JP2009295534A - Fuel cell system and operation method for fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to use a light-emitting element for a long period. <P>SOLUTION: A bypass passage L2 is arranged in parallel with a modification heat exchanger passage L1 including a modification heat exchanger 2, a valve V1 is arranged on the modification heat exchanger passage L1, and a valve V2 is arranged on the bypass passage L2. For example, when power generation voltage V falls below a predetermined deterioration lower limit value VLth at the time of a baseline operation (an operation for making power load to a fuel cell system constant), temperature T1 of a modification device is adjusted by adjusting a position θ2 of the valve V2 so as to make the power generation voltage V return to a standard output VO (power generation voltage at the time of completion of a starting mode). When the temperature T1 of the modification device is raised, gas density of hydrogen and carbon monoxide in a fuel gas is increased, and the power generation voltage V is increased. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system using a fuel cell that operates at a high temperature, such as a solid oxide fuel cell, and a method for operating the fuel cell system.

  Conventionally, fuel cells have attracted attention as a clean power generation system that does not generate harmful substances. Among them, the solid oxide fuel cell operates at a higher temperature than the polymer electrolyte fuel cell, and is therefore energy efficient in terms of both power generation and utilization of high temperature energy.

A solid oxide fuel cell (hereinafter referred to as SOFC) has a laminated structure called a single cell in which a solid electrolyte layer made of an oxide ion conductor is sandwiched between an air electrode layer and a fuel electrode layer from both sides. An oxidant gas (oxygen) is supplied to the electrode layer side, and a fuel gas (H ₂ , CO, CH _4, etc.) is supplied to the fuel electrode layer side.

The oxidant gas supplied to the air electrode layer side passes through the pores in the air electrode layer and reaches the vicinity of the interface with the solid electrolyte layer, and receives electrons from the air electrode layer at this portion and receives oxide ions (O ^2- ) is ionized. The oxide ions diffuse and move in the solid electrolyte layer toward the fuel electrode layer.

Oxide ions that have reached the vicinity of the interface with the fuel electrode layer react with the fuel gas at this portion to generate reaction products (H ₂ O, CO _2, etc.), and discharge electrons to the fuel electrode layer. A structure in which a large number of single cells are stacked is called a stack, and fuel gas is supplied in units of cells or in units of stacks to generate (generate power) power to a load.

  The steady power generation temperature of the SOFC is 950 ° C., for example. When starting the SOFC, it is necessary to raise the SOFC in the normal temperature state to the steady power generation temperature. For this purpose, methods such as heating the entire SOFC with an electric heater, or providing an electric heater in the oxidant gas supply line, and supplying the heated oxidant gas to a high temperature by heating to the air electrode are adopted ( For example, see Patent Document 1).

  Hydrogen gas is most preferably used as the fuel gas. However, since hydrogen is difficult to obtain, a hydrocarbon-based fuel such as natural gas or propane gas is reformed into a hydrogen-rich fuel gas, and the fuel electrode is used. It is common to introduce into the layer. As the oxidant gas, it is most preferable to use oxygen gas, but air is generally used because of the problem of availability.

  FIG. 12 shows an outline of a conventional fuel cell system using SOFC. This fuel cell system includes a module 100 that is a power generation unit main body and a peripheral system that supplies fuel gas, oxidant gas, and the like to the module 100.

  The module 100 includes a power generation chamber 1 in which an SOFC (hereinafter referred to as a power generation element) that is supplied with fuel gas and an oxidant gas (air) is installed, and off-gas discharged from the power generation chamber 1 (not used for power generation). Combustion chamber 4 that burns fuel gas + air), air distributor 5 that sends air to the power generation chamber 1 and warms the air by using the heat generated by the power generation reaction and offgas, and the heat generated by the power generation reaction and offgas. And a reforming heat exchanger 2 that reforms fuel (city gas) into hydrogen-rich fuel gas (reformed gas).

  The peripheral system includes a heat supply source such as an air preheater (heater) 3 that preheats air supplied as an oxidant gas, in addition to a supply unit (not shown) such as fuel, air, and pure water. A heat supply source such as the air preheater 3 may be built in the module 100. Reference numeral 6 denotes a load connected to the power generation chamber 1.

  The reforming heat exchanger 2 includes an evaporator 2-1, a fuel preheater 2-2, and a reformer 2-3, and the evaporator 2-1 uses pure water as a steam to produce a fuel preheater 2-2. Included in the fuel. The fuel containing the steam is preheated in the fuel preheater 2-2, led to the reformer 2-3, and reformed into hydrogen-rich fuel gas.

  This reforming using steam is called steam reforming and is often used because of its high hydrogen generation efficiency. The reforming using steam is an endothermic reaction, and the temperature at which the reforming heat exchanger 2 can perform the reforming operation is generally about 400 ° C. or more in the case of steam reforming.

  In the reforming heat exchanger 2, heat is required for generating steam in the evaporator 2-1, preheating the fuel in the fuel preheater 2-2, and reforming the fuel in the reformer 2-3. An exhaust passage L1 for combustion gas from the combustion chamber 4 (hereinafter referred to as exhaust gas from the combustion chamber 4 including this combustion gas) is provided as a passage for receiving the supply of heat.

  In this fuel cell system, the operation mode is divided into three modes: a start mode, a steady mode, and a stop mode. At the start of the start-up mode, since the system is at room temperature, the system is brought to a temperature at which the power generation element in the power generation chamber 1 can generate power, and to a temperature at which the reformer 2-3 of the reforming heat exchanger 2 can perform a reforming operation. Need to warm up. In the steady mode, the power generation element is damaged when operated at a temperature exceeding the heat resistance temperature of the power generation element for a long time. Therefore, it is necessary to keep the power generation chamber 1 at a temperature lower than the heat resistance temperature. Further, since there is a power generation chamber temperature range in which power generation efficiency is increased, it is necessary to control the temperature of the power generation chamber 1 during operation. In the stop mode, it is necessary to stop the system while cooling a high temperature part such as the power generation chamber 1.

[Startup mode]
When the start of operation is instructed, the fuel cell system enters an activation mode. At the start of the start mode, the air preheater 3 is turned on with the purge gas being supplied instead of the fuel to the reforming heat exchanger 2, and the high-temperature air preheated by the air preheater 3 is supplied to the air distributor 5. To supply to the power generation chamber 1. In response to the supply of preheated air from the air preheater 3, the temperature of the power generation chamber 1 rises.

  The preheated air that contributes to the temperature increase in the power generation chamber 1, including the purge gas, passes around the combustion chamber 4 and the air distributor 5, and is discharged as exhaust gas through the discharge passage L <b> 1. Here, the evaporator 2-1 of the reforming heat exchanger 2, the fuel preheater 2-2, and the reformer 2-3 are gases [exhaust gas from the combustion chamber 4 (air + purge gas) passing through the discharge passage L1. ] Is supplied with the amount of heat.

  When the temperature of the reformer 2-3 (reformer temperature) reaches, for example, 700 ° C. in response to the supply of this heat amount, the supply of fuel to the reforming heat exchanger 2 is started instead of the purge gas used so far. Then, the fuel containing the vapor from the evaporator 2-1 is led to the reformer 2-3 through the fuel preheater 2-2, reformed into hydrogen-rich fuel gas, and supplied to the power generation chamber 1. The

  Upon receipt of this fuel gas supply, power generation in the power generation chamber 1 is started, and fuel and air off-gas discharged from the power generation chamber 1 are mixed and burned in the combustion chamber 4. Exhaust gas (combustion gas) passes through the periphery of the air distributor 5, passes through the discharge passage L1, and is discharged outside the module (hereinafter, the gas discharged outside the module is referred to as exhaust gas). At the start of power generation in the power generation chamber 1, a load 6 is connected to the power generation chamber 1, and a current from the power generation element flows to the load 6.

  Thus, the fuel gas is reformed in the reforming heat exchanger 2 by receiving the heat amount of the exhaust gas (combustion gas) from the combustion chamber 4 regardless of the preheating of the air in the air preheater 3. Can continue. Usually, at this time, the air preheater 3 is turned off.

