JP2006031989A - Method and system for power generation by solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a system for power generation by a solid oxide fuel cell wherein power generation efficiency is improved by improving a fuel utilization factor of the solid oxide fuel cell. <P>SOLUTION: In the method and the system for power generation by the solid oxide fuel cell, steam or steam and carbon dioxide are removed from anode off-gas of a solid oxide fuel cell to regenerate the anode off-gas, and the regenerated off-gas is utilized as a fuel for the solid oxide fuel cell to improve the fuel utilization factor of the solid oxide fuel cell. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power generation method and system using a solid oxide fuel cell, and more particularly to a power generation method and system that improve the fuel utilization rate in the solid oxide fuel cell itself and improve the power generation efficiency. .

A solid oxide fuel cell (hereinafter abbreviated as SOFC as appropriate) is characterized in that an oxide ion (O ²⁻ ) conductor is used as a solid electrolyte. (Fuel electrode) and cathode (air electrode or oxygen electrode) are both arranged. The SOFC generally has an operating temperature as high as about 800 to 1000 ° C., but an SOFC having an operating temperature of about 600 to 800 ° C., for example, about 750 ° C. is being developed. Hereinafter, the case where air is supplied to the cathode will be described as an example, but the same applies to the case where oxygen-enriched air or oxygen is supplied as the oxidant gas.

In the SOFC, during operation, electric power is taken out by supplying fuel to the anode side and supplying air to the cathode side to cause an electrochemical reaction. Oxygen in the air supplied from the air supply pipe becomes oxide ions (O ²⁻ ) at the cathode and reaches the anode through the electrolyte membrane. Here, it reacts with the fuel supplied from the fuel supply pipe and emits electrons to generate electricity and reaction products (H ₂ O and CO ₂ ).

  In SOFC, hydrogen and carbon monoxide are used as fuel. However, methane is steam reformed by the catalytic action of a metal that is a constituent component of the anode, for example, nickel, so that hydrogen and carbon monoxide are produced. In addition to hydrogen fuel, fuel containing hydrogen and carbon monoxide, or fuel containing hydrogen, carbon monoxide and methane is used.

  In SOFC, when hydrocarbon is used as raw fuel (in this specification, the fuel before preliminary reforming is referred to as raw fuel as appropriate), hydrogen, carbon monoxide and methane obtained by the preliminary reforming are electrochemically reacted. (Note that methane is reformed at the anode of SOFC and used for electrochemical reaction). In the SOFC, about 80 to 85% of the fuel supplied to the anode is normally used, and the remaining 20 to 15% is discharged outside the cell stack without being used. At that time, the unused gas is not released as it is, but is burned for heat recovery and used for preheating fuel and air.

  As such, the SOFC is normally operated at a fuel utilization rate of about 80 to 85%. However, if the fuel utilization rate is further increased, the fuel withering occurs, the cell potential drops, and the power generation efficiency decreases. It is. For this reason, one of the problems of SOFC is that the fuel utilization rate cannot be set high. The fuel supplied to the SOFC can theoretically be used up to about 95%, but in reality, there are problems such as slight fuel leakage and diffusion rate control inside the electrode, and it can be used at most about 80%. is the current situation.

  For this reason, the remaining 20% of the fuel discharged as anode off-gas burns and is only used as a heat source for SOFC by the preheating of the fuel and air supplied to the SOFC, or as a heat source in a cogeneration system, etc. (JP 2001-266924 A, JP 2002-56875 A). Further, in Japanese Patent Application Laid-Open No. 2004-6281, in the technology using hot water as in Japanese Patent Application Laid-Open No. 2002-56875, electric power and hot water are rarely used evenly. There are many cases where electricity is not used or electricity is used only with hot water, and energy generation devices that can use waste hydrogen generated in the process of power generation for hot water generation or power generation are proposed Has been.

JP 2001-266924 A JP 2002-56875 A JP 2004-6281 A

FIG. 1 shows a conventional SOFC system in which anode off-gas from an SOFC stack is added to fuel and air preheating and used in a hot water supply system in a cogeneration system or the like. As shown in FIG. 1, raw fuel such as city gas is supplied to a pre-reformer through a booster and a desulfurizer. Here, in the SOFC, in addition of the hydrogen and carbon monoxide, methane is also made to the fuel, ethane other than methane in the fuel supplied to the SOFC, include ethylene, propane, carbon number C ₂ or more hydrocarbons such as butane If so, carbon is produced in the pipes and anodes to the SOFC stack, which inhibits electrochemical reactions and degrades battery performance. For this reason, in the pre-reformer, the raw fuel is pre-reformed and converted into a pre-reformed gas containing hydrogen, carbon monoxide and methane.

