JP7148364B2 - Reactor and fuel cell power generation system - Google Patents

Description

The present invention relates to reactors and fuel cell power generation systems.

When carbon compound fuel is used in the fuel cell power generation system, the exhaust gas discharged from the fuel cell contains carbon dioxide gas. Separation of carbon dioxide gas from this exhaust gas has been considered (for example, see Patent Documents 1 to 5).

Japanese Patent No. 5581240 JP 2013-196890 A Japanese Patent No. 54137199 JP 2012-164423 A Japanese Patent No. 3334567

By liquefying carbon dioxide gas into liquefied carbon dioxide, it becomes easier to transport, fix by injection into reservoirs, and use in commerce and industry.
Since exhaust gas contains gases (impurities) other than carbon dioxide gas, it is necessary to remove gases other than carbon dioxide gas in order to obtain liquefied carbon dioxide with less impurities. Although there are apparatuses for obtaining high-concentration carbon dioxide gas by reacting unreacted components of exhaust gas with oxygen, it is desired to accelerate the reaction when obtaining carbon dioxide gas.

It is also known to produce and store carbon from the separated carbon dioxide gas so as not to release the carbon dioxide gas into the atmosphere. BACKGROUND ART There is known a carbon production apparatus that produces carbon by reacting carbon dioxide gas and hydrogen in the presence of a catalyst (reduction reaction) (see, for example, Patent Document 5). Also from the viewpoint of efficiently obtaining carbon dioxide gas used in the reduction reaction, it is desired to accelerate the reaction for obtaining carbon dioxide gas.

In order to promote the reaction when obtaining carbon dioxide gas, oxygen is selectively separated from the oxygen-containing gas using an oxygen permeable membrane, and the separated oxygen and unreacted components of the exhaust gas are oxidized to produce carbon dioxide. may generate. At this time, as the oxygen permeable film, a mixed conductive ceramic film containing LSCF (a compound consisting of La, Sr, Co, Fe and oxygen), BSCF (a compound consisting of Ba, Sr, Co, Fe and oxygen), etc. is used. be done.
However, when such a mixed conductive ceramic film is used, carbon dioxide generated by oxidation of carbon dioxide or oxygen contained in the exhaust gas and unreacted components of the exhaust gas reacts with LSCF, BSCF, etc., and the mixed conductivity Carbonate may form and accumulate on the ceramic membrane, significantly reducing the oxygen permeability of the oxygen permeable membrane.
Therefore, when using an oxygen permeable membrane, there is a reactor that suppresses the decrease in oxygen permeability, promotes the oxidation reaction between the separated oxygen and unreacted components of the exhaust gas, and obtains a gas with a high carbon dioxide concentration. desirable.

Moreover, it is desirable that a gas having a high carbon dioxide concentration can be obtained even in a reactor using a permeable membrane other than an oxygen permeable membrane.

One aspect of the present invention has been made in view of the above. and a fuel cell power generation system equipped with the reactor.
Another object of the present invention is to provide a reactor capable of obtaining a gas with a high carbon dioxide concentration by using a hydrogen permeable membrane, and a fuel cell power generation system equipped with the reactor.

<1> A first flow path to which a fuel gas is supplied, a second flow path to which a gas containing oxygen is supplied, and a flow path separating the first flow path and the second flow path to the second flow path an oxygen-permeable membrane that permeates oxygen contained in the supplied gas toward the first flow path; and an oxygen-permeable membrane that is provided in the first flow path and promotes an oxidation reaction between the fuel gas and oxygen that permeates the oxygen-permeable membrane. and a catalyst, wherein the oxygen permeable membrane comprises a zirconium oxide membrane.
According to the configuration <1>, by using the zirconium oxide film, LSCF (compound composed of La, Sr, Co, Fe and oxygen), BSCF (compound composed of Ba, Sr, Co, Fe and oxygen), etc. In comparison with the case of using a ceramic membrane containing, the formation and accumulation of carbonate due to the reaction between carbon dioxide and membrane components can be suppressed, and the decrease in oxygen permeability in the oxygen permeable membrane can be suppressed. This can promote the oxidation reaction between unreacted fuel gas and oxygen in the reactor. Thereby, a gas with a high carbon dioxide concentration can be obtained.

<2> The zirconium oxide film according to <1>, wherein the zirconium oxide film is a film obtained by doping zirconium oxide with at least one metal oxide selected from the group consisting of scandium oxide, yttrium oxide, cerium oxide, aluminum oxide, and ytterbium oxide. reactor.
According to the configuration <2>, the zirconium oxide film has the effect of realizing high durability and high oxygen transport properties.

<3> The reactor according to <2>, wherein the molar ratio of the zirconium oxide to the metal oxide in the zirconium oxide film (zirconium oxide/metal oxide) is 80/20 to 97/3.
According to the above configuration <3>, the zirconium oxide film has a high oxygen transport property because the molar ratio is 80/20 or more, and the molar ratio is 97/3 or less. As a result, the crystal structure becomes a tetragonal system or a cubic system and is stabilized, so that high durability can be realized.

<4> The reactor according to any one of <1> to <3>, wherein the zirconium oxide film is electrically short-circuited on the first channel side surface and the second channel side surface.
<5> The zirconium oxide film has a micro-via structure penetrating through the surface on the first channel side and the surface on the second channel side. The surface on the side of the first channel and the surface on the side of the second channel are internally short-circuited, or the surface on the side of the first channel and the surface on the side of the second channel further include current collectors, and the surface on the side of the first channel The reaction apparatus according to <4>, in which the surface of and the surface on the side of the second flow path are externally short-circuited.
According to the above configurations <4> and <5>, the zirconium oxide film is provided with electronic conductivity, and oxygen supplied to the second channel side is permeated to the first channel side as oxygen ions (O ²⁻ ). Oxygen permeability can be improved thereby.

<6> The reaction device according to any one of <1> to <5>, wherein the catalyst is laminated on the first channel side of the oxygen permeable membrane.
According to the configuration <6>, the unreacted fuel gas and the oxygen permeated through the oxygen permeable membrane can be favorably oxidized.

<7> A first flow path to which a fuel gas is supplied, a second flow path to which a gas containing oxygen is supplied, and a flow path separating the first flow path and the second flow path to the first flow path a hydrogen-permeable membrane for permeating hydrogen contained in the gas to be supplied to the second channel side; A reactor comprising a catalyst.
According to the above configuration <7>, the hydrogen contained in the gas supplied to the first channel can be separated by the hydrogen permeable membrane, and the oxygen and the hydrogen permeated through the hydrogen permeable membrane flow to the second channel side. oxidation reaction. As a result, a gas with a high carbon dioxide concentration is obtained on the first channel side.

<8> The reaction device according to <7>, wherein the catalyst is laminated on the second flow channel side of the hydrogen permeable membrane.
According to the configuration <8>, oxygen and hydrogen permeating through the hydrogen-permeable membrane can be favorably oxidized.

<9> The reaction apparatus according to any one of <1> to <6>, a fuel electrode, an air electrode, and an electrolyte layer disposed between the fuel electrode and the air electrode, wherein the fuel electrode The fuel gas supplied to the air electrode and the oxidant gas containing oxygen supplied to the air electrode generate power, and the fuel electrode off-gas containing the unreacted fuel gas is discharged from the fuel electrode, and the air a fuel cell in which an air electrode off-gas containing oxygen is discharged from an electrode, the fuel electrode off-gas is supplied to the first flow path, the air electrode off-gas is supplied to the second flow path, and the reaction apparatus 1. A fuel cell power generation system in which carbon dioxide is generated by an oxidation reaction between the unreacted fuel gas and oxygen permeating through the oxygen permeable membrane in the first flow path.
According to the above configuration <9>, the fuel electrode off-gas is supplied to the first channel of the reactor, and the air electrode off-gas is supplied to the second channel of the reactor. Oxygen contained in the air electrode off-gas passes through the oxygen permeable membrane in the reactor and is supplied to the first channel side, where it undergoes an oxidation reaction with unreacted fuel gas contained in the fuel electrode off-gas. At this time, as in the configuration <1> above, a decrease in the oxygen permeability of the oxygen permeable membrane can be suppressed, the oxidation reaction between unreacted fuel gas and oxygen in the reactor can be promoted, and the carbon dioxide concentration can be reduced. high gas can be obtained.

<10> The reaction device according to <7> or <8>, a fuel electrode, an air electrode, and an electrolyte layer disposed between the fuel electrode and the air electrode, wherein the Electricity is generated by the fuel gas and the oxidant gas containing oxygen supplied to the air electrode, and the fuel electrode off-gas containing the unreacted fuel gas is discharged from the fuel electrode and contains oxygen from the air electrode. a fuel cell from which air electrode off-gas is discharged, wherein the fuel electrode off-gas is supplied to the first flow path, the air electrode off-gas is supplied to the second flow path, and the second flow of the reactor A fuel cell power generation system in which the oxygen and the hydrogen permeating the hydrogen permeable membrane are oxidized in the passage to produce water, and unreacted hydrogen is separated from the fuel electrode off-gas.
According to the above configuration <10>, the fuel electrode off-gas is supplied to the first channel of the reactor, and the air electrode off-gas is supplied to the second channel of the reactor. Then, in the reactor, hydrogen contained in the fuel electrode off-gas passes through the hydrogen permeable membrane and is supplied to the second channel side, where it undergoes an oxidation reaction with oxygen contained in the air electrode off-gas. At this time, similarly to the configuration <7>, a gas with a high carbon dioxide concentration can be obtained.
Furthermore, when carbon monoxide is also contained in the fuel electrode off-gas, the chemical equilibrium changes due to the selective separation of hydrogen, and water vapor and carbon monoxide in the fuel electrode off-gas undergo a shift reaction to produce carbon monoxide. Converts to carbon and hydrogen. Therefore, the hydrogen in the fuel electrode off-gas is separated to the second channel side, so that a gas with a higher carbon dioxide concentration can be efficiently obtained.

