JP2005044572A - Hybrid type fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hybrid type fuel cell system in which the energy of the high temperature exhaust gas of a high temperature type fuel cell is effectively utilized and the starting time of a low temperature type fuel cell is shortened. <P>SOLUTION: The hybrid type fuel cell system is constructed of a pressurized high temperature type fuel cell 1 and a normal pressure low temperature type fuel cell 2 having a reformer 22. Bypass piping lines 101S, 102S are provided so that the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G of the high temperature fuel cell 1, or the combustion exhaust gas of these, may be utilized as a fuel or a heat source for the reformer burner 221 of the low temperature fuel cell 2. By combusting by the reformer burner 221 the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G, or by maintaining the reformer 22 in a hot banking state by making the air electrode exhaust air 102G and the combustion exhaust gas a heat source, the time required for starting at the time of restarting the fuel cell is shortened. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
[Technical field to which the invention belongs]
In the case where a high-temperature fuel cell and a low-temperature fuel cell are operated side by side as a power source for business or private power generation facilities having a power generation capacity of several kW to several hundred MW, and an electric power business, The present invention relates to a hybrid fuel cell power generation system that combines high operability and economy by reducing the startup time of a low-temperature fuel cell while being hybridized.
[0002]
[Prior art]
As one of the categories for classifying fuel cells, there is a classification according to the operating temperature of the battery, which is roughly divided into a high temperature type fuel cell having an operating temperature of about 600 to 1000 ° C. and a low temperature type fuel having an operating temperature of about 200 ° C. There is a battery.
[0003]
FIG. 8 is a block diagram showing an outline of a system configuration of a solid oxide fuel cell (SOFC), which is a typical high-temperature fuel cell. FIG. 8 (a) shows a pressurized SOFC, and FIG. 8 (b) shows a normal pressure type. Each SOFC is shown. In FIG. 8 (a), the fuel NG such as city gas is desulfurized by removing sulfur from the desulfurizer 81, then steam is added, and then heated by the preheater 82, and the operating temperature is 700 to 1000 ° C. It is introduced into the SOFC battery stack 80. While being reformed inside the battery stack 80 to hydrogen, carbon monoxide, and carbon dioxide, most of the hydrogen and carbon monoxide react with oxygen ions at the fuel electrode 801 to generate electricity. On the other hand, in the air electrode 802 of the battery stack 80, oxygen in the air is taken in and ionized, and the oxygen ions move to the fuel electrode 801 through the electrolyte 803. In the case of the pressurized type, it is necessary to send pressurized air to the air electrode 802. In this example, the compressor 843 is operated by a turbine 841 described later, and this is sent to the air electrode 802. . The basic configuration of the atmospheric pressure SOFC shown in FIG. 6B is substantially the same as that of the pressurized SOFC. However, since pressurized air is not sent to the air electrode 802, the difference is that atmospheric air is sent to the air electrode 802 by the air supply device 86 including the electric motor 860 and the blower 861.
[0004]
In general, the utilization rate of hydrogen at the fuel electrode 801 is about 70 to 80%, and the remaining hydrogen is discharged as surplus fuel electrode exhaust gas. The oxygen utilization rate in the air at the air electrode 802 is about 50 to 60%, and the remaining air is discharged as surplus air electrode exhaust air. In the high-temperature fuel cell stack, these fuel electrode exhaust gas and air electrode exhaust air are used to circulate again in the system or burn the fuel electrode exhaust gas and air electrode exhaust air to maintain the cell stack at a high temperature. Thereafter, it is discharged as a high-temperature gas at 400 to 600 ° C. Therefore, utilization of these surplus fuel electrode exhaust gas and air electrode exhaust air, or these combustion exhaust gas is important for improving the operability and economic efficiency of the fuel cell.
[0005]
When SOFC is a low pressure type, these surplus fuel electrode exhaust gas and air electrode exhaust air, or these combustion exhaust gas are also low pressure, and used as burner fuel for various boilers, etc. Stop on. However, when used as a heat source for boilers, it can only generate heat that is less valuable than electricity. In addition, there is a problem in that it is not economical because the necessity of heat utilization itself disappears when the heat demand is low such as in summer.
[0006]
On the other hand, when the SOFC is a pressurized type, the fuel electrode exhaust gas and the air electrode exhaust air, or the combustion exhaust gas thereof are also at a high pressure, and can be used, for example, as a burner fuel for a gas turbine generator or a high temperature / high pressure driving gas. . FIG. 8A shows an example in which such a power generation device 84 is arranged on the rear stage side of the battery stack 80. The fuel electrode exhaust gas and the air electrode exhaust air discharged from the battery stack 80 are combusted in the combustion chamber burner to become combustion exhaust gas, supplied to the power generation device 84 via the heat exchanger 83, and drive the gas turbine 841. Used as an energy source. Reference numeral 85 denotes an exhaust heat recovery boiler for recovering the exhaust energy of the gas turbine 841. The gas turbine 841 operates the generator 842 to generate electricity, and also operates the compressor 843 to generate compressed air, and supplies the compressed air to the air electrode 802 of the battery stack 80. Thus, in the pressurized SOFC, it becomes possible to obtain the pressurized air for reaction at the electricity and the air electrode 802 from surplus fuel electrode exhaust gas and air electrode exhaust air, or these combustion exhaust gas, and the fuel Polar exhaust gas and air exhaust gas, or these combustion exhaust gas can be used effectively.
[0007]
Another example of the high-temperature fuel cell is a molten carbonate fuel cell (MCFC). In the case of MCFC, the temperature of the fuel electrode exhaust gas and the air electrode exhaust air from the fuel cell is about 400 to 500 ° C., slightly lower than that of SOFC (700 to 1000 ° C.). Regarding the system configuration, because the battery operating temperature is low, there is no need to keep the battery warm by burning the fuel electrode exhaust gas and air electrode exhaust air, so the fuel electrode exhaust gas and air electrode exhaust air are separately taken out from the battery stack. Can be used. Usually, the fuel electrode exhaust gas is recirculated to the fuel electrode inlet side, and a part of the air electrode exhaust air is recirculated to the air electrode, but the rest is used as driving energy for the turbo compressor.
[0008]
Next, examples of the low temperature fuel cell include a phosphoric acid fuel cell (PAFC) and a polymer electrolyte fuel cell (PEFC). FIG. 9 is a block diagram showing the system configuration of PAFC. The fuel NG such as city gas is separated into hydrogen, carbon monoxide, and carbon dioxide while being reformed inside the reformer 92 that has been subjected to the removal of sulfur by the desulfurizer 91 and added with water vapor to 700-800 ° C. Is done. Through the heat exchanger 93, the carbon monoxide is converted into hydrogen and carbon dioxide by the carbon monoxide converter 94, and the carbon monoxide concentration is set to a certain value (several%) or less. Thereafter, the reformed gas is introduced into the PAFC battery stack 90, and most of the introduced hydrogen becomes hydrogen ions at the fuel electrode 901, and the hydrogen ions move to the air electrode 902 through the electrolyte 903. Pressurized air is introduced into the air electrode 902, and oxygen in the air is taken in and ionized. The oxygen ions and the hydrogen ions that have moved to the air electrode 902 react to generate electricity. is there.
