JP6698763B2 - Liquefied carbon dioxide recovery fuel cell power generation system - Google Patents

Description

  The present invention relates to a liquefied carbon dioxide recovery type fuel cell power generation system, and particularly to liquefied carbon dioxide which enables efficient liquefaction and recovery of carbon dioxide generated by power generation by using a carbon compound fuel. The present invention relates to a recoverable fuel cell power generation system.

  When a carbon compound fuel is used in a fuel cell power generation system, carbon dioxide gas is contained in the exhaust gas discharged from the fuel cell. It has been considered to separate carbon dioxide gas from this exhaust gas (see, for example, Patent Documents 1 to 4).

Japanese Patent No. 5581240 JP, 2013-196890, A Japanese Patent No. 5137199 JP 2012-164423A

By liquefying carbon dioxide gas into liquefied carbon dioxide, it becomes easier to transport, press fit into a reservoir, and use for commercial and industrial purposes. To liquefy carbon dioxide gas, a compressor and a cooling device are required. And are required.
However, when commercial power, that is, external energy is used for the compressor and the cooling device, it cannot be said that carbon dioxide gas is efficiently liquefied by effectively utilizing exhaust heat and generated power of the power generation system, and there is room for improvement. There is.

  The present invention has been made in consideration of the above facts, and carbon dioxide gas separated from exhaust gas of a fuel cell is efficiently liquefied by utilizing exhaust heat and generated power of a fuel cell power generation system to generate liquefied carbon dioxide. An object of the present invention is to provide a liquefied carbon dioxide recovery type fuel cell power generation system capable of performing the above.

The liquefied carbon dioxide recovery fuel cell power generation system according to claim 1 generates power by using a fuel gas containing a carbon compound and supplied to a fuel electrode, and an oxidant gas containing oxygen and supplied to an air electrode to generate off gas. A fuel cell for discharging, a carbon dioxide gas separating unit for separating carbon dioxide gas from the off gas, and an exhaust heat input type absorption refrigerator or adsorption for cooling water by using the off gas as a heat source for driving to generate cooling water. Type refrigerator and at least one of an electric turbo refrigerator that is driven by electric power obtained by power generation of the fuel cell to generate cold heat, and can be driven by electric power generated by the fuel cell, and the carbon dioxide gas separation has a compressor for compressing the separated the carbon dioxide gas in parts, a cooling device for generating a liquefied carbon dioxide compressed the carbon dioxide gas is cooled by at least one of the cooling water and the cold, the Power is generated by the fuel gas containing a carbon compound and supplied to the first fuel electrode and the oxidant gas containing oxygen and supplied to the first air electrode to generate a first fuel electrode off-gas from the first fuel electrode. A first fuel cell for sending to the first fuel electrode off-gas flow path, power generation using the first fuel electrode off-gas supplied to the second fuel electrode and the oxidant gas supplied to the second air electrode, A second fuel cell for delivering a second fuel electrode off-gas from the second fuel electrode to the second fuel electrode off-gas passage;
An air electrode off-gas passage for sending an air electrode off gas from at least one of the first air electrode and the second air electrode, and the air electrode off gas is connected to the air electrode off gas passage to supply the air electrode off gas. An oxygen separation unit that separates oxygen from the second fuel electrode off gas that has passed through the second fuel electrode off gas passage, and the oxygen separated by the oxygen separation unit is supplied to the second separation unit; A combustor that causes a fuel electrode off-gas to burn and react with the oxygen, and a carbon dioxide gas separator that separates the carbon dioxide gas and water by cooling the combustion off-gas sent from the combustor with the cooling water or the cold heat. And a section .

In the liquefied carbon dioxide recovery fuel cell power generation system according to the first aspect, the fuel cell generates power by the fuel gas supplied to the fuel electrode and the oxidant gas supplied to the air electrode, and discharges the off gas.
The off-gas discharged from the fuel cell is separated into carbon dioxide gas by the carbon dioxide gas separation unit.
The carbon dioxide gas separated by the carbon dioxide gas separation unit is compressed by the compressor that can be driven by the electric power generated by the fuel cell. Since the compressor can be driven by the power generated by the fuel cell, there is no need to use external power from a commercial power source, etc. during power generation, and there is no transmission loss, so drive the compressor efficiently. In addition, it is possible to continue high-efficiency fuel cell power generation while recovering liquefied carbon dioxide during a power failure such as commercial power supply.
The exhaust heat input type absorption refrigeration machine or the adsorption refrigeration machine uses the off gas discharged from the fuel cell as a driving heat source to cool water to generate cooling water. Since the off gas has a high temperature, it is possible to efficiently drive the exhaust heat input type absorption refrigerating machine or the adsorption refrigerating machine. Since the exhaust heat input absorption refrigerator or adsorption refrigerator uses the exhaust heat of offgas to generate cold heat to cool water, the compressor is driven by a motor driven by external power. It is possible to efficiently generate cold heat (used to cool water into cooling water) with less electric power as compared with the case where cold heat is generated in a refrigerator that compresses and expands the refrigerant by using ..
The electric turbo refrigerator is driven by the electric power obtained by the power generation of the fuel cell. Since the electric turbo chiller generally has high cooling efficiency, it is possible to operate the liquefied carbon dioxide recovery fuel cell power generation system with high efficiency even if the generated electric power is used. It is preferable to drive the electric turbo chiller with a direct current in order to efficiently use the generated electric power without converting it into an alternating current.
The carbon dioxide gas compressed by the compressor is, in the cooling device, at least one of the cooling water generated by the exhaust heat input absorption refrigerator or the adsorption refrigerator and the cooling water generated by the electric turbo refrigerator. Cooled to liquefied carbon dioxide.

Further, in the liquefied carbon dioxide recovery fuel cell according to claim 1 , the fuel cell is configured to include a first fuel cell and a second fuel cell.
In the first fuel cell, power generation is performed by the fuel gas supplied to the first fuel electrode and the oxidant gas supplied to the first air electrode. In the second fuel cell, power generation is performed by the first fuel electrode off-gas supplied from the first fuel electrode to the second fuel electrode and the oxidant gas supplied to the second air electrode.

  From at least one of the first air electrode and the second air electrode, the air electrode off-gas is sent to the air electrode off-gas passage, and the air electrode off-gas is supplied to the oxygen separation unit via the air electrode off-gas passage. In the oxygen separation unit, oxygen is separated from the air electrode off gas, and the separated oxygen is supplied to the combustion unit.

  Further, the second fuel electrode off-gas is delivered from the second fuel electrode to the fuel electrode off-gas passage, and the second fuel electrode off-gas is supplied to the combustion section via the fuel electrode off-gas passage. In the combustion section, a combustible component in the second fuel electrode off-gas and oxygen cause a combustion reaction, and the combustion off-gas is delivered from the combustion section.

  Combustion off-gas is sent to a carbon dioxide separation part, and carbon dioxide is separated from combustion off-gas.

In the fuel cell power generation system according to claim 1 , the second fuel electrode off-gas after being sent out from the second fuel cell is combusted in the combusting portion, so that the first fuel cell before being used for power generation in the second fuel cell is used. The amount of unreacted fuel gas supplied to the second fuel cell increases as compared with the case of burning the fuel electrode off-gas. Therefore, the power generation efficiency of the second fuel cell can be improved.

  Further, in the combustion section, carbon dioxide and water vapor are generated by the combustion reaction between the combustible component contained in the second fuel electrode off gas and oxygen. Therefore, it is possible to recover the high-concentration carbon dioxide by reducing the combustible gas from the second fuel electrode off-gas.

Further, the second fuel electrode off-gas has a smaller amount of unreacted fuel gas contained and a higher carbon dioxide content rate than the first fuel electrode off-gas. Therefore, the amount of unreacted fuel gas burned in the combustion section can be reduced, and the amount of oxygen required to burn the unreacted fuel gas can be reduced.
The liquefied carbon dioxide recovery fuel cell power generation system according to claim 2 generates power by a fuel gas containing a carbon compound and supplied to a fuel electrode and an oxidant gas containing oxygen and supplied to an air electrode, and an off gas. A fuel cell that discharges, a carbon dioxide gas separation unit that separates carbon dioxide gas from the off gas, an electric turbo refrigerator that is driven by electric power obtained by power generation of the fuel cell to generate cold heat, and the fuel cell A compressor that can be driven by generated electric power and that compresses the carbon dioxide gas separated by the carbon dioxide gas separation unit, and cools the compressed carbon dioxide gas with the cold heat to generate liquefied carbon dioxide. And a cooling device for controlling.
In the liquefied carbon dioxide recovery fuel cell power generation system according to the second aspect, the fuel cell generates power by the fuel gas supplied to the fuel electrode and the oxidant gas supplied to the air electrode, and discharges off gas.
The off-gas discharged from the fuel cell is separated into carbon dioxide gas by the carbon dioxide gas separation unit.
The carbon dioxide gas separated by the carbon dioxide gas separation unit is compressed by the compressor that can be driven by the electric power generated by the fuel cell. Since the compressor can be driven by the power generated by the fuel cell, there is no need to use external power from a commercial power source, etc. during power generation, and there is no transmission loss, so drive the compressor efficiently. In addition, it is possible to continue high-efficiency fuel cell power generation while recovering liquefied carbon dioxide during a power failure such as commercial power supply.
The electric turbo refrigerator is driven by the electric power obtained by the power generation of the fuel cell. Since the electric turbo chiller generally has high cooling efficiency, it is possible to operate the liquefied carbon dioxide recovery fuel cell power generation system with high efficiency even by using the generated power. Note that it is preferable to drive the electric turbo chiller with a direct current in order to efficiently use the generated power without converting it into an alternating current.
The carbon dioxide gas compressed by the compressor is cooled in the cooling device by the cold heat generated by the electric turbo refrigerator to become liquefied carbon dioxide.