  The pre-reformed gas is preheated by the heat exchanger 2 and then supplied to the anode of the SOFC stack to generate power by an electrochemical reaction with oxygen from the cathode. At that time, methane in the pre-reformed gas is reformed to hydrogen and carbon monoxide by internal reforming. On the other hand, the air is preheated by the heat exchanger 1 through the blower and then supplied to the cathode of the SOFC stack. In addition, the electric power obtained by the SOFC stack is converted into an alternating current by an inverter as necessary.

  The anode offgas from the SOFC stack is mixed with the cathode offgas in a combustor (offgas combustor in FIG. 1) and burned. The combustion gas is sequentially passed through the heat exchanger 1 and the heat exchanger 2 and used for preheating air and the pre-reformed gas, respectively, and then further passed through the heat exchanger 3. Here, after being used for heating water in the hot water supply system, it is discharged as exhaust gas.

  However, there is a limit to the heating of the air and the pre-reformed gas in the heat exchanger 1 and the heat exchanger 2 (the total amount of combustion gas is not necessary for pre-heating the air and the pre-reformed gas). Moreover, since there is a limit to the amount of hot water required in the hot water supply system, even if hot water exceeding the required amount is obtained, it will be wasted. Thus, the efficiency of the SOFC system is greatly influenced by the fuel utilization rate in the SOFC stack itself. And the limit of fuel utilization in the SOFC itself has lowered the efficiency of the SOFC system.

  By the way, paying attention to the spent fuel discharged from the SOFC stack, that is, the anode off gas, the anode off gas contains hydrogen, carbon monoxide, and the like that are not used in the SOFC. Therefore, the present invention pays attention to such anode off-gas containing unused hydrogen and carbon monoxide in the conventional SOFC system, and uses this for improving the fuel utilization rate in the SOFC stack itself. The purpose is to increase the efficiency.

  That is, the present invention removes (a) water vapor, (b) water vapor and carbon dioxide, or (c) water vapor, carbon dioxide and carbon monoxide from the anode off-gas of the SOFC stack. An object of the present invention is to provide a power generation method and system using SOFC that regenerates the anode off gas and recycles the regenerated off gas as fuel for the fuel cell to increase the fuel utilization rate in the SOFC and improve the power generation efficiency. is there.

  The present invention is (1) a power generation method using a solid oxide fuel cell, in which water vapor is removed from the anode offgas of the solid oxide fuel cell to regenerate the anode offgas, and the regenerated offgas is used as the solid oxide fuel cell. A power generation method using a solid oxide fuel cell is provided in which the fuel utilization rate of the solid oxide fuel cell itself is improved by being reused as a fuel.

  The present invention is (2) a power generation method using a solid oxide fuel cell, in which water vapor and carbon dioxide are removed from the anode offgas of the solid oxide fuel cell to regenerate the anode offgas, and the regenerated offgas is converted into a solid oxide. Provided is a power generation method using a solid oxide fuel cell, wherein the fuel utilization rate of the solid oxide fuel cell itself is improved by reusing it as a fuel for a fuel cell.

  The present invention is (3) a power generation method using a solid oxide fuel cell, which removes water vapor, carbon dioxide and carbon monoxide from the anode off gas of the solid oxide fuel cell to regenerate the anode off gas, The present invention provides a power generation method using a solid oxide fuel cell, characterized in that the fuel utilization rate is improved by using as a fuel for a polymer electrolyte fuel cell.

  The present invention is (4) a power generation system in which the solid oxide fuel cell itself improves the fuel utilization rate in the solid oxide fuel cell, and water vapor is generated from the anode off-gas of the solid oxide fuel cell. There is provided a power generation system using a solid oxide fuel cell, characterized in that the anode off gas is removed to regenerate and the regenerated off gas is reused as a fuel for the solid oxide fuel cell.

