JP2002141096A - Fuel cell power generating system and its operating control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operating control method which controls water level fluctuation in each collected water tank, and aims at a maintenance-free fuel cell power generating system and alleviation of lack of collecting water without inhibiting life of a water treatment device, in a system cooling together collected water for a plurality of fuel cell power generating devices by a cooling machine. SOLUTION: In a fuel cell generating system equipped with an air-cooled cooler 55 cooling together each collected water 41c of a plurality of fuel cell power generating devices by air and a collected water circulating line 57 flowing back the cooled collected water to a produced water collecting device 41, each collected water tank 41a is provided with a water-level gage 90 to measure a water level in the tank, and moreover control valves 80a, 80b equipped with a controlling device to control a returning flow volume to the produced water collecting device to make a water level in each collected water tank to be at a given value based on a measured value of each water-level gage, are provided at a returning line to the produced water collecting device 41.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for collecting recovered water in a plurality of fuel cell power generators having a generated water recovery device.
The present invention relates to a fuel cell power generation system having a recovered water circulation line for collectively cooling by a cooler and returning the cooled recovered water to a product water recovery device, and an operation control method thereof.

[0002]

2. Description of the Related Art There are various types of fuel cells to be incorporated in a fuel cell power generator, depending on the type of electrolyte, the type of reforming material, and the like. For example, a gas containing carbon dioxide obtained by reforming natural gas is used. 2. Description of the Related Art A phosphoric acid fuel cell using a high-concentration aqueous solution of phosphoric acid as an electrolyte, which has an advantage that it can be used as it is without purification, is known.

In this phosphoric acid type fuel cell, hydrogen in fuel gas and oxygen in air obtained by steam reforming of a raw fuel such as methane gas are supplied to a fuel electrode and an air electrode of the fuel cell, respectively. And generate power based on an electrochemical reaction. In order to reform raw fuel into fuel gas, a fuel reforming apparatus is used in which water vapor is added to methane as raw fuel and the reaction between water and methane is promoted by a catalyst. Therefore, it is necessary to supply water to the fuel reformer in accordance with the amount of steam used for reforming the fuel. As this water, ion-exchanged water from which impurities have been removed by an ion-exchange type water treatment device or the like is used.

A phosphoric acid type fuel cell incorporated in a fuel cell power generator generates heat during power generation, and therefore needs to be cooled. This cooling is performed by air cooling or water cooling. In a water-cooled fuel cell power generator, the operating temperature is maintained by cooling the fuel cell body by removing the heat with cooling water, and part of the heat obtained by this cooling is recovered by a heat exchanger. It is also provided to users.

FIG. 8 is an example of a basic system diagram of a gas system and a cooling water system of this type of conventional fuel cell power generator (see Japanese Patent Application Laid-Open No. 10-64566).

[0008] In FIG. 8, a fuel cell 1 is schematically shown, and is provided with a fuel electrode 2 and an air electrode 3 sandwiching a phosphoric acid electrolyte layer (not shown), and each time a plurality of unit cells composed of these are stacked. And a cooling plate 5 having a cooling pipe 4 to be formed.

On the other hand, the fuel reformer 7 separates raw fuel such as natural gas supplied through a fuel supply system 8 together with steam separated by a steam separator 21 described later and supplied through a steam supply system 10. Under the reforming catalyst, the fuel gas is heated by combustion heat generated by the combustion of off-gas described later in a burner (not shown), and reformed into a hydrogen-rich gas to generate a reformed gas.

[0008] The fuel cell 1 and the fuel reformer 7 include:
A reformed gas supply system 11 that supplies the reformed gas generated by the fuel reformer 7 to the fuel electrode 2 of the fuel cell 1 and an off-gas containing hydrogen that does not contribute to the cell reaction from the fuel electrode 2 Off-gas supply system 12 for supplying fuel to burners
And are connected.

Further, a blower 17 for supplying combustion air is connected to a burner of the fuel reforming device 7, and the combustion exhaust gas discharged from the fuel reforming device 7 is collected by a combustion exhaust gas system 18 into a generated water recovery device 41. Sent to.

