JP2007265669A - Leak detecting method in fuel cell power generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leak detecting method in a fuel cell power generation system capable of detecting a minute leak in a normal operation without relying on periodic inspection. <P>SOLUTION: The fuel cell power generation system is provided with a fuel cell body, and a dwelling means keeping the inner pressure of the fuel cell body and/or a fuel reforming device (hereinafter called objects for dwelling) at pressure higher than atmospheric pressure. The dwelling means is constituted of a sealing means for sealing the inside of the objects for dwelling, a dwelling gas supply source supplying the dwelling objects with dwelling gas, and a dwelling gas supply channel equipped with a switching valve on the way. In the leak detecting method of the fuel cell power generation system, in the case that the inner pressure of the objects for dwelling gets below a given value at the stoppage of operation, the switching valve is opened to supply the dwelling gas to the objects for dwelling, and then closing the switching valve to keep them at pressure higher than the atmospheric pressure. A leak is determined to occur in the case that number of times per hour of opening operations of the switching valve for supplying the fuel cell with dwelling gas exceeds a given number of times. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a leak detection method in a fuel cell power generation system.

  A fuel cell power generation system includes a fuel reformer that generates hydrogen-rich reformed gas from raw fuel, and a fuel cell body that generates electricity by chemically reacting the reformed gas and air. While supplying the hydrogen-rich reformed gas to the electrode and supplying air containing oxygen as an oxidant to the air electrode, DC power generation is performed, and usually the obtained DC current is converted into AC by an inverter and used. At the same time, exhaust heat from the fuel cell body is recovered and used.

  In this fuel cell power generation system, when the atmosphere enters the fuel cell main body from the outside when the operation is stopped, the activity of the catalyst used for the electrode is lost due to oxidation or the like, and water vapor in the air condenses in the fuel cell main body. There is a problem that the temperature of the fuel cell body decreases and the internal pressure of the fuel cell body becomes a negative pressure (a pressure lower than the external pressure), so that the fuel cell body is damaged. Thus, a system has been developed that prevents the internal pressure of the fuel cell main body from becoming negative when the operation is stopped (see, for example, Patent Document 1).

  The pressure holding means is composed mainly of a sealing means for sealing the inside of the fuel cell body, a pressure holding gas supply source, and a pressure holding gas supply path. After opening the on-off valve provided on the fuel cell and supplying the holding gas from the holding gas supply source to the fuel cell main body at a pressure higher than the external atmospheric pressure, the on-off valve is closed to set the internal pressure of the fuel cell main body to a positive pressure (external pressure). When the internal pressure of the fuel cell body falls below a predetermined value over time, the pressure-holding gas is again supplied to the fuel cell body and held at a positive pressure as described above. . This solved the above-described problem.

By the way, in such a conventional fuel cell power generation system, the leak of the flow path of the reformed gas, air, etc. of the fuel cell has been discovered by performing periodic inspection. Large leaks that affect normal power generation operation are discovered without inspection, but minute leaks are difficult to detect unless the periodic inspection is performed. If a leak occurs, the power generation efficiency is poor, and there is a possibility that it will develop into a larger leak. there were. In addition, in periodic inspections, it is necessary to inspect for leaks as inspection items, and the number of inspection items increases, which complicates work.
JP 2002-329520 A

  The present invention has been made in view of the above points, and an object of the present invention is to provide a leak detection method in a fuel cell power generation system that can detect a minute leak in a normal operation without performing periodic inspection. It is to provide.

  In order to solve the above problems, an invention according to claim 1 is directed to a fuel reformer that reforms a raw fuel gas to generate a hydrogen-rich reformed gas, and a chemical reaction between the reformed gas and air. A fuel cell main body for generating electric power, and a pressure holding means for holding the internal pressure of the fuel cell main body at a pressure higher than the external pressure when the fuel cell power generation is stopped, and the pressure holding means is disposed inside the fuel cell main body. A sealing means comprising a shut-off valve for sealing, a pressure holding gas supply source for supplying pressure holding gas to the fuel cell main body at a pressure higher than the external pressure, and a halfway from the pressure holding gas supply source to the fuel cell main body The pressure holding gas supply passage having an on / off valve is configured to close the fuel cell main body when the operation is stopped. When the internal pressure of the fuel cell main body becomes a predetermined value or less, the on / off valve is opened to hold the pressure holding gas. After supplying to the fuel cell body, close the open / close valve A leak detection method in a fuel cell power generation system that holds pressure at a pressure higher than the external pressure, and the number of opening operations of the on-off valve for supplying pressure holding gas to the fuel cell is greater than or equal to a predetermined number of times. In this case, it is determined that a leak has occurred.

