JP4476581B2 - FUEL CELL POWER GENERATION SYSTEM, CONTROL METHOD FOR THE FUEL CELL POWER GENERATION SYSTEM, CONTROL PROGRAM FOR IMPLEMENTING THE CONTROL METHOD, AND RECORDING MEDIUM CONTAINING THE CONTROL PROGRAM - Google Patents

Description

  The present invention relates to a fuel cell power generation system, a control method for the fuel cell power generation system, a control program for realizing the control method, and a recording medium on which the control program is recorded, and in particular, two types of fuel cell stacks. The present invention relates to a fuel cell power generation system that generates power in combination, a control method thereof, and a control program for realizing the control method.

  Conventionally, a fuel cell power generation system that generates power by combining two types of fuel cell stacks has been developed as exemplified in Non-Patent Document 1 below.

  FIG. 6 is a system configuration diagram showing the conventional fuel cell power generation system. In FIG. 6, 1 is a natural gas that is a fuel, 2 is a reformer that performs a steam reforming reaction of the natural gas 1 that is a fuel, and 3 is a solid oxide fuel cell that is a first fuel cell stack. Stack (hereinafter abbreviated as SOFC stack), 4 is a fuel electrode of SOFC stack 3, 5 is a solid oxide electrolyte of SOFC stack 3, 6 is an air electrode of SOFC stack 3, 7 is a combustor, and 8 is a reformer recycle. Gas 11 and desulfurized natural gas 39 mixed gas, 9 hydrogen-rich reformed gas, 10 SOFC stack 3 fuel electrode exhaust gas, 11 reformer recycle gas, 12 SOFC stack 3 air electrode exhaust Gas, 13 is combustion exhaust gas, 14 is a flow control valve that controls the supply amount of natural gas 1 as fuel, 15 is a flow control valve that controls the supply amount of reformer recycle gas 11, and 16 is SOF Hydrogen-rich reformed gas supplied to the fuel electrode 4 of the stack 3, 17 hydrogen-rich reformed gas supplied to the CO shift converter 20, and 18 a hydrogen-rich reformed gas 16 supplied to the fuel electrode 4 of the SOFC stack 19 is a flow rate control valve for controlling the supply amount of the hydrogen-rich reformed gas 17 supplied to the CO shift converter 20, 20 is a CO shift converter, 21 is a CO selective oxidizer, 22 Is a condenser, 23 is a polymer electrolyte fuel cell stack (hereinafter abbreviated as PEFC stack) as a second fuel cell stack, 24 is an air electrode of PEFC stack 23, and 25 is a solid polymer of PEFC stack 23. The electrolyte, 26 is the fuel electrode of the PEFC stack 23, 28 is water whose carbon monoxide concentration supplied to the CO selective oxidizer 21 is reduced to 1% or less. Rich reformed gas, 29 is a hydrogen-rich reformed gas whose carbon monoxide concentration is reduced to the ppm order, 30 is the oxidation air of the CO selective oxidizer 21, and 31 is the carbon monoxide concentration reduced to the ppm order. Hydrogen-rich reformed gas from which water vapor has been removed, 32 is power generation air for the PEFC stack 23, 33 is an air electrode exhaust gas for the PEFC stack 23, 34 is a fuel electrode exhaust gas for the PEFC stack 23, and 36 is power generation for the SOFC stack 3 Air, 37 is a flow control valve that controls the supply amount of the desulfurizer recycle gas, 38 is a desulfurizer, 39 is the desulfurized natural gas, and 40 is a flow control that controls the supply amount of the power generation air 36 of the SOFC stack 3. 41, a flow control valve 41 for controlling the supply amount of the power generation air 32 of the PEFC stack 23, and 42, a supply amount of the oxidation air 30 of the CO selective oxidizer 21 The flow control valve 43 controls the fuel electrode exhaust gas for combustion of the SOFC stack 3, 44 is a hydrogen-rich reformed gas whose carbon monoxide concentration is reduced to 1% or less, 45 is a desulfurizer recycle gas, 46 is Condensed water.

  Note that the above-mentioned “hydrogen rich” means containing hydrogen at a concentration sufficient to contribute to power generation by a battery reaction.

  FIG. 7 is a schematic diagram showing the SOFC stack 3. 7, the same components as those in FIG. 6 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 7, reference numeral 66 denotes a solid oxide fuel cell single cell (hereinafter referred to as a SOFC single cell).

  In FIG. 6, the SOFC stack 3 is shown as being constituted by a SOFC single cell 66 composed of a fuel electrode 4 of a set of SOFC stacks, a solid oxide electrolyte 5 of the SOFC stack, and an air electrode 6 of the SOFC stack 3. In reality, however, it is composed of a plurality of SOFC single cells 66 as shown in FIG. In FIG. 6, the SOFC stack 3, the reformer 2 and the combustor 7 are shown as being installed separately, but actually, as shown in FIG. 7, the SOFC stack 3, the reformer The combustor 2 and the combustor 7 are integrated.

  In FIG. 6, the PEFC stack 23 is shown as being constituted by a single cell comprising a fuel electrode 24 of a set of PEFC stack 23, a solid polymer electrolyte 25 of PEFC stack 23, and an air electrode 26 of PEFC stack 23. In reality, however, the PEFC stack 23 is composed of a plurality of single cells.

  Hereinafter, the operation of this conventional fuel cell power generation system will be described with reference to FIG. The natural gas 1 as the fuel is supplied to the desulfurizer 38. The supply amount of the natural gas 1 that is the fuel is determined by the preset generation current of the SOFC stack 3, the generation current of the PEFC stack 23, and the opening of the flow control valve 14 (that is, the supply amount of the natural gas 1 that is the fuel). Based on the relationship, the opening degree of the flow rate control valve 14 is controlled to set a value corresponding to the generated current of the SOFC stack 3 and the generated current of the PEFC stack 23.

  In the desulfurizer 38, the cobalt-molybdenum-based catalyst and the zinc oxide adsorbent of the filled desulfurization catalyst serve as a reforming catalyst for the reformer 2, an electrode catalyst for the fuel electrode 26 of the PEFC stack 23, and a fuel for the SOFC stack 3. The sulfur component contained in the odorant such as mercaptan in the natural gas 1 which is a fuel that causes deterioration of the electrode catalyst of the electrode 4 is adsorbed and removed by hydrodesulfurization. That is, sulfur and hydrogen are first reacted with a cobalt-molybdenum-based catalyst to generate hydrogen sulfide, and then the hydrogen sulfide and zinc oxide are reacted to generate zinc sulfide to remove the sulfur content. In order to supply the hydrogen necessary for the production of hydrogen sulfide, a part of the hydrogen-rich reformed gas 44 in which the carbon monoxide concentration discharged from the CO shift converter 20 is reduced to 1% or less is used as a desulfurizer recycle gas. 45 is recycled to the desulfurizer 38. The supply amount of the desulfurizer recycle gas 45 includes a preset opening degree of the flow control valve 14 (that is, supply amount of natural gas 1 as fuel) and an opening degree of the flow control valve 37 (that is, the desulfurizer recycle gas 45 of the desulfurizer recycle gas 45). By controlling the opening degree of the flow rate control valve 37 based on the relationship of the (supply amount), the value is set to a value commensurate with the supply amount of the natural gas 1 as the fuel. The generation reaction of hydrogen sulfide and zinc sulfide is an endothermic reaction, and the reaction heat necessary for the reaction is the heat generated by the aqueous shift reaction in the CO shift converter 20 which is an exothermic reaction described later from the CO shift converter 20 to the desulfurizer 38. It will be covered by supplying to.

  The natural gas 39 desulfurized by the desulfurizer 38 is mixed with the reformer recycle gas 11 containing water vapor generated in the SOFC stack 3, and is reformed as a mixed gas 8 of the reformer recycle gas 11 and the desulfurized natural gas 39. Supply to the quality device 2. The supply amount of the reformer recycle gas 11 includes the preset opening degree of the flow control valve 14 (that is, the supply amount of natural gas 1 as fuel) and the opening degree of the flow control valve 15 (that is, reformer recycle). Based on the relationship of the supply amount of the gas 11, the opening degree of the flow control valve 15 is controlled so as to be a value commensurate with the supply amount of the natural gas 1 as the fuel.

