JP2012064417A - Fuel cell power generation device and operation method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell power generation device which, when controlling temperature-rise of a reformer, can improve temperature-rise capability in cases where the reformer temperature tends to continuously drop even when the raw fuel is increased, and an operation method therefor.SOLUTION: The fuel cell power generation device includes a reformer 3 to which raw fuel is supplied; a fuel cell 10 which has reformer outlet gas directly supplied thereto from the reformer 3; a hydrogen purification unit 19 which has part of reformer outlet gas, branched from the reformer 3, supplied thereto via a control valve 17; a furnace temperature detection unit 23 which detects the furnace temperature of the reformer 3; and a control unit 21 which controls temperature-rise and temperature-fall of the reformer based on a temperature control set value MV which is calculated based on a deviation between a target furnace temperature and the furnace temperature detected by the furnace temperature detection unit 23. The control unit 21, when controlling temperature-rise of the reformer, uses raw fuel increasing control and opening reduction control for reducing the opening of the control valve 17 in combination.

Description

  The present invention uses a reformed gas rich in hydrogen obtained by reforming a raw fuel containing a hydrocarbon compound with a reformer as a fuel gas to be supplied to the fuel electrode of a fuel cell, and a part of the fuel gas. The present invention relates to a fuel cell power generator and a method for operating the fuel cell power generator.

As this type of fuel cell power generator, for example, a reformer obtained by reforming raw fuel with a reformer and using the obtained reformed gas as a fuel gas supplied to the fuel electrode of the fuel cell. 2. Description of the Related Art A fuel cell power generator is known in which a pipe that supplies gas to a fuel electrode of a fuel cell is connected to a branch pipe that branches a reformed gas to a hydrogen purification system that includes a compressor and a hydrogen purification apparatus (for example, Patent Document 1).
Similarly, a branch line is branched from a line for supplying hydrogen-rich gas from the fuel processing device to the fuel cell body, and a hydrogen purifier, a hydrogen storage device, and a hydrogen supply device are inserted in the branch line. An apparatus is known (see, for example, Patent Document 2).

  Further, a reformer for reforming raw fuel containing a hydrocarbon compound, a fuel cell for generating power using the reformed gas supplied from the reformer, and the reformed gas supplied from the reformer are compressed. A hydrogen purification system equipped with a compressor and a hydrogen purification device for purifying the compressed reformed gas in series, a branch pipe for branching from the reformer to the fuel cell and the hydrogen purification system, and a supply source of the reformed gas as fuel A method of operating a fuel cell power generation device including a valve provided on each of a fuel cell side and a hydrogen purification system side that freely branches between the battery and the hydrogen purification system, wherein the power generation amount of the fuel cell power generation device is reduced In some cases, a method of operating a fuel cell power generator is known in which part or all of the reformed gas is supplied to a hydrogen purification system (see, for example, Patent Document 3).

  A fuel cell power generator comprising a fuel cell using hydrogen reformed gas, and a hydrogen production and supply means for purifying high-purity hydrogen by supplying the reformed gas to a hydrogen purifier via a compressor, In a method of operating a fuel cell power generation device in which the hydrogen yield in the refining device is lower than the hydrogen utilization rate in the fuel cell, the fuel off-gas of the fuel cell and the residual gas of the hydrogen purifying device are supplied to the reformer burner. When the temperature of the reformer rises and reaches a predetermined temperature, the temperature of the reformer is increased by increasing the S / C of the raw fuel gas supplied to the reformer. A method of operating the fuel cell power generator to be reduced is also known (see, for example, Patent Document 4).

JP 2000-348750 A JP 2004-200042 A JP 2007-305601 A JP 2007-149489 A

However, in the conventional examples described in Patent Documents 1 and 2, the reformed gas supplied from the reformer to the fuel cell is branched and supplied to the hydrogen purifier. No temperature control is described.
Further, in the conventional example described in Patent Document 3, the fuel off-gas after the power generation reaction in the fuel cell and the residual gas after the hydrogen purification in the hydrogen purifier are supplied to the burner of the reformer and burned, When the power generation amount of the fuel cell power generation device is lowered, by supplying a part or all of the reformed gas to the hydrogen purification system, the reformer is operated while maintaining a predetermined temperature, so that the operation is stopped. Although it is possible to greatly reduce the frequency of the accompanying thermal cycle, there is no disclosure of substantial temperature control of the reformer.

