JP6459063B2 - Operation method of solid oxide fuel cell system - Google Patents

Description

  The present invention relates to a method for operating a fuel cell system including a hydrodesulfurizer.

  As a conventional fuel cell system for removing sulfur contained in a raw material gas by reacting with hydrogen in a hydrodesulfurizer, a fuel cell power generation system shown in Patent Document 1 is known. In this system, a raw material gas is supplied to a hydrodesulfurizer through a fuel blower. Moreover, a part of hydrogen-containing gas produced | generated in the reformer is used as recycle gas. By making the pressure of the hydrogen-containing gas downstream from the reformer higher than the pressure of the raw material gas upstream of the fuel blower, the recycle gas is supplied to the hydrodesulfurizer. And the flow volume of recycle gas is adjusted with the pressure adjustment part (adjustment orifice, governor) with which the upstream was provided from the fuel blower.

JP2013-225411A

  However, the fuel cell power generation system shown in Patent Document 1 still has room for improvement from the viewpoint of optimizing the flow rate of the recycled gas. An object of the present invention is to provide a method for operating a solid oxide fuel cell system in which the flow rate of the recycle gas is improved.

  An operation method of a fuel cell system according to an aspect of the present invention includes a hydrodesulfurizer that desulfurizes a source gas, and a reformed gas containing hydrogen obtained by reforming the source gas desulfurized by the hydrodesulfurizer with water. Generating a reformer, a reformed gas reformed by the reformer and a solid oxide fuel cell that generates electric power with air, and burning the reformed gas discharged from the solid oxide fuel cell A combustor, a raw material gas path through which the raw material gas flows to the reformer via the hydrodesulfurizer, and the reformer to the combustor via the solid oxide fuel cell. The reformed gas path through which the reformed gas circulates, branches from the reformed gas path at a branch point downstream of the reformer, and enters the source gas path at a connection point upstream of the hydrodesulfurizer. Recycle gas path to be connected and source gas upstream from the connection point A pressure regulator for adjusting the pressure of the raw material gas flowing through the channel, a booster for increasing the pressure of the raw material gas flowing through the raw material gas path downstream from the connection point, and water supplied to the reformer An operation method of a solid oxide fuel cell system, comprising: a water path that circulates; an air path through which air supplied to the solid oxide fuel cell circulates; and a controller, The pressure of the raw material gas at the connection point includes an air supply amount to the solid oxide fuel cell, a raw material gas supply amount to the reformer, a water supply amount to the reformer, and the solid oxidation. The pressure regulator is controlled to achieve a target pressure calculated based on at least one value of the target current of the physical fuel cell.

  The present invention has an effect that the flow rate of the recycle gas can be optimized.

It is a block diagram which shows an example of a functional structure of the solid oxide fuel cell system which concerns on 1st Embodiment. 2 is a flowchart showing an example of an operation method of the solid oxide fuel cell system of FIG. 1. It is a flowchart which shows an example of the arithmetic program of FIG. It is a block diagram which shows an example of a functional structure of the solid oxide fuel cell system which concerns on 2nd Embodiment. 5 is a flowchart showing an example of an operation method of the solid oxide fuel cell system of FIG. 4.

(Knowledge that is the basis of the present invention)
The present inventor has intensively studied to optimize the recycle gas flow rate in the solid oxide fuel cell system. As a result, the present inventor has found that the prior art has the following problems.

  In the fuel cell power generation system of Patent Document 1, the pressure adjustment unit is configured to provide a difference between the upstream pressure of the fuel blower and the downstream pressure of the reformer so that the recycle gas flow rate is a constant ratio with respect to the raw material gas flow rate. Is adjusted. Since this downstream pressure is determined according to the power generation output, the recycle gas flow rate is adjusted based on the power generation output.

  However, for example, when a solid oxide fuel cell (SOFC) is used as the fuel cell of this fuel cell power generation system, the recycle gas at an appropriate flow rate is hydrogenated only by adjusting the recycle gas flow rate based on the power generation output. Not supplied to the desulfurizer.

  That is, the SOFC is heated by the combustor and cooled by air. Such SOFC temperature adjustment is performed in consideration of efficiency and power generation output. That is, when increasing the temperature of the SOFC, first, the amount of air is decreased from the viewpoint of the efficiency of the fuel cell power generation system. If the temperature still needs to be raised, the amount of source gas is increased. On the other hand, in order to secure the amount of source gas necessary for power generation, the amount of source gas cannot be reduced much. For this reason, when lowering the temperature of the fuel cell, the amount of air is mainly increased. Thus, since the temperature of the SOFC is mainly adjusted by the amount of air, the amount of air supplied to the SOFC increases or decreases.

