Hydrogen generation system and method for operating hydrogen generation system
Patent Information
- Application Number
- PCT/JP2026/002224
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-24
- Filing Date
- 2026-01-23
- Publication Date
- 2026-10-01
Smart Images
Figure JP2026002224_01102026_PF_FP_ABST
Abstract
Description
Hydrogen generation system and operation method for hydrogen generation system
[0001] The present disclosure relates to a hydrogen generation system and an operation method for a hydrogen generation system.
[0002] Patent Document 1 discloses a hydrogen generator including: a reforming unit having a reforming catalyst body that reforms a hydrocarbon component as a raw material and water; a raw material supply unit that supplies the raw material to the reforming unit; a water supply unit that supplies water to the reforming unit; a reforming heating unit for the reforming unit; a shift unit provided with a shift catalyst body that causes a shift reaction between water and carbon monoxide and a shift heating means; and a shift catalyst temperature measurement unit that measures the temperature of the shift catalyst body.
[0003] Japanese Unexamined Patent Application Publication No. 2001-354404
[0004] An object of the present disclosure is to provide a hydrogen generation system and an operation method for a hydrogen generation system that have a simple configuration and are suitable for cost reduction.
[0005] The hydrogen generation system in this disclosure comprises: a hydrogen generation device; a raw material supply device that supplies water and a hydrocarbon-containing raw material gas to the hydrogen generation device; and a controller, wherein the hydrogen generation device comprises: an evaporation unit that evaporates the water to generate water vapor and generates a mixed gas of the water vapor and the raw material gas; a reforming unit filled with a reforming catalyst that generates a reformed gas containing hydrogen gas and carbon monoxide from the mixed gas; a CO reduction unit filled with a CO conversion catalyst that generates a hydrogen-containing gas with a reduced carbon monoxide concentration from the reformed gas; and a heating unit that heats the evaporation unit, the reforming unit, and the CO reduction unit, wherein the controller, after the start of the hydrogen generation system's startup operation, raises the temperature of the reforming catalyst using the heating unit and controls the raw material supply device to satisfy the following conditions (i), (ii), and (iii) during a first period from when the temperature of the reforming catalyst exceeds a first set temperature until it reaches a second set temperature. (i) The S / C ratio, which is the ratio of the number of moles of water molecules to the number of moles of carbon atoms in the mixed gas supplied to the reforming unit, is greater than 0 and less than or equal to 2.0; (ii) The dew point of the mixed gas supplied to the reforming unit is lower than the temperature of the reforming catalyst; (iii) The dew point of the reforming gas supplied to the CO reduction unit is lower than the temperature of the CO conversion catalyst.
[0006] In another aspect, the method for operating a hydrogen generation system in this disclosure is a method for operating a hydrogen generation system comprising: a hydrogen generation device; a raw material supplyer that supplies water and a hydrocarbon-containing raw material gas to the hydrogen generation device, wherein the hydrogen generation device comprises: an evaporation unit that evaporates the water to generate water vapor and generates a mixed gas of the water vapor and the raw material gas; a reforming unit filled with a reforming catalyst that generates a reformed gas containing hydrogen gas and carbon monoxide from the mixed gas; a CO reduction unit filled with a CO conversion catalyst that generates a hydrogen-containing gas with a reduced carbon monoxide concentration from the reformed gas; and a heating unit that heats the evaporation unit, the reforming unit, and the CO reduction unit, wherein after the start operation of the hydrogen generation system, the heating unit raises the temperature of the reforming catalyst, and during a first period from when the temperature of the reforming catalyst exceeds a first set temperature until it reaches a second set temperature, the raw material supplyer is controlled to satisfy the following conditions (i), (ii), and (iii). (i) The S / C ratio, which is the ratio of the number of moles of water molecules to the number of moles of carbon atoms in the mixed gas supplied to the reforming unit, is greater than 0 and less than or equal to 2.0; (ii) The dew point of the mixed gas supplied to the reforming unit is lower than the temperature of the reforming catalyst; (iii) The dew point of the reforming gas supplied to the CO reduction unit is lower than the temperature of the CO conversion catalyst.
[0007] According to this disclosure, it is possible to provide a hydrogen production system and a method for operating the hydrogen production system that have a simple configuration and are suitable for cost reduction.
[0008] A schematic diagram showing an example of the hydrogen generation system in Embodiment 1. A chart illustrating the control of operation during startup of the hydrogen generation system in Embodiment 1.
[0009] (Knowledge and other information forming the basis of this disclosure) Steam reforming is a known method for producing hydrogen using a hydrogen generation device. In steam reforming, a raw material gas containing hydrocarbons and water are subjected to a steam reforming reaction in a reforming section filled with a reforming catalyst to produce a reformed gas containing hydrogen gas. Carbon monoxide is produced as a by-component in the steam reforming reaction. Therefore, the concentration of carbon monoxide in the reformed gas is reduced by carrying out a reforming reaction in a CO reduction section filled with a CO reforming catalyst.
[0010] To ensure stable hydrogen production during normal operation of the hydrogen generator, the reforming catalyst and the CO conversion catalyst must be heated to temperatures suitable for their respective reactions during the generator's startup. For example, the suitable temperature for the reforming catalyst is 700°C. For example, the suitable temperature for the CO conversion catalyst is 200°C. At this time, the temperature of the reformed gas discharged from the reforming section located upstream is used to heat the CO conversion catalyst in the CO reduction section located downstream.
[0011] Incidentally, in the reforming catalyst packed into the reforming section, if the temperature exceeds a certain level, for example, the raw material gas decomposes and carbon precipitates. When carbon precipitates, the reforming catalyst deteriorates. Conventionally, in order to suppress carbon precipitation in the reforming catalyst, an amount of water exceeding the number of carbon atoms in the raw material gas supplied to the reforming section is supplied. Generally, water and raw material gas are supplied so that the steam / carbon ratio (S / C ratio), which is the ratio of the number of moles of water molecules (H2O) to the number of moles of carbon atoms (C) in the raw material gas supplied to the reforming section, is 2.5 or higher. As a result, the reforming gas produced in the reforming section contains a considerable amount of water vapor. The reforming gas containing water vapor easily condenses in the subsequent CO reduction section, generating condensed water. The generation of condensed water not only hinders the stabilization of the temperature of the CO conversion catalyst but also deteriorates the CO conversion catalyst. For example, in Patent Document 1, a heater is provided in the CO conversion section as a heating means to suppress the condensation of water in the CO conversion section.
