JPS62285366A - Fuel cell power generation system - Google Patents

Abstract

PURPOSE:To enable recycle operation to be carried out in high effeciency and high reliability so that a fuel cell power generation system with a low cost and high reliability may be secured, by providing, on a bypass line, a cooler for cooling the gas flowing in a line by means of a cooling medium. CONSTITUTION:A part of air exhaust gas is introduced in an oxider pole recycle line 23 branching from the outlet line of an oxider pole 11B, and after its steam component is removed by means of an oxider pole recycle gas steam separator 24, it is transported to an oxider pole recycle blower 25. The air exhaust gas mades circulation flowing through the oxider pole recycle blower 25 and an oxider pole blower bypass line 27, while being given compression work from the oxider pole recycle blower 25. In this case, the air exhaust gas is prevented from excessive rise of its temperature taking place at the entrance of the oxider pole recycle blower 25 by being cooled when it passes through an oxider pole bypass gas cooler 33 installed in the oxider pole recycle blower bypass line 27.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a fuel cell power generation system, and particularly relates to a fuel cell power generation system configured to prevent the fluid circulating through a recycle blower inside a recycle line from becoming high temperature. Regarding battery power generation systems.

[Technical background of the invention and its problems]

2. Description of the Related Art In recent years, fuel storage power generation systems have become known as systems that directly convert the energy contained in fuel into electrical energy. This fuel cell power generation system usually consists of a pair of porous electrodes arranged with an electrolyte in between, and a fuel such as hydrogen is brought into contact with the back of one electrode, and oxygen is brought into contact with the back of the other electrode. This method uses the electrochemical reaction that occurs when an oxidizing agent, such as a It is something that can extract electrical energy.

FIG. 3 shows the basic configuration of a typical fuel cell power generation system of this type. In the figure, natural gas,
Alternatively, the fuel 1 made of fossil fuel such as coal gas and the steam from the steam supply device 2 are controlled by the fuel control valve 3 and the steam control valve 4, respectively, so that the mixing molar ratio of steam and carbon is about 3 to 5. It is controlled and introduced into the reforming catalyst tube 6 in the fuel reformer 5. Here, the steam and fuel 1 are heated to about 500 to 600°C to perform a reforming reaction, and then pass through a shift converter 7 to become reformed fuel with a high hydrogen content. This reformed fuel with increased hydrogen content is sent to the fuel gas steam water separator 8 to remove surplus steam from reforming, and then sent to the auxiliary burner 9 by the auxiliary burner fuel control valve 10. Also, the fuel electrode 11 of the fuel cell 11
The reformed fuel is sent to A with its flow rate controlled by the reformed fuel control valve 12.

The reformed fuel that has flowed into the fuel electrode 11A of the fuel cell 11 undergoes a catalytic reaction with the air that has flowed into the oxidizer electrode 11B.
As a result, part of the fuel is consumed and electrical energy and reaction product water are obtained. The fuel exhaust gas that exits the fuel electrode 11A and contains a portion of the reaction product water generated in the fuel cell 11 is sent as fuel to the main burner 13 of the fuel reformer 5, but during this process, the gas The fuel electrode exhaust gas passes through a steam/water separator 14 in order to recover middle water.

Then, the fuel exhaust gas sent to the main burner 13 is burned in the fuel reformer 5 and is discharged as high-temperature exhaust gas 15 after heating the reforming catalyst tube 6. Furthermore, after combining with the air exhaust gas sent from the oxidizer electrode 11B of the fuel cell 11, it is sent to the mixer 16 and used as part of the energy for driving the turbo compressor 17. On the other hand, the reformed fuel sent to the auxiliary burner 9 is combusted within the auxiliary burner 9, and the combustion gas passes through the mixer 16 to drive the turbine 17A of the turbo compressor 17.

