Synthetic fuel generation system

Abstract

Suppress a decrease in the product concentration of the product gas in the synthetic fuel generation device while reducing costs. 【Solution means】 The synthetic fuel generation system includes a synthetic fuel generation device that reacts hydrogen and carbon dioxide to generate a synthetic compound and water, a product gas delivery path through which the product gas is sent out from the synthetic fuel generation device, a flow meter provided in the product gas delivery path for measuring the flow rate of the product gas, a re-supply path branched from the product gas delivery path for returning the product gas to the synthetic fuel generation device, and a switching unit that switches so that at least a part of the product gas is sent to the re-supply path when the ratio of the flow rate measured by the flow meter to the flow rate of the raw material gas supplied to the synthetic fuel generation device exceeds a specified ratio.

Description

Technical Field

[0001] The present disclosure relates to a synthetic fuel generation system.

Background Art

[0002] In recent years, a methane synthesis apparatus including a water electrolysis unit and a Sabatier reaction unit for synthesizing methane by reacting hydrogen with carbon dioxide has been developed. In this methane synthesis apparatus, hydrogen gas generated in the water electrolysis unit is supplied to the Sabatier reaction unit, and methane gas as a synthetic fuel is synthesized from this hydrogen gas and a carbon dioxide-containing gas separately supplied to the Sabatier reaction unit (see Patent Document 1). Further, Patent Document 2 discloses a technique in which when the methane concentration in the product gas obtained by methanation is less than a predetermined concentration, the gas is sent to an off-gas line and reused in the reactor for reaction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] As in Patent Document 2, when the concentration of methane in the product gas does not reach a predetermined concentration, the concentration of the product gas can be prevented from decreasing by separately recovering the gas as non-product gas. However, in Patent Document 2, since a methane concentration meter is used, the cost increases.

[0005] In consideration of the above facts, an object of the present disclosure is to suppress a decrease in the product concentration of the product gas in the synthetic fuel generation apparatus while reducing the cost.

Means for Solving the Problems

[0006] The synthetic fuel generation system of the first aspect includes a synthetic fuel generator that reacts hydrogen with carbon dioxide to generate a synthetic compound and water, a product gas delivery path through which the product gas is sent out from the synthetic fuel generator, a flow meter provided in the product gas delivery path for measuring the flow rate of the product gas, a re-supply path branched from the product gas delivery path for returning the product gas to the synthetic fuel generator, and a switching unit that switches so that at least a part of the product gas is sent to the re-supply path when the ratio of the flow rate measured by the flow meter to the flow rate of the raw material gas supplied to the synthetic fuel generator exceeds a specified ratio.

[0007] In the synthetic fuel generation system of the first aspect, when the ratio of the flow rate measured by the flow meter to the flow rate of the raw material gas supplied to the synthetic fuel generator exceeds a specified ratio, the switching unit switches so that at least a part of the product gas is sent to the re-supply path.

[0008] There is a correspondence relationship among the conversion rate in the synthetic fuel generator, the concentration of the synthetic fuel in the product gas, and the flow rate ratio of the product gas to the raw material gas. When the conversion rate is low, the concentration of the synthetic fuel also decreases, and the flow rate ratio of the product gas to the raw material gas increases. Therefore, when the ratio of the flow rate measured by the flow meter to the flow rate of the raw material gas supplied to the synthetic fuel generator exceeds a specified ratio and the concentration of the synthetic fuel in the product gas is less than a specified concentration, the product gas is supplied to the re-supply path. Thereby, the flow rate in the product gas can be measured using the flow meter, and a decrease in the product concentration of the product gas in the synthetic fuel generator can be suppressed.

[0009] Also, since a concentration sensor is not used, the cost can be suppressed.

[0010] In the synthetic fuel generation system of the second aspect, at the start-up of the synthetic fuel generator, the switching unit switches so that the entire amount of the product gas is sent to the re-supply path.

[0011] According to the synthetic fuel generation system of the second aspect, by returning all of the off-spec gas at the start-up to the synthetic fuel generator, the off-spec gas can be effectively utilized.

[0012] In the synthetic fuel generation system according to the third aspect, when the synthetic fuel generation device is not operating, the switching unit switches so that the generated gas in excess of the flow rate corresponding to the specified ratio is sent to the re-supply path by the switching unit.

[0013] According to the synthetic fuel generation system of the third aspect, the supply of the product gas can be continued when not operating.

