JP3220438B2 - Fuel cell power generation system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generation system provided with a hydrogen producing apparatus, and more particularly to a fuel cell power generation system provided with a buffer tank for responding to a load change.

[0002]

2. Description of the Related Art In a fuel cell power generation system, an electrode-electrolyte assembly having a pair of electrodes disposed on both sides of an ionic conductive electrolyte membrane is laminated via an electrically conductive separator having a reaction gas flow path. It is composed of a fuel cell having a structure, a fuel system for supplying a fuel gas to the fuel cell, and an air system for supplying an oxidizing gas.

For applications in which the load and power supply of a mobile power supply or the like are one-to-one, a proton conductive solid electrolyte is used as the electrolyte membrane because of operation at a relatively low temperature and high energy density. A polymer electrolyte fuel cell is generally used.

[0004] As a fuel system, a compound containing carbon and hydrogen, for example, a hydrocarbon such as methane, or an alcohol such as methanol is used as a fuel, and is subjected to steam reforming or partial oxidation and a reaction combining steam reforming and partial oxidation. A hydrogen production apparatus is used, which is provided with a unit for removing carbon monoxide in the steam reformed gas, and supplies the purified reformed gas to the fuel cell.

[0005] Since the steam reforming reaction is an endothermic reaction, the steam reforming apparatus is provided with a combustor as a heat source.

[0006] The combustor is directly supplied with fuel or the residual hydrogen in the fuel exhaust gas of the fuel cell is supplied and burned to generate a heat source. As a combustor, a method using a catalyst combustor capable of burning both fuel and fuel exhaust gas from a fuel cell,
There is a method using a combustor having two burner heads for direct combustion of fuel and combustion of fuel cell fuel exhaust gas, and the calorific value of the fuel cell fuel exhaust gas deficient is covered by the direct combustion of the fuel.

In a power generation system linked to a power system, a large number of loads are present and each of them fluctuates independently. Therefore, the power generation side must supply the rated power in a time of 1 s or less as a whole. No response to such a sudden load change is required.

On the other hand, in an application such as a mobile power supply, for example, an electric vehicle, a load and a power generation side have a one-to-one correspondence, so that a response to a sudden load change of about 100 ms is required. The load response speed of such a fuel cell system is governed by the response speed of hydrogen supplied to the fuel cell. The time required for the steam reformer to respond to the load is about several tens of seconds.

As means for the fuel cell power generation system to respond to a sudden change in the external load, Japanese Patent Laid-Open Publication No.
As described in JP-A-5-1983, a hybrid method with a storage means such as a secondary battery system is used, and the storage means directly supplies power to a sudden increase in load. JP-A-9-306
As described in JP-A-531, there has been proposed a method of installing a buffer tank and supplying hydrogen to a fuel cell in response to a sudden load change.

[0010]

However, the above-described power storage means causes a significant increase in weight, and significantly lowers efficiency and portability.

On the other hand, in the case of a fuel cell power generation system having a buffer tank, driving a 30 kW class fuel cell requires about 400 liter / min of reformed gas or about 200 liter / min of hydrogen gas. . That is, when a 5-liter tank is used, the reformed gas that must be held for driving the fuel cell for one minute requires 80 atm, and even when only hydrogen is extracted from the reformed gas, 40 atm is required.

When the load increases, the fuel in the buffer tank is released, but when the load decreases, the fuel needs to be stored in the buffer tank. This is a factor for increasing the auxiliary power.

In order to reduce the capacity of the buffer tank and to effectively utilize the buffer tank regardless of the increase or decrease of the load,
Control means for promptly setting the fuel gas storage amount in the buffer tank to a predetermined amount is required.

In view of the above, it is an object of the present invention to provide a fuel cell power generation system in which a buffer tank for responding to a load change is reduced in size.

[0015]

The gist of the present invention to achieve the above object is as follows.

[1] A fuel gas producing means for converting a fuel of a compound containing carbon and hydrogen into a fuel gas containing hydrogen in a reforming reactor, and a pair of electrodes and an ion-conductive electrolyte disposed between the electrodes And a buffer tank for storing fuel gas between the fuel gas producing means and the fuel cell, and generating electricity using the fuel gas produced by the fuel gas producing means as fuel for the fuel cell. A fuel cell power generation system connected to a load via an inverter, wherein a fuel gas pressure at an outlet of the fuel gas production means is higher than an operating pressure of the fuel cell.

[2] The fuel gas pressure at the outlet of the fuel gas producing means is 1 kg / cm higher than the operating pressure of the fuel cell.
^2. The fuel cell power generation system according to [1], which is higher by ² or more.

[3] The fuel cell power generation system according to [2], wherein the amount of fuel gas stored in the buffer tank is adjusted using a pressure difference between an outlet pressure of the fuel gas producing means and an operating pressure of the fuel cell.

