JP3461909B2 - Fuel cell surplus steam condensation type steam separator - Google Patents

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 separator for utilizing exhaust heat from a fuel cell.

[0002]

2. Description of the Related Art A fuel cell power generation system converts chemical energy of fuel such as city gas or propane gas into electric energy, and is an apparatus for producing hydrogen from a fuel cell body, fuel such as city gas or propane gas. , A converter for converting a direct current generated in the fuel cell main body into an alternating current, and a heat exchanger for maintaining the temperature of the working gas at a temperature suitable for the operation of the fuel cell main body and hydrogen generation. . The fuel cell main body is for directly converting the binding energy of hydrogen gas generated by hydrogen generation and oxygen in the air into electric energy, and a power generation system using this fuel cell is for power generation by a chemical reaction, It has been evaluated as a clean power generation system with high power generation efficiency, low emission of air pollutants, and low noise.

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. Cooling is taking place. Therefore, the cooling water system of the fuel cell power generation system is provided with a steam separator, a heat exchanger, and the like, and the exhaust heat extracted from the heat exchanger is used for various purposes. The 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. 5 is a characteristic diagram showing the relationship between general power generation load and total thermal efficiency of a fuel cell power generation system. The power generation efficiency with respect to the power generation load is about 40% as can be seen from this characteristic diagram. However, the total thermal efficiency is 80% or more when the low temperature exhaust heat recovery component of the hot water level and the high temperature exhaust heat recovery component of the steam level are all used. As described above, the fuel cell power generation system can effectively use not only power generation but also exhaust heat outside the system. Especially, high temperature exhaust heat of vapor level out of the exhaust heat is used as a drive source of the absorption chiller, steam. It is highly useful as a drive source for turbines.

FIGS. 6 and 7 utilize the surplus heat of the battery cooling water incorporating the conventional exhaust heat utilization system to heat the water of the secondary steam generation system separated from the battery cooling water system. It is a figure showing an example of composition of a fuel cell power generation system provided with a steam generator which generates steam. As shown in FIG. 6, the reaction heat generated in the fuel cell body 1 including the fuel electrode 1a, the air electrode 1b, and the cell cooler 1c is extracted by exchanging heat with the cell cooling water in the cell cooler 1c. The battery cooling water heated by this reaction heat is introduced into the steam-water separator 2 as a gas-liquid two-phase flow.

In the steam-water separator 2, the steam 2 of gas-liquid two-phase flow is used.
a is separated and liquefied to become the battery cooling water 2b, which is introduced into the steam generator 3 provided downstream of the steam separator 2.
The surplus heat of the battery cooling water 2b heats the water in the secondary steam generating system separated from the battery cooling water system to generate steam. Then, the battery cooling water 2b whose temperature has been lowered by the steam generator 3 is returned to the battery cooler 1c through the temperature adjusting heat exchanger 5 by the battery cooling water circulation pump 4.

On the other hand, the steam 2a separated by the steam separator 2
Is supplied to the fuel reforming steam superheater 6 to be superheated by the fuel reforming steam superheater 6 to become superheated steam, and the superheated steam is mixed with fuel at a certain ratio to form a catalyst in the fuel reformer 7. The hydrogen-rich gas is converted by the endothermic reaction of passing through the layer and being heated by the burner combustion gas in the fuel reformer 7 during this period.

In the case of FIG. 6, the burner flue gas burned in the fuel reformer 7 leaves the fuel reformer 7 and then heats air and heat as a heating source of the burner air preheater 8 of the fuel reformer 7. It is exchanged, merges with the exhaust air from the fuel cell body 1 on the downstream side, and is introduced into the integrated exhaust gas treatment device 9. This 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 body 1 and is discharged together with the generated steam, and is included in the exhaust gas. It has a condensed water recovery function that condenses and recovers the generated steam.

The saturated steam generated on the secondary side of the steam generator 3 is supplied to the secondary steam generation system of the steam exhaust heat utilization device 11 through the steam supply line 10, and is used there, after which condensed water is condensed. And is returned to the lower part of the steam generator 3 through the condensed water return pipe 13 by the steam generator feed water pump 12.