  Further, in the conventional example described in Patent Document 4, the fuel off-gas of the fuel cell and the residual gas of the hydrogen purifier are supplied to the reformer burner and combusted. At that time, the temperature of the reformer is When the temperature rises and reaches a predetermined temperature, reforming is performed by increasing the S / C of the raw fuel gas supplied to the reformer (ratio of moles of steam to 1 mole of carbon atoms in the raw fuel gas). Although it is described that the temperature of the reformer is lowered, there is no description about temperature drop control when the temperature of the reformer increases to a predetermined temperature or higher.

Normally, when controlling the reformer temperature, if the reformer temperature increases beyond a predetermined temperature, the amount of combustion air supplied to the reformer is increased to lower the reformer temperature. When the temperature of the reformer decreases below the predetermined temperature, the temperature of the reformer is set to the predetermined temperature by performing the temperature increase control for increasing the raw fuel supplied to the reformer. Control to maintain.
However, when performing such temperature decrease control and temperature increase control, the temperature decrease control can be controlled by increasing the flow rate of the combustion air. There is a certain limit to the increase, and it is necessary to optimally control the amount of primary energy input and the reformer temperature.
Therefore, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and when the temperature of the reformer is controlled to rise, the temperature of the reformer tends to decrease even if the raw fuel is increased. It is an object of the present invention to provide a fuel cell power generator and an operation method thereof that can improve the temperature raising capability when the operation is continued.

  In order to achieve the above object, a fuel cell power generator according to claim 1 includes a reformer to which raw fuel is supplied, a fuel cell to which reformed gas output from the reformer is directly supplied, A hydrogen purifier in which a part of the reformed gas output from the reformer is branched and supplied via a control valve, an in-furnace temperature detector for detecting the in-furnace temperature of the reformer, a target A controller for performing temperature increase control and temperature decrease control of the reformer based on a temperature control set value calculated based on a deviation between the furnace temperature and the furnace temperature detected by the furnace temperature detection unit The control device is characterized in that, during the temperature rise control of the reformer, the raw fuel increase control and the opening decrease control for decreasing the opening of the control valve are used in combination.

  According to this configuration, the increase control of the raw fuel and the opening decrease control for decreasing the opening of the control valve that supplies the reformed gas to the hydrogen purifier are used in combination with the temperature raising control of the reformer. When reformer furnace temperature drops below the target furnace temperature, supply of reformed gas to the hydrogen purifier will occur if the temperature rise is insufficient even if the increase in the raw fuel supplied to the reformer is controlled. By closing the control valve, the amount of reformed gas supplied to the fuel cell is increased, the fuel off-gas discharged from the fuel electrode outlet, supplied to the reformer and burned is increased, and the reformer rises. Do warm.

In the fuel cell power generation device according to claim 2, the control device performs the temperature decrease control when the temperature control set value exceeds a target value, and the temperature control set value becomes less than the target value. The temperature increase control is sometimes performed.
According to this configuration, when the furnace temperature of the reformer becomes higher than the target furnace temperature and the temperature control set value exceeds the target value, the temperature lowering control is performed to lower the reformer furnace temperature, and conversely When the furnace temperature of the reformer becomes lower than the target furnace temperature and the temperature control set value becomes less than the target value, the temperature rise control is performed to raise the reforming furnace temperature.

The fuel cell power generator according to claim 3 is the invention according to claim 1 or 2, wherein the temperature rise control of the reformer starts when the temperature control set value decreases from a target value. Maintaining the control valve at a predetermined opening, performing an increase control of the raw fuel, and starting the opening decrease control of the control valve when the temperature control set value becomes a predetermined value or less. It is a feature.
According to this configuration, when the temperature inside the reformer furnace falls below the target temperature and the temperature control set value decreases from the target value, the control valve that supplies the reformed gas to the hydrogen purifier is set to a predetermined opening. The temperature of the reformer is increased by controlling the increase of the raw fuel supplied to the reformer, and when the temperature control set value becomes a predetermined value or less, the control valve opening reduction control is performed. By increasing the amount of reformer gas supplied to the fuel cell, the amount of fuel off-gas discharged from the fuel electrode outlet of the fuel cell and combusted in the reformer is increased. To increase.

