JP2013089499A - Fuel cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell module that favorably maintains startability, following characteristics, and efficiency and increases power generation efficiency.SOLUTION: A fuel cell module 12 comprises: a fuel cell stack 24; a partial oxidation reformer 45; a steam reformer 46; a vaporizer 48; a heat exchanger 50; and an off-gas combustor 52. The fuel cell module 12 also includes: a junction 57b that allows a steam passage 59a communicating with a steam outlet 73 of the vaporizer 48, and a reformed gas passage 57a communicating with a reformed gas outlet 61b of the partial oxidation reformer 45, to be joined together and connected to the steam reformer 46; and a first thermoelectric conversion section 74a and a second thermoelectric conversion section 74b that perform thermoelectric conversion by a difference in temperature between the combustion gas and the oxidant gas.

Description

  The present invention relates to a fuel cell module including a fuel cell stack that generates electric power by an electrochemical reaction between a fuel gas and an oxidant gas.

  In general, a solid oxide fuel cell (SOFC) uses an oxide ion conductor, for example, stabilized zirconia, as a solid electrolyte, and an electrolyte / electrode in which an anode electrode and a cathode electrode are disposed on both sides of the solid electrolyte. A joined body (hereinafter also referred to as MEA) is sandwiched between separators (bipolar plates). This fuel cell is normally used as a fuel cell stack in which a predetermined number of electrolyte / electrode assemblies and separators are laminated.

  As the fuel gas supplied to the fuel cell, hydrogen gas generated from a hydrocarbon-based raw fuel by a reformer is usually used. In a reformer, a reformed gas (fuel gas) is generally generated by subjecting a hydrocarbon-based raw fuel such as fossil fuel such as methane or LNG to partial oxidation reforming or steam reforming, for example. Has been.

  In this case, since the partial oxidation reformer is an exothermic reaction, the reaction is started at a relatively low temperature and the startability and followability are excellent, but the reforming efficiency is low.

  On the other hand, the steam reformer has high reforming efficiency, but has an endothermic reaction, so that there is a problem that startability and followability at a low temperature are lowered.

  Therefore, for example, a startup method disclosed in Patent Document 1 is known. As shown in FIG. 15, this patent document 1 relates to a method for starting an SOFC system having a reformer 1a having a reforming catalyst and an SOFC 2a using reformed gas as fuel.

  In the reformer 1a, a reforming reaction tube 3a that accommodates a reforming catalyst is provided in the container 4a or through the container 4a. In the reforming reaction tube 3a, the partial oxidation reforming catalyst A is filled in the former stage and the steam reforming catalyst B is filled in the latter stage to form the reforming catalyst layer.

  In this start-up method, the catalyst A having a partial oxidation reforming (POX) function and the catalyst B having a steam reforming (SR) function are used, and the temperature of the catalyst A is raised to a temperature at which the POX reaction can proceed by combustion heat or electricity. A step of heating the catalyst B with POX reaction heat and supplying a reformed gas to the anode to raise the temperature of the SOFC 2a and a step of heating the catalyst B with the combustion heat obtained by burning the reformed gas discharged from the anode, or A step of heating the catalyst B with the POX reaction heat and supplying the combustion gas obtained by burning the reformed gas to the cathode to raise the temperature of the SOFC 2a and heating the catalyst B with this combustion gas; After the temperature is reached, there is a step of performing SR by reducing the rate of the POX reaction or stopping the POX reaction.

  Further, in the fuel cell disclosed in Patent Document 2, as shown in FIG. 16, a solid oxide fuel cell main body 1b and fuel to the anode side of the fuel cell main body 1b during power generation of the fuel cell main body 1b. A first fuel gas supply system 2b for supplying gas; and a second fuel gas supply system for supplying a small amount of fuel gas as an antioxidant gas to the anode side of the fuel cell main body 1b during the operation start and stop periods of the fuel cell main body 1b. And an oxidizing gas supply system 4b for supplying air as an oxidizing gas to the cathode side of the fuel cell body 1b throughout the entire period.

  The fuel cell main body 1b includes a cylindrical battery cell FC that is laminated with an electrode-attached solid electrolyte plate sandwiched between a plurality of interconnectors, a burner 5b that preheats the battery cell FC at the start of operation, and an operation start. In combination with the battery cell FC, a heat exchanger 6b that preheats together with the battery cell FC in the period and exchanges the exhaust gas discharged from the battery cell FC with the oxidant gas to preheat the oxidant gas. The steam reformer 7b and the partial oxidation reformer 8b, which are two types of reformers that are preheated together with the battery cell FC by a burner 5b or the like and heated by the heat generated in the battery cell FC during power generation, etc. Have.

  Then, the first fuel gas supply system 2b is used during power generation to supply a large amount of fuel gas necessary for power generation to the fuel cell main body 1b. During the power generation start period and power generation stop period, the fuel cell main body 1b is When passing through the cell oxidation temperature region, the second fuel gas supply system 3b is used to supply fuel gas by partial oxidation reforming to the fuel cell main body 1b at a small flow rate necessary for preventing oxidation.

JP 2006-190605 A JP 2005-293951 A

  In the above-mentioned Patent Document 1, the reforming reaction tube 3a is filled with the partial oxidation reforming catalyst A and the steam reforming catalyst B, and even when only partial oxidation reforming is performed, Is supplied with water vapor. For this reason, the amount of heat for evaporating water is required at the time of partial oxidation reforming, and there is a problem in that heat efficiency is reduced and pressure loss due to water vapor occurs. Moreover, there is a problem that the temperature control in the reforming reaction tube 3a becomes complicated.

  Moreover, in said patent document 2, the steam reformer 7b and the partial oxidation reformer 8b are paralleled, and many electromagnetic valves SV1-SV5 are provided. Therefore, there is a problem that the circuit becomes complicated, the cost increases, and the sequence becomes complicated.

  The present invention solves this type of problem, and provides a fuel cell module capable of maintaining good startability, followability, and efficiency, and improving durability and power generation efficiency. With the goal.

  The present invention includes a fuel cell stack that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas, a partial oxidation reformer that reforms a mixed gas of a raw fuel mainly composed of hydrocarbons and an oxidant gas, A steam reformer that reforms a mixed gas of the raw fuel and steam, an evaporator that evaporates water and supplies steam to the steam reformer, and the oxidant gas by heat exchange with a combustion gas A heat exchanger that supplies the oxidant gas to the fuel cell stack, a fuel exhaust gas that is the fuel gas discharged from the fuel cell stack, and an oxidant exhaust gas that is the oxidant gas. The present invention relates to a fuel cell module including an exhaust gas combustor that burns and generates the combustion gas.

  The fuel cell module joins a steam passage communicating with the steam outlet of the evaporator and a reformed gas passage communicating with the reformed gas outlet of the partial oxidation reformer to connect to the steam reformer. And a thermoelectric conversion unit that performs thermoelectric conversion by a temperature difference between the combustion gas and the oxidant gas.

  In this fuel cell module, the combustion gas is sequentially supplied to the heat exchanger, the steam reformer, and the evaporator, and the oxidizing gas is supplied from the partial oxidation reformer to the fuel cell stack. It is preferable that the thermoelectric converter is provided on the downstream side of the evaporator in the combustion gas passage and on the upstream side of the partial oxidation reformer in the oxidant gas passage.

  For this reason, it is possible to recover the temperature difference between the combustion gas and the oxidant gas, that is, the heat energy as electric energy without hindering the heat self-supporting, and to improve the power generation efficiency. Moreover, since the temperature of the combustion gas is lowered, waste heat is suppressed, while the temperature of the oxidant gas is raised, so that heat self-sustainment is promoted. Here, the heat self-sustained means that the operating temperature of the fuel cell system is maintained only by the heat generated by itself without adding the total amount of heat necessary for the operation of the fuel cell system from the outside.

