METHOD FOR PRODUCING SYNTHESIS GAS AND FUEL PRODUCTION SYSTEM

Abstract

A method for producing a synthesis gas for producing a fuel from a biomass raw material includes supplying hydrogen to the biomass raw material such that a mass ratio represented by [mass of hydrogen gas]/[mass of biomass] is 0.01 to 0.03, in which supplying steam is not provided.

Claims

1. A method for producing a synthesis gas for producing a fuel from a biomass raw material, the method comprising: supplying hydrogen to the biomass raw material such that a mass ratio represented by [mass of hydrogen gas]/[mass of biomass] is 0.01 to 0.03, wherein supplying steam is not provided.

2. The method for producing a synthesis gas according to claim 1, wherein gasification of the biomass raw material is performed at 700 C. or higher and lower than 850 C.

3. The method for producing a synthesis gas according to claim 1, wherein a supply amount of the hydrogen gas is 100 L/day or more.

4. A fuel production system that produces a liquid fuel from a biomass raw material, comprising: a gasification device including a gasification furnace configured to produce a synthesis gas containing hydrocarbons by reacting the biomass raw material, hydrogen, carbon monoxide, and carbon dioxide using the method for producing a synthesis gas according to claim 1; a hydrogen supply unit for supplying hydrogen to the gasification device such that a mass ratio represented by [mass of hydrogen gas]/[mass of biomass] is 0.01 to 0.03; and a steam supply control unit for stopping supply of steam from the steam supply unit for supplying steam to the gasification device.

5. The fuel production system according to claim 4, further comprising: a first hydrogen gas supply control unit for supplying hydrogen to the gasification device in a case where a temperature in the gasification furnace is 700 C. or higher and lower than 850 C.

6. The fuel production system according to claim 4, further comprising: a second hydrogen gas supply control unit for supplying hydrogen to the gasification device in a case where a supply amount of the hydrogen gas to be supplied to the gasification device is 100 L/day or more.

7. The fuel production system according to claim 4, further comprising: a first synthesis gas supply unit for using the synthesis gas as a raw material of the liquid fuel in a case where a gasification rate of the biomass raw material is 50 mol % or more; and a second synthesis gas supply unit for using the synthesis gas as a heat source of the gasification furnace in a case where the gasification rate of the biomass raw material is less than 50 mol %.

8. A method for producing a liquid fuel, comprising: producing a synthesis gas using the method of claim 1, and producing a Fischer-Tropsch oil by subjecting the synthesis gas to a Fischer-Tropsch synthesis reaction.

9. The method for producing a liquid fuel according to claim 8, further comprising subjecting a biomass raw material to a gasification at 700 C. or higher and lower than 850 C.

10. The method for producing a liquid fuel according to claim 8, further comprising supplying a hydrogen gas at an amount of 100 L/day or more.

11. A method for producing a synthesis gas for producing a fuel from a biomass raw material, the method comprising: supplying hydrogen to the biomass raw material such that a mass ratio represented by [mass of hydrogen gas]/[mass of biomass] is 0.01 to 0.03; and supplying steam to the biomass raw material such that a mass ratio represented by [mass of steam]/[mass of biomass] is 1.0 or less.

12. The method for producing a synthesis gas according to claim 11, wherein gasification of the biomass raw material is performed at 700 C. or higher and lower than 850 C.

13. The method for producing a synthesis gas according to claim 11, wherein a supply amount of the hydrogen gas is 100 L/day or more.

14. A fuel production system that produces a liquid fuel from a biomass raw material, comprising: a gasification device including a gasification furnace configured to produce a synthesis gas containing hydrocarbons by reacting the biomass raw material, hydrogen, carbon monoxide, and carbon dioxide using the method for producing a synthesis gas according to claim 11; a hydrogen supply unit for supplying hydrogen to the gasification device such that a mass ratio represented by [mass of hydrogen gas]/[mass of biomass] is 0.01 to 0.03; and a steam supply control unit for supplying steam to the gasification device, from the steam supply unit for supplying steam to the gasification device, such that a mass ratio represented by [mass of steam]/[mass of biomass] is 1.0 or less.

15. The fuel production system according to claim 14, further comprising: a first hydrogen gas supply control unit for supplying hydrogen to the gasification device in a case where a temperature in the gasification furnace is 700 C. or higher and lower than 850 C.

16. The fuel production system according to claim 14, further comprising: a second hydrogen gas supply control unit for supplying hydrogen to the gasification device in a case where a supply amount of the hydrogen gas to be supplied to the gasification device is 100 L/day or more.

17. The fuel production system according to claim 14, further comprising: a first synthesis gas supply unit for using the synthesis gas as a raw material of the liquid fuel in a case where a gasification rate of the biomass raw material is 50 mol % or more; and a second synthesis gas supply unit for using the synthesis gas as a heat source of the gasification furnace in a case where the gasification rate of the biomass raw material is less than 50 mol %.

18. A method for producing a liquid fuel, comprising: producing a synthesis gas using the method of claim 1, and producing a Fischer-Tropsch oil by subjecting the synthesis gas to a Fischer-Tropsch synthesis reaction.

19. The method for producing a liquid fuel according to claim 18, further comprising subjecting a biomass raw material to a gasification at 700 C. or higher and lower than 850 C.

20. The method for producing a liquid fuel according to claim 18, further comprising supplying a hydrogen gas at an amount of 100 L/day or more.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] FIG. 1 is a flowchart showing a configuration of a fuel production method according to an embodiment of the present disclosure.

[0060] FIG. 2 is a schematic diagram showing a fuel production system according to the embodiment of the present disclosure.

[0061] FIG. 3 is a schematic diagram showing a fuel production system according to another embodiment of the present disclosure.

[0062] FIG. 4 is a graph showing a relationship between a concentration of each component of a synthesis gas in a gasification furnace and a hydrogen supply amount to the gasification furnace.

