JP2000133295A - Solid electrolyte fuel cell composite power generation plant system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance power generating efficiency and reliability by installing an exhaust fuel cooling heat exchanger for cooling fuel side exhaust gas of a fuel cell. SOLUTION: A fuel heating heat exchanger 60 and an exhaust fuel cooling heat exchanger 61 are installed in a fuel side exhaust line 58, exhaust fuel whose temperature is lowered compared with outlet exhaust fuel of a fuel cell 53 is supplied to a combustor 59, and an oxygen heating heat exchanger 69 and an exhaust oxygen cooling heat exchanger 70 are installed in an oxygen side exhaust line 68, exhaust oxygen whose temperature is lowered compared with outlet exhaust oxygen of the fuel cell 53 is supplied to the combustor 59. Steam heated by heat exchange when passes through the heat exchanger 61 and the heat exchanger 70 is supplied to the combustor 59. The temperature of steam generated in the combustor 59 can be lowered than allowable temperature of a steam turbine 75 locating downstream of the combustor 59, the maximum amount of steam kept at allowable temperature can be supplied to the steam turbine 75, and power is efficiently generated with a generator 76.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid oxide fuel cell combined cycle power plant system.

[0002]

2. Description of the Related Art Conventionally, as a combined cycle power plant system having a hydrogen / oxygen combustion turbine, a Rankine cycle system shown in FIG. 2 and a topping regeneration cycle system shown in FIG. 3 are known.

In the Rankine cycle type combined cycle power plant system shown in FIG. 2, a high-temperature steam turbine 1 has a high-pressure steam generated in a first heat exchanger 3 using steam at an outlet of an ultra-high-temperature turbine 2 as a heating source and an outlet of a high-temperature turbine 4. Is driven by the high-pressure steam generated in the second heat exchanger 5 using the steam as a heating source. The steam at the outlet of the high-temperature steam turbine 1 is as follows:
The ultrahigh-temperature turbine 2 is driven by using ultrahigh-temperature steam that is introduced into the first hydrogen / oxygen combustor 6 and generated by burning with hydrogen and oxygen separately supplied here. The steam at the outlet of the ultrahigh-temperature turbine 2 is introduced into the second hydrogen / oxygen combustor 7 after heat exchange in the first heat exchanger 3, and is generated by burning together with hydrogen and oxygen separately supplied here. The high-temperature turbine 4 is driven using the high-temperature steam generated. The steam at the outlet of the high-temperature turbine 4 is supplied to the low-temperature turbine 8 after being cooled in the second heat exchanger 5. The generator 9 includes the turbines 1, 2, 2,
Electric power is generated by the power generators 4, 8.

[0004] The steam at the outlet of the low-temperature turbine 8 is supplied to a condenser 10 where it is condensed into water. Among the condensed water, condensed water corresponding to the water generated in the first and second hydrogen / oxygen combustors 6 and 7 is discharged out of the system by the submergence pump 11 and collected, and has an amount corresponding to the load. The condensate is supplied as the first water and the second water in a state of being compressed by the water supply pump 12.
Are supplied to the heat exchangers 3 and 5.

On the other hand, in the combined power plant system of the topping regeneration cycle system shown in FIG. 3, the high-temperature steam turbine 21 passes through first to third heat exchangers 23 to 25 using steam at the outlet of the high-temperature turbine 22 as a heating source. It is driven by high-pressure steam that has been heat-exchanged. The steam at the outlet of the high-temperature steam turbine 21 is supplied to the ultrahigh-pressure turbine 26.

The heat exchangers 23 to 25 and a third heat exchanger 25 among them are arranged in parallel with each other and pass through a fourth heat exchanger 27 which exchanges heat with steam from a high-pressure compressor described later. The steam at the outlet of the high-temperature turbine 22 is supplied to the low-pressure compressor 2
The pressure is supplied to a high-pressure compressor 29 through 8 and the pressure is increased. The pressure is introduced into the hydrogen / oxygen combustor 30 via the fourth heat exchanger 27, and is generated by burning with hydrogen and oxygen separately supplied here. The ultra-high-temperature turbine 26 and the high-temperature turbine 22 disposed at a subsequent stage are driven by using the high-temperature steam.