  Further, the fuel cell module includes a raw fuel passage for supplying raw fuel to the partial oxidation reformer, and an oxidant gas passage joins the raw fuel passage upstream of the partial oxidation reformer, It is preferable that a thermoelectric converter is disposed in the oxidant gas passage. Therefore, the temperature difference between the combustion gas and the oxidant gas, that is, the heat energy can be recovered as electric energy, and the power generation efficiency can be improved. Moreover, since the temperature of the combustion gas is lowered, waste heat is suppressed, while the temperature of the oxidant gas is raised, so that heat self-sustainment is promoted.

  Furthermore, in this fuel cell module, the oxidant gas passage includes a first oxidant gas supply passage for supplying an oxidant gas to the partial oxidation reformer, and a second oxidant gas for supplying the oxidant gas to the heat exchanger. It is preferable that an oxidant gas adjusting valve for branching to the oxidant gas supply path and for adjusting the distribution amount of the oxidant gas is disposed at the branch part.

  As a result, the temperature of the fuel cell stack and the FC peripheral device (BOP) including the steam reformer, the evaporator and the heat exchanger can be raised at the same time, and the startup time can be shortened. On the other hand, the steam reforming catalyst and the anode side can be reduced, and the startup time is shortened.

  In addition, even when insufficient reforming by the steam reformer is caused by insufficient heat due to load fluctuation of the fuel cell stack, the partial oxidation reformer can compensate for the insufficient reforming. For this reason, it becomes possible to follow the load fluctuation, and it is possible to suppress fuel depletion due to insufficient reforming, and to easily improve durability.

  Moreover, in this fuel cell module, it is preferable that the thermoelectric converter is disposed in the oxidant gas passage so as to be located upstream of the oxidant gas regulating valve. For this reason, it is possible to recover the temperature difference between the combustion gas and the oxidant gas, that is, the heat energy as electric energy without hindering the heat self-supporting, and to improve the power generation efficiency. Moreover, since the temperature of the combustion gas is lowered, waste heat is suppressed, while the temperature of the oxidant gas is raised, so that heat self-sustainment is promoted.

  Furthermore, in this fuel cell module, it is preferable that the thermoelectric converter is disposed at least on the first oxidant gas supply path or the second oxidant gas supply path and located downstream of the oxidant gas regulating valve. . Therefore, the temperature difference between the combustion gas and the oxidant gas, that is, the heat energy can be recovered as electric energy without hindering the heat self-sustained, and the power generation efficiency can be improved. Moreover, since the temperature of the combustion gas is lowered, waste heat is suppressed, while the temperature of the oxidant gas is raised, so that heat self-sustainment is promoted. In addition, since the temperature of the oxidant gas is raised on the downstream side of the oxidant gas regulating valve, the durability of the oxidant gas regulating valve is not impaired.

  Furthermore, in this fuel cell module, it is preferable that the thermoelectric conversion unit includes a plurality of thermoelectric conversion elements in which the combustion gas and the oxidant gas are set in parallel flow and at different thermoelectric conversion temperatures. Thereby, for example, since the temperature difference between the combustion gas and the oxidant gas becomes large on the upstream side of the parallel flow, the high temperature type thermoelectric conversion element is used, while the temperature difference becomes small on the downstream side of the parallel flow. Therefore, a low temperature type thermoelectric conversion element can be used. For this reason, since the optimal thermoelectric conversion element is used according to a temperature difference, efficient thermoelectric conversion can be performed reliably.

  Moreover, in this fuel cell module, it is preferable that the thermoelectric conversion unit includes a plurality of thermoelectric conversion elements set to have a predetermined thermoelectric conversion temperature while the combustion gas and the oxidant gas are set to counterflow with each other. Therefore, the thermoelectric conversion element set to the optimal thermoelectric conversion temperature can be used in the thermoelectric conversion part according to the assumed temperature difference. Thereby, efficient thermoelectric conversion can be reliably performed.

  Further, in this fuel cell module, the thermoelectric conversion unit is set to a flow in which the combustion gas and the oxidant gas cross each other or a symmetric flow, and a plurality of thermoelectric conversion elements set to a predetermined thermoelectric conversion temperature. It is preferable to provide. For this reason, in the thermoelectric conversion part, the thermoelectric conversion element set to the optimal thermoelectric conversion temperature can be used according to the assumed temperature difference. Therefore, efficient thermoelectric conversion can be reliably performed.

  Furthermore, in this fuel cell module, it is preferable that an exhaust gas combustor is integrally provided in the heat exchanger, and a steam reformer is provided adjacent to one end of the heat exchanger. Thereby, the heat radiation of the fuel cell module can be suppressed to the minimum, and the loss of thermal energy can be suppressed satisfactorily. In other words, heat independent operation is promoted. In addition, since the combustion circuit (piping and the like) is simplified and the number of parts is reduced, the size and cost can be reduced.

  The fuel cell module is preferably a solid oxide fuel cell module. This is particularly suitable for high-temperature fuel cells such as SOFC.

  According to the present invention, the steam passage that communicates with the steam outlet of the evaporator and the reformed gas passage that communicates with the reformed gas outlet of the partial oxidation reformer merge at the junction and communicate with the steam reformer. doing. For this reason, since the high-temperature (about 600 ° C.) reducing gas from the partial oxidation reformer is guided to the steam reformer, the startup time (temperature increase and reduction time) of the steam reformer is shortened.

  In addition, since the high-temperature reducing gas is supplied from the steam reformer to the fuel cell stack, the start-up time (temperature increase and reduction time) of the fuel cell stack is favorably shortened.

  Further, since the high-temperature reducing gas is introduced into the exhaust gas combustor, the oxidant gas, the steam reformer, and the evaporator before being supplied to the fuel cell stack can be heated. Therefore, the startup period of the fuel cell module can be shortened.

  Furthermore, the steam generated in the evaporator does not flow into the partial oxidation reformer. Thereby, it becomes possible to suppress the steam oxidation of the catalyst of the partial oxidation reformer, and the durability can be easily improved.

  Further, when insufficient reforming by the steam reformer is caused by insufficient heat due to load fluctuation of the fuel cell stack, the partial oxidation reformer can compensate for the insufficient reforming. For this reason, it becomes possible to follow the load fluctuation, and it is possible to suppress fuel depletion due to insufficient reforming, and to easily improve durability.

  Furthermore, the fuel cell module includes a thermoelectric conversion unit that performs thermoelectric conversion based on a temperature difference between the combustion gas and the oxidant gas. Therefore, the temperature difference between the combustion gas and the oxidant gas, that is, the heat energy can be recovered as electric energy, and the power generation efficiency can be improved without impairing the start-up time. Moreover, since the temperature of the combustion gas is lowered, waste heat is suppressed, while the temperature of the oxidant gas is raised, so that heat self-sustainment is promoted.

  Here, the combustion gas is a gas generated in an exhaust gas combustor, which means a heating medium capable of giving heat energy by exchanging heat with an object to be heated, such as another gas, and releasing heat energy. After that, it is called exhaust gas.

  Further, the heat self-sustainment means that the operating temperature of the fuel cell system is maintained only by the heat generated by itself without adding the whole amount of heat necessary for the operation of the fuel cell system.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration explanatory diagram of a fuel cell system in which a fuel cell module according to a first embodiment of the present invention is incorporated. FIG. 3 is a perspective explanatory view of a main part of an FC peripheral device constituting the fuel cell module. It is a principal part disassembled perspective explanatory drawing of the said FC peripheral device. It is a principal part disassembled perspective explanatory drawing of the 1st and 2nd thermoelectric conversion part which comprises the said fuel cell module. It is a flowchart explaining operation | movement from starting of the said fuel cell system to electric power generation. It is a flowchart explaining the operation | movement of low load driving | operation from the electric power generation of the said fuel cell system. It is an explanatory view of the relationship between the output and efficiency of partial oxidation reforming and steam reforming. 4 is a flowchart illustrating an operation of stopping power generation in the fuel cell system. It is schematic structure explanatory drawing of the fuel cell system in which the fuel cell module which concerns on the 2nd Embodiment of this invention is integrated. It is schematic structure explanatory drawing of the fuel cell system in which the fuel cell module which concerns on the 3rd Embodiment of this invention is integrated. It is schematic structure explanatory drawing of the fuel cell system in which the fuel cell module which concerns on the 4th Embodiment of this invention is integrated. It is a principal part disassembled perspective explanatory drawing of the thermoelectric conversion part which comprises the fuel cell module which concerns on the 5th Embodiment of this invention. It is a principal-part exploded perspective explanatory drawing of the thermoelectric conversion part which comprises the fuel cell module which concerns on the 6th Embodiment of this invention. It is a principal-part exploded perspective explanatory drawing of the thermoelectric conversion part which comprises the fuel cell module which concerns on the 7th Embodiment of this invention. It is explanatory drawing of the starting method currently disclosed by patent document 1. FIG. 6 is a schematic explanatory diagram of a fuel cell disclosed in Patent Document 2. FIG.

