JP2002100382A - Fuel cell power generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel power generator allowing for efficient utilization of an waste heat and prevention of smoke generation in an exhaust gas discharged from the water recovery system. SOLUTION: The generator comprises a fuel cell main body 1, a fuel reformer 7, a steam separator 21, a water recovery system 51 for cooling the discharged air from the fuel cell and a flue gas from the fuel reformer 7 and recovering air and water contained in the flue gas, and a heat transfer equipment 54 for recovering the heat received from the fuel cell out of a cooling water, and supplying the heat to the external waste heat utilization facility. The water recovery system 51 is provided with a heat exchanger 52 for heating the discharged air after water recovery and the flue gas. Further, the system 51 is provided with a cooling water circulation circuit 55, in which, after cooling the water recovered from the separator 21 by sending it to the heat transfer equipment 54 for cooling and further cooling it by sending to the exchanger 52, the cooled water and the drain water from the separator 21 are combined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generator, and more particularly, to a configuration of an exhaust heat recovery system and a water recovery system thereof.

[0002]

2. Description of the Related Art There are various types of fuel cells to be incorporated in a fuel cell power generator, depending on the type of electrolyte, the type of reforming material, and the like. For example, a gas containing carbon dioxide obtained by reforming natural gas is used. 2. Description of the Related Art A phosphoric acid fuel cell using a high-concentration aqueous solution of phosphoric acid as an electrolyte, which has an advantage that it can be used as it is without purification, is known.

[0003] This phosphoric acid type fuel cell converts hydrogen in fuel gas and oxygen in air obtained by steam reforming a hydrocarbon-based raw fuel such as methane gas into a fuel electrode and an air electrode of the fuel cell. To generate electricity based on the electrochemical reaction. In order to reform raw fuel into fuel gas, a fuel reforming apparatus is used in which water vapor is added to methane as raw fuel and the reaction between water and methane is promoted by a catalyst. Therefore,
It is necessary to supply water to the fuel reformer in accordance with the amount of steam used for reforming the fuel. As this water, ion-exchanged water from which impurities have been removed by an ion-exchange type water treatment device or the like is used.

A phosphoric acid type fuel cell incorporated in a fuel cell power generator generates heat during power generation, and therefore needs to be cooled. This cooling is performed by air cooling or water cooling. In a water-cooled fuel cell power generator, the operating temperature is maintained by cooling the fuel cell body by removing the heat with cooling water, and part of the heat obtained by this cooling is recovered by a heat exchanger. To the user.

FIG. 4 is an example of a basic system diagram focusing on an exhaust heat recovery system and a water recovery system of this type of conventional fuel cell power generator (see Japanese Patent Application Laid-Open No. 10-64566).

In FIG. 4, a fuel cell main body 1 is schematically shown, and a fuel electrode 2 and an air electrode 3 sandwiching a phosphoric acid electrolyte layer (not shown) are arranged, and each time a plurality of unit cells composed of these are stacked, they are arranged. And a cooling plate 5 having a cooling pipe 4 provided.

On the other hand, the fuel reformer 7 separates raw fuel such as natural gas supplied through a fuel supply system 8 together with steam separated by a steam separator 21 described later and supplied through a steam supply system 10. Under the reforming catalyst, the fuel gas is heated by combustion heat generated by the combustion of off-gas described later in a burner (not shown), and reformed into a hydrogen-rich gas to generate a reformed gas.

The fuel cell body 1 and the fuel reformer 7 include a reformed gas supply system 11 for supplying the reformed gas generated by the fuel reformer 7 to the fuel electrode 2 of the fuel cell body 1; The fuel electrode 2 is connected to an off-gas supply system 12 that supplies off-gas containing hydrogen that does not contribute to the cell reaction to the burner of the fuel reformer 7 as fuel.

Further, a blower 17 for supplying combustion air is connected to a burner of the fuel reformer 7.
Is discharged to the water recovery device 41 by the flue gas system 18.

The fuel cell body 1 has an air supply system 1 having a reaction air blower 13 for supplying air to the air electrode 3.
4 and an air discharge system 15 for supplying the air after the battery reaction to the water recovery device 41 are connected.

The cooling pipe 4 of the cooling plate 5 of the fuel cell body 1 circulates cooling water during power generation of the fuel cell body 1.
Steam separator 21, cooling water circulation pump 22, and steam generator (kettle type heat exchanger) 24 as cooling water cooler
Is connected.

