JP2003288927A - Fuel cell control system - Google Patents

Abstract

(57) [Summary] To facilitate the operation control of a reformer and shorten the waiting time until the start of starting of a fuel cell. The fuel cell includes a fuel cell and a reformer.
Performs a reforming process by causing a supplied raw material to undergo a reforming reaction, and generates fuel at a fuel flow rate according to the reforming amount of the raw material. The fuel cell 2 generates necessary electric power according to the flow rate of the fuel supplied from the reformer 3. Reformer 3
The operating conditions are set based on the reforming processing amount set in accordance with the fuel flow rate, the operating parameters of the reformer 3 are set in a plurality of stages, and are set by selecting the operating parameters. Based on this, fuel generation control is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell control system used as, for example, a power source of an electric vehicle, a portable power source, a household power source or a building power source, and more particularly, hydrogen gas as a fuel. The present invention relates to a method of operating a reformer that produces hydrogen by a reforming reaction.

[0002]

2. Description of the Related Art For example, Japanese Patent Application Laid-Open No. 11-1302 discloses a fuel reformer for a reformer in a fuel cell. This fuel reformer uses methanol, gasoline,
Alternatively, it has a reformer to which a raw material made of a hydrocarbon-based organic substance such as natural gas, water, and air are supplied. In this reformer, a fuel (hydrogen gas) is generated by subjecting the raw material to a reforming reaction on a high temperature catalyst. In this case, the operation of the reformer is controlled by setting various conditions such as the raw material and air supply amount, or the catalyst temperature.

For example, when methanol is used as a raw material, steam reforming of methanol with water (endothermic reaction)
And partial oxidation reforming of methanol with air (exothermic reaction)
A reforming reaction occurs with the reforming gas and the reforming gas containing hydrogen gas is generated. The reformed gas generated by this reforming reaction is supplied to the fuel cell together with air, and the hydrogen in the reformed gas and the oxygen in the air are chemically reacted to generate electric power.

As described above, there are steam reforming method and partial oxidation method as the reforming method of the raw material by the reformer. For example, when the partial oxidation method of methanol is taken as an example, it is expressed by a theoretical formula as shown in the following formula (1). However, as the actual oxidation reaction of methanol, complete oxidation is general as shown in the following formula (2). Further, as other oxidation reactions of methanol, partial oxidation reactions such as the following expressions (3) to (5) also occur.

[0005]

(1) 2CH ₃ OH + O ₂ → 2CO ₂ + 4H ₂ (2) 2CH ₃ OH + 3O ₂ → 2CO ₂ + 4H ₂ O (3) 2CH ₃ OH + O ₂ → 2CO + 2H ₂ O + 2H ₂ (4) 2CH ₃ OH + O ₂ → CO ₂ + CO + H ₂ O + 3
H ₂ (5) 2CH ₃ OH + 2O ₂ → 2CO ₂ + 2H ₂ O + 2
H ₂

[0006]

However, the above-mentioned oxidation reaction in the reformer is a chemical reaction between methanol and oxygen, and it is impossible to select the reaction depending on the raw materials. Moreover, in the reaction using the same element as the raw material,
It is not easy to selectively cause only a specific reaction. What kind of reaction mainly occurs depends on the amount of methanol treated by the reformer (reforming amount), the amount of air (oxygen) supplied, the composition of the catalyst, the catalyst temperature (reforming reaction temperature), or the pressure. It is decided by setting various conditions such as. In the operation of such a reformer,
In order to cause more partial oxidation as shown in the formula (1), it is necessary to finely control the above-mentioned conditions.

Since the operation of the reformer in the conventional fuel reformer is controlled by setting the above-mentioned various conditions, the operating conditions may become infinite. As a result, the operation control of the reformer becomes extremely difficult, and the waiting time until the start of the fuel cell start is greatly affected by the delay in the reforming time.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a novel fuel cell control system for easily controlling the operation of a reformer.

Another object of the present invention is to produce a larger amount of fuel in the reforming reaction of the raw material by the reformer and to emit harmful substances such as carbon monoxide (CO) discharged from the reformer. Is to reduce.