  As shown in FIG. 1, the fuel cell system 10 incorporates the fuel cell module 12 according to the first embodiment of the present invention, and is used for various purposes such as in-vehicle use as well as stationary use.

  The fuel cell system 10 includes a fuel cell module (SOFC module) 12 that generates power by an electrochemical reaction between a fuel gas (for example, a gas in which hydrogen gas is mixed with methane and carbon monoxide) and an oxidant gas (air). A raw fuel supply device (including a fuel gas pump) 14 for supplying raw fuel (for example, city gas) mainly composed of hydrocarbons to the fuel cell module 12, and an oxidant for supplying the oxidant gas to the fuel cell module 12 A gas supply device (including an air pump) 16, a water supply device (including a water pump) 18 that supplies water to the fuel cell module 12, and a control device 20 that controls the power generation amount of the fuel cell module 12. Prepare.

  The fuel cell module 12 includes a solid oxide fuel cell stack 24 in which a plurality of solid oxide fuel cells 22 are stacked in the vertical direction (or horizontal direction). The fuel cell 22 includes, for example, an electrolyte / electrode assembly (MEA) 32 in which a cathode electrode 28 and an anode electrode 30 are provided on both surfaces of an electrolyte 26 made of an oxide ion conductor such as stabilized zirconia.

  On both sides of the electrolyte / electrode assembly 32, a cathode side separator 34 and an anode side separator 36 are disposed. The cathode side separator 34 is formed with an oxidant gas flow path 38 for supplying an oxidant gas to the cathode electrode 28, and the anode side separator 36 is supplied with a fuel gas flow path 40 for supplying fuel gas to the anode electrode 30. Is formed. As the fuel cell 22, various SOFCs conventionally used can be used.

  In the fuel cell stack 24, an oxidant gas inlet communication hole 42 a that communicates integrally with the inlet side of each oxidant gas flow path 38, and an oxidant gas outlet communication that communicates integrally with the outlet side of the oxidant gas flow path 38. A hole 42b, a fuel gas inlet communication hole 44a that communicates integrally with the inlet side of each fuel gas flow path 40, and a fuel gas outlet communication hole 44b that communicates integrally with the outlet side of the fuel gas flow path 40 are provided.

  The fuel cell module 12 reforms a mixed gas of the raw fuel and water vapor, and a partial oxidation reformer (POX) 45 for reforming a mixed gas of raw fuel mainly composed of hydrocarbon and oxidant gas. A steam reformer (SR) 46, an evaporator 48 for evaporating water and supplying steam to the steam reformer 46, and raising the temperature of the oxidant gas by heat exchange with the combustion gas, and the fuel A heat exchanger 50 for supplying the oxidant gas to the battery stack 24; a fuel exhaust gas as the fuel gas discharged from the fuel cell stack 24; and an oxidant exhaust gas as the oxidant gas; And an exhaust gas combustor 52 for generating gas.

  The fuel cell module 12 basically includes a fuel cell stack 24 and an FC peripheral device 56. The FC peripheral device 56 includes a partial oxidation reformer 45, a steam reformer 46, an evaporator 48, a heat exchanger 50, and an exhaust gas combustor 52. As will be described later, the steam reformer 46, the heat No piping for combustion gas is provided between the exchanger 50 and the exhaust gas combustor 52.

  The raw fuel supply device 14 includes a raw fuel passage 57 that supplies the raw fuel to the partial oxidation reformer 45. The oxidant gas supply device 16 includes an oxidant gas passage 58 that supplies oxidant gas from the heat exchanger 50 to the fuel cell stack 24, and the water supply device 18 includes a water passage 59 that supplies water to the evaporator 48. Is provided.

  In the FC peripheral device 56, the exhaust gas combustor 52 is integrally provided in the heat exchanger 50, and the steam reformer 46 is provided adjacent to one end of the heat exchanger 50.

  As shown in FIGS. 2 and 3, the heat exchanger 50 is arranged in a standing posture, and circulates the oxidant gas from the vertically downward direction to the vertically upward direction, as will be described later. The steam reformer 46 is disposed in a standing posture, and causes the reformed gas to flow from the vertically downward direction to the vertically upward direction. A steam reformer 46 is directly attached to one side (one end) of the heat exchanger 50. The steam reformer 46 and the heat exchanger 50 (including the exhaust gas combustor 52) are stacked in the horizontal direction (arrow A direction).

  Below the heat exchanger 50 and the steam reformer 46, an evaporator 48, a partial oxidation reformer 45, and a desulfurizer 60 for removing sulfur compounds contained in city gas (raw fuel) are disposed. The

The steam reformer 46 converts higher hydrocarbons (C ₂₊ ) such as ethane (C ₂ H ₆ ), propane (C ₃ H ₈ ) and butane (C ₄ H ₁₀ ) contained in city gas (raw fuel). , A pre-reformer for steam reforming to a fuel gas mainly containing methane (CH ₄ ), hydrogen, and CO, and is set to an operating temperature of several hundred degrees Celsius.

The partial oxidation reformer 45 includes higher hydrocarbons (C ₂₊ ) such as ethane (C ₂ H ₆ ), propane (C ₃ H ₈ ) and butane (C ₄ H ₁₀ ) contained in city gas (raw fuel). Is a preliminary reformer for partial oxidation reforming to a fuel gas mainly containing hydrogen and CO, and is set to an operating temperature of several hundred degrees Celsius.

  The operating temperature of the fuel cell 22 is as high as several hundred degrees Celsius. In the anode electrode 30, methane in the fuel gas is reformed to obtain hydrogen and CO. The hydrogen and CO are the anode electrode 30 of the electrolyte 26. Supplied to the side.

  As shown in FIG. 1, the raw fuel supply device 14 includes a desulfurizer 60, and the desulfurizer 60 is disposed in the raw fuel passage 57. The raw fuel passage 57 communicates with the mixed gas inlet 61 a of the partial oxidation reformer 45. A reformed gas passage 57a communicates with the reformed gas outlet 61b of the partial oxidation reformer 45, and steam reforming is performed via a junction 57b between the reformed gas passage 57a and a steam passage 59a (described later). It is connected to the mixed gas supply chamber 62a of the mass device 46.

  As shown in FIGS. 2 and 3, the mixed gas supply chamber 62 a communicates with the lower ends of the plurality of reforming pipelines 64, and the fuel gas discharge chamber 62 b communicates with the upper ends of the reforming pipelines 64. . One end of the fuel gas passage 66 communicates with the fuel gas discharge chamber 62b, and the other end of the fuel gas passage 66 communicates with the fuel gas inlet communication hole 44a of the fuel cell stack 24 (see FIG. 1). Each reforming line 64 is filled with a pellet-shaped catalyst (not shown) for reforming or carries a particulate catalyst (not shown).

  A heating space 68 is formed between the reforming pipes 64. One end of the combustion gas passage 70 is opened in the heating space 68, and a heating passage 72 of the evaporator 48 is provided in the middle of the combustion gas passage 70 as shown in FIG. 1. A second thermoelectric converter 74b and a first thermoelectric converter 74a are connected in series to the other end of the combustion gas passage 70.

