Liquid fuel synthesis system and method for controlling same
The liquid fuel synthesis system addresses high costs and inefficiencies by using tail gas as boiler fuel and optimizing its supply, achieving cost-effective and energy-efficient operation.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- MITSUBISHI HEAVY IND LTD
- Filing Date
- 2025-08-19
- Publication Date
- 2026-06-11
Smart Images
Figure JP2025029100_11062026_PF_FP_ABST
Abstract
Description
Liquid fuel synthesis system and its control method 【0001】 The present disclosure relates to a liquid fuel synthesis system and its control method. 【0002】 Conventionally, a system for liquid fuel synthesis that synthesizes liquid fuel from a raw material containing a carbon component is known. For example, in Patent Document 1, a technique for synthesizing a fuel containing hydrocarbons from carbon monoxide and hydrogen by Fischer-Tropsch (FT) synthesis has been reported. 【0003】 Japanese Patent Application Laid-Open No. 2024-504733 【0004】 Conventionally, as in Patent Document 1, for example, in a Sustainable Aviation Fuel (SAF) manufacturing process, in order to increase the fuel yield after FT synthesis, a system for recycling the tail gas after FT synthesis is provided to steam reform the tail gas after FT synthesis and recycle it to the upstream side of the FT synthesizer. However, with this configuration, although it leads to an increase in yield, it is necessary to additionally install a reactor for steam reforming or the like, resulting in high costs and being easily restricted by the installation space. Also, for example, steam reforming requires high-temperature heat at the level of 800 to 1000 °C, so it cannot be said that the energy efficiency is necessarily good. 【0005】 The present disclosure has been made in view of such circumstances, and an object thereof is to provide a liquid fuel synthesis system that can suppress costs, is advantageous in terms of space, and is also advantageous in terms of energy efficiency. 【0006】 To solve the above problems, the liquid fuel synthesis system of the present disclosure includes a boiler that burns a carbon-containing fuel to generate steam, a liquid fuel synthesizer that synthesizes liquid fuel from a raw material containing a carbon component, and a tail gas supply line that connects the boiler and the liquid fuel synthesizer and supplies the tail gas containing hydrocarbons discharged from the liquid fuel synthesizer to the boiler. 【0007】Furthermore, the control method for a liquid fuel synthesis system of the present disclosure is a control method for a liquid fuel synthesis system comprising a boiler that burns a carbon-containing fuel to generate steam, and a liquid fuel synthesizer that synthesizes liquid fuel from raw materials containing carbon components, the method comprising a tail gas supply step of supplying tail gas containing hydrocarbons discharged from the liquid fuel synthesizer to the boiler. 【0008】 The liquid fuel synthesis system and control method described herein offer cost savings, space advantages, and energy efficiency advantages. 【0009】 This is a diagram of a liquid fuel synthesis system according to the first embodiment of this disclosure. This is a diagram of a liquid fuel synthesis system according to the second embodiment of this disclosure. This is a schematic configuration diagram showing an example of a measuring device applied to the liquid fuel synthesis system according to the second embodiment of this disclosure. This is a schematic configuration diagram showing another example of a measuring device applied to the liquid fuel synthesis system according to the second embodiment of this disclosure. This is a flowchart showing a control method for the liquid fuel synthesis system according to the second embodiment of this disclosure. This is a diagram of a liquid fuel synthesis system according to the third embodiment of this disclosure. This is a flowchart showing a control method for the liquid fuel synthesis system according to the third embodiment of this disclosure. This is a diagram of a liquid fuel synthesis system according to the fourth embodiment of this disclosure. 【0010】 An embodiment of the liquid fuel synthesis system and its control method according to this disclosure will be described below with reference to the drawings. In the following description, a biomass boiler will be used as the boiler that burns carbon-containing fuel to generate steam, and an FT synthesizer will be used as the liquid fuel synthesizer that synthesizes liquid fuel from raw materials containing carbon components, but the invention is not limited to this example. 【0011】 [First Embodiment] Hereinafter, a first embodiment of the present disclosure will be described with reference to Figure 1. The liquid fuel synthesis system 1A according to this embodiment comprises a boiler 10, a carbon dioxide recovery device 20, a water electrolyzer 30, a reverse shift reactor 40, and a liquid fuel synthesizer 50. 【0012】The boiler 10 generates steam by burning carbon-containing fuel. In this embodiment, the boiler 10 is a biomass boiler, and the carbon-containing fuel is biomass. The boiler 10 is connected to a steam turbine (not shown) driven by the steam from the boiler 10, and a generator (not shown) driven by the steam turbine. This makes it possible to generate electricity. The exhaust gas discharged from the boiler 10 is sent to the carbon dioxide recovery device 20 via the exhaust gas supply line L1. The electricity generated by the boiler 10 is supplied to the water electrolysis device 30 via the power supply line L2. 【0013】 The carbon dioxide recovery unit 20 recovers carbon dioxide from the exhaust gas discharged from the boiler 10. Specifically, it recovers carbon dioxide from the exhaust gas supplied from the boiler 10 via the exhaust gas supply line L1. The recovered carbon dioxide is supplied to the reverse shift reactor 40 via the carbon dioxide supply line L3. 【0014】 The water electrolysis device 30 uses electricity to electrolyze water and produce hydrogen from it. The electricity is supplied by the power supply line L2 from the power generated by the boiler 10. The produced hydrogen is supplied to the reverse shift reactor 40 by the hydrogen supply line L4. Oxygen, which is a by-product of electrolysis, is discharged. 