JPS63119164A - Fuel cell generating system - Google Patents

Abstract

PURPOSE:To prevent an incomplete combustion and a thermal fatigue of a reformer tube, by increasing the air flow fed to the burner of a combustion chamber by a correction amount arithmetic means, when the combustion gas temperature of a fuel reformer device is detected to exceed the upper limit value, so as to increase the excessive rate of the air. CONSTITUTION:When the combustion gas temperature g of a fuel reforming device 1 exceeds the combustion gas temperature upper limit value f, the temperature deflection value h is made positive. Depending on the value of h, a correction arithmetic unit 13 computes a positive correction amount i, and by adding the correction amount i to a preset flow b output from a set flow arithmetic unit 9, the correction set flow j is obtained. Depending on a flow deflection d resulting from the comparison of the set flow j and the air flow c, a control unit 11 outputs an opening instruction e to control an air flow control valve 8, and the flow of the combustion air 7 fed to the fuel reforming device 1 is increased.

Description

[Detailed Description of the Invention] [Objective of the Invention (Industrial Application Field) The present invention relates to a fuel cell power generation system comprising a fuel cell and a fuel reformer, and particularly relates to a fuel cell power generation system comprising a fuel cell and a fuel reformer. The present invention relates to a fuel cell power generation system that avoids incomplete combustion in a combustion chamber and at the same time prevents thermal fatigue of reforming tubes due to an abnormal rise in combustion temperature.

(Prior Art) Fuel cells are conventionally known as devices that directly convert chemical energy contained in fuel into electrical energy. This fuel cell normally has a pair of electrodes, a fuel electrode and an oxidizer electrode, with an electrolyte layer in between, and supplies fuel gas to the fuel electrode and oxidizer gas to the oxidizer electrode, and the electricity generated at this time. Electrical energy is extracted from between the two electrodes using a chemical reaction.
Electrical energy can be extracted with high conversion efficiency as long as the fuel gas and oxidant gas are supplied.

Now, fuel cells currently being considered include fuel cells using hydrazine as fuel, alkaline aqueous electrolyte, and phosphoric acid aqueous electrolyte as the electrolyte. Fuel cells of this type can be used in general because they can use reformed gas, and are increasingly being used for industrial or power generation purposes.

This type of fuel cell is equipped with a fuel reformer to obtain the fuel gas, a reformed gas containing a large amount of hydrogen.
Reformed gas obtained with this fuel reformer.

The gas is introduced into the fuel electrode of the fuel cell as a fuel gas.

Exhaust gas discharged from the fuel electrode after electrochemical reaction"1
Fuel cell power generation systems are often configured so that the fuel is recovered again as fuel for combustion in the fuel reformer.

FIG. 3 shows an example of the configuration of such a fuel cell power generation system. In FIG. 3, reference numeral 1 introduces methane as a raw fuel 2 mixed with water vapor into the inside of a reforming tube (not shown), which is provided with a reforming catalyst layer inside, and also introduces methane as raw fuel 2 into the outside of the reforming tube. The raw fuel 2 is reformed to generate a reformed gas 3 containing a large amount of hydrogen by circulating the high temperature combustion gas obtained by burning the fuel 6 and the combustion air 7 in a burner (not shown) in the combustion chamber. It is a fuel reformer. In addition, 5 refers to the reformed gas 3 obtained in the fuel reformer 1,
This is a fuel cell in which fuel gas is introduced into the fuel electrode through the fuel flow control valve 4, and air is introduced into the oxidizer electrode as oxidizer gas, and electrical energy is extracted from between the two electrodes through the electrochemical reaction that occurs. Then, the fuel cell 5
The fuel gas discharged from the fuel electrode without being used for power generation is recovered to the burner of the fuel reformer 1 as combustion fuel.

