JPH06103996A - Fuel cell power generating exhaust heat recovery system - Google Patents

Abstract

PURPOSE:To increase exhaust heat recovery efficiency and to miniaturise an exhaust heat recovery device by removing exhaust heat from a fuel cell power generating system as warm water and by removing excessive heat in a cell cooling water system as high-temp. steam. CONSTITUTION:Cold water such as city water is supplied to an integral type exhaust gas treatment device 9 at its low temp. side through a secondary cooling water system circulating pump 14 from a water supplying line 18. Heat exchange to the cold water and a high-temp. exhaust gas at the heat exchange part in the device 9 turns the cold water into high-temp. warm water. The warm water is supplied to a steam generator 3 at its secondary side as well as a warm water exhaust heat utilizing device 12. The warm water is additionally heated by excessive heat in a cell cooling water system and is supplied to a steam exhaust heat utilizing device 11. Meanwhile. the integral type exhaust gas treatment device 9 is provided with a function for condensing and recovering grown water vapor vaporized from an electrolyte in a fuel cell main body 1 and contained in the exhaust gas. The condensed and recovered water recovered by the device 9 is returned to a water treatment device 9 through condensation and recovery line 19 for subsequent use as a cell cooling water system.

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 generation system, and more particularly to a steam and hot water supply system using exhaust heat, condensed water recovery from exhaust gas and simplification of systems related thereto, The present invention relates to a miniaturized fuel cell power generation exhaust heat recovery system.

[0002]

2. Description of the Related Art As is well known, a fuel cell power generation system converts chemical energy of fuel such as city gas or propane gas into electric energy. A device for generating hydrogen, a converter for converting direct current generated by the fuel cell body into an alternating current, and a heat exchanger for maintaining the temperature of the working gas at a temperature suitable for operation of the fuel cell body and hydrogen generation Etc. The fuel cell main body directly converts the binding energy between hydrogen gas generated by hydrogen generation and oxygen in the air into electric energy, but at the same time, heat is also generated.

As described above, the fuel cell power generation system is evaluated as a clean power generation system having high power generation efficiency, low emission of air pollutants, and low noise due to power generation by a chemical reaction.

By the way, in order to efficiently carry out the electrochemical reaction of the fuel cell body, it is necessary to keep the temperature of the cell body at a constant temperature level. There is. Therefore, the cooling water system of the fuel cell power generation system is composed of a steam separator, a pump, a heat exchanger, etc., and exhaust heat taken out from the heat exchanger is used for various purposes. This exhaust heat is generally taken out as hot water, but in recent years, there has been a strong demand for taking out steam in order to expand the range of uses of the exhaust heat.

FIG. 4 is a characteristic diagram showing the relationship between the general power generation load and the total thermal efficiency of a fuel cell power generation system. As can be seen from this characteristic diagram, the power generation efficiency for the power generation load is
Although it is 40%, the total thermal efficiency will be 80% or more when all of the low temperature exhaust heat recovery component at the hot water level and the high temperature exhaust heat recovery component at the steam level are used. As described above, the fuel cell power generation system can effectively use not only power generation but also exhaust heat outside the system, and high-temperature waste heat of vapor level out of the exhaust heat, especially superheated steam of dry saturated steam or higher is high. As grade steam, it has a high utility value as a drive source for absorption chillers and a drive source for steam turbines.

FIG. 5 shows a steam generator for heating the water of the secondary steam generating system separated from the battery cooling water system to generate steam from the excess heat of the battery cooling water incorporating the exhaust heat utilization system. 2 shows an example of the configuration of a fuel cell power generation system. Proposals have already been made regarding a method of supplying steam generated from a steam generator in this fuel cell power generation system to an exhaust heat utilization device and a method of coping with diversification of exhaust heat utilization using this steam generator ( Japanese Patent Application No. 3-325738, Japanese Patent Application No. 3-325739, Japanese Patent Application No. 4-3014).

As shown in the figure, the fuel electrode 1a and the air electrode 1
The reaction heat generated in the fuel cell body 1 including the b and the cell cooler 1c is taken out by exchanging heat with the cell cooling water in the cell cooler 1c. This battery cooling water is introduced into the steam separator 2 as a gas-liquid two-phase flow. In the steam / water separator 2, the steam 2a of the gas-liquid two-phase flow is separated and liquefied to form the battery cooling water 2b, and further to the downstream of the steam / water separator 2, the excess heat of the battery cooling water 2b is removed from the battery cooling water system. The battery cooling water 2 whose temperature is lowered by providing the steam generator 3 for heating the separated water of the secondary steam generation system to generate steam
b is a battery cooling water circulation pump 4, a heat exchanger 5 for adjusting the temperature of the battery cooling water system, and an electric heater 6 for heating the battery cooling water.
To form a battery cooling water system that leads to the battery cooler 1c.