The steam at the outlet of the high-temperature turbine 22 after passing through the second heat exchanger 24 is supplied to a low-pressure turbine 31. The generator 32 includes the turbines 21, 22, 2
6, 31 generate electric power.

The steam at the outlet of the low-temperature turbine 31 is supplied to the condenser 35 directly and via the fifth and sixth heat exchangers 33 and 34, where it is condensed into water. Of this condensate, condensate corresponding to the water generated in the hydrogen / oxygen combustor 30 is discharged out of the system by the condensate pump 36 and collected. Further, a part of the condensed water of the amount corresponding to the load is condensed by the first feed pump 37 to the high-pressure compressor 29.
Supplied to The remaining condensate is heat-exchanged in the fifth and sixth heat exchangers 33 and 34 and then deaerated in a deaerator 38.
The first to third heat exchangers 2 are supplied by the second water pump 39.
The heat is exchanged at 3 to 25 and sent to the high-temperature steam turbine 21 as described above. The outlet steam of the low-temperature turbine 31 is introduced into the deaerator 38.

[0009]

However, the above-mentioned conventional combined cycle power plant system has the following problems.

(1) Since both of the two types of combined power plant systems use high-grade and expensive hydrogen as fuel, it is essential to achieve high power generation efficiency.
Even if a 700 ° C. high temperature turbine is applied, the efficiency is still 61%.
% And low.

(2) It is necessary to raise the temperature of the hydrogen combustion turbine used in any of the two types of combined cycle power plant systems in order to achieve high efficiency, but there is no prospect of developing a high temperature turbine of 1500 ° C. or higher. Is the actual situation,
Its development requires enormous costs and time.

(3) In a Rankine cycle combined cycle power plant system, an ultra-high pressure (several hundred kgf / cm ² ) is required, and the feasibility of a high-pressure turbine is low.

(4) The combined power plant system of the topping regeneration system requires a large number of high-temperature heat exchangers as shown in FIG. 3 described above, making the equipment complicated and expensive.

An object of the present invention is to provide a solid oxide fuel cell combined cycle power generation system with high power generation efficiency and high reliability.

[0015]

A solid electrolyte fuel cell combined cycle power plant system according to the present invention is provided with a solid electrolyte fuel supplied with hydrogen as fuel through a fuel supply line and supplied with oxygen as an oxidant through an oxygen supply line. A fuel cell, an exhaust fuel cooling heat exchanger for cooling fuel-side exhaust of the fuel cell, and an exhaust fuel cooled by the heat exchanger to the fuel supply line for controlling the temperature of the fuel cell. An exhaust fuel recirculation means for circulating, an exhaust fuel and an oxygen-side exhaust gas of the fuel cell are supplied, and a combustor for generating high-temperature steam; and Steam supply means for controlling the temperature, a high-temperature steam turbine driven by high-temperature steam generated in the combustor, and condensing steam from the turbine It is characterized in that it has and a fit of the condenser.

In the solid oxide fuel cell combined cycle power plant system according to the present invention, it is preferable that hydrogen and oxygen supplied through the fuel supply line and the oxygen supply line are in chemical equivalent amounts.

In the solid oxide fuel cell combined cycle power plant system according to the present invention, further, a heat exchanger for cooling the exhaust gas for cooling the oxygen-side exhaust gas of the fuel cell, and a heat exchanger for cooling the exhaust gas for cooling the oxygen supply line. Exhaust oxygen recirculation means for recirculating the exhaust oxygen cooled by the exchanger to control the temperature of the fuel cell may be provided.

In the solid oxide fuel cell combined cycle power plant system according to the present invention, it is permissible to further provide a fuel heating heat exchanger for exchanging heat between the fuel discharged from the fuel cell outlet and the fuel in the fuel supply line. I do.

In the solid oxide fuel cell combined cycle power plant system according to the present invention, it is permissible to further provide an oxygen heating heat exchanger for exchanging heat between the exhausted oxygen at the fuel cell outlet and the oxygen in the oxygen supply line. I do.