[0009]
In general, the utilization rate of hydrogen at the fuel electrode 901 is 70 to 80%, and the remainder is discharged as fuel electrode exhaust gas 901G. Further, the oxygen utilization rate in the air at the air electrode 902 is 50 to 60%, and the rest is discharged as air electrode exhaust air 902G. The fuel electrode exhaust gas 901 </ b> G and the air electrode exhaust air 902 </ b> G are introduced into the burner 921 of the reformer 92 and are used effectively as fuel for heating the reformer 92.
[0010]
On the other hand, PEFC has a battery operating temperature of 180 to 200 ° C., whereas PEFC is about 80 to 100 ° C., which is a relatively low temperature among low temperature fuel cells. Although there is a difference that the carbon monoxide concentration in the reformed gas composition entering the cell needs to be 10 ppm or less, it is basically the same system configuration as PAFC.
[0011]
PAFC and PEFC also have a pressurization type and a normal pressure type. However, the pressurization type has problems such as a complicated system and difficulty in control, and the manufacturing cost and technical difficulty are high. Therefore, there is little merit even if the pressurization type is adopted as a facility for private power generation in a factory of about several tens of kW or a factory of about several hundred kW, and the normal pressure type is generally popular.
In recent years, 3 to 5 kW, 30 kW, and 200 kW grades of PEFC for business use have been developed and are gradually being introduced to the market. Further, as factory PAFCs, 50 kW, 100 kW, 200 kW, 500 kW, and further 1000 kW class are being developed.
[0012]
[Patent Document 1]
JP 2002-75426 A
[0013]
[Problems to be solved by the invention]
The electricity and heat load demands of consumers vary depending on the industry, scale, day and night, or season of the consumer. As an example, FIG. 10 shows changes in the daily power / heat load demand of an office building for each season. In this way, the load changes depending on the season such as summer, winter, and intermediate period, and even during the day or even in the time zone. To operate a fuel cell of several kW to several hundred kW economically, Therefore, it is necessary to drive the system so as to follow the fluctuation of the load well and to reduce the generation of excess electricity and heat as much as possible.
[0014]
Despite such demands, the high-temperature fuel cell has a characteristic that its load change and start / stop are extremely limited due to its structure. That is, in the case of a solid electrolyte battery (SOFC), since the operating temperature of the battery is as high as 700 to 1000 ° C., the battery stack needs to be made of a heat-resistant material such as a ceramic material. Since a wide range of temperature changes ranging from room temperature to 1000 ° C will occur, and if this is repeated, cracks may occur in the ceramic material. I can't. In addition, regarding the load change, it is said that only a load change of about 75 to 100% is allowed because the battery temperature is lowered when the load is lowered.
[0015]
The situation is almost the same in the case of a molten carbonate fuel cell (MCFC), and tolerance for start / stop and load change is extremely small. In fact, when the operation of a high-temperature fuel cell is stopped due to periodic inspections, etc., it takes several tens of hours to several days to restart. Overall, the high-temperature fuel cell has high power generation efficiency but is flexible. It is evaluated that it cannot respond to start / stop and load fluctuation.
[0016]
For this reason, when installing a high-temperature fuel cell, a fuel cell having a capacity equivalent to the minimum load of the consumer is installed, and the design of a fuel cell system that can be operated at a substantially constant load throughout the year is aimed at. However, in reality, the demand for electricity and heat load is very small during holidays and late at night, so if the minimum load is matched as described above, the capacity of the fuel cell that can be installed must be a very small capacity machine. For example, the power load pattern of an office building shown in FIG. 10 shows that although there is a power load of about 30 kW in the daytime, it is only about 5 kW at night or on holidays, so only a high-temperature fuel cell of about 5 kW is available. There is an inconvenience that it cannot be installed.
[0017]
In contrast, low-temperature fuel cells such as phosphoric acid fuel cells (PAFCs) and polymer electrolyte fuel cells (PEFCs) can be said to have a strong resistance to starting and stopping and load changes. In the case of PAFC, since the battery operating temperature is as low as about 200 ° C., a large heat change is not added to the battery stack even when starting and stopping, and the allowable range of load change is as wide as 30 to 100%. For example, “WSS operation” in which activation and suspension are performed about once a week can be sufficiently handled. In the case of PEFC, the operating temperature is even lower, about 80 to 100 ° C, and the allowable range of load change is 30 to 100%. It can be used for "DSS operation" that starts and stops once a day. is there. However, the low temperature fuel cell generally has a fundamental problem that the power generation efficiency is considerably lower than that of the high temperature type, and the low temperature fuel cell alone has a problem that it is difficult to economically operate the fuel cell system.
[0018]
By the way, since the high temperature fuel cell is a high temperature system, the fuel can be reformed inside the cell stack. However, since the low temperature type fuel cell is a low temperature system, a separate reformer is installed and the fuel is modified in the reformer. It is necessary to introduce it into the battery stack after quality improvement. Although the low temperature fuel cell can be started and stopped as described above, there is a problem that it takes a certain time to start the reformer. For example, in the case of a 200 kW class PAFC, the start-up time is about 4 hours (3.5 hours for start-up of the reformer, about 1 hour for start-up of the battery, and 0.5 hours for overlap). The time required for starting up the reformer also has a problem that it hinders economical operation of the fuel cell system.
[0019]
In view of such circumstances, the present inventor has conceived that a high-efficiency high-temperature fuel cell and a low-temperature fuel cell with low power generation efficiency but high operability are provided side by side for economical operation as a whole power generation system. The present invention has been completed. That is, an object of the present invention is to provide a hybrid fuel cell system that effectively uses the energy of the high-temperature exhaust gas of a high-temperature fuel cell that is always in operation and shortens the startup time of the low-temperature fuel cell. .
[0020]
[Means for Solving the Problems]
In order to achieve the above object, a hybrid fuel cell system according to claim 1 of the present invention is a hybrid fuel cell system comprising a high-temperature fuel cell and a low-temperature fuel cell equipped with a reformer. Fuel electrode exhaust gas and / or air electrode exhaust air of the high temperature fuel cell, or combustion exhaust gas of the fuel electrode exhaust gas and air electrode exhaust air, at least partly from the time when the low temperature fuel cell is stopped until it is restarted In this time, the reformer is used as a direct or indirect energy source for maintaining the warmed state.