<11> A plurality of the fuel cells are provided, and the fuel electrodes in the plurality of fuel cells are arranged in series, and the fuel electrode off-gas discharged from the fuel electrode on the upstream side is supplied to the fuel electrode on the downstream side. and the fuel electrode off-gas discharged from the most downstream fuel electrode is supplied to the first flow path, and the air electrode off-gas discharged from at least one of the air electrodes in the plurality of fuel cells is supplied to the The fuel cell power generation system according to <9> or <10>, which is supplied to the second channel.
According to the configuration <11>, a plurality of fuel cells are provided, and the fuel electrode off-gas discharged from the more upstream fuel electrode is supplied to the more downstream fuel electrode and reused, thereby fuel cell power generation The power generation efficiency of the system can be improved.

<12> The fuel cell power generation system according to any one of <9> to <11>, further comprising a steam separation unit that separates steam from the gas discharged from the first channel of the reaction device.
According to the configuration <12> above, since the gas discharged from the first flow path contains water vapor and carbon dioxide as main components, by separating the water vapor from this gas, high-concentration carbon dioxide is recovered. be able to.

<13> A power generation device that generates power using renewable energy, a water electrolysis device that electrolyzes water using the power generated by the power generation device, and hydrogen generated by the water electrolysis device. and a carbon generator that generates carbon by a reduction reaction with carbon dioxide contained in the gas discharged from the first flow path of the reaction device. The fuel cell power system described.
According to the above configuration <13>, carbon can be produced by a reduction reaction between the recovered high-concentration carbon dioxide and hydrogen derived from renewable energy (CO ₂ -free hydrogen).

<14> Further comprising: a compression section that compresses carbon dioxide contained in the gas discharged from the first flow path of the reaction device; and a liquefying device that liquefies the carbon dioxide compressed in the compression section. The fuel cell power generation system according to any one of 9> to <13>.
According to the above configuration <14>, liquefied carbon dioxide can be efficiently obtained from the recovered high-concentration carbon dioxide.

According to one aspect of the present invention, a reactor capable of obtaining a gas with a high carbon dioxide concentration by having an oxygen permeable membrane with excellent oxygen permeability and enabling promotion of an oxidation reaction, and a fuel equipped with the reactor A battery power generation system can be provided.
Further, another aspect of the present invention can provide a reactor capable of obtaining a gas with a high carbon dioxide concentration by using a hydrogen permeable membrane, and a fuel cell power generation system including the reactor.

1 is a schematic diagram of a fuel cell power generation system according to a first embodiment; FIG. FIG. 2 is an axial cross-sectional view showing an oxidation reactor with an oxygen permeable membrane. 4 is an enlarged cross-sectional view showing an oxygen permeable membrane; FIG. It is a state diagram of carbon dioxide. FIG. 4 is an enlarged cross-sectional view showing an oxygen-permeable membrane short-circuited to the outside; FIG. 2 is a schematic diagram of a fuel cell power generation system according to a second embodiment; FIG. 3 is a schematic diagram of a fuel cell power generation system according to a third embodiment; FIG. 4 is a schematic diagram of a fuel cell power generation system according to a fourth embodiment;

In the present disclosure, a numerical range represented using "to" means a range including the numerical values described before and after "to" as lower and upper limits.
In the numerical ranges described step by step in the present disclosure, the upper limit or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described step by step. .

[First embodiment]
An example of an embodiment of the present invention will be described in detail below with reference to the drawings.
FIG. 1 shows a fuel cell power generation system 10A according to a first embodiment of the invention. The fuel cell power generation system 10A mainly includes a first fuel cell stack 12, a second fuel cell stack 14, an oxidation reactor 20 with an oxygen permeable membrane as a reactor, a condenser (water vapor separator) 26, The second heat exchanger 32, the exhaust heat input type absorption chiller 36, the water tank 27, the carbon dioxide gas liquefying unit 66, the tank 84, etc. are provided on-site. The fuel cell power generation system 10A also includes a control section (not shown).

As shown in FIG. 1, the first fuel cell stack 12 is a proton-conducting 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 the 1st fuel electrode (fuel electrode) 12A and the 1st air electrode (air electrode) 12B each laminated|stacked on the back surface.

The basic configuration of the second fuel cell stack 14 is the same as that of the first fuel cell stack 12, with a second fuel electrode 14A corresponding to the first fuel electrode 12A and a second fuel electrode 14A corresponding to the first air electrode 12B. It has two air electrodes 14B and an electrolyte layer 14C corresponding to the electrolyte layer 12C.

One end of the reformed gas pipe P1-2 is connected to the first fuel electrode 12A of the first fuel cell stack 12, and the other end of the fuel gas pipe P1-1 is connected to a reformer 54, which will be described later. ing. Fuel gas is sent from the reformer 54 to the first fuel electrode 12A. In this embodiment, methane is used as the fuel gas, but any gas capable of generating hydrogen by reforming is not particularly limited, and a hydrocarbon fuel can be used. Examples of hydrocarbon fuels include natural gas, LP gas (liquefied petroleum gas), biogas, reformed coal gas, and low 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 preferred. The hydrocarbon fuel may be a mixture of the above-mentioned lower hydrocarbon gases, and the above-mentioned lower hydrocarbon gases may be gases such as natural gas, city gas, and LP gas. If the fuel gas contains impurities, a desulfurizer or the like is required, but it is omitted in FIG.

A water vapor pipe P2 is connected to the reformed gas pipe P1-2, and water vapor is appropriately supplied from a water vapor source (not shown) at the time of starting or stopping. Methane and water vapor are combined in the fuel gas pipe P1 and supplied to the first fuel electrode 12A. The steam from the steam pipe P2 is supplementarily supplied when necessary during the starting and stopping processes of the fuel cell power generation system 10A.

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

CH ₄ +H ₂ O→3H ₂ +CO (1)
CO+ _H2O → _CO2 +H2 ( ₂ )

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

(Anode reaction)
H ₂ →2H ⁺ +2e ⁻ (3)

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

An oxidant gas (air) is supplied to the first air electrode 12B of the first fuel cell stack 12 from an 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 a second heat exchanger 32, and the air flowing through the oxidant gas pipe P5 is heated by heat exchange with the cathode offgas flowing through the cathode offgas pipe P6, which will be described later. The heated air is supplied to the first air electrode 12B.

In the first air electrode 12B, as shown in the following equation (4), hydrogen ions that have migrated from the first fuel electrode 12A through the electrolyte layer 12C and electrons that have migrated from the first fuel electrode 12A through the external circuit are , reacts with oxygen in the oxidant gas to produce 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 cathode off-gas is discharged from the first cathode 12B to the cathode off-gas pipe P6. The oxidant gas pipe P5 and the air electrode off-gas pipe P6 are also connected to the second air electrode 14B in the same manner, and the first air electrode 12B and the second air electrode 14B are connected in parallel.

One end of the 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 second fuel cell stack 14 of the second fuel cell stack 14. 2 is connected to the 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, water vapor, and the like.

One end of a second fuel electrode off-gas pipe P7-2 is connected to the second fuel electrode 14A of the second fuel cell stack 14, and the second fuel electrode off-gas is delivered from the second fuel electrode 14A. The other end of the second anode offgas pipe P7-2 is connected to the oxidation reactor 20 with an oxygen permeable membrane.

In the second fuel cell stack 14, a power generation reaction similar to that in the first fuel cell stack 12 occurs, and the cathode offgas is sent from the second cathode 14B to the cathode offgas pipe P6. The air electrode off-gas pipe P6 connected to the second air electrode 14B is branched upstream of the junction with the air electrode off-gas pipe P6 connected to the first air electrode 12B. -2 is formed. The branch air electrode offgas pipe P6-2 is provided with a flow control valve 42 capable of flow control. The flow control valve 42 is connected with the control section. The flow control valve 42 is controlled by the controller to adjust the flow rate of the cathode offgas branched to the branched cathode offgas pipe P6-2. The downstream end of the branched cathode offgas pipe P6-2 is connected to the oxidation reactor 20 with an oxygen permeable membrane.

(Oxidation reactor with oxygen permeable membrane)
As shown in FIG. 2, the oxidation reactor 20 with an oxygen permeable membrane includes an outer cylinder 20A, a cylindrical oxygen permeable membrane 23 disposed inside the outer cylinder 20A, and an outer cylinder 20A and the cylindrical oxygen permeable membrane. 23 and a closing member 20B for closing the opening on the end side in the cylinder axis direction.