The invention according to claim 3, in liquefied carbon dioxide capture fuel cell power generation system according to claim 1, wherein the first fuel cell, and the second fuel cell, a hydrogen ion-conductive solid oxide fuel cell (PCFC: Proton Ceramic Solid Oxide Fuel Cell).

  In the hydrogen ion conductive type solid oxide fuel cell, water vapor is generated by the power generation reaction on the air electrode side. Therefore, since the amount of water vapor contained in the first fuel electrode off-gas is small, the decrease in the concentration of the fuel gas supplied to the second fuel electrode is small, and the power generation efficiency in the second fuel cell can be improved. Further, since the amount of water vapor contained in the second fuel electrode off-gas also decreases, the amount of water vapor removed from the second fuel electrode off-gas can be reduced.

The invention according to claim 4 is the liquefied carbon dioxide recovery fuel cell power generation system according to claim 1 or 3 , wherein the oxygen separation part has an oxygen permeable membrane that selectively permeates oxygen, The combustion section has a combustion space disposed on the permeation side of the oxygen permeable membrane and is integrated with the oxygen separation section.

  According to the liquefied carbon dioxide recovery fuel cell power generation system of the fourth aspect, the combustion section can be disposed adjacent to the oxygen permeable membrane of the oxygen separation section, and the combustion section and the oxygen separation section can be made compact. .

The invention according to claim 5 is the liquefied carbon dioxide recovery fuel cell power generation system according to claim 1 or 3 , wherein the oxygen separation part is configured to include a PSA device, and the PSA device is It can be driven by the electric power generated by the fuel cell.

  In the liquefied carbon dioxide recovery fuel cell power generation system according to the fifth aspect, the oxygen separation unit separates oxygen from the air electrode off-gas in the PSA device, so that oxygen can be separated without using external power.

The invention according to claim 6 is the liquefied carbon dioxide recovery fuel cell power generation system according to any one of claims 1, 3, 4, and 5 , wherein the compressor is the The carbon gas is compressed to 4 MPa or more, and the exhaust heat input type absorption refrigerating machine or the adsorption refrigerating machine is cooled at a temperature in the range of −5° C. to 20° C. and lower than the critical temperature of carbon dioxide gas. Water is supplied to the cooling device.

In the liquefied carbon dioxide recovery type fuel cell power generation system according to claim 6, the compressor compresses carbon dioxide gas to 4 MPa or more.
The exhaust heat input type absorption refrigerating machine or the adsorption refrigerating machine uses the cooling device for cooling water having a temperature in the range of −5° C. to 20° C. and lower than the critical temperature (31.1° C.) of carbon dioxide gas. Supply to. Thereby, the compressed carbon dioxide gas can be cooled to a temperature lower than the critical temperature.

  From the state diagram of carbon dioxide gas, carbon dioxide gas compressed to 4 MPa or more liquefies when cooled to a temperature lower than the critical temperature (31.1° C.), so the liquefied carbon dioxide recovery fuel cell according to claim 5. In the power generation system, the carbon dioxide gas can be easily converted into liquefied carbon dioxide by using the cooling water.

  The invention described in claim 7 is the tank for storing the liquefied carbon dioxide produced by the cooling device in the liquefied carbon dioxide recovery fuel cell power generation system according to any one of claims 1 to 6. The carbon dioxide gas separation unit, the compressor, the cooling device, and the tank are connected by a pipe in the order of the carbon dioxide gas separation unit, the compressor, the cooling device, and the tank. ..

  In the liquefied carbon dioxide recovery fuel cell power generation system according to claim 7, a tank for storing the liquefied carbon dioxide generated by the cooling device is provided, and the carbon dioxide gas separation unit, the compressor, the cooling device, and the tank are Since the carbon gas separation unit, the compressor, the cooling device, and the tank are connected by piping in this order, the steps of liquefying and storing the carbon dioxide gas while generating power can be efficiently performed on-site.

The invention according to claim 8 is the liquefied carbon dioxide recovery fuel cell power generation system according to any one of claims 1 and 3 to 6 , wherein the carbon dioxide gas separation unit separates the gas. The exhaust heat input type is provided with a supply unit that supplies water to the cooling water path of the exhaust heat input type absorption refrigerator, the cooling water path of the adsorption type refrigerator, or the cooling water path of the electric turbo refrigerator. The cooling water path of the absorption refrigerating machine, the cooling water path of the adsorption refrigerating machine, or a part of the cooling water of the cooling water path of the electric turbo refrigerator, the carbon dioxide gas separation section is separated Water is used.

  In the liquefied carbon dioxide recovery fuel cell power generation system according to claim 8, the water separated by the carbon dioxide gas separation unit is used as a cooling water path for an exhaust heat input type absorption refrigerator and a cooling water path for an adsorption refrigerator. Alternatively, it can be supplied to the cooling water path of the electric turbo refrigerator by the supply unit. Therefore, when there is a shortage of cooling water in the cooling water path, there is no need to supply water from outside water supply or the like, and the amount of external dependence on water can be reduced.

The invention described in claim 9 is the liquefied carbon dioxide recovery fuel cell power generation system according to any one of claims 1, 3 to 6 and 8 , wherein the carbon dioxide gas separation section is used. The separated water is provided with a supply unit that supplies to the cooling water replenishment path of the cooling tower that constitutes the exhaust heat input type absorption refrigerator or the cooling water replenishment path of the cooling tower that constitutes the adsorption refrigerator. , A part of the cooling water replenishing water of the cooling tower that constitutes the exhaust heat input type absorption refrigerating machine or the cooling water replenishing water of the cooling tower that constitutes the adsorption type refrigerating machine is separated by the carbon dioxide gas separation section. The water is used.

  In the liquefied carbon dioxide recovery type fuel cell power generation system according to claim 9, the water separated by the carbon dioxide gas separation part is supplied to a cooling water replenishment path of a cooling tower constituting an exhaust heat input type absorption refrigerating machine or adsorption. It can be supplied to the cooling water replenishment path of the cooling tower that constitutes the rotary refrigerator by the supply unit. Therefore, when there is a shortage of cooling water in the cooling water replenishment path of the cooling tower, there is no need to supply water from an external water supply or the like, and the amount of external dependence of water can be reduced.

  According to the liquefied carbon dioxide recovery fuel cell power generation system of the present invention, it is possible to efficiently produce liquefied carbon dioxide while improving power generation efficiency.

1 is a schematic diagram of a fuel cell power generation system according to a first embodiment. It is a block diagram of a control system of the fuel cell power generation system according to the first embodiment. It is a flowchart of the flow volume adjustment process of 1st Embodiment. It is a flow chart of cooling water temperature adjustment processing of a 1st embodiment. It is a schematic diagram of the fuel cell power generation system concerning a 2nd embodiment. It is a schematic diagram of the fuel cell power generation system concerning a 3rd embodiment. It is a schematic diagram of a fuel cell power generation system concerning a 4th embodiment. It is a schematic diagram of a fuel cell power generation system concerning a 5th embodiment. It is a schematic diagram of a fuel cell power generation system concerning a 6th embodiment. It is a schematic diagram of a fuel cell power generation system concerning a 7th embodiment. It is a schematic diagram of the fuel cell power generation system concerning an 8th embodiment. It is a schematic diagram of the fuel cell power generation system concerning a 9th embodiment. It is a phase diagram of carbon dioxide. It is a schematic diagram of the fuel cell power generation system concerning the modification of a 1st embodiment.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 shows a fuel cell power generation system 10A according to a first embodiment as an example of a carbon dioxide recovery fuel cell power generation system of the present invention. The fuel cell power generation system 10A has, as main components, a first fuel cell stack 12, a second fuel cell stack 14, an oxygen permeable membrane-equipped combustor 20, a condenser 26, a first heat exchanger 30, and a second heat exchanger. An exchanger 32, an exhaust heat input type absorption refrigerating machine 36, a water tank 27, a carbon dioxide gas liquefying section 66, a tank 84 and the like are provided, and these are provided on-site. In addition, the fuel cell power generation system 10A includes a control unit 40 that controls the fuel cell power generation system 10A, as shown in FIG.

  As shown in FIG. 1, the first fuel cell stack 12 is a hydrogen ion conductive solid oxide fuel cell (PCFC: Proton Ceramic Solid Oxide Fuel Cell), and includes an electrolyte layer 12C and a surface of the electrolyte layer 12C. It has a first fuel electrode (fuel electrode) 12A and a first air electrode (air electrode) 12B, which are respectively laminated on the back surface.

  The basic structure of the second fuel cell stack 14 is the same as that of the first fuel cell stack 12, and the second fuel electrode 14A corresponding to the first fuel electrode 12A and the first fuel electrode 14B corresponding to the first air electrode 12B. The second air electrode 14B and the electrolyte layer 14C corresponding to the electrolyte layer 12C are included.

  One end of the fuel gas pipe P1 is connected to the first fuel electrode 12A of the first fuel cell stack 12, and the other end of the fuel gas pipe P1 is connected to a fuel gas source (not shown). From the fuel gas source, fuel gas is delivered to the first fuel electrode 12A by the fuel supply blower B1. In this embodiment, methane is used as the fuel gas, but it is not particularly limited as long as it is a gas that can generate hydrogen by reforming, and a hydrocarbon fuel can be used. Examples of hydrocarbon fuels include natural gas, LP gas (liquefied petroleum gas), biogas, coal reformed gas, and lower hydrocarbon gas. Examples of the lower hydrocarbon gas include lower hydrocarbons having 4 or less carbon atoms such as methane, ethane, ethylene, propane and butane, and methane used in the present embodiment is preferable. The hydrocarbon fuel may be a mixture of the above-mentioned lower hydrocarbon gas, and the above-mentioned lower hydrocarbon gas may be a gas such as natural gas, city gas or LP gas. If the source gas contains impurities, a desulfurizer or the like is required, but it is omitted in the figure.

