JPH0410360A - Fuel cell power generating device - Google Patents

Abstract

PURPOSE:To improve the energy availability of a fuel cell by using an inert gas as a substitution gas at the starting or stopping time of power generation by separating and forming from the gas or air of a reformed burner by using dump power which a fuel cell generates even at the time of a light load. CONSTITUTION:The output current control portion 6 of a fuel cell 1 outputs a signal 6 to command a start of the driving motor 14M of a compressor 14 to an auxiliary power source 8 when the total of a load current IL and an auxiliary current Is drops to a prescribed level or less, and concurrently controls the fuel cell 1 and a fuel reformer 2 so that the driving current Ib of the motor 14M is additionally supplied. For this, inert gas for substitution is produced by making use of dump power at the time of a light load. A required quantity of CO2 enriched gas 11B is stored all times in a tank 15 to create a waiting state of gas substitution. It is thereby possible to use inert gas as substitution gas at the time of start or stop of power generation and improve the energy availability of a fuel cell.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a fuel cell power generation system, in particular, a method for replacing all of the reactant gas in the reactant gas system of the fuel cell with inert gas when starting and stopping the fuel cell. Regarding the generation of replacement gas and the configuration of the supply system.

[Conventional technology]

As is well known, a fuel cell consists of a cell stack formed by stacking a plurality of single cells (unit cells) each having a pair of fuel electrodes and an oxidizer electrode with an electrolyte layer sandwiched between them, and this cell stack contains hydrogen as a reactive gas. 1! Supplying fuel gas and oxidizing gas containing oxygen such as air! Direct light by pond reaction
In this case, there are known fuel cells of dialkali type, phosphoric acid type, molten carbonate type, etc. depending on the electrolyte used and the operating temperature.

By the way, 1. Starting up a fuel cell with the supply of reactant gas stopped,
Fuel for safety management when stopped! Gas replacement is carried out by replacing the entire pond body and the system that supplies and discharges reaction gas to it with an inert gas, such as nitrogen.In particular, the fuel gas system contains hydrogen, so gas replacement is essential for safety management. There is. This is fuel at a standstill! If you supply fuel gas with air or oxidizer gas remaining in the fuel gas system when starting up the fuel gas system, there is a risk of an explosive reaction forming with the oxygen. This is because it is necessary to replace the gas with active gas.

In addition, if the fuel cell is left with no fuel gas remaining inside the fuel cell when it is stopped, the pressure of the fuel gas will decrease due to internal discharge of the fuel cell or a change in the filling rate, causing air to enter the fuel gas system from outside the system. There is a risk that the gas may enter the air and form explosive gas as described above, and in this case as well, it is necessary to replace the gas with an inert gas.

In the case of an oxidizing gas system, in the unlikely event that fuel gas leaks from the fuel gas system, it will form an explosive atmosphere and cause an explosive reaction, so as with the fuel gas system, inert gas should be replaced. is required.

Conventionally, the inert gas for gas replacement as mentioned above is procured from outside, and is stored in a storage tank such as a pressure cylinder, and the inert gas is transferred from the storage tank to the reaction gas system when starting or stopping the fuel cell. A device that supplies active gas is known.

[The problem that the invention attempts to solve]

The operating temperature of a fuel cell is as high as 170'C to 2°C, and when the fuel cell is put into a light load or no-load state under these conditions, the voltage-current characteristic diagram of the fuel cell is shown in Figure 3. As an example, steady operation (current density 50 to 2
00 mA/crI)T is said to be that the voltage of a single cell kept below about 0°8°C rises to K, which is close to the so-called open circuit voltage of about IVk to 1.1°C, and the deterioration of the unit cell electrode is accelerated. A problem occurs. Conventionally, in order to avoid such problems, a negative F such as an electric heater was installed on the output side of the fuel cell.
By installing a T-equipment +T, the power can be reduced even when there is no load.
Measures have been taken to maintain the single cell voltage below 0.8V, but there are limits to the recovery of the heat generated by electric heaters, especially when using fuel cells as a mobile power source. However, there are problems in that it is not easy to radiate the generated heat to the outside, and there is a need to improve the energy efficiency of power generation equipment.