In the reformer 2, the steam reforming reaction of hydrocarbons in the natural gas 1 as a fuel is performed by the action of the filled reforming catalyst, and a hydrogen-rich reformed gas is produced. The steam reforming reaction of methane, which is the main component of natural gas, is expressed by equation (1).

_{CH 4 + H 2 O → CO} + 3H 2 (1)

The steam reforming reaction of hydrocarbons such as the steam reforming reaction of methane shown in the equation (1) is an endothermic reaction, and the reaction heat required from the outside of the reformer 2 in order to efficiently generate hydrogen. It is necessary to maintain the temperature of the reformer 2 at 700 to 750 ° C. For this reason, the exhaust heat of the SOFC stack 3 that generates power at 800 to 1000 ° C. installed in the vicinity of the reformer 2 described later is supplied to the reformer 2 as reaction heat necessary for the steam reforming reaction of hydrocarbons. To do.

  A part of the reformed gas 9 produced by the reformer 2 is supplied to the CO shift converter 20, and the rest is supplied to the fuel electrode 4 of the SOFC stack 3. The supply amount of the reformed gas 17 to be supplied to the CO shift converter 20 includes a preset power generation current of the PEFC stack 23 and the opening of the flow control valve 19 (that is, the supply amount of the reformed gas 17 to be supplied to the CO shift converter 20). ) To control the opening degree of the flow control valve 19 to set a value corresponding to the generated current of the PEFC stack. On the other hand, the supply amount of the reformed gas 16 supplied to the fuel electrode 4 of the SOFC stack 3 is determined based on the preset power generation current of the SOFC stack 3 and the opening of the flow rate control valve 18 (that is, supplied to the fuel electrode 4 of the SOFC stack 3). Based on the relationship of the supply amount of the reformed gas 16), the opening degree of the flow control valve 18 is controlled to set a value commensurate with the generated current of the SOFC stack 3.

  The power generation air 36 of the SOFC stack 3 is supplied to the air electrode 6 of the SOFC stack 3. The supply amount of the power generation air 36 of the SOFC stack 3 is based on a preset relationship between the power generation current of the SOFC stack 3 and the opening of the flow control valve 40 (that is, the supply amount of the power generation air 36 of the SOFC stack 3). By controlling the opening degree of the flow control valve 40, a value corresponding to the generated current of the SOFC stack 3 is set.

In the air electrode 6 of the SOFC stack 3, the oxygen in the power generation air 36 of the SOFC stack 3 reacts with electrons by the air electrode reaction shown in the equation (2) and changes into oxygen ions by the action of the metal oxide electrode catalyst. .

^{_{1 / 2O 2 + 2e - →}} O 2- (2)

Oxygen ions generated at the air electrode 6 of the SOFC stack 3 move inside the solid oxide electrolyte 5 of the SOFC stack 3 such as stabilized zirconia (YSZ) and reach the fuel electrode 4 of the SOFC stack 3. The fuel electrode 4 of the SOFC stack 3 moves from the air electrode 6 of the SOFC stack 3 to the inside of the solid oxide electrolyte 5 of the SOFC stack 3 by the action of a metal electrode catalyst such as nickel-YSZ cermet or ruthenium-YSZ cermet. Oxygen ions react with hydrogen and carbon monoxide in the reformed gas 16 supplied to the fuel electrode 4 of the SOFC stack 3 by the reactions shown in the equations (3) and (4), and steam or carbon dioxide and electrons Produces.

H ₂ + O ²⁻ → H ₂ O + 2e ⁻ (3)
CO + O ²⁻ → CO ₂ + 2e ⁻ (4)

Electrons generated at the fuel electrode 4 of the SOFC stack 3 travel through an external circuit and reach the air electrode 6 of the SOFC stack 3. The electrons that have reached the air electrode 6 of the SOFC stack react with oxygen by the reaction shown in the equation (2). In the process in which the electrons move through the external circuit, electric energy can be taken out as a power generation output of the SOFC stack 3.

Summarizing the formulas (2) and (3) and the formulas (2) and (4), the battery reaction of the SOFC stack 3 is represented by the hydrogen oxidation reaction shown in the formula (5) and the formula (6). It can be expressed as an oxidation reaction of carbon monoxide.

H ₂ + 1 / 2O ₂ → H ₂ O (5)
CO + 1 / 2O ₂ → CO ₂ (6)

The power generation temperature of the SOFC stack 3 is generally 900 to 1000 ° C., and the power generation temperature is maintained by the heat generated by the battery reaction. The exhaust heat of the SOFC stack 3 is used as the reaction heat of the steam reforming reaction of hydrocarbons in the natural gas 1 that is the fuel in the reformer 2 as described above.

  A part of the fuel electrode exhaust gas 10 of the SOFC stack 3 containing the steam generated by the cell reaction in the fuel electrode 4 of the SOFC stack 3 is necessary for the steam reforming reaction of hydrocarbons in the reformer 2 as described above. In order to supply fresh steam, it is mixed with the natural gas 39 desulfurized as the reformer recycle gas 11 and supplied to the reformer 2. On the other hand, the remainder of the fuel electrode exhaust gas 10 of the SOFC stack 3 is used as the combustion fuel electrode exhaust gas 43 of the SOFC stack 3 together with the air electrode exhaust gas 12 of the SOFC stack 3 and the fuel electrode exhaust gas of the PEFC stack 23. To supply.

  In the combustor 7, unreacted fuel, unreacted hydrogen and unreacted carbon monoxide in the combustion fuel electrode exhaust gas 43 of the SOFC stack 3, and unreacted fuel and unreacted hydrogen in the fuel electrode exhaust gas 34 of the PEFC stack 23. Is subjected to a combustion reaction with oxygen in the air electrode exhaust gas 12 of the SOFC stack 3. Although not shown in FIG. 6, the combustion exhaust gas 13 is used to raise the temperature of the natural gas 1 that is fuel and the power generation air 36 of the SOFC stack 3.

Since the hydrogen-rich reformed gas 9 contains carbon monoxide that causes deterioration of the electrode catalyst of the fuel electrode 26 of the PEFC stack 23, the hydrogen-rich reformed gas 9 that is not supplied to the fuel electrode 4 of the SOFC stack 3. The quality gas is supplied to the CO shift converter 20 filled with a shift catalyst such as a copper-zinc catalyst, and the water shift reaction shown in the equation (7) is performed by the action of the shift catalyst, whereby the reformed gas 9 The carbon monoxide concentration is reduced to 1% or less.

CO + H ₂ O → CO ₂ + H ₂ (7)

The aqueous shift reaction is an exothermic reaction, and the generated heat is supplied to the desulfurizer 38 and used as reaction heat for the above-described endothermic hydrogen sulfide and zinc sulfide generation reaction.

A part of the reformed gas 44 produced by the CO shift converter 20 with the carbon monoxide concentration reduced to 1% or less is supplied to the desulfurizer 38 as the desulfurizer recycle gas 45 as described above, and the rest is modified. If the carbon monoxide concentration in the gas is 100 ppm or more, it will cause deterioration of the electrode catalyst when supplied to the fuel electrode 26 of the PEFC stack 23. Therefore, in order to reduce the carbon monoxide concentration to the ppm order, CO As a reformed gas 28 in which the concentration of carbon monoxide supplied to the selective oxidizer 21 is reduced to 1% or less, a precious metal catalyst such as platinum or ruthenium is supplied to the CO selective oxidizer 21 filled as a CO selective oxidation catalyst. . Further, air is supplied to the CO selective oxidizer 21 as the oxidizing air 30 of the CO selective oxidizer 21. In the CO selective oxidizer 21, the carbon monoxide contained in the reformed gas 28 in which the concentration of carbon monoxide supplied to the CO selective oxidizer 21 is reduced to 1% or less is converted into the oxidation air 30 of the CO selective oxidizer 21. It is converted to carbon dioxide by reacting with oxygen in it and performing the CO selective oxidation reaction shown in the equation (8), which is an exothermic reaction, and the concentration of carbon monoxide supplied to the CO selective oxidizer 21 is reduced to 1% or less. The carbon monoxide concentration in the reformed gas 28 is reduced to the order of ppm.

