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

Abstract

The hydrogen production apparatus (10) includes: a reactor (12) that produces hydrogen by thermally decomposing a hydrocarbon gas, which is a raw material gas, using a catalyst, and forming a flow layer of catalyst inside by introducing the raw material gas from the bottom. The hydrogen production apparatus also includes: a differential pressure sensor (43) configured to detect the pressure difference between the upper part of the reactor that has separated from the flow layer and the lower part of the reactor corresponding to the flow layer; a supply device (21) configured to supply new catalyst to the reactor; an extraction device (31) configured to extract catalyst with reduced 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 is constant.

Description

Hydrogen production device, hydrogen production method, and hydrogen production program The present disclosure relates to a hydrogen production device, a hydrogen production method, and a hydrogen production program. Conventionally, a technique for producing hydrogen by thermal decomposition of methane has been known. For example, the hydrogen production device of Patent Document 1 includes a reactor containing a catalyst. Methane is introduced into the interior of the reactor. Methane is decomposed into hydrogen and carbon by contacting the catalyst inside the reactor. A mixed gas of hydrogen as the product gas and unreacted methane is taken out of the reactor. [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2019-73411 [Technical Problem to be Solved by the Invention] For a hydrogen production device, it is required to maintain the decomposition rate of the raw material gas in order to stably produce hydrogen. [Technical Solution for Solving the Problem] A hydrogen production device according to an aspect of the present disclosure includes: a reactor that uses a catalyst to thermally decompose a hydrocarbon gas as a raw material gas to produce hydrogen, and forms a fluidized bed of the catalyst inside by introducing the raw material gas from below. The hydrogen production device includes: a pressure difference sensor configured to detect a pressure difference between an upper part of the reactor from which the fluidized bed is separated and a lower part of the reactor corresponding to the fluidized bed; a supply device configured to supply new catalyst to the reactor; a extraction device configured to extract the catalyst with reduced activity from the reactor; and a control device configured to control the operations of the supply device and the extraction device so that the pressure difference detected by the pressure difference sensor becomes constant. A hydrogen production method according to an aspect of the present disclosure includes: a step of introducing the raw material gas from a lower part of a reactor that uses a catalyst to thermally decompose a hydrocarbon gas as a raw material gas to produce hydrogen to form a fluidized bed of the catalyst inside the reactor; and a step of 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 from which the fluidized bed is separated and a lower part of the reactor corresponding to the fluidized bed becomes constant. A hydrogen production program according to an aspect of the present disclosure causes a computer to execute: a process of introducing the raw material gas from a lower part of a reactor that uses a catalyst to thermally decompose a hydrocarbon gas as a raw material gas to produce hydrogen to form a fluidized bed of the catalyst inside the reactor; and a process of 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 from which the fluidized bed is separated and a lower part of the reactor corresponding to the fluidized bed becomes constant. Next, an embodiment of a hydrogen production device will be described. 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-sectional shape and extend in the vertical direction. The inside of the pressure vessel 11 maintains 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 the same over the entire length. Inside the reactor 12, a distributor 13 is provided. The distributor 13 is, for example, a plate-shaped member that extends in a direction orthogonal to the axial direction of the reactor 12 and has a plurality of holes. The holes penetrate the distributor 13 in the plate thickness direction. The distributor 13 is disposed at a position closer to the lower end portion of the reactor 12 than the central position in the axial direction of the reactor 12. The distributor 13 divides the inside of the reactor 12 into two upper and lower spaces. 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 communicate with each other through the holes of the distributor 13. On the upper surface of the distributor 13, a catalyst 14 is accumulated. That is, inside the reaction chamber 12A, the catalyst 14 is filled to a predetermined accumulation height relative to the distributor 13. The upper surface is the surface of the distributor 13 on the reaction chamber 12A side. The catalyst 14 is, for example, iron (Fe) or fine individual particles having iron as a main component, and is a metal particle. The inside of the reactor 12 and even the catalyst 14 are heated to a predetermined reaction temperature by a heating device. The heating device is, for example, a heater or a sleeve through which exhaust gas or steam flows. The lower end portion of the reactor 12 is connected to an inlet pipe 15. The inlet pipe 15 penetrates the lower end portion of the pressure vessel 11. The inlet pipe 15 is a gas flow path for introducing a raw material gas into the inside of the reactor 12. The raw material gas is a hydrocarbon gas. The hydrocarbon gas is, for example, methane or a gas having methane as a main component. The hydrocarbon gas is decomposed into hydrogen and carbon by contacting the catalyst 14 inside the reactor 12. The carbon is in powder form. At the upper end portion of the reactor 12, an outlet pipe 16 is connected. The outlet pipe 16 penetrates the upper end portion of the pressure vessel 11. The outlet pipe 16 is a gas flow path for discharging the generated gas to the outside of the reactor 12. The generated gas is a gas generated inside the reactor 12 and is a mixed gas of hydrogen generated by thermal decomposition and unreacted hydrocarbon. The raw material gas is supplied to the reaction chamber 12A through the air chamber 12B and the distributor 13. The raw material gas is rectified and diffused by the distributor 13. Thereby, the raw material gas uniformly flows into the reaction chamber 12A from below. By blowing the raw material gas into the reaction chamber 12A from below, the catalyst 14 as individual particles becomes a state of floating to a certain height and moving violently everywhere. That is, a fluidized bed as a layer of the catalyst 14 moving violently everywhere is formed. By the flow of the catalyst 14, a good mixing state of the catalyst 14 and the raw material gas can be obtained.Thereby, the contact between the raw material gas and the catalyst 14 is promoted. Accordingly, the thermal decomposition reaction of the raw material gas caused by the catalyst 14 is promoted. The reactor 12 is a fluidized bed type reaction vessel. The catalyst 14 is a fluid medium. The raw material gas is a fluidizing gas for fluidizing the catalyst 14. <Reaction temperature> When producing