JP2008217999A - Operation method of high temperature type fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation method of a high temperature fuel cell system, capable of protecting an anode without requiring storage and replenishment of hydrogen. <P>SOLUTION: This operation method of the fuel cell system having a reformer to manufacture reformed gas from hydrocarbon-based fuel and a high temperature fuel cell generating power using the reformed gas obtained from the reformer, has a process to bring the anode into a reducing gas atmosphere by supplying hydrogen produced in the electrolysis of water to the anode of the fuel cell when the reformer cannot manufacture the reformed gas from the hydrocarbon-based fuel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for operating a high-temperature fuel cell system having a reformer that reforms a hydrocarbon-based fuel such as kerosene and a high-temperature fuel cell that generates power using reformed gas obtained from the reformer. .

  In solid oxide fuel cells (Solid Oxide Fuel Cell, hereinafter referred to as SOFC in some cases), hydrocarbon fuels (reformed raw materials) such as kerosene and city gas are usually generated by reforming in a reformer. Hydrogen-containing gas (reformed gas) is supplied. In the SOFC, the reformed gas and air are reacted electrochemically to generate electricity.

  The SOFC is usually operated at a high temperature of about 550 to 1000 ° C. The reformer is operated at a temperature of, for example, about 400 ° C to 1000 ° C. For this reason, in the SOFC system, the temperature of these devices is increased to a predetermined temperature when starting up, and the temperature is decreased from the predetermined temperature when stopping.

  Patent Document 1 describes that hydrogen generated in a water electrolysis tank is supplied to a reformer to prevent deterioration of the reforming catalyst.

Patent Document 2 describes an SOFC system having an activation stack in addition to a normal stack, and describes that hydrogen supplied to the activation cell is generated by electrolysis of water.
JP 2006-8418 A JP 2006-278074 A

  When starting up an SOFC system that reforms and uses hydrocarbon fuel, the temperature of the reformer reaches a temperature at which the hydrocarbon fuel can be reformed, and the reformer can produce reformed gas. During this time, hydrogen is supplied to the anode in order to prevent oxidation of the SOFC anode. When the reformed gas can be produced, the reformed gas may be supplied to the anode. Even when the SOFC system is stopped, hydrogen is supplied to the anode after the reformer cannot obtain the reformed gas.

  As described above, hydrogen stored in a cylinder can be used as hydrogen for protecting the anode of the SOFC. However, in this case, hydrogen storage facilities and hydrogen replenishment are required, and the entire system becomes large and it takes time to procure hydrogen cylinders, which increases costs.

  As mentioned above, when the reformer cannot produce reformed gas, such as at start-up or shut-down, protecting the anode by making the anode into a reducing atmosphere using hydrogen is an SOFC or molten carbonate type. It is performed in a high-temperature fuel cell such as a fuel cell (hereinafter referred to as MCFC).

  An object of the present invention is to provide a method for operating a high-temperature fuel cell system that can protect an anode without requiring storage or replenishment of hydrogen.

According to the present invention, there is provided a method of operating a fuel cell system having a reformer that produces reformed gas from a hydrocarbon-based fuel and a high-temperature fuel cell that generates electric power using the reformed gas obtained from the reformer. And
When the reformer cannot produce reformed gas from hydrocarbon fuel, hydrogen generated by electrolysis of water is supplied to the anode of the high-temperature fuel cell, so that the anode is brought into a reducing gas atmosphere. A method for operating a high-temperature fuel cell system having a process is provided.

  The process can be performed when the reformer is at a temperature lower than the temperature at which the reformed gas can be produced from the hydrocarbon-based fuel.

  Hydrogen generated by electrolysis of the water can be supplied to the anode via the reformer.

  Hydrogen supplied to the anode is discharged from the anode, and at least one of the high-temperature fuel cell and the reformer can be heated by thermal energy obtained by burning the discharged hydrogen.

  The high temperature fuel cell may be a solid oxide fuel cell or a molten carbonate fuel cell.

  The present invention provides a method of operating a high-temperature fuel cell system that can protect the anode without requiring storage or replenishment of hydrogen.

  The present invention relates to a method of operating a fuel cell system having a reformer that produces reformed gas from a hydrocarbon-based fuel and a high-temperature fuel cell that generates power using the reformed gas obtained from the reformer.