  A steam pipe P2 is connected to the fuel gas pipe P1 so that steam is appropriately fed from a steam source (not shown) at the time of starting or stopping. Methane and water vapor are merged in the fuel gas pipe P1 and supplied to the first fuel electrode 12A. In the present embodiment, as will be described later, part of the second fuel electrode off-gas is returned to the first fuel electrode 12A and the water vapor is reused. Therefore, the water vapor from the water vapor pipe P2 is used in the fuel cell power generation system 10A. It is supplied supplementally when necessary in the starting and stopping steps of.

  At the first fuel electrode 12A, the fuel gas is steam-reformed to generate hydrogen and carbon monoxide, as shown in the following formula (1). Further, as shown in the following formula (2), carbon dioxide and hydrogen are produced by the shift reaction between the produced carbon monoxide and water vapor.

CH ₄ +H ₂ O→3H ₂ +CO (1)
CO+H ₂ O→CO ₂ +H ₂ (2)

  Then, in the first fuel electrode 12A, hydrogen is separated into hydrogen ions and electrons as shown in the following formula (3).

(Fuel electrode reaction)
_{^{H 2 → 2H + + 2e -}} ... (3)

  Hydrogen ions move to the first air electrode 12B through the electrolyte layer 12C. The electrons move to the first cathode through an external circuit (not shown). As a result, power is generated in the first fuel cell stack 12. During power generation, the first fuel cell stack 12 generates heat.

  The oxidant gas (air) is supplied to the first air electrode 12B of the first fuel cell stack 12 from the oxidant gas pipe P5. Air is introduced into the oxidant gas pipe P5 by the oxidant gas blower B2. The oxidant gas pipe P5 is provided with the second heat exchanger 32, and the air flowing through the oxidant gas pipe P5 is heated by heat exchange with the air electrode off-gas flowing through the air electrode off-gas pipe P6 described later. The heated air is supplied to the first air electrode 12B.

  In the first air electrode 12B, as shown in the following formula (4), hydrogen ions moving from the first fuel electrode 12A through the electrolyte layer 12C and electrons moving from the first fuel electrode 12A through the external circuit are generated. , Reacts with oxygen in the oxidant gas to generate water vapor.

(Air electrode reaction)
2H ⁺ +2e ⁻ +1/2O ₂ →H ₂ O (4)

  An air electrode offgas pipe P6 is connected to the first air electrode 12B. The air electrode off gas is discharged from the first air electrode 12B to the air electrode off gas pipe P6. The oxidant gas pipe P5 and the air electrode off-gas pipe P6 are similarly connected to the second air electrode 14B, and the first air electrode 12B and the second air electrode 14B are connected in parallel.

  One end of a first fuel electrode off-gas pipe P7 is connected to the first fuel electrode 12A of the first fuel cell stack 12, and the other end of the first fuel electrode off-gas pipe P7 is connected to the first fuel electrode off-gas pipe P7 of the second fuel cell stack 14. It is connected to the two fuel electrode 14A. The first fuel electrode off-gas is delivered from the first fuel electrode 12A to the first fuel electrode off-gas pipe P7. The fuel electrode off-gas contains unreformed fuel gas components, unreacted hydrogen, unreacted carbon monoxide, carbon dioxide, steam and the like.

  One end of a second fuel electrode offgas pipe P7-2 is connected to the second fuel electrode 14A of the second fuel cell stack 14, and the second fuel electrode offgas is delivered from the second fuel electrode 14A. The other end of the second fuel electrode off-gas pipe P7-2 is connected to the combustor 20 with an oxygen permeable film. A circulation gas pipe P3 is branched from the second fuel electrode off-gas pipe P7-2, and the circulation gas pipe P3 is connected to the fuel gas pipe P1 connected to the first fuel electrode 12A. The circulating gas pipe P3 is provided with a circulating gas blower B3.

  In the second fuel cell stack 14, the same power generation reaction as in the first fuel cell stack 12 is performed, and the air electrode off gas is sent from the second air electrode 14B to the air electrode off gas pipe P6. The air electrode off-gas pipe P6 connected to the second air electrode 14B is branched on the upstream side of the confluence portion with the air electrode off-gas pipe P6 connected to the first air electrode 12B, and a branched air electrode off-gas pipe P6. -2 is formed. The branch air electrode offgas pipe P6-2 is provided with a flow rate adjusting valve 42 capable of adjusting the flow rate. The flow rate adjustment valve 42 is connected to the control unit 40. The flow rate adjustment valve 42 is controlled by the control unit 40, and the flow rate of the air electrode offgas branched to the branch air electrode offgas pipe P6-2 is adjusted. The downstream end of the branched air electrode off-gas pipe P6-2 is connected to the combustor 20 with an oxygen permeable membrane.

(Combustor with oxygen permeable membrane)
The oxygen-permeable membrane-equipped combustor 20 has a multi-cylindrical shape, and has a combustion section 22 forming an outer cylinder of the multi-cylinder, and an oxygen separation section 24 arranged inside the combustion section 22 in the radial direction. .. A combustion space 22A is formed in the combustion section 22.

  The oxygen separation section 24 is arranged inside the combustion section 22 in the radial direction, and an air flow path 24A is formed adjacent to the combustion space 22A. The air passage 24A and the combustion space 22A are partitioned by the oxygen permeable membrane 23. As the oxygen permeable film 23, for example, a mixed conductive ceramic of electrons and oxygen ions such as LSCF, or an oxygen ion conductive dense film such as YSZ can be used. The other end of the second fuel electrode offgas pipe P7-2 is connected to the inlet of the combustion space 22A, and the downstream end of the branch air electrode offgas pipe P6-2 is connected to the inlet of the air flow passage 24A. An oxidation catalyst is arranged inside the combustion space 22A. As the oxidation catalyst, for example, nickel or ruthenium can be used.

  The second air electrode off-gas is supplied to the air flow path 24A, and oxygen contained in the second air electrode off-gas permeates the oxygen permeable membrane 23 and moves to the combustion space 22A. The second air electrode off-gas that does not move to the combustion space 22A is exhausted to the outside from the exhaust pipe P12 connected to the outlet side of the air flow path 24A.

  The second fuel electrode off-gas is supplied to the combustion space 22A and mixed with oxygen that has moved from the oxygen separation section 24 through the oxygen permeable membrane 23. As a result, a combustion reaction occurs between the combustible gas components (unreformed methane, unreacted hydrogen, unreacted carbon monoxide, etc.) in the second fuel electrode off-gas and oxygen via the oxidation catalyst, and carbon dioxide And steam is generated. A combustion off gas pipe P8 is connected to the outlet side of the combustion space 22A, and the combustion off gas is delivered from the combustion space 22A.

  The combustion off-gas pipe P8 passes through the first heat exchanger 30 and the other end is connected to the condenser 26. In the first heat exchanger 30, the fuel gas is heated by the heat exchange between the fuel gas and the combustion off gas. A cooling water circulation flow path 26A is piped in the condenser 26, and cooling water from an exhaust heat input type absorption refrigerator 36 described later is circulated and supplied by driving a pump 26P to cool the combustion off-gas. As a result, the water vapor in the combustion off gas is condensed. The condensed water is sent to the water tank 27 through the water pipe P9.

  The combustion off-gas from which the water vapor has been separated and removed is sent to the carbon dioxide gas pipe P10. The combustion offgas from which water (liquid phase) has been removed by the condenser 26 has a high carbon dioxide concentration, and the combustion offgas is referred to as a carbon dioxide rich gas. A composition detector 44 is provided in the carbon dioxide gas pipe P10. The composition detector 44 detects the composition of the carbon dioxide rich gas sent from the condenser 26. Specifically, one or more of the concentrations of combustible gases such as methane, carbon monoxide, and hydrogen, carbon dioxide, and oxygen are detected. The composition detection unit 44 is connected to the control unit 40, and the composition information of the detected carbon dioxide rich gas is transmitted to the control unit 40. The control unit 40 performs various controls so as to increase the concentration of carbon dioxide gas.

  A carbon dioxide gas liquefying unit 66, which will be described later, is provided on the downstream side of the carbon dioxide gas pipe P10.

  A second heat exchanger 32 is provided on the downstream side of the confluence portion where the air electrode off-gas pipes P6 from the first air electrode 12B and the second air electrode 14B are merged. In the second heat exchanger 32, heat exchange is performed between the air electrode off gas flowing through the air electrode off gas pipe P6 and the oxidant gas flowing through the oxidant gas pipe P5, the oxidant gas is heated, and the air electrode off gas is changed. To be cooled. The air electrode off gas is supplied to the exhaust heat input type absorption refrigerating machine 36 via the second heat exchanger 32.

(Exhaust heat input absorption refrigerator)
The exhaust heat input type absorption refrigerator 36 is a heat pump that uses the exhaust heat to generate cold heat, and a steam/exhaust heat input type absorption refrigerator can be used as an example. In a steam/exhaust heat input absorption refrigerator, the absorption liquid that has absorbed water vapor (for example, lithium bromide aqueous solution or ammonia aqueous solution) is heated by the heat of the air electrode offgas to separate water from the absorption liquid and regenerate it. To do. Water vapor is condensed in the air electrode off-gas that is obtained by heating and absorbing the absorbing liquid, and the condensed water is supplied to the water tank 27 through the water pipe P36-2. The air electrode off-gas after the steam is condensed and removed is sent to the exhaust pipe P36-1 and is exhausted to the outside of the exhaust heat input type absorption refrigerator 36.

  A pump that circulates the absorbing liquid and a pump (not shown) that circulates the water separated from the absorbing liquid are provided inside the exhaust heat input type absorption refrigerator 36. These pumps are driven by a DC motor, and the DC motor can be driven by the DC power generated by the first fuel cell stack 12 and the second fuel cell stack 14.