The steam separator 21 separates the cooling water, which has become a two-phase flow with the steam discharged from the cooling pipe 4 of the fuel cell main body 1, into steam and cooling water. The steam separated here is sent out through the steam supply system 10 so as to be mixed with the raw fuel toward the fuel reformer 7.
At that time, an ejector pump 9 is used to mix with the raw fuel having a low original pressure. This ejector pump 9
Uses steam as a driving fluid and raw fuel as a driven fluid.

The steam generator (kettle type heat exchanger) 2
Reference numeral 4 denotes an external waste heat utilization facility that cools the fuel cell and removes heat from the returned cooling water, cools and recovers the recovered heat, that is, a part of the heat generated during power generation of the fuel cell as steam. To the user via. The recovered heat is used for cooling, heating and hot water supply, but excess heat is discarded to maintain the heat balance. When the heat medium is steam, the steam-cooked absorption chiller / heater can be operated, so that highly efficient heat utilization can be achieved.

The water recovery unit 41 is connected to a flue gas system 18, an air discharge system 15, and a process exhaust system 19. In addition, a recovery water circulation pump 42, a recovery water cooler 43, and a nozzle 44 are connected to the water recovery device 41. The recovery circulation pump 42 is connected to the bottom of the water recovery device 41,
A part of the recovered water stored at the bottom is recovered and sent to the recovered water cooler 43.

The recovered water cooler 43 includes a user-side cooling water system 4.
5 is inserted as a heat recovery system, and supplies cooled recovery water to the nozzle 44. The nozzle 44 sprays the cooling recovery water from the upper part of the water recovery device 41 and
The cooling water acts on the exhaust air containing the generated water and the combustion exhaust gas containing the generated water in the cooling water 1 to directly cool the recovered water in the air, and each generated water is separated into the water recovery device 41. At the bottom.

It should be noted that instead of the method of spraying water from the nozzles 44 as described above, water is recovered by cooling the user-side cooling water system 45 by directly contacting it with exhaust air and combustion exhaust gas. You can also.

The recovered water stored at the bottom of the water recovery device 41 as described above is supplied to the steam separator 21 via a recovery system provided with a supply pump 46 and a water treatment device 47.

As described above, the user-side cooling water 45 is connected to the recovered-water cooler 43 to cool the recovered water. , 40 ° C. or lower, and therefore, its value as thermal energy is low. Usually, the waste gas is discharged to the outside air by a cooling tower or a radiator for treatment.

In FIG. 4, reference numeral 26 denotes the cooling water circulation system 20 and the cooling pipe 4 and the flow path of the cooling water cooler 24.
This is a bypass pipe that short-circuits the flow path between the steam generator 24 and the steam separator 21, and reference numeral 27 is a three-way control valve for that purpose. Reference numeral 28 denotes the steam separator 21
It is a pressure gauge that measures the internal pressure.

As a conventional fuel cell power generator different from FIG. 4, there is also known a power generator having a configuration shown in FIG. 5 in which a steam-cooked absorption chiller / heater is directly connected to a cooling system of a fuel cell (JP-A-Hei. No. 9-14786).

In the system diagram of FIG. 5, devices having the same functions as the devices shown in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. Note that FIG. 5 omits the fuel reformer 7, the water recovery device 41, and their peripheral devices and piping systems shown in FIG.

In FIG. 5, the battery cooling water systems 20a, 20a
Reference numeral 0b denotes a piping configuration for connecting the steam separator 21, the fuel cell main body 1, the absorption type water heater / heater 40, and the heat exchanger 50 for heat radiation. The heat generated by the fuel cell body 1 is absorbed
After being effectively used at 0, the excess heat is removed in the heat-radiating heat exchanger 50, and the temperature or pressure of the steam separator 21 is kept constant.

The temperature of the steam separator 21 is controlled by controlling the flow controllers 60 and 80. 110
Is a temperature or pressure detector, 70 is a flow regulator 60
And controls the flow rate of the fuel cell cooling water introduced from the fuel cell main body 1 to the absorption type water heater / water heater 40 based on the detection result of the detector 110.

[0024]

The above-mentioned conventional fuel cell power generator has the following problems.

In the conventional apparatus, since the exhaust air and the combustion exhaust gas discharged from the fuel cell main body and the fuel reformer are cooled to recover water contained in the exhaust gas, the water is discharged from the water recovery apparatus. The exhaust gas is in a water-saturated state. When the exhaust gas in the water-saturated state is cooled by the outside air, the water vapor in the exhaust gas turns into white smoke. This white smoke is regarded as a problem depending on the installation location of the fuel cell power generator.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to effectively use the exhaust heat of a fuel cell and to convert the exhaust gas discharged from a water recovery device into white smoke. It is an object of the present invention to provide a fuel cell power generation device which prevents the occurrence of a fuel cell.