[4] A fuel gas producing means for converting a fuel of a compound containing carbon and hydrogen into a fuel gas containing hydrogen in a reforming reactor, and a pair of electrodes and a proton conductive electrolyte disposed between the electrodes. A fuel cell having stacked cells containing
A buffer tank for storing fuel gas was provided between the fuel gas producing means and the fuel cell, power was generated using the fuel gas produced by the fuel gas producing means as fuel for the fuel cell, and connected to a load via an inverter. In the fuel cell power generation system, a load request detecting unit, a pressure detecting unit of the buffer tank, an outlet hydrogen flow detecting unit of the fuel gas producing unit,
And a fuel cell outlet hydrogen flow rate detecting means, wherein the buffer tank, the inverter, and each of the control means respond to a load change based on a detection result of each of the detecting means. And a controller for transmitting a control signal in accordance with the response speed of the fuel gas producing means so as to approach the reference value of the amount of fuel gas stored in the buffer tank.

[5] The fuel cell power generation system according to [4], wherein a reference value of an amount of fuel gas stored in the buffer tank is determined according to a required load amount.

[6] The fuel cell power generation system according to [4], wherein the reference value of the fuel gas amount stored in the buffer tank is 40 to 85% by volume of the maximum fuel gas amount stored in the buffer tank.

[7] A power storage means having means for detecting the amount of stored power is connected in parallel with the fuel cell via a second inverter, and the controller operates the second power supply in response to a load change.
The fuel cell power generation system according to [4], wherein the control of the inverter and the control in accordance with the response speed of the fuel gas producing means are performed so as to approach a reference value of the amount of electricity stored in the electricity storing means.

[8] 20 to 8 times the volume of the buffer tank
The fuel cell power generation system according to [1] or [4], filled with 5% of a hydrogen storage alloy.

[0024]

[9] A heat exchange unit through which a refrigerant flows in the fuel cell and the buffer tank is provided, and a cooling mechanism is configured by a heat exchange unit in the fuel cell, a heat exchange unit in the buffer tank, a radiator, and a refrigerant pump. The fuel cell power generation system according to [8], wherein the refrigerant circulates through the inside of the cooler premises in the order of the heat exchange unit in the fuel cell, the heat exchange unit in the buffer tank, and the radiator.

[10] The fuel cell power generation system according to [8], wherein the hydrogen storage alloy contains 3% or more of lanthanum and 50% or more of nickel by mole fraction.

[11] The fuel cell power generation system according to [4], further comprising a bypass pipe connecting an inlet and an outlet of the buffer tank.

[12] The difference between the fuel gas pressure at the outlet of the fuel gas producing means and the operating pressure of the fuel cell is recovered as power, and the power is used to send air to the air electrode of the fuel cell [11]. 3. The fuel cell power generation system according to item 1.

[13] The fuel cell power generation system according to [11] or [12], wherein a second bypass pipe is provided from the buffer tank to a pipe connected to a combustor in the fuel gas producing means.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fuel gas producing means for converting a fuel comprising a compound containing carbon and hydrogen into a fuel gas containing hydrogen in a reforming reactor, and a pair of electrodes and a proton conductive material located between both electrodes And a buffer tank for storing a fuel gas between the fuel production means and the fuel cell, wherein a fuel gas produced by the fuel gas production means is used as fuel for the fuel cell. To generate power, and connected to the load via the inverter. Power storage means connected in parallel to the load via an inverter may be provided.

Next, a procedure for responding to a load change will be described. The basic procedure consists of a measuring step, a step of responding to a load change in a short time, and a step of adjusting the fuel production amount such that the hydrogen storage amount in the buffer tank becomes a reference value according to the response speed of the fuel producing means. It consists of three steps.

In the measuring step, load detecting means corresponding to the accelerator opening in the case of an electric vehicle, pressure detecting means of the buffer tank, detecting means for detecting the state in the fuel cell system, and the outlet of the fuel producing means are used as detecting means. It has a hydrogen flow detecting means and a hydrogen flow detecting means in the fuel exhaust gas of the fuel cell. When the power storage means is provided, a means for detecting the charge / discharge capacity of the power storage means is also provided.

The measurement by each of the detection means is performed at predetermined intervals, and the measurement result at least last time, preferably at least two times before, is stored in a random access memory on the controller.

The procedure for responding to a load change is as follows. The hydrogen utilization rate in the fuel cell is the same as the heat balance hydrogen utilization rate in which the fuel gas production means can cover the necessary heat by burning the fuel exhaust gas from the fuel cell, and the hydrogen deficiency does not occur in the fuel cell. It is operated at a suitable utilization between the maximum utilization, the maximum hydrogen utilization.

First, a heat balance hydrogen utilization rate, a maximum hydrogen utilization rate, and a reference hydrogen utilization rate which is an appropriate hydrogen utilization rate between the heat balance hydrogen utilization rate and the maximum hydrogen utilization rate with respect to a required load. Required hydrogen flow rate, and
Calculate the flow rate of hydrogen produced.

Next, it is determined whether or not a response to the load is possible by a change in the utilization ratio between the heat balance hydrogen utilization ratio and the maximum hydrogen utilization ratio.