Generated on the primary side of the integrated exhaust gas treatment device 9,
The condensed water in the recovered exhaust gas is introduced into the water treatment device 15 via the condensed water recovery line 14, and the water-treated cooling water is combined with the battery cooling water flowing out from the steam generator 3 to cool the cooler 1c. Will be introduced to.

FIG. 7 is a diagram showing another example of the configuration around the steam separator 2 and the steam generator 3 in FIG. 6, in which the saturated steam generated on the secondary side of the steam generator 3 is vaporized. It flows into the heat transfer tube group 20 provided in the water separator 2 and is further heated there to become superheated steam, which is supplied as high-quality superheated steam to the secondary steam generation system of the exhaust heat utilization device, and Condensate excess steam of battery cooling water on the outer surface of the heat transfer tube group,
The amount of steam generated in the steam separator is maintained at a desired value.

[0012]

However, in the conventional fuel cell power generation system incorporating such a steam exhaust heat utilization device, in the case as shown in FIG. There is no function of condensing and recovering the excess vapor of the cell cooling water taken out as a phase flow, which is more than the required supply amount to the fuel reformer 7, and the temperature of the cell cooling water system is controlled by the fuel cell main body. There is a problem that it is difficult to maintain an appropriate temperature. Here, in order to increase the operation performance of the fuel cell main body 1, for example, to reduce the amount of cell cooling water in order to increase the operating performance of the fuel-cell separator 2, it is necessary to reduce the amount of surplus steam that exceeds the required supply amount to the fuel reformer 7. In order to increase the gas-liquid two-phase flow region at a certain saturation temperature so that the temperature distribution of the cell cooler 1c inside the fuel cell body 1 becomes uniform, the ratio of the gas phase at the outlet of the cell cooler 1c May increase.

On the other hand, in the structure shown in FIG. 7, although the above problems can be solved, due to the internal structure of the fuel cell body, for example, when phosphoric acid inside the battery is operating, exhaust gas from the cell outlet, exhaust air, etc. In order to prevent the mixture from flowing out to the outside, there is a restriction that the battery inlet temperature of the battery cooling water must be lowered to some extent. However, in order to lower the battery inlet temperature of the battery cooling water, it is necessary to release the heat of the battery cooling water system to the outside through a heat exchanger etc. in front of the battery cooling water system battery inlet, which is of high quality. The amount of high-temperature exhaust heat recovery from the highly useful battery cooling water system decreases, which lowers the high-temperature exhaust heat recovery efficiency, leading to a reduction in the efficiency of the fuel cell power plant.

Further, when the fuel cell system is operated only for power generation operation and it is not necessary to supply high temperature exhaust heat, that is, when it is not necessary to supply steam to the secondary steam generating system of the exhaust heat utilization device. In addition, since a surplus vapor content that is more than the required supply amount to the fuel reformer 7 is generated in the steam separator 2, on the fuel cell system side that maintains the steam amount at a desired value, It is necessary to condense excess steam of the battery cooling water system by means.

Further, in order to improve the efficiency of exhaust heat recovery from the fuel cell system, the amount of steam supplied from the steam separator to the reformer is reduced, and the operation is carried out with a reduced steam / carbon ratio (S / C). The same applies to cases.

In view of the above points, the present invention provides a fuel reformer for a cell cooling water system, in addition to a heat transfer tube group and the like provided for supplying steam to a secondary steam generation system in a steam separator. By providing the steam separator with the function of condensing and recovering excess steam of more than the required supply amount, it is possible to support indirect steam extraction of the fuel cell power generation system, downsize plant equipment, and diversify exhaust heat utilization. The purpose is to obtain a steam separator that can be adapted.

[0017]

SUMMARY OF THE INVENTION According to the present invention, cooling water that has been heated by the reaction heat of a fuel cell body and turned into a two-phase flow is separated into a gas phase and a liquid phase, and the separated cooling water is stored in the fuel cell body. In a steam separator in a fuel cell power generation system that is made to recirculate to a cooler, cooling means for condensing excess steam in cooling water generated by passing through the fuel cell, and water condensed by the cooling means Water treatment device for treatment, water treatment water line for supplying water treated by the water treatment device as cooling water to the cooling means, cooling provided in the water treatment water line and supplied to the cooling means And a flow rate control means for controlling the flow rate of water.