  According to such a method, it is possible to easily detect a minute leak that hardly influences in a normal power generation operation in a normal operation, and it is possible to prevent a decrease in power generation efficiency due to the leak and to repair it. It is possible to eliminate such a situation that the power generation operation is suspended for a long period of time for preparation and work.

  In order to solve the above-mentioned problem, the invention according to claim 2 is directed to a fuel reformer that reforms a raw fuel gas to generate a hydrogen-rich reformed gas, and a chemical reaction between the reformed gas and air. A fuel cell main body that generates electricity by reacting; and a pressure holding means that holds the internal pressure of the fuel reformer at a pressure higher than the external pressure when the fuel cell power generation is stopped. A sealing means comprising a shut-off valve for sealing the inside of the gas storage device, a pressure-holding gas supply source for supplying pressure-holding gas to the fuel reformer at a pressure higher than the external pressure, and a fuel modification from the pressure-holding gas supply source. When the internal pressure of the fuel reformer becomes a predetermined value or less as a state in which the inside of the fuel reformer is sealed when the operation is stopped Open / close after opening the on-off valve and supplying the gas for holding pressure to the fuel reformer Is a leak detection method in a fuel cell power generation system in which the pressure is maintained at a pressure higher than the external pressure, and the number of opening operations of the on-off valve for supplying the pressure holding gas to the fuel cell is greater than or equal to a predetermined number of times. In this case, it is determined that a leak has occurred.

  According to such a method, it is possible to easily detect a minute leak that hardly influences in a normal power generation operation in a normal operation, and it is possible to prevent a decrease in power generation efficiency due to the leak and to repair it. It is possible to eliminate such a situation that the power generation operation is suspended for a long period of time for preparation and work.

  In the present invention, it is possible to easily detect a minute leak that has almost no effect in a normal power generation operation in a normal operation, and to prevent a decrease in power generation efficiency due to the leak. It is not necessary to stop the power generation operation for a long time for repair preparation and work, and it is possible to keep down the loss due to the suspension of power generation operation and the cost of repair . In addition, it is not necessary to inspect for leaks during regular inspections, and the number of inspection items can be reduced to facilitate work. In this case, since it is only necessary to count the number of times of opening and closing the on-off valve, it is not necessary to provide a device for detecting a leak, and this can be achieved at low cost.

  Hereinafter, an embodiment of the present invention will be described. First, the basic configuration of the fuel cell power generation system will be described. FIG. 1 shows an overall schematic configuration diagram of the fuel cell power generation system, and FIG. 2 shows an explanatory diagram of the fuel cell main body.

  A fuel cell power generation system includes a fuel reformer that generates reformed gas from raw fuel, and a fuel cell main body that generates power by chemically reacting the reformed gas and an oxidant as essential components. An inverter that converts the direct current generated into alternating current, and exhaust heat recovery means (such as a condenser) that recovers exhaust heat from the fuel cell main body by cooling water that cools the fuel cell main body. In this embodiment, the polymer electrolyte fuel cell will be described, but is not particularly limited.

  As shown in FIG. 1, the fuel reformer 1 uses gas such as city gas or natural gas as raw fuel, and heats the raw fuel a and water vapor b to a high temperature by a burner 11 of heating means in the presence of a catalyst. In this way, the reformed gas is reformed into a hydrogen-rich reformed gas c. As shown in FIG. 2, the fuel cell main body 2 includes an air electrode 21 and a flow path 22 on the air electrode 21 side, a fuel electrode 23 and a flow path 24 on the fuel electrode 23 side, and the flow paths 22 and 24. The intervening electrolyte membrane 25 constitutes a cell, and a cell stack is constituted by stacking a plurality of cells via a separator (not shown). However, only one cell is shown in FIG. Hydrogen in the reformed gas c flowing in the flow path 24 on the fuel electrode 23 side is ionized into hydrogen ions and electrons by the catalyst provided in the fuel electrode 23, and a current i generated when the generated electrons flow to the air electrode 21 is generated. Used as electric power. Reference numeral 3 in the figure denotes an inverter. Hydrogen ions generated on the fuel electrode 23 side move to the flow path 22 on the air electrode 21 side through which the air d flows through the electrolyte membrane 25, accept electrons in the flow path 22 on the air electrode 21 side, and serve as an oxidizing agent. Water is produced by a chemical reaction with oxygen in the air d. Although not shown, cooling water is flowed through the cell stack to cool the fuel cell body 2 and the exhaust heat is recovered and used.