On the other hand, the combustion air 7 is supplied to the burner of the fuel reformer 1 by controlling its meteor flow by an air flow control valve 8 provided in the combustion air supply line ``2''. . That is, the air flow control valve 8 is configured to control the combustion air set flow fskb calculated by the set flow rate calculator 9 based on the cell output a of the fuel cell 5, and the air flow mc detected by the flow rate detector 10. Based on the flow rate deviation d of
The controller 11 gives an opening command e to the air flow rate control valve 8 to control the valve opening.

However, in such a conventional fuel cell power generation system, the combustion air 7 is controlled regardless of the combustion state in the combustion chamber of the fuel reformer 1.
In some cases, there is a problem of incomplete combustion.

This point will be explained in detail below using FIG. 4.

That is, FIG. 4 shows the relationship between the flow rate of the combustion fuel 6 and the combustion temperature when the combustion air 7 is kept constant in the fuel reformer 1. In FIG. 4, the combustion temperature increases until a certain point due to complete combustion, but begins to decrease when incomplete combustion occurs. This means that the combustion temperature and fuel flow rate are Ff.

Air flow rate is Fa, specific heat of fuel is Cpf, specific heat of air is C
This is because it is expressed by the following equation, where pa is the flow rate of the actually burned fuel, F is fa, and Hu is the calorific value of the fuel.

In other words, in the case of complete combustion, due to the relationship F fe = F r, increasing the fuel tLm F f will increase the combustion temperature, but if incomplete combustion occurs, the flow rate of fuel actually combusted will not increase beyond a certain value. Therefore, no matter how much the fuel flow rate Ff is increased, the combustion temperature does not increase by 1 but only decreases. In addition, in FIG. 3, the combustion temperature becomes extremely high near the boundary between the complete combustion region and the incomplete combustion region, which increases the thermal fatigue of the reforming tube in the fuel reformer 1, causing the fuel cell This is not desirable from the standpoint of protecting the power generation system.

(Problems to be Solved by the Invention) As mentioned above, in conventional fuel cell power generation systems, the set value of the combustion air flow rate to the fuel reformer is determined based only on the output of the fuel cell. Therefore, there was a problem that there was no sufficient ability to suppress incomplete combustion in the fuel reformer and thermal fatigue of the reformer tube.

The present invention was made in order to solve the above-mentioned problems, and the first objective is to maintain the combustion chamber of a fuel reformer in a good combustion state by adjusting the excess air ratio to an appropriate value. , provides a highly reliable fuel cell power generation system that can avoid incomplete combustion in the combustion chamber of a fuel reformer and at the same time prevent thermal fatigue of the reformer tube due to an abnormal rise in combustion temperature. It's about doing.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides raw fuel mixed with water vapor inside a reforming tube in which a reforming catalyst layer is provided. At the same time, combustion fuel and combustion air are burned on the outside of the two-legged reforming tube with a burner in the combustion chamber.11)
A fuel reformer generates reformed gas by circulating high-temperature combustion gas, and the reformed gas obtained in this fuel reformer is used as a fuel gas to be supplied to a fuel electrode, and the oxidizing gas is used as an oxidizing agent. and a fuel cell that extracts electrical energy from between the two electrodes through an electrochemical reaction that occurs, and the exhaust gas discharged from the fuel electrode of the fuel cell is used for combustion in the fuel reformer. In a fuel cell power generation system in which the fuel is recovered as fuel for use, the combustion gas temperature of the fuel reformer described in 1. is compared with the combustion gas temperature upper limit value, and as a result, the combustion gas temperature is higher than the combustion gas temperature upper limit value. Correction for correcting the flow rate of combustion air or combustion fuel supplied to the burner of the combustion chamber in the fuel reformer to prevent incomplete combustion and thermal fatigue of the reforming tube, on the condition that The present invention is characterized in that it includes a quantity calculation means.

(Function) In the above-described fuel cell power generation system, when the combustion gas temperature of the fuel reformer becomes higher than the combustion gas temperature limit value, that is, the combustion gas temperature near the incomplete combustion region mentioned above becomes 1. When the increase is detected, the flow rate of the fluid supplied to the burner of the combustion chamber in the fuel reformer is determined by the correction amount calculation means.

