JP2014231816A - Power generator including fuel battery and gas turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power generator capable of operating both a fuel battery and a gas turbine at appropriate temperatures.SOLUTION: A power generator 100 comprises: a compressor C compressing air; a first heat exchanger R1 heating the air compressed by the compressor C; a fuel battery 17 having an air electrode Ca to which the air heated by the first heat exchanger R1 is supplied and a fuel electrode An to which fuel is supplied, and generating electric power by causing a reaction between oxygen in the air and the fuel; a second heat exchanger R2 heating exhaust air from the air electrode Ca; a combustion chamber CC mixing up and burning the exhaust air heated by the second heat exchanger R2 and exhaust gas from the fuel electrode An; and a turbine T driven by the combustion gas from the combustion chamber CC. The exhaust gas from the turbine T is supplied to the second heat exchanger R2 to heat the exhaust air from the air electrode Ca, and then supplied to the first heat exchanger R1 to heat the air compressed by the compressor C.

Description

  The present application relates to a combined power generation apparatus in which a fuel cell and a gas turbine are combined.

  There is known a combined power generation apparatus that supplies air compressed by a compressor of a gas turbine to a fuel cell and drives the gas turbine using high-temperature and high-pressure exhaust gas from the fuel cell. According to such a power generator, in addition to increasing the efficiency of the fuel cell by increasing the pressure of air supplied to the fuel cell, the output of the generator driven by the surplus shaft power of the gas turbine can be obtained. High power generation efficiency can be achieved as compared with the fuel cell or gas turbine. Such a combined power generator is disclosed in Non-Patent Documents 1 and 2, for example.

"Effect of fuel composition on performance of gas turbine / solid oxide fuel cell hybrid system", Masahito Kimishima, JSME Thermal Engineering Conference, 2005, pp271-272 "Cycle analysis of micro gas turbine / solid oxide fuel cell hybrid system", Hideyuki Uechi, Masahito Kimishima, Nobuhide Kasaki, Transactions of the Japan Society of Mechanical Engineers (B), 2002, 68, 666, pp336-345

  However, the above-described conventional combined power generation apparatus has a problem that it is difficult to operate both the fuel cell and the gas turbine at an appropriate temperature.

  One non-limiting exemplary embodiment of the present application provides a power generator that can operate both a fuel cell and a gas turbine at a suitable temperature.

  A power generation apparatus according to an aspect of the present disclosure is provided with a compressor that compresses air, a first heat exchanger that heats the air compressed by the compressor, and the air that is heated by the first heat exchanger. A fuel cell that has an air electrode to be supplied and a fuel electrode to which fuel is supplied, and that generates electric power by reacting oxygen in the air with the fuel, and second heat exchange that heats exhaust from the air electrode A combustor for mixing and combusting the exhaust gas heated by the second heat exchanger and the exhaust gas from the fuel electrode, and a turbine driven by combustion gas from the combustor. The exhaust from the turbine is supplied to the second heat exchanger to heat the exhaust from the air electrode, and is then supplied to the first heat exchanger to heat the air compressed by the compressor. .

  The general and specific aspects described above can be implemented using systems, methods and computer programs, or can be implemented using combinations of systems, methods and computer programs.

  According to the power generator according to one aspect of the present invention, both the fuel cell and the gas turbine can be operated at an appropriate temperature.

Cycle system diagram of power generator in exemplary embodiment 1 of the present disclosure The figure which shows the structural example of heat exchanger R1, R2 in Embodiment 1. FIG. The figure which shows the other structural example of heat exchanger R1, R2 in Embodiment 1. FIG. Cycle system diagram when the combined power generator of the comparative example is operated under certain conditions Temperature-entropy diagram for the cycle of FIG. 3A Cycle system diagram when operating the power generator in exemplary embodiment 1 under certain conditions Temperature-entropy diagram for the cycle of FIG. 4A Cycle system diagram of the composite power generator of the comparative example (when the cell temperature is lowered) Cycle system diagram in the first embodiment (when the cell temperature is lowered) Diagram showing an example of an integrated plate fin heat exchanger Diagram showing an example of an integrated shell and tube heat exchanger Cycle diagram in exemplary embodiment 2 of the present disclosure The figure which shows the structural example of heat exchanger R2, R3 in Embodiment 2. FIG. The figure which shows the other structural example of heat exchanger R2, R3 in Embodiment 2. FIG. Cycle system diagram in a modification of the second embodiment The figure which shows the other structural example of heat exchanger R2, R3 in Embodiment 2. FIG. The figure which shows the further another structural example of heat exchanger R2, R3 in Embodiment 2. FIG. The figure which shows the example with which heat exchanger R1, R2, R3 was integrated. The figure which shows the other example with which heat exchanger R1, R2, R3 was integrated. Cycle system diagram of power generator in exemplary embodiment 3 Cycle system diagram in modification of exemplary embodiment 3 The figure which shows the electric power generating apparatus in other embodiment. Cycle system diagram showing the prior art described in Non-Patent Document 1 Cycle system diagram showing the prior art described in Non-Patent Document 2

  Before describing a specific embodiment of the present disclosure, first, a problem in a conventional combined power generation device found by the present inventors and an outline of a configuration for solving the problem will be described.

