JP2011103213A - Power generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power generation system capable of collecting carbon dioxide from exhaust gas without deteriorating power generation efficiency. <P>SOLUTION: The power generation system is provided with a fuel cell (200) generating power through electrochemical reaction of fuel gas and an oxidant, a pressure vessel (210) housing the fuel cell, coolant gas supply portions (30, 200, 502, 503) supplying coolant gas to the pressure vessel and maintaining temperature of the fuel cell generating heat owing to the electrochemical reaction at an operating temperature, an absorption tower (601) making gas containing carbon dioxide at absorption temperature in contact with absorption liquid absorbing carbon dioxide at absorption temperature and discharging carbon dioxide at a regeneration temperature higher than the absorption temperature, a heat exchanger (603) exchanging heat of coolant gas exhausted from the pressure vessel and the absorption liquid exhausted from the absorption tower and heating the absorption liquid above the regeneration temperature, and a regeneration tower (602) making carbon dioxide discharged from the heated absorption liquid. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power generation system.

  In thermal power generation using coal, it is necessary to reduce the amount of carbon dioxide emission and reduce the environmental load. Therefore, the coal gasification fuel cell combined cycle (IGFC) efficiently converts coal energy into electric power and collects carbon dioxide from exhaust gas containing carbon dioxide discharged after power generation. It is known to do. In addition, IGFC gasifies coal, produces | generates fuel gas containing hydrogen, carbon monoxide, etc., and while operating a fuel cell with this fuel gas, it drives a gas turbine and a steam turbine, and generates electricity collectively. It is a form of power generation.

  Such a power generation system using IGFC includes a gasification furnace that generates fuel gas by partially burning coal using oxygen, a fuel cell that generates electricity by electrochemical reaction of fuel gas and oxidant, fuel, 2. Description of the Related Art A gas turbine and a steam turbine that generate power using gas or fuel cell exhaust gas, and a carbon dioxide recovery unit that recovers carbon dioxide contained in the fuel cell exhaust gas are known.

  Further, as the carbon dioxide recovery unit, for example, an absorption liquid such as an alkanolamine aqueous solution that absorbs carbon dioxide at an absorption temperature of about 40 degrees and releases carbon dioxide at a regeneration temperature of about 120 degrees, for example, is discharged. What collects carbon dioxide from gas is known (for example, refer to patent documents 1). This carbon dioxide recovery unit makes contact with the absorption liquid and the exhaust gas at the absorption temperature, absorbs the carbon dioxide in the exhaust gas into the absorption liquid, and steam generated in order to obtain power in the power generation system as a heat source And a regeneration tower that raises the temperature of the absorbent above the regeneration temperature and releases carbon dioxide from the absorbent.

JP-A-5-98910

However, the power generation system described above has a problem in that power generation efficiency is lowered because the temperature of the absorbing liquid is increased from the absorption temperature to the regeneration temperature or higher by using water vapor generated to obtain electric power.
This invention is made | formed in view of the subject which concerns, and the place made into the objective is providing the electric power generation system which can collect | recover carbon dioxide from exhaust gas, without reducing electric power generation efficiency.

  In order to solve the above problems, a power generation system of the present invention includes a fuel cell that generates electricity by electrochemically reacting a fuel gas and an oxidant, a pressure vessel that houses the fuel cell, and a refrigerant gas that is supplied to the pressure vessel. A refrigerant gas supply unit that maintains the temperature of the fuel cell that generates heat by the electrochemical reaction at an operating temperature, and an absorbing solution that absorbs carbon dioxide at an absorption temperature and releases carbon dioxide at a regeneration temperature higher than the absorption temperature. Heat exchange between the absorption tower for contacting a gas containing carbon dioxide at the absorption temperature, the refrigerant gas discharged from the pressure vessel, and the absorption liquid discharged from the absorption tower, It is characterized by comprising a heat exchanger for heating above the regeneration temperature, and a regeneration tower for releasing carbon dioxide from the heated absorption liquid.

  In this power generation system, the refrigerant gas after cooling the fuel cell discharged from the pressure vessel and the absorption liquid at the absorption temperature discharged from the absorption tower are heat-exchanged by a heat exchanger, thereby adjusting the temperature of the absorption liquid. Raise above regeneration temperature. That is, the carbon dioxide can be released in the regeneration tower by heating the absorption liquid to the regeneration temperature or higher without using energy such as fuel gas or water vapor generated to obtain power in the power generation system. Therefore, in this power generation system, carbon dioxide in the exhaust gas can be recovered without reducing the power generation efficiency.

  In this power generation system, for example, a molten carbonate fuel cell (MCFC) using a molten carbonate as an electrolyte is preferably used as the fuel cell. The operating temperature of this MCFC is about 650 degrees, but the temperature of MCFC rises due to the electrochemical reaction during operation. For this reason, refrigerant gas is supplied to the pressure vessel that houses the MCFC so as to maintain the MCFC at the operating temperature.