[0063] FIG. 5 is a graph comparing an amount of carbon dioxide generated in an entire system and a breakdown thereof in a case where a predetermined amount of synthesis gas having a predetermined target ratio is generated, between a fuel production system of the related art and the fuel production system according to the present embodiment.

[0064] FIG. 6 is a diagram showing various threshold values set for a hydrogen remaining amount in a hydrogen tank.

[0065] FIG. 7 is a flowchart showing a specific procedure of a normal control process.

[0066] FIG. 8 is a flowchart showing a specific procedure during a low-temperature operation.

[0067] FIG. 9 is a graph showing a relationship between the concentration of each component of the synthesis gas generated in the gasification furnace and a temperature of the gasification furnace in a case where the hydrogen supply amount from outside the gasification furnace is zero.

[0068] FIG. 10 is a graph representing a result of Example 1 and is a graph representing a relationship between an H/B ratio and a gasification rate of a biomass raw material in a case where steam is supplied.

[0069] FIG. 11 is a graph representing a result of Example 2 and is a graph representing a relationship between an S/B ratio, an H/B ratio, and a gasification rate of a biomass raw material in a case where steam is supplied.

[0070] FIG. 12 is a graph representing a result of Example 3 and is a graph representing a relationship between an H/B ratio and a gasification rate of the biomass raw material in a case where steam is supplied and a case where no steam is supplied.

[0071] FIG. 13 is a graph representing a result of Example 3 and is a graph representing a relationship between an H/B ratio and a temperature in the gasification furnace in a case where steam is supplied.

[0072] FIG. 14 is a graph representing a result of Example 3 and is a graph representing a relationship between an H/B ratio and a temperature in the gasification furnace in a case where no steam is supplied.

[0073] FIG. 15 is a graph representing a result of Example 4 and is a graph representing a relationship between an H/B ratio and a gasification rate of the biomass raw material in a case where no steam is supplied under a low-temperature condition in the gasification furnace.

DETAILED DESCRIPTION OF THE INVENTION

[0074] Hereinafter, embodiments of a fuel production method in the present disclosure will be specifically described. Note that the present disclosure is not limited to the following embodiments.

Fuel Production Method

[0075] The fuel production method according to one embodiment of the present disclosure includes supplying a hydrogen gas such that a mass ratio represented by [mass of hydrogen gas]/[mass of biomass] is 0.01 to 0.05 in gasification of a biomass raw material.

[0076] FIG. 1 is a flowchart showing a configuration of the fuel production method according to the present embodiment.

[0077] As shown in FIG. 1, the fuel production method according to the embodiment includes a biomass raw material supply step S2 of supplying a biomass raw material to a gasification furnace for producing a synthesis gas, a hydrogen supply step S12 of supplying hydrogen to the gasification furnace, a synthesis gas production step S3 of reacting the biomass raw material, hydrogen, steam, and the like to produce a synthesis gas containing hydrocarbons, a Fischer-Tropsch synthesis step S6 of subjecting the generated synthesis gas to a Fischer-Tropsch (hereinafter, sometimes referred to as FT) synthesis reaction to produce a Fischer-Tropsch oil, a hydrocracking step S7 of subjecting a heavy fraction (generally, C.sub.21 or more) contained in the Fischer-Tropsch oil to hydrocracking using a hydrogen gas to reduce the carbon number to C.sub.20 or less, and a distillation step S8 of distilling the Fischer-Tropsch oil after hydrocracking to separate a liquid fuel and the FT off-gas.

[0078] In the fuel production method according to the embodiment, in the hydrogen supply step S12 of supplying hydrogen to the gasification furnace, the hydrogen gas is supplied such that a mass ratio represented by [mass of hydrogen gas]/[mass of biomass] is 0.01 to 0.05.

[0079] In the biomass raw material supply step S2, a predetermined pretreatment is performed on the biomass raw material such as rice husks, bagasse, and wood, and the biomass raw material subjected to the pretreatment is supplied to the gasification furnace of a gasification device that performs the synthesis gas production step S3 via a raw material supply path. Here, the pretreatment for the biomass raw material includes, for example, a drying step of drying the raw material, a grinding step of grinding the raw material, and the like.

[0080] In the hydrogen supply step S12, hydrogen is supplied to the gasification furnace of the gasification device. Hydrogen may be supplied by, for example, generating hydrogen through electrolysis of water.

[0081] The supply amount of hydrogen is such that the mass ratio represented by [mass of hydrogen gas]/[mass of biomass] is 0.01 to 0.05, preferably 0.01 to 0.04, and more preferably 0.01 to 0.03. When the mass ratio is within the above-described range, the proportion of hydrogen contained in the synthesis gas to be supplied to the Fischer-Tropsch synthesis step S6 is more easily adjusted to be larger, making it easier to consume carbon dioxide as a raw material. Therefore, the synthesis gas can be produced even in a case where no steam is supplied, and hydrogen can be effectively used, facilitating further improvement in energy efficiency.

[0082] In the fuel production method according to the present embodiment, a steam supply step S9 of supplying steam to the gasification furnace of the gasification device is not required, but the fuel production method according to another embodiment may include supplying steam such that a mass ratio represented by [mass of steam]/[mass of biomass] is 1.0 or less.

[0083] In a case where steam is supplied, the mass ratio represented by [mass of steam]/[mass of biomass] is preferably 0.01 to 1.0, more preferably 0.05 to 0.8, and still more preferably 0.1 to 0.6. When the mass ratio is within the above-described range, the proportion of hydrogen contained in the synthesis gas to be supplied to the Fischer-Tropsch synthesis step S6 is more easily adjusted to be larger, making it easier to consume carbon dioxide as a raw material. Therefore, further improvement in energy efficiency is facilitated.

