Fuel preparation system

Abstract

The present invention provides a fuel preparation system, comprising a synthesis gas generation device (4) for generating synthesis gas including hydrogen and carbon monoxide using carbon-containing raw materials; a fuel preparation device (5) for preparing fuel using the synthesis gas generated by the synthesis gas generation device; a water electrolysis device (2) for generating hydrogen by electrolyzing water; a hydrogen supply unit (3) for supplying the hydrogen generated by the water electrolysis device to the synthesis gas generation device (4); a calculation unit (13) for calculating input energy based on a first energy of the carbon-containing raw materials, a second energy consumed when the water electrolysis device generates hydrogen, a third energy consumed when the synthesis gas generation device generates synthesis gas, and a fourth energy consumed when the fuel preparation device prepares the fuel, and for calculating recovered energy based on a fifth energy of the fuel prepared by the fuel preparation device; and a control unit (14) for controlling the water electrolysis device based on the input energy and the recovered energy calculated by the calculation unit.

Description

Technical Field

[0001] The present invention relates to a fuel preparation system for preparing fuel by electrolysis of water. Background Art

[0002] As such an apparatus, an apparatus for producing methanol using biomass as a raw material is known in the past (see, for example, Patent Document 1). The apparatus described in Patent Document 1 uses electricity generated by solar power generation and wind power generation to electrolyze water to generate hydrogen, and adds the hydrogen to a gas including carbon monoxide and hydrogen obtained by gasifying biomass to adjust the ratio of carbon monoxide to hydrogen to a ratio suitable for methanol synthesis.

[0003] However, when fuel is produced using renewable electricity such as solar power generation, wind power generation, etc. as in Patent Document 1, although carbon emissions can be reduced, energy loss and fuel production costs may increase.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2002-193858 (JP 2002-193858 A). Summary of the invention

[0007] A fuel preparation system according to a technical solution of the present invention comprises: a synthesis gas generating device which generates synthesis gas including hydrogen and carbon monoxide using a carbon-containing raw material; a fuel preparation device which prepares fuel using the synthesis gas generated by the synthesis gas generating device; a water electrolysis device which generates hydrogen by electrolyzing water; a hydrogen supply unit which supplies the hydrogen generated by the water electrolysis device to the synthesis gas generating device; a calculation unit which calculates an input energy based on a first energy possessed by the carbon-containing raw material, a second energy consumed when the water electrolysis device generates hydrogen, a third energy consumed when the synthesis gas generating device generates synthesis gas, and a fourth energy consumed when the fuel preparation device prepares the fuel, and calculates a recovered energy based on a fifth energy possessed by the fuel prepared by the fuel preparation device; and a control unit which controls the water electrolysis device based on the input energy and the recovered energy calculated by the calculation unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The objects, features and advantages of the present invention will be further clarified through the following description of the embodiments in conjunction with the accompanying drawings.

[0009] Figure 1 This is a block diagram schematically showing an example of the overall configuration of a fuel preparation system according to an embodiment of the present invention.

[0010] Figure 2This is a block diagram schematically showing an example of the main part configuration of the fuel preparation system according to the embodiment of the present invention.

[0011] Figure 3 It is used to illustrate Figure 1 Diagram of the energy budget of the fuel preparation system.

[0012] Figure 4 It is used to illustrate Figure 1 A diagram showing the relationship between the electrolysis efficiency of a water electrolysis device and the energy conversion efficiency of a fuel preparation system.

[0013] Figure 5 It is used to illustrate Figure 1 A diagram showing the relationship between the amount of hydrogen supplied by a hydrogen supply unit and an evaluation value of the energy balance of a fuel preparation system.

[0014] Fig. 6A It is shown from Figure 1 A diagram showing an example of the recovery amount of each gas component recovered by the gasification device.

[0015] Figure 6B It is shown from Figure 1 A diagram showing another example of the amount of each gas component recovered by the gasification device.

[0016] Figure 7 It is shown by Figure 2 A flowchart of an example of a process performed by a controller. DETAILED DESCRIPTION

[0017] The following reference Figure 1 to Figure 7 The embodiment of the present invention is described. The fuel preparation system of the embodiment of the present invention uses renewable electricity such as solar power generation and wind power generation to electrolyze water to generate hydrogen (water electrolysis hydrogen), and uses the water electrolysis hydrogen to prepare so-called electrosynthetic fuel (e-fuel) using carbon-containing raw materials such as biomass. The following specifically describes an example of gasifying biomass to generate synthesis gas including hydrogen and carbon monoxide, and using the generated synthesis gas to prepare methanol fuel.