  Since the power generation element in the power generation chamber 1 can generate power from about 600 ° C., supply of fuel to the reforming exchanger 2 when the temperature of the power generation chamber 1 (power generation chamber temperature) reaches about 600 ° C. The power generation reaction heat is sometimes used as a heat source for temperature rise at the start-up by causing the power generation chamber 1 to generate power (see, for example, Patent Document 2).

(Steady mode)
When the temperature of the power generation chamber 1 rises and the current to the load 6 (load current) rises to a value set in steady operation, the steady mode (steady operation operation) is entered. Since the power generation reaction is an exothermic reaction, it is necessary to control the temperature of the power generation chamber 1 below the heat resistance temperature of the power generation element during power generation. Moreover, it is necessary to control so that it does not fall below the power generation possible temperature of the power generation element. Therefore, in this steady mode, the air preheater 3 is turned on / off, or the flow rate of air supplied to the power generation chamber 1 via the air preheater 3 is increased or decreased to change the temperature of the power generation chamber 1 to the steady power generation temperature. Keep on.

[Stop mode]
When stopping the system, the air preheater 3 is turned off and purge gas is introduced instead of fuel to the reforming heat exchanger 2 to stop the exothermic reaction of power generation in the power generation chamber 1 and combustion in the combustion chamber 4. Then, the power generation chamber 1 is cooled by the air introduced through the air preheater 3 and the purge gas.

JP 2006-261005 A JP 2004-087377 A JP 2007-087686 A "Evaluation of long-term life and deterioration behavior of medium-temperature cylindrical plate stack" (H19.5): NEDOH FY17-18 results report (research and development on solid oxide fuel cell system technology development and reliability improvement). “Research and development of a consumer thermal self-supporting solid oxide fuel cell system using kerosene as raw fuel” (H18.6): Summary of the 20th Technology Development Research Results Presentation Meeting.

  However, in such a fuel cell system, the power generation element deteriorates according to the duration of operation, and the output of the fuel cell system (device output [W] = load current [A] × power generation voltage [V]) decreases. Go.

  FIG. 13 shows the deterioration behavior of SOFC (results of long-term durability test of a cylindrical flat plate single cell) obtained in “Research and Development for Reliability Improvement” (see Non-Patent Document 1) conducted in the NEDO project. This figure shows a state in which the power generation element (cell) deteriorates with time and the generated voltage decreases.

  This change over time does not depend on operation methods such as baseline operation (operation in which the power load on the fuel cell system is constant) and load fluctuation operation (operation in which the output of the fuel cell system follows the fluctuation of the power load on the combustion cell system). Occur. As shown in the figure, the degree of deterioration of the power generating element also depends on the magnitude of the load current density. In addition, it has been pointed out that the deterioration of the power generation element may depend on the frequency of starting and stopping. At present, the cause and mechanism of the degradation of the power generation element are not sufficiently elucidated, but it is said that one of the causes is thermal diffusion of materials used for the power generation element.

  For example, when this fuel cell system is used as a cogeneration system, it is expected that it will be difficult to supply necessary power due to a decrease in the generated voltage due to deterioration of the power generation element. As a method of avoiding this, it is conceivable to use a fuel cell system having a power generation capacity with a sufficient margin with respect to the required amount of electric power. Excessive costs are required.

  Further, as another avoidance method, a method of periodically replacing the power generation element in accordance with a decrease in the generated voltage can be considered. However, in this method, the cost and labor required for replacing the power generation element are large, and the running cost of the system increases. Further, in a system in which the power generating elements can be partially replaced, there is a possibility that the remaining power generating elements that are not required to be replaced may be deteriorated by stopping and restarting the system. As described above, the deterioration of the power generation element and the start / stop associated therewith shorten the life of the power generation element and further increase the running cost of the system.

  Reference 3 discloses an automatic operation mode in which the fuel cell power generator is operated by controlling the flow rate of the fuel gas and the flow rate of the oxidant gas according to the external load, and the flow rate of the fuel gas and, if necessary, It is possible to select an evaluation mode that measures the output voltage when the drawn current is almost constant while the air flow rate is controlled to be substantially constant. In the evaluation mode, the current output voltage is stored in the storage means. A fuel cell power generation device is shown that compares a stored past output voltage or an output voltage calculated by simulation and diagnoses the deterioration state of the fuel cell power generation device based on the comparison result.

  In the fuel cell power generation device shown in this cited document 3, since the deterioration state of the fuel cell power generation device can be accurately diagnosed even during operation, the fuel cell power generation device can always be operated in a good state. The effect is obtained. However, in this fuel cell power generation device, when it is diagnosed that the fuel cell power generation device is deteriorated, it is only notified to the operator by displaying that fact on the monitor. In this case, upon receiving the notification, the operator stops the operation of the fuel cell power generation device, performs processing such as maintenance and inspection, and if it is determined that the power generation device needs to be replaced, replaces the power generation device. Do.

  In the fuel cell power generation device shown in this cited document 3, when it is diagnosed as a deteriorated state, there is no idea to continue the operation by compensating for the deteriorated state. Therefore, even in the fuel cell power generation device disclosed in the cited document 3, the frequency of replacement of the power generation elements is increased, and it cannot be said that a solution to the above-described problem is provided.

  The present invention has been made in order to solve such problems. The object of the present invention is to compensate for the deterioration of the output of the fuel cell system accompanying the deterioration of the power generation element, so that the power generation element can be compared with the conventional one. Another object of the present invention is to provide a fuel cell system that can be used for a long time and a method for operating the fuel cell system.

  In addition, the frequency of replacement of the power generation elements can be reduced, and the required system output can be maintained for a long time compared to the conventional system, even if the system does not have an output capacity more than necessary for the required power. It is an object to provide a fuel cell system and a method for operating the fuel cell system.

  Also provided is a fuel cell system capable of knowing the deterioration state of the power generation element and notifying that it is time to replace the power generation element before the damage caused by the deterioration of the power generation element occurs, and a method for operating the fuel cell system There is to do.

  In order to achieve such an object, the fuel cell system of the present invention combusts a power generation unit using a fuel cell that is supplied with fuel gas and oxidant gas to generate power, and gas discharged from the power generation unit. A fuel cell system comprising a combustion section and a fuel reforming section that uses a calorific value of exhaust gas from the combustion section as a fuel gas to a power generation section using a reformer that reforms fuel. A control unit for controlling the reformer temperature of the reforming unit is provided.

  The amount of hydrogen produced by the reforming reaction depends on the reformer temperature of the fuel reforming section according to the chemical equilibrium theory. FIG. 14 shows the relationship between the reformer temperature of the fuel reforming section and the reformed gas composition when methane, which is the main component of city gas, is reformed. From this figure, the reforming reaction of methane starts from a reformer temperature of about 400 ° C. in the fuel reforming section, almost all methane is reformed at a temperature of 700 ° C. or higher, and reformed gas in the temperature range of 400 to 700 ° C. It can be seen that changes in the concentration of hydrogen and carbon monoxide are occurring. FIG. 15 shows the relationship between the hydrogen and carbon monoxide concentrations in the fuel gas shown in Non-Patent Document 2 and the power generation voltage (cell voltage) of the power generation element (cell). From this figure, it can be seen that the higher the hydrogen and carbon monoxide concentrations in the fuel gas, the higher the generated voltage.

  In the fuel cell system of the present invention, the concentration of hydrogen or carbon monoxide in the fuel gas is changed by controlling the reformer temperature of the fuel reforming section. For example, when the reformer temperature in the initial fuel reforming section is set to 600 ° C. and the power generation voltage decreases, the reformer temperature in the fuel reforming section is increased, and the gas concentrations of hydrogen and carbon monoxide in the fuel gas are increased. increase. As a result, it is possible to prevent a decrease in the generated voltage and compensate for the deterioration in the output of the fuel cell system.

  As an example of the fuel cell system of the present invention, a first passage for guiding exhaust gas from the combustion section to the fuel reforming section, a second passage that bypasses the first passage including the fuel reforming section, And a control unit for controlling the reformer temperature of the fuel reforming unit by adjusting the calorific value of the exhaust gas from the combustion unit passing through the calorie adjusting unit. The structure which provides is considered.

