JP2015084280A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to avoid an increase in a number of equipment and complication of a system by negating the need of monitoring an amount of water of a condensed water tank by a water level indicator.SOLUTION: A fuel cell system comprises: a fuel cell main body 1 for performing power generation; a heat medium circulation passage 3 through which a heat medium for performing heat exchange of at least one off-gas of off-fuel gas being fuel gas exhausted from the fuel cell main body 1 and off-oxidant gas being oxidant gas exhausted from the fuel cell main body 1 circulates; a temperature detector 6 for detecting a temperature of the heat medium prior to the heat exchange of the off-gas; a heat exchanger 4 provided in the heat medium circulation passage 3 for condensing moisture vapor in the off-gas and generating condensed water by performing the heat exchange between the off-gas and the heat medium; a condensed water tank 5 for storing the condensed water generated in the heat exchanger 4; and a controller 7. Further, the controller 7 calculates an amount of water in the condensed water tank 5 on the basis of the temperature detected by the temperature detector 6 and cumulative time when the temperature is detected.

Description

  The present invention relates to a fuel cell system including a fuel cell main body.

  The hydrogen-rich fuel gas generated by the steam reforming reaction of the raw material gas containing hydrocarbons and the oxidant gas such as oxygen in the air are reacted in the fuel cell body to extract electric energy with high efficiency, and the power generation A combination of a fuel cell system and a hot water supply system is known as a cogeneration system capable of recovering exhaust heat accompanying heat and using it as thermal energy (see, for example, Patent Document 1).

  In the fuel cell system disclosed in Patent Document 1, heat is exchanged between the off-fuel gas and / or off-oxidant gas discharged from the fuel cell main body and water from the hot water supply system by a heat exchanger, and then discharged. The water contained in the off-gas is condensed, and the water obtained by the condensation is stored as water necessary for the operation of the fuel cell system. The amount of water stored in the condensate tank is monitored by a water level meter, and the circulation pump performs control such as changing the amount of pumped water according to the amount of stored water.

  Further, there is known a fuel cell system configured such that when the amount of water in a condensed water tank provided in the fuel cell system is reduced, water is supplied to the condensed water tank from the outside of the fuel cell system (for example, Patent Document 2).

  In the fuel cell system disclosed in Patent Document 2, a condensed water tank provided in the fuel cell system and a hot water storage tank of a hot water supply system are connected by piping. An electromagnetic valve or the like is provided in the middle of the path so that city water can be supplied from the hot water storage tank to the condensed water tank when the amount of water in the condensed water tank decreases.

  The above two fuel cell systems are configured to include a path and a solenoid valve for monitoring the amount of condensed water or supplying water with a water level meter in order to secure water necessary for operation, and the water level in the condensed water tank is reduced. When it comes, control to promote the generation of condensed water, or supply city water.

JP 2001-325882 A JP 2004-111208 A

  However, the method of monitoring the amount of water in the condensed water tank with a water level meter is effective as a means for accurately grasping the amount of water, but using the water level meter increases the number of equipment and complicates the system. The water level gauge is affected by the water quality in the condensate tank, and may reduce the reliability of the fuel cell system by erroneous detection. In addition, when the amount of water in the condensate tank decreases, the method of supplying city water to the condensate tank increases the ion exchange resin capacity required for the deionization treatment of the city water. There is a problem that the number of devices increases and the system becomes complicated.

Furthermore, the temperature of the water flowing from the hot water supply system is high in the conventional fuel cell system,
If the conditions in which the water contained in the off-fuel gas and / or off-oxidant gas cannot be condensed in the heat exchanger continue, the operation is stopped because there is not enough water to continue power generation in the fuel cell body. It was.

  The present invention solves the above-described conventional problems, and provides a fuel cell system that can be simplified by avoiding an increase in the number of devices and complication of the system. Moreover, even if the temperature of the water which flows in from a hot water supply system becomes high, the fuel cell system which can continue the electric power generation of a fuel cell main body is provided.