  Such a change in the air amount affects the downstream pressure of the reformer. Therefore, when the downstream pressure is obtained based on the power generation output without considering the influence of the air amount, the recycle gas flow rate becomes excessive or insufficient.

  Furthermore, in the SOFC system, the reformer and the SOFC are hot. For this reason, a pressure gauge cannot be provided between them, and the downstream pressure of the reformer cannot be directly measured. In the SOFC system, the reformer and the SOFC are integrally incorporated in the hot module. For this reason, it is very difficult to preset a downstream pressure of the reformer by providing a pressure loss between them. Therefore, it is difficult to obtain the downstream pressure of the reformer affected by the air amount.

  The present invention has been made based on the above knowledge, and provides a method for operating a solid oxide fuel cell system capable of optimizing the recycle gas flow rate.

(Embodiment)
An operation method of a solid oxide fuel cell system according to a first embodiment of the present invention includes a hydrodesulfurizer for desulfurizing a source gas, and reforming the source gas desulfurized by the hydrodesulfurizer with water. A reformer that generates reformed gas containing hydrogen, a solid oxide fuel cell that generates electric power using the reformed gas reformed by the reformer and air, and the solid oxide fuel cell A combustor for burning the reformed gas discharged; a raw material gas path through which the raw material gas flows to the reformer via the hydrodesulfurizer; and the solid oxide fuel cell from the reformer A reformed gas path through which the reformed gas flows to the combustor, and a branch point on the downstream side of the reformer branches from the reformed gas path, and is upstream of the hydrodesulfurizer. Recycle gas path connected to the source gas path at a connection point, and the connection point A pressure regulator for adjusting the pressure of the source gas flowing through the upstream source gas path, a booster for increasing the pressure of the source gas flowing through the source gas path downstream from the connection point, and the reformer An operation method of a solid oxide fuel cell system comprising: a water path through which water supplied to the air flows; an air path through which air supplied to the solid oxide fuel cell flows; and a controller. The controller is configured such that the pressure of the raw material gas at the connection point is such that the air supply amount to the solid oxide fuel cell, the raw material gas supply amount to the reformer, and the water supply amount to the reformer. And the pressure regulator is controlled so that the target pressure is calculated based on at least one value of the target current of the solid oxide fuel cell.

  In the operating method of the solid oxide fuel cell system according to the second aspect of the present invention, in the first aspect, the solid oxide fuel cell system is located downstream of the pressure regulator and the connection point. A pressure gauge for detecting the pressure of the raw material gas flowing through the raw material gas path on the upstream side may further be provided, and the controller may acquire the pressure of the raw material gas at the connection point from the pressure gauge.

  In the operation method of the solid oxide fuel cell system according to the third aspect of the present invention, in the first or second aspect, the solid oxide fuel cell system is the solid oxide fuel cell. A first supply device for supplying air; and a first flow meter for detecting a flow rate of air supplied from the first supply device, wherein the controller supplies the air supply amount from the first flow meter. May be obtained.

  In the operation method of the solid oxide fuel cell system according to the fourth aspect of the present invention, in any one of the first to third aspects, the solid oxide fuel cell system is connected to the reformer. A second supply device for supplying a source gas; and a second flow meter for detecting a flow rate of the source gas supplied from the second supply device. You may acquire the amount of raw material gas supply to a quality device.

  In the operation method of the solid oxide fuel cell system according to the fifth aspect of the present invention, in any one of the first to fourth aspects, a third supply device for supplying water to the reformer; And a third flow meter for detecting a flow rate of water supplied from the third supply device, wherein the controller acquires a water supply amount from the third flow meter to the reformer. Good.

(First embodiment)
A solid oxide fuel cell system (SOFC system) 100 according to a first embodiment will be described with reference to FIG. FIG. 1 is a block diagram illustrating an example of a functional configuration of the SOFC system 100 according to the first embodiment. The SOFC system 100 is a solid oxide fuel cell system, which is a hydrodesulfurizer 16, a reformer 11, a solid oxide fuel cell (SOFC) 21, a combustor 25, a raw material gas path 12a, a reformed gas. A path 12b, a recycle gas path 17, a pressure regulator 13, a booster 14, a water path 19, an air path 23, and a controller 27 are provided. The SOFC system 100 may further include a second supplier 10, a third supplier 18, and a first supplier 22.

  The 2nd supply device 10 is a supply device which supplies raw material gas, Comprising: It has the function to adjust the flow volume of raw material gas. Examples of the second supplier 10 include at least one of a booster 14 and a flow rate adjustment valve, or a constant displacement pump. The raw material is, for example, a gas containing an organic compound composed of at least carbon and hydrogen, such as city gas mainly composed of methane, natural gas, and LPG.