[0012] During the startup operation of a hydrogen generation system, a large amount of water is required to maintain an S / C ratio of 2.5 or higher in order to suppress carbon precipitation in the reforming section, which increases the operating costs. On the other hand, in order to suppress the generation of condensate in the CO reduction section, a heater is required to heat the CO reduction section, which increases the equipment costs. Since these two requirements are conflicting regarding water, it has been considered difficult to resolve these conflicting issues until now.
[0013] Under these circumstances, the inventors focused on setting a low S / C ratio during the startup operation of the hydrogen generation device in order to reduce costs. By setting a low S / C ratio, the dew point of the reformed gas can be lowered. By lowering the dew point of the reformed gas, the condensation of water vapor in the CO reduction section can be suppressed. As a result, a heater for heating the CO reduction section becomes unnecessary.
[0014] As a result of diligent research, the inventors have found that even when the S / C ratio is set low during the startup operation of a hydrogen generation device, the decomposition reaction of the raw material gas is suppressed by the small amount of water vapor present on the surface of the reforming catalyst, thereby suppressing carbon deposition. Based on these findings, the inventors have arrived at the subject matter of this disclosure.
[0015] This disclosure provides a hydrogen production system and a method for operating the hydrogen production system that have a simple configuration and are suitable for cost reduction.
[0016] The embodiments will be described in detail below with reference to the drawings. However, unnecessary details may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art.
[0017] The attached drawings and the following description are provided to help the parties fully understand this disclosure and are not intended to limit the subject matter described in the claims.
[0018] (Embodiment 1) Embodiment 1 will be described below with reference to Figures 1 and 2.
[0019] [1-1. Configuration] Figure 1 is a schematic diagram showing an example of a hydrogen generation system in Embodiment 1. The hydrogen generation system 500 comprises a hydrogen generation device 100, a raw material supply device 200, and a controller 300. The hydrogen generation device 100 comprises a heating unit 101, an evaporation unit 102, a reforming unit 103, and a CO reduction unit 104.
[0020] During normal operation of the hydrogen generation system 500, the raw material supplier 200 controls the flow rate of water W and raw material gas G0 supplied to the evaporation unit 102. The raw material gas G0 contains hydrocarbons. The raw material gas G0 is, for example, a hydrocarbon gas such as city gas or liquefied petroleum gas. In this embodiment, "normal operation" means the operating state in which the hydrogen generation system 500 is operating continuously. Normal operation includes rated operation. "Rated operation" means the operating state at the maximum output in which the hydrogen generation system 500 can operate continuously.
[0021] During normal operation, the evaporation unit 102 evaporates water W to generate water vapor and also generates a mixed gas G1 of water vapor and raw material gas G0.
[0022] The reforming section 103 is filled with a reforming catalyst 103c. The reforming section 103 is a device for generating hydrogen gas from a mixed gas G1 by a reforming reaction such as a steam reforming reaction represented by the following formulas (1) and (2).
[0023] CH4+H2O → CO+3H2...Equation (1) CH4+2H2O → CO2+4H2...Equation (2)
[0024] In the reforming section 103, the reforming reaction proceeds with the reforming catalyst 103c. During normal operation, the reforming section 103 uses a mixed gas G1 of steam and raw material gas G0 to generate a reformed gas G2 containing hydrogen gas and carbon monoxide.
[0025] The reforming catalyst 103c may contain at least one selected from the group consisting of Rh, Ru, Ni, Ir, Pd, Pt, Re, Co, and Fe. With such a configuration, the reforming reaction in the reforming section 103 can be effectively carried out. The reforming catalyst 103c can be selected from the above depending on durability, performance, cost, etc. From the viewpoint of cost reduction, the reforming catalyst 103c may be Ni.
[0026] The CO reduction section 104 is filled with a CO modification catalyst 104c. During normal operation, the CO modification catalyst 104c generates a hydrogen-containing gas G3 with a reduced carbon monoxide concentration from the reformed gas G2 by a modification reaction represented by the following formula (3). The modification reaction represented by the following formula (3) is also called a CO shift reaction.
[0027] CO+H2O → CO2+H2...Formula (3)
[0028] The CO reduction unit 104 provides a hydrogen-rich hydrogen-containing gas G3 in which, for example, the carbon monoxide concentration is reduced to 0.1% or less.
[0029] The heating unit 101 heats, for example, the evaporation unit 102, the reforming unit 103, and the CO reduction unit 104. During normal operation, for example, the heating unit 101 heats the evaporation unit 102 so that the internal temperature of the evaporation unit 102 becomes suitable for the evaporation of water W. As a result of heating, water W evaporates in the evaporation unit 102 and water vapor is generated. For example, the heating unit 101 heats the reforming unit 103 so that the temperature of the reforming catalyst 103c becomes suitable for the reforming reaction. The suitable temperature for the reforming reaction of the reforming catalyst 103c is, for example, 700°C. As a result of heating, the reforming reaction proceeds in the reforming unit 103 and reformed gas G2 is generated. For example, the heating unit 101 heats the CO reduction unit 104 so that the temperature of the CO reforming catalyst 104c becomes suitable for the reforming reaction. The suitable temperature for the reforming reaction of the CO reforming catalyst 104c is, for example, 200°C. Upon heating, a denaturation reaction proceeds in the CO reduction section 104, generating hydrogen-containing gas G3.
[0030] The hydrogen-containing gas G3 generated during normal operation is supplied to a fuel cell, for example, and used for generating electricity in the fuel cell.