On the other hand, the air discharged from the compressor 17B connected to and driven by the turbine 17A is sent to the auxiliary burner 9 and the main burner 13 with the air-fuel ratio controlled by the auxiliary burner air control valve 18 and the main burner air control valve 19, respectively. At the same time, the oxidizer electrode 11 of the fuel cell 11 is controlled by the air control valve 20.
B, and the surplus is sent to the mixer 16 as part of the energy for driving the turbo compressor 17. A part of the air sent to the oxidizer electrode 11B is
After it is consumed by reacting with the hydrogen of A, it is discharged containing the moisture generated in the oxidizer electrode 11B. Similar to the fuel exhaust gas, this discharged air exhaust gas is sent from the fuel reformer 5 after a part of the steam in the air exhaust gas is removed as condensation by the oxidizer electrode exhaust gas steam/water separator 21. It merges with high temperature exhaust gas 15.

Bare Mosoyu I110 ←; 6j 90 injections - Ganmori Tsuge + jA output Due to the catalytic reaction between a small amount of hydrogen and oxygen in the oxidizer electrode 11B, the oxidizer electrode 11B becomes a positive electrode (cathode) and the fuel electrode 11A becomes a negative electrode. (anode) to generate electrical energy,
Electric load 2 connected between both electrodes 11A and 118
The electrical energy is supplied to 2. At this time, both electrodes 11
The hydrogen and oxygen supplied to the inlets of A and IIB react to obtain reaction product water, and the unreacted gas containing this steam is discharged from the outlets of both electrodes 11A and IIB.

On the other hand, an oxidizer electrode recirculation line (recycle line) 23 is branched from the outlet of the oxidizer electrode 11B, and a part of the air exhaust gas containing steam is sent to the oxidizer electrode recycle gas steam-water separator 24. After removing the condensate, the oxidizing agent is sent to the cycle blower 25. The air exhaust gas discharged from the oxidizing agent cycle blower 25 is returned to the inlet line of the oxidizing agent electrode 11B after adjusting the recycling amount with the oxidizing agent electrode recycling gas control valve 26, and the surplus is returned to the oxidizing agent electrode 11B. The oxidant is returned to the inlet line of the oxidant cycle blower 25 by a bypass line 27 branching from the outlet line of the oxidant cycle blower 25 . The purpose of the oxidizer electrode recycled gas steam/water separator 24 is as follows. In other words, if the air exhaust gas containing a large amount of moisture exceeding a certain limit is returned to the inlet of the oxidizer electrode 11B, moisture molecules inside the oxidizer electrode 11B will prevent the adsorption of oxygen molecules onto the electrode surface. Moisture is removed by the oxidant electrode recycled gas steam/water separator 24, since the electrode reaction may deteriorate and good fuel cell characteristics may not be obtained.

Similarly, a fuel electrode recirculation line (recycle line) 28 is branched from the outlet of the fuel electrode 11A, and a part of the fuel exhaust gas containing steam is recycled at the fuel electrode recycling gas steam/water separator 29. After removing the water, the fuel is sent to the cycle blower 30.

The fuel exhaust gas discharged from the fuel pole cycle blower 30 is returned to the inlet line of the fuel pole 11A after the recycling amount is adjusted by the fuel pole recycling gas control valve 31, and the surplus is returned to the fuel pole cycle blower 30. An anode cycle blower bypass line 32 branching from the outlet line of the blower 30 returns to the inlet line of the anode cycle blower 30.

The purpose of the fuel electrode recycled gas steam/water separation device 29 being installed here is as follows. Namely.

If fuel exhaust gas containing a large amount of moisture exceeding a certain limit is returned to the inlet of the fuel electrode 11A, the fuel electrode 11
Not only is the water vapor partial pressure of the electrolyte inside A not kept uniform, but if the amount of moisture exceeds a certain limit level, part of the electrolyte may scatter, making it impossible to obtain good fuel cell characteristics. Therefore, moisture is removed by the fuel electrode recycled gas steam/water separator 29.

These recycle lines at both poles are provided for the purpose of circulating and reusing unreacted gas after the cell reaction, and have the effect of effectively using fuel gas and air.

