Method for operating a cascade reformer, device and sofc power generation system

Abstract

This application discloses an operation control method, device, and SOFC power generation system for a cascaded reformer. For a cascaded reformer with a stepped design, the operation control method determines the reformer level that should respond to the gas supply based on the current state, target state, and reforming gas demand of the SOFC stack. Different levels of reformers respond to the reforming gas flow required to switch to different operating states. In other words, the reforming gas flow fluctuations caused by the power fluctuations of the SOFC stack are distributed to each level of reformer, avoiding the situation where only one level or only one reformer responds to all flow fluctuations. This maximizes the protection of the reformers and the SOFC stack, significantly improves the overall reliability of the SOFC power generation system, and makes the overall system response time to reforming gas flow fluctuations shorter, greatly improving the system's efficiency and stability.

Description

Technical Field

[0001] This invention pertains to reformer control technology, and particularly relates to a method, apparatus, and SOFC power generation system for controlling the operation of a cascaded reformer. Background Technology

[0002] Solid oxide fuel cells (SOFCs) belong to the third generation of fuel cells. They are all-solid-state chemical power generation devices that efficiently and environmentally convert the chemical energy stored in fuel and oxidant into electrical energy directly at medium to high temperatures. SOFCs have the highest theoretical energy density among various types of fuel cells. Hydrogen gas is commonly used as the fuel for SOFCs; however, hydrogen presents significant challenges in storage and transportation. Therefore, hydrogen production technology is a hot topic of widespread interest in the energy sector both domestically and internationally.

[0003] There are various ways to produce hydrogen, such as reforming of organic matter, thermal decomposition, photolysis, water electrolysis, and biological hydrogen production. However, reforming hydrogen production using hydrocarbons and alcohols as basic raw materials is still the main method of industrial hydrogen production, especially alcohol reforming hydrogen production, which is mainly carried out by steam reforming or partial oxidation.

[0004] A typical SOFC (SOFC Combined Heat and Power) system includes the SOFC itself, a fuel processing module, and a heat recovery module. Required equipment includes a steam generator, a reforming reactor, a heat exchanger, and a burner. In actual operation, the SOFC stack system experiences varying power fluctuations. This necessitates that the reformed gas flow rate generated by the methanol reformer fluctuate in response to these power fluctuations. Repeated flow fluctuations are detrimental to both the reforming reactor catalyst and the reactor itself, easily shortening reactor lifespan, causing catalyst deactivation under certain conditions, and resulting in a long response time due to the system's significant thermal inertia. Summary of the Invention

[0005] Based on this, the present invention aims to provide a method, apparatus and SOFC power generation system for operating a cascaded reformer, so as to at least overcome the shortcomings of the prior art.

[0006] In a first aspect, the present invention provides an operation control method for a cascaded reformer, wherein the cascaded reformer includes at least two stages of reformers, each stage of the reformer is configured according to the available gas flow rate, and the reforming gas flow rate required for each operating state of the SOFC stack is responded to by the reformers at different stages. The operation control method includes:

[0007] Obtain the current status, target status, and reforming gas demand of the SOFC stack;

[0008] Determine the reformer level for adjusting the gas supply based on the current and target states;

[0009] Control commands for the cascaded reformer are generated based on the reformer gas demand.

[0010] According to the control command, the gas supply of the cascaded reformer corresponding to the determined level is adjusted so that the gas supply meets the reforming gas requirements of the SOFC stack.

[0011] Furthermore, determining the reformer level for adjusting the gas supply based on the current and target states includes:

[0012] Determine the first reformer stage in response to the first reformer gas flow rate required to switch the SOFC stack from its current state to a target state;

[0013] Determine the second reformer stage in response to the second reformer gas flow rate required to maintain the SOFC stack in the target state.

[0014] Furthermore, when the SOFC stack transitions from its current state to the target state through an intermediate state, the reformer level for responding to gas supply regulation is determined based on the current state and the target state, including:

[0015] The third reformer stage is determined to respond to the third reformer flow rate required to switch the SOFC stack from its current state to an intermediate state.

[0016] The fourth reformer stage is determined to respond to the fourth reformer flow rate required to switch the SOFC stack from an intermediate state to a target state.

[0017] Furthermore, the above-mentioned operation control method includes:

[0018] When the demand for reformed gas is less than the lower limit of the allowable gas supply of the highest-level reformer among the activated reformers, the highest-level reformer among the activated reformers is controlled to stop supplying gas, and the other reformers among the activated reformers are supplied with gas.

[0019] When the demand for reformed gas is higher than the lower limit of the allowable gas supply of the highest-level reformer among the activated reformers but lower than its upper limit, the other reformers among the activated reformers except the highest-level reformer will stop supplying gas, and only the highest-level reformer among the activated reformers will supply gas.

[0020] Furthermore, the above-mentioned operation control method also includes:

[0021] Obtain temperature change information of SOFC stack;

[0022] The reforming gas requirement of the SOFC stack is determined based on temperature change information.

[0023] Furthermore, the above-mentioned operation control method also includes:

[0024] Obtain equipment information for SOFC stacks;

[0025] The reformer level for responding to gas supply adjustment is determined based on the correspondence between equipment information and reformer level.

[0026] In a second aspect, the present invention provides an operation control device for a cascaded reformer, comprising:

[0027] The status information acquisition unit is configured to acquire the current status and target status of the SOFC stack;

[0028] The reforming gas acquisition unit is configured to acquire the reforming gas demand of the SOFC stack.

[0029] The reformer level determination unit is configured to determine the reformer level for response gas supply adjustment based on the current state and the target state.

