JP3448568B2 - Exhaust heat recovery apparatus and method in fuel cell power supply system - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to reforming a raw fuel gas such as city gas into a hydrogen-rich gas and supplying the reformed gas and air to a fuel cell to generate an electromotive force by a chemical reaction. And a method for recovering exhaust heat in a fuel cell power supply system.

[0002]

2. Description of the Related Art There is a fuel cell power supply system developed for home use. For example, as shown in FIG. 3, a fuel cell power supply device A is installed adjacent to the outside to supply raw fuel gas such as city gas. To generate electric power, convert the direct current into the alternating current with the inverter B, and supply the electric power to indoor electric equipment. Since the fuel cell power supply device A discharges heat during power generation, the exhaust heat is used to generate hot water from city water to supply hot water around the indoor kitchen, washroom, bathroom, etc. ing. Therefore, the hot water storage tank C is connected to the fuel cell power supply device A.

City water is supplied to the bottom of the hot water storage tank C, and a part of the city water is sent to a plurality of heat exchangers arranged in the fuel cell power supply device A to obtain hot water. The water is returned to the upper part of the tank C to store hot water, and when hot water is supplied, hot water is taken out from the upper part to supply hot water to indoor water supply areas as described above.

As shown in FIG. 4, the heat exchange between the water in the hot water storage tank C and the heat exchanger in the fuel cell power supply device A is performed by the combustion exhaust gas passing through the burner 1a of the reformer 1 in the reformer as shown in FIG. No. 1 heat exchanger H1 and first circulation path R1
And the second heat exchanger H2 through which the combustion exhaust gas from the PG burner 2 passes, and the unreacted oxygen gas discharged from the air electrode of the fuel cell 3 passes through. Third circulation path R3 performed with the third heat exchanger H3
It depended on That is, in each of the first heat exchanger H1 to the third heat exchanger H3, heat is exchanged between the water sent from the hot water storage tank C and the combustion exhaust gas or the unreacted oxygen gas. is there.

[0005]

The city water layer at room temperature exists at the bottom of the hot water storage tank C, and the warmed and lightened water layer exists at the top, but when the water is not supplied, the city water at the bottom does not exist. Since the water is warmed by the heat exchanger and returned to the upper part, the warm water layer may gradually increase and eventually become a warm water layer. On the other hand, at the time of hot water supply, the hot water in the upper part is taken out, so that the hot water layer gradually decreases, and the city water is replenished in the bottom part according to the amount of hot water supplied, so that the city water layer increases. Therefore, the temperature of the water sent from the bottom of the hot water storage tank C to the heat exchanger is not always constant, and the heat exchange efficiency in the heat exchanger varies. Since the temperatures of the combustion exhaust gas or the unreacted oxygen gas passing through the three heat exchangers H1 to H3 are also different from each other, the heat exchange efficiency varies depending on the temperature difference of the water sent from the hot water storage tank C. If the temperature difference is small, the heat exchange efficiency will decrease.

The present invention has been made in view of such a conventional situation, and relates to a fuel cell power supply system capable of efficiently exchanging heat between a hot water storage tank and a plurality of heat exchangers of a fuel cell power supply device. The purpose is to provide a method for recovering exhaust heat.

[0007]

As means for achieving this object, a fuel cell power source according to claims 1 and 3 of the present invention.
Exhaust heat recovery apparatus and method in the system, a reformer for reforming a raw fuel gas into hydrogen-rich reformed gas is supplied from the reforming external and hydrogen gas in the reformed gas supplied from the device A fuel cell that generates an electromotive force by causing a chemical reaction with oxygen gas in the air and a hot water storage tank that stores hot water
When, a fuel cell power system comprising, a fuel collector
It is installed in the pond power supply system and exchanges heat with the water in the hot water storage tank.
At least unreacted acid discharged from the fuel cell
Between the heat exchanger with the raw gas and the cooling water supplied to the fuel cell
A plurality of heat exchangers including a heat exchanger, and a hot water storage tank and a plurality of heat exchangers are connected by pipes to form a loop-shaped pipe, and water in the hot water storage tank is formed through the pipes. JP to the hot water by passing in sequence against the heat exchanger
To collect.