【0015】 The reverse shift reactor 40 produces carbon monoxide using hydrogen generated by the water electrolysis unit 30 and carbon dioxide recovered by the carbon dioxide recovery unit 20 as raw materials. Specifically, it produces carbon monoxide using carbon dioxide supplied by the carbon dioxide supply line L3 and hydrogen supplied by the hydrogen supply line L4 as raw materials. The hydrogen and the produced carbon monoxide are supplied to the liquid fuel synthesizer 50 via the carbon monoxide supply line L5. 【0016】 A cooling device (heat exchanger) 41 is provided in the carbon monoxide supply line L5 located between the reverse shift reactor 40 and the liquid fuel synthesizer 50. The cooling device 41 cools the synthesis gas flowing through the carbon monoxide supply line L5. 【0017】The liquid fuel synthesizer 50 synthesizes liquid fuel from raw materials containing carbon components. In this embodiment, the liquid fuel synthesizer 50 is an FT synthesizer that produces liquid fuel from synthesis gas containing carbon monoxide generated in the reverse shift reactor 40. The produced liquid fuel is sent to a downstream device for purification. During the production of liquid fuel, tail gas containing hydrocarbons is produced as a by-product. The tail gas contains C1 to C10 hydrocarbons, hydrogen, carbon dioxide, etc. 【0018】 In the liquid fuel synthesis system 1A according to this embodiment, a boiler 10 and a liquid fuel synthesizer 50 are connected, and a tail gas supply line L6 is provided to supply tail gas containing hydrocarbons discharged from the liquid fuel synthesizer 50 to the boiler. The tail gas discharged from the liquid fuel synthesizer 50 is supplied to the boiler 10 via the tail gas supply line L6. 【0019】 A heating means 51 is provided in the middle of the tail gas supply line L6. The heating means 51 is a heat exchanger and heats the gas flowing through the tail gas supply line L6 by exchanging heat with it. The heat source for the heating means (heat exchanger) 51 can be the waste heat generated during cooling by the cooling device 41 described above. It is also possible to use heat from another reaction as the heat source for the heating means 51. Furthermore, the heating means 51 can be configured to extract a portion of the gas from the tail gas supply line L6 and supply it to a burner, and then use the heat obtained by the burner to heat the gas flowing through the tail gas supply line L6. 【0020】 The control method for the liquid fuel synthesis system 1A of this embodiment includes a tail gas supply step of supplying tail gas containing hydrocarbons discharged from the liquid fuel synthesizer 50 to the boiler 10. The tail gas is supplied to the boiler 10 via the tail gas supply line L6. The supply of tail gas to the boiler 10 may be controlled manually, but a flow control valve may also be provided in the tail gas supply line L6, and the opening degree of the flow control valve may be controlled by a control device. The flow control valve can have the same configuration as the tail gas flow control valve 53 described later, and the control device can have the same configuration as the control device 100 described later. 【0021】As described above, this embodiment provides the following advantages. The liquid fuel synthesis system 1A of this embodiment is equipped with a tail gas supply line L6 that supplies tail gas containing hydrocarbons discharged from the liquid fuel synthesizer 50 to the boiler 10. As a result, tail gas containing hydrocarbons can be supplied to the boiler 10, and the tail gas can be used as fuel for the boiler 10. Therefore, the amount of fuel required in the boiler 10 can be reduced. Furthermore, compared to a configuration in which the tail gas is recirculated upstream of the liquid fuel synthesizer 50, it is advantageous in terms of cost and space because it does not require the addition of reactors, etc. Also, since it is not necessary to heat the tail gas to a high temperature, it is advantageous in terms of energy efficiency. 【0022】 Furthermore, because biomass is a solid, its fluidity is unstable, which can easily lead to fluctuations in the amount supplied to the boiler 10. Consequently, the amount of biomass supplied to the boiler 10 may temporarily decrease, causing the boiler 10's output to become unstable. The liquid fuel synthesis system 1A of this embodiment can be suitably used in biomass boilers that are prone to such output instability. 【0023】 Furthermore, the tail gas has a temperature of 40-50°C, which is slightly too low for supply to the boiler 10. In this embodiment, the liquid fuel synthesis system 1A is provided in the tail gas supply line L6 and includes a heat exchanger 51 that transfers waste heat from the cooling device 41 to the tail gas flowing through the tail gas supply line L6. Therefore, the heat exchanger 51 can preheat the tail gas to a temperature suitable for supply to the boiler 10. Moreover, since the heat used for preheating is waste heat generated from the cooling device 41 that cools the synthesis gas containing carbon monoxide produced in the reverse shift reactor 40, the heat can be utilized effectively. 【0024】Furthermore, the control method for the liquid fuel synthesis system 1A of this embodiment includes a tail gas supply step that supplies the tail gas containing hydrocarbons discharged from the liquid fuel synthesizer 50 to the boiler 10. As a result, the tail gas containing hydrocarbons can be supplied to the boiler 10, and the tail gas can be used as fuel for the boiler 10. Therefore, the amount of fuel required in the boiler 10 can be reduced. In addition, compared to a configuration in which the tail gas is recirculated to the upstream side of the liquid fuel synthesizer 50, it does not require the addition of reactors, etc., so costs can be reduced and it is advantageous in terms of space. Also, since it is not necessary to heat the tail gas to a high temperature, it is advantageous in terms of energy efficiency. 