[0030] The instruction generation unit is configured to generate control instructions for the cascaded reformer based on the reformer gas demand.

[0031] The control unit is configured to control the reformer corresponding to the determined level in the cascaded reformer to adjust the gas supply according to the control command, so that the gas supply meets the reforming gas requirements of the SOFC stack.

[0032] Furthermore, the aforementioned operation control device also includes:

[0033] The temperature information acquisition unit is configured to acquire temperature change information of the SOFC stack.

[0034] Thirdly, the present invention provides an SOFC power generation system based on a cascaded reformer, including a cascaded reformer, a controller, and an SOFC stack system;

[0035] A cascaded reformer includes at least two stages of reformers. Each stage of reformer is set according to the available gas volume. Reformers of the same stage are connected in parallel. The reformed gas generated by each stage of reformer is controlled and distributed to the SOFC stack system by the controller. The reformed gas flow rate required for the SOFC stack system to switch to different target states is responded to by the reformers of different stages.

[0036] The controller and the cascaded reformer are connected to the SOFC stack system, respectively.

[0037] The controller uses the above-mentioned operation control method to control the gas supply of each stage of the cascaded reformer.

[0038] Furthermore, the gas supply range of each reformer is set according to the reforming gas demand corresponding to the operating status of the SOFC stack and the number of SOFC stacks in the SOFC stack system.

[0039] As can be seen from the above technical solutions, the present invention has the following beneficial effects:

[0040] This invention provides a method, apparatus, and SOFC power generation system for controlling the operation of a cascaded reformer. For a cascaded reformer with a stepped design, the operation control method determines the reformer level that responds to the gas supply based on the current state, target state, and reforming gas demand of the SOFC stack. Different levels of reformers respond to the reforming gas flow required to switch to different operating states. In other words, the reforming gas flow fluctuations caused by power fluctuations in the SOFC stack are distributed to each level of reformer, avoiding the situation where only one level or one reformer responds to all flow fluctuations. This maximizes the protection of the reformers and SOFC stack, significantly improves the overall reliability of the SOFC power generation system, and extends the service life of each system component. Each level of reformer is set according to the available gas supply. When responding to flow fluctuations, the dynamic condition changes of the large units are reduced, and the flow fluctuations that would normally be handled by the large units are handled by the smaller units. Since the stabilization time of the smaller units is shorter than that of the large units, the overall system response time to reforming gas flow fluctuations is shorter, greatly improving system efficiency and stability. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0042] Figure 1 A schematic diagram of the structure of an SOFC power generation system based on a cascaded methanol reformer is provided for an embodiment of the present invention;

[0043] Figure 2 A flowchart illustrating the operation control method of a cascaded reformer provided in this embodiment of the invention;

[0044] Figure 3 This is a schematic diagram of the operation control device for a cascaded reformer provided in an embodiment of the present invention;

[0045] Figure 4 A schematic diagram of the operation control device for another cascaded reformer provided in an embodiment of the present invention. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] A solid oxide fuel cell (SOFC) is a type of fuel cell that uses a solid oxide electrolyte, which conducts negative oxygen ions from the cathode to the anode. At the anode, these negative oxygen ions electrochemically oxidize hydrogen or carbon monoxide. The hydrogen in the fuel primarily comes from the reforming of natural gas, methanol, etc., while the oxygen originates from air. Typically, the fuel undergoes a reforming reaction upstream of the SOFC anode. The reforming products include hydrogen (H2), carbon monoxide (CO), and carbon dioxide (CO2). The fuel typically undergoes a reforming reaction to produce hydrogen in the reformer. The combustion reaction in the burner or combustion chamber provides the energy for the reforming reaction. The high-temperature flue gas generated during combustion enters the reformer and exchanges heat with the fuel, allowing the fuel to reform and produce hydrogen under the action of a catalyst.

[0048] In actual operation, SOFC stack systems mainly have four states: normal operation, standby, shutdown, and startup. During operation, various power fluctuations need to be switched according to the state transitions. Consequently, the reformed gas flow rate generated by the methanol reforming module also needs to fluctuate with the power fluctuations of the SOFC stack system. However, currently used are often large-scale methanol reformers. All gas flow changes caused by power fluctuations in the stack system are handled by a single level or the same reformer. In particular, from the startup and gas supply of the reformer to the first startup of the SOFC stack system, i.e. the entire SOFC stack system from shutdown to operation, there is a lack of corresponding operation control strategies. This results in a lack of effective handling of the system's thermal inertia and adversely affects the response when the stack system switches operating states.

[0049] Methanol-to-hydrogen has the advantages of low reforming reaction temperature and fewer hydrogen purification steps. Methanol-to-hydrogen steam reforming can produce hydrogen-rich gas with a high hydrogen content. However, this reforming reaction is an endothermic reaction with a high reaction temperature of around 200-300℃. The initial reaction rate is slow, and frequent and large-scale flow fluctuations have adverse effects on both the reformer and the catalyst.

[0050] To address the aforementioned technical problems, this application provides a cascaded reformer operation control method, apparatus, and SOFC power generation system through the following series of embodiments. The cascaded reformer includes at least two stages of reformers, with each stage set according to the available gas volume. The reforming gas flow rate required for the SOFC stack to switch to different target states is responded to by different stages of reformers. By controlling the operation of the cascaded reformer, the response to the reforming gas flow rate required for the SOFC stack system to switch operating states or operate at different temperatures is realized, i.e., the process of determining which stages of reformers reduce or increase the gas supply.

[0051] In one embodiment, this application provides a SOFC power generation system based on a cascaded reformer, including a cascaded reformer, a controller, and an SOFC stack system.