[0031] The heating unit 101 may have a combustion unit for burning air Ga and fuel gas Gf. When air Ga and fuel gas Gf are burned, fuel exhaust gas Ge is produced. The fuel exhaust gas Ge is discharged to the outside of the heating unit 101. The heating unit 101 may also be a burner. In this case, the combustion unit is the opening of the burner. The fuel gas Gf is, for example, residual hydrogen gas and unreacted raw material gas G0 discharged from the fuel cell.
[0032] The controller 300 controls, for example, the hydrogen generator 100 and the raw material supplier 200.
[0033] In this embodiment, during the startup operation of the hydrogen production system 500, the controller 300 calculates the S / C ratio of the mixed gas G1 supplied to the reforming unit 103, the dew point of the mixed gas G1 supplied to the reforming unit 103, and the dew point of the reformed gas G2 supplied to the CO reduction unit 104, based on the flow rate of the raw material gas G0 and the water W supplied from the raw material supplyer 200 to the evaporation unit 102. In this way, the controller 300 may calculate the S / C ratio and each dew point during startup operation. In this embodiment, "startup operation" means the startup operation state until the hydrogen production system 500 is ready for normal operation.
[0034] In this embodiment, the controller 300 controls the raw material supplier 200 to start supplying raw material gas G0 to the evaporation unit 102 when the startup operation begins.
[0035] When the hydrogen generation system 500 starts up, the evaporation unit 102 is heated by the heating unit 101 until the internal temperature of the evaporation unit 102 exceeds the set temperature Tv. The set temperature Tv is the internal temperature of the evaporation unit 102 at which water vapor can be generated by the evaporation of water W during startup. The set temperature Tv is, for example, 100°C or higher.
[0036] When the hydrogen generation system 500 starts up, the reforming unit 103 is heated by the heating unit 101 until the temperature of the reforming catalyst 103c exceeds a first set temperature T1. The first set temperature T1 is the temperature at which water W is supplied from the raw material supplier 200 to the evaporation unit 102 during startup. The first set temperature T1 is, for example, 70°C or higher and less than 100°C.
[0037] When the hydrogen generation system 500 starts up, the CO reduction unit 104 is heated by the heating unit 101 until the temperature of the CO-modified catalyst 104c exceeds the set temperature Ts. The set temperature Ts is the temperature at which water W is supplied from the raw material supplier 200 to the evaporation unit 102 during startup. The set temperature Ts is, for example, 70°C or higher and less than 100°C.
[0038] In the hydrogen production system 500, it is desirable to install the heating unit 101 near the reforming unit 103, which requires heating to a higher temperature. This allows, for example, during startup, the temperature of the reforming catalyst 103c to be rapidly heated to a first set temperature T1, and the temperature of the CO conversion catalyst 104c to be rapidly heated to a set temperature Ts. Furthermore, for example, during normal operation, the temperatures of the reforming catalyst 103c and the CO conversion catalyst 104c can be heated to the optimal temperatures for each reaction.
[0039] In this embodiment, the controller 300 controls the raw material feeder 200 to satisfy the following conditions (i), (ii), and (iii) during the first period from when the temperature of the reformed catalyst 103c exceeds the first set temperature T1 until it reaches the second set temperature T2, after the start of the startup operation. (i) The steam / carbon ratio (S / C ratio), which is the ratio of the number of moles of water molecules to the number of moles of carbon atoms in the mixed gas G1 supplied to the reforming unit 103, is greater than 0 and 2.0 or less. (ii) The dew point D1 of the mixed gas G1 supplied to the reforming unit 103 is lower than the temperature of the reformed catalyst 103c. (iii) The dew point D2 of the reformed gas G2 supplied to the CO reduction unit 104 is lower than the temperature of the CO-modified catalyst 104c.
[0040] In this embodiment, during the first period, the heating unit 101 continues to heat the reforming catalyst 103c while controlling the raw material supply unit 200 to satisfy the above conditions (i), (ii), and (iii). The first period is, for example, the period during which water W can be supplied from the raw material supply unit 200 to the evaporation unit 102. As described above, the first set temperature T1 is, for example, 70°C or more and less than 100°C. The second set temperature T2 is, for example, 300°C. "Dew point D1 of mixed gas G1" means the dew point of the mixed gas G1 that is generated in the evaporation unit 102 and supplied to the reforming unit 103 during startup operation, and is distinguished from the dew point of the mixed gas G1 that is generated in the evaporation unit 102 and supplied to the reforming unit 103 during normal operation, especially during rated operation. "Dew point D2 of reformed gas G2" refers to the dew point of reformed gas G2 generated in the reforming unit 103 and supplied to the CO reduction unit 104 during startup operation, and is distinct from the dew point of reformed gas G2 generated in the reforming unit 103 and supplied to the CO reduction unit 104 during normal operation, especially during rated operation.
[0041] The inventors have found that during startup, the small amount of water vapor present on the surface of the reforming catalyst 103c suppresses the decomposition reaction of the raw material gas G0, thereby suppressing carbon deposition. As a result, in the hydrogen production system 500, the S / C ratio during startup can be set to a low value of more than 0 and 2.0 or less, thereby lowering the dew point D2 of the reformed gas G2. Consequently, during startup, the condensation of water vapor in the CO reduction section 104 can be suppressed, eliminating the need to provide a heater to heat the CO reduction section 104. Furthermore, during startup, water W can be supplied to the evaporation section 102 before the temperature of the reforming catalyst 103c rises too high, thus suppressing carbon deposition in the reforming section 103 caused by insufficient water W supply. In other words, the hydrogen production system 500 makes it possible to suppress both carbon deposition in the reforming section 103 and the generation of condensed water in the CO reduction section 104 during startup without providing a heater. The hydrogen generation system 500 has a simple configuration, yet is suitable for cost reduction.
[0042] The S / C ratio may be more than 0 and 1.9 or less. The upper limit of the S / C ratio may be 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, or further 1.0.
[0043] The S / C ratio may be more than 0 and less than 1.0. The upper limit of the S / C ratio may be 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or further 0.1.
