JPH0922716A - Cooling water refilling device of water-cooled fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent liquid junction phenomenon and scale generation by sensing the concentration of impurities in cooling water, and giving a degree-of-opening command to a blow water control valve furnished in a blow water system. SOLUTION: Impurities in a cooling water are condensed gradually in the process that the steam separated by a water-vapor separator 4 is supplied to a fuel reforming device 2, and in the course of operation, the concentration of the impurities in the cooling water rises gradually. The concentration is is sensed by a sensor 21 for measuring electroconductivity and a sensor 22 for silica concentration, and a degree-of-opening command 23S is given to a blow water control valve 28 from a control part 23 when either of the sensing values exceeds the reference value, and thereupon the rate of the flow of blow water 10C is controlled. The pure water 10E obtained by a purifying device 6 is fed back to the separator 4 to dilute the concentration of the impurities contained in the cooling water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling water replenishing device provided for the purpose of replenishing cooling water and maintaining water quality in a water-cooled fuel cell used in an on-site power generator or the like.

[0002]

2. Description of the Related Art FIG. 2 is a schematic system diagram of a conventional apparatus showing a water-cooled phosphoric acid fuel cell power generator as an example. A fuel cell (stack) 1 composed of a unit cell stack has a plurality of unit cells. Fuel gas 2 from a fuel reformer 2 for steam reforming a raw fuel, comprising a cooling plate 3 having stacked water cooling pipes
Upon receiving F and reaction air from a supply device (not shown), electricity is generated based on an electrochemical reaction. The electrode reaction of the fuel cell 1 is an exothermic reaction as a whole, and the heat generated by power generation is connected to the cooling pipe of the cooling plate 3 by the cooling water circulation system 10 having the circulation pump 7A and the water vapor separator 4 for circulating the cooling water 10A. Cooled, fuel cell temperature about 190 ° C
The operation is performed with the operating temperature maintained at.

The cooling water 10A, which has taken away the heat generated by power generation from the fuel cell 1 and has been heated, is cooled by separating the steam in the steam separator 4, and the steam 4S separated in the steam separator 4 is separated. Is mixed with the raw fuel and supplied to the fuel reformer 2 to be used for the steam reforming reaction. further,
Hydrogen in the fuel gas 2F that has been left unused in the fuel electrode is sent to the burner of the fuel reformer and burned, and is used as the heat of reforming reaction.

The cooling water circulation system 10 supplies the steam 4S separated by the steam separator 4 to the fuel reformer 2 to reduce the cooling water 10A. Therefore, a cooling water replenishing device 11 is provided to replenish the shortage of the cooling water. The cooling water supply device 11 is composed of a water vapor recovery tower 5, a deionized water device 6, pumps 7C and 7D, and a blow water system 9 having a blow valve 8. The water vapor recovery tower 5 includes a heat exchanger that uses the recovered mixed water 10B as a cooling medium, and condenses and recovers the power generation water contained in the air off-gas on the air electrode side of the fuel cell 1 as water vapor. The mixed water 10B to which tap water is added as needed is supplied to the pure water device 6 via the pump 7B. The pure water device 6 includes a filter, an ion-exchange resin type water purifier, and the like, and negative ions such as chlorine ions contained in the mixed water, cations (metal ions) such as calcium ions and magnesium ions, and silica and microorganisms. The ion-exchanged water (pure water) 10E from which the solid impurities have been removed is supplied to, for example, the steam separator 4 of the cooling water circulation system 10.

By the way, in the deionized water device 6, the impurity ions in the mixed water 10B become a load, and the ion adsorption performance of the ion exchange resin gradually decreases. Therefore, in the conventional device, the conductivity meter 12 is provided on the outlet side of the pure water device 6, and when the detected value exceeds a predetermined value, for example, 0.1 μS / cm, the ion exchange resin of the pure water device 6 is removed. By replacing the pure water in the cooling water circulation system 10 with a new one, the electric conductivity and the impurity ion concentration are kept at a certain level.

The pure water 10E supplied to the cooling water circulation system 10 contains a small amount of impurities, which are gradually concentrated in the process of supplying the steam 4S to the fuel reforming device 2. Cooling water 10A as time passes
The impurity concentration in the inside increases. Therefore, in the conventional example, a blow water system 9 is provided between the water vapor separator 4 and the recovery tower 5, and the blow valve 8 is always slightly opened, or the blow water is sent to the recovery tower 5 by performing on / off control periodically. Pure water device 6
Measures are taken to suppress the increase of the impurity concentration in the cooling water 10A by replenishing pure water 10E from the above.