In the solid oxide fuel cell combined cycle power plant system according to the present invention, the oxygen is preferably air.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a solid oxide fuel cell combined cycle power plant system according to the present invention will be described in detail with reference to FIG.

Hydrogen from the hydrogen fuel tank 51 is supplied through a fuel supply line 52 to a solid oxide fuel cell (SOFC).
53. The solid electrolyte fuel cell 53 has a structure including a power generation membrane 54, and a fuel chamber 55 and an oxygen chamber 56 partitioned by the power generation membrane 54. The power generation film 5
Reference numeral 4 includes a fuel electrode, a solid electrolyte membrane, and an oxygen electrode, and is connected to a cross-current converter 57. The fuel chamber 55 of the fuel cell 53 is connected to a combustor 59 through a fuel-side exhaust line 58. A fuel heating heat exchanger 60 for heating the fuel in the fuel supply line 52 is interposed across the fuel supply line 52 and the fuel-side exhaust line 58.

The exhaust fuel cooling heat exchanger 61 is connected to the fuel-side exhaust line 5 between the heat exchanger 60 and the combustor 59.
8 is interposed. The fuel side branch line 62 is configured to supply the exhaust fuel cooled by the exhaust fuel cooling heat exchanger 61 to the fuel supply line 52 located between the hydrogen fuel tank 51 and the heat exchanger 60. The fuel supply line 52 and the fuel-side exhaust line 58 are connected.
The boosting fan 63 and the control valve 64 are interposed in the fuel-side branch line 62 sequentially from the fuel-side exhaust line 58. The control valve 64 has a function of adjusting the amount of recirculated exhaust fuel so as to control hydrogen supplied to the fuel cell to a predetermined temperature. The fuel-side branch line 62, the booster fan 63, and the control valve 64 constitute an exhaust fuel recirculation mechanism 65.

The oxygen from the oxygen tank 66 is supplied to the oxygen chamber 56 of the fuel cell 53 through an oxygen supply line 67. The oxygen chamber 56 of the fuel cell 53 is connected to the combustor 59 through an oxygen-side exhaust line 68.
An oxygen heating heat exchanger 69 for heating oxygen in the oxygen supply line 67 is interposed across the oxygen supply line 67 and the oxygen-side exhaust line 68.

The exhaust oxygen cooling heat exchanger 70 is interposed in the oxygen side exhaust line 68 between the oxygen heating heat exchanger 69 and the combustor 59. Oxygen side branch line 71
The oxygen supply line is configured to supply the exhaust oxygen cooled by the exhaust oxygen cooling heat exchanger 70 to the oxygen supply line 67 located between the oxygen tank 66 and the oxygen heating heat exchanger 69. 67 and an oxygen-side exhaust line 68. The booster fan 72 and the control valve 73 are
The oxygen side exhaust line 68 is connected to the oxygen side branch line 71.
Are installed sequentially. The control valve 73 has a function of adjusting the recirculation amount of the exhausted oxygen so as to control the oxygen supplied to the fuel cell to a predetermined temperature. Such an oxygen-side branch line 71, a booster fan 72, and a control valve 7
3 constitutes an exhaust oxygen recirculation mechanism 74.

The steam generated in the combustor 59 is supplied to a steam turbine 75, which generates a generator 76. The steam turbine 75 includes a pipe 77
Through to the condensate tank 78. The piping 7
7 has an evaporator (feed water heater) from the turbine 75 side.
79 and a condenser 80 are sequentially provided.

The condensate tank 78 includes a water supply line 81 and first and second branched water supply lines 8 branched therefrom.
2 and 83 are connected to the evaporator 79. A water supply pump 84 is interposed in the water supply line 81. The condensed water corresponding to the water generated in the combustor 59 is recovered outside the system through the recovery line 85. The first and second branch water supply lines 82 and 83 are provided with flow control valves 86 and 87, respectively. The flow rate control valve 86 has a function of adjusting the amount of water supply so that the outlet temperature of the exhaust fuel cooling heat exchanger 61 and the inlet temperature of the combustor 59 become predetermined temperatures. The flow control valve 87 is
It has a function of adjusting the water supply amount so that the outlet temperature of the exhaust oxygen cooling heat exchanger 70 and the inlet temperature of the combustor 59 become predetermined temperatures.

