JP2003288936A - Fuel cell power generating system and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive fuel cell power generating system and its operation method, capable of normally conducting water self sustaining with recovered water, and replenishing high purity water without using a water treatment device even in a special case where the self sustaining is impossible for a short time. <P>SOLUTION: This fuel cell power generating system is equipped with a fuel cell 10 generating electricity based on electrochemical reaction of fuel obtained by steam-reformed hydrocarbon-based fuel gas with air acting as oxidizing agent gas, a fuel reforming apparatus 20; a cooling water apparatus 50, a water recovering apparatus 30 recovering water in exhaust air of the fuel cell and combustion gas of a fuel reformer. The water recovering apparatus is equipped with a recovered water tank 31, a sprinkling device installed in the upper part inside the recovered water tank, a recovered water cooler 34, a level gauge 37 detecting a liquid level inside the recovered water tank, and a purified water bottle 38 replenishing purified water according to a liquid level measured result of the level gauge. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell that generates electricity based on an electrochemical reaction between a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel and an oxidant gas (air), A fuel reforming system device, a fuel cell cooling water system device,
The present invention relates to a fuel cell power generation device having a recovery water system device that recovers water in exhaust air of a fuel cell and combustion exhaust gas of a fuel reformer, and an operating method thereof.

[0002]

2. Description of the Related Art There are various types of fuel cells incorporated in a fuel cell power generator, which vary depending on the type of electrolyte, the type of reforming raw material, and the like. For example, a solid polymer membrane is used as an electrolyte and its operating temperature is A solid polymer electrolyte fuel cell is well known as a fuel cell of a relatively low temperature of about 80 ° C.

This solid polymer electrolyte fuel cell is similar to the phosphoric acid fuel cell, for example, methane gas (city gas).
Hydrogen in the fuel gas and oxygen in the air obtained by steam reforming a hydrocarbon-based raw fuel such as is supplied to the fuel electrode and air electrode of the fuel cell, respectively, to generate electricity based on an electrochemical reaction. It is something to do.

Further, when reforming raw fuel into fuel gas, a method is adopted in which steam is added to raw fuel to promote reforming by a catalyst in a fuel reformer, but reforming is carried out constantly. It is necessary to constantly replenish the required amount of water vapor, and it is necessary to constantly replenish the water vapor supply device with water corresponding thereto. The water used must be highly pure water, and ion-exchanged water from which impurities have been removed by an ion-exchange water treatment device is usually used.

On the other hand, power generation water is generated in the electrochemical reaction of the fuel cell, and in the fuel reformer, combustion water is generated with combustion for heating the catalyst for constantly performing the steam reforming reaction which is an endothermic reaction. However, these generated waters have less impurities than ordinary tap water, and if these generated waters are used as raw water, it is possible to reduce the load on the water treatment device. A method in which these generated waters are additionally collected and used as feed water for generating reformed steam is usually adopted.

Further, in the electrochemical reaction of the fuel cell, heat is generated along with the reaction, and a part of this exhaust heat energy is stored as hot water in the hot water storage tank and used for hot water supply or heating.

FIG. 2 is a system diagram showing an example of a conventional solid polymer electrolyte fuel cell power generator using city gas as a raw fuel.

A fuel cell 1 schematically shown in FIG.
0 is configured by disposing and stacking a cooling plate or a cooling plate (not shown) having a cooling groove each time a plurality of unit cells having the fuel electrode 10a and the air electrode 10b are stacked.

The raw fuel is first supplied to the reformer 11 together with the reforming steam, and is reformed into hydrogen and carbon monoxide by the following reaction. As the reforming catalyst, a noble metal catalyst or a nickel catalyst is used.

CH ₄ + H ₂ O → 3H ₂ + CO (Endothermic reaction) Thereafter, this reformed gas is supplied to the CO shift converter 12,
By the following reaction, carbon dioxide in the reformed gas is reduced to about 1%. A noble metal catalyst or a copper-zinc catalyst is used as the CO conversion catalyst.

CO + H ₂ O → H ₂ + CO ₂ (exothermic reaction) After that, the monooxidation in the reformed gas is performed by the following reaction in which CO is selectively oxidized by the air supplied to the CO remover 13 and supplied by the blower. After the carbon is reduced to about 10 ppm, it is supplied to the fuel electrode 10a of the fuel cell.

CO + 1 / 2O ₂ → CO ₂ (exothermic reaction) As described above, when the reforming reaction is carried out in the reformer 11,
It is necessary to supply water vapor, and in the polymer electrolyte fuel cell power generator, it is common to use the sensible heat of the combustion exhaust gas of the reformer 11 and the reaction heat of the CO shift converter 12 and the CO remover 13 as its heat source. Target. Therefore, the reforming water supplied by the pump 54 is supplied to the CO shift converter 12 and the CO remover 1.
3, a reforming steam supply line 15 for sequentially flowing each reactor of the steam generator 14 in series is provided, receives heat from each of the reactors to be steam, and mixes the steam with the raw fuel, It is configured to be introduced from the reforming steam supply line 15 to the reformer 11. Note that, in FIG. 2, the flow line of the reforming water to the CO shift converter 12 and the CO remover 13 is omitted.

