raw material gas is terminated when the carbon dioxide concentration in the residual gas is greater than 100 ppm, but the timing for terminating the supply of the raw material gas is not limited to this. For example, the time for occluding CO2 in the reactor may be set to a predetermined time.

[0107] In the fifth embodiment, an example was shown in which the hydrocarbon production apparatus 1D includes two reactors, but the number of reactors is not limited to that in the above embodiment and may be three or more.

[0108] In the fourth and fifth embodiments, the outlet of the vacuum pump can be selectively directed to either the exhaust or the produced gas tank, but this is not limiting. For example, the compressor in the hydrocarbon production apparatus of the fourth and fifth embodiments may be a compressor that can also be used as a vacuum pump.

[0109] In the fourth and fifth embodiments, three-way valves may be used instead of the fifth valve 82 and the sixth valve 84. This allows the number of valves to be reduced, which contributes to cost reduction.

[0110] In the above embodiment, an example was shown in which the hydrocarbon production apparatus was equipped with the product gas tank 70, but the hydrocarbon production apparatus does not have to be equipped with the product gas tank 70. For example, the downstream end of the second gas circulation pipe 63 may be directly connected to an apparatus that uses hydrocarbons.

[0111] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate. [Explanation of symbols]

[0112] 1, 1A, 1B, 1C, 1D...Hydrocarbon production equipment 10, 10M, 10N... reactor 12...Catalyst 14...Dehydrator 20, 20D...raw material gas supply section 22... Raw gas tank 24, 24M, 24N... Raw material gas supply valve 26... Raw material gas supply pipe 30...Hydrogen supply unit 32...Hydrogen gas tank 34, 34M, 34N...Hydrogen supply valve 36...Hydrogen supply pipe 40...Gas exhaust section 42, 42M, 42N...Second valve 44...Vacuum pump 46...Pressure gauge 48...5th gas distribution pipe 50...Control unit 61, 61M, 61N...First gas distribution pipe 62, 62M, 62N...Carbon dioxide concentration sensor 63, 63M, 63N...Second gas distribution pipe 64, 64M, 64N...First valve 65, 65M, 65N...Third gas distribution pipe 66...Compressor 67...4th gas distribution pipe 68, 68M, 68N...Third valve 69, 69M, 69N...4th valve 70...Produced gas tank 82...5th valve 84...6th valve

Claims

1. A hydrocarbon production apparatus for producing hydrocarbons from carbon dioxide and hydrogen, a reactor containing a catalyst including a metal having hydrocarbon synthesis catalytic performance and a metal having carbon dioxide storage performance; a raw material gas supply unit connected to the reactor and configured to supply a raw material gas containing carbon dioxide to the reactor; a hydrogen supply unit connected to the reactor and supplying hydrogen to the reactor; a gas discharge unit connected to the reactor and discharging gas from the reactor by creating a negative pressure inside the reactor; a control unit that controls the raw material gas supply unit, the hydrogen supply unit, and the gas discharge unit; Equipped with The control unit After the raw material gas is supplied from the raw material gas supply unit to the reactor, the gas inside the reactor is discharged by the gas discharge unit, and then hydrogen is supplied from the hydrogen supply unit to the reactor. Hydrocarbon production equipment.

2. The hydrocarbon production apparatus according to claim 1, moreover, a pressure acquisition unit that acquires a pressure value inside the reactor; a reactor outlet valve capable of opening and closing an outlet for a gas in the reactor; Equipped with The control unit when the pressure value acquired by the pressure acquisition unit satisfies a low-pressure condition under which a hydrocarbon synthesis reaction in the reactor does not easily proceed, the reactor outlet valve is closed to supply hydrogen to the reactor. Hydrocarbon production equipment.

3. The hydrocarbon production apparatus according to claim 1, moreover, a reactor outlet valve capable of opening and closing an outlet for a gas in the reactor; The control unit When hydrogen is supplied to the reactor, the reactor outlet valve is closed, hydrogen is supplied to the reactor for a predetermined time, and then the reactor outlet valve is opened to supply hydrogen to the reactor. Hydrocarbon production equipment.

4. The hydrocarbon production apparatus according to any one of claims 1 to 3, the gas discharge section is disconnectably connected to a recovery tank that recovers the hydrocarbons; The control unit before supplying the raw material gas to the reactor, the gas in the reactor is recovered into the recovery tank by the gas discharge part; Hydrocarbon production equipment.

5. 1. A method for producing hydrocarbons, comprising: a raw material gas supplying step of supplying a raw material gas containing carbon dioxide to a reactor containing a catalyst containing a metal having hydrocarbon synthesis catalytic performance and a metal having carbon dioxide occlusion performance; a gas discharge step of discharging gas from the reactor by creating a negative pressure inside the reactor after the raw material gas supply step; A hydrogen supplying step of supplying hydrogen to the reactor after the gas discharging step. Hydrocarbon production methods.

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