On the other hand, the steam 2a separated by the steam separator 2a
Is supplied to the fuel reforming steam superheater 21 and becomes superheated steam heated by the fuel reforming steam superheater 21. This superheated steam is mixed with fuel at a certain ratio and passes through the catalyst layer in the fuel reformer 7, and during this period, the endothermic reaction is heated by the burner fuel gas in the fuel reformer 7 to become hydrogen-rich gas. Further, the burner flue gas that has been burnt in the fuel reformer 7 is discharged from the fuel reformer 7 and then exchanges heat with air as a heating source of the burner air preheated air 8 of the fuel reformer 7. In the subsequent flow, it merges with the exhaust air from the fuel cell body 1 and flows into the integrated exhaust gas treatment device 9. The integrated exhaust gas treatment device 9 has a phosphoric acid removing function of removing and recovering phosphoric acid from exhaust gas containing a phosphoric acid solution which is diffused from the electrolyte of the fuel cell main body 1 and discharged together with the generated steam, and is included in the exhaust gas. It has a condensate water recovery function for condensing and recovering the generated water vapor, and proposals for its function and configuration have already been made (Japanese Patent Application No. 4-203650).

By the way, in the conventional fuel cell power generation system, in order to collectively recover the exhaust heat from the cell cooling water system of the fuel cell power generation system, as shown in FIG. On the low temperature side of the processing device 9 and the heat exchanger 5 for adjusting the temperature of the battery cooling water system, a secondary cooling water system which is a loop different from the battery cooling water system is formed to recover exhaust heat, and the exhaust heat recovered by this secondary cooling water system Is supplied to the hot water exhaust heat utilization device 12 etc. to lower the temperature of the secondary cooling water system in the hot water exhaust heat recovery heat exchanger 13, and the secondary cooling water system cooler 15 further releases excess heat to the outside air. The secondary cooling water circulation pump 14 is used for circulation.

In the figure, 3a is secondary generated steam, 3b is high temperature water, 3c is a steam generator blow line, 3d is a steam generator feed line, 3e is a steam supply line, 16 is a water treatment device, and 17 is steam. Generator make-up water pump, 18 make-up water supply line, 19 condensation recovery line, 20 blowdown water line,
24 is a steam generator bypass line, 25 is a steam generator inlet control valve, and 26 is a steam generator bypass control valve.

[0011]

However, in a fuel cell power generation system incorporating such a conventional exhaust heat utilization device, a device relating to exhaust heat recovery from the fuel cell power generation system, particularly the steam generator 3, integrated type The heat exchangers such as the exhaust gas treatment device 9 are individually dispersed, the fuel cell power generation device incorporating the exhaust heat utilization device becomes large, which leads to an increase in cost, and the piping route becomes long, and the exhaust gas recovered from the system is exhausted. There is a problem that the exhaust heat recovery efficiency decreases due to an increase in the amount of heat released to the outside of the system.

Further, the refrigerant flowing to the low temperature side of the integrated exhaust gas treatment device 9 and the heat exchanger 5 for adjusting the temperature of the battery cooling water system is the secondary cooling water system, and a circulation loop separate from the exhaust heat recovery system is formed. Since the surplus heat recovered in the secondary cooling water system is further transferred to the exhaust heat recovery system, for example, the recovery efficiency of high-temperature exhaust heat at the steam level of the exhaust heat is reduced, or the total exhaust heat from the system is reduced. There are problems such as a decrease in collection efficiency.

In addition, not only high temperature water is always required as a form of extracting high temperature exhaust heat from the surplus heat of the fuel cell power generation system, but also high temperature steam, particularly high quality exhaust heat, is used as superheated steam above dry saturated steam. Taking out is highly useful as a drive source for an absorption chiller, a drive source for a steam turbine, etc., but in the conventional system, it is not possible to take out these high-temperature water and high-temperature superheated steam at the same time, so that the exhaust heat cannot be used. It is difficult to cope with diversification and to take out waste heat as high-quality waste heat.