The fuel cell power generator according to claim 4 is the invention according to any one of claims 1 to 3, wherein the increase control of the raw fuel is performed when the temperature control set value decreases from a target value. Control is performed to increase the amount of increase in raw fuel per unit time in accordance with the amount of decrease.
According to this configuration, when the temperature control set value decreases from the target value, the raw fuel increase control is performed by increasing the raw fuel increase amount per unit time, that is, the raw fuel increase rate, according to the decrease amount. The raw fuel supplied to the vessel is increased to control the temperature rise.

The fuel cell power generator according to claim 5 is the fuel cell power generator according to any one of claims 1 to 4, wherein the temperature drop control is performed when the temperature control set value increases from a target value. Accordingly, control is performed to increase the supply amount of combustion air per unit time to the reformer.
According to this configuration, the fuel air supplied to the reformer by increasing the combustion air supply amount per unit time, that is, the combustion air flow rate increase rate, to the reformer according to the increase amount from the target value of the temperature control set value. To control the temperature drop.

An invention relating to an operation method of a fuel cell power generator according to claim 6 includes a reformer to which raw fuel is supplied, a fuel cell to which reformed gas output from the reformer is directly supplied, A hydrogen purifier in which a part of the reformed gas output from the reformer is branched and supplied via a control valve, an in-furnace temperature detector for detecting the in-furnace temperature of the reformer, a target A controller for performing temperature increase control and temperature decrease control of the reformer based on a temperature control set value calculated based on a deviation between the furnace temperature and the furnace temperature detected by the furnace temperature detection unit In the operation method of the fuel cell power generation device, the temperature raising control of the reformer is performed in a state where the control valve is maintained at a predetermined opening when the temperature control set value is less than a target value. The raw fuel increase control for the reformer is started, and the temperature control set value becomes less than a predetermined value. Occasionally, it is characterized by initiating the opening reduction control of the control valve.
With this configuration, it is possible to obtain the same effect as that of the third aspect described above.

  According to the present invention, during the temperature increase control of the reformer, the increase control of the raw fuel and the opening decrease control for decreasing the opening of the control valve are used together. In the case where the temperature rise of the reformer is insufficient, the amount of reformed gas output from the reformer to the hydrogen purifier is reduced by controlling the opening of the control valve to reduce the fuel cell. The amount of reformed gas supplied to the fuel cell can be increased, thereby increasing the amount of fuel off-gas discharged from the fuel electrode outlet of the fuel cell and burned in the reformer, thereby enhancing the temperature rise effect of the reformer The effect is obtained.

1 is a system configuration diagram showing an embodiment of a fuel cell power generator according to the present invention. It is a functional block diagram of the control apparatus of FIG. It is a characteristic diagram which shows the relationship between the temperature control set value in a reformer temperature control process, a combustion air flow rate increase rate, a raw fuel increase rate, and a control valve opening degree. It is a flowchart which shows an example of the reformer temperature control processing procedure which the control apparatus of FIG. 1 performs.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a system configuration diagram showing a fuel cell power generator according to the present invention. In the figure, 1 is a fuel cell power generator. The fuel cell power generation apparatus 1 supplies raw fuel containing a hydrocarbon compound such as natural gas or LPG to a reformer 3 via a raw fuel flow rate control valve 2.
The reformer 3 includes a combustion burner 3a and a reforming catalyst layer 3b heated by the combustion burner 3a. Carbonization is performed by a steam reforming reaction in the reforming catalyst layer 3b heated by the combustion burner 3a. The hydrogen compound is converted into a reformed gas containing hydrogen, carbon dioxide, and carbon monoxide as main components and output.