[0084] In a case where steam is supplied, a temperature of the steam is preferably lower than 500 C. The temperature of the steam is preferably 100 C. or more, and more preferably 150 C. or more. When the temperature of the steam is within the above-described range, an amount of energy consumption for heating the steam is more easily reduced.

[0085] In the synthesis gas production step S3, the biomass raw material, hydrogen, carbon monoxide, and carbon dioxide are reacted to produce the synthesis gas containing hydrocarbons.

[0086] When hydrogen, carbon monoxide, and carbon dioxide are fed into the gasification furnace into which the biomass raw material has been fed, for example, a total of eight types of gasification reactions and reverse reactions thereof, as shown in Formulas (1-1) to (1-8), proceed in the gasification furnace, and the synthesis gas containing hydrogen, carbon monoxide, and hydrocarbons is generated.

C+H.sub.2OCO+H.sub.2(1-1)

C+CO.sub.22CO(1-2)

C+2H.sub.2CH.sub.4(1-3)

C+2H.sub.2OCO.sub.2+2H.sub.2(1-4)

CO+H.sub.2OCO.sub.2+H.sub.2(1-5)

2CO+2H.sub.2CO.sub.2+CH.sub.4(1-6)

CO+3H.sub.2H.sub.2O+CH.sub.4(1-7)

CO.sub.2+4H.sub.22H.sub.2O+CH.sub.4(1-8)

CH.sub.4+H.sub.2OCO+3H.sub.2(1-9)

[0087] In the present disclosure, since hydrogen is supplied, the reactions shown in Formulas (1-3) and (1-5) to (1-7) using hydrogen as a raw material proceed more easily, and the content of a hydrocarbon gas in the synthesis gas tends to increase.

[0088] In the synthesis gas, the content of the hydrocarbon gas is preferably 10% by mass or less and more preferably 8% by mass or less with respect to the total mass of the synthesis gas. The content may be 0% by mass. The above-described numerical range can be achieved by appropriately adjusting the reaction temperature (gasification furnace temperature) in the gasification, the supply amount of the hydrogen gas, and the supply amount of steam. When the content of the hydrocarbon gas is within the above-described range, the synthesis gas containing the hydrocarbon gas can be used as a fuel for heating the gasification furnace or can be used as a raw material for liquid fuel production, thereby improving energy efficiency.

[0089] The gasification of the biomass raw material is preferably performed at 700 C. or higher and lower than 900 C. and more preferably at 700 C. or higher and lower than 850 C. When the temperature of gasification is within the above-described range, energy consumption for heating the gasification furnace is more easily reduced.

[0090] The supply amount of the hydrogen gas is preferably 100 L/day or more, more preferably 200 L/day or more, and still more preferably 300 L/day or more. The supply amount of the hydrogen gas is preferably 2000 L/day or less, more preferably 1500 L/day or less, and still more preferably 1000 L/day or less. When the supply amount of the hydrogen gas is within the above-described range, the hydrogen gas can be supplied to the gasification of the biomass raw material, and the surplus hydrogen gas can also be supplied as a fuel for heating the gasification furnace.

[0091] Hereinafter, a fuel production system according to one embodiment of the present disclosure will be described with reference to the drawings.

[0092] FIG. 2 is a diagram showing a configuration of a fuel production system 1 according to the present embodiment. The fuel production system 1 includes a biomass raw material supply device 2 that supplies the biomass raw material, a gasification device 3 that gasifies the biomass raw material supplied from the biomass raw material supply device 2 to generate a synthesis gas containing hydrogen and carbon monoxide, an FT device 6 that produces a liquid fuel from the synthesis gas supplied from the gasification device 3, a hydrogen production device 10 that generates hydrogen, a hydrogen tank 12 that stores a hydrogen gas generated by the hydrogen production device 10, and a control device 13 that controls these, and uses these to produce the liquid fuel from the biomass raw material.

[0093] The biomass raw material supply device 2 performs a predetermined pretreatment on the biomass raw material such as rice husks, bagasse, and wood and supplies the biomass raw material subjected to the pretreatment to the gasification furnace of the gasification device 3 via the raw material supply path. Here, the pretreatment for the biomass raw material includes, for example, a drying step of drying the raw material, a grinding step of grinding the raw material, and the like.

[0094] A method for supplying the biomass raw material to the gasification furnace is not particularly limited, and a known supply method can be employed.

[0095] The gasification device 3 may include the gasification furnace for gasifying the biomass raw material supplied via the raw material supply path, a gasification furnace sensor group composed of a plurality of sensors that detect a state inside the gasification furnace, a steam supply device that supplies steam into the gasification furnace, an oxygen supply device that supplies oxygen into the gasification furnace, a heating device that heats the gasification furnace, a scrubber that cleans the synthesis gas discharged from the gasification furnace, and a desulfurization device that removes a sulfur component from the synthesis gas cleaned by the scrubber and that supplies the synthesis gas to the FT device 6.

[0096] The reaction conditions in the synthesis gas production are not particularly limited, and known reaction conditions can be employed.

[0097] A steam supply device 9 vaporizes water stored in a water tank (not shown) and supplies the vaporized water into the gasification furnace. The heating device consumes fuel supplied from a fuel tank (not shown) or electric power supplied from a power supply (not shown) to heat the gasification furnace. The control device 13 controls a steam supply amount from the steam supply device to the gasification furnace and an input heat amount from the heating device to the gasification furnace. In the fuel production system 1 according to the present embodiment, by supplying hydrogen from the hydrogen production device 10 to be described below into the gasification furnace or the raw material supply path, it may not be necessary to actively supply steam from the steam supply device into the gasification furnace. In this case, the steam supply device can also be removed from the fuel production system 1.

[0098] A method for producing and supplying steam is not particularly limited, and a known production and supply method can be employed. A method for heating the gasification furnace is not particularly limited, and a known heating method can be employed.

