JP2008159461A - Fuel cell device and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell device capable of extending the life of a water supply valve for supplying water to a reformer. <P>SOLUTION: A fuel cell device is equipped with a fuel cell 1, the reformer 4 for forming reformed gas to be supplied to the fuel cell 1, a water tank 10 for storing water for supplying to the reformer 4, a water supply pipe 5 having a water supply valve 6 for supplying water to the water tnak 10, a water pump 11 supplying water stored in the water tank 10 to the reformer 14, a water level detecting device for detecting a water level in the water tank 10, and furthermore equipped with a control part 6 opening the water supply valve 6 when a prescribed time is passed after the water level detecting device detects the water level drop of the water tank 10, and thereby, frequent opening and closing of the water supply valve 6 can be suppressed and the life of the water supply valve 6 is extended. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell device that generates power using a fuel gas generated by steam reforming and an operation method thereof.

  In recent years, as a next-generation energy, a fuel cell in which a fuel cell stack formed by arranging a plurality of fuel cells is housed in a storage container, and a fuel cell in which supplementary notes for operating the fuel cell are housed in an outer case Various devices and their operation methods (systems) have been proposed.

  In this fuel cell power generation, the reformed gas (hydrocarbon fuel) is reformed by a reformer, and the reformed gas (fuel gas) and oxygen-containing gas are supplied to the fuel cell to generate power. Done.

  As a method of reforming a gas to be reformed (hydrocarbon fuel), a steam reforming method in which a reforming reaction is performed using water (steam), a partial oxidation reforming method in which a reforming reaction is performed using oxygen, A combined reforming method (autothermal) in which a reforming reaction is performed using these in combination is known.

  Then, when steam reforming the gas to be reformed (hydrocarbon fuel), in the conventional fuel cell device, water is stored in a water tank by adjusting a water supply valve provided in a water supply pipe. The water is supplied to the reformer by a water pump.

Here, for the purpose of measuring the level of water stored in the water tank, it is known to provide a water level detection device (for example, a water level detection switch or an electrode type sensor) in the water tank. As an example of a fuel cell in which a water detection device is provided in a water tank, a fuel cell using a float switch as a water level detection switch has been proposed (see, for example, Patent Document 1). In such a fuel cell, the float switch detects the amount of water stored in the water tank, opens and closes the water supply valve according to the detected amount of stored water, and is adjusted so that the amount of water stored in the water tank falls within a certain range. .
JP 2006-155982 A

  By the way, for example, in a domestic fuel cell device, since a reduction in size and weight is particularly required, each member constituting a fuel cell device that generates power from a fuel cell using a reformed gas obtained by steam reforming In, for example, it is necessary to downsize a water tank or the like for storing water to be supplied to the reformer.

  Here, when installing a water level detection device in a miniaturized water tank, for example, a method for controlling the water supply valve with a water level detection device that detects only one point of the water level in the water tank, or a water level detection for detecting the upper limit of the water tank A water level detection device that detects the lower limit of the water level of the device and the water tank, and a method of controlling the water supply valve based on the water level of the water tank or a single water level detection device that detects the upper and lower limits of the water level of the water tank. A method for controlling the water supply valve can be considered.

  However, for example, in the case where a water level detection device is provided in a downsized water tank so as to detect the upper and lower limits of the water level of the water tank, the switch is turned on and off with a water level difference of only a few millimeters. There is a problem that the service life of the water supply valve is shortened because the water supply valve frequently opens and closes accordingly.

  In addition, in order to prevent the water supply valve from frequently opening and closing, when trying to widen the difference in water level detected by the water level detection device, the water level detection device, the water tank, and the fuel cell device are enlarged, and the household fuel cell In some cases, the reduction in size and weight required by the apparatus could not be satisfied.

  SUMMARY OF THE INVENTION Therefore, the present invention provides a fuel cell device that can extend the life of a water supply valve for supplying water to a water tank, and that can be adapted particularly to the reduction in size and weight required for household fuel cells. Objective.

  A fuel cell device according to the present invention includes a fuel cell, a reformer that performs steam reforming to generate reformed gas to be supplied to the fuel cell, and water for storing water to be supplied to the reformer. A water tank, a water supply pipe having a water supply valve for supplying water to the water tank, a water pump for supplying water stored in the water tank to the reformer, and detecting a water level in the water tank And a control unit that opens the water supply valve after a predetermined time has elapsed since the water level detection device detected a drop in the water level of the water tank.