  In order to solve the conventional problems, a fuel cell system of the present invention includes a fuel cell main body that generates power using a fuel gas and an oxidant gas generated from a reforming reaction between a raw material gas and condensed water, A heat medium that exchanges heat with at least one of an off-fuel gas that is a fuel gas discharged from the fuel cell body and an off-oxidant gas that is an oxidant gas discharged from the fuel cell body circulates. A heat medium circulation path, a temperature detector that detects the temperature of the heat medium before heat exchange with the off gas, and a heat medium circulation path provided by exchanging heat between the off gas and the heat medium. The heat exchanger which condenses the water vapor | steam in the said off gas and produces | generates the said condensed water, the condensed water tank which accumulate | stores the said condensed water produced | generated with the said heat exchanger, and the controller are provided. And the said controller calculates the amount of water in the said condensed water tank based on the temperature which the said temperature detector detects, and the accumulation time which detects the said temperature. This eliminates the need to monitor the amount of water in the condensate tank with a water level gauge, thereby avoiding an increase in the number of devices and system complexity, and simplification is possible.

  Further, in the fuel cell system of the present invention, when the temperature detector detects a predetermined first temperature or higher, the controller determines the condensed water in the condensed water tank in advance. When the amount is equal to or greater than the first amount of water, the fuel cell main body continues to generate power.

  Thereby, even if the temperature of the heat medium flowing into the heat exchanger becomes high, it is possible to continue the power generation of the fuel cell main body.

  In the fuel cell system of the present invention, it is not necessary to monitor the amount of water in the condensate tank with a water level gauge, so that an increase in the number of devices and the complexity of the system can be avoided and simplification is possible. Further, even if the temperature of the water flowing from the hot water supply system becomes high, it is possible to continue the power generation of the fuel cell main body.

1 is a block diagram showing the configuration of a fuel cell system according to Embodiment 1 of the present invention. Fuel cell system configuration block diagram in Embodiment 4 of the present invention Fuel cell system configuration block diagram in Embodiment 5 of the present invention

A first invention is a fuel cell main body that generates power using a fuel gas and an oxidant gas generated from a reforming reaction between a raw material gas and condensed water, and a fuel gas discharged from the fuel cell main body. A heat medium circulation path through which a heat medium that exchanges heat with at least one of the off-fuel gas and the off-oxidant gas that is an oxidant gas discharged from the fuel cell body circulates, and exchanges heat with the off-gas. A temperature detector for detecting a temperature of the heat medium before the heat medium, and the heat medium circulation path, the off gas and the heat medium are subjected to heat exchange to condense the water vapor in the off gas, thereby condensing the condensed water. The heat exchanger which produces | generates, the condensed water tank which accumulate | stores the condensed water produced | generated with the said heat exchanger, and the controller are provided. And the said controller is a fuel cell system characterized by calculating the water quantity in the said condensed water tank based on the temperature which the said temperature detector detects, and the accumulation time which detects the said temperature.

  By adopting such a configuration, the fuel cell system does not need to monitor the amount of water in the condensed water tank with a water level gauge, so that an increase in the number of devices and the complexity of the system can be avoided and simplification is possible.

  According to a second aspect of the invention, in the fuel cell system of the first aspect of the invention, in particular, when the temperature detector detects a temperature equal to or higher than a predetermined first temperature, the controller In the fuel cell system, when the condensed water is equal to or more than a predetermined first water amount, power generation of the fuel cell main body is continued.

  By adopting such a configuration, the fuel cell system can continue the power generation of the fuel cell body even when the temperature of the heat medium flowing into the heat exchanger becomes high.

  According to a third aspect of the invention, in particular, in the fuel cell system of the first or second aspect of the invention, when the temperature detector detects a predetermined first temperature or higher, the condensed water The fuel cell system is characterized in that power generation of the fuel cell main body is stopped when the condensed water in the tank becomes less than a predetermined second water amount.