  When the reformer cannot produce reformed gas from hydrocarbon fuel, the method of the present invention supplies the hydrogen generated by electrolysis of water to the anode of the high-temperature fuel cell, thereby reducing the anode to the reducing gas. A step of creating an atmosphere.

  As a case where the reformer cannot produce reformed gas from hydrocarbon fuel, a case where the reformer is at a temperature lower than the temperature at which the reformed gas can be produced from hydrocarbon-based fuel can be cited. When the system is started or stopped, the reformer, especially the reforming catalyst layer, is lower than the reformable temperature, and it is necessary to prevent oxidation of the anode. Can be in a reducing atmosphere. The temperature at which the reformed gas can be produced depends on the reforming catalyst and reforming raw material to be used, but can be known by conducting a preliminary test.

  In addition, as a case where the reformer cannot produce the reformed gas from the hydrocarbon fuel, a case where the reformed gas cannot be produced due to some abnormality can be cited. For example, when the reformed gas cannot be produced due to abnormalities during normal operation (rated operation or partial load operation), the anode is made a reducing atmosphere with hydrogen obtained by electrolysis of water, and the anode is protected. However, the operation can be stopped.

  An example of an abnormality in which the reformed gas cannot be produced is a decrease in the temperature of the reformer. In order to deal with such an abnormality, the temperature is measured by a thermometer installed in the reformer. For example, when the reformer temperature falls below a reformable temperature, it can be detected that the temperature is abnormal. Further, it can be mentioned that some clogging occurs on the line for supplying the reformed gas to the anode and the reformed gas cannot be supplied. In order to deal with such an abnormality, a pressure abnormality can be detected by installing a pressure gauge.

  Hydrogen generated by electrolysis of water can be supplied to the anode via a reformer. More specifically, the hydrogen can be passed through the reforming catalyst layer and then supplied to the anode. Thereby, in addition to the anode, the reforming catalyst accommodated in the reformer can also be in a reducing atmosphere, which is useful when it is necessary to prevent oxidative degradation of the reforming catalyst.

  Hydrogen supplied to the anode is discharged from the anode, and at least one of the high-temperature fuel cell and the reformer can be heated by thermal energy obtained by burning the discharged hydrogen. Thereby, combustible material processing can be performed and at the same time effective use of heat can be achieved.

  As the high-temperature fuel cell, a solid oxide fuel cell or a molten carbonate fuel cell can be used.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  FIG. 1 is a schematic flow diagram of an SOFC system, particularly an indirect internal reforming SOFC system, which can implement the operation method of the present invention. This system includes an indirect internal reforming SOFC having a reformer 3, a SOFC 4, and a module container 10 which is a container for housing the reformer and the SOFC. In the figure, A and C attached to SOFC mean an anode and a cathode, respectively.

  In the indirect internal reforming SOFC, the reformer 3 uses the steam reforming reaction to produce reformed gas from hydrocarbon fuel. The reforming is an overall endothermic reaction. The reformer is disposed at a position that receives heat radiation from the SOFC, and the reformer can be heated by radiant heat from the SOFC in order to supply heat necessary for reforming. In the system shown in FIG. 1, steam reforming is performed in a reformer. However, the reforming reaction is not limited to steam reforming, and the reforming reaction can be performed by partial oxidation reforming or autothermal reforming.

  The reformed gas produced by the reformer 3 is supplied to the anode of the SOFC 4. Air is supplied as an oxygen-containing gas to the cathode of the SOFC. In the SOFC, hydrogen contained in the anode gas and oxygen contained in the cathode gas cause an electrochemical reaction to generate power.

  This indirect internal reforming SOFC includes a combustion chamber 5. A separate container is provided inside the module container, and the interior serves as a combustion chamber. An anode off gas discharged from the anode of the SOFC and a cathode off gas discharged from the cathode are supplied to the combustion chamber. The combustible component contained in the anode off gas is combusted by oxygen contained in the cathode off gas. However, this combustion can be performed in at least a part of the region in the container module container without providing a separate container.

  The combustion gas generated in the combustion chamber 5 heats the reformer 3 by heat exchange. Here, it is possible to further heat the gas supplied to the SOFC by the heat of the combustion gas, or to use this heat in a heat utilization device.