  FIGS. 16 and 17 are views showing the fuel cell / micro gas turbine combined power generation apparatus disclosed in Non-Patent Document 1 and Non-Patent Document 2, respectively. The numerical values in the figure are based on the cycle analysis results assuming a total output of 30 kW. 16 and 17 includes a stack of solid oxide fuel cells (hereinafter sometimes simply referred to as “fuel cell” or “SOFC”), a compressor that supplies compressed air to the SOFC, and And a combustor for mixing and burning exhaust gas from the cathode (air electrode) and anode (fuel electrode) of the SOFC, and a turbine driven by the exhaust gas from the combustor. The turbine and the compressor are connected to a generator through a shaft, and the generator generates power and the compressor compresses air by the rotation of the turbine. In the combined power generation cycle shown in FIGS. 16 and 17, since the temperature of the exhaust gas from the turbine is higher than the temperature of the air compressed by the compressor, the exhaust heat is recovered and the compressed air at the cathode inlet is heated. A regenerative heat exchanger (Recuperator) is provided.

  In the SOFC anode, the concentration of fuel (such as methane) decreases as the power generation reaction proceeds. Even if the fuel concentration is uneven or fluctuates, the fuel has a concentration at which a certain percentage of unreacted fuel remains (generally, the fuel utilization rate is around 80%) so that the fuel near the outlet will not be depleted. To the anode. The oxygen supplied to the cathode is also supplied in an amount greater than that required for a chemical reaction for power generation (hereinafter sometimes referred to as “power generation reaction” or “battery reaction”). This is to keep the cell temperature constant by cooling the cell that becomes high temperature due to the exhaust heat generated by the power generation reaction with the air passing through the cathode.

  Unreacted fuel discharged from the anode is mixed with exhaust from the cathode and burned in a combustor. The turbine is driven by the high-temperature and high-pressure gas discharged from the combustor. At this time, the higher the temperature at the turbine inlet, the higher the power generation efficiency by the gas turbine.

  However, since the temperature rise ΔTcc of the exhaust gas by the combustor (873 ° C.−800 ° C. = 73 ° C. in the example of FIG. 16) is determined by the mixing ratio of the cathode exhaust air flow rate and the unreacted fuel, the increase is more than a certain level. difficult. The flow rate of unreacted fuel is determined from the power generation output of the SOFC, and the air flow rate is determined so that the heat generation and cooling of the cell are balanced as described above. It is possible to reduce the air flow rate by lowering the cathode inlet temperature and increasing the temperature difference from the cell temperature (air-fuel ratio decrease → ΔTcc increase). However, in such a case, the temperature efficiency of the regenerative heat exchanger is reduced, that is, the thermal energy recovered from the exhaust gas of the turbine is sacrificed, so that the power generation efficiency of the entire system is reduced. ΔTcc also increases by injecting extra fuel into the combustor, but the amount of fuel used increases, so power generation efficiency decreases.

  In the cycle of Non-Patent Document 1 (FIG. 16), in order to keep the turbine inlet temperature low, the air flow rate is increased as compared with the cycle of Non-Patent Document 2 (FIG. 17) (0.0384 kg / s → 0. 065 kg / s). For this reason, in the cycle shown in FIG. 16, the work by the compressor increases as compared with the cycle shown in FIG. 17, and the ratio of the amount of power generated by the gas turbine with relatively low power generation efficiency increases. As a result, the overall power generation efficiency is reduced.

  After all, under the condition that the power generation efficiency is maximized, ΔTcc is about 150 ° C. to about 200 ° C. as in the cycle of Non-Patent Document 2 shown in FIG. That is, when the temperature of the combustion gas at the turbine inlet is TIT and the cell temperature is Tcell, there is a design constraint that TIT≈Tcell + 200 ° C.

  The cell temperature is determined by a balance between the power generation efficiency of the SOFC and the durability of the stack, and is typically 700 ° C to 1000 ° C. The higher the turbine inlet temperature, the higher the power generation efficiency of the gas turbine, but there is a problem that it cannot be determined independently of the cell temperature due to the above-mentioned restrictions.

  Based on the above findings, the present inventors have completed a new fuel cell / gas turbine combined power generator that solves this problem. According to the embodiment of the present invention, not only the air supplied to the cathode but also the air discharged from the cathode is heated by the exhaust heat from the turbine, thereby increasing the difference between the cell temperature Tcell and the turbine inlet temperature TIT. can do. Thereby, for example, since the turbine inlet temperature TIT can be increased without increasing the operating temperature of the SOFC, the power generation efficiency can be improved. Alternatively, since the operating temperature of the SOFC can be lowered without lowering the power generation efficiency, the fuel cell stack can be reduced in cost and extended in life.

  The outline | summary of embodiment of this indication is as follows.

  (1) A power generation apparatus according to an aspect of the present disclosure includes a compressor that compresses air, a first heat exchanger that heats the air compressed by the compressor, and the heat that is heated by the first heat exchanger. A fuel cell that has an air electrode to which air is supplied and a fuel electrode to which fuel is supplied, and that generates power by reacting oxygen in the air with the fuel; and a heater that heats exhaust from the air electrode Two heat exchangers, a combustor that mixes and burns the exhaust gas heated by the second heat exchanger and the exhaust gas from the fuel electrode, and a turbine that is driven by combustion gas from the combustor. Prepare. The exhaust from the turbine is supplied to the second heat exchanger to heat the exhaust from the air electrode, and is then supplied to the first heat exchanger to heat the air compressed by the compressor. .

