JP2009117054A - Power generation method and system using high-temperature fuel cell - Google Patents

Abstract

Power generation efficiency is improved by increasing the fuel utilization rate of the entire high-temperature operating fuel cell and by increasing the fuel utilization rate of the entire fuel cell including fuel cells other than the high-temperature operating fuel cell and the high-temperature operating fuel cell.
After cooling the anode off-gas of a high-temperature operating fuel cell, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated to produce the same or another high-temperature operating fuel. A power generation method and a power generation system using a high-temperature operating fuel cell, wherein the power generation efficiency is improved while improving the fuel utilization rate of the entire high-temperature operating fuel cell by being reused as fuel for the battery.
[Selection] Figure 3

Description

  The present invention relates to a power generation method and system using a high-temperature operating fuel cell, and more specifically, in a high-temperature operating fuel cell such as a solid oxide fuel cell or a molten carbonate fuel cell, the anode off-gas is used as the high-temperature operating fuel cell itself. Alternatively, by reusing it in combination with another fuel cell, the fuel utilization rate of the high-temperature operating fuel cell as a whole and the fuel utilization rate of the fuel cell as a whole including other fuel cells are improved, and the power generation efficiency is improved. The present invention relates to a power generation method and a power generation system using a high-temperature operating fuel cell.

A solid oxide fuel cell (hereinafter abbreviated as “SOFC” where appropriate) is characterized in that an oxide ion (O ²⁻ ) conductor is used as a solid electrolyte. In this configuration, both an anode (fuel electrode) and a cathode (air electrode or oxygen electrode) are 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 ).

A molten carbonate fuel cell (hereinafter abbreviated as “MCFC” where appropriate) is characterized in that a carbonate ion (CO ₃ ²⁻ ) conductor is used as an electrolyte. The anode (fuel electrode) and the cathode (air electrode or oxygen electrode) are arranged with an electrolyte such as a mixed molten salt of lithium carbonate or potassium carbonate alkali metal salt immersed in a porous matrix. The The operating temperature is about 600 to 700 ° C., and it is generally operated at around 650 ° C.

In MCFC, electric power is taken out by supplying fuel to the anode side and supplying air to the cathode side to cause an electrochemical reaction during the operation. Oxygen in the air supplied from the air supply pipe reacts with CO ₂ supplied separately at the cathode to become carbonate ions (CO ₃ ²⁻ ), and passes through the electrolyte to the anode. 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 ). A method of separating the produced CO ₂ and returning it to the cathode is generally used.

  By the way, in SOFC and MCFC, hydrogen and carbon monoxide are fuels. Methane is steam-reformed to hydrogen and carbon monoxide by internal reforming by the catalytic action of a metal that is a component of the anode, such as nickel, at these high operating temperatures, so that it is introduced into the anode of SOFC and MCFC. As the fuel, a fuel containing hydrogen, a fuel containing carbon monoxide, a fuel containing hydrogen and carbon monoxide, or a fuel containing hydrogen, carbon monoxide and methane is used.

  Hydrocarbon fuels such as city gas, alcohol fuels such as ethanol, and ether liquid fuels such as dimethyl ether can be converted into hydrogen, carbon monoxide, and methane by a steam reforming reaction in a pre-reformer. Methane is reformed to hydrogen and carbon monoxide by so-called internal reforming at the anode of a high-temperature operating fuel cell and is subjected to an electrochemical reaction.

  Note that methane may also be reformed and supplied to the high-temperature operating fuel cell. In this case, the reformer is not a preliminary reformer but a reformer, and the reformer generates reformed gas. . In this specification, the pre-reformer or the fuel before reforming by the reformer is referred to as “raw fuel”, and the reformed gas generated by reforming the raw fuel by the pre-reformer is “roughly modified”. It is called “quality gas”.

  Since the steam reforming reaction is an endothermic reaction, the heat of combustion of carbon monoxide and hydrogen after reforming is higher than that of the raw fuel, so the function of a so-called chemical heat pump is exhibited by using exhaust heat. The power generated by the subsequent electrochemical reaction is increased, resulting in improved power generation efficiency.

  In addition, the high operating temperature of a high-temperature operating fuel cell is that the chemical reaction rate is high and the overvoltage, that is, the loss in the cell is small. Become. In addition, the high exhaust heat temperature is expected to have excellent performance from the fact that heat can be used, such as a combined power generation combined with a turbine or an absorption refrigerator.

  By the way, in SOFC and MCFC, about 70 to 85% of the fuel supplied to the anode is normally used, and the remaining 30 to 15% is unused and discharged outside the fuel cell as anode off gas. At that time, the unused fuel is not discharged outside the fuel cell as it is, but it is burned for heat recovery to preheat raw fuel and air, a heat source for self-sustaining heat to maintain the operating temperature, or a cogeneration system, etc. It is used for heat utilization in the latter process.

  As such, SOFC and MCFC are usually operated at a fuel utilization rate of about 70 to 85%. However, if the fuel utilization rate is further increased, fuel depletion occurs near the SOFC or MCFC fuel outlet. This is because the electric potential of the battery is lowered and the power generation efficiency is lowered. For this reason, one of the problems of SOFC and MCFC is that the fuel utilization rate cannot be set high. Theoretically, it is possible to use up to 95% of the fuel utilization rate, but in reality, there are problems such as slight leakage of fuel and diffusion control inside the electrode, and it is currently possible to use about 80% at most. is there.

  For this reason, the remaining 20% of the fuel discharged as the anode off-gas is burned with the cathode off-gas, for the heat self-sustaining of the fuel cell due to the generation of water vapor for reforming the raw fuel or the preheating of the air supplied to the fuel cell, or It is only used as a heat source in a cogeneration system (Japanese Patent Laid-Open Nos. 2001-266924 and 2002-56875).

  Japanese Patent Laid-Open No. 2004-6281 discloses a technique for generating hot water by using exhaust heat generated by power generation as in Japanese Patent Application Laid-Open No. 2002-56875, which uses only electric power and does not use hot water. In some cases, only hot water is used and electric power is not used.Electricity and hot water are rarely used without waste, and waste hydrogen generated in the process of power generation is used for hot water generation or for electric power generation. An energy generator that can be used has been proposed.

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

  JP-A-2006-31989 discloses (a) removing water vapor, (b) removing water vapor and carbon dioxide, or (c) removing water vapor, carbon dioxide and carbon monoxide from the SOFC anode off-gas. A method of removing the anode off gas by removing it has been proposed. In this technology, unused hydrogen in the regenerated anode off-gas is reused as fuel for the fuel cell, thereby increasing the fuel utilization rate in the SOFC and improving the power generation efficiency.

In JP 2002-334714 A, an anode off gas of SOFC is passed through a CO converter to convert carbon monoxide in the anode off gas to hydrogen as much as possible, and then carbon dioxide is removed by a CO ₂ adsorbent or a CO ₂ absorbent. Thus, a method for producing high purity hydrogen and a fuel cell system using the produced high purity hydrogen have been proposed.

  In JP-A-2004-71312, an SOFC stack, an off-gas combustion unit, and a heat storage material layer are arranged in a heat insulating container, an air introduction pipe and a lead-out pipe are arranged in the heat storage material layer, and the flow path is A bypass passage is provided, and the fuel electrode off-gas conduit from the stack is sequentially connected to the CO converter and the hydrogen storage container, and during full load operation, excess heat is stored in the heat storage material layer and air Is bypassed to the bypass flow path and supplied to the stack, and the fuel electrode off-gas is passed through the CO transformer and passed through the hydrogen storage container to store hydrogen, and during partial load operation, air is passed through the heat storage material to full load. A heat self-supporting SOFC system has been proposed in which the heat stored during operation is recovered and returned to the stack, and power is generated using hydrogen in the hydrogen storage container as fuel.

  Further, JP-A-2006-342014 discloses that a reformed gas containing carbon monoxide, hydrogen and carbon dioxide is brought into contact with a carbon monoxide adsorbent in which copper halide is supported on silica, alumina or other carrier. There has been proposed a method for obtaining high-purity hydrogen by adsorbing and removing carbon monoxide and then storing the hydrogen in the hydrogen storage body and releasing the stored hydrogen from the storage body.

JP 2006-31989 JP 2002-334714 A Japanese Patent Laid-Open No. 2004-71312 JP 2006-342014 A

  However, these technologies are: (a) heat generated by combustion of anode off-gas discharged during operation of a high-temperature operating fuel cell is used to generate steam for raw fuel reforming, preheat air supplied to the fuel cell, or (B) branch off the anode offgas and recycle it to the pre-reformer for reuse, or (c) carbon monoxide in the anode offgas by a CO converter. The carbon monoxide itself in the anode off-gas is not recovered and reused.