[0018] Figure 1 1 is a block diagram schematically showing an example of the overall structure of the fuel preparation system 100 according to the embodiment of the present invention. Figure 1 As shown, the fuel preparation system 100 includes a power generation device 1 , a water electrolysis device 2 , a hydrogen supply unit 3 , a gasification device 4 , and a fuel preparation device 5 .

[0019] The power generation device 1 is configured as, for example, a solar power generation device that converts solar energy into electrical energy using semiconductor elements, or a wind power generation device that converts wind energy into electrical energy using a windmill, to generate renewable electricity. The renewable electricity generated by the power generation device 1 is supplied to the water electrolysis device 2, the hydrogen supply unit 3, the gasification device 4, and the fuel preparation device 5.

[0020] The water electrolysis device 2 generates water electrolysis hydrogen by electrolyzing water using the renewable electricity generated by the power generation device 1. The water electrolysis device 2 is provided with sensors for measuring the electrolysis voltage of the water electrolysis device 2, the amount of electricity consumed by the water electrolysis device 2, the amount of water electrolysis hydrogen generated (e.g., mass flow rate) m, etc.

[0021] The hydrogen supply unit 3 includes a hydrogen storage tank 3a for storing the water electrolysis hydrogen generated by the water electrolysis device 2, and a flow control valve 3b disposed on the piping between the hydrogen storage tank 3a and the gasification device 4. The hydrogen supply unit 3 supplies the water electrolysis hydrogen from the hydrogen storage tank 3a to the gasification device 4 using the pressure of the water electrolysis hydrogen stored in the hydrogen storage tank 3a, that is, the internal pressure of the hydrogen storage tank 3a. The flow control valve 3b adjusts the supply amount (e.g., mass flow rate) m of the water electrolysis hydrogen supplied from the hydrogen storage tank 3a to the gasification device 4.

[0022] A sensor is provided in the hydrogen supply unit 3, and the sensor measures the internal pressure of the hydrogen storage tank 3a, the supply amount m of the water electrolysis hydrogen supplied from the hydrogen storage tank 3a to the gasification device 4, etc. When the internal pressure of the hydrogen storage tank 3a is lower than the lower limit value corresponding to the lower limit of the storage amount, the water electrolysis hydrogen cannot be supplied from the hydrogen storage tank 3a to the gasification device 4. In addition, when the internal pressure of the hydrogen storage tank 3a exceeds the upper limit value corresponding to the upper limit of the storage amount, the water electrolysis hydrogen cannot be stored in the hydrogen storage tank 3a. A buffer tank is also provided in the hydrogen supply unit 3, and the buffer tank temporarily stores excess water electrolysis hydrogen during the period from when the storage amount of the hydrogen storage tank 3a exceeds the upper limit until the water electrolysis device 2 stops generating water electrolysis hydrogen.

[0023] The hydrogen storage tank 3a is configured as a gas storage tank capable of storing hydrogen in a gaseous form. The higher the upper limit pressure of the storage amount, the higher the volumetric efficiency of water electrolysis hydrogen can be stored. The hydrogen storage tank 3a can also be configured as a liquid storage tank capable of storing hydrogen in a liquid form. In this case, a cooling device for converting hydrogen from a gaseous state to a liquid state is required as the hydrogen supply unit 3. When hydrogen is stored in a liquid form, energy is required for cooling and maintaining the cooling state, but water electrolysis hydrogen can be stored at a volumetric efficiency approximately 800 times that of when stored in a gaseous form. The hydrogen storage tank 3a can be composed of a hydrogen storage alloy that absorbs hydrogen. In this case, a heating device for extracting hydrogen is required as the hydrogen supply unit 3. When hydrogen is absorbed and stored, water electrolysis hydrogen can be stored at a volumetric efficiency approximately 1000 times that of when stored in a gaseous form.

[0024] The gasification device 4 mainly includes a gasification furnace, and the gasification furnace is heated by using the renewable electricity generated by the power generation device 1 to perform gasification and generate synthesis gas. Biomass such as rice husk, bagasse, wood, etc. that has been pre-treated by drying and pulverization, oxygen and water (steam) are supplied to the gasification furnace of the gasification device 4, and synthesis gas containing hydrogen and carbon monoxide is generated according to the reaction of the following formulas (i) to (v). Here, the reaction of the following formulas (ii) to (v) is an equilibrium reaction.

[0025] C+O2→CO2……(i)

[0026] C+H2O→CO+H2……(ii)

[0027] C+2H2→CH4……(iii)

[0028] C+CO2→2CO……(iv)

[0029] CO+H2O→CO2+H2……(v)

[0030] The water electrolysis hydrogen generated by the water electrolysis device 2 is also supplied to the gasifier of the gasifier 4 through the hydrogen supply unit 3. The gasifier 4 is provided with a sensor that measures the amount of electricity consumed by the gasifier 4, the temperature and pressure of the synthesis gas in the gasifier, the amount of synthesis gas generated (e.g., mass flow rate), and the partial pressure (concentration) of each gas component, etc. Based on the measured values ​​of these sensors, the supply amounts of biomass, oxygen, water, and water electrolysis hydrogen supplied to the gasifier can be adjusted.