[0021]
According to such a configuration, the fuel electrode exhaust gas and / or the air electrode exhaust air or the fuel electrode exhaust gas of the high temperature fuel cell that must be always operated when the low temperature fuel cell is stopped at midnight or on weekends. The reformer is put into a kind of warm-up operation state by the heat generated directly or indirectly using the combustion exhaust gas of the gas and the cathode exhaust air as an energy source, so it is improved when the low-temperature fuel cell is restarted. The time required for temperature raising of the mass device can be shortened, and thus the start-up time of the low temperature fuel cell can be shortened. For example, in the case of the above-mentioned 200 kW class PAFC, it is possible to shorten the start-up time of the reformer from the current 4 hours to about 1 hour by applying such heating to the reformer.
[0022]
Here, the “directly used as an energy source” mode is modified by the heat held by one or both of the fuel electrode exhaust gas and the air electrode exhaust air of the high-temperature fuel cell, or by the combustion exhaust gas itself. This is a mode of heating the mass device, for example, introducing the fuel electrode exhaust gas or air electrode exhaust air into the combustion furnace of the reformer and heating it from the inside, or heating around the reformer There is a specific mode in which piping is installed and the fuel electrode exhaust gas or air electrode exhaust air is circulated there. Further, the mode of “indirectly used as an energy source” is a method in which a heat generation source such as a burner is operated by using fuel electrode exhaust gas and air electrode exhaust air of a high-temperature fuel cell as fuel, and secondary exhaust gas such as combustion exhaust gas obtained thereby. A mode in which the reformer is heated in the same manner as described above with a typical heat medium can be mentioned.
[0023]
A hybrid fuel cell system according to a second aspect is the fuel cell system according to the first aspect, wherein the fuel cell exhaust gas and the air electrode exhaust air of the high temperature fuel cell are respectively introduced into the reformer burner of the low temperature fuel cell as burner fuel. This allows the reformer burner to operate in a hot banking mode that keeps the reformer warm, and at least a portion of the time between the low temperature fuel cell shutdown and restart. The reformer burner is operated in the hot banking mode.
[0024]
This configuration is a preferred mode of “indirectly using as an energy source” the fuel electrode exhaust gas and the air electrode exhaust air of the high-temperature fuel cell, and the reformer itself serves as a heat source for heating the reformer. The reformer burner possessed uses the fuel electrode exhaust gas and air electrode exhaust air as fuel for the reformer burner, and operates the reformer burner in the hot banking mode when the low-temperature fuel cell is stopped. Since the configuration is adopted, there is an advantage that it is not necessary to newly install heating equipment. Specifically, there is an embodiment in which the reformer is heated by introducing a part or all of the combustion gas obtained by operating the reformer burner into the combustion furnace of the reformer. .
[0025]
A hybrid fuel cell system according to claim 3 is the hybrid fuel cell system according to claim 1, wherein combustion exhaust gas or air electrode exhaust air obtained by burning the fuel electrode exhaust gas and air electrode exhaust air of the high temperature fuel cell is used as the low temperature fuel. It is possible to introduce into the furnace of the battery reformer, and at least part of the time from when the low-temperature fuel cell is stopped to when it is restarted, combustion exhaust gas of the fuel electrode exhaust gas and air electrode exhaust air, Alternatively, the reformer is maintained in a heated state by introducing the air electrode exhaust air into the furnace of the reformer.
[0026]
This configuration is an aspect in which the air exhaust gas of the high-temperature fuel cell is directly used as an energy source, or the combustion exhaust gas of the fuel electrode exhaust gas and the air electrode exhaust air is indirectly used as an energy source. For example, when a solid electrolyte type (SOFC) battery is used as the high-temperature fuel cell used in the present invention, the air cathode exhaust air reaches about 500 ° C. to 600 ° C., and this is introduced into, for example, a reformer combustion furnace. Then, the reformer can be warmed to such an extent that the startup time can be shortened.
[0027]
The hybrid fuel cell system according to claim 4 is characterized in that, in the system according to any one of claims 1 to 3, the reformer is brought into a warmed state immediately before the restart. is there.
[0028]
The reformer does not necessarily have to be heated during the entire time from when the low-temperature fuel cell is stopped to when it is restarted. That is, if the heating state is secured immediately before the restart, the effect of shortening the start time can be obtained. Therefore, heating of the reformer according to the present invention is performed at least in a time zone immediately before restart (for example, several hours before restart), and in other time zones, the fuel electrode exhaust gas of the high-temperature fuel cell and By using the air electrode exhaust air or the energy of these combustion exhaust gases for other purposes, more effective energy utilization can be achieved.
[0029]
The hybrid fuel cell system according to claim 5 is characterized in that, in the system according to any one of claims 1 to 3, the reformer is maintained in a warmed state at a constant temperature.
[0030]
If the reformer is warmed to a certain level or higher, and if it is warmed for at least part of the time between when the low-temperature fuel cell is stopped and restarted, the start-up time can be shortened. Obtainable. However, when a heat cycle is applied to the reformer, the adverse effect of shortening the life of the reformer tube tends to occur. However, the reformer is added at a constant temperature from the time when the low-temperature fuel cell is stopped until it is restarted. It is desirable to keep the temperature of the reforming tube so that a large heat change is not applied to the reforming tube.
[0031]
The hybrid fuel cell system according to claim 6 is the system according to any one of claims 1 to 3, wherein the reformer includes at least a desulfurizer and a carbon monoxide transformer as ancillary equipment, and the ancillary equipment is provided. Is provided with a heat medium circulation system, and when the reformer is heated, the auxiliary equipment is also heated so that the catalyst temperature is maintained in the vicinity of the operating temperature. And
[0032]
Thus, if the auxiliary equipment of the reformer is also heated, the catalyst temperature of the desulfurizer and the carbon monoxide converter can be maintained in the vicinity of the operating temperature. As a result, the reformer and its It is possible to shorten the temperature raising time of the entire reformer composed of incidental facilities.
[0033]
A hybrid fuel cell system according to a seventh aspect is the system according to any one of the first to third aspects, wherein the low-temperature fuel cell is provided with a cell cooling water system, and is restarted when the low-temperature fuel cell is stopped. The battery cooling water system is kept warm by heat generated directly or indirectly by the high-temperature fuel cell during at least a part of the time.
[0034]
The temperature of the battery cooling water and the battery stack also affects the start-up time of the low temperature fuel cell. Therefore, the fuel cell exhaust water of the high temperature fuel cell and the air electrode exhaust air, or the steam generated by the exhaust heat boiler heated by the combustion exhaust gas, is used to keep the battery cooling water system warm. The startup time can be further shortened.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First embodiment]
FIG. 1 shows a configuration of a case where a pressurized high temperature fuel cell (HTFC) 1 and an atmospheric pressure low temperature fuel cell (LTFC) 2 are provided as an example of a basic system according to the hybrid fuel cell system of the present invention. FIG. The combination of fuel cells is not limited to this, and other than this, a pressurized high temperature fuel cell / pressurized low temperature fuel cell, a normal pressure high temperature fuel cell / pressurized low temperature fuel cell, a normal pressure high temperature Type fuel cell / normal pressure low temperature type fuel cell can be considered. In the fuel cell format, solid oxide fuel cells (SOFC) and molten carbonate fuel cells (MCFC) are used as high temperature fuel cells, while phosphoric acid fuel cells (PAFC) are used as low temperature fuel cells. And a polymer electrolyte fuel cell (PEFC) can be selected.