[0052] A cascaded reformer includes at least two stages of reformers. Each stage of reformer is set according to the available gas volume. Reformers of the same stage are connected in parallel. The reformed gas generated by each stage of reformer is controlled and distributed to the SOFC stack system by the controller. The required reformed gas flow rate for each operating state of the SOFC stack is responded to by the reformers of different stages.

[0053] The controller is connected to the SOFC stack system along with the cascaded reformers. The controller determines the appropriate reformer level based on the current state, target state, and reforming gas demand of the SOFC stack, and controls each level of the cascaded reformer to reduce or increase the gas supply, enabling the SOFC stack to switch between different operating states or temperatures.

[0054] Specifically, an SOFC stack system typically includes more than one SOFC stack, which are connected in parallel and each SOFC stack is connected to a controller. The controller can read the intrinsic parameters and time series variables of each SOFC stack to determine the current operating state of the SOFC stack and the target state to be switched to, and calculate the reforming gas flow rate required for each SOFC stack based on the power fluctuation data of the SOFC stack.

[0055] When the system is working, each level of reformer adjusts the gas supply according to the control command of the controller. For example, the gas supply may be reduced or increased according to the control command, or the current gas supply may be maintained. The generated reformed gas is distributed to each SOFC stack by the controller.

[0056] For example, the reformed gas generated by each stage of the reformer flows into the central pipeline, where it is uniformly controlled and distributed by the controller before flowing into each SOFC stack for power generation.

[0057] In a further embodiment, the gas supply range of each stage of the reformer is set according to the reforming gas demand corresponding to the SOFC stack operating state and the number of SOFC stacks.

[0058] Specifically, the gas flow rate of the reformer is positively correlated with its volume, and the reforming gas demand varies in different operating states of the SOFC stack. In addition to meeting the safe variable range of gas flow rate, the gas supply of each stage of the reformer can also meet the requirements of the tiered setup by designing reformers of different volumes. Taking a three-stage reformer as an example, the maximum gas supply of the lowest stage reformer can meet the reforming gas flow rate required for the operation of two SOFC stacks, the maximum gas supply of the secondary stage reformer can meet the reforming gas flow rate required for the operation of five SOFC stacks, and the maximum gas supply of the highest stage reformer can meet the reforming gas flow rate required for the operation of ten SOFC stacks. The reforming gas flow rate required when the SOFC stack switches to different operating states is responded to by different stages of the reformer. For example, the operating state corresponding to low gas flow rate demand is responded to by the reformer with a smaller maximum gas supply, and the operating state corresponding to high gas flow rate demand is responded to by the reformer with a larger maximum gas supply. Under this setting, the controller can determine which stage of the reformer should respond and adjust the gas supply according to the SOFC stack's state switching requirements and reforming gas demand.

[0059] The cascaded reformer settings in this embodiment allow different levels of reformers to respond to the required reforming gas flow rates when switching to different operating states. This distributes the reforming gas flow rate fluctuations caused by power fluctuations in the SOFC stack to each level of reformer, preventing only one level or single reformer from responding to all flow fluctuations. This maximizes the protection of the reformers and SOFC stack, significantly improving the overall reliability of the SOFC power generation system and extending the lifespan of all system equipment. The reformers at each level are configured according to the available gas volume. When responding to flow fluctuations, this reduces the dynamic changes in the large units while allowing smaller units to respond to flow fluctuations that would otherwise be handled by the large units. Since smaller units require less time to stabilize, the overall system response time to reforming gas flow rate fluctuations is shorter, greatly improving system efficiency and stability.

[0060] For example, Figure 1 A schematic diagram of an SOFC power generation system based on a cascaded methanol reformer is provided. Figure 1 The SOFC power generation system 100 shown includes an SOFC stack system 110, a controller 120, and a cascaded methanol reformer 130. The SOFC stack system includes n SOFC stacks connected in parallel. The controller 120 and the cascaded methanol reformer 130 are electrically connected to the SOFC stack system 110. The cascaded methanol reformer 130 is a three-stage cascaded configuration, including a first-stage reformer 131, a second-stage reformer 132, and a third-stage reformer 133. The first-stage reformer 131 has the largest gas supply capacity, and the third-stage reformer 133 has the smallest gas supply capacity.

[0061] In a further embodiment, considering that the different gas supply volumes of each stage of the reformer result in varying equipment sizes, the gas flow rates of multi-stage linked reformers have a large range of variation, and the burner also needs to supply heating and insulation for multiple fuel cell stacks, if the existing internal burner design is still adopted, the required burner volume will be large because the reformer with a large gas supply volume needs to produce a large gas flow rate. Placing the burner inside the reformer may lead to an even larger reformer volume. Therefore, the burner can be externally mounted. There are various methods for burner ignition, such as electric spark; the burner and reformer are connected via a gas flow pipe; the reformer has a high-temperature flue gas passage, and the high-temperature flue gas enters the connected high-temperature flue gas passage from the external burner outlet, thereby heating the reformer and providing the thermal conditions for the reforming reaction.

[0062] The operation control flow of the cascade methanol reformer controlled by the controller in the above example in this application embodiment refers to the management of increasing, decreasing, or stopping the gas supply to the reformer during operation by instructions containing abstract and detailed levels for a set of programmable hard automation devices. These managements are time-ordered and have a form of expression suitable for and understood by computer control elements.

[0063] The control device or controller mentioned in the embodiments of the present invention can control physical systems such as reformers or SOFC stacks through control signals, thereby allowing components in the physical system to establish, modify and adapt motion profiles, thereby successfully executing the expected motion profiles and processing commands.