[0044] The first set temperature T1 is lower than, for example, the decomposition temperature at which hydrocarbons contained in the raw material gas G0 are decomposed by the reforming reaction in the reforming unit 103. According to this configuration, the reforming reaction in the reforming unit 103 can be allowed to proceed at a temperature lower than the decomposition temperature. As a result, carbon precipitation in the reforming unit 103 can be more effectively suppressed.
[0045] In the present embodiment, during the first period, the controller 300 may control the raw material feeder 200 to start supplying water W to the evaporation unit 102 before the temperature of the CO shift catalyst 104c reaches the dew point d2 of the reformed gas G2 during normal operation, particularly during rated operation. According to this configuration, during start-up operation, in addition to being able to supply water W to the evaporation unit 102 before the temperature of the reforming catalyst 103c excessively rises, water W can be supplied to the evaporation unit 102 before the temperature of the CO shift catalyst 104c excessively rises. As a result, carbon precipitation in the reforming unit 103 caused by insufficient supply of water W can be suppressed, and deterioration of the CO shift catalyst caused by generation of condensed water can be suppressed. The "dew point d2 of the reformed gas G2 during normal operation, particularly during rated operation" means the dew point of the reformed gas G2 generated in the reforming unit 103 and supplied to the CO reduction unit 104 during normal operation, particularly during rated operation. The dew point d2 of the reformed gas G2 during normal operation, particularly during rated operation, is calculated and set in advance by, for example, the controller 300. The dew point d2 of the reformed gas G2 during normal operation, particularly during rated operation, is, for example, 90°C.
[0046] In the present embodiment, the controller 300 causes the heating unit 101 to continue increasing the temperature of the reforming catalyst 103c during the second period from when the temperature of the reforming catalyst 103c exceeds the second set temperature T2 until it reaches the third set temperature T3. The second period is a period for further increasing the temperature of the reforming catalyst 103c in preparation for transition to normal operation. The third set temperature T3 is, for example, 700°C.
[0047] In the present embodiment, when the temperature of the reforming catalyst 103c exceeds the third set temperature T3, the controller 300 terminates the startup operation and transitions to normal operation. The normal operation is as described above.
[0048] As described above, in the present embodiment, the controller 300 calculates the S / C ratio during startup operation, the dew point of the mixed gas G1, and the dew point of the reformed gas G2. However, for example, a gas analyzer for confirming the S / C ratio of the mixed gas G1 supplied to the reforming unit 103 and a dew point sensor for detecting the dew point of the mixed gas G1 supplied to the reforming unit 103 may be provided near the inlet of the reforming unit 103. A dew point sensor for detecting the dew point of the reformed gas G2 supplied to the CO reduction unit 104 may be provided near the inlet of the CO reduction unit 104.
[0049] As shown in FIG. 1, the reforming unit 103 may be provided with a temperature sensor 503 for detecting the temperature of the reforming catalyst 103c.
[0050] As shown in FIG. 1, the CO reduction unit 104 may be provided with a temperature sensor 505 for detecting the temperature of the CO shift catalyst 104c.
[0051] In the present embodiment, the hydrogen generation system 500 further includes a raw material path 400. The raw material path 400 is a path that guides water W from the raw material supplier 200 to the evaporation unit 102. The raw material path 400 connects the raw material outlet of the raw material supplier 200 and the raw material inlet of the evaporation unit 102.
[0052] The raw material supplier 200 may include a raw material gas supply unit 201 for supplying the raw material gas G0 to the evaporation unit 102, and a water supply unit 202 for supplying water W to the evaporation unit 102.
[0053] The controller 300 can individually control the raw material gas supply unit 201 and the water supply unit 202. For example, during the first period, the controller 300 controls the flow rate of the raw material gas G0 supplied from the raw material gas supply unit 201 to the evaporation unit 102 and the flow rate of the water W supplied from the water supply unit 202 to the evaporation unit 102 so as to satisfy the above conditions (i), (ii), and (iii).
[0054] The raw material path 400 may include a raw material gas path 401 and a water path 402. The raw material gas path 401 is a path that guides raw material gas G0 from the raw material gas supply unit 201 to the evaporation unit 102. The raw material gas path 401 connects the raw material gas outlet of the raw material gas supply unit 201 to the raw material gas inlet of the evaporation unit 102. The water path 402 is a path that guides water W from the water supply unit 202 to the evaporation unit 102. The water path 402 connects the water outlet of the water supply unit 202 to the water inlet of the evaporation unit 102.
[0055] The raw material gas supply unit 201 is, for example, a pump that supplies raw material gas G0 to the evaporation unit 102 through the raw material gas path 401. The water supply unit 202 is, for example, a pump that supplies water W to the evaporation unit 102 through the water path 402.
[0056] The water supply unit 202 may be configured to switch between an intermittent supply method, which alternately supplies and stops the water W, and a continuous supply method, which continuously supplies the water W.
[0057] The controller 300 may control the supply method of the water supply unit 202 during the first period. In order to continuously supply a small amount of water W that satisfies the above condition (i) to the evaporation unit 102, high-precision control using a precision pump or the like may be required separately. However, by controlling the water supply unit 202 to switch to an intermittent method during the first period using the controller 300, a small amount of water W can be supplied to the evaporation unit 102 without installing a precision pump or the like. As a result, costs can be further reduced and energy savings can be achieved.
[0058] The hydrogen generation system 500 may further include a fuel supplyer 205 and an air supplyer 206. The fuel supplyer 205 supplies fuel gas Gf to the heating unit 101. The air supplyer 206 supplies air Ga to the heating unit 101.
[0059] The heating unit 101, which is supplied with fuel gas Gf and air Ga, burns the fuel gas Gf using the air Ga to generate heat.
[0060] The hydrogen generation system 500 may further include a fuel gas path 405 and an air path 406. The fuel gas path 405 is a path that guides fuel gas Gf from the fuel supply unit 205 to the heating unit 101. The fuel gas path 405 connects the fuel gas outlet of the fuel supply unit 205 to the fuel gas inlet of the heating unit 101. The air path 406 is a path that guides air Ga from the air supply unit 206 to the heating unit 101. The air path 406 connects the air outlet of the air supply unit 206 to the air inlet of the heating unit 101.
