JP4578787B2 - Hybrid fuel cell system - Google Patents

Description

[0001]
[Industrial application fields]
The present invention hybridizes a normal-pressure high-temperature fuel cell and a pressurized low-temperature fuel cell 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 system having both high power generation efficiency and wide load operability.
[0002]
[Prior art]
As one of the categories for classifying the fuel cell, there is a classification according to the operating temperature of the battery, which is roughly divided into a high-temperature fuel cell (for example, Patent Document 1) having an operating temperature of about 600 to 1000 ° C. and an operating temperature of 200 ° C. There are low-temperature fuel cells of less than about. In addition, there is a division depending on whether fuel gas and air to be supplied to the battery stack are supplied in a pressurized state, a pressurized fuel cell that supplies pressurized gas, and a normal pressure type (low pressure) that supplies without pressing Type) fuel cell.
[0003]
FIG. 7 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. 7 (a) shows a pressurized SOFC, and FIG. 7 (b) shows a normal pressure type. Each SOFC is shown. In FIG. 7 (a), the fuel NG such as city gas is desulfurized by removing sulfur from the desulfurizer 71 and added with water vapor, and then heated by the preheater 72, and the operating temperature is 700 to 1000 ° C. It is introduced into the SOFC battery stack 70. While being reformed into hydrogen, carbon monoxide, and carbon dioxide inside the battery stack 70, most of the hydrogen and carbon monoxide react with oxygen ions at the fuel electrode 701 to generate electricity. On the other hand, the air electrode 702 of the battery stack 70 takes in oxygen in the air and ionizes it, and the oxygen ions diffuse into the electrolyte 703 and move to the fuel electrode 701. In the case of the pressurized type, it is necessary to send pressurized air to the air electrode 702. In this example, the compressor 743 is operated by a turbine 741 described later, and this is sent to the air electrode 702. .
[0004]
The basic configuration of the atmospheric pressure type SOFC shown in FIG. 7B is substantially the same as that of the pressurized type SOFC. However, since the pressurized air is not sent to the air electrode 702, the difference is that normal pressure air is sent to the air electrode 702 by the air supply device 76 including the electric motor 760 and the blower 761.
[0005]
In such an SOFC, the utilization rate of hydrogen at the fuel electrode 701 is generally 70 to 80%, and the remaining hydrogen is discharged as fuel electrode exhaust gas. Further, the oxygen utilization rate in the air at the air electrode 702 is 50 to 60%, and the remaining air is discharged as air electrode exhaust air. These fuel electrode exhaust gas and air electrode exhaust air are burned in a combustion chamber incorporated in the battery stack or an externally installed burner, and are used to maintain the battery stack at a high temperature, and then a high temperature gas of 400 to 600 ° C. As discharged.
Thus, utilization of these fuel electrode exhaust gas, air electrode exhaust air, or these combustion exhaust gas is important for improving the operability and economic efficiency of the fuel cell.
[0006]
By the way, in the case of the normal pressure type SOFC shown in FIG. 7B, these fuel electrode exhaust gas and air electrode exhaust air, or these combustion exhaust gas are also at normal pressure, and therefore these fuel electrode exhaust gas and air electrode exhaust air, or combustion The exhaust gas is also sent to the exhaust heat recovery boiler 75 via the heat exchanger 73, and is used as a burner fuel or heating heat source for the boiler, and is only used for producing steam and high-temperature water. However, when it is used as a heat source for heating a boiler, 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.
[0007]
On the other hand, in the case of the pressurized SOFC shown in FIG. 7 (a), the fuel electrode exhaust gas and the air electrode exhaust air, or these combustion exhaust gases are also high in pressure, for example, burner fuel of a gas turbine generator or high temperature / high pressure driving gas. Can be used as FIG. 7A shows an example in which such a power generation device 74 is arranged on the rear stage side of the battery stack 70.
The fuel electrode exhaust gas and the air electrode exhaust air discharged from the battery stack 70 are burned in the burner of the combustion chamber 704 in the battery stack 70 to become combustion exhaust gas, and are supplied to the power generator 74 via the heat exchanger 73. , And used as an energy source for driving the gas turbine 741. Reference numeral 75 denotes an exhaust heat recovery boiler for recovering the exhaust energy of the gas turbine 741. The gas turbine 741 operates the generator 742 to generate electricity, and also operates the compressor 743 to generate compressed air, and supplies the compressed air to the air electrode 702 of the battery stack 70. Thus, in the pressurized SOFC, it becomes possible to obtain the pressurized air for reaction at the electricity and the air electrode 702 from the surplus fuel electrode exhaust gas and the air electrode exhaust air, or these combustion exhaust gas, and the fuel electrode Exhaust gas and air electrode exhaust air, or these combustion exhaust gas can be used effectively.
[0008]
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 (500 to 1000 ° C.). Regarding the system configuration, since the battery operating temperature is low, there is no need to keep the battery stack 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 removed from the battery stack. It can be taken out and used separately.
[0009]
As described above, it is necessary to employ a pressurized type in order to generate power by using the fuel electrode exhaust gas and the air electrode exhaust air from the SOFC or MCFC battery stack, or these combustion exhaust gases in the gas turbine. However, when the pressure type is used, the power generation efficiency of the SOFC and MCFC fuel cell main body is higher than that of the normal pressure type, but the pressure resistance of the seal part in the battery stack is required to be strict, and the system becomes complicated and difficult to control. Since problems from other viewpoints such as this occur, it is generally difficult to say that the pressure type is superior to the normal pressure type. In particular, since there are few merits in adopting the pressurization type for business use of about tens of kW or in-house power generation of about several hundred kW, considering the manufacturing cost and technical difficulty, this class is normal pressure type. Is the main force. Currently, 3 to 5 kW, several tens of kW, and 200 kW classes are developed as high-temperature fuel cells, and are gradually being introduced to the market.
[0010]
Next, examples of the low temperature fuel cell include a phosphoric acid fuel cell (PAFC) and a polymer electrolyte fuel cell (PEFC). FIG. 8 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 82 which has been subjected to removal of sulfur by the desulfurizer 81 and steam is added to 700 to 800 ° C. Is done. Through the heat exchanger 83, the carbon monoxide is converted into hydrogen and carbon dioxide by the carbon monoxide converter 84, and the carbon monoxide concentration is set to a certain value (several%) or less. Thereafter, the mixed gas is introduced into the PAFC battery stack 80, and most of the introduced hydrogen becomes hydrogen ions at the fuel electrode 801, and the hydrogen ions move to the air electrode 802 through the electrolyte 803. Pressurized air is introduced into the air electrode 802, oxygen in the air is taken in and ionized, and the oxygen ions and the hydrogen ions that have moved to the air electrode 802 react to generate electricity. is there.
