JP2011141967A - Power generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power generation system capable of recovering efficiently carbon dioxide contained in a gas, while carrying out power generation utilizing the gas containing carbon dioxide. <P>SOLUTION: The power generation system is provided with a fuel cell which has a cathode 111 to which a gas containing carbon dioxide and oxygen is supplied in a pressurized state and an anode 113 to which a gas containing hydrogen is supplied in a pressurized state, and moves the carbon dioxide supplied to the cathode 111 to the anode 113 as a carbonate ion under an operation temperature, and exhausts an anode exhaust gas containing carbon dioxide in a pressurized state from the anode 113, refrigerators 44, 45 which cool carbon dioxide contained in the anode exhaust gas until liquefied and generate a liquefied anode exhaust gas containing liquid carbon dioxide, and a separator which separates the liquid carbon dioxide from the liquefied anode exhaust gas. Then, the refrigerators 44, 45 which generate the liquefied anode gas is an absorption type refrigerator driven by exhaust heat of the anode exhaust gas. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power generation system.

  In a molten carbonate fuel cell (MCFC), oxygen and carbon dioxide react at the cathode to form carbonate ions, and carbonate ions and hydrogen that have migrated from the cathode through the electrolyte react at the anode. To carbon dioxide and water. That is, the MCFC has a so-called carbon dioxide concentration function for concentrating carbon dioxide in order to collect carbon dioxide supplied to the cathode at the anode and discharge it as anode exhaust gas.

  Therefore, using the carbon dioxide concentration function of MCFC, for example, a power generation system that efficiently recovers carbon dioxide from exhaust gas containing carbon dioxide discharged from a coal-fired power plant or the like (hereinafter referred to as power plant exhaust gas). Is known (see, for example, Patent Document 1).

  In this power generation system, the power plant exhaust gas is supplied to the MCFC cathode to generate power, and the carbon dioxide in the power plant exhaust gas is concentrated as the MCFC anode exhaust gas. And by separating carbon dioxide from the anode exhaust gas, carbon dioxide can be efficiently recovered from the power plant exhaust gas.

JP 2009-43486 A

  As a method of separating carbon dioxide from the anode exhaust gas, a chemical absorption method in which carbon dioxide is absorbed by an absorbent, a physical adsorption method in which carbon dioxide is adsorbed by an adsorbent, and a polymer film formed of carbon dioxide and another gas are used. A membrane separation method using a difference in speed generated during permeation, a cryogenic separation method in which carbon dioxide is liquefied and separated by compressing and cooling anode exhaust gas are known.

  However, when carbon dioxide is separated from anode exhaust gas by chemical absorption, physical adsorption, membrane separation, etc., the absorbent, adsorbent, polymer membrane, etc. are expensive and the capacity of the anode exhaust that can be processed is high. There was a problem that it was limited and it was difficult to increase the size of the system.

  Furthermore, in these methods, carbon dioxide is recovered in the form of gas. However, since the recovered carbon dioxide needs to be made liquid during transportation and storage, the gaseous carbon dioxide should be compressed and cooled to become liquid. It is necessary to drive a refrigerator or the like separately. As this refrigerator, the thing provided with the compressor was common.

  In addition, when carbon dioxide is separated from anode exhaust gas by a cryogenic separation method, carbon dioxide is recovered as a liquid, but when recovering carbon dioxide, the anode exhaust gas is cooled to liquefy the carbon dioxide. There is no substitute for needing to drive. When driving the refrigerator, there is a problem that a large amount of energy is required because the power consumption of the compressor provided in the refrigerator is particularly large.

  The present invention has been made in view of such problems, and the object of the present invention is to provide a power generation system capable of efficiently recovering carbon dioxide contained in this gas while performing power generation using a gas containing carbon dioxide. It is to provide.

  The power generation system of the present invention for solving the above problems includes a cathode supplied with a gas containing carbon dioxide and oxygen pressurized, and an anode supplied with a gas containing hydrogen pressurized. A fuel cell that moves carbon dioxide supplied to the cathode as carbonate ions to the anode under an operating temperature, and discharges the anode exhaust gas containing carbon dioxide from the anode in a pressurized state; The anode exhaust gas is cooled until carbon dioxide contained in the anode exhaust gas is liquefied, and a refrigerator that generates liquefied anode exhaust gas containing liquid carbon dioxide, and the liquid carbon dioxide is separated from the liquefied anode exhaust gas. And a separator, wherein the refrigerator is an absorption refrigerator driven by exhaust heat of the anode exhaust gas.

  In this power generation system, carbon dioxide can be concentrated in the anode exhaust gas of the fuel cell by pressurizing the fuel cell at the operating temperature. Since this anode exhaust gas has a temperature comparable to the operating temperature of the fuel cell (hereinafter simply referred to as the operating temperature), the absorption refrigerator can be driven using the exhaust heat of this anode exhaust gas. That is, this refrigerator can be driven by utilizing the exhaust heat of the anode exhaust gas without driving a compressor or the like that consumes a large amount of power.