  In this configuration, the heat quantity adjusting unit may be provided in both the first passage and the second passage, or may be provided only in one of the first passage and the second passage. When only one side is provided with a calorific value adjusting unit, by adjusting the calorific value of the exhaust gas from the combustion unit that passes through the calorific value adjusting unit, the correlation is utilized, and the combustion unit that passes through the remaining one passage is used. It is possible to adjust the amount of heat of the exhaust gas. It should be noted that a gas flow rate adjusting mechanism such as a valve may be used as the heat amount adjusting unit. Further, in the case where both of the heat quantity adjusting parts are provided, it is preferable that the opening degree of the other heat quantity adjusting part is adjusted in a state where any one of the heat quantity adjusting parts is fully opened.

  In this configuration, an external heat source device may be provided, and the temperature-adjusted gas from the external heat source device may be added to the first passage. Moreover, you may make it provide a mixing space part in the location where the temperature-controlled gas from the external heat source device of a 1st channel | path is added. Moreover, you may make it provide the gas mixing promotion means which accelerates | stimulates mixing of the gas in the space part in the mixing space part. In addition, an auxiliary heat source device may be provided in the reformer of the fuel reforming unit.

  The operating method of the fuel cell system of the present invention includes a power generation unit using a fuel cell that generates power by being supplied with fuel gas and oxidant gas, a combustion unit that burns gas discharged from the power generation unit, Using a reformer that reforms the fuel using the amount of heat of the exhaust gas from the combustion section, the fuel reforming section that converts the fuel gas to the power generation section, and the exhaust gas from the combustion section is guided to the fuel reforming section. A fuel cell system comprising: a first passage; a second passage that bypasses the first passage including the fuel reforming portion; and a heat amount adjustment unit provided in at least one of the first passage and the second passage. As a fuel cell system output deterioration compensation operation, the fuel reforming is performed by adjusting the heat quantity of the exhaust gas from the combustion section that passes through the heat quantity adjustment section so as to keep the output value of the fuel cell system at a predetermined standard output. The reformer temperature In which it was to be an integer.

  The operating method of the fuel cell system of the present invention includes a power generation unit using a fuel cell that generates power by being supplied with fuel gas and oxidant gas, a combustion unit that burns gas discharged from the power generation unit, Using a reformer that reforms the fuel using the amount of heat of the exhaust gas from the combustion section, the fuel reforming section that converts the fuel gas to the power generation section, and the exhaust gas from the combustion section is guided to the fuel reforming section. A fuel cell system comprising: a first passage; a second passage that bypasses the first passage including the fuel reforming portion; and a heat amount adjustment unit provided in at least one of the first passage and the second passage. In order to compensate the deterioration of the output of the fuel cell system, the operation is performed under the condition where a predetermined operation parameter is set, and the output value of the fuel cell system at that time is adjusted to a predetermined standard output. Pass through It is obtained so as to adjust the reformer temperature of the fuel reformer unit by regulating the amount of heat of exhaust gas from the combustion section.

  In the operation method of the fuel cell system of the present invention, the output deterioration compensation operation of the fuel cell system is performed when the output value of the fuel cell system satisfies a predetermined condition. For example, it is performed in accordance with a predetermined cycle, performed when the output value of the fuel cell system falls below a predetermined threshold (deterioration lower limit value), or manually.

  In the operation method of the fuel cell system of the present invention, a warning may be issued when the reformer temperature of the fuel reforming unit deviates from a predetermined range. Further, when the reformer temperature of the fuel reforming unit deviates from a predetermined range, the subsequent deterioration compensation operation of the output of the fuel cell system is prohibited, and thereafter, the output value of the fuel cell system is determined in advance. The operation of the fuel cell system may be stopped when the lower limit is exceeded. Further, it is possible to detect the damage of the power generation element of the fuel cell, and to prohibit the deterioration compensation operation of the output of the fuel cell system when the damage of the power generation element is detected.

  Further, in the operation method of the fuel cell system of the present invention, when the auxiliary heat source device is provided in the reformer of the fuel reforming unit and the deterioration of the fuel cell system is compensated, the reformer temperature of the fuel reforming unit is adjusted by the amount of heat. If it becomes impossible to adjust by adjusting the amount of heat of the combustion gas passing through the section, the reformer temperature of the fuel reforming section is adjusted by adjusting the amount of heat supplied from the auxiliary heat source to the reformer of the fuel reforming section. May be.

  According to the present invention, the gas concentration of hydrogen or carbon monoxide in the fuel gas can be adjusted by controlling the reformer temperature of the fuel reforming section. As a result, even if the output of the system decreases due to deterioration of the power generation element over time, the concentration of hydrogen or carbon monoxide in the combustion gas is increased to prevent a decrease in power generation voltage and compensate for the deterioration of the output of the fuel cell system. This makes it possible to use the power generating element for a longer period of time than in the past.

  In addition, according to the present invention, it is possible to lengthen the replacement cycle of the power generation element and reduce the frequency of replacement of the power generation element, and to prevent a long-term output decrease of the system due to the time-dependent change of the power generation element. Even if the system does not have an output capacity more than necessary with respect to the generated power, it is possible to maintain the required system output for a long period of time compared to the conventional system.

  In addition, it is said that starting and stopping the system may deteriorate the power generation element. In the present invention, since the start / stop of the system can be reduced, it is possible to further suppress the deterioration of the power generation element, and therefore, it is possible to suppress the generation of costs associated with the replacement of the power generation element.

  In addition, according to the present invention, it is possible to know the state of deterioration of the power generation element, and to notify that the time for replacement of the power generation element has come before damage due to deterioration of the power generation element occurs.

Hereinafter, the present invention will be described in detail with reference to the drawings.
[Embodiment 1]
FIG. 1 is a system configuration diagram showing an outline of an embodiment of a fuel cell system according to the present invention. In this figure, the same reference numerals as those in FIG. 12 denote the same or equivalent components as those described with reference to FIG.

  In this embodiment, the exhaust gas exhaust passage L1 from the combustion chamber 4 to the reforming heat exchanger 2 is used as a first exhaust passage (hereinafter referred to as a reforming heat exchanger passage), and reforming heat exchange is performed. A second discharge passage (hereinafter referred to as a bypass passage) L2 is provided in parallel with the reforming heat exchanger passage L1 including the cooler 2, a valve V1 is provided in the reforming heat exchanger passage L1, and the bypass passage L2. Is provided with a valve V2.

  In this embodiment, the junction P1 on the inlet side of the reforming heat exchanger flow path L1 and the bypass flow path L2 is also referred to as an inflow (exhaust gas inflow from the combustion chamber 4). The junction P2 on the outlet side of the vessel channel L1 and the bypass channel L2 is also referred to as an exhaust port (exhaust gas exhaust port from the combustion chamber 4). The gas discharged from the discharge port P2 can be sent to a waste heat utilization device such as a turbine system or a steam generator for effective use.

  The reforming heat exchanger 2 is provided with a fuel supply passage L3 to the reforming heat exchanger 2 and a purge gas supply passage L5 used in the start-up mode and the stop mode. A valve V3 is provided in L3, and a valve V5 is provided in the purge gas supply passage L5.

  Further, a valve V4 is provided in the supply path L4 for the oxidant gas to the air preheater (heater) 3, and for the reforming heat exchanger 2, the temperature in the reforming unit 2-3 is changed. A temperature sensor 7 that detects the temperature T1 is provided. For the power generation chamber 1, a temperature sensor 8 that detects the temperature in the power generation chamber 1 as the power generation chamber temperature T2 and a voltmeter 9 that detects the voltage of the power generation element in the power generation chamber 1 as the power generation voltage V are provided. It has been.

  In addition, the reformer temperature T1 from the temperature sensor 7, the power generation chamber temperature T2 from the temperature sensor 8, and the power generation voltage V from the voltmeter 9 are input to this fuel cell system, and valves V1 to V5 and an air preheater are input. A controller 10 is provided as a control device that controls the operation of the third control. The controller 10 is realized by hardware including a processor (CPU) 10a and a storage device 10b, and a program that realizes various functions as a control device in cooperation with these hardware. The controller 10 is provided with a notification device 11 that notifies various information from the controller 10.