CO + 1 / 2O ₂ → CO ₂ (8)

The supply amount of the oxidizing air 30 of the CO selective oxidizer 21 is determined by the preset opening degree of the flow control valve 19 (that is, the supply amount of the reformed gas 17 supplied to the CO shift converter 20) and the flow control valve 42. The reformed gas 17 supplied to the CO shift converter 20 is controlled by controlling the opening of the flow control valve 42 based on the relationship of the opening (that is, the supply amount of the oxidizing air 30 of the CO selective oxidizer 21). Set to a value commensurate with the supply volume.

  Unreacted water vapor contained in the reformed gas 29 in which the carbon monoxide concentration produced by the CO selective oxidizer is reduced to the order of ppm is recovered as condensed water 46 by being cooled to 100 ° C. or lower by the condenser 22. The reformed gas 31 having the carbon monoxide concentration reduced to the ppm order by condensing unreacted water vapor in the condenser 22 and removing the water vapor is supplied to the fuel electrode 26 of the PEFC stack 23. On the other hand, the power generation air 32 of the PEFC stack 23 is supplied to the air electrode 24 of the PEFC stack 23. The supply amount of the power generation air 32 of the PEFC stack 23 is based on a preset relationship between the power generation current of the PEFC stack 23 and the opening of the flow control valve 41 (that is, the supply amount of the power generation air 32 of the PEFC stack 23). Thus, by controlling the opening degree of the flow control valve 41, a value corresponding to the generated current of the PEFC stack 23 is set. The power generation temperature of the PEFC stack 23 is generally 60 to 80 ° C., and the power generation temperature is maintained by the heat generated by the battery reaction.

In the fuel electrode 26 of the PEFC stack 23, about 80% of the hydrogen contained in the reformed gas 31 in which the carbon monoxide concentration is reduced to the ppm order and the water vapor is removed by the action of the platinum-based electrode catalyst is represented by the formula (9). It changes into hydrogen ions and electrons due to the fuel electrode reaction shown in.

H ₂ → 2H ⁺ + 2e ⁻ (9)

Hydrogen ions generated at the fuel electrode 26 of the PEFC stack 23 move inside the solid polymer electrolyte 25 composed of a fluorine-based polymer having a sulfonic acid group such as Nafion and reach the air electrode 24 of the PEFC stack 23. To do. On the other hand, the electrons generated at the fuel electrode 26 of the PEFC stack 23 travel through an external circuit and reach the air electrode 24 of the PEFC stack 23. In the process that the electrons move through the external circuit, electric energy can be taken out as generated power. In the air electrode 24 of the PEFC stack 23, hydrogen ions that have moved from the fuel electrode 26 of the PEFC stack 23 to the air electrode 24 of the PEFC stack 23 from the fuel electrode 26 of the PEFC stack 23 by the action of the platinum-based electrode catalyst. Electrons that have traveled from the fuel electrode 26 of the PEFC stack 23 to the air electrode 24 of the PEFC stack 23 and oxygen in the power generation air 32 of the PEFC stack 23 supplied to the air electrode 24 of the PEFC stack 23 are ( 10) It reacts by the air electrode reaction shown in Formula, and water produces | generates.

2H ⁺ + _1/2 O ₂ + 2e ⁻ → H ₂ O (10)

Summarizing the equations (9) and (10), the battery reaction of the PEFC stack 23 can be expressed as an electrochemical oxidation reaction of hydrogen shown in the equation (11).

H ₂ + 1 / 2O ₂ → H ₂ O (11)

The power generation air 32 of the PEFC stack 23 is discharged as an air electrode exhaust gas 33 of the PEFC stack 23 after a part of oxygen is consumed by the air electrode reaction shown in the equation (10) at the air electrode 24 of the PEFC stack 23. . On the other hand, the reformed gas 31 from which the carbon monoxide concentration has been reduced to the ppm order and water vapor has been removed consumes about 80% of the hydrogen by the fuel electrode reaction shown in the equation (9) at the fuel electrode 26 of the PEFC stack 23. , And discharged as the fuel electrode exhaust gas 34 of the PEFC stack 23. As described above, the fuel electrode exhaust gas 34 of the PEFC stack 23 is supplied to the combustor 7 and burned.

  FIG. 8 is a flowchart showing a control method of the conventional fuel cell power generation system shown in FIG.

  As shown in FIG. 8, in the conventional fuel cell power generation system, the opening degree of the flow rate control valve 14 (that is, the supply amount of the natural gas 1 as fuel) and the opening degree of the flow rate control valve 15 (that is, the preset amount). , The supply amount of the reformer recycle gas 11 is uniquely obtained with respect to the supply amount of the natural gas 1 as the fuel, and the flow control valve 15 is opened. The supply amount of the reformer recycle gas 11 was set by controlling the degree.

Papers “AL Dicks, RG Fe11oes, CM Mesca1, and C. Seymour:“ A study of SOFC-PEM hybrid systems ”, Journal 1 of Power Source, 86, pp. 442-4482. "

  Next, problems of the conventional fuel cell power generation system will be described. In the conventional fuel cell power generation system, as shown in Table 1, when the power generation conditions are different, the gas composition of the reformer recycle gas 11 is not uniquely determined with respect to the supply amount of the natural gas 1 as the fuel. Therefore, when the conventional control method (FIG. 8) for uniquely determining the supply amount of the reformer recycle gas 11 is applied to the supply amount of the natural gas 1 as the fuel, it is desulfurized from the reformer recycle gas 11. The molar ratio of carbon in the natural gas 1 which is the fuel of the water vapor in the mixed gas 8 with the natural gas 39 (hereinafter abbreviated as “steam carbon ratio”) cannot be controlled to a preset value.

その結果、改質器リサイクルガス１１と脱硫された天然ガス３９との混合ガス８のスチームカーボン比が予め設定した所定の値より低下し、改質器の改質触媒上に炭素が析出することによって改質器の性能低下が起こり、燃料電池発電システムの発電を安定に継続することが困難となる恐れがある。

As a result, the steam carbon ratio of the mixed gas 8 of the reformer recycle gas 11 and the desulfurized natural gas 39 is lowered from a predetermined value set in advance, and carbon is deposited on the reforming catalyst of the reformer. As a result, the performance of the reformer deteriorates, and it may be difficult to stably continue the power generation of the fuel cell power generation system.

  The present invention has been made in view of the above problems, and an object of the present invention is to mix reformer recycle gas and fuel in a fuel cell power generation system that generates power by combining two types of fuel cell stacks. A fuel cell power generation system in which the steam carbon ratio of gas is controlled to be a predetermined value set in advance and stably continues power generation, a control method for the fuel cell power generation system, a control program for realizing the control method, and the control It is to provide a recording medium on which a program is recorded.

In order to solve the above problems, in the present invention, as described in claim 1,
A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas to carbon dioxide and hydrogen by reacting with water vapor, and carbon monoxide in the exhaust gas of the CO shift converter to carbon dioxide by reacting with oxygen A CO selective oxidizer to be converted, and a second fuel cell unit for generating electricity by electrochemically reacting hydrogen in the exhaust gas of the CO selective oxidizer with oxygen. Have a, the first fuel cell stack is a solid oxide fuel cell stack, the second fuel cell stack in a fuel cell power generation system is a solid polymer fuel cell stack,
Measurement or estimation of the water vapor content in the fuel electrode exhaust gas of the first fuel cell stack, and the reforming of the fuel electrode exhaust gas according to the water vapor content value obtained thereby and the amount of fuel supplied The fuel cell power generation system is characterized by having a flow rate control means for controlling the supply amount to the vessel.