The fuel cell 1 has an air supply system 14 having a reaction air blower 13 for supplying air to the air electrode 3.
And an air discharge system 15 that supplies the air after the battery reaction to the product water recovery device 41.

The cooling pipe 4 of the cooling plate 5 of the fuel cell 1 circulates cooling water during power generation of the fuel cell 1, so that a steam separator 21, a cooling water circulation pump 22, and a steam generator (cooling water cooler) are provided. A cooling water circulation system 20 including a kettle type heat exchanger) 24 is connected.

The steam separator 21 separates the cooling water, which has become a two-phase flow with the steam discharged from the cooling pipe 4 of the fuel cell 1, into steam and cooling water. The steam separated here is sent out through the steam supply system 10 so as to be mixed with the raw fuel toward the fuel reformer 7. At that time, an ejector pump 9 is used to mix with the raw fuel having a low original pressure. This ejector pump 9
The steam is used as the driving fluid, and the raw fuel is used as the driven fluid.

The steam generator (kettle type heat exchanger) 2
Reference numeral 4 denotes an external waste heat utilization facility that cools the fuel cell and removes heat from the returned cooling water, cools and recovers the recovered heat, that is, a part of the heat generated during power generation of the fuel cell as steam. To the user via. When the heating medium is steam,
Since the steam-cooked absorption chiller / heater can be operated, highly efficient heat utilization can be achieved.

The generated water recovery device 41 is connected to a flue gas system 18, an air discharge system 15, and a process exhaust system 19. In addition, to the generated water recovery device 41, a recovered water generation and circulation system including a recovered water circulation pump 42, a recovered water cooler 43, and a nozzle 44 is connected. The recovered water circulation pump 42 is
And collects a part of the collected water stored in the bottom and sends it to the collected water cooler 43. Recovered water cooler 4
A user-side cooling water system 45 is inserted in 3 as a heat recovery system, and supplies cooled recovery water to the nozzle 44. The nozzle 44 sprays the cooling recovery water from the upper part of the generated water recovery device 41 to cause the cooling water to act on the reaction air containing the generated water in the generated water recovery device 41 and the combustion exhaust gas containing the combustion generated water. Preferably, in a cooling water direct contact condenser (not shown), which will be described later, the recovered water in the air is directly cooled, and each generated water is generated at the bottom of the recovery device 41.

As described above, the recovered water obtained by condensing the water contained in the reaction air off-gas (power generation water) and the water contained in the combustion exhaust gas of the burner of the fuel reformer (combustion water) is used for steam reforming. There is an advantage that the use of the replenishing water has less impurities than tap water and can reduce the load on the ion-exchange type water treatment apparatus.

The recovered water stored at the bottom of the generated water recovery device 41 as described above is supplied to the supply pump 46 and the water treatment device 4.
7 is supplied to the steam separator 21 through a recovery system provided with the steam separator 7.

As described above, the user-side cooling water 45 is connected to the recovered water cooler 43 to cool the recovered water. , 40 ° C. or lower, and therefore, its value as thermal energy is low. Usually, the waste gas is discharged to the outside air by a cooling tower or a radiator for treatment. The recovered water cooler 43 and its cooling system will be described later in detail.

In FIG. 8, reference numeral 26 denotes a cooling water circulation system 20 and a cooling pipe 4 and a flow path of a cooling water cooler 24.
This is a bypass pipe that short-circuits the flow path between the steam generator 24 and the steam separator 21, and reference numeral 27 is a three-way control valve for that purpose. Reference numeral 28 denotes the steam separator 21
It is a pressure gauge that measures the internal pressure.

Next, as shown in FIG. 7, the recovered water in a plurality of fuel cell power generators having the generated water recovery device is collectively cooled by one cooler, and the cooled recovered water is returned to the generated water recovery device. A conventional fuel cell power generation system having a recovered water circulation line and an operation control method thereof will be described.

As a method for ensuring a stable supply of electric power, there is a case where a plurality of fuel cell power generators are installed. In this case, cooling equipment is required for the number of power generation devices. However, cooling equipment is often integrated and one large cooling equipment is installed due to restrictions on the installation location. In this case, as shown in FIG. 7, a plurality of fuel cell power generators 30A, 30B
The waste heat held by the recovered water in the generated water recovery device 41 is processed by a single cooling facility 50 via the intermediate heat exchanger 60.