[0014] The synthetic fuel generation system according to the fourth aspect has a raw material supply path for combining hydrogen and carbon dioxide and supplying them to the synthetic fuel generation device. The raw material supply path is formed by a reuse supply path provided with a fluid drive source and a direct supply path not provided with the fluid drive source in parallel, and the re-supply path is connected to the upstream side of the fluid drive source in the reuse supply path.

[0015] According to the synthetic fuel generation system of the fourth aspect, when there is a return of the generated gas from the re-supply path, since a driving force for gas supply is required, the raw material gas is supplied from the reuse supply path provided with a fluid drive source to the synthetic fuel generation device. On the other hand, when there is no return of the generated gas from the re-supply path, since the hydrogen output can be used as the driving force for gas supply, by using the direct supply path not provided with the fluid drive source, the driving energy of the fluid drive source can be saved.

[0016] The synthetic fuel generation system according to the fifth aspect includes a water electrolysis device that generates hydrogen and oxygen by water electrolysis and supplies hydrogen to the synthetic fuel generation device.

[0017] According to the synthetic fuel generation system of the fifth aspect, synthetic fuel can be generated using the hydrogen generated by the water electrolysis device.

Advantages of the Invention

[0018] According to the present disclosure, it is possible to suppress a decrease in the product concentration of the generated gas in the synthetic fuel generation device while suppressing costs.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0020] Hereinafter, an example of an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0021] As shown in FIG. 1, the synthetic fuel generation system 10 of this embodiment includes a water electrolysis device 12, a synthetic fuel generation device 14, and a control device 40.

[0022] A water supply source 20 is connected to the water electrolysis device 12, and a power supply source (not shown) is also connected. In the water electrolysis device 12, using the supplied electrical energy, water is decomposed into hydrogen and oxygen by the water electrolysis reaction shown in the following formula (1).

[0023] H 2 O → H 2 +(1 / 2)O 2 (1)

[0024] A hydrogen delivery path 21 for delivering the generated hydrogen and an oxygen delivery path 22 for delivering the generated oxygen are connected to the water electrolysis device 12. The hydrogen delivery path 21 merges with the carbon dioxide supply source 30 and is connected to the merging path 23. In the merging path 23, carbon dioxide from the carbon dioxide supply source 30 and hydrogen from the water electrolysis device 12 are mixed.

[0025] The confluence path 23 is branched into a reuse supply path 23A and a direct supply path 23B, and an ejector 16 is provided in the reuse supply path 23A. The downstream end of a reuse supply path 25 described later is connected to the ejector 16. Downstream of the ejector 16, the reuse supply path 23A and the direct supply path 23B merge. The downstream end of the re-merged confluence path 23 is connected to the synthetic fuel generation device 14, and a mixed gas of carbon dioxide and hydrogen is supplied to the synthetic fuel generation device 14 via the valve V1. Oxygen and water are sent out from the oxygen delivery path 22.

[0026] The valve V1 is capable of adjusting the flow rate of the gas sent to the downstream side, and is connected to the confluence path 23, the reuse supply path 23A, and the direct supply path 23B. The valve V1 is connected to the control device 40, and the gas flowing into the confluence path 23 is switched so as to flow out to either the reuse supply path 23A or the direct supply path 23B, and the outflow flow rate is controlled by adjusting the opening degree.

[0027] The synthetic fuel generation device 14 has a reactor (not shown), and in the reactor, for example, methane and water are generated by a methane synthesis reaction as shown in the following formula (2).

[0028] 4H 2 +CO 2 →CH 4 +2H 2 O (2)

[0029] The synthetic fuel generation device 14 is provided with a temperature sensor 17 for detecting the temperature inside the synthetic fuel generation device 14. The temperature sensor 17 may detect the temperature of the reactor inside the synthetic fuel generation device 14, or may detect the temperature of other auxiliary equipment or the like. The temperature sensor 17 is connected to the control device 40, and outputs the detected temperature T to the control device 40.

[0030] The synthesis fuel generation device 14 is connected to a product gas delivery path 24, and the product gas generated by the synthesis fuel generation device 14, for example, methane and water, is sent to the product gas delivery path 24. A flow meter 18 for measuring the flow rate of the product gas is provided in the product gas delivery path 24. The flow meter 18 is connected to the control device 40 and outputs the measured flow rate value C to the control device 40. The flow meter 18 measures the volume flow rate value of the product gas flowing per unit time.

