JPS60107268A - Control system for fuel cell power generation plant - Google Patents

Abstract

PURPOSE:To enable the conversion rate of hydrogen in a reformer to be controlled within a given range with high reliability by using both a temperature set on the basis of the flow rate of an original gas and a delay element to control the temperature of the reaction chamber of the reformer. CONSTITUTION:The detected value (k) obtained by and sent from an original gas flow rate detector 11 is converted into a detected flow-rate value (l) including a delay by means of a delay element 12. The detected value (l) is then passed through a set-temperature-computing element to produce a temperature-setting value (m) which is based on the value (l). According to the difference (e) between the value (m) and the detected value (d) sent from the representative temperature detector 7 of a reaction chamber, a controller 8 produces a command signal (f) corresponding to the deviation of the temperature of the reaction chamber. The command signal (f) is added to a set flow rate (b) for a d.c. current to obtain a final set flow rate (g). According to the difference (i) between the detected value (h) obtained by a fuel electrode flow rate detector 10 and the set flow rate (g), an opening degree command (j) is delivered from a controller 9 to control a fuel electrode flow rate control valve 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a fuel cell power plant, and particularly to a control device for a fuel cell power plant that is capable of stably supplying hydrogen gas into a cell body.

[Technical background of the invention]

A fuel cell has a series of systems that generate hydrogen gas from raw material gas through a reformer, supply this hydrogen gas to the cell body, cause an electrode reaction, and then recover it back to the reformer. .

Therefore, stable supply of hydrogen gas to the battery main body is achieved by stably supplying the fuel electrode flow rate to the battery main body and the proportion of hydrogen contained therein. The final control is the fuel electrode flow rate control within the battery body.

FIG. 1 is a block diagram of a conventional fuel electrode flow rate control configuration, and will be explained using this diagram. In Fig. 1, 1 is a reformer, 2 is a battery main body, gas reformed in the reformer 1 is consumed in the battery main body 2 according to the load, and then returned to the reformer 1. It returns and is recovered as fuel for combustion in the reformer. Note that 3 is a fuel supply line to components such as fuel for the auxiliary burner of the Tardecon Sorezza. At this time, the supply of reformed gas to the cell main body is performed by the fuel electrode flow control valve 4 as follows.

That is, the fuel electrode flow rate set value g is determined by dividing the DC current a corresponding to the magnitude of the load into the set flow rate for the DC current derived via the set flow rate calculator 5, and then converting the DC current a into the set temperature calculator 6. Adding the command signal f based on the reaction chamber temperature deviation from the regulator 8 based on the temperature deviation e between the reaction chamber representative temperature set value C for the DC current derived from the temperature sensor 7 and the detected temperature d from the temperature detector 7. obtained from. When the fuel electrode flow rate setting value g is given here, the regulator 9 adjusts the fuel electrode flow rate based on the flow rate deviation i between the fuel electrode flow rate setting value g and the fuel electrode flow rate detection value (actual flow rate) h from the flow rate detector 10. Flow rate control is performed by giving an opening command j to the valve 4.

[Problems with background technology]

In the conventional device having the above configuration, when the load is large, that is, when the DC current is large, the amount of hydrogen required in the battery body is larger than when the current is small, so the fuel electrode flow rate inevitably increases. Accordingly, more reforming capacity is required in the reformer in order to achieve a constant hydrogen conversion rate.

However, the hydrogen conversion rate of the reformer is determined by the flow rate of the raw material gas in the reformer and the temperature environment of the reaction chamber, but in the conventional control method, the DC current a is one indicator of the flow rate of the raw material gas. This was dealt with by increasing the reaction chamber temperature set value C using the set temperature calculator 6.

That is, as shown in FIG. 2, the DC current value a may be 82
When this occurs, the reaction chamber set temperature T is raised from TI to T2 to further speed up the reforming reaction rate in the reformer, thereby increasing the reforming capacity.

However, in addition to the fuel flowing into the fuel electrode, the raw material gas for the reformer also contains fuel for the auxiliary nozzle of the turbo compressor and, in some cases, fuel for the steam generation burner in the temperature control system of the cell body. If the flow rate of the fuel supply line 3 to other components increases for some reason, the direct current value and the reformer raw material gas flow rate do not necessarily correspond uniquely. Therefore, even if the reaction chamber temperature is controlled to a set value, it cannot be said that the hydrogen conversion rate in the reformer is maintained within a certain range at that time.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a control device for a fuel cell power plant that can reliably control the hydrogen conversion rate in a reformer within a certain range. It is an object.

[Summary of the invention]

In the present invention, a reaction chamber temperature setting is set for the actual flow rate of the reformer raw material gas, and the hydrogen conversion rate in the reformer is maintained within a certain range by controlling the actual reaction chamber temperature to the set temperature. It is.