Combustion air is introduced into the combustion burner 3a through a combustion air supply system 4 provided with a blower 4a for supplying combustion air. A fuel electrode off-gas containing unreacted hydrogen discharged from a fuel electrode 10b of the fuel cell 10 to be described later is introduced into the combustion burner 3a via an off-gas supply system 6. Furthermore, the residual gas output from the hydrogen purifier 19 described later is introduced into the combustion burner 3a through the residual gas supply system 7.
The reformed gas output from the reformer 3 is supplied to the fuel cell 10 via the reformed gas supply system 8. The fuel cell 10 includes an air electrode 10a into which reaction air is introduced through a reaction air supply system 11 having a reaction air blower 11a, and a fuel electrode to which reformed gas is supplied through a reformed gas supply system 8. 10b, and a cooling plate 10c stored in a water vapor separator (not shown) and supplied with pure water having low electrical conductivity and less mineral foreign matter such as silica as cooling water.

  In the fuel cell 10, when a cell reaction is caused by sending a reformed gas rich in hydrogen supplied from the reformer 3 to the fuel electrode 10 b, hydrogen corresponding to a predetermined utilization rate is associated with the cell reaction. Is consumed. Since the fuel off-gas discharged from the fuel electrode 10b still contains a certain amount of hydrogen, in order to use it effectively, it is returned to the combustion burner 3a of the reformer 3 via the off-gas supply system 6, It is mixed with combustion air supplied separately and burned, and used for heating the reforming catalyst layer 3b.

Moreover, reaction air is supplied to the air electrode 10a from the reaction air supply system 11 provided with the reaction air blower 11a, and oxygen contained in this reaction air contributes to the cell reaction. The cooling plate 10c removes heat generated by the power generation of the fuel cell 10 and maintains the temperature of the fuel cell 10 at a predetermined operating temperature.
Further, the air electrode off gas discharged from the air electrode 10a is sent to the generated water recovery device 12, and the generated water recovery device 12 recovers the reaction product water generated in association with the battery reaction contained in the air electrode off gas. And then released to the atmosphere. Further, the fuel exhaust gas discharged from the combustion burner 3a of the reformer 3 described above is also supplied to the generated water recovery device 12, and after recovering the combustion generated water generated by the combustion reaction, it is diffused to the atmosphere.

On the other hand, a reformed gas supply system 15 branches from the reformed gas supply system 8, and a part of the reformed gas is stored in the buffer tank 16 through the reformed gas supply system 15. The reformed gas supply system 15 is provided with a flow rate control valve 17 whose opening degree is controlled by a control device 21 described later.
The reformed gas stored in the buffer tank 16 is compressed by a compressor 18 and supplied to a hydrogen purification device 19 such as a pressure swing adsorption (PSA) device or a membrane separation device. Is separated and purified to obtain hydrogen. Of the reformed gas supplied to the hydrogen purifier 19, the residual gas from which purified hydrogen has been separated is sent to the combustion burner 3 a of the reformer 3 in the same manner as the fuel electrode off-gas of the fuel cell 10. The hydrogen inside is burned and used to heat the reforming catalyst layer 3b. Further, excess reformed gas stored in the buffer tank 16 is discharged out of the system through the control valve 20.

  And the furnace temperature of the reformer 3 is controlled by the control apparatus 21 comprised by a programmable controller etc. The control device 21 is supplied with a raw fuel flow rate FFd detected by a raw fuel flow meter 22 disposed upstream of the raw fuel flow rate control valve 2, and at a reformer furnace temperature detector 23. The detected in-furnace temperature detection value PV of the reformer 3 is input, and reformer temperature control processing is executed based on the raw fuel flow rate FFd and the in-furnace temperature detection value PV.

