Hydrogen production device, hydrogen production method, and hydrogen production program

Abstract

A hydrogen production device (10) has a reactor (12) that thermally decomposes a hydrocarbon gas, which is a raw material gas, using a catalyst to produce hydrogen, wherein a fluidized bed of the catalyst is formed inside the reactor by introducing the raw material gas from a lower part of the reactor. The hydrogen production device comprises: a differential pressure sensor (43) configured to detect a pressure difference between an upper part of the reactor away from the fluidized bed and a lower part of the reactor corresponding to the fluidized bed; a supply device (21) configured to newly supply a catalyst to the reactor; an extraction device (31) configured to extract the catalyst with decreased activity from the reactor; and a control device (45) configured to control the operation of the supply device and the extraction device so that the pressure difference detected by the differential pressure sensor becomes constant.

Description

Hydrogen production device, hydrogen production method, and hydrogen production program

[0001] The present disclosure relates to a hydrogen production device, a hydrogen production method, and a hydrogen production program.

[0002] Conventionally, there are known techniques for producing hydrogen by thermal decomposition of methane. For example, a hydrogen production apparatus disclosed in Patent Document 1 has a reactor containing a catalyst. Methane is introduced into the reactor. The methane is decomposed into hydrogen and carbon by contacting with the catalyst inside the reactor. A mixture of hydrogen, which is the product gas, and unreacted methane is taken out of the reactor.

[0003] Japanese Patent Application Laid-Open No. 2019-73411

[0004] A hydrogen production device is required to maintain a decomposition rate of the raw material gas in order to produce hydrogen stably.

[0005] A hydrogen production apparatus according to one aspect of the present disclosure is a reactor that produces hydrogen by thermally decomposing a hydrocarbon gas as a feed gas using a catalyst, the reactor having a fluidized bed of the catalyst formed inside by introducing the feed gas from a lower part of the reactor. The hydrogen production apparatus includes a differential pressure sensor configured to detect a pressure difference between an upper part of the reactor that is separated from the fluidized bed and a lower part of the reactor that corresponds to the fluidized bed, a supply device configured to supply new catalyst to the reactor, an extraction device configured to extract the catalyst with reduced activity from the reactor, and a control device configured to control the operation of the supply device and the extraction device so that the pressure difference detected by the differential pressure sensor is constant.

[0006] A hydrogen production method according to one aspect of the present disclosure includes: forming a fluidized bed of the catalyst inside a reactor that produces hydrogen by thermally decomposing a hydrocarbon gas, which is a feed gas, using a catalyst, by introducing the feed gas from a lower part of the reactor; and controlling the supply of new catalyst to the reactor and the extraction of the catalyst with reduced activity from the reactor so that a pressure difference between an upper part of the reactor that is separated from the fluidized bed and a lower part of the reactor that corresponds to the fluidized bed is constant.

[0007] A hydrogen production program according to one embodiment of the present disclosure causes a computer to execute the following processes: forming a fluidized bed of the catalyst inside a reactor that produces hydrogen by thermally decomposing a hydrocarbon gas, which is a raw material gas, using a catalyst, by introducing the raw material gas from the bottom of the reactor; and controlling the supply of new catalyst to the reactor and the extraction of catalyst with reduced activity from the reactor so that the pressure difference between the top of the reactor that is outside the fluidized bed and the bottom of the reactor that corresponds to the fluidized bed is constant.

[0008] Fig. 1 is a configuration diagram of an embodiment of a hydrogen production device. Fig. 2 is a block diagram showing the electrical configuration of an embodiment of the hydrogen production device. Fig. 3 is a graph showing the relationship between the height of the catalyst layer and the methane conversion rate according to an embodiment.

[0009] An embodiment of a hydrogen production device will be described below. As shown in FIG. 1, the hydrogen production device 10 includes a pressure vessel 11 and a reactor 12. The pressure vessel 11 and the reactor 12 are each cylindrical with a circular cross section and extend in the vertical direction. The interior of the pressure vessel 11 is maintained at a predetermined pressure. The pressure is, for example, higher than atmospheric pressure. The reactor 12 is accommodated inside the pressure vessel 11 in a non-contact state. The inner diameter of the reactor 12 may be constant throughout its entire length.

[0010] A disperser 13 is provided inside the reactor 12. The disperser 13 is, for example, in the shape of a plate extending in a direction perpendicular to the axial direction of the reactor 12, and has a large number of holes. The holes penetrate the disperser 13 in the plate thickness direction. The disperser 13 is disposed at a position closer to the lower end of the reactor 12 than the axial center position of the reactor 12. The disperser 13 divides the inside of the reactor 12 into two spaces, an upper space and an lower space. The upper space is the reaction chamber 12A, and the lower space is the air chamber 12B. The reaction chamber 12A and the air chamber 12B are in communication with each other via the holes in the disperser 13.

[0011] The catalyst 14 is deposited on the upper surface of the disperser 13. That is, the inside of the reaction chamber 12A is filled with the catalyst 14 up to a predetermined deposition height relative to the disperser 13. The upper surface is the surface of the disperser 13 on the reaction chamber 12A side. The catalyst 14 is, for example, iron (Fe) or fine solid particles containing iron as a main component, i.e., metal particles. The inside of the reactor 12, and therefore the catalyst 14, are heated to a predetermined reaction temperature by a heating device. The heating device is, for example, a heater or a jacket through which exhaust gas or steam flows.

[0012] An inlet pipe 15 is connected to the lower end of the reactor 12. The inlet pipe 15 penetrates the lower end of the pressure vessel 11. The inlet pipe 15 is a gas flow path for introducing a raw material gas into the reactor 12. The raw material gas is a hydrocarbon gas. The hydrocarbon gas is, for example, methane or a gas containing methane as a main component. The hydrocarbon gas is decomposed into hydrogen and carbon by coming into contact with the catalyst 14 inside the reactor 12. The carbon is in powder form.

[0013] An outlet pipe 16 is connected to the upper end of the reactor 12. The outlet pipe 16 passes through the upper end of the pressure vessel 11. The outlet pipe 16 is a gas flow path for discharging the produced gas to the outside of the reactor 12. The produced gas is a gas produced inside the reactor 12, and is a mixed gas of hydrogen produced by thermal decomposition and unreacted hydrocarbons.