[0036]
In FIG. 1, a pressurized high-temperature fuel cell 1 includes a desulfurizer 11, a heat exchanger 13, and a battery stack 10 as a battery body as a basic configuration. The battery stack 10 includes a fuel electrode 101 and an air electrode 102, and a power generator 14 that is operated by utilizing the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G that are discharged therefrom, and the exhaust heat recovery boiler 3 are additionally provided. Has been.
[0037]
In the pressurized high-temperature fuel cell 1 configured as described above, the fuel NG1 supplied from the fuel source NG such as natural gas (propane gas, naphtha, kerosene, etc.) is first pressurized by the fuel boosting compressor 1C. And sent to the desulfurizer 11. In the desulfurizer 11, sulfur as an odorant contained in the fuel is removed and sent to the fuel electrode 101 of the battery stack 10 through the heat exchanger 13. Here, for example, when a molten carbonate fuel cell (MCFC) is adopted as the pressurized high-temperature fuel cell 1, the operating temperature of the battery stack 10 is about 650 ° C., and the steam is sent to the battery stack 10 together with water vapor. While the fuel NG1 is reformed inside the battery stack 10 to hydrogen, carbon monoxide, and carbon dioxide, most of the hydrogen and carbon monoxide react with carbonate ions at the fuel electrode 101 to produce water and carbon dioxide. Generate electricity and generate electricity. On the other hand, in the air electrode 102 of the battery stack 10, oxygen and carbon dioxide in the air are taken into carbonate ions, and these carbonate ions move to the fuel electrode 101 through the electrolyte 103, and carbonate ions as the reaction source. Supply.
[0038]
As described above, in the MCFC, the utilization rate of hydrogen in the fuel electrode 101 is generally about 70 to 80%, and the remaining hydrogen is discharged as the fuel electrode exhaust gas 101G. The oxygen utilization rate in the air at the air electrode 102 is about 50 to 60%, and the remaining air is discharged as air electrode exhaust air 102G. In the case of MCFC, the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G are discharged separately from the battery stack 10. The discharged fuel electrode exhaust gas 101G and the air electrode exhaust air 102G are returned to the fuel system and the air system by the recirculation blower for effective use. A part of the fuel electrode exhaust gas 101G is sent to the air system, and carbon dioxide is supplied to the air electrode 102 for reuse. Further, surplus fuel electrode exhaust gas 101G and air electrode exhaust air 102G can also be used as a drive source for the gas turbine.
[0039]
In this embodiment, the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G are guided to the burner 15 by the pipe lines 101M and 102M, respectively, and burned, and the gas turbine 141 of the power generator 14 is rotated by the combustion gas. The generator 140 is configured to generate power, and the exhaust gas from the battery stack 10 is utilized. A compressor 142 is connected to the rotating shaft of the turbine 141, and the compressor 142 takes in outside air to generate pressurized air, which is sent to the air electrode 102. As described above, the exhaust gas from the battery stack 10 is also used as an operation source of its own air electrode 102.
[0040]
In addition, in order to utilize the combustion exhaust gas 15G of the burner 15, the combustion exhaust gas 15G is guided to the exhaust heat recovery boiler 3 to recover the heat. Inside the exhaust heat recovery boiler 3, steam, high-temperature water, and low-temperature water are generated by the steam generator 31, the high-temperature water generator 32, and the low-temperature water generator 33, respectively, and are used for refrigerators, heating, hot water supply, etc. To be served. On the other hand, the combustion exhaust gas 15G recovered by heat is led out to the water recovery unit 34 after leaving the exhaust heat recovery boiler 3, and the water recovery unit 34 recovers and discharges moisture contained in the combustion exhaust gas 15G. It is discharged from the cylinder 35.
[0041]
Next, the normal pressure low temperature fuel cell (LTFC) 2 includes a desulfurizer 21, a reformer 22, heat exchangers 23 and 26, a carbon monoxide converter 24, a steam separator 25, and a battery body as basic components. The battery stack 20 is provided as a part.
[0042]
In the normal-pressure low-temperature fuel cell 2 configured as described above, the fuel NG2 supplied from the fuel source NG is sent to the desulfurizer 21 to remove the sulfur component, and sent to the reformer 22 together with the steam. Here, when a polymer electrolyte fuel cell (PEFC) is adopted as the atmospheric pressure low temperature fuel cell 2, the desulfurized fuel and water vapor introduced into the reformer 22 are modified to 700 to 800 ° C. The reformer 22 is heated and reacted inside and separated into hydrogen, carbon monoxide, and carbon dioxide to generate reformed gas. Subsequently, through the heat exchanger 23, carbon monoxide is converted into hydrogen and carbon dioxide by the carbon monoxide converter 24, and the carbon monoxide concentration is set to a certain value (several percent) or less. Thereafter, the hydrogen-rich reformed gas is introduced into the fuel electrode 201 of the PEFC battery stack 20 via the steam separator 25 and the heat exchanger 26. The operating temperature of the battery stack 20 is 80 to 100 ° C., and most of the introduced hydrogen becomes hydrogen ions at the fuel electrode 201, and the hydrogen ions move to the air electrode 202 through the electrolyte 203. Atmospheric pressure air is introduced into the air electrode 202 from the air supply device 27 including the electric motor 270 and the blower 271, oxygen in the air is taken in, ionized, and moved to the oxygen ion and the air electrode 202. The hydrogen ions react with each other to generate electricity.
[0043]
The utilization rate of hydrogen at the fuel electrode 201 is 70 to 80%, and the remainder is discharged as fuel electrode exhaust gas 201G. Further, the oxygen utilization rate in the air at the air electrode 202 is 50 to 60%, and the rest is discharged as air electrode exhaust air 202G. Therefore, the fuel electrode exhaust gas 201G and the air electrode exhaust air 202G are introduced into the burner 221 of the reformer 22 through the pipe lines 201S and 202S, and can be used effectively as fuel for heating the reformer 22. It is illustrated.