In such a power generation system, the absorption liquid discharged from the absorption tower is heated and discharged to the regeneration tower, and the absorption liquid discharged from the regeneration tower is absorbed by the absorption liquid discharged from the absorption tower. It is preferable that another heat exchanger that is cooled and supplied to the absorption tower is provided, and the heat exchanger heats the absorption liquid stored in the regeneration tower to the regeneration temperature or higher.
In this power generation system, the absorption liquid at the absorption temperature discharged from the absorption tower can be heated by the absorption liquid at the regeneration temperature discharged from the regeneration tower and then supplied to the regeneration tower for storage. Moreover, the stored absorption liquid can be maintained at the regeneration temperature or higher by heating with the refrigerant gas after cooling the fuel cell. This can reduce the load on the heat exchanger that heats the absorbing liquid to the regeneration temperature or higher, and can simplify the configuration for maintaining the absorbing liquid at the regeneration temperature. In addition, after the absorption liquid at the regeneration temperature discharged from the regeneration tower is cooled by the absorption liquid at the absorption temperature discharged from the absorption tower, the absorption liquid can absorb carbon dioxide again by supplying the absorption liquid to the absorption tower. it can. That is, the absorption liquid can be circulated between the absorption tower and the regeneration tower while being efficiently heated and cooled, so that the efficiency of the power generation system can be improved.

In such a power generation system, the refrigerant gas is preferably an inert gas that does not cause a combustion reaction with the fuel gas.
In this power generation system, an inert gas is supplied into the pressure vessel as a refrigerant gas. For this reason, even when the fuel gas leaks from the fuel cell, the combustion gas can be prevented from causing a combustion reaction, and the safety of the power generation system can be improved.

Such a power generation system is separated by a gasification unit that reacts oxygen with carbon obtained by pyrolysis of coal to generate the fuel gas, a separation unit that separates oxygen and nitrogen from air, and the separation unit. It is preferable that the refrigerant gas supply unit supplies the pressure vessel with nitrogen separated by the separation unit as the refrigerant gas.
In this power generation system, nitrogen by-produced in the separation unit is supplied as a refrigerant gas for cooling the fuel cell into a pressure vessel that houses the fuel cell. Then, the absorbing liquid can be heated to a regeneration temperature or higher by nitrogen whose temperature has been increased by cooling the fuel cell. For this reason, the carbon dioxide in exhaust gas can be collect | recovered, without reducing electric power generation efficiency. Moreover, the nitrogen from a separation part can be utilized effectively and the efficiency of a power generation system can be improved. In addition, since nitrogen, which is an inert gas, is supplied into the pressure vessel as a refrigerant gas, even if the fuel gas leaks from the fuel cell, the combustion gas can be prevented from causing a combustion reaction, and safety can be improved. Can be increased. Moreover, since it is not necessary to separately provide an apparatus for generating refrigerant gas, a storage tank for storing the procured refrigerant gas, etc., the facilities of the power generation system can be simplified.

In such a power generation system, it is preferable that the refrigerant gas supply unit includes a cooler that cools the fuel cell exhaust gas discharged from the fuel cell to the operating temperature or less to obtain the refrigerant gas.
In this power generation system, the fuel cell exhaust gas discharged from the fuel cell is cooled to below the operating temperature by the cooler, and becomes a refrigerant gas for cooling the fuel cell. Then, the absorbing liquid can be heated to the regeneration temperature or higher by the fuel cell exhaust gas whose temperature has been increased by cooling the fuel cell. For this reason, the carbon dioxide in exhaust gas can be collect | recovered, without reducing electric power generation efficiency. Moreover, since it is not necessary to separately procure or generate refrigerant gas, the efficiency of the power generation system can be improved. Moreover, since it is not necessary to separately provide an apparatus for generating refrigerant gas, a storage tank for storing the procured refrigerant gas, etc., the facilities of the power generation system can be simplified.

  ADVANTAGE OF THE INVENTION According to this invention, the electric power generation system which can collect | recover carbon dioxide from exhaust gas, without reducing electric power generation efficiency can be provided.

It is a schematic diagram which shows the structural example of the electric power generation system which concerns on 1st Embodiment. It is a figure for demonstrating the electrochemical reaction of a fuel cell. It is a schematic diagram which shows the structural example of the electric power generation system which concerns on 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 and 2. FIG. 1 is a schematic diagram illustrating a configuration example of the power generation system 1. FIG. 2 is a diagram for explaining an electrochemical reaction of a molten carbonate fuel cell (MCFC) 200 provided in the power generation system 1 shown in FIG.