[Embodiments of the invention]

Examples will be described below with reference to the drawings. FIG. 3 is a configuration diagram of an embodiment of a control device for a fuel cell power generation plant according to the present invention. Reference numerals 1 to 5 and 7 to 10 in the figure correspond to those in FIG. 11 is a raw material gas detector, 12 is a delay element (described later), and 13 is a set temperature calculator. In this embodiment, the raw material gas detection value k from the raw material gas detector 11
is the flow rate detection value t which takes into account the delay due to the delay element 12, and further derives the temperature set value m based on the above t via the set temperature calculator 13, and combines this with the value from the representative temperature detector 7 of the reaction chamber. A command signal f for the reaction chamber temperature deviation is given by the controller 8 from the deviation C from the detected value d, and this is added to the set flow rate S for the DC current to obtain the final set flow rate g. From then on, as in Figure 1, the fuel electrode flow rate detector 1
Based on the deviation 1 between the detected value 0 and g, the opening command j is output from the regulator 9 to control the fuel electrode flow rate control valve 4. In other words, in addition to the hydrogen gas consumed in the battery itself according to the load, there is also fuel consumption by other components, so a correction that takes these into consideration is derived from the detected value of the raw material gas flowing into the reformer, and this This allows for very fine control of the deviation between the temperature and the typical temperature of the reaction chamber.

FIG. 4 is a characteristic diagram of the reaction chamber set temperature based on the reformer raw material gas flow rate. According to this example, when the reformer raw material gas flow rate increases from G1 to 02, the reaction chamber set temperature is TI The reaction chamber temperature is also controlled to follow iL.

FIG. 5 is a diagram comparing and showing the difference in operation between the conventional control method and the temperature setting according to this embodiment. In the figure, the upper figure shows the effect of the conventional DC current value, and the lower figure shows the effect of the present embodiment 911.

Solid lines La and LG are set temperature lines based on the DC current value and the reformer raw material gas flow rate, respectively. In addition, the set temperature line La takes into account the balance under ttTh1 conditions of the fuel required for the entire battery body and reformer burner, as well as the auxiliary burner for the turbo compressor and the steam generation burner in the battery body temperature control system. It is given as follows.

Now, considering the case where such a balance is maintained, when the DC current value as a load is 81, the balance point Pal in the conventional control and the balance point P in the present implementation ψ11. 1 and 1 are both set temperatures TI, and bring about the same effect. Also, when the DC current value reaches 82,
The balance points are P8□ respectively.

The temperature becomes PG2, and the set temperature becomes T2, which is the same.

However, even though the DC current value corresponding to the load is al, for some reason the amount of fuel required by the auxiliary burner of the turbo compressor is large, and therefore the fuel flow rate in the fuel supply line 3 to other components increases. think of.

In this case, if the fuel gas flow rate leaving the reformer 1 is the same, the fuel gas flow rate to the battery body will decrease by the amount of fuel gas diverted to other components; Since the amount of hydrogen consumed does not change, the flow rate of fuel gas flowing into the reformer l from the battery main body 2 decreases, resulting in a decrease in the temperature of the reformer reaction chamber. Here, the broken line "AI + La2" in FIG. 5 shows this relationship, and the raw material gas flow rate and reaction chamber temperature before and after the fuel flow rate in the fuel supply line 3 increases when the DC current is 81, respectively. Show relationships.

Let's compare and consider these cases. In the case of the conventional method, even if there is an increase in fuel to the fuel supply line to other components,
As long as the DC current value a1 corresponding to the load current does not change, the reaction chamber set temperature Tl remains unchanged, and the state is therefore settled at the point marked Pa. Therefore, in this case, the Even though the raw material gas flow rate has increased, the temperature environment of the reaction chamber remains unchanged.

On the other hand, in the case of this embodiment, when the fuel flow rate in the fuel supply line 3 increases, a correction amount is added based on the increased inflow of the raw material gas, so the relationship between the reformer raw material gas and the reaction chamber temperature changes from La□. Moved to LaS, resulting in points marked in the figure) P. Balance at '.

In this way, in this embodiment, when the flow rate of raw material gas to the reformer increases and the burden of reaction processing on the reformer becomes heavier, the temperature in the reaction chamber is reliably raised to facilitate the reaction. do.

Further, in this embodiment, the controlled variable, ie, the set value of the reformer reaction chamber temperature, is given by the raw material gas flow rate that has almost no delay with the fuel electrode flow rate, which is determined by the manipulated variable. Therefore, if the delay element 12 is not taken into account, when the raw material gas flow rate value k increases, the reaction chamber temperature set value m immediately increases, whereas the reaction chamber actual temperature d increases after the raw material gas in the reformer increases. This does not increase immediately due to the delay in the flow rate while it becomes fuel in the reformer combustion chamber via the battery body and the delay in the temperature rising after this increase.