Therefore, an object of the present invention is to deal with diversification of exhaust heat utilization, and to configure an exhaust heat recovery system from a fuel cell power generation system so as to enhance exhaust heat recovery efficiency, and to be involved in exhaust heat recovery. The equipment, especially the steam generator and the heat exchangers of the integrated exhaust gas treatment equipment are improved in performance, the volume of these exhaust heat recovery equipment is made smaller, and the cost is reduced to cope with the diversification of exhaust heat utilization. An object of the present invention is to provide a fuel cell power generation exhaust heat recovery system capable of performing the above.

[0015]

In order to achieve the above object, the present invention provides a fuel cell main body having a fuel electrode, an air electrode and a cooler, and a hydrogen gas produced by reforming the fuel. A fuel reformer that supplies the fuel electrode of the cell body, a steam separator that separates the two-phase flow-cooled cell cooling water that is heated by the reaction heat of the fuel cell into a gas phase and a water phase, and this gas-water separation Cell cooling water system that circulates the cell cooling water separated by the reactor through the cooler of the fuel cell main body, and in the form separated from the cell cooling water by the excess heat of the cell cooling water system on the downstream side of the water phase outlet of the steam separator. Phosphoric acid that removes and recovers phosphoric acid from exhaust gas containing phosphoric acid solution that diffuses from the electrolyte of the steam generator and fuel cell body that supplies steam to the secondary steam generation system of the steam exhaust heat utilization device and that is discharged with the generated steam Removal function and generated water vapor contained in exhaust gas In a fuel cell power generation system that is configured with an integrated exhaust gas treatment device that has a condensed water recovery function that condenses and recovers The hot water is supplied to the exhaust heat utilization device and the like, and the hot water is supplied to the secondary side of the steam generator.

On the other hand, a steam superheater for converting the saturated secondary steam generated on the low temperature side of the steam generator into the superheated steam which is further dried by the thermal energy of the exhaust gas and is equal to or higher than the saturated steam is installed downstream of the steam generator. As a result, the superheated steam that is dry and saturated steam or more is separated from the fuel cell cooling water system in the form of being separated from the fuel cell cooling water system in the secondary steam generation system of the steam exhaust heat utilization device. The secondary steam generation system can be supplied to the fuel reformer system of the fuel reformer, or the superheated steam of dry saturated steam or more can be supplied.

[0017]

By supplying cold water to the low temperature side of the integrated exhaust gas treatment equipment, the function of collecting coagulated water for condensing and recovering the generated water vapor contained in the exhaust gas can be improved, and the volume of the integrated exhaust gas treatment equipment itself can be increased. Can be miniaturized. This uses a secondary cooling water system as the refrigerant flowing to the low temperature side of the conventional integrated exhaust gas treatment device, and the exhaust heat recovery system forms a separate exhaust heat recovery circulation loop from this secondary cooling water system through the exhaust heat recovery heat exchanger. This is because, as compared with the case where it is performed, lower temperature cold water such as city water can be supplied to the low temperature side of the integrated exhaust gas treatment device. Also, by supplying this exhaust heat recovery hot water obtained on the low temperature side of the integrated exhaust gas treatment device to the secondary side of the steam generator, the evaporation performance of the steam generator can be improved, and the volume of the steam generator can be increased. Can be downsized, the plant equipment can be downsized as compared with the conventional one, and it is economically advantageous.

Further, the steam generator is installed in the downstream of the secondary side of the integrated exhaust gas treatment device, and hot water heated from cold water on the low temperature side of the integrated exhaust gas treatment device is supplied to the hot water exhaust heat utilization device or the like. Not only this, this hot water is also supplied to the secondary side of the steam generator, so that the hot water heated on the secondary side of the integrated exhaust gas treatment device is further heated by the excess heat of the battery cooling water system. However, steam can be generated separately from the battery cooling water system, and the efficiency of steam generation can be improved.