[0061] The fuel supply unit 205 is, for example, a pump that supplies fuel gas Gf to the heating unit 101 through the fuel gas path 405. The air supply unit 206 is, for example, a fan that supplies air Ga to the heating unit 101 through the air path 406.
[0062] The controller 300 can control the fuel supply unit 205 and the air supply unit 206 individually.
[0063] [1-2. Operation] Below, an example of the operation and function of the hydrogen generation system 500 in Embodiment 1 will be described with reference to Figure 2. Figure 2 is a chart for explaining the control of operation during startup of the hydrogen generation system 500. Startup of the hydrogen generation system 500 can be performed by the controller 300.
[0064] Before the hydrogen generation system 500 is started up, the raw material supplier 200, fuel supplier 205, and air supplier 206 are shut down.
[0065] When the controller 300 receives a start command, it starts the hydrogen generation system 500. Specifically, it starts the hydrogen generation system 500 according to the following procedure.
[0066] First, the controller 300 operates the fuel supply unit 205 and the air supply unit 206 to start supplying fuel gas Gf and air Ga to the heating unit 101. By performing an ignition operation in the heating unit 101, the fuel gas Gf is burned using air Ga. The flow rate of fuel gas Gf supplied from the fuel supply unit 205 to the heating unit 101 is, for example, 1 L / min. The flow rate of air Ga supplied from the air supply unit 206 to the heating unit 101 is, for example, 20 L / min.
[0067] Next, the controller 300 controls the raw material supplier 200 to start supplying the raw material gas G0 to the evaporation unit 102. Specifically, it operates the raw material gas supply unit 201 to start supplying the raw material gas G0 to the evaporation unit 102 (step S101). The flow rate of the raw material gas G0 supplied from the raw material gas supply unit 201 to the evaporation unit 102 is, for example, 1.0 L / min.
[0068] Next, the controller 300 determines whether the temperature of the reformed catalyst 103c has exceeded the first set temperature T1 (step S102). The controller 300 measures the temperature of the reformed catalyst 103c using, for example, a temperature sensor 503 provided in the reforming unit 103, and determines whether the temperature of the reformed catalyst 103c has exceeded the first set temperature T1. If the determination shows that the temperature of the reformed catalyst 103c is lower than the first set temperature T1, step S102 is repeated until the temperature of the reformed catalyst 103c exceeds the first set temperature T1. As described above, the first set temperature T1 is, for example, 70°C or higher and less than 100°C.
[0069] After the start-up operation begins, during the first period from when the temperature of the reformed catalyst 103c exceeds the first set temperature T1 until it reaches the second set temperature T2, the controller 300 controls the raw material feeder 200 to satisfy the following conditions (i), (ii), and (iii) (step S104). (i) The S / C ratio, which is the ratio of the number of moles of water molecules to the number of moles of carbon atoms in the mixed gas G1 supplied to the reforming unit 103, is greater than 0 and less than or equal to 2.0. (ii) The dew point D1 of the mixed gas G1 supplied to the reforming unit 103 is lower than the temperature of the reformed catalyst 103c. (iii) The dew point D2 of the reformed gas G2 supplied to the CO reduction unit 104 is lower than the temperature of the CO-modified catalyst 104c.
[0070] By performing step S104, it is possible to suppress both the precipitation of carbon in the reforming section 103 and the generation of condensed water in the CO reduction section 104 during startup.
[0071] With respect to the above condition (ii), the controller 300 may control the dew point D1 of the mixed gas G1 supplied to the reforming unit 103 to be lower than the temperature of the reforming catalyst 103c in the reforming unit 103 by not supplying water W from the raw material feeder 200 to the evaporation unit 102, or by reducing the flow rate of water W supplied from the raw material feeder 200. When water W is supplied from the raw material feeder 200 to the evaporation unit 102, if the flow rate of water W supplied is high and the dew point D1 of the mixed gas G1 supplied to the reforming unit 103 rises, the controller 300 may control the raw material feeder 200 to reduce the S / C ratio of the mixed gas G1 supplied to the reforming unit 103.
[0072] With respect to the above condition (iii), the controller 300 may control the system so that the dew point D2 of the reformed gas G2 supplied to the CO reduction unit 104 is lower than the temperature of the CO-modified catalyst 104c in the CO reduction unit 104, either by not supplying water W from the raw material feeder 200 to the evaporation unit 102, or by reducing the flow rate of water W supplied from the raw material feeder 200. When water W is supplied from the raw material feeder 200 to the evaporation unit 102, if the flow rate of water W supplied is high and the dew point D2 of the reformed gas G2 supplied to the CO reduction unit 104 rises, the controller 300 may control the raw material feeder 200 so that the S / C ratio of the mixed gas G1 supplied to the reforming unit 103 decreases.
[0073] If the determination does not satisfy the above conditions (i), (ii), and (iii), then step S104 is repeated during the first period until the above conditions (i), (ii), and (iii) are satisfied.
[0074] However, in this embodiment, during the first period, the controller 300 controls the raw material feeder 200 to start supplying water W to the evaporation unit 102 before the temperature of the CO-modified catalyst 104c reaches the dew point d2 of the reformed gas G2 during normal operation, especially during rated operation. Specifically, the water supply unit 202 is operated to start supplying water W to the evaporation unit 102 (step S103). The flow rate of water W supplied from the water supply unit 202 to the evaporation unit 102 is, for example, 0.5 L / min. The dew point d2 of the reformed gas G2 during normal operation, especially during rated operation, is, for example, 90°C. With this configuration, in addition to being able to supply water W to the evaporation unit 102 before the temperature of the reformed catalyst 103c rises too high, water W can also be supplied to the evaporation unit 102 before the temperature of the CO-modified catalyst 104c rises too high. As a result, carbon deposition in the reforming section 103 caused by insufficient water supply can be suppressed, and deterioration of the CO conversion catalyst due to the generation of condensed water can be suppressed.