  (2) In one embodiment, the fuel cell is a solid oxide fuel cell.

  (3) In one embodiment, the first heat exchanger and the second heat exchanger are integrated.

  (4) In a certain embodiment, the temperature of the said combustion gas in the inlet_port | entrance of the said turbine is 1000 degreeC or more.

  (5) In a certain embodiment, the temperature of the said combustion gas in the inlet_port | entrance of the said turbine is 1200 degreeC or more.

  (6) In a certain embodiment, at least one part of the rotor of the said turbine is comprised by the member made from ceramics.

  (7) In one embodiment, a cooling mechanism for cooling the rotor of the turbine is further provided.

  (8) In a certain embodiment, at least one part of the said combustor is comprised with the member made from ceramics.

  (9) In a certain embodiment, it further has the 3rd heat exchanger which heats the exhaust_gas | exhaustion from the said fuel electrode of the said fuel cell by making the exhaust_gas | exhaustion from the said turbine into a heating medium.

  (10) In one embodiment, the second heat exchanger and the third heat exchanger are integrated.

  (11) In one embodiment, the first heat exchanger, the second heat exchanger, and the third heat exchanger are integrated.

  (12) In one embodiment, the power generation device includes: a first pipe that bypasses the air electrode of the fuel cell; and a first valve that adjusts a flow rate of a fluid flowing in the first pipe. Is further provided.

  (13) In an embodiment, the power generator is configured to adjust a flow rate of a fluid flowing in the second pipe and a second pipe that bypasses a low-temperature-side flow path of the second heat exchanger. And a second valve.

  (14) In one embodiment, the power generator is configured to adjust a flow rate of a fluid flowing in the third pipe and a third pipe that bypasses a low-temperature-side flow path of the first heat exchanger. And a third valve.

  (15) In an embodiment, the power generation device further includes a Rankine cycle power generation device that uses the exhaust from the turbine that has passed through the first heat exchanger as a heat source.

  (16) In one embodiment, the power generator further includes a generator connected to the turbine and the compressor via a shaft.

  Hereinafter, more specific embodiments will be described. In the following description, common or similar elements are given the same reference numerals.

(Embodiment 1)
FIG. 1 is a diagram illustrating a schematic configuration of a combined fuel cell / gas turbine power generation apparatus 100 according to the first embodiment of the present disclosure. As shown in FIG. 1, the power generation apparatus 100 according to the present embodiment includes a solid oxide fuel cell stack (SOFC) 17, a gas turbine 18, and other auxiliary devices. The auxiliary equipment includes a fuel pump FP, a first regenerative heat exchanger R1, and a second regenerative heat exchanger R2. In the following description, the term “regenerative heat exchanger” may be omitted and simply referred to as “heat exchanger”. Each element shown in FIG. 1 is connected by a pipe (flow path) as indicated by an arrow in the figure. Sustained power generation is realized by circulating a fluid such as air or fuel in the pipe.

  The gas turbine 18 includes a compressor C that compresses air, a combustor CC that combusts exhaust gas from the SOFC 17, a turbine T that is driven by high-temperature and high-pressure combustion gas from the combustor CC, and a generator that generates AC power. MG. The compressor C, the turbine T, and the generator MG are connected by a shaft 19 and can transmit the rotational torque generated by the turbine T to the compressor C and the generator MG. As a result, power generation and air compression are performed. The gas turbine 18 in the present embodiment may be a known micro gas turbine having a power generation output of, for example, about several tens kW to several hundreds kW, but is not limited thereto, and may be a larger gas turbine.

The SOFC 17 is a battery that generates DC power by a chemical reaction between oxygen in the air and fuel (such as methane). The SOFC 17 includes a cathode (air electrode) Ca to which air (Air) is supplied, an anode (fuel electrode) An to which fuel is supplied, and oxygen ions (O ²⁻ ) obtained by ionizing oxygen molecules flowing into the cathode Ca. And an electrolyte 16 transported from the cathode Ca to the anode An. Thereby, the heat generated by the chemical reaction can be transferred between the electrodes. Hydrogen is required for the cell reaction at the anode An. For this reason, methane is supplied from the fuel pump FP to the anode An. Methane is internally reformed near the inlet of the anode An to generate hydrogen.

  For the SOFC 17, for example, a known configuration such as a cylindrical vertical stripe type, a cylindrical horizontal stripe type, a flat plate type, or a cylindrical flat plate type can be adopted. For the electrolyte 16, for example, a material having oxygen ion conductivity such as yttria stabilized zirconia (YSZ) or perovskite oxide can be used. The electrolyte 16 may be made of a heat resistant metal in addition to such oxygen ion conductive ceramics. For the anode An that is the fuel electrode, various conductive materials that are likely to cause hydrogen adsorption / dissociation and that have a thermal expansion matching with the surrounding materials such as the electrolyte 16 can be used. For example, when YSZ is used for the electrolyte 16, a material (cermet) obtained by mixing the powder and a metal (for example, Co, Pt, Ru, etc.) excellent in catalytic activity can be used. For the cathode Ca, which is an air electrode, various materials having conductivity and oxygen transportability and excellent in catalytic activity that easily cause an oxygen dissociation reaction can be used. For example, conductive ceramics such as Mn-based perovskite can be used.