hydrogen, the inside of the reactor 12 and even the catalyst 14 are heated to a predetermined reaction temperature. The reaction temperature is the temperature at which the thermal decomposition reaction of the raw material gas caused by the catalyst 14 proceeds favorably. The reaction temperature is a value set within a predetermined temperature range in accordance with product specifications and the like. The lower limit value of the temperature range is set, for example, based on the starting temperature of thermal decomposition. The upper limit value of the temperature range is set, for example, according to the heat resistance of the reactor 12. If the reaction temperature is below the lower limit value of the temperature range, there is a risk that the thermal decomposition reaction of the raw material gas will not proceed. This is because, since the reaction temperature is lower than the starting temperature of thermal decomposition, the function of the raw material gas for decomposing the catalyst 14 becomes inactivated. The higher the reaction temperature, the more the thermal decomposition of the raw material gas will proceed. However, if the reaction temperature exceeds the upper limit value of the temperature range, there is a risk that the reliability of the reactor 12 cannot be ensured. <Relationship between the pressure of the reactor 12 and the hydrogen production amount> The relationship between the pressure of the reactor 12 and the hydrogen production amount will be described below. The pressure is the pressure inside the reactor 12. The pressure inside the reactor 12 is the pressure corresponding to the pressure of the raw material gas supplied to the inside of the reactor 12. Here, the case where the raw material gas is methane will be described as an example. The thermal decomposition reaction of methane is represented by the following formula (1). Further, when methane is thermally decomposed to a reaction equilibrium state, the following formula (2) holds regardless of the pressure of the reactor 12. However, "P H2 2 ", is the partial pressure of hydrogen inside the reactor 12, and is the pressure corresponding to the hydrogen production amount. "P CH4", is the partial pressure of methane inside the reactor 12 and is the pressure corresponding to the pressure of the methane supplied to the reactor 12. " / ", represents a division formula. Assuming that the pressure of the reactor 12, that is, the supply pressure of methane, becomes 4 times, at first glance, the partial pressure of methane and the partial pressure of hydrogen also become 4 times. However, according to the previous formula (2), the partial pressure of hydrogen becomes 2 times. That is, the production amount of hydrogen becomes 1 / 2 compared to before the pressure increase. Thus, if the pressure of the reactor 12, that is, the supply pressure of methane, is increased, in terms of the reaction equilibrium, the production amount of hydrogen is less compared to before the pressure increase. In other words, the conversion rate of methane decreases. The conversion rate represents the degree of the thermal decomposition reaction in the reactor 12 and indicates the conversion rate from methane as the raw material gas to hydrogen. The pressure of the reactor 12, that is, the supply pressure of methane, is set according to product specifications, etc. <Regarding the supply and discharge of the catalyst 14> During the operation of the hydrogen production device 10, the activity of the catalyst 14 gradually decreases as the thermal decomposition reaction proceeds. 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 extract the catalyst 14 with reduced activity from the reactor 12. The catalyst 14 with reduced activity includes the catalyst 14 that has lost its activity. Losing activity means that the catalyst 14 loses its activity and does not cause the thermal decomposition reaction of the raw material gas. The decomposition rate is the ratio of the raw material gas decomposed by the function of the catalyst 14 within a certain period. The catalyst 14 with reduced activity has a smaller particle diameter and density compared to the new catalyst 14. Since the catalyst 14 with reduced activity has a smaller particle diameter and particle density, the terminal velocity is below the superficial velocity. Therefore, the catalyst 14 with reduced activity is basically led out of the reactor 12 through the outlet pipe 16 together with the product gas to the outside of the reactor 12. The superficial velocity is the flow velocity of the raw material gas calculated assuming that the catalyst 14 as the packed particles does not exist in the reactor 12. The terminal velocity is the velocity at which the resistance of the raw material gas applying an upward force to the particle and the gravity applying a downward force to the particle are balanced. However, among the catalyst 14 with reduced activity, there are those that combine with the carbon generated by the thermal decomposition of the raw material gas and remain inside the reactor 12. This is because the particle diameter or particle density of the catalyst 14 with reduced activity becomes larger due to the combination with the generated carbon. Therefore, it is necessary to discharge the catalyst 14 with reduced activity from the reactor 12. Thus, in this embodiment, as the hydrogen production device 10, the following structure is adopted. <Structure for supplying the catalyst 14> As shown in FIG. 1, the hydrogen production device 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. The supply device 21 is provided on the first supply path 22A. The first supply path 22A is a path for supplying new catalyst 14 to the reactor 12 and is constituted by, for example, a pipe. The first supply path 22A penetrates the lower end portion of the pressure vessel 11 and is connected to the lower end portion of the reactor 12.The supply device 21 includes a receiving hopper 23, an intermediate hopper 24, and a supply hopper 25. They are arranged in the order of the supply hopper 25, the intermediate hopper 24, and the receiving hopper 23 from the side closer 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 the new catalyst 14. The receiving hopper 23 receives the new catalyst 14 supplied from the outside and temporarily stores the received new catalyst 14. The pressure of the receiving hopper 23 is maintained at atmospheric pressure, for example. In the intermediate hopper 24, a pipe for pressure adjustment is connected through a valve. By introducing high-pressure gas into the intermediate hopper 24 through the pipe, the pressure inside the intermediate hopper 24 can be increased to a pressure higher than atmospheric pressure. In addition, by discharging the pressure inside the intermediate hopper 24 through the pipe, the pressure inside the intermediate hopper 24 can be reduced to atmospheric pressure. The high-pressure gas is an inert gas such as nitrogen or argon. The pressure of the supply hopper 25 is maintained at a pressure higher than the pressure of the reactor 12 over time. This is because, for example, it is used to suppress the backflow of the catalyst 14. A first isolation valve 26 is provided in the first supply path 22A between the receiving hopper 23 and the intermediate hopper 24. The first isolation valve 26 opens and closes the first supply path 22A between the receiving hopper 23 and the