[0075] The S / C ratio during startup may be greater than 0 and 1.9 or less. The upper limit of the S / C ratio may be 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, or even 1.0.
[0076] The S / C ratio during startup may be greater than 0 and less than 1.0. The upper limit of the S / C ratio may be 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or even 0.1.
[0077] The controller 300 may control the water supply method of the water supply unit 202 during the first period. By controlling the water supply method of the water supply unit 202 to be switched to an intermittent method by the controller 300, a small amount of water W can be supplied to the evaporation unit 102 without installing a precision pump or the like. As a result, costs can be further reduced and energy savings can be achieved.
[0078] By doing so, it is possible to suppress both the precipitation of carbon in the reforming section 103 and the generation of condensed water in the CO reduction section 104 during startup.
[0079] Next, the controller 300 determines whether the temperature of the reformed catalyst 103c has exceeded the second set temperature T2 (step S105). The controller 300 measures the temperature of the reformed catalyst 103c using, for example, a temperature sensor 503 provided in the reforming unit 103, and determines whether the temperature of the reformed catalyst 103c has exceeded the second set temperature T2. If the determination shows that the temperature of the reformed catalyst 103c is lower than the second set temperature T2, step S105 is repeated until the temperature of the reformed catalyst 103c exceeds the second set temperature T2. As described above, the second set temperature T2 is, for example, 300°C.
[0080] During the second period, from when the temperature of the reformed catalyst 103c exceeds the second set temperature T2 until it reaches the third set temperature T3, the controller 300 continues to raise the temperature of the reformed catalyst 103c using the heating unit 101 (step S106). Step S106 is a step to further raise the temperature of the reformed catalyst 103c in preparation for transitioning to normal operation. As described above, the third set temperature T3 is, for example, 700°C.
[0081] Next, the controller 300 determines whether the temperature of the reformed catalyst 103c has exceeded the third set temperature T3 (step S107). The controller 300 measures the temperature of the reformed catalyst 103c using, for example, a temperature sensor 503 provided in the reforming unit 103, and determines whether the temperature of the reformed catalyst 103c has exceeded the third set temperature T3. If the determination shows that the temperature of the reformed catalyst 103c is lower than the third set temperature T3, step S107 is repeated until the temperature of the reformed catalyst 103c exceeds the third set temperature T3.
[0082] When the temperature of the reformed catalyst 103c exceeds the third set temperature T3, the controller 300 terminates the startup operation and transitions to normal operation.
[0083] At the end of the startup operation, the evaporation unit 102, the reforming unit 103, and the CO reduction unit 104 are in a state where they have risen to a certain temperature. Therefore, the controller 300 can smoothly transition the hydrogen generator 100 to normal operation based on normal operation conditions, including, for example, the temperature conditions for normal operation, the flow rate of the raw material gas G0 and the flow rate of water W during normal operation, and a preset S / C ratio. During normal operation, the S / C ratio of the mixed gas G1 supplied to the reforming unit 103 remains constant. Normal operation of the hydrogen generation system 500 may also be rated operation. Normal operation of the hydrogen generation system 500 is performed, for example, by the following procedure.
[0084] First, the controller 300 controls the flow rate of the raw material gas G0 and the flow rate of water W supplied from the raw material supplier 200 to the evaporation unit 102. At this time, the temperature inside the evaporation unit 102 has already reached 100°C. Therefore, water W evaporates in the evaporation unit 102, generating water vapor. The generated water vapor mixes with the raw material gas G0 to produce a mixed gas G1.
[0085] Next, the controller 300 controls the flow rate of the mixed gas G1 supplied from the evaporation unit 102 to the reforming unit 103. The flow rate of the mixed gas G1 supplied from the evaporation unit 102 to the reforming unit 103 is, for example, 4 L / min. At this time, the temperature of the reforming catalyst 103c has already been heated to a temperature suitable for the reaction (for example, 700°C). As a result, the reforming reaction by the reforming catalyst 103c generates a reformed gas G2 containing hydrogen gas and carbon monoxide from the mixed gas G1.
[0086] Next, the controller 300 controls the flow rate of the reformed gas G2 supplied from the reforming unit 103 to the CO reduction unit 104. The flow rate of the reformed gas G2 supplied from the reforming unit 103 to the CO reduction unit 104 is, for example, 4 L / min. At this time, the temperature of the CO modification catalyst 104c has already been heated to a temperature suitable for the reaction (for example, 200°C). As a result, hydrogen-containing gas G3 with a reduced carbon monoxide concentration is produced from the reformed gas G2 by the modification reaction by the CO modification catalyst.
[0087] The hydrogen-containing gas G3 produced by the hydrogen generator 100 is supplied to, for example, a fuel cell. For example, in the fuel cell, power generation is started using the hydrogen-containing gas G3 and oxygen from the air.
[0088] (Other Embodiments) As described above, Embodiment 1 has been explained as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this and can be applied to embodiments that have been modified, added to, or omitted. Furthermore, it is possible to create new embodiments by combining the components described in the above embodiment and its modifications.
[0089] The embodiments described above are for illustrative purposes only and may be modified, replaced, added, or omitted within the scope of the claims or equivalents.
[0090] (Note) The above description of embodiments discloses the following technology.
[0091] (Technology 1) A hydrogen generation system comprising: a hydrogen generator; a raw material supplyer that supplies water and a hydrocarbon-containing raw material gas to the hydrogen generator; and a controller, wherein the hydrogen generator comprises: an evaporation unit that evaporates the water to generate water vapor and generates a mixed gas of the water vapor and the raw material gas; a reforming unit filled with a reforming catalyst that generates a reformed gas containing hydrogen gas and carbon monoxide from the mixed gas; a CO reduction unit filled with a CO conversion catalyst that generates a hydrogen-containing gas with a reduced carbon monoxide concentration from the reformed gas; and a heating unit that heats the evaporation unit, the reforming unit, and the CO reduction unit, wherein the controller, after the start of the hydrogen generation system's startup operation, raises the temperature of the reforming catalyst using the heating unit and controls the raw material supplyer to satisfy the following conditions (i), (ii), and (iii) during a first period from when the temperature of the reforming catalyst exceeds a first set temperature until it reaches a second set temperature. (i) The S / C ratio, which is the ratio of the number of moles of water molecules to the number of moles of carbon atoms in the mixed gas supplied to the reforming section, is greater than 0 and less than or equal to 2.0; (ii) The dew point of the mixed gas supplied to the reforming section is lower than the temperature of the reforming catalyst; (iii) The dew point of the reforming gas supplied to the CO reduction section is lower than the temperature of the CO conversion catalyst.