[0027]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a fuel cell body having a cooling plate through which battery cooling water flows, and a hydrogen reforming reaction between hydrocarbon and steam. A fuel reformer for generating a rich reformed gas, a steam separator for separating cooling water discharged from the cooling plate into steam and water, and a waste gas discharged from the fuel cell body and the fuel reformer. A water recovery device that cools air and flue gas to recover the water contained in the air and flue gas, and waste heat that recovers the heat of the cooling water received from the fuel cell and supplies it to external waste heat utilization equipment A fuel cell power generation apparatus provided with a utilization heat exchange device, wherein the water recovery device has an exhaust gas heating heat exchanger for heating exhaust water and combustion exhaust gas collected with water, and the water vapor separator Cooling water derived from After flowing through the exhaust heat utilizing heat exchanger and cooling, the cooling water flows through the exhaust gas heating heat exchanger for further cooling, and the cooled water is combined with water derived from the steam separator. A water circulation circuit is provided (the invention of claim 1).

According to the first aspect of the present invention, the cooling water derived from the steam separator flows through the waste heat utilizing heat exchange device to effectively use the waste heat, and thereafter, the cooling water is supplied to the water collecting device. By heating the exhaust gas discharged from the water recovery device through the heat exchanger for exhaust gas heating provided in the exhaust gas by the excess heat of the cooling water, it is possible to prevent the exhaust gas from becoming white smoke.

Further, as an embodiment of the first aspect of the invention, the following second to fourth aspects of the invention are preferable. That is, in the fuel cell power generator according to claim 1, the steam separator includes a pressure gauge, and the cooling water circulation circuit controls the pressure in the steam separator to be constant based on a measurement value of the pressure gauge. A flow control valve is provided (the invention of claim 2). Thus, the supply of steam to the fuel reformer can be stably performed, and the excess heat can be effectively used as described above.

Further, in the fuel cell power generator according to claim 2, the waste heat utilization facility includes a thermometer, and the cooling water circulation circuit uses the waste heat utilization facility water based on a measurement value of the thermometer. And a second flow control valve for controlling the temperature of the fuel cell to be constant (the invention of claim 3). Thus, heat can be supplied to the waste heat utilization equipment in accordance with the use situation, and the excess heat can be effectively used to prevent white smoke as described above.

Further, in the fuel cell power generator according to claim 2, the waste heat utilization equipment includes a thermometer,
Further, instead of the cooling water circulation circuit, cooling water derived from the steam separator flows through the exhaust heat utilizing heat exchange device and the exhaust gas heating heat exchanger to be cooled, and the cooled water is cooled. There is no cooling water circulation circuit that merges with the cooling water derived from the steam separator, and between the steam separator and the waste heat utilizing heat exchange device in the cooling water circulation circuit, the measured values of the pressure gauge and the thermometer are used. A flow control valve A for controlling the pressure in the steam separator constant and for controlling the temperature of the water used in the exhaust heat utilization equipment based on the flow rate, and heating the steam separator and the exhaust gas in the cooling water circulation circuit. A flow control valve B for controlling the pressure in the steam separator to be constant based on the measurement value of the pressure gauge is provided between the heat exchanger and the heat exchanger (the invention of claim 4).

[0032] Thereby, heat can be supplied to the waste heat utilization equipment in accordance with the use situation, and
The surplus heat can be effectively used to prevent white smoke as described above. Furthermore, since the flow control of the cooling water to the heat exchanger for exhaust gas heating and the flow control to the heat exchanger utilizing waste heat are separate systems, the heat exchange for exhaust gas heating should be performed in summer when white smoke is relatively low. The amount of heat in the heater, that is, the amount of waste heat used by the fuel cell is reduced, and the amount of heat used in the waste heat utilization equipment can be increased accordingly.

[0033]

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

FIGS. 1 to 3 show an embodiment of the present invention. The same functional members as those in FIG. 4 are denoted by the same reference numerals and description thereof will be omitted. Further, in FIG. 1, the water treatment apparatus 47 in FIG. 4 and its peripheral devices and piping system and other parts are omitted. 2 and 3, a part is further omitted from FIG.