In the present invention, as described in claim 2,
A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with steam, a hydrogen separator that selectively separates hydrogen in the exhaust gas of the CO shift converter, and It has a second fuel cell stack which generates power by reacting the hydrogen separated by the hydrogen separator oxygen electrochemically, the first fuel cell stack solid A product fuel cell stack, the second fuel cell stack in a fuel cell power generation system is a solid polymer fuel cell stack,
Measurement or estimation of the water vapor content in the fuel electrode exhaust gas of the first fuel cell stack, and the reforming of the fuel electrode exhaust gas according to the water vapor content value obtained thereby and the amount of fuel supplied The fuel cell power generation system is characterized by having a flow rate control means for controlling the supply amount to the vessel.

In the present invention, as described in claim 3,
A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with water vapor, and power generation by electrochemically reacting hydrogen in the exhaust gas of the CO shift converter with oxygen have a second fuel cell stack to perform, the first fuel cell stack is a solid oxide fuel cell stack, the second fuel cell Serusuta' In the fuel cell power generation system is a phosphoric acid fuel cell stack,
Measurement or estimation of the water vapor content in the fuel electrode exhaust gas of the first fuel cell stack, and the reforming of the fuel electrode exhaust gas according to the water vapor content value obtained thereby and the amount of fuel supplied The fuel cell power generation system is characterized by having a flow rate control means for controlling the supply amount to the vessel.

In the present invention, as described in claim 4,
A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas to carbon dioxide and hydrogen by reacting with steam, and carbon dioxide in the exhaust gas of the CO shift converter to carbon dioxide by reacting with oxygen A CO selective oxidizer to be converted, and a second fuel cell unit for generating electricity by electrochemically reacting hydrogen in the exhaust gas of the CO selective oxidizer with oxygen. Have a, the first fuel cell stack is a solid oxide fuel cell stack, the control method of the fuel cell power generation system wherein said second fuel cell stack is a solid polymer fuel cell stack In
Measure or estimate the water vapor content in the anode discharge gas of the first fuel cell stack, and supply the reformer based on the water vapor content obtained thereby and the amount of fuel supplied A fuel cell power generation characterized in that the supply amount of the fuel electrode exhaust gas to the reformer is controlled so that the ratio of water vapor in the fuel electrode exhaust gas and carbon in the fuel becomes a preset value. Configure the system control method.

In the present invention, as described in claim 5,
A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with steam, a hydrogen separator that selectively separates hydrogen in the exhaust gas of the CO shift converter, and It has a second fuel cell stack which generates power by reacting the hydrogen separated by the hydrogen separator oxygen electrochemically, the first fuel cell stack solid A product fuel cell stack, the second fuel cell stack in the control method of the fuel cell power generation system is a solid polymer fuel cell stack,
Measure or estimate the water vapor content in the anode discharge gas of the first fuel cell stack, and supply the reformer based on the water vapor content obtained thereby and the amount of fuel supplied A fuel cell power generation characterized in that the supply amount of the fuel electrode exhaust gas to the reformer is controlled so that the ratio of water vapor in the fuel electrode exhaust gas and carbon in the fuel becomes a preset value. Configure the system control method.

In the present invention, as described in claim 6,
A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with water vapor, and power generation by electrochemically reacting hydrogen in the exhaust gas of the CO shift converter with oxygen have a second fuel cell stack to perform, the first fuel cell stack is a solid oxide fuel cell stack, the second fuel cell Serusuta' In the control method of the fuel cell power generation system is a phosphoric acid fuel cell stack,
Measure or estimate the water vapor content in the anode discharge gas of the first fuel cell stack, and supply the reformer based on the water vapor content obtained thereby and the amount of fuel supplied A fuel cell power generation characterized in that the supply amount of the fuel electrode exhaust gas to the reformer is controlled so that the ratio of water vapor in the fuel electrode exhaust gas and carbon in the fuel becomes a preset value. Configure the system control method.

In the present invention, as described in claim 7,
A control program for realizing a control method for a fuel cell power generation system is provided, which causes a computer to execute the control method for a fuel cell power generation system according to claim 4, 5 or 6.

In the present invention, as described in claim 8,
The recording medium which recorded the control program which implement | achieves the control method of the fuel cell power generation system characterized by recording the control program which implement | achieves the control method of the fuel cell power generation system of Claim 7 is comprised.

In the present invention, as described in claim 9,
A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas to carbon dioxide and hydrogen by reacting with water vapor, and carbon monoxide in the exhaust gas of the CO shift converter to carbon dioxide by reacting with oxygen A CO selective oxidizer to be converted, and a second fuel cell unit for generating electricity by electrochemically reacting hydrogen in the exhaust gas of the CO selective oxidizer with oxygen. Have a, the first fuel cell stack is a solid oxide fuel cell stack, the second fuel cell stack in a fuel cell power generation system is a solid polymer fuel cell stack,
Temperature detection means for detecting the temperature of the fuel electrode outlet of the first fuel cell stack, and the temperature value detected by the temperature detection means and the supply amount of the fuel. The fuel cell power generation system includes a flow rate control unit that controls a supply amount to the reformer.

In the present invention, as described in claim 10,
A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with steam, a hydrogen separator that selectively separates hydrogen in the exhaust gas of the CO shift converter, and It has a second fuel cell stack which generates power by reacting the hydrogen separated by the hydrogen separator oxygen electrochemically, the first fuel cell stack solid A product fuel cell stack, the second fuel cell stack in a fuel cell power generation system is a solid polymer fuel cell stack,
Temperature detection means for detecting the temperature of the fuel electrode outlet of the first fuel cell stack, and the temperature value detected by the temperature detection means and the supply amount of the fuel. The fuel cell power generation system includes a flow rate control unit that controls a supply amount to the reformer.

In the present invention, as described in claim 11,
A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with water vapor, and power generation by electrochemically reacting hydrogen in the exhaust gas of the CO shift converter with oxygen have a second fuel cell stack to perform, the first fuel cell stack is a solid oxide fuel cell stack, the second fuel cell Serusuta' In the fuel cell power generation system is a phosphoric acid fuel cell stack,
Temperature detection means for detecting the temperature of the fuel electrode outlet of the first fuel cell stack, and the temperature value detected by the temperature detection means and the supply amount of the fuel. The fuel cell power generation system includes a flow rate control unit that controls a supply amount to the reformer.

In the present invention, as described in claim 12,
A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas to carbon dioxide and hydrogen by reacting with water vapor, and carbon monoxide in the exhaust gas of the CO shift converter to carbon dioxide by reacting with oxygen A CO selective oxidizer to be converted, and a second fuel cell unit for generating electricity by electrochemically reacting hydrogen in the exhaust gas of the CO selective oxidizer with oxygen. Have a, the first fuel cell stack is a solid oxide fuel cell stack, the control method of the fuel cell power generation system wherein said second fuel cell stack is a solid polymer fuel cell stack In
The anode discharge gas of the first fuel cell stack is detected, and the anode discharge gas is assumed to be in a thermodynamic equilibrium state at the detected temperature. And the ratio of the water vapor in the fuel electrode exhaust gas supplied to the reformer and the carbon in the fuel becomes a preset value based on the gas composition and the supply amount of the fuel. In addition, a control method for a fuel cell power generation system is provided in which the supply amount of the fuel electrode exhaust gas to the reformer is controlled.

In the present invention, as described in claim 13,
A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with steam, a hydrogen separator that selectively separates hydrogen in the exhaust gas of the CO shift converter, and It has a second fuel cell stack which generates power by reacting the hydrogen separated by the hydrogen separator oxygen electrochemically, the first fuel cell stack solid A product fuel cell stack, the second fuel cell stack in the control method of the fuel cell power generation system is a solid polymer fuel cell stack,
The anode discharge gas of the first fuel cell stack is detected, and the anode discharge gas is assumed to be in a thermodynamic equilibrium state at the detected temperature. And the ratio of the water vapor in the fuel electrode exhaust gas supplied to the reformer and the carbon in the fuel becomes a preset value based on the gas composition and the supply amount of the fuel. In addition, a control method for a fuel cell power generation system is provided in which the supply amount of the fuel electrode exhaust gas to the reformer is controlled.