  By adopting such a configuration, the fuel cell system can hold the amount of water necessary for restarting the system after stopping the power generation of the fuel cell main body and restarting the power generation of the fuel cell main body in the condensed water tank, so that it can be stopped. In addition to continuing power generation, the fuel cell system does not require water supply from outside the fuel cell system, such as city water, to restart the fuel cell system and restart the fuel cell body next time, in addition to continuing power generation. .

  The fourth aspect of the invention is particularly the fuel cell system of the first, second or third aspect of the invention, further comprising a heat medium circulator disposed in the heat medium circulation path for circulating the heat medium, wherein the controller When the temperature detector detects a temperature equal to or higher than a predetermined second temperature, the flow rate of the heat medium flowing through the heat medium circulation path is larger than before the temperature reaches the second temperature or higher. The fuel cell system is characterized by controlling the heat medium circulator.

  By adopting such a configuration, the fuel cell system is configured such that when the temperature of the heat medium flowing into the heat exchanger becomes high and there is a risk that the water necessary for continuing power generation of the fuel cell body may be insufficient. The flow rate of the heat medium is made larger than before the temperature of the heat medium increases. As a result, since the heat exchange efficiency in the heat exchanger can be increased, the fuel cell system has a simple configuration, and in addition to continuing power generation, generation of condensed water necessary for continuing power generation of the fuel cell body Can be promoted.

  According to a fifth aspect of the invention, particularly in the fuel cell system according to the first, second, or third aspect of the invention, the fuel cell system further includes an oxidant gas supply device that supplies an oxidant gas to the fuel cell body, and the controller includes the temperature When the detector detects a predetermined second temperature or higher, the oxidant gas supply device is controlled so that the flow rate of the off-oxidant gas becomes smaller than before the second temperature or higher. This is a fuel cell system.

By adopting such a configuration, the fuel cell system is configured such that when the temperature of the heat medium flowing into the heat exchanger becomes high and there is a risk that the water necessary for continuing power generation of the fuel cell body may be insufficient. Since the water vapor released outside the fuel cell system can be reduced by reducing the flow rate of the off-oxidant gas compared to before the temperature of the fuel cell rises, the fuel cell system has a simple configuration and generates power. In addition, the generation of condensed water necessary for continuing the power generation of the fuel cell main body can be promoted.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
Embodiments of a fuel cell system according to the present invention will be described with reference to the drawings.

  1 is a block diagram showing a system configuration of a fuel cell system according to Embodiment 1. FIG. As shown in FIG. 1, the fuel cell system according to the present embodiment includes a fuel cell main body 1 that generates power using fuel gas and oxidant gas. The fuel cell main body 1 includes a polymer electrolyte fuel cell (PEFC). ) Or a solid oxide fuel cell (SOFC) or the like.

  The fuel gas is obtained by a steam reforming reaction by supplying a raw material gas containing hydrocarbons and water supplied from a city gas infrastructure or the like to the reformer 2. Both the raw material gas and water are pumped by a blower, a pump or the like (not shown) and supplied to the reformer 2. The present invention can also be applied to a fuel cell system that is not provided with the reformer 2 and is directly connected to a hydrogen source such as a hydrogen gas infrastructure as a fuel gas.

  A gas containing an oxidant gas such as air is pumped by a blower or the like through the air supply path 10 and supplied to the fuel cell main body 1.

  The heat medium circulation path 3 circulates water or antifreeze as a heat medium, thereby generating heat generated by the power generation of the fuel cell main body 1, exhaust heat of each off-gas discharged from the fuel cell main body 1, a reformer, and the like. The exhaust heat generated in the fuel cell system, such as exhaust heat of combustion exhaust gas generated by combustion in the fuel cell, is recovered.

  The heat medium circulation path 3 includes a heat exchanger 4 that cools and condenses water vapor in at least one of the off-fuel gas and the off-oxidant gas discharged from the fuel cell main body 1.

  A plurality of heat exchangers 4 may be provided for each off-gas. In general, in a fuel cell system, off-fuel gas discharged from the fuel cell body 1 is burned by a burner such as a reformer and used for maintaining the catalyst temperature. In the present invention, the off-fuel gas may be a combustion exhaust gas after being burned by a burner.