On the other hand, with conventional gas replacement methods, it is necessary to always keep a certain amount of inert gas in the storage tank, which not only complicates management tasks such as replenishing the inert gas, but also makes it difficult to maintain the capacity of the mobile power supply. However, since the storage tank has to be mounted on the vehicle (C tower), the weight of the button car increases, resulting in an economic disadvantage.

The purpose of this invention is to create a fuel cell power generation system that is equipped with a replacement gas separation and generation device that has high energy utilization efficiency and can save labor on maintenance. It's about getting.

[A precautionary measure to solve the problem]

The above issue? According to the present invention, a fuel cell that generates electricity by receiving fuel gas generated by a fuel reformer and reaction air sent from a blower into a fuel chamber and an air chamber, respectively, starts generating electricity and #! of the fuel reformer in which the fuel gas and reaction air remaining in the fuel chamber and air chamber are replaced with inert gas upon shutdown. A separation membrane type separator that receives Akatsuki waste gas and separates and recovers carbon dioxide-enriched gas in the combustion phosphorus waste gas, a compressor for the recovered carbon dioxide-enriched gas, and a compressor for the compressed carbon dioxide-enriched gas. A complete replacement gas separation and generation device consisting of a storage tank and a piping system that supplies the stored carbon dioxide-enriched gas to the fuel chamber and air chamber when power is stopped, and the mud compressor. is the fuel 'I! A device configured to operate by receiving surplus electricity from a pond during light loads;
Or # The replacement gas separation and generation device includes a separation membrane type separation device that separates and recovers nitrogen-enriched gas from the air, a compressor for the recovered nitrogen-enriched gas, and a storage tank for the compressed nitrogen-enriched gas. and a piping system for supplying the stored nitrogen-enriched gas to the fuel chamber and air chamber when power generation starts and stops.

[Effect]

In the structure of the present invention, the replacement gas separation and generation device is used to separate and recover carbon dioxide in the combustion waste gas of the fuel reformer burner, and nitrogen in the atmosphere is separated and recovered by a separation membrane type separation device, and the surplus gas is removed from the fuel cell. It is configured to pressurize with a compressor with an intake function driven by electricity, store it in an inert gas storage tank, and supply it to the reaction gas chamber of the fuel cell to perform gas replacement when the fuel cell starts or stops power generation. By doing so, it is possible to separate and recover the inert gas using the generated power during light loads, and also to maintain the single cell voltage to, sv or less to prevent deterioration of the electrodes. In addition, since the inert gas can be automatically separated and generated, there is no need for complicated maintenance management such as replenishing the inert gas, and the amount of storage can be reduced by generating all the inert gas by itself, so the mobile power supply This provides functions that can reduce the weight of storage tanks to be mounted on vehicles.

〔Example〕

The present invention will be explained below based on examples.

Figure 1 shows a complete electrical system fl' for a fuel cell according to an embodiment of the present invention.
It is a system configuration diagram showing a simplified version of the system. In the figure,
The fuel cell 1 is composed of a laminate of unit cells 1U in which a pair of electrodes are arranged with an electrolyte chamber or a mud +, + box in between. Fuel chamber 1F consisting of multiple grooves formed in the direction of
An oxidizer chamber (air chamber in the embodiment) IA is formed. The fuel reformer 2 includes a raw material superheater 2H and a reaction tube 2 that performs steam reforming in a furnace body that has a burner 2B that supplies reaction heat.
Ri preparation, liquefied natural gas (LNG) as a reforming raw material,
By sending a mixture of liquefied petroleum gas (LPG), naphtha, methanol, etc. and steam to the reaction tube 2R via the raw material superheater 2H, it is reformed into hydrogen-rich fuel gas 2F, and the fuel gas is supplied. It is supplied to the fuel chamber 1F of the fuel cell 1 via the system 4. On the other hand, the air chamber iAK is supplied with 3A of reaction air from a reaction air blower (compressor 3) via its supply system 5, and a pair of t
Direct power generation based on electrochemical reactions takes place at a distance. In addition, the off-gas 2G of the fuel gas 2F that has completed the reaction and the off-gas 3G of the reaction air 3A are sent to the reformer burner 2B, and the reformer 62 is maintained at a predetermined operating temperature by the combustion heat, and the necessary Reaction heat is supplied to reaction tube 2RK.