  The power generation system 1 includes a first power generation unit 20 having an MCFC 200 and a pressure vessel 210, a cryogenic separation device 30 (refrigerant gas supply unit, separation unit, oxygen supply unit), an absorption tower 601, a heat exchanger 603 (heat exchange). And a carbon dioxide recovery unit 60 including a regeneration tower 602. Furthermore, the power generation system 1 includes a gasification unit 10 that gasifies coal to generate fuel gas, a second power generation unit 40 that generates power using cathode exhaust gas discharged from the cathode 201 of the MCFC 200 described later, and steam. And a third power generation unit 50 that generates power by using the power generation unit.

  In the power generation system 1, composite power generation is performed by the MCFC 200, the second power generation unit 40, and the third power generation unit 50. That is, the MCFC 200 of the first power generation unit 20 is operated using the fuel gas generated in the gasification unit 10. Further, the second power generation unit 40 is driven using the cathode exhaust gas, and water vapor is generated by the heat from the gasification unit 10 and the MCFC 200 to drive the third power generation unit 50. Then, carbon dioxide contained in the anode exhaust gas discharged from the anode 202 of the MCFC 200 described later is recovered by the carbon dioxide recovery unit 60. Hereinafter, each configuration of the power generation system 1 will be described.

<<< Cryogenic separator >>>
The cryogenic separator 30 cools the air from which carbon dioxide and moisture have been adsorbed and removed until oxygen and nitrogen are liquefied, and then maintains the liquid state of oxygen and raises the temperature until nitrogen becomes a gas. Separate oxygen and nitrogen from the air. Therefore, in this cryogenic separation device 30, oxygen and nitrogen in a compressed and cooled state can be obtained. The cryogenic separation device 30 supplies the obtained oxygen to the gasification unit 10 and supplies the obtained nitrogen as the refrigerant gas of the MCFC 200 into the pressure vessel 210. At this time, since the oxygen and nitrogen are in a compressed state, the cryogenic separator 30 can efficiently transport oxygen to the gasification unit 10 and can efficiently transport nitrogen into the pressure vessel 210. Further, since the cryogenic separator 30 can supply cooled nitrogen as the refrigerant gas into the pressure vessel 210, the MCFC 200 can be efficiently cooled and maintained at the operating temperature. Therefore, the efficiency of the power generation system 1 can be improved.

<<< Gasification Department >>>
The gasification unit 10 includes a coal gasification furnace 100, a steam generation unit 110, a dust removal device 120, a desulfurization device 130, and a shift reactor 140.

  The coal gasification furnace 100 is an intermediate fuel gas containing hydrogen, carbon monoxide, carbon dioxide and the like by pyrolyzing coal into carbon and reacting the obtained carbon with oxygen supplied from the cryogenic separator 30. Is generated.

  The steam generation unit 110 generates steam by using the exhaust heat of the intermediate fuel gas discharged from the coal gasification furnace 100, and includes a gas cooler 101 and a condenser 102. The gas cooler 101 cools the intermediate fuel gas and generates water vapor by exchanging heat between the water supplied from the condenser 102 and the intermediate fuel gas. A part of the steam generated by the gas cooler 101 is supplied to the shift reactor 140 and the rest is supplied to the third power generation unit 50. The condenser 102 collects the water vapor used in the third power generation unit 50, changes it into liquid water, and supplies it to the gas cooler 101 again. That is, in the water vapor generation unit 110, water is circulated through the gas cooler 101 and the condenser 102 while changing the water into a liquid and a gas.

  The dust removing device 120 includes, for example, a porous filter, and removes solid impurities contained in the intermediate fuel gas by passing the intermediate fuel gas discharged from the gas cooler 101 through the porous filter. For example, the desulfurization device 130 makes the intermediate fuel gas discharged from the dust removal device 120 come into contact with a sulfur absorbent such as lime water or calcium carbonate to remove sulfur components contained in the intermediate fuel gas.

The shift reactor 140 shifts the carbon monoxide contained in the intermediate fuel gas discharged from the desulfurization device 130 and the water vapor supplied from the gas cooler 101 as shown in the following equation, so that carbon dioxide and Generate hydrogen.
CO + H ₂ O → CO ₂ + H ₂

  In the shift reactor 140, the fuel gas is generated by changing the composition of the intermediate fuel gas so that carbon monoxide decreases and hydrogen increases. Note that the fuel gas discharged from the shift reactor 140 is, for example, approximately the same temperature as the operating temperature of the MCFC 200 of about 650 degrees (hereinafter simply referred to as the operating temperature). Then, it is supplied to the MCFC 200 of the first power generation unit 20.

<<< First power generation unit >>>
The first power generation unit 20 includes an MCFC 200, a pressure vessel 210, a regulator 220, a combustor 230, a compressor 240, a circulation blower 250, and a heat exchanger 260.

  The compressor 240 conveys air to the MCFC 200. The MCFC 200 reaches an operating temperature when, for example, fuel gas is supplied from the shift reactor 140, and at this operating temperature, the fuel gas and air supplied from the compressor 240 are electrochemically reacted to generate power.