On the other hand, by installing a steam superheater for making superheated steam of dry saturated steam or more into the downstream of the steam generator of the secondary steam generation system, the steam exhaust heat is separated from the fuel cell cooling water system. It is possible to supply superheated steam above dry saturated steam to the secondary steam generation system of the utilization device, and to provide an exhaust heat recovery device from the fuel cell power generation system including the integrated exhaust gas treatment device, steam generator and steam superheater. It is possible to integrate them together, improve the simultaneous exhaust heat recovery performance of hot water and steam from the plant, and reduce the volume of the exhaust heat recovery device. It can be installed externally, and the integrated exhaust heat recovery device can be easily designed according to the exhaust heat utilization form of each plant.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same parts as those in FIG. 5 will be assigned the same reference numerals and overlapping description will be omitted. FIG. 1 is a configuration diagram of a fuel cell power generation exhaust heat recovery system according to an embodiment of the present invention (hereinafter referred to as a first embodiment). The first embodiment has a system configuration in which cold water such as city water is supplied to the low temperature side of the integrated exhaust gas treatment device, and the cold water is turned into hot water by the heat energy of the exhaust gas and is supplied to the hot water exhaust heat utilization device and the like. .

The system of the first embodiment differs from the system of the conventional fuel cell power generation exhaust heat recovery system shown in FIG. 4 in that the conventional system has an integrated exhaust gas treatment device 9 and a battery cooling water system temperature adjustment. The coolant that flows to the low temperature side of the heat exchanger 5 is a secondary cooling water system, and a circulation loop that is separate from the exhaust heat recovery system is formed. The refrigerant flows to the secondary side (low temperature side) of these heat exchangers. The refrigerant is used as an exhaust heat recovery system that directly supplies the exhaust heat to the exhaust heat utilization device, and the same exhaust heat recovery system is provided on the downstream side of the water phase outlet of the steam separator 2 by the excess heat of the battery cooling water system. By adding a steam generator 3 for supplying steam to the secondary steam generation system of the steam exhaust heat utilization device 11 in a form separated from the fuel cell cooling water system, steam exhaust heat and hot water exhaust heat can be extracted from the same exhaust heat recovery system. Both types of exhaust heat recovery are possible, and equipment related to the exhaust heat recovery system is installed. It makes it possible to integrate Te, aims to improve the exhaust heat recovery efficiency from the plant, a point which attained the size of the exhaust heat recovery system.

In the figure, first, cold water such as city water is introduced from the makeup water supply line 18 through the secondary cooling water system circulation pump 14 from the low temperature side inlet nozzle of the integrated exhaust gas treatment device 9, and this integrated type High-temperature water is produced by exchanging heat with high-temperature exhaust gas in the heat exchange section inside the exhaust gas treatment device 9,
It is made to flow out from the low temperature side exit nozzle of the integrated exhaust gas treatment device 9.

The integrated exhaust gas treatment device 9 has a phosphoric acid removing function for removing and recovering phosphoric acid from exhaust gas containing a phosphoric acid solution which is diffused from the electrolyte of the fuel cell body 1 and is discharged together with the generated steam. It has a condensed water recovery function that condenses and recovers the generated water vapor contained in it.
The details of the structure are as described in the one already proposed (Japanese Patent Application No. 4-203650). The condensed and recovered water recovered by the integrated exhaust gas treatment device 9 is returned to the water treatment device 16 through the condensed and recovered water line 19 and reused as a battery cooling water system, so that makeup water from the outside is supplied to the plant. Independent operation is possible without it.

Hot water such as city water flowing out from the low temperature side exit nozzle heated by the thermal energy of the exhaust gas in the integrated exhaust gas treatment device 9 is used as hot water depending on the usage form and operating conditions on the waste heat utilization side. May be supplied to the hot water exhaust heat utilization device 12 as it is, but in order to further supply it to the exhaust heat utilization device as high temperature water or high temperature steam, as shown in FIG. Is supplied to the secondary side of the steam generator 3. As a result, in the steam generator 3, the hot water heated by the integrated exhaust gas treatment device 9 is supplied to the secondary side of the steam generator 3 and exchanges heat with the battery cooling water as the heat source on the temporary side. Saturated steam is generated from the upper part of the steam generator 3.

In the figure, this saturated steam is further supplied to the secondary steam superheater 22 through the steam supply line 3e. However, depending on the usage form of the steam exhaust heat of the steam exhaust heat utilization device 11, the saturated steam is Or, if the moist steam of less than that has a sufficient utility value, the steam generated by the steam generator 3 is directly passed through the steam supply line 3e without passing through the secondary steam superheater 22 and exhausted from the steam exhaust heat. A system for supplying to the utilization device 11 can also be used. In addition, the warm water blown from the lower part of the steam generator 3 is used in the steam generator blow line 3
It can be supplied to the hot water exhaust heat utilization device 12 through c and used as the hot water exhaust heat.

