JP5105926B2 - Fuel cell device - Google Patents

Description

  The present invention relates to a fuel cell that generates power by being supplied with a fuel gas and an oxygen-containing gas, a reformer that performs steam reforming to supply the fuel gas to the fuel cell, and water to the reformer The present invention relates to a fuel cell device including a shot pump, raw fuel supply means for supplying raw fuel to a reformer, and a control unit that controls the shot pump.

  In recent years, various fuel cells in which a fuel cell stack formed by arranging a plurality of fuel cells is accommodated in a storage container and its operation method have been proposed as next-generation energy.

  Hydrogen gas is used as a fuel gas used for power generation in this fuel cell, hydrogen gas and an oxygen-containing gas (usually air) are supplied to the fuel cell, and the oxygen-containing gas is supplied to the oxygen electrode in the fuel cell. And the hydrogen gas is brought into contact with the fuel electrode in the fuel battery cell to cause a predetermined electrode reaction to generate electric power.

  As a method for generating hydrogen gas, which is a fuel gas, for example, a hydrocarbon such as natural gas is supplied from a raw fuel supply means to a reformer, and water vapor is supplied from a water supply means, so that natural gas and water vapor are A steam reforming method or the like in which hydrogen is produced by reacting the above is known.

  Here, the water supplied to the reformer is preferably pure water that has little influence on the reformer and the fuel cell. Therefore, for example, when water supplied from tap water or the like is supplied to the reformer by the water supply means, it is supplied to the reformer after passing through various filters in order to remove impurities contained in tap water or the like. It is preferable that such a water supply method is conventionally known (see, for example, Patent Document 1).

  Moreover, since the amount of pure water used for steam reforming in a reformer is small in a household fuel cell, a shot pump is used as a pump that can supply a small amount of pure water (for example, Patent Document 2). 3).

In Patent Document 3, a shot pump is used as a pump for supplying fuel, and the number of shots of the shot pump is counted and controlled by a control unit, and the supply amount is theoretically controlled.
JP 2005-129334 A JP 2006-258057 A JP 2006-294471 A

  Although the shot pump is used when supplying a small amount of water, there is a possibility that dust may be clogged or a phenomenon in which air cannot enter the shot pump and push out the water, that is, so-called air biting may occur. Garbage may be present in the supply pipe from the time of manufacture, for example, and air may be generated in the water treatment device.

  In the case of such clogging or air biting, the shot pump may actually perform shots with the number of shots from the control unit, even though a command for the number of shots per fixed time is issued from the control unit. The water supply actually flowing is less than the theoretical water supply for the shot number command (defined by a value obtained by multiplying the number of shots per predetermined time by the command by the amount of water per shot) and accurate. There was a problem that a sufficient amount of water supply could not be obtained. As a result, there is a problem of affecting the optimum operation of the fuel cell.

In particular, recent fuel cells for household use have a power generation amount of 1 kW or less, and are required to quickly follow the household load and generate an optimal amount of power. Therefore, it is necessary to supply an optimal amount of fuel gas (H ₂ ) to the fuel cell, which requires accurate control of the amount of water supplied to the reformer.

  When air biting occurs, the shot pump is controlled so as to increase the number of shots per unit time, for example, the maximum number of shots. For example, water can be forced out together.

  However, even if the number of shots of the shot pump is increased, the air biting is not canceled immediately, and it is normal that a predetermined time is required until the air biting or the like is completely canceled and the air is not bitten. . Even when it is determined that the shot pump is in a steady state (determined by the control unit or the like), in order to improve the water supply stability by the shot pump, even after it is determined that the shot pump is in a steady state, It is usual to control the number of shots to increase.

  Therefore, when the number of shots of the shot pump is increased, the amount of water supplied to the reformer increases more than usual, and when excess water is supplied to the reformer in this way, the water vapor partial pressure increases. In addition, there is a possibility that the power generation efficiency of the fuel cell is greatly reduced due to a significant change in the temperature balance.

  An object of the present invention is to provide a fuel cell device capable of suppressing problems associated with an increase in the amount of water supplied to a reformer even when the number of shots of a shot pump is increased.

A fuel cell apparatus according to the present invention includes a fuel cell that generates electric power by being supplied with a fuel gas and an oxygen-containing gas, and a reformer that performs steam reforming by supplying raw fuel and water to supply the fuel gas to the fuel cell. A shot pump for supplying water to the reformer, a raw fuel supply means for supplying raw fuel to the reformer, a controller for controlling the shot pump, and an intermittent flow of water from the shot pump. A water flow sensor that senses and detects the actual number of shots from the shot pump, and the actual number of shots detected by the water flow sensor is less than the number of shots commanded per unit time by the control unit If the control unit, the number of shots command to increase the number of shots per unit time to control so as to enter into the shot pump, increasing the raw fuel supply amount to the reformer And controlling the Kihara fuel supply means so as to.