  In this MCFC 200, pressurized fuel gas and air are supplied and pressurized operation is performed in order to efficiently electrochemically react fuel gas and air to increase power generation efficiency.

  For example, as shown in FIG. 2, the MCFC 200 includes a cathode 201 made of a porous nickel oxide plate, an anode 202 made of a porous nickel plate, and an electrolyte 203 made of a carbonate of a mixture of lithium carbonate and sodium carbonate. have. The cathode 201 and the anode 202 are connected by an external circuit 204 via a load 205 that consumes power obtained by the MCFC 200.

At the cathode 201, oxygen (O ₂ , oxidant) and carbon dioxide (CO ₂ , oxidant) contained in the air supplied from the compressor 240 react with electrons (2 e ⁻ ) supplied from the external circuit 204. Thus, carbonate ions (CO ₃ ²⁻ ) are generated. Further, from the cathode 201, water containing the later-described combustion exhaust gas, air containing unreacted carbon dioxide, oxygen and the like is discharged as the cathode exhaust gas. The cathode exhaust gas has an operating temperature, for example. A part of the cathode exhaust gas is supplied to the combustor 230. A part of the remaining cathode exhaust gas is returned to the cathode 201 by the circulation blower 250 and reused for the electrochemical reaction of the MCFC 200. In this way, by returning a part of the cathode exhaust gas to the cathode 201, the temperature of the air supplied to the cathode 201 can be increased to near the operating temperature, and the efficiency of the power generation system 1 can be increased. The remaining cathode exhaust gas is supplied to the second power generation unit 40.

  The electrolyte 203 is in a molten state at the operating temperature and moves carbonate ions generated at the cathode 201 to the anode 202.

In the anode 202, hydrogen (H ₂ ) in the fuel gas supplied from the shift reactor 140 reacts with carbonate ions that have moved from the cathode 201 via the electrolyte 203, so that carbon dioxide (CO ₂ ) and Water vapor (H ₂ O) is generated, and electrons (2e ⁻ ) are emitted at the same time. The emitted electrons move to the cathode 201 through the external circuit 204, and electricity is generated by repeating this. Also, anode exhaust gas mainly containing carbon dioxide and water vapor and unreacted fuel gas, for example, having reached the operating temperature, is discharged from the anode 202. In the MCFC 200, carbon dioxide supplied to the cathode 201 is converted to carbonate ions and moves to the anode 202, so that anode exhaust gas enriched with carbon dioxide is discharged from the anode 202. A part of the anode exhaust gas is supplied to the combustor 230, and the remaining anode exhaust gas is supplied to the third power generation unit 50 via the heat exchanger 260.

  The combustor 230 causes the oxygen in the cathode exhaust gas and the fuel gas in the anode exhaust gas to undergo a combustion reaction, and discharges the combustion exhaust gas mainly containing carbon dioxide and water vapor. The combustion exhaust gas is supplied to the cathode 201 by the circulation blower 250. This can increase the power generation efficiency of the MCFC 200 by increasing the concentration of carbon dioxide supplied to the cathode 201.

  As described above, the circulation blower 250 circulates a part of the cathode exhaust gas and the combustion exhaust gas and supplies it to the cathode 201.

  The pressure vessel 210 houses the MCFC 200 and the combustor 230. Further, nitrogen having a temperature lower than the operating temperature is supplied from the cryogenic separator 30 as a refrigerant gas into the pressure vessel 210. With this refrigerant gas, the MCFC 200 suppresses the temperature rise accompanying the heat generation of the electrochemical reaction and maintains the operating temperature. Therefore, nitrogen produced as a by-product when oxygen is separated from air by the cryogenic separator 30 can be effectively used as the refrigerant gas of the MCFC 200, and the power generation efficiency of the power generation system 1 can be improved. Furthermore, since it is not necessary to separately provide an apparatus for generating refrigerant gas, a storage tank for storing the procured refrigerant gas, and the like, the facilities of the power generation system 1 can be simplified.

  Incidentally, the nitrogen supplied into the pressure vessel 210 becomes, for example, about 300 to 400 degrees by cooling the MCFC 200, and is supplied to the heat exchanger 603 of the carbon dioxide recovery unit 60 described later via the regulator 220. Is done.

  The regulator 220 is composed of, for example, a flow regulating valve, and regulates the flow rate of the refrigerant gas discharged from the pressure vessel 210 so that the pressure in the pressure vessel 210 is approximately the same as the pressure of the fuel gas and air supplied to the MCFC 200. Or it adjusts to a pressure higher than this pressure. This can prevent fuel gas and the like from leaking from the inside of the MCFC 200 to the outside, and the MCFC 200 can be efficiently pressurized. As a result, the power generation efficiency of the MCFC 200 can be increased and the efficiency of the power generation system 1 can be improved.