[0031] By utilizing water electrolysis of hydrogen, the equilibrium reaction (conversion reaction) in formula (v) is converted to the direction of promoting the generation of carbon monoxide and inhibiting the generation of carbon dioxide. In addition, by adjusting the supply amount m of water electrolysis hydrogen generated by the water electrolysis device 2 and supplied by the hydrogen supply unit 3, the synthesis gas can be adjusted to a composition suitable for subsequent fuel preparation. For example, when the fuel preparation device 5 prepares methanol fuel later, it can be adjusted in combination with the methanol synthesis reaction of the following formula (vi) so that the ratio (partial pressure ratio) of hydrogen to carbon monoxide in the synthesis gas becomes "2".

[0032] CO + 2H2 → CH3OH……(vi)

[0033] The fuel preparation device 5 mainly includes a reactor and a distillation tower. The synthesis gas generated by the gasification device 4 and subjected to post-treatment such as washing to remove ash and desulfurization is supplied to the reactor of the fuel preparation device 5, and methanol fuel is generated through the exothermic reaction of formula (vi). More specifically, the generated gas is heated in the distillation tower by using the renewable electricity generated by the power generation device 1 to distill and obtain methanol fuel. Sensors for measuring temperature, pressure, the amount of methanol fuel generated (e.g., mass flow rate) and concentration are provided in the reactor and distillation tower of the fuel preparation device 5.

[0034] The fuel preparation system 100 is provided with a compressor between the gasification device 4 and the fuel preparation device 5, and the synthesis gas is transported from the gasification device 4 to the fuel preparation device 5 using the renewable electricity generated by the power generation device 1. The fuel preparation system 100 is also provided with a sensor for measuring the amount of electricity consumed by the compressor.

[0035] In this way, the fuel preparation system 100 can suppress the emission of carbon dioxide as a whole by using renewable energy. However, when the energy loss increases during the conversion of renewable energy, the energy loss and fuel preparation cost of the entire system may increase. Therefore, in this embodiment, the fuel preparation system is configured as follows so that by paying attention to the energy balance of the entire system, the emission of carbon dioxide during fuel preparation can be suppressed while suppressing the energy loss and fuel preparation cost.

[0036] Figure 2 1 is a block diagram schematically showing an example of the main structure of the fuel preparation system 100 according to the embodiment of the present invention. Figure 2 As shown, the fuel preparation system 100 has a controller 10, and the sensor group 6 including the above-mentioned sensors, the water electrolysis device 2, and the hydrogen supply unit 3 are connected to the controller 10. The controller 10 performs a predetermined process based on the signal from the sensor group 6, thereby controlling the operation of the water electrolysis device 2 and the hydrogen supply unit 3.

[0037] The controller 10 is composed of a computer having a CPU (central processing unit) or the like, a storage unit 12 such as a ROM (read only memory) and a RAM (random access memory), and other peripheral circuits not shown, such as an I / O (input / output) interface. The storage unit 12 stores various control programs, information such as threshold values ​​used in the programs, etc. The operation unit 11 has a calculation unit 13 and a control unit 14 as functional structures. That is, the CPU or the like of the controller 10 The operation unit 11 functions as the calculation unit 13 and the control unit 14.

[0038] Figure 3 This is a diagram for explaining the energy balance of the fuel preparation system 100, showing an example of the energy input per unit of raw material and the energy recovered when preparing methanol fuel using biomass as raw material. The energy input includes the energy (calorific value) E1 of a unit amount of biomass and the energies E2 to E5 required for gasification of the raw material (heating of the gasifier), distillation of the fuel, transportation of the synthesis gas, and electrolysis of water. The energy recovered includes the energy (calorific value) E6 of the methanol fuel produced using a unit amount of biomass.

[0039] exist Figure 3In the figure, the dotted line represents the energy E(0) when water is not used for hydrogen electrolysis, and the solid line represents the energy E(m) when water is used for hydrogen electrolysis. Figure 3 As shown, when using water electrolysis hydrogen, the energy E5(m) required for electrolysis is input according to the supply amount m of water electrolysis hydrogen, and the energy E2(m) to E4(m) required for gasification, distillation and transportation increases. On the other hand, the energy E6(m) recovered as methanol fuel increases.