An annular oxidation reaction section 22 is provided between the outer cylinder 20A and the oxygen permeable membrane 23, and an oxygen separation section 24 is provided on the inner peripheral side of the cylindrical oxygen permeation membrane 23. The oxidation reaction section 22 and the oxygen separation section are provided. 24 is isolated by an oxygen permeable membrane 23 .

The oxidation reaction section 22 is provided with an outer spiral passage forming member 28 having a spiral shape inside, and an oxidation reaction space 22A is formed in a spiral shape toward the axial direction of the outer cylinder 20A.
The outer spiral passage forming member 28 is, for example, a belt-shaped member formed in a spiral shape, and has an inner peripheral edge fixed to the outer peripheral surface of the oxygen permeable membrane 23 and an outer peripheral edge fixed to the inner peripheral surface of the outer cylinder 20A. ing.

The oxygen separating portion 24 is provided with a spiral inner spiral passage forming member 29 inside, and a spiral air flow path 24A is formed in the axial direction of the outer cylinder 20A.
The inner spiral passage forming member 29 is, for example, a belt-like member formed in a spiral shape, and the outer peripheral edge thereof is fixed to the inner peripheral surface of the oxygen permeable membrane 23 . Note that the inner spiral passage forming member 29 may have a spiral staircase shape in which the inner peripheral edge is fixed to the outer peripheral surface of a shaft (not shown) provided in the shaft core portion.

As shown in FIGS. 2 and 3, the oxygen permeable membrane 23 of this embodiment includes a porous ceramic membrane 23A, a zirconium oxide membrane 23B provided on the air flow path 24A side of the ceramic membrane 23A, and a ceramic membrane 23A. and a porous reaction catalyst film 23C provided on the oxidation reaction space 22A side. is laminated with The ceramic film 23A and the zirconium oxide film 23B constitute a high temperature oxygen permeable film. Moreover, the ceramic film 23A functions as a support for the zirconium oxide film 23B, and a porous support may be provided instead of the ceramic film 23A.

Examples of the porous ceramic film 23A include porous films containing stabilized zirconia, partially stabilized zirconia, and the like. Specific examples of stabilized zirconia include yttria-stabilized zirconia (YSZ) and scandia-stabilized zirconia (ScSZ). Specific examples of partially stabilized zirconia include yttria partially stabilized zirconia (YSZ) and scandia partially stabilized zirconia (ScSZ). Stabilized zirconia, partially stabilized zirconia, etc. may be doped with nickel, cobalt, ruthenium, etc., and may be, for example, Ni--YSZ.

The zirconium oxide film 23B is a film containing zirconium oxide, and may be a dense film containing zirconium oxide. The zirconium oxide film 23B is compared with a ceramic film containing LSCF (a compound consisting of La, Sr, Co, Fe, and oxygen), BSCF (a compound consisting of Ba, Sr, Co, Fe, and oxygen), and the like. The formation and accumulation of carbonate due to reaction with components is suppressed, and the decrease in oxygen permeability in the oxygen permeable membrane 23 can be suppressed. As a result, a gas with a high carbon dioxide concentration can be obtained on the oxidation reaction space 22A side.

The zirconium oxide film 23B is made of zirconium oxide (ZrO ₂ ), scandium oxide (Sc ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), cerium oxide (CeO ₂ ), a film doped with at least one metal oxide selected from the group consisting of aluminum oxide (Al ₂ O ₃ ) and ytterbium oxide (Yb ₂ O ₃ ).

The molar ratio of zirconium oxide to the metal oxide (zirconium oxide/metal oxide) in the zirconium oxide film 23B is preferably 80/20 to 97/3, more preferably 85/15 to 95/5. more preferred. When the aforementioned molar ratio is 80/20 or more, high oxygen transport properties can be achieved. When the aforementioned molar ratio is 97/3 or less, the crystal structure becomes tetragonal or cubic and is stabilized, so high durability can be achieved. As an example, the zirconium oxide film 23B may be made of metal oxide-doped zirconium oxide with a zirconium oxide/metal oxide (molar ratio) of 92/8, preferably ZrO ₂ /Sc ₂ O, Y _{Sc2O3 -} doped ZrO2, _{Y2O3 -} doped ZrO2, _{CeO2 -} doped ZrO2 _, Al2 with _{2O3 , CeO2 , Al2O3} or _{Yb2O3 (} molar ratio) _{= 92/8} It may consist of _{O3 -} doped _ZrO2 or _{Yb2O3 -} doped ZrO2.

The zirconium oxide film 23B is endowed with electronic conductivity, and the oxygen supplied to the air flow path 24A side is permeated to the oxidation reaction space 22A side as oxygen ions (O ²⁻ ), thereby increasing the oxygen permeability. The zirconium film 23B is preferably electrically short-circuited on the oxidation reaction space 22A side and the air flow path 24A side.

For example, the zirconium oxide film 23B has a micro-via structure penetrating through the surfaces on the oxidation reaction space 22A side and the air flow path 24A side, and a material having electronic conductivity is embedded in the micro-via structure. The surface on the side of the oxidation reaction space 22A and the surface on the side of the air flow path 24A may be internally short-circuited. The microvia structure may be, for example, a microcylindrical hole structure.

Materials embedded in the microvia structure include metal oxides, metal doped metal oxides, metals, combinations thereof, and the like. More specifically, metal oxides such as SrFeO _3-δ , LaCrO _3-δ doped with Sr, Ca, Mg, etc., LaFeO _3-δ doped with Sr, Co, etc., BaFeO doped with Sr, Co, etc. Metal oxides doped with metals such as _3-δ , Pd, Pd—Ag alloys, metals such as Ni and Co, combinations of two or more of these, and the like. When two or more of these are combined, different materials may be embedded in the oxidation reaction space 22A side and the air flow path 24A side in the microvia structure. For example, a metal may be embedded in the oxidation reaction space 22A side. A metal oxide, a metal oxide doped with a metal, or the like may be embedded in the path 24A side.

Alternatively, as shown in FIG. 5, the zirconium oxide film 23B is provided with current collectors (not shown) on the oxidation reaction space 22A side and the air flow path 24A side surface, and the air flow path 24A side surface and the air flow path 24A side are provided with current collectors (not shown). The surface on the side of the oxidation reaction space 22A may be externally short-circuited by a conductor 25 or the like.

The reaction catalyst film 23C is not particularly limited as long as it is a catalyst that promotes the oxidation reaction between unreacted fuel gas and oxygen. good too. Further, instead of arranging the reaction catalyst film 23C, at least part of the oxidation reaction space 22A may be arranged or filled with the catalyst for the oxidation reaction described above.

The thickness of the oxygen permeable membrane 23 is not particularly limited, and is preferably in the range of 10 μm to 3000 μm, more preferably in the range of 10 μm to 500 μm, even more preferably in the range of 15 μm to 150 μm, from the viewpoint of oxygen permeability and mechanical strength. .

The thickness of the zirconium oxide film 23B is preferably in the range of 100 nm to 100 μm, more preferably in the range of 100 nm to 50 μm, from the viewpoint of suitably ensuring oxygen permeability.
Also, the thickness of the ceramic film 23A (preferably larger than the thickness of the zirconium oxide film 23B) is preferably in the range of 10 μm to 500 μm, more preferably in the range of 30 μm to 300 μm.

As shown in FIGS. 1 and 2, the other end of the second anode offgas pipe P7-2 is connected to the inlet of the oxidation reaction space 22A, and the branched cathode offgas pipe P7-2 is connected to the inlet of the air flow path 24A. The downstream end of P6-2 is connected.

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

The second fuel electrode off-gas is supplied to the oxidation reaction space 22A and mixed with oxygen that has migrated from the oxygen separator 24 through the oxygen permeable membrane 23 . As a result, an oxidation reaction occurs between unreacted fuel gas components (unreformed methane, unreacted hydrogen, unreacted carbon monoxide, etc.) in the second anode off-gas and oxygen, and carbon dioxide and water vapor are produced. generated. A complete oxidation gas pipe P8-1 is connected to the exit side of the oxidation reaction space 22A, and the complete oxidation gas is delivered from the oxidation reaction space 22A.

As shown in FIG. 1, the complete oxidation gas pipe P8-1 is connected to an inner flow path 55B of the reformer 54, which will be described later.

(reformer)
The reformer 54 of this embodiment has a multi-cylindrical shape, and includes an annular vaporization passage 55A arranged radially outward, and an inner passage radially arranged adjacent to the vaporization passage 55A. 55B. A partition wall 57 separates the vaporization channel 55A and the inner channel 55B.

The vaporization flow path 55A has an upper annular space filled with a reforming catalyst 58, and a lower side is a spiral flow path 55A-2 that is spirally formed in the axial direction of a cylindrical cylinder.
One end of the fuel gas pipe P1-1 and one end of the water supply pipe P2-2 are connected to the lower end (upstream side of the flow channel) of the vaporization flow channel 55A.
A fuel supply blower B1 is connected to the other end of the fuel gas pipe P1-1, and methane from the fuel gas source is supplied to the vaporization flow path 55A of the reformer 54 by the fuel supply blower B1.
The other end of the water supply pipe P2-2 is connected to the water tank 27. As shown in FIG. The water supply pipe P2-2 is provided with an ion exchange resin 56 and a pump 27B. The water stored in the water tank 27 is supplied to the reformer 54 through the ion exchange resin 56 by driving the pump 27B.