[0092] Technology 1's hydrogen generation system has a simple configuration and is suitable for cost reduction.
[0093] (Technology 2) The hydrogen production system according to Technology 1, wherein the controller controls the raw material supplier so that during the first period, the supply of water to the evaporation section begins before the temperature of the CO-modified catalyst reaches the dew point of the reformed gas during normal operation. With this configuration, the deposition of carbon in the reforming section due to insufficient water supply can be suppressed, and the deterioration of the CO-modified catalyst due to the generation of condensed water can be suppressed.
[0094] (Technology 3) The hydrogen generation system according to Technology 1 or 2, wherein the first set temperature is lower than the decomposition temperature at which hydrocarbons contained in the raw material gas decompose in the reforming section. With such a configuration, carbon deposition in the reforming section can be suppressed more effectively.
[0095] (Technical 4) The hydrogen production system according to any one of Technical 1 to 3, wherein the reforming catalyst comprises at least one selected from the group consisting of Rh, Ru, Ni, Ir, Pd, Pt, Re, Co, and Fe. With such a configuration, the reforming reaction in the reforming section can be effectively carried out.
[0096] (Technology 5) The hydrogen generation system according to any one of the technologies 1 to 4, wherein the raw material supplier includes a water supply unit that can switch between an intermittent supply method, which alternates between supplying and stopping the water, and a continuous supply method, which continuously supplies the water, and the controller controls the supply method of the water supply unit during the first period. With such a configuration, a small amount of water can be supplied to the evaporation unit without installing a precision pump or the like. As a result, costs can be further reduced and energy savings can be achieved.
[0097] (Technical 6) A hydrogen production system according to any one of Technical 1 to 5, wherein the controller continues to raise the temperature of the reforming catalyst by the heating unit during a second period from when the temperature of the reforming catalyst exceeds the second set temperature until it reaches the third set temperature. With such a configuration, the transition to normal operation can be made smoothly.
[0098] (Technical 7) The hydrogen production system according to Technical 6, wherein the controller terminates the startup operation and transitions to normal operation when the temperature of the reforming catalyst exceeds the third set temperature. With such a configuration, normal operation can be started smoothly.
[0099] (Technical 8) A method for operating a hydrogen generation system comprising: a hydrogen generation device; and a raw material supplyer that supplies water and a hydrocarbon-containing raw material gas to the hydrogen generation device, wherein the hydrogen generation device comprises: an evaporation unit that evaporates the water to generate steam and generates a mixed gas of the steam and the raw material gas; a reforming unit filled with a reforming catalyst that generates a reformed gas containing hydrogen gas and carbon monoxide from the mixed gas; a CO reduction unit filled with a CO conversion catalyst that generates a hydrogen-containing gas with a reduced carbon monoxide concentration from the reformed gas; and a heating unit that heats the evaporation unit, the reforming unit, and the CO reduction unit, wherein after the start operation of the hydrogen generation system, the heating unit raises the temperature of the reforming catalyst, and during a first period from when the temperature of the reforming catalyst exceeds a first set temperature until it reaches a second set temperature, the raw material supplyer is controlled to satisfy the following conditions (i), (ii), and (iii). A method for operating a hydrogen production system, wherein (i) the S / C ratio, which is the ratio of the number of moles of water molecules to the number of moles of carbon atoms in the mixed gas supplied to the reforming unit, is greater than 0 and less than or equal to 2.0; (ii) the dew point of the mixed gas supplied to the reforming unit is lower than the temperature of the reforming catalyst; and (iii) the dew point of the reforming gas supplied to the CO reduction unit is lower than the temperature of the CO conversion catalyst.
[0100] According to the operating method of the hydrogen generation system of Technology 8, hydrogen-containing gas can be generated while simultaneously suppressing carbon deposition in the reforming section and suppressing the generation of condensed water in the CO reduction section.
[0101] (Technical 9) A method for operating the hydrogen production system according to Technical 8, comprising controlling the raw material feeder so that, during the first period, the supply of water to the evaporation section is started before the temperature of the CO-modification catalyst reaches the dew point of the reformed gas during normal operation. With such a configuration, the deposition of carbon in the reforming section due to insufficient water supply can be suppressed, and the deterioration of the CO-modification catalyst due to the generation of condensed water can be suppressed.
[0102] (Technical 10) A method for operating a hydrogen production system according to Technical 8 or 9, wherein the first set temperature is lower than the decomposition temperature at which hydrocarbons contained in the raw material gas decompose in the reforming section. With such a configuration, carbon deposition in the reforming section can be suppressed more effectively.
[0103] (Technical 11) A method for operating a hydrogen production system according to any one of Technical 8 to 10, wherein the reforming catalyst comprises at least one selected from the group consisting of Rh, Ru, Ni, Ir, Pd, Pt, Re, Co, and Fe. With such a configuration, the reforming reaction in the reforming section can be effectively carried out.
[0104] (Technical 12) A method for operating a hydrogen generation system according to any one of Technical 8 to 11, wherein the raw material feeder includes a water supply unit that can switch between an intermittent supply method that alternately supplies and stops the water and a continuous supply method that continuously supplies the water, and the method includes controlling the supply method of the water supply unit during the first period. With such a configuration, a small amount of water can be supplied to the evaporation unit without installing a precision pump or the like. As a result, costs can be further reduced and energy can be saved.
