JPH025367A - Combustion control device of catalytic burner for fuel cell - Google Patents

Abstract

PURPOSE:To lengthen the life of combustion catalyst by controlling the flow of exhaust fuel gas such that a part of exhaust fuel gas is led to the first gas chamber and the remaining thereof, to the second gas chamber through a main supply line equipped with a flow control valve and the first combustion catalyst is not overheated. CONSTITUTION:A supply line 12 of exhaust fuel gas is constituted of a main supply line 22 connected to the first gas chamber 2 at the first combustion step 4 and a sub-supply line 23 branched from the main supply line 22 and connected to the second gas chamber 5 at the second combustion step 7, and the main line 22 is equipped with a flow control valve 24 to control the flow of fuel gas and the second gas chamber 5 is equipped with a sensor 25 to detect gas temperature, and further, a combustion catalyst layer 3 at the first combustion step 4 is equipped with a temperature setter 27 so as to prevent overheating, and the opening of the flow control valve 24 is controlled by an output signal given from the setter 27 and a detection signal given from the temperature sensor 25, and an adjuster 28 is provided so that the combustion gas temperature of the second gas chamber becomes a set temperature. Even if a load rapidly decreases, the temperature of the gas chamber 5 is controlled to a set temperature so that the combustion catalyst layer 3 having a poor durability at a high temperature becomes free from deterioration, and its life is lengthened.

Description

Detailed Description of the Invention [Field of Industrial Application] 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 an exhaust 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, is there a way to obtain high-temperature combustion gas by burning the exhaust fuel gas under the catalyst in the combustion catalyst layer? Catalytic combustors with I devices are known.

FIG. 3 is a system diagram of a catalytic combustor equipped with a conventional combustion control device. In FIG. A combustion catalyst layer 3 that burns the fuel under the catalyst using an oxidizer.
A first combustion stage 4 consisting of a first combustion stage 4, followed by a combustion stage 7 consisting of a gas chamber 5 in which fuel is combusted and a combustion catalyst layer 6,
Furthermore, following this, there is 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 that has poor low-temperature ignitability but good high-temperature durability, such as 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 bridge 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. ! J1 controller 17 is temperature setting device 1
The opening degree of the three-way flow control valve 14 is set to 11 mL based on the deviation between the set temperature from 6 and the temperature detected from the temperature sensor 15.

to control the flow rate of the exhaust oxidant gas.

With this configuration, the exhaust fuel gas discharged from the fuel cell corresponding to its load, that is, the cell output, passes through the exhaust gas supply system 12 to the gas chamber 2, and the exhaust oxidant gas is discharged from the exhaust oxidant gas system 13. The exhaust fuel gas is ignited and combusted in the fuel catalyst layer 3 by the exhaust oxidant gas even at low temperatures, and then passes through the second gas chamber 5 of the combustion stage 7 to the combustion catalyst layer 6. Combustion 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 output signal of the temperature of the combustion chamber 11 detected by the temperature sensor 15 and the output signal of the set temperature set by the temperature setting device 16 are input to the regulator 17, and the difference signal is used to control the three-way flow control valve 14. The opening degree is adjusted to control the flow rate of the exhaust oxidant gas supplied to the gas chamber 2 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 and the three-way flow control valve 14
Even if the flow rate of the exhaust oxidant gas is controlled and sent to the catalytic combustor to the set temperature for complete combustion, the temperature of the combustion catalyst layer of each combustion stage will be lower than the normal temperature under steady load when the load is reduced. There is a problem with the combustion catalyst layer becoming misaligned and becoming overheated.

Figure 4 shows the gases in each combustion stage when the exhaust fuel gas and exhaust oxidant gas from the fuel cell are sent to the catalytic combustor l and the exhaust fuel gas is combusted in the combustion catalyst layers 3 and 6.9 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. The broken line 30 shows the temperature distribution when the load on the fuel cell is stable and when the load suddenly increases. 31 is the temperature distribution when the load suddenly decreases, and tl+ tt+ L 31 t4 are respectively gas chamber 2 and gas chamber 5. Gas chamber8. It can be seen from Figure 0, which shows the temperature of the combustion chamber 11, that the temperature 1t of the gas chamber 5 increases as shown by the solid line when the load suddenly decreases, that is, the temperature of the combustion catalyst layer 3 increases.

By the way, the combustion catalyst layer 3 has good ignitability but poor high-temperature durability, so there is a problem that the temperature increase 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. An object of the present invention is to provide a combustion control device for a catalytic combustor.