As for the cooling equipment 50, the generated water recovery device in the power generator requires recovered water of about 40 ° C. Therefore, considering the temperature loss in the intermediate heat exchanger 60, the cooling water It is common to employ a water-cooled cooling tower capable of cooling to about 37 ° C.

Next, the fuel cell power generator 30 shown in FIG.
A and 30B will be described. FIG. 7 shows the water recovery device 41 of FIG. 8 in detail. 7, components having the same functions as those of the components of the fuel cell power generator shown in FIG. 8 described above are denoted by the same reference numerals, and description thereof is omitted.
The generated water recovery device 41 shown in FIG.
Is provided, and an overflow pipe 41d is provided in communication with the recovery tank. Further, below the nozzle, the above-mentioned cooling water direct contact condenser 41b is provided.

The recovered water 41c is collected from the recovery tank 41a.
Is cooled by flowing through the intermediate heat exchanger 60, and further circulated between the intermediate heat exchanger 60 and the cooling equipment 50 composed of a water-cooled cooling tower by a cooling water pump 50a.
Finally, the heat is released to the outside air.

The cooling water direct contact condenser 41b is composed of a packed bed such as a Raschig ring, and allows the reaction air off-gas containing steam and the combustion exhaust gas to flow upward from the bottom of the packed bed.
On the other hand, from the top, the external cooling equipment 50 and the intermediate heat exchanger 60
Spraying the recovered water of about 40 ° C cooled in the above, and condensing and recovering the water vapor in the gas while directly contacting the gas and the cooling water in the packed bed part. There is an advantage of improving.

Although not shown in FIG. 7, a line which is supplied to the steam separator 21 by the makeup water pump 46 and used as makeup water for steam reforming is connected to the bottom of each water recovery device 41 as in FIG. Have been. The overflow pipe 41 of FIG.
“d” has a function of discharging surplus recovered water, which is a difference between the supply water for steam reforming and the amount of water vapor recovered in the gas in the water recovery device 41, to the outside of the system.

Although not shown in FIGS. 7 and 8, when there is no excess recovered water, the water level of each recovered water tank 41a is too low and the makeup water pump 46 is emptied. An off-type water gauge is installed to supply city water from outside.

[0027]

The above-mentioned external cooling equipment 50 has the following three cooling systems.

An open cooling tower system (a system shown in FIG. 7) in which water and air are brought into direct contact with a packed bed for cooling,
Internal water (cooling water) is passed through the tube, external water is sprayed on the tube, and a closed cooling tower system is used to remove heat by evaporating water on the outer wall of the tube, and cooling water is passed through the finned tube. An air-cooled cooling system in which the outside of the tube is forcibly air-cooled by a blower is used.

The open cooling tower system has the advantage that high heat transfer performance can be obtained because water and air are brought into direct contact with the filling tank for cooling, but the disadvantage is that corrosion, slurry and dirt are generated on the cooling water side. There is. Also, in order to keep the content of impurities in the cooling tower circulating water at a certain level or less, it is necessary to perform forced blowdown to discharge a part of the circulating water out of the system, and to compensate for the loss due to scattering and evaporation to the outside air. Therefore, it is necessary to replenish the water amount of several% of the circulating water amount. In addition, periodic chemical cleaning is required to prevent Legionella bacteria. That is, this open cooling tower has a disadvantage that the initial cost is low but the running cost is high.

In the closed cooling tower system, cooling water is passed through the inside of a tube, external water is sprayed on the outside of the tube, and heat is removed by evaporation of water on the outer wall of the tube to cool the water inside. Therefore, contamination of water inside does not occur, but contamination of water for external cooling occurs. Therefore, the amount of forced blowdown and the amount of water replenishment are reduced as compared with the open cooling tower system, but the above countermeasures need to be taken.