  The power generation apparatus 100 in the present embodiment further includes a second regenerative heat exchanger R2 that heats the exhaust gas from the cathode Ca of the SOFC 17 in addition to the first regenerative heat exchanger R1 that heats the air compressed by the compressor C. Yes. 2A and 2B are diagrams schematically illustrating a configuration example of the heat exchangers R1 and R2. In the example shown in FIG. 2A, both heat exchangers R1 and R2 have a plate fin type structure. This type of heat exchanger uses a plurality of plates and a plurality of fins to exchange heat between air and exhaust gas from the turbine T flowing in the pipe. In the example shown in FIG. 2B, the heat exchangers R1 and R2 both have a shell-and-tube structure. This type of heat exchanger exchanges heat between exhaust gas from the turbine T flowing in a shell (cylinder) and air flowing in a number of tubes. The heat exchangers R1 and R2 may be other types of heat exchangers. The heat exchanger R1 and the heat exchanger R2 are not necessarily the same type, and different types of heat exchangers can be used.

  Next, operation | movement of the electric power generating apparatus 100 is demonstrated.

  The compressed air discharged from the compressor C enters the low temperature side of the regenerative heat exchanger R1, is preheated by the exhaust heat of the turbine T, and then is supplied to the cathode Ca. Part of the oxygen contained in the compressed air (cathode intake 10) flowing into the cathode Ca is lost by the cell reaction, and the remaining compressed air (cathode exhaust 11) enters the low temperature side of the regenerative heat exchanger R2. The cathode exhaust 11 is heated by the exhaust heat of the turbine T in the regenerative heat exchanger R2, and then flows into the combustor CC.

  The fuel (methane) is increased in pressure by the fuel pump FP and supplied to the anode An. Oxygen ions flowing from the electrolyte 16 and a part of the fuel supplied from the fuel pump FP (this ratio is referred to as a fuel utilization rate Uf) are reactants of the cell reaction at the anode An. Products such as water and carbon dioxide due to the cell reaction are discharged as anode exhaust 12 together with unreacted fuel. The anode exhaust 12 contains high-temperature water vapor, a part of which is recirculated to the inlet of the anode An and mixed with the discharge gas of the fuel pump FP. The water vapor mixed with the fuel is a component necessary for fuel reforming in the anode An. The anode exhaust 12 that is not recirculated flows into the combustor CC.

At the inlet of the anode An, a part of the refluxed anode exhaust 12 reacts with methane supplied from the fuel pump FP. At this time, the reaction proceeds using heat generated from each cell of the SOFC 17. The reaction occurring here is represented by the following formulas (1) and (2).
CH ₄ + H ₂ O → 3H ₂ + CO (1)
CO + H ₂ O → H ₂ + CO ₂ (2)

  The reforming reaction represented by the formula (1) is an endothermic reaction, and the shift reaction represented by the formula (2) is an exothermic reaction.

Inside the anode An, hydrogen and oxygen ions transported from the electrolyte 16 react to generate water vapor, and electrons are released to the external circuit. Thereby, electric power is generated. At this time, carbon dioxide is also generated by the reaction between carbon monoxide and oxygen ions generated by the reforming reaction. That is, in the anode An, reactions represented by the following formulas (3) and (4) occur.
H ₂ + O ²⁻ → H ₂ O + 2e ⁻ (3)
CO + O ²⁻ → CO ₂ + 2e ⁻ (4)

  Water vapor and carbon dioxide generated by these reactions are discharged as anode exhaust 12 together with unreacted fuel.

  In the combustor CC, the cathode exhaust 11 (oxygen) and the anode exhaust 12 (unreacted fuel) burn. In the example of FIG. 1, only the unreacted fuel in the anode exhaust 12 is used as the fuel, but in addition to this, the fuel may be directly supplied to the combustor CC from the fuel pump FP or another fuel pump. As a result of the combustion, the temperature of the cathode exhaust increases by ΔTcc, and a high-temperature high-pressure gas having a turbine inlet temperature TIT is generated. This high-temperature high-pressure gas drives the turbine T. Exhaust gas (turbine exhaust gas) expanded by the driving of the turbine flows in this order through the flow path on the high temperature side of the regenerative heat exchangers R2 and R1, and is cooled between them and discharged from the power generation apparatus 100.

  As described above, the power generation apparatus 100 according to this embodiment includes the compressor C that compresses air, the first regenerative heat exchanger R1 that heats the air compressed by the compressor C, and the first regenerative heat exchanger. A fuel cell having an air electrode (cathode Ca) to which air heated by R1 is supplied and a fuel electrode (anode An) to which fuel is supplied, and generating electricity by reacting oxygen in the air and the fuel ( SOFC) 17, the second regenerative heat exchanger R2 that heats the exhaust gas from the air electrode, the exhaust gas heated by the second regenerative heat exchanger R2, and the combustion gas that mixes and combusts the exhaust gas from the fuel electrode And a turbine T driven by the combustion gas from the combustor CC. In the power generation apparatus 100, after the exhaust from the turbine is supplied to the second regenerative heat exchanger R2 to heat the exhaust from the air electrode, the exhaust is supplied to the first regenerative heat exchanger R1 and compressed by the compressor C. It is configured to heat the air.