intermediate hopper 24. A second isolation valve 27 is provided in the first supply path 22A between the intermediate hopper 24 and the supply hopper 25. The second isolation valve 27 opens and closes the first supply path 22A between the intermediate hopper 24 and the supply hopper 25. A third isolation valve 28 and a first electric valve 29 are provided in the first supply path 22A between the supply hopper 25 and the reactor 12. The third isolation valve 28 is provided in the first supply path 22A between the supply hopper 25 and the first electric valve 29. The third isolation valve 28 opens and closes the first supply path 22A between the supply hopper 25 and the first electric valve 29. The first electric valve 29 is a rotary valve, for example. The first electric valve 29 has a motor and a rotor that rotates by the drive of the motor. By controlling the rotation speed of the rotor, the discharge amount of the catalyst 14 as fine individual particles can be controlled. A second supply path 22B is connected to the first supply path 22A between the first electric valve 29 and the reactor 12. The second supply path 22B is a path for supplying carrier gas to the first supply path 22A between the first electric valve 29 and the reactor 12 and is constituted by a pipe, for example. The carrier gas is a gas for transporting the catalyst 14 inside the first supply path 22A between the first electric valve 29 and the reactor 12 to the inside of the reactor 12, and is an inert gas such as nitrogen or argon, for example. The catalyst 14 moves together with the flow of the carrier gas. <Structure for discharging the catalyst 14> As shown in FIG. 1, the hydrogen production device 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 the extraction path 32 of 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 constituted by, for example, piping. The first end of the extraction path 32 is connected to a portion in the reactor 12 corresponding to the upper part of the fluidized bed of the catalyst 14. The upper part is the part of the fluidized bed on the side farther from the disperser 13 in the axial direction of the reactor 12. The extraction device 31 includes a cooler 33, a second electric valve 34, and an extraction hopper 35. They are arranged in the order of the cooler 33, the second electric valve 34, and the extraction hopper 35 from the side closer to the reactor 12. The second electric valve 34 is located between the cooler 33 and the extraction hopper 35. The extraction hopper 35 is connected to the second end of the extraction path 32. The second end is the end of the extraction path 32 on the side opposite to the first end. The cooler 33 cools the catalyst 14 with reduced activity 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 rotates by the drive of the motor. By controlling the rotation speed of the rotor, the discharge amount of the catalyst 14 as fine individual particles can be controlled. The extraction hopper 35 continuously extracts the catalyst 14 with reduced activity and temporarily stores the extracted catalyst 14. <Electrical Structure of the Hydrogen Production Device 10> Hereinafter, the electrical structure of the hydrogen production device 10 will be described. As shown in FIG. 2, the hydrogen production device 10 includes a first temperature sensor 41, a second temperature sensor 42, a differential pressure sensor 43, a concentration sensor 44, and a control device 45. The first temperature sensor 41 is provided in the reactor 12. The first temperature sensor 41 detects the 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. The second temperature sensor 42 is provided in the reactor 12. The second temperature sensor 42 detects the 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. 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 and the lower part of the reaction chamber 12A. The upper part of the reaction chamber 12A is the empty tower part in the reactor 12 that is separated from the fluidized bed of the catalyst 14. The lower part of the reaction chamber 12A is the part in the reactor 12 corresponding to the fluidized bed of the catalyst 14, for example, the part directly above the disperser 13. The concentration sensor 44 is provided in the outlet pipe 16. The concentration sensor 44 detects the hydrogen concentration M in the product gas generated by the thermal decomposition of the raw material gas. The control device 45 has a processing circuit including any one of the following three structures A1, A2, and A3. A1. One or more processors that operate according to a computer program as software. The processor includes a CPU (central processing unit) and a memory. A2. One or more dedicated hardware circuits such as an application specific integrated circuit (ASIC) that perform at least a part of various processes. The ASIC includes a CPU and a memory.A3. The hardware circuit of the combined structures A1 and A2. The memory is a medium readable by a computer (here the CPU), which stores a program describing the processing or commands relative to the computer. The memory includes RAM (random access memory) and ROM (read only memory). The CPU executes various controls in such a way that the program stored in the memory is executed at a determined calculation cycle. The control device 45 controls the operations of the supply device 21 and the extraction device 31. The control device 45, for example, controls the supply of the new catalyst 14 to the reactor 12 through the supply device 21 according to the detection results of various sensors (41 - 44). The control device 45, for example, controls the extraction of the catalyst 14 with reduced activity from the reactor 12 through the extraction device 31 according to the detection results of various sensors (41 - 44). <Supply process of catalyst 14> When the control device 45 supplies the catalyst 14 to the reactor 12, it controls the supply device 21 as follows. That is, the control device 45 first opens the first partition valve 26. Thereby, the new catalyst 14 stored in the receiving hopper 23 moves to the intermediate hopper 24 by gravity. After the control device 45 moves a predetermined amount of the catalyst 14, it closes the first partition valve 26. Next, the control device 45 introduces high-pressure gas into the interior of the intermediate hopper 24 through the pressure-adjusting pipe. Thereby, the pressure inside the intermediate hopper 24 is increased to the same level as the pressure of the supply hopper 25. The pressure of the supply hopper 25 is maintained at a pressure above the pressure of the reactor 12. Thereafter, the control device 45 opens the second partition valve 27. Thereby, the catalyst 14 inside the intermediate hopper 24 is discharged to the supply hopper 25. After the discharge of the catalyst 14 to the supply hopper 25 is completed, the control device 45 closes the second partition valve 27 and releases the gas inside the intermediate hopper 24 through the pressure-adjusting pipe to reduce the pressure inside the intermediate hopper 24 to atmospheric pressure. Thereby, the intermediate hopper 24 can receive the catalyst 14 from the receiving hopper 23 again. Next, the control device 45 opens the third partition valve 28. Thereby, the catalyst 14 inside the supply hopper 25 is discharged to the first electric valve 29. The control device 45 controls the first electric valve 29 to continuously