If the above load response is possible with the above change in the utilization rate, the inverter connected to the fuel cell and the amount of air supplied to the fuel cell are changed so as to respond to the load by changing the hydrogen utilization rate. Control, and the flow rate of hydrogen in the fuel exhaust gas of the fuel cell also changes, so the fuel supply to the combustor is increased to secure the necessary heat in the combustor of the fuel production means, and the amount of air is adjusted. I do.

If a load response is not possible due to the change in the utilization rate, the fuel is stored and released in the buffer tank, or if a power storage means is provided, the fuel cell is charged and discharged to respond to the load.

When the amount of produced hydrogen is insufficient, the fuel cell is operated at the maximum hydrogen utilization rate, the load is followed by discharging the fuel in the buffer tank or discharging the electric storage means, and the fuel cell is operated at the thermal balance hydrogen utilization rate. A method of following load by discharging fuel in the buffer tank or discharging the power storage means, or by operating the fuel cell at an appropriate reference hydrogen utilization rate between the maximum hydrogen utilization rate and the heat balance hydrogen utilization rate, There is a method of following the load by discharging the fuel inside or discharging the power storage means, and the control is performed according to the fuel storage amount of the buffer tank and the power storage amount of the power storage means.

After the above-described response operation to the load, the fuel production amount is adjusted according to the response speed of the fuel production means so that the hydrogen utilization rate of the fuel cell, the hydrogen storage amount in the buffer tank, and the like become reference values. Perform the operation. In this step, the utilization rate of the fuel cell, the amount of hydrogen stored in the buffer tank, and the predicted amount of power stored by the power storage means are obtained, and the fuel is set so that each predicted value approaches the reference value within the load response limit range of the fuel production means. The amount of fuel supplied to the combustor, the amount of air supplied, the amount of fuel supplied to the reactor, and the amount of water supplied to the reactor are controlled.

In order to increase the load response speed of the fuel production means, there is a method in which air is supplied to the reactor of the fuel production means to carry out two reactions, a steam reforming reaction and a partial oxidation reaction.

The reference value of the hydrogen gas storage amount in the buffer tank is 40 to 85 with respect to the maximum fuel gas amount determined by the maximum pressure of the buffer tank in order to discharge the fuel when the load increases and to store the fuel when the load decreases. % Is desirable.
It is desirable that the reference value of the hydrogen gas storage amount be an appropriate value according to the power generation amount of the fuel cell. That is, when the power generation amount of the fuel cell is close to the maximum, the necessary hydrogen amount is unlikely to increase, and when the load demand decreases, there is a high possibility that surplus fuel is generated. More preferably, when the power generation amount of the fuel cell is small, it is desirable that the storage amount is large.

A fuel cell system having a buffer tank
It can respond to a sudden load change without having a power storage means.For example, in the case of an application such as an electric vehicle, it is possible to recover the energy at the time of deceleration by generating electric power with a motor at the time of deceleration, and to improve energy efficiency Can be enhanced. When a power storage means is provided, it is desirable to perform control in cooperation with a fuel cell system other than the power storage means as described above.

To make the fuel cell system compact, the operating pressure of the fuel gas producing means is increased to increase the volume of the reactors in the fuel gas producing means, ie, the reforming reactor, the shift reactor, and the CO remover. Can be reduced.

In order to increase the pressure of the reactor, the fuel and water to be supplied to the reforming reactor may be pressurized in a liquid state, so that an increase in auxiliary power for pressurization is small.

On the other hand, the performance of the fuel cell can be enhanced by increasing the operating pressure of the fuel cell. However, the performance is enhanced by increasing the pressure on the air electrode side, and the blower on the air electrode side is driven. There is little merit because the power of auxiliary equipment also increases. Therefore, the pressure of the fuel gas producing means is made higher than the operating pressure of the fuel cell.

In order to make the fuel gas producing means compact, it is desirable that the difference in operating pressure from the fuel cell is at least 1 kg / cm ² or more.

Since there is a difference in operating pressure between the fuel gas producing means and the fuel cell, the pressure in the buffer tank is adjusted by using a control valve provided at the entrance and exit of the buffer tank, so that the fuel gas stored in the buffer tank is adjusted. The amount can be adjusted.
Therefore, a booster such as a compressor is not required, and energy loss due to auxiliaries can be suppressed.

Furthermore, by using a hydrogen storage tank filled with a hydrogen storage alloy as the buffer tank, only hydrogen reacting at the fuel electrode of the fuel cell can be stored in the buffer tank, and the volume of the tank can be made more compact. can do. The hydrogen storage alloy can reduce 400 liters of hydrogen to about 1 liter (10 kilograms) at room temperature and atmospheric pressure.

In this case, hydrogen can be stored / released in the buffer tank by using the difference between the operating pressures of the fuel gas producing means and the fuel cell, and the auxiliary power for operating the buffer tank is not required. In addition, the speed of hydrogen storage / release in the buffer tank must satisfy the fluctuation speed of the load requirement, the contact area between the hydrogen storage alloy and the fuel gas is increased, and the pressure loss when the fuel gas flows in the buffer tank is increased. Must be reduced. For this reason, the amount of the hydrogen storage alloy in the buffer tank is desirably 20 to 85% of the volume of the buffer tank.