[0011]
In general, in the PAFC, the utilization rate of hydrogen at the fuel electrode 801 is 70 to 80%, and the remainder is discharged as fuel electrode exhaust gas 801G. Further, the oxygen utilization rate in the air at the air electrode 802 is 50 to 60%, and the remainder is discharged as air electrode exhaust air 802G. The fuel electrode exhaust gas 801 </ b> G and the air electrode exhaust air 802 </ b> G are introduced into the burner 821 of the reformer 82 and are used effectively as fuel for heating the reformer 82.
[0012]
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.
[0013]
The PAFC and PEFC also have a pressure type and a normal pressure type. When compared with the power transmission end power generation efficiency (HHV), the normal pressure type is 36 to 38%, whereas the pressure type is 41 to 42%. Therefore, it can be said that the pressurization type is preferable when the power source is used for the electric power business or the electric power generation equipment. However, the pressurization type has problems such as complicated system and difficult 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.
[0014]
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.
[0015]
[Patent Document 1]
JP 2001-76750 A
[0016]
[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. 9 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.
[0017]
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.
[0018]
The situation is almost the same in the case of a molten carbonate fuel cell (MCFC), and the 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.
[0019]
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, in the power load pattern of an office building shown in FIG. 9, 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.
[0020]
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, low-temperature fuel cells generally have a fundamental problem that power generation efficiency is considerably lower than that of high-temperature fuel cells, and there is a problem that it is difficult to economically operate a fuel cell system with a low-temperature fuel cell alone.
[0021]
On the other hand, as described above, in the case of an atmospheric pressure type fuel cell, the fuel electrode exhaust gas and the air electrode exhaust air, or these combustion exhaust gases can be used only to the extent that they can be used as burner fuels for various boilers. The fuel electrode exhaust gas and the air electrode exhaust air, or the combustion exhaust gas thereof are also at a high pressure, and it is possible to construct a cogeneration system using, for example, a burner fuel for a gas turbine generator.
[0022]
In view of such circumstances, the inventor of the present invention has a high-efficiency high-temperature fuel cell, a low-temperature fuel cell with low power generation efficiency but high operability, a normal pressure type that can constitute a system relatively easily, and a fuel The present invention has been completed by conceiving that the pressurized type capable of effectively utilizing the polar exhaust gas and the polar exhaust air is effectively combined by making use of the respective characteristics and economically operated as the entire power generation system. That is, the present invention hybridizes a high-temperature fuel cell and a low-temperature fuel cell, and effectively uses the energy of the high-temperature exhaust gas of the high-temperature fuel cell and the energy of the high-pressure exhaust gas of the pressurized fuel cell. An object of the present invention is to provide a hybrid fuel cell system with high efficiency and high operability.
[0023]
[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 including an atmospheric pressure high temperature fuel cell, a pressurized low temperature fuel cell, and a turbine generator. Then, the fuel electrode exhaust gas and the air electrode exhaust air of the normal pressure high temperature fuel cell are used as fuel for heating in the furnace of the reformer provided in the pressurized low temperature fuel cell, and the pressurized low temperature fuel The fuel electrode exhaust gas and the air electrode exhaust air of the battery are configured to be used as a turbine drive source of the turbine generator.
[0024]
The hybrid fuel cell system according to claim 2 is a hybrid fuel cell system comprising an atmospheric pressure high temperature fuel cell, a pressurized low temperature fuel cell, and a turbine generator, wherein the atmospheric pressure high temperature fuel cell. The combustion exhaust gas produced by burning the fuel electrode exhaust gas and the air electrode exhaust air is used as a heat source for in-furnace heating of the reformer provided in the pressurized low temperature fuel cell, and the pressurized low temperature fuel The fuel electrode exhaust gas and the air electrode exhaust air of the battery are configured to be used as a turbine drive source of the turbine generator.
[0025]
According to such a configuration, first, regarding operability, the (normal pressure) high-temperature fuel cell and the (pressurized) low-temperature fuel cell are combined, which is a drawback of the above-described high-temperature fuel cell. The low temperature fuel cell can flexibly compensate for the problem of rigidity against start-stop and load fluctuation. For example, if a high temperature fuel cell is loaded with a capacity corresponding to the minimum load of a consumer, and a low temperature fuel cell is loaded with a capacity obtained by subtracting the minimum load from the peak load, both of them are always used. The system can be operated efficiently, such as driving and stopping the operation of the low-temperature fuel cell on holidays or late at night.
[0026]
Secondly, regarding the efficiency of energy recovery, according to the present invention, since it is a configuration combining a normal pressure (high temperature) type fuel cell and a pressurized (low temperature) type fuel cell,
(1) The reformed gas supplied to the fuel electrode of the pressurized low-temperature fuel cell by operating the reformer with the fuel electrode exhaust gas and air electrode exhaust air of the normal pressure (high temperature) type fuel cell or these combustion exhaust gas Is generated, and a pressurized (low temperature) fuel cell generates electricity.
(2) The turbine generator is operated using the fuel electrode exhaust gas and air electrode exhaust air of the pressurized (low temperature) type fuel cell as driving sources to generate electricity.
The usage relationship is established. In other words, the fuel electrode exhaust gas and air electrode exhaust air of the normal pressure high-temperature fuel cell, or these combustion exhaust gases themselves are at high temperature but are at normal pressure. For example, a turbo compressor generator cannot be driven immediately, but reforming By using it as a heating heat source for the generator, a reformed gas for the fuel electrode of a pressurized low-temperature fuel cell is generated and the generator is driven by the exhaust gas. Is something that can be done.
[0027]
The hybrid fuel cell system according to claim 3 is the system according to claim 1 or 2, wherein the turbine generator is a turbo compressor generator, and the fuel electrode exhaust gas of the pressurized low-temperature fuel cell is supplied to the turbo generator. It is used as fuel for a burner for driving a turbine of a compressor generator, and the air cathode exhaust air of the pressurized low-temperature fuel cell is used as an oxidant for combustion of the burner.
[0028]
With this configuration, the turbo compressor generator can be operated using the fuel electrode exhaust gas and the air electrode exhaust air of the pressurized low-temperature fuel cell, and is based on the fuel electrode exhaust gas and the air electrode exhaust air. Large power generation is possible.