One end of a reformed gas pipe P1-2 is connected to the upper end (downstream side of the flow path) of the vaporization flow path 55A. 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. As shown in FIG.

One end of the complete oxidizing gas pipe P8-1 is connected to the upper end of the inner channel 55B (on the upstream side of the channel), and the other end of the complete oxidizing gas pipe P8-1 is connected to the oxidation reactor 20 with the oxygen permeable membrane. is connected to the oxidation reaction space 22A. The inner flow path 55B is supplied with the high-temperature complete oxidant gas delivered from the oxidation reaction space 22A through the complete oxidant gas pipe P8-1.

One end of the complete oxidation gas pipe P8-2 is connected to the lower end (downstream side of the flow channel) of the inner flow channel 55B, and the other end of the complete oxidation gas pipe P8-2 is connected to the condenser 26, which will be described later. there is The completely oxidizing gas discharged from the inner flow path 55B is sent to the later-described condenser 26 through the completely oxidizing gas pipe P8-2.

Since the high-temperature complete oxidation gas passes through the inner flow path 55B, the partition wall 57 separating the vaporization flow path 55A and the inner flow path 55B is heated by the complete oxidation gas. Therefore, in the vaporization channel 55A adjacent to the inner channel 55B, the reforming catalyst 58, the fuel gas, and the water are heated by the heat of the completely oxidized gas, the fuel gas is steam-reformed, and the steam-reformed fuel is The gas is delivered to the first fuel electrode 12A of the first fuel cell stack 12 through the reformed gas pipe P1-2, lowers the temperature of the high-temperature fully oxidized gas, and removes the water vapor contained in the fully oxidized gas. can be condensed and separated.

(Condenser)
A cooling water circulation flow path 26A is connected to the condenser 26, and cooling water from an exhaust heat input type absorption chiller 36, which will be described later, is circulated and supplied by driving a pump 26P, and sent out from the reformer 54. The fully oxidized gas is further cooled. This condenses the water vapor in the fully oxidized gas and separates and removes most of the water vapor contained in the fully oxidized gas. The condensed water is delivered to the water tank 27 through the water pipe P9.

The completely oxidized gas from which the water (liquid phase) has been removed by the condenser 26 is a gas with a high carbon dioxide concentration, and the gas is called a carbon dioxide-rich gas. The carbon dioxide rich gas is delivered to the carbon dioxide gas pipe P10. 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 delivered from the condenser 26 . Specifically, the concentration of any one or more of fuel gas such as methane, carbon monoxide, and hydrogen, carbon dioxide, and oxygen is detected. The composition detection unit 44 is connected to the control unit, and transmits the detected composition information of the carbon dioxide-rich gas to the control unit. Note that the control unit performs various controls so as to maximize the concentration of carbon dioxide gas and minimize components other than carbon dioxide.

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 downstream of the junction where the air electrode offgas pipes P6 from the first air electrode 12B and the second air electrode 14B are merged. In the second heat exchanger 32, heat is exchanged between the cathode offgas flowing through the cathode offgas pipe P6 and the oxidizing gas flowing through the oxidizing gas pipe P5, the oxidizing gas is heated, and the cathode offgas is converted into Cooled. The cathode off-gas passes through the second heat exchanger 32 and is supplied to the exhaust heat input type absorption chiller 36 .

(exhaust heat input type absorption chiller)
The exhaust heat input type absorption chiller 36 is a heat pump that uses exhaust heat to generate cold heat, and as an example, a steam/exhaust heat input type absorption chiller can be used. In the steam/exhaust heat input type absorption chiller, the water is separated from the absorbent by heating the absorbent (for example, lithium bromide aqueous solution, ammonia aqueous solution, etc.) that has absorbed water vapor with the heat of the air electrode off-gas. Reproduce. Water vapor is condensed in the air electrode off-gas obtained by heating and cooling the absorbing liquid, and the condensed water is supplied to the water tank 27 through the water pipe P36-2. After the water vapor is condensed and removed, the air electrode off-gas is sent to the exhaust pipe P36-1 and exhausted to the outside of the exhaust heat input type absorption chiller .

A pump for circulating the absorbing liquid and a pump for circulating water separated from the absorbing liquid (both not shown) are provided inside the exhaust heat input type absorption chiller 36 . These pumps are driven by DC motors, which can be driven by DC power generated by the first fuel cell stack 12 and the second fuel cell stack 14 . Although these pumps may be driven by AC motors, they are preferably driven by DC motors in terms of efficiency with less energy loss.

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

The cold heat generated by the exhaust heat input type absorption chiller 36 is sent to the condenser 26 via the cooling water flowing through the cooling water circulation flow path 26A, where the completely oxidized gas is cooled, and the completely oxidized gas is further cooled. The water vapor inside is condensed out.

The water tank 27 is connected to a cooling water circulation channel 26A, a heat dissipation circuit 37, and a heat medium channel (not shown) through which water flows as a heat medium for the absorption chiller 36 with waste heat input. In the cooling water circulation flow path 26A, the heat dissipation circuit 37, and the heat medium flow path, water is appropriately replenished from the water tank 27 through the replenishment system 67 described below when the water is insufficient.
Note that the exhaust heat input type absorption chiller 36 has, as an example, the ability to generate cooling water at -5°C to 12°C.

(replenishment system)
The water tank 27 is connected to a replenishment system 67 including a pipe P11, a pump 27A, and the like. 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, which will be 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. In addition, the pump 27A and the electromagnetic valve are controlled by a control section which will be 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. A liquid level sensor (not shown) is provided to detect the This liquid level sensor is connected to a control section, which will be described later, and outputs detection data of the liquid level (reserved amount of cooling water) to the control section. Thereby, the controller can grasp the amount of cooling water stored in each of the cooling tower 38, the cooling water circulation passage 26A, and the cooling water circulation passage 70A for liquefaction.

(Carbon dioxide gas liquefaction part)
The carbon dioxide-rich gas delivered to the carbon dioxide gas pipe P10 is sent to a carbon dioxide gas liquefaction unit 66 that includes a compressor (compression unit) 68, a cooling device (liquefaction device) 70, and the like.
The carbon dioxide-rich gas sent to the carbon dioxide gas liquefying section 66 is first compressed by the compressor 68 . The compressor 68 is driven by a DC motor (not shown) and can compress the carbon dioxide gas to 4 MPa or more. In addition, the DC motor of the compressor 68 is driven by the electric power obtained from the first fuel cell stack 12 and the second fuel cell stack 14. For example, when the system is started, an external commercial power source is used. or by power (surplus power) obtained from renewable energy power generation (not shown). Examples of renewable energy power generation include photovoltaic 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, and the like. good. The compressor 68 is not limited to being driven by a DC motor, and may be driven by an AC motor.

Since the DC motor of the compressor 68 can be directly driven using the DC power obtained from 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 is converted into AC power, and the AC power is used to drive the AC motor. Note that the DC motor of the compressor 68 is controlled by the controller.

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

A liquefaction cooling water circulation path 70A is piped to the cooling device 70, and a circulation pump 78 controlled by a control unit is attached to the liquefaction cooling water circulation path 70A. The liquefaction cooling water circulation path 70A is circulated with cooling water from the exhaust heat input type absorption chiller 36, and cools the compressed carbon dioxide-rich gas supplied from the compressor 68 to generate liquefied carbon dioxide.

A temperature sensor 80 that detects the temperature of the cooling water flowing into the cooling device 70 is provided in the liquefaction cooling water circulation path 70A. Cooling water temperature data measured by the temperature sensor 80 is sent to the controller. A flow rate sensor (not shown) for measuring the flow rate of the cooling water may be provided in the liquefaction cooling water circulation path 70A.

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

The fuel cell power generation system 10A is provided with a control section (not shown) that controls the entire system. It is composed of a CPU, a ROM, a RAM, a memory, and the like. The memory stores data, procedures, and the like necessary for flow rate adjustment processing, cooling water temperature adjustment processing, and processing during normal operation, which will be described later. The control unit is connected to the flow control valve 42, the composition detection unit 44, the exhaust heat input type absorption chiller 36, and the like. The control unit controls the flow control valve 42, the composition detection unit 44, the exhaust heat input type absorption chiller 36, and the like. Note that the control unit is also connected to devices other than those described above.

In the fuel cell power generation system 10A, pumps, blowers, and other accessories are driven by electric power generated by the fuel cell power generation system 10A. In order to efficiently use the direct current power generated by the fuel cell power generation system 10A without converting it to alternating current, the auxiliary equipment is preferably driven by direct 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, the fuel supply blower B1 sends fuel gas (methane) from the fuel gas source to the reformer 54 through the fuel gas pipe P1-1, and the reformer 54 reforms the fuel gas. quality is done.
The reformed fuel gas is supplied to the first fuel electrode 12A of the first fuel cell stack 12 through the fuel gas pipe P1-2.
Steam for steam reforming is supplied from the steam pipe P2 to the first fuel electrode 12A through the fuel gas pipe P1-2.