  The absorption liquid regenerated by heating promotes evaporation of water by absorbing water vapor, and contributes to generation of cold heat. The exhaust heat input type absorption refrigerator 36 is connected to a cooling tower 38 via a heat radiation circuit 37. A pump 37P is installed in the heat dissipation circuit 37, and cooling water is supplied to the heat dissipation circuit 37 by the pump 37P. Absorption heat generated when the absorption liquid absorbs water vapor in the exhaust heat input type absorption refrigerator 36 is released from the cooling tower 38 to the atmosphere via the cooling water flowing through the heat radiation circuit 37.

  The cold heat generated by the exhaust heat input type absorption refrigerating machine 36 is sent to the condenser 26 via the cooling water flowing through the cooling water circulation passage 26A, the combustion off-gas is cooled by the condenser 26, and further the combustion off-gas is cooled. Water vapor is condensed off.

The water tank 27 is connected to the cooling water circulation flow path 26A, the heat radiation circuit 37, and a heat medium flow path (not shown) through which water as a heat medium of the exhaust heat input type absorption refrigerator 36 flows. When water is insufficient in the cooling water circulation flow path 26A, the heat radiation circuit 37, and the heat medium flow path, water is appropriately replenished from the water tank 27 via a replenishment system 67 described below.
The exhaust heat input type absorption refrigerator 36 has, for example, the ability to generate cooling water at -5°C to 12°C.

(Replenishment system)
A replenishment system 67 including a pipe P11, a pump 27A and the like is connected to the water tank 27. One end of the pipe P11 is connected to the water tank 27, and the other end of the pipe P11 is branched into three and connected to the cooling tower 38, the cooling water circulation passage 26A, and the liquefaction cooling water circulation passage 70A described later. ing. The pump 27A is provided in the pipe P11 before branching, and an electromagnetic valve (not shown) is attached to each of the three branched pipes. The pump 27A and the solenoid valve are controlled by the control unit 40 described later.

  The cooling tower 38, the cooling water circulation passage 26A, and the liquefaction cooling water circulation passage 70A are each provided with a buffer tank (not shown) for storing cooling water, and the buffer tank has a storage amount of cooling water. A liquid level sensor (not shown) for detecting The liquid level sensor is connected to a control unit 40 described later, and the detection data of the liquid level (cooling water storage amount) is output to the control unit 40. As a result, the control unit 40 can grasp the storage amount of the cooling water in each of the cooling tower 38, the cooling water circulation passage 26A, and the liquefaction cooling water circulation passage 70A.

(Carbon dioxide gas liquefaction section)
The carbon dioxide-rich gas sent to the carbon dioxide gas pipe P10 is sent to the carbon dioxide gas liquefying unit 66 including a compressor 68, a cooling device 70, and the like.
The carbon dioxide rich gas sent to the carbon dioxide gas liquefying unit 66 is first compressed by the compressor 68. The compressor 68 is operated by a DC motor (not shown) and can compress carbon dioxide gas to 4 MPa or more. Further, the DC motor of the compressor 68 is driven by the electric power obtained by the first fuel cell stack 12 and the second fuel cell stack 14, but, for example, when the system is started, an external commercial power source is used. It is also possible to drive with electric power (surplus electric power) obtained by renewable energy power generation (not shown). Examples of renewable energy power generation include solar power generation, solar thermal power generation, hydroelectric power generation, wind power generation, geothermal power generation, wave power generation, temperature difference power generation, biomass power generation, etc. Good.

  Since the DC motor of the compressor 68 can be directly driven by using the DC power obtained by the first fuel cell stack 12 and the second fuel cell stack 14, for example, the first fuel cell stack 12 and the second fuel cell stack 14 converts the DC power to AC power and drives the AC motor with AC power, resulting in less energy loss and higher efficiency. The DC motor of the compressor 68 is controlled by the control unit 40 described later.

  The carbon dioxide gas compressed by the compressor 68 is sent to the cooling device 70 via the pipe P14. A temperature sensor 74 and a pressure sensor 76 are provided in the pipe P14, and the temperature data of carbon dioxide gas measured by the temperature sensor 74 and the pressure data of carbon dioxide gas measured by the pressure sensor 76 are controlled respectively. Sent to section 40.

  A liquefaction cooling water circulation passage 70A is installed in the cooling device 70, and a circulation pump 78 controlled by the control unit 40 is attached to the liquefaction cooling water circulation passage 70A. Cooling water from the exhaust heat input type absorption refrigerator 36 is circulated and supplied to the liquefying cooling water circulation path 70A to cool the compressed carbon dioxide rich gas supplied from the compressor 68 to generate liquefied carbon dioxide.

  The liquefaction cooling water circulation path 70A is provided with a temperature sensor 80 that detects the temperature of the cooling water flowing into the cooling device 70. The temperature data of the cooling water measured by the temperature sensor 80 is sent to the control unit 40. A flow rate sensor (not shown) that measures the flow rate of the cooling water may be provided in the liquefying cooling water circulation path 70A.

  The liquefied carbon dioxide generated by the cooling device 70 is sent to and stored in the tank 84 via the pipe P15 and the pump 82.

(Control unit)
The control unit 40 controls the entire fuel cell power generation system 10A, and includes a CPU, a ROM, a RAM, a memory, and the like. The memory stores data and procedures necessary for the flow rate adjustment processing, the cooling water temperature adjustment processing, and the processing during normal operation, which will be described later. As shown in FIG. 2, the control unit 40 is connected to the flow rate adjustment valve 42, the composition detection unit 44, the exhaust heat input type absorption refrigerator 36, and the like. The flow rate adjusting valve 42, the composition detecting unit 44, the exhaust heat input type absorption refrigerator 36, etc. are controlled by the control unit 40. 2 shows a part of the connection relationship of the control unit 40 in the fuel cell power generation system 10A, and the control unit 40 is also connected to other devices not shown in FIG.

  In the fuel cell power generation system 10A, pumps, blowers, and other auxiliary equipment are driven by the electric power generated by the fuel cell power generation system 10A. In order to efficiently use the electric power generated by the fuel cell power generation system 10A without converting it to AC as it is, it is preferable that the auxiliary machine be driven by DC current.

(Action, effect)
Next, the operation of the fuel cell power generation system 10A of this embodiment will be described.

  In the fuel cell power generation system 10A, methane is delivered from the fuel gas source to the fuel gas pipe P1 by the fuel supply blower B1, heated by passing through the first heat exchanger 30, and supplied to the first fuel electrode 12A. . From the steam pipe P2, steam for steam reforming is supplied to the first fuel electrode 12A via the fuel gas pipe P1. The supply of steam is at the time of startup and at the time of shortage, and during the rated operation, as will be described later, the steam in the second fuel electrode off-gas returned from the circulating gas pipe P3 is used.

  At the first fuel electrode 12A of the first fuel cell stack 12, the fuel gas is steam-reformed to generate hydrogen and carbon monoxide. Further, carbon dioxide and hydrogen are generated by the shift reaction between the generated carbon monoxide and water vapor.

  Air is supplied to the first air electrode 12B of the first fuel cell stack 12 through the oxidant gas pipe P5. In the first fuel cell stack 12, hydrogen ions move in the first fuel electrode 12A and the first air electrode 12B, and the above-mentioned reaction occurs to generate power. The first fuel electrode off-gas is delivered from the first fuel electrode 12A of the first fuel cell stack 12 to the first fuel electrode off-gas pipe P7. Further, the air electrode off-gas is delivered from the first air electrode 12B to the air electrode off-gas pipe P6.

  The first fuel electrode off-gas sent from the first fuel electrode 12A is guided to the first fuel electrode off-gas pipe P7 and supplied to the second fuel electrode 14A of the second fuel cell stack 14. Air is supplied to the second air electrode 14B of the second fuel cell stack 14 through the oxidant gas pipe P5. Power generation is also performed in the second fuel cell stack 14 similarly to the first fuel cell stack 12. The second fuel electrode offgas is delivered from the second fuel electrode 14A of the second fuel cell stack 14 to the second fuel electrode offgas pipe P7-2. Further, the air electrode off-gas is delivered from the second air electrode 14B to the air electrode off-gas pipe P6. A part of the air electrode off-gas sent from the second air electrode 14B is branched to the branched air electrode off-gas pipe P6-2, and the other part is joined with the air electrode off-gas sent from the first air electrode 12B.

  The air electrode off-gas is supplied to the exhaust heat input type absorption refrigerating machine 36 via the second heat exchanger 32. In the second heat exchanger 32, heat exchange is performed between the air electrode off-gas and the oxidant gas, and the oxidant gas is heated by the air electrode off-gas. In the exhaust heat input type absorption refrigerating machine 36, as described above, cold heat is generated by utilizing the heat of the air electrode off gas.

  A part of the second fuel electrode off-gas branches to the circulating gas pipe P3 and is returned to the first fuel electrode 12A. The other second fuel electrode off-gas is supplied to the combustion section 22 of the combustor 20 with an oxygen permeable film and flows through the combustion space 22A.

  The air electrode off-gas branched to the branched air electrode off-gas pipe P6-2 is supplied to the oxygen separation unit 24 of the combustor 20 with an oxygen permeable membrane. The air electrode off gas supplied to the oxygen separation unit 24 flows through the air flow path 24A. In the air flow path 24A, oxygen contained in the air electrode off gas permeates the oxygen permeable membrane 23 and moves to the combustion space 22A side. In the combustion space 22A, a combustion reaction of combustible gas (methane, hydrogen, carbon monoxide, etc.) in the second fuel electrode off-gas with oxygen occurs, and carbon dioxide and water vapor are generated. The combustion off-gas containing carbon dioxide and water vapor is delivered from the combustion space 22A to the combustion off-gas pipe P8. The combustion offgas sent to the combustion offgas pipe P8 is supplied to the condenser 26 via the first heat exchanger 30.