[0105] (Technical 13) A method for operating a hydrogen production system according to any one of Technical 8 to 12, comprising continuing to raise the temperature of the reforming catalyst by the heating unit during a second period from when the temperature of the reforming catalyst exceeds the second set temperature until it reaches the third set temperature. With such a configuration, a smooth transition to normal operation can be made.
[0106] (Technical 14) An operating method for the hydrogen production system according to Technical 13, comprising terminating the startup operation and transitioning to normal operation when the temperature of the reforming catalyst exceeds the third set temperature. With such a configuration, normal operation can be started smoothly.
[0107] The hydrogen generation system and operating method of the hydrogen generation system described herein can be combined with fuel cells and the like.
Claims
1. A hydrogen generation system comprising: a hydrogen generator; a raw material supplier that supplies water and a hydrocarbon-containing raw material gas to the hydrogen generator; and a controller, wherein the hydrogen generator comprises: an evaporation unit that evaporates the water to generate water vapor and generates a mixed gas of the water vapor and the raw material gas; a reforming unit filled with a reforming catalyst that generates a reformed gas containing hydrogen gas and carbon monoxide from the mixed gas; a CO reduction unit filled with a CO conversion catalyst that generates a hydrogen-containing gas with a reduced carbon monoxide concentration from the reformed gas; and a heating unit that heats the evaporation unit, the reforming unit, and the CO reduction unit, wherein the controller, after the start of the hydrogen generation system's startup operation, raises the temperature of the reforming catalyst using the heating unit and controls the raw material supplier to satisfy the following conditions (i), (ii), and (iii) during a first period from when the temperature of the reforming catalyst exceeds a first set temperature until it reaches a second set temperature. (i) The S / C ratio, which is the ratio of the number of moles of water molecules to the number of moles of carbon atoms in the mixed gas supplied to the reforming section, is greater than 0 and less than or equal to 2.0; (ii) The dew point of the mixed gas supplied to the reforming section is lower than the temperature of the reforming catalyst; (iii) The dew point of the reforming gas supplied to the CO reduction section is lower than the temperature of the CO conversion catalyst.
2. The hydrogen production system according to claim 1, wherein the controller controls the raw material supplier so that during the first period, the supply of water to the evaporator begins before the temperature of the CO-modification catalyst reaches the dew point of the reformed gas during normal operation.
3. The hydrogen generation system according to claim 1, wherein the first set temperature is lower than the decomposition temperature at which hydrocarbons contained in the raw material gas decompose in the reforming unit.
4. The hydrogen generation system according to claim 1, wherein the reforming catalyst comprises at least one selected from the group consisting of Rh, Ru, Ni, Ir, Pd, Pt, Re, Co, and Fe.
5. The hydrogen generation system according to claim 1, wherein the raw material supplier includes a water supply unit that can switch between an intermittent supply method that alternately supplies and stops the water and a continuous supply method that continuously supplies the water, and the controller controls the supply method of the water supply unit during the first period.
6. The hydrogen generation system according to claim 1, wherein the controller continues to raise the temperature of the reforming catalyst by the heating unit during a second period from when the temperature of the reforming catalyst exceeds the second set temperature until it reaches the third set temperature.
7. The hydrogen generation system according to claim 6, wherein the controller terminates the startup operation and transitions to normal operation when the temperature of the reforming catalyst exceeds the third set temperature.
8. A method for operating a hydrogen generation system comprising: a hydrogen generation device; and a raw material supplyer that supplies water and a hydrocarbon-containing raw material gas to the hydrogen generation device, wherein the hydrogen generation device comprises: an evaporation unit that evaporates the water to generate steam and generates a mixed gas of the steam and the raw material gas; a reforming unit filled with a reforming catalyst that generates a reformed gas containing hydrogen gas and carbon monoxide from the mixed gas; a CO reduction unit filled with a CO conversion catalyst that generates a hydrogen-containing gas with a reduced carbon monoxide concentration from the reformed gas; and a heating unit that heats the evaporation unit, the reforming unit, and the CO reduction unit, wherein after the start operation of the hydrogen generation system, the heating unit raises the temperature of the reforming catalyst, and during a first period from when the temperature of the reforming catalyst exceeds a first set temperature until it reaches a second set temperature, the raw material supplyer is controlled to satisfy the following conditions (i), (ii), and (iii). A method for operating a hydrogen production system, wherein (i) the S / C ratio, which is the ratio of the number of moles of water molecules to the number of moles of carbon atoms in the mixed gas supplied to the reforming unit, is greater than 0 and less than or equal to 2.0; (ii) the dew point of the mixed gas supplied to the reforming unit is lower than the temperature of the reforming catalyst; and (iii) the dew point of the reforming gas supplied to the CO reduction unit is lower than the temperature of the CO conversion catalyst.
9. A method for operating a hydrogen production system according to claim 8, comprising controlling the raw material feeder to start supplying water to the evaporator before the temperature of the CO-modification catalyst reaches the dew point of the reformed gas during normal operation during the first period.
10. The method for operating a hydrogen production system according to claim 8, wherein the first set temperature is lower than the decomposition temperature at which hydrocarbons contained in the raw material gas decompose in the reforming unit.
11. The method for operating a hydrogen production system according to claim 8, wherein the reforming catalyst comprises at least one selected from the group consisting of Rh, Ru, Ni, Ir, Pd, Pt, Re, Co, and Fe.
12. The method for operating a hydrogen generation system according to claim 8, wherein the raw material supplier includes a water supply unit that can switch between an intermittent supply method that alternately supplies and stops the water and a continuous supply method that continuously supplies the water, and the method includes controlling the supply method of the water supply unit during the first period.
13. A method for operating a hydrogen production system according to claim 8, comprising continuing to raise the temperature of the reforming catalyst by the heating unit during a second period from when the temperature of the reforming catalyst exceeds the second set temperature until it reaches the third set temperature.
14. A method for operating a hydrogen production system according to claim 13, comprising terminating the startup operation and transitioning to normal operation when the temperature of the reforming catalyst exceeds the third set temperature.