[0099] When water, oxygen, heat, and the like are fed into the gasification furnace into which the biomass raw material has been fed, by the steam supply device, the oxygen supply device, and the heating device as described above, in the gasification furnace, for example, a total of eight types of gasification reactions and reverse reactions thereof, as shown in Formulas (1-1) to (1-8), proceed, and the synthesis gas containing hydrogen, carbon monoxide, and hydrocarbons is generated.

[0100] The gasification furnace sensor group includes, for example, a pressure sensor that detects a pressure in the gasification furnace, a temperature sensor that detects a temperature in the gasification furnace, an H.sub.2/CO sensor that detects an H.sub.2/CO ratio of the synthesis gas that corresponds to a ratio of hydrogen to carbon monoxide in the gasification furnace, a CO.sub.2 sensor that detects carbon dioxide in the gasification furnace, and the like. Detection signals of these sensors constituting the gasification furnace sensor group are transmitted to the control device 13.

[0101] The gasification device 3 may mix hydrogen supplied from the hydrogen production device 10 to be described below with the synthesis gas generated by the gasification reactions and the reverse reactions thereof shown in Formulas (1-1) to (1-8) to adjust the H.sub.2/CO ratio of the synthesis gas to a predetermined target ratio corresponding to the liquid fuel to be produced (for example, in a case of producing methanol, the target ratio of the H.sub.2/CO ratio is 2), and then may supply this synthesis gas to the FT device 6.

[0102] The hydrogen production device 10 includes an electrolytic device (not shown) and generates hydrogen using electric power. The device that generates hydrogen using electric power is not particularly limited, and a known device can be employed. Examples thereof include a device that generates hydrogen through electrolysis of water.

[0103] The hydrogen tank 12 stores hydrogen generated by the hydrogen production device 10. Hydrogen is supplied from the hydrogen tank 12 to the gasification device 3. The hydrogen tank is not particularly limited, and a known tank can be employed. Examples thereof include a pressure-resistant tank. The hydrogen tank may be made of metal or resin.

[0104] A hydrogen filling pump (not shown) may be provided between the hydrogen production device 10 and the hydrogen tank 12. The hydrogen filling pump compresses the hydrogen generated by the electrolytic device and fills the hydrogen tank 12 with the compressed hydrogen. A hydrogen filling amount from the hydrogen filling pump is controlled by the control device 13. The hydrogen tank 12 stores hydrogen compressed by the hydrogen filling pump. The pressure sensor detects an internal tank pressure of the hydrogen tank 12 and transmits a detection signal to the control device 13. A hydrogen remaining amount in the hydrogen tank 12 is calculated by the control device 13 based on the detection signal of the pressure sensor. Therefore, in the present embodiment, a hydrogen remaining amount acquisition device (not shown) that acquires the hydrogen remaining amount in the hydrogen tank 12 is configured by the pressure sensor and the control device 13.

[0105] A hydrogen supply pump (not shown) may be provided as a hydrogen supply unit for supplying hydrogen from the hydrogen tank 12 to the gasification device 3. The hydrogen supply pump supplies hydrogen stored in the hydrogen tank 12 into the gasification furnace of the gasification device 3. The hydrogen supply amount from the hydrogen supply pump to the gasification furnace is controlled by the control device 13. In the fuel production system 1 according to the present embodiment, a case where hydrogen stored in the hydrogen tank 12 is supplied into the gasification furnace by the hydrogen supply pump will be described, but the present disclosure is not limited thereto. The hydrogen stored in the hydrogen tank 12 may be supplied upstream of the gasification furnace, more specifically, into the raw material supply path of the biomass raw material.

[0106] The control device 13 is a computer that controls the steam supply amount from the steam supply device, the input heat amount from the heating device, the hydrogen generation amount from the electrolytic device, the hydrogen filling amount from the hydrogen filling pump, the hydrogen supply amount from the hydrogen supply pump, and the like based on the detection signals from the gasification furnace sensor group, the detection signal from the pressure sensor of the hydrogen tank 12, and the like.

[0107] A first hydrogen gas supply control unit for supplying hydrogen stored in the hydrogen tank to the gasification device in a case where the temperature in the gasification furnace is 700 C. or higher and lower than 850 C. may be provided. A second hydrogen gas supply control unit for supplying hydrogen stored in the hydrogen tank to the gasification device in a case where the supply amount of the hydrogen gas that can be supplied to the gasification device is 100 L/day or more may be provided.

[0108] A Steam supply control unit for stopping the supply of the steam from the steam supply unit to the gasification device in a case where the temperature of the steam is lower than 500 C. may be provided.

[0109] Alternatively, a steam supply control unit for supplying steam from the steam supply unit to the gasification device such that the mass ratio represented by [mass of steam]/[mass of biomass] is 1.0 or less in a case where the temperature of the steam is lower than 500 C. may be provided.

[0110] It is preferable that a first synthesis gas supply unit for using the synthesis gas as a raw material of the liquid fuel in a case where a gasification rate of the biomass raw material is 50 mol % or more is provided. It is preferable that a second synthesis gas supply unit for using the synthesis gas as a heat source of the gasification furnace in a case where the gasification rate of the biomass raw material is less than 50 mol % is provided.

[0111] A specific procedure for controlling the hydrogen supply amount and the like by the control device 13 will be described.

[0112] The control device 13 calculates an optimal operating point of the gasification furnace based on the detection signals from the gasification furnace sensor group. Here, the operating point of the gasification furnace includes the biomass raw material supply amount from the biomass raw material supply device, the steam supply amount from the steam supply device, the hydrogen supply amount from the hydrogen supply pump, and the input heat amount from the heating device. In addition, the optimal operating point refers to an operating point where the H.sub.2/CO ratio of the synthesis gas discharged from the gasification furnace is the target ratio. The control device 13 stores a basic map that associates the detection signals from the gasification furnace sensor group with the optimal operating point, and the control device 13 calculates the optimal operating point by searching the basic map based on the detection signals from the gasification furnace sensor group.