  With the above configuration, the electrical output of the generator MG driven by the surplus shaft power of the gas turbine 18 and the electrical output of the SOFC 17 are used as the electrical output of the combined power generator 100. In the present embodiment, since the regenerative heat exchanger R2 is provided, the turbine inlet temperature TIT can be increased as compared with the conventional techniques such as Non-Patent Documents 1 and 2 in which heat exchange does not occur. The turbine inlet temperature TIT varies depending on various conditions such as the material composing the combustor CC and the turbine T, and may be set to 1000 ° C. or more and 1500 ° C. or less, for example. In an example, the turbine inlet temperature TIT may be set to 1200 ° C. or higher and 1500 ° C. or lower. As a result, the power generation efficiency of the gas turbine generator MG increases, so that power generation with higher efficiency than before can be performed.

  Further, according to the present embodiment, the operating temperature of the SOFC 17 can be lowered without lowering the turbine inlet temperature TIT, that is, without lowering the power generation efficiency of the gas turbine generator MG. For this reason, it is possible to reduce the cost and extend the life of the stack.

  Hereinafter, the specific effect of this embodiment compared with a prior art is demonstrated using a Ts diagram.

  FIG. 3A is a cycle system diagram when a combined power generation apparatus having a configuration similar to that of Non-Patent Documents 1 and 2 is operated under certain conditions. FIG. 3B is a Ts diagram in this combined power generation device. In this example, the total output is 100 kW, the turbine inlet temperature TIT is 900 ° C., the cell temperature Tcell is 746 ° C., the pressure ratio of the air before and after compression by the compressor C is 3, the ratio of the number of moles of steam and methane before reforming It is assumed that (S / C ratio) is set to 4 and air at 15 ° C. is supplied at a flow rate of 0.221 kg / s. Under this condition, the power generation efficiency η is 62.4%.

  The state of the air circulating through the power generator changes in a cycle of (1) → (2) → (3) → (4) → (5) → (6) → (7) → (1). This cycle is called a “basic cycle”. Let Q1 be the amount of heat exchanged in the regenerative heat exchanger R1.

  The air is first compressed by the compressor C ((1) → (2)), and enters the cathode of the SOFC 17 through a temperature raising process ((2) → (3)) in the regenerative heat exchanger R1. This air rises to the cell temperature Tcell due to the exhaust heat of the fuel cell stack ((3) → (4)), and becomes cathode exhaust and enters the combustor CC. In the combustor CC, the cathode exhaust is mixed with the anode exhaust containing unreacted fuel, and burns to reach the maximum temperature ((4) → (5)). After the expansion process in the turbine T ((5) → (6)), exhaust heat is recovered through the regenerative heat exchanger R1 ((6) → (7)) and exhausted. By providing the heat exchanger R1, the work performed in the entire cycle is increased by the area surrounded by (2), (3), (6), and (7) in FIG. 3B, compared to the case without the heat exchanger R1. To do.

  FIG. 4A is a cycle system diagram when the combined power generation apparatus according to the present embodiment is operated at the same outside air temperature and cell temperature as described above. FIG. 4B is a Ts diagram in this combined power generation device. In this example, parameters such as the pressure ratio and the S / C ratio are set to the same values as in the above example. However, in order to set the cell temperature Tcell to 746 ° C., the air flow rate is 0.132 kg / s. Since the heat exchanger R2 is provided, the turbine inlet temperature TIT is increased to 1200 ° C., and the cathode intake air is decreased to 560 ° C. In this cycle, the power generation efficiency η is 63.9%. In the present embodiment, the cycle is (1) → (2) → (3) → (4) → (4 ′) → (5 ′) → (6 ′) → (6 ″) → (7) → (1 ). FIG. 4B shows the states (5) and (6) in the configuration of FIG. 2A for comparison. The amount of heat exchanged by the heat exchanger R1 is Q1, and the amount of heat exchanged by the heat exchanger R2 is Q2.

  The process of states (1) to (4) is the same process as states (1) to (4) in the configuration shown in FIGS. 3A and 3B. In the present embodiment, the cathode exhaust is heated by the regenerative heat exchanger R2 ((4) → (4 ′)) before entering the combustor CC. For this reason, the maximum temperature, that is, the turbine inlet temperature TIT increases by the amount of heat exchanged here. After undergoing the expansion process ((5 ′) → (6 ′)) in the turbine T, the exhaust from the turbine T is exhausted heat recovery process ((6 ′) → (6 ″)) in the regenerative heat exchanger R2. Further, the temperature is sequentially lowered by the exhaust heat recovery process ((6 ″) → (7)) in the regenerative heat exchanger R1, and is discharged to the outside.