  The present invention is (5) a power generation system in which the solid oxide fuel cell itself improves the fuel utilization rate in the solid oxide fuel cell, wherein the solid oxide fuel cell's anode off-gas is supplied with water vapor and Provided is a power generation system using a solid oxide fuel cell, wherein carbon dioxide is removed to regenerate the anode off gas, and the regenerated off gas is reused as a fuel for the solid oxide fuel cell.

  The present invention is (6) a power generation system in which the fuel utilization rate in a solid oxide fuel cell is improved by removing water vapor, carbon dioxide and carbon monoxide from the anode off-gas of the solid oxide fuel cell. Provided is a power generation system using a solid oxide fuel cell, wherein the anode off gas is regenerated and the regenerated off gas is used as a fuel for a polymer electrolyte fuel cell.

  The present inventions (1) and (4) are SOFC power generation methods and systems. Then, water vapor is removed from the anode offgas of the SOFC to regenerate the anode offgas, and the recycled offgas is reused as fuel for the SOFC, thereby improving the fuel utilization rate. Here, the SOFC that removes water vapor from the SOFC anode off-gas and regenerates the SOFC that reuses the regenerated off-gas as fuel may be the same SOFC, or may be separate SOFCs.

  The present inventions (2) and (5) are SOFC power generation methods and systems. The fuel off rate is improved by removing water vapor and carbon dioxide from the anode offgas of the SOFC to regenerate the anode offgas, and reusing the regenerated offgas as the fuel for the SOFC. Here, the SOFC that regenerates by removing water vapor and carbon dioxide from the anode offgas of the SOFC and the SOFC that reuses the regenerated offgas as fuel may be the same SOFC, or may be separate SOFCs. .

  The present inventions (3) and (6) are SOFC power generation methods and systems. Then, the water vapor, carbon dioxide and carbon monoxide are removed from the SOFC anode off-gas to regenerate the anode off-gas, and the regenerated off-gas is a fuel for a polymer electrolyte fuel cell (hereinafter abbreviated as PEFC as appropriate). It is characterized by improving the fuel utilization rate.

  In the present invention (3) and (6), in addition to power generation by SOFC, power generation by PEFC is performed, and the regenerated anode off-gas of SOFC is used as fuel for PEFC. In the case of PEFC, the allowable concentration of CO in the fuel is about 100 ppm (ppm = vol ppm, the same applies hereinafter), and about 10 ppm depending on the constituent material of the anode, etc. The SOFC anode off-gas removes water vapor and carbon dioxide as well as carbon monoxide and uses it as a fuel for PEFC.

  FIG. 2 is a diagram for explaining the operation and effect of the present invention, and shows the relationship between the fuel utilization rate and the cell voltage in SOFC. As shown in FIG. 2, when the fuel utilization rate in the SOFC is increased, the cell voltage gradually decreases. Then, the cell voltage rapidly decreases at a fuel utilization rate exceeding about 90%. In addition, the fuel utilization rate is actually limited to about 80 to 85% due to fuel depletion, that is, concentration overvoltage and slight fuel leakage.

If the fuel utilization rate U _f is 80%, the battery efficiency η _cell is 70%, the inverter efficiency η _inv is 90%, and the auxiliary machine efficiency η _aux is 90%, the final power generation efficiency η is η = U _f × η _cell × η _inv × η _aux = 0.8 × 0.7 × 0.9 × 0.9≈0.45, that is, about 45%.

When the remaining 20% anode off-gas is regenerated and used as a 100% hydrogen fuel in SOFC or PEFC, the power generation efficiency at the remaining 20% is η = U _f × η _cell × η _inv × η _aux = 0.2 × 0.7 × 0.9 × 0.9≈0.11, that is, about 11% is added, and the total power generation efficiency can be increased to 56%.

  In the present invention, by utilizing this fact, the anode off-gas is regenerated by removing (a) water vapor, (b) water vapor and carbon dioxide, or (c) water vapor, carbon dioxide and carbon monoxide in the anode off-gas. By reusing the regenerated offgas as fuel, the fuel utilization rate in SOFC is increased and the power generation efficiency is improved. In addition to city gas, natural gas, petroleum gas, gasoline, kerosene, or alcohols (methanol or ethanol) are used as raw fuel in the present invention.

  EXAMPLES Hereinafter, although this invention is demonstrated in more detail based on an Example, it cannot be overemphasized that this invention is not limited to these Examples.