【0025】 [Second Embodiment] A second embodiment of the present disclosure will be described below with reference to Figures 2 to 5. In this embodiment, the parts that differ from the first embodiment will be described, and the description of other overlapping parts will be omitted. Also, the same reference numerals will be used for components that are the same as in the first embodiment, and the redundant description will be omitted. In addition, the cooling device 41 and heating means 51 of the first embodiment are omitted in Figure 2. 【0026】 In the liquid fuel synthesis system 1B of this embodiment, a tail gas storage tank 52 for storing tail gas is provided in the middle of the tail gas supply line L6. A tail gas flow rate control valve 53 is provided downstream of the tail gas storage tank 52 in the tail gas supply line L6. By closing the tail gas flow rate control valve 53, tail gas is stored in the tail gas storage tank 52. Conversely, by opening the tail gas flow rate control valve 53, the tail gas stored in the tail gas storage tank 52 is supplied to the boiler 10. 【0027】 The opening degree of the tail gas flow control valve 53 is controlled by the control device 100. The control device 100 controls the opening degree of the tail gas flow control valve 53 according to predetermined parameters relating to the carbon-containing fuel, the boiler 10, or the tail gas. The predetermined parameters can include the properties of the fuel (carbon-containing fuel) in the boiler 10, the amount of heat input to the boiler 10, the temperature inside the boiler 10, fluctuations in the amount of power generated by the boiler 10, the calorific value of the tail gas, the composition of the tail gas, etc. 【0028】 The control device 100 is composed of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions are stored in the storage medium in the form of a program, for example. The CPU reads this program into the RAM and performs information processing and calculations to realize the various functions. The program may be pre-installed on the ROM or other storage medium, provided in a state where it is stored on a computer-readable storage medium, or distributed via wired or wireless communication. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memory, etc. 【0029】 The liquid fuel synthesis system 1B is equipped with a measuring device 54 that measures tail gas property parameters based on the properties of the tail gas stored in the tail gas storage tank 52. The measuring device 54 is connected to the tail gas storage tank 52. The measuring device 54 extracts a portion of the tail gas stored in the tail gas storage tank 52 and measures the tail gas property parameters (predetermined parameters). The control device 100 obtains the tail gas property parameters from the measuring device 54 and controls the opening degree of the tail gas flow rate control valve 53 according to the obtained tail gas property parameters. The tail gas property parameters can include the composition of the tail gas and the calorific value calculated from the gas composition. 【0030】 Figure 3 shows a measuring device 54A as an example of a measuring device 54. The measuring device 54A shown in Figure 3 is an example of a measuring device that uses a tunable semiconductor laser absorption method. This enables continuous measurement of the tail gas component concentration (composition) and the amount of tail gas calories calculated from the gas component composition. 【0031】The measuring device 54A includes a container 55. Infrared light-transmitting windows 56 are provided on both the upper and lower sides of the container 55. Depending on the properties of the tail gas, a mechanism may be provided to flow an inert gas through the windows 56 to prevent window soiling. Nitrogen gas is an example of such an inert gas. Furthermore, if it is necessary to prevent condensation of tail gas components, the container 55 and the inert gas line for preventing window soiling may be insulated. The container 55 allows tail gas to be introduced from one side (left side in Figure 3) and exhausted from the other side (right side in Figure 3). 【0032】 An infrared light source 57, such as a semiconductor laser, is provided on the upper side of the container 55. An infrared photodetector 58 is provided on the lower side of the container 55 to detect infrared light emitted from the infrared light source 57. The infrared light emitted from the infrared light source 57 passes through the inside of the container 55 from top to bottom. The infrared light that has passed through is detected by the infrared photodetector 58. The infrared light source 57 and the infrared photodetector 58 are connected to a data processing device 59. The data processing device 59 controls the irradiation of infrared light by the infrared light source 57. The data processing device 59 also processes the infrared light data detected by the infrared photodetector 58. 【0033】 The method for measuring tail gas property parameters using the measuring device 54A shown in Figure 3 is as follows. First, tail gas extracted from the tail gas storage tank 52 is introduced into the container 55 from one side. When sending the introduced tail gas to the other side of the container 55, the tail gas flow path is widened from one side to the other of the container 55 in order to ensure a long distance between the two windows 56 (corresponding to the effective laser beam path length for measurement). 【0034】 Next, infrared light is irradiated from the infrared light source 57 towards the tail gas flowing through the container 55. The intensity of the irradiated infrared light is I ０ This is the case. Furthermore, the infrared intensity I ０ The measuring instrument used to take the measurement is not shown. 【0035】 Next, the infrared light intensity after passing through the tail gas is measured using the infrared light detector 58. １ Let's assume that. 【0036】Finally, the data processing device 59 determines the transmittance of the tail gas component (I １ / I ０ The concentration of the tail gas component is derived by calculating the following. By setting the infrared wavelength, it becomes possible to selectively measure the concentration of the tail gas component. This allows for the measurement of the tail gas component composition and the calculation of the calorific value of the gas. 