[0113] Specifically, the control device 13 stores a map that associates the biomass raw material supply amount, the steam supply amount, and the hydrogen supply amount as described above with a synthesis gas generation amount. In the control device 13, the biomass raw material supply amount, the steam supply amount, and the hydrogen supply amount, which minimize the carbon dioxide emission intensity of the liquid fuel, are calculated based on the map using the above-described procedure.

[0114] The optimal operating point of the gasification furnace changes depending on the type and properties of the biomass raw material fed into the gasification furnace. Therefore, it is preferable that the control device 13 stores a basic map different for each type and property of the biomass raw material and calculates the optimal operating point by switching to a basic map to be referred to according to the type and property of the biomass raw material fed into the gasification furnace. Consequently, the control device 13 can change the hydrogen supply amount from the hydrogen supply pump and the like according to the type and properties of the biomass raw material fed into the gasification furnace, thereby adjusting the H.sub.2/CO ratio of the synthesis gas discharged from the gasification furnace to the target ratio.

[0115] Additionally, in the present embodiment, a case where the optimal operating point is calculated based on the basic map has been described, but the present disclosure is not limited thereto. The optimal operating point may be calculated by performing a predetermined calculation based on the detection signals of the gasification furnace sensor group or the type and properties of the biomass raw material fed into the gasification furnace.

[0116] The control device 13 controls the biomass raw material supply amount from the biomass raw material supply device, the steam supply amount from the steam supply device, the hydrogen supply amount from the hydrogen supply pump, and the input heat amount from the heating device such that the calculated optimal operating point is achieved.

[0117] In a case where the hydrogen remaining amount of the hydrogen tank 12 is maintained within a normal range without large fluctuations, it is preferable that the control device 13 adjusts the hydrogen generation amount from the hydrogen production device and the hydrogen filling amount to the hydrogen tank 12 to match the hydrogen supply amount from the hydrogen supply pump.

[0118] In the fuel production system 1, the hydrogen tank 12 is filled with the hydrogen generated by the electrolytic device while the hydrogen extracted from the hydrogen tank 12 is supplied to the gasification device 3. Therefore, as a unit for reducing the hydrogen remaining amount, the control device 13 can selectively execute any of a hydrogen usage amount increase control of increasing a hydrogen usage amount in the gasification device 3 and the hydrogen supply amount from the hydrogen supply pump to reduce the hydrogen remaining amount, or a hydrogen generation amount reduction control of reducing the hydrogen generation amount from the hydrogen production device and the hydrogen filling amount from the hydrogen filling pump to reduce the hydrogen remaining amount.

[0119] The control device 13 changes the operating point from the optimal operating point during execution of a normal control process to reduce the H.sub.2/CO ratio of the synthesis gas generated by the reaction in the gasification furnace.

[0120] The control device 13 can execute either or both of the following processes in combination: a furnace temperature reduction process of reducing the temperature of the gasification furnace; and a water reduction process of reducing the steam supply amount into the gasification furnace, as a unit for reducing the H.sub.2/CO ratio of the synthesis gas.

[0121] FIG. 3 is a diagram showing a configuration of a fuel production system 11 according to another embodiment. The configuration is the same as that in FIG. 2 except that the order of a distillation device (L) 8 and a hydrocracking device 7 is changed and a hydrogenation purification device 17 is provided downstream of the distillation device (L) 8.

[0122] Next, an effect of supplying hydrogen into the gasification furnace in the gasification device 3 or into the raw material supply path will be described with reference to FIGS. 4 and 5.

[0123] FIG. 4 is a graph showing a relationship between a concentration [% by volume] of each component of the synthesis gas in the gasification furnace and the hydrogen supply amount [kg/h] to the gasification furnace. The result shown in FIG. 4 is obtained by performing a simulation under predetermined conditions. In FIG. 4, a thick solid line indicates a hydrogen concentration of the synthesis gas in the gasification furnace, a thick dashed line indicates a carbon monoxide concentration of the synthesis gas in the gasification furnace, and a thin solid line indicates a carbon dioxide concentration of the synthesis gas in the gasification furnace. In addition, in FIG. 4, an amount [kg/h] of carbon dioxide generated in the entire system in a case where a predetermined amount of synthesis gas having a predetermined target ratio is generated by the gasification device 3 is indicated by a thin dashed line.

[0124] FIG. 5 is a graph comparing the amount [kg/h] of carbon dioxide generated in the entire system and a breakdown thereof in a case where a predetermined amount of synthesis gas having a predetermined target ratio is generated, between a fuel production system of the related art and the fuel production system 1 according to the present embodiment. Here, the fuel production system of the related art uses water to adjust the H.sub.2/CO ratio of the synthesis gas generated by the gasification device 3 to the target ratio without supplying hydrogen from the outside to the gasification device 3.

[0125] As shown in FIG. 4, when the hydrogen supply amount to the gasification furnace is zero, the H.sub.2/CO ratio of the synthesis gas in the gasification furnace is smaller than the target ratio. Therefore, in order to increase the H.sub.2/CO ratio of the synthesis gas generated by the gasification device 3 to the target ratio, it is necessary to further perform an H.sub.2/CO ratio adjustment step of reacting the excess carbon monoxide and water in the synthesis gas generated in the gasification furnace to increase the H.sub.2/CO ratio. However, when such an H.sub.2/CO ratio adjustment step is performed, carbon dioxide is generated. Therefore, in the fuel production system of the related art, carbon dioxide is generated not only in the gasification step in the gasification furnace but also in the H.sub.2/CO ratio adjustment step, as shown in FIG. 5.

