JP2003282105A - Fuel cell power generating system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell power generating system rationally preventing the freezing of water in a variety of circulation passages. <P>SOLUTION: This fuel cell power generating system is equipped with a fuel cell body 10 generating electricity and heat energy based on the electrochemical reaction of fuel gas obtained by steam reforming of hydrocarbon base raw fuel and air acting as an oxidizing agent; a fuel reforming apparatus 20; a cooling apparatus 50 of a fuel cell; a water recovery apparatus 30 recovering water in the exhaust gas of the fuel cell and combustion exhaust gas in a fuel reformer; a water treatment device 35 purifying the recovered water; and a hot water storing tank 60 storing part of the heat energy as hot water, and in order to prevent the freezing of water inside the apparatuses and the devices, freezing preventing piping 70 is furthermore installed in at least a part in the cooling apparatus 50, the water recovery apparatus 30, and the water treatment device 35. <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 for producing electricity and heat energy based on an electrochemical reaction between a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel and an oxidant gas (air). The present invention relates to a fuel cell power generator that includes a battery and a hot water storage tank that stores a part of the thermal energy as hot water.

[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. 3 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.

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%.

CO + H ₂ O → H ₂ + CO ₂ (exothermic reaction) After that, the carbon monoxide in the reformed gas is further supplied to the CO remover 13, and the carbon monoxide in the reformed gas is reduced to about 100 ppm by the following reaction. Is supplied to the fuel electrode 10a.

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. 3, 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.

The city gas is first introduced into the desulfurizer 16 by the city gas pressurization blower 17 to remove the sulfur component contained in the city gas, and then introduced into the catalytic reactor of the reformer 11 for the combustion. It is reformed while being supplied with heat by the exhaust gas and becomes a hydrogen-rich fuel gas.

Next, the cooling water system device 50 and the recovery water system device 30 of the fuel cell in FIG. 3 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 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. 3). 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.

As described above, the recovered water is purified by the water treatment device and used as makeup water. A liquid level gauge is also provided below the collected water tank 31, and when the water in the collected water tank is insufficient, city water is supplied as makeup water.

[0020]

By the way, the above-mentioned conventional fuel cell power generator has the following problems.

As described above, when the fuel cell power generator having various water circulation paths is installed in a low temperature environment such as outdoors in a cold region and the apparatus is stopped for a certain time or longer, the water in the circulation path is However, there was a problem that it could freeze up and damage the pipes and equipment.

Further, even when the fuel cell is not stopped, the supply of makeup water supplied to the pure water tank via the water treatment device is intermittent as described above. The related piping may be frozen because exhaust heat of the fuel cell is not supplied. Usually, in the case of freeze prevention, for example, a method of winding an electric heater for heating around the pipe or a method of directly using exhaust heat of the fuel cell for heating can be considered, but the method is rational in terms of energy consumption. is not.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a fuel cell power generator capable of rationally preventing water from freezing in various circulation paths. To provide.

[0024]

In order to solve the above-mentioned problems, in the present invention, an electrochemical reaction of a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel and air as an oxidant gas Fuel cell main body that generates electricity and thermal energy based on reaction, fuel reforming system equipment, cooling water system equipment of fuel cell, exhaust air of fuel cell and water in combustion exhaust gas of fuel reformer In a fuel cell power generator including a recovered water system device, a water treatment device for purifying recovered water, and a hot water storage tank that stores a part of the thermal energy as hot water, in order to prevent water from freezing in the devices and the device. Furthermore, it is assumed that the hot water in the hot water storage tank is provided with an antifreezing pipe for flowing through at least a part of the cooling water system device, the recovery water system device, and the water treatment device (the invention of claim 1).

According to the above-mentioned configuration, according to the embodiment described later, hot water in the hot water storage tank is used as exhaust heat of the fuel cell,
Reasonable protection against freezing can be achieved.

As an embodiment of the invention of claim 1,
The inventions of claims 2 to 5 below are preferable. That is, in the fuel cell power generator according to claim 1, the antifreezing pipe draws hot water from the upper part of the hot water storage tank and is provided in at least a part of the cooling water system device, the recovered water system device, and the water treatment device. After flowing through, it is configured to flow back to the lower part of the hot water storage tank (the invention of claim 2).

When hot water in the hot water storage tank is used by a customer, city water (tap water) is supplied from the lower portion of the hot water storage tank, and the hot water in the upper portion of the hot water storage tank (for example, 70 (° C) is extruded to supply hot water. Therefore, even if the water supplied for freezing is returned to the tap water supply area at the lower part of the hot water storage tank as described above, the hot water in the upper space of the hot water storage tank is hardly affected by temperature. It is retained without any damage and rational freeze prevention can be achieved.