The hydrogen storage alloy absorbs about 20 to 30 kJ / molH ₂ when releasing hydrogen, and generates heat when storing hydrogen. When the temperature of the hydrogen storage alloy changes due to the heat of reaction at the time of hydrogen storage and release, the dissociation pressure of the hydrogen storage alloy changes and storage and release become impossible. Therefore,
A means for suppressing a temperature change of the hydrogen storage alloy is required.

For this reason, there is a method of connecting a refrigerant circulation system for keeping the fuel cell temperature constant to a heat exchanger provided in the buffer tank. By setting the circulation path of the refrigerant circulation system in the order of the heat exchange part in the fuel cell, the heat exchange part in the buffer tank, and the radiator, the temperature in the buffer tank is not affected by the outside air temperature.
The temperature can be close to the fuel cell temperature.

The hydrogen storage alloy used for the buffer tank may have an alloy composition that is hardly poisoned by carbon dioxide and a trace amount of carbon monoxide contained in the fuel gas when the dissociation pressure is in the range of 1 to 10 kg / cm ^2. desirable. Such alloy compositions include a lanthanum-nickel alloy and a misch metal-nickel alloy in which lanthanum is at least 3% by mole and nickel is at least 50%.

In general, a third element such as aluminum, chromium, manganese, cobalt or silica is added to the above alloy for the purpose of adjusting the dissociation pressure. The present invention prevents the addition of such a third element. Not something.

The buffer tank is disposed between the fuel gas producing means and the fuel cell. A bypass pipe for directly connecting the fuel gas producing means and the fuel cell is provided, and an inlet / outlet of the buffer tank and a control valve for the bypass pipe are provided. When the control is performed to adjust the storage amount of the buffer tank, the control becomes easier than the configuration without the bypass pipe. That is, the control valve of the bypass pipe is closed, the control valve at the buffer tank inlet is opened, and before and after the control valve at the buffer tank outlet, the pressure difference between the fuel gas production means and the fuel cell is adjusted. Maximum storage speed.

The control valve at the buffer tank inlet is closed, and the pressure difference between the fuel gas producing means and the fuel cell before and after the bypass pipe control valve, and the pressure difference between the buffer tank and the fuel cell before and after the buffer tank outlet control valve. When the adjustment is made so that the fuel gas is supplied from the buffer gas tank, the discharge speed from the buffer tank is maximized, and the fuel supply speed to the fuel cell is maximized.

The difference between the operating pressure of the fuel gas producing means B1 and the operating pressure of the fuel cell 9 can be recovered as blower power for the air electrode of the fuel cell 9. In this case, the fuel gas producing means B
Since the amount of fuel gas supplied from 1 to the fuel cell 9 is proportional to the power, and the amount of air required for the air electrode is also proportional to the amount of fuel gas, control becomes easy.

When a hydrogen storage alloy is used for the buffer tank 8, the hydrogen concentration in the outlet gas of the buffer tank is low and the concentrations of carbon dioxide gas and carbon monoxide gas are relatively high during the hydrogen storage of the alloy.

A second bypass pipe connected from the outlet of the buffer tank 8 to the combustor 17 in the fuel gas producing means B1 is installed, and the outlet gas of the buffer tank is led directly to the combustor 17 during storage of hydrogen. The fuel cell 9 uses the fuel directly supplied from the fuel gas producing means B1 to increase the hydrogen utilization rate, so that it is not necessary to use the fuel with a low hydrogen concentration discharged from the buffer tank 8.

The above-described fuel cell power generation system is preferably applied to a usage method having a large load variation, for example, a mobile power source, an electric vehicle, and the like. As the fuel cell, a polymer solid electrolyte type fuel cell having a high output density is used. It is suitable.

[0060]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an example of a fuel cell power generation system including a buffer tank 8. A fuel gas production means B1 for converting a fuel of a compound containing carbon and hydrogen into a fuel gas containing hydrogen in the reforming reactor 4, a fuel cell system B2 for receiving a supply of the fuel gas and performing DC power generation, And a buffer tank system B4 installed between the fuel gas producing means B1 and the fuel cell system B2.

In the fuel gas producing means B 1, fuel supplied from a fuel tank (not shown) by the steam reformer fuel pump 1 is sent to the fuel vaporizer 3 by sending water to the fuel vaporizer 3 by the steam reformer water pump 2. And introduced into the reforming reactor 4.

In the reforming reactor 4, a synthesis gas, which is a mixed gas of hydrogen, carbon monoxide, carbon dioxide, water, and a small amount of unreacted fuel gas, is produced by a steam reforming reaction.
This synthesis gas is reacted with carbon monoxide and water vapor in a shift converter 5 to produce hydrogen and carbon dioxide, and after the carbon monoxide concentration is about 1%, the carbon monoxide is selectively combusted in a CO selective oxidizer 6. To carbon dioxide.

The CO selective oxidizer 6 has CO as an oxidizing agent.
Air is appropriately supplied by the selective oxidizer blower 7 to produce a fuel gas having a carbon monoxide concentration of 100 ppm or less.