[0040] The calculation unit 13 calculates the sum of the respective energies E1(0) to E4(0) and E1(m) to E5(m) as the reference input energy Ein(0) and input energy Ein(m) respectively when water electrolysis of hydrogen is not used and when water electrolysis of hydrogen is used according to the following equations (vii) and (viii). In addition, as shown in the following equations (ix) and (x), the respective energies E6(0) and E6(m) are calculated as the reference recovery energy Eout(0) and recovery energy Eout(m) respectively when water electrolysis of hydrogen is not used and when water electrolysis of hydrogen is used.

[0041] Ein(0)=E1(0)+E2(0)+E3(0)+E4(0)……(vii)

[0042] Ein(m)=E1(m)+E2(m)+E3(m)+E4(m)+E5(m)……(viii)

[0043] Eout(0)=E6(0)……(ix)

[0044] Eout(m)=E6(m)……(x)

[0045] The energy E2 required for gasification of the raw material can be calculated based on the standard reaction enthalpy and the amount of synthesis gas generated using a unit amount of biomass, but can also be calculated based on the amount of electricity consumed by the gasification device 4. The energy E3 required for distillation of the fuel can be calculated based on the amount and concentration of methanol fuel generated using a unit amount of biomass, but can also be calculated based on the amount of electricity consumed by the fuel preparation device 5. The energy E4 required for transporting the synthesis gas can be calculated based on the compression work per unit amount and the amount of synthesis gas generated using a unit amount of biomass, but can also be calculated based on the amount of electricity consumed by the compressor.

[0046] The energy E5 required for the electrolysis of water can be calculated according to the following formula (xi) based on the standard reaction enthalpy, the amount of hydrogen generated by water electrolysis using a unit amount of biomass, and the electrolysis efficiency p of the water electrolysis device 2. The electrolysis efficiency p of the water electrolysis device 2 can be calculated according to the following formula (xii) based on the electrolysis voltage (e.g., 1.48V) at an electrolysis efficiency of 100% and the electrolysis voltage of the water electrolysis device 2. The energy E5 required for the electrolysis of water can also be calculated based on the amount of electricity consumed by the water electrolysis device 2. It should be noted that when water is electrolyzed using renewable electricity such as solar power generation and wind power generation, sometimes the water electrolysis device 2 cannot be operated at rated speed due to insufficient electricity due to meteorological conditions. In such a case, the electrolysis efficiency p of the water electrolysis device 2 is reduced.

[0047] E5 = (standard reaction enthalpy) × (amount of hydrogen produced by water electrolysis) / p……(xi)

[0048] p=1.48 / (electrolysis voltage)……(xii)

[0049] The calculation unit 13 calculates the difference ΔEin(m) between the reference input energy Ein(0) and the input energy Ein(m) and the difference ΔEout(m) between the reference recovery energy Eout(0) and the recovery energy Eout(m) according to the following equations (xiii) and (xiv). In addition, the energy conversion efficiency of the fuel preparation system 100 is calculated according to the following equation (xv). In addition, the evaluation value of the energy balance is calculated according to the following equation (xvi).

[0050] ΔEin(m)=Ein(m)-Ein(0)……(xiii)

[0051] ΔEout(m)=Eout(m)-Eout(0)……(xiv)

[0052] (Energy conversion efficiency) = Eout / Ein

[0053] =E6 / (E1+E2+E3+E4+E5)……(xv)

[0054] (Evaluation value of energy balance) = ΔEout(m) / ΔEin(m)……(xvi)

[0055] Figure 4 2 is a diagram for explaining the relationship between the electrolysis efficiency p of the water electrolysis device 2 and the energy conversion efficiency of the fuel preparation system 100. Figure 4 In the figure, the dotted line represents the energy conversion efficiency Eout(0) / Ein(0) when water electrolysis is not used for hydrogen, and the solid line represents the energy conversion efficiency Eout(m) / Ein(m) when water electrolysis is used for hydrogen. Figure 4As shown, the higher the electrolysis efficiency p of the water electrolysis device 2, the higher the energy conversion efficiency Eout(m) / Ein(m) of the fuel preparation system 100 when using water electrolysis for hydrogen. Therefore, under operating conditions above the specified electrolysis efficiency p0, the energy conversion efficiency is improved compared to when not using water electrolysis due to the use of water electrolysis for hydrogen, but under operating conditions below the specified electrolysis efficiency p0, the energy conversion efficiency is reduced compared to when not using water electrolysis for hydrogen due to the use of water electrolysis. The threshold value of the electrolysis efficiency p (specified electrolysis efficiency p0) at which the energy conversion efficiency Eout(m) / Ein(m) when using water electrolysis for hydrogen is higher than the energy conversion efficiency Eout(0) / Ein(0) when not using water electrolysis for hydrogen changes according to the amount of water electrolysis for hydrogen generated. The storage unit 12 stores information on the specified electrolysis efficiency p0 measured in advance.