For example, by correcting to increase the flow rate of combustion air to increase the excess air ratio, incomplete combustion in the fuel reformer and thermal fatigue of the reforming tubes can be prevented.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows in block form an example of the configuration of a fuel cell power generation system according to the present invention. The same parts as those in FIG. . That is, FIG. 1 shows a temperature detector 12 that detects the combustion gas temperature of the fuel reformer 1, and a comparison of the combustion gas temperature g detected by this temperature detector 12 with the combustion gas temperature -] two limit value f. Then, on the condition that the combustion gas temperature g is higher than the combustion gas temperature upper limit value f, based on the temperature deviation which is the comparison result, a correction amount i is determined to make the set flow rate S a more appropriate value. Calculating correction amount calculator 1
3 to FIG. 5, and by combining the correction amount i calculated by the correction amount calculator 13 with the setting flow Wb calculated by the set flow rate calculator 9, a corrected set flow rate j is obtained, Further, a flow rate deviation d, which is a comparison result between the corrected set flow rate j and the air flow mc, is provided as an input to the regulator 11.

Here, for example, when the temperature deviation is positive, that is, when the combustion gas temperature g becomes higher than the combustion gas temperature upper limit value f, the correction amount calculator 13 calculates a positive correction according to the size of the temperature deviation. The amount i is calculated and output, and when the temperature deviation is negative, that is, when the combustion gas temperature g is lower than the combustion gas temperature upper limit f, the correction amount l is not output.

Next, the operation of the fuel cell power generation system configured as described above will be explained.

In FIG. 1, first, the combustion gas temperature g of the fuel reformer 1 is
When becomes higher than the combustion gas temperature - limit value f, the temperature deviation becomes positive. Then, the correction amount calculator 13 calculates and outputs a positive correction amount i based on the magnitude of this temperature deviation, and adds this correction Mi to the set flow mb output from the original set flow rate calculator 9. , the corrected set flow rate, that is, the corrected set flow rate j is obtained. Then, based on the flow rate deviation d which is the comparison result between the correction set flow rate j and the air flow fAc, the regulator 11 outputs the opening command e, so that the flow rate is increased by the amount of the above-mentioned correction amount i. The deviation d increases. As a result, the opening command e
increases, the flow rate c of the combustion air 7 increases, and by increasing the excess air ratio, incomplete combustion is avoided, and at the same time, the combustion gas temperature g decreases, thereby preventing thermal fatigue of the reforming tube. It will affect.

In this example, raw fuel 2 mixed with water vapor is introduced into the reforming tube in which a reforming catalyst layer is provided, and combustion is carried out outside the reforming tube described in 1. A fuel reformer 1 generates reformed gas 3 by circulating high-temperature combustion gas obtained by burning fuel 6 and combustion air 7 in a burner in a combustion chamber, and The reformed gas 3 is introduced into the fuel electrode as a fuel gas, and the oxidant gas is introduced into the oxidizer electrode, respectively, and electrical energy is extracted from between the two electrodes by the electrochemical reaction that occurs at this time.
In a fuel cell power generation system configured to include the following, exhaust gas discharged from the fuel electrode of the fuel cell 5 is recovered as fuel for combustion in the fuel reformer 1,
1. Calculate the set flow rate of combustion air based on the air flow control valve 8 provided on the line that supplies combustion air 7 to the burner of the fuel reformer 1 and the output a of the fuel cell 5. a set flow rate calculator 9; a temperature detector 12 for detecting the combustion gas temperature of the fuel reformer 1;
Combustion gas temperature g detected in step 2 is set as combustion gas temperature upper limit f
and the combustion gas temperature g is the combustion gas temperature upper limit f
In order to prevent incomplete combustion in the fuel reformer 1 and thermal fatigue of the reforming tube, the correction amount of the set flow ff1b is determined according to the temperature deviation which is the comparison result on the condition that it is higher than the temperature deviation. The correction amount calculator 13 calculates i, combines the set flow ff1b calculated by the set flow rate calculator 9, and the correction amount i calculated by the correction amount calculator 13, and combines this combined amount with Compare the combustion air flow me of the combustion air supply line above, and based on the flow rate deviation d that is the result of this comparison.
1. Combustion air flow rate control means comprising a regulator 11 that outputs an opening degree command for adjusting the valve opening degree of the air flow rate control valve 8.

