Synthetic fuel generation system

Abstract

Heat up the synthetic fuel generation device and reduce the greenhouse gas emissions. 【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 combustion unit to which the generated gas produced by the synthetic fuel generation device is supplied and that burns the generated gas, and a heat supply unit that supplies the heat of combustion in the combustion unit to the synthetic fuel generation device.

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 section and a Sabatier reaction section for synthesizing methane by reacting hydrogen with carbon dioxide has been developed. In this methane synthesis apparatus, hydrogen gas generated in the water electrolysis section is supplied to the Sabatier reaction section, 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 section (see Patent Document 1). Further, Patent Document 2 discloses a technique of burning the gas obtained by methanation in a combustor and supplying heat to a water electrolysis apparatus.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a methane synthesis apparatus, since it takes time for the temperature of auxiliary equipment such as a Sabatier reactor and a heat medium oil system to rise at startup, the startup time of the entire system becomes long. Further, especially at startup, there is a problem that the greenhouse gas emission amount at startup increases by discharging off-spec gas containing greenhouse gases such as methane to the atmosphere.

[0005] In consideration of the above facts, an object of the present disclosure is to raise the temperature of a synthetic fuel generation apparatus and reduce the greenhouse gas emission amount.

Means for Solving the Problems

[0006] The synthetic fuel generation system according to the first aspect includes a synthetic fuel generation device that reacts hydrogen and carbon dioxide to generate a synthetic compound and water, a combustion unit to which the generated gas generated by the synthetic fuel generation device is supplied and that burns the generated gas, and a heat supply unit that supplies the heat of combustion in the combustion unit to the synthetic fuel generation device.

[0007] In the synthetic fuel generation system according to the first aspect, the generated gas generated by the synthetic fuel generation device is burned in the combustion unit, and the obtained heat of combustion is supplied to the synthetic fuel generation device by the heat supply unit. Therefore, particularly at the time of starting the synthetic fuel generation device, the temperature of the synthetic fuel generation device can be raised, and the start-up time can be shortened. Further, compared with the case where the generated gas generated by the synthetic fuel generation device is discharged to the atmosphere for reasons such as the concentration of the synthetic compound not reaching a predetermined specified value (off-spec), the amount of greenhouse gas emissions can be reduced.

[0008] The synthetic fuel generation system according to the second aspect includes a generated gas delivery path through which the generated gas is sent out from the synthetic fuel generation device, a combustion supply path that branches from the generated gas delivery path and supplies the generated gas to the combustion unit, a combustion mode in which the generated gas is sent out to the combustion supply path, and a switching control unit that switches between the combustion mode and a non-combustion mode in which the generated gas is not sent out to the combustion supply path.

[0009] According to the synthetic fuel generation system of the second aspect, by switching between the combustion mode and the non-combustion mode by the switching control unit, the presence or absence of combustion of the generated gas in the combustion unit can be controlled.

[0010] In the synthetic fuel generation system according to the third aspect, the switching control unit switches to the combustion mode when the concentration of the synthetic compound in the generated gas sent out to the generated gas delivery path is less than a predetermined specified concentration.

[0011] According to the synthetic fuel generation system of the third aspect, when the concentration of the synthetic compound in the product gas is less than a predetermined specified concentration, by burning it, the greenhouse gas emissions can be reduced compared to the case of discharging it into the atmosphere without burning.

[0012] Moreover, particularly at the time of starting the synthetic fuel generation device, since the concentration of the synthetic compound in the product gas is less than a predetermined specified concentration, this off-spec product gas can be effectively utilized to raise the temperature of the synthetic fuel generation device, and the start-up time can be shortened.

[0013] In the synthetic fuel generation system of the fourth aspect, the switching control unit switches to the combustion mode when the temperature of the synthetic fuel generation device is less than a predetermined specified temperature.

[0014] According to the synthetic fuel generation system of the fourth aspect, when the temperature of the synthetic fuel generation device is less than a predetermined specified temperature, by burning it, the combustion heat obtained in the combustion unit can be used to raise the temperature of the synthetic fuel generation device.

[0015] The synthetic fuel generation system of 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, and a sub heat supply unit that supplies the combustion heat in the combustion unit to the water electrolysis device.

[0016] According to the synthetic fuel generation system of the fifth aspect, the combustion heat obtained in the combustion unit can be used to raise the temperature of the water electrolysis device.