【0037】 As another example of the measuring device 54, the measuring device 54B shown in Figure 4 can also be applied. The measuring device 54B is directly attached to the piping that constitutes the tail gas supply line L6. The tail gas supply line L6 has infrared light-transmitting windows 60 on both sides in the direction of tail gas flow. An infrared light source 57 is provided on one side of the window 60 (left side in Figure 4), and an infrared light detector 58 is provided on the other side of the window 60 (right side in Figure 4). The infrared light source 57 and the infrared light detector 58 are connected to a data processing device 59. Direct attachment to the tail gas supply line L6 allows measurement without extracting tail gas, thus enabling measurement with reduced time lag and further reducing the cost of the measurement system. To prevent contamination of the windows 60, a gas purging mechanism using inert gas may be provided. Nitrogen gas is an example of an inert gas. The temperature of the inert gas should be equal to or higher than the temperature of the tail gas in the attached piping. 【0038】 It is also possible to install the measuring device 54B in the tail gas storage tank 52. In this case, the tail gas storage tank 52 is provided with a window that can transmit infrared light. 【0039】 In addition to the above, the measuring device 54 can also be a device that measures the tail gas composition from the extracted tail gas using a gas chromatograph and calculates the calorific value of the tail gas. A measuring device using the Raman scattering method can also be used. 【0040】 Next, a control method for the liquid fuel synthesis system 1B according to this embodiment will be described. Figure 5 is a flowchart showing the control method for the liquid fuel synthesis system 1B according to this embodiment. 【0041】In step S101, data is acquired from various sensors. The data is a predetermined parameter regarding carbon-containing fuel, the boiler 10, or tail gas. In this flowchart, the case where the heat input amount to the boiler 10 is used as a predetermined parameter will be described as an example. 【0042】 In step S102, it is confirmed whether the acquired heat input amount to the boiler 10 exceeds a threshold value. If the heat input amount to the boiler 10 exceeds the threshold value (YES in step S102), the process proceeds to step S103 and the operation of the boiler 10 is continued as it is. On the other hand, if the heat input amount to the boiler 10 does not exceed the threshold value (NO in step S102), the process proceeds to step S104. 【0043】 In step S104, tail gas is supplied to the boiler 10. Based on the acquired heat input amount to the boiler 10, the tail gas flow rate adjustment valve 53 is opened to a predetermined opening degree, and tail gas is supplied from the tail gas storage tank 52 to the boiler 10. 【0044】 With the configuration described above, according to the present embodiment, the following operational effects can be achieved. In the liquid fuel synthesis system 1B of the present embodiment, a tail gas storage tank 52 provided in the tail gas supply line L6 for storing tail gas and a tail gas flow rate adjustment valve 53 provided on the downstream side of the tail gas storage tank 52 in the tail gas supply line L6 are provided. Thereby, when it is not necessary to supply tail gas to the boiler 10, the tail gas can be stored in the tail gas storage tank 52 by closing the tail gas flow rate adjustment valve 53. Also, when it becomes necessary to supply tail gas to the boiler 10, the tail gas can be supplied to the boiler 10 by opening the tail gas flow rate adjustment valve 53. Thereby, since tail gas can be supplied to the boiler 10 at the required timing, the output of the boiler 10 can be stabilized. 【0045】Also, in the liquid fuel synthesis system 1B of the present embodiment, the control device 100 controls the opening degree of the tail gas flow rate adjustment valve 53 according to predetermined parameters regarding the carbon-containing fuel, the boiler 10, or the tail gas. By controlling the amount of tail gas supplied to the boiler 10 based on these parameters, the output of the boiler can be accurately managed. 【0046】 The liquid fuel synthesis system 1B of the present embodiment includes a measuring device 54 that measures tail gas property parameters based on the properties of the tail gas stored in the tail gas storage tank 52. Thereby, the properties of the tail gas supplied to the boiler 10 can be grasped. 【0047】 The liquid fuel synthesis system 1B of the present embodiment includes a measuring device 54A configured to measure tail gas property parameters based on the wavelength-variable semiconductor laser absorption method. By setting the infrared wavelength, it becomes possible to selectively measure the concentration of tail gas components. Thereby, the tail gas component composition can be measured and the calorific value of the same gas can be calculated. 【0048】 In the liquid fuel synthesis system 1B of the present embodiment, the control device 100 acquires the tail gas property parameters from the measuring device 54 and controls the opening degree of the tail gas flow rate adjustment valve 53 according to the acquired tail gas property parameters. Therefore, since the amount of tail gas supplied to the boiler 10 can be adjusted according to the properties of the tail gas, the output of the boiler 10 can be more accurately and reliably stabilized. 【0049】 [Third Embodiment] Hereinafter, the third embodiment of the present disclosure will be described with reference to FIGS. 6 to 7. In the present embodiment, the parts different from the second embodiment will be described, and the description of other overlapping parts will be omitted. Further, the same components as those in the second embodiment are denoted by the same reference numerals and the overlapping description thereof is omitted. Further, the cooling device 41 and the heating means 51 of the first embodiment are omitted in FIG. 6. 