The buffer tank system B4 includes the fuel gas producing means B
1 and a fuel cell system B2, installed in parallel with a pipe, and a buffer tank 8 and a buffer tank filling blower 26 for filling the buffer tank 8 with fuel gas, and a buffer tank inlet for adjusting the flow rate at the entrance and exit of the buffer tank 8 It comprises a valve 18 and a buffer tank outlet valve 19.

The fuel cell system B2 comprises a fuel cell 9 comprising a pair of electrodes and a cell having a proton conductive electrolyte located between the electrodes, and a fuel for humidifying the fuel gas introduced into the fuel cell 9. Polar humidification water pump 14 and fuel electrode humidifier 15, fuel cell air electrode blower 10 for air introduced into fuel cell 9, air electrode humidification water pump 12 for humidifying air supplied from blower 10, and air electrode Humidifier 13.

The electric system B3 comprises a fuel cell system inverter 51 for converting the DC output of the fuel cell 9 into AC, and an electric load 52 connected to the AC output of the inverter.

In the electric system B3, as shown in FIG. 1, an inverter 54 for a power storage means may be installed in parallel with the inverter 51 for the fuel cell system, and a power storage means 53 composed of a secondary battery or the like may be connected. . In addition, the fuel cell 9 and the power storage
There is also a method of connecting with a C / DC converter and connecting the electric load 52 and the power storage means 53 with the power storage means inverter 54.

The oxidant exhaust gas discharged from the fuel cell 9 is subjected to gas-liquid separation in the condenser 11, and the condensed water is supplied to the steam reformer water pump 2, the air electrode humidification water pump 12, and the fuel electrode humidification water pump. 14 as a source of water. Condenser 1
The gas discharged from 1 is discharged out of the system.

The fuel exhaust gas discharged from the fuel cell 9 is
Mixed with air supplied from the combustor blower 16,
It is led to the combustor 17. The heat of combustion in the combustor 17 becomes the reaction heat required in the reforming reactor 4. If the reforming reactor 4 cannot cover the required amount of heat with the fuel exhaust gas from the fuel cell 9, the fuel supplied from the fuel tank is passed through the combustor fuel vaporizer 21 by the combustor fuel pump 20. To the combustor 17.

In the above configuration, each device does not need to be separate. For example, a fuel processor in which the fuel vaporizer 3, the reforming reactor 4, the shift converter 5, the CO selective oxidizer 6, and the combustor fuel vaporizer 21 of the fuel production means B1 are integrated, a fuel cell of the fuel cell system B2 9, an internal humidifier fuel cell in which the air electrode humidifier 13 and the fuel electrode humidifier 15 are integrated.

FIG. 2 shows the configuration of the controller C1 for controlling the load response of the fuel cell power generation system having the above configuration.

The controller C1 comprises a memory C2 for storing data, a memory C3 for storing programs, and an arithmetic unit C4. A load request D1, a hydrogen gas flow rate D2 at the outlet of the fuel gas production means B1,
Buffer tank 8 temperature, pressure D3, power storage means 53 power storage amount D
4. Input data such as the hydrogen flow rate D5 at the outlet of the fuel cell system B2, the fuel supply amount D6 for the combustor fuel pump 20, the air supply amount D16 for the combustor blower D7, the buffer tank system B4 control value D
8, steam reformer fuel pump 1 fuel supply amount D9, steam reformer water pump 2 water supply amount D10, fuel cell system B2
Control value D13, output D1 of fuel cell system inverter 51
1 and the output D12 of the inverter 54 for the electric storage means.

The controller C1 inputs, for example, the flow rate of carbon monoxide at the outlet of the shift converter 5 for controlling the blower 7 for the CO selective oxidizer, and controls the blower 7 for the CO selective oxidizer.
It is also possible to double as an input / output for control other than the above items, such as outputting the air supply amount. Further, a controller for control other than the above items can be separately provided.

FIGS. 3 and 4 show an example of the operation of the controller C1 as a flowchart. This operation procedure is held in the program storage memory C3 and becomes the operation procedure of the arithmetic unit C4.

The basic procedure consists of a measurement step (SB10) in FIG. 3 and a step (S10) corresponding to a load change in a short time.
B20), and a step (SB30) of adjusting the fuel production amount so that the hydrogen storage amount or the like in the buffer tank becomes a reference value according to the response speed of the fuel gas producing means in FIG.

In the above-mentioned measuring step (SB10), as the detecting means for detecting the state in the fuel cell system, the load request 52 detecting means corresponding to the accelerator opening in the case of an electric vehicle, the fuel gas producing means B1 outlet , A means for detecting the temperature and pressure of the buffer tank 8, and a means for detecting the amount of hydrogen in the fuel exhaust gas of the fuel cell system B2.

In this embodiment, since the power storage means 53 is provided, a means for detecting the charge / discharge capacity of the power storage means 53 is also provided. The measurement result of the detecting means is input to the data storage memory C2 of the controller C1 (S10), and the data storage memory C2 holds at least the previous measurement result, preferably two or more previous measurement results.