  In this embodiment, compared with the basic cycle, the power generation output per unit flow rate is increased by the area surrounded by (5), (5 '), (6'), and (6) in FIG. 4B. Since the fuel flow rate is reduced, the power generation efficiency is improved. In the example shown in FIG. 4A, the exhaust gas temperature is higher than that in the basic cycle, but since the air flow rate is about half, the exhaust heat amount (enthalpy) is reduced. Moreover, both the SOFC 17 and the gas turbine 16 can be reduced in size by reducing the air flow rate. For this reason, the output density, which is the ratio between the electrical output and the device dimensions, is improved.

  Further, since the heat exchange amounts of the regenerative heat exchangers R1 and R2 can be arbitrarily designed, the cell temperature Tcell of the fuel cell and the turbine inlet temperature TIT can be arbitrarily set, and the degree of freedom in design is improved. For example, the cell temperature Tcell of the fuel cell can be lowered without changing the turbine inlet temperature TIT. A specific example in that case will be described with reference to FIGS.

  The example shown in FIG. 5 is an example in which the cell temperature Tcell is lowered by 146 ° C. to 600 ° C. as compared with the basic cycle shown in FIGS. 3A and 3B. In this example, the air flow rate is increased to 0.308 kg / s. The turbine inlet temperature TIT is also decreased by 180 ° C. to 720 ° C. in conjunction with the decrease in the cell temperature Tcell. As a result, the power generation efficiency decreased by 3.8% from 62.4% to 58.6%.

  The example shown in FIG. 6 is an example in which the cell temperature Tcell is lowered to 600 ° C. in the configuration of the present embodiment. In this example, the air flow rate is 0.183 kg / s. The cell temperature Tcell has dropped to 600 ° C. as described above, but the turbine inlet temperature TIT remains at 900 ° C. For this reason, it is possible to reduce the cost and extend the life of the cell stack material while suppressing the decrease in power generation efficiency to 2.5 (= 62.4-59.9)%.

  Thus, according to the present embodiment, the turbine inlet temperature TIT and the cell temperature Tcell can be determined flexibly, so that both high efficiency and low cost / long life can be achieved. In order to achieve the same thing with the conventional configuration, it was necessary to improve the performance and durability of each component. According to this embodiment, while using individual components as described above, it is possible to achieve excellent characteristics that are not found in the past as described above.

  Then, the modification of this embodiment is demonstrated.

  As described above, according to the present embodiment, the turbine inlet temperature TIT can be increased to a high temperature exceeding 1000 ° C. In such a high temperature state, when the metal turbine T and the combustor CC are used, their heat resistant temperatures may be exceeded. In such a case, ceramic (for example, silicon nitride) members may be used for at least part of the rotor of the turbine T and the combustor CC. Or the cooling mechanism (cooling blade etc.) which cools the rotor of the turbine T may be provided. Thereby, since heat resistance improves, the operation | movement in the high temperature state over 1200 degreeC becomes possible, for example.

  The regenerative heat exchangers R1 and R2 in the present embodiment are physically separated, but the regenerative heat exchanger R1 and the regenerative heat exchanger R2 may be integrated. 7A and 7B are diagrams illustrating an example of an integrated heat exchanger. FIG. 7A shows a plate fin type heat exchanger, and FIG. 7B shows a shell and tube type heat exchanger. The arrangement of the heat exchangers R1 and R2 shown in the figure may be reversed. That is, an integrated heat exchanger in which a heat exchanger R2 for heating the cathode intake air is provided at a subsequent stage of the heat exchanger R1 for heating the cathode exhaust 11 may be used. By integrating, effects such as downsizing of the apparatus, simplification of piping, and cost reduction can be obtained.

  The power generation apparatus 100 may further include a fuel pump that directly supplies fuel methane or the like to the combustor CC, in addition to the fuel pump FP. Alternatively, the fuel pump FP may be configured to supply fuel to the combustor CC. According to such a configuration, combustion in the combustor CC is possible even when there is a shortage of unreacted fuel discharged from the anode An.

  The SOFC 17 in the present embodiment is configured such that internal reforming of fuel is performed at the entrance of the anode An, but a reformer may be provided separately. Further, the SOFC 17 is not limited to one but may have a plurality of stacks in which many cells are connected in series. In that case, it is possible to adopt a configuration in which exhausts from the cathodes of the cells in the plurality of stacks are collectively led to the heat exchanger R2 and heated.

(Embodiment 2)
Next, a second embodiment will be described. In the present embodiment, in addition to the second regenerative heat exchanger R2, the power generation apparatus 100 further includes a third regenerative heat exchanger R3 that heats the anode exhaust 12 flowing into the combustor CC by exhaust heat from the turbine T. It differs from Embodiment 1 in the point provided. Hereinafter, differences from the first embodiment will be mainly described, and descriptions of common matters will be omitted.

  FIG. 8 is a cycle system diagram of the power generation device 100 according to the present embodiment. As shown in FIG. 8, the power generation apparatus 100 according to the present embodiment further includes a third regenerative heat exchanger R3 that passes the anode exhaust 12 flowing into the combustor CC and heats the anode exhaust 12 by exhaust heat from the turbine T. I have. According to such a configuration, the temperature of the fuel (hydrogen with reformed methane) flowing into the combustor CC increases, and thermal dissociation before the combustion reaction is promoted, so the combustion efficiency in the combustor CC increases. To do.