  The first thermoelectric converter 74 a is disposed in the first oxidant gas supply path 58 a that constitutes the oxidant gas passage 58, while the second thermoelectric converter 74 b is the second that constitutes the oxidant gas path 58. It arrange | positions at the oxidizing agent gas supply path part 58b. An oxidant gas is distributed and supplied to the first oxidant gas supply path 58a and the second oxidant gas supply path 58b through an oxidant gas adjustment valve 75 provided in the oxidant gas path 58.

  A water passage 59 constituting the water supply device 18 is connected to a water inlet 73 a of the evaporator 48. The water flowing through the water passage 59 is heated by the combustion gas flowing along the heating path 72 to generate water vapor. One end of a steam passage 59 a is connected to the steam outlet 73 b of the evaporator 48, and the other end of the steam passage 59 a joins a position downstream of the partial oxidation reformer 45 with respect to the raw fuel passage 57. And a junction 57b is provided.

  In addition, for example, an ejector (not shown) is disposed in the merging portion 57b, and the raw fuel (or reformed gas) flows through the raw fuel passage 57, so that the steam passage 59a passes to the raw fuel passage 57. Water vapor is aspirated.

  As shown in FIG. 3, the heat exchanger 50 is provided with an oxidant gas supply chamber 76a on the lower side and an oxidant gas discharge chamber 76b on the upper side. Both ends of a plurality of oxidant gas conduits 78 communicate with the oxidant gas supply chamber 76a and the oxidant gas discharge chamber 76b.

  In the oxidant gas supply chamber 76a, one end of a second oxidant gas supply path part 58b constituting the oxidant gas path 58 is disposed. One end of the oxidant gas passage 82 is disposed in the oxidant gas discharge chamber 76b, and the other end of the oxidant gas passage 82 is connected to the oxidant gas inlet communication hole 42a of the fuel cell stack 24. (See FIG. 1).

  Inside the heat exchanger 50, a combustion chamber 84 that forms the exhaust gas combustor 52 and that includes a space in which a plurality of oxidant gas pipes 78 are accommodated is formed. The combustion chamber 84 functions as a heat source that raises the temperature of the oxidant gas by a combustion reaction between the fuel gas (specifically, the fuel exhaust gas) and the oxidant gas (specifically, the oxidant exhaust gas).

  One end of the oxidant exhaust gas passage 86 and one end of the fuel exhaust gas passage 88 are arranged in the combustion chamber 84 from the oxidant gas discharge chamber 76b side. As shown in FIG. 1, the other end of the oxidant exhaust gas passage 86 is connected to the oxidant gas outlet communication hole 42 b of the fuel cell stack 24, and the other end of the fuel exhaust gas passage 88 is connected to the fuel cell stack 24. It is connected to the fuel gas outlet communication hole 44b.

  As shown in FIG. 3, a wall plate (wall portion) 90 is disposed between the steam reformer 46 and the heat exchanger 50. A wall plate 90 is sandwiched between the flange portion 92 of the steam reformer 46 and the flange portion 94 of the heat exchanger 50, and these are integrally fixed by a plurality of bolts 96 and nuts 97. The wall plate 90 is formed with an opening (combustion gas passage) 98 for supplying the combustion gas generated in the combustion chamber 84 of the heat exchanger 50 to the heating space 68 of the steam reformer 46.

  As shown in FIG. 1, the oxidant gas supply device 16 supplies the oxidant gas from the oxidant gas passage 58 to the partial oxidation reformer 45 and the heat exchanger 50, that is, the first oxidant gas supply passage portion 58a. And the second oxidant gas supply path 58b are provided with an oxidant gas regulating valve 75 for distribution. The first oxidant gas supply passage 58 a is located between the desulfurizer 60 and the partial oxidation reformer 45 and communicates with the raw fuel passage 57.

  As shown in FIG. 4, the first thermoelectric converter 74 a is different from the first passage member 112 that circulates the oxidant gas that is the object to be heated and the second passage member 114 that circulates the combustion gas that is the heating medium. A plurality of thermoelectric conversion elements 116a, 116b and 116c, each set to a thermoelectric conversion temperature.

  The first passage member 112 has a box shape and is provided with an oxidant gas meandering channel 112c that meanders between the oxidant gas inlet 112a and the oxidant gas outlet 112b. The oxidant gas meandering channel 112c is formed by partition plates 112d arranged alternately and in a staggered manner in the first passage member 112.

  The second passage member 114 has a box shape and is provided with a combustion gas meandering channel 114c that meanders between the combustion gas inlet 114a and the combustion gas outlet 114b. The combustion gas meandering flow path 114c is formed by partition plates 114d arranged alternately and in a staggered manner in the second passage member 114. The combustion gas meandering channel 114c and the oxidant gas meandering channel 112c are set in parallel to each other.

  The thermoelectric conversion elements 116a, 116b, and 116c have a function of generating an electromotive force by causing both ends to be sandwiched between the first passage member 112 and the second passage member 114 and causing a temperature difference between the both ends. A plurality of thermoelectrics (three are arranged in FIG. 4, but the number can be arbitrarily set, the same applies hereinafter) arranged upstream of the oxidant gas meandering channel 112c and the combustion gas meandering channel 114c. The conversion element 116a is a high temperature type thermoelectric conversion element set to a high temperature thermoelectric conversion temperature.

  The plurality of thermoelectric conversion elements 116b arranged on the midstream side of the oxidant gas meandering channel 112c and the combustion gas meandering channel 114c are medium temperature type thermoelectric conversion elements set to a medium temperature thermoelectric conversion temperature. The plurality of thermoelectric conversion elements 116c arranged on the downstream side of the oxidant gas meandering channel 112c and the combustion gas meandering channel 114c are low temperature type thermoelectric conversion elements set to a low temperature thermoelectric conversion temperature.

  In addition, the 2nd thermoelectric conversion part 74b is comprised similarly to said 1st thermoelectric conversion part 74a, The same referential mark is attached | subjected to the same component and the detailed description is abbreviate | omitted.

  The operation of the fuel cell system 10 configured as described above will be described below along the flowcharts of FIG.

First, when the fuel cell system 10 is started, the opening degree of the oxidant gas adjustment valve 75 is set (step S1). Specifically, air (oxidant gas) necessary for partial oxidation reforming and raw fuel, for example, city gas (including CH ₄ , C ₂ H ₆ , C ₃ H ₈ , C ₄ H ₁₀ ), etc. are input. In this manner (step S2), the raw fuel supply device 14 is driven and the opening degree of the oxidant gas adjustment valve 75 is adjusted. The partial oxidation reforming is controlled by the air-fuel ratio (O ₂ / C) (number of moles of oxygen in the input air / number of carbon moles in the input raw fuel). Fuel is introduced at an optimal air / fuel ratio.

  In the raw fuel supply device 14, the raw fuel supplied to the raw fuel passage 57 is desulfurized by the desulfurizer 60 and then supplied to the mixed gas inlet 61 a of the partial oxidation reformer 45. On the other hand, in the oxidant gas supply device 16, the air supplied to the oxidant gas passage 58 is supplied to the first oxidant gas supply passage 58 a and the second oxidant gas supply passage 58 b through the oxidant gas adjustment valve 75. And a predetermined amount of each. The air distributed to the first oxidant gas supply path 58 a is mixed with the raw fuel in the raw fuel passage 57 and supplied to the mixed gas inlet 61 a of the partial oxidation reformer 45.

For this reason, the partial oxidation reforming by the partial oxidation reformer 45 is started (step S3). For example, when O ₂ /C=0.5, a partial oxidation reaction of 2CH ₄ + O ₂ → 4H ₂ + 2CO occurs. This partial oxidation reaction is an exothermic reaction, and high-temperature (about 600 ° C.) reducing gas is generated from the partial oxidation reformer 45.