  The combustion off-gas supplied to the condenser 26 is cooled by the cooling water from the exhaust heat input type absorption refrigerating machine 36 circulated and supplied through the cooling water circulation flow path 26A, and the steam in the combustion off-gas is condensed. The condensed water is sent to the water tank 27 through the water pipe P9 and stored in the water tank 27.

  The combustion off gas from which water vapor has been removed by the condenser 26 becomes a carbon dioxide rich gas having a high carbon dioxide concentration, is sent to the carbon dioxide gas pipe P10 by the carbon dioxide blower B4, and is sent to the composition detection unit 44. The composition detector 44 detects the composition of the carbon dioxide-rich gas, and the detected information is transmitted to the controller 40.

  Based on the composition information transmitted from the composition detection unit 44, the control unit 40 controls the flow rate adjustment valve 42 to adjust the air electrode off-gas amount branched to the branch air electrode off-gas pipe P6-2, and the exhaust heat input. The type absorption refrigerator 36 controls the temperature of the cooling water sent to the cooling water circulation flow path 26A and the like. Specifically, the control unit 40 executes the following flow rate adjustment processing and cooling water temperature adjustment processing.

  As shown in FIG. 3, in the flow rate adjustment process, in step S10, it is determined whether or not the concentration of the combustible gas is within the threshold value G1 in the composition information of the carbon dioxide rich gas detected by the composition detection unit 44. Here, the threshold value G1 is a sufficiently low concentration in the carbon dioxide rich gas, and can be set to about 0.1 to 5 vol%, more preferably in the range of 0.1 to 1 vol%. When the concentration of the combustible gas is higher than the threshold value G1, the flow rate adjustment valve 42 is controlled in step S12 to increase the flow rate of the air electrode offgas branched to the branch air electrode offgas pipe P6-2. As a result, the amount of oxygen that permeates the oxygen permeable film 23 and moves to the combustion space 22A increases, and the combustible gas contained in the carbon dioxide rich gas can be reduced by causing the combustion reaction in the combustion space 22A.

  When the concentration of the combustible gas is equal to or lower than the threshold value G1 in step S10, it is determined in step S14 whether the oxygen concentration is within the threshold value O1 in the composition information of the carbon dioxide rich gas detected by the composition detection unit 44. Here, the threshold value O1 is a sufficiently low concentration in the carbon dioxide-rich gas, and can be set to about 0.1 to 5 vol%, more preferably in the range of 0.1 to 1 vol%. If the oxygen concentration is higher than the threshold value O1, the flow rate adjustment valve 42 is controlled in step S16 to reduce the flow rate of the air electrode offgas branched to the branch air electrode offgas pipe P6-2. As a result, the amount of oxygen that permeates the oxygen permeable film 23 and moves to the combustion space 22A is reduced, and it is possible to reduce the amount of oxygen that remains in the combustion space 22A without being used for the combustion reaction.

  After steps S12, S14, and S16, the process returns to step S10 and the above-described processing is repeated. This flow rate adjustment processing is started by starting the operation of the fuel cell power generation system 10A, continued during the operation, and ended by stopping the operation.

  Further, as shown in FIG. 4, in the condensation amount adjustment processing, in step S20, it is determined whether or not the water vapor concentration is within the threshold value M in the composition information of the carbon dioxide rich gas detected by the composition detection unit 44. Here, the threshold value M is a sufficiently low concentration in the carbon dioxide rich gas, and can be set to about 0.1 to 5 vol%, more preferably 0.1 to 1 vol%. When the water vapor concentration is higher than the threshold value M, the condensation strengthening is performed in step S22. Specifically, the exhaust heat input type absorption refrigerating machine 36 is controlled to lower the temperature of the cooling water sent to the cooling water circulation passage 26A or to increase the circulation flow rate of the cooling water. As a result, the amount of water separated from the combustion off gas by condensation in the condenser 26 increases, and the proportion of water vapor contained in the carbon dioxide rich gas can be reduced.

  After steps S20 and S22, the process returns to step S20 and the above-described processing is repeated. The present condensation amount adjustment processing is started by starting the operation of the fuel cell power generation system 10A, continues during the operation, and ends by stopping the operation.

  The carbon dioxide-rich gas sent to the carbon dioxide gas pipe P10 is sent to the compressor 68 of the carbon dioxide gas liquefying unit 66 and compressed, and the compressed carbon dioxide-rich gas is sent to the cooling device 70. The cooling device 70 cools the carbon dioxide rich gas compressed with the cooling water from the exhaust heat input type absorption refrigerator 36 to generate liquefied carbon dioxide.

  Since the exhaust heat input type absorption refrigerating machine 36 uses the exhaust heat of the air electrode off-gas to generate cold heat, the motor drives the compressor to compress and expand the refrigerant (for example, a turbo). As compared with a case where cold energy is generated by a refrigerator or the like), cold energy (used for cooling water to be cooling water) can be efficiently generated with less electric power.

From the state diagram of carbon dioxide gas shown in FIG. 13, as an example, carbon dioxide gas compressed to 4 MPa or more liquefies when cooled to a temperature lower than the critical temperature (31.1° C.) of carbon dioxide gas.
In the carbon dioxide gas liquefying unit 66 of the present embodiment, as an example, the carbon dioxide gas is compressed to 4 MPa by the compressor 68, and then, in the cooling device 70, the compressed carbon dioxide gas is cooled to -5°C to 12°C. Liquefied carbon dioxide is obtained by cooling with. The pressure of the carbon dioxide gas and the cooling temperature are not limited to the above values and can be changed as appropriate.

(Control of liquefaction)
Either the temperature of the high-pressure carbon dioxide gas that has passed through the compressor 68 (measured by the temperature sensor 74), the pressure (measured by the pressure sensor 76), or the amount of carbon dioxide gas remaining without being liquefied According to one or more measurement results, the control unit 40 controls the temperature of the cooling water supplied to the cooling device 70 (measured by the temperature sensor 80) and the flow rate (measured by a flow rate sensor (not shown)) of the exhaust heat input type. The operation of the absorption chiller 36 and the operation of the circulation pump 78 are controlled to efficiently convert carbon dioxide gas into liquefied carbon dioxide.

  That is, in the present embodiment, the control unit 40 calculates the amount of cold heat for maximizing the liquefaction amount of carbon dioxide gas according to the temperature and pressure of the recovered carbon dioxide gas or the amount of residual carbon dioxide gas at the time of liquefaction. However, it is possible to lower the temperature of the cooling water according to this, increase the flow rate of the circulating cooling water, or to use both of them together.

  In the cooling device 70, liquefied carbon dioxide accumulates downward, and unliquefied carbon dioxide gas remains above the liquefied carbon dioxide. Therefore, the liquid surface of the liquefied carbon dioxide accumulated inside the cooling device 70 By measuring the level, it is possible to indirectly measure the amount of carbon dioxide gas that remains inside the cooling device 70 without being liquefied (the internal space volume of the cooling device 70 is known).

  The liquefied carbon dioxide thus generated in the carbon dioxide gas liquefying unit 66 is sent to and stored in the tank 84 via the pipe P15 and the pump 82. The liquefied carbon dioxide stored in the tank 84 can also be used for commercial and industrial purposes as in the past.

  In the fuel cell power generation system 10A of the present embodiment, since the first fuel cell stack 12, and the second fuel cell stack 14 to the tank 84 are continuously connected and provided on-site, during power generation, Liquefied carbon dioxide can be efficiently produced continuously and stored in the tank 84. The liquefied carbon dioxide stored in the tank 84 may be transported by the lorry 86 or the like, or by a pipeline or the like.

  In the fuel cell power generation system 10A of the present embodiment, the second fuel electrode off-gas sent from the second fuel electrode 14A of the second fuel cell stack 14 is combusted in the combusting section 22, so the second fuel cell stack 14 The amount of unreacted fuel gas used for power generation in the second fuel cell stack 14 is larger than that in the case where the first fuel electrode off-gas before being used for power generation is burned. Therefore, the power generation efficiency of the second fuel cell stack 14 can be increased.

  Further, in the combustion section 22, carbon dioxide and water vapor are generated by the combustion reaction between the combustible gas contained in the second fuel electrode off gas and oxygen. Therefore, it is possible to recover the high-concentration carbon dioxide by reducing the combustible gas from the second fuel electrode off-gas. Further, only oxygen in the air electrode off gas is supplied to the combustion section 22, and the second fuel electrode off gas contains less unreacted fuel gas compared to the first fuel electrode off gas, and carbon dioxide Content rate is high. Therefore, it is possible to reduce the amount of unreacted fuel gas burned in the combustion unit 22 and the amount of oxygen required to burn the unreacted fuel gas.

  Further, since the fuel cell power generation system 10A of the present embodiment has the branched air electrode off-gas pipe P6-2 branched from the air electrode off-gas pipe P6, the composition of the carbon dioxide rich gas detected by the composition detection unit 44. Based on the information, it is possible to easily adjust the air electrode off-gas flow rate to be branched to the branch air electrode off-gas pipe P6-2. As a result, the amount of oxygen flowing into the combustion space 22A of the combustion section 22 can be adjusted so that the amounts of combustible gas and oxygen contained in the combustion off gas become lower than the predetermined threshold value.

  Further, in the fuel cell power generation system 10A of the present embodiment, by adjusting the amount of water condensed in the condenser 26 based on the composition information of the carbon dioxide rich gas detected by the composition detection unit 44, The carbon dioxide concentration can be increased.

  Further, in the fuel cell power generation system 10A of the present embodiment, since the hydrogen ion conductive type solid oxide fuel cell is used for the fuel cell stack, water vapor is not generated in the first fuel electrode 12A. Therefore, the amount of water vapor contained in the first fuel electrode off-gas is reduced, so that the power generation efficiency in the second fuel cell can be improved. Further, since the amount of water vapor contained in the second fuel electrode off-gas also decreases, the amount of water vapor removed from the second fuel electrode off-gas can be reduced.