As the fuel cell is pressurized, the anode exhaust gas is discharged in a pressurized state. For this reason, the partial pressure of carbon dioxide is higher than the pressure at the triple point of carbon dioxide, and by cooling the anode exhaust gas with an absorption refrigerator, the carbon dioxide contained in the anode exhaust gas is made liquid. Carbon dioxide can be efficiently recovered in a liquid state.
Therefore, carbon dioxide contained in this gas can be efficiently recovered while generating power using a gas containing carbon dioxide.

In such a power generation system, the absorption chiller vaporizes the refrigerant absorbed in the absorption liquid by heat exchange with the anode exhaust gas, and separates the vaporized refrigerant from the absorption liquid, whereby the absorption liquid The anode exhaust gas after the heat exchange in the regenerator is cooled by vaporizing the liquid refrigerant. It is preferable to have an evaporator that generates the liquefied anode exhaust gas, and an absorber that absorbs the refrigerant vaporized by the evaporator into the absorbing liquid regenerated by the regenerator and returns the refrigerant to the regenerator.
In this power generation system, the absorption refrigerator includes an absorber and a regenerator instead of a compressor, and the absorption liquid absorbs the refrigerant in the absorber and the absorption liquid that absorbs the refrigerant in the regenerator is heated and absorbed. When the refrigerant is separated from the liquid, the refrigerant circulates in the refrigerator. And an absorption refrigerating machine can be driven efficiently by using anode exhaust gas as a heat source for heating absorption liquid with a regenerator.

In such a power generation system, the residual anode exhaust gas obtained by separating the liquid carbon dioxide from the anode exhaust gas is heat-exchanged with the anode exhaust gas before heat exchange in the regenerator, and the residual anode exhaust gas is heated. And a heat exchanger that cools the anode exhaust gas, a combustor that causes a combustion reaction between the remaining anode exhaust gas heated by the heat exchanger and the cathode exhaust gas discharged from the cathode, and combustion discharged from the combustor It is preferable to further include a reforming unit that uses the exhaust gas as a heating source to cause a reforming reaction between fuel gas and water vapor and generate hydrogen to be supplied to the cathode.
In this power generation system, the temperature of the remaining anode exhaust gas obtained by the separator is approximately the same as the temperature of the liquefied anode exhaust gas generated by cooling the anode exhaust gas until carbon dioxide is liquefied. For this reason, the anode exhaust gas is cooled by causing the heat exchanger to exchange heat between the remaining anode exhaust gas and the anode exhaust gas having the same temperature as the operating temperature before supplying the exhaust heat to the regenerator. A temperature suitable for heating the absorbing solution in the regenerator can be set. As a result, the absorption refrigerator can be driven efficiently, and the efficiency of the power generation system can be increased.

  In addition, the residual anode exhaust gas contains hydrogen discharged without being consumed at the anode of the fuel cell. Therefore, by supplying the residual anode exhaust gas heated by the heat exchanger to the combustor, the residual anode exhaust gas The hydrogen gas and oxygen contained in the cathode exhaust gas of the fuel cell can be subjected to a combustion reaction to generate combustion exhaust gas. By using the exhaust heat of the combustion exhaust gas as a heat source, the reforming reaction between the fuel gas and the water vapor in the reforming section makes it possible to effectively use the hydrogen contained in the remaining anode exhaust gas. As a result, the efficiency of the power generation system can be increased.

In such a power generation system, the anode exhaust gas after heat exchange with the regenerator and the remaining anode exhaust gas are heat-exchanged to cool the anode exhaust gas and to heat the remaining anode exhaust gas. It is preferable to further provide.
In this power generation system, the remaining anode exhaust gas and the anode exhaust gas after supplying exhaust heat to the regenerator of the refrigerator are heat-exchanged by another heat exchanger. As a result, the anode exhaust gas after being cooled by another heat exchanger can be supplied to the evaporator of the absorption refrigerating machine to form a liquefied anode exhaust gas, so that the load on the refrigerator can be reduced. Further, since the remaining anode exhaust gas after being heated by another heat exchanger can be supplied to the heat exchanger, the load on the heat exchanger can also be reduced. Therefore, the efficiency of the power generation system can be increased.

The power generation system further includes another absorption refrigerator that cools the anode exhaust gas before being supplied to the evaporator to a cooling temperature higher than a temperature at which carbon dioxide contained in the anode exhaust gas is liquefied. The absorption refrigerator of the present invention vaporizes the refrigerant absorbed in the absorption liquid by heat exchange with the anode exhaust gas, and separates the vaporized refrigerant from the absorption liquid, thereby regenerating the absorption liquid. A regenerator, another condenser that cools the vaporized refrigerant to a liquid state, and vaporizing the liquid refrigerant, thereby cooling the anode exhaust gas after heat exchange in the other regenerator It is preferable to include another evaporator that cools to a temperature, and an absorber that absorbs the refrigerant vaporized by the evaporator into the absorption liquid regenerated by the regenerator and returns the refrigerant to the regenerator.
In this power generation system, the anode exhaust gas cooled by another absorption refrigerator can be further cooled by the absorption refrigerator to form a liquefied anode exhaust gas. Therefore, anode exhaust gas can be cooled more efficiently.