<Example 1>
FIG. 3 is a diagram showing an embodiment of the present invention (1) and (4), in which water vapor is removed from the anode off-gas from the SOFC to regenerate the anode off-gas, and the recycled off-gas is reused as SOFC fuel. It is. As shown in FIG. 3, the SOFC stack A and the SOFC stack B are used in the SOFC system of this example.

  Raw fuel such as city gas is supplied to a pre-reformer through a booster and a desulfurizer, where it is pre-reformed and converted into a pre-reformed gas containing hydrogen, carbon monoxide and methane. The pre-reformed gas is preheated by the heat exchanger 2 and then supplied to the anode of the SOFC stack A to generate electric power by an electrochemical reaction with oxygen from the cathode. At that time, methane in the pre-reformed gas is reformed to hydrogen and carbon monoxide by internal reforming at the anode and used as fuel. In some cases, a reformer for reforming may be disposed in the SOFC stack A or in front of the SOFC stack A together with or instead of internal reforming at the anode. This also applies to the following embodiments. On the other hand, the air is sequentially preheated by the heat exchanger 4 and the heat exchanger 1 through the blower and then supplied to the cathode of the SOFC stack A. The heat source in the heat exchanger 4 is the anode off gas from the SOFC stack A.

  The anode off-gas from the SOFC stack A is cooled by heat exchange with the air supplied to the SOFC stack A in the heat exchanger 4 and further cooled by water from the hot water supply system in the heat exchanger 5 to condense and remove water vapor. Then, it is heated by the heat exchanger 6 and supplied to the anode of the SOFC stack B. Here, the hot water supply system may be a hot water supply system in a cogeneration system or the like, or another cooling source may be used instead of the hot water supply system. At this time, since the cooling source itself is heated, the heat can be effectively used. This also applies to the following examples.

  On the other hand, air branches through the blower and is supplied to the cathode of the SOFC stack B. The anode off-gas from which the water vapor has been condensed and removed generates power by an electrochemical reaction with oxygen from the cathode of the SOFC stack B. In this manner, the water vapor is condensed and removed from the anode off-gas from the SOFC stack A and regenerated, and the regenerated anode off-gas is used as fuel for the SOFC stack B. Thereby, the fuel utilization rate as a total in this system can be raised. The condensed water vapor is discharged from a drain pipe branched from the anode off-gas conduit according to a conventional method.

  The spent fuel from the SOFC stack B, that is, the anode off gas, is mixed with the cathode off gas from the SOFC stack B in an off gas combustor and burned. The combustion gas passes through the heat exchanger 6 and is used as a heating source for the air supplied to the SOFC stack B and the regenerated anode off gas (regenerated by removing water vapor in the heat exchanger 5). Exhaust as exhaust. A part of the anode off-gas from the SOFC stack A may be branched and recycled in front of the heat exchanger 4 and supplied to the pre-reformer as shown as “fuel recycling” in FIG. This also applies to the following embodiments. The electric power obtained in the SOFC stacks A and B is converted into alternating current by the inverter.

  Further, the cathode off-gas from the SOFC stack A is sequentially passed through the heat exchanger 1 and the heat exchanger 2 and used as a heating source for air and pre-reformed gas, respectively, and further passed to the heat exchanger 3. Is done. Here, it is used for heating water from the hot water supply system and discharged as air exhaust.

<Example 2>
FIG. 4 is a diagram showing an embodiment of the present invention (2) and (5), in which water vapor and carbon dioxide are removed from the SOFC anode off-gas to regenerate the anode off-gas, and the regenerated off-gas is reused as SOFC fuel. This is an example. As shown in FIG. 4, the SOFC stack A and the SOFC stack B are used in the SOFC system of this example.

  Raw fuel such as city gas is supplied to a pre-reformer through a booster and a desulfurizer, where it is pre-reformed and converted into a pre-reformed gas containing hydrogen, carbon monoxide and methane. The pre-reformed gas is preheated by the heat exchanger 2 and then supplied to the anode of the SOFC stack A to generate electric power by an electrochemical reaction with oxygen from the cathode. At that time, methane in the pre-reformed gas is reformed to hydrogen and carbon monoxide by internal reforming at the anode.

  On the other hand, the air is sequentially preheated by the heat exchanger 4 and the heat exchanger 1 through the blower and then supplied to the cathode of the SOFC stack A. The heat source in the heat exchanger 4 is the anode off gas from the SOFC stack A. A part of the anode off-gas from the SOFC stack A may be branched and recycled before the heat exchanger 4 and supplied to the pre-reformer.