As described above, in the first embodiment, the hot water heated by the integrated exhaust gas treatment apparatus 9 is supplied to the secondary side of the steam generator 3 and heated by the excess heat of the battery cooling water system to generate steam. Therefore, the steam can be supplied to the steam exhaust heat utilization device 11 in a state of being separated from the battery cooling water system, and the high temperature water further heated on the secondary side of the steam generator 3 can be supplied to the hot water exhaust heat utilization device 12. Since it can be supplied as high-temperature water at the same time, it is possible to respond to diversification of exhaust heat utilization, facilitate operation of the plant that meets the needs of the exhaust heat utilization side, and use steam that uses the exhaust heat of the fuel cell power generation system. Also, the utilization efficiency of the hot water supply system can be improved.

Further, the saturated secondary steam generated on the secondary side of the steam generator 3 is further dried by the thermal energy of the burner combustion exhaust gas of the fuel reformer 7 to become superheated steam equal to or higher than the saturated steam, so that the secondary steam A superheater 22 is installed downstream of the steam generator 3 to supply dry steam to the secondary steam generation system of the steam exhaust heat utilization device 11 in a form separated from the fuel cell cooling water system. I am able to do it. In the system in the figure, the secondary steam superheater 22 is arranged in the downstream of the burner combustion exhaust gas that has exited the fuel reformer 7 after heat exchange with the air in the burner air preheater 8. It is needless to say that the secondary steam generator 22 can be arranged immediately after the fuel reformer 7, that is, before the burner air preheater 8 depending on the performance and the efficiency of the plant.

Furthermore, in the first embodiment, by supplying cold water to the low temperature side of the integrated exhaust gas treatment apparatus 9, the condensed water recovery function of condensing and recovering the generated water vapor contained in the exhaust gas can be improved, The volume of the integrated exhaust gas treatment device 9 itself can be reduced, and in addition, the exhaust heat recovered water that has been preheated to be warm water on the low temperature side of the integrated exhaust gas treatment device 9 is supplied to the secondary side of the steam generator 3. By supplying the steam generator 3, the vaporization performance of the steam generator 3 can be improved, whereby the volume of the steam generator 3 can be downsized, and the plant equipment can be downsized as compared with the conventional one, and also economically. It is advantageous.

Here, an example of the operation control of the first embodiment will be described. As shown in the figure, by installing the hot water supply three-way valve 23 in the low temperature side hot water outlet piping line of the integrated exhaust gas treatment device 9, the hot water generated on the low temperature side of the integrated exhaust gas treatment device 9 is discharged into the hot water exhaust heat. This hot water can be supplied to the secondary side of the steam generator 3 at the same time as it is supplied to the utilization device 12 and the like, and the secondary steam of the steam exhaust heat utilization device 11 can be adjusted by adjusting the opening degree of the hot water supply three-way valve 23. It is possible to control the ratio between the steam supply amount for supplying steam to the generation system and the hot water supply amount for supplying hot water to the hot water exhaust heat utilization device 12 and the like. In this case, a steam generator inlet control valve 25 is provided in the battery cooling water system piping line that connects the steam separator 2 and the steam generator 3, and the steam generator bypass control valve is provided in the bypass piping line 24 of this piping line. 26 is provided. In the figure, 27 is a pressure detector that detects the steam pressure in the steam generator 3, and 28 is a pressure controller that adjusts the opening of the pressure adjusting valve 29 so that the pressure of the steam generator 3 is maintained at a predetermined value. .

Next, the operation of the first embodiment constructed as above will be described. Now, when the fuel cell main body 1 is operated in a state where only the hot water exhaust heat recovery is being performed without the steam exhaust heat recovery being performed, the steam generator bypass control valve 26 of the bypass piping line 24 is opened to generate the steam. The device inlet control valve 25 is closed, and the hot water supply three-way valve 23 is in a state in which the entire amount is supplied to the hot water exhaust heat utilization device 12 side. In such a state, in order to perform steam exhaust heat recovery operation by generating steam from the steam generator 3, the steam generator bypass control valve 26 of the bypass piping line 24 is closed to control the steam generator inlet. When the valve 25 is opened, the battery cooling water flowing out from the steam separator 2 flows through the battery cooling water system through the primary side of the steam generator 3. At this time,
A hot water supply three-way valve depending on the amount of exhaust heat recovered from the battery cooling water system, the secondary steam supply condition to the secondary steam generation system of the steam exhaust heat utilization device 11 and the hot water exhaust heat supply condition to the hot water exhaust heat utilization device 12.
Adjust the opening of 23. As a result, the water in the secondary steam generation system of the steam generator 3 is heated by the excess heat of the battery cooling water system to generate steam and high-temperature water, and the steam is supplied to the steam exhaust heat utilization device 11 via the pressure adjustment valve 29. Supplied. The condensed hot water after the steam exhaust heat utilization device 11 has used the steam exhaust heat is a hot water exhaust heat utilization device.
12 or is returned to the secondary side of the steam generator 3 again (not shown). In this case, the opening degree is controlled by the pressure controller 28, and the steam pressure in the steam generator 3 is kept constant, thereby forming the system as described above, so that the integrated exhaust gas treatment device 9 and the steam generator 3 are formed.
And the secondary steam superheater 22 is combined with each equipment as shown by the one-dot chain line in the same figure, for example, as a high temperature exhaust heat recovery integrated heat exchanger 30, the utilization form of the high temperature exhaust heat utilization device of each plant ， It becomes possible to design according to operating conditions.

