JPH01298651A - Combustion controlling device for catalyst combustor for fuel cell - Google Patents

Abstract

PURPOSE:To increase the life by making incomplete combustion of waste fuel gas at a set temperature for incomplete combustion in the first combustion stage, and sending waste oxidizer gas to get to a predetermined temperature for complete combustion in the second combustion stage and on. CONSTITUTION:Waste combustion gas flows through a waste fuel gas supply system 12 to gas chambers, where it is burnt at combustion catalyst layers 3, 6, 9. The flow quantity of waste oxidizer gas supplied to the gas chamber 2 is controlled to make the temperature detected by a temperature senser 25 in the gas chamber 5 burnt at the layer 3 at a set temperature of a temperature setter 26 by a flow controller 21 controlled by a regulator 27, and waste fuel gas makes incomplete combustion at the set temperature. This gas is burned at the layers 6, 9 while the flow quantity of waste oxidizer gas supplied to the gas chamber 5 is controlled by a three-way flow control valve 23 controlled by a deviation signal from a regulator 29 to make the temperature detected by a temperature senser 15 at a set temperature by a temperature setter 28. Waste combustion gas can thus by burnt completely at a set temperature.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a fuel cell catalyst for producing high-temperature combustion gas by burning exhaust fuel gas discharged from a fuel cell in a combustion catalyst layer using a wandering oxidant gas. The present invention relates to a combustion control device for a combustor.

[Conventional technology]

A fuel cell generates electricity by causing a cell reaction by supplying a fuel gas containing hydrogen to a fuel electrode and an oxidizing gas such as air containing oxygen to an oxidizing electrode. Exhaust fuel gas and exhaust oxidant gas containing unreacted hydrogen and oxygen, which do not contribute to the cell reaction, are discharged from the fuel electrode and the oxidizer electrode, respectively. This exhaust fuel gas is combusted with exhaust oxidant gas to obtain high-temperature combustion gas, and this combustion gas is used as fuel gas to produce heat during the reforming reaction in the fuel reformer that produces hydrogen-rich reformed gas. used as a medium. In this case, as a method of burning exhaust fuel gas to obtain high-temperature combustion gas, a catalytic combustor equipped with a combustion control device that causes combustion under the catalyst of a combustion catalyst layer is known.

FIG. 3 is a system diagram of a catalytic combustor equipped with a conventional combustion control device. In FIG. A first combustion stage 4 consisting of a combustion catalyst layer 3 in which attached fuel is combusted under the catalyst by an oxidizing agent, followed by a combustion stage consisting of a gas chamber 5 in which the fuel is combusted and a combustion catalyst layer 6. 7, and subsequently a combustion stage 10 consisting of a gas chamber 8 in which fuel is combusted and a combustion catalyst layer 9.

The combustion catalyst layer 3 of the combustion stage 4 is formed from a catalyst made of, for example, platinum, which has poor high-temperature durability but good low-temperature ignitability. The combustion catalyst layer 9 is formed of a catalyst having poor low-temperature ignitability but good high-temperature durability, for example, a palladium-based catalyst.

Reference numeral 11 denotes a combustion chamber that guides high-temperature combustion gas that has been completely combusted in the combustion catalyst layer 9 of the final combustion stage, and corresponds to, for example, a combustion chamber in a furnace vessel constituting a fuel reformer.

The exhaust fuel gas supply system 12 is provided to connect a fuel cell (not shown) and the gas chamber 2, and guides exhaust fuel gas containing unreacted hydrogen discharged from the fuel electrode of the fuel cell to the gas chamber 2. Further, the exhaust oxidant gas supply system 13 is provided with a three-way flow control valve 14 and is provided to connect the fuel cell and the gas chamber 2, and the exhaust oxidant gas containing unreacted oxygen is discharged from the oxidizer electrode of the fuel cell. is led to gas chamber 2.

A temperature sensor 15 is provided in the combustion chamber 11 to detect the temperature of the completely combusted gas from the combustion catalyst layer 9. Reference numeral 16 denotes a temperature setting device for setting the temperature of combustion gas to be completely combusted in the combustion chamber 11. The regulator 17 controls the flow rate of the wandering oxidant gas by adjusting the opening degree of the three-way flow control valve 14 based on the deviation between the set temperature from the temperature setting H16 and the temperature detected from the temperature sensor 15.