[0010]

In order to solve the above problems, the present invention provides a control system for a fuel cell. This control system has a reformer and a fuel cell. The reformer performs a reforming process in which the supplied raw material undergoes a reforming reaction to generate a fuel having a fuel flow rate according to the reforming amount of the raw material. The fuel cell generates necessary electric power according to the flow rate of fuel supplied from the reformer. The operating conditions of the reformer are set by setting the operating parameters of the reformer in a plurality of stages based on the reforming processing amount set according to the fuel flow rate and selecting the operating parameters. The control unit controls fuel generation based on the set operating conditions.

In the present invention, the operating conditions of the reformer are preferably set by selectively combining operating parameters. In this case, it is preferable that the operation of the reformer is alternately performed for each selected operation parameter, and the averaged operation conditions are set.

[0012]

1 is a block diagram of a control system for an electric vehicle according to the present embodiment. The control system 1 includes a solid polymer fuel cell 2 as a power source, and a reformer 3 that supplies fuel (hydrogen gas) to the fuel cell 2. The reformer 3 is provided with a combustor 4 and, for example, a raw material tank 5 containing methanol as a raw material and a water tank 6 containing water.
And a compressor (air compressor) 7 that supplies air. As a result, the reformer 3 is supplied with methanol from the raw material tank 5, water from the water tank 6, and air from the compressor 7. That is, in the reformer 3, a reforming reaction occurs between steam reforming (endothermic reaction) with water and methanol and partial oxidation reforming (exothermic reaction) with air and methanol. The reforming reaction temperature (catalytic reaction) in the reformer 3 is heated to a predetermined set temperature by the heat generated by the exothermic reaction of the partial oxidation reforming of air and methanol, and hydrogen gas as a fuel The contained reformed gas is generated. The reformer 3 performs a reforming process in which the methanol supplied from the raw material tank 5 undergoes a reforming reaction to generate a reformed gas (fuel) having a fuel flow rate according to the reforming amount of methanol.

After the reforming reaction, the high-temperature reformed gas is used as the reformer 3
Is sent into the fuel cell 2 together with the air from the compressor 7. At this time, the cooling water W is circulated and supplied into the fuel cell 2, and the cooling water W cools the high temperature reformed gas fed into the fuel cell 2 to a predetermined set temperature. There is. The reformed gas cooled to a predetermined set temperature is supplied to an anode electrode and a cathode electrode (not shown) in the fuel cell 2. As a result, the fuel cell 2 is start-controlled by the reformer 3 to generate electric power by a chemical reaction between hydrogen in the reformed gas and oxygen in the air. The fuel cell 2 generates necessary electric power according to the flow rate of the fuel supplied from the reformer 3.

A part of hydrogen in the reformed gas and oxygen in the air fed into the fuel cell 2 is fed into the combustor 4 of the reformer 3 and supplied from the raw material tank 5. It is combusted together with the generated methanol and the air sent from the compressor 7. The heat generated by the combustion reaction in the combustor 4 is reused in order to vaporize the methanol and water supplied into the reformer 3 and promote the generation of reformed gas by the endothermic reaction of steam reforming. At the same time, the combustion gas in the combustor 4 is discharged outside the vehicle.

Further, a concentration sensor 8 and a three-way flow control valve 9 are provided along the flow path from the reformer 3 to the fuel cell 2. The concentration sensor 8 detects the carbon monoxide concentration (CO value) and the hydrocarbon concentration (HC value) in the reformed gas. As shown in FIG. 2, the three-way flow control valve 9 has a first valve 9A, a second valve 9B, and a third valve 9C, respectively.

Each of the valves 9A, 9B and 9C in the three-way flow control valve 9 has a concentration sensor 8 as described later.
Based on the CO value and the HC value in the reformed gas detected by, the control device 13 controls the opening and closing freely. When the first valve 9A is opened, the reformed gas from the reformer 3 is supplied into the fuel cell 2 while controlling the flow rate. When the second valve 9B is opened, the reformed gas from the reformer 3 is supplied into the combustor 4 of the reformer 3 and used for combustion. Then, when the third valve 9C is opened, the reformed gas from the reformer 3 is discharged outside the vehicle.