  In this embodiment, the power generation chamber 1 corresponds to the power generation section referred to in the present invention, the reforming heat exchanger 2 including the reformer 2-3 corresponds to the fuel reforming section, and the combustion chamber 4 burns. The controller 10 corresponds to the control unit, and the valves V1 and V2 correspond to the heat amount adjusting unit. In the present embodiment, the system including the reforming heat exchanger 2 in which the evaporator 2-1, the fuel preheater 2-2, and the reformer 2-3 are integrated is shown. Some of the evaporator 2-1 and the fuel preheater 2-2 are installed separately from the reformer 2-3, and the fuel reforming unit includes at least the reformer 2-3. Shall.

  Further, in this embodiment, the power generation chamber temperature T2 is not limited to that measured at one representative point. For example, when measuring multiple points as the temperature of the power generation chamber, in order to control within the heat resistant temperature range of the power generation element, the point where the temperature rises most easily as the module structure is used as a control point, thereby preventing damage to the power generation element. Control becomes possible.

  In addition, regarding the measurement of the power generation chamber temperature T2, a method using a calculation result (for example, a point having the highest temperature change rate) of a multipoint measurement value, a state quantity of a temperature increase value with respect to a multipoint measurement value other than the representative point There is also a method that uses a control law (for example, model predictive control) that can take constraints into consideration, and the method may be selected according to the module structure.

  Moreover, as a structure of a module, the power generation chamber may be unitized for every appropriate power generation unit. Even in such a case, the power generation chamber temperature T <b> 2 may be determined by measuring the temperature for each unit and using the same method as when measuring a plurality of temperatures.

  Hereinafter, a control operation unique to the present embodiment executed by the controller 10 will be described. In addition, as a state before the start of operation for entering this control operation, it is assumed that the valves V1 to V5 are all turned off (fully closed) and the air preheater 3 is also turned off.

[Startup mode]
When the controller 10 is instructed to start operation, this time is set as the start time of the start mode, the valves V1, V4, V5 are turned on (fully opened), and the air preheater 3 is turned on (see FIG. 2). Thereby, supply of the oxidant gas (air) to the air preheater 3 is started. In addition, supply of purge gas to the reforming heat exchanger 2 is started.

  The air that has flowed into the air preheater 3 is warmed by the air preheater 3, and sent to the air electrode in the power generation chamber 1 through the air distributor 5. The purge gas that has flowed into the reforming heat exchanger 2 passes through the reforming heat exchanger 2 and is sent to the fuel electrode of the power generation chamber 1. The reason for supplying the purge gas during startup is to prevent oxidation of the reforming catalyst. As the purge gas, for example, a weakly reducing gas obtained by mixing 3% or less of hydrogen with nitrogen is used.

  The air from the air preheater 3 supplied to the power generation chamber 1 reaches the combustion chamber 4 while warming the power generation chamber 1 and is mixed with the purge gas discharged from the power generation chamber 1. Then, this mixed gas reaches the inflow port P1 as exhaust gas from the combustion chamber 4, and is sent to the reforming heat exchanger passage L1. In this case, since the valve V2 is fully closed, the entire amount of exhaust gas from the combustion chamber 4 is sent to the reforming heat exchanger passage L1. The exhaust gas from the combustion chamber 4 sent to the reforming heat exchanger passage L1 contributes to the temperature increase of the reforming heat exchanger 2, and is then discharged as exhaust gas.

  When the reformer temperature T1 reaches 500 ° C., the controller 10 turns off the valve V5 and turns on the valve V3 (see FIG. 3). Thereby, supply of the purge gas from the supply passage L5 to the reforming heat exchanger 2 is cut off, and supply of fuel (city gas) to the reforming heat exchanger 2 from the supply passage L3 is started.

  When the supply of fuel from the supply passage L3 is started, the reforming heat exchanger 2 includes the steam from the evaporator 2-1 in the fuel, and the reformer 2 passes through the fuel preheater 2-2. -3, reformed into hydrogen-rich fuel gas, and supplied to the power generation chamber 1. Thereby, the fuel gas and air discharged from the power generation chamber 1 are mixed in the combustion chamber 4. Here, if the temperature in the combustion chamber 4 exceeds the ignition temperature (450 ° C. to 500 ° C.) of the fuel, combustion starts in the combustion chamber 4.

  When the power generation chamber temperature T2 becomes 600 ° C. or higher, power generation in the power generation chamber 1 is started. In this case, a load 6 is connected to the power generation chamber 1, and a current from the power generation element is passed through the load 6. This is because the heat of the power generation reaction is used for the initial temperature rise. In addition, if the capability of the air preheater 3 is high, you may move to power generation operation in the vicinity of the steady power generation temperature.

  When the power generation chamber temperature T2 approaches the steady power generation temperature (for example, 950 ° C.), the controller 10 controls the opening degree of the valves V3 and V4, and adjusts the gas flow rate to the fuel utilization rate η1, air according to the system specifications. Adjust to utilization factor η2.

  At this time, when the air flow rate becomes small, the power generation chamber temperature T2 rises. In this case, the controller 10 performs PID control on the opening degree of the valve V2 of the bypass flow path L2 while monitoring the power generation chamber temperature T2. That is, by performing PID control on the opening degree of the valve V2 of the bypass flow path L2, the flow rate of the exhaust gas flowing through the reforming heat exchanger flow path L1 is reduced, the reformer temperature T1 is lowered, and the carbonization contained in the fuel gas Internal reforming for reforming a part of hydrogen on the power generation element is generated in the power generation chamber 1, and the increase in the power generation chamber temperature T2 is suppressed by the reforming reaction heat (endothermic reaction heat) at this time.

  Then, the controller 10 ends the startup when the fuel utilization rate η1, the air utilization rate η2, the load current I, and the power generation chamber temperature T2 are in the steady operation state, and shifts to the steady mode. In the present embodiment, the reformer temperature T1 at the end of startup is, for example, about 600 ° C. In addition, at the end of startup, the valve V2 of the bypass flow path L2 is not in a fully closed state but is in a PID control state, and the exhaust gas from the combustion chamber 4 flows in the bypass flow path L2 in a diverted state. (See FIG. 4).

  When the controller 10 shifts to the steady mode, the output of the fuel cell system (hereinafter simply referred to as the system output) at that time (start-up end time) is set as an initial output, and this initial output is standardized in the storage device 10b. Save as output. In this example, the generated voltage V at the end of startup is stored in the storage device 10b as the standard output V0. If the power output specification of the system is determined in advance, the rated power generation voltage obtained from the power output specification may be stored as a standard output.

  Further, when the controller 10 shifts to the steady mode, it is necessary to obtain the standard output V0 such as the fuel utilization rate η1, the air utilization rate η2, the load current I, the reformer temperature T1, etc. at that time (starting end time). The operation parameter indicating the standard state, which is an unfavorable condition, is stored in the storage device 10b.

(Steady mode)
The controller 10 supplies the power generation chamber 1 with on / off control of the air preheater 3 so that the power generation chamber temperature T2 is maintained at 950 ° C. (steady power generation temperature) with the end of the start mode as the start of the steady mode. Air temperature control) and PID control (control of the flow rate of air supplied to the power generation chamber 1) of the opening degree θ4 of the valve V4 are started (see FIG. 5).

[Degradation compensation]
In this fuel cell system, the power generation element deteriorates according to the duration of operation, and the output of the system (device output [W] = load current [A] × power generation voltage [V]) decreases. In the present embodiment, the controller 10 compensates for the deterioration of the output of the system in the steady mode as follows.

[Degradation compensation during baseline operation]
During baseline operation (operation in which the power load on the fuel cell system is constant), the controller 10 monitors the power generation voltage V and compares this power generation voltage V with the deterioration lower limit value VLth defined as the threshold for deterioration determination. To do. The deterioration lower limit value VLth may be determined in advance as a specification of the apparatus, or may be determined as a ratio with respect to the standard output V0, such as 98% of the standard output V0 as the deterioration lower limit value VLth. In this case, it is preferable that the deterioration lower limit value VLth is set to be a value larger than or equivalent to the lowest power generation voltage VL _MIN in the system specifications.