Incidentally, the cycle amount of the air exhaust gas sent to the oxidizer electrode 1113 from the oxidizer electrode recycle gas control valve 26 has been conventionally adjusted in accordance with the load current of the fuel cell 11. Therefore, in a certain load range, the amount of recycling may be very small or may not be recycled at all. In this case, most of the air exhaust gas on the high temperature blower outlet side receives the compression work by the oxidizer cycle blower 25 and passes through the oxidizer cycle blower bypass line 27 to complete the oxidizer cycle. After being returned to the inlet of the blower 25, the oxidizer passes through the cycle blower 25 again and receives compression work. Therefore, by circulating the air exhaust gas through the oxidizer cycle blower 25 and the oxidizer cycle blower bypass line 27, the air exhaust gas is circulated through the oxidizer cycle blower 25 and the oxidizer cycle blower 25 until it reaches an equilibrium state with the amount of heat dissipated from the piping, etc. The temperature of the discharged air exhaust gas will increase.

As a result, the air exhaust gas taken in by the oxidizer cycle blower 25 becomes high temperature, which not only reduces the volumetric efficiency of the oxidizer cycle blower 25, but also reduces the volumetric efficiency of the oxidizer cycle blower 25. Because of the high temperature, if the temperature rises beyond the allowable value, the impeller and casing may come into contact with each other due to thermal expansion inside the blower, and the seal portion may deteriorate. In the worst case, the oxidizer cycle blower 25 may suddenly stop rotating during operation. In this case, if the fuel cell 11 is in a power generation state and even a small amount of air exhaust gas is recycled to the oxidizer electrode 11B via the oxidizer electrode recycle gas control valve 26, the oxidizer electrode cycle blower 25 When this stops, the supply of the air exhaust gas recycled to the oxidizer electrode 11B also immediately stops, so that the air utilization rate suddenly increases. The air utilization rate refers to the amount of oxygen supplied to the oxidizer electrode 1113 in the fuel cell 1.
1. This is a value that indicates the percentage of oxygen consumed internally for power generation. Generally speaking, the higher the air utilization rate, the lower the battery output voltage will be, and if the air utilization rate exceeds a certain allowable level, the battery output voltage will decrease. This may lead to a reduction in the lifespan of the product.

In other words, when the oxidizing cycle blower 25 stops, the battery characteristics sharply deteriorate, which not only makes it difficult to perform power generation with a stable battery voltage, but also shortens the battery life. is possible.

Similarly, the fuel electrode recycle gas control valve 31
The amount of recycled fuel exhaust gas sent to the IA is adjusted according to the load current of the fuel cell 11.

Therefore, in certain load ranges, the amount of recycling may be very small, or may not be recycled at all. In this case, the fuel pole cycle blower 30
Most of the fuel exhaust gas on the outlet side of the blower, which receives compression work and has reached a high temperature, passes through the bypass line 32 to the fuel terminal cycle blower.
After being returned to the inlet of fuel cell 30, it passes through the fuel pole cycle blower 30 again and receives compression work. Therefore, by circulating the fuel exhaust gas through the fuel pole cycle blower 30 and the fuel pole cycle blower bypass line 32, the fuel exhaust gas is discharged from the fuel pole cycle blower 30 until it reaches an equilibrium state with the amount of heat dissipated from the piping, etc. The temperature of the fuel exhaust gas will rise.