[0044]
The pressurized high-temperature fuel cell 1 and the normal-pressure low-temperature fuel cell 2 configured as described above are juxtaposed, and the high-efficiency (pressurized) high-temperature fuel cell 1 is excellent in start / stop characteristics and load changeability ( Normal pressure) Utilizing the characteristics of the low-temperature fuel cell 2 respectively, only the pressurized high-temperature fuel cell 1 is operated at night and on holidays, and the normal-pressure low-temperature fuel cell 2 is stopped. A hybrid fuel cell system can be constructed such that the low temperature fuel cell 2 is also operated in combination. In such a hybrid fuel cell system, in the present invention, the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G of the (pressurized) high-temperature fuel cell 1 or the energy of these combustion gases is further provided. This is characterized in that the reformer 22 is kept in a hot banking state when the (normal pressure) low-temperature fuel cell 2 is stopped, and the time required for restarting is greatly reduced.
[0045]
There are no particular limitations on the mode of utilization of the energy provided in the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G, as long as the reformer 22 can be kept in the hot banking state, but the preferred mode is as shown in FIG. And the air electrode exhaust air 102G are introduced into the reformer burner 221 as fuel and burned to maintain the reformer 22 in a hot banking state. Specifically, control valves 101B and 102B are respectively provided at intermediate portions of the pipelines 101M and 102M for supplying the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G to the burner 15, and the bypass pipelines 101S and 102S are drawn out, Connected to the fuel supply port of the reformer burner 221.
[0046]
The operation of the hybrid fuel cell system configured as described above will be described. During high loads such as daytime, the pressurized high temperature fuel cell 1 and the normal pressure low temperature fuel cell 2 are operated in combination. At this time, the control valves 101B and 102B close the flow paths to the bypass piping lines 101S and 102S, and send the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G only to the burner 15 that operates the power generation device 14. . On the other hand, the reformer burner 221 generates combustion gas exclusively from the fuel electrode exhaust gas 201G and the air electrode exhaust air 202G exhausted from the PEFC battery stack 20.
[0047]
On the other hand, at low loads such as late at night or on holidays, the pressurized high-temperature fuel cell 1 continues to operate, but the normal-pressure low-temperature fuel cell 2 is stopped. At this time, the control valves 101B and 102B also open the flow paths to the bypass piping lines 101S and 102S, and reform the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G, not only the burner 15 but also a part thereof. It is also sent to the burner 221. The supply of the fuel electrode exhaust gas 201G and the air electrode exhaust air 202G from the pipelines 201S and 202S to the reformer burner 221 is stopped because the atmospheric pressure low temperature fuel cell 2 is stopped. The reformer burner 221 can be operated by supplying the exhaust gas 101G and the cathode exhaust air 102G, and combustion gas is generated in a hot banking mode in which the reformer 22 is kept in a heated state (hot banking state) by a control device (not shown). It is controlled as follows.
[0048]
Subsequently, when the pressurized high temperature fuel cell 1 is switched from the single operation state to the combined operation state of the pressurized high temperature fuel cell 1 and the normal pressure low temperature fuel cell 2, the control valves 101B and 102B are bypassed. The flow paths to 101S and 102S are “closed”.
[0049]
Here, when the normal pressure low temperature fuel cell 2 is started, the reformer 22 is in a hot banking state during the stop period, so that the reformer 22 is operated as compared with the case where the temperature is raised from room temperature. The time required to reach the temperature can be greatly shortened.
[0050]
The reformer 22 does not necessarily have to be heated during the entire time from when the atmospheric pressure low temperature fuel cell 2 is stopped to when it is restarted. That is, if the warmed state is secured immediately before the reformer 22 is restarted, the effect of shortening the startup time can be obtained. Therefore, when the load pattern is fixed to some extent, it is desirable to control so that the reformer 22 is heated in the time zone immediately before the restart (for example, several hours before the restart). If such control is performed, in the time zone when the reformer 22 is not heated, for example, the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G of the pressurized high-temperature fuel cell 1 are supplied only to the burner 15, The power generator 14 can be operated at a high output.
[0051]
In addition, if the reformer 22 is in a warmed state of a certain level or more, the effect of shortening the startup time can be obtained. However, when a heat cycle is applied to the reformer 22, there is also a disadvantage that the adverse effect that the life of the reforming tube is shortened easily occurs. When this point of view is emphasized, a “constant” temperature (for example, a constant temperature of 600 to 700 ° C.) at which the operation is resumed in the entire time from when the atmospheric pressure low temperature fuel cell 2 is stopped to when it is restarted. It is desirable that the reformer 22 is always heated at the temperature) so that a large heat change is not given to the reforming pipe.
[0052]
Further, in the embodiment shown in FIG. 1, not only the reformer 22 but also its incidental equipment can be heated to prepare for a quick restart. That is, in order to perform warming for starting up the adjacent equipment of the reformer 22, such as the desulfurizer 21, the reformer 22, the heat exchanger 23, the carbon monoxide converter 24, and the steam separator 25. The pipe line 4M is laid so as to circulate through these facilities. A heat medium 41 such as nitrogen gas can freely flow through the pipe line 4M and is circulated through the pipe line by a blower 42.
[0053]
If such a configuration is added, when the reformer 22 is in a hot banking state, this heat is circulated through the pipeline 4M and transferred to the incidental equipment, so that the desulfurizer 21 and the monoxide can be obtained. The carbon transformer 24 and the like can also be brought into a hot banking state. As a result, the catalyst temperature of these devices can be maintained in the vicinity of the operating temperature, and as a result, the temperature raising time of the entire reformer comprising the reformer 22 and its associated equipment can be shortened.
[0054]
In the system of the above embodiment, the amount of the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G required for hot banking of the reformer 22 and its ancillary equipment is determined by each reaction of the reformer 22, desulfurizer 21, and the like. Since it varies depending on the size of the container, the capacity of the piping and the heat dissipation characteristics from the surface area, it may be set according to the situation as appropriate. For example, in the case of a 500 kW class atmospheric pressure low temperature phosphoric acid fuel cell (PAFC), the LNG fuel flow rate (20 to 40 Nm) required for the reformer burner at start-up is used. ³ / H) is 30 Nm, which is the LNG fuel flow rate conversion amount of the fuel electrode exhaust gas at the rated load ³ / H (153Nm ³ /H×0.2), and the amount of heat required to operate the reformer burner 221 in the hot banking mode is further reduced.
[0055]
By the way, generally, the conditions for maintaining the low temperature fuel cell in the restart standby state are as follows.
Reformer temperature 600-700 ° C
Desulfurizer temperature 250-300 ° C
Carbon monoxide transformer temperature 150-200 ° C
This temperature is determined by the operating temperature of the catalyst filled in each reaction vessel. By keeping the temperature in the vicinity of the operating temperature, the starting characteristics can be greatly improved.