At the first fuel electrode 12A of the first fuel cell stack 12, the fuel gas is steam reformed to produce hydrogen and carbon monoxide. In addition, carbon monoxide and hydrogen are produced by a shift reaction between the produced 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 reactions described above occur to generate power. From the first fuel electrode 12A of the first fuel cell stack 12, the first fuel electrode off-gas is sent to the first fuel electrode off-gas pipe P7. Further, from the first air electrode 12B, the air electrode off-gas is sent to the air electrode off-gas pipe P6.

The first fuel electrode off-gas sent out 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.
Electric power is generated in the second fuel cell stack 14 in the same manner as in the first fuel cell stack 12 . The second fuel electrode off-gas is delivered from the second fuel electrode 14A of the second fuel cell stack 14 to the second fuel electrode off-gas pipe P7-2. Further, from the second air electrode 14B, the air electrode off-gas is delivered to the air electrode off-gas pipe P6.

The cathode off-gas is supplied to the exhaust heat input type absorption chiller 36 via the second heat exchanger 32 . In the second heat exchanger 32, heat is exchanged between the cathode off-gas and the oxidizing gas, and the oxidizing gas is heated by the cathode off-gas. In the exhaust heat input type absorption chiller 36, as described above, cold heat is generated using the heat of the air electrode off-gas.

The second fuel electrode off-gas is supplied to the oxidation reaction section 22 of the oxidation reactor 20 with an oxygen permeable membrane and flows through the oxidation reaction space 22A.

The cathode offgas branched to the branched cathode offgas pipe P6-2 is supplied to the oxygen separator 24 of the oxidation reactor 20 with an oxygen permeable membrane. The air electrode off-gas supplied to the oxygen separation section 24 flows through the air flow path 24A. In the air channel 24A, oxygen contained in the cathode off-gas permeates the oxygen permeable membrane 23 and moves to the oxidation reaction space 22A side. In the oxidation reaction space 22A of the oxidation reaction section 22, an oxidation reaction occurs between unreacted fuel gas (methane, hydrogen, carbon monoxide, etc.) in the second fuel electrode offgas and oxygen to produce carbon dioxide and water vapor.

In the oxidation reactor 20 with an oxygen-permeable membrane, since the oxygen-permeable membrane 23 includes the zirconium oxide membrane 23B, LSCF (compound composed of La, Sr, Co, Fe and oxygen), BSCF (Ba, Sr, Co, Fe and oxygen), etc., the formation and accumulation of carbonate due to the reaction between carbon dioxide and membrane components is suppressed, and the decrease in oxygen permeability in the oxygen permeable membrane 23 can be suppressed. . Thereby, the oxidation reaction between the unreacted fuel gas and oxygen in the oxidation reaction section 22 of the oxidation reactor 20 with the oxygen permeable membrane can be promoted.

In the oxidation reaction section 22 of the oxygen permeable membrane equipped oxidation reactor 20, the reaction catalyst membrane 23C accelerates the oxidation reaction between the oxygen permeated through the oxygen permeable membrane 23 and the unreacted fuel gas to produce carbon dioxide gas. to generate Furthermore, since the oxidation reaction space 22A is formed spirally and has a long passage length, it is possible to take a long time for the oxidation reaction, and a sufficient amount of air flows from the air passage 24A to the oxidation reaction space 22A side. Oxygen can be transferred to carry out the oxidation reaction sufficiently and efficiently. As a result, complete oxidation gas with an increased concentration of carbon dioxide gas can be discharged from the oxidation reaction section 22 .

A fully oxidizing gas containing carbon dioxide and water vapor is delivered from the oxidation reaction space 22A to the fully oxidizing gas pipe P8-1. The fully oxidizing gas sent to the fully oxidizing gas pipe P8-1 is supplied to the condenser 26 through the inner flow path 55B of the reformer 54. As shown in FIG.

In the reformer 54, in the vaporization passage 55A, the mixed gas of fuel gas and steam and the reforming catalyst 58 are heated by heat exchange with the completely oxidizing gas, and the steam reforming reaction produces hydrogen and carbon monoxide. generated. In addition, carbon monoxide and hydrogen are produced by a shift reaction between the produced carbon monoxide and water vapor. A reformed gas containing unreacted fuel gas (methane), hydrogen, carbon monoxide and carbon dioxide is supplied to the first fuel electrode 12A through a reformed gas pipe P1-2.

Since the lower side of the vaporization flow path 55A is a long spiral flow path 55A-2 spirally formed in the direction of the cylinder axis of the cylindrical shape, the water supplied together with the fuel gas has a long spiral flow path 55A. It is sufficiently heated to become water vapor while passing through -2 over time. After the heated fuel gas and water vapor flow through the spiral flow path 55A-2, they pass through the reforming catalyst 58 heated by the heat of the complete oxidizing gas. occur. On the other hand, the temperature of the high-temperature fully oxidized gas decreases in the process of effectively utilizing the heat, and part of the water vapor contained in the fully oxidized gas can be condensed and recovered, or it can be contained in the fully oxidized gas with a small amount of cold heat supply. The temperature is lowered so that most of the water vapor can be easily condensed and separated.

The fully oxidized gas supplied to the condenser 26 is cooled by the cooling water from the exhaust heat input type absorption chiller 36 circulated and supplied through the cooling water circulation passage 26A, and the water vapor in the fully oxidized gas is condensed. be. The condensed water is sent to the water tank 27 through the water pipe P9 and stored in the water tank 27 .

The completely oxidized gas from which water vapor has been removed by the condenser 26 becomes a carbon dioxide-rich gas having a high carbon dioxide concentration, and is sent to the composition detector 44 via the carbon dioxide gas pipe P10. The composition detector 44 detects the composition of the carbon dioxide-rich gas and transmits the detected information to the controller.

Based on the composition information transmitted from the composition detection unit 44, the control unit controls the flow rate adjustment valve 42 to adjust the amount of air electrode offgas branched to the branch air electrode offgas pipe P6-2, and exhaust heat input type The absorption chiller 36 controls the temperature of cooling water sent to the cooling water circulation passage 26A and the like.

In the flow rate adjustment process, it is determined whether or not the concentration of the fuel gas is within the threshold value G1 in the composition information of the carbon dioxide rich gas detected by the composition detector 44 . Here, the threshold G1 is a sufficiently low concentration in the carbon dioxide rich gas and can be set to about 0.1% by volume to 5% by volume, and more preferably in the range of 0.1% to 1% by volume. preferable. When the fuel gas concentration is higher than the threshold value G1, the flow control valve 42 is controlled to increase the flow rate of the cathode offgas branched to the branched cathode offgas pipe P6-2. As a result, the amount of oxygen that permeates the oxygen permeable membrane 23 and moves to the oxidation reaction space 22A increases, and the oxidation reaction takes place in the oxidation reaction space 22A, thereby reducing the amount of unreacted fuel gas contained in the carbon dioxide-rich gas. be able to.

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 section 66 and compressed, and the compressed carbon dioxide-rich gas is sent to the cooling device 70 . The cooling device 70 cools the compressed carbon dioxide-rich gas with cooling water from the exhaust heat input type absorption chiller 36 to generate liquefied carbon dioxide.

Since the exhaust heat input type absorption chiller 36 uses the exhaust heat of the air electrode off-gas to generate cold heat, it is a type of chiller that compresses and expands the refrigerant by driving the compressor with a motor (for example, a turbo It is possible to efficiently generate cold energy (used for cooling water to make cooling water) with less power than when cold energy is generated by a refrigerator or the like.

From the phase diagram of carbon dioxide gas shown in FIG. 4, as an example, carbon dioxide gas compressed to 4 MPa or more is liquefied 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, 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. with cooling water. liquefied carbon dioxide is obtained by cooling with Note that 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)
Any one of the temperature (measured by the temperature sensor 74) and pressure (measured by the pressure sensor 76) of the high-pressure carbon dioxide gas that has passed through the compressor 68, or the amount of carbon dioxide gas remaining without being liquefied According to one or more measurement results, the control unit determines the temperature of the cooling water supplied to the cooling device 70 (measured by a temperature sensor 80), the flow rate (measured by a flow sensor (not shown)), etc. The operation of the refrigerator 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 calculates the amount of cold heat for maximizing the amount of liquefaction of carbon dioxide gas according to the temperature and pressure of the collected carbon dioxide gas, or the amount of carbon dioxide gas remaining at the time of liquefaction. , the temperature of the cooling water can be lowered accordingly, the flow rate of the circulating cooling water can be increased, or both of these can be used in combination.

In addition, inside the cooling device 70, liquefied carbon dioxide accumulates at the bottom, and unliquefied carbon dioxide gas remains above the liquefied carbon dioxide, so 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 without being liquefied inside the cooling device 70 (the internal space volume of the cooling device 70 is known).

The liquefied carbon dioxide generated in the carbon dioxide gas liquefying section 66 in this manner is sent to the tank 84 via the pipe P15 and the pump 82 and stored therein. Note that the liquefied carbon dioxide stored in the tank 84 can also be used for commercial and industrial purposes as in the conventional case.

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 . Note that the liquefied carbon dioxide stored in the tank 84 may be transported by a lorry 86 or the like, or may be transported by a pipeline or the like.