[0029]
According to a fourth aspect of the present invention, there is provided the hybrid fuel cell system according to the third aspect, wherein the turbo compressor generator includes at least a turbine, a generator, and a compressor for generating a pressurized gas, which are on one drive shaft. And the compressor is detachable from a power transmission system by the drive shaft via a clutch.
[0030]
If a compressor is provided in the generator as in this configuration, for example, compressed air to be sent to the air electrode of the pressurized low-temperature fuel cell can be generated by the compressor. However, in the system of the present invention, it is assumed that the pressurized low-temperature fuel cell is stopped according to the load as described above, so that the compressor does not need to be operated when stopped. In view of this, the clutch is configured to be able to be removed from the drive system when operation is unnecessary, thereby reducing power loss.
[0031]
The hybrid fuel cell system according to claim 5 is the system according to claim 1, further comprising an exhaust heat recovery boiler, wherein a part of the fuel electrode exhaust gas and the air electrode exhaust air of the atmospheric pressure high temperature fuel cell is exhausted. It is characterized by being used as fuel by bypass supply to the drive burner of the heat recovery boiler.
[0032]
The hybrid fuel cell system according to claim 6 is the system according to claim 2, further comprising an exhaust heat recovery boiler, and is generated by burning the fuel electrode exhaust gas and the air electrode exhaust air of the normal pressure high temperature fuel cell. A part of the exhausted combustion exhaust gas is bypass-supplied to the exhaust heat recovery boiler and used as a heat source for heating the exhaust heat recovery boiler.
[0033]
According to the configuration of claim 5 or 6, surplus fuel electrode exhaust gas and air electrode exhaust air, or combustion exhaust gas thereof is used to produce steam, high temperature water, or low temperature water in an exhaust heat recovery boiler. In addition to the above, when the load of the pressurized low-temperature fuel cell being hybridized is changed or stopped (when the power of the reformer is changed or stopped), the fuel electrode exhaust gas and the air electrode exhaust air, or These combustion exhaust gases can be bypassed, and a system with high operability can be constructed.
[0034]
  The hybrid fuel cell system according to claim 7 is the system according to claim 1 or 2, wherein the pressurized low-temperature fuel cell includes a water vapor separator.The steam separator includes a container having cooling water, and the cooling water is circulated through a circulation pipe line laid in a battery stack of the pressurized low-temperature fuel cell. Cooling, and by the coolingThe steam generated by the steam separator is used as a part of a turbine drive source of the turbine generator.
[0035]
If the steam separator is provided in this way, the generated steam can be used for a steam absorption type refrigerator heating device and the like, as well as the steam of the turbo compressor generator in the system of the present invention. By doing so, it can be effectively used as a power source for the generator. In addition, in summer when there is power demand but there is no heat load, the power generation can be increased and the heat generation can be reduced as much as possible. It is possible to construct a system that can flexibly respond to changes in the heat demand generated by the system.
[0036]
  The hybrid fuel cell system according to claim 8, wherein the exhaust heat recovery boiler is the system according to claim 5.Steam generator that generates steam insideComprisingSteam generatorThe steam generated by is used as a part of a turbine drive source of the turbine generator.
[0037]
Also in this configuration, the generated steam can be effectively used as a power source for the turbine generator.
[0038]
  The hybrid fuel cell system according to claim 9 is the system according to claim 1 or 2, wherein a steam turbine generator is additionally provided, and the pressurized low-temperature fuel cell is further provided with a steam separator. ,The steam separator includes a container having cooling water, and the cooling water is circulated through a circulation pipe line laid in a battery stack of the pressurized low-temperature fuel cell. Cooling, and by the coolingThe steam generated by the steam separator is used as a turbine drive source of the steam turbine generator.
[0039]
With such a configuration, it is possible to perform an operation such that the additionally provided steam turbine generator is operated using, for example, an excess of the steam generated by the steam separator of the pressurized low-temperature fuel cell. . In other words, when there is not much heat load demand, surplus exhaust heat is used to operate a steam turbine as a bottoming cycle to recover exhaust heat as electricity, and a hybrid fuel cell with further improved power generation efficiency It can be a system.
[0040]
  A hybrid fuel cell system according to claim 10 is the system according to claim 1 or 2, wherein an additional steam turbine generator is further provided.The surplus fuel electrode exhaust gas and air electrode exhaust air of the normal pressure high temperature type fuel cell or the combustion exhaust gas thereof is used as an operation source, and a steam generator is provided inside the exhaust gas.An exhaust heat recovery boiler having the exhaust heat recovery boiler is provided.Steam generatorThe steam generated is used as a turbine drive source of the steam turbine generator.
[0041]
Also in this configuration, it is possible to construct a hybrid fuel cell system that can effectively utilize the surplus steam of the exhaust heat recovery boiler to recover exhaust heat as electricity and further improve power generation efficiency.
[0042]
The hybrid fuel cell system according to claim 11 is the hybrid fuel cell system according to any one of claims 1 to 10, wherein the pressurized low-temperature fuel cell is capable of performing a pressure-transforming operation. Features.
[0043]
If the pressurized low-temperature fuel cell is subjected to pressure transformer operation, the minimum load decreases, and high power generation efficiency can be maintained even when partial load operation is unavoidable. Therefore, if the pressure-transforming operation can be performed, the system of the present invention as a whole can be a system that can be operated efficiently over a wide load range.
[0044]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First embodiment]
FIG. 1 shows, as an example of a basic system according to the hybrid type fuel cell system of the present invention, an atmospheric pressure high temperature type fuel cell 1 and a pressurized low temperature type fuel cell 2 which are provided together with a turbo compressor generator 3. And a system that hybridizes the exhaust heat recovery boiler 4, and by effectively linking these elements, it is higher than the conventional combined system of pressurized high-temperature fuel cell and turbo compressor generator It provides a system with operability and economy.
[0045]
In FIG. 1, an atmospheric pressure high-temperature fuel cell 1 is an air supply device including an electric motor 130 and a blower 131 for sending air to a battery stack 10 as a battery main body, a desulfurizer 11, and an air electrode 102 of the battery stack 10. 13 is provided. First, the fuel NG1 supplied from the fuel source NG such as natural gas (which may be propane gas, naphtha, kerosene, etc.) is normally removed after the sulfur as an odorant contained in the fuel is removed by the desulfurizer 11. The pressure is supplied to the fuel electrode 101 of the battery stack 10.
[0046]
Here, for example, when a molten carbonate fuel cell (MCFC) is adopted as the atmospheric high-temperature fuel cell 1, the operating temperature of the battery stack 10 is about 650 ° C., and 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.
[0047]
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. The surplus fuel electrode exhaust gas 101G and air electrode exhaust air 102G can also be used as a drive source for the gas turbine.