  The hydrodesulfurizer 16 is a reactor that desulfurizes the source gas. In the hydrodesulfurizer 16, the sulfur compound contained in the raw material gas is desulfurized by a hydrodesulfurization reaction with hydrogen in the presence of a catalyst. Examples of the hydrodesulfurization catalyst include a CuZn-based catalyst and a catalyst composed of a CoMo-based catalyst and an adsorbent provided downstream thereof. The CuZn-based catalyst has both a function of converting a sulfur compound into hydrogen sulfide and a function of adsorbing hydrogen sulfide. The CoMo-based catalyst has a function of converting a sulfur compound in the raw material into hydrogen sulfide. The adsorbent has a function of adsorbing hydrogen sulfide, and examples thereof include a ZnO-based catalyst and a CuZn-based catalyst.

  The reformer 11 is a reactor that generates a reformed gas containing hydrogen by reforming the raw material gas desulfurized by the hydrodesulfurizer 16 with water. In the reformer 11, the raw material gas undergoes a reforming reaction with water vapor in the presence of a catalyst to generate a hydrogen-containing reformed gas. The reformer 11 is heated to an appropriate temperature of the reforming catalyst, for example, 600 to 700 ° C. Further, the reformer 11 is provided with an evaporator (not shown), in which steam is generated from the water supplied from the third supplier 18.

  The SOFC 21 is a solid oxide fuel cell that generates electric power from the reformed gas generated by the reformer 11 and air. The SOFC 21 is provided with a cell, a reformed gas passage, a power generation air passage, and a cooling air passage. The reformed gas flow path is connected to the reformed gas path 12 b, and the power generation air flow path and the cooling air flow path are connected to the air path 23. The air supplied from the air path 23 is used for the power generation air and the cooling air.

  The cell is composed of an electrolyte and an anode and a cathode that sandwich the electrolyte. Examples of the cell structure include a so-called flat plate type, cylindrical type, and cylindrical flat plate type. Examples of the electrolyte include yttria-stabilized zirconia (YSZ) which is zirconia (ZrO2) to which yttrium (Y) oxide (Y2O3) is added, or zirconia-based solid electrolytes doped with ytterbium (Yb) or scandium (Sc). Illustrated. Examples of the anode include a mixture of nickel (Ni) and YSZ, or a mixture obtained by adding gadolinium (Gd) to an oxide (CeO2) of nickel and cerium (Ce). Examples of the cathode include oxides containing lanthanum, strontium, and manganese, and oxides containing lanthanum, strontium, cobalt, and iron.

  The SOFC 21 is heated to an appropriate temperature for the catalyst. For example, when YSZ is used for the electrolyte, the appropriate temperature is, for example, 500 ° C. to 1000 ° C., although it depends on the thickness of the electrolyte. The SOFC 21 may be incorporated in the hot module together with the reformer 11. The SOFC 21 is provided with a temperature detector (not shown). The temperature detector detects the temperature of the SOFC 21 and outputs the detected temperature to the controller 27.

  The combustor 25 is a device that burns the reformed gas (off-reformed gas) discharged from the SOFC 21. An example of the combustor 25 is a burner. The combustor 25 is disposed in the vicinity of the reformer 11 and the SOFC 21 and heats them. The off-reforming gas contains a combustible gas and oxygen. The combustible gas includes a reformed gas that was not used for the reforming reaction and a reformed gas that was not used for the power generation reaction. Oxygen is oxygen in the air that was not used for the power generation reaction. The combustor 25 is connected to the combustion exhaust gas path 26. The flue gas discharged by the combustor 25 is discharged outside the SOFC system 100 via the flue gas path 26.

  The raw material gas path 12 a is a path through which the raw material gas flows from the second supplier 10 through the hydrodesulfurizer 16 to the reformer 11. The upstream end of the source gas path 12 a is connected to the second supply device 10, and the downstream end is connected to the reformer 11. A pressure regulator 13, a booster 14, and a hydrodesulfurizer 16 are provided in this order in the raw material gas path 12a.

  The reformed gas path 12b is a path through which the reformed gas flows from the reformer 11 via the SOFC 21 to the combustor 25. The reformed gas path 12 b has an upstream end connected to the reformer 11 and a downstream end connected to the combustor 25. The SOFC 21 is provided in this order in the reformed gas path 12b.

  The recycle gas path 17 is a path that branches from the reformed gas path 12 b at a branch point downstream from the reformer 11 and is connected to the raw material gas path 12 a at a connection point upstream from the hydrodesulfurizer 16. Through this recycle gas path 17, a part of the reformed gas (recycle gas) is supplied from the downstream of the reformer 11 to the upstream of the hydrodesulfurizer 16. The recycle gas path 17 may be provided with a device for adjusting the flow rate of the recycle gas. Examples of the device include a variable orifice, a booster pump, and a fixed orifice. Among these, a fixed orifice is preferable from the viewpoint of cost and a load caused by a high-temperature recycle gas containing water vapor.