As a result, the fuel exhaust gas taken in by the fuel pole cycle blower 30 becomes a high-temperature gas, which not only reduces the volumetric efficiency of the fuel pole cycle blower 30, but also causes the fuel pole cycle blower 30 itself to become hot. Therefore, if the temperature rises beyond the allowable value, the impeller and casing may come into contact with each other due to thermal expansion inside the blower, and the bearing portion may deteriorate. In the worst case, the fuel pole cycle blower 30 may suddenly stop rotating during operation. In this case, the fuel cell 11
is in power generation state, even if the fuel electrode recycling gas control valve 3
If the fuel exhaust gas is recycled to the fuel electrode lIA through the fuel electrode cycle blower 30
When the fuel electrode 11A suddenly stops, the supply of fuel exhaust gas recycled to the fuel electrode 11A also stops immediately, so that the fuel utilization rate suddenly increases. Fuel utilization rate refers to fuel electrode 1
This is a numerical value that indicates the ratio of the amount of hydrogen consumed for power generation inside the fuel cell 11 to the amount of hydrogen supplied to the fuel cell 1A.Generally, when the fuel utilization rate is very high, the cell output voltage decreases, and the battery This may lead to a reduction in service life. In other words, if the fuel pole cycle blower 30 stops and the fuel utilization rate becomes extremely high, the battery characteristics will rapidly deteriorate,
Not only will it be difficult to perform power generation operation with a stable battery voltage, but it is conceivable that the battery life will be shortened. Further, when the fuel pole cycle blower 30 is stopped, the composition of the fuel exhaust gas sent to the main burner 13 of the fuel reformer 5 changes significantly.

Therefore, the amount of heat given to the reforming catalyst tube 6 changes.

It is conceivable that the change in the amount of reforming in the fuel reformer 5 may disrupt the balance of the entire plant, making it difficult to perform stable power generation operation.

Therefore, one method to improve the above-mentioned problems and obtain highly reliable plant operation is to use an oxidizer cycle blower 25 and a fuel cycle blower 30 that can withstand large temperature increases. It is conceivable to use a high-temperature type blower with special performance that can be used. However, such high-temperature type blowers use special heat-resistant materials and are expensive, which increases the overall system cost. Further, such high-temperature type blowers generally have a characteristic that compression efficiency is maximized at high temperatures. In other words, inside the blower, the gap between the impeller and the casing is set large at room temperature in consideration of thermal expansion. The amount of leakage is large and the compression efficiency of the blower is low. Therefore, oxidizer electrode 1
In the load zone of the fuel cell 11 where a large amount of oxidant is recycled to 1B and the amount of oxidant flowing through the oxidant cycle blower bypass line 27 is small, the oxidant cycle blower 25 body does not reach a very high temperature. The oxidizer cycle blower 25 will be operated with low compression efficiency, ie low energy efficiency. Similarly, in the load zone of the fuel cell 11 where a large amount is recycled to the fuel electrode 11A and the amount flowing through the fuel electrode cycle blower bypass line 32 is small,
Since the main body of the fuel electrode recycle blower 30 does not reach a very high temperature, the fuel electrode cycle blower 30 is operated with low compression efficiency, that is, low energy efficiency. As a result, using a high-temperature blower as described above in a peak-load type fuel cell power generation plant where the load is frequently changed becomes a factor that increases operating costs in a certain load range.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and its purpose is to apply a low-cost oxidizer cycle blower or fuel pole cycle blower, and to To enable highly efficient and reliable recycling operation using a recycle blower or a fuel pole cycle blower, and as a result, to provide a low cost and highly reliable fuel cell power generation system. It is in.

[Summary of the invention]

A pair of electrodes, a fuel electrode and an oxidizer electrode, are arranged with an electrolyte layer in between, and a fuel is supplied to the fuel electrode and an oxidizer is supplied to the oxidizer electrode, and an electrochemical reaction occurs at this time to create a gap between the electrodes. A fuel cell extracts electrical energy from the fuel cell, and a part of the exhaust gas discharged through the outlet line of the fuel electrode and/or the oxidizer electrode of the fuel cell is branched and recirculated. a recirculation line configured to recirculate the gas to the corresponding electrode inlet side line through the recirculation line; and a bypass line that branches part of the exhaust gas discharged from each of the recirculation blowers and connects it to the upstream side of the corresponding recirculation blower. The fuel cell power generation system is characterized in that a cooler is provided on the bypass line to cool the gas flowing through the line with a cooling medium.

[Embodiments of the invention]

An embodiment of the present invention shown in the drawings will be described below.