send a predetermined amount of the catalyst 14 from the first electric valve 29. The catalyst 14 sent out from the first electric valve 29 is supplied to the reactor 12 by pneumatic transportation. That is, the catalyst 14 sent out from the first electric valve 29 converges with the carrier gas at the connection part of 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 partition valve 26 during the supply of the catalyst 14 to the reactor 12. The intermediate hopper 24 receives the catalyst 14 from the hopper 23 again.The control device 45 closes the first partition valve 26 when the amount of the catalyst 14 in the supply hopper 25 decreases to near the lower limit, and introduces high-pressure gas into the intermediate hopper 24 through the pipe for pressure adjustment. Thereby, the pressure inside the intermediate hopper 24 is pressurized to the same level as the pressure of the supply hopper 25. Thereafter, the control device 45 opens the second partition valve 27. Thereby, the catalyst 14 in the intermediate hopper 24 is discharged into the supply hopper 25. After the discharge of the catalyst 14 into the supply hopper 25 is completed, the control device 45 closes the second partition valve 27 and releases the gas inside the intermediate hopper 24 through the pipe for pressure adjustment to reduce the pressure inside the intermediate hopper 24 to atmospheric pressure. When the pressure inside the intermediate hopper 24 is atmospheric pressure, that is, the same as the pressure of the receiving hopper 23, the control device 45 opens the first partition valve 26. Thereby, the intermediate hopper 24 receives the catalyst 14 from the receiving hopper 23 again. By repeatedly executing the above processes, the control device 45 continuously supplies the catalyst 14 to the reactor 12. The catalyst 14 is supplied to the reactor 12 by being transported in an air stream by the carrier gas. <Process of extracting the catalyst 14 from the reactor 12> When extracting the catalyst 14 from the reactor 12, the control device 45 controls the extraction device 31 as follows. That is, the control device 45 actuates the cooler 33 and the second electric valve 34. Thereby, the catalyst 14 with reduced activity is extracted from the reactor 12. The extracted catalyst 14 is cooled by the cooler 33. The cooled catalyst 14 is sent to the extraction hopper 35 by the second electric valve 34. Moreover, the control device 45 may execute the extraction process of the catalyst 14 and the supply process of the catalyst 14 at the same time sequence. In this case, the discharge amount of the catalyst 14 may be, for example, the same as the supply amount of the catalyst 14 of the supply device 21. In addition, the discharge speed of the catalyst 14 may be the same as the supply speed of the catalyst 14 of the supply device 21. By doing so, the change in the height of the catalyst layer becomes moderate, and it is also easy to maintain a uniform catalyst layer. Depending on the product specifications, etc., the control device 45 may execute the extraction process of the catalyst 14 and the supply process of the catalyst 14 at different time sequences. <Control of the decomposition rate of the raw material gas> As shown in the previous formula (1), the thermal decomposition reaction of the raw material gas is an endothermic reaction. An endothermic reaction is a reaction accompanied by heat absorption. Therefore, as the thermal decomposition reaction of the raw material gas proceeds, heat is taken away from the fluidized bed. If the temperature of the fluidized bed decreases, only that part will undergo the thermal decomposition reaction of the raw material gas. If the catalyst 14 loses its activity, heat will not be taken away from the fluidized bed. Therefore, the temperature of the fluidized bed tends to rise. In addition, 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 will proceed. Therefore, the progress of the thermal decomposition reaction of the raw material gas can be determined based on the first temperature T1 of the fluidized bed, the second temperature T2 of the fluidized bed, and the concentration M of hydrogen in the product gas.The pressure difference ΔP between the upper part and the lower part of the reaction chamber 12A is determined by the weight of the catalyst 14 as solid particles 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 varies according to the progress of the thermal decomposition reaction of the raw material gas. This is because, according to the progress of the thermal decomposition reaction of the raw material gas, the weight of the catalyst 14 as solid particles forming the fluidized bed changes. The particles of the catalyst 14 are decomposed and pulverized along with the diffusion of the raw material gas molecules into the particles and the generation of hydrogen and carbon due to 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 becomes smaller. Along with this, the decomposition rate of the raw material gas changes, and the pressure difference ΔP also changes. In other words, by controlling the pressure difference ΔP, the decomposition rate of the raw material gas can be controlled. Controlling the decomposition rate of the raw material gas is also controlling the conversion rate of the raw material gas. The control device 45 controls the supply amount of the new catalyst 14 to the reactor 12 and the discharge amount of the catalyst 14 with reduced activity from the reactor 12 so that the pressure difference ΔP detected by the pressure difference sensor 43 becomes constant. The target pressure difference ΔP is, for example, the pressure difference at which the decomposition rate of the raw material gas is optimal. The optimal decomposition rate is determined according to product specifications and the like. The control device 45 performs feedback control of the pressure difference ΔP so that the pressure difference ΔP detected by the pressure difference sensor 43 coincides with the target pressure difference. The feedback control is, for example, PID control, including proportional control, integral control, and derivative control. The control device 45 calculates the target action amounts of the first electric valve 29 and the second electric valve 34 by performing feedback control of the pressure difference ΔP. The target action amount of the first electric valve 29 is the target supply amount of the catalyst 14 of the supply device 21. The target action amount of the second electric valve 34 is the target discharge amount of the catalyst 14 of the extraction device 31. The control device 45 controls the actions of the first electric valve 29 and the second electric valve 34 so that when the pressure difference ΔP deviates from the target pressure difference, the pressure difference ΔP coincides with the target pressure difference. Controlling the action of the first electric valve 29 is controlling the supply amount of the catalyst 14 to the reactor 12. Controlling the action of the second electric valve 34 is controlling the discharge amount of the catalyst 14 from the reactor 12. The control device 45 controls the action of the first electric valve 29 to supply the catalyst 14 of the target supply amount to the reactor 12. The control device 45 controls the action of the second electric valve 34 to discharge the catalyst 14 of the target supply amount from the reactor 12. The control device 45 calculates the target pressure difference. The control device 45 calculates the difference between the target conversion rate of the raw material gas and the measured value of the conversion rate, and performs feedback control of the conversion rate to eliminate the calculated difference. The target conversion rate is the target value of the conversion rate required according to product specifications and is stored in the memory. The feedback control is, for example, PID control, including proportional control, integral control, and derivative control.The control device 45 calculates the target pressure difference by performing feedback control of the conversion rate. 