[0048]
In the present invention, the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G are effectively used. That is, the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G discharged from the battery stack 10 are modified to generate reformed gas for the pressurized low-temperature fuel cell 2 via the pipe lines 101M and 102M, respectively. It is configured to be supplied as fuel to the in-furnace heating burner 221 of the quality device 22.
[0049]
In addition, in order to utilize the combustion exhaust gas 22G of the burner 221, the combustion exhaust gas 22G is sent to the exhaust heat recovery boiler 4 via the heat exchanger 222, and heat recovery is performed. Inside the exhaust heat recovery boiler 4, steam, high-temperature water (about 90 ° C.), and low-temperature water (about 40 ° C.) are generated by the steam generator 41, the high-temperature water generator 42, and the low-temperature water generator 43, respectively. Used in applications such as refrigerators, heating and hot water supply. On the other hand, the combustion exhaust gas 22G recovered by heat is led out to the water recovery unit 44 after leaving the exhaust heat recovery boiler 4, and the water recovery unit 44 recovers and discharges moisture contained in the combustion exhaust gas 22G. It is discharged from the cylinder 45.
[0050]
Next, the pressurized low-temperature fuel cell 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 main body as a basic configuration. A battery stack 20 is provided. In such a configuration, the fuel NG2 supplied from the fuel source NG is pressurized by the fuel pressurizing compressor 2C, sent to the desulfurizer 21, and the sulfur content is removed. It is sent after being preheated to about 500 ° C. to the reformer 22 operated by the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G. The reforming side of the reformer 22 has a pressure reaction, and the combustion furnace side has a structure of normal pressure combustion.
[0051]
The desulfurized fuel and water vapor introduced into the reformer 22 are heated and reacted inside the reformer 22 heated to the reforming temperature, and separated into hydrogen, carbon monoxide, and carbon dioxide to produce reformed gas. Generated. Subsequently, through the heat exchanger 23, carbon monoxide is converted into hydrogen and carbon dioxide by the carbon monoxide converter 24, and the reformed gas is subjected to removal of excess moisture by the steam separator 25. It is introduced into the fuel electrode 201 of the battery stack 20 through the heat exchanger 26.
[0052]
About 80% of the introduced hydrogen becomes hydrogen ions at the fuel electrode 201, and the hydrogen ions move to the air electrode 202. Pressurized air is introduced into the air electrode 202 from a compressor 34 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 202. It generates electricity. Here again, hydrogen and oxygen are not completely used at the fuel electrode 201 and the air electrode 202, and the unused amount is discharged from the battery stack 20 as excess fuel electrode exhaust gas 201G and air electrode exhaust air 202G.
[0053]
In the present invention, the fuel electrode exhaust gas 201G and the air electrode exhaust air 202 are also effectively used. That is, the turbo compressor generator 3 is disposed at the subsequent stage of the pressurized low-temperature fuel cell 2, and the generator is driven using the fuel electrode exhaust gas 201G and the air electrode exhaust air 202G discharged from the battery stack 20, It is configured to generate electricity. Specifically, the turbo compressor generator 3 includes a generator 30 and a turbine 32, and the turbine 32 is rotated by the combustion gas of the burner 31, and the fuel electrode exhaust gas 201G is used as the burner fuel to produce air. The polar exhaust air 202G is used as a combustion oxidant, and both are subjected to a combustion reaction in the burner 31, and the turbine 32 is driven by the combustion gas.
[0054]
The turbo compressor generator 3 further includes a turbine 32 and a generator 30 and a compressor 34 disposed on one drive shaft. The compressor 34 takes in outside air and is driven by the rotation of the turbine 32 to be compressed air. A is manufactured. The pressurized air A is sent to the air electrode 202 of the battery stack 20 and used as an operation source of the air electrode 202. A clutch 33 is interposed between the rotating shaft of the turbine 32 and the rotating shaft of the compressor 34, and when the pressurized air A is not required (the operation of the pressurized low-temperature fuel cell 2 is stopped). In this case, only the compressor 34 can be detached from the rotating shaft system so that power loss can be reduced. Further, the combustion exhaust gas 32G of the burner 31 after the turbine 32 is driven is guided to the exhaust heat recovery boiler 4 through the piping and is recovered.
[0055]
Incidentally, the battery stack 20 is provided with a water vapor separator 28 for cooling the cells. The water vapor separator 28 is provided with cooling water W in the container 280 and cools the water by separating the cooling water W through a circulation pipe line laid in the battery stack 20. The cooling water W that has vaporized by absorbing the heat in the battery stack 10 is returned into the container 280 and escaped from the container 280, but in this embodiment, in the pipe line 28 </ b> M from the container 280 to the turbine 32. The steam is guided to the turbine 32 and used as a driving source.
[0056]
In addition to this, in this embodiment, the pipe 41M is extended from the steam port of the steam generator (steam generator) 41 of the exhaust heat recovery boiler 4 and joined to the pipe 28M. The generated steam can be supplied to the turbine 32 of the turbo compressor generator 3. As a result, the turbo compressor generator 3 can be driven by the steam from the steam generator 41, the operation of the pressurized low-temperature fuel cell 2 is stopped, and the combustion gas of the burner 31 and the supply of steam from the steam separator are stopped. Even if not, the generator 3 can be operated. In such a case, it is desirable to reduce the rotational load of the turbine 32 by operating the clutch 33 to remove the compressor 34 from the drive shaft system.
[0057]
As described above, according to the hybrid fuel cell system in which the normal pressure high temperature fuel cell 1 and the pressurized low temperature fuel cell 2 are juxtaposed, the high efficiency (normal pressure) high temperature fuel cell 1, start / stop performance, Utilizing the characteristics of the low-pressure fuel cell 2 with excellent load changeability (pressurization), and operating only the normal-pressure high-temperature fuel cell 1 at night and on holidays, the pressurized low-temperature fuel cell 2 is stopped. The operation such that the normal-pressure low-temperature fuel cell 2 is also operated in accordance with the load is possible.
[0058]
Therefore, while the pressurized low-temperature fuel cell 2 is stopped, generation of reformed gas by the reformer 22 is not necessary, so the fuel electrode exhaust gas 101G and the air electrode exhaust gas of the normal pressure high-temperature fuel cell 1 are eliminated. The air 102G becomes surplus. Therefore, bypass piping passages 101S and 102S are provided in the middle of the piping passages 101M and 102M connecting the battery stack 10 and the reformer burner 221 to the burner 40 of the exhaust heat recovery boiler 4, The fuel electrode exhaust gas 101G and the air electrode exhaust air 102G are configured to be used for driving the exhaust heat boiler 4.