[0064] The following section will further detail the object manipulation part of the operation control process of the cascade methanol reformer. It can be mainly described as the control device or controller generating control signals according to control instructions to control the reformers at each stage of the cascade methanol reformer to adjust the gas supply in response to gas flow fluctuations, and further complete the execution steps of SOFC power generation.

[0065] Figure 2 This is an optional execution flow of an operation control method for a cascaded reformer provided in an embodiment of this application, which may include the following steps:

[0066] Step S21. Obtain the current state, target state, and reforming gas requirement of the SOFC stack.

[0067] Step S22. Determine the reformer level that responds to adjusting the gas supply based on the current state and the target state.

[0068] Step S23. Generate control commands for the cascaded reformer based on the reformer gas demand.

[0069] Step S24. According to the control command, control the reformer corresponding to the determined level in the cascaded reformer to adjust the gas supply so that the gas supply meets the reforming gas requirements of the SOFC stack.

[0070] In some embodiments, step S22 includes the following steps:

[0071] Step S221. Determine the first reformer level in response to the first reformer gas flow rate required to switch the SOFC stack from the current state to the target state.

[0072] Step S222. Determine the second reformer stage in response to the second reformer gas flow rate required to maintain the SOFC stack in the target state.

[0073] Specifically, in the technical solution provided in this application, it is believed that the switching of the SOFC stack from the current state to the target state includes a dynamic process and a relatively static maintenance process, that is, the dynamic switching process of switching from the current state to the target state, and the relatively static process of maintaining the SOFC stack in the target state. At this time, in order to make the gas supply of the cascaded reformer more stable, the gas flow demand of the two processes is responded to by the reformers at different levels.

[0074] For example, taking the transition of an SOFC stack from standby to operating state as an example, since the SOFC stack is currently in standby state, and gas supply is still required in standby state to prevent oxidation of the SOFC stack's anode during cooling or heating, a reformer at one level must be responding to the gas supply at this time. That is, standby state and operating state each correspond to a certain level of reformer. The gas flow rate required in operating state is often greater than that in standby state, meaning the total gas flow rate demand of the SOFC stack system increases. At this time, the reformer at the level corresponding to operating state can be controlled to respond to the gas supply, that is, the reformer at that level can be controlled to increase the gas supply. When the SOFC stack has switched to operating state, the reformer at the level corresponding to standby state can be controlled to reduce the gas supply, and the reformer at the level corresponding to operating state mainly responds to the gas supply.

[0075] In some examples, when the total gas flow demand of the system exceeds the gas supply capacity of the rectifier at the corresponding level in the working state, it is still possible to control the rectifier at the corresponding level in the standby state to increase the gas supply, that is, multiple levels of rectifiers supply gas together.

[0076] To facilitate control and maintain relatively stable system airflow fluctuations, the correspondence between the operating state of the SOFC stack and the reformer level can be such that the operating state with lower airflow demand is responded to by a reformer with lower air supply capacity, and the operating state with higher airflow demand is responded to by a reformer with higher air supply capacity.

[0077] For example, if the operating states of an SOFC stack are divided into operating, standby, shutdown, and startup states, the change in the number of stacks in the operating state causes the largest change in reforming gas flow rate, the change in the number of stacks in the standby state causes a smaller change in reforming gas flow rate, and the change in the number of shutdown and startup stacks causes the smallest change in reforming gas flow rate. Therefore, when designing a cascaded reformer, the maximum available gas flow rate of each stage of the reformer should be able to match the change in the number of operating stacks. That is, each stage of the reformer should be able to handle the state switching change of at least one stack. It is more economical and reasonable when it can precisely match the flow rate fluctuations caused by adding or removing a stack in each operating state.

[0078] For example, with Figure 1 Taking the example of a three-stage cascaded reformer, when the operating states of the SOFC stack are divided into operating state, standby state, shutdown state, and startup state, the following control strategy applies:

[0079] The first-stage reformer responds to the operating state, that is, to the gas flow fluctuation caused by the change in the number of SOFC stacks in the operating state. For example, the number of stacks in the operating state increases or decreases. An increase means that a stack switches from another state to the operating state, and a decrease means that a stack switches from the operating state to another state.

[0080] The secondary reformer responds to the standby state, that is, to the gas flow fluctuation caused by the change in the number of SOFC stacks in the standby state. For example, the number of stacks in the standby state increases or decreases. An increase means that a stack switches from other states to the standby state, and a decrease means that a stack switches from the standby state to other states.

[0081] The three-stage reformer responds to shutdown and startup states, that is, to gas flow fluctuations caused by changes in the number of SOFC stacks in shutdown or startup states. For example, the number of stacks in shutdown or startup states may increase or decrease. An increase means that a stack switches from other states to shutdown or startup states, and a decrease means that a stack switches from shutdown or startup states to other states.

[0082] In some embodiments, when the SOFC stack transitions from the current state to the target state through an intermediate state, step S22 includes the following steps:

[0083] Step S223. Determine the third reformer level in response to the third reformer flow rate required to switch the SOFC stack from its current state to an intermediate state.

[0084] Step S224. Determine the fourth reformer level in response to the fourth reformer flow rate required to switch the SOFC stack from the intermediate state to the target state.

[0085] Specifically, when a SOFC stack switches operating states, it often does not switch directly from the current state to the target state. This would cause excessive flow fluctuations, which is not conducive to system stability. Therefore, the state switching process will go through one or more intermediate states. That is, there is a switching process between the current state and the intermediate state, and then there is another switching process between the intermediate state and the target state. At this time, the intermediate state can be regarded as a temporary target state, which corresponds to a certain reformer level that responds to the gas supply adjustment.