The power generation system of the present invention for solving the above problems includes a cathode supplied with a gas containing carbon dioxide and oxygen pressurized, and an anode supplied with a gas containing hydrogen pressurized. A fuel cell that moves carbon dioxide supplied to the cathode as carbonate ions to the anode under an operating temperature, and discharges the anode exhaust gas containing carbon dioxide from the anode in a pressurized state; The anode exhaust gas and water are heat-exchanged to cool the anode exhaust gas, and the anode exhaust gas contains the steam generation part using the water as water vapor and the anode exhaust gas after heat exchange in the steam generation part. A chiller that cools until the liquefied carbon dioxide is liquefied and generates liquefied anode exhaust gas containing liquid carbon dioxide, and Comprising a separator for separating the liquid carbon dioxide, wherein the refrigerator is characterized by an absorption chiller driven by the exhaust heat of the anode exhaust gas.
In this power generation system, the exhaust heat of the anode exhaust gas having a temperature approximately equal to the operating temperature is used to generate water vapor at the steam generation unit, and the absorption refrigerator is driven using the exhaust heat of the water vapor. For this reason, the heat source of the temperature suitable for an absorption refrigerator can be ensured, and cooling can be made efficient.

  According to the present invention, it is possible to provide a power generation system capable of efficiently liquefying and recovering carbon dioxide contained in this gas while efficiently generating power using a gas containing carbon dioxide.

It is a block diagram which shows the structural example of the electric power generation system which concerns on 1st Embodiment. It is a schematic diagram for demonstrating the electric power generation reaction of a fuel cell. It is a schematic diagram which shows the structural example of a refrigerator. It is an example of a state diagram. It is a block diagram which shows the structural example of the electric power generation system concerning 2nd Embodiment.

=== About the power generation system according to the first embodiment ===
Hereinafter, the power generation system 1 according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is a block diagram illustrating a configuration example of the power generation system 1. FIG. 2 is a schematic diagram for explaining the power generation reaction of the molten carbonate fuel cell (MCFC) 110 provided in the power generation system 1 shown in FIG. FIG. 3 is a schematic diagram illustrating a configuration example of the refrigerators 44 and 45 provided in the power generation system 1. FIG. 4 is an example of a state diagram of carbon dioxide.

  The power generation system 1 includes a first power generation unit 10 including an MCFC 110, and a carbon dioxide recovery unit 40 including refrigerators 44 and 45, a gas-liquid separator 47 (separator), and the like. In this power generation system 1, the carbon dioxide in the power plant exhaust gas is used to generate power in the MCFC 110, and the carbon dioxide is collected in the anode exhaust gas of the MCFC 110 and liquefied and recovered by the refrigerators 44 and 45 and the gas-liquid separator 47. To do.

Further, the power generation system 1 generates water vapor using the second power generation unit 20 that generates power using the cathode exhaust gas discharged from the cathode 111 of the MCFC 110, and the cathode exhaust gas from which power is recovered by the second power generation unit 20. And a third power generation unit 30 that generates power using this water vapor.
Hereinafter, each structure of the electric power generation system 1 is demonstrated.

<<< First power generation unit >>>
The first power generation unit 10 includes a compressor 100, an MCFC 110, a pressure vessel 120, a circulation blower 130, and a fuel gas adjustment unit 140.

  The compressor 100 pressurizes mixed exhaust gas obtained by mixing power plant exhaust gas containing carbon dioxide with air to, for example, 1.2 MPa and supplies the compressed exhaust gas to the cathode 111 of the MCFC 110.

  In the MCFC 110, mixed exhaust gas is supplied to the cathode 111, and a reformed fuel gas, which will be described later, is supplied to the anode 113 from the fuel gas adjusting unit 140 in a pressurized state of, for example, 1.2 MPa. Then, the MCFC 110 generates electricity by causing an electrochemical reaction between carbon dioxide and oxygen contained in the mixed exhaust gas and hydrogen contained in the reformed fuel gas at an operating temperature of, for example, 600 degrees. In the MCFC 110, since the mixed exhaust gas and the reformed fuel gas are supplied in a pressurized state and operated under pressure, it is possible to increase the efficiency of the electrochemical reaction and increase the power generation efficiency.

  For example, as shown in FIG. 2, the MCFC 110 includes a cathode 111 made of a porous nickel oxide plate, an electrolyte 112 made of a carbonate of a mixture of lithium carbonate and sodium carbonate, and an anode 113 made of a porous nickel plate. And have. The cathode 111 and the anode 113 are connected by an external circuit 115 via a load 114 that consumes power obtained by the MCFC 110.