  In such a fuel cell device, the control unit increases the number of shots per unit time of the shot pump, and water to the reformer by the shot pump (when supplied to the reformer, it becomes steam) The control unit controls the raw fuel supply means and increases the raw fuel supply amount to the reformer, so that the water and raw fuel are supplied to the reformer. The supply ratio is limited to a certain range, the water supply to the reformer does not increase significantly, the steam partial pressure increases, and the power generation efficiency of the fuel cell decreases due to a significant change in temperature balance Can be suppressed.

  That is, in the steady state, the water supply amount to the reformer and the raw fuel supply amount are within a certain range.For example, in the case of an unsteady state in which the shot pump pumps air and cannot supply water. The control unit controls the shot pump to increase the number of shots per unit time.

  Therefore, the number of shots of the shot pump is increased to push out the air, but even if the number of shots is increased, the air biting is not immediately eliminated, and a predetermined time is required. Even when it is determined that the condition has been reached, in order to improve the water supply stability by the shot pump, control is performed to increase the number of shots of the shot pump for a predetermined time. If excessive water is supplied to the reformer in this way, the partial pressure of water vapor increases, and the power generation efficiency of the fuel cell may be significantly reduced due to a significant change in temperature balance. However, in the present invention, when the amount of water supplied to the reformer by the shot pump increases, the control unit increases the amount of raw fuel supplied to the reformer. The ratio of raw fuel is Is suppressed to a certain range, the power generation efficiency of the fuel cell can be suppressed to decrease.

  Shot pumps are used to supply a small amount of water at low cost. However, there is a possibility that dust may be clogged or air may not enter the shot pump and push out water, so-called air biting may occur. Although the amount of water that actually flows may be less than the amount of water supplied, in the present invention, the liquid flow sensor senses the intermittent flow of water that is actually pushed out by the shot pump. Even if the situation where water cannot be supplied automatically, the accurate water supply amount per unit time can be determined from the set value of the discharge amount per shot by the shot pump and the signal from the liquid flow sensor in the control unit. Can be calculated.

  Normally, an intermittent flow should be detected by the water flow sensor corresponding to the number of shots of the shot pump.However, as described above, if the dust is clogged or air is caught, the shot pump will drain water. Since it cannot be pushed out, an intermittent signal corresponding to the shot number command per unit time of the shot pump is not output, and the intermittent signal of the water flow sensor is smaller than the command shot number. In such a state, the control unit inputs a shot number command for increasing the number of shots per unit time to the shot pump. Even when clogged or air bites occur, water can be forced out together with dust and air.

Furthermore, the fuel cell device of the present invention includes a fuel cell that is supplied with fuel gas and an oxygen-containing gas to generate power, and a reformer that performs steam reforming by supplying raw fuel and water to supply the fuel gas to the fuel cell. , A shot pump that supplies water to the reformer, a raw fuel supply means that supplies raw fuel to the reformer, a control unit that controls the shot pump, and a current detection unit that detects the drive current of the shot pump when, as well as provided with a, when the drive current of the shot pump detected is smaller than the driving current of the steady state of the shot pump by current detection unit, wherein the control unit, the number of shots per unit time A command for increasing the number of shots is input to the shot pump, and the raw fuel supply means is controlled to increase the amount of raw fuel supplied to the reformer .

  Shot pumps are used to supply a small amount of liquid at a low cost, but there is a possibility that dust may be clogged or air may not enter the shot pump and push out the liquid, so-called air biting may occur. In the present invention, the current detection unit that detects the drive current of the shot pump detects the pulse signal of the drive current according to the drive of the shot pump. Even if the so-called air biting occurs and the situation where the liquid cannot be supplied temporarily occurs, only the pulse signal of the steady-state driving current is extracted, and one shot by the shot pump is added to the number of pulse signals. By multiplying the set value of the hit discharge amount, an accurate water supply amount by the shot pump can be obtained.

  Normally, a pulse signal based on the drive current of the current detection unit should be generated corresponding to the number of shots of the shot pump, but as described above, when dust is clogged or air biting occurs Since the shot pump cannot push out water, the actual number of shots of the shot pump is smaller than the number of shots per unit time of the shot pump. In such a state, the control unit inputs a shot number command that increases the number of shots per unit time to the shot pump, for example, it is input so as to be the maximum number of shots, garbage is clogged, Even when air biting occurs, water can be forced out together with dust and air.