[0031] The product gas delivery path 24 branches into a re-supply path 25 and a product flow path 26 at a branch portion D1 on the downstream side of the flow meter 18. A valve V2 is provided in the re-supply path 25. The downstream end of the re-supply path 25 merges with the upstream side of the ejector 16 of the re-use supply path 23A. The valve V2 is adjustable in flow rate and is connected to the control device 40. The valve V2 adjusts the opening degree according to a signal from the control device 40 to adjust the flow rate of the product gas branched into the re-supply path 25. A valve V3 is provided in the product flow path 26. The valve V3 is an on-off valve and is connected to the control device 40. The valve V3 is controlled to open and close according to a signal from the control device 40.

[0032] Next, the control of the valves V1, V2, and V3 will be described. In this embodiment, it is controlled in the patterns of a start-up mode M1, a flow rate adjustment mode M2, and a specified concentration mode M3.

[0033] In the start-up mode M1, it is the mode from immediately after the start-up of the synthesis fuel generation system 10 until the concentration of the synthetic compound (for example, methane) in the product gas reaches a predetermined specified concentration (hereinafter referred to as "product gas specified concentration value C1"). The valve V1 is open on the re-use supply path 23A side, closed on the direct supply path 23B side, the valve V2 is open (fully open), and the valve V3 is closed. At this time, since the concentration of the synthetic compound in the product gas is lower than the product gas specified concentration value C1, the total amount of the product gas is sent to the re-supply path 25.

[0034] In the flow rate adjustment mode M2, it is a mode adopted when the concentration of the synthetic compound in the product gas is lower than the product gas specified concentration value C1 when the synthetic fuel generation system 10 is not in operation. In this embodiment, when not in operation, it means the normal operation after shifting from the start-up to the normal operation mode. The valve V1 is opened on the reuse supply path 23A side, closed on the direct supply path 23B side, the valve V2 is opened, and the valve V3 is opened. The product gas with a flow rate exceeding the specified concentration flow rate value C1 corresponding to the product gas specified concentration value C1 is sent to the reuse path 25 by the valve V2, and the remaining product gas (the flow rate corresponding to the specified concentration flow rate value C1) is sent to the product flow path 26. When the load of the water electrolysis device 12 and the synthetic fuel generation device 14 fluctuates due to changing the required flow rate of the product gas or the like when not in operation, it is considered that the concentration of the synthetic compound will drop below the product gas specified concentration value C1. In the flow rate adjustment mode M2, the product gas with a synthetic compound concentration lower than the product gas specified concentration value C1 is sent to the product flow path 26, but the product gas with a certain concentration of the synthetic compound is supplied to the synthetic fuel generation device 14. Therefore, the concentration of the synthetic compound in the gas sent to the product flow path 26 can be increased as compared with the case where the raw material gas without the synthetic compound mixed therein is supplied to the synthetic fuel generation device 14.

[0035] In the specified concentration mode M3, it is a mode adopted when the concentration of the synthetic compound in the product gas is equal to or higher than the product gas specified concentration value C1. The valve V1 is closed on the reuse supply path 23A side, opened on the direct supply path 23B side, the valve V2 is closed, and the valve V3 is opened, and all the product gas is sent to the product flow path 26.

[0036] Here, the specified concentration value C1 and the specified concentration flow rate value C1 will be described.

[0037] The specified concentration value C1 is a value required in the normal operation of the synthetic fuel generation system 10 and can be appropriately set by the user. The conversion rate of the reaction in the synthetic fuel generator 14 has a corresponding relationship with the concentration of the synthetic compound in the generated gas and the ratio of the volume flow rate of the gas sent out from the synthetic fuel generator 14 to the volume flow rate of the gas supplied to the synthetic fuel generator 14 (generated gas volume flow rate / raw material gas volume flow rate). If the conversion rate of the reaction is high, the concentration of the synthetic compound in the generated gas will be high, and the ratio of the volume flow rate of the gas sent out from the synthetic fuel generator 14 to the volume flow rate of the gas supplied to the synthetic fuel generator 14 (generated gas volume flow rate / raw material gas volume flow rate) will be low. The flow rate value C measured by the flow meter 18 when the concentration of the synthetic compound in the generated gas is the specified concentration value C1 is defined as the specified concentration flow rate value C1. The flow rate value C measured by the flow meter 18 at the specified concentration value C1 changes depending on the raw material gas flow rate, but the raw material gas flow rate can be obtained according to the required amount of generated hydrogen in the water electrolysis device 12. Therefore, when the flow rate value C is greater than the specified concentration flow rate value C1, the generated gas is less than the specified concentration value C1, and when the flow rate value C is less than or equal to the specified concentration flow rate value C1, the generated gas is greater than or equal to the specified concentration value C1.