Further, since each of the above reactors performs a chemical reaction by a catalyst, it is necessary to raise the temperature to an appropriate temperature in advance when the fuel cell power generator is started. The proper temperature of each reactor is as follows. Reformer: 500 to 700 ° C, CO shifter: 200 to 300 ° C, CO remover: 100 to 250 ° C.

Therefore, the reformer 11 is normally heated by burning the hydrogen supplied from the exhaust hydrogen supply line 19 of the fuel cell with the burner installed in the reformer. During startup, the temperature is raised by burning the raw fuel with a burner. The steam generator 14 is also heated by the combustion exhaust gas from the reformer. On the other hand, each of the CO shift converter 12 and the CO remover 13 is heated by an electric heater (not shown) provided individually. Combustion air is introduced into the burner by a combustion air blower 18. Reference numeral 18a is a reaction air blower for supplying reaction air and CO selective oxidation air in the CO remover to the air electrode of the fuel cell body.

The city gas is a city gas booster blower 1
7, the sulfur component contained in the city gas is first introduced into the desulfurizer 16 and then introduced into the catalytic reactor of the reformer 11 and reformed while being supplied with heat by the combustion exhaust gas. , Becomes hydrogen-rich fuel gas.

Next, the cooling water system device 50 and the recovery water system device 30 of the fuel cell in FIG. 2 will be described below.
The cooling water system device 50 includes a battery cooling water cooler 51, a cathode off-gas cooler 52, and an exhaust gas cooler 5 for combustion exhaust gas.
3, a pure water tank 55, a battery cooling water circulation pump 54,
Including other piping.

As described above, the fuel cell 10 is operated at about 80 ° C., cooled by the cell cooling water circulation pump 54 by the water flowing from the pure water tank 55, and removed by the cell cooling water cooler 51. . The battery cooling water cooler 51 is supplied with water at a temperature of, for example, about 50 ° C., which is supplied from a circulating water outlet line 56 connected to a hot water storage tank (not shown in FIG. 2). After that, the temperature is raised to, for example, about 60 ° C. via the cathode off-gas cooler 52 and the exhaust gas cooler 53 for the combustion exhaust gas, and is returned to the hot water storage tank from the circulating water outlet line 57.
A liquid level gauge is provided in the pure water tank 55, and when the liquid level reaches the lower limit, recovered water, which will be described later, is intermittently supplied through the water treatment device 35.

Next, the recovered water system device 30 will be described.
The recovered water system device 30 includes a recovered water tank 31, a recovered water pump 33, a recovered water cooler 34, and the like. Off-air and combustion exhaust gas cooled by a cathode off-gas cooler 52 and a combustion exhaust gas exhaust gas cooler 53 are introduced to the upper part of the recovered water tank 31, and the water content in the air and the gas is sprayed on the upper part. The cooling water is sprayed from the device to be condensed and collected in the lower part of the collected water tank 31. The recovered water is cooled by the recovered water cooler 34 and introduced into the sprinkler. In some cases, a cooling water direct contact condenser equipped with a packed bed such as Raschig rings may be provided at the subsequent stage of this water sprinkler.

In this case, the off-air containing the steam and the combustion exhaust gas are made to flow upward from the lower part of the packed bed (not shown in FIG. 2), while being cooled by the recovered water cooler 34 from the upper part.
It collects recovered water at about ℃ and directly condenses the gas and cooling water in the packed bed while condensing and recovering the water vapor content in the air and gas. With a simple structure, recovery efficiency is improved. There are advantages.

As mentioned above, the recovered water is purified by the water treatment device and used as makeup water. A liquid level gauge is also provided under the collected water tank 31, and when the water in the collected water tank is insufficient, city water (tap water) is supplied as makeup water, and this city water is a water treatment device. Will be purified in.

[0021]

By the way, the conventional fuel cell power generation device in which city water is used as makeup water and purification is performed in the water treatment device as described above has the following problems.

In the water treatment device, the life of the ion exchange resin is short, and the maintenance cost including the exchange work of the ion exchange resin is high. Since this cost accounts for a large proportion of the total cost including the running cost of the fuel cell power plant,
This is one of the bottleneck in terms of economic efficiency when adopting a fuel cell power generator.

Further, since the water treatment device does not supply heat from the inside of the system even during operation of the fuel cell, there is a risk of freezing in cold regions, and anti-freezing measures also increase the overall cost. It is also one of the factors.