  Water is supplied from the water tank 1 and kerosene is appropriately vaporized from the kerosene tank 2 and then supplied to the reformer 3, particularly the reforming catalyst layer housed therein.

  This system further includes a water electrolysis hydrogen production apparatus 21. The water electrolysis hydrogen production apparatus can be appropriately selected from apparatuses capable of producing hydrogen by electrolyzing water.

  Water electrolysis generates oxygen as well as hydrogen. This oxygen may flow to the cathode of the SOFC or may be discharged out of the system.

  As electric power necessary for electrolysis of water, electric power stored in the secondary battery can be used. The secondary battery can store the power generated by the fuel cell at the time of fuel cell power generation. Moreover, the electric power required for electrolysis can also be supplied from natural energy utilization power generators, such as a solar cell and wind power generation. Alternatively, electrolysis may be performed using system power.

  The system has a heater 22 that heats the reformer. Here, the heater 22 is an electric heater, and the reformer is heated using air heated by the electric heater.

  The present invention can also be applied to high-temperature fuel cell systems other than the indirect internal reforming SOFC system, such as an external reforming SOFC system, an internal reforming type, or an external reforming MCFC system.

  Although a so-called atmospheric pressure type SOFC system is shown here, the operating pressure is arbitrary, and the present invention can be applied to a pressurized fuel cell system.

  The situation where the water electrolysis hydrogen production apparatus 21 is used will be described in the system shown in FIG.

1) At system startup Here, the system startup is from when the system temperature is at room temperature until the reformed gas can be produced by the reformer and power generation is started by SOFC. At start-up, the reformer, particularly the reforming catalyst and the SOFC, must be heated to a temperature at which the reforming raw material can be reformed and a temperature at which power generation can be performed.

  The SOFC and the reformer are heated during the temperature raising process of the system. When the temperature of SOFC is raised, oxidation may occur and the anode may be deteriorated unless the anode is kept in a reducing atmosphere. In order to maximize the performance of the reforming catalyst, it is preferable to bring the reforming catalyst into a reducing atmosphere at the time of raising the temperature of the reformer.

  The hydrogen gas is produced by the water electrolysis hydrogen production apparatus and supplied to the system at the time of starting the system, particularly until the reformer can produce the reformed gas. Oxidation can be prevented, and consequently performance degradation can be prevented.

  As a specific method, water is supplied from the water tank 1 to the water electrolysis hydrogen production apparatus 21 to produce hydrogen gas. Hydrogen gas is supplied to the reformer 3 and supplied to the anode of the SOFC 4 via the reforming catalyst layer of the reformer. As a result, the reforming catalyst and the anode are maintained in a reducing atmosphere, and oxidation of the reforming catalyst and the anode is prevented. In addition, when it is not necessary to supply the hydrogen gas produced by the water electrolysis hydrogen production apparatus to the reforming catalyst layer, hydrogen can be directly supplied to the SOFC anode.

  For the purpose of preventing oxidation, the amount of hydrogen supplied from the water electrolysis hydrogen production apparatus to the reformer and the anode may be such that the reducing atmosphere is maintained in the reforming catalyst layer and the anode. In addition to preventing oxidation of the reforming catalyst layer and the anode, when there is a purpose of burning the hydrogen and heating the SOFC system, the amount of hydrogen gas produced by the water electrolysis hydrogen production apparatus can be appropriately increased.

  The reformer 3 is heated by the heater 22. The hydrogen gas that has passed through the anode of the SOFC 4 is mixed with the air that has passed through the cathode of the SOFC 4 in the combustion chamber 5 and burned. The reformer can be heated by using the combustion heat. Thus, the state shown in FIG. 2 is obtained. In FIG. 2, the portion where the line indicating the process line is bold indicates that a fluid is flowing through the line. Moreover, when the line which shows the wiring for direct-current power supplied to a water electrolysis hydrogen production apparatus is made into the thick line, it shows that direct-current power is supplied. (The same applies to FIGS. 3 to 6). However, in FIGS. 2, 4 and 5, a line for supplying hydrogen to the SOFC anode from the water electrolysis hydrogen production apparatus 21 via the reformer 3, and the water electrolysis hydrogen production apparatus 21 without passing through the reformer 3. Both of the lines for supplying hydrogen to the SOFC anode are shown in bold lines, but it is not necessary to use both of these lines.