Further, in the fuel cell power generator according to the first aspect, the antifreezing pipe draws hot water from the middle part of the hot water storage tank, and the cooling water system device, the recovered water system device,
After flowing through at least a part of the water treatment device, it flows through a battery cooling water cooler, a cathode off-gas cooler and a combustion exhaust gas exhaust gas cooler in the cooling water system equipment, and is heated by the thermal energy of the fuel cell. Then, the water is returned to the upper part of the hot water storage tank (the invention of claim 3).

In this case, it is premised that the fuel cell is in operation, but since the water supplied for freezing rises in temperature due to the exhaust heat of the fuel cell, the exhaust heat can be used effectively. Therefore, rational freeze prevention can be achieved. When the fuel cell is not operated, the piping circuit may be switched so that the fuel cell is returned to the lower part of the hot water tank.

Further, in the fuel cell power generator according to claim 1 or 2, the antifreezing pipe allows hot water derived from the hot water storage tank to flow in series to the cooling water system device and the recovered water system device. The water treatment device is configured to flow in parallel with the two devices, and each of the parallel pipelines is provided with an on-off valve or a flow control valve (invention of claim 4). .

As described above, when the fuel cell is operating, only the water treatment device and its associated pipes may freeze. Therefore, by dividing the water treatment device and the cooling water system device and the recovery water system device and configuring the antifreezing pipe, it is possible to perform a rational operation of operating the antifreezing function as necessary.

Furthermore, the invention of claim 5 is preferable from the viewpoint of performing fine antifreeze operation as necessary. That is, in the fuel cell power generator according to claim 4, a temperature sensor is provided in each of the parallel pipelines, and the hot water is passed through the on-off valve or the flow control valve based on the measurement value of the temperature sensor. It shall be equipped with a control device that controls the flow rate.

[0033]

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. 3 are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1, the power generator 100 and FIG.
A hot water storage tank 60 not shown in FIG.
And a part of the power generator are connected by an antifreezing pipe 70, and the power generator 100 in FIG. 1 shows the system shown in FIG.
Detailed connection relationships in the system are omitted. Based on the above, the power generation device 100 includes the fuel cell body 10, the reforming system device 20, the recovered water system device 30, and the water treatment device 35.
And the cooling water system device 50 and other auxiliary devices 40.

In FIG. 1, the antifreezing pipe 70 draws hot water from the upper portion of the hot water storage tank 60, and the cooling water system equipment 5
0, the recovered water system device 30, and the pipe (74 provided near or in contact with at least a part of the water treatment device 35).
b, 74a, 73a) and then is returned to the lower part of the hot water storage tank 60. Further, the hot water discharged from the upper part of the hot water storage tank flows through the recovered water system device 30 and the cooling water system device 50 in series. The water treatment device 35 is configured to flow in parallel with the two devices. Further, on-off valves or flow rate control valves 76 and 75 are provided on the parallel piping lines 74 and 73, respectively.

Below the hot water storage tank 60, for example, an auxiliary heat source 6 such as an electric heater or a gas-fired burner that uses late-night power.
1 is provided so that heat is supplied when the hot water supply is insufficient. When using hot water supply, as described above, city water is supplied from the lower part of the hot water storage tank, and hot water in the upper part of the hot water storage tank is supplied by this city water pressure. Therefore, even if the water supplied to the portions 74b, 74a, 73a for preventing freezing flows back to the lower part of the hot water storage tank as described above, the hot water storage tank 6
The hot water in the upper space of 0 is retained without being affected by temperature, and it is possible to prevent the freezing reasonably. The hot water for freezing prevention is supplied by the pump 72, but the pump capacity may be extremely small because only a small flow rate flows through the antifreezing pipe. Further, when the auxiliary heat source 61 is operating, in the hot water storage tank 60,
Since the driving force of water based on the density gradient of water is generated, the power of the pump 72 is reduced accordingly.

Further, in FIG. 1, when the fuel cell is in operation, there is a possibility that only the water treatment device and its associated pipes may freeze, so that, for example, 73a in each of the parallel pipe paths 73 and 74. And 74a are provided with temperature sensors (not shown) at predetermined locations, respectively, and the flow rate of hot water for freezing prevention is not shown, which is controlled based on the measured value of the temperature sensor via the on-off valve or the flow control valve 75 or 76. Providing a control device enables proper antifreeze operation.