[0007]

In the prior art, the control of the concentration of impurities contained in pure water in the cooling water circulation system relies on manual control of the flow rate of blow water, so that, for example, a fuel cell power generator is turned on. When a plurality of site power supply devices are used in different places, the water quality control tends to be mixed depending on the flow control method of the blow water, which causes the cooling water to increase as the impurity ion concentration in the cooling water 10A increases. When the conductivity increases, a liquid junction phenomenon occurs in which a part of the generated current leaks between the unit cells via the cooling water, which easily causes a disadvantage that a difference occurs in the power generation efficiency of the fuel cell power generator. . In addition, an increase in the concentration of calcium, magnesium, or silica as a solid impurity causes the generation of scale on the inner wall surface of the cooling pipe or the cooling water circulation system, which has an adverse effect that the fuel cell temperature rises due to an increase in heat resistance on the heat exchange surface. In addition to the above-mentioned problems, a fuel cell power generation device that causes inconveniences such as an increase in fluid resistance of pipes due to the accumulation of peeled scale and a blockage of valves is also generated.

An object of the present invention is to provide a cooling water replenishing device for a water cooling type fuel cell which has no difference in water quality control between the sites and can prevent a liquid junction phenomenon and scale from occurring. .

[0009]

In order to achieve the above-mentioned object, the invention according to claim 1 provides a fuel cell comprising a laminate of a plurality of unit cells and a cooling plate, and a cooling plate of the fuel cell. In a water-cooled fuel cell having a circulation pump for circulating cooling water and a cooling water circulation system having a steam separator,
A tower for collecting water in exhaust gas of the fuel cell, a blow water system for supplying blow water from the water vapor separator to the tower, and a mixed water of the recovery tower, blow water, and tap water are purified. A cooling water replenishing device comprising a pure water device for converting into pure water and supplying it to the cooling water circulation system, wherein a sensor for detecting the concentration of impurities contained in the cooling water of the cooling water circulation system, and The cooling water water quality control system includes a control unit that issues an opening degree command to the blow water control valve of the blow water system when the detection level exceeds a predetermined reference value.

According to the second aspect of the present invention, the sensor comprises a sensor for measuring conductivity and a sensor for measuring silica concentration, and the control unit detects the detection level of any one of the sensors exceeds a predetermined reference value. At this time, the opening command may be issued to the blow water control valve. Also,
The invention according to claim 3 may be configured to include an abnormality notifying unit that issues a notification command to the abnormality notifying device when the control unit detects an abnormal detection signal that greatly exceeds a predetermined reference value.

[0011]

According to the first aspect of the invention, the water quality control system detects the concentration of impurities contained in the cooling water in the cooling water circulation system by the sensor, and blows when the detection level of the sensor exceeds a predetermined reference value. Since the opening command is issued to the water control valve, the blow water system, the power generation water recovery tower, and the deionized water device that are conventionally provided are linked to automatically concentrate impurities in the cooling water circulation system. A water quality control function to prevent it is obtained. Also, when the cooling water replenishing devices of the plurality of fuel cell power generators for the on-site power supply have different water qualities of the mixed water and the adsorption capacity of the ion exchange resin,
By controlling the amount of blow water, the water quality in the cooling water circulation system of each fuel cell power generator is automatically maintained at a constant level.

According to the second aspect of the present invention, the sensors for detecting the impurity concentration in the cooling water are the conductivity measuring sensor and the silica concentration measuring sensor, and the control unit detects the detection level of either one of the sensors. Since the opening command is issued to the blow water control valve when it exceeds a predetermined reference value, concentration of chlorine ions, calcium ions, magnesium ions, etc. is detected as a decrease in ionic conductivity by the conductivity measuring sensor. The silica as a solid impurity that cannot be detected as a decrease in conductivity is detected by the sensor for measuring silica concentration. Therefore, the accuracy of the combination of the function of preventing the decrease in the conductivity of the cooling water that causes the liquid junction phenomenon and the function of preventing the accumulation of calcium ions, magnesium ions, and silica that cause the scale accumulation A high water quality management function can be obtained.