  When the temperature of the reformer, particularly the reforming catalyst reaches a temperature at which kerosene as the reforming raw material can be reformed, kerosene is supplied from the kerosene tank 2 and water is supplied from the water tank 1 to the reformer. Manufacturing. This reformed gas is supplied to the SOFC anode.

  When the anode can be brought into a reducing atmosphere with the reformed gas, the production of hydrogen gas by the water electrolysis hydrogen production apparatus is stopped. Further, the heater can be stopped when it is no longer necessary to heat the reformer with the heater. When the SOFC reaches a predetermined temperature at which power can be generated, power generation is started. Up to this point, the state shown in FIG.

  When the system is started, the system can be started by preventing the oxidative deterioration of the reforming catalyst and the SOFC anode by using the water electrolysis hydrogen production apparatus as described above.

2) When the system is shut down Here, when the system is shut down, the SOFC power generation and the reformed gas production by the reformer are stopped, and the system temperature is at room temperature. Until. When the engine is stopped, power generation of the SOFC is stopped, and the amount of reformed gas produced in the reformer is reduced, so that the heat generation of the SOFC is stopped and the heat supply to the SOFC and the reformer is reduced. This lowers the temperature of the system.

  In the temperature lowering process of the system, when the temperature of the reformer decreases and reaches a temperature at which the reforming raw material cannot be reformed, the reformed gas cannot be supplied to the anode. When the SOFC is hot, it may be oxidized if the anode is not kept in a reducing atmosphere, and the anode may be deteriorated. Further, when the temperature of the reformer is lowered, it is preferable that the reforming catalyst is in a reducing atmosphere in order to maximize the performance of the reforming catalyst.

  Prevents oxidation of SOFC anode and reforming catalyst by producing hydrogen gas with water electrolysis hydrogen production equipment and supplying it to the system when the system is shut down, especially before the reformer can no longer produce the reformed gas As a result, performance degradation can be prevented.

  As a specific method, power generation by the SOFC is stopped, the amount of reformed gas produced by the reformer is reduced, and the amount of reformed gas supplied to the SOFC is reduced, so that the system temperature falls. Before the reformer temperature decreases and the reformer cannot produce reformed gas, water is supplied from the water tank 1 to the water electrolysis hydrogen production device 21 to produce hydrogen gas. Hydrogen gas is supplied to the reformer 3 and supplied to the anode of the SOFC 4 via the reforming catalyst layer of the reformer. As a result, the reforming catalyst and the anode are maintained in a reducing atmosphere, and oxidation of the reforming catalyst and the anode is prevented. In addition, when it is not necessary to supply the hydrogen gas produced by the water electrolysis hydrogen production apparatus to the reforming catalyst layer, hydrogen can be directly supplied to the SOFC anode. However, the supply of hydrogen gas to the reforming catalyst and SOFC by the water electrolysis hydrogen production apparatus may be performed before the power generation of the SOFC is stopped, or at any time before the supply of the reformed gas to the SOFC anode is stopped. The supply of hydrogen gas can be started. Up to this point, the state shown in FIG. 4 is obtained.

  For the purpose of preventing oxidation, the amount of hydrogen supplied from the water electrolysis hydrogen production apparatus to the reformer and the anode may be such that the reducing atmosphere is maintained in the reforming catalyst layer and the anode.

  When the anode can be brought into a reducing atmosphere by the hydrogen gas produced by the water electrolysis hydrogen production apparatus, production of the reformed gas by the reformer is stopped. Thus, the state shown in FIG. 5 is obtained.

  The hydrogen gas that has passed through the anode of the SOFC 4 is mixed with the air that has passed through the cathode of the SOFC 4 in the combustion chamber 5 and combusted for the treatment of combustible materials, but the supplied hydrogen gas is oxidized in the reforming catalyst layer and the anode. The system can be cooled down by natural heat dissipation or the like by setting the minimum amount to prevent the above.

  When the temperature of the SOFC anode and the reforming catalyst is lowered to a temperature at which the SOFC anode and the reforming catalyst are not deteriorated, the supply of hydrogen gas by the water electrolysis hydrogen production apparatus is stopped, and the water supply from the water tank to the water electrolysis hydrogen production apparatus is stopped. Stop system operation.

  When the system is stopped, the system can be stopped by preventing the oxidative deterioration of the reforming catalyst and the SOFC anode by using the water electrolysis hydrogen production apparatus as described above.