On the other hand, the electric power generated by the fuel cell 2 is supplied to the drive motor 12 via a power regulator 11 to which a battery 10 which is a secondary battery as an auxiliary power source is connected. The drive motor 12 rotationally drives the drive wheels 14 of the vehicle body based on an instruction from the control device 13 connected to the power regulator 11. The control device 13 is connected to a drive operation device 15 including an operation member such as an accelerator pedal, an ignition switch 16 and the like.
Further, the sensor signal from the concentration sensor 8 and the sensor signal from the temperature sensor provided in the reformer 3 are combined into the control device 1.
Input to 3. This temperature sensor is a sensor for detecting the reforming reaction temperature. The drive operation device 15 outputs to the control device 13 the amount of depression of the accelerator pedal (accelerator opening degree) and the like accompanying acceleration and deceleration during operation. The power adjuster 11 adjusts the power distribution based on an instruction from the control device 13, distributes the power required for acceleration and deceleration to the drive motor 12, and at the same time, the reformer 3, the combustor 4,
Electric power is distributed to auxiliary equipment such as the compressor 7. The ignition switch 16 instructs the control device 13 to turn on / off the control system 1, and turns on the power switch 17 of the reformer 3 when the control system 1 is turned on. When the fuel cell 2 does not obtain sufficient traveling power consumed by the drive motor 12 or sufficient power consumed by the auxiliary machine, the battery 10 is discharged to compensate for the insufficient power.

By the way, as in this embodiment, for example,
In the case where the load-responsive reformer 3 is provided, the amount of fuel produced changes infinitely depending on the accelerator opening and the required amount of electric power. Moreover, when the fuel production amount is made to respond to the load variation of the accelerator opening degree or the required electric power amount, the reforming treatment amount of the raw material methanol varies. Therefore, harmful substances such as carbon monoxide (CO) discharged from the reformer 3 may increase, leading to environmental damage. Further, in order to efficiently generate a larger amount of fuel in the reformer 3, it is important to find the optimum air supply amount based on the reforming reaction temperature and pressure at that time.

Therefore, in the present embodiment, the methanol treatment amount (reformation treatment amount) of the reformer 3 according to the supply amount of methanol supplied from the raw material tank 5 is set as a target value,
The operating conditions of the reformer 3 are set. This target value (methanol processing amount) is set by the amount of reformed gas generated in the reformer 3 (fuel flow rate) and the amount of electric power generated by the fuel cell 2 in accordance with this fuel flow rate. .

FIG. 3 is a flow chart showing the procedure of fuel production control by the control device 13. First, the required power, that is, the power required to control the rotation of the drive motor 12 during operation is determined (step 1), and the fuel flow rate required to generate this required power is set (step 2). Then, the methanol throughput required to generate this fuel flow rate is set (step 3), thereby setting the target value. Based on this target value (processed amount of methanol), the supply of methanol from the raw material tank 5 is controlled (step 4), and the fuel (reformed gas) is generated by the operation of the reformer 3 (step 5). ). The generated fuel is supplied to the fuel cell 2 (step 6), and power generation is started (step 7). And
It is determined whether or not the fuel flow rate to the fuel cell 2 has reached a predetermined set flow rate (step 8). When it is determined in step 8 that the fuel flow rate has not reached the predetermined set flow rate, the process proceeds to step 4, in which the raw material is supplied to the reformer 3 to generate the fuel and the fuel cell 2 Generation of electric power continues by supplying fuel to. On the other hand, when it is determined in step 8 that the fuel flow rate has reached the predetermined set flow rate, the operation of the reformer 3 is stopped and the fuel generation is terminated.

Regarding the operation of the reformer 3, first, the reforming processing amount is set according to the fuel flow rate, and then the operating conditions of the reforming device 3 are set based on the set reforming processing amount. As the operating conditions of the reformer 3, by setting the operating parameters in a plurality of stages for each of the above target values (methanol throughput) and selecting these operating parameters based on the operating conditions,
Fuel generation control is performed.

That is, in the present embodiment, the above-mentioned operating conditions are "95% operation", "70% operation", "50% operation" with respect to the maximum fuel flow rate due to the operation of the reformer 3. It is set to 6 levels of operation parameters such as "25% operation", "5% operation", and "0% operation (operation stop)". For example, when the operating condition is selected as the operating parameter of “70% operation”, the supply amount of methanol to the reformer 3 and the operating time are adjusted to meet the target value (methanol treatment amount). Generation control of fuel at the fuel flow rate is performed. In addition, for example, under the operating condition in which the operating parameter is not set, such as the operating condition is “40% operating”, a plurality of operating parameters of “50% operating” and “25% operating” are selected and operated. It The operation control of the reformer 3 in this case is performed by alternately adjusting each operation time for each operation parameter and averaging the operation conditions to "40% operation". As a result, the operation control of the reformer 3 can be simplified, the weight of the entire control system can be reduced, and the number of parts such as sensors can be reduced.
Moreover, since the target value (methanol treatment amount), which is the operating condition of the reformer 3, is set finitely, the reforming rate can be increased and the fuel consumption can be improved.