A first steam line 88 extending from the evaporator 79 and communicating with the first branch water supply line 82 and a second steam extending from the evaporator 79 and communicating with the second branch water supply line 83 The line 89 is integrated via the exhaust fuel cooling heat exchanger 61 and the exhaust oxygen cooling heat exchanger 70, respectively, and the integrated steam line 90 is connected to the combustor 59.

Next, the operation of the solid oxide fuel cell combined cycle power plant system shown in FIG. 1 will be described.

First, hydrogen is supplied from the hydrogen fuel tank 51 to the fuel chamber 55 of the solid electrolyte fuel cell 53 through the fuel supply line 52, and oxygen is supplied from the oxygen tank 66 through the oxygen supply line 67 to the oxygen chamber 56 of the fuel cell 53. To supply. At this time, the hydrogen and oxygen are supplied to the fuel cell 53 so as to have a chemical equivalent. Due to such supply of hydrogen and oxygen, a cell reaction is caused by the power generation film 54 disposed between the fuel chamber 55 and the oxygen chamber 56, and the cross-current converter 5 connected to the power generation film 54
7 is output as an AC voltage.

The exhaust gas (exhaust fuel; including steam) at the outlet of the fuel chamber 55 of the fuel cell 53 passes through a fuel-side exhaust line 58 in which a fuel heating heat exchanger 60 and an exhaust fuel cooling exchanger 61 are interposed. It is supplied to the combustion chamber 59. In this way, the hydrogen passing through the fuel supply line 52 is heated and exchanged while the exhaust fuel passes through the fuel heating heat exchanger 60. Exhaust fuel is supplied to the fuel heating heat exchanger 6.
In the process of passing through zero, heat is exchanged with hydrogen in the fuel supply line 52 for cooling, and in the process of passing through the exhaust fuel cooling exchanger 61, the heat is exchanged with low-temperature steam in the first steam line 88 for cooling. For this reason, it becomes possible to supply to the combustor 59 exhaust fuel whose temperature is lower than that of the exhaust fuel at the outlet of the fuel chamber 55. Further, the fuel-side branch line 62,
By supplying the exhausted fuel cooled by an exhausted fuel recirculation mechanism 65 composed of a booster fan 63 and a control valve 64 to a fuel supply line 52 upstream of the fuel heating heat exchanger 60, the fuel cell 53 The outlet temperature can be reduced to an appropriate temperature.

On the other hand, the exhaust gas (exhaust oxygen; including steam) at the outlet of the oxygen chamber 56 of the fuel cell 53 is supplied to the oxygen-exhaust heat exchanger 69 and the oxygen-exhaust heat exchanger 70 in which the exhaust oxygen cooling heat exchanger 70 is interposed. The fuel is supplied to a combustion chamber 59 through a line 68. As described above, the oxygen passing through the oxygen supply line 67 is heated and exchanged while the exhausted oxygen passes through the oxygen heating heat exchanger 69. Further, the exhaust oxygen is cooled by being exchanged with hydrogen in the fuel supply line 52 in the course of passing through the oxygen heating heat exchanger 69, and further cooled.
In the process of passing through zero, heat is exchanged with the low-temperature steam in the second steam line 89 to be cooled. Therefore, the discharged oxygen whose temperature is lower than the discharged oxygen at the outlet of the oxygen chamber 56 is supplied to the combustor 59.
Can be supplied to Further, the exhausted oxygen that has been cooled by the exhausted oxygen recirculation mechanism 74 including the oxygen-side branch line 71, the booster fan 72, and the control valve 73 is supplied to the oxygen supply line 67 upstream of the oxygen heating heat exchanger 69.
The outlet temperature of the fuel cell 53 can be reduced to an appropriate temperature.