[0014] The raw material gas is supplied to the reaction chamber 12A via the airflow chamber 12B and the disperser 13. The raw material gas is rectified and diffused by the disperser 13. This allows the raw material gas to flow uniformly into the reaction chamber 12A from below. When the raw material gas is blown into the reaction chamber 12A from below, the catalyst 14, which is a solid particle, is suspended to a certain height and moves around vigorously. In other words, a fluidized bed, which is a layer of catalyst 14 that moves around vigorously, is formed. The fluidization of the catalyst 14 results in a good mixture of the catalyst 14 and the raw material gas. This promotes contact between the raw material gas and the catalyst 14. Therefore, the thermal decomposition reaction of the raw material gas by the catalyst 14 is promoted.

[0015] The reactor 12 is a fluidized bed reaction vessel. The catalyst 14 is a fluidizing medium. The raw material gas is a fluidizing gas for fluidizing the catalyst 14. <Reaction Temperature> When hydrogen is produced, the inside of the reactor 12, and therefore the catalyst 14, is heated to a predetermined reaction temperature. The reaction temperature is a temperature at which the thermal decomposition reaction of the raw material gas by the catalyst 14 proceeds efficiently. The reaction temperature is set to a value within a predetermined temperature range depending on product specifications, etc. The lower limit of the temperature range is set, for example, based on the starting temperature of thermal decomposition. The upper limit of the temperature range is set, for example, based on the heat resistance of the reactor 12.

[0016] If the reaction temperature is below the lower limit of the temperature range, the thermal decomposition reaction of the raw material gas may not proceed. This is because the reaction temperature is lower than the starting temperature of thermal decomposition, and the function of the catalyst 14 to decompose the raw material gas is not activated. The higher the reaction temperature, the more the thermal decomposition of the raw material gas proceeds. However, if the reaction temperature exceeds the upper limit of the temperature range, the reliability of the reactor 12 may not be ensured.

[0017] <Relationship Between Pressure in Reactor 12 and Amount of Hydrogen Generated> Next, the relationship between the pressure in the reactor 12 and the amount of hydrogen generated will be described. The pressure is the pressure inside the reactor 12. The pressure inside the reactor 12 is a pressure that corresponds to the pressure of the raw material gas supplied into the reactor 12. Here, the case where the raw material gas is methane will be described as an example.

[0018] The thermal decomposition reaction of methane is represented by the following formula (1): CH４ +90kJ / mol→2H ２ +C (1) Furthermore, when the methane thermal decomposition is in a reaction equilibrium state, the following formula (2) holds regardless of the pressure in the reactor 12.

[0019] P Ｈ２ ２ / P ＣＨ４ = constant ... (2) However, "P Ｈ２ ２ " is the partial pressure of hydrogen inside the reactor 12, and is a pressure that depends on the amount of hydrogen generated. ＣＨ４ " is the partial pressure of methane inside the reactor 12, which is a pressure that depends on the pressure of the methane fed to the reactor 12. " / " indicates division.

[0020] If the pressure in the reactor 12, i.e., the methane supply pressure, is increased fourfold, it would appear at first glance that the methane partial pressure and the hydrogen partial pressure would also increase fourfold. However, according to equation (2), the hydrogen partial pressure would actually double. In other words, the amount of hydrogen generated would be halved compared to before the pressure increase.

[0021] In this way, when the pressure in the reactor 12, i.e., the methane supply pressure, is increased, the amount of hydrogen generated in the reaction equilibrium becomes less than before the pressure was increased. In other words, the methane conversion rate decreases. The conversion rate is the degree of the thermal decomposition reaction in the reactor 12 and indicates the rate of conversion of the raw material gas, methane, to hydrogen. The pressure in the reactor 12, i.e., the methane supply pressure, is set according to product specifications, etc.

[0022] <Regarding supply and discharge of catalyst 14> During operation of the hydrogen production device 10, the activity of the catalyst 14 gradually decreases as the thermal decomposition reaction progresses. Therefore, in order to maintain the decomposition rate of the raw material gas, it is necessary to supply new catalyst 14 to the reactor 12 and remove catalyst 14 with reduced activity from the reactor 12. Catalyst 14 with reduced activity includes deactivated catalyst 14. Deactivation occurs when the catalyst 14 loses its activity and no longer causes the thermal decomposition reaction of the raw material gas. The decomposition rate is the rate at which the raw material gas is decomposed over a certain period of time by the action of the catalyst 14.

[0023] The catalyst 14 with reduced activity has smaller particle size and density than new catalyst 14. The reduced particle size and particle density of the catalyst 14 cause the terminal velocity to be equal to or less than the superficial velocity. Therefore, the catalyst 14 with reduced activity is basically discharged from the reactor 12 to the outside of the reactor 12 via the discharge pipe 16 together with the product gas. The superficial velocity is the flow velocity of the feed gas calculated assuming that the catalyst 14, which is a packed particle, is not present in the reactor 12. The terminal velocity is the velocity at which the drag force of the feed gas, which applies an upward force to the particles, and the gravity, which applies a downward force to the particles, are balanced.

[0024] However, some of the catalyst 14 with reduced activity binds with carbon generated by thermal decomposition of the raw material gas and remains inside the reactor 12. This is because the particle size or particle density of the catalyst 14 with reduced activity increases as a result of binding with the generated carbon. For this reason, it is necessary to discharge the catalyst 14 with reduced activity to the outside of the reactor 12. Therefore, in this embodiment, the following configuration is adopted as the hydrogen production device 10.

[0025] 1, the hydrogen production apparatus 10 has a supply device 21 for supplying new catalyst 14 to the reactor 12. The supply device 21 is, for example, a lock hopper system.

[0026] The supply device 21 is provided on a first supply line 22A. The first supply line 22A is a line for supplying new catalyst 14 to the reactor 12 and is formed, for example, by piping. The first supply line 22A passes through the lower end of the pressure vessel 11 and is connected to the lower end of the reactor 12.