【0050】The liquid fuel synthesis system 1C of this embodiment connects the boiler 10 and the water electrolyzer 30, and includes an oxygen supply line L7 that supplies oxygen (by-product oxygen) discharged from the water electrolyzer 30 to the boiler 10. With this configuration, by-product oxygen is supplied to the boiler 10 as a combustion aid in the boiler 10, separately from the tail gas. 【0051】 An oxygen flow control valve 31 is provided in the oxygen supply line L7. The opening degree of the oxygen flow control valve 31 is controlled by a control device 100. The control device 100 controls the opening degree of the oxygen flow control valve 31 according to predetermined parameters relating to the carbon-containing fuel or the boiler 10. 【0052】 It is also possible to configure the system to include an oxygen storage tank for storing by-product oxygen in the oxygen supply line L7. In this case, the oxygen storage tank is installed upstream of the oxygen flow control valve 31. This allows the amount of oxygen supplied to the boiler 10 to be controlled by controlling the opening degree of the oxygen flow control valve 31 based on predetermined parameters. 【0053】 Alternatively, hydrogen can be supplied to the boiler 10 as fuel instead of by-product oxygen during electrolysis. Since hydrogen is generated immediately upon power input to the water electrolysis device 30, it has the advantage of being easy to control and having good responsiveness. In addition, there are cases where an excess of steam is required during system startup. Specifically, a large amount of heating steam may be required to start up the carbon dioxide recovery device 20 and the reverse shift reactor 40. On the other hand, not much steam is generated when the boiler 10 is started up. Therefore, by supplying power to the water electrolysis device 30 to generate hydrogen and supplying the generated hydrogen to the boiler 10, the steam necessary for system startup can be obtained quickly. This allows for faster system startup. 【0054】 In a configuration where hydrogen is supplied to the boiler 10 as fuel instead of by-product oxygen during electrolysis, a hydrogen supply line is provided instead of the oxygen supply line L7. That is, a hydrogen supply line is provided to connect the boiler 10 and the water electrolysis device 30, and to supply the hydrogen discharged from the water electrolysis device 30 to the boiler 10. Alternatively, both the oxygen supply line L7 and the hydrogen supply line can be provided. 【0055】 Next, a control method for the liquid fuel synthesis system 1C according to this embodiment will be described. Figure 7 is a flowchart showing the control method for the liquid fuel synthesis system 1C according to this embodiment. 【0056】 In step S201, data is acquired from various sensors. The data consists of predetermined parameters related to the carbon-containing fuel, the boiler 10, or the tail gas. This flowchart explains the case where the heat input to the boiler 10 is used as a predetermined parameter. 【0057】 In step S202, it is checked whether the acquired heat input to boiler 10 exceeds a threshold. If the heat input to boiler 10 exceeds the threshold (YES in step S202), the process proceeds to step S203 and the operation of boiler 10 continues. On the other hand, if the heat input to boiler 10 does not exceed the threshold (NO in step S202), the process proceeds to step S204. 【0058】 In step S204, tail gas is supplied to the boiler 10. Based on the acquired amount of heat input to the boiler 10, the tail gas flow control valve 53 is opened to a predetermined degree, and tail gas is supplied from the tail gas storage tank 52 to the boiler 10. 【0059】 In step S205, by-product oxygen is supplied to the boiler 10. Based on the acquired amount of heat input to the boiler 10, the oxygen flow control valve 31 is opened to a predetermined degree, and by-product oxygen is supplied from the water electrolysis device 30 to the boiler 10. 【0060】As described above, this embodiment provides the following effects. In this embodiment, the boiler 10 and the water electrolysis device 30 are connected, and an oxygen supply line L7 is provided to supply oxygen discharged from the water electrolysis device 30 to the boiler 10, and an oxygen flow rate control valve 31 is provided in the oxygen supply line L7. Therefore, oxygen produced as a byproduct during electrolysis of the water electrolysis device 30 can be supplied to the boiler 10 as a combustion aid. This makes it possible to effectively utilize the oxygen produced as a byproduct during the electrolysis of water. In addition, if the properties of the tail gas are undesirable for input to the boiler 10, the properties of the tail gas can be adjusted. Furthermore, since tail gas is not a gas that is intentionally generated, it is difficult to adjust the amount, and in some situations, there may be a shortage of tail gas when needed. Therefore, when there is a shortage of tail gas, oxygen can be supplied to the boiler 10 as a combustion aid instead of tail gas. 【0061】 [Fourth Embodiment] Hereinafter, a fourth embodiment of the present disclosure will be described with reference to Figure 8. In this embodiment, the parts that differ from the third embodiment will be described, and other overlapping parts will be omitted from the description. Also, the same reference numerals will be used for components that are the same as in the third embodiment, and their redundant descriptions will be omitted. In addition, the cooling device 41 and heating means 51 of the first embodiment are omitted in Figure 8. 【0062】 The liquid fuel synthesis system 1D of this embodiment includes a battery 70 that stores electricity from a generator (not shown) connected to a boiler 10. The boiler 10 and the battery 70 are connected by a power supply line L8, and the electricity generated by the boiler 10 can be supplied to the battery 70 via the power supply line L8. That is, if the electricity generated by the boiler 10 becomes excessive, the boiler 10 supplies power to the battery 70. 【0063】 A power supply line L9 is connected to the battery 70 so that power can be supplied from the battery 70 to the reactors in the liquid fuel synthesis system 1D (water electrolyzer 30 and liquid fuel synthesizer 50 in Figure 8). When the output of the boiler 10 is insufficient, the power supply to the reactors is appropriately supplemented by the power from the battery 70. 