[0017] The synthetic fuel generation system of the sixth aspect includes a water electrolysis temperature detection unit that detects the temperature of the water electrolysis device. The switching control unit switches to an electrolyzer heating mode in which the combustion heat in the combustion unit is supplied from the sub heat supply unit to the water electrolysis device when the temperature detected by the water electrolysis temperature detection unit is less than a predetermined suitable water electrolysis temperature, and switches to an electrolyzer non-heating mode in which the combustion heat in the combustion unit is not supplied to the water electrolysis device when the temperature detected by the water electrolysis temperature detection unit is equal to or higher than the predetermined suitable water electrolysis temperature.

[0018] According to the synthetic fuel generation system of the sixth aspect, when the temperature of the water electrolysis device is lower than the appropriate temperature for water electrolysis, the water electrolysis device can be effectively heated up.

Advantages of the Invention

[0019] According to the present disclosure, the synthetic fuel generation device can be heated up while reducing the greenhouse gas emissions.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

Figure 7

Modes for Carrying Out the Invention

[0021] Hereinafter, an example of an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0022] As shown in FIG. 1, the synthetic fuel generation system 10 of the present embodiment includes a water electrolysis device 12, a synthetic fuel generation device 14, a combustor 16, a flow meter 19, and a control device 40.

[0023] The water electrolysis device 12 is connected to a water supply source 20 and a power supply source (not shown). 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).

[0024] H 2 O → H 2 +(1 / 2)O 2 (1)

[0025] 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 a carbon dioxide supply source 30 and is connected to a 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. The downstream end of the merging path 23 is connected to a synthetic fuel generation device 14, and a mixed gas of carbon dioxide and hydrogen is supplied to the synthetic fuel generation device 14. Oxygen and water are delivered from the oxygen delivery path 22.

[0026] The synthetic fuel generation device 14 has a reactor (not shown). In the reactor, as an example, methane and water are generated by a methane synthesis reaction as shown in the following formula (2).

[0027] 4H 2 +CO 2 →CH 4 +2H 2 O (2)

[0028] The synthetic fuel generation device 14 is provided with a temperature sensor 18 for detecting the temperature inside the synthetic fuel generation device 14. The temperature sensor 18 may detect the temperature of the reactor inside the synthetic fuel generation device 14, or may detect the temperature of other auxiliary machines and the like. The temperature sensor 18 is connected to a control device 40 and outputs the detected temperature T to the control device 40.

[0029] The synthesis fuel generation device 14 is connected to a product gas delivery path 24, and product gas generated by the synthesis fuel generation device 14, for example, methane and water, is sent to the product gas delivery path 24.

[0030] The product gas delivery path 24 has a combustion supply path 25 branched off at a branch section D1. A valve V1 is provided at the branch section D1. A combustor 16 is connected to the downstream end of the combustion supply path 25. A flow meter 19 is provided on the upstream side of the branch section D1 of the product gas delivery path 24. The flow meter measures the flow rate of the gas sent from the synthesis fuel generation device 14 to the product gas delivery path 24. The flow meter 19 is connected to a control device 40 and outputs the measured flow rate data to the control device 40.

[0031] The combustor 16 burns the product gas supplied from the combustion supply path 25. The combustor 16 is connected to a combustion exhaust gas path 27, and the combustion exhaust gas generated by combustion is sent to the combustion exhaust gas path 27. The combustion exhaust gas path 27 has a combustion exhaust gas dispersion path 26 branched off at a branch section D2. A valve V2 is provided at the branch section D2. The combustion exhaust gas path 27 is open to the atmosphere from an exhaust path 29 via the synthesis fuel generation device 14 and the water electrolysis device 12. The combustion exhaust gas sent into the combustion exhaust gas path 27 exchanges heat with the synthesis fuel generation device 14 and is sent to a sub-combustion exhaust gas path 28, and after heat exchange with the water electrolysis device 12, it is dispersed to the atmosphere from the exhaust path 29. The combustion exhaust gas functions as a heat medium for heating the synthesis fuel generation device 14 and the water electrolysis device 12.

[0032] The valves V1 and V2 are three-way valves and are connected to the control device 40. The valves V1 and V2 are three-way valves, and the switching of the outflow destination is controlled. In the valve V1, when the combustion supply path 25 side is open and the delivery side to the downstream side of the product gas delivery path 24 is closed, it becomes a combustion mode A1 in which product gas is supplied to the combustor 16. In the valve V1, when the combustion supply path 25 side is closed and the delivery side to the downstream side of the product gas delivery path 24 is open, it becomes a non-combustion mode A2 in which product gas is not supplied to the combustor 16.