[0126] On the other hand, as indicated by a dashed line 2a in FIG. 4, when the hydrogen supply amount to the gasification furnace is increased, the hydrogen concentration of the synthesis gas in the gasification furnace increases accordingly. Therefore, by controlling the hydrogen supply amount to the gasification furnace to a predetermined amount, the H.sub.2/CO ratio of the synthesis gas in the gasification furnace can be adjusted to the target ratio. Accordingly, with the fuel production system 1 according to the present embodiment, since there is no need to actively perform the H.sub.2/CO ratio adjustment step, the amount of carbon dioxide can be reduced by at least that amount as compared to the fuel production system of the related art.

[0127] In addition, when the hydrogen supply amount to the gasification furnace is increased, the steam supply amount to the gasification furnace can be reduced as compared to the fuel production system of the related art, resulting in the suppression of reactions generating carbon monoxide and carbon dioxide among the reactions in the gasification furnace shown in Formulas (1-1) to (1-8). Therefore, as the hydrogen supply amount to the gasification furnace is increased, the carbon monoxide concentration and the carbon dioxide concentration of the synthesis gas in the gasification furnace decrease, as shown in FIG. 4. Therefore, as shown in FIG. 5, with the fuel production system 1 according to the present embodiment, it is possible to reduce the amount of carbon dioxide generated in the gasification step in the gasification furnace as compared to the fuel production system of the related art. As described above, with the fuel production system 1 according to the present embodiment, the amount of carbon dioxide generated in the entire fuel production system 1 can be suppressed.

[0128] FIG. 6 is a diagram showing various threshold values set for the hydrogen remaining amount of the hydrogen tank 12 and is a diagram illustrating the concept of a synthesis gas production process shown in FIGS. 7 and 8. A normal range in FIG. 6 is, for example, a range in which the supply amount of the hydrogen gas to the gasification device can be maintained at 100 L/day or more and 300 L/day or less.

[0129] A hydrogen upper limit amount in FIG. 6 corresponds to an upper limit of the amount of hydrogen that can be stored in the hydrogen tank 12. Therefore, the hydrogen tank 12 cannot be filled with hydrogen beyond the hydrogen upper limit amount. Additionally, a hydrogen lower limit amount in FIG. 6 corresponds to the minimum amount of hydrogen that should be secured in the hydrogen tank 12 in order to supply hydrogen in the hydrogen tank 12 into the gasification furnace by the hydrogen supply pump. Therefore, when the hydrogen remaining amount falls below the hydrogen lower limit amount, hydrogen cannot be supplied into the gasification furnace by the hydrogen supply pump.

[0130] In the synthesis gas production process, an upper limit threshold value that is slightly smaller than the hydrogen upper limit amount, and a lower limit threshold value that is smaller than the upper limit threshold value and that is slightly larger than the hydrogen lower limit amount are set with respect to the hydrogen remaining amount, and the gasification device 3 and the hydrogen production device 10 are controlled such that the hydrogen remaining amount of the hydrogen tank 12 is maintained within the normal range between the upper limit threshold value and the lower limit threshold value as much as possible, in other words, the hydrogen remaining amount does not deviate from the above-described normal range and does not reach the hydrogen upper limit amount or the hydrogen lower limit amount.

[0131] FIG. 7 is a flowchart showing a specific procedure of the normal control process.

[0132] First, the control device 13 confirms that the temperature of the gasification furnace is in a normal state, that is, 850 C. or higher, based on the detection signal of the temperature sensor.

[0133] Next, the control device 13 determines whether or not the temperature of the steam is 500 C. or higher based on the detection signal of the temperature sensor. In a case where the determination result is YES, the control device 13 further calculates the hydrogen remaining amount of the hydrogen tank 12 based on the detection signal of the pressure sensor and determines whether or not the hydrogen remaining amount is equal to or greater than the upper limit threshold value. In a case where the determination result is YES, the control device 13 supplies both steam and hydrogen gas to produce the synthesis gas, and in a case where the determination result is NO, the control device 13 supplies steam without supplying the hydrogen gas to the biomass raw material to produce the synthesis gas.

[0134] On the other hand, in a case where the determination of whether or not the temperature of the steam is 500 C. or higher is NO, the hydrogen remaining amount of the hydrogen tank 12 is further calculated based on the detection signal of the pressure sensor, and it is determined whether or not the hydrogen remaining amount is equal to or greater than the upper limit threshold value. In a case where the determination result is YES, the control device 13 supplies only the hydrogen gas to the biomass raw material without supplying steam to produce the synthesis gas, and in a case where the determination result is NO, the control device 13 does not produce the synthesis gas.

[0135] It can be said that in a case where the determination result of the hydrogen remaining amount is NO, that is, in a case where the hydrogen remaining amount of the hydrogen tank 12 is within the normal range, there is a margin for receiving the hydrogen generated by the electrolytic device and there is a margin for supplying the amount of hydrogen required in the gasification furnace. For example, the supply amount of the hydrogen gas to the gasification device is less than 100 L/day.

[0136] In a case where the hydrogen remaining amount of the hydrogen tank 12 is equal to or greater than the upper limit threshold value, the control device 13 increases the supply amount of hydrogen as a raw material for synthesis gas production. As shown in FIG. 6, in a case where the hydrogen remaining amount is equal to or greater than the upper limit threshold value, it is necessary to reduce the hydrogen remaining amount such that the hydrogen remaining amount does not exceed the hydrogen upper limit amount. As mentioned above, when the hydrogen remaining amount exceeds the hydrogen upper limit amount, the hydrogen tank 12 cannot be filled with hydrogen. Therefore, the control device 13 reduces the hydrogen remaining amount by increasing the supply amount of hydrogen as a raw material for synthesis gas production.