[0018]

Since the cooling means for supplying a part of the cooling water to be supplied to the fuel cell is provided in the air / water separator, the surplus vapor component of the cell cooling water system is converted into the liquid phase by the operation of the cooling means or the like. By returning to minutes, the amount of water vapor generated in the steam separator can be maintained at a desired value. Therefore, it is possible to increase the amount of indirect superheated steam taken out by supplying superheated steam to the secondary steam generation system of the indirect exhaust heat utilization device separated from the battery cooling water system from the steam separator. Therefore, the high temperature exhaust heat recovery rate from the system can be increased.

Also, when it is not necessary to supply steam to the secondary steam generation system of the waste heat utilization device, or when operation is performed with a reduced steam / carbon ratio, excess steam of the battery cooling water system is used. By condensing the components, the amount of water vapor generated in the steam separator can be set to a desired value. Therefore, it is not necessary to discharge the surplus steam component to the outside or to condense the surplus steam component through a heat exchanger or the like, and the plant equipment can be made compact and economical.

[0020]

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

In FIG. 1, the cell cooling water is introduced into the gas-water separator 2 from the fuel cell cooler 1c through the cell cooling water inlet nozzle 21, and the cell is separated and liquefied from the vapor of the gas-liquid two-phase flow there. Cooling water is introduced into the steam generator 3 via the water phase outlet downcomer 22 and the steam generator inlet control valve 23. The battery cooling water that has exchanged heat with the water of the secondary steam generation system in the heat transfer tube group 3c of the steam generator 3 is transferred to the battery cooler 1 via the temperature adjusting heat exchanger 5 by the battery cooling water circulation pump 4.
is returned to c. In the figure, reference numeral 24 is a steam generator bypass line, and 25 is a bypass valve.

On the other hand, the condensed water of the secondary steam generation system introduced from the steam exhaust heat utilization device 11 to the steam generator 3 through the condensed water return pipe 13 by the steam generator feed water pump 12 is the steam generator 3 described above. It is heated to become saturated steam, and is supplied to the steam / water separator heat transfer tube group 20 through the saturated steam supply pipe 26,
After being heated there, it is supplied to the steam exhaust heat utilization device 11 via the secondary steam pressure adjusting valve 27. Here, the opening degree of the secondary steam pressure adjusting valve 27 is controlled by the pressure controller 29 according to the pressure signal detected by the steam pressure detector 28, and the steam pressure introduced into the steam exhaust heat utilization device 11 is controlled. Is controlled.

Further, a part of the saturated water in the steam generator 3 is introduced into the water treatment device 15 through the hot water supply pipe 30, and the water treated by the water treatment device 15 is the water treatment makeup water supply line. After passing through 31, the battery cooling water circulation pump 4 joins with the battery cooling water at the inlet side.

The above-mentioned structure is the same as that of the conventional apparatus shown in FIG. 9, but a water treatment line 38 is connected to the water treatment apparatus 15, and the other end of the water treatment water line 38 has the above-mentioned steam separation. It is connected to the water spray nozzle 34 which is arranged in the gas phase portion of the vessel 2. In addition, in the gas phase portion in the water / water separator 2, the spray water sprayed from the water spray nozzle 34 is provided between the water spray nozzle 34 and the steam nozzle 35 that supplies steam to the reformer. A baffle plate 36 is provided to prevent it from flowing into 35. Reference numeral 37 in the figure is a flow control valve.

Therefore, first, the two-phase flow of the cell cooling water in the cell cooler 1c of the fuel cell main body 1 flows into the steam separator 2 through the cell cooling water inlet nozzle 21 and vapor (upper part) It is separated into a gas phase portion 2a) and cooling water (lower liquid phase portion 2b). On the other hand, bypass water is sprayed from the spray nozzle 34 into the upper gas phase portion 2a, and the spray water sprayed toward the liquid surface of the gas-liquid separation and the steam separated in the steam separator 3 are directly connected to each other. Upon contact, the vapor condenses while the water spray particles reach the surface. That is, heat exchange is performed on the surface of the sprayed particles of the battery cooling water on the low temperature side before inflow of the battery, and the latent heat of the saturated steam in the portion in contact with the sprayed particles is removed, so that steam condensation proceeds.