In the air-cooled cooling system, water to be cooled is passed through a tube with fins, and forced air is blown to the outside of the tube by a blower to cool the air. Since there is no problem of external water contamination as in the system, maintenance is greatly reduced as compared with the former two. In addition, even when an open-type cistern tank is employed, the required amount of replenishment water is sufficient to replenish the evaporation amount, which is significantly reduced as compared with the former two. Therefore, the running cost can be significantly reduced in the air-cooled cooling system.

As is clear from the above, it is desirable to employ an air-cooled cooler for the cooling equipment at sites requiring maintenance-free or at sites such as hospitals where legionella countermeasures are required. However, in the case of the air-cooled cooler, the cooling capacity in summer is insufficient, and the recovered water cannot be cooled via the intermediate heat exchanger 60 as in the system of FIG. It needs to be supplied directly to the vessel and cooled directly.

However, as in the system of FIG.
Since the recovered water tank 41a in the generated water recovery device 41 of the fuel cell power generation device is directly connected to the recovered water circulation system, if the recovered water circulation flow rate changes, the water level in the recovered water tank will change.

Due to the effect of piping pressure loss due to the installation location of the cooling equipment (air-cooled cooler) and the plurality of fuel cell power generators, and the difference in cooling water pumps, there is a difference in the amount of water flowing into and out of the recovered water tank. The overflow occurs in the recovered water tank, and the other recovered water tank needs to be refilled.

When the make-up water is supplied from city water having a large ion load, there is a problem that the service life of the resin of the ion-exchange type water treatment apparatus becomes shorter as the amount of the make-up water increases.

The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a system for collectively cooling recovered water in a plurality of fuel cell power generators by a single cooling facility. The water level fluctuation in the recovered water tank was suppressed, and a maintenance-free fuel cell power generation system using an air-cooled cooler could be provided without reducing the life of the water treatment device, and the shortage of recovered water was reduced. An object of the present invention is to provide an operation control method.

[0037]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a reformer for reforming a raw fuel with steam to generate a hydrogen-rich reformed gas; A fuel cell that generates electricity by electrochemically reacting an oxidizing gas (air) with an exhaust gas such as combustion exhaust gas discharged from the reformer and exhaust air discharged from the fuel cell, and directly contacts cooling water A plurality of fuel cell power generators each having a generated water recovery device that cools and collects water in a recovery water tank by causing the water to be recovered, and a plurality of fuel cell power generators each having a pump for circulating recovered water. An air-cooled cooler that flows into the cooling pipe and collectively cools with air from the outside of the cooling pipe; and the collected water flows to the air-cooled cooler by the pump, and the cooled recovered water is sent to the generated water recovery device. Recirculated recovered water circulation line A fuel cell power generation system comprising: a flow rate for measuring an introduction flow rate and a return flow rate of the recovered water to a recovered water introduction line to the air-cooled cooler and a return line to a generated water recovery device in the recovered water circulation line. A control valve provided with a control device for controlling the return flow so that the return flow is equal to the introduction flow based on the measurement value of each of the flow meters, It is provided on the return line (the invention of claim 1).

As described above, the amount of incoming and outgoing water in the water tank can be the same up to the range of the measurement error of the flow meter. By collecting the excess recovered water with the above measurement error by the generated water recovery device, external water supply is not required,
The load on the ion exchange type water treatment equipment can be reduced,
Since the use of the air-cooled cooler is enabled, the maintenance-free operation can be realized.

Further, according to the second or third aspect of the invention, substantially the same effects as those of the first aspect can be obtained.

That is, in the fuel cell power generation system according to claim 1, each of the recovered water tanks is provided with a water level meter for measuring the water level in the tank, instead of the flow meter and the control valve. Based on the measured value of each of the water level gauges, the control valve provided with a control device for controlling the return flow rate to the generated water recovery device so that the water level in each recovered water tank becomes a predetermined value. It is provided on the return line to the device (the invention of claim 2). According to this configuration, the water level in the recovered water tank can be detected, and the recovered water return water amount can be adjusted so that the water level becomes constant, and the same effect as the first aspect of the invention can be obtained.