[0056]
In the above-described embodiment, the case where the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G of the pressurized high-temperature fuel cell 1 are burned by the reformer burner 221 has been described. If only the air electrode exhaust air 102G is surplus after being recirculated in the above, if the temperature of the air electrode exhaust air 102G itself is sufficient to heat the reformer 22 to the hot banking state, It can be used as a direct energy source. For example, when a molten carbonate type (MCFC) fuel cell is used as the high-temperature fuel cell 1 used in the present invention, the air electrode exhaust air reaches about 500 ° C to 600 ° C. It is possible to warm the reformer 22 to the restart standby temperature. Therefore, in this case, if the cathode exhaust air 102G is directly introduced into the combustion furnace of the reformer 22, the reformer 22 can be heated to such a degree that it can be quickly restarted. In this manner, the reformer 22 may be held in a hot banking state.
[0057]
[Second Example]
As another embodiment of the present invention, FIG. 2 shows a hybrid fuel cell system of an atmospheric high temperature fuel cell (HTFC) 5 and a pressurized low temperature fuel cell (LTFC) 6. The outline of this system is that a fuel electrode exhaust gas and an air electrode exhaust air respectively generated at the fuel electrode 501 and the air electrode 502 of the atmospheric pressure high-temperature fuel cell 5 are combusted in a combustion chamber 505 provided in the fuel cell. After the stack 50 is kept at a high temperature, the combustion exhaust gas 505G is discharged. And this reformed gas is manufactured by using this combustion exhaust gas 505G as a fuel for heating in the furnace of the reformer 62 of the pressurized low temperature type fuel cell 6, and the reformed gas is used as a pressurized type as a pressurized low temperature type. The fuel electrode 6 is supplied to the fuel electrode 601 to generate electric power. Further, the fuel electrode exhaust gas 601G of the pressurized low-temperature fuel cell 6 is used as fuel for the burner 67 for operating the turbo compressor generator 68, and the air electrode exhaust air 602G is used for combustion. It is used as an oxidizing agent. In other words, this hybrid system is a system that effectively uses the high-temperature combustion exhaust gas from the normal-pressure high-temperature fuel cell 5 as the fuel for the reformer 62 of the pressurized low-temperature fuel cell 6, and aims to increase the power generation efficiency. Yes. Hereinafter, the system of the present embodiment will be described in detail.
[0058]
In FIG. 2, the normal pressure high temperature fuel cell 5 includes a battery stack 50 as a battery main body, a desulfurizer 51, an electric motor 530 for sending air to the air electrode 502 of the battery stack 50, and a blower 531. It has. The fuel NG3 supplied from the fuel source NG is supplied to the fuel electrode 501 of the battery stack 50 at normal pressure after the sulfur content is removed by the desulfurizer 51.
[0059]
While the fuel NG3 sent to the fuel electrode 501 is reformed into hydrogen, carbon monoxide, and carbon dioxide inside the high-temperature battery stack 50, most of the hydrogen and carbon monoxide are oxygen ions in the fuel electrode 501. It reacts to generate electricity. On the other hand, in the air electrode 502 of the battery stack 50, oxygen in the air sent from the air supply device 53 is taken in and ionized, and the oxygen ions move to the fuel electrode 501 to convert oxygen ions as the reaction source. Supply.
[0060]
The fuel electrode exhaust gas and the air electrode exhaust air discharged from the fuel electrode 501 and the air electrode 502 undergo a combustion reaction in the combustion chamber 505 inside the battery stack 50 to become high-temperature gas. The heat of this high-temperature gas is used to maintain the battery stack 50 at a high temperature (700 to 1000 ° C. in the case of a solid oxide type) that is the operating temperature of the high-temperature fuel cell, and then discharged from the cell stack 50 as combustion exhaust gas 505G. Is done. The combustion exhaust gas 505G is configured to be supplied to the burner unit 621 of the reformer 62 that generates the reformed gas for the pressurized low-temperature fuel cell 6 via the pipe line 505M. Further, the combustion exhaust gas 62-G1 of the burner portion 621 is sent to the exhaust heat recovery boiler 3 via the heat exchanger 622 through the piping 62-M1, and heat recovery is performed.
[0061]
The pressurized low temperature fuel cell 6 includes a desulfurizer 61, a reformer 62, heat exchangers 63 and 66, a carbon monoxide converter 64, a steam / water separator 65, and a battery stack 60 as a battery main body as basic components. It has. In such a configuration, the fuel NG4 supplied from the fuel source NG is pressurized by the fuel pressurizing compressor 6C, sent to the desulfurizer 21, the sulfur content is removed, and sent to the reformer 62 together with steam. The desulfurized fuel and water vapor introduced into the reformer 62 are heated and reacted inside the reformer 62 heated to the reforming temperature, and separated into hydrogen, carbon monoxide, and carbon dioxide to produce reformed gas. Generated. Subsequently, the carbon monoxide is converted into hydrogen and carbon dioxide by the carbon monoxide converter 64 via the heat exchanger 63, and the reformed gas passes through the steam separator 65 and the heat exchanger 66 to be battery stack. 60 fuel electrodes 601 are introduced.
[0062]
Most of the introduced hydrogen becomes hydrogen ions at the fuel electrode 601, and the hydrogen ions move to the air electrode 602. Pressurized air is introduced into the air electrode 602 from a compressor 682 to be described later, oxygen in the air is taken in and ionized, and the oxygen ions react with the hydrogen ions that have moved to the air electrode 602. It generates electricity.
[0063]
In the present embodiment, a turbo compressor generator 68 is disposed at the subsequent stage of the pressurized low-temperature fuel cell 6, and the fuel electrode exhaust gas 601G and the air electrode exhaust air 602G discharged from the battery stack 60 are discharged from the generator. It is configured to generate electricity by being driven using. The turbo compressor generator 68 includes a generator 680 and a turbine 681, and the turbine 681 is rotated by the combustion gas in the burner unit 67. A piping path is installed to supply the fuel electrode exhaust gas 601G and the air electrode exhaust air 602G as fuel for the burner portion 67.
[0064]
The turbo compressor generator 68 includes a compressor 682 disposed coaxially with the turbine 681, and the compressor 682 is driven as the turbine 681 rotates to produce compressed air A. The pressurized air A is sent to the air electrode 602 of the battery stack 60.
[0065]
The combustion exhaust gas from the burner portion 67 is guided to the exhaust heat recovery boiler 3 through the piping 68M and recovered. A pipe line 62-M2 for sending the combustion exhaust gas 62-G2 of the reformer burner 621 is connected to the pipe line 68M so that the combustion exhaust gas of the burner part 67 and the combustion exhaust gas of the reformer burner part 621 are merged. Alternatively, the exhaust heat recovery boiler 3 may be supplied.
[0066]
In such a hybrid fuel cell system, the generation of reformed gas by the reformer 62 is not necessary while the pressurized low temperature fuel cell 6 is stopped at midnight or on weekends. The combustion exhaust gas 505G of the fuel cell 5 becomes redundant. Therefore, a bypass pipe 505S is provided in the middle of the pipe line 505M that connects the battery stack 50 and the reformer burner part 621 to the burner part of the exhaust heat recovery boiler 3, and the combustion exhaust gas 505G is provided. Is used as a heat source for heating the exhaust heat boiler 3.