As described above, the hydrogen heated to a predetermined temperature by supplying the exhaust fuel from the exhaust fuel recirculation mechanism 65 to the fuel supply line 52 and heating the hydrogen in the fuel heating heat exchanger 60 is supplied to the fuel cell. 53 can be supplied to the fuel chamber 55,
The oxygen heated to a predetermined temperature by the supply of the exhaust oxygen from the exhaust oxygen recirculation mechanism 74 to the oxygen supply line 57 and the heating of the oxygen by the oxygen heating heat exchanger 69 is supplied to the oxygen chamber 56 of the fuel cell 53. Since the supply can be performed, the above-described cell reaction in the fuel cell 53 can be smoothly performed, the AC voltage can be efficiently output from the cross-current converter 57 connected to the power generation film 54, and the outlet temperature of the fuel cell 53 becomes excessive. Can be prevented from rising.

The steam generated by the combustion in the combustor 59 is supplied to a steam turbine 75 to generate a generator 76.
Is generated.

The outlet steam of the steam turbine 75 is condensed in the course of passing through a pipe 77 in which an evaporator 79 and a condenser 80 are interposed, and is stored in a condensate tank 78 as condensate. Of the condensate in the condensate tank 78, condensate corresponding to the water generated in the combustor 59 is collected outside the system through a collection line 85, and the amount of condensate according to the load is supplied as a water supply pump 84. The compressed water is supplied to the evaporator 79 through the water supply pipe 81 and the first and second branch water supply lines 82 and 83, where the heat is exchanged with the outlet steam of the turbine 75 and heated to generate low-temperature steam. I do. The low-temperature steam is supplied to the first and second steam lines 88 and 89, respectively.
In the process of passing through the exhaust fuel cooling exchanger 61 and the exhaust oxygen cooling exchanger 70 through heat exchange and heat exchange with the above-described exhaust fuel and exhaust oxygen, respectively, the steam is heated. Is supplied to the vessel 59.

As described above, the fuel-exchanger 61 for exchanging heat with the low-temperature steam in the first steam line 88 and the heat-exchanging heat exchanger 60 for exchanging heat with hydrogen in the fuel supply line 52 to the fuel-side exhaust line 58. Are supplied to the combustor 59 at a lower temperature than the exhaust fuel at the outlet of the fuel chamber 55 of the fuel cell 53, and the oxygen-exhaust line 68 exchanges heat with oxygen in the oxygen supply line 67. And a heat exchanger 69 for exchanging heat with the low-temperature steam of the second steam line 89 to provide heat exchange with the low-temperature steam in the second steam line 89. The exhausted oxygen is supplied to the combustor 59, and further, the exhausted fuel cooling exchanger 61 and the exhausted oxygen cooling exchanger 7
In the process of passing through each of the combustors 59, the steam that has been subjected to heat exchange and heated in the process of passing through the combustor 59 is supplied to the combustor 59.
The steam generated by the combustion of the steam turbine 75 can be suppressed below the allowable temperature of the steam turbine 75 on the downstream side of the combustor 59, and the maximum amount of steam can be reduced at the allowable temperature to the steam turbine 75.
Can be supplied to As a result, the power generator 76 can efficiently generate power.

Therefore, according to the present invention, the solid electrolyte fuel cell 53, the combustor 59 and the steam turbine 75 are combined, and the cooled exhaust fuel containing steam from the exhaust fuel recirculation mechanism 65 to the fuel supply line 52 is supplied. By cooling the exhaust fuel at the outlet of the fuel chamber of the fuel cell and the exhaust oxygen at the outlet of the oxygen chamber and supplying steam to the combustor, the fuel cell 53 can be efficiently maintained at an appropriate temperature (about 1000 ° C.). The power generation can be performed, and the unused hydrogen, the residual oxygen, and the steam of the fuel cell 53 are introduced into the combustor 59 to generate steam at a temperature not exceeding the allowable temperature of the steam turbine 75 at the subsequent stage. Since it is possible to perform efficient power generation of 76, it is possible to provide a solid oxide fuel cell combined power generation system system that achieves ultra-high efficiency.

Next, the improvement of the reaction efficiency of the fuel cell and the improvement of the power generation efficiency by the combustor and the steam turbine will be described by modeling.