[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 arranged in series. A catalytic combustor is equipped with a catalytic combustor, in which the exhaust fuel gas discharged from the fuel cell is guided to the gas chamber via the exhaust fuel gas supply system, and the exhaust oxidant gas is passed through the exhaust oxidant gas supply system to the catalyst. The exhaust fuel gas is introduced into the first gas chamber of the first combustion stage at the end of the combustor and guided to each combustion stage, where it is combusted in the combustion catalyst layer, and the temperature of the combustion gas exiting from the final combustion stage increases. In combustion control vL1 of a catalytic combustor for a fuel cell, which controls the flow rate of wandering oxidant gas supplied to the catalytic combustor so as to reach a preset temperature, the exhaust fuel gas supply system is connected from the fuel cell to the first The main supply system connecting to the first gas chamber of the combustion stage and the second gas chamber of the second combustion stage following the first combustion stage.
The main supply system is equipped with an exhaust fuel gas flow control valve that controls the flow rate of exhaust fuel gas, and the second gas chamber detects the gas temperature of this gas chamber. A temperature sensor is provided, and the temperature detected by this sensor is the first temperature sensor.
Control means shall be provided to control the opening degree of the exhaust gas flow rate control valve so that the combustion of the exhaust gas in the combustion catalyst layer of the combustion stage reaches a preset temperature that does not overheat the combustion catalyst layer. .

[Effect]

A part of the exhaust fuel gas discharged from the fuel cell is sent to the first gas chamber of the first combustion stage through a main supply system equipped with an exhaust gas flow rate control valve, and the remainder is sent to the second gas chamber through a sub-supply system. The entire amount flows into the catalytic combustor and is combusted. At this time, the flow rate of the exhaust gas flowing into the catalytic combustor, which contributes to combustion, is adjusted so that the exhaust gas is completely combusted in the catalytic combustor and the temperature of the combustion gas exiting from the catalytic combustor reaches the set temperature. controlled. in this case,
The exhaust fuel gas introduced into the first gas chamber is combusted in the combustion catalyst layer of the first combustion stage by the exhaust oxidant gas flowing in while the flow rate is controlled from the fuel cell. an exhaust fuel gas flow rate control valve controlled by a control means so that the temperature detected by the temperature sensor provided in the second gas chamber is a preset temperature that does not overheat the combustion catalyst layer of the first combustion stage due to combustion; The flow rate is controlled by the opening degree of the cylinder, and excess air is combusted. Then, the exhaust fuel gas flowing into the second gas chamber is completely combusted by the exhaust oxidant gas whose flow rate is controlled in the combustion catalyst layer after the second combustion stage, and high-temperature combustion gas is sent out from the catalytic combustor. .

〔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. 3 are given the same reference numerals, and their explanations will be omitted.

What is different from the conventional example in the figure is a main supply system 22 that connects the exhaust fuel gas supply system 12 from the fuel cell to the first gas chamber 2 of the first combustion stage 4, and a main supply system 22 that is branched from this main supply system 22. The second combustion stage 7 is provided with a second gas chamber power valve ←flow control valve 24, and the second gas chamber 5 is provided with a temperature sensor 25 for detecting the gas temperature in this gas chamber. A temperature setting device 27 is provided to set in advance the temperature at which exhaust fuel gas burns in the combustion catalyst 113 of stage 4 so as not to overheat the combustion catalyst layer 3, and an output signal from this temperature setting device 27 and a detection from the temperature sensor 25 are provided. A temperature signal is input, and this deviation signal causes the exhaust fuel gas flow rate control valve 24 to be
A regulator 28 is provided to control the opening degree of the combustion gas chamber so that the temperature of the combustion gas in the second gas chamber becomes the set temperature of the temperature setting device 27.

With this configuration, a part of the total amount of exhaust fuel gas corresponding to the cell output from the fuel cell flows into the gas chamber 2 via the main supply system 22, and the rest flows into the gas chamber 5 via the sub-supply system 23. . On the other hand, the exhaust oxidant gas is detected by the temperature sensor 15 as described above. Temperature setting device 16°! The flow rate of the exhaust fuel gas is controlled via the J1 moderator 17 so that the temperature of the completely combusted combustion gas discharged from the combustion catalyst layer 9 after being combusted in the combustion catalyst layer is controlled to a preset temperature. and flows into the gas chamber 2. Combustion is performed in the catalytic combustor with the exhaust fuel gas and exhaust oxidant gas flowing in as described below.