  In such a fuel cell device, in a fuel cell device that is required to be downsized, when the water tank is downsized, the water level detecting device is also downsized. When installing a water level detection device to detect the upper and lower limits of the water level, the range of the upper and lower limits of the water level detected by the water level detection device becomes very narrow, and the water level detection device with a water level difference of only a few millimeters Even when the water level detection device has a control unit that opens the water supply valve after a certain period of time has elapsed since the water level detection device detected a decrease in the water level of the water tank, it prevents the water supply valve from opening and closing frequently. The life of the water supply valve can be extended.

  Further, in the fuel cell device of the present invention, the time from when the water level detection device detects a decrease in the water level of the water tank to when the water supply valve is opened is the amount of gas to be reformed supplied to the reformer. It is preferable to set according to the amount.

  That is, the control unit controls the water supply valve to open after a certain time has elapsed since the water level detection device detected the water level drop of the water tank, but the water tank water level drop rate was stored in the water tank. The amount varies depending on the amount of water supplied to the reformer by the water pump, in other words, the amount of gas to be reformed necessary for steam reforming in the reformer.

  Here, according to the amount of gas to be reformed supplied to the reformer, by setting the time until the control unit opens the water supply valve, the reformer corresponding to the amount of gas to be reformed is set. Since the amount of water to be supplied is set, it is possible to prevent the water tank from becoming empty, and the time set according to the amount of gas to be reformed supplied to the reformer has elapsed. By opening the water supply valve later, water can be stored in the water tank.

  Thereby, it can suppress that a water supply valve opens and closes frequently, and can extend the lifetime of a water supply electromagnetic valve.

  In the fuel cell device of the present invention, the water level detection device is preferably a float switch.

  In the present invention, since the water level detection device provided in the water tank is a float switch, the water level detection device can be reduced in size and cost. In addition, the water tank can be reduced in size, and further, the fuel cell device can be reduced in size.

  In the fuel cell device of the present invention, the water level detection device is preferably an electrode type sensor.

  Even when the water level detection device is an electrode type sensor, the water level detection device can be reduced in size and cost. In addition, the water tank can be reduced in size, and further, the fuel cell device can be reduced in size.

  An operation method of a fuel cell device according to the present invention includes a fuel cell, a reformer that performs steam reforming to generate reformed gas supplied to the fuel cell, and water stored in the reformer. A water tank having a water supply valve for supplying water to the water tank, a water pump for supplying water stored in the water tank to the reformer, A method for operating a fuel cell comprising a water level detection device for detecting a water level, wherein the water supply valve is opened after a certain time has elapsed since the water level detection device detected a drop in the water level of the water tank. It is characterized by.

  In such an operation method of the fuel cell device, when the water tank and the water level detection device are downsized and the water level detection device is provided so as to detect the upper limit and the lower limit of the water level of the water tank, only a few water level detection devices are provided. Even when operating with a water level difference of about millimeters, the water supply valve opens and closes frequently since the water supply valve is opened after a certain period of time has elapsed since the water level detection device detected a drop in the water level of the water tank. This can be suppressed, and the life of the water supply valve can be extended.

  The present invention includes a control unit that opens a water supply valve after a predetermined time has elapsed since a water level detection device provided in a water tank detects a decrease in the water level of the water tank in a fuel cell device that is required to be downsized. Therefore, it is possible to provide a fuel cell device and an operation method thereof that can suppress frequent opening and closing of the water supply valve and can extend the life of the water supply valve.

  FIG. 1 is a configuration diagram showing an example of the configuration of the fuel cell device of the present invention. The fuel cell device of the present invention includes a power generation unit that generates power, a hot water storage unit that stores hot water after heat exchange, and a circulation pipe that circulates water between these units.

  A fuel cell apparatus shown in FIG. 1 includes a fuel cell 1, a reformed gas supply means 2 for supplying a gas to be reformed such as natural gas, and an oxygen-containing gas supply means 3 for supplying an oxygen-containing gas to the fuel cell 1. A reformer 4 for steam reforming with fuel gas and steam is provided.

  Here, the water supply means X which is a means for supplying pure water to the reformer 4 includes a water supply pipe 5, a water supply valve 6 provided in the water supply pipe 5 for adjusting water supplied from the water supply pipe 5, and an activated carbon filter 7. , Reverse osmosis membrane 8 (hereinafter referred to as RO membrane), ion exchange resin 9, water tank 10, and water pump 11. The configuration of these water supply means X will be described later.

  The fuel cell 1, the reformed gas supply device 2, the oxygen-containing gas supply means 3, the reformer 4, and the water supply means X constitute a main power generation unit.