  Here, when the controller 10 confirms that the generated voltage V has fallen below the deterioration lower limit VLth (point t1 shown in FIG. 6 (d)), the controller 10 uses the generated voltage V as the standard output V0 as a system output deterioration compensation operation. Then, the reformer temperature T1 is adjusted by adjusting the opening degree θ2 of the valve V2.

  That is, by adjusting the opening degree θ2 of the valve V2 in the closing direction, the flow rate of the exhaust gas flowing through the reforming heat exchanger flow path L1 is increased, and the reformer temperature T1 is raised. When the reformer temperature T1 increases, the concentration of hydrogen and carbon monoxide in the fuel gas increases, and the power generation voltage V increases. In this way, the controller 10 increases the reformer temperature T1 by adjusting the opening θ2 of the valve V2 in the closing direction until the generated voltage V matches the standard output V0.

  Similarly, the controller 10 controls the valve V2 so as to return the generated voltage V to the standard output V0 every time the generated voltage V falls below the deterioration lower limit value VLth (points t2 and t3 shown in FIG. 6 (d)). The reformer temperature T1 is adjusted by adjusting the opening degree θ2.

  After adjusting the reformer temperature T1, the controller 10 stores the adjusted reformer temperature T1 in the storage device 10b as the reformer temperature set value T1set so that the reformer temperature T1 becomes T1set. The opening degree θ2 of the valve V2 is controlled. As a result, the power generation voltage V is prevented from being lowered and the deterioration of the output of the system is compensated.

  Each time the deterioration compensation operation is performed, the reformer temperature defining the standard state stored in the storage device 10b may be rewritten and used as an operation parameter in the next deterioration compensation operation.

  In this example, the deterioration compensation operation is performed when the power generation voltage V falls below the deterioration lower limit value VLth. However, the deterioration compensation operation is performed periodically (for example, every 500 hours (long cycle)). You may make it (refer FIG. 7). Further, the deterioration compensation operation may be performed in a control cycle (for example, 1 to 2 seconds (short cycle)) for determining opening degree control of the valves V1, V2, and the like. In addition, a degradation compensation operation (non-constant period degradation compensation operation) performed when the generated voltage V falls below the degradation lower limit value VLth, and a degradation compensation operation (constant period) (periodic) (periodically long) or control cycle (short period). (Period degradation compensation operation) may be combined, and the degradation compensation operation may be performed in response to an instruction from the user.

[Deterioration compensation during load fluctuation operation]
During load fluctuation operation (operation in which the output of the fuel cell system follows the fluctuation of the power load on the combustion cell system), the controller 10 periodically (for example, every 500 hours) stores the standard state stored in the storage device 10b. Adjust the system operating conditions. That is, operating parameters indicating standard conditions, which are necessary conditions for obtaining the standard output V0 such as the fuel utilization rate η1, the air utilization rate η2, the load current I, the reformer temperature T1 at the end of startup, are acquired. Adjust the operating conditions of the system to the standard state according to the operating parameters. At this time, if necessary, an electronic load device that simulates an electric power load may be used.

  After the adjustment of the system operating condition to the standard state, the controller 10 compares the generated voltage V after adjusting the system operating condition to the standard state with the standard output V0 as the system output deterioration compensation operation. Then, the reformer temperature T1 is adjusted by adjusting the opening degree θ2 of the valve V2 so as to return the generated voltage V to the standard output V0.

  That is, by adjusting the opening degree θ2 of the valve V2 in the closing direction, the flow rate of the exhaust gas flowing through the reforming heat exchanger flow path L1 is increased, and the reformer temperature T1 is raised. When the reformer temperature T1 increases, the concentration of hydrogen and carbon monoxide in the fuel gas increases, and the power generation voltage V increases. In this way, the controller 10 increases the reformer temperature T1 by adjusting the opening θ2 of the valve V2 in the closing direction until the generated voltage V matches the standard output V0.

  The controller 10 returns the generated voltage V to the standard output V0 by the deterioration compensation operation, and then stores the reformer temperature T1 at that time in the storage device 10b as the set value T1set of the reformer temperature, and performs the original load fluctuation operation. Return to. In this load fluctuation operation, the reformer temperature set value T1set stored in the storage device 10b is used until the next deterioration compensation operation is performed, and the valve V2 is opened so that the reformer temperature T1 becomes T1set. The degree θ2 is controlled.

  Each time the deterioration compensation operation is performed, the reformer temperature defining the standard state stored in the storage device 10b may be rewritten and used as an operation parameter in the next deterioration compensation operation.

  In this example, the deterioration compensation operation is periodically performed. However, in the same manner as the deterioration compensation during the baseline operation, the deterioration compensation operation is performed when an instruction from the user is given. Also good.

[Changes in the temperature of the power generation chamber due to changes in the reformer temperature]
When the concentration of hydrogen or carbon monoxide in the fuel gas supplied to the power generation chamber 1 is changed by changing the reformer temperature T1, the power generation chamber temperature T2 changes. If the power generation chamber temperature T2 rises too much, the power generation element may be deteriorated, and thus the power generation chamber temperature T2 may need to be adjusted. In this case, the controller 10 controls the opening degree of the valve V4 to increase or decrease the air flow rate to the power generation chamber 1 and adjust the power generation chamber temperature T2.

  Increasing or decreasing the air flow rate to the power generation chamber 1 may change the temperature of the exhaust gas from the combustion chamber 4. Thereby, even when the opening degree of the valve V2 is not changed, the reformer temperature T1 may change and the output of the system may change. In this case, the controller 10 controls the opening degree θ2 of the valve V2 so as to be the set value T1set of the reformer temperature stored in the storage device 10b. There is no change in output.

[Opening control of valves V1 and V2]
In the embodiment described above, as one form, the valve V1 is fully opened and the opening degree of the valve V2 is controlled (PID control). However, the opening degree of the valve V2 is fully opened and the opening degree of the valve V1 is controlled. (PID control) may be performed. If the valves V1 and V2 are closed at the same time, the pressure inside the power generation chamber 1 may increase and the power generation element may be damaged. Therefore, it is necessary to control the state in which either of the valves V1 and V2 is always open. To realize this, the valve V1 is fully opened to control the opening of the valve V2, or the opening of the valve V2 is controlled. A sequence that controls the opening of the valve V1 as fully open is employed.

  In this sequence, the reformer temperature T1 can be increased by decreasing the opening degree of the valve V2, and the reformer temperature T1 can be increased by increasing the opening degree of the valve V1. Therefore, by adopting this sequence, it is possible to control the temperature of the reformer without damaging the power generating element. In some cases, the opening degree of the valves V1 and V2 may be controlled on condition that both the valves V1 and V2 are not fully closed.

  For example, in a state where the valve V1 is fully opened and the valve V2 is controlled, a method of starting control of the valve V1 when the valve V2 is also fully opened can be considered. Thereby, the reformer temperature T1 can be controlled in a larger temperature range than when only one of the valves V1 and V2 is controlled.

  Further, in the embodiment described above, the valve V1 is provided in the reforming heat exchanger flow path L1, and the valve V2 is provided in the bypass flow path L2, but the valve V1 is provided in the reforming heat exchanger flow path L1. Alternatively, only the valve V2 may be provided in the bypass flow path L2. In this case, the exhaust gas having the minimum flow rate determined by the pressure loss relationship of each flow path flows through the flow path in which no valve exists, and the opening degree of the valve provided in one of the flow paths is adjusted. Thus, the reformer temperature T1 can be adjusted.

  However, when only the valve V2 is provided in the bypass flow path L2, a minimum temperature (for example, 450 ° C.) is required for reforming in the reforming heat exchanger 2, so this temperature is secured. It is important to design the pipeline of the reforming heat exchanger flow path L1 in such a form that it can be performed.