  Further, the fuel cell power generation system 10A of the present embodiment includes a circulating gas pipe P3 that supplies a part of the second fuel electrode off-gas to the first fuel electrode 12A from the upstream side of the combustion unit 22. Therefore, a part of the unreacted fuel gas and steam in the second fuel electrode off-gas can be reused for power generation and steam reforming of the fuel gas, respectively.

  In addition, in the fuel cell power generation system 10A of the present embodiment, the combustion section 22 is disposed adjacent to the oxygen permeable membrane 23 of the oxygen separation section 24, so that the combustion section 22 and the oxygen separation section 24 are formed in a compact structure. The film combustor 20 can be configured.

  Further, in the fuel cell power generation system 10A of the present embodiment, the heat of the air electrode off-gas is used for cold heat generation in the exhaust heat input type absorption refrigerator 36, so the first fuel cell stack 12, the second fuel cell stack 10 The exhaust heat from 14 can be effectively used. Further, since the air electrode off-gas contains a large amount of water vapor, the heat of condensation can also be effectively used by condensing the water vapor in the exhaust heat input type absorption refrigerator 36 during heat exchange.

  Further, in the fuel cell power generation system 10A of the present embodiment, the control unit 40 controls the storage amount of the cooling water in each buffer tank of the cooling tower 38, the cooling water circulation passage 26A, and the liquefaction cooling water circulation passage 70A from the liquid level sensor. When it is determined that the amount of stored cooling water is less than the preset lower limit value, the solenoid valve and the pump 27A are controlled to supply the water used for cooling water to the water tank. It can be replenished from 27. As described above, when the cooling water is insufficient, it is not necessary to supply the water from the external water supply or the like, and it is possible to reduce the amount of external dependence of water.

  In this embodiment, the carbon dioxide is separated from the combustion off gas by condensing and removing the water vapor in the combustion off gas with the condenser 26, but other means, for example, the carbon dioxide separation membrane separates the carbon dioxide. Alternatively, carbon dioxide may be separated by a so-called PSA (Pressure Swing Adsorption) device that separates and produces gas by changing the pressure using an adsorbent.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In this embodiment, the same parts as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

  As shown in FIG. 5, the fuel cell power generation system 10B of the present embodiment includes a high temperature oxygen production apparatus 50 and a combustor 52, instead of the oxygen permeable membrane-equipped combustor 20 of the first embodiment. The configuration other than the high temperature oxygen production apparatus 50 and the combustor 52 is the same as that of the first embodiment.

The downstream end of the branched air electrode offgas pipe P6-2 is connected to the inlet side of the high temperature oxygen production device 50. The high temperature oxygen production apparatus 50 is an apparatus that separates oxygen from the air electrode off gas, and as an example, a PSA apparatus that performs adsorption and desorption at high temperature can be used. One end of an oxygen supply pipe PO is connected to the oxygen outlet side of the high temperature oxygen production device 50. An exhaust pipe P13 is connected to the air electrode off-gas outlet side of the high temperature oxygen production apparatus 50 after the oxygen is separated. The other end of the oxygen supply pipe PO is connected to the inlet side of the combustor 52. The exhaust pipe P13 is open to the outside of the fuel cell power generation system 10B. In addition, this high temperature oxygen production apparatus 50 is
As an example, it is a HT-PSA (High Temperature-Pressure Swing Adsorption) device using a perovskite type oxide as an adsorbent, and oxygen can be efficiently produced by using a high temperature air electrode off gas. The high temperature oxygen production apparatus 50 can be driven by the DC power generated by the first fuel cell stack 12 and the second fuel cell stack 14.

  The other end of the oxygen supply pipe PO and the downstream end of the second fuel electrode off-gas pipe P7-2 are connected to the inlet side of the combustor 52. Inside the combustor 52, combustible gas components (unreformed methane, unreacted hydrogen, unreacted carbon monoxide, etc.) in the second fuel electrode off-gas, and oxygen supplied from the oxygen supply pipe PO. A combustion reaction occurs and carbon dioxide and water vapor are produced. A combustion offgas pipe P8 is connected to the outlet side of the combustor 52, and the combustion offgas is delivered from the combustor 52.

  Next, the operation of the fuel cell power generation system 10B of this embodiment will be described.

  In the present embodiment as well, similar to the fuel cell power generation system 10A of the first embodiment, power generation is performed in the first fuel cell stack 12 and the second fuel cell stack 14. The second air electrode off-gas sent from the second air electrode 14B and branched to the branched air electrode off-gas pipe P6-2 is supplied to the high temperature oxygen production device 50. In the high temperature oxygen production apparatus 50, oxygen is separated from the second air electrode off-gas, and the separated oxygen is supplied to the combustor 52 via the oxygen supply pipe PO. The air electrode off gas after the oxygen is separated is discharged to the outside from the exhaust pipe P13.

  In the combustor 52, a combustible gas component (unreformed methane, unreacted hydrogen, unreacted carbon monoxide, etc.) in the second fuel electrode off-gas, and oxygen cause a combustion reaction to generate carbon dioxide and water vapor. Is generated. The combustion off-gas is sent to the combustion off-gas pipe P8, the water is separated in the condenser 26 as in the first embodiment, the separated water is recovered in the water tank 27, and the carbon dioxide-rich gas is liquefied into carbon dioxide gas. It is supplied to the part 66.

  Also in the present embodiment, carbon dioxide and water vapor are generated in the combustor 52 by the combustion reaction between the combustible gas contained in the second fuel electrode off-gas and oxygen. Therefore, it is possible to reduce the combustible gas from the second fuel electrode off-gas, recover high-concentration carbon dioxide, and efficiently obtain liquefied carbon dioxide.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In this embodiment, the same parts as those in the first and second embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

  The fuel cell power generation system 10C of the present embodiment mainly includes the reformer 54, does not include the circulating gas pipe P3, and the piping flow paths related to these configurations are the same as those of the first embodiment. Is different from Other configurations are similar to those of the first embodiment.

  As shown in FIG. 6, the fuel cell power generation system 10C includes a reformer 54. One end of the fuel gas pipe P1-1 is connected to the inlet side of the reformer 54. Further, one end of a water supply pipe P2-2 is connected to the inlet side of the reformer 54. The other end of the water supply pipe P2-2 is connected to the water tank 27. An ion exchange resin 56 and a pump 27B are provided in the water supply pipe P2-2. By driving the pump 27B, the water stored in the water tank 27 is supplied to the reformer 54 through the ion exchange resin 56.

  One end of the reformed gas pipe P1-2 is connected to the outlet side of the reformer 54. The other end of the reformed gas pipe P1-2 is connected to the first fuel electrode 12A of the first fuel cell stack 12.

  Next, the operation of the fuel cell power generation system 10C of this embodiment will be described.

  In the reformer 54, the mixed gas of fuel gas and steam is heated by heat exchange with the combustion off gas, and hydrogen and carbon monoxide are generated by the steam reforming reaction. Further, carbon dioxide and hydrogen are generated by the shift reaction between the generated carbon monoxide and water vapor. The reformed gas containing unreacted fuel gas (methane), hydrogen, carbon monoxide, and carbon dioxide is supplied to the first fuel electrode 12A through the reformed gas pipe P1-2. In the first fuel cell stack 12 and the second fuel cell stack 14, power generation is performed as in the first embodiment.

  The second fuel electrode off-gas is delivered from the second fuel electrode 14A to the second fuel electrode off-gas pipe P7-2. The second fuel electrode off-gas is supplied to the combustion part 22 of the oxygen-permeable membrane-equipped combustor 20 without being branched. From the second air electrode 14B, the air electrode off-gas is delivered to the air electrode off-gas pipe P6, and as in the first embodiment, a part of the air electrode off-gas is branched to the branch air electrode off-gas pipe P6-2, and the others are It is merged with the air electrode off-gas sent from the first air electrode 12B.

  In the oxygen-permeable membrane-equipped combustor 20 and the condenser 26, the same processing as in the first embodiment is performed, and the carbon dioxide-rich gas is supplied to the carbon dioxide gas liquefying unit 66.

  Also in this embodiment, in the combustor 20 with an oxygen permeable membrane, carbon dioxide and water vapor are generated by the combustion reaction between the combustible gas contained in the second fuel electrode off gas and oxygen. Therefore, it is possible to reduce the combustible gas from the second fuel electrode off-gas, recover high-concentration carbon dioxide, and efficiently obtain liquefied carbon dioxide.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. In this embodiment, the same parts as those in the first to third embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

  The fuel cell power generation system 10D of the present embodiment includes a high temperature oxygen production apparatus 50 of the second embodiment and a combustor 52 in place of the oxygen permeable membrane-equipped combustor 20 of the third embodiment. The configurations other than the high temperature oxygen production apparatus 50 and the combustor 52 are the same as those in the third embodiment.

  As shown in FIG. 7, the downstream end of the branched air electrode off-gas pipe P6-2 is connected to the inlet side of the high temperature oxygen production device 50, and the oxygen outlet side of the high temperature oxygen production device 50 is connected to the oxygen supply pipe PO. One end is connected. An exhaust pipe P13 is connected to the air electrode off-gas outlet side of the high temperature oxygen production apparatus 50 after the oxygen is separated. The other end of the oxygen supply pipe PO is connected to the inlet side of the combustor 52. The exhaust pipe P13 is open to the outside of the fuel cell power generation system 10D.

  The other end of the oxygen supply pipe PO and the downstream end of the second fuel electrode off-gas pipe P7-2 are connected to the inlet side of the combustor 52. Inside the combustor 52, combustible gas components (unreformed methane, unreacted hydrogen, unreacted carbon monoxide, etc.) in the second fuel electrode off-gas, and oxygen supplied from the oxygen supply pipe PO. A combustion reaction occurs and carbon dioxide and water vapor are produced. A combustion offgas pipe P8 is connected to the outlet side of the combustor 52, and the combustion offgas is delivered from the combustor 52.