FIG. 6 is a response diagram between the set temperature of the reaction chamber and the actual temperature when the DC current increases when no delay element is used in this embodiment. That is, as shown in FIG.
Considering the case where it is necessary to increase the fuel electrode flow rate due to an increase in the DC current value in step 1, the reaction chamber actual temperature shown by the broken line increases with respect to the increase in the reaction chamber set temperature over time shown by the solid line in the figure. The temperature increase cannot keep up, and the temperature deviation DT between the set temperature and the actual temperature increases, and both temperatures continue to rise without limit. This is because the delay in the process in which the increase in the flow rate of the reformer appears as a rise in the reaction chamber temperature is not taken into account.

Therefore, the problem can be solved by adding a delay element and setting a delay time so that the response speed of the set temperature is at least slower than the actual temperature of the reaction chamber in response to a change in the raw material gas flow rate.

Figure 7 is a response diagram between the reaction chamber set temperature and actual temperature when a delay element is used in this example.The solid line shows the set temperature response, and the broken line shows the actual temperature response, and stable control is achieved. It becomes possible.

FIG. 8 is a block diagram of another embodiment of the present invention. In this embodiment, fine control is attempted by detecting the produced gas flow rate instead of the raw material gas flow rate. Reference numerals 1 to 5, 7 to 10, and 12.13 in the figure correspond to those in FIG.

Reference numeral 14 denotes a flow rate detector that detects the flow rate of generated gas from the reformer 1. That is, based on the detected value n of the produced gas, the set temperature calculator 13 first determines the reaction chamber set temperature 0 without taking into account the delay, and then gives the set temperature m from the delay element 12. The other configurations are the same as in FIG. 3. The subsequent operations are the same as those shown in FIG. 3, and will therefore be omitted.

Note that giving the set temperature based on the generated gas flow rate is basically the same as giving the set temperature based on the raw material gas flow rate.
Regarding the delay element 12, it goes without saying that adding a delay after giving a set temperature is the same as adding a delay to the detected flow rate value and then giving a set temperature.

〔Effect of the invention〕

As explained above, according to the present invention, the temperature set based on the raw material gas flow rate is used and a delay element is provided to control the temperature of the reformer reaction chamber, so that the hydrogen conversion rate in the reformer can be controlled within a certain range. Accordingly, it is possible to provide a control device for a fuel cell power generation plant that can reliably control the power generation plant.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional fuel electrode flow rate control configuration;
The figure is a diagram showing the relationship between reaction chamber temperature settings based on the DC current value used in conventional control, Figure 3 is a configuration diagram of an embodiment of the control system for a fuel cell starting plant according to the present invention, and Figure 4 is a raw material for the reformer. A characteristic diagram of the temperature set in the reaction chamber based on the gas flow rate. Figure 5 is a diagram comparing the effects of conventional control and the present invention. Figure 6 is a diagram showing the characteristics of the temperature set in the reaction chamber based on the gas flow rate. Figure 7 is a diagram showing the response between the reaction chamber set temperature and actual temperature when the DC current is increased when the DC current is increased, Figure 7 is a diagram showing the response when a delay element is used, and Figure 8 is a diagram showing another implementation of the present invention. Example configuration 1. DESCRIPTION OF SYMBOLS 1... Reformer, 2... Battery body, 3... Fuel supply line to other components, 4... Fuel electrode flow rate control valve, 5... Set flow rate calculator, 6. 13... Set temperature calculator, 7... Temperature detector, 8.9... Controller,
10, 11.14... Flow rate detection value, 12... Delay element, a... DC current value, b... Set flow rate for DC current, C... Reaction chamber temperature set value, d...・Reaction chamber temperature detection value, C...Temperature deviation, f...Command signal based on reaction chamber temperature deviation, g...Fuel electrode flow rate setting value, h.
...Fuel electrode flow rate detection value, l...Flow rate deviation, j...
Opening command, k...Detected raw gas flow rate, t...Detected raw gas flow rate with delay taken into account, m...
Reaction chamber temperature set value, n...Produced gas flow rate detection value, 0.
...Reaction chamber temperature set value without taking into account delay. Patent applicant Tokyo Shibaura Electric Co., Ltd. Representative Patent attorney Nori Ishii Figure 1 Figure 4 has been changed to the original vibration system @ raw material flow rate G Figure 5 revised I, raw material power 2M, amount G Mama L Figure 8

Claims (1)

[Claims] In a fuel cell power generation plant, the reformed gas from the reformer is introduced into the cell main body via the fuel pole flow control valve, and the exhaust gas after the electrode reaction in the cell main body is collected into the reformer. a representative temperature detector that detects the temperature of the raw material, a flow rate detector that detects the flow rate of the raw material to the reformer, a delay element that gives a delay time to the value detected by the flow rate detector, and a signal from the delay element. and a set temperature calculator that gives a representative room set temperature based on the difference between the temperature set value by the set temperature calculator and the detected value by the representative temperature detector, and 1. A control device for a fuel cell power generation plant, characterized in that control is performed via a power regulator based on an IS value added to a flow rate command value according to a load.