First, the embodiment of FIG. 1 will be described. The basic differences between FIG. 1 and FIG. 4 are the water recovery device 52, the exhaust heat utilizing heat exchange device 54, and the peripheral equipment and piping system in FIG. In FIG. 1, the water recovery device 52 includes an exhaust gas heating heat exchanger 52 for heating the exhaust air and the combustion exhaust gas whose water has been recovered, above an exhaust gas cooler 53 for water recovery. Further, the cooling water derived from the steam separator 21 flows through the exhaust heat utilizing heat exchange device 54 to be cooled, and then flows through the exhaust gas heating heat exchanger 52 for further cooling. , A cooling water circulation circuit 55 that merges with water derived from the steam separator 21.

The steam separator 21 has a pressure gauge 32, and the cooling water circulation circuit 55 has a flow rate control valve 33 for controlling the pressure in the steam separator 21 to be constant based on the value measured by the pressure gauge 32. . Reference numeral 30 denotes a battery cooling water circulation pump, and reference numeral 31 denotes a makeup water pump.

In the above configuration, a part of the battery cooling water is branched, flows through the exhaust heat utilizing heat exchange device 54 to be cooled, and then flows through the exhaust gas heating heat exchanger 52 for further cooling. In addition, the amount of heat generated and the amount of heat removed in the fuel cell can be balanced. By the way, FIG.
The temperature of each part shown by 1 to T10 is exemplified as follows. At the following temperatures, numerical values shown in parentheses are representative temperatures.

T1: 160 to 170 ° C. (160 ° C.), T2: 140 to 170 ° C. (145 ° C.) T3: 85 to 95 ° C. (95 ° C.), T4: 50 to 90 ° C. (60 ° C.) T5: 70 to 85 ° C (85 ° C), T6: 80 to 95 ° C (90 ° C) T7: 30 to 40 ° C (40 ° C), T8: 40 to 60 ° C (50 ° C) T9: 40 to 45 ° C (45 ° C), T10: 45 to 55 ° C. (50 ° C.) As described above, the temperature T9 of the exhaust gas cooled and recovered in the water recovery device 51 is 40 to 45 ° C., and the exhaust gas is supplied to the exhaust gas heating heat exchanger 52. And the temperature T10 is increased by 45-55.
By setting the temperature to ° C., even if the water vapor in the exhaust gas is exposed to the outside air, the white smoke of the water vapor is not immediately generated, and the white smoke of the exhaust gas can be prevented.

Next, the embodiment shown in FIG. 2 will be described. The difference between FIG. 1 and FIG. 2 is that in FIG.
Is provided with a thermometer 35, and the cooling water circulation circuit 55 is provided with a second flow control valve 34 for controlling the temperature of the water used in the exhaust heat utilization facility 54 based on the measurement value of the thermometer 35. is there. Thereby, heat can be output in accordance with the heat utilization state of the exhaust heat utilization facility. In addition, the excess heat is consumed by the exhaust gas heating heat exchanger 52, so that the exhaust gas can be prevented from becoming white smoke.

Next, the embodiment shown in FIG. 3 will be described. In FIG. 3, the cooling water derived from the steam separator 21 is used as a heat exchanger utilizing waste heat 54 and a heat exchanger 52 for heating exhaust gas.
To form a cooling water circulating circuit in which the cooled water is combined with the cooling water derived from the steam separating device 21.
1 and the waste heat utilization heat exchange device 54, the pressure in the steam separator 21 is controlled to be constant based on the measurement values of the pressure gauge 32 and the thermometer 35, and the temperature of the water used in the waste heat utilization facility Is provided between the steam separator 21 and the exhaust gas heating heat exchanger 52 in the cooling water circulation circuit based on the measurement value of the pressure gauge 32. The difference from FIG. 1 is that a flow control valve B of a part number 37 for controlling the pressure in the steam separator 21 to be constant is provided.

In the embodiment shown in FIGS. 1 and 2, the cooling water discharged from the steam separator 21 is
4 and the exhaust gas heating heat exchanger 52 in series, whereas in FIG. 3, the water passage circuits are parallel and the exhaust heat utilization and exhaust gas heating can be individually controlled. So
Efficient use of exhaust heat is possible. For example, as mentioned above,
In summer, when the generation of white smoke is relatively small, the amount of heat in the exhaust gas heating heat exchanger, that is, the amount of waste heat used by the fuel cell is reduced, and the amount of heat used in the waste heat utilization equipment can be increased accordingly. Further, in the waste heat utilization equipment, when heat is not required, the exhaust gas can be sufficiently heated to reliably prevent the emission of white smoke.