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 the memory. The initial value is the target value of the pressure difference ΔP set according to the pressure of the reactor 12 determined by product specifications and the like and the temperature inside the reactor 12. 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 is consistent with the initial value. 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 by performing feedback control of the conversion rate. That is, 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 is consistent with the target pressure difference according to the feedback control of the conversion rate. <Calculation method of conversion rate> The control device 45 calculates the conversion rate of the raw material gas according to any one of the following three calculation methods. The raw material gas is methane, for example. The first calculation method is as follows. That is, the conversion rate α of methane is expressed by the following formula (3). The control device 45 uses the following formula (3) to calculate the conversion rate α of methane.. However, "G1 in " is the volume flow rate or the number of moles of methane introduced into the reactor 12. "G1 out " is the volume flow rate or the number of moles of methane导出 from the reactor 12 to the outside. "G2 in " is the volume flow rate or the number of moles of hydrogen introduced into the reactor 12. "G2 out It should be noted that there is an unclear expression "导出" in the original text, which may need to be further clarified in the actual context for more accurate translation.", which is the volume flow rate or the number of moles of hydrogen导出外部 from the reactor 12. Since the hydrogen production device 10 is a single-stage type, hydrogen is not supplied to the reactor 12. That is, the hydrogen concentration at the inlet of the reactor 12 is 0%. The single-stage type is a type having one reactor 12. Therefore, the conversion rate α of methane can be obtained by analyzing the hydrogen concentration at the outlet of the reactor 12, that is, the hydrogen concentration in the product gas导出外部 the reactor 12 through the outlet pipe 16. " / " represents a division formula. The second calculation method is as follows. That is, as shown in the previous formula (1), the thermal decomposition reaction of methane is an endothermic reaction. Therefore, when the raw material gas is preheated to a predetermined temperature, that is, when the raw material gas is not heated in the reactor 12, the control device 45 can calculate the conversion rate α of methane 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. The third calculation method is as follows. That is, when the raw material gas is heated in the reactor 12 and the inside of the reactor 12 is maintained at a constant temperature, when the heating amount inside the reactor 12 can be measured, the control device 45 can use the following formula (4) to calculate the conversion rate α of methane. However, "Q1" is the amount of heat inside the reactor 12. "Q2" is the endothermic heat of the thermal decomposition reaction of methane. In the previous formula (1), the endothermic heat Q2 is 90 kJ / mol. The heating amount of the reactor 12 can be obtained, for example, from the calorific value of the heating device that heats the inside of the reactor 12. For example, when the heating device is a heater, the heating amount of the reactor 12 can be calculated based on the calorific value of the heater per unit time. When the heating device is a casing through which exhaust gas or steam flows, the heating amount of the reactor 12 can be calculated based on the supply amount of the exhaust gas or steam to the casing. In addition, as shown in the graph of Figure 3, when the thermal decomposition reaction of methane has not reached equilibrium, that is, when the height of the catalyst layer is not high enough, the conversion rate α of methane 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 the height based on the disperser 13. As the height of the catalyst layer increases, the conversion rate α of methane gradually increases. After the height of the catalyst layer reaches a certain height, even if the height of the catalyst layer increases, the conversion rate α remains at a certain value. The height of the catalyst layer is proportional to the residence time of the raw material gas in the catalyst layer. In addition, the height of the catalyst layer is also proportional to the reciprocal of GHSV (Gaseous Hourly Space Velocity). GHSV is the reciprocal of the catalyst passing time of the raw material gas under the standard state of 1 atm and 0 °C, and is one of the indicators representing the catalyst passing speed of the reactor 12. Moreover, depending on the product specifications, instead of the target pressure difference, a target range of the pressure difference ΔP can be set. The target range is the range of the pressure difference ΔP that is allowable in the product specifications, and is defined by the upper limit value and the lower limit value of the pressure difference ΔP. The control device 45 controls the operations of the first electric valve 29 and the second electric valve 34 so that when the pressure difference ΔP is outside the target range, the pressure difference ΔP is within the target range. <Effects of the Embodiment> The present embodiment can achieve the following effects. (1) The control device 45 controls the operations of the supply device 21 and the extraction device 31 so that the pressure difference ΔP detected by the pressure difference sensor 43 becomes constant. That is, the control device 45 controls the supply amount of the new catalyst 14 to the reactor 12 and the discharge amount of the catalyst 14 with reduced activity from the reactor 12 so that the pressure difference ΔP becomes constant. According to this structure, by maintaining the pressure difference ΔP constant, the decomposition rate of the raw material gas can be maintained. Therefore, hydrogen can be stably produced. (2) The control device 45 performs feedback control of the pressure difference ΔP using the target pressure difference calculated by performing feedback control through the conversion rate α. That is, 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 detected by the pressure difference sensor 43 coincides with the target pressure difference. Thereby, the conversion rate α of the raw material gas can follow the target conversion rate. And the decomposition rate of the raw material gas can be maintained at the decomposition rate corresponding to the target conversion rate.