At the cathode 111, oxygen (O ₂ ), carbon dioxide (CO ₂ ), and electrons (2e ⁻ ) supplied from the external circuit 115 react to generate carbonate ions (CO ₃ ²⁻ ). Carbon dioxide and oxygen that have not been consumed in the reaction at the cathode 111, and water vapor derived from combustion exhaust gas, which will be described later, are discharged as cathode exhaust gas. This cathode exhaust gas has a temperature that is, for example, about the same as the operating temperature. Part of the cathode exhaust gas is supplied to the fuel gas adjustment unit 140. A part of the remaining cathode exhaust gas is returned to the cathode 111 by the circulation blower 130. In this way, by returning a part of the cathode exhaust gas to the cathode 111, the cathode exhaust gas can be reused for the electrochemical reaction of the MCFC 110, and the temperature of the gas supplied to the cathode 111 is raised to near the operating temperature. Therefore, the efficiency of the power generation system 1 can be increased. The remaining cathode exhaust gas is supplied to the second power generation unit 20.

  The electrolyte 112 is in a molten state at the operating temperature and moves carbonate ions generated at the cathode 111 to the anode 113.

At the anode 113, hydrogen (H ₂ ) in the reformed fuel gas reacts with carbonate ions that have moved from the cathode 111 via the electrolyte 112, so that carbon dioxide (CO ₂ ) and water vapor (H ₂ O) are reacted. Are generated, and at the same time, electrons (2e ⁻ ) are emitted. The emitted electrons move to the cathode 111 through the external circuit 115, and electricity is generated by repeating this.

  Thus, in the MCFC 110, carbon dioxide supplied to the cathode 111 becomes carbonate ions and moves to the anode 113, and the carbonate ions become carbon dioxide at the anode 113. Therefore, in the MCFC 110, carbon dioxide is selectively transferred to the anode 113 among the gas components supplied to the cathode 111, so that carbon dioxide can be collected at the anode 113. Carbon dioxide collected at the anode 113, water vapor generated at the anode 113, and hydrogen not consumed in the reaction at the anode 113 are discharged as anode exhaust gas. This anode exhaust gas is also at a temperature similar to the operating temperature. A part of the anode exhaust gas is supplied to the fuel gas adjustment unit 140, and the remaining anode exhaust gas is supplied to the carbon dioxide recovery unit 40.

  The fuel gas adjustment unit 140 generates a reformed fuel gas containing hydrogen to be supplied to the anode 113 by performing a reforming reaction between a fuel gas such as natural gas and the water vapor supplied from the third power generation unit 30. . The fuel gas adjustment unit 140 includes a fuel preheater 141, a combustor 142, and a reforming unit 145.

  Cathode exhaust gas and anode exhaust gas are supplied from the MCFC 110 to the combustor 142, and oxygen in the cathode exhaust gas and hydrogen in the anode exhaust gas undergo a combustion reaction. By this combustion reaction, combustion exhaust gas mainly containing water vapor and carbon dioxide is discharged from the combustor 142. This combustion exhaust gas is supplied to the heating chamber 143 of the reforming unit 145.

  The fuel preheater 141 is supplied with a mixed fuel gas of fuel gas and water vapor, and heat is exchanged between the mixed fuel gas and the reformed fuel gas discharged from the reformer 144 of the reformer 145. Thus, the mixed fuel gas is heated and supplied to the reformer 144, and the reformed fuel gas is supplied to the anode 113 of the MCFC 110 in a state adjusted to the operating temperature, for example.

The reformer 145 includes a heating chamber 143 and a reformer 144. In the reformer 144, as shown in the following formula, methane and water vapor contained in the mixed fuel gas heated by the fuel preheater 141 undergo a reforming reaction, and hydrogen and carbon monoxide are generated. Thereby, reformed fuel gas containing hydrogen is generated.
CH ₄ + H ₂ O → CO + 3H ₂
The reformed fuel gas discharged from the reformer 144 is supplied to the anode 113 of the MCFC 110 after the temperature is adjusted by the fuel preheater 141.

  The heating chamber 143 maintains the temperature of the reformer 144 at a temperature suitable for the reforming reaction by the exhaust heat of the combustion exhaust gas discharged from the combustor 142. The combustion exhaust gas discharged from the heating chamber 143 is supplied to the cathode 111 of the MCFC 110 by the circulation blower 130. As a result, the combustion exhaust gas can be used for the electrochemical reaction of the MCFC 110, and the temperature of the gas supplied to the cathode 111 can be raised to near the operating temperature. As a result, the efficiency of the power generation system 1 can be increased.

  The pressure vessel 120 accommodates the MCFC 110 and the fuel gas adjustment unit 140. The inside of the pressure vessel 120 is boosted to a pressure that is the same as or higher than the pressure of the mixed exhaust gas and the reformed fuel gas (for example, 1.2 MPa) supplied to the MCFC 110 by an inert gas such as nitrogen. Has been. As a result, it is possible to prevent gas from leaking from the inside of the MCFC 110 to the outside, etc., so that the MCFC 110 can be efficiently pressurized and power generation efficiency can be increased.

  As described above, the circulation blower 130 circulates a part of the cathode exhaust gas and the combustion exhaust gas and supplies it to the cathode 111 of the MCFC 110.