[0027] The supply device 21 has a receiving hopper 23, an intermediate hopper 24, and a supply hopper 25. The supply hopper 25, the intermediate hopper 24, and the receiving hopper 23 are arranged in this order from the side closest to the reactor 12. The intermediate hopper 24 is located between the receiving hopper 23 and the supply hopper 25. The hoppers are devices for temporarily storing new catalyst 14.

[0028] The receiving hopper 23 receives new catalyst 14 supplied from the outside and temporarily stores the received new catalyst 14. The pressure in the receiving hopper 23 is maintained at atmospheric pressure, for example.

[0029] A pressure adjustment pipe is connected to the intermediate hopper 24 via a valve. By introducing high-pressure gas into the intermediate hopper 24 via the pipe, it is possible to increase the pressure inside the intermediate hopper 24 to a pressure higher than atmospheric pressure. In addition, by releasing the pressure inside the intermediate hopper 24 via the pipe, it is possible to reduce the pressure inside the intermediate hopper 24 to atmospheric pressure. The high-pressure gas is an inert gas such as nitrogen or argon.

[0030] The pressure in the supply hopper 25 is always maintained higher than the pressure in the reactor 12. This is to suppress backflow of the catalyst 14, for example. A first gate valve 26 is provided in the first supply path 22A between the receiving hopper 23 and the intermediate hopper 24. The first gate valve 26 opens and closes the first supply path 22A between the receiving hopper 23 and the intermediate hopper 24.

[0031] A second gate valve 27 is provided in the first supply path 22A between the intermediate hopper 24 and the supply hopper 25. The second gate valve 27 opens and closes the first supply path 22A between the intermediate hopper 24 and the supply hopper 25.

[0032] A third gate valve 28 and a first electric valve 29 are provided on first supply path 22A between supply hopper 25 and reactor 12. Third gate valve 28 is provided on first supply path 22A between supply hopper 25 and first electric valve 29. Third gate valve 28 opens and closes first supply path 22A between supply hopper 25 and first electric valve 29.

[0033] The first electric valve 29 is, for example, a rotary valve. The first electric valve 29 has a motor and a rotor that is rotated by the motor. By controlling the rotation speed of the rotor, it is possible to control the amount of catalyst 14, which is a fine solid particle, discharged.

[0034] A second supply line 22B is connected to the first supply line 22A between the first motor-operated valve 29 and the reactor 12. The second supply line 22B is a line for supplying a carrier gas to the first supply line 22A between the first motor-operated valve 29 and the reactor 12, and is formed, for example, by piping. The carrier gas is a gas for transporting the catalyst 14 in the first supply line 22A between the first motor-operated valve 29 and the reactor 12 into the reactor 12, and is, for example, an inert gas such as nitrogen or argon. The catalyst 14 moves with the flow of the carrier gas.

[0035] 1 , the hydrogen production apparatus 10 has an extraction device 31 for extracting the catalyst 14 with reduced activity from the reactor 12. The extraction device 31 is provided in an extraction path 32 for the catalyst 14. The extraction path 32 is a path for extracting the catalyst 14 with reduced activity to the outside of the reactor 12, and is formed, for example, by piping. A first end of the extraction path 32 is connected to a portion of the reactor 12 that corresponds to an upper portion of the fluidized bed of the catalyst 14. The upper portion is a portion of the fluidized bed that is farther from the distributor 13 in the axial direction of the reactor 12.

[0036] The discharge device 31 has a cooler 33, a second electric valve 34, and a discharge hopper 35. The cooler 33, the second electric valve 34, and the discharge hopper 35 are arranged in this order from the side closest to the reactor 12. The second electric valve 34 is located between the cooler 33 and the discharge hopper 35. The discharge hopper 35 is connected to a second end of the discharge path 32. The second end is an end of the discharge path 32 opposite to the first end.

[0037] The cooler 33 cools the catalyst 14 with reduced activity that is extracted from the reactor 12. The second electric valve 34 is, for example, a rotary valve. The second electric valve 34 has a motor and a rotor that is rotated by the motor. By controlling the rotation speed of the rotor, it is possible to control the amount of catalyst 14, which is a fine solid particle, that is discharged. The extraction hopper 35 continuously extracts the catalyst 14 with reduced activity and temporarily stores the extracted catalyst 14.

[0038] <Electrical Configuration of the Hydrogen Production Device 10> Next, a description will be given of the electrical configuration of the hydrogen production device 10. As shown in Fig. 2, the hydrogen production device 10 has a first temperature sensor 41, a second temperature sensor 42, a differential pressure sensor 43, a concentration sensor 44, and a control device 45.

[0039] The first temperature sensor 41 is provided in the reactor 12. The first temperature sensor 41 detects a first temperature T1 of the fluidized bed of the catalyst 14. The first temperature T1 is the temperature of the upper part of the fluidized bed.

[0040] The second temperature sensor 42 is provided in the reactor 12. The second temperature sensor 42 detects a second temperature T2 of the fluidized bed of the catalyst 14. The second temperature T2 is the temperature of the lower part of the fluidized bed.

[0041] The differential pressure sensor 43 is provided in the reactor 12. The differential pressure sensor 43 detects the pressure difference ΔP between the upper part of the reaction chamber 12A and the lower part of the reaction chamber 12A. The upper part of the reaction chamber 12A is an empty part of the reactor 12 that is outside the fluidized bed of the catalyst 14. The lower part of the reaction chamber 12A is a part of the reactor 12 that corresponds to the fluidized bed of the catalyst 14, for example, a part that corresponds directly above the disperser 13.

[0042] The concentration sensor 44 is provided in the outlet pipe 16. The concentration sensor 44 detects the concentration M of hydrogen in the product gas generated by thermal decomposition of the raw material gas. The control device 45 has a processing circuit including any one of the following three configurations A1, A2, and A3.

[0043] A1. One or more processors that operate according to a computer program, which is software. A processor includes a CPU (central processing unit) and memory. A2. One or more dedicated hardware circuits, such as an application specific integrated circuit (ASIC), that perform at least some of the various processes. An ASIC includes a CPU and memory.

[0044] A3. A hardware circuit that combines configurations A1 and A2. The memory is a medium that can be read by a computer (here, the CPU) and stores a program that describes processes or instructions for the computer. The memory includes RAM (random access memory) and ROM (read only memory). The CPU performs various controls by executing the program stored in the memory at a set calculation cycle.