In the present invention, as described in claim 14,
A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with water vapor, and power generation by electrochemically reacting hydrogen in the exhaust gas of the CO shift converter with oxygen have a second fuel cell stack to perform, the first fuel cell stack is a solid oxide fuel cell stack, the second fuel cell Serusuta' In the control method of the fuel cell power generation system is a phosphoric acid fuel cell stack,
The anode discharge gas of the first fuel cell stack is detected, and the anode discharge gas is assumed to be in a thermodynamic equilibrium state at the detected temperature. And the ratio of the water vapor in the fuel electrode exhaust gas supplied to the reformer and the carbon in the fuel becomes a preset value based on the gas composition and the supply amount of the fuel. In addition, a control method for a fuel cell power generation system is provided in which the supply amount of the fuel electrode exhaust gas to the reformer is controlled.

In the present invention, as described in claim 15,
A control program for realizing a control method for a fuel cell power generation system, which causes a computer to execute the control method for a fuel cell power generation system according to claim 12, 13 or 14 is configured.

In the present invention, as described in claim 16,
The recording medium which recorded the control program which implement | achieves the control method of the fuel cell electric power generation system characterized by recording the control program which implement | achieves the control method of the fuel cell electric power generation system of Claim 15 is comprised.

  By implementing the present invention, a fuel cell power generation system in which the steam carbon ratio of the mixed gas of reformer recycle gas and fuel is controlled to be a predetermined value set in advance and power generation is stably continued, and the fuel cell power generation thereof It is possible to provide a system control method, a control program for realizing the control method, and a recording medium on which the control program is recorded.

(Embodiment 1)
FIG. 1 is a system configuration diagram showing an embodiment (referred to as Embodiment 1) of a fuel cell power generation system of the present invention. In FIG. 1, the same components as those in FIGS. 6 and 7 are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 1, reference numeral 65 denotes a temperature detection means for detecting the fuel electrode outlet temperature of the fuel electrode exhaust gas of the SOFC stack 3, and 70 denotes reforming of the fuel electrode exhaust gas according to the temperature value detected by the temperature detection means 65. It is a flow rate control valve opening degree control means for controlling the opening degree of the flow rate control valve 15, which is a flow rate control means for controlling the supply amount to the container 2.

  FIG. 2 shows an installation example in the SOFC stack 3 of the temperature detecting means 65 for detecting the temperature of the fuel electrode outlet gas fuel electrode outlet of the SOFC stack 3.

  The configuration of the present embodiment shown in FIG. 1 includes temperature detection means 65 for detecting the fuel electrode exhaust gas fuel electrode outlet temperature of the SOFC stack 3, and flow control valve opening control means for controlling the opening of the flow control valve 15. 70, and detects the temperature of the fuel electrode exhaust gas fuel electrode outlet of the SOFC stack 3, and controls the opening degree of the flow rate control valve 15 according to the detection result, the conventional fuel cell shown in FIG. It is different from the power generation system.

  FIG. 3 is a flowchart showing an embodiment of the control method of the fuel cell power generation system of the present invention.

  The operation of the present embodiment shown in FIG. 1 will be described with reference to FIG. In the present embodiment, as shown in FIG. 3, the temperature detection means 65 for detecting the temperature of the fuel electrode exhaust gas fuel electrode outlet of the SOFC stack 3 is used to measure the temperature of the fuel electrode exhaust gas fuel electrode outlet temperature of the SOFC stack 3. Assuming that the fuel electrode exhaust gas 10 of the SOFC stack 3 is in a thermodynamic equilibrium state at the fuel electrode outlet temperature, the gas composition of the fuel electrode exhaust gas 10 of the SOFC stack 3, that is, the reformer recycle gas 11 is Ask.

  Next, from the opening degree of the flow control valve 14, that is, the supply amount of the natural gas 1 as the fuel and the obtained gas composition of the reformer recycle gas 11, the reformer recycle gas 11 and the desulfurized natural gas 39 are obtained. The supply amount of the reformer recycle gas 11 necessary for setting the steam carbon ratio of the mixed gas 8 to a preset value is obtained, and the preset supply amount of the reformer recycle gas 11 and the flow control valve 15 Based on the opening degree relationship, the opening degree of the flow rate control valve 15 is controlled so that the steam carbon ratio of the mixed gas 8 of the reformer recycle gas 11 and the desulfurized natural gas 39 becomes a preset value. .

  The flow control valve opening degree control means 70 receives the temperature information detected by the temperature detection means 65 and the opening degree information of the flow control valve 14, and obtains the gas composition of the reformer recycle gas 11 based on the information. Then, a calculation for obtaining the supply amount of the reformer recycle gas 11 necessary for setting the steam carbon ratio of the mixed gas 8 to a preset value is performed, and the preset supply amount and flow rate of the reformer recycle gas 11 are calculated. Based on the relationship of the opening degree of the control valve 15, the flow control valve 15 is opened so that the steam carbon ratio of the mixed gas 8 of the reformer recycle gas 11 and the desulfurized natural gas 39 becomes a preset value. Control the degree.

  By controlling the opening degree of the flow rate control valve 15 as described above, the steam carbon ratio of the mixed gas 8 of the reformer recycle gas 11 and the desulfurized natural gas 39 is set to a predetermined value even if the power generation condition changes. It is possible to control, and it is possible to suppress a decrease in performance caused by carbon deposition on the reforming catalyst of the reformer 2 due to a decrease in the steam carbon ratio, and to stably continue the power generation of the fuel cell power generation system. .

  In addition, since the fuel electrode exhaust gas 10 of the SOFC stack 3 is as high as 700 to 800 ° C., it can be said that the composition thereof is in a substantially thermodynamic equilibrium state.

  As described above, when the opening degree of the flow control valve 15 is controlled, a control program for causing a computer to perform an operation is created according to the procedure shown in FIG. 3, and the control program is executed by the computer. The control program is recorded on a recording medium such as a magnetic disk.

  Instead of the temperature detection means 65 and the flow rate control valve opening degree control means 70 of the present embodiment, the water vapor content in the fuel electrode exhaust gas 10 of the SOFC stack 3 is measured or estimated using, for example, a dew point meter, Means for controlling the opening degree of the flow rate control valve 15 according to the water vapor content value obtained thereby and the supply amount of the natural gas 1 as the fuel, that is, the water vapor content in the fuel electrode exhaust gas 10 is measured or estimated. Even if a flow rate control means for controlling the supply amount of the fuel electrode exhaust gas 10 to the reformer 2 in accordance with the water vapor content value obtained thereby and the supply amount of fuel is used, the same effect as in the present embodiment can be obtained. can get. Also in this case, a control program for causing the computer to perform calculations necessary for control is created, and the computer executes the control program. The control program is recorded on a recording medium such as a magnetic disk.

(Embodiment 2)
FIG. 4 is a system configuration diagram showing another embodiment of the fuel cell power generation system of the present invention (this is referred to as Embodiment 2). 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. In FIG. 4, 48 is a hydrogen separator, 50 is a reformed gas for a hydrogen separator whose carbon monoxide concentration is reduced to 1% or less, 51 is hydrogen, 52 is a hydrogen separator exhaust gas, 67 is a purge valve, 68 is The purge gas 69 is a fuel electrode hydrogen exhaust gas.

  The present embodiment shown in FIG. 4 is different from the embodiment shown in FIG. 1 in that a hydrogen separator 48 is provided instead of the CO selective oxidizer 21 and the condenser 22.