<<< CO2 recovery department >>>
The carbon dioxide recovery unit 40 liquefies and recovers carbon dioxide contained in the anode exhaust gas supplied from the first power generation unit 10. The carbon dioxide recovery unit 40 includes a heat exchanger 41, a heat exchanger 42 (another heat exchanger), a cooler 43, a refrigerator 44 (another refrigerator), and a refrigerator 45 (a main refrigeration unit). Machine), a dehumidifier 46, and a gas-liquid separator 47.

  The anode exhaust gas supplied to the carbon dioxide recovery unit 40 is first provided with the regenerator 440 and the refrigerator 45 included in the refrigerator 44 to drive the refrigerators 44 and 45 after the temperature is lowered by the heat exchanger 41. Waste heat is supplied to each of the regenerators 450. The anode exhaust gas cooled by the regenerators 440 and 450 is further cooled to, for example, around 0 degrees by the cooler 43, the heat exchanger 42, and the refrigerator 44 (evaporator 442). Then, after the anode exhaust gas cooled to around 0 degrees is dehydrated by the dehumidifier 46, it is cooled to, for example, around -56 degrees by the refrigerator 45 (evaporator 452). As a result, the anode exhaust gas becomes a liquefied anode exhaust gas containing liquid carbon dioxide. The liquefied anode exhaust gas is separated into liquid carbon dioxide by the gas-liquid separator 47 and becomes the remaining anode exhaust gas. The remaining anode exhaust gas is heated by the heat exchangers 42 and 41 and then supplied to the combustor 142 of the first power generation unit 10, and hydrogen contained in the remaining anode exhaust gas is used for the combustion reaction in the combustor 142. (Described later).

  That is, by collecting the liquid carbon dioxide separated by the gas-liquid separator 47, the carbon dioxide can be liquefied and recovered from the anode exhaust gas.

Hereinafter, each structure of the carbon dioxide collection part 40 is demonstrated.
The heat exchanger 41 is exhausted from the anode 113 of the MCFC 110 and has the same operating temperature as the anode exhaust gas, and the remaining anode exhaust gas after being heated by the heat exchanger 42 (the gas that has passed through the gas-liquid separator 47) And heat exchange. Thereby, in the heat exchanger 41, for example, the anode exhaust gas can be cooled to a temperature close to a temperature suitable for supplying the exhaust heat to the regenerators 440 and 450, so that the refrigerators 44 and 45 can be driven efficiently. Can do. As a result, the efficiency of the power generation system 1 can be increased. In the heat exchanger 41, for example, the remaining anode exhaust gas can be heated to a temperature suitable for the combustion reaction in the combustor 142.

  The refrigerator 45 is, for example, a so-called ammonia absorption refrigerator that uses ammonia as a refrigerant and water as an absorption liquid. As shown in FIG. 3, a regenerator 450, a condenser 451, an evaporator 452, and an absorption Instrument 453.

  The regenerator 450 heat-exchanges the anode exhaust gas discharged from the heat exchanger 41 and the absorbing liquid that has absorbed the refrigerant, thereby vaporizing the refrigerant contained in the absorbing liquid and separating the gaseous refrigerant from the absorbing liquid. . The refrigerant vaporized by the regenerator 450 is supplied to the condenser 451, and the regenerated liquid regenerated by separating the refrigerant is supplied to the absorber 453.

  The condenser 451 makes the refrigerant vaporized by the regenerator 450 by cooling it with cooling water or the like. The refrigerant that has become liquid in the condenser 451 is supplied to the evaporator 452.

  The evaporator 452 vaporizes the refrigerant that has become liquid in the condenser 451 by exhaust heat of the anode exhaust gas. That is, in the evaporator 452, the anode exhaust gas is cooled by the refrigerant taking heat from the anode exhaust gas and evaporating. The evaporative gas 452 liquefies carbon dioxide contained in the anode exhaust gas, for example, by cooling the anode exhaust gas to around −56 degrees to generate liquefied anode exhaust gas.

  At this time, as the MCFC 110 is pressurized, the anode exhaust gas is discharged in a state of being pressurized to, for example, 1.2 MPa. Further, due to the carbon dioxide concentration function of MCFC 110, the composition of carbon dioxide in the anode exhaust gas is, for example, 80%. For this reason, the partial pressure of carbon dioxide is, for example, 0.96 MPa, and is higher than 0.518 MPa, which is the pressure at the triple point of carbon dioxide, as shown in FIG. For this reason, by cooling the anode exhaust gas to around -56 degrees, carbon dioxide contained in the anode exhaust gas can be made liquid, and carbon dioxide can be efficiently recovered in a liquid state.

  The absorber 453 absorbs the refrigerant vaporized by the evaporator 452 in the absorbing liquid regenerated by the regenerator 450. As a result, the partial pressure of the refrigerant in the evaporator 452 can be prevented from increasing, and the evaporator 452 can keep the refrigerant continuously vaporized. Then, the absorbing liquid that has absorbed the refrigerant is returned to the regenerator 450.