In the steam-water separator 2 in the figure, the battery cooling water in the separator is steam (upper gas phase portion 2a) in the upper half and cooling water (lower liquid phase portion 2b) in the lower half. It is separated and the arrangement of the water spray nozzle 34 and the heat transfer tube group 20 is modeled and shown, and the installation state, tube arrangement, shape, type, etc. of the water spray nozzle 34 and the heat transfer tube group 20 are the design method. It goes without saying that various forms can be considered depending on.

Here, for example, the temperature of the upper gas phase portion 2a and the lower liquid phase portion 2b in the steam separator 2 is 185 ° C., and the temperature of 185 ° C. on the primary side of the steam generator 3 under ideal conditions. Even if it flows in, the temperature on the secondary side of the steam generator 3 is limited by the design of the steam generator 3 (for example, the heat transfer area is unnecessarily increased due to the relationship between the pinch temperature of the heat exchanger and the heat transfer area). Therefore, the steam generator 3 cannot be made large), so that it is only possible to take out steam as saturated steam at 160 ° C. to 170 ° C., and it is difficult to take out steam as superheated steam, but the tubes of the heat transfer tube group 20. Superheated steam can be generated by flowing this saturated steam inside and further heating it with the heat of the upper gas phase portion 2a in the steam separator 2, depending on the operating temperature in the steam separator 2. , Slightly below the temperature in the steam separator 2 It is possible to generate every one hundred seventy to one hundred eighty-four ° C. superheated steam. On the other hand, the temperature of the water treated in the water treatment device that is sprinkled from the water spray nozzle is relatively low, and this low temperature water is used as the steam separator 2
Water can be sprayed directly into the interior, and the spray nozzle 34 is designed according to the operating conditions, and the flow control valve 3
By controlling the amount of spray water by the control of 7, it is possible to efficiently condense the excess steam content in the steam separator 2, and to maintain the desired amount of steam generated in the steam separator. it can.

Since the excess steam of the cell cooling water system can be condensed outside the heat transfer tube group 20 in the steam separator 2, the amount of this excess steam is output from the battery cooler 1c of the fuel cell main body to the battery. By adjusting the two-phase flow ratio of the cooling water by the amount of battery cooling water or the amount of battery bypass water that bypasses the battery main body 1 or the like, the amount of superheated steam supplied to the steam exhaust heat utilization device 11 can be adjusted to a load change. You can

In the above embodiment, the saturated steam generated by heating on the secondary side of the steam generator 3 installed on the downstream side of the steam separator 2 is further transferred to the steam separator 2. It flows into the heat pipe group 20, becomes superheated steam, and is supplied to the secondary steam generation system of the steam exhaust heat utilization device 11,
Depending on the form of utilization of steam exhaust heat, the system can be applied to a system in which saturated steam generated in the steam generator 3 is directly supplied to the secondary steam generation system of the steam exhaust heat utilization device 11.

FIG. 2 is a diagram showing another embodiment of the present invention, in which the water vapor separator 2 is provided with a water spray pallet 39 in the upper gas phase portion 2a. 39
The treated water from the water treatment device 15 is supplied to the water treatment device 15 and is sprinkled on the liquid surface in the vessel through the water spout provided on the lower surface of the sprinkling pallet 39. Therefore, also in this case, the same operation as that of the embodiment shown in FIG.

FIG. 3 is a view showing still another embodiment of the present invention, in which a heat transfer tube group 40 is provided in the upper gas phase part 2a in the steam separator 2, and this heat transfer tube is used. The treated water from the water treatment device 15 is circulated to the group 40. Then, in this case, the excess steam in the steam separator 2 can be condensed in the steam separator on the outer surface of the heat transfer tube group 40. On the other hand, the water flowing in the heat transfer tube group 40 becomes saturated steam or superheated steam by being heated at the temperature in the steam separator, and can be supplied to the steam exhaust heat utilization device as secondary steam. .

Further, FIG. 4 shows still another embodiment, in which a surplus steam condensing function bypass line 41 is branched out to the water treatment line 38, and a water spray nozzle 34 and the surplus steam are provided in the branch portion. A three-way valve 42 that controls the flow rate of the battery cooling water flowing to the condensation function bypass line 41 is provided.