  As shown in FIGS. 2 and 3, the high-temperature reducing gas is supplied to the mixed gas supply chamber 62a of the steam reformer 46 through the merging portion 57b, and then the plurality of reforming pipes 64 are moved to the lower end side. Move from the top to the top. The hot reducing gas is once supplied to the fuel gas discharge chamber 62b and then supplied to the fuel gas inlet communication hole 44a of the fuel cell stack 24 through the fuel gas passage 66 (see FIG. 1).

  In the fuel cell stack 24, the hot reducing gas flows through the fuel gas passage 40 and is then discharged from the fuel gas outlet communication hole 44 b to the fuel exhaust gas passage 88. Thus, the steam reformer 46 and the fuel cell stack 24 are heated by the high-temperature reducing gas generated from the partial oxidation reformer 45.

  On the other hand, as shown in FIG. 3, the fuel exhaust gas passage 88 opens into a combustion chamber 84 that constitutes the exhaust gas combustor 52, and the fuel gas is introduced into the combustion chamber 84. In the combustion chamber 84, the reducing gas (fuel gas) and the oxidant gas are ignited by an ignition device such as an igniter or a glow (not shown), and combustion gas is generated (step S4).

  The combustion gas generated in the combustion chamber 84 heats the heat exchanger 50 and warms the air supplied from the second oxidant gas supply path 58b. Further, the combustion gas moves to the heating space 68 of the steam reformer 46 through the opening 98 formed in the wall plate 90. Thereby, the steam reformer 46 is heated. A combustion gas passage 70 communicates with the heating space 68, and the combustion gas passage 70 communicates with a heating passage 72 of the evaporator 48. For this reason, after raising the temperature of the evaporator 48, the combustion gas is supplied to the second thermoelectric converter 74b and the first thermoelectric converter 74a.

  As shown in FIG. 4, in the first thermoelectric conversion unit 74a and the second thermoelectric conversion unit 74b, the oxidant gas, which is external air, flows from the oxidant gas inlet 112a of the first passage member 112 to the oxidant gas meandering channel 112c. Meanwhile, the combustion gas is supplied from the combustion gas inlet 114a of the second passage member 114 to the combustion gas meandering channel 114c. Therefore, a plurality of thermoelectric conversion elements 116a, 116b, and 116c disposed between the oxidant gas meandering channel 112c and the combustion gas meandering channel 114c generate temperature differences at both ends, and heat energy is reduced. It is recovered as electrical energy.

  Next, the process proceeds to step S5, where it is determined whether or not the steam reformer 46 is at or above the set temperature T1 and the evaporator 48 is at or above the set temperature T2. The set temperature T1 is, for example, 550 ° C., and the set temperature T2 is, for example, 150 ° C. If it is determined that the steam reformer 46 is equal to or higher than the set temperature T1 and the evaporator 48 is equal to or higher than the set temperature T2 (YES in step S5), the process proceeds to step S6.

  In this step S6, in order to shift from the partial oxidation reforming reaction to the steam reforming reaction, the opening degree of the oxidant gas regulating valve 75 is adjusted and the water supply device 18 is driven. By adjusting the opening degree of the oxidant gas adjustment valve 75, the supply of air to the first oxidant gas supply path part 58a is stopped, while being supplied to the heat exchanger 50 from the second oxidant gas supply path part 58b. The air volume is increased. Accordingly, since only the raw fuel is supplied to the partial oxidation reformer 45, the partial oxidation reaction is not induced, and the raw fuel is supplied to the junction 57b.

  At that time, in the water supply device 18, water is supplied to the evaporator 48. The water evaporated by the evaporator 48 is supplied from the water vapor passage 59a to the junction 57b, mixed with the raw fuel, and supplied to the mixed gas supply chamber 62a.

As shown in FIGS. 2 and 3, the mixed gas of raw fuel and water vapor supplied to the mixed gas supply chamber 62 a moves in the plurality of reforming pipes 64 from the lower end side to the upper end side. In the meantime, the mixed gas is heated by the combustion gas introduced into the heating space 68 and is steam-reformed through a pellet-shaped catalyst to remove (reform) C ₂₊ hydrocarbons to mainly produce methane. A reformed gas as a component and a steam reforming reaction of CH ₄ + H ₂ O → 3H ₂ + CO occur (step S7).

  This reformed gas is once supplied to the fuel gas discharge chamber 62b as heated fuel gas, and then supplied to the fuel gas inlet communication hole 44a of the fuel cell stack 24 through the fuel gas passage 66 (FIG. 1). reference).

  In the fuel cell stack 24, the heated fuel gas flows through the fuel gas passage 40 and is then discharged from the fuel gas outlet communication hole 44 b to the fuel exhaust gas passage 88. As shown in FIG. 3, the fuel exhaust gas passage 88 opens into a combustion chamber 84 that constitutes the exhaust gas combustor 52, and fuel gas is introduced into the combustion chamber 84.

  On the other hand, in the oxidant gas supply device 16, air is supplied to the second oxidant gas supply path 58 b via the oxidant gas adjustment valve 75, and this air is supplied to the oxidant gas supply chamber 76 a of the heat exchanger 50. be introduced.

  As shown in FIG. 3, the air introduced into the oxidant gas supply chamber 76 a is introduced into the combustion chamber 84 while moving from the lower end side to the upper end side in the plurality of oxidant gas conduits 78. Is heated (heat exchange). The heated air is once supplied to the oxidant gas discharge chamber 76b and then supplied to the oxidant gas inlet communication hole 42a of the fuel cell stack 24 through the oxidant gas passage 82 (see FIG. 1).

  In the fuel cell stack 24, the heated air flows through the oxidant gas flow path 38 and is then discharged from the oxidant gas outlet communication hole 42 b to the oxidant exhaust gas passage 86. As shown in FIG. 3, the oxidant exhaust gas passage 86 opens into a combustion chamber 84 that constitutes the exhaust gas combustor 52, and air is introduced into the combustion chamber 84.

  As described above, the temperature of the fuel cell stack 24 is increased by circulating the heated air and the heated fuel gas. Then, the process proceeds to step S8, and it is determined whether or not the fuel cell stack 24 is in a state capable of generating power. Specifically, the OCV (open circuit voltage) of the fuel cell 22 is measured, and when the OCV reaches a predetermined value, it is determined that the fuel cell stack 24 can generate power (YES in step S8). . Thereby, the fuel cell stack 24 starts power generation (step S9).

  During power generation of the fuel cell stack 24, air flows through the oxidant gas flow path 38 while fuel gas flows through the fuel gas flow path 40 in the same manner as at the time of startup. Accordingly, air is supplied to the cathode electrode 28 of each fuel cell 22 and fuel gas is supplied to the anode electrode 30 to generate power by a chemical reaction.

  The air used for the reaction (including unreacted air) is discharged to the oxidant exhaust gas passage 86 as an oxidant exhaust gas. Further, the fuel gas (including unreacted fuel gas) used for the reaction is discharged to the fuel exhaust gas passage 88 as fuel exhaust gas. The oxidant exhaust gas and the fuel exhaust gas are sent to the exhaust gas combustor 52 and burned. In the exhaust gas combustor 52, combustion by air and fuel gas is started in the combustion chamber 84 when the self-ignition temperature of the fuel gas is exceeded.

  Next, the operation from the power generation by the fuel cell system 10 to the low load operation will be described below along the flowchart of FIG.

  First, after the required power of the fuel cell stack 24 is confirmed (step S101), the process proceeds to step S102, where it is determined whether or not the required power is within the high efficiency operation range in steam reforming. As shown in FIG. 7, the driving range by steam reforming is, for example, a range of output 40% to 100%, while the driving range (thermal self-sustaining range) by partial oxidation reforming is, for example, output 10% to 40%. % Range.

  Therefore, if it is determined that the required power is within the high-efficiency operation range in steam reforming (YES in step S102), the process proceeds to step S103, where power generation by steam reforming is performed and high-efficiency power is supplied. Is made.