[0059]
Here, when the pressurized low temperature fuel cell 2 is stopped and the reformer 22 is cooled to room temperature, the reformer 22 is heated to an equivalent temperature when the pressurized low temperature fuel cell 2 is restarted. Power generation cannot be started until it is done, and it takes a long time to restart.
In order to eliminate such inconvenience, the energy of the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G of the normal pressure high temperature fuel cell 1 is utilized, and the reformer 22 is stopped when the pressurized low temperature fuel cell 2 is stopped. It is desirable to keep the device in a hot banking state so that the time required for restarting is greatly reduced.
[0060]
Therefore, in the present embodiment, not all of the surplus fuel electrode exhaust gas 101G and the air electrode exhaust air 102G are supplied to the burner 40 of the exhaust heat recovery boiler 4, but a part thereof is modified in the pressurized low temperature fuel cell 2. The reformer 22 can be maintained in a hot banking state when the pressurized low temperature fuel cell 2 is stopped by introducing the combustion gas into the mass burner 221 and burning it, and introducing the combustion gas into the furnace of the reformer 22. It is configured as follows. When such a hot banking operation is performed, the control valves 101B and 102B are reformed by setting the flow path to the bypass piping lines 101S and 102S to “closed” when the pressurized low temperature fuel cell 2 is operating. The fuel electrode exhaust gas 101G and the air electrode exhaust air 102G are supplied only to the burner 221. When the pressurized low-temperature fuel cell 2 is stopped, the flow paths to the bypass piping lines 101S and 102S are changed to “open”. The fuel electrode exhaust gas 101G and the air electrode exhaust air 102G are controlled to be branched and supplied to the mass burner 221 and the burner 40 of the exhaust heat recovery boiler 4.
[0061]
Of course, even when the pressurized low-temperature fuel cell 2 is operating, when the load on the pressurized low-temperature fuel cell 2 may be small, or when there is a large heat demand, the control valves 101B and 102B are adjusted. Thus, the amount of the fuel electrode exhaust gas 101G and the air electrode exhaust air 102G supplied to the reformer burner 221 is reduced, and the amount of fuel sent to the burner 40 of the exhaust heat boiler 4 is increased so that steam, high temperature water, and low temperature water are supplied. The generation amount may be increased.
[0062]
[Second Example]
FIG. 2 is a block diagram showing a modified embodiment of the hybrid fuel cell system described in FIG. 1. The difference from the system of FIG. 1 is that the fuel electrode exhaust gas and air generated in the atmospheric high-temperature fuel cell 1 The system is configured such that combustion exhaust gas generated by burning polar exhaust air is used as a heat source for heating in the furnace of the reformer 22 of the pressurized low-temperature fuel cell 2. Hereinafter, this difference will be mainly described, and the description of the same points as the system shown in FIG. 1 will be omitted.
[0063]
In the present embodiment, the battery stack 10 of the atmospheric pressure high-temperature fuel cell 1 having a combustion chamber 105 therein is used. A piping path 105 </ b> M that guides the combustion exhaust gas to the reformer 22 is connected to the exhaust port of the combustion chamber 105. Further, a control valve 105B is interposed in the middle of the pipe line 105M, and a bypass pipe line 105S leading to the exhaust heat recovery boiler is connected to the control valve 105B. Is guided to the exhaust heat recovery boiler 4.
[0064]
In such a configuration, the fuel electrode exhaust gas and the air electrode exhaust air respectively generated in the fuel electrode 101 and the air electrode 102 of the battery stack 10 are introduced into the combustion chamber 105 and burned in the combustion chamber 105. By such combustion, the battery stack 10 is kept warm near the operating temperature of the high-temperature fuel cell.
[0065]
As described above, the fuel electrode exhaust gas and the air electrode exhaust air are burned in the combustion chamber 105 of the battery stack 10, and the combustion exhaust gas 105 </ b> G having a high temperature (about 400 to 600 ° C.) is generated by the combustion. In the present embodiment, this high-temperature combustion exhaust gas 105G is guided to the reformer 22 through the pipe line 105M and used as a heat source for heating the reformer 22 in the furnace. That is, the reformer 22 is operated by the heat held by the combustion exhaust gas 105G, but if the combustion heat is not sufficient for the operation of the reformer 22, the reformer burner 221 is operated to make additional cooking. You may make it do.
[0066]
Further, by controlling the control valve 105B, a part or all of the combustion exhaust gas 105G can be introduced into the exhaust heat recovery boiler 4 through the bypass pipe line 105S. For example, the control valve 105B is adjusted. Thus, half of the combustion exhaust gas 105G can be led for heating in the furnace of the reformer 22, and the other half can be led for heating the exhaust heat recovery boiler 4, so that heat recovery can be achieved. Alternatively, when the pressurized low-temperature fuel cell 2 is stopped, the entire amount of the combustion exhaust gas 105G is passed through the bypass pipe line 105S to guide the heating of the exhaust heat recovery boiler 4, or a part of the combustion exhaust gas 105G is used. In order to shorten the restart time, the reformer 22 may be used as a heating source for maintaining the hot banking state.
[0067]
In order to confirm the practical effects of the hybrid fuel cell system described above, the power generation efficiency and the exhaust heat efficiency were calculated. Here, the calculation is based on the case where a solid oxide fuel cell (SOFC) is used as the normal pressure high temperature fuel cell 1 and a phosphoric acid fuel cell (PAFC) is used as the pressurized low temperature fuel cell 2. In the SOFC, both the fuel electrode exhaust gas temperature and the air electrode exhaust air temperature are 500 to 600 ° C., while the PAFC air electrode exhaust air temperature is 550 ° C., which is almost equivalent to the SOFC, and the fuel electrode exhaust gas temperature is 183 ° C. Although the SOFC is higher, the ratio of the fuel flow rate to the air volume is as small as about 15%, and the influence of the temperature difference is considered to be slight.
[0068]
As examination conditions, the capacity of SOFC was set to 5000 kW, and the amount of exhaust heat with respect to the efficiency was determined as follows (1) and (2) under the following conditions.