[0137] In a case where the hydrogen remaining amount of the hydrogen tank 12 is less than the lower limit threshold value, the control device 13 does not increase the supply amount of hydrogen as a raw material for synthesis gas production or does not perform the synthesis gas production. As shown in FIG. 6, in a case where the hydrogen remaining amount is less than the lower limit threshold value, it is necessary to increase the hydrogen remaining amount such that the hydrogen remaining amount does not fall below the hydrogen lower limit amount, but the amount of energy consumption may increase because it is necessary to operate the hydrogen production device in order to supply hydrogen. In addition, the hydrogen production device produces high-purity and high-pressure hydrogen in order to supply hydrogen to the FT device, the hydrocracking device, the hydrogenation purification device, and the like. Therefore, supplying high-purity and high-pressure hydrogen as a raw material for producing the synthesis gas results in poor energy efficiency. Further, as mentioned above, when the hydrogen remaining amount falls below the hydrogen lower limit amount, hydrogen cannot be supplied to the FT device, the hydrocracking device, the hydrogenation purification device, and the like by the hydrogen supply pump. Therefore, in a case where the hydrogen remaining amount of the hydrogen tank 12 is less than the lower limit threshold value, the control device 13 does not increase the supply amount of hydrogen as a raw material for synthesis gas production or does not perform the synthesis gas production.

[0138] The gasification rate is calculated from a substance amount of the obtained synthesis gas and the biomass raw material supply amount, and it is determined whether or not the gasification rate is 50 mol % or more. In a case where the determination result is YES, the synthesis gas is supplied to the subsequent FT device, and fuel production proceeds. On the other hand, in a case where the determination result is NO, the synthesis gas is combusted as a fuel for heating the gasification furnace of the gasification device 3.

[0139] The gasification rate is calculated by the following formula.

Gasification rate (mol %)=[substance amount of carbon-containing gas (CO, CO.sub.2, CH.sub.4, C.sub.2H.sub.4, and the like) contained in synthesis gas]/[substance amount of carbon component in biomass raw material]100

[0140] As described above, in the synthesis gas production process shown in FIG. 7, in a case where the hydrogen remaining amount is equal to or greater than the upper limit threshold value, the supply amount of hydrogen as a raw material for synthesis gas production is increased, and in a case where the hydrogen remaining amount is less than the lower limit threshold value, the supply amount of hydrogen as a raw material for synthesis gas production is not increased or the synthesis gas production is not performed, ensuring that the hydrogen remaining amount is maintained within the normal range.

[0141] FIG. 8 is a flowchart showing a specific procedure during a low-temperature operation.

[0142] First, the control device 13 determines whether or not the temperature of the gasification furnace is in a low-temperature state, that is, 700 C. or higher and lower than 850 C., based on the detection signal of the temperature sensor. Here, in a case where the determination result is NO because the temperature of the gasification furnace is less than 700 C., the production of the synthesis gas is not performed. In a case where the determination result is YES, the subsequent flow is the same as the normal control process of FIG. 7.

[0143] As described above, in the synthesis gas production process shown in FIG. 8, as in the synthesis gas production process shown in FIG. 7, in a case where the hydrogen remaining amount is equal to or greater than the upper limit threshold value, the supply amount of hydrogen as a raw material for synthesis gas production is increased, and in a case where the hydrogen remaining amount is less than the lower limit threshold value, the supply amount of hydrogen as a raw material for synthesis gas production is not increased or the synthesis gas production is not performed, ensuring that the hydrogen remaining amount is maintained within the normal range.

[0144] Hereinafter, the operations of the present disclosure during a low-temperature operation will be described.

[0145] FIG. 9 is a graph showing a relationship between the concentration of each component of the synthesis gas generated in the gasification furnace and the temperature of the gasification furnace in a case where the hydrogen supply amount from outside the gasification furnace is zero. As shown in FIG. 9, when the temperature of the gasification furnace is reduced, the proportion of carbon monoxide in the synthesis gas increases, whereas the proportions of hydrogen and carbon dioxide in the synthesis gas decrease. That is, when the temperature of the gasification furnace is reduced, the H.sub.2/CO ratio of the synthesis gas generated by the reaction in the gasification furnace decreases. Using this, in the furnace temperature reduction process, the control device 13 reduces the input heat amount from the heating device with respect to the optimal operating point determined in the normal control process to forcibly reduce the temperature of the gasification furnace, thereby reducing the H.sub.2/CO ratio generated by the reaction in the gasification furnace.

[0146] As shown in FIG. 9, in a case where the temperature of the gasification furnace is reduced, the proportion of carbon dioxide in the synthesis gas decreases. Additionally, when the input heat amount from the heating device is reduced, the amount of energy consumption in the heating device also decreases, so that the amount of carbon dioxide generated in the gasification device 3 can be reduced.

[0147] Hereinafter, the operations of the present disclosure in a case where no steam or a small amount of steam is supplied will be described.

[0148] As shown in Formulas (1-1) to (1-8), when the amount of water to be supplied to the gasification furnace is reduced, the proportion of hydrogen in the synthesis gas decreases. Using this, in the water reduction process, the control device 13 reduces the steam supply amount from the steam supply device with respect to the optimal operating point determined in the normal control process, thereby reducing the H.sub.2/CO ratio generated by the reaction in the gasification furnace. When the steam supply amount to the gasification furnace is reduced, the latent heat of water and the input heat amount from the heating device can also be reduced. Therefore, the control device 13 may maintain the temperature in the gasification furnace constant by reducing the steam supply amount from the steam supply device and reducing the input heat amount from the heating device.

[0149] As shown in Formulas (1-1) to (1-8), when the steam supply amount to the gasification furnace is reduced, the proportion of carbon dioxide in the synthesis gas decreases. In addition, when the input heat amount from the heating device is reduced, the amount of energy consumption in the heating device also decreases, so that the amount of carbon dioxide generated in the gasification device 3 can be reduced.

[0150] Hereinafter, the operations of the present disclosure achieved by increasing the supply amount of hydrogen will be described.