Exhaust fuel gas that has flowed into the gas chamber 2 does not overheat the combustion catalyst layer 3 whose combustion gas temperature is set by the temperature setting device 27 due to the above-mentioned flow rate-controlled wandering oxidant gas. The exhaust fuel gas flow rate control valve 24 is controlled by a deviation signal between the temperature detected by the temperature sensor 25 and the set temperature of the temperature setting device 27 from the adjustment a28 so that the temperature
The amount of flow is controlled by the opening degree of the combustion chamber. The combustion is performed at a low temperature where the combustion gas does not overheat the combustion catalyst layer 3, resulting in excess air combustion performed under a very large excess air ratio, but since the combustion uses a catalyst, misfires occur. There is no such thing.

The exhaust fuel gas that has flowed into the gas chamber 5 is completely combusted by the wandering oxidant gas whose flow rate is controlled so that the combustion catalyst layer 6°9 reaches a preset temperature for complete combustion by the temperature setting device 7. High temperature combustion gas is discharged from layer 9 and supplied to combustion chamber 11 .

The temperatures of the gas chamber 2,5°8, the combustion catalyst layer 3,6,9 and the combustion chamber 11 of the catalytic combustor 1 when the load of the fuel cell is suddenly frozen by such a combustion control method are as shown in Fig. 4. In the same way, the temperature distribution becomes as shown by the solid line 32 in FIG. 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.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, part of the exhaust fuel gas from the fuel cell is supplied to the first gas chamber of the first combustion stage through a main supply system equipped with a flow rate control valve, and the remaining part is supplied to the first gas chamber of the first combustion stage. is led to the second gas chamber of the second combustion stage by a sub-supply system,
The flow rate of the exhaust fuel gas flowing into the first gas chamber is set in advance so that the degree of combustion gas due to excess air combustion in the combustion catalyst layer of the first combustion stage does not overheat the combustion catalyst layer of the first combustion stage. By controlling the temperature to a certain temperature, high-temperature combustion gas can be obtained from the catalytic combustor, and even if there is a sudden decrease in the load on the fuel cell, the combustion catalyst layer in the first combustion stage will not reach a high temperature. Abnormal temperature rise in a specific combustion catalyst layer of the combustion catalyst layer consisting of multiple combustion stages is eliminated.
This has the effect of reducing deterioration of the combustion catalyst layer and lengthening its life.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a catalytic combustor for a fuel cell equipped with a combustor m device according to an embodiment of the present invention, and Fig. 2 shows the temperature distribution during combustion of the catalytic combustor of Fig. 1. ;(--II
I) J-Do J1-1 Noraf 3 Figure 3 shows a fuel equipped with a conventional combustion control device 1: catalytic combustor, 2 = first gas chamber, 3
．． 69: Combustion catalyst layer, 4: First combustion stage, 5: Second gas chamber, 7: Second combustion stage, 8: Gas chamber, lO: Combustion film,
11: Combustion chamber, 12: Exhaust fuel gas supply system, 13: Exhaust oxidant gas supply system, 22: Main supply system, 23: Sub supply system, 24: Exhaust fuel gas flow rate control valve, 25: Temperature sensor,
27: Temperature setter, 2nd: Adjuster. □ Temperature Figure 4 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 combustion catalyst layer in which combustion is performed by fuel and oxidizer introduced into the gas chamber,
Exhaust fuel gas discharged from the fuel cell is guided to the gas chamber via the exhaust fuel gas supply system, while exhaust oxidant gas is passed through the exhaust oxidant gas supply system to the first combustion chamber at the end of the catalytic combustor. The exhaust fuel gas is introduced into the first gas chamber of the stage and guided to each combustion stage, where it is combusted in the combustion catalyst layer, and the exhaust gas is oxidized so that the temperature of the combustion gas coming out of the final combustion stage reaches a preset temperature. A combustion control device for a catalytic combustor for a fuel cell that controls the supply flow rate of agent gas to a catalytic combustor, which includes a main supply system that connects the exhaust gas supply system from the fuel cell to a first gas chamber; The main supply system is provided with an exhaust fuel gas flow rate control valve for controlling the flow rate of exhaust fuel gas, and the main supply system is provided with an exhaust fuel gas flow rate control valve that controls the flow rate of exhaust fuel gas. A temperature sensor is provided in the gas chamber to detect the gas temperature in the gas chamber, and the temperature detected by this sensor is set in advance to prevent the combustion catalyst layer of the first combustion stage from overheating due to combustion of exhaust fuel gas in the combustion catalyst layer. 1. A combustion control device for a catalytic combustor for a fuel cell, comprising a control means for controlling the opening degree of an exhaust gas flow rate control valve so that the temperature reaches a certain temperature.