Next, the embodiment shown in FIG. 2 will be described. Figure 2
Is a systematic diagram mainly showing an embodiment relating to the invention of claim 3, and the members having the same functions as those in FIG. In the embodiment shown in FIG. 2, the anti-freezing pipe 70a is arranged from the middle portion of the hot water storage tank 60 to the part number 5 shown in FIG.
The hot water is drawn out by the pump 58 to the line indicated by 6a,
This warm water is branched from the line 56a to collect the recovered water system device 3
0 and the cooling water system device 50 in series, and the water treatment device 35 flows in parallel with the two devices, and then returns to the line 56a to further cool the battery cooling water in the cooling water system device 50. Cooler, cathode off-gas cooler, and exhaust gas cooler for combustion exhaust gas (part numbers 51, 5 in FIG. 3
2, 53) and is heated by the thermal energy of the fuel cell to be returned to the upper part of the hot water storage tank 60.

According to the embodiment of FIG. 2, as compared with the embodiment of FIG. 1, the pump 72 of FIG. 1 is not required, so that the apparatus can be simplified and the power can be reduced.

[0041]

As described above, according to the present invention, electric and thermal energy is generated based on an electrochemical reaction between a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel and air as an oxidant gas. Fuel cell main body, fuel reforming system equipment, fuel cell cooling water system equipment, recovered water system equipment that collects water in the exhaust air of the fuel cell and combustion exhaust gas of the fuel reformer, and purified purified water In a fuel cell power generator including a water treatment device for water and a hot water storage tank for storing a part of the thermal energy as hot water, hot water in the hot water storage tank is provided in order to prevent freezing of water in the devices and equipment. Is provided with an anti-freezing pipe that flows through at least a part of the cooling water system device, the recovered water system device, and the water treatment device, so that it is possible to accurately prevent the freezing of water in various circulation paths. Save energy consumption It is possible in reasonably performed.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a fuel cell power generator of the present invention.

FIG. 2 is a system diagram showing another embodiment of the fuel cell power generator of the present invention.

FIG. 3 is a system diagram showing an example of a conventional fuel cell power generator.

[Explanation of symbols]

10: fuel cell main body, 20: reforming system device, 30: recovered water system device, 35: water treatment device, 50: cooling water system device, 6
0: hot water storage tank, 70: antifreeze piping, 75, 76: open / close valve or flow control valve, 100: power generator.

Claims (5)

[Claims] 1. A fuel cell main body that generates electricity and thermal energy based on an electrochemical reaction between a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel and air as an oxidant gas, and a fuel reformer. Quality system equipment, cooling water system equipment for fuel cells, recovered water system equipment for recovering exhaust air of fuel cells and water in combustion exhaust gas of a fuel reformer, water treatment device for purifying recovered water, and the thermal energy In a fuel cell power generator including a hot water storage tank for storing a part of the above as hot water, in order to prevent water from freezing in the above-mentioned various devices and devices,
A fuel cell power generator comprising: a pipe for freezing, which allows hot water in the hot water storage tank to flow through at least a part of the cooling water system device, the recovery water system device, and the water treatment device. 2. The fuel cell power generator according to claim 1, wherein the antifreezing pipe draws hot water from the upper part of the hot water storage tank, and at least one of the cooling water system device, the recovered water system device, and the water treatment device. A fuel cell power generator characterized in that the fuel cell power generator is configured to flow back to the lower part of the hot water storage tank after flowing into the section. 3. The fuel cell power generator according to claim 1, wherein the antifreezing pipe draws hot water from the middle part of the hot water storage tank, and at least one of the cooling water system device, the recovered water system device, and the water treatment device. After passing through a part, it is passed through a battery cooling water cooler, a cathode off-gas cooler and a combustion exhaust gas exhaust gas cooler in the cooling water system device, heated by the thermal energy of the fuel cell and returned to the upper part of the hot water tank. A fuel cell power generator having the above structure. 4. The fuel cell power generator according to claim 1, wherein the antifreezing pipe allows hot water derived from the hot water storage tank to flow in series to the cooling water system device and the recovered water system device. The fuel cell power generator, wherein the water treatment device is configured to flow in parallel with the two devices, and each of the parallel pipelines is provided with an on-off valve or a flow control valve. 5. The fuel cell power generator according to claim 4, wherein each of the parallel pipes is provided with a temperature sensor, and the temperature sensor is used to transmit the temperature sensor through the on-off valve or the flow control valve. A fuel cell power generator comprising a controller for controlling the hot water flow rate.