Therefore, by adjusting the opening of the three-way valve 42, the amount of water vapor generated in the steam separator can be maintained at a desired value. Further, the water that has left the bypass line 41 can be made to flow into the outlet of the steam generator 3 of the battery cooling water system.

[0034]

As described above, in the present invention, in addition to the heat transfer tube group for supplying the steam to the secondary steam generating system in the steam separator, the water treatment from the water treatment device 15 is performed. Since the cooling means is provided to condense the excess steam in the cooling water generated by the water supplied and passing through the fuel cell, the steam generated in the steam-water separator is effectively condensed by the excess steam in the cell cooling water system. The amount can be maintained at the desired value.

Therefore, by supplying superheated steam or the like to the secondary steam generation system of the indirect exhaust heat utilization device in a form separated from the battery cooling water system from the steam separator, the indirect superheated steam extraction amount is increased. It is possible to increase the efficiency of high temperature exhaust heat recovery from the system.

Further, when the fuel cell system is operated only for power generation operation and it is not necessary to supply high temperature exhaust heat, that is, when it is not necessary to supply steam to the secondary steam generation system of the exhaust heat utilization device, Furthermore, in order to improve the efficiency of exhaust heat recovery from the fuel cell system, the amount of steam supplied from the steam separator to the reformer is reduced, and the steam / carbon ratio (S / C) is also reduced when the operation is performed. It is possible to condense the excess steam of the cooling water system and return it to the liquid phase part of the battery cooling water system to maintain the amount of water vapor generated in the steam separator at a desired value.

Further, the function of condensing the excess steam, that is, the spray nozzle, the pallet for spraying, and the heat transfer tube group as the secondary steam superheater are also incorporated in the steam separator to make the plant equipment compact. it can.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a surplus vapor condensing steam / water separator of a fuel cell power generation system of the present invention.

FIG. 2 is a view showing another embodiment of the steam separator of the present invention.

FIG. 3 is a view showing still another embodiment of the steam separator of the present invention.

FIG. 4 is a view showing another embodiment of the steam separator of the present invention.

FIG. 5 is a characteristic diagram showing the relationship between the power generation load and the total thermal efficiency of the fuel cell power generation system.

FIG. 6 is a diagram showing a schematic configuration of a conventional fuel cell power generation system.

FIG. 7 is a diagram showing an example of a conventional steam separator.

[Explanation of symbols]

1 Fuel main body 1c Battery cooler 2 steam separator 3 steam generator 7 Fuel reformer 11 Steam exhaust heat utilization device 15 Water treatment equipment 20 Heat transfer tube group 21 Battery cooling water inlet nozzle 34 Water spray nozzle 36 baffle board 38 Water treatment water line 39 Watering pallet 40 heat transfer tube group 41 Surplus vapor condensation function bypass line 42 three-way valve

Claims (4)

(57) [Claims] 1. A two-phase flow of cooling water heated by reaction heat of a fuel cell body is separated into a gas phase and a liquid phase, and the separated cooling water is returned to a cooler of the fuel cell body. In a steam separator in a fuel cell power generation system, cooling means for condensing excess steam in cooling water generated by passing through the fuel cell, a water treatment device for treating water condensed by the cooling means, and A water treatment water line for supplying the water treated by the water treatment device as cooling water to the cooling means, and a flow rate control provided on the water treatment water line for controlling the flow rate of the cooling water supplied to the cooling means. A fuel cell surplus vapor condensing steam-water separator, comprising: 2. The fuel cell surplus vapor condensation type gas according to claim 1, wherein the cooling means is a water spray nozzle for spraying cooling water to the gas phase portion in the upper part of the steam water separator. Water separator. 3. The fuel cell surplus vapor condensation type steam-water separator according to claim 1, wherein the cooling means is a heat transfer tube arranged in a gas phase portion in an upper part of the steam-water separator. vessel. 4. The fuel cell surplus vapor condensing steam / water separator according to claim 1, wherein the cooling means is a water spray pallet provided in a gas phase portion in an upper portion of the steam / water separator.