This control device 21 is configured as shown in FIG. 2 in terms of a functional block diagram, and is set by a target value setting unit 31 that sets a target value SV that is a furnace target temperature, and the target value setting unit 31. The subtractor 32 that calculates the temperature deviation ΔT (= SV−PV) by subtracting the furnace temperature detection value PV detected by the reformer furnace temperature detector 23 from the target value SV, and the output from the subtractor 32 The set value calculated from the increase or decrease of the raw fuel flow rate proportional to the battery current is calculated to the temperature deviation ΔT, and the respective heat resistance upper limit temperature and catalyst layer temperature of the constituent material are remarkably lowered and the reforming rate does not decrease. The furnace temperature is considered to be the upper and lower limit values, and is output as MV in the PID control calculation unit 33. For example, based on the PID control calculation unit 33 that calculates the temperature control value MV by performing the PID control processing calculation represented by the following equation (1), and the temperature control value MV output from the PID control calculation unit 33 Then, the command value calculation unit (process characteristic approximation calculation unit) 34 calculates the raw fuel increase rate (Nm ³ / h) FI for the raw fuel flow rate control valve 2 and the combustion air supply blower 4a from the command value calculation control map shown in FIG. The combustion gas flow rate increase rate AI (Nm ³ / h) with respect to the reformed gas flow rate control valve 17 and the reformed gas flow rate control valve FK with respect to the reformed gas flow rate control valve 17 are calculated. The calculation is performed with the process characteristics according to the heat capacity and the load state, and command values θft, θgt and Qt for the raw fuel flow rate control valve 2, the reformed gas flow rate control valve 17 and the combustion air blower 4 are output.
MV = Kp {ΔT + (1 / Ti) ∫ΔTdt + Td (dΔT / dt)} (1)
Here, Kp is a proportional gain, 1 / Ti is an integral gain, and Td is a differential gain.

As shown in the command value calculation control map of FIG. 3, when the temperature control value MV is the target value MVt, the raw fuel increase rate FI and the combustion air flow rate increase rate AI are both “0”. The calculation is performed from the process characteristic and the load characteristic approximate value by 34, and θft, θt, and θgt are output.
When the temperature control value MV increases beyond the target value MVt from this state, the characteristic line L1 is set so that the combustion air flow rate increase rate AI increases from “0” in accordance with the increase of the temperature control value MV. When the temperature control value MV decreases below the target value MVt from the state where the temperature control value MV is the target value MVt, the raw fuel increase rate FI increases from “0” according to the amount of decrease in the temperature control value MV. A characteristic line L2 is set. This characteristic line L2 is set so that when the temperature control value MV at which the raw fuel increase rate FI reaches the upper limit value FIu decreases to the predetermined value MV1, the upper limit value FIu is maintained even if the temperature control value MV decreases thereafter. ing.

When the temperature control value MV further decreases and becomes equal to or less than the predetermined value MV2 smaller than the predetermined value MV1, a characteristic line L3 for gradually decreasing the reformed gas extraction flow rate reduction rate is set according to the amount of decrease in the temperature control value MV. Has been.
Here, the temperature control value MV, the furnace temperature detection value PV, and the target value SV are all scale-converted and subjected to control calculation processing by the PID control calculation unit 33. For example, the furnace temperature detection value PV and The target value SV is a value up to 800 ° C. converted to 0 to 1000000 and input to the PID control calculation unit 33. The temperature control value MV output from the PID control calculation unit 33 is also output from 0 to 1000000, as a result. The temperature control value MV is converted to 0 to 100% to create a command value calculation control map.

Next, the reformer temperature control process executed by the control device 21 will be described with reference to FIG.
In this reformer temperature control process, first, the process proceeds to step S1, and the in-furnace temperature detection value PV detected by the reformer furnace temperature detector 23 and the raw fuel flow rate detection value detected by the raw fuel flow meter 22. Read FFd, then proceed to step S2, calculate the temperature deviation ΔT (= SV−PV) by subtracting the furnace temperature detection value PV from the preset target value SV, and then proceed to step S3 Then, the temperature control value MV serving as the PID manipulated variable is calculated by performing the PID control calculation process of the equation (1) on the temperature deviation ΔT.

Next, the process proceeds to step S4, where it is determined whether or not the temperature control value MV matches the target value MVt. When MV = MVt, the process proceeds to step S5 and the command calculation unit 34 determines process characteristics and load. Θft, θt, and θgt calculated from the calculated values according to the characteristics are output, and the process proceeds to step S6.
In step S6, a raw fuel flow rate command value FF for the raw fuel flow rate control valve 2 corresponding to the raw fuel increase rate FI is calculated, and a discharge flow rate command for the fuel air supply blower 4a corresponding to the fuel air flow rate increase rate AI. The value Qt is calculated and calculated.