[0045] The control device 45 controls the operations of the supply device 21 and the withdrawal device 31. The control device 45 controls the supply of new catalyst 14 to the reactor 12 through the supply device 21 based on, for example, the detection results of the various sensors (41 to 44). The control device 45 controls the withdrawal of catalyst 14 with reduced activity from the reactor 12 through the withdrawal device 31 based on, for example, the detection results of the various sensors (41 to 44).

[0046] <Catalyst 14 Supply Process> When supplying catalyst 14 to reactor 12, the control device 45 controls the supply device 21 as follows. That is, the control device 45 first opens the first gate valve 26. As a result, new catalyst 14 stored in the receiving hopper 23 moves by gravity to the intermediate hopper 24. After moving a predetermined amount of catalyst 14, the control device 45 closes the first gate valve 26.

[0047] Next, the control device 45 introduces high-pressure gas into the intermediate hopper 24 through the pressure adjustment pipe. As a result, the pressure inside the intermediate hopper 24 is increased to the same level as the pressure in the supply hopper 25. The pressure in the supply hopper 25 is maintained at a pressure equal to or higher than the pressure in the reactor 12. Thereafter, the control device 45 opens the second gate valve 27. As a result, the catalyst 14 in the intermediate hopper 24 is discharged into the supply hopper 25.

[0048] After the catalyst 14 has been completely dispensed into the supply hopper 25, the control device 45 closes the second gate valve 27 and releases the gas in the intermediate hopper 24 through a pressure adjustment pipe, thereby reducing the pressure inside the intermediate hopper 24 to atmospheric pressure. This makes it possible for the intermediate hopper 24 to receive the catalyst 14 from the receiving hopper 23 again.

[0049] Next, the control device 45 opens the third gate valve 28. As a result, the catalyst 14 in the supply hopper 25 is dispensed into the first motor-operated valve 29. The control device 45 controls the first motor-operated valve 29 so that a fixed amount of catalyst 14 is continuously discharged from the first motor-operated valve 29. The catalyst 14 discharged from the first motor-operated valve 29 is supplied to the reactor 12 by air current transport. That is, the catalyst 14 discharged from the first motor-operated valve 29 merges with the carrier gas at the connection portion between the first supply path 22A and the second supply path 22B and is supplied to the reactor 12 together with the carrier gas. The control device 45 opens the first gate valve 26 while the catalyst 14 is being supplied to the reactor 12. The intermediate hopper 24 receives the catalyst 14 again from the receiving hopper 23.

[0050] When the amount of catalyst 14 in supply hopper 25 decreases to near the lower limit, control device 45 closes first gate valve 26 and introduces high-pressure gas into intermediate hopper 24 through pressure adjustment piping. This increases the pressure inside intermediate hopper 24 to the same level as the pressure in supply hopper 25. Thereafter, control device 45 opens second gate valve 27. This causes catalyst 14 in intermediate hopper 24 to be dispensed into supply hopper 25.

[0051] After the control device 45 has completed dispensing of the catalyst 14 to the supply hopper 25, it closes the second gate valve 27 and releases the gas in the intermediate hopper 24 through a pressure adjustment pipe, thereby reducing the pressure inside the intermediate hopper 24 to atmospheric pressure. When the pressure inside the intermediate hopper 24 becomes approximately the same as atmospheric pressure, i.e., the pressure in the receiving hopper 23, the control device 45 opens the first gate valve 26. This allows the intermediate hopper 24 to again receive catalyst 14 from the receiving hopper 23.

[0052] The control device 45 repeatedly executes the above process to continuously supply the catalyst 14 to the reactor 12. The catalyst 14 is supplied to the reactor 12 by being transported by the carrier gas.

[0053] <Process for withdrawing catalyst 14 from reactor 12> When withdrawing catalyst 14 from reactor 12, the control device 45 controls the withdrawing device 31 as follows. That is, the control device 45 activates the cooler 33 and the second electric valve 34. As a result, the catalyst 14 with reduced activity is withdrawn from the reactor 12. The withdrawn catalyst 14 is cooled by the cooler 33. The cooled catalyst 14 is sent to the withdrawing hopper 35 by the second electric valve 34.

[0054] The control device 45 may execute the catalyst 14 extraction process and the catalyst 14 supply process at the same timing. In this case, the amount of catalyst 14 discharged may be the same as the amount of catalyst 14 supplied by the supply device 21, for example. The catalyst 14 discharge rate may also be the same as the catalyst 14 supply rate by the supply device 21. In this way, fluctuations in the height of the catalyst layer are gradual, and it is easier to maintain a uniform catalyst layer. Depending on product specifications, the control device 45 may execute the catalyst 14 extraction process and the catalyst 14 supply process at different times.

[0055] <Control of the Decomposition Rate of the Raw Material Gas> As shown in the above formula (1), the thermal decomposition reaction of the raw material gas is an endothermic reaction. An endothermic reaction is a reaction that involves the absorption of heat. Therefore, as the thermal decomposition reaction of the raw material gas progresses, heat is removed from the fluidized bed. If the temperature of the fluidized bed decreases, the thermal decomposition reaction of the raw material gas progresses accordingly. If the catalyst 14 is deactivated, heat is no longer removed from the fluidized bed. Therefore, the temperature of the fluidized bed tends to rise. Furthermore, the higher the concentration of hydrogen in the product gas generated by the thermal decomposition of the raw material gas, the more the thermal decomposition reaction of the raw material gas progresses. Therefore, it is possible to determine the degree of progress of the thermal decomposition reaction of the raw material gas based on the first temperature T1 of the fluidized bed, the second temperature T2 of the fluidized bed, and the hydrogen concentration M in the product gas.