  If it is determined that the required power of the fuel cell stack 24 is not within the high-efficiency operation range in steam reforming (NO in step S102), the process proceeds to step S104. In this step S104, it is determined whether or not the required power is within the heat self-supporting range in the partial oxidation reforming.

  When it is determined that the required power is within the heat self-supporting range in partial oxidation reforming (YES in step S104), the process proceeds to step S105, and power generation by partial oxidation reforming is performed. On the other hand, if it is determined that it is not within the range of thermal self-sustainment in partial oxidation reforming (NO in step S104), the process proceeds to step S106 and minimum thermal self-sustaining power generation by partial oxidation reforming (for example, output 10 in FIG. %) Is performed.

  Next, the operation of stopping power generation by the fuel cell system 10 will be described below along the flowchart of FIG.

  First, power generation is stopped and returned to the OCV (step S201). Furthermore, it progresses to step S202 and the opening amount of the fuel gas input amount and oxidant gas adjustment valve 75 for shifting to partial oxidation reforming reaction are set. The fuel gas input amount is set to a necessary input amount for maintaining the reduction state on the anode side of the fuel cell stack 24.

  As described above, after the partial oxidation reforming is started (step S203), air necessary for slow cooling of the fuel cell stack 24 is supplied to the heat exchanger 50 while monitoring the temperature T3 of the fuel cell stack 24. (Step S204). At this time, the reducing gas (fuel gas) and air are not ignited in the combustion chamber 84 of the exhaust gas combustor 52.

  Therefore, when the inside of the fuel cell stack 24 is gradually cooled and the temperature T3 of the fuel cell stack 24 is lowered to less than 400 ° C. (YES in step S205), the process proceeds to step S206, and the partial oxidation reforming is stopped. Is done. Further, when the temperature T3 of the fuel cell stack 24 is lowered to less than 100 ° C. (YES in step S207), the process proceeds to step S208, and the supply of air is stopped.

  In this case, in the first embodiment, as shown in FIG. 1, the reformed gas communicated with the steam passage 59a communicating with the steam outlet 73b of the evaporator 48 and the reformed gas outlet 61b of the partial oxidation reformer 45. The passage 57 a joins at the joining portion 57 b and communicates with the steam reformer 46.

  Accordingly, since the high temperature (about 600 ° C.) reducing gas generated in the partial oxidation reformer 45 is led to the steam reformer 46, the start-up time (temperature rise and reduction time) of the steam reformer 46 is shortened. Is done.

  Moreover, the hot reducing gas is supplied from the steam reformer 46 to the fuel gas inlet communication hole 44 a of the fuel cell stack 24 through the fuel gas passage 66. Thereby, the starting time (temperature increase and reduction time) of the fuel cell stack 24 is favorably shortened.

  Further, high-temperature reducing gas is supplied from the fuel cell stack 24 to the exhaust gas combustor 52. For this reason, it is possible to raise the temperature of the oxidant gas, the steam reformer 46 and the evaporator 48 through the combustion gas generated in the exhaust gas combustor 52, and the start-up time of the fuel cell module 12 is effectively shortened. .

  Furthermore, the steam generated in the evaporator 48 does not flow into the partial oxidation reformer 45. Therefore, it is possible to suppress the steam oxidation of the catalyst of the partial oxidation reformer 45, and the durability can be easily improved.

  In addition, even when insufficient reforming by the steam reformer 46 is caused by insufficient heat due to load variation of the fuel cell stack 24, the partial oxidation reformer 45 can compensate for the insufficient reforming.

  Specifically, the reformed gas amount X is calculated based on the required power of the fuel cell stack 24. When the reformed gas amount X is larger than the reformed gas amount Y obtained from the steam reformer 46 (X> Y), the reformed gas amount Y is processed by the steam reformer 46. The partial reforming gas amount Z (XY) is processed by the partial oxidation reformer 45. For this reason, it becomes possible to follow low output and load fluctuations, suppress fuel depletion and carbon deposition due to insufficient reforming, and easily improve durability.

  Furthermore, the fuel cell module 12 includes a first thermoelectric conversion unit 74a and a second thermoelectric conversion unit 74b that perform thermoelectric conversion based on a temperature difference between the combustion gas and the oxidant gas. As shown in FIG. 4, the first thermoelectric conversion unit 74 a and the second thermoelectric conversion unit 74 b include a first passage member 112 that circulates an oxidant gas that is an object to be heated and a combustion gas that is a heating medium. A two-pass member 114 and a plurality of thermoelectric conversion elements 116a, 116b, and 116c that are disposed between the first and second passage members 112 and 114 and set to different thermoelectric conversion temperatures.

  Therefore, the first thermoelectric conversion unit 74a and the second thermoelectric conversion unit 74b can recover the temperature difference between the combustion gas and the oxidant gas, that is, the heat energy as electric energy, and do not particularly impair the startup time. It becomes possible to improve the power generation efficiency. Moreover, since the temperature of the combustion gas is lowered, waste heat is suppressed, while the temperature of the oxidant gas is raised, so that heat self-sustainment is promoted. Note that at least one of the first thermoelectric conversion unit 74a and the second thermoelectric conversion unit 74b may be provided.

  Here, the combustion gas is a gas generated in the exhaust gas combustor 52 and refers to a heating medium capable of giving heat energy by exchanging heat with an object to be heated such as another gas. After release, it is called exhaust gas.

  Thermal self-sustainment means that the operating temperature of the fuel cell system 10 is maintained only by the heat generated by itself without adding the entire amount of heat necessary for the operation of the fuel cell system 10 from the outside.

  In the fuel cell module 12, the combustion gas is supplied from the combustion gas passage 70 sequentially to the heat exchanger 50, the steam reformer 46 and the evaporator 48, and the oxidizing gas is supplied from the partial oxidation reformer 45 to the fuel cell. And the first thermoelectric converter 74a is provided downstream of the evaporator 48 in the combustion gas passage 70 and in the partial oxidation of the oxidant gas passage 58. It is provided on the upstream side of the reformer 45.

  For this reason, it is possible to recover the temperature difference between the combustion gas and the oxidant gas, that is, the heat energy as electric energy without hindering the heat self-supporting, and to improve the power generation efficiency. Moreover, since the temperature of the combustion gas is lowered, waste heat is suppressed, while the temperature of the oxidant gas is raised, so that heat self-sustainment is promoted.

  Further, the fuel cell module 12 includes a raw fuel passage 57 that supplies raw fuel to the partial oxidation reformer 45, and the oxidant gas passage 58 is located upstream of the partial oxidation reformer 45 in the raw fuel passage 57. The first thermoelectric conversion part 74a is disposed in the oxidant gas passage 58. Therefore, the temperature difference between the combustion gas and the oxidant gas, that is, the heat energy can be recovered as electric energy, and the power generation efficiency can be improved. Moreover, since the temperature of the combustion gas is lowered, waste heat is suppressed, while the temperature of the oxidant gas is raised, so that heat self-sustainment is promoted.

  Furthermore, the oxidant gas passage 58 includes a first oxidant gas supply path 58a that supplies the oxidant gas to the partial oxidation reformer 45, and a second oxidant that supplies the oxidant gas to the heat exchanger 50. While branching to the gas supply path 58b, an oxidant gas adjusting valve 75 for adjusting the distribution amount of the oxidant gas is disposed at the branch portion.

  As a result, the fuel cell stack 24 and the FC peripheral device 56 including the steam reformer 46, the evaporator 48, and the heat exchanger 50 can be heated at the same time, and the startup time can be shortened. Become. On the other hand, the steam reforming catalyst and the anode side can be reduced, and the startup time is shortened.

  Moreover, the partial oxidation reformer 45 can compensate for the insufficient reforming even when the reforming by the steam reformer 46 is caused by insufficient heat due to the load fluctuation of the fuel cell stack 24 or the like. For this reason, it becomes possible to follow the load fluctuation, and it is possible to suppress fuel depletion due to insufficient reforming, and to easily improve durability.