  The refrigerator 44 is, for example, a so-called lithium bromide absorption refrigerator that uses water as a refrigerant and lithium bromide as an absorption liquid. The refrigerator 44 having a cooling temperature higher than that of the refrigerator 45 includes the regenerator 440 and the like. , A condenser 441, an evaporator 442, and an absorber 443. Similarly to the refrigerator 45, the refrigerator 44 regenerates the absorbing liquid by exchanging heat between the absorbing liquid that has absorbed the refrigerant and the anode exhaust gas by the regenerator 440, and the regenerator 440 The resulting refrigerant is cooled to form a liquid refrigerant. Then, the evaporator 442 vaporizes the liquid refrigerant and cools the anode exhaust gas to, for example, around 0 ° C., and thereby the gas refrigerant is absorbed by the absorption liquid by the absorber 443 and returned to the regenerator 440. After the anode exhaust gas is cooled to around 0 degrees by the evaporator 442 of the refrigerator 44, it can be cooled to -56 degrees by the evaporator 452 of the refrigerator 45 so that carbon dioxide is liquefied. The anode exhaust gas can be cooled.

  The cooler 43 cools the anode exhaust gas after heat exchange with the absorption liquid in the regenerator 450 of the refrigerator 45 and the regenerator 440 of the refrigerator 44 by, for example, cooling water.

  The heat exchanger 42 heat-exchanges the anode exhaust gas cooled by the cooler 43 and the remaining anode exhaust gas discharged from the gas-liquid separator 47, thereby cooling the anode exhaust gas and evaporating the evaporator 442 of the refrigerator 44. And the remaining anode exhaust gas is heated and supplied to the heat exchanger 41. As a result, the anode exhaust gas after being cooled by the heat exchanger 42 can be supplied to the evaporators 442 and 452 to be liquefied anode exhaust gas, so that the load on the refrigerators 44 and 45 can be reduced. Moreover, since the residual anode exhaust gas heated by the heat exchanger 42 can be supplied to the heat exchanger 41, the load applied to the heat exchanger 41 can also be reduced. Therefore, the efficiency of the power generation system 1 can be increased.

  The dehumidifier 46 removes moisture from the anode exhaust gas cooled by the evaporator 442 of the refrigerator 44. For the dehumidifier 46, for example, activated alumina is used.

  The gas-liquid separator 47 separates liquid carbon dioxide from the liquefied anode exhaust gas. The liquid carbon dioxide separated by the gas-liquid separator 47 is recovered. The remaining residual anode exhaust gas from which carbon dioxide was recovered from the liquefied anode exhaust gas by the gas-liquid separator 47 mainly contains hydrogen and gaseous carbon dioxide because the moisture has been removed by the dehumidifier 46. Therefore, the residual anode exhaust gas is heated by the heat exchangers 41 and 42 and supplied to the combustor 142 of the first power generation unit 10, whereby hydrogen contained in the residual anode exhaust gas is converted into the combustion reaction in the combustor 142 described above. Can be used. Thereby, the efficiency of the power generation system 1 can be increased.

<<< Second power generation section >>>
The second power generation unit 20 generates power using the cathode exhaust gas supplied from the first power generation unit 10. This 2nd electric power generation part 20 is provided with the gas turbine 21 and the generator 22 which were connected to the same rotating shaft, for example. The gas turbine 21 rotates the rotating shaft when the cathode exhaust gas is supplied. The generator 22 generates power when the gas turbine 21 rotates the rotating shaft. The compressor 100 is also connected to the same rotating shaft as the gas turbine 21 and the generator 22 and is driven in conjunction with the rotation of the gas turbine 21.
The cathode exhaust gas whose power is recovered by driving the gas turbine 21 is supplied to the third power generation unit 30.

<<< Third power generation section >>>
The third power generation unit 30 generates water vapor using the cathode exhaust gas supplied from the second power generation unit 20 and generates power using the water vapor. The third power generation unit 30 includes an exhaust heat recovery boiler 31, a gas-liquid separator 32, a circulation pump 33, a steam turbine 34, a generator 35, and a condenser 36.

  The exhaust heat recovery boiler 31 heat-exchanges the cathode exhaust gas discharged from the gas turbine 21 of the second power generation unit 20 and the cooling water supplied by the circulation pump 33, thereby cooling the cathode exhaust gas to The water vapor is water and the cooling water is heated to water vapor. A part of the steam generated in the exhaust heat recovery boiler 31 is supplied to the steam turbine 34, and the remaining steam is mixed with the fuel gas and supplied to the fuel preheater 141 of the first power generation unit 10. The cathode exhaust gas cooled by the exhaust heat recovery boiler 31 is supplied to the gas-liquid separator 32.

  The gas-liquid separator 32 separates water in the cathode exhaust gas that has become liquid by being cooled by the exhaust heat recovery boiler 31 from the cathode exhaust gas. The cathode exhaust gas from which water has been separated by the gas-liquid separator 32 is exhausted. The water separated by the gas-liquid separator 32 is supplied to the exhaust heat recovery boiler 31 by the circulation pump 33 as cooling water for cooling the cathode exhaust gas discharged from the gas turbine 21 of the second power generation unit 20. The

  The circulation pump 33 supplies water discharged from the gas-liquid separator 32 and water discharged from the condenser 36 to the exhaust heat recovery boiler 31 as cooling water.