  Next, the operation of the fuel cell power generation system 10D of this embodiment will be described.

  Also in this embodiment, similar to the fuel cell power generation system 10C of the third embodiment, the reformer 54 steam-reforms the fuel gas to generate reformed gas, and the first fuel cell stack 12, the second fuel cell stack 12, Power generation is performed in the fuel cell stack 14. The second air electrode off-gas sent from the second air electrode 14B and branched to the branched air electrode off-gas pipe P6-2 is supplied to the high temperature oxygen production device 50. In the high temperature oxygen production apparatus 50, oxygen is separated from the second air electrode off gas, and the separated oxygen is supplied to the combustor 52 via the oxygen supply pipe PO. The air electrode off gas after the oxygen is separated is discharged to the outside from the exhaust pipe P13.

  In the combustor 52, a combustible gas component (unreformed methane, unreacted hydrogen, unreacted carbon monoxide, etc.) in the second fuel electrode off-gas, and oxygen cause a combustion reaction to generate carbon dioxide and water vapor. Is generated. The combustion off-gas is sent to the combustion off-gas pipe P8, the water is separated in the condenser 26 as in the first embodiment, the separated water is recovered in the water tank 27, and the carbon dioxide-rich gas is liquefied into carbon dioxide gas. It is supplied to the part 66.

  Also in the present embodiment, carbon dioxide and water vapor are generated in the combustor 52 by the combustion reaction between the combustible gas contained in the second fuel electrode off-gas and oxygen. Therefore, it is possible to reduce the combustible gas from the second fuel electrode off-gas, recover high-concentration carbon dioxide, and efficiently obtain liquefied carbon dioxide.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described. In this embodiment, the same parts as those in the first to fourth embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

  The fuel cell power generation system 10E of the present embodiment is different from the first embodiment in that a third heat exchanger 34 and a condenser 35 are provided in the path of the first fuel electrode offgas pipe P7.

  As shown in FIG. 8, the first fuel electrode off-gas pipe P7 extends from the first fuel electrode 12A and is connected to the condenser 35 via the third heat exchanger 34. The first fuel electrode off-gas pipe P7 from the first fuel electrode 12A to the condenser 35 is indicated by reference numeral P7A. The first fuel electrode off-gas pipe P7A extends from the gas side outlet of the condenser 35 and is connected to the second fuel electrode 14A via the third heat exchanger 34. The first fuel electrode off-gas pipe P7 from the condenser 35 to the second fuel electrode 14A is shown by reference numeral P7B. One end of a water pipe P9-2 is connected to the liquid side outlet of the condenser 35. The other end of the water pipe P9-2 is connected to the water tank 27. A cooling water circulation flow passage 35A is piped to the condenser 35, and the cooling water from the exhaust heat input type absorption refrigerator 36 is circulated and supplied by driving the pump 35P. As a result, the first fuel electrode off-gas is cooled and the water vapor in the first fuel electrode off-gas is condensed. The condensed water is sent to the water tank 27 via the water pipe P9-2.

  Next, the operation of the fuel cell power generation system 10E of this embodiment will be described.

  In the present embodiment as well, similar to the fuel cell power generation system 10A of the first embodiment, power generation is performed in the first fuel cell stack 12. The first fuel electrode off-gas sent from the first fuel electrode 12A to the first fuel electrode off-gas pipe P7-1 is cooled by heat exchange with regenerated fuel gas described later in the third heat exchanger 34, and is supplied to the condenser 35. To be done. In the condenser 35, the first fuel electrode off-gas is further cooled by the cooling water circulating in the cooling water circulation passage 35A, and the water vapor in the first fuel electrode off-gas is condensed. Here, the temperature of the cooling water circulating through the cooling water circulation flow path 35A is set such that the amount of water vapor remaining in the regenerated fuel gas improves the power generation efficiency of the second fuel cell stack 14 and the water vapor in the first fuel electrode off-gas. Are set to condense. The condensed water is sent to the water tank 27 via the water pipe P9-2.

  The first fuel electrode off-gas from which the condensed water has been separated is sent to the first fuel electrode off-gas pipe P7B as regenerated fuel gas, and the heat of the first fuel electrode off-gas before the water separation in the third heat exchanger 34 is performed. It is heated by exchange and supplied to the second fuel electrode 14A. In the second fuel cell stack 14, power generation is performed as in the fuel cell power generation system 10A of the first embodiment.

  In the present embodiment, since the regenerated fuel gas generated by separating a part of the water vapor from the first fuel electrode off-gas is supplied to the second fuel electrode 14A, it is possible to improve the power generation efficiency in the second fuel cell stack 14. You can

  Also in this embodiment, carbon dioxide and water vapor are generated in the combustion section 22 of the combustor 20 with an oxygen permeable film by the combustion reaction between the combustible gas contained in the second fuel electrode off gas and oxygen. Therefore, it is possible to reduce the combustible gas from the second fuel electrode off-gas, recover high-concentration carbon dioxide, and efficiently obtain liquefied carbon dioxide.

[Sixth Embodiment]
Next, a sixth embodiment of the present invention will be described. In this embodiment, the same parts as those in the first to fifth embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

  As shown in FIG. 9, in the fuel cell power generation system 10F of the present embodiment, the first fuel cell stack 62 and the second fuel cell stack 64 are the hydrogen ion conductive solid oxide fuel cell of the first embodiment. Instead of this, a solid oxide fuel cell (SOFC) is used. Therefore, the following reactions occur at the first fuel electrode 62A (fuel electrode) and the first air electrode 62B (air electrode). The same applies to the second fuel electrode 64A and the second air electrode 64B.

  At the first air electrode 62B, oxygen ions are generated by the reaction between oxygen and electrons in the oxidant gas, as shown in the following formula (5). The generated oxygen ions reach the first fuel electrode 62A of the first fuel cell stack 62 through the electrolyte layer 62C.

(Air electrode reaction)
1/2O ₂ +2e ⁻ →O ^{2 −} (5)

  On the other hand, in the first fuel electrode 62A of the first fuel cell stack 62, as shown in the following formulas (6) and (7), the oxygen ions that have passed through the electrolyte layer 62C are hydrogen and monoxide in the fuel gas. It reacts with carbon to produce water vapor, carbon dioxide and electrons. Electrons generated at the first fuel electrode 62A move from the first fuel electrode 62A to the first air electrode 62B through an external circuit, thereby generating power.

(Fuel electrode reaction)
^{_{H 2 + O 2- → H 2}} O + 2e - ... (6)
CO+O ^{2 −} →CO ₂ +2e ⁻ (7)

  In the solid oxide fuel cell, since water vapor is generated in the first fuel electrode 62A and the second fuel electrode 64A, compared with the hydrogen ion conduction type solid oxide fuel cell, the first fuel electrode off gas, 2 The amount of water vapor contained in the fuel electrode offgas is large. On the other hand, the first air electrode 62B and the second air electrode 64B do not generate water vapor. The air electrode off-gas supplied to the exhaust heat input type absorption refrigerator 36 is exhausted from the exhaust pipe P36-1 after heat exchange.

  The other configurations of the fuel cell power generation system 10F of the present embodiment are the same as those of the fifth embodiment, and the third heat exchanger 34 and the condenser 35 are provided in the path of the first fuel electrode offgas pipe P7. ing. Here, since the amount of water vapor contained in the first fuel electrode off-gas and the second fuel electrode off-gas is larger than that in the fuel cell power generation system 10E, the amount of water vapor removed by condensation in the condenser 35 is increased, The temperature of the cooling water circulating in the cooling water circulation passage 35A is set. The condensed water is sent to the water tank 27 via the water pipe P9-2.

  In the present embodiment, since the regenerated fuel gas generated by separating a part of the water vapor from the first fuel electrode off-gas is supplied to the second fuel electrode 14A, it is possible to improve the power generation efficiency in the second fuel cell stack 14. You can

  Also in this embodiment, carbon dioxide and water vapor are generated in the combustion section 22 of the combustor 20 with an oxygen permeable film by the combustion reaction between the combustible gas contained in the second fuel electrode off gas and oxygen. Therefore, it is possible to reduce the combustible gas from the second fuel electrode off-gas, recover high-concentration carbon dioxide, and efficiently obtain liquefied carbon dioxide.

[Seventh Embodiment]
Next, a seventh embodiment of the present invention will be described. In this embodiment, the same parts as those in the first to sixth embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

  As shown in FIG. 10, in the fuel cell power generation system 10G of the present embodiment, instead of the oxygen permeable membrane-equipped combustor 20 of the sixth embodiment, a high-temperature oxygen production device 50 similar to that of the second embodiment, and a combustion The container 52 is provided. The configurations other than the high temperature oxygen production apparatus 50, the combustor 52, and the pipes related to these are the same as those in the sixth embodiment.

  Also in the present embodiment, since the regenerated fuel gas generated by separating a part of the water vapor from the first fuel electrode off-gas is supplied to the second fuel electrode 14A, the power generation efficiency in the second fuel cell stack 14 is improved. be able to.

  Also in the present embodiment, carbon dioxide and water vapor are generated in the combustor 52 by the combustion reaction between the combustible gas contained in the second fuel electrode off-gas and oxygen. Therefore, it is possible to reduce the combustible gas from the second fuel electrode off-gas, recover high-concentration carbon dioxide, and efficiently obtain liquefied carbon dioxide.

[Eighth Embodiment]
Next, an eighth embodiment of the invention will be described. In this embodiment, the same parts as those in the first to seventh embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

  As shown in FIG. 11, in the fuel cell power generation system 10H of the present embodiment, as in the third embodiment, the reformer 54 is provided, the circulating gas pipe P3 is not provided, and these The piping channel related to the configuration is different from that of the sixth embodiment. Other configurations are similar to those of the sixth embodiment.