3) When the reformed gas cannot be supplied due to an abnormality Here, when the reformed gas cannot be supplied due to an abnormality, the reformer cannot produce the reformed gas from the reforming raw material due to some abnormality or the SOFC It is in a state where it cannot be supplied to the anode.

  Examples of abnormalities in which the reformed gas cannot be produced include a case where the reforming reaction cannot be performed due to a decrease in the temperature of the reformer, or a case where the supply of the reforming raw material to the reformer is stopped. Further, as an example of an abnormality in which the reformed gas cannot be supplied, there is a case where some clogging occurs on the line for supplying the reformed gas to the anode.

  For example, during normal operation (rated operation or partial load operation), if the reformed gas cannot be supplied to the anode due to an abnormality, the SOFC4 anode is not kept in the reducing atmosphere, but is oxidized and deteriorates the anode. There is a possibility of letting you.

  When the reformed gas cannot be supplied due to an abnormality, hydrogen gas is produced by the water electrolysis hydrogen production apparatus and supplied to the SOFC anode, whereby the anode can be prevented from being oxidized and performance degradation can be prevented.

  As a specific method, water is supplied from the water tank 1 to the water electrolysis hydrogen production apparatus 21 to produce hydrogen gas. When the hydrogen gas cannot be supplied to the SOFC anode via the reformer as the hydrogen gas supply path, the hydrogen gas is supplied directly to the SOFC anode. This keeps the anode in a reducing atmosphere and prevents anode oxidation. This state is shown in FIG.

  In addition, when hydrogen gas can be supplied to the SOFC anode via the reforming catalyst layer of the reformer as a hydrogen gas supply path, hydrogen gas is supplied to the anode via the reformer as necessary. can do. This prevents oxidation of the reforming catalyst and the anode.

  For the purpose of preventing oxidation, the amount of hydrogen supplied from the water electrolysis hydrogen production apparatus to the reformer and the anode may be such that the reducing atmosphere is maintained in the reforming catalyst layer and the anode.

  The hydrogen gas that has passed through the anode of the SOFC 4 is mixed with the air that has passed through the cathode of the SOFC 4 in the combustion chamber 5 and combusted for the treatment of combustible materials. The hydrogen gas to be supplied is at least the reforming catalyst layer and the anode, By setting the minimum amount that can prevent the oxidation of the anode, the system can be cooled by natural heat dissipation or the like.

  When the temperature of the SOFC anode and the reforming catalyst is lowered to a temperature at which the SOFC anode and the reforming catalyst are not deteriorated, the supply of hydrogen gas by the water electrolysis hydrogen production apparatus is stopped, and the water supply from the water tank to the water electrolysis hydrogen production apparatus is stopped. Stop system operation.

  When the reformed gas cannot be supplied due to an abnormality, the system can be stopped by preventing the oxidative deterioration of the reforming catalyst and the SOFC anode, or at least the SOFC anode, by using the water electrolysis hydrogen production apparatus as described above. it can.

[High-temperature fuel cell]
The present invention can be applied to a system including a high-temperature fuel cell that requires prevention of oxidative deterioration of the anode. When a metal electrode is used for the anode, the oxidative degradation of the anode may occur at about 200 ° C., for example. Such fuel cells include SOFC and MCFC.

  As the SOFC, various known shapes such as a flat plate type and a cylindrical type can be appropriately selected and used. In the SOFC, oxygen ion conductive ceramics or proton ion conductive ceramics are generally used as an electrolyte.

  The MCFC can be appropriately selected from known MCFCs.

  The SOFC or MCFC may be a single cell, but in practice, a stack in which a plurality of single cells are arranged (in the case of a cylindrical type, it may be called a bundle, but the stack referred to in this specification also includes a bundle) Is preferably used. In this case, one or more stacks may be used.

[Reformer]
The reformer produces a reformed gas containing hydrogen from a hydrocarbon fuel. In the reformer, any of steam reforming, partial oxidation reforming, and autothermal reforming accompanied by a partial oxidation reaction in the steam reforming reaction may be performed.

  The reformer appropriately uses a steam reforming catalyst having steam reforming ability, a partial oxidation reforming catalyst having partial oxidation reforming ability, and an autothermal reforming catalyst having both partial oxidation reforming ability and steam reforming ability. be able to.