  Next, the operation of the present embodiment shown in FIG. 4 will be described. The hydrogen separator reformed gas 50 is supplied to a hydrogen separator 48 having a hydrogen separation membrane such as a palladium membrane to separate the hydrogen 51. At that time, in order to perform efficient hydrogen separation, the reforming gas 50 for the hydrogen separator is pressurized as necessary. Hydrogen 51 is supplied to the fuel electrode 26 of the PEFC stack 23. The hydrogen separator exhaust gas 52 is supplied to the combustor 7, and unreacted fuel and hydrogen in the hydrogen separator exhaust gas 52 are used as unreacted fuel and unreacted hydrogen in the combustion fuel electrode exhaust gas 43 of the SOFC stack 3. Along with the unreacted carbon monoxide, it is subjected to a combustion reaction with oxygen in the air electrode exhaust gas 12 of the SOFC stack 3. The hydrogen 51 separated by the hydrogen separator 48 is supplied to the fuel electrode 26 of the PEFC stack 23, and the PEFC stack 23 generates power by electrochemically reacting with oxygen in the air. The fuel electrode hydrogen exhaust gas 69 of the PEFC stack 23 made of unreacted hydrogen is all recycled to the fuel electrode 26 of the PEFC stack 23 in order to improve the power generation efficiency of the PEFC stack 23. However, since the fuel electrode hydrogen exhaust gas 69 of the PEFC stack 23 contains some impurities other than hydrogen, the purge valve 67 is opened intermittently and the purge gas 68 is released.

  Also in the present embodiment shown in FIG. 4, the temperature detection means 65 for detecting the temperature of the fuel electrode exhaust gas fuel electrode outlet of the SOFC stack 3 is used to measure the temperature of the fuel electrode exhaust gas fuel electrode outlet of the SOFC stack 3 and Assuming that the third fuel electrode exhaust gas 10 is in a thermodynamic equilibrium state at the fuel electrode outlet temperature, the gas composition of the fuel electrode exhaust gas 10 of the SOFC stack 3, that is, the reformer recycle gas 11 is obtained. Next, from the opening degree of the flow control valve 14, that is, the supply amount of the natural gas 1 as the fuel and the obtained gas composition of the reformer recycle gas 11, the reformer recycle gas 11 and the desulfurized natural gas 39 are obtained. The supply amount of the reformer recycle gas 11 necessary for setting the steam carbon ratio of the mixed gas 8 to a preset value is obtained, and the preset supply amount of the reformer recycle gas 11 and the flow control valve 15 Based on the opening degree relationship, the opening degree of the flow rate control valve 15 is controlled so that the steam carbon ratio of the mixed gas 8 of the reformer recycle gas 11 and the desulfurized natural gas 39 becomes a preset value. . For this reason, even if the power generation conditions change, the steam carbon ratio of the mixed gas 8 of the reformer recycle gas 11 and the desulfurized natural gas 39 can be controlled to a predetermined value, and the modification due to the reduction of the steam carbon ratio. It is possible to suppress a decrease in performance due to carbon deposition on the reforming catalyst of the mass device 2 and stably continue power generation of the fuel cell power generation system.

  As described above, when the opening degree of the flow control valve 15 is controlled, a control program for performing calculation is created according to the procedure shown in FIG. 3, and the computer executes the control program. The control program is recorded on a recording medium such as a magnetic disk.

  Instead of the temperature detection means 65 and the flow rate control valve opening degree control means 70 of the present embodiment, the water vapor content in the fuel electrode exhaust gas 10 of the SOFC stack 3 is measured or estimated using, for example, a dew point meter, Means for controlling the opening degree of the flow rate control valve 15 according to the water vapor content value obtained thereby and the supply amount of the natural gas 1 as the fuel, that is, the water vapor content in the fuel electrode exhaust gas 10 is measured or estimated. Even if a flow rate control means for controlling the supply amount of the fuel electrode exhaust gas 10 to the reformer 2 in accordance with the water vapor content value obtained thereby and the supply amount of fuel is used, the same effect as in the present embodiment can be obtained. can get. In this case as well, a control program is generated that causes the computer to perform calculations necessary for control, and the computer executes the control program. The control program is recorded on a recording medium such as a magnetic disk.

(Embodiment 3)
FIG. 5 is a system configuration diagram showing another embodiment (referred to as Embodiment 3) of the fuel cell power generation system of the present invention. 5, the same components as those in FIGS. 1 and 4 are denoted by the same reference numerals, and the description of these components is omitted.

  In FIG. 5, 55 is a reformed gas for a phosphoric acid fuel cell stack (hereinafter referred to as PAFC stack), 56 is a PAFC stack, 57 is an air electrode of the PAFC stack 56, 58 is a phosphoric acid electrolyte of the PAFC stack 56, 59 is a fuel electrode of the PAFC stack 56, 60 is power generation air of the PAFC stack 56, 61 is a flow control valve for controlling the supply amount of the power generation air 60 of the PAFC stack 56, 62 is an air electrode exhaust gas of the PAFC stack 56, 63 is a fuel electrode exhaust gas of the PAFC stack 56.

  The present embodiment shown in FIG. 5 differs from the first embodiment shown in FIG. 1 in that the CO selective oxidizer 21 and the condenser 22 are unnecessary, and a PAFC stack is used instead of the PEFC stack 23 as the second fuel cell stack. 56 is different.

  Next, the operation of the present embodiment shown in FIG. 5 will be described. A part of the reformed gas 44 having the carbon monoxide concentration produced by the CO shift converter 20 reduced to 1% or less is supplied to the fuel electrode 59 of the PAFC stack 56 as the reformed gas 55 for the PAFC stack. On the other hand, the power generation air 60 of the PAFC stack 56 is supplied to the air electrode 57 of the PAFC stack 56. The supply amount of the power generation air 60 of the PAFC stack 56 is based on a preset relationship between the generation current of the PAFC stack 56 and the opening of the flow control valve 61 (that is, the supply amount of the power generation air 60 of the PAFC stack 56). Thus, by controlling the opening degree of the flow control valve 61, a value corresponding to the generated current of the PAFC stack 56 is set. The power generation temperature of the PAFC stack 56 is generally 190 ° C., and the power generation temperature is maintained by the heat generated by the battery reaction.

  In the fuel electrode 59 of the PAFC stack 56, about 80% of the hydrogen contained in the reformed gas 55 for the PAFC stack is made into the fuel shown in the formula (9) as in the PEFC stack 23 by the action of the platinum-based electrode catalyst. It changes into hydrogen ion and electron by polar reaction.

  Hydrogen ions generated at the fuel electrode 59 of the PAFC stack 56 move inside the phosphate electrolyte 58 and reach the air electrode 57 of the PAFC stack 56. On the other hand, the electrons generated at the fuel electrode 59 of the PAFC stack 56 move through an external circuit and reach the air electrode 57 of the PAFC stack 56. In the process that the electrons move through the external circuit, electric energy can be taken out as generated power.

  In the air electrode 57 of the PAFC stack 56, hydrogen ions that have moved from the fuel electrode 59 of the PAFC stack 56 to the air electrode 57 of the PAFC stack 56 from the fuel electrode 59 of the PAFC stack 56 due to the action of the platinum-based electrode catalyst. Electrons that have moved from the fuel electrode 59 through the external circuit to the air electrode 57 of the PAFC stack 56 and oxygen in the power generation air 60 of the PAFC stack 56 supplied to the air electrode 57 of the PAFC stack 56 are the case of the PEFC stack 23. Similarly, water reacts by the air electrode reaction shown in the equation (10).

  When the equations (9) and (10) are put together, the battery reaction of the PAFC stack 56 can be expressed as an electrochemical oxidation reaction of hydrogen shown in the equation (11) as in the case of the PEFC stack 23.

  The power generation air 60 of the PAFC stack 56 is discharged as the air electrode exhaust gas 62 of the PAFC stack 56 after a part of oxygen is consumed by the air electrode reaction shown in the equation (10) at the air electrode 24 of the PAFC stack 56. . On the other hand, the reformed gas 55 for the PAFC stack consumes about 80% of hydrogen in the fuel electrode 59 of the PAFC stack 56 by the fuel electrode reaction shown in the equation (9), and then is used as the fuel electrode exhaust gas 63 of the PAFC stack 56. Discharge. The unreacted fuel and unreacted hydrogen in the fuel electrode exhaust gas 63 of the PAFC stack 56 together with the unreacted fuel, unreacted hydrogen and unreacted carbon monoxide in the combustion fuel electrode exhaust gas 43 of the SOFC stack 3. 3 is reacted with oxygen in the air electrode exhaust gas 12.