-10,000, the electric power generated by the fuel cell 1 is controlled by the current controller 6 to
llJa, is converted by the power converter 7 into, for example, constant voltage AC power adapted to the external load and supplied to the external load circuit, and a part of the output current is sent to the auxiliary equipment via the source 8 to the reaction air blower 3. It is supplied to the drive motor 3M, a raw material pump (not shown), an electric heater for discharging, an operating valve, etc.

10 is a replacement gas separation and generation device, and a reformer burner 2
A part of the combustion waste gas 12B of B is received through the damper 12, and after removing moisture from the waste gas in the moisture condenser 15, it is sent to the carbon dioxide (Cot) separator 11 for 002 minutes 11[
1 Membrane 11A removes carbon dioxide C, the main component of waste gas.
Separate O-kura. Recovered CO1 enriched gas 11B
is converted into high pressure gas by the compressor 14, and the operation valve 1
4Bt- is stored in the storage tank 15. The storage tank 15 is equipped with a piping system 17 including a pressure reducing valve 18 on its outlet side, and at the start of the fuel cell generation 1, the supply of reactant gas is stopped and the valves 19F and 19A are opened. CO2-enriched gas 71B is supplied to the fuel gas system containing the fuel chamber 1F+ and the reaction air system containing one air chamber, respectively, and the fc fuel gas and air remaining in the system are purged to the outside of the system and the inert CO1 Replace with enriched gas.

The output cuff flow control unit 6 of the fuel cell 1 supervises the flow Is of the load current 1 and the auxiliary equipment using current detectors 9A, 9B, etc. When the sum decreases to a predetermined level or less (for example, 2OFF of the rated current; or less), a signal 6S is output to the auxiliary power supply 8 to instruct the start of the drive motor 14M of the compressor 14, and a button is pressed to start the drive motor 14M. a fuel cell to additionally supply stream 1b;
Controls the fuel reformer JIT. This makes it possible to generate inert gas for replacement using surplus power during light loads, and at the same time reduce the output of the fuel cell by reducing the rise in single cell voltage caused by too much flow and the 1i electrode caused by this. deterioration can be prevented.

9. The gas pressure in the storage tank 15 is detected by the pressure switch 16, and when the pressure reaches a predetermined level, the control signal 16St-damper 12. By outputting to the operation valve 14E and the compressor 14, a predetermined amount of CO! is constantly stored in the storage tank 15. The enriched gas 11B can be stored and placed in a standby state for gas replacement. Note that the compressor 14 preferably has a suction function to generate a pressure difference across the separation membrane 11A. In addition, in the case of a mobile power supply unit having a brake air compressor and pressure tank, these can also be used as the compressor and storage tank of the displacement gas separation and generation device.
! This can contribute to reductions in equipment costs and equipment costs.

FIG. 2 is a system configuration diagram showing a different embodiment of the present invention, in which a separation device 21 separates air pressurized by a comb 24 into a total M/element enriched gas 27 and a nitrogen enriched gas 26. The difference from the previous embodiment is that an oxygen permeable membrane 21A is provided, and oxygen permeates through the multiple stages of permeable membranes, whereby most of the oxygen is separated and the remaining nitrogen-enriched gas 26 is sent to the compressor. 14 and stored in a storage tank 15.