  The pressure regulator 13 is a device that regulates the pressure of the raw material gas flowing through the raw material gas path 12a upstream from the connection point. As the pressure regulator 13, for example, a variable orifice provided with a stepping motor is exemplified.

  The booster 14 is a device that increases the pressure of the raw material gas flowing through the raw material gas path 12a downstream from the connection point. Examples of the booster 14 include a motor-driven constant volume pump and an electromagnetic diaphragm pump.

  The third supplier 18 is a device that supplies water to the reformer 11 and has a function of adjusting the flow rate of water. An example of the third feeder 18 is a plunger pump capable of quantitative discharge. The water path 19 is a path through which water supplied to the reformer 11 flows. The upstream end of the water path 19 is connected to the third feeder 18, and the downstream end is connected to the reformer 11.

  The first supplier 22 is a device that supplies air to the SOFC 21 and has a function of adjusting the flow rate of air. As the 1st supply device 22, an electromagnetic drive type diaphragm pump is illustrated, for example. The air path 23 is a path through which air supplied to the SOFC 21 flows. The air path 23 has an upstream end connected to the first feeder 22 and a downstream end connected to the SOFC 21.

  The controller 27 is a device that controls each part of the SOFC system 100. The controller 27 has only to have a control function, and includes an arithmetic processing unit (not shown) and a storage unit (not shown). For example, the arithmetic processing unit is exemplified by a processor such as an MPU and a CPU, and the storage unit is exemplified by a memory. The storage unit stores a control program, and the arithmetic processing unit reads the control program from the storage unit and executes it. In other words, the control program causes the arithmetic processing unit to execute the programmed control. The controller 27 may be configured as a single device that performs centralized control, or may be configured as a device that performs distributed control in cooperation with each other.

  The controller 27 determines the target current generated by the SOFC 21 based on the demand amount of the power load (not shown). Then, the controller 27 controls the power converter (not shown), the second supplier 10, the third supplier 18, and the first supplier 22 so that the SOFC 21 generates power of the target current. The demand amount of the power load is output to the controller 27 from a power load measuring device (not shown) provided in an AC power path connecting the power converter and the power load. Further, the controller 27 controls the first supplier 22 so that the temperature of the SOFC 21 detected by the temperature detector becomes an appropriate temperature of the SOFC 21.

  The controller 27 is configured so that the pressure of the raw material gas at the connection point is the air supply amount to the SOFC 21, the raw material gas supply amount to the reformer 11, the water supply amount to the reformer 11, and the target current of the SOFC 21. Control is performed by the pressure regulator 13 so that the target pressure is calculated based on at least one of the values.

  Next, the operation of the SOFC system 100 (operating method of the SOFC system 100) will be described with reference to FIG. The operation of the SOFC system 100 is realized by the controller 27.

  In the power generation state in which the SOFC 21 generates predetermined power, the raw material gas is supplied from the second supply device 10, passes through the pressure regulator 13, is boosted by the booster 14, and flows into the hydrodesulfurizer 16. Here, the sulfur compound in the raw material gas is removed by a hydrodesulfurization reaction with hydrogen. Then, the desulfurized source gas is supplied to the reformer 11. At the same time, water is supplied from the third supply unit 18 to the reformer 11 and is converted into water vapor by the evaporator. In the reformer 11, the raw material gas and the water vapor undergo a reforming reaction to generate a reformed gas containing hydrogen.

  A part of the reformed gas flows into the recycle gas path 17 from the branch point of the reformed gas path 12 b and flows into the raw material gas path 12 a from the connection point of the recycle gas path 17. The reformed gas is mixed with the raw material gas and pressurized by the booster 14 and then supplied to the hydrodesulfurizer 16. This reformed gas hydrogen is used in the hydrodesulfurization reaction.

  The remaining reformed gas is supplied to the SOFC 21 and air is supplied from the first supplier 22 to the SOFC 21. Here, this air cools the cell as cooling air, and a part of this air is used as power generation air. Then, off-reformed gas including reformed gas that has not been used in power generation is supplied to the combustor 25. Further, the air discharged from the SOFC 21 is also mixed with the off-reformed gas and supplied to the combustor 25. Here, the off-reformed gas burns with air. The SOFC 21 and the reformer 11 are heated by this combustion heat, and the hydrodesulfurizer 16 is heated by the combustion exhaust gas discharged from the combustor 25.

  Next, an operation method (operation) of the SOFC system 100 will be described in detail with reference to FIGS. FIG. 2 is a flowchart showing an example of a method for operating the SOFC system 100. FIG. 3 is a flowchart illustrating an example of the calculation process of FIG. This operation method is executed under the control of the controller 27.