  Also in the present embodiment shown in FIG. 5, the temperature detection means 65 for detecting the temperature of the fuel electrode exhaust gas fuel electrode outlet of the SOFC stack 3 is used to measure the temperature of the fuel electrode exhaust gas fuel electrode outlet of the SOFC stack 3 and Assuming that the third fuel electrode exhaust gas 10 is in a thermodynamic equilibrium state at the fuel electrode outlet temperature, the gas composition of the fuel electrode exhaust gas 10 of the SOFC stack 3, that is, the reformer recycle gas 11 is obtained. Next, from the opening degree of the flow control valve 14, that is, the supply amount of the natural gas 1 as the fuel and the obtained gas composition of the reformer recycle gas 11, the reformer recycle gas 11 and the desulfurized natural gas 39 are obtained. The supply amount of the reformer recycle gas 11 necessary for setting the steam carbon ratio of the mixed gas 8 to a preset value is obtained, and the preset supply amount of the reformer recycle gas 11 and the flow control valve 15 Based on the opening degree relationship, the opening degree of the flow rate control valve 15 is controlled so that the steam carbon ratio of the mixed gas 8 of the reformer recycle gas 11 and the desulfurized natural gas 39 becomes a preset value. . For this reason, even if the power generation conditions change, the steam carbon ratio of the mixed gas 8 of the reformer recycle gas 11 and the desulfurized natural gas 39 can be controlled to a predetermined value, and the modification due to the reduction of the steam carbon ratio. It is possible to suppress a decrease in performance due to carbon deposition on the reforming catalyst of the mass device 2 and stably continue power generation of the fuel cell power generation system.

  As described above, when the opening degree of the flow control valve 15 is controlled, a control program for performing calculation is created according to the procedure shown in FIG. 3, and the computer executes the control program. The control program is recorded on a recording medium such as a magnetic disk.

  Instead of the temperature detection means 65 and the flow rate control valve opening degree control means 70 of the present embodiment, the water vapor content in the fuel electrode exhaust gas 10 of the SOFC stack 3 is measured or estimated using, for example, a dew point meter, Means for controlling the opening degree of the flow rate control valve 15 according to the water vapor content value obtained thereby and the supply amount of the natural gas 1 as the fuel, that is, the water vapor content in the fuel electrode exhaust gas 10 is measured or estimated. Even if a flow rate control means for controlling the supply amount of the fuel electrode exhaust gas 10 to the reformer 2 in accordance with the water vapor content value obtained thereby and the supply amount of fuel is used, the same effect as in the present embodiment can be obtained. can get. In this case as well, a control program is generated that causes the computer to perform calculations necessary for control, and the computer executes the control program. The control program is recorded on a recording medium such as a magnetic disk.

  As described above, if the fuel cell power generation system of the present invention, the control method of the fuel cell power generation system, the control program for realizing the control method, and the recording medium storing the control program are used, the power generation conditions change. However, the steam carbon ratio of the fuel and steam-containing gas supplied to the reformer can be controlled to be a predetermined value set in advance, and the reformer catalyst on the reformer can be controlled by the reduction of the steam carbon ratio. It is possible to suppress the performance degradation caused by carbon deposition on the fuel cell and to continue the power generation of the fuel cell power generation system stably.

It is a system configuration figure showing one embodiment of a fuel cell power generation system of the present invention. It is a schematic diagram showing the SOFC stack of the fuel cell power generation system of the present invention. It is a flowchart showing one Embodiment of the control method of the fuel cell power generation system of this invention. It is a system block diagram showing other one Embodiment of the fuel cell power generation system of this invention. It is a system block diagram showing other one Embodiment of the fuel cell power generation system of this invention. It is a system configuration | structure figure showing one Embodiment of the conventional fuel cell power generation system. It is a schematic diagram showing the SOFC stack of the conventional fuel cell power generation system. It is a flowchart showing the control method of the conventional fuel cell power generation system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Natural gas, 2 ... Reformer, 3 ... SOFC stack, 4 ... Fuel electrode, 5 ... Solid oxide electrolyte, 6 ... Air electrode, 7 ... Combustor, 8 ... Reformer recycled gas and desulfurized natural gas Mixed gas, 9 ... reformed gas, 10 ... fuel electrode exhaust gas, 11 ... reformer recycle gas, 12 ... air electrode exhaust gas, 13 ... combustion exhaust gas, 14 ... flow control valve, 15 ... flow control valve, 16 ... reformed gas for SOFC stack, 17 ... reformed gas for CO shift converter, 18 ... flow control valve, 19 ... flow control valve, 20 ... CO shift converter, 21 ... CO selective oxidizer, 22 ... condenser, 23 ... PEFC stack, 24 ... air electrode, 25 ... solid polymer electrolyte, 26 ... fuel electrode, 28 ... reformed gas with carbon monoxide concentration reduced to 1% or less, 29 ... reducing carbon monoxide concentration to ppm order Reformed gas, 30 ... Air for O selective oxidizer, 31... Reformed gas whose carbon monoxide concentration has been reduced to the ppm order and removed water vapor, 32... Air for PEFC stack 23, 33 ... Air electrode exhaust gas, 34 ... Fuel electrode exhaust gas, 36. SOFC stack air, 37 ... Flow control valve, 38 ... Desulfurizer, 39 ... Desulfurized natural gas, 40 ... Flow control valve, 41 ... Flow control valve, 42 ... Flow control valve, 43 ... SOFC stack anode discharge Gas, 44 ... reformed gas with carbon monoxide concentration reduced to 1% or less, 45 ... desulfurizer recycle gas, 46 ... condensate, 48 ... hydrogen separator, 50 ... carbon monoxide concentration reduced to 1% or less Reformed gas, 51 ... hydrogen, 52 ... hydrogen separator exhaust gas, 55 ... reformed gas for PAFC stack, 56 ... PAFC stack, 57 ... air electrode, 58 ... phosphoric acid electrolyte, 59 ... fuel electrode, DESCRIPTION OF SYMBOLS 0 ... PAFC stack air, 61 ... Flow control valve, 62 ... Air electrode exhaust gas, 63 ... Fuel electrode exhaust gas, 65 ... Temperature detection means, 66 ... SOFC single cell, 67 ... Purge valve, 68 ... Purge gas, 69 ... Fuel electrode hydrogen exhaust gas, 70...

Claims (16)