  When the opening degree of the valve V2 is fully opened and the opening degree of the valve V1 is controlled, the valve V1 may be fully closed. If such a state continues for a long period of time, the reformer temperature T1 may decrease and the system may not operate normally. However, in this case, since the valve V1 is controlled so as to maintain the set value T1set of the reformer temperature determined after the deterioration compensation operation, the valve V1 is not fully closed for a long period of time, and there is a problem in the operation of the system. Does not occur.

  Here, the temperature control method of the reformer is shown on the condition that the internal pressure of the power generation chamber 1 is not reliably increased. However, if the control conditions that do not block the exhaust portion are known, model control or the like It is also possible to perform control such that the opening degree of the valves V1 and V2 is changed at the same time using an advanced control method using.

  In this embodiment, in the start-up mode, the high-temperature air preheated by the air preheater 3 is supplied to the power generation chamber 1 through the air distributor 5, but the reducing gas due to incomplete combustion is supplied. A burner (reducing combustion burner) that can be used may be provided, and the reducing gas from the reducing combustion burner may be supplied to the power generation chamber 1. In this case, the reducing gas is supplied to the fuel electrode of the power generation chamber 1.

[Embodiment 2]
FIG. 8 shows an outline of another embodiment (Embodiment 2) of the fuel cell system according to the present invention. In the second embodiment, an external heat source device 12 for supplying a temperature-adjusted gas to an exhaust gas inlet P1 to the reforming heat exchanger 2 is provided. In this example, as an external heat source device 12, a burner (external heating source) 12-1 and a blower (external cooling source) 12-2 are provided. A valve V6 is provided in the fuel supply passage L6 to the burner 12-1.

In the second embodiment, the minimum opening θ1 _MIN (for example, θ1 _MIN = 10%) is determined for the valve V1. This minimum opening θ1 _MIN is stored in the storage device 10 b of the controller 10. Further, the temperature of the gas at the inlet P1 is detected by the temperature sensor 13 as T3, and the gas temperature T3 detected by the temperature sensor 13 is sent to the controller 10.

  In the second embodiment, when the valve V1 is fully open and the valve V2 is fully closed in the steady mode, it indicates that the heat supplied to the reforming heat exchanger 2 is insufficient. Yes. In this case, the controller 10 turns on the valve V6 to supply fuel to the burner 12-1, and sends the combustion gas from the burner 12-1 to the inflow port P1. At this time, the controller 10 adjusts the supply amount of the combustion gas from the burner 12-1 so that the gas temperature T3 at the inlet P1 is adjusted to a predetermined gas temperature.

Conversely, when the valve V2 is fully open and the valve V1 reaches the minimum opening degree θ1 _MIN , it indicates that the reforming heat exchanger 2 is overheated. In this case, the controller 10 operates the blower 12-2 and sends a cooling gas (for example, air) to the inlet P1. At this time, the controller 10 adjusts the supply amount of the cooling gas from the blower 12-2 so as to adjust the gas temperature T3 at the inlet P1 to a predetermined gas temperature.

In the second embodiment, the reason why the minimum opening θ1 _MIN is determined for the valve V1 is that even if the temperature of the exhaust gas at the inlet P1 is lowered by sending the cooling gas, the valve V1 is closed. This is because the exhaust gas does not flow through the reforming heat exchanger flow path L1, and the reformer temperature T1 cannot be lowered. Even when the valve V1 is fully closed, the reformer temperature acts in a direction to decrease due to the endothermic reaction of reforming. Therefore, depending on the case, it is possible to control the valve V1 to be fully closed.

  When the external heat source 12 is used, as shown in FIG. 9, a buffer 14 is provided at the inlet P1 as a mixed space portion of the exhaust gas from the combustion chamber 4 and the gas from the external heat source 12, and the buffer 14 The mixer 15 may be provided as a gas mixing promoting means for promoting the mixing of the gas in the space. By providing such a buffer 14 and a mixer 15, it is possible to make it difficult for the gas temperature to be biased.

  In the second embodiment, the burner 12-1 and the blower 12-2 are used as the external heat source device 12, but the external heat source device 12 is not limited to such a burner or blower. Moreover, it is good also as a structure which does not control the temperature of exhaust gas with the burner 12-1 or the blower 12-2, but heats and cools the gas sent to the reformer 2-3. Various other methods for heating and cooling the gas sent to the reforming heat exchanger 2 are conceivable, and any method may be used.

[Embodiment 3]
FIG. 10 shows an example (Embodiment 3) in which a heater 16 is installed in the reformer 2-3 as an auxiliary heat source. In Embodiment 3, when the valve V1 is fully open and the valve V2 is fully closed in the steady mode, the controller 10 turns on the heater 16 and directly heats the reformer 2-3.

  In this method, when the heater 16 is operated, the valve V1 is fully opened and the valve V2 is fully closed, so that the control of the heater 16 does not depend on the opening degree of the valves V1 and V2. It will be. Therefore, there is no interference with the valve control, and the reformer temperature T1 can be controlled by the heater 16 alone.

  If necessary, a cooling source such as a Peltier element may be provided as an auxiliary heat source installed in the reformer 2-3. Further, the auxiliary heat source installed in the reformer 2-3 is not limited to a heater or a Peltier element.

[When the reformer temperature deviates from the reformer operating temperature range]
If the temperature of the reformer 2-3 is too low, the reforming operation cannot be performed. If the temperature is too high, the reforming catalyst and the reformer casing in the reformer may be damaged. The temperature at which the reforming operation is possible depends on the material used as the reforming catalyst, but is generally 450 ° C. or higher. The upper limit of the heat resistance of the reformer is 800 ° C. even when heat resistant stainless steel is used. Therefore, the reformer 2-3 has an operable temperature range (reformer operable temperature range).

  Therefore, the controller 10 monitors the reformer temperature T1 so as not to damage the reformer 2-3, and the reformer temperature T1 does not deviate from the reformer operable temperature range. Regulate the adjustment of T1. Specifically, the reformer operable temperature range is stored in the storage device 10b in the controller 10, and when the reformer temperature T1 deviates from the reformer operable temperature range, the reformer temperature T1 is regulated by the upper limit value and the lower limit value of the reformer operable temperature range, the subsequent deterioration compensation operation is prohibited, and the reformer temperature T1 exceeding the reformer operable temperature range is not adjusted. To. Further, a warning is issued to the user via the notification device 11.

  The deterioration of the power generation element appears as a monotonic decrease in the output of the system. For this reason, the condition that the reformer temperature T1 deviates from the reformer operable temperature range usually means that the reformer temperature T1 has reached the high temperature side limit of the reformer operable temperature range. If the power generation element further deteriorates in this state, the reformer 2-3 may be damaged if the deterioration compensation operation is performed to raise the reformer temperature T1.

  When the reformer temperature T1 deviates from the high temperature side limit of the reformer operable temperature range, the controller 10 regulates the reforming temperature T1 with the upper limit value of the reformer operable temperature range, and thereafter deteriorates. The compensation operation is prohibited. Therefore, the reformer temperature T1 does not rise beyond the high temperature side limit of the reformer operable temperature range, and the possibility that the reformer 2-3 is damaged can be avoided. In this case, since a warning is issued to the user via the notification device 11, it is possible to know that it is time to replace the power generating element used by this warning.

  In addition, when the reformer temperature T1 reaches the high temperature side limit of the reformer operable temperature range, it may be notified together with a warning that the power generation element replacement time has come. The operation is continued while the temperature T1 is set to the upper limit value of the reformer operable temperature range, and the system is reached when the output of the system reaches a lower limit value set in advance as a threshold value for judging the replacement timing of the power generation element. The operation may be stopped and notification that the time for replacement of the power generation element has come may be provided.

  In this case, the lower limit value for determining the replacement timing of the power generation element is not necessarily the same as the lower limit value for deterioration when performing the deterioration compensation operation, and may be a value lower than the lower limit value for deterioration. Even in such a case, when the reformer temperature T1 reaches the high temperature side limit of the reformer operable temperature range, it is effective as information for knowing that the power generation element replacement time is near by issuing a warning. Can be used. Thereby, the operation of the system can be continued for a long time while avoiding damage to the power generation element due to deterioration of the power generation element.