FIG. 1 is a block diagram showing an example of the configuration of a fuel cell power generation system according to the present invention.

Note that the same parts in FIG. 1 as in FIG. 3 are given the same reference numerals.

In addition, although the description of the embodiment here is only about the oxidizer electrode recycle line, the fuel electrode recycle line has exactly the same line configuration, so the explanation thereof will be omitted.

(Structure of the Invention) In the figure, the oxidizer electrode 11B is similar to the case of FIG.
A part of the exhausted air exhaust gas containing more steam is introduced into the oxidizer electrode recirculation line 23 branched from the oxidizer electrode 11B outlet line, and is converted into steam in the oxidizer electrode recycle gas steam/water separator 24. After removing the oxidizing agent, the oxidizing agent is sent to the cycle blower 25. Next, the air exhaust gas discharged after being compressed by the oxidizer cycle blower 25 is recycled in an oxidizer electrode recycle gas control valve 26, and is returned to the inlet line of the oxidizer electrode 11B, leaving the excess The oxidizer is introduced into an oxidant cycle blower bypass line 27 which branches off from the outlet line of the oxidant cycle blower 25. The air exhaust gas introduced into the oxidizer cycle blower bypass line 27 is
Next, a newly installed oxidizer electrode bypass gas cooler 33
After passing through the oxidizing agent, the oxidizing agent is returned to the inlet line of the cycle blower 25.

(Operation of the Invention) In the fuel cell power generation system configured as described above, while the air exhaust gas is subjected to compression work by the oxidizer cycle blower 25, the oxidizer cycle blower 25 and the oxidizer cycle blower bypass line are connected to each other. Even if the oxidizer is circulated through the oxidant cycle blower bypass line 27, the air at the inlet of the oxidizer cycle blower 25 is cooled by passing through the oxidizer bypass gas cooler 33 provided in the oxidizer bypass line 27. This will prevent an excessive rise in the temperature of the exhaust gas.

(Effects of the Invention) As described above, by providing the fuel cell power generation system with such a configuration, the oxidant cycle blower bypass line 27 can be Since the air exhaust gas can always be supplied to the oxidizer 25 at a temperature below a certain level, the oxidizer cycle blower 25 can be used as a low-temperature type blower that is inexpensive and can always perform highly efficient recycling operation. .

In addition, the possibility of contact between the impeller and casing or deterioration of the seal due to thermal expansion inside the blower is extremely reduced, allowing reliable cycle blower operation without sudden stoppage due to blower failure. I can do it. As a result, it is possible to provide a fuel cell power generation system that is highly efficient and highly reliable at lower cost.

(Other Embodiments) Next, FIG. 2 is a block diagram showing another configuration example of the fuel cell power generation system according to the present invention.

In FIG. 2, the same parts as in FIG. 3 are given the same reference numerals. Furthermore, although the description of the embodiment here is only about the oxidizer electrode recycle line, the fuel electrode recycle line has exactly the same line configuration, so the explanation thereof will be omitted. In Fig. 1, even if the air exhaust gas circulates between the oxidant maximum cycle blower 25 and the oxidizer maximum cycle blower bypass line 27, the oxidizer maximum cycle is Although the configuration is such that the oxidant electrode bypass gas cooler 33 is installed in the blower bypass line 27, the oxidant electrode recycle gas steam/water separation device 24 installed in the oxidant electrode recirculation line 23 is used for cooling and recovery. If it is a water type, as shown in Figure 2, the outlet line of the oxidizer cycle blower bypass line 27, which is branched from the outlet line of the oxidizer cycle blower 25, is connected to the oxidizer pole recycled gas air, water, It may also be configured to return to the inlet line of the separator 24.

In other words, after receiving the compression work by the oxidant cycle blower 25, the oxidizer cycle blower is
The air exhaust gas introduced into the bypass line 27 joins with the air exhaust gas introduced into the oxidizer electrode recirculation line 23 from the outlet of the oxidizer electrode 11B, and then returns to the oxidizer electrode recycle gas steam/water separator 24. will be introduced to The oxidizer pole recycled gas steam/water separator 24 cools the air exhaust gas containing high-temperature steam and removes the steam as condensation. Air exhaust gas can be supplied under conditions below the temperature level, and an effect similar to that achieved by the configuration shown in FIG. 1 can be obtained.