The present invention is not limited to the above-described first embodiment, but various modifications can be made.

FIG. 2 is a block diagram of a fuel cell power generation exhaust heat recovery system according to a second embodiment of the present invention. In the second embodiment, the combination of the integrated exhaust gas treatment device 9 and the steam generator 3 as in the first embodiment is used, and the low temperature side of the integrated exhaust gas treatment device 9 is treated by the water treatment device 16. Not only the cold water is supplied and the hot water that has been water-treated by the integrated exhaust gas treatment device 9 is supplied to the secondary side of the steam generator 3,
A water treatment hot water three-way valve 31 is installed in the low temperature side hot water outlet piping line of the integrated exhaust gas treatment device 9 so that this hot water can be supplied also to the battery cooling water system, and the opening degree of the water treatment hot water three way valve 31 is adjusted. This makes it possible to control the ratio of the steam supply amount that supplies steam to the secondary steam generation system of the steam exhaust heat utilization device 11 and the hot water supply amount that supplies hot water that has undergone water treatment to the battery cooling water system. The other system, operation and the like are the same as those in the first embodiment.

As described above, by installing the water treatment hot water three-way valve 31 in the low temperature side hot water outlet piping line of the integrated exhaust gas treatment device 9, the hot water heated from the cold water in the integrated exhaust gas treatment device 9 is replaced with this water. By adjusting the opening degree of the treatment hot water three-way valve 32, the steam supply amount for supplying steam to the secondary steam generation system of the steam exhaust heat utilization device 11 and the hot water supply amount for supplying hot water to the hot water exhaust heat utilization device, etc. Can be controlled, and hot water heated from cold water treated by the water treatment device 16 to the low temperature side of the integrated exhaust gas treatment device 9 is supplied to the secondary side of the steam generator 3. In addition, a water treatment hot water three-way valve 31 is installed in the low temperature side hot water outlet piping line of the integrated exhaust gas treatment device 9 so that the hot water heated by the integrated exhaust gas treatment device 9 can be supplied to the battery cooling water system. Treated hot water three-way valve 32 By adjusting the opening degree, the ratio of the steam supply amount for supplying steam to the secondary steam generation system of the steam exhaust heat utilization device 11 and the hot water supply amount for supplying the hot water treated with water to the battery cooling water system is controlled. Therefore, the redundancy between the fuel cell power generation system and the exhaust heat utilization device can be improved. Here, similarly to the first embodiment, in the second embodiment, the saturated secondary steam generated on the secondary side of the steam generator 3 is further dried and saturated by the thermal energy of the burner fuel exhaust gas of the fuel reformer 7. A secondary steam superheater 22 is installed downstream of the steam generator 3 in order to obtain superheated steam above the steam, and the secondary steam of the steam exhaust heat utilization device 11 is separated from the fuel cell cooling water system. It is designed to be able to supply dry steam with superheated steam over saturated steam. In the system in the figure,
The secondary steam superheater 22 is arranged in the downstream of the burner combustion exhaust gas that has exited the fuel reformer 7 after heat exchange with the air in the burner air preheater 8, but the performance of the fuel reformer 7 and the efficiency of the plant Therefore, it goes without saying that the secondary steam superheater 22 can be arranged immediately after the fuel reformer 7, that is, before the burner air preheater 8.