In the fuel cell power generation system 10A of the present embodiment, since the second fuel electrode off-gas sent from the second fuel electrode 14A of the second fuel cell stack 14 is oxidized in the oxidation reaction section 22, the second fuel cell stack The amount of unreacted fuel gas used for power generation in the second fuel cell stack 14 increases compared to the case where the first fuel electrode off-gas is oxidized before being used for power generation in 14 . Therefore, power generation efficiency in the second fuel cell stack 14 can be enhanced.

Further, in the oxidation reaction section 22, carbon dioxide and water vapor are generated by an oxidation reaction between the unreacted fuel gas contained in the second fuel electrode off-gas and oxygen. Therefore, it is possible to recover high-concentration carbon dioxide by subtracting the fuel gas from the second anode off-gas. In addition, only oxygen in the air electrode off-gas is supplied to the oxidation reaction section 22, and the second fuel electrode off-gas contains a smaller amount of unreacted fuel gas than the first fuel electrode off-gas, High carbon content. Therefore, the amount of unreacted fuel gas to be oxidized in the oxidation reaction section 22 and the amount of oxygen required to oxidize the unreacted fuel gas can be reduced.

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

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

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

In addition, in the fuel cell power generation system 10A of the present embodiment, by arranging the oxidation reaction section 22 adjacent to the oxygen permeable membrane 23 of the oxygen separation section 24, the oxidation reaction section 22 and the oxygen separation section 24 are integrally formed to form a compact structure. An oxidation reactor 20 with an oxygen permeable membrane can be constructed.

In addition, in the fuel cell power generation system 10A of the present embodiment, the heat of the air electrode off-gas is used to generate cold heat in the exhaust heat input type absorption chiller 36, so the first fuel cell stack 12 and the second fuel cell stack Exhaust heat from 14 can be effectively used. Further, since the air electrode off-gas contains a large amount of water vapor, the water vapor is condensed during heat exchange in the exhaust heat input type absorption chiller 36, and the heat of condensation can also be effectively used.

In addition, in the fuel cell power generation system 10A of the present embodiment, the control unit detects the amount of cooling water stored in each buffer tank of the cooling tower 38, the cooling water circulation passage 26A, and the cooling water circulation passage 70A for liquefaction from the liquid level sensor. It is grasped based on the detection data, and when it is determined that the amount of stored cooling water is less than the preset lower limit, the solenoid valve and the pump 27A are controlled, and the water used for the cooling water is stored in the water tank 27. can be replenished from In this way, when the cooling water runs short, there is no need to supply water from an external water supply or the like, and the amount of external dependence on water can be reduced.

In the present embodiment, carbon dioxide is separated from the fully oxidized gas by condensing and removing the water vapor in the fully oxidized gas with the condenser 26, but carbon dioxide is separated from the fully oxidized gas by other means, for example, a carbon dioxide separation membrane. may be separated, or 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.

In addition, in the oxidation reactor 20 with an oxygen permeable membrane of the present embodiment, the outside is the oxidation reaction section 22 and the inside is the oxygen separation section 24, but the outside is the oxygen separation section 24 and the inside is the oxidation reaction section. 22 may be used. When the outer side is the oxygen separation section 24 and the inner side is the oxidation reaction section 22, the zirconium oxide film 23B, the ceramic film 23A, and the reaction catalyst film 23C are laminated in this order from the outer oxygen separation section 24 to the inner oxidation reaction section 22. It is

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

FIG. 6 shows a fuel cell power generation system 10B according to a second embodiment of the invention. The fuel cell power generation system 10B is a system that produces carbon from carbon dioxide gas. A carbon production section 166 is provided on the downstream side of the carbon dioxide gas pipe P10 instead of the carbon dioxide gas liquefaction section 66 of the fuel cell power generation system 10B of the first embodiment.

In this embodiment, 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). there is
Further, in the present embodiment, the circulating gas pipe P3 is branched from the second anode offgas pipe P7-2, and the circulating gas pipe P3 is connected to the fuel gas pipe P1. A circulation gas blower B3 is provided in the circulation gas pipe P3.

A first heat exchanger 30 is provided in an intermediate portion of the fuel gas pipe P1. A complete oxidizing gas pipe P8 for delivering a complete oxidizing gas is connected to the outlet side of the oxidation reaction space 22A of the oxidation reactor 20 with an oxygen permeable membrane. via and the other end is connected to the condenser 26 . In the first heat exchanger 30, the fuel gas is heated by heat exchange between the fuel gas and the fully oxidized gas, while the high-temperature fully oxidized gas is cooled to condense part of the water vapor contained in the fully oxidized gas. It can be separated or cooled so that most of the water vapor can be condensed off with little cold supply.

The completely oxidized gas that has passed through the first heat exchanger 30 is sent to the condenser 26, and the completely oxidized gas from which water vapor has been removed by the condenser 26 becomes a carbon dioxide-rich gas with a high carbon dioxide concentration. It is sent to the carbon dioxide gas pipe P10 and sent to the composition detector 44 . The composition detector 44 detects the composition of the carbon dioxide-rich gas and transmits the detected information to the controller.

Based on the composition information transmitted from the composition detection unit 44, the control unit controls the flow rate adjustment valve 42 to adjust the amount of air electrode offgas branched to the branch air electrode offgas pipe P6-2, and exhaust heat input type The absorption chiller 36 controls the temperature of the cooling water sent to the cooling water circulation passage 26A. Specifically, the controller executes a flow rate adjustment process and a cooling water temperature adjustment process.
The carbon dioxide gas sent to the carbon dioxide gas pipe P10 is sent to the carbon production section 166 .

(Structure of carbon production department)
The carbon production unit 166 includes a water electrolysis device 170, a pipe P114, a hydrogen blower 172, a pipe P115, an oxygen blower 174, an oxygen tank 176, a powder carbon generator (carbon generation unit) 178, and the like.

Water in the water tank 27 is supplied to the water electrolysis device 170 through a pipe P116, a pump 180, and a water purification device 182. The water purifier 182 purifies the water from the water tank 27 (removes foreign matter, adjusts pH, etc.). The water electrolysis device 170 can generate hydrogen gas and oxygen gas by electrolyzing purified water using power obtained from the first fuel cell stack 12 and the second fuel cell stack 14 . . The water electrolysis device 170 can also electrolyze water using power (so-called “clean energy”) obtained by renewable energy generation (not shown). Examples of renewable energy power generation include photovoltaic 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, and the like. good. That is, from the viewpoint of reducing carbon dioxide in the atmosphere or suppressing the release of carbon dioxide into the atmosphere, the DC power obtained in the first fuel cell stack 12 and the second fuel cell stack 14 and the regeneration It is preferable to use power obtained from renewable energy power generation.

The water electrolysis device 170 electrolyzes water using the DC power obtained from the first fuel cell stack 12 and the second fuel cell stack 14 or the power obtained from renewable energy power generation. , water can be electrolyzed more efficiently than in the case where the AC power of a power generator that emits carbon dioxide gas is converted into DC power and used for electrolysis. Note that the water electrolysis device 170 is controlled by a control unit.

Hydrogen gas generated by the water electrolysis device 170 is sent to the powdered carbon generator 178 via the pipe P114 and the hydrogen blower 172, and oxygen gas is sent to the oxygen tank 176 via the pipe P115 and the oxygen blower 174. It is stored in tank 176 . The hydrogen blower 172 and the oxygen blower 174 are controlled by the controller.

(Configuration of powder carbon generator)
The powdered carbon generator 178 includes an outer cylinder 171, a cylindrical partition wall 173 disposed inside the outer cylinder 171, and a closing member that closes the openings of the outer cylinder 171 and the cylindrical partition wall 173 on the end side in the cylinder axis direction. The inside formed by the member 175 is sealed and has a multiple cylindrical shape.

A gas channel 178A is provided between the outer cylinder 171 and the partition wall 173, and a carbon fixation portion 178B is provided on the inner peripheral side of the cylindrical partition wall 179. The gas flow channel 178A and the carbon fixation portion 178B are separated by the partition wall. 173 is isolated.

The gas flow path 178A has a spiral passage forming member 177 arranged therein, and is formed in a spiral shape toward the cylinder axis direction of the powdered carbon generator 178 .

Carbon dioxide gas sent from the condenser 26 and hydrogen gas sent from the water electrolysis device 170 are supplied to the carbon fixing section 178B. In the carbon fixing section 178B, a reduction reaction such as the following formula (5) is caused by using a reduction catalyst for carbon dioxide gas and hydrogen gas.
_CO2 + _2H2- >C ₊ 2H2O (5)

The C produced by the reduction reaction is powdered carbon and can be discharged from the lower portion of the carbon fixing portion 178B. Further, the H ₂ O generated by the reduction reaction is specifically water vapor, and the water vapor is sent to the condenser 26 via the pipe P117.

The memory of the control unit of the present embodiment stores data, procedures, and the like necessary for flow rate adjustment processing, cooling water temperature adjustment processing, and processing during normal operation, which will be described later. The control unit is connected to the flow control valve 42, the composition detection unit 44, the exhaust heat input type absorption chiller 36, and the like. The control unit controls the flow control valve 42, the composition detection unit 44, the exhaust heat input type absorption chiller 36, and the like.