According to the third aspect of the invention, when the control unit detects an abnormal detection signal that greatly exceeds a predetermined reference value, the abnormality notification unit is provided for issuing a notification command to the abnormality notification device. Therefore, it is determined that the alarm of the abnormality alarm is a signal to notify the deterioration of the performance of the deionizer, and the filter unit of the filter is replaced or the ion exchange resin is replaced to keep the deionizer clean. The water quality can be controlled with high accuracy by maintaining the condition.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
Since the members having the same reference numerals as those of the conventional example have the same functions as those of the conventional example, the description thereof will be omitted. FIG. 1 is a schematic system diagram showing an embodiment of the present invention as an example of a cooling water supply device for a water-cooled phosphoric acid fuel cell power generator. In the figure, the water quality control system 20 has a conductivity measuring sensor 21 for detecting the ionic conductivity of the cooling water 10A in the water vapor separator 4 and a silica concentration measuring sensor 22, and the detection level of either sensor is When the predetermined reference value is exceeded, the opening command 23 is directed toward the blow water control valve 28.
And a control unit 23 that emits S. Further, the water quality control system 20 is connected to the blow water system 9, the power generation water recovery tower 5, and the deionized water device 6 which are conventionally provided, so that the cooling water 10A in the cooling water circulation system 10 is operated.
A cooling water replenishing device having a function of automatically preventing the concentration of impurities contained in is formed.

That is, in the embodiment, the conductivity of the ion-exchanged water 10E obtained by the pure water device 6 is 0.1 μS / cm,
When the silica concentration is 0.02 ppm, the control unit 23 is preset with a value about several times the above value as a reference value. When the power generation operation is performed in this state, the steam separator 4
In the process of supplying the separated steam 4S to the fuel reformer 2, solid ions such as impurity ions and silica in the cooling water 10A are gradually concentrated, and the impurity concentration in the cooling water 10A gradually increases as the operation time elapses. Rise to. The feature of this embodiment is that chlorine ions, which cause the liquid junction phenomenon,
Concentration of calcium ions, magnesium ions, etc. is detected by the conductivity measuring sensor 21 as a decrease in ionic conductivity by the conductivity measuring sensor, and solid impurities such as silica that cannot be detected by the conductivity measuring sensor 21 are for silica concentration measuring. The point is that it is detected by the sensor 22. Therefore, when one of the detected values exceeds the respective reference value, the control unit 23 outputs the opening degree command 23S toward the blow water control valve 28, and the flow rate of the blow water 10C is controlled based on this, and the flow rate of the blow water 10C is controlled. The pure water 10E processed by the pure water device 6 is returned to the water vapor separator 4 to dilute the impurity concentration in the cooling water 10A, which lowers the power generation performance due to the liquid junction phenomenon and the cooling performance due to scale accumulation. Can be prevented in advance.

Further, even when the cooling water replenishing devices of a plurality of fuel cell power generators for on-site power supplies have different water qualities of mixed water and adsorption capacities of ion-exchange resins, automatic control of the flow rate of blow water is performed. Since the water quality in the cooling water circulation system 10 can be maintained at a constant level, there is an advantage that the water quality of the cooling water circulation system of the plurality of fuel cell power generators can be controlled to a constant level with almost no labor required.

Which of the conductivity measuring sensor 21 and the silica concentration measuring sensor 22 operates depends on the water quality of the mixed water 10B and the impurity removing performance of the pure water device 6. Therefore, by deciding the combination of sensors with this point in mind, it is possible to obtain a sophisticated water quality control function capable of automatically preventing the occurrence of a liquid junction phenomenon due to the decrease in conductivity and the accumulation of scale. On the contrary, in the case of a device in which the concentration of impurity ions is likely to occur, only the conductivity measuring sensor is provided, and in the device in which solid impurities are likely to accumulate, only the silica concentration measuring sensor is provided to simplify the configuration of the water quality control system. May be.