【0064】 Furthermore, an external power supply line L10 is connected to the battery 70 so that it can receive power from an externally installed renewable energy grid. The battery 70 is primarily supplied with power from the renewable energy grid via the external power supply line L10. 【0065】 As described above, this embodiment provides the following effects. The liquid fuel synthesis system 1D of this embodiment includes a steam turbine, a generator, and a battery 70 for storing electricity from the generator. This allows electricity to be stored in the battery 70 when the amount of electricity generated by the boiler 10 is excessive. Furthermore, when the amount of electricity stored in the battery 70 is sufficient and the output of the boiler 10 is insufficient, the system can be operated to prioritize the use of electricity from the battery 70. In addition, when the amount of electricity stored in the battery 70 falls below a threshold, the system can be operated to supply tail gas to the boiler 10. In this way, the amount of electricity generated by the boiler 10 can be made more stable. 【0066】 In the embodiments described above, an example was given in which an FT synthesizer was used as the liquid fuel synthesizer 50, but the invention is not limited to this. It is also possible to apply MtJ (Methanol to Jet) or AtJ (Alcohol to Jet) liquid fuel synthesizers. 【0067】 Furthermore, although the embodiments described above used a biomass boiler as the boiler 10, the invention is not limited to this. Examples of boilers 10 that generate steam by burning carbon-containing fuel include biomass boilers, recovery boilers used in paper mills, waste boilers, and the like. Also, the carbon-containing fuel is not limited to biomass; known fuels containing carbon components can be used. 【0068】<Note> The liquid fuel synthesis system and control method described in the embodiments described above can be understood, for example, as follows. The liquid fuel synthesis system (1A) according to the first aspect of the present disclosure comprises a boiler (10) that burns a carbon-containing fuel to generate steam, a liquid fuel synthesizer (50) that synthesizes liquid fuel from raw materials containing carbon components, and a tail gas supply line (L6) that connects the boiler and the liquid fuel synthesizer and supplies tail gas containing hydrocarbons discharged from the liquid fuel synthesizer to the boiler. 【0069】 The liquid fuel synthesis system of this disclosure includes a tail gas supply line that supplies the hydrocarbon-containing tail gas discharged from the liquid fuel synthesizer to a boiler. This allows the hydrocarbon-containing tail gas to be supplied to the boiler, enabling its use as boiler fuel. Therefore, the amount of fuel required in the boiler can be reduced. Furthermore, compared to a configuration that recirculates the tail gas upstream of the liquid fuel synthesizer, this system eliminates the need for additional reactors, resulting in lower costs and space advantages. Additionally, since there is no need to heat the tail gas, it is also energy-efficient. 【0070】 Examples of boilers that generate steam by burning carbon-containing fuels include biomass boilers, recovery boilers used in paper mills, and waste boilers. 【0071】 In the liquid fuel synthesis system according to a second aspect of this disclosure, in the first aspect, the carbon-containing fuel is biomass and the boiler is a biomass boiler. 【0072】 Because biomass is a solid, its fluidity is unstable, which can lead to fluctuations in the amount supplied to the boiler. Consequently, the amount of biomass supplied to the boiler may temporarily decrease, causing the boiler's output to become unstable. The liquid fuel synthesis system of this disclosure can be suitably used in biomass boilers that are prone to such output instability. 【0073】A liquid fuel synthesis system according to a third aspect of the present disclosure, in the first or second aspect, comprises a tail gas storage tank provided in the tail gas supply line for storing the tail gas, a tail gas flow rate control valve (53) provided downstream of the tail gas storage tank in the tail gas supply line, and a control device (100), wherein the control device controls the opening degree of the tail gas flow rate control valve according to predetermined parameters relating to the carbon-containing fuel, the boiler, or the tail gas. 【0074】 The liquid fuel synthesis system of this disclosure includes a tail gas storage tank provided in the tail gas supply line for storing tail gas, and a tail gas flow control valve provided downstream of the tail gas storage tank in the tail gas supply line. This allows the tail gas to be stored in the tail gas storage tank by closing the tail gas flow control valve when it is not necessary to supply tail gas to the boiler. When it becomes necessary to supply tail gas to the boiler, the tail gas can be supplied to the boiler by opening the tail gas flow control valve. This allows the boiler to be supplied with tail gas at the required time, thereby stabilizing the boiler's output. 【0075】 Furthermore, in the liquid fuel synthesis system of this disclosure, the control device controls the opening degree of the tail gas flow control valve according to predetermined parameters relating to the carbon-containing fuel, boiler, or tail gas. By controlling the amount of tail gas supplied to the boiler based on these parameters, the boiler output can be managed with high precision. 【0076】 The specified parameters may include the properties of the boiler fuel (carbon-containing fuel), the amount of heat input to the boiler, the internal boiler temperature, fluctuations in boiler power generation, the calorific value of the tail gas, and the composition of the tail gas. 【0077】A liquid fuel synthesis system (1B) according to a fourth aspect of the present disclosure, in a third aspect, includes a measuring device (54) for measuring tail gas property parameters based on the properties of the tail gas stored in the tail gas storage tank, wherein the predetermined parameters are the tail gas property parameters, and the control device acquires the tail gas property parameters from the measuring device and controls the opening degree of the tail gas flow rate control valve according to the acquired tail gas property parameters. 