(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 applicable to the case where the raw material gas preheated to a determined temperature is supplied to the reactor 12. (4) The control device 45 can calculate the conversion rate α of the raw material gas based on the concentration M of hydrogen detected by the concentration sensor 44. This calculation method is applicable to the hydrogen production device 10 that is single-stage and does not supply hydrogen to the reactor 12. (5) The control device 45 can calculate the conversion rate α of the raw material gas based on the heating amount Q1 inside the reactor 12 and the endothermic amount Q2 of the thermal decomposition reaction of the raw material gas. This calculation method is applicable to the case 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 obtain the heating amount of the reactor 12, for example, based on the heat generation amount of the heating device that heats the inside of the reactor 12. (6) The pressure of the reactor 12 is higher than the atmospheric pressure. The supply device 21 continuously conveys the new catalyst 14 by pressurizing it to a pressure higher than the pressure of the reactor 12. According to this structure, the new catalyst 14 can be supplied to the reactor 12 by gas flow conveyance. (7) The catalyst 14 with reduced activity is discharged from the reactor 12 by the extraction device 31. Therefore, it is possible to suppress the combination of carbon generated by the thermal decomposition of the raw material gas and the catalyst 14 with reduced activity and the situation of remaining inside the reactor 12. <Other Embodiment Modes> Moreover, this embodiment mode can also be implemented by making the following changes. - The raw material gas can be used as the carrier gas. By doing so, the new catalyst 14 can be supplied to the reactor 12 by utilizing the flow of the raw material gas. - A flow material can be mixed into the catalyst 14. The flow material is used to improve the fluidity of the catalyst 14. The flow material is fine individual particles, such as inert particles like silicon. The catalyst 14 is, for example, iron or fine metal particles with iron as the main component. Therefore, when only the catalyst 14 is accommodated in the reactor 12, the following situation is a concern. That is, when the hydrogen production device 10 is started, the catalyst 14s are welded to each other as the temperature of the reactor 12 rises, which may hinder the flow of the catalyst 14. By mixing the flow material in the catalyst layer, the welding of the catalyst 14s to each other can be suppressed. Accordingly, the catalyst 14 flows stably. - The pressure of the reactor 12 can also be maintained at the atmospheric pressure. In this case, as the hydrogen production device 10, a structure omitting the pressure vessel 11 can also be adopted. The lower the pressure of the reactor 12, the higher the methane conversion rate. - As shown by the two-dot chain line in FIG. 1, when the pressure of the reactor 12 and the supply hopper 25 are equal, the catalyst 14 can also be supplied to the reactor 12 by gravity fall. The pressure can be, for example, the atmospheric pressure. In this case, the supply hopper 25 is connected to the upper part of the reactor 12 through, for example, the third isolation valve 28 and the first electric valve 29.- The catalyst 14 may be a metal such as nickel and cobalt, or fine metal particles mainly composed of such metals. - The terms "cylinder" or "cylindrical" used in this specification may refer to any structure having a peripheral wall. The terms "cylinder" or "cylindrical" may refer to, for example, any structure having a cross-sectional shape of a circle, an ellipse, and a polygon with sharp corners or rounded corners, but are not limited to these. <Supplementary Note> The hydrogen production device described in this embodiment mode is grasped as follows, for example. 1. The hydrogen production device (10) of the first aspect, which has: a reactor (12) that thermally decomposes a hydrocarbon gas as a raw material gas using a catalyst (14) to produce hydrogen, and forms a fluidized bed of the catalyst (14) inside by introducing the raw material gas from below. The hydrogen production device (10) has: a pressure difference sensor (43) configured to detect a pressure difference (ΔP) between the upper part of the reactor (12) separated from the fluidized bed and the 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); a 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 operations of the supply device (21) and the extraction device (31) so that the pressure difference (ΔP) detected by the pressure difference sensor (43) becomes constant. By the hydrogen production device of the first aspect, by maintaining the pressure difference detected by the pressure difference sensor constant, the decomposition rate of the raw material gas can be maintained. Therefore, hydrogen can be stably produced. 2. The hydrogen production device (10) of the second aspect is the hydrogen production device (10) of the first aspect, wherein the control device (45) is configured to perform: a process of calculating the conversion rate (α) of the raw material gas based on the state variables (T, T2, M, Q1) of the reactor (12); a process of calculating a target pressure difference as the target value of the pressure difference (ΔP) by performing feedback control of the conversion rate (α) so that the calculated conversion rate (α) follows a determined target conversion rate; and a process of calculating the target supply amount of the catalyst (14) of the supply device (21) and the target discharge amount of the catalyst (14) of the extraction device (31) by performing feedback control of the pressure difference (ΔP) so that the pressure difference (ΔP) detected by the pressure difference sensor (43) follows the target pressure difference. By the hydrogen production device of the second aspect, the target pressure difference calculated by performing feedback control of the conversion rate is used to perform feedback control of the pressure difference. That is, the supply amount of the catalyst to the reactor and the discharge amount of the catalyst from the reactor are controlled so that the pressure difference detected by the pressure difference sensor is consistent with the target pressure difference. Thereby, the conversion rate of the raw material gas can be made to follow the target conversion rate. And the decomposition rate of the raw material gas can be maintained at the decomposition rate corresponding to the target conversion rate.3. The hydrogen production device (10) of the third aspect has, in the hydrogen production device (10) of the second aspect, a first temperature sensor (41) that detects a first temperature (T1) which is the temperature of the upper part of the aforementioned fluidized bed, and a second temperature sensor (42) that detects a second temperature (T2) which is the temperature of the lower part of the aforementioned fluidized bed. The aforementioned control device (45) is configured to calculate the conversion rate (α) of the aforementioned raw material gas based on the difference between the aforementioned first temperature (T1) detected by the aforementioned first temperature sensor (41) and the aforementioned second temperature (T2) detected by the aforementioned second temperature sensor (42). With the hydrogen production device of the third aspect, the conversion rate of the raw material 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 for the case where the raw material gas preheated to a determined temperature is supplied to the reactor. 