[0151] By increasing the supply amount of hydrogen, the reactions shown in Formulas (1-3) and (1-5) to (1-7) using hydrogen as a raw material proceed more easily, and the content of the hydrocarbon gas tends to increase. Consequently, the obtained synthesis gas can also be used as a fuel for heating the gasification furnace, and the synthesis gas can also be supplied for FT synthesis and used as a raw material for fuel production. That is, by using hydrogen as a raw material rather than directly as a fuel, hydrogen can be effectively utilized.

[0152] Additionally, by supplying hydrogen, there is no longer a need to actively supply steam into the gasification furnace. Consequently, the energy efficiency can be improved.

[0153] Further, by increasing the supply amount of hydrogen, the content of carbon dioxide in the synthesis gas tends to decrease. As a result, the amount of carbon dioxide generated in the entire fuel production system can be suppressed.

[0154] One embodiment of the present disclosure has been described above, but the present disclosure is not limited thereto. The detailed configuration may be appropriately changed within the scope of the gist of the present disclosure.

EXAMPLES

[0155] Hereinafter, the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to the following examples.

Example 1

[0156] A gasification furnace reaction tube having a diameter of 90 mm and a length of 1100 mm was used, the supply amount of the biomass raw material was set to 0.5 g/min, and the temperature of the gasification furnace was set to 850 C. for the production of the synthesis gas. Steam was supplied such that a mass ratio represented by [mass of steam]/[mass of biomass raw material] (hereinafter, also referred to as an S/B ratio) was 1.0, and the supply amount of hydrogen was adjusted such that mass ratios represented by [mass of hydrogen]/[mass of biomass raw material] (hereinafter, also referred to as an H/B ratio) were 0, 0.01, 0.02, 0.03, and 0.04. The gasification rate was calculated for each hydrogen supply amount. The results are shown in FIG. 10.

[0157] As shown in FIG. 10, by supplying hydrogen such that the H/B ratio was within a range of 0.01 to 0.04, the gasification rate increased by a maximum of 13 mol %. Additionally, it was found that even in a case where the supply amount of steam is small, increasing the supply amount of hydrogen leads to an improvement in the gasification rate.

Example 2

[0158] The production of the synthesis gas was performed in the same manner as in Example 1, except that steam was supplied such that the mass ratios represented by [mass of steam]/[mass of biomass raw material] were 0.5 and 1, and the supply amount of hydrogen was adjusted such that the mass ratios represented by [mass of hydrogen]/[mass of biomass raw material] were 0 and 0.01. The gasification rate was calculated for each hydrogen supply amount. The results are shown in FIG. 11.

[0159] As shown in FIG. 11, in a case where the S/B ratio is 0.5 and the H/B ratio is 0.01, the gasification rate increased by a maximum of 13 mol % as compared to a case where the S/B ratio is 1.0 and the H/B ratio is 0. Additionally, it was found that even in a case where the supply amount of steam is small, increasing the supply amount of hydrogen leads to an improvement in the gasification rate.

Example 3

[0160] A gasification furnace reaction tube having a diameter of 30 mm and a length of 600 mm was used, the supply amount of the biomass raw material was set to 0.5 g/min, the temperature of the gasification furnace was set to 850 C., and the supply amount of hydrogen was adjusted such that the mass ratios represented by [mass of hydrogen]/[mass of biomass raw material] were 0, 0.02, and 0.04 for the production of the synthesis gas. The gasification rate was calculated for each hydrogen supply amount in a case where steam was supplied and in a case where no steam was supplied. The results are shown in FIG. 12.

[0161] As shown in FIG. 12, when comparing a case where steam was supplied and a case where no steam was supplied, it was confirmed that the gasification rate was improved in a case where no steam was supplied. In addition, it was found that even in a case where no steam is supplied, increasing the supply amount of hydrogen leads to an improvement in the gasification rate.

[0162] FIG. 13 is a graph showing a change in temperature in the gasification furnace in a case where steam was supplied in Example 3, and FIG. 14 is a graph showing a change in temperature in the gasification furnace in a case where no steam was supplied in Example 3.

[0163] When comparing FIGS. 13 and 14, it was found that since the temperature changes are completely different, the types of reactions that preferentially occur among the reactions of Formulas (1-1) to (1-8) differ between a case where steam was supplied and a case where no steam was supplied. Specifically, the content of hydrocarbons contained in the generated synthesis gas increased by 3 mol % in a case where no steam was supplied, as compared to a case where steam was supplied. From this, it was also found that the types of reactions in the gasification differ between a case where steam was supplied and a case where no steam was supplied.

Example 4

[0164] The production of the synthesis gas was performed in the same manner as in Example 3, except that the temperature of the gasification furnace was set to 700 C., the supply amount of hydrogen was adjusted such that the mass ratios represented by [mass of hydrogen]/[mass of biomass raw material] were 0, 0.02, and 0.04, and no steam was supplied. The gasification rate was calculated for each hydrogen supply amount. The results are shown in FIG. 15.

[0165] As shown in FIG. 15, it was confirmed that even under a relatively low-temperature condition and in a case where no steam was supplied, the gasification rate was improved by supplying hydrogen. In addition, it was found that even in a case where no steam was supplied, the gasification rate was improved when the H/B ratio was within a specific range.

[0166] While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the invention. Accordingly, the invention is not to be considered as being limited by the foregoing description and is only limited by the scope of the appended claims.

EXPLANATION OF REFERENCES

[0167] 1, 11: fuel production system [0168] 2: biomass raw material supply device [0169] 3: gasification device [0170] 4: gas purification device [0171] 5: gas pressurization device [0172] 6: Fischer-Tropsch device (FT device) [0173] 7: hydrocracking device [0174] 8: distillation device [0175] 9: steam supply device [0176] 10: hydrogen production device [0177] 12: hydrogen tank [0178] 17: hydrogenation purification device