[0056] The pressure difference ΔP between the upper and lower portions of the reaction chamber 12A is determined by the weight of the catalyst 14, which is a solid particle forming the fluidized bed, and the cross-sectional area of ​​the reactor 12. The cross-sectional area of ​​the reactor 12 is equal to the cross-sectional area of ​​the fluidized bed. The pressure difference ΔP changes depending on the progress of the thermal decomposition reaction of the raw material gas. This is because the weight of the catalyst 14, which is a solid particle forming the fluidized bed, changes depending on the progress of the thermal decomposition reaction of the raw material gas. The catalyst 14 particles are crushed as the raw material gas molecules diffuse into the particles and hydrogen and carbon are generated by the decomposition of the raw material gas. Therefore, as the thermal decomposition reaction of the raw material gas progresses, the particle size of the catalyst 14 decreases. As a result, the decomposition rate of the raw material gas changes, and the pressure difference ΔP also changes. In other words, the decomposition rate of the raw material gas can be controlled by controlling the pressure difference ΔP. Controlling the decomposition rate of the raw material gas also controls the conversion rate of the raw material gas.

[0057] The control device 45 controls the amount of fresh catalyst 14 supplied to the reactor 12 and the amount of catalyst 14 with reduced activity discharged from the reactor 12 so that the pressure difference ΔP detected by the differential pressure sensor 43 remains constant. The target pressure difference ΔP is, for example, the pressure difference at which the decomposition rate of the raw material gas is optimized. The optimal decomposition rate is determined by product specifications, etc.

[0058] The control device 45 executes feedback control of the pressure difference ΔP so that the pressure difference ΔP detected by the differential pressure sensor 43 matches the target pressure difference. The feedback control is, for example, PID control, which includes proportional control, integral control, and derivative control. The control device 45 calculates a target operation amount of the first electric valve 29 and a target operation amount of the second electric valve 34 through the execution of feedback control of the pressure difference ΔP. The target operation amount of the first electric valve 29 is the target supply amount of the catalyst 14 by the supply device 21. The target operation amount of the second electric valve 34 is the target discharge amount of the catalyst 14 by the withdrawal device 31.

[0059] When the pressure difference ΔP deviates from the target pressure difference, the control device 45 controls the operation of the first motor-operated valve 29 and the second motor-operated valve 34 so as to make the pressure difference ΔP match the target pressure difference. Controlling the operation of the first motor-operated valve 29 controls the amount of catalyst 14 supplied to the reactor 12. Controlling the operation of the second motor-operated valve 34 controls the amount of catalyst 14 discharged from the reactor 12. The control device 45 controls the operation of the first motor-operated valve 29 so that a target amount of catalyst 14 is supplied to the reactor 12. The control device 45 controls the operation of the second motor-operated valve 34 so that a target amount of catalyst 14 is discharged from the reactor 12.

[0060] The control device 45 calculates a target pressure difference. The control device 45 calculates the difference between the target conversion rate of the raw material gas and the measured conversion rate, and executes feedback control of the conversion rate to eliminate the calculated difference. The target conversion rate is a target value of the conversion rate required according to product specifications, etc., and is stored in memory. The feedback control is, for example, PID control, which includes proportional control, integral control, and differential control. The control device 45 calculates the target pressure difference through the execution of feedback control of the conversion rate.

[0061] However, when the hydrogen production device 10 is started up, the control device 45 performs feedback control of the pressure difference ΔP using the initial value of the target pressure difference stored in memory. The initial value is a target value of the pressure difference ΔP that is set according to the pressure of the reactor 12, which is determined by product specifications, etc., and the temperature inside the reactor 12. The control device 45 controls the amount of catalyst 14 supplied to the reactor 12 and the amount of catalyst 14 discharged from the reactor 12 so that the pressure difference ΔP matches the initial value.

[0062] After the pressure difference ΔP reaches the initial value of the target pressure difference, the control device 45 performs feedback control of the pressure difference ΔP using the target pressure difference calculated through the execution of feedback control of the conversion rate. The control device 45 controls the supply amount of the catalyst 14 to the reactor 12 and the discharge amount of the catalyst 14 from the reactor 12 so that the pressure difference ΔP matches the target pressure difference based on the feedback control of the conversion rate.

[0063] <Method of Calculating Conversion Rate> The control device 45 calculates the conversion rate of the raw material gas by one of the following three calculation methods: The raw material gas is, for example, methane.

[0064] The first calculation method is as follows. That is, the methane conversion rate α is expressed by the following formula (3). The control device 45 calculates the methane conversion rate α using the following formula (3): α=(G1 ｉｎ -G1 ｏｕｔ ) / G1 ｉｎ = (1 / 2) × (G2 ｏｕｔ -G2 ｉｎ ) / G1 ｉｎ ... (3) However, "G1 ｉｎ " is the volumetric flow rate, or number of moles, of methane introduced into the reactor 12. ｏｕｔ " is the volumetric flow rate or number of moles of methane discharged from the reactor 12 to the outside. "G2 ｉｎ " is the volumetric flow rate, or number of moles, of hydrogen introduced into the reactor 12. "G2 ｏｕｔ " is the volumetric flow rate, or number of moles, of hydrogen leaving the reactor 12.

[0065] Since the hydrogen production device 10 is a single-stage type, no hydrogen is supplied to the reactor 12. In other words, the hydrogen concentration at the inlet of the reactor 12 is 0%. A single-stage type is a type having one reactor 12. For this reason, it is possible to determine the methane conversion rate α by analyzing the hydrogen concentration at the outlet of the reactor 12, i.e., the hydrogen concentration in the product gas discharged to the outside of the reactor 12 via the discharge pipe 16. " / " indicates division.

[0066] The second calculation method is as follows. That is, as shown in the above formula (1), the thermal decomposition reaction of methane is an endothermic reaction. Therefore, when the raw material gas is preheated to a predetermined temperature, i.e., when the raw material gas is not heated in the reactor 12, the control device 45 can calculate the methane conversion rate α based on the difference between the first temperature T1 detected by the first temperature sensor 41 and the second temperature T2 detected by the second temperature sensor 42.

[0067] The third calculation method is as follows: In other words, when the raw material gas is heated in the reactor 12 and the inside of the reactor 12 is maintained at a constant temperature, if the amount of heat inside the reactor 12 can be measured, the control device 45 can calculate the methane conversion rate α using the following equation (4):

[0068] Q1 / Q2 (4) where "Q1" is the amount of heat generated inside the reactor 12. "Q2" is the amount of heat absorbed in the thermal decomposition reaction of methane. In the above formula (1), the amount of heat absorbed Q2 is 90 kJ / mol.