[0056] Figure 5 is a diagram for explaining the relationship between the supply amount m of water electrolysis hydrogen gas of the hydrogen supply unit 3 and the evaluation value of the energy balance of the fuel preparation system 100, and shows the relationship between the supply amount m of water electrolysis hydrogen gas of the hydrogen supply unit 3 and the evaluation value of the energy balance of the fuel preparation system 100. Figure 4 An example of the evaluation value when the supply amount m of water electrolysis hydrogen is changed under the operating conditions corresponding to the electrolysis efficiency p1. Figure 5 As shown, there is an optimal amount m1 corresponding to the operating conditions such as the electrolysis efficiency p in the supply amount m of the water electrolysis hydrogen. By adjusting the supply amount m of the water electrolysis hydrogen to the appropriate range m1a~m1b where the evaluation value of the energy balance is greater than 1, the energy conversion efficiency can be improved relative to the case where the water electrolysis hydrogen is not used. On the other hand, when the excess amount m2 of the water electrolysis hydrogen exceeding the appropriate range m1a~m1b (for example, 1.5 times the optimal amount m1) is supplied, the evaluation value of the energy balance is lower than 1, and the energy conversion efficiency is lower than when the water electrolysis hydrogen is not used.

[0057] Fig. 6A and Figure 6B It is a diagram showing an example of the recovery amount (for example, mass flow rate) of each gas component recovered by the gasification device 4, wherein the recovery amount when no water electrolysis of hydrogen is used is represented by a dotted line, and the recovery amount when water electrolysis of hydrogen is used is represented by a solid line. Fig. 6A Show Figure 5 An example of the recovery amount of each gas component when the supply amount m of hydrogen gas from water electrolysis is the optimal amount m1, Figure 6B An example of the recovery amount of each gas component when the supply amount m of water electrolysis hydrogen gas is an excess amount m2 is shown.

[0058] exist Fig. 6A In the example, the supply amount m of water electrolysis hydrogen is adjusted to the optimal amount m1, and the amount of carbon monoxide recovered corresponding to the amount of methanol fuel produced is increased to 1.5 times that when water electrolysis hydrogen is not used. Figure 6BIn the example, the supply amount m of water electrolysis hydrogen is adjusted to an excess amount m2 that is 1.5 times the optimal amount m1, and the recovery amount of carbon monoxide increases to 1.7 times that of when water electrolysis hydrogen is not used. Fig. 6A Examples and Figure 6B When compared with the example of , the supply amount m of water electrolysis hydrogen corresponding to the input energy increases to 1.5 times, while the recovery amount of carbon monoxide corresponding to the recovered energy increases to about 1.1 times. In this way, when the supply amount m of water electrolysis hydrogen is increased beyond the appropriate range, the energy conversion efficiency is reduced compared to when water electrolysis hydrogen is not used.

[0059] The calculation unit 13 also calculates the cost C and the benefit B generated by using water electrolysis to generate hydrogen, and calculates the evaluation value ε(m) of the cost advantage of using water electrolysis to generate hydrogen according to the following formula (xvii).

[0060] ε(m)=C / B……(xvii)

[0061] The cost C generated by using water electrolysis to generate hydrogen can be calculated based on the amount of electricity consumed by, for example, the water electrolysis device 2 for electrolyzing water, the gasification device 4 for gasifying biomass, the fuel preparation device 5 for distilling methanol fuel, and the compressor for transporting synthesis gas. In this case, the cost C generated by using water electrolysis to generate hydrogen can be calculated based on the respective amount of electricity and the unit price of electricity when water electrolysis to generate hydrogen is not used and when water electrolysis to generate hydrogen is used.

[0062] Specifically, the profit B obtained by using water electrolysis to hydrogen can be calculated as the profit brought by the increase in the production of methanol fuel. In this case, the profit B obtained by using water electrolysis to hydrogen can be calculated based on the production of each methanol fuel and the fuel unit price of methanol fuel when water electrolysis to hydrogen is not used and when water electrolysis to hydrogen is used.

[0063] The control unit 14 controls the operation of the water electrolysis device 2 and the flow regulating valve 3b of the hydrogen supply unit 3 based on the electrolysis efficiency p of the water electrolysis device 2 calculated by the calculation unit 13, the evaluation value ε(m) of the cost advantage, and the internal pressure of the hydrogen storage tank 3a detected by the sensor group 6. More specifically, the switching operation of the water electrolysis device 2 is controlled based on the electrolysis efficiency p of the water electrolysis device 2 so that water electrolysis hydrogen is generated only when the energy conversion efficiency is improved compared to when water electrolysis hydrogen is not used. In addition, the switching operation of the water electrolysis device 2 is controlled based on the evaluation value ε(m) of the cost advantage so that water electrolysis hydrogen is generated only when the cost advantage is generated by using water electrolysis hydrogen. In addition, based on the internal pressure of the hydrogen storage tank 3a, the operation of the flow regulating valve 3b is controlled in such a way that the storage amount of water electrolysis hydrogen stored in the hydrogen supply unit 3 is maintained at an appropriate amount between the lower limit and the upper limit.