  9A and 9B are diagrams illustrating a configuration example of the heat exchangers R2 and R3. FIG. 9A shows an example where the heat exchangers R2 and R3 are plate fin type heat exchangers, and FIG. 9B shows an example where the heat exchangers R2 and R3 are shell and tube type heat exchangers. Show. The arrangement relationship between the heat exchangers R2 and R3 may be reversed. That is, the heat exchangers R2 and R3 may be arranged so that the heat exchanger R2 heats the cathode exhaust 11 after the heat exchanger R3 heats the anode exhaust 12 by the exhaust from the turbine T.

  The heat exchangers R2 and R3 may be integrated. FIG. 10 is a diagram illustrating an example in which the second heat exchanger R2 and the third heat exchanger R3 are integrated. 11A and 11B are diagrams showing a configuration example of the heat exchangers R2 and R3 in this case. Thus, by integrating the heat exchangers R2 and R3, it is possible to reduce the size of the apparatus, simplify the piping, and reduce the cost.

  In the present embodiment, in addition to the heat exchangers R2 and R3, the heat exchanger R1 may be further integrated. 12A and 12B are diagrams showing examples of such heat exchangers. By integrating three heat exchangers as in these examples, further downsizing of the apparatus, simplification of piping, and cost reduction can be realized.

  In addition, each heat exchanger is not limited to said structure, As long as heat exchange is possible, it may have what kind of structure.

(Embodiment 3)
Next, a third embodiment will be described. In the present embodiment, the first pipe 13 that bypasses the air electrode (cathode Ca) of the SOFC 17, the first flow rate adjustment valve V1 for adjusting the flow rate of the first pipe, and the second heat exchanger R2 This embodiment is different from the first embodiment in that a second pipe 14 that bypasses the low temperature side flow path and a second flow rate adjustment valve V2 for adjusting the flow rate of the second pipe are provided. Hereinafter, the description will focus on the points different from the first embodiment, and description of common matters will be omitted.

  FIG. 13 is a diagram illustrating a configuration of the power generation device 100 according to the present embodiment. In the present embodiment, the power generation apparatus 100 includes a flow rate adjustment valve V1 for controlling the cell temperature Tcell of the SOFC 17 and a flow rate adjustment valve V2 for controlling the turbine inlet temperature TIT. By changing the opening degree of the flow rate adjusting valve V1, the flow rate of the cathode exhaust flowing through the pipe 13 bypassing the cathode Ca can be adjusted. Moreover, the flow rate of the piping 14 which bypasses the low temperature side flow path of the regenerative heat exchanger R2 can be adjusted by changing the opening degree of the flow rate adjusting valve V2. According to the present embodiment, the cell temperature Tcell of the SOFC 17 and the turbine inlet temperature TIT can be controlled during the operation of the power generation apparatus 100.

  When partial load operation is performed due to fluctuations in electric power load or the like, the amount of heat generated in the SOFC stack decreases, so the gas turbine rotational speed is decreased so that the air flow rate is maintained so as to keep the cell temperature constant. However, when the rotational speed of the gas turbine is fixed, or when the partial load factor is 50% or less even if the rotational speed is variable, it cannot be reduced to a desired air flow rate. Or even if it can reduce to the desired air flow rate, since it remove | deviates from the appropriate operating range of a gas turbine, power generation efficiency will fall.

  According to the present embodiment, by adjusting the opening degree of the flow rate adjusting valve V1, a part of the air flowing into the cathode Ca can be bypassed, and a desired cathode flow rate can be realized. However, if the cathode flow rate is decreased too much to maintain the cell temperature Tcell, oxygen necessary for the battery reaction may be insufficient. For this reason, control is performed in a range in which the amount of oxygen necessary for the battery reaction can be secured.

  When the proportion of air that bypasses the cathode Ca increases, the temperature Tcell at the low-temperature inlet of the regenerative heat exchanger R2 decreases (the amount of decrease is ΔT). As a result, the temperature difference between the high temperature side and the low temperature side of the regenerative heat exchanger R2 becomes large, the heat exchange amount increases, and the temperature at the low temperature side outlet of the regenerative heat exchanger R2 decreases (the decrease amount is the above ΔT). Less than). As a result, the turbine inlet temperature TIT also decreases. In order to maintain the turbine inlet temperature TIT, the opening degree of the flow rate adjustment valve V2 may be decreased and the low temperature side flow rate of the regenerative heat exchanger R2 may be increased.

  As shown in FIG. 14, the power generation apparatus 100 further includes a third pipe 15 that bypasses the flow path on the low temperature side of the regenerative heat exchanger R1, and a third flow rate adjustment valve V3 for adjusting the flow rate. You may have. With such a configuration, it is possible to control the heat exchange amount and the cathode inlet temperature by the regenerative heat exchanger R1. For this reason, even when the temperature of the air discharged from the compressor C fluctuates due to fluctuations in the outside air temperature, the cathode inlet temperature can be kept constant by adjusting the opening of the flow rate adjustment valve V3.