[0033] The switching between the combustion mode A1 and the non-combustion mode A2 is performed by controlling the opening and closing of the flow destination of the valve V1 such that when the concentration of the synthetic compound (e.g., methane) in the product gas generated by the synthetic fuel generation device 14 is equal to or higher than a predetermined specified concentration (hereinafter referred to as "specified concentration value C1"), the non-combustion mode A2 is entered, and when it is less than the specified concentration value C1, the combustion mode A1 is entered.

[0034] Here, the specified concentration value C1 and the specified concentration flow value C1 will be described. 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 generation device 14 has a corresponding relationship with the concentration of the synthetic compound in the product gas and the ratio of the flow rate of the gas sent out from the synthetic fuel generation device 14 to the flow rate of the gas supplied to the synthetic fuel generation device 14 (product gas flow rate / raw material gas flow rate). If the conversion rate of the reaction is high, the concentration of the synthetic compound in the product gas will be high, and the ratio of the flow rate of the gas sent out from the synthetic fuel generation device 14 to the flow rate of the gas supplied to the synthetic fuel generation device 14 (product gas flow rate / raw material gas flow rate) will be low. The flow value C measured by the flow meter 19 when the concentration of the synthetic compound in the product gas is the specified concentration value C1 is defined as the specified concentration flow value C1. Therefore, when the flow value C is greater than the specified concentration flow value C1, the product gas is less than the specified concentration value C1, and when the flow value C is less than or equal to the specified concentration flow value C1, the product gas is equal to or higher than the specified concentration value C1.

[0035] In the valve V2, when the combustion exhaust gas path 27 side is open and the combustion exhaust gas dissipation path 26 side is closed, it is in the heating mode B1 in which the combustion exhaust gas is supplied to the synthetic fuel generation device 14 and the water electrolysis device 12. In the valve V2, when the combustion exhaust gas path 27 side is closed and the combustion exhaust gas dissipation path 26 side is open, it is in the non-heating mode B2 in which the combustion exhaust gas is not supplied to the synthetic fuel generation device 14.

[0036] The switching between the heating mode B1 and the non - heating mode B2 is performed by controlling the opening and closing of the flow destination of the valve V2 such that when the temperature T detected by the temperature sensor 18 is equal to or higher than the operating appropriate value T1 of the synthetic fuel generation device 14, it becomes the non - heating mode B2, and when it is less than the operating appropriate value T1, it becomes the heating mode B1. The operating appropriate value T1 is a value required for an appropriate reaction in the normal operation of the synthetic fuel generation device 14 and can be appropriately set by the user.

[0037] 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.

[0038] 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 via the I / O 46 and the CPU 42.

[0039] 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 (prescribed concentration flow value C1, temperature appropriate value T1, etc.) are stored. Note that this control program and various data may be stored in the ROM 43.

[0040] The temperature sensor 18, the flow meter 19, the valve V1, and the valve V2 are connected to the control device 40 via the I / O 46.

[0041] Next, the operation of the synthetic fuel generation system 10 will be described.

[0042] When a start instruction is input to the synthetic fuel generation system 10 at startup, 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.

[0043] In the reactor of the synthetic fuel generation device 14, a synthetic compound and water, for example, methane and water are generated and sent to the generated gas delivery path 24.

[0044] In the control device 40, the flow rate concentration determination switching process shown in FIG. 3 is executed by the input of the start instruction.

[0045] In step S10, the flow rate value C is acquired, and in step S12, it is determined whether the flow rate value C is greater than the specified concentration flow rate value C1 (the flow rate value corresponding to the generated gas specified concentration value C1). If the determination is affirmative, since the concentration of the synthetic compound in the generated gas has not reached the specified concentration, the combustion mode is switched in step S14. Specifically, for the valve V1, with the combustion supply path 25 side open and the downstream side of the generated gas delivery path 24 closed, the generated gas is supplied to the combustor 16. The generated gas supplied to the combustor 16 is burned in the combustor 16.

[0046] If the determination in step S12 is negative, the non - combustion mode is switched in step S16. Specifically, for the valve V1, with the combustion supply path 25 side closed and the downstream side of the generated gas delivery path 24 open for sending as product gas, the generated gas is not supplied to the combustor 16. After step S16, the process proceeds to step S26.