Therefore, the set flow rate ff1b of combustion air is corrected based on the temperature deviation between the combustion gas temperature g and the upper limit value f of the combustion gas temperature, thereby adjusting the excess air ratio to an appropriate value and reforming the fuel. While maintaining the combustion chamber of the device 1 in a good combustion state and avoiding incomplete combustion in the combustion chamber of the fuel reformer 1, the combustion gas temperature g is controlled to be below the combustion gas temperature upper limit value f. Therefore, it is possible to prevent thermal fatigue of the reforming tube due to abnormal rise.

It should be noted that the present invention is not limited to the embodiments described above, but can also be implemented in the following manner.

FIG. 2 shows in block form an example of the configuration of a fuel cell power generation system according to another embodiment of the present invention, and the same parts as in FIG. Only the different parts will be described. That is, FIG. 2 shows the temperature detector 12 that detects the combustion gas temperature of the fuel reformer 1, and the comparison of the combustion gas temperature g detected by this temperature detector 12 with the combustion gas temperature upper limit f, and Correction for calculating a correction amount 1 for setting the set flow rate S to a more appropriate value based on the temperature deviation which is the comparison result on the condition that the combustion gas temperature g is higher than the upper limit value f of the combustion gas temperature. A quantity calculator 13 and a fuel flow control device 14 that outputs an opening command k to the fuel flow control valve 4 are provided, and the correction amount l calculated by the two-legged correction amount calculator 13 is calculated as follows. By subtracting the set flow ff1b output from the flow rate control device 14, a corrected opening command l is obtained, and by giving this corrected opening command l to the fuel flow control valve 4, the fuel is supplied to the fuel electrode of the fuel cell 5. It is configured to control the amount of gas, in other words, the flow rate of the combustion fuel 6 to the burner of the combustion chamber of the fuel reformer 1.

In other words, the embodiment shown in FIG.
The set flow rate of the combustion air 7 supplied to the burner of the combustion chamber of the fuel reformer 1 is corrected by the correction amount 1 calculated in 3. In the embodiment shown, the correction amount 1 calculated by the correction amount calculator 13 is used to issue an opening command 1 ( It is designed to correct.

Also in the fuel cell power generation system shown in FIG.
The same effects as described above can be obtained. That is, in the original fuel flow control device 14, the set value of the fuel flow rate is corrected using the metal temperature of the reformer tube (not shown), but in this embodiment, the response is faster than that of the metal temperature of the reformer tube. Since the original opening command k is corrected using the combustion gas temperature that more accurately represents the combustion state, it is possible to avoid incomplete combustion in the combustion chamber of the fuel reformer 1 in advance, and at the same time , it is possible to suppress the rise in combustion gas temperature g and prevent thermal fatigue of the reforming tube due to an abnormal rise.

In addition, the present invention can be modified and implemented in various ways without changing the gist thereof.