Although the solid electrolyte fuel cell varies depending on the design quality, the maximum power generation amount (power generation efficiency) is usually 50.
%, Heat generation amount 35%, and unburned portion 15%. The operating temperature of the fuel cell is 1000 ° C., and it is necessary to keep the temperature as constant as possible.

For example, assuming that 1 kmol of hydrogen is supplied to the fuel cell, its stored energy is about 57000 kcal / kmol, of which about 27000 kcal / kmol.
0000 kcal becomes heat. The amount of vapor generated by 1 kmol of hydrogen is [H ₂ + (１ ／ O ₂ )] in 1 mol of hydrogen.
= About 18kg of H ₂ O]. Exhaust fuel recirculation mechanism 6
In the case where steam is not supplied from the fuel supply line 52 to the fuel supply line 52, 20,000 (kcal / kg) / [18 (kg / k
mol) × 0.57 (kcal / kg ° C.)] (where 0.57 kcal / kg ° C. indicates the specific heat of steam), the temperature rises to about 2000 ° C., and the operation of the fuel cell becomes impossible. Therefore, the exhaust fuel recirculation mechanisms 65 to 7
Approximately 100 kg of low temperature steam of 00 ° C is supplied to the fuel supply line 52.
By supplying the fuel, the outlet temperature of the fuel cell can be set to about 1000 ° C. from the calorific value calculation.

On the other hand, the exhaust fuel cooled to about 1000 ° C. at the outlet of the fuel cell 53 exchanges heat with the low-temperature steam of the first steam line 88 in the process of passing through the exhaust fuel cooling exchanger 61, and is cooled. In the process of passing the exhaust oxygen cooled to about 1000 ° C. through the exhaust oxygen cooling exchanger 70, the exhaust fuel and the exhaust oxygen are each reduced to about 700 ° C. by cooling by exchanging heat with the low-temperature steam in the second steam line 89. It becomes possible to lower. In the process of supplying such exhaust fuel and exhaust oxygen to the combustor 59 and passing the exhaust fuel cooling exchanger 61 and the exhaust oxygen cooling exchanger 70 through the first and second steam lines 88 and 89, respectively. By supplying heated steam that has been heat-exchanged with the above-described exhaust fuel and exhaust oxygen to the combustor 59 through a steam line 90,
The combustor outlet temperature can be maintained at the allowable temperature of the relatively low-temperature steam turbine 75 at the subsequent stage, and at the same time, the steam amount can be substantially increased, so that the turbine output can be maximized.

For example, the temperature of the outlet of the combustor 59 when heating steam is not injected into the combustor 59 from the steam line 90 is calculated. As already mentioned, 1 kmol of hydrogen has an energy of about 57000 kcal / kmol. Further, the fuel utilization rate when 1 kmol of hydrogen is supplied to the fuel cell 53 is approximately 85%.
Exhaust fuel (exhaust hydrogen) at the exit is 15%, ie 0.15km
ol, and the calorific value of the discharged hydrogen is 57000 kcal
It becomes 8550 kcal from the calculation of /kmol×0.15. Further, 1 km of hydrogen supplied to the fuel cell 53
Assuming that all of the ol reacts with oxygen and changes into steam, about 18 kg of steam will be supplied to the combustor 59. Therefore, when exhausted hydrogen and exhausted oxygen at about 700 ° C. are supplied to the combustor 59, the outlet temperature of the combustor 59 can be obtained from the following equation.

Combustor 59 outlet temperature = 700 ° C. + ｛855
0 (kcal / kmol) / [18 (kg / kmol)
× 0.57 (kcal / kg · ° C.)]｝ = 1533 ° C. Here, 0.57 kcal / Kg ° C. indicates the specific heat of steam.

Therefore, when heating steam is not introduced into the combustor 59 from the steam line 90, the outlet temperature of the combustor 59 becomes higher than the allowable temperature of the steam turbine 75.

On the other hand, as in the present invention, the steam line 9
When heating steam from 0 to, for example, 22 kg is injected into the combustor 59, the steam amount becomes 18 + 22 = 40 (kg / kmol), so the outlet temperature of the combustor 59 can be obtained from the following equation.