In the fuel cell device of the present invention, the control unit increases the number of shots per unit time of the shot pump, and water is supplied to the reformer by the shot pump (when supplied to the reformer, it is steam. The control unit controls the raw fuel supply means and increases the raw fuel supply amount to the reformer, so that the water and raw fuel are supplied to the reformer. The ratio is kept within a certain range, the water supply to the reformer does not increase significantly, the water vapor partial pressure increases, and the power generation efficiency of the fuel cell decreases due to a significant change in temperature balance Can be suppressed. Moreover, the exact amount of water supply by a shot pump can be obtained.

  FIG. 1 is a configuration diagram showing an example of a fuel cell device of the present invention. The fuel cell device of the present invention is composed of a power generation unit for generating power, a hot water storage unit for storing hot water after heat exchange, and a circulation pipe for circulating hot water between these units.

  The fuel cell device of the present invention includes a fuel cell 1, a raw fuel supply device 2 for supplying raw fuel such as natural gas, an oxygen-containing gas supply device 3 for supplying oxygen-containing gas such as air to the fuel cell 1, A reformer 4 that performs steam reforming with fuel 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 electromagnetic valve 6 for adjusting water supplied from the water supply pipe 5, an activated carbon filter 7, and a reverse osmosis membrane 8. (Hereinafter referred to as RO membrane), water tank 9, ion exchange resin 10, shot pump 11, and flow switch (water flow sensor) 25. The water supply electromagnetic valve 6, the activated carbon filter 7, the RO membrane 8, the water tank 9, the ion exchange resin 10, the shot pump 11, the flow switch 25, and the reformer 4 are connected by piping.

  The shot pump 11 is configured so that, for example, when a piston provided in a cylinder rises by motor drive or hydraulic drive, water is sucked into the cylinder from the inlet and discharged from the cylinder outlet when the piston is lowered. Thereby, the water in the pipe flows intermittently, and the discharge amount per shot is determined by the movement amount of the piston. Since the shot pump 11 is inexpensive, it is suitably used when supplying a liquid with a minute flow rate. Note that the shot pump 11 is not limited to the above-described configuration, and may be any pump that pumps liquid for each shot.

  The flow switch 25 is configured to detect an intermittent flow of water from the shot pump 11 and to generate a signal. For example, a float is provided in the fluid passage so as to be movable up and down, a magnet is fixed to the peripheral surface of the float, and a Hall IC for detecting a magnetic force is installed on the wall of the fluid passage to constitute the flow switch 25. .

  In such a flow switch 25, when no fluid flows in the fluid passage, the float is supported by the lower stopper and remains in that position. In this state, the magnetic force of the float magnet does not affect the Hall IC, but when the fluid flows in the fluid passage, the float moves upward, abuts the upper stopper, and stays at that position. The magnetic force of the magnet acts on the Hall IC. Therefore, whether or not the fluid is flowing in the fluid passage can be confirmed depending on whether or not the magnetic force is detected by the Hall IC. When the fluid intermittently flows, the flow switch 25 is intermittently turned ON and OFF, It is comprised so that an intermittent signal may be emitted.

  The water flow sensor is not limited to the flow switch 25, and may be a sensor that senses an intermittent flow of water from the shot pump 11 and generates a signal, for example, a flow sensor or a flow meter, but is inexpensive. Therefore, the flow switch 25 is desirable.

  Then, the control unit 14 calculates the supply amount of water per unit time from the set value of the discharge amount per shot by the shot pump 11 and the intermittent signal from the flow switch 25. That is, for example, when the discharge amount per shot from the shot pump 11 is 0.5 cc and the signal of the flow switch 25 per minute is 10 times, the supply amount of water is 5 cc / min.

  The fuel cell 1, the raw fuel supply device 2, the oxygen-containing gas supply device 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 includes 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.

  The arrows in the figure indicate the flow directions of fuel gas, oxygen-containing gas, and water, and the wavy line is the main signal path transmitted to the control unit 14 or the main signal path transmitted from the control unit 14. Signal paths are shown. The same components are denoted by the same reference numerals, and so on. Further, although not shown, a fuel humidifier for humidifying the raw fuel may be provided between the raw fuel supply device 2 and the reformer 4.

  Here, a method of operating the fuel cell device shown in FIG. 1 will be described.