The heat exchanger 260, for example, heat-exchanges the anode exhaust gas at the operating temperature and the CO ₂ separation gas discharged from the absorption tower 601 of the carbon dioxide recovery unit 60 described later, cools the anode exhaust gas, and also cools the CO ₂ separation gas. Heat. The anode exhaust gas discharged from the heat exchanger 260 is supplied to the third power generation unit 50, and the CO ₂ separation gas is supplied to the anode 202.

<<< Second power generation section >>>
The second power generation unit 40 generates electricity using cathode exhaust gas, and includes a gas turbine 401 and a generator 402 connected to the same rotating shaft. The gas turbine 401 rotates the rotating shaft when the cathode exhaust gas is supplied. The generator 402 generates power when the gas turbine 401 rotates the rotation shaft. The compressor 240 is also connected to the same rotating shaft as the gas turbine 401 and the generator 402 and is driven in conjunction with the rotation of the gas turbine 401.

<<< Third power generation section >>>
As described above, the third power generation unit 50 generates power using water vapor. That is, water vapor generated using the anode exhaust gas discharged from the heat exchanger 260 of the first power generation unit 20 and the cathode exhaust gas discharged from the gas turbine 401 of the second power generation unit 40, and the gas of the gasification unit 10 Electric power is generated using the water vapor discharged from the cooler 101.

  The third power generation unit 50 includes exhaust heat recovery boilers 501 and 502, a steam / water separator 503, a circulation pump 504, a generator 505, steam turbines 506 and 507, and a condenser 508. .

  The exhaust heat recovery boiler 501 performs heat exchange between the anode exhaust gas discharged from the heat exchanger 260 and the water supplied by the circulation pump 504, thereby cooling the anode exhaust gas to, for example, about 40 degrees (absorption temperature). Generates water vapor. Note that the steam generated by the exhaust heat recovery boiler 501 is supplied to the steam turbine 507. Further, the anode exhaust gas, for example, having an absorption temperature in the exhaust heat recovery boiler 501 is supplied to the absorption tower 601 of the carbon dioxide recovery unit 60.

  The exhaust heat recovery boiler 502 heat-exchanges the cathode exhaust gas discharged from the gas turbine 401 and the water supplied by the circulation pump 504, thereby cooling the cathode exhaust gas and generating water vapor. The steam generated by the exhaust heat recovery boiler 502 is supplied to the steam turbine 507 together with the steam generated by the exhaust heat recovery boiler 501. Moreover, the cathode exhaust gas cooled by the exhaust heat recovery boiler 502 is supplied to the steam separator 503.

  The steam separator 503 separates water liquefied by being cooled by the exhaust heat recovery boiler 502 from the cathode exhaust gas. The cathode exhaust gas from which water has been separated by the steam separator 503 is exhausted. Further, the water taken out by the steam separator 503 is supplied to the exhaust heat recovery boilers 501 and 502 by the circulation pump 504.

  The steam turbine 507 is connected to the same rotating shaft as the generator 505 and rotates the rotating shaft with water vapor supplied from the exhaust heat recovery boilers 501 and 502. Note that the steam discharged from the steam turbine 507 is supplied to the condenser 508.

  The steam turbine 506 is connected to the same rotating shaft as the steam turbine 507 and the generator 505, and rotates the rotating shaft with water vapor supplied from the gas cooler 101 of the gasification unit 10. The steam discharged from the steam turbine 506 is supplied to the condenser 102 of the gasification unit 10. The generator 505 generates power by causing the steam turbines 506 and 507 to rotate the rotation shaft.

  The condenser 508 changes the water vapor supplied from the steam turbine 507 into liquid water. The water discharged from the condenser 508 is supplied to the exhaust heat recovery boilers 501 and 502 together with the water discharged from the steam separator 503 by the circulation pump 504.

<<< CO2 recovery department >>>
The carbon dioxide recovery unit 60 recovers carbon dioxide from the anode exhaust gas discharged from the exhaust heat recovery boiler 501 of the third power generation unit 50 using an absorbing liquid such as an alkanolamine aqueous solution. The absorption liquid absorbs carbon dioxide because carbon dioxide is bonded to amino groups at an absorption temperature of about 40 degrees. Moreover, since the carbon dioxide which couple | bonded with the amino group is desorbed at the regeneration temperature of about 120 ° C., the absorbing solution releases carbon dioxide.

  The carbon dioxide recovery unit 60 includes an absorption tower 601, a regeneration tower 602, a heat exchanger 603, a heat exchanger 604 (another heat exchanger), and a separator 605. In the carbon dioxide recovery unit 60, the absorption liquid absorbs carbon dioxide in the absorption tower 601, is heated to a regeneration temperature or higher in the heat exchangers 603 and 604, and releases carbon dioxide in the regeneration tower 602. Then, it is cooled again by the heat exchanger 604 and returned to the absorption tower 601.