[0069] The amount of heat generated by the reactor 12 can be calculated based on, for example, the amount of heat generated by a heating device that heats the inside of the reactor 12. For example, if the heating device is a heater, the amount of heat generated by the reactor 12 can be calculated based on the amount of heat generated by the heater per unit time. If the heating device is a jacket through which exhaust gas or steam flows, the amount of heat generated by the reactor 12 can be calculated based on the amount of exhaust gas or steam supplied to the jacket.

[0070] As shown in the graph of FIG. 3 , when the methane thermal decomposition reaction does not reach equilibrium, i.e., when the height of the catalyst layer is not sufficiently high, the methane conversion rate α depends not only on the temperature and pressure of the reactor 12 but also on the height of the catalyst layer. The height of the catalyst layer is measured relative to the disperser 13. As the height of the catalyst layer increases, the methane conversion rate α gradually increases. After the height of the catalyst layer reaches a predetermined height, the conversion rate α remains constant regardless of the increase in the height of the catalyst layer. The height of the catalyst layer is proportional to the residence time of the feed gas in the catalyst layer. The height of the catalyst layer is also proportional to the reciprocal of the GHSV (Gaseous Hourly Space Velocity). GHSV is the reciprocal of the time that the feed gas passes through the catalyst under standard conditions of 1 atm and 0°C, and is one indicator of the catalyst passing speed in the reactor 12.

[0071] Depending on the product specifications, a target range of the pressure difference ΔP may be set instead of the target pressure difference. The target range is the range of the pressure difference ΔP that is allowable in the product specifications and is defined by an upper limit and a lower limit of the pressure difference ΔP. When the pressure difference ΔP is outside the target range, the control device 45 controls the operation of the first electric valve 29 and the second electric valve 34 so that the pressure difference ΔP falls within the target range.

[0072] Effects of the Embodiment The present embodiment has the following effects. (1) The control device 45 controls the operation of the supply device 21 and the withdrawal device 31 so that the pressure difference ΔP detected by the differential pressure sensor 43 is constant. That is, the control device 45 controls the amount of fresh catalyst 14 supplied to the reactor 12 and the amount of catalyst 14 with reduced activity discharged from the reactor 12 so that the pressure difference ΔP is constant. With this configuration, the pressure difference ΔP is maintained constant, thereby maintaining the decomposition rate of the raw material gas. Therefore, hydrogen can be produced stably.

[0073] (2) The control device 45 performs feedback control of the pressure difference ΔP using the target pressure difference calculated through the execution of feedback control of the conversion rate α. That is, the control device 45 controls the supply amount of catalyst 14 to the reactor 12 and the discharge amount of catalyst 14 from the reactor 12 so that the pressure difference ΔP detected by the differential pressure sensor 43 matches the target pressure difference. This makes it possible to make the conversion rate α of the feed gas follow the target conversion rate. In addition, it is possible to maintain the decomposition rate of the feed gas at a decomposition rate corresponding to the target conversion rate.

[0074] (3) The control device 45 can calculate the conversion rate α of the raw material gas based on the difference between the first temperature T1 detected by the first temperature sensor 41 and the second temperature T2 detected by the second temperature sensor 42. This calculation method is suitable when the raw material gas heated to a predetermined temperature is supplied to the reactor 12.

[0075] (4) The control device 45 can calculate the conversion rate α of the raw material gas based on the hydrogen concentration M detected by the concentration sensor 44. This calculation method is suitable for a single-stage hydrogen production device 10 in which hydrogen is not supplied to the reactor 12.

[0076] (5) The control device 45 can calculate the conversion rate α of the raw material gas based on the amount of heat Q1 inside the reactor 12 and the amount of heat Q2 absorbed in the thermal decomposition reaction of the raw material gas. This calculation method is suitable for cases where the raw material gas is heated in the reactor 12 and the inside of the reactor 12 is maintained at a constant temperature. The control device 45 can calculate the amount of heat of the reactor 12 based on the amount of heat generated by a heating device that heats the inside of the reactor 12, for example.

[0077] (6) The pressure in the reactor 12 is higher than atmospheric pressure. The supply device 21 pressurizes new catalyst 14 to a pressure equal to or higher than the pressure in the reactor 12 and continuously transports it by airflow. With this configuration, new catalyst 14 can be supplied to the reactor 12 by airflow transport.

[0078] (7) The catalyst 14 with reduced activity is discharged from the reactor 12 by the discharge device 31. This prevents carbon generated by thermal decomposition of the raw material gas from binding with the catalyst 14 with reduced activity and remaining inside the reactor 12.

[0079] Other Embodiments This embodiment may be modified as follows: The raw material gas may be used as the carrier gas. In this way, new catalyst 14 can be supplied to the reactor 12 by utilizing the flow of the raw material gas.

[0080] The catalyst 14 may be mixed with a fluidizing material. The fluidizing material is intended to increase the fluidity of the catalyst 14. The fluidizing material is fine solid particles, such as inert particles of silicon. The catalyst 14 is, for example, fine metal particles of iron or iron-based particles. Therefore, if only the catalyst 14 is contained in the reactor 12, the following concerns arise. That is, when the hydrogen production device 10 is started up, the catalyst 14 may fuse together as the temperature of the reactor 12 rises, which may hinder the flow of the catalyst 14. By mixing a fluidizing material into the catalyst layer, the fusion of the catalyst 14 can be suppressed. Therefore, the catalyst 14 flows stably.

[0081] The pressure in the reactor 12 may be maintained at atmospheric pressure. In this case, the hydrogen production device 10 may have a configuration in which the pressure vessel 11 is omitted. The lower the pressure in the reactor 12, the higher the methane conversion rate.

[0082] 1, when the pressure in the reactor 12 and the pressure in the supply hopper 25 are equal, the catalyst 14 may be supplied to the reactor 12 by gravity. The pressure may be, for example, atmospheric pressure. In this case, the supply hopper 25 is connected to the upper part of the reactor 12 via, for example, a third gate valve 28 and a first electric valve 29.