Further , the fuel cell according to claims 2 and 4 of the present invention
An exhaust heat recovery device and method in a power supply system is claimed.
In the fuel cell power supply system of No. 1, the hot water storage tank and the
A heat exchanger for unreacted oxygen gas discharged from the fuel cell
A loop-shaped pipe line is formed by pipe connection with the heat exchanger containing
Along with this, a first switching valve is provided in this pipe,
Is branched from the upstream side of the switching valve of the
Under the first switching valve via a heat exchanger with cooling water
Form a branch path to the flow side and supply this branch path to the fuel cell.
A second switching bar is provided upstream of the heat exchanger with the supplied cooling water.
The temperature of the cooling water during fuel cell power generation
Is above a predetermined temperature, the first switching valve is closed.
Open the second switching valve and pass water through the branch passage to cool.
Heat is recovered from the wastewater and the temperature of the cooling water falls below the specified temperature.
If it does, open the first switching valve and switch to the second switching valve.
The valve is closed so that water is not supplied to the branch passage.
And In the present invention, the hot water storage tank and the plurality of heat exchangers are not separately connected to each other to form a plurality of circulation paths, but a series of loop-shaped pipelines including a plurality of heat exchangers are configured.
Since the can even if variations in the temperature of the water from the hot water storage tank enhances the thermal efficiency of the heat exchanger.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of an exhaust heat recovery method in a fuel cell power supply system according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing the configuration of the fuel cell power supply system, which includes the reformer and the fuel cell 3 as described above, and incorporates the PG burner 2, the water tank 4, the hot water storage tank C, and the like. The reformer is composed of a desulfurizer 5, a reformer 1, a CO shift converter 6, and a CO remover 7. The reformer 1 is provided with a burner 1a.

The first heat exchanger H1 through which the combustion exhaust gas from the burner 1a of the reformer 1 passes, the second heat exchanger H2 through which the combustion exhaust gas from the PG burner 2 passes, and the fuel cell 3
Through which unreacted oxygen gas discharged from the air electrode of
And the heat exchangers H3 and H3 of FIG.

The combustion exhaust gas or unreacted oxygen gas that has passed through the first heat exchanger H1 to the third heat exchanger H3 flows into the duct 8 and is discharged to the outside from the discharge hole of the fuel cell power supply device. However, at that time, it is discharged after passing through the fourth heat exchanger H4 provided in the duct 8.

The first heat exchanger H1 to the fourth heat exchanger H4
Is connected to the hot water storage tank C to form a loop-shaped conduit. That is, from the bottom of the hot water storage tank C to the pump P1
A first pipe S1 for sending water taken out via the fourth heat exchanger H4, and a second pipe S2 for sending water from the fourth heat exchanger H4 to the third heat exchanger H3; A third conduit from the third heat exchanger H3 to the first heat exchanger H1, a fourth conduit S4 from the first heat exchanger H1 to the second heat exchanger H2, It is composed of a second pipe S5 which is sent from the second heat exchanger H2 to the upper part of the hot water storage tank C.

Further, a sixth pipe S6 branched from the fifth pipe S5 and fed to the water tank 4 and a return pipe from the water tank 4 join the fifth pipe S5 to join the hot water storage tank C. A seventh conduit S7 for feeding to the upper part is provided, and a first switching valve V1 is provided in the fifth conduit S5 near the branch point, and a second switching valve V2 is provided in the sixth conduit S6. It is installed.

In the fuel cell power supply device configured as described above, the raw fuel gas such as city gas and the air taken in by the air fan F1 at the time of startup are burner 1a of the reformer 1.
Is supplied to. When the burner 1a is ignited, the raw fuel gas burns to raise the temperature of the catalyst filled in the reformer 1 to an appropriate temperature. The combustion exhaust gas from the burner 1a passes through the first heat exchanger H1 and flows into the duct 8 as described above.