  The water cooled and condensed by heat exchange with the heat medium flowing through the heat medium circulation path 3 in the heat exchanger 4 is stored in the condensed water tank 5. The collected water is used as a steam source for the reforming reaction of the raw material gas or the cooling water of the fuel cell main body 1 after purification (deionization) such as ion exchange with an ion exchange resin or the like. In the present invention, the purified water can be stored in the condensed water tank 5.

  In addition, the fuel cell system of the present embodiment includes a temperature detector 6 that detects the temperature of the heat medium before exchanging heat with off-gas, a temperature that is detected by the temperature detector 6, and an accumulated time that detects the temperature. A controller 7 for calculating the amount of water in the condensed water tank 5 is provided.

  The temperature detector 6 is provided in the heat medium circulation path 3 and configured to directly detect or predict the temperature of the heat medium flowing into the heat exchanger 4.

  The operation and action of the fuel cell system configured as described above will be described.

  First, in the fuel cell system of the present embodiment, the amount of condensed water that is cooled and condensed by the heat exchanger 4 and flows into the condensed water tank 5 based on the temperature detected by the temperature detector 6 and the accumulated time for detecting the temperature. calculate. The amount of water vapor contained in the off-gas flowing into the heat exchanger 4 is roughly determined by the power generated by the fuel cell body 1. The amount of condensed water that can be recovered by cooling and condensing the offgas is determined by the temperature at which the offgas can be cooled. Therefore, if the temperature flowing into the heat exchanger 4 and the duration of the temperature are known, the condensation generated in the heat exchanger 4 It is possible to determine the amount of water.

  In general, when the fuel cell system is operated for the first time to generate electric power, it is necessary to finish the work of filling the water tank or water pipe in the fuel cell system with water from the outside. In the fuel cell system of the present embodiment, the amount of condensed water flowing into the condensed water tank 5 can be calculated by calculation after power generation of the fuel cell main body 1 is started. If the controller 7 can grasp the amount of water supplied, the amount of water in the condensed water tank 5 can be calculated thereafter by calculation.

  For example, the operation of the fuel cell system is started in a state where 2 L of water is filled in the condensed water tank 5 from the outside. Thereby, the controller 7 can calculate the amount of water used for reforming and the amount of condensed water recovered by the heat exchanger 4. Since the amount of water in the condensed water tank 5 is calculated by increasing / decreasing them from 2 L, it is not necessary to monitor the amount of water in the condensed water tank 5 with a water level gauge, and an increase in the number of devices and the complexity of the system can be avoided. It becomes possible.

(Embodiment 2)
The fuel cell system according to the second embodiment is the same as the fuel cell system according to the first embodiment, in which the temperature detector 6 detects a predetermined first temperature or higher and the amount of condensed water in the condensed water tank is predetermined. When the amount of water is equal to or greater than the first water amount, the controller 7 is configured to continue the power generation of the fuel cell main body 1.

  The first temperature is a temperature of a heat medium that makes it impossible to generate water by sufficiently cooling and condensing the water vapor contained in the off-gas in the heat exchanger 4, and in the conventional fuel cell system, the power generation of the fuel cell main body 1 is performed. Had stopped. The first water amount means the amount of water in the condensate tank 5 sufficient to continue the power generation of the fuel cell main body 1. When the controller 7 calculates the first water amount or more, the temperature detector The power generation of the fuel cell main body 1 can be continued regardless of the temperature detected at 6. In addition, when the heat demand of a consumer can be easily predicted and power generation is stopped, deterioration of the energy efficiency of the system can be avoided, it may be configured to stop.

  Generally, in the fuel cell system, when the temperature flowing into the heat exchanger 4 is about 45 ° C. or higher, the amount of water vapor released outside the system system without being cooled and condensed increases. As a result, there is a concern that the water necessary for continuing the power generation of the fuel cell body 1 may not be self-sufficient, so it is necessary to stop the power generation or to provide a mechanism for forcibly cooling the water temperature in order to continue the power generation. was there.