In the absorption tower 601, the absorption liquid and the anode exhaust gas cooled to the absorption temperature, for example, by the exhaust heat recovery boiler 501 are brought into contact with each other, and the carbon dioxide in the anode exhaust gas is absorbed by the absorption liquid as shown in the following equation. In addition, R shown in the formula is an alkyl group.
R—NH ₂ + H ₂ O + CO ₂ → R—NH ₃ HCO ₃

As a result of carbon dioxide being separated from the anode exhaust gas by the absorption tower 601, a CO ₂ separation gas mainly containing hydrogen and carbon monoxide is generated. The CO ₂ separation gas is heated by the heat exchanger 260 of the first power generation unit 20 and then supplied to the anode 202 of the MCFC 200 to be reused for the electrochemical reaction. Thereby, the efficiency of the power generation system 1 can be improved.

  The heat exchanger 604 exchanges heat between the absorption liquid at the absorption temperature discharged from the absorption tower 601 and the absorption liquid at the regeneration temperature discharged from the regeneration tower 602. The heat exchanger 604 heats the absorption liquid discharged from the absorption tower 601 and supplies it to the regeneration tower 602, cools the absorption liquid discharged from the regeneration tower 602, and supplies it to the absorption tower 601.

In the regeneration tower 602, the absorption liquid heated by the heat exchanger 604 to be higher than the absorption temperature and further maintained by the heat exchanger 603 to be higher than the regeneration temperature is stored. Then, in the regeneration tower 602, carbon dioxide is released from the absorbing solution as shown in the following equation. In addition, R shown in the formula is an alkyl group.
R—NH ₃ HCO ₃ → R—NH ₂ + H ₂ O + CO ₂

  In the regeneration tower 602, carbon dioxide released from the absorbing solution is supplied to the separator 605 together with a gas component such as water vapor.

  The heat exchanger 603 exchanges heat between the absorption liquid stored in the regeneration tower 602 and the refrigerant gas of about 300 to 400 degrees supplied from the regulator 220 of the first power generation unit 20, and stores in the regeneration tower 602. Maintain the absorbed liquid above the regeneration temperature. The cooled refrigerant gas is exhausted by the heat exchanger 603.

  The separator 605 cools the carbon dioxide and water vapor supplied from the regeneration tower 602, liquefies the water vapor and the like, and separates carbon dioxide from water and the like by gas-liquid separation. The carbon dioxide separated by the separator 605 is collected in a tank (not shown), for example. Further, the water or the like separated by the separator 605 is returned to the regeneration tower 602.

  As described above, in the power generation system 1 according to the first embodiment, the absorption liquid at the absorption temperature discharged from the absorption tower 601 is heated by the absorption liquid at the regeneration temperature discharged from the regeneration tower 602 and then regenerated. It can be supplied to the tower 602 and stored. Moreover, this stored absorption liquid can be heated by the refrigerant gas which became about 300 to 400 degree | times by cooling MCFC200, and can be maintained at regeneration temperature. Therefore, carbon dioxide can be released from the absorbent in the regeneration tower 602 without using energy such as fuel gas or water vapor generated to obtain power in the power generation system 1. As a result, carbon dioxide in the exhaust gas can be recovered without reducing the power generation efficiency, and the efficiency of the power generation system 1 can be improved. Moreover, the load of the heat exchanger 603 for maintaining the absorbing liquid at the regeneration temperature can be reduced, and the configuration for maintaining the absorbing liquid at the regeneration temperature can be simplified.

In the power generation system 1, the absorption liquid having the absorption temperature discharged from the absorption tower 601 can be cooled and supplied to the absorption tower 601 after being cooled from the regeneration tower 602. Carbon dioxide can be absorbed. Therefore, using the exhaust heat of the absorption liquid, the absorption liquid can be efficiently heated and cooled, and the absorption liquid can be circulated between the absorption tower 601 and the regeneration tower 602, thereby improving the efficiency of the power generation system 1. In the power generation system 1, the anode exhaust gas enriched with carbon dioxide is discharged from the anode 202 of the MCFC 200, and this anode exhaust gas is supplied to the absorption tower 601 of the carbon dioxide recovery unit 60. Carbon can be recovered.

  In the power generation system 1, nitrogen produced as a by-product when the oxygen supplied to the coal gasification furnace 100 is separated from the air by the cryogenic separator 30 is supplied into the pressure vessel 210 as a refrigerant gas for cooling the MCFC 200. Is done. For this reason, nitrogen produced as a by-product in the cryogenic separator 30 can be used effectively, and the efficiency of the power generation system 1 can be improved. Moreover, since it is not necessary to separately provide an apparatus for generating refrigerant gas, a storage tank for storing the procured refrigerant gas, and the like, the facilities of the power generation system 1 can be simplified.