  Supply hydrocarbon-based fuel (pre-vaporized if necessary), water vapor, and oxygen-containing gas such as air, if necessary, individually or appropriately mixed to the reformer (reforming catalyst layer) can do. The reformed gas is supplied to the anode of the SOFC.

  Among high temperature fuel cells, the indirect internal reforming SOFC is superior in that it can increase the thermal efficiency of the system. The indirect internal reforming SOFC includes a reformer that produces a reformed gas containing hydrogen from a hydrocarbon-based fuel using a steam reforming reaction, and the SOFC. In this reformer, a steam reforming reaction can be performed, and autothermal reforming accompanied by a partial oxidation reaction in the steam reforming reaction may be performed. From the viewpoint of power generation efficiency of SOFC, it is preferable that the partial oxidation reaction does not occur. In autothermal reforming, steam reforming is dominant, and therefore the reforming reaction becomes endothermic in overall. Then, heat necessary for the reforming reaction is supplied from the SOFC. The reformer and SOFC are accommodated in one module container and modularized. The reformer is disposed at a position that receives heat radiation from the SOFC. By doing so, the reformer is heated by heat radiation from the SOFC during power generation. In addition, the SOFC can be heated by burning the anode off-gas discharged from the SOFC at the cell outlet.

  In the indirect internal reforming SOFC, the reformer is preferably arranged at a position where direct heat transfer from the SOFC to the outer surface of the reformer is possible. Therefore, it is preferable that a shielding object is not substantially disposed between the reformer and the SOFC, that is, a gap is provided between the reformer and the SOFC. Further, it is preferable to shorten the distance between the reformer and the SOFC as much as possible.

  Each supply gas is appropriately preheated as necessary and then supplied to the reformer or SOFC.

  As the module container, an appropriate container capable of accommodating the SOFC and the reformer can be used. As the material, for example, an appropriate material having resistance to the environment to be used, such as stainless steel, can be used. The container is appropriately provided with a connection port for gas exchange and the like.

  In particular, when the cell outlet is open in the module container, the module container is preferably airtight so that the inside of the module container and the outside (atmosphere) do not communicate with each other.

[Water electrolysis hydrogen production equipment]
Water electrolysis hydrogen production equipment is used to produce hydrogen gas by water electrolysis and flow to the anode to protect the SOFC anode from oxidation when the reformed reformed gas cannot be produced by the reformer. Used. Further, it is used to flow through the reforming catalyst layer in order to protect the reforming catalyst from oxidation as required. For example, when the reformer reaches a temperature at which the hydrocarbon feedstock can be reformed when the system starts up, and when the reformer becomes lower than the temperature at which the hydrocarbon feedstock can be reformed when the system is shut down It is done.

  The water electrolysis hydrogen production apparatus only needs to produce a minimum amount of hydrogen gas sufficient to protect the anode (and the reforming catalyst if necessary). In addition, when hydrogen combustion heat is used to heat the reformer or SOFC, the necessary amount may be further manufactured and supplied. The production amount varies depending on the type of SOFC module, the structure and scale of the system, and cannot be determined unconditionally, but can be known by preliminary tests.

〔Heater〕
The heater is used to heat equipment in the high temperature fuel cell system. The type of the heater can be appropriately selected from an electric heater, a burner, a catalytic combustor (combustion catalyst), and the like. The electric heater may be installed in the device and directly heated, or the fluid may be heated to heat the device with the heating fluid. Burners and catalytic combustors are used to burn combustible materials to generate combustion gases and to heat equipment with the combustion gases. Instead of the burner or the catalytic combustor, known combustion means capable of burning combustible materials can be used.

  As a combustible material combusted by a combustion means such as a burner, a combustible material combustible by a combustion means to be used can be appropriately selected and used. From the viewpoint of ease of handling, it is preferable to use a gas or liquid combustible material. In particular, liquid combustibles such as kerosene are preferable because they are easy to handle and store. When using a gaseous combustible material, it is preferable to use what is supplied continuously from the outside, such as city gas, and does not require a storage facility.

  It is preferable to use the same combustible material as the combustible material to be combusted by a combustion means such as a burner as a raw material for reforming in the reformer because the supply source can be shared. In the system shown in FIG. 1, kerosene is used as a reforming raw material, and a burner can be used as a heater, and kerosene can be used as fuel for the burner.