When the temperature of the catalyst of the reformer 1 rises to a predetermined temperature, the raw fuel gas desulfurized by the desulfurizer 5 is supplied into the reformer 1 and, at that time, steam is supplied from the vaporizer 9 (heat exchanger). Is mixed in. As a result, steam reforming is performed and reformed gas containing hydrogen, carbon dioxide, and carbon monoxide is generated from the raw fuel gas. The combustion exhaust gas from the burner 1a passes through the vaporizer 9, and the water taken out by the pump P2 from the water tank 4 is sent to the vaporizer 9 to perform heat exchange between the water and the combustion exhaust gas. As a result, water vapor is generated.

The reformed gas steam-reformed by the reformer 1 is
The carbon monoxide sent to the CO shift converter 6 and contained in the reformed gas is transformed into carbon dioxide. Next, the transformed gas is sent to the CO remover 7, where it is selectively oxidized by oxygen in the air taken in by the air fan F2, and the concentration of carbon monoxide contained in the reformed gas is 1.
It is reduced to 0 ppm or less.

The reformed gas thus generated in the hydrogen-rich gas having a low CO concentration is not stable at the start-up stage, and therefore is not supplied to the fuel cell 3 and the PG burner 2 is used.
Send it to and burn it. The combustion exhaust gas from the PG burner 2 passes through the second heat exchanger H2 and flows into the duct 8 as described above.

When the reformed gas becomes stable, the supply to the PG burner 2 is cut off, and thereafter it is supplied to the fuel cell 3 to generate power. In this case, the fuel cell 3 is a solid polymer type, and the reformed gas is supplied to the fuel electrode. The hydrogen gas in the reformed gas supplied to the fuel electrode and the oxygen gas in the air supplied to the air electrode cause an electrochemical reaction through the solid polymer electrolyte membrane to generate electricity and water. It The air is supplied to the air electrode by temporarily feeding the air taken in by the air fan F4 into the water tank 4, moistening the air therein, and then supplying the air to the air electrode. This is for appropriately wetting the solid polymer electrolyte membrane, and if the wetting is insufficient, the power generation of the fuel cell 3 cannot be normally performed. In some cases, the reformed gas supplied to the fuel electrode may be moistened and supplied to appropriately moisten the solid polymer electrolyte membrane.

The unreacted oxygen gas that has not reacted at the air electrode of the fuel cell 3 passes through the third heat exchanger H3 and flows into the duct 8 as described above. On the other hand, the reformed gas that has not reacted at the fuel electrode of the fuel cell 3 is sent to the burner 1a of the reformer 1 or the PG burner 2 by the switching valve and burned.

The fuel cell 3 operates normally at about 80 ° C., but the temperature rises due to the heat generated by the electrochemical reaction. In order to prevent this temperature rise, the pump P from the water tank 4 is
By supplying water to the cooling portion of the fuel cell 3 by means of 3, cooling is performed. The water after cooling is returned to the water tank 4, but the amount of water in the water tank 4 gradually decreases, so it is appropriately replenished. This replenishment is performed from the auxiliary tank 11 in which city water is purified by the ion exchange resin 10 and the pure water is stored. Water (water in unreacted oxygen gas) generated in the third heat exchanger H3 is mixed in the auxiliary tank 11.

By the way, during operation of the fuel cell power supply,
In the hot water storage tank C, water at the bottom (normal temperature, for example, 20 ° C.) is taken out by the pump P1 and sent to the fourth heat exchanger H4 via the first pipe line S1. The exhaust gas passing through the fourth heat exchanger H4 is the combustion exhaust gas from the reformer burner 1a, which merges in the duct 8, the combustion exhaust gas from the PG burner 2, and the unreacted oxygen gas from the fuel cell 3. And are merged. The combustion exhaust gas from the reformer burner 1a is in the middle of the carburetor 9 and the first heat exchanger H1.
The temperature of the combustion exhaust gas from the PG burner 2 is lowered because it passes through the second heat exchanger H.
Since it has passed 2, the temperature is lowered. The unreacted oxygen gas from the fuel cell 3 is supplied to the third heat exchanger H.
The temperature is lowered because it has passed No. 3. Therefore,
The temperature level of the combined gas passing through the fourth heat exchanger H4 is low and is about 50 to 60 ° C.