FIG. 4 is a flow chart of a switching control routine of the three-way flow control valve 9 executed in the control device 13. This routine is repeatedly executed at predetermined intervals, and in each execution cycle, the CO value detected at that time,
The HC value and the reforming reaction temperature are read. First, in step 11, it is determined whether or not the CO value in the reformed gas is less than a predetermined set value. If the CO value is lower than the predetermined set value, the routine proceeds to step 12, where it is determined whether the HC value is less than the predetermined set value. If an affirmative decision is made in this step 12, that is, if the HC value is lower than the set value, then the processing advances to step 13, and whether the reforming reaction temperature in the reformer 3 is equal to or higher than a predetermined set value. Is determined.

When it is determined in step 13 that the reforming reaction temperature is equal to or higher than the predetermined set value, the process proceeds to step 14, the first valve 9A is opened, and this routine is exited. As a result, high-temperature reformed gas having a low CO value and a low HC value is supplied into the fuel cell 2 and electric power is generated. As a result, poisoning of the electrodes and the like in the fuel cell 2 is prevented, and the power generation efficiency of electric power is increased,
Prevent harmful gas from being emitted outside the vehicle.

On the other hand, if the determination in step 13 is negative, that is, if the reforming reaction temperature is lower than the set value, the process proceeds to step 15 and the second valve 9B is operated.
Opens and exits this routine. As a result, the reformed gas is supplied into the combustor 4, and the reforming reaction temperature in the reformer 3 rises due to the combustion of the reformed gas. As a result, the reforming rate of the raw material in the reformer 3 is increased, and the fuel efficiency can be improved. Moreover, since the reformed gas having a low reforming reaction temperature is not supplied into the fuel cell 2, a decrease in power generation efficiency of electric power in the fuel cell 2 is prevented.

On the other hand, when a negative determination is made in step 11, that is, when the CO value is equal to or greater than the set value, the process proceeds to step 17, and the second valve 9B is opened. And
In the following step 18, it is determined whether the reforming reaction temperature in the reformer 3 is equal to or higher than a predetermined set value. When the affirmative judgment is made in this step 18, that is, when the reforming reaction temperature is equal to or higher than the predetermined set value, the routine proceeds to step 19, the third valve 9C is opened, and this routine is exited.
As a result, the reformed gas having a high CO value is discharged outside the vehicle.

On the other hand, when it is determined in step 18 that the reforming reaction temperature is not higher than the predetermined set value, this routine is exited without opening the third valve 9C. As a result, the reformed gas is supplied into the combustor 4, the reforming reaction temperature in the reformer 3 rises, the reforming rate of the raw material in the reformer 3 is increased, and the fuel consumption is improved. Can be achieved.

If a negative determination is made in step 12, that is, if the HC value in the reformed gas is equal to or greater than the set value, the process proceeds to step 16. In this step 16, it is determined whether or not it is necessary to generate electric power urgently. When it is necessary to urgently generate electric power (that is, during emergency operation), the process proceeds to step 13 and the same control as the above-described procedure is performed. On the other hand, step 16
When it is determined that it is not necessary to generate electric power urgently, the process proceeds to step 17, the second valve 9B is opened, and the same control as the above-described procedure is performed.

According to this embodiment, the amount of methanol to be processed in the reformer 3 is set according to the flow rate of the fuel supplied to the combustion cell 2. Based on the amount of methanol to be processed, the operating parameters of the reformer 3 are plural. It is set in stages. Then, the operating conditions of the reformer 3 are set by selecting these operating parameters, and the generation control of the reformed gas that is the fuel is performed based on the set operating conditions. The operation of the reformer 3 can be controlled stepwise under selected finite operating conditions, and compared with the operating conditions in the reformer 3 that change indefinitely as in the past, The operation control of the container 3 becomes easy. As a result, the waiting time until the start of the fuel cell 2 is shortened, and the reformer 3 can be reduced in weight and size. Moreover, it is possible to reduce the number of parts such as the sensor, so that the cost can be reduced.
On the other hand, the reformed gas whose reforming reaction temperature in the reformer 3 is lower than a predetermined set temperature is supplied to the combustor 4 of the reformer 3 and burned in the heater 4, so that Contributes to the increase of the reaction temperature. As a result, the reforming rate in the reformer 3 can be improved, and the fuel consumption can be improved. Moreover, the reduction of the power generation efficiency of the electric power in the fuel cell 2 is prevented.