  For example, the steam turbine 34 is connected to the same rotation shaft as the generator 35, and rotates the rotation shaft by steam supplied from the exhaust heat recovery boiler 31. The steam after driving the steam turbine 34 is supplied to the condenser 36. The generator 35 generates electric power when the steam turbine 34 rotates the rotation shaft.

  The condenser 36 changes the water vapor supplied from the steam turbine 34 into liquid water. The water discharged from the condenser 36 is mixed with the water discharged from the gas-liquid separator 32, and as described above, the cooling pump cools the cathode exhaust gas discharged from the gas turbine 21 by the circulation pump 33. It is supplied to the exhaust heat recovery boiler 31.

  As described above, in the power generation system 1 according to the first embodiment, the carbon dioxide contained in the power plant exhaust gas is used to generate power with the MCFC 110, and the carbon dioxide is concentrated in the anode exhaust gas. Further, when separating carbon dioxide from the anode exhaust gas enriched with carbon dioxide, it is not necessary to use an absorbent, an adsorbent, a polymer membrane or the like. Furthermore, the refrigerators 44 and 45 can be driven using the exhaust heat of the anode exhaust gas having a temperature similar to the operating temperature of the MCFC 110 without driving a compressor or the like that consumes a large amount of power. As a result, carbon dioxide contained in the power plant exhaust gas can be efficiently and easily liquefied and recovered while performing power generation using the carbon dioxide in the power plant exhaust gas.

  In addition, since the second power generation unit 20 and the third power generation unit 30 that generate power using the cathode exhaust gas of the MCFC 110 perform combined power generation, the power generation efficiency of the power generation system 1 can be increased.

=== About the power generation system according to the second embodiment ===
Hereinafter, the power generation system 2 according to the second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a block diagram illustrating a configuration example of the power generation system 2. In FIG. 5, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The power generation system 2 includes a carbon dioxide recovery unit 40A instead of the carbon dioxide recovery unit 40 in the power generation system 1 described above. The carbon dioxide recovery unit 40A includes a steam generation unit 50 in addition to the carbon dioxide recovery unit 40 described above. The steam generator 50 generates water vapor using the anode exhaust gas cooled by the heat exchanger 41, and includes an exhaust heat recovery boiler 51, a circulation pump 52, and a condenser 53. ing.

  The exhaust heat recovery boiler 51 cools the anode exhaust gas and supplies it to the cooler 43 by exchanging heat between the anode exhaust gas after being cooled by the heat exchanger 41 and the water supplied from the circulation pump 52. The cooling water is heated to steam. Water vapor generated in the exhaust heat recovery boiler 51 is supplied to the regenerators 440 and 450, respectively. In the regenerators 440 and 450, the water vapor and the absorption liquid that has absorbed the refrigerant exchange heat, whereby the absorption liquid is separated from the refrigerant and the absorption liquid is regenerated.

  The condenser 53 cools the water vapor after heat exchange by the regenerators 440 and 450 and changes the water vapor into liquid water. The circulation pump 52 supplies the water discharged from the condenser 53 to the exhaust heat recovery boiler 51.

  As described above, in the power generation system 2 according to the second embodiment, steam is generated in the steam generation unit 50 using the exhaust heat of the anode exhaust gas, and the refrigerators 44 and 45 are driven using the exhaust heat of the steam. Can be made. Thus, by driving the refrigerators 44 and 45 using the exhaust heat of water vapor, the regenerators 440 and 450 can regenerate the absorbing liquid at a more appropriate temperature.

=== Other Embodiments ===
The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The present invention is changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

  For example, in the power generation systems 1 and 2 described above, the refrigerator 44 is provided, and the anode exhaust gas cooled by the evaporator 442 of the refrigerator 44 is cooled by the evaporator 452 of the refrigerator 45 to generate the liquefied anode exhaust gas. It was. However, the present invention is not particularly limited to this, and in the case of the power generation system 1, for example, the refrigerator 44 is not provided, and the anode exhaust gas is, for example, It is good also as producing | generating a liquefied anode exhaust gas by cooling with the evaporator 452 after cooling to 0 degree vicinity. Further, in the case of the power generation system 2, for example, the refrigerator 44 is not provided, and after the anode exhaust gas is cooled to, for example, around 0 degrees by the heat exchangers 41 and 42, the exhaust heat recovery boiler 51, and the cooler 43, It is good also as producing | generating a liquefied anode exhaust gas by cooling with the evaporator 452. FIG.

  In the cooler 43 of the power generation systems 1 and 2 described above, the anode exhaust gas is cooled by the cooling water. However, the present invention is not limited to this, and the anode exhaust gas may be cooled by, for example, air cooling. .