[conditions]
Fuel calorific value: 11000kcal / Nm^Three
Expenditure allocation of fuel energy; power generation = 50%, exhaust heat = 40%, heat dissipation = 10%
Combustion gas temperature when exhaust gas is burned; 1200 ° C
Combustor gas reformer outlet temperature: 500 ° C
(1) When the power generation efficiency of the SOFC system is 50%
Fuel flow rate: 5000 x 860 x 100 / (11000 x 50) = 782 Nm^Three/ h
Waste heat energy: 782 x 11000 x 0.4 = 3440 Mcal / h
Amount of energy available in the reformer;
3440 × (1200−500) /1200×0.9=1806Mcal/h
(2) When the power generation efficiency of the SOFC system is 45%
Fuel flow rate: 5000 x 860 x 100 / (11000 x 45) = 868 Nm^Three/ h
Waste heat energy: 868 x 11000 x 0.4 = 3820 Mcal / h
Amount of energy available in the reformer;
3820 × (1200−500) /1200×0.9=2005Mcal/h
[0069]
As described above, the amount of exhaust heat when using SOFC fuel electrode exhaust gas air electrode exhaust air is 3820 Mcal when the power generation efficiency is 45%, and 3440 Mcal when the power generation efficiency is 50%.
[0070]
On the other hand, as a pressurized phosphoric acid fuel cell (PAFC), there is an example of an urban energy center type 5000 kW PAFC implemented in a national project, and the design value of this system was adopted. The specifications of this PAFC system are shown in FIG.
[0071]
As shown in FIG. 4, the reformer burner has 183 ° C. and 2360 Nm as the fuel electrode exhaust gas.^Three/ h, 550 ° C, 15000 Nm as exhaust air^ThreeFuel / air of about / h is used, and the hydrogen gas required by the PAFC reformer is produced with this amount of heat.
The heat load required for the reformer burner is about 3600 Mcal, and the capacity is from 0.95 (power generation efficiency 50%) to 1.06 (power generation efficiency 45%) relative to the exhaust heat energy of the SOFC. When this is applied, the PAFC capacity when the SOFC is 5000 kW capacity is about 4750 (power generation efficiency 50%) kW to 5300 kW (power generation efficiency 45%). This is the maximum capacity and is actually expected to be about 1000 to 3000 kW, but here, SOFC and PAFC are considered as capacity of 5000 kW.
[0072]
In the present invention, the fuel electrode exhaust gas 201 </ b> G and the air electrode exhaust air 202 </ b> G discharged from the PAFC (pressurized low temperature fuel cell 2) are used as driving energy for the turbo compressor generator 3. In the case of a pressurized PAFC system with a capacity of 5000 kW, the inlet gas condition to the turbine 32 is 6 kg / cm.², 280 ° C, 13210 Nm^ThreePower generation of 1800 kW is possible using exhaust gas of / h. In contrast, in the hybrid fuel cell system of the present invention, 6 kg / cm.²The fuel electrode exhaust gas 201G and the air electrode exhaust air 202G containing 20% hydrogen at 190 to 200 ° C. are burned by the burner 31 to produce high temperature exhaust gas. Therefore, it is possible to operate with high efficiency by supplying high-temperature combustion gas of about 1200 to 1300 ° C. to the gas turbine 32. When the generator 30 is driven by the gas turbine 32 from 1200 ° C. to 500 ° C. using this energy, the energy supplied to the gas turbine 32 is 2508 Mcal, the efficiency of the gas turbine is about 90%, and the generator When calculated with an efficiency of 98%, it is possible to generate 2572 kW as shown in the following equation.
2508Mcal × 0.9 × 0.98 / 860 = 2572kW (in case of 5000kW reformer)
However, the compressor 34 for supplying the reaction air to the air electrode 202 of the battery stack 20 is required, and a 5000 kW class 6 kg / cm²PAFC requires about 1300 kW of power, so the net amount of power generated by the turbo compressor generator 3 is about 1270 kW.
[0073]
Based on the above assumptions and calculating the power generation efficiency of the 5000 kW class SOFC-PAFC hybrid system,
Normal pressure 5000kW SOFC system: NG required for transmission end efficiency 50% (HHV) is 782Nm^Three/ h,
Pressurized 5000kW PAFC system: NG required amount of 862Nm for transmission end efficiency 42% (HHV)^Three/ h,
Therefore, the power generation efficiency is
[5000 kW (SOFC) + 5000 kW (PAFC) + 1270 kW (TCG)] x 860 x 100 / [(782 + 862) x 11000] = 53.6%
It becomes. On the other hand, in the case of a conventional atmospheric pressure 5000 kW class SOFC system with a transmission end efficiency of 45% (HHV), the fuel efficiency of SOFC is 869 Nm^Three/ h, PAFC fuel amount is 862 Nm^Three/ h, so
[5000 kW (SOFC) + 5000 kW (PAFC) + 1270 kW (TCG)] x 860 x 100 / [(869 + 862) x 11000] = 50.9% (Details of utilization / efficiency calculation with gas turbine from 1200 ° C to 500 ° C) (See Figure 5)
Therefore, it can be seen that the hybrid system according to the present invention can obtain almost the same power generation efficiency as that of a simple system of atmospheric pressure SOFC or pressurized PAFC.
[0074]
In this embodiment, the combustion exhaust gas 22G and the turbo compressor exhaust gas 32G of the reformer burner 221 are configured to be sent to the exhaust heat recovery boiler 4. The steam generated in the exhaust heat recovery boiler 4 can be introduced into the turbine 32. When the steam is actually introduced to generate power, the power generation amount further increases.
[0075]
[Third embodiment]
In the present invention, in order to utilize steam generated in the pressurized low-temperature fuel cell 2, in addition to the turbo compressor generator 3, a steam turbine power generation system 5 as a bottoming cycle is installed to generate power. This is preferable because the power generation amount can be further increased. FIG. 3 shows a configuration example of a hybrid fuel cell system including such a steam turbine power generation system 5.
[0076]
In FIG. 3, the normal pressure high temperature type fuel cell 1 and the pressurized low temperature type fuel cell 2 are provided side by side, and in addition to these, the turbo compressor generator 3 and the exhaust heat recovery boiler 4 are hybridized. Although it is the same as that of the Example shown in FIG. 1, in this Example, the steam turbine power generation system 5 is installed in addition to these. The steam turbine power generation system 5 includes a steam turbine 52, a generator 50, and a condenser 53. As the steam supplied to the steam turbine 52, steam 28S generated by the steam separator 28 that bears the cooling system of the battery stack 20 and steam 41S generated by the steam generator 41 of the exhaust heat recovery boiler 4 are used.
[0077]
The steam 28S is a pipeline 28M, and the steam 41S is a pipeline 41M, which is led out from the steam separator 28 and the steam generator 41, respectively, and these pipelines 28M and 41M are directly connected to the steam turbine 52. The steam turbine 52 is rotated by this, and the generator 50 is driven to generate power. The discharged steam 52S after operating the steam turbine 52 is introduced into the condenser 53. The recovered water generated there can be sent to, for example, the steam generator 41 and used for generating new steam.