In FIG. 3, the step (SB20) according to the load fluctuation is as follows. As shown in FIG. 5, the hydrogen utilization rate in the fuel cell includes a heat balance hydrogen utilization rate U1 at which the fuel gas producing means can cover the required heat by burning the fuel exhaust gas from the fuel cell, and a hydrogen utilization rate within the fuel cell. The operation is performed at an appropriate utilization rate between the maximum utilization rate U2, which is the maximum utilization rate at which no hydrogen deficient portion is generated.

First, a heat balance hydrogen utilization rate U1, a maximum hydrogen utilization rate U2, and a reference hydrogen utilization rate U3 which is an appropriate hydrogen utilization rate between the heat balance hydrogen utilization rate and the maximum hydrogen utilization rate for a required load. In each case, the required hydrogen flow rate and the hydrogen flow rate to be produced are calculated.

The required amount of hydrogen is obtained as in the following equation [1]. The output of the fuel cell 9 is W, the number of stacks is m,
When the voltage of the n-cell and V _n,

[0081]

(Equation 1)

Here, the cell voltage V _n is a function of the load current I, the hydrogen utilization rate u _H2 , the oxygen utilization rate u _O2 , and the battery temperature T. In addition, the humidification amounts of fuel and air, and the total operating time And other parameters can be added. At this time, the required amount of hydrogen is represented by the following equation [2].

[0083]

(Equation 2)

Here, the required molar flow rate of hydrogen is f _H2 and the Faraday constant is F. In this embodiment, the oxygen utilization rate u _O2
Is fixed at 40%, and the heat balance hydrogen utilization rate U1 is 70%.
% And the maximum hydrogen utilization rate U2 are set to 90%, so that the required hydrogen amount f _H2 in each case can be obtained from the equations [1] and [2].

The amount of hydrogen being produced is determined by the arrival time of the pipe volume between the outlet of the fuel gas producing means B2 and the fuel cell 9 based on the hydrogen flow rate D2 at the outlet of the fuel gas producing means B1 held in the data storage memory C2. It is obtained by calculation (S20).

At S30 in FIG. 3, the magnitude of the flow rate of the produced hydrogen and the required amount of hydrogen are compared. When the production hydrogen amount is within the range between the required hydrogen amount at the heat balance hydrogen utilization ratio and the required hydrogen amount at the maximum hydrogen utilization ratio, the process branches to S220, and when it is outside the range, the process branches to S40.

In S210, it is determined whether or not the amount of stored power in the buffer tank 8 and the system provided with the power storage means 53 satisfy the reference value. If the reference value is not satisfied, the process branches to S40, and if it is satisfied, the process branches to S210.

In this embodiment, as the fuel storage amount reference value of the buffer tank 8, 10% of the maximum storage amount when the output of the fuel cell 9 is the maximum value, and 9% of the maximum storage amount when the output is 0.
0%, the relationship between the output of the fuel cell 9 and the reference value of the fuel storage amount was set as a first-order relationship, and the reference range was set as the determination condition of S210 within a range of the reference value ± 10%.

When the output of the fuel cell 9 is at the maximum value, the reference range of the storage amount is 20% of the maximum storage amount, and when the output is 0, the reference range is 80% of the maximum storage amount.
The output of the fuel cell 9 and the reference value of the fuel storage amount were set as a first-order relationship, and the reference range was set as the determination condition of S210 within a range of the reference value ± 20%.

In S40, the hydrogen utilization rate is maximized when the production hydrogen amount <the maximum required hydrogen utilization rate, and the hydrogen utilization rate is regarded as the balanced hydrogen utilization rate when the production hydrogen quantity> the required balance hydrogen utilization rate. The buffer tank system B4 control value (D8) and the output of the inverter 51 (D1) are set so that the buffer tank 8 and the power storage means 53 are operated to satisfy the required value.
1) Calculate the inverter 54 output (D12) and the fuel cell system B2 control value (D13).

In S250, the amount of fuel flowing into and out of the buffer tank 8 and the amount of charge of the power The output of the inverter 51 (D11) and the output of the inverter 54 (D1
2) Calculate the buffer tank system B4 control value (D8) and the fuel cell system B2 control value (D13). At this time, the power generation amount of the fuel cell 9 is set to a control value that allows operation between the maximum hydrogen utilization rate and the heat balance hydrogen utilization rate. In S50, S4
The control value calculated in step S250 is output to each device.

In step S230, the control value calculated in step S220 is output to each device. In step S240, the output of the inverter 54 (D12) and the buffer tank system B4 control value (D8) are output to the charge / discharge of the power storage means 53 and the buffer tank 8. A control signal is output to make the fuel inflow / outflow of zero.

In S60, a control value for adjusting the amount of fuel and air supplied to the combustor 17 to compensate for the change in combustion heat of the fuel exhaust gas discharged from the fuel cell 9 is calculated according to the instruction in S50 or S230. I do. That is, the control value (D6) of the combustor fuel pump 20 and the control value (D7) of the combustor blower 16 are calculated. In S70, S
The control values of D6 and D7 calculated in 60 are output.