  In addition, adjustment of the opening degree of the flow rate adjusting valves V1, V2, and V3 may be performed by, for example, electronic control using a flow rate sensor or a control circuit (not shown), or may be manually adjusted by the user. . In addition to the above configuration, only one of the flow rate adjustment valves V1, V2, and V3 is provided, only the flow rate adjustment valves V1 and V3 are provided, or only the flow rate adjustment valves V2 and V3. You may employ | adopt the structure provided. If at least one of the flow rate adjusting valves V1, V2, and V3 is provided, a partial effect can be obtained although it is partial.

(Other embodiments)
The technology in the present disclosure is not limited to the above-described embodiment, and can be applied to an embodiment in which changes, replacements, additions, omissions, and the like are appropriately performed. Moreover, it is also possible to combine each component demonstrated by said embodiment into a new embodiment. Hereinafter, other embodiments will be exemplified.

  In the above embodiment, a solid oxide fuel cell (SOFC) is used as the fuel cell, but other types of fuel cells may be used. For example, other types of fuel cells that operate at high temperatures such as molten carbonate fuel cells can be used.

  For example, as illustrated in FIG. 15, the power generation apparatus 100 may further include a Rankine cycle power generation apparatus G that uses exhaust gas from the turbine T that has passed through the first heat exchanger R1 as a heat source. Since the exhaust gas from the heat exchanger R1 is still sufficiently high in temperature, the power generation efficiency can be further improved by combining the bottoming cycle using this exhaust heat. The Rankine cycle power generation device G may include a generator driven by, for example, another gas turbine or a steam turbine. By adding such a power generation device G, the exhaust heat from the turbine T can be used more effectively, and further improvement in the total power generation efficiency can be expected. 15 is based on the configuration of the third embodiment, but may be based on the configurations of the first and second embodiments.

  The fuel cell / gas turbine combined power generation device of the present disclosure is useful as a power generation device for a stationary generator, a mobile power supply vehicle, a household CHP, a power plant, and the like.

C Compressor T Turbine MG Generator FP Fuel pump R1 Regenerative heat exchanger R2 Regenerative heat exchanger Ca Fuel cell cathode An An anode of fuel cell CC Combustor V1 Bypass flow adjustment valve for cathode V2 Bypass flow adjustment for regenerative heat exchanger R2 Valve V3 Bypass flow adjustment valve for regenerative heat exchanger R1 10 Cathode intake 11 Cathode exhaust 12 Anode exhaust 13 Bypass piping for cathode 14 Bypass piping for regenerative heat exchanger R2 15 Bypass piping for regenerative heat exchanger R1 16 Electrolyte 17 Solid oxide Fuel cell (SOFC)
18 gas turbine 19 shaft 100 power generator

Claims (16)

A compressor that compresses the air;
A first heat exchanger for heating the air compressed by the compressor;
A fuel cell having an air electrode to which the air heated by the first heat exchanger is supplied, and a fuel electrode to which fuel is supplied, and generating electricity by reacting oxygen in the air and the fuel; ,
A second heat exchanger for heating the exhaust from the air electrode;
A combustor for mixing and combusting the exhaust gas heated by the second heat exchanger and the exhaust gas from the fuel electrode;
A turbine driven by combustion gas from the combustor;
With
The exhaust from the turbine is supplied to the second heat exchanger to heat the exhaust from the air electrode, and is then supplied to the first heat exchanger to heat the air compressed by the compressor. , Power generator.   The power generator according to claim 1, wherein the fuel cell is a solid oxide fuel cell.   The power generator according to claim 1 or 2, wherein the first heat exchanger and the second heat exchanger are integrated.   The power generator according to any one of claims 1 to 3, wherein a temperature of the combustion gas at an inlet of the turbine is 1000 ° C or higher.   The power generation device according to claim 4, wherein a temperature of the combustion gas at an inlet of the turbine is 1200 ° C. or higher.   The power generator according to any one of claims 1 to 5, wherein at least a part of the rotor of the turbine is made of a ceramic member.   The power generator according to any one of claims 1 to 6, further comprising a cooling mechanism for cooling the rotor of the turbine.   The power generator according to any one of claims 1 to 7, wherein at least a part of the combustor is made of a ceramic member.   The power generator according to any one of claims 1 to 6, further comprising a third heat exchanger that heats the exhaust from the fuel electrode of the fuel cell using the exhaust from the turbine as a heating medium.   The power generation device according to claim 9, wherein the second heat exchanger and the third heat exchanger are integrated.   The power generator according to claim 10, wherein the first heat exchanger, the second heat exchanger, and the third heat exchanger are integrated. A first pipe that bypasses the air electrode of the fuel cell;
A first valve for adjusting a flow rate of fluid flowing in the first pipe;
The power generator according to any one of claims 1 to 11, further comprising: A second pipe that bypasses the low-temperature channel of the second heat exchanger;
A second valve for adjusting the flow rate of the fluid flowing in the second pipe;
The power generator according to any one of claims 1 to 12, further comprising: A third pipe bypassing the low temperature side flow path of the first heat exchanger;
A third valve for adjusting the flow rate of the fluid flowing in the third pipe;
The power generator according to any one of claims 1 to 13, further comprising:   The power generator according to any one of claims 1 to 14, further comprising a Rankine cycle power generator that uses the exhaust from the turbine that has passed through the first heat exchanger as a heat source.   The power generator according to any one of claims 1 to 15, further comprising a generator connected to the turbine and the compressor via a shaft.

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