  Further, in the power generation system 1, since nitrogen from the cryogenic separator 30 is supplied as the refrigerant gas into the pressure vessel 210, even if the fuel gas leaks from the MCFC 200, the combustion gas causes a combustion reaction. Can be prevented, and the safety of the power generation system 1 can be improved.

  Further, in the power generation system 1, oxygen and nitrogen in a compressed and cooled state can be obtained by the cryogenic separation device 30, so that oxygen can be efficiently conveyed to the coal gasification furnace 100 and nitrogen can be supplied to the pressure vessel 210. Can be transported efficiently. Further, the MCFC 200 can be efficiently cooled by the nitrogen supplied to the pressure vessel 210.

=== 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 FIGS. 2 and 3. FIG. 3 is a schematic diagram illustrating a configuration example of the power generation system 2. In FIG. 3, 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 does not include the gasification unit 10 and the cryogenic separation device 30 in the power generation system 1 described above. In addition, the first power generation unit 20 further including the fuel gas adjustment unit 270 is provided in the first power generation unit 20 described above. In this power generation system 2, instead of the fuel gas generated in the shift reactor 140 of the gasification unit 10, the fuel gas such as natural gas is adjusted to the reformed fuel gas by the fuel gas adjustment unit 270, and then the MCFC 200 Supplied to the anode 202.

  Further, in the power generation system 2, the cathode exhaust gas discharged from the gas turbine 401 is cooled below the operating temperature by the exhaust heat recovery boiler 502 (cooler) instead of nitrogen discharged from the cryogenic separator 30, After being separated from water by the water separator 503, it is supplied into the pressure vessel 210 as a refrigerant gas. That is, in the power generation system 2, the MCFC 200, the exhaust heat recovery boiler 502, and the steam separator 503 serve as the refrigerant gas supply unit. In the following description, the exhaust gas discharged from the steam separator 503, which is the refrigerant gas of the MCFC 200, is referred to as a steam / water separation exhaust gas.

  The power generation system 2 includes a third power generation unit 51 in place of the third power generation unit 50 in the power generation system 1 described above. The third power generation unit 51 is different in that it does not include the steam turbine 506 in the third power generation unit 50 described above.

  In the power generation system 2, the MCFC 200 of the first power generation unit 21 is operated using fuel gas such as natural gas. Further, the second power generation unit 40 is driven using the cathode exhaust gas of the MCFC 200, and the third power generation unit 51 is driven using water vapor generated by the heat from the MCFC 200. Then, the carbon dioxide contained in the anode exhaust gas of the MCFC 200 is collected by the carbon dioxide collecting unit 60. At this time, the absorption liquid stored in the regeneration tower 602 is maintained at the regeneration temperature or higher by the heat of the steam-water separation exhaust gas after cooling the MCFC 200. Hereinafter, a configuration different from the configuration of the power generation system 1 described above will be described.

<<< Fuel gas adjustment section >>
The fuel gas adjustment unit 270 is accommodated in the pressure vessel 210 and includes a fuel preheater 271, a reformer 272, and a heating chamber 273.

The fuel preheater 271 is supplied with a mixed gas of a fuel gas such as natural gas, a part of water vapor generated by the exhaust heat recovery boiler 501, and a CO ₂ separation gas heated by the heat exchanger 260. Heat exchange is performed between the mixed gas and the reformed fuel gas discharged from the reformer 272. As a result, the mixed gas is heated and supplied to the reformer 272, and the reformed fuel gas is cooled and supplied to the anode 202.

In the reformer 272, as shown in the following equation, methane and water vapor contained in the mixed gas heated by the fuel preheater 271 undergo a reforming reaction to generate hydrogen and carbon monoxide. Thereby, the reformed fuel gas mainly containing hydrogen, carbon monoxide and the like is generated.
CH ₄ + H ₂ O → CO + 3H ₂

  The reformed fuel gas discharged from the reformer 272 is cooled to, for example, the operating temperature by the fuel preheater 271 and then supplied to the anode 202 of the MCFC 200.

  The heating chamber 273 maintains the temperature of the reformer 272 at a temperature suitable for the above-described reforming reaction by the heat of the combustion exhaust gas supplied from the combustor 230. The combustion exhaust gas discharged from the heating chamber 273 is supplied to the cathode 201 by the circulation blower 250.

<<< Third power generation section >>>
In the third power generation unit 51, the remaining steam generated by the exhaust heat recovery boiler 501 is supplied to the steam turbine 507. The generator 505 generates power by causing the steam turbine 507 to rotate the rotating shaft with the steam supplied from the exhaust heat recovery boilers 501 and 502. A part of the steam-water separation exhaust gas discharged from the steam-water separator 503 is supplied to the pressure vessel 210 as a refrigerant gas for cooling the MCFC 200, and the remaining steam-water separation exhaust gas is exhausted.