In addition, when the fuel cell 1 is a pressurized type, it may be constructed so that a part of the air pressurized by the reaction air floor 3 (in this case, a compressor) is supplied to the separation device 21, similar to the above embodiment. Effectively utilizes surplus electricity during light loads to generate inert gas for replacement.

In addition to being able to store electricity, it is possible to completely prevent the deterioration of electricity that occurs in the fuel cell due to light loads.

〔Effect of the invention〕

As mentioned above, this invention provides a displacement gas separation and generation device that separates and stores inert gas from the waste gas or air of a reforming burner using surplus electricity generated by a fuel cell even under light load. The system was designed so that the inert gas stored at the time of shutdown is used as replacement gas before starting power generation. As a result, the power generated during light loads, which was previously wasted by installing electric heaters, can be used effectively by separating and storing inert gas, and the stored inert gas can be used as replacement gas. Therefore, it is possible to improve the energy utilization efficiency of the fuel cell, and at the same time, there is an advantage that the operating cost can be reduced. Furthermore, since it is possible to prevent the load on the fuel cell from dropping below a predetermined level, the rfl function can prevent deterioration of the electrodes due to an increase in single cell voltage, which has the effect of extending the life of the fuel cell. can get.

In addition, since the replacement gas separation and generation device can always generate and store the required amount of inert gas, it is possible to reduce inert gas supplementation and the cost required for this, which in turn reduces fuel cell management costs. operating costs.

In addition, in the mobile power supply device, the amount of inert gas mounted on the vehicle and the storage cylinder thereof can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a system configuration diagram showing a simplified fuel cell power generation device according to an embodiment of the present invention, Fig. 2 is a system configuration diagram showing a different embodiment of the invention, and Fig. 3 is a voltage-current diagram of the fuel cell. FIG. 3 is a characteristic diagram showing an example of characteristics. 7...Fuel cell, 1 person...Air chamber, 1F...Fuel chamber, 1U...Unit cell, 2...Fuel reformer, 2E...
...Burner 2H...Superheater, 2R...Reaction tube, 2F
... Fuel gas 3 ... Reaction air blower, 3A ... Reaction air, 4, 5 ... Reaction gas supply system, 6 ... Current control section, 7 ... Power converter, 8.・・Auxiliary power supply, 9・
... Current detector, 10... Replacement gas separation and generation device,
11.21...Separator, 11A, 21A...Separation membrane, 12...Damper 13...#Compressor, 14.24
...Compressor, 15...Storage tank, 16...Pressure switch, 17...Piping, 16.18, 19A
, 1 9B, *, 71B...co2 g-ganu 26...N1 enriched gas, 3M, 14M, 24M...
.

Claims (1)

[Scope of Claims] 1) A fuel cell that generates electricity by receiving fuel gas generated by a fuel reformer and reaction air sent from a blower into a fuel chamber and an air chamber, respectively, when starting and stopping power generation, In a device in which the fuel gas and reaction air remaining in the fuel chamber and the air chamber are replaced with inert gas, the combustion waste gas from the fuel reformer is received, and the carbon dioxide enriched gas in the combustion waste gas is separated and recovered. A separation membrane type separation device,
A compressor for the recovered carbon dioxide-enriched gas, a storage tank for the compressed carbon dioxide-enriched gas, and piping for supplying the stored carbon dioxide-enriched gas to the fuel chamber and the air chamber at the time of starting or stopping power generation. What is claimed is: 1. A fuel cell power generation device comprising: a replacement gas separation and generation device comprising a system, wherein the compressor is configured to operate in response to a supply of surplus power from the fuel cell during light loads. 2) The replacement gas separation and generation device includes a separation membrane type separation device that separates and recovers nitrogen-enriched gas in the air, a compressor for the recovered nitrogen-enriched gas, and a storage tank for the compressed nitrogen-enriched gas. and a piping system for supplying the stored nitrogen-enriched gas to the fuel chamber and the air chamber at the time of starting or stopping power generation.