  Further, in addition to the main power generation unit described above, a power conditioner 12 for switching the DC power generated by the fuel cell 1 to AC power and supplying it to an external load, exhaust gas (exhaust heat) generated by the power generation of the fuel cell 1 Heat exchanger 13 for exchanging heat with water, outlet water temperature sensor 15 for measuring the temperature of water (circulated water flow) provided at the outlet of heat exchanger 13 and flowing through the outlet of heat exchanger 13, and circulating water The power generation unit is configured by the circulation pump 16 for controlling the operation and the control unit 14 for controlling the operation of the circulation pump 16.

  The hot water storage unit is constituted by a hot water storage tank 18 for storing hot water after heat exchange.

  Furthermore, a circulation pipe 17 for circulating water between the heat exchanger 13 and the hot water storage tank 18 is provided, and the fuel cell device is configured by combining the power generation unit, the hot water storage unit, and the circulation pipe 17.

  In addition, the arrow in a figure shows the flow direction of fuel gas, oxygen-containing gas, and water, and a dotted line is a main signal path | route transmitted from a control part, or a main signal transmitted from a control part. The route is shown. The same components are denoted by the same reference numerals, and so on. Further, although not shown, a to-be-reformed gas humidifier for humidifying the to-be-reformed gas may be provided between the to-be-reformed gas supply means 2 and the reformer 4.

  Various types of fuel cells are known as the fuel cell 1, but a solid oxide fuel cell can be used to reduce the size of the fuel cell. Thereby, in addition to the fuel cell, auxiliary machinery necessary for the operation of the fuel cell can be reduced in size, and the fuel cell device can be reduced in size. At the same time, it is possible to perform a load following operation that follows a fluctuating load required for a household fuel cell.

  Here, the operation method of the fuel cell apparatus of the present invention will be described using the fuel cell apparatus shown in FIG.

  The water (pure water) used in the reformer 4 for obtaining the reformed gas used for power generation of the fuel cell 1 is opened by the water supply valve 6 constituting the water supply means X, and the activated carbon filter is passed through the water supply pipe 5. 7 is supplied with water. The water that has passed through the activated carbon filter 7 subsequently passes through the RO membrane 8. The water that has passed through the RO membrane 8 is subsequently passed through the ion exchange resin 9 to produce pure water. Pure water generated by passing the ion exchange resin 9 is stored in the water tank 10 and supplied to the reformer 4 by the water pump 11.

  In FIG. 1, the activated carbon filter 7, the RO membrane 8, the ion exchange resin 9, and the water tank 10 are arranged in this order from the water supply valve 6 to the water pump 11, but for example, the order of the ion exchange resin 9 and the water tank 10. Can be reversed. Thereby, the water required for the reformer 4 can be rapidly supplied, and the water responsiveness to the reformer 4 can be improved.

  In the reformer 4, steam reforming is performed using the pure water supplied by the water pump 11 and the reformed gas supplied from the reformed gas supply means 2. The reformed gas (fuel gas) generated in the reformer 4 is sent to the fuel cell 1 and reacts with the oxygen-containing gas supplied from the oxygen-containing gas supply means 3 to generate power in the fuel cell 1. It is. The electric power generated by the power generation of the fuel cell 1 is supplied to an external load through the power conditioner 12.

  On the other hand, the exhaust gas (exhaust heat) generated by the power generation of the fuel cell 1 is mainly used to increase or maintain the temperature of the fuel cell 1, but the surplus exhaust gas is supplied from the fuel cell 1 to the heat exchanger 13. Is done.

  The exhaust gas supplied to the heat exchanger 13 is heat-exchanged with water circulating (circulating) in the heat exchanger 13. The heat-exchanged water (hot water) is circulated through the circulation pipe 17 and stored in the hot water storage tank 18.

  Here, the water stored in the water tank 10 is supplied to the reformer 4 by the water pump 11 and is supplied by opening the water supply valve 6 so that the water level of the water tank 10 fluctuates. To do.

  Therefore, a water level detection device is provided in the water tank 10, and the water level information of the water tank 10 is transmitted to the control unit 14 by the water level detection device, and the control unit opens and closes the water supply valve 6 based on the water level information. The water storage amount of 10 is adjusted to be within a certain range. Here, examples of such a water level detection device include a float switch and an electrode type sensor.

  FIG. 2 shows the members constituting the water supply means X and the control unit 14 in an extracted manner. (A) shows the case where the float switch 19 is used as the water level detection device, and (b) shows the water level detection. The case where the electrode type sensor 20 is used as an apparatus is shown. In addition, in (a), the float switch 19 which can detect the upper limit water level and the lower limit water level of the water level of the water tank 10 with one float switch 19 is shown.