  Note that the gas-water separation exhaust gas whose temperature has been increased by cooling the MCFC 200 is supplied from the pressure vessel 210 to the heat exchanger 603 of the carbon dioxide recovery unit 60 via the regulator 220.

  As described above, in the power generation system 2 according to the second embodiment, in the heat exchanger 603, the heat / water separation exhaust gas and the absorption liquid stored in the regeneration tower 602 are heat-exchanged to be stored in the regeneration tower 602. Can be maintained above the regeneration temperature. Therefore, in the power generation system 2, the temperature of the absorbing liquid can be maintained at the regeneration temperature or higher without using water vapor or the like generated to obtain electric power, so that carbon dioxide is emitted from the exhaust gas without reducing the power generation efficiency. Can be recovered. Moreover, since it is not necessary to separately procure or generate refrigerant gas, the efficiency of the power generation system 2 can be improved. Moreover, since it is not necessary to separately provide an apparatus for generating refrigerant gas, a storage tank for storing the procured refrigerant gas, and the like, the facilities of the power generation system 2 can be simplified.

=== 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 cryogenic separator 30 separates oxygen and nitrogen from the air. However, the present invention is not particularly limited to this. For example, air may be separated into oxygen and nitrogen by a membrane separation method using a difference in permeation speed for each gas component in the polymer membrane.

  In the power generation system 2 described above, the fuel gas such as natural gas is adjusted to the reformed fuel gas by the fuel gas adjusting unit 270 and supplied to the anode 202 of the MCFC 200. However, the present invention is not particularly limited to this. For example, it is only necessary that a hydrocarbon serving as a hydrogen source is supplied to the anode 202 of the MCFC 200 via the fuel gas adjusting unit 270.

DESCRIPTION OF SYMBOLS 1, 2 ... Power generation system 10 ... Gasification part 20, 21 ... 1st power generation part 30 ... Cryogenic separator 40 ... 2nd power generation part 50, 51 ... 3rd power generation part 60 ... Carbon dioxide collection part 100 ... Coal gasification Furnace 101 ... Gas cooler 102, 508 ... Condenser 110 ... Steam generation unit 120 ... Dedusting device 130 ... Desulfurization device 140 ... Shift reactor 200 ... MCFC
DESCRIPTION OF SYMBOLS 201 ... Cathode 202 ... Anode 203 ... Electrolyte 204 ... External circuit 205 ... Load 210 ... Pressure vessel 220 ... Regulator 230 ... Combustor 240 ... Compressor 250 ... Circulation blower 260, 603, 604 ... Heat exchanger 270 ... Fuel gas adjustment part 271 ... Fuel preheater 272 ... Reformer 273 ... Heating chamber 401 ... Gas turbine 402, 505 ... Generator 501, 502 ... Waste heat recovery boiler 503 ... Steam separator 504 ... Circulation pump 506, 507 ... Steam turbine 601 ... Absorption tower 602 ... Regeneration tower 605 ... Separator

Claims (5)

A fuel cell that generates electricity by electrochemically reacting a fuel gas and an oxidant; and
A pressure vessel containing the fuel cell;
Supplying a refrigerant gas to the pressure vessel, and maintaining a temperature of the fuel cell that generates heat by the electrochemical reaction at an operating temperature; and
An absorption tower that absorbs carbon dioxide at an absorption temperature and contacts a gas containing carbon dioxide at the absorption temperature with an absorption liquid that releases carbon dioxide at a regeneration temperature higher than the absorption temperature;
A heat exchanger that exchanges heat between the refrigerant gas discharged from the pressure vessel and the absorption liquid discharged from the absorption tower, and heats the absorption liquid to the regeneration temperature or higher;
A regeneration tower for releasing carbon dioxide from the heated absorption liquid;
A power generation system comprising: The absorption liquid discharged from the absorption tower is heated and discharged to the regeneration tower, and the absorption liquid discharged from the regeneration tower is cooled by the absorption liquid discharged from the absorption tower to absorb the absorption. Install another heat exchanger to supply the tower,
The heat exchanger is
The power generation system according to claim 1, wherein the absorption liquid stored in the regeneration tower is heated to the regeneration temperature or higher.   The power generation system according to claim 1, wherein the refrigerant gas is an inert gas that does not cause a combustion reaction with the fuel gas. A gasification unit that generates oxygen by reacting carbon with carbon obtained by pyrolysis of coal to generate the fuel gas;
A separation unit for separating oxygen and nitrogen from air;
An oxygen supply unit for supplying oxygen separated in the separation unit to the gasification unit,
The power generation system according to claim 1, wherein the refrigerant gas supply unit supplies nitrogen separated by the separation unit as the refrigerant gas to the pressure vessel.   2. The power generation system according to claim 1, wherein the refrigerant gas supply unit includes a cooler configured to cool the fuel cell exhaust gas discharged from the fuel cell to the operating temperature or lower to obtain the refrigerant gas.

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