Step of Adjusting Fuel Production (SB3)
0) is as follows. In S310, the system operation statuses D1 to D5 input in SB10 and SB20
Based on the control values D6 to D13 output in step (1), changes in the hydrogen storage amount of the buffer tank 8 and the power storage amount of the power storage unit 53 are predicted.

In S320, the reforming reactor 4 and the combustor 17
The fuel pump 20 for the combustor for the hydrogen storage amount of the buffer tank 8 and the power storage amount of the power storage means 53 to approach the reference value in accordance with the response speed of the reformer determined by the heat conductivity and the heat capacity between The operation procedure of the combustor blower 16, the steam reformer fuel pump 1, and the steam reformer water pump 2 is calculated.

In S330, the operation procedure calculated in S320 is output as control values D6, D7, D9 and D10, and the procedure of the load response ends.

The controller performing the above operation was applied to the 3 kW fuel cell system shown in FIG. 1 to perform a load responsiveness test.

In order to obtain a load response at 100 ms, the load response procedure shown in FIGS. 3 and 4 was operated every 100 ms.
The load response was possible without excess or deficiency in the amount of stored electricity.

Since it is not necessary to control the operation of the reformer at intervals of 100 ms, the procedure shown in FIG.
Is set to 10 and the control of SB10 and SB20 is set to 100 m
Even when a load responsiveness test in which the s interval and the SB 30 were controlled at 1 s intervals was performed, the load response was possible without any excess or deficiency of the hydrogen storage amount of the buffer tank 8 and the power storage amount of the power storage means 53.

FIG. 7 shows a configuration in which the buffer tank filling blower 26 of the configuration of FIG. 1 is omitted. Fuel gas production means B1
Operating pressure of the fuel cell system B2, and the pressure difference between the fuel gas production means B1 and the fuel cell system B2 causes the buffer tank system B to operate.
4 is operated. That is, when filling the buffer tank 8 with fuel, the buffer tank inlet valve 18 is opened and the buffer tank outlet valve 1 is opened.
The pressure of the buffer tank 8 is brought close to the pressure of the fuel gas producing means B1 by reducing the pressure of the fuel cell 9. When fuel is released from the buffer tank 8, the buffer tank inlet valve 18 is throttled and the buffer tank outlet valve 19 is opened.

In this embodiment, the operating pressure of the fuel cell system B2 is set to 0 kg / cm ² G (atmospheric pressure),
Operating pressure of 5 kg / cm ² G, LaNi _4.7 Al
A hydrogen storage alloy tank filled with _0.3 alloy at a volume ratio of 80% was used.

For a 3 kW fuel cell, the buffer tank 8
As a result, when a 0.1-liter hydrogen storage alloy tank was applied, the load could be controlled within the capacity range of the buffer tank 8 during load responsiveness control.

At this time, in order to control the temperature of the buffer tank 8 using the hydrogen storage alloy tank, a cooling system comprising a cooling water pump 41, a heat exchange section 42 in a fuel cell, and a radiator 44 shown in FIG. And a heat exchange section 43 in the buffer tank, and the temperature of the buffer tank 8 is set to about 75 ° C. which is almost equal to the operating temperature of the fuel cell 9.

FIG. 9 shows a configuration provided with a buffer tank bypass pipe 22 connecting the inlet and outlet of the buffer tank 8 having the configuration shown in FIG.

The buffer tank bypass pipe 22 has a buffer tank bypass valve 23. When filling the buffer tank 8 with fuel, the buffer tank inlet valve 18 is opened, and the openings of the buffer tank bypass valve 23 and the buffer tank outlet valve 19 are adjusted. When discharging fuel from the buffer tank 8, the buffer tank inlet valve 18 is closed, and the openings of the buffer tank bypass valve 23 and the buffer tank outlet valve 19 are adjusted. When shutting out the fuel from the buffer tank 8,
The buffer tank inlet valve 18 and the buffer tank outlet valve 19 are closed, and the opening of the buffer tank bypass valve 19 is adjusted.

FIG. 10 shows a configuration in which the pressure difference between the fuel gas producing means B1 and the fuel cell system B2 is recovered as power. The expansion turbine 2 is connected to the buffer tank bypass pipe 22.
3 'and the buffer tank bypass valve 23, and the power recovery blower 10' is driven by the power of the expansion turbine 23 '.

FIG. 11 shows, in addition to the structure of FIG. 10, a fuel cell system bypass pipe 24 connected from the outlet of the buffer tank 8 to the combustor 17 in the fuel gas producing means B1, and a fuel cell system bypass pipe 24. The fuel cell system bypass valve 25 was installed.

When storing hydrogen in the buffer tank 8 using a hydrogen storage alloy, the buffer tank outlet valve 19 is closed,
By adjusting the fuel cell system bypass valve 25, the outlet gas of the buffer tank 8 is led directly to the combustor 17. When filling the buffer tank 8 with fuel, the fuel cell bypass valve 25 and the buffer tank inlet valve 18 are closed, and the buffer tank bypass valve 23 is closed.
The fuel is supplied to the fuel cell 8 by adjusting the opening of the buffer tank outlet valve 19.