[0064] Figure 7This is a flowchart showing an example of processing executed by the calculation unit 11 of the controller 10 . Figure 7 The processing starts when the fuel preparation system 100 is powered on, for example, and is repeated at a predetermined cycle. Figure 7 In the process, first, in S1 (S: processing step), it is determined whether the electrolysis efficiency p of the water electrolysis device 2 is within the prescribed electrolysis efficiency p0 ( Figure 4 )above.

[0065] When S1 is affirmative (S1: Yes), it is determined that the energy conversion efficiency is improved by using water electrolysis hydrogen. Enter S2 to determine whether the storage amount of the hydrogen storage tank 3a is above the upper limit. When S2 is affirmative (S2: Yes), enter S3 to adjust the supply amount m of water electrolysis hydrogen from the hydrogen storage tank 3a to the gasification device 4 to be larger than the optimal amount m1 so that the water electrolysis of the water electrolysis device 2 can continue. It is also possible to stop the water electrolysis of the water electrolysis device 2 and sell the renewable electricity generated by the power generation device 1 to the commercial power system. When S2 is negative (S2: No), enter S4 to determine whether the storage amount of the hydrogen storage tank 3a is below the lower limit. When S4 is negative (S4: No), enter S5 to continue the water electrolysis of the water electrolysis device 2 with the supply amount m of water electrolysis hydrogen as the optimal amount m1. When S4 is positive (S4: Yes), the process proceeds to S6 to adjust the supply amount m of water electrolysis hydrogen gas to be smaller than the optimal amount m1 so as to continue the supply of water electrolysis hydrogen gas. The amount of electricity supplied to the water electrolysis device 2 can also be supplemented by purchasing electricity from the commercial power system.

[0066] When S1 is negative (S1: No), it is determined that the energy conversion efficiency is reduced due to the use of water electrolysis hydrogen gas, and the process proceeds to S7 to determine whether the evaluation value ε(m) of the cost advantage brought by the use of water electrolysis hydrogen gas exceeds 1. When S7 is positive (S7), it is determined that although the energy conversion efficiency is reduced, it is in the operating area with cost advantage, and the process proceeds to S2. On the other hand, when S7 is negative (S7: No), it is determined that the energy conversion efficiency is reduced due to the use of water electrolysis hydrogen gas and is in the operating area without cost advantage, and the process proceeds to S8.

[0067] In S8, it is determined whether the storage amount of the hydrogen storage tank 3a is above the upper limit. When S8 is affirmative (S8), the process proceeds to S9, the water electrolysis of the water electrolysis device 2 is stopped, and the remaining water electrolysis hydrogen temporarily stored in the buffer tank of the hydrogen supply unit 3 is supplied to the gasification device 4. In this case, the renewable electricity generated by the power generation device 1 can also be sold to the commercial power system. When S8 is negative (S8: No), the process proceeds to S10, the water electrolysis of the water electrolysis device 2 is stopped, and the supply of water electrolysis hydrogen from the hydrogen storage tank 3a to the gasification device 4 is stopped. In this case, the renewable electricity generated by the power generation device 1 can also be sold to the commercial power system.

[0068] In this way, by switching the switch of the water electrolysis device 2 (S1, S7) according to the monitoring results of the electrolysis efficiency p of the water electrolysis device 2 and the evaluation value ε(m) of the cost advantage, the fuel preparation system 100 can be operated in the area where the energy loss and the fuel preparation cost are suppressed. That is, the water electrolysis device 2 is controlled so that water is used to electrolyze hydrogen only when the energy conversion efficiency is improved and the cost advantage is generated, thereby suppressing the energy loss and the fuel preparation cost (S3, S5, S6, S9, S10).

[0069] The present embodiment can achieve the following effects.