In the fuel cell power generation system according to the second aspect, the water level meter and the control valve are connected to the plurality of fuel cell power generation devices so that the water level in each of the recovered water tanks is substantially the same. Instead, a water tank communication pipe for interconnecting the collected water tanks is provided (the invention of claim 3). According to this configuration, even if the water level in the recovered water tank fluctuates due to the imbalance of the amount of water flowing out of the recovered water tank and the amount of water returning to the recovered water tank, the retained water is moved through the communication pipe between the recovered water tanks. And the level of water level fluctuation between the collected water tanks can be leveled.

As the operation control method of the fuel cell power generation system, the following inventions 4 to 6 are preferable from the viewpoint of reducing the shortage of recovered water in each fuel cell power generation device.
That is, the operation control method of the fuel cell power generation system according to claim 2, wherein, among the plurality of fuel cell power generation devices, water in a recovery water tank in one fuel cell power generation device overflows, and The return flow rate to the generated water recovery device is controlled by the control valve so that the water level in the recovered water tank in the fuel cell power generation device becomes a predetermined value (the invention of claim 4).

According to the above-mentioned method, surplus recovered water from a plurality of fuel cell power generators overflows from only one fuel cell power generator. Can be minimized.

As an embodiment of the fourth aspect of the present invention, the following fifth aspect of the present invention is preferable. That is, in the operation control method of the fuel cell power generation system according to claim 4, wherein the water level in the recovered water tank in the other fuel cell power generation device that does not overflow is controlled by adjusting the opening of the control valve, and the overflow is performed. The control valve corresponding to the fuel cell power generator to be controlled normally has its valve opening fully opened, and when at least one valve opening of the control valve performing the water level control reaches full opening, the opening is reduced. Then, control is performed to reduce the flow rate.

Further, as a specific control method for implementing the above method, the invention of the following claim 6 is preferable. That is, in the operation control method of the fuel cell power generation system according to claim 4 or 5, the control valve converts the PID control device and a valve operation signal output by the PID control device into a signal of a valve opening command. And a control device having a converter that performs a conversion.The measured value of the water level meter in the recovered water tank that does not overflow is input to the control device, and the input value is compared with a predetermined reference water level. The converter converts the operation signal of the valve of the PID control device into a signal of a valve opening command by the converter, and controls the opening of each control valve based on the valve opening command value corresponding to each control valve. I will do it.

[0046]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment according to the first aspect of the present invention. The same functional members as those in the system of FIG.

In the system shown in FIG. 1, each recovered water 41 in a plurality of fuel cell power generators 30A, 30B
c into the cooling pipe 56 of the air-cooled cooler 55
, And are collectively cooled by cooling air from outside the cooling pipe 56. The cooled recovered water is supplied to a recovered water circulation line 5
By 7, the cooling water is returned to the cooling water direct contact cooler 41 b in the generated water recovery device 41.

Further, a recovered water introduction line to the air-cooled cooler 55 of the recovered water circulation line 57 and the generated water recovery device 41
Flow meters 70a and 70b for measuring the introduction flow rate and return flow rate of the recovered water are provided in the return line corresponding to each fuel cell power generator. Further, based on the measurement values of the respective flow meters 70a and 70b, the control valve 80 having a control device (not shown) for controlling the return flow so that the return flow becomes the same as the introduction flow is provided to the generated water recovery device 41.
On the return line to

According to this configuration, the amount of water flowing into and out of the collection tank can be adjusted up to the measurement error of each flow meter, and as a result, the fluctuation of the water level in the water tank is greatly reduced. Further, in the generated water recovery device in each fuel cell power generation device, by recovering excess recovered water exceeding the measurement error, external water replenishment is not required, and the life of the ion exchange type water treatment device is not hindered. Thus, a maintenance-free air-cooled cooler can be used.

FIG. 2 is a system diagram showing an embodiment according to the second aspect of the present invention. In the system shown in FIG. 2, each of the recovered water tanks 41a includes a water level gauge 90 for measuring the water level in the tank, and based on the measured value of each of the water level gauges, the water level in each of the recovered water tanks is determined. The control valves 80A and 80B provided with a control device (not shown) for controlling the return flow rate to the generated water recovery device 41 so as to have the value of are provided in the return line to the generated water recovery device.