[0038] As shown in FIG. 2, the control device 40 includes a CPU (Central Processing Unit) 42, a ROM (Read Only Memory) 43, a RAM (Random Access Memory) 44, an input / output interface (I / O) 46, and a storage unit 45.

[0039] The CPU 42, ROM 43, RAM 44, and I / O 46 are each connected via a bus 47. To the I / O 46, each functional unit including the storage unit 45 is connected. These functional units can communicate with each other with the CPU 42 via the I / O 46.

[0040] As the storage unit 45, for example, an HDD (Hard Disk Drive), an SSD (Solid State Drive), a flash memory, etc. are used. In the storage unit 45, a control program for controlling the water electrolysis device 12, the synthetic fuel generation device 14, etc., and various data (specified concentration flow values C1, etc.) are stored. Note that this control program and various data may be stored in the ROM 45.

[0041] The temperature sensor 17, the flow meter 18, the valves V1, V2, and V3 are connected to the control device 40 via the I / O 46.

[0042] Next, the operation of the synthetic fuel generation system 10 will be described.

[0043] At startup, the valves V1, V2, and V3 are closed, and the startup mode flag is set to on.

[0044] When a startup instruction is input to the synthetic fuel generation system 10, water is supplied from the water supply source 20 to the water electrolysis device 12, and power is supplied from the power supply source. In the water electrolysis device 12, the supplied water is decomposed into hydrogen and oxygen, the hydrogen is sent to the hydrogen delivery path 21, and the oxygen and water are sent to the oxygen delivery path 22. Carbon dioxide is sent from the carbon dioxide supply source 30, and in the confluence path 23, the carbon dioxide from the carbon dioxide supply source 30 and the hydrogen from the water electrolysis device 12 are mixed and supplied to the synthetic fuel generation device 14.

[0045] In the reactor of the synthetic fuel generation device 14, synthetic fuel and water, for example, methane and water are generated and sent to the generated gas delivery path 24.

[0046] In the control device 40, upon input of the startup instruction, the flow rate concentration determination switching process shown in FIG. 3 is executed.

[0047] In step S10, the flow rate value C is obtained, and in step S12, it is determined whether the flow rate value C is greater than the specified concentration flow rate value C1. If the determination is affirmative, since the concentration of the synthesized compound in the generated gas has not reached the specified concentration, the process proceeds to step S14 to determine whether the startup mode is ON. If the startup mode is ON, it is determined that the synthesis fuel generation system 10 is in the startup state, and the process proceeds to step S16. In step S16, the startup mode M1 process is executed. That is, the valve V1 is opened on the side of the reuse supply path 23A, the direct supply path 23B side is closed, the valve V2 is opened (fully open), and the valve V3 is closed. As a result, the entire amount of the generated gas is sent to the reuse path 25.

[0048] If the determination in step S14 is negative, that is, if the startup mode is not ON, it is determined that the synthesis fuel generation system 10 is not in the startup state, and the process proceeds to step S18. In step S18, the flow rate adjustment mode M2 process is executed. That is, the valve V1 is opened on the side of the reuse supply path 23A, the direct supply path 23B side is closed, the valve V2 is opened, and the valve V3 is opened. The generated gas in an amount exceeding the specified concentration flow rate value C1 corresponding to the specified gas concentration value C1 is sent to the reuse path 25 by the valve V2, and the remaining generated gas is sent to the product flow path 26.

[0049] If the determination in step S12 is negative, that is, if the flow rate value C is less than or equal to the specified concentration flow rate value C1, since the concentration of the synthesized compound in the generated gas has reached the specified concentration, the process proceeds to step S20, and the specified concentration mode M3 process is executed. That is, the valve V1 is closed on the side of the reuse supply path 23A, the direct supply path 23B side is opened, the valve V2 is closed, and the valve V3 is opened. All of the generated gas is sent to the product flow path 26.

[0050] After step S20, in step S22, it is determined whether the startup mode is ON. If the determination is negative, in step S24, the startup mode flag is set to OFF. Thereby, if the generated gas has reached the specified concentration C1 even once, it is determined that the system has shifted from the startup time to the steady state.

[0051] After the processes of steps S16, S18, and S24, or if the determination in step S22 is negative, the process proceeds to step S26.