4. The hydrogen production device (10) of the fourth aspect has, in the hydrogen production device (10) of the second aspect, a concentration sensor (44) that detects the hydrogen concentration (M) in the product gas generated by the thermal decomposition of the aforementioned raw material gas and led out of the aforementioned reactor (12) to the outside. The aforementioned control device (45) is configured to calculate the conversion rate (α) of the aforementioned raw material gas based on the hydrogen concentration (M) detected by the aforementioned concentration sensor (44). With the hydrogen production device of the fourth aspect, the conversion rate of the raw material 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 that does not supply hydrogen to the reactor. 5. The hydrogen production device (10) of the fifth aspect has, in the hydrogen production device (10) of the second aspect, the aforementioned control device (45) configured to calculate the conversion rate (α) of the aforementioned raw material gas based on the heating amount (Q1) inside the aforementioned reactor (12) and the endothermic amount (Q2) of the thermal decomposition reaction of the aforementioned raw material gas. With the hydrogen production device of the fifth aspect, the conversion rate of the raw material gas can be calculated based on the heating amount inside the reactor and the endothermic amount of the thermal decomposition reaction of the raw material gas. This calculation method is suitable for the case where the raw material gas is heated in the reactor and the inside of the reactor is maintained at a constant temperature. 6. The hydrogen production device (10) of the sixth aspect is one of the hydrogen production devices (10) of the first aspect to the fifth aspect, wherein the pressure of the aforementioned reactor (12) is higher than atmospheric pressure, and the aforementioned supply device (21) is configured to continuously convey the new aforementioned catalyst (14) by pressurizing it to a pressure higher than the pressure of the aforementioned reactor (12). With the hydrogen production device of the sixth aspect, new catalyst can be supplied to the reactor by pneumatic conveying. 7. The hydrogen production device (10) of the seventh aspect is the hydrogen production device (10) of the sixth aspect, and the carrier gas for the aforementioned pneumatic conveying is the aforementioned raw material gas. With 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 apparatus (10) according to the eighth aspect is one of the hydrogen production apparatuses (10) according to any one of the first to fifth aspects. In the new catalyst (14), it is supplied to the reactor (12) by gravity drop. With the hydrogen production apparatus according to the eighth aspect, a new catalyst can be supplied to the reactor by gravity drop. 9. The hydrogen production apparatus (10) according to the ninth aspect is one of the hydrogen production apparatuses (10) according to any one of the first to eighth aspects. The catalyst (14) is fine metal particles; in the catalyst (14), a flow material as an inert particle for improving the fluidity of the catalyst is mixed. With the hydrogen production apparatus according to the ninth aspect, for example, it is possible to suppress the welding of the catalysts to each other with the temperature rise of the reactor when the hydrogen production apparatus is started. 10. The hydrogen production method according to the tenth aspect is a hydrogen production method in which a raw material gas is introduced from the lower part of a reactor (12) that thermally decomposes a hydrocarbon gas as a raw material gas using a catalyst (14) to form a fluidized bed of the catalyst (14) inside the reactor (12). The supply of the new catalyst (14) to the reactor (12) and the extraction of the catalyst (14) with reduced activity from the reactor (12) are controlled so that the pressure difference (ΔP) between the upper part of the reactor (12) that detaches from the fluidized bed and the lower part of the reactor (12) corresponding to the fluidized bed becomes constant. With the hydrogen production method according to the tenth aspect, by maintaining the pressure difference between the upper part of the reactor that detaches from the fluidized bed and the lower part of the reactor corresponding to the fluidized bed as constant, the decomposition rate of the raw material gas can be maintained. Therefore, hydrogen can be stably produced. 11. The hydrogen production program according to the eleventh aspect is a hydrogen production program that causes a computer to execute a process of introducing the raw material gas from the lower part of a reactor (12) that thermally decomposes a hydrocarbon gas as a raw material gas using a catalyst (14) to form a fluidized bed of the catalyst (14) inside the reactor (12). It has a stage of controlling the supply of the new catalyst (14) to the reactor (12) and the extraction of the catalyst (14) with reduced activity from the reactor (12) so that the pressure difference (ΔP) between the upper part of the reactor (12) that detaches from the fluidized bed and the lower part of the reactor (12) corresponding to the fluidized bed becomes constant. With the hydrogen production program according to the eleventh aspect, by maintaining the pressure difference between the upper part of the reactor that detaches from the fluidized bed and the lower part of the reactor corresponding to the fluidized bed as constant, the decomposition rate of the raw material gas can be maintained. Therefore, hydrogen can be stably produced. 10: Hydrogen production device 11: Pressure vessel 12: Reactor 12A: Reaction chamber 12B: Wind chamber 13: Disperser 14: Catalyst 15: Inlet pipe 16: Outlet pipe 21: Supply device 22A: First supply path 22B: Second supply path 23: Receiving hopper 24: Intermediate hopper 25: Supply hopper 26: First isolation valve 27: Second isolation valve 28: Third isolation valve 29: First electric valve 31: Extraction device 32: Extraction path 33: Cooler 34: Second electric valve 35: Extraction hopper 41: First temperature sensor 42: Second temperature sensor 43: Differential pressure sensor 44: Concentration sensor 45: Control device T1: First temperature T2: Second temperature ΔP: Pressure difference M: Hydrogen concentration [Fig. 1] is a structural diagram of an embodiment of a hydrogen production device. [Fig. 2] is a block diagram showing the electrical structure of an embodiment of a hydrogen production device. [Fig. 3] is a chart showing the relationship between the height of a catalyst layer and the methane conversion rate in an embodiment. 10: Hydrogen production device 11: Pressure vessel 12: Reactor 12A: Reaction chamber 12B: Wind chamber 13: Disperser 14: Catalyst 15: Inlet pipe 16: Outlet pipe 21: Supply device 22A: First supply path 22B: Second supply path 23: Receiving hopper 24: Intermediate hopper 25: Supply hopper 26: First isolation valve 27: Second isolation valve 28: Third isolation valve 29: First electric valve 31: Extraction device 32: Extraction path 33: Cooler 34: Second electric valve 35: Extraction hopper 41: First temperature sensor 42: Second temperature sensor 43: Differential pressure sensor 44: Concentration sensor M: Hydrogen concentration