Next, the process proceeds to step S7, where the PID control process is performed based on the deviation between the raw fuel flow rate command value FF and the raw fuel flow rate detection value FFd detected by the raw fuel flow meter 22, and the opening degree relative to the raw fuel flow rate control valve 2 is determined. The command value θft is calculated and calculated.
Next, the process proceeds to step S8, and the calculated opening command values θft, θgt and the discharge flow rate command value Qt are output to the raw fuel flow rate control valve 2, the reformed gas flow rate control valve 17 and the combustion air supply blower 4a, respectively. Then, the process returns to step S1.

If the determination result in step S4 is MV ≠ MVt, the process proceeds to step S9 to determine whether or not the temperature control value MV is greater than the target value MVt. If MV> MVt, the process proceeds to step S10. The process proceeds to step S6 after calculating the combustion air flow rate increasing rate AI with reference to the characteristic line L1 of the control map of FIG. 3 described above.
If the determination result in step S9 is MV <MVt, the process proceeds to step S11 to determine whether or not the temperature control value MV is less than the predetermined value MV2, and if MV> MV2, the process proceeds to step S12. Referring to the characteristic line L2 of the control map in FIG. 3, the raw fuel increase rate FI is calculated, and this is updated and stored in the raw fuel increase rate storage area. Then, the process proceeds to step S6.

Further, when the determination result in step S11 is MV <MV2, the process proceeds to step S13, and the opening degree of the reformed gas flow control valve 17 is referred to with reference to the characteristic line L3 of the control map of FIG. After calculating and calculating the command value θgt, the process proceeds to step S8.
4 corresponds to the PID control calculation unit 33, and the processing of steps S4 to S13 corresponds to the command value calculation unit 34.

Next, the operation of the above embodiment will be described.
Now, the raw fuel containing the hydrocarbon compound is flow-controlled by the raw fuel flow control valve 2 and supplied to the reformer 3, and the reforming catalyst layer 3b of the reformer 3 performs hydrogen reforming by the steam reforming reaction. It is converted into a reformed gas mainly composed of carbon and carbon monoxide and outputted. Since carbon monoxide in the reformed gas poisons platinum used for the electrode of the fuel cell 10 and degrades performance, after carbon monoxide is converted into carbon dioxide by a carbon monoxide transformer (not shown). The hydrogen concentration is 70% or more, the carbon dioxide concentration is about 20%, and the remainder is output to the reformed gas supply system 8 as hydrogen-rich gas of water vapor, methane, and a small amount of carbon monoxide.

The reformed gas output to the reformed gas supply system 8 is supplied to the fuel electrode 10b of the fuel cell 10 and is generated by the cell reaction. At this time, oxygen in the reaction air supplied to the air electrode 10a contributes to the electric reaction. And the heat_generation | fever produced by electric power generation is cooled by the battery cooling water supplied to the cooling plate 10c.
On the other hand, the reformed gas of the reformed gas supply system 8 is stored in the buffer tank 16 through the reformed gas flow control valve 17 through the reformed gas supply system 15 branched from the reformed gas supply system 8. The reformed gas stored in 16 is compressed by the compressor 18 and supplied to the hydrogen purifier 19, and hydrogen is obtained by separation and purification.

At this time, the in-furnace temperature of the reformer 3 is controlled by the control device 21.
That is, in the state where the furnace temperature detection value PV detected by the furnace temperature detector 23 is substantially equal to the target value SV, the temperature deviation ΔT between the two becomes substantially zero. And the opening degree command θft of the raw fuel control valve 2, the flow rate command Qt of the combustion air blower 4a, and the opening degree command θgt of the reformed gas flow rate control valve 17 are output.
Therefore, in this state, there is no change in the flow rate of the raw fuel supplied to the reformer 3, and there is no change in the flow rate of the reformed gas supplied from the reformer 3 to the fuel cell 10 and the buffer tank 16. The fuel cell off gas output from the 10 fuel electrodes 10b and the residual gas output from the hydrogen purifier 19 do not change in flow rate, and a good power generation state in the fuel cell 10 is continued.