The anode off gas from the SOFC stack A is cooled by the air supplied to the SOFC stack A by the heat exchanger 4 and then supplied to the carbon dioxide remover (CO ₂ remover in FIG. 4). In the carbon dioxide remover, for example, carbon dioxide may be selectively removed from the anode off-gas with an absorbent or the like, and examples of the absorbent include lithiated zirconia (Li ₂ ZrO ₃ and Li ₄ ZrO ₄ ). . This absorbent reacts with carbon dioxide and absorbs and removes carbon dioxide, but this reaction proceeds at about 700 ° C. or less, and absorbs carbon dioxide at a volume ratio of about 520 times that of lithiated zirconia around 600 ° C. To do. Although the temperature of the anode off-gas that has passed through the heat exchanger 4 is lower than about 700 ° C., and is still high, for example, carbon dioxide in the anode off-gas can be selectively removed using such an absorbent.

  The anode off gas is further cooled by water from the hot water supply system in the heat exchanger 5, and water vapor in the anode off gas is condensed and removed. Thus, the anode off gas of the SOFC stack A regenerated by removing carbon dioxide and water vapor is supplied to the anode of the SOFC stack B through the heat exchanger 6. On the other hand, the air branches through the blower and is supplied to the cathode of the SOFC stack B.

  The regeneration anode off gas generates power by an electrochemical reaction with oxygen from the cathode of the SOFC stack B. The electric power obtained in the SOFC stacks A and B is converted into alternating current by the inverter. The anode off gas from the SOFC stack B is also mixed with the cathode off gas from the stack B and burned. The combustion gas is regenerated by passing through the heat exchanger 6 and supplying air to the SOFC stack B and the regenerated anode off-gas (removing carbon dioxide with the CO remover and removing water vapor with the heat exchanger 5). ) And then exhausted as exhaust.

  In this way, the anode off-gas from the SOFC stack A is regenerated by removing carbon dioxide and water vapor therein and used as fuel for the SOFC stack B, thereby increasing the fuel utilization rate as a total in this system. be able to.

  Further, the cathode off-gas from the SOFC stack A is sequentially passed through the heat exchanger 1 and the heat exchanger 2 and used as a heating source for air and pre-reformed gas, respectively, and further passed to the heat exchanger 3. Is done. Here, it is used for heating water from the hot water supply system and discharged as air exhaust.

<Example 3>
FIG. 5 is a diagram showing an embodiment of the present invention (3) and (6). The anode offgas is regenerated by removing water vapor, carbon dioxide and carbon monoxide from the anode offgas of SOFC, and the regenerated offgas is converted into PEFC. This is an example of use as fuel. In the system of this example, an SOFC stack and a PEFC stack are used.

  Raw fuel such as city gas is supplied to a pre-reformer through a booster and a desulfurizer, where it is pre-reformed and converted into a pre-reformed gas containing hydrogen, carbon monoxide and methane. The pre-reformed gas is preheated by the heat exchanger 2 and then supplied to the anode of the SOFC stack to generate power by an electrochemical reaction with oxygen from the cathode. At that time, methane in the pre-reformed gas is reformed to hydrogen and carbon monoxide by internal reforming. On the other hand, the air is sequentially preheated by the heat exchanger 4 and the heat exchanger 1 through the blower and then supplied to the cathode of the SOFC stack.

The anode off gas from the SOFC stack is cooled by the air supplied to the SOFC stack by the heat exchanger 4, and then carbon dioxide and carbon monoxide are removed. In FIG. 5, this is the location indicated as “CO ₂ , CO removal unit”. There are no particular limitations on the means for removing both components of carbon dioxide and carbon monoxide here, and any means capable of removing both components from the anode off-gas may be used. For example, as shown in FIGS. It carries out like this.

First, the anode off gas from the heat exchanger 4 is passed through, for example, a CO ₂ remover filled with the lithiated zirconia absorbent to remove CO ₂ . Subsequently, CO is removed by a CO shift reaction (CO + 2H ₂ O → CO ₂ + 2H ₂ ) by supplying a CO shifter filled with a CO shift catalyst (= shift catalyst). As the shift catalyst, for example, a copper-zinc catalyst or a platinum catalyst can be used. As water vapor required for the CO shift reaction, water vapor in the anode off-gas is used.