The gas discharged from the buffer tank 8 is directly introduced into the combustor 17, and the fuel cell 9 uses the fuel directly supplied from the fuel gas producing means B 1 to increase the hydrogen utilization rate, thereby reducing the low hydrogen discharged from the buffer tank 8. There is no need to use a concentration of fuel.

[0110]

According to the control of dividing the load response control and the fuel production amount control of the present invention and setting the reference value of the amount of fuel to be charged into the buffer tank 8 according to the load amount, the minimum buffer tank 8 Load response is possible without excess or shortage of fuel by capacity.

The operating pressure of the fuel gas producing means B1 is made higher than the operating pressure of the fuel cell system B2, and the buffer tank system B4 is controlled by the pressure difference, so that the buffer tank filling blower 26 becomes unnecessary. Since the operating pressure of the fuel gas producing means B1 increases and the fuel gas producing means B1 becomes compact, a fuel cell power generation system with a high output density can be configured.

That is, load response can be made possible with a small-capacity buffer tank, and the operating pressure of the fuel gas producing means is increased to make the fuel gas producing means compact, and the operating pressure of the fuel gas producing means and the pressure applied to the fuel cell are reduced. By providing the difference, a blower for filling the buffer tank with fuel can be omitted, and a fuel cell power generation system capable of responding to a sudden load change can be provided.

[Brief description of the drawings]

FIG. 1 is a conventional configuration diagram of a fuel cell system including a buffer tank.

FIG. 2 is a block diagram showing input / output of a controller of the fuel cell system.

FIG. 3 is a flowchart showing a measurement step of load response control and a step of responding to a load change in a short time.

FIG. 4 is a flowchart showing a step of adjusting a fuel production amount in load response control.

FIG. 5 is a diagram showing the hydrogen utilization rate dependency of the cell voltage of the fuel cell.

FIG. 6 is a flowchart showing a second procedure of the load response control.

FIG. 7 is a first configuration diagram showing a fuel cell system of the present invention.

FIG. 8 is a configuration diagram showing a method for controlling the temperature of the hydrogen storage alloy tank of the present invention.

FIG. 9 is a second configuration diagram showing the fuel cell system of the present invention.

FIG. 10 is a third configuration diagram showing the fuel cell system of the present invention.

FIG. 11 is a fourth configuration diagram showing the fuel cell system of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pump for steam reformer fuel, 2 ... Water pump for steam reformer, 3 ... Fuel vaporizer, 4 ... Reforming reactor, 5 ... Shift converter, 6 ... CO selective oxidizer, 7 ... CO selective oxidizer Blower, 8: buffer tank, 9: fuel cell, 10: blower for fuel cell air electrode, 10 ': power recovery blower, 11 ...
Condenser, 12 ... Air electrode humidification water pump, 13 ... Air electrode humidifier, 14 ... Fuel electrode humidification water pump, 15 ... Fuel electrode humidifier, 16 ... Combustor blower, 17 ... Combustor, 18 ...
Buffer tank inlet valve, 19: Buffer tank outlet valve, 20: Fuel pump for combustor, 21: Vaporizer for combustor fuel, 22 ...
Buffer tank bypass pipe, 23 ... Buffer tank bypass valve, 23 '... Expansion turbine, 24 ... Fuel cell system bypass pipe, 25 ... Fuel cell system bypass valve, 26 ... Buffer tank filling blower, 41 ... Cooling water pump, 42 ... Heat exchange part in fuel cell, 43 ... Heat exchange part in buffer tank, 44 ... Radiator, 51 ... Inverter for fuel cell system, 52 ... Electric load, 53 ... Electric storage means, 54 ... Inverter for electric storage means,
B1: fuel gas production means, B2: fuel cell system, B3: electric system, B4: buffer tank system, C1: controller, C2
... memory for data storage, C3 ... memory for program storage, C4 ... arithmetic unit.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Yuichi Kamo 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (56) References JP-A-7-320763 (JP, A) JP-A-7-49037 (JP, A) JP-A-61-71560 (JP, A) JP-A-9-306531 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 8/00-8/24

Claims (2)

(57) [Claims] 1. A fuel gas producing means for converting a fuel of a compound containing carbon and hydrogen into a fuel gas containing hydrogen in a reforming reactor, and a pair of electrodes and an ion-conductive electrolyte disposed between the electrodes. A fuel cell in which cells are stacked, a buffer tank for storing fuel gas between the fuel gas producing means and the fuel cell is provided, and power is generated using the fuel gas produced by the fuel gas producing means as fuel for the fuel cell, In a fuel cell power generation system connected to a load via an inverter, the fuel gas pressure at the outlet of the fuel gas producing means is higher than the operating pressure of the fuel cell, and the outlet pressure of the fuel gas producing means and the operation of the fuel cell A fuel cell power generation system, wherein the amount of fuel gas stored in the buffer tank is adjusted using a pressure difference. 2. The fuel cell power generation system according to claim 1, wherein a fuel gas pressure at an outlet of the fuel gas producing means is higher than an operating pressure of the fuel cell by 1 kg / cm ² or more.