Claims

1. A hydrogen production apparatus comprising: a reactor for producing hydrogen by thermally decomposing a hydrocarbon gas as a raw material gas using a catalyst, and forming a flow layer of the catalyst inside by introducing the raw material gas from the bottom; characterized in that it comprises: a differential pressure sensor configured to detect the pressure difference between the upper part of the reactor that has detached from the flow layer and the lower part of the reactor corresponding to the flow layer; 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 to make the pressure difference detected by the differential pressure sensor constant; wherein the hydrocarbon gas is methane or a gas with methane as the main component; and the catalyst is fine metal particles with iron, nickel, cobalt, or such metals as the main component.

2. The hydrogen production apparatus as claimed in claim 1, wherein, The aforementioned control device is configured to perform: processing to calculate the conversion rate of the aforementioned raw material gas based on the state variables of the aforementioned reactor; processing to calculate the target pressure difference as the target value of the aforementioned pressure difference by executing feedback control of the aforementioned conversion rate in order to make the calculated conversion rate follow the determined target conversion rate; and processing to calculate the target supply amount of the aforementioned catalyst of the aforementioned supply device and the target discharge amount of the aforementioned catalyst of the aforementioned extraction device by executing feedback control of the aforementioned pressure difference in order to make the aforementioned pressure difference detected by the aforementioned differential pressure sensor follow the aforementioned target pressure difference.

3. The hydrogen production apparatus as claimed in claim 2, comprising: a first temperature sensor for detecting a first temperature as the temperature of the upper part of the aforementioned flow layer; and a second temperature sensor for detecting a second temperature as the temperature of the lower part of the aforementioned flow layer, wherein the aforementioned control device is configured to calculate the conversion rate of the aforementioned feed gas based on the difference between the aforementioned first temperature detected by the aforementioned first temperature sensor and the aforementioned second temperature detected by the aforementioned second temperature sensor.

4. The hydrogen production apparatus as claimed in claim 2, comprising: a concentration sensor for detecting the hydrogen concentration of the generated gas produced by the thermal decomposition of the aforementioned feedstock gas and discharged from the aforementioned reactor; the aforementioned control device being configured to calculate the conversion rate of the aforementioned feedstock gas based on the hydrogen concentration detected by the aforementioned concentration sensor.

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

6. A hydrogen production apparatus as described in any one of claims 1 to 5, wherein, The pressure of the aforementioned reactor is higher than atmospheric pressure, and the aforementioned supply device is configured to continuously transport gas by pressurizing the new aforementioned catalyst to a pressure higher than that of the aforementioned reactor.

7. The hydrogen production apparatus as claimed in claim 6, wherein, The carrier gas used in the aforementioned pneumatic transport is the aforementioned raw material gas.

8. A hydrogen production apparatus as described in any one of claims 1 to 5, wherein, The new catalyst is supplied to the reactor by falling down by gravity.

9. A hydrogen production apparatus as described in any one of claims 1 to 5, wherein, In the aforementioned catalyst, a flow material consisting of inert particles is mixed in to improve the flowability of the aforementioned catalyst.

10. A method for producing hydrogen, comprising: introducing the raw material gas into the lower part of a reactor for producing hydrogen by thermally decomposing a hydrocarbon gas as a raw material gas using a catalyst to form a flow layer of the catalyst inside the reactor; detecting the pressure difference between the upper part of the reactor that has detached from the flow layer and the lower part of the reactor corresponding to the flow layer; and controlling the supply of new catalyst to the reactor and the extraction of catalyst with reduced activity from the reactor, based on the result of the detection, to ensure that the pressure difference is constant, wherein the hydrocarbon gas is methane or a gas with methane as the main component, and the catalyst is fine metal particles with iron, nickel, cobalt, or such metals as the main component.

11. A hydrogen production process for use in a hydrogen production apparatus having a reactor that uses a catalyst to thermally decompose a hydrocarbon gas as a feedstock gas to produce hydrogen and introduces the feedstock gas from the bottom to form a flow layer of the catalyst inside it, the hydrogen production apparatus comprising: a differential pressure sensor configured to detect the pressure difference between the upper part of the reactor that has detached from the flow layer and the lower part of the reactor corresponding to the flow layer; 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, wherein the control device performs, by means of the hydrogen production process, a process of controlling the supply of new catalyst to the reactor and the extraction of the catalyst with reduced activity from the reactor to a constant pressure difference as detected by the differential pressure sensor, wherein the hydrocarbon gas is methane or a gas with methane as the main component, and the catalyst is fine metal particles with iron, nickel, cobalt, or such metals as the main component.

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