[0070] (1) The fuel preparation system 100 comprises: a gasification device 4 that uses biomass to generate synthesis gas including hydrogen and carbon monoxide; a fuel preparation device 5 that uses the synthesis gas generated by the gasification device 4 to prepare methanol fuel; a water electrolysis device 2 that generates hydrogen by electrolyzing water; a hydrogen supply unit 3 that supplies the hydrogen generated by the water electrolysis device 2 to the gasification device 4; a calculation unit 13 that calculates input energy Ein(m) based on energy E1 of the biomass, energy E5 consumed when the water electrolysis device 2 generates hydrogen, energy E2 consumed when the synthesis gas is generated by the gasification device 4, and energy E3 consumed when the methanol fuel is prepared by the fuel preparation device 5, and calculates recovery energy Eout(m) based on energy E6 of the methanol fuel prepared by the fuel preparation device 5; and a control unit 14 that controls the water electrolysis device 2 based on the input energy Ein(m) and recovery energy Eout(m) calculated by the calculation unit 13. Figure 1 to Figure 3 ).

[0071] That is, the operating conditions are monitored so that the energy conversion efficiency Eout(m) / Ein(m) representing the ratio of the recovered energy Eout(m) to the input energy Ein(m) becomes higher than the energy conversion efficiency Eout(0) / Ein(0) when water electrolysis of hydrogen is not used. For example, the electrolysis efficiency p of the water electrolysis device 2 is monitored to see whether the energy conversion efficiency Eout / Ein is higher than the specified electrolysis efficiency p0 when water electrolysis of hydrogen is not used. In this way, the energy conversion efficiency of the entire fuel preparation system 100 is monitored by input energy Ein(m) and recovered energy Eout(m), thereby suppressing the energy loss and fuel preparation cost during fuel preparation. That is, when the energy loss in the conversion process of renewable energy increases according to meteorological conditions, the energy loss and fuel preparation cost of the entire system increase. Therefore, by controlling the water electrolysis device 2 according to the monitoring result of the energy conversion efficiency, for example, so that water electrolysis hydrogen is generated only when the energy conversion efficiency is improved compared to when water electrolysis of hydrogen is not used, it is possible to suppress the energy loss and fuel preparation cost.

[0072] (2) The calculation unit 13 further calculates the cost C required for obtaining energy E5, energy E2, and energy E3, and calculates the benefit B obtained by using the methanol fuel prepared by the fuel preparation device 5. The control unit 14 further controls the water electrolysis device 2 based on the cost C and benefit B calculated by the calculation unit 13. For example, the water electrolysis device 2 is controlled so that water electrolysis hydrogen is generated only when the evaluation value ε(m) representing the cost advantage of the ratio of benefit B to cost C exceeds 1. In this way, by controlling the water electrolysis device 2 so that water electrolysis hydrogen is generated only when a cost advantage is generated by using water electrolysis hydrogen, the fuel preparation cost of the fuel preparation system 100 can be suppressed.

[0073] (3) The calculation unit 13 calculates the energy E5 consumed when hydrogen is generated by the water electrolysis device 2 based on the amount of hydrogen generated by the water electrolysis device 2 and the electrolysis efficiency p of the water electrolysis device 2. In this case, the electrolysis efficiency p can be calculated based on the actually measured electrolysis voltage, and the energy E5 consumed when hydrogen is generated by the water electrolysis device 2 can be calculated.

[0074] (4) The calculation unit 13 calculates the energy E5 consumed when the water electrolysis device 2 generates hydrogen based on the amount of electricity consumed when the water electrolysis device 2 generates hydrogen. In this case, the energy E5 consumed when the water electrolysis device 2 generates hydrogen can be calculated based on the actually measured amount of electricity.

[0075] (5) The water electrolysis device 2 uses renewable electricity to electrolyze water. When using renewable electricity such as solar power generation and wind power generation, there may be a shortage of electricity due to meteorological conditions, and the water electrolysis device 2 may not be able to operate at rated speed. In such a case, the electrolysis efficiency p of the water electrolysis device 2 is reduced, and sometimes the use of water electrolysis to hydrogen gas reduces the energy conversion efficiency of the entire fuel preparation system 100. By monitoring the energy conversion efficiency of the entire fuel preparation system 100 using the input energy Ein(m) and the recovered energy Eout(m), the energy loss during fuel preparation can be appropriately suppressed.

[0076] In the above embodiment, Figure 1 In the examples of the gasification device 4 generating synthesis gas using biomass, the synthesis gas generating device that generates synthesis gas including hydrogen and carbon monoxide using carbon-containing raw materials is described, but the synthesis gas generating device is not limited to this. For example, carbon dioxide can be separated and recovered from factory exhaust gas, etc. by DAC (Direct Air Capture), and hydrogen can be electrolyzed using the recovered carbon dioxide and water according to the reverse equilibrium reaction (reverse conversion reaction) of formula (v) to generate carbon monoxide and water.

[0077] In the above embodiment, Figure 1 In the examples of preparing methanol fuel by the fuel preparation device 5, the fuel preparation device using synthesis gas is not limited to this. For example, methanol can be further synthesized into gasoline fuel by the MTG (methanol-to-gasoline) method, and light oil fuel can be synthesized by the FT (Fischer-Tropsch) method using synthesis gas.