  The present invention pays attention to the recovery and reuse of carbon monoxide itself in the anode off gas, and the carbon monoxide itself in the anode off gas discharged during the operation of the high temperature operation fuel cell is used as the fuel for the high temperature operation fuel cell. Effectively reuse to improve the fuel utilization rate of the entire high-temperature operating fuel cell, and improve the fuel utilization rate of the entire fuel cell including high-temperature operating fuel cells and fuel cells other than high-temperature operating fuel cells It is an object of the present invention to provide a power generation method and a power generation system using a high-temperature operating fuel cell for improving the power consumption.

  The present invention (1) is a power generation method using a high temperature operation fuel cell using carbon monoxide and hydrogen as fuel. (A) After cooling the anode off-gas of the high-temperature operation fuel cell, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated to perform the same or different high-temperature operation. By reusing it as fuel for the fuel cell, (b) the power generation efficiency is improved while improving the fuel utilization rate of the entire high-temperature operating fuel cell.

  The present invention (11) is a power generation system using a high-temperature operating fuel cell using carbon monoxide and hydrogen as fuels corresponding to the power generation method of the present invention (1). (A) After cooling the anode off-gas of the high-temperature operation fuel cell, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated to perform the same or different high-temperature operation. By being reused as the fuel of the fuel cell, (b) the power generation efficiency is improved while improving the fuel utilization rate of the entire high-temperature operating fuel cell.

  The present invention (2) is a power generation method using a high temperature operation fuel cell using carbon monoxide and hydrogen as fuel. (A) After cooling the anode off-gas of the high-temperature operation fuel cell, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated to perform the same or different high-temperature operation. Hydrogen containing carbon dioxide and water as impurities, which is an anode off-gas from which carbon monoxide has been removed by adsorption and recovery of carbon monoxide by the CO adsorbent. Is used as a fuel for a fuel cell different from the high-temperature operating fuel cell, and (c) the power generation efficiency is improved while improving the fuel utilization rate of the entire fuel cell.

  The present invention (12) is a power generation system using a high-temperature operating fuel cell using carbon monoxide and hydrogen as fuels corresponding to the power generation method of the present invention (2). (A) After cooling the anode off-gas of the high-temperature operation fuel cell, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated to perform the same or different high-temperature operation. It is reused as fuel for fuel cells, and (b) contains carbon dioxide and water as impurities, which is an anode off-gas from which carbon monoxide has been removed by adsorption and recovery of carbon monoxide by the CO adsorbent. By using hydrogen to be used as a fuel for a fuel cell different from the high-temperature operating fuel cell, (c) the power generation efficiency is improved while improving the fuel utilization rate of the entire fuel cell. .

  The present invention (3) is a power generation method using a high-temperature operating fuel cell using carbon monoxide and hydrogen as fuel. (A) After cooling the anode off-gas of the high-temperature operation fuel cell, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated to perform the same or different high-temperature operation. (B) Adsorbing and recovering carbon monoxide by the CO adsorbent container, and introducing the anode off-gas from which carbon monoxide has been removed into the hydrogen storage container to absorb and recover hydrogen. (C) the entire fuel cell by desorbing and regenerating the adsorbed hydrogen and reusing it as the fuel of the same or different high-temperature operating fuel cell, or as the fuel of a fuel cell different from the high-temperature operating fuel cell. It is characterized by improving the power generation efficiency while improving the fuel utilization rate.

  The present invention (13) is a power generation system using a high-temperature operating fuel cell using carbon monoxide and hydrogen as fuels corresponding to the power generation method of the present invention (3). (A) After cooling the anode off-gas of the high-temperature operation fuel cell, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated to perform the same or different high-temperature operation. (B) The anode off-gas from which carbon monoxide has been removed by adsorbing and recovering carbon monoxide by the CO adsorbent container is introduced into the hydrogen storage container and hydrogen is removed. By adsorbing and recovering, desorbing and regenerating the adsorbed hydrogen and reusing it as fuel for the same or different high temperature fuel cell, or by using it as fuel for a fuel cell different from the high temperature fuel cell (C) It is characterized in that the power generation efficiency is improved while improving the fuel utilization rate in the whole fuel cell.

  The present invention (4) is a power generation method using a high-temperature operating fuel cell using carbon monoxide and hydrogen as fuel. (A) A CO converter is disposed after the high-temperature operating fuel cell to change carbon monoxide in the anode off-gas to hydrogen, thereby reducing the carbon monoxide concentration in the anode off-gas and relative hydrogen concentration. (B) After cooling the anode off-gas that has passed through the CO converter, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated to be the same or different. By reusing the fuel as a fuel for a high-temperature operating fuel cell, (c) the power generation efficiency is improved while improving the fuel utilization rate of the entire high-temperature operating fuel cell.

  The present invention (14) is a power generation system using a high-temperature operating fuel cell using carbon monoxide and hydrogen as fuels corresponding to the power generation method of the present invention (4). (A) A CO converter is disposed after the high-temperature operating fuel cell to change carbon monoxide in the anode off-gas to hydrogen, thereby reducing the carbon monoxide concentration in the anode off-gas and relative hydrogen concentration. (B) After cooling the anode off-gas that has passed through the CO converter, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated to be the same or different. By reusing the fuel as a fuel for the high-temperature operating fuel cell, (c) the power generation efficiency is improved while improving the fuel utilization rate of the entire high-temperature operating fuel cell.

  The present invention (5) is a power generation method using a high-temperature operating fuel cell using carbon monoxide and hydrogen as fuel. (A) A CO converter is disposed after the high-temperature operating fuel cell to change carbon monoxide in the anode off-gas to hydrogen, thereby reducing the carbon monoxide concentration in the anode off-gas and relative hydrogen concentration. (B) After cooling the anode off-gas that has passed through the CO converter, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated to be the same or different. Recycled as fuel for high-temperature operating fuel cells, (c) Hydrogen in the anode off-gas from which carbon monoxide has been removed by adsorbing and recovering carbon monoxide by the CO adsorbent is a fuel different from high-temperature operating fuel cells By using it as a fuel for the battery, (d) it is characterized in that the power generation efficiency is improved while improving the fuel utilization rate of the entire fuel cell.

  The present invention (15) is a power generation system using a high-temperature operating fuel cell using carbon monoxide and hydrogen as fuels corresponding to the power generation method of the present invention (5). (A) A CO converter is disposed after the high-temperature operating fuel cell to change carbon monoxide in the anode off-gas to hydrogen, thereby reducing the carbon monoxide concentration in the anode off-gas and relative hydrogen concentration. (B) After cooling the anode off-gas that has passed through the CO converter, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated to be the same or different. (C) The hydrogen in the anode off-gas from which carbon monoxide has been removed by adsorbing and recovering carbon monoxide by the CO adsorbent is separated from the high-temperature operating fuel cell. (D) It is characterized by improving the power generation efficiency while improving the fuel utilization rate of the whole fuel cell.

  The present invention (6) is a power generation method using a high-temperature operating fuel cell using carbon monoxide and hydrogen as fuel. (A) A CO converter is disposed after the high-temperature operating fuel cell to change carbon monoxide in the anode off-gas to hydrogen, thereby reducing the carbon monoxide concentration in the anode off-gas and relative hydrogen concentration. (B) After cooling the anode off-gas that has passed through the CO converter, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated to be the same or different. (C) The anode off-gas from which carbon monoxide has been removed by adsorbing and recovering carbon monoxide by the CO adsorbent container is introduced into a hydrogen storage container container to recycle hydrogen. Adsorbed and recovered, and the adsorbed hydrogen is desorbed and regenerated and reused as fuel for the same or different high temperature fuel cell, or used as fuel for a fuel cell different from the high temperature fuel cell. , Characterized in that to improve the power generation efficiency while improving fuel utilization rate of the entire (d) fuel cells.