Further, in the second embodiment, the secondary steam superheater is used.
The superheated steam generated in 22 is passed through the pipe to the fuel reformer 7
The gas phase (saturated steam) 2a generated in the steam-water separator 2 was heated by the fuel reforming steam superheater 21 so that it could be supplied to the fuel reforming system of FIG. The system is such that it joins the downstream fuel reformer superheated steam supply pipe 33. As a result, the superheated steam generated in the secondary steam superheater 22 can be supplied to the fuel reforming system of the fuel reformer 7, and it is generated in the conventional steam-water separator 2 to generate the fuel reformer 7.
The amount of the vapor phase (saturated steam) supplied to the fuel reforming system can be reduced, and the required amount of the fuel reforming steam superheater 21 can be reduced or omitted. The quality system can also be made compact.

The gas phase (saturated steam) 2a generated in the steam-water separator 2 is heated by the fuel reforming steam superheater 21 and is necessary for the endothermic reaction of the fuel reforming system of the fuel reformer 7. However, the surplus steam amount exceeding the required steam amount in the fuel reformer 7 is merged into the secondary steam generation system of the steam generator 3 through the steam / water separator saturated steam supply pipe 34, and the secondary steam is overheated. It is heated in the reactor 22 and, as described above, the steam exhaust heat utilization device 11
It can also be used to supply superheated steam to the fuel reformer 7 or to supply superheated steam to the fuel reforming system of the fuel reformer 7. Thus, directly joining the steam generated in the battery cooling water system to the secondary steam generation system has an advantage that the steam having a high temperature level can be taken out, but the secondary steam generation system and the steam exhaust heat utilization device 11 Since the secondary steam circulation loop is in the same piping system as the battery cooling water system, it is necessary to take measures to prevent leakage and water pollution in the secondary steam circulation loop, increasing the capacity of equipment used, materials, and water treatment equipment. There is a drawback that However, it is effective as a means for utilizing the excess steam exhaust heat of the battery cooling water system. In the figure, 35 is a condensed and recovered water heat exchanger,
36 indicates a water treatment cold water supply pump.

In the second embodiment as well, by forming the system as described above, the integrated exhaust gas treatment device 9, the steam generator 3 and the steam superheater 22 are shown in the same dotted line as in the first embodiment. It becomes possible to combine the respective equipment as shown in the box with, for example, a high temperature exhaust heat recovery integrated heat exchanger 30 and design according to the usage pattern and operating conditions of the high temperature exhaust heat utilization device of each plant. .

FIG. 3 is a configuration diagram of a fuel cell power generation exhaust heat recovery system according to a third embodiment of the present invention. In the third embodiment, when the battery cooling water blowdown water is returned to the water treatment device 16, it exchanges heat with the hot water at the low temperature side outlet of the integrated exhaust gas treatment device 9 to further raise the temperature of the hot water and recover the high temperature exhaust heat. In order to further improve the efficiency, the blowdown water warm water preheater 37 is installed in the low temperature side outlet piping line of the integrated exhaust gas treatment device 9. In the above-described first embodiment, the blowdown water line 20 is provided downstream of the battery cooling water circulation pump 4, and in the system that returns the battery cooling water blowdown water to the water treatment device 16, the heat quantity of the blowdown water that is this high temperature water. In order to effectively use the water, a blowdown water heat exchanger 10 is installed, where hot water and heat which are heated by the integrated exhaust gas treatment device 9 and are supplied to the hot water exhaust heat utilization device 12 via the hot water supply three-way valve 23. A system is provided in which the temperature of the blowdown water is lowered and then returned to the water treatment device 16 while at the same time increasing the temperature of the hot water by exchanging the hot water to enhance the recovery efficiency of the hot water exhaust heat. On the other hand, in the third embodiment, since the blowdown water warm water preheater 37 is installed in the low temperature side outlet piping line of the integrated exhaust gas treatment device 9, the high temperature exhaust heat recovery efficiency is further increased, and Since the blowdown water warm water preheater 37 is a water-water heat exchanger, it can be used with a general shell & tube type or plate type heat exchanger, and the waste heat recovery system water is the blowdown water warm water. Since the preheater 37 is heated to the vicinity of saturated water, the volume of the steam generator 3 can be reduced, so that the plant equipment can be downsized and the cost can be reduced. The other system, operation, etc. are similar to those of the first and second embodiments.