【0078】 The liquid fuel synthesis system of this disclosure includes a measuring device that measures tail gas property parameters based on the properties of tail gas stored in a tail gas storage tank. This makes it possible to understand the properties of the tail gas supplied to the boiler. 【0079】 In the liquid fuel synthesis system of this disclosure, the control device acquires tail gas property parameters from a measuring device and controls the opening degree of the tail gas flow control valve according to the acquired tail gas property parameters. Therefore, the amount of tail gas supplied to the boiler can be adjusted according to the properties of the tail gas, thereby enabling more accurate and reliable stabilization of the boiler output. 【0080】 Furthermore, the tail gas property parameters can include the tail gas composition and the calorific value calculated from that gas composition. 【0081】 In the liquid fuel synthesis system according to the fifth aspect of this disclosure, in the fourth aspect, the measuring device is configured to measure the tail gas property parameters based on a tunable semiconductor laser absorption method. 【0082】 With the liquid fuel synthesis system of this disclosure, by setting an infrared wavelength, it becomes possible to selectively measure the concentration of tail gas components. This allows for the measurement of the tail gas component composition and the calculation of the calorific value of the gas. 【0083】A liquid fuel synthesis system (1C) according to a sixth aspect of the present disclosure, in any of the first to fifth aspects, comprises: a carbon dioxide recovery device (20) for recovering carbon dioxide from exhaust gas discharged from the boiler; a water electrolyzer (30) for generating hydrogen from water using electricity; a reverse shift reactor (40) for generating carbon monoxide using the hydrogen generated by the water electrolyzer and the carbon dioxide recovered by the carbon dioxide recovery device as raw materials; an oxygen supply line (L7) connecting the boiler and the water electrolyzer and supplying oxygen discharged from the water electrolyzer to the boiler; an oxygen flow rate control valve (31) provided in the oxygen supply line; and a control device. The liquid fuel synthesizer is an FT synthesizer that generates the liquid fuel from the synthesis gas containing the carbon monoxide generated in the reverse shift reactor, and the control device controls the opening degree of the oxygen flow rate control valve according to predetermined parameters relating to the carbon-containing fuel or the boiler. 【0084】 This disclosure provides a boiler and a water electrolysis device connected by an oxygen supply line that supplies oxygen discharged from the water electrolysis device to the boiler, and an oxygen flow rate control valve provided in the oxygen supply line. Therefore, oxygen produced as a by-product during electrolysis of the water electrolysis device can be supplied to the boiler as a combustion aid. This makes it possible to effectively utilize the oxygen produced as a by-product during the electrolysis of water. In addition, if the properties of the tail gas are undesirable for input into the boiler, the properties of the tail gas can be adjusted. Furthermore, since tail gas is not a gas that is intentionally generated, it is difficult to adjust the amount, and in some situations, there may be a shortage of tail gas when needed. Therefore, when tail gas is insufficient, oxygen can be supplied to the boiler as a combustion aid instead of tail gas. 【0085】Furthermore, it is also possible to supply hydrogen to the boiler as fuel instead of the by-product oxygen during electrolysis. Hydrogen has the advantage of being easy to control and responsive because it is generated immediately when power is supplied to the water electrolysis device. In addition, there are cases where an excess of steam is required when starting up the system. Specifically, a large amount of heating steam may be required to start up the carbon dioxide capture device or the reverse shift reactor. On the other hand, not much steam is generated when starting up the boiler. Therefore, by supplying power to the water electrolysis device to generate hydrogen and supplying the generated hydrogen to the boiler, the steam necessary for starting up the system can be obtained quickly. This allows for faster system startup. 【0086】 A liquid fuel synthesis system according to a seventh aspect of the present disclosure, in a sixth aspect, includes a cooling device (41) provided between the reverse shift reactor and the FT synthesizer for cooling the synthesis gas containing carbon monoxide produced in the reverse shift reactor, and a heat exchanger (51) provided in the tail gas supply line for transferring waste heat from the cooling device to the tail gas flowing through the tail gas supply line. 【0087】 The tail gas has a temperature of 40-50°C, which is slightly too low for supply to the boiler. The liquid fuel synthesis system of this disclosure is equipped with a heat exchanger installed in the tail gas supply line, which transfers waste heat from the cooling device to the tail gas flowing through the tail gas supply line. Therefore, the heat exchanger can preheat the tail gas to a temperature suitable for supply to the boiler. Furthermore, since the heat used for preheating is waste heat generated from the cooling device that cools the synthesis gas containing carbon monoxide produced in the reverse shift reactor, the heat can be utilized effectively. 【0088】 A liquid fuel synthesis system (1D) according to the eighth aspect of the present disclosure, in any of the first to seventh aspects, comprises a steam turbine driven by steam from the boiler, a generator driven by the steam turbine, and a battery (70) for storing electricity from the generator. 