The water warmed in the fourth heat exchanger H4 is sent to the third heat exchanger H3 via the second pipe line S2. In the third heat exchanger H3, heat is exchanged with the unreacted oxygen gas discharged from the air electrode of the fuel cell 3, and the temperature level there is about 70 to 80 ° C.

Next, the hot water is passed through the third pipeline S3 to the first hot water.
Of the first heat exchanger H1.
The heat is exchanged with the combustion exhaust gas passing through. This combustion exhaust gas is the combustion exhaust gas from the reformer burner 1a,
Since it has passed through the vaporizer 9 as described above, the temperature level is about 100 to 120 ° C.

Further, hot water is supplied from the first heat exchanger H1 to the fourth heat exchanger H1.
Is sent to the second heat exchanger H2 through the pipe line S4 of
Heat is exchanged with the combustion exhaust gas from the G burner 2. The temperature level in this second heat exchanger H2 is about 150-18.
It is 0 ° C. From this second heat exchanger H2 to the fifth conduit S
Hot water is supplied to the upper part of the hot water storage tank C via 5. At this time, the first switching valve V1 is opened and the second switching valve V2 is closed.

As described above, the PG burner 2 is burned when the reformed gas is not yet stable at the time of start-up, and is stopped after the reformed gas is stabilized. No heat exchange is performed in the heat exchanger H2. on the other hand,
The burner 1a of the reformer 1 continues to burn even during power generation of the fuel cell 3 in order to keep the catalyst filled in the reformer 1 at a predetermined temperature. The fuel supply necessary for that purpose is made by sending the unreacted reformed gas discharged from the fuel electrode of the fuel cell 3 to the burner 1a as described above.

In this way, the water at the bottom of the hot water storage tank C gradually passes through the heat exchanger having a low temperature level and then the heat exchanger having a high temperature level in order to become hot water of about 60 to 70 ° C. Returned to the top of Tank C. In this case, the temperature of the water is gradually raised and heat is exchanged in the heat exchanger at a temperature level corresponding to the temperature, so that the heat exchange efficiency in each heat exchanger can be increased.

FIG. 2 shows another embodiment of the exhaust heat recovery method according to the present invention, and is a block diagram showing only the main part of the configuration of the fuel cell power supply system in FIG.
In this case, from the hot water storage tank C to the fourth heat exchanger H4,
A loop-shaped pipe line is formed which returns to the hot water storage tank C through the third heat exchanger H3 and the first heat exchanger H1 in this order, and the first heat exchanger H1 and the hot water storage tank C in this pipe line are formed. A first switching valve V1 is provided between the two. Further, a branch path is formed from a middle portion between the first switching valve V1 and the first heat exchanger H1 to a hot water storage tank C through a water tank 4 that supplies cooling water to the fuel cell 3. A second switching valve V2 is provided upstream of the water tank 4 in this branch passage.

When the water temperature of the water tank 4 is equal to or higher than a predetermined temperature (for example, 80 ° C.) during the power generation of the fuel cell 3, the first switching valve V1 is closed and the second switching valve V2 is closed at the same time. Open. The water taken out from the bottom of the hot water storage tank C by the pump P1 is the fourth heat exchanger H4,
After passing through the third heat exchanger H3 and the first heat exchanger H1 in this order, and further passing through the water tank 4 via the branch passage, the water is returned to the hot water storage tank C. In this way, by circulating the water in the hot water storage tank C, the heat in the water tank 4 can be recovered.

The water temperature of the water tank 4 is a predetermined temperature (for example, 7
6 ° C.) or lower, the first switching valve V1 is opened and the second switching valve V2 is closed at the same time. As a result, the water taken out from the bottom of the hot water storage tank C by the pump P1 passes through the fourth heat exchanger H4, the third heat exchanger H3, and the first heat exchanger H1 in this order, and enters the hot water storage tank C. It is returned and is not supplied to the water tank 4 via the branch path. That is, when the temperature is 76 ° C. or lower, heat is not recovered from the water tank 4.