  The controller 27 determines whether or not the SOFC 21 is in a power generation state (step S1). Here, if the power generated by the SOFC 21 is less than the predetermined power, the controller 27 determines that the SOFC 21 is not in a power generation state (step S1: NO), and repeats the process of step S1.

  On the other hand, if the power generated by the SOFC 21 is equal to or greater than the predetermined power, the controller 27 determines that the SOFC 21 is in a power generation state (step S1: YES) and proceeds to step S2. Here, the controller 27 is at least one value of the air supply amount to the SOFC 21, the raw material gas supply amount to the reformer 11, the water supply amount to the reformer 11, and the target current of the SOFC 21. And get.

  That is, the controller 27 acquires the flow rate of air supplied to the SOFC 21 (the amount of air supplied to the SOFC 21). The air supply amount includes a flow rate of air used as power generation air (amount of power generation air) and a flow rate of air used as cooling air (amount of cooling air). The power generation air amount is set based on the target current of the SOFC 21. The cooling air amount is set based on the temperature (detected temperature) of the SOFC 21 detected by the temperature detector. Then, the controller 27 controls the first supply unit 22 to supply air at a flow rate including the power generation air amount and the cooling air amount from the first supply unit 22. If the detected temperature is higher than the appropriate temperature of the SOFC 21, the controller 27 controls the first supplier 22 to increase the air supply amount. On the other hand, if the detected temperature is lower than the appropriate temperature of the SOFC 21, the controller 27 controls the first supplier 22 to reduce the air supply amount. In this way, air at a flow rate corresponding to the power generation and temperature of the SOFC 21 is supplied from the first supply device 22. For this reason, the controller 27 acquires an air supply amount from the 1st supply device 22 etc. which have the function to adjust the flow volume of air, for example.

  Further, the controller 27 acquires at least one value of the raw material gas supply amount to the reformer 11, the water supply amount to the reformer 11, and the target current of the SOFC 21. When the controller 27 acquires the flow rate of the source gas supplied to the reformer 11 (source gas supply amount to the reformer 11), for example, the source gas supply amount is acquired from the second supplier 10 or the like. . The second supplier 10 is controlled so that a raw material gas having a flow rate based on the target current of the SOFC 21 is supplied to the reformer 11. Therefore, the source gas supply amount according to the power generation of the SOFC 21 can be obtained from the second supplier 10.

  When the raw material gas supply amount is acquired and the water supply amount and the target current are not acquired, the controller 27 obtains the water supply amount based on the raw material gas supply amount. For example, when the molar ratio between the raw material gas supply amount and the water supply amount is determined based on the reaction formula or the like, the controller 27 obtains the water supply amount from the raw material gas supply amount according to this molar ratio.

  Alternatively, when the controller 27 acquires the flow rate of water supplied to the reformer 11 (water supply amount to the reformer 11), for example, the water supply amount is acquired from the third supply device 18 or the like. The third supplier 18 is controlled so that water having a flow rate based on the target current of the SOFC 21 is supplied to the reformer 11. Therefore, a water supply amount corresponding to the power generation of the SOFC 21 can be obtained from the third supplier 18.

  When the water supply amount is acquired and the raw material gas supply amount or the target current is not acquired, the raw material gas supply amount is obtained based on the water supply amount. For example, when the molar ratio between the raw material gas and the water supply amount is determined based on the reaction formula or the like, the controller 27 obtains the raw material gas supply amount from the water supply amount according to this molar ratio.

  Alternatively, when the controller 27 acquires the target current of the SOFC 21, the controller 27 obtains the flow rate of the reformed gas used for power generation based on the target current of the SOFC 21. Then, the controller 27 obtains the flow rate of the raw material gas and the flow rate of water according to the flow rate of the reformed gas based on the reforming reaction equation or the like, and supplies the raw material gas flow rate to the reformer 11 The flow rate of water is acquired as the amount of water supplied to the reformer 11. When the second supply device 10 and the third supply device 18 are controlled based on such a flow rate, source gas and water at a flow rate corresponding to the power generation of the SOFC 21 are supplied.

  Thus, the air supply amount corresponding to the power generation and temperature of the SOFC 21 is determined by the air supply amount. Moreover, the raw material gas supply amount and the water supply amount corresponding to the power generation of the SOFC 21 are obtained from the raw material gas supply amount, the water supply amount, and / or the target current. Therefore, by obtaining the air supply amount and at least one of the raw material gas supply amount, the water supply amount, and the target current, the raw material gas, water, and various air gases corresponding to the power generation and temperature of the SOFC 21 are obtained. Supply quantity is obtained.