A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas to carbon dioxide and hydrogen by reacting with water vapor, and carbon monoxide in the exhaust gas of the CO shift converter to carbon dioxide by reacting with oxygen A CO selective oxidizer to be converted, and a second fuel cell unit for generating electricity by electrochemically reacting hydrogen in the exhaust gas of the CO selective oxidizer with oxygen. Have a, the first fuel cell stack is a solid oxide fuel cell stack, the second fuel cell stack in a fuel cell power generation system is a solid polymer fuel cell stack,
Measurement or estimation of the water vapor content in the fuel electrode exhaust gas of the first fuel cell stack, and the reforming of the fuel electrode exhaust gas according to the water vapor content value obtained thereby and the amount of fuel supplied A fuel cell power generation system comprising flow rate control means for controlling the supply amount to the vessel. A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with steam, a hydrogen separator that selectively separates hydrogen in the exhaust gas of the CO shift converter, and It has a second fuel cell stack which generates power by reacting the hydrogen separated by the hydrogen separator oxygen electrochemically, the first fuel cell stack solid A product fuel cell stack, the second fuel cell stack in a fuel cell power generation system is a solid polymer fuel cell stack,
Measurement or estimation of the water vapor content in the fuel electrode exhaust gas of the first fuel cell stack, and the reforming of the fuel electrode exhaust gas according to the water vapor content value obtained thereby and the amount of fuel supplied A fuel cell power generation system comprising flow rate control means for controlling the supply amount to the vessel. A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with water vapor, and power generation by electrochemically reacting hydrogen in the exhaust gas of the CO shift converter with oxygen have a second fuel cell stack to perform, the first fuel cell stack is a solid oxide fuel cell stack, the second fuel cell Serusuta' In the fuel cell power generation system is a phosphoric acid fuel cell stack,
Measurement or estimation of the water vapor content in the fuel electrode exhaust gas of the first fuel cell stack, and the reforming of the fuel electrode exhaust gas according to the water vapor content value obtained thereby and the amount of fuel supplied A fuel cell power generation system comprising flow rate control means for controlling the supply amount to the vessel. A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas to carbon dioxide and hydrogen by reacting with steam, and carbon dioxide in the exhaust gas of the CO shift converter to carbon dioxide by reacting with oxygen A CO selective oxidizer to be converted, and a second fuel cell unit for generating electricity by electrochemically reacting hydrogen in the exhaust gas of the CO selective oxidizer with oxygen. Have a, the first fuel cell stack is a solid oxide fuel cell stack, the control method of the fuel cell power generation system wherein said second fuel cell stack is a solid polymer fuel cell stack In
Measure or estimate the water vapor content in the anode discharge gas of the first fuel cell stack, and supply the reformer based on the water vapor content obtained thereby and the amount of fuel supplied A fuel cell power generation characterized in that the supply amount of the fuel electrode exhaust gas to the reformer is controlled so that the ratio of water vapor in the fuel electrode exhaust gas and carbon in the fuel becomes a preset value. How to control the system. A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with steam, a hydrogen separator that selectively separates hydrogen in the exhaust gas of the CO shift converter, and It has a second fuel cell stack which generates power by reacting the hydrogen separated by the hydrogen separator oxygen electrochemically, the first fuel cell stack solid A product fuel cell stack, the second fuel cell stack in the control method of the fuel cell power generation system is a solid polymer fuel cell stack,
Measure or estimate the water vapor content in the anode discharge gas of the first fuel cell stack, and supply the reformer based on the water vapor content obtained thereby and the amount of fuel supplied A fuel cell power generation characterized in that the supply amount of the fuel electrode exhaust gas to the reformer is controlled so that the ratio of water vapor in the fuel electrode exhaust gas and carbon in the fuel becomes a preset value. How to control the system. A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with water vapor, and power generation by electrochemically reacting hydrogen in the exhaust gas of the CO shift converter with oxygen have a second fuel cell stack to perform, the first fuel cell stack is a solid oxide fuel cell stack, the second fuel cell Serusuta' In the control method of the fuel cell power generation system is a phosphoric acid fuel cell stack,
Measure or estimate the water vapor content in the anode discharge gas of the first fuel cell stack, and supply the reformer based on the water vapor content obtained thereby and the amount of fuel supplied A fuel cell power generation characterized in that the supply amount of the fuel electrode exhaust gas to the reformer is controlled so that the ratio of water vapor in the fuel electrode exhaust gas and carbon in the fuel becomes a preset value. How to control the system.   A control program for realizing a control method for a fuel cell power generation system, which causes a computer to execute the control method for the fuel cell power generation system according to claim 4, 5 or 6.   A recording medium recording a control program for realizing a control method for a fuel cell power generation system, wherein a control program for realizing the control method for the fuel cell power generation system according to claim 7 is recorded. A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas to carbon dioxide and hydrogen by reacting with water vapor, and carbon monoxide in the exhaust gas of the CO shift converter to carbon dioxide by reacting with oxygen A CO selective oxidizer to be converted, and a second fuel cell unit for generating electricity by electrochemically reacting hydrogen in the exhaust gas of the CO selective oxidizer with oxygen. Have a, the first fuel cell stack is a solid oxide fuel cell stack, the second fuel cell stack in a fuel cell power generation system is a solid polymer fuel cell stack,
Temperature detection means for detecting the temperature of the fuel electrode outlet of the first fuel cell stack, and the temperature value detected by the temperature detection means and the supply amount of the fuel. A fuel cell power generation system comprising flow rate control means for controlling a supply amount to the reformer. A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with steam, a hydrogen separator that selectively separates hydrogen in the exhaust gas of the CO shift converter, and It has a second fuel cell stack which generates power by reacting the hydrogen separated by the hydrogen separator oxygen electrochemically, the first fuel cell stack solid A product fuel cell stack, the second fuel cell stack in a fuel cell power generation system is a solid polymer fuel cell stack,
Temperature detection means for detecting the temperature of the fuel electrode outlet of the first fuel cell stack, and the temperature value detected by the temperature detection means and the supply amount of the fuel. A fuel cell power generation system comprising flow rate control means for controlling a supply amount to the reformer. A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with water vapor, and power generation by electrochemically reacting hydrogen in the exhaust gas of the CO shift converter with oxygen have a second fuel cell stack to perform, the first fuel cell stack is a solid oxide fuel cell stack, the second fuel cell Serusuta' In the fuel cell power generation system is a phosphoric acid fuel cell stack,
Temperature detection means for detecting the temperature of the fuel electrode outlet of the first fuel cell stack, and the temperature value detected by the temperature detection means and the supply amount of the fuel. A fuel cell power generation system comprising flow rate control means for controlling a supply amount to the reformer. A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas to carbon dioxide and hydrogen by reacting with steam, and carbon dioxide in the exhaust gas of the CO shift converter to carbon dioxide by reacting with oxygen A CO selective oxidizer to be converted, and a second fuel cell unit for generating electricity by electrochemically reacting hydrogen in the exhaust gas of the CO selective oxidizer with oxygen. Have a, the first fuel cell stack is a solid oxide fuel cell stack, the control method of the fuel cell power generation system wherein said second fuel cell stack is a solid polymer fuel cell stack In
The anode discharge gas of the first fuel cell stack is detected, and the anode discharge gas is assumed to be in a thermodynamic equilibrium state at the detected temperature. And the ratio of the water vapor in the fuel electrode exhaust gas supplied to the reformer and the carbon in the fuel becomes a preset value based on the gas composition and the supply amount of the fuel. And a control method of the fuel cell power generation system, wherein the supply amount of the fuel electrode exhaust gas to the reformer is controlled. A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with steam, a hydrogen separator that selectively separates hydrogen in the exhaust gas of the CO shift converter, and It has a second fuel cell stack which generates power by reacting the hydrogen separated by the hydrogen separator oxygen electrochemically, the first fuel cell stack solid A product fuel cell stack, the second fuel cell stack in the control method of the fuel cell power generation system is a solid polymer fuel cell stack,
The anode discharge gas of the first fuel cell stack is detected, and the anode discharge gas is assumed to be in a thermodynamic equilibrium state at the detected temperature. And the ratio of the water vapor in the fuel electrode exhaust gas supplied to the reformer and the carbon in the fuel becomes a preset value based on the gas composition and the supply amount of the fuel. And a control method of the fuel cell power generation system, wherein the supply amount of the fuel electrode exhaust gas to the reformer is controlled. A reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of the fuel, and electricity is generated by electrochemically reacting hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen, A first fuel cell stack that supplies exhaust gas generated with the power generation to the reformer, and supplies fuel electrode exhaust gas containing water vapor generated with the power generation to the reformer; A CO shift converter that converts carbon monoxide in the reformed gas into carbon dioxide and hydrogen by reacting with water vapor, and power generation by electrochemically reacting hydrogen in the exhaust gas of the CO shift converter with oxygen have a second fuel cell stack to perform, the first fuel cell stack is a solid oxide fuel cell stack, the second fuel cell Serusuta' In the control method of the fuel cell power generation system is a phosphoric acid fuel cell stack,
The anode discharge gas of the first fuel cell stack is detected, and the anode discharge gas is assumed to be in a thermodynamic equilibrium state at the detected temperature. And the ratio of the water vapor in the fuel electrode exhaust gas supplied to the reformer and the carbon in the fuel becomes a preset value based on the gas composition and the supply amount of the fuel. And a control method of the fuel cell power generation system, wherein the supply amount of the fuel electrode exhaust gas to the reformer is controlled.   A control program for realizing a control method for a fuel cell power generation system, which causes a computer to execute the control method for the fuel cell power generation system according to claim 12, 13 or 14.   A recording medium recording a control program for realizing a control method for a fuel cell power generation system, wherein a control program for realizing the control method for the fuel cell power generation system according to claim 15 is recorded.

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