In the fuel cell power generation system 10B, pumps, blowers, and other accessories are driven by electric power generated by the fuel cell power generation system 10B. In order to efficiently use the direct current power generated by the fuel cell power generation system 10B without converting it to alternating current, the auxiliary equipment is preferably driven by direct current.

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

The water electrolysis device 170 electrolyzes the water sent from the water purification device 182 to generate hydrogen gas and oxygen gas. The carbon dioxide-rich gas delivered to the carbon dioxide gas pipe P10 is sent to the powdered carbon generator 178.
In the carbon fixing section 178B, the carbon dioxide gas sent from the condenser 26 and the hydrogen gas sent from the water electrolysis device 170 are supplied to cause a reduction reaction such as the formula (5) described above.

In order to initiate the above reaction, it is necessary to raise the ambient temperature to a high temperature. However, since heat is generated by the reaction, it is not necessary to apply heat from the outside once the reaction has started.

When starting the powdered carbon generator 178, first, hydrogen gas and oxygen gas are supplied to the gas flow path 178A and ignited. The combustion flame generated by the combustion reaction between the hydrogen gas and the oxygen gas and the high-temperature exhaust gas (water vapor) pass through the gas passage 178A, and the heat of the combustion flame and the exhaust gas fixes carbon through the partition wall 173. is transmitted to conversion unit 178B. Exhaust gas (water vapor) is discharged from the end of the gas flow path 178A.

The gas flow path 178A of this embodiment is spirally formed in the direction of the cylinder axis of the powdered carbon generator 178, and has a long flow path length. It can be sufficiently applied to the carbon fixing portion 178B. As a result, a reduction reaction such as the above formula (5) can be reliably caused.

After ignition, if heat is generated by the reaction of the above formula (5), the supply of oxygen gas and hydrogen gas to the gas passage 178A is stopped.
Carbon dioxide gas and hydrogen gas are continuously supplied to the carbon fixing section 178B, which is heated to a high temperature, so that powdered carbon ("C" in formula (5)) can be continuously produced. The generated powdered carbon can be taken out from below the carbon fixing portion 178B. Also, the water vapor (H ₂ O in formula (5)) generated by the reaction between the carbon dioxide gas and the hydrogen gas is discharged from below the carbon fixation portion 178B. Note that the water vapor discharged from the carbon fixation portion 178B is sent to the condenser 26 via the pipe P117, and cooled by the condenser 26 to become water.

In the fuel cell power generation system 10B of the present embodiment, the first fuel cell stack 12 and the second fuel cell stack 14 to the carbon production unit 166 are continuously connected and provided on-site. can efficiently produce powdered carbon continuously.
Powdered carbon is not released into the atmosphere as carbon dioxide gas unless it is ignited and burned, and can suppress the release of carbon dioxide gas into the atmosphere.
In addition, powdered carbon can be easily transported to a storage site, and if it is not placed under conditions where an ignition source and oxygen are available, it can be stably fixed for a long period of time even if it is simply dumped on the ground or landfilled underground. becomes possible. The produced powdery carbon can also be used commercially and industrially as carbon black or the like.

In the fuel cell power generation system 10B of the present embodiment, powdered carbon is produced from carbon dioxide gas, but a carbon product manufacturing device 184 that converts the powdered carbon into graphite, carbon nanotubes, diamond, or the like may be further added. In the carbon product manufacturing apparatus 184, for example, the collected powdered carbon is processed into high temperature (electric heater temperature rise), high pressure (electric high pressure press ) environment, synthetic diamond powder can be obtained by a known technique. Further, for example, the collected powdered carbon is carbonized by a known technique such as an arc discharge method, a laser ablation method, a CVD method, etc., using power generated by the fuel cell power generation system 10B or power from renewable energy. Nanotubes can be obtained. Furthermore, graphite can be obtained from the collected powdered carbon by a known technique using power generated by the fuel cell power generation system 10B, power generated by renewable energy, or the like.
By using graphite, carbon nanotubes, or diamond powder as the carbon powder, it does not burn easily even if there is an ignition source or oxygen, and even if it is piled up on the ground, it can safely and stably fix carbon for a long time. As a result, there are no restrictions on storage locations, and energy loss and costs associated with transportation and injection can be reduced. Graphite can be used in pencil leads and brake pads for automobiles, carbon nanotubes can be used as semiconductors and structural materials, and synthetic diamond powder can be used in construction and as diamond cutter blades for machine tools. can.
Note that this carbon product manufacturing device 184 is also a part of the carbon manufacturing section 166, and is provided on-site in the fuel cell power generation system 10B. In addition, products manufactured using powdered carbon are not limited to the above carbon products, and carbon materials such as carbon nanohorns and fullerenes may be manufactured by known techniques and used in commerce and industry.

In the powdered carbon generator 178 of the present embodiment, the outer side is the gas flow path 178A, and the inner side is the carbon fixing portion 178B. may be used as the carbon immobilization portion 178B.

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

The fuel cell power generation system 10C of this embodiment differs from the first embodiment mainly in that a third heat exchanger 34 and a condenser 35 are provided in the path of the first anode offgas pipe P7.

As shown in FIG. 7, 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 . A first anode offgas pipe P7 from the first anode 12A to the condenser 35 is denoted by P7A. The first fuel electrode offgas 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 . A first fuel electrode offgas pipe P7 from the condenser 35 to the second fuel electrode 14A is denoted by P7B. One end of a water pipe P9-2 is connected to the liquid side outlet of the condenser . The other end of the water pipe P9-2 is connected to the water tank 27. As shown in FIG. A cooling water circulation passage 35A is connected to the condenser 35, and the cooling water from the exhaust heat input type absorption chiller 36 is circulated and supplied by driving a pump 35P. As a result, the first anode off-gas is cooled and water vapor in the first anode off-gas is condensed. The condensed water is sent to the water tank 27 through the water pipe P9-2.

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

Also in this embodiment, power generation is performed in the first fuel cell stack 12 in the same manner as in the fuel cell power generation system 10A of the first embodiment. 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 the regenerated fuel gas described later in the third heat exchanger 34 and supplied to the condenser 35. be done. In the condenser 35, the first fuel electrode off-gas is further cooled by cooling water circulating in the cooling water circulation flow path 35A, and water vapor in the first fuel electrode off-gas is condensed. Here, the temperature of the cooling water circulating in the cooling water circulation flow path 35A is such that the amount of water vapor remaining in the regenerated fuel gas is such that the power generation efficiency in the second fuel cell stack 14 is improved. is set to condense. The condensed water is sent to the water tank 27 through 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 from the first fuel electrode off-gas before water is separated by the third heat exchanger 34 is It is heated by the exchange and supplied to the second fuel electrode 14A. In the second fuel cell stack 14, power is generated in the same manner 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 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 can be improved. can be done.

Also in the present embodiment, in the oxidation reaction section 22 of the oxidation reactor 20 with an oxygen permeable membrane, carbon dioxide and water vapor are produced by an oxidation reaction between oxygen and unreacted fuel gas contained in the second fuel electrode off-gas. generated. Therefore, the fuel gas can be reduced from the second fuel electrode off-gas, high-concentration carbon dioxide can be recovered, and liquefied carbon dioxide can be efficiently obtained.

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

As shown in FIG. 8, in the fuel cell power generation system 10D of the present embodiment, the first fuel cell stack 62 and the second fuel cell stack 64 are the hydrogen ion conducting solid oxide fuel cells of the first embodiment. Instead, a solid oxide fuel cell (SOFC: Solid Oxide Fuel Cell) is used. Therefore, the following reaction occurs 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 and electrons in the oxidant gas react with each other to generate oxygen ions, as shown in the following formula (6). 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⁻ (6)

On the other hand, in the first fuel electrode 62A of the first fuel cell stack 62, as shown in the following equations (7) and (8), oxygen ions passing through the electrolyte layer 62C are converted into hydrogen and monoxide in the fuel gas. It reacts with carbon to produce water vapor, carbon dioxide and electrons. Electrons generated in the first fuel electrode 62A move from the first fuel electrode 62A through an external circuit to the first air electrode 62B, thereby generating power.

(Anode reaction)
H ₂ +O ²⁻ →H ₂ O+2e ⁻ (7)
CO+O ²⁻ →CO ₂ +2e ⁻ (8)

In the solid oxide fuel cell, water vapor is generated at the first fuel electrode 62A and the second fuel electrode 64A. 2 The amount of water vapor contained in the fuel electrode off-gas is large. On the other hand, no water vapor is generated at the first air electrode 62B and the second air electrode 64B. The air electrode off-gas supplied to the exhaust heat input type absorption chiller 36 is exhausted from the exhaust pipe P36-1 after heat exchange.

Other configurations of the fuel cell power generation system 10D of the present embodiment are the same as those of the third embodiment, and a third heat exchanger 34 and a condenser 35 are provided in the path of the first anode 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 large compared to the fuel cell power generation system 10C, the water vapor amount to be removed by condensation in the condenser 35 is increased. The temperature of the cooling water circulating in the cooling water circulation flow path 35A is set. The condensed water is sent to the water tank 27 through the water pipe P9-2.

In the present embodiment, since the regenerated fuel gas generated by separating a part of 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 64 can be improved. can be done.