Originally, power generation water is generated in the electrochemical reaction of the fuel cell, and combustion water is also generated in the fuel reformer due to combustion. As described above, these water are collected and reformed steam is generated. As for the supply water for generation, the recovered water is superior to the necessary supply water, and the recovered water usually overflows from the recovered water tank. Further, the recovered water has less impurities than normal tap water, and the polymer electrolyte fuel cell does not have a phosphoric acid component in the recovered water unlike the phosphoric acid fuel cell, and therefore has no water treatment device. Both should be able to operate independently.

However, in the summer, for example, when the outside air temperature is 35 ° C. or higher, the performance of the recovered water cooler 34 deteriorates, and the steam in the air and gas cannot be condensed, and the direct contact heat exchanger is used. There will be a situation where the performance of the product deteriorates and the amount of recovered water becomes insufficient. Even when the outside air temperature is 35 ° C. or lower, when slime adheres to the packed bed such as Raschig rings described above or the nozzle of the sprinkler is clogged with water stains or the like during long-term operation. However, the performance of the direct contact heat exchanger deteriorates, and the situation may occur where the recovered water becomes insufficient. In this case, since the city water of low purity is replenished, the water treatment device is indispensable.

The present invention has been made in view of the above problems, and an object of the present invention is to enable water self-sustaining operation with recovered water at all times, and even in a short-time special case where self-sustaining operation is impossible. It is an object of the present invention to provide an inexpensive fuel cell power generation device and a method of operating the same, which makes it possible to supply high-purity water without a treatment device.

[0027]

In order to solve the above-mentioned problems, according to the present invention, electricity of a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel gas and air as an oxidant gas is used. A fuel cell that generates electricity based on a chemical reaction, a fuel reforming system device, a cooling water system device of the fuel cell, and a recovery water system device that collects water in the exhaust air of the fuel cell and the combustion exhaust gas of the fuel reformer. In the fuel cell power generator having the above, the recovered water system device includes a recovered water tank, a sprinkler device provided in an upper part of the recovered water tank, and a recovered water cooler,
A liquid level gauge for detecting the liquid level in the recovered water tank and a purified water supply container for supplying purified water based on the liquid level measurement result of the liquid level gauge are provided (the invention of claim 1).

According to the first aspect of the present invention, as will be described later, during steady operation, the water self-sustaining operation is performed by the recovered water without supplementing the purified water, and the water self-sustaining operation is impossible due to the liquid level measurement result. When the situation is found, the purified water can be replenished from the purified water supply container to continue the operation. As a purified water supply container, an inexpensive purified water bottle commercially available at a pharmacy or the like (for example, a 350 ml bottle is 9
8 yen) is available. In addition, the purified water purchased can be stored in the purified water supply tank.

As an embodiment of the invention of claim 1,
The inventions of claims 2 to 3 below are preferable. Further, as an operating method, the inventions of claims 4 to 5 below are preferable.
The operation and effect of the inventions of claims 2 to 5 are as roughly explained in the description of the prior art and the like. Note that details will be supplementarily described in Examples described later.

That is, in the fuel cell power generator according to claim 1, the recovered water tank is such that cooling water is directly provided between the sprinkler device and the exhaust air introduction port and the combustion exhaust gas introduction port in the upper part of the recovered water tank. A packed bed such as Raschig rings as a contact type condenser is provided (the invention of claim 2).

Further, in the fuel cell power generator according to claim 1 or 2, the recovered water tank is provided with an overflow pipe for discharging excess recovered water (invention of claim 3). .

Further, in the operating method of the fuel cell power generator according to any one of claims 1 to 3, during steady operation in which the liquid level measurement result of the liquid level gauge is higher than a predetermined level (L). When the water level measurement result reaches a predetermined level (L) by performing water self-sustaining operation with the recovered water without supplying the purified water, the purified water is supplied from the purified water supply container to the predetermined level (H). Then, the operation is continued (the invention of claim 4).

Furthermore, in the operating method according to claim 4, the water self-sustaining operation becomes impossible for some reason, and the liquid level measurement result of the liquid level gauge reaches a predetermined minimum level (LL). When it arrives, stop supplying purified water,
In addition, the operation of the fuel cell power generator is stopped (the invention of claim 5).

[0034]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment according to the present invention. Members having the same functions as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. Further, in FIG. 1, for the sake of convenience of explanation, in the system system shown in FIG. 2, mainly the recovered water system device 30 is shown with some additional modifications, such as a fuel cell, a fuel reforming system device, and a battery cooling water system. The other lines of are omitted.