[0083] The catalyst 14 may be metals such as nickel and cobalt, or fine metal particles primarily composed of these metals. As used herein, the terms "cylinder" or "cylindrical" may refer to any structure having a peripheral wall. For example, but not limited to, the terms "cylinder" or "cylindrical" may refer to any structure having a cross-sectional shape that is circular, oval, or polygonal with sharp or rounded corners.

[0084] <Additional Notes> The hydrogen production device described in this embodiment can be understood, for example, as follows: 1. A hydrogen production device (10) according to a first aspect has a reactor (12) that produces hydrogen by thermally decomposing a hydrocarbon gas, which is a raw material gas, using a catalyst (14), and has the reactor (12) into which a fluidized bed of the catalyst (14) is formed by introducing the raw material gas from the bottom. The hydrogen production apparatus (10) includes a differential pressure sensor (43) configured to detect a pressure difference (ΔP) between an upper part of the reactor (12) separated from the fluidized bed and a lower part of the reactor (12) corresponding to the fluidized bed, a supply device (21) configured to supply new catalyst (14) to the reactor (12), an extraction device (31) configured to extract the catalyst (14) with reduced activity from the reactor (12), and a control device (45) configured to control the operation of the supply device (21) and the extraction device (31) so that the pressure difference (ΔP) detected by the differential pressure sensor (43) is constant.

[0085] According to the hydrogen production device of the first aspect, the pressure difference detected by the differential pressure sensor is maintained constant, thereby maintaining the decomposition rate of the source gas, thereby enabling stable production of hydrogen.

[0086] 2. A hydrogen production apparatus (10) according to a second aspect is the hydrogen production apparatus (10) according to the first aspect, wherein the control device (45) is configured to execute the following processes: a process of calculating a conversion rate (α) of the raw material gas based on state variables (T1, T2, M, Q1) of the reactor (12); a process of calculating a target pressure difference, which is a target value of the pressure difference (ΔP), through execution of feedback control of the conversion rate (α) so that the calculated conversion rate (α) follows a predetermined target conversion rate; and a process of calculating a target supply amount of the catalyst (14) by the supply device (21) and a target discharge amount of the catalyst (14) by the withdrawal device (31) through execution of feedback control of the pressure difference (ΔP) so that the pressure difference (ΔP) detected by the differential pressure sensor (43) follows the target pressure difference.

[0087] According to the hydrogen production device of the second aspect, feedback control of the pressure difference is performed using the target pressure difference calculated through the execution of feedback control of the conversion rate. That is, the amount of catalyst supplied to the reactor and the amount of catalyst discharged from the reactor are controlled so that the pressure difference detected by the differential pressure sensor matches the target pressure difference. This allows the conversion rate of the feed gas to track the target conversion rate. Furthermore, the decomposition rate of the feed gas can be maintained at a decomposition rate corresponding to the target conversion rate.

[0088] 3. A hydrogen production device (10) according to a third aspect is the hydrogen production device (10) according to the second aspect, further comprising a first temperature sensor (41) for detecting a first temperature (T1) that is the temperature of an upper portion of the fluidized bed, and a second temperature sensor (42) for detecting a second temperature (T2) that is the temperature of a lower portion of the fluidized bed. The control device (45) is configured to calculate a conversion rate (α) of the raw material gas based on the difference between the first temperature (T1) detected by the first temperature sensor (41) and the second temperature (T2) detected by the second temperature sensor (42).

[0089] According to the hydrogen production device of the third aspect, the conversion rate of the feed gas can be calculated based on the difference between the first temperature detected by the first temperature sensor and the second temperature detected by the second temperature sensor. This calculation method is suitable when the feed gas heated to a predetermined temperature is supplied to the reactor.

[0090] 4. A hydrogen production device (10) according to a fourth aspect is the hydrogen production device (10) according to the second aspect, further comprising a concentration sensor (44) for detecting a hydrogen concentration (M) in the product gas, which is generated by thermal decomposition of the raw material gas and discharged to the outside from the reactor (12). The control device (45) is configured to calculate a conversion rate (α) of the raw material gas based on the hydrogen concentration (M) detected by the concentration sensor (44).

[0091] According to the hydrogen production device of the fourth aspect, the conversion rate of the feed gas can be calculated based on the hydrogen concentration detected by the concentration sensor. This calculation method is suitable for a single-stage hydrogen production device in which hydrogen is not supplied to the reactor.

[0092] 5. A hydrogen production apparatus (10) according to a fifth aspect is the hydrogen production apparatus (10) according to the second aspect, wherein the control device (45) is configured to calculate a conversion rate (α) of the raw material gas based on an amount of heat (Q1) inside the reactor (12) and an amount of heat absorbed in a thermal decomposition reaction of the raw material gas (Q2).

[0093] According to the hydrogen production device of the fifth aspect, the conversion rate of the raw material gas can be calculated based on the amount of heat inside the reactor and the amount of heat absorbed in the thermal decomposition reaction of the raw material gas. This calculation method is suitable for cases where the raw material gas is heated in the reactor and the inside of the reactor is maintained at a constant temperature.

[0094] 6. A hydrogen production device (10) according to a sixth aspect is the hydrogen production device (10) according to any one of the first to fifth aspects, wherein the pressure in the reactor (12) is higher than atmospheric pressure, and the supply device (21) pressurizes new catalyst (14) to a pressure equal to or higher than the pressure in the reactor (12) and continuously transports it in a gas stream.

[0095] According to the hydrogen production device of the sixth aspect, a new catalyst can be supplied to the reactor by gas flow transport. 7. The hydrogen production device (10) of the seventh aspect is the hydrogen production device (10) of the sixth aspect, in which the carrier gas used for the gas flow transport is the raw material gas.

[0096] According to the hydrogen production device of the seventh aspect, new catalyst can be supplied to the reactor by utilizing the flow of the raw material gas. 8. The hydrogen production device (10) of the eighth aspect is the hydrogen production device (10) of any one of the first to fifth aspects, in which new catalyst (14) is supplied to the reactor (12) by gravity.