[0052] In step S26, it is determined whether the operation of the synthetic fuel generation system 10 is instructed to end. If the determination is affirmative, this process ends. If the determination is negative, the process returns to step S10 and the above processes are repeated.

[0053] In the synthetic fuel generation system 10 of this embodiment, based on the flow rate value C of the generated gas sent from the synthetic fuel generator 14, it is determined whether the concentration of the generated gas has reached a predetermined specified value. Since no concentration sensor is used, the cost can be suppressed.

[0054] Also, at startup, when the concentration of the generated gas has not reached the predetermined specified value, the entire amount of the generated gas is sent to the recirculation path 25 and subjected to the reaction again. Therefore, off-spec gas can be effectively utilized and a decrease in the concentration of the product gas can be suppressed.

[0055] Also, in this embodiment, when not starting up, the generated gas exceeding the specified concentration flow rate value C1 is sent to the recirculation path, and the generated gas corresponding to the specified concentration flow rate value C1 is sent to the product flow path 26. Therefore, the supply of the product gas can be continued when not starting up.

[0056] Also, in this embodiment, when there is return generated gas from the recirculation path 25, the ejector 16 of the reuse supply path 23A can be used to send the raw material gas to the synthetic fuel generator 14. On the other hand, when there is no return generated gas from the recirculation path 25, the hydrogen output from the water electrolysis device 12 can be used as the driving force for gas supply. Therefore, by using the direct supply path 23B without an ejector 16, the driving energy can be saved.

[0057] Note that in this embodiment, the ejector 16 is used to send the raw material gas to the synthetic fuel generator 14, but a pump may be used instead of the ejector 16.

[0058] In addition, in this embodiment, when the generated gas reaches the specified concentration C1 even once, it is determined that the transition from the start-up state to the steady state has occurred. However, based on the temperature T detected by the temperature sensor 17, when the steady-state temperature T1 is reached, it may be determined that the transition to the steady state has occurred.

[0059] Note that the synthesis reaction in the synthesis fuel generation device 14 of this embodiment is not limited to the case of synthesizing methane using hydrogen and carbon dioxide as raw materials, and may also be a reaction for generating other synthetic fuels using hydrogen and carbon dioxide as raw materials. For example, the reverse shift reaction for generating carbon monoxide and water, the reaction for generating ethylene and water, the reaction for generating methanol and water, and further, the reaction for generating e-fuel represented by (CH 2 ) n and water can be used.

[0060] Also, in this embodiment, hydrogen is supplied to the synthesis fuel generation device 14 from the water electrolysis device 12. However, other hydrogen supply means may be used, for example, hydrogen supply from other devices such as a steam reforming device or hydrogen supply from a hydrogen tank.

Explanation of Reference Numerals

[0061] 10 Synthesis fuel generation system 12 Water electrolysis device 14 Synthesis fuel generation device 16 Ejector (fluid drive source) 18 Flow meter 23 Confluence path (raw material supply path) 23A Reuse supply path 23B Direct supply path 24 Generated gas delivery path 25 Re-supply path 40 Control device (switching unit) V2 Valve (switching unit) V3 Valve (switching unit)

Claims

1. a synthetic fuel generator that reacts hydrogen with carbon dioxide to produce synthetic compounds and water; a product gas delivery passage through which a product gas is delivered from the synthetic fuel production device; a flow meter provided in the generated gas delivery line for measuring a flow rate of the generated gas; a re-supply passage branching from the product gas delivery passage and returning the product gas to the synthetic fuel production device; a switching unit which, when a ratio of the flow rate measured by the flow meter and the flow rate of the raw material gas supplied to the synthetic fuel generator exceeds a specified ratio, switches so that the entire amount of the generated gas is sent to the re-supply path when the synthetic fuel generator is started, and switches so that an amount of the generated gas that exceeds a flow rate corresponding to the specified ratio is sent to the re-supply path when the synthetic fuel generator is not started; Equipped with Synthetic fuel generation systems.

2. A raw material supply line is provided for combining hydrogen and carbon dioxide and supplying the combined hydrogen and carbon dioxide to the synthetic fuel production device, The raw material supply path is formed in parallel with a reuse supply path equipped with a fluid drive source and a direct supply path not equipped with a fluid drive source, and the re-supply path is connected to the upstream side of the fluid drive source in the reuse supply path. The synthetic fuel production system of claim 1 .

3. 3. The synthetic fuel production system according to claim 1, further comprising a water electrolysis device that generates hydrogen and oxygen by water electrolysis and supplies the hydrogen to the synthetic fuel production device.

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