  In addition, the fuel cell system stops the power generation of the fuel cell main body 1 once, and in order to start the power generation again, a large amount of energy must be used for raising the temperature of the reformer 2 and operating auxiliary equipment such as a blower. Don't be. These are usually supplied from raw material gas or commercial power, and frequent shutting down of the fuel cell system leads to deterioration of the energy efficiency of the system.

The fuel cell system according to the present embodiment determines whether or not the fuel cell main body 1 can continue the power generation based on the amount of condensed water stored, regardless of the temperature of the heat medium such as water flowing into the heat exchanger 4. When the amount of condensed water is sufficient, the fuel cell main body 1 continues to generate power without depending on the temperature of the water flowing into the heat exchanger 4, so that the energy efficiency of the system deteriorates due to repeated stoppage and restart of power generation or cooling fan operation. Can be avoided. If the amount of condensed water is not secured, power generation is stopped.

(Embodiment 3)
In the fuel cell system of the present embodiment, in the fuel cell system of Embodiment 1 or 2, the temperature detector 6 detects a predetermined first temperature or higher, and the amount of condensed water in the condensed water tank 5 is The controller 7 is configured to stop the power generation of the fuel cell main body 1 when it becomes less than the predetermined second water amount.

  The second amount of water means the amount of water in the condensed water tank 5 required for the fuel cell main body 1 to reach the power generation state from the stopped state. When the water vapor cannot be generated by sufficiently cooling and condensing the water vapor contained in the off-gas in the heat exchanger 4, the fuel cell main body 1 is detected even if the controller 7 detects that the amount of water is less than the second water amount. If this power generation is continued, the amount of water required to bring the power generation stop state into the power generation state again will be reduced. In that case, in order to start the fuel cell system next time, city water or the like must be supplied from the outside.

  In the fuel cell system according to the present embodiment, the amount of water in the condensed water tank necessary for the fuel cell main body 1 to change from a stopped state to a power generation state can be secured and stopped, so that there is no need for external water supply. This eliminates the need for a water supply path and a valve for opening and closing the path, thereby avoiding an increase in the number of devices and complication of the system.

(Embodiment 4)
FIG. 2 is a block diagram showing a system configuration in Embodiment 4 of the fuel cell system according to the present invention. The fuel cell system according to the present embodiment further includes a heat medium circulator 8 that is disposed on the heat medium circulation path 3 and circulates the heat medium in the fuel cell system according to the first, second, or third embodiment. Then, when the temperature detector 6 detects the second temperature or higher that is determined in advance, the controller 7 has a larger flow rate of the heat medium flowing through the heat medium circulation path 3 than when the temperature detector 6 is higher than or equal to the second temperature. Thus, the heat medium circulator 8 is controlled.

  With this configuration, in the fuel cell system, when the temperature of the heat medium flowing into the heat exchanger 4 becomes high and there is a possibility that the water necessary for continuing the power generation of the fuel cell body 1 may be insufficient, the temperature of the heat medium is high. The flow rate of the heat medium is made larger than before. Thereby, since the heat exchange efficiency in the heat exchanger 4 can be improved, the production | generation of the condensed water required for the continuation of electric power generation of the fuel cell main body 1 is accelerated | stimulated, and the water collection | recovery performance to the condensed water tank 5 can be improved. it can.

By setting the second temperature to a temperature lower than the first temperature, the operation of improving the water recovery performance can be performed before the condition that the heat exchanger 4 cannot generate condensed water is satisfied. . For example, when 45 ° C. is set as the first temperature and 40 ° C. is set as the second temperature, the fuel cell system of the present invention operates to improve the water recovery performance under the condition between 40 ° C. and 45 ° C. The fuel cell system can be operated for a long time.
Moreover, you may make it comprise by adding the water quantity in the condensed water tank 5 calculated by calculation as a monitoring object of the controller 7. FIG. For example, when the amount of water in the condensed water tank 5 calculated by the controller 7 is lower than the first amount of water and the temperature detected by the temperature detector 6 is equal to or higher than the second temperature, an operation for improving the water recovery performance is performed. You may comprise.