  In FIG. 2, the water level information of the water tank 10 is transmitted to the control unit 14 by the float switch 19 and the electrode type sensor 20, and a signal is transmitted from the control unit 14 to open or close the water supply valve 6 based on the water level information. . Thereby, the water level of the water tank 10 is controlled to be within a certain range.

  By the way, since the fuel cell device for home use is particularly required to be reduced in size and weight, each member constituting the fuel cell device is also reduced in size. As a result, the water tank 10 and the water level detection device are also downsized.

  Here, as the water tank 10 is downsized, the water level detection device is downsized, and when the water level detection device is provided so as to detect the upper limit water level and the lower limit water level of the water tank 10, the water level of the water tank 10 is detected. In doing so, the range for measuring the upper and lower water levels detected by the water level detection device becomes very narrow. For example, the water level detection device operates with a water level difference of only a few millimeters, and the water supply valve 6 is frequently opened and closed accordingly. There is a case.

  Specifically, when water is supplied from the water tank 10 to the reformer 4 by the water pump 11, the water level detection device detects the lower limit water level and the water supply valve 6 is opened, and the water supply valve 6 is opened and water is supplied. When the water level of the tank 10 rises, the water level detection device detects the upper limit water level and closes the water supply valve 6. And when this water level detection apparatus is reduced in size and the range which measures an upper limit water level and a lower limit water level is very narrow, the water supply valve 6 will repeat opening and closing frequently.

  Therefore, in the present invention, in order to extend the life of the water supply valve 6, the control unit 14 opens the water supply valve 6 after a certain period of time has elapsed after the water level detection device detects a decrease in the water level of the water tank 10. And

  Specifically, the control of the water supply valve 6 will be described with reference to the configuration of FIG. 2A. When the water level of the water tank 10 is lowered, the float is lowered along with the lowering of the water surface and is provided in the float switch 19. The switch is turned on (that is, the water level of the water tank 10 is lowered). Here, information that the switch provided in the float switch 19 is turned on is transmitted to the control unit 14, and a signal for opening the water supply valve is transmitted to the water supply valve 6 after a predetermined time has elapsed. When the water supply valve 6 is opened, the water supplied from the water supply valve 6 is stored in the water tank 10 through the activated carbon filter 7, the RO membrane 8, and the ion exchange resin 9. Then, as the water surface of the water tank 10 rises, the float floats, and the switch provided in the float switch 19 is turned off (that is, the water tank 10 is full). Then, information that the switch provided in the float switch 19 is turned off is transmitted to the control unit 14, and a signal for closing the water supply valve 6 is transmitted from the control unit 14.

  Thereby, it can suppress that the water supply valve 6 opens and closes frequently, and the lifetime of the water supply valve 6 can be lengthened.

  In addition, after the water level detection device detects a decrease in the water level of the water tank 10 and a certain time has elapsed, the type of the water level detection device, the size of the water tank 10, and the gas to be reformed supplied to the reformer It can be set appropriately according to the amount of

  Further, in the present invention, the water supply valve 6 is opened and water is supplied to the water tank 10 after a certain period of time has elapsed since the water level detection device has detected a drop in the water level of the water tank 10. It is not preferable that the water tank 10 becomes empty after a lapse of time. Therefore, the fixed time is preferably the time until the water tank 10 becomes empty at the longest. Moreover, it is preferable that the fixed time is a time until the amount of water remaining in the water tank 10 when the water level detection device detects a drop in water level becomes half to ¼. Thereby, it can prevent that a water tank becomes empty, and can suppress that the water supply valve 6 opens and closes frequently.

  Here, the rate at which the water level of the water tank 10 decreases is the amount of water stored in the water tank 10 supplied from the water tank 10 to the reformer 4 by the water pump 11, in other words, at the reformer 4. It varies depending on the amount of gas to be reformed necessary for steam reforming. Therefore, the time from when the water level detection device detects a drop in the water level of the water tank 10 until the water supply valve 6 is opened can be set according to the amount of the reformed gas supplied to the reformer 4. preferable.

  Therefore, for example, when the amount of water in the water tank 10 (the remaining amount of water in the water tank 10) when the water level detection device detects a drop in the water level in the water tank 10 is 300 mL, the reformer 4 supplied to the reformer 4 When the amount of quality gas is 3 L / min, the amount of water supplied to the reformer 4 by the water pump 11 is 7 mL / min. It can be set to less than 40 minutes after the water level drop is detected, and is preferably set to 20 to 30 minutes in consideration of the opening / closing frequency of the water supply valve 6 and the amount of water stored in the water tank 10.