[0086] For example, taking the transition of an SOFC stack from an operating state to a shutdown state as an example, to avoid excessive flow fluctuations, an intermediate standby state is used. That is, the current state is the operating state, the intermediate state is the standby state, and the target state is the shutdown state. Assume that... Figure 1 Taking the illustrated cascaded reformer as an example, the gas flow fluctuation caused by switching from the operating state to the standby state is responded to by the second-stage reformer adjusting the gas supply. The gas flow fluctuation caused by switching from the standby state to the shutdown state is responded to by the third-stage reformer adjusting the gas supply. It's easy to understand that the reformers responding to the gas supply here only illustrate the reformer level corresponding to maintaining the SOFC stack in a target state. When other levels of reformers are supplying gas, it's still possible to control the other activated reformers to stop or increase their gas supply. For example, when the first-stage reformer is supplying gas, and the SOFC stack needs to switch from the operating state to the standby state, the first-stage reformer can be controlled to reduce its gas supply, and the second-stage reformer can be controlled to increase its gas supply. This does not conflict with the aforementioned description of different levels of reformers responding to the required reforming gas flow for each operating state of the SOFC stack. Those skilled in the art can flexibly set this according to the number of levels in the cascaded reformer.

[0087] Taking the aforementioned switch from operating state to shutdown state as an example, if all gas flow fluctuations were handled by a single-level reformer, two flow changes would occur. By splitting the gas flow fluctuations according to the correspondence between state and reformer level, the second-level reformer responds to gas flow fluctuations caused by changes in the number of fuel cells in standby state, and the third-level reformer responds to gas flow fluctuations caused by changes in the number of fuel cells in shutdown state. This splits the dynamic changes across two different levels of reformers, simplifying the control difficulty of a single-level reformer and reducing the number of fluctuations. In actual operating scenarios, the response time to flow changes is very fast, but flow changes also mean changes in the reaction process. The reaction process needs time to stabilize, so repeated flow changes must be avoided, preventing the reaction process from being in an unstable operating state for extended periods. Therefore, the operation control scheme provided in this application splits the reforming gas flow fluctuations caused by SOFC fuel cell stack switching operating states, reducing the types of flow fluctuations responded to by a single-level reformer and improving the stability of system operation.

[0088] In some embodiments, in addition to considering the correspondence between operating states and reformer levels, it is also necessary to consider the relationship between the system's reforming gas demand and the gas supply capacity of each reformer level. Based on this, the above-mentioned operation control method includes:

[0089] When the demand for reformed gas is less than the lower limit of the allowable gas supply of the highest-level reformer among the activated reformers, the highest-level reformer among the activated reformers is controlled to stop supplying gas, and the other reformers among the activated reformers are supplied with gas.

[0090] When the demand for reformed gas is higher than the lower limit of the allowable gas supply of the highest-level reformer among the activated reformers but lower than its upper limit, the other reformers among the activated reformers except the highest-level reformer will stop supplying gas, and only the highest-level reformer among the activated reformers will supply gas.

[0091] Specifically, taking a three-stage cascaded reformer as an example, when all stages of the reformer are started, because the first-stage reformer has a stronger gas supply capacity, if the reforming gas demand is higher than the lower limit of the allowable gas supply of the highest-level reformer among the started reformers but lower than its upper limit, it means that the gas supply of the first-stage reformer can meet the reforming gas flow required for all SOFC stacks to maintain their operating state. In this case, the second- and third-stage reformers can be controlled to stop supplying gas to the SOFC stacks. If the reforming gas demand is lower than the lower limit of the allowable gas supply of the highest-level reformer among the started reformers, that is, the reforming gas demand of the entire system is lower than the lower limit of the allowable gas supply of the first-stage reformer, it means that the gas flow demand can be met by the second- and third-stage reformers supplying gas together or individually. At this time, the gas supply of the first-stage reformer is cut off. Similarly, when the reforming gas demand is lower than the lower limit of the allowable gas supply of the second-stage reformer, the second-stage reformer stops supplying gas, and the third-stage reformer supplies gas. This control strategy keeps the gas supply to the cascaded reformer within a safe flow range, thus protecting the large reformer as much as possible.

[0092] After the reformer stops supplying reformed gas, it will not cool down to room temperature. For example, after the secondary and tertiary reformers stop supplying gas, the high-temperature flue gas used to keep the primary reformer warm will also flow through the secondary and tertiary reformers for insulation, so that the reformers can respond in a timely manner to the changes in reformed gas flow caused by the power changes of the SOFC stack.

[0093] In a further embodiment, step S21 further includes:

[0094] Obtain temperature change information of SOFC stack;

[0095] The reforming gas requirement of the SOFC stack is determined based on temperature change information.

[0096] Specifically, generally speaking, the operating temperature of an SOFC stack is constant, but the maintenance temperature is different for each operating state. The state switching is accompanied by the temperature change of the SOFC stack. The controller can determine the reforming gas demand based on the temperature change information of the SOFC stack, and then control the gas supply adjustment of different levels of reformers in combination with the gas supply capacity of each level of reformer.

[0097] In a further embodiment, step S22 further includes the following steps:

[0098] Step S225. Obtain the equipment information of the SOFC stack.

[0099] Step S226. Determine the reformer level that responds to the adjustment of the gas supply based on the correspondence between the equipment information and the reformer level.