By forming the system as described above, the integrated exhaust gas treating apparatus 9, the steam generator 3 and the steam superheater 22 are formed as in the first and second embodiments.
Is combined with each equipment as shown by the one-dot chain line in the figure to form, for example, a high temperature exhaust heat recovery integrated heat exchanger 30, which is designed according to the usage pattern and operating conditions of the high temperature exhaust heat utilization device of each plant. It becomes possible to

Further, in the third embodiment, as shown in the figure, three heat exchangers are combined upstream of the water treatment device 16 to form, for example, a low temperature exhaust heat recovery integrated heat exchanger 38. . Similar to the high temperature exhaust heat recovery integrated heat exchanger 30 described above, the high temperature water from the steam generator 3, the blowdown water that has passed through the blowdown water warm water preheater 37, and the integrated exhaust gas treatment are also provided on the high temperature side. The condensed and recovered water from the device 9 is respectively flowed to heat the low temperature side fluid by exchanging heat with cold water such as low temperature side city water, and is heated to the low temperature side of the battery cooling water system temperature adjusting heat exchanger 5. A fluid can be supplied, and the low temperature exhaust heat recovery system can be made compact.

[0040]

As described above, according to the present invention, not only the waste heat from the fuel cell power generation system can be taken out as hot water, but also the surplus heat of the cell cooling water system is indirectly separated from the cell cooling water system. Can be extracted as high-temperature steam with high utility value, and in addition to facilitating operation control of the plant that matches the load of the hot water exhaust heat and steam exhaust heat utilization equipment, plant equipment, especially exhaust heat The size of the recovery device can be reduced, which is economically advantageous.

Further, by providing the secondary steam superheater, the superheated steam of dry saturated steam or more can be supplied to the secondary steam generation system of the steam exhaust heat utilization device in a form separated from the fuel cell cooling water system. At the same time, it is possible to integrate the exhaust heat recovery device from the fuel cell power generation system including the integrated exhaust gas treatment device, steam generator and steam superheater into one unit, and recover the simultaneous exhaust heat of hot water and steam from the plant. It is possible to provide a fuel cell power generation exhaust heat recovery system which has improved performance and can cope with downsizing of the exhaust heat recovery device.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing another embodiment (second embodiment) of the present invention.

FIG. 3 is a configuration diagram showing still another embodiment (third embodiment) of the present invention.

FIG. 4 is a characteristic diagram showing the relationship between the power generation load and the total thermal efficiency of the fuel cell power generation system related to the present invention.

FIG. 5 is a configuration diagram showing an example of a conventional fuel cell power generation system.

[Explanation of symbols]

1 ... Fuel cell, 2 ... Steam separator, 3 ... Steam generator, 3e
... Steam supply line, 4 ... Battery cooling circulation pump, 5 ... Heat exchanger for temperature adjustment, 7 ... Fuel reformer, 8 ... Burner air preheater, 9 ... Integrated exhaust gas treatment device, 10 ... Blowdown water heat exchange Heater, 11 ... Steam waste heat utilization device, 12 ... Hot water waste heat utilization device, 14 ... Secondary cooling water circulation pump, 16 ... Water treatment device, 18 ...
Make-up water supply line, 21 ... Fuel reforming steam superheater, 22 ... Secondary steam superheater, 23 ... Hot water supply three-way valve.

Claims (1)

[Claims] 1. A fuel cell main body having a fuel electrode, an air electrode, and a cooler, a fuel reformer for supplying hydrogen gas produced by reforming fuel to the fuel electrode of the fuel cell main body, A steam separator for separating the two-phase flow of the cell cooling water heated by the reaction heat of the fuel cell body into a gas phase and an aqueous phase, and the cell cooling water separated by the steam separator to the fuel cell body. A battery cooling water system to be circulated through the cooler, and a secondary steam of the steam exhaust heat utilization device in a form separated from the battery cooling water by the excess heat of the battery cooling water system on the downstream side of the water phase outlet of the steam separator. Included in the exhaust gas and a phosphoric acid removing function for removing and recovering phosphoric acid from the exhaust gas containing a phosphoric acid solution discharged together with the steam generator that supplies steam to the generating system and the generated steam vaporized from the electrolyte of the fuel cell main body Condensation to condense and recover the generated steam In a fuel cell power generation system composed of an integrated exhaust gas treatment device having a water recovery function, cold water is supplied to the low temperature side of the integrated exhaust gas treatment device, and the cold water is turned into warm water by the heat energy of the exhaust gas, and the hot water is exhausted. A fuel cell power generation exhaust heat recovery system characterized in that the hot water is supplied to a secondary side of the steam generator while being supplied to a utilization device or the like.