  Subsequently, the controller 27 executes a flow rate calculation program (step S3). In this flow rate calculation program, each program of steps S31 to S33 shown in FIG. 3 is executed. First, the controller 27 executes a flow rate calculation program (step S31). In this program, the flow rate of the combustion exhaust gas discharged from the exhaust port of the SOFC system 100 is obtained by an arithmetic expression from the supply amounts of various gases such as source gas, water, and air. The flow rate of the combustion exhaust gas depends on the supply amount of various gases and the pressure loss of various devices and piping of the SOFC system 100. This pressure loss depends on the supply amounts of various gases. Therefore, by obtaining the relationship between the flow rate of the combustion exhaust gas and the supply amount of various gases by data obtained through experiments or simulation, an arithmetic expression showing this relationship is created.

  Then, the controller 27 executes a pressure calculation program (step S32). In this pressure calculation program, the pressure of the reformed gas flowing through the reformed gas path 12b at the branch point of the recycle gas path 17 is obtained from the flow rate of the combustion exhaust gas by an arithmetic expression. The pressure of the reformed gas at the branch point depends on the flow rate of the combustion exhaust gas and the pressure loss in the SOFC 21, the combustor 25, and the combustion exhaust gas path 26 located downstream from the branch point. This pressure loss depends on the flow rate of the combustion exhaust gas. For this reason, an arithmetic expression indicating this relationship is created by obtaining the relationship between the pressure of the reformed gas at the branch point and the flow rate of the combustion exhaust gas by data obtained through experiments or simulation.

  Then, the controller 27 executes a differential pressure calculation program (step S33). In this differential pressure calculation program, the difference between the pressure of the reformed gas at the branch point and the pressure of the source gas flowing through the source gas path 12a at the connection point with the recycle gas path 17 is obtained by an arithmetic expression. This differential pressure is determined so that the reformed gas having a flow rate of a predetermined ratio with respect to the supply amount of the raw material gas flows through the recycle gas path 17. For this reason, the differential pressure depends on the raw material supply amount and the pressure loss of the recycle gas path 17, and the pressure loss depends on the raw material supply amount. Therefore, an arithmetic expression indicating this relationship is created by obtaining the relationship between the differential pressure and the raw material supply amount by data obtained through experiments or simulation.

  When the differential pressure is obtained, the process proceeds to step S4 in FIG. Here, the controller 27 determines a target value (target pressure) of the pressure of the reformed gas flowing through the raw material gas path 12a at the connection point with the recycle gas path 17 based on the differential pressure. That is, by subtracting the differential pressure from the reformed gas pressure at the branch point, the pressure of the raw material gas at the connection point with the recycle gas path 17 is obtained, and this is set as the target pressure.

  And the controller 27 controls the pressure regulator 13 so that the pressure of the raw material gas in a connection point may turn into target pressure (step S5). For example, the pressure of the raw material gas is adjusted by adjusting the opening of the pressure regulator 13 based on the raw material supply amount and the flow rate-pressure loss characteristic data of the pressure regulator 13. Thereby, the differential pressure between the pressure of the reformed gas at the branch point and the pressure of the raw material gas at the connection point is adjusted, and a recycle gas having a flow rate corresponding to this differential pressure is supplied to the hydrodesulfurizer 16.

  According to the above configuration, the pressure of the raw material gas at the connection point becomes a target pressure calculated based on the air supply amount and at least one of the raw material gas supply amount, the water supply amount, and the target current. The pressure regulator 13 is adjusted. This air supply amount is a flow rate corresponding to the power generation output and temperature of the SOFC 21. Therefore, the pressure of the raw material gas at the connection point is determined based on not only the power generation output of the SOFC 21 but also the air supply amount that changes according to the temperature of the SOFC 21. Thereby, even if the pressure of the reformed gas at the branch point is affected by the increase or decrease of the air supply amount, the pressure of the raw material gas at the connection point reflecting this is set. As a result, the recycle gas flow rate determined by the differential pressure of the reformed gas between the connection point and the branch point is appropriately adjusted.

  Further, the pressure of the raw material gas at the connection point is adjusted without directly obtaining the pressure of the reformed gas at the branch point. For this reason, even in the SOFC system 100 in which the reformer 11 and the SOFC 21 are at a high temperature, it is possible to supply a recycle gas with an appropriate flow rate.

(Modification 1)
In the above configuration, the air supply amount is acquired from the first supplier 22. On the other hand, the air supply amount may be acquired from the first flow meter 24. The first flow meter 24 is an air flow meter that detects the flow rate of air supplied from the first supply device 22. Examples of the first flow meter 24 include a thermal flow sensor, or an ultrasonic or differential pressure flow meter.

  In the operation method of the SOFC 21 shown in FIG. 2, in the power generation state (step S1: YES), the controller 27 sets the air supply amount, the raw material gas supply amount, the water supply amount, and at least one of the target current values. Is acquired (step S2). This air supply amount is acquired from the first flow meter 24. Then, a differential pressure is obtained by executing the arithmetic program (step S3), and a target pressure corresponding to the differential pressure is set (step S4). And the controller 27 controls the pressure regulator 13, and adjusts the pressure of the raw material gas in a connection point to target pressure (step S5).