[Hydrocarbon fuel]
As a hydrocarbon fuel reformed by a reformer, carbon and hydrogen are contained in a molecule known in the field of a high-temperature fuel cell system as a raw material of reformed gas (may contain other elements such as oxygen). A compound or a mixture thereof can be used as appropriate, and compounds having carbon and hydrogen in the molecule such as hydrocarbons and alcohols can be used. For example, hydrocarbon fuel such as methane, ethane, propane, butane, natural gas, LPG (liquefied petroleum gas), city gas, gasoline, naphtha, kerosene, light oil, etc., alcohol such as methanol and ethanol, ether such as dimethyl ether, etc. is there.

  Of these, kerosene, LPG, and city gas are preferable because they are easily available. Since kerosene is reformed at a relatively high temperature, it takes a relatively long time to start the reformer (internal reformer). For this reason, when kerosene is used as the hydrocarbon-based fuel, the effect of the present invention that does not require the use of hydrogen storage means is particularly remarkable.

[Reforming catalyst]
Any of the steam reforming catalyst, partial oxidation reforming catalyst, and autothermal reforming catalyst used in the reformer can be a known catalyst. Examples of the partial oxidation reforming catalyst include platinum-based catalysts, examples of the steam reforming catalyst include ruthenium-based and nickel-based catalysts, and examples of the autothermal reforming catalyst include rhodium-based catalysts.

  The temperature at which the partial oxidation reforming reaction can proceed is, for example, 200 ° C. or higher, and the temperature at which the steam reforming reaction can proceed is, for example, 400 ° C. or higher.

  Hereinafter, rated operation conditions in the reformer will be described for each of steam reforming, autothermal reforming, and partial oxidation reforming.

In steam reforming, steam is added to reforming raw materials such as kerosene. The steam reforming reaction temperature is, for example, 400 ° C to 1000 ° C, preferably 500 ° C to 850 ° C, more preferably 550 ° C to 800 ° C. The amount of steam introduced into the reaction system is defined as the ratio of the number of moles of water molecules to the number of moles of carbon atoms contained in the raw material for hydrogen production (steam / carbon ratio), and this value is preferably 1-10, more preferably 1.5-7, more preferably 2-5. When the raw material for hydrogen production is liquid, the space velocity (LHSV) at this time is A / B when the flow rate in the liquid state of the raw material for hydrogen production is A (L / h) and the volume of the catalyst layer is B (L). This value is preferably set in the range of 0.05 to 20 h ⁻¹ , more preferably 0.1 to 10 h ⁻¹ , and still more preferably 0.2 to 5 h ⁻¹ .

  In autothermal reforming, an oxygen-containing gas is added to the reforming raw material in addition to steam. The oxygen-containing gas may be pure oxygen, but air is preferred because of its availability. An oxygen-containing gas can be added so that the endothermic reaction accompanying the steam reforming reaction is balanced, and a heat generation amount capable of maintaining the temperature of the reforming catalyst layer and SOFC or raising the temperature thereof can be obtained. The addition amount of the oxygen-containing gas is preferably 0.005 to 1, more preferably 0.01 to 0.00 as the ratio of the number of moles of oxygen molecules to the number of moles of carbon atoms contained in the raw material for hydrogen production (oxygen / carbon ratio). 75, more preferably 0.02 to 0.6. The reaction temperature of the autothermal reforming reaction is set, for example, in the range of 400 ° C to 1000 ° C, preferably 450 ° C to 850 ° C, and more preferably 500 ° C to 800 ° C. When the raw material for hydrogen production is liquid, the space velocity (LHSV) at this time is preferably selected in the range of 0.05 to 20, more preferably 0.1 to 10, and still more preferably 0.2 to 5. The amount of steam introduced into the reaction system is preferably 1 to 10, more preferably 1.5 to 7, and still more preferably 2 to 5 as a steam / carbon ratio.