[0100] Specifically, due to differences in fuel cell stack models, different fuel cell stacks may require different intake flow rates under different operating conditions. Cascaded reformers can also be designed so that each stage of the reformer corresponds to the different intake flow rate requirements of the fuel cell stack. For example, for a five-stage cascaded reformer, the intrinsic parameters of the fuel cell stack can be obtained through a controller, and the first-stage reformer can respond to the high intake flow rate under operating conditions (assuming the flow rate is V). max The gas flow fluctuation caused by the change in the number of fuel cells is responded to by the secondary reformer. Under normal operating conditions, the inlet gas flow is moderate (assuming the flow rate is V). MID The gas flow fluctuation caused by the change in the number of a certain type of fuel cell stack is provided by the three-stage reformer. Under operating conditions, the inlet gas flow is small (assuming the flow rate is V). MIN The gas flow fluctuations caused by changes in the number of other types of fuel cells are handled by the fourth-stage reformer. The gas flow fluctuations caused by changes in the number of standby fuel cells are handled by the fifth-stage reformer.

[0101] by Figure 1 Taking the three-stage cascaded methanol reformer shown as an example, and assuming an SOFC stack system consisting of 10 SOFC stacks connected in parallel, the operation and control of the cascaded methanol reformer will be further introduced below.

[0102] The operating states of SOFC stacks are divided into four types: normal operation, standby, shutdown, and startup, with required reformer gas flow rates of V1, V2, V3, and V4 for each state, respectively. For a single SOFC stack, under normal circumstances, V1 > V2 > V3 ≈ V4. The required reformer gas flow rates during shutdown and startup may be the same (V3 = V4) or different (V3 ≈ V4).

[0103] Assuming a standard reformer has a safe variable gas flow rate range of 50%-100%, and the reformer is configured as a three-stage cascade structure, the relationship between the maximum gas supply capacity and the safe variable range of gas supply capacity of each stage of the reformer and the gas flow rate ratio of a standard reformer is as follows:

[0104] The first-stage reformer can supply a maximum gas volume of 100%, which is sufficient for the normal operation of all SOFC stacks, and its safe range of gas volume variation is 50%-100%. In actual operation, the maximum gas flow rate of the first-stage reformer can be greater than 100%, and its actual flow rate only needs to meet the safe range of 50%-100%. Typically, the reforming gas flow rate required for SOFC stack operation is greater than or equal to the lower limit of the gas supply capacity of the first-stage reformer.

[0105] The second-stage reformer can supply a maximum gas volume of 50%, which is sufficient to meet the normal operation requirements of 50% of the SOFC stacks. Simultaneously, its maximum outlet gas flow rate is greater than or equal to the reforming gas flow rate required for all SOFC stacks in hot standby mode, and its safe range of gas supply variation is 25%-50%. Similarly, in actual operation, the maximum flow rate of the second-stage reformer can exceed 50%, as long as the actual flow rate meets the safe variation range of 25%-50%.

[0106] The maximum gas supply capacity of the three-stage reformer is 25%. Its maximum outlet gas flow rate is greater than or equal to the reforming gas flow rate required when all SOFC stacks are shut down, and its safe range of gas flow rate variation is 12.5%-25%. Since V3≈V4 under normal circumstances, the three-stage reformer also meets the reforming gas flow rate required for all SOFC stacks to reach startup. Similarly, in actual operation, the maximum flow rate of the three-stage reformer can be greater than 25%, and its actual flow rate only needs to meet the safe range of 12.5%-25%.

[0107] It is important to note that the above settings are merely for a visual comparison with the gas flow rate of a hypothetical standard reformer, to facilitate understanding of the differences between different stages of the reformer, and should not be considered as limitations on the absolute volume and gas flow rate of the reformer. In practical applications, the assumed gas flow rate of the standard reformer can be specifically designed according to the actual needs of the SOFC stack system it is connected to.

[0108] Based on the above-mentioned upper and lower limits of flow rate for each stage of the reformer, and the operation control scheme provided by this invention, for the above-mentioned three-stage cascaded reformer, the operating states of each stage of the SOFC stack and the reformers at each stage have the following relationship:

[0109] The first-stage reformer responds to gas flow fluctuations caused by changes in the number of SOFC stacks in the operating state, such as an increase or decrease in the number of stacks in the operating state. An increase refers to a stack switching from another state to the operating state, and a decrease refers to a stack switching from the operating state to another state.

[0110] The secondary reformer responds to gas flow fluctuations caused by changes in the number of SOFC stacks in standby mode, such as an increase or decrease in the number of stacks in standby mode. An increase refers to a stack switching from other modes to standby mode, while a decrease refers to a stack switching from standby mode to other modes.

[0111] The three-stage reformer responds to gas flow fluctuations caused by changes in the number of SOFC stacks in shutdown and startup states. For example, the number of stacks in shutdown or startup states may increase or decrease. An increase refers to a stack switching from other states to shutdown or startup, while a decrease refers to a stack switching from shutdown or startup to other states.

[0112] When all levels of reformers are activated, taking a scenario where a SOFC stack in the system needs to switch from operating to shutdown as an example, for the system, it is equivalent to reducing one operating stack and adding one shutdown stack. Since the switch from operating to shutdown will go through a standby state, the cascaded reformers will perform two flow regulation operations.

[0113] Assuming the required reforming gas flow rate of the fuel cell stack is V6 under operating conditions, then the required reforming gas flow rate of the entire system is V7. After switching, the required reforming gas flow rate of the fuel cell stack under shutdown conditions is V8, and the required reforming gas flow rate of the entire system is V9. Therefore, the gas supply of the cascaded reformer will be adjusted from V7 to V9.

[0114] If both flow regulation responses are handled by a single-stage rectifier, two flow changes are required. According to the operation control method provided by this invention, the flow change is broken down into stages. When the flow rate V7 in the operating state is switched to the flow rate in the standby state, the first-stage rectifier is controlled to reduce the gas supply, and the second-stage rectifier to increase the gas supply. When the flow rate in the standby state is switched to the flow rate V9 in the shutdown state, the second-stage rectifier is controlled to reduce the gas supply, and the third-stage rectifier to increase the gas supply.