  Pure water used in the reformer 4 for obtaining the reformed gas used for power generation of the fuel cell 1 is supplied to the activated carbon filter 7 through the water supply pipe 5 with the water supply electromagnetic valve 6 opened. The water that has passed through the activated carbon filter 7 is subsequently passed through the RO membrane 8 and stored in the water tank 9. The water stored in the water tank 9 is made into highly purified water (pure water) through the ion exchange resin 10 and supplied to the reformer 4 by the shot pump 11.

  In the reformer 4, steam reforming is performed using the purified water supplied by the shot pump 11 and the raw fuel (reformed gas) supplied from the raw fuel supply device 2. The reformed 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 device 3 to generate power in the fuel cell 1. Then, the surplus reformed gas (hydrogen gas) and surplus oxygen-containing gas that have not been used for the power generation reaction are burned and released to the outside as exhaust gas. Further, 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.

  Then, the control unit 14 drives the shot pump 11 with a predetermined number of shots per unit time. In the present invention, the flow switch 25 senses the intermittent flow of water that actually flows, and the intermittent signal is sent to the control unit 14. The controller 14 can calculate an accurate water supply amount per unit time from the set value of the discharge amount per shot by the shot pump 11 and the intermittent signal from the flow switch 25. Thereby, the conditions of steam reforming in the reformer 4 can be optimized, and the power generation performance can be improved.

  That is, the shot pump 11 may be clogged with dust or may cause a phenomenon that air cannot enter the shot pump 11 and push out water, that is, so-called air biting. In the present invention, since the flow switch 25 senses the intermittent flow of water that is actually pushed out by the shot pump 11, so-called air biting occurs and water is temporarily supplied. Even if a situation in which it cannot be performed occurs, the control unit 14 calculates an accurate water supply amount per unit time from the set value of the discharge amount per shot from the shot pump 11 and the intermittent signal from the flow switch 25. Can do.

  Even though the control unit 14 issues a shot number command per unit time to the shot pump 11, the intermittent signal corresponding to the shot number command per unit time is less than the command shot number from the flow switch 25. In the case (including the case where there is no intermittent signal), the control unit 14 controls the shot pump 11 to input a shot number command in which the number of shots per unit time is increased to the shot pump 11. For example, by controlling the maximum number of shots, water can be forcibly pushed out together with the dust and air even when the dust is clogged or the air is bitten.

  In this case, the control unit 14 increases the number of shots per unit time of the shot pump 11, and when the amount of water supplied to the reformer 4 by the shot pump 11 increases, the control unit 14 In order to control the raw fuel supply device 2 and increase the raw fuel supply amount to the reformer 4, the ratio of water and raw fuel to the reformer 4 is kept within a certain range, It is possible to suppress a reduction in power generation efficiency of the fuel cell due to a significant increase in the water vapor partial pressure without a significant increase in the water supply amount and a significant change in the temperature balance.

  In the type in which the fuel gas and the oxygen-containing gas are supplied to the fuel cell 1 and the mixed gas of surplus fuel gas and oxygen-containing gas that has not been used for the power generation reaction burns, the number of shots per unit time of the shot pump 11 However, in this case, the ratio of the raw fuel supply amount to the water supply amount becomes low and combustion due to excess fuel gas and oxygen-containing gas may be misfired. However, according to the present invention, when the amount of water supplied to the reformer 4 by the shot pump 11 increases, the control unit 14 increases the amount of raw fuel supplied to the reformer 4. The ratio of water and raw fuel to 4 is kept within a certain range, and misfire can be prevented.

  In a fuel cell in which surplus fuel gas and oxygen-containing gas burn, even if the number of shots per unit time of the shot pump 11 is increased, water cannot be supplied to the reformer 4 so much, and the raw fuel ratio Even if the fuel cell 1 is supplied to the fuel cell 1 in an insufficiently reformed state (partly as raw fuel), it is internally reformed by using an internal reforming type fuel cell, and the fuel gas ( As the raw fuel is partially burned), power generation efficiency is not particularly reduced.

  FIG. 2 shows another embodiment of the fuel cell device of the present invention. In this embodiment, a current sensor (current detector) 26 for detecting the drive current of the shot pump 11 is used instead of the flow switch 25 of FIG. The control unit 14 has a function of controlling the number of shots per unit time of the shot pump 11 by a signal from the current sensor 26, and the drive current of the shot pump 11 is constant for the shot pump 11. When the driving current is lower than the driving current in the state, the control unit 14 controls the shot pump 11 to input a shot number command in which the number of shots per unit time is increased.