  The present invention (16) is a power generation system using a high-temperature operating fuel cell using carbon monoxide and hydrogen as fuel corresponding to the power generation method of the present invention (6). (A) A CO converter is disposed after the high-temperature operating fuel cell to change carbon monoxide in the anode off-gas to hydrogen, thereby reducing the carbon monoxide concentration in the anode off-gas and relative hydrogen concentration. (B) After cooling the anode off-gas that has passed through the CO converter, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated to be the same or different. (C) An anode off gas from which carbon monoxide has been removed by adsorbing and recovering carbon monoxide by the CO adsorbent container is introduced into the hydrogen storage container. Hydrogen is adsorbed and recovered, and the adsorbed hydrogen is desorbed and regenerated and reused as fuel for the same or different high-temperature fuel cell, or used as fuel for a fuel cell different from the high-temperature fuel cell By formed by way, characterized in that to improve the power generation efficiency while improving fuel utilization rate of the entire (d) fuel cells.

  According to the present invention, carbon monoxide in the anode off-gas of high-temperature operating fuel cells such as SOFC and MCFC is adsorbed and recovered and reused as fuel for the same or another high-temperature operating fuel cell. The fuel utilization rate of the fuel cell as a whole can be improved, and the power generation efficiency can be improved. For example, when using SOFC anode off-gas, it can be reused as fuel for the SOFC, or it can be reused as fuel for MCFC, which is another high-temperature operation fuel cell. Thus, the power generation efficiency can be improved.

  According to the present invention, by applying the anode off-gas treatment of a high-temperature operating fuel cell, the features of both the high-temperature operating fuel cell and the hydrogen purification method can be complemented to satisfy both needs. In other words, by effectively utilizing high-temperature exhaust heat, the anode off-gas of high-temperature operating fuel cells is separated and recovered in high concentrations of carbon monoxide, hydrogen, and carbon dioxide, respectively, thereby increasing the fuel utilization rate of the fuel cell and improving power generation efficiency. Can be improved.

  According to the present invention, after the anode off-gas of the high-temperature operating fuel cell is cooled, carbon monoxide is adsorbed and recovered, and hydrogen is recovered from the anode off-gas after the removal of carbon monoxide. Recycle as fuel and use hydrogen as fuel for high temperature operation fuel cell, or use as fuel for fuel cell different from high temperature operation fuel cell, or the fuel utilization rate of the whole high temperature operation fuel cell, or other The fuel utilization rate of the entire fuel cell including the fuel cell can be increased, the generated power can be increased, and the power generation efficiency can be improved.

  The SOFC is called a SOFC stack, SOFC module, or SOFC bundle depending on the cell structure such as a cylindrical method, a flat plate method, and an integral lamination method, or an arrangement structure of cell groups. It is called “unit”. The same applies to the MCFC, which is also referred to as “MCFC unit”.

  In the present specification, the SOFC system is meant to include SOFC units, auxiliary equipment such as a pre-reformer and a heat exchanger, related piping systems, and the like. The same applies to the MCFC. The MCFC system includes MCFC units, auxiliary equipment such as a pre-reformer and a heat exchanger, and related piping systems.

  In the following description, an example in which an SOFC unit is arranged as a high-temperature operating fuel cell unit will be mainly described. However, the same applies to a case where an MCFC unit is arranged as a high-temperature operating fuel cell unit. In the following, the case where city gas is used as the raw fuel is taken as an example, but the same applies to the case where other fuel is used as the raw fuel. In the case of a raw fuel which does not substantially contain a sulfur compound, the desulfurizer is It is unnecessary.

  FIG. 1 shows a high-temperature operating fuel cell system used for a hot water supply system in a cogeneration system or the like, in addition to using the anode off-gas from the SOFC unit for preheating fuel and air, as an example of the technology underlying the present invention. It is a figure explaining.

  In the pre-reformer, the raw fuel is reformed by a steam reforming method to generate a crude reformed gas containing hydrogen, carbon monoxide, and methane. As shown in FIG. 1, the crude reformed gas generated in the pre-reformer is heated by the heat exchanger 2 and supplied to the anode of the SOFC unit, that is, the anode of each cell in the SOFC unit.

  The raw fuel is supplied to the pre-reformer through a booster and a desulfurizer. Here, in SOFC, in addition to hydrogen and carbon monoxide, methane is also used as a fuel. However, ethane other than methane, ethylene, propane, butane and other hydrocarbons having 2 or more carbon atoms such as ethane, ethylene, propane, butane, etc. If it is contained, carbon is generated in the piping to the SOFC unit and the anode, which inhibits the electrochemical reaction and degrades the battery performance. For this reason, in the pre-reformer, the raw fuel is pre-reformed and changed to a crude reformed gas containing hydrogen, carbon monoxide and methane. Note that methane may also be reformed and supplied to the SOFC unit. In this case, a reformer is provided.

  The crude reformed gas is preheated by the heat exchanger 2 and then supplied to the anode of the SOFC unit. On the other hand, the air is preheated by the heat exchanger 1 through a blower (= blower), and then supplied to the cathode of the SOFC unit.

  The crude reformed gas supplied to the anode of the SOFC unit generates power by an electrochemical reaction with oxygen from the cathode of the SOFC unit. At that time, methane in the crude reformed gas is reformed to hydrogen and carbon monoxide by internal reforming at the anode of the SOFC unit and contributes to the electrochemical reaction. The electric power obtained by the SOFC unit is converted into an alternating current through an inverter by adjusting the voltage as necessary.

  The anode off-gas from the SOFC unit is mixed with the cathode off-gas in the combustor (“off-gas combustor” in FIG. 1) and burned. The combustion exhaust gas is sequentially passed through the heat exchanger 1 and the heat exchanger 2 and used for preheating air and the crude 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 air and crude reformed gas in the heat exchanger 1 and the heat exchanger 2. That is, the total heat quantity of the combustion exhaust gas is not necessary for preheating the air and the rough reformed gas. In addition, 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 is wasted. Thus, the fuel utilization rate of the SOFC unit itself greatly affects the efficiency of the SOFC system, and the limit of the fuel utilization rate of the SOFC unit itself lowers the efficiency of the SOFC system.

  Therefore, paying attention to the SOFC and MCFC, that is, the anode offgas discharged from the high temperature operation fuel cell, the anode offgas contains carbon monoxide and hydrogen that are not used in the high temperature operation fuel cell. In the present invention, carbon monoxide contained in the anode off-gas is concentrated and recovered and reused as fuel for the high-temperature operating fuel cell itself, and power is also generated for the hydrogen contained in the anode off-gas. Or is reused as fuel for fuel cells other than other fuel cells, that is, high-temperature operation fuel cells.

  As an aspect of concentrating and recovering the carbon monoxide contained in the anode off gas and reusing it as the fuel for the high temperature operation fuel cell itself, for example, when using the SOFC anode off gas, is it reused as the SOFC fuel? When reusing as MCFC fuel for another high temperature operation fuel cell and using MCFC anode off gas, reuse as MCFC fuel or reuse as SOFC fuel for another high temperature operation fuel cell By doing so, the fuel utilization rate of the whole high temperature operation fuel cell can be improved, and the power generation efficiency can be improved.

  As a result, the fuel utilization rate of the high-temperature operating fuel cell is increased, and in a mode in which another fuel cell is used in combination with the high-temperature operating fuel cell, the fuel utilization rate of the fuel cell including both fuel cells is increased to increase the fuel consumption. It will change to electric power as much as possible. Thereby, it is possible to eliminate or reduce the excessive amount of hot water exceeding the required amount of hot water even in a mode in which a hot water supply system such as a cogeneration system is used in combination.

  FIG. 2 is a diagram for explaining the facts and effects that are the premise of the present invention, and shows the relationship between the fuel utilization rate and the cell voltage in the SOFC cell. As shown in FIG. 2, when the fuel utilization rate in the SOFC cell is increased, the cell voltage gradually decreases. When the fuel utilization rate exceeds about 90%, the cell voltage rapidly decreases. 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% of the 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%. Here, the description is made on the assumption that carbon monoxide is converted to 100% hydrogen fuel, but the same applies to the case where carbon monoxide in the anode off-gas is recovered and used as it is.

  In the present invention, on the premise of such a fact, carbon monoxide or carbon monoxide and hydrogen in the anode off-gas from the high temperature operating fuel cell is recovered and regenerated, and the regenerated gas is the same or different. By reusing it in combination with other fuel cells such as high-temperature operating fuel cells or polymer electrolyte fuel cells (PEFC), the fuel utilization rate of the SOFC system as a whole is improved and power generation efficiency is improved. .

  In addition to the PEFC, a phosphoric acid fuel cell (PAFC) can be used as another fuel cell to be combined with the high-temperature operating fuel cell. In this case as well, it is assumed that the main fuel cell is SOFC or MCFC. is there.