Note that the CO shift reaction in the CO shift converter is an exothermic reaction, and thus proceeds at a lower temperature in terms of chemical equilibrium. For this reason, depending on the temperature of the anode off-gas that has passed through the CO ₂ remover, the reaction temperature can be increased by arranging a cooler in the front stage of the CO converter or by providing a cooling mechanism inside or outside the CO converter. To avoid. FIG. 6 (b) shows a case where a cooler is arranged in front of the CO transformer. As the refrigerant, for example, water from a hot water supply system can be used.

In PEFC, the limit is about 100 ppm for carbon monoxide in the fuel and 10 ppm depending on the constituent materials of the anode, etc. If this is exceeded, battery performance will be significantly degraded. It needs to be removed. For this reason, the anode off-gas is reduced to about 1% (% = vol%) or less by a CO converter, and then supplied to the CO selective oxidizer to oxidize the CO (CO + 1 / 2O ₂ = CO ₂ ). To reduce CO to 100 ppm or less, preferably 10 ppm or less. Since it is necessary to selectively oxidize only CO in the CO selective oxidizer, a CO selective oxidation catalyst such as Ru-based (supported on a carrier such as alumina) is used. Here, an oxidizing gas such as air is added as the oxidizing oxygen.

  Thus, the anode off-gas from the SOFC stack from which carbon dioxide and carbon monoxide have been removed is further cooled with water in the heat exchanger 5 to condense and remove water vapor, and supplied to the anode of the PEFC stack. On the other hand, air branches through the blower and is supplied to the cathode of the PEFC stack.

  The regenerated anode offgas from the SOFC stack generates electricity by an electrochemical reaction with oxygen from the cathode of the PEFC stack. The electric power obtained in the SOFC stack and PEFC stack is converted into alternating current by the inverter. The anode off-gas from the PEFC stack is mixed with the cathode off-gas from the PEFC stack, burned, and discharged as exhaust.

  In this way, carbon dioxide, carbon monoxide, and water vapor are removed from the SOFC stack anode off-gas and regenerated, and the regenerated anode off-gas is used as fuel for the PEFC stack. Can be raised.

  Further, the cathode off-gas from the SOFC stack is sequentially passed through the heat exchanger 1 and the heat exchanger 2 and used as a heating source for air and pre-reformed gas, respectively, and further passed through the heat exchanger 3. The Here, after being used for heating water from the hot water supply system, it is discharged as air exhaust. A part of the anode off-gas from the SOFC stack may be branched and recycled in front of the heat exchanger 4 and supplied to the pre-reformer.

In the CO removal process in the CO converter and the CO selective oxidizer, the carbon dioxide in the regeneration anode offgas increases, but the carbon dioxide contained in the anode offgas itself from the SOFC stack is already in the CO ₂ before the CO converter. It has been removed with a remover. For this reason, since the carbon dioxide in the regeneration anode offgas from the CO selective oxidizer is substantially the amount produced by the CO selective oxidizer, the regeneration anode offgas can be used as fuel for the PEFC stack as it is. However, in order to remove carbon dioxide so as to be reduced and supply it to the PEFC stack, a CO ₂ remover may be arranged after the CO selective oxidizer. FIG. 7 is a diagram showing a mode in this case.

As shown in FIG. 7, the anode off-gas from the SOFC stack is passed through a CO converter to transform and remove CO, and then passed through a CO selective oxidizer (CO oxidizer in FIG. 7) to further reduce CO. The gas passed through the CO selective oxidizer, in addition to carbon dioxide contained in the anode off-gas itself, because it contains also carbon dioxide generated by the CO selective oxidizer, the carbon dioxide partial through CO ₂ remover It is removed and supplied to the anode of the PEFC stack and used as fuel. At this time, outlet gas from the CO selective oxidizer, so that a high temperature in the combustion reaction of CO, can be used as a CO ₂ absorbent in a CO ₂ remover such as above lithium zirconia.

Here, when using the lithiated zirconia as the CO ₂ absorbent as described above, if the gas temperature from the CO selective oxidizer is insufficient, the gas is heated and then passed through the CO ₂ remover. Good. FIG. 8 is a diagram showing an example thereof. FIG. 8 shows an example in which the heat exchanger 7 is arranged and exhaust such as cathode off gas from a SOFC system separately arranged for heating is used, but an appropriate heating source is used as the heating source. be able to. Since the CO converter and CO selective oxidizer have appropriate temperatures depending on the type of catalyst, etc., a catalyst suitable for each system is used. For adjustment to the appropriate temperature, water from the hot water supply system, off-gas from the SOFC stack, etc. Is available.