The difference between FIG. 1 and FIG. 2 is that the recovered water tank 31 in FIG. 1 has a filling layer 36 provided between the sprinkler 32 and the exhaust air inlet and the combustion exhaust gas inlet, and a liquid level gauge. 37, a purified water bottle 38, and an open / close control valve 3 for controlling the supply of purified water based on the liquid level measurement result of this level gauge.
9 and an overflow pipe 40 for discharging excess recovered water.

The liquid level gauge 37 includes H, L and L shown in FIG.
Output the liquid level of three stages of L to the control device (not shown),
It is configured to control the supply of purified water and the stop of the device described later. That is, as described above, the open / close control valve 39 is closed during the steady operation in which the liquid level is measured by the liquid level gauge 37 and is higher than the predetermined level (L), and the recovered water is used without supplementing the purified water. Perform independent operation. When the liquid level measurement result reaches a predetermined level (L), the open / close control valve 39 is opened, and purified water is supplied from the purified water bottle 38 to a predetermined level (H) to continue the operation.

Further, when the water self-sustaining operation becomes impossible for some reason and the liquid level measurement result of the liquid level gauge 37 reaches a predetermined minimum level (LL), the opening / closing control valve 39
Closed to stop the supply of purified water and stop the operation of the fuel cell power generator.

By the way, when the water self-sustaining operation with the recovered water is continued for a long period of time, since the water in the system is not purified by the ion exchange resin in the water treatment device, the electric conductivity of the water in the system gradually increases. It is possible. In this regard, a follow-up investigation was conducted on the examples, and it was found that a saturation state (saturation within about 10 μS / cm) was reached after about 48 hours. Therefore, the water self-sustaining operation with the recovered water can be continued for a long time without any problems by, for example, replacing the water in the system with pure water after the operation for 40,000 hours (about once every five years).

[0040]

As described above, according to the present invention, electricity is generated based on an electrochemical reaction between a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel gas and air as an oxidant gas. In a fuel cell power generation device having a fuel cell, a fuel reforming system device, a cooling water system device for the fuel cell, and a recovery water system device for recovering the exhaust air of the fuel cell and the water in the combustion exhaust gas of the fuel reformer The collected water system device includes a collected water tank, a sprinkler provided in an upper portion of the collected water tank, a collected water cooler, a liquid level gauge for detecting a liquid level in the collected water tank, and a liquid level gauge. Since it is equipped with a purified water supply container that supplies purified water based on the liquid level measurement results of the Supplement of high-purity water without treatment equipment And then it can be performed cheaper fuel cell power generation system and an operation method thereof can be provided.

[Brief description of drawings]

FIG. 1 is a system diagram of mainly recovered water system equipment related to an embodiment of a fuel cell power generator of the present invention.

FIG. 2 is a system diagram showing an example of a conventional fuel cell power generator.

[Explanation of symbols]

10: fuel cell, 20: reforming system device, 30: recovered water system device, 31: recovered water tank, 32: sprinkler device, 33: recovered water pump, 34: recovered water cooler, 36: packed bed, 37:
Liquid level gauge, 38: Purified water bottle, 39: Open / close control valve, 4
0: overflow pipe, 50: cooling water system device.

Claims (5)

[Claims] 1. A fuel cell for generating electricity based on an electrochemical reaction between a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel gas and air as an oxidant gas, and a fuel reforming apparatus. And a cooling water system device for the fuel cell, and a recovery water system device for recovering water in the exhaust air of the fuel cell and the combustion exhaust gas of the fuel reformer, wherein the recovery water system device is a recovery water tank. , A sprinkler installed in the upper part of the recovered water tank, a recovered water cooler, a level gauge for detecting the liquid level in the recovered water tank, and purified water based on the level measurement result of this level gauge. A fuel cell power generation device comprising: a purified water supply container for supply. 2. The fuel cell power generator according to claim 1, wherein the recovered water tank is in direct contact with cooling water between the sprinkler device and the exhaust air introduction port and the combustion exhaust gas introduction port in the upper part of the recovered water tank. A fuel cell power generation device comprising a packed bed such as Raschig rings as an electric condenser. 3. The fuel cell power generator according to claim 1, wherein the recovered water tank includes an overflow pipe for discharging excess recovered water. 4. The method for operating the fuel cell power generator according to claim 1, wherein the liquid level measurement result of the liquid level gauge is higher than a predetermined level (L) during steady operation. The water self-sustaining operation by the recovered water is performed without supplying the purified water, and when the liquid level measurement result reaches the predetermined level (L), the purified water is supplied from the purified water supply container to the predetermined level (H). A method for operating a fuel cell power generation device, characterized by continuously operating the fuel cell power generator. 5. The operating method according to claim 4, wherein the water self-sustaining operation is disabled for some reason, and the liquid level measurement result of the liquid level gauge reaches a predetermined minimum level (LL). In this case, the method for operating the fuel cell power generator is characterized in that the supply of purified water is stopped and the operation of the fuel cell power generator is stopped.