Further, in the present embodiment, in order to set the target value (methanol treatment amount) under the operating conditions of the reformer 3, for example, as a first setting example, the drive operating device 15 is used.
It is conceivable to set it according to the accelerator opening degree. In addition, as a second setting example, it may be set by the electric power used by the drive motor 12. As a third setting example, for example, it may be set by the residual electricity amount of the auxiliary power source in the secondary battery such as the battery 10. As a fourth setting example, for example, when a capacitor is used as the auxiliary power supply, the setting may be made according to the remaining electricity amount of the capacitor. As a fifth setting example, for example, when a hydrogen capacitor is used as the auxiliary power supply, the setting may be made according to the remaining amount of hydrogen in the hydrogen capacitor.
As a sixth example of setting, the number of rotations of the drive motor 12 may be set. As a seventh setting example, by combining the above-described first, second and sixth setting examples, the accelerator opening degree in the drive operating device 15, the power usage amount of the drive motor 12, the motor rotation speed of the drive motor 12, etc. You may set by calculating from a numerical value. And the eighth
As an example of the setting of the above, for example, it may be set by a map created from the accelerator opening degree in the drive operation device 15, the amount of electric power used by the drive motor 12, the motor rotation speed of the drive motor 12, and the like.

According to each example of setting the target value under the operating conditions of the reformer 3 described above, even if there is no system for continuously controlling the amount of methanol to be processed in the reformer 3, the amount of power required during operation can be adjusted. It is possible to generate a high fuel flow rate. Moreover, it is possible to generate a fuel flow rate sufficiently corresponding to the accelerator opening, the amount of power used by the drive motor 12, the amount of remaining electricity of the auxiliary power source, the remaining amount of the hydrogen capacitor, the number of rotations of the motor of the drive motor 12, and the like.

[0032]

As described above, in the present invention, the amount of raw material processed in the reformer is set according to the flow rate of the fuel supplied to the combustion cell, and based on this raw material processed amount, the reformer Operation parameters are set in multiple stages. Then, the operating conditions of the reformer are set by selecting these operating parameters, and the fuel generation control is performed based on these operating conditions. Therefore, the operation of the reformer can be controlled stepwise under the selected finite operating conditions. As a result, the operation control of the reformer can be easily performed, and the waiting time until the start of the fuel cell can be shortened.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a control system for an electric vehicle.

FIG. 2 is a block configuration diagram of a control unit.

FIG. 3 is a flowchart showing a schematic flow of fuel generation control.

FIG. 4 is a flowchart of a switching control routine for a three-way flow control valve.

[Explanation of symbols]

1 control system 2 Fuel cell 3 reformer 4 Combustor 5 raw material tank 6 water tank 7 Compressor (air compressor) 8 Concentration sensor 9 Three-way flow control valve 9A First valve 9B Second valve 9C Third valve 10 secondary battery 11 Power regulator 12 Drive motor 13 Control device 14 drive wheels 15 Drive operating device 16 ignition switch 17 Power switch for reformer

Claims (3)

[Claims] 1. A fuel cell control system comprising: a reformer for performing a reforming process for reforming a supplied raw material to generate a fuel having a fuel flow rate according to the reforming amount of the raw material; A fuel cell that supplies fuel from a quality device and generates necessary electric power according to the fuel flow rate, and the reforming treatment amount is set according to the fuel flow rate, and the reforming treatment amount is set based on the reforming treatment amount. Setting the operating parameters of the quality control device in a plurality of stages, and setting the operating conditions of the reformer by selecting the operating parameters, and based on the operating conditions that have been set, a control unit that performs the fuel generation control, A fuel cell control system having: 2. The fuel cell control system according to claim 1, wherein the control unit sets the operating condition by a plurality of combinations of the operating parameters and controls the operation of the reformer. . 3. The fuel cell according to claim 2, wherein the controller averages the operating conditions by alternately controlling the reformer for each of the operating parameters. Control system.