  Here, as a mode of reusing the regenerated gas of the anode off gas in the same or another high-temperature operating fuel cell, (a) when the anode off gas is an anode off gas from SOFC, the regenerated gas is used as fuel for the SOFC. Alternatively, the fuel cell may be used as a fuel for a high temperature operation fuel cell, that is, an MCFC different from the SOFC. (B) When the anode off gas is an anode off gas from the MCFC, the regeneration gas is used as the fuel for the MCFC. Or may be used as a fuel for a high-temperature operating fuel cell different from the MCFC, that is, SOFC.

<Aspects of the present invention (1) to (2), (11) to (12)>
In the present invention (1), after the anode off-gas of the high-temperature operating fuel cell is cooled, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated to be the same or different. A power generation method using a high temperature operation fuel cell that improves the power generation efficiency while improving the fuel utilization rate of the entire high temperature operation fuel cell by reusing it as a fuel for the high temperature operation fuel cell. The present invention (11) relates to the power generation method. It is a system for carrying out.

  In the present invention (2), in addition to the structure provided in the present invention (1), carbon monoxide is removed as an impurity by removing carbon monoxide by adsorption and recovery of carbon monoxide with a CO adsorbent. This is a power generation method that requires the use of hydrogen containing water as fuel for a fuel cell separate from the high-temperature operating fuel cell, and the present invention, (12), is a system for implementing the power generation method. .

  FIG. 3 is a diagram for explaining the present inventions (1) to (2) and (11) to (12). As shown in FIG. 3, an SOFC unit, an anode offgas cooler, and a CO adsorbent container are sequentially arranged. Of these, two CO adsorbent containers, A and B, are arranged and are switched by switching valves a and b. FIG. 3A shows a process in which carbon monoxide is adsorbed in the CO adsorbent container A and carbon monoxide is desorbed in the CO adsorbent container B. FIG. 3B shows the CO adsorbent container B. Shows the process of adsorbing carbon monoxide and desorbing carbon monoxide in the CO adsorbent container A. In FIG. 3, a pre-reformer for generating the crude reformed gas is disposed in the previous stage of the SOFC unit, but the illustration is omitted.

  During the operation of the SOFC unit, the anode off-gas discharged from the SOFC unit is cooled and then introduced into the CO adsorbent container A. As the CO adsorbent, a CO adsorbent in which copper (I) halide or copper (II) halide is supported on a carrier such as silica, alumina, activated carbon, graphite, or styrene resin is used. In the following, the copper halide CO adsorbent is taken as an example, but the same applies to other CO adsorbents. In addition, although the said copper halide type CO adsorbent itself is a well-known thing as described in above-mentioned Unexamined-Japanese-Patent No. 2006-342014, in this invention, such CO adsorbent is utilized.

  Since the adsorption of carbon monoxide by the copper halide-based CO adsorbent is carried out at 80 ° C. or less, preferably 60 ° C. or less, the cooling by the anode off-gas cooler is cooled to those temperatures or less by the cooling medium. The adsorbed carbon monoxide is desorbed by passing a carrier gas, that is, a purge gas. Since the desorption temperature is 250 ° C. or lower, preferably 80 to 150 ° C., higher than that during adsorption, the CO adsorbent is removed by a heating medium. Heat to that temperature.

  As a heating medium for detachment, various devices constituting the SOFC system, for example, exhaust heat of the SOFC unit, exhaust heat of the anode off-gas cooler, exhaust heat of PEFC which is another fuel cell, that is, a high temperature operation fuel cell, or SOFC system It is possible to use anode off-gas, cathode off-gas, combustion off-gas of both off-gases discharged from the exhaust gas, exhaust heat from a generator or other power generation means by a gas turbine, and the like. Moreover, when arrange | positioning a CO converter like this invention (4)-(6), (14)-(16) mentioned later, the waste heat of the CO converter can also be utilized. As an example, in the embodiment shown in FIG. 6 described later, if the combustion exhaust gas discharged from the heat exchanger 3 is used, the heat of the combustion exhaust gas can be utilized without substantially losing the heat balance of the SOFC system as a whole. .

  In the CO adsorbent container A, only carbon monoxide in the anode off gas is selectively adsorbed, and the carbon monoxide is concentrated here. Since CO adsorbent selectively adsorbs only carbon monoxide from multi-component gas mixture by chemical adsorption, it can recover even a small amount of carbon monoxide and is practical even if there is no pressure difference between adsorption and desorption cycles. It is possible to ensure a sufficient capacity for adsorption / desorption treatment. Of course, a pressure difference may be used for the cycle of adsorption and desorption.

  In the adsorption of carbon monoxide by the CO adsorbent, it is not adsorbed by the CO adsorbent until the adsorption capacity limit, and the gas passing through contains almost no carbon monoxide, so even if it is released to the atmosphere, it is toxic to the living body. Carbon monoxide is not released out of the system. Further, as will be described later, there is no adverse effect even if a hydrogen recovery process using a hydrogen storage alloy whose storage performance is likely to deteriorate due to carbon monoxide poisoning is connected to the subsequent stage.

  Since the anode off-gas that has passed through the CO adsorbent container A contains hydrogen as well as carbon dioxide and water as impurities, the anode off-gas is used as a fuel cell other than the high-temperature operating fuel cell, for example, fuel of PEFC. Use. This corresponds to the configuration of the present invention (2), (12). In PEFC, if carbon monoxide is contained in the fuel, the cell performance will be significantly deteriorated, so it is necessary to reduce the concentration to 10 ppm or less. However, carbon monoxide is removed to a very small amount by the CO adsorbent container A. And is not substantially contained, so there is no adverse effect on the PEFC cell.

  A part of the anode off-gas that has passed through the CO adsorbent container A is branched and introduced into the CO adsorbent container B. In the CO adsorbent container B, carbon monoxide is adsorbed and concentrated in the carbon monoxide adsorption process that is the preceding stage. Used as a purge gas. As shown in FIG. 3 (a), the branched anode off-gas is introduced into the CO adsorbent vessel B, and carbon monoxide is desorbed, recovered and mixed into the crude reformed gas introduced into the SOFC unit, and power generation in the SOFC unit. To use.

  Adsorption of carbon monoxide by the CO adsorbent container A proceeds, the introduction of the anode off-gas to the CO adsorbent container A is stopped immediately before the carbon monoxide is in an adsorption saturated state, that is, the breakthrough point, and the switching valves a and b are turned on. By operating, the flow of the anode off gas from the SOFC unit is switched so as to be introduced into the CO adsorbent container B juxtaposed with the CO adsorbent container A. The state and operation after this switching are shown in FIG.

  The carbon monoxide adsorption process in the CO adsorbent container B after switching is the same as the adsorption process in the CO adsorbent container A described above, and the carbon monoxide purge process in the CO adsorbent container A is as follows. This is the same as the purge process in the CO adsorbent container B described above. The anode off-gas that has passed through the CO adsorbent vessel B is partially branched and used as a carbon monoxide purge gas for the CO adsorbent vessel A, and the remaining anode off-gas is used as fuel for PEFC in this embodiment.

  In the present embodiment, an example in which carbon monoxide is adsorbed and recovered, and an example in which two towers of CO adsorbent containers are alternately switched as a process has been shown. However, three or more towers may be sequentially switched and used. When three or more towers are sequentially switched and used, the temperature raising process during regeneration becomes advantageous in terms of time. In this respect, the same applies to the exemplary embodiments described below.

<Aspects of the present invention (3), (13)>
In the present invention (3), after the anode off-gas of the high-temperature operating fuel cell is cooled, it is introduced into a CO adsorbent container to adsorb and recover the carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated. The anode off-gas from which carbon monoxide has been removed by adsorbing and recovering carbon monoxide by the CO adsorbent container is introduced into the hydrogen storage container, and hydrogen is adsorbed and recovered. By desorbing and regenerating the adsorbed hydrogen and reusing it as fuel for the same or different high temperature operating fuel cell, or by using it as fuel for a fuel cell different from the high temperature operating fuel cell, the fuel utilization rate of the entire fuel cell can be reduced. This is a power generation method using a high-temperature operating fuel cell that improves power generation efficiency while improving, and the present invention (13) is a system for carrying out the power generation method.