[When the power generation element is damaged]
In the first to third embodiments described above, the operating conditions may not be set correctly due to abnormalities in peripheral devices, and the power generation elements in the power generation chamber 1 may be damaged. When the power generation element is damaged, the output of the system is reduced as is the case with deterioration over time. In this case, the degradation compensation operation is performed for the decrease in the output of the system due to the breakage of the power generation element, similarly to the decrease in the output of the system due to the degradation of the power generation element.

  However, the output reduction of the system due to the breakage of the power generating element is generally caused by the decrease of the fuel concentration due to the direct reaction between fuel and air (oxygen) at the breakage point. For this reason, even if the concentration of hydrogen or carbon monoxide in the fuel gas is increased, the output of the system cannot be increased.

  Therefore, when the power generating element is damaged, the reformer temperature T1 rises to the high temperature side limit of the reformer operable temperature range by repeated deterioration compensation operation. In this case, a warning is issued or the time for replacing the power generation element is notified. Therefore, even when the power generation element is damaged, it is possible to quickly cope with it.

[When using multiple power generation elements]
The power generation chamber 1 often uses a large number of power generation elements, and often measures the potential during power generation for each power generation element or for each power generation element at an appropriate interval. If the power generating element is damaged in such a situation, it can be confirmed that the power generation potential at the damaged position is lowered. In addition, it is known that the temperature locally rises due to the direct reaction between fuel and air at the position where the power generating element is damaged. Therefore, if a damaged power generation element can be detected by measuring such a local decrease in power generation potential or local temperature increase, a power generation element replacement warning is immediately issued without performing deterioration compensation operation. You may make it carry out.

  For example, when a large number of power generation elements are used, a sensor (power generation element breakage detection sensor) 17 for detecting breakage of the power generation element is provided and the output of the sensor 17 is given to the controller 10. In this case, when the sensor 17 is informed of the breakage of the power generation element from the sensor 17, the controller 10 prohibits the subsequent deterioration compensation operation, and immediately issues a warning to replace the power generation element to the user via the notification device 11.

[Embodiment 4]
With regard to the deterioration compensation operation, considering only that the reformer temperature is controlled independently, the heater is connected to the reformer 2-3 without controlling the flow rate of the exhaust gas flowing through the reforming heat exchanger flow path L1. It is also possible to adjust the reformer temperature T1 by installing an auxiliary heat source device such as a Peltier element and adjusting the amount of heat supplied from the auxiliary heat source device to the reformer 2-3.

  FIG. 11 shows an example (Embodiment 4) in which a heater 18 is installed as an auxiliary heat source in the reformer 2-23 without providing the bypass channel L2 with respect to the reforming heat exchanger channel L1.

  In this system, when the output of the system decreases due to deterioration of the power generation element, the controller 10 raises the reformer temperature T1 by warming the reformer 2-3 with the heater 18 as a deterioration compensation operation, and the combustion gas Increase the concentration of hydrogen and carbon monoxide in it. The heater 18 is controlled by using a method such as PID control by monitoring the reformer temperature T1.

  When the reformer temperature T1 deviates from the reformer operable temperature range during the control of the heater 18, the reformer 2-3 is controlled by regulating the operation of the heater 18 within the reformer operable temperature range. Protect. When the reformer temperature T1 reaches the high temperature limit of the reformer operable temperature range due to the operation of the heater 18, the subsequent deterioration compensation operation is prohibited, a warning is generated, Notification that the replacement time has been reached.

  As shown in FIG. 11, the concentration of hydrogen or carbon monoxide in the fuel gas at the outlet of the reformer 2-3 is controlled by installing a heater 18 near the outlet of the reformer 2-3. This is a preferable configuration for performing the deterioration compensation operation. However, the installation position of the heater 18 is not limited to this.

  In addition, in each embodiment, although the system provided with the reforming heat exchanger 2 which integrated the evaporator 2-1, the fuel preheater 2-2, and the reformer 2-3 was shown, it is not limited to this form. . The thing which installs the evaporator 2-1, the fuel preheater 2-2, or both separately from the reformer 2-3 is also included. Further, the reforming method is not limited to steam reforming, and can be applied to a partial oxidation reforming method, a combined reforming method, and the like.

  Further, in each embodiment, a valve is used as a heat amount adjusting unit for adjusting the heat amount of the combustion gas to the fuel reforming unit, and PID control is shown as the control method thereof, but the present invention is not limited thereto.

  As described above, according to the present invention, it is possible to adjust the gas concentration of hydrogen or carbon monoxide in the fuel gas by controlling the reformer temperature of the fuel reforming section. As a result, even if the output of the system decreases due to deterioration of the power generation element over time, the concentration of hydrogen or carbon monoxide in the combustion gas is increased to prevent a decrease in power generation voltage and compensate for the deterioration of the output of the fuel cell system. This makes it possible to use the power generating element for a longer period of time than in the past.

  In addition, according to the present invention, it is possible to lengthen the replacement cycle of the power generation element and reduce the frequency of replacement of the power generation element, and to prevent a long-term output decrease of the system due to the time-dependent change of the power generation element. Even if the system does not have an output capacity more than necessary with respect to the generated power, it is possible to maintain the required system output for a long period of time compared to the conventional system.

1 is a system configuration diagram showing an outline of an embodiment (Embodiment 1) of a fuel cell system according to the present invention. It is a figure explaining the control operation at the time of the start of the starting mode which the controller in this fuel cell system performs. It is a figure explaining the operation | movement at the time of the fuel supply start in the starting mode which the controller in this fuel cell system performs. It is a figure explaining control operation at the time of the end of starting mode which a controller in this fuel cell system performs. It is a figure explaining the control action at the time of the steady mode start which the controller in this fuel cell system performs. It is a time chart explaining the deterioration compensation operation | movement (deterioration compensation operation | movement of a non-fixed period) performed whenever the power generation voltage V falls below the degradation lower limit VLth at the time of a baseline operation. It is a time chart explaining the deterioration compensation operation | movement (deterioration compensation operation | movement of a fixed period) at the time of making it perform periodically at the time of a baseline driving | operation. It is a system block diagram which shows the outline of other embodiment (Embodiment 2) of the fuel cell system which concerns on this invention. FIG. 6 is a diagram showing an example in which a buffer and a mixer are provided at an inlet of exhaust gas from combustion gas to a reforming heat exchanger in the configuration of the second embodiment. It is a system block diagram which shows the outline of another embodiment (Embodiment 3) of the fuel cell system concerning this invention. It is a system block diagram which shows the outline of another embodiment (Embodiment 4) of the fuel cell system concerning this invention. It is a figure which shows the outline of the fuel cell system using the conventional SOFC. It is a figure which shows the deterioration behavior (the long-term durability test result of a cylindrical flat plate single cell) of SOFC shown by the nonpatent literature 1. It is a figure which shows the relationship between the reformer temperature at the time of reforming methane which is a main component of city gas, and a reformed gas composition. It is a figure which shows the relationship between the hydrogen and the carbon monoxide density | concentration in the fuel gas shown by the nonpatent literature 2, and the power generation voltage (cell voltage) of a power generation element (cell).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Power generation chamber, 2 ... Reformation heat exchanger, 3 ... Air preheater (heater), 2-1 ... Evaporator, 2-2 ... Fuel preheater, 2-3 ... Reformer, 4 ... Combustion chamber, DESCRIPTION OF SYMBOLS 5 ... Air distributor, 6 ... Load, 7, 8 ... Temperature sensor, 9 ... Voltmeter, 10 ... Controller, 10a ... Processor (CPU), 10b ... Memory | storage device, 11 ... Notification apparatus, V1-V6 ... Valve, 12 ... External heat source, 12-1 ... Burner, 12-2 ... Blower, 13 ... Temperature sensor, 14 ... Buffer, 15 ... Mixer, 16 ... Heater, 17 ... Sensor (power generation element breakage detection sensor), 18 ... Heater, L1 ... first discharge passage (reform heat exchanger passage), L2 ... second discharge passage (bypass passage), L3, L6 ... fuel supply passage, L4 ... oxidant gas supply passage, L5 ... purge gas passage Supply passage, P1 ... inlet (exhaust gas inlet), P2 ... discharge port (exhaust) Outlet of the gas), 100 ... module.