With this configuration, the exhaust fuel gas discharged from the fuel cell in accordance with its load, that is, the cell output, passes through the exhaust gas supply system 12 to the gas chamber 2, and the wandering oxidant gas flows through the exhaust oxidant gas system 13. The exhaust fuel gas is ignited and combusted in the fuel catalyst layer 3 by the wandering oxidant gas even at low temperatures, and then passes through the second gas chamber 5 of the combustion stage 7 and is combusted in the combustion catalyst N6. is sustained, followed by combustion stage 10
The combustion gas passes through the gas chamber 8 and is combusted in the combustion catalyst layer 9, and the combustion gas is discharged into the combustion chamber 11. At this time, the temperature sensor 15
The output signal of the temperature of the combustion chamber 11 detected by the controller 1 and the output signal of the set temperature set by the temperature setting device 16 are
7 and the deviation signal is input to the three-way flow control valve 14.
The flow rate of the exhaust oxidant gas supplied to the gas chamber 2 is controlled so that the exhaust fuel gas is completely combusted at a set temperature.

In this way, high-temperature complete combustion gas is discharged from the combustion catalyst layer 9 of the final combustion stage into the combustion chamber 11. Note that the excess exhaust oxidant gas other than the flow rate controlled by the three-way flow control valve 14 and flowing into the first gas chamber 2 is discharged to the outside through the pipe line 18 from another valve port of the three-way flow control valve 14.

[Problem to be solved by the invention]

The amount of hydrogen in the exhaust fuel gas and the amount of oxygen in the exhaust oxidant gas depend on the load connected to the fuel cell, that is, the cell output, so if the load changes, for example if the load increases, the fuel cell As the amount of hydrogen and oxygen consumed in The amount of hydrogen in the gas and the amount of oxygen in the exhaust oxidant gas increase. Therefore, when the load fluctuates, the temperature of the combustion gas is detected by the temperature sensor 15, the fit of the exhaust oxidizing gas is controlled by the three-way flow control valve 14, and the fit is sent to the catalytic combustor 1, and the temperature is controlled to a set temperature for complete combustion. There is a problem that when the load is reduced, the temperature of the combustion catalyst layer of each combustion stage deviates from the normal temperature under steady load, causing the combustion catalyst layer to become overheated.

Figure 4 shows the gas in each combustion stage when the exhaust fuel gas and exhaust oxidant gas from the fuel cell are sent to the catalytic combustor 1 and the wandering combustion gas is combusted in the combustion catalyst layers 3 and 6.8 of each combustion stage. This is a graph showing the temperature distribution between the chamber and the combustion catalyst layer, where the vertical axis shows the position of the gas chamber and the combustion catalyst layer, and the horizontal axis shows the temperature of the gas chamber and the combustion catalyst layer. 30 is the temperature distribution when the load on the fuel cell is stable or when the load increases rapidly, while the solid line 31 is the temperature distribution when the load suddenly decreases, and t +, tz, t ff + t 4 are respectively Gas chamber 2, gas chamber 51. Gas chamber8. From figure 0 showing the temperature of the combustion chamber 11, the temperature t of the gas chamber 5 when the load suddenly decreases.
2 is increasing as shown by the solid line, that is, it is understood that the temperature of the combustion catalyst, layer 3, is increasing.

By the way, the combustion catalyst N3 has good ignitability but poor high-temperature durability, so there is a problem that the temperature rise when the load suddenly decreases as described above deteriorates the combustion catalyst layer 3.

An object of the present invention is to provide a fuel cell that does not overheat the combustion catalyst layer when the load of the fuel cell fluctuates, especially when the load suddenly decreases, when exhaust fuel gas and exhaust oxidant gas from a fuel cell are combusted in multiple stages of combustion catalyst layers. The purpose of the present invention is to provide a combustion control device for a combustion catalytic converter.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, a plurality of combustion stages each consisting of a defined gas chamber and a combustion catalyst layer in which combustion is performed by fuel and oxidizer introduced into the gas chamber are connected in series. The catalytic combustor is equipped with a catalytic combustor, in which the exhaust gas discharged from the fuel cell is passed through an exhaust gas supply system to a first gas chamber of a first combustion stage at an end of the catalytic combustor. The exhaust oxidizer gas is led to the combustion stage, and the exhaust oxidizer gas is led to the gas chamber via the exhaust oxidizer gas supply system, and the exhaust fuel gas is combusted in the combustion catalyst layer, and the combustion gas from the combustion catalyst layer of the final combustion stage is combusted. In the catalytic combustor for a fuel cell, the main supply system connects the supply system of the exhaust oxidant gas from the fuel cell to the first gas chamber, and the second combustion stage of the second combustion stage following the first combustion stage. a first flow control valve that controls the flow rate of the exhaust oxidant gas provided in the main supply system, and a first flow control valve that detects the temperature of the second gas chamber. a temperature sensor; and a first flow control valve that controls the opening degree of the first flow control valve so that the temperature detected by the sensor reaches a preset temperature at which exhaust fuel gas is incompletely combusted in the combustion catalyst layer of the first combustion stage. a second 21L amount control valve that controls the flow rate of the exhaust oxidant gas provided in the first inlet control means and the sub-supply system;
A second temperature sensor detects the temperature of combustion gas in the combustion chamber, and the temperature detected by this sensor is set to a preset temperature at which the exhaust fuel gas is completely combusted in the combustion catalyst layer after the second combustion stage. A second flow control valve that controls the opening degree of the second flow control valve.
control means shall be provided.