[0047] Following step S14, the temperature T is acquired in step S18, and it is determined in step S20 whether the temperature T is lower than the operation appropriate value T1. If the determination is affirmative, the heating mode is switched in step S22. Specifically, for the valve V2, the side of the combustion exhaust gas passage 27 is opened and the side of the combustion exhaust gas dissipation passage 26 is closed, and the combustion exhaust gas is supplied as a heat medium to the synthetic fuel generation device 14 and the water electrolysis device 12. Thereby, the synthetic fuel generation device 14 and the water electrolysis device 12 are heated. After step S22, the process proceeds to step S26.

[0048] If the determination in step S20 is negative, the non-combustion mode is switched in step S24. Specifically, for the valve V2, the side of the combustion exhaust gas passage 27 is closed and the side of the combustion exhaust gas dissipation passage 26 is opened, and the combustion exhaust gas is dissipated to the atmosphere. After step S24, the process proceeds to step S26.

[0049] In step S26, it is determined whether an instruction to end the operation of the synthetic fuel generation system 10 has been given. If the determination is affirmative, this process ends. If the determination is negative, the process returns to step S10 and the above process is repeated.

[0050] In the synthetic fuel generation system 10 of the present embodiment, based on the flow rate value C of the generated gas sent from the synthetic fuel generation device 14, it is determined whether the concentration of the synthetic compound of the generated gas has reached a predetermined specified value. If the determination is negative, the generated gas generated by the synthetic fuel generation device 14 is burned in the combustor 16, and the obtained combustion heat is supplied to the synthetic fuel generation device 14. Therefore, particularly at the time of starting the synthetic fuel generation device 14, the temperature of the synthetic fuel generation device 14 can be raised, and the start-up time can be shortened.

[0051] In addition, compared with the case where the generated gas generated by the synthetic fuel generation device 14 is dissipated to the atmosphere because the concentration of the synthetic compound has not reached the predetermined specified value, the greenhouse gas emission amount can be reduced.

[0052] In addition, in this embodiment, the combustion mode A1 and the non-combustion mode A2 are switched based on the flow rate value C obtained by the flow meter 19. However, the combustion mode A1 and the non-combustion mode A2 may be switched based on the temperature T obtained by the temperature sensor 18.

[0053] In this case, as shown in FIG. 4, the temperature T is acquired in step S30, and it is determined in step S32 whether the temperature T is lower than the operation appropriate value T1. If the determination is affirmative, the combustion mode is switched in step S14. As a result, the synthetic fuel generation device 14 and the water electrolysis device 12 are heated.

[0054] If the determination in step S32 is negative, the non-combustion mode is switched in step S16. After steps S14 and S16, the process proceeds to step S26.

[0055] When burning the generated gas in the combustor 16, since the synthetic fuel generation device 14 is always below the temperature T, the valve V2 may be set to be in the constant heating mode.

[0056] In step S26, it is determined whether an instruction to end the operation of the synthetic fuel generation system 10 has been given. If the determination is affirmative, this process ends. If the determination is negative, the process returns to step S30 and the above process is repeated.

[0057] In addition, in this embodiment, the concentration of the synthetic compound in the generated gas is determined from the flow rate of the generated gas using a flow meter. However, instead of the flow meter, a concentration meter may be used to determine the concentration of the synthetic compound in the generated gas. In particular, by using a flow meter as in this embodiment, the cost can be kept lower compared to the case of using a concentration meter.

[0058] In addition to the configuration of the present embodiment, the supply of the combustion exhaust gas to the water electrolysis device 12 may be controlled based on the temperature of the water electrolysis device 12. In this case, as shown in FIG. 5, a temperature detection unit 12A for detecting the temperature TE of the water electrolysis device 12 is provided. Further, a branch portion D3 and a three-way valve V3 are provided in the combustion exhaust gas discharge path 26, and a branch portion D4 and a three-way valve V4 are provided between the synthetic fuel generation device 14 and the water electrolysis device 12 in the sub-combustion exhaust gas path 28. The three-way valve V3 is connected to a bypass circuit 27A that branches from the combustion exhaust gas discharge path 26 and joins the sub-combustion exhaust gas path 28 at a junction C without passing through the synthetic fuel generation device 14. The three-way valve V4 is provided on the upstream side of the junction C and branches one side to the water electrolysis device 12 side (sub-combustion exhaust gas path 28) and the other side to the atmosphere discharge path 28A. As shown in FIG. 6, the temperature detection unit 12A, the three-way valves V3, and V4 are connected to the control device 40. When the temperature TE detected by the temperature detection unit 12A is less than the operating appropriate temperature in the water electrolysis device 12 (less than the water electrolysis appropriate temperature TE0), the control device 40 controls so that the bypass circuit 27A side of the three-way valve V3 or the water electrolysis device 12 side of the three-way valve V4 is opened. When the temperature TE detected by the temperature detection unit 12A is equal to or higher than the operating appropriate temperature in the water electrolysis device 12 (equal to or higher than the water electrolysis appropriate temperature TE0), the control device 40 controls so that the combustion exhaust gas discharge path 26 side of the three-way valve V3 or the atmosphere discharge side of the three-way valve V4 is opened. The water electrolysis appropriate temperature TE is the lower limit value of the temperature suitable for the operation of the water electrolysis device 12.