  The control unit 14 drives the shot pump 11 with a predetermined number of shots per unit time. In the present invention, when the shot pump 11 is driven to supply water, the drive current of the shot pump 11 is a current sensor. 26, for example, a pulse signal of a driving current corresponding to the driving of the shot pump 11 is detected, and the control unit 14 detects the set value of the discharge amount per shot by the shot pump 11 and the signal from the current sensor 26. From the number of pulses based on, the amount of water supply per unit time in a steady state can be accurately calculated. Thereby, the conditions of steam reforming in the reformer 4 can be optimized, and the power generation performance can be improved.

  That is, the shot pump 11 may cause a phenomenon in which air cannot enter the shot pump 11 and push out water, that is, so-called air biting, and the amount of water actually flowing is less than the theoretical amount of water relative to the number of shots. However, since water cannot be pushed out when air is caught in the shot pump 11, the pulse signal of the drive current corresponding to the drive of the shot pump 11 has a small drive current as shown by a solid line in FIG. Thus, the current becomes smaller than the driving current in the steady state when water is pushed out. Therefore, the control unit 14 extracts only the pulse signal of the driving current in the steady state and multiplies the number of pulse signals by the set value of the discharge amount per shot by the shot pump 11, so that the accurate by the shot pump 11 is obtained. A water supply can be obtained.

  The number of shots per unit time obtained from the signal from the current sensor 26 is the unit from the control unit 14 even though the control unit 14 issues a shot number command per unit time to the shot pump 11. When the number of shots per time is smaller (including the case where there is no intermittent signal), the control unit 14 gives the shot pump 11 a shot number command for increasing the number of shots per unit time to the shot pump 11. Control to input. For example, by controlling so that the maximum number of shots is obtained, water can be forcibly pushed out together with air even when air biting occurs.

  In the present invention, when the amount of water supplied to the reformer 4 by the shot pump 11 increases, the control unit 14 increases the amount of raw fuel supplied to the reformer. The ratio of water and raw fuel can be suppressed within a certain range, and the power generation efficiency of the fuel cell 1 can be suppressed from decreasing.

  In the present invention, the number of shots is, in principle, the number of shots actually driven by the shot pump 11, and the command shot number is the number of shots based on the shot number command input to the shot pump 11 from the control unit 14. The shot number command is a command related to the number of shots from the control unit 14 to the shot pump 11.

  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, when the increased shot number command per unit time, for example, the maximum shot number command is continued for a certain time from the control unit 14 to the shot pump 11, the control unit 14 can also issue a signal of an abnormal water supply amount. Even when operating at the maximum number of shots for a certain period of time or more, water cannot be forced out together with dust and air, so the control unit issues a water supply error signal and performs appropriate processing thereafter, for example, Inspection, repair, replacement, or stop of the fuel cell device can be performed quickly, and the influence on the fuel cell device can be minimized.

It is a block diagram which shows the fuel cell apparatus which has the flow switch of this invention. It is a block diagram which shows the fuel cell apparatus which has the current sensor of this invention. It is a figure which shows typically the detection state of the drive current by a current sensor.

Explanation of symbols

1: Fuel cell 4: Reformer 11: Shot pump 14: Control unit 25: Flow sensor (water flow sensor)
26: Current sensor (current detection unit)

Claims (2)

A fuel cell that is supplied with fuel gas and oxygen-containing gas to generate electricity;
A reformer for performing steam reforming by supplying raw fuel and water to supply fuel gas to the fuel cell;
A shot pump for supplying water to the reformer;
Raw fuel supply means for supplying raw fuel to the reformer;
A control unit for controlling the shot pump ;
A water flow sensor that senses the intermittent flow of water from the shot pump and detects the actual number of shots from the shot pump , and
When the actual shot number detected by the water flow sensor is smaller than the command shot number per unit time by the control unit,
The control unit controls to input a shot number command for increasing the number of shots per unit time to the shot pump, and to increase the raw fuel supply amount to the reformer. The fuel cell device characterized by controlling. A fuel cell that is supplied with fuel gas and oxygen-containing gas to generate electricity;
A reformer for performing steam reforming by supplying raw fuel and water to supply fuel gas to the fuel cell;
A shot pump for supplying water to the reformer;
Raw fuel supply means for supplying raw fuel to the reformer;
A control unit for controlling the shot pump;
As well as comprising a, a current detection unit for detecting the driving current of the shot pump,
If the driving current of the shot pump detected by said current detecting unit is reduced than the drive current of the steady state of the shot pump,
The control unit inputs a shot number command for increasing the number of shots per unit time to the shot pump, and controls the raw fuel supply means so as to increase a raw fuel supply amount to the reformer. fuel cell device it said.

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