  When the temperature control of the reformer 3 is in an appropriate state, the hydrogen concentration of the gas composition of the raw fuel increases, and the amount of hydrogen contained in the fuel electrode off-gas discharged from the fuel electrode 10b of the fuel cell 10 increases, By increasing the amount of hydrogen contained in the residual gas from the purifier 19 or by increasing the fuel electrode off-gas flow rate or the residual gas flow rate, the combustion temperature in the combustion burner 3a of the reformer 3 increases. Assume that the furnace temperature has increased. In this state, the temperature control value MV calculated by the PID control calculation unit 33 becomes larger than the target value MVt. Therefore, when the command value calculation map of FIG. 3 is referred to, the combustion air flow rate increase rate AI increases as the temperature control value MV increases, so that the control device 21 causes the combustion air to be supplied to the combustion air supply blower 4a. The discharge flow rate command value increases and the flow rate of combustion air discharged from the combustion air supply blower 4a increases. Therefore, when the amount of combustion air supplied to the combustion burner 3a of the reformer 3 increases, the combustion temperature of the combustion burner 3a decreases and the furnace temperature decreases.

  On the other hand, when the in-furnace temperature detection value PV detected by the in-furnace temperature detector 23 becomes lower than the target value SV and the temperature control value MV calculated by the PID control calculation unit 33 decreases from the target value MVt. First, the raw fuel increase rate FI is increased according to the decrease in the temperature control value MV by the characteristic line L2 in FIG. For this reason, the opening degree command value θft of the raw fuel flow control valve 2 is increased, and the flow rate of the raw fuel supplied to the reformer 3 is increased accordingly. Accordingly, the flow rate of the reformed gas output from the reformer 3 also increases, so that the flow rate of the fuel electrode off-gas discharged from the fuel electrode 10 b of the fuel cell 10 increases and the remaining gas discharged from the hydrogen purifier 19. The gas flow rate also increases. For this reason, the flow rate of the combustion gas supplied to the combustion burner 3a of the reformer 3 is increased, and the furnace temperature of the reformer 3 is increased.

  However, even if the raw fuel increase rate FI is increased to the upper limit value FIu, the decrease in the in-furnace temperature detection value PV of the reformer 3 does not stop, and the temperature control value MV further decreases to decrease below the predetermined value MV1. The raw fuel increase rate FI is controlled to a constant value at the upper limit value FIu. In this state, when the temperature control value MV decreases below the predetermined value MV2, the opening command value θgt of the reformed gas flow control valve 17 is gradually decreased with reference to the characteristic line L3 in FIG. As described above, when the opening command value θgt of the reformed gas flow rate control valve 17 decreases, the reformed gas flow rate supplied to the buffer tank 16 decreases, and the reduced amount of the reformed gas flow rate supplied to the buffer tank 16 decreases. Therefore, the flow rate of the reformed gas supplied to the fuel cell 10 increases, and the flow rate of the fuel electrode off-gas discharged from the fuel electrode 10b increases. For this reason, when the amount of hydrogen contained in the combustion gas supplied to the combustion burner 3a of the reformer 3 is increased, the combustion temperature is increased and the furnace temperature of the reformer 3 is increased. At this time, although the raw fuel increase rate is maintained at the upper limit FIu, the flow rate of the raw fuel passing through the raw fuel flow rate control valve 2 continues to increase, so the raw fuel increase control and the reformed gas flow rate are maintained. Combined with the reduction control, the temperature raising capability can be improved, the temperature inside the furnace of the reformer 3 is prevented from lowering, the temperature inside the furnace is surely changed to an upward trend, and the temperature control value MV is targeted. It can be restored to the value MVt.