  The float switch 19 that is the water level detection device shown in FIG. 2A only needs to be able to detect the water level of the water tank 10. In this case, one float switch that detects the water level at one point of the water tank 10 is provided. Can be provided. Furthermore, it is preferable that the upper limit and the lower limit of the water level of the water tank 10 can be detected. In this case, for example, a float switch that detects the upper limit of the water level of the water tank 10 according to the size of the water tank 10 and the lower limit of the water level When the water tank 10 is further downsized, it is preferable to provide a float switch that can detect the upper limit and the lower limit of the water level with a single float switch.

  Thereby, while being able to make a water level detection apparatus small and cheap, also in the water tank 10 reduced in size, the water level of the water tank 10 can be detected.

  Even when the water level detection device is an electrode type sensor (hereinafter referred to as an electrode sensor) 20, the water level detection device can be reduced in size and cost.

  2B shows a case where two electrodes are provided in the electrode sensor, but three or more electrodes may be used in accordance with the size of the water tank 10. Here, when three electrodes are provided, the upper limit and the lower limit of the water level of the water tank 10 can be detected by one electrode sensor. In this case, the lengths of the three electrodes can be appropriately changed in accordance with the portion where the upper limit and the lower limit of the water level of the water tank 10 are measured.

  When the electrode sensor has two or more electrodes, the electromagnetic sensor 20 can measure the conductivity of the water stored in the water tank 10 together. In this case, it can be seen that not only the water level stored in the water tank 10 but also the water supply means X such as the activated carbon filter 7, the RO membrane 8, and the ion exchange resin 10 are broken.

  That is, in this case, as the water level of the water tank 10 decreases, the conductivity of the water tank 10 also decreases. However, if the conductivity does not decrease or shows an abnormal value, the water supply means X such as the activated carbon filter 7 It turns out that it is out of order. On the contrary, it can be seen that the water supply means X such as the activated carbon filter 7 is broken even when the conductivity does not increase or shows an abnormal value as the water level of the water tank 10 increases.

  Although the present invention has been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and improvements can be made without departing from the scope of the present invention.

  For example, as the water supplied to the water supply means X, rain water, well water, or the like can be used. In this case, a filter, a UV lamp, or the like other than those described above can be provided in order to remove more various impurities contained in rainwater, well water, and the like.

  The water level detection device may be any device that can measure the water level of the water tank 10 and can be miniaturized. For example, a pressure sensor or an optical sensor such as an LED can be used.

  Moreover, when using an electrode-type sensor, it is also possible to provide an alarm device that issues an alarm when the conductivity of the water stored in the water tank 10 shows an abnormal value.

It is a block diagram which shows the structure of the fuel cell apparatus of this invention. It is a block diagram which shows a part of structure of the fuel cell apparatus of this invention, and shows the structure of the member relevant to the water supply means X.

Explanation of symbols

1: Fuel cell 2: Fuel supply device 3: Oxygen-containing gas supply device 4: Reformer 5: Water supply pipe 6: Water supply valve 7: Activated carbon filter 8: RO membrane 9: Ion exchange resin 10: Water tank 11: Water Pump 14: Control unit 19: Float switch 20: Electrode sensor

Claims (5)

A fuel cell, a reformer for generating reformed gas to be supplied to the fuel cell, a water tank for storing water to be supplied to the reformer, and for supplying water to the water tank A water supply pipe having a water supply valve, a water pump for supplying water stored in the water tank to the reformer, a water level detection device for detecting the water level in the water tank, and the water level detection device A fuel cell device comprising: a control unit that opens the water supply valve after a predetermined time has elapsed after detecting a drop in the water level of the water tank. The time from when the water level detection device detects a drop in the water level of the water tank to when the water supply valve opens is set according to the amount of the reformed gas supplied to the reformer. The fuel cell device according to claim 1, wherein The fuel cell device according to claim 1 or 2, wherein the water level detection device is a float switch. 3. The fuel cell device according to claim 1, wherein the water level detection device is an electrode type sensor. A fuel cell, a reformer for generating reformed gas to be supplied to the fuel cell, a water tank for storing water to be supplied to the reformer, and for supplying water to the water tank A fuel cell comprising: a water supply pipe having a water supply valve; a water pump for supplying water stored in the water tank to the reformer; and a water level detection device for detecting a water level in the water tank. A method for operating a fuel cell device, comprising: opening the water supply valve after a predetermined time has elapsed since the water level detection device detected a drop in the water level of the water tank.

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