According to the system configuration shown in FIG. 2, the same effect as that of the system shown in FIG. 1 can be obtained, and the recovered water tank can be recovered without recovering the excess recovered water by the generated water recovery device as described above. Because the water level inside can be kept constant,
More stable water self-sustaining operation can be maintained.

FIG. 3 is a system diagram showing an embodiment according to the third aspect of the present invention. The system shown in FIG. 3 is a water tank communication pipe 1 for interconnecting the recovered water tanks 41a.
In this configuration, even if the water level in the recovered water tank fluctuates due to imbalance in the amount of water flowing into and out of the recovered water tank, the water tank communication pipe 10
0, the recovered water tank holding water can move,
The water level fluctuation in the recovered water tank can be suppressed. Also,
As shown in FIGS. 1 and 2, the same effects as those of the systems in FIGS. 1 and 2 can be obtained without specially performing the flow rate measurement and the flow rate control.

Next, embodiments according to the fourth to sixth aspects of the present invention will be described below with reference to FIG. 2 and FIGS.

FIG. 4 is a control block diagram of the control device according to the fourth to sixth aspects of the present invention. The control device shown in FIG. 4 is incorporated in a programmable logic controller (PLC) as a control device for controlling the entire fuel cell power generation device, and the control is performed.

In FIG. 2, a pump 42 for circulating recovered water
Is adjusted by providing a manual valve or a throttle for restricting the flow rate (not shown) at the pump outlet, or by controlling the frequency of the cooling water pump so as to flow at a predetermined flow rate.

In FIG. 2, the fuel cell power generator 3
0A is a device for controlling the water level in the recovered water tank to be constant, and the water level A, which is a measurement value of the water level gauge 90, is input to the PLC and compared with a reference water level set as a constant in the PLC. , An operation output A (MV) is output by a PID control device incorporated in the PLC.

The operation output A (MV) is converted by the converters A and B into signals of the control valve 80A opening command and the control valve 80B opening command according to the relationship shown in FIG. Control.

As shown in FIG. 6, control valves 80A and 80A
When the water level in the fuel cell power generator 30A tends to decrease depending on the state of the operation load of the fuel cell power generators 30A and 30B, the operation of the control valve 80A is performed in a direction in which the control valve 80A is opened, and the control valve 80A operates at the upper limit. When the water level tends to decrease even when the opening degree is reached, the control valve 80B operates in the closing direction,
The amount of recovered water returned to the fuel cell power generation device 30A is controlled so as to increase and suppress a decrease in water level. Fuel cell power generator 3
When the water level at 0A is on the rise, the reverse operation is performed.

FIG. 5 is a control block diagram when three fuel cell power generators are operated. The illustration of the fuel cell power generation system is omitted, but the system system is as follows. That is, the configuration of the fuel cell power generator is the same as that of FIG. 2, and three fuel cell power generators 30A and 30B and a fuel cell power generator 30C not shown in FIG. The recovered water 41C in these three devices is joined at the outlet of the pump 42, and the fuel cell power generation devices 30A, 30B, 3
Control valves 80A, 80B, 8 on the recovered water return line side of OC
0C is provided to control the amount of return water.

In the three fuel cell power generators, the fuel cell power generators for adjusting the water level are 30A and 30C,
30 fuel cell power generators to overflow collected water
B.

In FIG. 5, the control device (PLC) includes:
The signals of the water level A and the water level C are input, the respective water levels are compared with the reference water level, and the operation outputs A and C (MV) are output by the PID control device incorporated in the PLC. Operation output A, C (MV)
Is converted into an opening command for the control valves 80A and 80C by the converters A and A 'and output. For the operation outputs A and C, a signal having a large MV is selected by a level selector, and
, And is converted into an opening command for the control valve 80B and output.

The relationship between the operation output (MV) and the control valve opening command is as follows.
As in FIG. 6, the fuel cell power generator 30A for controlling the water level,
The operation output (MV) is divided by the control valves 80A and 80C on the 30C side and the control valve 80B on the fuel cell power generation device 30B side to overflow.