In the above embodiment, the case where the opening degree of the reformed gas flow control valve 17 is set to 100% of the fully opened state when the temperature control value MV is equal to or greater than the predetermined value MV2 has been described. However, the opening degree of the reformed gas flow rate control valve 17 can be set to a predetermined opening degree that is arbitrarily determined according to the specifications of use.
Further, in the above embodiment, when the temperature control value MV is less than the predetermined value MV1 and equal to or larger than the predetermined value MV2 in the command value calculation control map of FIG. 3, the opening degree of the reformed gas flow control valve 17 is fully opened. Although the case of maintaining the state has been described, the present invention is not limited to this, and the opening degree reduction control of the reformed gas flow rate control valve 17 is started when the temperature control value MV becomes less than the predetermined value MV1. May be.
Furthermore, although the case where the temperature control value MV is calculated by applying the PID control calculation unit 33 has been described in the above embodiment, the present invention is not limited to this, and the temperature control responsiveness of the reformer 3 is considered. Then, the temperature control value MV may be calculated by applying a PI calculation unit or a PD calculation unit.

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell power generation device, 2 ... Raw fuel flow control valve, 3 ... Reformer, 3a ... Combustion burner, 3b ... Reforming catalyst layer, 4 ... Combustion air supply system, 4a ... Blower for combustion air supply, 6 ... Fuel electrode off-gas supply system, 7 ... Residual gas supply system, 8 ... Reformed gas supply system, 10 ... Fuel cell, 10a ... Air electrode, 10b ... Fuel electrode, 10c ... Cooling plate, 11 ... Reaction air supply system, 11a ... Reaction air blower, 12 ... generated water recovery device, 15 ... reformed gas supply system, 16 ... buffer tank, 17 ... reformed gas flow rate control valve, 18 ... compressor, 19 ... hydrogen purifier, 21 ... control device, 22 ... Raw fuel flow meter, 23 ... Furnace temperature detector, 31 ... Furnace temperature target value setting unit, 32 ... Subtractor, 33 ... PID control computation unit, 34 ... Command value computation unit

Claims (6)

A reformer to which raw fuel is supplied;
A fuel cell to which the reformed gas output from the reformer is directly supplied;
A hydrogen purifier in which part of the reformed gas output from the reformer is branched and supplied via a control valve;
A furnace temperature detector for detecting the furnace temperature of the reformer;
A control device for performing temperature increase control and temperature decrease control of the reformer based on a temperature control set value calculated based on a deviation between the target furnace temperature and the furnace temperature detected by the furnace temperature detector; Prepared,
The said control apparatus uses the increase control of raw fuel, and the opening degree reduction control which decreases the opening degree of the said control valve together at the time of temperature rising control of the said reformer, The fuel cell power generator characterized by the above-mentioned.   The control device performs the temperature decrease control when the temperature control set value exceeds a target value, and performs the temperature increase control when the temperature control set value becomes less than the target value. The fuel cell power generator according to claim 1.   The temperature raising control of the reformer starts when the temperature control set value decreases from a target value, maintains the control valve at a predetermined opening, performs increase control of the raw fuel, and 3. The fuel cell power generator according to claim 1, wherein when the temperature control set value becomes equal to or less than a predetermined value, the opening degree reduction control of the control valve is started.   2. The increase control of the raw fuel is performed such that when the temperature control set value decreases from a target value, the increase of the raw fuel per unit time is increased according to the decrease amount. 4. The fuel cell power generator according to any one of items 1 to 3.   The temperature lowering control, when the temperature control set value increases from a target value, performs a control to increase the flow rate of combustion air per unit time to the reformer according to the increase amount. 5. The fuel cell power generator according to any one of 1 to 4. A reformer to which raw fuel is supplied, a fuel cell to which reformed gas output from the reformer is directly supplied, and a part of the reformed gas output from the reformer is branched and controlled. A hydrogen purifier supplied via a valve, a furnace temperature detector for detecting the furnace temperature of the reformer, and a deviation between the target furnace temperature and the furnace temperature detected by the furnace temperature detector A control device for performing temperature increase control and temperature decrease control of the reformer based on a temperature control set value calculated based on
In the temperature raising control of the reformer, when the temperature control set value becomes less than the target value, the increase control of the raw fuel to the reformer is started with the control valve maintained at a predetermined opening degree. And when the said temperature control set value becomes less than predetermined value, the opening degree reduction control of the said control valve is started, The operating method of the fuel cell power generator characterized by the above-mentioned.

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