On the other hand, in FIG. 1, when the control unit 23 receives an abnormal detection signal from the conductivity measuring sensor 21 or the metal ion concentration measuring sensor 22 that greatly exceeds a predetermined reference value, an abnormality alarm (not shown) is shown. If it is configured to output the alarm command 23A to the operator, the operator who receives the alarm of the abnormality alarm determines that the deionized water device has deteriorated in capacity and, for example, replaces the filtering material of the filter or ion. By exchanging the exchange resin, the water quality control system 20 can be utilized to evenly manage the maintenance timing of the deionized water device 6, and therefore, a plurality of fuel cell power generators for on-site power supplies can be used. The advantage is that the water quality control of the cooling water circulation system can be made more uniform.

[0019]

As described above, the cooling water replenishing device for a water-cooling type fuel cell of the present invention is provided with a water quality control system including an ion concentration measuring sensor and its controller in the cooling water circulating system of the water-cooling type fuel cell. The flow rate of blow water is increased when the ion concentration in water exceeds a specified value. As a result, the cooling water supply device automatically supplies pure water according to the flow rate of blow water to dilute the ion concentration in the cooling water. It is possible to provide a water-cooled fuel cell power generator equipped with a cooling water replenishing device that can be avoided and can obtain stable cooling performance without occurrence of a liquid junction phenomenon or scale. In particular, even when the cooling water replenishing devices of multiple fuel cell power generators for on-site power supply have different water quality of mixed water and adsorption capacity of ion exchange resin, cooling is performed by automatic control of the flow rate of blow water. Since the water quality in the water circulation system can be maintained at a constant level, there is an advantage that the water quality of the cooling water circulation system of the plurality of fuel cell power generators can be controlled to a constant level with almost no labor required.

Further, by providing the conductivity measuring sensor and the metal ion concentration measuring sensor, there is an advantage that the water quality can be controlled with higher accuracy by utilizing the complementary action of the both. On the other hand, by adding an alarm function to the water quality control system, it is possible to manage the maintenance timing of the deionized water device evenly. Therefore, the cooling water circulation system of multiple fuel cell power generators for on-site power supplies can be controlled. The advantage is that water quality management can be made more even.

[Brief description of drawings]

FIG. 1 is a schematic system diagram showing an embodiment of the present invention as an example of a cooling water supply device for a water-cooled phosphoric acid fuel cell power generator.

FIG. 2 is a schematic system diagram of a conventional device showing a water-cooled phosphoric acid fuel cell power generator as an example.

[Explanation of symbols]

 1 Fuel Cell 2 Fuel Reforming Device 3 Cooling Plate 4 Water Vapor Separator 5 Recovery Tower of Generated Water 6 Pure Water Device 8 Blow Valve 9 Blow Water System 10 Cooling Water Circulation System 10A Cooling Water 10B Mixed Water 10E Pure Water (Ion Exchange Water) 11 Cooling Water Supply Device 12 Conductivity Meter 20 Water Quality Control System 21 Conductivity Measurement Sensor 22 Metal Ion Concentration Measurement Sensor 23 Control Unit 23S Notification Command 28 Blow Water Control Valve

Claims (3)

[Claims] 1. A water-cooled fuel having a fuel cell comprising a stack of a plurality of unit cells and a cooling plate, and a cooling water circulation system having a circulation pump for circulating cooling water and a steam separator on the cooling plate of the fuel cell. In the battery, a recovery tower for water in exhaust gas of the fuel cell, a blow water system for supplying blow water from the steam separator to the recovery tower, mixed water of the recovery tower, blow water, and mixed water of tap water A cooling water replenishing device including a pure water device that converts the purified water into purified water and supplies the purified water to the cooling water circulation system, and a sensor that detects the concentration of impurities contained in the cooling water of the cooling water circulation system, A cooling water quality control system comprising a control unit for issuing an opening degree command to the blow water control valve of the blow water system when the detection level of the sensor exceeds a predetermined reference value. Water-cooled fuel cell cooling water supply device. 2. The cooling water replenishing device for a water-cooled fuel cell according to claim 1, wherein the sensor comprises a sensor for measuring conductivity and a sensor for measuring silica concentration, and the control unit controls the detection level of any one of the sensors. A cooling water replenishing device for a water-cooled fuel cell, which issues an opening command toward a blow valve when a predetermined reference value is exceeded. 3. The cooling water replenishing device for a water-cooled fuel cell according to claim 1, wherein when the control unit detects an abnormal detection signal that greatly exceeds a predetermined reference value, an alarm is sent to an alarm. A cooling water supply device for a water-cooled fuel cell, which is provided with an abnormality notification unit for issuing a command.