[0115] In the scenario where the lower-level reformers are shut down, assuming that only 9 SOFC stacks are needed when starting the SOFC stack system, the number of SOFC stacks started gradually increases as the controller starts each level of reformers and the gas supply gradually increases. When the first-level reformer reaches its operating temperature, the second- and third-level reformers are operating at full power. Since the maximum allowable gas supply of the second- and third-level reformers is 75%, which is greater than the lower limit of the allowable gas supply of the first-level reformer (50%), the first-level reformer can immediately operate within a safe variable flow range after startup.

[0116] At this time, the total gas demand of the system is greater than the lower limit of the gas supply of the first-stage rectifier but less than its upper limit. The controller will control the second-stage and third-stage rectifiers to stop supplying gas and increase the gas supply of the first-stage rectifier to 90%. This is equivalent to switching all current gas supply tasks to the first-stage rectifier, thus demonstrating the supporting role of the small rectifier for the large rectifier.

[0117] After the SOFC stack is started and the secondary and tertiary reformers exit the flow fluctuation response, if no stack in the system needs to switch from operating state to hot standby or from operating state to shutdown, only the primary reformer needs to respond to supply gas.

[0118] For example, a tertiary rectifier is smaller in size than a tertiary rectifier, meaning it may be less affected by fluctuations. Therefore, the gas supply rate of a tertiary rectifier can decrease faster than that of a tertiary rectifier. In other words, the controller will instruct the tertiary rectifier to exit the gas supply at a higher rate, while the tertiary rectifier exits the gas supply at a slower rate, resulting in less flow fluctuations for the tertiary rectifier and thus protecting it.

[0119] After the secondary and tertiary reformers are shut down, the high-temperature flue gas used to insulate the primary reformer will also flow through the secondary and tertiary reformers for insulation, so that the reformers can respond promptly to changes in reforming gas flow caused by changes in SOFC stack power.

[0120] In the scenario where a higher-level reformer shuts down its gas supply, assuming that the system only requires four fuel cell stacks to operate and all levels of reformers have started supplying gas, the total gas flow demand of the system is lower than the lower limit of the allowable gas supply of the first-level reformer. The controller will control the first-level reformer to shut down its gas supply. The second-level reformer can be regarded as the highest level among the reformers that are started. The flow fluctuations caused by the operating and standby states of the four fuel cell stacks are all responded to by the second-level reformer. The third-level reformer still responds to the start and stop states of the four fuel cell stacks.

[0121] Similarly, if the total gas flow demand of the system is lower than the allowable gas supply limit of the secondary reformer, for example, if the system only needs one fuel cell stack to operate, the controller will control the secondary reformer to stop supplying gas. The tertiary reformer is regarded as the highest level among the reformers that are activated, and the flow fluctuations caused by all states of one fuel cell stack are responded to by the tertiary reformer.

[0122] In some embodiments, each SOFC stack can be independently configured with a cascaded reformer. In this case, if some SOFC stacks are in standby mode while other stacks are in operation, the reformer corresponding to the working stack in response to hot standby is idle. Therefore, the maximum number of hot standby stacks can be determined according to the system's grid connection requirements, and the number of secondary reformers can be determined based on the maximum number and the size of the secondary reformer in a single stack.

[0123] The three-stage cascade methanol reformer mentioned in the above embodiments is only an example of a three-stage ladder configuration. The system can be designed as other multi-stage linked reformer structures, such as two-stage, four-stage, five-stage or even more.

[0124] When referring to fuels used for hydrogen production and SOFC power generation, any SOFC stack or stack system that has fluctuating requirements for intake flow rate is acceptable. It is not limited to methanol reforming; it can be the reforming of other compounds, such as natural gas.

[0125] See Figure 3 An embodiment of this application also provides an operation control device 300 for a cascaded reformer, comprising:

[0126] The status information acquisition unit 310 is configured to acquire the current status and target status of the SOFC stack.

[0127] The reforming gas acquisition unit 320 is configured to acquire the reforming gas demand of the SOFC stack.

[0128] The reformer level determination unit 330 is configured to determine the reformer level in response to adjusting the gas supply based on the current state and the target state.

[0129] The instruction generation unit 340 is configured to generate control instructions for the cascaded reformer based on the reformer gas demand.

[0130] The control unit 350 is configured to control the reformer corresponding to the determined level in the cascaded reformer to adjust the gas supply according to the control command, so that the gas supply meets the reforming gas requirements of the SOFC stack.

[0131] In some embodiments, such as Figure 4 As shown, the above-mentioned operation control device 300 also includes a temperature information acquisition unit 360, which is configured to acquire temperature change information of the SOFC stack, so that the reforming gas acquisition unit 320 determines the reforming gas demand of the SOFC stack based on the temperature change information.

[0132] The operation control device 300 of the cascaded reformer adopts the operation control method provided in the above embodiments. The specific implementation logic can be referred to the relevant introduction of the operation control method provided in the foregoing embodiments, which will not be repeated here.

[0133] The invention has been described in particular detail above with respect to possible scenarios, and those skilled in the art will recognize that the invention can be practiced through other embodiments. Specific naming of components, capitalization of terms, attributes, data structures, or any other programming or structural aspects are not mandatory or important, and the mechanisms or features of implementing the invention may have different names, forms, or procedures. The system can be implemented through a combination of hardware and software (as described), entirely through hardware elements, or entirely through software elements. The specific division of functions among the various system components described herein is merely exemplary and not mandatory; rather, the functions performed by a single system component can be performed by multiple components, or the functions performed by multiple components can be performed by a single component.