Claims (19)

A power generation unit using a fuel cell that is supplied with fuel gas and an oxidant gas to generate power, a combustion unit that burns the gas discharged from the power generation unit, and a fuel that uses the amount of heat of exhaust gas from the combustion unit In a fuel cell system comprising a fuel reforming unit that uses a reformer to reform the fuel gas to the power generation unit,
A fuel cell system comprising a control unit for controlling a reformer temperature of the fuel reforming unit. A power generation unit using a fuel cell that is supplied with fuel gas and an oxidant gas to generate power, a combustion unit that burns the gas discharged from the power generation unit, and a fuel that uses the amount of heat of exhaust gas from the combustion unit In a fuel cell system comprising a fuel reforming unit that uses a reformer to reform the fuel gas to the power generation unit,
A first passage for guiding exhaust gas from the combustion section to the fuel reforming section;
A second passage that bypasses the first passage including the fuel reforming section;
A calorific value adjusting portion provided in at least one of the first passage and the second passage;
And a controller that controls the reformer temperature of the fuel reforming unit by adjusting the amount of heat of exhaust gas from the combustion unit that passes through the calorific value adjusting unit. The fuel cell system according to claim 2, wherein
A fuel cell system comprising: an external heat source device for adding a temperature-adjusted gas to the first passage. The fuel cell system according to claim 3, wherein
A fuel cell system, wherein a mixing space is provided in the first passage where a temperature-adjusted gas from the external heat source is added. The fuel cell system according to claim 4, wherein
A gas mixing promoting means for promoting mixing of the gas in the space is provided in the mixing space. The fuel cell system according to claim 2, wherein
An auxiliary heat source is provided in the reformer of the fuel reforming section. A fuel cell system comprising: A power generation unit using a fuel cell that is supplied with fuel gas and an oxidant gas to generate power, a combustion unit that burns the gas discharged from the power generation unit, and a fuel that uses the amount of heat of exhaust gas from the combustion unit In a fuel cell system comprising: a fuel reforming unit that uses a reformer that reforms the fuel as a fuel gas to the power generation unit; and an auxiliary heat source provided in the reformer of the fuel reforming unit.
A fuel cell system comprising: a control unit that controls a reformer temperature of the fuel reforming unit by controlling the auxiliary heat source unit. A power generation unit using a fuel cell that is supplied with fuel gas and an oxidant gas to generate power, a combustion unit that burns the gas discharged from the power generation unit, and a fuel that uses the amount of heat of exhaust gas from the combustion unit A fuel reformer that uses the reformer to reform the fuel as fuel gas to the power generation unit, a first passage that guides exhaust gas from the combustion unit to the fuel reformer, and the fuel reformer An operation method of a fuel cell system, comprising: a second passage that bypasses the first passage including a portion; and a heat amount adjusting portion provided in at least one of the first passage and the second passage. ,
As the output deterioration compensation operation of the fuel cell system, the adjustment of the amount of heat of the exhaust gas from the combustion unit that passes through the heat amount adjustment unit so as to keep the output value of the fuel cell system at a predetermined standard output. A method for operating a fuel cell system, comprising: a deterioration compensation step of adjusting a reformer temperature of a fuel reforming section. A power generation unit using a fuel cell that is supplied with fuel gas and an oxidant gas to generate power, a combustion unit that burns the gas discharged from the power generation unit, and a fuel that uses the amount of heat of exhaust gas from the combustion unit A fuel reformer that uses the reformer to reform the fuel as fuel gas to the power generation unit, a first passage that guides exhaust gas from the combustion unit to the fuel reformer, and the fuel reformer An operation method of a fuel cell system, comprising: a second passage that bypasses the first passage including a portion; and a heat amount adjusting portion provided in at least one of the first passage and the second passage. ,
As the output deterioration compensation operation of the fuel cell system, the operation is performed under a condition in which a predetermined operation parameter is set, and the output value of the fuel cell system at that time is maintained at a predetermined standard output. A method for operating a fuel cell system, comprising: a deterioration compensation step of adjusting a reformer temperature of the fuel reforming unit by adjusting an amount of heat of exhaust gas from the combustion unit passing through the adjusting unit. The operation method of the fuel cell system according to claim 8 or 9,
The fuel cell system includes:
An auxiliary heat source provided in the reformer of the fuel reforming section,
The deterioration compensation step includes:
When it becomes impossible to adjust the reformer temperature of the fuel reforming unit by adjusting the heat quantity of the combustion gas passing through the calorific value adjusting unit, the reformer temperature of the fuel reforming unit is changed from the auxiliary heat source to the fuel reforming unit. A method for operating a fuel cell system, comprising adjusting the amount of heat supplied to the reformer of the mass part. The operation method of the fuel cell system according to claim 8 or 9,
The deterioration compensation step includes:
An operating method of a fuel cell system, wherein the opening degree of the other heat quantity adjusting unit is adjusted in a state where any one of the heat quantity adjusting units provided in the first passage and the second passage is fully opened. . A power generation unit using a fuel cell that is supplied with fuel gas and an oxidant gas to generate power, a combustion unit that burns the gas discharged from the power generation unit, and a fuel that uses the amount of heat of exhaust gas from the combustion unit A fuel cell system comprising: a fuel reforming unit that uses a reformer that reforms the fuel as fuel gas for the power generation unit; and an auxiliary heat source device provided in the reformer of the fuel reforming unit Because
As an output deterioration compensation operation of the fuel cell system, the reformer temperature of the fuel reforming unit is controlled by controlling the auxiliary heat source so as to keep the output value of the fuel cell system at a predetermined standard output. A method for operating a fuel cell system, comprising a deterioration compensation step for adjusting. A power generation unit using a fuel cell that is supplied with fuel gas and an oxidant gas to generate power, a combustion unit that burns the gas discharged from the power generation unit, and a fuel that uses the amount of heat of exhaust gas from the combustion unit A fuel cell system comprising: a fuel reforming unit that uses a reformer that reforms the fuel as fuel gas for the power generation unit; and an auxiliary heat source device provided in the reformer of the fuel reforming unit Because
As the output deterioration compensation operation of the fuel cell system, the auxiliary operation is performed so that the operation is performed under a condition in which a predetermined operation parameter is set, and the output value of the fuel cell system at that time is maintained at a predetermined standard output. A method of operating a fuel cell system, comprising: a deterioration compensation step of adjusting a reformer temperature of the fuel reforming unit by controlling a heat source device. In the driving | operation method of the fuel cell system described in any one of Claims 8-13,
The deterioration compensation step includes:
An operation method of a fuel cell system, comprising performing an output deterioration compensation operation of the fuel cell system when an output value of the fuel cell system satisfies a predetermined condition. In the driving | operation method of the fuel cell system described in any one of Claims 8-13,
The deterioration compensation step includes:
An operation method of a fuel cell system, comprising performing an output deterioration compensation operation of the fuel cell system according to a predetermined cycle. In the operation method of the fuel cell system according to any one of claims 8 to 15,
A method of operating a fuel cell system, comprising the step of issuing a warning when the reformer temperature of the fuel reforming section deviates from a predetermined range. In the operation method of the fuel cell system according to any one of claims 8 to 15,
A fuel cell system comprising a step of prohibiting a subsequent output deterioration compensation operation of the fuel cell system when the reformer temperature of the fuel reforming unit deviates from a predetermined range. Driving method. In the operation method of the fuel cell system according to any one of claims 8 to 15,
When the reformer temperature of the fuel reforming unit deviates from a predetermined range, the subsequent deterioration compensation operation of the fuel cell system is prohibited, and thereafter, the output value of the fuel cell system is A method of operating the fuel cell system, comprising: stopping the operation of the fuel cell system when a predetermined lower limit value is reached. In the operation method of the fuel cell system according to any one of claims 8 to 15,
Detecting breakage of the power generating element of the fuel cell;
And a step of prohibiting a subsequent deterioration compensation operation of the output of the fuel cell system when damage to the power generation element is detected.

Images