DESCRIPTION OF SYMBOLS 1, 2 ... Power generation system 10 ... 1st power generation part 20 ... 2nd power generation part 21 ... Gas turbine 22, 35 ... Generator 30 ... 3rd power generation part 31, 51 ... Waste heat recovery boiler 32, 47 ... Gas-liquid separator 33, 52 ... Circulation pump 34 ... Steam turbine 36, 53 ... Condenser 40, 40A ... Carbon dioxide recovery unit 41, 42 ... Heat exchanger 43 ... Cooler 44, 45 ... Refrigerator 46 ... Dehumidifier 100 ... Compressor 110 ... MCFC 111 ... cathode 112 ... electrolyte 113 ... anode 114 ... load 115 ... external circuit 120 ... pressure vessel 130 ... circulation blower 140 ... fuel gas regulator 141 ... fuel preheater 142 ... combustor 143 ... heating chamber 144 ... reformer 145 ... reforming section 440, 450 ... regenerator 441, 451 ... condenser 442, 452 ... evaporator 443, 453 ... absorber 50 ... steam generating section

Claims (6)

A cathode supplied with a gas containing carbon dioxide and oxygen in a pressurized state; and an anode supplied with a gas containing hydrogen under pressure, and supplied to the cathode under an operating temperature. A fuel cell that moves the carbon dioxide as carbonate ions to the anode and discharges the anode exhaust gas containing carbon dioxide from the anode in a pressurized state;
A refrigerator that cools the anode exhaust gas until the carbon dioxide contained in the anode exhaust gas is liquefied, and generates liquefied anode exhaust gas containing liquid carbon dioxide;
A separator for separating the liquid carbon dioxide from the liquefied anode exhaust gas,
The refrigerator is
The power generation system is an absorption chiller driven by exhaust heat of the anode exhaust gas. The absorption refrigerator is
A regenerator that regenerates the absorbing liquid by evaporating the refrigerant absorbed in the absorbing liquid by heat exchange with the anode exhaust gas, and separating the evaporated refrigerant from the absorbing liquid;
A condenser that cools the vaporized refrigerant to form a liquid;
An evaporator that cools the anode exhaust gas after heat exchange in the regenerator by vaporizing the liquid refrigerant, and generates the liquefied anode exhaust gas;
An absorber that absorbs the refrigerant vaporized in the evaporator into the absorption liquid regenerated in the regenerator and returns it to the regenerator;
The power generation system according to claim 1, comprising: The residual anode exhaust gas obtained by separating the liquid carbon dioxide from the anode exhaust gas and the anode exhaust gas before heat exchange in the regenerator are heat-exchanged to heat the residual anode exhaust gas, and the anode exhaust gas A heat exchanger for cooling,
A combustor for causing a combustion reaction between the residual anode exhaust gas heated by the heat exchanger and the cathode exhaust gas discharged from the cathode;
A reforming unit that uses a combustion exhaust gas discharged from the combustor as a heating source, causes a reforming reaction between fuel gas and water vapor, and generates hydrogen to be supplied to the cathode;
The power generation system according to claim 2, further comprising:   The anode exhaust gas after heat exchange with the regenerator and the remaining anode exhaust gas are heat-exchanged to cool the anode exhaust gas and further include another heat exchanger that heats the remaining anode exhaust gas. The power generation system according to claim 2 or 3. And further comprising another absorption refrigerator that cools the anode exhaust gas before being supplied to the evaporator to a cooling temperature higher than a temperature at which carbon dioxide contained in the anode exhaust gas is liquefied,
The other absorption refrigerator is
Another regenerator that regenerates the absorbing liquid by vaporizing the refrigerant absorbed in the absorbing liquid by heat exchange with the anode exhaust gas, and separating the evaporated refrigerant from the absorbing liquid;
Another condenser that cools the vaporized refrigerant to form a liquid;
Another evaporator that cools the anode exhaust gas after heat exchange in the other regenerator to the cooling temperature by vaporizing the liquid refrigerant;
An absorber that absorbs the refrigerant vaporized in the evaporator into the absorption liquid regenerated in the regenerator and returns it to the regenerator;
The power generation system according to any one of claims 2 to 4, further comprising: A cathode supplied with a gas containing carbon dioxide and oxygen in a pressurized state; and an anode supplied with a gas containing hydrogen under pressure, and supplied to the cathode under an operating temperature. A fuel cell that moves the carbon dioxide as carbonate ions to the anode and discharges the anode exhaust gas containing carbon dioxide from the anode in a pressurized state;
The anode exhaust gas and water are subjected to heat exchange to cool the anode exhaust gas, and a steam generation unit that uses the water as water vapor,
A refrigerator that cools the anode exhaust gas after heat exchange in the steam generation unit until carbon dioxide contained in the anode exhaust gas is liquefied, and generates liquefied anode exhaust gas containing liquid carbon dioxide,
A separator for separating the liquid carbon dioxide from the liquefied anode exhaust gas,
The refrigerator is
The power generation system is an absorption chiller driven by exhaust heat of the anode exhaust gas.

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