  Also in the present embodiment, since the regenerated fuel gas generated by separating a part of the water vapor from the first fuel electrode off-gas is supplied to the second fuel electrode 14A, the power generation efficiency in the second fuel cell stack 14 is improved. be able to.

  Also in this embodiment, carbon dioxide and water vapor are generated in the combustion section 22 by the combustion reaction between the combustible gas contained in the second fuel electrode off-gas and oxygen. Therefore, it is possible to reduce the combustible gas from the second fuel electrode off-gas, recover the high-concentration carbon dioxide, and efficiently obtain the liquefied carbon dioxide.

[Ninth Embodiment]
Next, a ninth embodiment of the present invention will be described. In this embodiment, the same parts as those in the first to eighth embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

  As shown in FIG. 11, in the fuel cell power generation system 10I of the present embodiment, instead of the oxygen permeable membrane-equipped combustor 20 of the eighth embodiment, the high temperature oxygen production apparatus 50 and the combustor 52 of the seventh embodiment are provided. Is equipped with. The configuration other than the high temperature oxygen production device 50 and the combustor 52 is the same as that of the eighth embodiment.

  Also in the present embodiment, since the regenerated fuel gas generated by separating a part of the water vapor from the first fuel electrode off-gas is supplied to the second fuel electrode 14A, the power generation efficiency in the second fuel cell stack 14 is improved. be able to.

  Also in the present embodiment, carbon dioxide and water vapor are generated in the combustor 52 by the combustion reaction between the combustible gas contained in the second fuel electrode off-gas and oxygen. Therefore, it is possible to reduce the combustible gas from the second fuel electrode off-gas, recover high-concentration carbon dioxide, and efficiently obtain liquefied carbon dioxide.

[Other Embodiments]
Although one embodiment of the liquefied carbon dioxide recovery fuel cell power generation system of the present invention has been described above, the present invention is not limited to the above, and various other than the above without departing from the scope thereof. Of course, it can be modified and implemented.

  As the fuel cell of the present invention, other fuel cells such as a molten carbonate fuel cell (MCFC), a phosphoric acid fuel cell (PAFC), and a polymer electrolyte fuel cell (PEFC) can be used.

  In the above-described first to ninth embodiments, cold heat is generated using the exhaust heat input type absorption refrigerator 36, but instead of the exhaust heat input type absorption refrigerator 36, for example, a known adsorption refrigerator May be used to generate cold heat.

  Further, instead of the exhaust heat input type absorption refrigerator 36, a fuel cell power generation system 10J may be used that uses an electric turbo refrigerator 60 that generates cold heat by using electric power without using exhaust heat. In FIG. 14, as an example, a configuration in which the exhaust heat input type absorption refrigerator 36 is replaced with an electric turbo refrigerator 60 in the fuel cell power generation system 10A of the first embodiment is shown. The second to ninth embodiments can be similarly replaced. In the fuel cell power generation system 10J, the air electrode off gas is exhausted to the outside of the system after heat exchange in the second heat exchanger 32. The electric turbo refrigerator 60 can be driven by the electric power generated by the fuel cell power generation system 10J. Since the electric turbo chiller 60 generally has high cooling efficiency, it is possible to operate the fuel cell power generation system 10J with high efficiency even if the generated electric power is used. In this case as well, it is preferable to drive the electric turbo refrigerator 60 with a direct current in order to efficiently use the generated electric power without converting it into an alternating current.

10A-10J Fuel cell power generation system (liquefied carbon dioxide recovery type fuel cell power generation system)
12, 62 First fuel cell stack (first fuel cell)
12A, 62A 1st fuel electrode 12B, 62B 1st air electrode 14, 64 2nd fuel cell stack (2nd fuel cell)
14A, 64A 2nd fuel electrode 14B, 64B 2nd air electrode 20 Combustor 22 with an oxygen permeable membrane 22 Combustion part,
22A combustion space 23 oxygen permeable membrane,
24 Oxygen Separation Section 26 Condenser (Carbon Dioxide Separation Section)
35 Condenser (fuel regeneration section)
36 Exhaust Heat Input Type Absorption Refrigerator 50 High Temperature Oxygen Production Device (Oxygen Separation Section)
52 Combustor (combustion section),
54 reformer,
60 electric turbo refrigerator 67 replenishment system (supply unit)
68 Compressor 70 Cooling device 84 Tank P3 Circulating gas pipe (circulating flow path)
P6 air electrode off-gas pipe (air electrode off-gas passage)
P6-2 Branch air electrode off-gas pipe (branch air electrode off-gas passage)
P7 2nd fuel electrode offgas pipe (2nd fuel electrode offgas flow path)

Claims (9)

A fuel cell that generates electricity by a fuel gas containing a carbon compound and supplied to a fuel electrode and an oxidant gas containing oxygen and supplied to an air electrode, and discharges an off gas,
A carbon dioxide gas separation unit for separating carbon dioxide gas from the off gas,
An exhaust heat input type absorption refrigeration machine or adsorption refrigeration machine that cools water by using the off gas as a heat source for driving to generate cooling water, and generates cold heat by being driven by electric power obtained by power generation of the fuel cell. At least one of the electric turbo refrigerators,
A compressor that can be driven by electric power generated by the fuel cell and that compresses the carbon dioxide gas separated by the carbon dioxide gas separation unit,
A cooling device that cools the compressed carbon dioxide gas by at least one of the cooling water and the cold heat to generate liquefied carbon dioxide,
Have
Electric power is generated by the fuel gas containing a carbon compound and supplied to the first fuel electrode and the oxidant gas containing oxygen and supplied to the first air electrode, and the first fuel electrode off-gas is first generated from the first fuel electrode. Electric power is generated using the first fuel cell that is sent to the fuel electrode off-gas passage, the first fuel electrode off gas that is supplied to the second fuel electrode, and the oxidant gas that is supplied to the second air electrode, and the second fuel cell is used. A second fuel cell for delivering a second fuel electrode off-gas from the fuel electrode to a second fuel electrode off-gas passage;
An air electrode off-gas flow path for delivering an air electrode off gas from at least one of the first air electrode and the second air electrode;
An oxygen separation unit that is connected to the air electrode off-gas passage and is supplied with the air electrode off gas, and separates oxygen from the air electrode off gas,
The second fuel electrode off-gas that has passed through the second fuel electrode off-gas flow path is supplied, and the oxygen separated by the oxygen separation unit is supplied to cause the second fuel electrode off-gas to burn and react with the oxygen. Combustion section,
Combustion off-gas sent from the combustion unit, the cooling water, or the carbon dioxide gas separation unit for cooling with the cold heat to separate the carbon dioxide gas and water,
Liquefied carbon dioxide recovery type fuel cell power generation system equipped with. A fuel cell that generates electric power by a fuel gas containing a carbon compound and supplied to a fuel electrode and an oxidant gas containing oxygen and supplied to an air electrode, and discharges an off gas,
A carbon dioxide gas separation unit for separating carbon dioxide gas from the off gas,
An electric turbo refrigerator that is driven by electric power obtained by power generation of the fuel cell to generate cold heat ,
A compressor that can be driven by the electric power generated by the fuel cell and that compresses the carbon dioxide gas separated by the carbon dioxide gas separation unit,
A cooling device that cools the compressed carbon dioxide gas with the cold heat to generate liquefied carbon dioxide,
Liquefied carbon dioxide recovery fuel cell power generation system equipped with. The liquefied carbon dioxide recovery fuel cell power generation system according to claim 1, wherein the first fuel cell and the second fuel cell are hydrogen ion conductive solid oxide fuel cells. The oxygen separation unit has an oxygen permeable membrane that selectively permeates oxygen,
The liquefied carbon dioxide recovery fuel cell power generation system according to claim 1 or 3, wherein a combustion space is arranged on the permeation side of the oxygen permeable membrane, and the combustion section is integrated with the oxygen separation section. The oxygen separation unit includes a PSA device,
The PSA device can be driven by the electric power generated by the fuel cell,
The liquefied carbon dioxide recovery type fuel cell power generation system according to claim 1 or 3 . The compressor compresses the carbon dioxide gas to 4 MPa or more,
The heat-up type absorption refrigerator, or adsorption refrigerator supplies the cooling water temperature lower than the critical temperature of carbon dioxide gas to the cooling apparatus, according to claim 1, claim 3, claim 4 The liquefied carbon dioxide recovery fuel cell power generation system according to claim 5 . A tank for storing the liquefied carbon dioxide produced by the cooling device,
The carbon dioxide gas separation unit, the compressor, the cooling device, and the tank are connected by a pipe in the order of the carbon dioxide gas separation unit, the compressor, the cooling device, and the tank. ~ The liquefied carbon dioxide recovery type fuel cell power generation system according to any one of claims 6 to 7. The water separated by the carbon dioxide gas separation unit is supplied to a cooling water path of the exhaust heat input type absorption refrigerator, a cooling water path of the adsorption refrigerator, or a cooling water path of the electric turbo refrigerator. Equipped with a supply unit that
In the cooling water path of the exhaust heat input type absorption refrigerating machine, the cooling water path of the adsorption refrigerating machine, or a part of the cooling water of the cooling water path of the electric turbo refrigerator, the carbon dioxide gas separation unit The liquefied carbon dioxide recovery fuel cell power generation system according to any one of claims 1 and 3 to 6 , wherein the water separated in step 1 is used. The water separated in the carbon dioxide gas separation unit, the cooling water replenishment path of the cooling tower constituting the exhaust heat input type absorption refrigerator, or the cooling water replenishment path of the cooling tower constituting the adsorption refrigerator A supply unit for supplying
The cooling water replenishing water of the cooling tower that constitutes the exhaust heat input type absorption refrigerating machine, or a part of the cooling water replenishing water of the cooling tower that constitutes the adsorption refrigerating machine, the separated by the carbon dioxide gas separation unit The liquefied carbon dioxide recovery type fuel cell power generation system according to any one of claims 1, 3 to 6, and 8 , wherein water is used.