  4-6 is a figure explaining this invention (3) and (13). FIG. 4 is an embodiment in which the anode off-gas from which carbon monoxide has been removed is introduced into a hydrogen storage container, and hydrogen is adsorbed and recovered, and the adsorbed hydrogen is desorbed and regenerated and reused as fuel for a high-temperature operating fuel cell. FIG. 5 is an embodiment in which the anode off-gas from which carbon monoxide has been removed is introduced into a hydrogen storage container, and hydrogen is adsorbed and recovered, and the adsorbed hydrogen is desorbed and regenerated and reused as fuel for a high-temperature operating fuel cell. FIG. 6 shows an embodiment in which a CO adsorbent container and a hydrogen storage container are set in an SOFC system close to the actual machine level or its heat exchange configuration.

  As shown in FIG. 4, an SOFC unit, an anode off-gas cooler, a CO adsorbent container, and a hydrogen storage container are sequentially arranged. Of these, two CO adsorbent containers, A and B, and two hydrogen storage containers C and D are arranged. The hydrogen storage container C is connected to the CO adsorbent container A to constitute a unit of “CO adsorbent container A-hydrogen storage container C”, and the hydrogen storage container D is connected to the CO adsorbent container B. A unit of CO adsorbent container B-hydrogen storage container D ″ is configured, and these two units are switched by switching valves a and b.

  FIG. 4 (a) shows the adsorption of carbon monoxide in the CO adsorbent container A, the subsequent adsorption of hydrogen in the hydrogen storage container C, and the desorption of hydrogen in the hydrogen storage container D. FIG. 4 (b) shows the process of desorbing carbon monoxide in the CO adsorbent container B. FIG. 4 (b) shows the adsorption of carbon monoxide in the CO adsorbent container B and the subsequent hydrogen adsorption in the hydrogen storage container D. In addition, a process of desorbing hydrogen in the hydrogen storage container C and desorbing carbon monoxide in the CO adsorbent container A is shown.

  During the operation of the SOFC unit, the anode off gas discharged from the SOFC unit is cooled by a cooler and then introduced into the CO adsorbent container A. In the CO adsorbent container A, only carbon monoxide in the anode off gas is selectively adsorbed, and the carbon monoxide is concentrated here. Since the anode off-gas that has passed through the CO adsorbent vessel A contains hydrogen as well as carbon dioxide and water as impurities, the anode off-gas is introduced into the hydrogen storage vessel C. In the hydrogen storage container C, only hydrogen in the anode off-gas is adsorbed and stored, and the hydrogen is concentrated and recovered here.

  The hydrogen storage material is not particularly limited as long as it is a material that selectively adsorbs hydrogen from a hydrogen-containing gas and does not adsorb gas other than hydrogen or does not substantially adsorb, but examples thereof include, for example, a hydrogen storage alloy. , Chemical hydride, and carbon nanotube. Any two or more of these may be used. Thus, hydrogen in the anode off gas is selectively adsorbed, and the adsorbed hydrogen is released by heating.

Examples of the hydrogen storage alloy include TiFe _0.9 Mn _0.1 , Mg ₂ Ni, CaNiS, LaNi ₅ , LaNi _4.7 Al _0.3 , MmNi _4.5 Al _0.5 (Mm = Mish metal), MmNi _4.15 Fe _0.85 (Mm = Mish metal), and other various types. Although there is, it is not limited to these. As hydrogen storage alloys, hydrogen storage alloys whose surfaces are fluorinated with fluorine or a fluorine-containing compound have been developed (Japanese Patent Laid-Open Nos. 8-183601, 2000-328160, and 2001-110438). In the present invention, any of them can be used.

JP-A-8-183601 JP 2000-328160 A JP 2001-110438 A

  The carbon monoxide adsorbed by the CO adsorbent and the hydrogen adsorbed by the hydrogen occlusion body are desorbed by heating, mixed in the roughly reformed gas supplied to the SOFC unit, and used as fuel for the SOFC unit. As the heating medium, various devices constituting the SOFC system, such as exhaust heat of the SOFC unit, exhaust heat of the anode off-gas cooler, exhaust heat of PEFC which is a fuel cell other than a high-temperature operating fuel cell, or SOFC Exhaust gas discharged from the system can be used.

  In FIG. 4A, the hydrogen storage container D and the CO adsorbent container B are in the process of desorbing hydrogen and carbon monoxide, respectively, but the hydrogen desorbed from the hydrogen storage container D is converted into the CO adsorbent container B. And used as a carrier gas for desorbing carbon monoxide from the CO adsorbent container B, and mixed with the roughly reformed gas supplied to the SOFC unit and used as fuel for the SOFC unit.

  Adsorption of carbon monoxide by the CO adsorbent container A proceeds, the introduction of the anode off-gas to the CO adsorbent container A is stopped immediately before the carbon monoxide is in an adsorption saturated state, that is, the breakthrough point, and the switching valves a and b are turned on. By operating, the flow of the anode off gas is switched so as to be introduced into the CO adsorbent container B juxtaposed to the CO adsorbent container A, but the hydrogen storage container D following the CO adsorbent container B is also switched at the same time. The operation after this switching is shown in FIG.

  The carbon monoxide adsorption process in the CO adsorbent container B and the hydrogen adsorption process in the hydrogen storage container D after the switching are the same as the processes in the CO adsorbent container A and the hydrogen storage container C described above. The hydrogen desorption process in the hydrogen storage container C and the carbon monoxide purge process in the CO adsorbent container A are the same as the processes in the hydrogen storage container D and the CO adsorbent container B described above.

  The hydrogen storage container C and the CO adsorbent container A are in the process of desorbing hydrogen and carbon monoxide, respectively. The hydrogen adsorbed from the hydrogen storage container C is introduced into the CO adsorbent container A and the CO adsorbent container B After being used as a carrier gas for desorbing carbon monoxide from the fuel, it is mixed with the crude reformed gas supplied to the SOFC unit and used as fuel for the SOFC unit.

  As described above, in the embodiment using the CO adsorbent container and the hydrogen storage container, the regenerated hydrogen from the hydrogen storage container is used as a purge gas for desorbing the adsorbed carbon monoxide in the CO adsorbent container. By generating a mixed gas of carbon and hydrogen and mixing it in the crude reformed gas, carbon monoxide and hydrogen effective as fuel components can be maintained at a high concentration in the gas supplied to the anode of the SOFC unit.

  Further, both carbon monoxide and hydrogen in the anode off-gas are reused as fuel for the SOFC unit, thereby improving the fuel utilization rate in the SOFC unit. Further, since the hydrogen desorbed from the hydrogen storage material is used as the purge gas necessary for desorbing the carbon monoxide adsorbed by the CO adsorbent, the process becomes an appropriate process. The components of the anode off-gas that have passed through the hydrogen storage container are carbon dioxide and moisture, and are discharged out of the system. This also applies to the embodiments shown in FIGS. 5A to 5B and FIG.

  FIG. 5 shows an anode off-gas from which carbon monoxide has been removed by a CO adsorbent container, which is introduced into a hydrogen storage container to adsorb and recover hydrogen, and the adsorbed hydrogen is desorbed and regenerated and reused as fuel for a high-temperature operating fuel cell. It is an example of an aspect. In relation to FIG. 4, in the embodiment of FIG. 4, hydrogen desorbed from the hydrogen storage container is used as the carrier gas of the CO adsorbent container. In the embodiment of FIG. 5, desorption from the hydrogen storage container is performed. The hydrogen thus used is used not only as a fuel for PEFC but also as a carrier gas for a CO adsorbent container.

  In this embodiment, the hydrogen used as the carrier gas for the CO adsorbent container is reduced by the amount used as the fuel for the PEFC, but the regenerated hydrogen from the hydrogen storage container is absorbed into the CO adsorbent container. Since it is used as a purge gas for desorbing carbon oxide, a mixed gas of carbon monoxide and hydrogen is generated and mixed into the crude reformed gas, and is supplied to the anode of the SOFC unit. In the gas, carbon monoxide and hydrogen effective as fuel components can be maintained at a high concentration.

  In FIG. 5 (a), the adsorption of carbon monoxide by the CO adsorbent container A proceeds, and the introduction of the anode off-gas to the CO adsorbent container A is stopped immediately before the carbon monoxide is in an adsorption saturated state, that is, the breakthrough point. The switching valves a and b are operated. Thereby, the flow of the anode off gas is switched to be introduced into the CO adsorbent container B juxtaposed to the CO adsorbent container A, but the hydrogen storage container D following the CO adsorbent container B is also switched at the same time. The state and operation after this switching are shown in FIG.