[0134] Those skilled in the art should understand that the various steps of the disclosed methods can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Optionally, they can be implemented using device-executable program code, which can then be stored in a storage device for execution by the computing device. Alternatively, they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Therefore, the embodiments disclosed in this invention are not limited to any specific hardware and software combination.

[0135] The programs (also referred to as programs, software, software applications, or code) executable by these computing devices include machine instructions of a programmable processor and can be implemented using high-level procedural and / or object-oriented programming languages, and / or assembly / machine languages. As used herein, the terms “machine-readable medium” and “computer-readable medium” refer to any computer program product, device, and / or apparatus (e.g., disk, optical disk, memory, programmable logic device (PLD)) used to provide machine instructions and / or data to a programmable processor, including machine-readable media that receive machine instructions as machine-readable signals. The term “machine-readable signal” refers to any signal used to provide machine instructions and / or data to a programmable processor.

[0136] Certain aspects of this invention include the process steps and instructions described herein in algorithmic form. It should be noted that the process steps and instructions of this invention can be implemented in software, firmware, and / or hardware, and when implemented in software, they can be downloaded, stored on various operating systems and operated from said platforms.

[0137] Those skilled in the art will understand that the structures shown in the figures are merely block diagrams of some structures related to the present application and do not constitute a limitation on the terminal device to which the present application is applied. Specific terminal devices may include more or fewer components than those shown in the figures, or combine certain components, or have different component arrangements.

[0138] In the description of this specification, the use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "possible design," etc., refers to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0139] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of operating a cascade reformer, characterized by, The cascaded reformer includes at least two stages of reformers. Each stage of the cascaded reformer is configured according to the available gas flow rate. The required reforming gas flow rate for each operating state of the SOFC stack is responded to by different stages of the reformers. The operation control method includes: Obtain the current status, target status, and reforming gas demand of the SOFC stack; The reformer level for responding to gas supply adjustment is determined based on the current state and the target state. Control commands for the cascaded reformer are generated based on the reformer gas demand. According to the control command, the cascaded reformer adjusts the gas supply of the reformer that has been determined to respond to the gas supply adjustment, so that the gas supply of the cascaded reformer meets the reforming gas requirements of the SOFC stack. The process of determining the reformer level for adjusting the gas supply based on the current state and the target state includes: Determine the first reformer stage in response to the first reformer gas flow rate required to switch the SOFC stack from the current state to the target state; Determine the second reformer stage in response to the second reformer gas flow rate required to maintain the SOFC stack in the target state; When an SOFC stack transitions from the current state to the target state through an intermediate state, determining the reformer level for responding to gas supply adjustment based on the current state and the target state includes: A third reformer stage is determined in response to the third reforming gas flow rate required to switch the SOFC stack from the current state to the intermediate state. Determine the fourth reformer stage in response to the fourth reformer flow rate required to switch the SOFC stack from the intermediate state to the target state; The operation control method also includes: When the demand for reformed gas is less than the lower limit of the allowable gas supply of the highest-level reformer among the activated reformers, the highest-level reformer among the activated reformers is controlled to stop supplying gas, and the other reformers among the activated reformers are supplied with gas. When the demand for reformed gas is higher than the lower limit of the allowable gas supply of the highest-level reformer among the activated reformers but lower than its upper limit, the other reformers among the activated reformers except the highest-level reformer will stop supplying gas, and only the highest-level reformer among the activated reformers will supply gas.

2. The operation control method according to claim 1, characterized by, The operation control method also includes: Obtain temperature change information of SOFC stack; The reforming gas requirement of the SOFC stack is determined based on the temperature change information.

3. The operation control method according to claim 1, characterized by, The operation control method also includes: Obtain equipment information for SOFC stacks; The corresponding reformer level for responding to gas supply adjustment is determined based on the correspondence between the equipment information and the reformer level.

4. An operation control device for a cascaded reformer, characterized in that, The operation control device uses the operation control method as described in claim 1, and the operation control device includes: The status information acquisition unit is configured to acquire the current status and target status of the SOFC stack; The reforming gas acquisition unit is configured to acquire the reforming gas demand of the SOFC stack. The reformer level determination unit is configured to determine the reformer level in response to gas supply adjustment based on the current state and the target state. The instruction generation unit is configured to generate control instructions for the cascaded reformer based on the reformer gas demand. The control unit is configured to control the cascaded reformer, which has a known response to gas supply adjustment, to adjust the gas supply according to control commands, so that the gas supply of the cascaded reformer meets the reforming gas requirements of the SOFC stack.

5. The operation control device according to claim 4, characterized by The operation control device also includes: The temperature information acquisition unit is configured to acquire temperature change information of the SOFC stack.

6. A SOFC power generation system based on a cascade reformer, characterized by, This includes cascaded reformers, controllers, and SOFC stack systems; The cascaded reformer includes at least two stages of reformers. Each stage of the reformer is set according to the available gas volume. Reformers of the same stage are connected in parallel. The reformed gas generated by each stage of the reformer is distributed to the SOFC stack system by the controller. The reformed gas flow rate required for the SOFC stack system to switch to different target states is responded to by the reformers of different stages. The controller and the cascaded reformer are respectively connected to the SOFC stack system; The controller uses the operation control method as described in any one of claims 1 to 3 to control the gas supply of each stage of the cascaded reformer.

7. The SOFC power generation system of claim 6, wherein, The gas supply range of each stage of the reformer is set according to the reforming gas demand corresponding to the operating state of the SOFC stack and the number of SOFC stacks in the SOFC stack system.

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