[0078]
The power generation efficiency of such a hybrid fuel cell system was calculated.
First, since the required amount of heat of the 5000 kW reformer is 3440 Mcal as described above, the amount of exhaust heat energy from the reformer 22 is the net amount of heat that can be used effectively, assuming that it is used in a turbine from 1200 ° C. to 500 ° C. Assuming 1/2
3440Mcal / h × 1/2 × 500/1200 = 716Mcal / h
Also, the amount of waste heat energy (500 ° C) from the turbo compressor 3 is 2500 Mcal / h (5000 kW) because the change in enthalpy from 1200 ° C to 500 ° C is
2500Mcal / h × 1/2 × 5/7 = 892Mcal / h
Therefore, the total inflow heat in the exhaust heat recovery boiler is
716 Mcal / h + 892 Mcal / h = 1608 Mcal / h
It becomes. Using this amount of heat and assuming that the power generation efficiency of the steam cycle is about 30%, the power generation output is
1608000kcal / h × 0.3 ÷ 860 = 561kW
Therefore, the power generation efficiency of the entire system is
[5000 kW (SOFC) + 5000 kW (PAFC) + 1270 kW (TCG) + 561 kW (ST)] x 860 x 100 / [(782 + 862) x 11000] = 56.3%
It becomes. In this calculation, the steam component generated by the steam separator 28 is not added, and when this steam is also introduced into the steam turbine 52 of the bottoming cycle to generate power, the power generation amount further increases, and the pressurized SOFC and the turbine generator The power generation efficiency of the hybrid system can be almost the same as 57%.
[0079]
By the way, the hybrid system in which the pressurized SOFC alone and the turbine generator as shown in FIG. 7A are combined with the turbine generator, as described above, is difficult to start and stop or change in load due to the nature of SOFC. There is a major operational problem that must be met. Therefore, even if the power generation efficiency is high, it can be said that there are significant operational restrictions. In this regard, according to the hybrid system of the present invention, the load change of the SOFC (normal pressure high temperature fuel cell 1) itself is 75 to 100%, but the PAFC (pressurized low temperature fuel cell 2) is not started or stopped. It is possible, and the load change width can correspond in the range of 30 to 100%. Therefore, the load can be adjusted in the load range of 40 to 100% for the entire system, and the minimum load can be reduced. Therefore, the fuel cell capacity is increased to improve the operability and installation of the fuel cell at midnight. Benefits arise.
[0080]
By combining a high-temperature fuel cell that is highly efficient but difficult to respond to load fluctuations and difficult to start and stop, and a low-temperature fuel cell that is slightly less efficient but that can freely change load and start and stop, The basic configuration of the present invention makes it possible to share the load with the former fuel cell and share the portion higher than the base load with the latter fuel cell to improve the efficiency of the entire system. Examples of the former include solid oxide fuel cells (SOFC) and molten carbonate fuel cells (MCFC). Examples of the latter include phosphoric acid fuel cells (PAFC) and polymer electrolyte fuel cells (PEFC). Is mentioned. In the present invention, a system can be constructed by appropriately selecting a normal pressure high temperature fuel cell 1 and a pressurized low temperature fuel cell 2 from these. When PEFC is selected, the temperature of the fuel gas entering the battery needs to be about 80 ° C., the concentration of carbon monoxide in the fuel gas must be 10 ppm or less, and a carbon monoxide selective oxidizer needs to be installed.
[0081]
As for the suitability for the power generation capacity, PAFC is suitable for a relatively large power generation capacity of 50 kW to 11 MW, whereas PEFC is suitable for a relatively small capacity machine of 1 kW to 250 kW. For this reason, the SOFC-PEFC-TCG (turbo compressor / generator) hybrid system is suitable for business use of several kW to 250 kW. Although PEFC has lower power generation efficiency than PAFC, there is a possibility that it can be manufactured at a lower cost than PAFC in the future, and PEFC is adopted even in large capacity machines if cost is more important than power generation efficiency. there is a possibility.
[0082]
In the present invention, it is desirable that the pressurized low-temperature fuel cell 2 be capable of performing the pressure transformation operation. Here, the pressure-transforming operation means that the operation pressure of the fuel cell can be switched from pressurization to normal pressure. FIG. 6 shows the power generation efficiency of a pressurized and normal pressure phosphoric acid fuel cell (PAFC) at each load factor. The power generation efficiency at the rated load is high for the pressurization type, but according to the pressurization type, the minimum load of the compressor 34 of the turbo compressor generator 5 is limited to 75% load in the system of the present invention. With the following loads, the in-house power increases and the power generation efficiency decreases significantly. On the other hand, in the normal pressure type, since the load of the air blower that sends the normal pressure air to the battery stack can be reduced, the in-house power does not significantly decrease, and the power generation efficiency at the partial load is small.
[0083]
In order to take advantage of both of these characteristics, the operating pressure of the fuel cell may be increased at the rated pressure and normal pressure at the lowest load, and the operation may be performed by sliding the pressure during that time. As a result, the power generation efficiency of the PAFC can be made high between the lowest load and the rated load as shown by the one-dot chain line in FIG. 6, and economical operation is possible. Therefore, also in the system of the present invention, it is desirable that the operating pressure in the cell stack 20 of the pressurized low-temperature fuel cell 2 is controlled so as to be able to perform such a pressure-transforming operation so as to increase the power generation efficiency. . Specifically, the outputs of the fuel boosting compressor 2C that boosts the fuel NG1 sent to the fuel electrode 201 and the compressor 34 that sends the pressurized air A to the air electrode 202 may be controlled according to the load.
[0084]
【The invention's effect】
According to the hybrid fuel cell system of the present invention as described above, the normal pressure high temperature fuel cell operates at almost one rated load, and the pressurized low temperature fuel cell and the turbine generator such as a turbo compressor generator are connected. In order to perform load change and start / stop, the entire system can cope with a wide load change of about 40 to 100%. For this reason, it is possible to install a large capacity machine without being restricted by the installation capacity corresponding to the minimum load of the customer, which is a drawback when installing the high temperature fuel cell, and the operability is improved.