Also in the present embodiment, in the oxidation reaction section 22 of the oxidation reactor 20 with an oxygen permeable membrane, carbon dioxide and water vapor are produced by an oxidation reaction between oxygen and unreacted fuel gas contained in the second fuel electrode off-gas. generated. Therefore, the fuel gas can be reduced from the second fuel electrode off-gas, high-concentration carbon dioxide can be recovered, and liquefied carbon dioxide can be efficiently obtained.

[Fifth embodiment]
Next, a fifth embodiment of the present invention will be described. In the fuel cell power generation system of the fifth embodiment, instead of the oxygen permeable membrane used in the first to fourth embodiments, hydrogen contained in the fuel electrode off-gas supplied to the first flow path is used as the second Using a hydrogen permeable membrane permeable to the channel side, and a catalyst layered on the first channel side of the oxygen permeable membrane, layered on the second channel side of the hydrogen permeable membrane, and permeating the oxygen and hydrogen permeable membranes It was changed to a catalyst that accelerates the oxidation reaction with hydrogen. In the fuel cell power generation system of this embodiment, oxygen and hydrogen permeated through the hydrogen permeable membrane undergo an oxidation reaction on the second channel side, and a gas with a high carbon dioxide concentration is obtained on the first channel side.

Furthermore, when carbon monoxide is also contained in the fuel electrode off-gas, the chemical equilibrium changes due to the selective separation of hydrogen, and water vapor and carbon monoxide in the fuel electrode off-gas undergo a shift reaction to produce carbon monoxide. Converts to carbon and hydrogen. Therefore, the hydrogen in the fuel electrode off-gas is separated to the second channel side, so that a gas with a higher carbon dioxide concentration can be efficiently obtained.

In this embodiment, water (water vapor) generated by the oxidation reaction between oxygen and hydrogen permeating the hydrogen-permeable membrane is exhausted to the outside through an exhaust pipe connected to the outlet side of the second flow path.

The fuel cell power generation system of this embodiment may further include a water vapor separation section that separates water vapor from the gas discharged from the first flow path of the reaction device in the same manner as in the first to fourth embodiments described above. Alternatively, the water vapor separation section may not be provided. For example, when hydrogen ion conducting solid oxide fuel cells are used as the two fuel cells, if carbon monoxide is contained in the fuel electrode off-gas, etc., The concentration of water vapor contained in the gas is low, and a gas with a higher carbon dioxide concentration can be obtained without providing a water vapor separation section.

The hydrogen-permeable membrane used in the present embodiment is not particularly limited as long as it has hydrogen permeability, and examples thereof include a palladium alloy membrane.

[Other embodiments]
Although one embodiment of the fuel cell power generation system of the present invention has been described above, the present invention is not limited to the above, and can be implemented in various modifications without departing from the spirit of the present invention. It goes without saying that

Other fuel cells such as molten carbonate fuel cells (MCFC), phosphoric acid fuel cells (PAFC), and polymer electrolyte fuel cells (PEFC) can also be used in the present invention.

The fuel cell in the fuel cell power generation system of the present invention may be a fuel cell comprising an air electrode, an electrolyte and a fuel electrode, or may be a fuel cell stack in which a plurality of fuel cells are stacked.

For example, the fuel cell power generation system of the present invention is not limited to having two fuel cells, and may have one fuel cell or three or more fuel cells. When the fuel cell power generation system of the present invention includes a plurality of fuel cells, the fuel electrodes in the plurality of fuel cells are arranged in series, and the fuel electrode off-gas discharged from the fuel electrode on the upstream side is discharged from the fuel electrode on the downstream side. The fuel electrode off-gas supplied to the fuel electrode and discharged from the most downstream fuel electrode is supplied to the first flow path, and the air electrode off-gas discharged from at least one of the air electrodes in the plurality of fuel cells is supplied to the first flow path. It may be configured to be supplied to two channels.

Further, the gas sent out from the first flow path is not limited to the gas in which all the unreacted fuel gas is oxidized, and may be a gas containing a part of the unreacted fuel gas.

10A, 10B, 10C, 10D Fuel cell power generation system 12, 62 First fuel cell stack (fuel cell)
12A, 62A first fuel electrode (fuel electrode)
12B, 62B first air electrode (air electrode)
14, 64 second fuel cell stack (fuel cell)
14A, 64A Second fuel electrode (fuel electrode)
14B, 64B Second air electrode (air electrode)
20 Oxidation reactor with oxygen permeable membrane (reactor)
22A oxidation reaction space (first channel)
23 Oxygen permeable membrane 23C Reaction catalyst membrane (catalyst)
24A air flow path (second flow path)
26 Condenser (water vapor separation section)
68 compressor (compression part)
70 cooling device (liquefying device)
170 water electrolysis device 178 powder carbon generator (carbon generator)

Claims (11)

a first flow path to which fuel gas is supplied;
a second flow path to which a gas containing oxygen is supplied;
an oxygen permeable membrane that separates the first channel and the second channel and allows oxygen contained in the gas supplied to the second channel to permeate to the first channel side;
a catalyst that is provided in the first flow path and promotes an oxidation reaction between the fuel gas and oxygen that permeates the oxygen permeable membrane;
with
The oxygen permeable film comprises a zirconium oxide film ,
The cylindrical oxygen permeable membrane is arranged inside the outer cylinder,
The annular first flow path or the annular second flow path is positioned between the outer cylinder and the oxygen permeable membrane, and the second flow path or the first flow path is located on the inner peripheral side of the oxygen permeable membrane. the road is located
When the annular first channel is positioned between the outer cylinder and the oxygen permeable membrane, and the second channel is positioned on the inner peripheral side of the oxygen permeable membrane, the first channel is A belt-shaped outer spiral passage forming member is spirally formed in the cylinder axial direction, and the second flow path is formed by spirally forming a belt-shaped inner spiral passage forming member in the cylinder axial direction,
When the annular second flow path is positioned between the outer cylinder and the oxygen permeable membrane, and the first flow path is positioned on the inner peripheral side of the oxygen permeable membrane, the second flow path is A band-shaped outer spiral passage forming member is spirally formed in the cylinder axial direction, and the first flow path is formed by a band-shaped inner spiral passage forming member spirally formed in the cylinder axial direction. Reactor . 2. The reactor according to claim 1, wherein said zirconium oxide film is a film obtained by doping zirconium oxide with at least one metal oxide selected from the group consisting of scandium oxide, yttrium oxide, cerium oxide, aluminum oxide and ytterbium oxide. . 3. The reactor according to claim 2, wherein the molar ratio of said zirconium oxide to said metal oxide (zirconium oxide/metal oxide) in said zirconium oxide film is 80/20 to 97/3. The reactor according to any one of claims 1 to 3, wherein the zirconium oxide film has an electrically short-circuited surface on the first channel side and a surface on the second channel side. The zirconium oxide film has a micro-via structure penetrating a surface on the side of the first flow channel and a surface on the side of the second flow channel, and a material having electronic conductivity is embedded in the micro-via structure. and a surface on the side of the second flow path are internally short-circuited, or a current collector is further provided on the surface on the side of the first flow path and the surface on the side of the second flow path, and the surface on the side of the first flow path and 5. The reactor according to claim 4, wherein the surface on the side of the second channel is externally short-circuited. The reactor according to any one of claims 1 to 5, wherein the catalyst is laminated on the oxygen permeable membrane on the first channel side. The reactor according to any one of claims 1 to 6,
A fuel electrode, an air electrode, and an electrolyte layer disposed between the fuel electrode and the air electrode, wherein the fuel gas is supplied to the fuel electrode, and the oxidant containing oxygen is supplied to the air electrode. a fuel cell that generates electricity with a gas, discharges a fuel electrode off-gas containing the unreacted fuel gas from the fuel electrode, and discharges an air electrode off-gas containing oxygen from the air electrode;
with
The fuel electrode off-gas is supplied to the first flow path, the air electrode off-gas is supplied to the second flow path,
A fuel cell power generation system in which carbon dioxide is produced by an oxidation reaction between the unreacted fuel gas and oxygen permeating through the oxygen-permeable membrane in the first flow path of the reactor. comprising a plurality of the fuel cells,
The fuel electrodes in the plurality of fuel cells are arranged in series, and the fuel electrode off-gas discharged from the more upstream fuel electrode is supplied to the more downstream fuel electrode,
The fuel electrode off-gas discharged from the most downstream fuel electrode is supplied to the first flow path, and the air electrode off-gas discharged from at least one of the air electrodes in the plurality of fuel cells is supplied to the second flow path. 8. The fuel cell power generation system according to claim 7, wherein the fuel is supplied to the channel. 9. The fuel cell power generation system according to claim 7 , further comprising a steam separation section for separating steam from the gas discharged from the first channel of the reactor. a power generator that generates power using renewable energy;
a water electrolysis device that electrolyzes water using power generated by the power generation device;
a carbon generation unit that generates carbon through a reduction reaction between hydrogen generated in the water electrolysis device and carbon dioxide contained in the gas discharged from the first flow path of the reaction device;
10. The fuel cell power generation system according to any one of claims 7 to 9 , further comprising: a compression unit that compresses carbon dioxide contained in the gas discharged from the first flow path of the reactor;
a liquefying device for liquefying the carbon dioxide compressed by the compression unit;
The fuel cell power generation system according to any one of claims 7 to 10 , further comprising:

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