[0097] According to the hydrogen production device of the eighth aspect, new catalyst can be supplied to the reactor by gravity. 9. The hydrogen production device (10) of the ninth aspect is the hydrogen production device (10) of any one of the first to eighth aspects, wherein the catalyst (14) is fine metal particles, and a fluidizing material, which is inert particles, is mixed into the catalyst (14) to increase the fluidity of the catalyst.

[0098] According to the hydrogen production device of the ninth aspect, for example, during start-up of the hydrogen production device, it is possible to prevent the catalysts from fusing together as the temperature of the reactor rises. 10. A hydrogen production method according to the tenth aspect is a hydrogen production method in which a reactor (12) that produces hydrogen by thermally decomposing a hydrocarbon gas, which is a raw material gas, using a catalyst (14) is introduced from a lower part of the reactor (12) to form a fluidized bed of the catalyst (14) inside the reactor (12), and the supply of new catalyst (14) to the reactor (12) and the extraction of catalyst (14) with reduced activity from the reactor (12) are controlled so that a pressure difference (ΔP) between an upper part of the reactor (12) outside the fluidized bed and a lower part of the reactor (12) corresponding to the fluidized bed is constant.

[0099] According to the hydrogen production method of the tenth aspect, the pressure difference between the upper part of the reactor outside the fluidized bed and the lower part of the reactor corresponding to the fluidized bed is maintained constant, thereby maintaining the decomposition rate of the raw material gas and enabling stable production of hydrogen.

[0100] 11. A hydrogen production program according to an eleventh aspect is a hydrogen production program that causes a computer to execute a process for forming a fluidized bed of the catalyst (14) inside a reactor (12) that produces hydrogen by thermally decomposing a hydrocarbon gas, which is a raw material gas, using a catalyst (14), by introducing the raw material gas from the lower part of the reactor (12), and the hydrogen production program includes a step of controlling the supply of new catalyst (14) to the reactor (12) and the extraction of catalyst (14) with reduced activity from the reactor (12) so that the pressure difference (ΔP) between an upper part of the reactor (12) that is outside the fluidized bed and a lower part of the reactor (12) that corresponds to the fluidized bed is constant.

[0101] According to the hydrogen production program of the eleventh aspect, the pressure difference between the upper part of the reactor outside the fluidized bed and the lower part of the reactor corresponding to the fluidized bed is maintained constant, thereby maintaining the decomposition rate of the raw material gas and enabling stable production of hydrogen.

Claims

1. A hydrogen production device having a reactor that produces hydrogen by thermally decomposing a hydrocarbon gas, which is a raw material gas, using a catalyst, and into which a fluidized bed of the catalyst is formed by introducing the raw material gas from a lower part, the hydrogen production device having: a differential pressure sensor configured to detect a pressure difference between an upper part of the reactor that is separated from the fluidized bed and a lower part of the reactor that corresponds to the fluidized bed; a supply device configured to supply new catalyst to the reactor; an extraction device configured to extract the catalyst whose activity has decreased from the reactor; and a control device configured to control the operation of the supply device and the extraction device so that the pressure difference detected by the differential pressure sensor is constant.

2. The hydrogen production apparatus of claim 1, wherein the control device is configured to execute the following processes: a process of calculating a conversion rate of the raw material gas based on state variables of the reactor; a process of calculating a target pressure difference, which is a target value of the pressure difference, through execution of feedback control of the conversion rate so that the calculated conversion rate follows a determined target conversion rate; and a process of calculating a target supply amount of the catalyst by the supply device and a target discharge amount of the catalyst by the extraction device through execution of feedback control of the pressure difference so that the pressure difference detected by the differential pressure sensor follows the target pressure difference.

3. A hydrogen production device as described in claim 2, further comprising a first temperature sensor for detecting a first temperature which is the temperature of an upper portion of the fluidized bed, and a second temperature sensor for detecting a second temperature which is the temperature of a lower portion of the fluidized bed, wherein the control device is configured to calculate a conversion rate of the raw material gas based on a difference between the first temperature detected through the first temperature sensor and the second temperature detected through the second temperature sensor.

4. A hydrogen production device as described in claim 2, further comprising a concentration sensor for detecting the hydrogen concentration in the product gas generated by thermal decomposition of the raw material gas and discharged to the outside from the reactor, and the control device is configured to calculate the conversion rate of the raw material gas based on the hydrogen concentration detected by the concentration sensor.

5. The hydrogen production device according to claim 2, wherein the control device is configured to calculate the conversion rate of the raw material gas based on the amount of heat inside the reactor and the amount of heat absorbed in the thermal decomposition reaction of the raw material gas.

6. The hydrogen production device according to any one of claims 1 to 5, wherein the pressure in the reactor is higher than atmospheric pressure, and the supply device is configured to pressurize new catalyst to a pressure equal to or higher than the pressure in the reactor and continuously transport it in a gas flow.

7. The hydrogen production device according to claim 6, wherein the carrier gas used for transporting the gas flow is the raw material gas.

8. A hydrogen production device according to any one of claims 1 to 5, wherein the new catalyst is supplied to the reactor by gravity drop.

9. A hydrogen production device according to any one of claims 1 to 5, wherein the catalyst is made of fine metal particles, and a fluidizing material, which is inert particles, is mixed into the catalyst to increase the fluidity of the catalyst.

10. A method for producing hydrogen, comprising: introducing a raw material gas from a lower part of a reactor in which hydrogen is produced by thermally decomposing a hydrocarbon gas as a raw material gas using a catalyst, thereby forming a fluidized bed of the catalyst inside the reactor; and controlling the supply of new catalyst to the reactor and the withdrawal of catalyst with reduced activity from the reactor so that a pressure difference between an upper part of the reactor outside the fluidized bed and a lower part of the reactor corresponding to the fluidized bed is constant.

11. A hydrogen production program that causes a computer to execute the following processes: forming a fluidized bed of the catalyst inside a reactor that produces hydrogen by thermally decomposing a hydrocarbon gas, which is a raw material gas, using a catalyst by introducing the raw material gas from the bottom of the reactor; and controlling the supply of new catalyst to the reactor and the removal of catalyst with reduced activity from the reactor so that the pressure difference between the upper part of the reactor outside the fluidized bed and the lower part of the reactor corresponding to the fluidized bed is constant.

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