  The first thermoelectric converter 74a and the second thermoelectric converter 74b are located downstream of the oxidant gas adjustment valve 75 in the first oxidant gas supply path 58a and the second oxidant gas supply path 58b. Has been placed. Therefore, the temperature difference between the combustion gas and the oxidant gas, that is, the heat energy can be recovered as electric energy without hindering the heat self-sustained, and the power generation efficiency can be improved.

  Moreover, since the temperature of the combustion gas is lowered, waste heat is suppressed, while the temperature of the oxidant gas is raised, so that heat self-sustainment is promoted. In addition, since the temperature of the oxidant gas is raised on the downstream side of the oxidant gas adjustment valve 75, the durability of the oxidant gas adjustment valve 75 due to thermal influence is not impaired.

  Further, in the first thermoelectric converter 74a and the second thermoelectric converter 74b, the combustion gas flowing through the combustion gas meandering channel 114c and the oxidant gas flowing through the oxidant gas meandering channel 112c are in parallel flow with each other. A plurality of thermoelectric conversion elements 116a, 116b, and 116c that are set to different thermoelectric conversion temperatures are provided.

  Therefore, as shown in FIG. 4, for example, the upstream side of the parallel flow has a large temperature difference between the combustion gas and the oxidant gas, so that the high-temperature type thermoelectric conversion element 116a is used, while the downstream side of the parallel flow. Since the temperature difference is small, a low-temperature thermoelectric conversion element 116c can be used. Thereby, since the optimal thermoelectric conversion elements 116a, 116b, and 116c are used according to the temperature difference, efficient thermoelectric conversion can be reliably performed.

  Furthermore, an exhaust gas combustor 52 is integrally provided in the heat exchanger 50, and a steam reformer 46 is provided adjacent to one end of the heat exchanger 50. For this reason, the heat radiation of the fuel cell module 12 can be suppressed to a minimum, and the loss of thermal energy can be suppressed satisfactorily. In other words, heat independent operation is promoted. In addition, since the combustion circuit (piping and the like) is simplified and the number of parts is reduced, the size and cost can be reduced.

  The fuel cell module 12 is a solid oxide fuel cell module. This is particularly suitable for high-temperature fuel cells such as SOFC.

  As shown in FIG. 9, the fuel cell system 10a includes a fuel cell module 12a according to the second embodiment of the present invention. Note that the same components as those of the fuel cell module 12 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Similarly, in the third embodiment described below, detailed description thereof is omitted.

  The fuel cell module 12 a includes a thermoelectric conversion unit 74, and the thermoelectric conversion unit 74 is disposed in the oxidant gas passage 58 on the upstream side of the oxidant gas adjustment valve 75. The thermoelectric converter 74 is supplied with oxidant gas via the oxidant gas passage 58 and is supplied with combustion gas via the combustion gas passage 70. The thermoelectric conversion unit 74 is configured similarly to the first thermoelectric conversion unit 74a (and the second thermoelectric conversion unit 74b) of the first embodiment.

  In the second embodiment configured as described above, the temperature difference between the combustion gas and the oxidant gas, that is, the heat energy can be recovered as electric energy without hindering thermal self-sustainment, and the power generation efficiency is improved. It becomes possible to make it. In addition, since the temperature of the combustion gas is lowered, waste heat is suppressed, while the temperature of the oxidant gas is raised, so that heat self-sustainment is promoted, and the like, as in the first embodiment. An effect is obtained.

  Furthermore, since the thermoelectric conversion unit 74 is disposed in the oxidant gas passage 58 on the upstream side of the oxidant gas regulating valve 75, only the single thermoelectric conversion unit 74 can be provided. Therefore, it is possible to obtain an advantage that the configuration is simplified and the cost is economical.

  As shown in FIG. 10, the fuel cell system 120 includes a fuel cell module 122, a water supply device 124, a raw fuel supply device 126, and an oxidant gas supply device 16 according to the third embodiment of the present invention. And a control device 20. The water supply device 124 is connected to the mixed gas supply chamber 62a of the steam reformer 46 through the water passage 59, the evaporator 48, the steam passage 59a, and the merging portion 59b.

  In the raw fuel supply device 126, the desulfurizer 60 and the partial oxidation reformer 45 are disposed in the raw fuel passage 57, and the reformed gas passage 57a joins the steam passage 59a. In addition, for example, an ejector (not shown) is disposed in the merging portion 59b, and when the steam flows through the steam passage 59a, the raw fuel (or reformed gas) is transferred from the reformed gas passage 57a to the steam passage 59a. ) Is aspirated.

  A first thermoelectric converter 74a and a second thermoelectric converter 74b are connected in series to the combustion gas passage 70 connected to the water inlet 73a of the evaporator 48. The first thermoelectric converter 74a and the second thermoelectric converter 74b are disposed in the first oxidant gas supply path 58a and the second oxidant gas supply path 58b.

  In the third embodiment configured as described above, the steam generated in the evaporator 48 does not flow into the partial oxidation reformer 45, and the catalyst of the partial oxidation reformer 45 is steam oxidized. The same effect as the first embodiment can be obtained.

  As shown in FIG. 11, the fuel cell system 120a includes a fuel cell module 122a according to the fourth embodiment of the present invention. Note that the same components as those of the fuel cell module 122 according to the third embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The fuel cell module 122 a includes a thermoelectric conversion unit 74, and the thermoelectric conversion unit 74 is disposed in the oxidant gas passage 58 on the upstream side of the oxidant gas adjustment valve 75.

  In the fourth embodiment configured as described above, the temperature difference between the combustion gas and the oxidant gas, that is, the heat energy can be recovered as electric energy without hindering thermal self-sustainment, and the power generation efficiency is improved. It becomes possible to make it. In addition, since the temperature of the combustion gas is lowered, waste heat is suppressed, while the temperature of the oxidant gas is raised, so that effects such as promotion of heat self-sustaining can be obtained.

  FIG. 12 is an exploded perspective view of a main part of a thermoelectric conversion unit 130 constituting a fuel cell module according to the fifth embodiment of the present invention.

  The thermoelectric conversion unit 130 can be used in place of at least one of the first thermoelectric conversion unit 74a and the second thermoelectric conversion unit 74b (thermoelectric conversion unit 74) according to the first to fourth embodiments. The same applies to the sixth and subsequent embodiments described below.

  The thermoelectric conversion unit 130 is disposed between the first passage member 132 that circulates the oxidant gas, the second passage member 134 that circulates the combustion gas, and between the first passage member 132 and the second passage member 134. And a plurality of thermoelectric conversion elements 136 set to the thermoelectric conversion temperature.

  The first passage member 132 has an oxidant gas meandering channel 132c that meanders between the oxidant gas inlet 132a and the oxidant gas outlet 132b. The oxidant gas meandering channel 132c is formed by partition plates 132d that are alternately arranged in the first passage member 132 in a staggered manner.

  The second passage member 134 has a combustion gas meandering channel 134c that meanders between the combustion gas inlet 134a and the combustion gas outlet 134b. The combustion gas meandering channel 134c is formed by partition plates 134d arranged alternately and in a staggered manner in the second passage member 134. The combustion gas meandering channel 134c and the oxidant gas meandering channel 132c are set to face each other.

  In the fifth embodiment configured as described above, the thermoelectric conversion unit 130 includes a plurality of thermoelectric conversion elements in which the combustion gas and the oxidant gas are set to counterflow with each other and set to a predetermined thermoelectric conversion temperature. 136. For this reason, in the thermoelectric conversion part 130, the thermoelectric conversion element 136 set to the optimal thermoelectric conversion temperature can be used according to the assumed temperature difference. Therefore, an effect is obtained that efficient thermoelectric conversion can be reliably performed.

  FIG. 13 is an exploded perspective view of a main part of a thermoelectric conversion unit 140 constituting a fuel cell module according to the sixth embodiment of the present invention.