As described above, by adopting a fuel cell power generation system having such a configuration, air exhaust gas is transferred from the oxidizer cycle blower bypass line 27 to the oxidizer cycle blower 25 regardless of the load fluctuation of the fuel cell 11. Since the oxidizing agent can be supplied at a temperature below a certain level at all times, the oxidizing agent cycle blower 25 can be used as a low-cost, room-temperature type blower to perform highly efficient recycling operations at all times.

In addition, the possibility of contact between the windshield and claws or deterioration of the sealing part occurring inside the blower is extremely small, so the reliability can be improved without sudden stoppage due to blower failure. Able to operate high cycle blower. As a result, it is possible to provide a fuel cell power generation system that is highly efficient and highly reliable at lower cost.

〔Effect of the invention〕

As explained above, according to the present invention, a low-cost oxidizer cycle blower 1 or fuel cycle blower is applied, and the oxidizer cycle blower or fuel cycle blower is By using this method, it is possible to perform highly efficient and reliable recycling operation, thereby making it possible to provide a low-cost and highly reliable fuel cell power generation system.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of 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. 1... Fuel 2... Steam supply device 3... Fuel control valve 4... Steam control valve 5... Fuel reformer 6... Reforming catalyst tube 7... Shift converter 8... ...Fuel gas steam/water separation device 9...Auxiliary burner 10...Auxiliary burner fuel control valve 11...Fuel cell 11A...Fuel electrode 11B...Oxidizer electrode 12...Reformed fuel control Valve 13... Main burner 14... Fuel exhaust gas steam water separation device 15... High temperature exhaust gas 16... Mixer 17... Turbo compressor 17A... Turbine 17B... Compressor 18... - Auxiliary burner air control valve 19... Main burner air control valve 20... Air control valve 21... Oxidizer electrode exhaust gas steam/moisture device 22...
Electrical load 23... Oxidizer pole recycle line 24... Oxidizer pole recycled gas steam/water separation device 25.
... Oxidizer cycle blower 26... Oxidizer pole recycling gas control valve 27... Oxidizer pole cycle blower bypass line 28... Fuel electrode recirculation line 29... Fuel electrode recycling gas Steam/water separation device 30...
・Fuel pole cycle blower 31... Fuel pole recycling gas control valve 32... Fuel pole cycle blower bypass line 33... Oxidizer pole bypass gas cooler Agent Patent attorney Nori Chika
Borrowed Questions Hirofumi Mitsumata

Claims (2)

[Claims] (1) A pair of electrodes, a fuel electrode and an oxidizer electrode, are arranged with an electrolyte layer in between, and a fuel is supplied to the fuel electrode, and an oxidizer is supplied to the oxidizer electrode, so that an electrochemical reaction occurs. A fuel cell that extracts electrical energy from between the electrodes, and a part of the exhaust gas discharged through the fuel electrode and/or the oxidizer electrode of the fuel cell, and a part of the exhaust gas discharged through the electrode outlet line is branched and recirculated. A recirculation line configured to recirculate the gas to the corresponding electrode inlet side line via a blower, and a gas provided upstream of each of the recirculation blowers to remove steam in the gas flowing through the line. A fuel cell power generation system comprising a water separator and a bypass line that branches part of the exhaust gas discharged from each of the recirculation blowers and connects to the upstream side of each of the recirculation blowers, the bypass line A fuel cell power generation system characterized by further comprising a cooler for cooling gas flowing through the line. (2) In the fuel cell power generation system according to claim 1, the steam/water separation device is of a cooling condensing type, and a bypass line branched from the recirculation blower discharge side is provided upstream of the steam/water separation device. A fuel cell power generation system characterized by connection to a side recirculation line.