[0085]
Also, the fuel electrode exhaust gas and air electrode exhaust air of the normal pressure high temperature type fuel cell, or the combustion exhaust gas thereof is used as the in-furnace heating fuel of the reformer of the pressurized low temperature fuel cell, that is, hybridized. Since the fuel electrode exhaust gas / air electrode exhaust air of one fuel cell is used to generate power of the other fuel cell, the power generation efficiency of the system can be improved. In addition, by incorporating a bottoming cycle of a gas turbine or a steam turbine, power generation efficiency equivalent to that of the conventional method combining a pressurized high-temperature fuel cell unit and a gas turbine can be obtained, and load change and start-up as described above can be achieved. There is also an effect that it is possible to construct a highly efficient and highly operable hybrid system that can flexibly cope with a stop.
[0086]
In addition, when the demanded load is low, operating the pressurized low-temperature fuel cell to shut it down cuts the minimum load on the entire system, enabling operation in a wide load range, and improving the economics of the system. Can be made. Also, when the demand for heat is high and the demand for electricity is low, the pressurized low-temperature fuel cell is stopped, and the exhaust heat generated by the normal-pressure high-temperature fuel cell is actively used by a waste heat recovery boiler, etc. By setting the operation mode to generate a lot of water, it is possible to generate heat according to the heat demand in a wide load region of the entire system. As a result, there is an advantage that it is possible to flexibly cope with a change in demand for electricity and heat for each consumer and a change in heat demand according to the season.
[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 block diagram showing a third embodiment of a hybrid fuel cell system according to the present invention.
FIG. 4 is a tabular diagram showing specifications of a 5000 kW pressurized PAFC.
FIG. 5 is a diagram of a tabular form in which the output of the turbine generator is calculated based on the specification of FIG.
FIG. 6 is a graph showing the power generation efficiency of normal-pressure and pressurized-type phosphoric acid fuel cells (PAFC).
FIG. 7 is a block diagram showing an example of a conventional high-temperature fuel cell.
FIG. 8 is a block diagram showing an example of a conventional low-temperature fuel cell.
FIG. 9 is a block diagram showing an example of a customer load pattern.
[Explanation of symbols]
1 Normal pressure high temperature fuel cell
101G Fuel electrode exhaust gas
102G air electrode exhaust air
105G combustion exhaust gas
11, 21 Desulfurizer
2 Pressurized low temperature fuel cell
201G Fuel electrode exhaust gas
202G Air electrode exhaust air
22 Reformer
221 reformer burner
28 Steam separator
3 Turbo compressor generator (turbine generator)
31 (for turbine rotation) burner
32 Turbine
33 Clutch
34 Compressor
4 Waste heat recovery boiler
41 Steam generator
5 Steam turbine generator
51 turbine

Claims (11)

A hybrid fuel cell system comprising an atmospheric high temperature fuel cell, a pressurized low temperature fuel cell, and a turbine generator,
The fuel electrode exhaust gas and air electrode exhaust air of the normal pressure high temperature fuel cell are used as fuel for heating in the furnace of the reformer provided in the pressurized low temperature fuel cell, and the pressurized low temperature fuel cell A hybrid fuel cell system configured to use fuel electrode exhaust gas and air electrode exhaust air as a turbine drive source of the turbine generator. A hybrid fuel cell system comprising an atmospheric high temperature fuel cell, a pressurized low temperature fuel cell, and a turbine generator,
Combustion exhaust gas produced by burning the fuel electrode exhaust gas and air electrode exhaust air of the normal pressure high temperature fuel cell is used as a heat source for heating in the furnace of the reformer provided in the pressurized low temperature fuel cell, Further, the hybrid fuel cell system is configured to use the fuel electrode exhaust gas and the air electrode exhaust air of the pressurized low-temperature fuel cell as a turbine drive source of the turbine generator. The turbine generator is a turbo compressor generator;
The fuel electrode exhaust gas of the pressurized low-temperature fuel cell is used as fuel for a burner that drives the turbine of the turbo compressor generator,
3. The hybrid fuel cell system according to claim 1, wherein the air electrode exhaust air of the pressurized low-temperature fuel cell is used as an oxidant for combustion of the burner.   The turbo compressor generator includes at least a turbine, a generator, and a compressor that generates pressurized gas, which are disposed on one drive shaft, and the compressor is powered by the drive shaft via a clutch. 4. The hybrid fuel cell system according to claim 3, wherein the hybrid fuel cell system is detachable from the transmission system. The hybrid fuel cell system according to claim 1, further comprising an exhaust heat recovery boiler,
A hybrid fuel cell system, wherein a portion of the fuel electrode exhaust gas and air electrode exhaust air of the normal pressure high-temperature fuel cell is supplied to the drive burner of the exhaust heat recovery boiler as a bypass and used as fuel. The hybrid fuel cell system according to claim 2, further comprising an exhaust heat recovery boiler,
A part of the combustion exhaust gas generated by burning the fuel electrode exhaust gas and the air electrode exhaust air of the normal pressure high-temperature fuel cell is bypass-supplied to the exhaust heat recovery boiler for heating the exhaust heat recovery boiler. A hybrid fuel cell system characterized by being used as a heat source. The hybrid fuel cell system according to claim 1 or 2, wherein the pressurized low-temperature fuel cell includes a water vapor separator,
The steam separator includes a container having cooling water, and the cooling water is circulated through a circulation pipe line laid in a battery stack of the pressurized low-temperature fuel cell. Cooling,
A hybrid fuel cell system, wherein steam generated by the steam separator by the cooling is used as a part of a turbine drive source of the turbine generator. The hybrid fuel cell system according to claim 5, further comprising a steam generator for generating steam inside the exhaust heat recovery boiler,
The hybrid fuel cell system, wherein steam generated by the steam generator is used as a part of a turbine drive source of the turbine generator. The hybrid fuel cell system according to claim 1 or 2, wherein a steam turbine generator is additionally provided, and the pressurized low-temperature fuel cell is further provided with a steam separator,
The steam separator includes a container having cooling water, and the cooling water is circulated through a circulation pipe line laid in a battery stack of the pressurized low-temperature fuel cell. Cooling,
The hybrid fuel cell system, wherein steam generated by the steam separator by the cooling is used as a turbine drive source of the steam turbine generator. 3. The hybrid fuel cell system according to claim 1 or 2, wherein a steam turbine generator is additionally provided, and excess fuel electrode exhaust gas and air electrode exhaust air of the normal pressure high temperature fuel cell, or these An exhaust heat recovery boiler with a steam generator inside is provided as an operating source .
A hybrid fuel cell system, wherein steam generated by a steam generator of the exhaust heat recovery boiler is used as a turbine drive source of the steam turbine generator.   11. The hybrid fuel cell system according to claim 1, wherein the pressurized low-temperature fuel cell is configured to be capable of performing a pressure-transforming operation.

Images