The figure explaining the example of the conventional SOFC system which adds anode off gas from SOFC to the hot water supply system in addition to fuel and air preheating The figure explaining the present invention (relationship between fuel utilization and cell voltage in SOFC) The figure which shows Example 1. The figure which shows Example 2. The figure which shows Example 3. The figure which shows Example 3. The figure which shows Example 3. The figure which shows Example 3.

Explanation of symbols

1-7 heat exchanger

Claims (10)

  A power generation method using a solid oxide fuel cell, in which water vapor is removed from the anode off gas of the solid oxide fuel cell to regenerate the anode off gas, and the regenerated off gas is reused as fuel for the solid oxide fuel cell. A power generation method using a solid oxide fuel cell, wherein the fuel utilization rate of the solid oxide fuel cell itself is improved.   2. The power generation method using a solid oxide fuel cell according to claim 1, wherein the solid oxide fuel cell is regenerated by removing water vapor from the anode off gas of the solid oxide fuel cell, and the regenerated off gas is used as fuel. A power generation method using a solid oxide fuel cell, wherein the solid oxide fuel cell to be used is a separate solid oxide fuel cell.   A power generation method using a solid oxide fuel cell, in which water vapor and carbon dioxide are removed from the anode off gas of the solid oxide fuel cell to regenerate the anode off gas, and the regenerated off gas is reused as fuel for the solid oxide fuel cell. A power generation method using a solid oxide fuel cell, wherein the utilization rate of the fuel in the solid oxide fuel cell itself is improved.   4. The power generation method using a solid oxide fuel cell according to claim 3, wherein the solid oxide fuel cell is regenerated by removing water vapor and carbon dioxide from the anode offgas of the solid oxide fuel cell, and the regenerated offgas. A power generation method using a solid oxide fuel cell, wherein the solid oxide fuel cell to be reused as fuel is a separate solid oxide fuel cell.   A power generation method using a solid oxide fuel cell, which removes water vapor, carbon dioxide and carbon monoxide from the anode off gas of the solid oxide fuel cell to regenerate the anode off gas, and uses the regenerated off gas as a solid polymer fuel cell. A power generation method using a solid oxide fuel cell, wherein the fuel utilization rate is improved by using the fuel as a fuel.   A power generation system that improves the fuel utilization rate of a solid oxide fuel cell in a solid oxide fuel cell, and regenerates the anode off gas by removing water vapor from the anode off gas of the solid oxide fuel cell. A power generation system using a solid oxide fuel cell, wherein the regenerated off-gas is reused as a fuel for the solid oxide fuel cell.   7. The power generation system using a solid oxide fuel cell according to claim 6, wherein the solid oxide fuel cell is regenerated by removing water vapor from the anode off gas of the solid oxide fuel cell, and is regenerated using the regenerated off gas as fuel. A power generation system using a solid oxide fuel cell, wherein the solid oxide fuel cell to be used is a separate solid oxide fuel cell.   A power generation system that improves the fuel utilization rate of a solid oxide fuel cell itself in a solid oxide fuel cell, and removes water vapor and carbon dioxide from the anode off-gas of the solid oxide fuel cell to form an anode A power generation system using a solid oxide fuel cell, wherein the off gas is regenerated and the regenerated off gas is reused as fuel for the solid oxide fuel cell.   9. The power generation system using a solid oxide fuel cell according to claim 8, wherein the solid oxide fuel cell is regenerated by removing water vapor and carbon dioxide from the anode offgas of the solid oxide fuel cell, and the regenerated offgas is regenerated. A power generation system using a solid oxide fuel cell, wherein the solid oxide fuel cell to be reused as fuel is a separate solid oxide fuel cell. A power generation system with improved fuel utilization in a solid oxide fuel cell, which removes water vapor, carbon dioxide and carbon monoxide from the anode off gas of the solid oxide fuel cell to regenerate and regenerate the anode off gas A power generation system using a solid oxide fuel cell, wherein off-gas is used as a fuel for the polymer electrolyte fuel cell.

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