  In partial oxidation reforming, an oxygen-containing gas is added to the reforming raw material. The oxygen-containing gas may be pure oxygen, but air is preferred because of its availability. In order to secure a temperature for proceeding the reaction, the amount added is appropriately determined in terms of heat loss and the like. The amount is preferably 0.1 to 3, more preferably 0.2 to 0.7 as the ratio of the number of moles of oxygen molecules to the number of moles of carbon atoms contained in the raw material for hydrogen production (oxygen / carbon ratio). . The reaction temperature of the partial oxidation reaction can be set, for example, in the range of 450 ° C to 1000 ° C, preferably 500 ° C to 850 ° C, and more preferably 550 ° C to 800 ° C. When the raw material for hydrogen production is liquid, the space velocity (LHSV) at this time is preferably selected in the range of 0.1-30. In order to suppress the generation of soot in the reaction system, steam can be introduced, and the amount thereof is preferably 0.1 to 5, more preferably 0.1 to 3, more preferably 1 to 1, as a steam / carbon ratio. 2.

[Other equipment]
In addition to the above devices, known components of the high-temperature fuel cell system can be appropriately provided as necessary. Specific examples include desulfurizers for desulfurizing hydrocarbon fuels, vaporizers for vaporizing liquids, pumps for pressurizing various fluids, pressurizing means such as compressors and blowers, and for adjusting the flow rate of fluids. Various devices such as flow rate control means such as valves for shutting off / switching fluid flow and flow path shutting / switching means, heat exchangers for heat exchange and heat recovery, condensers for condensing gas, steam, etc. These include heating / heat-retaining means for externally heating the fuel, storage means for hydrocarbon fuels and combustibles, instrumentation air and electrical systems, control signal systems, control devices, output and power electrical systems, and the like.

  As described above, in a high-temperature fuel cell system that generates power using a reformed gas obtained by reforming a hydrocarbon-based fuel with a reformer, when the reformed gas cannot be obtained at the time of starting or stopping, By supplying hydrogen obtained by electrolyzing water to the high-temperature fuel cell, the anode of the fuel cell and, if necessary, the reforming catalyst are protected from oxidation without using hydrogen etc. purified elsewhere. It becomes possible to do.

  Also, as shown in FIG. 1, when kerosene is used as the hydrocarbon-based fuel supplied to the reformer and kerosene is used as the fuel for combustion of a combustion means such as a burner, the kerosene is easily stored in the tank. it can. If a secondary battery is used to store water in the water tank and supply power to the water electrolysis hydrogen production apparatus, power generation by SOFC is performed even if there is no external fuel and water supply line or power supply. It is useful as an emergency power source. The same applies when LPG is used instead of kerosene. In this case, LPG may be stored in a cylinder.

  The present invention can be applied to, for example, a stationary or mobile power generation system, and a high-temperature fuel cell system used for a cogeneration system.

It is a flowchart which shows the outline of an example of the indirect internal reforming type | mold SOFC system which can implement the operating method of this invention. It is a schematic flowchart for demonstrating the example of the driving | running method of this invention. It is a schematic flowchart for demonstrating the example of the driving | running method of this invention. It is a schematic flowchart for demonstrating the example of the driving | running method of this invention. It is a schematic flowchart for demonstrating the example of the driving | running method of this invention. It is a schematic flowchart for demonstrating the example of the driving | running method of this invention.

Explanation of symbols

1: Water tank 2: Kerosene tank 3: Reformer 4: SOFC
5: Combustion chamber 10: Module container 21: Water electrolysis hydrogen production device 22: Heater

Claims (5)

A method for operating a fuel cell system, comprising: a reformer that produces reformed gas from a hydrocarbon-based fuel; and a high-temperature fuel cell that generates electric power using the reformed gas obtained from the reformer,
When the reformer cannot produce reformed gas from hydrocarbon fuel, hydrogen generated by electrolysis of water is supplied to the anode of the high-temperature fuel cell, so that the anode is brought into a reducing gas atmosphere. A method for operating a high-temperature fuel cell system having a process.   The method according to claim 1, wherein the step is performed when the reformer is at a temperature lower than a temperature at which the reformed gas can be produced from the hydrocarbon-based fuel.   The method according to claim 1 or 2, wherein hydrogen generated by electrolysis of water is supplied to the anode via the reformer.   The hydrogen supplied to the anode is discharged from the anode, and at least one of the high-temperature fuel cell and the reformer is heated by thermal energy obtained by burning the discharged hydrogen. The method described.   The method according to any one of claims 1 to 4, wherein the high-temperature fuel cell is a solid oxide fuel cell or a molten carbonate fuel cell.

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