  Further, the unburned gas e containing hydrogen that has not been used for power generation and is discharged from the flow path 24 on the fuel electrode 23 side of the fuel cell body 2 is used as fuel for the burner 11 of the heating means of the fuel reformer 1. Is done. The exhaust gas f of the burner of the fuel reformer 1 and the exhaust g discharged from the flow path 22 on the air electrode 21 side of the fuel cell main body 2 are recovered by the condenser 4 and used as exhaust heat. The collected condensed water h is used as steam b by the steam generator 6 or as cooling water for the fuel cell main body 2.

  Here, the details of the cooling means and the use of the cooling water are not particularly limited. Although not specifically described, a CO converter for performing CO conversion of the reformed gas c generated by the fuel reforming means, a CO remover for removing CO, the reformed gas c supplied to the fuel cell main body 2, There is no particular limitation on the details and presence of devices such as a humidifier that humidifies the air d.

  The fuel device power generation system includes a pressure holding means 5 that holds the internal pressure of the fuel cell main body 2 at a pressure higher than the external pressure when the operation of the fuel cell power generation is stopped. The pressure holding means 5 includes a sealing means for sealing the inside of the fuel cell main body 2, a pressure holding gas supply source 51 for supplying the pressure holding gas to the fuel cell main body 2 at a pressure higher than the external pressure, and the pressure holding gas supply source. The pressure holding gas supply path 53 is provided with an on-off valve 52 in the middle of the flow path from 51 to the fuel cell body 2 to the fuel cell body 2. As the holding gas, a stable gas such as nitrogen gas, methane gas, or city gas is preferably used. The sealing means is a flow path connected to the fuel cell body 2, that is, a supply / exhaust flow path to the flow path 24 on the fuel electrode 23 side of the fuel cell body 2 and a supply / exhaust flow to the flow path 22 on the air electrode 21 side. The fuel cell main body 2 can be sealed by closing a stop valve and an on-off valve 52 described later.

  The pressure-holding gas supply source 51 includes a high-pressure cylinder, a tank, or the like that stores the pressure-holding gas, and is usually supplied to the pressure-holding gas supply path 53 by reducing the pressure to a predetermined pressure via a pressure reducing valve (not shown). The The pressure-holding gas supply path 53 is connected to the flow path of the fuel cell main body 2, and an open / close valve 52 formed of an electromagnetic valve is provided in the middle. Hereinafter, the operation when the fuel cell power generation is stopped will be described.

  First, the shutoff valve is closed to close the flow path of the fuel cell main body 2. Next, the on-off valve 52 is opened, and the holding pressure gas is supplied into the fuel cell main body 2 at a pressure higher than the external pressure (atmospheric pressure) (hereinafter referred to as a positive pressure), and the on-off valve 52 is closed (this is a holding operation). ). Thereby, the internal pressure in the fuel cell main body 2 is held at a positive pressure by the holding pressure gas. Even if no leak as a malfunction has occurred, the temperature decreases with time and the internal pressure of the fuel cell body 2 decreases, so this pressure decrease occurs. When the internal pressure of the fuel cell main body 2 falls below a predetermined value, the above-described pressure holding operation is performed again to increase the internal pressure of the fuel cell main body 2 to the pressure at the start of pressure holding. The main body 2 is protected. The opening and closing of these valves and the control of other devices are controlled by a control unit (not shown).

  When the fuel cell main body 2 is normal, as shown in FIG. 3, the pressure holding operation per time is stable at a predetermined number of times. However, if the fuel cell main body 2 has leaked as a problem, As shown in FIG. 4, the number of pressure holding operations per time is increased from the predetermined number. “A” in the figure indicates the time when the on-off valve for the pressure holding operation is opened. Therefore, when the pressure holding operation per time exceeds a predetermined number of times, it is determined that a leak as a malfunction has occurred, and the leak is detected. Detection of leak, that is, counting of the number of times of pressure holding operation and determination of whether or not the number of times is equal to or greater than a predetermined number is performed by the control unit, and when leak is detected, it is notified by voice, light, or other methods.

  By adopting the leak detection method as described above, it is possible to easily detect a minute leak that hardly affects the normal power generation operation in a normal operation, and to prevent a decrease in power generation efficiency due to the leak. Can be detected at an early minute stage, and there is no need to suspend power generation for a long period of time to prepare for and work on repairs. In this case, it is only necessary to count the number of times of opening / closing of the on-off valve 52. In particular, it is not necessary to provide a device for detecting a leak and can be achieved at low cost. In addition, it is not necessary to inspect for leaks during periodic inspections, and the number of inspection items can be reduced to facilitate work, thereby reducing costs.