[Effect]

The entire amount of exhaust fuel gas discharged from the fuel cell is guided from the first gas chamber to a catalytic combustor consisting of multiple combustion stages, and the exhaust oxidant gas is supplied to the main supply system and sub-supply system of the exhaust oxidant gas. It is divided into two systems and guided to the catalytic combustor. Then, in the main supply system, the combustion of exhaust gas in the first combustion stage is
The first temperature sensor is set so that the temperature detected by the first temperature sensor in the gas chamber reaches a preset temperature at which incomplete combustion occurs.
The control means controls the first flow rate control valve to control the flow rate of the exhaust oxidant gas flowing into the first gas chamber, and the sub-supply system controls the exhaust oxidant gas in the second and subsequent combustion stages. The combustion of the fuel gas is controlled by the second control means to control the second flow rate control valve so that the temperature detected by the second temperature sensor in the combustion chamber reaches a preset temperature for complete combustion. This is done by the wandering oxidant gas that flows into the gas chamber with a controlled flow rate. Therefore, even if the load suddenly decreases, the temperature in the second gas chamber is controlled to the set temperature by controlling the flow rate of the exhaust oxidant gas in the main supply system. So the first
The combustion catalyst layer of the combustion stage is not overheated, while high-temperature combustion gas is introduced into the combustion chamber at a set temperature for complete combustion of the exhaust gas.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a system diagram of a catalytic combustor for a fuel cell equipped with a combustion control device according to an embodiment of the present invention. In FIG. 1, parts that are the same as those in the conventional example shown in FIG. 2 are given the same reference numerals, and their explanations will be omitted.

What is different from the conventional example in FIG. 1 is that a non-oxidizing gas supply system 20 that supplies non-oxidizing gas from a fuel cell (not shown) to the catalytic combustor 1 is connected between the fuel cell and the first gas chamber 2. A main supply system 22 equipped with a first flow control valve 21 that supplies non-oxidant gas to the gas chamber 2, and a second gas chamber branched from the main supply system 22 and connected to the second gas chamber 2, which supplies non-oxidant gas to the gas chamber 2. and a sub-supply system 24 equipped with a second three-way flow rate control valve 23 that supplies the gas to the gas chamber 5, and further controls the temperature of the combustion gas at which the exhaust fuel gas is incompletely combusted in the combustion catalyst layer 3 in the gas chamber 2. The output signals from the temperature sensor 25 and the temperature setting device 26 are input to the first temperature sensor 25 for detection, the temperature setting device 26 for presetting the temperature at which incomplete combustion occurs, and the opening degree of the flow rate control valve 21 is inputted. and a temperature setting device 28 for setting the temperature at which the exhaust fuel gas is completely combusted in the combustion catalysts N6 and N9, and the outputs of the second temperature sensor 2 and the temperature setting device 28. signal is input,
A regulator 29 for controlling the opening degree of the three-way flow control valve 23 is provided.

With such a control system, the entire amount of exhaust gas corresponding to the load from the fuel cell flows into the gas chamber 2 via the exhaust fuel gas supply system 12. On the other hand, the non-oxidizing gas is supplied to the gas chamber 2.5 from the non-oxidizing gas main supply system 22 and the sub-supply system 24, respectively, and the exhaust fuel gas is combusted in the combustion catalyst layers 3, 6.9. However, at this time, the flow rate of the non-oxidant gas supplied to the gas chamber 2 is determined by the temperature sensor 25 of the combustion gas in the gas chamber 5 where the exhaust fuel gas is combusted in the combustion catalyst layer 3.
The flow control valve 21 is controlled by the opening degree of the flow control valve 21, which is controlled by the deviation signal between the detected temperature and the set temperature from the regulator 27, so that the detected temperature becomes the set temperature of the temperature setting device 26. The gas is controlled to undergo incomplete combustion in the combustion catalyst layer 3 at a set temperature. This incompletely combusted exhaust fuel gas is combusted in the combustion catalyst layers 6 and 9 by the non-oxidant gas supplied to the gas chamber 5 via the sub-supply system 24; The flow rate of oxidant gas is
The temperature setter 2 detects the temperature detected by the temperature sensor 15 of the combustion gas in the combustion chamber 10 that has burned in the combustion catalyst layer 6.9.
The opening of the three-way flow control valve 29 is controlled by the deviation signal between the detected temperature and the set temperature from the regulator 29 so that the set temperature of 8 is reached, and the exhaust fuel gas is completely combusted at the set temperature. controlled.