Outlet temperature of combustor 59 = 700 ° C. + ｛855
0 (kcal / kmol) / [40 (kg / kmol)
× 0.57 (kcal / kg · ° C.)]｝ = 1075 ° C. Therefore, when heating steam is injected into the combustor 59 from the steam line 90, the outlet temperature of the combustor 59 becomes
Below the allowable temperature of the combustor 59.
By supplying heated steam to the turbine, the steam amount can be substantially increased, so that the turbine output can be maximized.

[0047]

As described above in detail, according to the present invention, a solid electrolyte fuel cell and a combustor are combined, and a supply of cooled exhaust fuel containing steam from an exhaust fuel recirculation mechanism to a fuel supply line is provided. Cooling of exhaust fuel at the outlet of the fuel chamber of the fuel cell, exhaust oxygen at the outlet of the oxygen chamber, and supply of steam to the combustor, thereby increasing the efficiency of the cell reaction in the fuel cell and the efficient power generation by the steam turbine. It is possible to provide a solid oxide fuel cell combined cycle power plant system which can improve the overall thermal efficiency of the plant, and further improve the reliability by preventing the temperature of the fuel cell from excessively rising and preventing the steam turbine from being heated above the allowable temperature.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a solid oxide fuel cell combined cycle power plant system of the present invention.

FIG. 2 is a schematic diagram showing a conventional Rankine cycle system combined cycle power plant system.

FIG. 3 is a schematic diagram showing a combined power plant system of a topping regeneration cycle system.

[Explanation of symbols]

 51: hydrogen fuel tank, 52: fuel supply line, 53: solid electrolyte fuel cell, 59: combustor, 60: heat exchanger for heating fuel, 61: heat exchanger for cooling exhaust fuel, 65: exhaust fuel recirculation mechanism 66, an oxygen tank, 67, an oxygen supply line, 69, a heat exchanger for heating oxygen, 70, a heat exchanger for cooling exhaust oxygen, 74, an exhaust oxygen recirculation mechanism, 75, a steam turbine, 76, a generator, 78 ... condensate tank, 88, 89, 90 ... steam line.

Claims (6)

[Claims] 1. A solid electrolyte fuel cell supplied with hydrogen as a fuel through a fuel supply line and supplied with oxygen as an oxidant through an oxygen supply line, and exhaust fuel cooling for cooling fuel-side exhaust of the fuel cell. Exhaust heat recirculation means for recirculating exhaust fuel cooled by the heat exchanger to the fuel supply line to control the temperature of the fuel cell; exhaust fuel and an oxygen side of the fuel cell Exhaust gas is supplied, a combustor for generating high-temperature steam, steam supply means for supplying steam at the heat exchanger outlet to the combustor for controlling the combustor outlet temperature, and generated by the combustor And a high-temperature steam turbine driven by the high-temperature steam, and a condenser for condensing the steam from the turbine. System. 2. The solid oxide fuel cell combined cycle power plant system according to claim 1, wherein hydrogen and oxygen supplied through said fuel supply line and said oxygen supply line are in a chemical equivalent amount. 3. An exhaust oxygen cooling heat exchanger for cooling the oxygen-side exhaust gas of the fuel cell, and an exhaust oxygen cooled by the exhaust oxygen cooling heat exchanger to the oxygen supply line. 3. An exhaust gas recirculation means for recirculating for controlling temperature is provided.
The solid electrolyte fuel cell combined cycle power plant system according to the above. 4. A fuel heating heat exchanger for exchanging heat between fuel discharged from the fuel cell outlet and fuel in the fuel supply line, according to claim 1, further comprising: Solid electrolyte fuel cell combined cycle power plant system. 5. An oxygen heating heat exchanger for exchanging heat between oxygen discharged from the fuel cell outlet and oxygen in the oxygen supply line, further comprising an oxygen heating heat exchanger. Solid electrolyte fuel cell combined cycle power plant system. 6. The solid oxide fuel cell combined cycle power plant system according to claim 1, wherein said oxygen is air.