  Further, in the above embodiment shown in FIG. 1, the object of pressure holding by the pressure holding means 5 is in the fuel cell main body 2, and the flow path of the reformed gas c, the flow path of the air d, the fuel reaching the fuel cell main body 2 The inside is sealed by a not-shown stop valve provided in the middle of the flow path of unburned gas e from the battery body 2 and the flow path of the exhaust g, and the sealed portion is held in pressure. As shown, the fuel reformer 1 may be a pressure holding target. By a closing valve provided in the middle of the flow path of the raw fuel a leading to the fuel reformer 1, the flow path of the unburned gas e, the flow path of the reformed gas c from the fuel reformer 1, and the flow path of the exhaust gas f A sealing means for sealing the inside, a pressure-holding gas supply source 51 for supplying pressure-holding gas to the casing at a pressure higher than the external pressure, and an on-off valve 52 in the middle are provided from the pressure-holding gas supply source 51 to the casing. And a pressure holding means 5 constituted by a pressure holding gas supply path 53.

  The pressure holding operation and leak detection in this case are the same as in the above embodiment, and by doing so, the same effect as described above can be obtained even when the fuel reformer 1 is a pressure holding target. Is obtained. Moreover, even if the fuel cell main body 2 and the fuel reforming apparatus 1 are intended for holding pressure, the same effect can be obtained.

1 is an overall configuration diagram of a fuel cell power generation system. It is a block diagram of a fuel cell main body same as the above. It is a time-pressure relationship diagram which shows the operation | movement condition of an on-off valve when the leak has not generate | occur | produced. It is a time-pressure relationship diagram which shows the operation | movement condition of an on-off valve when the leak has generate | occur | produced. It is a whole block diagram of other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel reformer 11 Burner of heating means 2 Fuel cell main body 3 Inverter 4 Condenser 5 Holding pressure means 51 Holding pressure gas supply source 52 On-off valve 53 Holding pressure gas supply path 6 Steam generator a Raw fuel c Reformed gas d air

Claims (2)

  A fuel reformer that reforms the raw fuel gas to produce a hydrogen-rich reformed gas, a fuel cell main body that generates electricity by chemically reacting the reformed gas and air, and a suspension of fuel cell power generation Pressure holding means for holding the internal pressure of the fuel cell body at a pressure higher than the external pressure, and the pressure holding means includes a sealing means comprising a shut-off valve for sealing the inside of the fuel cell body, and a pressure holding gas. A pressure-holding gas supply source that supplies the fuel cell body with a pressure higher than the external pressure, and a pressure-holding gas supply path that includes an on-off valve from the pressure-holding gas supply source to the fuel cell body. When the internal pressure of the fuel cell body falls below a predetermined value with the fuel cell main body sealed when the operation is stopped, the on-off valve is opened and the holding gas is supplied to the fuel cell main body. Fuel cell power generation with higher pressure A method for detecting a leak in a stem, wherein a determination is made that a leak has occurred when the number of opening operations of the on-off valve for supplying the holding pressure gas to the fuel cell exceeds a predetermined number of times. A leak detection method in a fuel cell power generation system. A fuel reformer that reforms the raw fuel gas to produce a hydrogen-rich reformed gas, a fuel cell main body that generates electricity by chemically reacting the reformed gas and air, and a suspension of fuel cell power generation Pressure holding means for holding the internal pressure of the fuel reformer at a pressure higher than the external pressure, and the pressure holding means includes a sealing means including a shut-off valve for sealing the inside of the fuel reformer. A pressure-holding gas supply source for supplying the pressure gas to the fuel reformer at a pressure higher than the external pressure, and a pressure-holding gas supply path having an on-off valve from the pressure-holding gas supply source to the fuel reformer. After the fuel reformer is sealed when the operation is stopped, the on-off valve is opened and the holding pressure gas is supplied to the fuel reformer when the internal pressure of the fuel reformer falls below a predetermined value. Fuel cell power generation that closes the on-off valve and keeps the pressure higher than the outside A method for detecting a leak in a stem, wherein a determination is made that a leak has occurred when the number of opening operations of the on-off valve for supplying the holding pressure gas to the fuel cell exceeds a predetermined number of times. A leak detection method in a fuel cell power generation system.

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