【0089】The liquid fuel synthesis system of this disclosure comprises a steam turbine, a generator, and a battery for storing electricity from the generator. This allows electricity to be stored in the battery when the boiler's power generation is excessive. Furthermore, when the battery's charge is sufficient and the boiler's output is insufficient, the system can be operated to prioritize the use of battery power. In addition, when the battery's charge falls below a threshold, the system can be operated to supply tail gas to the boiler. In this way, the boiler's power generation can be made more stable. 【0090】 A control method for a liquid fuel synthesis system according to a ninth aspect of the present disclosure is a control method for a liquid fuel synthesis system comprising a boiler that burns a carbon-containing fuel to generate steam, and a liquid fuel synthesizer that synthesizes a liquid fuel from raw materials containing carbon components, the method comprising a tail gas supply step of supplying tail gas containing hydrocarbons discharged from the liquid fuel synthesizer to the boiler. 【0091】 The control method for a liquid fuel synthesis system of this disclosure includes a tail gas supply step for supplying tail gas containing hydrocarbons discharged from the liquid fuel synthesizer to a boiler. As a result, the tail gas containing hydrocarbons can be supplied to the boiler and used as fuel for the boiler. Therefore, the amount of fuel required in the boiler can be reduced. Furthermore, compared to a configuration in which the tail gas is recirculated to the upstream side of the liquid fuel synthesizer, this method does not require the addition of reactors, thus reducing costs and offering advantages in terms of space. In addition, since it is not necessary to heat the tail gas to a high temperature, it is also advantageous in terms of energy efficiency. 【0092】1A, 1B, 1C, 1D Liquid Fuel Synthesis System 10 Boiler 20 Carbon Dioxide Recovery Unit 30 Water Electrolyzer 31 Oxygen Flow Control Valve 40 Reverse Shift Reactor 41 Cooling Unit 50 Liquid Fuel Synthesizer (FT Synthesizer) 51 Heating Means (Heat Exchanger) 52 Tail Gas Storage Tank 53 Tail Gas Flow Control Valve 54, 54A, 54B Measuring Device 55 Container 56 Window 57 Infrared Light Source 58 Infrared Photodetector 59 Data Processing Unit 60 Window 70 Battery 100 Control Device L1 Exhaust Gas Supply Line L2 Power Supply Line L3 Carbon Dioxide Supply Line L4 Hydrogen Supply Line L5 Carbon Monoxide Supply Line L6 Tail Gas Supply Line L7 Oxygen Supply Line L8 Power Supply Line L9 Power Supply Line L10 External Power Supply Line
Claims
1. A liquid fuel synthesis system comprising: a boiler that burns a carbon-containing fuel to generate steam; a liquid fuel synthesizer that synthesizes liquid fuel from raw materials containing carbon components; and a tail gas supply line that connects the boiler and the liquid fuel synthesizer and supplies tail gas containing hydrocarbons discharged from the liquid fuel synthesizer to the boiler.
2. The liquid fuel synthesis system according to claim 1, wherein the carbon-containing fuel is biomass and the boiler is a biomass boiler.
3. A liquid fuel synthesis system according to claim 1, comprising: a tail gas storage tank provided in the tail gas supply line for storing the tail gas; a tail gas flow rate control valve provided downstream of the tail gas storage tank in the tail gas supply line; and a control device, wherein the control device controls the opening degree of the tail gas flow rate control valve according to predetermined parameters relating to the carbon-containing fuel, the boiler, or the tail gas.
4. A liquid fuel synthesis system according to claim 3, comprising a measuring device for measuring tail gas property parameters based on the properties of the tail gas stored in the tail gas storage tank, wherein the predetermined parameter is the tail gas property parameter, and the control device acquires the tail gas property parameter from the measuring device and controls the opening degree of the tail gas flow control valve according to the acquired tail gas property parameter.
5. The liquid fuel synthesis system according to claim 4, wherein the measuring device is configured to measure the tail gas property parameters based on a tunable semiconductor laser absorption method.
6. A liquid fuel synthesis system according to claim 1, comprising: a carbon dioxide recovery device for recovering carbon dioxide from exhaust gas discharged from the boiler; a water electrolysis device for generating hydrogen from water using electricity; a reverse shift reactor for generating carbon monoxide using hydrogen generated by the water electrolysis device and carbon dioxide recovered by the carbon dioxide recovery device as raw materials; an oxygen supply line connecting the boiler and the water electrolysis device and supplying oxygen discharged from the water electrolysis device to the boiler; an oxygen flow rate control valve provided in the oxygen supply line; and a control device, wherein the liquid fuel synthesizer is an FT synthesizer that generates the liquid fuel from the synthesis gas containing the carbon monoxide generated in the reverse shift reactor, and the control device controls the opening degree of the oxygen flow rate control valve according to predetermined parameters relating to the carbon-containing fuel or the boiler.
7. A liquid fuel synthesis system according to claim 6, comprising: a cooling device provided between the reverse shift reactor and the FT synthesizer for cooling the synthesis gas containing carbon monoxide produced in the reverse shift reactor; and a heat exchanger provided in the tail gas supply line for transferring waste heat from the cooling device to the tail gas flowing through the tail gas supply line.
8. A liquid fuel synthesis system according to any one of claims 1 to 7, comprising: a steam turbine driven by steam from the boiler; a generator driven by the steam turbine; and a battery for storing electricity from the generator.
9. A method for controlling a liquid fuel synthesis system comprising a boiler that burns a carbon-containing fuel to generate steam, and a liquid fuel synthesizer that synthesizes liquid fuel from raw materials containing carbon components, the method comprising a tail gas supply step of supplying tail gas containing hydrocarbons discharged from the liquid fuel synthesizer to the boiler.