[0059] In the case of the flow rate concentration determination switching process in this case, as shown in FIG. 7, when proceeding to step S22, in step S40, the temperature TE of the water electrolysis device 12 is acquired from the temperature sensor 12A, and in step S42, it is determined whether the temperature TE of the water electrolysis device 12 is less than the water electrolysis appropriate temperature TE0. If the determination is affirmative, in step S44, the water electrolysis device 12 side of the three-way valve V4 is opened, and if the determination is negative, in step S45, the atmosphere discharge 28A side of the three-way valve V4 is opened.

[0060] When proceeding to step S24, in step S46, the temperature TE of the water electrolysis device 12 is acquired from the temperature sensor 12A. In step S47, it is determined whether the temperature TE of the water electrolysis device 12 is less than the appropriate water electrolysis temperature TE0. If the determination is affirmative, in step S48, the bypass 27A side of the three-way valve V3 is opened. If the determination is negative, in step S49, the combustion gas discharge path 26 side of the three-way valve V3 is opened. After steps S44, S45, S48, and S49, proceed to step S26.

[0061] Further, as the synthesis reaction in the synthesis fuel generation device 14 of the present embodiment, it is not limited to the case of synthesizing methane using hydrogen and carbon dioxide as raw materials, and it may also be a reaction for generating other synthesis 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.

[0062] In the present embodiment, hydrogen is supplied to the synthesis fuel generation device 14 from the water electrolysis device 12, but it may also be supplied from other hydrogen supply means, for example, other devices such as a steam reforming device or from a hydrogen tank.

Explanation of Reference Numerals

[0063] 10 Synthesis fuel generation system 12 Water electrolysis device 14 Synthesis fuel generation device 16 Combustor (combustion section) 27 Combustion exhaust gas path (heat supply section) 28 Sub-combustion exhaust gas path (sub-heat supply section) 40 Control device (switching control section) A1 Combustion mode A2 Non-combustion mode B1 Heating mode B2 Non-heating mode V1 Valve (switching control section)

Claims

1. a synthetic fuel generator that reacts hydrogen with carbon dioxide to produce synthetic compounds and water; a combustion section that is supplied with a product gas generated by the synthetic fuel production device and combusts the product gas; a heat supply unit that supplies combustion heat in the combustion unit to the synthetic fuel production device; a product gas delivery passage through which the product gas is delivered from the synthetic fuel production device; a combustion supply passage branched from the generated gas delivery passage and configured to supply the generated gas to the combustion section; A switching control unit that switches between a combustion mode in which the generated gas is sent to the combustion supply passage and a non-combustion mode in which the generated gas is not sent to the combustion supply passage; A synthetic fuel production system comprising:

2. The switching control unit switches to the combustion mode when a concentration of the synthetic compound in the generated gas delivered to the generated gas delivery path is less than a predetermined specified concentration. The synthetic fuel production system of claim 1 .

3. The switching control unit switches to the combustion mode when the temperature of the synthetic fuel production device is lower than a predetermined specified temperature. The synthetic fuel production system of claim 1 .

4. a water electrolysis device that generates hydrogen and oxygen by water electrolysis and supplies the hydrogen to the synthetic fuel production device; a sub-heat supplying unit that supplies combustion heat generated in the combustion unit to the water electrolysis apparatus; The synthetic fuel production system according to any one of claims 1 to 3, comprising:

5. a water electrolysis temperature detection unit that detects a temperature of the water electrolysis device; the switching control unit switches to an electrolysis device heating mode in which combustion heat in the combustion unit is supplied from the sub-heat supply unit to the water electrolysis device when the temperature detected by the water electrolysis temperature detection unit is lower than a predetermined optimum water electrolysis temperature, and switches to an electrolysis device non-heating mode in which combustion heat in the combustion unit is not supplied to the water electrolysis device when the temperature detected by the water electrolysis temperature detection unit is equal to or higher than a predetermined optimum water electrolysis temperature. A synthetic fuel production system according to claim 4 which recites claim 3.

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