[0067]
Here, in the present invention, not all of the surplus combustion exhaust gas 505G is supplied to the burner portion of the exhaust heat recovery boiler 3, but a part thereof is introduced into the reformer burner portion 621 of the pressurized low temperature fuel cell 6. And make it burn. Therefore, the switching valve 505B supplies the combustion exhaust gas 505G only to the reformer burner unit 621 with the flow path to the bypass pipe line 505S closed when the pressurized low temperature fuel cell 6 is in operation. When the low-temperature fuel cell 6 is stopped, the flow path to the bypass pipeline 505S is opened, and the combustion exhaust gas 505G is branched to the reformer burner section 621 and the burner section of the exhaust heat recovery boiler 3. Controlled to supply.
[0068]
Thereby, the inside of the furnace of the reformer 62 can be maintained in a hot banking state of about 500 to 600 ° C., and the time required for restarting the pressurized low-temperature fuel cell 6 can be shortened. Further, similarly to the above-described embodiment, a piping 4M for performing warming for starting is also provided for the incidental equipment (reaction vessel) of the reformer 62, and a heat medium 41 such as nitrogen is supplied by the blower 42. If it is circulated, the desulfurizer 61, the carbon monoxide transformer 64, and the like can be kept in a startup standby state of about 120 to 150 ° C., which can contribute to shortening of the startup time.
[0069]
In the above embodiment, when a polymer electrolyte fuel cell (PEFC) is selected as the pressurized low-temperature fuel cell 6 to form a hybrid system, the temperature of the fuel gas entering the cell stack is about 80 ° C. The carbon monoxide concentration inside must be 10 ppm or less, and it is necessary to install a carbon monoxide selective oxidizer.
[0070]
FIG. 3 shows a temperature rising time characteristic of a general reformer, and FIG. 4 shows a temperature rising time characteristic of a carbon monoxide converter and a steam / water separator (steam separator), respectively. In the case of having such temperature rising time characteristics, the inside of the furnace of the reformer 62 is about 500 to 600 ° C., and the desulfurizer 61 and the carbon monoxide transformer 64 are about 120 to 150 ° C. In the hot banking state, when actually restarting the pressurized low temperature fuel cell 6 and starting power generation, the required operating temperature can be shortened by about 3 hours and the operation can be started in about 1 hour. It can be done.
[0071]
By the way, since the cell temperature of the low-temperature fuel cell is lowered during the stop, it is necessary to raise the temperature of the fuel cell to the operating temperature when starting up the battery stack. The temperature increase rate must maintain a temperature increase rate of about 50 ° C./h from the viewpoint of cell protection. For example, in the case of a phosphoric acid fuel cell, the operating temperature of the cell is about 200 ° C. as shown in FIG. 5, but when the holding temperature at the time of stop is 60 ° C., the temperature increases from 60 ° C. to 200 ° C. It will take about 3 hours. Further, the cell operating temperature of the polymer electrolyte fuel cell is as low as 80 to 100 ° C. However, if the temperature is raised from room temperature, it takes about 0.5 to 1 hour.
[0072]
As described above, there is a situation that takes a considerable time to start the battery stack. However, if the cell temperature can be maintained at a high level within a range that does not affect the cell life, it is effective to shorten the start-up time. It can be said. Since the fuel gas and air inside the cell are replaced with nitrogen while the low temperature fuel cell is stopped, even if the cell is held at a high temperature, the cell life is not adversely affected. Therefore, the present invention provides a hybrid fuel cell system that keeps the cell temperature at a high temperature when the low-temperature fuel cell is stopped and prepares for further quick restart. Specific examples are described in detail below.
[0073]
[Third embodiment]
FIG. 6 shows a system similar to the hybrid fuel cell system previously shown in FIG. 1 in which the pressurized high temperature fuel cell (HTFC) 1 and the atmospheric pressure low temperature fuel cell (LTFC) 2 are provided. However, in this embodiment, the steam generator 31 of the exhaust heat recovery boiler 3 that operates by the exhaust heat of the pressurized high temperature fuel cell 1 is used as the steam separator 7 that is responsible for cooling the cell stack 200 of the atmospheric pressure low temperature fuel cell 2. The case where the structure which heat-insulates a cell using the cooling water system piping path 7M of the said battery stack 200 by introducing the vapor | steam produced | generated is shown is shown. A combustion chamber 105 for burning the fuel electrode exhaust gas and the air electrode exhaust air is provided inside the battery stack 10 of the pressurized high-temperature fuel cell 1, and the combustion exhaust gas 105G is exhausted by the pipe line 105M and the bypass pipe line 105, respectively. 1 is different from the configuration of FIG. 1 in that the heat recovery boiler 3 is guided to the burner portion 15 of the heat recovery boiler 3 and the burner portion 221 of the reformer 22.
[0074]
FIG. 7 is a detailed view of the steam separator 7 portion. The steam separator 7 has cooling water W inside the container 70, and a cooling plate (cooling) in which the cooling water system pipe line 7 </ b> M is laminated at a rate of one per several cells laminated inside the battery stack 200. The water pipe is installed to return to the container 70 again. The cooling water W is allowed to flow freely through the pipe line 7M by the battery cooling water circulation pump 7P. While the normal pressure low-temperature fuel cell 2 is in operation, the pipe line 7M functions as an original cooling water system, absorbs heat generated in the battery stack 200, returns to the container 70, and heat is generated. It works to escape as steam.
[0075]
On the other hand, while the normal pressure low temperature fuel cell 2 is stopped, the pipe line 7M functions as a warm water system. That is, the heat exchanger 31H is disposed in the container 70 so as to be in contact with the cooling water W, and the steam generated by the steam generator 31 of the exhaust heat recovery boiler 3 can flow through the piping 3M. . Thereby, the cooling water W is heated by the steam, and the heated water is sent into the battery stack 200 by the circulation pump 7P, and the inside of the battery stack 200 is kept at a constant temperature.
[0076]
In order to prevent excessive heating, a control valve 30B is provided in the pipe line 3M, a thermometer 30T for measuring the temperature of the cooling water W is disposed in the container 70, and the temperature measurement result of the thermometer 30T. It is desirable to control the steam supply amount from the steam generator 31 so that the control valve 30B can be adjusted based on the above, so that the water temperature is maintained at a constant temperature.
[0077]
By adopting such a configuration, for example, in a phosphoric acid fuel cell, if the temperature of the cell stack is kept at about 150 ° C., the portion of 60 ° C. to 150 ° C. in the startup curve of FIG. Time can be greatly reduced.