Fuel cell power generator 3 to overflow
The control valve 80B on the 0B side tends to lower the water level of the fuel cell power generator 30A or 30C, and works in the direction in which the control valve 80B closes after the opening of the control valve 80A or 80C reaches the upper limit. In this case, the control valve 80A or 80C that has not reached the upper limit opening tends to rise in water level due to an increase in the amount of recovered water recovered due to the operation of the control valve 80B in the closing direction. 80
Since C works in the closing direction, the water level is controlled to be constant.

According to the above control method, the error of the overflow water amount due to the error of the flow meter is eliminated, and the overflow is performed only when the recovered water becomes excessive, so that the external supply water can be minimized. Also, depending on the operating conditions of the fuel cell power generator, the balance between the amount of water used in the power generator and the amount of recovered water may be lost, and the amount of recovered water may be insufficient (for details, see Japanese Patent Application Laid-Open No. 10-92455). According to the control method of the present invention,
There is an advantage that the excess or deficiency of water can be averaged by a plurality of fuel cell power generators and the deficiency of recovered water can be minimized without providing a special control means as described in Japanese Patent No. 92455.

[0066]

As described above, according to the present invention, a reformer for reforming a raw fuel with steam to generate a hydrogen-rich reformed gas, and a reforming gas and an oxidizing gas (air) are provided. A fuel cell that generates electricity by electrochemically reacting the same, and cools and recovers the exhaust gas such as the combustion exhaust gas discharged from the reformer and the exhaust air discharged from the fuel cell by directly contacting the cooling water. A generated water recovery device that collects water in a water tank, a plurality of fuel cell power generators having a pump for circulating recovered water, and each recovered water in the plurality of fuel cell power generators are passed through a cooling pipe. An air-cooled cooler that collectively cools with air from the outside of the cooling pipe, and a recovered water circulation line that allows the recovered water to flow through the air-cooled cooler by the pump and returns the cooled recovered water to the generated water recovery device. Equipped with fuel cell power generation A stem, wherein a recovered water introduction line to the air-cooled cooler of the recovered water circulation line and a return line to the generated water recovery device are provided with a flow meter for measuring an introduction flow rate and a return flow rate of the recovered water, A control valve provided with a control device for controlling the return flow rate so that the return flow rate is the same as the introduction flow rate based on the measurement value of each of the flow meters, provided in a return line to the generated water recovery device. (Invention of claim 1), and in the above,
Instead of the flow meter and the control valve, each of the recovered water tanks is provided with a water level meter for measuring the water level in the tank, and further, based on the measurement value of each of the water level meters, the water level in each of the recovered water tanks A control valve provided with a control device for controlling the return flow rate to the generated water recovery device so that the value becomes a predetermined value is provided in the return line to the generated water recovery device (the invention of claim 2). Further, in the above, in order to make the water level in each of the collected water tanks in the plurality of fuel cell power generators substantially the same level, the collected water tanks are replaced with the water level gauge and the control valve. By providing a water tank communication pipe interconnected to each other (the invention according to claim 3), in a system in which collective cooling of collected water in a plurality of fuel cell power generators by one cooling facility is performed, Fluctuation of water level in tank Suppressing, without inhibiting the life of the water treatment apparatus, it is possible to provide a maintenance-free fuel cell power generation system using the air-cooled condenser.

Further, in the operation control method of the fuel cell power generation system according to claim 2, the water in the recovery water tank in one fuel cell power generation device among the plurality of fuel cell power generation devices overflows, By controlling the return flow rate to the generated water recovery device by the control valve so that the water level in the recovered water tank in another fuel cell power generation device becomes a predetermined value (the invention of claim 4), The excess or deficiency is averaged by the plurality of fuel cell power generators, and the shortage of recovered water can be minimized without providing any special control means.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram showing an embodiment of a fuel cell power generation system according to the present invention.

FIG. 2 is a schematic system diagram showing a different embodiment of the fuel cell power generation system of the present invention.

FIG. 3 is a schematic system diagram showing still another embodiment of the fuel cell power generation system of the present invention.

FIG. 4 is a control block diagram of a control device according to the present invention.

FIG. 5 is a control block diagram of a control device when three fuel cell power generators are provided.

FIG. 6 is a relationship diagram between a control valve opening command and a PID operation output according to the present invention.