〔Effect of the invention〕

As explained above, according to the present invention, it is detected that the combustion gas temperature of the fuel reformer has become higher than the combustion gas temperature limit value, that is, the combustion gas temperature has increased in the vicinity of the incomplete combustion region. Based on the detected condition, the flow rate of the fluid supplied to the burner of the combustion chamber in the fuel reformer is corrected, so the excess air ratio is adjusted to an appropriate value and the combustion chamber of the fuel reformer is adjusted. Extremely reliable, capable of maintaining good combustion conditions and avoiding incomplete combustion in the combustion chamber of the fuel reformer, while at the same time preventing thermal fatigue of the reformer tube due to an abnormal rise in combustion temperature. A fuel cell power generation system with high efficiency can be provided.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of a fuel cell power generation system according to the present invention, Fig. 2 is a block diagram showing another embodiment of the present invention, and Fig. 3 is a block diagram showing a conventional fuel cell power generation system. The configuration block diagram shown in FIG. 4 is for a case where the combustion air flow rate is constant. FIG. 3 is a diagram showing the relationship between combustion fuel flow rate and combustion temperature. DESCRIPTION OF SYMBOLS 1...Fuel reformer, 2...Raw fuel, 4...Fuel flow rate control device...Fuel cell, 6...Combustion fuel,
8...Air flow rate control valve, 9...Setting flow rate calculator, 10
...Flow rate detector, 11...Adjuster, 12...Temperature detector, 13...Correction amount calculator, 14...Fuel flow rate control device. 1 representative Patent attorney Takehiko Suzue Figure 1 Figure 3 Figure 4

Claims (2)

[Claims] (1) Raw fuel mixed with water vapor is introduced into the inside of the reforming tube, which has a reforming catalyst layer inside, and combustion fuel and combustion air are introduced to the outside of the reforming tube to the burner of the combustion chamber. A fuel reformer generates reformed gas by circulating high-temperature combustion gas obtained by combustion in is introduced into each oxidizer electrode, and electrical energy is extracted from between the two electrodes through an electrochemical reaction that occurs, and the exhaust gas discharged from the fuel electrode of the fuel cell is used to reform the fuel. In a fuel cell power generation system in which fuel is recovered as fuel for combustion in the device, an air flow control valve provided on a line that supplies combustion air to the fuel reformer and a combustion A set flow rate calculator that calculates a set flow rate of service air, a temperature detector that detects the combustion gas temperature of the fuel reformer, and a comparison of the combustion gas temperature detected by the temperature detector with a combustion gas temperature upper limit value. and, on the condition that the combustion gas temperature is higher than the combustion gas temperature upper limit value, the set flow rate is adjusted according to the comparison result in order to prevent incomplete combustion in the fuel reformer and thermal fatigue of the reforming tube. a correction amount calculation means for calculating a correction amount of the combustion air; and combustion air flow rate control means for comparing the flow rate of combustion air in the supply line and outputting an opening degree command for adjusting the valve opening degree of the air flow rate control valve based on the comparison result. A fuel cell power generation system characterized by: (2) Introducing raw fuel mixed with water vapor into the inside of the reforming tube, which has a reforming catalyst layer inside, and supplying combustion fuel and combustion air to the outside of the reforming tube to the burner of the combustion chamber. A fuel reformer generates reformed gas by circulating high-temperature combustion gas obtained by combustion in is introduced into each oxidizer electrode, and electrical energy is extracted from between the two electrodes through an electrochemical reaction that occurs, and the exhaust gas discharged from the fuel electrode of the fuel cell is used to reform the fuel. In a fuel cell power generation system in which fuel is recovered as fuel for combustion in a device, a fuel flow control valve provided on a line that supplies fuel gas to the fuel electrode of the fuel cell, and an opening command for the fuel flow control valve. a temperature detector that detects the combustion gas temperature of the fuel reformer; a temperature detector that compares the combustion gas temperature detected by the temperature sensor with an upper limit value of the combustion gas temperature; On the condition that the temperature is higher than the combustion gas temperature upper limit value, the correction amount of the opening command is adjusted according to the comparison result in order to prevent incomplete combustion in the fuel reformer and thermal fatigue of the reforming tube. The correction amount calculation means to calculate, the opening command output from the fuel flow control device, and the correction amount calculated by the correction amount calculation means are combined, and this combined amount is applied to the valve of the fuel flow control valve. 1. A fuel cell power generation system comprising: combustion fuel flow rate control means for outputting a final opening command for adjusting an opening.