[0042]

As described above, according to the present invention, a fuel cell main body provided with a cooling plate through which battery cooling water flows, and a hydrogen-rich reformed gas is produced by a reforming reaction between hydrocarbons and steam. A fuel reformer, a steam separator for separating cooling water discharged from the cooling plate into water vapor and water, and cooling exhaust air and combustion exhaust gas discharged from the fuel cell body and the fuel reformer. A water recovery device for recovering air and water contained in the combustion exhaust gas, and an exhaust heat utilization heat exchange device for recovering the heat of the cooling water received from the fuel cell and supplying it to external waste heat utilization equipment. In the fuel cell power generation device, the water recovery device shall have an exhaust gas heating heat exchanger for heating exhaust water and combustion exhaust gas whose water has been recovered, and cooling water derived from the steam separator.
After cooling by flowing through the heat exchanger utilizing waste heat, the cooling water circulates through the heat exchanger for exhaust gas heating to further cool, and combines the cooled water with water derived from the steam separator. Since the circuit is provided, it is possible to effectively use the exhaust heat of the fuel cell and to prevent the exhaust gas discharged from the water recovery device from becoming white smoke.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing an embodiment of a different fuel cell power generator according to the present invention.

FIG. 3 is a diagram showing another embodiment of the fuel cell power generator according to the present invention.

FIG. 4 is a diagram showing a schematic system configuration of a conventional fuel cell power generator.

FIG. 5 is a diagram showing a schematic system configuration of a conventional fuel cell power generator different from FIG. 4;

[Explanation of symbols]

1: Fuel cell body, 7: Fuel reformer, 21: Steam separator, 32: Pressure gauge, 33: Flow control valve, 34: Second flow control valve, 35: Thermometer, 36: Flow control valve A , 37:
Flow control valve B, 51: water recovery device, 52: heat exchanger for exhaust gas heating, 54: heat exchange device using waste heat, 55: cooling water circulation circuit.

Claims (4)

[Claims] 1. A fuel cell body having a cooling plate through which battery cooling water flows, a fuel reformer for generating a hydrogen-rich reformed gas by a reforming reaction between hydrocarbons and steam, and the cooling plate A steam separator for separating the cooling water discharged from the fuel cell into water vapor and water; and cooling the discharged air and the combustion exhaust gas discharged from the fuel cell body and the fuel reformer to remove water contained in the air and the combustion exhaust gas. A fuel cell power generator comprising: a water recovery device for recovering water; and a waste heat utilizing heat exchange device for recovering heat of the cooling water received from the fuel cell and supplying heat to an external waste heat utilizing facility. The apparatus has an exhaust gas heating heat exchanger for heating the exhaust gas and the combustion exhaust gas collected with water, and the cooling water derived from the steam separator flows through the exhaust heat utilizing heat exchange apparatus. After cooling, the exhaust A fuel cell power generator, comprising: a cooling water circulation circuit that flows through a heat exchanger for gas heating to further cool the water, and merges the cooled water with water derived from the steam separator. 2. The fuel cell power generator according to claim 1, wherein the steam separator includes a pressure gauge, and the cooling water circulation circuit keeps the pressure in the steam separator constant based on a measurement value of the pressure gauge. A fuel cell power generator comprising a flow control valve for controlling. 3. The fuel cell power generator according to claim 2, wherein the waste heat utilization equipment includes a thermometer, and the cooling water circulation circuit uses the waste heat utilization equipment water based on a measurement value of the thermometer. A fuel cell power generator comprising a second flow control valve for controlling the temperature to be constant. 4. The fuel cell power generator according to claim 2, wherein the waste heat utilization equipment includes a thermometer, and further comprises, instead of the cooling water circulation circuit, cooling water derived from the steam separator. There is no cooling water circulation circuit that flows through the use heat exchange device and the exhaust gas heating heat exchanger and cools, and the cooled water is combined with the cooling water derived from the steam separator. Between the steam separator and the waste heat utilization heat exchange device, the pressure in the steam separator is controlled to be constant based on the measurement values of the pressure gauge and the thermometer, and the water used in the waste heat utilization facility is used. A flow control valve A for controlling the temperature to be constant is provided, and between the steam separator and the exhaust gas heating heat exchanger in the cooling water circulation circuit, the inside of the steam separator is measured based on the measurement value of the pressure gauge. Constant pressure A fuel cell power generator, comprising a flow control valve B to be controlled.