When the operation of the fuel cell power supply is stopped, the fuel cell 3 is cooled and the temperature of the water in the water tank 4 is lowered, so that the water tank 4 may be frozen in winter.
In such a case, hot water is sent into the water tank 4 at the time of startup. The hot water is supplied to the water tank 4 by the switching valve V
1 is closed and the switching valve V2 is opened to introduce hot water into the branch passage and send it into the water tank 4. After this,
The warm water is returned to the hot water storage tank C.

When the water in the water tank 4 rises to a certain temperature (for example, 76 ° C.) during the power generation of the fuel cell 3, the switching valve V2 is closed and the switching valve V1 is opened, and the water tank 4 is closed.
The supply of hot water to the hot water is stopped and the hot water is sent to the hot water storage tank C. When the water in the water tank 4 rises to a certain temperature (for example, 80 ° C.), the switching valve V2 is opened and the switching valve V2 is opened.
1 is closed and hot water is supplied to the water tank 4 to recover the heat in the water tank 4 and send the recovered heat to the upper part of the hot water storage tank C.

When the water in the water tank 4 is warmed, the air sent to the air electrode of the fuel cell 3 through the water tank 4 is warmed as described above, so that the fuel cell 3 is warmed in a short time and the operation start time is set. It can be hastened.

[0033]

As described above, according to the present invention, when the waste heat of the fuel cell power supply system is used to warm the water in the hot water storage tank, the water taken out from the bottom of the hot water storage tank is stored in the fuel cell power supply device. A plurality of heat exchangers are made to pass through a series of pipes formed in a loop, and from the heat exchangers with a low temperature level to the heat exchangers with a high temperature level gradually. The heat exchange efficiency in the vessel can be improved. Further, during power generation of the fuel cell, heat can be recovered from the water tank by operating the two switching valves depending on the water temperature of the water tank.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an exhaust heat recovery method in a fuel cell power supply system according to the present invention.

FIG. 2 is a block diagram of a main part of a heat recovery route showing another embodiment of the exhaust heat recovery method.

FIG. 3 is an explanatory view showing a usage state of a fuel cell power supply device and a hot water storage tank.

FIG. 4 is a block diagram showing an exhaust heat recovery method in a conventional fuel cell power supply system.

[Explanation of symbols]

1 ... reformer 1a ... Burner 2 ... PG burner 3 ... Fuel cell 4 ... Water tank 5 ... Desulfurizer 6 ... CO transformer 7 ... CO remover 8 ... Duct 9 ... Vaporizer 10 ... Ion exchange resin 11 ... Auxiliary tank C ... Hot water storage tank H1 ... First heat exchanger H2 ... Second heat exchanger H3 ... Third heat exchanger H4 ... Fourth heat exchanger S1 ... the first conduit S2 ... Second conduit S3 ... third conduit S4 ... Fourth conduit S5 ... 5th pipeline S6 ... Sixth pipeline S7 ... Seventh pipeline V1 ... First switching valve V2 ... Second switching valve

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Tajima 2-5-5 Keihan Hondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Satoshi Yamamoto 2--5 Keihanhondori, Moriguchi-shi, Osaka No. 5 In Sanyo Electric Co., Ltd. (72) Inventor Shoten Kadowaki 2-5-5 Keihan Hondori, Moriguchi City, Osaka Prefecture No. 5-5 Sanyo Electric Co., Ltd. (72) Osamu Tajima 2-5 Keihan Hondori, Moriguchi City, Osaka Prefecture Number 5 Sanyo Electric Co., Ltd. (72) Inventor Akira Fujio 2-5-5 Keihan Hondori, Moriguchi City, Osaka Prefecture 5-5 Sanyo Electric Co., Ltd. (72) Katsuya Oda 2-5 Keihan Main Street, Moriguchi City, Osaka Prefecture No. 5 In Sanyo Electric Co., Ltd. (72) Inventor Ryuji Hatayama 2-5-5 Keihan Hondori, Moriguchi City, Osaka Prefecture 5-5 Sanyo Denki Co., Ltd. (72) Inventor Taketoshi Koki 2 Keihan Hondori, Moriguchi City, Osaka Prefecture Ding No. 5-5 Sanyo Electric Co., Ltd. (72) Inventor Masatoshi Ueda 2-chome, Keihan Hondori, Moriguchi City, Osaka Prefecture 5-5 Sanyo Denki Co., Ltd. (72) Ryuji Yukawa, 2-chome Keihan Hondori, Moriguchi City, Osaka Prefecture No. 5-5 Sanyo Electric Co., Ltd. (56) Reference JP 2001-255010 (JP, A) JP 2002-25591 (JP, A) JP 2001-185167 (JP, A) JP 2002-170583 ( JP, A) JP 2001-23668 (JP, A) JP 2001-313053 (JP, A) JP 2001-185197 (JP, A) JP 2001-185196 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 8/00-8/24