  The thermoelectric conversion unit 140 is disposed between the first passage member 142 that circulates the oxidant gas, the second passage member 144 that circulates the combustion gas, and the first passage member 142 and the second passage member 144. And a plurality of thermoelectric conversion elements 146 set to the thermoelectric conversion temperature.

  The first passage member 142 has an oxidant gas meandering channel 142c that meanders between the oxidant gas inlet 142a and the oxidant gas outlet 142b. The oxidant gas meandering channel 142c is formed by partition plates 142d arranged alternately and in a staggered manner in the first passage member 142.

  The second passage member 144 has a combustion gas meandering channel 144c that meanders between the combustion gas inlet 144a and the combustion gas outlet 144b. The combustion gas meandering channel 144c is formed by partition plates 144d arranged alternately and in a staggered manner in the second passage member 144. The combustion gas meandering channel 144c and the oxidant gas meandering channel 142c are set to flow mutually intersecting.

  In the sixth embodiment configured as described above, the thermoelectric conversion unit 140 is set to a flow in which the combustion gas and the oxidant gas intersect each other, and a plurality of thermoelectric conversions set to a predetermined thermoelectric conversion temperature. An element 146 is provided. Thereby, in the thermoelectric conversion part 140, the thermoelectric conversion element 146 set to the optimal thermoelectric conversion temperature can be used according to the assumed temperature difference. For this reason, the effect that efficient thermoelectric conversion can be performed reliably is acquired.

  FIG. 14 is an exploded perspective view of a main part of a thermoelectric conversion unit 150 constituting the fuel cell module according to the seventh embodiment of the present invention.

  The thermoelectric converter 150 is disposed between a first passage member 152 that circulates the oxidant gas, a second passage member 154 that circulates the combustion gas, and the first passage member 152 and the second passage member 154. And a plurality of thermoelectric conversion elements 156 set to the thermoelectric conversion temperature.

  The first passage member 152 has an oxidant gas meandering flow path 152c that meanders between the oxidant gas inlet 152a and the oxidant gas outlet 152b. The oxidant gas meandering flow path 152c is formed by partition plates 152d that are alternately arranged in the first passage member 152 in a staggered manner.

  The second passage member 154 has a combustion gas meandering channel 154c that meanders between the combustion gas inlet 154a and the combustion gas outlet 154b. The combustion gas meandering channel 154c is formed by partition plates 154d arranged alternately and in a staggered manner in the second passage member 154. The combustion gas meandering channel 154c and the oxidant gas meandering channel 152c are set to flow symmetrical to each other.

  In the seventh embodiment configured as described above, the thermoelectric conversion unit 150 includes a plurality of thermoelectric conversions in which the combustion gas and the oxidant gas are set in a mutually symmetrical flow and set to a predetermined thermoelectric conversion temperature. An element 156 is provided. Thereby, in the thermoelectric conversion part 150, the thermoelectric conversion element 156 set to the optimal thermoelectric conversion temperature can be used according to the assumed temperature difference. For this reason, the effect that efficient thermoelectric conversion can be performed reliably is acquired.

10, 10a, 120, 120a ... Fuel cell system 12, 12a, 122, 122a ... Fuel cell module 14, 126 ... Raw fuel supply device 16 ... Oxidant gas supply device 18, 124 ... Water supply device 20 ... Control device 22 ... Fuel cell 24 ... Fuel cell stack 26 ... Electrolyte 28 ... Cathode electrode 30 ... Anode electrode 32 ... Electrolyte / electrode assembly 34 ... Cathode side separator 36 ... Anode side separator 38 ... Oxidant gas channel 40 ... Fuel gas channel 45 ... Partial oxidation reformer 46 ... steam reformer 48 ... evaporator 50 ... heat exchanger 52 ... exhaust gas combustor 56 ... FC peripheral device 57 ... raw fuel passage 57b, 59b ... merging portion 58, 82 ... oxidant gas passage 59 ... Water passage 59a ... Steam passage 60 ... Desulfurizer 66 ... Fuel gas passage 70 ... Combustion gas passages 74, 74a, 74b, 130 140,150 ... thermoelectric conversion unit 75 ... oxidant gas regulating valve 98 ... opening 112,114,132,134,142,144,152,154 ... passage member 116 a - c, 136, 146 and 156 ... thermoelectric conversion element

Claims (11)

A fuel cell stack that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas;
A partial oxidation reformer for reforming a mixed gas of hydrocarbon-based raw fuel and oxidant gas;
A steam reformer for reforming a mixed gas of the raw fuel and steam;
An evaporator for evaporating water and supplying steam to the steam reformer;
A heat exchanger that raises the temperature of the oxidant gas by heat exchange with a combustion gas and supplies the oxidant gas to the fuel cell stack;
An exhaust gas combustor for burning the fuel exhaust gas as the fuel gas discharged from the fuel cell stack and the oxidant exhaust gas as the oxidant gas to generate the combustion gas;
A fuel cell module comprising:
The fuel cell module joins a steam passage that communicates with a steam outlet of the evaporator and a reformed gas passage that communicates with a reformed gas outlet of the partial oxidation reformer and connects to the steam reformer And
A thermoelectric conversion unit that performs thermoelectric conversion by a temperature difference between the combustion gas and the oxidant gas;
A fuel cell module comprising: 2. The fuel cell module according to claim 1, wherein the combustion gas is sequentially supplied to the heat exchanger, the steam reformer, and the evaporator.
An oxidant gas passage for supplying the oxidant gas from the partial oxidation reformer to the fuel cell stack;
With
The fuel cell module, wherein the thermoelectric converter is provided on the downstream side of the evaporator in the combustion gas passage and on the upstream side of the partial oxidation reformer in the oxidant gas passage. The fuel cell module according to claim 2, further comprising a raw fuel passage for supplying the raw fuel to the partial oxidation reformer,
The oxidant gas passage joins the raw fuel passage on the upstream side of the partial oxidation reformer,
The fuel cell module, wherein the thermoelectric converter is disposed in the oxidant gas passage. 4. The fuel cell module according to claim 2, wherein the oxidant gas passage includes a first oxidant gas supply passage that supplies the oxidant gas to the partial oxidation reformer,
A second oxidant gas supply path for supplying the oxidant gas to the heat exchanger;
Branch to
An oxidant gas adjusting valve for adjusting a distribution amount of the oxidant gas is disposed at the branch portion.   5. The fuel cell module according to claim 4, wherein the thermoelectric converter is disposed in the oxidant gas passage at an upstream side of the oxidant gas regulating valve. 6.   5. The fuel cell module according to claim 4, wherein the thermoelectric converter is located at least downstream of the oxidant gas regulating valve in the first oxidant gas supply path or the second oxidant gas supply path. A fuel cell module which is arranged. The fuel cell module according to any one of claims 1 to 6, wherein the thermoelectric converter is configured such that the combustion gas and the oxidant gas are set in parallel flow with each other,
A fuel cell module comprising a plurality of thermoelectric conversion elements set to different thermoelectric conversion temperatures. The fuel cell module according to any one of claims 1 to 6, wherein the thermoelectric conversion unit is configured such that the combustion gas and the oxidant gas are set to counter flow with each other,
A fuel cell module comprising a plurality of thermoelectric conversion elements set to a predetermined thermoelectric conversion temperature. The fuel cell module according to any one of claims 1 to 6, wherein the thermoelectric converter is set to a flow in which the combustion gas and the oxidant gas cross each other or a symmetrical flow,
A fuel cell module comprising a plurality of thermoelectric conversion elements set to a predetermined thermoelectric conversion temperature. The fuel cell module according to any one of claims 1 to 9, wherein the exhaust gas combustor is integrally provided in the heat exchanger,
The fuel cell module, wherein the steam reformer is provided adjacent to one end of the heat exchanger.   The fuel cell module according to any one of claims 1 to 10, wherein the fuel cell module is a solid oxide fuel cell module.

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