[0078]
When a polymer electrolyte fuel cell (PEFC) is selected as the low-temperature fuel cell 2, the PEFC has a low cell operating temperature of 80 ° C., so that the exhaust heat recovery boiler 3 serves as a heat source for keeping the battery stack 200 warm. High temperature water at 90 ° C. generated by the high temperature water generator 32 may be used.
[0079]
As a specific method of operating the hybrid fuel cell system described above, it is necessary to predict when to start the low-temperature fuel cell based on seasonal or monthly heat / electric load time-specific data. Taking time into account, it is necessary to prepare for operation before the load increases. That is, the reformer, the incidental equipment, and the battery stack of the low-temperature fuel cell are made to reach the hot banking state in accordance with the startup plan. In this way, the activation pattern is determined in advance, and after the activation, the load of the low temperature fuel cell is controlled to follow the demand load.
[0080]
【The invention's effect】
According to the hybrid fuel cell system of the present invention as described above, by setting the reformer to a heated state when the low-temperature fuel cell is stopped, for example, in the case of a 200 kW class PAFC, the startup time is reduced to the current level. It can be shortened from 4 hours to 1 hour. Therefore, the current startup time for DSS operation of a steam power plant is 150 to 160 minutes, and the startup time for DSS operation of a gas turbine combined power plant is about 70 to 80 minutes. The time required to start up to a level comparable to that can be reduced. In addition, since the fuel electrode exhaust gas and air electrode exhaust air of the high temperature fuel cell, or these combustion exhaust gases are utilized, no fuel or electric power required for heating the reformer is required, and DSS operation and WSS operation are not required. The merit of improving the economic efficiency in is produced. Therefore, there is an effect that the usability of the system in which the high / low temperature fuel cell is hybridized is greatly improved.
[0081]
In addition, shortening the start-up time of the low-temperature fuel cell enables flexible hybrid operation. When the demand load is low, stopping the low-temperature fuel cell reduces the minimum load in the entire fuel cell system, resulting in a wide range. Operation in the load area is possible. That is, the high temperature fuel cell operates at a substantially constant rated load, and the low temperature fuel cell bears the load change and load of starting and stopping, thereby enabling a wide load change of about 40 to 100% for the entire system. Become. Such a hybrid fuel cell system is not limited by the installation capacity equivalent to the minimum load of the consumer, which is a drawback when installing a high-temperature fuel cell, and it is possible to install a larger capacity machine and improve operability. Also play.
[0082]
Even when the low-temperature fuel cell is stopped, the reformer can be kept warm by using the fuel electrode exhaust gas and air electrode exhaust air of the high-temperature fuel cell, or these combustion exhaust gas, and is cooled to room temperature. Therefore, it is possible to prevent the temperature history (normal temperature to 800 ° C.) repeated at each start and stop from being applied to the reforming tube. Therefore, thermal cycle fatigue of the reforming tube does not occur, and there is an effect that the life of the reforming tube can be extended.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment of a hybrid fuel cell system according to the present invention.
FIG. 2 is a block diagram showing a second embodiment of the hybrid fuel cell system according to the present invention.
FIG. 3 is a graph showing a temperature rise time characteristic of a general reformer.
FIG. 4 is a graph showing the temperature rise time characteristics of a general carbon monoxide converter and a steam / water separator (steam separator).
FIG. 5 is a graph showing a cell stack starting curve of a low-temperature fuel cell (PAFC), where (a) shows a normal pressure type and (b) shows a pressurized type curve.
FIG. 6 is a block diagram showing a third embodiment of the hybrid fuel cell system according to the present invention.
7 is a block diagram showing details of a water vapor separator portion in FIG. 6. FIG.
FIG. 8 is a block diagram showing an example of a conventional high-temperature fuel cell.
FIG. 9 is a block diagram showing an example of a conventional low-temperature fuel cell.
FIG. 10 is a block diagram illustrating an example of a customer load pattern.
[Explanation of symbols]
1 (Pressure) High-temperature fuel cell
101G Fuel electrode exhaust gas
102G air electrode exhaust air
11, 21, 51, 61 Desulfurizer
2 (Normal pressure) Low temperature fuel cell
22 Reformer
221 reformer burner
24,64 carbon monoxide transformer
3 Waste heat recovery boiler
5 (Normal pressure) High-temperature fuel cell
501G Fuel electrode exhaust gas
502G Air electrode exhaust air
6 (Pressure) Low-temperature fuel cell
62 Reformer
621 Reformer burner
7 Steam separator

Claims (7)

In a hybrid fuel cell system comprising a high-temperature fuel cell and a low-temperature fuel cell equipped with a reformer,
Fuel electrode exhaust gas and / or air electrode exhaust air of the high temperature fuel cell, or combustion exhaust gas of the fuel electrode exhaust gas and air electrode exhaust air, at least partly from the time when the low temperature fuel cell is stopped until it is restarted The hybrid fuel cell system is used as a direct or indirect energy source for keeping the reformer in a heated state at a time of 2. The hybrid fuel cell system according to claim 1, wherein the fuel electrode exhaust gas and the air electrode exhaust air of the high temperature fuel cell can be freely introduced as burner fuel into the reformer burner of the low temperature fuel cell, respectively. Make the reformer burner operable in hot banking mode to keep the reformer warm,
The hybrid fuel cell system, wherein the reformer burner is operated in the hot banking mode during at least a part of time from when the low temperature fuel cell is stopped to when it is restarted. 2. The hybrid fuel cell system according to claim 1, wherein combustion exhaust gas obtained by burning the fuel electrode exhaust gas and air electrode exhaust air of the high temperature fuel cell or the air electrode exhaust air is used as a reformer for the low temperature fuel cell. Can be introduced into the furnace,
During at least part of the time from when the low-temperature fuel cell is stopped to when it is restarted, the combustion exhaust gas of the fuel electrode exhaust gas and the air electrode exhaust air, or the air electrode exhaust air is fed into the furnace of the reformer. A hybrid fuel cell system characterized in that the reformer is maintained in a heated state by being introduced. 4. The hybrid fuel cell system according to claim 1, wherein the reformer is in a warmed state immediately before restarting. 5. 4. The hybrid fuel cell system according to claim 1, wherein the reformer is maintained in a warmed state at a constant temperature. 5. The hybrid fuel cell system according to any one of claims 1 to 3, wherein the reformer includes at least a desulfurizer and a carbon monoxide converter as auxiliary equipment.
The auxiliary equipment is provided with a heat medium circulation system, and when the reformer is heated, the auxiliary equipment is also heated so that the catalyst temperature is maintained in the vicinity of the operating temperature. A hybrid fuel cell system characterized by that. The hybrid fuel cell system according to any one of claims 1 to 3, wherein the low-temperature fuel cell includes a cell cooling water system.
The battery cooling water system is kept warm by heat generated directly or indirectly by the high-temperature fuel cell during at least a part of time from when the low-temperature fuel cell is stopped to when it is restarted. Hybrid fuel cell system.

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