FIG. 7 is a schematic system diagram showing an example of a conventional fuel cell power generation system.

FIG. 8 is a diagram showing an example of a schematic system configuration of a conventional fuel cell power generator.

[Explanation of symbols]

1: fuel cell, 7: reformer, 30A, 30B: fuel cell power generator, 41: generated water recovery device, 41a: recovered water tank, 41b: cooling water direct contact cooler, 41c: recovered water, 41d: Overflow pipe, 42: pump, 55:
Pneumatic cooler, 56: cooling pipe, 57: recovered water circulation line, 70a, 70b: flow meter, 80, 80a, 80b:
Control valve, 90: water level gauge, 100: water tank communication pipe.

Claims (6)

[Claims] 1. A reformer for reforming raw fuel with steam to produce a hydrogen-rich reformed gas, and generating electricity by electrochemically reacting the reformed gas with an oxidizing gas (air). Produced water recovery in which a fuel cell and a combustion exhaust gas discharged from the reformer and an exhaust gas such as exhaust air discharged from the fuel cell are brought into direct contact with cooling water to cool the water and collect water in a recovery water tank. A plurality of fuel cell power generators each having a device and a pump for circulating recovered water, and each of the collected water in the plurality of fuel cell power generators flows into a cooling pipe and is collectively cooled by air from outside the cooling pipe. An air-cooled cooler, and the recovered water is passed through the air-cooled cooler by the pump,
A recovered water circulation line for returning cooled recovered water to the generated water recovery device, comprising: a recovered water introduction line to the air-cooled cooler of the recovered water circulation line; and a generated water recovery device. In the return line to the, provided a flow meter to measure the introduction flow rate and return flow rate of the recovered water,
Further, based on the measurement value of each of the flow meters, a control valve provided with a control device for controlling the return flow rate so that the return flow rate is equal to the introduction flow rate is provided in a return line to the generated water recovery device. A fuel cell power generation system characterized in that: 2. The fuel cell power generation system according to claim 1, wherein each of the recovered water tanks is provided with a water level gauge for measuring a water level in the tank, instead of the flow meter and the control valve. A control valve having a control device for controlling a return flow rate to the generated water recovery device so that the water level in each recovered water tank becomes a predetermined value based on the measurement value of each water level gauge, A fuel cell power generation system, which is provided on a return line to a fuel cell. 3. The fuel cell power generation system according to claim 2, wherein the water level gauge and the control valve are used in place of the water level gauge and the control valve so that the water level in each of the recovered water tanks in the plurality of fuel cell power generation devices is substantially the same. A fuel tank power generation system, wherein a water tank communication pipe connecting the respective recovered water tanks to each other is provided. 4. The operation control method for a fuel cell power generation system according to claim 2, wherein water in a recovery water tank in one of the plurality of fuel cell power generation devices is overflowed. Operating the fuel cell power generation system, wherein the control valve controls a return flow rate to the generated water recovery device so that a water level in a recovered water tank in another fuel cell power generation device has a predetermined value. Control method. 5. The operation control method for a fuel cell power generation system according to claim 4, wherein the water level in the recovered water tank in the other fuel cell power generation device that does not overflow is controlled by adjusting the opening of the control valve. The control valve corresponding to the fuel cell power generator to be overflowed always has its valve opening fully opened at all times, and opens when at least one of the control valves performing the water level control reaches the fully opened position. An operation control method for a fuel cell power generation system, characterized in that control is performed to reduce the flow rate and decrease the flow rate. 6. The operation control method for a fuel cell power generation system according to claim 4, wherein the control valve includes a PID control device and an operation signal of the valve output by the PID control device, the control signal being a command of a valve opening degree command. A control device having a converter for converting the signal into a signal; inputting a measured value of a water level meter in the recovered water tank which does not cause overflow to the control device; comparing the input value with a predetermined reference water level; The operation signal of the valve of the PID control device output based on the comparison value is converted into a signal of a valve opening command by the converter, and based on the valve opening command value corresponding to each control valve, the opening of each control valve is performed. An operation control method for a fuel cell power generation system, comprising performing degree control.