[0078] In the above embodiment, an example of using renewable electricity in gasification of raw materials (heating of gasifier) ​​and distillation of fuel is described, but it is also possible to use a heat source such as waste heat in these processes. In this case, the third energy consumed when the synthesis gas is generated by the synthesis gas generation device and the fourth energy consumed when the fuel preparation device prepares the fuel can be calculated based on the heat required for gasification and distillation and the heat unit price.

[0079] In the above embodiment, Figure 3 In the examples above, specific examples of energy input to the fuel preparation system 100 and energy recovered are shown and described, but the energy input and energy recovered are not limited to these.

[0080] In the above embodiment, Figure 1In the examples of supplying all the water electrolysis hydrogen generated by the water electrolysis device 2 to the gasification device 4, the structure of the hydrogen supply unit for supplying the hydrogen generated by the water electrolysis device to the synthesis gas generation device is not limited to this. For example, it can also be a structure with a hydrogen storage tank for storing water electrolysis hydrogen, a flow regulating valve for adjusting the flow rate of water electrolysis hydrogen supplied to the gasification device, etc. In addition, when the electrolysis efficiency p of the water electrolysis device 2 is lower than the specified electrolysis efficiency p0 due to meteorological conditions, etc., the operation of the water electrolysis device 2 can also be stopped.

[0081] One or more of the above-described embodiments and modifications may be arbitrarily combined, and modifications may be combined with each other.

[0082] According to the present invention, energy loss and fuel preparation cost during fuel preparation can be suppressed.

[0083] The present invention has been described above in conjunction with the preferred embodiments, but it should be understood by those skilled in the art that various modifications and changes can be made without departing from the scope of the disclosure of the claims set forth below.

Claims

1. A fuel preparation system (100), characterized in that: have: A synthesis gas generating device (4) which generates synthesis gas including hydrogen and carbon monoxide by using carbon-containing raw materials; A fuel preparation device (5) for preparing fuel using the synthesis gas generated by the synthesis gas generation device (4); A water electrolysis device (2) which generates water electrolytic hydrogen by electrolyzing water; a hydrogen supply unit (3) for supplying the water electrolysis hydrogen generated by the water electrolysis device (2) to the synthesis gas generation device (4); a calculation unit (13) for calculating input energy based on a first energy of the carbon-containing raw material, a second energy consumed when the water electrolysis hydrogen is generated by the water electrolysis device (2), a third energy consumed when the synthesis gas is generated by the synthesis gas generation device (4), and a fourth energy consumed when the fuel is prepared by the fuel preparation device (5), and calculating recovered energy based on a fifth energy of the fuel prepared by the fuel preparation device (5); as well as a control unit (14) for controlling the water electrolysis device (2) based on the input energy and the recovered energy calculated by the calculation unit (13); The calculation unit (13) further calculates the cost required for obtaining the second energy, the third energy, and the fourth energy, and calculates the profit obtained by using the fuel prepared by the fuel preparation device (5). When the control unit (14) determines that the electrolysis efficiency of the water electrolysis device (2) is above a specified electrolysis efficiency corresponding to the current water electrolysis hydrogen production, the water electrolysis device (2) is controlled to continue water electrolysis and supply water electrolysis hydrogen to the synthesis gas generation device (4); when the control unit (14) determines that the electrolysis efficiency of the water electrolysis device (2) is less than the specified electrolysis efficiency, it is further determined whether the evaluation value of the cost advantage brought by the use of water electrolysis hydrogen exceeds 1. When the evaluation value of the cost advantage exceeds 1, the water electrolysis device (2) is controlled to continue water electrolysis and supply water electrolysis hydrogen to the synthesis gas generation device (4). The specified electrolysis efficiency is the electrolysis efficiency of the water electrolysis device (2) when the energy conversion efficiency of the fuel preparation system (100) when not using water electrolysis for hydrogen is the same as the energy conversion efficiency of the fuel preparation system (100) when using water electrolysis for hydrogen. The energy conversion efficiency is the ratio of the recovered energy to the input energy. The evaluation value of the cost advantage is the ratio of the cost to the benefit.

2. The fuel preparation system (100) according to claim 1, characterized in that: The calculation unit (13) calculates the second energy based on the amount of hydrogen generated by water electrolysis and the electrolysis efficiency.

3. The fuel preparation system (100) according to claim 1, characterized in that: The calculation unit (13) calculates the second energy based on the amount of electricity consumed when the water electrolytic hydrogen is generated.

4. The fuel preparation system (100) according to any one of claims 1 to 3, characterized in that: The water electrolysis device (2) uses renewable electricity to electrolyze water.

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