  The carbon monoxide adsorption process in the CO adsorbent container B and the hydrogen adsorption process in the hydrogen storage container D after the switching are the same as the processes in the CO adsorbent container A and the hydrogen storage container C described above. The hydrogen desorption process in the hydrogen storage container C, the carbon monoxide purge process in the CO adsorbent container A, and the process of using unbranched hydrogen as a fuel for PEFC are the same as the hydrogen storage container D, CO adsorption described above. This is the same as the process in the agent container B.

  That is, the hydrogen storage container C and the CO adsorbent container A are in the process of desorbing hydrogen and carbon monoxide, respectively, but the hydrogen desorbed from the hydrogen storage container C is branched and introduced into the CO adsorbent container A. It is used as a carrier gas for desorbing carbon monoxide from the CO adsorbent container B, and is mixed with the roughly reformed gas supplied to the SOFC unit and used as fuel for the SOFC unit. Of the hydrogen from the hydrogen storage container C, hydrogen that does not branch as a carrier gas is used as fuel for PEFC.

  FIG. 6 is a view showing an example in which a CO adsorbent container and a hydrogen storage container according to the present invention are set in the SOFC system and its heat exchange configuration. In FIG. 6, the approximate temperature at each location when a 100 kW class SOFC unit is set is shown. As shown in FIG. 6, the combustion exhaust gas that has passed through the heat exchanger 2, the pre-reformer, and the heat exchanger 1 has a temperature of about 400 ° C., which is pre-reforming by the retained heat of the combustion exhaust gas that has passed through the heat exchanger 2. This is because the heat exchange amount in the heat exchanger 1 is controlled so as to be such a temperature.

  In FIG. 6, desulfurized raw fuel is introduced into a pre-reformer through a heat exchanger 1 and supplied with steam from a separately provided steam generator (vaporizer, heat exchanger 5) to roughen it. A quality gas is generated and introduced into the heat exchanger 2. The crude reformed gas is heated by the combustion gas from the off-gas combustor in the heat exchanger 2 and supplied to the anode of the SOFC unit, that is, the anode of each cell constituting the SOFC unit.

  On the other hand, air is supplied to the SOFC unit through a blower. The air that has passed through the blower is sequentially preheated by the heat exchangers 3 and 4 and supplied to the cathode of the SOFC unit, that is, the cathode of each cell constituting the SOFC unit. The anode off-gas and cathode off-gas discharged from the SOFC unit are burned in an off-gas combustor. Then, the combustion exhaust gas is used as a heat source for preliminary reforming by passing it through the heat exchangers 4 and 2 and further passing through the heat exchangers 1 and 3 to preheat raw fuel and air.

  Among these devices, the SOFC unit, the off-gas combustor, the heat exchangers 2 and 4 and their piping system constitute an SOFC system, and these devices are usually arranged in an insulated container. The heat exchangers 1 and 3, the pre-reformer, the vaporizer, the heat exchanger 5, and their piping system constitute a pre-reform system. The temperature of the pre-reforming system is lower than that of the SOFC system, but is still high so that these equipment is placed in an insulated container as needed. Here, “in the heat insulating container” means to include those devices covered with a heat insulating material.

  In this embodiment, the anode off gas discharged from the SOFC unit is branched and taken out of the SOFC system, and carbon monoxide is adsorbed and recovered by the CO adsorbent containers A and B, or the CO adsorbent containers A and B, Carbon monoxide and hydrogen are adsorbed and recovered by the hydrogen storage containers C and D and mixed into the crude reformed gas that has passed through the preliminary reformer. Instead of being mixed with the crude reformed gas that has passed through the pre-reformer, it may be mixed with the raw fuel supplied to the pre-reformer. FIG. 6 shows this case.

  6 is a portion including the CO adsorbent containers A and B and the hydrogen storage containers C and D in the frame indicated by Z in FIG. 6, and this is the same as the frame indicated by Z in FIG. It corresponds to a part including the CO adsorbent containers A and B, and the hydrogen storage container containers C and D, and in FIG. 5 described above, the CO adsorbent container A in the frame indicated by Z in FIG. B, corresponding to a portion including the hydrogen storage container C, D. The operation and process during the operation of the SOFC unit are the same as those described with reference to FIGS. 4 (a) to 4 (b).

  Further, when hydrogen desorbed from the hydrogen storage container is used as a carrier gas for desorbing carbon monoxide from the CO adsorbent container and used as a fuel for PEFC, it is indicated by a one-dot chain line in FIG. The PEFC is placed in This case corresponds to the embodiment shown in FIG. 5, and the operation and process during the operation of the SOFC unit are the same as described with reference to FIGS. 5 (a) to 5 (b).

  4 to 5, the “anode off-gas cooler” is arranged after the SOFC unit. In FIG. 6, “heat exchanger 5” and “vaporizer” shown in the lower center of FIG. "Corresponds to the cooler. In FIG. 6, the anode off-gas that has passed through the heat exchanger 5 is reduced to 80 ° C. or less by countercurrent heat exchange with water in the vaporizer, so the cooling medium shown in the “cooler” section in FIGS. As a result, the anode off-gas decreased to 80 ° C. or lower after passing through the vaporizer in 6.

  As described above, by using a CO adsorbent and a hydrogen occluding material in combination, followed by carbon monoxide recovery using a CO adsorbent, and then recovering hydrogen using a hydrogen occluding material, a high carbon monoxide and hydrogen recovery rate can be obtained. Achieved. Moreover, since purge gas is required for desorption of carbon monoxide from the CO adsorbent, hydrogen is effectively used as the purge gas. Since the concentration of the regenerated carbon monoxide and hydrogen is almost 100% in total, it can be used as a fuel for SOFC and MCFC.

  In the present embodiment, an example in which two hydrogen storage containers are alternately switched and used as the hydrogen recovery step is shown, but three or more may be arranged and sequentially switched. In addition, a single hydrogen storage container and a buffer tank are combined, and high-purity hydrogen is continuously supplied from the buffer tank to the subsequent fuel cell or the like, while hydrogen is stored by the hydrogen storage material in the single hydrogen storage material container. Hydrogen may be stored in the buffer tank only at the time of discharge while repeating occlusion and release. In this respect, the same applies to other embodiments using the hydrogen storage container.

<Aspects of the present invention (4) to (6), (14) to (16)>
In the present invention (4), a CO converter is disposed at the rear stage of the high-temperature operating fuel cell to change the carbon monoxide in the anode offgas to hydrogen, thereby reducing the carbon monoxide concentration in the anode offgas and reducing the hydrogen concentration. After cooling the anode off-gas that has passed through a CO converter and cooling it relatively, it is introduced into a CO adsorbent vessel to adsorb and recover carbon monoxide, and the adsorbed carbon monoxide is desorbed and regenerated to operate at the same or different high temperature. A power generation method using a high-temperature operating fuel cell that improves power generation efficiency while improving the fuel utilization rate of the entire high-temperature operating fuel cell by being reused as fuel for a fuel cell, and the present invention (14) implements the power generation method. It is a system to do.

  According to the present invention (5), in addition to the configuration of the present invention (4), hydrogen in the anode off-gas from which carbon monoxide has been removed by adsorbing and recovering carbon monoxide by the CO adsorbent is used as a high-temperature operating fuel cell. Is a power generation method using a high-temperature operation fuel cell that improves the power generation efficiency while improving the fuel utilization rate of the entire fuel cell by using as a fuel of another fuel cell, and the present invention (15) implements the power generation method It is a system to do.

  According to the present invention (6), in addition to the configurations of the present inventions (4) to (5), the anode off-gas from which carbon monoxide has been removed by adsorbing and recovering carbon monoxide by the CO adsorbent container is used as a hydrogen occlusion body. It is introduced into a container and adsorbed and recovered, and the adsorbed hydrogen is desorbed and regenerated and reused as fuel for the same or different high-temperature operating fuel cell, or used as fuel for a fuel cell different from the high-temperature operating fuel cell Thus, this is a power generation method using a high-temperature operating fuel cell that improves the power generation efficiency while improving the fuel utilization rate of the entire fuel cell, and the present invention (16) is a system for implementing the power generation method.

  FIGS. 7 to 8 are diagrams for explaining the present inventions (4) to (6) and (14) to (16). When the concentration of carbon monoxide in the anode off gas of the SOFC unit is relatively high, It is a figure which shows the example of an aspect which arrange | positions a CO converter between an anode offgas cooler. The configuration shown in FIGS. 4 to 5 differs from the configuration shown in FIGS. 4 to 5 in that a CO converter is disposed immediately before the anode off-gas cooler, and other configurations and operations are the same as those shown in FIGS. It is.