  Thus, the target pressure is set based on the air supply amount detected by the first flow meter 24. Therefore, since the target pressure is set with higher accuracy, it is possible to supply recycle gas at an appropriate flow rate based on this target pressure.

(Modification 2)
In the above configuration, the supply amount of the source gas is acquired from the second supply device 10. On the other hand, the source gas supply amount may be acquired from the second flow meter 15. The second flow meter 15 is a raw material flow meter that detects the flow rate of the raw material gas supplied from the second supply device 10. Examples of the second flow meter 15 include a thermal flow sensor, or an ultrasonic or differential pressure flow meter.

  In the operation method of the SOFC 21 shown in FIG. 2, in the power generation state (step S1: YES), the controller 27 sets the air supply amount, the raw material gas supply amount, the water supply amount, and at least one of the target current values. Is acquired (step S2). This source gas supply amount is acquired from the first flow meter 24. Then, a differential pressure is obtained by executing the arithmetic program (step S3), and a target pressure corresponding to the differential pressure is set (step S4). And the controller 27 controls the pressure regulator 13, and adjusts the pressure of the raw material gas in a connection point to target pressure (step S5).

  Thus, the target pressure is set based on the raw material gas supply amount detected by the second flow meter 15. Therefore, since the target pressure is set with higher accuracy, it is possible to supply recycle gas at an appropriate flow rate based on this target pressure.

  In the second modification, as in the first modification, the air supply amount may be acquired from the first flow meter 24.

(Modification 3)
In the above configuration, the water supply amount is acquired from the third supply device 18. On the other hand, the water supply amount may be acquired from the third flow meter 20. The third flow meter 20 is a water flow meter that detects the flow rate of water supplied from the third supplier 18. Examples of the third flow meter 20 include an electromagnetic flow meter.

  In the operation method of the SOFC 21 shown in FIG. 2, in the power generation state (step S1: YES), the controller 27 sets the air supply amount, the raw material gas supply amount, the water supply amount, and at least one of the target current values. Is acquired (step S2). This water supply amount is acquired from the third flow meter 20. Then, a differential pressure is obtained by executing the arithmetic program (step S3), and a target pressure corresponding to the differential pressure is set (step S4). And the controller 27 controls the pressure regulator 13, and adjusts the pressure of the raw material gas in a connection point to target pressure (step S5).

  Thus, the target pressure is set based on the water supply amount detected by the third flow meter 20. Therefore, since the target pressure is set with higher accuracy, it is possible to supply recycle gas at an appropriate flow rate based on this target pressure.

  In the second modification, as in the first modification, the air supply amount may be acquired from the first flow meter 24. Also in the third modification, as in the second modification, the raw material gas supply amount may be acquired from the second flow meter 15.

(Second Embodiment)
The configuration of the SOFC system 200 according to the second embodiment is the same as the configuration of the SOFC system 100 according to the first embodiment except that a pressure gauge 201 is further provided. FIG. 4 is a block diagram illustrating an example of a functional configuration of the SOFC system 200 according to the second embodiment.

  As shown in FIG. 4, the pressure gauge 201 is a device that is provided in the raw material gas path 12 a downstream from the pressure regulator 13 and upstream from the connection point, and detects the pressure of the reformed gas flowing therethrough. As the pressure gauge 201, for example, a semiconductor pressure sensor using a diaphragm or a capacitance pressure sensor is exemplified.

  In the operation method of the SOFC system 200, the process of step S6 shown in FIG. 5 is performed after the process of step S5 shown in FIG. FIG. 5 is a flowchart illustrating an example of an operation method of the SOFC system 200 according to the second embodiment.

  Specifically, in the operation method of the SOFC 21 shown in FIG. 5, in the power generation state (step S1: YES), the controller 27 is at least one of the air supply amount, the raw material gas supply amount, the water supply amount, and the target current. One value is acquired (step S2). Then, a differential pressure is obtained by executing the arithmetic program (step S3), and a target pressure corresponding to the differential pressure is set (step S4). And the controller 27 controls the pressure regulator 13, and adjusts the pressure of the raw material gas in a connection point to target pressure (step S5).

  After this pressure adjustment, the controller 27 acquires the pressure detected by the pressure gauge 201. The detected pressure is the pressure of the raw material gas flowing through the raw material gas path 12a downstream from the pressure regulator 13 and upstream from the connection point. Since there is almost no pressure loss between the detection position by the pressure gauge 201 and the connection point, the controller 27 acquires the detected pressure as the pressure of the raw material gas at the connection point.