Claims (4)

(57) [Claims] 1. A reforming apparatus for reforming a raw fuel gas into hydrogen-rich reformed gas, oxygen in the air supplied from outside and hydrogen gas in the reformed gas supplied from the reformer A fuel cell that produces an electromotive force by causing a chemical reaction with gas,
A fuel cell power supply system including a hot water storage tank for storing hot water, the hot water storage tank being provided in the fuel cell power supply system.
Heat exchange with water in the fuel cell, at least from the fuel cell
Heat exchanger for discharging unreacted oxygen gas and the fuel cell
Heat exchangers including heat exchangers with cooling water supplied to
When exhaust heat recovery apparatus of a fuel cell power system comprising: a, a conduit Le <br/>-loop shape with the connection between the hot water storage tank a plurality of heat exchangers tubes. 2. The fuel cell power supply system according to claim 1.
The unreacted acid discharged from the hot water storage tank and the fuel cell.
A loop connection with a heat exchanger including a heat exchanger for the raw gas
-Shaped pipe line, a first switching valve provided in the pipe line, and the fuel cell branched from the upstream side of the first switching valve.
The first switching via a heat exchanger with cooling water supplied to
Heat exchange between a branch passage leading to the downstream side of the valve and cooling water supplied to the fuel cell in the branch passage
Provided upstream of the container and switched with the first switching valve
And a second switching valve that
Exhaust heat recovery device for battery power system. 3. Reforming raw fuel gas into hydrogen-rich reformed gas
And a reformer supplied from the reformer.
Hydrogen gas in the gas and oxygen gas in the air supplied from the outside
A fuel cell that produces an electromotive force by causing a chemical reaction with
A fuel cell power supply system including a hot water storage tank for storing hot water
A hot water storage tank provided in the fuel cell power supply system.
Heat exchange with water in the fuel cell, at least from the fuel cell
Heat exchanger for discharging unreacted oxygen gas and the fuel cell
Heat exchangers including heat exchangers with cooling water supplied to
And a pipe connection between the hot water storage tank and the plurality of heat exchangers.
Forming a loop-shaped pipe, and through the pipe, the hot water storage tank
By passing the water in the passage through the heat exchanger in order
A fuel cell power supply system that features warm water
Exhaust heat recovery method. 4. The fuel cell power supply system according to claim 1, wherein unreacted acid discharged from the hot water storage tank and the fuel cell.
To form the rule <br/> looped conduit which connects the heat exchanger tubes containing a heat exchanger with a hydrogen gas, a first switching valve provided in said conduit, said first switching valve Branching from the upstream side of the fuel cell
The first switching via a heat exchanger with cooling water supplied to
Forming a branch path to the downstream side of the valve , and exchanging heat with the cooling water supplied to the fuel cell in the branch path.
A second switching valve is provided on the upstream side of the reactor, and when the temperature of the cooling water is equal to or higher than a predetermined temperature during fuel cell power generation, the first switching valve is closed and the second switching valve is opened to branch the branch. road to recover heat from the cooling water through the water, when said coolant temperature is equal to or less than a predetermined temperature, the water in the branch passage by closing the second switching valve is opened the first switching valve Exhaust heat recovery method in a fuel cell power supply system that does not supply heat.