In the CO transformer, the carbon monoxide concentration can be reduced to usually 1% (volume%). For this reason, the amount of CO adsorbent in the CO adsorbent container disposed in the subsequent stage can be reduced. In the CO converter, since the carbon monoxide reduced here is converted into hydrogen by reaction with water (water vapor) (CO + H ₂ O → CO ₂ + H ₂ ), the amount of hydrogen is relatively reduced. When the PEFC is juxtaposed as shown in FIG. 7, the amount of fuel hydrogen supplied to the PEFC can be increased accordingly.

  FIG. 8 shows an embodiment in which the CO converter, the CO adsorbent container, and the hydrogen storage container according to the present invention are set in the SOFC system in which the SOFC unit of 100 kW class close to the actual machine level or the actual machine level is set and its heat exchange configuration FIG. 8 differs from the configuration shown in FIG. 6 in that a [CO transformer] indicated by * in FIG. 8 is arranged. The other configuration is the same as the configuration shown in FIG. 6, and the operation and the like are the same as those in the above-described embodiment of FIG.

  The CO conversion temperature in the CO converter varies depending on the type of the conversion catalyst used, but is approximately 180 to 300 ° C. Therefore, for example, (a) the combustion exhaust gas that has passed through the heat exchanger 1 is branched as the heating source. (B) An appropriate heat source such as (b) branching off and using the anode off-gas discharged from the SOFC unit and cooled to about 300 ° C. or less by the heat exchanger 5 can be used.

<Unique aspect when using MCFC>
When MCFC is used as a high-temperature operating fuel cell, carbon dioxide (CO ₂ ) can be recycled and used as a carbon monoxide purge gas from a CO adsorbent container. As shown in FIG. 9, carbon dioxide discharged from the hydrogen storage container is supplied to the CO adsorbent container as a purge gas, adsorbed carbon monoxide is desorbed and mixed into the crude reformed gas, and reused as MCFC fuel. To do. Thereby, the power generation efficiency can be further improved. FIG. 9 is for simplifying and explaining this aspect.

<Deformation in the present invention>
In the present invention, in addition to the above embodiments, various modifications can be made.

<Deformation mode 1>
In the above description, an example in which the switching operation of adsorption / regeneration of the CO adsorbent and hydrogen storage / hydrogen release from the hydrogen storage body is mainly performed by the temperature increase / decrease, that is, the temperature swing has been described as an example. It may be performed only by the pressure swing, or may be performed by appropriately combining both the temperature swing and the pressure swing.

<Deformation mode 2>
In the above description, an example in which exhaust heat from a high-temperature operating fuel cell is used as a heat source when CO adsorbent regeneration and hydrogen release from a hydrogen storage body are performed by temperature swing has been described. It can also be carried out using sensible heat of combustion exhaust gas, heat generated during carbon monoxide recovery in a CO adsorbent container, heat generated during hydrogen recovery in a hydrogen storage container, or any two or more of these. The heat generated in the hydrogen storage container may be used as a heat source during regeneration of the CO adsorbent, and the heat generated during the recovery of carbon monoxide from the CO adsorbent container as a heat source for releasing hydrogen from the hydrogen storage body. Can also be used.

  Of these, the pre-reformer is roughly composed of a combustion section in which a burner or a combustion catalyst is arranged and a reforming section in which a reforming catalyst is arranged. The raw fuel reacts with water vapor to produce a crude reformed gas by supplying combustion heat generated by burning fuel with air in the combustion section to the reforming section. This is used as a heat source when the regeneration of the CO adsorbent and the release of hydrogen from the hydrogen occlusion body are performed by a temperature swing.

<Deformation mode 3>
In addition, when desorbing and recovering adsorbed carbon monoxide from the CO adsorbent, that is, when regenerating it and when desorbing hydrogen from the hydrogen storage body, the pressure may be reduced to normal pressure using a decompressor, and the efficiency is further improved. Therefore, the pressure may be reduced to a negative pressure using a vacuum pump or the like.

  As described above, city gas has been mainly described as an example, but as raw fuel, hydrocarbon gas fuel such as methane, ethane, ethylene, propane, butane, mixed gas of these two or more, natural gas, petroleum gas, coal Gas fuels such as generator gas, water gas, blast furnace gas, petroleum cracking gas, hydrocarbon liquid fuel such as gasoline, light oil, kerosene, diesel oil, ether liquid fuel such as dimethyl ether, alcohol such as methanol and ethanol Liquid fuels, biomass fuels obtained by gasification of various organic wastes such as methane fermentation and wood chips, etc., as well as mixed fuels of these gaseous fuels and liquid fuels, that is, mixing of two or more gaseous fuels Fuel, a mixture of two or more liquid fuels such as a mixture of gasoline and ethanol, at least one gaseous fuel and at least one A mixed fuel of a liquid fuel may also be used.

  The SOFC includes a flat plate type, a cylindrical type, and other various types. The present invention can be applied to any type of SOFC.

The figure explaining the high temperature operation fuel cell system used as the premise of this invention FIG. 4 is a diagram for explaining the facts and effects that are the premise in the present invention. The figure explaining this invention (1)-(2), (11)-(12) The figure explaining this invention (3) and (13) The figure explaining this invention (3) and (13) The figure which shows the example of the aspect which set the CO adsorbent container which concerns on this invention, and the hydrogen storage container to the SOFC system and its heat exchange structure The figure explaining this invention (4)-(6), (14)-(16) The figure which shows the example of an aspect which set the CO converter which concerns on this invention, CO adsorption agent container, and hydrogen storage body container to SOFC system and its heat exchange structure Diagram explaining unique aspects when using MCFC

Explanation of symbols

1-3 heat exchanger

Claims (16)