  And the controller 27 determines whether the pressure of the raw material gas in a connection point is a target pressure (step S6). If the pressure of the source gas at the connection point is not the target pressure (step S6: NO), the controller 27 controls the pressure regulator 13 (step S5). For example, if the pressure of the raw material gas at the connection point is lower than the target pressure, the opening degree of the pressure regulator 13 is increased. On the other hand, if the pressure of the source gas at the connection point is the target pressure (step S6: YES), the controller 27 returns to the process of step S1 and repeats the processes of steps S1 to S6.

  According to the above configuration, the controller 27 acquires the pressure of the source gas at the connection point from the pressure gauge 201. For this reason, since the pressure of the raw material gas at the connection point can be more accurately adjusted to the target pressure, it is possible to supply the recycle gas at an appropriate flow rate.

  In the second embodiment, the air supply amount may be acquired from the first flow meter 24 as in the first modification. Also in the second embodiment, the source gas supply amount may be acquired from the second flow meter 15 as in the second modification. Furthermore, also in the second embodiment, the water supply amount may be acquired from the third flow meter 20 as in the third modification.

  In addition, all the above embodiments may be combined with each other as long as they do not exclude each other. From the foregoing description, many modifications and other embodiments of the present invention are obvious to one skilled in the art. Accordingly, the foregoing description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and / or function may be substantially changed without departing from the spirit of the invention.

  The operation method of the solid oxide fuel cell system according to the present invention is useful as an operation method of the solid oxide fuel cell system in which the flow rate of the recycle gas is improved.

10: 2nd feeder 11: Reformer 12a: Raw material gas path 12b: Reformed gas path 13: Pressure regulator 14: Booster 15: Second flow meter 16: Hydrodesulfurizer 17: Recycle gas path 18: Third feeder 19: Water path 20: Third flow meter 21: SOFC (solid oxide fuel cell)
22: First supply unit 23: Air path 24: First flow meter 25: Combustor 26: Combustion exhaust gas path 27: Controller 100: SOFC system (solid oxide fuel cell system)
200: SOFC system (solid oxide fuel cell system)
201: Pressure gauge

Claims (5)

A hydrodesulfurizer for desulfurizing the raw material gas;
A reformer for reforming the raw material gas desulfurized by the hydrodesulfurizer with water to produce a reformed gas containing hydrogen;
A solid oxide fuel cell that generates electricity with the reformed gas and air reformed by the reformer;
A combustor for burning the reformed gas discharged from the solid oxide fuel cell;
A source gas path through which the source gas flows to the reformer via the hydrodesulfurizer;
A reformed gas path through which the reformed gas flows from the reformer to the combustor via the solid oxide fuel cell;
A recycle gas path branched from the reformed gas path at a branch point downstream from the reformer and connected to the raw material gas path at a connection point upstream from the hydrodesulfurizer;
A pressure regulator for adjusting the pressure of the source gas flowing through the source gas path upstream of the connection point;
A booster that increases the pressure of the source gas flowing through the source gas path downstream from the connection point;
A water path through which water supplied to the reformer flows;
An air path through which air supplied to the solid oxide fuel cell flows;
A solid oxide fuel cell system comprising a controller,
The controller is configured such that the pressure of the raw material gas at the connection point is an air supply amount to the solid oxide fuel cell, a raw material gas supply amount to the reformer, a water supply amount to the reformer, And a method of operating the solid oxide fuel cell system, wherein the pressure regulator is controlled to achieve a target pressure calculated based on at least one value of a target current of the solid oxide fuel cell . The solid oxide fuel cell system further includes a pressure gauge for detecting the pressure of the raw material gas flowing through the raw material gas path downstream from the pressure regulator and upstream from the connection point,
The operation method of the solid oxide fuel cell system according to claim 1, wherein the controller acquires the pressure of the raw material gas at the connection point from the pressure gauge. The solid oxide fuel cell system includes a first supply for supplying the air to the solid oxide fuel cell, a first flow meter for detecting a flow rate of air supplied from the first supply, Further comprising
The operation method of the solid oxide fuel cell system according to claim 1 or 2, wherein the controller acquires the air supply amount from the first flow meter. The solid oxide fuel cell system includes: a second supply device that supplies the raw material gas to the reformer; and a second flow meter that detects a flow rate of the raw material gas supplied from the second supply device. In addition,
The operation method of the solid oxide fuel cell system according to any one of claims 1 to 3, wherein the controller acquires a supply amount of a raw material gas from the second flow meter to the reformer. The solid oxide fuel cell system further includes a third supply for supplying the water to the reformer, and a third flow meter for detecting a flow rate of the water supplied from the third supply. ,
The operation method of the solid oxide fuel cell system according to any one of claims 1 to 4, wherein the controller acquires a water supply amount from the third flow meter to the reformer.

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