When there is a sudden decrease in the load on the fuel cell using this control method, the temperatures of the gas chamber 2,5°8, combustion catalyst layer 3,6,9 and combustion chamber 11 of the catalytic combustor 1 are as shown in Figure 4. The temperature distribution becomes as shown by the solid line 32 in Fig. 2 shown in the same way, and even if the load on the fuel cell suddenly decreases, the temperature of the gas chamber 5 is controlled to the set temperature, so the combustion catalyst layer 3 is not overheated as in the conventional case. Not done.

Therefore, the combustion catalyst layer 3, which has good low-temperature ignitability but poor high-temperature durability, is less likely to deteriorate and has a longer life. Note that in the combustion chamber 11, high-temperature combustion gas is obtained by complete combustion of the exhaust fuel gas by the combustion catalyst layer 6.9.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in a catalytic combustor consisting of multiple combustion stages, the temperature is set at which the exhaust fuel gas from the fuel cell is incompletely combusted in the combustion catalyst layer of the first combustion stage. The flow rate is controlled so that the inflowing non-oxidant gas causes incomplete combustion, and then the second
The flow rate is controlled so that the combustion catalyst layer after the combustion stage reaches a predetermined temperature for complete combustion of the exhaust fuel gas, and the non-oxidizing gas flowing into the second gas chamber causes complete combustion. In the combustion chamber, high-temperature combustion gas is obtained at a set temperature for complete combustion, and the combustion catalyst layer of the first combustion stage is not overheated. Therefore, in a plurality of stages of combustion catalyst layers, since there is no abnormal temperature rise in a particular combustion catalyst layer, the deterioration of the combustion catalyst layer is reduced and the life of the combustion catalyst layer is extended.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a catalytic combustor for fuel cells equipped with a combustion control device according to an embodiment of the present invention, Fig. 2 is a graph showing the temperature distribution during combustion of the catalytic combustor of Fig. 1, and Fig. 3 is a system diagram of a catalytic combustor for fuel cells equipped with a conventional combustion control device,
FIG. 4 is a graph showing the temperature distribution during combustion in the catalytic combustor of FIG. DESCRIPTION OF SYMBOLS 1... Catalytic combustor, 2... First gas chamber, 3,6°9... Combustion catalyst layer, 4... First combustion stage, 5...
Second gas chamber, 7... Second combustion stage, 8... Gas chamber, 10... Combustion stage, 11... Combustion chamber, 12... Exhaust fuel gas supply system, 16°26 , 28...Temperature setting device, 15...Second temperature sensor, 17°27, 29...
- Regulator, 20... Exhaust oxidant gas supply system, 21...
- Flow rate control valve, 22... Main supply system, 23... Three-way flow control valve, 24... Sub supply system, 25... First temperature sensor. 33 Figure 11 ◆ is also 51 degrees 34 Figure

Claims (1)

[Claims] 1) A catalytic combustor comprising a plurality of combustion stages installed in series, each consisting of a defined gas chamber and a fuel catalyst layer in which combustion is carried out by fuel and oxidizer introduced into the gas chamber; Exhaust fuel gas discharged from the battery is guided through an exhaust gas supply system to the first gas chamber of the first combustion stage at the end of the catalytic combustor and to each combustion stage, while the exhaust oxidant gas is In a catalytic combustor for a fuel cell, the exhaust gas is guided to the gas chamber via the exhaust oxidant gas supply system, the exhaust fuel gas is combusted in the combustion catalyst layer, and the combustion gas from the combustion catalyst layer of the final combustion stage is guided to the combustion chamber. , a main supply system that connects the exhaust oxidant gas supply system from the fuel cell to the first gas chamber, and a sub supply system that connects the exhaust oxidant gas supply system to the second gas chamber of the second combustion stage following the first combustion stage. A first flow control valve that controls the flow rate of the exhaust oxidant gas provided in the main supply system, a first temperature sensor that detects the gas temperature in the second gas chamber, and a temperature detected by this sensor. a first control means for controlling the opening degree of the first flow rate control valve so that the temperature reaches a preset temperature at which exhaust fuel gas is incompletely combusted in the combustion catalyst layer of the first combustion stage; and a sub-supply system. A second flow control valve is provided to control the flow rate of the exhaust oxidant gas, and a second flow control valve is provided to detect the temperature of the combustion gas in the combustion chamber.
a second temperature sensor, and a second flow control valve that controls the opening degree of the second flow control valve so that the temperature detected by this sensor becomes a preset temperature at which exhaust fuel gas is completely combusted in the combustion catalyst layer of the second stage and subsequent stages. 1. A combustion control device for a catalytic combustor for a fuel cell, comprising a control means.