(Embodiment 5)
FIG. 3 is a block diagram showing a system configuration in Embodiment 5 of the fuel cell system according to the present invention.

  The fuel cell system according to the present embodiment further includes an oxidant gas supply device 9 that supplies an oxidant gas to the fuel cell main body 1 in the fuel cell system according to the first, second, or third embodiment. When the temperature detector 6 detects a predetermined second temperature or higher, the oxidant gas supply device 9 is controlled so that the flow rate of the off-oxidant gas is smaller than that at the second temperature or higher. .

  With this configuration, in the fuel cell system, when the temperature of the heat medium flowing into the heat exchanger 4 becomes high and there is a possibility that the water necessary for continuing the power generation of the fuel cell body 1 may be insufficient, the temperature of the heat medium is high. By reducing the flow rate of the off-oxidant gas from before, the water vapor released from the fuel cell system without being cooled and condensed can be reduced, so that it is necessary for the fuel cell main body 1 to continue power generation. The generation of condensed water can be promoted and the water recovery performance to the condensed water tank 5 can be enhanced. The details of the operation for improving the water recovery performance are the same as those in the fourth embodiment, and thus the description thereof is omitted.

  As described above, in the fuel cell system of the present invention, it is not necessary to monitor the amount of water in the condensed water tank with a water level gauge, so that an increase in the number of devices and the complexity of the system can be avoided and simplification is possible.

DESCRIPTION OF SYMBOLS 1 Fuel cell main body 2 Reformer 3 Heat medium circulation path 4 Heat exchanger 5 Condensate tank 6 Temperature detector 7 Controller 8 Heat medium circulator 9 Oxidant gas supply apparatus 10 Air supply path

Claims (5)

A fuel cell body that generates power using a fuel gas and an oxidant gas generated from a reforming reaction between the raw material gas and the condensed water;
A heat medium that exchanges heat with at least one of an off-fuel gas that is a fuel gas discharged from the fuel cell body and an off-oxidant gas that is an oxidant gas discharged from the fuel cell body circulates. A heat medium circulation path;
A temperature detector for detecting the temperature of the heat medium before exchanging heat with the off gas;
A heat exchanger provided in the heat medium circulation path to condense water vapor in the off gas by exchanging heat between the off gas and the heat medium to generate the condensed water;
A condensed water tank for accumulating the condensed water generated in the heat exchanger;
A controller;
With
The controller is
Based on the temperature detected by the temperature detector and the accumulated time for detecting the temperature, the amount of water in the condensed water tank is calculated.
Fuel cell system. The controller is
When the temperature detector detects a predetermined first temperature or higher,
When the condensed water in the condensed water tank is equal to or more than a predetermined first water amount,
Continuing the power generation of the fuel cell body,
The fuel cell system according to claim 1. The controller is
When the temperature detector detects a predetermined first temperature or higher,
When the condensed water in the condensed water tank becomes less than a predetermined second water amount,
Stopping power generation of the fuel cell body,
The fuel cell system according to claim 1 or 2. A heat medium circulator disposed in the heat medium circulation path and circulating the heat medium;
The controller is
In the case where the temperature detector detects a predetermined second temperature or higher,
Before becoming the second temperature or higher,
The fuel cell system according to any one of claims 1 to 3, wherein the heat medium circulator is controlled such that a flow rate of the heat medium flowing through the heat medium circulation path is increased. An oxidant gas supplier for supplying an oxidant gas to the fuel cell body;
The controller is
In the case where the temperature detector detects a predetermined second temperature or higher,
Before becoming the second temperature or higher,
Controlling the oxidant gas supply so that the flow rate of the off-oxidant gas is reduced;
The fuel cell system according to any one of claims 1 to 3.

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