  A power generation method using a high temperature operation fuel cell using carbon monoxide and hydrogen as fuel, (a) after cooling the anode off-gas of the high temperature operation fuel cell, introducing it into a CO adsorbent container to adsorb and recover carbon monoxide. The adsorbed carbon monoxide is desorbed and regenerated and reused as fuel for the same or another high-temperature operating fuel cell. (B) The power generation efficiency is improved while improving the fuel utilization rate of the entire high-temperature operating fuel cell. A power generation method using a high-temperature operating fuel cell. A power generation method using a high temperature operation fuel cell using carbon monoxide and hydrogen as fuel, (a) after cooling the anode off-gas of the high temperature operation fuel cell, introducing it into a CO adsorbent container to adsorb and recover carbon monoxide. The adsorbed carbon monoxide is desorbed and regenerated and reused as fuel for the same or another high-temperature operating fuel cell. (B) Carbon monoxide is removed by adsorption and recovery of carbon monoxide by the CO adsorbent. By using hydrogen containing carbon dioxide and water as impurities, which is an anode off-gas, as a fuel for a fuel cell different from a high-temperature operating fuel cell,
(C) A power generation method using a high-temperature-operated fuel cell, which improves power generation efficiency while improving the fuel utilization rate of the entire fuel cell.   A power generation method using a high temperature operation fuel cell using carbon monoxide and hydrogen as fuel, (a) after cooling the anode off-gas of the high temperature operation fuel cell, introducing it into a CO adsorbent container to adsorb and recover carbon monoxide. The adsorbed carbon monoxide is desorbed and regenerated and reused as fuel for the same or another high-temperature operating fuel cell. (B) Carbon monoxide is removed by adsorption and recovery of carbon monoxide by the CO adsorbent container. The anode off-gas is introduced into a hydrogen storage container and hydrogen is adsorbed and recovered, and the adsorbed hydrogen is desorbed and regenerated and reused as fuel for the same or another high-temperature operating fuel cell, or separate from the high-temperature operating fuel cell. (C) A power generation method using a high-temperature operation fuel cell, wherein the power generation efficiency is improved while improving the fuel utilization rate of the entire fuel cell.   A power generation method using a high temperature operation fuel cell using carbon monoxide and hydrogen as a fuel, wherein (a) a CO converter is disposed at the rear stage of the high temperature operation fuel cell, and carbon monoxide in the anode off-gas is changed to hydrogen. The carbon monoxide concentration in the anode off-gas is reduced and the hydrogen concentration is relatively increased. (B) After the anode off-gas passing through the CO converter is cooled, the carbon monoxide is introduced into the CO adsorbent vessel to adsorb carbon monoxide. By recovering, desorbing and regenerating the adsorbed carbon monoxide and reusing it as fuel for the same or another high-temperature operating fuel cell, (c) improving power generation efficiency of the entire high-temperature operating fuel cell A power generation method using a high-temperature operating fuel cell.   A power generation method using a high temperature operation fuel cell using carbon monoxide and hydrogen as a fuel, wherein (a) a CO converter is disposed at the rear stage of the high temperature operation fuel cell, and carbon monoxide in the anode off-gas is changed to hydrogen. The carbon monoxide concentration in the anode off-gas is reduced and the hydrogen concentration is relatively increased. (B) After the anode off-gas passing through the CO converter is cooled, the carbon monoxide is introduced into the CO adsorbent vessel to adsorb carbon monoxide. The adsorbed carbon monoxide is recovered and reused as fuel for the same or another high-temperature operating fuel cell. (C) The carbon monoxide is recovered by adsorbing and recovering carbon monoxide with the CO adsorbent. By using the hydrogen in the removed anode off-gas as fuel for a fuel cell different from the high-temperature operating fuel cell, (d) improving power generation efficiency while improving the fuel utilization rate of the entire fuel cell Power generation method according to the high temperature operation fuel cells, which comprises causing.   A power generation method using a high temperature operation fuel cell using carbon monoxide and hydrogen as a fuel, wherein (a) a CO converter is disposed at the rear stage of the high temperature operation fuel cell, and carbon monoxide in the anode off-gas is changed to hydrogen. The carbon monoxide concentration in the anode off-gas is reduced and the hydrogen concentration is relatively increased. (B) After the anode off-gas passing through the CO converter is cooled, the carbon monoxide is introduced into the CO adsorbent vessel to adsorb carbon monoxide. And the adsorbed carbon monoxide is desorbed and regenerated and reused as fuel for the same or another high-temperature operating fuel cell, and (c) carbon monoxide is adsorbed and recovered by the CO adsorbent container. The anode off-gas from which is removed is introduced into a hydrogen storage container to adsorb and recover hydrogen, and the adsorbed hydrogen is desorbed and regenerated and reused as fuel for the same or another high-temperature operating fuel cell, By utilizing a fuel of another fuel cell and the temperature operating fuel cell power generation method according to the high temperature operation fuel cells, characterized in that to improve the power generation efficiency while improving fuel utilization rate of the entire (d) fuel cells.   7. The power generation method using a high-temperature operating fuel cell according to claim 6, wherein the high-temperature operating fuel cell is a molten carbonate fuel cell, and carbon dioxide, which is the remaining anode off-gas obtained by recovering hydrogen by the hydrogen storage container, is used. A power generation method using a high-temperature operating fuel cell, characterized by recycling to the anode of a molten carbonate fuel cell.   The power generation method using the high-temperature operating fuel cell according to claim 3 or 6, wherein the regenerated hydrogen from the hydrogen storage container is also used as a purge gas for desorption of carbon monoxide in a CO adsorbent container, thereby mixing carbon monoxide and hydrogen. A power generation method using a high-temperature operating fuel cell, characterized in that gas is generated to maintain a high concentration of fuel gas.   9. The power generation method using a high-temperature operating fuel cell according to claim 1, wherein desorption and regeneration of carbon monoxide from a CO adsorbent container is performed using exhaust heat from the high-temperature operating fuel cell and exhaust from the anode off-gas cooler. A power generation method using a high-temperature operating fuel cell, which utilizes heat, exhaust heat from a CO transformer, exhaust heat from a fuel cell other than a high-temperature operating fuel cell or other power generation means.   10. A power generation method using a high-temperature operating fuel cell according to claim 1, wherein the high-temperature operating fuel cell is a solid oxide fuel cell or a molten carbonate fuel cell. A power generation method using a fuel cell.   A power generation system using a high temperature operation fuel cell using carbon monoxide and hydrogen as fuel, (a) after cooling the anode off-gas of the high temperature operation fuel cell, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide. By desorbing and regenerating the adsorbed carbon monoxide and reusing it as the fuel for the same or another high-temperature operating fuel cell, (b) power generation while improving the fuel utilization rate of the entire high-temperature operating fuel cell A power generation system using a high-temperature operating fuel cell, characterized by improving efficiency.   A power generation system using a high temperature operation fuel cell using carbon monoxide and hydrogen as fuel, (a) after cooling the anode off-gas of the high temperature operation fuel cell, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide. The adsorbed carbon monoxide is desorbed and regenerated to be reused as fuel for the same or another high-temperature operating fuel cell, and (b) carbon monoxide is adsorbed and recovered by the CO adsorbent. By using hydrogen that is carbon dioxide and water as impurities, which is the removed anode off gas, as a fuel for a fuel cell different from the high-temperature operating fuel cell, (c) the entire fuel cell A power generation system using a high-temperature-operated fuel cell characterized by improving the power generation efficiency while improving the fuel utilization rate.   A power generation system using a high temperature operation fuel cell using carbon monoxide and hydrogen as fuel, (a) after cooling the anode off-gas of the high temperature operation fuel cell, it is introduced into a CO adsorbent container to adsorb and recover carbon monoxide. The adsorbed carbon monoxide is desorbed and regenerated to be reused as fuel for the same or another high-temperature operating fuel cell, and (b) carbon monoxide is recovered by adsorbing and recovering carbon monoxide by the CO adsorbent container. The removed anode off-gas is introduced into a hydrogen storage container to adsorb and recover hydrogen, and the adsorbed hydrogen is desorbed and regenerated and reused as fuel for the same or another high-temperature operating fuel cell. Is used as a fuel for another fuel cell, and (c) a high-temperature operation fuel cell characterized by improving the power generation efficiency while improving the fuel utilization rate of the entire fuel cell Power generation system due.   A power generation system using a high-temperature operating fuel cell fueled with carbon monoxide and hydrogen, (a) by disposing a CO converter at the subsequent stage of the high-temperature operating fuel cell to convert carbon monoxide in the anode offgas to hydrogen The carbon monoxide concentration in the anode off-gas is reduced and the hydrogen concentration is relatively increased. (B) After the anode off-gas passing through the CO converter is cooled, the carbon monoxide is introduced into the CO adsorbent vessel to adsorb carbon monoxide. By recovering and desorbing and regenerating the adsorbed carbon monoxide and reusing it as the fuel for the same or another high temperature operating fuel cell, (c) improving the fuel utilization rate of the entire high temperature operating fuel cell A power generation system using a high-temperature operating fuel cell, characterized by improving power generation efficiency.   A power generation system using a high-temperature operating fuel cell fueled with carbon monoxide and hydrogen, (a) by disposing a CO converter at the rear stage of the high-temperature operating fuel cell to convert carbon monoxide in the anode offgas to hydrogen The carbon monoxide concentration in the anode off-gas is reduced and the hydrogen concentration is relatively increased. (B) After the anode off-gas passing through the CO converter is cooled, it is introduced into a CO adsorbent container to adsorb carbon monoxide. And the adsorbed carbon monoxide is desorbed and regenerated to be reused as fuel for the same or another high-temperature operating fuel cell. (C) Carbon monoxide is adsorbed and recovered by the CO adsorbent. By using hydrogen in the anode off-gas from which carbon has been removed as fuel for a fuel cell different from the high-temperature operating fuel cell, (d) fuel use of the entire fuel cell Power generation system due to high temperature operation fuel cells, characterized in that to improve the improved while power generation efficiency. A power generation system using a high-temperature operating fuel cell fueled with carbon monoxide and hydrogen, (a) by disposing a CO converter at the subsequent stage of the high-temperature operating fuel cell to convert carbon monoxide in the anode offgas to hydrogen The carbon monoxide concentration in the anode off-gas is reduced and the hydrogen concentration is relatively increased. (B) After the anode off-gas passing through the CO converter is cooled, the carbon monoxide is introduced into the CO adsorbent vessel to adsorb carbon monoxide. And the adsorbed carbon monoxide is desorbed and regenerated to be reused as fuel for the same or another high-temperature operating fuel cell, and (c) carbon monoxide is adsorbed and recovered by the CO adsorbent container. The anode off-gas from which carbon oxide has been removed is introduced into a hydrogen storage container, and hydrogen is adsorbed and recovered, and the adsorbed hydrogen is desorbed and regenerated as fuel for the same or another high-temperature operating fuel cell. (D) By improving the fuel utilization rate of the entire fuel cell, the power generation efficiency is improved by using the fuel cell or by using it as a fuel of a fuel cell different from the high-temperature operating fuel cell. A power generation system using high-temperature fuel cells.

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